A long strip of ultra-high-purity silica sol and its synthesis method and application

Abstract

The present invention discloses a long strip of ultra-high purity silica sol, its synthesis method and application. The synthesis method comprises: mixing ultra-pure water, alcohol and an alkaline catalyst to obtain an alkaline solution with a pH of 7.5 or above; adding a silicon source to the alkaline solution, stirring to obtain a silica sol initial particle solution, then adding a silane coupling agent, stirring to obtain a silica sol functional particle solution; adding an alkaline solution to the silica sol functional particle solution, maintaining the solution pH of 8.5 or above, then adding a silicon source to complete seed growth to obtain a long strip of silica sol particle solution; using a constant liquid level evaporation method to perform solvent replacement and concentration to obtain a long strip of ultra-high purity silica sol. The present invention changes the normal hydrolysis and condensation process of the silicon source to cause the silica particles to grow unevenly, thereby producing silica particles with a long strip structure. The long strip of ultra-high purity silica sol particles has a larger contact area with the polished material, and can greatly improve the polishing efficiency when used in chemical mechanical polishing technology.

Description

Technical Field

[0001] The present invention relates to the field of nano-scale silicon dioxide material synthesis, and in particular to a long strip of ultra-high purity silica sol, a synthesis method and application thereof. Background Art

[0002] Silica sol is a suspended colloidal liquid composed of nano-sized silicon dioxide dispersed in a solvent. It is a non-toxic, odorless, and pollution-free non-metallic material widely used in polishing, coatings, textiles, catalysts, refractory materials, and many other fields. In recent years, with the rapid development of the semiconductor chip industry, the requirements for chemical mechanical polishing (CMP) technology have become increasingly stringent. Ultra-high-purity silica sol, due to its extremely low metal impurity content (Na ion content ≤500ppb, Al ion content ≤50ppb, Fe ion content ≤20ppb, Cu ion content ≤5ppb) and excellent stability, can ensure that semiconductor materials are not damaged by metal impurities during the fine polishing process. Therefore, ultra-high-purity silica sol has been widely used in CMP technology in recent years and is an indispensable component of modern microelectronics polishing fluids.

[0003] Currently, the most common method for preparing ultra-high-purity silica sols is to use hydrolyzable organosilanes as the silicon source, water and alcohol as solvents, and an alkali as a catalyst, through a hydrolysis and condensation reaction. However, the silica sol particles produced by current processes are typically spherical, which can lead to low polishing efficiency and cannot meet the high requirements of chemical mechanical polishing technology.

[0004] On this basis, the present application improves the preparation process of traditional ultra-high purity silica sol, so that by changing the hydrolysis and condensation process of the silicon source, the silica particles grow unevenly, thereby producing heterogeneous silica particles, and obtaining elongated ultra-high purity silica sol particles, so that the ultra-high purity silica sol particles have a larger contact area with the polished material, and ultimately greatly improve the polishing efficiency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for synthesizing elongated ultra-high-purity silica sol, which changes the hydrolysis and condensation process of the silicon source to make the silica particles grow unevenly, thereby producing heterogeneous silica particles, and obtaining elongated ultra-high-purity silica sol particles. This allows the ultra-high-purity silica sol particles to have a larger contact area with the polished material, ultimately greatly improving the polishing efficiency, thereby overcoming the shortcomings of existing ultra-high-purity silica sol synthesis methods.

[0006] In order to solve the above technical problems, the present invention provides a method for synthesizing an elongated ultra-high purity silica sol, the synthesis method comprising the following steps: (1) mixing ultrapure water, alcohol and an alkaline catalyst in a certain proportion to obtain an alkaline solution, wherein the pH of the alkaline solution is above 7.5; (2) adding a silicon source to the alkaline solution, stirring to obtain a silica sol initial particle solution, and then adding a silane coupling agent, stirring to obtain a silica sol functional particle solution; (3) adding the alkaline solution to the silica sol functional particle solution, maintaining the solution pH at above 8.5, and then adding a silicon source to complete seed growth to obtain an elongated silica sol particle solution; and (4) using a constant liquid level evaporation method to perform solvent replacement on the elongated silica sol particle solution, and concentrating to obtain the elongated ultra-high purity silica sol.

[0007] The purpose of adding a silane coupling agent in the present invention is to modify a portion of the surface of the silica sol primary particles with aniline groups through a co-condensation reaction between the silica sol primary particles and the silane coupling agent. This modification, on the one hand, inhibits the subsequent hydrolysis and polymerization of the functional particles under alkaline conditions due to the hydrophobicity of the aniline groups, resulting in uneven growth of the silica particles and a heterogeneous structure. On the other hand, the steric hindrance effect inhibits contact and aggregation between the particles, ultimately resulting in silica sol particles with an elongated structure.

[0008] As an embodiment of the present invention, in step (1), the alcohol is one or more of methanol, ethanol and isopropanol, and the alkaline catalyst is one or more of ammonia water, tetramethylammonium hydroxide and diethanolamine. Preferably, the alkaline catalyst is ammonia water. It should be noted that the term "multiple" in this application includes two or more.

[0009] As an embodiment of the present invention, the volume ratio of ultrapure water to alcohol in step (1) is 2.5-5:1, more preferably, the volume ratio of ultrapure water to alcohol is 3-4:1.

[0010] The pH of the alkaline solution is 7.5-8.5. A pH value less than 7.5 or greater than 8.5 is not conducive to the subsequent co-condensation reaction of the silicon source and the silane coupling agent.

[0011] As an embodiment of the present invention, in step (2), the silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate. Preferably, the silicon source is methyl orthosilicate.

[0012] The silane coupling agent is an organic compound with a structure of Y-R1-Si(OR2)3, wherein Y is an aniline group, R1 is an alkylene group with 1 to 3 carbon atoms, and R2 is an alkyl group with 1 to 3 carbon atoms. Preferably, R1 is -CH2- and R2 is -CH3.

[0013] As an embodiment of the present invention, in step (2), the silicon source is added to the alkaline solution so that the silicon dioxide content in the obtained silica sol initial particle solution is 10%-40%; preferably, the silicon dioxide content is 15%-25%.

[0014] The volume ratio of the silane coupling agent to the silicon source is 1-5:30. If the volume ratio of the silane coupling agent to the silicon source is less than 1:30, the number of functional groups modified on the particles will be too small, resulting in a low degree of irregular shape. If the volume ratio of the silane coupling agent to the silicon source is greater than 5:30, the number of functional groups modified on the particles will be too large, resulting in completely irregularly shaped particles.

[0015] As an embodiment of the present invention, step (2) is specifically: adding a silicon source to the alkaline solution, maintaining the reaction temperature at 40-50°C, the stirring speed at 200-800 r / min, and the reaction time at 0.5-2h; and after the reaction is completed, the temperature of the reaction solution is lowered to room temperature, and the silane coupling agent is added dropwise. After the addition of the silane coupling agent is completed, the reaction temperature is maintained at 55-70°C, the stirring speed is maintained at 500-1000 r / min, and the reaction time is 4-8h.

[0016] Preferably, a silicon source is added to the alkaline solution, the reaction temperature is maintained at 45-50°C, the stirring speed is 300-600 r / min, and the reaction time is 1-1.5 h; and after the reaction is completed, the temperature of the reaction solution is lowered to room temperature, and the silane coupling agent is added dropwise. After the addition of the silane coupling agent is completed, the reaction temperature is maintained at 60-65°C, the stirring speed is 600-800 r / min, and the reaction time is 5-6 h.

[0017] As one embodiment of the present invention, the conditions for adding the silane coupling agent dropwise are: diluting the silane coupling agent to 5-10 times its volume with the alkaline solution, and then slowly adding the diluted silane coupling agent dropwise at a dropping rate of (0.01-0.05)·V / min, where V is the volume of the diluted silane coupling agent in L. Preferably, the dropping rate is (0.02-0.04)·V / min.

[0018] As one embodiment of the present invention, in step (3), the alkaline solution is added to the silica sol functional particle solution to maintain the solution pH at 8.5-10. When the pH is less than 8.5, the resulting silica particles have a low degree of irregular shape; when the pH is greater than 10, the proportion of the resulting elongated silica particles is low.

[0019] The amount of the silicon source added in step (3) is greater than the amount of the silicon source added in step (2) to ensure that the seed crystals of the functional particles are fully grown.

[0020] As another improvement of the present invention, the present invention provides a long strip of ultra-high purity silica sol prepared by the above-mentioned synthesis method of the long strip of ultra-high purity silica sol.

[0021] The silicon dioxide particles in the long strip ultra-high purity silica sol are in a curved long strip structure, and the silicon dioxide particles are interwoven with each other. The particle size of the silicon dioxide particles is 5-15 nm, and the length of the silicon dioxide particles is 50-150 nm.

[0022] The elongated ultra-high-purity silica sol has a pH of 7.5-12, a silica mass fraction greater than 20%, a viscosity of 0.5-10 mPa·s, and a proportion of elongated silica particles greater than 90%. Furthermore, the elongated ultra-high-purity silica sol has a sodium ion content less than 200 ppb, an aluminum ion content less than 40 ppb, an iron ion content less than 15 ppb, and a copper ion content less than 2 ppb.

[0023] The long strip ultra-high purity silica sol obtained by the above method is applied in chemical mechanical polishing (CMP) technology, and has high polishing efficiency.

[0024] After adopting such a design, the present invention has at least the following advantages:

[0025] The synthesis method of the long strip ultra-high purity silica sol of the present invention affects the crystal growth of silicon dioxide by changing the normal hydrolysis and condensation process of the silicon source, causing the silicon dioxide particles to grow unevenly, thereby producing long strip ultra-high purity silica sol particles. The synthesized silicon dioxide particles have a high proportion of long strip structures, uniform shape, and good stability.

[0026] The present invention features a simple preparation process, resulting in a high proportion of elongated silica particles with uniform shape. The elongated ultra-high-purity silica sol particles provide a larger contact area with the material being polished. Furthermore, the ultra-high-purity silica sol contains an extremely low metal ion content and exhibits excellent stability, meeting the requirements of chemical mechanical polishing (CMP) technology while achieving high polishing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0028] Figure 1 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Example 1 of the present invention.

[0029] Figure 2 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Example 2 of the present invention.

[0030] Figure 3 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Example 3 of the present invention.

[0031] Figure 4 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Example 4 of the present invention.

[0032] Figure 5 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Comparative Example 1 of the present invention.

[0033] Figure 6 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Comparative Example 2 of the present invention.

[0034] Figure 7 This is a scanning electron microscope image of the silica sol in Comparative Example 3 of the present invention.

[0035] Figure 8 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Comparative Example 4 of the present invention.

[0036] Figure 9 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Comparative Example 5 of the present invention.

[0037] Figure 10 This is a scanning electron microscope image of the ultra-high purity silica sol obtained in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0038] Example 1

[0039] (1) 800 ml of ultrapure water, 200 ml of ethanol, and 2 ml of aqueous ammonia were mixed to prepare an alkaline solution with a pH of 7.8.

[0040] (2) 60 ml of the alkaline solution and 10 ml of anilinemethyltrimethoxysilane were mixed and stirred evenly to obtain a diluted silane coupling agent solution.

[0041] (3) 500 ml of the alkaline solution was heated to 45° C., and then 240 ml of methyl orthosilicate was added. The stirring speed was 400 r / min. After 1.3 hours, a silica sol initial particle solution was obtained.

[0042] (4) The silica sol initial particle solution was cooled to room temperature, and 70 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 2.4 ml / min. After the addition was completed, the solution was heated to 60°C, stirred at a speed of 700 r / min, and reacted for 5.2 h to obtain a silica sol functional particle solution.

[0043] (5) 300 ml of methyl orthosilicate and 10 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 9.0-9.5. The seed crystal growth was completed in 60 minutes to obtain silica sol particles 1.

[0044] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 22%.

[0045] Example 2

[0046] (1) Mix 800 ml ultrapure water, 200 ml ethanol, and 3.8 ml ammonia water to prepare an alkaline solution with a pH of 8.3.

[0047] (2) Take 60 ml of alkaline solution and 10 ml of aniline methyl trimethoxysilane, mix them and stir them evenly to prepare a diluted silane coupling agent solution.

[0048] (3) Take 500 ml of alkaline solution and heat it to 48°C, then add 240 ml of ethyl orthosilicate and stir at a speed of 500 r / min. After 1.5 hours, the silica sol initial particle solution is obtained.

[0049] (4) The silica sol initial particle solution was cooled to room temperature, and 70 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 2.4 ml / min. After the addition was completed, the solution was heated to 62°C, stirred at a speed of 800 r / min, and reacted for 5.5 h to obtain a silica sol functional particle solution.

[0050] (5) 300 ml of ethyl orthosilicate and 10 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 9.0-9.5. The seed crystal growth was completed in 60 minutes to obtain silica sol particles 2.

[0051] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 22%.

[0052] Example 3

[0053] (1) 800 ml of ultrapure water, 200 ml of ethanol, and 2 ml of aqueous ammonia were mixed to prepare an alkaline solution with a pH of 8.3.

[0054] (2) 60 ml of the alkaline solution and 10 ml of anilinemethyltrimethoxysilane were mixed and stirred evenly to prepare a diluted silane coupling agent solution.

[0055] (3) Take 500 ml of alkaline solution and heat it to 50°C, then add 280 ml of methyl orthosilicate and stir at a speed of 450 r / min. After 1.2 hours, a silica sol initial particle solution is obtained.

[0056] (4) The silica sol initial particle solution was cooled to room temperature, and 70 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 2.4 ml / min. After the addition was completed, the solution was heated to 65°C, stirred at a speed of 700 r / min, and reacted for 5 h to obtain a silica sol functional particle solution.

[0057] (5) 310 ml of methyl orthosilicate and 10 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 9.0-9.5. It took 58 minutes to complete the seed growth and obtain silica sol particles 3.

[0058] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 21%.

[0059] Example 4

[0060] (1) 800 ml of ultrapure water, 200 ml of ethanol, and 2 ml of aqueous ammonia were mixed to prepare an alkaline solution with a pH of 7.8.

[0061] (2) 90 ml of the alkaline solution and 10 ml of anilinemethyltrimethoxysilane were mixed and stirred evenly to obtain a diluted silane coupling agent solution.

[0062] (3) 500 ml of the alkaline solution was heated to 46° C., and then 240 ml of propyl orthosilicate was added. The stirring speed was 490 r / min. After 1.4 hours, a silica sol initial particle solution was obtained.

[0063] (4) The silica sol initial particle solution was cooled to room temperature, and 100 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 2.4 ml / min. After the addition was completed, the solution was heated to 63°C, stirred at a speed of 750 r / min, and reacted for 5.4 h to obtain a silica sol functional particle solution.

[0064] (5) 300 ml of propyl orthosilicate and 10 ml of ammonia water were simultaneously added dropwise to the functional silica sol particle solution, maintaining the pH at 9.0-9.5. The seed crystal growth was completed in 65 minutes to obtain silica sol particles 4.

[0065] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 24%.

[0066] Comparative Example 1

[0067] (1) Mix 800 ml ultrapure water, 200 ml ethanol, and 0.8 ml ammonia water to prepare an alkaline solution with a pH of 7.2.

[0068] (2) Take 60 ml of alkaline solution and 10 ml of aniline methyl trimethoxysilane, mix them and stir them evenly to prepare a diluted silane coupling agent solution.

[0069] (3) 500 ml of the alkaline solution was heated to 50° C., and then 240 ml of ethyl orthosilicate was added. The stirring speed was 500 r / min. After 1.5 hours, a silica sol initial particle solution was obtained.

[0070] (4) The silica sol initial particle solution was cooled to room temperature, and 70 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 2.4 ml / min. After the addition was completed, it was heated to 68°C, stirred at a speed of 800 r / min, and reacted for 5.2 h to obtain a silica sol functional particle solution.

[0071] (5) 300 ml of ethyl orthosilicate and 10 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 9.0-9.5. It took 65 minutes to complete the seed growth and obtain silica sol particles 5.

[0072] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 25%.

[0073] Comparative Example 2

[0074] (1) Mix 800 ml ultrapure water, 200 ml ethanol, and 5.2 ml ammonia water to prepare an alkaline solution with a pH of 11.3.

[0075] (2) 60 ml of alkaline solution and 10 ml of anilinemethyltrimethoxysilane were mixed and stirred evenly to prepare a diluted silane coupling agent solution.

[0076] (3) 500 ml of the alkaline solution was heated to 48° C., and then 240 ml of methyl orthosilicate was added. The stirring speed was 400 r / min. After 1.5 hours, a silica sol initial particle solution was obtained.

[0077] (4) The silica sol initial particle solution was cooled to room temperature, and 70 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 2.4 ml / min. After the addition was completed, it was heated to 58°C, stirred at a speed of 700 r / min, and reacted for 6.0 h to obtain a silica sol functional particle solution.

[0078] (5) 300 ml of methyl orthosilicate and 10 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 9.0-9.5. The seed crystal growth was completed in 60 minutes to obtain silica sol particles 6.

[0079] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 24%.

[0080] Comparative Example 3

[0081] (1) 800 ml of ultrapure water, 200 ml of ethanol, and 2 ml of aqueous ammonia were mixed to prepare an alkaline solution with a pH of 7.8.

[0082] (2) 60 ml of alkaline solution and 10 ml of anilinemethyltrimethoxysilane were mixed and stirred evenly to prepare a diluted silane coupling agent solution.

[0083] (3) 500 ml of the alkaline solution was heated to 50° C., and then 240 ml of methyl orthosilicate was added. The stirring speed was 450 r / min. After 1 hour, a silica sol initial particle solution was obtained.

[0084] (4) The silica sol initial particle solution was cooled to room temperature, and 20 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 0.8 ml / min. After the addition was completed, it was heated to 65°C, stirred at a speed of 780 r / min, and reacted for 5.0 h to obtain a silica sol functional particle solution.

[0085] (5) 300 ml of methyl orthosilicate and 10 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 9.0-9.5. The seed crystal growth was completed in 50 minutes to obtain silica sol particles 7.

[0086] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 23%.

[0087] Comparative Example 4

[0088] (1) 800 ml of ultrapure water, 200 ml of ethanol, and 2 ml of aqueous ammonia were mixed to prepare an alkaline solution with a pH of 7.8.

[0089] (2) 185 ml of alkaline solution and 45 ml of anilinemethyltrimethoxysilane were mixed and stirred evenly to prepare a diluted silane coupling agent solution.

[0090] (3) 500 ml of the alkaline solution was heated to 45° C., and then 240 ml of ethyl orthosilicate was added. The stirring speed was 500 r / min. After 1.4 hours, a silica sol initial particle solution was obtained.

[0091] (4) The silica sol initial particle solution was cooled to room temperature, and 230 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 5.2 ml / min. After the addition was completed, it was heated to 62°C, stirred at a speed of 650 r / min, and reacted for 5.0 h to obtain a silica sol functional particle solution.

[0092] (5) 300 ml of methyl orthosilicate and 10 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 9.0-9.5. The seed crystal growth was completed in 60 minutes to obtain silica sol particles 8.

[0093] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 24%.

[0094] Comparative Example 5

[0095] (1) 800 ml of ultrapure water, 200 ml of ethanol, and 2 ml of aqueous ammonia were mixed to prepare an alkaline solution with a pH of 7.8.

[0096] (2) 60 ml of alkaline solution and 10 ml of anilinemethyltrimethoxysilane were mixed and stirred evenly to prepare a diluted silane coupling agent solution.

[0097] (3) 500 ml of the alkaline solution was heated to 50° C., and then 240 ml of methyl orthosilicate was added with stirring at a speed of 460 r / min. After 1.3 h, a silica sol initial particle solution was obtained.

[0098] (4) The silica sol initial particle solution was cooled to room temperature, and 70 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 15 ml / min. After the addition was completed, it was heated to 65°C, stirred at a speed of 770 r / min, and reacted for 5.5 h to obtain a silica sol functional particle solution.

[0099] (5) 300 ml of methyl orthosilicate and 6 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 8.0-8.5. It took 62 minutes to complete the seed growth and obtain silica sol particles 9.

[0100] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 22%.

[0101] Comparative Example 6

[0102] (1) 800 ml of ultrapure water, 200 ml of ethanol, and 2 ml of aqueous ammonia were mixed to prepare an alkaline solution with a pH of 7.8.

[0103] (2) 60 ml of alkaline solution and 10 ml of anilinemethyltrimethoxysilane were mixed and stirred evenly to prepare a diluted silane coupling agent solution.

[0104] (3) 500 ml of the alkaline solution was heated to 50° C., and then 240 ml of ethyl orthosilicate was added. The stirring speed was 400 r / min. After 1.3 hours, a silica sol initial particle solution was obtained.

[0105] (4) The silica sol initial particle solution was cooled to room temperature, and 70 ml of the diluted silane coupling agent solution was added dropwise at a flow rate of 2.4 ml / min. After the addition was completed, it was heated to 62°C, stirred at a speed of 700 r / min, and reacted for 5.2 h to obtain a silica sol functional particle solution.

[0106] (5) 300 ml of ethyl orthosilicate and 18 ml of ammonia water were simultaneously added dropwise to the silica sol functional particle solution, maintaining the pH at 10.5-11.0. The seed crystal growth was completed in 60 minutes to obtain silica sol particles 10.

[0107] (6) The obtained silica sol particle solution is heated to boiling, while ultrapure water is added dropwise to maintain a constant liquid level, and evaporated until the organic solvent content in the system is less than 100 ppm, and then evaporated again to concentrate until the mass content of silica is 23%.

[0108] Detection Example

[0109] The silica sol particles 1-4 obtained in the above examples 1-4 and the silica sol particles 5-10 obtained in the comparative examples 1-6 were examined by scanning electron microscopy. The results are shown in the attached figures. Figure 1-10 .

[0110] Figure 1 shows a scanning electron microscope image of the ultra-high purity silica sol particles 1 obtained in Example 1; Figure 2 shows a scanning electron microscope image of the ultra-high purity silica sol particles 2 obtained in Example 2; Figure 3 shows a scanning electron microscope image of the ultra-high purity silica sol particles 3 obtained in Example 3; Figure 4 shows a scanning electron microscope image of the ultra-high purity silica sol particles 4 obtained in Example 4; Figure 5 The scanning electron microscope image of the ultra-high purity silica sol particles 5 obtained in Comparative Example 1 is shown. Figure 6The scanning electron microscope image of the ultra-high purity silica sol particles 6 obtained in Comparative Example 2 is shown. Figure 7 A scanning electron microscope image of the ultra-high purity silica sol particles 7 obtained in Comparative Example 3 is shown. Figure 8 A scanning electron microscope image of the ultra-high purity silica sol particles 8 obtained in Comparative Example 4 is shown. Figure 9 A scanning electron microscope image of the ultra-high purity silica sol particles 9 obtained in Comparative Example 5 is shown. Figure 10 A scanning electron microscope image of the ultra-high purity silica sol particles 10 obtained in Comparative Example 6 is shown.

[0111] from Figure 1-4 It can be seen that the ultra-high purity silica sol particles 1-4 obtained in Examples 1-4 all show silicon dioxide particles with an interwoven long strip structure, the silicon dioxide particles have a uniform structure, and the long strip silicon dioxide particles account for a high proportion, all greater than 90%.

[0112] From the attached Figure 5 It can be seen that the ultra-high purity silica sol particles 5 obtained in Comparative Example 1 present a non-interwoven spherical structure. Figure 6 It can be seen that the ultra-high purity silica sol particles 6 obtained in Comparative Example 2 present an irregular structure that is not long and strip-shaped and has no interweaving. Figure 5 and 6 The results show that the pH of the alkaline solution has a great influence on the morphology of silica sol particles.

[0113] From the attached Figure 7 It can be seen that the ultra-high purity silica sol particles 7 obtained in Comparative Example 3 present a disordered and irregular structure, and the proportion of long strip structure particles is relatively small. Figure 8 It can be seen that the ultra-high purity silica sol particles 8 obtained in Comparative Example 4 present a spherical and uneven irregular structure. Figure 7 and 8 The results show that the amount of silane coupling agent has a significant effect on the shape of silica sol particles.

[0114] From the attached Figure 9 It can be seen that the ultra-high purity silica sol particles 9 obtained in Comparative Example 5 are spherical and have an uneven irregular structure, indicating that the dropping speed of the silane coupling agent also has a significant effect on the shape of the silica sol particles.

[0115] From the attached Figure 10 It can be seen that most of the ultra-high purity silica sol particles 10 obtained in Comparative Example 6 are irregular in shape, and a few are long strips, that is, the proportion of long strip structure particles is relatively small. Figure 10 The results show that the pH value in the seed growth step has an impact on the morphology of silica sol particles.

[0116] In summary, the present invention changes the normal hydrolysis and condensation process of the silicon source by screening the reaction raw materials, reaction steps and reaction conditions of the silica sol synthesis reaction, affects the crystal growth of silica, and causes the silica particles to grow unevenly, thereby obtaining silica particles with an interwoven elongated structure, and the elongated silica particles have a high proportion, uniform shape and good stability.

[0117] Furthermore, the long strips of ultra-high-purity silica sol obtained by the synthesis method of the ultra-high-purity silica sol of the present invention have an extremely low content of metal particles and good stability. The long strips of ultra-high-purity silica sol particles have a larger contact area with the material to be polished. Therefore, when the long strips of ultra-high-purity silica sol are used in chemical mechanical polishing (CMP) technology, the polishing efficiency can be greatly improved.

[0118] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Those skilled in the art can make some simple modifications, equivalent changes or modifications based on the technical content disclosed above, which all fall within the scope of protection of the present invention.

Claims

1. A method for synthesizing an elongated ultra-high purity silica sol, characterized in that: The synthesis method comprises the following steps: (1) ultrapure water, alcohol and alkaline catalyst are mixed in a certain proportion to obtain an alkaline solution, wherein the pH of the alkaline solution is 7.5-8.5; (2) adding a silicon source to the alkaline solution and stirring to obtain a silica sol initial particle solution, and then adding a silane coupling agent and stirring to obtain a silica sol functional particle solution; the silane coupling agent is an organic compound with a structure of Y-R1-Si(OR2)3, wherein Y is an aniline group, R1 is an alkylene group with 1 to 3 carbon atoms, and R2 is an alkyl group with 1 to 3 carbon atoms, and the volume ratio of the silane coupling agent to the silicon source is 1-5:30; The conditions for adding the silane coupling agent dropwise are: diluting the silane coupling agent to 5-10 times its volume with the alkaline solution, and then slowly adding the diluted silane coupling agent dropwise at a dropping rate of (0.01-0.05)·V / min, where V is the volume of the diluted silane coupling agent in L; (3) adding the alkaline solution to the silica sol functional particle solution, maintaining the solution pH at 8.5-10, and then adding a silicon source to complete seed growth to obtain a long strip silica sol particle solution; (4) The solvent of the elongated silica sol particle solution is replaced by a constant liquid surface evaporation method, and the solution is concentrated to obtain the elongated ultra-high purity silica sol.

2. The method for synthesizing the long strip ultra-high purity silica sol according to claim 1, characterized in that: In step (1), the alcohol is one or more of methanol, ethanol and isopropanol, and the alkaline catalyst is one or more of ammonia water, tetramethylammonium hydroxide and diethanolamine.

3. The method for synthesizing the long strip ultra-high purity silica sol according to claim 2, characterized in that: The volume ratio of ultrapure water to alcohol in step (1) is 2.5-5:

1.

4. The method for synthesizing the long strip ultra-high purity silica sol according to claim 1, characterized in that: In step (2), the silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate.

5. The method for synthesizing the long strip ultra-high purity silica sol according to claim 4, characterized in that: In step (2), the silicon source is added to the alkaline solution so that the content of silicon dioxide in the obtained silica sol initial particle solution is 10%-40%.

6. The method for synthesizing the long strip ultra-high purity silica sol according to claim 5, characterized in that: Step (2) is specifically as follows: adding a silicon source to the alkaline solution, maintaining the reaction temperature at 40-50°C, the stirring speed at 200-800 r / min, and the reaction time at 0.5-2h; and after the reaction is completed, cooling the reaction solution temperature to room temperature, and then adding the silane coupling agent dropwise. After the addition of the silane coupling agent is completed, maintaining the reaction temperature at 55-70°C, the stirring speed at 500-1000 r / min, and the reaction time at 4-8h.

7. The method for synthesizing the long strip ultra-high purity silica sol according to claim 1, characterized in that: The amount of the silicon source added in step (3) is greater than the amount of the silicon source added in step (2).

8. A long strip of ultra-high purity silica sol, characterized in that: The long strip of ultra-high purity silica sol is prepared by the synthesis method of the long strip of ultra-high purity silica sol according to any one of claims 1 to 7. The silicon dioxide particles in the long strip ultra-high purity silica sol are in a curved long strip structure, and the silicon dioxide particles are interwoven with each other. The particle size of the silicon dioxide particles is 5-15 nm, and the length of the silicon dioxide particles is 50-150 nm.

9. Use of the long strip ultra-high purity silica sol according to claim 8 in chemical mechanical polishing.

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