JP3078752B2 - Method and apparatus for high frequency heating and melting of polycrystalline raw material for single crystal production - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for efficiently melting a polycrystalline raw material by high-frequency heating when the polycrystalline raw material is supplied to a single crystal growing pulling furnace from the outside in a molten state.

[0002]

2. Description of the Related Art In the Czochralski method in which a single crystal such as Si is pulled from a melt and grown, a single crystal having a crystal characteristic according to the orientation of the seed crystal is brought into contact with a melt contained in a quartz crucible. Nurture. The single crystal is pulled up according to the degree of growth, but the melt in the quartz crucible is consumed and the liquid level of the melt fluctuates accordingly. In the batch pulling method, the liquid level fluctuation is corrected by raising the quartz crucible in accordance with the growth of the single crystal, and the growth interface is maintained under a constant condition. However, for that purpose, a complicated control device is required, and it is necessary to control the liquid level with high accuracy. In addition, since it is a batch type, there is naturally a limit in increasing the diameter or pulling a long single crystal.

Therefore, a method of pulling a single crystal while continuously charging a semiconductor raw material has been used. In this method, a granular polycrystalline raw material produced by a fluidized bed method or the like is used, and the granular polycrystalline raw material is supplied to and melted in a quartz crucible, or the polycrystalline raw material dissolved outside is supplied to a quartz crucible. For example, in Japanese Patent Application Laid-Open No. 5-105576, a pellet-shaped raw material is fed into a melting vessel provided in a vacuum chamber, and the melted raw material is supplied to a crystal growing crucible. Japanese Patent Application Laid-Open No. 3-215383 discloses that a polycrystalline raw material is dissolved in a double-structured container and supplied to a crystal growth section.

[0004]

The polycrystalline raw material fed into the quartz crucible is heated and melted by, for example, a high-frequency heating device. However, when the polycrystalline raw material is melted by the high-frequency heating device, if the degree of vacuum around the coil is high, discharge is likely to occur, and the raw material cannot be melted. However, the pulling furnace is maintained at a vacuum of about 10 to 50 Torr in a normal operation state. Therefore, if the inside of the pulling furnace communicates with the raw material melting section, the raw material melting section also has the same degree of vacuum, and it becomes difficult to melt the raw material due to discharge. The discharge itself can be prevented by lowering the degree of vacuum to about normal pressure, but as a result, contamination of the raw material melting section due to pressure rise and operating conditions in the crystal growth section maintained at the same pressure are reduced. Restrictions arise. The present invention has been devised in order to solve such a problem, and by preventing the high-frequency heating device from being shut off atmospherically and maintaining the same at a normal pressure or a low degree of vacuum, it is possible to prevent the occurrence of electric discharge and stabilize the discharge. It is an object of the present invention to easily feed a polycrystalline raw material dissolved under conditions to a crystal growth part.

[0005]

In order to achieve the object, a high-frequency heating and melting method according to the present invention comprises a high-frequency heating coil housed in a sealed container maintained in an atmosphere of normal pressure or a low degree of vacuum. Is placed in the center of the high-frequency heating coil under an atmosphere of the same pressure as the crystal growth section, and the high-frequency heating coil is energized to heat and melt the polycrystalline raw material in the melting vessel. Features. The sealed container is preferably maintained at an Ar atmospheric pressure of 100 Torr or more. By using an Ar atmosphere, damage to the raw material melting section can be minimized even when the enclosure is damaged. Also, by reducing the pressure difference between the coil section and the raw material melting section as much as possible, damage to the raw material melting section is suppressed.
In addition, the high-frequency heating and melting apparatus includes a melting vessel divided into a raw material melting section and a melt storage section by a suspension weir, and a sealing vessel arranged around the melting vessel and maintained in an atmosphere of normal pressure or low vacuum. And a high-frequency heating coil housed in the enclosure,
A melt supply pipe communicating the melt storage section with a crystal growth section, wherein a space between the melting vessel and the high-frequency heating coil is separated by a vessel wall made of a material having low conductivity, such as quartz. It is characterized by the following.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a high-frequency heating and melting method according to the present invention, equipment having a high-frequency heating coil 2 surrounding a melting vessel 1 as shown in FIG. 1 is used. When the melting vessel 1 is made of polycrystalline Si as a raw material, a high-purity quartz crucible is placed inside so that the melt can be held without contamination, and a crucible support having good conductivity such as carbon is placed outside, if necessary. Is used. A highly conductive material such as carbon promotes indirect heating by heat conduction. The melting vessel 1 includes, for example, a hanging weir 3 as shown in the drawing.
And is divided into a raw material dissolving section 4 and a melt storage section 5. A feeder 7 into which the polycrystalline solid raw material 6 is charged faces the raw material melting section 4. Also, it is sent from the air supply pipe 8,
The atmosphere is maintained in an inert atmosphere by the Ar gas 10 discharged through the exhaust pipe 9.

The high-frequency heating coil 2 is housed in a container 11 in which Ar gas is sealed. The sealed container 11 is maintained at a normal pressure or a low vacuum atmosphere by sealing Ar gas. Even if a frequency of several tens of kHz is used, the atmosphere in the enclosure 11 may be discharged at a high degree of vacuum such as a normal Czochralski furnace pressure (10 to 50 Torr). It is preferable to maintain the atmospheric pressure at or above Torr. The vessel wall 12 of the enclosure 11 that separates the melting vessel 1 and the high-frequency heating coil 2 is preferably made of a material having low conductivity, such as quartz, in order to prevent loss due to induced current. The dissolving section including the dissolving vessel 1
Ar gas 10 is blown from the air supply pipe 8. Surplus Ar
The gas is exhausted from the exhaust pipe 9. By adjusting the inflow amount and the discharge amount of the Ar gas 10, the inside of the melting vessel 1 is maintained at the same pressure as the crystal growth part.

When the granular or chip-like polycrystalline raw material supplied from the feeder 7 is melted into the melting vessel 1, in the initial stage of melting the raw material, the conductivity of the raw material is increased to efficiently generate an eddy current effective for melting. For this purpose, a preheated raw material is used as necessary. In addition, a highly conductive support such as carbon provided outside the quartz crucible also effectively acts to promote heating. The molten raw material 13 melted by the high frequency heating flows under the suspension weir 3 from the raw material melting section 4 into the melt storage section 5. Then, it overflows the side wall 14 of the melt storage section 5 and is sent to the crystal growth section (FIG. 2) as a melt 16 via a melt supply pipe 15. The side wall 14 has an effect of adjusting the supply amount of the melt 16 by overflow. The melt storage unit 5 includes a melt supply pipe 15.
, And is maintained in the same atmosphere as the crystal growth portion. On the other hand, the raw material dissolving section 4 is separated from the melt storage section 5 by the suspension weir 3 and is independent of the atmosphere of the crystal growth section.

As described above, when the raw material dissolving section is maintained in an inert gas atmosphere independent of the crystal growth section, the contamination of the crystal growth section with the atmosphere is prevented. Further, since the high-frequency coil 2 is sealed in the relatively high-pressure enclosure 11, the supplied power is efficiently consumed for heating and melting the solid raw material 6 without causing a discharge phenomenon during high-frequency heating. The melt 16 adjusted by the high-frequency heating is fed into the crucible 17 of the crystal growth part from the melt supply pipe 15. At this time,
When the melt supply pipe 15 around which the heater 18 is wound is used, the temperature of the melt 16 fed into the crystal growth crucible 17 can be controlled. The crystal growth crucible 17 is divided into an outer peripheral portion 20 and an inner peripheral portion 21 by a partition plate 19, and a heater 22 for temperature adjustment is arranged outside. Outer part 1
The melt 16 sent into the melt 9 from the melt supply pipe 15 flows into the inner peripheral portion 21 through the communication hole 23 provided in the partition plate 19, and is consumed for growing the single crystal 24.

[0010]

EXAMPLE 1 kg of polycrystalline S was placed in a melting vessel 1 having a capacity of 2 kg.
Raw material 6 was fed and dissolved in an Ar atmosphere of 20 Torr. At this time, the high-frequency heating coil 2 housed in the enclosing container 11 maintained in the Ar atmosphere of 200 Torr causes the carbon provided outside the quartz crucible of the melting container 1 with a frequency of 20 kHz and a supply power of about 40 kW. The support was heated. When the temperature of the Si raw material 6 reached about 800 ° C. and the conductivity became sufficient, induction heating was performed at a high frequency,
Melt 16 was prepared. When high-frequency heating was performed under these conditions, the supplied electric power was efficiently consumed for dissolving the polycrystalline raw material 6 without generating discharge due to the reduced-pressure atmosphere. For comparison, when the polycrystalline raw material 6 was heated by energizing the high-frequency heating coil 2 maintained in the same atmosphere as the melting container 1 without using the enclosure 11, discharge was remarkable, and the raw material was continuously charged. Could not be dissolved. The melted melt raw material 13 is fed from the melt supply pipe 15 to the crystal growth section, and has a diameter of 2 at a pulling rate of 0.8 mm / min.
A 00 mm Si single crystal was pulled. 6 with crystal growth
The melt 16 was continuously supplied at a rate of 5 g / min.
The supply, dissolution, and transfer of the i raw material 6 to the crystal growth section were continued without any problem. Observation of the obtained single crystal revealed no defect due to the contaminated atmosphere gas in the raw material melting portion, and it was a high quality single crystal.

[0011]

As described above, in the present invention, the high-frequency heating coil used for preparing the melt for growing a single crystal by dissolving the polycrystalline raw material is used in an atmosphere under normal pressure or low vacuum. It is housed in a sealed container maintained at
The supplied electric power is efficiently consumed for melting the raw material without causing a discharge phenomenon caused by the high vacuum. In addition, since the raw material melting part and the crystal growth part are maintained in independent reduced-pressure atmospheres, it is possible to grow a high-quality single crystal without defects caused by a contaminated atmosphere being taken into the pulled single crystal. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a raw material melting section according to the present invention.

Fig. 2 Crystal growth part where melt is fed from raw material melting part

[Explanation of symbols]

1: melting vessel 2: high-frequency heating coil 3: hanging weir 4: raw material melting section 5: melt storage section 6: solid raw material 7: feeder
8: Air supply pipe 9: Exhaust pipe 10: Ar gas 1
1: enclosure 12: vessel wall 13: molten material 14: side wall 15: melt supply pipe 16: melt 1
7: Crystal growth crucible 18: Heater 19: Partition plate 20: Outer periphery
21: Inner circumference 22: Heater 23: Communication hole 2
4: Single crystal

(72) Inventor Nobumitsu Takase 1-4-2 Marunouchi, Chiyoda-ku, Tokyo (72) Inventor Tetsuhiro Iida 1-4-2, Marunouchi, Chiyoda-ku, Tokyo (72) Inventor Junichi Matsubara Marunouchi, Chiyoda-ku, Tokyo 1-4-2 (56) References JP-A-52-58080 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (4)

(57) [Claims] 1. A high-frequency heating coil is housed in a sealed container maintained at normal pressure or a low vacuum atmosphere, and a melting vessel into which a polycrystalline raw material is charged is heated under an atmosphere at the same pressure as a crystal growth part. A high-frequency heating and melting method of a polycrystalline raw material for producing a single crystal, wherein the polycrystalline raw material in the melting vessel is heated and melted by disposing the high-frequency heating coil and energizing the high-frequency heating coil. 2. A high-frequency heating and melting method for a polycrystalline raw material for producing a single crystal, wherein the sealed container according to claim 1 is maintained at an Ar atmospheric pressure of 100 Torr or more. 3. A dissolving vessel divided by a hanging weir into a raw material dissolving section and a melt storing section, an enclosing vessel disposed around the dissolving vessel and maintained in an atmosphere of normal pressure or low vacuum, A high-frequency heating coil housed in a sealed container, and a melt supply pipe communicating the melt storage unit with a crystal growing unit are provided, and a space between the melting vessel and the high-frequency heating coil is made of a material having low conductivity. High-frequency heating and melting equipment for polycrystalline raw materials for producing single crystals, which are separated by vessel walls. 4. A high-frequency heating and melting apparatus for a polycrystalline raw material for producing a single crystal, wherein a space between the melting vessel and the high-frequency heating coil according to claim 3 is separated by a quartz vessel wall.