JP3821501B2 - Method for producing quartz glass article - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for welding a quartz glass body, and more particularly to a method for welding a thick quartz glass material.
[0002]
[Prior art]
Conventionally, in the semiconductor manufacturing industry, it has been used in various jigs or containers made of quartz glass, and also in various facilities in order to satisfy chemical stability and heat elution in order to avoid elution of impurities. Such a quartz glass material has a softening temperature as high as 1600 ° C. or higher, and is supplied as a tube or a flat plate from the supplier. In the case of forming a square container by welding five flat quartz glass plates that form the bottom surface and four side surfaces from the flat plate to form a rectangular container, the welding marks of the container are removed with a grinder or the like. However, it is extremely difficult to completely remove the welding marks located at the corners of the corners.
[0003]
In particular, when welding thick plates, it is extremely difficult to weld to the inside by welding. For this reason, conventionally, air bubbles remain inside due to insufficient welding, or welding marks etc. remain due to excessive welding. In such a state, if it is used as a heat treatment furnace, for example, the remaining portion may have insufficient strength, or when used as a treatment tank for introducing a chemical solution or a cleaning solution, for example, in bubbling cleaning etc. When fine dust such as particles transferred to the cleaning liquid enters the welding trace, even if the tank is cleaned with hydrofluoric acid, it cannot be easily removed, and it will reattach to the wafer when reused. In some cases, effective cleaning cannot be performed due to product defects.
[0004]
In order to eliminate such drawbacks, the present applicant has developed various techniques.
One of them is a quartz glass square tank formed by welding joint portions of a plurality of quartz glass members as disclosed in JP-A-2-102141, and at least an arc-shaped member formed by dividing a cylindrical tube vertically, A part of the plate-shaped member and a flat plate-shaped member formed with a width smaller than the width of each wall surface of the square tank, the selected members are combined to form the square tank, and each of these There has been proposed a quartz glass square tank in which a joint portion between members is provided at a position deviated from at least a corner portion where a ridge line and a plurality of ridge lines gather.
[0005]
According to such a technique, since the welding position is not located at the ridge line and the corner corner, the welding of the corner corner and the ridge line can be avoided, but in the present invention, the basis of removing the welding and grinder welding traces is also provided. There is a configuration, so it is difficult to weld thick plates.
In particular, even in the above-described technique, thermal strain occurs due to local heating, and it is necessary to remove the thermal strain by heating each time one surface is welded. In particular, if the thickness exceeds 10 mm, the thermal strain becomes excessive, and the quartz glass is broken during or immediately after welding. In particular, it is impossible to weld a thick quartz glass plate of 15 mm or more.
[0006]
As a method for producing such a thick quartz glass product, for example, in Japanese Patent Application Laid-Open No. 58-88129, a quartz glass raw material and a core are used, and a quartz glass is formed in the gap between the inner wall surface of the rotary melting furnace and the core. A technique for filling the powder and pulling out the core while rotating the furnace and then heating and melting the raw material powder with an arc flame or a gas flame to form the square tank has been proposed. Since the raw material powder is directly melted, it is difficult to form a quartz glass article having a corner like a square tank and the raw material powder is in direct contact with the furnace wall, so impurities are easily mixed. Thus, it is not suitable for a manufacturing process for processing a large number of wafers having a large diameter and high integration.
[0007]
Japanese Patent Application Laid-Open No. 62-241840 discloses a cylindrical mold having a curved bottom as a method for producing a large quartz container applied as a crucible, chamber, or bell jar used for semiconductor single crystal production. Inside, a quartz glass disc and a quartz glass cylinder having the same outer diameter as the disc are sequentially set in contact with each other so that their outer edges form the same circumference, and then arc melting A technique is disclosed in which a mold body is heated while being heated by means, whereby both members are heat-sealed to each other.
[0008]
In such a technique, in order to take a configuration in which the tube body or the plate material is brought into contact with each other in a state where the tube body or the plate material are in contact with each other in a mold having sufficient heat resistance, such as graphite and ceramics, The possibility of impurities being mixed can be completely eliminated by performing surface grinding after heat fusion.
[0009]
[Problems to be solved by the invention]
However, since the above-described technique uses a heating means called arc melting and a rotating mold, it is preferable for forming a cylindrical article, but for forming a rectangular container as an object of the present invention, as shown in FIG. Further, since the distance 50A between the wall surface of each side of the quartz glass plate 51 and the heating source 52 is closer than the distance 50B to the welded portion (diagonal corner), when the welded portion is sufficiently heated, each side 51 is deformed by heating. Will occur.
[0010]
In view of the drawbacks of the prior art, the present invention has a precise outer shape without causing deformation on each side even when manufacturing a thick rectangular quartz glass article such as a rectangular container or a rectangular cylinder. It aims at providing the manufacturing method of a glass article.
Another object of the present invention is to prevent the generation of bubbles and cracks when forming a quartz glass article having a predetermined shape while heat-sealing plate materials, and also to improve the mechanical strength and appearance. It is to provide a method for producing a preferable quartz glass article.
Another object of the present invention is to provide a method for producing a quartz glass article of high quality without the occurrence of cracks and bubbles even when the tube or plate to be fused is thick.
Further, another object of the present invention is that the entire contact surface to be thermally welded can be completed by a single heat-sealing process, in other words, the work process related to welding can be greatly shortened. It is an object to provide a method for producing a quartz glass article.
[0011]
[Means for Solving the Problems]
The present invention provides a first heat-resistant mold having an inner wall side shape corresponding to the outer shape of the target quartz glass article, and an outer wall side corresponding to the inner shape of the target quartz glass article. A second heat-resistant mold having a shape;
A flat plate member such as a disk, a rectangular plate or the like having a shape to be a part of the quartz glass article, or an element glass body such as a tube, an arc, or a rod,
After setting the element glass body gas escape path is formed in an appropriate position on the heat-sealing surface thermally fusing the elements glass bodies in the two mold elements, placing a set body in which the set in a furnace And forming a quartz glass article of a predetermined shape by heating and heat-sealing the element glass bodies while including a heating step of heating while maintaining the furnace space under a substantially vacuum. Features.
Specifically, a set body in which the element glass body is set between two mold bodies is put into a vacuum furnace, and after evacuating the vacuum furnace, the furnace temperature is increased to 1600 to 1850 ° C. A first step of maintaining the furnace temperature for a fixed time;
After maintaining the furnace temperature under a vacuum or negative pressure for a certain period of time, after nitrogen and other inert gases are sealed in the furnace until the pressure reaches approximately atmospheric pressure, the furnace temperature is maintained again at approximately atmospheric pressure for a predetermined time. It is characterized by including these processes.
That is, when the furnace temperature is set to 1850 ° C. or higher, the element glass body is softened and deformed. Also, at 1600 ° C. or lower, complete heat fusion becomes difficult.
In order to Mataawa preventing the warming rate at 1 700 ° C. or more that put in the first step, 9 ° C. / min or less, preferably 1 to 6 ° C. / min, more preferably 2 to 5 ° C. / min It is good to set to.
In this case, for example, the gas escape path may be formed at the fusion interface between the element glass bodies extending in the substantially horizontal direction, such as a fusion interface between the bottom surface and the side plates or between the upper and lower plates.
The gas escape path may be an engraved groove, preferably a mesh-shaped groove, extending to the open surface of the glass body along the heat fusion interface.
In addition, when there is a fusion interface between element glass bodies extending in a substantially vertical direction, such as a fusion interface between side plates, the heat resistant mass of the same material as the mold body from the upper surface of the element glass body. It is preferable to heat-bond the element glass bodies to each other by heating the set space in a state where the body and other weights are applied and the weight is applied.
[Action]
In the present invention, in order to perform only the joining of the element glass bodies without deforming the element glass bodies themselves as in the prior art, the element glass bodies are sandwiched between the outer mold and the inner mold, and heat molding is performed. The first feature is to do.
The second feature is that a set body in which the element glass bodies are set in both mold bodies is placed in a furnace, and includes a heating step of heating while maintaining the space in the furnace substantially under vacuum. It is in heating.
Thereby, bubbles are prevented from appearing as bubbles on the heat-sealing surface, and a clean heat-sealing surface can be formed.
In this case, the foam mixing is further prevented by performing heat fusion in a state where a gas escape path is formed on the heat fusion interface.
In particular, the bubbles are less likely to occur on the welding surfaces extending in the vertical direction like the side plates, but the contact surface between the plate materials extends in the horizontal direction, for example, heat fusion between the side plates and the bottom plate. Bubbles are easily manifested as bubbles on the contact surface, and more bubbles are generated as the plate becomes thicker. However, the generation of bubbles can be completely prevented by the vacuum heating and formation of the gas escape path.
[0012]
In addition, when the furnace temperature is maintained for a certain period of time in a vacuum state until the thermal fusion bonding is completed in a vacuum atmosphere, the element glass body in a softened state may be deformed.
Therefore, the furnace temperature maintenance time until the heat fusion bonding is completed is divided into two, the furnace temperature is maintained under vacuum or negative pressure for a predetermined time in the first half, and then nitrogen and other inert gases are brought to atmospheric pressure in the second half. Then, the furnace temperature is again maintained at a substantially atmospheric pressure for a predetermined time.
[0013]
Furthermore, the present invention provides a thermal fusion of the element glass body, such as a fusion interface between the left and right side plates, so that the upper end of the tube or the plate material to be fused is not cracked. In the case where there is a vertical fusion interface extending in a substantially vertical direction, a weight is applied from the upper surface of the adjacent element glass body forming the vertical fusion interface, and the weight is applied. Perform heat fusion.
As a result, even when the tube or plate material to be fused is thick, a predetermined pressing force toward the fusion interface is required during the thermal fusion. In this case, when a load is applied from the upper surface of the element glass body in a slightly softened state, a predetermined pressure contact force is generated also on the upper joint surface due to the bulging output toward the slight side surface, and the upper end crack is cracked. Is prevented from occurring.
In this case, the weight biasing means is preferably a heat-resistant mass body made of the same material as the mold, and the load is 1 to 10 kgf / cm ² , 3 to 6 kgf / cm ² , preferably about 5 kgf / cm ^2. It is good to be.
[0014]
Embodiment
Hereinafter, embodiments of the present invention will be exemplarily described in detail with reference to the drawings.
However, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.
[0015]
FIG. 4 shows an overall schematic view of a molding apparatus for carrying out the present invention, in which 1 is a vacuum furnace to which a vacuum pump 2 is connected, surrounding a heat insulating material 3 inside the furnace wall, Nitrogen gas or other inert gas can be introduced into the internal space surrounded by the heat insulating material 3 from the gas inlet 4.
In the internal space, a pedestal 5 having a mold mounting base 5a fixed on the upper surface is erected, and the mold body 10 in which the element glass bodies 21 and 22 are accommodated in the inner wall is placed on the mold mounting base 5a. In addition to being configured to be able to be placed, a graphite heater 6 is surrounded around the mold body 10 and the pedestal 5 so that the element glass bodies 21 and 22 in the mold body 10 can be heated uniformly.
[0016]
As shown in FIG. 2 (A), the mold comprises a rectangular graphite outer frame 12 and an inner frame 11 and a graphite upper plate 13 and a bottom plate 14 that function as a weighted urging member.
Next, the rectangular quartz glass article 20 was molded using the molding apparatus 1 in the following manner, for example, using the element glass bodies 21 and 22 shown in FIG.
First, as shown in FIG. 1A, the element glass bodies 21 and 22 made of four side plates are made of quartz glass for forming, for example, a rectangular hollow body quartz glass article 20 having an upper and lower opening. The element glass bodies 21 and 22 are shown.
[0017]
Then, as shown in FIGS. 1B and 2B, the pair of side plates (element glass body 21) forming the long side has a shape of, for example, L × H × t: 200 × 140 × 8 (mm). In addition, the pair of side plates (element glass body 22) forming the short sides are set on the graphite bottom plate 14 with their shapes set to, for example, W × H × t: 140 × 140 × 8 (mm). The said element glass bodies 21 and 22 are set along the space | gap between the inner wall surface of the provided graphite outer frame 12, and the outer wall surface of the graphite inner frame 11. FIG.
[0018]
That is, the graphite outer frame 12 has an inner shape whose inner wall substantially matches the outer dimension of the element glass bodies 21 and 22 assembled, and the graphite inner frame 11 has the inner walls assembled the element glass bodies 21 and 22. The element glass bodies 21, 22 have an outer shape that substantially matches the inner dimension, and extend along a gap between the inner wall surface of the graphite outer frame 12 and the outer wall surface of the graphite inner frame 11 that are erected on the graphite bottom plate 14. Set as shown in FIG.
[0019]
At this time, after finishing the bonded surfaces of the element glass bodies 21 and 22 to the finish-finished surface or the mirror-polished surface, respectively, as shown in FIGS. 1 (B) and 2 (B), the respective element glass bodies 21, 22 is set directly along the gap between the inner wall surface of the graphite outer frame 12 and the outer wall surface of the graphite inner frame 11 erected on the graphite bottom plate 14, and the upper plate 13 made of graphite is placed on the upper surface. .
The upper plate 13 determines the mass of the upper plate 13 so that a weighted pressure of about 5 kgf / cm ² is applied to the entire upper surfaces of the element glass bodies 21 and 22.
[0020]
Next, after the outer frame 12 and the like pressed by the upper plate 13 are set on the mold setting table 5a in the vacuum furnace 1 as shown in FIG. 4 and evacuated, the heater 6 raises the temperature by 10 ° C./min. Heating is performed at a rate, and when the temperature reaches 1550 ° C., the rate of temperature rise is reduced to 3 ° C./min, for example, and after heating to a temperature of about 1800 ° C., 1800 ° C. is maintained for a certain time (30 minutes).
[0021]
Next, nitrogen is sealed in the furnace until atmospheric pressure is reached, and then maintained at 1800 ° C. for a predetermined time (30 minutes).
Then, after gradually cooling to 900 ° C., the heater 6 is turned off, and then naturally cooled to room temperature. Then, the inside of the furnace is returned to atmospheric pressure, and the quartz glass article shown in FIG. When 20 was taken out (premise technology) , as shown in FIG. 6B, there was no crack 23 at the upper end portion of the fusion interface 20a, and no bubble 24 was generated.
Next, as shown in FIG. 6A, when the graphite-type upper plate 13 is not placed and the manufacturing procedure similar to that of the base technology is performed, cracks 23 are formed at positions corresponding to the upper ends of the side plates 21 and 22. The quartz glass article which generate | occur | produced has been manufactured (comparative example 1) .
[0022]
Next, as shown in FIG. 3A, a method for producing a vertically long quartz glass article in which the side plates 21A and 22A and the side plates 21B and 22B shown in the base technology are vertically stacked will be described.
[0023]
First, as shown in FIG. 3A, mesh-like (grid-like) grooves 25 are formed vertically and horizontally on the fusion interface 20a of the side plates 21B and 22B located on the lower side as shown in FIG. When the quartz glass article was manufactured using the side plates 21 and 22 put in the same manufacturing procedure as in the base technology (Example 1 ), no bubbles 24 were generated as shown in FIG. It was confirmed that there was no deformation in both dimensions and dimensions.
In this case, as shown in FIG. 3B, grooves 25 may be provided on the bottom surfaces of the upper side plates 21A and 22A.
[0024]
Next, when the quartz glass article was manufactured by the same procedure as described above without providing the groove 25 (Comparative Example 2 ), generation of bubbles 24 was observed as shown in FIG.
[0025]
Next, the lower side plates 21B and 22B with mesh-like (grid-like) grooves 25 and the upper side plates 21A and 22A were used, and the upper plate 13 was not placed, and the manufacturing procedure was the same as that of the base technology . However, a quartz glass article having a crack 23 as shown in FIG. 6 (A) at the upper end of the upper side plates 21A and 22A has been manufactured.
[0026]
【The invention's effect】
As described above, according to the present invention, even when manufacturing a thick rectangular quartz glass article such as a rectangular container or a rectangular cylinder, each side is not deformed by heating, and the quartz glass has a precise outer shape. You can get the goods.
Further, according to the present invention, when forming a quartz glass article having a predetermined shape while heat-sealing plate materials, the generation of the bubbles and the generation of cracks are prevented, and the mechanical strength and the appearance are preferable. Quartz glass articles can be obtained.
In particular, the present invention can produce a high-quality quartz glass article without the occurrence of cracks and bubbles even when the tube or plate to be fused is thick or when producing a square quartz glass article.
Furthermore, according to the present invention, a manufacturing method in which the entire contact surface to be heat-welded can be completed by the first-floor heat-sealing process, in other words, manufacturing a quartz glass article that can greatly shorten the work process related to welding. Can do.
It has various effects such as.
[Brief description of the drawings]
FIG. 1 shows a manufacturing procedure which is a prerequisite technology of the present invention, (A) is a perspective view of an element glass body, (B) is a cut front view showing a state in which an element glass body and an upper plate are set in a mold body, (C) is a perspective view showing a quartz glass article manufactured according to the present invention.
2A and 2B are supplementary drawings of FIG. 1, in which FIG. 1A is a perspective view of a mold frame, and FIG. 2B is a plan view showing a state in which an element glass body and an upper plate are set in the mold body.
FIGS. 3A and 3B show a manufacturing procedure in the case where the element glass bodies according to the embodiment of the present invention are also welded up and down, wherein FIG. 3A is a perspective view of the upper and lower element glass bodies, and FIG. FIG. 1C is a perspective view showing a quartz glass article manufactured according to the present invention.
FIG. 4 shows an overall schematic view of a molding apparatus for carrying out the present invention.
FIG. 5 illustrates the disadvantages of prior art welding methods.
FIG. 6 is an operation diagram showing a welding state when an upper plate is weighted (B) and not weighted (A).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum furnace 10 Heat-resistant type | mold body 11 Graphite inner frame 12 Graphite outer frame 13 Weighting means (upper plate)
20 Quartz glass article 20a Fusion interface 21, 22 Element glass body (side plate)
25 Gas escape route (groove)

Claims (4)

A first heat-resistant mold having an inner wall side shape corresponding to the outer shape of the target quartz glass article, and an outer wall side shape corresponding to the inner shape of the target quartz glass article. A second heat resistant mold,
A flat plate member such as a circular plate, a rectangular plate or the like having a shape to be a part of the quartz glass article, or an element glass body such as a tube, an arc, or a rod,
After setting the element glass body gas escape path is formed in an appropriate position on the heat-sealing surface thermally fusing the elements glass bodies in the two mold elements, placing a set body in which the set in a furnace And forming a quartz glass article having a predetermined shape by heating and heat-sealing the element glass bodies while including a heating step in which the furnace space is heated under a substantially vacuum condition. A method for producing a quartz glass article. 2. The method for producing a quartz glass article according to claim 1, wherein the gas escape passage is formed at a fusion interface between the element glass bodies extending in a substantially horizontal direction. A set body in which the element glass body is set between two mold bodies is put into a vacuum furnace. After the vacuum furnace is evacuated, the furnace temperature is increased to 1600 to 1850 ° C. and the furnace temperature is maintained for a certain time. A first step of:
After maintaining the furnace temperature under a vacuum or negative pressure for a certain period of time, after nitrogen and other inert gases are sealed in the furnace until the pressure reaches approximately atmospheric pressure, the furnace temperature is maintained again at approximately atmospheric pressure for a predetermined time. The method for producing a quartz glass article according to claim 1, comprising the steps of: Wherein the first heating rate at 1 700 ° C. or more that put the process method according to claim 3 quartz glass article, wherein a set under 9 ° C. / min or less.

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