CN115611286B

CN115611286B - Preparation method of peanut-shaped ultra-high-purity silica sol, ultra-high-purity silica sol and application of ultra-high-purity silica sol

Info

Publication number: CN115611286B
Application number: CN202110803654.8A
Authority: CN
Inventors: 王建宇; 卫旻嵩
Original assignee: Wanhua Chemical Group Electronic Materials Co ltd; Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Electronic Materials Co ltd; Wanhua Chemical Group Co Ltd
Priority date: 2021-07-16
Filing date: 2021-07-16
Publication date: 2024-04-09
Anticipated expiration: 2041-07-16
Also published as: CN115611286A

Abstract

The invention discloses a preparation method of peanut-shaped ultra-high purity silica sol, the ultra-high purity silica sol and application thereof, wherein the silica sol is prepared by an alkoxide method, the relative dielectric constant of a system is regulated and controlled by the proportion and the proportion of different solvents, and then the ultra-high purity silica sol with the mass fraction of more than 20%, the primary particle size of 30-150nm and the association degree of 1.7-2.3 is obtained by a series of steps of sol gel, concentration, water replacement, filtration and the like, and the metal ion content of the silica sol is less than 1ppm. The method solves the problem of difficult control of the special-shaped morphology by the traditional alkoxide method, and has good batch-to-batch stability.

Description

Preparation method of peanut-shaped ultra-high-purity silica sol, ultra-high-purity silica sol and application of ultra-high-purity silica sol

Technical Field

The invention belongs to the field of nano material preparation, and particularly relates to a method for preparing peanut-shaped ultra-high purity silica sol by an alkoxide method, a product and application of the peanut-shaped ultra-high purity silica sol in the field of semiconductor CMP (chemical mechanical polishing).

Background

Silica sol is a colloidal substance obtained by dispersing silica particles in water or other solvents, and is widely used in the industries of papermaking, catalysts, casting, paints, and the like. In recent years, high purity silica sol is widely used in polishing of silicon wafer and Chemical Mechanical Polishing (CMP) step of semiconductor device, and there is a severe requirement for the content of metal impurities in silica sol because the presence of metal impurities during CMP polishing may cause metal diffusion into silicon wafer or electronic device and eventually short circuit.

Currently, methods commonly used for preparing silica sols include alkoxide method, simple substance silica hydrolysis method, ion exchange method, and the like. The simple substance silicon hydrolysis method is to prepare silica sol by taking simple substance silicon and water as reactants and inorganic strong base (NaOH, KOH and the like) and organic strong base (amine and the like) as catalysts. The silica sol prepared by inorganic strong alkali also has the problem of exceeding the concentration of metal ions, and the silica sol prepared by the simple substance silica method has higher hardness although the ultra-pure silica sol can be obtained by taking ammonia water or organic amine as a catalyst, and scratches can be caused in the polishing process, so that the silica sol is not suitable for the subsequent fine polishing. The ion exchange method cannot produce ultra-high purity silica sol with ion content less than 1ppm due to its own process characteristics.

The alkoxide method is a relatively mature process for producing ultra-high purity silica sol at present, under the action of a base catalyst, alkoxy silane reacts with water to generate silicon dioxide and alcohol, and organic solvent is replaced by water to obtain water-based silica sol, and the purity of the silica sol prepared by the alkoxide method is directly related to the purity of raw materials.

The particle morphology of the silica sol prepared by the alkoxide method can be divided into a sphere and an non-sphere, wherein the non-sphere particles can be divided into a peanut type and a special shape according to different association degrees, the association degrees refer to the ratio of the secondary particle size to the primary particle size of the particles, the particles are spherical when the association degree is smaller than 1.7, the particles are associated in pairs when the association degree is between 1.7 and 2.3, and the particles are special shapes when the association degree is larger than 2.3. In downstream polishing applications, peanut-shaped or profiled particles have been found to significantly increase the polishing rate and reduce scratching. CN101495409A is prepared by mixing TMOS and methanol at a volume ratio of 3:1 as a raw material solution, mixing methanol, water and ammonia water as a reaction solvent, wherein the concentrations of water and ammonia water in the reaction solvent are 15wt% and 1wt%, respectively, dropwise adding 1 volume of the raw material solution into 9 volumes of the reaction solvent at 20 ℃, and obtaining silica sol with a primary particle size of 32.1nm and a secondary particle size of 74.8nm after the reaction. Silica sol with different association degrees can be prepared by strictly controlling the concentration of reactants and catalysts in a reaction system and the addition speed of reaction raw materials, but the whole process parameters are difficult to control, particularly in industrial production, obvious amplification effect exists, the stability among batches is difficult to control, and the stability of the batches is important to the application of downstream CMP.

Disclosure of Invention

Aiming at the problems, the invention creatively provides a method for preparing peanut-shaped ultra-high-purity silica sol by an alkoxide method, and the dielectric constant of a reaction system is regulated and controlled through the proportion of different reaction solvents, so that the peanut-shaped silica sol can be easily prepared, the amplification effect is small, and the batch-to-batch stability of the particle morphology is good.

It is another object of the present invention to provide such an ultra-high purity silica sol product.

It is a further object of the present invention to provide the use of such ultra-high purity silica sols in CMP.

In order to achieve the aim of the invention, the invention adopts the following technical scheme:

the preparation method of the peanut-shaped ultra-high purity silica sol comprises the following steps:

1) And (3) preparing a solution A: uniformly mixing an organic solvent, ultrapure water and a base catalyst in a certain proportion to ensure that the relative dielectric constant of the solution A is between 43 and 50;

2) And (3) preparing a solution B: uniformly mixing an organic solvent and alkoxy silane;

3) Initial silica sol preparation: adding the solution B into the solution A at a certain temperature, and stirring and reacting to obtain initial silica sol;

4) Concentrating: concentrating the initial silica sol to obtain a concentrated silica sol with the mass fraction of 10-20%; preferably, the concentration adopts a vacuum heating concentration mode;

5) Solvent replacement: replacing the organic solvent in the concentrated silica sol with ultrapure water, and concentrating to more than 20% by mass;

6) And (3) filtering: and filtering the concentrated silica sol to remove large particles, thereby obtaining the peanut-shaped ultra-high purity silica sol.

In a specific embodiment, the organic solvent in the step 1) and the step 2) is one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, ethyl propyl ether and the like; preferably, the organic solvent in the liquid B is the same as the organic solvent in the liquid a.

In a specific embodiment, the ultrapure water in step 1) has a resistivity of 10 M.OMEGA.cm or more, preferably a resistivity of 18.2 M.OMEGA.cm or more; more preferably, the relative dielectric constant of the liquid A in the step 1) is between 43.5 and 46.5.

In a specific embodiment, the base catalyst in step 1) is selected from at least any one of alkali metal hydroxide, ammonia, organic amine or guanidine compound; preferably, the alkali metal hydroxide is selected from at least any one of potassium hydroxide, sodium hydroxide and lithium hydroxide, the organic amine is selected from at least any one of ethylenediamine, triethanolamine and tetramethyl ammonium hydroxide, and the guanidine compound is selected from at least any one of tetramethyl guanidine, trimethyl guanidine and guanidine carbonate; more preferably, the base catalyst is selected from ammonia, ethylenediamine or tetramethylammonium hydroxide.

In a specific embodiment, the mass fraction of the organic solvent in the liquid a in the step 1) is 50% -80%, the mass fraction of the ultrapure water is 19% -49%, and the mass fraction of the base catalyst is 0.5% -1.5%.

In a specific embodiment, the alkoxysilane in step 2) is one or more of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, preferably tetramethoxysilane.

In a specific embodiment, the volume ratio of the organic solvent to alkoxysilane in step 2) is from 1:3 to 3:1, the molar ratio of alkoxysilane to water in step 1) being less than 1; preferably, the volume ratio of the organic solvent to the alkoxysilane is 1:3-1:1, wherein the molar ratio of the alkoxy silane to water is less than 1:4.

In a specific embodiment, the initial silica sol preparation in step 3) is carried out at a reaction temperature of between 5 and 50 ℃, preferably between 5 and 30 ℃; the dripping time of the solution B to the solution A is 0.1min-10min, preferably 0.1min-5min, the stirring speed is 200r/min-1000r/min, and the reaction time is 0.5h-3h.

In a specific embodiment, the solvent replacement in step 5) is performed by adding ultrapure water while heating, evaporating the solvent from the water, or by ultrafiltration, adding ultrapure water while concentrating until the solvent content in the silica sol is reduced to 200ppm or less, preferably 100ppm or less; more preferably, the concentration in the step 5) adopts vacuum heating concentration or ultrafiltration membrane concentration, and the mass fraction of the silica sol is concentrated to more than 20%.

In a specific embodiment, the filtering in the step 6) is performed by using a filter element made of PFA material, and two-stage or three-stage filtering is performed, wherein the filtering precision is 0.2 μm to 5 μm.

In another aspect of the invention, the ultra-high purity silica sol prepared by the method has the morphology of most of peanut-shaped silica sol particles, the primary particle size is between 30 and 150nm, the association degree is between 1.7 and 2.3, and the total content of metal ions is less than 1ppm.

In yet another aspect of the invention, the ultra-high purity silica sol described above is used in Chemical Mechanical Polishing (CMP).

Compared with the prior art, the invention has the following beneficial effects:

1) The invention creatively provides a peanut-shaped ultra-high purity silica sol for the first time, which is prepared by adjusting the dielectric constant of a reaction system by changing the proportion of an organic solvent, ultrapure water and an alkali catalyst in an alkoxide method and controlling the association degree of the prepared silica sol through the dielectric constant.

2) Compared with the traditional alkoxide method, the method can realize batch-to-batch stability through fine control of process conditions, and the method ensures that the batch-to-batch stability is easier to control through regulating and controlling the dielectric constant of the system.

Drawings

Fig. 1 is a TEM image of silica sol particles prepared in a solvent system of different dielectric constants.

Detailed Description

In order to better understand the technical solution of the present invention, the following further illustrates the preparation method of the present invention by way of more specific examples, without any limitation.

The method for preparing peanut-shaped ultra-high purity silica sol by using alkoxide method comprises the following steps:

1) And (3) preparing a solution A: uniformly mixing an organic solvent, ultrapure water and an alkaline catalyst in a certain proportion;

3) Initial silica sol preparation: adding the solution B into the solution A at a specific speed at a specific temperature, and stirring and reacting for a period of time to obtain initial silica sol;

4) Concentrating: concentrating the initial silica sol to obtain a concentrated silica sol with the mass fraction of 10-20%;

5) Solvent replacement: replacing methanol in the concentrated silica sol with ultrapure water, concentrating until the mass fraction is 20% or more;

6) And (3) filtering: and filtering the concentrated silica sol to remove large particles, thus obtaining the high-purity silica sol product.

The organic solvent in the step 1) is any one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, ethyl propyl ether and the like, and preferably methanol. The ultrapure water is deionized water having a resistivity of 10 M.OMEGA.cm or more, and is prepared by using a mil-q direct water purifier, for example, and includes, but is not limited to, deionized water having a resistivity of 10 M.OMEGA.cm, 11 M.OMEGA.cm, 12 M.OMEGA.cm, 13 M.OMEGA.cm, 14 M.OMEGA.cm, 15 M.OMEGA.cm, 16 M.OMEGA.cm, 17 M.OMEGA.cm, 18 M.OMEGA.cm, 19 M.OMEGA.cm, 20 M.OMEGA.cm, and preferably having a resistivity of 18.2 M.OMEGA.cm or more. The base catalyst is alkali metal hydroxide such as potassium hydroxide and sodium hydroxide, ammonia water or organic amine such as ethylenediamine, triethanolamine and tetramethyl ammonium hydroxide, or guanidine compound such as: one or more of tetramethyl guanidine, trimethyl guanidine and guanidine carbonate, preferably ammonia water, ethylenediamine and tetramethyl ammonium hydroxide.

The contents of the three substances in the solution A are as follows: the mass fraction of the organic solvent is 50% -80%, the mass fraction of the ultrapure water is 19% -49%, and the mass fraction of the alkali catalyst is 1%. By adjusting the proportions and proportions of different types of solvents, the dielectric constant of the system is adjusted to be 43-50, such as 43, 43.5, 44, 44.5, 45, 45.5, 46, 46.5, 47, 47.5, 48, 48.5, 49, 49.5 and 50, and preferably 43.5-46.5. The dielectric constant is the relative dielectric constant of the solution A, and is specifically detected by the following method.

The organic solvent in the step 2) is one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, ethyl propyl ether and the like, and preferably, the type and the proportion of the organic solvent in the liquid B are the same as those in the liquid A. The alkoxysilane is one or more of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane, preferably tetramethoxysilane. Wherein the volume ratio of the organic solvent to the alkoxysilane is 1:3-3:1, the molar ratio of the alkoxysilane to the water is less than 1, preferably the volume ratio of the organic solvent to the alkoxysilane is 1:3-1:1, the molar ratio of alkoxysilane to water is less than 1:4 and greater than 1:170.

the initial silica sol preparation in said step 3), for example, is carried out at a reaction temperature of between 5 and 50 ℃, including, for example, but not limited to, 5 ℃,10 ℃, 15 ℃,20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, preferably 5 to 30 ℃. Adding the solution B into the solution A under the temperature condition, wherein the dripping time of the solution B into the solution A is 0.1min-10min, such as 0.1min, 0.5min, 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min, 5min, 5.5min, 6min, 6.5min, 7min, 7.5min, 8min, 8.5min, 9min, 9.5min, 10min, preferably 0.1min-5min; stirring speeds of 200r/min to 1000r/min, including for example but not limited to 200r/min, 300r/min, 400r/min, 500r/min, 600r/min, 700r/min, 800r/min, 900r/min, 1000r/min, preferably 600r/min; the reaction time is 0.5h-3h, including for example but not limited to 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, preferably 2h, by which step the initial silica sol is prepared.

Concentrating in the step 4) by vacuum heating to concentrate the initial silica sol into a concentrated silica sol with the mass fraction of 10-20%. The vacuum heating concentration mode can refer to the prior art, and is well known to those skilled in the art. In the concentration process, as the solid content of the silica sol increases, the stability of the silica sol is deteriorated, so that alkali, such as ammonia water, organic amine and the like, organic acid, such as citric acid, benzoic acid, polyacrylic acid and the like, or high polymer surfactant, such as polyvinylpyrrolidone, polyether P123 and the like, are added to increase the stability of the silica sol, and the yield and stability of the silica sol can be further improved by adding a dispersing agent.

The solvent replacement in the step 5) is carried out by replenishing ultrapure water while heating, and evaporating the solvent in the water, so that the organic solvent in the concentrated silica sol is replaced by the ultrapure water; or concentrating while supplementing ultrapure water by ultrafiltration, the final purpose of which is to remove the solvent content in the silica sol to below 200ppm, preferably below 100ppm, regardless of the concentration mode used. When the solvent is replaced until the solvent content is 200ppm or less than 100ppm, the mass fraction of the silica sol is concentrated to more than 20% by adopting a vacuum heating concentration or ultrafiltration membrane concentration mode. The vacuum heating concentration can refer to scraping plate evaporation, forced circulation evaporation or rectification which are common in industry, and the ultrafiltration membrane concentration can refer to an ultrafiltration membrane concentration device which is common in industry.

And 6) filtering the concentrated silica sol to remove large particles to obtain the peanut-shaped ultra-high purity silica sol, wherein a filter element made of PFA material is adopted for filtering, two-stage or three-stage filtering is adopted for filtering, the filtering precision is 0.2-5 mu m, the ultra-high purity silica sol is obtained after filtering, the morphology of the silica sol particles is mostly peanut-shaped, the association degree is 1.7-2.3, and the total content of metal ions is less than 1ppm. .

The preparation process of the present invention is further illustrated by the following more specific examples, without any limitation.

The main raw materials used in the following examples and comparative examples are as follows:

raw materials	Manufacturer' s	Specification of specification
			Ultrapure water	Self-made by adopting mil-q direct water purifier	18.2MΩ.cm
Ammonia water	SUZHOU CRYSTAL CLEAR CHEMICAL Co.,Ltd.	UP level
			Methanol	SUZHOU CRYSTAL CLEAR CHEMICAL Co.,Ltd.	UP level
Ethanol	SUZHOU CRYSTAL CLEAR CHEMICAL Co.,Ltd.	UP level
			Isopropyl alcohol	SUZHOU CRYSTAL CLEAR CHEMICAL Co.,Ltd.	UP level
Acetone (acetone)	Nanjing chemical reagent	Electronic grade
			Methyl ethyl ketone	SUZHOU CRYSTAL CLEAR CHEMICAL Co.,Ltd.	UP level
Ethyl propyl ether	Alatine	UP level
			Tetramethoxysilane	Nantongsojier	99.5％

The detection method comprises the following steps:

the solid content test method refers to HGT 2521-2008 industrial silica sol.

Secondary particle size malvern Zetasizer Nano ZS for silica sol colloidal particles, primary particle size measured by BET specific surface areaThe specific surface area S is obtained by the method _bet Primary particle size of 2727/S _bet . The degree of association is the ratio of the secondary particle size to the primary particle size.

The apparent morphology of the silica sol was characterized by TEM.

The concentration of metal ions was tested using Agilent 7900 ICP-MS.

The relative permittivity of the organic solvent was measured by the following method: the QS18A universal bridge is adopted, and the capacitance C when the medium is filled is measured by the universal bridge ₁ Then measuring the size of the plate capacitor, and calculating the vacuum capacitance C ₂ ，C ₂ ＝ε ₀ * S/d, where ε ₀ Is the dielectric constant under vacuum, S is the area of the opposite polar plate, d is the distance between the two polar plates, the dielectric constant of the medium is epsilon _r ＝C ₁ /C ₂ . The relative permittivity of the solvent A was measured in the present invention.

The main process conditions of table 1 are followed for each example and comparative example:

example 1

117.75g of isopropanol, 70.55g of water and 7.61g of ammonia water are mixed and stirred uniformly to obtain a solution A, 15ml of isopropanol and 5ml of Tetramethoxysilane (TMOS) are mixed uniformly to obtain a solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 10 seconds. Reacting for 3h at 20 ℃ and 300r/min to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. At this time, ultra-pure silica sol having a mass concentration of 20%, a primary particle diameter of 100nm, a secondary particle diameter of 200nm, a degree of association of 2 and a total metal ion content of less than 1ppm was obtained, and the content of a part of metal impurities was shown in Table 2.

Example 2

117.75g of acetone, 70.55g of water and 7.61g of ammonia water are mixed and stirred uniformly to obtain a solution A, 15ml of acetone and 5ml of Tetramethoxysilane (TMOS) are mixed uniformly to obtain a solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 10 s. Reacting for 3h at 20 ℃ and 300r/min to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. At this time, ultra-high purity silica sol having a mass concentration of 20%, a primary particle diameter of 100nm, a secondary particle diameter of 190nm, a degree of association of 1.9 and a total metal ion content of less than 1ppm was obtained, and the content of a part of metal impurities was shown in Table 2.

Example 3

41.18g of methanol, 76.57g of ethyl propyl ether, 70.55g of water and 7.61g of ammonia water are mixed and stirred uniformly to obtain solution A, 15ml of organic solvent (the mixture with the same proportion of the organic solvent in the solution A) and 5ml of Tetramethoxysilane (TMOS) are mixed uniformly to obtain solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 10 s. Reacting for 3h at 20 ℃ and 300r/min to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. At this time, ultra-pure silica sol having a mass concentration of 20%, a primary particle diameter of 98nm, a secondary particle diameter of 208nm, a degree of association of 2.1 and a total metal ion content of less than 1ppm was obtained, and the content of a part of metal impurities was shown in Table 2.

Example 4

11.07g of methanol, 106.68g of methyl ethyl ketone, 70.55g of water and 7.61g of ammonia water are mixed and stirred uniformly to obtain solution A, 15ml of organic solvent (the mixture with the same proportion of the organic solvent in the solution A) and 5ml of Tetramethoxysilane (TMOS) are mixed uniformly to obtain solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 10 s. Reacting for 3h at 20 ℃ and 300r/min to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. At this time, ultra-high purity silica sol having a mass concentration of 20%, a primary particle diameter of 102nm, a secondary particle diameter of 195nm, a degree of association of 2 and a total metal ion content of less than 1ppm was obtained, and the content of part of metal impurities was shown in Table 2.

Example 5

74.15g of ethanol, 43.6g of ethyl propyl ether, 70.55g of water and 7.61g of ammonia water are mixed and stirred uniformly to obtain solution A, 15ml of organic solvent (the mixture with the same proportion of the organic solvent in the solution A) and 5ml of Tetramethoxysilane (TMOS) are mixed uniformly to obtain solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 10 s. Reacting for 3h at 20 ℃ and 300r/min to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. At this time, ultra-pure silica sol having a mass concentration of 20%, a primary particle diameter of 100nm, a secondary particle diameter of 200nm, a degree of association of 2 and a total metal ion content of less than 1ppm was obtained, and the content of a part of metal impurities was shown in Table 2.

Example 6

The amplification effect was verified by comparably amplifying example 1 100-fold and 1000-fold, and the amplification experiment was repeated three times by 1000-fold, and the particle size and TEM image of the obtained silica sol are shown in table 1 and fig. 1, respectively.

Example 7

140g of methanol, 16.73g of ethyl propyl ether, 35.26g of water and 3.92g of ammonia water are mixed and stirred uniformly to obtain solution A, 5ml of organic solvent (the mixture with the same proportion of the organic solvent in the solution A) and 15ml of Tetramethoxysilane (TMOS) are mixed uniformly to obtain solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 10 s. Reacting at 5 ℃ and 1000r/min for 0.5h to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. At this time, ultra-high purity silica sol having a mass concentration of 20%, a primary particle diameter of 45nm, a secondary particle diameter of 100nm, a degree of association of 2.22 and a total metal ion content of less than 1ppm was obtained, and the content of a part of metal impurities was shown in Table 2.

Example 8

5g of methanol, 91.6g of ethyl propyl ether, 87.56g of water and 11.75g of ammonia water are mixed and stirred uniformly to obtain solution A, 5ml of organic solvent (the mixture with the same proportion of the organic solvent in the solution A) and 15ml of Tetramethoxysilane (TMOS) are mixed uniformly to obtain solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 10 minutes. Reacting for 1h at 50 ℃ and 1000r/min to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. At this time, ultra-high purity silica sol having a mass concentration of 20%, a primary particle diameter of 60nm, a secondary particle diameter of 105nm, a degree of association of 1.75 and a total metal ion content of less than 1ppm was obtained, and the content of a part of metal impurities was shown in Table 2.

Comparative example 1

117.75g of methanol, 70.55g of water and 7.61g of ammonia water are mixed and stirred uniformly to obtain solution A, 15ml of methanol and 5ml of Tetramethoxysilane (TMOS) are mixed uniformly to obtain solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 10 s. Reacting for 3h at 20 ℃ and 300r/min to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. At this time, ultra-high purity silica sol having a mass concentration of 20%, a primary particle diameter of 100nm, a secondary particle diameter of 120nm, a degree of association of 1.2 and a total metal ion content of less than 1ppm was obtained, and the content of a part of metal impurities was shown in Table 2.

Comparative example 2

173.77g of methanol, 26.07g of water and 1.74g of ammonia water are mixed and stirred uniformly to obtain solution A, 17ml of tetramethoxysilane and 5.67ml of methanol are mixed uniformly to obtain solution B, the solution B is added into the solution A by a peristaltic pump, and the addition is completed after 20 minutes. Reacting for 3h at 20 ℃ and 300r/min to obtain the initial silica sol. Then, the silica sol was concentrated to about 20% by heating under reduced pressure at 10Kpa and 100 ℃. Then adding ultrapure water, evaporating until the content of organic matters in the silica sol is reduced to below 100ppm, and then adopting filter cores of 5 mu m and 0.3 mu m for secondary filtration respectively to filter out large particles. This experiment was repeated 3 times and was designated as comparative example 2-1, comparative example 2-2, comparative example 2-3, the results of particle size and degree of association are shown in Table 1, and the partial metal impurities are shown in Table 2.

Comparative example 3

Comparative example 2 was amplified by 100-fold and 1000-fold, corresponding to comparative example 3-1 and comparative example 3-2, respectively, and the amplification effect was verified, the particle size and association degree of the obtained silica sol are shown in Table 1, and the content of part of metal impurities is shown in Table 2.

Table 1 amounts and ratios of solvents in examples and comparative examples

Table 2 partial metal impurity levels (ppb) for the preparation of silica sols in various examples

	Na	K	Cr	Cu	Fe	Ni	Ti
								Example 1	98	82	10	9	30	25	10
Example 2	84	70	10	8	25	17	9
								Example 3	77	69	9	10	20	22	11
Example 4	90	75	10	11	22	20	10
								Example 5	87	74	9	10	22	21	9
Example 6-1	90	81	11	10	30	25	11
								Example 6-2	98	87	12	13	31	24	10
Examples 6 to 3	90	79	15	14	29	26	9
								Examples 6 to 4	94	80	13	11	30	22	8
Example 7	92	79	16	10	29	23	10
								Example 8	94	77	18	15	27	22	9
Comparative example 1	92	79	10	9	25	23	7
								Comparative example 2-1	93	84	13	8	27	21	10
Comparative examples 2 to 2	95	90	11	7	28	22	11
								Comparative examples 2 to 3	86	82	8	11	29	26	10
Comparative example 4-1	92	83	9	10	28	27	11
								Comparative example 4-2	95	85	10	9	29	25	8

In examples 1-5, the relative dielectric constant of solution a is controlled to be 43-50 by controlling the amount and the ratio of the solvent in a, and the peanut-shaped silica sol can be prepared in different solvent systems, whereas in comparative example, the silica sol prepared according to the method described in patent CN101495409a has a degree of association of 1.35-1.6, and the experimental repeatability is poor, a strong amplification effect exists in the amplification experiment, the degree of association shows a tendency to decrease after the amplification of the same proportion, and the spherical particles are more prone to be obtained.

Fig. 1 shows TEM images of example 1, example 6, comparative example 1 and comparative example 2-1 of the present invention, corresponding to a, b, c, d in fig. 1, respectively. As can be seen, the particles of examples 1 and 2 are predominantly associated with each other in pairs and exhibit a peanut shape. Whereas the particles of comparative example 1 mostly take the shape of spheres with little association, comparative example 1 differs from the examples only in that the type and ratio of organic solvents in solution a lead to a difference in the relative dielectric constant of the final solution a. Whereas the silica sol prepared in comparative example 2-1 exhibited a spherical shape in most cases, only a small number of associations were observed.

Therefore, the high-purity silica sol prepared by the method has peanut-shaped particle morphology, particle association degree of about 2, metal ion content of less than 1ppm and mass fraction of more than 20%, and can be used for polishing large semiconductor silicon wafers or wafers.

While the present invention has been described in detail through the foregoing description of the preferred embodiment, it should be understood that the foregoing description is not to be considered as limiting the invention. Those skilled in the art will appreciate that certain modifications and adaptations of the invention are possible and can be made under the teaching of the present specification. Such modifications and adaptations are intended to be within the scope of the present invention as defined in the appended claims.

Claims

1. The preparation method of the peanut-shaped ultra-high purity silica sol is characterized by comprising the following steps of:

2) And (3) preparing a solution B: uniformly mixing an organic solvent and alkoxy silane, wherein the volume ratio of the organic solvent to the alkoxy silane is 1:3-3:1;

3) Initial silica sol preparation: adding the solution B into the solution A at the temperature of 5-50 ℃, and stirring and reacting to obtain initial silica sol;

6) And (3) filtering: filtering the concentrated silica sol to remove large particles to obtain the peanut-shaped ultra-high purity silica sol;

the organic solvent in the step 1) and the step 2) is one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether and ethyl propyl ether; the organic solvent in the solution B is the same as the organic solvent in the solution A;

the mass fraction of the organic solvent in the solution A in the step 1) is 50-80%, the mass fraction of the ultrapure water is 19-49%, and the mass fraction of the base catalyst is 0.5-1.5%;

the molar ratio of the alkoxysilane in step 2) to the water in step 1) is less than 1;

the initial silica sol in the step 3) is prepared, the dripping time of the solution B to the solution A is 0.1-10 min, and the stirring speed is 200-1000 r/min.

2. The method for producing a peanut-shaped ultra-high purity silica sol according to claim 1, wherein the resistivity of the ultra-pure water in the step 1) is not less than 10mΩ·cm.

3. The method for preparing peanut-shaped ultra-pure silica sol according to claim 2, wherein the resistivity of the ultra-pure water in the step 1) is 18.2M Ω -cm.

4. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the relative dielectric constant of the liquid a in the step 1) is 43.5-46.5.

5. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the alkali catalyst in the step 1) is at least one selected from alkali metal hydroxide, ammonia water, organic amine and guanidine compound.

6. The method for preparing peanut-shaped ultra-pure silica sol according to claim 5, wherein the alkali metal hydroxide is at least one selected from potassium hydroxide, sodium hydroxide and lithium hydroxide, the organic amine is at least one selected from ethylenediamine, triethanolamine and tetramethylammonium hydroxide, and the guanidine compound is at least one selected from tetramethylguanidine, trimethylguanidine and guanidine carbonate.

7. The method for preparing peanut-shaped ultra-pure silica sol according to claim 5, wherein the base catalyst is selected from ammonia, ethylenediamine or tetramethylammonium hydroxide.

8. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the alkoxysilane in the step 2) is one or more of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane.

9. The method for preparing peanut-shaped ultra-pure silica sol according to claim 8, wherein the alkoxysilane in the step 2) is tetramethoxysilane.

10. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the volume ratio of the organic solvent to the alkoxysilane in the step 2) is 1:3-1:1, wherein the molar ratio of the alkoxy silane to water is less than 1:4.

11. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the initial silica sol in the step 3) is prepared, the dropwise adding time of the solution B to the solution A is 0.1-5 min, and the reaction time is 0.5-3 h.

12. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the initial silica sol in the step 3) is prepared at a reaction temperature of 5-30 ℃.

13. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the concentration in the step 4) adopts a vacuum heating concentration mode.

14. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the solvent replacement in step 5) is performed by adding ultrapure water while heating, evaporating the solvent in the water, or concentrating while adding ultra-pure water by ultrafiltration until the solvent content in the silica sol is reduced to 200ppm or less.

15. The method of preparing peanut-shaped ultra-pure silica sol according to claim 14, wherein the solvent content in the silica sol is reduced to less than 100 ppm.

16. The method for preparing peanut-shaped ultra-pure silica sol according to claim 15, wherein the concentration in the step 5) is vacuum heating concentration or ultrafiltration membrane concentration, and the mass fraction of the silica sol is concentrated to more than 20%.

17. The method for preparing peanut-shaped ultra-pure silica sol according to claim 1, wherein the filtering in the step 6) is performed by a PFA filter element, and the filtering precision is 0.2 μm-5 μm by two-stage or three-stage filtering.

18. The ultra-high purity silica sol according to any one of claims 1 to 17, wherein the silica sol particles have a morphology of mostly peanut shape, a primary particle size of 30 to 150nm, a degree of association of 1.7 to 2.3, and a total metal ion content of less than 1ppm.

19. Use of the ultra-high purity silica sol of claim 18 in chemical mechanical polishing.