Non-spherical nano silicon dioxide sol as well as preparation method and application thereof

Abstract

The invention discloses a non-spherical nano silicon dioxide sol and a preparation method and application thereof, and the method comprises synthesis of silicon dioxide particle seed crystal and further growth of the seed crystal: preparing monodispersed seed crystal particles, and adding a trace of amphiphilic nonionic multi-block copolymer into a seed crystal growth solution to assist anisotropic growth of the seed crystal, so as to obtain the non-spherical nano silicon dioxide sol. The method comprises the following steps: adjusting the proportion and dosage of amphipathic nonionic multi-block copolymer groups, so that monodispersed seed crystals generate silica sol of non-spherical silicon dioxide particles with different morphologies, and the amphipathic nonionic multi-block copolymer has hydrophilic groups for capturing and positioning silicon dioxide; and the hydrophobic group improves the stability of the non-spherical silica sol product, and the non-spherical silica sol is not easy to agglomerate. The mass fraction is more than 15%, the primary particle size is 30-70nm, and the non-spherical ultra-high-purity silica sol is peanut-shaped, short-chain-shaped, long-chain-shaped and the like. The invention further relates to the non-spherical ultra-high-purity silica sol and application of the non-spherical ultra-high-purity silica sol in CMP.

Description

Technical Field

[0001] This invention belongs to the field of silica nanomaterial preparation, specifically relating to a method for preparing non-spherical nano-silica silica sol with assisted self-assembly, the product, and its application in semiconductor CMP polishing. Background Technology

[0002] With the ever-increasing performance demands of electronic products, the integration density of integrated circuits has also improved, entering the nanometer era. Simultaneously, higher requirements have been placed on electronic chip manufacturing processes. Metal contamination, organic contamination, and surface quality on silicon wafer surfaces severely affect the yield and performance of precision components, posing new challenges to wafer surface processing. Chemical mechanical polishing (CMP) is the only technology capable of achieving global planarization. One of its most important consumables, the polishing slurry, is primarily composed of high-purity silica sol. Traditional silica sol uses fumed silica particles, which offer the advantage of high polishing speed but are prone to causing scratches on the wafer surface. To address this issue, non-spherical silica abrasives have gradually replaced fumed silica particles, offering the advantage of both high polishing speed and low defect rate.

[0003] Currently, methods for preparing non-spherical silica particles include template methods, ionic polymer-induced methods, and metal salt solution-induced methods. However, these methods typically rely on adding surfactants, macromolecular polymers, or metal salt solutions to the system to prepare micelles, inorganic porous microspheres, or organic porous microspheres as templates to prepare micron-sized non-spherical silica. CN109574021B uses hydroxyethyl cellulose as a template to prepare non-spherical mesoporous silica materials, but the large particle size and porous structure make them unsuitable for use as abrasives in chemical mechanical polishing. CN103896287B uses a divalent metal ion-induced method to prepare non-spherical seed crystals, introducing additional metal ions into the synthesis system, further accelerating agglomeration and making storage stability difficult to control. This results in numerous scratches during chemical mechanical polishing applications and fails to meet the metal ion requirements. CN107522868B uses block polymers and nano-silica particles to prepare non-spherical silica, but the particle uniformity is poor, making it unsuitable for use in chemical and mechanical polishing industries. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a non-spherical nano-silica sol, its preparation method, and its application. It is prepared using amphiphilic nonionic multiblock copolymers assisted by the self-growth of spherical seed crystals. By selecting different types of amphiphilic nonionic multiblock copolymers or adjusting the concentration of the amphiphilic nonionic multiblock copolymers, silica sols with different particle sizes, particle size distributions, and morphologies can be prepared, with a small scale-up effect and good batch-to-batch stability of particle morphology.

[0005] Another object of the present invention is to provide the silica sol.

[0006] Another object of the present invention is to provide applications of the said silica sol.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A method for producing non-spherical nano-silica sol includes the following steps:

[0009] 1) Preparation of catalyst solution: Mix organic solvent, ultrapure water and alkaline catalyst evenly;

[0010] 2) Preparation of silicon source solution: Mix the organic solvent and alkoxysilane evenly;

[0011] 3) Preparation of monodisperse silica sol seed crystals: A portion of the silicon source solution prepared in step 2) is added dropwise to the catalyst solution prepared in step 1), and the mixture is stirred to react, thereby obtaining a monodisperse silica sol seed crystal solution;

[0012] 4) Self-assembly aid for monodisperse silica sol seed crystal self-assembly: Add the self-assembly aid to the monodisperse silica sol seed crystal solution in step 3) and mix evenly, keep for 2-4 hours; then add the remaining silicon source solution dropwise and stir the reaction to obtain silica sol containing non-spherical particles.

[0013] 5) Post-treatment of silica sol: The organic solvent in the concentrated silica sol is replaced with ultrapure water through solvent replacement, concentration and filtration, and the concentration and filtration are carried out until the mass fraction is above 20%.

[0014] In one specific embodiment, the organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, and ethyl propyl ether, preferably methanol; preferably, the mass ratio of the organic solvent to ultrapure water in the catalyst solution of step 1) is 2:1 to 2.5:1, for example 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, and 2.5:1.

[0015] In one specific embodiment, the alkaline catalyst is selected from one or more of alkali metal hydroxides, ammonia, or organic amines; preferably, the alkali metal hydroxide is selected from potassium hydroxide and / or sodium hydroxide; the organic amine is selected from one or more of ethylenediamine, triethanolamine, tetramethylamine hydroxide, and guanidine compounds; preferably, the guanidine compound is selected from one or more of tetramethylguanidine, trimethylguanidine, and guanidine carbonate; and the alkaline catalyst is preferably ammonia.

[0016] More preferably, the mass concentration of the alkaline catalyst in the catalyst solution of step 1) is 3% to 5%, for example, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0017] In one specific embodiment, the alkoxysilane is selected from one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, preferably tetramethoxysilane; preferably, the mass ratio of the organic solvent to the alkoxysilane in step 2) is 2:1 to 5:1, for example 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, and 5:1.

[0018] In one specific implementation, the total mass ratio of the silicon source solution prepared in step 2) to the catalyst solution in step 1) is 3:50 to 1:10, for example, 3:50, 7:100, 4:50, 9:100, or 1:10.

[0019] In one specific implementation, the mass ratio of the silicon source solution used in step 3) to the total mass of the silicon source prepared in step 2) is 1:3 to 3:5, for example, 1:3, 2:5, 1:2, or 3:5.

[0020] In one specific implementation, in step 3), the stirring reaction time is 0.5h-3h, for example 1h, 1.5h, 2h, 2.5h, or 3h.

[0021] In one specific embodiment, the self-assembly aid is an amphiphilic nonionic multiblock copolymer containing nonionic hydrophilic and hydrophobic segments, preferably an amphiphilic diblock copolymer and / or an amphiphilic triblock copolymer; preferably, the amphiphilic diblock copolymer is selected from one or more of polyethylene glycol-polylactic acid copolymer, polyethylene glycol-polycaprolactone copolymer, and polyethyleneimine-polylactic acid copolymer. Preferably, the amphiphilic triblock copolymer is selected from one or more of Poloxamer 124, Poloxamer 188, Poloxamer 237, polyethylene glycol-polylactic acid-polyhydroxyethyl methacrylate copolymer, and polycaprolactone-polyethylene glycol-poly(2-hydroxyethyl methacrylate) copolymer; more preferably, the self-assembly aid is selected from one or more of Poloxamer 124, Poloxamer 188, and Poloxamer 237.

[0022] In one specific implementation, the mass concentration of the self-assembly aid in step 4) is 1-50 ppm, based on the product mass of step 4).

[0023] In one specific implementation, the prepared catalyst solution and silicon source solution are placed in a water bath and kept at 5-50°C, for example, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C, preferably 40°C.

[0024] In one specific implementation, the preparation processes in steps 3) and 4) are maintained at a temperature of 5-50°C, preferably 40°C.

[0025] In one specific implementation, the stirring speed in steps 3) and 4) is 200 r / min to 1000 r / min, for example, 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min, preferably 350 r / min; preferably, the dropping speed is 0.1 g / s to 1 g / s, for example, 0.1 g / s, 0.2 g / s, 0.3 g / s, 0.4 g / s, 0.5 g / s, 0.6 g / s, 0.7 g / s, 0.8 g / s, 0.9 g / s, 1.0 g / s, preferably 0.7 g / s.

[0026] In one specific implementation, the stirring reaction time in step 4) is 0.5h-3h, for example 1h, 1.5h, 2h, 2.5h, 3h.

[0027] In a specific implementation, the process of step 5) can refer to existing technology, such as patent CN102390838A. For example, it involves vacuum heating concentration at 10 kPa and 100°C until it reaches approximately 20%, resulting in a concentrated silica sol. Then, ultrapure water is added while evaporating the organic solvent until an ultra-high purity silica sol with a mass concentration of 20% is obtained.

[0028] On the other hand, the present invention also provides a non-spherical nano-silica sol prepared by the method described above.

[0029] Furthermore, the present invention also provides an application of the aforementioned non-spherical nano-silica sol in the field of semiconductor CMP polishing.

[0030] Compared with the prior art, the beneficial effects of the present invention include:

[0031] 1) This invention prepares non-spherical silica sol by using amphiphilic nonionic multiblock copolymers to assist the self-assembly of spherical seed crystals. The size of the spherical seed crystals can be adjusted to control the self-assembled non-spherical silica particles. The morphology of the non-spherical silica particles can be adjusted by selecting different types of amphiphilic nonionic multiblock copolymers or changing the amount of amphiphilic nonionic multiblock copolymers. The silica sol of this invention has high storage stability and is not prone to agglomeration and sedimentation. The preparation method is simple, and the particle size, particle size distribution, and particle morphology can be easily controlled. Different morphologies of silica sol can be used according to the different polishing rates required by different processes.

[0032] 2) The raw materials used in the preparation method of the present invention are all of high purity, so the prepared silica sol has high purity and few metal impurities and organic residues.

[0033] 3) This invention uses an amphiphilic nonionic multiblock copolymer as a self-assembly initiator, which requires very little dosage and is highly efficient. In addition, its hydrophilic and hydrophobic amphiphilic properties can also be used as a stabilizer for the reaction system.

[0034] 4) Compared with the process of preparing non-spherical silica particles by adding surfactants, ionic polymer induction, and metal salt solution, the preparation method of the present invention can prepare silica abrasive silica sol with a large proportion of particles with the target morphology, nano-sized particles, dense structure, high storage stability, good batch-to-batch stability, and suitable for chemical mechanical polishing by precisely controlling the process conditions. Attached Figure Description

[0035] Figure 1-8 The images shown are TEM images of the silica sol particles prepared in Examples 1-7 and Comparative Example 1, respectively. Detailed Implementation

[0036] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0037] To better understand the technical solution of the present invention, the preparation method of the present invention will be further explained and illustrated below through more specific embodiments, but this does not constitute any limitation.

[0038] The main raw materials used in the following examples and comparative examples are shown in Table 1:

[0039] Table 1 Raw Materials

[0040]

[0041]

[0042] Detection method:

[0043] The test method for solid content is based on HGT 2521-2008 Industrial Silica Sol.

[0044] The secondary particle size and particle size distribution (PDI) of the silica sol particles were measured using a Malvern Zetasizer NanoZS90 particle size analyzer.

[0045] The surface morphology of the silica sol was characterized by TEM.

[0046] Example 1

[0047] A catalyst solution was prepared by mixing 240g methanol, 100g water, and 14g ammonia. A silicon source solution was prepared by mixing 20g methanol and 7g tetramethoxysilane (TMOS). 9g of the silicon source solution was added to the 354g catalyst solution using a peristaltic pump, with the addition completed within 13 seconds. The reaction was carried out at 40℃ and 350r / min for 1 hour to obtain a seed crystal solution. Then, 0.04g of Poloxamer 124 was added to the reaction system as a self-assembly aid. After reacting for 2 hours, the remaining 18g of the silicon source solution was added to the reaction system using a peristaltic pump, with the addition completed within 26 seconds. The reaction was continued for 1 hour while maintaining the same speed and temperature. The solution was then concentrated under reduced pressure at 10KPa and 100℃ to approximately 20%, yielding a concentrated silica sol. Ultrapure water was then added while evaporation continued until a silica sol with a mass concentration of 20% and a particle size distribution of 0.05 μm was obtained.

[0048] Example 2

[0049] A catalyst solution was prepared by mixing 240g methanol, 100g water, and 14g ammonia. A silicon source solution was prepared by mixing 20g methanol and 7g tetramethoxysilane (TMOS). 9g of the silicon source solution was added to the 354g catalyst solution using a peristaltic pump, with the addition completed within 13 seconds. The reaction was carried out at 40℃ and 350r / min for 1 hour to obtain a seed crystal solution. Then, 0.95g of Poloxamer 124 was added to the reaction system as a self-assembly aid. After reacting for 2 hours, the remaining 18g of the silicon source solution was added to the reaction system using a peristaltic pump, with the addition completed within 26 seconds. The reaction was continued for 1 hour while maintaining the same speed and temperature. The solution was then concentrated under reduced pressure at 10KPa and 100℃ to approximately 20%, yielding a concentrated silica sol. Ultrapure water was then added while evaporation continued until a silica sol with a mass concentration of 20% and a particle size distribution of 0.09 μm was obtained.

[0050] Example 3

[0051] A catalyst solution was prepared by mixing 240g methanol, 100g water, and 14g ammonia. A silicon source solution was prepared by mixing 20g methanol and 7g tetramethoxysilane (TMOS). 9g of the silicon source solution was added to the 354g catalyst solution using a peristaltic pump, with the addition completed within 13 seconds. The reaction was carried out at 40℃ and 350r / min for 1 hour to obtain a seed crystal solution. Then, 1.9g of Poloxamer 124 was added to the reaction system as a self-assembly aid. After reacting for 2 hours, the remaining 18g of the silicon source solution was added to the reaction system using a peristaltic pump, with the addition completed within 26 seconds. The reaction was continued for 1 hour while maintaining the same speed and temperature. The solution was then concentrated under reduced pressure at 10KPa and 100℃ to approximately 20%, yielding a concentrated silica sol. Ultrapure water was then added while evaporation continued until a silica sol with a mass concentration of 20% and a particle size distribution of 0.17 was obtained.

[0052] Example 4

[0053] A catalyst solution was prepared by mixing 240g methanol, 100g water, and 14g ammonia. A silicon source solution was prepared by mixing 20g methanol and 7g tetramethoxysilane (TMOS). 9g of the silicon source solution was added to the 354g catalyst solution using a peristaltic pump, with the addition completed within 13 seconds. The reaction was carried out at 40℃ and 350r / min for 1 hour to obtain a seed crystal solution. Then, 0.95g of Poloxamer 188 was added to the reaction system as a self-assembly aid. After reacting for 2 hours, the remaining 18g of the silicon source solution was added to the reaction system using a peristaltic pump, with the addition completed within 26 seconds. The reaction was continued for 1 hour while maintaining the same speed and temperature. The solution was then concentrated under reduced pressure at 10KPa and 100℃ to approximately 20%, yielding a concentrated silica sol. Ultrapure water was then added while evaporation continued until a silica sol with a mass concentration of 20% and a particle size distribution of 0.12mm was obtained.

[0054] Example 5

[0055] A catalyst solution was prepared by mixing 240g methanol, 100g water, and 14g ammonia. A silicon source solution was prepared by mixing 20g methanol and 7g tetramethoxysilane (TMOS). 9g of the silicon source solution was added to the 354g catalyst solution using a peristaltic pump, with the addition completed in 13 seconds. The reaction was carried out at 40℃ and 350r / min for 1 hour to obtain a seed crystal solution. Then, 0.04g of Poloxamer 237 was added to the reaction system as a self-assembly aid. After reacting for 2 hours, the remaining 18g of the silicon source solution was added to the reaction system using a peristaltic pump, with the addition completed in 26 seconds. The reaction was continued for 1 hour while maintaining the same speed and temperature. The solution was then concentrated under reduced pressure at 10KPa and 100℃ to approximately 20%, yielding a concentrated silica sol. Ultrapure water was then added while evaporation continued until a silica sol with a mass concentration of 20% and a particle size distribution of 0.14 was obtained.

[0056] Example 6

[0057] A catalyst solution was prepared by mixing 256.1 g of ethyl propyl ether, 128.1 g of water, and 20.3 g of ethylenediamine. A silicon source solution was prepared by mixing 16.4 g of ethyl propyl ether with 8.2 g of tetraethoxysilane (TEOS). 12.3 g of the silicon source solution was added to 404.5 g of the catalyst solution using a peristaltic pump, with the addition completed within 123 seconds. The reaction was carried out at 40 °C and 350 r / min for 1 hour to obtain a seed crystal solution. Then, 0.5 g of polycaprolactone-polyethylene glycol-polymethacrylic acid (2-hydroxyethyl ester) copolymer was added to the reaction system as a self-assembly aid. After reacting for 2 hours, the remaining 12.3 g of the silicon source solution was added to the reaction system using a peristaltic pump, with the addition completed within 123 seconds. The reaction was continued for 1 hour while maintaining the same speed and temperature. The solution was then concentrated under reduced pressure at 10 kPa and 100 °C to approximately 20%, yielding a concentrated silica sol. Then, while adding ultrapure water, the mixture was evaporated until a silica sol with a mass concentration of 20% and a particle size distribution of 0.12 was obtained.

[0058] Example 7

[0059] A catalyst solution was prepared by mixing 234.3 g of isopropanol, 93.7 g of water, and 10.2 g of tetramethylguanidine. A silicon source solution was prepared by mixing 28 g of isopropanol with 5.6 g of tetrapropoxysilane (TPOS). 20 g of the silicon source solution was added to 404.5 g of the catalyst solution using a peristaltic pump, with the addition completed within 20 seconds. The reaction was carried out at 40 °C and 350 r / min for 1 hour to obtain a seed crystal solution. Then, 1.4 g of polyethylene glycol-polylactic acid copolymer was added to the reaction system as a self-assembly aid. After reacting for 2 hours, the remaining 13.6 g of the silicon source solution was added to the reaction system using a peristaltic pump, with the addition completed within 14 seconds. The reaction was continued for 1 hour while maintaining the same speed and temperature. The solution was then concentrated under reduced pressure at 10 kPa and 100 °C to approximately 20%, yielding a concentrated silica sol. Ultrapure water was then added while evaporation continued until a silica sol with a mass concentration of 20% and a particle size distribution of 0.06 mm was obtained.

[0060] Comparative Example 1

[0061] A catalyst solution was prepared by mixing 240g methanol, 100g water, and 14g ammonia. A silicon source solution was prepared by mixing 20g methanol and 7g tetramethoxysilane (TMOS). 9g of the silicon source solution was added to the 354g catalyst solution using a peristaltic pump, with the addition completed within 13 seconds. The reaction was carried out at 40℃ and 350 rpm for 1 hour to obtain a seed crystal solution. After 2 hours of reaction, the remaining 18g of the silicon source solution was added to the reaction system using a peristaltic pump, with the addition completed within 26 seconds. The reaction was continued for 1 hour while maintaining the same speed and temperature. The solution was then concentrated under reduced pressure at 10 kPa and 100℃ to approximately 20%, yielding a concentrated silica sol. Ultrapure water was then added while evaporation continued until a silica sol with a mass concentration of 20% and a particle size distribution of 0.01 μm was obtained.

[0062] In the examples, by controlling the type and content of different amphiphilic nonionic multiblock copolymers, silica sols with a particle size distribution of 0.05–0.17 mm and a non-spherical morphology could be prepared. Figure 1-8 TEM images of Examples 1-7 and Comparative Example 1 are shown. By comparing Examples 1-3 and Comparative Example 1, the effect of adjusting the mass concentration of the self-assembly aid on particle morphology was investigated. In Comparative Example 1, without the amphiphilic nonionic multiblock copolymer, the particles were monodisperse spherical. In Examples 1-8, the addition of the amphiphilic nonionic multiblock copolymer as a self-assembly aid resulted in non-spherical particles. TEM images of Examples 1-3 show that adding different amounts of the same type of amphiphilic nonionic multiblock copolymer during the preparation process affected the particle size distribution and morphology. As the content of the amphiphilic nonionic multiblock copolymer increased, the particles gradually changed from a peanut-like shape to a short-chain or even a long-chain shape. In Examples 2, 4, and 5, different types of amphiphilic nonionic multiblock copolymers with the same amount were added as self-assembly inducers during the preparation process, which also affected the degree of particle self-assembly and thus the morphology.

[0063] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing non-spherical nanosilica sol, comprising the following steps: 1) preparing catalyst solution: mixing organic solvent, ultrapure water and alkaline catalyst uniformly; 2) preparing silicon source solution: mixing organic solvent and alkoxysilane uniformly; 3) preparing monodisperse silica sol seed solution: adding part of the silicon source solution prepared in step 2) into the catalyst solution prepared in step 1) dropwise, and stirring to react, to obtain monodisperse silica sol seed solution; 4) self-assembly of monodisperse silica sol seed solution assisted by self-assembly assistant: adding self-assembly assistant into the monodisperse silica sol seed solution prepared in step 3) and mixing uniformly, keeping for 2-4 hours; then adding the remaining silicon source solution dropwise, and stirring to react, to obtain non-spherical silica sol; 5) post-treatment of silica sol: replacing organic solvent in the concentrated silica sol with ultrapure water by solvent replacement, concentrating and filtering, to obtain silica sol with mass fraction of more than 20%. The organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether and ethyl propyl ether, and is preferably methanol; preferably, the mass ratio of the organic solvent to ultrapure water in the catalyst solution of step 1) is 2:1-2.5:

1. The alkaline catalyst is selected from one or more of alkali metal hydroxide, aqueous ammonia and organic amine; preferably, the alkali metal hydroxide is selected from potassium hydroxide and / or sodium hydroxide; the organic amine is selected from one or more of ethylenediamine, triethanolamine, tetramethylammonium hydroxide and guanidine compound; preferably, the guanidine compound is selected from one or more of tetramethylguanidine, trimethylguanidine and guanidine carbonate; and the alkaline catalyst is preferably aqueous ammonia. The alkoxysilane is selected from one or more of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane, and is preferably tetramethoxysilane; preferably, the mass ratio of the organic solvent to alkoxysilane in step 2) is 2:1-5:

1. The mass ratio of the total mass of the silicon source solution prepared in step 2) to the mass of the catalyst solution of step 1) is 3:50-1:

10. The mass ratio of the part of the silicon source solution used in step 3) to the total mass of the silicon source prepared in step 2) is 1:3-3:

5.

2. The method of claim 1, wherein, The self-assembly assistant is an amphiphilic non-ionic multi-block copolymer containing non-ionic hydrophilic segment and hydrophobic segment, and is preferably selected from amphiphilic two-block copolymer and / or amphiphilic three-block copolymer; preferably, the amphiphilic two-block copolymer is selected from one or more of polyethylene glycol-poly(lactic acid) copolymer, polyethylene glycol-poly(e-caprolactone) copolymer and poly(ethyleneimine)-poly(lactic acid) copolymer; preferably, the amphiphilic three-block copolymer is selected from one or more of Poloxamer 124, Poloxamer 188, Poloxamer 237, poly(ethylene glycol)-poly(lactic acid)-poly(hydroxyethyl methacrylate) copolymer and poly(e-caprolactone)-poly(ethylene glycol)-poly(2-hydroxyethyl methacrylate) copolymer.

3. The method of claim 1, wherein, The mass concentration of the self-assembly assistant in step 4) is 1-50 ppm based on the mass of the product of step 4).

4. The method of claim 1, wherein, ​ 5. The method of claim 1, wherein, ​ 6. The method of claim 1, wherein, ​ 7. The method of claim 1, wherein, ​ 8. The method of claim 1, wherein, ​ 9. A non-spherical nanosilica sol prepared by the method of any one of claims 1 to 8.

10. Use of a non-spherical nanosilica sol prepared by the method of any one of claims 1 to 8 or of the non-spherical nanosilica sol of claim 9 in the field of semiconductor CMP polishing.

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