Single crystal growth apparatus and single crystal growth method

Abstract

In a single crystal growth apparatus used for growing single crystals containing raw materials with high vapor pressure, the objective is to eliminate the need for sealing after the crucible is placed inside the quartz tube, and to prevent contamination of the furnace with volatile raw materials during growth through a simple operation. [Solution] The single crystal growth apparatus is a single crystal growth apparatus for the unidirectional solidification crystal growth method, comprising: a crucible capable of storing and holding a raw material molten liquid; a heating means capable of heating the crucible; a crucible housing that covers at least the sides of the crucible; and a crucible stand that supports the crucible housing, wherein the top of the crucible housing is open, and a breathable capture lid is installed in the opening.

Description

Technical Field

[0001] The present invention relates to a single crystal growth apparatus and a single crystal growth method.

Background Art

[0002] With the recent trend of power saving in IoT devices, the development of replacing the power source of IoT devices with a self - power source is in progress. Also, the demand for technologies that reuse factory waste heat and the like as electric power to suppress greenhouse gas emissions is increasing. In particular, in recent years, the development of thermoelectric power generation, which obtains electrical energy from a temperature difference, has been continuously promoted.

[0003] Some thermoelectric materials are under development. Among them, there are Mg - based alloy materials. For example, there are Mg2Sn alloy and Mg2Si alloy. Mg2Sn is an alloy of magnesium and tin. Mg2Sn is a semiconductor with a band gap of 0.23 eV and is expected to be applied as a thermoelectric material in the medium - temperature range from 350K to 500K. Also, unlike Bi2Te3 and PbTe, which are commonly used as thermoelectric materials, its main components are composed of elements with low toxicity to the human body and the environment, so it has high safety.

[0004] Single crystals of such Mg - based alloy materials are grown by the VGF method and the vertical Bridgman method. In Patent Document 1, Mg and Sn raw materials are filled into a tantalum tube (crucible), and the tantalum tube is loaded into a quartz tube. The quartz tube is filled with an inert gas (for example, Ar gas). Then, it is described that a single crystal can be obtained by heating to the melting temperature until the raw materials melt and then cooling at a predetermined speed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the manufacturing method described in Patent Document 1, a crucible containing the raw materials is sealed inside a quartz tube. Mg is a material with high vapor pressure, and it volatilizes during the dissolution of the Mg raw material and during crystal growth, adhering to the area around the crucible and contaminating the furnace. Therefore, by sealing the crucible inside a quartz tube, the diffusion of Mg due to volatilization during growth can be contained within the quartz tube. However, this method requires the crucible to be placed inside the quartz tube and sealed, which is time-consuming and laborious. In particular, sealing requires the use of special equipment with an inert gas such as argon gas, which is time-consuming and laborious.

[0007] Therefore, the present invention has been made in view of the above problems, and provides a single crystal growth apparatus and a single crystal manufacturing method for growing single crystals containing raw materials with high vapor pressure such as Mg-based alloys, which eliminates the need for sealing work after the crucible is placed inside the quartz tube and prevents contamination of the furnace with volatile raw materials during growth with simple work. [Means for solving the problem]

[0008] According to one aspect of the present invention, a single crystal growth apparatus for a unidirectional solidification crystal growth method is provided, comprising: a crucible capable of storing and holding a raw material molten liquid; a heating means capable of heating the crucible; a crucible housing covering at least the sides of the crucible; and a crucible stand supporting the crucible housing, wherein the top of the crucible housing is open, and a permeable capture lid is installed in the opening.

[0009] According to one aspect of the present invention, the crucible housing may be cylindrical with open ends on both sides. Alternatively, the crucible housing may be cylindrical with a bottom, with an open end on the side opposite the bottom, and the crucible may be installed on the bottom surface inside the cylindrical crucible housing. The capture lid may also be made of inorganic fiber. The position of the capture lid may be set by adjusting the length of the crucible housing so that the temperature of the capture lid is below the boiling point of the substance to be captured from the start to the end of single crystal growth. Furthermore, the present invention may further include an insulating material arranged to cover the heating means, and a first insulating layer that divides the space inside the insulating material into a space below the heating means and a space above the space below the heating means. The device may also have a second insulating layer, which is arranged to cover the heating means and divides the space inside the insulating material into a space above the heating means and a space below the upper space. Alternatively, the device may include a pressure control device for controlling the pressure in the space within the single crystal growth apparatus. Furthermore, a crucible lid may be installed at the upper end of the crucible.

[0010] According to one aspect of the present invention, a method for growing a single crystal by a unidirectional solidification crystal growth method using a single crystal growth apparatus of the above aspect is provided, characterized by comprising: a melting step of filling a crucible with raw materials and melting the raw materials in the crucible with a heating means; a growth step of growing a single crystal in the crucible; and a cooling step of cooling the grown single crystal after the growth of the single crystal is completed. [Effects of the Invention]

[0011] According to the present invention, in a single crystal growth apparatus used for growing single crystals containing raw materials with high vapor pressure, such as Mg-based alloys, there is no need for sealing work after the crucible is placed inside the quartz tube, and contamination of the furnace with volatile raw materials during growth can be prevented with simple work. [Brief explanation of the drawing]

[0012] [Figure 1]This diagram schematically shows the configuration of the single crystal growth apparatus according to the embodiment. [Figure 2] This figure shows another example of a crucible container in the single crystal growth apparatus shown in Figure 1. [Figure 3] This diagram schematically shows other apparatus configurations in the single crystal growth apparatus according to the embodiment. [Figure 4] This diagram schematically shows other apparatus configurations in the single crystal growth apparatus according to the embodiment. [Modes for carrying out the invention]

[0013] Embodiments will be described below with reference to the attached drawings. Note that the present invention is not limited to the following embodiments, and can be modified as appropriate without altering the essence of the invention. To facilitate understanding of the explanation, the same reference numerals are used for identical components in each drawing whenever possible, and redundant explanations are omitted. Note that in each drawing, some or all of the components are depicted schematically, and the scale is changed as appropriate. Furthermore, in the following explanation, directions in the figures will be described using the XYZ coordinate system. In this XYZ coordinate system, the plane parallel to the horizontal plane is defined as the XY plane. Any direction parallel to this XY plane is denoted as the X direction, and the direction perpendicular to the X direction is denoted as the Y direction. The direction perpendicular to the XY plane (up and down direction) is denoted as the Z direction. In the X, Y, and Z directions, the direction of the arrow in the figure is the + direction, and the direction opposite to the direction of the arrow is the - direction. Furthermore, in the following explanation, "A~B" means "A or greater and B or less" as appropriate.

[0014] [Single crystal growth apparatus] Figures 1 and 2 are schematic diagrams showing the apparatus configuration in the single crystal growth apparatus according to this embodiment. Figures 1 and 2 are cross-sectional views of the single crystal growth apparatus. Figure 2 is a diagram showing another example of the crucible container in the single crystal growth apparatus of Figure 1. The single crystal growth apparatus 1 shown in Figures 1 and 2 is a single crystal growth apparatus using the unidirectional solidification crystal growth method. The single crystal growth apparatus 1 comprises a crucible 2, a crucible stand 4, a crucible container 5, a capture lid 6, a heating means 7, an insulating material 8, a chamber 9, a first insulating layer 10 (insulating layer), and a pressure control device 12. The unidirectional solidification crystal growth method applicable to the single crystal growth apparatus 1 is a method of growing crystals by solidifying a molten material in a crucible, such as the vertical Bridgman method (VB method) and the vertical temperature gradient solidification method (VGF method).

[0015] (raw materials) The composition of the single crystal and its raw materials applicable to the single crystal growth apparatus 1 are not limited. As described later, the single crystal growth apparatus 1 can prevent contamination of the furnace with volatile raw materials during growth, and therefore can suitably use raw materials with high vapor pressure. High vapor pressure raw materials are those with low melting points and are volatile, such as Mg, Al, Ga, Zn, P, S, and Tl. This specification mainly describes an example of producing a Mg2Sn single crystal, but is not limited to this. For example, when producing a Mg2Sn single crystal, the raw materials may be Mg raw material and Sn raw material, or an Mg-Sn alloy may be used. In the examples and comparative examples described later, granular Mg raw material with a particle size of 5 mm and granular Sn raw material with a particle size of 100 to 500 μm are used, but the elements contained in the raw materials are important, and the particle size is not limited.

[0016] (crucible) The crucible 2 can store and hold the raw material melt. In the drawing, reference numeral 3 indicates the raw material melt. The raw material is heated in the crucible 2 to store the raw material melt that has become liquid. The material of the crucible 2 is not limited, but a high melting point material with low chemical reactivity with the raw material melt is used. For example, the material of the crucible 2 includes alumina, magnesia, pyrolytic boron nitride, etc., and alumina is preferred in terms of being a high melting point material. The size and shape of the crucible 2 are not particularly limited. A known crucible 2 can be used. In addition, the open upper side of the crucible 2 may be covered with a crucible lid. The crucible lid is preferably made of the same material as the crucible 2.

[0017] (Heating means) The heating means 7 can heat the crucible. The heating means 7 is a heating heater, for example, a carbon resistance heater. The heating means 7 is a cylindrical heater. The heating means 7 can use a known configuration. The heating means 7 is arranged inside the heat insulating material 8 to be described later. The heating means 7 forms a so-called hot zone. The heating means 7 is electrically connected to a power source, and the power to the heating means 7 is supplied from the power source. The temperature generated by the heating means 7 is controlled by controlling the applied power. In addition, when growing a single crystal by the temperature gradient method, etc., a configuration including a plurality of heating heaters may be used as the heating means 7.

[0018] (Heat insulating material) The heat insulating material 8 is arranged to cover the heating means 7. The heat insulating material 8 has a cylindrical shape. The heat insulating material 8 is arranged outside the heating means 7 and contributes to maintaining the temperature of the space inside the heat insulating material 8. The material of the heat insulating material 8 is not particularly limited, and examples include carbon, boron nitride (BN), silicon nitride (Si3N4), mullite (3Al2O3·2SiO2~2Al2O3·SiO2), and alumina (Al2O3), etc. The configuration of the heat insulating material 8 can adopt a known configuration.

[0019] (The first heat insulating layer) The first heat insulating layer 10 (heat insulating layer) is disposed below the heating means 7. The first heat insulating layer 10 has a cylindrical shape. In the cylindrical hole of the first heat insulating layer 10, the crucible container 5 is disposed. The first heat insulating layer 10 and the crucible container 5 to be described later are arranged with a certain gap. The first heat insulating layer 10 partitions the space below the heating means 7 in the space inside the heat insulating material 8 and divides the space inside the heat insulating material 8. The space inside (inside) the heat insulating material 8 arranged to cover the heating means 7 is divided into the space below the heating means 7 and the space above the lower space. By the first heat insulating layer 10, the space above the first heat insulating layer 10 where the heating means 7 is disposed and the space below the first heat insulating layer 10 located below the heating means 7 are divided, and the heat transfer between these spaces is suppressed. Thereby, when moving the crucible 2 downward during single crystal growth, it is possible to suppress the heat generated by the heating means 7 from entering below the heating means 7 (below the first heat insulating layer 10). The material of the first heat insulating layer 10 is not particularly limited, and may be the same as the heat insulating material 8, or may be a material different from the heat insulating material 8 or a material with a different thermal conductivity.

[0020] (Crucible container · Capture lid) The crucible container 5 is disposed so as to cover at least the side of the crucible 2. The crucible container 5 is disposed inside the heating means 7 in the horizontal direction. The crucible container 5 is disposed between the heating means 7 and the crucible 2 in the horizontal direction. The crucible container 5 has, for example, a shape having a space inside, and the crucible 2 is accommodated therein. For example, the crucible container 5 has a bottomed cylindrical shape as shown in FIG. 1 or a cylindrical shape as shown in FIG. 2. The cylindrical shape may be a cylindrical shape or a shape other than a cylindrical shape. The upper end (+Z side end) of the crucible container 5 is open. The lower end of the crucible container 5 may be bottomed and sealed as shown in FIG. 1 or may not be sealed as shown in FIG. 2. The crucible container 5 can use, for example, a quartz tube.

[0021] A capture lid 6 is provided at the opening at the upper end of the crucible container 5. The crucible container 5 guides gases and liquids generated from the molten raw materials in the crucible 2 during single crystal growth into the internal space of the crucible container 5. The capture lid 6 captures (sometimes abbreviated as "capture") the gases and liquids generated from the molten raw materials in the crucible 2. In this way, the crucible container 5, together with the capture lid 6, can contain the gases and liquids generated from the molten raw materials in the crucible 2 during single crystal growth. It is preferable that the crucible container 5 can capture gases and liquids generated from the molten raw materials in the crucible 2 on its inner surface. For example, in the case of a quartz tube, as shown in the example, it is possible to capture gases and liquids generated from the molten raw materials on its inner surface.

[0022] In this embodiment, the capture lid 6 is permeable. Because the capture lid 6 is permeable, the atmosphere and atmospheric pressure inside the crucible container 5 can be manipulated by manipulating the atmosphere and atmospheric pressure introduced into the chamber 9, which will be described later. The pressure inside the crucible container 5 can be made equal to the pressure inside the chamber 9, which will be described later. Such a capture lid 6 is preferably made of inorganic fiber, from the viewpoint of permeability, capture, and heat resistance; for example, silica fiber (cotton made of SiO2) can be used.

[0023] In this embodiment, the temperature of the capture lid 6 (temperature of the upper end portion of the crucible container 5) is preferably set to be below the boiling point of the substance to be captured, and more preferably below the melting point, from the start to the end of single crystal growth. This allows the capture by the capture lid 6 to be carried out more effectively. The temperature of the capture lid 6 is set by the distance from the heating means 7, for example, by adjusting the length (height, dimension in the Z direction) of the crucible container 5. In the case where the crucible 2 (crucible stand 4) moves in the vertical direction, even if the crucible stand 4 moves, the temperature of the capture lid 6 can be set to the above-mentioned preferred range by lengthening the crucible container 5 so that the upper end of the crucible container 5 is below the boiling point of Mg. The length of the crucible container 5 can be determined by preliminary experiments. As shown in the embodiment, the crucible container 5 and the capture lid 6 were able to contain the Mg vapor in the crucible container 5 so that the Mg vapor would not scatter into the hot zone (outside the crucible container 5). In the embodiment, a quartz tube with an inner diameter of 50 mm and an outer diameter of 55 mm was used as the crucible container 5, but the inner diameter and outer shape of the crucible container 5 are not limited to this example. Not limited to the hot zone configuration shown in Figures 1 to 4, it was effective in implementing this embodiment for the upper end of the crucible container 5 to be below the boiling point of the raw material (Mg in the embodiment). In the case of a configuration in which the crucible 2 moves vertically, the crucible container 5 needs to be longer than in a configuration in which the crucible 2 does not move vertically so that the upper end of the crucible container 5 remains below the boiling point of the raw material even when the crucible 2 moves.

[0024] (crucible stand) The crucible stand 4 supports the crucible container 5. Furthermore, the crucible stand 4 directly or indirectly supports the crucible 2. That is, the crucible stand 4 supports either the crucible container 5, or both the crucible 2 and the crucible container 5. In the example shown in Figure 1, the crucible stand 4 supports the crucible container 5 and indirectly supports the crucible 2 placed on the bottom surface of the crucible container 5. In the example shown in Figure 2, the crucible stand 4 supports the lower end of the crucible container 5 and the crucible 2 placed on the inner circumference of the crucible container 5.

[0025] The crucible stand 4 moves vertically by a drive device (not shown). The configuration of the crucible stand 4 that moves vertically can be a known configuration, for example, the configuration described in Japanese Patent Application Publication No. 2022-146328 by the present applicant. The crucible stand 4 moves, allowing the crucible 2 to be moved. When using the Bridgman method, the crucible can be moved away from the heater at a predetermined speed to slowly cool the molten metal. When using the temperature gradient method, the crucible shaft is not moved, and the molten metal can be slowly cooled by adjusting the heater output.

[0026] (chamber) The single crystal growth apparatus 1 of this embodiment includes a chamber 9. The chamber 9 is formed to seal and cover each part of the single crystal growth apparatus 1. Each part of the single crystal growth apparatus 1 is housed in the sealed space within the chamber 9. The chamber 9 creates a sealed space inside and maintains the internal atmosphere.

[0027] (Pressure control device) The single crystal growth apparatus 1 of this embodiment includes a pressure control device 12. The pressure control device 12 controls the pressure in the space inside the single crystal growth apparatus. The pressure control device 12 is connected to the chamber 9. The pressure control device 12 includes a gas introduction means for introducing an inert gas such as argon or nitrogen into the chamber, and a means for discharging the gas inside the chamber (inside the single crystal growth apparatus), and controls the pressure inside the chamber 9 to a predetermined pressure in a predetermined atmosphere. The pressure control device 12 also controls the type of atmosphere inside the chamber 9. Such a pressure control device 12 can be a known type. The pressure control device 12 can control the pressure inside the chamber 9 to 8 atm or less.

[0028] In the case of Patent Document 1 mentioned above, in order to obtain a high-performance thermoelectric material, the crucible is sealed in a quartz tube under a pressurized inert atmosphere. However, the method described in Patent Document 1 has drawbacks, such as the time required for sealing the quartz tube and the inability to freely change the atmospheric pressure during the heat treatment. In this embodiment, when the single crystal growth apparatus 1 is equipped with a pressure control device 12, the heat treatment can be performed while adjusting the pressure, so the atmospheric pressure inside the crucible container 5 can be changed (controlled) at any time during the heat treatment. Furthermore, when the atmospheric pressure can be controlled during the raw material heat treatment, as in this embodiment, the yield for each production batch is stabilized, and as a result, inexpensive and stable quality single crystals such as Mg-based crystals can be manufactured. In addition, in this embodiment, the type of atmosphere inside the crucible container 5 can be controlled during the raw material heat treatment.

[0029] As described above, the single crystal growth apparatus according to this embodiment is a single crystal growth apparatus for the unidirectional solidification crystal growth method, comprising a crucible capable of storing and holding a raw material molten liquid, a heating means capable of heating the crucible, a crucible housing that covers at least the sides of the crucible, and a crucible stand that supports the crucible housing, wherein the top of the crucible housing is open, and a permeable capture lid is installed in the opening. The single crystal growth apparatus according to this embodiment is a single crystal growth apparatus used for growing single crystals containing raw materials with high vapor pressure, such as Mg-based alloys, and eliminates the need for sealing work after installing the crucible in the quartz tube, and prevents contamination of the furnace with volatile raw materials during growth with simple work.

[0030] For example, since magnesium (Mg) is highly flammable, it becomes difficult to dispose of if it is scattered during cultivation. However, according to the present invention, scattering during cultivation can be prevented as described above.

[0031] [Single crystal growth apparatus (second example)] Another example of the single crystal growth apparatus 1 according to this embodiment will be described. Figure 3 shows a second example of the single crystal growth apparatus 1. Figure 3 is a schematic diagram showing the apparatus configuration in the single crystal growth apparatus according to this embodiment. Figure 3 is a cross-sectional view of the single crystal growth apparatus. The single crystal growth apparatus 1 in Figure 3 is a single crystal growth apparatus using the unidirectional solidification crystal growth method. The single crystal growth apparatus 1 in Figure 3 is equipped with a second heat insulating layer 11.

[0032] (Second insulation layer) The second insulation layer 11 (insulation layer) is positioned above the heating means 7. The second insulation layer 11 is cylindrical in shape. The crucible housing 5 is positioned in the cylindrical hole of the second insulation layer 11. The second insulation layer 11 and the crucible housing 5 are positioned with a slight gap between them. The second insulation layer 11 is positioned below the capture lid 6 (upper end portion of the crucible housing 5). The second insulation layer 11 partitions the space inside the insulation material 8 above the heating means 7, dividing the space inside the insulation material 8. The second insulation layer 11 divides the space inside the insulation material 8, which is positioned to cover the heating means 7, into a space above the heating means 7 and a space below the space above the heating means 7. The second insulating layer 11 divides the space above the second insulating layer 11 from the space below the second insulating layer 11 where the heating means 7 is located, thereby suppressing heat transfer between these spaces. This prevents heat generated by the heating means 7 from penetrating above the heating means 7 (above the second insulating layer 11) during single crystal growth, thus lowering the temperature of the capture lid 6 (upper end portion of the crucible housing 5). As a result, the capture efficiency of the capture lid 6 can be improved. Furthermore, the length of the crucible housing 5 (dimension in the Z direction) can be shortened compared to the single crystal growth apparatus 1 in Figure 1, making the apparatus more compact. The material of the second insulating layer 11 is not particularly limited; it may be the same as the insulating material 8, or it may be a different material or material with a different thermal conductivity than the insulating material 8.

[0033] [Single crystal growth apparatus (third example)] Another example of the single crystal growth apparatus 1 according to this embodiment will be described. Figure 4 shows a third example of the single crystal growth apparatus 1. Figure 4 is a schematic diagram showing the apparatus configuration in the single crystal growth apparatus according to this embodiment. Figure 4 is a cross-sectional view of the single crystal growth apparatus. The single crystal growth apparatus 1 in Figure 4 is a single crystal growth apparatus using the unidirectional solidification crystal growth method. The single crystal growth apparatus 1 in Figure 4 is equipped with a second heat insulating layer 11 as described in Figure 3, and a heat insulating material 8 that is shorter in height than the heat insulating material 8 of the single crystal growth apparatus 1 in Figure 1.

[0034] When a second insulating layer 11 is provided, as described above, the heat generated by the heating means 7 during single crystal growth can be prevented from penetrating above the heating means 7 (above the second insulating layer 11), thereby lowering the temperature of the capture lid 6 (upper end portion of the crucible housing 5). As a result, the capture efficiency of the capture lid 6 can be improved. In the single crystal growth apparatus shown in Figure 4, the insulating material 8 is shorter in height compared to the insulating material 8 of the single crystal growth apparatus 1 in Figure 1, and the capture lid 6 (upper end portion of the crucible housing 5) is not covered by the insulating material 8. This allows the temperature of the capture lid 6 (upper end portion of the crucible housing 5) to be lowered even further. As a result, the capture efficiency of the capture lid 6 can be improved, similar to the single crystal growth apparatus shown in Figure 3. Furthermore, the length of the crucible housing 5 (dimension in the Z direction) can be made shorter than that of the single crystal growth apparatus 1 in Figure 1, and the insulation material 8 is shorter in height than that of the insulation material 8 in Figure 3, so the size of the apparatus can be made even more compact than that in Figure 3. Note that there are no particular restrictions on the material of the second insulation layer 11; it may be the same as the insulation material 8, or it may be a different material or a material with a different thermal conductivity than the insulation material 8.

[0035] (Method for manufacturing single crystals) Next, the method for growing a single crystal according to this embodiment will be described. One embodiment of the present invention is a method for growing a single crystal using the one-directional solidification crystal growth method with the single crystal growing apparatus of the embodiment described above. In this single crystal growing method, the explanation given for the single crystal growing apparatus above can be applied as appropriate, and the previously stated explanations will be omitted or simplified. Furthermore, the matters described in this single crystal growing method can also be applied as appropriate to the single crystal growing apparatus described above.

[0036] The single crystal growth method of this embodiment is a single crystal growth method that uses the single crystal growth apparatus of this embodiment described above to grow a single crystal by the unidirectional solidification crystal growth method, and comprises a melting step of filling a crucible 2 with raw material 3 and melting the raw material 3 in the crucible 2 with a heating means 7, a growth step of growing a single crystal in the crucible 2, and a cooling step of cooling the grown single crystal after the single crystal growth is completed.

[0037] The single crystal growth method of this embodiment, when performed by the vertical Bridgman method (VB method), includes a melting step in which raw materials 3 are filled into a crucible 2, a crucible housing 5 is installed covering at least the sides of the crucible 2, and a capture lid 6 is installed on the upper end of the crucible housing 5, a growth step in which the crucible stand 4 is moved closer to the heating means 7 to melt the raw materials 3 in the crucible 2, a growth step in which the crucible stand 4 is moved away from the heating means 7 to grow a single crystal in the crucible 2, and a cooling step in which the grown single crystal is cooled after the growth of the single crystal is completed, and the capture lid 6 is characterized in that it is below the boiling point temperature of the raw materials between the melting step and the single crystal cooling step. The above explanation describes an example of moving the crucible stand 4 in the vertical Bridgman method (VB method) to melt the raw material 3 in the crucible 2 or grow a single crystal. However, in the vertical temperature gradient solidification method (VGF method), instead, the melting of the raw material 3 in the crucible 2 or the growth of a single crystal may be performed by increasing or decreasing the amount of heat supplied from the heating means.

[0038] The melting process involves filling a crucible 2 with raw materials 3 and melting the raw materials 3 in the crucible 2 using a heating means 7. First, the raw materials 3 are filled into the crucible 2. The crucible and raw materials are not particularly limited. Next, as shown in Figure 1, a crucible housing 5 is placed to cover the sides of the crucible 2, and a capture lid 6 is placed on the upper end of the crucible housing 5. For example, in the VB method, the crucible stand 4 is then moved closer to the heating means 7 to melt the raw materials 3 in the crucible 2. Each condition of the melting process, such as the melting temperature, is appropriately determined according to the composition, raw materials, and size of the single crystal to be manufactured, and known methods can also be used.

[0039] Following the melting process, a growth process is carried out. The growth process involves growing a single crystal in the crucible 2. For example, in the VB method, after the melting process, the crucible stand 4 is moved away from the heating means 7 to grow a single crystal in the crucible 2. The conditions of the growth process, such as the movement speed, are appropriately determined according to the composition, raw materials, and size of the single crystal to be manufactured, and known methods can also be used.

[0040] A cooling process is carried out after the growth process. The cooling process involves cooling the grown single crystal after its growth is complete. The conditions of the cooling process, such as the cooling temperature, are determined appropriately according to the composition, raw materials, and size of the single crystal intended for production, and known methods can also be used.

[0041] In the single crystal growth method of this embodiment, the temperature of the capture lid 6 (temperature of the upper end portion of the crucible container 5) is kept below the boiling point of the raw material 3, more preferably below the melting point of the raw material 3, between the melting step and the single crystal cooling step. As a result, as described above, the crucible container 5 guides the gas and liquid generated from the molten raw material in the crucible 2 during single crystal growth into the internal space of the crucible container 5. The capture lid 6 captures the gas and liquid generated from the molten raw material in the crucible 2 (sometimes abbreviated as "capture"). As a result, the crucible container 5, together with the capture lid 6, can contain the gas and liquid generated from the molten raw material in the crucible 2 during single crystal growth. It is preferable that the crucible container 5 is capable of capturing the gas and liquid generated from the molten raw material in the crucible 2 on its inner surface. For example, in the case of a quartz tube, as shown in the example, it is possible to capture gases and liquids generated from the molten raw material on its inner surface. This single crystal growth method is used in a single crystal growth apparatus for growing single crystals containing raw materials with high vapor pressure, such as Mg-based alloys, and eliminates the need for sealing work after the crucible is placed inside the quartz tube. Furthermore, it is possible to prevent contamination of the furnace with volatile raw materials during growth with simple operations.

[0042] Furthermore, in the single crystal growth method of this embodiment, as described above, because the capture lid 6 is permeable, the atmosphere and atmospheric pressure inside the crucible container 5 can also be manipulated (controlled) by manipulating the atmosphere and atmospheric pressure introduced into the chamber 9, which will be described later. The pressure inside the crucible container 5 can be made to match the pressure inside the chamber 9 by the pressure control device 12. This allows for heat treatment while adjusting the pressure, so the atmospheric pressure can be changed at any time during the heat treatment. Moreover, when the atmospheric pressure can be controlled during the raw material heat treatment, as in this embodiment, the yield for each production batch is stabilized, and as a result, inexpensive and stable quality single crystals such as Mg-based crystals can be manufactured. [Examples]

[0043] The embodiments of the present invention will be described in detail below with reference to comparative examples.

[0044] [Example 1] An alumina crucible with an inner diameter of 10 mm and a height of 100 mm was used. The raw material was a master alloy consisting of Mg and Sn with a Mg to Sn ratio of 2:1. The single crystal growth apparatus used was the one shown in Figure 1. The hot zone was one in which a first insulating layer was installed below the heater (heating means) as shown in Figure 1. The insulating material was made of carbon felt, which is lightweight and has high heat resistance. A porous material made of SiO2 cotton was used as the retaining lid. The master alloy was placed in the crucible and the crucible lid was placed on top, and the crucible, crucible container, retaining lid, heater, etc. were arranged as shown in Figure 1. A quartz tube was used as the crucible container. The quartz tube used was bottomed and open at the top as shown in Figure 1, and the length of the upper end was set to 700 mm so that it was below the boiling point of Mg.

[0045] Next, argon gas was introduced into the growth furnace to adjust the furnace to an inert atmosphere of 1 atmosphere. Then, the crucible was heated by applying power to the heater over a period of 9 hours from the start of heating until the temperature of the raw material reached the melting point of Mg2Sn, and this was maintained for 3 hours. After that, the crucible was cooled at a rate of 5°C per hour to grow crystals, and then cooled to room temperature before the sample was collected.

[0046] After the above work was completed, the inside of the growth furnace (chamber) was observed to confirm that no raw materials had scattered outside the crucible containment (outside the quartz tube). Brownish material was observed on the inside of the quartz tube and on part of the crucible side of the capture lid.

[0047] [Example 2] The hot zone was constructed using a system with a first and second insulating layer above and below the heater (heating means), as shown in Figure 3, and the same material preparation method as in Example 1 was carried out. The master alloy was placed in the crucible and the lid was placed on top, and the crucible, crucible housing, capture lid, heater, etc. were arranged as shown in Figure 3. A quartz tube was used as the crucible housing. The quartz tube used was a bottomed, open-topped type as shown in Figure 1, and its length was set to 360 mm so that the upper end was below the boiling point of Mg. After the above work was completed, the inside of the growth furnace (inside the chamber) was observed to confirm that no raw material had scattered outside the quartz tube. Brownish material was observed on the inside of the quartz tube and on part of the crucible side of the capture lid.

[0048] [Example 3] Before starting the heat treatment, the atmospheric pressure inside the chamber was set to 1 atm. After the raw material melted, the pressure of the argon introduced into the chamber was changed to 5 atm, and the process of solidifying the molten material was carried out in the same manner as in Example 1 to produce the material. After the work was completed, the inside of the growth furnace (chamber) was observed to confirm that no raw material had scattered outside the quartz tube. Brownish material was observed on the inside of the quartz tube and on part of the crucible side of the capture lid.

[0049] [Example 4] Using a quartz tube crucible housing with open ends on both sides, as shown in Figure 2, the same material preparation method as in Example 3 was carried out. After the work was completed, the inside of the growth furnace was observed to confirm that no raw materials had scattered outside the quartz tube. Brownish material was observed on the inside of the quartz tube and on a part of the crucible side of the capture lid.

[0050] [Example 5] The same material preparation method as in Example 4 was carried out without placing a crucible lid on the crucible. After the work was completed, the inside of the growth furnace (chamber) was observed to confirm that no raw materials had scattered outside the quartz tube. Brownish material was observed on the inside of the quartz tube and on part of the crucible side of the capture lid, and needle-shaped Mg was observed on the crucible side of the capture lid.

[0051] [Comparative Example 1] Referring to Patent Document 1 mentioned above, a lid was placed on a crucible containing the raw materials, and the mixture was sealed inside a quartz tube along with 1.6 atm of Ar. The quartz tube was then inserted into a tubular furnace and heat-treated. The inside of the quartz tube was sealed and airtight. The heat-treatment conditions were the same as in Example 1. After the work was completed, it was confirmed that no raw materials had scattered outside the quartz tube.

[0052] [Comparative Example 2] In Example 1, the raw materials were changed to an iron (Fe) to gallium (Ga) ratio of 82:18, and the single crystal growth apparatus was changed to one without a capture body and retaining lid, and an FeGa alloy single crystal was grown. The single crystal was grown under the same atmospheric conditions as in Example 1, by introducing argon gas to create an inert atmosphere of 1 atmosphere inside the furnace. The crucible was heated by applying power to the heater so that the temperature of the center of the seed crystal reached the melting point of the FeGa alloy, and then held for a predetermined time. After that, the crucible was cooled to grow the crystal, and the sample was collected after it had cooled to room temperature.

[0053] After completing the above work, observation of the inside of the growth furnace revealed that the raw material had been scattered. The scattered raw material was adhering to the inner wall of the chamber.

[0054] Table 1 shows the manufacturing conditions and evaluation results for Examples 1-5 and Comparative Examples 1-2.

[0055] [Table 1]

[0056] As shown in Examples 1-5 and Comparative Examples 1-2, the single crystal growth apparatus and single crystal growth method according to this embodiment were confirmed to achieve the effects described above.

[0057] Furthermore, the technical scope of the present invention is not limited to the embodiments described above. One or more of the requirements described above may be omitted. Also, the requirements described above may be combined as appropriate. In addition, to the extent permitted by law, all disclosures of the documents cited above shall be incorporated as part of the description herein. [Explanation of symbols]

[0058] 1. Single crystal growth apparatus 2 Crucible 3 Raw materials 4 Crucible stand 5 Crucible containment 6 Capture lid 7. Heating means (heating heater) 8. Insulation 9 Chambers 10. First insulation layer 11. Second insulation layer 12 Pressure control device

Claims

1. A single crystal growth apparatus for unidirectional solidification crystal growth, A crucible capable of storing and holding molten raw materials, A heating means capable of heating the crucible, A crucible housing that covers at least the sides of the crucible, It comprises a crucible stand that supports the crucible housing, The top of the crucible housing is open, and a breathable trap cover is installed in the opening. Single crystal growth apparatus.

2. The single crystal growth apparatus according to claim 1, wherein the crucible housing is cylindrical and has open ends on both sides.

3. The crucible container is cylindrical with a bottom, and the end opposite the bottom is open. The single crystal growth apparatus according to claim 1, wherein the crucible is installed at the bottom surface inside the cylindrical body of the crucible housing.

4. The single crystal growth apparatus according to claim 1, wherein the capture lid is made of inorganic fiber.

5. The single crystal growth apparatus according to claim 1, wherein the position of the capture lid is set by adjusting the length of the crucible container so that the temperature of the capture lid is below the boiling point of the substance to be captured from the start to the end of single crystal growth.

6. The single crystal growth apparatus according to claim 1, further comprising an insulating material disposed to cover the heating means, and a first insulating layer that divides the space inside the insulating material into a space below the heating means and a space above the space below the heating means.

7. The single crystal growth apparatus according to claim 1, further comprising a second insulating layer that is arranged to cover the heating means, and which divides the space inside the insulating material into a space above the heating means and a space below the upper space.

8. The single crystal growth apparatus according to claim 1, further comprising a pressure control device for controlling the pressure in the space within the single crystal growth apparatus.

9. The single crystal growth apparatus according to claim 1, wherein a crucible lid is installed on the upper end of the crucible.

10. A method for growing a single crystal by unidirectional solidification crystal growth using a single crystal growth apparatus according to any one of claims 1 to 9, A melting step in which raw materials are filled into the crucible and the raw materials in the crucible are melted by the heating means, The process involves growing a single crystal in the aforementioned crucible, A method for growing a single crystal, characterized by having a cooling step for cooling the grown single crystal after the growth of the single crystal is completed.

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