CN111717923B

CN111717923B - Preparation method of ultra-pure uniform silica sol

Info

Publication number: CN111717923B
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: 2023-04-14
Anticipated expiration: 2040-07-16
Also published as: CN111717923A

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 the potassium water glass with ultrapure water until the mass fraction of silicon dioxide is 3-10%, and passing through anion-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 by using a peristaltic pump according to the speed of first quick and then slow, dropping a catalyst by using the peristaltic pump according to the speed of first quick and then slow 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 to 100nm. The silica sol has the characteristics of high-temperature stability, insulativity, water resistance, no pollution and the like, so that the silica sol is widely applied to the textile industry, the coating industry, the papermaking industry, the rubber industry, the ceramic industry, the precision casting industry, the electronic industry and the like. The requirements of different industries on the purity of silica sol are different, the requirements of the semiconductor industry on the purity of silica sol are extremely high, and the ultra-pure silica sol is mainly applied to the semiconductor industry, such as the precision polishing of silicon wafers, wafers \37754andthe 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 existing synthetic silica sol mostly uses water glass as a raw material, ion exchange is carried out through ion exchange resin to obtain active silicic acid, and then nucleation and gradual growth are carried out. 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 problems, the domestic patent application number 201710885866.9, namely a 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 spherical abrasive for chemical mechanical polishing, which has moderate particle hardness, is not easy to break, and is wear-resistant and durable. 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 seed crystals 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 ℃, then a quantitative catalyst is added, stirring is started, and then the mixture 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 according to the speed of first quick and second slow, dripping a catalyst by using the peristaltic pump according to the speed of first quick and second slow 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 photovoltaic silicon powder contains more than 99.999 percent of silicon and has a particle size of 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 potash water glass is preferably Na ₂ O content less than 0.5%, K ₂ The O content is 35 to 40 percent, and the modulus is 2.5 to 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 H ₂ SO ₄ The concentration is 8-10%; KOH is preferably selected during the regeneration of the weak-base anion exchange resin, the concentration is 5 to 8 percent, the pH value of the obtained active silicic acid is between 2.0 and 3.0, and the obtained 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 liquid silicon powder is stirred by a stirrer until the liquid silicon powder is uniform, so that the adding amount and the adding speed of the materials are conveniently controlled, and the mass ratio of the adding amount to the photovoltaic silicon powder is about 10-4.

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, a peristaltic pump at a flow rate of 300ml/h/L and a rate of 10ml/h/L reduction in each half hour, dropping the diluted catalyst at a constant speed by using the peristaltic pump during 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 depend on 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 100ppb.

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 180-240min, 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 potash water glass with ultrapure water until the mass fraction of silicon dioxide is 4.6%, and respectively and sequentially passing through anion exchange resin KOH and cation exchange resin H ₂ SO ₄ (the ratio of the potassium water glass to the anion exchange resin is 6;

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

Example 2

The preparation of the silica sol seed solution, active silicic acid and fluid silica powder is the same as that of 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 the mixture into a silica sol seed solution by using a peristaltic pump, beginning to flow at 300ml/h/L, reducing the flow rate by 10ml L in each half hour, wherein the flow rate is increased first and then slowly, the addition is completed within about 4.5h, dropwise adding an ammonia water solution with the concentration of 5% in the whole process, keeping the pH of the system between 11.5 and 11.5, stirring at the constant temperature of 95 ℃ for 2h after the dropwise addition is completed, reacting for about 10h, stopping heating, and filtering to obtain the silica sol with the particle size of 10 to 60nm after the reaction is completed.

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 from beginning to end every half hour according to 300ml/h/L, and the addition is finished after 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 active silicic acid is reduced every half hour, and the fluid silicon powder is dripped into a four-neck flask by a peristaltic pump and is added after 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 to 75nm.

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 the same as those in example 3, and only in example 4, the raw materials are added at a constant speed, specifically as follows: 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 at 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 4h at constant temperature, reacting for about 20h, stopping heating, finishing the reaction, and filtering to obtain the silica sol with the particle size of 20 to 100nm.

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 from beginning to end at 300ml/h/L every half hour, and the addition is finished about 2 hours; and continuously taking the fluid silicon powder, keeping the speed at the end, reducing the speed by 10ml/h/L every half hour, dropwise adding the silicon powder into a four-neck flask by using a peristaltic pump, and finishing the addition 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, 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), stirring at the constant temperature of 95 ℃ for 5 hours after dropwise adding, stopping heating for about 30 hours after reaction, and filtering to obtain the ultra-pure uniform silica sol with the particle size of 75-85nm after reaction is finished.

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. And continuously taking 400ml of fluid silicon powder and 400ml of active silicic acid, adding the fluid silicon powder and the 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 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), stirring at the constant temperature of 95 ℃ for 5 hours after the dropwise adding is finished, stopping heating, finishing the reaction, and filtering to obtain the ultra-pure uniform silica sol with the particle size of 20-150nm.

The test results of the examples are shown in table 1:

table 1 test results of examples

From the detection results of the embodiment 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 can be avoided; the alkali metal content and the heavy metal content are extremely low, and the requirements of high-precision tip grinding and polishing abrasives 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 uniformly stirring to obtain fluid silicon powder for later use;

(4) Heating the silica sol seed solution prepared in the step (1) to 70-80 ℃, respectively and crossly dropwise adding 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), wherein the flow rates of the active silicic acid and the fluid silicon powder are started to be added according to 300ml/h/L, then the speed of 10ml/h/L is reduced every half hour, the active silicic acid and the fluid silicon powder are dropwise added according to the mass ratio of 1-2, a catalyst is dropwise added according to the speed of firstly fast and secondly slow in the reaction process, the pH value of the reaction system is controlled to be 11.50-12.50, the reaction time is 8-40 h, and the heating is stopped, wherein the crossly dropwise adding refers to adding the active silicic acid firstly and then the fluid silicon powder;

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

the catalyst in the steps (1) and (4) comprises one or more of TMAH, ethanolamine and ammonia water; the photovoltaic silicon powder contains more than 99.999 percent of silicon and has the particle size of 300-400 meshes; the adding amount of the catalyst is controlled to control the pH value of the silica sol seed solution to be between 11.80 and 12.50.

2. 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 H ₂ SO ₄ The concentration is 8-10%.

3. 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 filtration.