Colloidal silicon dioxide with low metal impurity content and preparation method and application thereof
By mixing the organic alkali solution with ultrapure water under stirring conditions, and heating the hydrolysate of alkyl silicate dropwise, colloidal silica with low metal impurity content, high purity and controllable particle size were prepared, which solved the problems of high metal impurity content, high production cost and difficult particle size control in the colloidal silica preparation method in the prior art. It is suitable for polishing applications in semiconductor manufacturing.
Patent Information
- Application Number
- CN202411945339.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2025-04-04
AI Technical Summary
The existing colloidal silica preparation methods have problems such as high metal impurities content, high production costs and difficult to control particle size, which is difficult to meet the demand for high purity, low cost and controllable abrasive particles in semiconductor manufacturing.
The organic alkali solution was mixed with ultrapure water under stirring to obtain a mother liquor, and the mother liquor was heated to a reflux state, and the alkyl silicate hydrolysate was added dropwise at a uniform speed, while an alkaline catalyst was added to maintain the pH value of the reaction solution from 7 to 10, and colloidal silica with low metal impurity content was obtained by heating and concentration.
The preparation of colloidal silica with low metal impurity content, high purity, low production cost and controllable particle size is achieved. It is suitable as abrasive particles of CMP polishing liquid and is suitable for large-scale production.
Smart Images
Figure CN119750592A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of polishing liquid, and in particular to colloidal silicon dioxide with low metal impurity content and a preparation method and application thereof. Background Art
[0002] Chemical mechanical polishing (CMP) combines the advantages of chemical corrosion and mechanical grinding. It is widely used in semiconductor manufacturing to flatten the surface of wafers. Among them, CMP polishing liquid is one of the key factors affecting polishing quality and polishing efficiency. As an important component of polishing liquid, the physical and chemical properties of abrasive particles directly affect the mechanical grinding effect, material removal rate, chemical reaction and corrosion, adsorption and transportation of the wafer surface. At present, many abrasive particles such as silicon dioxide, aluminum oxide and cerium dioxide have been gradually developed to meet different polishing needs. Among them, colloidal silica is widely used in the semiconductor field due to its advantages such as high polishing efficiency, excellent surface quality, good dispersibility and stability.
[0003] The preparation methods of colloidal silica mainly include ion exchange method, one-step dissolution method of elemental silicon and silanol hydrolysis method. The ion exchange method is the most mature and widely used process at present. It uses water glass as the main raw material to prepare a dilute polysilicic acid solution through a strong acid cation exchange resin. After that, the polysilicic acid solution is added to the mother liquor containing seed particles for growth to obtain a silica sol with a low content of metal impurities. However, this process often requires strict control of the concentration of reactants, and the reuse of ion exchange resins will produce a large amount of wastewater. The one-step dissolution method of elemental silicon uses elemental silicon as a raw material, and reacts it with pure water under the catalysis of inorganic or organic bases to obtain silica sol. The particle size, viscosity, pH value, density, purity and other indicators of the silica sol product obtained by this method are also easier to control than other methods. However, most of its particles are non-spherical and the morphology cannot be controlled. In addition, the silanol hydrolysis method requires the participation of organic solvents and has high preparation costs. Therefore, there is an urgent need to find a method for preparing high-purity colloidal silica with low manufacturing cost, low metal impurity content and controllable particle size. Summary of the invention
[0004] The purpose of the present invention is to provide a colloidal silicon dioxide with low metal impurity content and a preparation method and application thereof. The colloidal silicon dioxide prepared by the method provided by the present invention has low metal impurity content, high purity, low production cost and controllable particle size.
[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0006] The present invention provides a method for preparing colloidal silicon dioxide with low metal impurity content, comprising the following steps:
[0007] (1) mixing an organic base solution with ultrapure water under stirring to obtain a mother liquor;
[0008] (2) The mother liquor obtained in step (1) is heated to reflux, and the alkyl silicate hydrolyzate is added dropwise at a uniform rate, and an alkaline catalyst is added to maintain the pH value of the reaction liquid at 7 to 10, and the reaction liquid is concentrated by heating to obtain colloidal silica with a low metal impurity content.
[0009] Preferably, the concentration of the organic base in the organic base solution in step (1) is 20 to 30 wt %.
[0010] Preferably, the pH value of the mother liquor in step (1) is 7-9.
[0011] Preferably, the alkyl silicate in the alkyl silicate hydrolyzate in step (2) is at least one of methyl orthosilicate and ethyl orthosilicate.
[0012] Preferably, the concentration of silicon dioxide in the alkyl silicate hydrolyzate in step (2) is 1 to 12 wt %.
[0013] Preferably, in step (2), the dropping speed of the alkyl silicate hydrolyzate is 0.7 to 41 g silicon dioxide / hour / kg mother liquor, and the injection time of the alkyl silicate hydrolyzate is 700 to 2000 min.
[0014] Preferably, the alkaline catalyst in step (2) is at least one of tetramethylammonium hydroxide, triethanolamine and ammonia.
[0015] Preferably, the pH value of the reaction solution in step (2) is maintained at 8-9.
[0016] The present invention also provides colloidal silicon dioxide with low metal impurity content prepared by the preparation method described in the above technical solution, characterized in that the average primary particle size of the colloidal silicon dioxide with low metal impurity content is 10 to 20 nm.
[0017] The present invention also provides the use of the colloidal silicon dioxide with low metal impurity content described in the above technical solution in polishing.
[0018] The present invention provides a method for preparing colloidal silica with low metal impurity content. The present invention mixes an organic alkaline solution with ultrapure water under stirring conditions to obtain a mother liquor; the mother liquor is heated to a reflux state, and an alkyl silicate hydrolyzate is added dropwise at a uniform speed to control the growth rate of silica particles, thereby obtaining silica particles with few residual silanol groups, and an alkaline catalyst is added to maintain the pH value of the reaction liquid at 7 to 10, promote further hydrolysis of the alkyl silicate, and prevent the reaction liquid from gelling, thereby ensuring the normal progress of the hydrolysis reaction, and obtain colloidal silica with low metal impurity content after heating and concentration. The colloidal silica prepared by the method provided by the present invention has low metal impurity content and controllable particle size, uniform particle size, regular morphology, and can be used as CMP polishing liquid grinding particles, and the method of the present invention is simple to operate, low in cost, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a TEM image of colloidal silicon dioxide with low metal impurity content prepared in Example 3 of the present invention. DETAILED DESCRIPTION
[0020] The present invention provides a method for preparing colloidal silicon dioxide with low metal impurity content, comprising the following steps:
[0021] (1) mixing an organic base solution with ultrapure water under stirring to obtain a mother liquor;
[0022] (2) The mother liquor obtained in step (1) is heated to reflux, and the alkyl silicate hydrolyzate is added dropwise at a uniform rate, and an alkaline catalyst is added to maintain the pH value of the reaction liquid at 7 to 10, and the reaction liquid is concentrated by heating to obtain colloidal silica with a low metal impurity content.
[0023] In the present invention, unless otherwise specified, the raw materials used are conventional commercial products in the art.
[0024] The invention mixes the organic alkali solution with ultrapure water under stirring conditions, and obtains a mother liquor by adjusting the pH.
[0025] In the present invention, the concentration of the organic base in the organic base solution is preferably 20 to 30 wt %. In the present invention, the organic base is preferably at least one of tetramethylammonium hydroxide (TMAH), 3-ethoxypropylamine (3-EOPA), triethylamine (TEA), and dipropylamine (DPA).
[0026] In the present invention, the pH value of the mother liquor is preferably 7 to 9. In the present invention, the reagent used to adjust the pH is preferably an alkaline catalyst; the alkaline catalyst is preferably at least one of tetramethylammonium hydroxide, 3-ethoxypropylamine, triethylamine and dipropylamine. The present invention adjusts the hydrolysis rate of the alkyl silicate by controlling the pH value of the mother liquor to control the growth rate of the silicon dioxide particles and reduce the residue of the alkyl silicate in the prepared silicon dioxide particles.
[0027] After obtaining the mother liquor, the present invention heats the mother liquor to reflux state, uniformly drops the alkyl silicate hydrolyzate, and simultaneously adds an alkaline catalyst to maintain the pH value of the reaction liquid at 7-10, and heats and concentrates to obtain colloidal silicon dioxide with low metal impurity content.
[0028] In the present invention, the alkyl silicate in the alkyl silicate hydrolyzate is preferably at least one of methyl orthosilicate and ethyl orthosilicate.
[0029] In the present invention, the method for preparing the alkyl silicate hydrolyzate preferably comprises:
[0030] At room temperature and under stirring conditions, alkyl silicate is added to ultrapure water, and after the reaction solution gradually changes into a clear state, a hydrolysis reaction is carried out for 1 to 2 hours to obtain an alkyl silicate hydrolyzate.
[0031] In the present invention, the mass ratio of the ultrapure water to the alkyl silicate is preferably (10-14):1, more preferably 12:1.
[0032] In the present invention, the concentration of silicon dioxide in the alkyl silicate hydrolyzate is preferably 1 to 12 wt%, more preferably 3 to 9 wt%. The present invention controls the concentration of silicon dioxide in the alkyl silicate hydrolyzate within the above range to prevent the gelation of the alkyl silicate hydrolyzate and ensure the normal progress of the hydrolysis reaction. In the present invention, the dripping speed of the alkyl silicate hydrolyzate is preferably 0.7 to 41 g silicon dioxide / hour / kg mother liquor. In the present invention, the injection time of the alkyl silicate hydrolyzate is preferably 700 to 2000 min, more preferably 720 to 1800 min. The present invention adjusts the hydrolysis rate of the alkyl silicate by controlling the dripping speed and injection time of the alkyl silicate hydrolyzate to control the growth rate of the silica particles, and combines the principle of economy to reduce the residue of the alkyl silicate in the prepared silica particles.
[0033] In the present invention, the alkaline catalyst is preferably at least one of tetramethylammonium hydroxide, triethanolamine and ammonia.
[0034] In the present invention, the pH value of the reaction solution is preferably maintained at 8 to 9. The present invention controls the pH value of the reaction solution to avoid gelation, thereby ensuring that the hydrolysis reaction proceeds normally under the condition that the alkyl silicate is completely hydrolyzed.
[0035] In the present invention, the heating and concentration method is preferably distillation. The present invention has no special limitation on the distillation method, and the purpose of concentration and alcohol removal can be achieved by using technical solutions well known in the art.
[0036] The present invention also provides colloidal silicon dioxide with low metal impurity content prepared by the preparation method described in the above technical solution.
[0037] In the present invention, the average primary particle size of the colloidal silica having a low metal impurity content is preferably 10 to 20 nm.
[0038] The present invention also provides the use of the colloidal silicon dioxide with low metal impurity content described in the above technical solution in polishing.
[0039] In the present invention, the colloidal silica with low metal impurity content is preferably used as abrasive particles in the CMP polishing liquid.
[0040] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. 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.
[0041] Example 1
[0042] A method for preparing colloidal silicon dioxide with low metal impurity content, comprising the following steps:
[0043] (1) Under stirring conditions, 0.05 g of a 25 wt% TMAH solution was added to 500 g of ultrapure water and mixed evenly to obtain a mother solution with a pH value of 8;
[0044] (2) adding the mother liquor obtained in step (1) into a 3L glass reactor with four ports containing a thermometer, a condenser, a stirrer and an injection port, and continuously heating the mother liquor to a reflux state under stirring, and then dropping TMOS hydrolyzate at a uniform rate, the injection rate is 9 g silica / h / kg mother liquor, and the continuous injection time is 720 min. Since TMOS hydrolyzate is weakly acidic, the introduction of TMOS hydrolyzate will cause the pH of the reaction solution to decrease. The pH of the reaction solution needs to be detected every half an hour, and the corresponding TMAH is added to stabilize the pH of the reaction solution at 8 to obtain a reaction solution;
[0045] The preparation method of the TMOS hydrolyzate is as follows: 34.2 g of TMOS is weighed in a beaker, and 415.8 g of ultrapure water is weighed in another beaker; 34.2 g of TMOS weighed in advance is gradually added to the weighed 415.8 g of ultrapure water under room temperature and stirring, and after TMOS is added to the ultrapure water, the solution immediately becomes turbid, and after 15 minutes, the solution gradually becomes clear, and the hydrolysis reaction is continued for 1 hour to obtain a TMOS hydrolyzate with a silicon dioxide content of 3 wt%;
[0046] The mass ratio of the ultrapure water to the alkyl silicate is 12:1;
[0047] 500 mL of the reaction solution was added to a 1 L 2 L glass reactor with four ports including a thermometer, a condenser, a stirrer and an injection port, and heated and concentrated. During the concentration process, the reaction solution of the same volume as the fraction was added to maintain a constant liquid level, and finally colloidal silica with a silica content of 12% and low metal impurity content was obtained.
[0048] Example 2
[0049] Colloidal silica with low metal impurity content was prepared according to the method of Example 1, except that the injection rate of the TMOS hydrolyzate was 7.2 g silica / h / kg mother liquor, and the injection time of the TMOS hydrolyzate was 900 min.
[0050] Example 3
[0051] Colloidal silica with low metal impurity content was prepared according to the method of Example 1, except that the injection rate of the TMOS hydrolyzate was 5.4 g silica / h / kg mother liquor, and the injection time of the TMOS hydrolyzate was 1200 min.
[0052] Figure 1 This is a TEM image of colloidal silicon dioxide with low metal impurity content prepared in Example 3 of the present invention. Figure 1 It can be seen that the colloidal silicon dioxide prepared in Example 3 has uniform particle size and good dispersibility.
[0053] Example 4
[0054] Colloidal silica with low metal impurity content was prepared according to the method of Example 1, except that the injection rate of the TMOS hydrolyzate was 3.6 g silica / h / kg mother liquor, and the injection time of the TMOS hydrolyzate was 1800 min.
[0055] The colloidal silica prepared in Example 3 was detected by inductively coupled plasma mass spectrometry and found that the alkali metal impurity content was less than 300 ppb, and the heavy metal impurity content was less than 100 ppb.
[0056] The properties of the mother solutions and TMOS hydrolyzate prepared in Examples 1 to 4, and the colloidal silicon dioxide with low metal impurity content are shown in Table 1.
[0057] In Table 1, the injection rate of TMOS hydrolyzate is calculated based on the mass of TMOS hydrolyzate added per minute; the specific gravity (20 / 4°C) is measured by a hydrometer, the viscosity (mPa·s) is measured by a viscometer, the PDI is measured by a nanoparticle size and Zeta potential analyzer, and the BET (m 2 / g), and the alkali metal impurity content and heavy metal impurity content were detected by inductively coupled plasma mass spectrometry;
[0058] The method for determining the average primary particle size is as follows: drying the corresponding colloidal silica obtained at 140°C for 24 hours, and then calcining at 800°C for 1 hour to obtain a sample; using the prepared sample to determine BET, and using the value of 2727 / BET as the average primary particle size of the silica particles in the colloidal silica;
[0059] Average secondary particle size: measured by nanoparticle size and Zeta potential analyzer (DLS);
[0060] Aggregation ratio: The ratio of the average secondary particle size to the average primary particle size is taken as the aggregation ratio.
[0061] Performance of the mother solution and TMOS hydrolyzate prepared in Examples 1 to 4, and colloidal silicon dioxide with low metal impurity content
[0062]
[0063]
[0064] Example 5
[0065] Colloidal silicon dioxide with low metal impurity content was prepared according to the method of Example 3, except that:
[0066] The mother liquor is prepared by adding 0.05 g of 25 wt% 3-ethoxypropylamine (3-EOPA) solution to 500 g of ultrapure water under stirring and mixing evenly to obtain a mother liquor with a pH value of 7.7.
[0067] Example 6
[0068] Colloidal silicon dioxide with low metal impurity content was prepared according to the method of Example 3, except that:
[0069] The mother solution is prepared by adding 0.05 g of a 25 wt % triethylamine (TEA) solution to 500 g of ultrapure water under stirring and mixing the mixture evenly to obtain a mother solution with a pH value of 8.
[0070] Example 7
[0071] Colloidal silicon dioxide with low metal impurity content was prepared according to the method of Example 3, except that:
[0072] The mother liquor is prepared by adding 0.05 g of a 25 wt% dipropylamine (DPA) solution to 500 g of ultrapure water under stirring and mixing the mixture evenly to obtain a mother liquor with a pH value of 7.85.
[0073] The properties of the mother solutions and TMOS hydrolyzate prepared in Examples 5 to 7, and the colloidal silicon dioxide with low metal impurity content were measured by the same detection method as in Table 1, as shown in Table 2.
[0074] Performance of the mother liquor and TMOS hydrolyzate prepared in Examples 5 to 7, and the colloidal silicon dioxide with low metal impurity content
[0075]
[0076]
[0077] In summary, as the injection speed of TMOS hydrolyzate gradually decreases and the injection time gradually prolongs, the primary particle size of the silica particles gradually increases, indicating that a lower injection speed of TMOS hydrolyzate and a longer injection time are more conducive to the growth of silica particles. In addition, by adding different types of alkaline catalysts, the particle size, specific gravity and viscosity of the silica particles did not change significantly, so adjusting the type of alkaline catalyst had a weak effect on the silica particles. And the colloidal silica prepared by the method provided by the present invention has a low content of metal impurities.
[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing colloidal silicon dioxide with low metal impurity content, characterized in that: The following steps are involved: (1) mixing an organic base solution with ultrapure water under stirring to obtain a mother liquor; (2) The mother liquor obtained in step (1) is heated to reflux, and the alkyl silicate hydrolyzate is added dropwise at a uniform rate, and an alkaline catalyst is added to maintain the pH value of the reaction liquid at 7 to 10, and the reaction liquid is concentrated by heating to obtain colloidal silica with a low metal impurity content.
2. The preparation method according to claim 1, characterized in that: The concentration of the organic base in the organic base solution in step (1) is 20 to 30 wt%.
3. The preparation method according to claim 1, characterized in that: The pH value of the mother liquor in step (1) is 7-9.
4. The preparation method according to claim 1, characterized in that: In the step (2), the alkyl silicate in the alkyl silicate hydrolyzate is at least one of methyl orthosilicate and ethyl orthosilicate.
5. The preparation method according to claim 1, characterized in that: The concentration of silicon dioxide in the hydrolyzate of alkyl silicate in step (2) is 1 to 12 wt %.
6. The preparation method according to claim 1, characterized in that: In the step (2), the dropping speed of the alkyl silicate hydrolyzate is 0.7 to 41 g silicon dioxide / hour / kg mother liquor, and the injection time of the alkyl silicate hydrolyzate is 700 to 2000 min.
7. The preparation method according to claim 1, characterized in that: In the step (2), the alkaline catalyst is at least one of tetramethylammonium hydroxide, triethanolamine and ammonia.
8. The preparation method according to claim 1, characterized in that: In the step (2), the pH value of the reaction solution is maintained at 8-9.
9. Colloidal silicon dioxide with low metal impurity content prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The average primary particle size of the colloidal silicon dioxide with low metal impurity content is 10 to 20 nm.
10. Use of the colloidal silicon dioxide with low metal impurity content as claimed in claim 9 in polishing.