Efficient silica sol impurity removal method
Through the dialysis method combined with the technical means of chelating agent, the residual metal ions in the silica sol are efficiently removed, solving the problem of difficult to remove metal ions in the existing technology, and achieving efficient and safe silicon sol removal effect, which is suitable for the needs of large-scale production and chip manufacturing.
Patent Information
- Application Number
- CN202510204767.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-24
- Publication Date
- 2025-05-23
AI Technical Summary
The prior art is difficult to efficiently remove metal ions in silicon sol, resulting in impurity metal ions remaining on components during chip manufacturing, affecting the efficient preparation and long-term use of the chip.
The dialysis method combined with chelating agent is used to separate the metal cations in the silica gel solution from the product. Through multiple dialysis and replacement of the dialysis solution, the effect of efficiently removing metal ions is achieved.
The metal cation removal content in the silica gel solution is achieved with an extremely high removal rate of more than 99%. For some metal ions with smaller content, it can reach the ppb level, which is suitable for the needs of large-scale production and large-scale chip mechanical polishing.
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of chemical mechanical polishing, and relates to a method for removing impurities from silica sol, specifically to a method for efficiently removing metal ions in silica sol by applying the dialysis method. Background Art
[0002] With the booming development of the semiconductor industry, the requirements for the fineness of chips are gradually increasing. As a main component of a chip polishing solution, silica sol is a suspension of silicon dioxide particles in water and is indispensable in the chip manufacturing process. However, due to the presence of residual metal ions in the production process of silica sol, after mechanical polishing treatment, impurity metal ions are left on the produced components. To ensure the efficient preparation and long-term use of chips, it is crucial to remove impurities, and most of the metal ions therein should be removed. The development of a silica sol impurity removal method that can be applied on a large scale should be emphasized. Summary of the Invention
[0003] The present invention provides an efficient method for removing impurities from silica sol. This method combines the dialysis method with a chelating agent to separate metal cations in the silica sol solution from the product, thereby achieving the effect of impurity removal, and is suitable for the efficient removal of metal cations in the silicon solution for the mechanical polishing of large-scale integrated circuits. The present invention can remove a large amount of metal cation impurities in the product to reach the ppb level. The reaction requires a relatively low temperature, and the raw materials and reagents used are safe and non-toxic, suitable for large-scale production.
[0004] The object of the present invention is achieved through the following technical solutions:
[0005] An efficient method for removing impurities from silica sol, comprising the following steps:
[0006] Step (1) Pretreat the dialysis bag. Cut the dialysis bag into an appropriate length, place it in a sodium bicarbonate solution with a volume of 1 - 5% (W / V) and boil for 5 - 15 minutes, and thoroughly wash the dialysis bag with distilled water, wherein: the dialysis bag is selected from one of the following specifications: 8000 - 14000KD, 300KD, 100KD, 50KD, 30KD, 20KD, 10KD, 1KD;
[0007] Step (2) Place the dialysis bag in 0.5 - 1.5 mmol / L EDTA (pH = 8) and boil it for 5 - 15 minutes. After cooling, soak the dialysis bag in the solution and store it at 4°C for later use;
[0008] Step (3) Before use, wash the dialysis bag with distilled water, clamp a dialysis clamp on one side of the dialysis bag, add the silica gel solution to be removed into the dialysis bag, and leave a surplus, and clamp the dialysis clamp at a distance of 3 to 5 mm from the edge, wherein: the silica gel content in the silica gel solution is 1 to 50 wt%, the particle size of the silica gel is 1 to 500 nm, and the total amount of cations is 200 to 10000 ppm;
[0009] Step (4) placing the dialysis bag in a dialysis device, adding a dialysate, wherein the amount of the dialysate added is 80 to 120 times the volume of the silica gel solution to be dialyzed, adding an appropriate amount of a chelating agent to the dialysate, starting stirring, and performing a dialysis process, wherein: the chelating agent is one or more of ethylenediamine, 2,2'-bipyridine, 1,10-phenanthroline, oxalate, and ethylenediaminetetraacetic acid, and the amount added is 0.01 to 5% of the mass of the silica gel solution; the dialysate is deionized water; and the dialysis temperature is controlled at 20 to 60°C;
[0010] Step (5) After dialysis for 4 h, the dialysate was replaced with distilled water without a chelating agent, and stirring was continued while the temperature was controlled at 20 to 60° C.;
[0011] Step (6) The dialysate is replaced every 4 hours until the impurity content is reduced to below the requirement, and the temperature is controlled at 20-60°C.
[0012] In the above method, steps (4) to (6) can be replaced by:
[0013] Step (4) placing the dialysis bag into a dialysis device, adding dialysis fluid therein, wherein the amount of dialysis fluid added is 80 to 120 times the volume of the silica gel solution to be dialyzed, starting stirring, and performing the dialysis process, wherein: the temperature is controlled at 20 to 60° C.;
[0014] Step (5) The dialysate is replaced every 4 hours until the impurity content is reduced to below the requirement, and the temperature is controlled at 20-60°C.
[0015] Compared with the prior art, the present invention has the following advantages:
[0016] 1. The present invention draws inspiration from protein dialysis, and separates metal cations from the suspension by the difference between the particle size of silica gel suspension and the particle size of metal cations. In the first dialysis, a chelating agent that can complex with metal cations is added to the dialysate to chelate most of the metal ions in the silica gel solution, and then the remaining impurity metal cations are removed by conventional distilled water dialysis.
[0017] 2. The present invention can remove a very high content of metal cations in silica gel solution, and can remove up to 99% of sodium, iron, aluminum, calcium, magnesium and other ions. For metal ions with lower content such as copper, nickel, chromium, zinc, this method can remove them to the ppb level or even completely remove them.
[0018] 3. As an efficient means of removing impurities from silica gel solution, the present invention has a very low cost in production and can be used continuously as long as the dialysis bag is not damaged. The temperature required for the reaction is relatively low, and the raw materials and reagents used are safe and non-toxic. It is suitable for large-scale production and is applicable to the removal of cations in silica gel solution for mechanical polishing of large chips. DETAILED DESCRIPTION
[0019] The technical solution of the present invention is further described below in conjunction with the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.
[0020] Example 1
[0021] In this embodiment, a dialysis bag with a specification of 8000-14000KD is selected, the silica content in the silica gel to be purified is about 20%, the particle size is about 120nm, the total amount of metal cations is about 2000ppm, and the chelating agent used is EDTA. The steps for purifying the silica sol are as follows:
[0022] (1) Pre-treat the dialysis bag by cutting it into a suitable length, boiling it in a 2% (W / V) sodium bicarbonate solution for ten minutes, and then thoroughly washing the dialysis bag with distilled water.
[0023] (2) Place the dialysis bag in 1 mmol / L EDTA (pH=8) and boil it for ten minutes. After cooling, immerse the dialysis bag in the solution and store it at 4°C for later use.
[0024] (3) Before use, wash the dialysis bag with distilled water, clamp the dialysis clamp on one side of the dialysis bag, add the silica gel solution to be removed into the dialysis bag, leaving a surplus, and clamp the dialysis clamp 3 to 5 mm away from the edge.
[0025] (4) Place the dialysis bag in the dialysis device, add 100 times the amount of the silica gel solution to be dialyzed, deionized water, add EDTA (1% by mass of the silica gel solution to be dialyzed) to the dialysis solution, start stirring, and perform the dialysis process at room temperature of 25°C.
[0026] (5) After 4 h of dialysis, the dialysate was replaced with distilled water without chelating agent and stirring was continued.
[0027] (6) Replace the dialysate every 4 hours until the impurity content is reduced to below the requirement.
[0028] The silica sol after purification in this example did not swell, and its volume remained the same as that before purification, wherein the total amount of ions was less than 10 ppm.
[0029] Example 2
[0030] In this embodiment, a 50KD dialysis bag is selected, the silica content in the silica gel to be purified is about 20%, the particle size is about 20nm, the total amount of metal cations is about 4000ppm, and the chelating agent used is EDTA. The steps for purifying the silica sol are as follows:
[0031] (1) Pre-treat the dialysis bag by cutting it into a suitable length, boiling it in a 2% (W / V) sodium bicarbonate solution for ten minutes, and then thoroughly washing the dialysis bag with distilled water.
[0032] (2) Place the dialysis bag in 1 mmol / L EDTA (pH=8) and boil it for ten minutes. After cooling, immerse the dialysis bag in the solution and store it at 4°C for later use.
[0033] (3) Before use, wash the dialysis bag with distilled water, clamp the dialysis clamp on one side of the dialysis bag, add the silica gel solution to be removed into the dialysis bag, leaving a surplus, and clamp the dialysis clamp 3 to 5 mm away from the edge.
[0034] (4) Place the dialysis bag in a dialysis device, add a dialysate that is 100 times the mass of the silica gel solution to be dialyzed, add EDTA that is 1% of the mass of the silica gel solution to be dialyzed into the dialysis solution, start stirring, and control the dialysis process at room temperature of 25°C.
[0035] (5) After 4 h of dialysis, the dialysate was replaced with distilled water without chelating agent and stirring was continued.
[0036] (6) Replace the dialysate every 4 hours until the impurity content is reduced to below the requirement.
[0037] The silica sol after purification in this embodiment has no swelling phenomenon, and its volume remains the same as that before purification, wherein the total amount of ions is less than 50 ppm.
[0038] Example 3
[0039] In this example, a 10KD dialysis bag was used, the silica content in the silica gel to be purified was about 20%, the particle size was about 120nm, the total amount of metal cations was about 2000ppm, and no chelating agent was used. The steps for purifying the silica sol are as follows:
[0040] (1) Pre-treat the dialysis bag by cutting it into a suitable length, boiling it in a 2% (W / V) sodium bicarbonate solution for ten minutes, and then thoroughly washing the dialysis bag with distilled water.
[0041] (2) Place the dialysis bag in 1mmol / L EDTA (pH=8) and boil it for ten minutes. After cooling, soak the dialysis bag in the solution and store it at 4°C for later use.
[0042] (3) Before use, wash the dialysis bag with distilled water, clamp the dialysis clamp on one side of the dialysis bag, add the silica gel solution to be removed into the dialysis bag, leaving a surplus, and clamp the dialysis clamp 3 to 5 mm away from the edge.
[0043] (4) Place the dialysis bag into the dialysis device, add 100 times the amount of dialysis solution to be dialyzed, start stirring, and control the temperature at room temperature 25°C to carry out the dialysis process.
[0044] (5) Replace the dialysate every 4 hours until the impurity content is reduced to below the requirement.
[0045] The silica sol after purification in this embodiment has no swelling phenomenon, and its volume remains the same as that before purification, wherein the total amount of ions is less than 10 ppm.
[0046] Example 4
[0047] This embodiment uses a dialysis bag with a specification of 8000-14000KD, the silica content in the silica gel to be purified is about 20%, the particle size is about 120nm, the total amount of metal cations is about 2000ppm, and the chelating agent used is 2,2'-bipyridine. The steps for purifying the silica sol are as follows:
[0048] (1) Pre-treat the dialysis bag by cutting it into a suitable length, boiling it in a 2% (W / V) sodium bicarbonate solution for ten minutes, and then thoroughly washing the dialysis bag with distilled water.
[0049] (2) Place the dialysis bag in a solution containing 1 mmol / L EDTA (pH=8) and boil it for ten minutes. After cooling, immerse the dialysis bag in the solution and store it at 4°C for later use.
[0050] (3) Before use, wash the dialysis bag with distilled water, clamp the dialysis clamp on one side of the dialysis bag, add the silica gel solution to be removed into the dialysis bag, leaving a surplus, and clamp the dialysis clamp 3 to 5 mm away from the edge.
[0051] (4) Place the dialysis bag in a dialysis device, add a dialysate that is 100 times the mass of the silica gel solution to be dialyzed, add 2,2'-bipyridine that is 1% of the mass of the silica gel solution to be dialyzed into the dialysis solution, start stirring, and control the temperature at room temperature of 25°C to carry out the dialysis process.
[0052] (5) After 4 h of dialysis, the dialysate was replaced with distilled water without chelating agent and stirring was continued.
[0053] (6) Replace the dialysate every 4 hours until the impurity content is reduced to below the requirement.
[0054] The silica sol after purification in this embodiment has no swelling phenomenon, and its volume remains the same as that before purification, wherein the total amount of ions is less than 10 ppm.
Claims
1. A highly efficient silica sol impurity removal method, characterized in that The method comprises the following steps: Step (1) pre-treating the dialysis bag by boiling it in a sodium bicarbonate solution and thoroughly washing the dialysis bag with distilled water; Step (2) placing the dialysis bag in EDTA and boiling it, and after cooling, immersing the dialysis bag in the solution and storing it at 4° C. for later use; Step (3) Before use, wash the dialysis bag with distilled water, clamp a dialysis clamp on one side of the dialysis bag, add the silica gel solution to be removed into the dialysis bag, and clamp the dialysis clamp at a distance of 3 to 5 mm from the edge; Step (4) placing the dialysis bag into a dialysis device, adding dialysis fluid therein, adding a chelating agent to the dialysis fluid, starting stirring, and performing a dialysis process; Step (5) After dialysis for 4 h, the dialysate was replaced with distilled water without a chelating agent and stirring was continued; Step (6) The dialysate is replaced every 4 hours until the impurity content is reduced to below the requirement.
2. The high-efficiency silica sol impurity removal method according to claim 1, characterized in that In the step (1), the dialysis bag is selected from one of the following specifications: 8000-14000KD, 300KD, 100KD, 50KD, 30KD, 20KD, 10KD, 1KD.
3. The high-efficiency silica sol impurity removal method according to claim 1, characterized in that In the step (1), the concentration of the sodium bicarbonate solution is 1 to 5% (W / V), and the boiling time is 5 to 15 minutes.
4. The high-efficiency silica sol impurity removal method according to claim 1, characterized in that In the step (2), the concentration of EDTA is 0.5-1.5 mmol / L, pH=8, and the boiling time is 5-15 minutes.
5. The high-efficiency silica sol impurity removal method according to claim 1, characterized in that In the step (3), in the silica gel solution, the silica gel content is 1 to 50 wt%, the silica gel particle size is 1 to 500 nm, and the total amount of cations is 200 to 10000 ppm.
6. The high-efficiency silica sol impurity removal method according to claim 1, characterized in that In the step (4), the amount of dialysate added is 80 to 120 times the volume of the silica gel solution to be dialyzed, the amount of chelating agent added is 0.01 to 5% of the mass of the silica gel solution, and the dialysis temperature is controlled at 20 to 60°C.
7. The high-efficiency silica sol impurity removal method according to claim 6, characterized in that The chelating agent is one or more of ethylenediamine, 2,2'-bipyridine, 1,10-phenanthroline, oxalate, and ethylenediaminetetraacetic acid; and the dialysate is deionized water.
8. The high-efficiency silica sol impurity removal method according to claim 1, characterized in that In the step (5), the dialysis temperature is controlled at 20-60°C.
9. The high-efficiency silica sol impurity removal method according to claim 1, characterized in that In the step (6), the dialysis temperature is controlled at 20-60°C.
10. The high-efficiency silica sol impurity removal method according to claim 1, characterized in that The steps (4) to (6) are replaced by: Step (4) placing the dialysis bag into a dialysis device, adding dialysis fluid therein, wherein the amount of dialysis fluid added is 80 to 120 times the volume of the silica gel solution to be dialyzed, starting stirring, and performing the dialysis process, wherein: the temperature is controlled at 20 to 60° C.; Step (5) The dialysate is replaced every 4 hours until the impurity content is reduced to below the requirement, and the temperature is controlled at 20-60°C.