Electronic-grade perfluorohexyl sulfonic acid for photoresist top anti-reflection film and preparation method of electronic-grade perfluorohexyl sulfonic acid

Abstract

The preparation method comprises the following steps: firstly, converting crude perfluorohexyl sulfonic acid into potassium perfluorohexyl sulfonate, then dissolving the potassium perfluorohexyl sulfonate and other impurity sulfonate in electronic-grade pure water at a high temperature by utilizing the solubility characteristic of the potassium perfluorohexyl sulfonate, and finally, preparing the electronic-grade perfluorohexyl sulfonic acid for the top anti-reflection film of the photoresist, so as to obtain the electronic-grade perfluorohexyl sulfonic acid for the top anti-reflection film of the photoresist and the preparation method of the electronic-grade perfluorohexyl sulfonic acid. Then cooling and crystallizing to separate out potassium perfluorohexyl sulfonate, and remaining other trace impurities (sulfonate and other water-soluble impurities) in the electronic-grade pure water. And repeatedly dissolving and crystallizing for multiple times to obtain the electronic-grade potassium perfluorohexyl sulfonate, wherein the impurity metal ions are all below 2ppb. Finally, the potassium perfluorohexyl sulfonate is converted into the perfluorohexyl sulfonic acid by using the electrolyzed and purified resin, so that the problem that the mixed acid of sulfuric acid and the perfluorohexyl sulfonic acid is difficult to separate when the perfluorohexyl sulfonic acid is prepared by using strong acid is solved, and the contents of various impurity metal ions in the finally obtained perfluorohexyl sulfonic acid are all lower than 1ppb and reach the E3 standard; and the added value of the product is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of photolithography, in particular to an electronic-grade perfluorohexyl sulfonic acid used for an anti-reflection film on the top of a photoresist. The invention also relates to a preparation method of the electronic-grade perfluorohexyl sulfonic acid. Background Art

[0002] Photolithography technology is a method of transferring the semiconductor circuit pattern on a photomask to a silicon wafer. The pattern transfer process is completed by irradiating the photomask template with a laser or electron beam, causing the photosensitive material on the wafer to change its material properties due to light exposure.

[0003] The existing photolithography technology has the technical problem of light scattering, which leads to low dimensional accuracy of photoresist imaging. The current mainstream solution is to add a top anti-reflection film formed by a fluorine-containing compound with low refractive index and high transmittance before and after photoresist coating to reduce the interference of light in the photoresist and prevent the change of photolithography line width due to the change of photoresist thickness. The composition used to form the top anti-reflection film for photolithography in the prior art still has certain deficiencies in processability, film forming property, refractive index, coating amount or raw material cost.

[0004] Based on the above, patent CN114035405B discloses a composition for preparing a top anti-reflection film for photoresist, a top anti-reflection film for photoresist and a fluorine-containing composition, which indicates that the part of the photoresist irradiated by a specific light source undergoes a photochemical reaction to produce H + When the pH value of the top anti-reflection layer is high, the generated hydrogen ions diffuse into the anti-reflection layer, the hydrogen ions in the photoresist area are reduced, and the development is incomplete. The developer cannot be fully removed during the development process, thus forming a T-shaped top, which leads to light scattering and standing wave effects during the photolithography process. Adding an appropriate amount of acid to the top anti-reflection layer system can inhibit the H in the photoresist. + The acid diffuses toward the anti-reflection film to avoid the formation of a T-shaped top. Based on the total weight of the composition for preparing the top anti-reflection film, the amount of the acid added is usually preferably 0.5-3wt%, the composition has good stability and film-forming properties, and can be coated with a smaller amount to form an anti-reflection film with equivalent performance to the anti-reflection film in the prior art. The anti-reflection film has a refractive index of 1.41-1.44 at 248nm, which can effectively reduce the refractive index under 248nm wavelength laser irradiation and can be used as a top anti-reflection film for photoresist.

[0005] The above patents first mentioned that adding an appropriate amount of acid to the top anti-reflection layer system can inhibit the diffusion of H+ in the photoresist to the anti-reflection film to avoid the formation of T-tops. The acid regulator selected perfluorohexyl sulfonic acid (Example 6), and the content of perfluorohexyl sulfonic acid is usually preferably 0.5-3wt%. However, the perfluorohexyl sulfonic acid that can be used in the semiconductor industry has strict requirements for the impurity metal ions therein. There are few existing data on perfluorohexyl sulfonic acid, which basically belongs to a blank field. The impurity metal ion content in the perfluorohexyl sulfonic acid generally available is quite high and cannot be used to prepare the top anti-reflection film of the photoresist. Therefore, perfluorohexyl sulfonic acid is purified, and the total amount of its metal impurity ions is reduced to below the customer's requirements for compounding the top anti-reflection film, which is of great significance.

[0006] At present, the removal of impure metal ions in perfluorohexane sulfonic acid has the following difficulties:

[0007] Perfluorohexyl sulfonic acid has a long carbon chain and a large molecular weight, and high-concentration perfluorohexyl sulfonic acid has a high viscosity, resulting in few methods for purifying perfluorohexyl sulfonic acid to remove metal ions, and traditional purification methods have little effect. For example, distillation is generally the best method for liquid purification, but when perfluorohexyl sulfonic acid is distilled and purified, a colloidal solid perfluorohexyl sulfonic acid will be formed after the solvent water is evaporated, and distillation cannot be used for purification again, resulting in almost no effect on removing metal ions. In addition, the applicant tried to use ion exchange, freezing, distillation, salt conversion purification, and polymer adsorbent adsorption, but none of them had a good purification effect. The content of a single impurity metal ion was still above 10ppb, which could not meet customer requirements.

[0008] Based on the above, the applicant prepared electronic grade perfluorohexane sulfonic acid by combining resin impurity removal with electrolytic impurity removal, but the following problems still exist:

[0009] (1) In GB / T41881-2022, the electronic grade sulfuric acid standard is divided into 5 standards, namely E1, E2, E3, E4 and E5. The customer requires the applicant to benchmark the metal ions in the perfluorosulfonic acid of the metal ion requirements of the four levels of electronic grade sulfuric acid, namely E1, E2, E3 and E4. The metal ions are controlled within the range of E4-E1, preferably reaching the E1 level. The higher the level, the higher the added value. The minimum requirement is to reach the E4 level. In the industry, ion exchange is generally used to prepare electronic grade pure water, and electronic grade resin is used for multi-stage impurity removal. However, the present invention is a strongly acidic system. Since ion exchange is a reversible process, when the acidity of the system is strong, the impurity metal ions on the resin will be reversed into the acid solution, which does not achieve the ideal impurity removal effect. The most difficult impurity ions to remove are sodium ions. After the resin is removed, the sodium ions in the acid solution are still between 100-200ppb.

[0010] (2) In the early stage of the electrolytic decontamination process, the applicant has been using primary purified perfluorohexane sulfonic acid to adjust the current. However, due to the high price of primary purified perfluorohexane sulfonic acid, the purification cost has increased significantly, and the product profit margin is relatively low. Based on this, the applicant tried to convert perfluorohexane sulfonic acid with a high impurity metal ion content into perfluorohexane sulfonate, and then purify it several times to obtain perfluorohexane sulfonate with a low impurity metal ion content, and finally convert it into acid to obtain perfluorohexane sulfonic acid with a low impurity metal ion content. However, converting perfluorohexane sulfonate with a low impurity metal ion content into perfluorohexane sulfonic acid is a technical difficulty. Conventionally, salts are converted into acids, and the principle of strong acid to weak acid is often used for conversion. However, since perfluorohexane sulfonic acid has excellent water solubility, and the potassium perfluorohexane sulfonate converted by the present invention contains a large amount of water, after the strong acid conversion is completed, the strong acid and perfluorohexane sulfonic acid will both dissolve in water, resulting in a mixed solution with no solubility difference, and the two are not separated, and the desired perfluorohexane sulfonic acid cannot be separated.

[0011] In addition, since the commercially available electronic-grade resin contains a small amount of sodium ions and trace amounts of other metal ions, it will affect whether the perfluorohexane sulfonic acid with a metal ion content of less than 1 ppb can be obtained in the end. In addition, the resin has a poor selective adsorption effect on sodium ions under acidic conditions, which will cause a high sodium ion content in the converted perfluorohexane sulfonic acid. Therefore, the applicant tried to use electronic-grade acid to perform long-term and multiple countercurrent washing on the resin, continuously replacing the sodium ions and other impurity metal ions therein with the hydrogen ions in the acid solution, so that the impurity ions in the resin are continuously precipitated into the electronic-grade acid, and the primary impurity removal of the resin was performed. However, the ability of washing treatment under acidic conditions to replace the metal ions in the resin structure into hydrogen ions is limited, and there will always be a certain amount of sodium ions in the resin. When using this treated resin to treat commercially available perfluorohexane sulfonic acid, the sodium ion content in the obtained perfluorohexane sulfonic acid solution is relatively high, between 100-200 ppb, which cannot meet the use requirements of the acid regulator in the preparation process of the anti-reflective film on the top of the photoresist. Summary of the invention

[0012] The purpose of the present invention is to solve the above technical problems existing in the prior art and to provide an electronic grade perfluorohexyl sulfonic acid for use in an anti-reflective film on the top of a photoresist, wherein the content of various impurity metal ions is less than 1 ppb.

[0013] Another object of the present invention is to provide a method for preparing the above-mentioned electronic grade perfluorohexyl sulfonic acid.

[0014] To achieve its purpose, the present invention adopts the following technical solution:

[0015] A method for preparing electronic grade perfluorohexyl sulfonic acid used in an anti-reflective film on top of a photoresist comprises the following steps:

[0016] (1) taking perfluorohexane sulfonic acid, diluting it with electronic grade pure water to a mass fraction of 2-12%, then adding a high-grade pure potassium hydroxide solution dropwise to react until the pH of the solution reaches 7, and performing solid-liquid separation to obtain a crude product of potassium perfluorohexane sulfonate;

[0017] (2) taking the crude potassium perfluorohexane sulfonate product in step (1) and placing it in a container, adding electronic grade pure water, starting stirring, and heating to 85-95°C to dissolve the potassium perfluorohexane sulfonate; after complete dissolution, filtering while hot, cooling the filtrate to 0°C-60°C at a high-speed stirring speed of 1000 r / min to precipitate potassium perfluorohexane sulfonate, filtering it twice while cold to obtain a first purified potassium perfluorohexane sulfonate; repeating the above steps with the first purified potassium perfluorohexane sulfonate to obtain a second purified potassium perfluorohexane sulfonate , repeating the aforementioned steps with the twice purified potassium perfluorohexanyl sulfonate to obtain 3 times purified potassium perfluorohexanyl sulfonate, repeating the aforementioned steps with the 3 times purified potassium perfluorohexanyl sulfonate to obtain 4 times purified potassium perfluorohexanyl sulfonate, repeating the aforementioned steps with the 4 times purified potassium perfluorohexanyl sulfonate to obtain 5 times purified potassium perfluorohexanyl sulfonate, repeating the aforementioned steps with the 5 times purified potassium perfluorohexanyl sulfonate to obtain 6 times purified potassium perfluorohexanyl sulfonate, until the content of all metal ions is less than or equal to 2 ppb, thereby obtaining pure potassium perfluorohexanyl sulfonate;

[0018] (3) loading the hydrogen-type cationic resin into an ion exchange column, and diluting electronic-grade hydrofluoric acid into a 5% by mass hydrofluoric acid dilute solution, using the hydrofluoric acid dilute solution to wash the ion exchange column in a countercurrent manner, and then using electronic-grade pure water to wash in a downstream manner until the pH of the washing water is 6-7;

[0019] (4) Take E1 grade electronic grade sulfuric acid, dilute it with electronic grade pure water to a mass fraction of 3-5%, place it in the anode chamber, then add the hydrogen type cationic resin treated in step (3), fill the cathode chamber with electronic grade pure water and perform electrolysis five times continuously, adjust the electrolysis voltage to 30-55V, add the diluted electronic grade sulfuric acid to the cathode chamber until the electrolysis current is 0.8-3.2A, raise the temperature of each cathode chamber to 40-70°C, and perform electrolysis for 0.7-1h; after the single electrolysis is completed, take out all the cathode chamber solution, add electronic grade pure water to wash until the metal ion in the washing water is less than 1ppb, and then add electronic grade pure water to perform the next electrolysis until the electrolysis is completed; after the electrolysis is completed, separate the electronic grade sulfuric acid in the anode chamber from the resin, and then wash the resin with electronic grade pure water until the pH of the washing liquid is 6-7;

[0020] (5) loading the washed resin in step (4) into an ion exchange column, and then circulating electronic grade pure water heated to 90° C. through the resin, preheating the resin to 85° C., and then passing high-purity nitrogen into the ion exchange column to squeeze out the water in the resin; adding electronic grade pure water to the six-stage purified potassium perfluorohexyl sulfonate in step (2) to prepare a slurry, and then heating it to 85-90° C. to form an aqueous solution of potassium perfluorohexyl sulfonate, and passing it through the aforementioned ion exchange column while hot to remove impurities and convert perfluorohexyl sulfonic acid, and passing it through twice continuously to obtain perfluorohexyl sulfonic acid;

[0021] (6) Connect filter elements of 0.05 μm, 0.02 μm, 0.01 μm, and 0.01 μm in series, first use electronic grade pure water for dynamic circulation washing for 24-50 hours, and then test the number of particles in the water. When the number of 0.5 μm particles in the water is less than 10 ea / ml, the number of 0.3 μm particles is less than 50 ea / ml, and the number of 0.2 μm particles is less than 100 ea / ml, the perfluorohexane sulfonic acid in step (5) is dynamically circulated and filtered to obtain electronic grade perfluorohexane sulfonic acid.

[0022] As a further preferred embodiment of the technical solution of the present invention, in step (3), the number of the ion exchange columns is three and connected in series.

[0023] Furthermore, in step (4), the volume ratio of the hydrogen-type cationic resin to the diluted electronic-grade sulfuric acid is 1:2-1:5.

[0024] Furthermore, in the first electrolysis of step (5), the electrolysis voltage is 30-35V, and the electrolysis current is 0.8-1.2A; the temperature of each electrode chamber is raised to 40-70°C, and the electrolysis is performed for 0.7-1h.

[0025] In the secondary electrolysis, the electrolysis voltage is 35-40V, and the electrolysis current is 1.3-1.7A; the temperature of each electrode chamber is raised to 40-70°C, and the electrolysis is carried out for 0.7h-1h.

[0026] During the three electrolysis steps, the electrolysis voltage was 40-45 V, and the electrolysis current was 1.8-2.2 A. The temperature of each electrode chamber was raised to 40-70° C., and the electrolysis was performed for 0.7 h to 1 h.

[0027] During the four electrolysis cycles, the electrolysis voltage was 45-50 V, and the electrolysis current was 2.3-2.7 A. The temperature of each electrode chamber was raised to 40-70° C., and the electrolysis was performed for 0.7 h to 1 h.

[0028] During the five electrolysis cycles, the electrolysis voltage was 50-55 V, and the electrolysis current was 2.8-3.2 A. The temperature of each electrode chamber was raised to 40-70° C., and the electrolysis was performed for 0.7 h to 1 h.

[0029] Furthermore, in step (6), the dynamic circulation filtration time is 24-50 hours.

[0030] The method can be used to obtain electronic grade perfluorohexane sulfonic acid used in the anti-reflection film on the top of the photoresist.

[0031] By adopting the above technical solution, the beneficial effects of the present invention are:

[0032] 1. The method of the present invention can produce E3 level electronic grade perfluorohexane sulfonic acid, filling the gap in the research direction of using crude perfluorohexane sulfonic acid to prepare high value-added and high-tech E3 level electronic grade perfluorohexane sulfonic acid.

[0033] 2. The present invention is simple to operate, and the electrolytic decontamination process uses low voltage and low current for operation, which has low energy consumption, low cost and high safety factor. In addition, the present invention no longer uses primary purified perfluorohexyl sulfonic acid for current regulation, which reduces the waste of perfluorohexyl sulfonic acid and greatly reduces the purification cost.

[0034] 3. Since the selectivity of special high-purity resin for sodium ion adsorption is poor, but the selectivity for potassium ion adsorption is excellent (the selectivity of potassium ions and sodium ions has been experimentally verified, and the selectivity of hydrogen-type cationic resin for potassium ions is better). In the experiment, the applicant found that the sodium ions in the acid after the resin acidification of perfluorohexyl sulfonic acid sodium salt after primary impurity removal are between 100-200ppb, while the potassium ions in the acid after the resin acidification of perfluorohexyl sulfonic acid potassium salt after primary impurity removal are less than 10ppb. Based on this, the present invention first converts crude perfluorohexyl sulfonic acid into potassium perfluorohexyl sulfonate, and then utilizes the solubility characteristics of potassium perfluorohexyl sulfonate to dissolve potassium perfluorohexyl sulfonate and other impurity sulfonates such as sodium perfluorohexyl sulfonate in electronic grade pure water at high temperature, and then cools the aqueous solution of potassium perfluorohexyl sulfonate to crystallize, precipitate potassium perfluorohexyl sulfonate, and other trace impurities (sulfonates and other water-soluble impurities) are left in electronic grade pure water. After repeated dissolution and crystallization, electronic grade potassium perfluorohexane sulfonate is obtained, in which the impurity metal ions are less than or equal to 2ppb. In addition, in order to prevent potassium perfluorohexane sulfonate from encapsulating other impurity metal ions during cooling and crystallization, it is necessary to precipitate under high-speed stirring conditions to form high shear force, thereby obtaining potassium perfluorohexane sulfonate with very fine particles; and after the crystals are precipitated, it is necessary to filter for as long as possible to prevent the potassium perfluorohexane sulfonate from containing too much water and affecting the impurity removal effect.

[0035] 4. In the process of converting the purified potassium perfluorohexane sulfonate into perfluorohexane sulfonic acid, the present invention selects to use resin to convert potassium perfluorohexane sulfonate into perfluorohexane sulfonic acid, thereby solving the problem of difficulty in separating the mixed acid of sulfuric acid and perfluorohexane sulfonic acid obtained by using strong acid to prepare perfluorohexane sulfonic acid.

[0036] 5. The present invention places the resin after primary impurity removal in an acid solution obtained by diluting E1 grade sulfuric acid, and utilizes the hydrogen ions in the acid and the electrical force to forcibly exchange and migrate the trace sodium ions and trace amounts of other impurity metal ions remaining in the resin to the cathode chamber, thereby obtaining a resin with extremely low content of sodium ions and other metal ions, and finally utilizes the resin to convert the potassium perfluorohexyl sulfonate after multiple purifications into perfluorohexyl sulfonic acid. After the potassium perfluorohexyl sulfonate with extremely low metal ions is converted by the resin with extremely low metal ions, the content of various impurity metal ions in the finally obtained perfluorohexyl sulfonic acid is lower than 1ppb, reaching the E3 standard, further improving the added value of the product. DETAILED DESCRIPTION

[0037] The preparation method of electronic grade perfluorohexane sulfonic acid for anti-reflective film on top of photoresist of the present invention is described in detail below with reference to specific embodiments.

[0038] In the following examples, all operations are carried out in a Class 100 clean room, and electronic grade pure water is electronic water with metal ions less than 1 ppb. The electrolytic cell is composed of an anode chamber, an anode plate, a cathode chamber, a cathode plate, and an intermediate diaphragm. In the electrolytic cell, the anode plate is a high-purity platinum plate, and the cathode plate is a high-purity graphite plate.

[0039] Perfluorohexane sulfonic acid in step (1) was purchased from Shanghai Jizhi Biochemical Co., Ltd. The full element analysis results are shown in Table 1.

[0040] Table 1 All element analysis results of commercially available perfluorohexane sulfonic acid (unit: ppb)

[0041] Al Ba Ca Cd Co Cr Cu Fe K Mg Mn Na Zn Ni 319 56 3493 0 0 211 607 734 1500 348 6.3 1659 0 12

[0042] Example 1

[0043] A method for preparing electronic grade perfluorohexyl sulfonic acid used in an anti-reflective film on top of a photoresist comprises the following steps:

[0044] (1) taking 2000 ml of 30% perfluorohexane sulfonic acid, adding 6000 ml of electronic grade pure water to dilute to 10% by mass, then adding dropwise 100 g / L of high-grade pure potassium hydroxide solution to react until the pH of the solution is 7, and performing solid-liquid separation to obtain a crude product of potassium perfluorohexane sulfonate;

[0045] (2) taking 100 g of the crude potassium perfluorohexane sulfonate obtained in step (1), placing it in a polytetrafluoroethylene beaker, adding 3333 ml of electronic grade pure water, and stirring at a speed of 300 r / min; and heating, heating the crude potassium perfluorohexane sulfonate aqueous solution to 85° C. to completely dissolve the potassium perfluorohexane sulfonate, and filtering while hot; cooling the obtained filtrate to 10° C. at a high-speed stirring speed of 1000 r / min, and filtering it twice while it is cold to obtain primary purified potassium sulfonate; and obtaining primary purified potassium perfluorohexane sulfonate; Repeat the above steps with the purified potassium perfluorohexane sulfonate once to obtain purified potassium perfluorohexane sulfonate twice, repeat the above steps with the purified potassium perfluorohexane sulfonate twice to obtain purified potassium perfluorohexane sulfonate three times, repeat the above steps with the purified potassium perfluorohexane sulfonate three times to obtain purified potassium perfluorohexane sulfonate four times, repeat the above steps with the purified potassium perfluorohexane sulfonate four times to obtain purified potassium perfluorohexane sulfonate five times, repeat the above steps with the purified potassium perfluorohexane sulfonate five times to obtain purified potassium perfluorohexane sulfonate six times, until all metal ion contents are

[0046] Less than or equal to 2ppb, pure potassium perfluorohexane sulfonate was obtained; the results of full element analysis are shown in Table 2;

[0047] Table 2 The results of elemental analysis of crude potassium perfluorohexane sulfonate after purification are as follows (unit: ppb)

[0048] Al Ba Ca Cd Co Cr Cu Fe Mg Mn Na Zn Ni thick 110 19 1087 0 0 68 194 210 99 2 579 0 4 Pure 1 10 6 118 0 0 8 21 20 16 0 69 0 0 Pure 2 6 0 34 0 0 4 9 12 8 0 33 0 0 Pure 3 3 0 15 0 0 2 6 7 5 0 19 0 0 Pure 4 2 0 7 0 0 2 4 4 3 0 8 0 0 Pure 5 2 0 3 0 0 2 2 3 2 0 4 0 0 Pure 6 2 0 2 0 0 1 2 2 1 0 2 0 0

[0049] (3) Load 10 L of hydrogen-type cationic resin into three ion exchange columns connected in series, and dilute electronic-grade hydrofluoric acid into a 5% by mass hydrofluoric acid dilute solution. Use 30 L of hydrofluoric acid dilute solution to wash the ion exchange column in countercurrent for 48 h, and then use electronic-grade pure water to wash in downstream until the pH of the wash water is 7;

[0050] (4) Take 100 ml of E1 grade electronic grade sulfuric acid and dilute it with electronic grade pure water to a mass fraction of 3%. Take 1000 ml of 3% dilute sulfuric acid and place it in the anode chamber, then add 500 ml of hydrogen-type cationic resin treated in step (3), and put 100 ml of electronic grade pure water into the cathode chamber for one electrolysis. Adjust the electrolysis voltage to 30 V, add diluted electronic grade sulfuric acid to the cathode chamber until the electrolysis current is 0.8 A, raise the temperature of each anode chamber to 60°C, and electrolyze for 1 hour; after one electrolysis, take out all the cathode chamber solution, add electronic grade pure water to wash until the metal ions in the washing water are less than 1 ppb;

[0051] Add electronic grade pure water to the cathode chamber for secondary electrolysis, adjust the electrolysis voltage to 35V, add diluted electronic grade sulfuric acid to the cathode chamber until the electrolysis current is 1.3A, raise the temperature of each chamber to 60°C, and electrolyze for 1h; after the secondary electrolysis, take out all the cathode chamber solution, add electronic grade pure water to wash until the metal ions in the washing water are less than 1ppb;

[0052] The cathode chamber was filled with electronic grade pure water for three electrolysis, the electrolysis voltage was adjusted to 40V, diluted electronic grade sulfuric acid was added to the cathode chamber until the electrolysis current was 1.8A, the temperature of each chamber was raised to 60°C, and the electrolysis was performed for 1h; after the three electrolysis, all the cathode chamber solutions were taken out, and electronic grade pure water was added for washing until the metal ions in the washing water were less than 1ppb;

[0053] The cathode chamber was filled with electronic grade pure water for four electrolysis cycles, the electrolysis voltage was adjusted to 45 V, diluted electronic grade sulfuric acid was added to the cathode chamber until the electrolysis current was 2.3 A, the temperature of each chamber was raised to 60 ° C, and the electrolysis was performed for 1 hour; after the four electrolysis cycles, all the cathode chamber solutions were taken out, and electronic grade pure water was added for washing until the metal ions in the washing water were less than 1 ppb;

[0054] Add electronic grade pure water to the cathode chamber for five electrolysis cycles, adjust the electrolysis voltage to 50 V, drip diluted electronic grade sulfuric acid into the cathode chamber until the electrolysis current is 2.8 A, raise the temperature of each chamber to 60 ° C, and electrolyze for 1 hour; after the electrolysis is completed, separate the electronic grade sulfuric acid in the anode chamber from the resin, and then wash the resin with electronic grade pure water until the pH of the washing solution is 7;

[0055] (5) loading the washed resin in step (4) into an ion exchange column, first heating electronic grade pure water to 90° C., then circulating the heated electronic grade pure water through the resin, preheating the resin to 85° C., then quickly passing high-purity nitrogen through the resin column to squeeze out the water in the resin, adding electronic grade pure water to the six-stage purified potassium perfluorohexyl sulfonate in step (2) to prepare a slurry (solid-liquid mass ratio of 1:33), then heating to 85° C. to form an aqueous solution of potassium perfluorohexyl sulfonate, and passing the ion exchange column while hot to remove impurities and convert perfluorohexyl sulfonic acid, and passing through the ion exchange column twice continuously to obtain perfluorohexyl sulfonic acid;

[0056] (6) 0.05 μm, 0.02 μm, 0.01 μm, and 0.01 μm filter elements were connected in series and first washed with electronic grade pure water in a dynamic circulation for 48 hours. The number of particles in the water was then tested. The number of 0.5 μm particles in the water was 8 ea / ml, the number of 0.3 μm particles was 47 ea / ml, and the number of 0.2 μm particles was 89 ea / ml. The perfluorohexane sulfonic acid in step (5) was dynamically circulated and filtered for 48 hours to obtain electronic grade perfluorohexane sulfonic acid with low metal ions and low particle count that can be used in the semiconductor industry. The metal ions were compared with E3 electronic grade sulfuric acid. The results of full element analysis are shown in Table 3.

[0057] Table 3 Full element analysis results of electronic grade perfluorohexane sulfonic acid (unit: ppb)

[0058] Al Ba Ca Cd Co Cr Cu Fe Mg Mn Na K Zn Ni product 0.4 0.1 0.7 0.2 0.2 0.3 0.2 0.4 0.6 0.5 0.6 0.6 0.6 0.2

[0059] Example 2-Example 12

[0060] The other steps of Example 2 to Example 14 are the same as those of Example 1, except that the mass fraction of perfluorohexyl sulfonic acid after dilution in step (1) is changed. When the mass fraction of perfluorohexyl sulfonic acid after dilution is other values, whether the total metal ions in the final product can meet the E3 standard is shown in Table 4.

[0061] Table 4 Effect of the mass fraction of perfluorohexane sulfonic acid after dilution on the total metal ion content in the product

[0062]

[0063] From the above examples, it can be seen that when the mass fraction of the perfluorohexane sulfonic acid after dilution in step (1) is 2-12%, the total metal ions in the obtained perfluorohexane sulfonic acid meet the E3 standard, and the effect is good. Therefore, the mass fraction of the perfluorohexane sulfonic acid after dilution is preferably selected to be 2-12%.

[0064] Example 15-Example 27

[0065] The other steps of Example 15 to Example 27 are the same as those of Example 1, except that the temperature of the crude potassium perfluorohexyl sulfonate aqueous solution is increased to other values ​​in step (2). When the temperature of the crude potassium perfluorohexyl sulfonate aqueous solution is increased to other values, whether the crude potassium perfluorohexyl sulfonate is completely dissolved is shown in Table 5.

[0066] Table 5 Effect of heating temperature of crude potassium perfluorohexane sulfonate aqueous solution on crude product dissolution effect

[0067]

[0068]

[0069] From the above examples, it can be seen that when the crude potassium perfluorohexane sulfonate aqueous solution is heated to 85-95°C in step (2), the soluble salt of the crude potassium perfluorohexane sulfonate is completely dissolved. Therefore, it is preferred to heat the crude potassium perfluorohexane sulfonate aqueous solution to 85-95°C.

[0070] Example 28-Example 34

[0071] The other steps of Example 28 to Example 34 are the same as those of Example 1, except that the number of continuous purifications of crude potassium perfluorohexyl sulfonate in step (2) is changed. When the number of continuous purifications of crude potassium perfluorohexyl sulfonate is other values, whether the total metal ions in the final product can meet the E3 standard is shown in Table 6.

[0072] Table 6 Effect of continuous purification times of crude potassium perfluorohexane sulfonate on the total metal ion content in the product

[0073] Continuous purification times of crude potassium perfluorohexanesulfonate Does the final product meet the E3 standard? Embodiment 28 1 no Embodiment 29 2 no Embodiment 30 3 no Embodiment 31 4 no Embodiment 32 5 no Example 1 6 yes Embodiment 33 7 yes Embodiment 34 8 yes

[0074] From the above examples, it can be seen that when the number of continuous purification times of the crude potassium perfluorohexyl sulfonate in step (2) is greater than or equal to 6 times, the metal ions in the obtained perfluorohexyl sulfonic acid can meet the E3 standard. Therefore, the number of continuous purification times of the crude potassium perfluorohexyl sulfonate is preferably selected to be 6 times.

[0075] Example 35-Example 46

[0076] The other steps of Examples 35 to 46 are the same as those of Example 1, except that the filtrate temperature in step (2) is changed. When the filtrate temperature is reduced to other values, whether potassium perfluorohexane sulfonate crystallizes is shown in Table 7.

[0077] Table 7 Effect of filtrate cooling temperature on crystallization results of potassium perfluorohexane sulfonate

[0078]

[0079] From the above examples, it can be seen that when the filtrate temperature in step (2) is reduced to 0-60°C, potassium perfluorohexane sulfonate will precipitate. Since the lower the temperature, the more potassium perfluorohexane sulfonate will precipitate, considering the yield and the reduction of energy consumption, the filtrate temperature is preferably reduced to 10-20°C.

[0080] Example 47-Example 53

[0081] The other steps of Example 47-Example 53 are the same as those of Example 1, except that the number of continuous electrolysis in step (4) is changed. When the number of continuous electrolysis is other values, whether the total metal ions in the final product can meet the E3 standard is shown in Table 8.

[0082] Table 8 Effect of the number of consecutive electrolysis times in step (4) on the total metal ion content in the product

[0083]

[0084] From the above examples, it can be seen that when the number of continuous electrolysis in step (4) is 5-7 times, the metal ions in the obtained perfluorohexane sulfonic acid can reach the E3 standard. Therefore, the number of continuous electrolysis is preferably selected to be 5 times.

[0085] Example 54-Example 68

[0086] The other steps of Examples 54 to 68 are the same as those of Example 1, except that the electrolysis temperature in step (4) is changed. When the electrolysis temperature is at other values, whether the total metal ions in the final product meet the E3 standard as shown in Table 9.

[0087] Table 9 Effect of electrolysis temperature in step (4) on total metal ion content in the product

[0088]

[0089]

[0090] From the above examples, it can be seen that when the electrolysis temperature in step (4) is 40°C-70°C, the total metal ions in the obtained perfluorohexane sulfonic acid meet the E3 standard, and the effect is good. Considering the reduction of energy consumption and cost, the electrolysis temperature is preferably selected to be 40°C.

[0091] Example 69-Example 76

[0092] The other steps of Example 69-Example 76 are the same as those of Example 1, except that the electrolysis voltage in step (4) is changed. When the electrolysis voltage is at other values, whether the total metal ions in the final product meet the E3 standard is shown in Table 10.

[0093] Table 10 Effect of electrolysis voltage in step (4) on total metal ion content in the product

[0094]

[0095] From the above embodiment, it can be seen that when in step (4), 30V≤1 electrolysis voltage≤35V, 35V≤2 electrolysis voltage≤40V, 40V≤3 electrolysis voltage≤45V, 45V≤4 electrolysis voltage≤50V, 50V≤5 electrolysis voltage≤55V, the metal ion content in the obtained electronic grade perfluorohexyl sulfonic acid reaches E3 level, and the effect is good. Considering reducing energy consumption and reducing costs, the electrolysis voltage is preferably 30V for 1 time, 35V for 2 times, 40V for 3 times, 45V for 4 times, and 50V for 5 times.

[0096] Example 77-Example 91

[0097] The other steps of Example 77-Example 91 are the same as those of Example 1, except that the electrolysis current in step (4) is changed. When the electrolysis current is at other values, whether the total metal ions in the final product meet the E3 standard is shown in Table 11.

[0098] Table 11 Effect of electrolysis current in step (4) on total metal ion content in the product

[0099]

[0100] As can be seen from the above-described embodiments, when in step (4), 0.8A≤1 electrolysis current≤1.2A, 1.3A≤2 electrolysis current≤1.7A, 1.8A≤3 electrolysis current≤2.2A, 2.3A≤4 electrolysis current≤2.7A, 2.8A≤5 electrolysis current≤3.2A, the total metal ion content in the obtained perfluorohexyl sulfonic acid reaches the E3 level, and the effect is good. Considering energy consumption and reducing costs, therefore, preferentially selecting 1 electrolysis current is 0.8A, 2 electrolysis currents are 1.3A, 3 electrolysis currents are 1.8A, 4 electrolysis currents are 2.3A, and 5 electrolysis currents are 2.8A.

[0101] Example 92-Example 103

[0102] The other steps of Example 92-Example 103 are the same as those of Example 1, except that the electrolysis time in step (4) is changed. When the electrolysis time is at other values, whether the total metal ions in the final product can reach the E3 standard is shown in Table 12.

[0103] Table 12 Effect of electrolysis time in step (4) on total metal ion content in the product

[0104]

[0105] From the above embodiment, it can be seen that in step (4), when 0.7h≤1 electrolysis time≤1h, 0.7h≤2 electrolysis time≤1h, 0.7h≤3 electrolysis time≤1h, 0.7h≤4 electrolysis time≤1h, 0.7h≤5 electrolysis time≤1h, the total metal ion content in the obtained perfluorohexane sulfonic acid can reach the E3 standard, and the effect is good. Considering the reduction of energy consumption and cost, therefore, the electrolysis time is preferably selected as 0.7h for 1 time, 0.7h for 2 times, 0.7h for 3 times, 0.7h for 4 times, and 0.7h for 5 times.

[0106] Example 104-Example 119

[0107] The other steps of Examples 104 to 119 are the same as those of Example 1, except that the heating temperature in step (5) is changed. Whether potassium perfluorohexyl sulfonate is precipitated in the resin when the heating temperature is at other values ​​is shown in Table 13.

[0108] Table 13 Effect of the heating temperature in step (5) on whether potassium perfluorohexane sulfonate will precipitate in the resin during the acid conversion process

[0109]

[0110] From the above examples, it can be seen that when the heating temperature in step (5) is 85°C-95°C, potassium perfluorohexane sulfonate will not precipitate in the resin during the acid conversion process. However, when the temperature is higher than 90°C, the effect of impurity removal will be affected, so that the metal ions of the acid converted by the resin do not meet the standard. Therefore, the heating temperature is preferably selected between 85°C and 90°C.

[0111] Example 120-Example 141

[0112] The other steps of Examples 120-141 are the same as those of Example 1, except that the filtration time in step (6) is changed. When the filtration time is other values, whether the number of particles in the product meets the standard is shown in Table 14.

[0113] Table 14 Effect of filtration time in step (6) on the number of particles in the final product

[0114] Filtration time / h Is the number of particles up to standard? Embodiment 120 6 no Embodiment 121 8 no Embodiment 122 10 no Embodiment 123 12 no Embodiment 124 14 no Embodiment 125 16 no Embodiment 126 18 no Embodiment 127 20 no Embodiment 128 22 no Embodiment 129 24 yes Embodiment 130 26 yes Embodiment 131 28 yes Embodiment 132 30 yes Embodiment 133 32 yes Embodiment 134 34 yes Embodiment 135 36 yes Embodiment 136 38 yes Embodiment 137 40 yes Embodiment 138 42 yes Embodiment 139 44 yes Embodiment 140 46 yes Example 1 48 yes Embodiment 141 50 yes

[0115] From the above embodiment, it can be seen that when the filtration time in step (6) is 24h-50h, the number of particles in the final product meets the standard, and the filtration time is preferably selected as 24h.

Claims

1. A method for preparing electronic grade perfluorohexane sulfonic acid used in an anti-reflective film on top of a photoresist, characterized in that: The following steps are involved: (1) taking perfluorohexane sulfonic acid, diluting it with electronic grade pure water to a mass fraction of 2-12%, then adding a high-grade pure potassium hydroxide solution dropwise to react until the pH of the solution reaches 7, and performing solid-liquid separation to obtain a crude product of potassium perfluorohexane sulfonate; (2) taking the crude potassium perfluorohexane sulfonate product in step (1) and placing it in a container, adding electronic grade pure water, starting stirring, and heating to 85-95°C to dissolve the potassium perfluorohexane sulfonate; after complete dissolution, filtering while hot, cooling the filtrate to 0°C-60°C at a high-speed stirring speed of 1000 r / min to precipitate potassium perfluorohexane sulfonate, filtering it twice while cold to obtain a first purified potassium perfluorohexane sulfonate; repeating the above steps with the first purified potassium perfluorohexane sulfonate to obtain a second purified potassium perfluorohexane sulfonate , repeating the aforementioned steps with the twice purified potassium perfluorohexanyl sulfonate to obtain 3 times purified potassium perfluorohexanyl sulfonate, repeating the aforementioned steps with the 3 times purified potassium perfluorohexanyl sulfonate to obtain 4 times purified potassium perfluorohexanyl sulfonate, repeating the aforementioned steps with the 4 times purified potassium perfluorohexanyl sulfonate to obtain 5 times purified potassium perfluorohexanyl sulfonate, repeating the aforementioned steps with the 5 times purified potassium perfluorohexanyl sulfonate to obtain 6 times purified potassium perfluorohexanyl sulfonate, until the content of all metal ions is less than or equal to 2 ppb, thereby obtaining pure potassium perfluorohexanyl sulfonate; (3) loading the hydrogen-type cationic resin into an ion exchange column, and diluting electronic-grade hydrofluoric acid into a 5% by mass hydrofluoric acid dilute solution, using the hydrofluoric acid dilute solution to wash the ion exchange column in a countercurrent manner, and then using electronic-grade pure water to wash in a downstream manner until the pH of the washing water is 6-7; (4) Take E1 grade electronic grade sulfuric acid, dilute it with electronic grade pure water to a mass fraction of 3-5%, place it in the anode chamber, then add the hydrogen type cationic resin treated in step (3), fill the cathode chamber with electronic grade pure water and perform electrolysis five times continuously, adjust the electrolysis voltage to 30-55V, add the diluted electronic grade sulfuric acid to the cathode chamber until the electrolysis current is 0.8-3.2A, raise the temperature of each cathode chamber to 40-70°C, and perform electrolysis for 0.7-1h; after the single electrolysis is completed, take out all the cathode chamber solution, add electronic grade pure water to wash until the metal ion in the washing water is less than 1ppb, and then add electronic grade pure water to perform the next electrolysis until the electrolysis is completed; after the electrolysis is completed, separate the electronic grade sulfuric acid in the anode chamber from the resin, and then wash the resin with electronic grade pure water until the pH of the washing liquid is 6-7; (5) loading the washed resin in step (4) into an ion exchange column, and then circulating electronic grade pure water heated to 90° C. through the resin, preheating the resin to 85° C., and then passing high-purity nitrogen into the ion exchange column to squeeze out the water in the resin; adding electronic grade pure water to the six-stage purified potassium perfluorohexyl sulfonate in step (2) to prepare a slurry, and then heating it to 85-90° C. to form an aqueous solution of potassium perfluorohexyl sulfonate, and passing it through the aforementioned ion exchange column while hot to remove impurities and convert perfluorohexyl sulfonic acid, and passing it through twice continuously to obtain perfluorohexyl sulfonic acid; (6) Connect filter elements of 0.05 μm, 0.02 μm, 0.01 μm, and 0.01 μm in series, first use electronic grade pure water for dynamic circulation washing for 24-50 hours, and then test the number of particles in the water. When the number of 0.5 μm particles in the water is less than 10 ea / ml, the number of 0.3 μm particles is less than 50 ea / ml, and the number of 0.2 μm particles is less than 100 ea / ml, the perfluorohexane sulfonic acid in step (5) is dynamically circulated and filtered to obtain electronic grade perfluorohexane sulfonic acid.

2. The method for preparing electronic grade perfluorohexane sulfonic acid for use in an anti-reflection film on top of a photoresist according to claim 1, characterized in that: In step (3), there are three ion exchange columns connected in series.

3. The method for preparing electronic grade perfluorohexane sulfonic acid for use in an anti-reflection film on top of a photoresist according to claim 2, characterized in that: In step (4), the volume ratio of the hydrogen-type cationic resin to the diluted electronic-grade sulfuric acid is 1:2-1:

5.

4. The method for preparing electronic grade perfluorohexane sulfonic acid for use in an anti-reflection film on top of a photoresist according to claim 3, characterized in that: In step (5), in one electrolysis, the electrolysis voltage is 30-35 V, and the electrolysis current is 0.8-1.2 A; the temperature of each electrode chamber is raised to 40-70° C., and the electrolysis is performed for 0.7-1 h.

5. The method for preparing electronic grade perfluorohexane sulfonic acid for use in an anti-reflection film on top of a photoresist according to claim 4, characterized in that: In the secondary electrolysis of step (5), the electrolysis voltage is 35-40 V, and the electrolysis current is 1.3-1.7 A; the temperature of each electrode chamber is raised to 40-70° C., and the electrolysis is performed for 0.7 h-1 h.

6. The method for preparing electronic grade perfluorohexane sulfonic acid for use in an anti-reflection film on top of a photoresist according to claim 5, characterized in that: In step (5), during the three electrolysis steps, the electrolysis voltage is 40-45 V, and the electrolysis current is 1.8-2.2 A; the temperature of each electrode chamber is raised to 40-70° C., and the electrolysis is performed for 0.7 h to 1 h.

7. The method for preparing electronic grade perfluorohexane sulfonic acid for use in an anti-reflection film on top of a photoresist according to claim 6, characterized in that: In the four electrolysis steps (5), the electrolysis voltage is 45-50 V, and the electrolysis current is 2.3-2.7 A; the temperature of each electrode chamber is raised to 40-70° C., and the electrolysis is performed for 0.7 h to 1 h.

8. The method for preparing electronic grade perfluorohexane sulfonic acid for use in an anti-reflection film on top of a photoresist according to claim 7, characterized in that: In step (5), during the five electrolysis steps, the electrolysis voltage is 50-55 V, and the electrolysis current is 2.8-3.2 A; the temperature of each electrode chamber is raised to 40-70° C., and the electrolysis is performed for 0.7 h to 1 h.

9. The method for preparing electronic grade perfluorohexane sulfonic acid for use in an anti-reflection film on top of a photoresist according to claim 8, characterized in that: The dynamic circulation filtration time in step (6) is 24-50h.

10. Electronic-grade perfluorohexane sulfonic acid prepared by the method for preparing electronic-grade perfluorohexane sulfonic acid for use in an anti-reflective film on top of a photoresist as claimed in any one of claims 1 to 10.

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