A polishing liquid for processing a silicon wafer and a method for preparing the same

Abstract

This invention discloses a polishing slurry for silicon wafer processing and its preparation method, belonging to the field of polishing slurry preparation technology. It addresses the technical problem that the surface smoothness and defect control capabilities of existing polishing slurries for silicon wafer processing need further improvement. This invention involves the preparation of titanium-activated silica abrasive particles, an anchored amphoteric polymer, and a dynamic borate ester gel, which are then composited. The titanium-activated silica abrasive particles provide interfacial activity, the anchored amphoteric polymer regulates the abrasive particle dispersion and enhances interfacial bonding, and the dynamic borate ester gel forms a reversible network structure to achieve system control. During processing, the components form a synergistic relationship under flow and stress conditions, making the abrasive particle distribution, interfacial contact process, and load transfer mode more coordinated, thus resulting in better balance and stability during processing.

Description

Technical Field

[0001] This invention relates to the field of polishing slurry preparation technology, specifically to a polishing slurry for silicon wafer processing and its preparation method. Background Technology

[0002] Polishing slurries for silicon wafer processing are key process materials for achieving global planarization and micro-defect control on the wafer surface during integrated circuit manufacturing. They have become an important research direction in the field of semiconductor precision processing and are widely used in processes such as rough polishing, fine polishing, and ultra-fine polishing. These polishing slurries are usually composed of inorganic oxide abrasive particles, aqueous dispersion media, and functional additives such as dispersants, stabilizers, and complexing agents. They achieve material removal and surface morphology reconstruction through mechanical action and interfacial reaction. As device feature sizes continue to shrink and integration levels continue to increase, the requirements for silicon wafer surface roughness, morphology consistency, and processing stability are becoming increasingly stringent.

[0003] Existing polishing slurries for silicon wafer processing mostly use inorganic abrasives and conventional dispersants to form a dispersion system. While they can maintain a certain degree of suspension stability under static conditions, the abrasives are prone to spatial distribution fluctuations under continuous liquid supply and high shear operation conditions. Local areas may experience instantaneous enrichment or structural collapse. Some parts of the system may experience sedimentation, agglomeration, or viscosity fluctuations under the influence of flow field disturbances. This makes it difficult to maintain consistent transport state and rheological behavior over a long period of time, thereby affecting the material supply balance and interfacial contact stability within the processing area. As a result, there is room for further optimization of the overall coordination of the operation process.

[0004] Furthermore, existing abrasive systems primarily focus on improving material removal capabilities, while lacking a systematic approach to interfacial contact adjustment and load dispersion mechanisms. This results in abrasive particles, under conditions of combined pressure and shear, exhibiting disordered migration due to flow field fluctuations. The interfacial contact process also exhibits a degree of randomness, making it difficult to promptly mitigate localized load concentrations, which may lead to accelerated instantaneous erosion or uneven morphology reconstruction. With the accumulation of processing cycles, the silicon surface microstructure is prone to amplification of fluctuations or expansion of local trenches under repeated contact effects, indicating that there is still room for further improvement in interfacial integrity and morphological consistency.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a polishing slurry for silicon wafer processing and its preparation method, which solves the technical problem that the surface smoothness and defect control capabilities of polishing slurries for silicon wafer processing need to be further improved during use.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A polishing slurry for silicon wafer processing comprises the following raw materials in parts by weight: 4-6 parts titanium-activated silica abrasive particles, 1-2 parts anchored amphoteric polymer, 16-18 parts dynamic borate ester gel and 80-90 parts dispersant, wherein the dispersant is deionized water;

[0009] The titanium-activated silica abrasive particles are prepared by the following method:

[0010] A1. Add silicon-oxygen framework particles, tetraisopropoxy titanium and anhydrous isopropanol to a reaction vessel, stir evenly under nitrogen protection, heat the reaction vessel to 70-75℃, keep it at the temperature and stir for 3-5 hours, filter to collect the filter cake and dry to constant weight to obtain titanium-modified silicon-oxygen framework particles.

[0011] A2. Add titanium-modified silica abrasive particles and activation liquid to a reactor, heat the reactor to 25-30℃, keep it warm and stir for 2-3 hours, filter and collect the filter cake and dry it to constant weight, then perform wet grinding and particle size classification to control particle D50=0.8-1.0μm to obtain titanium-activated silica abrasive particles.

[0012] Furthermore, in step A1, the ratio of the amount of the silicon-oxygen framework particles, tetraisopropoxy titanium, and anhydrous isopropanol is 9-12g:5-6mL:45-50mL.

[0013] Furthermore, in step A2, the ratio of the titanium-modified silicon bone particles to the activation solution is 7-9g:40-50mL, wherein the activation solution is a 15-20wt% hydrogen peroxide aqueous solution.

[0014] Furthermore, the preparation method of the silicon-oxygen framework particles is as follows: tetraethyl orthosilicate and anhydrous ethanol are added to a reaction vessel and stirred until uniform. Then, deionized water and 1wt% hydrochloric acid aqueous solution are added. After stirring at room temperature for 15 minutes, the reaction vessel is heated to 35-45℃ and kept at this temperature for 2-3 hours. The silicon-oxygen framework particles are then obtained through post-treatment.

[0015] Furthermore, in the process of preparing silicon-oxygen framework particles, the ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water and 1wt% hydrochloric acid aqueous solution is 16-18mL:120mL:21-25mL:1-2mL. The post-treatment includes: after the reaction is completed, the reaction solution is poured into a mold and allowed to stand for aging for 16-20 hours to obtain a gel material. The gel material is then chopped into 2-4mm particles and dried to constant weight to obtain silicon-oxygen framework particles.

[0016] Furthermore, the anchoring amphoteric polymer is prepared by the following method:

[0017] B1. Add dopamine hydrochloride and anhydrous dichloromethane to a reaction vessel, stir evenly, then add triethylamine and control the reaction vessel temperature at 0-5℃. Then add methacrylamide chloride in ten equal batches with an interval of 5 min between additions. After the addition is complete, keep the reaction vessel at the temperature for 1 h. Then raise the temperature of the reaction vessel to 25℃ and keep it at the temperature for 3-4 h with stirring. Post-treatment yields acylated dopamine derivatives.

[0018] B2. Add acylated dopamine derivative, methacryloyl ethyl sulfobetaine, azobisisobutyronitrile and anhydrous ethanol to a reaction vessel. After stirring evenly under nitrogen protection, heat the reaction vessel to 65-70℃ and keep it at this temperature for 6-8 hours. Post-treatment yields the anchored amphoteric polymer.

[0019] Further, in step B1, the ratio of dopamine hydrochloride, anhydrous dichloromethane, triethylamine and methacryloyl chloride is 10-12g:100mL:8-10mL:9-11mL. The post-treatment includes: after stirring, removing the solvent under reduced pressure, recrystallizing with diethyl ether, and then drying to constant weight to obtain the acylated dopamine derivative.

[0020] Further, in step B2, the ratio of the acylated dopamine derivative, methacryloyl ethyl sulfobetaine, azobisisobutyronitrile, and anhydrous ethanol is 8-10g:18-21g:1g:100mL. The post-treatment includes: after stirring, pouring the reaction solution into five times its volume of diethyl ether to precipitate. After precipitation is complete, filter to collect the filter cake and dry to constant weight to obtain the anchored amphoteric polymer.

[0021] Furthermore, the preparation method of the dynamic borate ester gel is as follows: polyvinyl alcohol and deionized water are added to a reaction vessel and heated and stirred until dissolved. The reaction vessel is then cooled to 40°C and terephthalic acid and anhydrous ethanol are added. The mixture is kept warm and stirred for 2-3 hours, and then post-processed to obtain the dynamic borate ester gel.

[0022] Furthermore, in the preparation of the dynamic borate ester gel, the ratio of polyvinyl alcohol, deionized water, terephthalic acid and anhydrous ethanol is 12-15g:200mL:6-8g:40-60mL. The post-treatment includes: after stirring, sieving through a 200-300 mesh stainless steel sieve, then centrifuging at 3000-5000rpm for 5-10min, taking the supernatant gel and dividing it into cubes with a side length of 2-4mm to obtain the dynamic borate ester gel.

[0023] The present invention also discloses a method for preparing a polishing slurry for silicon wafer processing, comprising the following steps: adding deionized water to a mixing vessel and stirring, then purging with nitrogen for protection, controlling the temperature of the mixing vessel to 25-35℃, and adding dynamic borate ester gel when the system pH is 6.5-7.5, continuing to stir until the system is homogeneous, then adding titanium-activated silica abrasive particles and anchored amphoteric polymer and continuing to stir and disperse for 60-100 min, and finally allowing it to stand for 20 min to degas, thereby obtaining the polishing slurry for silicon wafer processing.

[0024] The present invention has the following beneficial effects:

[0025] 1. The anchored amphoteric polymer molecular chain segments prepared by this invention simultaneously contain catechol structural units that can interact with the surface of inorganic abrasive particles and highly hydrated zwitterionic structural units. They form a stable hydration shell in the aqueous phase and uniformly disperse the abrasive particles in the continuous phase through interfacial anchoring. The dynamic borate gel constructs a flexible network structure through reversible borate bonds, exhibiting a certain structural response capability under external shear force. During the polishing process, the above-mentioned dispersed structure and dynamic network coexist synergistically, so that the abrasive particles maintain a uniform spatial distribution under circulating liquid supply and shearing environment, while avoiding local structural collapse or instantaneous aggregation. The resulting flow system has a stable transport state and is not prone to flow field fluctuations caused by sedimentation or agglomeration, exhibiting relatively coordinated rheological behavior and operational stability.

[0026] 2. The titanium-activated silica abrasive particles prepared by this invention form a stable composite structure through the combination of surface active sites and silica framework, which undertakes the main removal function in the polishing contact interface. The anchored amphoteric polymer forms a transition layer structure between the abrasive particles and the silicon surface through interfacial adsorption, making the contact state more uniform. The network configuration of the dynamic borate ester gel plays a role in dispersing and buffering local loads during the stress process. During operation, the above structures coexist synergistically, making the action mode of the abrasive particles on the interface tend to be continuous and gentle, reducing the amplification of local fluctuations caused by instantaneous uneven contact. The material removal process thus presents a relatively stable interface evolution state. The micromorphology of the silicon surface gradually tends to be uniformly reconstructed in multiple contact cycles, and the overall surface contour maintains a relatively smooth morphological feature.

[0027] 3. The titanium-activated silica abrasive particles prepared in this invention form uniform removal units after particle size control and surface functionalization treatment, and their participation in the interface is relatively consistent. The anchored amphoteric polymer restricts the disordered migration of abrasive particles through interfacial bonding, reducing the random sliding behavior of free particles in the polishing area. The flexible network composed of dynamic borate ester gel constrains the movement path of abrasive particles under mechanical loading conditions. In actual operation, the abrasive particles exhibit a relatively stable action trajectory under pressure and shear conditions, the interfacial contact process tends to be controllable, and it is difficult to form sharp or sudden deep etching morphologies. This allows the silicon surface to maintain a relatively complete structural state after continuous processing, suppresses the tendency to form local trenches or wide scratches, and maintains the interface integrity during the overall processing. Detailed Implementation

[0028] 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.

[0029] In this application, the polyvinyl alcohol used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with the product number P674983.

[0030] Example 1

[0031] This embodiment provides a method for preparing titanium-activated silica abrasive particles, including the following steps:

[0032] Step ①: Preparation of silicon-oxygen framework particles

[0033] Weigh out 16.0 mL of tetraethyl orthosilicate and 120.0 mL of anhydrous ethanol and add them to the reaction vessel. Stir and mix evenly. Then add 21.0 mL of deionized water and 1.0 mL of 1 wt% hydrochloric acid aqueous solution. Stir at room temperature for 15 min, then heat the reaction vessel to 35 °C and keep it at that temperature for 2 h. After the reaction is complete, pour the reaction solution into a mold and let it stand for aging for 16 h to obtain a gel material. Crush the gel material into 2 mm particles and dry it to constant weight to obtain silicon-oxygen framework particles.

[0034] Step 2: Preparation of titanium-modified silica bone particles

[0035] Weigh out 9.0g of silicon-oxygen framework particles, 5.0mL of tetraisopropoxy titanium and 45.0mL of anhydrous isopropanol and add them to the reaction vessel. Stir evenly under nitrogen protection, then heat the reaction vessel to 70℃ and keep it at this temperature for 3 hours. Filter the mixture, collect the filter cake and dry it to constant weight to obtain titanium-modified silicon-oxygen framework particles.

[0036] Step ③: Preparation of titanium-activated silica abrasive particles

[0037] Weigh 7.0g of titanium-modified silica abrasive particles and 40.0mL of 15wt% hydrogen peroxide aqueous solution and add them to the reactor. Heat the reactor to 25℃, keep it warm and stir for 2h. Filter the filter cake and dry it to constant weight. Then perform wet grinding and particle size classification to control the particle D50=0.8μm to obtain titanium-activated silica abrasive particles.

[0038] The reaction principle for preparing titanium-activated silica abrasive particles is as follows:

[0039] Under acid catalysis, tetraethyl orthosilicate undergoes hydrolysis and condensation to form a three-dimensional silicon-oxygen network structure dominated by Si-O-Si bonds. Subsequently, tetraisopropoxy titanium undergoes alcoholysis and partial hydrolysis in the alcohol phase system, coordinating or condensing with hydroxyl groups on the surface of the silicon-oxygen framework to form Ti-O-Si bonds, thereby introducing and dispersing titanium species in the silicon-oxygen network. Further treatment with a certain concentration of hydrogen peroxide causes the surface titanium centers to form coordination structures with peroxide species, allowing titanium elements to exist stably on the surface of the silicon-oxygen framework in the form of peroxide complexes. The entire process involves reactions such as silanol condensation, metal alkoxide conversion, and metal-oxygen-silicon bond construction, ultimately yielding a silicon-oxygen composite structure containing titanium active sites.

[0040] The mechanism of action of titanium-activated silica abrasive particles in polishing slurries for silicon wafer processing is as follows:

[0041] This process constructs a silicon-oxygen framework with a three-dimensional Si–O–Si network structure using the sol-gel method, providing a stable structure and surface hydroxyl sites for subsequent functionalization. Tetraisopropoxy titanium is then introduced, undergoing alcoholysis and condensation reactions on the framework surface to form stable Ti-O-Si bonds, achieving uniform loading of titanium species within the silicon-oxygen structure. Further treatment with a certain concentration of hydrogen peroxide constructs peroxide-coordinated titanium active sites on the particle surface, endowing the material with surface oxidation activity. Finally, wet grinding and particle size classification yield titanium-activated silicon-oxygen abrasive grains with controllable particle size. These grains possess both good mechanical strength and surface chemical activity. During polishing, the synergistic effect of chemical activation and mechanical removal improves removal efficiency and surface quality.

[0042] Example 2

[0043] This embodiment provides a method for preparing titanium-activated silica abrasive particles, including the following steps:

[0044] Step ①: Preparation of silicon-oxygen framework particles

[0045] Weigh out 18.0 mL of tetraethyl orthosilicate and 120.0 mL of anhydrous ethanol and add them to the reaction vessel. Stir and mix evenly. Then add 25.0 mL of deionized water and 2.0 mL of 1 wt% hydrochloric acid aqueous solution. Stir at room temperature for 15 min, then heat the reaction vessel to 45 °C and keep it at that temperature for 3 h. After the reaction is complete, pour the reaction solution into a mold and let it stand for 20 h to age, and obtain a gel material. Crush the gel material into 4 mm particles and dry it to constant weight to obtain silicon-oxygen framework particles.

[0046] Step 2: Preparation of titanium-modified silica bone particles

[0047] Weigh out 12.0g of silicon-oxygen framework particles, 6.0mL of tetraisopropoxy titanium and 50.0mL of anhydrous isopropanol and add them to the reaction vessel. Stir evenly under nitrogen protection, then heat the reaction vessel to 75℃ and keep it at this temperature for 5 hours. Filter the mixture, collect the filter cake and dry it to constant weight to obtain titanium-modified silicon-oxygen framework particles.

[0048] Step ③: Preparation of titanium-activated silica abrasive particles

[0049] Weigh 9.0g of titanium-modified silica particles and 50.0mL of 20wt% hydrogen peroxide aqueous solution and add them to the reactor. Heat the reactor to 30℃, keep it at the temperature and stir for 3h. Filter the filter cake and dry it to constant weight. Then perform wet grinding and particle size classification to control the particle D50=1.0μm to obtain titanium-activated silica abrasive particles.

[0050] Example 3

[0051] This embodiment provides a method for preparing titanium-activated silica abrasive particles, including the following steps:

[0052] Step ①: Preparation of silicon-oxygen framework particles

[0053] Weigh out 18.0 mL of tetraethyl orthosilicate and 120.0 mL of anhydrous ethanol and add them to the reaction vessel. Stir and mix evenly. Then add 25.0 mL of deionized water and 2.0 mL of 1 wt% hydrochloric acid aqueous solution. Stir at room temperature for 15 min, then heat the reaction vessel to 45 °C and keep it at that temperature for 3 h. After the reaction is complete, pour the reaction solution into a mold and let it stand for 20 h to age, and obtain a gel material. Crush the gel material into 3 mm particles and dry it to constant weight to obtain silicon-oxygen framework particles.

[0054] Step 2: Preparation of titanium-modified silica bone particles

[0055] Weigh out 10.0g of silicon-oxygen framework particles, 5.4mL of tetraisopropoxy titanium and 50.0mL of anhydrous isopropanol and add them to the reaction vessel. Stir evenly under nitrogen protection, then heat the reaction vessel to 75℃ and keep it at this temperature for 5 hours. Filter the mixture, collect the filter cake and dry it to constant weight to obtain titanium-modified silicon-oxygen framework particles.

[0056] Step ③: Preparation of titanium-activated silica abrasive particles

[0057] Weigh 8.0g of titanium-modified silica abrasive particles and 45.0mL of 18wt% hydrogen peroxide aqueous solution and add them to the reactor. Heat the reactor to 30℃, keep it at the temperature and stir for 3h. Filter the filter cake and dry it to constant weight. Then perform wet grinding and particle size classification to control the particle D50=0.9μm to obtain titanium-activated silica abrasive particles.

[0058] Example 4

[0059] This embodiment provides a method for preparing an anchored amphoteric polymer, including the following steps:

[0060] Step I: Preparation of acylated dopamine derivatives

[0061] Weigh out 10.0 g of dopamine hydrochloride and 100.0 mL of anhydrous dichloromethane and add them to a reaction vessel. After stirring evenly, add 8.0 mL of triethylamine and control the temperature of the reaction vessel at 0 °C. Then, add methacryloyl chloride in ten equal batches with an interval of 5 min between additions, for a total addition of 9.0 mL. After the addition is complete, keep the reaction vessel at the temperature for 1 h. Then, raise the temperature of the reaction vessel to 25 °C and keep it at the temperature with stirring for 3 h. After stirring is complete, remove the solvent under reduced pressure and recrystallize with diethyl ether. Then dry to constant weight to obtain the acylated dopamine derivative.

[0062] Step II: Preparation of anchored amphoteric polymer

[0063] Weigh out 8.0 g of acylated dopamine derivative, 18.0 g of methacryloyl ethyl sulfobetaine, 1.0 g of azobisisobutyronitrile and 100.0 mL of anhydrous ethanol and add them to a reaction vessel. After stirring evenly under nitrogen protection, heat the reaction vessel to 65 °C and keep it at this temperature for 6 h. After stirring is complete, pour the reaction solution into five times its volume of diethyl ether to precipitate. After precipitation is complete, filter to collect the filter cake and dry it to constant weight to obtain the anchored amphoteric polymer.

[0064] The reaction principle for preparing anchored amphoteric polymers is as follows:

[0065] Dopamine hydrochloride is dehydrated with triethylamine under alkaline conditions to form a free amine. The primary amine group in the molecule undergoes an acyl chloride-amine condensation reaction with methacryloyl chloride to introduce a methacryloyl group structure, while retaining the phenolic hydroxyl group on the catechol ring, thus obtaining an acylated dopamine derivative containing polymerizable double bonds. Subsequently, under the initiation of azobisisobutyronitrile, the acylated dopamine derivative and a zwitterionic monomer containing a methacryloyl group undergo a chain addition reaction via free radical polymerization. The double bond is opened to form a copolymer structure with carbon-carbon single bonds as the main chain. This process involves the construction of amide bonds and the free radical copolymerization reaction of vinyl monomers, realizing the covalent introduction of catechol structural units into the polymer backbone, and obtaining a copolymer polymer system containing catechol structural units and zwitterionic structural units.

[0066] The mechanism of action of anchored amphoteric polymers in polishing slurries for silicon wafer processing is as follows:

[0067] First, using dopamine hydrochloride as a raw material, hydrochloric acid is removed under the action of triethylamine to generate free amine, which then undergoes an acyl chloride-amine condensation reaction with methacryloyl chloride to introduce a polymerizable methacryloyl group structure. At the same time, the catechol functional group in the molecule is retained, resulting in an acylated dopamine derivative with double bond activity. Subsequently, under the initiation of azobisisobutyronitrile, this monomer and a zwitterionic monomer containing methacryloyl group undergo a free radical copolymerization reaction to form a copolymer polymer with a carbon-carbon bond structure in the main chain. The resulting anchored zwitterionic polymer has both catechol anchoring groups and zwitterionic hydration structural units. The catechol structural units can form coordination or hydrogen bonding with inorganic surfaces to achieve strong adsorption, while the zwitterionic groups can form a stable hydration layer in the aqueous phase, improving dispersion stability and anti-agglomeration ability, thereby enhancing the interface regulation and stability of the system.

[0068] Example 5

[0069] This embodiment provides a method for preparing an anchored amphoteric polymer, including the following steps:

[0070] Step I: Preparation of acylated dopamine derivatives

[0071] Weigh 12.0 g of dopamine hydrochloride and 100.0 mL of anhydrous dichloromethane and add them to a reaction vessel. After stirring evenly, add 10.0 mL of triethylamine and control the temperature of the reaction vessel at 5 °C. Then, add methacryloyl chloride in ten equal batches with an interval of 5 min between additions, for a total addition of 11.0 mL. After the addition is complete, keep the reaction vessel at the temperature for 1 h. Then, raise the temperature of the reaction vessel to 25 °C and keep it at the temperature with stirring for 4 h. After stirring is complete, remove the solvent under reduced pressure and recrystallize with diethyl ether. Then dry to constant weight to obtain the acylated dopamine derivative.

[0072] Step II: Preparation of anchored amphoteric polymer

[0073] Weigh out 10.0g of acylated dopamine derivative, 21.0g of methacryloyl ethyl sulfobetaine, 1.0g of azobisisobutyronitrile and 100.0mL of anhydrous ethanol and add them to a reaction vessel. After stirring evenly under nitrogen protection, heat the reaction vessel to 70℃ and keep it at this temperature for 8 hours. After stirring, pour the reaction solution into five times its volume of diethyl ether to precipitate. After precipitation is complete, filter to collect the filter cake and dry it to constant weight to obtain the anchored amphoteric polymer.

[0074] Example 6

[0075] This embodiment provides a method for preparing an anchored amphoteric polymer, including the following steps:

[0076] Step I: Preparation of acylated dopamine derivatives

[0077] Weigh out 11.0 g of dopamine hydrochloride and 100.0 mL of anhydrous dichloromethane and add them to a reaction vessel. After stirring evenly, add 9.0 mL of triethylamine and control the temperature of the reaction vessel at 3 °C. Then, add methacryloyl chloride in ten equal batches with an interval of 5 min between additions, for a total addition of 10.0 mL. After the addition is complete, keep the reaction vessel at the temperature for 1 h. Then, raise the temperature of the reaction vessel to 25 °C and keep it at the temperature with stirring for 4 h. After stirring is complete, remove the solvent under reduced pressure and recrystallize with diethyl ether. Then dry to constant weight to obtain the acylated dopamine derivative.

[0078] Step II: Preparation of anchored amphoteric polymer

[0079] Weigh out 9.0 g of acylated dopamine derivative, 20.0 g of methacryloyl ethyl sulfobetaine, 1.0 g of azobisisobutyronitrile and 100.0 mL of anhydrous ethanol and add them to a reaction vessel. After stirring evenly under nitrogen protection, heat the reaction vessel to 70 °C and keep it at this temperature for 7 h. After stirring is complete, pour the reaction solution into five times its volume of diethyl ether to precipitate. After precipitation is complete, filter to collect the filter cake and dry it to constant weight to obtain the anchored amphoteric polymer.

[0080] Example 7

[0081] This embodiment provides a method for preparing an abrasive slurry for silicon wafer processing, including the following steps:

[0082] Step 1: Preparation of dynamic borate ester gel

[0083] Weigh 12.0g of polyvinyl alcohol and 200.0mL of deionized water and add them to the reaction vessel. Heat and stir until dissolved. Then, cool the reaction vessel to 40℃ and add 6.0g of terephthalic acid and 40.0mL of ethanol. Keep warm and stir for 2 hours. After stirring, sieve through a 200-mesh stainless steel sieve and centrifuge at 3000rpm for 5 minutes. Take the supernatant gel and divide it into cubes with a side length of 2mm to obtain dynamic borate ester gel.

[0084] The reaction principle for preparing dynamic borate gel is as follows:

[0085] Polyvinyl alcohol (PVA) molecules are rich in ortho-diol structures, which can undergo a reversible condensation reaction with the boric acid groups in terephthaloboric acid under certain temperature conditions to form BOC-type borate ester bonds. This reaction is essentially an esterification equilibrium process between diols and boric acids, accompanied by the generation and dissociation of water molecules, establishing a dynamic chemical equilibrium in the water / alcohol mixture. Since terephthaloboric acid molecules contain two boric acid groups, they can form bridging structures between different PVA segments, thereby constructing a three-dimensional cross-linked network. The borate ester bonds are reversible, and their formation and dissociation are affected by the water activity and local chemical environment in the system, achieving a polymer network configuration characterized by dynamic covalent bonds.

[0086] The mechanism of action of dynamic borate ester gel silicon wafer processing polishing slurry is as follows:

[0087] Using polyvinyl alcohol (PVA) as the main chain segment, terephthaloboric acid is introduced after complete dissolution in an aqueous phase. Under certain temperature conditions, the borate groups undergo a reversible condensation reaction with the ortho-diol structures on the PVA molecular chain to form BOC-type borate ester bonds, thereby constructing a three-dimensional cross-linked network structure. Since the terephthaloboric acid molecule contains two borate groups, it can form a bridging effect between different PVA chains, establishing a spatial network structure. At the same time, the borate ester bonds have dynamic reversible characteristics, and their formation and dissociation are in equilibrium, giving the resulting gel dynamic covalent network characteristics. Finally, after sieving and centrifugation, a uniform gel system is obtained and divided into gel particles of regular size, ultimately yielding a dynamic borate ester gel with reversible cross-linking characteristics and good structural stability.

[0088] Step 2: Preparation of polishing slurry for silicon wafer processing

[0089] Weigh out 80 parts by weight of deionized water and add it to the mixing tank. After purging with nitrogen for protection, control the temperature of the mixing tank at 25°C. After the pH of the system is 6.5, add 16 parts of dynamic borate ester gel and continue stirring until the system is homogeneous. Then add 4 parts of titanium-activated silica abrasive particles prepared in Example 1 and 1 part of anchored amphoteric polymer prepared in Example 4 and continue stirring and dispersing for 60 min. Finally, let it stand for 20 min to remove bubbles and obtain the polishing slurry for silicon wafer processing.

[0090] The reaction principle for preparing polishing slurry for silicon wafer processing is as follows:

[0091] Dynamic borate gels maintain a reversible cross-linked network structure composed of borate bonds in aqueous systems. Their molecular chains form a continuous dispersed phase with water molecules through hydrogen bonds and physical entanglement. The surface of titanium-activated silica abrasive particles contains hydroxyl groups and Ti-O-Si structural units, which can form hydrogen bonds or weak coordination with water molecules and polymer chains in the system. Anchored amphoteric polymer molecules contain both catechol structural units and zwitterionic structures. Their main chains are dispersed in the aqueous phase through van der Waals forces and intermolecular interactions. The catechol structure can form coordination or hydrogen bond interactions with the inorganic surface, while the zwitterionic groups form a solvation structure in the aqueous phase. The above-mentioned multiple components together constitute a composite dispersion system through dynamic covalent bonds, hydrogen bonds, and coordination interactions.

[0092] Example 8

[0093] This embodiment provides a method for preparing an abrasive slurry for silicon wafer processing, including the following steps:

[0094] Step 1: Preparation of dynamic borate ester gel

[0095] Weigh 15.0g of polyvinyl alcohol and 200.0mL of deionized water and add them to the reaction vessel. Heat and stir until dissolved. Then, cool the reaction vessel to 40℃ and add 8.0g of terephthalic acid and 60.0mL of ethanol. Keep warm and stir for 3h. After stirring, sieve through a 300-mesh stainless steel sieve and centrifuge at 5000rpm for 10min. Take the supernatant gel and divide it into cubes with a side length of 4mm to obtain dynamic borate ester gel.

[0096] Step 2: Preparation of polishing slurry for silicon wafer processing

[0097] Weigh out 90 parts by weight of deionized water and add it to the mixing tank. After purging with nitrogen for protection, control the temperature of the mixing tank at 35°C. After the pH of the system is 7.5, add 18 parts of dynamic borate ester gel and continue stirring until the system is homogeneous. Then add 6 parts of titanium-activated silica abrasive particles prepared in Example 2 and 2 parts of anchored amphoteric polymer prepared in Example 5 and continue stirring and dispersing for 100 min. Finally, let it stand for 20 min to remove bubbles and obtain the polishing slurry for silicon wafer processing.

[0098] Example 9

[0099] This embodiment provides a method for preparing an abrasive slurry for silicon wafer processing, including the following steps:

[0100] Step 1: Preparation of dynamic borate ester gel

[0101] Weigh 13.5g of polyvinyl alcohol and 200.0mL of deionized water and add them to the reaction vessel. Heat and stir until dissolved. Then, cool the reaction vessel to 40℃ and add 7.0g of terephthalic acid and 50.0mL of ethanol. Keep warm and stir for 3h. After stirring, sieve through a 250-mesh stainless steel sieve and centrifuge at 4000rpm for 8min. Take the supernatant gel and divide it into cubes with a side length of 3mm to obtain dynamic borate ester gel.

[0102] Step 2: Preparation of polishing slurry for silicon wafer processing

[0103] Weigh out 85 parts of deionized water by weight and add it to the mixing tank. After stirring, purging with nitrogen and controlling the temperature of the mixing tank at 30°C, add 17 parts of dynamic borate ester gel after the pH of the system reaches 7.0. Continue stirring until the system is homogeneous, then add 5 parts of titanium-activated silica abrasive particles prepared in Example 3 and 2 parts of anchored amphoteric polymer prepared in Example 6 and continue stirring and dispersing for 80 min. Finally, let it stand for 20 min to remove bubbles and obtain the polishing slurry for silicon wafer processing.

[0104] Comparative Example 1

[0105] The difference between this comparative example and Example 9 is that, in the preparation process of the titanium-activated silica abrasive particles used in step two, step ③ is omitted, and the titanium-modified silica particles prepared in step two are used to replace the titanium-activated silica abrasive particles in an equal amount.

[0106] Comparative Example 2

[0107] The difference between this comparative example and Example 9 is that, in the preparation process of the anchoring amphoteric polymer used in step two, step II is omitted, and the acylated dopamine derivative prepared in step I is used to replace the anchoring amphoteric polymer in an equal amount.

[0108] Comparative Example 3

[0109] The difference between this comparative example and Example 9 is that the dynamic borate gel is omitted in step two.

[0110] Performance testing:

[0111] A 100mm diameter single-crystal silicon wafer was processed on a single-sided CMP polisher. An IC1000 polyurethane polishing pad was selected and a Suba IV buffer layer was used. Before polishing, the wafer was pre-conditioned with deionized water at a disk speed of 60 rpm, a carrier speed of 55 rpm, and a surface pressure of 3 psi for 5 minutes. Then, the wafer was installed, and the disk speed was set to 60 rpm, the carrier speed to 55 rpm, the surface pressure to 3 psi, and the silicon wafer processing polishing fluid prepared in Examples 7-9 and Comparative Examples 1-3 was used at a flow rate of 180 mL / min and a temperature of 25°C. Polishing was continued for 3 minutes. 30 seconds before the end of polishing, the surface pressure was reduced to 1 psi and the wafer was rinsed with deionized water. After stopping the machine, the wafer was rinsed with deionized water for another 60 seconds. The wafer was then removed, rinsed with deionized water, and dried with nitrogen to obtain the processed silicon wafer sample.

[0112] The arithmetic mean deviation of the roughness profile Ra, the root mean square of the roughness profile Rq, the maximum height of the roughness profile Rz, the maximum scratch depth, and the maximum scratch width of the silicon wafer samples processed using the polishing slurry prepared in Examples 7-9 and Comparative Examples 1-3 were tested in accordance with the standard GB / T 30860-2014 "Test Method for Surface Roughness and Cutting Marks of Silicon Wafers for Solar Cells".

[0113] The kinematic viscosity of the polishing slurries for silicon wafer processing prepared using Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 10247-2008 "Viscosity Measurement Methods".

[0114] See Table 1 for specific data;

[0115] Table 1 - Performance Test Data for Each Sample

[0116] Project Group Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 Comparative Example 3 Ra / nm 0.35 0.34 0.34 0.52 0.48 0.60 Rq / nm 0.46 0.45 0.44 0.68 0.63 0.75 Rz / nm 2.8 2.7 2.7 4.1 3.9 4.8 Maximum scratch depth / nm 18.1 17.9 17.9 27.5 25.2 33.6 Maximum scratch width / nm 0.9 0.9 0.9 1.3 1.2 1.6 <![CDATA[Kinematic viscosity / mm 2 ·s]]> 2.6 2.6 2.6 2.6 2.3 1.9

[0117] Data Analysis:

[0118] A comparative analysis of the data in Table 1 reveals that the kinematic viscosity of the polishing slurry for silicon wafer processing prepared in this invention is 2.6 mm. 2 Furthermore, the silicon wafer sample processed using the polishing slurry prepared according to this invention exhibits an arithmetic mean deviation of roughness profile of 0.34 nm, a root mean square roughness profile of 0.44 nm, a maximum roughness profile height of 2.7 nm, a maximum scratch depth of 17.9 nm, and a maximum scratch width of 0.9 nm. All these data are superior to the comparative example, indicating that…

[0119] In Comparative Example 1, after step ③ was removed, no oxygen-coordination active structure was formed on the surface of the titanium-modified silicon particles. The titanium species maintained a relatively stable coordination state, and the number of active sites that could participate in dynamic reactions at the interface decreased. As a result, during the polishing process, the interaction between the abrasive particles and the silicon surface tended to be singular, and there was a lack of regulatory transition links between the interfacial reaction and mechanical contact. Under the superposition of pressure and shear, the material removal behavior relied more on instantaneous physical action, and the local load was difficult to disperse and release through chemical processes. The continuity of the interfacial evolution process decreased, and as the processing cycle progressed, the surface microstructure showed more obvious non-equilibrium changes in multiple contacts. The overall morphology control tended to be unstable, and the ability to maintain processing consistency and integrity was relatively weakened.

[0120] In Comparative Example 2, after step II was removed, the amphoteric polymer with a spatial chain segment structure was no longer formed in the system. The interfacial hydration layer and spatial covering structure established by the polymer configuration were lost. Although the acylated dopamine derivative can exhibit interfacial adsorption behavior, it is difficult to form a continuous and stable regulating layer around the abrasive grains due to the limited molecular scale. Moreover, during the polishing process, the abrasive grains are more likely to undergo relative migration and local concentration fluctuations in the shear flow field. The interfacial contact state changes more significantly over time. At the same time, without the coordination and buffering of the interfacial perturbation by the chain segment structure, the rhythmicity of the material removal process decreases, and the surface morphology is more likely to show an uneven evolution trend under repeated loading conditions. The overall synergy of the system is relatively weakened.

[0121] In Comparative Example 3, after the removal of the dynamic borate ester gel, the three-dimensional flexible network structure constructed by reversible borate ester bonds no longer exists in the system. Consequently, the spatial support and dynamic adjustment mechanism disappear. As a result, the abrasive particles in the continuous phase mainly rely on physical dispersion to maintain their distribution state. Under pressure and shear conditions, there is a lack of network structure to constrain their motion trajectory and adjust the load dispersion path. During the polishing process, abrasive particle aggregation or instantaneous enrichment is more likely to occur in local areas, the force distribution at the interface tends to be concentrated, and since the impact and shear energy is difficult to absorb and release through the network structure, the contact stability decreases. The surface microstructure is more prone to fluctuations during continuous processing, and the overall balance and controllability of the processing process are relatively reduced.

[0122] Ultimately, it is demonstrated that when the peroxide-activated structure, the amphoteric polymer segment structure, and the dynamic borate ester network structure are removed sequentially, the multi-level synergistic relationship within the system changes significantly. Specifically, without activation treatment, the number of structural units on the abrasive surface that can participate in interface regulation decreases, and the material removal process tends to follow a single contact path. Without the amphoteric polymer segments, it is difficult to form an interfacial hydration layer and spatial coverage configuration, resulting in decreased distribution stability of abrasive particles in the flow field. Without the dynamic network, the system no longer possesses a mechanism for dispersing and mitigating load transfer and instantaneous impact, making the abrasive particle trajectory more prone to fluctuations. Thus, it is evident that the abrasive active structure, interface regulation structure, and network regulation structure constructed in this application form a hierarchical connection and functional coordination relationship during operation. The material configuration is not simply a parallel superposition but exhibits a mutually supportive synergistic state under the flow environment and contact conditions, and the overall processing performance changes accordingly with the degree of structural integrity.

[0123] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0124] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0125] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A polishing slurry for silicon wafer processing, characterized in that, The raw material composition includes the following parts by weight: 4-6 parts titanium-activated silica abrasive particles, 1-2 parts anchored amphoteric polymer, 16-18 parts dynamic borate ester gel and 80-90 parts dispersant, wherein the dispersant is deionized water; The titanium-activated silica abrasive particles are prepared by the following method: A1. Add silicon-oxygen framework particles, tetraisopropoxy titanium and anhydrous isopropanol to a reaction vessel, stir evenly under nitrogen protection, heat the reaction vessel to 70-75℃, keep it at the temperature and stir for 3-5 hours, filter to collect the filter cake and dry to constant weight to obtain titanium-modified silicon-oxygen framework particles. A2. Add titanium-modified silica abrasive particles and activation liquid to a reactor, heat the reactor to 25-30℃, keep it warm and stir for 2-3 hours, filter and collect the filter cake and dry it to constant weight, then perform wet grinding and particle size classification to control particle D50=0.8-1.0μm to obtain titanium-activated silica abrasive particles.

2. The polishing slurry for silicon wafer processing according to claim 1, characterized in that, In step A1, the ratio of the silicon-oxygen framework particles, tetraisopropoxy titanium, and anhydrous isopropanol is 9-12g:5-6mL:45-50mL; in step A2, the ratio of the titanium-modified silicon framework particles to the activation solution is 7-9g:40-50mL, wherein the activation solution is a 15-20wt% hydrogen peroxide aqueous solution.

3. The polishing slurry for silicon wafer processing according to claim 1, characterized in that, The preparation method of the silicon-oxygen framework particles is as follows: tetraethyl orthosilicate and anhydrous ethanol are added to a reaction vessel and stirred until uniform. Then, deionized water and 1wt% hydrochloric acid aqueous solution are added. After stirring at room temperature for 15 minutes, the reaction vessel is heated to 35-45℃ and kept at this temperature for 2-3 hours. The silicon-oxygen framework particles are then obtained through post-treatment.

4. The polishing slurry for silicon wafer processing according to claim 3, characterized in that, In the process of preparing silicon-oxygen framework particles, the ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water and 1wt% hydrochloric acid aqueous solution is 16-18mL:120mL:21-25mL:1-2mL.

5. The polishing slurry for silicon wafer processing according to claim 1, characterized in that, The anchored amphoteric polymer was prepared by the following method: B1. Add dopamine hydrochloride and anhydrous dichloromethane to a reaction vessel, stir evenly, then add triethylamine and control the reaction vessel temperature at 0-5℃. Then add methacrylamide chloride in ten equal batches with an interval of 5 min between additions. After the addition is complete, keep the reaction vessel at the temperature for 1 h. Then raise the temperature of the reaction vessel to 25℃ and keep it at the temperature for 3-4 h with stirring. Post-treatment yields acylated dopamine derivatives. B2. Add acylated dopamine derivative, methacryloyl ethyl sulfobetaine, azobisisobutyronitrile and anhydrous ethanol to a reaction vessel. After stirring evenly under nitrogen protection, heat the reaction vessel to 65-70℃ and keep it at this temperature for 6-8 hours. Post-treatment yields the anchored amphoteric polymer.

6. The polishing slurry for silicon wafer processing according to claim 5, characterized in that, In step B1, the ratio of dopamine hydrochloride, anhydrous dichloromethane, triethylamine, and methacryloyl chloride is 10-12 g: 100 mL: 8-10 mL: 9-11 mL.

7. The polishing slurry for silicon wafer processing according to claim 5, characterized in that, In step B2, the ratio of the acylated dopamine derivative, methacryloyl ethyl sulfobetaine, azobisisobutyronitrile, and anhydrous ethanol is 8-10g:18-21g:1g:100mL.

8. The polishing slurry for silicon wafer processing according to claim 1, characterized in that, The preparation method of the dynamic borate ester gel is as follows: polyvinyl alcohol and deionized water are added to a reaction vessel and heated and stirred until dissolved. The reaction vessel is then cooled to 40°C and terephthalic acid and anhydrous ethanol are added. The mixture is kept warm and stirred for 2-3 hours. The dynamic borate ester gel is then obtained through post-treatment.

9. The polishing slurry for silicon wafer processing according to claim 8, characterized in that, In the preparation of dynamic borate gel, the ratio of polyvinyl alcohol, deionized water, terephthalic acid and anhydrous ethanol is 12-15g:200mL:6-8g:40-60mL.

10. A method for preparing a polishing slurry for silicon wafer processing as described in any one of claims 1-9, characterized in that, Includes the following steps: Deionized water was added to the mixing vessel and stirred. After nitrogen protection, the temperature of the mixing vessel was controlled at 25-35℃. After the pH of the system was 6.5-7.5, dynamic borate ester gel was added. Stirring was continued until the system was homogeneous. Then, titanium-activated silica abrasive particles and anchored amphoteric polymer were added and stirred and dispersed for 60-100 minutes. Finally, the mixture was allowed to stand for 20 minutes to remove bubbles, and the polishing slurry for silicon wafer processing was obtained.