A preparation method and application of high-purity silica sol

Abstract

The present invention provides a preparation method and application of high-purity silica sol, and relates to the field of inorganic compound materials. The preparation method includes: sodium silicate, water and flocculant are mixed and diluted to a silica mass fraction of 4% to 8%, supernatant is taken after centrifugation, silicic acid is obtained by cation exchange resin, pH regulator is added and stirred evenly until the pH value is 8 to 12, cation exchange resin, anion exchange resin and cation exchange resin in resin exchange column are passed through successively, active silicic acid is passed into reactor, and the reactor is also connected with a membrane filter, pure water is added into the reactor, and the membrane filter is opened after heating to 60-99°C, and active silicic acid is continuously added to obtain high-purity silica sol. The present invention can synthesize large-particle size silica sol at a relatively low temperature, and has the advantages of high purity, low cost and simple process, is suitable for mass production, and can be applied to the polishing operation of semiconductor devices.

Description

Technical Field

[0001] The invention relates to the field of electronic-grade high-purity inorganic silicon compound materials, and in particular to a preparation method and application of high-purity silica sol for electronic polishing. Background Art

[0002] Silica sol is a dispersion of nano-scale silicon dioxide particles in water or solvent. Since SiO2 in silica sol contains a large amount of water and hydroxyl groups, silica sol can also be expressed as SiO2.nH2O. It is a colloidal solution with properties such as odorlessness, non-toxicity, high dispersibility and high temperature resistance. It is widely used in papermaking, casting, coatings and chemical mechanical polishing. In recent years, high-purity silica sol has been widely used in chemical mechanical polishing of semiconductor devices and semiconductor materials such as silicon, germanium, and indium phosphide. With the development of semiconductor devices, the requirements for device surface quality and precision are getting higher and higher. The metal ions contained in silica sol have a serious impact on its application. At present, high-purity silica sol is prepared with silicate as raw material. Silicate will decompose organic solvents and is difficult to remove. In addition, the price of silicate is relatively high, and the cost of the obtained high-purity silica sol is high. When high-purity silica sol is prepared with elemental silicon as raw material, elemental silicon cannot be completely dissolved and cannot be completely separated, resulting in elemental silicon particles in silica sol, which affects the polishing effect. High-purity silica sol is prepared using sodium silicate as raw material. The content of various metal ions in sodium silicate is high, and it is difficult to achieve a high level of purity.

[0003] Therefore, how to further optimize the preparation method of low-cost and high-purity silica sol to improve the purity of silica sol and meet the requirements of electronic polishing has become a technical problem that needs to be solved. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art or related technology, and provides a preparation method and application of high-purity silica sol, which has the advantages of low-temperature synthesis of large-particle silica sol, high purity (total metal ion content <10ppm), low cost and simple process, and is suitable for mass production.

[0005] The first aspect of the present invention discloses a method for preparing high-purity silica sol, comprising: diluting sodium silicate, water and a flocculant to a silica mass fraction of 4% to 8%, taking the supernatant as liquid A after centrifugation; passing liquid A through a cation exchange resin to obtain silicic acid, adding a pH adjuster and stirring evenly until the pH value is 8 to 12, and obtaining liquid B; passing liquid B through a cation exchange resin, an anion exchange resin and a cation exchange resin in sequence to obtain a high-purity active silica solution, and obtaining liquid C; adding liquid C and ultrapure water into a reactor, and the reactor is connected to a membrane filter so that during the reaction process Separate the excess water in the kettle, maintain the liquid level stable, adjust the pH value of the mixture in the reactor to 8-12 with a pH adjuster, and heat it to 60°C-99°C; while opening the membrane filter, continue to add liquid C to react until the particle size of the silica sol is 5nm-30nm, as liquid D; add liquid D and ultrapure water to the next reactor, adjust the pH value of the mixture in the reactor to 8-12 with a pH adjuster, and heat it to 60°C-99°C; while opening the membrane filter, continue to add liquid C to react until the particle size of the silica sol is 30-150nm, and obtain high-purity silica sol.

[0006] In this technical solution, a set of membrane filter equipment and resin exchange column are first connected to the reactor, and then active silicate and pure water are added to the reactor, and the membrane filter equipment is turned on after heating to 60-99°C, and active silicate is prepared at the same time, and the active silicate directly enters the reactor from the resin exchange column to react and obtain high-purity silica sol. The present invention generates silica sol at a low temperature, which greatly reduces the production cost.

[0007] According to the method for preparing high-purity silica sol provided by the present invention, preferably, the flocculant is disodium ethylenediaminetetraacetate and / or polyacrylamide.

[0008] According to the method for preparing high-purity silica sol provided by the present invention, preferably, the pH regulator is one or more of ammonia water, tetramethylammonium hydroxide and diethanolamine.

[0009] According to the method for preparing high-purity silica sol provided by the present invention, preferably, the storage time of liquid C does not exceed 10 minutes.

[0010] According to the method for preparing high-purity silica sol provided by the present invention, preferably, the total metal ion content in the high-purity silica sol is less than 10 ppm.

[0011] According to the method for preparing high-purity silica sol provided by the present invention, preferably, liquid B passes through a cation exchange resin, an anion exchange resin and a cation exchange resin in sequence in an exchange column to prepare a high-purity active silicic acid solution, and the exchange column is connected to a reaction kettle.

[0012] The second aspect of the present invention further discloses a high-purity silica sol, which is prepared according to the preparation method of the high-purity silica sol disclosed in any of the above technical solutions.

[0013] The third aspect of the present invention also discloses an application method of the high-purity silica sol provided by the above technical solution: using the high-purity silica sol with a total metal ion content of less than 10ppm and a particle size of 30nm to 150nm for polishing semiconductor devices.

[0014] The beneficial effects achieved by the present invention include at least: sodium silicate is passed through a multi-stage cation resin exchange column and anion exchange column, and a pH regulator is added to prepare active silicate with high purity. A membrane filter is installed on the reactor to allow the produced silicate to flow out of the exchange column and directly enter the reactor, thereby avoiding spontaneous polymerization of silicate, so that high-purity silica sol can be generated at 60-99°C; compared with the traditional evaporation method for preparing silica sol, the present invention improves the purity of silica sol while ensuring the use effect, and greatly reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The figure shows a schematic flow chart of a method for preparing high-purity silica sol according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] like Figure 1 As shown, according to one embodiment of the present invention, a method for preparing high-purity silica sol is disclosed, comprising:

[0018] Step S1, diluting sodium silicate, water and flocculant to a silica mass fraction of 4% to 8%, and taking the supernatant as liquid A after centrifugation;

[0019] Step S2, passing liquid A through a cation exchange resin to obtain silicic acid, and then adding a pH adjuster and stirring evenly until the pH value is 8-12, which is liquid B;

[0020] Step S3, passing liquid B through a cation exchange resin, an anion exchange resin and a cation exchange resin in sequence to obtain a high-purity active silicic acid solution as liquid C;

[0021] Step S4, adding liquid C and ultrapure water into a reactor, the reactor is connected to a membrane filter so as to separate excess water in the reactor during the reaction process and maintain a stable liquid level, adjusting the pH value of the mixture in the reactor to 8-12 with a pH regulator, and heating to 60°C-99°C; while opening the membrane filter, continuously adding liquid C, reacting until the particle size of the silica sol is 5nm-30nm, as liquid D;

[0022] Step S5, adding liquid D and ultrapure water to the next-stage reactor, adjusting the pH value of the mixture in the reactor to 8-12 with a pH adjuster, and heating to 60°C-99°C; while opening the membrane filter, continuously adding liquid C, reacting until the particle size of the silica sol is 30-150nm, to obtain high-purity silica sol.

[0023] According to the above embodiment, further, the flocculant is disodium ethylenediaminetetraacetate and / or polyacrylamide.

[0024] According to the above embodiment, further, the pH adjuster is one or more of ammonia water, tetramethylammonium hydroxide and diethanolamine.

[0025] According to the above embodiment, further, the storage time of liquid C does not exceed 10 minutes.

[0026] According to the above embodiment, further, the total metal ion content in the high-purity silica sol is less than 10 ppm.

[0027] According to the above embodiment, further, step S3 is carried out in an exchange column, liquid B passes through a cation exchange resin, an anion exchange resin and a cation exchange resin in the exchange column in sequence to prepare a high-purity active silicic acid solution, and the exchange column is connected to a reactor.

[0028] Example 1

[0029] The specific implementation process of the method for preparing the high-purity silica sol provided in the above embodiment in a laboratory environment includes:

[0030] S1, 1 kg of commercially available sodium silicate, 3.6 kg of pure water and 4.6 g of disodium ethylenediaminetetraacetate were mixed, the mass fraction of silicon dioxide was 6.1%, and 4.1 kg of supernatant was obtained after centrifugation, which was used as liquid A;

[0031] S2, liquid A is passed through a cation exchange resin to obtain 3.8 kg of silicic acid, and then 300 g of 25% ammonia water is added. After stirring evenly, the pH value is 10.2, which is used as liquid B;

[0032] S3, liquid B is passed through a cation exchange resin, an anion exchange resin, and a cation exchange resin in sequence, and flows into a 1L five-necked flask as liquid C;

[0033] S4, first put 100g of liquid C, then add 500g of ultrapure water into a 1L five-necked flask, adjust the pH value to 10.3 with ammonia water, start stirring, set the temperature to 80°C, and when the temperature reaches the requirement, open the membrane filter and continue to add liquid C. The drainage flow rate of the membrane filter is 2ml / min, and the speed of adding liquid C is 2ml / min. During the reaction, 3ml of ammonia water is added every hour, and the reaction is carried out for 8 hours to obtain liquid D with a particle size of 20nm;

[0034] S5, add 60g D solution and 540g ultrapure water into a 1L five-necked flask, adjust the pH value to 9.8 with ammonia water, start stirring, set the temperature to 80°C, and when the temperature reaches the requirement, open the membrane filter and continue to add C solution. The drainage flow rate of the membrane filter is 2ml / min, and the C solution is added at a rate of 2ml / min. During the reaction, 3ml of ammonia water is added every hour. The reaction is carried out for 20 hours to obtain a high-purity silica sol with a particle size of 81nm; the silicon dioxide content is 24%, and the total metal ion content is 2.3ppm.

[0035] Example 2

[0036] In Example 2, in step S3, the five-necked flask is no longer used to collect the C solution. Instead, a peristaltic pump is used to transport the C solution to the subsequent reaction container (five-necked flask). The specific implementation process includes:

[0037] S1, 1 kg of commercially available sodium silicate, 3.6 kg of pure water and 4.6 g of disodium ethylenediaminetetraacetate were mixed, the mass fraction of silicon dioxide was 6.1%, and 4.3 kg of supernatant was obtained after centrifugation, which was used as liquid A;

[0038] S2, liquid A is passed through a cation exchange resin to obtain 3.9 kg of silicic acid, and then 300 g of 25% ammonia water is added. After stirring evenly, the pH value is 10.1, which is used as liquid B;

[0039] S3, liquid B is passed through a cation exchange resin, an anion exchange resin and a cation exchange resin in sequence to obtain 3.5 kg of high-purity active silicic acid as liquid C;

[0040] S4, add 100g of liquid C and 500g of ultrapure water into a 1L five-necked flask, adjust the pH value to 10.3 with ammonia water, start stirring, set the temperature to 80°C, turn on the membrane filter and the peristaltic pump to continuously add liquid C when the temperature reaches the requirement (use a peristaltic pump to add), the drainage flow rate of the membrane filter is 2ml / min, the addition rate of liquid C is 2ml / min, 3ml of ammonia water is added every hour during the reaction, react for 8 hours, and obtain liquid D with a particle size of 15nm;

[0041] S5, add 60g D liquid and 540g ultrapure water into a 1L five-necked flask, adjust the pH value to 9.8 with ammonia water, start stirring, set the temperature to 80℃, turn on the membrane filter and the peristaltic pump when the temperature reaches the requirement, the drainage flow rate of the membrane filter is 2ml / min, the addition rate of C liquid is 2ml / min, 3ml ammonia water is added every hour during the reaction, react for 20 hours, and obtain high-purity silica sol with a particle size of 31nm; the silicon dioxide content is 23%, and the total metal ion content is 3.8ppm.

[0042] Example 3

[0043] The specific implementation process of preparing silica sol with larger particle size includes:

[0044] S1, 1 kg of commercially available sodium silicate, 6.0 kg of pure water and 35 g of disodium ethylenediaminetetraacetate were mixed, the mass fraction of silicon dioxide was 4.2%, and 6.4 kg of supernatant was obtained after centrifugation, which was used as liquid A;

[0045] S2, liquid A is passed through a cation exchange resin to obtain 6.0 kg of silicic acid, and then 200 g of 10% tetramethylammonium hydroxide solution is added. After stirring evenly, the pH value is 10.4, which is used as liquid B;

[0046] S3, liquid B is passed through a cation exchange resin, an anion exchange resin and a cation exchange resin in sequence, and flows into a 1L five-necked flask as liquid C.

[0047] S4, first put 100g of liquid C, then add 500g of ultrapure water into a 1L five-necked flask, adjust the pH value to 10.0 with tetramethylammonium hydroxide solution, start stirring, set the temperature to 80°C, and when the temperature reaches the requirement, open the membrane filter and continue to add liquid C. The drainage flow rate of the membrane filter is 3ml / min, and the speed of adding liquid C is 3ml / min. During the reaction process, 2ml of tetramethylammonium hydroxide solution is added every 2 hours, and the reaction is carried out for 8 hours to obtain liquid D with a particle size of 22nm;

[0048] S5, add 40g D solution and 560g ultrapure water into a 1L five-necked flask, adjust the pH value to 9.8 with tetramethylammonium hydroxide solution, start stirring, set the temperature to 80°C, and when the temperature reaches the requirement, open the membrane filter and continue to add C solution. The drainage flow rate of the membrane filter is 3ml / min, and the C solution is added at a rate of 3ml / min. During the reaction, 2ml of tetramethylammonium hydroxide solution is added every 2 hours. The reaction is carried out for 25 hours to obtain a high-purity silica sol with a particle size of 121nm; the silicon dioxide content is 29%, and the total metal ion content is 3.6ppm.

[0049] In Example 3, if no flocculant is added and the pH adjuster is replaced with pure water in step S2, the total metal ion content in the final product will reach 1331 ppm. Therefore, the flocculant and the pH adjuster can greatly improve the purity of the silica sol (reduce metal ion contamination).

[0050] Example 4

[0051] Compared with the above embodiment, this embodiment increases the amount of raw materials and discloses a specific preparation process:

[0052] S1, 10 kg of commercially available sodium silicate, 46 kg of pure water and 112 g of polyacrylamide were mixed, the mass fraction of silica was 5.3%, and 54 kg of supernatant was obtained after centrifugation, which was used as liquid A;

[0053] S2, liquid A is passed through a cation exchange resin to obtain 50 kg of silicic acid, and then 1000 g of 10% tetramethylammonium hydroxide solution is added, and the pH value is 11.3 after stirring evenly, which is used as liquid B;

[0054] S3, liquid B is passed through a cation exchange resin, an anion exchange resin, and a cation exchange resin in sequence, and flows into a 2L five-necked flask as liquid C;

[0055] S4, first put 200g of C solution, then add 1000g of ultrapure water into a 2L five-necked flask, adjust the pH value to 10.6 with tetramethylammonium hydroxide solution, start stirring, set the temperature to 80°C, and when the temperature reaches the requirement, open the membrane filter and continue to add C solution. The drainage flow rate of the membrane filter is 6ml / min, and the C solution is added at a rate of 6ml / min. During the reaction process, 3ml of tetramethylammonium hydroxide solution is added every 2 hours, and the reaction is carried out for 8 hours to obtain D solution with a particle size of 20nm;

[0056] S5, add 160g of D solution and 1200g of ultrapure water into a 2L five-necked flask, adjust the pH value to 9.8 with tetramethylammonium hydroxide solution, start stirring, set the temperature to 80°C, and when the temperature reaches the requirement, turn on the membrane filter and continue to add C solution. The drainage flow rate of the membrane filter is 6ml / min, and the C solution is added at a rate of 6ml / min. During the reaction, 3ml of tetramethylammonium hydroxide solution is added every 2 hours. The reaction is carried out for 30 hours to obtain a high-purity silica sol with a particle size of 123nm; the silicon dioxide content is 38%, and the total metal ion content is 6.1ppm.

[0057] According to yet another embodiment of the present invention, a high-purity silica sol is further disclosed. The high-purity silica sol is prepared according to the preparation method of the high-purity silica sol disclosed in any of the above embodiments.

[0058] According to another embodiment of the present invention, a method for applying high-purity silica sol is also disclosed: high-purity silica sol with a total metal ion content of less than 10 ppm and a particle size of 30 nm to 150 nm is used for polishing semiconductor devices.

[0059] In summary, flocculants and centrifugal processes are added to sodium silicate to further remove metal ions and impurities in sodium silicate. At the same time, high-purity active silicic acid can be obtained by alternating the use of anion and cation resins and adding pH regulators in the intermediate process. A membrane filter and an exchange column are connected to the reactor to achieve a reaction temperature of 60-99°C to prepare high-purity silica sol. The membrane filter can separate excess water in the reactor during the reaction process to maintain a stable liquid level. The exchange column is connected to the reactor to ensure that the prepared high-purity silicic acid is added to the reactor for reaction in a very short time.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high-purity silica sol, characterized in that: include: Sodium silicate, water and flocculant were mixed and diluted to a silica mass fraction of 4% to 8%, and the supernatant was taken as liquid A after centrifugation; The liquid A is passed through a cation exchange resin to obtain silicic acid, and a pH adjuster is added and stirred evenly until the pH value is 8 to 12, which is used as liquid B; The liquid B is passed through a cation exchange resin, an anion exchange resin and a cation exchange resin in an exchange column in sequence to obtain a high-purity active silicic acid solution as liquid C, and the exchange column is connected to a reaction kettle; The C liquid and ultrapure water are added to a reaction kettle, the reaction kettle is connected to a membrane filter so as to separate excess water in the kettle during the reaction process and maintain a stable liquid level, the pH value of the mixture in the reaction kettle is adjusted to 8-12 with a pH adjuster, and the mixture is heated to 60° C.-99° C.; while the membrane filter is turned on, the C liquid is continuously added to react until the particle size of the silica sol is 5nm-30nm, which is used as the D liquid; The D liquid and ultrapure water are added to the next-stage reactor, the pH value of the mixture in the reactor is adjusted to 8-12 with a pH adjuster, and the mixture is heated to 60°C-99°C; while the membrane filter is turned on, the C liquid is continuously added, and the reaction is carried out until the particle size of the silica sol is 30-150nm, thereby obtaining a high-purity silica sol.

2. The method for preparing high-purity silica sol according to claim 1, characterized in that: The flocculant is disodium ethylenediaminetetraacetate and / or polyacrylamide.

3. The method for preparing high-purity silica sol according to claim 1, characterized in that: The pH regulator is one or more of ammonia water, tetramethylammonium hydroxide and diethanolamine.

4. The method for preparing high-purity silica sol according to claim 1, characterized in that: The storage time of the C liquid does not exceed 10 minutes.

5. The method for preparing high-purity silica sol according to claim 1, characterized in that: The total metal ion content in the high-purity silica sol is less than 10 ppm.

6. The high-purity silica sol obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the high-purity silica sol according to claim 6 in polishing semiconductor devices.

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