JP7162395B2 - Manufacturing method for multilayer structure quartz glass material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a multilayer structure quartz glass material. More particularly, the present invention relates to a method of manufacturing a multi-layered quartz glass material having transparent layers on both sides of an opaque layer.

A multi-layer structure quartz glass material is a multi-layer structure material mainly intended for use in fields where heat insulation is required. The multi-layer structure material is particularly used as a heat insulating material for a heating furnace for heat treatment that constitutes a bell jar for manufacturing semiconductors, a furnace core tube for a diffusion furnace, a boat holding jig, and the like.

A heating furnace for heat-treating silicon wafers has, for example, a heating element 1, a furnace core tube 2, a boat 4 for supporting silicon wafers 3, a heat insulating cylinder 5, and a base 6, as shown in FIG. A flange 9 is provided at the bottom of the furnace core tube 2 . The flange 9 is made of opaque quartz glass and integrally joined to the core tube 2 made of transparent glass by welding with an oxyhydrogen flame. The flange 9 acts as a heat insulating material and suppresses the heat transfer to the packing 7 and the base 6 which are inferior in heat resistance. Further, the inside of the furnace core tube is kept at a predetermined atmosphere by sealing the flange 9 and the base 6 via the packing 7 .

Opaque quartz glass material with a transparent part on the surface is used for the flange part. The opaque part contains uniformly dispersed bubbles and has excellent high-temperature viscosity and heat shielding properties. have a smooth surface. A ring member made of opaque quartz glass suitable for a flange member of a furnace core tube of various heat treatment apparatuses in semiconductor manufacturing and a manufacturing method thereof are disclosed in Patent Documents 1 to 4, for example.

JP-A-2004-067456 JP-A-07-300326 JP-A-11-116265 JP-A-11-209135

In recent years, from the standpoint of energy conservation and the uniformity of the temperature distribution in the heating furnace, the performance of opaque quartz glass materials used in such semiconductor devices has been required to be improved in terms of blocking heat from radiation and conduction from the heating furnace. There is

However, the opaque quartz glass materials having a transparent portion described in Patent Documents 2 to 4 have a high thermal conductivity and cannot meet the above requirements. In addition, the high thermal conductivity results in a large energy loss and an increase in operating costs, or the thickness of the material used for heat shielding increases, resulting in an increase in equipment costs.

Patent Document 1 describes a method of manufacturing a multilayer quartz glass plate in which an opaque quartz glass plate is welded between two transparent quartz glass plates by a burner flame. In this method, if each glass plate is as thin as several millimeters, it is easy to join them. For this reason, there is a concern that impurities may enter and separation between the transparent layer and the opaque layer may occur during the process of raising or lowering the temperature. In addition, the opaque layer of the multilayer quartz glass plate that can be produced by this method has a high apparent density, and the thermal conductivity of the multilayer quartz glass plate is also high. . Furthermore, although it is advantageous for manufacturing a rectangular multi-layer structure quartz glass material, in practice, in the case of semiconductor device applications, there are many round and ring shapes, and there is also the problem of a low yield in commercialization.

With the object of providing a multi-layered quartz glass material for solving the above-mentioned problems, the present inventors filled silica powder between two transparent quartz glass plates and then heated to melt the silica powder. developed a method for manufacturing a multi-layer quartz glass material having an opaque layer between transparent quartz glass plates, and filed a patent application. According to this method, it was possible to provide a multi-layered quartz glass material having an opaque quartz glass layer with an apparent density of 2.0 g/cm ³ or less.

Furthermore, the present inventors have attempted to prepare a large-sized multi-layered silica glass material and directly prepare a circular or ring-shaped multi-layered silica glass material using the above method. As a result, it is not easy to evenly fill silica powder between two transparent quartz glass plates in the case of a large size or a circular or ring shape. It has been found that no structural fused silica material is obtained.

Therefore, in the present invention, a method for uniformly filling silica powder between two transparent quartz glass plates is found, and by melting the silica powder uniformly filled between the two transparent quartz glass plates, desired performance can be obtained. The object of the present invention is to provide the preparation of large-sized multi-layered quartz glass materials and the direct preparation of circular or ring-shaped multi-layered quartz glass materials.

Desired performance is the performance of having an opaque layer with a low apparent density and having a low thermal conductivity of the multi-layer quartz glass plate, and as a result, being able to sufficiently block heat due to radiation and conduction from the heating furnace.

As a result of various investigations, it was found that by supplying silica powder between two transparent quartz glass plates tilted at a predetermined angle while vibrating the two transparent quartz glass plates, the silica powder was placed between the two transparent quartz glass plates. By melting this silica powder between transparent quartz glass plates, it is possible to prepare large-sized multi-layered quartz glass materials or directly prepare circular or ring-shaped multi-layered quartz glass materials with desired performance. The present invention was completed by discovering that it provides.

The present invention is as follows.
[1]
(1) Forming a temporary assembly in which the first transparent quartz glass plate and the second transparent quartz glass plate are supported via spacers so that the opposing surfaces of the transparent quartz glass plate and the second transparent quartz glass plate are substantially parallel at a predetermined interval,
(2) A sealing material having a raw material powder input portion is placed on the outer periphery of the formed temporary assembly material, and the temporary assembly material and the sealing material are sandwiched between a lower mold and an upper mold from above and below to form a mold for filling the raw material powder. to form
(3) In the space between the first transparent quartz glass plate and the second transparent quartz glass plate of the temporary assembled material in the inclined mold, the raw material powder input portion of the sealing material is positioned substantially above. , while continuously or intermittently vibrating the mold, the raw material powder for the opaque layer is continuously or intermittently filled to prepare a multilayer structure having a raw material powder layer between two glass plates;
(4) Taking out the multi-layered structure from the temporary assembly, heating the taken-out multi-layered structure to melt the raw material powder, and then cooling to obtain a multi-layered quartz glass material.
A method for manufacturing a multilayer structure quartz glass material, comprising:
[2]
The manufacturing method according to [1], wherein when the planar shape of the temporary assembled material is ring-shaped, the casting mold for filling the raw material powder is provided with a sealing material for sealing the inner peripheral edge of the ring of the temporary assembled material.
[3]
The manufacturing method according to [1] or [2], wherein the spacer has a multilayer structure of a heat-resistant material and a combustible material.
[4]
The manufacturing method according to any one of [1] to [3], wherein the inclination angle of the mold is in the range of 20 to 70°.
[5]
The production method according to any one of [1] to [4], wherein the filling of the raw material powder is performed using a vibrating feeder.
[6]
The manufacturing method according to any one of [1] to [5], wherein the multilayer structure removed from the temporary assembly is subjected to a heating and melting step after confirming the uniformity of the raw material powder layer.
[7]
The production method according to any one of [1] to [6], wherein the raw material powder is silica powder or a mixed powder of silica powder and silicon nitride powder.
[8]
Any one of [1] to [7], wherein the heating of the multilayer structure is performed while applying a load from the outside of the first transparent quartz glass plate and the second transparent quartz glass plate of the multilayer structure in opposing directions. Method of manufacture as described.
[9]
The manufacturing method according to any one of [1] to [8], wherein the multilayer structure is heated using an electric furnace.
[10]
The manufacturing method according to any one of [1] to [9], wherein the planar shapes of the first transparent quartz glass plate and the second transparent quartz glass plate are rectangular, circular, or ring-shaped.
[11]
The manufacturing method according to [10], wherein the planar shape of the first transparent quartz glass plate and the second transparent quartz glass plate is ring-shaped, and a temporary assembled material in which the inner periphery between the two glass plates is sealed is used.
[12]
The manufacturing method according to any one of [1] to [11], wherein the multilayer structure quartz glass material has an apparent density of the opaque quartz glass layer of 2.0 g/cm ³ or less.
[13]
The manufacturing method according to any one of [1] to [12], wherein the multilayer structure quartz glass material has a thermal conductivity of 1.1 W/(m·K) or less at 500°C.

According to the present invention, silica powder is supplied between two transparent quartz glass plates tilted at a predetermined angle while vibrating the two transparent quartz glass plates, whereby the silica powder is spread between the two transparent quartz glass plates. Preparation of large-sized multi-layered silica glass material and direct preparation of circular or ring-shaped multi-layered silica glass material with desired performance by melting this silica powder between transparent silica glass plates, which can be uniformly filled between plates. can be provided. Desired performance is the performance of having an opaque layer with a low apparent density and having a low thermal conductivity of the multi-layer quartz glass plate, and as a result, being able to sufficiently block heat due to radiation and conduction from the heating furnace.

An example of arrangement of first and second transparent quartz glass plates and spacers in a temporary assembly having a circular planar shape is shown. An example of arrangement of the first and second transparent quartz glass plates and spacers in the case of a temporary assembly having a ring-shaped planar shape is shown. An example of a lower mold 40 having an outer peripheral edge sealing material 50 arranged on the upper surface thereof is shown. An example is shown in which a planar temporary assembly 1 that fits inside the inner peripheral edge 51 of the outer peripheral edge sealing material 50 of the lower mold 40 on which the outer peripheral edge sealing material 50 is arranged is shown. The upper mold 60 is provided after the outer peripheral edge sealing material 50 is arranged on the upper surface of the lower mold 40 and the temporary assembled material 1 is set in the inner peripheral edge 51 of the outer peripheral edge sealing material 50 . FIG. 4 is an explanatory diagram of a method of filling a raw material powder between two glass plates of a temporary assembly to prepare a multilayer structure having a raw material powder layer. An example of a method for confirming the uniformity of the raw material powder layer will be shown. Explanatory drawing of the heating furnace for heat processing of a silicon wafer.

<Manufacturing method for multilayer structure quartz glass material>
A method of manufacturing a multilayered quartz glass material according to the present invention includes the following steps (1) to (4).
(1) Forming a temporary assembly in which the first transparent quartz glass plate and the second transparent quartz glass plate are supported via spacers so that the opposing surfaces of the transparent quartz glass plate and the second transparent quartz glass plate are substantially parallel at a predetermined interval,
(2) A sealing material having a raw material powder input part is placed around the periphery of the formed temporary assembly material, and the temporary assembly material and the sealing material are sandwiched between a lower mold and an upper mold from above and below to form a mold for filling the raw material powder. form,
(3) In the space between the first transparent quartz glass plate and the second transparent quartz glass plate of the temporary assembled material in the inclined mold, the raw material powder input portion of the sealing material is positioned substantially above. , while continuously or intermittently vibrating the mold, the raw material powder for the opaque layer is continuously or intermittently filled to prepare a multilayer structure having a raw material powder layer between two glass plates;
(4) Taking out the multi-layered structure from the temporary assembly, heating the taken-out multi-layered structure to melt the raw material powder, and then cooling to obtain a multi-layered quartz glass material.

(1) Formation of Temporary Assembled Material In this step, the first transparent quartz glass plate and the second transparent quartz glass plate are temporarily assembled by supporting them via spacers so that the facing surfaces are substantially parallel with each other at a predetermined interval. form the material.
The first and second transparent quartz glass plates are materials that form transparent quartz glass layers, which are the surface layers (first layer and third layer) of the multilayer structure quartz glass material. The first and second transparent quartz glass plates are made of highly transparent glass containing no air bubbles. Although the thickness of the first and second transparent quartz glass plates is not particularly limited, they can each independently range, for example, from 1 to 10 mm. However, it is not intended to be limited to this range, and can be appropriately determined according to the application. The densities of the first and second transparent quartz glass plates are not particularly limited, but can be independently in the range of, for example, 2.0 to 2.5 g/cm ³ .

The planar shape of the first transparent quartz glass plate and the second transparent quartz glass plate can be rectangular, circular, or ring-shaped.

The first transparent quartz glass plate and the second transparent quartz glass plate are supported via spacers so that the opposing surfaces are substantially parallel with a predetermined spacing. The spacer is suitably made of a carbon material from the viewpoint of excellent heat resistance and releasability, and may be, for example, carbon felt. The height of the spacer is appropriately determined according to the amount of raw material powder for the opaque layer to be put between the first transparent quartz glass plate and the second transparent quartz glass plate. The spacers need only be able to keep the distance between the two transparent quartz glass plates substantially constant, and are provided at a plurality of locations, for example 3 to 12 locations, at approximately equal intervals on the outer peripheral edges of the first and second transparent quartz glass plates. be able to. When the planar shape of the first and second transparent quartz glass plates is ring-shaped, spacers are provided not only on the outer peripheral edges of the first and second transparent quartz glass plates but also on the inner peripheral edges at a plurality of locations, for example, 3 to 12 locations can be provided at approximately equal intervals.

FIG. 2 is an explanatory diagram showing an example of arrangement of first and second transparent quartz glass plates and spacers in the temporary assembly having a circular planar shape shown in FIG. 1 ; The upper figure is a plan view, and the lower figure is a cross-sectional view along AB. The first transparent quartz glass plate 11 and the second transparent quartz glass plate 12 are supported via a plurality of spacers 20 so that their facing surfaces are substantially parallel with each other at a predetermined interval. In the example of the temporary assembly shown in FIG. 1, a plurality of spacers 20 are provided at six locations on the outer peripheral edges of the first and second transparent quartz glass plates 11 and 12 at approximately equal intervals. FIG. 2 is an explanatory diagram showing an example of arrangement of first and second transparent quartz glass plates and spacers in the case of a temporary assembly 1a having a ring-shaped planar shape. The upper figure is a plan view, and the lower figure is a cross-sectional view along AB. The first transparent quartz glass plate 11a and the second transparent quartz glass plate 12a are provided with a plurality of spacers 20a on the outer peripheral edge side and a plurality of spacers 20b on the inner peripheral edge side so that the opposing surfaces are substantially parallel at a predetermined interval. supported through In the example of the temporary assembly shown in FIG. 2, spacers 20a are provided at six locations on the outer peripheral edges of the first and second transparent quartz glass plates 11a and 12a at approximately equal intervals, so that the first and second transparent quartz glass plates 11a , 12a are provided with spacers 20b at approximately equal intervals.

The spacer can have multiple layers of heat resistant and combustible materials. The heat-resistant material can be, for example, a carbon material, and the combustible material can be, for example, an organic polymeric material. The thickness of the heat-resistant material is set to the desired thickness of the opaque layer formed through heating and melting, and the thickness of the combustible material is determined according to the ease of filling the raw material powder for the opaque layer, the density of the raw material powder, etc. Consideration can be made as appropriate. Combustible materials volatilize and scatter when heated and melted. The spacer can be a sandwich structure of two combustible materials sandwiching a heat resistant material.

(2) Formation of mold for filling raw material powder An outer peripheral edge sealing material having a raw material powder input part is placed on the outer peripheral edge of the temporary assembled material formed in step (1), and the temporary assembled material and the outer peripheral edge sealing material are placed. is sandwiched from above and below by a lower mold and an upper mold to form a mold for filling raw material powder. The lower mold and the upper mold can have a shape and dimensions that can cover the temporary assembly and the peripheral edge sealing material. FIG. 3 shows an example of a lower die 40 having an outer peripheral edge sealing material 50 arranged on the upper surface thereof. The upper figure is a plan view, and the lower figure is a cross-sectional view along AB. The outer peripheral edge sealing material 50 has an inner peripheral edge 51 that conforms to the shape of the outer peripheral edge of the temporary assembly, and has a raw material powder input portion 52 . FIG. 4 shows an example in which a planar temporary assembly 1 that fits inside the inner peripheral edge 51 of the outer peripheral edge sealing material 50 of the lower mold 40 on which the outer peripheral edge sealing material 50 is arranged is shown. The upper figure is a plan view, and the lower figure is a cross-sectional view along AB. The peripheral edge sealing material 50 has substantially the same thickness as the temporary assembly 1 . The raw material powder input part 52 is used when filling the temporary assembly 1 with the raw material powder. It is suitable for the raw material powder introduction part 52 to have a width approximately equal to 1/2 of the width of the frontage of the temporary assembled member 1, because the raw material powder can be easily introduced and the raw material powder can be uniformly filled. is. When the planar shape of the temporary assembly is ring-shaped or the like and there is a space inside, a sealing material for sealing the inner peripheral edge is used in addition to the outer peripheral edge. That is, when the planar shape of the temporary assembled material is ring-shaped or the like, the mold for filling the raw material powder includes the inner peripheral edge sealing material for sealing the inner peripheral edge inside the ring of the temporary assembled material in addition to the outer peripheral edge sealing material. prepare. It is suitable that the inner peripheral edge sealing material has an outer diameter substantially equal to the inner diameter of the ring of the temporary assembly.

The planar shape of the upper mold and lower mold of the mold is not particularly limited, and can be appropriately determined according to the shape of the peripheral edge sealing material and the multilayer structure quartz glass material. Although not intended to be limiting, the planar shape of the mold can be, for example, rectangular, circular, irregular, and the like. The lower mold is a flat plate member having a constant thickness, and at least the upper surface thereof is flat and preferably smooth because it is used to support the first transparent quartz glass plate of the temporary assembly. The upper mold is flat, preferably smooth, so that at least the lower surface is used to support the second transparent quartz glass plate of the temporary assembly. After placing the outer peripheral edge sealing material 50 on the upper surface of the lower mold 40 and setting the temporary assembly 1 in the inner peripheral edge 51 of the outer peripheral edge sealing material 50, the upper mold 60 is provided. This state is shown in FIG. The upper figure is a plan view, and the lower figure is a cross-sectional view along AB. It is appropriate to fix the lower mold 40 and the upper mold 60, for example, at the peripheral edges of both molds for the convenience of subsequent filling of the raw material powder. Both types of fixation can be made using, for example, bolts or the like, but this is not intended to be limiting.

(3) Raw Material Powder Filling A raw material powder is filled between two glass plates of a temporary assembly to prepare a multilayer structure having a raw material powder layer. Description will be made with reference to FIG. A raw material powder filling mold 70 in which a temporary assembly member and an outer peripheral edge sealing material (or an inner peripheral edge sealing material in the case of a ring shape) are fixed by upper and lower molds is set on an inclined table 80 . The powder filling mold 70 positions the raw material powder input portion of the peripheral edge sealing material substantially upward. The tilt angle of the tilting table 80 is not limited, but can be, for example, in the range of 20 to 70 degrees. The raw material powder is supplied to the space between the first transparent quartz glass plate and the second transparent quartz glass plate of the temporary assembly in the mold inclined at this angle. The raw material powder is supplied by continuously or intermittently vibrating the mold and continuously or intermittently supplying the raw material powder for the opaque layer. In the example of FIG. 6, the tilting table 80 is installed on the shaking table 81 . In the present invention, the temporary assembly material in the mold is tilted, for example, in the range of 20 to 70°, and the raw material powder is supplied while continuously or intermittently vibrating the mold, so that the raw material powder is uniformly distributed to the first. and the second transparent quartz glass plate. The tilt of the mold can be, for example, in the range of 25-65°, 30-60°, 35-55°, or even 40-50°. The vibration applied to the mold is, for example, in the range of 1-250 Hz, preferably 50-150 Hz. However, it is not intended to be limited to this range. In the temporary assembly in the mold, the facing surfaces of the first transparent quartz glass plate and the second transparent quartz glass plate are supported so as to be parallel with each other at a predetermined interval. The gap is filled with raw material powder for the opaque layer.

Filling of the raw material powder can be performed using, for example, a vibrating feeder. In the example of FIG. 6, the raw material powder is supplied to the powder filling mold 70 via the vibrating feeder 82 . There is no limit to the feed rate of the raw material powder, and from the viewpoint of productivity, it can be, for example, 1 kg/h or more. However, if the feed rate is too high (for example, 10 kg/h or more), depending on the type of raw material powder, the powder supply may become unstable and uneven filling may occur.

The raw material powder can be, for example, silica powder or a mixed powder of silica powder and silicon nitride powder. When the silica powder is crystalline powder derived from natural quartz, the raw material powder for the opaque layer is suitably a mixed powder of silica powder and silicon nitride powder. When the silica powder is an amorphous powder, the silica powder alone may be used without using the silicon nitride powder. The method for producing the amorphous powder is not particularly limited, and it can be produced, for example, by the method (plasma melting of natural quartz powder) described in JP-A-06-287012.

Silica powder melts into quartz glass, and when silicon nitride powder is included, silicon nitride is the source of bubble formation. However, in the case of amorphous silica powder, it is possible to form air bubbles by controlling the degree of sintering of the powder itself, because melting at a temperature higher than the melting point of quartz is not necessary. The content of silicon nitride powder in the mixed powder can be appropriately determined in consideration of the desired amount of air bubbles in the opaque layer. For example, the content of silicon nitride powder in the mixed powder can range from 0.002 to 0.5% by mass. However, it is not intended to be limited to this range.

The particle size of the silica powder can be appropriately determined in consideration of the ease of filling, the size of bubbles formed during melting, and the like. For example, it can range from 10 to 500 μm, preferably from 50 to 250 μm, more preferably from 100 to 200 μm.

The particle size of the silicon nitride powder can be appropriately determined mainly by considering the size of bubbles formed during melting. For example, it can range from 0.1 to 5 μm, preferably from 0.2 to 3 μm, more preferably from 0.5 to 1.5 μm.

When the raw material powder is a mixed powder, it can be prepared by mixing silica powder and silicon nitride powder by a conventional method before filling.

(4) Heating and melting After filling the raw material powder, the multilayer structure in which the gap between the two transparent quartz glass plates of the temporary assembly was filled with the raw material powder for the opaque layer was taken out from the mold for filling the raw material powder, and then taken out. The multilayer structure is heated to melt the raw material powder. After that, it is cooled to obtain a multilayer structure quartz glass material.

After confirming the uniformity of the raw material powder layer, the multilayer structure removed from the mold can be subjected to a heating and melting process. The uniformity of the raw material powder layer can be confirmed, for example, by the method shown in FIG. 7, by measuring the variation of the transmittance of visible light within the plane of the multilayer structure.

The heating of the multilayer structure can be performed using an electric furnace, and the first transparent quartz glass plate and the second transparent quartz glass plate of the multilayer structure are heated from outside in opposite directions. It is preferable to carry out while applying a load.

For example, the multilayer structure is heated in an electric furnace to melt and foam the raw material powder. At this time, it is appropriate to apply a load from the outside of the first transparent quartz glass plate and the second transparent quartz glass plate in the direction facing each other by the weight of the upper die. This makes it possible to form an opaque layer having a thickness corresponding to the height of the spacer while suppressing the formation of large bubbles and controlling the size of the bubbles. The load applied by the weight of the upper mold can range, for example, from 1 to 20 g/cm ² . However, it is not intended to be limited to this range. During melting and foaming, the upper mold can move up and down, and an opaque layer can be easily formed with a volume (thickness) corresponding to the weight of the upper mold and the filling amount and composition of the raw material powder.

The heating temperature in the electric furnace may be any condition as long as the raw material powder can be melted and foamed. The heating and melting time is not particularly limited, and can be appropriately determined in consideration of the heating temperature and foaming conditions. For example, it can be determined appropriately within the range of 10 minutes to 6 hours.

More specifically, the heat treatment conditions in the high-temperature vacuum furnace are 1,500 to 1,650°C (in the case of amorphous powder) or 1,700 to 1,850°C (in the case of crystalline powder), 15 minutes to 3 hours, molding load: An opaque quartz glass layer is synthesized by heat treatment in a nitrogen atmosphere at 10 to 20 g/cm ² , and a transparent quartz glass plate is welded at the same time to manufacture a multi-layered quartz glass material.

In the multilayered silica glass material obtained by the manufacturing method of the present invention, the apparent density of the opaque silica glass layer can be 2.0 g/cm ³ or less. When the apparent density is 2.0 g/cm ³ or less, the thermal conductivity of the opaque quartz glass layer can be made a desired low value (for example, 1.2 W/(m·K) or less at 500° C.). The apparent density of the opaque silica glass layer is preferably 0.7 or more and 1.7 g/cm ³ or less from the viewpoint of obtaining a lower thermal conductivity. An opaque quartz glass layer having an apparent density within this range contains fine bubbles dispersed in the quartz glass in a sufficient amount and not too large. When the apparent density is within this range, the thermal conductivity at 500°C can be 1.1 W/(m·K) or less. The thermal conductivity at 500°C is preferably 0.2 or more and 1.1 W/(m·K) or less.

Hereinafter, the present invention will be described in more detail based on examples. However, the examples are illustrative of the present invention, and the present invention is not intended to be limited to the examples.

Example 1
1) Temporary assembly material and setting process ・For the transparent quartz glass plate material, a cylindrical ingot or a rectangular parallelepiped ingot was cut and processed into a plate. In this example, a disk-shaped transparent glass plate (φ=300 mm, t=1 mm) was produced from a cylindrical ingot.
- A spacer was attached between two transparent glass plates, and the transparent glass plates were pasted together to form a temporary assembly having a space for filling the mixed powder.
・The spacer has a structure in which a base material (quartz glass) is laminated with polymer materials on both sides.
- The thickness of the spacer was adjusted by adjusting the thickness of the base material and the thickness of the polymer material so that the opaque layer had a set thickness after the heat treatment. In this embodiment, it is set to 5 mm.

- This temporary assembly was set in a powder-filled mold consisting of a lower mold provided with a sealing material shown in Fig. 3, as shown in Fig. 4.
- The powder filling mold was provided with a supply port for the prepared powder in one direction, the three directions of the temporary assembly material were sealed with sealing materials attached to the filling mold, and the upper mold was fixed as shown in FIG.

2) Mixed powder filling step As the mixed powder, a mixture of natural quartz powder and 0.06 wt% silicon nitride powder was used.
・As shown in Fig. 6, the powder filling device consists of a hopper for putting the prepared powder, a valve, a vibrating feeder (with a trough), an inclined table and a vibrating table.
- The angle of the tilting table 80 was fixed at a set angle (45° in this embodiment), and the bottom thereof was vibrated by the vibrating table 81 to fill the prepared powder while preventing clogging.
・Fixing the filling mold on an inclined table, activating the vibration table at the bottom, it was possible to continuously and stably supply the mixed powder from the vibration feeder while spreading it evenly.
Vibration frequency of vibration table 81: about 120 Hz
Preparation powder supply time: about 40 minutes Preparation powder supply amount: about 700 g

- After finishing supplying the mixed powder to the filling mold, the upper mold of the filling mold was removed, and the temporary assembled material filled with the mixed powder was taken out. The filled state of the mixed powder in the taken out temporary assembly was observed and confirmed.
・Fig. 7 shows a method for confirming the uniformity of the filling state. A green laser light source was placed on the back side of the powder-filled temporary assembly, and a photodiode for light intensity measurement was installed on the front side. The uniformity of the filling state was evaluated by measuring the distribution.
・The uniformity of the filling state was evaluated by the amount of deviation from the average value of the light amount, which was set to 100.
・Table 1 shows an example of the light amount difference when filled under various conditions. The light amount difference means the difference between the maximum value and the minimum value when the average value is 100. It was confirmed that if the light amount difference is less than 10 (conditions 1 and 2), there is no problem in the uniformity of quality after vitrification. Condition 1 is the filling condition of this embodiment.

3) Heat treatment process ・The temporary assembly was set in the mold for heat treatment.
・At 500°C or higher, the spacer polymeric material and the adhesive of the temporary assembly were thermally decomposed, and the heat treatment progressed while the transparent quartz glass of the 1st and 3rd layers and the mixed powder were in contact with each other.
・In this example, the heat treatment was performed in a high-temperature vacuum furnace at 1,750° C. for 15 minutes.

Example 2
A transparent glass plate material was produced in the same manner as in Example 1 except that the transparent quartz glass plate material was ring-shaped (outer diameter=300 mm, inner diameter=200 mm, t=1 mm). Furthermore, in the same manner as in Example 1, a multi-layered silica glass material was manufactured through the blended powder filling process and the heat treatment process. Table 2 shows the results of measuring the apparent specific gravity, thermal conductivity, and infrared transmittance of the obtained multilayer structure quartz glass material.

Example 3 and Comparative Example 1
A multilayer structure quartz glass material was produced in the same manner as in Example 1 except that the raw material powder and the heat treatment conditions were changed to the conditions shown in Table 1. Example 3 and Comparative Example 1 were produced. The apparent specific gravity, thermal conductivity, and infrared transmittance of the obtained multilayer structure quartz glass material were measured. Table 2 shows the results. In Comparative Example 1, since the heat treatment time was too long, vitrification progressed, and desired physical property values could not be obtained.

Examples 4 and 5
A multi-layered quartz glass material was produced in the same manner as in Example 1, except that an amorphous powder obtained by plasma-melting natural quartz powder was used as the raw material powder, and the treatment was performed under the heat treatment conditions shown in Table 2. Table 2 shows the results of measuring the apparent specific gravity, thermal conductivity, and infrared transmittance of the obtained multilayer structure quartz glass material.

[Evaluation method]
(apparent density)
A sample for evaluation of 30 mm×30 mm was cut out from the manufactured multilayer structure quartz glass material, dried, and the total weight was weighed. The length, width and thickness of the sample were measured using vernier calipers. The thicknesses of the first layer, the second layer, and the third layer were measured on the cut cross section with a microscope.

Density of transparent quartz glass = 2.2 g/cm ³
Weight of transparent layer g = length cm x width cm x (first layer thickness + second layer thickness) cm x 2.2 g/ ^cm3
Volume of opaque layer ^cm3 : length cm x width cm x second layer thickness cm
Apparent density of opaque layer g/cm ³ : (total weight - weight of transparent layer) g/volume cm ³ of opaque layer

(Thermal conductivity)
From the opaque layer, samples for evaluation with a diameter of 10 mm and a thickness of 1 mm were machined. Thermal diffusivity is measured according to JISR1611, and thermal conductivity at 500°C is calculated.
Thermal conductivity W/(m・K) = Thermal diffusivity heat m ² /s × density kg/m ³ × specific heat J/(kg・K)

(Transmittance)
The opaque layer was processed to a thickness of 2 mm, and the transmittance in the infrared region (wavelength 1 to 3 μm) was measured using UV-3150 manufactured by Shimadzu Corporation.

From the results shown in Table 1, it can be seen that there are no particular restrictions on the heat treatment conditions, and the heat treatment can be performed under appropriate conditions depending on the physical properties and size of the powder to be used.

・When using natural quartz powder, add silicon nitride to the quartz powder to generate air bubbles. Addition concentration is adjusted to achieve the required density. 0.05-0.15wt% based on the weight of quartz powder. The appropriate heat treatment temperature is 1,700 to 1,850°C. If the temperature is low, it will take a long time. If the temperature is high, the bubbles will grow.

・When fused silica powder is used, no additives are required because bubbles remain at the grain boundaries during the sintering process, similar to the sintering mechanism of ceramics. The appropriate heat treatment temperature is 1,500 to 1,650°C. If the treatment temperature is low, the treatment time will be long, resulting in poor productivity. If the time is high, the time can be shortened, but the melting is accelerated and the control of residual bubbles becomes difficult.

It is useful in fields related to materials used in manufacturing parts for semiconductors.

Claims (12)

(1) Forming a temporary assembly in which the first transparent quartz glass plate and the second transparent quartz glass plate are supported via spacers so that the opposing surfaces of the transparent quartz glass plate and the second transparent quartz glass plate are substantially parallel at a predetermined interval,
(2) A sealing material having a raw material powder input portion is placed on the outer periphery of the formed temporary assembly material, and the temporary assembly material and the sealing material are sandwiched between a lower mold and an upper mold from above and below to form a mold for filling the raw material powder. to form
(3) In the space between the first transparent quartz glass plate and the second transparent quartz glass plate of the temporary assembled material in the inclined mold, the raw material powder input portion of the sealing material is positioned substantially above. , while continuously or intermittently vibrating the mold, the raw material powder for the opaque layer is continuously or intermittently filled to prepare a multilayer structure having a raw material powder layer between two glass plates;
(4) Taking out the multilayer structure from the temporary assembly, heating the taken-out multilayer structure to melt the raw material powder, and then cooling to obtain an opaque quartz glass layer having an apparent density of 2.0 g/cm ³ or less. obtaining a multilayered quartz glass material having
A method for manufacturing a multilayer structure quartz glass material, comprising: 2. The manufacturing method according to claim 1, wherein when the planar shape of the temporary assembled material is ring-shaped, the casting mold for filling the raw material powder is provided with a sealing member for sealing the inner peripheral edge of the ring of the temporary assembled material. 3. The manufacturing method according to claim 1 or 2, wherein the spacer has a multilayer structure of heat resistant material and combustible material. The manufacturing method according to any one of claims 1 to 3, wherein the inclination angle of the mold is in the range of 20 to 70°. The manufacturing method according to any one of claims 1 to 4, wherein the filling of the raw material powder is performed using a vibrating feeder. The manufacturing method according to any one of claims 1 to 5, wherein the multilayer structure removed from the temporary assembly is subjected to a heating and melting step after confirming the uniformity of the raw material powder layer. The production method according to any one of claims 1 to 6, wherein the raw material powder is silica powder or a mixed powder of silica powder and silicon nitride powder. 8. The multi-layer structure according to any one of claims 1 to 7, wherein the heating of the multi-layer structure is performed while a load is applied from outside the first transparent quartz glass plate and the second transparent quartz glass plate of the multi-layer structure in opposing directions. Production method. The manufacturing method according to any one of claims 1 to 8, wherein the multilayer structure is heated using an electric furnace. The manufacturing method according to any one of claims 1 to 9, wherein the planar shapes of the first transparent quartz glass plate and the second transparent quartz glass plate are rectangular, circular, or ring-shaped. 11. The manufacturing method according to claim 10, wherein the planar shape of the first transparent quartz glass plate and the second transparent quartz glass plate is ring-shaped, and a temporary assembly is used in which the inner periphery between the two glass plates is sealed. The manufacturing method according to any one of claims 1 to 11 , wherein the multilayer structure quartz glass material has a thermal conductivity of 1.1 W/(m·K) or less at 500°C.

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