Polishing solution for improving storage and application stability of high-viscosity fine polishing solution and preparation method of polishing solution

Abstract

The invention relates to a polishing solution for improving storage and application stability of a high-viscosity fine polishing solution. The polishing solution is mainly composed of the following raw materials in percentage by weight: 10-35wt% of a polishing abrasive; 0.5 to 2.0 wt% of a water-soluble polymer; 0.05 to 0.2 wt% of an active agent; 5-10 wt% of a pH regulator; 0.01 to 0.05 wt% of a defoaming agent; and the balance of water. The polishing solution is alkaline. According to the polishing solution, silica sol is adopted as a grinding material, a water-soluble polymer is introduced to form a coating structure on the surface of the silica sol, and the steric hindrance effect of organic alkali is combined, so that the stability of the fine polishing solution in a high-viscosity system is effectively improved, the gelation phenomenon caused by high viscosity is avoided, the surface roughness Ra of a polished and cleaned silicon surface is smaller than 0.15 nm, and the surface particle number (larger than or equal to 0.2 mu m) is smaller than 100; the particle size, the viscosity and the pH value of a prepared sample are not greatly changed after the sample is stored at room temperature for 6 months, and the sample has excellent long-term storage stability.

Description

Technical Field

[0001] This invention belongs to the field of silicon wafer substrate CMP polishing technology, specifically relating to a polishing slurry for improving the storage and application stability of high-viscosity polishing slurry and its preparation method. Background Technology

[0002] Silicon wafers are the most important basic material in the semiconductor industry and the cornerstone of integrated circuits. Their applicability in manufacturing chips and microchips for electronic products is extremely wide. In recent years, as the size of silicon wafers has increased from 25.4 mm to 300 mm or even larger, higher demands have been placed on silicon wafer processing technology. In integrated circuit (IC) manufacturing, various electronic components are assembled on a silicon substrate to perform specific functions. As IC technology enters the 3-90nm nanoelectronics era, the development model of "diversified wires and miniaturized structures" requires large-size silicon single-wafer wafers to have atomic-level surface roughness and nanometer-level surface accuracy. Therefore, to improve the surface quality of large-size silicon wafers after polishing, the industry's evaluation standards for the surface quality of finely polished silicon wafers are becoming increasingly stringent. For large-size silicon wafers, the surface roughness Ra after fine polishing and cleaning should be <0.15nm, and the lower the better, while strict requirements are placed on the residual rate of large particles on the surface. CMP technology removes different materials at the micron / nano scale from the surface of a substrate / wafer by combining surface chemical action and mechanical polishing. It can not only perform local treatment on the silicon wafer surface, but also planarize the entire silicon wafer surface (nanoscale). It is currently the only technology that can take into account both global and local surface planarization.

[0003] Silicon wafer CMP polishing slurry, as a core material of CMP technology, is mainly composed of abrasives, water-soluble polymers, pH adjusters, and surfactants formulated in a specific ratio. The synergistic effect of the water-soluble polymers and surfactants not only regulates the wetting properties of the system and improves the spreading performance of the polishing slurry on the silicon wafer surface, but also enhances the repulsive force between particles through steric hindrance and electrostatic stabilization mechanisms. This complex mechanism makes increasing the viscosity of the polishing slurry key to optimizing the dispersion system and achieving better stability and uniform particle dispersion. However, high-viscosity polishing slurries are easily affected by external temperature and mechanical fields during room temperature storage and polishing, leading to polymer chain entanglement and gel formation, rendering them unusable.

[0004] Many scholars have conducted research on silicon wafer polishing solutions. Chinese patent CN116554788A discloses a silicon wafer polishing solution that introduces a macromolecular polymer as a viscosity modifier, thereby altering the interfacial energy between the polishing solution and the silicon wafer surface, increasing the hydrophilicity of the silicon wafer surface, and effectively preventing the adhesion of silica sol particles from the polishing solution to the silicon wafer surface after chemical mechanical polishing, thus effectively reducing particle residue on the silicon wafer surface. However, this patent does not study the stability of the system after introducing the macromolecular polymer, and cannot ensure that excellent polishing results can still be achieved after long-term storage. Chinese patent CN113881347A discloses a chemical mechanical polishing solution that uses a composite of abrasives with different morphologies to effectively reduce scratches on silicon wafers while increasing the polishing rate. However, the polyellipsoidal abrasives used in this patent currently lack a stable and mature preparation process, which to some extent limits the widespread application and further development of this polishing solution. Chinese patent CN117801684A discloses a method for preparing a silicon wafer polishing solution. It enhances the material removal rate during the polishing process by introducing a mixture of amine and azole compounds as a polishing accelerator. The introduction of a thickener increases the viscosity of the polishing solution, forming a buffer layer between the solution and the silicon wafer during polishing, significantly reducing surface scratches. However, the polishing solution prepared in this patent produces a surface Ra > 0.15 nm after polishing, and the azole compounds used in the patent have high procurement costs and poor large-scale supply stability, potentially limiting its practical industrial application.

[0005] To address the shortcomings of existing technologies, this invention develops a polishing slurry and its preparation method for improving the storage and application stability of high-viscosity polishing solutions. It utilizes silica sol as the abrasive, adsorbing a layer of water-soluble polymer onto the silica sol surface to form a "core-shell" structure. Then, an organic base is introduced to adjust the pH and charge density of the system, creating a strong steric hindrance effect between particles. This forms a "core-shell-bridge" structure composed of nanoparticles, water-soluble polymers, and organic base, effectively improving the dispersion uniformity and macroscopic stability of nanoparticles in the high-viscosity polishing solution and avoiding gelation caused by high viscosity. The high-viscosity polishing solution ensures uniform distribution of silica sol on the silicon wafer surface during polishing, effectively reducing scratches caused by silica sol accumulation and improving the surface quality of the silicon wafer. The final results show that after 6 months of storage at room temperature, the particle size, viscosity, and pH of the prepared sample did not change significantly; after polishing and cleaning, the surface roughness Ra (10µm × 10µm) was <0.15nm, and the number of surface particles (≥0.2µm) was <100. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art and provide a polishing fluid and its preparation method for improving the storage and application stability of high-viscosity polishing fluid. It uses silica sol as an abrasive and introduces water-soluble polymers to form a coating structure on the silica sol surface. Combined with the steric hindrance effect of organic base, it effectively improves the stability of the polishing fluid in high-viscosity systems and avoids the gelation phenomenon caused by high viscosity. After polishing and cleaning, the surface roughness Ra of the silicon surface is <0.15nm, and the number of surface particles (≥0.2um) is <100. Moreover, the particle size, viscosity and pH value of the prepared sample did not change significantly after being stored at room temperature for 6 months, which shows excellent long-term storage stability.

[0007] The present invention also provides a method for preparing the above-mentioned polishing fluid for improving the storage and application stability of high-viscosity polishing fluid.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, wherein the polishing slurry is mainly composed of the following raw materials by weight percentage: Polishing abrasive 10-35wt%; Water-soluble polymer 0.5-2.0 wt% Surfactant 0.05-0.2 wt%; pH adjuster 5-10 wt% Defoamer 0.01-0.05 wt%; The remainder is water; The polishing solution is alkaline (preferably with a pH of 11.0-12.0).

[0009] Specifically, the abrasive can be silica sol abrasive grains; the specific gravity (density) of the abrasive is preferably 1.05 or higher, more preferably 1.1 or higher, and even more preferably 1.2 or higher. Here, the specific gravity (density) of the abrasive refers to the specific gravity of the silica particles in the abrasive grains composed of silica particles. Furthermore, the shape (external shape) of the abrasive grains is spherical.

[0010] Furthermore, the abrasive content is higher than 20 wt%, more preferably higher than 25 wt%, and more preferably lower than 35 wt% of the silica sol abrasive. Furthermore, the particle size of the abrasive is preferably 50 nm or more, more preferably 60 nm or more. From the viewpoint of the localized pressure exerted by the abrasive on the surface of the object being polished, the particle size of the abrasive is preferably 150 nm or less, more preferably 130 nm or less, and even more preferably 120 nm or less.

[0011] Specifically, the water-soluble polymer can be any water-soluble polymer suitable for forming intermolecular forces on the silica sol surface, thereby fixing it to the silica sol surface. Further, the water-soluble polymer is selected from at least one of cellulose-based materials and polyacrylic acid-based materials. More preferably, the water-soluble polymer material is a polyacrylic acid-based material. Further, the surface of the water-soluble polymer has a large number of -OH groups, which can serve as intermolecular force binding sites and form hydrogen bonds with the silica sol surface, thereby adsorbing onto the silica sol surface and forming a protective layer. Preferably, the Mw of the above-mentioned water-soluble polymer is ≥1×10⁻⁶. 4 More preferably ≥ 2×10 4 From the perspective of improving wettability, a value greater than 5×10 is preferred. 4 More preferably greater than 10×10 4 However, considering the dispersibility of the polymer itself and the entanglement of molecular chains, Mw is preferably ≤ 50 × 10⁻⁶. 4 More preferably ≤ 30×10 4 In this specification, the molecular weight Mw is determined by gel permeation chromatography (GPC).

[0012] Specifically, the cellulose-based substances include cellulose derivatives, which may include, but are not limited to, at least one of the following: hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, phenyl cellulose, methyl hydroxypropyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl ethyl cellulose, hydroxypropyl hydroxybutyl cellulose, ethyl hydroxypropyl cellulose, hydroxyethyl benzyl cellulose, methyl benzyl cellulose, hydroxypropyl cyanoethyl cellulose, hydroxypropyl benzyl cellulose, hydroxyethyl phenyl cellulose, and cyanoethyl benzyl cellulose. Methyl cellulose is preferred.

[0013] Preferably, the polyacrylic acid material includes, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, polyacrylate, polymethyl methacrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, acrylic acid-acrylamide copolymer, acrylic acid-maleic anhydride copolymer, acrylic acid-styrene copolymer, acrylic acid-vinylpyrrolidone copolymer, acrylic acid-vinyl acetate copolymer, quaternized polyacrylic acid, sulfonated polyacrylic acid, silicone-modified polyacrylic acid, and fluorinated polyacrylic acid. Polybutyl methacrylate is preferred. Preferably, the water-soluble polymer comprises at least 0.5 wt% (weight percentage), more preferably at least 0.8 wt%, and even more preferably at least 1.0 wt%.

[0014] Specifically, the surfactant can effectively reduce the haze and improve the surface morphology after polishing during the polishing process. The surfactant can be any one of anionic, cationic, and nonionic surfactants. Further, anionic or nonionic surfactants are preferred. More preferably, considering the foaming properties and solvent charge balance during the polishing process, nonionic surfactants are preferred, including, but not limited to, polyvinyl alcohols (polyethylene glycol, polypropylene glycol, polybutanediol, etc.), polyoxyalkylene copolymers (e.g., block copolymers of ethylene oxide and propylene oxide, PEO-PPO-PEO triblock copolymers, PPO-PEO-PPO triblock copolymers, random copolymers, cross-polymers), polyoxyethylene monolaurate, polyoxyethylene dioleate, polyoxyethylene sorbitan tetraoleate, polyoxyethylene castor oil, and other nonionic surfactants. Preferably, the surfactant contains a polyvinyl alcohol structure. Furthermore, the molecular weight of the surfactant is higher than Mw > 1 × 10⁻⁶. 4 Furthermore, some candidates selected values ​​higher than Mw > 1.5 × 10 4 The molecular weight of the above-mentioned active agent is determined by molecular gel chromatography (MGC). Preferably, the active agent contains at least 0.05 wt%, more preferably at least 0.08 wt%, and even more preferably at least 0.1 wt%.

[0015] Specifically, the pH adjuster is preferably selected from various alkaline compounds that have the function of increasing the pH of an aqueous solution when dissolved in water. Further, the pH adjuster is preferably at least one of quaternary ammonium compounds, ammonia, and amine compounds (preferably water-soluble amines). The quaternary ammonium compound can be at least one of tetraalkylammonium salts, hydroxyalkyltrialkylammonium salts, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the amine includes at least one of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, diethanolamine, and triethanolamine; among these, ethylenediamine is more preferred. Further, the pH adjuster contains at least 5.0 wt%, more preferably at least 6 wt%, and more preferably at least 6.5 wt%.

[0016] Specifically, the defoamer may be a polyoxysilane defoamer, containing at least 0.01 wt%, and more preferably at least 0.02 wt%. Further, the polyoxysilane defoamer includes, but is not limited to, at least one of BYK028 (BYK Chemical), DF689 (Guanzhi Chemical), and AF9000 NE (Momentive).

[0017] This invention provides a method for preparing the above-mentioned polishing fluid for improving the storage and application stability of high-viscosity polishing fluid, which includes the following steps: Step 1: Weigh out the water-soluble polymer and surfactant, add them to deionized water, and stir until completely dissolved to obtain mother liquor L1; Step 2: Weigh the polishing abrasive, add some pH adjuster, and stir until evenly dispersed to obtain mother liquor L2. Step 3: Add the above mother liquor L1 to mother liquor L2, stir for more than 10 hours, add defoamer in the last hour, stir evenly to obtain mixed solution L3; Step 4: Add the remaining pH adjuster to the above mixed solution L3, stir well, and filter to obtain the final product.

[0018] In a further preferred embodiment, the pH adjuster added in step two accounts for 30% to 50% of the total pH adjuster. The specific amount can be determined based on the amount of water-soluble polymer in step one, ensuring that the mass ratio of pH adjuster to water-soluble polymer is between 2.5 and 3.5:1.

[0019] The present invention also provides the application of the above-mentioned polishing slurry for improving the storage and application stability of high viscosity polishing slurry in silicon wafer polishing.

[0020] This invention innovatively develops a polishing fluid for improving the storage and application stability of high-viscosity fine polishing fluid and its preparation method. It uses silica sol as an abrasive, introduces water-soluble polymers to form a coating structure on the surface of silica sol, and combines the steric hindrance effect of organic base to effectively improve the stability of fine polishing fluid in high-viscosity systems and avoid gelation phenomenon caused by high viscosity.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention employs a water-soluble polymer to encapsulate silica sol, forming a "core-shell" structure. The outer layer of non-ionic water-soluble polymer exhibits low intermolecular attraction, thus preventing agglomeration of silica sol nanoparticles due to mutual attraction and improving the dispersibility of silica sol particles and the stability of the system. Simultaneously, the enhanced dispersibility prevents abrasive particles in the polishing slurry from self-aggregating, thereby preventing precipitation and caking, improving the surface quality of the polished silicon wafer, and reducing scratches and large particle residue.

[0022] 2) This invention introduces a small amount of organic base during the preparation of water-soluble polymer-coated silica sol. Through the steric hindrance of the organic base and the nonionic water-soluble polymer, the increased viscosity caused by the entanglement of the polymer chains under mechanical forces is alleviated. Simultaneously, the introduction of silica sol creates molecular repulsion between the organic base and the coated structure, forming a "core-shell-bridge" quasi-three-dimensional network structure, enhancing the overall stability of the system. With changes in temperature and mechanical fields during storage and polishing, this quasi-three-dimensional structure can improve the situation of polymer chains entangled or having many interconnected particles in the polishing solution, effectively avoiding gelation during storage and polishing.

[0023] 3) This invention achieves excellent dispersibility and anti-coagulation properties of silica sol particles, effectively reducing scratches caused by silica sol accumulation during polishing. Furthermore, the construction of the high-viscosity polishing slurry enables better spreading of nanoparticles on the silicon wafer surface, significantly improving the surface quality of the silicon wafer. Attached Figure Description

[0024] Figure 1 The surface roughness test of the polishing slurry prepared in Example 2 before polishing is performed using an atomic force microscope. Figure 2 The surface roughness test under an atomic force microscope after polishing with the polishing slurry prepared in Example 2; Figure 3 The surface roughness of the polishing slurry prepared in Comparative Example 1 was measured under an atomic force microscope before polishing. Figure 4 The surface roughness test under an atomic force microscope after polishing with the polishing slurry prepared in Comparative Example 1; Figure 5 The surface roughness of the polishing slurry prepared in Comparative Example 4 was measured under an atomic force microscope before polishing. Figure 6 The surface roughness of the polishing solution prepared in Comparative Example 4 was measured under an atomic force microscope. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the content of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] The polishing abrasive used in the following examples is selected from silica sol abrasive grains. The abrasive grains are spherical in shape, have a specific gravity of 1.25, and a particle size range of 60-120nm. They are purchased from commercially available products.

[0027] Example 1 A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, the polishing slurry being mainly composed of the following raw materials by weight percentage: The polishing solution contains 20% silica sol with a polishing abrasive particle size of 80nm, 1.0% water-soluble high molecular weight methylcellulose (Mw≈25w), 0.1% activator polyethylene glycol (Mw≈1.5w), 7.5% pH adjuster ethylenediamine, 0.02% defoamer DF689 (Guanzhi Chemical), and the balance is water; the pH of the polishing solution is 11.55.

[0028] The above-mentioned method for preparing a polishing slurry to improve the storage and application stability of high-viscosity polishing solutions includes the following steps: Step 1: Weigh water-soluble polymer methylcellulose and surfactant polyethylene glycol, add them to deionized water, and stir until completely dissolved to obtain mother liquor L1; Step 2: Weigh out silica sol with a polishing abrasive particle size of 80nm, add a portion of pH adjuster (the amount added accounts for about 40% of the total mass of pH adjuster), stir until evenly dispersed, and obtain mother liquor L2. Step 3: Add the above mother liquor L1 to mother liquor L2 and stir for more than 12 hours. Add defoamer DF689 in the last hour and stir evenly to obtain mixed solution L3. Step 4: Add the remaining pH adjuster to the above mixed solution L3, stir well, and obtain mixed solution L4; Step 5: Filter the mixed solution L4 prepared above to finally obtain the high-viscosity silica sol system silicon wafer polishing solution.

[0029] Example 2 A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, the polishing slurry being mainly composed of the following raw materials by weight percentage: The polishing solution contains 25% silica sol with a particle size of 90 nm, 1.2% polybutyl methacrylate (Mw≈25w), 0.15% polybutanediol (Mw≈2w), 8% ethylenediamine, 0.03% defoamer AF9000 NE (Momentive), and the balance is water; the pH of the polishing solution is 11.76.

[0030] The preparation method of the polishing fluid used to improve the storage and application stability of high-viscosity polishing fluid is described above, referring to Example 1.

[0031] Example 3 A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, the polishing slurry being mainly composed of the following raw materials by weight percentage: The polishing solution contains 20% silica sol with a particle size of 100 nm, 0.85% polybutyl methacrylate (Mw≈30w), 0.2% PEO-PPO-PEO triblock copolymer (Mw≈2w), 8% tetraethylammonium hydroxide, 0.02% defoamer AF9000 NE (Momentive), and the balance is water; the pH of the polishing solution is 11.75.

[0032] The preparation method of the polishing fluid used to improve the storage and application stability of high-viscosity polishing fluid is described above, referring to Example 1.

[0033] Example 4 A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, the polishing slurry being mainly composed of the following raw materials by weight percentage: The polishing solution contains 26% silica sol with a particle size of 70 nm, 1.7% polyacrylate (Mw≈10w), 0.2% polyoxyethylene monolaurate (Mw≈2w), 9% dimethylamine, 0.02% defoamer DF689 (Guanzhi Chemical), and the balance is water; the pH of the polishing solution is 11.83.

[0034] The preparation method of the polishing fluid used to improve the storage and application stability of high-viscosity polishing fluid is described above, referring to Example 1.

[0035] Example 5 A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, the polishing slurry being mainly composed of the following raw materials by weight percentage: The polishing solution contains 15% silica sol with a particle size of 110 nm, 0.98% hydroxypropyl cellulose (Mw≈37w), 0.1% polyoxyethylene monolaurate (Mw≈2w), 9% ethylenediamine, 0.02% defoamer BYK028 (BYK Chemical), and the balance is water; the pH of the polishing solution is 11.85.

[0036] The preparation method of the polishing fluid used to improve the storage and application stability of high-viscosity polishing fluid is described above, referring to Example 1.

[0037] Example 6 A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, the polishing slurry being mainly composed of the following raw materials by weight percentage: The polishing solution contains 20% silica sol with a particle size of 90 nm, 1.2% ethyl cellulose (Mw≈18w), 0.15% polyoxyethylene castor oil (Mw≈2w), 7.5% monoethanolamine, 0.03% BYK028 (BYK Chemical) defoamer, and the balance is water; the pH of the polishing solution is 11.62.

[0038] The preparation method of the polishing fluid used to improve the storage and application stability of high-viscosity polishing fluid is described above, referring to Example 1.

[0039] Example 7 A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, the polishing slurry being mainly composed of the following raw materials by weight percentage: The polishing solution contains 15% silica sol with a particle size of 120 nm, 2% carboxymethyl cellulose (Mw≈10w), 0.1% polyethylene glycol (Mw≈2w), 9.5% diethanolamine, 0.04% defoamer BYK028 (BYK Chemical), and the balance is water; the pH of the polishing solution is 11.85.

[0040] The preparation method of the polishing fluid used to improve the storage and application stability of high-viscosity polishing fluid is described above, referring to Example 1.

[0041] Example 8 A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, the polishing slurry being mainly composed of the following raw materials by weight percentage: The polishing solution contains 30% silica sol with a particle size of 60 nm, 0.92% polybutyl methacrylate (Mw≈35w), 0.2% polypropylene glycol (Mw≈2w), 10.0% ethylenediamine, 0.02% defoamer BYK028 (BYK Chemical), and the balance is water; the pH of the polishing solution is 11.90.

[0042] The preparation method of the polishing fluid used to improve the storage and application stability of high-viscosity polishing fluid is described above, referring to Example 1.

[0043] Comparative Example 1 The specific formulation ratios for comparison sample 1 are as follows: The polishing solution contains 25% silica sol with a particle size of 90 nm, 1.2% polybutyl methacrylate (Mw≈25w), 0.15% polybutanediol (Mw≈2w), 8% ethylenediamine, 0.03% defoamer AF9000 NE (Momentive), and the balance is water; the pH of the polishing solution is 11.74.

[0044] The preparation process of the above-mentioned comparative sample 1 is as follows: Step 1: Weigh water-soluble polybutyl methacrylate and activator polybutanediol, add them to deionized water, and stir until completely dissolved to obtain mother liquor L1; Step 2: Weigh out silica sol with a polishing abrasive particle size of 90nm, stir until evenly dispersed, and obtain mother liquor L2; Step 3: Add the above mother liquor L1 to mother liquor L2 and stir for more than 12 hours. Add defoamer AF9000NE in the last hour and stir evenly to obtain mixed solution L3. Step 4: Add pH adjuster to the above mixed solution L3, stir well to obtain mixed solution L4; Step 5: Filter the mixed solution L4 prepared above to obtain the final product.

[0045] Comparative Example 2 The specific formulation ratios for comparison sample 2 are as follows: The polishing solution contains 25% silica sol with a particle size of 90 nm, 1.2% polybutyl methacrylate (Mw≈25w), 0.15% polybutanediol (Mw≈2w), 8% ethylenediamine, 0.03% defoamer AF9000 NE (Momentive), and the balance is water; the pH of the polishing solution is 11.76.

[0046] The preparation process of the above-mentioned comparative sample 2 is as follows: Step 1: Weigh water-soluble polybutyl methacrylate and activator polybutanediol, add them to deionized water, and stir until completely dissolved to obtain mother liquor L1; Step 2: Add defoamer to mother liquor L1 to obtain mixed solution L2; Step 3: Weigh out silica sol with a polishing abrasive particle size of 90nm, add it to mixed solution L2, stir evenly to obtain mixed solution L3; Step 4: Add pH adjuster to the above mixed solution L3, stir well to obtain mixed solution L4; Step 5: Filter the mixed solution L4 prepared above to obtain the final product.

[0047] Comparative Example 3 A commercially available high-viscosity CMP polishing slurry for silicon wafers from Company A was selected as Comparative Example 3. During polishing, the slurry was diluted with water at a ratio of 1:30.

[0048] Comparative Example 4 The mainstream high-viscosity CMP polishing slurry for silicon wafers from commercially available company B was selected as Comparative Example 4. When polishing, the slurry was diluted with water at a ratio of 1:30.

[0049] Figure 1 The surface roughness test of the polishing slurry prepared in Example 2 before polishing is shown under an atomic force microscope. The figure shows that the roughness of the silicon substrate before polishing is 0.43 nm, and scratches are clearly visible on the surface.

[0050] Figure 2 The surface roughness test under an atomic force microscope is shown after polishing with the polishing slurry prepared in Example 2. The figure shows that the roughness of the silicon substrate after polishing in Example 2 is 0.11 nm, indicating a good surface morphology.

[0051] Figure 3 The surface roughness test of the polishing slurry prepared in Comparative Example 1 before polishing is shown under an atomic force microscope. The figure shows that the roughness of the silicon substrate before polishing is 0.42 nm.

[0052] Figure 4 The surface roughness test under an atomic force microscope is shown after polishing with the polishing slurry prepared in Comparative Example 1. The figure shows that the roughness of the silicon substrate after polishing with Comparative Example 1 is 0.26 nm.

[0053] Figure 5 The surface roughness test results of the polishing slurry prepared in Comparative Example 4 before polishing are shown under an atomic force microscope. The figure shows that the roughness of the silicon substrate before polishing is 0.42 nm.

[0054] Figure 6 The surface roughness test results under an atomic force microscope after polishing with the polishing slurry prepared for Comparative Example 4 are shown. The figure shows that the roughness of the silicon substrate after polishing with Comparative Example 4 is 0.19 nm.

[0055] Testing and Inspection The prepared silicon wafer CMP polishing slurry was used for comparative testing under the following conditions and polishing parameters: a Chuangji single-sided polishing machine was used, a black damping cloth pad was used as the polishing pad, a 6-inch silicon wafer was used for rough polishing, and the pressure was 100-150 g / cm². 2 The relevant data testing methods include visual inspection under high-intensity light, Malvern nanoparticle size analyzer, rotational viscometer, scanning electron microscope, wafer surface particle size inspection system, optical microscope, and atomic force microscope.

[0056] The physicochemical properties of the polishing solutions obtained in Examples 1 to 8 and Comparative Examples 1 to 4 of this invention during storage at room temperature are as follows: Table 1 Comparison of physicochemical properties of the examples and comparative examples before and after 6 months of storage at room temperature From the physicochemical properties of the samples before and after 6 months of storage at room temperature, the self-constructed molecular bridging and coating structure effectively improved the uniform dispersion and stability of the particles during room temperature storage. As shown in the table above, the particle size, viscosity, and pH value of the prepared sample did not change significantly after 6 months, and no gelation or adhesion was observed visually after 6 months. However, as shown in Comparative Example 1, the silica sol particles that only formed a surface coating structure during preparation, under the influence of the external temperature field during long-term storage, caused the polymer chains in the system to overcome their steric hindrance and begin to entangle. During long-term storage, this phenomenon leads to particle aggregation and accumulation, resulting in larger particle size; furthermore, the polymer chains have many hydrogen bond donors and acceptors, which can cause self-entanglement, increasing the system viscosity. As shown in Comparative Example 2, the high-viscosity system without surface coating of the silica sol particles easily leads to gelation, which is detrimental to long-term storage and use.

[0057] The polishing solutions obtained in Examples 1 to 8 and Comparative Examples 1 to 4 of this invention were stored at room temperature for 6 months and then used to polish 6-inch silicon wafers. The surface quality data after polishing are as follows.

[0058] Table 2 Polishing results of the examples and comparative examples after 6 months of storage at room temperature As can be seen from the table above, after six months of storage at room temperature, the high-viscosity silicon wafer polishing solution sample prepared according to the formulation and process of this application resulted in a surface particle count of <100 and Ra <0.15nm after polishing and cleaning. Comparative Example 1 showed that after six months of storage, the particle size of the system had increased, resulting in more residual particles and a larger Ra on the polished surface. Comparative Example 2 sample gelled and could not be tested for polishing. Furthermore, the polishing results of two mainstream commercially available silicon wafer polishing solutions showed relatively large surface Ra and particle residue. The product provided by this invention exhibits superior performance in all aspects after polishing compared to similar commercially available products, demonstrating better application results.

[0059] In summary, the method for constructing a high-viscosity anti-coagulation silica sol system for CMP polishing and the polishing composition samples provided by this invention did not show significant changes in particle size, viscosity, and pH value after 6 months of storage at room temperature. After polishing and cleaning, the surface roughness Ra (10um × 10um) was <0.15nm, and the number of surface particles (≥0.2um) was <100.

Claims

1. A polishing slurry for improving the storage and application stability of high-viscosity polishing solutions, characterized in that, The polishing slurry is mainly composed of the following raw materials by weight percentage: Polishing abrasive 10-35 wt%; water-soluble polymer 0.5-2.0 wt%; surfactant 0.05-0.2 wt%; pH adjuster 5-10 wt%; defoamer 0.01-0.05 wt%; balance: water; The polishing solution is alkaline.

2. The polishing fluid for improving the storage and application stability of high-viscosity polishing fluid as described in claim 1, characterized in that, The abrasive is silica sol abrasive grains; the shape of the abrasive grains is spherical.

3. The polishing slurry for improving the storage and application stability of high-viscosity polishing solutions as described in claim 1, characterized in that, The water-soluble polymer is selected from at least one of cellulose-based substances and polyacrylic acid-based substances; the Mw of the water-soluble polymer is 1×10⁻⁶. 4 ≤ Mw ≤ 50×10 4 .

4. The polishing slurry for improving the storage and application stability of high-viscosity polishing solutions as described in claim 3, characterized in that, The cellulose-based substances include at least one of hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, phenyl cellulose, methyl hydroxypropyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl ethyl cellulose, hydroxypropyl hydroxybutyl cellulose, ethyl hydroxypropyl cellulose, hydroxyethyl benzyl cellulose, methyl benzyl cellulose, hydroxypropyl cyanoethyl cellulose, hydroxypropyl benzyl cellulose, hydroxyethyl phenyl cellulose, and cyanoethyl benzyl cellulose.

5. The polishing slurry for improving the storage and application stability of high-viscosity polishing solutions as described in claim 3, characterized in that, The polyacrylic acid substances include at least one of polyacrylic acid, sodium polyacrylate, polyacrylate, polymethyl methacrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, acrylic acid-acrylamide copolymer, acrylic acid-maleic anhydride copolymer, acrylic acid-styrene copolymer, acrylic acid-vinylpyrrolidone copolymer, acrylic acid-vinyl acetate copolymer, quaternized polyacrylic acid, sulfonated polyacrylic acid, silicone-modified polyacrylic acid, and fluorinated polyacrylic acid.

6. The polishing fluid for improving the storage and application stability of high-viscosity polishing fluid as described in claim 1, characterized in that, The surfactant includes any one of anionic, cationic, and nonionic surfactants; the nonionic surfactant includes at least one of polyethylene glycol, polypropylene glycol, polybutylene glycol, block copolymers of ethylene oxide and propylene oxide, PEO-PPO-PEO triblock copolymers, PPO-PEO-PPO triblock copolymers, PPO-PEO-PPO random copolymers, PPO-PEO-PPO cross copolymers, polyoxyethylene monolaurate, polyoxyethylene dioleate, polyoxyethylene sorbitan tetraoleate, and polyoxyethylene castor oil.

7. The polishing fluid for improving the storage and application stability of high-viscosity polishing fluid as described in claim 1, characterized in that, The pH adjuster is at least one of quaternary ammonium compounds, ammonia, and amine compounds; the quaternary ammonium compounds include at least one of tetraalkylammonium salts, hydroxyalkyltrialkylammonium salts, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the amine compounds include at least one of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, diethanolamine, and triethanolamine.

8. The polishing fluid for improving the storage and application stability of high-viscosity polishing fluid as described in claim 1, characterized in that, The defoamer is a polyoxysilane defoamer, and the polyoxysilane defoamer includes at least one of BYK028, DF689, and AF9000 NE.

9. The method for preparing the polishing slurry for improving the storage and application stability of high-viscosity polishing fluid as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Weigh out the water-soluble polymer and surfactant, add them to deionized water, and stir until completely dissolved to obtain mother liquor L1; Step 2: Weigh the polishing abrasive, add some pH adjuster, and stir until evenly dispersed to obtain mother liquor L2. Step 3: Add the above mother liquor L1 to mother liquor L2, stir for more than 10 hours, and finally add defoamer and stir evenly to obtain mixed solution L3. Step 4: Add the remaining pH adjuster to the above mixed solution L3, stir well, and filter to obtain the final product.

10. The application of the polishing slurry according to any one of claims 1 to 8 for improving the storage and application stability of high-viscosity polishing slurry in silicon wafer polishing.

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