JP3101574B2 - Magnetic field generator for single crystal puller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field generator for a single crystal pulling apparatus which can easily inject liquid helium.

[0002]

2. Description of the Related Art As a typical method for pulling a single crystal from a melt, the Czochralski method is known. In the Czochralski method, as shown in FIG.
To make the single crystal 3 grow. Obtained single crystal 3
Is greatly influenced by the melt interface. For example, if the vibration of the melt surface or the heat convection is large, the crystal once grown is partially redissolved, which causes crystal defects, swirl-like defects, growth stripes and the like. Vibration and thermal convection of the melt surface can be suppressed by applying a magnetic field to the single crystal growing atmosphere. In the method of pulling a single crystal from a melt while applying a magnetic field, that is, the MCZ method, a magnetic field generator 4 for applying a horizontal magnetic field is arranged on the outer periphery of a pulling device main body 5 as shown in FIG. When a magnetic field in the horizontal direction is applied to the melt 1, the effective viscosity of the melt having electrical conductivity increases, and the generation of convection in the vertical direction inside the melt 1 is suppressed. As a result, the growth interface between the single crystal 3 being pulled and the melt 2 is stabilized, and a single crystal 3 of constant quality is grown.

[0003]

As the magnetic field generator 4, a superconducting magnet capable of applying a strong magnetic field of 3,000 gauss or more is used. The superconducting magnet uses a magnetic field generated by supplying a current to a coil around which a superconducting wire is wound. In order to drive the superconducting magnet in the superconducting mode, the magnetic field generator 4 is operated at a very low temperature. Cooling is required. Liquid helium is usually used as the refrigerant at this time, and is charged into a cryostat containing a superconducting coil. The liquid helium filling the cryostat evaporates as a result of cooling the superconducting coil. Therefore, periodic replenishment of liquid helium is required. For filling and replenishment of liquid helium, for example, a system shown in FIG. 2 has been conventionally used. That is, the long tube 7 is inserted into the cryostat 6, and the adapter 8 attached to the upper end of the tube 7 and the liquid helium source 9 are connected by the flexible transport tube 10. Then, an appropriate valve provided on the liquid helium source 9 or the transport pipe 10 is opened, and a predetermined amount of liquid helium is sent from the liquid helium source 9 into the cryostat 6.

However, in this method, since a long tube having a length of 1 to 2 m is inserted vertically into the magnetic field generator 4, a difficult operation is required. In addition, since the work is performed on the upper surface of the cryostat 6 that reaches a height of 2 m,
Multiple workers are required, and this is a dangerous work at height.
The present invention has been devised to solve such a problem, and by making it possible to attach a flexible transport tube extending from a liquid helium source when working from the side of a cryostat, it is difficult and dangerous. The purpose is to eliminate work and facilitate filling and refilling of liquid helium.

[0005]

SUMMARY OF THE INVENTION A magnetic field generator for a single crystal pulling device according to the present invention is a magnetic field generating device arranged around a pulling device body for pulling a single crystal from a melt in order to achieve the object. A cryostat accommodating a superconducting coil therein, a tube vertically inserted and fixed inside the cryostat, and an adapter attached to an upper end opening of the tube and having a connection portion facing a peripheral surface side of the cryostat. The distal end of a flexible transport tube extending from the liquid helium source is connected to the connection of the adapter.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic field generator 4 according to the present invention is shown in FIG.
As shown in the figure, a vertical tube 7 for receiving liquid helium is inserted and fixed inside the cryostat 6. At the upper end of the preset tube 7, an adapter 8 having a connection portion facing the side of the magnetic field generator 4 is attached. In order to easily connect the flexible transport tube 10 to the tube 7, it is preferable to provide a bayonet connector 11 on the adapter 8 as shown in FIG. 4 and attach the other bayonet connector 12 to the distal end of the flexible transport tube 10. . Thus, the flexible transport pipe 10 is connected to the tube 7 by a simple operation of inserting and rotating the bayonet connector 12 on the transport pipe 10 side into the bayonet connector 11 on the adapter 8 side. The adapter 8 includes a valve 13 and has a structure in which liquid helium does not leak from the cryostat 6.

When the valve 13 is opened after the connection, the liquid helium of the liquid helium source 9 is sent into the cryostat 6 via the flexible transport tube 10 and the tube 7. The flow rate of the liquid helium is adjusted so that the liquid level of the liquid helium 14 is located above the superconducting coil 15 in the cryostat 6. Thereby, superconducting coil 15 is cooled so as to maintain the superconducting mode. On the other hand, the helium gas vaporized by the cooling rises in the cryostat 6, cools the upper part of the tube 7 and the adapter 8, and is discharged outside through the exhaust port 17. Thus, by cooling the vicinity of the adapter 8, the vaporization loss of the liquid helium is suppressed as much as possible. In addition, in order to cool the vicinity of the adapter 8, a cool air guide tube 18 can be provided inside the cryostat 6 as necessary. As described above, since the connection portion to the transport pipe 10 is provided on the side, the worker does not move to the upper surface of the cryostat 6 without moving.
The liquid helium source 9 can be connected to the cryostat 6 via the transport pipe 10 by working from a work floor (not shown) arranged around the cryostat 6. Therefore, the work does not require human labor, and the work itself is safe.

[0008]

As described above, in the magnetic field generator of the present invention, since the connection for supplying the cooling liquid helium into the cryostat is provided on the side of the cryostat, it extends from the liquid helium source. The transport pipe can be connected to the magnetic field generator with simple and safe operation.

[Brief description of the drawings]

Fig. 1 Single crystal pulling device used in MCZ method

Fig. 2 Conventional method of connecting a liquid helium source to a magnetic field generator

FIG. 3 shows a magnetic field generator connected to a liquid helium source using a tube preset in a cryostat according to the invention.

FIG. 4 is a main part showing the connection between the tube and the transport tube.

[Explanation of symbols]

1: melt 2: seed crystal 3: single crystal 4: magnetic field generator 5: pulling device body 6: cryostat 7: tube 8: adapter 9: liquid helium source 10: flexible transport tube 11, 12: bayonet connector 13 : Valve 14: liquid helium 15: superconducting coil 16: vaporized helium gas 17: exhaust port 18: cold air induction tube

────────────────────────────────────────────────── ─── Continued on the front page (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 Tokyo 1-4-2 Marunouchi, Chiyoda-ku (56) References JP-A-63-112489 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 1/00-35/00 F17C3 / 08 H01F 6/00 H01L 21/208 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A cryostat having a superconducting coil housed therein and a tube vertically inserted and fixed inside the cryostat. And an adapter attached to the upper end opening of the tube and having a connection portion facing the peripheral surface of the cryostat, and a distal end portion of a flexible transport tube extending from the liquid helium source is connected to the connection portion of the adapter. Magnetic field generator for single crystal pulling device.