Ultrahigh-purity special-shaped silica sol and preparation method thereof

Abstract

The invention discloses ultra-pure special-shaped silica sol and a preparation method thereof, and belongs to the field of silicon dioxide material preparation, and the preparation method comprises the following steps: S1, preparing a component A which is prepared from a silicate ester monomer or a mixture of the silicate ester monomer and silane as a raw material through hydrolytic polymerization; s2, preparing hydrolysate 1, wherein the hydrolysate 1 is hydrolysate of the component A; s3, preparing hydrolysate 2, wherein the hydrolysate is silicate ester monomer hydrolysate; s4, preparing mother liquor; s5, adding the hydrolysate 1 into the mother liquor; s6, preparing a seed crystal; and S7, adding the hydrolysate 2 into the mixed solution containing the seed crystal to obtain the special-shaped silica sol. According to the method, control is carried out from the raw material end, the component A and the silicate ester monomer are adopted as hydrolysate raw materials respectively, the ultra-pure special-shaped silica sol in the same shape is prepared under the alkaline condition, morphology control over the special-shaped silica sol is achieved, the post-treatment step of preparation completion is not needed, the production cost is reduced, the quality of the raw materials is ensured, and the method is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the field of silicon dioxide material preparation, and particularly relates to an ultra-high purity special-shaped silica sol and a preparation method thereof. Background Art

[0002] In recent years, with the continuous development of semiconductor technology, the market demand for integrated circuit (IC) chip manufacturing has been increasing. Chemical mechanical polishing (CMP) is currently the only key high-precision polishing technology that can achieve both local and global flattening of the wafer surface. It can improve efficiency and reduce costs, and is an indispensable part of the current IC manufacturing process. Silicon dioxide is the most widely used and largest-volume abrasive. When the conventionally used spherical monodisperse silica sol is used as a polishing liquid abrasive, although a relatively perfect surface quality can be obtained, the spherical silica is easy to roll and has a small contact area, resulting in low polishing efficiency; when polishing harder materials (sapphire polishing), the processing time is too long, the efficiency is low, and the cost increases; therefore, some non-spherical silica sols came into being. These silicas have unique shapes, such as dumbbells, peanuts, potatoes, linear and curved structures. These silicas have the characteristics of large specific surface area, soft texture, and not easy to produce scratches. They have great application prospects in semiconductor CMP polishing.

[0003] Existing methods for preparing heterogeneous silica sols can be divided into three categories. The first method uses divalent metal ions, including calcium ions, magnesium ions, etc. as inducers to prepare heterogeneous silica sols, such as patents CN103896287B, CN101626979A, US005221497A, etc. Although such patents can prepare heterogeneous silica sols, they will cause a large amount of metal ions to exist in the product, limiting its application in semiconductor polishing. The second method uses the water glass ion exchange method to prepare active silicate, and then uses inorganic bases as catalysts and organic bases as morphology control agents to prepare heterogeneous silica sols; such as patent CN110655087A, although the water glass method is used to prepare silicate, it can handle most metal ions, but there is an upper limit to the removal of metal ions, resulting in the presence of more metal ions in its product, which is not conducive to its application in semiconductor polishing. The third method adopts hydrolysis of orthosilicate monomers or a Stober-like method, and uses organic bases as morphology control to prepare ultra-high purity silica sol, such as patents CN102390838A, CN108862291A, CN102164853B, CN111470510A, CN115611286A, CN112390262, CN113544093A, etc. This method can prepare ultra-high purity non-spherical silica sol, but this method cannot prepare monodisperse heteromorphic silica sol, the degree of heteromorphism is limited, and the reaction needs to be carried out in an alcohol system, which will lead to an increase in later costs and is not conducive to industrial-scale production; some of them also need to be continuously centrifuged to remove organic carbon, but it is difficult to completely remove it, resulting in impurities accumulated on the surface of the material after polishing, which are difficult to remove, affecting product quality and subsequent applications. Summary of the invention

[0004] The object of the present invention is to provide an ultra-high purity heterogeneous silica sol and a preparation method thereof, so as to solve the problems of excessive metal ions in the preparation of heterogeneous silica sol, high cost of removing alcohol in the preparation system and difficulty in controlling the heterogeneity of the product.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An ultra-high purity special-shaped silica sol, comprising: hydrolyzate 1, hydrolyzate 2 and mother liquor;

[0007] The hydrolyzate 1 is a hydrolyzate of component A, to which 1.5-2.5 parts by weight of component A is added, wherein component A is prepared by hydrolysis polymerization in ultrapure water using a silicate monomer or a mixture of a silicate monomer and a silane as a raw material and catalyzed by an acidic catalyst;

[0008] The hydrolyzate 2 is a silicate monomer hydrolyzate, to which 15-65 parts by weight of silicate monomer is added;

[0009] The hydrolyzate 1 and the hydrolyzate 2 are both acidic solutions;

[0010] The mother liquor is an alkaline solution.

[0011] Furthermore, it comprises, by weight: 15-35 parts of hydrolyzate 1, 160-260 parts of hydrolyzate 2 and 30-45 parts of mother liquor; the pH of the hydrolyzate 1 is 2-4.5; the pH of the hydrolyzate 2 is 2-4.5; and the pH of the mother liquor is 7-12.

[0012] Furthermore, when component A is prepared using silicate monomer as raw material, the ratio of silicate monomer to ultrapure water is 60-85:2-4 in parts by weight, and the reaction pH is 3-6.

[0013] Furthermore, when component A is prepared with silicate monomer and silane as raw materials, the weight ratio of silicate monomer, silane and ultrapure water is 40-65:15-25:2-4, and the reaction pH is 3-6.

[0014] A method for preparing ultra-high purity special-shaped silica sol comprises the following steps:

[0015] S1, preparing component A; using silicate monomer, or a mixture of silicate monomer and silane as raw materials, catalyzing with an acidic catalyst in ultrapure water, and hydrolyzing and polymerizing to obtain component A;

[0016] S2, preparing a hydrolysis solution 1; mixing an acidic catalyst and ultrapure water in a predetermined ratio to obtain an acidic solution, and then adding component A to the acidic solution and stirring until complete hydrolysis;

[0017] S3, preparing hydrolysis solution 2; mixing an acidic catalyst and ultrapure water to obtain an acidic solution, then adding a silicate monomer to the acidic solution, and stirring until complete hydrolysis;

[0018] S4, preparing a mother liquor; mixing the alkaline catalyst and ultrapure water in a predetermined ratio to obtain an alkaline solution as the mother liquor;

[0019] S5, adding the hydrolyzate 1 to the mother liquor to obtain a mixed solution;

[0020] S6, treating the mixed solution to prepare seed crystals;

[0021] S7, adding the hydrolyzed solution 2 to the mixed solution containing the seed crystals to obtain a heteromorphic silica sol.

[0022] Furthermore, in step S1, the acidic catalyst is an electronic grade inorganic acid or an electronic grade organic acid; in step S1, the temperature of the polymerization process is 60-200°C.

[0023] Furthermore, in step S4, the alkaline catalyst is at least one of ammonia water, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, primary, secondary and tertiary amines, and isopropylamine.

[0024] Furthermore, in steps S5 and S7, alkaline substances are gradually added to the mixed solution.

[0025] Furthermore, in the steps S1 and S3, the silicate monomers are all electronic grade silicate monomers, and the electronic grade silicate is at least one of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate.

[0026] Furthermore, in step S1, the silane is electronic grade silane, and the electronic grade silane is at least one of methyltrimethoxysilane, ethyltrimethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltriethoxysilane, 3-(2,3-epoxypropyloxy)propyltrimethoxysilane and γ-mercaptopropyltriethoxysilane.

[0027] The present invention has the following beneficial effects:

[0028] 1. The present invention provides an ultra-high purity heterogeneous silica sol and a preparation method thereof, which controls the raw materials, uses component A and silicate monomers prepared from silicate monomers or silicate monomers and silane with different molecular weights as hydrolyzate raw materials, respectively, and prepares ultra-high purity heterogeneous silica sols of the same shape under alkaline conditions, thereby achieving morphology control of the heterogeneous silica sol, and does not require post-processing steps after the preparation is completed, thereby reducing production costs, ensuring the quality of raw materials, and being suitable for industrial production.

[0029] 2. The present invention provides an ultra-high purity special-shaped silica sol and a preparation method thereof, wherein the metal ion content of the obtained silica sol is less than 500 ppb, meeting the requirements of electronic-grade products.

[0030] 3. The present invention provides an ultra-high purity heterogeneous silica sol and a preparation method thereof, wherein a silicate monomer or a silicate monomer and a silane are treated to prepare component A; component A is first hydrolyzed into long-chain silanols by an acidic catalyst, and the long-chain silanols are dehydrated and condensed by an alkaline catalyst to form heterogeneous crystal nuclei, and a hydrolysis solution 2 is added at this time. The hydrolysis solution 2 contains a silicic acid monomer produced by the hydrolysis of the silicate monomer, and the silicic acid monomer grows on the surface of the long-chain silanol, thereby obtaining a heterogeneous silica sol. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a product observation diagram of Example 1 of the present invention;

[0032] Figure 2 This is a product observation diagram of Example 2 of the present invention;

[0033] Figure 3This is a product observation diagram of Example 3 of the present invention;

[0034] Figure 4 This is a product observation diagram of Example 4 of the present invention;

[0035] Figure 5 This is a product observation diagram of Example 5 of the present invention;

[0036] Figure 6 This is a product observation diagram of Comparative Example 1 of the present invention;

[0037] Figure 7 This is a product observation diagram of Comparative Example 2 of the present invention;

[0038] Figure 8 This is a product observation diagram of Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] An ultra-high purity special-shaped silica sol comprises, by weight: 15-35 parts of hydrolyzate 1, 160-260 parts of hydrolyzate 2 and 30-45 parts of mother liquor;

[0041] The hydrolyzate 1 is a hydrolyzate of component A, to which 1.5-2.5 parts of component A are added, wherein component A is prepared by hydrolysis polymerization in ultrapure water using a silicate monomer or a mixture of a silicate monomer and a silane as a raw material and catalyzed by an acidic catalyst;

[0042] The hydrolyzate 2 is a silicate monomer hydrolyzate, to which 15-65 parts of silicate monomer are added;

[0043] Both hydrolyzate 1 and hydrolyzate 2 are acidic solutions;

[0044] The mother liquor is an alkaline solution.

[0045] Optionally, when component A is prepared with silicate monomer and silane as raw materials, the weight ratio of silicate monomer, silane and ultrapure water is 40-65:15-25:2-4, and the reaction pH is 3-6.

[0046] Optionally, when component A is prepared using silicate monomer as raw material, the ratio of silicate monomer to ultrapure water is 60-85:2-4 in parts by weight, and the reaction pH is 3-6.

[0047] Optionally, the pH of the hydrolyzate 1 is 2-4.5.

[0048] Optionally, the pH of the hydrolyzate 2 is 2-4.5.

[0049] Optionally, the pH of the mother liquor is 7-12.

[0050] A method for preparing ultra-high purity special-shaped silica sol comprises the following steps:

[0051] S1, preparing component A; using silicate, or a mixture of silicate and silane as raw materials, catalyzed by an acidic catalyst in ultrapure water, and obtaining component A by hydrolysis polymerization;

[0052] S2, preparing a hydrolysis solution 1; mixing an acidic catalyst and ultrapure water in a predetermined ratio to obtain an acidic solution, and then adding component A to the acidic solution and stirring until complete hydrolysis;

[0053] S3, preparing hydrolysis solution 2; mixing an acidic catalyst and ultrapure water to obtain an acidic solution, then adding a silicate monomer to the acidic solution, and stirring until complete hydrolysis;

[0054] S4, preparing a mother liquor; mixing the alkaline catalyst and ultrapure water in a predetermined ratio to obtain an alkaline solution as the mother liquor;

[0055] S5, adding the hydrolyzate 1 to the mother liquor to obtain a mixed solution;

[0056] S6, treating the mixed solution to prepare seed crystals;

[0057] S7, adding the hydrolyzed solution 2 to the mixed solution containing the seed crystals to obtain a heteromorphic silica sol.

[0058] Step S1 is specifically as follows: adding silicate monomer or a mixture of silicate monomer and silane to ultrapure water, catalyzing with an acidic catalyst, to prepare component A; during the polymerization process, gradually increasing the temperature, controlling the temperature between 60-200°C, recovering the alcohol produced by the polymerization by evaporation, and collecting component A separately after cooling.

[0059] Optionally, in step S1, electronic grade silicate monomer or a mixture of electronic grade silicate monomer and electronic grade silane is used as raw material to prepare component A. Electronic grade silicate monomer and electronic grade silane can be purchased directly from the market. The base and acid used in each step are all commercially available electronic grade products.

[0060] The electronic grade silicate monomer is at least one of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate; the electronic grade silane is at least one of methyltrimethoxysilane, ethyltrimethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltriethoxysilane, 3-(2,3-epoxypropyloxy)propyltrimethoxysilane and γ-mercaptopropyltriethoxysilane.

[0061] Optionally, in step S1, the acidic catalyst may be an electronic grade inorganic acid or an electronic grade organic acid; the electronic grade inorganic acid may be at least one of sulfuric acid, nitric acid and hydrochloric acid; the electronic grade organic acid may be at least one of oxalic acid, formic acid, acetic acid and sulfinic acid.

[0062] As an embodiment of the present invention, sulfuric acid is used as an acidic catalyst in step S1. Inorganic acid can avoid esterification reaction with alcohol produced during the polymerization process, and sulfuric acid is not easy to volatilize, which can ensure the pH stability of the solution and further improve the preparation efficiency.

[0063] Optionally, in step S1, the temperature of the polymerization process is 67.5-120°C.

[0064] Furthermore, in step S1, the temperature of the polymerization process is 67.5-100°C.

[0065] The specific method of step S2 is: mixing an acidic catalyst and ultrapure water to obtain an acidic solution; then, adding component A to the acidic solution, stirring fully at room temperature until completely hydrolyzed, to obtain a hydrolyzate 1, the pH of the hydrolyzate 1 is 2-4.5, preferably, the pH of the hydrolyzate 1 is 2.5-3.2.

[0066] The specific method of step S3 is: mixing an acidic catalyst and ultrapure water to obtain an acidic solution; then, adding electronic grade silicate to the acidic solution, stirring thoroughly at room temperature until completely hydrolyzed, to obtain hydrolyzate 2, the pH of hydrolyzate 2 is 2-4.5, preferably, the pH of hydrolyzate 2 is 2.5-3.2.

[0067] In step S3, the electronic grade silicate is at least one of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate.

[0068] In steps S2 and S3, the acidic catalyst may be an electronic grade organic acid; the electronic grade organic acid is at least one of oxalic acid, formic acid, acetic acid, and sulfinic acid.

[0069] As an embodiment of the present invention, in steps S2 and S3, oxalic acid is used as the acid catalyst.

[0070] As an embodiment of the present invention, in steps S2 and S3, the acidic catalyst used is the same.

[0071] The specific method of step S4 is: mixing the alkaline catalyst and ultrapure water to prepare an alkaline solution as a mother liquor, and further, the pH of the mother liquor is 10-12.

[0072] As an embodiment of the present invention, in step S4, the alkaline catalyst is at least one of ammonia water, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, primary, secondary and tertiary amines (without -OH), and isopropylamine.

[0073] The specific method of step S5 is: adding the hydrolyzate 1 dropwise to the mother liquor at a dropping speed of not less than 1 g / min; during the adding of the hydrolyzate 1 dropwise, gradually adding alkaline substances to stabilize the pH of the mixed liquor between 7 and 12.

[0074] As an embodiment of the present invention, in step S5, the dripping speed of the hydrolyzate 1 is 1-10 g / min.

[0075] As an embodiment of the present invention, in step S5, the pH of the mixed solution is between 8.5-10.5, and further, the pH of the mixed solution is between 9-9.5.

[0076] As an embodiment of the present invention, in step S5, the alkaline substance used is an organic base, and further, the alkaline substance used is at least one of tetrabutylammonium hydroxide, tetramethylammonium hydroxide, tetramethylammonium bromide, and tetraethylammonium bromide.

[0077] The specific method of step S6 is: after the hydrolysis solution 1 is added dropwise, the temperature of the mixed solution is adjusted to 90° C.-100° C. to prepare seed crystals.

[0078] The specific method of step S7 is: adding the hydrolyzed solution 2 dropwise to the mixed solution containing the seed crystals at a dropping speed of not less than 1 g / min; during the adding of the hydrolyzed solution 2 dropwise, gradually adding alkaline substances to stabilize the pH of the mixed solution between 8.5 and 9.5.

[0079] As an embodiment of the present invention, in step S7, the alkaline substance used is the same as the alkaline substance in step 5.

[0080] The present invention is further described in detail below with reference to specific examples.

[0081] This embodiment 1

[0082] (1) Preparation of component A: Weigh 609 g of electronic grade methyl silicate, 27 g of ultrapure water and 0.1 g of electronic grade sulfuric acid respectively and add them into a reaction flask in sequence, stir well, slowly raise the temperature and control the temperature of taking out to be 67.8-68° C., the reaction is terminated when no methanol is taken out, cool down to obtain electronic grade methyl silicate tetramer as component A, and the solid content of silicon dioxide is 50.4%;

[0083] (2) preparing hydrolyzate 1; respectively weighing 152 g of ultrapure water, 0.46 g of electronic grade oxalic acid and 20 g of component A, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 1, the pH of which is 3.1;

[0084] (3) preparing hydrolyzate 2; respectively weighing 1744 g of ultrapure water, 5.2 g of electronic grade oxalic acid and 256 g of electronic grade methyl silicate monomer, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 2, the pH of which is 2.6;

[0085] (4) preparing a mother liquor; weighing 350 g of ultrapure water and 0.51 g of electronic grade ammonia water, and adding them into a reaction kettle in sequence and stirring them evenly to obtain a mother liquor, the pH of which was 10.45;

[0086] (5) adding hydrolyzate 1 dropwise at a rate of 5 g / min, adding 0.1 g of tetrabutylammonium hydroxide for every 100 g of hydrolyzate 1 added, and controlling the pH of the mixed solution to be between 8.5 and 9.0;

[0087] (6) After the addition of hydrolyzate 1 is completed, the temperature of the mixed solution is raised and maintained at 98° C. to prepare seed crystals;

[0088] (7) adding hydrolyzate 2 dropwise at a rate of 15 g / min, adding 1.2 g of tetrabutylammonium hydroxide for every 1000 g of hydrolyzate 2 added, and controlling the pH of the mixed solution to be between 8.5 and 9.0; adding dropwise at a constant liquid level until the solid content reaches 30%, the reaction is completed, and the silica sol product is obtained after natural cooling;

[0089] (8) Observe the silica sol product by electron microscope. The results are as follows: Figure 1 As shown by Figure 1 It can be seen that the particles in the silica sol are basically dumbbell-shaped; the metal ion content of the silica sol product detected by ICP-MS is shown in Table 1.

[0090] Table 1

[0091]

[0092] Example 2

[0093] (1) The electronic grade methyl silicate tetramer prepared in Example 1 is used as component A;

[0094] (2) preparing hydrolyzate 1; respectively weighing 152 g of ultrapure water, 0.46 g of electronic grade oxalic acid and 20 g of component A, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 1, the pH of which is 3.1;

[0095] (4) preparing hydrolyzate 2; respectively weighing 1744 g of ultrapure water, 5.2 g of electronic grade oxalic acid and 256 g of electronic grade methyl silicate monomer, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 2, the pH of which is 2.6;

[0096] (5) preparing a mother liquor; weighing 350 g of ultrapure water and 0.51 g of electronic grade ammonia water, and adding them into a reaction kettle in sequence and stirring them evenly to obtain a mother liquor, the pH of which was 10.45;

[0097] (6) adding hydrolyzate 1 dropwise at a rate of 5 g / min, adding 0.15 g of tetrabutylammonium hydroxide for every 100 g of hydrolyzate 1 added, and controlling the pH of the mixed solution to be between 9 and 9.5;

[0098] (7) After the addition of hydrolyzate 1 is completed, the temperature of the mixed solution is raised and maintained at 98° C. to prepare seed crystals;

[0099] (8) adding hydrolyzate 2 dropwise at a rate of 15 g / min, adding 1.6 g of tetrabutylammonium hydroxide for every 1000 g of hydrolyzate 2 added, and controlling the pH of the mixed solution to be between 9 and 9.5; adding dropwise at a constant liquid level until the solid content reaches 30%, the reaction is completed, and the silica sol product is obtained after natural cooling;

[0100] (9) Observe the silica sol product by electron microscope. The results are as follows: Figure 2 As shown by Figure 2 It can be seen that the particles in the silica sol are spherical and dumbbell-shaped; the metal ion content of the silica sol product detected by ICP-MS is shown in Table 2.

[0101] Table 2

[0102]

[0103] The difference between Example 2 and Example 1 is that in Example 2, the pH of the solution when the hydrolyzed solution 1 is added to the mother solution and when the mixed solution 2 is added to the mixed solution is increased by 0.5, so that the silica sol particles of the two groups of examples show differences in shape.

[0104] Example 3

[0105] (1) Preparation of component A: 835.52 g of electronic grade ethyl silicate, 27 g of ultrapure water and 0.21 g of electronic grade sulfuric acid were weighed and added into a reaction flask in sequence, stirred thoroughly, and slowly heated to 78-79° C. The reaction was terminated when no ethanol was removed, and cooled to obtain electronic grade ethyl silicate polymer (ethyl silicate 32) as component A. The solid content of silicon dioxide was 31.9%;

[0106] (2) preparing hydrolyzate 1; respectively weighing 300 g of ultrapure water, 0.62 g of electronic grade oxalic acid and 20 g of component A, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 1, the pH of which is 2.7;

[0107] (3) preparing hydrolyzate 2; respectively weighing 1875 g of ultrapure water, 7.8 g of electronic grade oxalic acid and 625 g of electronic grade ethyl silicate monomer, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 2, the pH of which is 3.1;

[0108] (4) preparing a mother liquor; weighing 400 g of ultrapure water, 0.51 g of electronic grade ammonia water and 0.1 g of electronic grade diethanolamine, and adding them into a reaction kettle in sequence and stirring evenly to obtain a mother liquor, the pH of which was 10.45;

[0109] (5) adding hydrolyzate 1 dropwise at a rate of 3 g / min, adding 0.11 g of tetramethylammonium hydroxide for every 100 g of hydrolyzate 1 added, and controlling the pH of the mixed solution to be between 8.5 and 9.5;

[0110] (6) After the addition of hydrolyzate 1 is completed, the temperature of the mixed solution is raised and maintained at 98° C. to prepare seed crystals;

[0111] (7) adding hydrolyzate 2 dropwise at a rate of 10 g / min, adding 1.4 g of tetramethylammonium hydroxide for every 1000 g of hydrolyzate 2 added, and controlling the pH of the mixed solution to be between 8.5 and 9.5; adding dropwise at a constant liquid level until the solid content reaches 30%, the reaction is completed, and the silica sol product is obtained after natural cooling;

[0112] (8) Observe the silica sol product by electron microscope. The results are as follows: Figure 3 As shown by Figure 3 It can be seen that the particles in the silica sol are basically peanut-shaped; the metal ion content of the silica sol product detected by ICP-MS is shown in Table 3.

[0113] Table 3

[0114]

[0115] Example 4

[0116] (1) Preparation of component A: Weigh 626.64 g of electronic grade ethyl silicate, 178.3 g of electronic grade methyltriethoxysilane, 27 g of ultrapure water, and 0.21 g of electronic grade sulfuric acid, add them into a reaction flask in sequence, stir well, slowly raise the temperature and control the distillation temperature to 78-79° C., and the reaction is completed when no ethanol is taken out, cool and obtain electronic grade ethyl silicate and electronic grade methyltriethoxysilane polymer as component A, and the solid content of silicon dioxide is 31.9%;

[0117] (2) preparing hydrolyzate 1; respectively weighing 320 g of ultrapure water, 0.51 g of electronic grade oxalic acid and 20 g of component A, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 1, the pH of which is 2.75;

[0118] (3) preparing hydrolyzate 2; respectively weighing 2100 g of ultrapure water, 7.8 g of electronic grade oxalic acid and 337 g of electronic grade ethyl silicate monomer, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 2, wherein the pH of hydrolyzate 2 is 2.8;

[0119] (4) preparing a mother liquor; weighing 350 g of ultrapure water, 3.5 g of electronic grade ammonia water and 0.27 g of isopropylamine, and adding them into a reaction kettle in sequence and stirring evenly to obtain a mother liquor, the pH of which is 10.45;

[0120] (5) adding hydrolyzate 1 dropwise at a rate of 8 g / min, adding 0.2 g of tetramethylammonium bromide for every 100 g of hydrolyzate 1 added, and controlling the pH of the mixed solution to be between 8.5 and 9.5;

[0121] (6) After the addition of hydrolyzate 1 is completed, the temperature of the mixed solution is raised and maintained at 98° C. to prepare seed crystals;

[0122] (7) adding hydrolyzate 2 dropwise at a rate of 18 g / min, adding 0.8 g of tetramethylammonium bromide for every 1000 g of hydrolyzate 2 added, and controlling the pH of the mixed solution to be between 8.5 and 9.5; adding dropwise at a constant liquid level until the solid content reaches 30%, the reaction is completed, and the silica sol product is obtained after natural cooling;

[0123] (8) Observe the silica sol product by electron microscope. The results are as follows: Figure 4 As shown by Figure 4 It can be seen that the particles in the silica sol are basically chain-shaped and curved; the metal ion content of the silica sol product detected by ICP-MS is shown in Table 4.

[0124] Table 4

[0125]

[0126] Example 5

[0127] (1) Preparation of component A: Weigh 456.75 g of electronic grade methyl silicate, 236.34 g of electronic grade 3-(2,3-epoxypropyloxy)propyltrimethoxysilane, 27 g of ultrapure water and 0.1 g of electronic grade sulfuric acid respectively and add them into a reaction flask in sequence, stir well, slowly raise the temperature and control the distillation temperature at 67.8-68° C., and terminate the reaction when no methanol is taken out, cool and obtain electronic grade methyl silicate and electronic grade 3-(2,3-epoxypropyloxy)propyltrimethoxysilane polymer as component A, and detect the silicon dioxide solid content to be 50.4%;

[0128] (2) preparing hydrolyzate 1; respectively weighing 320 g of ultrapure water, 0.66 g of electronic grade oxalic acid and 17.3 g of component A, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 1, the pH of which is 2.68;

[0129] (3) preparing hydrolyzate 2; respectively weighing 1500 g of ultrapure water, 7.8 g of electronic grade oxalic acid and 172.8 g of electronic grade methyl silicate monomer, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use, to obtain hydrolyzate 2, wherein the pH of hydrolyzate 2 is 2.8;

[0130] (4) preparing a mother liquor; weighing 350 g of ultrapure water, 1.5 g of electronic grade ammonia water and 0.47 g of isopropylamine, and adding them into a reaction kettle in sequence and stirring evenly to obtain a mother liquor, the pH of which is 10.45;

[0131] (5) adding hydrolyzate 1 dropwise at a rate of 7 g / min, adding 0.15 g of tetraethylammonium bromide for every 100 g of hydrolyzate 1 added, and controlling the pH of the mixed solution to be between 8.5 and 9.5;

[0132] (6) After the addition of hydrolyzate 1 is completed, the temperature of the mixed solution is raised and maintained at 98° C. to prepare seed crystals;

[0133] (7) adding hydrolyzate 2 dropwise at a rate of 18 g / min, adding 0.71 g of tetraethylammonium bromide for every 1000 g of hydrolyzate 2 added, and controlling the pH of the mixed solution to be between 8.5 and 9.5; adding dropwise at a constant liquid level until the solid content reaches 30%, the reaction is completed, and the silica sol product is obtained after natural cooling;

[0134] (8) Observe the silica sol product by electron microscope. The results are as follows: Figure 5 As shown by Figure 5 It can be seen that the particles in the silica sol are curved and peanut-shaped; the metal ion content of the silica sol product detected by ICP-MS is shown in Table 5.

[0135] Table 5

[0136]

[0137] It can be seen from Examples 1-5 that by adopting the present scheme, by adjusting component A, pH of the reaction process and other conditions, it is possible to prepare heteromorphic silica sols. Furthermore, by adopting electronic grade methyl silicate tetramer or polyethyl silicate 32 as component A, dumbbell-shaped and peanut-shaped heteromorphic electronic grade silica sols can be prepared; by adopting electronic grade silicate and electronic grade silane polymer as component A, chain-shaped and curved heteromorphic electronic grade silica sols can be prepared.

[0138] In this solution, the metal ion content of the silica sol product is less than 500 ppb, meeting the requirements of electronic-grade products.

[0139] Comparative Example 1

[0140] (1) preparing a hydrolyzate; weighing 2000 g of ultrapure water, 6 g of electronic grade oxalic acid and 293.58 g of electronic grade methyl silicate monomer, respectively, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use; the pH of the hydrolyzate is 2.75;

[0141] (2) preparing a mother liquor; weighing 500 g of ultrapure water and 0.51 g of electronic grade ammonia water and adding them to a reaction kettle in sequence and stirring evenly to obtain a mother liquor, the pH of which was 10.37;

[0142] (3) Add the hydrolyzate to the mother liquor at a rate of 6.5 g / min. For every 100 g drop, add 0.1 g of tetrabutylammonium hydroxide to control the pH of the mixed solution to between 8.5 and 9.5.

[0143] (4) After 500 g of the hydrolyzate is added, the addition is stopped, the temperature is raised and maintained at 98° C., and the hydrolyzate is continued to be added, the addition rate is controlled at 12 g / min, and 1.2 g of tetrabutylammonium hydroxide is added for each 1000 g addition, and the pH of the mixed solution is controlled between 8.5 and 9.5; the mixture is added at a constant liquid level until the solid content reaches 30%, the reaction is completed, and the final silica sol product is obtained after natural cooling;

[0144] (5) Observe the silica sol product through an electron microscope. The results are as follows Figure 6 As shown by Figure 6 It can be seen that the particles in the silica sol are monodisperse spherical, and it can be concluded that monodisperse spherical silica sol can be prepared using methyl silicate monomer; the metal ion content of the silica sol product detected by ICP-MS is shown in Table 6.

[0145] Table 6

[0146]

[0147] Comparative Example 2

[0148] (1) preparing a hydrolyzate; weighing 2000 g of ultrapure water, 6.3 g of electronic grade oxalic acid and 408.92 g of electronic grade ethyl silicate monomer, respectively, and adding them into a reaction beaker in sequence, stirring them thoroughly until a colorless clear liquid is obtained for later use; the pH of the hydrolyzate is 2.88;

[0149] (2) preparing a mother liquor; weighing 500 g of ultrapure water and 0.51 g of electronic grade ammonia water, and adding them into a reaction kettle in sequence and stirring them evenly to obtain a mother liquor, the pH value of which is 10.37;

[0150] (3) adding the hydrolyzate to the mother liquor dropwise at a rate of 3.7 g / min, adding 0.22 g of diethanolamine for each 100 g dropwise addition, and controlling the pH of the mixed solution to be between 8.5 and 9.5;

[0151] (4) After 500 g of hydrolyzate is added, the addition is stopped, the temperature is raised and maintained at 98° C.; the hydrolyzate is continued to be added, the addition speed is controlled at 11 g / min, and 1.2 g of diethanolamine is added for each 1000 g addition, and the pH of the mixed solution is controlled between 8.5 and 9.5; the mixture is added at a constant liquid level until the solid content reaches 30%, and the reaction is completed. After the reaction is completed, the final silica sol product is obtained after natural cooling;

[0152] (5) Observe the silica sol product through an electron microscope. The results are as follows Figure 7 As shown by Figure 7 It can be seen that the particles in the silica sol are monodisperse spherical, and it can be concluded that monodisperse spherical silica sol can be prepared using ethyl silicate monomer; the metal ion content of the silica sol product detected by ICP-MS is shown in Table 7.

[0153] Table 7

[0154]

[0155] Comparative Example 3

[0156] (1) preparing a hydrolyzate; weighing 2000 g of ultrapure water, 6.3 g of electronic grade oxalic acid and 408.92 g of electronic grade ethyl silicate monomer, respectively, and adding them into a reaction beaker in sequence, stirring thoroughly until a colorless clear liquid is obtained for later use, and detecting the pH value: 2.88;

[0157] (2) preparing a mother liquor; weighing 500 g of ultrapure water and 2.51 g of electronic grade ammonia water, and adding them into a reaction kettle in sequence and stirring them evenly to obtain a mother liquor, the pH of which was 11.07;

[0158] (3) adding the hydrolyzate to the mother liquor at a rate of 5 g / min, adding 0.35 g of tetramethylammonium hydroxide for each 100 g drop, and controlling the pH of the mixed solution to be between 10 and 11;

[0159] (4) After 500 g of the hydrolyzate is added, the addition is stopped, the temperature is raised and maintained at 98° C.; the hydrolyzate is continued to be added, the addition speed is controlled at 13 g / min, and 2.5 g of tetramethylammonium hydroxide is added for each 1000 g addition, and the pH of the mixed solution is controlled between 10 and 11; the mixture is added at a constant liquid level until the solid content reaches 30%, and the reaction is completed. After the reaction is completed, the final silica sol product is obtained after natural cooling;

[0160] (5) Observe the silica sol product through an electron microscope. The results are as follows Figure 8 As shown by Figure 8 It can be seen that the particles in the silica sol are spherical and unevenly distributed. It can be concluded that by using ethyl silicate monomer and increasing the reaction pH, unevenly distributed spherical particles are obtained; the metal ion content of the silica sol product detected by ICP-MS is shown in Table 8.

[0161] Table 8

[0162]

[0163] It can be seen from Comparative Examples 1-3 that monodisperse spherical silica sol can be prepared by using silicate monomer as raw material and controlling the reaction pH between 8.5 and 9.5; in Comparative Example 3, since the pH is controlled too high, the raw material is hydrolyzed too quickly during the dropwise addition process, which affects the growth of the crystal nucleus and results in more small particles in the product.

[0164] The silica sol products prepared in the above examples 1, 3, 5 and comparative examples 1 and 2 were used to prepare silica polishing liquids, respectively, and the silica polishing liquids were prepared according to the silica sol silica content of 5.0% and the potassium permanganate content of 1%; and polishing experiments were carried out, and the experimental conditions were as follows:

[0165] Polishing machine: 36B single-sided polishing machine;

[0166] Workpiece: Silicon carbide wafer;

[0167] Polishing pad: SUBA800 polishing pad;

[0168] Polishing pressure: 238g / cm2;

[0169] Sample plate speed: 30rpm;

[0170] Polishing disc speed: 40rpm;

[0171] Polishing time: 1h;

[0172] After polishing, the silicon carbide wafer was washed and dried in the order of cleaning liquid, deionized water, and ethanol. The mass of the silicon carbide wafer before and after polishing was weighed with a precision analytical balance, and the material removal rate MRR was calculated. The polishing effect is shown in Table 9.

[0173] Table 9

[0174] Polishing rate Embodiment 1 Embodiment 3 Embodiment 5 Comparative Example 1 Comparative Example 2 Silicon surface polishing rate: μm / h 0.541 0.601 0.527 0.473 0.404 Carbon surface polishing rate: μm / h 2.352 2.441 2.419 2.236 2.159

[0175] It can be seen from Table 9 that the polishing effect of the irregular silica sol is better than that of the spherical silica sol. The reason is that compared with spherical silica, the irregular silica sol has a larger contact area and is not easy to roll, which improves the polishing effect.

[0176] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-high purity special-shaped silica sol, characterized in that: include: Hydrolyzate 1, hydrolyzate 2 and mother liquor; The hydrolyzate 1 is a hydrolyzate of component A, to which 1.5-2.5 parts by weight of component A is added, wherein component A is prepared by hydrolysis polymerization in ultrapure water using a silicate monomer or a mixture of a silicate monomer and a silane as a raw material and catalyzed by an acidic catalyst; The hydrolyzate 2 is a silicate monomer hydrolyzate, to which 15-65 parts by weight of silicate monomer is added; The hydrolyzate 1 and the hydrolyzate 2 are both acidic solutions; The mother liquor is an alkaline solution.

2. The ultra-high purity special-shaped silica sol according to claim 1, characterized in that: The invention comprises, by weight: 15-35 parts of hydrolyzate 1, 160-260 parts of hydrolyzate 2 and 30-45 parts of mother liquor; the pH of the hydrolyzate 1 is 2-4.5; the pH of the hydrolyzate 2 is 2-4.5; and the pH of the mother liquor is 7-12.

3. The ultra-high purity special-shaped silica sol according to claim 1, characterized in that: When component A is prepared using silicate monomer as raw material, the ratio of silicate monomer to ultrapure water is 60-85:2-4 in parts by weight, and the reaction pH is 3-6.

4. The ultra-high purity special-shaped silica sol according to claim 1, characterized in that: When component A is prepared from silicate monomer and silane as raw materials, the weight ratio of silicate monomer, silane and ultrapure water is 40-65:15-25:2-4, and the reaction pH is 3-6.

5. A method for preparing ultra-high purity special-shaped silica sol according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, preparing component A; using silicate monomer, or a mixture of silicate monomer and silane as raw materials, catalyzing with an acidic catalyst in ultrapure water, and hydrolyzing and polymerizing to obtain component A; S2, preparing a hydrolysis solution 1; mixing an acidic catalyst and ultrapure water in a predetermined ratio to obtain an acidic solution, and then adding component A to the acidic solution and stirring until complete hydrolysis; S3, preparing hydrolysis solution 2; mixing an acidic catalyst and ultrapure water to obtain an acidic solution, then adding a silicate monomer to the acidic solution and stirring until complete hydrolysis; S4, preparing a mother liquor; mixing the alkaline catalyst and ultrapure water in a predetermined ratio to obtain an alkaline solution as the mother liquor; S5, adding the hydrolyzate 1 to the mother liquor to obtain a mixed solution; S6, treating the mixed solution to prepare seed crystals; S7, adding the hydrolyzed solution 2 to the mixed solution containing the seed crystals to obtain a heteromorphic silica sol.

6. The method for preparing ultra-high purity special-shaped silica sol according to claim 5, characterized in that: In step S1, the acidic catalyst is an electronic grade inorganic acid or an electronic grade organic acid; in step S1, the temperature of the polymerization process is 60-200°C.

7. The method for preparing ultra-high purity special-shaped silica sol according to claim 5, characterized in that: In step S4, the alkaline catalyst is at least one of ammonia water, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, primary, secondary and tertiary amines, and isopropylamine.

8. The method for preparing ultra-high purity special-shaped silica sol according to claim 5, characterized in that: In steps S5 and S7, alkaline substances are gradually added to the mixed solution.

9. The method for preparing ultra-high purity special-shaped silica sol according to claim 5, characterized in that: In the steps S1 and S3, the silicate monomers are all electronic grade silicate monomers, and the electronic grade silicate is at least one of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate.

10. The method for preparing ultra-high purity special-shaped silica sol according to claim 5, characterized in that: In the step S1, the silane is electronic grade silane, and the electronic grade silane is at least one of methyltrimethoxysilane, ethyltrimethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltriethoxysilane, 3-(2,3-epoxypropyloxy)propyltrimethoxysilane and γ-mercaptopropyltriethoxysilane.

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