JPH03183688A - Device for continuously pulling up single crystal - Google Patents

Abstract

PURPOSE:To enhance the pulling-up velocity of single crystal, productivity and yield and to make the price of a crucible inexpensive by providing a reflection plate of infrared rays between single crystal to be pulled up and the inside crucible of a double crucible. CONSTITUTION:In a single crystal pulling-up device equipped with a double crucible, a reflection plate 3 of infrared rays is provided to the upper part of the inside of the inside crucible 2 of the double crucible 1. Infrared rays emitted from the surface of melt 5 are reflected. The vicinity 14 of the inner face of the inside crucible which touches the melt 5 is locally heat insulated. The temp. of melt is locally held at high temp. in comparison with a growth region 15 of crystal. Thereby the temp. of the whole melt is lowly preset and the melt does not start to be solidified from the inner wall of the inside crucible 2. The pulling-up velocity of single crystal can be held at high velocity. Further the need for using the crucible having a large bore diameter is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a single crystal continuous pulling device equipped with a raw material i1 continuous supply device and a double crucible.

[Prior Art] As a single crystal pulling device, a device using the Czochralski method is known.

-e When pulling a single crystal from a melt using the Czochralski method, a predetermined amount of solid raw material is placed in the crucible, and the solid raw material is turned into a melt and pulled. The diameter and length are determined. In addition, impurities contained in the melt cause a segregation phenomenon and become concentrated as the crystals are pulled up. Therefore, the impurity concentration in the pulling direction of the pulled crystal is higher on the tail side of the crystal, making it difficult to make it uniform.

For this reason, Japanese Patent Application Laid-Open No. 58-36997 discloses that, as shown in FIG. 4, which is a schematic vertical cross-sectional view of a single crystal production apparatus, the apparatus is equipped with a raw material continuous supply apparatus 16, and the crucible is a double crucible 1. By continuously supplying a weight of raw material corresponding to the weight of the crystal, or an amount of raw material that maintains the impurity concentration in the melt between the outer crucible 9 and the inner crucible 2 during crystal pulling, A continuous pulling device is disclosed that is capable of pulling a long crystal or a crystal with a uniform impurity concentration.

The double crucible structure prevents the raw materials supplied during pulling from adhering to the single crystal and disturbing the crystallinity.

In addition, this structure is essential for continuous pulling in order to prevent disturbance of the melt surface during raw material injection from affecting crystal growth.

However, feeding raw materials into the melt tends to lower the melt temperature near the supply well. Therefore, if raw materials are continuously supplied, heating by an external heater (heater 4 in Fig. 4) will not be able to prevent the temperature of the melt from decreasing due to the supply of raw materials. Near the inner surface of the inner crucible, where the temperature is lower than the outer crucible (
The melt solidifies from step 14) in FIG. 4, making it impossible to pull it up.

Therefore, - for boat fishing, ■Set the melt temperature of the entire crucible to be high.

(2) Use a large diameter crucible and keep the melt temperature near the inner surface of the inner crucible sufficiently higher than the melt temperature near the crystal growth region (15 in Figure 4).

This method was used.

However, each of the above methods ■The pulling speed of single crystal becomes slow and productivity decreases.

(2) The cost of the crucible is high, and there are also problems in that the yield decreases because the amount of melt remaining at the end of pulling increases.

[Problem to be Solved by the Invention 1] The present invention solves the above-mentioned drawbacks of the prior art, and provides a continuous single crystal pulling device that can pull a single crystal at a high speed, has a high yield, and can reduce the cost of the crucible. That is.

[Means for Solving the Problems 1] In order to solve the above problems, the present invention provides a single crystal pulling device equipped with a raw material continuous supply device and a double crucible, in which the single crystal to be pulled and the inner crucible of the double crucible are A continuous single crystal pulling device characterized in that a reflecting plate is provided between the inner crucible and the melt surface that reflects infrared rays emitted from the melt surface in the inner crucible toward the melt surface close to the inner surface of the inner crucible. This is what we provide.

[Function] The present invention will be explained using FIG. 1, which shows a schematic vertical cross-sectional view of an embodiment.

By providing a reflecting plate 3 that reflects infrared radiation as shown in FIG. 1 above the inside of the inner crucible 2 of the double crucible 1, infrared radiation from the surface of the melt 5 is reflected and The area near the inner surface of the inner crucible I4, where the inner surface and the melt 5 are in contact, is locally kept warm, and the temperature of the melt is kept locally higher than that near the crystal growth region 15. By this, assimilation of the melt starts for the first time. Since the vicinity of the inner surface 14 of the crucible 2 can be maintained at a locally high temperature, even if the temperature of the entire melt is set to a low value, the assimilation of the melt does not start from the inner wall of the inner crucible 2, and the pulling speed of the single crystal can be increased. It also eliminates the need to use a large-diameter crucible.

The reflecting plate 3 is preferably made of a material that easily reflects infrared rays and has excellent heat resistance, such as molybdenum.

The apparatus of the present invention is suitably used for pulling single crystals of silicon, GaAs, etc.

f implementation IN) A schematic vertical cross-sectional view of an embodiment of the present invention is shown in FIG.

The graphite crucible 7 is supported by a support rod 8 and given rotational motion by the rotation of the support rod 8. The double crucible 1 supported by this graphite crucible 7 consisted of an inner crucible 2 and an outer crucible 9, the diameter of the inner crucible 2 was 300 mm, and the diameter of the outer crucible 9 was 400 mm.

The solid raw material 10 is transferred to the inner crucible 2 by the raw material continuous supply bag a16.
and the outer crucible 9 into the melt. solid raw material IO
The melted liquid reaches the inner crucible 2 through the through hole 11. The heater 4 is a heater for melting the solid raw material within the crucible.

The reflecting plate 3 according to the present invention was made of molybdenum, which easily reflects infrared rays and has excellent heat resistance.

This is a vertical cross-sectional view showing the shape of the reflector 3 used in FIG. 2, which has a thickness (d) of 2 mm and a length (a) of 50 mm.

Angle 1) The zero reflection plate 3, which has a truncated inverted conical shape with a 45 degree angle, is placed above the melt inside the inner crucible 2 by a supporting member 13 so that the closest distance to the melt surface is 30 mm, and the closest distance to the inner crucible 2 is 30 mm. It was installed so that the approach distance was 30 mm.

All of these members are housed in chamber I2.

A σ silicon single crystal having a diameter of 6 inches was pulled using the apparatus configured as described above. Polycrystalline silicon 10 was supplied from the raw material continuous supply device 16 in an amount equal to the weight of the pulled product 6, so that the amount of the melt 5 was always kept at a constant level.

FIG. 3 is a graph showing the change in pulling speed over time when a silicon single crystal is pulled using this embodiment and the conventional device shown in FIG. It is. Compared to conventional devices, by using the device of the present invention, it was possible to significantly improve the pulling speed without using a large crucible.

[Effects of the Invention J] By using the continuous single crystal pulling apparatus according to the present invention, (1) Even if a crucible smaller than the conventional one is used, the pulling speed can be made about three times faster than the conventional one, and productivity is improved.

■In the case of continuous pulling of a silicon single crystal with a diameter of 6 inches,
Conventionally, it was essential to use a crucible with a diameter of 450 mm or more, but it is now possible to pull a crucible with a diameter of 400 mm, reducing the cost of crucibles by about 40% compared to conventional methods.

The amount of remaining melt was also reduced by about 20%, and the yield was improved.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of an example of the present invention, FIG. 2 is a vertical cross-sectional view of a reflector in the example, and FIG. 3 is a graph showing changes over time in the single crystal pulling rate of the example and the conventional apparatus. FIG. 4 is a schematic vertical cross-sectional view of a conventional device. 1...Double crucible 2...-Inner crucible 3...-Reflector 4-...Heater 5...Melt 6...Single crystal 7...Graphite crucible 8...Support rod 9... -Outer crucible 10...Solid raw material 1]...Through hole 12...Chamber 13...-Supporting member 14...Near the inner surface of the crucible 15...Near the single crystal growth region 16...-Raw material Continuous feeding device applicant Kawasaki Steel agent

Claims (1)

[Claims] 1. In a single crystal pulling device equipped with a raw material continuous supply device and a double crucible, infrared rays emitted from the melt surface in the inner crucible are placed between the single crystal to be pulled and the inner crucible of the double crucible. A single crystal continuous pulling device characterized by being provided with a reflector that reflects toward the melt surface close to the inner surface of the inner crucible.