JP6162052B2 - Method for producing quartz glass crucible - Google Patents

Description

The present invention relates to the manufacture how the quartz glass crucible, for producing how the quartz glass crucible for use in particularly a silicon single crystal pulling.

A quartz glass crucible used for pulling a silicon single crystal by the Czochralski method (CZ method) is generated from an electrode placed around the axis of the mold against a molded body made of quartz powder formed in a crucible shape in the mold. It is manufactured by heating and melting by arc discharge.
As shown in FIG. 5A, generally, the crucible manufacturing apparatus 50 includes a crucible forming die 51 that is rotatably provided around a shaft by a rotating mechanism 55, and a center axis C of the forming die 51 above the crucible forming die 51. A plurality of (for example, three) straight rod-like carbon electrodes 52 (52a, 52b, 52c) arranged at intervals are provided.

  The carbon electrode 52 can be moved up and down by a lifting mechanism (not shown), and the tip portions 52 a 1, 52 b 1 and 52 c 1 are respectively directed to the central axis C of the lower mold 51. More specifically, as shown in FIG. 5 (b), the tip portions 52a1, 52b1, and 52c1 of the carbon electrode 52 are positioned on concentric circles (indicated by a one-dot chain line in the drawing) centered on the central axis C. It is arranged in a ring shape.

In such a crucible manufacturing apparatus 50, quartz powder is supplied into the crucible forming mold 51, the crucible forming mold 51 is rotated by the rotation mechanism 55, and the quartz powder is solidified on the inner peripheral surface of the forming mold 51 by centrifugal force. Thus, the molded body P is molded.
Next, after the carbon electrode 52 located above the crucible mold 51 is lowered and inserted into the crucible mold 51, arc discharge is started between the three electrodes.
The formed body P is melted by the heat generated by the arc discharge, and a quartz glass crucible is formed in the crucible mold 51.

By the way, as described above, the carbon electrode for generating the arc discharge has been mainly arranged in a ring shape as described above. However, in recent years, as the diameter of the quartz glass crucible is increased, the number of the three carbon electrodes is increased. In the electrode 52, the distance to the body portion P1 of the molded body P was too far, and there was a problem that it could not be heated and melted sufficiently. Further, if the distance between the tips of the electrodes 52, that is, the distance between the tip portions 52a1, 52b1, and 52c1 is increased in order to expand the heating range, there is a problem that the arc is easily cut and is not stable.
In order to deal with such a problem, in Patent Document 1, the number of carbon electrodes 52 is increased to, for example, six, and the tips of these electrodes are arranged in a ring shape so as to be located on a concentric circle centering on the crucible central axis C. A configuration has been proposed.
Thus, by increasing the number of carbon electrodes 52, the diameter of the ring formed by the electrodes increases and the distance between adjacent electrodes decreases, so that stable arc discharge is maintained and the inside of the body of the molded body is maintained. It can be sufficiently heated and melted with respect to the peripheral surface.

JP 2003-335532 A

  However, when the number of the carbon electrodes 52 is increased as described above and arranged in a ring shape so that the tip portions thereof are concentrically arranged, even if the tip portions of the electrodes are closed as much as possible, Since the formed ring has a large diameter, the amount of heat at the center thereof is lowered, and there is a problem that the bottom region P2 (see FIG. 5A) of the crucible molded body P cannot be sufficiently heated.

In addition, before heating and melting by arc discharge, the inner surface layer of the crucible molded body P is contaminated with impurities such as alkali metal and SUS metal during molding in the furnace atmosphere or molding, but most of them are vaporized (evaporated) by heating and melting. ) And discharged outside the furnace.
However, if the bottom region P2 of the crucible molded body P cannot be heated sufficiently, the amount of vaporization at the bottom of the crucible decreases, and the impurities contained therein are concentrated, resulting in an increase in the amount of contamination on the surface layer.
Furthermore, when the tip portions of many carbon electrodes are arranged in a ring shape so as to be positioned concentrically, a large space portion that penetrates vertically is formed at the center thereof, and the amount of heat at the center portion is reduced as described above. Therefore, when the particles in the furnace pass through the space during heating and melting, there is a problem that the particles cannot be burned and adhere to the bottom region P2 of the crucible molded body P to be contaminated.

The present invention has been made under the circumstances as described above. In the method for producing a silica glass crucible, the entire crucible can be sufficiently heated and melted regardless of the size of the crucible, and the amount of contamination of the crucible. An object of the present invention is to provide a method for producing a quartz glass crucible capable of reducing the above.

A method for producing a quartz glass crucible according to the present invention, which has been made to solve the above problems,
A method for producing a quartz glass crucible in which quartz powder is supplied to a crucible mold, the crucible mold is rotated around an axis to form a molded body, and the molded body is melted by arc discharge to form a quartz glass crucible. The first electrode group consisting of a plurality of electrodes is arranged in a ring shape around the central axis of the crucible mold, and the tip portion is inserted into the crucible mold to cause arc discharge between adjacent electrodes. An angle formed between the center electrode of the crucible mold and the two adjacent electrodes in the first electrode group is the difference between the center axis of the crucible mold and the other two adjacent electrodes. The second electrode group consisting of a plurality of electrodes provided so as to be able to move up and down selected to be equal to the angle formed is lowered, and the tip of the second electrode group is made to be closer to the central axis side of the crucible mold Arrangement, and characterized in that comprising the step of performing arc discharge by adjacent electrodes each other.
The first electrode group is composed of six electrodes, and the second electrode group is composed of the first electrode group and two adjacent electrodes that are one adjacent to the central axis of the crucible mold. It is preferable that the formed angle is composed of three electrodes arranged so as to be movable up and down so that the angle formed by the central axis of the crucible mold and the other two adjacent electrodes is the same.
Further, in the step of lowering the second electrode group and disposing the tips of the second electrode group closer to the central axis side of the crucible mold and performing arc discharge between adjacent electrodes, a plurality of electrodes remaining in the upper position Stop arc discharge caused by.
Moreover, it is preferable that the absolute value of the phase difference of an alternating current is 120 degrees between adjacent electrodes.

According to such a method, regardless of the size of the crucible, arc discharge between the carbon electrodes can be generated not only in the vicinity of the straight body portion of the crucible molded body but also in the vicinity of the bottom portion, It can be sufficiently melted by the atmosphere.
Therefore, the contamination layer on the inner surface of the entire crucible can be baked to remove the contamination.

According to the present invention, in the method for producing a silica glass crucible, the entire crucible can be sufficiently heated and melted regardless of the size of the crucible, and the amount of contamination of silicon contained and melted inside the crucible is reduced. A method for producing a vitreous silica crucible can be obtained.

FIG. 1 is a cross-sectional view showing a partial configuration of a manufacturing apparatus capable of performing the method for manufacturing a silica glass crucible according to the present invention. 2A and 2B are plan views showing the arrangement of the tip portions of the electrodes provided in the manufacturing apparatus of FIG. FIG. 3 is a cross-sectional view showing the arrangement of electrodes when arc discharge is performed with six electrodes in the manufacturing apparatus of FIG. 1. FIG. 4 is a cross-sectional view showing the arrangement of electrodes when arc discharge is performed with three electrodes in the manufacturing apparatus of FIG. 1. FIG. 5 is a cross-sectional view for explaining a conventional quartz glass crucible manufacturing apparatus.

Hereinafter, an embodiment of a method for producing a silica glass crucible according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a partial configuration of a manufacturing apparatus in which a method for manufacturing a quartz glass crucible according to the present invention is implemented.
This quartz glass crucible manufacturing apparatus 1 (hereinafter referred to as a crucible manufacturing apparatus 1) includes a crucible forming mold 2 that is rotatably provided on a support shaft 9 in a furnace body 11, and the crucible forming mold 2 is connected to a support shaft. And a rotation driving device 10 that rotates around the axis via 9.

Further, a plurality (six in the figure) of straight rod-like carbon electrodes 3 (electrodes) are provided above the crucible mold 2 so as to be movable up and down. These six carbon electrodes 3 are arranged in a state where tip portions 3a1, 3b1, 3c1, 3d1, 3e1, and 3f1 directed downward are inclined at a predetermined angle toward the central axis C (that is, inverted conical shapes). Yes.
Further, as shown in FIG. 2A, at the basic position, the tip portions 3a1, 3b1, 3c1, 3d1, 3e1, 3f1 of the six electrodes 3 are concentric circles (indicated by a one-dot chain line) centered on the central axis C. ) It is arranged at regular intervals in a ring shape so as to be positioned above. That is, the tip portions 3a1, 3b1, 3c1, 3d1, 3e1, 3f1 are arranged at the vertices of a regular hexagon, and a first electrode group composed of six carbon electrodes 3 is formed.
Adjacent electrodes 3 have different phases of alternating current when energized, and the absolute value of the phase difference is set to 120 °. Thereby, an arc discharge is generated between the adjacent electrodes 3.

The six carbon electrodes 3 can be moved back and forth with respect to the crucible mold 2 by moving up and down. That is, the horizontal frame 4c is suspended between a pair of vertical frames 4a and 4b which are erected in parallel, and the six carbon electrodes 3 are held on the horizontal frame 4c along the vertical frames 4a and 4b. It is designed to move up and down.
Specifically, the vertical frames 4a and 4b are suspended from the ceiling 11a of the furnace body 11 that accommodates the entire apparatus, and the horizontal frame 4c is moved up and down along the vertical frames 4a and 4b via wires 12. It is supposed to move. The wire 12 is configured to be wound and fed out by a motor-driven wire winding device 13 provided on the ceiling portion 11a.

  Further, out of the six carbon electrodes 3, three carbon electrodes 3a, 3b, 3c arranged every other one are fixed to the horizontal frame 4c, and the remaining three carbon electrodes 3a, 3b, 3c are arranged. The carbon electrodes 3d, 3e, and 3f can be further moved up and down by a lift drive unit 5 provided on the horizontal frame 4c. That is, the three carbon electrodes 3d, 3e, and 3f are configured to move up and down in two stages.

More specifically, as shown in FIG. 2B, the three carbon electrodes 3d, 3e, 3f (tip portions 3d1, 3e1, 3f1) are adjacent to the central axis C of the crucible mold. The angle θ1 formed by the two matching electrodes is selected to be the same as the angles θ2 and θ3 formed by the central axis C of the crucible mold and the other two adjacent electrodes, that is, the six carbons It is selected so as to be evenly arranged without being biased from the electrode 3.
The three carbon electrodes 3d, 3e, 3f are configured to be movable up and down, and the three carbon electrodes 3d, 3e, 3f are moved up and down at the same timing along the electrode axis while maintaining the inclined state. It is provided to do.
When these carbon electrodes 3d, 3e, 3f are at the highest position by the elevating drive unit 5, as shown in FIG. 3, the heights of the tips 3a1, 3b1, 3c1, 3d1, 3e1, 3f1 of the six carbon electrodes 3 are increased. Are the same (that is, the basic position) (the arrangement of the tip portion in plan view is as shown in FIG. 2A).

On the other hand, when the carbon electrodes 3d, 3e, 3f are at the lowest position, the tip portions 3d1, 3e1, 3f1 are disposed below the three carbon electrodes 3a, 3b, 3c as shown in FIG. As the portion approaches the central axis C, the distance between the tip portions becomes closer (the arrangement of the tip portions is as shown in FIG. 2B in plan view).
At this time, as shown in FIG. 2B, the carbon electrodes 3d, 3e, 3f have tip portions 3d1, 3e1, 3f1 in the inner region closer to the central axis C than the carbon electrodes 3a, 3b, 3c. It arrange | positions at equal intervals in a ring shape so that it may be located on the concentric circle (it shows with a dashed-dotted line) centering on the central axis C. FIG. That is, the tip portions 3d1, 3e1, and 3f1 are arranged at the vertices of an equilateral triangle to form a second electrode group.
In the carbon electrodes 3d, 3e, and 3f, in order to cause arc discharge between the adjacent electrodes, the absolute value of the phase difference between the adjacent electrodes is preferably 120 °.

The crucible molding die 2 has a holding body 7 and a carbon mold 8 housed in the holding body 7, and is supported by the rotation driving device 10 via a rotating shaft 9 provided on the holding body 7. ing.
Quartz raw material powder is supplied into the carbon mold 8 of the crucible mold 2, and the rotation driving device 10 rotates the crucible molding mold 2 to solidify the quartz raw material powder on the inner peripheral surface of the carbon mold 8. The body P is molded.

Next, a process for manufacturing a quartz glass crucible in the quartz glass crucible manufacturing apparatus 1 configured as described above will be described.
First, quartz raw material powder is supplied from a raw material powder supply device (not shown) to the crucible mold 2, and the quartz raw material powder is crucible-shaped by a forming jig (not shown) while rotating the crucible forming die 2 by the rotation drive device 10. Molded into molded body P.

Next, the crucible molding die 2 is disposed immediately below the six carbon electrodes 3. In addition, the six carbon electrodes 3 are arranged adjacent to each other by forming a first electrode group with the mutual positional relationship being a basic position (that is, the state shown in FIGS. 2A and 3) and being energized. Arc discharge is started between the electrodes 3.
When the arc is stabilized after a predetermined time has elapsed from the start of the arc discharge, the wire take-up device 13 is operated to lower the horizontal frame 4c, and the tips of the six carbon electrodes 3 in which the arc is in a stable state are inserted into the crucible mold 2 Insert inside.
Here, when the carbon electrode 3 is inserted into the crucible mold 2, in the first stage, the six arrangements have the same height as shown in FIG. 3 and as shown in FIG. The tip portions 3a1, 3b1, 3c1, 3d1, 3e1, and 3f1 are arranged at the apexes of a regular hexagon. In the six carbon electrodes 3, arc discharge is performed between adjacent electrodes, and the body P1 of the molded body P is melted in a high-temperature atmosphere to form a transparent layer.

When a predetermined time elapses in the state of the first stage, among the six carbon electrodes 3, the angle θ1 formed by the center axis C of the crucible mold and two adjacent electrodes is the crucible mold. The three carbon electrodes 3d, 3e, and 3f selected so as to be equal to the angles θ2 and θ3 formed by the central axis C of the other two adjacent electrodes are lowered by the elevating drive unit 5 to be the second An electrode group is formed and the process proceeds to the second stage.
That is, as shown in FIG. 4, the tip portions 3d1, 3e1, 3f1 of the three carbon electrodes 3d, 3e, 3f are arranged at a lower position, and as shown in FIG. Arranged in the vicinity of the axis C.
Then, in the carbon electrodes 3d, 3e, and 3f, an arc discharge occurs between the adjacent electrodes when energized, and the bottom region P2 of the molded body P is melted in a high-temperature atmosphere to form an opaque layer. At this time, the driving of the upper carbon electrodes 3a, 3b, and 3c is stopped, and thereby consumption of the electrodes can be suppressed.
Thus, when the trunk | drum P1 and bottom part area | region P2 of the crucible molded object P are fuse | melted, the contamination layer of the surface of the whole crucible will be vaporized and the quartz glass crucible of the state from which contamination was removed will be manufactured.

  As described above, according to the embodiment of the present invention, arc discharge between the carbon electrodes can be generated not only in the vicinity of the body portion P1 of the crucible molded body P but also in the vicinity of the bottom region P2, and the entire crucible Can be sufficiently heated and melted. Therefore, the contamination layer on the entire surface of the crucible can be vaporized to remove the contamination.

In the above-described embodiment, the carbon electrodes 3d, 3e, and 3f out of the six carbon electrodes 3 are configured to move downward with respect to the carbon electrodes 3a, 3b, and 3c. , 3c may also be configured to be movable downward relative to the carbon electrodes 3d, 3e, 3f by a lift drive unit (not shown).
By configuring in this way, every time the quartz glass crucible is manufactured, the carbon electrodes 3 constituting the second electrode group to be controlled to be lowered can be alternately switched, and uneven wear of the carbon electrodes 3 can be suppressed. Can do.

  In the above embodiment, the first electrode group has six electrodes and the second electrode group has three electrodes. However, the number of electrodes is not limited. One electrode group may be composed of eight electrodes, and the second electrode group may be composed of four electrodes.

About the method for manufacturing a silica glass crucible according to the present invention will be further described based on examples. In this example, a quartz glass crucible was manufactured using the quartz glass crucible manufacturing apparatus described in the above embodiment, and verification was performed based on the obtained quartz glass crucible.

[Example 1]
In Example 1, the quartz glass crucible manufacturing apparatus shown in FIG. 1 was used, and the carbon electrodes 3d, 3e, 3f were lowered as shown in FIG. 4 (that is, the state shown in FIG. 2B). The bottom of the crucible was heated and melted, and the impurity concentration (wt · ppb) at the center of the bottom of the obtained silica glass crucible was measured.
The manufactured quartz glass crucible had a diameter of 36 inches, and the measured area of the bottom of the crucible was an area having a diameter of 180 cm including the center of the bottom.

[Comparative Example 1]
In Comparative Example 1, the three carbon electrodes are arranged so that the tips of the carbon electrodes are positioned at the vertices of an equilateral triangle (that is, only the carbon electrodes 3d, 3e, and 3f in the arrangement shown in FIG. 2B) and the arc. The bottom of the crucible was heated and melted by discharge, and the impurity concentration (wt · ppb) at the center of the bottom of the obtained quartz glass crucible was measured.
The manufactured quartz glass crucible had a diameter of 36 inches, and the measured area of the bottom of the crucible was an area having a diameter of 180 cm including the center of the bottom.

[Comparative Example 2]
In Comparative Example 2, it was obtained by arranging the tip portions of the six carbon electrodes so as to be positioned at the vertices of a regular hexagon as shown in FIG. 2 (a), and in this state, the bottom of the crucible was heated and melted by arc discharge. The impurity concentration (wt · ppb) at the bottom center of the quartz glass crucible was measured.
The manufactured quartz glass crucible had a diameter of 36 inches, and the measured area of the bottom of the crucible was an area having a diameter of 180 mm including the center of the bottom.
Table 1 shows the results of Example 1 and Comparative Examples 1 and 2.

As a result of Example 1, it was confirmed that impurities were vaporized in substantially the same manner as Comparative Example 1.
From the results of the above examples, according to the present invention, even with a large silica glass crucible such as 36 inches, the entire crucible can be sufficiently heated, and in particular, the amount of contamination at the bottom of the crucible can be reduced. confirmed.

1 Manufacturing equipment for quartz glass crucible 2 Crucible mold 3 Carbon electrode (electrode)
4a Vertical frame 4b Vertical frame 4c Horizontal frame 5 Lifting drive unit 7 Holding body 8 Carbon mold 9 Rotating shaft 10 Rotating drive device 11 Furnace body 12 Wire 13 Wire take-up device C Center shaft P Molded body θ1, θ2, θ3 Crucible mold The angle between the center axis of the electrode and two adjacent electrodes

Claims (4)

A method for producing a quartz glass crucible in which quartz powder is supplied to a crucible mold, the crucible mold is rotated around an axis to form a molded body, and the molded body is melted by arc discharge to form a quartz glass crucible. Because
Arranging a first electrode group composed of a plurality of electrodes around the central axis of the crucible mold in a ring shape, inserting a tip portion into the crucible mold, and performing arc discharge between adjacent electrodes;
In the first electrode group, an angle formed between the central axis of the crucible mold and two adjacent electrodes is the same as an angle formed between the central axis of the crucible mold and the other two adjacent electrodes. And lowering the second electrode group composed of a plurality of electrodes provided so as to be able to move up and down, and disposing their tip portions closer to the central axis side of the crucible molding die, And a step of performing arc discharge by the method of manufacturing a quartz glass crucible.   The first electrode group is composed of six electrodes, and the second electrode group is an angle formed by two adjacent electrodes, one of the first electrode group and the central axis of the crucible mold. Is composed of three electrodes arranged so as to be movable up and down so as to be the same as the angle formed by the central axis of the crucible mold and the other two adjacent electrodes. A method for producing a quartz glass crucible described in 1. In the step of lowering the second electrode group, disposing the tip of the second electrode group on the central axis side of the crucible mold, and performing arc discharge between adjacent electrodes,
The method for producing a quartz glass crucible according to claim 1 or 2, wherein arc discharge by a plurality of electrodes remaining in an upper position is stopped.   The method for producing a quartz glass crucible according to any one of claims 1 to 3, wherein an absolute value of a phase difference of alternating current is 120 ° between the adjacent electrodes.

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