Ultrahigh-purity silica sol with controllable morphology as well as preparation method and application thereof

Abstract

The invention relates to a preparation method and application of shape-controllable ultra-pure silica sol, the preparation method adopts an alkoxy silane hydrolysis method, carbonyl derivatives are utilized to control the shape of hydrolysis monomers, and then the preparation of the silica sol is further completed under the catalytic action of a catalyst. And finally, performing operations such as solvent concentration and replacement, filtration and the like to obtain the ultra-pure silica sol with the mass fraction of 5-30% and controllable morphology. The total metal impurity content of the ultra-high-purity silica sol is less than 1ppm, and the ultra-high-purity silica sol is stable in property and high in batch repetition stability.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of nanomaterials, and particularly relates to a method for preparing a super-high-purity silica sol with controllable morphology based on hydrolysis of alkoxysilane and its application. Background Art

[0002] Silica sol is a dispersion of nanoscale silicon dioxide particles in water or a solvent, and is currently widely used in the fields of papermaking, casting, coating, catalysts, and CMP (chemical mechanical polishing). In recent years, with the continuous development of semiconductor technology, silica sol plays an increasingly important role in the CMP field. It is of crucial significance to specifically regulate the morphology of silica sol particles to adapt to different polishing occasions and meet different polishing requirements. In addition, the polishing process of semiconductor and other electronic devices with increasing processes also puts forward higher purity requirements for silica sol abrasives. If there are metal impurities in the silica sol, it may cause metal diffusion into the silicon wafer or electronic device, resulting in short circuits and the failure of the entire device. Therefore, there are strict requirements for the content of metal impurities in the silica sol applied to the CMP field.

[0003] Currently, the commonly used methods for preparing silica sol include elemental silicon hydrolysis method, ion exchange method, and alkoxysilane hydrolysis (Stober preparation method), etc. The elemental silicon hydrolysis method uses elemental silicon and water as reactants under the action of strong alkali, usually obtaining spherical silica sol particles. In addition, the silica sol prepared by this method has a relatively high hardness and is extremely easy to cause scratches during the polishing process, and is not suitable for high-process polishing in electronic devices. The ion exchange method mainly uses water glass as a raw material, and it is difficult to obtain super-high-purity silica sol due to the process.

[0004] The alkoxysilane hydrolysis method (Stober preparation method) is to react alkoxysilane as a monomer with water in the presence of an alkali catalyst to obtain silicic acid, and then carry out condensation and particle growth. This method has a large research space in terms of particle morphology control. In addition, the product purity under this method is directly related to the purity of the raw materials and equipment used in the preparation process, and no other impurity metal ions will be introduced. Therefore, it is a relatively mature process for preparing super-high-purity silica sol at present.

[0005] The Stober preparation method is generally also commonly used to prepare spherical particles. Although different-shaped particles can also be obtained by regulating the reactant ratio and parameters, the morphology controllability is poor and the proportion of spherical particles is large. CN101495409A can prepare silica sol with different morphologies by strictly controlling the concentrations of reactants and catalysts in the reaction system and the addition rate of reaction raw materials. However, the parameter control of the whole process is relatively difficult, especially in industrial production, there is an obvious amplification effect, and the batch-to-batch stability is difficult to control, which is not conducive to the downstream CMP application. Summary of the Invention

[0006] In view of the deficiencies existing in the existing Stober preparation method, the present invention innovatively proposes a method for preparing ultra-high-purity silica sol with controllable morphology. Different types of carbonyl derivatives are used to control the morphology of hydrolysis monomers, and then the monomer condensation is controlled under the action of a catalyst, thereby preparing silica sol with controllable morphology. The batch-to-batch stability of the prepared particle morphology is good, and the scale-up effect is small.

[0007] Another object of the present invention is to provide an ultra-high-purity silica sol product prepared by the foregoing preparation method, the metal impurity content of which is less than 1 ppm.

[0008] Another object of the present invention is to provide the application of this ultra-high-purity silica sol in the field of semiconductor CMP polishing.

[0009] To achieve the above invention objects, the present invention adopts the following technical solutions:

[0010] A method for preparing ultra-high-purity silica sol with controllable morphology, comprising the following steps:

[0011] 1) Prepare solution A: Mix water and an alkali catalyst evenly.

[0012] 2) Prepare solution B: Uniformly mix an optional organic solvent, an alkoxysilane and water, then add a carbonyl derivative, and stir and mix evenly at a certain temperature.

[0013] 3) Prepare the initial silica sol: At a certain temperature, drop solution B into solution A which is being stirred, and obtain the initial silica sol after reacting for a period of time.

[0014] 4) Concentrate the initial silica sol, and then replace it with an aqueous system to obtain an aqueous silica sol with a mass fraction of 5-30%.

[0015] 5) Filter the concentrated aqueous silica sol to remove large particles and a small amount of metal impurities to obtain ultra-high-purity silica sol.

[0016] In the present invention, the water described in steps 1) and 2) is ultrapure water, and the resistivity of the ultrapure water is ≥10 MΩ·cm, preferably the resistivity is ≥18.2 MΩ·cm.

[0017] In the present invention, the alkali catalyst used in step 1) is selected from at least one of alkali metal hydroxides, organic bases, and ammonia water; preferably, the alkali metal oxides are selected from at least one of sodium hydroxide, potassium hydroxide, lithium hydroxide, etc., and the organic bases are selected from at least one of ethylenediamine, diisopropylamine, triethanolamine, tetramethylammonium hydroxide, trimethylguanidine, tetramethylguanidine, etc.; more preferably, the alkali catalyst is selected from at least one of ammonia water, diisopropylamine or tetramethylammonium hydroxide.

[0018] In the present invention, the mass fraction of water in the liquid A in step 1) is 95% - 99.5%, and the mass fraction of the base catalyst is 0.5% - 5%.

[0019] In the present invention, the organic solvent in step 2) is one or more of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, acetonitrile, and methyl tert-butyl ether, preferably methanol or ethanol.

[0020] In the present invention, the alkoxysilane used in step 2) is one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, preferably tetramethoxysilane.

[0021] In the present invention, the carbonyl derivatives used in step 2) are selected from at least one of amide compounds, ester compounds, and acid anhydride compounds; preferably, the amide compounds are selected from at least one of acetamide, propionamide, butyramide, isobutyramide, and benzamide, the ester compounds are selected from at least one of methyl formate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, and methyl benzoate, and the acid anhydride compounds are selected from at least one of formic anhydride, acetic anhydride, and phthalic anhydride; more preferably, the carbonyl compounds are selected from any one of propionamide, methyl acetate, and acetic anhydride.

[0022] In the present invention, different types of carbonyl derivatives have the following effects in morphology regulation: different types of carbonyl derivatives can react with the hydroxyl groups of silicic acid under different conditions, and carbonyl derivatives with different structures will produce different monomer structures with silicic acid, resulting in different morphologies during subsequent regrowth; after reaction with silicic acid monomers, amide compounds, ester compounds, or acid anhydride compounds can respectively produce small molecules with different properties such as ammonia, esters, or carboxylic acids, which will affect the hydrolysis and condensation rates of monomers in the system to different degrees, thereby resulting in different morphologies; differences in carbonyl derivatives will affect the pH of the system, thereby regulating the morphology of silica sol; finally, the carbonyl derivatives modified on the silicon surface have lone pairs of electrons, which can interact with silicon hydroxyl groups through hydrogen bonds to control the morphology of hydrolysis monomers. In addition, the steric hindrance of their own alkyl chains also plays a role in stabilizing the morphology of silica sol.

[0023] In the present invention, the mass fraction of the organic solvent in step 2) is 0 - 20%, and the molar ratio of alkoxysilane to water is less than 1:4, preferably 1:8 - 1:16.

[0024] In the present invention, the molar ratio of the carbonyl derivatives to alkoxysilane in step 2) is 1:20 - 1:200, preferably 1:20 - 1:100; the stirring time is 30 - 120 min, and the stirring temperature is 25 - 55 °C.

[0025] In some preferred embodiments, when the temperature is 25 - 35°C, the stirring time is 30 - 60 min, and a carbonyl derivative is used as an amide compound, it is beneficial to form spherical particles; when the temperature is 35 - 45°C, the stirring time is 60 - 90 min, and a carbonyl derivative is used as an ester compound, it is beneficial to form peanut-shaped particles; when the temperature is 45 - 55°C, the stirring time is 90 - 120 min, and a carbonyl derivative is used as an acid anhydride compound, it is beneficial to form heart-shaped, trimeric or long-chain-shaped particles.

[0026] In the present invention, for the preparation of the initial silica sol in step 3), the reaction temperature is between 25 - 60°C, preferably between 25 - 40°C; the liquid B is added dropwise to the liquid A, the dropping time is 0.1 min - 60 min, preferably 0.1 min - 10 min, the stirring speed is 200 r / min - 1000 r / min, and the reaction time is 0.5 h - 5 h.

[0027] In the present invention, the concentration method adopted in step 4) is heating concentration under a vacuum condition of 5 kPa - 50 kPa or ultrafiltration membrane concentration; the replacement method is to replace while adding water, the pressure is 10 - 101 kPa, preferably 60 - 101 kPa, and the temperature during replacement is 80 - 150°C, preferably 130 - 140°C.

[0028] In the present invention, the filter element material used during filtration in step 5) is PTFE, PFA or nylon material; the filtration is carried out in two-stage, three-stage or four-stage filtration, preferably three-stage filtration.

[0029] On the other hand, the present invention provides a morphology-controllable ultra-high purity silica sol prepared by the method for preparing a morphology-controllable ultra-high purity silica sol described above. The morphology of the prepared silica sol is spherical, peanut-shaped, heart-shaped, trimeric or long-chain-shaped, and the total metal ion content is less than 1 ppm.

[0030] On yet another aspect, the present invention further provides the application of the aforementioned morphology-controllable ultra-high purity silica sol in chemical mechanical polishing (CMP).

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention innovatively proposes a method for preparing a morphology-controllable ultra-high purity silica sol. Different types of carbonyl derivatives can be used to prepare silica sols with different morphologies. The batch-to-batch stability of the prepared particle morphology is good, and the scale-up effect is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1TEM images of the silica sols of the examples and comparative examples of the present invention, where a - spherical particles of Example 1, b - peanut-shaped particles of Example 3, c - trimeric or long-chain-shaped particles of Example 6, d - network structure of Comparative Example 1. Detailed implementation manners

[0034] To better understand the technical solution of the present invention, the preparation method of the present invention will be further explained and illustrated by more specific examples below, but it does not constitute any limitation.

[0035] A preparation method of a super-high-purity silica sol with controllable morphology, comprising the following steps:

[0036] 1) Prepare solution A: Mix water and an alkali catalyst evenly in a certain proportion;

[0037] 2) Prepare solution B: Uniformly mix the selected organic solvent, alkoxysilane and water in a certain proportion, then add a certain amount of carbonyl derivatives, and stir and mix evenly at a certain temperature;

[0038] 3) Prepare the initial silica sol: Drop solution B into the stirring solution A at a certain temperature, and obtain the initial silica sol after reacting for a period of time;

[0039] 4) Concentrate the initial silica sol, and then continuously replace it with a water system to obtain an aqueous silica sol with a mass fraction of 5 - 30%;

[0040] 5) Filter the concentrated aqueous silica sol to remove large particles and a small amount of metal impurities to obtain a super-high-purity silica sol.

[0041] The water used in steps 1) and 2) is ultrapure water, for example, prepared by a Mili-Q direct water purifier, for example, including but not limited to resistivity of 10 MΩ·cm, 11 MΩ·cm, 12 MΩ·cm, 13 MΩ·cm, 14 MΩ·cm, 15 MΩ·cm, 16 MΩ·cm, 17 MΩ·cm, 18 MΩ·cm, 19 MΩ·cm, 20 MΩ·cm, preferably with a resistivity ≥ 18.2 MΩ·cm.

[0042] The alkali catalyst used in step 1) is sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water or an organic base, such as one or several of ethylenediamine, diisopropylamine, triethanolamine, tetramethylammonium hydroxide, trimethylguanidine, tetramethylguanidine, preferably ammonia water, diisopropylamine or tetramethylammonium hydroxide. The mass fraction of the alkali catalyst is 0.5% - 5%, for example, 1%, 2%, 3%, 4%, 5%, etc., and the rest is ultrapure water.

[0043] The organic solvent used in step 2) is one or more of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, acetonitrile, and methyl tert-butyl ether, preferably methanol or ethanol, with a mass fraction of 0-20%, such as 0, 1%, 3%, 5%, 8%, 10%, 12%, 15%, 17%, 20%, etc. The alkoxysilane used is one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, preferably tetramethoxysilane. The molar ratio of the alkoxysilane to water is less than 1:4, such as 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:16, 1:18, 1:20, etc., preferably 1:8-1:16.

[0044] In step 2), the carbonyl derivatives used are selected from at least one of amide compounds, ester compounds, and acid anhydride compounds; preferably, the amide compounds are selected from at least one of acetamide, propionamide, butyramide, isobutyramide, and benzamide, the ester compounds are selected from at least one of methyl formate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, and methyl benzoate, and the acid anhydride compounds are selected from at least one of formic anhydride, acetic anhydride, and phthalic anhydride; more preferably, the carbonyl compounds are selected from propionamide, methyl acetate, and acetic anhydride.

[0045] In step 2), by adjusting the dosage of the carbonyl derivatives, as well as the stirring hydrolysis time and temperature, silica sol particles with controllable morphology can be obtained. The molar ratio of the carbonyl derivatives to the alkoxysilane is 1:20-1:200, such as 1:30, 1:50, 1:60, 1:80, 1:100, 1:125, 1:150, 1:180, 1:200, etc., preferably 1:20-1:100; the stirring time is 30-120 min, such as 35 min, 40 min, 50 min, 55 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc., and the stirring temperature is 25-55 °C, such as 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, etc. Preferably, when the temperature is 25-35 °C and the stirring time is 30-60 min, and the carbonyl derivatives used are amide compounds, it is beneficial to generate spherical particles; when the temperature is 35-45 °C and the stirring time is 60-90 min, and the carbonyl derivatives used are ester compounds, it is beneficial to generate peanut-shaped particles; when the temperature is 45-55 °C and the stirring time is 90-120 min, and the carbonyl derivatives used are acid anhydride compounds, it is beneficial to generate heart-shaped, trimeric, or long-chain-shaped particles.

[0046] In step 3) for the preparation of the initial silica sol, the reaction temperature is between 25 - 60°C, including but not limited to 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, preferably between 25 - 40°C; at this temperature, the liquid B is added dropwise to the liquid A, and the dropping time is 0.1 min - 60 min, such as including but not limited to 0.1 min, 1 min, 3 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, preferably 0.1 min - 10 min; the stirring speed is 200 r / min - 1000 r / min, such as including but not limited to 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min; the reaction time is 0.5 h - 5 h, such as including but not limited to 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h.

[0047] In step 4), the concentration method used is heating concentration or ultrafiltration membrane concentration under a vacuum condition of 5 kPa - 50 kPa. The methods of vacuum heating concentration and membrane concentration can refer to the prior art and are well-known to those skilled in the art. The replacement method is to replace while adding water, and the pressure is 10 - 101 kPa, such as 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, 100 kPa, etc., preferably 60 - 101 kPa, and the temperature during replacement is 80 - 150°C, such as 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., preferably 130 - 140°C.

[0048] In step 5), the filter element material used for filtration is PTFE, PFA or nylon material; the filtration adopts 2 - stage, 3 - stage or 4 - stage filtration, preferably 3 - stage filtration. The morphology of the silica sol obtained after filtration is spherical, peanut - shaped, heart - shaped, trimeric or long - chain shape, and the total metal ion content is less than 1 ppm.

[0049] The preparation method of the present invention will be further explained and illustrated through more specific examples below, but it does not constitute any limitation.

[0050] The main raw materials used in the following examples and comparative examples are as follows:

[0051]

[0052]

[0053] Detection method:

[0054] The test method for solid content refers to HG / T 2521-2008 Industrial silica sol.

[0055] The concentration of metal ions was tested by Agilent 7900 ICP-MS.

[0056] The apparent morphology of the silica sol was characterized by TEM images taken by JEOL JEM2100plus.

[0057] Example 1

[0058] 7.01 g of ammonia water was mixed with 167.99 g of water and stirred evenly to obtain solution A. 5.61 g of methanol, 15.22 g of tetramethoxysilane and 7.21 g of water were evenly mixed, 0.0365 g of propionamide was added under microwave irradiation, and then stirred at 25 °C for 30 min to obtain solution B. Solution B was added dropwise to solution A using a peristaltic pump, and the addition was completed in 10 min. Subsequently, the reaction was continued at 25 °C and 200 r / min for 3 h to obtain the initial silica sol. The initial silica sol was concentrated under reduced pressure and heated at 5 kPa and 80 °C until it was concentrated to about 30% to obtain the concentrated silica sol. Then, it was evaporated at 130 °C and 101 kPa while continuously adding ultrapure water using a peristaltic pump until the methanol content in the silica sol was reduced to less than 100 ppm to obtain the aqueous silica sol. Finally, the aqueous silica sol was filtered through 5-μm, 1-μm and 0.3-μm filters in three stages to filter out large particles and a small amount of metal impurities, and an ultrapure silica sol with spherical particle morphology and total metal ion content less than 1 ppm was obtained. The content of some metal impurities is shown in Table 1.

[0059] Example 2

[0060] 0.84 g of tetramethylammonium hydroxide was mixed with 167.99 g of water and stirred evenly to obtain solution A. 5.61 g of ethanol, 15.22 g of tetramethoxysilane and 7.21 g of water were evenly mixed, 0.0365 g of propionamide was added under microwave irradiation, and then stirred at 30 °C for 45 min to obtain solution B. Solution B was added dropwise to solution A using a peristaltic pump, and the addition was completed in 5 min. Subsequently, the reaction was continued at 30 °C and 300 r / min for 0.5 h to obtain the initial silica sol. The initial silica sol was concentrated under reduced pressure and heated at 50 kPa and 100 °C until it was concentrated to about 30% to obtain the concentrated silica sol. Then, it was evaporated at 80 °C and 10 kPa while continuously adding ultrapure water using a peristaltic pump until the methanol content in the silica sol was reduced to less than 100 ppm to obtain the aqueous silica sol. Finally, the aqueous silica sol was filtered through 5-μm, 1-μm and 0.3-μm filters in three stages to filter out large particles and a small amount of metal impurities, and an ultrapure silica sol with spherical particle morphology and total metal ion content less than 1 ppm was obtained. The content of some metal impurities is shown in Table 1.

[0061] Example 3

[0062] Mix 7.01 g of ammonia water and 167.99 g of water and stir evenly to obtain Solution A. Mix 3.29 g of methanol, 15.22 g of tetramethoxysilane and 14.42 g of water evenly, add 0.074 g of methyl acetate under microwave irradiation, and then stir at 35 °C for 60 min to obtain Solution B. Drop Solution B into Solution A with a peristaltic pump, finish dropping in 30 min, and then continue to react at 35 °C and 400 r / min for 3 h to obtain the initial silica sol. Carry out vacuum heating concentration on the initial silica sol at 5 KPa and 80 °C until it is concentrated to about 20% to obtain the concentrated silica sol, and then continue to evaporate at 130 °C and 101 KPa while adding ultrapure water with a peristaltic pump until the methanol content in the silica sol drops below 100 ppm to obtain the aqueous silica sol. Finally, carry out three-stage filtration on the aqueous silica sol with filters of 5 μm, 1 μm and 0.3 μm to filter out large particles and a small amount of metal impurities, and obtain an ultra-high purity silica sol with peanut-shaped particles and a total metal ion content of less than 1 ppm. The contents of some metal impurities are shown in Table 1.

[0063] Example 4

[0064] Mix 14.02 g of ammonia water and 55.5 g of water and stir evenly to obtain Solution A. Mix 1.97 g of methanol, 1.32 g of acetonitrile, 15.22 g of tetramethoxysilane and 14.42 g of water evenly, add 0.148 g of methyl acetate under microwave irradiation, and then stir at 35 °C for 60 min to obtain Solution B. Drop Solution B into Solution A with a peristaltic pump, finish dropping in 45 min, and then continue to react at 35 °C and 400 r / min for 3 h to obtain the initial silica sol. Carry out vacuum heating concentration on the initial silica sol at 5 KPa and 80 °C until it is concentrated to about 20% to obtain the concentrated silica sol, and then continue to evaporate at 130 °C and 101 KPa while adding ultrapure water with a peristaltic pump until the methanol content in the silica sol drops below 100 ppm to obtain the aqueous silica sol. Finally, carry out three-stage filtration on the aqueous silica sol with filters of 5 μm, 1 μm and 0.3 μm to filter out large particles and a small amount of metal impurities, and obtain an ultra-high purity silica sol with peanut-shaped particles and a total metal ion content of less than 1 ppm. The contents of some metal impurities are shown in Table 1.

[0065] Example 5

[0066] Mix 7.01 g of ammonia water with 167.99 g of water and stir evenly to obtain Solution A. Mix 2.32 g of methanol, 15.22 g of tetramethoxysilane with 28.84 g of water evenly, add 0.51 g of acetic anhydride under microwave irradiation, and then stir at 45 °C for 90 min to obtain Solution B. Drop Solution B into Solution A with a peristaltic pump, finish dropping in 60 min, and then continue to react at 45 °C and 800 r / min for 3 h to obtain the initial silica sol. Concentrate the initial silica sol under reduced pressure by heating at 5 KPa and 80 °C until it is concentrated to about 20%, obtaining the concentrated silica sol. Then continue to evaporate at 130 °C and 101 KPa while using a peristaltic pump to supplement ultrapure water until the methanol content in the silica sol drops below 100 ppm to obtain the aqueous silica sol. Finally, filter the aqueous silica sol through filters with pore sizes of 5 μm, 1 μm, and 0.3 μm in three stages to filter out large particles and a small amount of metal impurities, obtaining an ultrapure silica sol with a heart-shaped or trimeric particle morphology and a total metal ion content of less than 1 ppm. The content of some metal impurities is shown in Table 1.

[0067] Example 6

[0068] Mix 7.01 g of ammonia water with 167.99 g of water and stir evenly to obtain Solution A. Mix 15.22 g of tetramethoxysilane with 28.84 g of water evenly, add 0.905 g of benzoic anhydride under microwave irradiation, and then stir at 55 °C for 120 min to obtain Solution B. Drop Solution B into Solution A with a peristaltic pump, finish dropping in 60 min, and then continue to react at 60 °C and 1000 r / min for 5 h to obtain the initial silica sol. Concentrate the initial silica sol under reduced pressure by heating at 5 KPa and 80 °C until it is concentrated to about 20%, obtaining the concentrated silica sol. Then continue to evaporate at 150 °C and 101 KPa while using a peristaltic pump to supplement ultrapure water until the methanol content in the silica sol drops below 100 ppm to obtain the aqueous silica sol. Finally, filter the aqueous silica sol through filters with pore sizes of 5 μm, 1 μm, and 0.3 μm in three stages to filter out large particles and a small amount of metal impurities, obtaining an ultrapure silica sol with a trimeric or long-chain particle morphology and a total metal ion content of less than 1 ppm. The content of some metal impurities is shown in Table 1.

[0069] Example 7

[0070] Mix 140.2 g of ammonia water with 3359.8 g of water and stir evenly to obtain Solution A. Mix 65.8 g of methanol, 304.4 g of tetramethoxysilane with 288.4 g of water evenly, add 1.48 g of methyl acetate under microwave irradiation, and then stir at 35 °C for 60 min to obtain Solution B. Use a peristaltic pump to drip Solution B into Solution A, complete the dripping in 30 min, and then continue to react at 35 °C and 400 r / min for 3 h to obtain the initial silica sol. Concentrate the initial silica sol under reduced pressure and heating at 5 KPa and 80 °C until it is concentrated to about 20% to obtain the concentrated silica sol, and then continue to evaporate at 130 °C and 101 KPa while using a peristaltic pump to supplement ultrapure water until the methanol content in the silica sol drops below 100 ppm to obtain the aqueous silica sol. Finally, perform three-stage filtration on the aqueous silica sol using 5 μm, 1 μm, and 0.3 μm filters to filter out large particles and a small amount of metal impurities to obtain an ultrapure silica sol with a peanut-shaped particle morphology and a total metal ion content of less than 1 ppm. The content of some metal impurities is shown in Table 1.

[0071] Comparative Example 1

[0072] Mix 7.01 g of ammonia water with 167.99 g of water and stir evenly to obtain Solution A. Mix 5.61 g of methanol, 15.22 g of tetramethoxysilane with 7.21 g of water evenly, and then stir at 25 °C for 30 min to obtain Solution B. Use a peristaltic pump to drip Solution B into Solution A, complete the dripping in 10 min, and then continue to react at 25 °C and 200 r / min for 3 h to obtain the initial silica sol. Concentrate the initial silica sol under reduced pressure and heating at 5 KPa and 80 °C until it is concentrated to about 30% to obtain the concentrated silica sol, and then continue to evaporate at 130 °C and 101 KPa while using a peristaltic pump to supplement ultrapure water until the methanol content in the silica sol drops below 100 ppm to obtain the aqueous silica sol. Finally, perform three-stage filtration on the aqueous silica sol using 5 μm, 1 μm, and 0.3 μm filters to filter out large particles and a small amount of metal impurities to obtain an ultrapure silica sol with a reticular structure morphology and a total metal ion content of less than 1 ppm. The content of some metal impurities is shown in Table 1.

[0073] Comparative Example 2

[0074] Mix 7.01 g of ammonia water with 167.99 g of water and stir evenly to obtain Solution A. Mix 2.32 g of methanol, 15.22 g of tetramethoxysilane and 28.84 g of water evenly, add 0.96 g of citric acid under microwave irradiation, and then stir at 45 °C for 90 min to obtain Solution B. Use a peristaltic pump to drop Solution B into Solution A, and finish dropping in 60 min. Subsequently, continue the reaction at 45 °C and 800 r / min for 3 h to obtain the initial silica sol. Concentrate the initial silica sol under reduced pressure and heating at 5 KPa and 80 °C until it is concentrated to about 20% to obtain the concentrated silica sol. Then continue to evaporate at 130 °C and 101 KPa while using a peristaltic pump to supplement ultrapure water until the methanol content in the silica sol drops below 100 ppm to obtain the aqueous silica sol. Finally, filter the aqueous silica sol through filters with pore sizes of 5 μm, 1 μm and 0.3 μm in three stages to filter out large particles and a small amount of metal impurities, and obtain an ultrapure silica sol with a multi-polymerized shape and a total metal ion content of less than 1 ppm. The content of some metal impurities is shown in Table 1.

[0075] Comparative Example 3

[0076] Mix 100 g of isopropanol, 7.01 g of ammonia water and 67.99 g of water and stir evenly to obtain Solution A. Mix 5.61 g of isopropanol, 15.22 g of tetramethoxysilane and 7.21 g of water evenly, and then stir at 25 °C for 30 min to obtain Solution B. Use a peristaltic pump to drop Solution B into Solution A, and finish dropping in 10 s. Subsequently, continue the reaction at 25 °C and 200 r / min for 3 h to obtain the initial silica sol. The obtained silica sol shows particle agglomeration, and there are visible micron-sized particles adhering to the inner wall of the beaker or deposited at the bottom of the beaker. The content of some metal impurities in the supernatant is shown in Table 1.

[0077] Figure 1 TEM images of Example 1, Example 3, Example 6 and Comparative Example 1 of the present invention are given, corresponding to a, b, c, d in Figure 1 respectively. It can be seen from the figures that most of the particles in Example 1 are spherical; in Example 3, the majority of the particles are pairwise associated and present a peanut shape; in Example 6, most of the particles are trimeric or long-chain shaped. In Example 7, the reaction scale is enlarged by 20 times, and peanut-shaped silica sol can still be stably prepared. The batch-to-batch stability of the prepared particle morphology is good, and the scale-up effect is small. The difference between Comparative Example 1 and Example 1 is only whether a carbonyl derivative is added to Solution B. The hydrolysis product of the silicon source in Solution B without adding a carbonyl derivative will polymerize excessively to form a network structure, making it difficult to form particles. Compared with Example 5, in Comparative Example 2, when the carbonyl compound used is replaced with citric acid of the same molar amount, only a network structure or polymerized silica sol particles can be obtained, and the effect is not good. Comparative Example 3 uses the traditional method to prepare silica sol, which will cause abnormal particle agglomeration.

[0078] Table 1 shows the partial metal impurity contents of each example and comparative example. It can be seen that the content of each single metal impurity in each example is less than 100 ppb, and the total metal impurity content is less than 1 ppm.

[0079] Partial metal impurity contents in the preparation of colloidal silica in Examples and Comparative Examples in Table 1

[0080] K Na Ca Fe Cu Ni Cr Zn Ti Example 1 74 98 45 24 33 12 5 4 1 Example 2 78 95 48 22 38 14 8 5 2 Example 3 72 90 42 28 32 14 3 8 4 Example 4 84 99 36 26 30 20 9 11 1 Example 5 75 84 39 21 27 13 11 2 <1 Example 6 56 65 22 12 16 8 2 3 8 Example 7 98 88 35 22 39 22 5 8 6 Comparative Example 1 77 85 37 32 26 15 9 13 5 Comparative Example 2 72 76 22 23 33 6 2 15 3 Comparative Example 3 95 97 23 30 35 19 10 11 9

[0081] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. Those skilled in the art can understand that some modifications or adjustments can be made to the present invention under the teaching of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing ultra-high purity silica sol with controllable morphology, characterized in that, it comprises the following steps: 1) Prepare liquid A: Mix water and an alkali catalyst evenly; 2) Prepare liquid B: Evenly mix an optional organic solvent, an alkoxysilane and water, then add a carbonyl derivative, and mix evenly after stirring at a certain temperature; 3) Prepare the initial silica sol: Drop liquid B into the stirring liquid A at a certain temperature, and obtain the initial silica sol after reacting for a period of time; 4) Concentrate the initial silica sol, and then replace it with a water system to obtain an aqueous silica sol with a mass fraction of 5-30%; 5) Filter the concentrated aqueous silica sol to remove large particles and a small amount of metal impurities to obtain ultra-high purity silica sol.

2. The preparation method according to claim 1, characterized in that, the water described in steps 1) and 2) is ultrapure water, and the resistivity of the ultrapure water is ≥10 MΩ·cm, preferably the resistivity is ≥18.2 MΩ·cm.

3. The preparation method according to claim 1 or 2, characterized in that, the alkali catalyst described in step 1) is selected from at least one of alkali metal hydroxides, organic bases, and ammonia water; preferably, the alkali metal hydroxide is selected from at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide; and / or the organic base is selected from at least one of ethylenediamine, diisopropylamine, triethanolamine, tetramethylammonium hydroxide, trimethylguanidine, and tetramethylguanidine; more preferably, the alkali catalyst is selected from at least one of ammonia water, diisopropylamine, or tetramethylammonium hydroxide.

4. The preparation method according to any one of claims 1-3, characterized in that, in liquid A of step 1), the mass fraction of the water is 95%-99.5%, and the mass fraction of the alkali catalyst is 0.5%-5%.

5. The preparation method according to any one of claims 1-4, characterized in that, the organic solvent described in step 2) is selected from one or more of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, acetonitrile, and methyl tert-butyl ether, preferably methanol or ethanol; and / or the alkoxysilane is selected from one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, preferably tetramethoxysilane.

6. The preparation method according to any one of claims 1-5, characterized in that, the carbonyl derivative described in step 2) is selected from at least one of amide compounds, ester compounds, and acid anhydride compounds; preferably, the amide compound is selected from at least one of acetamide, propionamide, butyramide, isobutyramide, and benzamide; and / or the ester compound is selected from at least one of methyl formate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, and methyl benzoate; and / or the acid anhydride compound is selected from at least one of formic anhydride, acetic anhydride, and phthalic anhydride; more preferably, the carbonyl compound is selected from any one of propionamide, methyl acetate, and acetic anhydride.

7. The preparation method according to any one of claims 1-6, characterized in that, in liquid B of step 2), the mass fraction of the organic solvent is 0-20%; and / or The molar ratio of the alkoxysilane to water is less than 1:4, preferably 1:8 - 1:16; and / or The molar ratio of the carbonyl derivative to the alkoxysilane is 1:20 - 1:200, preferably 1:20 - 1:100; and / or The stirring time is 30 - 120 min, and the stirring temperature is 25 - 55 °C; Preferably, the stirring temperature is 25 - 35 °C, the stirring time is 30 - 60 min. When the added carbonyl derivative is an amide compound, spherical particles can be formed; and / or The stirring temperature is 35 - 45 °C, the stirring time is 60 - 90 min. When the added carbonyl derivative is an ester compound, peanut-shaped particles can be formed; and / or The stirring temperature is 45 - 55 °C, the stirring time is 90 - 120 min. When the added carbonyl derivative is an acid anhydride compound, heart-shaped, trimeric or long-chain-shaped particles can be formed.

8. The preparation method according to any one of claims 1 - 7, characterized in that the temperature in step 3) is 25 - 60 °C, preferably 25 - 40 °C; and / or the dropping time for dropping the liquid B into the liquid A is 0.1 min - 60 min, preferably 0.1 min - 10 min, the stirring speed is 200 r / min - 1000 r / min, and the reaction time is 0.5 h - 5 h.

9. The preparation method according to any one of claims 1 - 8, characterized in that the concentration method in step 4) is heating concentration or ultrafiltration membrane concentration under a vacuum condition of 5 kPa - 50 kPa; and / or the replacement method for replacement is replacement while adding water, the pressure is 10 - 101 kPa, preferably 60 - 101 kPa, and the temperature during replacement is 80 - 150 °C, preferably 130 - 140 °C; and / or the filter element material used for filtration in step 5) is any one of PTFE, PFA or nylon materials; preferably, the filtration is carried out in 2 - stage, 3 - stage or 4 - stage filtration, preferably 3 - stage filtration.

10. The ultra-high purity silica sol with controllable morphology prepared by the preparation method according to any one of claims 1 - 9, characterized in that the morphology of the ultra-high purity silica sol is any one of spherical, peanut-shaped, heart-shaped, trimeric or long-chain-shaped, and the total metal ion content is less than 1 ppm.

11. The application of the ultra-high purity silica sol with controllable morphology prepared by the preparation method according to any one of claims 1 - 9 or the ultra-high purity silica sol with controllable morphology according to claim 10 in chemical mechanical polishing (CMP).

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