Method for controlling the convection pattern of a silicon melt, method for manufacturing a silicon single crystal, convection pattern control device for a silicon melt, and silicon single crystal manufacturing apparatus.

Abstract

To provide a method for controlling the convection pattern of a silicon melt that can suppress variations in oxygen concentration among individual silicon single crystals. [Solution] The method for controlling the convection pattern of a silicon melt is a method for controlling the convection pattern of a silicon melt used in the manufacture of a silicon single crystal with a diameter of 300 mm or more of the straight body, wherein, when a horizontal magnetic field is applied to the silicon melt in a crucible heated by a heater using a magnetic field application device, a first counterclockwise convection is formed on the right side of a cross-section perpendicular to the magnetic field, perpendicular to the direction of application of the horizontal magnetic field and including the central axis of the crucible, and a second clockwise convection is formed on the left side.

Description

Technical Field

[0001] The present invention relates to a method for controlling the convection pattern of a silicon melt, a method for manufacturing a silicon single crystal, an apparatus for controlling the convection pattern of a silicon melt, and an apparatus for manufacturing a silicon single crystal.

Background Art

[0002] As a method for growing a silicon single crystal, a so-called MCZ method is known in which a silicon single crystal is grown while applying a horizontal magnetic field to a silicon melt. When a horizontal magnetic field is applied to a silicon melt using the MCZ method, in a state viewed from behind the direction of application of the horizontal magnetic field, a mode in which clockwise (right-handed) convection becomes dominant in the crucible (hereinafter sometimes referred to as the "right vortex mode"), or a mode in which counterclockwise convection becomes dominant (hereinafter sometimes referred to as the "left vortex mode") is initially formed.

[0003] Whether the convection mode becomes the right vortex mode or the left vortex mode is random, and the oxygen concentration of the silicon single crystal varies depending on the convection mode and the furnace environment. In order to obtain a silicon single crystal having a stable oxygen concentration, it is important to control the convection mode of the silicon melt during pulling. For this reason, studies have been conducted on a method for controlling the convection mode of the silicon melt in the crucible (for example, see Patent Document 1). Patent Document 1 discloses a method of forming only the right vortex mode or the left vortex mode by shifting the central axis of the heat shield in a direction different from the direction along the application direction of the magnetic field center of the horizontal magnetic field with respect to the central axis of the crucible and thereby deflecting the flow of the inert gas.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the method disclosed in Patent Document 1 may result in an unstable convection mode. If the convection mode is unstable, the oxygen concentration will also become unstable, and it may not be possible to obtain a silicon single crystal with the desired oxygen concentration.

[0006] For example, in a thermal environment where the amount of oxygen dissolving from the inner surfaces on both sides of the crucible is approximately the same when viewed from behind in the direction of application of a horizontal magnetic field, the amount of oxygen incorporated into the silicon single crystal will be approximately the same in the left vortex mode and the right vortex mode, resulting in approximately the same oxygen concentration in the silicon single crystal. However, in a thermal environment where oxygen easily dissolves from the inner surface on the right side of the crucible, in left-handed vortex mode, the dissolved oxygen reaches the silicon single crystal by convection that flows directly from the right side of the crucible towards the silicon single crystal. On the other hand, in right-handed vortex mode, the dissolved oxygen descends along the inner surface on the right side of the crucible, flows to the left along the bottom surface, rises along the inner surface on the left side, and then reaches the silicon single crystal by convection that flows from the left side towards the silicon single crystal. Therefore, in left-handed vortex mode, more oxygen is incorporated into the silicon single crystal compared to right-handed vortex mode, resulting in a higher oxygen concentration in the silicon single crystal. Conversely, in a thermal environment where oxygen easily dissolves from the inner surface on the left side of the crucible, in the left-handed vortex mode, less oxygen is incorporated into the silicon single crystal compared to the right-handed vortex mode, resulting in a lower oxygen concentration in the silicon single crystal.

[0007] The present invention aims to provide a method for controlling the convection pattern of a silicon melt that can suppress variations in oxygen concentration for each silicon single crystal, a method for manufacturing a silicon single crystal, a convection pattern control device for a silicon melt, and a silicon single crystal manufacturing apparatus. [Means for solving the problem]

[0008] The present invention relates to a method for controlling the convection pattern of a silicon melt used in the production of a silicon single crystal having a diameter of 300 mm or more in its straight body, wherein, when a horizontal magnetic field is applied to the silicon melt in a crucible heated by a heater using a magnetic field application device, a first counterclockwise convection is formed on the right side of a cross-section perpendicular to the magnetic field, perpendicular to the direction of application of the horizontal magnetic field and including the central axis of the crucible, and a second clockwise convection is formed on the left side.

[0009] The present invention provides a method for producing a silicon single crystal, comprising a convection control step of performing the above-described method for controlling the convection pattern of a silicon melt, and a growth step of growing the silicon single crystal by pulling up a seed crystal deposited in the silicon melt.

[0010] The silicon melt convection pattern control device of the present invention is a silicon melt convection pattern control device used in the production of silicon single crystals with a diameter of 300 mm or more of the straight body, and controls the heater and the magnetic field application device so as to form a first counterclockwise convection on the right side of a cross-section perpendicular to the magnetic field that is perpendicular to the direction of application of the horizontal magnetic field and includes the central axis of the crucible, and a second clockwise convection on the left side.

[0011] The silicon single crystal manufacturing apparatus of the present invention comprises a heater that heats a crucible to generate a silicon melt, a magnetic field application device that applies a horizontal magnetic field to the silicon melt, a convection pattern control device for the silicon melt, and a growth control device that grows the silicon single crystal by pulling up a seed crystal deposited in the silicon melt. [Brief explanation of the drawing]

[0012] [Figure 1] This is a longitudinal cross-sectional view showing the schematic configuration of a silicon single crystal manufacturing apparatus according to the first and second embodiments. [Figure 2] This is an explanatory diagram of the first and second measurement points according to the first and second embodiments. [Figure 3] This is a plan view showing the schematic configuration of the magnetic field application device according to the first and second embodiments. [Figure 4] This is a block diagram illustrating the schematic configuration of the control devices according to the first and second embodiments. [Figure 5] This is a flowchart showing a method for manufacturing a silicon single crystal according to the first embodiment. [Figure 6] This is a flowchart showing a method for manufacturing a silicon single crystal according to the second embodiment. [Modes for carrying out the invention]

[0013] [Background leading to the present invention] As in the invention of Patent Document 1, in a configuration that forms only one of two convection modes—a right-handed vortex mode consisting only of right-handed vortices and a left-handed vortex mode consisting only of left-handed vortices—if the convection mode becomes unstable, as described above, the oxygen concentration will also become unstable, and there is a risk that a silicon single crystal with the desired oxygen concentration cannot be obtained. The inventors believed that if they could avoid situations where the convection mode becomes unstable, they could solve the problems of the invention described in Patent Document 1. As a result of diligent research, the inventors came up with an invention in which, when a horizontal magnetic field is applied to the silicon molten liquid in a crucible, a first counterclockwise convection is formed on the right side of a cross-section perpendicular to the direction of application of the horizontal magnetic field and including the central axis of the crucible, and a second clockwise convection is formed on the left side.

[0014] According to this invention, since the first and second convection currents are formed to coexist simultaneously, the occurrence of situations in which the convection mode becomes unstable can be suppressed. Therefore, for example, when viewed from behind in the direction of application of a horizontal magnetic field, in any thermal environment where oxygen easily dissolves from the inner surface on the right side of the crucible, where oxygen easily dissolves from the inner surface on the left side, or where the amount of oxygen dissolving from both the left and right inner surfaces is approximately the same, the amount of oxygen incorporated into the silicon single crystal can be made approximately the same, thereby suppressing variations in oxygen concentration from one silicon single crystal to another.

[0015] [First Embodiment] [Configuration of Silicon Single Crystal Manufacturing Apparatus] Next, the configuration of the silicon single crystal manufacturing apparatus according to the first embodiment of the present invention will be described. In the first embodiment and the second embodiment described later, the description may be made based on the vertical direction, horizontal direction, and front - rear direction shown in FIG. 1 or FIG. 2 etc.

[0016] The silicon single crystal manufacturing apparatus 1 shown in FIG. 1 manufactures a silicon single crystal SM with a diameter of 300 mm or more in the straight body part SM1 by the MCZ method. During the manufacture of the silicon single crystal SM, the silicon single crystal manufacturing apparatus 1 applies a horizontal magnetic field so that the central magnetic force line GC is directed from the front to the rear, and forms a first convection C1 in the counter - clockwise direction on the right side and a second convection C2 in the clockwise direction on the left side in the cross - section perpendicular to the magnetic field. The silicon single crystal manufacturing apparatus 1 includes a manufacturing unit 10 and a control device 20.

[0017] The manufacturing unit 10 includes a chamber 11, a crucible 12, a heater 13, a heat - retaining cylinder 14, a shield 15, a pulling - up unit 16, and a temperature - measuring unit 17. The chamber 11 is provided with a gas inlet 111 for introducing an inert gas such as argon gas into the chamber 11. At the lower part of the chamber 11, an exhaust port 112 is provided for sucking and discharging the gas in the chamber 11 by driving a vacuum pump (not shown). The crucible 12 is provided in the chamber 11. The crucible 12 has a double - structure composed of an outer graphite crucible 121 and an inner quartz crucible 122. The silicon melt M is accommodated in the quartz crucible 122. The crucible 12 is fixed to a support shaft 124 of a crucible driving unit 123 that rotates and raises and lowers the crucible 12.

[0018] The heater 13 comprises a cylindrical upper heater 131 that heats the upper part of the crucible 12, and a cylindrical lower heater 132 located below the upper heater 131 that heats the lower part of the crucible 12. The upper heater 131 and the lower heater 132 are configured to surround the entire crucible 12 in the vertical direction during the production of silicon single crystal SM. The upper heater 131 is positioned such that a part of it is located to the side of the interface M1 of the silicon melt M (hereinafter sometimes referred to as "melt interface M1") during the production of silicon single crystal SM. The heater 13 is configured so that the heat generation ratio, obtained by dividing the heat generation amount of the upper heater 131 by the heat generation amount of the lower heater 132, can be adjusted to any value. The heat-insulating cylinder 14 is installed inside the chamber 11 so as to surround the heater 13. The shield 15 is provided to surround the silicon single crystal SM being pulled out of the silicon molten liquid M, and blocks radiant heat from the heater 13 to the silicon single crystal SM. The heater 13, the insulation tube 14, and the shield 15 are arranged such that their respective central axes lie on the same axis as the central axis 12C of the crucible 12 (hereinafter sometimes referred to as the "crucible central axis 12C"). The lifting section 16 comprises a wire 161 to which a seed crystal SC is attached at its lower end, and a lifting drive section 162 (see Figure 4) that raises, lowers, and rotates the wire 161. The wire 161 is located coaxially with the crucible central axis 12C.

[0019] The temperature measuring unit 17 measures the temperature of a first measurement point P1 and a second measurement point P2 at the melt interface M1. The positions of the first measurement point P1 and the second measurement point P2 are between the outer circumferential surface of the straight body portion SM1 and the inner circumferential surface of the lower end of the shield 15. The temperature measuring unit 17 comprises a pair of reflectors 171 and a pair of radiation thermometers 172. The pair of reflectors 171 are provided inside the chamber 11, on both the left and right sides of the central axis of the chamber 11. Preferably, each reflector 171 is positioned such that the angle between the reflecting surface 173 of each reflector 171 and the horizontal plane is between 40° and 50°. A pair of radiation thermometers 172 are installed on the left and right sides outside the chamber 11. Each radiation thermometer 172 receives the radiation light L incident on it through the quartz windows 113 provided in the chamber 11 and measures the temperatures of the first and second measurement points P1 and P2 non-contact.

[0020] As shown in Figure 2, the first and second measurement points P1 and P2 are positioned point-symmetric with respect to the center of the melt interface M1 (a point on the crucible central axis 12C) and are set within the measurement tolerance range A that satisfies the following equations (1) and (2). (X 2 +Y 2 ) 0.5 >R+30mm … (1) |Y| <R … (2) X: The X-coordinate of the first measurement point P1 or the second measurement point P2 in an XY coordinate system where the center of the melt interface M1 is the origin O, the axis extending horizontally from the origin O is the X-axis, and the axis extending vertically from the origin O is the Y-axis. Y: The Y coordinate of the first measurement point P1 or the second measurement point P2 in the aforementioned XY coordinate system. R: Radius of the straight section SM1

[0021] The area approximately 30 mm from the outer surface of the straight body section SM1 corresponds to the boundary between the molten interface M1 and the straight body section SM1. A meniscus is formed at this boundary. The reason why equation (1) must be satisfied is that, due to the influence of ambient light caused by its shape, the temperature cannot be accurately measured near the meniscus. The first and second convection currents C1 and C2 collide near the Y-axis in the region above the silicon molten M. Such collisions occur below the silicon single crystal SM in the region where they overlap with the silicon single crystal SM along the Y-axis, but near the molten interface M1 both forward and backward of the silicon single crystal SM. The temperature at the collision site near the molten interface M1 is lower than the temperature at other locations. Since the collision site is determined by the flow strength, it moves in the X-axis direction, i.e., left-right, and is therefore unstable. The reason why equation (2) must be satisfied is that, in the forward and backward regions of the silicon single crystal SM, the temperature at the molten interface M1 is unstable due to the instability of the collision site.

[0022] The absolute value of the temperature difference ΔT obtained by subtracting the measured temperature at the second measurement point P2 from the measured temperature at the first measurement point P1 is 5°C or less when the first and second convection currents C1 and C2 are formed. On the other hand, when the first and second convection currents C1 and C2 are not formed, the absolute value of the temperature difference ΔT is greater than 5°C. When only counterclockwise convection occurs, the temperature difference ΔT is greater than +5°C, and when only clockwise convection occurs, the temperature difference ΔT is less than -5°C.

[0023] As shown in Figure 3, the manufacturing unit 10 further comprises a magnetic field application device 18. The magnetic field application device 18 includes a left magnetic field application unit 181 located outside the chamber 11, to the left of a first virtual plane H1 that includes the crucible central axis 12C and is perpendicular to the left-right direction, and a right magnetic field application unit 182 located to the right. The left magnetic field application unit 181 includes a first left electromagnetic coil 183 located in front of a second virtual plane H2 that includes the crucible central axis 12C and is orthogonal to the first virtual plane H1, and a second left electromagnetic coil 184 located behind it. The left magnetic field application unit 181 is configured such that when current flows through the first and second left electromagnetic coils 183 and 184, the magnetic field lines G1 generated approach the crucible central axis 12C from the first left electromagnetic coil 183, then move away from the crucible central axis 12C and pass through the second left electromagnetic coil 184. The right magnetic field application unit 182 comprises a first right electromagnetic coil 185 and a second right electromagnetic coil 186. The first right electromagnetic coil 185 and the first left electromagnetic coil 183, and the second right electromagnetic coil 186 and the second left electromagnetic coil 184 are respectively positioned symmetrically with respect to the first virtual plane H1. The right magnetic field application unit 182 is configured such that when current flows through the first and second right electromagnetic coils 185 and 186, the magnetic field lines G2 generated approach the crucible central axis 12C from the first right electromagnetic coil 185, then move away from the crucible central axis 12C and pass through the second right electromagnetic coil 186. As a result of the generation of magnetic field lines G1 and G2 as described above, a central magnetic field line GC is generated in the silicon melt M, passing through the crucible central axis 12C, perpendicular to the second virtual plane H2, and extending from front to back. The magnetic field application device 18 applies a horizontal magnetic field including these magnetic field lines G1, G2 and the central magnetic field line GC to the silicon melt M.

[0024] The magnetic field application device 18 forms a horizontal magnetic field (hereinafter sometimes referred to as the "first horizontal magnetic field") such that when a current of the first set condition flows through each electromagnetic coil 183, 184, 185, 186, the magnetic field strength at two first positions Q1 is 0.1 Tesla or more, and the magnetic field strength at two second positions Q2 is 0.04 Tesla or less. The magnetic field application device 18 forms a horizontal magnetic field (hereinafter sometimes referred to as the "second horizontal magnetic field") such that the magnetic field strength at each first and second position Q1 and Q2 is approximately the same, 0.1 Tesla or more, when a current of the second set condition flows through each electromagnetic coil 183, 184, 185, 186. The first position Q1 is a position located at a distance from the crucible central axis 12C in a direction perpendicular to the direction of application of the horizontal magnetic field, that is, in the left-right direction, by the maximum inner diameter of the crucible 12. The second position Q2 is located at a distance from the crucible's central axis 12C in a direction parallel to the direction of application of the horizontal magnetic field, that is, in the front-to-back direction, by the maximum inner diameter of the crucible 12. When a first horizontal magnetic field is applied to the silicon molten M heated by a heater 13 with a heat generation ratio of 1, first and second convection currents C1 and C2 are formed.

[0025] Here, we will explain why the first and second convection currents C1 and C2 are formed by controlling the heat generation ratio and magnetic field strength as described above. The silicon molten liquid M contains silicon, which is a metal. Therefore, when a horizontal magnetic field is applied to the silicon molten liquid M in which flow is occurring, an electric current will flow according to Fleming's right-hand rule. However, the current generation situation differs depending on the direction of the horizontal magnetic field relative to the inner surface 12A of the crucible. When an electric current flows through the silicon molten liquid M, a Lorentz force is generated according to Fleming's left-hand rule. Assuming that the above phenomena occur, we first consider the case where a second horizontal magnetic field is applied to the silicon molten liquid M.

[0026] When no horizontal magnetic field is applied to the silicon melt M, and the entire crucible 12 is heated vertically by a heater 13 with a heat generation ratio of 1, the temperature of the upper part of the silicon melt M becomes lower than the temperature of the lower part due to the effects of heat dissipation from the melt interface M1. Since silicon melt M is denser at lower temperatures, the upper part becomes denser than the lower part. This state, where the heavier upper part is above the lighter lower part, is thermodynamically unstable. To resolve this unstable state caused by the vertical temperature difference, convection is formed in the silicon melt M, rising in the outer periphery and descending in the central part.

[0027] When a second horizontal magnetic field is applied to the silicon molten M, counterclockwise convection is formed on the right side and clockwise convection is formed on the left side in a cross-sectional area perpendicular to the magnetic field that coincides with the second virtual plane H2, or in a cross-sectional area perpendicular to the magnetic field that is parallel to the second virtual plane H2. In the cross-sectional area perpendicular to the magnetic field that coincides with the second virtual plane H2, near each first position Q1, the direction of the horizontal magnetic field is parallel to the inner surface 12A of the crucible (hereinafter sometimes referred to as "crucible inner surface 12A"), and two convection currents are formed that rise along the crucible inner surface 12A and descend near the crucible central axis 12C. Therefore, near the first position Q1 on the left, the current tries to flow into the left portion of the crucible inner surface 12A. Near the first position Q1 on the right, the current tries to start flowing from the right portion of the crucible inner surface 12A. However, since these currents cannot form a circuit, no current flows near each first position Q1. Because no current flows, no Lorentz force is generated. Thus, since no Lorentz force is generated near each first position Q1, a state is maintained in which two convection currents are formed in a cross-section perpendicular to the magnetic field that coincides with the second virtual plane H2, rising along the inner surface 12A of the crucible and descending near the central axis 12C of the crucible. These two convection currents are also formed in cross-sections perpendicular to the magnetic field that do not coincide with the second virtual plane H2.

[0028] On the other hand, in the cross-section cut by the first virtual plane H1, near each second position Q2, the direction of the horizontal magnetic field is perpendicular to the inner surface 12A of the crucible, and the two downward convection flows described above exist. In this case, near each second position Q2, currents tend to flow from left to right. Since these currents can form circuits, currents flow near each second position Q2, generating an upward Lorentz force. Here, the unstable state caused by the temperature difference in the vertical direction can be resolved by a single convection current that rises near one of the first positions Q1 to the left or right and descends near the other first position Q1, that is, a single convection current that is either clockwise or counterclockwise. Therefore, near each second position Q2, the upward Lorentz force causes the position of the descending flow to gradually shift to the left or right, and the two convection currents change into one. This phenomenon also occurs in other parts of the cross-section cut by the first virtual plane H1. Thus, when a second horizontal magnetic field is applied to the silicon molten M heated by the heater 13 with a heat generation ratio of 1, a convection current is formed.

[0029] Therefore, a first horizontal magnetic field is applied to the silicon molten M heated by the heater 13 with a heat generation ratio of 1. By increasing the magnetic field strength at each first position Q1 to 0.1 Tesla or higher, the two convection currents described above are formed. By decreasing the magnetic field strength at each second position Q2 to 0.04 Tesla or lower, the downdraft passes through the two second positions Q2, and thus the downdraft forms along an imaginary line connecting the two second positions Q2. As a result, as shown in Figure 1, the first and second convection currents C1 and C2 are formed in the silicon molten M.

[0030] As shown in Figure 4, the control device 20 is configured to send and receive various information between the crucible drive unit 123, the heater 13, the lifting drive unit 162, the temperature measurement unit 17, and the magnetic field application device 18. The control device 20 includes a storage unit 201 and a control unit 202.

[0031] The memory unit 201 stores various information related to the manufacturing of silicon single crystals (SM) in a way that allows the control unit 202 to read it. The control unit 202 comprises a heating control unit 203, a magnetic field control unit 204, a convection determination unit 205, and a growth control unit 206. The heating control unit 203 and the magnetic field control unit 204 constitute the convection pattern control device 21.

[0032] The heating control unit 203 controls the heater 13 such that the amount of heat generated by the upper heater 131 and the lower heater 132 is sufficient to melt the silicon raw material, and the heat generation ratio is 1. The magnetic field control unit 204 applies a current of a first set condition to each of the electromagnetic coils 183, 184, 185, and 186 of the magnetic field application device 18 in order to form a first horizontal magnetic field. The convection determination unit 205 determines whether or not the first and second convection currents C1 and C2 are formed based on the temperature measurement results from the temperature measurement unit 17. The growth control unit 206 controls the growth state of the silicon single crystal SM.

[0033] <Method for manufacturing silicon single crystals> Next, we will describe a method for manufacturing silicon single crystals SM using the silicon single crystal manufacturing apparatus 1. As shown in Figure 5, the heating control unit 203 of the control device 20 heats the silicon melt M with a heater 13 having a heat generation ratio of 1 (Step S1: Heating control step). For example, the heating control unit 303 heats the crucible 12 containing the silicon raw material with the heater 13 having a heat generation ratio of 1 to melt the silicon raw material and produce silicon melt M, and then maintains the heat generation ratio at 1. Due to the heating control step in Step S1, the temperature of the upper part of the silicon melt M becomes lower than the temperature of the lower part.

[0034] The magnetic field control unit 204 controls the magnetic field application device 18 to apply a first horizontal magnetic field to the silicon molten M contained in the rotating crucible 12 (step S2: magnetic field control step). After a predetermined time has elapsed since the magnetic field control step S2, first and second convection currents C1 and C2 are formed in the silicon molten M. The heating control step in step S1 and the magnetic field control step in step S2 constitute a method for controlling the convection pattern of the silicon melt M.

[0035] The convection determination unit 205 obtains temperature measurement results at the first and second measurement points P1 and P2 from the temperature measurement unit 17 and determines whether the absolute value of the temperature difference ΔT is 5°C or less (Step S3: Convection determination step). In the convection determination step of Step S3, if the first and second convections C1 and C2 are formed, it is determined that the temperature is 5°C or less, and if the first and second convections C1 and C2 are not formed, it is determined that the temperature is greater than 5°C.

[0036] If the convection determination unit 205 determines that the absolute value of the temperature difference ΔT exceeds 5°C (step S3: NO), it performs the process of step S3 again after a predetermined time has elapsed. On the other hand, if the convection determination unit 205 determines that the absolute value of the temperature difference ΔT is 5°C or less (Step S3: YES), the growth control unit 206 controls the pulling drive unit 162 to deposit the seed crystal SC into the silicon melt M in which the first and second convections C1 and C2 are formed, and then pull it up, thereby growing a silicon single crystal SM with a diameter of 300 mm or more (Step S4: Growth process). In this way, by performing the convection determination step in step S3 before the growth step in step S4, it is possible to grow silicon single crystals SM using a silicon melt M in which the first and second convections C1 and C2 are reliably formed, and variations in oxygen concentration for each silicon single crystal SM can be suppressed.

[0037] [Second Embodiment] <Configuration of silicon single crystal manufacturing equipment> Next, the configuration of a silicon single crystal manufacturing apparatus according to a second embodiment of the present invention will be described. As shown in Figure 1, silicon single crystal manufacturing apparatus 1A differs from silicon single crystal manufacturing apparatus 1 of the first embodiment in that it is equipped with a control device 30 instead of a control device 20.

[0038] As shown in Figure 4, the control device 30 differs from the control device 202 of the first embodiment in that the control unit 302 is different. The control unit 302 also differs from the heating control unit 203 and magnetic field control unit 204 of the first embodiment in that the heating control unit 303 and magnetic field control unit 304 that constitute the convection pattern control device 31 are different. The heating control unit 303 controls the heater 13 such that the amount of heat generated by the upper heater 131 and the lower heater 132 is sufficient to melt the silicon raw material, and the heat generation ratio is between 2 and 3.5. The magnetic field control unit 304 applies a second set current to each of the electromagnetic coils 183, 184, 185, and 186 of the magnetic field application device 18 to form a second horizontal magnetic field. In this way, when a second horizontal magnetic field is applied to the silicon molten M heated by the heater 13 with a heat generation ratio of 2 or more, first and second convection currents C1 and C2 are formed.

[0039] Here, we will explain why the first and second convection currents C1 and C2 are formed by controlling the heat generation ratio and magnetic field strength as described above. As described in the first embodiment, when a second horizontal magnetic field is applied to a silicon molten M heated by a heater 13 with a heat generation ratio of 1, a convection current is formed to eliminate the unstable state caused by the temperature difference in the vertical direction.

[0040] Therefore, the silicon molten M is heated by a heater 13 with a heat generation ratio of 2 or more. In this case, the temperature difference between the upper and lower parts is almost eliminated. As a result, thermodynamically unstable states caused by temperature differences in the vertical direction are almost completely eliminated. On the other hand, a large temperature difference occurs between the outer periphery, which is close to the heater 13, and the central part, which is far from the heater 13. Since the surface tension of the molten interface M1 increases with increasing temperature, a Marangoni force is generated from the hotter outer periphery towards the cooler central part. Along with the generation of this Marangoni force, convection is formed that rises in the outer periphery and descends in the central part. In other words, convection is formed that rises in the outer periphery and descends in the central part to resolve the unstable state caused by the temperature difference between the outer and central parts.

[0041] When a second horizontal magnetic field is applied in this state, counterclockwise convection is formed on the right side of the cross-section perpendicular to the magnetic field, and clockwise convection is formed on the left side. At this time, as explained in the first embodiment, no Lorentz force is generated near each first position Q1, but an upward Lorentz force is generated near each second position Q2. Here, the unstable state caused by the temperature difference between the outer and central parts cannot be resolved by a single clockwise or counterclockwise convection. Therefore, even if an upward Lorentz force is generated near each second position Q2, the position of the downflow does not gradually shift to the left or right, and the two convections are maintained. This phenomenon also occurs in other parts of the cross-section cut by the first virtual plane H1. Thus, even when a second horizontal magnetic field is applied, if the silicon molten M is heated by the heater 13 with a heat generation ratio of 2 or more, two convection currents are formed.

[0042] On the other hand, if the heat generation ratio exceeds 3.5, the lower part of the molten silicon M may solidify, or the upper part of the crucible 12 may deform. For this reason, it is preferable that the heat generation ratio be 3.5 or less.

[0043] <Method for manufacturing silicon single crystals> Next, a method for manufacturing silicon single crystals SM using the silicon single crystal manufacturing apparatus 1A will be described. Note that the same reference numerals are used for the same processes as in the first embodiment, and the explanation is simplified or omitted.

[0044] As shown in Figure 6, the heating control unit 303 of the control device 30 heats the silicon melt M with a heater 13 having a heat generation ratio of 2 or more and 3.5 or less (step S11: heating control step). The heating control unit 303 heats the crucible 12 containing the silicon raw material with a heater 13 having a heat generation ratio of 1 to melt the silicon raw material and produce silicon melt M, and then may change the heat generation ratio to 2 or more and 3.5 or less. Alternatively, the heating control unit 303 heats the crucible 12 containing the silicon raw material with a heater 13 having a heat generation ratio of 2 or more and 3.5 or less to melt the silicon raw material and produce silicon melt M, and then may maintain the heat generation ratio to 2 or more and 3.5 or less. Due to the heating control step in step S1, the temperature of the central part of the silicon melt M becomes lower than the temperature of the outer part.

[0045] The magnetic field control unit 304 controls the magnetic field application device 18 to apply a second horizontal magnetic field to the silicon molten M contained in the rotating crucible 12 (step S12: magnetic field control step). After a predetermined time has elapsed since the magnetic field control step S12, first and second convection currents C1 and C2 are formed in the silicon molten M. The heating control step in step S11 and the magnetic field control step in step S12 constitute a method for controlling the convection pattern of the silicon melt M. Following this, the convection determination process in step S3 and the growth process in step S4 are carried out. Through the above process, silicon single crystals SM can be grown using a silicon melt M in which the first and second convection currents C1 and C2 are reliably formed, and variations in oxygen concentration among silicon single crystals SM can be suppressed.

[0046] [Differentiation] In the heating control step S1 of the first embodiment, the silicon melt M may be heated by a heater 13 with a heating ratio of 2 or more and 3.5 or less, as in the second embodiment. In the first embodiment, instead of the heater 13, a single cylindrical heater may be used that surrounds the entire crucible 12 in the vertical direction during the production of the silicon single crystal SM. In the second embodiment, the heat generation ratio may be controlled to 3.5 or higher. In the first and second embodiments, instead of the magnetic field application device 18 which is composed of four electromagnetic coils 183, 184, 185, and 186, a magnetic field application device composed of 2 × n (where n is an integer of 3 or more) electromagnetic coils may be used. In the second embodiment, instead of the magnetic field application device 18, a magnetic field application device in which one electromagnetic coil is arranged in front of and one in the rear of the chamber 11 may be used. In the first and second embodiments, the waiting time from the magnetic field control process in steps S2 and S12 until the first and second convections C1 and C2 are reliably formed may be determined in advance, and instead of the convection determination process in step S3, a waiting process of the aforementioned waiting time may be performed. [Examples]

[0047] Next, embodiments of the present invention will be described. However, the present invention is not limited to these embodiments.

[0048] [Experimental Example 1] <Configuration of silicon single crystal manufacturing equipment> First, four silicon single crystal manufacturing apparatuses (hereinafter sometimes referred to as "apparatus A to D") were prepared, each having the same configuration as the manufacturing section 10 of the first embodiment, except that the magnetic field application apparatus was different. The magnetic field application apparatuses of apparatuses A to D are equipped with two electromagnetic coils, one each positioned in front of and behind the chamber 11, similar to the magnetic field application section of the invention in Patent Document 1, and can apply a second horizontal magnetic field of 0.1 Tesla or more, with magnetic field strengths at the first and second positions Q1 and Q2 being approximately the same. In apparatuses A to D, the positions of the center of the melt interface M1 (a point on the crucible central axis 12C) and the first and second measurement points P1 and P2 with respect to the direction of application of the horizontal magnetic field were the same.

[0049] <Method for manufacturing silicon single crystals> (Comparative Example 1-1) As shown in Table 1, 25 silicon single crystal SMs of Comparative Example 1-1 were manufactured using apparatus A. When manufacturing each silicon single crystal SM, the silicon melt M was heated by heater 13 with a heat generation ratio of 1, and a second horizontal magnetic field was applied before the seed crystal SC was placed in the melt. The diameter of the silicon single crystal SM was 300 mm. (Comparative Example 1-2) Except for using apparatus B, 25 silicon single crystal SMs of Comparative Example 1-2 were manufactured under the same conditions as Comparative Example 1-1. (Comparative Examples 1-3) Except for using apparatus C, 25 silicon single crystal SMs of Comparative Example 1-3 were manufactured under the same conditions as Comparative Example 1-1. (Comparative Examples 1-4) Except for using apparatus D, 25 silicon single crystal SMs of Comparative Example 1-4 were manufactured under the same conditions as Comparative Example 1-1.

[0050] <Evaluation of Convection Generation Conditions> To confirm the state of convection during the growth (pulling) of each silicon single crystal (SM), the temperatures at the first and second measurement points P1 and P2 were measured. The number of growth cycles when the temperature difference ΔT exceeded +5°C or fell below -5°C, and the number of growth cycles when the absolute value of the temperature difference ΔT was 5°C or less were confirmed.

[0051] As shown in Table 1, in all of Comparative Examples 1-1 to 1-4, cultivation was carried out under conditions where the temperature difference ΔT exceeded +5°C or was below -5°C, and cultivation was not carried out under conditions where the absolute value of the temperature difference ΔT was 5°C or less. From this, we were able to confirm that cultivation was carried out under conditions where only clockwise convection or only counterclockwise convection was occurring, and that cultivation was not carried out under conditions where the first and second convections C1 and C2 were occurring simultaneously.

[0052] <Evaluation of oxygen concentration ratio> The oxygen concentration ratio of each silicon single crystal SM in Comparative Example 1-1 was calculated. To calculate the oxygen concentration ratio, the oxygen concentration of each silicon single crystal SM was measured by FTIR. The oxygen concentration was measured at a position 1000 mm from the upper end of the straight body SM1. The oxygen concentration ratio was calculated as the ratio of the oxygen concentration of each silicon single crystal SM to the average oxygen concentration of 25 silicon single crystal SMs. The oxygen concentration ratio was also calculated for each of the silicon single crystal SMs in Comparative Examples 1-2 to 1-4.

[0053] As shown in Table 1, the oxygen concentration ratios in Comparative Examples 1-1 to 1-4 ranged from 0.78 to 1.26. Furthermore, the oxygen concentration ratios were 0.78 to 0.83 when the temperature difference ΔT during growth exceeded +5°C or was below -5°C, and 1.17 to 1.26 when the temperature difference was the other of the two conditions. From this, it was confirmed that when growing silicon in a state where only clockwise or only counterclockwise convection occurs, the oxygen concentration can become high or low depending on the direction of convection, resulting in large variations in oxygen concentration among individual silicon single crystals (SMs).

[0054] <Summary> Because the oxygen concentration ratio differed significantly depending on the direction of convection, it was confirmed that the thermal environment inside chambers 11 of devices A to D was asymmetrical on the left and right sides when viewed from behind in the direction of the applied horizontal magnetic field. When a second horizontal magnetic field is applied to a silicon molten M heated by a heater 13 with a heat generation ratio of 1 using a device with an asymmetrical thermal environment, it was confirmed that silicon single crystals SM are grown in a state where only clockwise or only counterclockwise convection occurs, and that variations in oxygen concentration among silicon single crystals SM cannot be suppressed.

[0055] [Table 1]

[0056] [Experimental Example 2] <Method for manufacturing silicon single crystals> (Comparative Example 2-1) Using apparatus A, 25 silicon single crystal SMs of Comparative Example 2-1 were manufactured. When manufacturing each silicon single crystal SM, the silicon molten M was heated by heater 13 with a heat generation ratio of 0.5, as shown in Table 2, except that the same conditions as in Comparative Example 1-1 were used to manufacture 25 silicon single crystal SMs of Comparative Example 2-1. (Comparative Example 2-2) Except for heating the silicon molten liquid M with a heater 13 having a heat generation ratio of 1, 25 silicon single crystals SM of Comparative Example 2-2 were manufactured under the same conditions as in Comparative Example 2-1. (Comparative Example 2-3) Except for heating the silicon molten liquid M with a heater 13 having a heat generation ratio of 1.5, 25 silicon single crystals SM of Comparative Example 2-3 were manufactured under the same conditions as in Comparative Example 2-1. (Example 2-1) Except for heating the silicon molten liquid M with a heater 13 having a heat generation ratio of 2, 25 silicon single crystals SM of Example 2-1 were manufactured under the same conditions as in Comparative Example 2-1. (Example 2-2) Except for heating the silicon molten liquid M with a heater 13 having a heat generation ratio of 3, 25 silicon single crystals SM of Example 2-2 were manufactured under the same conditions as in Comparative Example 2-1. (Examples 2-3) Except for heating the silicon molten liquid M with a heater 13 having a heat generation ratio of 3.5, 25 silicon single crystals SM of Example 2-3 were manufactured under the same conditions as in Comparative Example 2-1. (Comparative Example 2-4) Except for heating the silicon molten M with a heater 13 having a heat generation ratio of 4, the silicon single crystal SM of Comparative Example 2-4 was attempted under the same conditions as in Comparative Example 2-1. However, the amount of heating in the upper part of the crucible 12 was large, causing deformation, and therefore the silicon single crystal SM could not be produced.

[0057] <Evaluation of Convection Generation Conditions> Similar to Experimental Example 1, in order to confirm the state of convection during the growth of each silicon single crystal (SM), the number of growth cycles under conditions where the temperature difference ΔT was greater than +5°C or less than -5°C, and the number of growth cycles under conditions where the absolute value of the temperature difference ΔT was 5°C or less were confirmed.

[0058] As shown in Table 2, in Examples 2-1 to 2-3, cultivation was performed only under conditions where the absolute value of the temperature difference ΔT was 5°C or less, and cultivation was not performed under conditions where the temperature difference ΔT exceeded +5°C or was below -5°C. On the other hand, in Comparative Examples 2-1 to 2-3, cultivation was performed under conditions where the temperature difference ΔT exceeded +5°C or was below -5°C, and cultivation was not performed under conditions where the absolute value of the temperature difference ΔT was 5°C or less. From this, it was confirmed that in Examples 2-1 to 2-3, cultivation was carried out with the first and second convections C1 and C2 occurring simultaneously, while in Comparative Examples 2-1 to 2-3, cultivation was carried out with either only clockwise convection or only counterclockwise convection occurring.

[0059] <Evaluation of oxygen concentration ratio> Similar to Experimental Example 1, the oxygen concentration ratios of each silicon single crystal SM in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3 were calculated. As shown in Table 2, the oxygen concentration ratios in Examples 2-1 to 2-3 ranged from 0.95 to 1.06. On the other hand, in Comparative Examples 2-1 to 2-3, the oxygen concentration ratios ranged from 0.71 to 1.24. From this, it was confirmed that when growing silicon single crystals (SMs) while the first and second convection currents C1 and C2 are occurring simultaneously, the variation in oxygen concentration between individual silicon single crystals (SMs) can be suppressed compared to when growing them while only clockwise convection is occurring or only counterclockwise convection is occurring.

[0060] <Summary> Even when using a device with an asymmetrical thermal environment and applying a second horizontal magnetic field of 0.1 Tesla or higher, where the magnetic field strength at the first and second positions Q1 and Q2 is approximately the same, it was confirmed that when the silicon molten M is heated by a heater 13 with a heat generation ratio of 2 or more and 3.5 or less, silicon single crystals SM can be grown while the first and second convections C1 and C2 are generated simultaneously, thereby suppressing variations in oxygen concentration between silicon single crystals SM.

[0061] [Table 2]

[0062] [Experimental Example 3] <Method for manufacturing silicon single crystals> (Comparative Example 3-1) The magnetic field application device of device C was replaced with a Type 1 magnetic field application device. The Type 1 magnetic field application device is equipped with four electromagnetic coils, similar to the magnetic field application device 18 of the first embodiment. Using this apparatus C, 25 silicon single crystal SMs of Comparative Example 3-1 were manufactured. Except for applying a first horizontal magnetic field before the seed crystal SC was immersed, the 25 silicon single crystal SMs of Comparative Example 3-1 were manufactured under the same conditions as Comparative Example 1-3. As shown in Table 3, the magnetic field strength at the first position Q1 in the first horizontal magnetic field was 0.33 Tesla, and the magnetic field strength at the second position Q2 was 0.06 Tesla. (Example 3-1) Except for applying a first horizontal magnetic field with a magnetic field strength of 0.23 Tesla at the first position Q1 and a magnetic field strength of 0.04 Tesla at the second position Q2, 25 silicon single crystal SMs of Example 3-1 were manufactured under the same conditions as Comparative Example 3-1. (Example 3-2) Except for applying a first horizontal magnetic field with a magnetic field strength of 0.13 Tesla at the first position Q1 and a magnetic field strength of 0.02 Tesla at the second position Q2, 25 silicon single crystal SMs of Example 3-2 were manufactured under the same conditions as Comparative Example 3-1. (Example 3-3) Except for applying a first horizontal magnetic field with a magnetic field strength of 0.10 Tesla at the first position Q1 and a magnetic field strength of 0.02 Tesla at the second position Q2, 25 silicon single crystal SMs of Example 3-3 were manufactured under the same conditions as Comparative Example 3-1.

[0063] (Comparative Example 3-2) The Type 1 magnetic field application device of apparatus C was replaced with a Type 2 magnetic field application device. The Type 2 magnetic field application device has four electromagnetic coils, similar to the magnetic field application device 18 of the first embodiment, but the size of each electromagnetic coil and its position relative to the crucible differ from that of the Type 1 magnetic field application device. Using this apparatus C, 25 silicon single crystal SMs of Comparative Example 3-2 were manufactured under the same conditions as Comparative Example 3-1, except that a first horizontal magnetic field was applied with a magnetic field strength of 0.29 Tesla at the first position Q1 and a magnetic field strength of 0.06 Tesla at the second position Q2. (Examples 3-4) Except for applying a first horizontal magnetic field with a magnetic field strength of 0.20 Tesla at the first position Q1 and a magnetic field strength of 0.04 Tesla at the second position Q2, 25 silicon single crystal SMs of Example 3-4 were manufactured under the same conditions as Comparative Example 3-2. (Examples 3-5) Except for applying a first horizontal magnetic field with a magnetic field strength of 0.10 Tesla at the first position Q1 and a magnetic field strength of 0.02 Tesla at the second position Q2, 25 silicon single crystal SMs of Example 3-5 were manufactured under the same conditions as Comparative Example 3-2. (Comparative Example 3-3) The silicon single crystal SM of Comparative Example 3-3 was attempted to be manufactured under the same conditions as Comparative Example 3-2, except that a first horizontal magnetic field was applied with a magnetic field strength of 0.08 Tesla at the first position Q1 and a magnetic field strength of 0.02 Tesla at the second position Q2. However, the magnetic field strength of the first horizontal magnetic field was too weak, causing waves to be generated at the melt interface M1, and thus the silicon single crystal SM could not be manufactured.

[0064] <Evaluation of Convection Generation Conditions> Similar to Experimental Example 1, in order to confirm the state of convection during the growth of each silicon single crystal (SM), the number of growth cycles under conditions where the temperature difference ΔT was greater than +5°C or less than -5°C, and the number of growth cycles under conditions where the absolute value of the temperature difference ΔT was 5°C or less were confirmed.

[0065] As shown in Table 3, in Examples 3-1 to 3-5, cultivation was performed only under conditions where the absolute value of the temperature difference ΔT was 5°C or less, and cultivation was not performed under conditions where the temperature difference ΔT exceeded +5°C or was below -5°C. On the other hand, in Comparative Examples 3-1 and 3-2, cultivation was performed under conditions where the temperature difference ΔT exceeded +5°C or was below -5°C, and cultivation was not performed under conditions where the absolute value of the temperature difference ΔT was 5°C or less. From this, it was confirmed that in Examples 3-1 to 3-5, cultivation was carried out with the first and second convections C1 and C2 occurring simultaneously, while in Comparative Examples 3-1 and 3-2, cultivation was carried out with either only clockwise convection or only counterclockwise convection occurring.

[0066] <Evaluation of oxygen concentration ratio> Similar to Experimental Example 1, the oxygen concentration ratios of each silicon single crystal SM in Examples 3-1 to 3-5 and Comparative Examples 3-1 and 3-2 were calculated. As shown in Table 3, the oxygen concentration ratios in Examples 3-1 to 3-5 ranged from 0.91 to 1.09. On the other hand, in Comparative Examples 3-1 and 3-2, the oxygen concentration ratios ranged from 0.76 to 1.22. From this, it was confirmed that when growing silicon single crystals (SMs) while the first and second convection currents C1 and C2 are occurring simultaneously, the variation in oxygen concentration between individual silicon single crystals (SMs) can be suppressed compared to when growing them while only clockwise convection is occurring or only counterclockwise convection is occurring.

[0067] <Summary> Even when using a device with an asymmetrical thermal environment and heating the silicon molten M with a heater 13 having a heat generation ratio of 1, it was confirmed that applying a first horizontal magnetic field where the magnetic field strength at the first position Q1 is 0.1 Tesla or higher and the magnetic field strength at the second position Q2 is 0.04 Tesla or lower allows for the growth of silicon single crystals SM while the first and second convections C1 and C2 occur simultaneously, thereby suppressing variations in oxygen concentration between silicon single crystals SM.

[0068] [Table 3] [Explanation of Symbols]

[0069] 1,1A...Silicon single crystal manufacturing apparatus, 12...Crucible, 12C...Crucible central axis, 13...Heater, 21,31...Convection pattern control device, 17...Temperature measurement unit, 18...Magnetic field application device, 131...Upper heater, 132...Lower heater, 203,303...Heating control unit, 204,304...Magnetic field control unit, 205...Convection determination unit, 206...Growth control unit, C1...First convection, C2...Second convection, M...Silicon melt, M1...Melting interface, O...Origin, P1...First measurement point, P2...Second measurement point, Q1...First position, Q2...Second position, SC...Seed crystal, SM...Silicon single crystal, SM1...Straight body section.

Claims

1. A method for controlling the convection pattern of a silicon melt used in the production of a silicon single crystal with a straight body diameter of 300 mm or more, A method for controlling the convection pattern of a silicon melt, wherein, when a horizontal magnetic field is applied to the silicon melt in a crucible heated by a heater using a magnetic field application device, a first counterclockwise convection is formed on the right side of a cross-section perpendicular to the magnetic field, perpendicular to the direction of application of the horizontal magnetic field and including the central axis of the crucible, and a second clockwise convection is formed on the left side.

2. In the method for controlling the convection pattern of a silicon melt according to claim 1, A method for controlling the convection pattern of a silicon melt, comprising a magnetic field control step of controlling the magnetic field application device such that the magnetic field strength at two first positions, separated by the maximum inner diameter of the crucible in a direction perpendicular to the application direction from the central axis of the crucible, is 0.1 Tesla or more, and the magnetic field strength at two second positions, separated by the maximum inner diameter in a direction parallel to the application direction from the central axis, is 0.04 Tesla or less.

3. In the method for controlling the convection pattern of a silicon melt according to claim 1 or claim 2, The heater comprises an upper heater positioned such that a portion of it is located to the side of the interface of the silicon melt during the production of the silicon single crystal, and a lower heater positioned below the upper heater. The method for controlling the convection pattern of a silicon melt comprises a heating control step that controls the heaters such that the heat generation ratio obtained by dividing the heat generation amount of the upper heater by the heat generation amount of the lower heater is 2 or more.

4. In the method for controlling the convection pattern of a silicon melt according to claim 3, The heating control step is a method for controlling the convection pattern of a silicon melt, which controls the heater so that the heat generation ratio is 3.5 or less.

5. A convection control step for performing the convection pattern control method for a silicon melt described in claim 1, A method for producing a silicon single crystal, comprising a growth step of growing the silicon single crystal by pulling up a seed crystal that has been deposited in the silicon melt.

6. In the method for manufacturing a silicon single crystal according to claim 5, The system includes a convection determination step in which it is determined that the first and second convection currents are formed in the silicon melt if the absolute value of the temperature difference between the first and second measurement points, which are set at point-symmetric positions with respect to the center of the interface of the silicon melt, is 5°C or less. The first and second measurement points are set in an XY coordinate system where the center of the interface of the silicon melt is the origin, the X-axis is the axis extending perpendicular to the direction in which the horizontal magnetic field is applied and containing the origin, and the Y-axis is the axis extending in the direction in which the horizontal magnetic field is applied and containing the origin, such that the following equations (1) and (2) are satisfied. A method for manufacturing a silicon single crystal, wherein the growth step involves growing the silicon single crystal when it is determined that the first convection and the second convection have been formed. (X ２ +Y ２ ) ０．５ >R+30mm … (1) |Y| <R ... (2) X: The X-coordinate of the first measurement point or the second measurement point in the XY coordinate system. Y: The Y coordinate of the first measurement point or the second measurement point in the XY coordinate system. R: Radius of the straight body portion of the silicon single crystal.

7. A convection pattern control device for silicon molten material used in the manufacture of silicon single crystals with a straight body diameter of 300 mm or more, A convection pattern control device for a silicon melt, wherein, when a horizontal magnetic field is applied by a magnetic field application device to the silicon melt in a crucible heated by a heater, the heater and the magnetic field application device are controlled to form a first counterclockwise convection on the right side and a second clockwise convection on the left side in a cross-section perpendicular to the magnetic field that is perpendicular to the direction of application of the horizontal magnetic field and includes the central axis of the crucible.

8. In the silicon melt convection pattern control device according to claim 7, A convection pattern control device for a silicon melt, comprising a magnetic field control unit that controls the magnetic field application device such that the magnetic field strength at two first positions, separated by the maximum inner diameter of the crucible in a direction perpendicular to the application direction from the central axis of the crucible, is 0.1 Tesla or more, and the magnetic field strength at two second positions, separated by the maximum inner diameter in a direction parallel to the application direction from the central axis, is 0.04 Tesla or less.

9. In the silicon melt convection pattern control device according to claim 7 or claim 8, The heater comprises an upper heater positioned such that a portion of it is located to the side of the interface of the silicon melt during the production of the silicon single crystal, and a lower heater positioned below the upper heater. The convection pattern control device for the silicon melt includes a heating control unit that controls the heaters such that the heat generation ratio obtained by dividing the heat generation amount of the upper heater by the heat generation amount of the lower heater is 2 or more.

10. In the silicon melt convection pattern control device according to claim 9, The heating control unit is a convection pattern control device for a silicon melt that controls the heater so that the heat generation ratio is 3.5 or less.

11. A heater that heats the crucible to generate molten silicon, A magnetic field application device for applying a horizontal magnetic field to the aforementioned silicon melt, A convection pattern control device for a silicon melt according to claim 7, A silicon single crystal manufacturing apparatus comprising: a growth control unit for growing the silicon single crystal by pulling up a seed crystal deposited in the silicon melt.

12. In the silicon single crystal manufacturing apparatus according to claim 11, A thermometer side portion for measuring the temperature of a first measurement point and a second measurement point set at positions symmetrical with respect to the center of the interface of the silicon melt, The system includes a convection determination unit that determines that a first convection current and a second convection current are formed in the silicon melt when the absolute value of the temperature difference between the first measurement point and the second measurement point is 5°C or less. The first and second measurement points are set in an XY coordinate system where the center of the interface of the silicon melt is the origin, the X-axis is the axis extending perpendicular to the direction in which the horizontal magnetic field is applied and containing the origin, and the Y-axis is the axis extending in the direction in which the horizontal magnetic field is applied and containing the origin, such that the following equations (3) and (4) are satisfied. A silicon single crystal manufacturing apparatus, wherein the growth control unit determines that the first convection and the second convection have been formed, and grows the silicon single crystal. (X ２ +Y ２ ) ０．５ >R+30mm … (3) |Y| <R ... (4) X: The X-coordinate of the first measurement point or the second measurement point in the XY coordinate system. Y: The Y coordinate of the first measurement point or the second measurement point in the XY coordinate system. R: Radius of the straight body portion of the silicon single crystal.

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