Method for manufacturing single crystal

Abstract

[Problem] To provide a single crystal production method, a magnetic field generator, and a single crystal production device, which allow the in-plane distribution of oxygen concentration in a single crystal to be uniform. [Solution] This single crystal production method comprises pulling-up a single crystal 3 while applying a horizontal magnetic field onto a melt 2 in a crucible 11. During the crystal pull-up step, the crucible 11 is raised to meet the decrease in the melt 2, and the magnetic field distribution is controlled to meet the decrease in the melt 2 in such a manner that the orientation of the magnetic field on the melt surface 2s and the orientation of the magnetic field on the inner surface at the curved bottom portion of the crucible 11 are constant from the beginning to the end of a body portion growth step.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a single crystal, and particularly to a method for manufacturing a single crystal by a magnetic field applied Czochralski method in which a single crystal is pulled up while applying a horizontal magnetic field to a melt. The present invention also relates to a magnetic field generating device and a single crystal manufacturing device used in such an MCZ method.

Background Art

[0002] As one of the CZ methods for pulling up a silicon single crystal from a silicon melt in a quartz crucible, a so-called MCZ method in which a magnetic field is applied to the silicon melt while pulling up the silicon single crystal is known. According to the MCZ method, since melt convection is suppressed, the amount of oxygen dissolved in the silicon melt due to the reaction with the quartz crucible can be suppressed, and the oxygen concentration of the silicon single crystal can be kept low.

[0003] Several methods are known as methods for applying a magnetic field, and among them, the practical application of the HMCZ method for applying a transverse magnetic field (horizontal magnetic field) is progressing. In the HMCZ method, a transverse magnetic field substantially orthogonal to the side wall of the quartz crucible is applied, so that melt convection near the side wall of the crucible is effectively suppressed, and the amount of oxygen eluted from the crucible is reduced. On the other hand, the convection suppression effect on the melt surface is small, and the evaporation of oxygen (silicon oxide) from the melt surface is not so suppressed, so the oxygen concentration in the melt tends to decrease. Therefore, it is characterized in that a single crystal with a low oxygen concentration is likely to be grown.

[0004] Regarding the HMCZ method, for example, Patent Document 1 describes that the oxygen concentration incorporated into the single crystal is decreased or increased by moving the magnetic field center position in the vertical direction to approach or separate from the liquid surface in accordance with the progress of pulling up the single crystal. Patent Document 2 also describes generating a magnetic field so that the magnetic flux travels along the curved bottom of the crucible.

[0005] Patent Document 3 describes a single crystal manufacturing apparatus capable of pulling up not only a single crystal with a low oxygen concentration and suppressed growth stripes but also a single crystal with a high oxygen concentration by using a magnetic field generating device that can switch between two types of magnetic fields with the direction of magnetic field lines shifted by 90 degrees and different magnetic field distributions from each other.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the HMCZ method, the horizontal magnetic field applied near the melt surface preferably travels straight parallel to the melt surface. This is because, as described above, the magnetic field component orthogonal to the melt surface suppresses the melt convection in the melt surface and leads to an increase in the oxygen concentration. On the other hand, at the bottom of the crucible, the magnetic field preferably travels while bending along the curved bottom. This is because when the magnetic field component orthogonal to the inner wall surface of the crucible suppresses the melt convection, the diffusion of oxygen in the melt becomes insufficient, and unevenness in the oxygen concentration in the single crystal is likely to occur. Therefore, as described in Patent Document 2, it is effective to generate a magnetic field that bends along the curved bottom surface of the crucible.

[0008] However, during the crystal pulling process, it is necessary to raise the quartz crucible in accordance with the decrease in the melt due to crystal growth to maintain a constant height position of the melt surface. When the quartz crucible is raised, the magnetic field distribution and the positional relationship between the quartz crucible and the magnetic field change, making it difficult to align the magnetic field along the curved bottom surface of the quartz crucible. As described in Patent Document 1, it is possible to raise the magnetic field center position so that the magnetic field distribution follows the curved bottom surface of the crucible. However, in that case, the magnetic field does not become horizontal near the melt surface, and there is a problem that the oxygen concentration of the single crystal increases due to the stagnation of melt convection near the melt surface.

[0009] Fluctuations in the oxygen concentration distribution in the crystal growth direction of a silicon single crystal affect the in-plane distribution of the oxygen concentration of the silicon wafer. As shown in FIG. 14, when a wafer is cut out from a silicon single crystal having growth stripes in the oxygen concentration distribution in the crystal growth direction, the in-plane distribution of the oxygen concentration of the wafer becomes non-uniform.

[0010] Therefore, an object of the present invention is to provide a method for producing a single crystal capable of making the in-plane distribution of the oxygen concentration in the single crystal uniform. Another object of the present invention is to provide a magnetic field generating device and a single crystal manufacturing device used in such a method for producing a single crystal.

Means for Solving the Problems

[0011] To solve the above problems, the present inventors investigated the fluctuations in the oxygen concentration in a single crystal and found that in a specific range in the crystal growth direction, the growth stripes of the oxygen concentration become smaller, and in that range, the fluctuations in the crystal diameter are very small. As a result of further investigation, it was revealed that when growing a single crystal in a range where the growth stripes of the oxygen concentration are small, the direction of the magnetic field lines near the bottom surface of the crucible is close to parallel to the bottom surface of the crucible.

[0012] The present invention is based on such technical findings, and the method for manufacturing a single crystal according to the present invention is a method for manufacturing a single crystal in which a single crystal is pulled up while applying a horizontal magnetic field to the melt in a crucible, and during the crystal pulling process, the crucible is raised in accordance with the decrease in the melt, and the magnetic field distribution is controlled in accordance with the decrease in the melt so that the direction of the magnetic field at the melt surface and the direction of the magnetic field at the inner surface of the curved bottom of the crucible remain constant from the start to the end of the body part growth process.

[0013] In the method for manufacturing a single crystal according to the present invention, since the direction of the magnetic field near the melt surface and the direction of the magnetic field near the bottom of the crucible are maintained constant from the beginning to the end of the body part growth process, melt convection that affects the oxygen concentration in the single crystal can be suppressed as much as possible, and thereby not only the reduction of oxygen in the single crystal but also the uniformization of the in-plane distribution of the oxygen concentration can be achieved.

[0014] In the present invention, it is preferable that the direction of the magnetic field at the melt surface is parallel to the melt surface. The melt surface is the interface (gas-liquid interface) between the melt and the atmosphere in the pulling furnace, and is usually a horizontal plane. Thereby, the evaporation of oxygen from the melt surface can be activated to reduce the oxygen content in the single crystal.

[0015] When the rotation axis of the crucible is the Z-axis, the magnetic field central axis of the horizontal magnetic field orthogonal to the Z-axis is the Y-axis, the intersection of the Z-axis and the Y-axis is the origin, and the axis orthogonal to the YZ plane and passing through the origin is the X-axis, on the intersection line of the inner surface of the curved bottom of the crucible and the YZ plane, it is preferable to maintain the angle θ formed by the normal vector of the inner surface and the magnetic field vector at 75 degrees or more and 105 degrees or less. Thereby, the melt convection at the bottom of the crucible can be suppressed, and the in-plane distribution of the oxygen concentration in the single crystal can be made uniform.

[0016] In the method for manufacturing a single crystal according to the present invention, while maintaining the strength of the magnetic field at the origin constant, the integral value at the bottom of the square of the inner product of the normal vector of the inner surface of the curved bottom of the crucible and the magnetic field vector is minimized. It is preferable to adjust the magnetic field distribution. Alternatively, the magnetic field distribution may be adjusted so that the second derivative in the Y direction of the shape of the bottom and the magnetic field coincides at the center of the bottom. Thereby, the direction of the magnetic field near the bottom of the crucible can be made to follow the curved inner surface of the bottom.

[0017] When the radius of the crucible is R, it is preferable that the bottom is in a range of 0.7R or less from the center of the bottom. Usually, in the pulling of a single crystal under a horizontal magnetic field with an undistorted magnetic field distribution, since the magnetic field distribution near the center is close to being parallel to the bottom surface of the crucible, if the set region of the bottom is narrow, the present invention is automatically satisfied and has no meaning. When the set region of the bottom is wider than 0.7R, it becomes difficult to satisfy the above conditions at the corner portion of the crucible where the curvature changes greatly toward the side wall portion.

[0018] In the method for manufacturing a single crystal according to the present invention, it is preferable to provide a plurality of coil elements around the crucible and control the magnetic field distribution by individually adjusting the magnetic field strength of each coil element. In this case, it is preferable that the plurality of coil elements constitute a plurality of coil element pairs with the coil axes coinciding. According to the present invention, while maintaining the direction of the magnetic field at the melt surface horizontal, the direction of the magnetic field near the bottom of the crucible can be changed in accordance with the change in the height position of the crucible.

[0019] The plurality of coil elements are preferably arranged symmetrically with respect to the XZ plane and are preferably arranged parallel to the XY plane. According to the present invention, a magnetic field distribution with high symmetry as viewed from the Z axis can be realized.

[0020] The plurality of coil elements constitute a first coil device that generates a first magnetic field and a second coil device that generates a second magnetic field different from the first magnetic field, and it is preferable to control the magnetic field distribution by individually adjusting the intensity of the first magnetic field and the intensity of the second magnetic field. Thereby, while maintaining the direction of the magnetic field at the molten surface level horizontally, the direction of the magnetic field near the bottom of the crucible can be changed according to the change in the height position of the crucible.

[0021] The first magnetic field has a magnetic field change in which the magnetic field in the positive direction of the Y-axis gradually weakens, then becomes zero, and further the magnetic field in the negative direction of the Y-axis gradually strengthens. The second magnetic field preferably has a magnetic field change in which the magnetic field in the negative direction of the Y-axis gradually weakens, then becomes zero, and further the magnetic field in the positive direction of the Y-axis gradually strengthens. Thereby, while maintaining the direction of the magnetic field at the molten surface level horizontally, the direction of the magnetic field near the bottom of the crucible can be changed according to the change in the height position of the crucible.

[0022] Further, the magnetic field generating device according to the present invention is a magnetic field generating device used for manufacturing a single crystal by the MCZ method, which applies a transverse magnetic field to the molten liquid in the crucible, and includes a first coil device that generates a first magnetic field and a second coil device that generates a second magnetic field different from the first magnetic field. When the rotation axis of the crucible is the Z-axis, the central axis of the application direction of the transverse magnetic field orthogonal to the Z-axis is the Y-axis, the intersection of the Z-axis and the Y-axis is the origin, and the axis orthogonal to the YZ plane and passing through the origin is the X-axis, the first coil device is arranged on the YZ plane and has at least a pair of coil elements whose coil axes coincide, the second coil device is arranged parallel to the XY plane and has at least two pairs of coil elements whose coil axes coincide, and the plurality of coil elements constituting the first coil device and the second coil device are arranged symmetrically with the XZ plane interposed therebetween.

[0023] According to the present invention, while maintaining the direction of the magnetic field at the melt surface horizontally, the direction of the magnetic field near the bottom of the crucible can be changed in accordance with the change in the height position of the crucible. By maintaining such a magnetic field distribution constant from the beginning to the end of the body part growth process, it is possible to suppress the melt convection that affects the oxygen concentration in the single crystal as much as possible, thereby not only reducing the oxygen content in the single crystal but also making the in-plane distribution of the oxygen concentration uniform.

[0024] In the present invention, the first coil device has first and second coil elements arranged on the YZ plane and symmetrically arranged across the Z axis. The second coil device has third and fourth coil elements arranged on the XY plane and symmetrically arranged across the Z axis, and fifth and sixth coil elements arranged on the XY plane and symmetrically arranged across the Z axis. It is preferable that the first to sixth coil elements are symmetrically arranged across the XZ plane. Thereby, a magnetic field distribution with high symmetry can be realized when viewed from the Z axis.

[0025] It is preferable that the angle formed by the coil axes of the third and fourth coil elements with the Y axis is +45 degrees, and the angle formed by the coil axes of the fifth and sixth coil elements with the Y axis is -45 degrees. Thereby, a magnetic field distribution with high symmetry can be realized when viewed from the Z axis.

[0026] It is preferable that the loop sizes of the loop coils constituting the first and second coil elements are the same, and the loop sizes of the loop coils constituting the third to sixth coil elements are the same. Thereby, a magnetic field distribution with high symmetry can be realized when viewed from the Z axis.

[0027] Furthermore, the single crystal manufacturing apparatus according to the present invention includes a crucible that supports the melt, a heater that heats the melt, a crystal pulling mechanism that pulls up a single crystal from the melt, a crucible lifting mechanism that drives the crucible to rotate and move up and down, the magnetic field generating apparatus according to the present invention that applies a transverse magnetic field to the melt, and a control unit that controls the heater, the crystal pulling mechanism, the crucible lifting mechanism, and the magnetic field generating apparatus.

[0028] The single crystal manufacturing apparatus according to the present invention maintains the direction of the magnetic field near the melt surface and the direction of the magnetic field near the bottom of the crucible constant regardless of the change in the height position of the crucible during the body part growth process. Therefore, it is possible to suppress the melt convection that affects the oxygen concentration in the single crystal as much as possible. As a result, not only can the single crystal be deoxygenated, but also the in-plane distribution of the oxygen concentration can be made uniform.

Advantages of the Invention

[0029] According to the present invention, it is possible to provide a method for manufacturing a single crystal, a magnetic field generating device, and a single crystal manufacturing apparatus that can make the in-plane distribution of the oxygen concentration in the single crystal uniform.

Brief Description of the Drawings

[0030]

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Embodiments for Carrying Out the Invention

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0032] Figure 1 is a side cross-sectional view schematically showing the configuration of a single crystal manufacturing apparatus according to an embodiment of the present invention.

[0033] As shown in FIG. 1, the single crystal manufacturing apparatus 1 includes a chamber 10, a quartz crucible 11 that holds a silicon melt 2 in the chamber 10, a graphite susceptor 12 that holds the quartz crucible 11, a rotating shaft 13 that supports the susceptor 12, a shaft drive mechanism 14 that rotates and vertically drives the rotating shaft 13, a heater 15 disposed around the susceptor 12, a heat insulating material 16 disposed outside the heater 15 and along the inner surface of the chamber 10, a heat shield 17 disposed above the quartz crucible 11, a wire 18 for pulling up a single crystal disposed above the quartz crucible 11 and coaxially with the rotating shaft 13, and a wire winding mechanism 19 disposed above the chamber 10.

[0034] The single crystal manufacturing apparatus 1 further includes a magnetic field generating device 20 disposed outside the chamber 10, a CCD camera 25 that photographs the inside of the chamber 10, an image processing unit 26 that processes an image photographed by the CCD camera 25, and a control unit 27 that controls the shaft drive mechanism 14, the heater 15, and the wire winding mechanism 19 based on the output of the image processing unit 26.

[0035] The chamber 10 is composed of a main chamber 10a and an elongated cylindrical pull chamber 10b connected to the upper opening of the main chamber 10a. The quartz crucible 11, the susceptor 12, the heater 15, and the heat shield 17 are provided in the main chamber 10a. The pull chamber 10b is provided with a gas inlet 10c for introducing an inert gas (purge gas) such as argon gas into the chamber 10, and the lower part of the main chamber 10a is provided with a gas outlet 10d for discharging the inert gas. Further, a viewing window 10e is provided in the upper part of the main chamber 10a, and the growth state (solid-liquid interface) of the silicon single crystal 3 can be observed through the viewing window 10e.

[0036] The quartz crucible 11 is a container made of quartz glass having a cylindrical side wall portion, a gently curved bottom portion, and a corner portion provided between the side wall portion and the bottom portion. The susceptor 12 is held so as to be in close contact with the outer surface of the quartz crucible 11 and wrap the quartz crucible 11 in order to maintain the shape of the quartz crucible 11 softened by heating. The quartz crucible 11 and the susceptor 12 constitute a double-structured crucible that supports the silicon melt in the chamber 10.

[0037] The susceptor 12 is fixed to the upper end portion of a rotary shaft 13 extending in the vertical direction. The lower end portion of the rotary shaft 13 penetrates the center of the bottom of the chamber 10 and is connected to a shaft drive mechanism 14 provided outside the chamber 10. The susceptor 12, the rotary shaft 13, and the shaft drive mechanism 14 constitute a crucible lifting mechanism that drives the quartz crucible 11 to move up and down while rotating.

[0038] The heater 15 is used to melt the silicon raw material filled in the quartz crucible 11 and maintain it in a molten state. The heater 15 is a carbon resistance heater and is a substantially cylindrical member provided so as to surround the entire circumference of the quartz crucible 11 in the susceptor 12. Further, the outside of the heater 15 is surrounded by a heat insulating material 16, thereby enhancing the heat retention property in the chamber 10.

[0039] The heat shield 17 is provided to suppress temperature fluctuations of the silicon melt 2 and form an appropriate hot zone near the solid-liquid interface, and to prevent heating of the silicon single crystal 3 by radiant heat from the heater 15 and the quartz crucible 11. The heat shield 17 is a graphite cylindrical member that covers the region above the silicon melt 2 excluding the pulling-up path of the silicon single crystal 3.

[0040] At the center of the lower end of the heat shield 17, a circular opening larger than the diameter of the silicon single crystal 3 is formed, ensuring a pulling-up path for the silicon single crystal 3. As shown in the figure, the silicon single crystal 3 is pulled upward through the opening. Since the diameter of the opening of the heat shield 17 is smaller than the diameter of the quartz crucible 11 and the lower end of the heat shield 17 is located inside the quartz crucible 11, the heat shield 17 will not interfere with the quartz crucible 11 even if the upper end of the rim of the quartz crucible 11 is raised above the lower end of the heat shield 17.

[0041] As the silicon single crystal 3 grows, the amount of melt in the quartz crucible 11 decreases. By raising the quartz crucible 11 so that the distance (gap) between the melt surface 2s and the heat shield 17 remains constant, the temperature fluctuation of the silicon melt 2 can be suppressed, and the evaporation rate of the dopant from the silicon melt 2 can be controlled by keeping the flow rate of the gas flowing in the vicinity (purging gas induction path) of the melt surface 2s constant. Therefore, the stability of the crystal defect distribution, oxygen concentration distribution, resistivity distribution, etc. in the pulling axis direction of the single crystal can be improved.

[0042] Above the quartz crucible 11, a wire 18 which is the pulling axis of the silicon single crystal 3 and a wire winding mechanism 19 for winding the wire 18 are provided, and these constitute a crystal pulling mechanism. The wire winding mechanism 19 has a function of rotating the single crystal together with the wire 18. The wire winding mechanism 19 is arranged above the pull chamber 10b, the wire 18 extends downward through the pull chamber 10b from the wire winding mechanism 19, and the tip of the wire 18 reaches the internal space of the main chamber 10a. Fig. 1 shows the state in which the growing silicon single crystal 3 is suspended from the wire 18. When pulling up the single crystal, the seed crystal is immersed in the silicon melt 2, and the single crystal is grown by gradually pulling up the wire 18 while rotating the quartz crucible 11 and the seed crystal respectively.

[0043] The magnetic field generating device 20 consists of a plurality of coils provided around the quartz crucible 11, and applies a transverse magnetic field (horizontal magnetic field) to the silicon melt 2. The maximum intensity of the transverse magnetic field on the rotation axis of the quartz crucible 11 (on the extension line of the crystal pulling axis) is preferably in the magnetic field intensity range of 0.15 to 0.6 (T) which is that of a general HMCZ. By applying a magnetic field to the silicon melt 2, the melt convection in the direction orthogonal to the magnetic field lines can be suppressed. Therefore, the elution of oxygen from the quartz crucible 11 can be suppressed, and the oxygen concentration in the silicon single crystal can be reduced.

[0044] An observation window 10e for observing the interior is provided at the upper part of the main chamber 10a, and the CCD camera 25 is installed outside the observation window 10e. During the single crystal pulling process, the CCD camera 25 takes an image of the boundary between the silicon single crystal 3 and the silicon melt 2 that can be seen through the opening 17a of the heat shield 17 from the observation window 10e. The CCD camera 25 is connected to the image processing unit 26, the captured image is processed by the image processing unit 26, and the processing result is used in the control of the crystal pulling conditions by the control unit 27.

[0045] FIG. 2 is a flowchart for explaining the method for manufacturing a silicon single crystal according to an embodiment of the present invention. Further, FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.

[0046] As shown in FIGS. 2 and 3, in the production of the silicon single crystal 3, the silicon raw material in the quartz crucible 11 is heated to generate a silicon melt 2 (step S11). Thereafter, the seed crystal attached to the tip of the wire 18 is lowered and made to land on the silicon melt 2 (step S12).

[0047] Next, a single crystal pulling process is performed in which the seed crystal is gradually pulled up while maintaining contact with the silicon melt 2 to grow a single crystal. In the single crystal pulling process, a necking process (step S13) for forming a neck portion 3a with a reduced crystal diameter for dislocation-free growth, a shoulder portion growth process (step S14) for forming a shoulder portion 3b with a gradually increasing crystal diameter to obtain a specified diameter, a body portion growth process (step S15) for forming a body portion 3c with a constant crystal diameter, and a tail portion growth process (step S16) for forming a tail portion 3d with a gradually decreasing crystal diameter are sequentially performed. The tail portion growth process ends when the silicon single crystal 3 is finally separated from the melt surface 2s. Thus, a silicon single crystal ingot 3 having a neck portion 3a, a shoulder portion 3b, a body portion 3c, and a tail portion 3d is completed in order from the upper end to the lower end of the single crystal.

[0048] During the single crystal pulling process, in order to control the diameter of the silicon single crystal 3 and the liquid level position of the silicon melt 2, a CCD camera 25 captures an image of the boundary between the silicon single crystal 3 and the silicon melt 2, and the diameter of the silicon single crystal 3 at the solid-liquid interface and the distance (gap) between the melt surface 2s and the heat shield 17 are calculated from the captured image. The control unit 27 controls the pulling conditions such as the pulling speed of the wire 18 and the power of the heater 15 so that the diameter of the silicon single crystal 3 becomes the target diameter. Further, the control unit 27 controls the height position of the quartz crucible 11 so that the distance between the melt surface 2s and the heat shield 17 becomes constant.

[0049] Next, the configuration of the magnetic field generating device 20 will be described in detail.

[0050] Figs. 4(a) to (c) are schematic perspective views showing the configuration of the magnetic field generating device 20 according to the first embodiment of the present invention, where (a) shows the overall configuration of the magnetic field generating device 20, (b) shows the configuration of the first coil device 21, and (c) shows the configuration of the second coil device 22.

[0051] As shown in Fig. 4(a), this magnetic field generating device 20 is composed of a combination of a first coil device 21 that generates a first transverse magnetic field and a second coil device 22 that generates a second transverse magnetic field different from the first transverse magnetic field. When the rotation axis (crystal central axis) of the quartz crucible 11 is defined as the Z-axis and the intersection point of the Z-axis and the molten surface is defined as the origin of the rectangular coordinate system, the application direction of the transverse magnetic field is the Y-axis direction. In this way, by preparing two coil devices and independently changing the intensity of the transverse magnetic field generated by each, the magnetic field distribution can be changed in accordance with the rise of the quartz crucible 11.

[0052] As shown in Fig. 4(b), the first coil device 21 includes a pair of coil elements made of loop coils. Specifically, the first coil device 21 includes a first coil element 21a and a second coil element 21b that faces the first coil element 21a with the Z-axis interposed therebetween. The first coil element 21a is arranged on the minus side in the Y-axis direction, and the second coil element 21b is arranged on the plus side in the Y-axis direction. In particular, the first coil element 21a and the second coil element 21b are symmetrically arranged with the XZ plane interposed therebetween.

[0053] The loop sizes of the first and second coil elements 21a and 21b are the same and have a relatively large diameter. The coil axes (coil central axes) of the first coil element 21a and the second coil element 21b coincide with the Y-axis. Therefore, the central axis of the magnetic field generated from the first coil device 21 coincides with the Y-axis.

[0054] In the operation of the first coil device 21, the magnetic field generation directions of the pair of coil elements are made to coincide with each other. That is, when it is desired to generate a magnetic field in the plus direction of the Y-axis from the first coil device 21, the directions of the magnetic fields of both the first and second coil elements 21a and 21b are set in the plus direction of the Y-axis (the direction from the first coil element 21a to the second coil element 21b). Conversely, when it is desired to generate a magnetic field in the minus direction of the Y-axis, the directions of the magnetic fields of both the first and second coil elements 21a and 21b are set in the minus direction of the Y-axis (the direction from the second coil element 21b to the first coil element 21a).

[0055] As shown in FIG. 4(c), the second coil device 22 includes two pairs of coil elements each formed of a loop coil. Specifically, the second coil device 22 includes a third coil element 22a, a fourth coil element 22b facing the third coil element 22a with the Z-axis therebetween, a fifth coil element 22c, and a sixth coil element 22d facing the fifth coil element 22c with the Z-axis therebetween. The third coil element 22a and the fifth coil element 22c are disposed on the minus side in the Y-axis direction, and the fourth coil element 22b and the sixth coil element 22d are disposed on the plus side in the Y-axis direction. In particular, the third and fifth coil elements 22a, 22c and the fourth and sixth coil elements 22b, 22d are symmetrically disposed with the XZ plane therebetween.

[0056] The loop sizes of the third to sixth coil elements 22a to 22d are the same and are further the same as the loop sizes of the first and second coil elements 21a, 21b. The coil axes of the third and fourth coil elements 22a, 22b are in the XY plane and are inclined 45 degrees (+45 degrees) counterclockwise with respect to the Y-axis. The coil axes of the fifth and sixth coil elements 22c, 22d are also in the XY plane but are inclined 45 degrees (-45 degrees) clockwise with respect to the Y-axis. Therefore, the coil axes of the fifth and sixth coil elements 22c, 22d are orthogonal to the coil axes of the third and fourth coil elements 22a, 22b.

[0057] Even in the operation of the second coil device 22, the magnetic field generation directions of the pair of coil elements are made to coincide with each other. That is, when it is desired to generate a magnetic field in the positive direction of the Y-axis from the second coil device 22, the directions of the magnetic fields of both the third and fourth coil elements 22a and 22b are set to the positive direction of the Y-axis (the direction from the third coil element 22a toward the fourth coil element 22b), and the directions of the magnetic fields of both the fifth and sixth coil elements 22c and 22d are set to the positive direction of the Y-axis (the direction from the fifth coil element 22c toward the sixth coil element 22d). Thereby, the direction of the combined magnetic field of the third to sixth coil elements 22a to 22d becomes the positive direction of the Y-axis. Conversely, when it is desired to generate a magnetic field in the negative direction of the Y-axis, the directions of the magnetic fields of both the third and fourth coil elements 22a and 22b are set to the negative direction of the Y-axis (the direction from the fourth coil element 22b toward the third coil element 22a), and the directions of the magnetic fields of both the fifth and sixth coil elements 22c and 22d are set to the negative direction of the Y-axis (the direction from the sixth coil element 22d toward the fifth coil element 22c). Thereby, the direction of the combined magnetic field of the third to sixth coil elements 22a to 22d becomes the negative direction of the Y-axis.

[0058] FIG. 5 is a graph showing changes in the magnetic field intensity generated from the first coil device 21 and the second coil device 22.

[0059] As shown in FIG. 5, in the early stage of the crystal pulling process, a relatively large magnetic field directed in the positive direction of the Y-axis is applied from the first coil device 21, and a relatively large magnetic field directed in the negative direction of the Y-axis is applied from the second coil device 22.

[0060] After that, as crystal growth progresses, the magnetic field (first magnetic field) of the first coil device 21 is gradually weakened, and the magnetic field (second magnetic field) generated from the second coil device 22 is gradually strengthened. The magnetic field generated from the first coil device 21 has a magnetic field change in which the magnetic field in the positive direction of the Y-axis gradually weakens to zero, and further, the direction of the magnetic field is reversed, and the magnetic field in the negative direction of the Y-axis gradually strengthens. The magnetic field generated from the second coil device 22 has a magnetic field change in which the magnetic field in the negative direction of the Y-axis gradually weakens to zero, and further, the direction of the magnetic field is reversed, and the magnetic field in the positive direction of the Y-axis gradually strengthens. Therefore, at the end of the crystal pulling process, a relatively large magnetic field directed in the negative direction of the Y-axis is applied from the first coil device 21, and a relatively large magnetic field directed in the positive direction of the Y-axis is applied from the second coil device 22. The timing at which the magnetic field profile of the first coil device 21 becomes zero does not coincide with the timing at which the magnetic field profile of the second coil device 22 becomes zero.

[0061] Figs. 6(a) to (c) are schematic diagrams showing the vector distribution of the composite magnetic field applied to the silicon melt 2 in the quartz crucible 11. Note that Fig. 6 shows only the magnetic field near the silicon melt, and the magnetic field spreading around the silicon melt is omitted. Also, the illustration of the silicon single crystal 3 pulled up from the melt surface 2s is omitted.

[0062] At the beginning of the crystal pulling process shown in Fig. 6(a), the remaining amount of the silicon melt in the quartz crucible 11 is large, and the melt surface 2s is sufficiently separated from the bottom of the crucible. Note that the melt surface 2s is the gas-liquid interface and is distinguished from the interface between the silicon melt 2 and the quartz crucible 11. At this time, by applying the magnetic field intensity profile when the crystal length is short shown in Fig. 5, the direction of the magnetic field applied near the bottom of the crucible can be fitted to the curved shape of the bottom of the crucible.

[0063] In the middle stage of the crystal pulling process shown in FIG. 6(b), the silicon melt in the quartz crucible 11 decreases, and the melt surface 2s drops and approaches the bottom of the crucible. In the final stage of the crystal pulling process shown in FIG. 6(c), the melt surface 2s further drops. However, as shown in FIG. 5, by changing the magnetic field strengths of the first coil device 21 and the second coil device 22 in accordance with the crystal length (remaining amount of silicon melt), from the initial stage to the final stage of the crystal pulling process, while maintaining the magnetic field near the melt surface 2s horizontally, the direction of the magnetic field applied near the bottom of the crucible can be fitted to the curved shape of the bottom of the crucible.

[0064] When the direction of the magnetic field applied near the bottom of the crucible does not follow the curved bottom of the crucible, convection is partially suppressed at the bottom of the crucible, and the shape of the large roll flow of the silicon melt fluctuates over time and becomes unstable. Therefore, the way oxygen dissolved in the silicon melt reaches the silicon single crystal at the bottom of the crucible also fluctuates over time, resulting in variations in the in-plane distribution of the oxygen concentration.

[0065] However, when the direction of the magnetic field applied near the bottom of the crucible follows the curved bottom of the crucible, a large roll flow is stably generated in the silicon melt, and oxygen easily evaporates from the melt surface 2s. Therefore, the amount of oxygen incorporated into the silicon single crystal decreases. When the direction of the magnetic field applied near the bottom of the crucible follows the curved bottom of the crucible, convection at the bottom of the crucible is not suppressed, so the amount of oxygen eluted from the crucible into the silicon melt increases. However, since the oxygen concentration in the silicon single crystal is strongly affected by the evaporation of oxygen from the melt surface, even if the amount of oxygen dissolved in the silicon melt increases slightly, the oxygen concentration in the silicon single crystal does not increase.

[0066] FIGS. 7(a) to (c) are schematic perspective views showing the configuration of the magnetic field generating device 20 according to the second embodiment of the present invention, where (a) shows the overall configuration of the magnetic field generating device 20, (b) shows the configuration of the first coil device 21, and (c) shows the configuration of the second coil device 22, respectively.

[0067] As shown in FIGS. 7(a) to 7(c), this magnetic field generating device 20 is different from the magnetic field generating device shown in the first embodiment in that the loop sizes of the coil elements constituting the first and second coil devices 21 and 22 are smaller. Other configurations are the same as those in the first embodiment. Even with such a configuration, the same effects as those in the first embodiment can be achieved.

[0068] FIGS. 8(a) to 8(c) are schematic perspective views showing the configuration of the magnetic field generating device 20 according to the third embodiment of the present invention, where (a) shows the overall configuration of the magnetic field generating device 20, (b) shows the configuration of the first coil device 21, and (c) shows the configuration of the second coil device 22.

[0069] As shown in FIGS. 8(a) to 8(c), in this magnetic field generating device 20, the coil elements 21a, 21b, 22a, 22b, 22c, and 22d in the first and second coil devices 21 and 22 shown in FIGS. 7(a) to 7(c) are replaced with upper and lower two-stage coil element pairs 21ap, 21bp, 22ap, 22bp, 22cp, and 22dp. That is, the first coil device 21 includes two pairs of coil elements formed of loop coils, and the second coil device 22 includes four pairs of coil elements formed of loop coils.

[0070] As shown in FIG. 8(b), the first coil device 21 includes a first coil element pair 21ap (21a 1 , 21a 2 ) and a second coil element pair 21bp (21b 1 , 21b 2 ) that faces the first coil element pair 21ap across the Z axis. The first coil element pair 21ap (21a 1 , 21a 2 ) is arranged on the minus side in the Y-axis direction, and the second coil element pair 21bp (21b 1 , 21b 2 ) is arranged on the plus side in the Y-axis direction, respectively.

[0071] The upper coil portion 21a of the first coil element pair 21ap 1 is on the opposite side of the XY plane from the lower coil portion 21a of the first coil element pair 21ap 2has a symmetrical positional relationship, and the upper coil portion 21b of the second coil element pair 21bp 1 is symmetrically positioned with respect to the lower coil portion 21b of the second coil element pair 21bp across the XY plane 2 . The upper coil portion 21a 1 and the upper coil portion 21b 1 constitute a pair of coil elements with coincident coil axes, and the lower coil portion 21a 2 and the lower coil portion 21b 2 also constitute a pair of coil elements with coincident coil axes.

[0072] As shown in FIG. 8(c), the second coil device 22 includes a third coil element pair 22ap (22a 1 , 22a 2 ), a fourth coil element pair 22bp (22b 1 , 22b 2 ) that faces the third coil element pair 22ap across the Z axis, a fifth coil element pair 22cp (22c 1 , 22c 2 ), and a sixth coil element pair 22dp (22d 1 , 22d 2 ) that faces the fifth coil element pair 22cp across the Z axis. The third coil element pair 22ap and the fifth coil element pair 22cp are respectively arranged on the negative side in the Y-axis direction, and the fourth coil element pair 22bp and the sixth coil element pair 22dp are respectively arranged on the positive side in the Y-axis direction.

[0073] The upper coil portion 22a of the third coil element pair 22ap 1 has a symmetrical positional relationship with respect to the lower coil portion 22a of the third coil element pair 22ap across the XY plane 2 , and the upper coil portion 22b of the fourth coil element pair 22bp 1 has a symmetrical positional relationship with respect to the lower coil portion 22b of the fourth coil element pair 22bp across the XY plane 2 . The upper coil portion 22a 1 and the upper coil portion 22b 1 constitute a pair of coil elements with coincident coil axes, and the lower coil portion 22a 2 and the lower coil portion 22b 2It also constitutes a pair of coil elements whose coil axes coincide.

[0074] The upper coil portion 22c of the fifth coil element pair 22cp 1 has a symmetrical positional relationship with the lower coil portion 22c of the fifth coil element pair 22cp across the XY plane, and the upper coil portion 22d of the sixth coil element pair 22dp 2 has a symmetrical positional relationship with the lower coil portion 22d of the sixth coil element pair 22dp across the XY plane. The upper coil portion 22c 1 and the upper coil portion 22d 2 constitute a pair of coil elements whose coil axes coincide, and the lower coil portion 22c 1 and the lower coil portion 22d 1 also constitute a pair of coil elements whose coil axes coincide. 2 2 2 It also constitutes a pair of coil elements whose coil axes coincide.

[0075] The magnetic field generating device 20 according to the third embodiment having the above configuration can also achieve the same effects as the first embodiment.

[0076] Figs. 9(a) to (c) are schematic perspective views showing the configuration of the magnetic field generating device 20 according to the fourth embodiment of the present invention, where (a) shows the overall configuration of the magnetic field generating device 20, (b) shows the configuration of the first coil device 21, and (c) shows the configuration of the second coil device 22, respectively.

[0077] As shown in Figs. 9(a) to (c), this magnetic field generating device 20 is characterized in that the first coil device 21 includes two pairs of coil elements (coil elements 21a 1 , 21a 2 , 21b 1 , 21b 2 ) made of loop coils, and the second coil device 22 includes two pairs of coil elements (coil elements 22a, 22b, 22c, 22d) made of loop coils. That is, the first coil device 21 has the same configuration as in Fig. 8, and the second coil device 22 adopts the same configuration as in Fig. 7. Also in this embodiment, the same effects as those of the other embodiments can be obtained.

[0078] The magnetic field parallel to the curved shape at the bottom of the quartz crucible can be obtained using mathematical formulas.

[0079] For example, the output of the magnetic field generator 20 is adjusted so as to minimize the integral value from Y = 0 to Y = Ymax of the square of the inner product of the normal vector n of the inner bottom surface Z = C(Y) of the quartz crucible and the magnetic field vector. That is, the following equation (1) is minimized while fixing the magnetic field intensity at the origin to a specific value.

[0080]

Equation

[0081] Here, B 1 is the magnetic field vector created by the first coil device 21 alone, and B 2 is the magnetic field vector created by the second coil device 22 alone.

[0082] Since the magnetic field distribution approaches horizontal near the central axis of the crucible, the shape of the crucible bottom and the magnetic field distribution are approximately parallel to some extent near the center of the crucible bottom. On the other hand, near the outer periphery of the crucible bottom, the magnetic field distribution and the crucible shape tend to deviate from parallel. Therefore, since the integrand of equation (1) becomes large where Y is large, in order to minimize equation (1), it is necessary to make the integrand small where Y is large, that is, to make the crucible shape and the magnetic field lines approach parallel.

[0083] It is desirable that Ymax be 70% or less of the crucible radius R (0 ≦ Ymax ≦ 0.7R). If Ymax is too small, the parallelism at the outer periphery of the crucible will not be satisfied. If Ymax is too large, the parallelism will deteriorate in the portion between the center and the outer periphery of the crucible bottom in order to match the outer periphery, and also, the crucible shape that changes abruptly toward the side wall surface of the crucible will greatly affect equation (1).

[0084] As a variation of equation (1), a method of evaluating using the direction vector of B instead of B is also conceivable.

[0085] That is, the second derivative in the Y direction of the crucible bottom shape and the magnetic field lines is made to coincide at the center of the crucible bottom. Specifically, the output of the magnetic field generating device 20 is adjusted so as to satisfy the following equation (2).

[0086]

Equation

[0087] Here, B 1,Y and B 1,Z are the Y - direction component and the Z - direction component of the magnetic field vector B 1 produced by the first coil device 21 alone, respectively, and B 2,Y and B 2,Z are the Y - direction component and the Z - direction component of the magnetic field vector B 2 produced by the second coil device 22 alone, respectively.

[0088] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to the above - described embodiments, and various modifications can be made without departing from the gist of the present invention, and it goes without saying that those are also included in the scope of the present invention.

[0089] For example, in the above - described embodiment, the method for manufacturing a single - crystal silicon has been taken as an example. However, the present invention is not limited to the method for manufacturing a single - crystal silicon, and is applicable to various methods for manufacturing single - crystals employing the HMCZ method.

Example

[0090] Using the magnetic field generating device 20 shown in FIG. 9, a silicon single - crystal was grown by the HMCZ method. As described above, this magnetic field generating device 20 is composed of a first coil device 21 consisting of four coil elements 21a 1 , 21a 2 , 21b 1 , 21b 2 arranged in a vertical plane, and a second coil device 22 consisting of four coil elements 22a, 22b, 22c, 22d arranged in a horizontal plane.

[0091] The magnetic field strength at the origin of the orthogonal coordinates (the intersection of the crystal center axis (Z-axis) and the magnetic field center axis (Y-axis)) was set to 3000 G. The diameter of the quartz crucible was 813 mm, and the radius of curvature of the curved bottom of the quartz crucible was 813 mm.

[0092] The magnetic fields created by the first and second coil devices were calculated using electromagnetic field analysis software. The magnetic field vector at the melt surface was made parallel to the Y-axis. Also, the angle formed between the normal to the inner surface of the bottom of the quartz crucible and the magnetic field vector in the YZ plane was calculated, and the magnetic field output with respect to the melt depth (the distance from the liquid surface to the bottom of the crucible) was calculated using the above equation (2). The results are shown in the graphs of FIGS. 10(a) and (b). In the graphs of FIGS. 10(a) and (b), the output required for each of the first and second coil devices to create a magnetic field strength independently at the crystal-melt surface center is set to 1.

[0093] As shown in FIGS. 10(a) and (b), the output of the first coil device (the first magnetic field) initially has a large magnetic field strength in the positive direction of the Y-axis, but as crystal growth progresses and the melt volume decreases, the magnetic field strength in the positive direction of the Y-axis gradually decreases and becomes zero in the middle, and then the magnetic field strength in the negative direction of the Y-axis gradually increases. Conversely, the output of the second coil device (the second magnetic field) initially has a large magnetic field strength in the negative direction of the Y-axis, but as crystal growth progresses and the melt volume decreases, the magnetic field strength in the negative direction of the Y-axis gradually decreases and becomes zero in the middle, and then the magnetic field strength in the positive direction gradually increases.

[0094] FIGS. 11(a) to (c) are graphs showing the angle θ formed between the magnetic field lines of the composite magnetic field generated using the magnetic field output profiles shown in FIGS. 10(a) and (b) and the inner surface of the crucible bottom, while comparing with the magnetic fields generated when the first and second coil devices operate independently.

[0095] As shown in Fig. 11(c), when the melt depth was 400 mm, the magnetic field angle with respect to the inner surface of the crucible bottom when a composite magnetic field was applied was about 90 degrees to 95 degrees. Also, as shown in Fig. 11(b), even when the melt depth was 300 mm, the magnetic field angle was about 90 degrees to 95 degrees. As shown in Fig. 11(a), when the melt depth was 200 mm, the magnetic field angle was almost 90 degrees, resulting in very good results.

[0096] Fig. 12 is a graph showing the oxygen concentration distribution in the crystal growth direction of a silicon single crystal according to an example manufactured while applying a composite magnetic field. As is clear from the illustrated graph, the oxygen concentration in the crystal growth direction was very stable within the range of 10×10 17 ~11×10 17 atoms / cm 3 ³.

[0097] Figs. 13(a) to (f) are graphs showing the evaluation results of the oxygen concentration of silicon single crystals according to comparative examples and examples. In particular, Figs. 13(a) to (c) are the evaluation results of the oxygen concentration of silicon single crystals according to comparative examples manufactured while applying a single magnetic field (conventional magnetic field), and are graphs showing the in-plane distribution (radial distribution) of the oxygen concentration at positions where the crystal lengths are 500 mm, 1100 mm, and 1700 mm. Also, Figs. 13(d) to (f) are the evaluation results of the oxygen concentration of silicon single crystals according to examples manufactured while applying a composite magnetic field, and are graphs showing the in-plane distribution (radial distribution) of the oxygen concentration at positions where the crystal lengths are 500 mm, 1100 mm, and 1700 mm.

[0098] As shown in Figs. 13(a) to (c), the oxygen concentration distribution of the silicon single crystal according to the comparative example had a large variation. On the other hand, as shown in Figs. 13(d) to (f), the oxygen concentration distribution of the silicon single crystal according to the example had a smaller variation.

Explanation of Reference Numerals

[0099] 1 Single crystal manufacturing apparatus 2 Silicon melt 3 Silicon single crystal (ingot) 3a Neck portion 3b Shoulder part 3c Body part 3d Tail part 10 Chamber 10a Main chamber 10b Pull chamber 10c Gas inlet 10d Gas outlet 10e Observation window 11 Quartz crucible 12 Susceptor 13 Rotating shaft 14 Shaft drive mechanism 15 Heater 16 Heat insulator 17 Heat shield 18 Wire 19 Wire winding mechanism 20 Magnetic field generating device 21a First coil element 21a 1 Upper coil part 21a 2 Lower coil part 21ap First coil element pair 21b Second coil element 21b 1 Upper coil part 21b 2 Lower coil part 21bp Second coil element pair 22a Third coil element 22a 1 Upper coil part 22a 2 Lower coil part 22ap Third coil element pair 22b Fourth coil element 22b 1 Upper coil part 22b 2 Lower coil part 22bp Fourth coil element pair 22c Fifth coil element 22c 1 Upper coil part 22c 2 Lower coil part 22cp 5th Coil Element Pair 22d 6th Coil Element 22d 1 Upper Coil Section 22d 2 Lower Coil Section 22dp 6th Coil Element Pair 25 CCD Camera 26 Image Processing Unit 27 Control Unit

Claims

1. A method for manufacturing a single crystal while applying a transverse magnetic field to a melt in a crucible, comprising: raising the crucible in accordance with a decrease in the melt during the crystal pulling process, and controlling the magnetic field distribution in accordance with the decrease in the melt so that the direction of the magnetic field at the melt surface and the direction of the magnetic field at the inner surface of the curved bottom of the crucible remain constant from the start to the end of the body portion growth process; The control of the magnetic field distribution is: When the rotation axis of the crucible is defined as the Z-axis, the central axis of the application direction of the transverse magnetic field orthogonal to the Z-axis is defined as the Y-axis, the intersection of the Z-axis and the Y-axis is defined as the origin, and the axis orthogonal to the YZ plane and passing through the origin is defined as the X-axis, A method for manufacturing a single crystal, characterized in that on the intersection line of the inner surface of the curved bottom of the crucible and the YZ plane, the angle θ formed by the normal vector of the inner surface and the magnetic field vector is maintained at 75 degrees or more and 105 degrees or less.

2. The method for manufacturing a single crystal according to claim 1, wherein the direction of the magnetic field at the melt surface is parallel to the melt surface.

3. The method for manufacturing a single crystal according to claim 1 or 2, wherein the magnetic field distribution is adjusted so as to minimize the integral value at the bottom of the square of the inner product of the normal vector of the inner surface of the curved bottom of the crucible and the magnetic field vector while maintaining the magnetic field strength at the origin constant.

4. The method for manufacturing a single crystal according to claim 1 or 2, wherein the magnetic field distribution is adjusted so that the shape of the bottom and the second derivative of the magnetic field in the Y direction coincide at the center of the bottom.

5. The method for manufacturing a single crystal according to any one of claims 1 to 4, wherein when the radius of the crucible is R, the bottom is in the range of 0.7R or less from the center of the bottom.

6. The method for manufacturing a single crystal according to any one of claims 1 to 5, wherein a plurality of coil elements are provided around the crucible, and the magnetic field distribution is controlled by individually adjusting the magnetic field strength of each coil element.

7. The method for manufacturing a single crystal according to claim 6, wherein the plurality of coil elements constitute a plurality of coil element pairs having coincident coil axes.

8. The method for manufacturing a single crystal according to claim 6 or 7, wherein the plurality of coil elements are arranged symmetrically with respect to the XZ plane.

9. The method for manufacturing a single crystal according to any one of claims 6 to 8, wherein the plurality of coil elements are arranged parallel to the XY plane.

10. The plurality of coil elements include a first coil device that generates a first magnetic field, It is configured with a second coil device that generates a second magnetic field different from the first magnetic field. The method for manufacturing a single crystal according to any one of claims 6 to 9, wherein the magnetic field distribution is controlled by individually adjusting the intensity of the first magnetic field and the intensity of the second magnetic field.

11. The first magnetic field has a magnetic field change in which the magnetic field in the positive direction of the Y-axis gradually weakens, then becomes zero, and further the magnetic field in the negative direction of the Y-axis gradually strengthens. The method for manufacturing a single crystal according to claim 10, wherein the second magnetic field has a magnetic field change in which the magnetic field in the negative direction of the Y-axis gradually weakens, then becomes zero, and further the magnetic field in the positive direction of the Y-axis gradually strengthens.

12. When the rotation axis of the crucible is the Z-axis, the central axis in the application direction of the transverse magnetic field orthogonal to the Z-axis is the Y-axis, the intersection of the Z-axis and the Y-axis is the origin, and the axis orthogonal to the YZ plane and passing through the origin is the X-axis, The first coil device is arranged on the YZ plane and has at least a pair of coil elements whose coil axes coincide. The second coil device is arranged parallel to the XY plane and has at least two pairs of coil elements whose coil axes coincide. The plurality of coil elements constituting the first coil device and the second coil device are arranged symmetrically with respect to the XZ plane. The method for manufacturing a single crystal according to claim 10 or 11.

13. The first coil device is arranged on the YZ plane and has first and second coil elements arranged symmetrically with respect to the Z-axis. The second coil device is arranged on the XY plane and has third and fourth coil elements arranged symmetrically with respect to the Z-axis, and fifth and sixth coil elements arranged symmetrically with respect to the Z-axis on the XY plane. The method for manufacturing a single crystal according to claim 12, wherein the first to sixth coil elements are arranged symmetrically with respect to the XZ plane.

14. The angle formed by the coil axes of the third and fourth coil elements and the Y-axis is +45 degrees. The method for manufacturing a single crystal according to claim 13, wherein the angle formed by the coil axes of the fifth and sixth coil elements and the Y-axis is -45 degrees.

15. The loop sizes of the loop coils constituting the first and second coil elements are the same. The method for manufacturing a single crystal according to claim 13 or 14, wherein the loop sizes of the loop coils constituting the third to sixth coil elements are the same.

Images