JPH09208367A - Initial charging of silicon material into double-layered crucible - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the productivity of silicon single crystal by inhibiting the initial deterioration of the inner crucible causing the crystal defect of a silicon single crystal. SOLUTION: An initial silicone raw material is charged in a double layered crucible which comprises an outer crucible and an inner crucible in which they communicate with each other through fine through-holes bored on the wall of the inner crucible. At this time, the initial silicon raw material is fed only to the outer crucible and fed to the inner crucible through the holes bored on the inner crucible.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the production of a silicon single crystal by a pulling method (Czochralski method, CZ method), while supplying a silicon raw material to a silicon melt in a quartz crucible while producing the silicon single crystal. Used in the so-called continuous charging method (continuous CZ method) of pulling up,
The present invention relates to a method for supplying an initial silicon raw material to a double crucible.

[0002]

2. Description of the Related Art In the continuous charge method, the silicon single crystal is pulled up while compensating for the decrease in the silicon melt in the quartz crucible due to the pulling of the silicon single crystal. Can be reduced. However, the quartz crucible gradually elutes and deteriorates due to contact with the high temperature silicon melt.
When the deterioration of the crucible becomes severe, a part of the quartz crucible peels off and floats on the molten surface of the silicon melt, or the molten metal surface of the silicon melt oscillates. Defects are generated, and as a result, the pulling of the silicon single crystal is forced to be stopped and the productivity is impaired. In the continuous charge method, since the silicon raw material is supplied during the pulling of the single crystal, the operation time is longer than in the normal CZ method which does not do this, and the silicon single crystal is pulled using the same quartz crucible. Therefore, it is especially important to prevent the deterioration of the quartz crucible.

Deterioration of the quartz crucible begins at the initial supply of the silicon raw material to the crucible and the melting thereof.
The initial supply of silicon raw material to the quartz crucible and its melting are usually performed in order to secure a predetermined amount of silicon melt.
It is carried out by depositing massive or granular polycrystalline silicon in a crucible, heating the deposited polycrystalline silicon and melting it from the bottom. At that time, the lump or granular polycrystalline silicon gradually moves downward and melts while falling, but the polycrystalline silicon at the top adheres to the crucible wall, and the downward movement and falling are smooth. It may cause deterioration such as deformation and damage of the crucible. Further, in this initial melting, in order to melt the polycrystalline silicon into a silicon melt, the heating performed to maintain the silicon melt when pulling the silicon single crystal due to its latent heat. Much stronger heating is required, and such strong heating is likely to cause deformation such as deformation and damage of the crucible.

Therefore, it is important to suppress the deterioration of the crucible that occurs at the initial supply and melting of the silicon raw material as much as possible in order to succeed the subsequent growth of the silicon single crystal by the continuous charge method.

[0005]

In the continuous charge method,
Since polycrystalline silicon is supplied while pulling a silicon single crystal, a double crucible consisting of an outer crucible and an inner crucible may be used to minimize the influence of this supply. The inner crucible of the crucible, during the initial supply of silicon raw material and its melting,
Degradation is particularly likely to occur. Because the wall of the outer crucible in the double crucible is supported by the graphite crucible, but the wall of the inner crucible does not have such support,
As shown in FIG. 3, when the inner crucible is filled with the silicon raw material as in the conventional initial method of supplying the silicon raw material,
At the time of melting, if the polycrystalline silicon supplied as a silicon raw material leans against the wall 3 ′ of the inner crucible 3 or if a large lump of polycrystalline silicon 7 falls from the upper portion and collides with it, the weight and impact may cause Easily transformed,
Because it will be damaged. Then, since the silicon single crystal is grown in the inner crucible, the deterioration of the inner crucible directly causes the disorder of the crystal of the silicon single crystal. Therefore, it is more important to protect the inner crucible from its deterioration than the outer crucible.

Therefore, as shown in FIG. 4, before the lower portion of the polycrystalline silicon 7 rugged in the crucible is melted, the upper polycrystalline silicon 7 in the inner crucible 3 is melted and the inner crucible wall is melted. It is not unthinkable to avoid the deformation and damage of 3 ', but the polycrystalline silicon in the upper part where melting started sticks to the upper part of the inner crucible wall 3', and the upper part of the inner crucible wall 3'is Since the silicon melt 9 is heated without being suppressed by the latent heat of the silicon melt 9 and is overheated, the deterioration of the inner crucible wall 3'progresses.

[0007]

As a result of various investigations in view of the above problems, the present inventors
By putting only the outer crucible, it is possible to prevent the initial deterioration of the inner crucible, and as a result, the crystal disorder due to the deterioration of the crucible does not easily occur in the continuous charging method for a long time, and the production of silicon single crystal is prevented. I found that it can improve the sex.

Therefore, the present invention comprises an outer crucible and an inner crucible, wherein the outer crucible and the inner crucible are connected by the pores provided in the wall of the inner crucible for producing a silicon single crystal by the pulling method. A method for supplying an initial silicon raw material to a double crucible, characterized in that the silicon raw material is introduced only into the outer crucible, and the initial silicon raw material is supplied to the inner crucible through the pores. The gist is the method of supplying the initial silicon raw material to the double crucible, and in particular, it is composed of an outer crucible and an inner crucible, and the outer crucible and the inner crucible communicate with each other through pores provided in the wall of the inner crucible. The initial silicon for the double crucible for producing a silicon single crystal by the pulling method, which is equipped with a supply pipe for introducing granular silicon raw material into the outer crucible. A charge supply method, first, a silicon material bulk or granular filled in the outer crucible, after reducing the molten volume it was heated, with heating,
Granular silicon raw material was introduced into the outer crucible via the supply pipe until the silicon raw material in the double crucible reached the required amount at the time of starting the pulling of the silicon single crystal. The gist is a method of initially supplying a silicon raw material to a double crucible, which is characterized in that the material is supplied in a molten state through a hole.

By thus introducing the silicon raw material only into the outer crucible, it is possible to suppress the initial deterioration of the inner crucible which causes the crystal disorder of the silicon single crystal when pulling up the silicon single crystal, and the silicon single crystal is suppressed. The productivity of crystals can be improved. In particular, by first filling the outer crucible with the lump or granular silicon raw material and then introducing the granular silicon raw material into the outer crucible through the supply pipe, it is possible to suppress the initial deterioration of the inner crucible and to form the double crucible. The initial silicon raw material can be quickly and smoothly supplied to the silicon, and the productivity of the silicon single crystal can be further improved.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic sectional view showing an example of an apparatus for producing a silicon single crystal by a continuous charge method, to which the present invention is applied. In FIG. 1, 1 is a double crucible made of quartz, 2 is an outer crucible,
The inner crucible 3 is housed in the furnace body 5.
The wall 2'of the outer crucible 2 is supported by the graphite crucible 4, whereas the wall 3'of the inner crucible 3 is only joined at its lower end to the bottom of the double crucible. The outer crucible 2 and the inner crucible 3 communicate with each other through pores (not shown) provided in the wall 3 ′ of the inner crucible. A rotary shaft 8 is attached to the graphite crucible 4 so that the double crucible 1 and the graphite crucible 4 can be rotated and moved up and down.

Further, the apparatus is provided with a supply pipe 10 for introducing granular polycrystalline silicon into the outer crucible 2. Granular polycrystalline silicon is supplied from the feeder 6 to the supply pipe 10. The feeder 6 can supply a fixed amount or a variable amount of granular polycrystalline silicon to the supply pipe 10 continuously or intermittently.

FIG. 2 is a cross-sectional view showing changes in the state of the double crucible when the initial silicon raw material is supplied to the double crucible by the supply method of the present invention. As shown in FIG. 2, first, the outer crucible 2 of the double crucible 1 is filled with polycrystalline silicon 11 as a silicon raw material. The polycrystalline silicon 11 used for this first filling may be granular or lumpy. The polycrystalline silicon 11 filled in the outer crucible 2 is melted from below by heating the double crucible 1. The silicon melt 9 flows into the inner crucible 3 through the pores provided in the wall 3 ′ of the inner crucible. However, with only the polycrystalline silicon 11 that is first filled in the outer crucible 2,
The required amount of silicon melt is not reached at the start of pulling a silicon single crystal. Therefore, using the supply pipe 10 (not shown), while heating the double crucible 1 until the amount of silicon melt required at the start of pulling the silicon single crystal is reached,
Granular polycrystalline silicon 1 in the outer crucible 2 via the supply pipe
Introduce 2. At this time, it is preferable to rotate the double crucible 1 by a rotating shaft (not shown).

Granular polycrystalline silicon 12 via a supply tube
The introduction of is started after heating the polycrystalline silicon 11 initially filled in the outer crucible 2 to melt it and reduce the volume. Although the granular polycrystalline silicon 12 may be introduced after the polycrystalline silicon 11 is completely melted, the introduction of the granular polycrystalline silicon 12 can be started even if the melting is incomplete, and thus the melting of the polycrystalline silicon 12 can be prevented. It is preferable to start the introduction of the granular polycrystalline silicon 12 while it is incomplete, because the initial supply time of the silicon raw material can be shortened. However, if the proportion of the unmelted polycrystalline silicon 11 is too large, the granular polycrystalline silicon 12 that is introduced may collide with it and jump out of the crucible. This is performed after the melting of the polycrystalline silicon 11 filled in the above has progressed to a state where such a situation does not occur. The introduction speed of the granular polycrystalline silicon 12 is adjusted by the feeder 6.

The amount of the silicon melt 9 in the double crucible 1 is
When the required amount is reached at the time of starting the pulling of the silicon single crystal, the supply of the granular polycrystalline silicon 12 is stopped, and after all the silicon raw material is melted, the pulling of the silicon single crystal is started.

[0015]

Embodiments of the present invention will be described below. A total of 40 kg of the initial silicon raw material is supplied to a double crucible having an outer crucible diameter of 18 inches φ and an inner crucible diameter of 14 inches φ. First, the outer crucible was first filled with 10 kg of massive polycrystalline silicon, and then the double crucible was heated to start melting from the lower part. After the raw material in the outer crucible gradually melts, the volume gradually decreases, and even after the granular polycrystalline silicon is introduced into the outer crucible via the supply pipe, it reaches a state where it does not pop out, and then the granular polycrystalline silicon is introduced. Started.
At this time, the supply rate is 2g / s, the heater power is 90k.
The rotation speed of W and the crucible was 2 rpm. A total of 30 kg of granular polycrystalline silicon was introduced. After the supplied initial silicon raw material was completely melted, a silicon single crystal having a diameter of 6 inches was pulled by the continuous charging method. As a result, deformation and deterioration of the inner crucible did not occur, and crystal disorder caused by this did not occur at all.

[0016]

According to the present invention, it is possible to prevent the initial deterioration of the inner crucible, and as a result, in the continuous charging method for a long time, the disorder of the crystal due to the deterioration of the crucible hardly occurs, and the silicon single crystal is prevented. Productivity can be improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus for producing a silicon single crystal by a continuous charge method, to which the present invention is applied.

2 (A) to (C) are cross-sectional views showing changes in the state of the double crucible during the initial supply of the silicon raw material to the double crucible according to the supply method of the present invention.

3 (A) to (C) show a conventional supply method,
FIG. 7 is a cross-sectional view showing changes in the state of the double crucible when the silicon raw material is initially supplied to the double crucible.

4A to 4C are cross-sectional views showing changes in the state of the double crucible during the initial supply of the silicon raw material to the double crucible according to another conventional supply method.

[Explanation of symbols]

1 ... Double crucible, 2 ... Outer crucible, 2 '... Outer crucible wall, 3 ... Inner crucible, 3' ... Inner crucible wall,
4 ... Graphite crucible, 5 ... Furnace body, 6 ... Feeder, 7 ... Polycrystalline silicon, 8 ... Rotating shaft, 9 ... Silicon melt, 10 ... Supply tube, 11 ... Polycrystalline silicon, 12 ... Granular polycrystalline silicon.

Claims (2)

[Claims] 1. A double crucible for producing a silicon single crystal by a pulling method, which comprises an outer crucible and an inner crucible, and the outer crucible and the inner crucible communicate with each other through pores provided in a wall of the inner crucible. The method of supplying the initial silicon raw material, wherein the silicon raw material is charged only into the outer crucible, and the initial crucible is supplied to the inner crucible through the pores. Method of supplying silicon raw material to the initial stage. 2. An outer crucible and an inner crucible, wherein the outer crucible and the inner crucible communicate with each other through pores provided in the wall of the inner crucible, and a supply pipe for introducing a granular silicon raw material into the outer crucible. A method of supplying an initial silicon raw material to a double crucible for producing a silicon single crystal by a pulling method, first, filling a bulk or granular silicon raw material in an outer crucible and heating it After melting and reducing the volume, while heating, the silicon raw material in the double crucible was introduced into the outer crucible through the supply pipe until the silicon raw material in the double crucible reached the amount required at the start of pulling the silicon single crystal, A method for supplying an initial silicon raw material to a double crucible, wherein the initial silicon raw material is supplied to the inner crucible in a molten state through the pores.