Preparation method of non-spherical high-purity silica sol, product and application thereof

Abstract

The present application relates to the technical field of silica sol preparation, and particularly relates to a preparation method of non-spherical high-purity silica sol, and a product and application thereof. The preparation method comprises the following steps: obtaining an active silicic acid component by subjecting a high-purity sodium silicate solution to cation exchange resin; mixing an alkaline catalyst and the active silicic acid component in different feeding sequences, and obtaining non-spherical seeds by aging; heating the seed mother liquor to boiling, adding the active silicic acid component dropwise and controlling pH, and cooling after constant liquid level growth; and obtaining non-spherical high-purity silica sol by ultrafiltration concentration. By controlling the feeding sequence and key process parameters, the present application can prepare a silica sol product with controllable morphology (linear, spherical or potato-shaped), uniform particle size and high purity. When the obtained product is used as a CMP abrasive, the polishing removal rate is increased by more than 25% compared with spherical silica sol, the product is suitable for industrial production, and can be widely applied to the field of semiconductor polishing.

Description

Technical Field

[0001] This invention relates to the field of silica sol preparation technology, and in particular to a method for preparing non-spherical high-purity silica sol, its products, and applications. Background Technology

[0002] In recent years, with the rapid development of semiconductor technology and the continuous shrinking of feature sizes, the requirements for wafer surface processing precision have become increasingly stringent. Substrate material processing must not only achieve high processing efficiency but also high surface quality. Chemical mechanical polishing (CMP) is currently the only high-precision polishing technology that can achieve both local and global planarization of the wafer surface.

[0003] Silica is the most widely used abrasive particle in the CMP polishing slurry market. While monodisperse silica particles can exhibit a relatively perfect surface quality when used as abrasives, spherical silica particles tend to roll easily and have a small contact area, resulting in low polishing efficiency and long polishing time. Non-spherical particles, with their unique shape, large specific surface area, and softer texture, can achieve a perfect combination of rapid polishing and high surface quality, making them a promising candidate for semiconductor CMP polishing.

[0004] Current research on the preparation of non-spherical silica sol mainly focuses on the following aspects: First, the "cation-induced method" is used, which selects suitable divalent or trivalent metal cations as morphology control agents to prepare non-spherical silica sol. The introduction of divalent or trivalent metal ions reduces the purity and stability of colloidal SiO2, making it difficult to form colloidal silica particles larger than 50 nm, thus limiting its application in high-end polishing processes such as integrated circuits (e.g., CN103896287B, CN101626979A, US005221497A). Second, by controlling the feeding ratio, material concentration, pH of the reaction solution, and reaction temperature during the reaction process, silica sol with a non-spherical structure can be directly prepared. Although this method has fewer side reactions, a shorter growth cycle, and a simpler process, without the need for additives, inorganic salts, or surface modification, the reaction needs to be carried out in an alcohol system, which leads to increased costs in the later stages and is not conducive to industrial-scale production. Thirdly, the isotropic growth of particles is achieved by adjusting the pH value with organic bases during the preparation process. Patent CN110655087A prepares active silica by water glass ion exchange, using inorganic bases as catalysts and organic bases as morphology control agents to prepare shaped silica sols. Although water glass can treat most metal ions through ion exchange, its removal of metal ions is still limited, resulting in a large number of metal ions, such as Al, Fe, and Na, still remaining in the silica sol. This is not conducive to its application in semiconductor polishing. Ultra-high purity silicon shaped silica sols can be prepared by hydrolyzing or using a Stober-like method with organic bases as morphology control agents, which can avoid the defect of high metal ion content. However, organic bases are not environmentally friendly and are not conducive to large-scale industrial production. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention prepares non-spherical seed crystals by different feeding sequences, and then controls the morphology of the subsequent non-spherical seed crystal regrowth process, which can easily prepare non-spherical silica sol. The resulting non-spherical silica sol particles have good batch stability and low metal ion content, and can be used in the field of semiconductor polishing.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] The first aspect of this invention provides a method for preparing non-spherical high-purity silica sol, comprising the following steps:

[0008] (1) Pass a high-purity sodium silicate solution through a cation exchange resin to obtain an active silicic acid component;

[0009] (2) Under stirring conditions, the alkaline catalyst and the active silica component obtained in step (1) are mixed in different order of addition, and then aged to obtain silica sol seed crystals.

[0010] (3) Heat the silica sol seed crystals obtained in step (2) to boiling as the mother liquor, add the active silicic acid component obtained in step (1) dropwise to the system, and at the same time maintain the pH value of the system in the alkaline range with an alkaline catalyst. After the reaction is completed, cool to obtain a dilute silica sol solution.

[0011] (4) The silica sol dilute solution obtained in step (3) is concentrated by ultrafiltration to obtain a non-spherical high-purity silica sol product.

[0012] In some embodiments of the present invention, in step (1), the content of silicon dioxide in the high-purity sodium silicate solution is 2wt%~5wt%.

[0013] In some embodiments of the present invention, in step (1), the high-purity sodium silicate solution is purified by membrane filtration before use.

[0014] In some embodiments of the present invention, in step (1), the cation exchange resin is selected from strong acid type cation exchange resins.

[0015] In some embodiments of the present invention, in step (1), the pH of the active silicic acid component is 2 to 4.

[0016] In some embodiments of the present invention, in step (2), the mixing method of the alkaline catalyst and the active silicic acid component is selected from any of the following: adding the active silicic acid component dropwise to the alkaline catalyst, adding the alkaline catalyst dropwise to the active silicic acid component, or adding the active silicic acid component and the alkaline catalyst dropwise to the reaction vessel at the same time.

[0017] In some embodiments of the present invention, in step (2), the temperature of the system is controlled to be 50~80°C during the mixing process.

[0018] In some embodiments of the present invention, in step (2), the pH of the mixed system is 7.5 to 8.5.

[0019] In some embodiments of the present invention, in step (2), the ripening temperature is 80~100°C.

[0020] In some embodiments of the present invention, in step (2), the ripening time is 0.5 to 2 hours.

[0021] In some embodiments of the present invention, in step (2), the alkaline catalyst is selected from any one or a combination of at least two of alkaline hydroxides, ammonia, and organic amine compounds; preferably, the organic amine compounds are selected from any one or a combination of at least two of tetramethylammonium hydroxide, tetrabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, isopropylamine, ethylenediamine, diethylenetriamine, and triethylenetetramine.

[0022] In some embodiments of the present invention, in step (2), the pH value of the mixture is controlled by adjusting the dropping ratio or dropping rate of the alkaline catalyst and the active silicic acid component.

[0023] In some embodiments of the present invention, in step (2), the alkaline catalyst and the active silicic acid component are added at a time of 1 to 60 min.

[0024] In some embodiments of the present invention, in step (3), the content of silicon dioxide in the silica sol seed mother liquor is 2wt%~10wt%.

[0025] In some embodiments of the present invention, in step (3), the mass ratio of the active silicic acid component to the silica sol seed mother liquor is 1:0.1~1.

[0026] In some embodiments of the present invention, in step (3), when the liquid level in the reaction vessel reaches 1 / 2 to 3 / 4 of its effective volume, the liquid level of the system is kept constant until the addition is completed.

[0027] In some embodiments of the present invention, in step (3), the dropping rate of the active silicic acid component is such that the ratio of the active silicic acid component added per hour to the initial mass of the mother liquor is 1:1 to 10.

[0028] In some embodiments of the present invention, in step (3), the concentration of the alkaline catalyst is 0.1wt% to 10wt%.

[0029] In some embodiments of the present invention, in step (3), the pH of the system is maintained between 9 and 10 during the dropwise addition process.

[0030] In some embodiments of the present invention, in step (4), the solid content of the non-spherical high-purity silica sol product obtained by ultrafiltration concentration is 40wt%~50wt%.

[0031] A second aspect of the present invention provides a non-spherical high-purity silica sol, which is prepared by the above-described method for preparing non-spherical high-purity silica sol.

[0032] In some embodiments of the present invention, the content of a single metal ion impurity in the silica sol is less than 2 ppm; preferably, the metal ion includes any one of Al, Fe, Ca, Mg, Cu, Cr, Ni, Zn, and Pb.

[0033] In some embodiments of the present invention, the average particle size of the silica sol is 40-120 nm, and its particle morphology is linear, spherical, or potato-shaped.

[0034] A third aspect of the present invention provides the application of the above-mentioned non-spherical high-purity silica sol in chemical mechanical polishing.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. The method for preparing non-spherical high-purity silica sol provided by this invention achieves precise control over the aggregation behavior and final particle morphology of the colloidal particles by accurately controlling the order of addition of the alkaline catalyst and active silicic acid components during the seed preparation stage, combined with the control of the polymerization temperature of the system. By simply changing the order of addition, silica sol seed crystals with different non-spherical morphologies such as linear, quasi-spherical, and potato-shaped can be obtained. The method is simple and has good morphology repeatability.

[0037] 2. The non-spherical high-purity silica sol provided by this invention, in the seed crystal growth stage, by controlling the synthesis temperature (boiling), maintaining a stable pH value and matching the optimal silica drop rate, successfully prepared a non-spherical silica sol with an average particle size of 40~120 nm and uniform particle size distribution (low PDI value), which can significantly improve the material removal rate while ensuring surface quality when used as a CMP abrasive.

[0038] 3. This invention uses high-purity active silica treated with ion exchange resin as raw material throughout the entire process, avoiding the introduction of metal cation inducers and ensuring the high purity of the product from the source. Testing shows that the silica sol prepared using this method has a single metal ion impurity content (excluding Na and K, such as Al, Fe, Ca, Mg, Cu, Cr, Ni, Zn, Pb, etc.) of less than 2 ppm, fully meeting the stringent requirements for metal impurities in polishing slurries in semiconductor manufacturing fields such as integrated circuits.

[0039] 4. The preparation method of the present invention has mild process conditions and is simple to operate. It does not require an alcohol system or the addition of organic bases as morphology control agents, resulting in lower production costs. In particular, when the process is scaled up (as shown in Examples 4 and 5), the particle size and morphology of the product show minimal scaling-up effects. It can be directly applied to existing ion exchange method equipment for preparing silica sol to achieve large-scale industrial production, demonstrating promising industrial application prospects. Attached Figure Description

[0040] Figure 1 This is a schematic diagram illustrating the effect of the order of adding active silicic acid and alkaline catalyst on the morphology of silica sol in this invention.

[0041] Figure 2 The image shows an electron microscope image of the non-spherical silica sol prepared in Example 1.

[0042] Figure 3 The image shows an electron microscope image of the non-spherical silica sol prepared in Example 2.

[0043] Figure 4 The image shows an electron microscope image of the non-spherical silica sol prepared in Example 3.

[0044] Figure 5 The image shows an electron microscope image of the non-spherical silica sol prepared in Example 4.

[0045] Figure 6 The image shows an electron microscope image of the non-spherical silica sol prepared in Example 5.

[0046] Figure 7 The image shown is an electron microscope image of the spherical silica sol prepared for Comparative Example 1.

[0047] Figure 8 The image shown is an electron microscope image of the spherical silica sol prepared for Comparative Example 2.

[0048] Figure 9 The image shown is an electron microscope image of the spherical silica sol prepared for Comparative Example 3. Detailed Implementation

[0049] The following details the non-spherical high-purity silica sol of the present invention, its preparation method, and its applications.

[0050] The term "linear" in this invention refers to particles that appear elongated under a scanning electron microscope, consisting of multiple primary particles linearly connected, with an aspect ratio greater than 3:1; "quasi-spherical" refers to particles that are approximately spherical, but with a smooth or slightly uneven surface, and an aspect ratio of 1.0 to 1.2; and "potato-shaped" refers to particles that are irregularly ellipsoidal or pebble-shaped, with a rough surface, and an aspect ratio of 1.2 to 2.5.

[0051] The inventors of this invention achieved precise control over the aggregation behavior of colloidal particles by controlling the feeding sequence of the alkaline catalyst and the active silicic acid component, combined with a specific system polymerization temperature and pH range. This resulted in the formation of non-spherical silica sol seed crystals with linear, quasi-spherical, or potato-shaped morphologies. Furthermore, by controlling the synthesis temperature, pH, and silicic acid dropping rate during the seed crystal growth process, high-purity non-spherical silica sol with uniform particle size was prepared. When the resulting silica sol is used as a CMP abrasive, it significantly improves the material removal rate while maintaining low surface roughness. Based on this, the invention was completed.

[0052] The first aspect of this invention provides a method for preparing non-spherical high-purity silica sol, comprising the following steps:

[0053] (1) Pass a high-purity sodium silicate solution through a cation exchange resin to obtain an active silicic acid component;

[0054] (2) Under stirring conditions, the alkaline catalyst and the active silica component obtained in step (1) are mixed in different order of addition, and then aged to obtain silica sol seed crystals.

[0055] (3) Heat the silica sol seed crystals obtained in step (2) to boiling as the mother liquor, add the active silicic acid component obtained in step (1) dropwise to the system, and at the same time maintain the pH value of the system in the alkaline range with an alkaline catalyst. After the reaction is completed, cool to obtain a dilute silica sol solution.

[0056] (4) The silica sol dilute solution obtained in step (3) is concentrated by ultrafiltration to obtain a non-spherical high-purity silica sol product.

[0057] In some embodiments of the present invention, in step (1), the silica content in the high-purity sodium silicate solution is 2wt%~5wt%, which can be 2wt%~2.5wt%, 2.5wt%~3wt%, 3wt%~3.5wt%, 3.5wt%~4wt%, 4wt%~4.5wt%, or 4.5wt%~5wt%. By controlling the concentration of the sodium silicate solution, the ion exchange efficiency and the stability of the subsequent active silicic acid components can be ensured.

[0058] In some embodiments of the present invention, in step (1), the high-purity sodium silicate solution is purified by membrane filtration before use to further remove any possible particulate impurities, colloidal impurities, and some high-valence metal ions, thereby improving the purity of the final product. The membrane filtration preferably uses a microfiltration membrane or an ultrafiltration membrane, more preferably an ultrafiltration membrane with a molecular weight cutoff of 10,000~100,000 Da, or a microfiltration membrane with a pore size of 0.05~0.5 μm. The preferred operating conditions for the membrane filtration are: operating pressure 0.1~0.5 MPa, temperature 20~40℃, and the filtration method can be dead-end filtration or cross-flow filtration.

[0059] In some embodiments of the present invention, in step (1), the cation exchange resin is selected from strong acid type cation exchange resins. Preferably, the strong acid type cation exchange resin is a sulfonic acid type cation exchange resin, for example, selected from any one of the 001×7 type, 732 type, D001 type, DIAIONSK series, DIAIONPK series, Dowex-50 series, or Amberlite IR-120 series. The activation treatment can be performed using conventional methods in the art, for example: regenerating the sodium type cation exchange resin with acid and then washing it with water until neutral to obtain the hydrogen type cation exchange resin. In one specific embodiment of the present invention, sodium-type cation exchange resin is packed into a resin column, and 4%~6% sulfuric acid is used as an acid solution to regenerate the sodium-type cation exchange resin. The amount of acid solution used is 2~3 times the volume of sodium-type cation exchange resin, and the flow rate of the acid solution is 1.5~2 BV / H. The acid solution is introduced into the resin column countercurrently to regenerate the resin. After the acid injection is completed, the residual acid solution in the resin column is drained, and then 3~4 times the volume of pure water is used for forward rinsing until the pH of the effluent is 5~7, thus obtaining hydrogen-type cation exchange resin.

[0060] In some embodiments of the present invention, in step (1), the pH of the active silicic acid component is 2~4, which can be 2~2.5, 2.5~3, 3~3.5, or 3.5~4.

[0061] In some embodiments of the present invention, in step (2), the mixing method of the alkaline catalyst and the active silicic acid component is selected from any of the following: adding the active silicic acid component dropwise to the alkaline catalyst, adding the alkaline catalyst dropwise to the active silicic acid component, or adding the active silicic acid component and the alkaline catalyst simultaneously to the reaction vessel. The present invention controls the number, size, and aggregation behavior of colloidal particles during the seed crystal formation process by controlling the order of addition of the alkaline catalyst and the active silicic acid component, thereby achieving control over the morphology of the silica sol. Figure 1 As shown, the specific details are as follows: (1) When active silica components are added first and then alkaline catalysts are added dropwise, the system transitions from acidic to weakly alkaline. The primary particles formed are relatively small in size and numerous in number. The average distance between particles is small and the collision frequency is high, making it easy to bond and form linear seed crystals. After growth, linear silica sol is obtained. (2) When alkaline catalysts are added first and then active silica components are added dropwise, the system is always in an alkaline environment. The primary particles formed are relatively large in size and few in number. The average distance between particles is large and the collision frequency is low, which can form seed crystals that tend to be spherical. After growth, spherical silica sol is obtained. (3) When active silica components and alkaline catalysts are added dropwise at the same time, the system is maintained in a weakly alkaline environment. The size and number of primary particles formed are moderate. The collision probability between particles is moderate. Some particles bond and form potato-shaped seed crystals. After growth, silica sol with the corresponding morphology is obtained. The reaction temperature (50~80℃) and subsequent ripening steps (80~100℃) involved in the above seed preparation process help accelerate particle collisions, promote morphology fixation, and ensure the morphological stability of the final product.

[0062] In some embodiments of the present invention, in step (2), the temperature of the system during the mixing process is controlled to be 50~80℃, which can be 50~55℃, 55~60℃, 60~65℃, 65~70℃, 70~75℃, or 75~80℃.

[0063] In some embodiments of the present invention, in step (2), the pH of the mixed system is 7.5~8.5, which can be 7.5~8.0 or 8.0~8.5.

[0064] In some embodiments of the present invention, in step (2), the ripening temperature is 80~100℃, or it can be 80~85℃, 85~90℃, 90~95℃, or 95~100℃.

[0065] In some embodiments of the present invention, in step (2), the ripening time is 0.5~2h, which can be 0.5~1h, 1~1.5h, or 1.5~2h.

[0066] In some embodiments of the present invention, in step (2), the alkaline catalyst is selected from any one or a combination of at least two of alkaline hydroxides, ammonia, and organic amine compounds; preferably, the organic amine compound is selected from any one or a combination of at least two of tetramethylammonium hydroxide, tetrabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, isopropylamine, ethylenediamine, diethylenetriamine, and triethylenetetramine. Preferably, the concentration of the alkaline catalyst is 0.1wt% to 10wt%, and can be 0.1wt% to 1wt%, 1wt% to 2wt%, 2wt% to 3wt%, 3wt% to 4wt%, 4wt% to 5wt%, 5wt% to 6wt%, 6wt% to 7wt%, 7wt% to 8wt%, 8wt% to 9wt%, or 9wt% to 10wt%.

[0067] In some embodiments of the present invention, in step (2), the pH value of the mixture is controlled by adjusting the dropping ratio or dropping rate of the alkaline catalyst and the active silicic acid component. Specifically, during the mixing process, an online pH meter is used to monitor the pH value of the mixture in real time. When the pH value deviates from the target range (e.g., 7.5~8.5), it is dynamically corrected by adjusting the dropping rate ratio of the alkaline catalyst and the active silicic acid component. For example, if the pH value is too low, the dropping rate of the alkaline catalyst is appropriately increased or the dropping rate of the active silicic acid component is decreased; if the pH value is too high, the opposite is true. The dropping rate ratio of the alkaline catalyst and the active silicic acid component can be adjusted according to the system scale and the required seed crystal characteristics. Preferably, the dropping rate of the alkaline catalyst is 0.5~10 g / min, the dropping rate of the active silicic acid component is 5~50 g / min, and the dropping rate ratio (alkaline catalyst: active silicic acid) is controlled between 1:5 and 1:50. By using the pH control method described above, a stable weakly alkaline environment (pH 7.5~8.5) can be maintained during the seed crystal formation stage, avoiding unintended nucleation or particle agglomeration caused by local over-acidity or over-alkaliness. This ensures the uniformity and controllability of the seed crystal morphology, laying the foundation for obtaining silica sol products with narrow particle size distribution and regular morphology in subsequent growth.

[0068] In step (2) of this invention, the dropping time of the alkaline catalyst and the active silicic acid component can be adjusted according to the system scale and the required seed characteristics, preferably controlled within the range of 1~60 min, specifically 1~2 min, 2~5 min, 5~10 min, 10~20 min, 20~30 min, 30~40 min, 40~50 min, or 50~60 min. By controlling the dropping time, the formation rate and collision frequency of primary particles can be regulated, thereby affecting the particle size and morphology of the seed. Too short a dropping time (<1 min) may lead to excessively high local concentrations and the formation of too many crystal nuclei; too long a dropping time (>60 min) will affect production efficiency and may cause overgrowth of the already formed seed.

[0069] In some embodiments of the present invention, in step (2), the ripening time is 0.5~2h, which can be 0.5~1h, 1~1.5h, or 1.5~2h, preferably 0.5h. The purpose of ripening is to keep the crystal seed morphology stable by maintaining it at a constant temperature for a period of time.

[0070] In some embodiments of the present invention, in step (3), the silica content in the silica sol seed mother liquor is 2wt%~10wt%, which can be 2wt%~3wt%, 3wt%~4wt%, 4wt%~5wt%, 5wt%~6wt%, 6wt%~7wt%, 7wt%~8wt%, 8wt%~9wt%, or 9wt%~10wt%. Controlling the concentration of the mother liquor helps to stabilize the growth process and avoids excessive concentration leading to particle agglomeration or the formation of new nuclei.

[0071] In some embodiments of the present invention, in step (3), the mass ratio of the active silicic acid component to the silica sol seed mother liquor is 1:0.1~1, which can be 1:0.1~0.2, 1:0.2~0.3, 1:0.3~0.4, 1:0.4~0.5, 1:0.5~0.6, 1:0.6~0.7, 1:0.7~0.8, 1:0.8~0.9, or 1:0.9~1. The above ratio range ensures sufficient growth space for the seed crystals while avoiding excessive silicic acid leading to self-nucleation.

[0072] In some embodiments of the present invention, in step (3), when the liquid level in the reaction vessel reaches 1 / 2 to 3 / 4 of its effective volume, the system liquid level is kept constant until the dropping is completed. In some preferred embodiments of the present invention, when the liquid level in the reaction vessel reaches 2 / 3 of its effective volume, the system liquid level is kept constant until the dropping is completed. "Keeping the system liquid level constant" means controlling the dropping rate to match the evaporation rate, so that the liquid level in the reaction vessel remains essentially unchanged during the reaction process, ensuring the stability of the growth environment.

[0073] In some embodiments of the present invention, in step (3), the dropping rate of the active silicic acid component is such that the ratio of the active silicic acid component added per hour to the initial mass of the mother liquor is 1:1~10, which can be 1:1~2, 1:2~3, 1:3~4, 1:4~5, 1:5~6, 1:6~7, 1:7~8, 1:8~9, or 1:9~10. By controlling the dropping rate, the stability of the growth system can be maintained, and a silica sol product with uniform particle size can be obtained.

[0074] In some embodiments of the present invention, in step (3), the alkaline catalyst may be the same as or different from the alkaline catalyst used in step (2), and its concentration is preferably 0.1wt% to 10wt%.

[0075] In some embodiments of the present invention, in step (3), the pH of the system is maintained between 9 and 10 during the dropwise addition process, which can be 9 to 9.5 or 9.5 to 10.

[0076] In some embodiments of the present invention, in step (4), the solid content of the non-spherical high-purity silica sol product obtained by ultrafiltration concentration is 40wt%~50wt%, which can be 40wt%~42wt%, 42wt%~44wt%, 44wt%~46wt%, 46wt%~48wt%, or 48wt%~50wt%. The non-spherical high-purity silica sol products with the above solid content range are convenient for storage and transportation, and also meet the actual needs of CMP polishing fluid preparation.

[0077] A second aspect of the present invention provides a non-spherical high-purity silica sol, which is prepared by the above-described method for preparing non-spherical high-purity silica sol.

[0078] In some embodiments of the present invention, the content of a single metal ion impurity in the silica sol is less than 2 ppm; preferably, the metal ion includes any one of Al, Fe, Ca, Mg, Cu, Cr, Ni, Zn, and Pb. ICP-MS analysis (as shown in Examples 1-5) shows that the content of the above-mentioned metal ions in the silica sol products of the present invention is far below the requirements for semiconductor polishing.

[0079] In some embodiments of the present invention, the average particle size of the silica sol is 40-120 nm, and its particle morphology is linear, quasi-spherical, or potato-shaped. The term "non-spherical" as used in this invention includes, but is not limited to, linear, quasi-spherical, dumbbell (peanut-shaped), and potato-shaped particles, encompassing all morphologies distinct from perfect spheres. Characterization was performed using a Malvern particle size analyzer and scanning electron microscopy (e.g., Figures 2-6 As shown in the figure, the product of the present invention has a uniform particle size distribution (PDI value < 0.25) and obvious morphological characteristics.

[0080] A third aspect of the present invention provides the application of the above-mentioned non-spherical high-purity silica sol in chemical mechanical polishing.

[0081] Furthermore, the applications include, but are not limited to, polishing of semiconductor substrate materials such as silicon wafers and silicon carbide wafers. When the silica sol of the present invention is formulated into a polishing slurry, under the same polishing conditions, its material removal rate is significantly higher than that of traditional spherical silica sols (as shown in Comparative Examples 1-3), while maintaining excellent surface quality (surface roughness <0.5 nm).

[0082] The following detailed description of specific embodiments of the present invention, in conjunction with preferred embodiments, further illustrates the relevant details. When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range, as well as any value between the two endpoints, may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by those skilled in the art. In addition to the specific methods, devices, and materials used in the embodiments, the present invention can be implemented using any prior art methods, devices, and materials similar to or equivalent to those described in the embodiments of the present invention, provided that those skilled in the art possess the prior art and the description of the present invention.

[0083] Example 1

[0084] (1) Preparation of active silicic acid components

[0085] High-purity concentrated sodium silicate purified by membrane was diluted with pure water to a silica content of 4.6 wt%. The diluted high-purity sodium silicate solution was then passed through a hydrogen-form cation exchange resin to obtain an active silicic acid component with a concentration of 4.5 wt% and a pH of 3.5.

[0086] (2) Seed preparation

[0087] Add 500g of active silica component to a 1L three-necked flask, stir and heat the reaction vessel to 55℃. Add 4.5g of 10wt% ammonia solution dropwise to the three-necked flask over 10min. Adjust the pH to 8.2 and stop adding the ammonia solution. Let it mature at 90℃ for 0.5h to obtain silica sol seed crystals with a concentration of 4.7wt%.

[0088] (3) Preparation of silica sol

[0089] Weigh 150g of the silica sol seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to boiling and keep it at a constant temperature for 5 minutes. Then, add the active silica component to the system at a dropping rate of 1.5g / min (90g / h). Use 10wt% ammonia water to maintain the pH of the system between 9 and 10. After adding for 5 hours (when the liquid level in the vessel is close to 2 / 3), maintain a constant liquid level and continue adding for a total of 12 hours. Then, stop adding and cool to obtain 70nm silica sol.

[0090] (4) Ultrafiltration concentration and testing

[0091] The above-mentioned 70 nm silica sol was concentrated by ultrafiltration to obtain a silica sol product with a solid content of 40 wt%.

[0092] The average particle size of the silica sol was measured to be 70.34 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) was 0.249. The morphology of the silica sol was observed using a scanning electron microscope, and the morphology is as follows. Figure 2 As shown, by Figure 2 It can be seen that the silica sol particles exhibit a linear morphology, with multiple primary particles sequentially connected along an approximately straight line to form a linear structure whose length is much greater than its width. Statistical measurements of at least 100 particles in the electron micrographs showed that the aspect ratio (ratio of the longest axis to the shortest axis) of the linear particles ranged from 3.0 to 8.0, with an average aspect ratio of approximately 4.5 to 5.5. The width (short axis) of the particles was relatively uniform, ranging from 30 to 60 nm, while the length (long axis) varied between 120 and 400 nm depending on the number of connected particles. The metal ion content of the silica sol product, as determined by ICP-MS, is shown in Table 1.

[0093] Table 1. Metal ion content of silica sol product in Example 1

[0094]

[0095] Note: "-" indicates that the item was not detected, and the same applies below.

[0096] Example 2

[0097] (1) Preparation of active silicic acid components

[0098] High-purity concentrated sodium silicate purified by membrane was diluted with pure water to a silica content of 4.0 wt%. The diluted high-purity sodium silicate solution was then passed through a hydrogen-form cation exchange resin to obtain an active silicic acid component with a concentration of 4.0 wt% and a pH of 2.8.

[0099] (2) Seed preparation

[0100] Add 150g of 0.3wt% NaOH solution to a 1L three-necked flask, stir and heat the temperature inside the reactor to 60℃. Add the active silica component prepared in step (1) dropwise to the flask. The dropwise addition time is 15min and the cumulative dropwise addition amount is 610g. After the dropwise addition is completed, test the pH value of the mixture to be 8.0. Raise the temperature of the material in the flask to 85℃ and mature the material in the reactor at 85℃ for 0.5h to prepare silica sol seed crystals with a concentration of 3.2wt%.

[0101] (3) Preparation of silica sol

[0102] Weigh 225g of the silica sol seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to boiling and keep it at 5min until the temperature stabilizes. Then, add the active silicic acid component to the system at a dropping rate of 2.0g / min (120g / h). Use 5wt% NaOH to maintain the pH of the system between 9 and 10. After adding for 2 hours (when the liquid level in the vessel is close to 2 / 3), maintain a constant liquid level and continue adding for a total of 7 hours. Then, stop adding and cool to obtain 60nm silica sol.

[0103] (4) Ultrafiltration concentration and testing

[0104] The above-mentioned 60nm silica sol was concentrated by ultrafiltration to obtain a silica sol product with a solid content of 40wt%.

[0105] The average particle size of the silica sol was measured to be 61.56 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) was 0.107. The morphology of the silica sol was observed using a scanning electron microscope, and the morphology is as follows. Figure 3 As shown, by Figure 3 It can be seen that the silica sol particles exhibit a near-spherical morphology. While generally approximating a sphere, these particles are not perfect spheres; their surfaces are relatively smooth, and some particles show a slight ellipsoidal shape. Statistical measurements of at least 100 particles in the electron micrographs revealed that the aspect ratio (ratio of the longest axis to the shortest axis) of the near-spherical particles ranged from 1.0 to 1.2, with an average aspect ratio of approximately 1.05 to 1.10. The particle size distribution was uniform, ranging from 50 to 70 nm, and the PDI value was low (0.107). The metal ion content of the silica sol product, as determined by ICP-MS, is shown in Table 2.

[0106] Table 2 Metal ion content of silica sol product in Example 2

[0107]

[0108] Example 3

[0109] (1) Preparation of active silicic acid components

[0110] High-purity concentrated sodium silicate purified by membrane was diluted with pure water to a silica content of 4.5 wt%. The diluted high-purity sodium silicate solution was then passed through a hydrogen-form cation exchange resin to obtain an active silicic acid component with a concentration of 4.4 wt% and a pH of 2.7.

[0111] (2) Seed preparation

[0112] Add 50g of pure water to a 1L three-necked flask, turn on the stirring and heating devices, and raise the temperature of the bottom liquid to 75℃. Simultaneously add the active silicic acid component prepared in step (1) and 1wt% NaOH solution to the flask. Maintain the pH at 8.0~8.5 during the addition process. The amount of silicic acid added is 600g, and the addition time is 40min. After the addition is completed, raise the temperature of the material in the flask to 90℃. The material in the vessel is aged at 90℃ for 0.5h to obtain silica sol seed crystals with a concentration of 3.4wt%.

[0113] (3) Preparation of silica sol

[0114] Weigh 300g of the silica sol seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to boiling and keep it at a constant temperature for 5 minutes. Then, add the active silicic acid component to the system at a dropping rate of 2.5g / min (150g / h). Use 5wt% NaOH to maintain the pH of the system between 9 and 10. After adding the solution for 2 hours (when the liquid level in the vessel is close to 2 / 3), maintain a constant liquid level and continue adding the solution for a total of 18 hours. Then, stop adding the solution and cool it to obtain 100nm silica sol.

[0115] (4) Ultrafiltration concentration and testing

[0116] The above-mentioned 100nm silica sol was concentrated by ultrafiltration to obtain a silica sol product with a solid content of 50wt%.

[0117] The average particle size of the silica sol was measured to be 101.06 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) was 0.107. The morphology of the silica sol was observed using a scanning electron microscope, and the morphology is as follows. Figure 4 As shown, by Figure 4 It can be seen that the silica sol particles have a potato-like morphology, with irregular ellipsoidal or pebble-like shapes and a relatively rough, uneven surface. Their overall outline approximates the shape of a potato or peanut. Statistical measurements of at least 100 particles in the electron microscope images showed that the aspect ratio (ratio of the longest axis to the shortest axis) of the potato-shaped particles ranged from 1.2 to 2.5, with an average aspect ratio of approximately 1.6 to 1.9. The particle size (equivalent diameter of a round circle) ranged from 90 to 110 nm, exhibiting a uniform particle size distribution. The metal ion content of the silica sol product, as determined by ICP-MS, is shown in Table 3.

[0118] Table 3 Metal ion content of silica sol product in Example 3

[0119]

[0120] Example 4

[0121] (1) Preparation of active silicic acid components

[0122] High-purity concentrated sodium silicate purified by membrane was diluted with pure water to a silica content of 3.5 wt%. The diluted high-purity sodium silicate solution was then passed through a hydrogen-form cation exchange resin to obtain an active silicic acid component with a concentration of 3.4 wt% and a pH of 2.9.

[0123] (2) Seed preparation

[0124] Add 80L of active silica component to a 100L reactor, stir and heat the reactor to 70℃. Add 10wt% ammonia solution dropwise to the 100L reactor at a rate of 785g over 15min. Adjust the pH to 8.3 and stop adding. Cure at 90℃ for 0.5h to obtain silica sol seed crystals with a concentration of 3.6wt%.

[0125] (3) Preparation of silica sol

[0126] Weigh 14.1 kg of the seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to boiling and keep it at a constant temperature for 5 min until the temperature stabilizes. Then, add the active silicic acid component to the system at a dropping rate of 120 g / min (7.2 kg / h). Use 10 wt% ammonia water to maintain the pH of the system between 9 and 10. After adding the solution for 10 hours, maintain the constant liquid level dropping method. After adding the solution for a total of 15 hours, stop the dropping and cool to obtain 70 nm silica sol.

[0127] (4) Ultrafiltration concentration and testing

[0128] The above-mentioned 70nm silica sol was concentrated by ultrafiltration to obtain a silica sol product with a solid content of 40wt%.

[0129] The average particle size of the silica sol was measured to be 71.69 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) was 0.223. The morphology of the silica sol was observed using a scanning electron microscope, and the morphology is as follows: Figure 5 As shown, by Figure 5 It can be seen that the silica sol particles have a linear morphology, similar to that of Example 1 ( Figure 2 The morphological characteristics shown are consistent with those of Example 4. Statistical measurements revealed that the aspect ratio of the scaled-up batch of products in Example 4 ranged from 3.0 to 7.8, with an average aspect ratio of 4.9; the particle width ranged from 32 to 55 nm, and the length ranged from 110 to 400 nm. All morphological parameters were basically consistent with those of Example 1, indicating that the preparation method of this invention can maintain good morphological controllability even at scale-up levels, with minimal process scale-up effect. The metal ion content of the silica sol products, as determined by ICP-MS, is shown in Table 4.

[0130] Table 4. Metal ion content of silica sol product in Example 4

[0131]

[0132] Example 5

[0133] (1) Preparation of active silicic acid components

[0134] High-purity concentrated sodium silicate purified by membrane was diluted with pure water to a silica content of 3.0 wt%. The diluted high-purity sodium silicate solution was then passed through a hydrogen-type cation exchange resin to obtain an active silicic acid component with a concentration of 2.9 wt% and a pH value of 2.81.

[0135] (2) Seed preparation

[0136] Add 5 kg of pure water to a 100 L three-necked flask, turn on the stirring and heating devices, and raise the temperature of the bottom liquid to 55 °C. Simultaneously add the active silicic acid component prepared in step (1) and a 10 wt% ammonia solution to the flask. Maintain the pH at 8.0~8.5 during the addition process. The amount of silicic acid added is 70 kg, and the addition time is 20 min. After the addition is completed, raise the temperature of the material in the flask to 95 °C. The material in the vessel is aged at 95 °C for 0.5 h to obtain silica sol seed crystals with a concentration of 2.3 wt%.

[0137] (3) Preparation of silica sol

[0138] Weigh 24 kg of the silica sol seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to boiling and keep it at a constant temperature for 5 min until the temperature stabilizes. Then, add the active silica component to the system at a dropping rate of 180 g / min (10.8 kg / h). Use 10 wt% KOH to maintain the pH of the system between 9 and 10. After adding the solution for 6 hours (when the liquid level in the vessel is close to 2 / 3), maintain a constant liquid level and continue adding the solution for a total of 15 hours. Then, stop adding the solution and cool it to obtain 80 nm silica sol.

[0139] (4) Ultrafiltration concentration and testing

[0140] The above-mentioned 80nm silica sol was concentrated by ultrafiltration to obtain a silica sol product with a solid content of 40wt%.

[0141] The average particle size of the silica sol was measured to be 80.16 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) was 0.119. The morphology of the silica sol was observed using a scanning electron microscope, and the morphology is as follows. Figure 6 As shown, by Figure 6 It can be seen that the silica sol particles have a potato-shaped morphology, similar to that of Example 3 ( Figure 4 The morphological characteristics shown are consistent. Statistical measurements of at least 100 particles in the electron microscope images revealed that the aspect ratio (ratio of the longest axis to the shortest axis) of the potato-shaped particles ranged from 1.2 to 2.5, with an average aspect ratio of approximately 1.6 to 1.9. The particle size (equivalent diameter of a round circle) ranged from 70 to 85 nm, exhibiting a uniform particle size distribution. The metal ion content of the silica sol product, determined by ICP-MS, is shown in Table 5.

[0142] Table 5. Metal ion content of silica sol product in Example 5

[0143]

[0144] Comparative Example 1

[0145] (1) Preparation of active silicic acid components

[0146] High-purity concentrated sodium silicate purified by membrane was diluted with pure water to a silica content of 3.5 wt%. The diluted high-purity sodium silicate solution was then passed through a hydrogen-type cation exchange resin to obtain an active silicic acid component with a concentration of 3.5 wt% and a pH of 2.9.

[0147] (2) Seed preparation

[0148] Add 150g of 0.35wt% NaOH solution to a 1L three-necked flask, turn on the stirrer and raise the temperature of the NaOH in the flask to 98℃. Then add the active silicic acid component prepared in step (1) dropwise to the flask. The dropwise addition time is 40min and the cumulative dropwise addition amount is 630g. After the dropwise addition is completed, the pH value of the mixed solution is 8.5. The material in the reactor is aged at 98℃ for 0.5h to obtain spherical seed crystals with a concentration of 3.0wt%.

[0149] (3) Preparation of silica sol

[0150] Weigh 220g of the seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to 100℃ and keep it for 5min until the temperature stabilizes. Then add the active silicic acid component to the system at a dropping rate of 2.0g / min (120g / h). Use 5wt% NaOH to maintain the pH of the system between 9 and 10. After adding for 2 hours (when the liquid level in the vessel is close to 2 / 3), maintain a constant liquid level and add for a total of 9 hours. Then stop adding and cool to obtain 70nm spherical silica sol.

[0151] (4) The above 70nm spherical silica sol was concentrated by ultrafiltration to obtain a spherical silica sol product with a solid content of 40wt%.

[0152] The average particle size of the silica sol was measured to be 72.34 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) was 0.083. The morphology of the silica sol was observed using a scanning electron microscope, and the morphology is as follows: Figure 7 As shown, by Figure 7 As can be seen, the silica sol particles are spherical. Statistical measurements of at least 100 particles in the electron microscope images showed that the aspect ratio of the spherical particles ranged from 1.0 to 1.05, with an average aspect ratio of approximately 1.02. The particle size ranged from 60 to 80 nm, and the surfaces were smooth without obvious linear or irregular features. The metal ion content of the silica sol product, as determined by ICP-MS, is shown in Table 6.

[0153] Table 6 Metal ion content of silica sol product in Comparative Example 1

[0154]

[0155] Comparative Example 2

[0156] (1) Preparation of active silicic acid components

[0157] High-purity concentrated sodium silicate purified by membrane was diluted with pure water to a silica content of 3.8 wt%. The diluted high-purity sodium silicate solution was then passed through a hydrogen-type cation exchange resin to obtain an active silicic acid component with a concentration of 3.7 wt% and a pH value of 2.95.

[0158] (2) Seed preparation

[0159] Add 240g of 0.35% NaOH solution to a 1L three-necked flask, turn on the stirrer, and raise the temperature of the NaOH in the flask to 100℃. Then, add the active silicic acid component prepared in step (1) dropwise to the flask. The dropwise addition time is 50min, and the cumulative dropwise addition amount is 600g. After the dropwise addition is completed, the pH value of the mixed solution is 10.5. The material in the reactor is aged at 100℃ for 0.5h to obtain spherical seed crystals with a concentration of 3.2wt%.

[0160] (3) Preparation of silica sol

[0161] Weigh 250g of the seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to 100℃ and keep it for 5min until the temperature stabilizes. Then, add the active silicic acid component to the system at a dropping rate of 2.5g / min (150g / h). Use 5wt% NaOH to maintain the pH of the system between 9 and 10. After adding the solution for 1.5 hours (when the liquid level in the vessel is close to 2 / 3), maintain a constant liquid level and continue adding the solution for a total of 10 hours. Then, stop adding the solution and cool it to obtain 80nm spherical silica sol.

[0162] (4) The above 80nm spherical silica sol was concentrated by ultrafiltration to obtain a spherical silica sol product with a solid content of 40wt%.

[0163] The average particle size of the silica sol was measured to be 81.33 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) was 0.013. The morphology of the silica sol was observed using a scanning electron microscope, and the morphology is as follows. Figure 8 As shown, by Figure 8 As can be seen, the silica sol particles are spherical. Statistical measurements show that the aspect ratio of the spherical particles ranges from 1.0 to 1.08, with an average aspect ratio of approximately 1.03. The particle size ranges from 70 to 90 nm, and there is no obvious aggregation or adhesion between the particles. The metal ion content of the silica sol product, as determined by ICP-MS, is shown in Table 7.

[0164] Table 7 Metal ion content of silica sol products in Comparative Example 2

[0165]

[0166] Comparative Example 3

[0167] (1) Preparation of active silicic acid components

[0168] High-purity concentrated sodium silicate purified by membrane was diluted with pure water to a silica content of 4.0 wt%. The diluted high-purity sodium silicate solution was then passed through a hydrogen-type cation exchange resin to obtain an active silicic acid component with a concentration of 3.9 wt% and a pH value of 3.41.

[0169] (2) Seed preparation

[0170] Add 500g of active silica component to a 1L three-necked flask, start stirring, control the material temperature in the reactor at 30℃, add 4.6g of 10wt% ammonia solution dropwise to the three-necked flask over a period of 10min, adjust the pH to 8.1 and stop adding, no aging is required, and seed crystals with a concentration of 3.7wt% are obtained.

[0171] (3) Preparation of silica sol

[0172] Weigh 191g of the seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to boiling and keep it at a constant temperature for 5 minutes. Then, add the active silicic acid component to the system at a dropping rate of 1.5g / min (90g / h). Use 10wt% ammonia water to maintain the pH of the system between 9 and 10. After adding the solution for 5 hours (when the liquid level in the vessel is close to 2 / 3), maintain a constant liquid level and continue adding the solution for a total of 16 hours. Then, stop adding the solution and cool it to obtain 60nm silica sol.

[0173] (4) The above 60nm silica sol was concentrated by ultrafiltration to obtain a silica sol product with a solid content of 40wt%.

[0174] The average particle size of the silica sol was measured to be 62.03 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) was 0.095. The morphology of the silica sol was observed using a scanning electron microscope, and the morphology is as follows. Figure 9 As shown, by Figure 9 As can be seen, the silica sol particles are spherical. Statistical measurements show that the aspect ratio of these spherical particles ranges from 1.0 to 1.06, with an average aspect ratio of approximately 1.02. The particle size ranges from 50 to 70 nm, exhibiting regular morphology and good monodispersity. The metal ion content of the silica sol product, as determined by ICP-MS, is shown in Table 8.

[0175] Table 8 Metal ion content of silica sol products in Comparative Example 3

[0176]

[0177] Comparative Example 4

[0178] (1) Preparation of active silicic acid components

[0179] Concentrated sodium silicate was diluted with pure water to a silica content of 4.5 wt%. The diluted sodium silicate solution was then passed through a hydrogen-form cation exchange resin to obtain an active silicic acid component with a concentration of 4.3 wt% and a pH of 3.2.

[0180] (2) Seed preparation

[0181] Add 523g of active silica component to a 1L three-necked flask, stir and heat the reaction vessel to 55℃. Add 4.8g of 10wt% ammonia solution dropwise to the three-necked flask over 8min. Adjust the pH to 8.0 and stop adding the ammonia solution. Let it mature at 95℃ for 0.5h to obtain silica sol seed crystals with a concentration of 4.1wt%.

[0182] (3) Preparation of silica sol

[0183] Weigh 160g of the silica sol seed crystals prepared in step (2) as the mother liquor. Heat the mother liquor to boiling and keep it at a constant temperature for 5 minutes. Then, add the active silica component to the system at a dropping rate of 2.0g / min (120g / h). Use 10wt% ammonia water to maintain the pH of the system between 9 and 10. After adding the solution for 4 hours (when the liquid level in the vessel is close to 2 / 3), maintain a constant liquid level and continue adding the solution for a total of 14 hours. Then, stop adding the solution and cool it to obtain 65nm silica sol.

[0184] (4) Ultrafiltration concentration and testing

[0185] The above-mentioned 65nm silica sol was concentrated by ultrafiltration to obtain a silica sol product with a solid content of 40wt%.

[0186] The average particle size of the silica sol was measured to be 65.95 nm using a Malvern particle size analyzer, and the polydispersity index (PDI) value was 0.213. The metal ion content of the silica sol product was determined by ICP-MS, as shown in Table 9.

[0187] Table 9 Metal ion content of silica sol products in Comparative Example 4

[0188]

[0189] As shown in Table 9, the content of metal impurities (especially Al, Fe, Ca, and Mg) in the finished silica sol product far exceeds that of the example, which does not meet the requirements for semiconductor polishing. Therefore, subsequent polishing performance testing and morphology characterization were not carried out.

[0190] Polishing performance test

[0191] The silica sol prepared above was formulated into polishing slurries with different abrasive systems according to the formula of SIPOL-1806, a commercially available silicon wafer coarse polishing solution from Bonaineren. The metal ion content and polishing performance of the prepared polishing slurries were tested, and the results are shown in the table below. The same specific polishing process conditions were used, specifically:

[0192] Polishing targets: 3 six-inch silicon wafers (p-type, crystalline phase) in a single polishing process <100> )

[0193] Polishing equipment: NTS NSC-4036 36B

[0194] Polishing pad: NWD-80 polyurethane polishing pad manufactured by Quzhou Bolainarun Electronic Materials Co., Ltd.

[0195] The rotational speed ratio of the polishing head to the polishing pad is 40 rpm: 30 rpm.

[0196] Polishing fluid flow rate: 750 mL / min

[0197] Polishing slurry dilution ratio: 1:20

[0198] Polishing pressure: 300g / cm 2

[0199] Polishing time: 20 minutes.

[0200] The test results are shown in Table 10 below.

[0201] Table 10 Metal ion content and polishing performance in polishing slurry

[0202]

[0203] As shown in Table 10, Example 1 (acid first, then alkali) yielded linear particles (70.34 nm); Example 2 (alkali first, then acid) yielded spherical particles (61.56 nm); and Example 3 (simultaneous addition) yielded potato-shaped particles (101.06 nm). The PDI values ​​of all examples were less than 0.25, indicating a narrow particle size distribution and good particle uniformity. This demonstrates that changing the order of adding the alkaline catalyst and active silicic acid can effectively control the morphology of the silica sol, verifying the... Figure 1 The mechanism is illustrated. Scale-up experiments show that the morphology of Example 4 (linear) and Example 5 (potato-shaped) is consistent with that of the small-scale sample, indicating a small scale-up effect. Comparative Example 1 (temperature 98℃), Comparative Example 2 (pH 10.5), and Comparative Example 3 (no ripening) all yielded spherical particles, demonstrating that temperature, pH, and whether or not a ripening step is performed have a significant impact on the formation of non-spherical morphology.

[0204] Examples 1-5 used membrane-purified high-purity sodium silicate as raw material. After ion exchange, the content of individual metal ions (Al, Fe, Ca, Mg, Cu, Cr, Ni, Zn, Pb) in the products was less than 2 ppm, meeting the requirements for semiconductor polishing. Comparative Example 4 used ordinary sodium silicate, with an Al content of 35.17 ppm, far exceeding the requirements for metal impurities in semiconductor polishing. Therefore, no subsequent polishing performance test was conducted, demonstrating that raw material purification is a crucial prerequisite.

[0205] The non-spherical silica sols prepared in Examples 1-5 exhibited polishing removal rates of 879-987 nm / min, representing a 25%-50% improvement compared to the spherical silica sols (657-702 nm / min) in Comparative Examples 1-3. After 20 cycles, the removal rate retention rate was 80.2%-89.5%, and the surface roughness after polishing was less than 0.5 nm. Example 2 demonstrated the best overall performance (removal rate 987 nm / min, Ra 0.253 nm).

[0206] In summary, this invention successfully prepared non-spherical silica sols with controllable morphology (linear, potato-shaped, and near-spherical), uniform particle size (40~120 nm), and high purity (metal ions <2 ppm) by controlling the feeding sequence and key process parameters. When used as a CMP abrasive, the obtained non-spherical silica sol product significantly improves the polishing removal rate while maintaining excellent surface quality. Its overall performance is superior to existing spherical silica sols, and the process scale-up effect is small, making it suitable for industrial production.

[0207] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing non-spherical high-purity silica sol, characterized in that, Includes the following steps: (1) Pass a high-purity sodium silicate solution through a cation exchange resin to obtain an active silicic acid component; (2) Under stirring conditions, the alkaline catalyst and the active silica component obtained in step (1) are mixed in different order of addition, and then aged to obtain silica sol seed crystals. (3) Heat the silica sol seed crystals obtained in step (2) to boiling as the mother liquor, add the active silicic acid component obtained in step (1) dropwise to the system, and at the same time maintain the pH value of the system in the alkaline range with an alkaline catalyst. After the reaction is completed, cool to obtain a dilute silica sol solution. (4) The silica sol dilute solution obtained in step (3) is concentrated by ultrafiltration to obtain a non-spherical high-purity silica sol product.

2. The method for preparing non-spherical high-purity silica sol as described in claim 1, characterized in that, Step (1) includes one or more of the following features: (a) The silica content in the high-purity sodium silicate solution is 2wt%~5wt%; (b) The high-purity sodium silicate solution is purified by membrane filtration before use; (c) The cation exchange resin is selected from strong acid type cation exchange resins; (d) The pH of the active silicic acid component is 2 to 4.

3. The method for preparing non-spherical high-purity silica sol as described in claim 1, characterized in that, Step (2) includes one or more of the following features: (a) The mixing method of the alkaline catalyst and the active silicic acid component is selected from any of the following: adding the active silicic acid component dropwise to the alkaline catalyst, adding the alkaline catalyst dropwise to the active silicic acid component, or adding the active silicic acid component and the alkaline catalyst dropwise to the reaction vessel simultaneously; (b) The temperature of the system is controlled at 50~80℃ during the mixing process; (c) The pH of the mixed system is 7.5~8.5; (d) The aging temperature is 80~100℃; (e) The ripening time is 0.5 to 2 hours.

4. The method for preparing non-spherical high-purity silica sol as described in claim 1 or 3, characterized in that, Includes one or more of the following characteristics: (i) The alkaline catalyst is selected from any one or a combination of at least two of alkaline hydroxides, ammonia, and organic amine compounds; preferably, the organic amine compounds are selected from any one or a combination of at least two of tetramethylammonium hydroxide, tetrabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, isopropylamine, ethylenediamine, diethylenetriamine, and triethylenetetramine. (ii) The pH value of the mixture is controlled by adjusting the dropping ratio or dropping rate of the alkaline catalyst and the active silicic acid component; (iii) The alkaline catalyst and the active silicic acid component are added at a time of 1 to 60 min.

5. The method for preparing non-spherical high-purity silica sol as described in claim 1, characterized in that, Step (3) includes one or more of the following features: (a) The silica content in the silica sol seed mother liquor is 2wt%~10wt%; (b) The mass ratio of the active silicic acid component to the silica sol seed mother liquor is 1:0.1~1; (c) When the liquid level in the reaction vessel reaches 1 / 2 to 3 / 4 of its effective volume, the liquid level of the system is kept constant until the addition is completed; (d) The dropping rate of the active silicic acid component is such that the ratio of the active silicic acid component added per hour to the initial mass of the mother liquor is 1:1~10; (e) The concentration of the alkaline catalyst is 0.1 wt% to 10 wt%; (f) The pH of the system is maintained between 9 and 10 during the dropwise addition process.

6. The method for preparing non-spherical high-purity silica sol as described in claim 1, characterized in that, In step (4), the solid content of the non-spherical high-purity silica sol product obtained by ultrafiltration concentration is 40wt%~50wt%.

7. A non-spherical high-purity silica sol, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 6.

8. The non-spherical high-purity silica sol as described in claim 7, characterized in that, The content of individual metal ion impurities in the silica sol is less than 2 ppm; preferably, the metal ions include any one of Al, Fe, Ca, Mg, Cu, Cr, Ni, Zn, and Pb.

9. The non-spherical high-purity silica sol as described in claim 7 or 8, characterized in that, The average particle size of the silica sol is 40~120 nm, and its particle morphology is linear, spherical or potato-shaped.

10. The application of the non-spherical high-purity silica sol as described in any one of claims 7 to 9 in chemical mechanical polishing.

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