An asymmetric sulfone polymer nanoscale filter membrane, its preparation method and application

Abstract

This application discloses an asymmetric sulfone polymer nanoscale filter membrane, its preparation method, and its application, belonging to the field of membrane material technology. The filter membrane includes a filter membrane body, which includes a pre-filtration layer and a separation layer for impurity retention. The separation layer has an average thickness of 0.5–12 μm and a porosity of 40–80%. The ratio between the maximum PMI pore size and the minimum PMI pore size of the filter membrane is 1.2–3.5. The filter membrane has a retention rate of ≥90% for 2 nm colloidal gold. Furthermore, the cross-sectional brightness of the filter membrane after retaining 2 nm colloidal gold is measured, and the ratio of the standard deviation of the area value of its brightness shift spectrum to the average area value is 0.01–2. The thin and uniform separation layer structure and the suitable pore size and pore size distribution of the filter membrane, combined with high porosity, ensure that the filter membrane has both high retention efficiency and high throughput and high cleanliness, making the filter membrane suitable for the nanoscale purification of liquid processing agents used in semiconductor wet processes.

Description

Technical Field

[0001] This application relates to the field of membrane materials technology, specifically to an asymmetric sulfone polymer nanoscale filter membrane, its preparation method, and its application. Background Technology

[0002] Semiconductor wet processing is an indispensable part of integrated circuit manufacturing, mainly used for critical processes such as wafer surface cleaning, etching, resist removal, and doping. These processes all require the use of large amounts of liquid processing reagents, such as deionized water and hydrofluoric acid solutions. Since even tiny contaminants can affect chip quality, ensuring the purity of the liquid processing reagents is crucial in the entire wet process. Although, theoretically, high-purity chemical reagents and ultrapure water can be used directly during operation to avoid introducing contaminants that deposit on the wafer surface and affect the yield and quality of semiconductor devices, in actual semiconductor wet processes, the liquids used may contain nanoscale particulate impurities (such as tiny impurity particles with a diameter of 1–10 nm), soluble impurities (such as metal ions), or other impurities. To ensure the stability and consistency of each process and improve chip yield and quality, it is necessary to filter each liquid processing reagent beforehand.

[0003] Currently, sulfone polymer filter membranes are favored for their high chemical and thermal stability, good compatibility, and resistance to various chemical substances. This allows them to maintain excellent performance in complex fluid filtration environments, facilitating stable and effective filtration with high retention efficiency. Therefore, sulfone polymer filter membranes can be used for high-precision filtration of various liquid reagents used in semiconductor wet processes, removing nanoscale impurities to further improve the purity of these liquid reagents and ensure process stability and consistency.

[0004] However, in practical applications, it is necessary to consider not only the filter membrane's impurity retention efficiency but also its flux. Currently, those skilled in the art generally believe that it is difficult to simultaneously achieve high retention efficiency and high flux in filter membranes. When retaining nanoscale impurity particles (especially extremely small impurity particles with a diameter of 1–10 nm), in order to ensure efficient impurity retention, the pores of the filter membrane separation layer are very small (even excessively small); once the pores become smaller, the membrane flux will decrease rapidly (by a geometric factor), which greatly affects the filtration efficiency of the filter membrane and reduces its practical value.

[0005] In view of this, it is indeed necessary to provide a technical solution to solve the above problems, so that the filter membrane has high throughput and high retention efficiency for nanoscale impurity particles when applied in semiconductor wet processes. Summary of the Invention

[0006] Based on the deficiencies of existing technologies, the purpose of this application is to provide an asymmetric sulfone polymer nanoscale filter membrane, its preparation method, and its application. This nanoscale filter membrane has a high retention efficiency for 2nm colloidal gold, and its separation layer is thin and relatively uniform. In addition, the filter membrane has high porosity and a wide pore size distribution, which together achieves efficient retention of nanoscale impurities and good flux. The membrane itself also has good cleanliness, making it particularly suitable for application in the semiconductor field.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0008] In a first aspect, this application provides an asymmetric sulfone polymer nanoscale filter membrane, comprising a filter membrane body having a non-directional tortuous pathway within the filter membrane body, wherein the filter membrane body comprises a pre-filtration layer and a separation layer for intercepting impurities in sequence along its thickness direction, and the average thickness of the separation layer is 0.5 μm to 12 μm;

[0009] The porosity of the filter membrane is 40% to 80%;

[0010] The ratio between the maximum PMI pore size and the minimum PMI pore size of the filter membrane is 1.2 to 3.5.

[0011] The filter membrane retains colloidal gold with a particle size of 2 nm, and the retention rate of the filter membrane for the colloidal gold is not less than 90%.

[0012] Furthermore, the cross-sectional brightness of the filter membrane after retaining 2 nm of colloidal gold was measured, and the ratio of the standard deviation of the area value of the brightness shift spectrum to the average value of the area value was 0.01 to 2.

[0013] In the membrane body structure of the filter membrane provided by the present invention, it can be found that the entire filter membrane body is mainly divided into two regions in the thickness direction. One region is a pre-filtration layer, whose internal pores have relatively large pore sizes and are mainly used to intercept large particulate impurities in the fluid. The pre-filtration layer has a large dirt holding capacity and a fast flow rate, which plays a pre-filtration role on the fluid and reduces the impact of large particulate impurities on the separation layer. The other region is a separation layer, whose internal pores have relatively small pore sizes (nanoscale) and are mainly used to intercept fine particulate impurities, such as various nanoscale fine impurity particles in the fluid (especially impurities with a particle size of 1-10nm), which plays a separation role and facilitates the filter membrane to have a high capture capacity for various fine impurities.

[0014] In this application, the overall pore size of the filter membrane is reflected to a certain extent by the retention efficiency of the filter membrane for 2nm colloidal gold, transforming the abstract "membrane pore structure" into a measurable parameter for substantial limitation. Research shows that the retention efficiency of the filter membrane for 2nm colloidal gold in this application is not less than 90%, which is a functional quantitative indicator of the membrane pore structure (especially the pore size, distribution, integrity, and connectivity of the separation layer). This indicates that the filter membrane has a nanoscale pore structure, primarily used to retain nanoscale impurity particles, further specifically impurity particles with a diameter of 1-10nm, and even further specifically impurity particles with a diameter of 1-5nm. This is fundamentally different from existing microfiltration membranes (which retain micron-sized impurity particles) and cannot be compared. Furthermore, all other features of this application work synergistically based on this foundation.

[0015] Existing technologies generally believe that improving the rejection rate of nanoscale impurities requires filter membranes with extremely narrow pore sizes. This is achieved by reducing the overall pore size of the filter membrane and strictly controlling its pore size uniformity to intercept small particles (especially nanoscale impurity particles of 1-10 nm). However, this application's research has found that excessively narrow pore size distribution of the filter membrane can easily lead to a reduction in the number of membrane pores and a decrease in porosity, directly causing a geometric decrease in the filter membrane's flux. This makes it impossible to meet the requirements of high-flow-rate, continuous filtration (such as high-purity reagent delivery) in semiconductor wet processes. In addition, some liquid processing reagents used in semiconductor wet processes have high ion concentrations. Traditional narrow-pore-size filter membranes are prone to pore deformation or failure due to particle blockage, thereby reducing the service life of the filter membrane.

[0016] Compared with the prior art, this application has a counterintuitive design that relaxes the restrictions on the pore size distribution of the filter membrane. Furthermore, research has found that the ratio between the maximum pore size and the minimum pore size of the filter membrane in the PMI is more suitable to represent the pore size distribution in this application, accurately locking the two key extreme values ​​of "maximum pore" and "minimum pore" in the whole membrane. For nanoscale retention scenarios (such as the retention of 2nm colloidal gold in the semiconductor field), the maximum pore size directly determines whether the filter membrane will experience leakage during filtration (if the maximum pore size is too large, target impurities will penetrate the filter membrane); the minimum pore size directly affects the probability of excessive clogging of the filter membrane during filtration and also affects the membrane's own cleanliness (if the minimum pore size is too small, impurities will accumulate rapidly due to narrow pores, leading to a sharp drop in flux and low cleanliness). By adjusting this ratio to 1.2–3.5, while maintaining a colloidal gold retention efficiency of no less than 90%, and through the synergistic effect of other characteristics (such as the average thickness of the separation layer, the uniformity of the separation layer thickness, and the porosity of the filter membrane), a balance between high retention efficiency and high flux is achieved. The synergistic mechanism of each characteristic is as follows:

[0017] (1) Regarding the average thickness of the separation layer: This application shortens the path of the fluid through the filter membrane by using a thinner separation layer (0.5-12 μm), thereby reducing the mass transfer resistance. Even if the membrane pores are small, the high flux can be maintained by the advantage of the short path (the flux decay is more significant in traditional thick membranes due to the long path).

[0018] (2) Regarding the thickness uniformity of the separation layer: By adjusting the thickness uniformity of the separation layer, this application makes it possible to measure the cross-sectional brightness of the filter membrane after retaining 2nm colloidal gold. The ratio of the standard deviation of the area value of the brightness shift spectrum to the average value of the area value is within 0.01 to 2. This avoids the pore size deformation caused by the stacking of membrane pores in the local overly thick area, ensures that the retention efficiency of the entire membrane surface is relatively uniform, and prevents the "edge leakage" problem common in existing thick membranes from occurring in the filter membrane of this application.

[0019] (3) Regarding the uniformity of filter membrane pore size distribution: This application controls the ratio between the maximum pore size of PMI and the minimum pore size of PMI within a reasonable range (1.2 to 3.5). This avoids the filter membrane from leaking large particulate impurities due to its excessively wide pore size distribution, and maintains the continuity of its fluid channels through a small number of slightly larger pores in the filter membrane. This prevents the problem of a sudden drop in flux during the filtration process caused by the "extremely small total pore size" of traditional narrow pore size filter membranes.

[0020] (4) Regarding the porosity of the filter membrane: The filter membrane of this application has a high porosity (≥40%), which can ensure a sufficient number of effective membrane pores per unit area. This avoids the problem of large fluctuations in the retention rate during filtration due to the allowable size difference of the membrane pores (widened pore size distribution). This balances the porosity and pore size distribution of the filter membrane, making it more suitable for filtering liquid treatment agents in semiconductor wet processes. For example, in solutions containing electrolytes (such as BOE etching solution), nanoparticles are prone to agglomeration due to increased ionic strength. This application moderately widens the pore size distribution of the filter membrane while ensuring that the porosity of the filter membrane is not less than 40%. This allows small agglomerates to pass through slightly larger pores, avoiding premature clogging of the membrane surface, while unagglomerated monodisperse particles are still retained, achieving a balance between "anti-clogging" and "high retention".

[0021] (5) Regarding the material of the filter membrane: The filter membrane of this application is made of sulfone polymer. This polymer has excellent chemical stability. Sulfone polymer is resistant to strong corrosive solutions (such as hydrofluoric acid solution) used in semiconductor wet processes, avoiding secondary pollution caused by swelling or degradation of the filter membrane material (traditional cellulose or nylon filter membranes are easily corroded, releasing particulate matter that contaminates the drug solution). The filter membrane made of sulfone polymer has the advantage of high mechanical strength, which allows the filter membrane to maintain its structural integrity even when its separation layer is ultra-thin (0.5-12μm).

[0022] (6) The above features work synergistically to improve the retention rate of the filter membrane. Specifically, although traditional thick membranes (such as those above 15 μm) can retain nanoparticles, the pore diffusion path is long and the flux is significantly reduced. However, the filter membrane made of PES material in this application, combined with an ultrathin separation layer, shortens the filtration path. Combined with the thin and uniformly distributed separation layer structure, the contact volume between the filter membrane and the corrosive solution can be reduced, avoiding the expansion of the filter membrane pores due to chemical erosion during long-term use, and ensuring that the retention efficiency of the filter membrane is more durable and stable. Under the interaction of the thin and uniformly distributed separation layer structure, the suitable pore size distribution of the filter membrane, and the specific membrane pore structure (the retention efficiency of the filter membrane for 2nm colloidal gold is not less than 90%), the retention rate of the filter membrane can be significantly improved. When the filter membrane described in this application is used to purify the liquid treatment agent used in the semiconductor wet process at the nanoscale, there will not be too many nanoparticle impurities entering the separation layer region, which is much less than the number of impurities reaching the separation layer when the filter membrane is used in other fields (such as biopharmaceuticals).

[0023] (7) The synergistic effect of each feature improves the flux of the filter membrane. Specifically, the thin and uniform separation layer structure and suitable pore size distribution of the filter membrane in this application, combined with high porosity (40-80%), can ensure that the filter membrane has enough channels to effectively participate in mass transfer. This not only ensures the high flux and flux stability of the filter membrane, but also makes the filter membrane easy to clean, improves the cleanliness of the filter membrane, and makes the components of the filter membrane less likely to dissolve during filtration and cleaning. Thus, the filter membrane described in this application is suitable for the nanoscale purification of liquid processing agents used in semiconductor wet processes.

[0024] In summary, the inventors of this application have made customized innovations for semiconductor wet processes. The filter membrane is made of PES material with good chemical stability. Combined with the structural design of its separation layer, it solves the problems of easy deformation of pore size and easy adsorption and clogging of traditional filter membranes in highly corrosive environments. This makes the filter membrane provided by this application have both anti-corrosion and anti-pollution properties, and is more suitable for the extreme working conditions of semiconductor wet processes.

[0025] This application allows for a moderate relaxation of the pore size distribution of the filter membrane, which essentially endows the filter membrane with dynamic retention adaptability to changes in the solution environment (such as changes in particle aggregation state and fluctuations in ionic strength). In contrast, traditional filter membranes with narrow pore size distribution are prone to failure due to "strict size sieving" when operating conditions fluctuate. Therefore, this application improves the robustness of the filter membrane in complex semiconductor wet processes.

[0026] This application addresses the unique filtration conditions in semiconductor wet processes (highly corrosive, nanoscale impurity particles, high flow rates, etc.) by precisely matching the material properties of the filter membrane with its structural design. This solves the long-standing industry problem of the difficulty in achieving both high-efficiency retention and high throughput in filter membranes. Instead of pursuing a "perfect filter membrane" with extremely narrow pore size distribution, it achieves a breakthrough in filter membrane performance through multi-parameter synergy. This overcomes the technical bottleneck of the incompatibility between "high retention and high throughput" in existing technologies, making the filter membrane of this application suitable for nanoscale filtration of liquid treatment agents used in semiconductor wet processes.

[0027] The filter membrane in this application has a single-layer asymmetric membrane structure, meaning it is integrally molded without any "composite" or other processes. The entire membrane is made of sulfone-based polymer materials, and the material is uniform throughout, with no variation in material composition. The only variation in the membrane's structure is its overall structure. In contrast, composite membranes have multiple layers, and the pore size changes abruptly when transitioning from one layer to another. In this application, non-directional tortuous pathways refer to randomly oriented groove structures and / or discretely distributed pore structures, and these non-directional tortuous pathways are interconnected.

[0028] The thickness of the separation layer in this application is determined by using colloidal gold with a particle size of 2 nm as an impurity particle for retention testing. The length of the colloidal gold retention area corresponding to the particle size in the filter membrane is the thickness of the separation layer. Multiple measurements are taken, and the average value is calculated, preferably at least five times, to obtain the average thickness of the separation layer. The distribution of colloidal gold on the filter membrane can be determined according to the test method in Chinese Patent CN105980038B - Virus Removal Membrane: a slice is cut from the virus-removing filter membrane after filtering the colloidal gold solution. The brightness distribution of multiple sites in the cross-section of the slice stained with colloidal gold is measured using an optical microscope. Because colloidal gold absorbs light, the brightness shift depends on the amount of colloidal gold captured. It should be noted that, if necessary, background noise can be removed by the brightness distribution. Then, a displacement graph with film thickness on the horizontal axis and brightness on the vertical axis is generated; thereby obtaining the region where colloidal particles of a certain size are trapped in the film thickness direction; (in this invention, the liquid inlet surface is 0% of the film thickness, and the liquid outlet surface is 100% of the film thickness); in addition, gold element determination can be performed on the film cross-section by EDS to understand the distribution of colloidal gold of corresponding particle size in the film cross-section; of course, those skilled in the art can also obtain the distribution of colloidal gold in the film cross-section by other measurement methods, and the above measurement methods are for reference only.

[0029] It should be noted that although a certain amount of colloidal gold is present in some regions along the membrane thickness direction, its content is very low. Therefore, these regions are not considered as regions where colloidal gold is retained; they merely contain some residual colloidal gold (rather than regions where colloidal gold is retained). Therefore, in the filter membrane of this application, it is preferable to form a region that continuously captures colloidal gold with a diameter of 2 nm along the membrane thickness direction, which is the region where 2 nm colloidal gold is truly retained, i.e., the separation layer region.

[0030] In this application, the uniformity of the separation layer thickness is reflected by measuring the cross-sectional brightness of the filter membrane after retaining 2nm colloidal gold. The ratio of the standard deviation of the area value of the brightness shift spectrum to the average value of the area value is used to represent the uniformity of the separation layer thickness. The smaller the ratio, the more uniform the separation layer thickness.

[0031] The aforementioned ratio was determined, for example, by the following method. A section was cut from the filter membrane after filtering a 2 nm colloidal gold solution. The brightness distribution of multiple sites in the colloidal gold-stained portion of the section was measured using an optical microscope. Since colloidal gold absorbs light, the brightness shift depends on the amount of colloidal gold captured. It should be noted that background noise can be removed from the brightness distribution if necessary. A graph with film thickness on the horizontal axis and brightness shift on the vertical axis was then constructed, and the spectral area of ​​the brightness shift shown in the graph was calculated. Furthermore, the ratio was calculated by dividing the standard deviation of the spectral area of ​​the brightness shift at multiple locations by the average of the spectral areas of the brightness shift at multiple locations.

[0032] The maximum PMI pore size and the minimum PMI pore size of the filter membrane described in this application can be directly measured by a PMI pore size tester.

[0033] In this application, common testing methods for porosity include mercury intrusion porosimetry, density method, and wet-dry film weighing method. Of course, those skilled in the art can also obtain the above parameters through other testing methods. The above testing methods are for reference only.

[0034] In one embodiment, the pre-filtration layer includes a liquid inlet surface located on the side of the pre-filtration layer opposite to the separation layer, and the liquid inlet surface includes a plurality of liquid inlet holes;

[0035] The separation layer includes a liquid outlet surface, which is located on the side of the separation layer opposite to the pre-filtration layer, and the liquid outlet surface includes a plurality of liquid outlet holes;

[0036] The average SEM pore size of the liquid outlet is 4 nm to 30 nm.

[0037] The ratio between the average SEM diameter of the inlet hole and the average SEM diameter of the outlet hole is not less than 15.

[0038] The inventors discovered that, in this application, the liquid outlet surface, serving as the "outlet end" of the filter, has an average SEM pore size of 4nm to 30nm, slightly larger than the corresponding particle size of the target impurity particles. This not only facilitates the rapid passage of fluid through the outlet pores, ensuring the flux of the filter membrane, but also mitigates the impact of larger surface tensions and pore resistance on fluid flow when passing through the membrane if the pore size is smaller than or equal to the minimum particle size of the target impurity particles. This results in a decrease in the flux of the filter membrane. Furthermore, the non-directional tortuous pathways within the filter membrane body—referring to randomly oriented trench structures and / or discretely distributed pore structures, with each pathway interconnected—further enhance the retention of target impurity particles when the average SEM pore size of the outlet pores is slightly larger than the particle size of the target impurity particles, working in conjunction with a suitable separation layer thickness. This reduces or prevents nanoscale impurity particles from flowing out of the filter membrane from the liquid outlet surface, ensuring efficient retention of nanoscale impurity particles and meeting the needs of practical semiconductor applications.

[0039] This application provides an "asymmetric" sulfone polymer nanoscale filter membrane. Specifically, the "asymmetric" aspect refers to the variation of the membrane pore structure with the membrane thickness, resulting in a significant difference in pore size between the inlet and outlet liquid surfaces. The ratio between the SEM average pore size of the inlet pore and the SEM average pore size of the outlet pore is not less than 15. This allows the inlet surface to intercept large particles in the fluid from entering the filter membrane, thereby preventing large impurities from directly impacting or clogging the outlet pores. This improves pore connectivity, guides the fluid from wider channels to narrower channels in the filter membrane body, reduces the load on the separation layer, slows down the flux decay of the filter membrane, and further increases the filtration speed of the filter membrane for the feed liquid.

[0040] This application achieves graded retention of impurity particles by synergistically combining the specific pore size of the liquid outlet (SEM average pore size of 4nm to 30nm) with the asymmetric pore size design of the inlet and outlet pores. This balances the retention efficiency and flux of the filter membrane, slows down flux decay, and improves the ease of cleaning the filter membrane. Specifically, this is manifested in the following ways:

[0041] On the one hand, the inlet surface with a larger pore size can intercept large particles from entering the filter membrane, preventing large particles from clogging the outlet surface or even the entire separation layer (i.e., protecting the outlet surface and even the entire separation layer), thereby ensuring the filter membrane's retention efficiency for nanoscale impurity particles (especially impurity particles of 1-10nm); on the other hand, the pore size of the outlet hole is slightly larger than the minimum particle size of the target impurity particles, reducing the resistance of fluid flowing out of the outlet hole, allowing the fluid to flow out of the outlet hole quickly, thereby increasing the flux of the filter membrane.

[0042] On the other hand, larger-diameter inlet holes are less prone to clogging by large particles, and impurities (such as colloids) have a larger adhesion area on the inlet surface (less force per unit area), making it easier to remove impurities attached to the inlet surface through backwashing. The outlet hole diameter is slightly larger than the particle size of the target impurity particles, allowing the filter membrane to mainly rely on the area near the outlet surface to trap nano-sized impurity particles. This avoids the outlet hole trapping too many trace residual impurity particles in the fluid due to its small diameter, thus preventing irreversible clogging of the outlet hole. Combined with the protective effect of the inlet surface, this can effectively slow down the flux decline of the filter membrane, and the filter membrane has a high degree of cleanliness after multiple rinses.

[0043] In this application, the average SEM pore size of the liquid outlet and the liquid inlet can be measured by characterizing the membrane structure using a scanning electron microscope, followed by measurement using computer software (such as Matlab, NIS-Elements, etc.) or manual measurement, and then performing corresponding calculations. During the membrane fabrication process, in the direction perpendicular to the membrane thickness (if the membrane is a flat sheet, this direction is planar; if the membrane is a hollow fiber membrane, this direction is perpendicular to the radius), its various characteristics, such as pore size distribution, are roughly uniform and consistent. Therefore, the average pore size of a portion of the corresponding plane can be used to reflect the overall average pore size of that plane. In actual measurement, the surface of the membrane (such as the liquid inlet and liquid outlet surfaces) can be characterized using an electron microscope to obtain the corresponding SEM images. Since the pores on the membrane surface are roughly uniform, a certain area, such as 1 μm, can be selected. 2 An area of ​​(1μm × 1μm) or 25μm 2 The area is (5μm×5μm), the specific area size depends on the actual situation. Then, the pore diameter of the hole in this area is measured by computer software or manually. Several tests are performed (preferably more than 10 times, the specific number depends on the situation), and the average value is taken to obtain the SEM average pore diameter of the corresponding hole (liquid outlet and liquid inlet). Of course, those skilled in the art can also obtain the above parameters by other measurement methods. The above measurement methods are for reference only.

[0044] In a preferred embodiment, the SEM average pore size of the liquid inlet is 0.7 μm to 2.5 μm;

[0045] The ratio between the maximum PMI pore size and the minimum PMI pore size of the filter membrane is 1.4 to 3; the pore size variation gradient of the filter membrane body is 7 nm / μm to 28 nm / μm;

[0046] The pore size variation gradient of the filter membrane body = (SEM average pore size of the inlet pore - SEM average pore size of the outlet pore) / average thickness of the filter membrane body.

[0047] The pore size of the filter membrane in this application varies with the thickness of the filter membrane. Research shows that the gradient of the pore size variation in this application reflects the change in pore size along its thickness direction. A larger gradient indicates a more significant change in pore size along the thickness direction, while a smaller gradient indicates a smaller change. In this application, the pore size variation gradient of the filter membrane is 7 nm / μm to 28 nm / μm. This demonstrates that the pore size of the filter membrane provided in this application changes reasonably with its thickness (based on the ability to efficiently retain 2 nm colloidal gold). On the one hand, this avoids interlayer stress caused by abrupt changes in the pore size gradient, which could lead to membrane delamination or rupture during use. On the other hand, it avoids a filter membrane with a small pore size variation gradient, which could result in excessively low retention rate and / or low flux, failing to meet the nanoscale purification requirements of liquid processing reagents used in semiconductor wet processes.

[0048] In this application, the large pore size on the liquid inlet side provides initial access and protection, while the slightly wider pore size distribution enhances anti-fouling and adaptability. The appropriate pore size gradient integrates the former two into an "orderly shrinking" pore structure that changes from the micron to the nanometer scale. This ensures that the separation layer can efficiently retain 2nm colloidal gold, and through the overall gradient distribution and moderately wide pore size, a balance is achieved between high retention rate, high throughput and long lifespan, while also giving the filter membrane a high degree of cleanliness.

[0049] In a preferred embodiment, the pore density of the liquid outlet holes on the liquid outlet surface is 80 holes / μm. 2 ~300 per 1μm 2 The pore density of the inlet holes on the inlet surface is 6 per 100 μm. 2 ~25 per 100μm 2 .

[0050] Pore ​​density refers to the number of pores per unit area, which can be observed, for example, by examining specific areas (e.g., 100 μm) of the inlet and outlet surfaces of a filter membrane. 2 (10μm x 10μm) or 1μm 2 The pore density of the inlet and outlet surfaces can be determined by taking a scanning electron microscope image (1 μm x 1 μm, the specific area depends on the actual situation) and calculating the number of pores within that specific area. Preferably, at least three non-adjacent areas are selected for testing, and the average value is taken to finally obtain the pore density of the inlet and outlet surfaces. It is understood that those skilled in the art can also obtain the above parameters through other measurement methods.

[0051] The inventors discovered through research that the average SEM pore size (4nm~30nm) and pore density (80 pores / 1μm) of the liquid outlet pores on the liquid outlet surface are related to the... 2 ~300 per 1μm2 This combination results in the outlet pores on the liquid outlet surface having a small pore size but slightly larger than the target impurity particle size, and a dense distribution. Combined with the non-directional tortuous pathway inside the filter membrane, it can play a fine interception role for the fluid, so that the filter membrane has a good interception efficiency for nano-sized impurity particles, while providing sufficient liquid outlet channels and reducing the outlet resistance of the fluid, thereby maintaining the high throughput of the filter membrane while ensuring the interception accuracy of the filter membrane.

[0052] SEM average pore size (0.7 μm ~ 2.5 μm) and pore density (6 pores / 100 μm) of the inlet holes on the inlet surface. 2 ~25 per 100μm 2 In combination with other features, the inlet holes on the inlet surface have large diameters and sparse distribution. This not only guides the fluid flow to the internal passage of the filter membrane, reducing surface turbulence loss and increasing flux, but also enables the inlet surface of the filter membrane to effectively intercept large particles of impurities, playing a coarse interception role. This prevents large particles of impurities from entering the filter membrane and impacting the small-diameter outlet holes on the outlet surface, thus providing pre-protection for the outlet surface and reducing the risk of blockage.

[0053] The average SEM pore size of the inlet pores in the filter membrane described in this application is much larger than that of the outlet pores, and the pore density of the inlet pores on the inlet surface is much lower than that of the outlet pores on the outlet surface. This forms an asymmetrical combination structure of "large pores and sparse distribution" on the inlet surface and "small pores (but slightly larger than the target impurity particle size) and dense distribution" on the outlet surface. On the one hand, during filtration, the fluid is first coarsely intercepted on the inlet surface to prevent large particles of impurities from clogging the outlet pores on the outlet surface, and then finely intercepted by the outlet surface to ensure the filter membrane's interception efficiency for impurity particles. The large pores on the inlet surface guide the fluid to enter the filter membrane quickly, reducing fluid retention on the inlet surface. The densely distributed outlet pores on the outlet surface disperse the fluid into multiple fine streams, reducing outlet resistance and allowing the fluid to transition more smoothly from the "large pore channel" to the "small pore channel," thereby increasing the total flux of the filter membrane while ensuring interception efficiency. On the other hand, large particles of impurities have a large adhesion area on the inlet surface, making them easier to remove during backwashing. The sparse distribution of inlet holes on the inlet surface reduces the number of aggregation points for impurities, thus minimizing irreversible blockage. Target nanoscale impurity particles are mainly trapped by the surface layer near the outlet surface (rather than the deep pores inside the filter membrane). Furthermore, the dense distribution of outlet holes on the outlet surface disperses the trapping pressure, making it easier for impurity particles trapped by the filter membrane to be removed by backwashing, which helps extend the service life of the filter membrane. Furthermore, this asymmetric combination structure makes the filter membrane adaptable to extreme operating conditions in semiconductor wet processes. For example, when using the filter membrane described in this application to filter dilute HF acid solution (etching solution), the "large pores and sparse distribution" of the inlet surface can intercept the debris generated by etching in the etching solution (whose particle size is usually greater than 50 nm), preventing it from entering the filter membrane and damaging the separation layer; while the "small pores (but slightly larger than the target impurity particle size) and dense distribution" of the outlet surface can allow HF molecules in the etching solution to pass freely without affecting the effective components of the etching solution, while the separation layer near the outlet surface traps nanoscale impurity particles (e.g., colloidal particles with a particle size of 1 to 10 nm).

[0054] In one embodiment, the specific surface area of ​​the filter membrane is 6 m². 2 / g~20m 2 / g;

[0055] The average thickness of the separation layer is 0.8 μm to 10 μm, and the ratio between the average thickness of the separation layer and the average thickness of the filter membrane body is not greater than 0.15.

[0056] The specific surface area of ​​the filter membrane is the total surface area per unit mass of the filter membrane (including the inner surface of the membrane pores). The specific surface area of ​​the filter membrane largely reflects the size of the pore wall area. The inventors have discovered that if the specific surface area of ​​the filter membrane is low (e.g., <6m²), 2 / g), the membrane pores are sparse, the total flow area is insufficient, the flux is limited, and pollutants tend to concentrate and deposit in a few channels, causing rapid clogging; if the specific surface area of ​​the filter membrane is high (e.g., >20m²), 2 The membrane has dense pores (especially nanoscale pores) and close spacing between channels, making it prone to cross-linking and blockage due to surface tension or charge attraction within the pore walls (such as the adsorption and aggregation of metal ions in semiconductor filtration). Simultaneously, an excessively high internal surface area of ​​the membrane pores increases the frictional resistance between the fluid and the membrane material, thus reducing the filter flux. This application controls the specific surface area of ​​the filter membrane to 6m². 2 / g~20m 2 Within a range of / g, the filter membrane can provide a sufficient number of channels (to ensure the total flow area) while avoiding excessively dense channels that could affect fluid flow. This allows impurities to be evenly distributed on the channel surface, reducing the risk of localized clogging of the filter membrane.

[0057] The separation layer is the core region for trapping impurity particles. A thin separation layer (more preferably with an average thickness of 0.8 μm to 10 μm) can reduce mass transfer resistance (mass transfer resistance is approximately proportional to the thickness of the separation layer), while a suitable specific surface area (6 m²) is also beneficial. 2 / g~20m 2 The combination of / g) ensures a sufficient number of pores, which significantly improves the flux of the filter membrane and shortens the residence time of the fluid in the separation layer. Impurity particles are more easily trapped in the separation layer (rather than in the deep pores inside the filter membrane). Combined with the coarse interception effect of the inlet surface, the filter membrane becomes "primarily surface-contaminated" after use. During backwashing, only low pressure is needed to remove contaminants from the filter membrane, ensuring its cleanliness. The moderate specific surface area reduces the "weak points" of the membrane material, which can improve the filter membrane's resistance to corrosion by chemicals commonly used in the semiconductor field (such as HF solution) and extend the service life of the filter membrane.

[0058] Since even minute contaminants can affect chip quality, when using the filter membrane described in this application to filter liquid processing reagents used in semiconductor wet processes, it is necessary to strictly control the leaching of various components (such as PES monomers and additives) in the membrane material. The thin separation layer and moderate specific surface area of ​​the filter membrane avoid the "excessive number of active sites on the material surface" (easily releasing small molecule impurities) caused by a high specific surface area. The two work together to effectively reduce the leaching of various components of the filter membrane during filtration, meeting the stringent requirements for reagent purification in semiconductor wet processes.

[0059] The specific surface area of ​​the filter membrane described in this application can be measured by the BET specific surface area test method.

[0060] In a preferred embodiment, the initial water contact angle of the liquid outlet surface is 35° to 65°;

[0061] The initial water contact angle of the inlet surface is greater than that of the outlet surface, and the difference between the water contact angles of the inlet surface and the outlet surface is 5° to 20°.

[0062] This application controls the initial water contact angle of the filter membrane outlet surface within the range of 35° to 65°, and the difference in water contact angle between the inlet and outlet surfaces within the range of 5° to 20°. This makes the outlet surface more hydrophilic than the inlet surface, but not to the point of being "overly hydrophilic." This "gradient hydrophilicity" design brings several advantages during the filtration process, making the filter membrane provided by this application suitable for scenarios in the semiconductor ultrapure filtration field where the flux stability and antifouling resistance of the filter membrane are extremely demanding. The specific advantages are as follows:

[0063] A moderately hydrophobic (but still weakly hydrophilic) inlet surface reduces the strong adsorption of water molecules, allowing fluid to more easily penetrate the membrane surface and enter its internal channels, thus reducing initial flow resistance. When fluid reaches the outlet surface from the membrane channels, the more hydrophilic outlet surface accelerates fluid detachment from the membrane surface (reducing water adhesion and retention), promoting rapid permeate removal from the membrane and preventing fluid accumulation bottlenecks at the outlet pores. The reduced fluid retention at the inlet surface and the accelerated fluid detachment at the outlet surface create a "push-pull" mass transfer dynamic, reducing concentration polarization across the membrane (excessive solute enrichment on the membrane surface) and maintaining long-term flux stability (especially in high-flow-rate, low-pollution ultrapure filtration, reducing flux decay caused by concentration polarization).

[0064] The liquid treatment reagents to be filtered (such as deionized water, hydrofluoric acid solution, etc.) may contain trace amounts of colloids (such as SiO2), organic matter (TOC) or metal ions. A moderately hydrophobic inlet surface can reduce the strong adsorption of polar contaminants (such as colloids with hydroxyl groups) (polar contaminants are more likely to adhere to strongly hydrophilic surfaces), thus reducing the risk of surface contamination of the filter membrane. A more hydrophilic outlet surface can prevent trace contaminants (such as detached microparticles) that may remain in the permeate from adhering to the outlet orifice, while also reducing "water bridge blockage" at the end of the membrane pores caused by hydrophobicity (water molecules form bubbles or remain at the hydrophobic orifice due to surface tension).

[0065] This application has repeatedly studied how to achieve a mass transfer effect of "easy entry at the inlet and easy exit" by adjusting the difference in water contact angle between the liquid surface and the inlet surface. At the same time, it balances the antifouling and stability of the filter membrane, making it particularly suitable for ultrapure filtration scenarios that are sensitive to flux decay and have complex types of pollutants, thus taking into account both filter membrane performance and practicality.

[0066] The initial water contact angle described in this application can be obtained by testing it using the following method: using water as the test liquid, a contact angle tester is used to test it. When 10μL to 100μL water droplets are uniformly applied to the material surface for an instant (within 0.4s), a regular contact angle is formed.

[0067] In one embodiment, in the thickness direction of the filter membrane body, the liquid inlet surface of the pre-filtration layer is taken as the position where the thickness of the filter membrane body is 0%, and the liquid outlet surface of the separation layer is taken as the position where the thickness of the filter membrane body is 100%.

[0068] In the wetted filter membrane body, the capture peak value for colloidal gold with a diameter of 2 nm is D. The D region is located in the area of ​​90% to 99.8% of the thickness of the filter membrane body, and the distance between the D region and the liquid outlet surface is 0.2 μm to 8 μm.

[0069] In semiconductor wet processes, the liquid reagent to be filtered contains nanoscale particulate impurities (typically a few nanometers to tens of nanometers). This application uses a filter membrane to retain 2nm colloidal gold. The distribution of colloidal gold in the filter membrane can reflect the filter membrane's retention effect on nanoscale particles.

[0070] In this application, the capture peak value for 2nm colloidal gold is defined as D, where D is the region where the membrane retains the most 2nm colloidal gold. If D is too far from the liquid outlet, the 2nm gold nanoparticles are prematurely trapped within the membrane, resulting in a capture peak value too far from the liquid outlet. This not only renders most of the membrane unused but also makes the membrane surface prone to blockage by nanoscale particulate impurities, causing the membrane flux to rapidly decrease during filtration and consequently leading to a sharp drop in the membrane's retention efficiency for nanoparticle impurities. Conversely, if D is too close to the liquid outlet, the gold nanoparticles have a long penetration distance within the membrane. When the separation layer is thinned, using the membrane described in this application to filter liquid treatment agents (such as hydrofluoric acid solutions) in semiconductor wet processes allows for complete penetration of nanoparticle impurities in the liquid treatment agents during filtration at higher pressures. Because the filter membrane body in this application has a suitable pore size gradient and a large pore size ratio between the inlet and outlet surfaces, there is a certain distance between the capture peak D and the outlet surface. This distance is from 90% to 99.8% of the thickness of the filter membrane body, and the distance between the D portion and the outlet surface is 0.2 μm to 8 μm. This structure ensures that the filter membrane can efficiently trap nanoparticle impurities, preventing nanoparticle impurities in the liquid treatment agent used in semiconductor wet processes from penetrating the filter membrane and reducing the risk of impurity leakage. It also ensures the high throughput of the filter membrane in this application. At the same time, the nanoparticle impurities are distributed inside the filter membrane body and are not concentrated on its two sides, thus reducing the flux decay rate of the filter membrane.

[0071] After filtering the 2nm colloidal gold solution, the filter membrane was cut into sections and measured with an optical microscope. The darkest part of the section was found to be the capture peak. Alternatively, after testing with an EDS spectrometer, the location of the peak was the capture peak. The part of the filter membrane that retains the most 2nm colloidal gold was found to be the part inside the filter membrane.

[0072] In a preferred embodiment, in the wet filter membrane body, the thickness of the region where the capture peak of colloidal gold with a diameter of 2 nm is not less than 80% of the capture peak value D is Q, where Q is 0.3 μm to 5 μm, and Q accounts for 0.5% to 8% of the thickness of the filter membrane body.

[0073] In this application, within the wetted filter membrane body, the thickness Q of the region containing the capture peak of 2 nm colloidal gold at a diameter not less than 80% of the capture peak value D (Q is the capture peak region; the existence of the capture peak region ensures that the porous membrane can fully retain 20 nm colloidal gold) reflects the retention distribution of gold nanoparticles within the filter membrane body. A smaller Q value indicates that the retention of gold nanoparticles is mainly concentrated in a thin layer region within the filter membrane (i.e., the capture peak region is more concentrated); a larger Q value indicates that the retention of gold nanoparticles is distributed over a wider thickness range within the filter membrane (i.e., the capture peak region is more dispersed).

[0074] If the Q value accounts for a small proportion of the thickness of the filter membrane, it indicates that the retention height of the gold nanoparticles is concentrated in the peak capture area of ​​the filter membrane (the area not less than 80% of the peak capture value D). Under these circumstances, the nanoparticles are prone to rapidly accumulate in this thin-layer area through aggregation or adsorption, filling the surface pores of the filter membrane. This leads to a sharp reduction in the effective filtration pore size of the filter membrane and a significant increase in mass transfer resistance, which in turn causes a sharp drop in the filter membrane flux.

[0075] If the Q value accounts for a large proportion of the filter membrane thickness, it indicates that the gold nanoparticles are trapped and distributed in a wider area within the filter membrane (the area spanning at least 80% of the capture peak D is large). In this case, the nanoparticles can easily penetrate into the deep areas of the filter membrane. In the early stages of use, the flow rate is relatively high because the surface pores are not heavily blocked. However, in the later stages of use, the nanoparticles will gradually accumulate in the deep pores, resulting in a reduction in the effective filtration pore size in the deep layers of the filter membrane. Furthermore, because the blockage is located in the deep layers, chemical reagents have difficulty penetrating, significantly increasing the difficulty of cleaning.

[0076] The filter membrane body of this application has a high porosity, which can ensure a sufficient number of effective membrane pores per unit area and ensure smooth mass transfer of the filter membrane. The thickness of the capture peak of colloidal gold with a diameter of 2 nm in the region not less than 80% of the capture peak value D is denoted as Q, where Q is 0.3 μm to 5 μm and Q accounts for 0.5% to 8% of the thickness of the filter membrane body. Under the synergistic effect of this structure and high porosity, the retention and dispersion of nanoparticles by the filter membrane body and the smooth mass transfer of the filter membrane body are balanced, ensuring that the retention depth of nanoparticles in the filter membrane body is appropriate, reducing the risk of filter membrane clogging, and improving the flux and retention efficiency of the filter membrane.

[0077] During EDS testing, the location of the peak area Q can be considered as an area where the gold content is not less than 80% of the gold content at the peak location (the CPS value of the peak area Q is usually not less than 80% of the CPS peak value); of course, those skilled in the art can also obtain the above parameters through other measurement methods, and the above measurement methods are for reference only.

[0078] In a preferred embodiment, the filter membrane body includes a flow guiding region located in an area of ​​3% to 85% of the thickness of the filter membrane body; the ratio of the average thickness of the flow guiding region to the average thickness of the filter membrane body is (0.1 to 0.6):1.

[0079] In this application, the guiding zone is defined as: the region along the film thickness direction where almost no colloidal gold residue remains when a retention test is performed using colloidal gold with a particle size of 2 nm as the target impurity particle. This region has high porosity and high fluid velocity, making it difficult for colloidal gold to remain, thus resulting in virtually no residue. The average thickness of the guiding zone is determined by performing multiple position measurements along the film thickness direction (preferably at least 5 measurements, with each measurement position evenly spaced along the film thickness direction to meet statistical representativeness requirements), and taking the average of the measurement results; if multiple discontinuous guiding zones exist within the film, the average thickness of the guiding zone is the sum of the thicknesses of each zone. The retention test can be performed using the following methods: ① Refer to the retention test method described in Chinese Patent CN105980038B (Title: Membrane for Virus Removal); ② Alternatively, the gold element distribution in the membrane cross-section can be determined by energy-dispersive X-ray spectroscopy (EDS): when scanning along the membrane thickness direction, the gold element characteristic peak count rate (CPS) in the flow-guiding region is close to the baseline level and the signal is stable (approximately linear). It should be noted that the flow-guiding region exists only in the pre-filter layer, and the gold element CPS value in other areas of the pre-filter layer, excluding the flow-guiding region, will show significant fluctuations rather than a stable linear trend due to the presence of colloidal gold residue. Of course, those skilled in the art can also use other measurement methods that can characterize the distribution of 2nm colloidal gold in the membrane cross-section; the above methods are merely examples.

[0080] The synergistic effect of the location of the flow guiding zone (3% to 85% of the filter membrane thickness) and the thickness ratio (the ratio of average thickness to average filter membrane thickness is (0.1 to 0.6):1) mainly achieves the following core effects by optimizing the fluid mass transfer path, balancing the functional zoning of the structure, and reducing filtration resistance:

[0081] 1. Efficient flow guidance reduces mass transfer resistance and improves flux stability.

[0082] The flow-guiding zone has high porosity (porosity can reach over 70%, often with a finger-like pore structure), extremely low fluid resistance, and its location is limited to 3%–85% of the filter membrane's main thickness (not the surface or excessively deep layer), forming a "high-efficiency flow-guiding channel" that runs through the middle and rear of the filter membrane. Combined with a thickness ratio of (0.1–0.6):1 (ensuring sufficient flow-guiding space while avoiding excessive occupation of the overall filter membrane thickness), this further increases the filter membrane's flux, reduces fluid residence time inside the filter membrane, and lowers local resistance increases caused by fluid accumulation, thereby maintaining high flux and reducing flux fluctuations.

[0083] 2. Avoid residue in non-retention areas to protect retention efficiency and reduce the risk of clogging.

[0084] The presence of virtually no colloidal gold residue in the flow-guiding zone indicates that it does not participate in nanoparticle retention but only serves a flow-guiding function. Its location (3%–85%) avoids the separation layer region where the main retention occurs, preventing nanoparticle accumulation in the flow-guiding zone. Simultaneously, the thickness ratio of (0.1–0.6):1 controls the "depth range" of the flow-guiding zone, preventing it from extending excessively into the deep layers of the filter membrane (avoiding the deep pores being occupied by irrelevant particles). This synergistic effect ensures that nanoparticles are retained only in the dedicated retention area of ​​the separation layer, while the flow-guiding zone remains unobstructed, reducing ineffective clogging in non-retention areas and indirectly extending the filter membrane's lifespan.

[0085] 3. Balanced structural functional zones ensure overall stability of the filter membrane.

[0086] The location and thickness ratio of the flow-guiding zone complement the retention zone (separation layer, Q zone) to form a functional division: the flow-guiding zone is responsible for rapid mass transfer, and the separation layer is responsible for efficient retention. A thickness ratio of (0.1~0.6):1 avoids compressing the effective thickness of the retention zone due to an excessively thick flow-guiding zone (ensuring the structural space required for retention), and also avoids insufficient flow-guiding capacity due to an excessively thin flow-guiding zone; at the same time, combined with the material stability of sulfone polymers, the integrity of the membrane structure can still be maintained under specific pressure environments, ensuring the functional stability of the filter membrane during long-term use.

[0087] The synergistic effect of the two, through the design of "directional flow guidance, zoned function and structural adaptation", ensures efficient retention of nanoparticles while minimizing mass transfer resistance and reducing ineffective clogging. Ultimately, it achieves comprehensive performance of high throughput, low attenuation and long life of the filter membrane, which is especially suitable for the stringent requirements of filtration efficiency, cleanliness and stability in semiconductor wet process.

[0088] In one embodiment, the flow rate of the filter membrane is 40–180 s @ 50 mL @ 20 ° C @ φ47 mm; the TOC leaching amount of the filter membrane does not exceed 0.5 ppb, and the metal ion precipitation amount does not exceed 10 ppt.

[0089] The flow rate of the filter membrane refers to the time required for 50 ml of water to pass through a 47 mm diameter filter membrane under a positive pressure of 0.03 MPa and a temperature of 20 °C. This value reflects the filtration rate of the filter membrane. The faster the flow rate of the filter membrane (the shorter the time), the faster the filtration rate and the greater the flux.

[0090] In this application, the amount of metal ion leaching from the filter membrane can be tested by the following method: The rinsed and dried filter membrane is prepared to have an effective filtration area of ​​0.2 m². 2 The filter element was then immersed in 0K73 test reagent (a mixed solvent of 70% by mass propylene glycol monomethyl ether and 30% by mass propylene glycol monomethyl ether acetate) for 24 hours. The impurity content in the test reagent (the impurities mainly include metal ions, which are measured by ICPMS) was then measured to determine the amount of metal ion leaching from the filter membrane. Of course, those skilled in the art can obtain the above parameters through other measurement methods; the above measurement methods are for reference only.

[0091] The TOC leaching amount of the filter membrane can be tested by the following method: The filter membrane, after rinsing and drying, is prepared to have an effective filtration area of ​​0.2 m². 2 The filter element was then rinsed with ultrapure water at a flow rate of 20L and a flow rate of 500ml / min. The downstream filtrate was then subjected to a total organic carbon (TOC) test (using a total organic carbon analyzer) to determine the TOC leaching amount from the filter membrane. Of course, those skilled in the art can obtain the above parameters through other measurement methods; the methods described above are for reference only.

[0092] Through water flux testing, the flow rate of the filter membrane of this invention is 40–180 s@50 mL@20℃@φ47 mm. The filter membrane has a large flux, which can perform nanoscale purification of a large volume of liquid treatment reagents used in semiconductor wet processes in a short time, resulting in high economic benefits. In addition, due to the relatively thin separation layer, the specific pore size of the liquid outlet (SEM average pore size of 4 nm–30 nm), and the asymmetric pore size of the inlet and outlet pores, its own impurities are easily cleaned, greatly reducing the cleaning difficulty, saving time and effort. At the same time, after cleaning, its own cleanliness is very high. Through testing, the TOC dissolution of the filter membrane of this application does not exceed 0.5 ppb, and the metal ion precipitation does not exceed 10 ppt, ensuring that no impurities are introduced during long-term filtration, enabling the filter membrane of this application to be used for nanoscale purification of liquid treatment reagents used in semiconductor wet processes.

[0093] Secondly, this application provides a method for preparing an asymmetric sulfone polymer nanoscale filter membrane as described in the first aspect, comprising the following steps:

[0094] S1. Prepare a casting solution and cast the casting solution onto a carrier to form a liquid film; the casting solution includes the following components: sulfone polymer, a first solvent, a volatile second solvent, and a pore-forming agent;

[0095] The weight-average molecular weight of the sulfone polymer is 20,000 to 150,000 (more preferably 30,000 to 100,000), and the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 2 to 4.5 (more preferably 2 to 3.6).

[0096] The pore-forming agent includes at least one of polyvinyl alcohol, polyethylene glycol, polyethyleneimine, and polyvinylpyrrolidone, and the solid content of the casting solution is 12% to 20%.

[0097] S2. Place the liquid film under the first phase separation condition for pre-phase separation treatment until the turbidity point is reached, and the pre-phase separation treatment is completed; wherein, the liquid film reaching the turbidity point and the pre-phase separation treatment being completed means that before the pre-phase separation treatment, the turbidity of the liquid film is A, and after the pre-phase separation treatment, the turbidity of the liquid film increases to 1.03A.

[0098] S3. The pre-phase-separated liquid film is placed in a coagulation bath for re-phase separation treatment to obtain a raw film; the coagulation bath includes water, a third solvent and an additive, the mass percentage of the third solvent in the coagulation bath is 5% to 15%, the mass percentage of the additive in the coagulation bath is 1% to 5% (more preferably 1.5% to 3.5%), and the re-phase separation treatment time is 10s to 80s (more preferably 25s to 75s);

[0099] S4. The biofilm obtained in step S3 is washed and dried to obtain an asymmetric sulfone polymer nanoscale filter membrane.

[0100] In one embodiment, the sulfone polymer is at least one selected from bisphenol A polysulfone, polyether sulfone, and polyphenylsulfone;

[0101] The first solvent includes at least one of dimethyl sulfoxide, N-ethylpyrrolidone, N-methylpyrrolidone, and dimethylacetamide;

[0102] The second solvent includes at least one of acetone, tetrahydrofuran, and ethyl acetate.

[0103] In one embodiment, the mass ratio of the first solvent to the second solvent in the casting solution is (2-7):1.

[0104] In one embodiment, the casting solution comprises the following components in parts by weight: 13 to 20 parts of sulfone polymer, 50 to 80 parts of a first solvent, 10 to 25 parts of a volatile second solvent, and 2 to 9 parts of a pore-forming agent.

[0105] In one embodiment, in step S2, the liquid film is placed under the first phase separation condition for pre-phase separation treatment, specifically, the liquid film is placed under the condition of 50°C to 80°C for pre-phase separation treatment, and the pre-phase separation treatment time is 0.5s to 10s.

[0106] In step S2, during the pre-phase separation treatment, a continuous airflow is blown onto the surface of the liquid film. The absolute humidity of the airflow is 5 g H2O / kg to 20 g H2O / kg, and the flow rate of the airflow is 5 m / min to 20 m / min.

[0107] In one embodiment, in step S3, the third solvent is acetone or tetrahydrofuran;

[0108] The molecular weight of the additive is less than 100, and the additive includes at least one of isopropanol, ethanol, ethylene glycol, propylene glycol, glycerol and sodium chloride.

[0109] And / or, the mass ratio of the third solvent to the additive is (2-8):1.

[0110] By adopting the above technical solution, in preparing the asymmetric sulfone polymer filter membrane of the present invention, a casting solution is first prepared. The casting solution includes a sulfone polymer (the film-forming substance, which has good film-forming processing properties), an organic solvent (for dissolving the sulfone polymer), and a pore-forming agent (for adjusting the pore structure). As one of the inventive aspects of the present invention, the preparation of the casting solution is quite unique. The organic solvent includes a first solvent and a second solvent. The first solvent includes at least one of dimethyl sulfoxide, N-ethylpyrrolidone, N-methylpyrrolidone, and dimethylacetamide. The second solvent includes at least one of acetone, tetrahydrofuran, and ethyl acetate. The second solvent is more volatile than the first solvent. Preferably... The mass ratio of the first solvent to the second solvent in the casting solution is (2-7):1, meaning that the content of the first solvent in the casting solution is slightly higher than that of the second solvent. The core function of the first solvent is to maintain the stability of the liquid film and regulate the thickness of the separation layer (suppressing excessive phase separation). The core function of the second solvent (which is easily volatile) is to trigger a uniform pre-phase separation treatment, laying the foundation for a thin separation layer. Under the synergistic effect of these two solvents, the phase separation rate and structural uniformity can be balanced, achieving a "thin and uniform" separation layer. Through the synergistic effect of a suitable pre-phase separation process, the moderate evaporation of the second solvent triggers uniform surface phase separation, while the first solvent maintains the internal stability of the liquid film, together forming a system where the surface first gels while the interior remains liquid. The asymmetric structure prototype lays the foundation for the "thinness" of the separation layer (surface layer). Subsequently, combined with a suitable re-phase separation process, through the exchange of the first solvent with the coagulation bath, and the pre-phase separation treatment already completed by the second solvent, the separation layer thickens uniformly during gelation (rather than growing randomly), ultimately forming a thin separation layer of uniform thickness. Furthermore, with appropriate solid content and suitable molecular weight and molecular weight distribution of the sulfone polymer, macropores or defects caused by local concentration abrupt changes during phase separation can be reduced, ensuring a more uniform pore distribution in the separation layer and facilitating a slightly wider overall pore size distribution while maintaining the core characteristic of efficient 2nm colloidal gold retention. This results in a separation layer (nanopores + high-efficiency retention). Furthermore, research has revealed that molecular chains with medium molecular weights (20,000 to 150,000, preferably 30,000 to 100,000) at a solid content of 12% to 20% can easily form relatively uniform nanoscale pores (just enough to efficiently retain 2nm colloidal gold) through moderate entanglement and ordered phase separation, and the structure is stable. Moreover, the wide molecular weight distribution (reflected by the ratio of the weight-average molecular weight to the number-average molecular weight of sulfone polymers being 2 to 4.5) works synergistically with a certain solid content, utilizing the phase separation differences of molecules with different chain lengths, while forming nanopores in the separation layer, a relatively large pore structure is formed in the membrane body, ultimately achieving a balance between "retention precision (nanoscale)" and "filtration efficiency (high porosity, wide distribution ensures flux)".

[0111] The pore-forming agent in the casting solution includes at least one of polyvinyl alcohol, polyethylene glycol, polyethyleneimine, and polyvinylpyrrolidone. These polymeric pore-forming agents have good compatibility with sulfone polymers in solvents. They are also highly hydrophilic and can diffuse rapidly in the coagulation bath, promoting the formation of membrane pore structures. This is beneficial for the final filter membrane to have an ideal pore size distribution and high porosity, achieving a balance between high flux and efficient retention of nanoparticles.

[0112] Then, a pre-phase separation treatment is performed. This is done by placing the nascent membrane under the first phase separation conditions until the turbidity point is reached, at which point the pre-phase separation treatment is complete. During the pre-phase separation treatment, the original solution components in the nascent membrane will exchange with external components at a suitable rate, causing the initial membrane to gradually become turbid from clear. In this invention, the moment when the nascent membrane changes from clear to turbid is recorded as the turbidity point. Before the pre-phase separation treatment, the turbidity of the nascent membrane is A. After the pre-phase separation treatment, when the turbidity of the nascent membrane increases to 1.03A, the nascent membrane reaches the turbidity point, which also marks the completion of the pre-phase separation treatment. Preferably, during the pre-phase separation process, a continuous airflow is blown onto the surface of the liquid film. Through the synergistic effect of temperature (50℃~80℃), airflow humidity (absolute humidity of 5gH2O / kg~20gH2O / kg), and a suitable casting solution formulation, the liquid film undergoes relatively rapid phase separation on the air side. This results in smaller pores on the air side (due to the limited airflow humidity, the pore size on this side is not too small), which is conducive to the formation of a relatively thin and uniform separation layer. In addition, the relative flow velocity between the airflow and the liquid film is 5m / min~20m / min, and the duration is 0.5s~10s. After such pre-phase separation treatment, both an ideal separation layer and an ideal membrane pore structure can be obtained.

[0113] The inventors discovered that if the turbidity of the nascent membrane after pre-phase separation is too low (<1.03 Å), the phase separation is insufficient, the surface polymer concentration is inadequate, and large pores or defects are easily formed on the effluent surface during subsequent phase separation, leading to a decrease in the membrane's retention rate. If the turbidity of the nascent membrane after pre-phase separation in step S2 is too high (>1.03 Å), the surface is excessively gelled, the membrane pore size is too small or closed, and the flux is significantly reduced. If the turbidity of the nascent membrane after pre-phase separation reaches the critical point of 1.03 Å, it can ensure the formation of a sufficiently thin and uniform separation layer while maintaining appropriate membrane pore size and connectivity to fully retain 2 nm colloidal gold, achieving a balance between retention rate and flux.

[0114] If the pre-phase separation temperature is too low (<50℃), the solvent evaporates slowly, delaying the start-up of phase separation, which may result in a thicker separation layer or uneven membrane pore size. If the pre-phase separation temperature is too high (>80℃), the solvent evaporates too quickly, and a dense separation layer will instantly form on the surface, hindering the exchange between solvent and non-solvent in subsequent steps. This leads to a smaller pore size at the liquid outlet or even closed pores, resulting in a high rejection rate but extremely low flux of the filter membrane. This invention controls the pre-phase separation temperature within the range of 50℃ to 80℃, matching the solvent evaporation rate with the phase separation rate, forming a uniform separation layer rudiment on the liquid membrane surface, laying the foundation for the formation of a thin and uniform separation layer in the future.

[0115] This invention achieves forced convection by continuously blowing airflow onto the surface of the liquid film, accelerating solvent evaporation and water vapor adsorption, while simultaneously removing solvent vapor from the liquid film surface, maintaining a stable mass transfer gradient, thereby optimizing the pore size and pore density of the liquid surface; the water vapor in the airflow will be adsorbed on the surface of the liquid film and gradually diffuse into the interior. As a non-solvent, the water vapor will reduce the solubility of the polymer by the solvent (such as DMF, NMP, etc.), further promoting phase separation. If the humidity of the airflow is too low (<5gH2O / kg), water vapor intrusion is too slow, and phase separation is mainly driven by solvent evaporation, easily forming membrane pores with large pore sizes but few in number, thus leading to insufficient filter membrane retention. If the humidity of the airflow is too high (>20gH2O / kg), water vapor intrusion is too fast, causing instantaneous surface gelation, forming a preliminary "glassy" separation layer with extremely small pore sizes or even no pores, thus leading to excessively high filter membrane retention but extremely low flux. This invention controls the humidity of the airflow within a suitable range (5gH2O / kg~20gH2O / kg), allowing water vapor to intrude slowly, working synergistically with solvent evaporation to form a membrane pore structure with "slightly larger pore sizes (greater than 2nm) and denser distribution" on the liquid outlet surface, thereby... This invention aims to improve the retention rate of 2nm colloidal gold in the filter membrane while ensuring high flux. If the airflow velocity is too low (<5m / min), the mass transfer efficiency will be too low, leading to uneven solvent evaporation and water vapor intrusion, resulting in an excessively wide pore size distribution in the separation layer, or even local defects (such as macropores or cracks). If the airflow velocity is too high (>20m / min), it may break the liquid membrane surface, disrupting the continuity of the separation layer, or causing rapid evaporation of the surface solvent, forming an overly dense layer. This invention controls the airflow velocity within a moderate range of 5m / min to 20m / min, ensuring uniform solvent evaporation and water vapor intrusion across the entire liquid membrane surface, forming a preliminary separation layer with relatively uniform thickness and a relatively dense pore distribution.

[0116] Therefore, this invention constructs an ideal separation layer structure through the synergistic effect of various pre-phase separation treatment conditions. First, by precisely controlling the turbidity from A to 1.03A, the optimal critical point for phase separation is locked, balancing the filter membrane's rejection rate and flux. Preferably, a suitable pre-phase separation treatment temperature (50℃~80℃) is used to moderately accelerate solvent evaporation, resulting in uniform phase separation on the liquid membrane surface and forming a thin and continuous preliminary separation layer. A suitable airflow humidity (5gH2O / kg~20gH2O / kg) is used to regulate the water vapor intrusion rate, inducing the formation of a membrane pore structure with a pore size slightly larger than 2nm and a dense number of pores. A suitable airflow velocity (5m / min~20m / min) ensures uniform exchange of solvent and water vapor on the liquid membrane surface, avoiding the formation of local defects and improving the uniformity of the membrane pore distribution on the liquid outlet surface. Under the synergistic effect of the above features, an ideal separation layer is finally formed. At the same time, a high-porosity internal structure is constructed through a subsequent re-phase separation process, achieving high overall filter membrane performance.

[0117] The turbidity described in this application can be determined by a turbidity meter; alternatively, several turbidity detection sensors can be installed in the corresponding membrane production line to monitor the turbidity of each section of the membrane in real time.

[0118] Next, after the pre-phase separation treatment, the nascent membrane after pre-phase separation treatment is placed in a coagulation bath for further phase separation treatment. The coagulation bath includes water, a third solvent, and an additive. The third solvent is acetone or tetrahydrofuran; the additive includes at least one of isopropanol, ethanol, ethylene glycol, propylene glycol, hexanol, heptanol, and octanol. The mass percentage of the third solvent in the coagulation bath is 5% to 15%, and the mass percentage of the additive in the coagulation bath is 1% to 5%. By controlling the content and ratio of the third solvent and the additive in the coagulation bath, the diffusion rate of non-solvent components in the coagulation bath to the casting solution can be accelerated, while promoting the migration of solvent components in the casting solution to the coagulation bath. This quickly breaks the homogeneous equilibrium, shortens the phase separation treatment time to 10s to 80s (more preferably 25s to 75s), and avoids membrane structure defects caused by excessively rapid phase separation.

[0119] This invention employs a unique formulation of water, a third solvent, and additives as a coagulation bath. Combined with the control of phase separation treatment time, it achieves regulation of gradient solvent exchange kinetics and interfacial physicochemistry, precisely shaping the asymmetric pore structure of the filter membrane (especially the separation layer and flow guiding zone structure), as detailed below:

[0120] (1) The third solvent in the coagulation bath (such as acetone, tetrahydrofuran, etc.) is miscible with the first solvent in the casting solution (such as DMF, NMP, etc.) and both have a certain solubility in water. When the liquid membrane is immersed in the coagulation bath, the presence of the third solvent will reduce the diffusion rate of water into the membrane to a certain extent. If the mass percentage of the third solvent in the coagulation bath is too low (<5%), water diffuses into the membrane rapidly, resulting in the instantaneous formation of a dense separation layer on the membrane surface, which in turn leads to a high rejection rate but extremely low flux of the filter membrane. If the mass percentage of the third solvent in the coagulation bath is too high (>15%), water diffuses into the membrane too slowly. This coarsens the pores of the prepared filter membrane, leading to a decrease in the filter membrane's rejection rate. The present invention controls the mass percentage of the third solvent in the coagulation bath to within the range of 5% to 15%, forming "bidirectional diffusion," where the solvent (such as the first solvent) diffuses from inside the membrane into the coagulation bath, while non-solvent water diffuses from the coagulation bath into the membrane. This bidirectional diffusion creates concentration gradients for both solvent and non-solvent within the membrane, triggering asymmetric growth of "liquid-liquid phase separation." It preferentially forms a flow-guiding region (porosity can reach 70% to 90%, often with a finger-like pore structure) on the membrane bulk (non-surface), providing a high-flux channel for the filter membrane.

[0121] (2) An additive is introduced into the coagulation bath. The mass percentage of the additive in the coagulation bath is 1% to 5% (more preferably 1.5% to 3.5%), which is beneficial to adjust the hydrophilicity and hydrophobicity of the inlet and outlet liquid surfaces, so that the inlet and outlet liquid surfaces have suitable water contact angles respectively.

[0122] (3) Under the combined effect of the third solvent, additives and the time of re-phase separation treatment, the final structural morphology of different regions is locked to form an ideal pre-filtration layer and liquid inlet membrane pore structure.

[0123] If the mass ratio of the third solvent to the additive is greater than 8:1 (too much third solvent and too little additive), the solvent exchange will be too slow, resulting in large membrane pores and a decreased retention rate. If the mass ratio of the third solvent to the additive is less than 2:1 (too little third solvent and too much additive), the gel may form a closed-pore structure too quickly. When the mass ratio of the third solvent to the additive is (2-8):1, the third solvent slows down the intrusion of water through the concentration gradient, while the additive accelerates local phase separation through physicochemical effects. This balance of "slow and fast" allows the separation layer of the filter membrane to maintain a nanoscale pore size while promoting the formation of a flow-guiding zone (with high porosity and finger-like pore structure) and an ideal pre-filtration layer inside the filter membrane. This ensures a continuous transition between the separation layer and the pre-filtration layer and avoids the generation of interface defects (such as delamination or cracks).

[0124] The filter membrane finally obtained in this application has an ideal structure, which not only balances flux and retention efficiency, but also has the advantage of high cleanliness. The amount of TOC dissolution and metal ion precipitation is extremely small, making it suitable for the nanoscale purification of liquid processing reagents used in semiconductor wet processes.

[0125] Thirdly, this application provides an application of a sulfone polymer nanoporous filter membrane as described in the first aspect, wherein the filter membrane is used for the nanoscale purification of liquid processing reagents used in semiconductor wet processes. Based on the physical and chemical properties of sulfone polymer materials, the filter membrane prepared by this invention has good hydrophilicity and chemical compatibility, and is suitable for use in low-temperature weak acid, alkali and aqueous solutions. It exhibits excellent and stable filtration performance for nanoscale impurities (preferably 1-10 nm) in common WEC solutions such as DHF (hydrofluoric acid), DIW (deionized water), ST250 (photoresist remover), CO2 water (carbon dioxide aqueous solution) and BOE (buffered oxide etchant, composed of hydrofluoric acid and ammonium fluoride). Attached Figure Description

[0126] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0127] Figure 1 This is a scanning electron microscope (SEM) schematic diagram of the overall cross-section of the filter membrane prepared in Example 3 of this application, and the magnification in the figure is 500×.

[0128] Figure 2 This is a scanning electron microscope (SEM) schematic diagram showing a further magnified cross-section of the filter membrane prepared in Example 3 of this application, with a magnification of 700×.

[0129] Figure 3 This is a scanning electron microscope (SEM) schematic diagram of the liquid inlet surface of the filter membrane prepared in Example 3 of this application, and the magnification in the figure is 5000×.

[0130] Figure 4 This is a scanning electron microscope (SEM) schematic diagram of the liquid outlet surface of the filter membrane prepared in Example 3 of this application, and the magnification of the figure is 50000×.

[0131] Figure 5 This is a schematic diagram of the distribution curve of 2nm colloidal gold in the thickness direction of the filter membrane after a 2nm colloidal gold retention experiment was performed in Example 3 of this application. Detailed Implementation

[0132] To better illustrate the purpose, technical solution, and advantages of this application, the following description, in conjunction with specific embodiments and comparative examples, aims to provide a detailed understanding of the content of this application, rather than to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this application.

[0133] Example 1

[0134] This embodiment provides an asymmetric sulfone polymer nanoscale filter membrane, the preparation method of which includes the following steps:

[0135] S1. Prepare a casting solution and cast it onto a carrier to form a liquid film. The casting solution comprises the following components in parts by weight: 20 parts of sulfone polymer, 2 parts of pore-forming agent, 54 parts of first solvent, and 24 parts of volatile second solvent. The solid content of the casting solution is 20%, and the mass ratio of the first solvent to the second solvent in the casting solution is 2.25:1. The sulfone polymer is bisphenol A polysulfone, the weight-average molecular weight of the sulfone polymer is 100,000, and the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 2. The pore-forming agent is polyethylene glycol, the first solvent is N-ethylpyrrolidone, and the second solvent is ethyl acetate.

[0136] S2. Place the liquid film under the first phase separation condition for pre-phase separation treatment until the turbidity point is reached, and the pre-phase separation treatment is completed; wherein, the liquid film reaching the turbidity point and the pre-phase separation treatment being completed means that before the pre-phase separation treatment, the turbidity of the liquid film is A, and after the pre-phase separation treatment, the turbidity of the liquid film increases to 1.03A.

[0137] In step S2, the liquid film is placed under the first phase separation condition for pre-phase separation treatment. Specifically, the liquid film is placed under the condition of 80°C for pre-phase separation treatment for 9 seconds. During the pre-phase separation treatment of the liquid film, airflow is continuously blown onto the surface of the liquid film. The absolute humidity of the airflow is 18 g H2O / kg and the flow rate of the airflow is 19 m / min.

[0138] S3. The pre-phase-separated liquid film is placed in a coagulation bath for re-phase separation treatment to obtain a raw film; the coagulation bath includes water, a third solvent and an additive, the mass percentage of the third solvent in the coagulation bath is 5%, the mass percentage of the additive in the coagulation bath is 2%, the mass ratio of the third solvent to the additive is 2.5:1, the third solvent is tetrahydrofuran, and the additive is ethanol; the re-phase separation treatment time is 25s.

[0139] S4. The biofilm obtained in step S3 is washed and dried to obtain an asymmetric sulfone polymer nanoscale filter membrane.

[0140] Example 2

[0141] This embodiment provides an asymmetric sulfone polymer nanoscale filter membrane, the preparation method of which includes the following steps:

[0142] S1. Prepare a casting solution and cast the casting solution onto a carrier to form a liquid film; the casting solution comprises the following components in parts by weight: 19 parts of sulfone polymer, 3 parts of pore-forming agent, 56 parts of first solvent, and 22 parts of volatile second solvent; wherein, the solid content of the casting solution is 19%, the mass ratio of the first solvent to the second solvent in the casting solution is 2.55:1, the sulfone polymer is polyphenylene sulfone, the weight-average molecular weight of the sulfone polymer is 90,000, the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 2.2, the pore-forming agent is polyvinyl alcohol, the first solvent is N-methylpyrrolidone, and the second solvent is acetone;

[0143] S2. Place the liquid film under the first phase separation condition for pre-phase separation treatment until the turbidity point is reached, and the pre-phase separation treatment is completed; wherein, the liquid film reaching the turbidity point and the pre-phase separation treatment being completed means that before the pre-phase separation treatment, the turbidity of the liquid film is A, and after the pre-phase separation treatment, the turbidity of the liquid film increases to 1.03A.

[0144] In step S2, the liquid film is placed under the first phase separation condition for pre-phase separation treatment. Specifically, the liquid film is placed under a temperature of 75°C for pre-phase separation treatment for 8 seconds. During the pre-phase separation treatment of the liquid film, airflow is continuously blown onto the surface of the liquid film. The absolute humidity of the airflow is 16 g H2O / kg, and the flow rate of the airflow is 18 m / min.

[0145] S3. The pre-phase-separated liquid film is placed in a coagulation bath for re-phase separation treatment to obtain a raw film; the coagulation bath includes water, a third solvent and an additive, the mass percentage of the third solvent in the coagulation bath is 6%, the mass percentage of the additive in the coagulation bath is 1.5%, the mass ratio of the third solvent to the additive is 4.0:1, the third solvent is acetone, and the additive is isopropanol; the re-phase separation treatment time is 30s.

[0146] S4. The biofilm obtained in step S3 is washed and dried to obtain an asymmetric sulfone polymer nanoscale filter membrane.

[0147] Example 3

[0148] This embodiment provides an asymmetric sulfone polymer nanoscale filter membrane, the preparation method of which includes the following steps:

[0149] S1. Prepare a casting solution and cast the casting solution onto a carrier to form a liquid film; the casting solution comprises the following components in parts by weight: 16 parts of sulfone polymer, 5 parts of pore-forming agent, 62 parts of first solvent, and 18 parts of volatile second solvent; wherein, the solid content of the casting solution is 16%, the mass ratio of the first solvent to the second solvent in the casting solution is 3.44:1, the sulfone polymer is polyethersulfone, the weight-average molecular weight of the sulfone polymer is 70,000, the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 2.8, the pore-forming agent is polyvinyl alcohol, the first solvent is dimethyl sulfoxide, and the second solvent is ethyl acetate;

[0150] S2. Place the liquid film under the first phase separation condition for pre-phase separation treatment until the turbidity point is reached, and the pre-phase separation treatment is completed; wherein, the liquid film reaching the turbidity point and the pre-phase separation treatment being completed means that before the pre-phase separation treatment, the turbidity of the liquid film is A, and after the pre-phase separation treatment, the turbidity of the liquid film increases to 1.03A.

[0151] In step S2, the liquid film is placed under the first phase separation condition for pre-phase separation treatment. Specifically, the liquid film is placed under a temperature of 67°C for pre-phase separation treatment for 6 seconds. During the pre-phase separation treatment of the liquid film, airflow is continuously blown onto the surface of the liquid film. The absolute humidity of the airflow is 12 g H2O / kg and the flow rate of the airflow is 14 m / min.

[0152] S3. The pre-phase-separated liquid film is placed in a coagulation bath for re-phase separation treatment to obtain a raw film. The coagulation bath includes water, a third solvent, and an additive. The mass percentage of the third solvent in the coagulation bath is 8%, the mass percentage of the additive in the coagulation bath is 2.5%, the mass ratio of the third solvent to the additive is 3.2:1, the third solvent is acetone, and the additive is isopropanol. The re-phase separation treatment time is 45s.

[0153] S4. The biofilm obtained in step S3 is washed and dried to obtain an asymmetric sulfone polymer nanoscale filter membrane.

[0154] Example 4

[0155] This embodiment provides an asymmetric sulfone polymer nanoscale filter membrane, the preparation method of which includes the following steps:

[0156] S1. Prepare a casting solution and cast the casting solution onto a carrier to form a liquid film; the casting solution comprises the following components in parts by weight: 15 parts of sulfone polymer, 6 parts of pore-forming agent, 65 parts of first solvent, and 16 parts of volatile second solvent; wherein, the solid content of the casting solution is 15%, the mass ratio of the first solvent to the second solvent in the casting solution is 4.06:1, the sulfone polymer is bisphenol A polysulfone, the weight-average molecular weight of the sulfone polymer is 60,000, the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 3, the pore-forming agent is polyvinylpyrrolidone, the first solvent is dimethylacetamide, and the second solvent is tetrahydrofuran;

[0157] S2. Place the liquid film under the first phase separation condition for pre-phase separation treatment until the turbidity point is reached, and the pre-phase separation treatment is completed; wherein, the liquid film reaching the turbidity point and the pre-phase separation treatment being completed means that before the pre-phase separation treatment, the turbidity of the liquid film is A, and after the pre-phase separation treatment, the turbidity of the liquid film increases to 1.03A.

[0158] In step S2, the liquid film is placed under the first phase separation condition for pre-phase separation treatment. Specifically, the liquid film is placed under the condition of 62°C for pre-phase separation treatment, and the pre-phase separation treatment time is 5s. During the liquid film pre-phase separation treatment, airflow is continuously blown onto the surface of the liquid film. The absolute humidity of the airflow is 10gH2O / kg, and the flow rate of the airflow is 12m / min.

[0159] S3. The pre-phase-separated liquid film is placed in a coagulation bath for re-phase separation treatment to obtain a raw film; the coagulation bath includes water, a third solvent and an additive, the mass percentage of the third solvent in the coagulation bath is 10%, the mass percentage of the additive in the coagulation bath is 3%, the mass ratio of the third solvent to the additive is 3.3:1, the third solvent is tetrahydrofuran, and the additive is ethylene glycol; the re-phase separation treatment time is 50s.

[0160] S4. The biofilm obtained in step S3 is washed and dried to obtain an asymmetric sulfone polymer nanoscale filter membrane.

[0161] Example 5

[0162] This embodiment provides an asymmetric sulfone polymer nanoscale filter membrane, the preparation method of which includes the following steps:

[0163] S1. Prepare a casting solution and cast the casting solution onto a carrier to form a liquid film; the casting solution comprises the following components in parts by weight: 14 parts of sulfone polymer, 8 parts of pore-forming agent, 70 parts of first solvent, and 12 parts of volatile second solvent; wherein, the solid content of the casting solution is 13%, the mass ratio of the first solvent to the second solvent in the casting solution is 5.83:1, the sulfone polymer is polyethersulfone, the weight-average molecular weight of the sulfone polymer is 40,000, the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 3.5, the pore-forming agent is polyethyleneimine, the first solvent is dimethyl sulfoxide, and the second solvent is tetrahydrofuran;

[0164] S2. Place the liquid film under the first phase separation condition for pre-phase separation treatment until the turbidity point is reached, and the pre-phase separation treatment is completed; wherein, the liquid film reaching the turbidity point and the pre-phase separation treatment being completed means that before the pre-phase separation treatment, the turbidity of the liquid film is A, and after the pre-phase separation treatment, the turbidity of the liquid film increases to 1.03A.

[0165] In step S2, the liquid film is placed under the first phase separation condition for pre-phase separation treatment. Specifically, the liquid film is placed under the condition of 55°C for pre-phase separation treatment, and the pre-phase separation treatment time is 3s. During the liquid film pre-phase separation treatment, airflow is continuously blown onto the surface of the liquid film. The absolute humidity of the airflow is 7gH2O / kg, and the flow rate of the airflow is 8m / min.

[0166] S3. The pre-phase-separated liquid film is placed in a coagulation bath for re-phase separation treatment to obtain a raw film. The coagulation bath includes water, a third solvent, and an additive. The mass percentage of the third solvent in the coagulation bath is 12%, the mass percentage of the additive in the coagulation bath is 1.5%, the mass ratio of the third solvent to the additive is 8:1, the third solvent is tetrahydrofuran, and the additive is glycerol. The re-phase separation treatment time is 65s.

[0167] S4. The biofilm obtained in step S3 is washed and dried to obtain an asymmetric sulfone polymer nanoscale filter membrane.

[0168] Example 6

[0169] This embodiment provides an asymmetric sulfone polymer nanoscale filter membrane, the preparation method of which includes the following steps:

[0170] S1. Prepare a casting solution and cast the casting solution onto a carrier to form a liquid film; the casting solution comprises the following components in parts by weight: 13 parts of sulfone polymer, 9 parts of pore-forming agent, 75 parts of first solvent, and 11 parts of volatile second solvent; wherein, the solid content of the casting solution is 12%, the mass ratio of the first solvent to the second solvent in the casting solution is 6.82:1, the sulfone polymer is polyphenylene sulfone, the weight-average molecular weight of the sulfone polymer is 30,000, the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 3.6, the pore-forming agent is polyvinylpyrrolidone, the first solvent is dimethylacetamide, and the second solvent is acetone;

[0171] S2. Place the liquid film under the first phase separation condition for pre-phase separation treatment until the turbidity point is reached, and the pre-phase separation treatment is completed; wherein, the liquid film reaching the turbidity point and the pre-phase separation treatment being completed means that before the pre-phase separation treatment, the turbidity of the liquid film is A, and after the pre-phase separation treatment, the turbidity of the liquid film increases to 1.03A.

[0172] In step S2, the liquid film is placed under the first phase separation condition for pre-phase separation treatment. Specifically, the liquid film is placed under the condition of 50°C for pre-phase separation treatment, and the pre-phase separation treatment time is 2s. During the liquid film pre-phase separation treatment, airflow is continuously blown onto the surface of the liquid film. The absolute humidity of the airflow is 6gH2O / kg, and the flow rate of the airflow is 6m / min.

[0173] S3. The pre-phase-separated liquid film is placed in a coagulation bath for re-phase separation treatment to obtain a raw film; the coagulation bath includes water, a third solvent and an additive, the mass percentage of the third solvent in the coagulation bath is 15%, the mass percentage of the additive in the coagulation bath is 3.5%, the mass ratio of the third solvent to the additive is 4.3:1, the third solvent is acetone, and the additive is ethanol; the re-phase separation treatment time is 75s.

[0174] S4. The biofilm obtained in step S3 is washed and dried to obtain an asymmetric sulfone polymer nanoscale filter membrane.

[0175] The filter membranes prepared in Examples 1-6 were structurally characterized. The morphology of the main membrane structure of each example sample was characterized using a scanning electron microscope (Hitachi S-5500), and the required data were obtained. Other tests were also conducted to obtain corresponding data. Specific results are shown in Table 1 and... Figures 1-5 .

[0176] Table 1

[0177]

[0178]

[0179] The results of Examples 1-6 show that when the prepared filter membrane has a thin and uniform separation layer structure, a suitable pore size (demonstrated by the efficient retention of 2nm colloidal particles), and a slightly larger pore size distribution, combined with high porosity, it can ensure that the filter membrane has both high retention efficiency and high throughput. The filter membrane has a retention rate of not less than 90% for 2nm colloidal gold, a flow rate of not more than 148s@50mL@20℃@φ47mm, and also has high cleanliness. The TOC leaching amount of the filter membrane does not exceed 0.5ppb, and the metal ion precipitation amount does not exceed 10ppt. Therefore, the filter membrane prepared in this application is suitable for the nanoscale purification of liquid processing agents used in semiconductor wet processes.

[0180] Comparative Example 1

[0181] This comparative example prepares an asymmetric sulfone polymer nanoscale filter membrane according to the preparation method of Example 3. The difference is that no volatile second solvent is added in step S1 of this comparative example, and the solid content of the sulfone polymer in the casting solution is controlled to be 10%. Compared with Example 3, the average thickness of the separation layer in the filter membrane prepared in this comparative example is only 0.2 μm. The filter membrane prepared in this comparative example has a rejection rate of less than 90% for colloidal gold with a particle size of 2 nm. Ultimately, this results in a filter membrane with too low rejection efficiency for impurity particles in the feed solution, making it impractical.

[0182] Comparative Example 2

[0183] This comparative example prepared an asymmetric sulfone polymer nanoscale filter membrane according to the preparation method of Example 3. The difference is that in step S1, the solid content of the casting solution in this comparative example was adjusted to 22%, and step S2 (i.e., no pre-phase separation treatment step) was performed, and step S3 (re-phase separation step) was performed directly. Compared with Example 3, the average thickness of the separation layer in the filter membrane prepared in this comparative example is 15 μm. The separation layer is too thick, resulting in a low flux. The flow rate of the filter membrane is only 240s@50mL@20℃@φ47mm, and the membrane cleanliness is affected. The cleanliness is too low and it is not practical.

[0184] Comparative Example 3

[0185] This comparative example prepares an asymmetric sulfone polymer nanoscale filter membrane according to the preparation method of Example 3. The difference is that in step S2 of this comparative example, the pre-phase separation treatment time is adjusted so that the pre-phase separation treatment is completed when the turbidity of the liquid membrane is A before the pre-phase separation treatment and the turbidity of the liquid membrane increases to 1.05A after the pre-phase separation treatment. In addition, no third organic solvent is added in step S3 of this comparative example, and the re-phase separation treatment time is 8s. Compared with Example 3, the separation layer thickness of the filter membrane prepared in this comparative example is not uniform enough. When the cross-sectional brightness of the filter membrane after retaining 2nm colloidal gold is measured, the ratio of the standard deviation of the area value of the brightness shift spectrum to the average value of the area value is too large, reaching 2.5, which makes the retention efficiency of the filter membrane poor. The filter membrane prepared in this comparative example retains colloidal gold with a particle size of 2nm, and the retention rate of the filter membrane for colloidal gold is less than 90%. In the end, the retention efficiency of the filter membrane for impurity particles in the feed liquid is too low, which makes it impractical.

[0186] Comparative Example 4

[0187] This comparative example prepares an asymmetric sulfone polymer nanoscale filter membrane according to the preparation method of Example 3. The difference is that in step S1 of this comparative example, the weight-average molecular weight of the sulfone polymer is 10,000, and the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 1.5. In step S3 of this comparative example, the mass percentage of additives in the coagulation bath is 7%. Compared with Example 3, the pore size distribution of the filter membrane prepared in this comparative example is too narrow. The ratio between the maximum PMI pore size and the minimum PMI pore size of the filter membrane is only 1.1, which makes the flux of the filter membrane low. The flow rate of the filter membrane is only 220s@50mL@20℃@φ47mm. Moreover, the cleanliness of the membrane is affected and the cleanliness is low, making it impractical.

[0188] Comparative Example 5

[0189] This comparative example prepares an asymmetric sulfone polymer nanoscale filter membrane according to the preparation method of Example 3. The difference is that in step S1 of this comparative example, the weight-average molecular weight of the sulfone polymer is 160,000, and the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 6. In addition, the coagulation bath used in step S3 of this comparative example does not contain any additives. Compared with Example 3, the filter membrane prepared in this comparative example has a wider pore size distribution, and the ratio between the maximum pore size and the minimum pore size of the PMI of the filter membrane reaches 3.8, resulting in poor retention efficiency of the filter membrane. The filter membrane prepared in this comparative example retains colloidal gold with a particle size of 2 nm, and the retention rate of the filter membrane for colloidal gold is less than 90%. Ultimately, this results in a low retention efficiency of the filter membrane for impurity particles in the feed solution, making it impractical.

[0190] The results from Comparative Examples 1 to 6 show that when the average thickness of the separation layer in the prepared filter membrane is too small, or the pore size distribution of the filter membrane is too wide, or when the cross-sectional brightness of the filter membrane after retaining 2nm colloidal gold is measured, the ratio of the standard deviation of the area value of the brightness shift spectrum to the average value of the area value is too large, resulting in a retention rate of less than 90% for 2nm colloidal gold by the filter membrane. This leads to a low retention efficiency of the filter membrane for impurity particles in the feed solution, rendering it impractical. When the average thickness of the separation layer in the prepared filter membrane is too thick, or the pore size distribution of the filter membrane is too narrow, the flux of the filter membrane is too small, the flow rate of the filter membrane is ≥220s@50mL@20℃@φ47mm, and the cleanliness is too low, rendering it impractical.

[0191] Example 7 group

[0192] The examples in this group prepared asymmetric sulfone polymer nanoscale filter membranes according to the preparation method of Example 3, except that:

[0193] In Example 7a, the second solvent in step S1 was 30 parts by weight, making the mass ratio of the first solvent to the second solvent 2.07:1, and the solid content of the casting solution 14%. In step S2, the pre-phase separation treatment was performed at 85°C for 15 seconds without any blowing air. The resulting filter membrane had a small SEM average pore size of only 3 nm at the outlet, and an average separation layer thickness of 11 μm, causing a rapid decrease in the filter membrane's flux. Furthermore, more ultrapure water is needed for repeated rinsing to ensure membrane cleanliness;

[0194] In Example 7b, the second solvent in step S1 was 8 parts by weight, making the mass ratio of the first solvent to the second solvent 7.75:1, and the solid content of the casting solution 18%. In step S2, the pre-phase separation treatment temperature was 45°C, the time was 0.3s, and there was no blowing air. The average SEM pore size of the obtained filter membrane was 32nm for the outlet pores and 384nm for the inlet pores, with a ratio of 12 between the average SEM pore size of the inlet pores and the average SEM pore size of the outlet pores. The average thickness of the separation layer was relatively thin, at 0.7μm. Ultimately, the retention efficiency and flux of the prepared filter membrane were not high. The filter membrane retained colloidal gold particles with a particle size of 2nm, and the retention rate of the filter membrane for colloidal gold was just over 90%, resulting in a low retention efficiency of the filter membrane for impurity particles in the feed solution. The flow rate of the filter membrane was... Its practicality is relatively low.

[0195] Example 8 group

[0196] The examples in this group prepared asymmetric sulfone polymer nanoscale filter membranes according to the preparation method of Example 3, except that:

[0197] In Example 8a, the weight-average molecular weight of the sulfone polymer in step S1 was 150,000, and the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer was 4.5. The re-phase separation time in step S3 was 10 s, and the mass percentage of the additive in the coagulation bath was 5% (making the mass ratio of the third solvent to the additive 1.6:1). The final filter membrane had an average SEM pore size of 18 nm for the outlet pores, an average SEM pore size of 0.58 μm for the inlet pores, an average thickness of 82 μm for the filter membrane body, a PMI maximum pore size to a PMI minimum pore size ratio of 1.2, and a pore size gradient of 6.85 nm / μm. This resulted in a lower flux of the filter membrane in this example compared to Example 3, and a lower flow rate of the filter membrane in this example. Furthermore, the cleanliness was worse than in Example 3, resulting in lower practicality. In Example 8b, the weight-average molecular weight of the sulfone polymer in step S1 was 20,000, and the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer was 3.7. The re-phase separation treatment in step S3 lasted for 80 seconds, and the mass percentage of the additive in the coagulation bath was 1% (making the mass ratio of the third solvent to the additive 8:1). The average SEM pore size of the outlet pores in the obtained filter membrane was 20 nm, and the average SEM pore size of the inlet pores was... The pore size is 2.6 μm, the average thickness of the filter membrane body is 76 μm, the ratio between the maximum PMI pore size and the minimum PMI pore size of the filter membrane is 3.2, and the pore size variation gradient of the filter membrane body is 33.95 nm / μm. This results in a low retention efficiency of the filter membrane in this embodiment. Taking colloidal gold with a particle size of 2 nm as an example, the retention rate of the filter membrane for colloidal gold is 91.3%. Ultimately, this leads to a low retention efficiency of the filter membrane for impurity particles in the feed solution and low practicality.

[0198] Example 9 group

[0199] The examples in this group prepared asymmetric sulfone polymer nanoscale filter membranes according to the preparation method of Example 3, except that:

[0200] In Example 9a, the absolute humidity of the airflow in step S2 was 25 H2O / kg, and the airflow velocity was 25 m / min; the mass percentage of the additive in the coagulation bath used in step S3 was 5% (making the mass ratio of the third solvent to the additive 1.6:1); the pore density of the liquid outlet pores on the liquid outlet surface of the finally obtained filter membrane was 75 pores / μm. 2 The pore density of the inlet holes on the inlet surface is 5 per 100 μm. 2 Compared to Example 3, the pore density of both the outlet and inlet surfaces in this example is smaller. Pore density affects the pore area ratio, meaning the pore area ratio of the inlet and outlet surfaces will be lower, which will affect the flux and cleanliness (the cleaning difficulty of the filter membrane will be greatly increased, requiring more ultrapure water to ensure the cleanliness of the filter membrane). The flow rate of the filter membrane is... Low flux, low practicality;

[0201] In Example 9b, the absolute humidity of the airflow in step S2 was 3 H2O / kg, and the airflow velocity was 2 m / min; the mass percentage of the additive in the coagulation bath used in step S3 was 1% (making the mass ratio of the third solvent to the additive 8:1); the pore density of the liquid outlet pores on the liquid outlet surface of the finally obtained filter membrane was 410 pores / 1 μm. 2 The pore density of the inlet holes on the inlet surface is 85 per 100 μm. 2 Compared to Example 3, the pore density of the liquid outlet and liquid inlet surfaces in this example is larger, which will affect the pressure resistance of the liquid outlet and liquid inlet surfaces. During repeated rinsing, the pore size of some membrane pores will be affected, which will in turn affect the retention efficiency of the filter membrane. Taking the colloidal gold with a particle size of 2nm as an example, the retention rate of the filter membrane for colloidal gold is 91.5%, which ultimately leads to a low retention efficiency of the filter membrane for impurity particles in the feed liquid and low practicality.

[0202] Example 10 group

[0203] The examples in this group prepared asymmetric sulfone polymer nanoscale filter membranes according to the preparation method of Example 3, except that:

[0204] In Example 10a, the weight percentage of the pore-forming agent in step S1 is 0.5 parts (making the solid content in the casting solution 17%), and the type of pore-forming agent is adjusted to isopropanol; the mass percentage of the third solvent in the coagulation bath used in step S3 is 3%, making the mass ratio of the third solvent to the additive 1.2:1. The final filter membrane has a larger initial water contact angle at the outlet surface, reaching 67°, and an initial water contact angle at the inlet surface, reaching 89°. The difference between the water contact angles at the inlet and outlet surfaces is 22°. Compared to Example 3, the larger initial water contact angle at the outlet surface in this example results in stronger hydrophobicity at the outlet surface, which reduces the retention efficiency of the filter membrane. For example, the filter membrane in this example retains colloidal gold with a particle size of 2nm, and the retention rate of the filter membrane for colloidal gold is 91.7%. Ultimately, this leads to a lower retention efficiency of the filter membrane for impurity particles in the feed solution, resulting in lower practicality.

[0205] In Example 10b, the pore-forming agent in step S1 is 12 parts by weight (making the solid content in the casting solution 15%), and the third solvent in the coagulation bath used in step S3 has a mass percentage of 22%, making the mass ratio of the third solvent to the additive 8.8:1. The resulting filter membrane has a smaller initial water contact angle at the outlet surface (32°) and a smaller initial water contact angle at the inlet surface (35°), with a difference of 3° between the inlet and outlet water contact angles. Compared to Example 3, the smaller difference in water contact angles between the inlet and outlet surfaces in this example leads to a decrease in the filter membrane flux, and the filter membrane flow rate is... Furthermore, the cleanliness of the filter membrane is affected, resulting in lower practicality.

[0206] Example 11 group

[0207] The examples in this group prepared asymmetric sulfone polymer nanoscale filter membranes according to the preparation method of Example 3, except that:

[0208] In Example 11a, the weight percentage of the sulfone polymer in the casting solution was 17 parts, and the weight percentage of the first solvent was 46 parts, making the solid content of the casting solution 20%, and the mass ratio of the first solvent to the second solvent 2.56:1. The re-phase separation treatment time in step S3 was 10 s. In the finally obtained filter membrane, region D was located at 89.2% of the thickness of the filter membrane body, and the distance between region D and the liquid outlet surface was 8.6 μm. The capture peak of colloidal gold with a diameter of 2 nm was not lower than The thickness of the region capturing the peak D80% is Q, which is 5.3 μm and accounts for 9.35% of the filter membrane's main thickness. Compared to Example 3, in this example, D is too far from the liquid outlet, resulting in a larger Q value and a higher proportion of Q to the filter membrane's main thickness. This affects the filter membrane's retention efficiency and makes it difficult to clean. For example, the filter membrane in this example retains colloidal gold particles with a diameter of 2 nm, achieving a retention rate of 91.3%. Ultimately, this leads to a lower retention efficiency for impurities in the feed solution, limiting its practicality. Low; In Example 11b, the weight percentage of sulfone polymer in the casting solution was 14 parts, and the weight percentage of the first solvent was 82 parts, making the solid content of the casting solution 12%, and the mass ratio of the first solvent to the second solvent 4.56:1. The re-phase separation time in step S3 was 80 s; In the finally obtained filter membrane, the D region was located at 99.2% of the thickness of the filter membrane body, and the distance between the D region and the liquid outlet surface was 0.6 μm; The capture peak of colloidal gold with a diameter of 2 nm was not lower than the capture peak. The thickness of the peak capture region D80% is Q, which is 0.3 μm and accounts for 0.43% of the main thickness of the filter membrane. Compared with Example 3, in this example, region D is closer to the liquid outlet, and the Q value is smaller. The high concentration of gold nanoparticles in the capture peak region of the filter membrane makes it easy for nanoparticles to rapidly accumulate in this thin layer region through aggregation or adsorption, filling the surface pores of the filter membrane. This results in a reduction in the effective filtration pore size of the filter membrane, a significant increase in mass transfer resistance, and consequently a decrease in the filter membrane flux. The flow rate of the filter membrane is [missing value].

[0209] Example 12 group

[0210] The examples in this group prepared asymmetric sulfone polymer nanoscale filter membranes according to the preparation method of Example 3, except that:

[0211] In Example 12a, the weight fraction of the first solvent in the casting solution used in step S1 was 45 parts, making the solid content of the casting solution 19%, and the mass ratio of the first solvent to the second solvent 2.5:1. The phase separation time in step S3 was 10 s. The final filter membrane had a flow guiding zone located in the region of 3.2%-17% of the filter membrane body thickness, and the ratio of the average thickness of the flow guiding zone to the average thickness of the filter membrane body was 0.082:1. Compared to Example 3, the flow guiding zone occupied a smaller portion of the overall filter membrane thickness in this example, resulting in a decrease in the filter membrane flux and a filter membrane flow rate of [missing information].

[0212] In Example 12b, the weight fraction of the first solvent in the casting solution used in step S1 was 85 parts, making the solid content of the casting solution 13%, and the mass ratio of the first solvent to the second solvent 4.72:1. The phase separation time in step S3 was 80 s. The final filter membrane had a flow guiding zone located in the region of 19%-88% of the filter membrane body thickness, and the ratio of the average thickness of the flow guiding zone to the average thickness of the filter membrane body was 0.6234:1. Compared to Example 3, the flow guiding zone in this example was thicker, which increased the risk of filter membrane breakage in some areas during filtration, reduced the filter membrane flux, and resulted in a filter membrane flow rate of [missing value].

[0213] Example 13

[0214] This embodiment prepares an asymmetric sulfone polymer nanoscale filter membrane according to the preparation method of Example 3, except that:

[0215] In this embodiment, the second solvent in the casting solution used in step S1 has a weight ratio of 34 parts, making the solid content of the casting solution 14%, and the mass ratio of the first solvent to the second solvent 1.82:1. The pre-phase separation treatment time in step S2 is 15s. The average thickness of the separation layer in the finally obtained filter membrane is 12μm, and the average thickness of the filter membrane body is 76μm, making the ratio between the average thickness of the separation layer and the average thickness of the filter membrane body greater than 0.15, and the specific surface area of ​​the filter membrane is 23m². 2 / g; Compared to Example 3, the separation layer in this example is thicker and has a slightly larger specific surface area, resulting in a lower flux of the filter membrane and a flow rate of [missing value]. In addition, more ultrapure water is needed for repeated rinsing to ensure membrane cleanliness.

[0216] The above-described Examples 7 and 13 verified the effect of the following factors on at least one of the filter membrane's retention efficiency, flux, and cleanliness:

[0217] (1) Average thickness of the separation layer, (2) Porosity of the filter membrane, (3) Pore size distribution of the filter membrane, (4) Measurement of the cross-sectional brightness of the filter membrane after retaining 2nm colloidal gold, and the ratio of the standard deviation of the area value of the brightness shift spectrum to the average value of the area value, (5) Pore size of the inlet and outlet pores, (6) Pore size variation gradient of the filter membrane body, (7) Specific surface area of ​​the filter membrane, (8) Initial water contact angle of the inlet and outlet liquid surfaces and the difference between the two, (9) The area where the capture peak D of the 2nm colloidal gold is located in the thickness of the membrane body and the distance between it and the outlet liquid surface, (10) The thickness Q of the capture peak of the 2nm colloidal gold in the area not less than 80% of the capture peak D and the area where it is located in the thickness of the membrane body, (11) The area where the flow guiding zone is located in the thickness of the membrane body and the ratio of it to the average thickness of the filter membrane body. This application utilizes a filter membrane with a thin and uniformly thick separation layer structure, suitable pore size (demonstrated by the efficient retention of 2nm colloids), and a slightly larger pore size distribution, combined with high porosity, to ensure that the filter membrane has both high retention efficiency and high throughput, as well as high cleanliness, thus making the filter membrane suitable for the nanoscale purification of liquid processing agents used in semiconductor wet processes.

[0218] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An asymmetric sulfone polymer nanoscale filter membrane, characterized in that, The filter membrane includes a filter membrane body with a non-directional tortuous path. The filter membrane body includes a pre-filtration layer and a separation layer for retaining impurities in sequence along its thickness direction. The average thickness of the separation layer is 0.5 μm to 12 μm. The porosity of the filter membrane is 40%~80%; The ratio between the maximum PMI pore size and the minimum PMI pore size of the filter membrane is 1.2 to 3.

5. The filter membrane retains colloidal gold with a particle size of 2 nm, and the retention rate of the filter membrane for the colloidal gold is not less than 90%. Furthermore, the cross-sectional brightness of the filter membrane after retaining 2nm colloidal gold was measured, and the ratio of the standard deviation of the area value of the brightness shift spectrum to the average value of the area value was 0.01~2.

2. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 1, characterized in that, The pre-filtration layer includes a liquid inlet surface, which is located on the side of the pre-filtration layer opposite to the separation layer, and the liquid inlet surface includes a plurality of liquid inlet holes; The separation layer includes a liquid outlet surface, which is located on the side of the separation layer opposite to the pre-filtration layer, and the liquid outlet surface includes a plurality of liquid outlet holes; The average SEM pore size of the liquid outlet is 4nm~30nm; The ratio between the average SEM diameter of the inlet hole and the average SEM diameter of the outlet hole is not less than 15.

3. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 2, characterized in that, The average SEM pore size of the liquid inlet is 0.7 μm to 2.5 μm; The ratio between the maximum PMI pore size and the minimum PMI pore size of the filter membrane is 1.4 to 3. The pore size variation gradient of the filter membrane body is 7nm / μm~28nm / μm; The pore size variation gradient of the filter membrane body = (SEM average pore size of the inlet pore - SEM average pore size of the outlet pore) / average thickness of the filter membrane body.

4. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 2, characterized in that, The pore density of the liquid outlet holes on the liquid outlet surface is 80 holes / 1μm. 2 ~300 / 1μm 2 ; The pore density of the inlet holes on the inlet surface is 6 per 100 μm. 2 ~25 per 100μm 2 .

5. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 1, characterized in that, The specific surface area of ​​the filter membrane is 6m². 2 / g~20m 2 / g; The average thickness of the separation layer is 0.8 μm to 10 μm, and the ratio between the average thickness of the separation layer and the average thickness of the filter membrane body is not greater than 0.

15.

6. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 2, characterized in that, The initial water contact angle of the liquid outlet surface is 35°~65°; The initial water contact angle of the inlet surface is greater than that of the outlet surface, and the difference between the initial water contact angles of the inlet surface and the outlet surface is 5° to 20°.

7. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 1, characterized in that, In the thickness direction of the filter membrane body, the liquid inlet surface of the pre-filtration layer is taken as the position where the thickness of the filter membrane body is 0%, and the liquid outlet surface of the separation layer is taken as the position where the thickness of the filter membrane body is 100%. In the wet filter membrane body, the capture peak value for colloidal gold with a diameter of 2 nm is D. The D region is located in the area of ​​90% to 99.8% of the thickness of the filter membrane body, and the distance between the D region and the liquid outlet surface is 0.2 μm to 8 μm.

8. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 7, characterized in that, In the wet filter membrane body, the thickness of the region where the capture peak of colloidal gold with a diameter of 2 nm is not less than 80% of the capture peak value D is Q, where Q is 0.3 μm to 5 μm and Q accounts for 0.5% to 8% of the thickness of the filter membrane body.

9. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 7, characterized in that, The filter membrane body includes a flow guiding region located in the region of 3% to 85% of the thickness of the filter membrane body; the ratio of the average thickness of the flow guiding region to the average thickness of the filter membrane body is (0.1 to 0.6):

1.

10. The asymmetric sulfone polymer nanoscale filter membrane as described in claim 1, characterized in that, The flow rate of the filter membrane is 40~180s@50mL@20℃@φ47mm; the TOC leaching amount of the filter membrane does not exceed 0.5ppb, and the metal ion precipitation amount does not exceed 10ppt.

11. A method for preparing an asymmetric sulfone polymer nanoscale filter membrane as described in any one of claims 1 to 10, characterized in that, Includes the following steps: S1. Prepare a casting solution and cast the casting solution onto a carrier to form a liquid film; the casting solution includes the following components: sulfone polymer, a first solvent, a volatile second solvent, and a pore-forming agent; The weight-average molecular weight of the sulfone polymer is 20,000 to 150,000, and the ratio between the weight-average molecular weight and the number-average molecular weight of the sulfone polymer is 2 to 4.

5. The pore-forming agent includes at least one selected from polyvinyl alcohol, polyethylene glycol, polyethyleneimine, and polyvinylpyrrolidone, and the solid content of the casting solution is 12% to 20%. S2. Place the liquid film under the first phase separation condition for pre-phase separation treatment until the turbidity point is reached, and the pre-phase separation treatment is completed; wherein, the liquid film reaching the turbidity point and the pre-phase separation treatment being completed means that before the pre-phase separation treatment, the turbidity of the liquid film is A, and after the pre-phase separation treatment, the turbidity of the liquid film increases to 1.03A. S3. The pre-phase-separated liquid film is placed in a coagulation bath for re-phase separation treatment to obtain a raw film; the coagulation bath includes water, a third solvent and an additive, the mass percentage of the third solvent in the coagulation bath is 5%~15%, the mass percentage of the additive in the coagulation bath is 1%~5%, and the re-phase separation treatment time is 10s~80s. S4. The biofilm obtained in step S3 is washed and dried to obtain an asymmetric sulfone polymer nanoscale filter membrane.

12. The method for preparing the asymmetric sulfone polymer nanoscale filter membrane as described in claim 11, characterized in that, The sulfone polymer is at least one of bisphenol A polysulfone, polyether sulfone, and polyphenyl sulfone; The first solvent includes at least one of dimethyl sulfoxide, N-ethylpyrrolidone, N-methylpyrrolidone, and dimethylacetamide; The second solvent includes at least one of acetone, tetrahydrofuran, and ethyl acetate; And / or, the mass ratio of the first solvent to the second solvent in the casting solution is (2~7):

1.

13. The method for preparing the asymmetric sulfone polymer nanoscale filter membrane as described in claim 11, characterized in that, In step S2, the liquid film is placed under the first phase separation condition for pre-phase separation treatment. Specifically, the liquid film is placed under the condition of 50℃~80℃ for pre-phase separation treatment, and the pre-phase separation treatment time is 0.5s~10s.

14. The method for preparing the asymmetric sulfone polymer nanoscale filter membrane as described in claim 13, characterized in that, In step S2, during the liquid film pre-phase separation treatment, a continuous airflow is blown onto the surface of the liquid film. The absolute humidity of the airflow is 5gH2O / kg to 20gH2O / kg, and the flow rate of the airflow is 5m / min to 20m / min.

15. The method for preparing the asymmetric sulfone polymer nanoscale filter membrane as described in claim 11, characterized in that, In step S3, the third solvent is acetone or tetrahydrofuran; And / or, the additive includes at least one of isopropanol, ethanol, ethylene glycol, propylene glycol, glycerol, and sodium chloride; And / or, the mass ratio of the third solvent to the additive is (2~8):

1.

16. The application of a sulfone polymer nanoporous filter membrane as described in any one of claims 1 to 10, characterized in that, The filter membrane is used for the nanoscale purification of liquid processing reagents used in semiconductor wet processes.

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