A metal chelating agent, its preparation method and application

Abstract

This invention relates to the field of silicon wafer cleaning agents, specifically to a metal chelating agent, its preparation method, and its application. The metal chelating agent comprises cellulose nanofibers, i.e., CNFs@PTA, with at least a portion of their surface coated with polytannic acid. Nanomaterials possess advantages such as small size effect, quantum effect, and surface effect. CNFs are rod-shaped nanomaterials with numerous hydroxyl groups, making them easy to surface modify. TA is a polyphenol compound that can undergo oxidative self-polymerization under alkaline conditions, rapidly combining with the matrix to deposit a polyphenol layer on the matrix surface. Furthermore, its ortho- and ortho-hydroxyl groups can undergo complexation reactions with metal ions. This invention coats polytannic acid onto the surface of CNFs through TA self-polymerization, resulting in CNFs@PTA with excellent metal ion chelating ability. Using CNFs@PTA in silicon wafer cleaning agents can effectively remove metal contamination.

Description

Technical Field

[0001] This invention relates to the field of silicon wafer cleaning agents, and more specifically, to a metal chelating agent, its preparation method, and its application. Background Technology

[0002] With the rapid development of solar silicon wafers, the demands for quality have exploded, posing new challenges to the efficiency and stability of silicon wafer cells. Among these challenges, the surface cleanliness of the silicon wafer is a key factor, directly affecting the power generation efficiency of the solar cell. Therefore, for high-efficiency solar cells, the cleaning treatment of the silicon wafer surface is crucial.

[0003] Silicon wafers are produced by cutting silicon rods. The contaminants generated during the cutting process can be categorized into four types: dust contamination, organic contamination (mainly from the cutting fluid used in the production process), metal contamination (mainly from production equipment and diamond wire), and silicon powder contamination (mainly from silicon powder generated during the cutting process).

[0004] Metal contamination is one of the most serious sources of pollution during silicon wafer production. It can degrade the structure and performance of the silicon wafer surface. For example, metal ions can form oxides on the wafer surface, causing charge loss, affecting electron migration, and leading to a decline in wafer performance. Currently, due to the use of diamond wire cutting, metal ion contamination introduced during silicon rod processing is becoming increasingly significant. To remove metal ions, amine-based cleaning agents with chelating properties are often added to cleaning agents, but their removal power for metal ions is weak, especially for Cu, Fe, and Ni ions. Therefore, developing a highly efficient metal chelating agent and a silicon wafer cleaning agent with high efficiency in removing metal contamination, along with their preparation methods and cleaning methods, is of great significance for ensuring silicon wafer quality and improving the performance and stability of solar silicon wafer cells.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The first objective of this invention is to provide a metal chelating agent that has a strong chelating ability for metal ions and can efficiently remove metal contaminants when used in cleaning agents.

[0007] The second objective of this invention is to provide a method for preparing the metal chelating agent as described above, wherein polytannic acid is deposited on the surface of CNFs through the self-polymerization of tannic acid, and the resulting CNFs@PTA has excellent metal chelating ability, and the preparation process is simple and controllable.

[0008] A third objective of this invention is to provide the use of the metal chelating agent as described above or the metal chelating agent prepared by the method described above in the preparation of silicon wafer cleaning agents.

[0009] The fourth objective of this invention is to provide a silicon wafer cleaning agent that can significantly improve the removal rate of metal ions and effectively remove metal contamination.

[0010] The fifth objective of this invention is to provide a method for preparing the silicon wafer cleaning agent as described above. This method has a simple preparation process, mild and controllable conditions, and is convenient for mass production.

[0011] The sixth objective of this invention is to provide a method for cleaning silicon wafers.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] A metal chelating agent comprising cellulose nanofibers, namely CNFs@PTA, with at least a portion of their surface coated with polytannic acid.

[0014] A method for preparing a metal chelating agent includes the following steps:

[0015] Cellulose nanofibers and a pH buffer were added to a tannic acid solution to obtain a mixed solution. The pH of the mixed solution was adjusted to 8.6-9.5, and the mixture was stirred, reacted, separated into solid and liquid components, and dried to obtain CNFs@PTA.

[0016] The use of the metal chelating agent described in the foregoing embodiments or the metal chelating agent prepared by the preparation method described in the foregoing embodiments in the preparation of silicon wafer cleaning agents.

[0017] A silicon wafer cleaning agent comprises a first metal chelating agent, a surfactant, an alkali, a corrosion inhibitor, an additive, and water;

[0018] The first metal chelating agent is the metal chelating agent described in the foregoing embodiments or a metal chelating agent prepared by the preparation method of the metal chelating agent described in the foregoing embodiments.

[0019] A method for preparing a silicon wafer cleaning agent includes the following steps:

[0020] Mix the surfactant with water, add the alkali while stirring, and continue stirring for 10-20 minutes; add the first metal chelating agent and / or the second metal chelating agent, corrosion inhibitor and auxiliaries, and stir until completely dissolved to obtain the final product.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The metal chelating agent provided by the present invention includes cellulose nanofibers, namely CNFs@PTA, with at least a portion of their surface coated with polytannic acid. Nanomaterials have advantages such as small size effect, quantum effect and surface effect, which can effectively improve the performance of materials. CNFs are rod-shaped nanomaterials and contain a large number of hydroxyl groups, which are easy to modify the surface. Tannic acid is a polyphenol compound that can undergo oxidative self-polymerization under alkaline conditions and rapidly combine with the matrix. At the same time, the ortho-phenolic hydroxyl structure on TA can undergo complexation reaction with metal ions. The present invention deposits polytannic acid on the surface of CNFs to form a polyphenol layer through TA self-polymerization. The obtained CNFs@PTA has excellent metal ion chelating ability and can effectively remove metal contamination when used in silicon wafer cleaning agents.

[0023] (2) The silicon wafer cleaning agent provided by the present invention includes a novel high-efficiency metal chelating agent component (CNFs@PTA), a surfactant with strong detergency, a corrosion inhibitor and an antifoaming agent. Compared with traditional cleaning agents, it greatly improves the removal rate of metal ions and the efficiency of metal cleaning. It has strong detergency and can effectively reduce the over-corrosion rate, reduce or prevent the generation of oxide wafers. It produces less cleaning foam, which not only saves water resources, reduces cleaning time and production electricity, but also relieves the pressure of subsequent water treatment. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in 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 the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 The structural formula for tannic acid;

[0026] Figure 2 The general structural formula of cellulose nanofibers provided in the embodiments of the present invention;

[0027] Figure 3 A cleaning process flow diagram provided for an embodiment of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0029] A first aspect of the present invention provides a metal chelating agent comprising cellulose nanofibers, namely CNFs@PTA, at least partially coated with polytannic acid.

[0030] like Figure 1 As shown, tannic acid (TA) is a polyphenolic compound rich in catechol and pyrogallol groups. Under alkaline conditions, it can undergo oxidative self-polymerization, rapidly combining with various matrices to deposit a polyphenol layer on the substrate surface, representing a highly efficient and environmentally friendly surface modification method. Furthermore, the multiple ortho- and tho-hydroxyl groups in TA can act as polyhydroxyl ligands, undergoing complexation reactions with metal ions. Two adjacent hydroxyl groups can form stable five-membered ring chelates with metal ions in the form of oxonions. Although the third hydroxyl group in the pyrogallol structure does not participate in complexation, it can promote the dissociation of the other two hydroxyl groups, thereby promoting the formation and stability of the complex.

[0031] Nanomaterials can effectively improve material properties due to their advantages such as small size effect, quantum effect, and surface effect. For example... Figure 2 As shown, cellulose nanofibers (CNFs) are rod-shaped nanomaterials with a large number of hydroxyl groups. Therefore, CNFs are also a material that is easy to modify on the surface.

[0032] This invention utilizes CNFs@PTA, obtained by coating CNFs with polytannic acid, which possesses excellent metal ion chelating ability. When used in silicon wafer cleaning agents, it can significantly improve the removal rate of metal ions such as Cu, Fe, and Ni compared to conventional amine complexing agents and tannic acid complexing agents. This effectively removes metal contaminants from solar silicon wafers and improves their performance.

[0033] A second aspect of the present invention provides a method for preparing the metal chelating agent described in the foregoing embodiments, comprising the following steps:

[0034] Cellulose nanofibers and a pH buffer were added to a tannic acid solution to obtain a mixed solution. The pH of the mixed solution was adjusted to 8.6-9.5, and the reaction was carried out by stirring, solid-liquid separation, and drying to obtain CNFs@PTA.

[0035] This invention involves oxidizing and self-polymerizing TA under alkaline conditions to form polytannic acid (PTA), which then combines with CNFs to deposit a polyphenol layer on the CNFs surface, resulting in cellulose nanofibers (CNFs@PTA) with at least a portion of their surface coated with polytannic acid. CNFs@PTA not only possesses excellent metal chelating ability but also has a simple and controllable preparation process, facilitating mass production and application.

[0036] In some implementations, typically but not limitingly, for example, the pH of the mixed solution can be adjusted to any one of 8.6, 8.8, 9.0, 9.2, 9.5 or a range of any two of these values.

[0037] In some specific embodiments of the present invention, the mass ratio of cellulose nanofibers to tannic acid in the mixed solution is 0.5-1:10. Typically, but not limitingly, it can be any one value or a range of any two values ​​from 0.5:10, 0.6:10, 0.7:10, 0.8:10, 0.9:10, 1:10. An excessively large or small mass ratio of CNFs to TA will reduce the metal ion chelating ability, thereby affecting the metal ion removal rate. This is because when the amount of TA is too large, the small size effect, quantum effect, and surface effect of CNFs cannot be manifested; while when the amount of CNFs is too large, the phenolic hydroxyl groups in the system are greatly reduced, and the chelating effect is reduced. Therefore, it is necessary to reasonably control the mass ratio of CNFs to TA.

[0038] In some specific embodiments of the present invention, the tannic acid solution can be an aqueous solution of tannic acid.

[0039] In some specific embodiments of the present invention, the mass concentration of tannic acid in the tannic acid solution is 0.2%-1%, typically but not limitingly, for example, it can be any one value or a range of any two values ​​from 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%.

[0040] In some specific embodiments of the present invention, the pH buffer includes a Tris buffer.

[0041] In some specific embodiments of the present invention, the stirring reaction time of the mixed solution is 20-30 h, typically but not limitingly, for example, the stirring reaction time can be any one value or a range of any two values ​​among 20 h, 22 h, 24 h, 26 h, 28 h, and 30 h.

[0042] A third aspect of the present invention provides the use of a metal chelating agent prepared by the method described in the foregoing embodiments or the metal chelating agent prepared by any of the foregoing embodiments in the preparation of a silicon wafer cleaning agent.

[0043] A fourth aspect of the present invention provides a silicon wafer cleaning agent comprising a first metal chelating agent, a surfactant, an alkali, a corrosion inhibitor, an additive, and water.

[0044] The first metal chelating agent is the metal chelating agent described in the foregoing embodiments or the metal chelating agent prepared by the method described in any one of the foregoing embodiments.

[0045] The silicon wafer cleaning agent provided by this invention, compared with traditional cleaning agents, adopts a novel metal chelating agent, which greatly improves the removal rate of metal ions; it also contains alkali and surfactants with strong detergency, resulting in strong detergency; the addition of corrosion inhibitors can effectively reduce the over-corrosion rate and reduce or prevent the formation of oxide wafers; the addition of defoaming agents results in less foam during cleaning, which not only saves water resources, reduces cleaning time and production electricity, but also alleviates the pressure on subsequent water treatment.

[0046] In some specific embodiments of the present invention, the silicon wafer cleaning agent comprises, by mass percentage, 10%-20% alkylphenol polyoxyethylene ether, 2%-5% fatty alcohol polyoxyethylene ether, 2%-4% alkali, 0.5%-5% first metal chelating agent, 2%-5.5% corrosion inhibitor, 0.1%-0.3% additives, and the balance being water. To avoid impurities, deionized water is preferred.

[0047] In some embodiments, typically but not limitingly, for example, in silicon wafer cleaning agents, the mass percentage of alkylphenol polyoxyethylene ether can be any one value or a range of any two values ​​from 10%, 12%, 14%, 16%, 18%, and 20%; the mass percentage of fatty alcohol polyoxyethylene ether can be any one value or a range of any two values ​​from 2%, 3%, 4%, and 5%; the mass percentage of alkali can be any one value or a range of any two values ​​from 2%, 2.5%, 3%, 3.5%, and 4%; the mass percentage of the first metal chelating agent can be any one value or a range of any two values ​​from 0.5%, 1%, 2%, 3%, 4%, and 5%; the mass percentage of corrosion inhibitor can be any one value or a range of any two values ​​from 2%, 3%, 4%, 5%, and 5.5%; and the mass percentage of additives can be any one value or a range of any two values ​​from 0.1%, 0.2%, and 0.3%.

[0048] In some specific embodiments of the present invention, the silicon wafer cleaning agent further includes a second metal chelating agent, which is selected from disodium ethylenediaminetetraacetate and / or diethylenetriaminepentaacetic acid; the first metal chelating agent and the second metal chelating agent can be used together to produce a synergistic effect, and the removal effect of metal contamination is better.

[0049] In some specific embodiments of the present invention, the mass concentration of disodium ethylenediaminetetraacetate in the silicon wafer cleaning agent is 0-1%.

[0050] In some specific embodiments of the present invention, the mass concentration of diethylenetriaminepentaacetic acid in the silicon wafer cleaning agent is 0%-2%.

[0051] In some specific embodiments of the present invention, the mass ratio of the first metal chelating agent, disodium ethylenediaminetetraacetate, and diethylenetriaminepentaacetic acid is 1-4:1-2:1-4.

[0052] In some specific embodiments of the present invention, the corrosion inhibitor includes at least one of diethanolamine, triethanolamine, and ethylenediamine. The use of organic base corrosion inhibitors reduces the over-corrosion rate and prevents the formation of oxide flakes. Furthermore, the corrosion inhibitors used all contain nitrogen (N) and possess a certain ability to complex metal ions, thus assisting metal chelating agents in removing metal ions.

[0053] In some specific embodiments of the present invention, the mass concentration of diethanolamine in the silicon wafer cleaning agent is 0%-0.5%; and / or, the mass concentration of triethanolamine in the silicon wafer cleaning agent is 0.1%-3%; and / or, the mass concentration of ethylenediamine in the silicon wafer cleaning agent is 0%-2%.

[0054] In some specific embodiments of the present invention, the alkali used in the silicon wafer cleaning agent includes NaOH and / or KOH.

[0055] In some specific embodiments of the present invention, the additives include at least one of organosilicon defoamers, fatty alcohol defoamers, and silicone defoamers. Adding defoamers results in less foam during cleaning, which not only saves water resources and reduces cleaning time and electricity consumption, but also alleviates the pressure on subsequent water treatment.

[0056] A fifth aspect of the present invention provides a method for preparing a silicon wafer cleaning agent as described in any of the foregoing embodiments, comprising the following steps:

[0057] Mix the surfactant with water, and slowly add alkali in small amounts multiple times while stirring at 300-500 rpm. Continue stirring for 10-20 minutes to ensure complete dissolution and mixing. Then add a metal chelating agent (here, the metal chelating agent refers to the first metal chelating agent or a combination of the first metal chelating agent and the second metal chelating agent), corrosion inhibitor, and additives to the above solution, and stir until completely dissolved to obtain the final product.

[0058] In some embodiments, typically but not limitingly, for example, the stirring speed during the preparation of the cleaning agent can be any value or a range of any two values ​​from 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm; and the time for continued stirring and dissolution after adding alkali can be any value or a range of any two values ​​from 10 min, 12 min, 14 min, 16 min, 18 min, and 20 min.

[0059] The following detailed description of some embodiments of the present invention is provided in conjunction with specific examples. The CNFs used in the embodiments are CNFs prepared mechanically by SCIENCEK; all other raw materials used, unless otherwise specified, can be purchased commercially.

[0060] Example 1

[0061] Preparation of CNFs@PTA:

[0062] Weigh 0.6g of TA powder, add 99.4g of deionized water to prepare a TA aqueous solution with a mass fraction of 0.6%, and add 0.04g of CNFs to make the mass ratio of CNFs to TA 1:15.

[0063] Add an appropriate amount of pH buffer Tris (tris(hydroxymethyl)aminomethane) to adjust the pH of the above solution to approximately 9. After stirring and reacting at room temperature for 24 hours, centrifuge and dry to obtain CNFs@PTA.

[0064] By weight percentage, the silicon wafer cleaning agent comprises the following components:

[0065] Alkylphenol polyoxyethylene ether (OP-9) 15%, fatty alcohol polyoxyethylene ether (AEO-9) 3%, NaOH 3%, CNFs@PTA 2%, disodium ethylenediaminetetraacetate 0.5%, diethylenetriaminepentaacetic acid 0.5%, diethanolamine 0.5%, triethanolamine 2%, ethylenediamine 1.5%, isopropanol 0.2%, water balance.

[0066] The preparation method of the above cleaning agent is as follows:

[0067] The surfactants alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and deionized water are mixed. NaOH is slowly added in small amounts multiple times while stirring at 400 rpm. Stirring is continued at room temperature for 15 minutes. Metal chelating agents (first metal chelating agent and second metal chelating agent), corrosion inhibitors, and isopropanol additives are added in sequence and stirred until completely dissolved to obtain the cleaning agent.

[0068] Example 2

[0069] Synthesize CNFs@PTA:

[0070] Weigh 0.6g of TA powder, add 99.4g of deionized water to prepare a TA aqueous solution with a mass fraction of 0.6%, and add 0.04g of CNFs to make the mass ratio of CNFs to TA 1:15.

[0071] Add an appropriate amount of pH buffer Tris (tris(hydroxymethyl)aminomethane) to adjust the pH of the above solution to approximately 9. After stirring and reacting at room temperature for 24 hours, centrifuge and dry to obtain CNFs@PTA.

[0072] By weight percentage, the silicon wafer cleaning agent comprises the following components:

[0073] Alkylphenol polyoxyethylene ether (OP-9) 20%, fatty alcohol polyoxyethylene ether (AEO-9) 5%, NaOH 4%, CNFs@PTA 2%, disodium ethylenediaminetetraacetate 1%, diethylenetriaminepentaacetic acid 2%, diethanolamine 0.5%, triethanolamine 3%, ethylenediamine 2%, isopropanol 0.3%, water balance.

[0074] The preparation method of the above cleaning agent is as follows:

[0075] The surfactants alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and deionized water are mixed. NaOH is slowly added in small amounts multiple times while stirring at 500 rpm. The mixture is stirred for 20 minutes at room temperature. Metal chelating agents (first metal chelating agent and second metal chelating agent), corrosion inhibitor, and isopropanol are added in sequence and stirred until completely dissolved to obtain the cleaning agent.

[0076] Example 3

[0077] Synthesize CNFs@PTA:

[0078] Weigh 0.6g of TA powder, add 99.4g of deionized water to prepare a TA aqueous solution with a mass fraction of 0.6%, and add 0.04g of CNFs to make the mass ratio of CNFs to TA 1:15.

[0079] Add an appropriate amount of pH buffer Tris (tris(hydroxymethyl)aminomethane) to adjust the pH of the above solution to approximately 9. After stirring and reacting at room temperature for 24 hours, the solid and liquid are separated and dried to obtain CNFs@PTA.

[0080] By weight percentage, the silicon wafer cleaning agent comprises the following components:

[0081] Alkylphenol polyoxyethylene ether (OP-9) 10%, fatty alcohol polyoxyethylene ether (AEO-9) 3%, NaOH 2%, CNFs@PTA 0.5%, diethanolamine 0.5%, triethanolamine 0.5%, ethylenediamine 1%, isopropanol 0.1%, water balance.

[0082] The preparation method of the above cleaning agent is as follows:

[0083] The surfactants alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and deionized water are mixed. NaOH is slowly added in small amounts multiple times while stirring at 300 rpm. Stirring is continued at room temperature for 10 minutes. Metal chelating agent, corrosion inhibitor, and isopropanol are added in sequence and stirred until completely dissolved to obtain the cleaning agent.

[0084] Example 4

[0085] The difference between Example 4 and Example 1 is that in the process of synthesizing CNFs@PTA, the amount of CNFs is changed so that the mass ratio of CNFs to TA is 1:10, and the other conditions are the same as in Example 1.

[0086] Example 5

[0087] The difference between Example 5 and Example 1 is that in the process of synthesizing CNFs@PTA, the amount of CNFs is changed so that the mass ratio of CNFs to TA is 1:20, and the other conditions are the same as in Example 1.

[0088] Example 6

[0089] The difference between Example 6 and Example 1 is that all metal chelating agents in the cleaning agent components are CNFs@PTA, and no disodium ethylenediaminetetraacetate and diethylenetriaminepentaacetic acid are added. The total amount of metal chelating agent remains unchanged, and the other conditions are the same as in Example 1.

[0090] Comparative Example 1

[0091] The difference between Comparative Example 1 and Example 1 is that CNFs@PTA in Example 1 was replaced with an equal amount of tannic acid, while the other conditions were the same as in Example 1.

[0092] Comparative Example 2

[0093] The difference between Comparative Example 2 and Example 1 is that the metal chelating agent in the cleaning agent components is entirely diethylenetriaminepentaacetic acid, and CNFs@PTA and disodium ethylenediaminetetraacetate are not added. The total amount of metal chelating agent remains unchanged, and the other conditions are the same as in Example 1.

[0094] Comparative Example 3

[0095] The difference between Comparative Example 3 and Example 1 is that the metal chelating agent in the cleaning agent components is all disodium ethylenediaminetetraacetate, CNFs@PTA and diethylenetriaminepentaacetic acid are not added, the total amount of metal chelating agent remains unchanged, and the other conditions are the same as in Example 1.

[0096] Test case

[0097] The silicon wafers were cleaned using the cleaning agents prepared in each embodiment and comparative example, and the cleaning effects were statistically analyzed. The cleaning process is as follows:

[0098] like Figure 3 As shown, tanks 1-2 are pure water tanks, tanks 3-5 are chemical tanks, and each chemical tank needs to add 3L of the cleaning agent from the example. Tanks 6-8 are the same as tanks 1-2. Tanks 9-10 are pure water tanks without ultrasound. The ultrasound power of tanks 1-8 is about 1.2KW. The water volume of each tank in tanks 1-10 is about 500L, and the time is 180s. Tank 11 is a slow lifting tank with a time of 120s. Tanks 12-13 are drying tanks with a temperature set at 110℃ and a time of 300s.

[0099] The over-etching rate of the silicon wafer surface after cleaning was obtained from the sorting results of the sorting machine, and the metal ion content was determined according to GB / T 39145-2020.

[0100] The experimental results are shown in Table 1.

[0101] Table 1

[0102]

[0103]

[0104] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A silicon wafer cleaning agent, characterized in that, It includes a first metal chelating agent, a surfactant, an alkali, a corrosion inhibitor, an additive, and water; The first metal chelating agent comprises cellulose nanofibers, i.e., CNFs@PTA, with at least a portion of their surface coated with polytannic acid; its preparation method includes the following steps: Cellulose nanofibers and a pH buffer are added to a tannic acid solution to obtain a mixed solution, wherein the mass ratio of cellulose nanofibers to tannic acid is 0.5-1:

10. The pH of the mixed solution is adjusted to 8.6-9.5, and the mixture is stirred, reacted, separated into solid and liquid components, and dried to obtain CNFs@PTA.

2. The silicon wafer cleaning agent according to claim 1, characterized in that, It contains at least one of the following features: (1) The mass concentration of tannic acid in the tannic acid solution is 0.2%-1%; (2) The pH buffer includes Tris buffer; (3) The stirring reaction time is 20-30h.

3. The silicon wafer cleaning agent according to claim 1, characterized in that, The silicon wafer cleaning agent comprises, by weight percentage, 10%-20% alkylphenol polyoxyethylene ether, 2%-5% fatty alcohol polyoxyethylene ether, 2%-4% alkali, 0.5%-5% first metal chelating agent, 2%-5.5% corrosion inhibitor, 0.1%-0.3% additives, and the balance being water.

4. The silicon wafer cleaning agent according to any one of claims 1-3, characterized in that, The silicon wafer cleaning agent further includes a second metal chelating agent, which is selected from disodium ethylenediaminetetraacetate and / or diethylenetriaminepentaacetic acid.

5. The silicon wafer cleaning agent according to claim 4, characterized in that, The mass concentration of the disodium ethylenediaminetetraacetate is 0-1%.

6. The silicon wafer cleaning agent according to claim 4, characterized in that, The mass concentration of the diethylenetriaminepentaacetic acid is 0-2%.

7. The silicon wafer cleaning agent according to claim 1, characterized in that, It meets at least one of the following characteristics: (1) The corrosion inhibitor includes at least one of diethanolamine, triethanolamine and ethylenediamine; (2) The alkali includes NaOH and / or KOH; (3) The additives include at least one of organosilicon defoamer, fatty alcohol defoamer and silicone defoamer.

8. The method for preparing the silicon wafer cleaning agent according to any one of claims 1-7, characterized in that, Includes the following steps: Mix the surfactant with water, add the alkali while stirring, and continue stirring for 10-20 minutes; add the metal chelating agent, corrosion inhibitor and auxiliary agent, and stir until completely dissolved to obtain the final product; The metal chelating agent refers to a first metal chelating agent or a combination of a first metal chelating agent and a second metal chelating agent.

9. A method for cleaning silicon wafers, characterized in that, The silicon wafer surface is cleaned using the silicon wafer cleaning agent according to any one of claims 1-7.

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