Single crystal manufacturing apparatus and single crystal manufacturing method

Abstract

A single crystal manufacturing apparatus that can manufacture large single crystals without using a crucible and a method for manufacturing single crystals using the apparatus are provided. The single crystal manufacturing apparatus is a single crystal manufacturing apparatus that grows a single crystal from a seed crystal upwards, comprising: a heat-insulating space that is heat-insulated from the space outside the apparatus; an induction heating coil disposed outside the heat-insulating space; a heat-insulating plate that divides the heat-insulating space into a first space including a crystal cultivation area for growing the single crystal and a second space above thereon, having an opening above the crystal cultivation area; a heating element disposed in the second space that heats the heat-insulating space by induction heating using the induction heating coil; and a support shaft for supporting the seed crystal from below and allowing the seed crystal to move vertically.

Description

Technical Field

[0001] This invention relates to a single crystal manufacturing apparatus and a method for manufacturing single crystals. Background Technology

[0002] Previously, an apparatus for manufacturing single crystals without using a crucible was known (see Patent Document 1). In the single crystal manufacturing apparatus described in Patent Document 1, a raw material molten liquid is supplied to a molten liquid formed on the upper surface of a seed crystal to form a mixed molten liquid, and a solid is precipitated from the mixed molten liquid as a single crystal to manufacture a single crystal. The molten liquid on the upper surface of the seed crystal is formed by irradiating the upper surface of the seed crystal with infrared light from an infrared irradiation device.

[0003] According to the single crystal manufacturing apparatus that does not use a crucible, there is no risk of a decrease in the purity of the single crystal due to the introduction of components contained in the crucible. In addition, when using a crucible, the material of the crucible is often very expensive, depending on the type of single crystal to be manufactured. Therefore, by adopting an apparatus that does not use a crucible, equipment costs can be significantly reduced.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6607651 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in the single crystal manufacturing apparatus described in Patent Document 1, although it is conceivable that this is to ensure the entry path of infrared radiation, the space around the upper surface of the grown single crystal is quite open. Therefore, when the melting point of the material is high, the heat dissipation from the crystal growth surface is so great that it adversely affects crystal growth (radiation energy is proportional to the difference between the fourth power of the object temperature and the fourth power of the surrounding temperature), making the manufacture of large single crystals difficult. Specifically, it is conceivable that the manufacture of materials with a melting point higher than silicon, such as those with a melting point above 1500°C, would be difficult.

[0009] The purpose of this invention is to provide a single crystal manufacturing apparatus that can manufacture large single crystals without using a crucible, and a method for manufacturing single crystals using the apparatus.

[0010] Solution for solving the problem

[0011] In order to achieve the above objectives, one aspect of the present invention provides a single crystal manufacturing apparatus as described below [1] to [7] and a single crystal manufacturing method as described below [8] to

[12] .

[0012] [1] A single crystal manufacturing apparatus for growing a single crystal from a seed crystal upwards includes: a heat-insulating space that is heat-insulated from a space outside the single crystal manufacturing apparatus; an induction heating coil disposed outside the heat-insulating space; a heat-insulating plate that divides the heat-insulating space into a first space including a crystal cultivation area for growing the single crystal and a second space above the first space, and has a hole above the crystal cultivation area; a heating element disposed in the second space that heats the heat-insulating space by induction heating of the induction heating coil; and a support shaft for supporting the seed crystal from below and enabling the seed crystal to move in the vertical direction.

[0013] [2] In the single crystal manufacturing apparatus described in [1] above, a heat-insulating material is provided in the first space in such a way as to surround the crystal growth area.

[0014] [3] In the single crystal manufacturing apparatus described in [1] or [2] above, a second heating element that generates heat by induction heating using the induction heating coil is provided in the first space above.

[0015] [4] The single crystal manufacturing apparatus according to any one of [1] to [3] above, wherein the thickness of the heat insulation plate has a distribution that makes the temperature of the outer periphery of the upper surface of the single crystal higher than the temperature of the inner region thereon.

[0016] [5] The single crystal manufacturing apparatus according to any one of [1] to [4] above, wherein a raw material supply port for the single crystal is provided on the upper side of the heat insulation space and directly above the center of the support shaft.

[0017] [6] The single crystal manufacturing apparatus according to any one of [1] to [5] above, wherein an annular member is provided inside the hole of the heat insulation plate, and the cross-sectional shape of the single crystal can be controlled by the shape of the opening region.

[0018] [7] The single crystal manufacturing apparatus according to any one of [1] to [6] above, wherein a funnel is provided for dripping the raw material molten liquid of the single crystal onto the upper surface of the single crystal.

[0019] [8] A method for manufacturing a single crystal includes: a step of placing a seed crystal below the hole in the first space of a heat-insulating space divided into a first space and a second space above the first space by a heat-insulating plate having holes; a step of induction heating a heating body disposed in the second space and melting the upper surface of the seed crystal by heat emitted from the heating body; a step of supplying molten raw material of the single crystal to the upper surface of the molten seed crystal through the second space and the hole in the heat-insulating plate; and a step of moving the seed crystal downward while continuing to supply the molten raw material and growing the single crystal upward from the seed crystal.

[0020] [9] In the method for manufacturing a single crystal as described in [8] above, in the process of supplying the raw material melt for the single crystal, the raw material melt obtained by melting the lower end of the raw material rod with the heat of the second space is dripped.

[0021]

[10] According to the single crystal manufacturing method described in [8] above, in the process of supplying the raw material melt of the single crystal, the raw material melt obtained by melting the lower end of the hollow raw material rod with the heat of the second space and melting the powder or granular raw material thrown into the interior of the hollow raw material rod with the heat of the second space at the lower end of the hollow raw material rod.

[0022]

[11] According to the single crystal manufacturing method described above [8], in the process of supplying the raw material melt of the single crystal, the raw material melt obtained by melting the powder or granular raw material that has been put into the funnel by the heat of the second space is dripped down.

[0023]

[12] In the method for manufacturing a single crystal according to

[10] or

[11] above, in the process of supplying the raw material melt for the single crystal, the metal is reacted with oxygen to form the powder or granular raw material.

[0024] Invention Effects

[0025] According to the present invention, a single crystal manufacturing apparatus capable of manufacturing large single crystals without using a crucible and a method for manufacturing single crystals using the apparatus are provided. Attached Figure Description

[0026] Figure 1 This is a vertical cross-sectional view of a single crystal manufacturing apparatus according to an embodiment of the present invention.

[0027] Figure 2 It is an enlarged vertical cross-sectional view of the perimeter of the heat insulation space of the single crystal manufacturing device.

[0028] Figure 3 (a) to (c) are vertical cross-sectional views showing the growth process of a single crystal.

[0029] Figure 4 (a) is a vertical cross-sectional view showing the shape of a single crystal during the growth process without necking but only shoulder expansion. Figure 4 (b) is a vertical cross-sectional view showing the shape of a single crystal during the growth process without necking or shoulder expansion.

[0030] Figure 5 (a) and (b) are vertical cross-sectional views showing a structure in which an annular insulating material surrounding the crystal growth region is disposed in the region surrounding the crystal growth region in the first space. Figure 5 (c) is a vertical cross-sectional view showing the structure in which a heating element is provided in the area surrounding the crystal growth region in the first space.

[0031] Figure 6 (a) and (b) are vertical cross-sectional views showing a structure provided with a distribution of insulation panels of thickness. Figure 6 (c) is a vertical cross-sectional view showing the structure with a reduced diameter of the annular heating element.

[0032] Figure 7 (a) is a vertical cross-sectional view showing a structure provided with a shape control component for controlling the shape of a single crystal. Figure 7 (b) is a vertical cross-sectional view of a structure having a shape control member with an increased width of the annular base.

[0033] Figure 8 (a) is a schematic vertical cross-sectional view showing how the raw material is supplied using a raw material bar. Figure 8 (b) is a schematic vertical cross-sectional view showing how a hollow feed bar is used to supply molten feed. Figure 8 (c) is a schematic vertical cross-sectional view showing how a funnel is used to supply molten raw materials.

[0034] Figure 9 It is a schematic vertical cross-sectional view showing how a powdered, granular, or liquid metal reacts with oxygen to obtain a raw material as an oxide.

[0035] Explanation of reference numerals in the attached figures

[0036] 1…Single crystal manufacturing apparatus, 10…Insulated space, 101…First space, 102…Second space, 103…Crystal cultivation area, 11…Induction heating coil, 12…Insulation plate, 121…Hole, 13…Heating element, 19…Support shaft, 20…Seed crystal, 21…Single crystal, 31, 32…Insulation material, 33…Heating element, 34…Insulation plate, 35…Shape control component, 40…Raw material rod, 41…Melted liquid, 42…Hollow raw material rod, 43…Raw material, 44…Function. Detailed Implementation

[0037] [Implementation Method]

[0038] (Composition of the manufacturing apparatus)

[0039] Figure 1 This is a vertical cross-sectional view of the single crystal manufacturing apparatus 1 according to an embodiment of the present invention. Figure 2 This is a vertical cross-sectional view of the enlarged perimeter of the heat-insulating space 10 of the single crystal manufacturing apparatus 1. The single crystal manufacturing apparatus 1 is an apparatus in which raw materials are supplied to the upper surface of the seed crystal 20 without using a crucible, and a single crystal 21 is grown upward from the seed crystal 20.

[0040] The single crystal manufacturing apparatus 1 includes: a heat-insulating space 10, which is heat-insulated from the space outside the apparatus; an induction heating coil 11, which is disposed on the outside of the heat-insulating space 10; a heat-insulating plate 12, which divides the heat-insulating space 10 into a first space 101 and a second space 102 above the first space 101; a heating element 13, which is disposed in the second space 102 and heats the space within the heat-insulating space 10 by induced current flowing through it through the electromagnetic induction of the induction heating coil 11; and a support shaft 19, which supports the seed crystal 20 from below and allows the seed crystal 20 to move vertically. Furthermore, in this embodiment, the vertical direction refers to a direction along or approximately along the vertical direction.

[0041] The first space 101 of the heat-insulating space 10 includes a crystal cultivation region 103, which serves as a region for cultivating single crystals 21. The crystal cultivation region 103 is located directly above the hole 181 of the substrate 18, which will be described later. The heat-insulating plate 12 has a hole 121 located above the crystal cultivation region 103. Therefore, the raw material for single crystal 21 can be supplied through the second space 102 and the hole 121 of the heat-insulating plate 12 to the upper surface of the seed crystal 20 or the upper surface of the single crystal 21 grown on the seed crystal 20.

[0042] In addition, the single crystal manufacturing apparatus 1 includes: a heat-insulating material 14, which serves as the sidewall of the heat-insulating space 10; a heat-insulating material 15, which serves as the upper wall of the heat-insulating space 10; a heat-insulating material 16, which is disposed on the heat-insulating material 15; an outer wall 17, which surrounds the heat-insulating materials 14, 15, and 16; and a substrate 18, which serves as the base for the heat-insulating materials 14, 15, 16 and the outer wall 17. These components are made of a heat-resistant material capable of withstanding temperatures near the melting point of the single crystal 21.

[0043] For example, if the single crystal 21 is a gallium oxide single crystal, the heat insulation material 14 is, for example, made of porous zirconia or zirconia fiber board. The heat insulation material 15 is, for example, made of porous zirconia or zirconia fiber board. The heat insulation material 16 is, for example, made of alumina fiber board. The outer wall 17 is, for example, made of alumina fiber board. The substrate 18 is, for example, made of alumina board.

[0044] Furthermore, since the insulation material 15 is most prone to deformation due to its shape or arrangement, it is preferable to use zirconia fiberboard that has undergone curing treatment, porous alumina that has undergone curing treatment, dense zirconia that has undergone curing treatment, dense alumina that has undergone curing treatment, or zirconia fiberboard with a zirconia cement coating as the insulation material 15. Moreover, the curing treatment of the aforementioned zirconia fiberboard, etc., employs high-temperature annealing before use, for example, high-temperature annealing at 1700–1900°C. Furthermore, the inventors of this invention first discovered that this prior high-temperature annealing cures the zirconia fiberboard, etc., thus suppressing deformation under high-temperature conditions.

[0045] In addition to the single crystal manufacturing apparatus 1, the heat insulation material 15 can also be used as a heat insulation material around the hottest heating element in various high-temperature heating devices such as crystal growth furnaces, sintering furnaces, and annealing furnaces. In any case, it can prevent deformation or cracking caused by deformation, thus stabilizing the temperature inside the furnace. Furthermore, since the heat insulation material 15 has a long lifespan, it can reduce the maintenance costs of the apparatus.

[0046] Furthermore, it is preferable to use an alumina fiberboard with an alumina blanket attached to its inner surface for the outer wall 17. In this case, the cushioning properties of the alumina blanket can be utilized to suppress cracking of the outer wall 17 when the insulation material 16 expands. The alumina blanket attached to the inner surface of the alumina fiberboard is required to have a thickness sufficient to cushion the expansion of the insulation material 16 disposed on the alumina blanket side. However, it is difficult to measure the expansion of the insulation material under high-temperature conditions, so it is preferable to use an alumina blanket with a thickness that is presumably sufficient to achieve the desired effect, for example, an alumina blanket with a thickness of 5 mm or more, preferably 10 mm or more. In addition, considering ease of operation, the alumina fiberboard to which the alumina blanket is attached preferably has a thickness of 10 mm or more. Furthermore, in addition to the single crystal manufacturing apparatus 1, the outer wall 17 can also be used in various high-temperature heating apparatuses such as crystal growth furnaces, sintering furnaces, and annealing furnaces. Furthermore, the inventors of this invention first discovered this method of absorbing the expansion of adjacent components by attaching an alumina blanket to the inner surface of the alumina fiberboard.

[0047] The aforementioned zirconia fiberboard is a fibrous thermal insulation material obtained by vacuum forming zirconia fibers. Additionally, alumina fiberboard is a fibrous thermal insulation material obtained by molding alumina fibers with inorganic and organic binders. Furthermore, alumina blankets are fibrous thermal insulation materials obtained by needle-punching alumina fibers to form a mat-like structure.

[0048] An induction heating coil 11 is positioned to surround the heating element 13 from the outside of the outer wall 17. When the magnetic field generated around the induction heating coil 11 by allowing current to flow through it passes through the inner side of the annular heating element 13, an induced current flows through the heating element 13, and the heating element 13 heats up due to its resistance.

[0049] The heating element 13 is made of a heat-resistant conductor capable of withstanding temperatures near the melting point of the single crystal 21. For example, in the case where the single crystal 21 is a gallium oxide-based single crystal, iridium or platinum-rhodium, or iridium or platinum-rhodium coated with zirconium oxide, is used as the material for the heating element 13. The heating element 13 is ring-shaped, typically as shown in the image. Figure 1 It is cylindrical as shown. The heating element 13 is positioned on the heat insulation plate 12 in such a way that it surrounds the space directly above the crystal growth region 103.

[0050] The heat insulation plate 12 is made of a heat-resistant material capable of withstanding temperatures near the melting point of the single crystal 21, such as porous zirconia. Furthermore, to suppress deformation, it is preferable to use the same material as the aforementioned heat insulation material 15, such as a zirconia fiberboard that has undergone curing treatment, as the material for the heat insulation plate 12. The heat insulation plate 12 is used to selectively melt the upper surface of the seed crystal 20, which becomes the growth surface of the single crystal 21, or the upper surface of the single crystal 21.

[0051] Radiation emitted from the heating element 13 passes directly through the holes 121 of the heat insulation plate 12 to the crystal growth region 103 of the first space 101. On the other hand, radiation emitted from the heating element 13 is weakened by the heat insulation plate 12 and reaches the region 104 surrounding the crystal growth region 103 of the first space 101. Therefore, for the seed crystal 20 and the single crystal 21 in the crystal growth region 103, the heating from above is stronger than the heating from the side. As a result, it is possible to selectively melt the upper surface of the seed crystal 20 or the upper surface of the single crystal 21, which becomes the growth surface of the single crystal 21.

[0052] To ensure the symmetry of the temperature distribution in the first space 101, the insulation plate 12 is preferably as follows: Figure 1 As shown, the surface is arranged horizontally. Furthermore, to suppress temperature drop at the outer periphery of the crystal growth surface and to prevent the heat insulation plate 12 from covering the outer periphery of the crystal growth surface, the outline of the hole 121 is preferably located outside the outline of the single crystal 21. The diameter of the hole 121 is, for example, set to a value equal to the diameter of the single crystal 21 plus 10 mm.

[0053] The support shaft 19 can move vertically within the shaft hole 181 that penetrates the substrate 18 in the vertical direction via a drive mechanism (not shown). Furthermore, the support shaft 19 can move vertically within the crystal growth region 103 of the first space 101 and the shaft hole 181 below it. Alternatively, the support shaft 19 can also be rotated around its central axis via the aforementioned drive mechanism. In this case, the seed crystal 20 supported by the support shaft 19 and the single crystal 21 grown from the seed crystal 20 can be rotated.

[0054] Alternatively, the support shaft 19 may also have a hole 191 extending through the support shaft 19 in the vertical direction. The temperature of the seed crystal 20 and the single crystal 21 can be measured via the hole 191 using a thermocouple or a radiation thermometer. The support shaft 19 is made of a heat-resistant material capable of withstanding temperatures near the melting point of the single crystal 21. For example, in the case of a gallium oxide-based single crystal, it may be made of a zirconia fiber plate, an alumina fiber plate, porous zirconia, porous alumina, or a combination thereof. Furthermore, the portion 192 of the support shaft 19 that contacts the single crystal 21 is made of a heat-resistant material capable of withstanding temperatures near the melting point of the single crystal 21 and does not react with the material of the single crystal 21. For example, it may be made of porous alumina, dense alumina, sapphire, or iridium. Figure 1 As shown, the support shaft 19 is composed of multiple blocks connected in the vertical direction.

[0055] The heat insulation material 15, which serves as the upper wall of the heat insulation space 10, has through holes 151 extending through the heat insulation material 15 in the vertical direction. Additionally, the heat insulation material 16 on the heat insulation material 15 has through holes 161 extending through the heat insulation material 16 in the vertical direction. The through holes 151 and 161 are continuous, connecting the heat insulation space 10 to the external space of the single crystal manufacturing apparatus 1. Therefore, raw materials for the single crystal 21 can be supplied to the heat insulation space 10 through the through holes 151 and 161. The diameters of the through holes 151 and 161 are, for example, 5 to 30 mm.

[0056] (Methods for manufacturing single crystals)

[0057] The following describes an example of a method for manufacturing a single crystal 21 using a single crystal manufacturing apparatus 1.

[0058] First, a seed crystal 20 is placed on the support shaft 19 below the hole 121, and the vertical position of the support shaft 19 is adjusted to place the seed crystal 20 in the first space 101 of the heat insulation space 10. At this time, in order to efficiently heat the upper surface of the seed crystal 20, it is preferable to place the seed crystal 20 at the highest possible position within the first space 101, for example, at a position where the height of the upper surface of the seed crystal 20 is the same as the height of the lower surface of the heat insulation plate 12.

[0059] Next, by flowing current through the induction heating coil 11, the heating element 13 disposed in the second space 102 is induction heated, and the upper surface of the seed crystal 20 is melted by the heat emitted from the heating element 13. At this time, as described above, the upper surface of the seed crystal 20 can be selectively melted by using the heat insulation plate 12.

[0060] Next, molten raw material for the single crystal 21 is supplied to the upper surface of the molten seed crystal 20 through the holes 121 of the second space 102 and the heat insulation plate 12. The method of supplying the molten raw material for the single crystal 21 will be described later.

[0061] Next, as Figure 3 As shown in (a) to (c), while continuing to supply molten raw material to the single crystal 21, the support shaft 19 is lowered to move the seed crystal 20 downwards, causing the molten material to gradually crystallize from below. Thus, the single crystal 21 grows upwards from the seed crystal 20. The growth rate of the single crystal 21 is set, for example, to 2 to 8 mm / h. When growing the single crystal 21 while rotating it, the rotation speed is set, for example, to 3 to 12 rpm.

[0062] exist Figure 3 In the examples shown in (a) to (c), necking was performed during the growth of single crystal 21, and the diameter of single crystal 21 was increased by shoulder widening (increasing the diameter). By performing necking, the quality of single crystal 21 can be improved even when the quality of seed crystal 20 is not high. Furthermore, by shoulder widening, the diameter of single crystal 21, which becomes smaller at the necking point, can be increased.

[0063] However, if the seed crystal 20 has sufficient mass, necking may not be necessary. When the diameter of the neck is small, it may be unable to support the weight of the grown single crystal 21 and break off from the neck. Alternatively, to prevent breakage from the neck, a mechanism for supporting the crystal at the shoulder could be incorporated into the single crystal manufacturing apparatus 1, but this would complicate the structure of the single crystal manufacturing apparatus 1. By not performing necking, this problem can be avoided.

[0064] Alternatively, if necking is not performed and a seed crystal 20 with a diameter approximately the same as the desired single crystal 21 (e.g., a difference within ±10%) is used, shoulder expansion can be omitted. In this case, problems such as twinning caused by shoulder expansion can be avoided, resulting in a higher quality single crystal 21.

[0065] Figure 4 (a) shows the shape of single crystal 21 during the growth process without necking but only shoulder expansion. Figure 4 (b) shows the shape of single crystal 21 during the growth process without necking or shoulder expansion.

[0066] In the single crystal manufacturing apparatus 1, the upper surface of the seed crystal 20, which serves as the crystal growth surface, or the upper surface of the single crystal 21, is located immediately below and adjacent to the high-temperature second space 102 where the heating element 13 is installed. Therefore, heat dissipation from the crystal growth surface is suppressed, and large single crystals 21 can be manufactured.

[0067] The atmosphere used in the cultivation of single crystal 21 can be selected based on the material of the heating element 13. For example, if the heating element 13 is made of a non-oxidizing material, an oxygen atmosphere can be used. When single crystal 21 is a gallium oxide-based single crystal, iridium is typically used as the material for the heating element 13. In this case, to suppress the oxidation of iridium, the oxygen concentration in the atmosphere is preferably less than 10% (e.g., 4%). If the surface of the iridium is coated with zirconium oxide, the oxygen concentration in the atmosphere is preferably less than 50%.

[0068] (Methods for controlling temperature distribution)

[0069] The following describes a method for controlling the temperature distribution on the growth surface of the single crystal 21 (the upper surface of the seed crystal 20 or the upper surface of the single crystal 21). Preferably, the temperature distribution on the growth surface of the single crystal 21 is one where the temperature in the central portion and the outer periphery are approximately equal (a flat distribution), or one where the temperature is lower in the central portion and higher at the outer periphery (a downwardly convex distribution). This allows the interface (solid-liquid interface) between the single crystal 21 and the molten liquid above it to be either flat or upwardly convex, suppressing the generation of crystal defects caused by the concentration of crystal deformation at the center.

[0070] Figure 5 (a) and (b) are vertical cross-sectional views showing that the regions 104 surrounding the crystal growth region 103 in the first space 101 are respectively provided with annular heat-insulating materials 31 and 32 surrounding the crystal growth region 103.

[0071] Figure 5 The insulation material 31 shown in (a) is the insulation material provided for the entire area of ​​region 104. Figure 5 The heat insulation material 32 shown in (b) is a heat insulation material disposed in a portion of the crystal growth region 103 of region 104. The heat insulation materials 31 and 32 are made of a material with heat resistance that can withstand temperatures near the melting point of the single crystal 21, such as porous zirconium oxide.

[0072] By using heat-insulating materials 31 and 32 surrounding the crystal growth region 103, heat dissipation from the side of the single crystal 21 can be suppressed, increasing the temperature of the outer periphery of the crystal growth surface. This makes it easier to make the temperature distribution on the growth surface of the single crystal 21 flat or convex.

[0073] Furthermore, by using heat-insulating materials 31 and 32, the difference in temperature distribution along the crystal growth direction (vertical direction) of the single crystal 21 can be reduced, thereby improving the quality of the single crystal 21. Moreover, these effects can be achieved equally when either heat-insulating material 31 or heat-insulating material 32 is used.

[0074] Figure 5(c) is a vertical cross-sectional view showing a structure in which a heating element 33, which is a component identical to the heating element 13, is provided in the region 104 surrounding the crystal growth region 103 in the first space 101. Like the heating element 13, the heating element 33 is inductively heated and generates heat by allowing an electric current to flow through the induction heating coil 11.

[0075] Since the heating element 33 heats the single crystal 21 from the side, it can raise the temperature of the outer periphery of the growth surface of the single crystal 21. As a result, it is easier to make the temperature distribution of the growth surface of the single crystal 21 flat or convex.

[0076] However, in order to suppress melting of the portion of the single crystal 21 other than its upper surface, the heating by the heating element 33 needs to be weaker than the heating by the heating element 13. For this purpose, for example, the following method can be adopted: simultaneously using the heating element 33 and... Figure 5 The heat insulation material 32 shown in (b) is used to reduce the radiation emitted from the heating body 33; or an induction heating coil 11 is provided only on the side of the heating body 13 to reduce the heat generated by the heating body 33.

[0077] Figure 6 (a) and (b) are vertical cross-sectional views showing the structure of a heat insulation plate 34 with a thickness distribution provided instead of heat insulation plate 12. In the heat insulation material 34, the portion 342 located above the region 104 surrounding the crystal growth region 103 has the thickest thickness, the portion 344 located above the outer periphery of the growth surface of the single crystal 21 has the thinnest thickness, and the portion 343 inside the portion 342 is thinner than the portion 342 but thicker than the portion 344.

[0078] The greater the thickness of the heat insulation material 34, the more significantly it reduces the radiation emitted from the heating element 13. Therefore, it is possible to make the temperature of the outer periphery of the growth surface of the single crystal 21 higher than the temperature of its inner region, and the temperature of the side surface of the single crystal 21 lower than the temperature of the growth surface. As a result, it is easier to make the temperature distribution of the growth surface of the single crystal 21 flat or convex.

[0079] exist Figure 6 In the thermal insulation material 34 shown in (a), portions 342 to 344 are integrally formed. Figure 6 In the thermal insulation material 34 shown in (b), the component containing part 342 and the component containing parts 343 and 344 are separately provided, but the same effect can be obtained in either way.

[0080] In addition, the heat insulation plate 34 has a hole 341 required for supplying raw material melt to the single crystal 21, but in order to suppress the temperature rise in the central part of the crystal growth surface, it is preferable to make the diameter of the hole 341 as small as possible without hindering the supply of raw material melt.

[0081] Furthermore, when using a transparent component such as sapphire, which can be used at high temperatures, as the material for the heat insulation plate 34, the same effect can be achieved by replacing the distribution of thickness with a distribution of surface roughness to create a distribution of radiation transmission emitted from the heating element 13. Specifically, for example, the surface of portion 344 can be made smooth, the surface roughness of portion 342 can be maximized, and the surface roughness of portion 343 can be smaller than that of portion 342.

[0082] Figure 6 (c) is shown to be related to Figure 2 The diagram shows a vertical cross-section of a structure with a reduced diameter of the annular heating element 13 compared to the structure shown. By reducing the diameter of the heating element 13, the ratio of the distance between the heating element 13 and the outer periphery of the crystal growth surface to the distance between the heating element 13 and the center of the crystal growth surface increases. Therefore, the temperature of the outer periphery of the crystal growth surface can be relatively increased. Thus, even when the diameter of the heating element 13 is large, if the temperature distribution of the crystal growth surface is convex upwards, reducing the diameter of the heating element 13 can make it flat or convex downwards.

[0083] Furthermore, by placing the through holes 151 and 161 for raw material supply directly above the center of the growth surface of the single crystal 21, that is, directly above the center of the support shaft 19, the temperature of the central portion of the growth surface can be reduced. This makes it easier to make the temperature distribution of the growth surface of the single crystal 21 flat or convex. In addition, to effectively reduce the temperature of the central portion of the growth surface, it is preferable to increase the diameter of the through holes 151 and 161 to a certain extent (for example, 10% to 60% of the diameter of the single crystal 21).

[0084] Alternatively, a hole for reducing the temperature of the central portion of the growth surface of the single crystal 21 can be provided directly above the center of the growth surface, independent of the through holes 151 and 161 for raw material supply. In this case, the through holes 151 and 161 for raw material supply are located off-center from the center of the growth surface of the single crystal 21. Therefore, the molten raw material needs to be dripped off-center from the center of the growth surface of the single crystal 21, but there is no problem as long as the single crystal 21 is rotated while growing. In addition, this case has the advantage that the distribution of impurities in the single crystal 21 becomes more gradual compared to dripping onto the center of the growth surface of the single crystal 21.

[0085] (Methods for controlling the cross-sectional shape of single crystals)

[0086] The following describes the method for controlling the cross-sectional shape of the single crystal 21. Here, cross-sectional shape refers to the shape of the radial cross-section. For example, the cross-sectional shape of a cylindrical single crystal 21 is circular, and the cross-sectional shape of a polygonal single crystal 21 is polygonal.

[0087] The cross-sectional shape of the single crystal 21 depends on the shape of the hole 121 in the heat insulation plate 12. This is because the temperature distribution on the upper surface of the single crystal 21 depends on the shape of the hole 121, and crystal growth occurs in the region on the upper surface of the single crystal 21 that has a shape similar to that of the hole 121. For example, when the hole 121 is circular, the cross-sectional shape of the single crystal 21 becomes circular; when the hole 121 is polygonal, the cross-sectional shape of the single crystal 21 becomes a polygon with rounded corners.

[0088] However, when using a heat insulation plate 12 with polygonal holes 121 to make the cross-sectional shape of the single crystal 21 polygonal, when the single crystal 21 is rotated around its central axis while it is being grown, the heat insulation plate 12 needs to be rotated in accordance with the rotation of the single crystal 21.

[0089] Figure 7 (a) is a vertical cross-sectional view showing the structure provided with a shape control member 35 for controlling the shape of the single crystal 21. The shape control member 35 is an annular member disposed inside the hole 121 of the heat insulation plate 12 and in contact with the molten material at the outer periphery of the upper surface of the single crystal 21. The crystal is mainly grown in the region inside the outer edge of the annular bottom surface 351 in contact with the molten material. Therefore, the cross-sectional shape of the single crystal 21 can be controlled by utilizing the planar shape of the outer edge of the bottom surface 351 of the annular shape control member 35.

[0090] Since the shape control component 35 comes into contact with the single crystal 21 and the molten liquid, it is made of a material that does not react with them. For example, if the single crystal 21 is a gallium oxide-based single crystal, iridium or sapphire is used as the material for the shape control component 35. Nevertheless, since the shape control component 35 comes into contact with the molten liquid, depending on the composition of the single crystal 21 (molten liquid) or the material of the shape control component 35, impurities from the shape control component 35 may sometimes contaminate the molten liquid. However, since the molten liquid flows from the non-contact area to the contact area of ​​the shape control component 35, the impurities are confined to the vicinity of the contact area. Therefore, even when using the shape control component 35, a high-purity single crystal 21 can be obtained. For example, when processing the single crystal 21 into a wafer, the contaminated portion can be removed by cutting away the outer peripheral portion that has come into contact with the shape control component 35.

[0091] Figure 7(b) is a vertical cross-sectional view showing the structure with a shape control member 35 having an increased width of the annular bottom surface 351. By increasing the width of the annular bottom surface 351 until a portion of the inner edge of the bottom surface 351 contacts the upper surface of the seed crystal 20, the shape control member 35 can be used not only for shape control of the single crystal 21, but also as a member to facilitate shoulder expansion (increasing the diameter). Since the molten material on the upper surface of the single crystal 21 (seed crystal 20) causes the interface between the single crystal 21 (seed crystal 20) and the bottom surface 351 to extend toward the outer edge of the annular bottom surface 351, the diameter of the single crystal 21 can be increased approximately from the diameter of the seed crystal 20 to the diameter of the outer edge of the bottom surface 351 during growth.

[0092] In addition, in such Figure 7 In the shape control member 35 with a large bottom surface 351 as shown in (b), the contact area between the bottom surface 351 and the molten metal is large. Therefore, the single crystal 21 is more susceptible to contamination from impurities from the shape control member 35. Therefore, by first using the shape control member 35 with a large bottom surface 351 to expand the shoulders to grow a large-diameter single crystal 21, and then using a large-diameter seed crystal 20 cut from this single crystal 21, without using the shape control member 35 with a large bottom surface 351, the single crystal 21 can be regrown. Thus, a large-diameter and high-purity single crystal 21 can be obtained.

[0093] (Method for supplying raw material melt)

[0094] The following describes the method for supplying molten raw material to the upper surface of the seed crystal 20 or the single crystal 21.

[0095] Figure 8 (a) is a schematic vertical cross-sectional view showing how the raw material rod 40 is used to supply the raw material molten material. The raw material rod 40 is a rod-shaped sintered body of the material constituting the single crystal 21. For example, in the case where a single crystal of a gallium oxide semiconductor is used as the single crystal 21, a sintered body of a gallium oxide semiconductor is used as the raw material rod 40.

[0096] The raw material rod 40 is inserted into the through holes 151 and 161, which serve as raw material supply ports, with its lower end positioned inside or near the second space 102. The heat of the second space 102 melts the molten material, causing the molten liquid 41 to accumulate and drip. At this point, the molten liquid 41 can be allowed to drip due to its own weight, or the raw material rod 40 can be vibrated to promote dripping. The dripping molten liquid 41 is supplied to the upper surface of the seed crystal 20 or the single crystal 21 through the holes 121 of the second space 102 and the heat insulation plate 12.

[0097] When the droplets of molten 41 are too large, they may scatter upon reaching the upper surface of the single crystal 21 or destabilize the solid-liquid interface. Therefore, it is preferable to adjust the droplet size according to the diameter of the raw material rod 40. Although the relationship between the diameter of the raw material rod 40 and the droplet size of the molten 41 varies depending on the specific gravity of the molten 41, for example, in the case where the raw material rod 40 is a sintered body of gallium oxide semiconductor, it is preferable to set its diameter to 5 mm or less.

[0098] Figure 8 (b) is a schematic vertical cross-sectional view showing how the hollow raw material rod 42 is used to supply the raw material molten material. The hollow raw material rod 42 is a hollow rod made of a sintered body of the material constituting the single crystal 21.

[0099] A hollow raw material rod 42 is inserted into the through holes 151 and 161, which serve as raw material supply ports, with its top end positioned inside or near the second space 102. The rod melts using the heat of the second space 102, forming a molten liquid 41. Then, powdered or granular raw material 43 is fed into the interior of the hollow raw material rod 42, melting at the lower end of the rod using the heat of the second space to increase the molten liquid accumulation. Similar to the hollow raw material rod 42, the raw material 43 is composed of a sintered body of the material constituting the single crystal 21.

[0100] The molten liquid 41 can be allowed to drip from the pooled liquid due to its own weight, or the raw material rod 40 can be vibrated to promote dripping. Alternatively, gas can be introduced through the interior of the hollow raw material rod 42 to promote dripping. The dripping molten liquid 41 is supplied to the upper surface of the seed crystal 20 or the single crystal 21 through the second space 102 and the hole 121 of the heat insulation plate 12.

[0101] Alternatively, a hollow tube can be used instead of the hollow raw material rod 42, and instead of the raw material 21, it can be made of a material that does not react with the raw material 43 and the molten liquid 41. In this case, by making the inner diameter of the hollow tube small enough, the raw material 43 that is dropped into the hollow tube can be melted at the lower end of the hollow tube to form a liquid accumulation.

[0102] Figure 8 (c) is a schematic vertical cross-sectional view showing how the molten raw material is supplied using a funnel 44. The funnel 44 is made of a material that does not react with the raw material 43 or the molten material 41. For example, in the case of manufacturing a single crystal 21 made of gallium oxide semiconductor, iridium or sapphire is used as the material of the funnel 44.

[0103] The funnel 44 is positioned with its lower end located within the second space 102. When raw material 43 is fed into the funnel 44 through the through holes 151 and 161, which serve as raw material supply ports, the raw material 43 melts within the funnel 44 due to the heat of the second space 102, becoming molten liquid 41. The molten liquid 41 dripping from the funnel 44 is supplied to the upper surface of the seed crystal 20 or the single crystal 21 through the holes 121 of the second space 102 and the heat insulation plate 12.

[0104] Alternatively, instead of using the hollow raw material rod 42 or funnel 44, the raw material 43 can be fed into the through holes 151 and 161. In this case, ideally, the raw material 43 melts as it falls due to the heat of the second space 102 and is supplied to the upper surface of the single crystal 21 in the form of molten liquid 41. However, even if it arrives at the upper surface of the single crystal 21 in the form of powder or particles without melting and melts on the upper surface of the single crystal 21, there will be no problem as long as the growth rate of the single crystal 21 is slowed down.

[0105] Figure 9 This is a schematic vertical cross-sectional view showing how metal 47 reacts with oxygen to obtain raw material 43 as an oxide. Metal 47 is a metal that is a raw material that becomes a metallic component of single crystal 21. For example, in the case of manufacturing a single crystal of gallium oxide as single crystal 21, Ga metal is used as metal 47 in order to obtain raw material 43 as a sintered body of gallium oxide.

[0106] Metal 47 is dropped into the interior of a hollow tube 46, which is connected to a through hole 161 and mounted on a heat-insulating material 16. Simultaneously with the dropping of metal 47, oxygen flows into the interior of the hollow tube 46. An induction heating coil 45 is wound around the hollow tube 46 to induction heat the metal 47. As the heated metal 47 descends within the hollow tube 46, it reacts with oxygen to produce a raw material 43 as an oxide.

[0107] By reacting the metal 47 with oxygen to form the raw material 43, it is possible to obtain a raw material 43 in powder or granular form with very high purity. For example, in the case of forming the raw material 43 as a sintered body of gallium oxide, a raw material 43 with a purity of around 7N can be obtained. Through this method, for example, it is possible to form... Figure 8 (b) or Figure 8 Raw material 43 is shown in (c).

[0108] When Ga metal is used as metal 47, if it is a small quantity, the frequency of induction heating (the frequency of the alternating current flowing through the induction heating coil 45) is preferably 100 kHz or higher. Here, "small quantity" refers, for example, to a total volume of 550 mm² of Ga metal added at one time. 3 the following.

[0109] Furthermore, at around 1000°C, only the surface of Ga metal is oxidized; therefore, to achieve complete oxidation of the Ga metal, it is preferable to heat it to a temperature of 1400°C or higher. When the heating temperature is set to 1400°C or higher, the Ga metal can be in any form, such as powder, granules, or liquid. Moreover, when a mist of Ga metal composed of nanoparticles is used as metal 47, complete oxidation can be achieved even at a heating temperature below 1400°C. Here, Ga metal nanoparticles can be formed, for example, by irradiating Ga metal with sound waves. Furthermore, since directly induction heating of Ga metal nanoparticles is difficult, it is necessary to place a heated body for induction heating inside the hollow tube 46 to indirectly heat the Ga metal nanoparticles using its radiant heat, etc.

[0110] Furthermore, based on the above-described method for obtaining high-purity powder or granular raw material 43, the following [1] to [3] methods for manufacturing gallium oxide can be provided.

[0111] [1] A method for manufacturing gallium oxide includes: a step of flowing oxygen into the interior of a hollow tube around which an induction heating coil is wound and then dropping Ga metal therein; and a step of induction heating the Ga metal inside the hollow tube by using a magnetic field generated by passing an alternating current through the induction heating coil, thereby causing the Ga metal to react with the oxygen to obtain gallium oxide.

[0112] [2] In the gallium oxide manufacturing method described in [1] above, the Ga metal is heated to a temperature of 1400°C or higher by induction heating.

[0113] [3] In the gallium oxide manufacturing method described in [1] or [2] above, the frequency of the induction heating is 100 kHz or higher.

[0114] (Effects of the implementation method)

[0115] The single crystal manufacturing apparatus 1 according to the above embodiment does not use a crucible, therefore, the amount of raw material metal used is small, which can significantly reduce equipment costs. Furthermore, since no crucible is used, there is no risk of a decrease in the purity of the single crystal 21 due to the inclusion of components contained in the crucible. Moreover, heat dissipation from the growth surface of the single crystal 21 is suppressed, thus enabling the manufacture of large-scale single crystals 21.

[0116] For example, in the process of manufacturing a single crystal using a single crystal manufacturing apparatus 1 (using Figure 7 (b) shows the shape control of the wide bottom surface 351 using component 35 and its application. Figure 8(Except for the funnel 44 shown in (c)) and using raw materials of purity 6N to manufacture a single crystal 21 made of gallium oxide, it is possible to cut a single crystal 21 with a carrier concentration of less than 1×10⁻⁶ without hole compensation from the single crystal 21. 16 cm -3 Furthermore, when a gallium oxide single crystal 21 was fabricated using a single crystal fabrication apparatus 1 and raw materials of purity 7N, it was possible to cut a single crystal 21 with a carrier concentration of less than 1 × 10⁻⁶ without hole compensation from the single crystal 21. 15 cm -3 These are wafers. Furthermore, by using these wafers, high-voltage devices can be fabricated without the need for an epitaxial layer to ensure voltage withstand capability. Additionally, [the technology / method] will be used... Figure 7 (b) shows the shape control of the wide bottom surface 351 using component 35 and its application. Figure 8 The reason for the exception to the funnel 44 shown in (c) is that sometimes the single crystal 21 is contaminated by impurities from the shape control component 35 or the funnel 44.

[0117] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. Furthermore, the constituent elements of the above embodiments can be arbitrarily combined without departing from the spirit of the invention.

[0118] Furthermore, the embodiments described above do not limit the invention covered by the claims. It should also be noted that not all combinations of features described in the embodiments are necessary for the solution to the problem of the invention.

Claims

1. A single crystal manufacturing apparatus, which grows a single crystal from a seed crystal upwards, characterized in that, have: The insulated space is insulated from the space outside the aforementioned single crystal manufacturing device; An induction heating coil is disposed on the outside of the aforementioned heat-insulating space; A heat insulation plate that divides the heat insulation space into a first space containing a crystal cultivation region for cultivating the single crystal and a second space above the first space, and has holes above the crystal cultivation region. A heating element, disposed in the aforementioned second space, heats the aforementioned insulated space by induction heating using the aforementioned induction heating coil; and A support shaft is used to support the seed crystal from below and allow the seed crystal to move in the vertical direction.

2. The single crystal manufacturing apparatus according to claim 1, wherein, In the first space mentioned above, a heat-insulating material is provided in a manner that surrounds the crystal growth area.

3. The single crystal manufacturing apparatus according to claim 1 or 2, wherein, In the first space described above, a second heating element is provided that generates heat through induction heating using the aforementioned induction heating coil.

4. The single crystal manufacturing apparatus according to claim 1 or 2, wherein, The thickness of the aforementioned heat insulation plate has a distribution that makes the temperature of the outer periphery of the upper surface of the aforementioned single crystal higher than the temperature of its inner region.

5. The single crystal manufacturing apparatus according to claim 1 or 2, wherein, The raw material supply port for the single crystal is provided on the upper side of the aforementioned heat insulation space, directly above the center of the aforementioned support shaft.

6. The single crystal manufacturing apparatus according to claim 1 or 2, wherein, The device has an annular component disposed inside the hole of the heat insulation plate, which allows the cross-sectional shape of the single crystal to be controlled by the shape of the opening region.

7. The single crystal manufacturing apparatus according to claim 1 or 2, wherein, It is equipped with a funnel for dripping the raw material molten liquid of the single crystal onto the upper surface of the single crystal.

8. A method for manufacturing a single crystal, characterized in that, Include: A process of placing seed crystals below the holes in the first space of a heat-insulating space that is divided into a first space and a second space above the first space by a heat-insulating plate with holes. The process of induction heating the heating element provided in the second space by induction heating coil disposed outside the above-mentioned heat insulation space, and melting the upper surface of the seed crystal by heat emitted from the above-mentioned heating element. The process of supplying molten raw material of single crystal to the upper surface of the molten seed crystal through the holes in the second space and the heat insulation plate; and The process of continuously supplying the above-mentioned raw material molten liquid while moving the above-mentioned seed crystal downwards and growing the above-mentioned single crystal upwards from the above-mentioned seed crystal.

9. The method for manufacturing a single crystal according to claim 8, wherein, In the process of supplying the raw material melt for the aforementioned single crystal, the raw material melt obtained by melting the lower end of the raw material rod with the heat of the aforementioned second space is dripped down.

10. The method for manufacturing a single crystal according to claim 8, wherein, In the process of supplying the raw material melt for the aforementioned single crystal, the raw material melt is obtained by dripping the lower end of the hollow raw material rod by melting it with the heat of the second space, and by melting the powder or granular raw material that is thrown into the interior of the hollow raw material rod with the heat of the second space at the lower end of the hollow raw material rod.

11. The method for manufacturing a single crystal according to claim 8, wherein, In the process of supplying the raw material melt for the aforementioned single crystal, the raw material melt obtained by melting the powder or granular raw material placed in the funnel with the heat of the aforementioned second space is dripped down.

12. The method for manufacturing a single crystal according to claim 10 or 11, wherein, In the process of supplying the raw material melt for the aforementioned single crystal, the metal is reacted with oxygen to form the aforementioned powder or granular raw material.

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