WO2001090015A1

WO2001090015A1 - Solution for treating surface of glass and treatment method

Info

Publication number: WO2001090015A1
Application number: PCT/EP2001/005685
Authority: WO
Inventors: Yoichiro Maruko; Tohru Segawa; Tatsuhiro Sato
Original assignee: Heraeus Quarzglas Gmbh & Co. Kg; Shin-Etsu Quartz Products Co., Ltd.
Priority date: 2000-05-19
Filing date: 2001-05-18
Publication date: 2001-11-29
Also published as: JP4367816B2; JP2001335342A

Abstract

A novel solution for treating the surface of glass, which can form uniform unevenness having no nonuniformity, does not give an irritative odor, can easily manage the concentration, and can be easily handled in winter, and also a method for the surface treatment of glass, which can effectively form uniform unevenness having non nonuniformity by using the solution for the surface treatment of glass, are provided. Hydrogen fluoride, ammonium fluoride, and at least one kind of hydrophilic carboxylic acid having from 3 to 7 carbon atoms and/or having 2 or 3 carboxylic groups are mixed with water.

Description

Solution for Treating Surface of Glass and Treatment Method

Technical field to which the Invention belongs

The present invention relates to a solution for treating the surface of a quarts glass for forming unevenness on the surface of glass product, for example, quartz glass jigs (tubes, core tubes, boats, etc.) for producing semiconductors and to a treatment method.

Prior Art

Glass products, particularly, quartz glass products are excellent in the high purity, the heat resistance, and the chemical resistance and recently have been widely used as the jigs for producing semiconductors, such as tubes, core tubes, boats, etc.

However, as the problems of quartz glass products, the following points have been indicated. (1) The radiant heat of infrared rays, etc., is transmitted through a quartz jig and deteriorates a sealing member and an organic material for connection at the end portion thereof (Japanese Patent Publication No. 24109/1996). (2) At growing of a polysilicon film by a LPCVD (Low Pressure Chemical Vapor Deposition) method, an accumulation occurs on the inside surface of a core tube, which is released at heat- treating a wafer (Japanese Utility Model Laid-Open No. 88233/1986). (3) At heat treatment, welding of a quartz glass boat and a wafer occurs (Japanese Patent Laid- Open No. 170019/1989).

As the improving plan for these problems, it has been carried out to form unevenness on the surface of a quartz glass product. By forming unevenness on the surface of a quarts glass product, (1) the insulating effect of heat, (2) the effect of particle prevention (peeling prevention) at heat treatment, and (3) the effect of preventing welding of a boat and a wafer at heat treatment can be expected, whereby it becomes possible to solve the above-described problems of quarts glass products.

For forming unevenness on the surface of a quarts glass product, there are a sand blast method and a chemical treatment method. In general, a sand blast method, which is a technique of mechanically breaking the surface, has been used. The surface treatment by the sand blast method has hitherto been existed as a technique of forming uneven rough surface on the surfaces of quartz glass products as a more general technique than the chemical treatment method.

The problem of the sand blast method is that microcracks (about max 100 μm) occur on the uneven surface on the surface of the quartz glass product, which gives damages to the quarts glass product. That is, when microcracks are formed, (1) contaminants enter the microcracks, whereby the troubles of (2) the deterioration of the strength of the glass by the microcracks, and (3) the discrepancy of the dimensional precision by hydrofluoric acid etching after the sand blast treatment occur.

On the other hand, the surface treatment with a chemical solution has hitherto been known as a technique of forming rough surface on a quartz glass surface. For example, a method of treating with a mixed solution of hydrogen fluoride, ammonium fluoride, acetic acid, and water is proposed (Japanese Patent Laid-Open No. 267679/1995).

The principle of the frost work (glazing work) is explained as follows in "Handbook of Glass" (edited by Sumio Sakuhana, page 30, published by Asakura Shoten K.K., 1985). That is, when a glass is etched with a corrosive liquid prepared by adding ammonium fluoride (NH F) to hydrofluoric acid,

SiO₂ + 4HF → SiF₄ + 2H₂O

2NH₄F + SiF₄ -> (NH₄)₂SiF₆ by the above reactions, ammonium silicon fluoride is formed and precipitated on the surface of the glass, whereby the corrosion with hydrofluoric acid is inhibited. By the combination of the inhibition with the corrosion with hydrofluoric acid, unevenness is formed on the surface.

As the chemical treatment method, the following embodiments are known. (1) Using a chemical solution prepared by mixing hydrofluoric acid, ammonium fluoride, pure water, and a treating agent (acetic acid, phosphoric acid, hydrochloric acid, sulfuric acid, or formic acid), unevenness is formed in the surface of glass (Japanese Patent Laid-Open No. 172866/1995). (2) Using a mixed solution of hydrofluoric acid, ammonium fluoride, pure water, and nitric acid as the treatment solution, flake patterns are formed on a quartz glass surface (Japanese Patent Laid-Open No. 80351/1990). (3) As a technique of forming unevenness on a quartz glass surface, it exists to treat with a mixed solution of hydrofluoric acid, ammonium fluoride, acetic acid, and water (Patent Laid-Open No. 267679/1995).

Problems that the Invention is to Solve

The chemical treatment is most suitable for forming unevenness required in the semiconductor industry but there is a problem that according to the kind of the chemical solution, nonuniformity of unevenness frequently forms on the surface of glass, that is, the surface roughness becomes nonuniform. For example, in the case of using the chemical solution obtained by mixing hydrofluoric acid, ammonium fluoride, and pure water, nonuniformity occurs on the unevenness of the surface, and even in the case of using the chemical solution obtained by mixing hydrofluoric acid, ammonium fluoride, pure water, and an inorganic acid (nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid, etc.), nonuniformity occurs on the unevenness of the surface, but it is known that the improvement method by the addition of acetic acid has an effect for the formation of unevenness having no nonuniformity (Japanese Patent Laid-Open No. 267679/1995).

However, because acetic acid is liable to volatile and is evaporated with the passage of time, the concentration management with the passage of time such as in the case of using acetic acid, become necessary, etc., so that the concentration management is difficult. Furthermore, practically speaking, while repeating the use of the chemical solution, the surface roughness of the treated glass becomes more rough, thereby for maintaining the surface roughness to the level of the beginning of the preparation of the chemical solution, it becomes necessary to supplement acetic acid with the passage of time.

Also, because acetic acid emits an irritative odor, the influence to the surrounding environment is large, and in the actual field, incidental facilities such as a scriber, etc., become necessary and the cost in the equipment is increased. Furthermore, acetic acid is a liquid but the freezing point thereof is high as 17°C, in winter, it is frozen and becomes glacial acetic acid, and has a problem that such acetic acid is hard to handle.

Thus, as the result of making various investigations for developing a novel chemical solution capable of forming uniform unevenness without having nonuniformity and without having the faults as described above, the present inventor has obtained the knowledge that for attaining the object, only the existent ratios of hydrofluoric acid, ammonium fluoride, and pure water are insufficient, and by adding acetic acid, an improvement is obtained. However, as mentioned above, acetic acid has the troubles that it is liable to be volatized and has an irritative odor.

Thus, by further making various investigations on what is to be added to a mixed solution of hydrofluoric acid, ammonium fluoride, and pure water to form uniform unevenness without having nonuniformity on a quartz glass surface, the present inventor has found that by using the chemical solution of hydrofluoric acid, ammonium fluoride, and pure water added with a hydrophilic organic acid having a carboxyl group, the uniform unevenness having no nonuniformity, as formed using the chemical solution of related art, can be formed.

Therefore, an object of the invention is to provide a novel solution for the surface treatment of glass, which can form uniform unevenness without having nonuniformity, has no irritative odor, can easily make a concentration administration, and can be easily handled even in winter, and to provide a method of the surface treatment of glass, which can efficiently form uniform unevenness without having nonuniformity by using the solution of the surface treatment of glass.

Means for Solving the Problems

For solving the above-described problems, the first embodiment of the solution of the surface treatment of glass of the invention is characterized by mixing hydrofluoric acid, ammonium fluoride, and at least one kind of a hydrophilic carboxylic acid having from 3 to 7 carbon atoms with water.

A preferred hydrophilic carboxylic acid used in the first embodiment of the invention, comprises one or more of the following acids: acrylic acid, propionic acid, methacrylic acid, benzoic acid, lactic acid, crotonic acid.

When the carbon atom number is 8 or more, the ratio occupied by an alkyl group, which is a hydrophobic group, become large as compared with the hydrophilic carboxyl group, the hydrophobic property becomes strong as the whole molecule, and the carboxylic acid does not mixed well with hydrofluoric acid, ammonium fluoride, and water, whereby a sufficient effect cannot be obtained.

Also, the carboxylic acids having 2 or less carbon atom are limited to formic acid and acetic acid, these acids were already investigated in the past investigations, in the case of formic acid, a nonuniformity is formed, and acetic acid has the problems that the acid is liable to be vaporized and the concentration administration is difficult.

The second embodiment of the solution of the surface treatment of glass of the invention is characterized by mixing hydrofluoric acid, ammonium fluoride and water, and at least one kind of a hydrophilic carboxylic acid having 2 or 3 carboxyl groups.

As the hydrophilic carboxylic acid used in the second emodiment of the invention, one or more of the following compositions are preferably used: oxalic acid, succinic acid, adipic acid, maleic acid, fumaric acid, malic acid, tartaric acid, citric acid, malonic acid, citraconic acid.

As chemical substance having four or more carboxyl groups, the existing substances are mostly high molecular compounds and substances having a hydrophilic property scarcely exist. Accordingly, the carboxylic acid of this kind is not mixed with hydrofluoric acid, ammonium fluoride, and water and sufficient effect as a chemical solution cannot be obtained. As the chemical substance having one carboxyl group, there are formic acid and acetic acid, which are not suitable as described above.

However, there are also suitable hydrophilic carboxylic acids having less than 2 caboxylic groups, which are included in the first embodiment of the invention as described above. However, these hydrophilic carboxylic acids are characertized by having from 3 to 7 carbon atoms, e.g. acrylic acid, propionic acid, methacrylic acid, benzoic acid, lactic acid, crotonic acid, etc.

Therefore, according to a third embodiment of the invention the solution for the surface treatment of glass contains hydrofluoric acid, ammonium fluoride and water and that it is characterized by that it contains at least one hydrophilic carboxylic acid selected from the following first group: acrylic acid, propionic acid, methacrylic acid, benzoic acid, lactic acid, and it contains at least one hydrophilic carboxylic acid selected from the following second group: oxalic acid, succinic acid, adipic acid, maleic acid, fumaric acid, malic acid, tartaric acid, citric acid.

The composition range of the solution of the surface treatment of glass of the invention is suitable; hydrofluoric acid (HF): 5 to 40% by weight, ammonium fluoride (NH F): 5 to 40% by weight, the hydrophilic carboxylic acid: 10 to 60% by weight, and water (H₂O): 10 to 50% by weight.

With regard to the surface treating method of the quartz glass, the invention is characterized by treating the surface of a the quartz glass using the solution for surface treating glass as described above. Practically, it is a method of immersing a quartz glass product in a solution according to the invention and treating it , e.g. in a stationary state.

The solution of the surface treatment of glass of the invention and the treating method of the invention are effective for a chemical solution treatment of not only quartz glass products but also all glass products. Examples

Then, the invention is more practically explained by referring to the examples but these examples are illustratively shown and, as a matter of course, shall not be limitedly construed.

Examples 1 to 13

By mixing hydrofluoric acid, ammonium fluoride, pure water, and each hydrophilic carboxylic acid shown in Table 1 , each of the solutions for the surface treatment of glass was obtained. The composition of the treating solution is; hydrofluoric acid: 25% by weight, ammonium fluoride: 25% by weight, pure water: 25% by weight, and the hydrophilic carboxylic acid: 25% by weight. In a polyvinyl chloride-made constant- temperature bath of 300 x 300 x 100 mm was filled with 7000 ml of the above- described treating solution and the temperature was established to 20°C. In the treating solution was immersed a quarts glass plate of the product size of 100 x 100 x 5 tmm made of a transparent quartz glass HERALUX-LA (trade name, manufactured by Shin-Etsu Quartz Products Co., Ltd.) for semiconductor Industry for 2 hours in a stationary state. After immersion, the plate was washed with pure water and the surface roughness of the quartz glass surface was measured. Also the observation of the quartz glass surface was also carried out. In the treatment of the quartz glass surface, about the first treatment (the 1st times) after the preparation of the solution of the surface treatment of glass and 2nd treatment of the 30th time, in each case, the surface roughness and the concentration of the acid added were measured as described below, and the surface observation was also carried out. The results of the evaluations were shown in Table 1 about the 1st time and in Table 2 about the 30th time.

Surface roughness: Measurements of Ra and Rmax

Using a surface roughness meter [Surcom 300B (manufactured by Tokyo Seiki K.K.), the surface roughness of the quartz glass after treatment was measured. The measurement was carried out 3 times on the quartz glass surface. The mean values thereof are shown in Table 1 and Table 2. Measurement of the concentration of the added hydrophilic carboxylic acid The concentration was measured by an ion-exchange chromatography [DX-300 (manufactured by Dionex Corporation)]. The acid concentration after the 1st treatment was shown in Table 1 and the acid concentration after the treatment of 30th time was shown in Table 2.

Surface observation

The surface was visually observed, and the observation results of the surface state after the treatment of the 1st time were shown in Table 1 and the results after the surface treatments of 30th time were shown in Table 2.

Comparative Example 1

By following the same procedure as Example 1 except that acetic acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 2

By following the same procedure as Example 1 except that formic acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 3

By following the same procedure as Example 1 except that phthalic acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 4

By following the same procedure as Example 1 except that palmitic acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2. Comparative Example 5

By following the same procedure as Example 1 except that stearic acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 6

By following the same procedure as Example 1 except that oleic acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 7

By following the same procedure as Example 1 except that nitric acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 8

By following the same procedure as Example 1 except that phosphoric acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 9

By following the same procedure as Example 1 except that sulfuric acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 10

By following the same procedure as Example 1 except that hydrochloric acid was used in place of propionic acid, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2. Comparative Example 11

By following the same procedure as Example 1 except that propionic acid was not added, the treatment of the quartz glass was carried out and the results were shown in Table 1 and Table 2.

Comparative Example 12

For a quarts glass plate of the product size of 100 x 100 x 5 tmm made of HERAJUX- LA (trade name, manufactured by Shin-Etsu Quartz Products Co., Ltd.), which was not subjected to the treatment of the formation of unevenness on the surface thereof, the surface evaluations as in Example 1 were carried out and the results were shown in Table 1 (the 1st time) and in Table 2 (the 30th time).

Table 1

Table 2

As is clear from the results of Table 1 and Table 2, it can be seen that when the surface treatment of the quartz glass is carried out using each of the processing solutions added with each of the hydrophilic carboxylic acids in Examples 1 to 13, unevenness having no nonuniformity or less nonuniformity, practically the uneven surface of 0.1 μm < Ra < 2.0 μm and 1 μm < Rmax <20 μm, is formed in the 1st time and the 30th time. Also, it can be confirmed that after the treatments of 30th time, the concentration of the acid added is not largely lowered and the treatments of many times can be carried out without need of specific concentration management.

When the surface treatment of the quartz glass was carried out using the treating solution added with acetic acid in Comparative Example 1 , in the treatment of the 1st time, the uneven surface having no or less nonuniformity, practically having the surface roughness of 0.1 μm < Ra < 2.0 μm and 1 μm < Rmax < 20 μm as the cases of Examples 1 to 13, was formed, but in the treatment of the 30th time, the concentration of acetic acid was reduced to 11 %, the transparent portion was markedly observed on the treated surface, as the uneven surface, the result was an insufficient finish, and the surface roughness became Ra > 2 μm and Rmax > 20 μm.

When the surface treatment of the quartz glass was carried out using the treating solution added with formic acid in Comparative Example 2, in the treatment of the 1st time, whiteness had nonuniformity and in the treatment of the 30th time, the transparent portion was markedly observed in the surface, the uneven surface was insufficiently finished, and the surface roughness became Ra > 2 μm and Rmax > 20 μm.

When the surface treatment of the quartz glass was carried out using each of the treating solutions each added with each of the hydrophilic carboxylic acids in Comparative Examples 3 to 6, even in the treatment of the 1st time and the treatment of the 30th time, transparent portions were markedly observed on the surfaces, the uneven surface was all insufficient finish, and also the surface roughnesses were Ra > 2 μm and Rmax > 20 μm in both the 1st time and the 30th time. When the surface treatment of the quartz glass was carried out using each of the treating solutions each added with each of the hydrophilic carboxylic acids in Comparative Examples 7 to 10, even in the treatment of the 1st time and the treatment of the 30th time, whiteness has nonuniformity, the uneven surface was all insufficient finish, and also the surface roughnesses were Ra > 2 μm and Rmax > 20 μm in both the 1st time and the 30th time.

When the treatment was carried out with the mixed solution of hydrogen fluoride, ammonium fluoride, and water without using a carboxylic acid in Comparative Example 11 , even in the treatment of the 1st time and the treatment of the 30th time, whiteness has nonuniformity, the uneven surface was all insufficient finish, and also the surface roughnesses were Ra > 2 μm and Rmax > 20 μm in both the 1st time and the 30th time.

In Comparative Example 12 for the quarts glass without subjected to the surface treatment, the surface thereof was transparent and was not uneven, and the also the surface roughnesses were Ra < 0.1 μm and Rmax < 1 μm.

Effect of the Invention

As mentioned above, according to the solution of the surface treatment of glass of the invention, the large effects that uniform unevenness having no nonuniformity can be formed on the surface of a glass such as a quartz glass, the solution does not give an irritative odor, the concentration management of the solution is easy, and the solution is easily handled even in winter, are attained.

Also, in the method of the surface treatment of glass of the invention, by using the solution of the surface treatment of glass of the invention, the effects that uniform unevenness having no nonuniformity can be effectively formed on the surface of, for example, a quartz glass can be obtained.

Claims

1. A solution for treating a surface of glass, comprising hydrofluoric acid, ammonium fluoride and water, characterized in that it contains at least a hydrophilic carboxylic acid having from 3 to 7 carbon atoms.

2. A solution according to Claim 1 , characterized in that the hydrophilic carboxylic acid is acrylic acid, propionic acid, methacrylic acid, benzoic acid, lactic acid, and/or crotonic acid.

3. A solution for treating a surface of a glass, comprising hydrofluoric acid, ammonium fluoride and water, characterized in that it contains at last a hydrophilic carboxylic acid having 2 or 3 carboxylic groups.

4. A solution according to Claim 3, characterized in that the hydrophilic carboxylic acid is a oxalic acid, succinic acid, adipic acid, maleic acid, fumaric acid, malic acid, tartaric acid, citric acid, malonic acid and/or citraconic acid.

5. A solution according to Claims 1 or 2 and Claims 3 or 4, characterized in that it contains at least one hydrophilic carboxylic acid selected from the following first group: acrylic acid, propionic acid, methacrylic acid, benzoic acid, lactic acid, and it contains at least one hydrophilic carboxylic acid selected from the following second group: oxalic acid, succinic acid, adipic acid, maleic acid, fumaric acid, malic acid, tartaric acid, citric acid.

6. A solution according to Claims 1 to 5, characterized in that it contains the hydrophilic carboxylic acid in the range between 10 to 60% by weight.

7. A method for treating a surface of quartz glass, characterized by using the solution as claimed in one of Claims 1 to 6.