Ultra-high purity silica sol with convex structure on surface, preparation method and application thereof

Abstract

The application discloses a kind of ultra-high purity silica sol with protruding structure on surface, preparation method and application thereof, the preparation method includes: (1) by the mixture of alkoxysilane and alcohol, with certain speed, is added to the mixture of alcohol, alkali and water, and the initial crystal seed with particle size of 5-10nm is prepared;(2) with the lye with pH as 8-11 as backing liquid, a certain amount of inorganic acid, organic acid or inorganic acid ammonium, organic acid ammonium is added in backing liquid one or several, and the above-mentioned crystal seed solution is used as silicon source, and is fed at a certain feed rate, secondary growth can be carried out, and the silica sol with protruding structure on surface can be prepared.The application provides a kind of simple preparation silica sol method for regulating and controlling the protruding morphology of particle surface.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation, specifically relating to an ultra-high purity silica sol with a surface protrusion structure, its preparation method, and its application in semiconductor CMP polishing. Background Technology

[0002] Silica sol is a colloidal substance obtained by dispersing silica particles in water or other solvents. It is widely used in industries such as papermaking, catalysts, casting, and coatings. In recent years, silica sol has been widely used in the semiconductor industry. The entire semiconductor chip manufacturing process requires dozens of CMP (Chemical Motion Processing) steps, and silica sol is a crucial raw material in CMP polishing slurries. With the development of the semiconductor and information industries, the demand for the quantity and performance of CMP consumables is increasing. As one of the core raw materials of CMP slurry, silica sol also faces higher requirements for its polishing performance and purity.

[0003] Chemical mechanical polishing (CMP) relies on the combined effects of chemicals and machinery. Under certain pressure and in the presence of a polishing slurry, a softened layer is formed under the corrosive medium of the slurry. Abrasive particles in the slurry then grind this softened layer, achieving nanoscale planarization. Therefore, the physical properties of the abrasive, such as particle size, morphology, and hardness, significantly influence the polishing rate. Currently, most commercially available silica sol particles are spherical with relatively smooth surfaces. During polishing, rolling friction occurs, resulting in a lower polishing rate compared to particles using sliding friction.

[0004] Patent JPA 2005060217 prepares a peanut-shaped, ultra-high-purity silica sol with an association degree of 2 by dropwise addition of a mixture of tetramethoxysilane and methanol to a mixture of methanol, ammonia, and water. Compared to spherical particles prepared by the same method, this improves the polishing rate. Patent CN103896287A provides a method for preparing non-spherical silica sol, but the preparation process uses divalent metals and styrene. The introduced metal ions pose a risk of remaining on the surface of the workpiece, which is fatal to semiconductor chip manufacturing. Moreover, the styrene coating on the particle surface is hydrophobic, affecting the storage stability of the silica sol. Patent JP 2006303507A uses quaternary ammonium salts as catalysts to prepare silica sols with a raised surface structure, effectively improving the polishing rate. Summary of the Invention

[0005] To improve the polishing rate of silica sol, this invention innovatively proposes a method for preparing ultra-high purity silica sol with a raised surface structure. The method involves first adding a mixture of alkoxysilane and alcohol dropwise to a mixture of alcohol, water, and an alkaline catalyst to prepare 5-10 nm seed crystals. Then, the seed crystal solution is added dropwise to an alkaline solution to prepare silica sol particles with a raised surface structure.

[0006] Another object of the present invention is to provide such an ultra-high purity silica sol with a raised surface structure.

[0007] Another object of the present invention is to provide applications of such ultra-high purity silica sol with a raised surface structure.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A method for preparing an ultra-high purity silica sol with a surface protrusion structure includes the following steps:

[0010] 1) Preparation of seed crystals: Mix alcohol and deionized water, then adjust the pH with alkali to form a base solution A1. Then, under stirring conditions, add a mixture of alkoxysilane and alcohol as silicon source B1 to the base solution A1 to obtain seed crystal solution B2.

[0011] 2) Secondary growth: Mix alcohol, alkali and water as base solution A2, adjust the pH of A2, add acidic compound to base solution A2, heat base solution A2, and add seed solution B2 from step 1) to base solution A2 as feed under stirring conditions, keeping the liquid level constant during the process. After the feed is completed, continue aging to obtain the initial silica sol.

[0012] 3) Solvent replacement and concentration: The alcohol in the initial silica sol is replaced with ultrapure water and concentrated to 20% or more;

[0013] 4) Filtration: The concentrated silica sol is filtered to remove large particles, resulting in an ultra-high purity silica sol with a surface protrusion structure of more than 20% by mass.

[0014] In some specific implementation schemes, the alkoxysilane mentioned in step 1) is one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, preferably tetramethoxysilane;

[0015] In some specific embodiments, the alcohol is a small molecule alcohol of C1 to C6, preferably one or more of methanol, ethanol, ethylene glycol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, and 1-hexanol, more preferably methanol or ethanol;

[0016] In some specific implementations, the resistivity of the deionized water is above 15 MΩ·cm, such as 15 MΩ·cm, 16 MΩ·cm, 17 MΩ·cm, 18 MΩ·cm, etc., preferably greater than 18 MΩ·cm;

[0017] In some specific implementations, the type of alkali in step 1) is selected from at least one of alkali metal hydroxides, ammonia, organic amines, or guanidine compounds; preferably, 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 ethylenediamine, triethanolamine, and tetramethylammonium hydroxide, and the guanidine compound is selected from at least one of tetramethylguanidine, trimethylguanidine, and guanidine carbonate; more preferably, the alkali catalyst is selected from any one of ammonia, ethylenediamine, or tetramethylammonium hydroxide.

[0018] In some preferred embodiments, the mass ratio of alcohol to water in the base coat A1 in step 1) is 0-10:1, for example 0:1, 1:1, 2:1, 3:1, 3.5:1, 4:1, 5:1, 6:1, 7:1, 7.5:1, 8:1, 9:1, 10:1, etc.; the pH of the base coat A1 is adjusted to 7.5-11 with alkali, for example 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, etc., preferably 9-11.

[0019] In some preferred embodiments, the mass ratio of alcohol to alkoxysilane in the silicon source B1 is between 1:3 and 10:1, for example, 1:3, 1:2, 1:1, 2:1, 2.5:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0020] In some preferred embodiments, the volume ratio of the silicon source B1 to the primer A1 is 1:20-5:1, such as 1:20, 1:15, 1:10, 1:5, 1:1, 2:1, 3:1, 4:1, 5:1, etc.

[0021] In some specific implementations, the stirring conditions in step 1) include a temperature of 10-100℃, such as 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, and 100℃, preferably 10-60℃.

[0022] In some specific implementations, the stirring time in step 1) is 0.5h-3h, for example 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, etc., preferably 0.5-1h; the stirring speed is 100-1000r / min, for example 100r / min, 200r / min, 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min, 900r / min, 1000r / min, etc., preferably 200-500r / min; the feeding time of the silicon source B1 is 10min-10h, for example 10min, 30min, 1h, 1.5h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, preferably 10min-5h.

[0023] In some specific implementations, the type of alkali in step 2) is selected from at least one of alkali metal hydroxides, ammonia, organic amines, or guanidine compounds; preferably, the alkali metal hydroxide is selected from at least one of potassium hydroxide, sodium hydroxide, or lithium hydroxide, the organic amine is selected from at least one of ethylenediamine, triethanolamine, or tetramethylammonium hydroxide, and the guanidine compound is selected from at least one of tetramethylguanidine, trimethylguanidine, or guanidine carbonate; more preferably, the alkali catalyst is selected from ammonia, ethylenediamine, or tetramethylammonium hydroxide; generally, the alkali catalyst used in step (2) is the same as the alkali catalyst used in step (1).

[0024] In some specific implementations, the pH of the base coat A2 in step 2) is between 8 and 11, for example, pH is 8, 9, 10, or 11, preferably between 8 and 10;

[0025] In some specific implementations, the volume ratio of the base solution A2 to the seed solution B2 in step 2) is 1:10-1:1, for example 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, preferably between 1:10 and 1:5.

[0026] In some specific implementations, the acidic compound in step 2) is selected from one or more inorganic acids, organic acids, or their ammonium salts; wherein the organic acid is one or more of formic acid, acetic acid, oxalic acid, malic acid, citric acid, tartaric acid, lactic acid, gluconic acid, ethylenediaminetetraacetic acid, fumaric acid, methanesulfonic acid, etc.; the inorganic acid is one or more of hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, and boric acid; and the ammonium salt is selected from one or more of the inorganic acid or the corresponding inorganic ammonium acid or organic ammonium acid.

[0027] In some specific embodiments, the amount of acidic compound added in step 2) is between 500 ppm and 5 wt% of the mass of the added alkoxysilane converted to silica, for example, 500 ppm, 1000 ppm, 2000 ppm, 5000 ppm, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc., preferably 500 ppm-2 wt%.

[0028] In some specific implementations, the stirring conditions in step 2) include a temperature of 20-100℃, such as 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, and 100℃, preferably 50-90℃; a stirring speed of 200-1000 r / min, such as 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, and 1000 r / min, preferably 200-500 r / min; and a feed rate of the seed solution B2 of 1-10 ml / min, such as 1 ml / min, 2 ml / min, 3 ml / min, 4 ml / min, 5 ml / min, 6 ml / min, 7 ml / min, 8 ml / min, 9 ml / min, and 10 ml / min, preferably 1.5-8 ml / min.

[0029] In some specific implementations, the solvent replacement in step 3) is carried out by heating and replenishing ultrapure water to evaporate and remove the solvent in the water, or by ultrafiltration to replenish ultrapure water and concentrate until the solvent content in the silica sol is reduced to below 200 ppm, preferably below 100 ppm.

[0030] In some specific implementations, the concentration in step 3) is achieved by vacuum heating concentration or ultrafiltration membrane concentration, to concentrate the mass fraction of silica sol to more than 20%.

[0031] In some specific implementations, the filtration in step 4) uses a filter element made of PFA or PP material, employing two-stage or three-stage filtration with a filtration accuracy of 0.2μm-5μm.

[0032] In one specific embodiment, the method for preparing the non-spherical silica sol of the present invention includes, for example, the following steps:

[0033] 1) Preparation of seed crystals: A certain proportion of alcohol and water are mixed, and the pH is adjusted with alkali to form a base solution A1. Then, at a certain temperature and stirring speed, a certain proportion of alkoxysilane and alcohol mixture is used as silicon source B1. B1 is added to the base solution A1 at a certain feed rate to obtain seed crystal solution B2.

[0034] 2) Secondary growth: A mixture of alcohol, alkali and water in a certain proportion is used as the base solution A2. The pH of A2 is adjusted within a certain range. A certain amount of inorganic acid, organic acid, inorganic ammonium acid or organic ammonium acid or one or more of them are added to the base solution. A2 is heated to a certain temperature. B2 is added to A2 at a certain feeding rate under a certain stirring speed. During this process, the liquid level is kept constant. After the addition is completed, the mixture is aged for a certain period of time to obtain the initial silica sol.

[0035] 3) Solvent replacement and concentration: The alcohol in the initial silica sol is replaced with ultrapure water and concentrated to 20% or more;

[0036] 4) Filtration: The concentrated silica sol is filtered to remove large particles, resulting in an ultra-high purity silica sol with a surface protrusion structure of 20% or more by mass.

[0037] On the other hand, the ultra-high purity silica sol prepared by the present invention has a raised structure on its surface and the total gold impurity content is less than 1 ppm.

[0038] Furthermore, the application of silica sol with a raised surface structure prepared by the preparation method described in this invention, or the aforementioned silica sol with a raised surface structure, in the field of semiconductor CMP polishing.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1) The method for preparing ultra-high purity silica sol with a raised surface structure of the present invention firstly prepares 5-10 nm seed crystals by dropping a mixture of alkoxysilane and alcohol into a mixture of alcohol, water and alkaline catalyst, and then drops the seed crystal solution into alkaline water to prepare silica sol particles with a raised surface structure by self-assembly between particles.

[0041] 2) The silica sol particles with raised structures of the present invention can effectively improve the polishing rate. Attached Figure Description

[0042] Figure 1 These are TEM images of the silica sol particles prepared in Example 1 and Comparative Example 1 of the present invention.

[0043] Figure 2 The images show SEM images of the silica sol particles prepared in Example 1 and Comparative Example 1 of this invention.

[0044] Figure 3 These are TEM images of the silica sol particles prepared in Comparative Examples 2 and 3 of this invention. Detailed Implementation

[0045] 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.

[0046] The main raw materials used in the following examples and comparative examples are as follows:

[0047]

[0048] Detection method:

[0049] The test method for solid content is based on HGT 2521-2008 Industrial Silica Sol.

[0050] The secondary particle size of the silica sol particles was measured using a Malvern Zetasizer Nano ZS90 particle size analyzer, and the primary particle size was determined using the BET surface area test method to obtain the specific surface area S. bet The primary particle size is 2727 / S bet The degree of association is the ratio of the secondary particle size to the primary particle size.

[0051] The surface morphology of the silica sol was characterized by TEM and SEM.

[0052] The concentration of metal ions was measured using an Agilent 8900 ICP-MS.

[0053] Example 1

[0054] Take 1500g methanol and 500g water, adjust the pH to 10 with ammonia, and mix thoroughly to obtain solution A1. Take 150g methyl orthosilicate and 50g methanol, mix thoroughly to obtain solution B1. At 50℃, add solution B1 to solution A1 at a feed rate of 5ml / min, and stir at 500r / min. After feeding, continue aging for 1 hour to obtain seed solution B2 with a primary particle size of 5nm. Take 600g water, adjust the pH to 10 with ammonia to obtain base solution A2, add 0.6g citric acid and mix thoroughly. At 80℃, add B2 dropwise to A2 at a rate of 2ml / min, and stir at 500r / min, maintaining a constant liquid level during the process. After feeding, continue aging for 3 hours to obtain the initial silica sol. A constant liquid level heating and concentration method was adopted, with water added and evaporated simultaneously until the methanol content of the silica sol dropped below 1000 ppm. Then, it was concentrated to 20%. After concentration, it was filtered using filter cartridges with 1 μm and 0.5 μm filtration grades to obtain ultra-high purity silica sol with a surface protrusion structure and a total metal ion content of less than 1 ppm.

[0055] Example 2

[0056] Take 1000g methanol and 1000g water, adjust the pH to 9.5 with ammonia, and mix thoroughly to obtain solution A1. Take 150g methyl orthosilicate and 450g methanol, mix thoroughly to obtain solution B1. At 30℃, add solution B1 to solution A1 at a feed rate of 15ml / min, and stir at 300r / min. After feeding, continue aging for 1 hour to obtain seed solution B2 with a primary particle size of 10nm. Take 400g water and 200g methanol, adjust the pH to 9.5 with ammonia to obtain base solution A2, add 0.06g acetic acid and mix thoroughly. Then, at 70℃, add B2 dropwise to A2 at a rate of 4ml / min, and stir at 300r / min, maintaining a constant liquid level during the process. After feeding, continue aging for 3 hours to obtain the initial silica sol. A constant liquid level heating and concentration method was adopted, with water added and evaporated simultaneously until the methanol content of the silica sol dropped below 1000 ppm. Then, it was concentrated to 20%. After concentration, it was filtered using filter cartridges with 1 μm and 0.5 μm filtration grades to obtain ultra-high purity silica sol with a surface protrusion structure and a total metal ion content of less than 1 ppm.

[0057] Example 3

[0058] Take 500g methanol and 1500g water, adjust the pH to 9 with ammonia, and mix thoroughly to obtain solution A1. Take 150g methyl orthosilicate and 750g methanol, mix thoroughly to obtain solution B1. At 40℃, add solution B1 to solution A1 at a feed rate of 22.5ml / min, and stir at 400r / min. After feeding, continue aging for 1 hour to obtain seed solution B2 with a primary particle size of 10nm. Take 300g water and 300g methanol, adjust the pH to 8.5 with ammonia to obtain base solution A2, then add 0.03g malic acid and mix thoroughly. At 60℃, add B2 dropwise to A2 at a rate of 6ml / min, and stir at 400r / min, maintaining a constant liquid level. After feeding, continue aging for 3 hours to obtain the initial silica sol. A constant liquid level heating and concentration method was adopted, with water added and evaporated simultaneously until the methanol content of the silica sol dropped below 1000 ppm. Then, it was concentrated to 20%. After concentration, it was filtered using filter cartridges with 1 μm and 0.5 μm filtration grades to obtain ultra-high purity silica sol with a surface protrusion structure and a total metal ion content of less than 1 ppm.

[0059] Example 4

[0060] Take 2000g of water, adjust its pH to 11 with ammonia, and mix thoroughly to obtain solution A1. Take 150g of methyl orthosilicate and 150g of methanol, mix thoroughly to obtain solution B1. At 35℃, add solution B1 to solution A1 at a feed rate of 7.5ml / min, and stir at 350r / min. After feeding, continue aging for 1 hour to obtain seed solution B2 with a primary particle size of 8nm. Take 600g of water, adjust its pH to 10 with ammonia to obtain base solution A2, then add 1.2g of formic acid and mix thoroughly. At 90℃, add B2 dropwise to A2 at a rate of 1.5ml / min, and stir at 350r / min, maintaining a constant liquid level during the process. After feeding, continue aging for 3 hours to obtain the initial silica sol. A constant liquid level heating and concentration method was adopted, with water added and evaporated simultaneously until the methanol content of the silica sol dropped below 1000 ppm. Then, it was concentrated to 20%. After concentration, it was filtered using filter cartridges with 1 μm and 0.5 μm filtration grades to obtain ultra-high purity silica sol with a surface protrusion structure and a total metal ion content of less than 1 ppm.

[0061] Example 5

[0062] Take 1000g of ethanol and 1000g of water, adjust the pH to 11 with tetramethylammonium hydroxide, and mix thoroughly to obtain solution A1. Take 100g of tetraethyl orthosilicate and 1000g of ethanol, mix thoroughly to obtain solution B1. At 50℃, add solution B1 to solution A1 at a feed rate of 2ml / min, and stir at 500r / min. After feeding, continue aging for 1 hour to obtain seed solution B2 with a primary particle size of 10nm. Take 600g of water, adjust the pH to 8.5 with tetramethylammonium hydroxide to obtain solution A2, then add 0.8g of malic acid and mix thoroughly. At 90℃, add B2 dropwise to A2 at a rate of 8ml / min, and stir at 500r / min, maintaining a constant liquid level during the process. After feeding, continue aging for 3 hours to obtain the initial silica sol. A constant liquid level heating and concentration method was adopted, with water added and evaporated simultaneously until the ethanol content of the silica sol dropped below 1000 ppm. Then, it was concentrated to 20%. After concentration, it was filtered using filter cartridges with 1 μm and 0.5 μm filtration grades to obtain ultra-high purity silica sol with a surface protrusion structure and a total metal ion content of less than 1 ppm.

[0063] Comparative Example 1

[0064] Take 1500g methanol and 500g water, adjust the pH to 10 with ammonia, and mix thoroughly to obtain solution A1. Take 50g methyl orthosilicate and 150g methanol, mix thoroughly to obtain solution B1. At 25℃, add solution B1 to solution A1 at a feed rate of 5ml / min, and stir at 500r / min. After feeding, continue aging for 1 hour to obtain an initial silica sol with a secondary particle size of 70nm. Use a constant liquid level heating concentration method, adding water while evaporating, until the methanol content of the silica sol drops below 1000ppm. Then concentrate to 20%. After concentration, filter using 1μm and 0.5μm filter cartridges to obtain an ultra-high purity silica sol with a smooth surface and no protruding structure, containing less than 1ppm of total metal ions.

[0065] Comparative Example 2

[0066] Take 1500g methanol and 500g water, adjust the pH to 10 with ammonia, and mix thoroughly to obtain solution A1. Take 150g methyl orthosilicate and 50g methanol, mix thoroughly to obtain solution B1. At 50℃, add solution B1 to solution A1 at a feed rate of 5ml / min, and stir at 500r / min. After feeding, continue aging for 1 hour to obtain seed solution B2 with a particle size of 10nm. Take 600g water, adjust the pH to 10 with ammonia to obtain base solution A2. At 80℃, add B2 dropwise to A2 at a rate of 2ml / min, and stir at 500r / min, maintaining a constant liquid level. After feeding, continue aging for 3 hours to obtain the initial silica sol. A constant liquid level heating and concentration method was adopted, with water added and evaporated simultaneously until the methanol content of the silica sol dropped below 1000 ppm. Then, it was concentrated to 20%. After concentration, it was filtered using filter cartridges with 1 μm and 0.5 μm filtration grades. The resulting silica sol particles had a smaller particle size and no surface protrusion structure compared to the surface.

[0067] Comparative Example 3

[0068] Take 1500g methanol and 500g water, adjust the pH to 10 with ammonia, and mix thoroughly to obtain solution A1. Take 150g methyl orthosilicate and 50g methanol, mix thoroughly to obtain solution B1. At 50℃, add solution B1 to solution A1 at a feed rate of 5ml / min, stirring at 500r / min. After feeding, continue aging for 1 hour to obtain seed solution B2 with a primary particle size of [specific value missing]. Use B2 as a base solution and add 0.6g citric acid, mixing thoroughly. Take 600g water, adjust the pH to 10 with ammonia to obtain solution A2. At 80℃, add A2 dropwise to B2 at a rate of 2ml / min, stirring at 500r / min, maintaining a constant liquid level during this process. After feeding, continue aging for 3 hours to obtain the initial silica sol. A constant liquid level heating concentration method was adopted, with water added and evaporated simultaneously until the methanol content of the silica sol dropped below 1000 ppm. Then, it was concentrated to 20%. After concentration, it was filtered using filter cartridges with 1 μm and 0.5 μm filtration grades. The resulting silica sol particles had no protruding structures on their surface.

[0069] The metal impurity content of the silica sol prepared in the embodiments of the present invention is shown in the table below:

[0070] Na / ppb K / ppb Ca / ppb Mg / ppb Fe / ppb Al / ppb Example 1 55 35 29 11 2 0.3 Example 2 62 37 25 15 3 0.7 Example 3 47 31 35 17 5 0.6 Example 4 70 29 32 16 4 0.9 Example 5 54 30 27 17 1 1

[0071] The only difference between Comparative Example 1 and Example 1 is the preparation process. Comparative Example 1 does not involve a secondary growth process. Figure 1 and Figure 2 It can be seen that there is a more obvious contrast change on the surface of the particles in Example 1, while the particle surface in Comparative Example 1 is relatively smooth. The only difference between Comparative Example 2 and Example 1 is that no organic acid is added during the growth process in Comparative Example 2. Due to the absence of organic acid, there is a greater repulsive force on the surface of the small particles, and the probability of contact between particles is small. Therefore, the primary particle size of the silica sol prepared in Comparative Example 2 is less different from the particle size of its seed crystal particles. The only difference between Comparative Example 3 and Example 1 is that Example 1 uses an alkaline solution as the base solution and a seed crystal solution as the silicon source, while Comparative Example 3 uses a seed crystal solution as the base solution and an alkaline aqueous solution as an additive, such as... Figure 3 As shown, it is also impossible to obtain silica sol with a raised surface structure.

[0072] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for producing an ultra-high purity silica sol having a surface with a convex structure, characterized by comprising the steps of: The method comprises the following steps: ​ 1) Preparation of seed crystals: mixing alcohol and deionized water, then adjusting pH with a base as a primer A1, then under stirring conditions, mixing alkoxy silane and alcohol as a silicon source B1, feeding silicon source B1 into primer A1 to obtain seed crystal solution B2; 2) Secondary growth: mixing alcohol, base and water as a primer A2, adjusting pH of A2, adding an acidic compound into primer A2, heating primer A2, under stirring conditions, feeding seed crystal solution B2 of step 1) into primer A2, maintaining constant liquid level during the feeding, after the feeding, continuing aging to obtain initial silica sol; the acidic compound is selected from organic acids; 3) Solvent replacement and concentration: replacing alcohol in the initial silica sol with ultrapure water, and concentrating the initial silica sol to 20% or above; 4) Filtration: removing large particles from the concentrated silica sol by filtration to obtain ultrahigh-purity silica sol with a mass fraction of 20% or above and protruding structures on the surface.

2. The production method according to claim 1, characterized by, The alkoxy silane in step 1) is one or more of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane; and / or The alcohol is a small molecule alcohol with a carbon number of 1-6; and / or The deionized water has a resistivity of 15 MΩ·cm or above; and / or The base is at least one of alkali metal hydroxides, aqueous ammonia, organic amines or guanidines.

3. The production method according to claim 2, characterized by, The alkoxy silane in step 1) is tetramethoxysilane; and / or The alcohol is one or more of methanol, ethanol, ethylene glycol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol and 1-hexanol; and / or The deionized water has a resistivity of 18 MΩ·cm or above; and / or The alkali metal hydroxide is at least one of potassium hydroxide, sodium hydroxide and lithium hydroxide, the organic amine is at least one of ethylenediamine, triethanolamine and tetramethylammonium hydroxide, and the guanidine compound is at least one of tetramethylguanidine, trimethylguanidine and guanidine carbonate.

4. The production method according to claim 3, characterized by, The alcohol is methanol or ethanol; and / or The base is at least one of aqueous ammonia, ethylenediamine and tetramethylammonium hydroxide.

5. The method of any one of claims 2 to 4, wherein the method further comprises, The mass ratio of alcohol to water in the primer A1 of step 1) is 0-10:1, and the pH is adjusted to 7.5-11 with a base; and / or The mass ratio of alcohol to alkoxy silane in the silicon source B1 is 1:3-10:

1.

6. The production method according to claim 5, wherein The mass ratio of alcohol to water in the primer A1 of step 1) is 0-5:1, and the pH is adjusted to 9-11 with a base.

7. The preparation method according to claim 5, characterized in that, The volume ratio of the silicon source B1 to the primer A1 is 1:20-5:

1.

8. The method of claim 1, wherein, The stirring conditions in step 1) are as follows: the temperature is 10-100℃, the stirring time is 0.5h-3h, and the stirring speed is 200-1000r / min; and / or The feeding time of the silicon source B1 in step 1) is 10min-10h.

9. The method of claim 1, wherein, The stirring conditions in step 1) are as follows: the temperature is 10-60℃, the stirring time is 0.5-1h, and the stirring speed is 200-500r / min; and / or The feeding time of the silicon source B1 in step 1) is 10min-5h.

10. The method of claim 1, wherein, The base in step 2) is selected from at least one of alkali hydroxide, ammonia, organic amine or guanidine compound.

11. The method of claim 10, wherein, The alkali hydroxide is selected from at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide; and / or The organic amine is selected from at least one of ethylenediamine, triethanolamine, tetramethylammonium hydroxide; and / or The guanidine compound is selected from at least one of tetramethylguanidine, trimethylguanidine, guanidine carbonate.

12. The method of claim 11, wherein, The base is selected from any one of ammonia, ethylenediamine or tetramethylammonium hydroxide.

13. The method of claim 12, wherein, The pH of the primer solution A2 in step 2) is between 8-11; and / or The volume ratio of the primer solution A2 to the seed solution B2 in step 2) is 1:10-1:

1. The pH of the primer solution A2 in step 2) is between 8-10; and / or 14. The method of claim 1, wherein, The volume ratio of the primer solution A2 to the seed solution B2 in step 2) is 1:10-1:

5. The organic acid in step 2) is selected from one or more of formic acid, acetic acid, oxalic acid, malic acid, citric acid, tartaric acid, lactic acid, gluconic acid, ethylenediaminetetraacetic acid, fumaric acid, methanesulfonic acid.

15. The method of claim 1, wherein, The amount of the acidic compound added is 500ppm-5wt% of the mass of the added alkoxysilane converted into silicon dioxide.

16. The method of claim 15, wherein, The amount of the acidic compound added is 500ppm-2wt% of the mass of the added alkoxysilane converted into silicon dioxide.

17. The method of claim 16, wherein the method further comprises, The stirring condition in step 2) is at a temperature of 20-100℃, a stirring speed of 200-1000r / min, and a feeding speed of the seed solution B2 of 1-10ml / min.

18. The method of claim 15, wherein, The stirring condition is at a temperature of 50-90℃, a stirring speed of 200-500r / min, and a feeding speed of the seed solution B2 of 1.5-8ml / min.

19. The method of claim 18, wherein, In step 3), the solvent replacement is performed by heating and supplementing ultrapure water, or evaporating to remove the solvent in water, or 20. The method of claim 1, wherein, In step 3), the solvent replacement is performed by supplementing ultrapure water while concentrating by ultrafiltration until the solvent content in the silica sol is reduced to below 200ppm. In step 3), the solvent replacement is performed by supplementing ultrapure water while concentrating by ultrafiltration until the solvent content in the silica sol is reduced to below 100ppm.

21. The method of claim 20, wherein, In step 3), the concentration is performed by vacuum heating and concentration or ultrafiltration membrane concentration to concentrate the mass fraction of the silica sol to above 20%.

22. The preparation method according to claim 20, characterized in that, In step 4), the filtration is performed by using a filter core made of PFA or PP material, and using two-stage or three-stage filtration with a filtration precision of 0.1-5μm.

23. The method of claim 1, wherein, 24. The ultra-high purity silica sol with protruding structures on the surface prepared by the preparation method of any one of claims 1-23. The total metal impurity content is less than 1ppm.

25. The ultra-high purity silica sol with a surface having a relief structure according to claim 24, characterized in that 26. The use of the ultra-high purity silica sol with protruding structures on the surface prepared by the preparation method of any one of claims 1-23 or the ultra-high purity silica sol with protruding structures on the surface of claim 24 or claim 25 in CMP polishing. ​

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