KR100894795B1 - A Manufacturing Method of Colloidal Silica by direct oxidation of silicon - Google Patents

Abstract

The present invention relates to a method for preparing a silica sol, which enables the production of a silica sol directly from silicon using an alkali catalyst, and a method for preparing a new silica sol having a large, uniform and large specific surface area of silica particles in the final silica sol. The purpose is to provide. In order to achieve the above object, the present invention is characterized by adding a weakly basic primary catalyst and a strong basic secondary catalyst after adding industrial silicon powder having a silicon content of 90% or more to distilled water. 1 can control the particle size by adjusting the time of the addition of the second catalyst followed by the addition of the primary catalyst of silica sol, in the large particles larger specific surface area and the circularity of the manufacturing high silica sol, the content of Na ⁺ ions Provided is a method for producing a low silica high purity silica sol.

Silica Sol, Particle Size Control, Catalyst

Description

A manufacturing method of colloidal silica by direct oxidation of silicon

1 is a process flowchart of the silica sol manufacturing method of the present invention.

Figure 2 is a graph showing the viscosity change when the concentration of silica sol 30%, 40%, 50%.

3A, 3B, 3C, and 3D are TEM photographs of silica sol of various sizes prepared by the present invention.

4A and 4B are TEM photographs comparing the shapes of silica sol particles prepared according to the silica sol manufacturing method of the present invention and silica sol particles prepared according to the ion exchange method.

5 is a graph showing a comparison of the specific surface area of the silica sol particles prepared according to the silica sol particles prepared by the method of the present invention and the silica sol particles prepared by the ion exchange method.

The present invention relates to a method for producing a silica sol, and more particularly, to a method for producing a silica sol having a large and uniform size of silica particles, excellent sphericity, and broad specific surface area.

Silica sol has been used for a long time as a functional additive in various fields and as a wafer or glass abrasive, and is widely used as an abrasive for a silicon oxide film, which is a cutting film, in a semiconductor manufacturing process, as well as an abrasive for a metal film for wiring such as copper and aluminum.

Conventional silica sol production methods include acid decomposition, electrodialysis, peptizing, ion exchange, hydrolysis. The double hydrolysis method is very advantageous in controlling the impurity content to be extremely low or increasing the sphericity, but in the case of the hydrolysis method, since SiCl ₄ or TEOS is used as a starting material, the manufacturing cost is high. The other method is mostly water glass (silicate) to prepare silica sol. In general, water glass is prepared by adding sodium carbonate (Na ₂ CO ₃ ) to pulverized mineral or sand and heating to high temperature. Sodium silicate (Na ₂ SiO ₃ ) and orthosilicate are used for water glass produced by this method. 20% to 50% of various types of sodium silicate salts, such as sodium (Na ₄ SiO ₄ ) and 2-sodium silicate salt (Na ₂ Si ₂ O ₅ ), are contained. Therefore, there is a limit in controlling the Na ⁺ ion content of the silica sol in the case of preparing the silica sol using such water glass.

In addition, according to the conventional silica sol manufacturing method, since the silica sol should be prepared using the water glass after manufacturing the water glass, the manufacturing process is not only complicated, but the conventional methods of preparing the silica sol are deoxidized and washed by acid reaction. After the process or the ion exchange reaction requires a washing process of the ion exchange resin, there is a problem that a large amount of waste water occurs in this process. In addition, all of the above-described methods for producing silica sol include an excess of cationic metals, which causes problems such as poor insulation of circuits, short circuits, and low dielectric constant due to the polished semiconductor substrate or alkali metal attached to the oxide film surface. do. In particular, sodium has a small particle, high diffusivity, and can remain in fine scratches of the polished film, causing many problems. Alkali metals contained in excess may be a factor influencing the stability of the sol in preparing the organic-inorganic composite coating.

In order to solve the above problems, a direct oxidation method for preparing silica sol directly from silicon using a strong base material as a catalyst has been proposed. This method eliminates the need for a separate cationic material removal process. In particular, the process of preparing a conventional complex silica sol is simplified, which saves energy, prevents waste of chemicals, eliminates wastewater treatment problems, reduces manufacturing time, and reduces costs. It has the advantage of being excellent. For example, the Republic of Korea Patent No. 10-0349632 in the reaction vessel containing sodium hydroxide aqueous solution is added to the silicon powder and reacted, after which the silicon powder and ammonia water is added and re-reacted to filter the final product with a press filter A method for producing a silica sol is disclosed.

However, in this method, (1) the added catalyst is a strong base, so that the reaction is rapid, but the particle size of the final silica sol is about ten nm, the size of the formed particles is small, and (2) large and small particles are mixed. There is a problem that it is difficult to obtain a silica sol containing a large particle diameter and uniform silica particles.

Accordingly, the present invention is to solve the above-mentioned problems, to prepare a novel silica sol having a large and uniform particle size and a large specific surface area of silica, and to manufacture a silica sol that can control the silica particle diameter by controlling the reaction time It is an object to provide a method.

In order to achieve the above object, the present invention is to prepare a first dispersion solution by adding silicon powder to distilled water (S1), 100 weight of silicon powder added a weakly basic catalyst to the first dispersion solution (S1) To 0.5 part by weight to 60 parts by weight, and reacting to prepare a second dispersion solution (S2), to 100 parts by weight of the silicon powder to which a strong basic catalyst was added to the second dispersion solution in step (S1). It provides a silica sol manufacturing method comprising the step of adding 0.5 parts by weight to 10 parts by weight and reacting to prepare a third dispersion solution (S3), filtering the third dispersion solution (S4).

In the production method, the amount of silicon powder added in the step (S1) is preferably 5 to 25 parts by weight relative to 100 parts by weight of distilled water.

The reaction process of the step (S2) is preferably made by adding a weakly basic catalyst to the first dispersion solution and reacting it at 5 ° C to 100 ° C for 1 hour to 10 hours.

In the step (S2), the weakly basic catalyst is methyl amine (methyl amine), ethyl amine (ethyl amine), n-propyl amine (n-propyl amine), n-butyl amine (n-butyl amine), dimethylamine (dimethyl amine, dityl amine, dipropyl amine, dibutyl amine, trimethyl amine, triethyl amine, tripropyl amine, It is preferably selected from the group consisting of tributyl amine and ammonium hydroxide.

The reaction process of the step (S3) is preferably made by adding a strong base catalyst to the second dispersion solution and reacting it for 10 hours to 36 hours at 5 ℃ to 100 ℃.

In the step (S3), the strong base catalyst is selected from the group consisting of sodium hydroxide, potassium hydroxide, barium hydroxide, barium hydroxide, cesium hydroxide, and lithium hydroxide. It is preferable.

The particle size of the silicon powder is preferably 50 mesh to 1000 mesh.

The silicon content of the silicon powder is preferably 90% by weight or more.

Hereinafter, the present invention will be described in more detail.

1 is a process flow diagram of a silica sol manufacturing method according to the present invention.

According to Figure 1 first to add a silicon powder to distilled water to prepare a first dispersion solution (S1).

The amount of silicon powder added to the distilled water in this step is preferably 5 to 25 parts by weight based on 100 parts by weight of distilled water.

When the amount of silicon powder added is less than 5 parts by weight with respect to 100 parts by weight of distilled water, the concentration of silica sol is light and the yield is considerably decreased after the final reaction, and when it exceeds 25 parts by weight, the yield is high but the concentration is too thick. There is.

When the concentration of silica sol is high, the viscosity increases. In the case of high viscosity silica sol, the gel is finally gelled, and thus, low viscosity is evaluated as having high stability. In particular, securing stability is an important factor in terms of transportation of silica sol and user storage.

2 is a graph showing the correlation between the concentration of silica sol and viscosity. Viscosity of three samples with the same particle diameter of 80 nm but different concentrations of 30%, 40% and 50%, respectively, was measured using a Rheometer viscometer (Brookfield DV-III Rheometer). It can be confirmed that the degree. The particle diameters were the same at 50 nm, but the concentrations of the three samples with different concentrations were 30%, 40% and 50%, respectively.

The particle size of the silicon powder is preferably 50 mesh to 1000 mesh. When small particles having a particle size of less than 1000 mesh are used, the reaction rate is so fast that there is insufficient time for the silica particles to grow in the silica sol, and the reaction is so intense that there is a risk of explosion. If the particle size exceeds 50 mesh, the reaction rate is slow, the time required for the entire reaction is too long, and the yield is also reduced.

The silicon content of the silicon powder is preferably used 90 wt% or more. Silica sol can be produced even when the purity is less than 90% by weight, but since the content of impurities is too high, the yield to be obtained within a certain time range is low, and the content of impurities is also high.

In the method for preparing silica sol of the present invention, silicon powder is used as a starting material, but in the method for preparing silica sol according to a hydrolysis method or a condensation polymerization method, TEOS or SiCl ₄ is used as a starting material. Silica sol production method using TEOS as a starting material has a disadvantage that the process is complicated and the manufacturing cost is expensive compared to the silica sol production method according to the present invention.

Next, a weakly basic primary catalyst is added to the first dispersion solution and reacted to prepare a second dispersion solution (S2).

The reaction process of step (S2) is performed by adding a weakly basic primary catalyst to the first dispersion solution and reacting it at 5 ° C. to 100 ° C. for 1 hour to 10 hours.

As described, since the silica sol tends to be gelated eventually when the concentration is high, it is very important in terms of stability to prepare a silica sol having a low viscosity. Viscosity tends to decrease as the size of particles increases, so rather than using a strong base such as sodium hydroxide as a primary catalyst to produce silica sol with large particles, use a weak base such as ammonium hydroxide or amines, and add the second catalyst after adding the first catalyst. It is desirable to increase the reaction time before adding the catalyst.

Weakly basic substances used as primary catalysts include methyl amine, ethyl amine, n-propyl amine, n-butyl amine, dimethylamine ( dimethyl amine, dityl amine, dipropyl amine, dibutyl amine, trimethyl amine, trietyl amine, tripropyl amine Tributyl amine and ammonium hydroxide are typical.

In the case of using a strong base such as sodium hydroxide as the primary catalyst, the reaction is very vigorous and proceeds rapidly, and the yield is high, but there is not enough time for the particles to grow sufficiently, so that the average particle diameter of the silica particles in the final silica sol exceeds 50 nm. Few. On the other hand, in the case of using a weakly basic catalyst such as ammonium hydroxide or amines, the reaction rate is slightly slow but there is an advantage that the particles can be sufficiently grown.

The amount of the weakly basic catalyst added in this step is preferably 0.5 parts by weight to 25 parts by weight based on 100 parts by weight of the silicon powder added in the step (S1).

When the amount of the catalyst is less than 0.5 parts by weight, the reaction hardly proceeds. When the amount of the catalyst is more than 60 parts by weight, the reaction rate increases, but the size of the silica particles in the silica sol is reduced by limiting the growth of the particles.

In the silica sol production method of the present invention, the smaller the amount of the first and second catalysts, the larger the reaction time after the addition of the first catalyst and before the addition of the second catalyst, the larger the size of the silica particles, the silica sol production method of the present invention By controlling the amount and reaction time of the silver catalyst there is an advantage that can control the size of the desired particles according to the application.

Next, a strong basic secondary catalyst is added to the second dispersion solution and reacted to prepare a third dispersion solution (S3).

The reaction process of the step (S3) is made by adding a strong base catalyst to the second dispersion solution and reacting it for 10 hours to 36 hours at 5 ℃ to 100 ℃.

The strong base catalyst used as the secondary catalyst is preferably sodium hydroxide, potassium hydroxide, barium hydroxide, cesium hydroxide and lithium hydroxide.

When using potassium hydroxide, barium hydroxide, cesium hydroxide and lithium hydroxide as the secondary catalyst, it is possible to prepare a very high purity silica sol by maintaining the concentration of Na ^{+ in} the final silica sol less than 10ppm. Since Na ⁺ has a small particle and high diffusivity and remains in fine scratches of the polished film, it causes many problems. Therefore, Na ⁺ is not suitable for use as an abrasive for semiconductor wafers when the Na ⁺ concentration in silica sol is high. Therefore, it is important to prepare silica sol with low Na ⁺ concentration. When preparing this silica sol using potassium hydroxide, barium hydroxide, cesium hydroxide and cesium hydroxide, the concentration of Na ^{+ in} the final silica sol is only determined by Since it is only affected by the purity, if a high purity silicon powder is used, the Na ⁺ concentration in the maximum silica sol can be maintained at less than 10 ppm to obtain a high purity silica sol having less impurities.

If sodium hydroxide is used as the secondary catalyst, the content of sodium hydroxide is less than 0.5%, so it is not advantageous in terms of impurities compared to conventional acid decomposition, electrodialysis, peptizing, and ion exchange. Compared to the silica sol prepared through the manufacturing method, the spherical degree is high and the specific surface area is high.

The amount of the strongly basic catalyst added in the step (S3) is preferably 0.5 parts by weight to 25 parts by weight based on 100 parts by weight of the silicon powder added in the step (S1).

If the secondary catalyst is added less than 0.5 parts by weight, the reaction does not proceed, if the amount exceeds 10 parts by weight, the yield of the final silica sol is increased, the particle size is small and the aggregation factor (aggregation factor) There was a tendency to increase.

Next, the third dispersion solution manufactured through the above process is filtered (S4).

Press filter may be preferably used as the filtering method in this step, but is not limited thereto. This step may be repeated several times as needed.

Through this step, the unreacted substance is removed, thereby obtaining a final product, silica sol. Silica sol prepared through the silica sol manufacturing method according to the present invention has a high content of generally 30% or more without a concentration process. And it is possible to control the content of Na ⁺ ions within a few ppm depending on the selection of the raw material.

Hereinafter, the present invention will be described in more detail with reference to the following experimental examples, but the following description is provided only to assist in understanding the present invention, and the present invention is not limited to the following description.

Experimental Example 1

34 g of silicon powder (97% purity, 325 mesh) was dispersed in 195 g of distilled water, and 5 ml of 28% NH ₄ OH aqueous solution was added thereto, and stirred at 100 ° C. for 1 hour to prepare a dispersion solution, and 0.6 g of NaOH granules (purity 97%) Into the dispersion solution was reacted at 100 ℃ 18 hours and filtered to prepare a silica sol.

Experimental Examples 2 and 3

In Experimental Example 2, 10 ml of 28% NH ₄ OH aqueous solution was added as a primary catalyst, and the other conditions were the same as in Experimental Example 1. In Experimental Example 3, 20 ml of 28% NH ₄ OH was added as a primary catalyst. And other conditions were the same as in <Experimental Example 1> to prepare a silica sol.

Experimental Example 4

34 g of silicon powder (97% purity, 325 mesh) was dispersed in 195 g of distilled water, and 5 ml of 28% NH ₄ OH aqueous solution was added thereto, stirred at 100 ° C. for 3 hours to prepare a dispersion solution, and 0.6 g of NaOH granules (purity 97%) Into the dispersion solution was reacted at 100 ℃ 18 hours and filtered to prepare a silica sol.

Experimental Examples 5 and 6

In Experimental Example 5, 10 ml of 28% NH ₄ OH aqueous solution was added as a primary catalyst, and other conditions were the same as in Experimental Example 4, and in Experimental Example 3, 20 ml of 28% NH ₄ OH was added as a primary catalyst. And the other conditions were the same as in <Experimental Example 4> to prepare a silica sol.

Experimental Example 7

34 g of silicon powder (97% purity, 325 mesh) was dispersed in 195 g of distilled water, and 5 ml of 28% NH ₄ OH aqueous solution was added thereto, stirred at 100 ° C. for 1 hour to prepare a dispersion solution, and 1.2 g of NaOH granules (purity 97%) was prepared. Into the dispersion solution was reacted at 100 ℃ 18 hours and filtered to prepare a silica sol.

Experimental Examples 8 and 9

In Experimental Example 8, 10 ml of 28% NH ₄ OH aqueous solution was added as the primary catalyst, and the other conditions were the same as in Experimental Example 7, and in Experimental Example 9, 20 ml of 28% NH ₄ OH was added as the primary catalyst. And other conditions were carried out in the same manner as in <Experimental Example 7>.

Experimental Example 10

34 g of silicon powder (97% purity, 325 mesh) was dispersed in 195 g of distilled water, and 5 ml of 28% NH ₄ OH aqueous solution was added thereto, and stirred at 100 ° C. for 3 hours to prepare a dispersion solution, and 1.2 g of NaOH granules (97% purity) were prepared. Into the dispersion solution was reacted at 100 ℃ 18 hours and filtered to prepare a silica sol.

<Experiment 11, 12>

In Experiment 11, 10 ml of 28% NH ₄ OH aqueous solution was added as a primary catalyst, and the other conditions were the same as in Experiment 10, and in Experiment 12, 20 ml of 28% NH ₄ OH was added as a primary catalyst. And other conditions were prepared in the same manner as in <Experimental Example 10>.

The size and agglomeration of the silicon particles in the silica sol were measured by using a light scattering photometer (Size 1) and a TEM (Size 2) for the prepared silica sol. Table 1 summarizes the measurement results of Experimental Examples 1 to 12.

TABLE 1

                                                             Unit: nm

No Size 1 Size 2 Cohesion Experimental Example 1 87 80 1.1 Experimental Example 2 75 60 1.3 Experimental Example 3 71 60 1.2 Experimental Example 4 113 100 1.1 Experimental Example 5 83 60 1.4 Experimental Example 6 76 50 1.5 Experimental Example 7 45 40 1.1 Experimental Example 8 58 40 1.4 Experimental Example 9 52 40 1.3 Experimental Example 10 94 50 1.9 Experimental Example 11 96 20 4.8 Experimental Example 12 76 20 3.8

Relationship between reaction time and particle size after addition of primary catalyst

The reaction time after the addition of the primary catalyst affects the size of the silica particles in the final silica sol. <Experimental Example 1> and <Experimental Example 4> of [Table 1] were the same as the type and amount of the primary catalyst and the secondary catalyst and the reaction time after the addition of the primary catalyst was changed to 1 hour and 3 hours, respectively In the case of <Experimental Example 1>, the particle size was 87 nm, and in <Experimental Example 4> 113 nm, the reaction time and the particle size were found to be proportional. Other experiments such as <Experiment 2>, <Experiment 5>, <Experiment 3> and <Experiment 6>, <Experiment 7> and <Experiment 10>, and <Experiment 9> and <Experiment 12> The same tendency was confirmed even when the examples were compared. Figure 3a is <Experimental Example 1>, Figure 3b is <Experimental Example 4>, Figure 3c is <Experimental Example 9>, Figure 3d is a TEM picture of the silica sol according to <Experimental Example 12>, through which the size of the particle diameter You can see different things.

Relationship between amount of catalyst and particle size

The larger the amount of catalyst, the faster the reaction but the limited growth of the particle size. The reaction time after the addition of the first catalyst was the same and the amount of ammonium hydroxide was added differently, and the results showed that the larger the amount of ammonium hydroxide, the smaller the particle size and the more the amount of sodium hydroxide, the second catalyst, was increased. When the size of the particles was found to be small. Comparing <Experimental Example 1>, <Experimental Example 2>, <Experimental Example 3> as the amount of NH ₄ OH increased it was confirmed that the particle size of 87nm, 75nm, 71nm, respectively, <Experimental Example 1 > And <Experimental Example 7>, <Experimental Example 4> and <Experimental Example 10> was confirmed that the size of the silica particles decreases as the amount of NaOH increases.

Silica particles of the silica sol prepared according to the silica sol manufacturing method of the present invention shows the advantage that the sphericality is more uniform than the silica particles of the silica sol prepared according to the other silica sol manufacturing method, and the surface roughness has a specific surface area It has a wide range of characteristics.

Figure 4a shows a TEM picture of the silica sol particles prepared according to the silica sol manufacturing method of the present invention, Figure 4b shows a TEM picture of the silica sol particles prepared by the ion exchange method. It can be observed that the silica particles of the silica sol prepared by the ion exchange method are entangled with the silica particles, whereas the silica particles of the silica sol prepared according to the silica sol manufacturing method of the present invention have spherical particles evenly formed. .

Figure 5 is a graph comparing the specific surface area of the silica particles of the silica sol prepared by the silica sol prepared according to the silica sol manufacturing method according to the present invention and the silica particles prepared by the ion exchange method. If the size of the silica particles are the same, it can be seen that the specific surface area of the silica particles produced by the present invention is wider.

As described above, the present invention is a silica sol manufacturing method characterized in that the catalyst is added by dividing the primary and secondary, the silica particles of the silica sol prepared by this method is large in size, uniform and excellent in sphericity. As a result, the particle surface is rough, so the specific surface area is very large.

On the other hand, the silica sol manufacturing method of the present invention can adjust the size of the silica particles according to the reaction time after the addition of a weak base material as the primary catalyst can be prepared silica sol having an appropriate particle size according to the application. In addition, when potassium hydroxide, barium hydroxide, cesium hydroxide and lithium hydroxide are used as secondary catalysts, high purity silica sol having a Na ⁺ content of 10 ppm or less can be prepared.

Claims (8)

(S1) preparing a first dispersion solution by adding 5 parts by weight to 25 parts by weight of silicon powder in 100 parts by weight of distilled water, (S2) adding a weakly basic catalyst to the first dispersion solution by adding 0.5 parts by weight to 60 parts by weight with respect to 100 parts by weight of the silicon powder added in the step (S1) to prepare a second dispersion solution, (S3) adding a strong basic catalyst to the second dispersion solution by adding 0.5 parts by weight to 10 parts by weight with respect to 100 parts by weight of the silicon powder added in the step (S1) to prepare a third dispersion solution, (S4) A silica sol production method comprising the step of filtering the third dispersion solution. delete The method of claim 1, The reaction process of the step (S2) is a method for producing a silica sol, characterized in that by adding the weakly basic catalyst to the first dispersion solution and reacting it for 5 hours to 100 ℃ for 1 hour to 10 hours. The method of claim 1, In the step (S2), the weakly basic catalyst is methyl amine (methyl amine), ethyl amine (ethyl amine), n-propyl amine (n-propyl amine), n-butyl amine (n-butyl amine), dimethylamine (dimethyl amine, dityl amine, dipropyl amine, dibutyl amine, trimethyl amine, triethyl amine, tripropyl amine, Method for producing silica sol, characterized in that selected from the group consisting of tributyl amine and ammonium hydroxide (ammonium hydroxide) The method of claim 1, The reaction process of step (S3) is a method for producing a silica sol, characterized in that by adding the strong base catalyst to the second dispersion solution and reacting it for 10 to 36 hours at 5 ℃ to 100 ℃. The method of claim 1, In the step (S3), the strong base catalyst is selected from the group consisting of sodium hydroxide, potassium hydroxide, barium hydroxide, barium hydroxide, cesium hydroxide and lithium hydroxide. Silica sol manufacturing method characterized in that The method of claim 1, The particle size of the silicon powder is a silica sol manufacturing method, characterized in that 50 to 1000 mesh. The method of claim 1, Method for producing a silica sol, characterized in that the silicon content of the silicon powder is more than 90% by weight.

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