JPH03170317A - Production of coated film of silicon dioxide - Google Patents

Abstract

PURPOSE:To form uniform an SiO2-coated film without pinhole on the surface of a base material of metal, etc., easily reacting with treating solution by forming the SiO2 coated film on the surface of base material at a low temperature to suppress the reaction of H2[SiF6] treating solution containing supersaturated SiO2 with the base material and re-forming the SiO2-coated film by heating the treating solution to a high temperature. CONSTITUTION:A coated film of SiO2 is provided on the surface of a base material at a low temperature in such a condition that the reaction of the above-mentioned H2[SiF6] treating solution with the base material composed of metal, etc., is suffressed. Then the base material is made to a protected state from the treating solution with said SiO2 coated film, thus said treating solution is heated to a high temperature and again the SiO2-coated film is formed. As a method bringing said treating solution into contact with said base material, dipping the base material in a dipping tank filled with the treating solution is preferable as ready and easy to obtain the coated film having uniform thickness. Besides, as the base material, metal such as Zn or Ti, etc., relatively reactive with the treating solution, or Cu or stainless reacting and dissolving by bringing into contact with the treating solution for relatively long time is effective.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a silicon dioxide film on the surface of a substrate by bringing the substrate into contact with a treatment solution containing a silicon dioxide supersaturated solution of hydrosilicofluoric acid. In particular, it relates to the case where a base material that easily reacts with and dissolves in a processing liquid is used as the base material.

[Conventional technology] Today, metals are used in a wide range of industrial fields, taking advantage of their characteristics as good conductors. However, when metal is treated as a good conductor, for example when used as an electric wire, an insulating coating is required for safety reasons. It is also necessary to prevent corrosion of metals, and anodic oxide films, paints, and the like are used as protective films for preventing corrosion.

Especially in fields where Sf02 coating is required in high-temperature environments or for special purposes, such as printed circuit boards for compact discs,
Applications include coatings to prevent corrosion and wear on steel-related rolling rolls, substrate protection for magneto-optical heads, protective coatings for stainless steel substrates on which amorphous silicon is attached for dry condenser solar cells, and substitutes for various anodic oxide coatings. Furthermore, in the field of semiconductors, silicon dioxide films are used as interlayer insulating films and the like.

Conventionally, as a silicon dioxide coating method, a method is known in which a silicon dioxide coating is formed on the surface of the substrate by immersing the substrate in a silicon dioxide supersaturated aqueous solution of hydrosilicofluoric acid (hereinafter referred to as the precipitation method). . (For example, JP-A-57-196744, JP-A-61-281-047, JP-A-62-20876) The above precipitation method has the advantage that a uniform silicon dioxide film can be formed on the surface of a base material of any shape; Because the treatment liquid, hydrofluorosilicic acid, is a strong acid and contains fluorine ions, it is easy to treat base materials such as metals (particularly metals that have a greater tendency to ionize than hydrogen, metals that react easily with fluoride ions, etc.) There was a problem that it could not be used as a base material because it would dissolve in water.

In order to solve the above-mentioned problems, a method (unexamined Japanese Patent Application Publication No. 2003-120002) is proposed in which a film containing silicon dioxide is formed on the surface of the substrate in advance by a method such as vacuum evaporation or sputtering CVD, and then a silicon dioxide film is formed by the above-mentioned precipitation method. 1986-21810 (hereinafter referred to as improved method 1) is known. Furthermore, a method has been proposed in which electrolytic deposition is carried out using the base material as an anode (JP-A-1-8296, hereinafter referred to as improved method 2). Regarding the temperature of the treatment liquid, it is stated that in the above-mentioned improved method 1, the treatment liquid was maintained at 35° C. when the substrate was immersed in the example. Further, in the improved method 2, it is stated that it is preferable to set the temperature of the processing liquid between -5°C and 70'C.

Regarding the temperature of the processing solution when forming a silicon dioxide film using the above-mentioned precipitation method, it is known that increasing the temperature of the processing solution improves the quality of the silicon dioxide film formed. (Unexamined Japanese Patent Publication No. 1-28377) [Problems to be Solved by the Invention] However, in the above-mentioned improved method 1, since a film containing silicon dioxide is formed on the surface of the substrate in advance by a method such as vacuum evaporation or sputtering CVD, It is not possible to form a uniform silicon dioxide coating on the surface of a base material of arbitrary shape. In addition, (2) the equipment is not simple and the cost required for silicon dioxide coating is high. Also, ■ it is difficult to process large area substrates. There was one issue during this period.

In addition, in the improved method 2, it is necessary to use a base material that has conductivity on at least a portion of its surface. Therefore, although it is effective when a material 41 such as a metal, an alloy, or a semiconductor is used as a base material, there is a problem in that it cannot be applied when a non-conductive material is used as a base material. Furthermore, improved method 2 has the advantage of fast film formation, but as estimated from its film formation mechanism, particles, complex ions, sol, gel, colloid, etc. that are similar to Si02 may have negative effects on the surface or as a whole. Because it is electrically charged and is electrically attracted to the anode to form a film, there are problems such as poor film surface flatness and pinholes.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems. In a method for producing a silicon dioxide film, the silicon dioxide film is deposited on the surface of a base material by contacting the base material,
A silicon dioxide coating is provided on the surface of the substrate at a low temperature under conditions that suppress the reaction between the treatment liquid and the substrate, and the treatment liquid is applied after the substrate is protected from the treatment liquid by this coating. The silicon dioxide coating is applied again at a high temperature, and the initial temperature of the treatment solution is determined by the reactivity of the treatment solution with the substrate on which the silicon dioxide coating is to be formed and the required formation. The optimum value differs depending on the membrane speed.

In other words, regarding the reactivity between the base material and the treatment liquid, the temperature of the treatment liquid must be lowered for base materials such as zinc and titanium that are highly reactive with the treatment liquid (easily soluble in the treatment liquid). In the case of base materials such as copper and stainless steel that have low reactivity with the treatment solution (hard to dissolve in the treatment solution), even if the temperature of the treatment solution is a little high, the base material will hardly dissolve and dioxide will remain on the surface. Silicon coating can be shaped. Regarding the film formation speed,
Since the above-mentioned precipitation method utilizes a chemical reaction, if the temperature of the processing solution is extremely low, the reaction rate becomes slow, and therefore the film formation rate may become slow. Therefore, it is necessary to appropriately select the temperature of the treatment liquid depending on the type of substrate.

Furthermore, as mentioned above, it is known that the film quality of a silicon dioxide film formed by the precipitation method changes depending on the temperature of the processing solution, and films formed at low temperatures generally have poor film quality. In order to solve this problem, we first applied a silicon dioxide coating to the entire surface of the substrate using a low-temperature treatment solution to prevent direct contact between the substrate and the treatment solution, and then applied a silicon dioxide coating to the substrate at a normal or higher temperature. It is effective to form a silicon dioxide film with good film quality using. In this case, the process of forming a high-quality silicon dioxide film using a treatment solution at a normal or higher temperature is the same equipment and process as the process of forming a silicon dioxide film on the substrate surface using a low-temperature treatment solution. The treatment may be carried out by increasing the temperature of the treatment liquid using a liquid, or it may be carried out using another device or a treatment liquid.

The method for preparing the treatment liquid containing the hydrosilicofluoric acid solution that has become supersaturated with silicon dioxide is not particularly limited. For example, H3
A method of adding a substance that promotes decomposition of hydrosilicofluoric acid such as BO3, A1, etc., a method of increasing the temperature of a hydrosilicic acid solution that has reached a substantially saturated state of silicon dioxide, etc. can be used.

Furthermore, as a method for bringing the treatment liquid into contact with the substrate, a method such as flowing the treatment liquid down onto the surface of the substrate may be used, but the method is not limited to a method such as allowing the treatment liquid to flow down onto the surface of the substrate. The method of dipping the material is preferred because it is simple and easy to obtain a coating of uniform thickness.

Substrates that can be applied to the present invention include metals such as zinc and titanium that relatively easily react with the processing solution, oxides such as magnesium oxide, and copper and stainless steel that react and dissolve when in contact with the processing solution for a relatively long period of time. However, the present invention is particularly effective in the case of copper, stainless steel, etc.

[Function] According to the present invention, a two-stage treatment is performed to suppress the reaction between the treatment liquid and the substrate by first lowering the temperature of the treatment liquid containing hydrosilicofluoric acid, which has reached a supersaturated state of silicon dioxide. Therefore, it is possible to form a uniform pinhole-free silicon dioxide film even on base materials such as metals, to which the above-mentioned deposition method could not be applied conventionally because they dissolve in processing liquids. This can also be applied to insulators such as oxides.

The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

[Example 1] As the first step, using the silicon dioxide film manufacturing apparatus shown in Fig. 1, a 18-layer film measuring 50 mm in length, 25 mm in width, and 3 mm in thickness was prepared.
-8 stainless steel AS B was used as a base material, and a silicon dioxide film was formed thereon by the following procedure.

The silicon dioxide coating manufacturing apparatus consists of an outer tank (1) and an inner tank (2), and the space between the inner tank and the outer tank is filled with water (3).

In this example, the temperature of this water was adjusted to 10° C. using a temperature controller (4).

Further, the water (3) is stirred by a stirrer (5) in order to equalize the temperature. The inner tank consists of a front part (6), a middle part (7), and a rear part (8), and each part is filled with an aqueous solution of hydrosilicic acid 62 with a concentration of 2.5 mol/Vχ and saturated with silica gel powder.
It is filled with X as a processing liquid.

First, start the circulation bomb (10), and then start the rear part of the inner tank (
8) Pour out a certain amount of the processing solution and pass it through the filter (l1
) and started circulating the treatment liquid, which was then returned to the front part of the inner tank (6). After that, add 50mm in length and 50mm in width to the rear part of the inner tank (8).
, A metal Al plate (12) with a thickness of 3 mm was immersed and held for 20 hours. In this state, the treatment liquid had an appropriate degree of silicon dioxide supersaturation.

Here, the absolute removal rate of the filter (1l) is 1.5μm.
And, the processing liquid circulation flow rate is 500 mI/m
in (since the total amount of processing liquid is 6vZ, the circulation flow rate is approximately 8vZ)
%/min).

Thereafter, the stainless steel substrate AS B (9) was vertically immersed in the middle part of the inner tank (7), and under the above conditions (a metal Al plate with a length of 50 mm, a width of 50 mm, and a thickness of 3 mm was immersed in the rear part of the inner tank (8), Circulate at 8%/min, absolute removal rate 1.5μ
Filter with m filter. ) for 6 hours for substrate A, and for 6 hours for substrate B.
was held for 12 hours.

The stainless steel base materials were hardly corroded in appearance in both base materials A and B, and the thickness of the silicon dioxide coating obtained by the above treatment was approximately 100 nm for A and approximately 190 nm for S B. As a result of observation using an electron microscope, the surface of the silicon dioxide film was relatively flat, and no pinholes or the like were observed. In addition, 48% HF as an etching solution:
70%H N Q3:H20=3:2:60 (
The enotylate of the silicon dioxide coating was measured at 22° C. using a mixed solution of (volume ratio). The etching rate was 38. It was 3 nm/sec.

As a second step, using the stainless steel substrate A coated with the silicon dioxide film with a thickness of about 100 nm prepared previously as a base material, a silicon dioxide film was formed using the same apparatus. However, in the second step, the temperature of the water (3) between the inner tank and the outer tank is
5℃, length 50mm, width 50mm, thickness 3mm
The metal AI plate (12) was immersed and held for 15 hours. In this state, the treatment liquid had an appropriate degree of silicon dioxide supersaturation.

After that, the stainless steel substrate A (9) is placed in the middle part of the inner tank (7).
under the above conditions (50 m vertically at the rear of the inner tank (8)).
A metal AI plate (12) with a width of 50 mm and a thickness of 3 mm is immersed, circulated at a rate of 8%/min, and filtered through a filter with an absolute removal rate of 1.5 μm. )
It was held for 2 hours.

The stainless steel base material has hardly changed in appearance, and the thickness of the silicon dioxide film obtained by the above treatment is approximately 10
It was 0 nm. Therefore, a silicon dioxide film with a total thickness of about 200 nm is formed on the stainless steel substrate. Here, 48% HF:7 as an etching solution
Etch rate measurement was performed at 22° C. using a mixed solution of 0% H, -NOa:H20=3:2:60 (volume ratio). The etching rate of the silicon dioxide film (formed in the second step) up to about 100 nm from the film surface is 13.
It was 8 nm/sec.

[Example 2] Similar effects were obtained by using a treatment solution containing an aqueous boric acid solution instead of the AI plate. Using the silicon dioxide film manufacturing apparatus shown in Figure 2, a film of 50 mm in length, 25 mm in width, and 3 in thickness was prepared.
A silicon dioxide film was formed on 18-8 mm stainless steel using the following procedure.

The silicon dioxide coating manufacturing apparatus consists of an outer tank (1) and an inner tank (12) (2), and the space between the inner tank and the outer tank is filled with water (3). In this example, the temperature of this water was adjusted to 10° C. using a temperature controller (4). Further, the water (3) is stirred by a stirrer (5) in order to equalize the temperature. The inner tank consists of a front part (6), a middle part (7), and a rear part (8), and each part has 2.5 moles/? of saturated silica gel powder dissolved therein. X
A concentration of 17) hydrosilicofluoric acid aqueous solution 61K is filled as a processing liquid.

First, start the circulation pump (10), and then start the rear part of the inner tank (
Pour out a certain amount of the processing solution from step 8 and pass it through the filter (step 11).
) and started circulating the treated liquid to return it to the front part of the inner barrel (6). After that, 12 ml/min of 0.5 mol/1 boric acid aqueous solution (12) was added to the rear part of the inner tank (8).
The mixture was continuously added dropwise at a rate of 1, and maintained for 10 hours. In this state, the treatment liquid had an appropriate degree of silicon dioxide supersaturation.

Here, the absolute removal rate of the filter (11) is 1.5 μm.
And the processing liquid circulation flow rate is 500ml/m
(Since the total amount of treatment liquid is 6 VX, the circulating flow rate is about 8%/min).

Thereafter, the stainless steel substrate (9) was vertically immersed in the middle part (7) of the inner tank, and under the above conditions (at the rear part (8) of the inner tank, 0.5 mo
1 2 m 1 /l of boric acid aqueous solution (12)
It was continuously added dropwise at a rate of min, circulated at a rate of 8%/min, and filtered through a filter with an absolute removal rate of 1.5 μm.

) for 14 hours.

The stainless steel base material is virtually uncorroded in appearance, and the thickness of the silicon dioxide film obtained by the above treatment is approximately 35 mm.
It was 0 nm. As a result of observation using an electron microscope, the surface of the silicon dioxide film was relatively flat, and no pinholes or the like were observed.

It was confirmed that the first step of the present invention could be carried out satisfactorily. The obtained substrate was further subjected to a second step of immersing it in a high-temperature treatment solution, and the desired product could be obtained.

Comparative Example A comparison will be made in the case where the stainless steel substrate is suddenly immersed in the second step treatment temperature (35° C.) without undergoing the first step treatment using the apparatus shown in FIG.

An 18-8 stainless steel substrate (9) with a length of 50 mm, a width of 25 mm, and a thickness of 3 mm was immersed vertically into the middle part of the inner tank (7), and under the above conditions (50 mm in length, 50 mm in width at the rear part of the inner tank (8),
A metal AI plate (12) with a thickness of 3 mm is immersed at a rate of 8%/m.
The mixture is circulated through a filter with an absolute removal rate of 1.5 μm. ) for 4 hours.

The thickness of the silicon dioxide film obtained by the above treatment is approximately 200 mm.
nm, but the entire surface of the stainless steel substrate was corroded and turned black.

[Effects of the Invention] According to the present invention, it is possible to form a uniform silicon dioxide film without holes even on the surface of a base material such as an insulator such as a metal or an oxide that easily reacts with a treatment liquid used in a precipitation method.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a system for manufacturing a silicon dioxide film used in an example of the present invention. FIG. 2 is a system explanatory diagram of a silicon dioxide coating manufacturing apparatus used in another embodiment of the present invention. -15 (1) Outer tank (2) Inner tank (4) Temperature controller (5) (6) Inner barrel front (7) (8) Inner barrel rear (9) (10) Circulation pump (11) (l2) Metal A1 plate (14) (3) Water (13) Stirrer inner tank middle base filter boric acid aqueous solution -16- Fig. 2

Claims (1)

[Claims] In a method for producing a silicon dioxide film, a silicon dioxide film is deposited on the surface of the substrate by contacting the substrate with a treatment solution of hydrosilicofluoric acid in which silicon dioxide is supersaturated. A step of forming a silicon dioxide film on the surface of the substrate at a low temperature that suppresses the reaction, and a step of forming the silicon dioxide film by contacting the substrate on which the silicon dioxide film has been formed with the treatment solution heated to a high temperature. A method for producing a silicon dioxide coating comprising the step of further depositing a silicon dioxide coating on the surface of the base material.