A dense shaped colloidal silicon dioxide and its preparation method and application

Abstract

The present invention discloses a kind of dense special-shaped ultra-high purity colloidal silica and its preparation method and application. The preparation method comprises the following steps: using traditional Stobre method to obtain initial spherical silica sol, by adjusting different aging time and aging temperature to further assemble it, finally by concentration and solvent replacement, filtering and other subsequent steps to obtain solid content greater than 20wt%, primary particle size between 20nm-150nm, association degree above 1.7, surface silanol accounts for less than 15% of the total silanol, total metal ion content is less than 1ppm of dense special-shaped ultra-high purity silica sol, non-spherical special-shaped particle number accounts for more than 50%. The present invention can realize certain regulation of the final morphology of silica sol, and the internal structure of the obtained silica particles is more dense, and its hardness and rigidity are stronger, which can increase its mechanical action during grinding.

Description

Technical Field

[0001] The invention belongs to the field of nano material preparation, and in particular relates to a dense heteromorphic colloidal silicon dioxide and a preparation method thereof, which can be used in the field of CMP polishing technology. Background Art

[0002] Colloidal silica (silica sol) is a system composed of amorphous silica particles distributed in a liquid medium. Nanostructured silica sols are widely used in various fields, such as adsorbents, catalysts, carriers, coatings, steel, and polishing semiconductor materials. In the semiconductor and electronics fields, silica sol is mainly used in the chemical mechanical polishing (CMP) process of semiconductor devices and is one of the important components of the abrasive in CMP. During the chemical mechanical polishing process, if there are metal impurity ions, the entire semiconductor device may eventually fail due to a short circuit. Therefore, the mandatory requirement for silica sol in the CMP polishing process is the high purity and stability of the product.

[0003] The synthesis of silica sol generally adopts methods such as alkali metal silicate ion exchange, elemental silicon hydrolysis, and alkoxysilane hydrolysis (stober). The ion exchange method is to perform ion exchange on sodium silicate to obtain an active silicic acid solution, and then add it dropwise to the seed solution under heating conditions (using NaOH to adjust the pH of the system) to re-grow particles. This method can obtain particles with a denser structure, but ion exchange contains a large amount of sodium impurities, and removing it requires an additional process, which complicates the entire technology and makes it difficult to meet high purity requirements. The elemental silicon hydrolysis method is to react elemental silicon and water as reactants to obtain silica sol particles, but the silica sol prepared by this method has a higher hardness and is very easy to cause scratches during the polishing process, and is not suitable for subsequent high-process polishing.

[0004] The alkoxysilane hydrolysis method (Stober method) is to hydrolyze tetraalkoxysilane in the presence of an alkaline catalyst while performing condensation and particle growth. In this method, the purity of the product is directly related to the purity of the raw materials and equipment used in the synthesis process, and other impurity metal ions will not be introduced. Therefore, it is currently a relatively mature process for preparing high-purity silica sol.

[0005] In the prior art, it is generally believed that the particles of silica sol obtained by hydrolysis and condensation reaction of alkoxysilane can be divided into spherical and non-spherical shapes, but if the parameters of the synthesis process are not strictly controlled, most of the prepared particles are spherical in shape. In downstream polishing applications, it is found that irregular particles can significantly increase the polishing rate and reduce scratches. And as far as the prior art is concerned, the particles synthesized by the Stober method have a low degree of condensation of silanol groups inside and on the surface, and the density of the particles finally obtained is also low. The hardness of the particles is reduced, the mechanical strength is poor, and it is easy to produce large deformation. If such silica particles with low condensation are used in the CMP process, the abrasive particles are easily destroyed, and even the broken abrasives may be attached to the surface of the wafer, which is difficult to clean and causes defects in the wafer. In addition, in the silica particles with low condensation, a large number of silanol groups remain, the reactive sites increase, and the storage stability deteriorates.

[0006] Patent CN101495409A uses a 3:1 volume ratio of TMOS and methanol as a raw material solution, and mixes methanol, water and ammonia as a reaction solvent. The concentrations of water and ammonia in the reaction solvent are 15wt% and 1wt%, respectively. At 20°C, 1 volume of the raw material solution is added dropwise to 9 volumes of the reaction solvent. After the reaction, a silica sol with a primary particle size of 32.1nm and a secondary particle size of 74.8nm is obtained. By strictly controlling the concentration of reactants and catalysts in the reaction system, as well as the addition rate of the reaction raw materials, silica sols with different association degrees can be prepared, but the whole process parameter control is difficult, especially in industrial production, there is a significant amplification effect, and batch stability is difficult to control, and batch stability is critical to downstream CMP applications. Summary of the invention

[0007] In view of the above problems, the present invention innovatively proposes a method for preparing dense shaped colloidal silica, which can be further assembled by regulating the reaction conditions during the pressurized aging process, and can easily prepare shaped silica particles with good batch stability of particle morphology. The density and mechanical strength of the obtained particles are significantly improved, and due to the enhanced particle stability, the subsequent solvent replacement step does not need to add any dispersant and has a significant stabilizing effect.

[0008] Another object of the present invention is to provide such a dense shaped colloidal silica product.

[0009] Another object of the present invention is to provide application of the dense shaped colloidal silica in CMP.

[0010] In order to achieve the purpose of the above invention, the technical solution adopted by the present invention is as follows:

[0011] The present invention provides a method for preparing dense shaped colloidal silica, comprising the following steps:

[0012] Preparation of spherical silica sol:

[0013] 1) mixing an alkali catalyst and a solvent to obtain a mother liquid;

[0014] 2) mixing alkoxysilane with a solvent to obtain a hydrolyzate of alkoxysilane;

[0015] 3) adding the hydrolyzate of step 2) to the mother solution of step 1), reacting under stirring to obtain spherical colloidal silica;

[0016] Preparation of special-shaped silica sol:

[0017] 4) adding a cationic polymer to the spherical colloidal silica in step 3) and performing an aging treatment to generate dense heteromorphic colloidal silica particles;

[0018] 5) Add water to the system of step 4), then concentrate to a solid content of more than 20 wt% and a pH of 6.5-7.3, and then filter to remove large particles to obtain the dense shaped colloidal silica.

[0019] In the present invention, the base catalyst in step 1) is selected from one or more of alkali metal hydroxides, ammonia water, organic amines, basic amino acids or guanidine compounds; the alkali metal hydroxide is selected from one or more of potassium hydroxide, sodium hydroxide and lithium hydroxide; the organic amines are selected from one or more of ethylenediamine, triethanolamine and tetramethylammonium hydroxide; the basic amino acids are selected from one or more of lysine, arginine and histidine; the guanidine compounds are selected from one or more of tetramethylguanidine, trimethylguanidine and guanidine carbonate; preferably, the base catalyst is selected from one or more of ammonia water (concentration is 25wt%), ethylenediamine and tetramethylammonium hydroxide.

[0020] In the present invention, the solvent in step 1) is selected from water and / or an organic solvent, and the organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, ethyl propyl ether, etc.; preferably ethanol.

[0021] In the present invention, the concentration of the base catalyst in step 1) in the mother liquor is 1-3 wt %.

[0022] In the present invention, the alkoxysilane in step 2) is selected from one or more of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane, preferably tetraethoxysilane.

[0023] In the present invention, the solvent in step 2) is selected from water and / or an organic solvent, and the organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, ethyl propyl ether, etc.; preferably ethanol;

[0024] Preferably, the same solvent as that of step 1) is used in step 2).

[0025] In the present invention, the volume ratio of the alkoxysilane to the solvent in step 2) is 3:1-1:3, preferably 3:1-1:1.

[0026] In the present invention, the volume ratio of the hydrolyzate of step 2) in step 3) to the mother liquor of step 1) is 1:9-1:12;

[0027] Preferably, the hydrolyzate in step 2) is added to the mother solution in step 1) in a continuous manner, preferably in a dropwise manner, and the addition time is 6-600s, preferably 6-300s.

[0028] In the present invention, the reaction is carried out under stirring in step 3), the reaction temperature is 5-100° C., preferably 5-30° C., the reaction time is 0.5-5h, preferably 0.5-3h, and the stirring speed is 200-1000r / min, preferably 600r / min.

[0029] In the present invention, the cationic polymer in step 4) is selected from one or more of cationic polyacrylamide, cationic polyacrylate, quaternary ammonium salt type cationic polymer, and quaternary phosphonium salt type cationic polymer, preferably cationic polyacrylamide;

[0030] The amount of the cationic polymer added is 50-500ppm of the mass of the spherical colloidal silica, preferably 100-300ppm. The present invention adds a cationic polymer as an auxiliary agent during the aging process, which can promote the self-assembly between particles in the whole process. In addition, during the pressurized high-temperature aging process, the cationic polymer can also be adsorbed on the particle surface at high temperature, reducing the electrostatic repulsion between the particles, thereby further condensing the surface and internal hydroxyl groups of the spherical particles, assembling between the particles, and achieving a transition from a spherical shape to a heteromorphic shape. In addition, the process requires further precise regulation of the amount of the additive. If the amount of the additive is too high, further polymerization will occur between the particles, resulting in the occurrence of sedimentation.

[0031] In the present invention, the aging treatment in step 4) adopts a pressurized heat aging method, the aging temperature is 80-220°C, preferably 90-220°C, and more preferably 100-150°C; the aging time is 0.5-6h, preferably 0.5-4h; the aging pressure is 0.18-2Mpa. (It should be noted that the aging is carried out in a closed container, so the aging pressure is determined by the saturated vapor pressure of the solvent system at a given temperature). If the temperature of the pressurized heating treatment is above 100°C, the condensation degree of the silica particles can be increased. If the temperature of the pressurized heating treatment is below 150°C, silica particles can be produced without significantly changing the average primary particle size, average secondary particle size, cv value, and agglomeration ratio, and the dispersion stability of the silica sol is excellent.

[0032] In the present invention, the amount of water added in step 5) is 0.6-3 times the mass of the system, preferably 1.5-2 times.

[0033] In the present invention, the concentration in step 5) is carried out by heating concentration, the temperature is 50-150°C, preferably 90-130°C, and the pressure is 20-101Kpa. Before concentration, a certain amount of water (ultrapure water) is added to the colloidal silica system after aging in step 4), and then the solvent is removed by heating evaporation until the organic solvent content in the silica sol is less than 100ppm. After that, the excess water can be removed by heating evaporation or membrane filtration to increase the solid content to more than 20wt%.

[0034] In the present invention, the filtration in step 5) has a filtration accuracy of 0.2-5 μm, preferably a filter element made of PFA material, and the filtration stage is preferably two-stage or three-stage filtration.

[0035] Another aspect of the present invention provides a dense shaped colloidal silica prepared by the above method, wherein the number of non-spherical shaped particles accounts for more than 50%, preferably more than 70%; the shapes of the shaped particles include peanut-shaped, heart-shaped, silkworm-shaped, curved, etc.;

[0036] The dense shaped colloidal silica has a primary particle size between 20-150 nm, an association degree of more than 1.7, a surface silanol ratio of less than 15% of the total silanol ratio, and a total metal ion content of less than 1 ppm.

[0037] According to another aspect of the present invention, there is provided application of the aforementioned dense shaped colloidal silica in chemical mechanical polishing (CMP).

[0038] Compared with the prior art, the present invention is beneficial in that:

[0039] 1) The present invention creatively proposes for the first time to prepare irregular silica sol particles by a pressurized aging method. The present invention prepares irregular silica particles by regulating the time, pressure, temperature, additives and other conditions during the pressurized aging process, and the batch stability of the particle morphology is good.

[0040] 2) Since the internal hydroxyl groups of the aged particles in the present invention are further condensed, the density, mechanical strength and stability of the obtained particles are greatly improved, and there is no need to add any stabilizer or dispersant to stabilize the particles during the subsequent concentration and solvent replacement process. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 TEM image of colloidal silica particles prepared in Example 1;

[0042] Figure 2 TEM image of colloidal silica particles prepared in Example 6;

[0043] Figure 3 TEM image of colloidal silica particles prepared in Comparative Example 2;

[0044] Figure 4 This is the TEM image of the colloidal silica particles prepared in Comparative Example 3. DETAILED DESCRIPTION

[0045] In order to better understand the technical solution of the present invention, the preparation method of the present invention is further explained below through more specific examples, but it does not constitute any limitation.

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

[0047]

[0048]

[0049] Quaternary phosphonium salt type METR-NIPAA: prepared according to the method disclosed in the document Synthesis of water-soluble thermosensitive polymers having phosphonium groups from methacryloyloxyethyl trialkylPhosphonium chlorides-N-isopropylacrylamide copolymers and their functions.

[0050] Quaternary ammonium salt type (phenylene vinylene) (PPV-NMe 3+): Prepared according to the method disclosed in the document Cationic conjugated polymers for discrimination of microbial pathogens.

[0051] The detection method of the silica particles involved in this embodiment is as follows:

[0052] The test method for solid content refers to HGT 2521-2008 industrial silica sol.

[0053] The secondary particle size of the silica sol particles was measured by a Malvern Zetasizer Nano ZS90 particle size analyzer, and the primary particle size was measured by the BET specific surface area test method to obtain the specific surface area Sbet, and the primary particle size was 2727 / Sbet. The degree of association is the ratio of the secondary particle size to the primary particle size.

[0054] The morphology of silica sol was characterized by TEM.

[0055] The concentration of metal ions was measured using an Agilent 7900 ICP-MS.

[0056] The surface silanol groups are measured by the Sears method (value is x), and the total silanol groups are measured by solid 29Si-DD / MAS-NMR (value is y). The ratio of the silanol groups present on the surface to the total silanol groups is expressed by (x / y)×100%.

[0057] The hardness of silica sol particles was characterized by nanoindentation.

[0058] Example 1

[0059] The steps for preparing dense shaped colloidal silica are as follows:

[0060] 1) 117.75 g of ethanol, 80.13 g of water and 6.12 g (concentration 25 wt%) of aqueous ammonia were mixed and stirred to obtain a mother solution.

[0061] 2) Mix 5 ml (6.34 g) of ethanol and 15 ml (15.96 g) of tetraethoxysilane (TEOS) to obtain a hydrolyzate.

[0062] 3) Using a peristaltic pump, the hydrolyzate from step 2) was added to the mother solution from step 1) at a volume ratio of 1:11.77, and the addition was completed in 20 seconds. The reaction was carried out at 25°C and 600 r / min for 3 hours to obtain spherical colloidal silica.

[0063] 4) The spherical colloidal silica prepared in step 3) is placed in a hydrothermal reactor, 100 ppm of cationic polyacrylamide is added thereto, and pressurized aging is performed at 100° C. and a pressure of 0.22 MPa for 4 hours to generate dense irregular colloidal silica particles.

[0064] 5) In step 4), 0.6 times the mass of ultrapure water is added to the system, and the system is concentrated by heating under reduced pressure at 20 KPa and 80°C to make the ethanol content in the system less than 100 ppm, the solid content is 20 wt%, and the pH is 7.3. Then, two-stage filtration is performed through 1 μm and 0.3 μm PFA filter elements to filter out large particles and obtain dense shaped colloidal silica.

[0065] The dense shaped colloidal silica prepared in this embodiment has non-spherical shaped particles accounting for 68%; the shapes of the shaped particles include peanut shape, heart shape, curved shape, etc.

[0066] The primary particle size is 35 nm, the secondary particle size is 80 nm, the mass concentration is 19.5%, the degree of association is 2.28, the hardness of a single particle is 2.78 Gpa, the proportion of surface silanol groups to total silanol groups is 10%, the total metal ion content is less than 1 ppm, and the content of some metal impurities is shown in Table 1.

[0067] Example 2

[0068] The steps for preparing dense shaped colloidal silica are as follows:

[0069] 1) 117.75 g of ethanol, 80.13 g of water and 4 g (concentration 25 wt%) of aqueous ammonia were mixed and stirred to obtain a mother solution.

[0070] 2) 7 ml (8.8 g) of ethanol and 13 ml (13.83 g) of tetraethoxysilane (TEOS) were mixed uniformly to obtain a hydrolyzate.

[0071] 3) Using a peristaltic pump, the hydrolyzate of step 2) was added to the mother solution of step 1) at a volume ratio of 1:11.66, and the addition was completed in 6 seconds. The reaction was carried out at 40°C and 1000 r / min for 2 hours to obtain spherical colloidal silica.

[0072] 4) The spherical colloidal silica prepared in step 3) is placed in a hydrothermal reactor, 50 ppm of quaternary phosphonium salt type METR-NIPAA is added thereto, and pressurized aging is performed at 140° C. and a pressure of 0.75 MPa for 1 hour to generate dense irregular colloidal silica particles.

[0073] 5) In step 4), add 2 times the mass of ultrapure water to the system, heat and concentrate at normal pressure at 101 KPa and 130°C to make the ethanol content in the system less than 100 ppm, the solid content is 20 wt%, and the pH is 7.1. Then, perform two-stage filtration through 1 μm and 0.3 μm PFA filter elements to filter out large particles and obtain dense shaped colloidal silica.

[0074] The dense shaped colloidal silica prepared in this embodiment has non-spherical shaped particles accounting for 80%; the shapes of the shaped particles include peanut shape, heart shape, curved shape, etc.

[0075] The primary particle size is 40nm, the secondary particle size is 82nm, the mass concentration is 20%, the degree of association is 2.05, the hardness of a single particle is 2.91Gpa, the proportion of surface silanol groups to total silanol groups is 13%, the total metal ion content is less than 1ppm, and the content of some metal impurities is shown in Table 1.

[0076] Example 3

[0077] The steps for preparing dense shaped colloidal silica are as follows:

[0078] 1) Mix 135 g of methanol, 51 g of water and 5.1 g of ethylenediamine and stir to obtain a mother liquor.

[0079] 2) 5 ml (6.41 g) of methanol and 15 ml (14.54 g) of tetramethoxysilane (TMOS) were mixed uniformly to obtain a hydrolyzate.

[0080] 3) Using a peristaltic pump, the hydrolyzate of step 2) was added to the mother solution of step 1) at a volume ratio of 1:11.34, and the addition was completed in 600 seconds. The reaction was carried out at 25°C and 200 r / min for 1 hour to obtain spherical colloidal silica.

[0081] 4) The spherical colloidal silica prepared in step 3) is placed in a hydrothermal reactor, 250 ppm of cationic polyacrylamide is added thereto, and pressurized aging is performed at 80° C. and a pressure of 0.18 MPa for 6 hours to generate dense irregular colloidal silica particles.

[0082] 5) In step 4), add 1 times the mass of ultrapure water to the system, and heat under reduced pressure and concentrate at 20KPa and 50°C to make the methanol content in the system less than 100ppm, the solid content is 20wt%, and the pH is 7.3. Then, perform two-stage filtration through 1μm and 0.3μm PFA material filter elements to filter out large particles and obtain dense shaped colloidal silica.

[0083] The dense shaped colloidal silica prepared in this embodiment has non-spherical shaped particles accounting for 60%; the shapes of the shaped particles include peanut-shaped, heart-shaped, curved, etc.

[0084] The primary particle size is 40nm, the secondary particle size is 88nm, the mass concentration is 20%, the degree of association is 2.2, the hardness of a single particle is 2.64Gpa, the proportion of surface silanol groups to total silanol groups is 11%, the total metal ion content is less than 1ppm, and the content of some metal impurities is shown in Table 1.

[0085] Example 4

[0086] The steps for preparing dense shaped colloidal silica are as follows:

[0087] 1) 140 g of isopropanol, 60 g of water and 2 g of tetramethylammonium hydroxide were mixed and stirred to obtain a mother liquor.

[0088] 2) Mix 5 ml (6.37 g) of isopropanol and 15 ml (14.56 g) of tetramethoxysilane (TMOS) to obtain a hydrolyzate.

[0089] 3) Using a peristaltic pump, the hydrolyzate from step 2) was added to the mother solution from step 1) at a volume ratio of 1:12, and the addition was completed in 20 seconds. The reaction was carried out at 50° C. and 600 r / min for 3 hours to obtain spherical colloidal silica.

[0090] 4) The spherical colloidal silica prepared in step 3) is placed in a hydrothermal reactor, 50 ppm of cationic polyacrylamide and 150 ppm of cationic acrylate are added thereto, and pressurized aging is performed at 220° C. and 2 MPa for 0.5 h to generate dense irregular colloidal silica particles.

[0091] 5) In step 4), 3 times the mass of ultrapure water is added to the system, and heated and concentrated at normal pressure at 101 KPa and 150°C to make the methanol content in the system less than 100 ppm, the solid content is 20 wt%, and the pH is 6.8. Then, two-stage filtration is performed through 1 μm and 0.3 μm PFA filter elements to filter out large particles and obtain dense shaped colloidal silica.

[0092] The dense shaped colloidal silica prepared in this embodiment has non-spherical shaped particles accounting for 50%; the shapes of the shaped particles include peanut shape, heart shape, curved shape, etc.

[0093] The primary particle size is 22nm, the secondary particle size is 40nm, the mass concentration is 21%, the degree of association is 1.82, the hardness of a single particle is 2.41Gpa, the proportion of surface silanol groups to total silanol groups is 12.7%, the total metal ion content is less than 1ppm, and the content of some metal impurities is shown in Table 1.

[0094] Example 5

[0095] The steps for preparing dense shaped colloidal silica are as follows:

[0096] 1) 117.75 g of ethanol, 80.13 g of water and 4 g (concentration 25 wt%) of aqueous ammonia were mixed and stirred to obtain a mother solution.

[0097] 2) 10 ml (12.69 g) of ethanol and 10 ml (11.36 g) of tetraethoxysilane (TEOS) were mixed uniformly to obtain a hydrolyzate.

[0098] 3) Using a peristaltic pump, the hydrolyzate of step 2) was added to the mother solution of step 1) at a volume ratio of 1:11.67, and the addition was completed in 20 seconds. The reaction was carried out at 50°C and 600 r / min for 0.5 h to obtain spherical colloidal silica.

[0099] 4) The spherical colloidal silica of step 3) is placed in a hydrothermal reactor, 500 ppm of quaternary ammonium salt type poly(phenylene vinylene) (PPV-NMe3+) is added thereto, and pressurized aging is performed at 130° C. and a pressure of 0.57 MPa for 4 hours to generate dense irregular colloidal silica particles.

[0100] 5) In step 4), add 2 times the mass of ultrapure water to the system, heat and concentrate at normal pressure at 101 KPa and 130°C to make the ethanol content in the system less than 100 ppm, the solid content is 20 wt%, and the pH is 7.1. Then, perform two-stage filtration through 1 μm and 0.3 μm PFA filter elements to filter out large particles and obtain dense shaped colloidal silica.

[0101] The dense shaped colloidal silica prepared in this embodiment has non-spherical shaped particles accounting for 60%; the shapes of the shaped particles include peanut-shaped, heart-shaped, curved, etc.

[0102] The primary particle size is 60nm, the secondary particle size is 117nm, the mass concentration is 20%, the degree of association is 1.95, the hardness of a single particle is 2.87Gpa, the proportion of surface silanol groups to total silanol groups is 10.7%, the total metal ion content is less than 1ppm, and the content of some metal impurities is shown in Table 1.

[0103] Example 6

[0104] The steps for preparing dense shaped colloidal silica are as follows:

[0105] 1) Mix 175 g of water and 5 g (concentration 25 wt%) of aqueous ammonia and stir to obtain a mother solution.

[0106] 2) Mix 15 ml (15 g) of water and 5 ml (4.85 g) of tetramethoxysilane (TMOS) to obtain a hydrolyzate.

[0107] 3) Using a peristaltic pump, the hydrolyzate from step 2) was added to the mother solution from step 1) at a volume ratio of 1:9, and the addition was completed in 20 seconds. The reaction was carried out at 100° C. and 600 r / min for 3 hours to obtain spherical colloidal silica.

[0108] 4) The spherical colloidal silica prepared in step 3) is placed in a hydrothermal reactor, 250 ppm of cationic polyacrylamide is added thereto, and pressurized aging is performed at 140° C. and a pressure of 0.36 MPa for 3 h to generate dense, irregular colloidal silica particles.

[0109] 5) In step 4), 1.8 times the mass of ultrapure water is added to the system, and the system is heated and concentrated at 101 KPa and 130°C under normal pressure to make the ethanol content in the system less than 100 ppm, the solid content is 20 wt%, and the pH is 7.2. Then, two-stage filtration is performed through 1 μm and 0.3 μm PFA filter elements to filter out large particles and obtain dense shaped colloidal silica.

[0110] The dense shaped colloidal silica prepared in this embodiment has non-spherical shaped particles accounting for 56%; the shapes of the shaped particles include peanut-shaped, heart-shaped, curved, etc.

[0111] The primary particle size is 30nm, the secondary particle size is 60nm, the mass concentration is 20%, the degree of association is 2, the hardness of a single particle is 3.18Gpa, the proportion of surface silanol groups to total silanol groups is 8%, the total metal ion content is less than 1ppm, and the content of some metal impurities is shown in Table 1.

[0112] Comparative Example 1

[0113] The preparation method is similar to that in Example 1, except that no cationic polymer is added during the aging process in step 4), and other operations remain unchanged to obtain colloidal silicon dioxide.

[0114] In the colloidal silica prepared in this comparative example, the number of non-spherical irregular particles accounts for 5%; the irregular particles include peanut-shaped particles;

[0115] The primary particle size is 37 nm, the mass concentration is 20%, the hardness of a single particle is 2.01 Gpa, the proportion of surface silanol groups to total silanol groups is 13%, the total metal ion content is less than 1 ppm, and the content of some metal impurities is shown in Table 1.

[0116] Comparative Example 2

[0117] The preparation method is similar to that in Example 1, except that in step 4), the cationic polymer is replaced by anionic polyacrylamide (APAM) during the aging process, and other operations remain unchanged to obtain colloidal silica.

[0118] The colloidal silica prepared in this comparative example has spherical particles in all its morphology, and almost no irregular particles are formed;

[0119] The particle size is 36.5 nm, the mass concentration is 19%, the hardness of a single particle is 2.1 GPa, the proportion of surface silanol groups to total silanol groups is 14%, the total metal ion content is less than 1 ppm, and the content of some metal impurities is shown in Table 1.

[0120] Comparative Example 3

[0121] The preparation method is similar to that in Example 1, except that in step 4), during the aging process, the cationic polymer is replaced by polymethacrylic acid (non-ionic polymer), and other operations remain unchanged to obtain colloidal silicon dioxide.

[0122] The colloidal silica prepared in this comparative example has spherical particles in all its morphology, and almost no irregular particles are formed;

[0123] The primary particle size is 34 nm, the mass concentration is 19.5%, the hardness of a single particle is 2.31 Gpa, the proportion of surface silanol groups to total silanol groups is 12%, the total metal ion content is less than 1 ppm, and the content of some metal impurities is shown in Table 1.

[0124] Comparative Example 4

[0125] The preparation method is similar to that in Example 1, except that the aging treatment is omitted in step 4, and other operations remain unchanged to obtain colloidal silicon dioxide.

[0126] When the colloidal silica prepared in this comparative example has a silica sol concentration greater than 15%, the viscosity of the entire system increases, the silica sol gels, and a high-concentration silica sol product cannot be prepared.

[0127] Table 1: Content of some metal impurities in colloidal silicon dioxide prepared in the examples and comparative examples (ppb)

[0128] Na K Cr Cu Fe Ni Ti Example 1 78 82 8 10 25 18 10 Example 2 84 67 10 11 22 26 9 Example 3 90 87 9 7 20 20 9 Example 4 96 77 11 12 30 21 8 Example 5 89 75 9 10 28 23 10 Example 6 70 65 8 10 30 19 11 Comparative Example 1 79 78 13 11 29 19 12 Comparative Example 2 98 85 8 8 31 25 9 Comparative Example 3 91 80 10 11 27 21 7

[0129] Figure 1 The TEM images of Example 1, Example 2, Comparative Example 2 and Comparative Example 3 of the present invention are given, corresponding to Figure 1-4 . As can be seen from the attached figure, compared with the spherical morphology of the comparative example, the silica sol particles prepared by the synthesis method of the present invention present obvious irregular morphology, and the majority of particles are associated with each other or even multiple particles, wherein the irregular morphology includes various structures such as peanut-shaped, heart-shaped, and curved. It can also be seen from the TEM image that compared with the comparative example, obvious white spots appear on the surface of the silica sol particles after aging, which may be related to the further condensation of the silanol groups on the surface of the particles during the aging process.

[0130] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing dense shaped colloidal silica, characterized in that: The following steps are included: 1) mixing an alkali catalyst and a solvent to obtain a mother liquid; 2) mixing alkoxysilane with a solvent to obtain a hydrolyzate of alkoxysilane; 3) adding the hydrolyzate of step 2) to the mother solution of step 1), reacting under stirring to obtain spherical colloidal silica; 4) adding a cationic polymer to the spherical colloidal silica in step 3) and performing an aging treatment to generate dense heteromorphic colloidal silica particles; 5) adding water to the system of step 4), and then concentrating it to a solid content of more than 20 wt% and a pH of 6.5-7.3, and then filtering to remove large particles therein to obtain dense shaped colloidal silica; Step 4) the cationic polymer is selected from one or more of cationic polyacrylamide, cationic polyacrylate, quaternary ammonium salt type cationic polymer, and quaternary phosphonium salt type cationic polymer; the cationic polymer is added in an amount of 50-500ppm of the mass of the spherical colloidal silica; Step 4) The aging treatment adopts a pressurized heat aging method, the aging temperature is 80-220° C., the aging time is 0.5-6 h, and the aging pressure is 0.18-2 Mpa.

2. The preparation method according to claim 1, characterized in that: Step 1) the base catalyst is selected from one or more of alkali metal hydroxides, ammonia, organic amines, basic amino acids or guanidine compounds; the alkali metal hydroxide is selected from one or more of potassium hydroxide, sodium hydroxide and lithium hydroxide; the organic amine is selected from one or more of ethylenediamine, triethanolamine and tetramethylammonium hydroxide; the basic amino acid is selected from one or more of lysine, arginine and histidine; the guanidine compound is selected from one or more of tetramethylguanidine, trimethylguanidine and guanidine carbonate; Step 1) the solvent is selected from water and / or an organic solvent, and the organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, and ethyl propyl ether; Step 1) The concentration of the base catalyst in the mother liquor is 1-3 wt %.

3. The preparation method according to claim 2, characterized in that: The alkaline catalyst is selected from one or more of ammonia water, ethylenediamine, and tetramethylammonium hydroxide.

4. The preparation method according to claim 2, characterized in that: Step 2) the alkoxysilane is selected from one or more of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane; Step 2) the solvent is selected from water and / or an organic solvent, and the organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, and ethyl propyl ether; Step 2) The volume ratio of the alkoxysilane to the solvent is 3:1-1:

3.

5. The preparation method according to claim 2, characterized in that: The volume ratio of the alkoxysilane to the solvent is 3:1-1:

1.

6. The preparation method according to claim 1, characterized in that: In step 2), the same solvent as in step 1) is used.

7. The preparation method according to claim 1, characterized in that: Step 3) The volume ratio of the hydrolyzate of step 2) to the mother liquor of step 1) is 1:9-1:

12.

8. The preparation method according to claim 1, characterized in that: The hydrolyzate of step 2) is added to the mother solution of step 1) continuously, and the feeding time is 6-600s.

9. The preparation method according to claim 8, characterized in that: The hydrolyzate of step 2) is added to the mother solution of step 1) in a dropwise manner.

10. The preparation method according to claim 8, characterized in that: The feeding time is 6-300s.

11. The preparation method according to claim 1, characterized in that: Step 3) The reaction is carried out under stirring at a temperature of 5-100° C., a reaction time of 0.5-5 h, and a stirring speed of 200-1000 r / min.

12. The preparation method according to claim 11, characterized in that: The reaction temperature is 5-100° C., the reaction time is 0.5-3 h, and the stirring speed is 600 r / min.

13. The preparation method according to claim 1, characterized in that: The amount of the cationic polymer added in step 4) is 100-300 ppm of the mass of the spherical colloidal silica; Step 4) The aging treatment adopts a pressurized heat aging method, the aging temperature is 90-220° C., the aging time is 0.5-4 h; and the aging pressure is 0.18-2 Mpa.

14. The preparation method according to claim 13, characterized in that: The aging temperature is 100-150°C.

15. The preparation method according to claim 1, characterized in that: Step 5) The amount of water added is 0.6-3 times the mass of the system; Step 5) The concentration is carried out by heating, the temperature is 50-150°C, and the pressure is 20-101Kpa; In step 5), the filtration has a filtration accuracy of 0.2-5 μm.

16. The preparation method according to claim 15, characterized in that: The amount of water added is 1.5-2 times the mass of the system.

17. The preparation method according to claim 15, characterized in that: The concentration temperature is 90-130°C.

18. The preparation method according to claim 15, characterized in that: The filtration uses a filter element made of PFA material.

19. The preparation method according to claim 18, characterized in that: The filtering stages are two-stage or three-stage filtering.

20. A dense shaped colloidal silica prepared by the preparation method according to any one of claims 1 to 19, characterized in that: Among them, the number of non-spherical irregular particles accounts for more than 50%; the shape of the irregular particles is curved.

21. The dense shaped colloidal silica according to claim 20, characterized in that The shapes of the special-shaped particles include peanut shape, heart shape and silkworm shape.

22. The dense shaped colloidal silica according to claim 20, characterized in that The non-spherical irregular particles account for more than 70%.

23. The dense shaped colloidal silica according to claim 20, characterized in that The primary particle size is between 20-150nm, the degree of association is above 1.7, the proportion of surface silanol groups to total silanol groups is less than 15%, and the total content of metal ions is less than 1ppm.

24. Use of the dense shaped colloidal silica prepared by the preparation method according to any one of claims 1 to 19 or the dense shaped colloidal silica according to any one of claims 20 to 23 in chemical mechanical polishing.

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