Electronic-grade perfluorohexyl sulfonic acid, preparation method thereof and application of electronic-grade perfluorohexyl sulfonic acid in photoresist top anti-reflection film

Abstract

The invention discloses electronic-grade perfluorohexyl sulfonic acid, a preparation method of the electronic-grade perfluorohexyl sulfonic acid and application of the electronic-grade perfluorohexyl sulfonic acid in an anti-reflection film on the top of photoresist. The electronic-grade perfluorohexyl sulfonic acid is obtained by removing impurities from commercially purchased perfluorohexyl sulfonic acid. The perfluorohexyl sulfonic acid treated by the method is high in treatment difficulty and high in complexity. According to the method disclosed by the invention, the E4-grade product meeting the requirement is obtained by skillfully utilizing the cooperative treatment of resin primary purification and electrolytic fine purification, and can be used for preparing the photoresist top anti-reflection film; furthermore, the resin is subjected to electrolytic purification, and the resin is put into an anode chamber for adsorbing high-content calcium ions, sodium ions and other metal impurity ions when being subjected to electrolytic impurity removal of perfluorohexyl sulfonic acid. And after the final electrolysis is finished, calcium ions, sodium ions and other metal ions in the product can be controlled below 1ppb, the standard of E3 in GB / T41881-2022 is met, and the additional value of the product is further improved on the basis of meeting the use standard of customers.

Description

Technical Field

[0001] The invention belongs to the technical field of photolithography, and in particular is an electronic-grade perfluorohexyl sulfonic acid, a preparation method thereof and an application thereof in an anti-reflection film on the top of a photoresist. 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 patent first mentioned that adding an appropriate amount of acid to the top anti-reflective layer system can inhibit the H +Diffusion to the anti-reflection film avoids the formation of T-top. Wherein the acid pH regulator selects 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 content of impurity metal ions and the number of particles therein. There are few existing data on perfluorohexyl sulfonic acid, and this field basically belongs to a blank field, and the impurity metal ion content and particle number in the perfluorohexyl sulfonic acid generally available are quite high, and cannot be used for compounding and preparing the anti-reflection film on the top of the photoresist. Therefore, it is necessary to purify perfluorohexyl sulfonic acid and reduce the number of particles therein, and reduce the total amount of its metal impurity ions to the requirements of customers. In addition, in GB / T41881-2022, the electronic grade sulfuric acid standards are divided into five standards: E1, E2, E3, E4, and E5. The customer requires the metal ions in the perfluorohexane sulfonic acid provided by the applicant to meet the metal ion requirements of the four levels of electronic grade sulfuric acid, E1, E2, E3, and E4. It is best to reach the E1 level. The higher the level, the higher the added value. Therefore, it is of great technical and economic significance to control the metal ions in perfluorohexane sulfonic acid at a high level for compounding the top anti-reflection film.

[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 removing metal ions from perfluorohexyl sulfonic acid through carbon purification, 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 is formed after the solvent water is evaporated, and distillation cannot be used for purification again, resulting in a high content of metal ions. In addition, the applicant tried to use ion exchange, freezing, distillation, salt conversion purification, and polymer adsorbent adsorption to treat perfluorohexyl sulfonic acid, but none of them had a good purification effect, and the content of a single impurity metal ion was still difficult to meet the customer's minimum requirements (E4 level in GB / T41881-2022).

[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) The commercially available electronic-grade resin uses conventional acid washing methods to replace all ions in the resin with hydrogen ions. However, even if the resin is washed with electronic-grade strong acids such as electronic-grade sulfuric acid, electronic-grade hydrochloric acid, and electronic-grade hydrofluoric acid for a long time and multiple cycles, although the metal ions in the acid solution will increase after each washing, the ability of the washing treatment under acidic conditions to replace the metal ions in the resin structure with hydrogen ions is limited. No matter how it is treated, there will always be a certain amount of sodium ions in the resin. When this resin is used to treat 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 requirements for use as an acid regulator in the preparation process of the anti-reflective film on the top of the photoresist.

[0010] (2) Different from conventional inorganic acids, the perfluorohexane sulfonic acid treated by the present invention is an organic acid with a carbon-fluorine bond in its skeleton structure. In addition, its high viscosity increases the difficulty and complexity of its treatment. During the treatment process, the applicant found that when further removing impurities by electrolysis, when the temperature of the solution is low, due to its high viscosity and the presence of carbon-fluorine bonds, the impurity ions move slowly. The impurity ion content in the perfluorohexane sulfonic acid obtained after multiple electrolysis is still very high, and the impurity removal effect is general. When the solution temperature is high, the electrolysis rate and ion movement are accelerated, which will also cause the impurity ions in the electrode plate to continuously precipitate, and the impurity ion content in the perfluorohexane sulfonic acid obtained after multiple electrolysis is still very high. In addition, perfluorohexane sulfonic acid is a surfactant. When the temperature is high, the electrode chamber will foam severely, which can easily cause bubbling; in addition, the foam will react after contacting the electrode clamp, causing the perfluorohexane sulfonic acid in the electrode chamber to turn green, which increases the difficulty of treatment again.

[0011] (3) After electrolysis and impurity removal, since the final product is in the anode area, the selected electrode plate will continuously precipitate metal impurity ions to contaminate the product under acidic conditions and electrolysis, so that the content of metal ions in the product is maintained at a certain level and will not decrease. Instead, the calcium ion and sodium content will continue to increase, approaching 10ppb, and the metal ion content in the final product can only reach the minimum standard E4 standard or cannot reach the standard, and the product rework rate is high. In addition, even if a high-purity inert anode plate is used, it cannot solve the problem that the anode plate will continuously precipitate impurity calcium ions and sodium ions into the product under electrical force and strong acidic conditions. Based on this, the applicant tried to use high-purity graphite inert plates as anodes and cathodes for electrolysis, but after a long period of electrolysis, the graphite anode plate will fall off and crack, and the small black graphite residue will enter the product liquid, thereby affecting the purity of the product. The subsequent applicant used high-purity iridium-tantalum-titanium plates and high-purity platinum plates to replace high-purity graphite plates. Although the problem of plate slag contaminating the product liquid was solved, the calcium ion and sodium ion content of the product after electrolysis was still close to 10ppb, which ultimately resulted in the metal ion content in the product only reaching the minimum standard E4 standard or failing to reach the standard. In addition, since high-purity iridium-tantalum-titanium plates and high-purity platinum plates are expensive, the use of high-purity iridium-tantalum-titanium plates and high-purity platinum plates for both the anode and cathode plates will significantly increase the initial investment cost. Summary of the invention

[0012] The purpose of the present invention is to provide an electronic grade perfluorohexyl sulfonic acid with a single impurity metal ion content of at least E4 level, which is used as an acid regulator in an anti-reflective film on the top of a photoresist.

[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 perfluorohexane sulfonic acid comprises the following steps:

[0016] (1) Dilute perfluorohexane sulfonic acid with electronic grade pure water to a mass fraction of 1.5-3%; perfluorohexane sulfonic acid has a large molecular weight, and the viscosity is too high when the concentration is too high, so it cannot be purified by resin. In addition, the concentration is too high and the acid is too strong, so the resin cannot play the role of primary purification. Generally, when the concentration is higher than 3%, the ions adsorbed on the resin will be dissolved into the solution, resulting in poor impurity removal effect. If the impurity removal in the front-end primary purification does not meet the required range, the subsequent electrolysis will not be able to obtain electronic grade perfluorohexane sulfonic acid that meets the requirements, and the more electrolysis times, the better. The applicant has verified through experiments that after too many electrolysis times, the content of calcium ions and sodium ions in the plate will exceed 10ppb, which cannot meet customer requirements. Therefore, only by properly processing the front end and then performing a limited number of electrolysis times can the product meet the standards required by customers;

[0017] (2) diluting electronic grade hydrofluoric acid with electronic grade pure water to a mass fraction of 3-6%;

[0018] (3) loading the hydrogen cationic resin into an ion exchange column, washing it in a countercurrent manner using the electronic grade hydrofluoric acid diluted in step (2), and then washing it in a downstream manner using electronic grade pure water until the pH of the washing water is 6-7;

[0019] (4) purifying the diluted perfluorohexane sulfonic acid in step (1) using the ion exchange resin treated in step (3), preferably purifying twice in succession, to obtain primary purified perfluorohexane sulfonic acid, wherein the metal ions and their contents are as shown in the following table, in ppb;

[0020] Al Ba Ca Cd Co Cr Cu Fe K Mg Mn Na Zn Ni ≤6 ≤4 ≤9 ≤1 ≤3 ≤4 ≤2 ≤4 ≤10 ≤6 ≤4 ≤200 ≤5 ≤7

[0021] (5) Wash the electrolytic cell and its components (anode chamber, anode plate, cathode chamber, cathode plate and intermediate diaphragm of the electrolytic cell. In the electrolytic cell, the anode plate is a high-purity platinum plate and the cathode plate is a high-purity graphite plate) with electronic grade pure water until the content of all metal ions in the washing water is less than 1 ppb;

[0022] The primary purified perfluorohexane sulfonic acid in step (4) is placed in the anode chamber, and electronic grade pure water is placed in the cathode chamber for five consecutive electrolysis operations, the electrolysis voltage is adjusted to 10-35 V, the primary purified perfluorohexane sulfonic acid is added dropwise to the cathode chamber until the electrolysis current is 0.5-3 A, the temperature of each anode chamber is raised to 40-70° C., and the electrolysis is performed for 1-1.5 hours; after the single electrolysis is completed, all the cathode chamber solution is taken out, and electronic grade pure water is added for washing until the metal ions in the washing water are less than 1 ppb, and then electronic grade pure water is added for the next electrolysis operation until the electrolysis is completed;

[0023] (6) After 5 consecutive electrolysis cycles, the post-electrolysis liquid in the anode chamber is taken and sampled for metal ions; then, filter elements of 0.05 μm, 0.02 μm, 0.01 μm, and 0.01 μm are connected in series, firstly washed with electronic grade pure water in a dynamic circulation for 24 hours, and then the number of particles in the water is tested. When the number of 0.3 μm particles in the water is less than 10 ea / ml, the number of 0.2 μm particles is less than 50 ea / ml, and the number of 0.1 μm particles is less than 100 ea / ml, the post-electrolysis liquid is dynamically circulated and filtered for 24-48 hours to obtain electronic grade perfluorohexane sulfonic acid.

[0024] As a further preferred embodiment of the technical solution of the present invention, a resin electrolysis purification operation is further included between step (4) and step (5):

[0025] Take E1-level 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, drip the diluted electronic-grade sulfuric acid into 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 a single electrolysis, 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, 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;

[0026] Step (5) Add the washed resin into the anode chamber.

[0027] Furthermore, in the resin electrolysis purification operation, the volume ratio of the hydrogen-type cationic resin to the diluted electronic-grade sulfuric acid is 1:2-1:5;

[0028] In one electrolysis, 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;

[0029] 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 performed for 0.7h-1h;

[0030] During the three electrolysis, the electrolysis voltage was 40-45V, and the electrolysis current was 1.8-2.2A; the temperature of each chamber was raised to 40-70°C, and the electrolysis was performed for 0.7h-1h;

[0031] In the four electrolysis, the electrolysis voltage is 45-50V, the electrolysis current is 2.3-2.7A; the temperature of each electrode chamber is raised to 40-70°C, and the electrolysis is performed for 0.7h-1h;

[0032] 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.

[0033] Furthermore, in step (5), the volume ratio of the resin after washing in the anode chamber to the primary purified perfluorohexane sulfonic acid is 1:1-1:3.

[0034] Furthermore, in step (3), there are three ion exchange columns connected in series, and the resin in the ion exchange columns is a hydrogen-type cationic resin.

[0035] Furthermore, in the first electrolysis of step (5), the electrolysis voltage is 10-15V, and the electrolysis current is 0.5-1A; the temperature of each electrode chamber is raised to 40-70°C, and the electrolysis is performed for 1-1.5h.

[0036] In the secondary electrolysis, the electrolysis voltage is 15-20V, and the electrolysis current is 1-1.5A; the temperature of each electrode chamber is raised to 40-70°C, and the electrolysis is carried out for 1-1.5h.

[0037] During the three electrolysis steps, the electrolysis voltage was 20-25V, and the electrolysis current was 1.5-2A. The temperature of each chamber was raised to 40-70°C, and the electrolysis was performed for 1-1.5h.

[0038] In the four electrolysis, the electrolysis voltage was 25-30V, and the electrolysis current was 2-2.5A; the temperature of each electrode chamber was raised to 40-70°C, and the electrolysis was performed for 1-1.5h.

[0039] During the five electrolysis cycles, the electrolysis voltage was 30-35 V, and the electrolysis current was 2.5-3 A. The temperature of each chamber was raised to 40-70° C., and the electrolysis was performed for 1-1.5 h.

[0040] The electronic grade perfluorohexane sulfonic acid can be prepared by the method, and the electronic grade perfluorohexane sulfonic acid can be used as an acid regulator for preparing an anti-reflective film on the top of a photoresist.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The present invention is simple to operate, and electronic-grade perfluorohexane sulfonic acid is prepared by resin impurity removal and electrolytic impurity removal, and the electrolytic impurity removal is performed under low voltage and low current conditions, with low energy consumption, low cost and high safety factor.

[0043] (2) As mentioned above, the perfluorohexane sulfonic acid treated by the present invention is an organic acid with a carbon-fluorine bond in its skeleton structure, which is difficult to treat and highly complex. In addition, due to its relatively long skeleton structure, the viscosity of its aqueous solution is very high. After the water in the high-concentration perfluorohexane sulfonic acid is distilled and separated, only colloidal perfluorohexane sulfonic acid is obtained, and the impurities therein cannot be separated and are enriched in the perfluorohexane sulfonic acid. However, the ion exchange method, freezing method, distillation method, salt conversion purification method, polymer adsorbent adsorption method, etc. have not made the content of single impurity metal ions in perfluorohexane sulfonic acid reach the minimum standard E4 level. The present invention cleverly uses high-purity special resin primary purification and electrolytic fine purification to make the indicators of the purified perfluorohexane sulfonic acid meet the minimum requirement E4 standard.

[0044] (3) In order to avoid the slow movement of impurity ions and poor electrolysis effect at low temperatures, as well as the accelerated electrolysis rate of high-temperature and high-acid electrode plates, which causes the trace metal ions therein to be electrolyzed into the product, leading to an increase in impurity ions in the product, the present invention keeps the product in the electrolytic cell body at a constant and moderate temperature at all times, which can not only keep the impurity ions at a faster movement speed but also prevent more impurity metal ions in the electrode plates from entering the product after multiple electrolysis. At the same time, it solves the problem of severe foaming in the electrode chamber at high temperatures, which easily causes foaming, and the problem of foam reacting after contacting the electrode clamp, causing the perfluorohexane sulfonic acid in the electrode chamber to turn green, which further increases the difficulty of treatment.

[0045] (4) The present invention uses expensive high-purity platinum plates as anodes and relatively cheap high-purity graphite as cathodes, thereby reducing production costs while ensuring product purity.

[0046] (5) During the electrolytic decontamination process, when a high-purity platinum plate with a purity of 99.99% is used as an anode plate, under acidic conditions, high temperature and electrolytic force, the sodium ions and calcium ions in the anode plate will continuously enter the product. Since the sodium ion movement effect is good and the calcium ion movement effect is general, the content of a single impurity metal ion in the obtained product is between 1-10ppb, which meets the E4 standard in GB / T41881-2022, but can only meet the customer's minimum use standard, and the product added value is not high; and the content of sodium ions and calcium ions in the obtained product is relatively close to 10ppb, and a slight deviation will cause the product to fail to meet the standard, and the product rework rate is high. Therefore, in order to facilitate stable control, reduce the rework rate and increase the product added value, so that the product quality can reach the E3 level, the present invention further electrolytically purifies the primary purification resin, and when performing perfluorohexane sulfonic acid electrolytic decontamination, it is placed in the anode chamber to adsorb high content of calcium ions, sodium ions and other metal impurity ions. After the final electrolysis is completed, the calcium ions, sodium ions and other metal ions in the product can be controlled below 1ppb, which meets the E3 standard in GB / T41881-2022. On the basis of meeting customer usage standards, the added value of the product is further improved. DETAILED DESCRIPTION

[0047] The preparation method of electronic grade perfluorohexane sulfonic acid of the present invention is described in detail below with reference to specific examples.

[0048] In the following examples, all operations are performed in a Class 100 clean room. The content of individual metal ions in electronic grade pure water is less than 1 ppb. The electrolytic cell and its components include an electrolytic cell 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.

[0049] The electronic grade hydrofluoric acid in step (2) is purchased from Polyfluoro Chemical Co., Ltd. After dilution, the content of individual metal ions in the electronic grade hydrofluoric acid is less than 1 ppb.

[0050] Perfluorohexane sulfonic acid in step (1) was purchased from Shanghai Jizhi Biochemical Co., Ltd. The results of full element analysis are shown in Table 1.

[0051] Table 1 All element analysis results of commercially available perfluorohexane sulfonic acid (unit: ppb)

[0052] 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

[0053] The full elemental analysis results of primary purified perfluorohexane sulfonic acid are shown in Table 2.

[0054] Table 2 Full element analysis results of primary purified perfluorohexane sulfonic acid (unit: ppb)

[0055] Al Ba Ca Cd Co Cr Cu Fe K Mg Mn Na Zn Ni 4 3 9 1 2 1 2 3 6 5 3 198 3 1

[0056] Example 1

[0057] A method for preparing electronic grade perfluorohexane sulfonic acid comprises the following steps:

[0058] (1) diluting perfluorohexane sulfonic acid with electronic grade pure water to a mass fraction of 2%;

[0059] (2) diluting electronic grade hydrofluoric acid with electronic grade pure water to a mass fraction of 5%;

[0060] (3) Take 10 L of hydrogen-type cationic resin and load it into three ion exchange columns connected in series. Use 30 L of electronic-grade hydrofluoric acid diluted in step (2) to wash in reverse flow for 24 h, and then use electronic-grade pure water to wash in downstream until the pH of the washing water is 7;

[0061] (4) purifying the diluted perfluorohexane sulfonic acid in step (1) twice continuously using the ion exchange resin treated in step (3) to obtain primary purified perfluorohexane sulfonic acid, wherein the metal ions and their contents are shown in Table 2;

[0062] (5) Wash the electrolytic cell and its components (anode chamber, anode plate, cathode chamber, cathode plate and intermediate diaphragm) with electronic grade pure water until the content of all metal ions in the washing water is less than 1 ppb;

[0063] 1000 ml of the primary purified perfluorohexane sulfonic acid in step (4) is placed in the anode chamber, and 100 ml of electronic grade pure water is placed in the cathode chamber for electrolysis. The electrolysis voltage is adjusted to 10 V, and the primary purified perfluorohexane sulfonic acid is added dropwise to the cathode chamber until the electrolysis current is 0.5 A. The temperature of each anode chamber is raised to 65° C. and electrolysis is performed for 1 hour. After the electrolysis is completed, all the cathode chamber solution is taken out, and electronic grade pure water is added for washing until the metal ion content in the washing water is less than 1 ppb.

[0064] Add electronic grade pure water to the cathode chamber for secondary electrolysis, adjust the electrolysis voltage to 15V, add primary purified perfluorohexane sulfonic acid to the cathode chamber until the electrolysis current is 1A, raise the temperature of each chamber to 65°C, and electrolyze for 1h; after the secondary electrolysis, take out all the cathode chamber solution, add electronic grade pure water for washing until the metal ions in the washing water are less than 1ppb;

[0065] The cathode chamber was filled with electronic grade pure water for three electrolysis, the electrolysis voltage was adjusted to 20V, primary purified perfluorohexane sulfonic acid was added to the cathode chamber until the electrolysis current was 1.5A, the temperature of each chamber was raised to 65°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;

[0066] The cathode chamber was filled with electronic grade pure water for four electrolysis cycles, the electrolysis voltage was adjusted to 25 V, primary purified perfluorohexane sulfonic acid was added to the cathode chamber until the electrolysis current was 2 A, the temperature of each chamber was raised to 65 ° 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;

[0067] The cathode chamber was filled with electronic grade pure water for five times of electrolysis, the electrolysis voltage was adjusted to 30 V, primary purified perfluorohexane sulfonic acid was added to the cathode chamber until the electrolysis current was 2.5 A, the temperature of each chamber was raised to 65 ° C, and the electrolysis was performed for 1 hour;

[0068] (6) After 5 consecutive electrolysis cycles, the post-electrolysis liquid in the anode chamber was taken and sampled for metal ions; then, filter elements of 0.05 μm, 0.02 μm, 0.01 μm, and 0.01 μm were connected in series, and electronic-grade pure water was used for dynamic circulation washing for 24 hours, and then the number of particles in the water was tested. The number of 0.3 μm particles in the water was measured to be 9 ea / ml, the number of 0.2 μm particles was 37 ea / ml, and the number of 0.1 μm particles was 88 ea / ml. The post-electrolysis liquid was dynamically circulated and filtered for 24 hours to obtain electronic-grade perfluorohexane sulfonic acid.

[0069] The full element analysis results of the electronic grade perfluorohexane sulfonic acid are shown in Table 3. The content of individual metal ions is less than 10 ppb, and the electronic grade perfluorohexane sulfonic acid can be used as an acid regulator in the anti-reflective film on the top of the photoresist.

[0070] Al Ba Ca Cd Co Cr Cu Fe K Mg Mn Na Zn Ni Product 2 2 9 1 2 1 2 1 4 2 1 8 2 1

[0071] Table 3 Full element analysis results of electronic grade perfluorohexane sulfonic acid in Example 1 (unit: ppb) Example 2-Example 10

[0072] The other steps of Example 2-10 are the same as those of Example 1, except that the mass fraction of the diluted perfluorohexane sulfonic acid in step (1) is changed. The results of the single metal ion content in the final electronic grade perfluorohexane sulfonic acid product are shown in Table 4.

[0073] Table 4 Single metal ion content in electronic grade perfluorohexane sulfonic acid products in Examples 2-10

[0074]

[0075] From the above examples, it can be seen that when the mass fraction of the perfluorohexane sulfonic acid after dilution in step (1) is 1.5-3%, the content of single metal ions in the obtained perfluorohexane sulfonic acid can reach E4 level, and the effect is good. Therefore, the mass fraction of the perfluorohexane sulfonic acid after dilution is preferably selected to be 1.5%-3%.

[0076] Examples 11-20

[0077] Examples 11-20 are the same as Example 1 in other steps, except that the mass fraction of the electronic-grade hydrofluoric acid after dilution in step (2) is changed. The results of the single metal ion content in the final electronic-grade perfluorohexane sulfonic acid product are shown in Table 5.

[0078] Table 5 Content of individual metal ions in electronic grade perfluorohexane sulfonic acid products in Examples 11-20

[0079]

[0080] From the above embodiment, it can be seen that when the mass fraction of the electronic grade hydrofluoric acid after dilution in step (2) is 3-6%, the content of single metal ions in the obtained electronic grade perfluorohexane sulfonic acid can reach the E4 level, and the effect is good. Considering the use of the least amount of hydrofluoric acid to reduce costs, the mass fraction of the electronic grade hydrofluoric acid after dilution is preferably selected to be 3%.

[0081] Examples 21-27

[0082] The other steps of Examples 21-27 are the same as those of Example 1, except that the number of electrolysis times in step (5) is changed. When the number of electrolysis times is other values, the full element analysis results of the electronic grade perfluorohexane sulfonic acid product are shown in Table 6.

[0083] Table 6 Full element analysis results of electronic grade perfluorohexane sulfonic acid products in Examples 21-27

[0084]

[0085]

[0086] It can be seen from the above embodiments that when the number of electrolysis is greater than or equal to 5-6 times, the metal ion content in the final product can reach E4 level, and 5 times of electrolysis is preferably selected.

[0087] Examples 28-42

[0088] The other steps of Examples 28-42 are the same as those of Example 1, except that the electrolysis temperature in step (5) is changed. When the electrolysis temperature is at other values, the results of the single metal ion content in the final electronic grade perfluorohexane sulfonic acid product are shown in Table 7.

[0089] Table 7 Content of individual metal ions in electronic grade perfluorohexane sulfonic acid products in Examples 28-42

[0090]

[0091]

[0092] From the above examples, it can be seen that when the electrolysis temperature in step (5) is 40-70°C, all metal ions in the obtained perfluorohexane sulfonic acid can reach E4 level, and the effect is good. Considering the reduction of energy consumption and cost, the electrolysis temperature is preferably selected to be 40°C.

[0093] Examples 43-46

[0094] The other steps of Examples 43-46 are the same as those of Example 1, except that the electrolysis voltage in step (5) is changed. When the electrolysis voltage is at other values, the results of the single metal ion content in the final electronic grade perfluorohexane sulfonic acid product are shown in Table 8.

[0095] Table 8 Content of individual metal ions in electronic grade perfluorohexane sulfonic acid products in Examples 43-46

[0096]

[0097] From the above embodiment, it can be seen that when the step (5) 10V≤1 electrolysis voltage≤15V, 15V≤2 electrolysis voltage≤20V, 20V≤3 electrolysis voltage≤25V, 25V≤4 electrolysis voltage≤30V, 30V≤5 electrolysis voltage≤35V, the metal ion content in the obtained electronic grade perfluorohexyl sulfonic acid can reach E4 level, with good effect. Considering the reduction of energy consumption and cost, the electrolysis voltage is preferably 10V for the first time, 15V for the second time, 20V for the third time, 25V for the fourth time, and 30V for the fifth time.

[0098] Examples 47-58

[0099] The other steps of Examples 47-58 are the same as those of Example 1, except that the electrolysis current in step (5) is changed. When the electrolysis current is at other values, the results of the single metal ion content in the final electronic grade perfluorohexane sulfonic acid product are shown in Table 9.

[0100] Table 9 Content of individual metal ions in electronic grade perfluorohexane sulfonic acid products in Examples 47-58

[0101]

[0102] As can be seen from the above embodiment, when step (5) 0.5A≤1 electrolysis current≤1A, 1A≤2 electrolysis current≤1.5A, 1.5A≤3 electrolysis current≤2A, 2A≤4 electrolysis current≤2.5A, 2.5A≤5 electrolysis current≤3A, all metal ions in the obtained perfluorohexyl sulfonic acid can reach E4 level, with good effect. Considering reducing energy consumption and reducing costs, therefore, the first electrolysis current is preferably 0.5A, the second electrolysis current is 1A, the third electrolysis current is 1.5A, the fourth electrolysis current is 2A, and the fifth electrolysis current is 2.5A.

[0103] Examples 59-78

[0104] The other steps of Examples 59-78 are the same as those of Example 1, except that the electrolysis time in step (5) is changed. When the electrolysis time is other values, the results of the single metal ion content in the final electronic grade perfluorohexane sulfonic acid product are shown in Table 10.

[0105] Table 10 Content of individual metal ions in electronic grade perfluorohexane sulfonic acid products in Examples 59-78

[0106]

[0107] From the above embodiment, it can be seen that when the electrolysis time of step (5) is 1h≤1 time≤1.5h, 1h≤2 time≤1.5h, 1h≤3 time≤1.5h, 1h≤4 time≤1.5h, 1h≤5 time≤1.5h, all metal ions in the obtained perfluorohexyl sulfonic acid can reach the E4 standard, and the effect is good. Considering the reduction of energy consumption and cost, the electrolysis time of 1h, ...

[0108] Embodiment 79-85 Embodiment

[0109] Examples 79-85 are the same as Example 1 in other steps, except that the resin electrolysis purification operation is added in step (4) and step (5), and the electrolysis purified washed resin is added to the anode chamber in step (5). During the resin electrolysis purification, only the volume ratio of the hydrogen-type resin and the diluted electronic-grade sulfuric acid is changed. When the volume ratio of the hydrogen-type resin and the diluted electronic-grade sulfuric acid is other values, the results of whether the metal ion content in the final electronic-grade perfluorohexane sulfonic acid product reaches the E3 level are shown in Table 11.

[0110] Table 11 Content of individual metal ions in electronic grade perfluorohexane sulfonic acid in Examples 79-85

[0111]

[0112] From the above examples, it can be seen that when the volume ratio of hydrogen resin to diluted electronic grade sulfuric acid is 1:2-1:8, the metal ion content of the final product can reach E3 level. The volume ratio of hydrogen resin to diluted electronic grade sulfuric acid is preferably 1:2-1:5.

[0113] Embodiment 86-93 Embodiment

[0114] The other steps of Examples 86-93 are the same as those of Example 1, except that the resin electrolysis purification operation is added in Step (4) and Step (5), and the electrolysis purified washed resin is added to the anode chamber in Step (5). During the resin electrolysis purification, only the number of electrolysis purification times of the hydrogen-type resin is changed. When the number of electrolysis purification times of the hydrogen-type resin is other values, the results of whether the metal ion content in the final electronic-grade perfluorohexane sulfonic acid product reaches the E3 level are shown in Table 12.

[0115] Table 12 Content of individual metal ions in electronic grade perfluorohexane sulfonic acid in Examples 86-93

[0116]

[0117] It can be seen from the above embodiments that when the hydrogen type resin is electrolyzed continuously for 5-7 times, the metal ion content of the final product can reach the E3 level, and it is preferred to electrolyze continuously for 5 times.

[0118] Embodiment 94-100 Embodiment

[0119] The other steps of Examples 94-100 are the same as those of Example 1, except that the volume ratio of the hydrogen-type resin and the perfluorohexyl sulfonic acid after electrolytic purification and washing in the anode chamber in step (5) is changed. When the volume ratio of the hydrogen-type resin and the perfluorohexyl sulfonic acid after electrolytic purification and washing is other values, the results of whether the metal ion content in the final electronic grade perfluorohexyl sulfonic acid product reaches the E3 level are shown in Table 13.

[0120] Table 13 Single metal ion content in electronic grade perfluorohexane sulfonic acid in Examples 94-100

[0121]

[0122] It can be seen from the above embodiments that when the volume ratio of the purified and washed hydrogen-type resin to perfluorohexane sulfonic acid in the anode chamber is 1:1-1:3, the metal ion content of the final product can reach E3 level.

[0123] Embodiment 101-109 Embodiment

[0124] The other steps of Examples 101-109 are the same as those of Example 1, except that the resin electrolysis purification operation is added in Step (4) and Step (5), and the electrolysis purified washed resin is added to the anode chamber in Step (5). During the resin electrolysis purification, only the voltage value in the resin electrolysis purification operation is changed. When the voltage value is other values, the results of whether the metal ion content in the final electronic grade perfluorohexane sulfonic acid product reaches the E3 level are shown in Table 14.

[0125] Table 14 Single metal ion content in electronic grade perfluorohexane sulfonic acid in Examples 101-109

[0126]

[0127] From the above embodiment, it can be seen that when the resin is electrolyzed and purified, the metal ion content in the obtained electronic grade perfluorohexane sulfonic acid reaches E3 level when 30V≤1 electrolysis voltage≤35V, 35V≤2 electrolysis voltage≤40V, 40V≤3 electrolysis voltage≤45V, 45V≤4 electrolysis voltage≤50V, 50≤5 electrolysis voltage≤55V. Considering the reduction of energy consumption and cost, 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.

[0128] Example 110-Example 125

[0129] The other steps of Examples 110-125 are the same as those of Example 1, except that the resin electrolysis purification operation is added in Step (4) and Step (5), and the electrolysis purified washed resin is added to the anode chamber in Step (5). During the resin electrolysis purification, only the current value in the resin electrolysis purification operation is changed. When the current value is other values, whether the metal ion content in the final electronic grade perfluorohexane sulfonic acid product reaches the E3 level is shown in Table 15.

[0130] Table 15 Single metal ion content in electronic grade perfluorohexane sulfonic acid in Examples 110-125

[0131]

[0132] As can be seen from the above embodiment, when the resin is electrolyzed and purified, 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 E3 level, and the effect is good. Considering reducing energy consumption and reducing costs, therefore, the first electrolysis current is preferably 0.8A, the second electrolysis current is 1.3A, the third electrolysis current is 1.8A, the fourth electrolysis current is 2.3A, and the fifth electrolysis current is 2.8A.

[0133] Embodiment 126-138 Embodiment

[0134] The other steps of Examples 126-138 are the same as those of Example 1, except that the resin electrolysis purification operation is added, and the resin washed after electrolysis purification is placed in the anode chamber to participate in the electrolysis reaction. During the resin electrolysis purification, only the electrolysis time in the resin electrolysis purification operation is changed. When the electrolysis time is other values, the results of whether the metal ion content in the final electronic grade perfluorohexane sulfonic acid product reaches the E3 level are shown in Table 16.

[0135] Table 16 Single metal ion content in electronic grade perfluorohexane sulfonic acid in Examples 126-138

[0136]

[0137] From the above embodiment, it can be seen that when the resin is electrolyzed and purified, 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 ions in the obtained perfluorohexyl sulfonic acid reach the E3 level, 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.

[0138] Example 139-Example 154

[0139] The other steps of Examples 139-154 are the same as those of Example 1, except that the resin electrolysis purification operation is added in Step (4) and Step (5), and the electrolysis purified washed resin is added to the anode chamber in Step (5). During the resin electrolysis purification, only the electrolysis temperature in the resin electrolysis purification operation is changed. When the electrolysis temperature is at other values, the results of whether the metal ion content in the final electronic grade perfluorohexane sulfonic acid product reaches the E3 level are shown in Table 17.

[0140] Table 17 Single metal ion content in electronic grade perfluorohexane sulfonic acid in Examples 139-154

[0141]

[0142] From the above examples, it can be seen that when the electrolysis temperature of the resin electrolysis purification is 40-70°C, the total metal ions in the obtained perfluorohexane sulfonic acid reach 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.

[0143] It can be seen from the above embodiments that when a resin electrolysis purification operation is added between step (4) and step (5), and the washed electrolysis purification resin is added to the anode chamber of step (5) for electrolysis, the grade of the obtained perfluorohexane sulfonic acid can be further improved, and the product grade is improved from E4 to E3, further improving the added value of the product.

Claims

1. A method for preparing electronic grade perfluorohexane sulfonic acid, characterized in that: The following steps are involved: (1) diluting perfluorohexane sulfonic acid with electronic grade pure water to a mass fraction of 1.5-3%; (2) diluting electronic grade hydrofluoric acid with electronic grade pure water to a mass fraction of 3-6%; (3) loading the hydrogen-type cationic resin into an ion exchange column, washing it in a countercurrent manner using the electronic-grade hydrofluoric acid diluted in step (2), and then washing it in a downstream manner using electronic-grade pure water until the pH of the washing water is 6-7; (4) purifying the diluted perfluorohexane sulfonic acid in step (1) using the ion exchange resin treated in step (3) to obtain primary purified perfluorohexane sulfonic acid, wherein the metal ions and their contents are as shown in the following table, in ppb; (5) Wash the electrolytic cell and its components with electronic grade pure water until the content of all metal ions in the washing water is less than 1 ppb; The primary purified perfluorohexane sulfonic acid in step (4) is placed in the anode chamber, and electronic grade pure water is placed in the cathode chamber for five consecutive electrolysis operations, the electrolysis voltage is adjusted to 10-35 V, the primary purified perfluorohexane sulfonic acid is added dropwise to the cathode chamber until the electrolysis current is 0.5-3 A, the temperature of each anode chamber is raised to 40-70° C., and the electrolysis is performed for 1-1.5 hours; after the single electrolysis is completed, all the cathode chamber solution is taken out, and electronic grade pure water is added for washing until the metal ions in the washing water are less than 1 ppb, and then electronic grade pure water is added for the next electrolysis operation until the electrolysis is completed; (6) After 5 consecutive electrolysis cycles, the post-electrolysis liquid in the anode chamber is taken and sampled for metal ions; then, filter elements of 0.05 μm, 0.02 μm, 0.01 μm, and 0.01 μm are connected in series, firstly washed with electronic grade pure water in a dynamic circulation for 24 hours, and then the number of particles in the water is tested. When the number of 0.3 μm particles in the water is less than 10 ea / ml, the number of 0.2 μm particles is less than 50 ea / ml, and the number of 0.1 μm particles is less than 100 ea / ml, the post-electrolysis liquid is dynamically circulated and filtered for 24-48 hours to obtain electronic grade perfluorohexane sulfonic acid.

2. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 1, characterized in that: The resin electrolysis purification operation is also included between step (4) and step (5): Take E1-level 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, drip the diluted electronic-grade sulfuric acid into 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 a single electrolysis, 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; Step (5) Add the washed resin into the anode chamber.

3. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 2, characterized in that: In the resin electrolysis purification operation, the volume ratio of the hydrogen-type cationic resin to the diluted electronic-grade sulfuric acid is 1:2-1:5; In one electrolysis, 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; 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 performed for 0.7h-1h; During the three electrolysis, the electrolysis voltage was 40-45V, and the electrolysis current was 1.8-2.2A; the temperature of each chamber was raised to 40-70°C, and the electrolysis was performed for 0.7h-1h; In the four electrolysis, the electrolysis voltage is 45-50V, the electrolysis current is 2.3-2.7A; the temperature of each electrode chamber is raised to 40-70°C, and the electrolysis is performed for 0.7h-1h; 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.

4. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 3, characterized in that: In step (5), the volume ratio of the resin after washing the anode chamber to the primary purified perfluorohexane sulfonic acid is 1:1-1:

3.

5. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 4, characterized in that: In step (3), there are three ion exchange columns connected in series.

6. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 5, characterized in that: In step (5), in one electrolysis, the electrolysis voltage is 10-15V, and the electrolysis current is 0.5-1A; the temperature of each electrode chamber is raised to 40-70°C, and the electrolysis is carried out for 1-1.5h.

7. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 6, characterized in that: In the secondary electrolysis of step (5), the electrolysis voltage is 15-20 V, and the electrolysis current is 1-1.5 A; the temperature of each electrode chamber is raised to 40-70° C., and the electrolysis is carried out for 1-1.5 hours.

8. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 7, characterized in that: In step (5), during the three electrolysis steps, the electrolysis voltage is 20-25 V, and the electrolysis current is 1.5-2 A; the temperature of each electrode chamber is raised to 40-70° C., and the electrolysis is performed for 1-1.5 hours.

9. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 8, characterized in that: In the four electrolysis steps (5), the electrolysis voltage is 25-30 V and the electrolysis current is 2-2.5 A; the temperature of each electrode chamber is raised to 40-70° C. and the electrolysis is performed for 1-1.5 h.

10. The method for preparing electronic grade perfluorohexane sulfonic acid according to claim 9, characterized in that: In step (5), during the five electrolysis steps, the electrolysis voltage is 30-35 V and the electrolysis current is 2.5-3 A; the temperature of each electrode chamber is raised to 40-70° C. and the electrolysis is performed for 1-1.5 h.

11. Electronic grade perfluorohexane sulfonic acid prepared by the method for preparing electronic grade perfluorohexane sulfonic acid according to any one of claims 1 to 10.

12. Use of electronic grade perfluorohexane sulfonic acid as claimed in claim 11 in an anti-reflective film on top of a photoresist.

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