JP4006540B2 - Quartz glass foam structure and manufacturing method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a quartz glass foam structure and a method for producing the same. More specifically, the present invention relates to a quartz glass foam structure having a transparent and uniform hard layer with no open bubbles on the surface, high structural mechanical strength and no generation of particles, and a method for producing the same.
[0002]
[Prior art]
Conventionally, quartz glass foam has been widely used for a heat insulating and heat insulating structural material of a furnace, a base of a light reflecting mirror, and the like because of its light weight, excellent heat insulation and chemical resistance, and low thermal expansion. However, the quartz glass foam is inferior in structural mechanical strength compared to quartz glass, especially the foam surface is very fragile, and when used as a storage insulation material in a heat treatment furnace for semiconductor wafers, it is ground from the foam surface. There was a problem that particles generated at times dropped out and adhered to the semiconductor wafer. In addition, there are problems such as contamination of the semiconductor wafer due to adhesion of grinding fluid or acid during acid cleaning to the open foam (opening foam) that opens during the grinding of the foam, which diffuses during heat treatment of the semiconductor wafer. there were. For this reason, the foam surface was burnt and finished with a burner or the like, and a structure with no open bubbles on the surface was proposed. However, if the foam surface is burned with a burner, a uniform hard layer of 0.5 mm or more can be formed. There were drawbacks that were difficult and inferior in structural mechanical strength. Therefore, a silica heat insulating heat insulating material in which a porous silica body is put in a heat-resistant container, and a plate-like silica glass sintered body and / or hard silica glass is brought into contact with the top, bottom, left and right, and is heated and integrated at 1400 to 1800 ° C. This was proposed in Japanese Patent Publication No. 6-94380. However, the silica heat insulating heat insulating material described in the above publication has a drawback that its manufacturing process is complicated, expensive and expensive.
[0003]
[Problems to be solved by the invention]
In view of the current situation, the present inventors have conducted intensive research, and as a result, the quartz glass foam is pressed against a heat-resistant member at a specific temperature with a specific pressure, so that the surface has no open bubbles and is transparent and has a uniform thickness. The present invention has been completed by finding that a quartz glass foamed structure having a hard layer having a high structural mechanical strength and no generation of particles can be obtained. That is,
[0004]
The present invention is a quartz that is lightweight, excellent in heat insulation and chemical resistance, has a transparent and uniform hard layer with no open bubbles on its surface, has high structural mechanical strength, and does not generate particles. An object is to provide a glass foam structure.
[0005]
Moreover, an object of this invention is to provide the manufacturing method of the said quartz glass foaming structure.
[0006]
[Means for Solving the Problems]
The present invention that achieves the above object provides a quartz glass foam structure composed of a transparent hard layer having no open bubbles and a quartz glass foam layer, wherein the hard layer has a uniform thickness of 0.5 to 3 mm. A quartz glass foam structure characterized by comprising a glass layer integrally formed on the surface of the foam layer and a method for producing the same.
[0007]
The quartz glass foam structure of the present invention is a structure in which a hard layer having a uniform thickness of 0.5 to 3 mm is laminated on a foam layer. Therefore, it is lightweight, has excellent heat insulation and chemical resistance, has high structural mechanical strength, does not generate particles due to grinding processing, and has no problem of contamination due to residual processing liquid because there are no open bubbles on the surface. A foam structure that does not occur. The “hard layer” refers to a layer made of transparent glass having no open bubbles. In particular, when the quartz glass foam structure of the present invention is used as a semiconductor member, the metal impurity content is preferably 100 ppm or less and the OH group concentration is 300 ppm or less. Examples of the metal impurities include alkali metal elements such as Na and K, alkaline earth elements such as Ca and Al, and transition metal elements such as Ce, Ni, Co, Cr, Fe, and Cu. If the content of exceeds 100 ppm, contamination by metal impurities occurs during the processing of the semiconductor wafer. On the other hand, when the OH group concentration exceeds 300 ppm, thermal deformation occurs at a temperature of 1000 ° C. or higher, which is the heat treatment temperature of the semiconductor.
[0008]
In the quartz glass foam structure of the present invention, the quartz glass foam is pressed against a heat resistant member at a pressure of 0.5 to 100 g / cm ² and heated to a temperature of 1300 to 1900 ° C. to the surface of the quartz glass foam. It is manufactured by forming a hard layer made of transparent glass having a uniform thickness of 0.5 to 3 mm and having no open bubbles. The quartz glass foam structure obtained by the above manufacturing method is shown in FIG. 1A, and the raw material quartz glass foam is shown in FIG. 1B. In FIG. 1, 1 is a hard layer, 2 is a foam, 3 is an open bubble. 4 indicates bubbles. The quartz glass foam is preferably a quartz glass foam having an apparent density of 0.3 to 1.4 g / cm ³ , and its production method is not particularly limited, but preferably amorphous silica is used in an ammonia atmosphere. A quartz glass foam obtained by heating to 800 to 1300 ° C. and heating and foaming at 1400 to 1900 ° C., foaming with an apparent density of 1 to 1.4 g / cm ³ while maintaining the atmosphere at atmospheric pressure during the heating and foaming. For example, a quartz glass foam obtained by a production method for forming a body and gradually increasing the bubble diameter under reduced pressure is preferable. In particular, the quartz glass foam obtained by the latter production method is preferable because the closed cells are uniformly dispersed and the bubble diameter is also uniform. If the apparent density is less than 0.3 g / cm ³ , the hard layer varies and the mechanical strength is low, which is not preferable. If the apparent density exceeds 1.4 g / cm ³ , the heat insulation and heat insulation properties deteriorate, and heat insulation or infrared rays Less effective as a scattering material.
[0009]
Examples of the heat-resistant member include high-purity graphite or graphite containers, plates or sheets. The heat-resistant member preferably has a purity of 10 ppm or less in total ash. In the manufacturing method of the present invention, as described above, the quartz glass foam is pressed against the heat-resistant member, and the pressing pressure is selected in the range of 0.5 to 100 g / cm ² . If the pressure is less than 0.5 g / cm ^2, it is difficult to form a thick and uniform hard layer. If the pressure exceeds 100 g / cm ² , the production apparatus is expensive and the pressing effect does not change. As the atmosphere at the time of pressurization, an inert atmosphere at atmospheric pressure or reduced pressure is adopted. The surface accuracy in the production method of the present invention depends on the surface state (surface roughness) of the heat-resistant member in contact with the foam surface. When the surface accuracy of the hard layer surface is required, the surface roughness of the heat-resistant member in contact with the foam may be reduced. Preferably, the center line average roughness (R _a ) is 25 μm or less as an example.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in detail based on specific examples, but the present invention is not limited thereto.
[0011]
【Example】
Example 1
An amorphous silica base material was produced on the target by a CVD method in which silicon tetrachloride was hydrolyzed in a hydrogen diffused flame. The amorphous silica base material is extracted from the target and pulverized to form flaky quartz glass powder, which is put in a quartz glass container (inner diameter 300 mm × depth 300 mm), and ammonia gas is nitrogen gas 0.5 Nm ³ / h. Was heated and held at 850 ° C. for 5 hours in an electric furnace while flowing 0.2 Nm ³ / h as a carrier gas. Then, the ammoniated quartz glass powder is taken out from the quartz glass container, transferred to a graphite container having an inner diameter of 300 mm and a depth of 300 mm, and heated and maintained at 1750 ° C. for 60 minutes in an atmospheric pressure atmosphere in which nitrogen is replaced with soot. A quartz glass foam was produced. The obtained quartz glass foam was ground to obtain a cylindrical quartz glass foam having an opening bubble diameter of 200 mm, a height of 100 mm, and an apparent density of 1.0 g / cm ³ as shown in FIG. It is transferred to a graphite container with an inner diameter of 200 mm and a height of 150 mm, a graphite lid is placed on the foam, and a pressure of 10 g / cm ² is applied on top of it and nitrogen is replaced with sulfur. The quartz glass foam structure shown in FIG. 1 (a) was produced by heating and holding at 1750 ° C. for 30 minutes in the atmospheric pressure atmosphere. When the cross section of the hard layer (1) of the foam structure of FIG. 1 (a) was observed, it was a transparent glass with no open bubbles and a uniform glass layer with a thickness of 2 mm. When this quartz glass foam structure was washed with 10% hydrofluoric acid for 30 minutes and then washed with water, the hydrofluoric acid washing solution could be easily removed. Further, even if the surface of the cylindrical quartz glass foam structure was lightly touched, no particles were dropped.
[0012]
Example 2
A cylindrical quartz glass foam having an apparent density of 0.4 g / cm ³ was produced by the same production method as in Example 1. The cylindrical quartz glass foam is transferred to a graphite container having an inner diameter of 200 mm and a height of 150 mm, a graphite lid is placed on the foam, and a weight of 10 g / cm ² is applied on the top of the graphite lid. And kept heated at 1700 ° C. under vacuum for 30 minutes. When the cross section of the hard layer of the obtained quartz glass foam structure was observed, it was a transparent glass with no open bubbles and a uniform glass layer with a thickness of 0.8 mm. The quartz glass foam structure was washed with 10% hydrofluoric acid for 30 minutes and then washed with water. As a result, the hydrofluoric acid washing solution could be easily removed. Further, even if the surface of the cylindrical quartz glass foam structure was touched lightly, no particles dropped out.
[0013]
Comparative Example 1
A cylindrical quartz glass foam having an apparent density of 0.4 g / cm ³ was produced by the same production method as in Example 1. The surface of the cylindrical quartz glass foam was baked with a burner to obtain a quartz glass foam structure shown in FIG. 2 having a hard layer formed on the surface. When the cross section of the quartz glass foam structure was cut and the hard layer was observed, there were variations in the thickness of the hard layer and there were portions where the hard layer was not formed. The quartz glass foam structure was washed with 10% hydrofluoric acid for 30 minutes and then washed with water. As a result, removal of the hydrofluoric acid cleaning solution was not easy, and particles dropped off easily.
[0014]
【The invention's effect】
The quartz glass foam structure of the present invention has a uniform thickness on the surface of the foam, no open bubbles, and a transparent hard layer is formed, so that it has excellent heat shielding properties and infrared scattering properties. In addition, it has high mechanical strength. In addition, it is useful as a semiconductor processing member because it can be easily purified. The quartz glass foam structure can be easily manufactured by pressing the quartz glass foam against a heat resistant member at a specific temperature under pressure, and has a high industrial value.
[Brief description of the drawings]
FIG. 1 shows a quartz glass foam structure of the present invention. (A) is sectional drawing of the quartz glass foam structure which has a hard layer, (b) shows sectional drawing of the quartz glass foam body which has the opening bubble after a grinding process.
FIG. 2 shows a cross-sectional view of a foamed quartz glass structure baked with a burner.
[Explanation of symbols]
1: Hard layer 2: Foam 3: Opening foam 4: Air bubble t: Hard layer thickness

Claims (3)

A transparent hard material characterized by pressing the surface of a quartz glass foam to a high-purity carbon or graphite heat-resistant member at a pressure of 0.5 to 100 g / cm ² and heating to a temperature of 1300 to 1900 ° C. A method for producing a quartz glass foam structure comprising a layer and a quartz glass foam layer . Heat resistance member container, a plate, or a manufacturing method of the formed silica glass foam structure with a transparent hard layer and the quartz glass foam layer of claim 1, wherein either the sheet. Transparent hard layer and composed of a quartz glass foam layer quartz glass foam structure of claim 1, wherein the apparent density of the quartz glass foam, characterized in that at the 0.3~1.4g / cm ³ Manufacturing method.

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