JPS623091A - Single crystal pulling up apparatus - Google Patents

Abstract

PURPOSE:To suppress the reduction in magnetic flux density in the crucible wall part in the direction crossing the coil axis while reducing the coil diameter to a small value, by providing a magnetic material at a magnetic flux- penetrating part or a position opposite thereto in a chamber. CONSTITUTION:A single crystal pulling up apparatus obtained by forming most of a chamber (3a) from a nonmagnetic material 31, forming a wall part facing coils (1a) and (1b) partially from a magnetic material 32, forming a circular region almost equal to a range obtained by projecting the coils (1a) and (1b) in the axial direction from a magnetic material 32 in the chamber (3a). When the coils (1a) and (1b) are brought near, most of the magnetic flux passes through the magnetic material 32. Therefore, the expansion of the lines of magnetic force in the direction crossing the coil axis slight and the magnetic flux distribution is equalized as much. As a result, the reduction in magnetic flux density near the point (D) of the coil wall is suppressed to improve the quality of the resultant single crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a single crystal pulling device for producing a single crystal by the Czochralski method, and particularly relates to a magnetic flux pulling device when applying a magnetic field to suppress convection of a melt. It is related to equalization of density.

[Technical background of the invention and its problems]

One type of crystal creation method is the Czochralski method.

This is a method in which a rod or seed crystal immersed in melt is slowly pulled up while the liquid adhering to the tip is solidified.

Recently, when pulling such single crystals, by applying a magnetic field to the melt and suppressing convection, it is possible to stabilize the melt temperature, suppress the contamination of impurities due to melting of the melt wall, and improve the quality of the single crystal. It has been proven that this can be achieved, and it has been put into practical use in some areas.

FIG. 4 is a cross-sectional view showing the configuration of this type of conventional single crystal pulling apparatus, in which a pair of coils Ia and 1b for creating a magnetic field are housed in a coil storage case 2, and these coils 1a and lb In between is provided a chamber 3 with cylindrical side walls. Further, a crucible 4 containing a raw material melt 5 is held in the center of the chamber 3, and a heater 7 is further installed around the crucible 4.

Here, the chamber 3 isolates the atmosphere that the raw material melt 5 comes into contact with from the atmosphere, and an inert gas such as argon is flowed inside. Then, a single crystal seed is immersed in the raw material melt 5 melted by the heater 7 and pulled up at low speed to form a single crystal 6.

By the way, the melt 5 during the production of a single crystal causes thermal convection along the arrow B as shown in the enlarged view in FIG. produce defects.

In addition, the melt 5 becomes boiling by being heated,
Causes severe temperature changes, i.e. thermal oscillations.

This thermal vibration causes microscopic re-dissolution at the solid-liquid interface of the growing single crystal, and generates dislocation loops, stacking faults, etc. in the grown single crystal.

In order to prevent defects caused by such thermal convection and thermal vibration, a magnetic field is applied to the melt 5, but at this time, the coils la,
When a horizontal magnetic field 10 is applied by lb, the movement of the melt, which is transferred by thermal convection and thermal vibration, is suppressed by Lenz's law, similar to a conductor moving perpendicular to the magnetic field.

In this case, the heater 7 is arranged concentrically with the crucible 4, and it can be said that the force for causing thermal convection is greatest near the crucible wall. Therefore, it is desirable to apply the magnetic field so that it is strongest near the crucible wall.

However, in reality, as shown in the cross-sectional view of FIG. 6, the magnetic flux density becomes minimum due to the spread of the magnetic flux near the crucible wall in the direction perpendicular to the coil axis, that is, point D.

To explain this, FIG. 7 is a miniature diagram showing the relationship between the radial distance from the center of the crucible and the magnetic flux density.

That is, the diameter of the crucible is 380 [length], the coils 1a, 1
b mutual spacing 11l100 (a, this coil Ia, 1b
(7) Assuming an outer diameter of 800 (m), curve 11 shows the change in magnetic flux density in the Xx' cross section of FIG. 6, and curve 12 shows the change in magnetic flux density in the YY' cross section in FIG.

Here, using the center point C of the crucible as a reference, the magnetic flux density is 38 (%) higher near point A on the crucible wall in the direction of the coil axis, whereas It can be seen that the value is reduced by 17% near the wall point.

To suppress the decrease in magnetic flux density at the crucible wall point, use coil Ia.
, it is possible to increase the diameter of lb, but in this method, the presence of a large coil significantly impedes the operability of pulling the single crystal, the structure becomes complicated and expensive, and it goes against the mold closure method of reducing the coil diameter. There was something.

[Purpose of the invention]

This invention was made in order to eliminate the drawbacks of the above-mentioned conventional devices, and provides a single crystal pulling device that can significantly suppress the decrease in magnetic flux density at the crucible wall in the direction perpendicular to the coil axis while keeping the coil diameter small. The purpose is to provide.

[Summary of the invention]

To achieve this objective, the present invention holds a crucible inside a chamber isolated from the atmosphere, and suppresses the convection of the Fa liquid in the crucible by applying a horizontal magnetic field from outside the chamber. In a single crystal pulling apparatus for producing a single crystal, a plate made of a magnetic material is disposed at a magnetic flux permeable wall of the chamber or at a position opposite to the magnetic flux permeable wall, and this plate acts on the melt. This is characterized by equalizing the magnetic flux density of the magnetic field.

[Embodiments of the invention]

FIG. 1 is a cross-sectional view showing the configuration of an embodiment of the present invention. In the figure, the same reference numerals (=j) as in FIGS. 4 and 6 indicate the same elements. , the chamber is usually formed of a non-magnetic material, but the shank 3a shown here is mostly formed of a non-magnetic material 31, and the coil 1a,
This device differs from the conventional device in that the wall portion facing 1b is partially formed of magnetic material 32.

Here, in the chamber 3a, a circular region approximately equal to the range projected in the axial direction of the coils 1a and 1b is formed of the magnetic material 32, and the coil 1a is located here.

1b, most of the magnetic flux passes through this magnetic body. Therefore, compared to the conventional device, the spread of the magnetic lines of force in the direction orthogonal to the coil axis is smaller, and the magnetic flux distribution is equalized accordingly, thereby suppressing a decrease in the magnetic flux density near the coil wall point.

FIG. 2 is a diagram showing the relationship between the distance from the center point C and the magnetic flux density in the YY' section of this embodiment in comparison with a conventional device.

In other words, in the conventional device, as shown in song 1i112,
When the magnetic flux density at the center point C is 4000 CQauss), the magnetic flux density at a point on the crucible wall in the direction perpendicular to the coil axis is 3330 (aauss), which is about 17%.
] decreased, whereas in this example, as shown by curve 12a, the magnetic flux density at the point on the wall in the direction perpendicular to the coil axis was 3840 (gauss), a decrease of approximately 4%. remains in place.

By the way, the magnetic flux density at point C, the center of the crucible, is 4000 (
gauss), the magnetic flux density at point E near the coil axis (Fig. 6) among the walls of the chamber 3 made of non-magnetic material is 9000 (gauss),] 1 which is deviated from the coil by the radius of the coil. The magnetic flux density at the point (Figure 6) is 7
800 Coauss).

This magnetic flux is passed through the magnetic material portion 32 shown in FIG.
In order to avoid magnetic saturation, it is necessary to
In order to obtain a magnetic flux density of about 100 (s), a plate thickness of about 100 (s) is required. However, even if the plate thickness was made to be 30 to 40 mm, it was sufficient to improve the magnetic flux distribution.

FIG. 3 is a cross-sectional view of another embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same elements. In FIG. 1, the magnetic flux passing wall of the chamber is made of a magnetic material, but here a plate 14 made of a magnetic material 'C' is disposed at a position facing the magnetic flux passing wall.

Although this configuration slightly increases the number of parts, it provides the same effects as described above and is advantageous in that the thickness and size of the plate can be freely selected. Although the embodiments have been described, the present invention is not limited thereto. In short, by arranging a plate made of a magnetic material at the magnetic flux passage wall of the chamber or at a position opposite to this magnetic flux passage wall, the magnetic flux density of the magnetic field acting on the melt can be equalized. can be converted into

〔Effect of the invention〕

As described above, according to the present invention, it is possible to suppress the decrease in magnetic flux density at the crucible wall in the direction orthogonal to the coil axis to a significantly low level while keeping the diameter of the coil for applying a magnetic field to the melt small. There is an effect that it can be done.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of one embodiment of the present invention, Fig. 26 is a diagram showing the relationship between the radial distance of the crucible and the magnetic flux density to explain the operation of the embodiment, and Fig. 3 is a diagram showing the relationship between the radial distance of the crucible and the magnetic flux density. A cross-sectional view of another embodiment, FIG. 4 is a vertical cross-sectional view of a conventional single crystal pulling apparatus, and FIG.
The figure is a partially enlarged sectional view of the same device, FIG. 6 is a cross-sectional view of the same device, and FIG. 7 is a diagram showing the relationship between the radial distance of the crucible and the magnetic flux density to explain the action of the device. It is. 1a, 1b...coil, 3a...chamber, 4...
- Crucible, 5... Melt, 6... Single crystal, 7... Heater, 14... Plate, 31... Non-magnetic material, 32...
・Magnetic material. Applicant's agent Kiyoshi Inomata, dd'21

Claims (1)

[Claims] 1. A crucible is held inside a chamber isolated from the atmosphere, and a single crystal is grown while suppressing convection of the melt in the crucible by applying a horizontal magnetic field from outside the chamber. In the single crystal pulling apparatus to be produced, a plate made of a magnetic material is disposed at the magnetic flux permeable wall of the chamber or at a position opposite to the magnetic flux permeable wall, and the plate acts on the melt. A single crystal pulling device characterized by equalizing the magnetic flux density of the magnetic field. 2. The single crystal pulling apparatus according to claim 1, wherein the plate body has a side wall facing the chamber partially formed of a magnetic material.