JPH04310514A - Production of silicon oxide-coated substrate - Google Patents

Abstract

PURPOSE:To readily produce the subject substrate having the silicon oxide coating film of a controlled thickness in a high purity in a short time by dialyzingly removing hydrogen fluoride from a hydrosilicofluoric acid aqueous solution containing a substrate immersed therein. CONSTITUTION:A dialysis chamber 4 and a diffusion chamber 5 are disposed through a dialysis membrane 3 to provide a diffusive dialysis device. A hydrosilicofluoric acid aqueous solution 1 is supplied into the dialysis chamber 4. Water is supplied into the diffusion chamber 5 and held at a pH of >=1. A substrate 2 such as an alkali glass plate is immersed in the dialysis chamber 4, and hydrogen fluoride in the aqueous solution 1 in the chamber 4 is passed through the dialysis member 4 to diffuse in the diffusion chamber 5. Silicon oxide is liberated in the dialysis chamber 4 and deposited on the surface of the substrate 2 to produce a silicon oxide-coated substrate.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a base material having a silicon oxide coating layer on its surface (hereinafter referred to as a silicon oxide coated base material).
This invention relates to a new manufacturing method.

0002

[Prior Art] Conventionally, by forming a silicon oxide layer on the surface of a base material such as glass, ceramics, metal, etc., it is possible to prevent elution of base material components, protect the base material surface, and provide insulation to the base material surface. Grants, etc. are being made.

Known methods for forming a silicon oxide film on the surface of the substrate include sputtering, vapor deposition, dry processes such as CVD, and the sol-gel method. Furthermore, the sol-gel method has the disadvantage that the film cannot be sufficiently thickened in one step. There is also a method in which silicon oxide is precipitated on the surface of the substrate by immersing the substrate in the aqueous solution of hydrosilicofluoric acid, and a method in which boric acid is added to the aqueous solution of hydrosilicofluoric acid. Various methods have been proposed in which the precipitation rate of silicon oxide is improved by the addition of silicon oxide (hereinafter, these are also simply referred to as "immersion methods").

0004

[Problems to be Solved by the Invention] The above-mentioned dipping method can be said to be an effective method for forming a silicon oxide film on the surface of a substrate, but it is difficult to improve the thickness of the silicon oxide layer, the purity of the layer, etc. There was room. In other words, although the rate of formation of the silicon oxide layer is somewhat fast in this immersion method, when the substrate is immersed in the immersion liquid for a long period of time in order to thicken the silicon oxide layer, salts accumulate in the immersion liquid, resulting in formation of a silicon oxide layer. The problem is that the speed gradually decreases. In addition, the use of salt contaminates the silicon oxide film formed on the surface of the substrate, which has a negative effect on the quality of the substrate, especially when the substrate is a semiconductor wafer.

[0005]

[Means for Solving the Problems] As a result of repeated research to develop a method for efficiently forming a high-purity silicon oxide layer on the surface of a substrate, the present inventors found that By removing hydrofluoric acid from the hydrosilicofluoric acid aqueous solution by dialysis in the presence of the base material, a highly pure silicon oxide layer containing no ionic substances can be formed on the surface of the base material at a rapid rate. ,
Furthermore, the present inventors have discovered that since the formation of such a silicon oxide layer can be carried out continuously for a long period of time, the thickness of the silicon oxide layer can be adjusted as desired, and the present invention has been completed.

[0006] The present invention provides a method for producing a silicon oxide-coated substrate, characterized in that hydrofluoric acid is removed by dialysis from an aqueous solution of hydrofluorosilicic acid in which the substrate is present, and silicon oxide is deposited on the surface of the substrate. It is.

[0007] In the present invention, the base material is not particularly limited;
Known base materials that conventionally require coating with a silicon oxide layer can be used without particular restriction. Examples include alkali-containing glasses such as soda lime glass and borosilicate glass, ceramics such as aluminum nitride and aluminum oxide, metals such as copper, iron, and stainless steel, and semiconductor materials such as silicon wafers.

In the present invention, the hydrosilicofluoric acid aqueous solution is
Known materials may be used without particular limitation, but in order to efficiently deposit a silicon oxide layer on the surface of the substrate, it is preferable to adjust the concentration of silicon oxide to saturation, or even supersaturation.

The greatest feature of the present invention is that a base material on which a silicon oxide layer is to be formed is present in the aqueous solution of hydrosilicofluoric acid, and hydrofluoric acid is removed from the aqueous solution of hydrosilicofluoric acid by dialysis. By this, a silicon oxide layer is deposited on the surface of the substrate. By removing hydrofluoric acid from an aqueous silicofluoric acid solution by dialysis and depositing a silicon oxide layer on the surface of the base material, it is possible to deposit a silicon oxide layer on the surface of the substrate. It is possible to significantly reduce the amount of impurities mixed in. Another feature is that the formation speed of the silicon oxide layer is fast. Moreover, surprisingly, it is possible to perform dialysis stably even when silicon oxide is deposited on the membrane used, and by adjusting the dialysis time, the thickness of the silicon oxide layer can be adjusted to any desired thickness. It is possible to adjust to

[0010] As the above-mentioned dialysis method, any known method can be employed without particular limitation, but diffusion dialysis, electrodialysis, etc. are generally preferred.

FIG. 1 is a conceptual diagram showing a basic embodiment of an apparatus for carrying out the method of the present invention by diffusion dialysis. The diffusion dialysis apparatus shown in FIG. 1 is basically constructed by forming a chamber dialysis chamber 4 and a diffusion chamber 5 via a dialysis membrane 3. The hydrosilicofluoric acid aqueous solution 1 is supplied to the chamber dialysis chamber 4, and the diffusion chamber 5
water is generally supplied. Further, the base material is immersed in the dialysis chamber 4. In this state, hydrogen fluoride in the hydrosilicofluoric acid aqueous solution in the dialysis chamber 4 passes through the dialysis membrane 3 and diffuses into the diffusion chamber 5. Then, in the dialysis chamber 4, silicon oxide is liberated and deposited on the surface of the base material, thereby forming a silicon oxide film.

In the above-mentioned diffusion dialysis, any known anion exchange membrane used in acid diffusion dialysis can be used without particular restriction as long as the dialysis membrane is resistant to hydrogen fluoride. Generally, anion exchange membranes having quaternary ammonium bases are preferably used.

[0013] Furthermore, the dialysis conditions for diffusion dialysis may be selected from those used in known diffusion dialysis. For example, dialysis may be performed in batches or continuously, but if the purpose is to form a thick silicon oxide film, it is preferable to perform dialysis continuously. When performing diffusion dialysis continuously, the dialysis chamber 4 may be replenished with the aqueous solution of hydrosilicic acid fluoride that has been reduced by the diffusion dialysis. Further, it is preferable to supply water to the diffusion chamber 5 so as to maintain the concentration difference of hydrogen fluoride with respect to the dialysis chamber 4 in order to increase the diffusion rate and maintain a high rate of formation of the silicon oxide film. Generally, it is preferable to adjust the amount of water supplied to the diffusion chamber so that the pH of the diffusion chamber is 1 or higher, preferably 1.5 or higher.

[0014] The hydrofluoric acid aqueous solution taken out from the above-mentioned diffusion chamber can be concentrated if necessary and used as a raw material for preparing a hydrosilicic acid aqueous solution.

FIG. 2 is a conceptual diagram showing a typical embodiment in which the method of the present invention is carried out by electrodialysis. The electrodialysis apparatus of FIG. 2 has an anion exchange membrane 3-a and a cation exchange membrane 3-b arranged between electrodes 8-a and 8-b, and a desalination chamber 1.
0 and a concentration chamber 11. The embodiment shown in FIG. 1 is particularly suitable for industrially implementing the present invention, and the electrodes are connected via a liquid- and ion-impermeable back plate 9 between a pair of electrodes. It is composed of a plurality of units whose electrodes are electrically connected bipolar electrodes. With the above configuration, it is possible to form silicon oxide films on a plurality of substrates 2 from one power source, prevent hydrogen fluoride from diffusing between units, and perform electrodialysis with high current efficiency. can. As the anion exchange membrane, cation exchange membrane, electrode, etc., known ones having resistance to hydrogen fluoride can be used without any particular restriction. For example, as the anion exchange membrane, an anion exchange membrane having a quaternary ammonium base is preferably used. Further, as the cation exchange membrane, a cation exchange membrane having a sulfonic acid group is preferably used. Furthermore, platinum is particularly preferred as the cathode and anode.

In the electrodialysis apparatus shown in FIG. 2, a hydrosilicofluoric acid aqueous solution 1 is supplied to a demineralization chamber 10, and water is supplied to a concentration chamber 11. By applying a voltage to the electrodes, fluorine ions and hydrogen ions pass through an anion exchange membrane and a cation exchange membrane, respectively, and move to the concentration chamber 11 where an anode and a cathode are present. In the demineralization chamber 10, silicon oxide is liberated due to the decrease in hydrofluoric acid and deposits on the surface of the base material, forming a silicon oxide film. The above-mentioned supply of water to the concentration chamber is preferable in order to prevent the diffusion of hydrofluoric acid from the concentration chamber and maintain a high rate of formation of the silicon oxide film. Generally, the concentration of hydrofluoric acid in the concentration chamber is preferably adjusted by a method such as supplying water so that the pH is 1 or more, preferably 1.5.

[0017] The aqueous hydrofluoric acid solution taken out from the concentration chamber can be concentrated if necessary and used as a raw material for an aqueous hydrosilicic acid fluoride solution.

In the present invention, it is also possible to color the silicon oxide layer formed on the surface of the substrate. As a typical embodiment of the coloring method, a method in which the dye is present in the liquid in which the substrate is immersed is particularly preferred. As the above-mentioned dye, any known dye can be used without any restriction as long as it is soluble in the aqueous hydrosilicofluoric acid solution and does not decompose. For example, Patent Blue V,
Methylene blue, macarite green, rhodamine 6G
, Victoria Blue, etc.

[0019]

[Effects of the Invention] As can be understood from the above explanation, according to the method of the present invention, hydrogen fluoride can be selectively removed by dialysis while the substrate is immersed in an aqueous solution of hydrosilicic acid. Since a silicon oxide layer is formed on the surface of the base material by adding a salt to the aqueous solution, compared to the conventional method of forming a silicon oxide layer on the surface of the base material by adding salt to the aqueous solution, impurities are less likely to enter the formed silicon oxide film. It is possible to significantly reduce the amount of contamination. Another feature is that the formation speed of the silicon oxide layer is fast. Moreover, even if silicon oxide precipitates on the membrane used during dialysis, it is possible to perform stable dialysis, and by adjusting the dialysis time, the thickness of the silicon oxide layer can be adjusted as desired. It is. It is also possible to color the silicon oxide film formed on the surface of the base material.

[0020]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. In addition, in the Examples and Comparative Examples, the purity of the silicon oxide film and the deposition rate of the silicon oxide film were measured by the following test method.

(1) Purity of silicon oxide film (impurity ions) After washing the base material on which the silicon oxide film was formed with pure water and drying it,
The voltage at which dielectric breakdown occurs was measured in vacuum between two points 0.1 mm apart on the silicon oxide film layer. It can be said that the larger the voltage, the smaller the amount of ions mixed into the silicon oxide film (the higher the purity).

(2) Formation rate The thickness of the silicon oxide layer was measured 2 hours after the substrate was immersed in a tank (chamber) containing an aqueous solution of hydrosilicofluoric acid and silicon oxide began to precipitate.

Example 1 Using the diffusion dialysis apparatus shown in FIG.
A silicon oxide layer was formed on the surface of a base material made of alkali glass measuring m x 1 mm. Neocepta AFN-7 (trade name: manufactured by Tokuyama Soda Co., Ltd.) is used as the dialysis membrane (anion exchange membrane), and in the dialysis room 4, a silicic acid hydrofluoric acid aqueous solution (Wako Pure Chemical Industries, Ltd.) with a silicic acid concentration of 40% by weight is used. (manufactured by Kogyo Co., Ltd.). on the other hand,
Water was supplied to the diffusion chamber 5 so that the pH of the hydrofluoric acid aqueous solution to be discharged was 1 to 2. One hour after the start of dialysis, a 10 mm x 20 mm x 1 mm alkali glass was immersed in the hydrosilicic acid aqueous solution as a base material. The fluid temperature during dialysis was maintained at 35°C.

[0024] In the above dialysis, it was confirmed that silicon oxide was precipitated. Further, the deposition rate of the silicon oxide layer on the surface of the substrate was 550 angstroms/hour, and the dielectric breakdown voltage was 23 kilovolts/mm.

[0025] Furthermore, as a result of performing dialysis for 10 hours while supplying a reduced amount of hydrosilicofluoric acid aqueous solution, the production rate of silicon oxide hardly decreased despite the fact that silicon oxide was attached to the membrane surface. , a silicon oxide layer with a thickness of 0.5 μm was formed.

Example 2 In Example 1, Patent Blue V (trade name: manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added as a dye to an aqueous solution of hydrosilicofluoric acid.
A silicon oxide layer was formed on the surface of the substrate in the same manner except that 0.1 g/100 cc of .

[0027] In the above dialysis, it was confirmed that silicon oxide was precipitated. Further, the deposition rate of the silicon oxide layer on the surface of the substrate was 350 angstroms/hour.

Furthermore, the obtained silicon oxide layer was colored green. Furthermore, as a result of performing dialysis for 10 hours while supplying a hydrosilicofluoric acid aqueous solution, the formation rate of the silicon oxide film hardly decreased, and the thickness of the silicon oxide film was 0, even though silicon oxide was attached to the film surface. A silicon oxide layer of .3 μm was formed.

Example 3 Using the same base material as in Example 1 using the electrodialysis apparatus shown in FIG. 2, a silicon oxide layer was formed on the surface of the base material. Neocepta AFX (product name: manufactured by Tokuyama Soda Co., Ltd.) was used as the anion exchange membrane 3-a, and Neocepta CMX (product name: manufactured by Tokuyama Soda Co., Ltd.) was used as the cation exchange membrane 3-b.
was used, and platinum was used for the cathode and anode. Desalination room 10
The same aqueous silicofluoric acid solution as that used in Example 1 is supplied to the concentration chamber 11, and the pH of the aqueous hydrofluoric acid solution to be discharged is
Water was supplied so that the ratio was 1 to 2. One hour after the start of dialysis, the base material was immersed in the aqueous hydrosilicofluoric acid solution, and electrodialysis was performed at a liquid temperature of about 35°C.

In the above dialysis, it was confirmed that silicon oxide was deposited on the surface of the substrate. Further, the deposition rate of the silicon oxide layer was 400 angstroms/hour, and the dielectric breakdown voltage was 24 kilovolts/mm.

Furthermore, as a result of performing dialysis for 10 hours while supplying an aqueous solution of hydrosilicofluoric acid, the production rate of the silicon dioxide film hardly decreased, despite the fact that silicon dioxide was attached to the membrane surface. A silicon oxide layer with a thickness of 0.38 μm was formed.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the basic structure of a diffusion dialysis apparatus used in the method of the present invention.

FIG. 2 is a conceptual diagram showing one embodiment of an electrodialysis apparatus used in the method of the present invention.

[Explanation of symbols]

1　　　　　Hydrosilicic acid aqueous solution 2 Base material 3-a Anion exchange membrane 3-b Cation exchange membrane 4 Dialysis room 5 Diffusion chamber 6 Water 7 Hydrofluoric acid aqueous solution 8-a Electrode 8-b Electrode 9　　　　　　Back plate 10　　　Demineralization room 11 Concentration chamber

Claims (1)

[Claims] 1. A method for producing a silicon oxide-coated substrate, which comprises removing hydrofluoric acid from an aqueous solution of hydrofluorosilicic acid in which the substrate is present by dialysis to precipitate silicon oxide on the surface of the substrate.