Method for preparing large-particle-size spherical silica sol by gradient addition of catalyst
The sol-gel method with controlled catalyst addition at room temperature addresses the challenges of silica sol uniformity and stability, producing high-purity, large-diameter silica sols with controlled particle size and reduced solvent hazards, enhancing semiconductor process reliability and safety.
Patent Information
- Application Number
- CN202411285402.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-13
- Publication Date
- 2024-12-31
AI Technical Summary
Existing silica sol preparation methods face challenges in achieving high-purity, large-diameter spherical silica sols with consistent morphology, good uniformity, and batch-to-batch stability, while also dealing with safety hazards and high production costs due to solvent evaporation at elevated temperatures.
A sol-gel method involving controlled addition of an alkaline catalyst using a peristaltic pump to manage hydrolysis and polymerization rates, conducted at room temperature (10-30°C) to produce silica sols with controlled particle size and uniformity, using ethanol, propanol, isopropanol, butanol, or toluene as organic solvents and ammonia water or ammonium bicarbonate/carbonate as catalysts to maintain pH stability and prevent metal ion pollution.
The method produces silica sols with particle sizes between 50-200 nm, ±5 nm batch-to-batch stability, metal content <10 ppm, and PDI <0.05, reducing solvent evaporation risks and costs, and ensuring high purity and uniformity.
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Figure CN119219001A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of silica sol preparation methods, and in particular to a preparation method of large-diameter spherical silica sol and a product thereof. Background Art
[0002] Chemical mechanical polishing technology combines the corrosive effect of chemical reagents with the mechanical grinding effect of nanoparticles to achieve the flattening of the surface of devices such as sapphire, infrared materials, silicon substrates, silicon carbide substrates, integrated circuit chips, etc. It is currently the best global flattening technology. Silicon oxide, aluminum oxide and cerium oxide sol are the three most commonly used polishing liquid abrasives, among which silica sol is the most widely used and has the largest amount. With the continuous development of technology, chemical mechanical polishing technology has higher and higher requirements for indicators such as particle size, uniformity and purity of silica sol.
[0003] The preparation methods of silica sol include ion exchange method, elemental silicon hydrolysis method and sol-gel method. Sol-gel method is the main method for preparing high-purity and ultra-high-purity silica sol. In this method, ethyl orthosilicate, water and organic solvent are dissolved in a certain proportion, and reacted at a certain temperature and under acid / base catalysis to obtain silica sol.
[0004] Consistent morphology, good uniformity and good stability between batches are key indicators of silica sol performance, which have an important impact on the performance and yield of the polished products. How to control the reaction conditions to obtain high-purity silica sol with controllable morphology, good uniformity and good stability between batches is a difficult problem that urgently needs to be solved in the field of high-purity silica sol. It is also a difficult problem that urgently needs to be solved in the semiconductor industry to break the monopoly of the United States and Japan and truly realize localization.
[0005] The sol-gel method for preparing large-size spherical silica sol generally adopts a one-time feeding method. The particle size and uniformity of the silica sol are controlled by the three steps of hydrolysis, nucleation and particle growth. The competition and balance between the three are the key to process control. Zhao Ruiyu et al. reported that hydrolysis is the controlling step of the entire reaction.
[0006] In addition, the existing technology mostly uses 40-70°C as the reaction temperature. Since the method involves organic solvents such as ethanol, the higher the temperature, the more solvent volatilization will increase, thereby increasing production costs. At the same time, there is a major safety hazard when organic solvents enter the working environment. Summary of the invention
[0007] The invention provides a method for preparing large-diameter spherical silica sol by a sol-gel method, which can produce silica sols of different purities with spherical morphology, good particle size uniformity and good stability between batches, and the particle size control has a high degree of automation.
[0008] The method for preparing a large-particle spherical silica sol of the present invention comprises the following steps:
[0009] (1) Mix ethyl orthosilicate, water and an organic solvent in a certain proportion to prepare material A, place material A in a constant temperature water bath reactor, stir evenly, and keep the temperature constant to a certain set temperature.
[0010] (2) Mix the alkaline catalyst and water in a certain proportion to prepare material B for later use.
[0011] (3) Material B is gradually added to material A in a manner of decreasing flow rate gradient or increasing flow rate gradient until all the catalyst is added.
[0012] (4) After adding material B (catalyst), the reaction is continued at the set temperature for several hours to obtain large-particle spherical silica sol.
[0013] Furthermore, in step (1), the mass ratio of tetraethyl orthosilicate, water and organic solvent is 1:(0.3-15.0):(3.3-19.8), wherein the purity of tetraethyl orthosilicate is electronic grade, the organic solvent is analytical grade, and the water is ultrapure water (resistivity>18MΩ).
[0014] Furthermore, the temperature range in step (1) is set to 10-30° C., and the reaction temperature is controlled within the room temperature range, which can reduce the safety hazards caused by the evaporation of organic solvents into the working environment, while reducing the evaporation amount and the reagent cost.
[0015] Furthermore, the organic solvent in step (1) is selected from one of ethanol, propanol, isopropanol, butanol and toluene.
[0016] Furthermore, the alkaline catalyst in step (2) is one of ammonia water, a mixture of ammonium bicarbonate and ammonium carbonate, and the mass concentration of NH3 or NH4 is 1.25% to 9.35%. The alkaline catalyst is selected from a reagent with pH buffering capacity to maintain pH stability during the reaction process, and at the same time cannot introduce metal ions, that is, it cannot cause metal element pollution to the polishing liquid using silica sol as a raw material, so ammonia water or a mixture of ammonium bicarbonate and ammonium carbonate is selected as the alkaline catalyst.
[0017] Furthermore, in step (3), the feed pump for the alkaline catalyst is a speed-adjustable peristaltic pump, and the hydrolysis rate and polymerization rate of ethyl orthosilicate are controlled by the catalyst addition speed, thereby controlling the particle size and uniformity of the silica sol.
[0018] Furthermore, in step (3), the flow rate gradient is reduced in a manner that the flow rate is 3-5 ml / min for 0-0.5 hours, 2-3 ml / min for 0.5-1 hours, and then reduced to 1 ml / min until the addition of material B is completed; the flow rate gradient is increased in a manner that the flow rate is 1 ml / min for 0-0.5 hours, 2-3 ml / min for 0.5-1 hours, and then reduced to 3-5 ml / min until the addition of material B is completed. Under the same other conditions, the particle size of the silica sol formed by the flow rate gradient increase method is larger than the particle size of the silica sol formed by the flow rate gradient reduction method.
[0019] Furthermore, in step (4), the reaction is continued for several hours, that is, for 1 to 5 hours.
[0020] The invention also provides a large-particle-size spherical silica sol prepared by the method.
[0021] The silica sol prepared by the present invention has the following characteristics and beneficial effects:
[0022] 1) Large-particle silica sol: The particle size of the silica sol prepared in the present invention is between 50 and 200 nm.
[0023] 2) Batch-to-batch stability: The silica sol prepared by the present invention has a particle size fluctuation of less than ±5 nm between different batches under the same raw material ratio and process parameters.
[0024] 3) High-purity silica sol: The silica sol prepared by the present invention has a metal content of sodium, potassium, calcium, iron, aluminum, magnesium, copper, zinc, nickel, titanium, chromium, boron, lithium, manganese, etc. lower than 10 ppm, and can reach 1-2 ppm when electronic grade ethyl orthosilicate is used.
[0025] 4) Good particle size uniformity: The silica sol prepared by the present invention has a dispersibility PDI (tested by Malvern laser particle size analyzer) of less than 0.05.
[0026] 5) The particle size and uniformity of silica sol are controlled by the three steps of hydrolysis, nucleation and particle growth. The competition and balance between the three are the key to process control. The present invention controls the balance between the three by adding catalysts in a gradient manner, and finally obtains large-particle spherical silica sol with controllable particle size and good uniformity.
[0027] 6) The prior art mostly uses 40-70°C as the reaction temperature. The higher the temperature, the more solvent volatilization will increase, which will lead to higher production costs. At the same time, there are also great safety hazards when organic solvents enter the working environment. The present invention mainly prepares large-particle spherical silica sol at room temperature (10-30°C), which can reduce these problems. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1: Scanning electron microscope image of 90nm large-particle silica sol prepared by the method of the present invention.
[0029] Figure 2 : Scanning electron microscope image of 180nm large-particle silica sol prepared by the method of the present invention. DETAILED DESCRIPTION
[0030] In order to facilitate the understanding of the present invention, several embodiments are described in detail below, but the present invention includes but is not limited to the embodiments described below.
[0031] Example 1
[0032] 43 grams of ethyl orthosilicate, 85 grams of ultrapure water, and 316 grams of ethanol are placed in a 1-liter flask to prepare material A. Stir well and place material A in a water bath to keep the temperature at 25°C. 43 grams of 25%wt ammonia water are added to 180 grams of water to prepare material B. Stir well and place in a sealed bottle with a lid for later use. Add material B to material A using a peristaltic pump, stirring A+B materials while adding, while keeping the temperature fluctuation less than ±1°C. The feeding method of material B is to adjust the speed of the peristaltic pump to 4ml / min for the first 30 minutes, reduce the feeding speed to 2ml / min for 30-60 minutes, and reduce the feeding speed to 1ml / min after 60 minutes until all the catalysts are added. After the end, maintain 25±1°C and continue stirring for 3 hours. Use ultrafiltration equipment to concentrate the product to a solid content of 20±2%, thereby obtaining a large-particle spherical silica sol. The scanning electron microscope image of the 90nm large-particle silica sol prepared by the method described in this embodiment is as follows Figure 1 shown.
[0033] Example 2
[0034] In order to demonstrate the batch-to-batch stability of the method, the formulation and control parameters of Example 1 were repeated.
[0035] Example 3
[0036] 43 grams of ethyl orthosilicate, 85 grams of ultrapure water, and 316 grams of ethanol are placed in a 1-liter flask to prepare material A, and the material A is placed in a water bath at a constant temperature of 25°C after stirring. 43 grams of 25% wt ammonia water is added to 180 grams of water to prepare material B, and the material is placed in a sealed bottle with a lid for standby use after stirring. Material B is added to material A with a peristaltic pump, and A+B materials are stirred while adding, while keeping the temperature fluctuation less than ±1°C. The feeding method of material B is to adjust the speed of the peristaltic pump to 1ml / min for the first 30 minutes, increase the feeding speed to 2ml / min for 30-60 minutes, and increase the feeding speed to 4ml / min after 60 minutes until all the catalysts are added. After the end, maintain 25±1°C and continue stirring for 3 hours. The product is concentrated to a solid content of 20±2% using ultrafiltration equipment to obtain a large-particle spherical silica sol.
[0037] Example 4
[0038] Place 43g of ethyl orthosilicate, 85g of ultrapure water and 316g of ethanol in a 1L flask to prepare material A. Stir evenly and place material A in a water bath to maintain a constant temperature of 25°C. Add 39.5g of ammonium bicarbonate and 24.0g of ammonium carbonate to 1L of ultrapure water to prepare NH4 + A mixture of 1mol / L ammonium bicarbonate and ammonium carbonate is prepared for use. Take 8ml of the above mixture and add it to 215g of water to make material B. After stirring evenly, place it in a sealed bottle with a lid for use. Add material B to material A with a peristaltic pump, stir A+B materials while adding, and keep the temperature fluctuation less than ±1°C. The feeding method of material B is to adjust the speed of the peristaltic pump to 1ml / min in the first 30min, increase the feeding speed to 2ml / min for 30-60min, and increase the feeding speed to 4ml / min after 60min until all the catalyst is added. After the end, maintain 25±1°C and continue stirring for 3 hours. Use ultrafiltration equipment to concentrate the product to a solid content of 20±2%, thereby obtaining a large-particle spherical silica sol.
[0039] Example 5
[0040] 43 grams of tetraethyl orthosilicate, 85 grams of ultrapure water, and 316 grams of ethanol were placed in a 1-liter flask to prepare material A, and the material A was placed in a water bath at a constant temperature of 12°C after stirring. 43 grams of 25% wt ammonia water was added to 180 grams of water to prepare material B, and the material was placed in a sealed bottle with a lid for standby use after stirring. Material B was added to material A using a peristaltic pump, and material A+B was stirred while adding, while keeping the temperature fluctuation less than ±1°C. The feeding method of material B was to adjust the speed of the peristaltic pump to 1ml / min for the first 30min, increase the feeding speed to 2ml / min for 30-60min, and reduce the feeding speed to 4ml / min after 60min until the catalyst was completely added. After the end, the temperature was maintained at 12±1°C and continued to stir for 3 hours. The product was concentrated to a solid content of 20±2% using an ultrafiltration device, thereby obtaining a large-particle spherical silica sol. The metal element content of the 180nm large-particle silica sol prepared by the method described in this embodiment is shown in Table 2. The scanning electron microscope image of the 180 nm large particle size silica sol prepared by the method described in this example is as follows: Figure 2 shown.
[0041] The silica sols obtained in Examples 1-5 were characterized, and their performance indicators are shown in Table 1.
[0042] Table 1. Properties of silica sols prepared in Examples 1-5
[0043]
[0044] Table 2. Metal element content of 180 nm large particle size silica sol prepared by the method of the present invention
[0045]
[0046] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and implement it accordingly. It can be understood by those skilled in the art that various replacements, changes and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the contents disclosed in the embodiments of this specification, and the scope of protection of the present invention shall be subject to the scope defined in the claims.
Claims
1. A method for preparing large-size spherical silica sol by gradient addition of catalyst, characterized in that: The following steps are involved: Mixing tetraethyl orthosilicate, water and an organic solvent in a certain proportion to prepare material A, placing material A in a constant temperature water bath reactor, stirring evenly, and keeping the temperature constant to a set temperature for later use; Mix the alkaline catalyst and water in a certain proportion to prepare material B for later use; Add material B gradually into material A in a manner of decreasing flow rate gradient or increasing flow rate gradient; After adding material B, the reaction is continued for several hours at the set temperature to obtain large-diameter spherical silica sol.
2. The method according to claim 1, characterized in that: The organic solvent is one of ethanol, propanol, isopropanol, butanol and toluene; the mass ratio of tetraethyl orthosilicate, water and organic solvent is 1:(0.3-15.0):(3.3-19.8); the tetraethyl orthosilicate is electronic grade, the other reagents are analytical grade, and the water is ultrapure water with a resistivity of >18MΩ; the set temperature is 10-30°C.
3. The method according to claim 1, characterized in that: The alkaline catalyst is ammonia water or a mixture of ammonium bicarbonate and ammonium carbonate, and the mass concentration of NH3 / NH4 is 1.25% to 9.35%.
4. The method according to claim 1, characterized in that A feed pump is used to gradually add material B into material A in a manner of decreasing flow rate gradient or increasing flow rate gradient, and the feed pump is a speed-adjustable peristaltic pump.
5. The method according to claim 1, characterized in that The flow rate gradient is reduced in the following manner: the flow rate is 3-5 ml / min for 0-0.5 hours, 2-3 ml / min for 0.5-1 hour, and then reduced to 1 ml / min until material B is added.
6. The method according to claim 1, characterized in that The flow rate gradient is increased in the following manner: the flow rate is 1 ml / min for 0-0.5 hours, 2-3 ml / min for 0.5-1 hour, and then reduced to 3-5 ml / min until the addition of material B is completed.
7. The method according to claim 1, characterized in that The said continuing the reaction for several hours means continuing the reaction for 1 to 5 hours.
8. The method according to claim 1, characterized in that The large-particle spherical silica sol is a silica sol dispersed in an organic phase, and the solid content of the silica sol is 0.5% to 5%.
9. The method according to claim 1, characterized in that: The method also includes the step of concentrating the obtained large-particle spherical silica sol, wherein the concentration is carried out by vacuum distillation or ultrafiltration concentration, and finally a large-particle spherical silica sol product with a solid content of 5% to 20% is obtained.
10. The large-particle spherical silica sol prepared by the method according to any one of claims 1 to 9.