Preparation method of strip-shaped silica sol
The problem of difficult to prepare stable strip silicon sol in the prior art is solved by ion exchange technology, and the preparation of silicon sols with high purity and low cost is achieved, which significantly improves the polishing effect of silicon wafers.
Patent Information
- Application Number
- CN202510101757.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-22
- Publication Date
- 2025-04-11
AI Technical Summary
It is difficult to prepare stable strip silicon sols in the prior art, and conventional orthosilicate hydrolysis can only produce spherical silicon sols, which cannot meet the demand for special-shaped silicon sols for chemical mechanical polishing of silicon wafers.
The formation of strip morphology is promoted through ion exchange technology, and the surface hydroxyl modification technology is used to improve the stability of strip silica sol to ensure its application in industrial production.
The preparation of strip silicon sol without introducing metal impurities is achieved, which meets the requirements of ultra-high-purity silicon sol for chemical mechanical polishing of silicon wafers and significantly improves the polishing effect of silicon wafers.
Smart Images
Figure CN119797376A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of silica sol preparation, and in particular relates to a method for preparing strip-shaped silica sol. Background Art
[0002] Chemical mechanical polishing (CMP) is currently recognized as the best global planarization technology for silicon wafers in the IC industry, and silica sol is the only abrasive available in silicon wafer CMP polishing liquid. The CMP process of silicon wafers is divided into edge polishing, rough polishing, medium polishing and fine polishing. Among them, the fine polishing process has extremely high requirements for the metal impurity content of silica sol abrasive. Usually, the sum of common metal contents such as sodium, potassium, calcium, magnesium, iron, and aluminum cannot exceed 1ppm. The orthosilicate hydrolysis process, that is, The process is the only technological solution that can meet this requirement and is also the method commonly used in the industry.
[0003] Conventional orthosilicate hydrolysis processes can usually only produce spherical silica sols. This is because the surface area of a sphere is the smallest under the same volume, so the surface energy of spherical particles is lower and they are more stable in thermodynamics. However, in the CMP process, it is sometimes desirable to use irregular silica sols, because irregular particles slide on the surface of the silicon wafer during polishing, while spherical particles are easy to roll. The friction coefficient of the former is much larger, so the polishing effect is often better.
[0004] There are some literatures on the preparation of shaped colloid particles by hydrolysis of orthosilicate, but most of the reports involve ellipsoidal or peanut-shaped products, and there are few reports on strip-shaped silica sol. In addition, the stability of strip-shaped silica sol is usually very poor, and appropriate measures must be taken to improve its stability in order to meet the requirements of silicon wafer CMP. Therefore, a method for preparing stable strip-shaped silica sol is urgently needed. Summary of the invention
[0005] The purpose of the present invention is to provide a method for preparing strip-shaped silica sol, which promotes the formation of strip-shaped morphology through ion exchange technology and improves the stability of strip-shaped silica sol by surface hydroxyl modification technology. The method is low-cost, does not introduce metal impurities, is suitable for industrial large-scale production, and can meet the strict requirements of chemical mechanical polishing of silicon wafers for ultra-high purity silica sol.
[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0007] A method for preparing strip-shaped silica sol comprises the following steps:
[0008] (1) adding anhydrous ethanol, water and tetraethyl orthosilicate into a flask and placing the flask in a high and low temperature water bath; preparing an ammonia solution and adding a portion of the ammonia solution into the flask using a peristaltic pump;
[0009] (2) subjecting the reactant obtained in step (1) to ion exchange through a strongly acidic cation exchange column, adjusting the solution to be acidic after the ion exchange, and continuing to stir to generate strip-shaped seed crystals;
[0010] (3) adding concentrated aqueous ammonia to the system of step (2) to adjust to alkalinity, adding all the remaining aqueous ammonia solution into the flask, and continuing to stir until the reaction is completed to obtain silica sol;
[0011] (4) Select a surface modification reagent, dilute it with ethanol to form a solution, add it to the silica sol obtained in step (3), and continue stirring until the reaction is completed to obtain a strip-shaped silica sol.
[0012] Furthermore, in step (1), the volume of anhydrous ethanol is 0.5 to 4.0 L, the volume of water is 200 to 750 mL, and the volume of tetraethyl orthosilicate is 100 to 400 mL.
[0013] Furthermore, in step (1), 100 to 600 mL of concentrated aqueous ammonia and 500 to 2000 mL of water are uniformly mixed to obtain an aqueous ammonia solution.
[0014] Furthermore, in step (1), the temperature of the water bath is maintained at 10-40° C.; the rate of adding the tax solution is 1-10 mL / min, and the amount added is 25%-50%.
[0015] Furthermore, in step (2), the strongly acidic cation exchange column is pre-activated with hydrochloric acid, and the rate at which the reactants pass through the strongly acidic cation exchange column is 50-200 mL / min.
[0016] Furthermore, after the ion exchange in step (2), the pH of the solution is adjusted to 4.0-6.0, and stirred at 10-40° C. for 10-100 min.
[0017] Furthermore, in step (3), the volume of concentrated ammonia water added is 20 to 100 mL, and the pH is adjusted to 9.0 to 10.5.
[0018] Furthermore, in step (3), the temperature is controlled at 10-40° C., and the rate of adding the aqueous ammonia solution is 1-10 mL / min.
[0019] Furthermore, the surface modification reagent in step (4) is selected from one of the modifiers containing a hydrophilic group such as γ-aminopropyltrimethoxysilane (KH-540), γ-aminopropyltriethoxysilane (KH-550), and γ-glycidyloxypropyltrimethoxysilane (KH-560).
[0020] Furthermore, in step (4), 5 to 25 mL of the surface modification reagent is diluted with 100 ml of ethanol to form a solution, and the solution addition rate is 0.5 to 5 mL / min.
[0021] The principle of the method of the present invention is as follows:
[0022] The method of the present invention adopts In the process, spherical small-particle seeds are first formed by hydrolysis of tetraethyl orthosilicate, and then the cations in the reactants are replaced with hydrogen ions using strong acid cation exchange technology, thereby reducing the pH value of the reaction system. The decrease in pH value leads to a decrease in the number of negative charges on the surface of the colloid particles, a decrease in Coulomb repulsion, and the promotion of the approach, collision and covalent connection of the spherical seeds, and finally the formation of strip-shaped seeds. Subsequently, the further growth of the strip-shaped seeds is promoted by adjusting the pH and reaction conditions. In order to solve the problem of poor storage stability of strip-shaped silica sol, after the particle size growth is completed, a surface modification reagent containing a hydrophilic group is used to partially modify the hydroxyl groups on the surface of the colloid particles to reduce the surface reactivity and improve the storage stability of the product.
[0023] The beneficial effects achieved by the present invention are as follows:
[0024] 1. The present invention promotes the formation of strip crystal seeds through ion exchange technology without introducing any metal impurities, thus meeting the requirements of chemical mechanical polishing of silicon wafers for ultra-high purity silica sol.
[0025] 2. The present invention adopts surface modification technology to effectively improve the storage stability of strip silica sol. Under the condition of 25% silicon dioxide content, it can be stably stored for more than one year.
[0026] 3. The present invention is low-cost, does not require special equipment, is suitable for industrial large-scale production, and has high economy and applicability.
[0027] 4. The strip-shaped silica sol prepared by the present invention has a large specific surface area and a high polishing friction coefficient, and can significantly improve the fine polishing effect of chemical mechanical polishing of silicon wafers. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 This is an electron microscope photograph of the strip-shaped silica sol prepared in Example 1.
[0029] Figure 2 This is an electron microscope photograph of the strip silica sol prepared in Example 2.
[0030] Figure 3 This is an electron microscope photograph of the strip-shaped silica sol prepared in Example 3. DETAILED DESCRIPTION
[0031] In order to make the various technical features and advantages or technical effects in the above technical solutions of the present invention more obvious and easy to understand, they are described in detail below in conjunction with embodiments.
[0032] Example 1
[0033] (1) Preparation of reactants: Add 4.0L of anhydrous ethanol, 750mL of water and 400mL of tetraethyl orthosilicate into a flask. Add 600mL of concentrated ammonia (mass fraction 25%) and 2000mL of water into a beaker and seal it with plastic wrap. Place the flask in a high and low temperature water bath, maintain the temperature at 20±1°C, then add ammonia into the flask at a rate of 10mL / min. When the volume of ammonia added reaches 1300mL, stop feeding ammonia and prepare for cation exchange.
[0034] (2) Formation of strip-shaped seed crystals: The above reactants were passed through a cation exchange column (pre-activated with hydrochloric acid) at a rate of 50 mL / min. After passing through, the pH was about 5.0. The temperature was maintained at 10±1°C and stirred for 100 minutes to form strip-shaped seed crystals.
[0035] (3) Strip crystal seed growth: add 20 mL of concentrated aqueous ammonia to the system of step (2), at which time the pH rises to 9.0, maintain the temperature at 20±1°C, and then continue to add all the ammonia water that has not been added in (1) at a rate of 10 mL / min. After adding, stir for 1 hour to obtain silica sol.
[0036] (4) Surface modification of strip-shaped particles: Prepare 5 mL of γ-aminopropyltrimethoxysilane (KH-540), dissolve and dilute it with 100 mL of ethanol, and add the solution to the silica sol at a rate of 0.5 mL / min. After adding, stir for 1 hour to fully react to obtain a strip-shaped silica sol product. The electron microscope photo is shown in Figure 1 .
[0037] Example 2
[0038] (1) Preparation of reactants: Add 0.5L of anhydrous ethanol, 200mL of water and 100mL of tetraethyl orthosilicate into a flask. Add 100mL of concentrated ammonia (mass fraction 25%) and 1200mL of water into a beaker and seal it with plastic wrap. Place the flask in a high and low temperature water bath, maintain the temperature at 10±1°C, then add ammonia into the flask at a rate of 1.2mL / min. When the volume of ammonia added reaches 400mL, stop feeding ammonia and prepare for cation exchange.
[0039] (2) Formation of strip-shaped seed crystals: The above reactants were passed through a cation exchange column (pre-activated with hydrochloric acid) at a rate of 80 mL / min. After passing through, the pH was about 4.0. The temperature was maintained at 20±1°C and stirred for 30 min to form strip-shaped seed crystals.
[0040] (3) Strip crystal seed growth: add 100 mL of concentrated aqueous ammonia to the system of step (2), at which time the pH rises to 10.5, maintain the temperature at 10±1°C, and then continue to add all the remaining aqueous ammonia at a rate of 1.2 mL / min. After adding, stir for 1 hour to obtain silica sol.
[0041] (4) Surface modification of strip-shaped particles: Prepare 10 mL of γ-aminopropyltriethoxysilane (KH-550), dissolve and dilute it with 100 mL of ethanol, and add the solution to the silica sol at a rate of 1.5 mL / min. After adding, stir for 1 hour to fully react to obtain a strip-shaped silica sol product. The electron microscope photo is shown in Figure 2 .
[0042] Example 3
[0043] (1) Preparation of reactants: Add 1L of anhydrous ethanol, 250mL of water and 120mL of tetraethyl orthosilicate into a flask. Add 600mL of concentrated ammonia water (mass fraction 25%) and 2000mL of water into a beaker and seal it with plastic wrap. Place the flask in a high and low temperature water bath, maintain the temperature at 40±1°C, then add ammonia water into the flask at a rate of 5mL / min. When the volume of ammonia water added reaches 550mL, stop feeding ammonia water and prepare for cation exchange.
[0044] (2) Formation of strip-shaped seed crystals: The above reactants were passed through a cation exchange column (pre-activated with hydrochloric acid) at a rate of 200 mL / min. The pH after passage was about 6.0. The temperature was maintained at 40±1°C and stirred for 10 min to form strip-shaped seed crystals.
[0045] (3) Strip crystal seed growth: add 80 mL of concentrated aqueous ammonia to the system of step (2), at which time the pH rises to 10.0, maintain the temperature at 40±1°C, and then continue to add all the remaining aqueous ammonia at a rate of 100 mL / min. After adding, stir for 1 hour to obtain silica sol.
[0046] (4) Surface modification of strip-shaped particles: Prepare 25 mL of γ-glycidyloxypropyltrimethoxysilane (KH-560), dissolve and dilute it with 100 mL of ethanol, add the solution to the silica sol at a rate of 5 mL / min, stir for 1 hour after addition to fully react, and obtain a strip-shaped silica sol product. The electron microscope photo is shown in Figure 3 .
[0047] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions of the technical solutions of the present invention made by ordinary technicians in the field should all be included in the protection scope of the present invention. The protection scope of the present invention shall be based on what is defined in the claims.
Claims
1. A method for preparing strip-shaped silica sol, characterized in that: The following steps are involved: (1) Add anhydrous ethanol, water and tetraethyl orthosilicate into a flask and place it in a high and low temperature water bath; Prepare an ammonia solution and add a portion of the ammonia solution into the flask using a peristaltic pump; (2) subjecting the reactant obtained in step (1) to ion exchange through a strongly acidic cation exchange column, adjusting the solution to be acidic after the ion exchange, and continuing to stir to generate strip-shaped seed crystals; (3) adding concentrated aqueous ammonia to the system of step (2) to adjust to alkalinity, adding all the remaining aqueous ammonia solution into the flask, and continuing to stir until the reaction is completed to obtain silica sol; (4) Select a surface modification reagent, dilute it with ethanol to form a solution, add it to the silica sol obtained in step (3), and continue stirring until the reaction is completed to obtain a strip-shaped silica sol.
2. The preparation method according to claim 1, characterized in that In step (1), the volume of anhydrous ethanol is 0.5-4.0 L, the volume of water is 200-750 mL, and the volume of tetraethyl orthosilicate is 100-400 mL.
3. The preparation method according to claim 1, characterized in that: In step (1), 100 to 600 mL of concentrated aqueous ammonia and 500 to 2000 mL of water are uniformly mixed to obtain an aqueous ammonia solution.
4. The preparation method according to claim 1, characterized in that: In step (1), the temperature of the water bath is maintained at 10-40° C.; the rate of adding the tax solution is 1-10 mL / min, and the amount added is 25%-50%.
5. The preparation method according to claim 1, characterized in that: In step (2), the strongly acidic cation exchange column is pre-activated with hydrochloric acid, and the rate at which the reactants pass through the strongly acidic cation exchange column is 50-200 mL / min.
6. The preparation method according to claim 1, characterized in that: After the ion exchange in step (2), the pH of the solution is adjusted to 4.0-6.0, and stirred at 10-40° C. for 10-100 minutes.
7. The preparation method according to claim 1, characterized in that: In step (3), the volume of concentrated ammonia water added is 20-100 mL, and the pH is adjusted to 9.0-10.
5.
8. The preparation method according to claim 1, characterized in that: In step (3), the temperature is controlled at 10-40° C., and the rate of adding the aqueous ammonia solution is 1-10 mL / min.
9. The preparation method according to claim 1, characterized in that: In step (4), the surface modification reagent is selected from one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane.
10. The preparation method according to claim 1 or 9, characterized in that: In step (4), 5 to 25 mL of the surface modification reagent is diluted with 100 mL of ethanol to form a solution, and the solution addition rate is 0.5 to 5 mL / min.