阅读说明：本技术 一种超高纯均匀型硅溶胶的制备方法 (Preparation method of ultra-pure uniform silica sol ) 是由 杨兴旺 郭建学 张倩 于 2020-07-16 设计创作，主要内容包括：本申请提供一种超高纯均匀型硅溶胶制备方法,用于解决现有的硅溶胶离子含量高、均匀性差的技术问题。本申请的制备方法包括如下步骤：将超纯水加热后,加入催化剂,搅拌,加热至95℃。缓缓加入定量光伏硅粉,得到硅溶胶种子溶液；将钾水玻璃用超纯水稀释至含二氧化硅质量分数为3～10%,过阴阳离子交换树脂,得到活性硅酸；在光伏硅粉中,加入超纯水,用搅拌机搅拌至均匀流体硅粉,待用；将硅溶胶种子溶液进行加热,将活性硅酸和流体硅粉用蠕动泵按先快后慢的速率交叉滴入硅溶胶种子溶液中,在反应过程中用蠕动泵按先快后慢的速率滴加催化剂,控制二氧化硅溶胶的pH值在11.50～12.50,反应时间8～40h,停止加热,反应结束,过滤得到超高纯均匀型硅溶胶。(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.)

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.

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