JPH0912325A - High-purity opaque quartz glass and its production as well as its application - Google Patents

Abstract

PURPOSE: To obtain high-purity opaque quartz glass having excellent heat ray shieldability by specifying the content of closed cells of a specific small diameter and the occupying ratio of closed cells of a specific large diameter and regulating the impurity contents of Li, Na, K, etc. CONSTITUTION: This quartz glass contains 1×10<6> to 9×10<6> pieces/cm<2> of the closed cells having an average grain size of 20 to 40μ. The ratio that the closed cells having the diameter of >=100μ occupy in the total cells is <=1% and the straight transmittance of light of a wavelength of 900nm when a thickness is 1mm is <=5%. For example, the powder of high-purity amorphous silica formed by refining the silica obtd. by bringing an aq. alkaline metal silicate soln. and acid into reaction has the average grain size of 0.5 to 10μ and contains the inevitable impurities of Li, Na, K, Mg, Ti, Fe, Cu, Ni, Cr and Al respectively at <=1ppm is used as the raw material. The molding obtd. after molding this powder is fired at 1,730 to 1,850 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a high heat ray shielding effect,
The present invention relates to a novel high-purity opaque quartz glass and a method for producing the same, and as its use, an opaque quartz glass flange and an opaque quartz glass tube, and methods for producing the same. Especially,
The high-purity opaque quartz glass of the present invention has excellent heat ray shielding performance, and is highly pure and free from the risk of contamination. Therefore, it is used in semiconductor manufacturing such as flanges, jigs, heat-insulating fins, core tubes, heat equalizing tubes, and chemical purification tubes. And the like can be used as a constituent material. In particular, the opaque quartz glass flange made of the high-purity opaque quartz glass of the present invention is useful as a flange portion of various furnace core tubes used in semiconductor manufacturing, for example, for heat treatment of silicon wafers.

[0002]

2. Description of the Related Art An opaque quartz glass tube and an opaque quartz glass flange made of high purity opaque quartz glass are suitable for use as a core tube or the like in a semiconductor wafer processing apparatus.
A typical example of such a semiconductor wafer processing apparatus is shown in FIG. The equipment consists of a heater-1, a core tube 2, and a semiconductor wafer.
It is composed of a ha 3, a wafer support boat 4, a heat insulating base 5, and a base 6. The flange 21 is completely bonded to the lower portion of the core tube 2, and the seal ring 7 is installed between the flange 21 and the base 6. The core tube 2 and the flange 21 are usually manufactured separately and joined by fusion or the like.

It is known that the opaque quartz glass used for such applications has excellent heat ray-shielding properties.
Since the heat rays are reflected on the surface of the bubbles present in the glass,
The heat ray-shielding property depends on the size of the surface area of bubbles. The larger the surface area, the higher the heat ray-shielding performance.

Most of the currently used opaque quartz glass has an average bubble diameter of 50 μm or more, and more than 100 μm.
There are a considerable number of bubbles exceeding m, and the number of bubbles is also 1 × 10 ^6.
The number is less than 1 / cm ³ , and is generally 1 × 10 ⁴ to 1 × 1.
It is 0 ⁵ pieces / cm ³ . Some have an average bubble diameter of 50
There is opaque quartz glass of less than μm, but the content of bubbles in such opaque quartz glass is 1 × 10 ⁶ cells / cm ^3.
Is less than. The total surface area of bubbles is 5 per cm ^3.
Since it is 0 cm ² or less, there is a limit to the heat ray blocking property.

The heat ray blocking property has a deep relationship with the transmittance of light, particularly near infrared rays, and it is considered that the lower the transmittance, the better. The opaque quartz glass currently used has a linear transmittance of about 10 to 50% for light with a wavelength of 900 nm when the thickness is 3 mm, and a linear transmittance of 30 to 60 when the thickness is 1 mm. % (Estimated), not a sufficient value.

Conventionally, opaque quartz glass is produced by a method of melting natural raw materials such as silica stone and quartz in an electric furnace, or a method of adding a foaming agent such as calcium carbonate to the above natural raw materials and melting it in a flame or an electric furnace. Was there. However, the opaque quartz glass manufactured by these methods, and the opaque quartz glass flange and the opaque quartz glass tube made of the opaque quartz glass contain impurities such as Na and Fe at 1 ppm or more. In addition, since the bubbles in those glasses have a large diameter and their distribution is wide,
The heat ray blocking property is low. Therefore, it is difficult to use them in the semiconductor manufacturing field.

Further, the conventional opaque quartz glass flange has been manufactured by a method of molding a bulk material by machining. Therefore, there is a problem that the cost required for processing is high because the material loss is large and the yield is extremely low. Further, since the seal surface of the flange is polished, air bubbles exposed on the seal surface are scraped off during the cleaning process, so that the seal surface partially collapses. It was

Further, the conventional opaque quartz glass tube is a method of melting natural raw materials such as silica stone and quartz, and drawing the raw materials, or putting the above-mentioned natural raw materials into a rotary melting furnace and making molten glass into a tubular shape by centrifugal force. It was manufactured by the method of molding. However, in these methods, a force is applied to the molten glass in the tube drawing or centrifugal molding process, and the bubbles in the glass are elongated and elongated, or the distribution becomes uneven,
There was a problem that the mechanical strength was remarkably reduced.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an opaque quartz glass which is more excellent in heat ray shielding property and higher in purity than existing opaque quartz glass and a method for producing the same.

Another object of the present invention is to provide an opaque quartz glass flange made of this high-purity opaque quartz glass having excellent smoothness and a method for producing the same. Still another object of the present invention is to provide an opaque quartz glass tube made of this high-purity opaque quartz glass and a method for producing the same.

[0011]

As a result of earnest research in view of the above problems, the inventors of the present invention have found that if a fine high-purity amorphous silica powder is molded and fired at a predetermined temperature, the purity of the opaque quartz glass obtained can be improved. It has been found that the heat resistance is high, the closed cells contained therein are fine, and the content per unit volume is large, so that the heat ray shielding property is excellent. Further, if a fine high-purity amorphous silica powder is molded into a flange shape or a tubular shape and fired at a predetermined temperature, the flange and the glass tube made of opaque quartz glass also have high purity. It has been found that the closed cells contained are fine and have a large content per unit volume, and therefore have excellent heat ray shielding properties. Furthermore, they have found that the high-purity opaque quartz glass of the present invention can be widely used as a member used in the field of semiconductors, and have completed the present invention. That is, the high-purity opaque quartz glass of the present invention, and the opaque quartz glass flange and the opaque quartz glass tube made of this high-purity opaque quartz glass have 1 × 10 ^{6 to} 9 × 10 closed cells having an average diameter of 20 to 40 μm. Contains ⁶ pieces / cm ³ , 100 μm
The ratio of closed cells having the above diameter to all the bubbles is 1
% And 90% when the thickness is 1 mm
The linear transmittance of light with a wavelength of 0 nm is 5% or less.

The method of the present invention for producing the above-mentioned high-purity opaque quartz glass is particles having an average particle size of 0.5 to 10 μm, and Li, Na, K, Mg, Ti, Fe, Cu,
The content of unavoidable impurities of Ni, Cr and Al is 1 each
After molding a high-purity amorphous silica powder having a ppm or less (including 0), the obtained molded body is 1730-18.
It is characterized by firing at 50 ° C.

Further, in the method for producing the high-purity opaque quartz glass flange, the high-purity amorphous silica powder is molded into a flange shape, and the molded body obtained is
It is characterized by firing at 730 to 1850 ° C.

Further, in the method for producing the above-mentioned high-purity opaque quartz glass tube, the above-mentioned high-purity amorphous silica powder is formed into a tubular shape, and the obtained formed body is heated at 1730 to 2000 ° C. using an electric furnace or a flame as a heat source. It is characterized by being fired at.

Hereinafter, the present invention will be described in detail.

[1] Opaque Quartz Glass (1) Composition and Shape The average diameter of the closed cells contained in the high-purity opaque quartz glass of the present invention is 20 to 40 μm. The content of closed cells is 1 × 10 ^{6 to} 9 × 10 ⁶ cells / cm ³ , preferably 5 × 10 ^{6 to} 9 × 10 ⁶ cells / cm ³ . In this way, due to the large amount of fine closed cells,
The total surface area of bubbles is 100 to ²⁰⁰ cm ² per 1 cm ^3.
It is extremely large and has a high rate of reflecting incident heat rays (light), so it has excellent heat ray shielding properties. On the other hand, in ordinary commercial products, the content of closed cells is less than 1 × 10 ⁶ cells / cm ³ , and the total surface area of bubbles is 50 per 1 cm ^3.
Since it is not more than cm ² , sufficient heat ray shielding performance cannot be achieved.

The high-purity opaque quartz glass of the present invention is also characterized by containing almost no large bubbles of 100 μm or more. That is, the ratio of large bubbles of 100 μm or more to the number of bubbles is 1% or less. This point is also a marked difference from a commercially available product, and the absence of large bubbles contributes to an increase in the total surface area of the bubbles.

The opaque quartz glass of the present invention has a thickness of 1 m.
The linear transmittance of light with a wavelength of 900 nm is 5
% Or less, preferably 0.1 to 2%. As described above, the heat ray-shielding property is deeply related to the transmittance of near infrared rays, so that the opaque quartz glass of the present invention having a low transmittance as described above has a very excellent heat-ray shielding property. Become.

The above-mentioned average diameter was determined by taking an optical microscope photograph of a glass sample whose surface was burnt-finished with an oxyhydrogen flame.
It is obtained by measuring the diameters of 0 or more bubbles and averaging them, and the bubble content is obtained from the relationship between the total number of bubbles in the photograph and the depth of focus of the optical microscope.

Furthermore, the high-purity opaque quartz glass of the present invention comprises Li, Na, K, Mg, Ti, V, Cr, Mn, and F.
In many cases, one or more of e, Co, Ni, Cu, Zn, and Al are unavoidably contained as impurities.
Among them, Li, Na, K, Mg, Ti, Cr, Fe, N
When one or more of i, Cu and Al are contained as unavoidable impurities, the content of each impurity is 1 pp.
m or less. Further, the contents of V and Mn are preferably 0.1 ppm or less (including 0) for each.

(2) Method for producing opaque quartz glass A method for producing the high-purity opaque quartz glass of the present invention will be described below.

(A) The amorphous silica powder, which is a starting raw material powder, is a silica powder obtained by subjecting an aqueous alkali silicate solution to an acid treatment in order to obtain an amorphous silica powder having high purity and good moldability. preferable. This method is disclosed, for example, in Japanese Patent Laid-Open No.
2-3011, JP-A-62-3012, JP-A-62
No. 283809 and JP-A No. 62-283810, an aqueous solution of an alkali silicate having a viscosity value in the range of 2 to 500 poise is passed through a nozzle having a pore diameter of 1 mm or less and a water-miscible organic medium or a concentration of 4N is specified. The fibrous or columnar gel obtained is extruded into a coagulation bath consisting of the following acid solutions to coagulate (coagulate), and the resulting fibrous or columnar gel is treated with a solution containing acid (acid treatment), followed by washing with water to remove impurities. And further heat treatment at a temperature of 1000 ° C. or higher, Li, Na, K, Mg, Ti, Fe, C
When one or more of u, Ni, Cr and Al are contained as unavoidable impurities, the content of each impurity is 1 p or less.
An amorphous silica powder having a particle size of pm or less can be obtained. This amorphous silica powder is pulverized by a process such as ball mill pulverization so as to have an average particle size of 0.5 to 10 μm, preferably 3 to 7 μm. Particle size is 0.
When it is less than 5 μm, the average diameter of bubbles in the resulting opaque quartz glass is less than 20 μm. On the other hand, the particle size is 10
If it exceeds μm, the average diameter of bubbles exceeds 40 μm and the number of generated bubbles decreases, so that sufficient heat ray blocking performance cannot be obtained. The average particle size of this amorphous silica powder is a value measured by a laser diffraction scattering method.

(B) Molding The amorphous silica powder can be molded by a usual wet or dry molding method. As the wet molding method, for example, a casting molding method in which amorphous silica powder is dispersed in pure water and the obtained slurry is poured into a gypsum mold or a porous resin mold and molded can be used. As the dry molding method, a cold isostatic pressing method or a die pressing method can be used.

(C) Firing The obtained molded product is, for example, in an electric furnace at 1730-
Baking is performed at 1850 ° C, preferably 1750 to 1800 ° C. If it is less than 1730 ° C., crystals are likely to be generated on the surface of the obtained fired body, and the glass obtained may be cracked due to the difference in thermal expansion coefficient between the crystal layer and the glass layer. On the other hand, when the temperature exceeds 1850 ° C., fine bubbles aggregate to generate coarse bubbles.

The firing time is preferably 1 to several tens of minutes, and particularly preferably 5 to 10 minutes in order to maintain the shape of the molded product. It is not preferable to let the material stay at a temperature of 1400 to 1600 ° C. for 2 hours or more while the temperature is raised to a baking temperature of 1730 to 1850 ° C. This is because crystallization is promoted in this temperature range and vitrification occurs at 1730 ° C. or higher, but the bubble content is drastically reduced.

The firing atmosphere is not particularly limited, but N
₂ , Ar or a mixed gas thereof is preferable. When firing in a carbon resistance heating furnace, a non-oxidizing gas such as N ₂ is preferable. The pressure during firing is 1 to 2 kgf / c.
m ² is preferable, and particularly 1.2 to 1.5 kgf /
cm ² is preferred. Firing under vacuum or reduced pressure may cause bubbles to expand.

By the above firing, the voids between the silica particles in the molded body become closed cells. Average particle size is 0.5-10μ
By using m amorphous silica powder, the average diameter of the closed cells can be adjusted within the range of 20 to 40 μm.

[2] Opaque quartz glass flange (1) Flange The flange of the present invention is an annular protrusion or the like provided at the lower end of a core tube or the like, and the “flange shape” means a flange shape of the tube or the like. . For example, it is shown by symbol 21 in FIG.

(2) Composition and Structure The flange of the present invention is made of the same high purity opaque quartz glass as the opaque quartz glass described in [1] above. That is, the opaque quartz glass flange has an average diameter of 20 to
40 μm closed cells 1 × 10 ^{6 to} 9 × 10 ⁶ cells / cm
³ contained, the proportion of closed cells having a diameter of 100 μm or more in all the bubbles is 1% or less, and the thickness is 1
The linear transmittance of light having a wavelength of 900 nm in mm is 5% or less.

(3) Manufacturing Method (a) Starting Material The starting material used for manufacturing the opaque quartz glass flange is the same as the high-purity amorphous silica powder described in [1] (2) (a). That is, the average particle size is 0.5 to
It is 10 μm, and preferably 3 to 7 μm. Also,
Li, Na, K, Mg, Ti, Fe, Cu, Ni, C
When one or more of r and Al are contained as unavoidable impurities, the content of each impurity is 1 ppm or less. The average particle size of this amorphous silica powder is closely related to the ease of molding, and when silica powder having an average particle size of less than 0.5 μm is used, the shrinkage due to drying is large and cracks are likely to occur. On the other hand, when the average particle diameter exceeds 10 μm, the strength of the molded product is poor and it is difficult to maintain the flange shape.

(B) Molding Molding can be performed by a cast molding method in which amorphous silica powder is dispersed in pure water, the obtained slurry is poured into a mold, and molded into a flange shape. The slurry used is the above-mentioned amorphous silica powder added to pure water,
It can be adjusted by ultrasonic dispersion or ball mill mixing. At this time, since it is not necessary to add a commonly used organic binder or dispersant, the obtained opaque quartz glass has extremely high purity. The amount of amorphous silica powder added to pure water is preferably 50 to 75% by weight. Further, in the case of ball-mill mixing, it is preferable to use a ball and a pot made of plastic, quartz glass, agate or the like in order to avoid contamination.

The mold used for the cast molding is
Gypsum molds and water-absorbent resin molds made of porous plastic and the like are preferably used. The resin material is preferably an epoxy resin or an acrylic resin. When using a gypsum mold, the Ca content increases to 2-3 ppm,
Ca does not affect the performance of the flange at all, and other harmful impurities such as Li, Na, K, Mg, Ti, Fe, C
When one or more of u, Ni, Cr and Al are contained as unavoidable impurities, the content of each impurity is 1 p
An opaque quartz glass flange of pm or less is obtained.
If a porous resin mold is used, the resulting opaque quartz glass flange will be as pure as the starting silica powder.

(C) Firing First, calcination is preferably performed at 1000 to 1400 ° C. for 1 to 20 hours. By this treatment, the structure of the molded body is made uniform, shrinkage due to firing uniformly occurs, and a fired body with extremely high dimensional accuracy is obtained.

Next, the calcined body is fired at 1730 to 1850 ° C, preferably 1750 to 1800 ° C. Below 1730 ° C, for example at 1600 ° C, the average diameter of bubbles is about 13 μm.
Although the content of bubbles is about 7 × 10 ⁶ cells / cm ³ , sufficient opacity cannot be ensured. If the temperature is 1600 ° C. or higher and lower than 1730 ° C., crystallization often occurs on the surface of the fired body, and the glass may crack due to the difference in thermal expansion coefficient between the surface crystal layer and the internal glass layer. . On the other hand, when the temperature exceeds 1850 ° C., it becomes difficult to maintain the shape of the flange due to deformation due to high temperature viscosity. In order to maintain the flange shape of the fired body, the firing time of 1730 to 1850 ° C is preferably 1 to several tens of minutes, and particularly preferably 5 to 10 minutes. For example, 1850
It is 5 minutes at ° C. The rate of temperature increase from 1400 ° C is preferably 300 ° C / hr or more, and particularly 500 to 70.
0 ° C./hr is preferable. The atmosphere and pressure during firing are
It is as described in [1] (2) (c).

[3] Opaque quartz glass tube (1) Composition and structure The opaque quartz glass tube of the present invention is made of the same high purity opaque quartz glass as the opaque quartz glass described in [1] above. That is, the opaque quartz glass tube has an average diameter of 2
1 × 10 ^{6 to} 9 × 10 ⁶ closed cells of 0 to 40 μm /
cm ³ and the proportion of closed cells having a diameter of 100 μm or more in the total cells is 1% or less, and the linear transmittance of light having a wavelength of 900 nm is 5% or less when the thickness is 1 mm. is there.

(2) Manufacturing Method (a) Starting Material The starting material used to manufacture the opaque quartz glass tube is
[1] The same as the high-purity amorphous silica powder described in (2) (a). That is, the average particle diameter is 0.5 to 10
μm, and preferably 3 to 7 μm. Also, L
i, Na, K, Mg, Ti, Fe, Cu, Ni, Cr,
When one or more kinds of Al are contained as unavoidable impurities, the content of each impurity is 1 ppm or less.

(B) Examples of the method for molding the molding powder include a casting molding method, a cold isostatic pressing method, a die pressing method, and the like. For molding the opaque quartz glass tube of the present invention, an amorphous silica powder is used. It is preferable to use a cast molding method in which is dispersed in pure water and the resulting slurry is poured into a porous resin mold for molding.

The slurry to be used can be adjusted by adding the above-mentioned amorphous silica powder to pure water and ultrasonically dispersing or mixing with a ball mill, as in the case of the opaque quartz glass flange. At this time, since it is not necessary to add a commonly used organic binder or dispersant, the obtained opaque quartz glass has extremely high purity. The amount of amorphous silica powder added to pure water is 50 to 75% by weight.
It is preferred that Further, in the case of ball-mill mixing, it is preferable to use a ball and a pot made of plastic, quartz glass, agate or the like in order to avoid contamination.

By pouring the obtained slurry into a porous cylindrical resin mold and removing only water through the porous mold, silica powder becomes a high-concentration slurry layer and reaches the mold surface (hereinafter referred to as " It is possible to form the silica powder into a tubular shape by means of "inking". Examples of the mold used for casting include a gypsum mold and a water-absorbent resin mold made of porous plastic or the like. The resin material is preferably an epoxy resin or an acrylic resin.

An example of an apparatus used for forming an opaque quartz glass tube is shown in FIG. This device comprises a porous cylindrical resin mold 11 on the outside, a vinyl chloride resin cylinder 12 on the inside, and a metal cover 14a set on the upper and lower surfaces of the cylindrical resin mold 11 via rubber seals 13a and 13b. , 14b, cylindrical resin mold 11, vinyl chloride resin cylinder 12, and metal cover-1
A cavity 15 defined by 4a and 14b, and a liquid reservoir 18 connected to the upper end of the cavity 15 by a connecting pipe 16 and connected to the lower end of the cavity 15 by a connecting pipe 17. From the connecting pipe 19
While applying a gas pressure of 5 kgf / cm ^2, a slurry 20 made of only amorphous silica powder and pure water is poured into the cavity 15 from the liquid reservoir 18 through one of the connecting pipes 16 and 17. After coating the silica powder layer on the mold, the metal covers 14a and 14b and the rubber seal 13 are formed.
Remove a and 13b, discharge excess slurry, and demold the molded body.

In the above-mentioned molding method, in order to obtain a uniformly solidified molded body, it is preferable to reverse the upper and lower sides of the resin mold 10 at regular intervals during the inking. When the resin mold 10 is fixed in the same direction and the inking is performed, the thickness of the upper portion of the obtained tubular molded body is smaller than that of the lower portion. In order to turn the resin mold 10 upside down, for example,
The connecting pipes 16 and 17 of FIG. 2 are stopped with a cock to prevent the backflow, and the resin mold 10 is turned upside down.

(C) Firing The following two firing methods are preferable for firing the obtained molded body.

One method is to use an oxyhydrogen flame to 173
It is a method of vitrifying by heating at 0 to 2000 ° C, preferably 1750 to 1800 ° C.

In this method, it is preferable that the tubular molded body is fixed to a glass lathe and the flame is applied from inside or outside the tubular molded body or both while rotating. In order to facilitate mounting on a glass lathe and to mitigate thermal shock due to flame, it is preferable to calcinate the molded body at 1000 to 1400 ° C for 1 to 20 hours before firing at 1730 ° C or higher.

The firing time is preferably 1 to 120 minutes, particularly preferably 30 to 60 minutes. The firing time is 173
It is the sum of the holding time after the temperature exceeds 0 ° C and the time required for raising and lowering the temperature. This method is suitable for producing long glass tubes of 300 mm or more.

Another method is to put the molded body in an electric furnace at 1730 to 2000 ° C., preferably 1750 to 1 ° C.
This is a method of firing at 850 ° C. for 1 to several tens of minutes, preferably 5 to 10 minutes. Below 1730 ° C, often
Crystallization may occur on the surface of the fired body, and the glass may be cracked due to the difference in thermal expansion coefficient between the surface crystal layer and the internal glass layer. On the other hand, when the temperature exceeds 1850 ° C., it becomes difficult to maintain the shape because of deformation due to high temperature viscosity.

Also, in order to soften the thermal shock,
The molded body is heated to 1000 to 140 before being baked at 2000 ° C.
It is preferable to calcine at 0 ° C. for 1 to 20 hours. 1400
The rate of temperature increase from 0 ° C to the above firing temperature is preferably 300 ° C / hr or more, and particularly preferably 500 to 700 ° C / hr.
The atmosphere and pressure during firing are as described in [1] (2) (c). This method is suitable for producing relatively short glass tubes of 300 mm or less.

By either of the above two firing methods,
The voids between the silica particles in the molded body become closed cells. By using an amorphous silica powder having an average particle diameter of 0.5 to 10 μm, the average diameter of the closed cells is 20 to 4
It can be adjusted within the range of 0 μm.

[0049]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 < Preparation of Raw Material Amorphous Silica Powder> JIS No. 3 water glass is heated and concentrated to give a viscosity value at 20 ° C. of 300 c.
ps. About 8 liters of this water glass was pressurized with a pump, passed through a filter (opening 70 μm), and then a nozzle (hole diameter:
0.2 mm, 50 holes), and extruded at a speed of 0.7 m / sec into a coagulation bath containing 300 liters of an 8 wt% sulfuric acid aqueous solution kept at 50 ° C.

The silica obtained in the fibrous form was immersed in 10 times amount of a freshly prepared 8 wt% sulfuric acid aqueous solution, and the temperature was adjusted to about 9
Impurities were extracted by stirring at 5 ° C. for about 1 hour, and then washed twice with 10 times the amount of pure water of silica. The above extraction and washing operations were repeated 5 times, and the wet silica obtained by dehydration with a centrifuge was dried with a hot air dryer at a temperature of 150 ° C for 8 hours to obtain a water content (weight reduction rate based on calcined silica).
3.7% water glass based amorphous silica
kg.

The obtained amorphous silica powder was further heat-treated in the air at 1200 ° C. for 10 hours and then pulverized with a ball mill made of quartz glass to obtain an average particle diameter of 3.5 μm.
Was obtained.

The powder was subjected to chemical analysis to measure the contents of various impurities. Table 1 shows the results.

[0054]

[Table 1]

<Molding and firing of raw material amorphous silica powder> The above amorphous silica powder was molded by a cold isostatic press at a pressure of 2 t, and the outer diameter was 200 mm and the height was 50 mm.
Then, a cylindrical molded body was prepared. The formed body is put into an electric furnace, heated in normal temperature (1 kgf / cm ² ) N ₂ atmosphere from room temperature to 1800 ° C. at a heating rate of 300 ° C./hr, and held at that temperature for 5 minutes for firing. did. The glass obtained after cooling was white and opaque.

The opaque quartz glass was chemically analyzed to measure the content of various impurities. Table 2 shows the results.

[0057]

[Table 2]

Further, the average diameter, content, total surface area, proportion of those having a diameter of 100 μm or more, and bulk density of the closed cells contained in the opaque quartz glass were measured. further,
This opaque quartz glass was processed into a thickness of 1 mm and 3 mm, light having a wavelength of 900 nm was transmitted, and its linear transmittance was measured. The bulk density was measured by the Archimedes method. Table 3 shows the results.

[0059]

[Table 3]

Example 2 < Preparation of Raw Amorphous Silica Powder> The average particle size was 5
The same procedure as in Example 1 was performed except that the thickness was set to μm. When the contents of the various impurities were measured, the results were the same as in Table 1 above.

<Molding and firing of raw material amorphous silica powder> The above-mentioned amorphous silica powder having an average particle diameter of 5 μm is dispersed and mixed in water, and cast molding is performed using a resin mold to obtain an outer diameter of 170 mm, an inner diameter of 90 mm, 40m height
A m-shaped flange-shaped molded body was obtained. After the molded body is dried, it is placed in an electric furnace and placed in an N ₂ atmosphere at atmospheric pressure (1 kgf /
cm ² ), after maintaining the temperature of 1100 ° C. for 10 hours,
Under a pressure of 1.3 kgf / cm ² , the temperature was raised to 1800 ° C. at a heating rate of 600 ° C./hr, and the temperature was maintained for 5 minutes for firing. The quartz glass obtained after cooling was white and opaque.

The average diameter, content, total surface area, ratio of those having a diameter of 100 μm or more and the bulk density of the closed cells contained in the opaque quartz glass were measured, and the opaque quartz glass was adjusted to a thickness of 1 mm and 3 mm. Processed, 9
The linear transmittance was measured by transmitting light with a wavelength of 00 nm. Table 3 shows the results. The bubble size distribution of this opaque quartz glass is shown in FIG.

Comparative Examples 1-2 Commercially available opaque quartz glass fused with silica stone and silica sand as raw materials (Comparative Example 1) and commercially available opaque quartz glass fused with silica as raw material and carbon as a foaming agent ( For Comparative Example 2), the average diameter, the content, the total surface area, the proportion of those having a diameter of 100 μm or more and the bulk density of the closed cells contained in each glass were measured, and the opaque quartz glass was used for the thicknesses of 1 mm and 3 mm. Processed into 90
The linear transmittance was measured by transmitting light having a wavelength of 0 nm. The results are shown in Table 3, and the bubble size distribution of each glass is shown in FIGS. 4 and 5.

As is clear from Table 2, the opaque quartz glass of Example 1 has high purity. In addition, Table 3 and FIGS.
As is clear from the above, the closed cells contained in the opaque quartz glass of Examples 1 and 2 have a finer diameter and a uniform diameter than the closed cells contained in the opaque quartz glass of Comparative Examples 1 and 2. In addition, the content of closed cells is large and the linear transmittance of heat rays is low.

Example 3 < Preparation of Raw Material Amorphous Silica Powder> The same procedure as in Example 2 was carried out. Also, when the impurity concentration was measured,
The results are shown in Table 4.

<Molding and Firing of Raw Material Amorphous Silica Powder> 2500 g of the amorphous silica powder having an average particle diameter of 5 μm was mixed with 1250 g of pure water and stirred for 6 hours while applying ultrasonic waves. The obtained slurry is poured into a resin mold, and a pressure of 3 kgf / cm ² is applied to mold the slurry.
A flange-shaped molded body having an inner diameter of 270 mm, an outer diameter of 390 mm and a height of 40 mm was prepared. After the molded body is dried, it is placed in an electric furnace and placed in an N ₂ atmosphere at atmospheric pressure (1 kgf / c).
m ² ) and calcined at 1100 ° C. for 10 hours. Then:
Under normal pressure from 3 ℃ f / cm ² to 350 ℃ / hr
The temperature was raised to 1800 ° C. at a heating rate of 1 and held for 1 minute for firing. After cooling down, the inner diameter is 240 mm, the outer diameter is 350 mm,
A flange-shaped opaque quartz glass having a height of 35 mm was obtained.

The obtained opaque quartz glass flange was subjected to chemical analysis to measure the content of each impurity. Table 4 shows the results.

[0068]

[Table 4]

The average diameter, content, total surface area of closed cells contained in the obtained opaque quartz glass flange, 1
The proportion and bulk density of those having a diameter of 00 μm or more were measured, and opaque quartz glass was processed into a thickness of 1 mm, light having a wavelength of 900 nm was transmitted, and its linear transmittance was measured. Table 6 shows the results. Further, this opaque quartz glass flange was machined with diamond abrasive grains, the surface roughness of the machined surface was measured, and it was compared with the conventional product manufactured by the electric melting method of quartz. Table 5 shows the two maximum surface roughnesses (Rmax).

[0070]

[Table 5]

Example 4 The same slurry as in Example 3 was poured into a gypsum mold and molded under normal pressure to obtain an inner diameter of 270 mm, an outer diameter of 390 mm and a height of 40.
A mm-shaped flange-shaped molded body was prepared. After drying the obtained molded body, it was placed in a carbon resistance heating furnace, and it was stored in a N ₂ atmosphere at 1150 ° C. under normal pressure (1 kgf / cm ² ) for 15 minutes.
After calcination for 3 hours, under pressure of 1.3 kgf / cm ² , 3
The temperature is raised to 1800 ° C. at a heating rate of 50 ° C./hr, and 5
It was held for minutes and baked. After cooling, a flange-shaped opaque quartz glass having an inner diameter of 250 mm, an outer diameter of 360 mm and a height of 35 mm was obtained.

As in Example 1, the obtained opaque quartz glass flange was subjected to chemical analysis. Table 4 shows the results.
Further, in the same manner as in Example 1, the average diameter, content, total surface area, ratio of those having a diameter of 100 μm or more and the bulk density of the closed cells contained in the obtained opaque quartz glass flange were measured, and the opaque quartz glass was also measured. Was processed to a thickness of 1 mm, light having a wavelength of 900 nm was transmitted, and its linear transmittance was measured. Table 6 shows the results.

[0073]

[Table 6]

As is clear from Tables 4 and 6, Example 3
And the opaque quartz glass flanges of 4 are of high purity,
Also, the linear transmittance is low and the heat ray blocking property is excellent. Further, as is clear from Table 5, the opaque quartz glass flange of Example 3 has a surface roughness of the processed surface smaller than that of the conventional product. It is presumed that this is because the bubbles in the opaque quartz glass flange of Example 3 contained fine closed cells.

Example 5 The same slurry as in Example 3 was applied with a pressure of 3 kgf / cm ² , and the inner diameter was 230 mm and the outer diameter was 300 m shown in FIG.
It was poured into the cavity -15 of the resin mold 10 having a height of m and a height of 300 mm, and it was inked for 80 minutes while turning upside down every 5 minutes. After discharging the remaining slurry, the cylindrical molded body was detached from the resin mold 10 to obtain a molded body having an outer diameter of 230 mm, an inner diameter of 214 mm and a height of 300 mm.

The obtained molded body was calcined at 1100 ° C. for 10 hours, and then the calcined body was fixed on a glass lathe, and while rotating, two oxyhydrogen flames were set on the outside and one inside the tube. It was baked for 40 minutes with a burner. After cooling, the outer diameter is 207m
An opaque quartz glass tube having a diameter of m, an inner diameter of 192 mm and a height of 270 mm was obtained.

In the same manner as in Example 1, the obtained opaque quartz glass was chemically analyzed. Table 7 shows the results. Further, as a comparative example, Table 7 shows the analytical values (catalog values) of a commercially available opaque quartz glass tube (T-100, Toshiba Ceramics Co., Ltd.).

[0078]

[Table 7]

Further, in the same manner as in Example 1, the average diameter, content, total surface area, ratio of those having a diameter of 100 μm or more and the bulk density of the closed cells contained in the obtained opaque quartz glass tube were measured. The opaque quartz glass was processed to a thickness of 1 mm, light having a wavelength of 900 nm was transmitted, and its linear transmittance was measured. Table 8 shows the results.

[0080]

[Table 8]

Example 6 The same slurry as in Example 3 was used as a cylindrical gypsum mold (inner diameter: 150 m).
m, outer diameter 200 mm, height 400 mm) and invert every 5 minutes while maintaining normal pressure (1 kgf / cm
² ) It was made to inhale for 60 minutes. After discharging the remaining slurry, the cylindrical shaped body was detached from the cylindrical plaster mold, and the outer diameter was 1
A molded body having a size of 50 mm, an inner diameter of 130 mm and a height of 400 mm was obtained. The obtained molded body was calcined at 1200 ° C. for 5 hours and then calcined by an oxyhydrogen flame burner in the same manner as in Example 5 to obtain an opaque quartz glass tube having an outer diameter of 135 mm, an inner diameter of 117 mm and a height of 370 mm. It was

As in Example 1, the obtained opaque quartz glass tube was subjected to chemical analysis. Table 7 shows the results. Further, as in Example 1, the average diameter, content, total surface area of the closed cells contained in the obtained opaque quartz glass tube, 10
The proportion and bulk density of those having a diameter of 0 μm or more were measured, and opaque quartz glass was processed to a thickness of 1 mm, light having a wavelength of 900 nm was transmitted, and its linear transmittance was measured. Table 8 shows the results.

Example 7 < Preparation of raw material amorphous silica powder> The average particle diameter was 3
The same procedure as in Example 1 was performed except that the thickness was changed to μm. The content of each impurity was in agreement with the values shown in Table 2 as a result of the analysis.

<Molding and Firing of Raw Material Amorphous Silica Powder> 2500 g of the above-mentioned amorphous silica powder having an average particle diameter of 3 μm was mixed with 1250 g of pure water and stirred for 6 hours while applying ultrasonic waves. The obtained slurry was cylindrical gypsum mold (inner diameter 360 mm, outer diameter 400 mm, height 100
mm), and while being turned upside down every 5 minutes, it was inoculated for 60 minutes at normal pressure (1 kgf / cm ² ). After discharging the remaining slurry, the cylindrical molded body was detached from the cylindrical plaster mold, and the outer diameter was 360 mm, the inner diameter was 340 mm, and the height was 1.
A molded body of 00 mm was obtained.

The obtained molded body was placed in a carbon resistance heating furnace and fired in a nitrogen atmosphere at 1150 ° C. for 15 hours.
The temperature was raised as it was to 1800 ° C. at a heating rate of 350 ° C./hr, and then held for 1 minute. After furnace cooling, an opaque quartz glass tube having an outer diameter of 324 mm, an inner diameter of 306 mm and a height of 90 mm was obtained.

As in Example 1, the obtained opaque quartz glass tube was chemically analyzed. Table 7 shows the results. Further, as in Example 1, the average diameter, content, total surface area of the closed cells contained in the obtained opaque quartz glass tube, 10
The proportion and bulk density of those having a diameter of 0 μm or more were measured, and opaque quartz glass was processed to a thickness of 1 mm, light having a wavelength of 900 nm was transmitted, and its linear transmittance was measured. Table 8 shows the results.

As is clear from Tables 7 and 8, the opaque quartz glass tubes of Examples 5, 6 and 7 have high purity, low linear transmittance, and excellent heat ray-shielding properties.

[0088]

As described above in detail, since the opaque quartz glass of the present invention contains a large amount of fine bubbles, it has excellent heat ray-shielding properties and high purity, and thus is particularly used in the semiconductor manufacturing field. As various core tubes, containers such as jigs and bell jars to be used, for example, as a constituent material for silicon wafer processing core tubes and their flanges, heat insulating fins, chemical solution purification tubes, silicon melting crucibles, etc. It is suitable. Further, it can also be used in the field of containers for burning various powders such as phosphors and heat ray reflectors.

In particular, such a flange made of opaque quartz glass contains fine closed cells, which causes a problem of the prior art (since the seal surface is polished, a seal is generated during cleaning treatment, etc.). -There is no problem that air bubbles exposed on the seal surface are scraped off and the seal surface of the flange partly collapses), and the smoothness of the processed surface is good. Furthermore, the manufacturing method of the present invention in which a flange-shaped powder compact is fired is compared with conventional methods.
The processing steps are largely omitted, and the processing cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a conventional semiconductor wafer heat treatment apparatus.

FIG. 2 is a cross-sectional view of a molding apparatus used for manufacturing the opaque quartz glass tube of the present invention.

FIG. 3 is a graph showing the bubble size distribution of the opaque quartz glass of Example 2.

FIG. 4 is a graph showing the bubble size distribution of the opaque quartz glass of Comparative Example 1.

5 is a graph showing the bubble size distribution of the opaque quartz glass of Comparative Example 2. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heater 2 Core tube 21 Flange 3 Semiconductor wafer 4 Support boat 5 Heat insulating base 6 Base 7 Seal ring 11 Cylindrical resin type 12 Vinyl chloride cylinder 13a Rubber seal 13b Rubber seal 14a Metal Cover 14b Metal cover 15 Cavity 16 Connection pipe 17 Connection pipe 18 Liquid reservoir 19 Connection pipe 20 Slurry

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukinobu Hara, Aomori Prefecture 3-1-1 Koyo, Hachinohe City Nitto Kagaku Kogyo Co., Ltd. (72) Kenji Kamo 2-4-17 Amakubo Tsukuba, Ibaraki ( 72) Inventor Tomoyuki Akiyama Yamagata City Yamagata City Sakurada Higashi 4-8-4-202 (72) Inventor Koichi Ono Tsuchiura City Ibaraki Prefecture 1-18-7-605 Fujisaki Inventor Takashi Tsukuma Tsuchiura City Ibaraki Prefecture Fujisaki 1-18-7-901 (72) Inventor Kazuchi Sudo 2-4-7 Tokamachi, Yamagata City Yamagata Prefecture Yoshikazu Kikuchi 43-7 Tsuruta, Sagae, Sagae City, Yamagata Prefecture

Claims (13)

[Claims] 1. A mean diameter contains closed cells 1 × 10 ⁶ cells to 9 × 10 ⁶ cells / cm ³ of 20 to 40 [mu] m, 100 microns
9 when the ratio of closed cells having a diameter of m or more to all cells is 1% or less and the thickness is 1 mm.
A high-purity opaque quartz glass having a linear transmittance of 5% or less for light having a wavelength of 00 nm. 2. The high-purity opaque quartz glass according to claim 1, wherein Li, Na, K, Mg, Ti, Fe and C are used.
A high-purity opaque quartz glass having a content of unavoidable impurities of u, Ni, Cr, and Al each being 1 ppm or less (including 0). 3. A method for producing a high-purity opaque quartz glass according to claim 1, which is a high-purity amorphous silica powder obtained by purifying silica obtained by reacting an alkali metal silicic acid aqueous solution with an acid. , The average particle size is 0.5 to
10 μm and Li, Na, K, Mg, Ti, F
The inevitable impurities of e, Cu, Ni, Cr, and Al each having a content of 1 ppm or less (including 0) were used as a raw material, and this powder was molded.
A method characterized by firing at 30 to 1850 ° C. 4. An opaque quartz glass flange made of the high-purity opaque quartz glass according to claim 1. 5. The method for producing a high-purity opaque quartz glass flange according to claim 4, which is a high-purity amorphous silica powder obtained by purifying silica obtained by reacting an aqueous solution of an alkali metal silicic acid with an acid. Has an average particle diameter of 0.5 to 10 μm, and Li, Na, K, Mg,
The powder having the content of inevitable impurities of Ti, Fe, Cu, Ni, Cr, and Al each being 1 ppm or less (including 0) was used as a raw material, and this powder was molded. A method comprising firing at ˜1850 ° C. 6. The method for producing an opaque quartz glass flange according to claim 5, which absorbs a slurry which comprises only the high-purity amorphous silica powder and water and contains no organic binder and dispersant. A method for producing a flange-shaped molded product by pouring it into a mold with a mold. 7. The method for producing an opaque quartz glass flange according to claim 5, wherein the powder compact is preliminarily 1000 to 1 before firing at 1730 to 1850 ° C.
A method characterized by calcining at 400 ° C. for a certain period of time. 8. An opaque quartz glass tube made of the high-purity opaque quartz glass according to claim 1. 9. The method for producing a high-purity opaque quartz glass tube according to claim 8, which is a high-purity amorphous silica powder obtained by purifying silica obtained by reacting an aqueous solution of an alkali metal silicic acid with an acid. And the average particle size is 0.5
10 μm, and Li, Na, K, Mg, Ti,
Fe powder, Cu, Ni, Cr, and Al unavoidable impurities each having a content of 1 ppm or less (including 0) were used as a raw material, and the powder was molded. A method comprising firing at 1730 to 2000 ° C. using a flame as a heat source. 10. The method for producing an opaque quartz glass tube according to claim 9, wherein a slurry made of only the high-purity amorphous silica powder and water is put into a cylindrical mold, and the mold is inlaid, A method of discharging a surplus slurry in a mold to obtain a tubular molded body. 11. The method for producing an opaque quartz glass tube according to claim 9, wherein a cylindrical mold filled with a slurry is erected and turned upside down at regular time intervals so that the inking is uniform. A method characterized by doing. 12. The method for producing an opaque quartz glass tube according to claim 9, wherein the powder compact is preliminarily 1000 to 1 before firing at 1730 to 2000 ° C. or higher.
A method characterized by calcining at 400 ° C. for a certain period of time. 13. The method for producing an opaque quartz glass tube according to claim 9, wherein the powder compact is installed in a rotating device such as a lathe when firing with a flame as a heat source and the tube is rotated. A method characterized by applying an oxyhydrogen flame from the outside or inside or both, and firing.