Crystal manufacturing method, crystal manufacturing apparatus, and single crystal

Abstract

To provide a method and apparatus for manufacturing a crystal, capable of manufacturing a single crystal having a large size.SOLUTION: A method for manufacturing a crystal comprises: arranging a raw material 1 having a tapered tip 1A above a crystal growth region 2U; selectively heating and melting the side surface of the tip 1A by radiant heat obliquely and upwardly advancing while maintaining the shape of the tip 1A; and physically connecting the side surface of the tip 1A and the upper surface of the crystal growth region 2U by a material melted from the side surface. An apparatus for manufacturing a crystal radiates radiant heat for melting the raw material from an electrical resistance heater R.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a crystal manufacturing method, a crystal manufacturing apparatus, and a single crystal. [Background technology]

[0002] Patent Document 1 discloses a floating zone (FZ) method for manufacturing semiconductor silicon (Si). In the FZ method, a magnetic field formed by a radio frequency (RF) heater is used to pass a current through the surface of a raw material, melting the raw material. The molten Si is conductive, so it can be held in place by the restraining force of an electromagnetic field in addition to surface tension. Therefore, by using the FZ method, which uses high frequency heating, it is possible to manufacture a single crystal Si having a size of φ6 inches (200 mm) (see Non-Patent Document 1). Single crystal Si formed by the FZ method can be used for high voltage elements that require high purity and high quality.

[0003] Patent Document 2 discloses a FZ method for producing single crystals of gallium oxide (Ga2O3). Gallium oxide (Ga2O3, etc.) has attracted attention as a new semiconductor material. The energy band gap of Ga2O3 is larger than that of Si, silicon carbide (SiC), and gallium nitride (GaN). Therefore, electronic devices using Ga2O3 are expected to have high voltage resistance, high output, low loss, and high temperature resistance. Ga2O3 has crystal structures such as α, β, γ, δ, ε, and κ. In these crystal structures, β-Ga2O3 has a crystal structure with a monoclinic β phase and has an energy band gap of about 4.8 eV. The melting point of β-Ga2O3 is about 1800°C. Non-Patent Document 2 and Non-Patent Document 3 disclose a method for producing a single crystal of β-Ga2O3 using the FZ method, but the diameter φ of the crystal is about 1 inch (about 2.5 cm).

[0004] Patent Document 3 discloses a vertical Bridgman (VB) method. The VB method uses a crucible. Known crystal manufacturing methods using a crucible include the EFG (Edge-defined Film-fed Growth) method and the Cz (Czochralski) method. The crucible can be made of, for example, platinum (Pt) doped with rhodium (Rh). The constituent material of the crucible (e.g., Rh) can affect the semiconductor characteristics as a dopant. Non-Patent Document 4 discloses the characteristics of Rh-doped platinum. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 2833432 [Patent Document 2] Patent No. 3679097 [Patent Document 3] JP 2017-193466 A [Non-patent literature]

[0006] [Non-Patent Document 1] "Reduced radial resistivity variation of FZ Si wafers with AdvancedNTD", Journal of Crystal Growth, 2019, Vol. 512, p.65 - p.68 [Non-Patent Document 2] "β-Ga2O3and single-crystal phosphors for high-brightness white LEDs & LDs, and β-Ga2O3 potential fornext generation of power devices", Proc. of SPIEVol.8987, Oxide-based Materials and Devices V, 2014, Vol. 89871, p. 89871U1 - 89871U12 [Non-Patent Document 3] "Large-size β-Ga2O3 single crystals and wafers", Journal of Crystal Growth, 2004, Vol.270, Issues 3-4, p. 420 - p.426 [Non-Patent Document 4] "Thermal Expansion of Rhodium-Platinum Alloys", Platinum Metals Rev., 1960, Vol. 4, (4), p.138 - p.140 Summary of the Invention [Problem to be solved by the invention]

[0007] However, according to conventional methods for producing gallium oxide and the like using RF heaters, the size of the single crystals that can be produced is small. There is a demand for single crystals having a large size, as well as a crystal production method and a crystal production apparatus capable of producing such single crystals. [Means for solving the problem]

[0008] The crystal production method of the present disclosure includes: Downwards With a tapered tip Solid A step of placing a raw material above a crystal growth region; selectively heating and melting the side surface of the tip portion by radiant heat traveling obliquely upward while maintaining the shape of the tip portion; The solid raw material Melted from the side Melting and a material physically connecting the side of the tip and a top surface of the crystal growth region. The radiant heat traveling obliquely upward is radiated from an electric resistance heater disposed between the tip and the crystal growth region. The RF heater not only generates heat in the material, but also melts the Melting The material is subjected to a restraining force by an electromagnetic field, whereas when radiant heat is selectively applied to the side of the tip to melt the material, this restraining force is suppressed, and the size of the produced single crystal can be increased.

[0009] The crystal manufacturing apparatus of the present disclosure is provided with a means for carrying out such a process. DownwardsThe apparatus includes a support for supporting a raw material having a tapered tip, an electric resistance heater for generating radiant heat for melting the raw material that advances obliquely upward, and a heat shield disposed below the electric resistance heater. The single crystal of the present disclosure is a single crystal produced by such means. With this crystal production apparatus, the size of the produced single crystal can be increased. Effect of the Invention

[0010] According to the crystal production method and crystal production apparatus of the present disclosure, a single crystal having a large size can be produced. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a vertical cross-sectional configuration and system of a crystal manufacturing apparatus according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a vertical cross-sectional structure around the tip of the feedstock. [Diagram 3] FIG. 3 is an exploded perspective view of a heating apparatus including a group of electrical resistance heaters, a reflector, and a thermal shield. [Figure 4] FIG. 4 is a plan view of an electrical resistance heater. [Diagram 5] FIG. 5 is a side view of an electrical resistance heater. [Figure 6] FIG. 6 is a diagram for explaining the positional relationship between the electric resistance heater and the reflector. [Figure 7] FIG. 7 is a diagram for explaining the positional relationship between the electric resistance heater and the reflector. [Figure 8] FIG. 8 is a perspective view of a reflector having another shape. [Figure 9] FIG. 9 is a circuit diagram showing an example of electrical connections of the electric resistance heater. [Figure 10] FIG. 10 is a diagram showing a vertical cross-sectional structure of a heating device having a cooling structure. [Figure 11] FIG. 11 is a diagram showing an example of the structure of a support for suspending raw materials. [Figure 12] FIG. 12 is a block diagram of the control system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Various exemplary embodiments will be described in detail below with reference to the drawings. Note that the same or corresponding parts in each drawing are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0013] 1 is a diagram showing a vertical cross-sectional configuration and system of a crystal manufacturing apparatus 100 according to an embodiment. For the purpose of explanation, an XYZ three-dimensional orthogonal coordinate system is set. The vertical upward direction is the positive direction of the Z axis. The horizontal plane is perpendicular to the Z axis and includes the X axis and the Y axis. The X axis and the Y axis are orthogonal to each other.

[0014] Crystal manufacturing apparatus 100 accommodates raw material 1 inside. Raw material 1 comprises tip portion 1A, raw material body portion 1B, and first engagement portion 1C. During the crystal growth period, crystal 2 is located below tip portion 1A. Crystal 2 comprises crystal body portion 2A and seed crystal 2B which serves as the source of growth of crystal body portion 2A. The upper surface of solid crystal body portion 2A constitutes crystal growth region 2U (see FIG. 2). Molten material 3 is located between raw material 1 and crystal 2. Molten material 3 is material that is melted on the side surface of tip portion 1A of raw material 1 during the crystal growth period.

[0015] The first engagement portion 1C located at the upper end of the raw material 1 is held by the feed holder 4. In this example, the first engagement portion 1C is a recess provided in the raw material 1, and the feed holder 4 engages in the recess. The feed holder 4 is connected to the upper shaft 6 via the connection block 5. The upper shaft 6 is supported by a first drive mechanism 31 fixed to the upper part of the treatment vessel 71. Therefore, the raw material 1 is supported by a support consisting of the feed holder 4, the connection block 5, the upper shaft 6, and the first drive mechanism 31. The basic function of the support is to suspend and support the solid raw material 1, and there are many possible structures that perform this function, and the structure is not limited to the one described here.

[0016] The first drive mechanism 31 can move the upper shaft 6 up and down (Z-axis movement) and rotate about the central axis of the upper shaft 6. There are several possible structures for the first drive mechanism 31. For example, an elevation gear having a horizontal rotation axis and a rotation gear having a vertical rotation axis are prepared. The elevation gear and rotation gear are fixed to the upper shaft 6. The first drive mechanism 31 is equipped with drive gears that engage with these gears. By rotating these drive gears, the upper shaft 6 can move up and down and rotate.

[0017] An upper Z-axis movement motor 33 is mechanically connected to the lifting drive gear of the first drive mechanism 31, and a driving force is transmitted from the upper Z-axis movement motor 33. An upper rotation motor 34 is mechanically connected to the rotation drive gear of the first drive mechanism 31, and a driving force is transmitted from the upper rotation motor 34.

[0018] The seed crystal 2B located at the bottom of the crystal 2 is held by a seed crystal holder 7. The seed crystal holder 7 is fixed to and supported at the upper end of a lower shaft 8. The lower shaft 8 is supported by a second driving mechanism 32 fixed to the bottom of the treatment vessel 71. Thus, the crystal 2 is supported by a support consisting of the seed crystal holder 7, the lower shaft 8, and the second driving mechanism 32. The basic function of the support is to support the solid crystal 2 from below, and there are many possible structures that can perform this function, and the structure is not limited to the one described here.

[0019] The second drive mechanism 32 can move the lower shaft 8 horizontally (X-axis movement, Y-axis movement), move up and down (Z-axis movement), and rotate around the central axis of the lower shaft 8. There are several possible structures for the second drive mechanism 32. For the lifting and rotational movements, for example, as in the case of the first drive mechanism 31, lifting gears and rotational gears are fixed to the lower shaft 8. The second drive mechanism 32 is equipped with drive gears that engage with these gears. By rotating these drive gears, the lower shaft 8 can move up and down and rotate. For the horizontal movement, an appropriate movement mechanism such as an XY stage may be used. For example, a rack-and-pinion type gear mechanism can move the rack linearly by rotating the pinion (drive gear). This gear mechanism can be applied to a mechanism for X-axis movement and a mechanism for Y-axis movement.

[0020] A lower X-axis movement motor 35 is mechanically connected to the X-axis movement drive gear of the second drive mechanism 32, and a driving force is transmitted from the lower X-axis movement motor 35. A lower Y-axis movement motor 36 is mechanically connected to the Y-axis movement drive gear of the second drive mechanism 32, and a driving force is transmitted from the lower Y-axis movement motor 36. A lower Z-axis movement motor 37 is mechanically connected to the lifting drive gear of the second drive mechanism 32, and a driving force is transmitted from the lower Z-axis movement motor 37. A lower rotation motor 38 is mechanically connected to the rotation drive gear of the second drive mechanism 32, and a driving force is transmitted from the lower rotation motor 38. The lifting mechanism of the second drive mechanism 32 may be a pantograph-type jack.

[0021] A heating device 10 is disposed around the tip 1A of the raw material 1. The heating device 10 includes an electric resistance heater group 11, a (heat) reflector 12, and a heat shield 13. The electric resistance heater group 11 is composed of a plurality of electric resistance heaters R. The heating device 10 is supported by a heating device support 14 that fixes the heat shield 13 to the processing vessel 71. The heating device 10 heats the side of the tip 1A of the raw material 1 by radiant heat emitted from the electric resistance heater R. The material on the side of the heated tip 1A melts and moves downward along the side due to gravity, before reaching the upper surface of the crystal 2 and crystallizing. The radiant heat is an infrared electromagnetic wave generated by the heating element.

[0022] The heater power supply 39 is electrically connected to the electric resistance heater group 11. When power is supplied from the heater power supply 39 to the electric resistance heater group 11, each electric resistance heater R generates heat and emits radiant heat. The lower end or the entirety of the tip portion 1A of the raw material 1 is observed by the detection element 41. The detection element 41 is a camera and / or a radiation thermometer. An observation window 72 is disposed between the lower end of the tip portion 1A of the raw material 1 and the detection element 41. The observation window 72 is made of a transparent material such as quartz glass, and is fixed to the side wall of the processing vessel 71.

[0023] A gas inlet 75 is provided on the side wall of the processing vessel 71. The processing vessel 71 is a vessel for isolating the internal space from the outside air and creating an atmosphere and environment different from the atmosphere. A gas is supplied from the gas source 61 through the flowmeter 42 and the gas inlet 75 into the processing vessel 71. This gas is, for example, a mixed gas of oxygen (O2) and argon (Ar). As a suitable example, the raw material 1 is made of Ga2O3. When an element (oxygen) contained in the raw material 1 is supplied from the gas source 61 into the processing vessel 71, it is possible to suppress the component of the contained element (oxygen) from escaping from the crystal. The partial pressure of the contained element (oxygen) in the processing vessel 71 can be set to 10% or more. The flowmeter 42 is a sensor that detects the gas flow rate, but may have a function of controlling the gas flow rate, such as a mass flow controller (MFC). Although FIG. 1 shows one gas source 61, the crystal manufacturing apparatus 100 may be provided with multiple gas sources that respectively supply multiple gas species.

[0024] A gas exhaust port 76 is provided on the side wall of the processing vessel 71. The gas inside the processing vessel 71 is exhausted by the pump 62 through the gas exhaust port 76. The gas pressure inside the processing vessel 71 is preferably, for example, 1 atmosphere. The gas pressure inside the processing vessel 71 can be controlled by controlling the gas supply amount and exhaust amount.

[0025] The inner wall of the processing vessel 71 is provided with a heat insulating material 73. The heat insulating material 73 surrounds the crystal 2 and the lower shaft 8. A heating element 74 separate from the electric resistance heater R can be provided around the crystal 2. The heating element 74 can heat the crystal 2 independently of the electric resistance heater R, and can provide the crystal 2 with a temperature distribution suitable for crystal growth and cooling. The heating element 74 is provided inside the heat insulating material 73. The heating element 74 surrounds the crystal 2 and heats the crystal 2. The type of the heating element 74 is not particularly limited as long as it can heat the crystal 2. The heating element 74 can also be constituted by an electric furnace constituted by an electric resistance heater. The heat from the upper heating device 10 is not transferred much to the lower crystal 2. Therefore, the heating element 74 independently controls the temperature of the crystal 2. For example, if the heating of the crystal 2 by the heating element 74 is weakened, the molten material 3 that reaches the crystal 2 is cooled and easily crystallized.

[0026] The controller 50 obtains signals from the above elements and outputs control signals to the elements of the controlled group. When the controller 50 obtains a detected value such as temperature from a sensor group (e.g., a temperature sensor), it can control the controlled element (e.g., the heater power supply 39) so that the detected value becomes a target value, and perform feedback control. Of course, the controller 50 also controls each of the above motors. Each motor is provided with a rotation sensor, and the Z-direction moving speed of the raw material, the raw material rotation speed, the X-direction moving speed of the crystal, the Y-direction moving speed of the crystal, the Z-direction moving speed of the crystal, and the crystal rotation speed can be indirectly obtained from the output signal of the rotation sensor. A sensor for detecting the gas pressure in the processing vessel 71 may be provided. The controller 50 displays the detected values ​​from the various sensors, an image of the raw material tip, and the like on the display 81.

[0027] 2 is a diagram showing a vertical cross-sectional configuration around the tip of the raw material. Note that the raw material and the crystal main body are shown in a side view as viewed from the Y-axis direction, not in a cross-sectional view.

[0028] The tip 1A of the raw material has a tapered shape. That is, the diameter of the tip 1A decreases toward the negative direction of the Z axis. The crystal main body 2A is disposed below the tip 1A. The upper surface of the crystal main body 2A constitutes the crystal growth region 2U. The tip 1A faces the crystal growth region 2U. The molten material 3 is interposed between the side surface of the tip 1A and the crystal growth region 2U of the crystal main body 2A. The molten material 3 physically connects the side surface of the tip 1A and the upper surface of the crystal growth region 2U.

[0029] The material on the side surface of the tip portion 1A is melted by radiant heat emitted from a plurality of electric resistance heaters R.

[0030] Focus on one electric resistance heater R. The first radiant heat radiated from this electric resistance heater R travels obliquely upward along a first radiant heat travel path H1 and reaches the side surface of the tip portion 1A. The electric resistance heater R has a resistive portion that extends at an incline with respect to the horizontal plane HS. This resistive portion has a smaller diameter than the horizontally extending portion. In the XZ cross section passing through the central axis CX of the raw material 1, in this example, the first radiant heat travel path H1 extends in a direction perpendicular to the resistive portion of the electric resistance heater R that extends at an incline.

[0031] The second radiant heat radiated from the electric resistance heater R first travels diagonally downward along the second radiant heat travel path H2, and after being reflected by the reflector 12, travels diagonally upward and reaches the side surface of the tip portion 1A. The side surface of the tip portion 1A is heated by the first radiant heat that directly reaches the side surface and the second radiant heat that reaches the side surface after being reflected.

[0032] The shape of the tip 1A is generally an inverted cone obtained by turning a cone upside down. The shape of the tip 1A may be an inverted truncated cone, and the intersection line between the XZ plane and the side surface may not be a straight line. The shape of the tip 1A is such that the material melted on the side surface of the tip 1A moves downward along the side surface without dripping directly downward in the vertical direction. From this viewpoint, in a vertical cross section (XZ cross section) including the central axis CX of the raw material 1, the acute angle θ formed by the side surface of the tip 1A and the horizontal plane HS located above this side surface is in the range of 30 degrees to 60 degrees. The acute angle θ may be in the range of 40 degrees to 50 degrees. An example of a suitable acute angle θ is θ=45 degrees. Note that, in a vertical cross section (XZ cross section) including the central axis CX of the raw material, the acute angle formed by the exposed surface of the reflector 12 and the horizontal plane may be set to the above acute angle θ.

[0033] The gravity acting on the molten material present on the side (slope of the cone part) of the tip 1A is divided into a force acting in a direction perpendicular to the slope and a force acting in a direction parallel to the slope. The force acting in a direction parallel to the slope causes the molten material 3 to gather at the apex of the lower end, and move from this position downward to the crystal growth region 2U. The amount of molten material generated on the slope (side) of the tip 1A, the amount of molten material moving on the slope, the force acting in a direction perpendicular to the slope, the surface tension of the molten material, and the binding force due to a slight electromagnetic field determine the amount of molten material 3 that can be held on the slope. By setting the acute angle θ as described above, the molten material 3 can be stably supplied onto the crystal growth region 2U.

[0034] It is preferable to rotate the raw material 1 so that the side surface of the tip portion 1A is melted evenly, but crystal growth can be performed even if the raw material 1 is not rotated. The outline shape of the raw material 1 is a shape with high rotational symmetry with respect to the central axis CX, and is preferably a cylindrical shape, but other shapes are also possible.

[0035] The electric resistance heater R is disposed between the tip 1A and the crystal growth region 2U, and radiates radiant heat that travels at least obliquely upward. The radiant heat traveling obliquely upward includes a first radiant heat radiated obliquely upward directly from the electric resistance heater R, and a second radiant heat radiated downward from the electric resistance heater R and reflected by the reflector 12.

[0036] The reflector 12 has a reflector opening S12. The thermal shield 13 has a ring shape with an opening in the central region. The reflector 12 is fixed to the inner slope of the opening of the thermal shield 13. The thermal shield 13 has a thermal shield opening S13. The reflector opening S12 and the thermal shield opening S13 are in communication with each other and form an information path 41P. The detection element 41 shown in FIG. 1 detects information (temperature, image) of the raw material 1 transmitted along the information path 41P via the reflector opening S12 and the thermal shield opening S13.

[0037] The outer peripheral surface of the thermal shield 13 is attached to the inner surface of the ring-shaped heating device support 14. There are various mounting methods. In addition to a mounting method using bolts and nuts, a mounting method in which the inner surface of the heating device support 14 is stepped and the outer peripheral surface of the thermal shield 13 is stepped to engage with it is possible to consider multiple mounting methods. The radiant heat radiated downward from the electric resistance heater R is blocked by the reflector 12 as well as the thermal shield 13 arranged between the electric resistance heater R and the crystal growth region 2U. The inner part of the thermal shield 13 is located directly above the peripheral region on the crystal growth region 2U. The outer part of the thermal shield 13 is not located on the crystal growth region 2U.

[0038] The molten material 3 has an exposed surface with a first outer diameter in a horizontal plane including the lower end of the solid tip portion 1A. The molten material 3 has an exposed surface with an outer diameter smaller than the first outer diameter in a horizontal plane including the lower end of the electric resistance heater R. In other words, the central portion of the molten material 3 is constricted. The lower end of the molten material 3 contacts the upper surface of the crystal growth region 2U, and the outer diameter of this contact region in the horizontal plane is larger than the first outer diameter.

[0039] A plurality of electric resistance heater holders B are fixed to the upper surface of the heating device support 14. The electric resistance heater holder B has a through hole extending in the radial direction of the heating device support 14. The electric resistance heater R has an electrode at the outer end, and this electrode is inserted into the through hole. The inner surface of the through hole of the electric resistance heater holder B is a conductor, and this conductor is connected to the heater power supply 39. One end of the electric resistance heater R is electrically connected to the ground potential GND, and the other end is electrically connected to the power supply potential V.

[0040] FIG. 3 is an exploded perspective view of a heating device 10 including a group of electrical resistance heaters 11, a reflector 12 and a thermal shield 13. As shown in FIG.

[0041] The thermal shield 13 has an opening in the central region, and the diameter of the inner surface of this opening becomes smaller toward the bottom. This thermal shield opening inner surface 133 is inclined with respect to the Z-axis direction in a vertical cross section (XZ cross section) including the central axis CX of the raw material. The opening in the central region of the thermal shield 13 extends from the thermal shield opening upper edge 131 of the thermal shield upper surface 134 to the thermal shield opening lower edge 132 of the thermal shield lower surface 135, and a through hole is formed.

[0042] The shape of the thermal shield opening inner side 133 in a horizontal plane (XY plane) is a ring shape including multiple continuous concave surfaces. The shape of each concave surface in the horizontal plane is an elliptical arc or an arc other than an elliptical arc. The reflector 12 is supported by the thermal shield opening inner side 133. The horizontal cross-sectional shape of the reflector inner side 123 includes a ring shape including multiple continuous concave surfaces, similar to the opening shape of the thermal shield 13. The reflector inner side 123 extends from the reflector upper end surface 121 to the reflector lower end surface 122, and has a through hole formed therein.

[0043] The electric resistance heater group 11 is composed of a plurality of electric resistance heaters R. In this example, twelve electric resistance heaters R are illustrated, and these electric resistance heaters R are arranged at equal intervals along the circumferential direction surrounding the central axis CX of the raw material.

[0044] The reflector inner side surface 123 has a plurality of concave surfaces (concave curves) having a shape such as an elliptical arc in a horizontal plane along the circumferential direction. The reflector 12 has concave surfaces that radiate from the central axis CX, and the plurality of concave surfaces are also grooves extending radially. The cross-sectional shape of this groove can be made approximately elliptical, with a resistor (heating element) of the electric resistance heater R disposed at a focal point on one side, and the other focal point disposed on the side surface of the tip portion 1A. It is preferable to dispose the heating elements located at the focal points of the ellipse at the respective focal positions, but a U-shaped or other heating element may have two parallel resistors, and the centers of these resistors may be disposed at the focal points.

[0045] When the radiant heat from the resistor of the electric resistance heater R is focused on the side of the tip of the material, localized heating becomes possible. By distributing the localized heating positions to multiple positions on the side of the tip of the material, the generation locations of the molten material can be dispersed. In addition, by rotating the material, the generation locations of the molten material on the side of the tip of the material can be averaged, making it easier to maintain the cone shape during melting.

[0046] The number of concave surfaces of the reflector 12 disposed below the group of electric resistance heaters 11 is the same as the number of electric resistance heaters R, that is, 12. The number of electric resistance heaters R does not have to be 12. The multiple electric resistance heaters R all have the same shape.

[0047] Each electric resistance heater R is, for example, a U-shaped heating element bent at an angle of 45 degrees, and is arranged in a plan view so as to extend radially from a central axis CX, thereby enabling radiation of radiant heat from the periphery to the center and from the bottom to the top.

[0048] FIG. 4 is a plan view of the electric resistance heater R.

[0049] The electric resistance heater R has a U-shaped planar shape when viewed from above, and has a structure that allows for easy handling. When viewed from above, the electric resistance heater R extends toward the central axis CX of the raw material. The electric resistance heater R includes a first electrode R1, a first conductor R11, a first resistor R12, a connecting resistor R3, a second resistor R22, a second conductor R21, and a second electrode R2, and each of these elements is rod-shaped and physically continuous.

[0050] The materials of each part that constitutes the electric resistance heater R are basically made of the same resistive material, but the first electrode R1 and the second electrode R2 are coated with a metal material that covers the resistive material. Examples of the resistive material include ceramic materials, and examples of the metal material for the electrodes include aluminum. Examples of resistive ceramic materials that are resistant to high temperatures include lanthanum chromite (LaCrO3) or molybdenum disilicide (MoSi2), but resistors using zirconia or carbon are also known.

[0051] As an example, the first electrode R1 and the second electrode R2 have a structure in which an aluminum film is provided on the surface of a conductor of MoSi2. The first conductor R11, the first resistor R12, the connecting resistor R3, the second resistor R22, and the second conductor R21 have a structure in which a SiO2 (quartz glass) film is provided on the surface of a conductor of MoSi2. The first resistor R12, the connecting resistor R3, and the second resistor R22 have small diameters, so they mainly function as resistors for generating heat. The first conductor R11 and the second conductor R21 have larger diameters than these resistors, so they function as conductors that supply current to the resistors. When a voltage is applied between the first electrode R1 and the second electrode R2 located at both ends, a current flows in the part connecting them, generating heat. The electric resistance heater R can be used up to about 1800°C.

[0052] In addition, β-Ga2O3 has a melting point of about 1800°C, and a decomposition reaction that loses oxygen occurs under an oxygen partial pressure of less than 10%. Therefore, when manufacturing β-Ga2O3, it is preferable that the electric resistance heater R is capable of heating to 1800°C or higher and is a heating element that can be used at an oxygen partial pressure of 10% or higher. Lanthanum chromite and molybdenum disilicide can meet these conditions.

[0053] FIG. 5 is a side view of an electrical resistance heater.

[0054] The acute angle α between the resistor central axis RX of the second resistor R22 (or the first resistor R12) and the horizontal plane HS is in the range of 30 degrees to 60 degrees. The acute angle α may be in the range of 40 degrees to 50 degrees. An example of a suitable acute angle α is α = 45 degrees. The angle of the side of the tip of the raw material (acute angle θ) and the inclination angle of the resistor (acute angle α) are set to angles that keep the shape of the side constant when the raw material is slowly moved downward while heating the side of the tip of the raw material.

[0055] FIG. 6 is a diagram for explaining the positional relationship between the electric resistance heater R and the reflector 12. As shown in FIG.

[0056] The inner surface of the reflector 12 has a shape in which a plurality of concave surfaces are continuous along the circumferential direction of the reflector 12. When the horizontal cross section of the reflector 12 is observed from above, the shape corresponding to each concave surface of the inner surface of the reflector 12 is, for example, an elliptical arc. In FIG. 6, the first concave surface 12A, the second concave surface 12B, and the third concave surface 12C of the reflector 12 are shown. An electric resistance heater R is disposed inside the second concave surface 12B. The second concave surface 12B shown in the figure is not a horizontal cross-sectional shape, but a cross-sectional shape perpendicular to the longitudinal direction of the first resistor R12 (resistor central axis RX (see FIG. 5)). The shape of the second concave surface 12B in the figure is an elliptical arc. Figure 6 also shows the positional relationship of the first concave surface 12A and the third concave surface 12C in a plane perpendicular to the central axis of the resistor of the electric resistance heater R arranged in each concave surface, and the shapes of the first concave surface 12A and the third concave surface 12C in Figure 6 are both elliptical arcs.

[0057] The first resistor R12 and the second resistor R22 of one electric resistance heater R are both disposed inside the second concave surface 12B. The intermediate position (center of gravity position on the diagram) between the first resistor R12 and the second resistor R22 is located on the first focal point G1 of an ellipse that constitutes an elliptical arc including the second concave surface 12B. The second focal point G2 of this ellipse is located on the side surface of the tip portion 1A. Therefore, the radiant heat virtually radiated from the first focal point G1 is reflected by the second concave surface 12B and reaches the second focal point G2. Since the position of the first focal point G1 is the center of gravity position of the resistor, the radiant heat radiated from the first and second resistors tends to gather in the vicinity of the position of the second focal point G2 on the side surface of the tip portion 1A as a whole. Similarly, the radiant heat is focused and reaches the vicinity of the position of the second focal point G2 corresponding to each of the other first concave surfaces 12A and third concave surfaces 12C. Therefore, the side surface of the tip portion 1A can be melted at a higher temperature by the focused radiant heat.

[0058] FIG. 7 is a diagram for explaining the positional relationship between the electric resistance heater R and the reflector 12. As shown in FIG.

[0059] In the above-mentioned FIG. 6, an example in which one electric resistance heater is arranged in one concave surface has been described. In FIG. 7, one first resistor R12 of one electric resistance heater R is arranged on the first focal point G1 inside the second concave surface 12B, and the other second resistor R22 is arranged on the first focal point G1 inside the third concave surface 12C. The other configurations in FIG. 7 are the same as those in FIG. 6. Each concave surface (first concave surface 12A, second concave surface 12B, third concave surface 12C) shown in FIG. 7 has a cross-sectional shape perpendicular to the longitudinal direction (resistor central axis RX (see FIG. 5)) of the first resistor R12 arranged inside the respective concave surface, but may have a horizontal cross-sectional shape.

[0060] The radiant heat emitted from the resistors (first resistor R12, second resistor R22) arranged at the first focal point G1 is reflected by the corresponding concave surfaces (second concave surface 12B, third concave surface 12C) and reaches the corresponding second focal points G2 on the side surface of the tip portion 1A. Since the radiant heat is focused and reaches the vicinity of the position of the second focal point G2, the side surface of the tip portion 1A can be melted at a high temperature. In addition, by rotating the raw material arranged at the top and / or the crystal arranged at the bottom by a rotating motor, the melting point can be changed and the uniformity of the molten material distribution in the circumferential direction can be improved.

[0061] FIG. 8 is a perspective view of a reflector 12 having another shape.

[0062] This reflector 12 has a simpler shape than the reflector 12 described above, and has a side shape of an inverted truncated cone. The angle (acute angle α) that the reflector inner side surface 123 makes with the horizontal plane is within a range of 30 degrees to 60 degrees. The acute angle α may be within a range of 40 degrees to 50 degrees. An example of a suitable acute angle α is α=45 degrees. In other words, the inclination angle (acute angle α) of the reflector inner side surface 123 may be set to be the same as the inclination angle (acute angle α) of the resistor shown in FIG. 5.

[0063] The inclination angle (acute angle α) of the reflector inner side surface 123 is the angle that a line segment connecting a point on the inner edge of the reflector upper end surface 121 and a point on the inner edge of the reflector lower end surface 122 makes with a radial axis (e.g., X-axis) of the reflector 12 within a plane (e.g., XZ plane) including the central axis CX of the reflector 12.

[0064] The radiant heat emitted from the electric resistance heater is reflected by the inner surface of the reflector 12 and reaches the side of the tip of the raw material. Compared to the structure in Fig. 7, the structure shown in Fig. 8 does not have a radiant heat focusing function, and therefore allows for heating with relatively high in-plane uniformity. In the structure of this example, the upper raw material and / or the lower crystal may also be rotated by a rotation motor.

[0065] FIG. 9 is a circuit diagram showing an example of electrical connections of the electric resistance heater.

[0066] Each electric resistance heater R constituting the electric resistance heater group 11 is a resistor. Electric power is supplied to the electric resistance heaters R from a heater power supply 39. There are various possible methods for connecting the electric resistance heaters R. In the figure, N electric resistance heaters R (e.g., N=4) are regarded as one resistance unit, and three resistance units are shown. In one resistance unit, the electric resistance heaters R are connected in series, one end of the resistance unit is connected to a ground potential GND, and the other end is connected to a power supply potential V. Each resistance unit (one or more electric resistance heaters) is connected in parallel to the heater power supply. All the electric resistance heaters R may be connected in series. One end of each electric resistance heater R may be connected to a ground potential GND, and the other end is connected to a power supply potential V.

[0067] The heater power supply 39 outputs a DC voltage or an AC voltage, so the power supply potential V is a DC potential or an AC potential. When a DC current is supplied to the electric resistance heater R, the resistance value of the electric resistance heater R depends on the cross-sectional area through which the current flows, and large heat is generated in the resistor portion having a small diameter. When an AC current is supplied to the electric resistance heater R, the AC current tends to flow near the surface, and large heat is generated in the resistor portion having a small diameter. Of course, the shape of the resistor is not limited to the above-mentioned form, and various shapes are possible, such as a simple rod-shaped resistor.

[0068] FIG. 10 is a diagram showing a vertical cross-sectional structure of a heating device 10 having a cooling structure.

[0069] The reflector 12 included in the heating device 10 is made of a material having high heat resistance and high reflectance. The reflector 12 can be made of platinum (Pt) as a whole. The reflector 12 can be made of a multilayer film as shown in FIG. 10. The reflector 12 includes a surface layer 12a, a main body layer 12b, and an adhesive layer 12c. The surface layer 12a is made of a material having high reflectance. The main body layer 12b is made of a material having a higher melting point and lower reflectance than the surface layer 12a. The adhesive layer 12c is made of a material containing the material contained in the main body layer 12b. The heat shield 13 is made of an insulator that is difficult to transmit radiant heat. The heat shield 13 can be made of a material having lower electrical conductivity, lower thermal conductivity, and higher infrared absorption than the reflector 12.

[0070] For example, the surface layer 12a is made of gold (Au), the main body layer 12b is made of platinum (Pt), the adhesive layer 12c is made of a mixed layer of platinum and aluminum oxide (alumina: Al2O3), and the thermal shield 13 is made of single crystal alumina. In the figure, a flow path for the cooling medium is formed inside the main body layer 12b, and the cooling medium CM is supplied to the flow path. There are various materials for the cooling medium CM, for example, water. Other known cooling media include heavy water, carbon dioxide, helium, metallic sodium, sodium potassium alloy, mercury, and air. The thermal shield 13 may be provided with a flow path for the cooling medium CM, and the flow path can be connected to the flow path of the main body layer 12b.

[0071] From the viewpoint of heat resistance and suppression of cracks due to thermal stress, the thermal shield 13 may be made of porous ceramic (insulator). For example, the thermal shield 13 may be made of porous alumina. In this case, the cooling medium to be supplied to the main body layer 12b is supplied to the main body layer 12b using a flow path (piping, etc.) made of a material different from that of the thermal shield 13. The material of the inner surface of this flow path is made of a metal such as platinum (Pt) or copper (Cu), and may be provided inside the thermal shield 13 or may be provided outside the thermal shield 13.

[0072] When growing β-Ga2O3 or the like, the material constituting the thermal shield 13 is preferably a material that is stable in an environment of 1800°C and oxygen partial pressure of 10% or more, similar to an electric resistance heater (heating element). For example, the material of the thermal shield 13 may contain at least one ceramic selected from the group consisting of aluminum oxide, magnesium oxide, and zirconium oxide. In particular, zirconium oxide (zirconia) is preferable as the material of the thermal shield 13 because of its low thermal conductivity. These materials can be made porous. The structure of the thermal shield 13 does not need to be made of a single insulating block, and may be made by combining multiple blocks.

[0073] FIG. 11 is a diagram showing an example of the structure of a support that supports the raw material by suspending it with a wire.

[0074] Although FIG. 1 shows the structure of a support in which the raw material 1 is supported by an upper shaft, the support may be a support wire 410. The upper end portion of the raw material 1 is provided with a second engagement portion 1D having a through hole for passing the support wire 410. The support wire 410 is engaged with this through hole and is connected to a weight 440 via a first pulley 420 and a second pulley 430. The position of the weight 440 can also be moved using a device such as the first drive mechanism shown in FIG. 1.

[0075] FIG. 12 is a block diagram of the control system.

[0076] The controller 50 comprises a central processing unit 51, a memory 52, a bus 53, and an input / output interface 54. The controller 50 controls the group of controlled objects 30 according to a program stored in the memory 52. ​​A plurality of detection signals are input to the controller 50 from the group of sensors 40, and the controller 50 can control the devices of the group of controlled objects 30 so that the detection values ​​of the plurality of detection signals become target values. The input / output device 80, which includes a display 81 and an input device 82 such as a keyboard and a mouse, constitutes an interface with a human.

[0077] The group of controlled objects 30 includes an upper Z-axis movement motor 33, an upper rotation motor 34, a lower X-axis movement motor 35, a lower Y-axis movement motor 36, a lower Z-axis movement motor 37, a lower rotation motor 38, and a heater power supply 39, as shown in FIG. 1.

[0078] The sensor group 40 includes a camera 41A as the detection element 41 shown in Fig. 1, a radiation thermometer 41B, and a flowmeter 42, as well as a weight detector 43. The weight detector 43 is a weighing scale (load cell) that measures the weight of the first driving mechanism 31 and / or the second driving mechanism 32 shown in Fig. 1. The weight detector 43 can measure the reduction in weight of the raw material and the increase in weight of the crystal during the crystal growth period. The weighing scale may measure the total weight of each driving mechanism, or may be configured to measure only a portion of the weight.

[0079] Next, an example of producing a β-Ga2O3 single crystal using the above-mentioned crystal production apparatus will be described.

[0080] First, the source material 1 and the seed crystal 2B to be placed inside the processing vessel 71 shown in FIG. 1 are prepared.

[0081] Since the raw material 1 is a material that is the source of the grown single crystal, it is preferable that the raw material 1 has a high purity. Specifically, the raw material 1 can be gallium oxide with a purity of 4N. The raw material 1 may contain a dopant (e.g., tin (Sn)) that functions in the crystal after production. The raw material 1 can be produced, for example, as follows. Gallium oxide powder is filled into a contractible rubber container, and the shape is adjusted, and then the mouth of the container is closed. Next, pressure is applied to the container to compress the gallium oxide powder, and a solidified raw material 1 is produced. Cold isostatic pressing (CIP) can be used as a pressure application method at this time. The compressed gallium oxide powder molded body may be further heated to sinter it and increase the density of the raw material 1. Note that hot isostatic pressing (HIP) may be performed instead of the above CIP.

[0082] When producing raw material 1 containing a dopant, the dopant and gallium oxide powder are thoroughly stirred to mix uniformly. The mixed powder raw material is subjected to the above-mentioned solidification and heat treatment to produce raw material 1. It is preferable not to add sintering aids to the powder raw material.

[0083] The pressure application process causes the shape of the raw material 1 to have a tapered tip 1A. The shape of the tip 1A is generally a cone shape (an inverted cone). The raw material 1 does not crack due to temperature changes in the crystal manufacturing process, and maintains strength and uniformity that prevent discontinuous changes in the amount of molten material, regardless of the crystal state such as grain size and orientation.

[0084] The seed crystal 2B is a material that serves as the starting point for crystal growth. The orientation of the growing crystal is determined by the orientation of the seed crystal 2B. A β-Ga2O3 single crystal is used as the seed crystal 2B. For example, a part of a crystal produced previously is used as the seed crystal 2B. A β-Ga2O3 single crystal produced by the MBE (molecular beam epitaxy) method or the like may also be used as the seed crystal 2B.

[0085] Next, the seed crystal 2B is fixed to the seed crystal holder 7. Furthermore, the raw material 1 with the tapered tip 1A is placed above the surface (crystal growth region) of the seed crystal 2B. The weight detector 43 shown in FIG. 12 detects the weight of the raw material 1 and the weight of the crystal 2 including the seed crystal 2B, and the detection signal is input to the controller 50. The central processing unit 51 displays the weight of the raw material 1 and the weight of the crystal 2 on the display 81 according to the program stored in the memory 52. ​​The upper Z-axis movement motor 33 and the lower Z-axis movement motor 37 are driven to adjust the distance between the raw material 1 and the seed crystal 2B to a desired value. Oxygen (O2) and argon (Ar) gas are supplied from the gas source 61 through the flowmeter 42 into the processing vessel 71. The oxygen partial pressure is set to 10% or more. The pump 62 is started to exhaust the gas inside the processing vessel 71. Before supplying oxygen into the processing vessel 71, the gas in the processing vessel 71 may be replaced with another gas, if necessary. When preparations for starting crystal growth are complete, the central processing unit 51 starts the crystal manufacturing process in accordance with the program stored in the memory 52. ​​The following operations are executed by the central processing unit 51 generating control signals based on the program and controlling the elements to be controlled based on the control signals.

[0086] First, the controller 50 supplies power to the heater power supply 39 to heat the electric resistance heater R. The camera 41A (e.g., a CCD camera) captures an image of the tip 1A, and the controller 50 displays the image on the display 81. The radiation thermometer 41B measures the temperature of the tip 1A and inputs the measured detection signal to the controller 50. The controller 50 feedback-controls the power supplied to the heater power supply 39 so that the temperature reaches the target temperature (approximately 1800°C). It takes several hours for the temperature to rise from room temperature to the target temperature.

[0087] During the temperature rise, it is preferable to hold the raw material 1 and the seed crystal 2B at a position away from the heating region. In this case, the radiation thermometer 41B measures the temperature of the electric resistance heater R instead of the tip 1A, and after the temperature of the electric resistance heater R reaches the target temperature and the temperature stabilization period has elapsed, the upper Z-axis movement motor 33 is driven to adjust the distance between the raw material 1 and the seed crystal 2B (the distance between the electric resistance heater R) to the first distance for crystal production. The controller 50 drives the upper rotation motor 34 to rotate the raw material 1.

[0088] When the side of the tip 1A starts to melt, the molten material 3 generated on the cone surface of the tip 1A gathers at the lower end and forms a drop. The camera 41A captures the image and displays it on the display 81. The controller 50 adjusts the power supplied to the heater power supply 39 so that the size of the drop of the molten material at the lower end becomes a predetermined size. This adjustment may be performed manually, or it may be performed automatically by image processing the video signal from the camera 41A. After maintaining this state for a predetermined time and waiting for the temperature to stabilize, the lower Z-axis movement motor 37 is driven to raise the seed crystal 2B and adjust the distance between the raw material 1 and the seed crystal 2B to the second distance for crystal production. This causes the molten material 3 located at the lower end of the tip 1A to come into contact with the upper surface of the seed crystal 2B. When the molten material 3 reaches the surface of the seed crystal 2B, the weight of the raw material 1 and the weight of the seed crystal 2B displayed on the display 81 change, so that the contact can be confirmed not only from the camera image but also from the output of the weight detector 43.

[0089] The controller 50 may control the temperature of the crystal 2 by controlling the heating element 74 shown in Fig. 1. For example, the heating element 74 may preheat the seed crystal 2B before crystal growth. This makes it possible to suppress abrupt temperature changes, thereby suppressing thermal stress applied to the seed crystal.

[0090] After the molten material 3 (liquid column) is formed between the lower end of the tip 1A and the upper end of the seed crystal 2B, a period is waited for this state to stabilize. When the molten material solidifies, the crystal body 2A is formed on the surface of the seed crystal 2B, and the upper surface of the crystal body 2A becomes a new crystal growth area. When crystal growth begins, the upper Z-axis movement motor 33 is driven to lower the raw material 1 by a predetermined distance, and the lower Z-axis movement motor 37 is driven to lower the seed crystal 2B by a predetermined distance. This predetermined distance depends on the reduced weight of the raw material 1 detected by the weight detector 43 and / or the increased weight of the crystal 2. The controller 50 controls the distance between the upper surface of the crystal growth area and the heated tip 1A to be constant. In other words, during the crystal growth period, the positions of the seed crystal holder and the raw material holder are raised and lowered by the first and second driving mechanisms so that the distance between the upper end of the crystal main body 2A growing on the seed crystal 2B and the lower end of the tip portion 1A located above is constant.

[0091] The controller 50 can also control the distance between the side surface of the tip 1A and the electric resistance heater R arranged below so as to be constant. Through these controls, heating is controlled so that the shape of the tip 1A does not change during the crystal growth period. Of course, the controller 50 may finely adjust the power supplied from the heater power supply 39. During the crystal growth period, the output from the sensor is constantly monitored and the above-mentioned control is continued.

[0092] When the size of the crystal 2 reaches the target value, the amount of molten material 3 supplied from the raw material 1 to the crystal growth region is reduced. The amount of molten material 3 supplied is reduced by reducing the power supplied from the heater power supply 39 or by moving the raw material 1 away from the electric resistance heater R. Finally, the upper Z-axis movement motor 33 is driven to raise the position of the raw material 1 and separate the molten material 3 from the crystal growth region. Thereafter, the power supplied from the heater power supply 39 and the power supplied to the heating element 74 are gradually reduced to cool the raw material 1 and the crystal 2 to room temperature. During cooling, the upper Z-axis movement motor 33 may be driven to significantly raise the position of the raw material 1, and the lower Z-axis movement motor 37 may be driven to significantly lower the position of the crystal 2.

[0093] During this cooling, the crystal growth region may be thermally insulated from the heating region (the side of the electric resistance heater R and the tip portion 1A). For example, thermal insulation can be performed by disposing another heat shielding plate on the crystal growth region. The temperature of the two spaces separated by the other heat shielding plate can be controlled independently. When the heating element 74 shown in FIG. 1 is a cylindrical electric furnace, the position of the crystal 2 may be moved to near the center of the electric furnace in the axial direction. Since the grown crystal is cooled in a uniform temperature environment, the thermal strain remaining in the crystal can be reduced. After the crystal 2 is cooled to room temperature, if necessary, the atmosphere in the processing vessel 71 is returned to the air, and then the crystal 2 is taken out of the processing vessel 71, and the crystal manufacturing process is completed.

[0094] The produced crystal 2 is a β-Ga2O3 single crystal, and the diameter φ of the top surface is, for example, 2 inches. It is also possible to produce a single crystal with a diameter φ of 2 inches or more. According to the above-mentioned crystal production apparatus, since a crucible is not used, there is no intrusion of impurities from the crucible, and there is no oxygen deficiency that occurs under low oxygen partial pressure, and it is possible to grow a large gallium oxide single crystal.

[0095] During the crystal growth period, the seed crystal 2B can also be rotated by the lower rotation motor 38. The first rotation direction RD1 and the first rotation speed RS1 of the raw material 1 and the second rotation direction RD2 and the second rotation speed RS2 of the seed crystal 2B have the following combinations.

[0096] In the case of unidirectional and synchronous rotation, the first rotation direction RD1 and the second rotation direction RD2 are the same, and the first rotation speed RS1 and the second rotation speed RS2 are the same. In this case, since there is no difference between the rotation speeds, no twisting force is applied to the molten material, and the formation of defects caused by such force is suppressed.

[0097] In the case of synchronous and asynchronous rotation, the first rotation direction RD1 and the second rotation direction RD2 are the same, and the first rotation speed RS1 and the second rotation speed RS2 are different. In this case, there is a slight difference between the two rotation speeds, which promotes the uniformity of the molten material along the circumferential direction to some extent.

[0098] In the case of reverse rotation, the first rotation direction RD1 and the second rotation direction RD2 are opposite, and the first rotation speed RS1 and the second rotation speed RS2 are necessarily different. In this case, a large twisting force acts on the molten material, which promotes uniformization of the molten material along the circumferential direction.

[0099] During the crystal growth period, the seed crystal 2B can also be moved horizontally by a lower X-axis movement motor 35 and a lower Y-axis movement motor 36. These motors drive a second drive mechanism 32 including a horizontal movement mechanism such as an XY stage. This allows the position in the horizontal plane of the molten material 3 supplied from the raw material 1 to be adjusted. By moving the seed crystal 2B widely in the horizontal plane, a crystal with a large area can be manufactured. For example, it can be moved in a spiral manner or in a scanning manner in the horizontal plane.

[0100] As described above, the crystal manufacturing method according to the embodiment includes a step of placing a feedstock having a tapered tip 1A above a crystal growth region 2U, and a step of selectively heating and melting the side of the tip 1A by radiant heat proceeding obliquely upward while maintaining the shape of the tip 1A, and the material (molten material 3) melted from the side physically connects the side of the tip 1A and the upper surface of the crystal growth region 2U. In the FZ method using a conventional RF heater, not only heat is generated in the material, but also a binding force by an electromagnetic field is applied to the molten material. On the other hand, unlike the conventional method, this crystal manufacturing method selectively irradiates the side of the tip 1A with radiant heat to melt the material, and such a binding force is suppressed, and the size of the manufactured single crystal can be increased.

[0101] In a vertical cross section (XZ plane) including the central axis CX of the raw material 1, the acute angle θ between the side surface of the tip portion 1A and a horizontal plane located above this side surface is preferably within a range of 30 degrees to 60 degrees. More preferably, the acute angle θ is within a range of 40 degrees to 50 degrees. When the acute angle θ is within such a range, the molten material 3 can be stably supplied onto the crystal growth region 2U, particularly in the case of producing a single crystal of a compound semiconductor such as gallium oxide.

[0102] In the above embodiment, the radiant heat traveling obliquely upward is radiated from the electric resistance heater R arranged between the tip 1A and the crystal growth region 2U. The side surface of the tip 1A is also the lower surface of the raw material 1, and can efficiently receive the radiant heat traveling obliquely upward. The radiant heat traveling obliquely upward can include radiant heat radiated downward from the electric resistance heater R and reflected by the (heat) reflector 12. The reflector 12 can increase the amount of radiant heat irradiated to the side surface of the tip 1A. When the electric resistance heater R is used, the restraining force of the molten material 3 by the electromagnetic field is weak, and a space sufficient for arranging the electric resistance heater R can be formed below the molten material 3.

[0103] In the above embodiment, the inner surface of the reflector 12 preferably includes a ring shape including a plurality of continuous concave surfaces along the circumferential direction of the reflector 12. The concave surfaces can focus radiant heat on the side surface of the tip portion 1A, and can heat it at a high temperature. The position where the radiant heat is focused by the concave mirror formed of the concave surfaces does not necessarily have to coincide with the side surface. As for the shape of the concave surface, it is preferable to configure an ellipsoidal mirror in a horizontal plane or a plane perpendicular to the resistor central axis RX, but other shapes such as a parabolic mirror are also possible.

[0104] In the above-described embodiment, the reflector 12 has a reflector opening S12, and detects information about the raw material 1 through the reflector opening S12. The shape of the reflector opening S12 can be a slit or a slot, in addition to a simple circular through-hole.

[0105] In the above-described embodiment, the radiant heat radiated downward from the electric resistance heater R is blocked by a heat shield disposed between the electric resistance heater R and the crystal growth region 2U. In this case, the crystal growth region 2U can have a solidification temperature lower than the melting point of the material, and the temperature can be easily controlled independently of the electric resistance heater R.

[0106] In the above-described embodiment, the crystal growth region may be moved horizontally during the crystal growth period, allowing a large-area crystal to be grown.

[0107] In the above embodiment, during the crystal growth period, the side surface of the tip 1A has a periodic temperature distribution along the circumferential direction due to radiation heat, and the tip 1A is rotated around the central axis of the tip 1A. This rotation increases the uniformity of heating of the tip 1A.

[0108] In the above-mentioned embodiment, the crystal manufacturing apparatus 100 includes a means for performing the above-mentioned steps. That is, the crystal manufacturing apparatus 100 includes a means for placing the raw material 1 having the tapered tip 1A above the crystal growth region 2U (e.g., a support consisting of the feed holder 4, the connection block 5, the upper shaft 6, and the first drive mechanism 31), and a means (electrical resistance heater R) for selectively heating and melting the side of the tip 1A by radiant heat proceeding obliquely upward while maintaining the shape of the tip 1A, and for the material melted from the side to physically connect the side of the tip 1A to the upper surface of the crystal growth region 2U.

[0109] The crystal manufacturing apparatus 100 includes a support (e.g., a support consisting of a feed holder 4, a connection block 5, an upper shaft 6, and a first drive mechanism 31) for supporting a raw material having a tapered tip 1A, an electric resistance heater R that generates radiant heat for melting the raw material that advances obliquely upward, and a heat shield disposed below the electric resistance heater R. The radiant heat radiated downward from the electric resistance heater R is shielded by the heat shield. The radiant heat that advances obliquely upward from the electric resistance heater R can selectively reach the side of the tapered tip 1A. When the material on the side melts, the molten material moves downward along the side and further reaches the crystal growth region located below. When a crystal is manufactured using the crystal manufacturing apparatus 100, the size of the crystal can be increased.

[0110] The crystal manufacturing apparatus 100 includes a first drive mechanism 31 for at least raising and lowering the support, an upper Z-axis movement motor 33 (motor) for operating the first drive mechanism 31, a detection element 41 for acquiring information on the tip 1A of the raw material 1, and a controller 50 connected to the output terminal of the detection element 41 and controlling the upper Z-axis movement motor 33 (and the lower Z-axis movement motor 37). The detection element 41 can acquire information (temperature, image) on the tip 1A. The controller 50 can perform feedback control so that the temperature detected by the tip 1A coincides with the target temperature and the inclination angle of the side of the molten material obtained from the image coincides with the target inclination angle. The objects to be controlled include the power supplied from the heater power supply 39, the distance between the electric resistance heater R and the tip 1A, the rotation speed of the raw material 1, and the like. For example, when the inclination angle of the side of the molten material 3 becomes large, it is determined that the temperature of the lower part of the tip 1A is higher than that of the upper part, and the raw material 1 is lowered. For example, when the inclination angle of the side surface of the molten material 3 varies depending on the rotation angle, the rotation speed is increased.

[0111] The above-mentioned single crystal has a tapered tip 1A, and the raw material 1 is placed above the crystal growth region 2U. The side of the tip 1A is selectively heated and melted by radiant heat proceeding obliquely upward while maintaining the shape of the tip 1A, and the material melted from the side physically connects the side of the tip 1A and the upper surface of the crystal growth region 2U, forming a single crystal on the crystal growth region 2U. The size of this crystal can be made large. In particular, when the raw material 1 is a solid containing gallium and oxygen and the single crystal to be produced is a gallium oxide, the above-mentioned manufacturing method and manufacturing apparatus are useful.

[0112] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, an electric resistance heater having a shape other than a U-shape may be used as the electric resistance heater R. In the above-described embodiment, a plurality of electric resistance heaters R are arranged to surround the tip portion 1A, and a periodic temperature distribution is formed along the circumferential direction in a horizontal plane on the side surface of the tip portion 1A. If the direction of travel of the radiant heat is diagonally upward, a configuration that does not form a periodic temperature distribution may be used. For example, an electric resistance heater having a shape forming a ring in a horizontal plane may be used.

[0113] The reflector 12 may be fixed to the thermal shield 13 via a spacer or may be in close contact with the thermal shield 13. The outer surface of the reflector 12 may be stepped as long as the reflector 12 is shaped to fit into the thermal shield 13. In the above, the inner side surface of the reflector is elliptical in a cross section perpendicular to the longitudinal direction of the first resistor R12 of the electric resistance heater R, and the resistor is disposed near the focal position, but the inner side surface of the reflector may be elliptical in a horizontal cross section, and the resistor may be disposed near the focal position.

[0114] The above-mentioned crystal manufacturing apparatus includes an area having a function of supplying raw material 1, an area having a function of heating raw material 1 with a heater or the like, and an area where crystal 2 is grown. The arrangement of each area can be modified in various ways as long as the function of crystal growth is achieved. Elements disclosed in the above-mentioned embodiments may be omitted, substituted, and / or modified as necessary to manufacture large-sized single crystals, improve the quality of single crystals, improve production efficiency, etc. [Explanation of symbols]

[0115] 100...crystal manufacturing apparatus, 1...raw material, 1A...tip, 1B...raw material body, 1C...first engagement part, 1D...second engagement part, 2...crystal, 2A...crystal body, 2B...seed crystal, 2U...crystal growth area, 3...molten material, 4...feed holder, 410...support wire, 420...first pulley, 430...second pulley, 440...weight, 5...connection block, 6...upper shaft, 7...seed crystal holder, 8...lower shaft, 10...heating device, 11...group of electrical resistance heaters, 12...reflector, 121...upper end surface of reflector, 122...lower end surface of reflector, 123...reflector inner side, 12A...first concave surface, 12B...second concave surface, 12C...third concave surface, 12a...surface layer, 12b...main body layer, 12c...adhesive layer, 13...thermal shield, 131...thermal shield opening upper edge, 132...thermal shield opening lower edge, 133...thermal shield opening inner side, 134...thermal shield upper surface, 135...thermal shield lower surface, 14...heating device support, 30...group of controlled objects, 31...first drive mechanism, 32...second drive mechanism, 33...upper Z-axis movement motor, 34...upper rotation motor, 35...lower X-axis movement motor 36...lower Y-axis movement motor, 37...lower Z-axis movement motor, 38...lower rotation motor, 39...heater power supply, 40...sensor group, 41...detection element, 42...flow meter, 43...weight detector, 50...controller, 51...central processing unit, 52...memory, 53...bus, 54...input / output interface, 61...gas source, 62...pump, 71...processing vessel, 72...observation window, 73...insulation, 74...heating element, 75...gas inlet, 76...gas outlet, 80...input / output device, 81...display, 82... Input device, R...electrical resistance heater, CX...central axis, HS...horizontal surface, S12...opening for reflector, S13...opening for thermal shield, 41P...information propagation path, H1...first radiant heat propagation path, H2...second radiant heat propagation path, V...power supply potential, GND...ground potential, B...electrical resistance heater holder, G1...first focal point, G2...second focal point, R1...first electrode, R11...first conductor, R12...first resistor, R2...second electrode, R21...second conductor, R22...second resistor, R3...connecting resistor, RX...resistor central axis, CM...cooling medium.

Claims

1. A method for producing a crystal growth apparatus comprising the steps of: placing a solid source material having a downwardly tapered tip above a crystal growth region; a step of selectively heating and melting the side of the tip by radiant heat proceeding obliquely upward while maintaining the shape of the tip, and the molten material melted from the side of the solid raw material physically connects the side of the tip and the upper surface of the crystal growth region; Equipped with The radiant heat traveling obliquely upward is radiated from an electric resistance heater disposed between the tip and the crystal growth region. Crystal manufacturing method.

2. In a vertical cross section including the central axis of the raw material, an acute angle formed between the side surface of the tip portion and a horizontal plane located above the side surface is within a range of 30 degrees to 60 degrees. The method for producing a crystal according to claim 1.

3. In a vertical cross section including the central axis of the raw material, an acute angle formed between the side surface of the tip portion and a horizontal plane located above the side surface is within a range of 40 degrees to 50 degrees. The method for producing a crystal according to claim 1.

4. The radiant heat traveling obliquely upward includes radiant heat radiated downward from the electric resistance heater and reflected by a reflector. The method for producing a crystal according to claim 1.

5. The inner surface of the reflector includes a ring shape including a plurality of concave surfaces continuous along the circumferential direction of the reflector. The method for producing a crystal according to claim 4.

6. the reflector has a reflector opening, and information about the raw material is detected through the reflector opening. The method for producing a crystal according to claim 4.

7. Radiant heat radiated downward from the electric resistance heater is blocked by a heat shield disposed between the electric resistance heater and the crystal growth region. The method for producing a crystal according to claim 1.

8. During the crystal growth period, the crystal growth region is moved in a horizontal direction. The method for producing a crystal according to claim 1.

9. During a crystal growth period, the side surface of the tip portion has a periodic temperature distribution along a circumferential direction due to the radiant heat, and the tip portion is rotated around a central axis of the tip portion. The method for producing a crystal according to claim 1.

10. A support for supporting a raw material having a downwardly tapered tip; an electric resistance heater that generates radiant heat for melting the raw material, the radiant heat moving obliquely upward; a thermal shield disposed below the electrical resistance heater; A crystal manufacturing apparatus comprising:

11. A drive mechanism for at least raising and lowering the support; A motor for operating the drive mechanism; A detection element for obtaining information on the tip of the raw material; a controller connected to an output terminal of the detection element and controlling the motor; The crystal manufacturing apparatus according to claim 10 .

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