Silica sol, preparation method thereof and composition for grinding

Abstract

The invention provides silica sol, a preparation method thereof and a composition for grinding, and relates to the technical field of silica sol preparation. The preparation method of the silica sol comprises the following steps: preparing a first alkaline solution and a second alkaline solution by taking tetramethoxysilane or tetraethoxysilane as hydrolysate; dropwise adding the hydrolysate and the second alkaline solution into the first alkaline solution at a preset speed at 100 DEG C to prepare spherical silica sol; the spherical silica sol is heated to boil, and byproducts are removed, so that the concentration is more than 30%. According to the preparation method of the silica sol, one-step synthesis can be achieved, the technological process is simplified, the silica sol is spherical, good in fluidity and more uniform in stress during grinding, surface defects can be reduced, and combination of low surface defects and high grinding rate is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of silica sol preparation, and particularly relates to a silica sol, a preparation method thereof, and a polishing composition. Background Art

[0002] With the continuous reduction of the integrated circuit technology node, the continuous increase of the number of interconnect layers, and the application of new materials and new processes, the number of uses and the importance of chemical mechanical polishing (CMP) in the chip process are continuously increasing. The reduction of the technology node puts forward higher quality requirements for the CMP polishing composition. "SiO2 chemical mechanical polishing composition" is the most used and effective important raw material.

[0003] How to combine high polishing rate with low surface defects is the main direction of future research on CMP polishing compositions. Spherical silica abrasives have better fluidity and are more evenly stressed during polishing, which helps to reduce surface defects. The current silica sol preparation process usually continuously drops the silicic acid hydrolysis solution and the alkaline liquid into the reactor through a continuous dropping device to continuously grow the silica particles. This process takes a long time and requires many control points in the intermediate links. Or, in the presence of an alkali catalyst, while hydrolyzing the alkyl silicate (tetraalkoxysilane), condensation and particle growth are carried out to manufacture silica particles, but this method is carried out in an organic solvent during the preparation process, with high risk. Summary of the Invention

[0004] The present application provides a silica sol, a preparation method thereof, and a polishing composition. The preparation method of the silica sol can achieve one-step synthesis, prepare spherical silica abrasives, simplifies the process flow, and the silica sol has better fluidity and is more evenly stressed during polishing, which helps to reduce surface defects, achieving the combination of low surface defects and high polishing rate.

[0005] In a first aspect, the present application provides a preparation method of a silica sol, including the following steps:

[0006] S1: Using tetramethoxysilane or tetraethoxysilane as a raw material and also as a hydrolysis solution, dissolving an inorganic base and / or an organic base in an aqueous solution to obtain a first alkaline solution, and dissolving an inorganic base in an aqueous solution to obtain a second alkaline solution;

[0007] S2: Heating the first alkaline solution to boiling, and at 100 °C, dropping the hydrolysis solution and the second alkaline solution into the first alkaline solution at a preset speed to prepare a spherical silica sol;

[0008] S3: Heating the spherical silica sol to boiling under normal pressure or reduced pressure to remove by-products such as methanol and ethanol and a part of water, and the concentration of the spherical silica sol is above 30%.

[0009] In a possible implementation, the inorganic base is selected from one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium aluminate, and potassium aluminate, the organic base is selected from one or more of ethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide, and choline, and the first alkaline solution at least includes sodium aluminate and / or potassium aluminate.

[0010] In a possible implementation, the Al in the first alkaline solution 3+ content is 0.005 - 1 wt%.

[0011] In a possible implementation, the content of aluminate in the first alkaline solution is 0.01 - 5 wt%, and the content of the base other than aluminate in the first alkaline solution is 0.1 - 0.5 wt%.

[0012] In a possible implementation, the content of the base in the second alkaline solution is 0.5 - 3 wt%.

[0013] In a possible implementation, the preset speed is 1 - 3 g / min.

[0014] In a possible implementation, the residual alcohol in the final product in step S3 is less than 10 ppm.

[0015] In a second aspect, the present application provides a silica sol, including the spherical silica sol obtained by using the preparation method according to any one of the implementation manners of the first aspect.

[0016] In a possible implementation, the DLS particle size of the spherical silica sol is 35 - 105 nm.

[0017] In a third aspect, the present application provides a grinding composition, including the spherical silica sol according to any one of the implementation manners of the second aspect, and the grinding composition is used for grinding copper.

[0018] In the above technical solution, by dropping the hydrolysis solution and the high-purity second alkaline solution into the first alkaline solution mixed with multiple bases together, one-step synthesis is achieved, the process flow is simplified, and the production efficiency is improved. The spherical silica abrasive is prepared, so that the fluidity of the silica sol is better, the force during grinding is more uniform, and at the same time, it is avoided that the surface of the silica sol has sharp corners and scratches the grinding layer, thereby helping to reduce surface defects. Moreover, both the first alkaline solution and the second alkaline solution are aqueous solutions, avoiding the preparation process in an organic solution, which is beneficial to improving the safety of the preparation process. Description of the Drawings

[0019] Figure 1 is the electron microscope picture of the silica sol prepared in Example 3;

[0020] Figure 2 It is a picture of the particle size distribution of the silica sol prepared in Example 3;

[0021] Figure 3 It is a TEM image of the silica sol prepared in Comparative Example 5;

[0022] Figure 4 It is a picture of the particle size distribution of the silica sol prepared in Comparative Example 5. Detailed implementation manners

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0024] It should be understood that the term "and / or" used in the description of the present application specification and the appended claims refers to any combination and all possible combinations of one or more of the related listed items, and includes these combinations.

[0025] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used for differential description and cannot be construed as indicating or implying relative importance.

[0026] It should be noted that the following embodiments are examples of the present application, which are only used to illustrate the present application and not to limit the present application. Without departing from the gist or scope of the present application, other combinations and various improvements within the concept of the present application can be made.

[0027] The silica sol provided by the present application, its preparation method, and the grinding composition will be specifically described below.

[0028] The preparation method of the silica sol in the embodiments of the present application includes the following steps:

[0029] S1: Using tetramethoxysilane or tetraethoxysilane as the raw material and also as the hydrolysis solution, dissolve an inorganic base and / or an organic base in an aqueous solution to obtain a first basic solution, and dissolve an inorganic base in an aqueous solution to obtain a second basic solution;

[0030] S2: Heat the first basic solution to boiling, and at 100 °C, add the hydrolysis solution and the second basic solution dropwise to the first basic solution at a preset speed to prepare spherical silica sol;

[0031] S3: Heat the spherical silica sol to boiling under normal pressure or reduced pressure to remove by-products such as methanol and ethanol and a part of the water, and the concentration of the spherical silica sol is above 30%.

[0032] The method for preparing silica sol provided by this application uses tetramethoxysilane or tetraethoxysilane as raw materials, undergoes a reflux reaction with various alkalis at 100 °C to prepare spherical silica abrasives, making the silica sol have better fluidity, more uniform stress during grinding, and avoiding sharp corners on the surface of the silica sol from scratching the grinding layer, thereby helping to reduce surface defects. In addition, this application drops the hydrolysis solution and a high-purity second alkaline solution into the first alkaline solution mixed with various alkalis at the same time, that is, the preparation method of this application is a one-step synthesis, which simplifies the process flow and improves production efficiency. Moreover, both the first alkaline solution and the second alkaline solution are aqueous solutions, avoiding the preparation process in organic solutions and being conducive to improving the safety of the preparation process.

[0033] In this application, the inorganic alkalis are selected from one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium aluminate, potassium aluminate, and the organic alkalis are selected from one or more of ethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide, choline. The first alkaline solution at least includes sodium aluminate and / or potassium aluminate. That is, the first alkaline solution is prepared by mixing at least 2 alkalis in an aqueous solution, wherein at least 2 alkalis at least include sodium aluminate and / or potassium aluminate, so that the first alkaline solution contains Al 3+ . Doping Al 3+ in the system can improve the stability and hardness of silica, thereby helping to increase the grinding rate during grinding, realizing the combination of low surface defects and high grinding rate.

[0034] In addition, since sodium and potassium ions have no effect on the grinding effect of general semiconductor materials, the silica sol prepared by this application has the same alkali resistance and grinding rate as the silica sol prepared by the water glass method. That is, the silica sol prepared by this application still has good stability and high grinding rate in a strong alkali environment. Moreover, the inorganic alkalis and organic alkalis in this application do not contain metal ions other than sodium, potassium, and aluminum, effectively controlling the content of metal ions in the system and avoiding the influence of metal impurities on the product during the CMP grinding process.

[0035] In this application, the content of Al 3+ in the first alkaline solution is 0.005 - 1 wt%. When the content of Al 3+ is lower than 0.005 wt%, the synthesized abrasive particles are too small and the hardness is insufficient; when the content of Al 3+ is higher than 1 wt%, Al 3+ may form its own oxide phase instead of being doped into the SiO2 network, without the effect of increasing the abrasive particle size, and may cause more surface defects at the same time. Controlling the content of Al 3+The method for controlling the content includes but is not limited to controlling the amount of aluminate in the first alkaline solution, wherein the content of aluminate in the first alkaline solution is 0.01-5wt%. The content of alkali other than aluminate in the first alkaline solution is 0.1-0.5wt%. When the concentration of alkali other than aluminate in the first alkaline solution is too low, the particle size of the abrasive is too small. When the concentration of alkali other than aluminate in the first alkaline solution is too high, the shape of the abrasive is anisotropic.

[0036] In the present application, the content of alkali in the second alkaline solution is 0.5-3wt%. The second alkaline solution is prepared by dissolving a single inorganic alkali in an aqueous solution. If the concentration of the alkali in the second alkaline solution is too high or too low, the shape of the silica abrasive will be anisotropic and precipitation will occur. Compared with the use of an organic base in the second alkaline solution, the alcohol content in the system is reduced, so that most of the alcohol solution in the system can be removed when heated and concentrated, which is beneficial to improving the safety of the preparation process. In addition, when preparing the grinding composition later, it is avoided that the silica sol introduces too much alcohol, which affects the grinding effect of the grinding composition.

[0037] In the present application, the preset speed in step S2 is 1-3 g / min. It is understandable that when the dripping speed is slow, the time cost is too high, and the effect of adjusting the particle size of the abrasive is also poor. When the dripping speed is fast, the particle size of the abrasive will become smaller, and the probability of morphological anisotropy will increase.

[0038] In the present application, the alcohol residue in the final product in step S3 is less than 10 ppm. In step S2, the polycondensation reaction produces alcohol as a byproduct. If these alcohol products are retained in the system, the grinding rate at the application end will be affected. Therefore, by heating to boiling under normal pressure or reduced pressure to remove byproducts such as methanol and ethanol and a portion of water, the alcohol residue is less than 10 ppm, thereby avoiding the influence of the alcohol residue on the preparation of the subsequent grinding composition.

[0039] In the present application, the DLS particle size of the spherical silica sol is 35-105nm. On the one hand, the silica abrasive can enter the microscopic unevenness on the surface of the material and selectively remove the protruding parts, so that the surface can achieve extremely high flatness, which can meet the strict requirements for wafer surface flatness in semiconductor chip manufacturing, ensuring the consistency and stability of chip performance. In addition, no obvious scratches or defects will be left on the surface of the material during the grinding process, which can effectively reduce surface defects. On the other hand, the appropriate particle size range enables the silica abrasive to have good suspension properties in the grinding liquid, which can better achieve uniform dispersion. The silica abrasive is fully in contact with the dispersion medium and interacts with each other to form a stable dispersion system, avoiding the agglomeration of abrasive particles.

[0040] The silica sol provided by this application can be applied in a polishing composition. This application also provides a polishing composition, which includes water, a pH regulator, and the spherical silica sol of any one of the above implementation manners. This polishing composition is used for polishing copper. The spherical silica sol has good fluidity, and the force during polishing is more uniform, avoiding scratching the polishing layer due to sharp corners on the surface of the silica sol, thereby helping to reduce surface defects. Moreover, this spherical silica sol has high stability and hardness, which helps to improve the polishing rate during polishing, achieving the combination of low surface defects and high polishing rate.

[0041] The pH regulator can be an organic base or an inorganic base, such as ammonia water, potassium hydroxide, sodium hydroxide, sodium methoxide, sodium ethoxide, triethylamine, triethanolamine, etc. The pH adjustment range is preferably between 9 and 11.

[0042] The water is preferably deionized water.

[0043] The technical solution of the present invention will be further elaborated below in conjunction with specific embodiments.

[0044] Example 1

[0045] S1: Prepare 240 g of tetramethoxysilane (TMOS) purified by distillation into container A as a hydrolysis solution; take 240 mL of 0.25 wt% potassium hydroxide aqueous solution and 80 mL of 0.05 wt% potassium metaaluminate aqueous solution and mix them into the first basic solution B1; take 200 mL of 1 wt% potassium hydroxide aqueous solution as the second basic solution B2;

[0046] S2: Heat the first basic solution B1 to boiling, and then drop the second basic solution B2 and TMOS into the first basic solution B1 at the same speed of 1 g / min. After the reaction is completed, keep warm for 30 min to obtain a dilute milky white spherical silica sol;

[0047] S3: Concentrate the dilute milky white spherical silica sol obtained in S2 under normal pressure, displace to remove the by-product methanol and part of the water. Finally, the concentration of the spherical silica sol is 30%, and pH = 10.5.

[0048] In step S3, a Malvern Zetasizer PRO type particle size analyzer is used to test the DLS particle size of SiO2. A Thermo Fisher APREO2 high-performance field emission scanning electron microscope is used to test the silica sol obtained in S3. A DC24000UHR type high-precision nano particle size analyzer is used for testing.

[0049] Example 2

[0050] Except that the concentration of potassium metaaluminate aqueous solution in step S1 is changed from 0.05 wt% to 1 wt%, and the dropping rate in step S2 is changed from 1 g / min to 3 g / min, the reaction is carried out in the same manner as the method described in Example 1 above, and pH = 10.7.

[0051] In step S3, a Malvern Zetasizer PRO particle size analyzer is used to test the DLS particle size of SiO2. A Thermo Fisher APREO2 high-performance field emission scanning electron microscope is used to test the silica sol obtained in S3. A DC24000UHR high-precision nano-particle size analyzer is used for testing.

[0052] Example 3

[0053] Except that the first alkaline solution B1 in step S1 is changed from potassium hydroxide to ethanolamine, the reaction is carried out in the same manner as the method described in Example 1 above, and pH = 9.98.

[0054] In step S3, a Malvern Zetasizer PRO particle size analyzer is used to test the DLS particle size of SiO2. A Thermo Fisher APREO2 high-performance field emission scanning electron microscope is used to test the silica sol obtained in S3. A DC24000UHR high-precision nano-particle size analyzer is used for testing.

[0055] Example 4

[0056] Except that TMOS in step S1 is replaced by tetraethoxysilane (TEOS), the reaction is carried out in the same manner as the method described in Example 1 above, and pH = 10.4.

[0057] In step S3, a Malvern Zetasizer PRO particle size analyzer is used to test the DLS particle size of SiO2. A Thermo Fisher APREO2 high-performance field emission scanning electron microscope is used to test the silica sol obtained in S3. A DC24000UHR high-precision nano-particle size analyzer is used for testing.

[0058] Example 5

[0059] Except that the second alkaline solution B2 in step S1 is changed from 1 wt% potassium hydroxide to 3 wt% potassium hydroxide, the reaction is carried out in the same manner as the method described in Example 1 above, and pH = 11.4.

[0060] In step S3, a Malvern Zetasizer PRO particle size analyzer is used to test the DLS particle size of SiO2. A Thermo Fisher APREO2 high-performance field emission scanning electron microscope is used to test the silica sol obtained in S3. A DC24000UHR high-precision nano-particle size analyzer is used for testing.

[0061] Example 6

[0062] The reaction was carried out in the same manner as in Example 1 except that the potassium aluminate in step S1 was replaced with sodium aluminate, and the pH was 10.1.

[0063] In step S3, the Malvern Zetasizer PRO particle size analyzer was used to test the DLS particle size of SiO2. The Thermo Fisher APREO2 high-performance field emission scanning electron microscope was used to test the silica sol obtained in S3. The DC24000UHR high-precision nanoparticle size analyzer was used for testing.

[0064] Example 7

[0065] The reaction was carried out in the same manner as in Example 1 except that the dripping rate in step S2 was changed from 1 g / min to 0.5 g / min, and the pH was 10.3.

[0066] In step S3, the Malvern Zetasizer PRO particle size analyzer was used to test the DLS particle size of SiO2. The Thermo Fisher APREO2 high-performance field emission scanning electron microscope was used to test the silica sol obtained in S3. The DC24000UHR high-precision nanoparticle size analyzer was used for testing.

[0067] Comparative Example 1

[0068] S1: prepare 240g of tetramethoxysilane (TMOS) purified by distillation into container A as a hydrolyzate; take 240mL of a 0.25wt% potassium hydroxide aqueous solution as a first alkaline solution B1; take 200mL of a 1wt% potassium hydroxide aqueous solution as a second alkaline solution B2;

[0069] S2: The first alkaline solution B1 is heated to boiling, and then the second alkaline solution B2 and TMOS are simultaneously added dropwise to the first alkaline solution B1 at a rate of 1 g / min. After the reaction is completed, the solution is kept warm for 30 min to obtain a dilute milky white spherical silica sol;

[0070] S3: The dilute milky white spherical silica sol obtained in S2 is concentrated under normal pressure and the by-product methanol and part of the water are removed by displacement. The final spherical silica sol concentration is 30% and the pH is 10.5.

[0071] In step S3, the Malvern Zetasizer PRO particle size analyzer was used to test the DLS particle size of SiO2. The Thermo Fisher APREO2 high-performance field emission scanning electron microscope was used to test the silica sol obtained in S3. The DC24000UHR high-precision nanoparticle size analyzer was used for testing.

[0072] Comparative Example 2

[0073] This comparative example adopts the traditional water glass method to prepare silica sol:

[0074] S1: Dilute water glass (Qingdao Gulf Chemical Co., Ltd., SSL3340) with pure water to a mass fraction of 5%, stir evenly and add to the regenerated strong acid sulfonic acid resin to perform cation exchange to obtain an active silicic acid solution. The pH of the active silicic acid solution is 2.2 and the silicon dioxide content is 4%.

[0075] S2: 500 g of active silicic acid solution was added dropwise to 500 g of 5 wt% potassium silicate aqueous solution at a rate of 5 g / min, stirred thoroughly and heated to boiling, and kept warm for 2 h to obtain silica sol;

[0076] S3: The dilute silica sol obtained in S2 is concentrated at normal pressure to remove the by-product water, and the final silica sol concentration is 30%

[0077] In step S3, the Malvern Zetasizer PRO particle size analyzer was used to test the DLS particle size of SiO2. The Thermo Fisher APREO2 high-performance field emission scanning electron microscope was used to test the silica sol obtained in S3. The DC24000UHR high-precision nanoparticle size analyzer was used for testing.

[0078] Comparative Example 3

[0079] The reaction was carried out in the same manner as in Example 1 except that in step S2, the hydrolyzate was first mixed with the second alkaline solution and then the mixed solution was added dropwise to the first alkaline solution, wherein the second alkaline solution was adjusted from 240 g of 1 wt % KOH solution to 480 g of 0.5 wt % KOH solution.

[0080] In step S3, the Malvern Zetasizer PRO particle size analyzer was used to test the DLS particle size of SiO2. The Thermo Fisher APREO2 high-performance field emission scanning electron microscope was used to test the silica sol obtained in S3. The DC24000UHR high-precision nanoparticle size analyzer was used for testing.

[0081] Comparative Example 4

[0082] Except that the second alkaline solution is not prepared in step S1, and only the hydrolyzed solution is added dropwise to the first alkaline solution in step S2, the other reactions are carried out in the same manner as described in the above-mentioned Example 1.

[0083] In step S3, a Malvern Zetasizer PRO particle size analyzer was used to measure the DLS particle size of SiO2. A Thermo Fisher APREO2 high-performance field emission scanning electron microscope was used to test the silica sol obtained in S3. A DC24000UHR high-precision nano-particle size analyzer was used for testing.

[0084] Comparative Example 5

[0085] Except that 0.05 wt% potassium metaaluminate in step S1 was replaced with 10 wt% potassium metaaluminate, the reaction was carried out in the same manner as described in the foregoing Example 1, and pH = 10.7.

[0086] In step S3, a Malvern Zetasizer PRO particle size analyzer was used to measure the DLS particle size of SiO2. A Thermo Fisher APREO2 high-performance field emission scanning electron microscope was used to test the silica sol obtained in S3. A DC24000UHR high-precision nano-particle size analyzer was used for testing.

[0087] Comparative Example 6

[0088] Except that 0.05 wt% potassium metaaluminate in step S1 was replaced with 0.05 wt% zirconium nitrate, the reaction was carried out in the same manner as described in the foregoing Example 1, and pH = 10.4.

[0089] In step S3, a Malvern Zetasizer PRO particle size analyzer was used to measure the DLS particle size of SiO2. A Thermo Fisher APREO2 high-performance field emission scanning electron microscope was used to test the silica sol obtained in S3. A DC24000UHR high-precision nano-particle size analyzer was used for testing.

[0090] Comparative Example 7

[0091] Except that the second alkaline solution B2 in step S1 was changed from 1 wt% potassium hydroxide to 5 wt% potassium hydroxide, the reaction was carried out in the same manner as described in the foregoing Example 1, and precipitation occurred.

[0092] Comparative Example 8

[0093] Except that the second alkaline solution B2 in step S1 was changed from 1 wt% potassium hydroxide to 1 wt% ethanolamine, the reaction was carried out in the same manner as described in the foregoing Example 1, and pH = 10.3.

[0094] In the examples and comparative examples, the physical properties of the silica sol were measured according to the following methods.

[0095] (1) The DLS particle size was measured using a Malvern Zetasizer PRO particle size analyzer;

[0096] (2) The particle size of CPS was measured using a DC24000 UHR high-precision nano particle size analyzer.

[0097] (3) SEM was measured using a Thermo Fisher APREO2 high-performance field emission scanning electron microscope.

[0098] Table 1 Physical property measurement results of Examples 1-7 and Comparative Examples 1-7

[0099]

[0100]

[0101]

[0102] As can be seen from Table 1, by comparing Examples 1-7 and Comparative Example 2, it can be known that compared with the traditional manufacturing method, the particle size of the silica sol prepared by the preparation method provided in this application is much larger than that of the traditional manufacturing method, and the adjustable range of its particle size is larger. Please refer to Figure 1 、 Figure 2 , the particle size of the silica sol prepared in Example 3 is larger.

[0103] By comparing Examples 1-7 and Comparative Examples 3-4, it can be known that when the hydrolysis solution is mixed with the second alkaline solution and then the first alkaline solution is added, or when only the hydrolysis solution is added to the first alkaline solution, the particle size of the silica sol prepared is much smaller than that of the silica sol provided in this application.

[0104] From Examples 1 and 3-4, it can be known that when the silicon source uses TMOS or TEOS and B1 uses an organic base or an inorganic base, the preparation method provided in this application can synthesize circular silica abrasives with corresponding particle sizes.

[0105] By comparing Example 1, Example 6 and Comparative Example 1, it can be known that compared with not adding aluminates, when doped with Al 3+ , the addition of aluminates can increase the particle size of the abrasive. By comparing Example 1, Example 6 and Comparative Example 5, it can be known that when the content of Al 3+ is too high, the particle size of the abrasive decreases instead. By comparing Example 1, Example 6 and Comparative Example 6, it can be known that when doped with other metal ions, the effect of regulating the particle size of the abrasive cannot be achieved. Please refer to Figure 3 、 Figure 4 , the particle size of the silica sol prepared in Comparative Example 5 is smaller.

[0106] By comparing Example 1, 5 and Comparative Example 7, it can be known that when the concentration of B2 is too high, precipitation will occur in the silica abrasive.

[0107] By comparing Examples 1, 2, and 7, it can be seen that the dropping speed has a great influence on the particle size. Generally speaking, the slower the dropping speed, the larger the particle size. When the dropping speed is lower than 1 g / min, the time cost increases significantly, but the particle size of the abrasive does not increase significantly; when the dropping speed is greater than 3 g / min, the particle size of the abrasive is smaller, and the morphology of some abrasives will be abnormal.

[0108] By comparing Example 1 and Example 8, it can be seen that when an organic base is used for B2, when the ethanolamine concentration is too high and the dropping speed is slow, the particle size of the silica sol is also small. If a silica sol with a larger particle size is desired, a slower dropping speed is required, and the time cost increases significantly.

[0109] Preparation of the polishing composition

[0110] The silica sol prepared in this application is diluted with pure water to a silica content of 5 wt%, glycine 1.5%, and triazole 0.2%, and stirred evenly to prepare a slurry precursor composition. The pH of the slurry precursor composition is adjusted to 9.5 using KOH, mixed with 1% hydrogen peroxide before polishing, and immediately stirred for 10 min to obtain a polishing composition for polishing copper.

[0111] Polishing experiment: The polishing composition is under a downward force of 1.3 psi, a platen rotation speed of 53 rpm, a head rotation speed of 50 rpm, a feeding rate of the polishing composition of 200 mL / min, the pad model is DH3410, and the disk model is AF38. By measuring the mass difference before and after polishing, the thickness is calculated as the polishing speed, and the results are listed in Table 2.

[0112] Table 2 Polishing results of Examples 1-7 and Comparative Examples 1-7

[0113]

[0114] As can be seen from Table 2, by comparing Examples 1-7 and Comparative Example 2, compared with the traditional manufacturing method, the polishing composition provided in this application has both increased OX polishing rate and Cu polishing rate. On the other hand, the number of surface defects of OX also has a certain decrease compared with the abrasives synthesized by the traditional method. While achieving a high polishing rate, low surface defects are also achieved. These results further illustrate that the abrasives synthesized by this method have both the same alkali resistance and polishing rate as the silica sol of the water glass method, and can have lower surface defects than the general water glass method silica sol. Among them, Examples 4 and 5 are the most preferred.

[0115] By comparing Examples 1-7 and Comparative Example 3, it can be seen that compared with the polishing composition provided in this application, the polishing composition prepared from the silica sol obtained by mixing the hydrolysis solution and the second alkaline solution and then adding the first alkaline solution has both lower OX polishing rate and Cu polishing rate, and a higher number of surface defects of OX.

[0116] By comparing Examples 1-7 with Comparative Example 4, it can be seen that compared with the polishing composition provided in the present application, the polishing composition prepared from the silica sol obtained by adding only the hydrolyzate to the first alkaline solution has lower OX polishing rate and Cu polishing rate.

[0117] By comparing Example 1, Example 6 with Comparative Example 1, compared with the method without adding aluminate, the polishing composition provided in the present application has increased OX polishing rate and Cu polishing rate, which is beneficial to improving the polishing efficiency and reducing the polishing time. By comparing Example 1, Example 6 with Comparative Example 5, it can be seen that when the content of Al 3+ is too high, the OX defects will increase significantly. By comparing Example 1, Example 6 with Comparative Example 6, it can be seen that when other metal ions are doped, the OX polishing rate and Cu polishing rate decrease, while the OX defects increase.

[0118] By comparing Example 1, 5 with Comparative Example 7, it can be seen that when the concentration of B2 is too high, precipitation of silica abrasive will occur and the polishing composition cannot be prepared.

[0119] By comparing Example 1, 2, 7, it can be seen that when the dropping rate is too low, the particle size of the abrasive is larger, although the polishing rate is higher, but the OX defects will increase. When the dropping rate is too high, the particle size of the abrasive is smaller and the polishing rate is lower.

[0120] By comparing Example 1 with 8, it can be seen that when organic base is used for B2, the particle size of the abrasive is smaller, the polishing rate is lower, and there are also more OX defects.

[0121] Although the embodiments of the present application have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present application. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present application is not limited to the specific details and the embodiments shown and described here.

Claims

1. A preparation method of silica sol, characterized in that It includes the following steps: S1: Using tetramethoxysilane or tetraethoxysilane as both the raw material and the hydrolysis solution, dissolve an inorganic base and / or an organic base in an aqueous solution to obtain a first basic solution, and dissolve an inorganic base in an aqueous solution to obtain a second basic solution; S2: Heat the first basic solution to boiling, and at 100 °C, add the hydrolysis solution and the second basic solution to the first basic solution at a preset rate to prepare spherical silica sol; S3: Heat the spherical silica sol to boiling under normal pressure or reduced pressure to remove by-products such as methanol and ethanol and a part of the water, and the concentration of the spherical silica sol is above 30%.

2. The preparation method of silica sol according to claim 1, wherein, The inorganic base is selected from one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium aluminate, and potassium aluminate, and the organic base is selected from one or more of ethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide, and choline. The first basic solution includes at least sodium aluminate or potassium aluminate.

3. The preparation method of the silica sol according to claim 2, characterized in that, Al in the first alkaline solution 3+ has a content of 0.005-1 wt%.

4. The preparation method of silica sol according to any one of claims 1-3, characterized in that, The content of aluminate in the first basic solution is 0.01 - 5 wt%, and the content of the base other than aluminate in the first basic solution is 0.1 - 0.5 wt%.

5. The preparation method of silica sol according to any one of claims 1-3, characterized in that, The content of the base in the second basic solution is 0.5 - 3 wt%.

6. The preparation method of silica sol according to any one of claims 1-3, characterized in that The preset rate is 1 - 3 g / min.

7. The preparation method of silica sol according to any one of claims 1 to 3, characterized in that, The alcohol residue in the final product in step S3 is less than 10 ppm.

8. A silica sol, characterized in that, It includes spherical silica sol obtained by using the preparation method described in any one of claims 1 - 7.

9. The silica sol according to claim 8, wherein The DLS particle size of the spherical silica sol is 35 - 105 nm.

10. A grinding composition, characterized in that, It includes the spherical silica sol described in any one of claims 8 - 9, and the grinding composition is used for grinding copper.

Images