Single crystal manufacturing method, single crystal manufacturing apparatus, and crucible

Abstract

To reduce impurity crystals generated in the solution.SOLUTION: A method for producing a single crystal includes: a first heating step of heating a solution so as to increase temperature of the solution coming into contact with a side face of a crucible to be higher than temperature of the solution coming into contact with a bottom face of the crucible; and a second heating step of heating the solution so as to increase temperature of the solution coming into contact with the bottom face of the crucible to be higher than temperature of the solution coming into contact with the side face of the crucible, where the first heating step and the second heating step are switched alternately.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a technique for producing a single crystal made of silicon carbide, a single crystal production apparatus and a crucible, and for example, relates to a technique that is effective when applied to a technique for producing a single crystal by a solution method.

Background Art

[0002] Japanese Patent No. 5746362 (Patent Document 1) describes a technique for controlling the degree of carbon supersaturation on a crystal surface by switching the temperature gradient in a solution during growth of the single crystal.

[0003] Japanese Unexamined Patent Publication No. 2018-184324 (Patent Document 2) describes a technique for heating the bottom surface of a crucible for a long time.

[0004] Japanese Unexamined Patent Publication No. Hei 2-217388 (Patent Document 3) describes a technique for heating a crucible by a side heater and a bottom heater.

[0005] Japanese Unexamined Patent Publication No. 2012-136388 (Patent Document 4) describes a technique related to an induction heating apparatus including an upper coil part arranged around an upper storage chamber and a lower coil part arranged around a lower storage chamber.

[0006] Japanese Unexamined Patent Publication No. Hei 7-25694 (Patent Document 5) describes a technique related to a crucible having a projection protruding from the bottom surface.

Prior Art Literature

Patent Literature

[0007]

Patent Literature 1

Patent Literature 2

Patent Literature 3

Patent Literature 4

[0008] For example, inverter circuits are used as control circuits for motors found in automobiles and home appliances. These inverter circuits utilize power semiconductor elements such as power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors).

[0009] Such power semiconductor devices are required to have not only high voltage resistance but also low on-resistance and low switching losses. Currently, the mainstream power semiconductor device is the field-effect transistor formed on a semiconductor substrate mainly composed of silicon, but this power semiconductor device is approaching its theoretical performance limit.

[0010] In this regard, semiconductor devices including field-effect transistors formed on semiconductor substrates mainly composed of semiconductor materials with a larger bandgap than silicon (hereinafter referred to as wide-bandgap power semiconductor devices) are attracting attention.

[0011] This is because a large band gap means that the dielectric breakdown strength is high, making it easier to achieve high voltage resistance.

[0012] Furthermore, if the semiconductor material itself has high dielectric breakdown strength, the dielectric strength can be maintained even if the drift layer that maintains the dielectric strength is thin. For example, by thinning the drift layer and increasing the impurity concentration, the on-resistance of the power semiconductor device can be reduced.

[0013] In other words, wide-bandgap power semiconductor devices excel in their ability to achieve both improved breakdown voltage and reduced on-resistance, which are typically in a trade-off relationship. Therefore, wide-bandgap power semiconductor devices are expected to be high-performance semiconductor devices.

[0014] Semiconductor materials with a larger bandgap than silicon include, for example, silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3), and diamond. The following explanation will focus on silicon carbide.

[0015] Single crystals made of silicon carbide (hereinafter referred to as silicon carbide single crystals) are manufactured, for example, by using the solution method. The solution method is a method of manufacturing silicon carbide single crystals by bringing a seed crystal attached to the tip of a shaft into contact with a solution containing carbon and silicon contained in a crucible, thereby growing a silicon carbide single crystal on the seed crystal while the shaft is pulled up.

[0016] In the solution method, it is important to reduce the amount of unwanted crystals that form in the solution contained in the crucible. This is because unwanted crystals are, for example, aggregates of silicon carbide particles about 1 mm to 3 mm in size, and if these unwanted crystals adhere to the seed crystal, the crystal that grows on the seed crystal will not be a single crystal. Therefore, in the solution method, from the viewpoint of growing silicon carbide single crystals on the seed crystal, it is desirable to devise ways to reduce the amount of unwanted crystals that form in the solution. [Means for solving the problem]

[0017] A single crystal manufacturing method in one embodiment comprises the steps of (a) moving an axis to which a seed crystal is attached at its tip downward so that the lower surface of the seed crystal comes into contact with a solution containing carbon and silicon contained in a crucible, and (b) growing a single crystal made of silicon carbide on the lower surface of the seed crystal.

[0018] Here, the single crystal production method comprises: (c1) a first heating step of heating the solution such that the temperature of the solution in contact with the side surface of the crucible is higher than the temperature of the solution in contact with the bottom surface of the crucible; and (c2) a second heating step of heating the solution such that the temperature of the solution in contact with the bottom surface of the crucible is higher than the temperature of the solution in contact with the side surface of the crucible, wherein the first heating step and the second heating step are alternately switched.

[0019] In one embodiment, the single crystal production apparatus allows a crucible accommodating a solution containing carbon and silicon to be arranged in a container. The single crystal production apparatus comprises: a pedestal arranged inside the container; a first heating unit that heats the crucible arranged on the pedestal; a second heating unit that heats the pedestal; and a control unit that controls electric power supplied to the first heating unit and electric power supplied to the second heating unit.

[0020] Here, the control unit alternately switches between: a first operation of adjusting the electric power supplied to the first heating unit and the electric power supplied to the second heating unit such that the temperature of the solution in contact with the side surface of the crucible is higher than the temperature of the solution in contact with the bottom surface of the crucible; and a second operation of adjusting the electric power supplied to the first heating unit and the electric power supplied to the second heating unit such that the temperature of the solution in contact with the bottom surface of the crucible is higher than the temperature of the solution in contact with the side surface of the crucible.

[0021] In one embodiment, the crucible can accommodate a solution containing carbon and silicon. The crucible comprises: a main body portion that accommodates the solution; and a heat transfer portion protruding from the bottom of the main body portion. [Effects of the Invention]

[0022] According to one embodiment, incidental crystals generated in the solution can be reduced. [Brief Description of Drawings]

[0023] [Figure 1] It is a diagram showing the configuration of the single crystal production apparatus in an embodiment. [Figure 2] It is a diagram explaining an example of dimensions of main parts of the pedestal and the crucible. [Figure 3]This is a diagram illustrating the operation of a single crystal manufacturing apparatus. [Figure 4] This is a diagram illustrating the operation of a single crystal manufacturing apparatus. [Figure 5] This figure shows an example of switching between the first operation and the second operation by the control unit. [Figure 6] This figure shows the temperature distribution of the solution achieved by the first operation. [Figure 7] This figure shows the temperature distribution of the solution achieved by the second action. [Figure 8] This diagram shows another example of switching between the first and second actions. [Figure 9] This figure shows an example of a configuration for heating the bottom surface of a crucible. [Figure 10] This diagram shows the configuration for heating the bottom surface of the crucible in the embodiment. [Figure 11] (a) is a schematic diagram showing the power supplied to the first coil when power is continuously supplied to the first coil, and (b) is a schematic diagram showing the power supplied to the second coil when power is continuously supplied to the second coil. [Figure 12] (a) is a schematic diagram showing the power supplied to the first coil when power is supplied to the first coil discontinuously, and (b) is a schematic diagram showing the power supplied to the second coil when power is supplied to the second coil discontinuously. [Figure 13] This is a block diagram showing the configuration of the heating section in the embodiment. [Figure 14] (a) is a schematic diagram showing the power supplied to the first coil when power is supplied to the first coil discontinuously, and (b) is a schematic diagram showing the power supplied to the second coil when power is supplied to the second coil discontinuously. [Figure 15] (a) is a schematic diagram showing the power supplied to the first coil when power is supplied to the first coil discontinuously, and (b) is a schematic diagram showing the power supplied to the second coil when power is supplied to the second coil discontinuously. [Figure 16]This graph shows the power supply current supplied to the first coil in the experiment. [Figure 17] This graph shows the power supply current supplied to the second coil in the experiment. [Figure 18] This is a cross-sectional view of a crucible containing a solidified solution during side heating. [Figure 19] This is a cross-sectional view of a crucible containing a solidified solution during bottom heating. [Figure 20] This is a cross-sectional view of the crucible containing the solidified solution during the heating switching process. [Modes for carrying out the invention]

[0024] In all the drawings illustrating the embodiments, the same reference numeral is used for identical components, and repeated explanations of them are omitted. Hatching may be used even in plan views to improve clarity.

[0025] <Consideration of improvements> When growing silicon carbide single crystals using a solution method, it is necessary to create a supersaturated state in the solution in order to precipitate the crystals. Therefore, in solution methods for growing silicon carbide single crystals, a temperature gradient is created in the solution to create a supersaturated state. In this case, a high-temperature region and a low-temperature region are formed in the solution, and a supersaturated state is achieved in the low-temperature region. Thus, by creating a temperature gradient in the solution so that the region of the solution in contact with the seed crystal is the low-temperature region where a supersaturated state is achieved, it is possible to grow crystals on the seed crystal.

[0026] When crystals with the same structure and orientation as the seed crystal grow on the surface of a seed crystal, a desirable silicon carbide single crystal will grow starting from the seed crystal. In contrast, even if crystal growth occurs on the surface of the seed crystal, crystals whose structure or orientation differs from that of the seed crystal are called miscellaneous crystals. When these miscellaneous crystals grow on the surface of the seed crystal, the growth of the silicon carbide single crystal is inhibited. Therefore, in solution-based methods, from the viewpoint of growing silicon carbide single crystals on a seed crystal, it is desirable to devise ways to reduce the generation of miscellaneous crystals in the solution.

[0027] Furthermore, in addition to miscellaneous crystals that form directly on the surface of the seed crystal, there are also miscellaneous crystals that form on the side walls or bottom of the crucible, and then grow by nuclei of these miscellaneous crystals floating in the solution and attaching to the seed crystal.

[0028] Such miscellaneous crystals inhibit the growth of silicon carbide single crystals starting from a seed crystal, and therefore, it is desirable to suppress their adhesion to the seed crystal. In other words, it is generally acceptable for miscellaneous crystals to form on the side walls and bottom of the crucible itself, rather than on the seed crystal. However, if the miscellaneous crystals formed on the side walls and bottom of the crucible become large, there is a higher risk that some of these large miscellaneous crystals will separate and float in the solution. For this reason, in order to reduce the amount of miscellaneous crystals that float in the solution and adhere to the seed crystal, it is desirable to suppress the growth of miscellaneous crystals formed on the side walls and bottom of the crucible. Furthermore, the growth of miscellaneous crystals formed on the side walls and bottom of the crucible leads to a decrease in the raw materials for growing silicon carbide single crystals on the seed crystal and a decrease in the growth rate of the silicon carbide single crystal.

[0029] Therefore, when growing silicon carbide single crystals using a solution method, it is necessary to suppress the enlargement of miscellaneous crystals that form on the side walls and bottom of the crucible. In this embodiment, measures are taken to reduce the amount of miscellaneous crystals formed in the solution and to suppress the enlargement of miscellaneous crystals that form on the side walls and bottom of the crucible.

[0030] The technical concept behind this embodiment, which incorporates this innovation, will be explained below.

[0031] <Basic Concept in the Embodiment> As mentioned above, in the technique of growing silicon carbide single crystals using the solution method, it is necessary to create a supersaturated state in the solution in order to precipitate crystals, and a temperature gradient is created in the solution to create this supersaturated state. Therefore, the solution contained in the crucible contains a mixture of high-temperature and low-temperature regions, and crystals precipitate in the low-temperature region, while they do not precipitate in the high-temperature region. From this, it can be assumed that, for example, if the low-temperature region where crystals have precipitated is changed to a high-temperature region, the precipitated crystals will dissolve again (insight).

[0032] By focusing on this finding, the inventors have conceived a basic concept that can reduce the amount of unwanted crystals generated in the solution and suppress the enlargement of unwanted crystals that form on the side walls and bottom of the crucible. This basic concept is explained below.

[0033] The basic idea in this embodiment is to switch between a high-temperature region and a low-temperature region contained in the crucible, thereby changing the low-temperature region where miscellaneous crystals precipitate to a high-temperature region and dissolving the precipitated miscellaneous crystals. According to this basic idea, the continuous precipitation of miscellaneous crystals can be suppressed, resulting in a reduction in the amount of miscellaneous crystals and suppression of their growth into large crystals.

[0034] Specifically, assuming that miscellaneous crystals are basically formed on the side walls and bottom surface of the crucible, the basic concept in this embodiment can be described as having a first heating step of heating the solution so that the temperature of the solution in contact with the side surface of the crucible is higher than the temperature of the solution in contact with the bottom surface of the crucible, and a second heating step of heating the solution so that the temperature of the solution in contact with the bottom surface of the crucible is higher than the temperature of the solution in contact with the side surface of the crucible, with the first heating step and the second heating step being switched alternately.

[0035] According to this basic concept, in the first heating step, miscellaneous crystals precipitate on the bottom surface of the crucible, while the miscellaneous crystals that had precipitated on the sides of the crucible dissolve. In contrast, in the second heating step, the miscellaneous crystals that had precipitated on the bottom surface of the crucible dissolve, while miscellaneous crystals precipitate on the sides of the crucible. As a result, by alternately switching between the first and second heating steps, the precipitation of miscellaneous crystals is prevented from continuing. Therefore, according to this basic concept, it is possible to reduce the amount of miscellaneous crystals and suppress their growth into large crystals. The following describes a single crystal manufacturing technology that embodies this basic concept.

[0036] <Configuration of a single crystal manufacturing apparatus> Figure 1 shows the configuration of the single crystal manufacturing apparatus 100 in this embodiment.

[0037] In Figure 1, the single crystal manufacturing apparatus 100 has a container 10. The internal space of this container 10 is filled with, for example, argon gas. A heat insulating member 13c is also provided inside the container 10, and a horizontally rotatable base 11 is positioned inside the area enclosed by the heat insulating member 13c. The container 10 is made of, for example, an iron-based material such as SUS.

[0038] Furthermore, as a structure for filling with argon gas, for example, a structure can be adopted in which quartz tubes are passed between the insulating member 13c and the coil 14a and between the insulating member 13c and the coil 14b, and the upper and lower ends of the quartz tubes are sealed with flanges to fill with argon gas.

[0039] Next, a crucible 12 is placed on the base 11. This crucible 12 is made of, for example, graphite and contains a high-temperature solution 20 containing silicon (Si) inside. Specifically, the crucible 12 comprises a main body capable of containing the solution 20 containing carbon and silicon, and a heat transfer part 12a protruding from the bottom of the main body.

[0040] In this configuration, the crucible 12 has a heat transfer section 12a that also functions as a "foot," and therefore the heat transfer section 12a also has the secondary function of stably supporting the crucible 12 upright. The heat transfer section 12a is configured to be in contact with a base 11 on which the crucible 12 can be placed. For example, as shown in Figure 1, the base 11 includes a first region R1 that is in contact with the heat transfer section 12a, a second region R2 surrounded by the first region R1, and a third region R3 surrounding the first region R1. An insulating member 13a is provided so as to be in contact with the second region R2, and an insulating member 13b is provided so as to be in contact with the third region R3.

[0041] The base 11 is connected to a crucible holding shaft 18 that holds the base 11. This crucible holding shaft 18 is configured to be movable in the vertical direction and to be able to rotate in either a clockwise or counterclockwise direction. As a result, the base 11 attached to the crucible holding shaft 18 and the crucible 12 placed on the base 11 can be moved vertically and rotated horizontally by the crucible holding shaft 18. The crucible holding shaft 18 has a hollow structure inside, and is configured to allow temperature measurement by inserting a thermocouple or radiation thermometer.

[0042] Furthermore, a coil through which a high-frequency current flows is provided on the outer circumference of the container 10 of the single crystal manufacturing apparatus 100, and the crucible 12 is heated by induction heating based on the high-frequency current flowing through the coil. Specifically, the single crystal manufacturing apparatus 100 has a heating section 25a and a heating section 25b. The heating section 25a is configured to heat the crucible 12 by induction heating caused by passing a high-frequency current through a coil 14a located opposite the side surface of the crucible 12. In other words, since the coil 14a functions as a heating section 25a that heats the crucible 12, the heating section 25a is shown together with the coil 14a in Figure 1. On the other hand, the heating section 25b is configured to heat the base 11 that supports the crucible 12 by induction heating caused by passing a high-frequency current through a coil 14b located opposite the base 11 that supports the crucible 12. The crucible 12 is then heated by heat conduction from the heated base 11. More specifically, heat is transferred from the base 11, which is heated by the heating unit 25b, to the heat transfer unit 12a, and then from the heat transfer unit 12a to the crucible 12 (main body), thereby heating the crucible 12. In this way, the heating unit 25b is configured to indirectly heat the crucible 12 via the base 11 by an induction heating phenomenon caused by passing a high-frequency current through a coil 14b located opposite the base 11 that supports the crucible 12. For this reason, since the coil 14b functions as a heating unit 25b that heats the crucible 12, the heating unit 25b is shown together with the coil 14b in Figure 1. Although not shown in Figure 1, the coils 14b and 14a are configured to allow cooling water to flow through them.

[0043] Thus, in the single crystal manufacturing apparatus 100, the crucible 12 is not only heated by the heating section 25a, but is also heated by heat conduction from the base 11 heated by the heating section 25b. The heat transfer section 12a of the crucible 12 has the function of conducting heat from the base 11 heated by the heating section 25b to the main body.

[0044] Here, in order to facilitate heating of the base 11 by the heating section 25b, the thickness of the base 11 is increased so that the portion facing the coil 14b is larger. Although it is possible to integrate the base 11 with the crucible 12, considering the need to replace the crucible 12 each time silicon carbide single crystals are manufactured and the high cost of manufacturing a single unit, it is desirable to construct the base 11 and the crucible 12 as separate units. When the base 11 and the crucible 12 are constructed as separate units, it is acceptable to simply place the heat transfer section 12a of the crucible 12 on the base 11, or the base 11 can be constructed so that the heat transfer section 12a can be fitted into the base 11.

[0045] These heating units 25a and 25b are controlled by a control unit 50. That is, the single crystal manufacturing apparatus 100 has a control unit 50 that controls the power supplied to heating unit 25a and the power supplied to heating unit 25b. For example, the power supply that provides power to heating unit 25a and the power supply that provides power to heating unit 25b are separate power supplies, and the control unit 50 is configured to control heating unit 25a and heating unit 25b, which are powered by different power supplies, respectively.

[0046] The control unit 50 is configured to alternately switch between a first operation, which adjusts the power supplied to the heating unit 25a and the power supplied to the heating unit 25b so that the temperature of the solution 20 in contact with the side surface of the crucible 12 is higher than the temperature of the solution 20 in contact with the bottom surface of the crucible 12, and a second operation, which adjusts the power supplied to the heating unit 25a and the power supplied to the heating unit 25b so that the temperature of the solution 20 in contact with the bottom surface of the crucible 12 is higher than the temperature of the solution 20 in contact with the side surface of the crucible 12.

[0047] The solution 20 contained in the crucible 12, which is heated by heating sections 25a and 25b, becomes hot, and the graphite (C) that makes up the crucible 12 dissolves, so the solution 20 contains carbon and silicon. The crucible 12 is fitted with a crucible lid 15, which has a cylindrical member 15a and a connecting member 15b that connects to the cylindrical member 15a. The connecting member 15b has the function of fixing and supporting the cylindrical member 15a and is configured to be in contact with the crucible 12, for example.

[0048] Next, the single crystal manufacturing apparatus 100 is provided with a crystal holding shaft 16 that is movable in the vertical direction. This crystal holding shaft 16, like the crucible holding shaft 18, may be configured to rotate clockwise or counterclockwise. In other words, the presence or absence of a rotation mechanism in the crystal holding shaft 16 and the crucible holding shaft 18 is optional.

[0049] A seed crystal (not shown in Figure 1) made of silicon carbide is attached to the tip of the crystal holding shaft 16. The crystal holding shaft 16 also has a fin structure 16a attached so as to intersect with the extending direction of the crystal holding shaft 16. Furthermore, the inside of the crystal holding shaft 16 is hollow, and a thermocouple 17 for measuring the temperature near the seed crystal is inserted inside the crystal holding shaft 16. Temperature measurement near the seed crystal can also be performed by placing a radiation thermometer with a measuring diameter smaller than the inner diameter of the crystal holding shaft 16 at the upper end of the crystal holding shaft 16 instead of inserting the thermocouple 17.

[0050] Furthermore, the control unit 50 of the single crystal manufacturing apparatus 100 is configured to control the vertical movement of the crystal holding shaft 16 having a fin structure 16a. Specifically, the control unit 50 is configured to control the crystal holding shaft 16 so that it moves vertically through the inside of the cylindrical member 15a. The control unit 50 is configured to move the crystal holding shaft 16, to which a seed crystal is attached at its tip, downward so that the lower surface of the seed crystal comes into contact with the surface of the solution 20 contained in the crucible 12. After the lower surface of the seed crystal comes into contact with the surface of the solution 20, the control unit 50 is configured to move the crystal holding shaft 16 upward so that a single crystal made of silicon carbide can be grown on the lower surface of the seed crystal. For example, Figure 1 shows a silicon carbide single crystal 40 growing on the lower surface of the seed crystal. The seed crystal only needs to be in contact with the solution 20, but it is particularly desirable to bring it into contact with the surface of the solution 20.

[0051] It should be noted that one example of a configuration is to allow a single crystal made of silicon carbide to grow on the underside of the seed crystal by moving the crystal holding axis 16 upward. For example, the configuration may be set up so that a single crystal made of silicon carbide grows on the underside of the seed crystal while the crystal holding axis 16 is stopped (maintained), or so that a single crystal made of silicon carbide grows on the underside of the seed crystal by moving the crystal holding axis 16 downward. This configuration takes into account, for example, the possibility that the surface of the solution 20 may sink due to evaporation of the solution 20. That is, if the surface of the solution 20 recedes due to evaporation of the solution 20, a single crystal can be reliably grown on the seed crystal by growing the single crystal while moving the crystal holding axis 16 downward.

[0052] The single crystal manufacturing apparatus 100 is configured as described above.

[0053] Figure 2 illustrates examples of the dimensions of the main parts of the base 11 and the crucible 12.

[0054] The dimensions of the main parts shown in Figure 2 are, for example, as follows: (1) "L1" = φ150mm (2) "L2" = φ250mm (3) "L3" = φ100mm (4) "L4" = φ190mm (5) "T1" = 100 mm (6) "T2" = 80mm (7) "T3" = 30mm (8) "T4" = 250mm (9) "A1" = 90mm (10) "A2" = φ330mm

[0055] <Example 1> In the single crystal manufacturing apparatus 100 shown in Figure 1, the heating section 25b that heats the base 11 utilizes the induction heating phenomenon generated by passing a high-frequency current through the coil 14b. However, the heating section 25b that heats the base 11 is not limited to this, and may, for example, be composed of a resistance heating heater located below the base 11.

[0056] However, if the heating section 25b is composed of a resistance heater, it is necessary to provide "holes" in the insulation material to route a pair of wires used to energize the resistance heater. In particular, if the crucible 12 itself is rotated, a circumferential opening must be provided in the insulation material to route a pair of wires. As a result, it may become difficult to ensure the high-temperature holding characteristics of the crucible 12. Therefore, from the viewpoint of improving the heat insulation effect of the insulation material and simplifying the configuration of the single crystal manufacturing apparatus 100, it is desirable that the heating section 25b that heats the base 11 be composed of an induction heater that utilizes the induction heating phenomenon as shown in Figure 1.

[0057] <Operation of single crystal manufacturing equipment (single crystal manufacturing method)> Next, we will explain the operation of the single crystal manufacturing apparatus 100.

[0058] Figures 3 and 4 are diagrams illustrating the operation of the single crystal manufacturing apparatus 100.

[0059] In Figure 3, first, the control unit 50 lowers the crystal holding shaft 16, to which a seed crystal 30 is attached at its tip. As a result, the seed crystal 30 attached to the crystal holding shaft 16 passes through the inside of the cylindrical member 15a provided on the crucible lid 15, and then comes into contact with the surface of the carbon and silicon solution 20 contained in the crucible 12. At this time, the fin structure 16a attached to the crystal holding shaft 16 is positioned opposite the inner wall of the cylindrical member 15a.

[0060] Next, in Figure 4, the control unit 50 slowly raises the crystal holding shaft 16. This causes the silicon carbide single crystal 40 to grow on the underside of the seed crystal 30 being pulled up. At this time, the fin structure 16a attached to the crystal holding shaft 16 moves while maintaining opposition to the inner wall of the cylindrical member 15a. Subsequently, if crystal growth is to be continued, the pulling up operation of the crystal holding shaft 16 is continued. On the other hand, if crystal growth is to be terminated, the control unit 50 further raises the crystal holding shaft 16 to isolate the silicon carbide single crystal 40 from the solution 20. This terminates the growth of the silicon carbide single crystal 40. At this time, the fin structure 16a attached to the crystal holding shaft 16 is maintained in a position facing the inner wall of the cylindrical member 15a.

[0061] As described above, silicon carbide single crystals can be produced by operating the single crystal manufacturing apparatus 100. Although it has been stated that crystal growth is terminated by further raising the crystal holding axis 16 to isolate the silicon carbide single crystal 40 from the solution 20, this is not the only method. For example, instead of raising the crystal holding axis 16, the crystal growth can also be terminated by lowering the crucible holding axis 18 to isolate the silicon carbide single crystal 40 from the solution 20.

[0062] <<Operation by the control unit>> As described above, silicon carbide single crystals are produced in the single crystal manufacturing apparatus 100 by the "solution method". In this embodiment, the single crystal manufacturing method involves alternately switching between a first heating step, in which the solution 20 in contact with the side surface of the crucible 12 is heated so that the temperature of the solution 20 in contact with the bottom surface of the crucible 12 is higher than the temperature of the solution 20 in contact with the bottom surface of the crucible 12, and a second heating step, in which the solution 20 in contact with the bottom surface of the crucible 12 is heated so that the temperature of the solution 20 in contact with the side surface of the crucible 12 is higher than the temperature of the solution 20 in contact with the side surface of the crucible 12.

[0063] In this embodiment, these processes are realized by the control of heating units 25a and 25b by the control unit 50 of the single crystal manufacturing apparatus 100. Specifically, the control unit 50 alternately switches between a first operation, which raises the temperature of the solution 20 in contact with the side surface of the crucible 12 to higher than the temperature of the solution 20 in contact with the bottom surface of the crucible 12 by adjusting the power supplied to heating unit 25a and the power supplied to heating unit 25b, and a second operation, which raises the temperature of the solution 20 in contact with the bottom surface of the crucible 12 to higher than the temperature of the solution 20 in contact with the side surface of the crucible 12 by adjusting the power supplied to heating unit 25a and the power supplied to heating unit 25b.

[0064] For example, when the first operation by the control unit 50 is performed, the temperature of the solution 20 in contact with the side surface of the crucible 12 is the temperature at which miscellaneous crystals dissolve, while the temperature of the solution 20 in contact with the bottom surface of the crucible 12 is the temperature at which miscellaneous crystals precipitate. In contrast, when the second operation by the control unit 50 is performed, the temperature of the solution 20 in contact with the bottom surface of the crucible 12 is the temperature at which miscellaneous crystals dissolve, while the temperature of the solution 20 in contact with the side surface of the crucible 12 is the temperature at which miscellaneous crystals precipitate.

[0065] As a result, by repeatedly switching between the first and second operations, the precipitated non-crystallized crystals can be dissolved again, preventing continuous precipitation of non-crystallized crystals, thereby reducing the amount of non-crystallized crystals and suppressing their growth into larger crystals.

[0066] Figure 5 shows an example of switching between the first operation and the second operation by the control unit 50.

[0067] In Figure 5, "A" indicates the period during which the first operation is performed, while "B" indicates the period during which the second operation is performed. Also in Figure 5, the solid line represents the power (coil output) supplied to the coil 14a of the heating unit 25a, while the dashed line represents the power (coil output) supplied to the coil 14b of the heating unit 25b.

[0068] In Figure 5, the first operation ("A") and the second operation ("B") are switched while crystal growth is being carried out. In other words, Figure 5 shows an example in which the switching between the first operation and the second operation is repeatedly performed in the process of growing a silicon carbide single crystal 40 on the lower surface of a seed crystal while moving the crystal holding axis 16 upward (see Figure 4).

[0069] For example, in the first operation, the power supplied to coil 14a is large, while the power supplied to coil 14b is small. This means that the amount of heating on the sides of the crucible 12 is greater than the amount of heating on the bottom of the crucible 12, thereby achieving a temperature distribution in which the temperature of the solution 20 in contact with the sides of the crucible 12 is higher than the temperature of the solution 20 in contact with the bottom of the crucible 12. In contrast, in the second operation, the power supplied to coil 14a is reduced, while the power supplied to coil 14b is increased. This means that the amount of heating on the bottom of the crucible 12 is greater than the amount of heating on the sides of the crucible 12, thereby achieving a temperature distribution in which the temperature of the solution 20 in contact with the bottom of the crucible 12 is higher than the temperature of the solution 20 in contact with the sides of the crucible 12.

[0070] In Figure 5, an example is shown where the power supplied to coil 14a is greater than the power supplied to coil 14b, not only in the first operation but also in the second operation. However, depending on the configuration of the crucible 12, it is conceivable that the power supplied to coil 14a may be less than the power supplied to coil 14b in order to achieve a temperature distribution in which the temperature of the solution 20 in contact with the bottom surface of the crucible 12 is higher than the temperature of the solution 20 in contact with the sides of the crucible 12. In other words, in the second operation, as long as a temperature distribution is achieved in which the temperature of the solution 20 in contact with the bottom surface of the crucible 12 is higher than the temperature of the solution 20 in contact with the sides of the crucible 12, the relative magnitude of the power (or current) supplied to coil 14a and the power (or current) supplied to coil 14b does not matter.

[0071] Since all components of the single crystal manufacturing apparatus 100 have heat capacity, the temperature distribution of the solution 20 transitions with a delay in response to changes in all control conditions, including power adjustment supplied to coils 14a and 14b, respectively. While the temperature distribution of the solution 20 is transitioning, it is not necessarily in a state suitable for single crystal growth.

[0072] For example, regarding the switch from the first operation to the second operation, if we define the transition time from the end of the conditions for the first operation until the temperature distribution of the solution 20 realized by the second operation reaches a steady state as the first transition time, then during the first transition time, a temperature distribution different from both the temperature distribution realized by the first operation and the temperature distribution realized by the second operation is realized.

[0073] Several methods can be considered for controlling the temperature distribution of solution 20 to a desired state during the first transition time. One example is a method that immediately transitions to the second operation after the completion of the first operation. This method has the advantage of enabling the growth of silicon carbide single crystals under stable conditions for a longer period of time, as it can achieve the temperature distribution of solution 20 achieved by the second operation in a short time, and is particularly effective in single crystal manufacturing equipment with small heat capacity. Another advantage is that, compared to the second and third examples described later, the power control conditions are simple and clear, and it can be implemented in single crystal manufacturing equipment that does not have a complex control mechanism.

[0074] As a second example, there is a method in which the power supplied to coil 14a and coil 14b, respectively, between the end of the first operation and the start of the second operation is changed gradually enough to absorb the delay in the transition due to the heat capacity. This method has the advantage that it is possible to change the temperature distribution of the solution 20 in a metastable manner during the first transition time, and that the temperature distribution of the solution 20 can be almost controlled by the power supplied to coil 14a and coil 14b, respectively. As a result, the first transition time almost coincides with the period between the end of the first operation and the start of the second operation, making it easier to achieve a temperature distribution suitable for the growth of silicon carbide single crystals during the first transition time compared to the first example and the third example described later.

[0075] As a power change process in the second example, as shown in Figure 5, one method is to maintain a constant power change rate from the end of the first operation to the start of the second operation. Alternatively, the power change rate may be increased or decreased at one or more points in time between the end of the first operation and the start of the second operation. Since coils 14a and 14b can be controlled independently, in the latter case, for example, it is possible to make the power change rate of one of them larger than in the first example and the power change rate of the other smaller than in the first example.

[0076] A third example involves supplying less power to coil 14a during a certain period between the end of the first operation and the start of the second operation than the power supplied to coil 14a under the second operation conditions, while simultaneously supplying more power to coil 14b than the power supplied to coil 14b under the second operation conditions. This method is called overshoot and has the effect of canceling out the delay in state change due to heat capacity. The advantage of this power change method utilizing overshoot is that, in a single crystal manufacturing apparatus with a large heat capacity, the temperature distribution of the solution 20, which undergoes the second operation, reaches a steady state earlier than in the first example.

[0077] Up to this point, we have shown a method for controlling the temperature distribution of solution 20 during the first transition time to a desired state when switching from the first operation to the second operation. It goes without saying that the same method can be applied to switching from the second operation to the first operation.

[0078] Figure 6 shows the results of a simulation of the temperature distribution of solution 20 achieved by the first operation. The simulation was performed using the software "CGSim|STR Japan Co., Ltd. <Crystal Growth Analysis Simulation Software> (str-soft.co.jp)".

[0079] Figure 6 shows that a temperature distribution is achieved in which the temperature (K) of the solution 20 in contact with the sides of the crucible is higher than the temperature (K) of the solution 20 in contact with the bottom of the crucible. In this case, the temperature of the solution 20 in contact with the sides of the crucible is high, so the miscellaneous crystals dissolve. On the other hand, the temperature of the solution 20 in contact with the bottom of the crucible is low, so the miscellaneous crystals are formed (precipitated).

[0080] Figure 7 shows the results of a simulation of the temperature distribution of solution 20 achieved by the second operation. In Figure 7, it can be seen that a temperature distribution is achieved in which the temperature (K) of solution 20 in contact with the bottom surface of the crucible is higher than the temperature (K) of solution 20 in contact with the sides of the crucible. In this case, since the temperature of solution 20 in contact with the bottom surface of the crucible is high, miscellaneous crystals dissolve. On the other hand, since the temperature of solution 20 in contact with the sides of the crucible is low, miscellaneous crystals are formed (precipitated).

[0081] Therefore, by repeatedly switching between the first and second operations, the temperature distribution shown in Figure 6 and the temperature distribution shown in Figure 7 alternate. As a result, the redissolution of precipitated non-crystallized crystals occurs, preventing the continuous precipitation of non-crystallized crystals. Thus, according to this embodiment, it is possible to reduce the amount of non-crystallized crystals and suppress their growth into large crystals.

[0082] Next, I will explain the timing for switching between the first and second actions.

[0083] Ideally, it is desirable to switch between the first and second operations when the size of the unwanted crystals exceeds a predetermined size. This is because determining the switching timing in this way effectively suppresses the growth of unwanted crystals.

[0084] However, it is difficult to measure the size of unwanted crystals during the manufacturing process of silicon carbide single crystals. For this reason, a control method that switches between the first and second operations when the size of unwanted crystals exceeds a predetermined size is not practical. Therefore, it is more practical to, for example, alternate between the first and second operations at predetermined time intervals.

[0085] In this case, if the first and second operations are switched alternately at predetermined time intervals, in order to effectively suppress the enlargement of unwanted crystals, it is conceivable to build a database that stores data showing the relationship between time intervals and unwanted crystal size, and then set the optimal time interval based on the data stored in this database.

[0086] <Modification 2> Figure 5 illustrates an example of switching between the first and second operations while crystal growth is being carried out, but the control unit 50 is not limited to this example of switching between the first and second operations. For example, one of the first or second operations may be performed during the crystal growth stage after the seed crystal has been brought into contact with the surface of the solution, while the other of the first or second operations may be performed with the silicon carbide single crystal grown on the underside of the seed crystal separated from the surface of the solution.

[0087] Figure 8 shows an example of switching between the first and second operations (modification 2).

[0088] Figure 8 shows an example in which crystal growth is stopped when the first operation is performed, while the second operation is performed while crystal growth is continuing. In other words, the switching operation shown in Figure 8 can also be used as an example of switching between the first and second operations by the control unit 50.

[0089] In this case, the following advantages can be obtained.

[0090] For example, in Figure 6, which shows the temperature distribution of the solution after performing the first operation, the surface temperature of the solution 20 in contact with the seed crystal is elevated.

[0091] Here, in order to grow a silicon carbide single crystal on the underside of the seed crystal, it is desirable to set the surface temperature of the solution in contact with the seed crystal to a low temperature within the solution's temperature distribution. This is because silicon carbide single crystals grow in a supersaturated state, and this supersaturated state is achieved in the low temperature range. Considering this, the temperature distribution of the solution resulting from the first operation is not necessarily suitable for the growth of silicon carbide single crystals. This is because, in the temperature distribution shown in Figure 6, the degree of supersaturation is small, resulting in a slow crystal growth rate, and therefore it is not necessarily a temperature distribution suitable for crystal growth.

[0092] In contrast, Figure 7, which shows the temperature distribution of the solution after performing the second operation, shows that the surface temperature of the solution 20 in contact with the seed crystal is lower. Therefore, the temperature distribution of the solution after performing the second operation can be said to be a suitable temperature condition for the growth of silicon carbide single crystals. In other words, the temperature distribution of the solution after performing the second operation has a higher degree of supersaturation, resulting in a faster crystal growth rate. As a result, it can be said that the temperature distribution of the solution after performing the first operation is more suitable for crystal growth.

[0093] Based on the above, the temperature distribution of the solution resulting from the first operation is not necessarily suitable for the growth of silicon carbide single crystals, while the temperature distribution of the solution resulting from the second operation is suitable for the growth of silicon carbide single crystals.

[0094] Therefore, as shown in Figure 8, when the first operation is performed, crystal growth is stopped, while the second operation is performed while crystal growth is ongoing. This allows for the growth of silicon carbide single crystals using only temperature conditions suitable for silicon carbide single crystal growth. As a result, the modified example 2 shown in Figure 8 has the advantage of being able to produce silicon carbide single crystals of superior quality. On the other hand, in the switching example shown in Figure 5, since the first and second operations are performed alternately while crystal growth is ongoing, the advantage of shortening the silicon carbide single crystal production time is obtained.

[0095] Regarding the switching time between the first and second operations, as mentioned above, a method of determining this based on a pre-established database is conceivable. However, from the perspective of shortening the crystal growth time, it is more desirable to shorten the execution time of the first operation to that of the second operation. Suitable conditions for obtaining a switching time that satisfies this objective include, for example, the dissolution rate of miscellaneous crystals in the solution 20 in contact with the side surface of the crucible 12 during the first operation being higher than the precipitation rate of miscellaneous crystals at the same location during the second operation. A method to satisfy this condition is to adjust the power supplied to coils 14a and 14b so that the temperature gradient of the solution 20 during the first operation is larger than that during the second operation.

[0096] In both the first and second operations, it is not necessary to keep the power supplied to the coils perfectly constant; it may be gradually reduced. The first and second operations from the second cycle onward do not necessarily have to use the exact same output power as the first cycle. For example, it is possible to slightly reduce the output power compared to the first cycle, or to slightly reduce the power supplied only to coil 14a. These methods take into account that as the crystal grows, the amount of solution to be heated decreases, and therefore, reducing the power supplied to the coils is necessary to create the same temperature distribution as the first cycle.

[0097] <Features of the Embodiment> Next, the distinctive features of this embodiment will be described.

[0098] The first characteristic feature of this embodiment is that, as shown in Figures 5 and 8, for example, by adjusting the power supplied to the heating unit 25a and the power supplied to the heating unit 25b, a first operation ("A") is performed to raise the temperature of the solution 20 in contact with the side surface of the crucible 12 to a higher temperature than the temperature of the solution 20 in contact with the bottom surface of the crucible 12, and a second operation ("B") is performed by adjusting the power supplied to the heating unit 25a and the power supplied to the heating unit 25b to raise the temperature of the solution 20 in contact with the bottom surface of the crucible 12 to a higher temperature than the temperature of the solution 20 in contact with the side surface of the crucible 12. This makes it possible to periodically change the temperature of the solution 20 in contact with the side surface and the bottom surface of the crucible 12 between the temperature at which miscellaneous crystals precipitate and the temperature at which miscellaneous crystals dissolve. This means that the amount of precipitated non-crystals can be reduced, and the growth of these non-crystals can be suppressed, thereby preventing a decrease in the quality of silicon carbide single crystals caused by these non-crystals.

[0099] Next, a second characteristic feature of this embodiment is that, for example, as shown in Figure 1, a heat transfer section 12a is provided on the crucible 12 that protrudes from the bottom of the main body of the crucible 12.

[0100] The technical significance of this second feature point will be explained below.

[0101] For example, in the second step, which involves raising the temperature of the solution 20 in contact with the bottom surface of the crucible 12 to the temperature at which the miscellaneous crystals dissolve, it is important to raise the temperature of the bottom surface of the crucible 12 uniformly. This is because if the temperature of the bottom surface of the crucible 12 cannot be raised uniformly, there is a high probability that there will be a low-temperature region in which the miscellaneous crystals do not dissolve even after performing the second step, and as a result, it will become impossible to dissolve the miscellaneous crystals in this region.

[0102] One possible configuration for heating the bottom surface of the crucible 12 is the one shown in Figure 9. In Figure 9, the crucible 12 is placed on a base 11, and the base 11 is configured to be heated by induction heating from a heating section 25b including a coil 14b. In this case, the heat from the heated base 11 is conducted to the bottom surface of the crucible 12, which is in direct contact with the base 11. However, induction heating by the coil 14b has the property that the outer part of the base 11 is heated more easily than the central part. As a result, in the configuration shown in Figure 9, the outer part of the bottom surface of the crucible 12 is mainly heated (see arrow in Figure 9), and it becomes difficult to heat the central part of the bottom surface of the crucible 12. In other words, in the configuration shown in Figure 9, it is difficult to raise the temperature of the bottom surface of the crucible 12 uniformly.

[0103] In contrast, in this embodiment, as shown in Figure 1, a heat transfer section 12a protruding from the bottom of the main body of the crucible 12 is provided on the crucible 12. In this case, as shown in Figure 10, heat can be preferentially conducted from the base 11, which is heated by the induction heating phenomenon from the heating section 25b including the coil 14b, to the center of the bottom surface of the crucible 12 via the heat transfer section 12a. As a result, according to this embodiment, the temperature of the bottom surface of the crucible 12 can be raised uniformly. In other words, the heat transfer section 12a has the function of preferentially inducing heat from the heated base 11 to the center of the bottom surface of the crucible 12.

[0104] Here, from the viewpoint of improving the uniformity of the temperature across the entire bottom surface of the crucible 12, it is desirable to provide an insulating member 13a inside the heat transfer section 12a, as shown in Figure 1, and to provide an insulating member 13b surrounding the heat transfer section 12a.

[0105] Furthermore, the position of the heat transfer section 12a is important for uniformly raising the temperature of the bottom surface of the crucible 12, and the dimensions of the main parts shown in Figure 2 are determined with this in mind.

[0106] In particular, from the perspective of uniformly raising the temperature of the entire bottom surface of the crucible 12 and causing the dissolution of miscellaneous crystals across the entire bottom surface, it is important that "L3" is smaller than "L1", and "L4" is larger than "L1" and smaller than "L2". This configuration prevents the sides of the crucible 12 from being preferentially heated.

[0107] <Considering further improvements> For example, in this embodiment, as shown in Figure 1, the crucible 12 is heated by induction heating by supplying power to coil 14a, and the base 11 is heated by induction heating by supplying power to coil 14b.

[0108] Herein, a distinctive feature of this embodiment is that, as shown in Figures 5 and 8, for example, a first operation ("A") is performed by adjusting the power supplied to coil 14a and the power supplied to coil 14b to raise the temperature of the solution 20 in contact with the side surface of the crucible 12 to a higher temperature of the solution 20 in contact with the bottom surface of the crucible 12, and a second operation ("B") is performed by adjusting the power supplied to coil 14a and the power supplied to coil 14b to raise the temperature of the solution 20 in contact with the bottom surface of the crucible 12 to a higher temperature of the solution 20 in contact with the side surface of the crucible 12.

[0109] In this case, as shown in Figures 5 and 8, power is supplied to both coil 14a and coil 14b in both the first operation ("A") and the second operation ("B"). This means that in both the first operation ("A") and the second operation ("B"), high-frequency current flows simultaneously through both coil 14a and coil 14b. Therefore, for example, the electromagnetic field generated due to the high-frequency current flowing through coil 14a may adversely affect the circuit including coil 14b, while the electromagnetic field generated due to the high-frequency current flowing through coil 14b may adversely affect the circuit including coil 14a. In other words, in both the first operation ("A") and the second operation ("B"), since high-frequency current flows simultaneously through both coil 14a and coil 14b, there is a concern that electromagnetic interference may occur as a result, leading to adverse effects such as circuit malfunction.

[0110] Therefore, this embodiment incorporates measures to suppress the aforementioned adverse effects. The technical concept behind this embodiment, which incorporates these measures, will be explained below.

[0111] <Technical Concept in the Embodiment> The technical concept in this embodiment is to exclusively control the power supply so that the periods for supplying power to coil 14a and coil 14b do not overlap, based on the premise that power is supplied to coil 14a and coil 14b discontinuously, rather than continuously. That is, the period for supplying power to coil 14a is the period for which power is not supplied to coil 14b, and the period for supplying power to coil 14b is the period for which power is not supplied to coil 14a. As a result, when power is supplied to one coil, power is not supplied to the other coil, thus preventing high-frequency current from flowing through both coils simultaneously. As a result, electromagnetic interference caused by high-frequency current flowing through both coils simultaneously can be suppressed, thereby preventing circuit malfunctions.

[0112] For example, Figure 11(a) is a schematic diagram showing the power supplied to coil 14a when power is continuously supplied to coil 14a. On the other hand, Figure 11(b) is a schematic diagram showing the power supplied to coil 14b when power is continuously supplied to coil 14b. In particular, Figure 11(a) shows the power supplied to coil 14a in the first operation ("A") of Figure 5, and Figure 11(b) shows the power supplied to coil 14b in the first operation ("A") of Figure 5. In this case, as shown in Figures 11(a) and 11(b), power is supplied to both coils 14a and 14b simultaneously. Therefore, in a configuration in which power is continuously supplied to each of coils 14a and 14b as shown in Figures 11(a) and 11(b), high-frequency current flows simultaneously through both coils 14a and 14b, raising concerns that electromagnetic interference may occur, leading to adverse effects such as circuit malfunction.

[0113] In Figure 11(a), when power is continuously supplied to coil 14a, the instantaneous power supplied to coil 14a P1H is equal to the average power supplied to coil 14a. <p1h>Equivalent to the average power supplied to coil 14b in Figure 11(b), when power is continuously supplied to coil 14b, the instantaneous power supplied to coil 14b P2L is equal to the average power supplied to coil 14b. <p2l>It is equal to.

[0114] In contrast, for example, Figure 12(a) is a schematic diagram showing the power supplied to coil 14a when power is supplied to coil 14a discontinuously. On the other hand, Figure 12(b) is a schematic diagram showing the power supplied to coil 14b when power is supplied to coil 14b discontinuously. In particular, Figure 12(a) shows the power supplied to coil 14a in the first operation ("A") of Figure 5, and Figure 12(b) shows the power supplied to coil 14b in the first operation 1 ("A") of Figure 5. In this case, as shown in Figures 12(a) and 12(b), it is possible to control the system so that power is not supplied to coil 14b during the period when power is supplied to coil 14a. In other words, as shown in Figures 12(a) and 12(b), by adopting a configuration in which power is supplied discontinuously to each of coil 14a and coil 14b, it can be seen that it is possible to control the system so that power is not supplied to both coils 14a and coil 14b simultaneously. Therefore, by adopting a configuration that supplies power discontinuously to each of the coils 14a and 14b, as shown in Figures 12(a) and 12(b), it is possible to prevent high-frequency current from flowing simultaneously through both coils 14a and 14b. As a result, the occurrence of electromagnetic interference caused by high-frequency current flowing simultaneously through both coils 14a and 14b can be suppressed, thereby reducing adverse effects such as circuit malfunction.

[0115] However, in Figure 12(a), when power is supplied discontinuously to coil 14a, the instantaneous power supplied to coil 14a P1H is equal to the average power supplied to coil 14a <p1h>It will be higher than. Similarly, in Figure 12(b), when power is supplied discontinuously to coil 14b, the instantaneous power supplied to coil 14b P2L is equal to the average power supplied to coil 14b <p2l>The power becomes higher than average. In other words, by adopting the technical concept of this embodiment, it is possible to prevent high-frequency current from flowing simultaneously through both coil 14a and coil 14b, while the instantaneous power supply becomes higher than the average power supply. However, considering that electromagnetic interference caused by high-frequency current flowing simultaneously through both coils can be suppressed, thereby suppressing circuit malfunction, the technical concept of this embodiment has great technical significance.

[0116] <Method of Realization> The following describes the embodiment of the aforementioned technical concept.

[0117] The embodiment of this design is based on the premise that power is supplied discontinuously to coils 14a and 14b, rather than continuously to each, and that the first inverter for supplying power to coil 14a and the second inverter for supplying power to coil 14b are operated exclusively. That is, when the first inverter for supplying power to coil 14a is turned on, the second inverter for supplying power to coil 14b is turned off, and when the second inverter for supplying power to coil 14b is turned on, the first inverter for supplying power to coil 14a is turned off. As a result, when power is supplied to one coil, no power is supplied to the other coil, thus preventing high-frequency current from flowing through both coils simultaneously. As a result, electromagnetic interference caused by high-frequency current flowing through both coils simultaneously can be suppressed, thereby preventing circuit malfunctions.

[0118] <<Configuration and operation of the heating element>> Figure 13 is a block diagram showing the configuration of the heating section in this embodiment.

[0119] Figure 13 shows an example configuration of heating section 25a and heating section 25b.

[0120] In Figure 13, the heating unit 25a comprises a first AC / DC converter 201a, a first inverter 202a, a first transformer 203a, and a coil 14a, and is configured to be controlled by the control unit 210. In the heating unit 25a configured in this way, first, the control unit 210 is given a target output power < <p1>> A signal (i.e., the target output signal) is input. Then the control unit 210 sets the target inverter voltage < to the first AC / DC converter 201a in order to achieve the input power PA to the first inverter 202a. <vi1>> is output. Next, the first AC / DC converter 201a outputs the target inverter voltage < input from the control unit 210. <vi1>Based on this, AC power from the first commercial power supply 200a is converted to DC power. As a result, the input power PA is output from the first AC / DC converter 201a to the first inverter 202a. Subsequently, the first inverter 202a receives the input power PA output from the first AC / DC converter 201a and outputs power <p1>It outputs the following. Specifically, the DC current converted by the first AC / DC converter 201a is converted to a high-frequency current (e.g., 10kHz) by the first inverter 202a. Then, the output voltage from the first inverter 202a is reduced in pressure by the first transformer 203a and then the high-frequency current (output power) is supplied to the coil 14a. <p1>) is supplied. That is, in order to prevent leakage current and arc generation in the heating furnace, the voltage is reduced by the first transformer 203a, and the large current equivalent to that is passed through the coil 14a to heat the heating furnace. Here, the control unit 210 controls the on / off of the first inverter 202a. As a result, there are periods when power is supplied to the coil 14a and periods when power is not supplied. Then, in the coil 14a, the supplied output power <p1>Based on this, induction heating is performed on the crucible 12. In this way, the crucible 12 is heated by the heating unit 25a.

[0121] Next, the heating unit 25b is equipped with a second AC / DC converter 201b, a second inverter 202b, a second transformer 203b, and a coil 14b, and is configured to be controlled by the control unit 210. In the heating unit 25b configured in this way, first, the control unit 210 is given a target output power < <p2>>A signal is input. Then the control unit 210 sets the target inverter voltage to achieve the input power PB to the second inverter 202b for the second AC / DC converter 201b. <vi2>> is output. Next, the second AC / DC converter 201b receives the target inverter voltage < from the control unit 210. <vi2>Based on this, the AC power from the second commercial power supply 200b is converted to DC power. This outputs the input power PB from the second AC / DC converter 201b to the second inverter 202b. Subsequently, the second inverter 202b receives the input power PB output from the second AC / DC converter 201b and outputs power <p2>It outputs the following. Specifically, the DC current converted by the second AC / DC converter 201b is converted to a high-frequency current (e.g., 10kHz) by the second inverter 202b. Then, the output voltage from the second inverter 202b is reduced in pressure by the second transformer 203b and then the high-frequency current (output power) is supplied to the coil 14b. <p2>) is supplied. That is, in order to prevent leakage current and arc generation in the heating furnace, the voltage is reduced by the second transformer 203b, and the large current equivalent to that is passed through coil 14b to heat the heating furnace. Here, the control unit 210 controls the on / off of the second inverter 202b. As a result, there are periods when power is supplied to coil 14b and periods when power is not supplied. Then, in coil 14b, the supplied output power <p2>Based on this, induction heating is performed on the base 11. In this way, the base 11 is heated by the heating unit 25b.

[0122] Thus, in this embodiment, power is supplied to coil 14a and coil 14b discontinuously, rather than continuously. At this time, the control unit 210 controls the first inverter 202a for supplying power to coil 14a and the second inverter 202b for supplying power to coil 14b so that they operate exclusively. In other words, when the first inverter 202a for supplying power to coil 14a is turned on, the second inverter 202b for supplying power to coil 14b is turned off, and when the second inverter 202b for supplying power to coil 14b is turned on, the first inverter 202a for supplying power to coil 14a is turned off. As a result, when power is supplied to one coil, no power is supplied to the other coil, thus preventing high-frequency current from flowing through both coils simultaneously. As a result, electromagnetic interference caused by high-frequency current flowing through both coils simultaneously can be suppressed, thereby preventing circuit malfunctions.

[0123] <<Specific waveform examples>> Next, we will explain specific waveform examples.

[0124] Figure 14(a) is a schematic diagram showing the power supplied to coil 14a when power is supplied to coil 14a discontinuously. On the other hand, Figure 14(b) is a schematic diagram showing the power supplied to coil 14b when power is supplied to coil 14b discontinuously. Specifically, Figure 14(a) shows the power supplied to coil 14a in the first operation ("A") of Figure 5, and Figure 14(b) shows the power supplied to coil 14b in the first operation ("A") of Figure 5. The lower part of Figure 14(a) also shows the current waveform flowing through coil 14a, and the lower part of Figure 14(b) also shows the current waveform flowing through coil 14b.

[0125] Here, the symbols in Figures 14(a) and 14(b) represent the following meanings. P1H: Instantaneous power supply to coil 14a P2L: Instantaneous power supply to coil 14b <p1h>: Average power supplied to coil 14a <p2l>: Average power supplied to coil 14b fa: On / Off switching frequency fs1: Frequency of the current flowing through coil 14a fs2: Frequency of the current flowing through coil 14b d1: On-time ratio of coil 14a d2: On-time ratio of coil 14b Furthermore, the relationship d1 + d2 < 1 holds true. That is, there exists a period when both the first and second inverters are turned off simultaneously.

[0126] Figure 15(a) shows the power supplied to coil 14a in the second operation ("B") of Figure 5, and Figure 15(b) shows the power supplied to coil 14b in the second operation ("B") of Figure 5. Figure 15(a) also shows the current waveform flowing through coil 14a, and Figure 15(b) also shows the current waveform flowing through coil 14b.

[0127] Here, the symbols in Figures 15(a) and 15(b) represent the following meanings. P1L: Instantaneous power supply to coil 14a P2H: Instantaneous power supply to coil 14b <p1l>: Average power supplied to coil 14a <p2h>: Average power supplied to coil 14b fa: On / Off switching frequency fs1: Frequency of the current flowing through coil 14a fs2: Frequency of the current flowing through coil 14b d3: On-time ratio of coil 14a d4: On-time ratio of coil 14b Furthermore, the relationship d3 + d4 < 1 holds true. That is, there exists a period when both the first inverter and the second inverter are turned off simultaneously.

[0128] In Figure 14, <p1h>Align it with the solid lines in Figures 5 and 8, <p2l>By assigning "d1", "d2", "P1H", and "P2L" to align with the dashed lines in Figures 5 and 8, the first operation ("A") in Figures 5 and 8 can be realized. Similarly, in Figure 15, <p1l>Align it with the solid lines in Figures 5 and 8, <p2h>By assigning "d3", "d4", "P1L", and "P2H" to align with the dashed lines in Figures 5 and 8, the second operation ("B") in Figures 5 and 8 can be realized.

[0129] In this embodiment, the power supply operation to coils 14a and 14b is intermittent. However, if the on / off switching frequency fa is sufficiently short compared to the time constant of the furnace temperature change, the intermittent operation does not affect the furnace temperature change. Furthermore, if the switching frequency of the first inverter 202a (frequency fs1 of the current flowing through coil 14a) and the switching frequency of the second inverter 202b (frequency fs2 of the current flowing through coil 14b) are sufficiently higher than the on / off switching frequency fa, induction heating becomes possible.

[0130] From the above, as shown in Figures 5 and 8, when there is an output from one coil, the output of the other coil is not zero. However, by performing the exclusive operation shown in Figure 14 or 15, it is possible to achieve the outputs in Figures 5 and 8 while simultaneously suspending the power supply to the other coil while power is being supplied to the first coil. Therefore, by operating the first inverter 202a, which supplies current to coil 14a, and the second inverter 202b, which supplies current to coil 14b, exclusively, malfunctions of the first inverter 202a or the second inverter 202b due to electromagnetic interference can be avoided, resulting in stable operation. Furthermore, according to this embodiment, since electromagnetic interference can be suppressed, there is no need to provide a magnetic shield between coil 14a and coil 14b, thus enabling cost reduction of the single crystal manufacturing equipment.

[0131] <Other features> Next, other features of this embodiment will be described.

[0132] In the single crystal manufacturing apparatus 100 of this embodiment, for example, as shown in Figure 1, the heating section 25a includes a coil 14a positioned opposite the side surface of the crucible 12 which is placed on the base 11, and the heating section 25b includes a coil 14b positioned opposite the base 11 which is located below the crucible 12 containing the solution 20. In this regard, another feature of this embodiment is that the coil 14b is positioned opposite the base 11 which is located below the solution 20 contained in the crucible 12.

[0133] As a result, the heating unit 25b can heat the base 11 by induction heating, which occurs when a high-frequency current is passed through a coil 14b located opposite the base 11. Then, the bottom surface of the crucible 12 can be heated by heat conduction from the heated base 11.

[0134] In detail, heat is transferred from the base 11, which is heated by the heating unit 25b, to the heat transfer unit 12a, and then from the heat transfer unit 12a to the crucible 12 (main body), heating the bottom surface of the crucible 12 that is in contact with the solution 20. That is, the heating unit 25b is configured to indirectly heat the bottom surface of the crucible 12 that is in contact with the solution via the base 11 by an induction heating phenomenon caused by passing a high-frequency current through a coil 14b located opposite the base 11 that supports the crucible 12. Thus, another characteristic feature is that the coil 14b, which is located on the outer side of the heat insulating member 13c, is positioned opposite the base 11, which is located below the solution 20 contained in the crucible 12, so that the bottom surface of the crucible 12 that is in contact with the solution 20 can be heated by the coil 14b.

[0135] As a result, according to the other features, the base 11 is heated by the induction heating phenomenon caused by passing a high-frequency current through the coil 14b, and the bottom surface of the crucible 12 in contact with the solution 20 is indirectly heated by heat conduction from the heated base 11. In other words, the technical significance of the other features lies in the fact that, instead of directly heating the bottom surface of the crucible 12 in contact with the solution 20, the coil 14b is positioned opposite the base 11 (other features), and a configuration is adopted in which the base 11 on which the crucible 12 is placed is heated, rather than the crucible 12 itself, thereby indirectly heating the bottom surface of the crucible 12 via the base 11.

[0136] <Further features> As described above, the first characteristic feature of this embodiment is that, for example, as shown in Figures 5 and 8, a first operation ("A") is performed by adjusting the power supplied to the heating unit 25a and the power supplied to the heating unit 25b to raise the temperature of the solution 20 in contact with the side surface of the crucible 12 higher than the temperature of the solution 20 in contact with the bottom surface of the crucible 12, and a second operation ("B") is performed by adjusting the power supplied to the heating unit 25a and the power supplied to the heating unit 25b to raise the temperature of the solution 20 in contact with the bottom surface of the crucible 12 higher than the temperature of the solution 20 in contact with the side surface of the crucible 12.

[0137] In this regard, this embodiment has another distinctive feature in that it adjusts the power supplied to the heating unit 25a and the power supplied to the heating unit 25b. That is, the other distinctive feature is that the power supplied to the heating unit 25a and the power supplied to the heating unit 25b are made different in order to realize the first operation and the second operation described above. In other words, the other distinctive feature is that the first operation and the second operation described above are realized simply by adopting a configuration in which the power supplied to the heating unit 25a and the power supplied to the heating unit 25b are made different. As a specific example, as shown in Figures 5 to 8, in order to realize the first operation, the "first power" supplied to the heating unit 25a is made greater than the "second power" supplied to the heating unit 25b. On the other hand, in order to realize the second operation, the "third power" supplied to the heating unit 25a is made greater than the "fourth power" supplied to the heating unit 25b. In this case, the "first power" is greater than the "third power," and the "second power" is less than the "fourth power." This allows for the implementation of both the first and second operations, in a specific example.

[0138] Thus, according to another feature, by simply differentiating the power supplied to the heating unit 25a and the power supplied to the heating unit 25b, the temperature of the solution 20 in contact with the sides and bottom of the crucible 12 can be periodically changed between the temperature at which impurities precipitate and the temperature at which impurities dissolve. As a result, according to this embodiment, the amount of impurities that precipitate can be reduced and the enlargement of impurities can be suppressed, thereby suppressing the deterioration of the quality of silicon carbide single crystals caused by impurities.

[0139] <Verification of effects based on experimental results> Next, based on actual experimental results rather than simulation results, we will explain how this embodiment can reduce the amount of unwanted crystals generated in the solution.

[0140] A distinctive feature of this embodiment is that, as shown in Figures 5 and 8, for example, a first operation ("A") is performed by adjusting the power supplied to the heating unit 25a and the power supplied to the heating unit 25b to raise the temperature of the solution 20 in contact with the side surface of the crucible 12 higher than the temperature of the solution 20 in contact with the bottom surface of the crucible 12, and a second operation ("B") is performed by adjusting the power supplied to the heating unit 25a and the power supplied to the heating unit 25b to raise the temperature of the solution 20 in contact with the bottom surface of the crucible 12 higher than the temperature of the solution 20 in contact with the side surface of the crucible 12.

[0141] Hereafter, the first operation (first heating step) described above will be referred to as "side heating," and the second operation (second heating step) described above will be referred to as "bottom heating." Furthermore, the operation of switching between the first and second operations alternately (a feature in this embodiment) will be referred to as "heating switching."

[0142] Figure 16 is a graph showing the power supply current supplied to coil 14a during the experiment. In Figure 16, the horizontal axis represents time (hours), while the vertical axis represents the value (A) of the power supply current supplied to coil 14a.

[0143] In Figure 16, the solid line shows the relationship between power supply current and time in "side heating." The dotted line shows the relationship between power supply current and time in "bottom heating," and the dashed line shows the relationship between power supply current and time in "heating switching."

[0144] Figure 17 is a graph showing the power supply current supplied to coil 14b during the experiment. In Figure 17, the horizontal axis represents time (hour), while the vertical axis represents the value (A) of the power supply current supplied to coil 14a.

[0145] In Figure 17, the solid line shows the relationship between power supply current and time during "side heating." The dotted line shows the relationship between power supply current and time during "bottom heating," and the dashed line shows the relationship between power supply current and time during "heating switching."

[0146] The experiment was conducted under the conditions shown in Figures 16 and 17 above. The power supply current was switched at the following timings: side heating 6 hours, switch 10 minutes, bottom heating 5 hours 50 minutes, switch 10 minutes, side heating 5 hours 50 minutes, switch 10 minutes, bottom heating 5 hours 50 minutes. After the solution contained in the crucible was cooled and solidified, a cross-sectional view was obtained by cutting the crucible. The experimental results will be explained below using the cross-sectional view obtained in this way.

[0147] Figure 18 is a cross-sectional view of the crucible 12 containing the solidified solution 20 during "side heating". In Figure 18, no miscellaneous crystals were observed in region RA on the side of the crucible 12, and it was confirmed that the side of the crucible 12 was dissolved to a maximum of about 3 mm. On the other hand, miscellaneous crystals of about 2 mm were observed in region RB on the bottom surface of the crucible 12.

[0148] This can be qualitatively understood by considering that in "side heating," the temperature of the solution 20 in contact with the side of the crucible 12 is higher than the temperature of the solution 20 in contact with the bottom of the crucible 12. As a result, miscellaneous crystals dissolve on the side of the crucible 12, while miscellaneous crystals precipitate on the bottom of the crucible 12.

[0149] Next, Figure 19 is a cross-sectional view of the crucible 12 containing the solidified solution 20 during "bottom heating". In Figure 19, it was confirmed that large miscellaneous crystals of about 5 mm in size were observed in region RA on the side of the crucible 12. On the other hand, no miscellaneous crystals were observed in region RB on the bottom of the crucible 12, and it was confirmed that the bottom of the crucible 12 was dissolved to a maximum of about 4 mm. Furthermore, miscellaneous crystals of about 1 mm in size were observed in region RC on the bottom of the crucible 12.

[0150] This can be qualitatively understood by considering that in "bottom heating," the temperature of the solution 20 in contact with the bottom surface of the crucible 12 is higher than the temperature of the solution 20 in contact with the sides of the crucible 12. As a result, while small crystals dissolve and even if small crystals form at the bottom surface of the crucible 12, larger crystals tend to precipitate at the sides of the crucible 12.

[0151] Next, Figure 20 is a cross-sectional view of the crucible 12 containing the solidified solution 20 during the "heating switching" stage. In Figure 20, in region RA on the side of the crucible 12, small-sized miscellaneous crystals were observed, and it was confirmed that the side of the crucible 12 was dissolved to a maximum of about 1 mm. On the other hand, in region RB on the bottom of the crucible 12, no miscellaneous crystals were observed, and it was confirmed that the bottom of the crucible 12 was dissolved to a maximum of about 2 mm. In addition, in region RC on the bottom of the crucible 12, miscellaneous crystals of about 1 mm were observed.

[0152] In the "heating switching" function, a first operation is performed to raise the temperature of the solution 20 in contact with the side surface of the crucible 12 to a higher temperature than the solution 20 in contact with the bottom surface of the crucible 12, and a second operation is performed to raise the temperature of the solution 20 in contact with the bottom surface of the crucible 12 to a higher temperature than the solution 20 in contact with the side surface of the crucible 12. These operations are alternately switched. Thus, in the "heating switching" function, the temperatures of the solutions 20 in contact with the side surface and the bottom surface of the crucible 12 can be periodically changed between the temperature at which miscellaneous crystals precipitate and the temperature at which miscellaneous crystals dissolve. Therefore, as shown in the experimental results in Figures 18 to 20, it can be qualitatively understood that in the "heating switching" function, the amount of miscellaneous crystals precipitated can be reduced and the growth of miscellaneous crystals can be suppressed compared to "side heating" and "bottom heating," and furthermore, the dissolution of the crucible 12 can also be suppressed.

[0153] Based on the above experimental results, it is confirmed that "heating switching" can reduce the amount of precipitated non-crystals and suppress the enlargement of non-crystals compared to "side heating" or "bottom heating," and furthermore, it can suppress the dissolution of crucible 12. Therefore, the experimental results confirm that the basic concept in this embodiment is an effective technical concept in that it can suppress the deterioration of the quality of silicon carbide single crystals caused by non-crystals (for example, in that silicon carbide single crystals without non-crystals can be obtained).

[0154] Although the present invention has been specifically described above based on its embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from its essence. [Explanation of Symbols]

[0155] 10 containers 11 Pedestal 12 Crucible 12a Heat transfer section 13a Insulation material 13b Insulation material 13c Insulation material 14a coil 14b coil 15 Crucible lid 15a Cylindrical member 15b Connecting member 16 Crystal holding shaft 16a Fin structure 17 Thermocouples 18 Crucible holding shaft 20 solution 25a Heating section 25b Heating section 30 seed crystals 40 Silicon carbide single crystal 50 Control Unit 100 Single crystal manufacturing equipment 200A First Commercial Power Supply 200b 2nd commercial power supply 201a First AC / DC Converter 201b Second AC / DC Converter 202a First Inverter 202b Second Inverter 203a Transformer No. 1 203b Second Transformer 210 Control Unit

Claims

1. (a) A step of moving an axis with a seed crystal attached to its tip downward so that the lower surface of the seed crystal comes into contact with a solution containing carbon and silicon contained in a crucible, (b) A step of growing a single crystal made of silicon carbide on the lower surface of the seed crystal, A single crystal manufacturing method comprising, (c1) A first heating step of heating the solution so that the temperature of the solution in contact with the side surface of the crucible is higher than the temperature of the solution in contact with the bottom surface of the crucible, (c2) A second heating step of heating the solution so that the temperature of the solution in contact with the bottom surface of the crucible is higher than the temperature of the solution in contact with the side surface of the crucible, It has, The single crystal manufacturing apparatus for carrying out the above single crystal manufacturing method is A first heating unit heats the crucible by passing a high-frequency current through a first coil provided at a position opposite the side surface of the crucible, A second heating unit heats the base by passing a high-frequency current through a second coil provided at a position opposite the base supporting the crucible, It has, In the first heating step, by adjusting the power supplied to the first heating unit and the power supplied to the second heating unit, the temperature of the solution in contact with the side surface of the crucible is made higher than the temperature of the solution in contact with the bottom surface of the crucible. In the second heating step, by adjusting the power supplied to the first heating unit and the power supplied to the second heating unit, the temperature of the solution in contact with the bottom surface of the crucible is made higher than the temperature of the solution in contact with the side surface of the crucible. A method for manufacturing single crystals, comprising alternately switching between the first heating step and the second heating step.

2. In the single crystal manufacturing method described in claim 1, In the first heating step, the temperature of the solution in contact with the side surface of the crucible is the temperature at which miscellaneous crystals dissolve, while the temperature of the solution in contact with the bottom surface of the crucible is the temperature at which miscellaneous crystals precipitate. A method for producing a single crystal, wherein in the second heating step, the temperature of the solution in contact with the bottom surface of the crucible is the temperature at which miscellaneous crystals dissolve, while the temperature of the solution in contact with the side surface of the crucible is the temperature at which miscellaneous crystals precipitate.

3. In the single crystal manufacturing method described in claim 1, A single crystal manufacturing method comprising the first heating step and the second heating step being carried out while alternately switching between them in step (b).

4. In the single crystal manufacturing method described in claim 1, A method for producing a single crystal, wherein either the first heating step or the second heating step is performed in step (b) after performing step (a), while the other of the first heating step or the second heating step is performed with the single crystal grown on the lower surface of the seed crystal separated from the surface of the solution.

5. In the single crystal manufacturing method described in claim 1, A single crystal manufacturing method wherein the alternating switching between the first heating step and the second heating step is performed at predetermined time intervals.

6. (a) Moving an axis with a seed crystal attached to its tip downward so that the lower surface of the seed crystal comes into contact with a solution containing carbon and silicon contained in a crucible, (b) A step of growing a single crystal made of silicon carbide on the lower surface of the seed crystal, A single crystal manufacturing method comprising, (c1) A first heating step of heating the solution so that the temperature of the solution in contact with the side surface of the crucible is higher than the temperature of the solution in contact with the bottom surface of the crucible, (c2) A second heating step of heating the solution so that the temperature of the solution in contact with the bottom surface of the crucible is higher than the temperature of the solution in contact with the side surface of the crucible, It has, The single crystal manufacturing apparatus for carrying out the above single crystal manufacturing method is A first coil is provided at a position opposite to the side surface of the crucible, A second coil is provided at a position opposite to the base supporting the crucible, It has, Each of the first heating step and the second heating step supplies power to the first coil and the second coil respectively such that the period during which power is supplied to the first coil and the period during which power is supplied to the second coil do not overlap. A method for manufacturing single crystals, comprising alternately switching between the first heating step and the second heating step.

7. (a) Moving an axis with a seed crystal attached to its tip downward so that the lower surface of the seed crystal comes into contact with a solution containing carbon and silicon contained in a crucible, (b) A step of growing a single crystal made of silicon carbide on the lower surface of the seed crystal, A single crystal manufacturing method comprising, (c1) A first heating step of heating the solution so that the temperature of the solution in contact with the side surface of the crucible is higher than the temperature of the solution in contact with the bottom surface of the crucible, (c2) A second heating step of heating the solution so that the temperature of the solution in contact with the bottom surface of the crucible is higher than the temperature of the solution in contact with the side surface of the crucible, It has, The single crystal manufacturing apparatus for carrying out the above single crystal manufacturing method is A first coil is provided at a position opposite to the side surface of the crucible, A first inverter for supplying power to the first coil, A second coil is provided at a position opposite to the base supporting the crucible, A second inverter for supplying power to the second coil, A control unit that controls the operation of the first inverter and the operation of the second inverter, It has, Each of the first heating step and the second heating step is performed by the exclusive operation of the first inverter and the second inverter by the control unit. A method for manufacturing single crystals, comprising alternately switching between the first heating step and the second heating step.

8. In the single crystal manufacturing method described in claim 1, A method for producing a single crystal, wherein the second coil is positioned opposite the base, which is located below the solution contained in the crucible.

9. In the single crystal manufacturing method described in claim 1, In the first heating step, the first power supplied to the first heating unit is greater than the second power supplied to the second heating unit. In the second heating step, the third power supplied to the first heating unit is greater than the fourth power supplied to the second heating unit. The first power is greater than the third power. A single crystal manufacturing method wherein the second power is smaller than the fourth power.

10. A single crystal manufacturing apparatus capable of arranging a crucible containing a solution of carbon and silicon inside a container, A base placed inside the container, A first heating unit for heating the crucible which is placed on the base, A second heating section for heating the base, A control unit that controls the power supplied to the first heating unit and the power supplied to the second heating unit, Equipped with, The control unit, A first operation involves adjusting the power supplied to the first heating unit and the power supplied to the second heating unit so that the temperature of the solution in contact with the side surface of the crucible is higher than the temperature of the solution in contact with the bottom surface of the crucible. A second operation involves adjusting the power supplied to the first heating unit and the power supplied to the second heating unit so that the temperature of the solution in contact with the bottom surface of the crucible is higher than the temperature of the solution in contact with the side surface of the crucible. A single crystal manufacturing apparatus that alternately switches between two states.

11. In the single crystal manufacturing apparatus according to claim 10, The first heating unit induces heating of the crucible, The second heating section is a single crystal manufacturing apparatus that induces heating of the base.

12. In the single crystal manufacturing apparatus according to claim 10 or 11, The aforementioned crucible is, A main body containing the aforementioned solution, A heat transfer section protruding from the bottom of the main body, It has, In the single crystal manufacturing apparatus, the heat transfer unit is brought into contact with the base, thereby heating the crucible by heat conduction from the base, which is heated by the second heating unit, through the heat transfer unit.

13. In the single crystal manufacturing apparatus according to claim 12, The aforementioned base is, A first region that comes into contact with the heat transfer section, The second region enclosed by the first region, The third region surrounding the first region, Includes, The single crystal manufacturing apparatus has a heat insulating member that is in contact with at least one of the second region and the third region.

14. In the single crystal manufacturing apparatus according to claim 10, The first heating section includes a first coil, The second heating section includes a second coil, A single crystal manufacturing apparatus in which the first operation and the second operation of the control unit can be performed by supplying power to the first coil and the second coil, respectively, such that the period for supplying power to the first coil and the period for supplying power to the second coil do not overlap.

15. In the single crystal manufacturing apparatus according to claim 10, The first heating section is, The first coil and A first inverter for supplying power to the first coil, Includes, The aforementioned second heating section is The second coil and A second inverter for supplying power to the second coil, Includes, A single crystal manufacturing apparatus in which the first operation and the second operation of the control unit can each be performed by the exclusive operation of the first inverter and the second inverter by the control unit.

16. In the single crystal manufacturing apparatus according to claim 10, The first heating unit includes a first coil provided at a position that can face the side surface of the crucible, which can be positioned above the base, A single crystal manufacturing apparatus, wherein the second heating section includes a second coil positioned opposite the base on which the crucible containing the solution can be positioned above.

17. In the single crystal manufacturing apparatus according to claim 10, In the first operation performed by the control unit, the first power supplied to the first heating unit is greater than the second power supplied to the second heating unit. In the second operation performed by the control unit, the third power supplied to the first heating unit is greater than the fourth power supplied to the second heating unit. The first power is greater than the third power. A single crystal manufacturing apparatus in which the second power is smaller than the fourth power.

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