JP2012017246A - Method for manufacturing quartz glass crucible for raising silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a quartz glass crucible for raising silicon single crystal which controls diffusion of heat from natural quartz glass material powder, and reduces power consumption by making it easy to melt the natural quartz glass material powder.SOLUTION: The method for manufacturing a quartz glass crucible for raising silicon single crystal comprises loading the natural quartz glass raw material powder into a crucible forming mold 11, further loading synthetic silica raw material powder on the inner surface, forming a quartz packed bed 20 of two layers of a crucible shape, heating the quartz packed bed 20 from the inside by turning on electricity to a carbon electrode 19, melting the natural quartz glass raw material powder and the synthetic silica raw material powder, then cooling to form a transparency quartz glass layer in the interior side and an opaque quartz glass layer in the external side, wherein natural quartz glass raw material powder in which the particle size is 10-500 μm and the specific surface area measured by a BET method is at least 20 m/g is used as the natural quartz glass raw material powder.

Description

  The present invention relates to a method for producing a quartz glass crucible for pulling up a silicon single crystal, and relates to a method for producing a quartz glass crucible for pulling up a silicon single crystal that can reduce the amount of power consumed for producing the crucible.

  Silicon single crystals used as substrates for semiconductor devices are mainly manufactured by Czochralski (CZ method). In this method, a polycrystalline silicon raw material is loaded into a crucible, the polycrystalline silicon raw material is melted by heating the crucible from the surroundings, and the suspended seed crystal is immersed in a silicon melt and gradually pulled up. A silicon single crystal ingot is grown.

Conventionally, as shown in FIG. 1, a crucible for carrying out the CZ method described above has a transparent quartz glass layer 2 on the inner surface side and a two-layered opaque quartz glass layer 3 on the outer periphery of the transparent quartz glass layer 2. Quartz glass crucible 1 is often used.
The transparent quartz glass layer 2 of the quartz glass crucible 1 is a bubble disposed on the inner peripheral side of the crucible in order to reduce the erosion to the silicon melt as much as possible and to ensure the stability of the melt surface. This is a quartz glass layer that substantially eliminates the above. The opaque quartz glass layer 3 is a quartz glass layer that is disposed on the outer peripheral side of the crucible and in which a large number of closed pores are uniformly dispersed in order to perform uniform heat transfer to the silicon melt.

  A method for manufacturing the quartz glass crucible will be described with reference to FIG. The crucible molding die 11 of the quartz glass crucible manufacturing apparatus 10 shown in FIG. 2 is composed of a gas permeable member such as a mold having a plurality of through holes or a highly purified porous carbon mold. The inner member 12 includes a ventilation portion 13 provided on the outer periphery thereof, and a holding body 14 that holds the inner member 12.

  A rotating shaft 15 connected to a rotating means (not shown) is fixed to the lower portion of the holding body 14 and is rotatably supported together with the crucible forming die 11. The vent 13 is connected to an exhaust port 17 provided in the center of the rotary shaft 15 through an opening 16 provided in the lower part of the holding body 14. The air passage 13 is connected to a pressure reducing mechanism 18. Furthermore, a pair of carbon electrodes 19 for arc discharge are provided on the upper part facing the inner member 12.

In order to manufacture the quartz glass crucible 1 using the manufacturing apparatus 10, first, a rotational drive source (not shown) is operated to rotate the rotating shaft 15 in the direction of the arrow and to rotate the crucible molding die 11 at a high speed. Meanwhile, the quartz glass raw material powder is supplied from the upper part in the crucible molding die 11.
When the quartz glass raw material powder is loaded into the rotated crucible mold 11, first, for example, coarse natural quartz glass raw material powder is loaded, and further, for example, fine synthetic silica raw material powder is loaded on the inner surface thereof. To do.

The natural quartz glass raw material powder supplied into the crucible molding die 11 is pressed against the inner member 12 of the crucible molding die 11 by centrifugal force to form one layer.
Following this natural quartz glass raw material powder, synthetic silica raw material powder is supplied into the crucible molding die 11, and the synthetic silica raw material powder is pressed against the natural quartz glass raw material powder layer by centrifugal force to form one layer. As a whole, a two-layered quartz filling layer 20 having a crucible shape is formed.

Thereafter, the carbon electrode 19 is energized and heated from the inside of the quartz filling layer 20 almost simultaneously with the decompression by the operation of the decompression mechanism 18 in the air atmosphere, and the quartz filling layer 20 is sequentially melted from the inside.
Thereafter, by cooling, the transparent quartz glass layer 2 having substantially no bubbles is formed on the inner surface side, and the opaque quartz glass layer 3 having many bubbles is formed on the outer surface side. Thus, the double-layered quartz glass crucible 1 is manufactured.

JP 2000-169164 A

  By the way, when manufacturing a quartz glass crucible as described above, the crucible is manufactured by energizing the carbon electrode and melting the natural quartz glass raw material powder and the synthetic silica raw material powder. Today, a reduction in power consumption used for energizing the carbon electrode is required from the viewpoint of energy saving.

  The inventors of the present invention diligently studied a method for reducing the amount of electric power during the production of the quartz glass crucible, and as a result, suppressed thermal diffusion from the natural quartz glass raw material powder forming the outer layer of the crucible, The inventors have found that the power consumption can be reduced by making the powder easy to melt, and the present invention has been conceived.

  The present invention has been made in view of the above circumstances, and suppresses the diffusion of heat from the natural quartz glass raw material powder, and makes it easy to melt the natural quartz glass raw material powder. An object of the present invention is to provide a method for producing a quartz glass crucible for use.

In order to achieve the above-described object, a method for producing a silica glass crucible for pulling a silicon single crystal according to the present invention comprises loading a natural silica glass raw material powder into a crucible molding die, and further providing a synthetic silica raw material powder on the inner surface thereof. To form a crucible-shaped two-layer quartz filling layer, and to the quartz filling layer, a carbon electrode is energized and heated from the inside to melt the natural quartz glass raw material powder and the synthetic silica raw material powder. Then, in the method for producing a quartz glass crucible for pulling a silicon single crystal in which a transparent quartz glass layer is formed on the inner surface side and an opaque quartz glass layer is formed on the outer surface side, the natural quartz glass raw material powder is cooled. A natural quartz glass raw material powder having a particle size of 10 to 500 μm and a specific surface area measured by the BET method of 20 m ² / g or more is used. .

Thus, natural quartz glass raw material powder having a particle size of 10 to 500 μm and a specific surface area measured by the BET method of 20 m ² / g or more is used as the natural quartz glass raw material powder. Diffusion can be suppressed, the heat retention of the molded body can be improved, and the amount of power can be reduced.
In particular, since the natural quartz glass raw material powder forming the opaque quartz glass layer on the outer surface side of the crucible has the above transmittance, when heated from the inside, the diffusion of heat can be suppressed, and the amount of power can be reduced.
The measurement by the BET method is measured based on JIS R1626.

Here, when the particle size is 10 to 500 μm and the specific surface area measured by the BET method is 20 m ² / g or more, if it is less than 20 m ² / g, the heat rays are transmitted, the heat retention is lowered, and the heat is diffused. This is because the amount of power cannot be reduced.
The reason why the particle size is 10 to 500 μm is to make the molding and melting conditions the same as those of the prior art.

Moreover, it is desirable that the natural quartz glass raw material powder is a natural quartz glass raw material surface-treated with hydrofluoric acid.
Thus, by etching the surface with hydrofluoric acid, the specific surface area of the natural quartz glass raw material powder can be increased, and the specific surface area can be easily increased to 20 m ² / g or more.

  According to the present invention, there is provided a method for producing a quartz glass crucible for pulling a silicon single crystal that suppresses the diffusion of heat from a natural quartz glass raw material powder and reduces the amount of electric power by making the natural quartz glass raw material powder easy to melt. Obtainable.

It is a conceptual diagram which shows the structure of the quartz glass crucible for recon single crystal pulling. It is a schematic block diagram which shows the manufacturing apparatus of the quartz glass crucible for recon single crystal pulling.

The method for producing a quartz glass crucible for pulling a silicon single crystal according to the present invention is characterized in that a natural quartz glass raw material powder having a particle size of 10 to 500 μm and a specific surface area measured by the BET method of 20 m ² / g or more is used. There is a conventional method for producing a quartz glass crucible.
That is, as shown in FIG. 2, the above-described manufacturing apparatus 10 is used to operate a rotational drive source (not shown) to rotate the rotating shaft 15 in the direction of the arrow and to rotate the crucible molding die 11 at a high speed, for crucible molding. From the upper part in the mold 11, a natural quartz glass raw material powder that is characteristic is initially charged, and further, a synthetic silica raw material powder is charged on the inner surface thereof.

As this natural quartz glass raw material powder, a natural quartz glass raw material powder having a particle size of 10 to 500 μm and a specific surface area measured by the BET method of 20 m ² / g or more as described above is used. The supplied natural quartz glass raw material powder is pressed against the inner member 12 of the crucible molding die 11 by centrifugal force to form one layer.
Then, following this natural quartz glass raw material powder, synthetic silica raw material powder is supplied into the crucible molding die 11, and the synthetic silica raw material powder is pressed against the natural quartz glass raw material powder layer by centrifugal force to form one layer. As a result, a two-layer quartz filling layer 20 having a crucible shape as a whole is formed.

Thereafter, the carbon electrode 19 is energized and heated from the inside of the quartz filling layer 20 almost simultaneously with the decompression by the operation of the decompression mechanism 18 in the air atmosphere, and the quartz filling layer 20 is sequentially melted from the inside.
Thereafter, by cooling, the transparent quartz glass layer 2 having substantially no bubbles is formed on the inner surface side, and the opaque quartz glass layer 3 having many bubbles is formed on the outer surface side. Thus, the double-layered quartz glass crucible 1 is manufactured.

Thus, the heat retention of a molded object improves by using the natural quartz glass raw material powder with a large specific surface area. That is, the heat of heating by the carbon electrode 19 can be prevented from diffusing from the mold to the outside, and as a result, the amount of electric power used for energizing the carbon electrode 19 can be reduced.
In particular, since the melting temperature of the natural silica glass raw material powder is higher than the melting temperature of the synthetic silica raw material powder forming the inner layer, by setting the specific surface area, when heated by the carbon electrode from the inside, outward of the heat Can be more easily suppressed and melted easily, and the amount of power consumption can be reduced.
Moreover, by making the natural quartz glass raw material powder which forms the opaque quartz glass layer arrange | positioned in the outer surface side of a crucible into the said specific surface area, the spreading | diffusion of heat outside can be suppressed more and electric energy can be reduced.

Next, the manufacturing method of the natural quartz glass raw material powder whose specific surface area measured by BET method is 20 m < ² > / g or more is demonstrated.
Natural quartz glass raw material powder usually has a specific surface area measured by the BET method of less than 20 m ² / g. Therefore, in order to increase the specific surface area, the surface of natural quartz glass raw material powder is etched with hydrofluoric acid.

The etching process using hydrofluoric acid is performed as follows.
First, pure water is used to remove dust and impurities that can be removed with water contained in the natural quartz glass raw material powder. Next, in order to remove the organic substance contained in the natural quartz glass raw material powder, it is cleaned using ozone water or a surfactant. The washed natural quartz glass raw material powder was immersed in hydrofluoric acid having a concentration of 50 wt% or more and a temperature of 40 ° C. for 2 hours or more. Finally, it was rinsed with pure water.

  Fine irregularities are formed on the surface of the natural quartz glass particles by the etching treatment of the natural quartz glass raw material powder with hydrofluoric acid. Light is diffusely reflected by the fine unevenness, and the transmittance is lowered. Moreover, since this natural quartz glass raw material powder is arranged outside the crucible (crucible type side), the heat that has passed through the synthetic silica raw material powder arranged inside is reflected inward, and the heat is diffused outward. Is suppressed.

Example 1
The washed natural quartz glass raw material powder was immersed in hydrofluoric acid having a concentration of 50 wt% for 2 hours. Thereafter, the natural quartz glass raw material powder was washed, and the specific surface area was measured by a BET method by nitrogen gas adsorption using a specific surface area measuring device.
As a result of this measurement, the specific surface area by the BET method was 30 m ² / g.

Then, using the manufacturing apparatus 10 shown in FIG. 2, first, coarse natural quartz glass raw material powder is loaded from the upper part in the crucible forming die 11 while rotating the crucible forming die 11 at a high speed. Further, a fine synthetic silica raw material powder was loaded on the inner surface thereof to form two crucible-shaped quartz packed layers 20. Thereafter, the carbon electrode 19 was energized and heated and melted from the inside of the quartz packed layer 20 almost simultaneously with the decompression by the operation of the decompression mechanism 18 in the air atmosphere. Thereafter, it was cooled to produce a quartz glass crucible 1 having a double layer structure in which a transparent quartz glass layer 2 was formed on the inner surface side and an opaque quartz glass layer 3 was formed on the outer surface side.
Thirty quartz glass crucibles were produced, and the average power consumption at that time was 352 kwh.

(Example 2)
Natural quartz glass raw material powder was immersed in hydrofluoric acid having a concentration of 60 wt% for 3 hours. Thereafter, the natural quartz glass raw material powder was washed, and the specific surface area was measured using a specific surface area measuring device.
As a result of this measurement, the specific surface area determined by the BET method was 50 m ² / g. A quartz glass crucible 1 having a double layer structure was produced under the same conditions as in Example 1.
Thirty quartz glass crucibles were produced, and the average power consumption at that time was 343 kwh.

(Comparative Example 1)
The specific surface area was measured using a specific surface area measuring apparatus without subjecting the natural quartz glass raw material powder to surface etching. As a result of this measurement, the specific surface area was 2 m ² / g.
A quartz glass crucible 1 having a double layer structure was produced under the same conditions as in Example 1.
30 quartz glass crucibles were manufactured, and the average power consumption at that time was 365 kwh.

(Comparative Example 2)
Natural quartz glass raw material powder was immersed in hydrofluoric acid having a concentration of 50 wt% for 1 hour. Thereafter, the natural quartz glass raw material powder was washed, and the light transmittance was measured using a transmittance measuring device.
As a result of this measurement, the specific surface area was 10 m ² / g. A quartz glass crucible 1 having a double layer structure was produced under the same conditions as in Example 1.
Thirty quartz glass crucibles were produced, and the average power consumption at that time was 360 kwh.

  As can be seen from the results of Examples 1 and 2 and Comparative Examples 1 and 2, the amount of power used (power consumption) can be reduced, and the energy saving effect was confirmed.

DESCRIPTION OF SYMBOLS 1 Quartz glass crucible 2 Transparent quartz glass layer 3 Opaque quartz glass layer 10 Quartz glass crucible manufacturing apparatus 11 Crucible mold 12 Inner member 13 Ventilation part 14 Holding body 15 Rotating shaft 16 Opening part 17 Exhaust port 18 Decompression mechanism 19 Carbon electrode 20 Quartz packed bed

(Comparative Example 2)
Natural quartz glass raw material powder was immersed in hydrofluoric acid having a concentration of 50 wt% for 1 hour. Thereafter, the natural quartz glass raw material powder was washed, and the specific surface area was measured using a specific surface area measuring device.
As a result of this measurement, the specific surface area was 10 m ² / g. A quartz glass crucible 1 having a double layer structure was produced under the same conditions as in Example 1.
Thirty quartz glass crucibles were produced, and the average power consumption at that time was 360 kwh.

Claims (2)

Natural quartz glass raw material powder is loaded into a crucible molding die, and further, synthetic silica raw material powder is loaded on its inner surface to form two crucible-shaped quartz packed layers. The electrode is energized and heated from the inside, the natural quartz glass raw material powder and the synthetic silica raw material powder are melted, then cooled, a transparent quartz glass layer is formed on the inner surface side, and an opaque quartz glass layer is formed on the outer surface side. In the method for producing a quartz glass crucible for pulling up a silicon single crystal to be formed,
A quartz for pulling a silicon single crystal, characterized in that a natural quartz glass raw material powder having a particle size of 10 to 500 μm and a specific surface area measured by the BET method of 20 m ² / g or more is used as the natural quartz glass raw material powder. A method for producing a glass crucible.   2. The method for producing a quartz glass crucible for pulling a silicon single crystal according to claim 1, wherein the natural quartz glass raw material powder is a natural quartz glass raw material powder surface-treated with hydrofluoric acid.

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