JP2009274928A - Segmentation-type heater and apparatus and method for pulling single crystal using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a segmentation-type cylindrical heater and an apparatus and a method for pulling a single crystal by a CZ method using the heater. <P>SOLUTION: (1) The heater 1 is a cylindrical heater (heat emitting body) to heat a raw material supplied in a crucible and to hold a molten state and is divided in a circumferential direction. A tall divided piece 1a and a short divided piece 1b in each divided piece are placed alternately and the upper part of the tall divided piece is extended upward of the short divided piece. (2) The single crystal pulling apparatus is assembled with the segmentation-type heater as the heater arranged to be concentric at the outside of the crucible, to heat the raw material supplied in the crucible and to hold the molten state. The prevention of the deformation of the upper part of the crucible and the rapid melting of the raw material supplied in the crucible can be performed by controlling heating states at the upper part and the lower part of the crucible when using the pulling apparatus. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cylindrical split heater used when a raw material supplied into a crucible is heated and held in a molten state, a single crystal pulling apparatus incorporating the split heater, and the pulling apparatus. The present invention relates to a single crystal pulling method to be used.

  Resistance-type heating furnaces (also called electrical resistance heating devices) are easier to operate and maintain than combustion-type heating furnaces, can heat the object to be processed at a high temperature, and can control the temperature with high accuracy. Because it can be adjusted, it is widely used in many industrial fields.

  Taking a cylindrical resistance heating furnace that heats the raw material (for example, silicon raw material for semiconductor) supplied into the crucible from the outside of the crucible as an example, the main part of this heating furnace has a cylindrical shape as a heating element. The heater includes a cylindrical heat insulating material attached in the vicinity of the outer periphery of the heater, and a heat insulating material protection cylinder for protecting the heat insulating material from the high temperature of the heater. Carbon is used as the material of the heater.

  FIG. 1 is a diagram illustrating a schematic shape of a heater (heating element) used in this cylindrical heating furnace, where (a) is a plan view and (b) is a longitudinal sectional view. As shown in FIG. 1, the heater 1 has a cylindrical shape and is disposed substantially concentrically outside the crucible 2. A heat insulating material 3 and a heat insulating material protection cylinder 4 for protecting the heat insulating material 3 are attached in the vicinity of the outer periphery of the heater 1. Although not shown, an electrode for supporting the heater 1 and energizing the heater 1 is installed below the heater 1.

  The heater is made of carbon, and a block-shaped material is made by a CIP (Cold Isostatic Pressing) method in which carbon powder is put into a mold and hardened by applying hydrostatic pressure, and the block material is cut out from the material to be integrally formed. As the heat insulating material, a felt material having a light weight and a large heat insulating effect is generally used. In order to protect the heat insulating material, a heat insulating material protective cylinder made of carbon or carbon composite material (CCM) is provided on the surface facing the heater of the heat insulating material. Arranged.

  The resistance heating furnace configured as described above is supplied into a crystal pulling crucible in a silicon single crystal pulling apparatus for growing and pulling a single crystal by, for example, the Czochralski method (hereinafter referred to as “CZ method”). In order to heat the raw material and keep it in a molten state, it is incorporated into the apparatus and used.

  FIG. 2 is a longitudinal sectional view schematically showing an example of the configuration of the main part of a conventional pulling apparatus suitable for carrying out the silicon single crystal pulling method by the CZ method. As shown in FIG. 2, this pulling apparatus heats a raw material (for example, massive or granular polycrystalline silicon) supplied into the crucible 5, and a heater 1 for maintaining the molten state is generally disposed outside the crucible 5. A heat insulating material 3 and a heat insulating material protection cylinder 4 for protecting the heat insulating material 3 are attached in the vicinity of the outer periphery thereof. Further, in this example, a heat shielding plate 8 is attached to surround the pulled single crystal and shield heat radiation from the surface of the silicon melt 7 in the crucible 5.

  The crucible 5 is a double-structured quartz inner-layer holding container (hereinafter referred to as “quartz crucible”) 5a having a bottomed cylindrical shape, and a similarly bottomed cylindrical shape adapted to hold the outside of the quartz crucible 5a. And a graphite outer layer holding container (hereinafter referred to as “graphite crucible”) 5b, which is fixed to the upper end of a support shaft 6 that can be rotated and moved up and down.

  On the central axis of the crucible 5 filled with the melt 7, a pulling wire 8 that rotates on the same axis as the support shaft 6 in the reverse direction or in the same direction at a predetermined speed is disposed. Holds the seed crystal 9.

  When pulling up a silicon single crystal using the pulling device configured as described above, a predetermined amount of silicon raw material for semiconductor (generally using massive or granular polycrystalline silicon) is put in the crucible 5. The raw material is heated and melted by a heater 1 disposed around the crucible 5 in an inert gas (usually Ar) atmosphere under reduced pressure, and then a pulling wire 8 is formed in the vicinity of the surface of the formed melt 7. The seed crystal 9 held at the lower end of the substrate is immersed. Subsequently, the wire 8 is pulled up while rotating the crucible 5 and the pulling wire 8, and the single crystal 10 is grown on the lower end surface of the seed crystal 9.

  When pulling, the diameter of the single crystal 10 grown on the lower end surface of the seed crystal 9 is adjusted to reduce the diameter, and after passing through a necking process (step) for forming a neck portion (squeezed portion), the pulling rate is lowered. The shoulder is formed by gradually increasing the crystal diameter, and the process proceeds to raising the constant diameter part. After the constant-diameter portion reaches a predetermined length, the crystal diameter is gradually reduced, and the leading edge is separated from the melt 7 to complete one pulling.

  In this silicon single crystal pulling melting process, when the raw material supplied into the crucible 5 is heated by the heater 1 and melted, the entire cylindrical heater 1 generates heat in the same manner. The upper part is heated in the same manner as the lower part of the crucible containing the raw material. For this reason, the upper part of the quartz crucible 5a may be deformed (hereinafter simply referred to as “deformation of the upper part of the crucible”) and fall down inside. In that case, the upper part of the crucible 5a that has fallen into contact with the heat shielding plate 8, and the pulling of the single crystal cannot be continued.

  Further, when heating and melting a silicon raw material for semiconductor (bulk and granular polycrystalline silicon) supplied into the crucible 5, generally, the melting of the raw material does not proceed uniformly in the crucible 5. When it becomes large, the raw material becomes difficult to dissolve uniformly.

  FIG. 3 is a diagram schematically showing the melting process of the raw material supplied into the crystal pulling crucible. As shown in the figure, the massive and granular raw material 11 supplied into the quartz crucible 5a (FIG. 3 (a)) is heated by a heater (not shown) arranged concentrically outside the crucible 5a. Heats and melts. In the melting process, the specific gravity of the silicon melt 7 is larger than that of the solid phase, so that the unmelted lump-like and granular raw material 11 floats in the vicinity of the melt surface (FIG. 3B). When additional charging is performed (FIG. 3 (c)), the supplied raw material 11 once floats in the vicinity of the melt surface in an unmelted state as shown in (b), and then is heated and melted ( FIG. 3 (d)).

  If only the granular or fine powdered polycrystalline silicon is used without using the bulk material, the raw material can be melted more quickly, but there are many cases where the bulk material is used.

  On the other hand, in response to the recent high integration, low cost, and improved productivity of semiconductor devices, wafers are also required to have a large diameter, and there is a great demand for the production of large-diameter silicon single crystals.

  In order to produce a large-diameter silicon single crystal, the crucible for crystal pulling must be enlarged, and the heater of the heating furnace incorporated in the single crystal pulling apparatus needs to be enlarged. For this reason, a large carbon block material (hereinafter referred to as “carbon material”) that can be cut out as a single unit of heater is required, but there is a limit to the size of the block material that can be manufactured by the CIP method. This limits the increase in the diameter of the silicon single crystal.

Upsizing of silicon single crystals has been carried out successively until now, and the increase in size of heaters required for this purpose has been performed by increasing the size of carbon materials produced by the CIP method. However, no attempt has been made to cope with the large diameter of the silicon single crystal by improving the heater shape and the heater side.
Japanese Patent Laid-Open No. 2007-261846

  The present invention has been made in view of such a situation, and avoids deformation of the upper part of the crucible (falling inward) in the melting process of the silicon single crystal pulling and interruption of the single crystal pulling caused thereby, and the crucible 5 Cylindrical split type that can melt silicon raw material for semiconductors (bulk and granular polycrystalline silicon) supplied inside efficiently and quickly, and can produce large-diameter silicon single crystals It is an object of the present invention to provide a heater, a single crystal pulling apparatus using the CZ method using the split heater, and a pulling method using the single crystal pulling apparatus.

  In order to solve the above problems, the inventors of the present invention have improved the shape of the heater, and tried to divide the cylindrical integral heater in the circumferential direction of the cylinder to obtain a divided heater. It was. Each divided part (hereinafter, each divided part is referred to as a “divided piece”) is incorporated into a cylindrical shape at the time of use, and is used as a cylindrical heater. If such a divided heater is used instead, a large heater can be manufactured by cutting out large divided pieces from a carbon material manufactured by the CIP method and incorporating them into a cylindrical shape.

  Note that the above-mentioned Patent Document 1 describes a method for producing a silicon single crystal using a multi-heater that is divided into at least two in the longitudinal direction. This method includes a pulling rate of a single crystal, a crucible, By adjusting the rotation speed of the single crystal and the ratio of the output of the lower heater to the output of the upper heater in the multi-heater, the temperature gradient of the side surface of the single crystal, the height of the solid-liquid interface, and the longitudinal direction of the single crystal This is a method for stably producing a defect-free silicon single crystal at a high speed by controlling the oxygen concentration, and the purpose of dividing the heater is different from the purpose of dividing the heater in the present invention, and the dividing direction is completely different. is doing.

  In addition to the above-mentioned division of the heater, if the heat insulating material attached to the heater and the heat insulating material protecting cylinder for protecting this heat insulating material are also divided in the circumferential direction, such heat insulating materials are attached and removed, Handling (handling) becomes easy.

  Further, in order to prevent the crucible upper part from deforming and falling inward in the raw material melting step, it is effective to heat the crucible upper part gently. Furthermore, in order to efficiently and quickly melt the silicon raw material for semiconductor (bulk and granular polycrystalline silicon) supplied into the crucible, the lower part of the crucible is heated strongly and in the vicinity of the melt surface in the crucible. It is considered effective to eliminate or reduce the remaining of the lump-like and granular raw materials.

  Therefore, the present inventors have divided a cylindrical heater in the circumferential direction of the cylinder, and devised the shape of each divided piece, and can be used to adjust the heating state of the upper and lower parts of the crucible. A heater was devised.

  If the pulling device incorporating the above-mentioned split heater is used as a silicon single crystal pulling device by the CZ method, it becomes possible to adjust the heating state of the upper and lower parts of the crucible. Therefore, it is possible to efficiently melt the bulk or granular raw material supplied into the crucible. Furthermore, a large-diameter silicon single crystal can be manufactured by increasing the size of the heater.

  The present invention has been made based on such an idea and the result of examination. The gist of the present invention is the following (1) split heater, the following (2) single crystal pulling apparatus equipped with this split heater, and this pulling. In the single crystal pulling method of (3) below using an apparatus.

  (1) A cylindrical heater for heating a raw material supplied into a crucible and maintaining it in a molten state, wherein the heater is divided in the circumferential direction, and each of the divided pieces is divided. A split-type heater in which tall split pieces and low split pieces are alternately arranged, and an upper portion of the tall split piece extends above the short split piece.

  Here, as described above, the “heater” refers to a heating element that is one of the main components of the cylindrical resistance heating furnace. In addition, the main part structural member of a heating furnace means the heat generating body (heater), the heat insulating material attached to the outer periphery vicinity, and a heat insulating material protection cylinder. “Divided in the circumferential direction” means that the cylindrical heater is divided in the circumferential direction of the cylinder (see FIG. 4 shown later).

  In addition, “a tall divided piece” is a divided piece in which the upper end of the divided piece reaches the highest part of the heater when each divided piece is incorporated into a cylindrical heater. Is a divided piece whose upper end does not reach the highest part.

  In the split heater of (1), an embodiment in which the heat insulating material and the heat insulating material protection cylinder attached to the heater are divided in the circumferential direction can be adopted.

  (2) Concentrically arranged outside the crucible, provided with a heater for heating the raw material supplied into the crucible and maintaining it in a molten state, and growing a single crystal from the melt in the crucible by the CZ method A single crystal pulling apparatus, wherein the heater is the split heater described in (1) (including the embodiment).

  (3) A single crystal pulling method using the single crystal pulling apparatus described in (2) above, wherein the heating state of the upper and lower parts of the crucible is controlled by a divided heater incorporated in the pulling apparatus, A method for pulling a single crystal, wherein the upper part of the crucible is prevented from being deformed and the raw material supplied into the crucible is rapidly dissolved.

  The split heater according to the present invention has a cylindrical shape, is divided in the circumferential direction, and is configured so that the heating state of the upper and lower portions of the crucible can be adjusted. According to the pulling method of the present invention using the single crystal pulling apparatus of the present invention in which this split heater is incorporated, deformation of the upper part of the crucible (falling inward) can be prevented and supplied into the crucible. It is possible to efficiently melt the bulk or granular raw material.

  In addition, it is possible to increase the size of the heater by cutting out large divided pieces, and it is possible to hold a silicon melt using a large quartz crucible. Can do.

  The split heater according to the present invention is a cylindrical heater for heating the raw material supplied into the crucible and maintaining the molten state, and the heater is divided in the circumferential direction. Among the individual divided pieces, the tall divided pieces and the low divided pieces are alternately arranged, and the upper portion of the tall divided pieces extends above the short divided pieces. It is a heater.

  4A and 4B are diagrams schematically illustrating the schematic shape of the split heater according to the present invention, in which FIG. 4A is a plan view and FIG. 4B is an elevational view taken along line AA in FIG. Similar to the heater illustrated in FIG. 1, the heater is used as a main component member of a cylindrical heating furnace that heats a raw material (for example, silicon raw material for semiconductor) supplied into the crucible.

  As shown in FIG. 4A, the heater 1 is divided in the circumferential direction. As shown in FIG. 4B, the tall divided piece 1a and the lower divided piece among the divided pieces. The upper portions of the tall divided pieces 1a extend above the short divided pieces 1b. In FIG.4 (b), the thinly-painted part is an extension part. In addition, although not shown in figure, the electrode (a positive electrode and a negative electrode) for supporting and supplying with electricity to each divided piece 1a, 1b is attached to each divided piece 1a, 1b, and the output of each divided piece 1a, 1b. It is configured to be able to adjust.

  The reason why the shape of the heater is such a combination of the tall divided piece 1a and the shorter divided piece 1b is to allow the heating state of the upper and lower parts of the crucible to be adjusted. For example, the divided piece 1a is a tall divided piece whose upper end reaches the highest part of the heater when the divided pieces are incorporated into a cylindrical heater, and the upper part of the divided piece 1b is a short piece. Since it extends upward, the amount of heat generated can be increased by increasing the output of the segment 1a, and the upper part of the crucible can be strongly heated. Moreover, it becomes possible to strengthen the heating state of the lower part of the crucible by increasing the output of the short segment 1b.

  The reason why the divided pieces 1a and 1b are alternately arranged is to prevent the heating effect of the divided pieces 1a or 1b from being biased to the local area in the crucible and to cover the entire crucible as much as possible. .

  Moreover, since the heater is a split type, it is suitable for producing a large heater. That is, when producing a cylindrical split heater, each split piece is cut out from the carbon material manufactured by the CIP method, and when used, these split pieces are incorporated into a cylindrical shape to form a cylindrical heater. The heater can be enlarged by cutting out large pieces. This makes it possible to produce a large heater necessary for producing a large-diameter silicon single crystal with the current CIP apparatus.

  If heaters of the same size are to be manufactured, the size of the carbon material to be machined can be reduced according to the divided pieces by dividing the heater, so the amount of material to be machined is reduced. Processing loss can be reduced. Since the processing loss increases as the heater increases in size, the effect of reducing the processing loss due to the division of the heater increases as the heater increases in size.

  When dividing the heater, as described in the above-mentioned Patent Document 1, dividing in the circumferential direction, not in the longitudinal direction, significantly reduces the size (volume) of the carbon material from which one piece is cut. Because it can.

  The divided heater illustrated in FIG. 4 has eight tall divided pieces 1a and eight tall divided pieces 1b, and is divided into sixteen pieces, but the number of divided pieces is not limited thereto. However, since the divided pieces 1a and 1b are alternately arranged in the circumferential direction, if the number of divided pieces is too small, the effect of each heating is limited to a part in the circumferential direction, while the divided pieces are separated. If the number is large, the heating effect can be exerted on the entire crucible, but the manufacturing cost of the heater increases. Therefore, it is desirable to determine the number of divided pieces in consideration of the purpose of heating, cost, and the like after empirically grasping the relationship between the number of divided pieces and the heating effects of the divided pieces 1a and 1b.

  In the split heater according to the present invention, it is desirable to adopt an embodiment in which the heat insulating material and the heat insulating material protection cylinder attached to the heater are also divided in the circumferential direction.

  In the split heater according to the present invention, a heater as a heating element is divided, and there is no provision for a heat insulating material and a heat insulating material protection cylinder attached to the heater. If these heat insulating materials are used without being divided and are used in a cylindrical shape, if the heat insulating materials are large in size, handling (handling) such as attachment and removal may become large. If the heat insulating material and the heat insulating material protection cylinder are also divided in the circumferential direction, the handling becomes easy. As the heater becomes larger, the heat insulating material becomes larger, so the effect of dividing the heat insulating material becomes larger.

  The single crystal pulling apparatus of the present invention is arranged concentrically outside the crucible, and includes a heater for heating the raw material supplied into the crucible to keep it in a molten state, and using the CZ method from the molten liquid in the crucible A single crystal pulling apparatus for growing a single crystal according to claim 1, wherein the heater is the split heater (including the above-described embodiment) of the present invention. Here, the “split-type heater” of the present invention incorporated in the single crystal pulling apparatus includes a heat insulating material attached to the heater and a heat insulating material protective cylinder. This is because the arrangement of a heat insulating material or the like is indispensable when the heater is used.

  FIG. 5 is a longitudinal sectional view schematically showing an example of the configuration of the main part of the single crystal pulling apparatus of the present invention. As shown in FIG. 5, the basic structure of this pulling apparatus is not different from that of the single crystal pulling apparatus shown in FIG. 2, but the raw material supplied into the crucible (for example, silicon raw material for semiconductor) A heater 1 for heating and maintaining a molten state is the split heater of the present invention illustrated in FIG. 4, and a heat insulating material 3 for protecting the heat insulating material 3 and the heat insulating material 3 in the vicinity of the outer periphery thereof. A cylinder 4 is attached.

  The broken line added in the crucible 5 in FIG. 5 represents the liquid level Ls of the silicon melt before the start of single crystal pulling. The heater 1 is arranged so that the upper surface of the short divided piece 1b among the individual divided pieces of the heater 1 divided in the circumferential direction is positioned in the vicinity of the liquid level Ls.

  The single crystal pulling method of the present invention uses the single crystal pulling apparatus of the present invention, controls the heating state of the upper and lower portions of the crucible with a divided heater incorporated therein, and deforms the upper portion of the crucible (inwardly). The pulling method is characterized in that the material supplied into the crucible is efficiently dissolved while preventing collapse. Here, the “upper portion of the crucible” means a portion above the vicinity of the liquid surface level Ls of the silicon melt before the start of pulling of the single crystal, and the “lower portion of the crucible” means lower than that. This part.

  The heating state of the upper and lower parts of the crucible is controlled by adjusting the outputs of the divided pieces 1a and 1b constituting the heater 1 to change the respective heat generation amounts.

  Normally, in the raw material melting step, the output of the divided piece 1a is lowered, and the upper part of the crucible (the part above the vicinity of the liquid level Ls) is gently heated to suppress deformation of the upper part of the crucible and to be divided. The output of the piece 1b is increased, and heating of the lower part of the crucible (the part below the vicinity of the liquid level Ls) is strengthened to dissolve the raw material. When increasing the output of the divided piece 1b, the raw material is rapidly dissolved, and the output of the divided piece 1a is decreased so that the residual of the bulky and granular raw material in the vicinity of the melt surface in the crucible can be eliminated or reduced. It is desirable to set the output so that a calorific value sufficiently exceeding the decrease in the calorific value due to.

  Also, in the single crystal pulling step, the output of the split piece 1a is increased and the output of the split piece 1b is lowered so that the temperature of the silicon melt can be maintained uniformly without causing a difference in the circumferential direction of the heater 1. The outputs of the pieces 1a and 1b are the same or similar. In the pulling process, both the inner and outer surfaces of the quartz crucible 5a are already sufficiently heated, so even if the output of the segment 1a is increased, the upper part of the crucible 5a is not deformed and falls inward.

  The single crystal pulling apparatus of the present invention incorporates the split heater (including the above-described embodiment) of the present invention that can control the heating state of the upper and lower parts of the crucible as described above. According to the pulling method of the present invention using the above, in the raw material melting step, it is possible to prevent the upper part of the crucible from being deformed and falling inward, thereby avoiding the situation where it is impossible to continue pulling the single crystal, and The lower part of the substrate can be heated strongly to dissolve the raw material efficiently and promptly.

  Furthermore, since the crucible is divided and a large heater can be manufactured as described above, a large-diameter silicon single crystal can be manufactured. For example, it is possible to use a large quartz crucible having a diameter of 36 to 44 inches, and to heat a silicon raw material for semiconductor to be supplied and keep it in a molten state, and a large diameter silicon single crystal having a diameter of 450 mm. Can be manufactured.

  In addition, in the single crystal pulling apparatus of the present invention, every time pulling is completed, the heater, heat insulating material, and other members constituting the crucible and the apparatus are removed, and cleaning and necessary repairs including piping are performed. Then, in preparation for the next single crystal pulling, each member is incorporated, but according to the preferred embodiment, the heat insulating material and the like are also divided. There is also an advantage that the constituent members can be easily removed and assembled.

  The split heater according to the present invention is a heater in which an integral heater having a cylindrical shape is divided in the circumferential direction of the cylinder, and is configured to control the heating state of the upper and lower portions of the crucible. According to the single crystal pulling apparatus and pulling method of the present invention using this divided heater, it is possible to prevent the upper part of the crucible from being deformed and to efficiently and promptly supply the bulk or granular raw material supplied into the crucible. Melting becomes possible. Moreover, a large-diameter silicon single crystal can be produced by increasing the size of the heater.

  Therefore, the split-type heater of the present invention and the single crystal pulling apparatus and pulling method of the present invention using this heater can be effectively used particularly in the manufacture of large-diameter silicon single crystals in the field of semiconductor device manufacturing.

It is a figure which illustrates the schematic shape of the heater (heating element) used for the cylindrical heating furnace, (a) is a top view, (b) is a longitudinal cross-sectional view. It is a longitudinal cross-sectional view which shows typically the example of a principal part structure of the conventional pulling apparatus suitable for implementing the pulling method of the silicon single crystal by CZ method. It is a figure which shows typically the melt | dissolution process of the raw material supplied in the crucible for crystal pulling. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which illustrates typically the schematic shape of the split-type heater of this invention, (a) is a top view, (b) is an AA arrow elevational view of (a). It is a longitudinal cross-sectional view which shows typically the example of a principal part structure of the single crystal pulling apparatus of this invention.

Explanation of symbols

1: heater, 2: crucible, 3: heat insulating material, 4: heat insulating material protection cylinder,
5: crucible, 5a: quartz crucible, 5b: graphite crucible,
6: support shaft, 7: melt, 8: pulling wire,
9: seed crystal, 10: single crystal, 11: raw material

Claims (4)

A cylindrical heater for heating the raw material supplied into the crucible and maintaining the molten state,
The heater is divided in the circumferential direction, and among the divided pieces, the tall divided pieces and the lower divided pieces are alternately arranged, and above the short divided pieces, A split-type heater characterized in that the upper part of a high-split piece is extended.   The split heater according to claim 1, wherein a heat insulating material and a heat insulating material protection cylinder attached to the heater are divided in a circumferential direction. A concentrically arranged outside the crucible, provided with a heater for heating the raw material supplied into the crucible and maintaining it in a molten state, a single crystal for growing a single crystal from the melt in the crucible by the Czochralski method. A crystal pulling device,
A single crystal pulling apparatus, wherein the heater is a split heater according to claim 1 or 2. A single crystal pulling method using the single crystal pulling apparatus according to claim 3,
The divisional heater incorporated in the pulling device controls the heating state of the upper and lower parts of the crucible to prevent deformation of the upper part of the crucible and efficiently dissolve the raw material supplied into the crucible. Single crystal pulling method.

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