A wet polishing aid for BC photovoltaic cells and a method for preparing the same

Abstract

The application belongs to the technical field of semiconductor polishing processing, and provides a wet polishing auxiliary agent for BC photovoltaic cells and a preparation method thereof. The auxiliary agent is composed of quaternary ammonium chitosan solution, chitosan imprint gel dispersion, betaine chitosan imprint gel dispersion, silane phosphonic acid polycarboxylic acid mother liquor, polyacrylic acid solution, sulfate inorganic electrolyte and deionized water. In the preparation, the chitosan is first quaternized, the pre-assembly system is constructed by using oil and fat model molecules, the imprint gel is formed by cross-linking sodium tripolyphosphate and geniposide and eluting the template, and the betaine imprint gel dispersion is obtained by grafting betaine monomers. The polycarboxylic acid mother liquor is prepared by copolymerizing acrylic acid, polyether monomers and sulfonic acid and phosphonic acid monomers and introducing silane groups. The finished product is obtained by mixing and filtering the components, and can be used for wet polishing to improve wetting and bubble removal, reduce surface defects and improve processing uniformity, and is conducive to obtaining more ideal texture morphology under the same weight reduction condition.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor polishing technology, and relates to a wet polishing aid for BC photovoltaic cells and its preparation method. Background Technology

[0002] In semiconductor manufacturing, wafers and silicon substrates typically undergo surface shaping processes such as dicing, grinding, and polishing to achieve a surface state that meets the requirements of subsequent critical processes such as photolithography, thin film deposition, diffusion, and bonding. Polishing involves not only material removal but also coupled processes such as interface wetting, particle transport, contamination control, and surface chemical state regulation. Among these processes, wet polishing and related wet cleaning play a crucial role in removing processing damage layers, reducing surface roughness, eliminating micro-defects, and controlling surface cleanliness.

[0003] Existing wet polishing systems still face several technical challenges in practical applications. First, polishing slurries are prone to generating and retaining bubbles under high-shear cycling and multiphase interface conditions. Bubble adhesion causes discontinuous liquid film coverage and leads to deviations in localized reactions and removal rates, resulting in defects such as flow marks and bubble imprints. Second, grease contaminants, residual organic matter, and fine particulate impurities introduced during polishing and handling tend to aggregate in the liquid phase and re-adsorb onto the substrate surface under surface energy, forming black spots, dirt, or particulate defects. While some additives can improve wetting and dispersion, they are prone to polyelectrolyte complexation, flocculation, or uncontrollable foaming in the presence of electrolytes or when pH fluctuates, thus introducing new sources of residue. Furthermore, the polishing slurry needs to maintain stability and repeatability over a wide process window, possessing both the ability to carry and inhibit redeposition of contaminants while avoiding adverse effects on subsequent thin film deposition, surface passivation, or metallization steps. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a wet polishing aid for BC photovoltaic cells and its preparation method. The aid is composed of a quaternary ammonium chitosan system, chitosan imprinted gel and its betaine-modified dispersion, silanephosphonic acid polycarboxylic acid mother liquor, polyacrylic acid, sulfate-based inorganic electrolytes, and water. A stable system is obtained through sequential mixing and acidity control, which enables contamination capture and redeposition inhibition, improves polishing uniformity, and reduces defect rate, thereby meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a wet polishing aid for BC photovoltaic cells, the method comprising:

[0007] S1, chitosan is added to deionized water to obtain a chitosan solution. Glycidyl trimethylammonium chloride is added to the chitosan solution to react and obtain a quaternary ammonium chitosan solution. Methyl palmitate and cholesterol are dispersed in anhydrous ethanol to obtain a template solution. The template solution is added dropwise to the quaternary ammonium chitosan solution and stirred to obtain a pre-assembled composite system. Sodium tripolyphosphate solution is added dropwise to the pre-assembled composite system. Gardenin is added and cured and crosslinked at room temperature to obtain an imprinted core microgel dispersion. The microgel dispersion is eluted to obtain a chitosan imprinted gel dispersion. Methacryloxyethyl sulfobetaine is added to the chitosan imprinted gel dispersion and nitrogen is passed through to deoxygenate it. Ammonium persulfate is added and reacted with tetramethylethylenediamine to obtain a betaine chitosan imprinted gel dispersion.

[0008] S2, under a nitrogen atmosphere, deionized water and acrylic acid are mixed, and then polyethylene glycol methyl ether acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, 3-mercaptopropyltrimethoxysilane and ammonium persulfate are added in sequence to react and obtain polycarboxylic acid mother liquor. Anhydrous ethanol is added to obtain silanephosphonic acid polycarboxylic acid mother liquor.

[0009] S3, deionized water, inorganic electrolyte, polyacrylic acid solution, silanephosphonic acid polycarboxylic acid mother liquor, quaternary ammonium chitosan solution, and betaine-chitosan imprinted gel dispersion are mixed evenly in sequence and filtered to obtain a wet polishing auxiliary agent for BC photovoltaic cells.

[0010] Specifically, it includes:

[0011] S1, chitosan is added to deionized water, and glacial acetic acid is added to adjust the pH to 4.2-4.8. The mixture is stirred to obtain a chitosan solution. Glycidyl trimethylammonium chloride is added to the chitosan solution, and the mixture is heated to a first temperature for reaction. After the reaction is complete, the mixture is cooled to room temperature, and unreacted small molecules are removed by ultrafiltration and the volume is adjusted to obtain a quaternary ammonium chitosan solution. Methyl palmitate and cholesterol are dispersed in anhydrous ethanol to obtain a template solution. The template solution is added dropwise to the quaternary ammonium chitosan solution and stirred to obtain a pre-assembled composite system. Sodium tripolyphosphate is dissolved under stirring conditions. Droplets were added to the pre-assembled composite system, followed by the addition of geniposide and curing crosslinking at room temperature to obtain an imprinted core microgel dispersion. The imprinted core microgel dispersion was eluted 3-5 times with an ethanol-water solution, each time with the ethanol-water solution as a replacement, to obtain a chitosan imprinted gel dispersion. Methacryl ethyl sulfobetaine was added to the chitosan imprinted gel dispersion and nitrogen was passed through to remove oxygen. Ammonium persulfate and tetramethylethylenediamine were added and reacted at room temperature. After the reaction was completed, ultrafiltration was used to remove free monomers and oligomers to obtain a betaine-chitosan imprinted gel dispersion.

[0012] S2, under a nitrogen atmosphere, deionized water and acrylic acid are mixed, and the pH of the system is adjusted to 5.8-6.5 using NaOH aqueous solution. Then, polyethylene glycol methyl ether acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, and 3-mercaptopropyltrimethoxysilane are added sequentially. The mixture is heated to a second temperature and ammonium persulfate is added to react and a polycarboxylic acid mother liquor is obtained. After the reaction is completed, the mixture is cooled to room temperature, anhydrous ethanol is added, and the pH is adjusted to 4.8-5.5. The mixture is then filtered to obtain a silanephosphonic acid polycarboxylic acid mother liquor.

[0013] S3, deionized water, inorganic electrolyte, polyacrylic acid solution, silanephosphonic acid polycarboxylic acid mother liquor, quaternary ammonium chitosan solution, and betaine-chitosan imprinted gel dispersion are mixed evenly in sequence, the pH is adjusted to 5.2-6.2 with acetic acid, and filtered to obtain a wet polishing auxiliary agent for BC photovoltaic cells.

[0014] In S1, chitosan is dissolved in water. Acetic acid is added to adjust the solution acidity, causing the amino groups on the chitosan molecular chains to exist as ammonium salts. After adding glycidyl trimethylammonium chloride and heating, the amino groups on the chitosan molecular chains undergo nucleophilic ring-opening reactions with the epoxy groups, generating substituted structures with quaternary ammonium groups, thus giving chitosan positively charged sites. Subsequently, methyl palmitate and cholesterol are introduced using ethanol as a medium. During the pre-assembly stage, hydrophobic molecules form complex states with hydrophobic association and hydrogen bonding interactions around the quaternary ammonium chitosan segments. After adding sodium tripolyphosphate, the polyanions undergo electrostatic coordination and ionic cross-linking with the cationic sites of the quaternary ammonium chitosan, forming a three-dimensional polyelectrolyte network and embedding the template molecules within the network pores. After adding geniposide, it undergoes ring-opening addition and condensation reactions with the residual primary amines of chitosan, forming covalent cross-linking points and reducing the structural rearrangement of the ionic cross-linked network under subsequent elution and shearing conditions. During the ethanol-water elution process, template molecules migrate from the network and are carried out by the solvent, transforming the local space previously occupied by the template into a cavity structure with spatial configuration and interaction sites. Subsequently, methacryloylethyl sulfobetaine is added and nitrogen is introduced for deoxygenation. Under the action of an initiation system composed of ammonium persulfate and tetramethylethylenediamine, free radicals are generated. In the system, large molecular free radical sites can be formed on the chitosan backbone through free radical initiation and chain transfer, causing the betaine monomer to undergo graft polymerization, resulting in a gel dispersion carrying zwitterionic side chains.

[0015] In S2, acrylic acid undergoes partial neutralization in the aqueous phase, allowing the carboxyl groups to coexist as carboxylic acid / carboxylate salts, thus simultaneously balancing the reactivity of free radical polymerization with the solubility of the resulting polymer in the aqueous phase. The addition of polyethylene glycol methyl ether acrylate forms polyether side chains on the copolymer chain, providing hydration segments and altering the polymer's conformation in solution. The addition of a sulfonic acid-containing comonomer introduces strongly ionizing groups into the main chain, changing the charge density and ionic strength response. The addition of vinylphosphonic acid introduces phosphonic acid groups, which can form adsorption sites through coordination and hydrogen bonding when subsequently contacting surfaces containing silicon-oxygen bonds or metal oxides. The addition of a mercaptotrimethoxysilane allows the mercapto group to participate in the reaction as a chain transfer group in free radical polymerization, altering the molecular weight growth path and enabling some chain ends to carry trimethoxysilane groups. After polymerization, ethanol is added and the acidity is adjusted. This is mainly used to change the solvent environment and the silane hydrolysis-condensation equilibrium, reduce the risk of gelation caused by self-condensation during storage, and at the same time help remove trace amounts of hydrophobic impurities introduced during polymerization and improve the permeability of the filtration process.

[0016] In S3, the inorganic electrolyte provides ionic strength upon entering the aqueous phase. The addition of polyacrylic acid solution provides anionic sites, which can reversibly associate with cationic sites in the system. Simultaneously, its adsorption at the solid-liquid interface alters the interfacial charge distribution and hydration layer structure. After adding silanephosphonic acid polycarboxylic acid mother liquor, carboxylates, sulfonates, and phosphonic acid groups jointly participate in charge regulation and complexation equilibrium in the solution. Phosphonic acid and hydrolyzable silane-related groups can form an adsorption layer near silicon-containing or silica surfaces. After adding quaternary ammonium chitosan solution, the complexation between cationic sites and anionic polymers is controlled by the order of addition, ionic strength, and acidity, resulting in a dispersed system. The cationic sites of quaternary ammonium chitosan can also adsorb and bridge with negatively charged particle surfaces or contaminants containing carboxylic acid / phosphate groups. After the addition of betaine-chitosan imprinted gel dispersion, the imprinted holes provide configuration-matched binding sites for lipid molecules, which are then captured and migrated with the dispersion through hydrophobic interactions and hydrogen bonds. The betaine side chains form electrically neutral hydration segments in the aqueous phase, which changes the interaction mode between the dispersion surface and the substrate surface, reduces the probability of non-specific adsorption, and affects the particle redeposition process.

[0017] As a preferred embodiment of the present invention, in S1, the mass ratio of chitosan, deionized water and glycidyltrimethylammonium chloride is (2-2.5):(90-110):(6-8), for example, it can be (2.0, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45 or 2.5):(90, 92, 94, 96, 98, 100, 102, 104, 106, 108 or 110):(6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2, 7.4, 7.6, 7.8 or 8.0), but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0018] In some optional embodiments, the degree of deacetylation of the chitosan is 80-95%, for example, it can be 80%, 81.5%, 83%, 84.5%, 86%, 87.5%, 89%, 90.5%, 92%, 93.5% or 95%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0019] In some alternative embodiments, the first temperature is 58-62°C, for example, it can be 58°C, 58.4°C, 58.8°C, 59.2°C, 59.6°C, 60.0°C, 60.4°C, 60.8°C, 61.2°C, 61.6°C or 62°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0020] In some alternative embodiments, the reaction time at the first temperature is 6-10 hours, for example, 6.0 hours, 6.4 hours, 6.8 hours, 7.2 hours, 7.6 hours, 8.0 hours, 8.4 hours, 8.8 hours, 9.2 hours, 9.6 hours, or 10.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0021] In some optional embodiments, the solid content of the quaternary ammonium chitosan solution is 1.8-2.2 wt.%, for example, it can be 1.8 wt.%, 1.84 wt.%, 1.88 wt.%, 1.92 wt.%, 1.96 wt.%, 2.0 wt.%, 2.04 wt.%, 2.08 wt.%, 2.12 wt.%, 2.16 wt.%, or 2.2 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the mass ratio of methyl palmitate, cholesterol, anhydrous ethanol, quaternary ammonium chitosan solution, sodium tripolyphosphate solution, geniposide, methacryloyl ethyl sulfobetaine, ammonium persulfate, and tetramethylethylenediamine is (0.6-1):(0.2-0.5):(6-10):(90-110):(30-40):(0.03-0.08):(0.6-1.5):(0.03-0.06):(0.03-0.06). For example, it can be... (0.6, 0.64, 0.68, 0.72, 0.76, 0.8, 0.84, 0.88, 0.92, 0.96, or 1.0): (0.2, 0.23, 0.26, 0.29, 0.32, 0.35, 0.38, 0.41, 0.44, 0.47, or 0.5): (6, 6.4, 6.8, 7.2, 7.6, 8.0, 8.4, 8.8, 9.2, 9.6, or 10): (90, 92, 94, 96, 98, 1) 00, 102, 104, 106, 108 or 110: (30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40): (0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075 or 0.08): (0.6, 0.69, 0.78, 0.87, 0.96, 1.05, 1.14, 1.23, 1.32, 1.41) Or 1.5): (0.03, 0.033, 0.036, 0.039, 0.042, 0.045, 0.048, 0.051, 0.054, 0.057 or 0.06): (0.03, 0.033, 0.036, 0.039, 0.042, 0.045, 0.048, 0.051, 0.054, 0.057 or 0.06), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0023] In some optional embodiments, the mass fraction of the sodium tripolyphosphate solution is 0.6 wt.% to 1.3 wt.%, for example, it can be 0.6 wt.%, 0.67 wt.%, 0.74 wt.%, 0.81 wt.%, 0.88 wt.%, 0.95 wt.%, 1.02 wt.%, 1.09 wt.%, 1.16 wt.%, 1.23 wt.%, or 1.3 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the room temperature curing crosslinking time is 2-6 hours, for example, it can be 2.0 hours, 2.4 hours, 2.8 hours, 3.2 hours, 3.6 hours, 4.0 hours, 4.4 hours, 4.8 hours, 5.2 hours, 5.6 hours or 6.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the mass ratio of anhydrous ethanol to deionized water in the aqueous ethanol solution is 1:1.

[0026] In some optional embodiments, the solid content of the chitosan imprinted gel dispersion is 0.8-1.5 wt.%, for example, it may be 0.8 wt.%, 0.87 wt.%, 0.94 wt.%, 1.01 wt.%, 1.08 wt.%, 1.15 wt.%, 1.22 wt.%, 1.29 wt.%, 1.36 wt.%, 1.43 wt.%, or 1.5 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the room temperature reaction time is 0.8-1.5 h, for example, it can be 0.8 h, 0.87 h, 0.94 h, 1.01 h, 1.08 h, 1.15 h, 1.22 h, 1.29 h, 1.36 h, 1.43 h or 1.5 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the solid content of the betaine-chitosan imprinted gel dispersion is 1.0-1.5 wt.%, for example, it may be 1.0 wt.%, 1.05 wt.%, 1.1 wt.%, 1.15 wt.%, 1.2 wt.%, 1.25 wt.%, 1.3 wt.%, 1.35 wt.%, 1.4 wt.%, 1.45 wt.%, or 1.5 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0029] As a preferred embodiment of the present invention, in S2, the mass ratio of deionized water, acrylic acid, polyethylene glycol methyl ether acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, 3-mercaptopropyltrimethoxysilane, ammonium persulfate, and anhydrous ethanol is (120-160):(16-20):(32-46):(0.8-1.8):(0.15-0.5):(0.25-0.8):(0.35- 0.65): (10-20), for example, it could be (120, 124, 128, 132, 136, 140, 144, 148, 152, 156 or 160): (16, 16.4, 16.8, 17.2, 17.6, 18.0, 18.4, 18.8, 19.2, 19.6 or 20): (32, 33.4, 34.8, 36.2, 37.6, 39, 40.4, 41). 8, 43.2, 44.6 or 46: (0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or 1.8): (0.15, 0.185, 0.22, 0.255, 0.29, 0.325, 0.36, 0.395, 0.43, 0.465 or 0.5): (0.25, 0.305, 0.36, 0.415, 0.47, 0. 525, 0.58, 0.635, 0.69, 0.745 or 0.8: (0.35, 0.38, 0.41, 0.44, 0.47, 0.5, 0.53, 0.56, 0.59, 0.62 or 0.65): (10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0030] In some optional embodiments, the mass fraction of the NaOH aqueous solution is 15-20 wt.%, for example, it can be 15 wt.%, 15.5 wt.%, 16 wt.%, 16.5 wt.%, 17 wt.%, 17.5 wt.%, 18 wt.%, 18.5 wt.%, 19 wt.%, 19.5 wt.%, or 20 wt.%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] In some alternative embodiments, the second temperature is 72-78°C, for example, it can be 72°C, 72.6°C, 73.2°C, 73.8°C, 74.4°C, 75.0°C, 75.6°C, 76.2°C, 76.8°C, 77.4°C or 78°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the reaction time for adding ammonium persulfate is 3-4 hours, for example, 3.0 hours, 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours, or 4.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the solid content of the silanephosphonic acid polycarboxylic acid mother liquor is 18-25 wt.%, for example, it can be 18 wt.%, 18.7 wt.%, 19.4 wt.%, 20.1 wt.%, 20.8 wt.%, 21.5 wt.%, 22.2 wt.%, 22.9 wt.%, 23.6 wt.%, 24.3 wt.%, or 25 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0034] As a preferred technical solution of the present invention, in S3, the mass ratio of deionized water, inorganic electrolyte, polyacrylic acid solution, polycarboxylic acid mother liquor with added silanephosphonic acid, quaternary ammonium chitosan solution, and betaine-chitosan imprinted gel dispersion is (760-820):(40-80):(10-25):(40-80):(8-18):(35-120), for example, it can be (760, 766, 772, 778, 784, 790, 796, 802, 808, 814 or 820):(40, 44, 48, 52, 56, 60, 64, 68) (72, 76 or 80): (10, 11.5, 13, 14.5, 16, 17.5, 19, 20.5, 22, 23.5 or 25): (40, 44, 48, 52, 56, 60, 64, 68, 72, 76 or 80): (8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18): (35, 43.5, 52, 60.5, 69, 77.5, 86, 94.5, 103, 111.5 or 120), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0035] In some optional embodiments, the inorganic electrolyte comprises sodium sulfate, sodium bisulfate, and ammonium sulfate, wherein the mass ratio of sodium sulfate, sodium bisulfate, and ammonium sulfate is 8:1:1.

[0036] In some optional embodiments, the solid content of the polyacrylic acid solution is 45-55 wt.%, for example, it can be 45 wt.%, 46 wt.%, 47 wt.%, 48 wt.%, 49 wt.%, 50 wt.%, 51 wt.%, 52 wt.%, 53 wt.%, 54 wt.%, or 55 wt.%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0037] In a second aspect, the present invention provides a wet polishing aid for BC photovoltaic cells prepared by the preparation method described in the first aspect.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: The wet polishing aid provided by the present invention addresses the interface and contamination control needs in the semiconductor polishing process. Through the synergistic effect of the quaternary ammonium chitosan system, chitosan imprinted gel and its betaine-modified dispersion and silanephosphonic acid polycarboxylic acid system, it simultaneously achieves selective capture and carrying of organic contaminants, dispersion stabilization of fine particles, and regulation of adsorption behavior at the solid-liquid interface in the wet polishing solution. This reduces the risk of secondary adsorption and redeposition of contaminants and particles on the substrate surface, and weakens the adhesion and pinning effect of bubbles on the substrate surface, improves the continuity of the liquid film and local mass transfer conditions, and reduces uneven processing and surface defects caused by bubble shielding. When applied to the wet polishing and related cleaning processes of semiconductor silicon substrates, it helps to improve surface cleanliness and morphological consistency, and enhances the stability and yield of subsequent photolithography, deposition and passivation processes. Attached Figure Description

[0039] Figure 1 The infrared spectrum of the betaine-chitosan imprinted gel dispersion provided in Example 1 of this invention;

[0040] Figure 2 The infrared spectrum of the silanephosphonic acid polycarboxylic acid mother liquor provided in Example 1 of the present invention. Detailed Implementation

[0041] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0042] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0043] Example 1

[0044] This embodiment provides a wet polishing aid for BC photovoltaic cells and its preparation method. The preparation method specifically includes the following steps:

[0045] S1, 2.0 g of chitosan with a degree of deacetylation of 95% was added to 90 g of deionized water, and glacial acetic acid was added to adjust the pH to 4.8. The mixture was stirred to obtain a chitosan solution. 6.0 g of glycidyltrimethylammonium chloride was added to the chitosan solution, and the mixture was heated to 58 °C and reacted for 10 h. After the reaction was completed, the mixture was cooled to room temperature, and unreacted small molecules were removed by ultrafiltration and the volume was adjusted to obtain a quaternary ammonium chitosan solution with a solid content of 2.2 wt.%. 0.6 g of methyl palmitate and 0.5 g of cholesterol were dispersed in 10 g of anhydrous ethanol to obtain a template solution. The template solution was added dropwise to 90 g of quaternary ammonium chitosan solution and stirred to obtain a pre-assembled composite system. Under stirring conditions, 40 g of sodium tripolyphosphate solution with a mass fraction of 0.6 wt.% was added dropwise to the pre-assembled composite system. In the composite system, 0.03 g of geniposide was then added and cured and crosslinked at room temperature for 6 h to obtain an imprinted core microgel dispersion. The imprinted core microgel dispersion was eluted three times with an ethanol aqueous solution, each time replacing the original solution with an ethanol aqueous solution. The mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 1:1, resulting in a chitosan imprinted gel dispersion with a solid content of 1.5 wt.%. 0.6 g of methacryloyl ethyl sulfobetaine was added to the chitosan imprinted gel dispersion and nitrogen was passed through to remove oxygen. 0.06 g of ammonium persulfate and 0.03 g of tetramethylethylenediamine were added and reacted at room temperature for 1.5 h. After the reaction, ultrafiltration was used to remove free monomers and oligomers to obtain a betaine chitosan imprinted gel dispersion with a solid content of 1.0 wt.%.

[0046] S2, under a nitrogen atmosphere, 160g of deionized water and 16g of acrylic acid were mixed, and the pH of the system was adjusted to 6.5 using a 15wt.% NaOH aqueous solution. Then, 32g of polyethylene glycol methyl ether acrylate, 1.8g of 2-acrylamide-2-methylpropanesulfonic acid, 0.50g of vinylphosphonic acid, and 0.25g of 3-mercaptopropyltrimethoxysilane were added sequentially. The mixture was heated to 78℃ and 0.35g of ammonium persulfate was added. The reaction was carried out for 4 hours to obtain a polycarboxylic acid mother liquor. After the reaction was completed, the mixture was cooled to room temperature, 20g of anhydrous ethanol was added, and the pH was adjusted to 4.8. The mixture was then filtered to obtain a silanephosphonic acid polycarboxylic acid mother liquor with a solid content of 25wt.%.

[0047] S3, 760g of deionized water, 80g of inorganic electrolyte, 10g of polyacrylic acid solution with a solid content of 55wt.%, 80g of silanephosphonic acid polycarboxylic acid mother liquor, 8g of quaternary ammonium chitosan solution, and 120g of betaine-chitosan imprinted gel dispersion are mixed evenly in sequence. The inorganic electrolyte includes sodium sulfate, sodium bisulfate, and ammonium sulfate in a mass ratio of 8:1:1. The pH is adjusted to 6.2 with acetic acid, and the mixture is filtered to obtain a wet polishing auxiliary agent for BC photovoltaic cells.

[0048] Figure 1 The infrared spectrum of the betaine-chitosan imprinted gel dispersion provided in this embodiment is shown in the range of 3600-3200 cm⁻¹. -1 The broad peaks were attributed to OH / NH stretching, indicating that the system is still mainly composed of a chitosan backbone and a hydrated hydrogen bond network; the peaks in the 1205-1175 cm⁻¹ range... -1 The absorption is attributed to antisymmetric stretching of the sulfonic acid group, proving that the sulfonic acid end of the betaine monomer has been introduced into the gel system; at 1600-1540 cm⁻¹ -1 With 1450-1400cm -1 The paired absorption can be attributed to the antisymmetric / symmetric stretching of carboxylate, indicating that there are ionizable / complexable sites in the system and they participate in the polyelectrolyte complexation and interfacial adsorption equilibrium. Figure 2 The infrared spectrum of the silanephosphonic acid polycarboxylic acid mother liquor provided in this embodiment is in the range of 1730-1715 cm⁻¹. -1 The absorption was attributed to C=O stretching of carboxyl or ester groups, proving that the polycarboxylic acid backbone constitutes the core functional group source of the mother liquor; at 1205-1175 cm⁻¹ -1 The absorption is attributed to the antisymmetric stretching of sulfonic acid groups; in the range of 1145-1080 cm⁻¹ -1 The absorption is attributed to the superposition region of Si-O and polyether COC.

[0049] Example 2

[0050] This embodiment provides a wet polishing aid for BC photovoltaic cells and its preparation method. The preparation method specifically includes the following steps:

[0051] S1, 2.5g of chitosan with a degree of deacetylation of 80% was added to 110g of deionized water, and glacial acetic acid was added to adjust the pH to 4.2. The mixture was stirred to obtain a chitosan solution. 8.0g of glycidyltrimethylammonium chloride was added to the chitosan solution, and the mixture was heated to 62℃ and reacted for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, and unreacted small molecules were removed by ultrafiltration and the volume was adjusted to obtain a quaternary ammonium chitosan solution with a solid content of 1.8 wt.%. 1.0g of methyl palmitate and 0.2g of cholesterol were dispersed in 6g of anhydrous ethanol to obtain a template solution. The template solution was added dropwise to 110g of the quaternary ammonium chitosan solution and stirred to obtain a pre-assembled composite system. Under stirring conditions, 30g of sodium tripolyphosphate solution with a mass fraction of 1.3 wt.% was added dropwise to the pre-assembled composite system. In the composite system, 0.08 g of geniposide was then added and cured and crosslinked at room temperature for 2 h to obtain an imprinted core microgel dispersion. The imprinted core microgel dispersion was eluted 5 times with an ethanol aqueous solution, each time with an ethanol aqueous solution replacing the original solution. The mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 1:1 to obtain a chitosan imprinted gel dispersion with a solid content of 0.8 wt.%. 1.5 g of methacryloyl ethyl sulfobetaine was added to the chitosan imprinted gel dispersion and nitrogen was passed through to remove oxygen. 0.03 g of ammonium persulfate and 0.06 g of tetramethylethylenediamine were added and reacted at room temperature for 0.8 h. After the reaction, ultrafiltration was used to remove free monomers and oligomers to obtain a betaine chitosan imprinted gel dispersion with a solid content of 1.5 wt.%.

[0052] S2, under a nitrogen atmosphere, 120g of deionized water and 20g of acrylic acid were mixed, and the pH of the system was adjusted to 5.8 using a 20wt.% NaOH aqueous solution. Then, 46g of polyethylene glycol methyl ether acrylate, 0.8g of 2-acrylamide-2-methylpropanesulfonic acid, 0.15g of vinylphosphonic acid, and 0.80g of 3-mercaptopropyltrimethoxysilane were added sequentially. The mixture was heated to 72℃ and 0.65g of ammonium persulfate was added. The reaction was carried out for 3 hours to obtain a polycarboxylic acid mother liquor. After the reaction was completed, the mixture was cooled to room temperature, 10g of anhydrous ethanol was added, and the pH was adjusted to 5.5. The mixture was then filtered to obtain a silanephosphonic acid polycarboxylic acid mother liquor with a solid content of 18wt.%.

[0053] S3, 820g of deionized water, 40g of inorganic electrolyte, 25g of polyacrylic acid solution with a solid content of 45wt.%, 40g of silanephosphonic acid polycarboxylic acid mother liquor, 18g of quaternary ammonium chitosan solution, and 35g of betaine-chitosan imprinted gel dispersion are mixed evenly in sequence. The inorganic electrolyte includes sodium sulfate, sodium bisulfate, and ammonium sulfate in a mass ratio of 8:1:1. The pH is adjusted to 5.2 with acetic acid, and the mixture is filtered to obtain a wet polishing auxiliary agent for BC photovoltaic cells.

[0054] Example 3

[0055] This embodiment provides a wet polishing aid for BC photovoltaic cells and its preparation method. The preparation method specifically includes the following steps:

[0056] S1, 2.2g of chitosan with a degree of deacetylation of 90% was added to 100g of deionized water, and glacial acetic acid was added to adjust the pH to 4.5. The mixture was stirred to obtain a chitosan solution. 7.0g of glycidyltrimethylammonium chloride was added to the chitosan solution, and the mixture was heated to 60℃ and reacted for 8 hours. After the reaction was completed, the mixture was cooled to room temperature, and unreacted small molecules were removed by ultrafiltration and the volume was adjusted to obtain a quaternary ammonium chitosan solution with a solid content of 2.0 wt.%. 0.8g of methyl palmitate and 0.4g of cholesterol were dispersed in 8g of anhydrous ethanol to obtain a template solution. The template solution was added dropwise to 100g of quaternary ammonium chitosan solution and stirred to obtain a pre-assembled composite system. Under stirring conditions, 35g of sodium tripolyphosphate solution with a mass fraction of 1.0 wt.% was added dropwise to the pre-assembled composite system. In the composite system, 0.05 g of geniposide was then added and cured and crosslinked at room temperature for 4 h to obtain an imprinted core microgel dispersion. The imprinted core microgel dispersion was eluted four times with an ethanol aqueous solution, each time with an ethanol aqueous solution as the mass ratio of anhydrous ethanol to deionized water was 1:1, to obtain a chitosan imprinted gel dispersion with a solid content of 1.2 wt.%. 1.0 g of methacryloyl ethyl sulfobetaine was added to the chitosan imprinted gel dispersion and nitrogen was passed through to remove oxygen. 0.04 g of ammonium persulfate and 0.04 g of tetramethylethylenediamine were added and reacted at room temperature for 1.0 h. After the reaction, ultrafiltration was used to remove free monomers and oligomers to obtain a betaine chitosan imprinted gel dispersion with a solid content of 1.2 wt.%.

[0057] S2, under a nitrogen atmosphere, 140g of deionized water and 18g of acrylic acid were mixed, and the pH of the system was adjusted to 6.0 using an 18wt.% NaOH aqueous solution. Then, 40g of polyethylene glycol methyl ether acrylate, 1.2g of 2-acrylamide-2-methylpropanesulfonic acid, 0.30g of vinylphosphonic acid, and 0.50g of 3-mercaptopropyltrimethoxysilane were added sequentially. The mixture was heated to 75℃ and 0.50g of ammonium persulfate was added. The reaction was allowed to proceed for 3.5h to obtain a polycarboxylic acid mother liquor. After the reaction was completed, the mixture was cooled to room temperature, 15g of anhydrous ethanol was added, and the pH was adjusted to 5.0. The mixture was then filtered to obtain a silanephosphonic acid polycarboxylic acid mother liquor with a solid content of 22wt.%.

[0058] S3, 780g of deionized water, 60g of inorganic electrolyte, 18g of polyacrylic acid solution with a solid content of 50wt.%, 60g of silanephosphonic acid polycarboxylic acid mother liquor, 12g of quaternary ammonium chitosan solution, and 80g of betaine-chitosan imprinted gel dispersion are mixed evenly in sequence. The inorganic electrolyte includes sodium sulfate, sodium bisulfate, and ammonium sulfate in a mass ratio of 8:1:1. The pH is adjusted to 5.8 with acetic acid, and the mixture is filtered to obtain a wet polishing auxiliary agent for BC photovoltaic cells.

[0059] Example 4

[0060] This embodiment provides a wet polishing aid for BC photovoltaic cells and its preparation method. The preparation method specifically includes the following steps:

[0061] S1, 2.4 g of chitosan with a degree of deacetylation of 85% was added to 105 g of deionized water, and glacial acetic acid was added to adjust the pH to 4.6. The mixture was stirred to obtain a chitosan solution. 7.5 g of glycidyltrimethylammonium chloride was added to the chitosan solution, and the mixture was heated to 61 °C and reacted for 9 h. After the reaction was completed, the mixture was cooled to room temperature, and unreacted small molecules were removed by ultrafiltration and the volume was adjusted to obtain a quaternary ammonium chitosan solution with a solid content of 1.9 wt.%. 0.9 g of methyl palmitate and 0.3 g of cholesterol were dispersed in 7 g of anhydrous ethanol to obtain a template solution. The template solution was added dropwise to 105 g of quaternary ammonium chitosan solution and stirred to obtain a pre-assembled composite system. Under stirring conditions, 38 g of sodium tripolyphosphate solution with a mass fraction of 0.8 wt.% was added dropwise to the pre-assembled composite system. In the composite system, 0.06 g of geniposide was then added and cured and crosslinked at room temperature for 5 h to obtain an imprinted core microgel dispersion. The imprinted core microgel dispersion was eluted four times with an ethanol aqueous solution, each time with an ethanol aqueous solution replacing the original solution. The mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 1:1, resulting in a chitosan imprinted gel dispersion with a solid content of 1.0 wt.%. 1.2 g of methacryloyl ethyl sulfobetaine was added to the chitosan imprinted gel dispersion and nitrogen was passed through to remove oxygen. 0.05 g of ammonium persulfate and 0.05 g of tetramethylethylenediamine were added and reacted at room temperature for 1.2 h. After the reaction, ultrafiltration was used to remove free monomers and oligomers to obtain a betaine chitosan imprinted gel dispersion with a solid content of 1.4 wt.%.

[0062] S2, under a nitrogen atmosphere, 150g of deionized water and 19g of acrylic acid were mixed, and the pH of the system was adjusted to 6.2 using a 16wt.% NaOH aqueous solution. Then, 38g of polyethylene glycol methyl ether acrylate, 1.5g of 2-acrylamide-2-methylpropanesulfonic acid, 0.40g of vinylphosphonic acid, and 0.60g of 3-mercaptopropyltrimethoxysilane were added sequentially. The mixture was heated to 76℃ and 0.45g of ammonium persulfate was added. The reaction was allowed to proceed for 3.8h to obtain a polycarboxylic acid mother liquor. After the reaction was completed, the mixture was cooled to room temperature, 18g of anhydrous ethanol was added, and the pH was adjusted to 5.2. The mixture was then filtered to obtain a silanephosphonic acid polycarboxylic acid mother liquor with a solid content of 20wt.%.

[0063] S3, 800g of deionized water, 50g of inorganic electrolyte, 20g of polyacrylic acid solution with a solid content of 48wt.%, 50g of silanephosphonic acid polycarboxylic acid mother liquor, 15g of quaternary ammonium chitosan solution, and 60g of betaine-chitosan imprinted gel dispersion are mixed evenly in sequence. The inorganic electrolyte includes sodium sulfate, sodium bisulfate, and ammonium sulfate in a mass ratio of 8:1:1. The pH is adjusted to 5.5 with acetic acid, and the mixture is filtered to obtain a wet polishing auxiliary agent for BC photovoltaic cells.

[0064] Comparative Example 1

[0065] This comparative example provides a wet polishing aid for BC photovoltaic cells and its preparation method. The difference between this example and Example 1 is that betaine-chitosan imprinted gel dispersion is not added in S3, but is replaced by an equal mass of deionized water. Other process parameters and operating conditions are exactly the same as in Example 1.

[0066] Comparative Example 2

[0067] This comparative example provides a wet polishing aid for BC photovoltaic cells and its preparation method. The difference between this example and Example 1 is that after completing template pre-assembly, sodium tripolyphosphate crosslinking, and curing and eluting with geniposide to obtain a chitosan imprinted gel dispersion in S1, the grafting reaction of methacryloyl ethyl sulfobetaine is not performed. The chitosan imprinted gel dispersion is directly obtained and used in S3. In S3, the chitosan imprinted gel dispersion is used to replace the betaine chitosan imprinted gel dispersion by an equal mass. Other process parameters and operating conditions are exactly the same as in Example 1.

[0068] Comparative Example 3

[0069] This comparative example provides a wet polishing aid for BC photovoltaic cells and its preparation method. The difference between this example and Example 1 is that silanephosphonic acid polycarboxylic acid mother liquor is not added in S3, but is replaced by an equal mass of deionized water. Other process parameters and operating conditions are exactly the same as in Example 1.

[0070] Standardized sample selection and pretreatment conditions: Monocrystalline silicon photovoltaic wafers from the same batch were selected, with specifications of pseudo-square wafers approximately 182mm in side length, approximately 160μm in thickness, and consistent surface condition; 5 wafers were taken from each sample group as duplicate samples. After wet polishing, the same rinsing process (multi-stage rinsing with deionized water) and the same spin-drying / drying conditions were immediately adopted. After drying, the wafers were left to stand in a clean environment for no less than 10 minutes before testing; the time window from the end of drying to the completion of all tests was controlled within 2 hours; powder-free gloves and anti-static tweezers were used throughout the process, and contact was only made with the edges to avoid human fingerprints and secondary dust accumulation.

[0071] The defect statistics method is performed in accordance with the unassisted visual inspection procedure for polished silicon wafer surfaces specified in SEMI MF523. Defects on the silicon wafer surface are classified, recorded and counted under uniform lighting and observation conditions.

[0072] Surface particle redeposition was performed in accordance with the evaluation criteria of ISO 14644-9 "Surface Cleanliness";

[0073] The test method for the foaming performance of the bath solution is based on GB / T 7462. The test results are shown in Table 1.

[0074] Table 1. Test results of wet polishing aids for BC photovoltaic cells in Examples 1-4 and Comparative Examples 1-3

[0075]

[0076] As shown in Table 1, compared to Example 1, Comparative Example 1 showed an increase in the total number of defects, an increase in particle redeposition, and a decrease in desorption time; Comparative Example 2 showed an increase in the total number of defects, an increase in particle redeposition, and a decrease in desorption time; and Comparative Example 3 showed an increase in the total number of defects, an increase in particle redeposition, and a decrease in desorption time. This is because Comparative Example 1 did not add betaine-chitosan imprinted gel dispersion, and oily contaminants and contaminant-carrying particles lacked specific binding sites, making them more prone to secondary adsorption and migration with the liquid film during polishing. Contaminants formed bubbles at the interface, leading to prolonged desorption time. Comparative Example 2 used chitosan imprinted gel dispersion instead of betaine-modified dispersion. Although imprinted cavities were retained, the surface hydration layer was insufficient, and polyelectrolyte complexation with polyacrylic acid / electrolyte caused local agglomeration. The agglomerates were more likely to adhere to and carry particles, resulting in increased particle redeposition and defects, and slower desorption. Comparative Example 3, without the addition of silanephosphonic acid polycarboxylic acid mother liquor, lacks an adsorbable carboxylic acid / phosphonic acid group hydration layer at the solid-liquid interface, resulting in decreased wetting, spreading, and anti-redeposition capabilities, increased particle adhesion to the surface, difficulty in bubble slippage and detachment, and increased desorption time and particle redeposition, leading to more defects.

[0077] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a wet polishing aid for BC photovoltaic cells, characterized in that, The preparation method includes: S1, chitosan is added to deionized water to obtain a chitosan solution. Glycidyl trimethylammonium chloride is added to the chitosan solution to react and obtain a quaternary ammonium chitosan solution. Methyl palmitate and cholesterol are dispersed in anhydrous ethanol to obtain a template solution. The template solution is added dropwise to the quaternary ammonium chitosan solution and stirred to obtain a pre-assembled composite system. Sodium tripolyphosphate solution is added dropwise to the pre-assembled composite system. Gardenin is added and cured and crosslinked at room temperature to obtain an imprinted core microgel dispersion. The microgel dispersion is eluted to obtain a chitosan imprinted gel dispersion. Methacryloxyethyl sulfobetaine is added to the chitosan imprinted gel dispersion and nitrogen is passed through to deoxygenate it. Ammonium persulfate is added and reacted with tetramethylethylenediamine to obtain a betaine chitosan imprinted gel dispersion. S2, under a nitrogen atmosphere, deionized water and acrylic acid are mixed, and then polyethylene glycol methyl ether acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, 3-mercaptopropyltrimethoxysilane and ammonium persulfate are added in sequence to react and obtain polycarboxylic acid mother liquor. Anhydrous ethanol is added to obtain silanephosphonic acid polycarboxylic acid mother liquor. S3, deionized water, inorganic electrolyte, polyacrylic acid solution, silanephosphonic acid polycarboxylic acid mother liquor, quaternary ammonium chitosan solution, and betaine-chitosan imprinted gel dispersion are mixed evenly in sequence and filtered to obtain a wet polishing auxiliary agent for BC photovoltaic cells.

2. The method for preparing a wet polishing aid for BC photovoltaic cells according to claim 1, characterized in that, In S1, The mass ratio of chitosan, deionized water and glycidyltrimethylammonium chloride is (2-2.5):(90-110):(6-8).

3. The method for preparing a wet polishing aid for BC photovoltaic cells according to claim 1, characterized in that, In S1, The degree of deacetylation of the chitosan is 80-95%; The solid content of the quaternary ammonium chitosan solution is 1.8-2.2 wt.%.

4. The method for preparing a wet polishing aid for BC photovoltaic cells according to claim 1, characterized in that, In S1, The mass ratio of methyl palmitate, cholesterol, anhydrous ethanol, quaternary ammonium chitosan solution, sodium tripolyphosphate solution, geniposide, methacryloyl ethyl sulfobetaine, ammonium persulfate and tetramethylethylenediamine is (0.6-1):(0.2-0.5):(6-10):(90-110):(30-40):(0.03-0.08):(0.6-1.5):(0.03-0.06):(0.03-0.06).

5. The method for preparing a wet polishing aid for BC photovoltaic cells according to claim 1, characterized in that, In S1, The solid content of the chitosan-imprinted gel dispersion is 0.8-1.5 wt.%. The solid content of the betaine-chitosan imprinted gel dispersion is 1.0-1.5 wt.%.

6. The method for preparing a wet polishing aid for BC photovoltaic cells according to claim 1, characterized in that, In S2, The mass ratio of deionized water, acrylic acid, polyethylene glycol methyl ether acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, 3-mercaptopropyltrimethoxysilane, ammonium persulfate and anhydrous ethanol is (120-160): (16-20): (32-46): (0.8-1.8): (0.15-0.5): (0.25-0.8): (0.35-0.65): (10-20).

7. The method for preparing a wet polishing aid for BC photovoltaic cells according to claim 1, characterized in that, In S2, The solid content of the silanephosphonic acid polycarboxylic acid mother liquor is 18-25 wt.

8. The method for preparing a wet polishing aid for BC photovoltaic cells according to claim 1, characterized in that, In S3 The mass ratio of the deionized water, inorganic electrolyte, polyacrylic acid solution, silanephosphonic acid polycarboxylic acid mother liquor, quaternary ammonium chitosan solution and betaine chitosan imprinted gel dispersion is (760-820):(40-80):(10-25):(40-80):(8-18):(35-120).

9. The method for preparing a wet polishing aid for BC photovoltaic cells according to claim 1, characterized in that, In S3 The inorganic electrolyte includes sodium sulfate, sodium bisulfate and ammonium sulfate, wherein the mass ratio of sodium sulfate, sodium bisulfate and ammonium sulfate is 8:1:1; The solid content of the polyacrylic acid solution is 45-55 wt.%.

10. A wet polishing aid for BC photovoltaic cells prepared by the preparation method according to any one of claims 1-9.

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