JPH11199366A - Single crystal silicon pulling device - Google Patents

Abstract

(57) [Abstract] [Problem] To reduce the weight, size and cost of a single crystal silicon pulling device. SOLUTION: In the single crystal silicon pulling apparatus,
The superconducting magnet, such as a cryogenic refrigerator that cools the superconducting magnet and the superconducting magnet's ports (current lead port and measurement port), are all provided in addition to the top of the superconducting magnet. To make it clear. [Effect] Since the stroke of the movable shaft can be shortened when single crystal silicon is taken out, the strength and rigidity of the movable shaft, the support, and the base can be reduced. This allows the single crystal silicon pulling apparatus to be lightweight, compact and inexpensive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal silicon pulling apparatus. In particular, the present invention relates to a single crystal silicon pulling apparatus using a so-called MCZ method (magnetic field applying Czochralski method).

[0002]

2. Description of the Related Art FIG. 6 shows a single crystal silicon pulling apparatus using a conventional MCZ method (magnetic field applying Czochralski method). This apparatus is similar to the single crystal silicon pulling apparatus described in, for example, page 1008 of Low Temperature Engineering and Superconductivity Handbook (Ohm Co., 1993). This is a magnetic field application type Czochralski method (MCZ
This method is called a method of applying a magnetic field to molten silicon to suppress convection and obtain high-quality single-crystal silicon. This method is most often used for manufacturing single-crystal silicon for semiconductor devices. Next, the operation of the single crystal silicon pulling apparatus using the magnetic field application type Czochralski method (MCZ method) will be described. The molten silicon 1 in the crucible 2 is heated by the heater 5 to a high temperature of about 1500 degrees Celsius through the crucible 2. Heated. Single crystal silicon 6 grown from molten silicon 1 is pulled up by wire winding mechanism 8 via wire 7. Convection occurs in the heated molten silicon 1 (see FIG. 7). It is said that this convection increases sharply as the diameter of the crucible 2 increases, and it is difficult to obtain a high-quality single crystal unless some convection suppressing measures are taken when pulling a single crystal silicon of 12 inches or more. By the way, the molten silicon 1 is a liquid having the same electrical conductivity as mercury. Therefore, when a magnetic field is applied thereto, the molten silicon 1 receives an electromagnetic braking force when crossing the magnetic field lines. The molten silicon 1
Is suppressed and high quality single crystal silicon 6 is obtained.
Therefore, application of a magnetic field to the molten silicon 1 by the superconducting magnet 10 has been widely attempted.

In FIG. 6, when all of the molten silicon 1 is changed to single crystal silicon 6, the single crystal silicon 6 is taken out. The single-crystal silicon 6 is taken out in the following procedure. (1) The heating by the heater 5 is stopped and the inside of the furnace 9 is cooled to room temperature. (2) Uncoupling the flange 15. (3) Extend the movable shaft 17 to make the single crystal silicon 6
From the furnace 9 (see FIG. 8). (4) The single-crystal silicon 6 is moved outside the gantry 13 by rotating the movable shaft 17 by 180 degrees (see FIG. 9). (5) The movable shaft 17 is contracted to make the single crystal silicon 6
Lower down. (6) Take out the single crystal silicon 6.

[0004]

As shown in FIG. 6, the above-mentioned single crystal silicon pulling apparatus includes ports (current lead ports and measurement ports) 11 which are auxiliary equipment of the superconducting magnet 10 and a cryogenic temperature. A refrigerator 12 is provided on the upper surface of the superconducting magnet 10. (Similarly, Low Temperature Engineering and Superconductivity Handbook (Ohm, 1993), 1
Also in the single crystal silicon pulling apparatus shown on page 008, current leads, measurement lines, small refrigerators, service ports, and the like are provided on the upper surface of the vacuum chamber. )
Thereby, wiring for current supply and measurement inside the vacuum chamber can be connected on the upper side of the single crystal silicon pulling device, and handling of the cryogenic refrigerator 12 and connection with external operation equipment are also easy. However, since the auxiliary equipment is provided on the upper surface of the superconducting magnet, the single crystal silicon 6 can be moved so that the lowermost surface of the single crystal silicon 6 is higher than the uppermost surfaces of the ports 11 and the cryogenic refrigerator 12 when the single crystal silicon 6 is taken out. The shaft 12 had to be extended. In order to increase the stroke of the movable shaft 12, it is necessary to make the movable shaft 12, the support 18 and the base 19 rigid and increase their rigidity. For this reason, the single crystal silicon pulling apparatus is large, heavy, and expensive.

An object of the present invention is to provide a single crystal silicon pulling apparatus that is lightweight, compact and inexpensive.

[0006]

According to the present invention, there is provided a single crystal silicon pulling apparatus, comprising: a furnace having a crucible for storing molten silicon; a heater for heating the molten silicon through the crucible; A superconducting magnet that applies a magnetic field to the molten silicon, a gantry that supports the furnace and the superconducting magnet, and a wire winding mechanism that is connected via a flange at the top of the furnace and pulls single-crystal silicon upward from the crucible And supporting the wire winding mechanism, and lifting the wire winding mechanism upward,
Further, a moving mechanism for moving to the outer periphery of the furnace is provided, and ancillary equipment of the superconducting magnet is provided at a place other than the upper surface of the superconducting magnet. Preferably, the accessory is provided on a lower surface of the superconducting magnet. Preferably, the moving mechanism is a column, a movable shaft supported by the column and vertically movable and rotatable around the column, an arm horizontally attached to the movable shaft, and attached to the arm, An arm head that houses a wire coupled to the single crystal silicon and a wire winding mechanism.
Preferably, the accessory device of the superconducting magnet includes a cryogenic refrigerator for cooling the superconducting magnet and ports (current lead port and measurement port). Preferably, the cryogenic refrigerator is a two-stage or three-stage Gifford McMahon refrigerator, a two-stage or three-stage Stirling refrigerator, a two-stage or three-stage pulse tube refrigerator, and a two-stage refrigerator. Or a three-stage Villemeier refrigerator. Preferably, the magnetic field applied to the molten silicon by the superconducting magnet is any one of a parallel magnetic field parallel to the crucible axis, a vertical magnetic field perpendicular to the crucible axis, and a cusp magnetic field. In a preferred embodiment, the superconducting magnet is comprised of one of the superconducting material, Nb ₃ Sn-based superconducting material and high temperature superconductive material NbTi system.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a single crystal silicon pulling apparatus according to an embodiment of the present invention. In this single crystal silicon pulling apparatus, the ports 11 and the cryogenic refrigerator 12
Are provided other than the upper surface of the superconducting magnet 10.
In the figure, a furnace 9 has a high temperature (about 15 degrees Celsius) of molten silicon 1, crucible 2, heater 5, single-crystal silicon 5 and the like.
00 degrees) is stored insulated. Crucible 2 contains molten silicon 1. The crucible drive motor 4 is supported by the base 19. The crucible drive motor 4 drives the crucible drive shaft 3 to rotate the crucible 2. The heater 5 heats the molten silicon 1 through the crucible 2. Wire winding mechanism 8
Pulls single crystal silicon 6 precipitated from molten silicon 1 by wire 7 in accordance with the crystal deposition rate. Superconducting magnet 10 for applying a magnetic field to molten silicon 1
Are arranged around the furnace 9. The furnace 9 and the superconducting magnet 10 are mounted on a pedestal 13, and the pedestal 13 is supported on a base 19. The ports 11 and the cryogenic refrigerator 12 which are auxiliary equipment of the superconducting magnet 10 are mounted on the superconducting magnet 10 except for the upper surface thereof. Exists in the interior space. Thereby, the upper surface of the superconducting magnet 10 becomes clear. Here, ports 1
1 is provided for taking out a current lead for supplying a current to the superconducting magnet 10 and a measuring lead for monitoring the state of the superconducting magnet 10 from the superconducting magnet 10. 10
Cool superconducting coils and heat shields inside to extremely low temperatures. Further, the arm head 14 that houses the wire 7 and the wire winding mechanism 8 is connected to the furnace 9 via a flange 15 for connecting and disconnecting the arm head 14 from the furnace 9. On the other hand, the strut 18 supporting the movable shaft 17
It is provided on the base 19 on the base 19 side. Prop 1
8 supports the movable shaft 17, and the movable shaft 17
Arms 16 and 17 supporting arm head 14 are arms 1
The arm head 14 is moved up and down via 6. The pulling device control unit 20 controls the growth and extraction of the silicon single crystal in the furnace 9, and the superconducting magnet control unit 21 controls the magnetic field generation in the superconducting magnet 10.

FIG. 2 shows the basic structure of the superconducting magnet 10 shown in FIG. This superconducting magnet 10
Then, the ports 11 and the cryogenic refrigerator 12
Are provided on the lower surface of the superconducting magnet 10. FIG.
, The superconducting coil 50 and the heat shield 130 are disposed inside the vacuum chamber 120. Current lead 110 supplies current to superconducting coil 50. The vacuum chamber 120 maintains a vacuum around the superconducting coil 50 for heat insulation. Heat shield 130 blocks heat radiation from vacuum chamber 120 to superconducting coil 50. The ports 11 are used to take out a current lead 110 for supplying a current to the superconducting coil 50, a measurement lead (not shown) for monitoring the state of the superconducting coil 50, a precooling tube, and the like from the vacuum chamber 120. Further, the cryogenic refrigerator 12 keeps the superconducting coil 50 and the heat shield 130 at a cryogenic temperature. The ports 11 and the cryogenic refrigerator 12 are attached to the lower surface of the superconducting magnet 10. Inside the vacuum chamber 120, one of the cooling stages of the cryogenic refrigerator 12 is responsible for cooling the heat shield 130, and the other of the cooling stages of the cryogenic refrigerator 12 is supercooled. A second cooling stage 150 for cooling the conduction coil 50 is provided between the low-temperature refrigerator 12 and the superconducting coil 50. Superconducting coil 50
Is formed of a metal-based superconducting material such as NbTi or Nb ₃ Sn or an oxide-based high-temperature superconducting material, and is set to an appropriate temperature (4 K in the case of NbTi) by the second cooling stage 150 of the cryogenic refrigerator 12. Near, around 10K for Nb ₃ Sn, around 50K for high temperature superconducting material)
Is kept. The heat shield 130 is cooled by the first cooling stage 140 of the cryogenic refrigerator 12. here,
The cryogenic refrigerator 12 is, for example, a two-stage or three-stage GM
(Gifford McMahon) A two-stage or three-stage Stirling refrigerator, a two-stage or three-stage pulse tube refrigerator, a two-stage or three-stage VM (Villmeyer) refrigerator.

Next, a magnetic field application type Czochralski method (M
The operation of the single crystal silicon pulling apparatus according to the CZ method will be described with reference to the apparatus shown in FIG. Molten silicon 1 is heater 5
To a high temperature of about 1500 degrees Celsius through the crucible 2. Single crystal silicon 6 grown from molten silicon 1 is pulled up by wire winding mechanism 8 via wire 7 at a speed of about 1 mm / min. At this time, the crucible 2 containing the molten silicon 1 is rotated by the crucible drive motor 4 via the crucible drive shaft 3. The single crystal silicon 6 is also rotated in the direction opposite to the crucible. To suppress convection in the molten silicon 1, a magnetic field is applied to the molten silicon 1 by the superconducting magnet 10. Since the molten silicon 1 is a liquid having the same electrical conductivity as mercury, when a magnetic field is applied to the liquid, the molten silicon 1 receives an electromagnetic braking force when crossing the magnetic field lines. The convection of the molten silicon 1 is suppressed by this braking force, and a high-quality single crystal silicon 6 is obtained.

In the single crystal silicon pulling apparatus shown in FIG. 1, when all of the molten silicon 1 is changed to single crystal silicon 6, the single crystal silicon 6 is taken out. The single-crystal silicon 6 is taken out in the following procedure. (1) The heating by the heater 5 is stopped and the inside of the furnace 9 is cooled to room temperature. (2) Uncoupling the flange 15. (3) Extend the movable shaft 17 to make the single crystal silicon 6
From the furnace 9. (4) The single-crystal silicon 6 is moved out of the gantry 13 by rotating the movable shaft 17 by 180 degrees. (5) The movable shaft 17 is contracted to make the single crystal silicon 6
Lower down. (6) Take out the single crystal silicon 6.

Here, since the ports 11 and the cryogenic refrigerator 12 which are the accessory equipment of the superconducting magnet are not provided on the upper surface of the superconducting magnet 10, there is no attached equipment on the upper surface of the superconducting magnet. , Is clear. Therefore, when taking out single crystal silicon, the movable shaft may be extended so that the lowermost surface of the single crystal silicon is at most higher than the uppermost surface of the superconducting magnet. Therefore, the stroke of the movable shaft may be shorter than before, and the strength and rigidity of the movable shaft 17, the support 18 and the base 19 can be reduced. This makes it possible to provide a single crystal silicon pulling apparatus that is lightweight, compact and inexpensive.

By the way, there are various methods in which the superconducting magnet 10 applies the lines of magnetic force to the molten silicon 1. FIG.
4 and 5 show typical methods. In each figure, 1 is molten silicon, 2 is a crucible, 10 is a superconducting magnet, 50 is a superconducting coil, 60 is magnetic lines of force indicating a magnetic field generated by the superconducting magnet 10, 7
0 indicates the liquid level of the molten silicon 1. FIG. 3 shows a method of applying magnetic lines of force in a direction perpendicular to the crucible 2. In this case, convection is suppressed when the molten silicon 1 flows to the outer peripheral side along the bottom surface of the crucible 2. FIG. 4 shows a method of applying magnetic lines of force to the crucible 2 in a horizontal direction.
In this case, convection is suppressed when the molten silicon 1 flows along the side wall of the crucible 2. FIG. 5 shows a method of applying a cusp magnetic field (a magnetic field shaped like two flowers of a morning glory) to the crucible 2. In this case, the movement is suppressed both when the molten silicon 1 flows on the bottom surface of the crucible 2 toward the outer periphery and when the molten silicon 1 rises on the side wall. The superconducting magnet control unit 21 suppresses convection by using one of the application methods.

[0013]

According to the present invention, the ports and the cryogenic refrigerator, which are the auxiliary equipment of the superconducting magnet, are provided on the superconducting magnet other than the upper surface, and the upper surface of the superconducting magnet is made clear. The moving distance at the time of taking out silicon is shortened, and the moving mechanism of single crystal silicon can be made lightweight and compact. In addition, since the accessory device of the superconducting magnet is provided on the lower surface of the superconducting magnet, the accessory device can be housed in the gantry, and the single crystal silicon pulling apparatus can be made compact. The moving mechanism includes a support, a movable shaft supported by the support, vertically moving up and down, and rotatable about the support, an arm mounted on the movable shaft in a horizontal direction, and an arm mounted on the arm. Since it is composed of the wire coupled to the crystalline silicon and the arm head that houses the wire winding mechanism, the strength and rigidity of the movable shaft, the support, and the like can be reduced. In addition, a cryogenic refrigerator that cools the superconducting magnet and ports (current lead port and measurement port), which are auxiliary devices of the superconducting magnet, are provided other than the upper surface of the superconducting magnet, so that the upper surface of the superconducting magnet can be cleaned up. .
In addition, as a cryogenic refrigerator as a supplementary facility, a two-stage or three-stage Gifford McMahon refrigerator, two-stage or three-stage
Any cryogenic refrigerator, a staged Stirling refrigerator, a two-stage or three-stage pulse tube refrigerator, and a two-stage or three-stage Villemeier refrigerator can be used. The superconducting magnet can use any of a parallel magnetic field parallel to the crucible axis, a vertical magnetic field perpendicular to the crucible axis, and a cusp magnetic field as the magnetic field applied to the molten silicon. Also,
The superconducting magnet is NbTi-based superconducting material, Nb ₃ S
It can be made of either an n-based superconducting material or a high-temperature superconducting material.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a single crystal silicon pulling apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a basic configuration of a superconducting magnet.

FIG. 3 is a diagram of a vertical magnetic field generated by a superconducting magnet.

FIG. 4 is a diagram of a horizontal magnetic field generated by a superconducting magnet.

FIG. 5 is a diagram of a cusp magnetic field generated by a superconducting magnet.

FIG. 6 is a cross-sectional view of a conventional single crystal silicon pulling apparatus.

FIG. 7 is a diagram illustrating convection of molten silicon.

FIG. 8 is a sectional view showing one step of taking out single crystal silicon by a conventional single crystal silicon pulling apparatus.

FIG. 9 is a cross-sectional view showing one step of taking out single-crystal silicon with a conventional single-crystal silicon pulling apparatus.

[Explanation of symbols]

1 molten silicon, 2 crucible, 5 heater, 6
Single crystal silicon, 8 wire winding mechanism, 9 furnace,
10 superconducting magnet, 11 ports, 12
Cryogenic refrigerator, 13 gantry, 15 flange, 1
6 arms, 17 movable shafts, 18 columns.

Claims (7)

[Claims] 1. A furnace having a crucible for containing molten silicon, a heater for heating the molten silicon through the crucible, a superconducting magnet disposed radially around the furnace and applying a magnetic field to the molten silicon; And a gantry supporting the superconducting magnet, a wire winding mechanism connected via a flange at the top of the furnace, and pulling the single crystal silicon upward from the crucible, and a wire winding mechanism supporting and supporting the wire winding mechanism. A single crystal silicon pulling apparatus, comprising: a moving mechanism for lifting upward and further moving to the outer periphery of the furnace, wherein ancillary equipment of the superconducting magnet is provided at a place other than the upper surface of the superconducting magnet. 2. The single crystal silicon pulling apparatus according to claim 1, wherein an accessory device of the superconducting magnet is provided on a lower surface of the superconducting magnet. 3. The moving mechanism includes a column, a movable shaft supported by the column, vertically movable and rotatable about the column, an arm mounted on the movable shaft in a horizontal direction, and an arm mounted on the arm. And a wire head connected to the single crystal silicon and a wire winding mechanism.
3. The single crystal silicon pulling apparatus according to any one of claims 1 to 2. 4. The single crystal silicon pulling apparatus according to claim 1, wherein the superconducting magnet auxiliary equipment includes a cryogenic refrigerator for cooling the superconducting magnet and ports. 5. A cryogenic refrigerator comprising a two-stage or three-stage Gifford McMahon refrigerator, a two-stage or three-stage Stirling refrigerator, a two-stage or three-stage pulse tube refrigerator, and a two-stage or three-stage refrigerator. The single crystal silicon pulling apparatus according to claim 4, wherein the single crystal silicon pulling apparatus is any of a Villemeier refrigerator. 6. The magnetic field applied to the molten silicon by the superconducting magnet is any one of a parallel magnetic field parallel to the crucible axis, a vertical magnetic field perpendicular to the crucible axis, and a cusp magnetic field. Or a single crystal silicon pulling apparatus. 7. A superconducting magnet superconductive material NbTi system, Nb ₃ Sn-based superconducting material and single according to any of claims 1 to 6 is constituted by any one of the high temperature superconductor material Crystal silicon pulling device.