JP2012136388A - APPARATUS FOR MANUFACTURING SiC SINGLE CRYSTAL AND CRUCIBLE USED FOR THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing SiC single crystal, which is easy to supply carbon in the vicinity of an SiC seed crystal in manufacturing the SiC single crystal by a solution growth method.SOLUTION: A crucible 6 in the manufacturing apparatus 100 includes: an upper storage chamber 621A having an inner diameter IDT; and a lower storage chamber 622A arranged at a lower part of the upper storage chamber 621A, which has an inner diameter smaller than the inner diameter IDT. An induction heating device 3 includes: an upper coil part 311 arranged around the upper storage chamber 621A; and a lower coil part 312 arranged around the lower storage chamber 622A. The lower coil part 312 generates an electromagnetic force larger than the electromagnetic force the upper coil part 311 generates in an SiC solution 8 in the upper storage chamber 621A, in the SiC solution 8 in the lower storage chamber 622A.

Description

  The present invention relates to an apparatus for producing a silicon carbide (SiC) single crystal and a crucible used therefor, and more particularly to an apparatus for producing an SiC single crystal by a solution growth method and a crucible used therefor.

  Silicon carbide (SiC) is a thermally and chemically stable compound semiconductor. SiC has a superior band gap, breakdown voltage, electron saturation rate and thermal conductivity compared to silicon (Si). For this reason, SiC is expected to be applied to technical fields such as power device materials with low operation loss, high-voltage high-frequency device materials, environment-resistant devices used in high-temperature environments, and radiation-resistant devices. In these technical fields, high-quality SiC single crystals with few crystal defects are required.

  The SiC single crystal production method includes a sublimation method and a solution growth method. The solution growth method can produce a SiC single crystal with fewer crystal defects than the sublimation method. In the SiC single crystal solution growth method, an SiC seed crystal is immersed in a solution (hereinafter referred to as an SiC solution) in which carbon (C) is dissolved in a melt containing Si or Si and an additive element. It is a method of training. Generally, a graphite crucible is used, and carbon is dissolved from the crucible and supplied into the SiC solution. The SiC seed crystal is attached to the lower end surface of the rod-shaped seed shaft and immersed in the SiC solution.

  In the solution growth method, the temperature of the peripheral portion of the immersed SiC seed crystal in the SiC solution is set lower than that of other SiC solution portions. Thereby, SiC around the SiC seed crystal is brought into a supersaturated state, and the growth of the SiC single crystal is promoted.

  As described above, the solution growth method can produce an SiC single crystal with fewer crystal defects than the sublimation method. However, the growth rate of the SiC single crystal in the liquid crystal growth method is slower than that in the sublimation method. For example, in the conventional solution growth method, when a pure Si solution at 1650 ° C. is used, the growth rate of the SiC single crystal in the liquid crystal growth method is about 5 to 12 μm / hr. This growth rate is 1/10 or less of the growth rate of the SiC single crystal in the sublimation method.

  The growth rate RA (m / s) of the SiC single crystal in the solution growth method is defined by the Wilson-Frenkel equation shown in the equation (A).

RA = A0 × ΔC × exp (−ΔG / (k × t)) (A)
Here, A0 is a coefficient. ΔC is the degree of supersaturation of carbon (unit: mol / m 3). ΔG is energy (unit: J / mol) required to remove solvent molecules from solute molecules. k is a gas constant (unit: J / K · mol). t is the absolute temperature (K).

  From formula (A), the growth rate RA of the SiC single crystal can be increased by increasing the degree of supersaturation (ΔC) of carbon in the SiC solution. If the amount of carbon supplied to the vicinity of the SiC seed crystal in the SiC solution is increased, the degree of carbon supersaturation (ΔC) can be increased.

  Japanese Patent Laying-Open No. 2006-117441 (Patent Document 1) discloses a technique for increasing the amount of carbon supplied to the vicinity of a SiC seed crystal. In Patent Document 1, an accelerated crucible rotation technique (hereinafter referred to as ACRT method) is applied to a solution growth method of a SiC single crystal. In the ACRT method, acceleration and deceleration are repeated with respect to the rotation of the SiC seed crystal and the rotation of the crucible. Thereby, a SiC solution is stirred and carbon becomes easy to be supplied to a SiC seed crystal vicinity.

JP 2006-117441 A

  However, even in a method other than the ACRT method, it is preferable that carbon is easily supplied to the vicinity of the SiC seed crystal.

  An object of the present invention is to provide an apparatus for producing an SiC single crystal that can easily supply carbon to the vicinity of an SiC seed crystal in an SiC solution in producing an SiC single crystal by a solution growth method.

  A manufacturing apparatus according to an embodiment of the present invention includes a crucible capable of storing a SiC solution, a chamber, a seed shaft, and an induction heating apparatus. The chamber houses the crucible. The seed shaft extends in the vertical direction of the chamber, and an SiC seed crystal immersed in the SiC solution is attached to the lower end. The induction heating device is disposed in the chamber and around the crucible. The crucible includes an upper storage chamber and a lower storage chamber. The upper storage chamber is disposed at the upper portion of the crucible and has a first inner diameter. The lower storage chamber is disposed below the upper storage chamber and has a second inner diameter that is smaller than the first inner diameter. The induction heating device includes an upper coil part, a lower coil part, and a power source. The upper coil portion is disposed around the upper storage chamber. The lower coil portion is disposed around the lower storage chamber, and generates an electromagnetic force in the SiC solution in the lower storage chamber that is larger than the electromagnetic force generated by the upper coil portion in the SiC solution in the upper storage chamber. The power supply supplies current to the upper coil portion and the lower coil portion.

  In the SiC single crystal manufacturing apparatus according to the embodiment of the present invention, the pressure and temperature of the SiC solution in the lower storage chamber are likely to be higher than the pressure and temperature of the SiC solution in the upper storage chamber. Therefore, the SiC solution in the lower storage chamber tends to rise toward the SiC seed crystal, and carbon near the SiC seed crystal is easily supplied.

  The crucible according to the present embodiment is used in the manufacturing apparatus described above. The manufacturing method of the SiC single crystal according to the present embodiment uses the manufacturing apparatus described above.

FIG. 1 is a configuration diagram of a SiC single crystal manufacturing apparatus according to the first embodiment. FIG. 2 is a configuration diagram of the crucible and the induction heating device in FIG. FIG. 3A is a flow velocity vector distribution diagram of the SiC solution in the crucible in FIG. FIG. 3B is a schematic diagram of a flow pattern in the SiC solution of FIG. 3. FIG. 4 is a configuration diagram of a SiC single crystal manufacturing apparatus according to the second embodiment. FIG. 5 is a configuration diagram of a crucible having a shape different from those in FIGS. 1 and 4. FIG. 6 is a configuration diagram of a crucible having a shape different from that of FIGS. 1, 4, and 5. FIG. 7 is a configuration diagram of a crucible having a shape different from those in FIGS. 1 and 4 to 6. FIG. 8 is a configuration diagram of a crucible having a shape different from those in FIGS. 1 and 4 to 7. FIG. 9 is a configuration diagram of a crucible having a shape different from those in FIGS. 1 and 4 to 8. 10A is a flow velocity vector distribution diagram of the SiC solution in the crucible obtained by the simulation of Example 1. FIG. FIG. 10B is a flow velocity vector distribution diagram of the SiC solution in the crucible different from that of FIG. 10A obtained by the simulation of Example 1. FIG. 10C is a flow velocity vector distribution diagram of the SiC solution in the crucible different from that of FIG. 10A and FIG. 10B obtained by the simulation of Example 1. FIG. 11 is a diagram showing the relationship between the ratio of the inner diameter of the lower storage chamber in the crucible in FIG. 1 to the inner diameter of the upper storage chamber and the average flow velocity of the upward flow generated in the crucible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[First Embodiment]
[Configuration of SiC single crystal manufacturing equipment]
FIG. 1 is a configuration diagram of a SiC single crystal manufacturing apparatus according to the present embodiment. Referring to FIG. 1, manufacturing apparatus 100 includes a chamber 1, a heat insulating member 2, an induction heating device 3, an elevating device 4, a rotating device 5, and a crucible 6.

  The chamber 1 is a housing and houses the heat insulating member 2, the induction heating device 3, and the crucible 6. When the SiC single crystal is manufactured, the chamber 1 is water-cooled.

  The rotating device 5 includes a rotating member 51 and a drive source 52. The rotating member 51 has a rod shape and extends in the vertical direction of the manufacturing apparatus 100. The crucible 6 is disposed at the upper end of the rotating member 51. The crucible 6 may be fixed to the upper end of the rotating member 51. The lower end portion of the rotating member 51 is connected to the drive source 52. When manufacturing the SiC single crystal, the rotating device 5 rotates the crucible 6. Specifically, the drive source 52 rotates the rotating member 51. Therefore, the crucible 6 rotates around the axis of the rotating member 51.

  The crucible 6 includes a main body 62 and a lid 61. The main body 62 is a housing whose upper end is open. The lid 61 is disposed at the upper end of the main body 62. The lid 61 is disk-shaped and has a through hole 611 at the center.

  The main body 62 is a cylindrical container having a step, and stores the SiC solution 8 therein. The SiC solution 8 is a raw material for SiC single crystal and contains silicon (Si) and carbon (C). The SiC solution 8 may further contain one or more metal elements other than Si and C. In other words, the SiC solution 8 is a solution in which carbon (C) is dissolved in a melt containing Si or Si and an additive element.

  The SiC solution 8 is generated by melting the raw material of the SiC solution by heating. The raw material may be a simple substance of Si or may contain Si and another metal element. The metal element contained in the raw material of the SiC solution is, for example, titanium (Ti), manganese (Mn), chromium (Cr), cobalt (Co), vanadium (V), iron (Fe), or the like. Preferred elements contained in the raw material of the SiC solution are Ti and Mn, and a more preferred element is Ti.

  The material of the crucible 6 is, for example, graphite. If the crucible 6 is made of graphite, the crucible 6 itself becomes a carbon source of the SiC solution. The material of the crucible 6 may be other than graphite. For example, the crucible 6 may be made of ceramics or a high melting point metal. When the crucible 6 cannot be used as a carbon supply source, the raw material of the SiC solution contains graphite (carbon).

  Preferably, at least the inner surface of the crucible 6 contains carbon. For example, a film made of SiC is formed on the inner surface of the crucible 6. In this case, carbon is dissolved in the SiC solution from the coating during the production of the SiC single crystal. More preferably, the crucible 6 contains carbon. In this case, the crucible 6 becomes a carbon supply source of the SiC solution.

  The lifting device 4 includes a seed shaft 41 and a drive source 42. The drive source 42 is disposed above the chamber 1. The seed shaft 41 has a rod shape and extends in the vertical direction of the chamber 1. The lower end of the seed shaft 41 is disposed in the chamber 1, and the upper end is disposed above the chamber 1. That is, the seed shaft 41 penetrates the chamber 1. The seed shaft 41 is disposed coaxially with the rotating member 51.

  The upper end portion of the seed shaft 41 is connected to the drive source 42. The drive source 42 moves the seed shaft 41 up and down. The drive source 42 further rotates the seed shaft 41 around the central axis of the seed shaft 41.

  The seed shaft 41 is inserted into the through hole 611 of the lid 61. The lower end of the seed shaft 41 is disposed in the crucible 6. The seed shaft 41 has a lower end surface 410 at the lower end. The SiC seed crystal 9 is attached to the lower end surface 410.

  The SiC seed crystal 9 has a disk shape and is made of a SiC single crystal. When an SiC single crystal is manufactured by the solution growth method, an SiC single crystal is generated and grown on the surface of the SiC seed crystal 9. When producing a SiC single crystal having a 4H polymorph crystal structure, the SiC seed crystal 9 is preferably a single crystal having a 4H polymorph crystal structure. More preferably, the surface of SiC seed crystal 9 (corresponding to the lower surface of SiC seed crystal 9 in FIG. 1) is a (0001) plane or a plane inclined at an angle of 8 ° or less from (0001) plane. In this case, the SiC single crystal tends to grow stably.

  When the SiC single crystal is manufactured, the seed shaft 41 is lowered, and the SiC seed crystal 9 is immersed in the SiC solution 8 as shown in FIG. At this time, the SiC solution 8 is kept at the crystal growth temperature. The crystal growth temperature depends on the composition of the SiC solution 8. A typical crystal growth temperature is 1600 to 2000 ° C.

  The heat insulating member 2 has a housing shape, and includes a side wall, an upper lid, and a lower lid. The side wall of the heat insulating member 2 is disposed around the crucible 6. The upper lid of the heat insulating member 2 is disposed above the crucible 6. The upper lid has a through hole 21 through which the seed shaft 41 is passed. The lower lid of the heat insulating member 2 is disposed below the crucible 6. The lower lid has a through hole 22 through which the rotating member 51 is passed. In short, the heat insulating member 2 covers the entire crucible 6.

  The heat insulating member 2 includes a well-known heat insulating material. The heat insulating material is a fiber-based or non-fiber-based molded heat insulating material. In order to form a SiC single crystal having a diameter of 2 inches or more, it is necessary to maintain high heating efficiency. The heat insulating member 2 can maintain high heating efficiency. However, the heat insulating member 2 may not be provided.

  The induction heating device 3 is disposed around the crucible 6. In FIG. 1, the induction heating device 3 is arranged around the heat insulating member 2. The induction heating device 3 includes a coil 31 and a power source 32. Induction heating device 3 induction-heats crucible 6 and melts the raw material stored in crucible 6 to produce SiC solution 8. The induction heating device 3 further applies electromagnetic force to the SiC solution 8 in the crucible 6 to stir the SiC solution 8.

[Configuration of the crucible 6]
FIG. 2 is a configuration diagram of the crucible 6 and the induction heating device 3 in FIG. With reference to FIG. 2, the main body 62 of the crucible 6 is a housing | casing which the upper end opened. In this example, the main body 62 has a cylindrical shape having a step.

  The main body 62 includes an upper cylindrical portion 621, a lower cylindrical portion 622, an upper storage chamber 621A, and a lower storage chamber 622A. The upper cylinder part 621 is arranged on the upper part of the crucible 6. The upper cylinder portion 621 has a cylindrical shape with an upper end opened and has an outer diameter ODT. An upper storage chamber 621A is disposed in the upper cylinder portion 621. The upper storage chamber 621A has a cylindrical inner surface. The upper storage chamber 621A has an inner diameter IDT.

  The lower cylinder portion 622 is disposed below the upper cylinder portion 621. The lower cylindrical portion 622 is cylindrical and has an outer diameter ODB that is smaller than the outer diameter ODT. A flange 623 is formed at the upper end of the lower cylindrical portion 622, and the lower end of the upper cylindrical portion 621 is coupled to the outer peripheral edge of the flange 623. The upper cylinder part 621 and the lower cylinder part 622 are integrally formed. The lower storage chamber 622A has a cylindrical inner surface. The lower storage chamber 622A has an inner diameter IDB that is smaller than the inner diameter IDT.

  The entire lower storage chamber 622A and at least the lower portion of the upper storage chamber 621A are filled with the SiC solution 8. The lower storage chamber 622A has a role of forming an upward flow toward the SiC seed crystal 9 in the SiC solution 8. For this reason, the lower storage chamber 622 is preferably disposed directly below the SiC seed crystal 9 and the seed shaft 41, and is preferably disposed coaxially with the seed shaft 41. Preferably, the upper storage chamber 621A is disposed coaxially with the lower storage chamber 622A. In this case, the SiC solution 8 is easily convected in an axial symmetry. The lower storage chamber 622 overlaps with the SiC seed crystal 9 in plan view.

  The upper storage chamber 621A is partitioned by the inner surface of the upper cylindrical portion 621 and the upper surface of the flange 623 of the lower cylindrical portion 622. The upper surface of the flange 623 corresponds to the bottom surface of the upper storage chamber 621A. Hereinafter, the bottom surface of the upper storage chamber 621A is referred to as a “step bottom surface” 621B.

  The inner diameter IDT of the upper storage chamber 621A is larger than the inner diameter IDB of the lower storage chamber 622A. In this case, the fluid (SiC solution 8) in the lower storage chamber 622A rises toward the SiC seed crystal 9, then moves toward the outer periphery of the upper storage chamber 621A and returns to the lower storage chamber 622A. That is, convection including an upward flow toward the SiC seed crystal 9 is easily formed stably in the SiC solution 8 by the upper storage chamber 621A.

[Configuration of induction heating device]
The induction heating device 3 includes a coil 31 and a power source 32. The coil 31 includes an upper coil part 311 and a lower coil part 312. The lower coil portion 312 may be coupled to the upper coil portion 311 or may be a separate body.

  The upper coil portion 311 and the lower coil portion 312 receive supply of current from the power supply 32 and generate electromagnetic force in the SiC solution 8 of the crucible 6. The generated electromagnetic force is directed from the outer periphery of the SiC solution 8 toward the center. The SiC solution 8 is agitated by this electromagnetic force, and convection is generated in the SiC solution 8.

  The lower coil portion 312 is disposed around the outer peripheral surfaces of the lower storage chamber 622A and the lower cylindrical portion 622. Therefore, the lower coil portion 312 generates electromagnetic force in the SiC solution 8 in the lower storage chamber 622A. On the other hand, the upper coil portion 311 is disposed around the outer peripheral surfaces of the upper storage chamber 621A and the upper cylindrical portion 621. Therefore, the upper coil unit 311 generates electromagnetic force in the SiC solution 8 in the upper storage chamber 621A.

  The lower coil portion 312 generates an electromagnetic force in the SiC solution 8 in the lower storage chamber 622A that is larger than the electromagnetic force generated by the upper coil portion 311 in the SiC solution 8 in the upper storage chamber 621A. Therefore, an upward flow is generated in the SiC solution 8 in the lower storage chamber 622A.

  In this example, as shown in FIG. 2, the outer diameter ODB of the lower cylindrical portion 622 is smaller than the outer diameter ODT of the upper cylindrical portion 621. Further, the lower coil part 312 is disposed below the upper cylinder part 621 and around the lower cylinder part 622. Accordingly, the diameter of the lower coil portion 312 is smaller than the diameter of the upper coil portion 311.

  When the current value flowing through the upper coil part 311 is the same as the current value flowing through the lower coil part 312 and the number of turns of the upper coil part 311 is the same as the number of turns of the lower coil part 312, the smaller the coil diameter, Magnetic flux density increases. Therefore, the electromagnetic force of the lower coil part 312 is larger than that of the upper coil part 311. Furthermore, since the inner diameter IDB of the lower storage chamber 622A is smaller than the inner diameter IDT of the upper storage chamber 621A, it is easy to apply a large electromagnetic force to the SiC solution 8 in the lower storage chamber 622A. Furthermore, since the outer diameter ODB of the lower cylinder part 622 is smaller than the outer diameter ODT of the upper cylinder part 621, the thickness of the peripheral wall of the lower cylinder part 622 can be suppressed. Therefore, the electromagnetic wave generated from the lower coil portion 312 can be suppressed from being attenuated by the thickness of the peripheral wall, and the electromagnetic force generated in the SiC solution 8 in the lower storage chamber 622A can be increased.

  The lower coil part 312 may be separate from the upper coil part 311, and the lower coil part 312 may be connected to the upper coil part 311.

[Outline of operation of manufacturing apparatus 100]
By using the crucible 6 and the induction heating device 3 described above, the manufacturing apparatus 100 stirs the SiC solution 8 in the crucible 6 and makes it easy to supply carbon near the SiC seed crystal 9. Hereinafter, this point will be described.

  As described above, in order to increase the growth rate of the SiC single crystal in the solution growth method, the supersaturation degree (ΔC) of the carbon in the vicinity of the SiC seed crystal 9 in the SiC solution 8 may be increased. In order to increase the supersaturation degree of carbon in the vicinity of the SiC seed crystal 9, the carbon in the SiC solution may be easily transported to the vicinity of the SiC seed crystal 9 during the production of the SiC single crystal.

  In order to supply carbon in the vicinity of the SiC seed crystal 9, a flow distribution including an upward flow toward the SiC seed crystal 9 may be formed in the SiC solution 8. It is even better if the upward flow rate is fast.

  In the present embodiment, a lower storage chamber 622A is disposed directly below SiC seed crystal 9, and an upper storage chamber 621A that is larger than lower storage chamber 622A is disposed above lower storage chamber 622A. The electromagnetic force generated by the lower coil unit 312 is larger than the electromagnetic force generated by the upper coil unit 311. Further, the inner diameter IDB of the lower storage chamber 622A is smaller than the inner diameter IDT of the upper storage chamber 621A. Therefore, in the SiC solution 8 stored in the crucible 6, the pressure of the fluid in the lower storage chamber 622A is larger than the pressure of the fluid in the upper storage chamber 621A.

  Therefore, the fluid in the lower storage chamber 622A rises due to the pressure difference. The SiC seed crystal 9 is disposed directly above the lower storage chamber 622A. Therefore, the upward flow generated in the lower storage chamber 622 </ b> A is directed to the SiC seed crystal 9.

  3A and 3B are diagrams showing a flow pattern of the SiC solution 8 when the manufacturing apparatus 100 according to the present embodiment is used. 3A and 3B were obtained by the following numerical analysis simulation.

  As an axisymmetric RZ system, electromagnetic field analysis was calculated by the finite element method, and heat flow analysis was calculated by the difference method. A manufacturing apparatus having the same configuration as in FIG. 1 was set as a calculation model. The inner diameter IDT of the upper storage chamber 621A of the crucible 6 was 130 mm, and the inner diameter IDB of the lower storage chamber 622A was 40 mm (see FIG. 3B). The height HB of the SiC solution 8 stored in the lower storage chamber 622A was 35 mm, and the height HT of the SiC solution 8 stored in the upper storage chamber 621A was 25 mm. The outer diameter DS of the SiC seed crystal 9 and the seed shaft 41 was 50 mm. The diameter of the upper coil part 311 was 250 mm, and the diameter of the lower coil part 312 was 110 mm. The thickness T of the side wall of the upper cylinder part 621 and the lower cylinder part 622 was 10 mm. The frequency of the current flowing through the coil 31 was 6 kHz. Under the above conditions, the flow velocity vector in the SiC solution 8 was analyzed.

  FIG. 3A shows a flow velocity vector distribution in the SiC solution 8 obtained by simulation. FIG. 3B is a schematic diagram of a flow pattern in the SiC solution 8 of FIG. 3A. 3A and 3B are both cross-sectional views of the right half from the central axis of the crucible 6. And the direction of the arrow in FIG. 3A shows the direction through which the SiC solution 8 flows, and the length of the arrow shows the magnitude | size of the flow velocity.

  3A and 3B, the electromagnetic force generated in the fluid in the lower storage chamber 622A by the lower coil portion 312 is greater than the electromagnetic force generated in the fluid in the upper storage chamber 621A by the upper coil portion 311. large. Therefore, the pressure of the fluid in the lower storage chamber 622A becomes larger than the pressure of the fluid in the upper storage chamber 621A. Therefore, an upward flow F1 (see FIG. 3B) that rises right above the lower storage chamber 622A is formed.

  The upward flow F <b> 1 rises right above and moves toward the surface of the SiC seed crystal 9. Since the upward flow F1 contains carbon, carbon is supplied in the vicinity of the SiC seed crystal 9. After the fluid that has formed the upward flow F1 reaches the SiC seed crystal 9, it forms a diffusion flow F2 that flows toward the outer periphery of the upper storage chamber 621A. Since the inner diameter IDT of the upper storage chamber 621A is larger than the inner diameter IDB of the lower storage chamber 622A, the fluid can form a diffusion flow F2. The fluid that forms the diffusion flow F2 descends in the vicinity of the inner peripheral surface of the upper storage chamber 621A, and forms a downward flow F3 that returns to the lower storage chamber 622A. When carbon is contained in at least the inner surface of the crucible 6, the carbon dissolves from the inner surface of the crucible 6 and is contained in the fluid constituting the diffusion flow F2 and the downward flow F3. The fluid containing carbon returns to the lower storage chamber 622A on the downward flow F3. The fluid that has returned to the lower storage chamber 622 </ b> A forms the upward flow F <b> 1 again by the electromagnetic force of the lower coil portion 312.

  In short, the upward flow can be stably formed in the SiC solution 8 by the upper storage chamber 621A and the lower storage chamber 622A. Thereby, SiC solution 8 is stirred, and carbon in the SiC solution is easily supplied to the vicinity of SiC seed crystal 9. Further, when the crucible 6 contains carbon, the carbon dissolved from the crucible 6 into the SiC solution 8 can be supplied to the vicinity of the SiC seed crystal 9 by forming the upward flow F1.

  With the above mechanism, in manufacturing apparatus 100 according to the present embodiment, carbon is easily supplied in the vicinity of SiC seed crystal 9 in crucible 6.

  Preferably, when the height of the SiC solution 8 in the lower storage chamber 622A is HB and the height of the SiC solution in the upper storage chamber 621A is HT (see FIG. 3B), the crucible 6 satisfies the formula (1).

(HB / (HB + HT)) × (HT / (HB + HT)) 1/2> 17.5 (1)
The height HB of the SiC solution in the lower storage chamber 622A affects the flow velocity of the upward flow F1 rather than the height HT of the SiC solution 8 in the upper storage chamber 621A. The higher the height HB, the larger the volume of the fluid that forms the upward flow F1. Therefore, the upward flow F1 is likely to be formed, and the flow velocity is likely to increase. On the other hand, the height HT does not significantly affect the formation of the upward flow F1. The height HT only needs to secure a flow path (a space for forming the diffusion flow F2 and the downward flow F3) for returning the fluid forming the upward flow F1 from the upper storage chamber 621A back to the lower storage chamber 622A. Therefore, the height HT has a small contribution to the flow velocity of the upward flow F1. If the formula (1) is satisfied, the flow velocity of the upward flow F1 is significantly increased.
Preferably, the inner diameter IDB of the lower storage chamber 622A is 0.25 to 0.65 times the inner diameter IDT of the upper storage chamber 621A. In other words, IDB / IDT is 0.25 to 0.65.

When growing a SiC single crystal, the preferable flow rate of the upward flow F1 is 10 mm / s or more. When IDB / IDT exceeds 0.65, the step bottom 621B between the lower storage chamber 622A and the upper storage chamber 621A becomes too narrow. Therefore, the diffusion flow F2 and the downward flow F3 are not easily formed, and the fluid that has risen up to the upper storage chamber 621A is less likely to return to the lower storage chamber 622A. Therefore, the upward flow F1 is difficult to be stably formed, and the flow velocity of the upward flow F1 is reduced. On the other hand, when IDB / IDT is less than 0.25, the step bottom 621B becomes too wide, and the raised fluid stays above the step bottom 621B, making it difficult to return to the lower storage chamber 622A. Therefore, it is difficult to stably form the upward flow, and as a result, the flow velocity of the upward flow F1 is reduced. If IDB / IDT is in the range of 0.25 to 0.65, the flow rate of the upward flow F1 is 10 mm / s or more.
A more preferable range of IDB / IDT is 0.30 to 0.60. In this case, the flow velocity of the upward flow F1 is significantly increased. Even if IDB / IDT is outside the range of 0.25 to 0.65, the upward flow F1 is formed to some extent.

[Method for producing SiC single crystal]
A method for manufacturing a SiC single crystal using manufacturing apparatus 100 having the above-described configuration will be described. In the SiC single crystal manufacturing method, first, the manufacturing apparatus 100 is prepared, and the SiC seed crystal 9 is attached to the seed shaft 41 (preparation step). Next, the crucible 6 is arrange | positioned in the chamber 1, and the SiC solution 8 is produced | generated (SiC solution production | generation process). Next, the SiC seed crystal 9 is immersed in the SiC solution 8 in the crucible 6 (immersion process). Next, a SiC single crystal is grown (growing process). In the growing process, the lower coil portion 312 generates an electromagnetic force larger than that of the upper coil portion 311, so that the upward flow F <b> 1 is stably formed in the SiC solution 8. Thereby, the supersaturation degree of carbon in the vicinity of the seed crystal 9 is increased, and the growth of the SiC single crystal is promoted. Hereinafter, details of each process will be described.

[Preparation process]
First, the manufacturing apparatus 100 provided with the seed shaft 41 is prepared. Then, the SiC seed crystal 9 is attached to the lower end surface 410 of the seed shaft 41.

[SiC solution generation process]
Next, the crucible 6 is disposed on the rotating member 51 in the chamber 1. The crucible 6 stores a raw material for the SiC solution. The crucible 6 is preferably disposed coaxially with the rotating member 51. In this case, when the rotating member 51 rotates, the temperature of the SiC solution in the crucible 6 is easily kept uniform.

  Next, the SiC solution 8 is generated. The chamber 1 is filled with an inert gas. The inert gas is, for example, helium or argon. Next, the induction heating device 3 heats the raw material of the SiC solution 8 in the crucible 6 to the melting point or higher by induction heating. When carbon is contained in the crucible 6, when the crucible 6 is heated, the carbon is dissolved from the crucible 6 into the melt, and the SiC solution 8 is generated. When the crucible 6 does not contain carbon, the raw material of the SiC solution 8 contains carbon. The SiC solution 8 contains Si and C, and may further contain other metal elements.

[Immersion process]
Next, SiC seed crystal 9 is immersed in SiC solution 8. Specifically, the seed shaft 41 is lowered by the drive source 42 and the SiC seed crystal 9 is immersed in the SiC solution 8.

[Growth process]
After immersing the SiC seed crystal 9 in the SiC solution 8, the induction heating device 3 induction-heats the SiC solution 8 and maintains the SiC solution 8 at the crystal growth temperature. At this time, the electromagnetic force that the lower coil portion 312 applies to the SiC solution 8 in the lower storage chamber 622A is larger than the electromagnetic force that the upper coil portion 311 applies to the SiC solution 8 in the upper storage chamber 621A. Therefore, the upward flow F <b> 1 is stably generated below the SiC seed crystal 9.

  Further, the area around the SiC seed crystal of SiC solution 8 is supercooled to bring SiC into a supersaturated state. The method of cooling the area around the SiC seed crystal is as follows. For example, the induction heating device 3 is controlled so that the temperature in the peripheral region of the SiC seed crystal 9 is lower than the temperature in the other part of the SiC solution 8. Further, the peripheral area of SiC seed crystal 9 may be cooled by a refrigerant. Specifically, the refrigerant is circulated inside the seed shaft 41. The refrigerant is an inert gas such as argon or helium. If the coolant is circulated in the seed shaft 41, the SiC seed crystal 9 is cooled. When the SiC seed crystal 9 is cooled, the vicinity is also cooled. If the peripheral region of SiC seed crystal 9 is in a supercooled state by the above method, the SiC concentration is increased and the supersaturated state is obtained.

  Subsequently, the SiC seed crystal 9 and the SiC solution 8 are rotated while the SiC in the peripheral region of the SiC seed crystal 9 in the SiC solution 8 is in a supersaturated state. By rotating the seed shaft 41, the SiC seed crystal 9 rotates. By rotating the rotating member 51, the crucible 6 rotates. The rotation direction of SiC seed crystal 9 may be the reverse direction to the rotation direction of crucible 6 or the same direction. Further, the rotation speed may be constant or may vary. The seed shaft 41 gradually rises while rotating. At this time, a SiC single crystal is generated and grown on the surface of the SiC seed crystal 9 immersed in the SiC solution 8.

  During the growth of the SiC single crystal, the upward flow F1 is stably formed below the SiC seed crystal 9 as described above. Therefore, carbon is frequently supplied in the vicinity of SiC seed crystal 9, and the supersaturation degree of carbon in the vicinity of SiC seed crystal 9 is maintained high.

[Second Embodiment]
The SiC single crystal manufacturing apparatus according to the present embodiment is not limited to the configuration shown in FIG.

  FIG. 4 is a configuration diagram of a manufacturing apparatus 200 according to the second embodiment. With reference to FIG. 4, as compared with manufacturing apparatus 100, manufacturing apparatus 200 includes a new crucible 60 instead of crucible 6, and includes a new induction heating apparatus 30 instead of induction heating apparatus 3. Other configurations of the manufacturing apparatus 200 are the same as those of the manufacturing apparatus 100.

  Referring to FIG. 4, crucible 60 includes a lid 61 and a main body 63. The outer surface of the main body 63 is a cylinder having a constant outer diameter. The crucible 60 further has an upper storage chamber 621A and a lower storage chamber 622A. The inner diameter IDB of the lower storage chamber 622A is smaller than the inner diameter IDT of the upper storage chamber 621A. Therefore, in the main body 63, the side wall thickness TB of the portion where the lower storage chamber 622A is disposed is thicker than the side wall thickness TT of the portion where the upper storage chamber 621A is disposed.

  The induction heating device 30 includes an upper coil part 311 and a lower coil part 313. The lower coil part 313 has the same diameter as the upper coil part 311. The lower coil portion 313 is not coupled to the upper coil portion 311 and is separated from the upper coil portion 311. The power supply 32 applies a larger current to the lower coil unit 313 than the upper coil unit 311. Specifically, the lower coil unit 313 is configured such that the electromagnetic force generated in the lower storage chamber 622A by the lower coil unit 313 is larger than the electromagnetic force generated in the upper storage chamber 621A by the upper coil unit 311. Is supplied with a current larger than that of the upper coil portion 311.

  Similarly to the manufacturing apparatus 100, the manufacturing apparatus 200 having the above configuration can form the upward flow F1 in the SiC solution 8 while growing the SiC single crystal. Therefore, it is easy to supply carbon to the vicinity of SiC seed crystal 9 in SiC solution 8.

[Other embodiments]
The shape of the crucible used in the SiC single crystal manufacturing apparatus according to the embodiment of the present invention is not limited to FIGS. 1 and 4. For example, as shown in FIG. 5, the inner diameter of the lower storage chamber 622A in the crucible 6 may gradually increase from the lower end to the upper end of the lower storage chamber 622A. That is, the surface of the lower storage chamber 622A may have a tapered shape. Furthermore, the inner diameter of the upper storage chamber 621A in the crucible 6 may gradually increase from the lower end to the upper end of the upper storage chamber. That is, the surface of the upper storage chamber 621A may have a tapered shape. In this case, the inner diameter IDT of the upper storage chamber 621A is defined as the average of the inner diameters at the respective height positions from the upper end to the lower end of the upper storage chamber 621A. Similarly, the inner diameter IDB of the lower storage chamber 622A is defined as the average of the inner diameters at each height position from the upper end to the lower end of the lower storage chamber 622A.

  Furthermore, the surfaces of the upper storage chamber 621A and the lower storage chamber 622A may not be flat and may have a curvature. For example, as shown in FIG. 6, the longitudinal shape of the surfaces of the upper storage chamber 621A and the lower storage chamber 622A may be arcuate. In this case, the definitions of the inner diameter IDT of the upper storage chamber 621A and the inner diameter IDB of the lower storage chamber 622A are the same as those in FIG.

  Furthermore, the step bottom 621B of the upper storage chamber 621A may not be horizontal. For example, as shown in FIG. 7, the step bottom 621B may have a tapered shape.

  Further, as shown in FIG. 8, a storage chamber 623A having an inner diameter smaller than the inner diameter IDB of the lower storage chamber 622A may be disposed below the lower storage chamber 622A. The storage chamber 623A is connected to the lower end of the lower storage chamber 622A. Therefore, a step bottom 622B is formed between the lower storage chambers 622A and 623A.

  Furthermore, as shown in FIG. 9, a storage chamber 624A having an inner diameter larger than the inner diameter IDB may be disposed below the lower storage chamber 622A. The storage chamber 624A is connected to the lower end of the lower storage chamber 622A.

  Even in the manufacturing apparatus including the crucible 6 having the shape shown in FIGS. 8 and 9, the upward flow F <b> 1 can be generated in the crucible 6 as in the manufacturing apparatuses 100 and 200.

  The induction heating device used for the manufacturing apparatus in the embodiment of the present invention is not limited to the induction heating devices 3 and 30. The induction heating apparatus includes an upper coil portion and a lower coil portion, and the electromagnetic force generated in the SiC solution 8 in the lower storage chamber 622A by the lower coil portion is generated in the SiC solution 8 in the upper storage chamber 621A. It only needs to be larger than the electromagnetic force to be generated.

  Therefore, in the induction heating apparatus, the power supply causes the current I1 to flow through the upper coil portion and the current I2 having a frequency lower than the current I1 to flow through the lower coil portion, so that the penetration depth of the electromagnetic wave in the lower coil portion can be reduced. The electromagnetic force acting on the SiC solution 8 in the lower storage chamber 622A may be made larger than the electromagnetic force acting on the SiC solution 8 in the upper storage chamber 621A.

  Further, in the induction heating device, the lower coil portion can be obtained by making the number of turns (units / m) per unit length of the lower coil unit larger than the number of turns (units / m) of the upper coil unit. The electromagnetic force generated in the lower storage chamber 622A may be larger than the electromagnetic force generated by the upper coil portion in the upper storage chamber 621A.

  The crucible 6 preferably contains carbon. In this case, the carbon in the crucible 6 dissolves in the SiC solution and is conveyed below the SiC seed crystal 9 by the upward flow F1. Therefore, the supersaturation degree of carbon in the vicinity of SiC seed crystal 9 tends to increase. Preferably, the crucible 6 is made of graphite.

  In the above-described embodiment, the manufacturing apparatus 100 includes the heat insulating member 2. However, the manufacturing apparatus 100 may not include the heat insulating member 2.

  A manufacturing apparatus having the same configuration as that of the above-described SiC single crystal manufacturing apparatus 100 was prepared. A plurality of conditions with different heights of the SiC solution in the crucible 6 were set, and the flow pattern in the SiC solution was analyzed by numerical analysis simulation. Then, the flow rate of the SiC solution below the SiC seed crystal was obtained.

[Simulation method]
The simulation was performed as follows. As an axisymmetric RZ system, the electromagnetic field analysis was calculated by the finite element method, and the thermal flow analysis was calculated by the difference method. A manufacturing apparatus 100 having the same configuration as that of FIG. 1 is set as a calculation model. The inner diameter IDT of the upper storage chamber 621A of the crucible 6 was 130 mm, the inner diameter IDB of the lower storage chamber 622A of the crucible 6 was 40 mm, and the wall thickness T of the crucible 6 was 10 mm. The diameter of the SiC seed crystal 9 was 50 mm. Table 1 shows the height HT of the SiC solution 8 in the upper storage chamber 621A and the height HB of the SiC solution 8 in the lower storage chamber 622A. Each corner portion in the upper storage chamber 621A and the lower storage chamber 622A of the crucible 6 was provided with a curvature (corner R) of R = 10 mm.

  Under each condition of the height HT and the height HB, the E1 value obtained by the following formula (2) was calculated. Expression (2) corresponds to the left side of Expression (1).

E1 = (HB / (HB + HT)) × (HT / (HB + HT)) 1/2 (2)
In Table 1, E1 value in each condition of HB and HT is shown.

  Electromagnetic field analysis and heat flow analysis were performed for each setting condition in Table 1, and flow analysis results as shown in FIGS. 10A to 10C were obtained. FIG. 10A shows a flow velocity vector distribution in the SiC solution 8 in the crucible 6 when HT = 25 mm and HB = 40 mm. FIG. 10B shows the flow velocity vector distribution in the SiC solution 8 when HT = 25 mm and HB = 35 mm. FIG. 10C shows a flow velocity vector distribution of the SiC solution 8 when HT = 25 mm and HB = 30 mm.

  Based on the flow velocity vector distribution obtained under each condition in Table 1, a range between the center of the SiC seed crystal 9 and the end of the SiC seed crystal 9 at a position 5 mm below the lower end of the SiC seed crystal 9 (that is, The average flow velocity (mm / s) of 25 mm width) was calculated. The average flow rate was defined as plus (+) in the direction from the bottom to the top in the SiC solution 8.

[simulation result]
The calculated average flow velocity is shown in Table 2.

  The value in each field in Table 2 indicates the average flow velocity (mm / s). Referring to Tables 1 and 2, the average flow velocity was positive for each set condition, and the upward flow F1 was formed under any set condition. Furthermore, the average flow velocity under the setting conditions satisfying the equation (1) was significantly larger than the setting conditions not satisfying the equation (1) (the corresponding numerical values in Tables 1 and 2 are underlined).

  The flow pattern in the SiC solution 8 was analyzed by changing the inner diameter IDB of the lower storage chamber 622A while keeping the inner diameter IDT of the upper storage chamber 621A constant. Then, the flow rate of the SiC solution 8 below the SiC seed crystal 9 was obtained.

[Simulation method]
As in Example 1, as an axially symmetric RZ system, the electromagnetic field analysis was calculated by the finite element method, and the thermal flow analysis was calculated by the difference method. A manufacturing apparatus 100 having the same configuration as that of FIG. 1 is set as a calculation model. The inner diameter IDT of the upper storage chamber 621A was 130 mm, and the thickness T of the side wall of the crucible 6 was 10 mm. The height HT of the SiC solution 8 in the upper storage chamber 621A was 25 mm, and the height HB of the SiC solution 8 in the lower storage chamber 622A was 40 mm. Each corner portion in the upper storage chamber 621A and the lower storage chamber 622A of the crucible 6 was provided with a curvature (corner R) of R = 10 mm.

As shown in Table 3, a plurality of setting conditions with different inner diameter IDBs of the lower storage chamber 622A were prepared. A simulation was performed for each set condition, and a flow pattern in the SiC solution 8 was analyzed. In the same manner as in Example 1, the average flow velocity of the SiC solution 8 below the SiC seed crystal 9 was obtained under each setting condition. The average flow rate was defined as plus (+) in the direction from the bottom to the top in the SiC solution 8.

[simulation result]
The calculated average flow velocity is shown in Table 3. In the “DIB / DIT” column, the ratio of the inner diameter IDB to the inner diameter IDT is shown. Fig. 11 is a diagram showing the relationship between "DIB / DIT" and "average flow velocity (mm / s)" in Table 3. The horizontal axis in Fig. 11 shows "DIB / DIT". The vertical axis in Table 3 represents “average flow velocity (mm / s)”.
Referring to Table 3 and FIG. 3, the average flow velocity was positive for each set condition, and the upward flow F1 was formed under any set condition. Furthermore, when the IDB / IDT value was 0.25 to 0.65, the average flow velocity of the upward flow F1 was 10 mm / s or more. Furthermore, when the IDB / IDT value was 0.30 to 0.60, the average flow velocity was significantly higher than that in other cases, exceeding 20 mm / s.

  While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

DESCRIPTION OF SYMBOLS 1 Chamber 3,30 Induction heating apparatus 6,60 Crucible 8 SiC solution 9 SiC seed crystal 31 Coil 32 Power supply 41 Seed shaft 100,200 Manufacturing apparatus 311 Upper coil part 312,313 Lower coil part 621A Upper storage room 622A Lower storage room

Claims (9)

A crucible capable of storing a SiC solution;
A chamber for storing the crucible;
A seed shaft extending in the vertical direction of the chamber and having a SiC seed crystal immersed in the SiC solution attached to a lower end;
An induction heating device disposed around the crucible,
The crucible is
An upper storage chamber disposed at an upper portion of the crucible and having a first inner diameter;
A lower storage chamber disposed below the upper storage chamber and having a second inner diameter smaller than the first inner diameter;
The induction heating device includes:
An upper coil portion disposed around the upper storage chamber;
A lower coil portion disposed around the lower storage chamber and generating an electromagnetic force in the SiC solution in the lower storage chamber that is larger than an electromagnetic force generated in the SiC solution in the upper storage chamber by the upper coil portion; ,
A manufacturing apparatus comprising: a power source for supplying current to the upper coil portion and the lower coil portion. The manufacturing apparatus according to claim 1,
The crucible is further
An upper cylinder portion disposed at an upper portion of the crucible, having a first outer diameter, in which the upper storage chamber is disposed;
A manufacturing apparatus comprising: a lower cylinder portion disposed below the upper cylinder portion, having a second outer diameter smaller than the first outer diameter, and in which the lower storage chamber is disposed. The manufacturing apparatus according to claim 2,
The upper coil portion is disposed around the upper cylindrical portion,
The lower coil portion is disposed around the lower cylindrical portion,
The diameter of the said lower coil part is a manufacturing apparatus smaller than the diameter of the said upper coil part. The manufacturing apparatus according to any one of claims 1 to 3,
The manufacturing apparatus in which the crucible satisfies the formula (1) when the height of the SiC solution in the lower storage chamber is HB and the height of the SiC solution in the upper storage chamber is HT.
(HB / (HB + HT)) × (HT / (HB + HT)) ^1/2 > 17.5 (1) The manufacturing apparatus according to any one of claims 1 to 4,
The ratio of the second inner diameter to the first inner diameter is 0.25 to 0.65. The manufacturing apparatus according to claim 1,
The power supply is
The manufacturing apparatus which supplies a 1st electric current to the said upper coil part, and supplies the 2nd electric current whose frequency is lower than the said 1st electric current to the said lower coil part.   The crucible used for the manufacturing apparatus of Claims 1-6. A crucible used in a method for producing a SiC single crystal by a solution growth method,
An upper storage chamber disposed at an upper portion of the crucible and having a first inner diameter;
A lower storage chamber disposed below the upper storage chamber and having a second inner diameter smaller than the first inner diameter;
An upper cylinder portion disposed at an upper portion of the crucible, having a first outer diameter, in which the upper storage chamber is disposed;
A crucible comprising a lower cylinder portion disposed below the upper cylinder portion, having a second outer diameter smaller than the first outer diameter, and having the lower storage chamber disposed therein. A crucible capable of storing a SiC solution, a chamber for storing the crucible, a seed shaft extending in the vertical direction of the chamber and attached to the lower end of a SiC seed crystal immersed in the SiC solution, and disposed around the crucible The crucible is disposed at an upper portion of the crucible and has an upper storage chamber having a first inner diameter, and a lower portion of the upper storage chamber that is smaller than the first inner diameter. A lower storage chamber having an inner diameter of 2, and the induction heating device is disposed around the upper storage chamber, and the upper coil portion is disposed around the lower storage chamber. An electromagnetic force larger than the electromagnetic force generated in the SiC solution in the storage chamber is supplied with current to the lower coil portion, the upper coil portion, and the lower coil portion that generate the SiC solution in the lower storage chamber. Preparing a production apparatus and a power supply for,
Immersing the SiC seed crystal attached to the seed shaft in the SiC solution in the crucible;
Heating the SiC solution in the crucible by the induction heating device;
A step of growing a SiC single crystal on the SiC seed crystal while rotating the seed shaft.

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