CN111717923A

CN111717923A - Preparation method of ultra-pure uniform silica sol

Info

Publication number: CN111717923A
Application number: CN202010686847.5A
Authority: CN
Inventors: 杨兴旺; 郭建学; 张倩
Original assignee: Kesh Chemical Industry Shenzhen Co ltd
Current assignee: Kesh Chemical Industry Shenzhen Co ltd
Priority date: 2020-07-16
Filing date: 2020-07-16
Publication date: 2020-09-29
Anticipated expiration: 2040-07-16
Also published as: CN111717923B

Abstract

The application provides a preparation method of ultra-pure uniform silica sol, which is used for solving the technical problems of high ion content and poor uniformity of the existing silica sol. The preparation method comprises the following steps: after heating the ultrapure water, the catalyst was added, stirred and heated to 95 ℃. Slowly adding a certain amount of photovoltaic silicon powder to obtain a silica sol seed solution; diluting potassium water glass with ultrapure water until the mass fraction of silicon dioxide is 3-10%, and passing through anion and cation exchange resin to obtain active silicic acid; adding ultrapure water into the photovoltaic silicon powder, and stirring the mixture by using a stirrer until the fluid silicon powder is uniform for later use; heating the silica sol seed solution, alternately dropping active silicic acid and fluid silica powder into the silica sol seed solution at a first-fast and second-slow speed by using a peristaltic pump, dropping a catalyst at a first-fast and second-slow speed by using the peristaltic pump in the reaction process, controlling the pH value of the silica sol to be 11.50-12.50, controlling the reaction time to be 8-40 h, stopping heating, finishing the reaction, and filtering to obtain the ultra-pure uniform silica sol.

Description

Preparation method of ultra-pure uniform silica sol

Technical Field

The invention relates to an ultra-pure uniform silica sol and a preparation method thereof, belonging to the technical field of inorganic nano materials.

Background

The silica sol is a sol liquid formed by uniformly dispersing amorphous silica hydrate particles in water, and the size of the colloidal particles is generally 20-100 nm. The silica sol adhesive has the characteristics of high-temperature stability, insulativity, water resistance, no pollution and the like, so the silica sol adhesive is widely applied to textile, coating, papermaking, rubber, ceramics, precision casting, electronic industry and the like. The requirements of different industries on the purity of silica sol and the like are different, the requirements of the semiconductor industry on the purity of silica sol are extremely high, and the ultra-high purity silica sol is mainly applied to the semiconductor industry, such as the precision polishing of silicon wafers, wafers and the like, and the Chemical Mechanical Planarization (CMP) process of integrated circuits and the like, and is one of essential consumables in the microelectronic industry.

The method has the defects that the silica sol contains a certain amount of metal impurities, about 2000ppm, the impurities pollute and mechanically damage semiconductors and greatly affect the quality of products, and the silica sol synthesized by the water glass method has relatively low particle hardness, is applied to the field of abrasives, has low removal rate and cannot meet the polishing application of the whole process. The alkali metal in the silica sol synthesized by the metal silicon reaction method cannot be completely removed, the hardness of particles is high, the distribution is uneven, and the silica sol is applied to the field of abrasive materials, so that the surface of the product is seriously scratched easily, and the silica sol cannot be applied to the field of high-precision grinding and polishing.

In order to solve the above problems, the domestic patent application No. 201710885866.9, namely preparation method of silica sol for CMP, adopts a mixed growth method combining an ion exchange method and a silicon powder hydrolysis method to develop a wear-resistant and durable abrasive for spherical chemical mechanical polishing with moderate particle hardness and difficult breakage. The silica sol synthesized by the method avoids the contradiction between the hardness and scratch of abrasive particles, but as the surface activity of colloidal particles is reduced along with the increase of the particle size, the added active silicic acid and the silicon powder can not react in time, so that the concentration of the active silicic acid is easily higher than the minimum nucleation concentration, new crystal seeds are generated, the uniformity of the produced large-particle silica sol is poor, and the requirement of high-precision abrasive materials can not be met.

The invention content is as follows:

the invention aims to provide an ultra-pure uniform silica sol and a preparation method thereof, which solve the high-precision abrasive material requirement in the existing semiconductor polishing industry. The specific scheme is as follows:

the ultra-pure homogeneous silica sol is characterized in that (1) ultrapure water is heated to 70-80 ℃, a quantitative catalyst is added, stirring is started, and then the ultra-pure homogeneous silica sol is heated to 95-100 ℃. Slowly adding a certain amount of photovoltaic silicon powder to obtain a silica sol seed solution;

(2) diluting high-purity potash water glass with ultrapure water until the mass fraction of silicon dioxide is 3-10%, and respectively passing through anion exchange resin and cation exchange resin to obtain active silicic acid with pH = 2-3

(3) Adding ultrapure water in a certain proportion into the photovoltaic silicon powder, and stirring the mixture by using a stirrer until the fluid silicon powder is uniform for later use;

(4) heating the silica sol seed solution prepared in the step (1), alternately dripping the active silicic acid prepared in the step (2) and the fluid silicon powder obtained in the step (3) into the silica sol seed solution prepared in the step (1) by using a peristaltic pump at a first-fast and second-slow rate, dripping a catalyst by using the peristaltic pump at a first-fast and second-slow rate in the reaction process, controlling the pH value of the silica sol to be 11.50-12.50, reacting for 8-40 h, stopping heating, finishing the reaction, and filtering to obtain the ultra-pure uniform silica sol.

The catalyst in the steps (1) and (4) comprises one or more of TMAH, ethanolamine and ammonia water; the silicon content of the photovoltaic silicon powder is more than 99.999%, and the particle size of the photovoltaic silicon powder is 300-400 meshes; the amount of the catalyst just maintains the pH value of a silica sol seed solution system between 11.80 and 12.50; slowly adding a certain amount of photovoltaic silicon powder, namely controlling the adding speed so that hydrogen generated in the process does not flush the silicon powder to the opening of the reaction kettle, wherein the using amount of the added silicon powder depends on the total synthesis amount and the target particle size.

The high-purity potassium water glass is preferably Na₂O content less than 0.5%, K₂The content of O is 35-40%, and the modulus is 2.5-2.8. Diluting with ultrapure water to content of silicon dioxide of 4.6 wt%, removing anions and cations in water glass with strong acid cation exchange resin and weak base anion exchange resin, and regenerating strong acid cation exchange resin preferably with H₂SO₄Concentration of8 to 10 percent; KOH is preferably selected during the regeneration of the weak-base anion exchange resin, the concentration is 5-8%, the pH value of the obtained active silicic acid is 2.0-3.0, and the active silicic acid is stored at the temperature below 20 ℃.

The method is characterized in that ultrapure water is added into the photovoltaic silicon powder in a certain proportion, and the silicon powder is stirred by a stirrer until the silicon powder is uniform, so that the adding amount and the adding rate of materials are conveniently controlled, and the mass ratio of the adding amount to the photovoltaic silicon powder is about 10: 3-4.

Heating the silica sol seed solution prepared in the step (1) to 70-80 ℃, alternately dropping the active silicic acid prepared in the step (2) and the fluid silicon powder obtained in the step (3) into the silica sol seed solution prepared in the step (1) at a mass ratio of 1:1-2 by using a peristaltic pump at a flow rate of 300ml/h/L and a rate of decreasing by 10ml/h/L every half hour, dropping the diluted catalyst at a constant speed by using the peristaltic pump in the reaction process, controlling the pH value of the silica sol to be 11.50-12.50, basically keeping the reaction time at 6-30 hours according to the required particle size, keeping the temperature of 95-100 ℃ for 2-5 hours after dropping, stopping heating, and filtering to obtain the ultra-pure uniform silica sol. The dosage of the silicon powder and the dosage of the active silicic acid are determined by the total synthesis amount and the size of the target particle size, and the dosage should be calculated in advance before the reaction starts. Secondly, all reactions should be run continuously, with both fragmentation and stoppages affecting product uniformity.

In the ultra-pure uniform silica sol and the preparation method thereof, active silicic acid and fluid silicon powder need to be added alternately.

The ultra-pure uniform silica sol has an alkali metal content of less than 100 ppb.

Drawings

FIG. 1 is an SEM photograph of a silica sol of example 1.

FIG. 2 is an SEM photograph of the silica sol of example 2.

FIG. 3 is an SEM photograph of the silica sol of example 3.

FIG. 4 is an SEM photograph of the silica sol of example 4.

FIG. 5 is an SEM photograph of a silica sol of example 5.

FIG. 6 is an SEM photograph of a silica sol of example 6.

Detailed Description

Example 1

5000ml of ultrapure water is added into a 10000ml four-neck flask, the flask is heated to 80 ℃, 35.5g of 5 percent ammonia water solution with the pH of the system being 11.9 is added, the stirring is started, the rotating speed is adjusted to 150r/min, and then the flask is continuously heated to 95 ℃. Slowly adding 1000g of fluid photovoltaic silicon powder, reacting for 180-240 min, dropwise adding an ammonia water solution with the concentration of 5% in the process, and keeping the pH value of the system between 11.5-12.5 to obtain a silica sol seed solution;

diluting high-purity potassium water glass with ultrapure water to the mass fraction of silicon dioxide of 4.6%, and respectively passing through anion exchange resin KOH and cation exchange resin H in sequence₂SO₄(the ratio of the potassium water glass to the anion exchange resin is 6:1, and the ratio of the potassium water glass to the cation exchange resin is 4: 1) to obtain active silicic acid;

adding ultrapure water with the mass 2 times that of the photovoltaic silicon powder into the photovoltaic silicon powder, and stirring the mixture until the fluid silicon powder is uniform for later use;

dripping 500ml of active silicic acid into the silica sol seed solution by using a peristaltic pump, wherein the flow rate is reduced by 10mlL after half an hour according to 300ml/h/L, and the addition is finished after about 2 hours; keeping the speed of active silicic acid at the end, dropwise adding 500ml of fluid silicon powder into the silica sol seed solution, reducing the volume by 10mlL every half hour, dropwise adding into a four-neck flask by a peristaltic pump, keeping the pH of the system at 11.5-11.5 after the addition is finished for about 2.5h (dropwise adding 5% ammonia water solution in the whole process), stirring at the constant temperature of 95 ℃ for 2h after the addition is finished, reacting for about 10h, stopping heating, finishing the reaction, and filtering to obtain the ultra-pure uniform silica sol with the particle size of 45-55 nm.

Example 2

The preparation of the silica sol seed solution, active silicic acid and fluid silica powder is the same as in example 1. The steps are the same as example 1, only the raw materials of the application are mixed and then added, and the specific steps are as follows: mixing 500ml of active silicic acid and fluid silicon powder together, stirring uniformly, dropwise adding into a silica sol seed solution by using a peristaltic pump, starting to flow at 300ml/h/L, reducing the speed of 10mlL in each half hour, completing the addition within about 4.5 hours, dropwise adding 5% ammonia water solution in the whole process to keep the pH of the system between 11.5 and 11.5, after dropwise adding, stirring at the constant temperature of 95 ℃ for 2 hours, reacting for about 10 hours, stopping heating, completing the reaction, filtering to obtain silica sol with the particle size of 10-60 nm.

Example 3

The preparation of the silica sol seed solution, active silicic acid and fluid silica powder is the same as in example 1. Dripping 500ml of active silicic acid into the silica sol seed solution by using a peristaltic pump, wherein the flow rate is reduced by 10ml first quickly and then slowly every half hour according to 300ml/h/L, and the addition is finished within about 2 hours; then 500ml of fluid silicon powder is taken, the speed of the active silicic acid at the end is kept, 10ml of the fluid silicon powder is reduced every half hour, the fluid silicon powder is dripped into a four-neck flask by a peristaltic pump, and the addition is finished within about 2.5 hours. And continuously taking 400ml of active silicic acid and 400ml of uniform fluid silicon powder, adding the active silicic acid and the uniform fluid silicon powder into a four-neck flask according to the flow rate change rule and the adding rule, (dropwise adding 5% ammonia water solution in the whole process to keep the pH of the system between 11.5 and 11.5), after dropwise adding, stirring at 95 ℃ for 4 hours at constant temperature, reacting for about 20 hours, stopping heating, finishing the reaction, and filtering to obtain the ultra-pure uniform silica sol with the particle size of 65-75 nm.

Example 4

The preparation of the silica sol seed solution, active silicic acid and fluid silica powder is the same as in example 1. The steps and the addition amount of each raw material are as shown in example 3, and only example 4 adopts uniform addition, which specifically comprises the following steps: dripping 500ml of active silicic acid into the silica sol seed solution by using a peristaltic pump, and adding the active silicic acid at a constant speed of 300ml/h/L after about 2 hours; and taking the fluid silicon powder, keeping the dropping rate of the active silicic acid, dropping the fluid silicon powder into the four-neck flask by using a peristaltic pump, and finishing the addition within about 2.0 hours. And continuously taking 400ml of active silicic acid and 400ml of uniform fluid silicon powder, adding into a four-neck flask in a crossed manner according to the flow rate, (dropwise adding 5% ammonia water solution in the whole process to keep the pH of the system between 11.5 and 11.5), after dropwise adding, stirring at 95 ℃ for 4 hours at constant temperature, reacting for about 20 hours, stopping heating, finishing the reaction, and filtering to obtain silica sol with the particle size of 20-100 nm.

Example 5

The preparation of the silica sol seed solution, active silicic acid and fluid silica powder is the same as in example 1. Dripping 500ml of active silicic acid into the silica sol seed solution by using a peristaltic pump, wherein the flow rate is reduced by 10ml/min/L at the beginning of half an hour according to 300ml/h/L, and the addition is finished after about 2 hours; and continuously taking the fluid silicon powder, keeping the speed at the end, reducing by 10ml/h/L every half hour, dropwise adding into the four-neck flask by using a peristaltic pump, and finishing the addition within about 2.5 hours. Continuously taking 400ml of active silicic acid and 400ml of uniform fluid silicon powder, adding the active silicic acid and the uniform fluid silicon powder into a four-neck flask according to the flow rate change rule and the adding rule, then taking 300ml of the active silicic acid and 300ml of the uniform fluid silicon powder, adding the active silicic acid and the uniform fluid silicon powder into the four-neck flask according to the flow rate change rule and the adding rule (dropwise adding 5% ammonia water solution in the whole process to keep the pH of the system between 11.5 and 11.5), after dropwise adding, stirring at the constant temperature of 95 ℃ for 5 hours, reacting for about 30 hours, stopping heating, finishing the reaction, and filtering to obtain the ultra-pure uniform silica sol with the particle size of 75.

Example 6

The preparation of the silica sol seed solution, active silicic acid and fluid silica powder is the same as in example 1. The sequence of adding the fluid silicon powder and the active silicic acid in the whole step is opposite to that of the step in example 5, and the steps are as follows: taking 500ml of fluid silicon powder, dropwise adding the fluid silicon powder into the silica sol seed solution by using a peristaltic pump, wherein the flow rate is reduced by 10ml/min/L from fast to slow every half hour according to 300ml/h/L, and the adding is finished after about 2 hours; then 500ml of active silicic acid is added dropwise, the rate at the end is reduced by 10ml/h/L every half hour, and the solution is added dropwise into a four-neck flask by a peristaltic pump for about 2.5 hours. Continuously taking 400ml of fluid silicon powder and 400ml of active silicic acid, adding the fluid silicon powder and 400ml of active silicic acid into a four-neck flask according to the flow rate change rule and the adding rule, then taking 300ml of the fluid silicon powder and 300ml of the active silicic acid, adding the fluid silicon powder and 300ml of the active silicic acid into the four-neck flask according to the flow rate change rule and the adding rule (dropwise adding 5% ammonia water solution in the whole process to keep the pH of the system between 11.5 and 11.5), after dropwise adding, stirring at the constant temperature of 95 ℃ for 5 hours, reacting for about 30 hours, stopping heating, finishing the reaction, and filtering to obtain the ultra-pure uniform silica sol with the particle.

The results of the tests are shown in Table 1:

table 1 test results of examples

From the detection results of the examples in table 1, the particle size of the ultra-pure uniform silica sol can be freely controlled; the particles are monodisperse, the particles are distributed concentratedly, and the uniformity is good; the product is stable in performance after being placed for a long time, and unstable phenomena such as mildew and layering do not occur; the content of alkali metal and heavy metal is extremely low, and the requirements of high-precision grinding and polishing abrasive materials can be completely met. .

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent variations and modifications made to the above embodiment according to the technical spirit of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of ultra-pure uniform silica sol is characterized by comprising the following steps:

(1) heating ultrapure water, adding a catalyst, starting stirring, heating to 95-100 ℃, and slowly adding photovoltaic silicon powder to obtain a silica sol seed solution;

(2) diluting potassium water glass with ultrapure water until the mass fraction of silicon dioxide is 3-10%, and respectively passing through anion exchange resin and cation exchange resin to obtain active silicic acid with pH = 2-3;

(3) adding ultrapure water with the mass 2-3 times that of the photovoltaic silicon powder into the photovoltaic silicon powder, and stirring to obtain uniform fluid silicon powder for later use;

(4) heating the silica sol seed solution prepared in the step (1), alternately dropping the active silicic acid prepared in the step (2) and the fluid silicon powder obtained in the step (3) into the silica sol seed solution prepared in the step (1) at a first-fast and second-slow rate, dropping a catalyst at a first-fast and second-slow rate in the reaction process, controlling the pH value of the reaction system to be 11.50-12.50, reacting for 8-40 h, and stopping heating;

and after the reaction is finished, filtering to obtain the ultra-pure uniform silica sol.

2. The method for preparing the ultra-high-purity uniform silica sol according to claim 1, wherein the catalyst in the steps (1) and (4) comprises one or more of TMAH, ethanolamine, and ammonia water; the silicon content of the photovoltaic silicon powder is more than 99.999%, and the particle size of the photovoltaic silicon powder is 300-400 meshes; the adding amount of the catalyst is controlled to control the pH value of the silica sol seed solution to be 11.80-12.50.

3. The method for preparing an ultra-high-purity uniform silica sol according to claim 1, wherein in the step (2), the anion exchange resin comprises KOH at a concentration of 5 to 8%; the cation exchange resin comprises H₂SO₄The concentration is 8-10%.

4. The method of preparing an ultra-high-purity homogeneous silica sol according to claim 1, wherein in the step (4), the silica sol seed solution is heated to 70 to 80 ℃, the active silicic acid and the fluidized silica powder are respectively added into the mixed solution in a cross-drop manner, the flow rates of the active silicic acid and the fluidized silica powder are started to be added at 300ml/h/L, and then the active silicic acid and the fluidized silica powder are added in a drop manner at a rate which is decreased by 10ml every half hour.

5. The method for producing the ultra-high-purity uniform silica sol according to claim 1, wherein the active silicic acid and the fluid silicon powder are in a mass ratio of 1: 1-2.

6. The method for preparing the ultra-high-purity uniform silica sol according to claim 1, wherein after the dropwise addition in the step (4) is completed, the temperature is kept at 95-100 ℃ for 2-5 hours, the heating is stopped, and the ultra-high-purity uniform silica sol is obtained by filtering.