Magnetic control device

Abstract

The present invention provides a magnetic device comprising a coil assembly, wherein the coil assembly covers the exterior of a silicon single crystal growth device and is movable along the axis of the silicon single crystal growth device. The coil assembly comprises a plurality of primary coils arranged circumferentially around the silicon single crystal growth device. The strength of the magnetic field component generated by the primary coils in the radial direction of the silicon single crystal growth device is higher than that of its component along the axis of the silicon single crystal growth device. In this arrangement, the strength of the magnetic field component generated by the primary coils in the radial direction of the silicon single crystal growth device is stronger than that of its component along the axis of the silicon single crystal growth device, thereby increasing the strength of the magnetic field component, which in turn effectively suppresses natural convection along the melt, and allows for flexible control of the content and radial uniformity of oxygen, carbon, and other impurities in the resulting crystal. Additionally, the mobility of the coil assembly along the axis of the silicon single crystal growth device adds further practicality and flexibility to the magnetic device.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor devices, and more particularly to magnetic devices.

Background Art

[0002] In the current state of the art of semiconductor manufacturing, the most commonly used method for producing single crystal silicon is the single crystal pulling method, also known as the Czochralski method (or simply the Cz method). In recent years, with the rapid development of semiconductor microelectronics and very large scale integration (VLSI) circuits, there has been a demand for higher quality and larger size single crystal silicon materials. To meet this demand, larger crucibles of polycrystalline silicon, and thus larger supplies of polycrystalline silicon, have been increasingly used, which has led to an increase in melt convection. This increase not only affects stable crystal growth but also limits the control of the concentration and uniformity of impurities in the crystal, such as oxygen and carbon. To overcome these problems, magnetic Czochralski (MCZ) technology has been developed, in which a magnetic field with a specific intensity is applied around the Czochralski crucible to generate a Lorentz force in the highly conductive molten silicon contained in the crucible, thereby effectively suppressing melt convection and the transport of impurities such as oxygen and carbon in the melt, and thereby obtaining single crystal silicon of improved quality.

[0003] In particular, the magnetic fields used in the MCZ method can be primarily axial, transverse, or cusp magnetic fields. Axial magnetic fields are mainly used to suppress transverse convection on the free melt surface, but are less preferred due to their limited effectiveness and are gradually being replaced by cusp and transverse magnetic fields. A cusp magnetic field can be generated using two coils positioned vertically, while a transverse magnetic field can be generated using symmetrically positioned coils on the left and right. For large Czochralski crucibles, typically with a maximum feed capacity of 450 kg, the cusp magnetic field cannot outperform the transverse horizontal magnetic field in terms of melt convection suppression performance, as its strength (at most about 100 mT) is considerably lower than that of the transverse horizontal magnetic field (200-400 mT). Therefore, most existing large Czochralski crucibles use the transverse horizontal magnetic field.

[0004] However, due to its asymmetric nature, the transverse magnetic field can only suppress the melt flow component parallel to it, doing nothing to the melt flow component perpendicular to it. Furthermore, once the intensity of the transverse magnetic field reaches a certain critical level, it ceases to provide significant oxygen reduction capacity. This greatly limits its ability to improve crystal quality. Additionally, under the action of a transverse magnetic field, the naturally flowing melt generates two-pillar convection cells, resulting in significantly higher temperatures in the crucible wall portion parallel to the magnetic field than in the portion perpendicular to it. Such an uneven circumferential temperature distribution of the crucible wall also contributes to the reduction of oxygen reduction capacity. Moreover, the transverse magnetic field induces electric currents in the rotating crystal, and these currents, when flowing within the melt, generate a magnetic force that counteracts the centrifugal force of the crystal rotation. As a result, not only can the melt be deflected during its rotation, but an uneven temperature distribution can also occur around the solid-liquid interface. The complex melt flow behavior and non-uniform temperature distribution around the solid-liquid interface can not only reduce process stability and increase the risk of crystal cracking, but can also reduce radial oxygen uniformity.

[0005] Japanese Patent Publication No. 2023-023707 discloses the generation of a cusp magnetic field using transverse magnetic field coils in one embodiment. However, an even number of coils must be used in pairs, and the magnetic field components directed toward the center of the melt and the magnetic field components directed toward away from the center of the melt alternate within the cross-section of the melt. In this arrangement, the induced currents cancel each other out at points A and B as shown in Figures 17 to 19, resulting in an unbalanced Lorentz force near the outer circumference of the crucible, and consequently, a non-uniform natural convection distribution along the periphery of the melt and more difficult control of the oxygen content of the crystals. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-023707 [Overview of the project] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide a magnetic device that overcomes the problems associated with conventional transverse magnetic fields, including limitations in the ability to control oxygen content when the intensity reaches a critical level, low radial oxygen uniformity and increased process variability resulting from the non-uniform temperature distribution along the outer circumference of the crucible and around the solid-liquid interface, as well as the problems associated with conventional cusp magnetic fields, including the difficulty in further increasing the intensity. This magnetic device uses a circumferential coil arrangement that can produce a magnetic field distribution similar to that of a cusp magnetic field. Such a magnetic field has both relatively high circumferential uniformity and increased intensity of the radial component, thereby making flexible control of the content and radial uniformity of oxygen, carbon, and other impurities extremely easy. [Means for solving the problem]

[0008] To achieve this, the present invention provides a magnetic device comprising a coil assembly.

[0009] The coil assembly covers the outside of the silicon single crystal growth device and is movable along the axis of the silicon single crystal growth device to change the position of the coil assembly relative to the free melt surface within the silicon single crystal growth device.

[0010] The coil assembly comprises multiple primary coils arranged around the circumference of a silicon single crystal growth device, wherein the intensity of the magnetic field component generated by the primary coils in the radial direction of the silicon single crystal growth device is higher than the intensity of the magnetic field component along the axis of the silicon single crystal growth device, within a given range.

[0011] Optionally, the primary coil can also generate a magnetic field oriented radially inward or outward in the silicon single-crystal growth device by applying an excitation current flowing in the same direction.

[0012] Optionally, the coil assembly may further include a secondary coil positioned above or below the primary coil, to which an excitation current is applied to increase or decrease the magnetic field strength.

[0013] Optionally, the magnetic field lines generated by the excitation current applied to the secondary coil may be oriented in the same direction as, or in the opposite direction to, the magnetic field lines generated by the primary coil.

[0014] Optionally, the magnetic device may further include a cryogenic cylinder having a housing chamber, in which the primary and secondary coils are housed.

[0015] Optionally, the inner and outer walls of the containment chamber are curved surfaces, the sides of the primary coil are curved surfaces, the curvature of the sides of the primary coil matches the curvature of the inner and / or outer walls of the containment chamber, and the sides of the primary coil are positioned parallel to the inner and / or outer walls of the containment chamber.

[0016] Optionally, the inner and outer walls of the containment chamber are curved surfaces, the sides of the primary coil are flat surfaces, and the coil is positioned along the axis of the silicon single crystal growth device.

[0017] The cross-section of the primary coil may optionally include a circular, elongated, or elliptical shape.

[0018] Optionally, the secondary coil may be a circular annular member, and the plane of the secondary coil is perpendicular to the plane of the primary coil.

[0019] Optionally, the primary and secondary coils may include superconducting magnetic field coils.

[0020] Optionally, multiple primary coils may be arranged aligned around the circumference of the silicon single crystal growth device, or offset from each other around the circumference of the cryogenic cylinder.

[0021] As noted above, the present invention provides a magnetic device including a coil assembly, the coil assembly covering the outside of a silicon single crystal growth device and movable along the axis of the silicon single crystal growth device to change the position of the coil assembly relative to the free melt surface within the silicon single crystal growth device. The coil assembly includes a plurality of primary coils arranged circumferentially around the silicon single crystal growth device, the current in each primary coil flows in the same direction to generate a magnetic field, and these magnetic fields are superimposed to create a cusp-like magnetic field. In the radial direction, the magnetic field is perpendicular to the melt walls within the silicon single crystal growth device, and in the axial direction, the magnetic field is parallel to the axis (Z direction) of the silicon single crystal growth device. Furthermore, along the melt, the intensity of the component of the magnetic field generated by the primary coils in the radial direction of the silicon single crystal growth device is higher than the intensity of its component along the axis of the silicon single crystal growth device.

[0022] In this arrangement, the components of the magnetic field applied along the periphery of the melt within the silicon single crystal growth device are all perpendicular to the surface of the wall and uniform in the circumferential direction. Symmetrically to the transverse magnetic field, this magnetic field can suppress the upward natural convection along the periphery of the melt while more efficiently and effectively controlling the contents of oxygen, carbon, and other impurities in the resulting crystal. In addition, along the periphery of the melt, the component of the magnetic field generated by the primary coil along the radial direction of the silicon single crystal growth device is stronger than its component along the axis of the silicon single crystal growth device. Compared with the conventional transverse magnetic field and cusp magnetic field, the strength of the radial component of the magnetic field is improved, thereby enabling more effective suppression of natural convection along the periphery of the melt and allowing flexible control of the contents and radial uniformity of oxygen, carbon, and other impurities in the resulting crystal. Furthermore, the mobility of the coil assembly along the axis of the silicon single crystal growth device adds further practicality and flexibility to the magnetic device.

Brief Description of the Drawings

[0023] [Figure 1] It is a schematic diagram of a conventional transverse magnetic field. [Figure 2] It is a schematic diagram of a conventional cusp magnetic field. [Figure 3] It is a schematic diagram of the radial and axial intensity distributions of a conventional cusp magnetic field. [Figure 4] It is a schematic diagram of a magnetic device according to an embodiment of the present invention. [Figure 5] It is a schematic diagram of the relative positions of the components during the operation of the magnetic device according to an embodiment of the present invention. [Figure 6] It is a schematic diagram of the radial and axial intensity profiles of the magnetic field generated by the magnetic device according to an embodiment of the present invention. [Figure 7] It is a schematic diagram of the arrangement of the primary coil according to the first embodiment of the present invention. [Figure 8] It is a top view of the magnetic device according to the first embodiment of the present invention. [Figure 9]This figure shows the magnetic field distribution in a cross-section cut along the XOY plane according to the first embodiment of the present invention. [Figure 10] This figure shows the magnetic field distribution in cross-sections cut along the XOZ and YOZ planes, respectively, according to the first embodiment of the present invention. [Figure 11] This is a schematic diagram of a coil assembly according to the present invention, including a secondary coil. [Figure 12] This is a top view of a magnetic device according to a second embodiment of the present invention. [Figure 13] This figure shows the magnetic field distribution in a cross-section cut along the XOY plane according to a second embodiment of the present invention. [Figure 14] This is a top view of a magnetic device according to a third embodiment of the present invention. [Figure 15] This figure shows the magnetic field distribution in a cross-section cut along the XOY plane according to a third embodiment of the present invention. [Figure 16] This is a schematic diagram of the Lorentz force generated by a magnetic field having a distribution according to the third embodiment of the present invention. [Figure 17] This is a schematic diagram of the Lorentz force generated by a conventional magnetic field. [Figure 18] This is a top view of a conventional magnetic device. [Figure 19] This figure shows the conventional magnetic field distribution within a cross-section cut along the XOY plane. [Explanation of Symbols]

[0024] 1 Coil, 2 Silicon single crystal growth device, 3 Coil assembly, 31 Primary coil, 32 Secondary coil, 4 Cryogenic cylinder, 41 Housing chamber [Modes for carrying out the invention]

[0025] The object, advantages, and features of the present invention will become clearer by reading the following more detailed description of its specific embodiments in conjunction with the accompanying figures. It should be noted that the figures are rather simplified and not necessarily to scale, and are intended solely to help illustrate the embodiments of the present invention disclosed herein in a more convenient and clearer manner. In addition, the illustrated structures are usually parts of their real-world counterparts. In particular, because figures tend to have a clear emphasis, they may also be depicted at different scales.

[0026] When used herein, the singular forms “a,” “an,” and “it” include multiple referents; the term “or” is used generally to mean “and / or”; “several” is used generally to mean “at least one”; and “at least two” is used generally to mean “two or more.” Additionally, the use of the terms “first,” “second,” and “third” herein is for descriptive purposes only and is not intended to indicate or suggest relative importance or implicitly indicate the number of items referred to. Thus, defining an item using “first,” “second,” or “third” is an explicit or implicit indication of the existence of one or at least two such items. The terms “one end” and “the other end,” as well as “proximal end” and “distal end,” may be used herein not only to refer to their respective endpoints but also to refer generally to both ends containing those endpoints. The terms “attach,” “join,” “connect,” and any variations thereof should be interpreted in a broad sense. For example, a connection may be a permanent connection, a detachable connection, or an integral connection, or a direct connection or an indirect connection with one or more intervening mediators, or an internal communication or interaction between two elements. When an element is “displaced” on another element as used herein, this is generally intended only to mean that there is a connection, joining, engagement, or communication relationship between the two elements, which may be direct or indirect with one or more intervening elements, and should not be interpreted as indicating or implying a specific spatial positional relationship between these elements. That is, an element may be located inside, outside, above, below, beside, or in any other location relative to another element, unless the context explicitly specifies otherwise. As used herein, the relative terms “upper,” “lower,” “top,” and “bottom” are used generally to describe a location along the direction of gravity. The terms “vertical” and “vertical direction” generally refer to directions that coincide with the direction of gravity, which is usually perpendicular to the ground. The terms “horizontal” and “horizontal direction” generally refer to directions that are parallel to the ground. Those skilled in the art will be able to understand the specific meanings of the terms used herein in their context.

[0027] The object of the present invention is to provide a magnetic device that overcomes problems associated with conventional transverse magnetic fields, including reduced process stability and low radial oxygen uniformity resulting from non-uniform temperature distribution along the outer circumference of the crucible and around the solid-liquid interface.

[0028] The present invention will be described below with reference to the attached figures.

[0029] Referring to Figures 1-3, conventionally, the Czochralski method generally utilizes either a transverse or cusp magnetic field. Figure 1 shows a schematic diagram of a conventional transverse magnetic field. Figure 2 shows a schematic diagram of a conventional cusp magnetic field. Figure 3 shows a schematic diagram of the radial and axial intensity distribution of a conventional cusp magnetic field. In the exemplary example shown in Figure 1, two coils 1 are placed spaced apart along the left-right direction with the same current direction, generating the horizontal magnetic field shown. In the exemplary example shown in Figure 2, two coils 1 are placed spaced apart along the vertical direction with opposite current directions, generating the cusp magnetic field shown. However, transverse and cusp magnetic fields are each associated with several drawbacks. A transverse magnetic field is asymmetric and therefore can only suppress melt flow components parallel to it, and does nothing to melt flow components perpendicular to it. Because the cusp magnetic field's strength (maximum of about 100 mT) is considerably less than that of the transverse magnetic field (200-400 mT), it cannot outperform the transverse magnetic field in terms of suppressing melt convection.

[0030] In view of this, referring to Figures 4-10, the present invention provides a magnetic device including a coil assembly 3, the coil assembly covering the outside of a silicon single crystal growth device 2 (see Figure 5), and movable along the axis of the silicon single crystal growth device 2 to change the position of the coil assembly 3 relative to the free melt surface within the silicon single crystal growth device 2. The coil assembly 3 includes a plurality of primary coils 31 (see Figures 7-8) arranged circumferentially around the silicon single crystal growth device 2. The intensity of the magnetic field component generated by the primary coils 31 along the radial distance of the silicon single crystal growth device 2 is higher than the intensity of the magnetic field component along the axis of the silicon single crystal growth device 2 within a given range (see Figures 6 and 9-10). It should be noted that in the exemplary examples shown in Figures 4-10, the radial direction of the silicon single crystal growth device 2 is defined by the X and Y directions, and the axis of the silicon single crystal growth device 2 defines the Z direction. In an optional embodiment, the coil assembly 3 may be held within a cryogenic cylinder 4 to maintain the superconducting magnet at a desired low temperature, for example, below -264.15°C (approximately 9K). The cryogenic cylinder 4 surrounds the outside of the silicon single-crystal growth device 2 (see Figures 4 and 5). In this case, the cryogenic cylinder 4 is movable along the axis of the silicon single-crystal growth device 2 to adjust the position of the coil assembly 3 relative to the free melt surface within the silicon single-crystal growth device 2. In this embodiment, the current in each primary coil 31 is the same, and the resulting magnetic fields are superimposed to create a cusp-like magnetic field having a radial component that is all perpendicular to the walls of the melt within the silicon single-crystal growth device 2 and an axial component (Z direction) that is all parallel to the axis of the silicon single-crystal growth device. Those skilled in the art will understand that the melt may be molten silicon contained in the crucible of the silicon single-crystal growth device 2, in which case the free melt surface may be the top surface of the melt in the crucible. In Figures 3 and 6, the axle coordinate may represent the distance from the free melt surface to the coil.As can be seen from Figures 3, 6, and 9-10, unlike conventional cusp magnetic fields which have an axial component stronger than the radial component along the melt periphery, in the magnetic field generated by embodiments of the present invention within a predetermined range, the intensity of the radial component is higher than the intensity of the axial component. Unless the radial component is sufficiently strong, upward natural convection near the melt periphery cannot be suppressed. In practical applications, the predetermined range can be adjusted by changing the axial position of the magnetic device and the silicon single crystal growth device 2, or by changing the magnitude of the current flowing within the magnetic device.

[0031] In this configuration, the magnetic field components applied along the melt within the silicon single crystal growth device 2 are all perpendicular to the wall surface and uniform in the circumferential direction. In contrast to transverse magnetic fields, this field can suppress upward natural convection along the melt while more efficiently and effectively controlling the content of oxygen, carbon, and other impurities in the crystal. In addition, the magnetic field component generated by the radially oriented primary coil 31 of the silicon single crystal growth device 2 is stronger than its component along the axis of the silicon single crystal growth device 2. Compared to conventional transverse and cusp magnetic fields, such a stronger radial component of the magnetic field can more effectively suppress natural convection along the melt and allow for flexible control of the content of oxygen, carbon, and other impurities in the crystal and their radial uniformity. Furthermore, the mobility of the cryogenic cylinder 4 along the axis of the silicon single crystal growth device 2 adds further practicality and flexibility to the magnetic device.

[0032] Referring to Figures 8, 12, and 14, the primary coil 31, when excited by a current flowing in the same direction, also generates a magnetic field having components that are directed inward or outward in the radial direction of the silicon single crystal growth device 2. Notably, the arrows in Figures 8, 12, and 14 indicate the direction of the excitation current, and the orientation of the magnetic field lines they produce can be determined by the right-hand rule. The magnitude of the excitation current of the primary coil 31 can be controlled independently of the magnitude of the excitation current of the secondary coil 32. The magnitude and direction of these excitation currents can be modified to allow for desired oxygen content in various products, adding further practicality and flexibility to the magnetic device.

[0033] Referring to Figure 11, the coil assembly 3 further includes a secondary coil 32, which is positioned above or below the primary coil 31 to apply an excitation current to strengthen or weaken the magnetic field. It should be noted that, in order to increase the magnetic field strength, both the primary coil 31 and the secondary coil 32 may be superconducting magnetic field coils. Additionally, the primary coil 31 and the secondary coil 32 may be positioned closer to the melt to allow for a further increase in magnetic field strength. In this arrangement, the direction of the excitation current in the secondary coil 32 may be in the direction of strengthening or weakening the magnetic field. This allows the operator to flexibly control the magnitude and direction of the current flowing through the secondary coil 32 to adjust the magnetic field strength, thereby achieving the desired oxygen content of different products. It should be noted that in the exemplary example of Figure 11, the arrows indicate the direction of the excitation current, and a single secondary coil 32 is present. Naturally, in alternative embodiments, multiple secondary coils 32 may be provided, each positioned above or below the primary coil 31. Those skilled in the art will understand how to configure these according to the actual situation.

[0034] Furthermore, the magnetic field lines generated by the excitation current applied to the secondary coil 32 can be oriented in the same direction as or opposite to the magnetic field lines generated by the primary coil 31. It should be noted that a higher magnetic field strength can be obtained when the magnetic field lines generated by the excitation current applied to the secondary coil 32 are oriented in the same direction as the magnetic field lines generated by the primary coil 31. Conversely, a reduced magnetic field strength can be obtained when the magnetic field lines generated by the excitation current applied to the secondary coil 32 are oriented in the opposite direction to the magnetic field lines generated by the primary coil 31. Those skilled in the art will understand that the orientation of the magnetic field lines can be determined by the right-hand rule, and that the magnetic field is perpendicular to the direction of the excitation current.

[0035] Furthermore, the magnetic device comprises a cryogenic cylinder 4 having a housing chamber 41, and the primary coil 31 and secondary coil 32 are housed within the housing chamber 41. In the exemplary examples shown in Figures 4 to 5 and 8, the cryogenic cylinder 4 is a circular annular member covering the outside of the silicon single crystal growth device 2. Naturally, in some alternative embodiments, the cryogenic cylinder 4 may also be a transversely elongated or other shaped member. Those skilled in the art will understand how to configure the shape of the cryogenic cylinder 4 depending on the shape of the silicon single crystal growth device 2.

[0036] Referring to Figures 8-10 and 12-13, the containment chamber 41 has curved inner and outer walls, and the sides of the primary coil 31 are also curved. The curvature of the sides of the primary coil 31 matches the curvature of the inner and / or outer walls of the containment chamber 41. Furthermore, the sides of the primary coil 31 are parallel to the inner and / or outer walls of the containment chamber 41. Note that in an optional embodiment, there are five primary coils 31 (for example, as shown in Figures 8-10), and these coils are evenly distributed around the circumference of the silicon single crystal growth device 2. As can be seen from Figures 9-10, the magnetic field generated by the primary coils 31 is essentially along the X and Y directions (i.e., along the radial direction of the silicon single crystal growth device 2), which effectively suppresses upward natural convection along the melt and improves the quality of the resulting product. In another optional embodiment, three primary coils 31 are present (for example, as shown in Figures 12-13), and these coils are evenly distributed around the circumference of the silicon single crystal growth device 2, generating a magnetic field essentially along the radial direction of the silicon single crystal growth device 2 to improve the quality of the resulting product. In some alternative embodiments, one or more primary coils 31 may be present. Those skilled in the art can select an appropriate number of primary coils 31 depending on the actual situation.

[0037] Referring to Figures 14-15, the inner and outer walls of the housing chamber 41 may have curved surfaces, and the primary coil 31 may have flat sides. Additionally, the sides of the primary coil 31 may be aligned with the axis of the silicon single crystal growth device 2. In an optional embodiment, the primary coil 31 may have flat sides and may be positioned at a specific angle with respect to the extension direction of the inner and / or outer walls of the housing chamber 41, and aligned with the axial direction of the silicon single crystal growth device 2. In this case, these can also generate a magnetic field essentially radially of the silicon single crystal growth device 2, which can also improve the quality of the resulting product. Those skilled in the art can flexibly configure the shape and arrangement of the primary coil 31 depending on the shape of the housing chamber 41.

[0038] In an optional embodiment, each primary coil 31 may have a circular, transverse, elliptical, or other shaped cross-section. In the exemplary examples shown in Figures 4 and 7, each primary coil 31 has a rounded transverse cross-section. According to some alternative embodiments, examples of the cross-sectional shapes of the primary coil 31 may include circular, transverse, elliptical, and any irregular shapes.

[0039] Referring to Figure 11, the secondary coil 32 is a circular annular member, and the plane comprising the secondary coil 32 is perpendicular to the plane comprising the primary coil 31. Note that the plane of the secondary coil 32 is a flat plane perpendicular to the axis of the silicon single crystal growth device 2, and the plane of the primary coil 31 is an arc-shaped plane parallel to the axis of the silicon single crystal growth device 2. In some other optional embodiments, the plane of the secondary coil 32 may form an angle with the planes of the respective primary coils 31, and the angle may be selected from a range of 0° to 90°, if possible.

[0040] In an alternative embodiment, the multiple primary coils 31 may be aligned around the circumference of the silicon single crystal growth device 2, or offset from each other around the circumference of the cryogenic cylinder 4. Note that when the multiple primary coils 31 are aligned around the circumference of the cryogenic cylinder 4, their centers lie in a single plane. However, when the multiple primary coils 31 are offset from each other around the circumference of the cryogenic cylinder 4, one or more of their centers lie in a single plane, while the centers of the remaining ones do not.

[0041] In summary, embodiments of the present invention provide a magnetic device including a coil assembly, the coil assembly covering the outside of a silicon single crystal growth device and movable along the axis of the silicon single crystal growth device to change the position of the coil assembly itself along that axis with respect to the free melt surface within the silicon single crystal growth device. The coil assembly includes a plurality of primary coils arranged around the circumference of the silicon single crystal growth device, wherein the intensity of the magnetic field component generated by the primary coils along the radial direction of the silicon single crystal growth device is higher than the intensity of the magnetic field component along the axis of the silicon single crystal growth device within a given range.

[0042] In this configuration, the magnetic field components applied along the melt within the silicon single-crystal growth device are all perpendicular to the wall surface and uniform in the circumferential direction. In contrast to transverse magnetic fields, this field can suppress upward natural convection along the melt while more efficiently and effectively controlling the content of oxygen, carbon, and other impurities in the resulting crystal. In addition, the magnetic field component generated by the primary coil, which is radially oriented along the melt, is stronger than its component along the axis of the silicon single-crystal growth device. Compared to conventional transverse and cusp magnetic fields, the strength of the radial component of the magnetic field is improved, thereby more effectively suppressing natural convection along the melt and enabling flexible control of the content of oxygen, carbon, and other impurities in the crystal and radial uniformity. Furthermore, the mobility of the coil assembly along the axis of the silicon single-crystal growth device adds practicality and flexibility to the magnetic device.

[0043] Compared to prior art, the number of magnetic field coils according to the present invention is no longer limited to either an odd or even number, and all magnetic field components are directed either toward the center of the melt or toward away from it. Such magnetic fields induce currents flowing in the same direction along the periphery of the melt, and the induced currents include annular forms as shown in Figure 16. All of these induced currents generate a downward Lorentz force along the circumference of the melt, and this Lorentz force suppresses melt convection, thereby resulting in effective control of the oxygen content.

[0044] The descriptions presented above are merely descriptions of some preferred embodiments of the present invention and are not intended to limit its scope in any sense. Any changes and modifications may be made by those skilled in the art based on the teachings above, which fall within the scope of the present invention.

Claims

1. A magnetic device comprising a coil assembly, The coil assembly covers the outside of the silicon single crystal growth device and is movable along the axis of the silicon single crystal growth device to change the position of the coil assembly relative to the free melt surface within the silicon single crystal growth device. The coil assembly comprises a plurality of primary coils arranged around the circumference of the silicon single crystal growth device, wherein the intensity of the magnetic field component generated by the primary coils in the radial direction of the silicon single crystal growth device is higher than the intensity of the magnetic field component along the axis of the silicon single crystal growth device within a predetermined range. A magnetic device characterized by the following features.

2. A magnetic device according to claim 1, The primary coil further generates a magnetic field oriented inward or outward in the radial direction of the silicon single crystal growth device by applying an excitation current flowing in the same direction. A magnetic device characterized by the following features.

3. A magnetic device according to claim 1, The coil assembly further comprises a secondary coil positioned above or below the primary coil, The secondary coil is subjected to an excitation current in order to increase or decrease the magnetic field strength. A magnetic device characterized by the following features.

4. A magnetic device according to claim 3, The magnetic field lines generated by the excitation current applied to the secondary coil are oriented in the same direction as or opposite to the magnetic field lines generated by the primary coil. A magnetic device characterized by the following features.

5. A magnetic device according to claim 3, The cryogenic cylinder further comprises a containment chamber, The primary coil and the secondary coil are housed in the housing chamber. A magnetic device characterized by the following features.

6. A magnetic device according to claim 5, The inner and outer walls of the aforementioned containment chamber are each curved surfaces. The side surface of the primary coil is a curved surface, The curvature of the side surface of the primary coil matches the curvature of the inner wall and / or outer wall of the housing chamber. The side surface of the primary coil is arranged parallel to the inner wall and / or outer wall of the housing chamber, A magnetic device characterized by the following features.

7. A magnetic device according to claim 5, The inner and outer walls of the aforementioned containment chamber are each curved surfaces. The side surface of the primary coil is a flat surface and is arranged along the axis of the silicon single crystal growth device, A magnetic device characterized by the following features.

8. A magnetic device according to claim 6 or 7, The cross-section of the primary coil includes a circular shape, a horizontally elongated shape, or an elliptical shape. A magnetic device characterized by the following features.

9. A magnetic device according to claim 5, The secondary coil is a circular annular member, The plane of the secondary coil is perpendicular to the plane of the primary coil. A magnetic device characterized by the following features.

10. A magnetic device according to claim 3, The primary coil and the secondary coil include a superconducting magnetic field coil. A magnetic device characterized by the following features.

11. A magnetic device according to claim 1, The plurality of primary coils are aligned and arranged around the circumference of the silicon single crystal growth device. A magnetic device characterized by the following features.

12. A magnetic device according to claim 5, The plurality of primary coils are arranged around the circumference of the cryogenic cylinder, offset from each other. A magnetic device characterized by the following features.

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