Cleaning method of PFA bottle for wet electronic chemicals

Abstract

The invention discloses a cleaning method of a PFA bottle for wet electronic chemicals, and belongs to the technical field of cleaning of high-purity polytetrafluoroethylene material packaging containers. The method adopts a multi-step and modularized cleaning process, and sequentially comprises the following steps: pre-cleaning physical particulate matters by using ultrapure water; a mixed solution of electronic-grade hydrofluoroether and isopropanol is used for cleaning organic matter such as fluorine-containing monomers, small-molecule fluorine-containing compounds, grease and release agents which are exposed on the surface and not completely polymerized; carrying out deep cleaning by using an electronic-grade nitric acid solution to remove metals and organic matters; carrying out special cleaning by using an electronic-grade sulfuric acid solution to remove metal sulfide; carrying out etching cleaning by using an electronic-grade hydrofluoric acid solution so as to remove the silicon-containing compound and the metal oxide; and finally, the ultrapure water is used for thorough rinsing again. According to the method, high-purity acid solutions with different properties are combined according to a specific sequence, and cleaning processes such as soaking and ultrasonic treatment are assisted, so that systematic and targeted removal of various pollutants in the PFA bottle is realized, cross contamination is effectively avoided, the PFA bottle can meet the cleanliness requirement for containing ultra-high-purity wet electronic chemicals, and the product quality is improved. And the packaging box is particularly suitable for packaging products with levels of SEMI G5 and the like.

Description

Technical Field

[0001] This invention relates to the field of cleaning technology for high-purity PTFE packaging containers, specifically to a cleaning method for PFA bottles used in wet electronic chemicals. Background Technology

[0002] Wet electronic chemicals are critical liquid chemical materials used in wet processes of microelectronics and optoelectronics. Their purity and cleanliness directly determine the performance and yield of products such as integrated circuits and flat panel displays. The electronics industry has relatively strict requirements for electronic chemical raw materials, purification methods, containers, storage and transportation, and testing applications. Electronic chemical companies need to undergo rigorous audits and certifications to enter the supply chains of downstream customers such as integrated circuit and display panel manufacturers. Among these, PFA bottles are widely used in the initial sample testing and verification stage due to their excellent chemical resistance, low metal ion release, and high purity.

[0003] However, during production, transportation, and storage, the inner walls of PFA bottles can absorb or retain various contaminants, mainly including: 1) physical particulate matter, such as dust, plastic processing debris, and particulate impurities embedded within the PFA material; 2) inorganic ionic contaminants, such as residual metal oxidants, metal ions (e.g., K, Na, Ca, Fe, Cu, Cr, Ni, etc.) carried by friction with metal equipment during extrusion, molding, and other processing, and sulfides; 3) organic contaminants, such as processing aids, incompletely polymerized fluorinated monomers, and trace amounts of polymer chain breakage, producing small-molecule fluorinated compounds and oil stains; 4) silicon-containing compounds, such as silica dust. If cleaning is not thorough, these contaminants can dissolve into high-purity wet electronic chemicals, causing product contamination and leading to wafer defects or even failures during downstream semiconductor customer production line verification. Existing cleaning methods mostly employ single acid immersion or conventional ultrasonic cleaning, which have the following shortcomings: 1) The cleaning steps are too simple to remove all types of contaminants, and they cannot effectively remove unpolymerized fluorinated monomers and small molecule fluorinated compounds with broken polymerization from the inner surface of the bottle; 2) The cleaning sequence is unreasonable, which may lead to cross-contamination or secondary adsorption of different contaminants; 3) The cleaning cleanliness level is not high enough to meet the packaging requirements of high-end wet electronic chemicals (such as SEMI G5 level).

[0004] Therefore, there is an urgent need to develop a systematic, efficient cleaning method specifically for PFA bottles that can achieve ultra-high cleanliness. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a cleaning method for PFA bottles used in wet electronic chemicals. This method is characterized by rigorous steps, high targeting, and excellent cleaning results, aiming to thoroughly remove various contaminants from the PFA bottles and ensure their cleanliness meets the requirements for containing high-end wet electronic chemicals. The technical solution of this invention is as follows: A method for cleaning PFA bottles used in wet electronic chemicals includes the following steps: Step 1: Physical particulate pre-cleaning: Add ultrapure water to the PFA bottle to be cleaned, so that the liquid level reaches 60%-80% of the PFA bottle volume; after capping, first tilt the bottle axially to the left at an angle of 35°-55° and shake it up and down 8-12 times, then tilt the bottle axially to the right at an angle of 35°-55° and shake it up and down 8-12 times, and then pour out the water; repeat this process 8-12 times to initially remove large particulate impurities that are not firmly attached to the bottle.

[0006] Step 2: Pretreatment of organic impurities: The PFA bottle treated in Step 1 is repeatedly immersed in a mixed solution and then subjected to short-time ultrasonic cleaning with heating. This step is repeated 2-3 times. Through the principle of low surface tension and synergistic dissolution, organic contaminants such as fluorinated monomers, small molecule fluorinated compounds, greases and release agents on the surface of the PFA container are effectively removed. Step 3: Deep cleaning of metals and organic matter: First, prepare an 8%-12% electronic-grade nitric acid solution and pour it into the PFA bottle cleaned in Step 2, filling the bottle to 95%-98% of its volume. After capping, soak the bottle at 60-80℃ for 24-48 hours. Then, place the capped PFA bottle into an ultrasonic cleaner and ultrasonically clean it at a frequency of 40-60kHz to the same temperature for 2-4 hours. After cleaning, pour the nitric acid solution into a hazardous waste container. Repeat this step 3-5 times to efficiently complex, dissolve, and remove residual metals, metal oxides, and organic contaminants, and passivate the material surface to reduce the re-adsorption of impurities.

[0007] Step 4: Special cleaning of metal sulfides: Prepare a 92%-98% electronic-grade sulfuric acid solution and pour it into the PFA bottle cleaned in Step 3, filling the bottle to 95%-98% of its volume. After capping, soak the bottle at 60-80℃ for 24-48 hours. Then, place the capped PFA bottle into an ultrasonic cleaner and ultrasonically clean it at 40-60kHz and 60-80℃ for 2-4 hours. After cleaning, pour the sulfuric acid solution into a hazardous waste container. Repeat this step 3-5 times to oxidize and remove metal sulfides that are difficult to dissolve with nitric acid.

[0008] Step 5: Etching and cleaning of silicon-containing compounds / metal oxides: Prepare an 8%-12% electronic-grade hydrofluoric acid solution and pour it into the PFA bottle cleaned in Step 4, filling the bottle to 95%-100% capacity. After capping, soak the bottle at 60-80℃ for 24-48 hours. Then, place the capped PFA bottle into an ultrasonic cleaner and ultrasonically clean it at 40-60kHz and 60-80℃ for 2-4 hours. After cleaning, pour the hydrofluoric acid solution into a hazardous waste container. Repeat this step 2-4 times to effectively remove residual silicon dioxide and other silicon-containing compounds from the bottle through etching.

[0009] Step 6: Final Rinse: Repeat Step 1 8-12 times to thoroughly remove any residual acids and trace ions that may be carried out again from the PFA bottle; finally, fill the bottle with ultrapure water for later use.

[0010] Preferably, step 2 specifically involves: adding the mixed solution to the PFA bottle until the liquid level is 95%-98% of the volume, immersing it in a water bath heated to 50-70°C for 4-6 hours, and then sonicating it at 40-60kHz for 2-4 hours, with each step repeated 3-5 times.

[0011] More preferably, the mixed solvent in step 2 comprises, by volume ratio: 4-6 parts of hydrofluoroether (HFE-7200), 2-4 parts of isopropanol (IPA), 1-2 parts of perfluoro-2-methyl-3-pentanone (Novec 1230), and 0.3-0.7 parts of hexafluoroisopropanol (HFIP). More preferably, the mixed solvent comprises, by volume ratio: 5 parts hydrofluoroether (HFE-7200), 3 parts isopropanol (IPA), 1.5 parts perfluoro-2-methyl-3-pentanone (Novec 1230), and 0.5 parts hexafluoroisopropanol (HFIP).

[0012] Preferably, the up-and-down shaking in steps 1 and 6 is repeated 10 times, and the cleaning in steps 2, 3, 4 and 5 is repeated 3 times.

[0013] Preferably, the soaking time in steps 2, 3, 4, and 5 is 36 hours.

[0014] Preferably, the liquid levels mentioned in steps 1, 2, 3, 4, 5, and 6 are 70%, 98%, 98%, 98%, 98%, and 70%, respectively.

[0015] Preferably, the acids and organic reagents used in steps 2, 3, 4, and 5 are all of electronic grade purity to prevent the cleaning agent from introducing secondary pollution. The beneficial effects of this invention are as follows: 1. This invention adopts a multi-step, modular cleaning process of "physical pre-cleaning - organic contaminant cleaning - nitric acid to remove metals / organic matter - sulfuric acid to remove sulfides - hydrofluoric acid to remove silicon compounds / metal oxides - final rinsing". Each step is aimed at specific types of contaminants, achieving full coverage and targeted removal of all major contaminants that may exist in PFA bottles.

[0016] 2. First, large particles are removed with water to prevent them from interfering with subsequent acid washing. Then, the low surface tension and polarity of organic solvents are used to remove difficult-to-dissolve fluorinated compounds, greases, and other organic matter. Next, nitric acid is used to remove most metals and organic matter. Subsequently, concentrated sulfuric acid, a strong oxidizing agent, is used to resolve sulfides that are difficult to treat with nitric acid. Finally, hydrofluoric acid is used to remove silicides and metal oxides, and the acid solution is washed with water. This sequence avoids cross-interference and secondary adsorption of contaminants during the treatment process, forming a highly efficient cleaning chain.

[0017] 3. The newly added organic cleaning step removes oily and fluorinated contaminants from the bottle wall at the source, effectively preventing these organic substances from reacting with acid in subsequent acid washing steps to form new complex contaminants or encapsulate other impurities, thus creating a cleaner reaction interface for subsequent acid washing steps. This "remove organic first, then inorganic" sequence ensures the high efficiency and smooth operation of the entire cleaning chain, ultimately resulting in a PFA bottle inner wall cleanliness level exceeding conventional levels. The total organic carbon (TOC) content in the rinsing solution can be stably controlled below 10 ppb, while ensuring that metal ion and particulate matter indicators meet or even exceed the requirements of SEMI G5 level.

[0018] 4. Operating Procedures: Parameters such as shaking angle, liquid level, time, and number of cycles have been optimized and limited to ensure consistent and repeatable cleaning results. Saturated cleaning can be achieved within 2-3 cycles, compared to 3-5 cycles required with conventional solvents, thus improving cleaning efficiency and reducing solvent consumption and waste liquid generation. Furthermore, all solvents are of electronic-grade purity and possess high volatility and low residue characteristics. Combined with subsequent rigorous rinsing steps, this completely eliminates potential secondary contamination from the cleaning agent itself, ensuring the reliability of the cleaning process and the absolute safety of the final packaged product. Detailed Implementation

[0019] The technical solution of the present invention will be further explained and described below with reference to specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0020] All experiments used 1L used and recycled PFA bottles of the same batch and with the same level of contamination. The mixed solution components were: hydrofluoroether (HFE-7200), isopropanol (IPA), perfluoro-2-methyl-3-pentanone (Novec 1230), and hexafluoroisopropanol (HFIP).

[0021] Example 1 Clean a new 1L PFA bottle for use in containing SEMI G5 grade hydrogen peroxide.

[0022] Step 1: Add ultrapure water to the PFA bottle until the liquid level reaches approximately 700 mL (70%). After capping, shake up and down at a 45° angle to the left 10 times, then shake up and down at a 45° angle to the right 10 times. Discard the water. Repeat this operation a total of 10 times.

[0023] Step 2: Add a mixed solution with a volume ratio of HFE-7200 : IPA : Novec 1230 : HFIP = 5 : 3 : 1.5 : 0.5 (volume ratio) to the PFA bottle until the liquid level reaches 980 mL (98%). After capping, soak in a constant temperature oven at 60℃ for 5 hours. Then, place the capped PFA bottle into a heated ultrasonic cleaner and ultrasonically clean it at a frequency of 50kHz and a temperature of 60℃ for 3 hours. After cleaning, pour the mixed solution into a dedicated waste container. Repeat this process a total of 3 times.

[0024] Step 3: Prepare a 10% electronic-grade nitric acid solution and pour it into the bottle until it is nearly full (approximately 98% full). Cap the bottle and heat it to 70°C for 36 hours. Afterward, place it in an ultrasonic cleaner (50kHz frequency) and heat it to 70°C for ultrasonic cleaning for 3 hours. Discard the nitric acid solution into a hazardous waste container. Repeat this soaking-ultrasonic process a total of 3 times.

[0025] Step 4: Change the operating environment. Use 96% electronic-grade sulfuric acid solution, pour it into the bottle to 98% of the liquid level, cover, and heat to 70°C for 36 hours. Afterward, place it in an ultrasonic cleaner (50kHz frequency) and heat to 70°C for ultrasonic cleaning for 3 hours. Discard the sulfuric acid solution into a hazardous waste container. Repeat this process a total of 3 times.

[0026] Step 5: In a dedicated, ventilated, and corrosion-resistant facility, pour a 10% electronic-grade hydrofluoric acid solution into a bottle until the liquid level reaches 98%. Cap the bottle and heat to 70°C for 48 hours. Afterward, place the bottle in an ultrasonic cleaner (50kHz frequency) and heat to 70°C for ultrasonic cleaning for 3 hours. Discard the hydrofluoric acid solution into a hazardous waste container. Repeat this process a total of 3 times.

[0027] Step 6: Finally, strictly follow the method in Step 1 and rinse 10 times with ultrapure water. After rinsing, fill the PFA bottle with ultrapure water and seal it for later use.

[0028] The 1L PFA bottle was soaked in SEMI G5 grade electronic sulfuric acid (stock sulfuric acid) for 48 hours. The total organic carbon, fluoride ions, metals, and particle size in the sulfuric acid were measured, as shown in Table 1 below. The test results showed that the number of particles >30nm in the rinsing solution of the PFA bottle cleaned using this method was less than 100 pcs / mL (Particles (≥0.03µm)), and the content of major metal elements was less than 10ppt, fully meeting the packaging requirements for SEMI G5 grade wet electronic chemicals.

[0029] Comparative Example 1 Step 2 Solvent ratio: HFE-7200 : IPA : Novec 1230 = 5 : 3 : 2, other details are the same as in Example 1.

[0030] Comparative Example 2 Step 2 Solvent ratio: HFE-7200 : IPA : Novec 1230 : HFIP = 5 : 3 : 1 : 1, other ratios are the same as in Example 1.

[0031] Comparative Example 3 Step 2 Solvent ratio: HFE-7200 : IPA : Novec 1230 : HFIP = 2.5 : 2.5 : 2.5 : 2.5, other ratios are the same as in Example 1.

[0032] Comparative Example 4 The traditional single-acid washing method uses 1L new PFA bottles from the same batch, employing only the industry-standard single-acid washing process: simply rinse three times with ultrapure water. Fill the bottles with a 10% electronic-grade nitric acid solution and soak at room temperature for 48 hours. Discard the acid solution and rinse five times with ultrapure water. Refill with ultrapure water for later use.

[0033] Comparative Example 5 Take a 1L new PFA bottle from the same batch, adopt the scheme of this invention but deliberately omit step 2, that is, directly perform step 1 and then jump to step 3 (nitric acid cleaning), and the subsequent steps are exactly the same as in Example 1.

[0034] Comparative Example 6: The order of steps was changed (organic cleaning was placed after acid washing). Steps: Step 1 (physical pre-cleaning) → Step 3 (nitric acid cleaning) → Step 4 (sulfuric acid cleaning) → Step 5 (hydrofluoric acid cleaning) → Step 2 (organic cleaning, same ratio as in Example 1) → Step 6 (final rinsing), the rest is the same as in Example 1.

[0035] Comparative Example 7: The specific sulfide cleaning step was omitted (no sulfuric acid step). Step 4 (sulfuric acid cleaning) is completely omitted.

[0036] Steps: Step 1 → Step 2 (same ratio as in Example 1) → Step 3 (nitric acid cleaning) → skip directly to Step 5 (hydrofluoric acid cleaning) → Step 6, the rest is the same as in Example 1.

[0037] Comparative Example 8: Insufficient final rinsing The number of repetitions of step 6 (final rinse) was reduced from 10 to 2, while the other steps were exactly the same as in Example 1.

[0038] Table 1

[0039] Testing showed that PFA bottles cleaned using this method had less than 100 particles >30nm in the rinsing solution, and the content of major metal elements was less than 10ppt, fully meeting the packaging requirements for SEMI G5 level wet electronic chemicals.

[0040] The test results from this example and comparative example show that nitric acid cleaning alone cannot effectively remove metals and fluorinated organic substances. Multi-acid synergistic cleaning can further improve the removal of particulate impurities and metals. However, for fluorinated monomers and carbonaceous organic substances, the cleaning effect can be significantly improved by adding a mixed solution of hydrofluoroether and isopropanol. By optimizing the composition and ratio of the mixed solution, the most efficient and safest mixed solution formula (volume ratio HFE-7200 : IPA : Novec 1230 : HFIP = 5 : 3 : 1.5 : 0.5) was finally obtained. This formula is used as an organic cleaning agent to target and remove organic pollutants. Combined with a scientifically efficient inorganic acid cleaning step, it ensures the ultimate removal of inorganic, organic, metal, and fluorinated compound impurities from PFA bottles, avoiding cross-contamination and secondary adsorption. This results in optimal cleaning of PFA bottles, fully meeting the packaging requirements of semiconductor SEMI G5 level products.

[0041] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for cleaning PFA bottles used in wet electronic chemicals, characterized in that: The method includes the following steps: Step 1: Physical particulate pre-cleaning: Use ultrapure water to repeatedly tilt, shake, and pour water from the PFA bottle to remove large particles with low adhesion and residue inside the bottle. Step 2: Pretreatment of organic impurities: The PFA bottle treated in Step 1 is repeatedly immersed in a mixed solution and then subjected to short-time ultrasonic cleaning with heating. Step 3: Deep cleaning of metals and organic matter: The PFA bottle treated in Step 2 is repeatedly immersed and ultrasonically cleaned using an 8%-12% electronic grade nitric acid solution. Step 4: Special cleaning of metal sulfides: The PFA bottle treated in Step 3 is repeatedly immersed and briefly heated for ultrasonic cleaning using a 92%-98% electronic grade sulfuric acid solution. Step 5: Etching and cleaning of silicon compounds and metal oxides: The PFA bottle treated in Step 4 is repeatedly immersed and heated for ultrasonic cleaning using an 8%-12% electronic grade hydrofluoric acid solution. Step 6: Final Rinse: Repeat the steps in Step 1 to remove any residual acid from the bottle.

2. The cleaning method for PFA bottles used in wet electronic chemicals according to claim 1, characterized in that, Step 1 is as follows: Add ultrapure water to the PFA bottle until the liquid level is 60%-80% of the volume. After capping, first shake it up and down at an angle of 35°-55° to the left for 8-12 times, then shake it up and down at an angle of 35°-55° to the right for 8-12 times. Then pour out the water and repeat this process 8-12 times.

3. The cleaning method for PFA bottles used in wet electronic chemicals according to claim 1, characterized in that, Step 2 specifically involves adding the mixed solution to the PFA bottle until the liquid level is 95%-98% of the volume, immersing it in a water bath heated to 50-70℃ for 4-6 hours, and then sonicating it at 40-60kHz for 2-4 hours. Each step is repeated 3-5 times.

4. The cleaning method for PFA bottles used in wet electronic chemicals according to claim 3, characterized in that, The mixed solvent in step 2 has the following components by volume ratio: 4-6 parts hydrofluoroether, 2-4 parts isopropanol, 1-2 parts perfluoro-2-methyl-3-pentanone, and 0.3-0.7 parts hexafluoroisopropanol.

5. The cleaning method for PFA bottles used in wet electronic chemicals according to claim 4, characterized in that, The mixed solvents, by volume ratio, are: 5 parts hydrofluoroether, 3 parts isopropanol, 1.5 parts perfluoro-2-methyl-3-pentanone, and 0.5 parts hexafluoroisopropanol.

6. The cleaning method for PFA bottles used in wet electronic chemicals according to claim 1, characterized in that, In steps 3, 4, and 5, the acid solution is poured into the PFA bottle to 95%-98% of its volume, the soaking time is 24-48 hours, the ultrasonic treatment time is 2-4 hours at a frequency of 40-60kHz, and each step is repeated 3-5 times.

7. The cleaning method for PFA bottles used in wet electronic chemicals according to claim 1, characterized in that, In step 3, the nitric acid solution needs to be soaked and sonicated in a water bath heated to 60-80°C.

8. The cleaning method for PFA bottles used in wet electronic chemicals according to claim 1, characterized in that, The liquid levels mentioned in steps 1, 2, 3, 4, and 5 are preferably 70%, 98%, 98%, 98%, and 98%, respectively.

9. A method for cleaning PFA bottles for wet electronic chemicals according to any one of claims 1 to 8, characterized in that, All acid and organic reagents used in the cleaning steps were of electronic grade purity.

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