Preparation method and application of peanut-shaped ultra-high purity silica sol

Abstract

The invention discloses a method for preparing and applying a peanut-shaped ultra-high purity silica sol, comprising the following steps: 1) preparing an active silicic acid solution; 2) adding part of the active silicic acid solution to an alkali solution, performing an aging reaction after the dropwise addition is completed, adjusting the pH to 9-11, and obtaining a seed mother solution; 3) adding a quantitative organic ammonium salt to the seed mother solution, mixing evenly, and continuing to age at a high temperature to obtain an initial silica sol; 4) heating the initial silica sol to 80-120° C., adding the remaining active silicic acid solution to the initial silica sol under stirring, and continuing the aging reaction after the addition is completed to obtain a silica sol; 5) using ultrapure water to perform solvent replacement on the alcohol generated by the reaction, and concentrating to a silicon dioxide mass content of 20-50%; 6) filtering and removing solids in the concentrated solution to obtain a peanut-shaped ultra-high purity silica sol. The method can provide a peanut-shaped ultra-high purity silica sol, which can be widely used in CMP polishing liquid.

Description

Technical Field

[0001] The invention relates to a silica sol, in particular to a preparation method and application of a peanut-shaped ultra-high purity silica sol. Background Art

[0002] Silica sol is a colloidal substance obtained by dispersing silicon dioxide particles in water. It is widely used in papermaking, catalysts, casting, coatings and other industries. In recent years, it has also been widely used in the semiconductor industry. In the entire semiconductor chip manufacturing process, dozens of chemical mechanical polishing (CMP) processes are required, and silica sol is a very important raw material in the CMP process. In the semiconductor manufacturing process, the presence of metal impurities, especially metal ions, may cause short circuits between circuits. Therefore, in the semiconductor manufacturing process, there are different degrees of requirements for the purity of metal impurities in the chemicals used. As the semiconductor manufacturing process gradually decreases, the purity requirements for silica sol are getting higher and higher.

[0003] The alkoxide method is a relatively mature process for producing ultra-high purity silica sol. Under the action of an alkaline catalyst and an alcohol solvent, alkoxysilane reacts with water to generate silicon dioxide and alcohol, and the organic solvent is replaced with water to obtain an aqueous silica sol. The purity of the silica sol prepared by the alkoxide method is directly related to the purity of the raw materials. Therefore, a large amount of high-purity alcohol solvent is required. Not only is the cost of raw materials high, but also the subsequent separation and recovery, waste liquid treatment, etc., the energy consumption cost and equipment cost are high. In addition, the ultra-high purity silica sol prepared by the traditional alkoxide method has a low synthesis temperature, resulting in a low hardness of the prepared silica sol, which leads to a low polishing rate. In addition, in order to increase the contact area between the abrasive particles and the wafer, thereby increasing the friction and improving the polishing rate, the shape of the abrasive is required to be peanut-shaped or irregular.

[0004] CN101641288A can control the growth rate of silica particles by adjusting the addition rate of alkyl silicate hydrolyzate to the mother liquor, and can produce silica particles with further reduced residual silanol groups, and accordingly, the siloxane skeleton has a high degree of completion and has higher grinding performance. However, the silica sol prepared by this method is spherical and the morphology cannot be controlled.

[0005] JP2013082584A also adopts the above process to prepare ultra-high purity silica sol with high hardness, and controls the addition rate and pH of the active silica solution to control the association degree of the prepared silicon dioxide, thereby preparing peanut-shaped or irregular silica sol. However, this process requires repeated preparation of the active silica solution and strict control of the pH of the system. The reaction conditions are harsh and the process is complicated, which is not conducive to industrial scale-up production, and the batch stability of the prepared silica sol is difficult to guarantee.

[0006] CN112299425A uses a base catalyst with a R1OR2NH2 structure, water and alkoxysilane as reactants to prepare a particle with a mace structure and a convex structure on the surface with a density of 2g / cm 3 Although the synthesized silica sol has a convex structure, which can significantly increase the roughness of the particle surface and improve the CMP polishing rate, the sharp surface structure will inevitably cause scratches or defects to the wafer or device during CMP, and the R1OR2NH2 catalyst used in the above synthesis method belongs to the organic ammonium with a boiling point greater than 100°C, which is difficult to remove in the subsequent treatment process, making it difficult to use in some polishing liquids that are sensitive to organic ammonium (such as metal polishing liquids), and it does not have universal applicability. Summary of the invention

[0007] In order to solve the above technical problems, the present invention proposes a method for preparing peanut-shaped ultra-high purity silica sol and its application. The method can provide peanut-shaped ultra-high purity silica sol, which can be widely used in CMP polishing liquid.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing peanut-shaped ultra-high purity silica sol comprises the following steps:

[0010] 1) adding alkoxysilane to a mixed solution of an organic acid and ultrapure water to prepare an active silicic acid solution;

[0011] 2) slowly adding the active silicate solution to the alkali solution, stirring and reacting, and adding alkali solution to maintain the pH value of the system at 9-11, and aging reaction after the addition is completed, maintaining the pH value of the system at 9-11 during the aging process, to obtain a seed mother solution;

[0012] 3) adding a quantitative amount of organic ammonium salt to the seed mother solution, mixing evenly and then continuing aging reaction at high temperature to prepare an initial silica sol;

[0013] 4) heating the initial silica sol to 80-120° C., preferably 90-110° C., slowly adding the active silicic acid solution under stirring, and continuing the aging reaction after the addition is completed to obtain the silica sol;

[0014] 5) using ultrapure water to perform solvent replacement on the alcohol generated by the reaction, and concentrating the alcohol to a silica mass content of 20-50%;

[0015] 6) Filter and remove the solid in the concentrated solution to obtain peanut-shaped ultra-high purity silica sol.

[0016] As a preferred embodiment, in step 1), the amount of the organic acid used is 100-1500 ppm, relative to the molar amount of the alkoxysilane;

[0017] Preferably, the amount of ultrapure water used in step 1) is 40-150 times the molar amount of alkoxysilane;

[0018] Preferably, the organic acid is one or more of formic acid, acetic acid, propionic acid, benzoic acid, salicylic acid, oxalic acid, malonic acid, maleic acid, fumaric acid, glycolic acid, glyceric acid, lactic acid, tartaric acid, malic acid, and citric acid;

[0019] Preferably, the alkoxysilane is one or more of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, preferably tetramethoxysilane or tetraethoxysilane.

[0020] As a preferred embodiment, in step 1), the reaction temperature is between 10-40°C, the stirring time is 0.5h-3h, and the stirring speed is 200-1000r / min;

[0021] Preferably, the reaction temperature is between 10-15°C, the stirring time is 0.5-1h, and the stirring speed is 200-500r / min.

[0022] As a preferred embodiment, in step 2), the alkali in the alkali solution is selected from alkali metal hydroxides, organic amines, and guanidine compounds; preferably, the alkali metal hydroxide is at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide, the organic amine is at least one of ammonia, ethylenediamine, triethanolamine, and tetramethylammonium hydroxide, and the guanidine compound is at least one of tetramethylguanidine, trimethylguanidine, and guanidine carbonate; the alkali solution is preferably aqueous ammonia.

[0023] Preferably, the mass concentration of alkali in the alkali solution in step 2) is 1-2%.

[0024] As a preferred embodiment, the reaction conditions of the active silicate solution and the alkali solution in step 2) are: reaction temperature 80-120°C, stirring speed 200-1000r / min, preferably reaction temperature 90-110°C, stirring speed 200-500r / min;

[0025] Preferably, in step 2), the time for adding the active silicate solution dropwise to the alkali solution is 3-6 hours;

[0026] Preferably, the aging time in step 2) is 2-8 h, preferably 3-6 h.

[0027] As a preferred embodiment, in step 3), the amount of organic ammonium salt added is 0.1-5%, preferably 0.5-2%, of the silicon dioxide content in the seed mother solution;

[0028] Preferably, the organic ammonium salt is ammonium formate, ammonium acetate, ammonium propionate, ammonium benzoate, ammonium salicylate, ammonium oxalate, ammonium malonate, ammonium maleate, ammonium fumarate, ammonium hydroxyacetate, ammonium glycerate, ammonium lactate, ammonium tartrate, ammonium malate, and ammonium citrate; the inorganic ammonium acid class includes one or more of ammonium phosphate, diammonium phosphate, ammonium bicarbonate, ammonium sulfate, ammonium chloride, ammonium nitrate, etc.

[0029] As a preferred embodiment, the high temperature aging conditions in step 3) are: aging temperature is 60-120°C, aging time is 2-8h, and stirring speed is 0-300r / min. Preferably, the aging temperature is 80-110°C, aging time is 3-6h, and stirring speed is 0-100r / min.

[0030] As a preferred embodiment, the amount of the active silicic acid solution in step 4) is 10-50 times the mass of the initial silica sol;

[0031] Preferably, in step 4), the time for adding the active silicic acid solution dropwise to the initial silica sol is 3-6 hours;

[0032] Preferably, in step 4), the stirring speed is 200-1000 r / min, preferably 200-500 r / min;

[0033] Preferably, the aging reaction time in step 4) is 2-8 h, preferably 3-6 h.

[0034] Preferably, the solvent replacement in step 5) is carried out by heating concentration or ultrafiltration concentration, more preferably vacuum heating concentration or ultrafiltration membrane concentration, so as to reduce the alcohol content to below 200 ppm, preferably below 100 ppm.

[0035] Preferably, in step 6), a PFA filter element is used for filtration, preferably two-stage or three-stage filtration with a filtration accuracy of 0.2-5 μm.

[0036] The invention adopts a two-step growth method and adds a quantitative organic ammonium salt to the seed mother solution to obtain a particle size of 20-100nm, a peanut shape, an association degree between 1.7-2.2, and a density greater than 2g / cm 3 The peanut-shaped ultra-high purity silica sol has a high hardness and can significantly increase the polishing rate. Moreover, since the colloidal particles have a smooth peanut morphology, the scratches on the substrate during polishing can be reduced.

[0037] An application of peanut-shaped ultra-high purity silica sol prepared by the method described above in CMP polishing liquid.

[0038] The beneficial effects of the present invention are as follows:

[0039] (1) The present invention adds an organic ammonium salt to the prepared seed mother solution, and then prepares a high-purity silica sol with high hardness and peanut-shaped particles through secondary growth.

[0040] (2) The silica sol prepared by the present invention has a high polishing rate, and the surface of the colloidal particles has a smooth structure. While ensuring the polishing rate, it can effectively reduce the scratches and defects formed during the polishing process, and can be widely used in polishing liquids.

[0041] (3) The silica sol prepared by the present invention does not contain an organic base catalyst that is difficult to separate, has stronger universality, and can be better applied to the field of high-end CMP polishing.

[0042] (4) The production process proposed by the present invention is simple, has higher batch stability, and is more conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the TEM morphology of the silica sol particles prepared in Example 1.

[0044] Figure 2 This is the TEM morphology of the silica sol particles prepared in Comparative Example 1. DETAILED DESCRIPTION

[0045] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0046] The raw materials and reagents used in the following examples and comparative examples were purchased from commercial sources.

[0047] The main test methods used in the following examples and comparative examples are as follows:

[0048] The test method for solid content refers to HGT 2521-2008 industrial silica sol.

[0049] The secondary particle size of silica sol particles was measured by using a Malvern Zetasizer Nano ZS90 particle size analyzer. The primary particle size was first measured by using the BET specific surface area test method to obtain the specific surface area S bet , and then through the formula 2727 / S bet The primary particle size is calculated. The degree of association is the ratio of the secondary particle size to the primary particle size.

[0050] The morphology of silica sol was characterized by TEM.

[0051] The concentration of metal ions was measured using an Agilent 8900 ICP-MS.

[0052] The true density of the colloid particles is tested by a true density meter.

[0053] Example 1

[0054] (1) 0.019 g of citric acid was added to 1800 g of water to prepare a citric acid aqueous solution, and then 152 g of tetramethoxysilane was added to the citric acid aqueous solution. The mixture was stirred at 15° C. for 1 h at a stirring speed of 200 r / min to obtain an active silicate aqueous solution with a mass concentration (in terms of SiO2) of 3.07%.

[0055] (2) 10 g of ammonia water (25 wt%) was dissolved in 185.2 g of deionized water to obtain an alkaline solution with a pH of 11. At 100°C, 1952 g of active silicic acid solution was slowly added dropwise to the alkaline solution for a total of 3 hours. During the addition, the pH of the system was monitored and the alkaline solution was added to maintain the pH at 9-10. After the addition of the alkaline solution, the aging reaction was continued for 3 hours. During the aging process, the alkaline solution was added to maintain the pH at 9-10. Finally, a spherical silica seed mother solution with a primary particle size of 15 nm was obtained, in which the SiO2 mass concentration was 2.79 wt%.

[0056] (3) 0.5% of ammonium citrate relative to the mass of silica in the seed solution was added to the seed solution, and the mixture was reacted at 90° C. for 3 h with a stirring speed of 100 r / min to obtain an initial silica sol with a secondary particle size of 35 nm and a primary particle size of 15 nm.

[0057] (4) 100 g of the initial silica sol was taken and heated to 100° C., and then 2882 g of the active silicic acid solution was slowly added dropwise to the initial silica sol for a total of 3 hours. The stirring speed during the addition was 200 r / min. After the addition was completed, the aging reaction was continued for 3 hours.

[0058] (5) Adopting the method of constant liquid level heating concentration, adding water while evaporating, until the alcohol content in the silica sol drops below 100 ppm, and then concentrating to a silicon dioxide content of 20%.

[0059] (6) After concentration, the mixture is filtered twice using filter cartridges with 1 μm and 0.5 μm filtration grades to remove solids, thereby obtaining peanut-shaped ultra-high purity silica sol.

[0060] [Example 2]

[0061] (1) 0.201 g of malic acid was added to 792 g of water to prepare a malic acid aqueous solution, and then 208 g of tetramethoxysilane was added to the malic acid aqueous solution. The mixture was stirred at 15° C. for 1 h at a stirring speed of 300 r / min to obtain an active silicic acid aqueous solution with a mass concentration (in terms of SiO2) of 6%.

[0062] (2) Dissolve 10g of tetramethylammonium hydroxide in 190g of deionized water to obtain an alkaline solution with a pH of 10. Slowly add 1000g of active silicic acid solution to the alkaline solution at 90°C for a total of 6h. During the addition, monitor the pH of the system and add alkaline solution to maintain the pH at 9-10. After the addition is completed, continue the aging reaction for 3h. During the aging process, add alkaline solution to maintain the pH at 9-10. Finally, a spherical silica seed mother solution with a primary particle size of 20nm is obtained, in which the SiO2 mass concentration is 5wt%.

[0063] (3) Add 2% ammonium malate relative to the mass of silica in the seed solution to the above seed solution, react at 90°C for 3 hours with a stirring speed of 100 r / min to obtain an initial silica sol with a secondary particle size of 45 nm and a primary particle size of 20 nm.

[0064] (4) Take 100 g of the initial silica sol and heat it to 90° C., then slowly add 1000 g of active silicic acid solution to the initial silica sol for a total of 6 hours. The stirring speed during the addition is 400 r / min. After the addition is completed, continue the aging reaction for 6 hours.

[0065] (5) Adopting the method of constant liquid level heating concentration, adding water while evaporating, until the alcohol content in the silica sol drops below 100 ppm, and then concentrating to a silicon dioxide content of 20%.

[0066] (6) After concentration, the mixture is filtered twice using filter cartridges with 1 μm and 0.5 μm filtration grades to remove solids, thereby obtaining peanut-shaped ultra-high purity silica sol.

[0067] [Example 3]

[0068] (1) 0.019 g of malonic acid was added to 1236 g of water to prepare a malonic acid aqueous solution. Then 264 g of tetrapropoxysilane was added to the malonic acid aqueous solution. The mixture was stirred at 10° C. for 1 h at a stirring speed of 200 r / min to obtain an active silicic acid aqueous solution with a mass concentration (in terms of SiO2) of 4.5%.

[0069] (2) Dissolve 0.01g potassium hydroxide in 200g deionized water to obtain an alkaline solution with a pH of 11. At 110°C, slowly add 1500g of active silicic acid solution to the alkaline solution for a total of 4.5h. During the addition, monitor the pH of the system and add alkaline solution to maintain the pH at 10-11. After the addition is completed, continue the aging reaction for 4.5h. During the aging process, add alkaline solution to maintain the pH at 10-11. Finally, a spherical silica seed mother solution with a primary particle size of 10nm is obtained, in which the SiO2 mass concentration is 3.97wt%.

[0070] (3) Add 1.5% ammonium phosphate relative to the mass of silica in the seed solution to the above seed solution, react at 110°C for 4.5 hours with a stirring speed of 100 r / min to obtain an initial silica sol with a secondary particle size of 20 nm and a primary particle size of 10 nm.

[0071] (4) Take 130 g of the initial silica sol and heat it to 110° C., then slowly add 2477 g of active silicic acid solution to the initial silica sol for a total of 4.5 hours. The stirring speed during the addition is 300 r / min. After the addition is completed, continue the aging reaction for 4.5 hours.

[0072] (5) Adopting the method of constant liquid level heating concentration, adding water while evaporating, until the alcohol content in the silica sol drops below 100 ppm, and then concentrating to a silicon dioxide content of 20%.

[0073] (6) After concentration, the mixture is filtered twice using filter cartridges with 1 μm and 0.5 μm filtration grades to remove solids, thereby obtaining peanut-shaped ultra-high purity silica sol.

[0074] [Example 4]

[0075] (1) 0.019 g of malic acid was added to 1800 g of water to prepare a malic acid aqueous solution, and then 152 g of tetramethoxysilane was added to the malic acid aqueous solution. The mixture was stirred at 15° C. for 1 h at a stirring speed of 200 r / min to obtain an active silicic acid aqueous solution with a mass concentration (in terms of SiO2) of 3.07%.

[0076] (2) 15 g of tetramethylguanidine was dissolved in 185.2 g of deionized water to obtain an alkaline solution with a pH of 10. At 100°C, 1952 g of active silicic acid solution was slowly added dropwise to the alkaline solution for a total of 3 hours. During the addition, the pH of the system was monitored and the alkaline solution was added to maintain the pH at 9-10. After the addition was completed, the aging reaction was continued for 3 hours. During the aging process, the alkaline solution was added to maintain the pH at 9-10. Finally, a spherical silica seed mother solution with a primary particle size of 20 nm was obtained, in which the SiO2 mass concentration was 2.78 wt%.

[0077] (3) Add 1% ammonium citrate relative to the mass of silica in the seed solution to the above seed solution, react at 90°C for 3 hours with a stirring speed of 100 r / min to obtain an initial silica sol with a secondary particle size of 42 nm and a primary particle size of 20 nm.

[0078] (4) Take 60 g of the initial silica sol and heat it to 100° C., then slowly add 3615 g of active silicic acid solution to the initial silica sol for a total of 3 hours. The stirring speed during the addition is 200 r / min. After the addition is completed, continue the aging reaction for 3 hours.

[0079] (5) Adopting the method of constant liquid level heating concentration, adding water while evaporating, until the alcohol content in the silica sol drops below 100 ppm, and then concentrating to a silicon dioxide content of 20%.

[0080] (6) After concentration, the mixture is filtered twice using filter cartridges with 1 μm and 0.5 μm filtration grades to remove solids, thereby obtaining peanut-shaped ultra-high purity silica sol.

[0081] [Example 5]

[0082] (1) 0.019 g of citric acid was added to 848 g of water to prepare a citric acid aqueous solution, and then 152 g of tetramethoxysilane was added to the citric acid aqueous solution. The mixture was stirred at 15° C. for 1 h at a stirring speed of 200 r / min to obtain an active silicate aqueous solution with a mass concentration (in terms of SiO2) of 6%.

[0083] (2) Dissolve 10g of ammonia water (25wt%) in 185.2g of deionized water to obtain an alkaline solution with a pH of 10. At 100°C, slowly add 1000g of active silicic acid solution to the alkaline solution for a total of 6h. During the addition, monitor the pH of the system and add alkaline solution to maintain the pH at 9-10. After the addition is completed, continue the aging reaction for 3h. During the aging process, add alkaline solution to maintain the pH at 9-10. Finally, a spherical silica seed mother solution with a primary particle size of 25nm is obtained, in which the SiO2 mass concentration is 5.02wt%.

[0084] (3) Add 1.5% ammonium citrate relative to the mass of silica in the seed solution to the above seed solution, react at 100°C for 3 hours with a stirring speed of 100 r / min to obtain an initial silica sol with a secondary particle size of 50 nm and a primary particle size of 25 nm.

[0085] (4) Take 90 g of the initial silica sol and heat it to 100° C., then slowly add 900 g of active silicic acid solution to the initial silica sol for a total of 6 hours. The stirring speed during the addition is 300 r / min. After the addition is completed, continue the aging reaction for 3 hours.

[0086] (5) Adopting the method of constant liquid level heating concentration, adding water while evaporating, until the alcohol content in the silica sol drops below 100 ppm, and then concentrating to a silicon dioxide content of 20%.

[0087] (6) After concentration, the mixture is filtered twice using filter cartridges with 1 μm and 0.5 μm filtration grades to remove solids, thereby obtaining peanut-shaped ultra-high purity silica sol.

[0088] [Comparative Example 1]

[0089] Silica sol was prepared in substantially the same manner as in Example 1, except that ammonium citrate was not added in step (3).

[0090] The silica sols prepared in each embodiment and comparative example were tested for the parameters in Table 1, and the test results are as follows. In addition, the TEM images of the silica sol particles prepared in Example 1 and Comparative Example 1 are shown in Figures 1 and 2. Figure 1 , Figure 2 shown.

[0091] Table 1. Silica sol test results

[0092]

[0093] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing peanut-shaped ultra-high purity silica sol, characterized in that: The following steps are involved: 1) adding alkoxysilane to a mixed solution of organic acid and ultrapure water to prepare an active silicic acid solution; 2) Slowly drop the active silicate solution into the alkali solution, react while stirring and add alkali solution to maintain the pH of the system at 9-11. After the addition is completed, age the solution and maintain the pH of the system at 9-11 during the aging process to obtain a seed mother solution; 3) Adding a certain amount of organic ammonium salt to the seed mother solution, mixing evenly and continuing the aging reaction at high temperature to prepare the initial silica sol; the amount of organic ammonium salt added is 0.1-5% of the silicon dioxide content in the seed mother solution; 4) The initial silica sol is heated to 80-120°C, and the active silicic acid solution is slowly added under stirring. After the addition is completed, the aging reaction is continued to obtain the silica sol; the amount of the active silicic acid solution used is 10-50 times the mass of the initial silica sol; 5) Using ultrapure water to replace the alcohol produced by the reaction, and concentrating it to a silica mass content of 20-50%; 6) Filter and remove the solids in the concentrated solution to obtain peanut-shaped ultra-high purity silica sol.

2. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 1, characterized in that: In step 4), the initial silica sol is heated to 90-110° C. and then the active silicic acid solution is added.

3. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 1, characterized in that: In step 1), the amount of the organic acid used is 100-1500 ppm, relative to the molar amount of the alkoxysilane.

4. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 3, characterized in that: The amount of ultrapure water used in step 1) is 40-150 times the molar amount of alkoxysilane.

5. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 3, characterized in that: The organic acid is one or more of formic acid, acetic acid, propionic acid, benzoic acid, salicylic acid, oxalic acid, malonic acid, maleic acid, fumaric acid, glycolic acid, glyceric acid, lactic acid, tartaric acid, malic acid, and citric acid.

6. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 3, characterized in that: The alkoxysilane is one or more of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane.

7. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 3, characterized in that: In step 1), the reaction temperature is between 10-40°C, the stirring time is between 0.5h-3h, and the stirring speed is between 200-1000r / min.

8. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 7, characterized in that: In step 1), the reaction temperature is between 10-15°C, the stirring time is 0.5-1h, and the stirring speed is 200-500r / min.

9. The method for preparing peanut-shaped ultra-high purity silica sol according to any one of claims 1 to 8, characterized in that: In step 2), the alkaline solution is at least one of an alkali metal hydroxide, an organic amine, and a guanidine compound solution.

10. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 9, characterized in that: The alkali metal hydroxide is selected from at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide; the organic amine is selected from at least one of ammonia, ethylenediamine, triethanolamine, and tetramethylammonium hydroxide; and the guanidine compound is selected from at least one of tetramethylguanidine, trimethylguanidine, and guanidine carbonate.

11. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 9, characterized in that: In step 2), the reaction conditions for adding the active silicate solution dropwise to the alkali solution are: reaction temperature 80-120° C., stirring speed 200-1000 r / min.

12. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 11, characterized in that: In step 2), the reaction conditions for adding the active silicate solution dropwise to the alkali solution are: reaction temperature 90-110° C., stirring speed 200-500 r / min.

13. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 11, characterized in that: In step 2), the time for adding the active silicate solution dropwise to the alkaline solution is 3-6 hours.

14. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 11, characterized in that: The aging time in step 2) is 2-8h.

15. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 14, characterized in that: The aging time in step 2) is 3-6 hours.

16. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 1, characterized in that: In step 3), the amount of organic ammonium salt added is 0.5-2% of the silicon dioxide content in the seed mother solution.

17. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 1, characterized in that: The organic ammonium salt is selected from ammonium formate, ammonium acetate, ammonium propionate, ammonium benzoate, ammonium salicylate, ammonium oxalate, ammonium malonate, ammonium maleate, ammonium fumarate, ammonium hydroxyacetate, ammonium glycerate, ammonium lactate, ammonium tartrate, ammonium malate, and ammonium citrate.

18. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 1, characterized in that: Step 3) The medium-high temperature aging conditions are: aging temperature is 60-120°C, aging time is 2-8h, and stirring speed is 0-300r / min.

19. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 18, characterized in that: Step 3) The medium-high temperature aging conditions are: aging temperature is 80-110°C, aging time is 3-6h, and stirring speed is 0-100r / min.

20. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 1, characterized in that: In step 4), the time for adding the active silicic acid solution dropwise to the initial silica sol is 3-6 hours.

21. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 20, characterized in that: In step 4), the stirring speed is 200-1000 r / min.

22. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 21, characterized in that: In step 4), the stirring speed is 200-500 r / min.

23. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 20, characterized in that: The aging reaction time in step 4) is 2-8 hours.

24. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 23, characterized in that: The aging reaction time in step 4) is 3-6 hours.

25. The method for preparing peanut-shaped ultra-high purity silica sol according to any one of claims 1 to 8, characterized in that: In step 5), the solvent replacement method is heating concentration or ultrafiltration concentration to reduce the alcohol content to below 200 ppm.

26. The method for preparing peanut-shaped ultra-high purity silica sol according to claim 25, characterized in that: In step 5), the solvent replacement method is heating concentration or ultrafiltration concentration to reduce the alcohol content to below 100 ppm.

27. Use of peanut-shaped ultra-high purity silica sol prepared by the method according to any one of claims 1 to 26 in CMP polishing liquid.

Images