JPS6278185A - Single crystal growth and apparatus therefor - Google Patents

Abstract

PURPOSE:The titled apparatus, having a magnet device for applying a magnetic field to a single crystal raw material melt and a coil spacing adjusting device for making the intensity of the applied magnetic field of the magnet device variable and capable of growing a high-quality single crystal. CONSTITUTION:A raw material melt 1 is charged into a crucible 2 to a level (H0) and kept in a molten state by a heater 3. An initial coil spacing (L10) is set by a coil spacing adjusting device 22 to provide a relative position of coils (15a) and (15b) to the crucible 2 shown in the figure. A single crystal 7 is then grown at a constant pulling up speed (V). Thereby, the surface of the raw material melt 1 is lowered and there is no region (H1) shown in the figure as it is. Since a solid-liquid interfacial boundary layer 6 enters a region of thermal convections 8 in a curve (B10), the size of the region containing left thermal convections, i.e. a region in which the magnetic field intensity is smaller than (B10) is reduced by an amount corresponding to the lowered level of the melt surface so that the thermal convection inhibiting region of the level (H1) may be kept even when the growth of the single crystal 7 pro ceeds.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a single crystal growth apparatus and a single crystal growth method equipped with a magnet device that applies a magnetic field to a single crystal raw material melt.

[Technical Background of the Invention] An example of a conventional single crystal growth apparatus using the Czochralski method (CZ method) is shown in FIG. That is, single crystal raw material melt 1 (hereinafter referred to as raw material melt)
The crucible 2 filled with is heated by a heater 3 so that the single crystal raw material always remains in a molten state. When the seed crystal 4 is inserted into this melt and the seed crystal 4 is pulled up at a certain speed by the pulling drive mechanism 5, the solid-liquid interface boundary 1i! The crystal grows in step 6, and a single crystal 7 is produced.

At this time, a liquid motion of the melt, that is, a thermal convection 8, induced by the heating of the heating means, such as the heater 3, occurs. The cause of this thermal convection 8 is explained as follows. Thermal convection generally occurs when the balance between the buoyant force due to thermal expansion of the fluid and the viscous force of the fluid is broken, and the dimensionless quantity representing the balance between the buoyant force and the viscous force is the Grashof number NGr.

Nor-a-α・ΔT-R3/shi3 Where, g: Gravitational acceleration α: Coefficient of thermal expansion of raw material melt ΔT Temperature difference in radial direction of Nil crucible R Nil crucible radius C: Kinematic viscosity coefficient of raw material melt Generally, Grashof number N. When r exceeds a critical value determined by the geometric dimensions of the melt, thermal boundary conditions, etc., thermal convection occurs within the melt. Usually, when NGr>10', the thermal convection of the melt becomes turbulent, and when NGr>10', the thermal convection of the melt becomes turbulent. In the case of the current raw material melt conditions for pulling a single crystal with a diameter of 3 to 4 inches, NC1r>10' (according to the formula for Nar), and the inside of the raw material melt is in a turbulent state. The liquid interface boundary layer 6 becomes undulating.

When thermal convection in such a disturbed state exists, temperature fluctuations in the raw material melt, especially at the solid-liquid interface, are severe, and the thickness of the boundary layer at the solid-liquid interface is greatly fluctuated in position and time. Visual remelting becomes noticeable and dislocation loops, stacking faults, etc. occur in the grown single crystal. Moreover, this defective portion is generated forcelessly in the single crystal pulling direction due to irregular fluctuations of the solid-liquid interface. Furthermore, high m raw material melt 1 (for example, 150
0℃P? ! The melting of raw material 1 on the inner surface of crucible 2, which is in contact with
Impurities 9 dissolved in the raw material melt are carried by this thermal convection 8 and dispersed throughout the interior of the raw material melt. This impurity 9
This causes dislocation loops, defects, growth streaks, etc. to occur in the single crystal, deteriorating the quality of the single crystal.

For this reason, integrated circuits (LSI') are better suited than such single crystals.
When manufacturing wafers, wafers containing defective parts have deteriorated electrical characteristics, making them unusable and resulting in poor yields. In the future, the diameter of single crystals will continue to increase, but as can be seen from the equation for Grashof's number above, as the crucible diameter increases, the Grashof's number will also increase, and the thermal convection of the raw material melt will become even more intense. In addition, the quality of single crystals will continue to deteriorate.

For this reason, conventionally, a single crystal generation device has been proposed that applies a DC magnetic field to the raw material melt 1 in order to suppress thermal convection and pull a single crystal under growth conditions close to thermal and chemical equilibrium. (Japanese Unexamined Patent Publication No. 57-149894). FIG. 7 shows this schematic structure, and the same parts as the sixth factor are given the same reference numerals, and the explanation thereof will be omitted. A magnet 10 is placed around the outer periphery of the crucible 2, and a magnetic field is applied to the raw material melt 1 in the direction of the arrow 11 (lit! Field application force application direction).A single crystal melt is generally a conductive pair having an electrical conductivity σ. Therefore, when a fluid having electrical conductivity σ moves due to thermal convection, the fluid moving in a direction not parallel to the magnetic field application method 11 is subjected to magnetic field resistance according to Lenz's law.

This prevents the movement of thermal convection. In general, the magnetoresistance force when a magnetic field is applied, that is, the magnetorheological coefficient νeft
is νeH-(μHD)2σ/ρ where μ: Magnetic permeability of the melt H: Magnetic field strength D Nil point diameter σ: Electrical conductivity of the melt ρ: Density of the melt, and as the magnetic field strength increases, the magnetic The viscosity coefficient eff increases, and ν in the formula for Grashof's number shown above increases, causing the Grashof's number to rapidly decrease, and the Grashof's number can be made smaller than the critical value by a certain magnetic field strength. This completely suppresses thermal convection of the melt.

By applying faii in this way, thermal convection is suppressed, so there is no impurity content in the single crystal, no generation of dislocation loops, no defects, no growth streaks, and the quality is uniform in the pulling direction. single crystals are obtained, improving the quality and yield of single crystals.

[Problems with Background Art] By the way, the single crystal growth apparatus equipped with the conventional magnet 10 shown in FIG. 7 has the following drawbacks.

In a so-called large single crystal growth apparatus in which the size of a single crystal to be grown is 4 inches or more, the chamber 12 that houses the crucible 2 and the heater 3 is large, with a diameter of several hundred or more, and the crucible 2 itself is 6 inches or more in diameter. It has a large diameter. The relationship between the diameter and depth of crucible 2 is usually diameter>depth, and raw material IN! 17' even when fully charged 11
It is about 2 diameters deep. Crucible 2 shaped like this
When a magnetic field is applied to the raw material melt 1 charged inside, the magnetic field intensity distribution becomes 13 in FIG. 7, and the temperature becomes almost uniform in the height direction of the crucible 2. Usually, the magnetic field strength B1 at the solid-liquid interface boundary layer 6 and the magnetic field strength B2 at the bottom of the crucible 2
The relationship with is 1 〈5%. Therefore, the Grashof number distribution of the raw material melt 1 corresponding to the magnetic field strength distribution 13 is as shown in 14 shown in FIG. It will be below C.

Here, Not and N. 2 correspond to the Grashof number of the solid-liquid interface boundary layer 6 and the raw material melt 1 at the bottom of the crucible 2, respectively. Therefore, thermal convection is suppressed everywhere in the raw material melt 1 inside the crucible 2, and the raw material melt 1 becomes completely stationary. In this state, there is no path for heat transfer due to convective heat transfer, and heat is supplied from the heater 3 to the raw material melt 1 only by thermal conduction.

Now, when the single crystal size is relatively small at 2 to 3 inches φ, the crucible 2 is also small at 4 to 5 inches φ, and even if the melt is completely still due to the application of a magnetic field, it is supplied from the heater 3. Heat is sufficiently transferred to the solid-liquid interface boundary layer 6 by thermal conduction of the raw material melt 1, so that the solid-liquid interface boundary layer 6 and the crucible 2
There is almost no temperature difference (usually within 10 degrees Celsius) with the surrounding area.

On the other hand, in large single crystal growth equipment with a single crystal size of 4 inches or more, the crucible 2 has a diameter of 6 inches to 14 inches.
Due to the large size of inch φ, the heat of the heater 3 is no longer sufficiently transmitted to the solid-liquid interface boundary layer 6 at the center of the crucible 2 by heat conduction alone. Therefore, there is a large temperature difference between the solid-liquid interface boundary layer 6 and the surrounding area of the crucible 2 (usually several tens of degrees Celsius).
will occur. Effective single crystal 7 in solid-liquid interface boundary layer 6
In order to carry out the growth, it is necessary that the temperature of the location is sufficiently higher than the melt temperature of the raw material melt 1. Therefore, it is necessary to increase the power of the heater 3 to overcome the temperature gradient and provide the solid-liquid interface boundary layer 6 with the required temperature. Furthermore, if the temperature gradient is large, a considerable temperature gradient will also occur within the solid-liquid interface boundary layer 6 when the single crystal size is large. In order to grow a homogeneous single crystal 7, temperature uniformity in the growth region is also required. Therefore, the existence of such a temperature gradient in the raw material melt 1 is not preferable in terms of single crystal growth. Additionally, if the temperature difference between the center and the periphery of the crucible 2 is too large, the thermal stress acting on the crucible 2 will be excessive and the crucible 2 will
cracks are more likely to occur.

[Purpose of the Invention] Therefore, the present invention has been made to eliminate the drawbacks of the conventional apparatus described above, and it is possible to reduce the temperature difference between the solid-liquid interface boundary layer and the surrounding area of the crucible, thereby achieving high quality ( The purpose of the present invention is to provide a single crystal growth apparatus and a single crystal growth method that can grow a uniform (uniform) single crystal.

[Summary of the Invention 1] In order to achieve the above object, the first invention heats a single crystal raw material in a container by a heating means to create a raw material melt, and a seed crystal is placed in this raw material melt. In a single crystal growth apparatus, the seed crystal is pulled up at a certain speed by a pulling drive mechanism and a single crystal is grown at the solid-liquid interface boundary sound. The magnet device is composed of a magnet device arranged so that the magnetic fields generated by the coils cancel each other's magnetic fields, and a coil spacing adjustment device for varying the strength of the magnetic field applied to the magnet device. In the second invention, a single crystal raw material in a container is heated by a heating means to create a raw material melt, a seed crystal is inserted into this raw material melt, and this seed crystal is pulled up at a certain speed by a pulling drive mechanism. A magnet device arranged so that a single crystal is grown in the solid-liquid interface boundary layer by pulling the raw material melt, and magnetic fields generated by coils facing each other through the crucible containing the raw material melt cancel out each other's magnetic fields. When growing a single crystal using a single crystal growth device equipped with a single crystal growth device, in response to the decrease in raw material melt accompanying single crystal growth, the coil spacing adjustment device is adjusted so that the volume of the raw material melt thermal convection suppression region is constant. to control the magnetic field distribution of the magnet device, and continue this control until the melt decreases to the minimum melt volume at which a thermal convection effect can exist, and thereafter suppress the thermal convection in the entire area of the raw material melt. The magnet device described above is a single crystal growth method in which a magnet spacing adjustment device is controlled to apply a magnetic field greater than the minimum magnetic field strength that can suppress thermal convection.

[Embodiments of the invention] The present invention will be explained below with reference to the drawings.

First, a first embodiment of the single crystal growth apparatus shown in FIG. 1 will be described. The same parts as in FIGS. 6 and 7 are given the same reference numerals, and the explanation thereof will be omitted.

For example, a superconducting circular coil 15a is placed on the outer periphery of the chamber 12.
and 15b, these circular coils 15a.

It is placed on the magnet stand 25 so that the central axis of the single crystal pulling machine 15b coincides with the central axis of the single crystal pulling machine. In this case, circular coil 1
Although the coils 5a and 15b have the same ampere-turn, they are arranged so that the direction of the current flowing through the coils is reversed so that the generated magnetic fields are in opposite directions. coil 15
The magnetic field generated by a and 15b is as shown in FIG. 2, for example.

That is, if the central axes of the coils 15a and 151) are the X-axis and Z-axis, respectively, the magnetic field Bo at the origin is zero, and in other regions it becomes an elliptical uniform magnetic field strength distribution as shown in the figure, and the magnetic field strength increases as the distance from the origin increases. increases. However, the magnetic field strength defined here is a composite value of the X-axis direction component magnetic field and the two-axis inner relative component magnetic field. The magnetic field on the X-axis is only the X-axis component everywhere, like BB, and the magnetic field on the Y-axis is B
4, there are only two components everywhere. For other regions, the magnetic field has X-axis and Z-axis components and is axially symmetrical about the Z-axis. The magnitude direction of the magnetic field is the second
As shown schematically in the figure, as 85°Bs and B7 increase, the intensity increases and the two components increase. Or Bs, Ba.

As it becomes BB, its strength decreases and the Z-axis component increases. - the coils 15a and 15b are housed in containers 16a and 16b, respectively, which are connected by a flexible connection 17; An excitation type 11118 supplies excitation current to the coils 15a and 15b. Container 16a
and 16b is a container 16a.

Drive shaft mounting portions 19a located at several locations in the circumferential direction of 16b,
The same number of drive shafts 20 as the drive shaft mounting portion 19a are connected via the drive shaft mounting portion 19b. This drive shaft 20 is connected to the same number of drive units 21. Here, drive shaft mounting parts 19a and 19b.

A mechanism consisting of the drive shaft 20 and the drive section 21 is referred to as a coil spacing adjustment device 22.

The pulling drive mechanism 5 and the central controller 23 are connected by a control circuit, and the pulling speed of the single crystal 7 is input to the central controller 23. The excitation current value supplied from the external power supply 18 is controlled by the central controller 23.

The drive 21 of the coil spacing adjustment device 22 , for example an electric motor, is controlled by a central control device 23 .

Next, the operation of the single crystal growth apparatus of the first embodiment of the present invention configured as described above will be explained.

A magnetic field having the magnetic field intensity distribution shown in FIG. 2 generated by the coils 15a and 15b is applied to the raw material melt 1 in the crucible 2 as shown in FIG.

In FIG. 3, the equal magnetic field strength curve BI is just at the critical Grashof number N of the raw material melt 1. Choose Be to correspond to C. For example, Bm is set to 1000 to 2000 Gauss. This value is based on the type of raw material melt 1, the initial charge amount,
It is determined by the inner diameter of the crucible 2, etc. In this way, in the region inside the curve B■, the applied magnetic field strength B becomes B×Bm, and the Grashof number N of the raw material melt 1 is increased. is N. 〉N
oC, so within this region the thermal convection 8 of the raw material melt 1
occurs.

On the other hand, in the region outside curve B-, on the contrary, B
I'm the 3rd and N. KuN. C, the thermal convection 8 of the raw material melt 1 is suppressed and it becomes completely stationary. here,
The length Hl of the region where the raw material melt 1 is stationary is the thickness of the solid-liquid interface boundary layer 6 by δ.

If the initial height of raw material melt 1 is Ha, then HO
So, the species number of raw material melt 1 and the initial charge amount.

It is determined by the inner diameter of the crucible 2, etc. However, for Hl, the minimum value of the determined values is used. Coil 15a.

The shape of 15b, amperage pattern, distance between coils, etc.
It is determined by magnetic field calculation to match the required Hl, D, Ha, Bm, etc. Since thermal convection 8 exists in the inner region of curve Bm, the heat from heater 3 is effectively transferred to the center by convective heat transfer due to this thermal convection. This results in a substantially uniform moisture distribution within this region. On the other hand, in the region outside curve B10, the raw material melt 1 is completely stationary, so there is no heat transfer due to convective heat transfer. In the conventional case where the thermal convection 8 of the raw material melt 1 is suppressed everywhere, the heat transfer from the heater 3 to the solid-liquid interface boundary layer 6 is only due to heat conduction from the periphery of the crucible 2. In the case of the embodiment of the present invention, the solid-liquid interface boundary layer 6 is formed by heat conduction from the uniform melt portion below the depth Hl (H1 = 1/2D) just below the solid-liquid interface boundary layer 6. Effectively heated.

Therefore, compared to conventional devices, the heat transfer effect to the solid-liquid interface boundary layer 6 is enhanced, and the temperature difference with the surrounding area of the crucible 2 is reduced. Moreover, since the solid-liquid interface boundary layer 6 is in a stationary state, the single crystal 7 can be grown in a thermally and chemically stable state, as in the conventional apparatus. In addition, the raw material melt 1 is heated by thermal convection 8 to just below the solid-liquid interface boundary layer 6 where the single crystal 7 is grown.
Since it is well stirred, a homogeneous raw material melt 1 is supplied to the growth section.

Next, the single crystal growing method of the present invention, that is, the operations in the process of growing the single crystal 7 will be explained in order.

(1) Initial setting The crucible 2 is charged with the raw material melt 1 up to Ha, and the heater 3 is used to melt it.

Next, the initial coil spacing LO is set by the coil spacing adjusting device 1ff22. With this initial setting, coil 15
The relative positions of a and 15b with respect to the crucible 2 are as shown in FIG.

The coil spacing adjustment device 22 is driven, for example, as follows.

The drive shaft 2o is rotated by the drive section 21, and the drive shaft mounting section 1
The coils 15a and 15b are driven in opposing directions or in the opposite direction at a common displacement speed of each coil by means of transmission mechanisms 9a and 19b that convert rotational motion into vertical motion.

Here, each drive section 21 is synchronized by a central control device 23, respectively.

(Two-coil spacing control (Part 1) The coils 15a and 15b are excited by the excitation power source 18, and the raw material melt 1 is in the state shown in FIG. 3. From now on, the single crystal 7
is grown at a constant pulling speed V (s+/Sec). As the single crystal 7 grows, the amount of the raw material melt 1 decreases, and the surface of the raw material melt 1 lowers. If the single crystal 7 is left in the pulled state as it is, the region H1 in FIG. 3 disappears, and the solid-liquid interface boundary layer 6 enters the region of thermal convection 8 within the curve B11.

Therefore, in order to maintain the heat convection suppressed region with the height Hl shown in FIG. 3 even as the growth of the single crystal 7 progresses, the heat convection remaining region, that is, the region where the magnetic field strength is smaller than B11 by the amount equivalent to the amount of decrease in the melt surface. I'll make it smaller.

To achieve such a state, the following coil spacing control may be performed. Generally, coil 15a, coil 15b
As the distance between the coils decreases, the magnetic field strength becomes weaker in the space between the coils, and the area where the magnetic field strength is smaller than B(l also decreases accordingly.Using this principle, , coils 15a and 1 correspond to the cause of the drop in the liquid level.
5b is controlled so that the height Hl in FIG. 3 is always kept constant.

This control is carried out, for example, by inputting the pulling speed (constant value) from the lifting drive example 5 to the central control device 23, and controlling the drive section 21 by the central control device 23. The coils 15a and 15b can be driven by driving both the coils 15a and 15b by the same amount of displacement to reduce the distance between the coils, or by fixing the lower coil 15b and displacing only the upper coil 15a. There is a method of reducing the coil spacing, but each method has the same effect.

In this way, as shown in FIG. 4, as the single crystal 7 grows, the area in which thermal convection 8 is suppressed near the solid-liquid interface boundary layer 6 is kept at a constant volume as shown in FIG. 4 (1). The area of heat convection 8 decreases. The heat convection area is the type of raw material melt 1,
This coil spacing control is continued until the height H2 shown in FIG. 4 (21), which is determined by the shape of the crucible 2, is reached.

(3) Coil spacing control (part 2) The area size H2 mentioned above is the minimum area size in which the thermal convection 8 can effectively exist. Therefore, in order to retain the effects of the present invention, at least H2 must be left. Therefore, from now on, the magnet position will be fixed and this area will be left. As the growth of the single crystal 7 progresses, the thermal convection suppressed area gradually decreases as shown in Fig. 4 (3).Generally, the melt l existing in the thermal convection suppressed area and the applied magnetic field strength are , and when an excessive magnetic field is applied, the raw material melt 1 at the solid-liquid interface boundary 16
It is known that the thermal and chemical stability of
Reduce the magnetic field strength applied to the

The following method is used to reduce the magnetic field strength. When the excitation currents of the coils 15a and 15b are kept constant and the distance between the coils is reduced, the intensity of the generated magnetic field is correspondingly reduced. Such a method is used, for example, when the coils 15a and 15b are superconducting coils, the containers 16a and 16 are used to maintain the superconducting coils at an extremely low temperature of 4.2 degrees.
The coil 15a is filled with liquid helium in order to reduce the amount of evaporation of this liquid helium.

Connect the current lead between the coil 15b and the excitation power source 18 to the coil 15.
A commonly used method is to remove magnets a and 15b after excitation to eliminate heat intrusion from the outside, and to operate the superconducting coil in persistent current mode using a persistent current switch attached to the coil side.

In order to change the magnetic field strength of a superconducting coil operating in persistent current mode, it is complicated to reattach the current lead that was once removed, cancel persistent current mode, and change the excitation current value. The drawback is that a large amount of liquid helium evaporates because the current leads are inserted into cryogenic liquid helium.

Therefore, the method of changing the magnetic field strength while keeping the excitation current constant, that is, in a persistent current state, as described above, is an effective method in the case of superconducting coils.

Of course, if the coils 15a and 15b are copper coils,
The magnetic field strength can be lowered by lowering the excitation UfI'l flow from the excitation power source 18, and even if the coils 15a and 15b are superconducting coils, if they are not used in persistent current mode, the excitation current can be similarly lowered.

The spacing between the coils 15a and 15b is controlled by adjusting the coil spacing so that the magnetic field strength suitable for the amount of raw material melt 1 is generated, since the amount of raw material melt 1 remaining is uniquely determined in accordance with the pulling speed. A device 22 adjusts the coil spacing. These commands are issued by the central controller 23.

In addition, when the coils 15a and 15b are superconducting coils operated in persistent current mode, the coils 15a and 15b connected via the persistent current switch must be connected in liquid helium. That is, as shown in FIG. 1, a coil 15a.

Containers 16a and 16b, in which 15b is housed, are connected by a flexible connecting part 17, and the inside of this flexible connecting part 17 is filled with liquid helium, and a current lead connecting the coils 15a and 15b passes through it. . When adjusting the coil spacing,
This flexible connection 17 expands and contracts accordingly.

(4) Completion of growth When the remaining raw material melt 1 reaches H3~δ (solid-liquid interface boundary layer) as shown in Figure 4 (3), completion of growth is determined by the following two steps.
Do it using one of the methods.

■ When the height H3 is sufficiently small and the remaining raw material melt 1 is small and the single crystal 7 cannot be grown any more, the tail of the single crystal ingot is formed using the remaining raw material melt 1, and the single crystal 7 is The forming part is cooled to complete the growth.

(2) When the single crystal 7 can still be grown using the remaining raw material melt 1, the remaining raw material melt 1 is transferred to an outer region from 81 in FIG. In other words, the rest of the growth is performed with thermal convection 8 suppressed in the entire region. In this case, raw material melt 1
Since the remaining amount of is sufficiently small, the temperature gradient is not severe during initial charging, and high quality single crystal 7 can be grown even when heat convection is completely suppressed.

Next, a second embodiment of the single crystal growth apparatus of the present invention will be explained with reference to FIG. 5. The same parts as those in the embodiment shown in FIG. Omitted. Circular coil 15a in FIG.

15b is placed facing the chamber 12 as shown in FIG. That is, both coils 15a.

The central axis Z of 15b is perpendicular to the pulling direction of single crystal 7.

At this time, the magnetic field distribution generated by the coils 15a and 15b is as shown in FIG. 2, and the X axis shown in FIG. 2 is the same as the pulling axis of the single crystal 7. This effect is the same as that shown in FIGS. 3 and 4. In addition, when driving the coils 15a, 15b with the coil spacing adjustment device 22, the coils 15a, 15b
A magnet stand 24 attached to the container can be driven horizontally by a rail 25.

The first or second single crystal growth apparatus of the present invention described above
According to the embodiment, the following effects can be obtained.

(1) Thermal convection 8 is suppressed near the solid-liquid interface boundary llll6, and growth conditions close to thermal and chemical equilibrium are satisfied. The liquid 1 is well stirred, the raw material melt 1 is homogenized, and the temperature is maintained uniform.

Therefore, the heat conduction effect to the solid-liquid interface boundary layer 6 is enhanced, the temperature difference between the periphery of the crucible 2 and the solid-liquid interface boundary layer 6 is reduced, and the sufficiently stirred raw material melt 1 becomes solid. Since it is supplied to the liquid interface boundary layer 6, a homogeneous single crystal 7 is grown.

(2) Since the temperature difference between the center and the periphery of the crucible 2 is small, cracking of the crucible 2 due to thermal stress is avoided.

(3) Since the intensity of the generated magnetic field can be varied by adjusting the interval between the coils 15a and 15b, in the case of a superconducting magnet, the magnetic field can be varied even in persistent current mode.

(4) The magnetic field applied to the raw material melt 1 is axially symmetrical and includes horizontal and vertical hanging components with respect to the pulling axis. Therefore, heat convection in all directions can be suppressed.

(5) Coil 15a because opposing coils 15a and 15b generate magnetic fields in opposite directions.

Since the leakage magnetic field of the container 15b to the outside of the containers 16a and 16b is canceled by the magnetic field generated by the opposing coils,
The leakage magnetic field becomes smaller.

[Effects of the Invention] According to the present invention described above, the temperature difference between the solid-liquid interface boundary layer and the surrounding area of the crucible can be reduced, thereby providing a single crystal growth apparatus and a single crystal growth method that can grow single crystals with high quality. can.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the single crystal growth apparatus of the present invention, FIG. 2 is a distribution diagram showing the magnetic field intensity distribution generated by the single crystal growth apparatus of the same embodiment, and FIG. Schematic diagram showing the magnetic field and melt situation of the single crystal growth apparatus of the same example, No. 4
Figure 5 is a diagram showing the operation of the single crystal growth apparatus of the same embodiment, Figure 5 is a schematic configuration diagram showing the second embodiment of the single crystal growth apparatus of the present invention, and Figure 6 is a conventional single crystal growth apparatus. 7 is a diagram for explaining the operation of the single crystal growth apparatus shown in FIG. 6. 1... Raw material melt, 2... Crucible, 3 ···heater,
4... Seed crystal, 5... Pulling drive mechanism, 6... Solid-liquid interface boundary layer, 7... Single crystal, 8... Thermal convection, 9...
・Impurity, 10... Magnet, 11... Magnetic field direction, 12
...Chamber, 13...Ffl field weight distribution 4...
・Grashoff number distribution, 15a...Circular coil, 15b
... Circular coil, 16a... Container, 16b... Container, 17... Flexible connection part, 18... Excitation power supply, 1
9a, 19b... Drive shaft mounting part, 20... Drive shaft,
21... Drive unit, 22... Coil interval adjustment device, 2
3... Central control device, 24... Rail, 25...
Magnetic mount. Applicant's agent Patent attorney Takehiko Suzue Figure 1 l121! l 3rdvA 4th Figure jI 5 Figure

Claims (5)

[Claims] (1) A single crystal raw material in a container is heated by a heating means to create a raw material melt, a seed crystal is inserted into this raw material melt, and the seed crystal is pulled up at a certain speed by a pulling drive mechanism to solidify it. - In a single crystal growth apparatus in which a single crystal is grown in a liquid interface boundary layer, magnets are arranged so that the magnetic fields generated by coils facing each other through the crucible containing the raw material melt cancel each other's magnetic fields. A single-crystal growth device comprising a coil spacing adjustment device for varying the strength of the magnetic field applied to the magnet device. (2) The single crystal growth apparatus according to claim (1), wherein the opposing coils are superconducting coils. (3) The single crystal growth apparatus according to claim (1), wherein the direction of the magnetic field generated by the opposing coils is perpendicular to the single crystal pulling direction. (4) The single crystal growth apparatus according to claim (1), wherein the direction of the magnetic field generated by the opposing coils is parallel to the single crystal pulling direction. (5) The single crystal raw material in the container is heated by a heating means to create a raw material melt, a seed crystal is inserted into this raw material melt, and the seed crystal is pulled up at a certain speed by a pulling drive mechanism to solidify it. - Equipped with a magnet device arranged so that a single crystal is grown in the liquid interface boundary layer and magnetic fields generated by coils facing each other through the crucible containing the raw material melt cancel each other's magnetic fields. When growing a single crystal using a single crystal growth device, in response to the decrease in the raw material melt due to single crystal growth, the coil spacing adjustment device is used to adjust the volume of the raw material melt thermal convection suppression region to be constant. The magnet device controls the magnetic field distribution of the magnet device, continues this control until the melt decreases to a minimum melt volume in which a thermal convection effect can exist, and thereafter suppresses thermal convection throughout the raw material melt. The device is a single crystal growth method that controls a magnet spacing adjustment device to apply a magnetic field greater than the minimum magnetic field strength that can suppress thermal convection.