JPH0694368B2 - Method for producing silicon dioxide film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a silicon dioxide coating, and more particularly, to a substrate by bringing a treatment liquid containing a silicon dioxide supersaturated solution of hydrosilicofluoric acid into contact with the substrate. It relates to an improved method of producing a silicon dioxide coating on a surface.

[Prior Art] Conventionally, as a method for forming a silicon dioxide film, there is a method of forming a silicon dioxide film on the surface of a base material by immersing the base material in a silicon dioxide supersaturated aqueous solution of hydrofluoric acid (hereinafter referred to as a precipitation method). Are known. (For example, JP-A-57-196744 and JP-A-61-28
1047, JP-A-62-20876) In order to increase the film formation rate by the above-mentioned precipitation method, increase the supply rate of a substance or thermal energy that accelerates the decomposition of hydrosilicofluoric acid as a processing liquid. Is effective, but it is known that if the supply rate is too fast, silicon dioxide particles are generated in the treatment liquid, and the film formation rate decreases conversely. This is because the film formation efficiency (hereinafter referred to as film formation efficiency) expressed by the ratio of (the amount of silicon dioxide film formed) / the amount of substance or thermal energy that accelerates the decomposition of hydrosilicofluoric acid) It means to decrease. In order to suppress the generation / growth of the silicon dioxide particles and to increase the film formation rate (that is, increase the film formation efficiency), a substance or thermal energy that accelerates the decomposition of hydrosilicofluoric acid is used. A method (hereinafter referred to as improved method 1) of continuously supplying and circulating a part of the treatment liquid to filter silicon dioxide particles generated in the treatment liquid is known. (For example, JP-A-60-33233, JP-A-63-102738) As a method of forming a dense silicon dioxide film by the above-mentioned precipitation method, a method of forming a silicon dioxide film at a high treatment liquid temperature (for example, Japanese Patent Application No. 62-184569 is referred to as improved method 2) and a method of using a high-concentration hydrofluoric acid aqueous solution as a treatment solution (for example, referred to as Japanese Patent Application No. 62-174561 is referred to as improved method 3) is known. There is.

[Problems to be Solved by the Invention] However, the film formation rate obtained by the above-mentioned improved method 1 is about 30 to 100 nm / h, although it is somewhat different depending on the processing conditions, which is not industrially sufficient. Further, also in the case of the above-mentioned improved method 1, silicon dioxide particles are generated, and the film forming efficiency is not always sufficient.

Moreover, in the above-mentioned improved method 2 and improved method 3,
Evaporation of the Si component (presumed to be H ₂ SiF ₆ or SiF ₄ ) is severe, and silicon dioxide particles are generated at the interface between the processing liquid and the atmosphere and the container wall above the surface of the processing liquid. It is presumed that these silicon dioxide particles could originally form a silicon dioxide film in the treatment liquid, and as a result of being scattered into the atmosphere, there was a problem that the film forming efficiency was lowered.

[Means for Solving Problems] The present invention has been made to solve the above problems, and a treatment liquid containing a hydrosilicofluoric acid solution in which silicon dioxide is supersaturated is used as a base material. In the method for producing a silicon dioxide film in which a silicon dioxide film is deposited on the surface of a base material by contacting with a substrate, in order to prevent evaporation of Si component from the treatment liquid, a treatment liquid containing the hydrofluoric acid solution and a gas The method of eliminating the interface is used.

As a method for eliminating the interface between the treatment liquid and the gas, a method of filling the treatment liquid in a closed container, floating a solid on the treatment liquid, or the like may be used, but the reactivity with the treatment liquid is low, and A method of suspending a liquid substance having a specific gravity lower than that of the treatment liquid is preferable because it is simple and can eliminate all the interfaces between the treatment liquid and gas.

The liquid substance is not particularly limited as long as it has low reactivity with the treatment liquid and has a lighter specific gravity than the treatment liquid. For example, as the aliphatic hydrocarbon represented by the general formula C _n H _{2n + 2} , those having n = 4 to 31 can be used, but the temperature of the treatment liquid when carrying out the present invention, the melting point and boiling point of the liquid substance, the treatment It is better to select in consideration of vapor pressure at liquid temperature.

The method for preparing the treatment liquid containing the hydrosilicofluoric acid solution in which the silicon dioxide is supersaturated is not particularly limited. For example, H ₃ BO may be added to the hydrofluoric acid solution in which silicon dioxide is approximately saturated.
₃ , a method of adding a substance such as Al that promotes the decomposition of hydrofluoric acid, a method of increasing the temperature of a hydrofluoric acid solution in which silicon dioxide is substantially saturated, and the like can be used.

The substrate applied to the present invention is not particularly limited, and various glasses such as alkali metal-containing glass, silica glass, and alkali-free glass, various ceramics, various semiconductors such as silicon and gallium arsenide, and the like, and are inconvenient with the treatment liquid. It can be applied to any base material that does not easily cause various reactions.

[Operation] According to the present invention, since the interface between the treatment liquid containing hydrofluoric acid in a supersaturated state of silicon dioxide and the gas is eliminated, the Si component (H ₂ SiF ₆ or SiF) from the treatment liquid is eliminated. (Estimated to be ₄ ) can be prevented. As a result, the film forming efficiency is significantly increased and the film forming rate is also increased. Particularly, when the concentration of the hydrosilicofluoric acid solution in the treatment liquid is high, the treatment liquid temperature is high, or a high film formation rate is obtained, the Si from the treatment liquid is increased.
It is effective when the evaporation of the components is severe.

An example in which C ₇ H ₁₆ (heptane) is used as a substance having a lower specific gravity than the treatment liquid will be described below.

[Example] Example 1 Using the silicon dioxide film manufacturing apparatus shown in FIG.
A silicon dioxide film was formed on a soda lime glass having a size of m, a width of 100 mm and a thickness of 1.1 mm by the following procedure.

The silicon dioxide film manufacturing apparatus comprises an outer tank (1) and an inner tank (2), and water (3) is filled between the inner tank and the outer tank.
In this example, the temperature of the water was adjusted to 35 ° C. by the temperature controller (4).

Further, the water (3) is stirred by the stirrer (5) in order to make the temperature uniform. The inner tank consists of a front part (6), a middle part (7) and a rear part (8), and each part has a solution of hydrofluoric acid hydrofluoric acid at a concentration of 2.5 mol / l in which silica gel powder is dissolved and saturated.
One liter is filled as the processing liquid.

Here, first, the circulation pump (10) is started, and the treatment liquid in the rear part (8) of the inner tank is pumped out by a fixed amount and the filter (1
Circulation of the treatment liquid which was filtered in 1) and returned to the front part (6) of the inner tank was started. After that, in the rear part (8) of the inner tank, length 50mm, width 50mm, thickness
Three 3 mm metal Al plates were dipped and held for 10 hours. In this state, the treatment liquid became a treatment liquid having an appropriate degree of supersaturation of silicon dioxide.

Here, the absolute removal rate of the filter (11) is 1.5 μm (1.5
The flow rate of the treatment liquid is 500 ml / min (the total treatment liquid is 6 liters, so the circulation flow rate is about 8% / min) and the interface between the treatment liquid and the gas is set to 100%. The heptane (14) was suspended on the treatment liquid for the purpose of eliminating the above.

Then, the soda lime glass substrate (9) was vertically dipped in the middle part (7) of the inner tank. Then, three metal Al plates having a length of 50 mm, a width of 50 mm and a thickness of 3 mm are immersed in the above-mentioned conditions (in the rear part of the inner tank (8)), circulated at 8% / min, and filtered with a filter having an absolute removal rate of 1.5 μm. ) Was continuously maintained for 8 hours.

After the treatment, no silicon dioxide particles were found on the interface between the treatment liquid and heptane, the interface between heptane and the atmosphere, and the container wall above the treatment liquid surface.

The amount of Al dissolved in 8 hours was 3.18 g, and the film thickness of the silicon dioxide film obtained by the above treatment was about 678 nm. Therefore, the average film forming rate is about 85 nm / hour, and the amount of (silicon dioxide film forming amount) / (the amount of substance or thermal energy that accelerates the decomposition of hydrosilicofluoric acid (in the case of this embodiment, Al The film formation efficiency expressed by the ratio of (dissolved amount)) is 0.02.
Can be silicic acid with 13 nm / mm ₂ · g.

Comparative Example 1 Using the same apparatus as in Example 1, a treatment liquid having an appropriate degree of silicon dioxide supersaturation was obtained.

Here, the absolute removal rate of the filter (11) was set to 1.5 μm, and the treatment liquid circulation flow rate was set to 500 ml / min (since the total treatment liquid amount is 6 liters, the circulation flow rate is about 8% / min). Nothing floated on the treatment liquid, and it was in direct contact with the atmosphere.

After that, the soda lime glass substrate (9) is vertically immersed in the middle part (7) of the inner tank, and the above condition (vertically in the rear part (8) of the inner tank)
Immerse 3 metal Al plates of 50mm, width 50mm, thickness 3mm, 8% /
Circulate for min and filter with an absolute removal rate of 1.5 μm. ) Held for 8 hours.

After the treatment was completed, a small amount of silicon dioxide particles were found on the interface between the treatment liquid and the atmosphere and on the container wall above the treatment liquid surface.

The amount of Al dissolved in 8 hours was 1.98 g, and the film thickness of the silicon dioxide film obtained by the above treatment was about 405 nm. Therefore, the average film forming rate is about 51 nm / hour, the amount of (silicon dioxide film forming amount) / (the amount of material or thermal energy that accelerates the decomposition of hydrosilicofluoric acid (in the case of this embodiment, Al The film formation efficiency, which is represented by the ratio of (dissolved amount)), is 0.
It can be calculated as 0205 nm / mm ₂ · g.

Example 2 An aqueous solution of hydrofluoric silicic acid having a concentration of 3.8 mol / l was added to -3.
It was cooled to 0 ° C., and silicon dioxide (industrial silica gel) was dissolved and saturated to obtain a treatment liquid.

100 ml of this treatment liquid was placed in four containers, and soda lime glass having a length of 50 mm, a width of 25 mm and a thickness of 1.1 mm was immersed in each container. Then, heptane was suspended on the treatment liquid in each container, and the container was immediately heated to 35 ° C. for 3 hours and 6 hours, respectively.
Hold for 16 hours, 24 hours. Then, the film thickness of the silicon dioxide film laminated on the glass surface was measured.

The results are shown in Table 1. It can be seen that the film thickness of the silicon dioxide film increases almost in proportion to the time during which the soda lime glass is kept in the treatment liquid.

In addition, no silicon dioxide particles were found on the interface between the processing solution and heptane after the completion of the processing, the interface between heptane and the atmosphere, and the container wall above the surface of the processing solution.

Comparative Example 2 A silicon dioxide film was formed on soda lime glass in the same manner as in Example 2. However, heptane was not suspended on the treatment liquid, and the treatment liquid and the atmosphere were in direct contact with each other.

The results are shown in Table 2. The film thickness of the silicon dioxide film is not much different from that of Example 2 in the treatment for 6 hours or less, but does not increase much in the treatment for 16 hours or more, and about 40% in the treatment for 16 hours, 24
The time treatment gave only a silicon dioxide film with a thickness of about 35%.

After the treatment, silicon dioxide particles can be seen on the interface between the treatment liquid and the atmosphere and on the container wall above the treatment liquid surface. Especially, in the case of 16 hours treatment and 24 hours treatment, a large amount of silicon dioxide particles are generated. Was.

[Advantages of the Invention] According to the present invention, it is possible to significantly increase the film formation efficiency and increase the film formation rate. Therefore, it is possible to reduce the supply amount of a substance or thermal energy that accelerates the decomposition of hydrosilicofluoric acid, which is advantageous in that the manufacturing cost is reduced.

Furthermore, the evaporation of Si components (presumed to be H ₂ SiF ₆ or SiF ₄ ) from the treatment liquid can be suppressed, and as a result, the generation of silicon dioxide particles outside the treatment liquid can be prevented. There is an effect that it is possible to prevent the deterioration of the working environment due to the above and the reduction of the product yield due to the silicon dioxide particles.

[Brief description of drawings]

FIG. 1 is a system diagram of a silicon dioxide film manufacturing apparatus used in an embodiment of the present invention. (1) Outer tank, (2) Inner tank (3) Water, (4) Temperature controller (5) Stirrer, (6) Inner tank front part (7) Inner tank middle part, (8) Inner tank rear part (9) ) Soda lime glass (10) Circulation pump, (11) Filter (12) Metal Al plate, (13) Stirrer (14) Light specific gravity material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Kawahara, 3-5-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka Prefecture Nippon Sheet Glass Co., Ltd. (72) Inventor, adult 41, Sumiyoshidai, Higashinada-ku, Kobe-shi, Hyogo 1-807

Claims (2)

[Claims] 1. A method for producing a silicon dioxide film, which comprises depositing a silicon dioxide film on the surface of a substrate by bringing a substrate into contact with a treatment liquid containing hydrofluoric acid in a supersaturated state of silicon dioxide. A method for producing a silicon dioxide film, characterized by eliminating an interface between a liquid and a gas. 2. A method for eliminating the interface between the processing liquid and the gas,
The method for producing a silicon dioxide film according to claim 1, which is a method of suspending a liquid substance having low reactivity with the treatment liquid and having a lower specific gravity than the treatment liquid on the treatment liquid.