Covalent organic framework self-supporting membrane for precise filtration of cmp ultra-pure cleaning solution and preparation method and application thereof

Abstract

The application provides a covalent organic framework self-supporting film for precision filtration of CMP ultra-pure cleaning solution and a preparation method thereof. The preparation method comprises the following steps: dissolving a first organic monomer, a second organic monomer and a sulfonamide additive in an organic solvent to obtain a coating solution; coating the coating solution on a substrate surface and performing programmed temperature treatment; evaporating most of the organic solvent at a temperature lower than the melting point of the additive to form a precursor film, and then performing a melting polymerization reaction at a temperature higher than the melting point of the additive to form a covalent organic framework film; and finally, peeling, washing and activating to obtain a covalent organic framework self-supporting film connected by imine bonds, olefin bonds or imide bonds. The method is green and universal, and is easy to scale up. The prepared film has a regular nanopore size and high purity, can be used for preparing a semiconductor CMP post-cleaning solution filtration device, can effectively intercept nanoscale pollutants, and can prevent wafer scratching, and has good application potential and commercial value in the field of semiconductor polishing.

Description

Technical Field

[0001] This invention belongs to the field of high-end semiconductor manufacturing and new materials technology, specifically relating to a covalent organic framework self-supporting thin film and its preparation method, and also relating to the application of the above-mentioned covalent organic framework self-supporting thin film in the precision filtration of ultrapure cleaning solution in the cleaning process after chemical mechanical polishing. Background Technology

[0002] In semiconductor chip manufacturing, chemical mechanical polishing (CMP) is a core step in achieving global wafer planarization. After CMP, a large amount of polishing slurry abrasive, reaction byproducts, and metallic contaminants remain on the wafer surface, which must be thoroughly removed through a subsequent ultrapure cleaning process. This cleaning step is crucial for preventing defects, ensuring device electrical performance, and achieving high final product yield. However, this cleaning process inherently carries an easily overlooked risk: the ultrapure cleaning solution may contain nanoscale contaminants.

[0003] These contaminants mainly originate from nanoscale metal sols (such as oxide sols of iron, copper, and nickel) formed in the cleaning equipment pipelines, or suspended particles introduced due to improper environmental control. The surface of the polished wafer has been ground to atomic level smoothness and is extremely delicate. If even nanoscale (e.g., 5~10 nm) hard sol particles or impurities (such as silica microspheres) are present in the cleaning solution, they will act like "tiny sandpaper" during the cleaning process, causing irreparable microscopic scratches, watermarks, or material residues on the wafer surface. These defects will be amplified in subsequent more refined photolithography and thin film processes, directly leading to fatal failures such as chip short circuits and leakage.

[0004] Currently, to ensure that the cleaning fluid delivered to the process chamber meets the purity requirements, the industry usually installs terminal filters in the ultrapure water or chemical cleaning agent delivery pipeline before the point cleaning machine. Most of these filters use traditional polymer porous membranes (such as nylon and polyvinylidene fluoride membranes). However, as chip manufacturing processes enter the sub-7 nm node, the limitations of existing filter membranes are becoming increasingly apparent: (1) The contradiction between retention accuracy and pore size uniformity: Traditional filter membranes are prepared through a non-directional phase separation process, and their pore structure is disordered with a wide pore size distribution. In order to achieve effective retention of nanoscale particles, membranes with extremely small nominal pore sizes must be selected, but this will lead to a sharp increase in filtration pressure difference, a significant decrease in flux, increased system energy consumption, and an impact on the efficiency of cleaning fluid supply. More seriously, the wide pore size distribution means that there are a small number of defective pores in the membrane that are much larger than the nominal pore size. These "holes" allow individual nanoscale impurities to pass through, becoming the source of scratch defects. (2) Risk of leachate and secondary contamination: When polymer membrane materials come into contact with specific chemical cleaning agents (such as dilute acids, dilute alkalis, or solvents), they may leach oligomers, additives, and other organic molecules. These leachate are themselves contaminants and can be adsorbed onto the wafer surface, forming defects. (3) Adsorption and capacity issues: Some polymer membranes have charges or functional groups on their surface, which may adsorb ionic additives in the cleaning solution, changing the concentration of the cleaning solution formula and affecting the cleaning effect. At the same time, their random pore structure is easily blocked by trapped impurities, resulting in a limited service life.

[0005] Covalent organic frameworks (COFs) are a class of crystalline porous materials formed by the precise connection of organic monomers through strong covalent bonds. Their greatest advantage lies in their long-range ordered, single-pore-size, and tunable (typically 1-5 nm) one-dimensional pore structure. If COF materials can be fabricated into large-area, defect-free self-supporting films, their regular nanopores can act like "molecular sieves," achieving "absolute filtration" of nanoscale impurities in cleaning solutions. Only water molecules, ions, and small molecule additives are allowed to pass through, while 100% of sol particles larger than their pore size are retained, fundamentally preventing wafer surface scratches caused by impurities in the cleaning solution.

[0006] However, the key bottleneck currently restricting the application of COF membranes in this cutting-edge application lies in their synthesis technology. The mainstream solvothermal method has significant drawbacks: (1) risk of solvent contamination: This method requires the use of a large amount of high-boiling-point and highly toxic organic solvents (such as dioxane, mesitylene, o-dichlorobenzene, etc.), and these solvent molecules are very likely to remain in the nanopores of the COF membrane. When filtering ultrapure cleaning solution in the subsequent process, the slow dissolution of the residual solvent will cause serious secondary pollution to the cleaning solution, which runs counter to the original purpose of purification. (2) Difficulty in controlling the quality of film formation: It is difficult to synthesize self-supporting membranes with good mechanical properties, no pinholes, and large-area continuity in the liquid phase. Common interface methods or substrate-assisted growth methods are complicated, and the membranes after peeling often have problems of damage or insufficient strength, which cannot meet the requirements of terminal filters for membrane integrity and mechanical strength.

[0007] Therefore, developing a solvent-free, efficient, and direct synthesis method for high-purity, high-strength COF self-supporting films via a casting-melting process is of urgent practical significance and great industrial value for overcoming the bottleneck in its application in ultra-precision filtration of post-CMP cleaning solutions in semiconductors and improving chip manufacturing yield. Summary of the Invention

[0008] One of the objectives of this invention is to provide a simple, green, and efficient method for preparing a covalent organic framework self-supporting membrane for precision filtration of CMP ultrapure cleaning fluid.

[0009] A second objective of this invention is to provide a covalent organic framework self-supporting film with physical properties suitable for precision filtration, including suitable thickness, high specific surface area, and regular nanopore size.

[0010] The third objective of this invention is to provide an application of a covalent organic framework self-supporting film in the precision filtration of ultrapure cleaning solution during the cleaning process after chemical mechanical polishing.

[0011] One of the technical solutions adopted by this invention to achieve its objective is: to provide a method for preparing a covalent organic framework self-supporting thin film for precision filtration of CMP ultrapure cleaning fluid, comprising the following steps:

[0012] S1. Dissolve the first organic monomer, the second organic monomer, and the auxiliary agent in an organic solvent to obtain a coating liquid; the auxiliary agent is selected from one or more of sulfonamides, sulfonyl hydrazides, and sulfonyl imides.

[0013] S2. The coating liquid is uniformly coated on the substrate surface and subjected to programmed temperature rise treatment: First, most of the organic solvent is evaporated and removed at a temperature lower than the melting point of the additive to form a precursor film, and then a melt polymerization reaction is carried out at a temperature higher than the melting point of the additive to form a covalent organic framework film on the substrate.

[0014] S3. After peeling, washing and activating the product obtained in step S2, a covalent organic framework self-supporting film is obtained; the functional groups of the first organic monomer and the second organic monomer are selected to react with each other, so that the covalent organic framework self-supporting film is a covalent organic framework structure connected by imine bonds, olefin bonds or imide bonds.

[0015] The overall concept and inventive principle of this invention are as follows:

[0016] This invention addresses the challenge of existing COF material synthesis methods in preparing self-supporting filter films suitable for high-end semiconductor processes, which struggle to simultaneously achieve macroscopic integrity, microstructural regularity, and extremely high chemical purity. It provides an integrated "solvent-assisted casting-evaporation-melt polymerization" preparation method. The core improvement of this method lies in the selection of sulfonamide, sulfonylhydrazine, or sulfonylimide compounds as key reaction aids and activating media. These aids possess unique dual-functional properties: firstly, the active amino groups in their molecules can act as centers for dynamic covalent reactions, participating in and regulating the formation of chemical bonds such as imines and imides, and the crystallization process of the material; secondly, their strongly electron-withdrawing sulfonyl groups can effectively activate monomers containing active methyl / methylene groups, promoting the construction of a highly crystalline COF framework with olefinic bonds.

[0017] In the above preparation method, the reactants are first dissolved and uniformly coated into a film using an organic solvent at room temperature. This step ensures the large-area uniformity and controllable thickness of the precursor film. Subsequently, the solvent is evaporated and removed by programmed temperature rise to form the precursor film. Then, melt polymerization and crystallization reactions are carried out at a temperature higher than the melting point of the additives. During this process, the liquid environment provided by the molten additives is conducive to the reaction. Their unique physicochemical properties (including a low melting point and suitable viscosity) provide an ideal environment for the orderly diffusion, arrangement, and covalent bonding of molecules within the confined two-dimensional film interface, thereby guiding the formation of a long-range ordered, highly crystalline COF framework. Finally, residual additives and solvent molecules can be completely removed by peeling, washing, and low-temperature activation, resulting in a self-supporting COF film with clean pores and a highly crystalline phase. The film's regular nanopores, high specific surface area, and defect-free dense structure enable it to efficiently retain nanoscale contaminants in CMP ultrapure cleaning solutions, much like a precise "molecular sieve." At the same time, its insoluble and infusible properties fundamentally eliminate secondary contamination, meeting the extreme purity requirements of semiconductor manufacturing.

[0018] Furthermore, by selecting specific combinations of monomers, this invention explicitly defines the final product as a stable framework structure linked by imine, olefin, or imide bonds. These three types of stable chemical bonds endow this type of COF film with excellent chemical stability and mechanical strength, forming the basis for its use as a self-supporting film and its ability to withstand mechanical stress during filtration. Those skilled in the art will recognize that conventional organic monomers capable of achieving the above-mentioned connections are applicable to this invention; for the sake of full disclosure, several representative monomers are listed below.

[0019] For the framework structure that forms an imine bond, the first organic monomer may be a compound containing at least two amino or hydrazide groups, including: p-phenylenediamine, biphenylenediamine, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT), 1,3,5-tris(4-aminophenyl)benzene (TAPB), or tris(4-aminophenyl)amine, etc.; the second organic monomer may be a compound containing at least two aldehyde groups, including: terephthalaldehyde, 4,4'-biphenyldialdehyde, 1,3,5-tris(4-aldehydephenyl)benzene, or 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, etc.

[0020] For the framework structure that forms an olefin bond, the first organic monomer may be a compound containing at least two active methyl or methylene groups, including: 1,3,5-trimethyl-2,4,6-triazine, 2,4,6-trimethylpyridine, or 2,5-dimethylpyrazine, etc.; the second organic monomer may be a compound containing at least two aldehyde groups, including: terephthalaldehyde, 4,4'-biphenyldialdehyde, 1,3,5-tris(4-aldehydephenyl)benzene, or 2,5-dimethoxyterephthalaldehyde, etc.

[0021] For the framework structure that forms an imide bond, the first organic monomer may be a compound containing at least two amino groups, including: p-phenylenediamine, biphenylenediamine, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) or 1,3,5-tris(4-aminophenyl)benzene (TAPB), etc.; the second organic monomer may be a compound containing at least two anhydride groups or carboxyl groups, including: pyromellitic dianhydride, pyromellitic acid, 1,4,5,8-naphthalenetetracarboxylic dianhydride or 3,3',4,4'-biphenyltetracarboxylic dianhydride, etc.

[0022] Preferably, the first organic monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, and the second organic monomer is pyromellitic dianhydride, forming a polyimide-linked covalent organic framework self-supporting film after the reaction in step S2; or, the first organic monomer is 1,3,5-trimethyl-2,4,6-triazine, and the second organic monomer is 2,5-dimethoxyterephthalaldehyde, forming an olefin-linked covalent organic framework self-supporting film after the reaction in step S2.

[0023] Further, the adjuvant is selected from one or more of sulfonamides, sulfonyl hydrazides, or sulfonylimides. These adjuvants have structures represented by general formulas (I), (II), (III), or (IV):

[0024]

[0025] In formulas (I), (II), (III), and (IV), R and R' are independently selected from one of the following groups: hydrogen atom, substituted or unsubstituted C1-C12 alkyl group, substituted or unsubstituted phenyl group, substituted or unsubstituted naphthyl group, substituted or unsubstituted fused ring group, or substituted or unsubstituted heterocyclic group; and R and R' may be the same or different. The substituent on the substituted group is selected from one or more of halogen, cyano, nitro, C1-C6 alkyl, C1-C6 haloalkyl, and C1-C6 alkoxy.

[0026] Based on the above general formula, the adjuvants specifically include, but are not limited to, the following compounds:

[0027] Sulfonamide compounds, such as: sulfonamides (both R and R' are H), p-methylbenzenesulfonamides (R is p-methylphenyl, R' is H), 4-trifluoromethylbenzenesulfonamides (R is 4-trifluoromethylphenyl, R' is H), benzenesulfonamides (R is phenyl, R' is H), N-ethylbenzenesulfonamides (R is phenyl, R' is ethyl), and methanesulfonamides (R is methyl, R' is H).

[0028] Sulfonamide compounds, such as: (bis(trifluoromethanesulfonyl)amine (R and R' are both trifluoromethyl) and (bis(fluorosulfonyl)amine (R and R' are both fluorine atoms).

[0029] Sulfonyl hydrazide compounds, such as p-toluenesulfonyl hydrazide (R is p-methylphenyl) and benzenesulfonyl hydrazide (R is phenyl).

[0030] Preferably, the auxiliary agent is p-toluenesulfonamide, 4-trifluoromethylbenzenesulfonamide, benzenesulfonamide, (bis(trifluoromethanesulfonyl)amine) or p-toluenesulfonylhydrazine. These auxiliary agents exhibit excellent solubility, moderate melting point, and good reaction control ability in the reaction.

[0031] In this invention, the auxiliary agent, as a key reaction regulator and crystal growth medium, effectively repairs defects during long-term crystallization by participating in and controlling the dynamic covalent chemical process. It is an indispensable component for achieving highly crystalline covalent organic framework self-supporting films. Its mechanism of action is mainly reflected in two aspects:

[0032] For COF films forming polyimide, imide, and other linkages: In reaction systems without additives, amines and functional groups such as acid anhydrides (or aldehydes) rapidly undergo irreversible condensation reactions, generating kinetically dominant disordered polymers that are difficult to form long-range ordered crystalline structures. However, when the sulfonamide additives of this invention are introduced, the amino groups in their molecules can rapidly and preferentially react with acid anhydrides (or aldehydes) to generate small-molecule imide (or imide) intermediates. Thanks to the regulation of the strongly electron-withdrawing sulfonyl groups, the covalent bonds in this intermediate exhibit significantly enhanced reversibility. This dynamic characteristic effectively reduces the reaction rate of direct polymerization between organic ligands, providing an opportunity to repair erroneous bonds in the molecules, thereby guiding the reaction towards a thermodynamically more stable crystalline COF structure.

[0033] For COF films forming olefin bonds, the success of the reaction hinges on the activation efficiency of the active methyl / methylene groups. This invention discovers that the sulfonyl group in the sulfonamide auxiliary can specifically interact with nitrogen / oxygen-containing active methyl monomers to form a sulfonyl-N group. + The activated intermediate structure of the positive ion. This structure lowers the deprotonation barrier of the adjacent methyl / methylene CH bond through a strong electron-withdrawing effect, thereby efficiently promoting its condensation reaction with the aldehyde group, ultimately generating a highly crystalline alkenyl COF.

[0034] However, not all compounds with similar functional groups can meet the requirements of this invention. Based on extensive experimental research, this invention specifically limits the use of sulfonamides, sulfonyl hydrazides, or sulfonyl imides as additives. The fundamental reason is that the physicochemical properties of these additives (such as suitable melting and boiling point ranges) are optimally matched with the unique "solvent-assisted casting-evaporation-melt polymerization" integrated process of this invention. Specifically, if additives with excessively high melting points (such as amides and phosphoramides) are used, two major problems will arise in the process: (1) Damage to film integrity: In the later stage of solvent evaporation, high-melting-point additives are prone to premature crystallization due to supersaturation. These precipitated crystal particles will act as physical defects, severely damaging the continuity and uniformity of the precursor film, resulting in the inability to form a complete, defect-free self-supporting film. (2) Deterioration of the film formation process: Higher evaporation temperatures used to match high-melting-point additives will cause the organic solvent to boil violently or evaporate rapidly. The large number of bubbles and internal stress generated during this process can cause cracks and holes in the film, or even cause it to rupture and pulverize due to stress concentration, resulting in film formation failure.

[0035] Further, in step S1, the molar ratio of the first organic monomer to the second organic monomer is 1:8-8:1; the molar ratio of the auxiliary agent to the first organic monomer is 12-60:1. Preferably, the molar ratio of the first organic monomer to the second organic monomer is 1:2-2:1; the molar ratio of the auxiliary agent to the first organic monomer is 15-25:1. Controlling the molar ratio of the first organic monomer to the second organic monomer aims to ensure that the number of reactive functional groups contained in both is close to stoichiometric equilibrium, maximizing the orderly growth and extension of the two-dimensional network structure, thereby obtaining a COF framework with high crystallinity and a complete structure. Controlling the molar ratio of the auxiliary agent to the first organic monomer directly affects whether the "melt polymerization" step can be carried out effectively. In this invention, the auxiliary agent needs to form a sufficient molten phase at the reaction temperature. Its role goes far beyond catalysis; more importantly, it serves as a liquid medium for the reaction, providing a uniform environment for molecular diffusion, directional arrangement, and crystallization. By optimizing the amount of auxiliary agent, it can be ensured that after the solvent evaporates, a sufficient amount of auxiliary agent remains to encapsulate the reactive monomer, forming a molten reaction system with suitable viscosity and uniformity. If the amount of additive is too small, an effective melting medium cannot be formed, and the reaction system essentially becomes solid-state sintering, making it difficult to form a crystalline thin film. On the other hand, excessive amounts will increase costs and the burden on subsequent washing and recycling. This invention achieves the optimal balance between ensuring film quality and environmental friendliness by precisely controlling this ratio.

[0036] Further, in step S1, the organic solvent includes one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and N-methylpyrrolidone (NMP).

[0037] In this invention, the purpose of using organic solvents to prepare the precursor coating solution is to achieve a controllable and stable transformation from solution to high-quality film. If reactants and additives are directly heated and melted before coating without using solvents, several insurmountable drawbacks will arise: First, the molten mixture typically has extremely high viscosity and poor flowability, making it difficult to form a smooth and uniform liquid film on the substrate using conventional coating processes (such as blade coating and spin coating). Even small height differences will be amplified in subsequent reactions, leading to uneven film thickness or even cracking. Second, the high viscosity environment greatly restricts the diffusion rate of molecules, making it difficult for various reactants to achieve uniform mixing at the molecular level in a short time, resulting in local component deviations and poor crystallinity in the final product. Furthermore, the reactants in the molten state are already in an activated state, and the polymerization reaction occurs rapidly, causing a sharp increase in system viscosity and solidification within a short time. This leaves an extremely short time window for the coating operation, resulting in low process tolerance, poor reproducibility, and difficulty in achieving large-scale preparation.

[0038] In contrast, the solvent-assisted casting strategy employed in this invention offers significant advantages: it allows for the formation of a precursor solution with good flowability and uniform composition at room temperature. This solution is stable at room temperature, resistant to polymerization, and not only facilitates mixing and transportation but also possesses commercial potential for long-term storage. Furthermore, this invention offers greater flexibility in film formation control, allowing for adjustment of the coating amount and fine-tuning of the film thickness by changing the solution concentration (lower precursor concentration results in a thinner film). This synergistic "concentration-thickness" control mechanism provides a universal and reliable approach for preparing high-quality COF self-supporting films of various specifications.

[0039] Further, in step S2, the substrate includes one of the following: a quartz plate, a glass plate, a silicon wafer, a polyimide film, a polytetrafluoroethylene plate, a ceramic sheet, and a metal sheet. Preferably, the substrate is a smooth glass plate or a silicon wafer, which has the advantages of low cost, extremely high surface flatness, and moderate interfacial force with the COF film, which is very beneficial for subsequent complete peeling and obtaining a large-area, defect-free self-supporting film.

[0040] Further, in step S2, during the programmed temperature rise process, the temperature used for solvent evaporation is 60-200℃; preferably, the temperature is raised to a second temperature to initiate the melt polymerization reaction when slight solid precipitation occurs, on the one hand evaporating the remaining solvent, and on the other hand melting and casting the additives; the temperature used for the melt polymerization reaction is 150-220℃; the melt polymerization reaction time is 6 hours to 7 days. Specifically, the temperature can be flexibly adjusted according to the type and boiling point of the solvent, the melting temperature of the additives, and the type of COFs.

[0041] Preferably, in step S2, the coating method includes one of casting, spin coating, scraping coating, dip coating, and spraying; the melt polymerization reaction vessel includes one of a high-pressure reactor, a sealed hard glass tube, a sealed thick-walled reaction flask, a tube furnace, a vacuum oven, a glove box filled with an inert atmosphere, or other devices capable of providing an inert atmosphere.

[0042] Further, in step S3, the reacted substrate is immersed in ethanol to wash away the additives; subsequently, the substrate is immersed in water, and the covalent organic framework film is peeled off from the substrate by the permeation of water, resulting in a self-supporting film. This step utilizes ethanol to effectively dissolve and remove sulfonamide additives, while the subsequent water immersion peeling is a gentle physical demolding method. This process avoids chemical damage to the COF film structure caused by strong acids, strong bases, or organic solvents, thus perfectly preserving the macroscopic integrity and microporous structure of the film.

[0043] Further, in step S3, the self-supporting film obtained by peeling is washed with ethanol and then activated. The activation method includes one or more of Soxhlet extraction, sublimation, freeze-drying, and rotary evaporation. Preferably, the ethanol-washed self-supporting film is activated in a vacuum or inert atmosphere at 40-80°C for 2-12 hours. This low-temperature drying process aims to thoroughly remove solvent molecules (such as water and ethanol) remaining in the COF nanopores, thereby "activating" the film and restoring its intrinsic high specific surface area and porosity. Performing the process in an inert atmosphere or vacuum prevents high-temperature oxidation and ensures that the final product has extremely high chemical purity.

[0044] Furthermore, the method also includes recovering the mixture of ethanol and additives obtained from washing in step S3, and separating and recovering the ethanol and additives by distillation for recycling. This invention achieves efficient recycling of additives and solvents through simple distillation, significantly reducing waste emissions and raw material consumption, laying a solid foundation for large-scale industrial application.

[0045] The second objective of this invention is achieved by providing a covalent organic framework self-supporting membrane for precision filtration of CMP ultrapure cleaning fluid, prepared by the method described in the first objective of this invention, wherein the thickness of the covalent organic framework self-supporting membrane is 5-100 μm and the BET specific surface area is not less than 100 m². 2 / g, and has a regular pore size of 1.0 to 5.0 nm.

[0046] The third objective of this invention is achieved by providing a covalent organic framework self-supporting film according to the second objective of this invention in the preparation of a cleaning solution filtration device after semiconductor chemical mechanical polishing. The covalent organic framework self-supporting film is used to retain and remove nanoscale metal sols and suspended particles with a particle size greater than 2 nm from the cleaning solution.

[0047] The method for preparing self-supporting covalent organic framework (COF) films provided by this invention uses sulfonamide-based additives. Due to their unique and strong activation capabilities, these additives can form self-supporting COF films with ultra-high crystallinity and regular nanopores, thereby achieving absolute retention accuracy and high throughput in filtration applications. Simultaneously, the excellent recyclability of these additives ensures the extremely high chemical purity of the final COF film product, fundamentally eliminating the risk of secondary contamination introduced by the filter membrane itself during the filtration process. This makes it particularly suitable for fields with stringent purity requirements, such as semiconductor CMP ultrapure cleaning solutions.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] (1) The present invention provides a method for preparing a covalent organic framework self-supporting film, which adopts a technical path combining solution casting and melt polymerization. This method utilizes a solvent to achieve uniform mixing and film formation of the reaction components at room temperature, and then completes the evaporation of the solvent and the subsequent polymerization reaction through programmed temperature rise. This method has strong versatility and can be applied to the preparation of highly crystalline COF films with various linkages such as imine and olefin bonds. At the same time, thanks to the excellent recyclability of sulfonamide additives and the mild water stripping process, the entire process not only has low equipment requirements and is easy to scale up, but also ensures the high purity and low production cost of the final product from the source, laying a solid foundation for industrial application.

[0050] (2) The covalent organic framework self-supporting film prepared by this invention possesses regular nanopores, high specific surface area, excellent mechanical strength, and extremely high chemical purity. When applied to the precision filtration of ultrapure cleaning solutions for semiconductor CMP, it exhibits performance advantages that traditional filter membranes cannot match. Like a precise "molecular sieve," it can reliably trap nanoscale metal sols and particulate contaminants in the cleaning solution, fundamentally eliminating the risk of scratches on the wafer surface and providing key material assurance for improving the yield of high-end chip manufacturing. Attached Figure Description

[0051] Figure 1 The X-ray diffraction pattern of the COF self-supporting film obtained in Example 1;

[0052] Figure 2 Fourier transform infrared spectrum of the COF self-supporting membrane obtained in Example 1;

[0053] Figure 3 This is a cross-sectional view of the COF self-supporting membrane obtained in Example 1 under a scanning electron microscope;

[0054] Figure 4 The surface image of the COF self-supporting film obtained in Example 1 is shown under a scanning electron microscope.

[0055] Figure 5 A digital photograph of the COF self-supporting membrane obtained in Example 1;

[0056] Figure 6 The nitrogen adsorption-desorption curve of the COF self-supporting membrane obtained in Example 1 at 77 K;

[0057] Figure 7 The stress-strain curve of the COF self-supporting membrane obtained in Example 1 is shown.

[0058] Figure 8 The X-ray diffraction pattern of the COF self-supporting film obtained in Example 2;

[0059] Figure 9This is a cross-sectional view of the COF self-supporting membrane obtained in Example 2 under a scanning electron microscope;

[0060] Figure 10 The surface image of the COF self-supporting film obtained in Example 2 is shown under a scanning electron microscope.

[0061] Figure 11 The X-ray diffraction pattern of the COF self-supporting film obtained in Example 4;

[0062] Figure 12 Fourier transform infrared spectrum of the COF self-supporting membrane obtained in Example 4;

[0063] Figure 13 The X-ray diffraction pattern of the COF material prepared by reusing the additives in Example 5;

[0064] Figure 14 The X-ray diffraction pattern of the imine-linked COF self-supporting film synthesized in Example 6;

[0065] Figure 15 The X-ray diffraction pattern of the material obtained in Comparative Example 1;

[0066] Figure 16 The X-ray diffraction pattern of the thin film obtained in Comparative Example 2;

[0067] Figure 17 Digital photographs of the Tyndall effect of colloid A and filtrate A1 in the application example;

[0068] Figure 18 The particle size distribution diagrams for colloid A and filtrate A1 in the application example are shown.

[0069] Figure 19 This is a scanning electron microscope (SEM) image of the surface of the COF thin film after filtration in an application example.

[0070] Figure 20 This is a particle size distribution diagram of colloid A and filtrate A2 in the application example. Detailed Implementation

[0071] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0072] This invention provides a method for preparing a covalent organic framework self-supporting thin film for precision filtration of CMP ultrapure cleaning fluid, comprising the following steps:

[0073] Step 1: Dissolve the first organic monomer, the second organic monomer, and the auxiliary agent in an organic solvent to obtain a coating solution; the auxiliary agent is selected from one or more of sulfonamides, sulfonyl hydrazides, and sulfonyl imides; the functional groups of the first and second organic monomers are selected to react with each other, such that the covalent organic framework self-supporting film is a covalent organic framework structure connected by imine bonds, olefin bonds, or imide bonds; the molar ratio of the first organic monomer to the second organic monomer is 1:8-8:1; the molar ratio of the auxiliary agent to the first organic monomer is 12-60:1; the organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0074] Step 2: The coating solution is uniformly coated onto the substrate surface and subjected to programmed temperature rise treatment: First, most of the organic solvent is evaporated at a temperature below the melting point of the additive to form a precursor film, and then a melt polymerization reaction is carried out at a temperature above the melting point of the additive to form a covalent organic framework film on the substrate; the substrate includes one of quartz plate, glass plate, silicon wafer, polyimide film, polytetrafluoroethylene plate, ceramic sheet, and metal sheet; in the programmed temperature rise treatment, the temperature used for solvent evaporation is 60-200℃; preferably, the temperature is raised to the second temperature to enter the melt polymerization reaction when slight solid precipitation occurs, on the one hand evaporating the remaining solvent, and on the other hand melting the additive to cast the film; the temperature used for melt polymerization reaction is 150-220℃; the melt polymerization reaction time is 12 hours to 7 days.

[0075] Step 3: Immerse the reacted substrate in ethanol to wash away the additives; then immerse the substrate in water, using the water's permeation to peel the covalent organic framework film from the substrate, obtaining a self-supporting film; wash the peeled self-supporting film with ethanol, then dry and activate it in a vacuum or inert atmosphere at 40-80°C for 2-12 hours to obtain the covalent organic framework self-supporting film. Recover the mixture of ethanol and additives obtained from washing, and separate the ethanol and additives by distillation for recycling.

[0076] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0077] Example 1

[0078] Weigh 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (28 mg, 0.08 mmol), pyromellitic dianhydride (26 mg, 0.12 mmol), and p-toluenesulfonamide (246 mg, 1.4 mmol). Place the above ingredients into a glass bottle, add DMF (2 mL), and stir at room temperature for 15 minutes until all solids dissolve, yielding a bright yellow, clear, transparent, viscous liquid. In a glove box (O2 ≤ 0.1 ppm, H2O ≤ 0.1 ppm), uniformly coat the liquid onto a clean glass slide. Using a heating plate, raise the temperature to 80°C and maintain for 1 hour to evaporate the solvent. When slight crystals precipitate, raise the temperature to 160°C and maintain for 1 hour. Then, raise the temperature to 190°C and crystallize for 1 day to obtain a glass slide coated with a COF film. After the reaction is complete, cool the temperature to room temperature, remove the COF-coated glass slide from the glove box, and immerse it in ethanol to thoroughly wash away the auxiliary agent (p-toluenesulfonamide). The glass slide coated with the COF film, after the additives have been removed, is then immersed in water to demold the COF film from the substrate (glass slide), yielding a self-supporting polyimide-linked COF film. After washing the self-supporting COF film with ethanol, it is transferred to an oven and dried at 60°C for activation, resulting in the final self-supporting polyimide-linked COF film. The ethanol solution used for washing can be recovered and separated using a rotary evaporator along with the additives (p-toluenesulfonamide). The recovered additives and solvents can be reused in subsequent reactions.

[0079] like Figure 1 As shown, powder X-ray diffraction results indicate that the polyimide-linked COF film obtained using this method exhibits high crystallinity. Figure 2 The Fourier transform infrared spectroscopy in the image confirms that the sample is a polyimide-linked COF film. Figure 3 The image shows a cross-sectional view of the obtained polyimide COF film under a scanning electron microscope, demonstrating that the obtained polyimide COF self-supporting film has a uniform and dense internal structure with a thickness of 10 micrometers. Figure 4 The image shows the surface of the obtained polyimide COF film under a scanning electron microscope, proving that the surface of the obtained polyimide COF film is smooth and defect-free. Figure 5 A digital photograph of the resulting polyimide COF film. Figure 6 The nitrogen adsorption-desorption curve of the obtained polyimide COF film at 77K proves that the obtained polyimide COF film has good porosity and large specific surface area. Figure 7 The stress-strain curves show that the polyimide COF film prepared in Example 1 has good mechanical properties.

[0080] This example demonstrates that, using para-alkyl-substituted sulfonamide additives (p-methylbenzenesulfonamide), under segmented heating process conditions, self-supporting COF films linked by imide bonds can be effectively synthesized.

[0081] Example 2

[0082] Weigh 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (28 mg, 0.08 mmol), pyromellitic acid (30.5 mg, 0.12 mmol), and p-trifluoromethylbenzenesulfonamide (i.e., 4-trifluoromethylbenzenesulfonamide) (315 mg, 1.4 mmol). Place the above raw materials into a glass bottle, add NMP (2 mL), and stir at room temperature for 15 minutes until all solids dissolve, yielding a bright yellow, clear, transparent, viscous liquid. In a glove box, uniformly coat the liquid onto a clean silicon wafer surface. Using a heating plate, heat to 190°C and maintain for 1 hour to evaporate the solvent and melt the reactants to form a COF precursor film. Transfer the silicon wafer coated with the COF precursor to a tube furnace and heat under vacuum at 200°C for 3 days. After the reaction is complete, cool to room temperature, remove the silicon wafer coated with the COF film from the tube furnace, and immerse it in ethanol to thoroughly wash away the additive (p-trifluoromethylbenzenesulfonamide). The silicon wafer coated with the COF film, after the additives have been removed, is then immersed in water to demold the COF film from the substrate (glass slide), yielding a self-supporting polyimide-linked COF film. The self-supporting COF film is then washed with ethanol to remove water, and subsequently transferred to an oven at 60°C for drying and activation, resulting in the final self-supporting polyimide-linked COF film. The ethanol solution used for washing can be recovered and separated using a rotary evaporator, along with the additives (p-trifluoromethylbenzenesulfonamide). The recovered additives and solvents can be reused in subsequent reactions.

[0083] Figure 8 The X-ray diffraction pattern of the obtained polyimide COF film demonstrates that the COF film obtained by this method has good crystallinity. Figure 9 The image shows a cross-sectional view of the obtained polyimide COF film under a scanning electron microscope, demonstrating that the obtained polyimide COF self-supporting film has a uniform and dense internal structure with a thickness of 20 micrometers. Figure 10 The image shows the surface of the obtained polyimide COF film under a scanning electron microscope, proving that the surface of the obtained polyimide COF film is smooth and defect-free.

[0084] This example demonstrates that using sulfonamide auxiliaries (p-trifluoromethylbenzenesulfonamide) with strong electron-withdrawing groups at the para position, and employing vacuum and high-temperature reaction conditions, is also applicable to self-supporting COF films formed by imide bonds from carboxylic acid monomers.

[0085] Example 3

[0086] Weigh 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (28 mg, 0.08 mmol), pyromellitic dianhydride (26 mg, 0.12 mmol), and p-toluenesulfonyl hydrazine (260 mg, 1.4 mmol). Place these ingredients in a glass bottle, add 2 mL of DMSO, and stir at room temperature for 15 minutes until all solids dissolve, yielding a bright yellow, clear, transparent, viscous liquid. In a glove box, uniformly coat the liquid onto a clean glass slide. Using a heating plate, heat to 200°C and maintain for 3 days, evaporating the solvent while melting the reactants and allowing the reactants to crystallize, obtaining a glass slide coated with a COF film. After the reaction is complete, cool to room temperature, remove the COF-coated glass slide from the glove box, and immerse it in ethanol to thoroughly wash away the additive (p-toluenesulfonyl hydrazine). Then, immerse the COF-coated glass slide (with additive removed) in water to demold the COF film from the substrate (glass slide), obtaining a self-supporting polyimide-linked COF film. After washing the self-supported COF film with ethanol to remove water, the film was transferred to an oven and dried at 60°C for activation, yielding the final self-supported polyimide-linked COF film. The ethanol solution used for washing can be recovered and separated using a rotary evaporator along with the auxiliary agent (p-methylbenzenesulfonyl hydrazine). The recovered auxiliary agent and solvent can be reused in subsequent reactions.

[0087] Example 4

[0088] Weigh 1,3,5-trimethyl-2,4,6-triazine (12.3 mg, 0.1 mmol), 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (29.1 mg, 0.15 mmol), and p-trifluoromethylbenzenesulfonamide (315 mg, 1.4 mmol). Place the above raw materials into a glass bottle, add 2 mL of DMSO, and stir at room temperature for 15 minutes until all solids dissolve, yielding a bright yellow, clear, transparent, viscous liquid. In a glove box, uniformly coat the liquid onto a clean glass slide. Using a heating plate, heat to 200°C and maintain for 3 days, evaporating the solvent while melting the reactants and allowing the reactants to crystallize, obtaining a glass slide coated with a COF film. After the reaction is complete, cool to room temperature, remove the COF-coated glass slide from the glove box, and immerse it in ethanol to thoroughly wash away the auxiliary agent (p-trifluoromethylbenzenesulfonamide). The glass slide coated with the COF film, after the additives have been removed, is then immersed in water to demold the COF film from the substrate (glass slide), yielding a self-supporting polyimide-linked COF film. After washing the self-supporting COF film with ethanol, it is transferred to an oven and dried at 60°C for activation, resulting in a final self-supporting polyimide-linked COF film with a thickness of 8 micrometers. The ethanol solution used for washing can be recovered and separated using a rotary evaporator, along with the additives (p-trifluoromethylbenzenesulfonamide). The recovered additives and solvents can be reused in subsequent reactions.

[0089] like Figure 11 As shown, powder X-ray diffraction results indicate that the sample obtained using this method has high crystallinity. Figure 12 The Fourier transform infrared spectroscopy confirmed that the sample was a COF thin film with alkene bonds. This example demonstrates that the method of the present invention is also applicable to the synthesis of self-supporting COF thin films with alkene bonds, and can be carried out using an isothermal integrated process.

[0090] Example 5

[0091] Resynthesis of recovered additives: Weigh 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (28 mg, 0.08 mmol), pyromellitic dianhydride (26 mg, 0.12 mmol), and p-toluenesulfonamide recovered in Example 1 (246 mg, 1.4 mmol); add the above raw materials to a glass bottle, add DMF (2 mL), and stir at room temperature for 15 minutes until all solids dissolve, obtaining a bright yellow, clear, transparent, viscous liquid. In a glove box (O2 ≤ 0.1 ppm, H2O ≤ 0.1 ppm), uniformly coat the above liquid onto the surface of a clean glass slide, and use a heating platform to heat to 80°C and hold for 1 hour to evaporate the solvent. When slight crystals precipitate, heat to 160°C and hold for 1 hour, then heat to 190°C for crystallization reaction for 1 day to obtain a glass slide coated with a COF film. After the reaction is complete and the temperature is lowered to room temperature, the glass slide coated with the COF film is removed from the glove box and immersed in ethanol to thoroughly wash away the auxiliary agent (p-toluenesulfonamide). Then, the glass slide with the auxiliary agent removed and coated with the COF film is immersed in water to demold the COF film from the substrate (glass slide), obtaining a self-supporting polyimide-linked COF film. After washing the water off the self-supporting COF film with ethanol, the film is transferred to an oven and dried at 60°C for activation, yielding a final self-supporting polyimide-linked COF film with a thickness of 10 micrometers. The ethanol solution used for washing can be recovered and separated using a rotary evaporator, along with the auxiliary agent (p-toluenesulfonamide). The recovered auxiliary agent and solvent can be reused in the next reaction.

[0092] like Figure 13 As shown, X-ray diffraction test results indicate that the sample obtained using this method has high crystallinity.

[0093] Example 6

[0094] Weigh 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (28 mg, 0.08 mmol), 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (23 mg, 0.12 mmol), and p-toluenesulfonamide (246 mg, 1.4 mmol). Place the above raw materials into a glass bottle, add DMF (2 mL), and stir at room temperature for 15 minutes until all solids dissolve, yielding a bright yellow, clear, transparent, viscous liquid. In a glove box (O2 ≤ 0.1 ppm, H2O ≤ 0.1 ppm), uniformly coat the liquid onto a clean glass slide. Evaporate the solvent by heating to 80°C for 1 hour. When slight crystals precipitate, raise the temperature to 160°C and hold for 1 hour. Then, raise the temperature to 170°C and crystallize for 2 days to obtain a glass slide coated with a COF film. After the reaction is complete and the temperature is lowered to room temperature, the glass slide coated with the COF film is removed from the glove box and immersed in ethanol to thoroughly wash away the auxiliary agent (p-toluenesulfonamide). Then, the glass slide with the COF film coated and the auxiliary agent removed is immersed in water to demold the COF film from the substrate (glass slide), resulting in a self-supporting imine-linked COF film. After washing the water off the self-supporting COF film with ethanol, the film is transferred to an oven and dried at 60°C for activation, yielding a final self-supporting imine-linked COF film with a thickness of 10 micrometers. The ethanol solution used for washing can be recovered and separated using a rotary evaporator, along with the auxiliary agent (p-toluenesulfonamide). The recovered auxiliary agent and solvent can be reused in the next reaction.

[0095] like Figure 14 As shown, X-ray diffraction test results indicate that the sample film obtained using this method has high crystallinity.

[0096] Comparative Example 1

[0097] Compared with Example 1, the materials in this comparative example were prepared without the use of additives.

[0098] Weigh 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (28 mg, 0.08 mmol) and pyromellitic dianhydride (26 mg, 0.12 mmol). Place the above raw materials into a glass bottle, add DMF (2 mL), and stir at room temperature for 15 minutes until all solids dissolve, yielding a bright yellow, clear, and transparent liquid. In a glove box (O2 ≤ 0.1 ppm, H2O ≤ 0.1 ppm), uniformly coat the above liquid onto a clean glass slide. Use a heating plate to raise the temperature to 80°C and maintain it for 1 hour to evaporate the solvent. Then raise the temperature to 160°C and maintain it for 1 hour, followed by a reaction at 190°C for 1 day to obtain the product, which is a discontinuous sheet composed of solid powder.

[0099] like Figure 15As shown, X-ray diffraction tests indicate that the product does not have a distinct crystalline state, demonstrating the necessity of the additive for forming a covalent organic framework self-supporting film.

[0100] Comparative Example 2

[0101] Compared with Example 1, this comparative example replaces the sulfonamide compound auxiliary agent (p-methylbenzenesulfonamide) with an equimolar amount of an amide compound (p-methylbenzamide), while the other raw materials, proportions, and preparation steps are exactly the same.

[0102] Weigh 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (28 mg, 0.08 mmol), pyromellitic dianhydride (26 mg, 0.12 mmol), and p-methylbenzamide (189 mg, 1.4 mmol). Place the above raw materials into a glass bottle, add DMF (2 mL), and stir at room temperature for 15 minutes until all solids dissolve, yielding a bright yellow, clear, transparent, viscous liquid. In a glove box (O2 ≤ 0.1 ppm, H2O ≤ 0.1 ppm), uniformly coat the liquid onto a clean glass slide. Using a heating plate, raise the temperature to 80°C and maintain for 1 hour to evaporate the solvent. When slight crystals precipitate, raise the temperature to 160°C and maintain for 1 hour. Then, raise the temperature to 190°C and crystallize for 1 day to obtain a glass slide coated with a COF film. After the reaction is complete, cool the temperature to room temperature, remove the coated glass slide from the glove box, and immerse it in ethanol to thoroughly wash away the auxiliary agent (p-methylbenzamide). The glass slide coated with the film after removing the additives was then immersed in water to demold the film from the substrate (glass slide) to obtain a self-supporting polyfilm. After rinsing the water off the self-supporting film with ethanol, the film was transferred to an oven and dried at 60°C.

[0103] like Figure 16 As shown, the film has almost no crystallinity. This demonstrates that in an open system, amide-based additives evaporate and sublimate prematurely due to their low boiling points, causing the reactants to detach from the crystallization effect of the additives, ultimately making it difficult to form highly crystalline COF films.

[0104] Application examples

[0105] This application example uses the polyimide COF self-supporting film prepared in Example 1 to test the filtration performance of SiO2 nanospheres, in order to verify its absolute retention capacity and reliability in a simulated semiconductor CMP ultrapure cleaning fluid precision filtration scenario.

[0106] Colloid A, a simulated CMP solution, was formed by ultrasonically dispersing a mixture of silica nanospheres with diameters of 5 nm and 35 nm in deionized water. The polyimide COF film synthesized in Example 1 was then installed in a sand core filter. SiO2 colloid A was added to the filter with the polyimide COF film, and the colloid A was filtered using a vacuum pump to obtain filtrate A1. A preliminary Tyndall effect assessment of colloid A and filtrate A1 was performed using a red laser lamp, and the results are as follows: Figure 17 As shown. Further particle size distribution tests were performed on colloid A and filtrate A1 using a Malvern laser particle size analyzer. The results are shown below. Figure 18 As shown. Furthermore, to confirm whether the membrane filters SiO2 through pore size retention or adsorption, scanning electron microscopy analysis was performed on the filtered COF self-supporting membrane, as shown. Figure 19 As shown. As a control group, a commercially available 0.22-micron polytetrafluoroethylene membrane was used to filter the above colloid A, and the resulting filtrate was denoted as filtrate A2.

[0107] Depend on Figure 17 It was observed that colloid A before filtration exhibited a significant Tyndall effect, proving it to be a colloid; however, the filtered liquid A1 did not show a Tyndall effect, proving it was not a colloid. Laser particle size analysis revealed distinct 5 nm and 40 nm particle size peaks in the particle size distribution of colloid A, while no particle size peaks were detected in the filtered liquid A1, confirming the complete retention of SiO2 particles in colloid A by the COF membrane. Scanning electron microscopy images of the filtered membrane showed that SiO2 microspheres were retained by the dense, self-supporting surface of the COF membrane, while the solvent could rapidly permeate through the regular nanoscale pores of the COF. Laser particle size analysis of the control group filtrate A2 yielded the following results: Figure 20 As shown, there is no significant difference in the particle size distribution of silica particles in the colloid before and after filtration, proving that the commercial 0.22-micron filter membrane does not have a significant retention effect on the colloid.

[0108] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for preparing a covalent organic framework self-supporting thin film for precision filtration of CMP ultrapure cleaning fluid, characterized in that, Includes the following steps: S1. Dissolve the first organic monomer, the second organic monomer, and the auxiliary agent in an organic solvent to obtain a coating liquid; the auxiliary agent is a sulfonamide and / or sulfonyl hydrazine compound; the molar ratio of the auxiliary agent to the first organic monomer is 12-60:1; S2. The coating liquid is uniformly coated on the substrate surface and subjected to programmed temperature rise treatment: First, most of the organic solvent is evaporated and removed at a temperature lower than the melting point of the additive to form a precursor film, and then a melt polymerization reaction is carried out at a temperature higher than the melting point of the additive to form a covalent organic framework film on the substrate. S3. After peeling, washing and activating the product obtained in step S2, a covalent organic framework self-supporting film is obtained; the functional groups of the first organic monomer and the second organic monomer are selected to react with each other, so that the covalent organic framework self-supporting film is a covalent organic framework structure connected by imine bonds, olefin bonds or imide bonds.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of the first organic monomer to the second organic monomer is 1:8-8:

1.

3. The preparation method according to claim 1, characterized in that, In step S1, the organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

4. The preparation method according to claim 1, characterized in that, In step S2, the substrate includes one of the following: quartz plate, glass plate, silicon wafer, polyimide film, polytetrafluoroethylene plate, ceramic sheet, and metal sheet.

5. The preparation method according to claim 1, characterized in that, In step S2, during the programmed temperature rise process, the temperature for solvent evaporation is 60-200℃; the temperature for melt polymerization is 150-220℃; and the time for melt polymerization is 6 hours to 7 days.

6. The preparation method according to claim 1, characterized in that, In step S3, the reacted substrate is immersed in ethanol to wash away the additives; then the substrate is immersed in water, and the covalent organic framework film is peeled off from the substrate by the permeation of water to obtain a self-supporting film.

7. The preparation method according to claim 1 or 6, characterized in that, In step S3, the self-supporting film obtained by peeling is cleaned with ethanol and then dried and activated in air, vacuum or inert atmosphere at 40-80°C for 2-12 hours.

8. The preparation method according to claim 1, characterized in that, The method further includes recovering the mixture of ethanol and additives obtained from washing in step S3, and recovering the ethanol and additives by distillation for recycling.

9. A covalent organic framework self-supporting membrane for precision filtration of CMP ultrapure cleaning fluid, prepared by the method according to any one of claims 1-8, characterized in that, The thickness of the covalent organic framework self-supporting film is 5-100 μm; the BET specific surface area is not less than 100 m². 2 / g, and has a regular pore size of 1.0 to 5.0 nm.

10. The application of a covalent organic framework self-supporting thin film according to claim 9 in a filtration apparatus for cleaning solutions after semiconductor chemical mechanical polishing, characterized in that, The covalent organic framework self-supporting film is used to trap and remove nanoscale metal sols and suspended particles with a particle size greater than 2 nm from the cleaning solution.

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