Single crystal growth equipment

Abstract

To provide a single crystal growth device that employs a unidirectionl solidification crystal growth method such as a vertical Bridgeman method and that can provided a sufficient temperature difference between an upper and a lower part of a seed crystal without using a specially long seed crystal for growth of a β-Ga2O3 single crystal.SOLUTION: There is provided a single crystal growth device 1 that grows a single crystal of a gallium oxide-based semiconductor, and also comprises a crucible 10 which has a seed crystal part 101 and a growth crystal part 102 located above it, a tubular susceptor 11 which surrounds the circumference of the seed crystal part 101 and supports the crucible 10 from below, and a molybdenum disilicide heating body 13, wherein the susceptor 11 has a thick part 111, which is thicker than any other part and short in horizontal distance to the seed crystal part 101, in part along its height direction, and the thick part 111 surrounds at least a height-directional part of the seed crystal part 101.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a single crystal growth apparatus using a directional solidification crystal growth method, and more particularly to a vertical Bridgman type single crystal growth apparatus. [Background technology]

[0002] Conventionally, a technique for growing gallium oxide single crystals by the vertical Bridgman method has been known (see, for example, Patent Document 1). In the vertical Bridgman method, a crucible filled with raw material is generally inserted into a crystal growth furnace with a vertical temperature gradient, and the crucible is then lowered to grow the single crystal. In order to control the crystal orientation and obtain high-quality crystals, a seeding step is required in which a portion of the seed crystal placed in the crucible is kept unmelted and brought into contact with the raw material melt.

[0003] In order to perform the seeding process stably, it is necessary to have a sufficient temperature difference between the top and bottom of the seed crystal. If the temperature difference between the top and bottom of the seed crystal is not large enough, the seed crystal may melt completely or some of the raw material may remain unmelted, leading to failure of the seeding process and a decrease in the yield of single crystal growth.

[0004] Typically, a heater capable of heating to a temperature sufficiently higher than the melting point of the crystal being grown is used to increase the vertical temperature gradient in the crystal growth furnace, thereby creating a sufficient temperature difference between the top and bottom of the seed crystal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-164415 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in growing β-GaO single crystals, an oxidizing atmosphere must be maintained in the crystal growth furnace to prevent the raw material melt from decomposing at high temperatures, and a molybdenum disilicide heating element, which is oxidation-resistant and can melt GaO, is used as a heater.

[0007] The maximum operating temperature of a molybdenum disilicide heating element is approximately 1850°C, which is close to the melting point of Ga2O3, which is approximately 1795°C. This inevitably reduces the vertical temperature gradient inside the crystal growth furnace, making it difficult to create a sufficient temperature difference between the top and bottom of the seed crystal.

[0008] Another method is to use a longer seed crystal than usual to create a sufficient temperature difference between the top and bottom of the seed crystal, but this method requires the length of the portion of the crucible that houses the seed crystal to be longer.Since crucibles made of expensive materials such as Pt-Rh alloys are used to grow β-Ga2O3 single crystals, lengthening the portion of the crucible that houses the seed crystal significantly increases the manufacturing cost of the crucible.

[0009] An object of the present invention is to provide a single crystal growth apparatus for a directional solidification crystal growth method such as the vertical Bridgman method, which is capable of providing a sufficient temperature difference between the top and bottom of a seed crystal in growing a β-GaO single crystal without using an especially long seed crystal. [Means for solving the problem]

[0010] In order to achieve the above object, one aspect of the present invention provides the following single crystal growth apparatuses [1] to [4].

[0011] [1] A single crystal growth apparatus for growing a single crystal of a gallium oxide-based semiconductor, comprising: a crucible having a seed crystal section for accommodating a seed crystal; and a growth crystal section located above the seed crystal section for crystallizing the accommodated raw material melt to grow the single crystal; a tubular susceptor surrounding the periphery of the seed crystal section and supporting the crucible from below; and a molybdenum disilicide heating element for melting the raw material in the growth crystal section to obtain the raw material melt, wherein the susceptor has a thick-walled section in a part of its height direction that is thicker than other parts and has a short horizontal distance from the seed crystal section, and the thick-walled section surrounds at least a part of the seed crystal section in the height direction. fruit , an upper end of the thick portion is located lower than an upper end of the seed crystal portion; Single crystal growth equipment. [2] The single crystal growth apparatus according to the above [1], wherein the ratio of the inner diameter of the thick-walled portion to the outer diameter of the seed crystal portion is 2.5 or less. [3] The single crystal growth apparatus according to [1] or [2] above, wherein the lower end of the thick-walled portion is located higher than the lower end of the seed crystal portion. [4] The single crystal growth apparatus according to any one of the above [1] to [3], wherein the width of the thick-walled portion in the height direction is 16 mm or more. [Effects of the Invention]

[0012] According to the present invention, there is provided a single crystal growth apparatus for a directional solidification crystal growth method such as the vertical Bridgman method, which is capable of providing a sufficient temperature difference between the top and bottom of a seed crystal in growing a β-GaO single crystal without using an especially long seed crystal. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a single crystal growth apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the single crystal growth apparatus around the susceptor. [Figure 3] 3(a) and (b) are vertical cross-sectional views showing the structures of two types of susceptors used in the demonstration experiment of Example 1. [Figure 4] FIG. 4 is a graph showing the measurement results of the temperature difference between the top and bottom of the seed crystal part of Sample A and Sample B according to Example 1. [Figure 5] FIG. 5 is a vertical cross-sectional view showing the configuration of the model used in the simulation of Example 2. [Figure 6] FIG. 6 is a graph showing the relationship between the value D1 / D2 of the ratio of the inner diameter D1 of the thick-walled portion to the outer diameter D2 of the seed crystal portion and TC1-TC2 according to Example 2. [Figure 7] FIG. 7 is a graph showing the relationship between the width W of the thick portion in the height direction and TC1-TC2 according to Example 2. [Figure 8] FIG. 8 is a graph showing the relationship between the thickness T1 of the susceptor not provided with the thick portion 111 and TC1-TC2 according to Example 2. In FIG. [Figure 9] FIG. 9 is a graph showing the relationship between the thickness T1 of the susceptor provided with the thick portion 111 and TC1-TC2 according to Example 2. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Embodiment] (Configuration of single crystal growth apparatus) 1 is a vertical cross-sectional view showing the schematic configuration of a single crystal growth apparatus 1 according to an embodiment of the present invention. The single crystal growth apparatus 1 is a vertical Bridgman type single crystal growth apparatus (vertical Bridgman furnace) that can grow single crystals of gallium oxide-based semiconductors. Here, gallium oxide-based semiconductors refer to β-Ga2O3 or β-Ga2O3 containing substitutional impurities such as Al or In or dopants such as Sn or Si.

[0015] The single crystal growth apparatus 1 comprises a crucible 10, a susceptor 11 that is movable in the vertical direction and supports the crucible 10 from below, a tubular furnace tube 14 that surrounds the crucible 10, the susceptor 11, and the crucible support shaft 12, a molybdenum disilicide heating element 13 installed outside the furnace tube 14, and a housing 15 made of a heat insulating material that houses the above-mentioned components of the single crystal growth apparatus 1.

[0016] The crucible 10 has a seed crystal section 101 that accommodates a seed crystal 20, and a growth crystal section 102 located above the seed crystal section 101 that crystallizes the accommodated raw material melt 21 to grow a single crystal 22 of a gallium oxide-based semiconductor.

[0017] As shown in Figure 1, the growing crystal portion 102 typically comprises a constant diameter portion having a constant inner diameter larger than the inner diameter of the seed crystal portion 101, and an increasing diameter portion located between the constant diameter portion and the seed crystal portion 101, the inner diameter of which increases from the seed crystal portion 101 side toward the constant diameter portion side.

[0018] The crucible 10 has a shape and size corresponding to the shape and size of the single crystal 22 to be grown. For example, when growing a single crystal 22 whose constant diameter portion is cylindrical and has a diameter of 2 inches, a crucible 10 is used in which the growing crystal portion 102 has a cylindrical constant diameter portion with an inner diameter of 2 inches. When growing a single crystal 22 whose constant diameter portion has a shape other than cylindrical, such as a square or hexagonal pillar, a crucible 10 is used in which the growing crystal portion 102 has a square or hexagonal pillar shape. A lid may be used to cover the opening of the crucible 10.

[0019] The crucible 10 is made of a material that has heat resistance enough to withstand the temperature of the molten gallium oxide semiconductor, which is the raw material melt 21 (a temperature equal to or higher than the melting point of the gallium oxide semiconductor), and that does not easily react with the molten gallium oxide semiconductor, such as a Pt—Rh alloy.

[0020] The susceptor 11 is a tubular member that surrounds the seed crystal portion 101 of the crucible 10 and supports the crucible 10 from below. The susceptor 11 has a part in its height direction that is thicker than the other part, and the horizontal distance D between the susceptor 11 and the seed crystal portion 101 is larger than the other part. t The thick portion 111 surrounds (is at the same height as) at least a part of the seed crystal portion 101 in the height direction.

[0021] 2 is an enlarged cross-sectional view of the single crystal growth apparatus 1 around the susceptor 11. As shown in FIG. 2, the susceptor 11 may be composed of a plurality of blocks (blocks 11a to 11c in the example shown in FIG. 2) connected in the vertical direction. In this case, the susceptor 11 may be thicker than the other blocks and have a horizontal distance D from the seed crystal part 101. t The block with a short length (block 11b in the example shown in FIG. 2) can be used as the thick portion 111.

[0022] The susceptor 11 is made of a material that has heat resistance capable of withstanding the growth temperature of a gallium oxide-based semiconductor single crystal and does not react with the crucible 10 at that growth temperature, such as zirconia or alumina.

[0023] A crucible support shaft 12 is connected to the underside of the susceptor 11, and by moving the crucible support shaft 12 up and down by a drive mechanism (not shown), the susceptor 11 and the crucible 10 supported by the susceptor 11 can be moved up and down. The crucible support shaft 12 may also be rotatable about a vertical axis by the drive mechanism. In this case, the crucible 10 supported by the susceptor 11 can be rotated inside the furnace tube 14.

[0024] The crucible support shaft 12 is made of a heat-resistant material that can withstand the temperature at which a gallium oxide-based semiconductor single crystal is grown, such as zirconia or alumina.

[0025] The crucible support shaft 12 is typically a tubular member, similar to the susceptor 11. In this case, a thermocouple for measuring the temperature of the crucible 10 can be passed through the inside of the susceptor 11 and the crucible support shaft 12.

[0026] The molybdenum disilicide heating element 13 is a resistance heating element made of molybdenum disilicide (MoSi2), and is a heater for melting the raw material of the gallium oxide-based semiconductor contained in the grown crystal portion 102 of the crucible 10 to obtain the raw material melt 21.

[0027] The molybdenum disilicide heating element 13 is inserted into the housing 15 through a hole provided in the housing 15, and is connected outside the housing 15 to an external device (not shown) for supplying current to the molybdenum disilicide heating element 13.

[0028] The furnace core tube 14 is used to adjust the heat flow around the crucible 10 and to prevent the incorporation of impurities such as Si and Mo from the molybdenum disilicide heating element 13. The furnace core tube 14 is typically cylindrical. Alternatively, the furnace core tube 14 may be made up of multiple stacked annular members.

[0029] 1, a lid 17 may be placed on the upper opening of the furnace tube 14. By using the lid 17, it is possible to prevent heat around the crucible 10 from escaping upward.

[0030] The furnace tube 14 and the lid 17 are made of a heat-resistant material that can withstand the temperature at which a single crystal of a gallium oxide-based semiconductor is grown, such as zirconia or alumina.

[0031] (Configuration with temperature difference between the top and bottom of the seed crystal) As mentioned above, the maximum operating temperature of the molybdenum disilicide heating element 13 is approximately 1850°C, which is close to the melting point of Ga2O3, which is approximately 1795°C. This inevitably reduces the vertical temperature gradient within the single crystal growth apparatus 1, making it difficult to achieve a sufficient temperature difference between the top and bottom of the seed crystal 20 by controlling the temperature of the molybdenum disilicide heating element 13. Therefore, in the single crystal growth apparatus 1, the susceptor 11 is provided with a thick portion 111, thereby increasing the temperature difference between the top and bottom of the seed crystal 20.

[0032] The thick-walled portion 111 is thicker than the other portions of the susceptor 11 and has a horizontal distance D tis shorter than the other parts, heat is less likely to be transmitted from the surroundings to the part surrounded by the thick-walled part 111 of the seed crystal part 101, and a rise in temperature is suppressed. In addition, the thick-walled part 111 blocks radiant heat transmitted from top to bottom outside the crucible 10, so a rise in temperature is suppressed in the part surrounded by the thick-walled part 111 of the seed crystal part 101 and the part below it.

[0033] To increase the temperature difference between the top and bottom of the seed crystal 20, it is preferable that the ratio of the inner diameter of the thick-walled portion 111 to the outer diameter of the seed crystal portion 101 be 2.5 or less.

[0034] In order to increase the temperature difference between the top and bottom of the seed crystal 20 , it is preferable that the bottom end of the thick portion 111 is located higher than the bottom end of the seed crystal portion 101 .

[0035] In order to increase the temperature difference between the top and bottom of seed crystal 20, it is preferable that thick portion 111 has a width in the height direction of 16 mm or more.

[0036] In addition, in order to increase the temperature difference between the top and bottom of the seed crystal 20, it is preferable that the upper end of the seed crystal portion 101 is not surrounded by the thick portion 111, and that the portion below the upper end is surrounded by the thick portion 111, i.e., the upper end of the thick portion 111 is located lower than the upper end of the seed crystal portion 101.

[0037] (Single crystal growth method) First, a gallium oxide-based semiconductor seed crystal 20 is placed in the seed crystal portion 101 of the crucible 10, and a gallium oxide-based semiconductor raw material such as a sintered body of β-Ga2O3 is placed in the growing crystal portion 102.

[0038] Next, the inside of the single crystal growth apparatus 1 (inside the housing 15) is heated by the molybdenum disilicide heating element 13, creating a temperature gradient in which the temperature is higher at the top and lower at the bottom, and the gallium oxide raw material in the crucible 10 is melted to obtain raw material melt 21.

[0039] In a typical method, first, the crucible support shaft 12 is moved up and down to adjust the height of the crucible 10 so that the temperature of the upper region in the growing crystal section 102 is equal to or higher than the melting point of gallium oxide. This melts a portion of the upper portion of the raw material in the growing crystal section 102. Next, the crucible support shaft 12 is moved upward at a predetermined speed, and the crucible 10 is raised at the same speed while melting the raw material down to the bottom, until all of the raw material and a portion of the seed crystal are melted.

[0040] Next, the crucible support shaft 12 is moved downward, and the crucible 10 is lowered at a predetermined speed, while the raw material melt 21 is crystallized from the bottom (the seed crystal 20 side) to grow a single crystal 22. The single crystal growth is performed in an oxidizing atmosphere. After the raw material melt 21 has entirely crystallized, the crucible 10 is removed and the single crystal 22 is taken out.

[0041] (Effects of the embodiment) In the single crystal growth apparatus 1 according to the embodiment of the present invention, the thick-walled portion 111 is provided in the susceptor 11, thereby increasing the temperature difference between the top and bottom of the seed crystal 20. As a result, a high-quality single crystal 22 of a gallium oxide-based semiconductor having a melting point close to the maximum operating temperature of the heating element can be grown by the vertical Bridgman method.

[0042] Furthermore, by providing a thick portion 111 on the susceptor 11, the temperature difference between the top and bottom of the seed crystal 20 can be increased without increasing the manufacturing cost of the device, as would be the case with a method using an especially long seed crystal.

[0043] Note that the larger the diameter of the grown single crystal 22, the greater the amount of heat required to melt the raw material, and the greater the amount of heat transferred to the seed crystal 20, which tends to reduce the temperature difference between the top and bottom of the seed crystal. For this reason, it is usually difficult to grow a large-diameter single crystal of a gallium oxide-based semiconductor by the vertical Bridgman method. However, according to the above-described embodiment of the present invention, for example, a cylindrical gallium oxide-based semiconductor single crystal (ingot) with a constant diameter portion having a diameter of 2 to 8 inches can be obtained, from which circular wafers having a diameter of 2 to 8 inches can be cut. [Example]

[0044] A demonstration experiment was carried out to investigate the effect of providing the thick-walled portion 111 to the susceptor 11 in the single crystal growth apparatus 1. The contents and results of the demonstration experiment will be described below.

[0045] 3(a) and 3(b) are vertical cross-sectional views showing the structures of two types of susceptors 11 used in the demonstration experiment of this example. The susceptor 11 shown in FIG. 3(a) (hereinafter referred to as sample A) does not have a thick portion 111 and has a constant thickness. On the other hand, the susceptor 11 shown in FIG. 3(b) (hereinafter referred to as sample B) has a thick portion 111 at a position surrounding a part of the seed crystal portion 101. In both sample A and sample B, the horizontal cross-sectional shapes of the susceptor 11 and the seed crystal portion 101 are circular.

[0046] Here, the thickness T of the sample A is 20 mm, and the horizontal distance D between the sample A and the seed crystal part 101 is t The thickness T1 of the portion of sample B other than the thick portion 111 is 20 mm, the thickness T2 of the thick portion 111 is 26 mm, and the horizontal distance D between the portion of sample B other than the thick portion 111 and the seed crystal portion 101 is t 1 is 7.2 mm, and the horizontal distance D between the thick part 111 and the seed crystal part 101 t 2 is 1.2mm.

[0047] 4 is a graph showing the measurement results of the temperature difference between the top and bottom of the seed crystal portion 101 of Sample A and Sample B. The vertical axis of FIG. 4 is TC1-TC2 [°C], which is the difference between the temperature TC1 at measurement point P1, which is the top of the seed crystal portion 101, and the temperature TC2 at measurement point P2, which is the bottom of the seed crystal portion 101. The horizontal axis is the elapsed time [h], with the reference time being 0. Here, the reference time is the time when the height of the crucible 10 and the output of the molybdenum disilicide heating element 13 reach the same predetermined value in each measurement.

[0048] 4, the TC1-TC2 of sample A at the reference time was approximately 6 to 9° C., whereas the TC1-TC2 of sample B was approximately 15° C. This result confirmed that providing the thick-walled portion 111 to the susceptor 11 was effective in increasing the temperature difference between the top and bottom of the seed crystal portion 101. [Example]

[0049] The relationship between the shape of the susceptor 11 in the single crystal growth apparatus 1 and the temperature difference between the top and bottom of the seed crystal portion 101 was investigated by simulation. The details of the simulation and the results thereof will be explained below.

[0050] Fig. 5 is a vertical cross-sectional view showing the configuration of the model used in the simulation of this example. The change in the temperature difference TC1-TC2, which is the temperature difference between the temperature TC1 at measurement point P1, which is the upper part of the seed crystal part 101, and the temperature TC2 at measurement point P2, which is the lower part of the seed crystal part 101, was simulated when parameters related to the shape of the susceptor 11 of the model shown in Fig. 5 were changed.

[0051] First, we investigated the change in TC1-TC2 when the inner diameter D1 of the thick-walled portion 111 of the susceptor 11 was changed. Here, the outer diameter D2 of the seed crystal portion 101 in the model shown in Figure 5 was 5.4 mm, the inner diameter D3 of the portion of the susceptor 11 other than the thick-walled portion 111 was 20 mm, the thickness T1 of the portion of the susceptor 11 other than the thick-walled portion 111 was 20 mm, the length L of the seed crystal portion 101 was 40 mm, and the distance D in the height direction between the top end of the seed crystal portion 101 and the thick-walled portion 111 was 10 mm. t The thickness W of the thick portion 111 in the height direction was set to 5 mm.

[0052] 6 is a graph showing the relationship between TC1-TC2 and the ratio D1 / D2 of the inner diameter D1 of the thick-walled portion 111 to the outer diameter D2 of the seed crystal portion 101. According to the results shown in FIG. 6, as D1 / D2 approaches 1, TC1-TC2 increases.

[0053] Because the temperature at the solid-liquid interface fluctuates within a range of about ±2°C during the seeding process and the temperature inside the single crystal growth apparatus 1 fluctuates within a range of about ±2°C even when maintained at this temperature, it is preferable that TC1-TC2 be 8°C or higher. Therefore, based on the results shown in Figure 6, it can be said that D1 / D2 is preferably 2.5 or lower. Table 1 below shows the values ​​of the plotted points in the graph of Figure 6.

[0054] [Table 1]

[0055] Next, the change in TC1-TC2 was investigated when the width W in the height direction of the thick-walled portion 111 of the susceptor 11 was changed. Here, the outer diameter D2 of the seed crystal portion 101 in the model shown in Figure 5 was 5.4 mm, the inner diameter D1 of the thick-walled portion 111 was 8 mm, the inner diameter D3 of the portion of the susceptor 11 other than the thick-walled portion 111 was 20 mm, the thickness T1 of the portion of the susceptor 11 other than the thick-walled portion 111 was 20 mm, the length L of the seed crystal portion 101 was 40 mm, and the distance D in the height direction between the top end of the seed crystal portion 101 and the thick-walled portion 111 was 10 mm. t 3 was set to 5 mm.

[0056] Fig. 7 is a graph showing the relationship between the width W in the height direction of the thick-walled portion 111 and TC1-TC2. According to the results shown in Fig. 7, as the width W increases and the height direction position of the lower end of the thick-walled portion 111 approaches the height direction position of the seed crystal portion 101, TC1-TC2 increases, and as the width W increases further and the height direction position of the lower end of the thick-walled portion 111 becomes lower than the height direction position of the lower end of the seed crystal portion 101, TC1-TC2 decreases by about 2°C.

[0057] The reason why TC1-TC2 decreases when the height position of the lower end of the thick-walled portion 111 is lower than the height position of the lower end of the seed crystal portion 101 is thought to be that when the thick-walled portion 111 surrounds the lower end of the seed crystal portion 101, it becomes difficult for radiant heat from the seed crystal portion 101 to escape downward. Therefore, it is preferable that the width W of the thick-walled portion 111 in the height direction is as large as possible, as long as the thick-walled portion 111 does not surround the lower end of the seed crystal portion 101.

[0058] 7, it can be seen that it is preferable that the lower end of thick portion 111 is located higher than the lower end of seed crystal portion 101, and that the width W in the height direction of thick portion 111 is, for example, 16 mm or more. Table 2 below shows the values ​​of the plotted points in the graph of FIG.

[0059] [Table 2]

[0060] Next, we investigated the change in TC1-TC2 when the thickness T1 of the susceptor 11 was changed without providing the thick-walled portion 111. The thickness T1 was changed by fixing the inner diameter D3 of the susceptor 11 and changing the outer diameter D4. Here, in the model shown in Figure 5, the outer diameter D2 of the seed crystal portion 101 was 5.4 mm, the inner diameter D3 of the susceptor 11 was 20 mm, and the length L of the seed crystal portion 101 was 40 mm.

[0061] Fig. 8 is a graph showing the relationship between the thickness T1 and TC1-TC2 of the susceptor 11 that does not have the thick portion 111. According to the results shown in Fig. 8, as the thickness T1 increases, TC1-TC2 increases.

[0062] Next, the change in TC1-TC2 was examined when the thickness T1 of the portion of the susceptor 11 other than the thick portion 111 was changed while the susceptor 11 was provided with the thick portion 111. The thickness T1 was changed by fixing the inner diameter D1 of the thick portion 111 of the susceptor 11 and the inner diameter D3 of the portion other than the thick portion 111, and changing the outer diameter D4. Note that because the outer diameter D4 of the thick portion 111 of the susceptor 11 is equal to that of the portion other than the thick portion 111, and the inner diameters D1 and D3 are both constant, the thickness excluding the thickness of the portion protruding inward of the thick portion 111 is equal to the thickness T1 of the portion other than the thick portion 111. Here, in the model shown in FIG. 5, the outer diameter D2 of the seed crystal portion 101 is 5.4 mm, the inner diameter D1 of the thick portion 111 is 8 mm, the inner diameter D3 of the portion of the susceptor 11 other than the thick portion 111 is 20 mm, the length L of the seed crystal portion 101 is 40 mm, and the distance D in the height direction between the upper end of the seed crystal portion 101 and the thick portion 111 is 10 mm. t The thickness W of the thick portion 111 in the height direction was set to 21 mm.

[0063] Fig. 9 is a graph showing the relationship between the thickness T1 of the portion other than the thick portion 111 of the susceptor 11 provided with the thick portion 111 and TC1-TC2. Fig. 9 also includes, as a comparative example, data for the case where the susceptor 11 shown in Fig. 8 is not provided with the thick portion 111.

[0064] According to the results shown in Figure 9, as the thickness T1 of the part of the susceptor 11 other than the thick portion 111 (thickness excluding the thickness of the protruding part of the thick portion 111) increases, TC1-TC2 becomes larger, and the degree of this difference (the slope of the straight line in the graph) is greater than when the thick portion 111 is not provided on the susceptor 11.

[0065] Even when using susceptors with the same structure, TC1-TC2 during the seeding process can vary by up to 7°C depending on the deterioration of the surrounding insulation and heater. Therefore, as mentioned above, TC1-TC2 is preferably 8°C or higher, but in order to perform stable seeding without being affected by the deterioration of surrounding components, it is more preferable that it be 15°C or higher. Therefore, based on the results shown in Figure 9, it can be said that the thickness T1 of the part of the susceptor 11 other than the thick-walled part 111 (thickness excluding the thickness of the protruding part of the thick-walled part 111) is preferably 20 mm or higher. Table 3 below shows the values ​​of the plotted points in the graph of Figure 9.

[0066] [Table 3]

[0067] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples and can be modified in various ways without departing from the spirit and scope of the invention. For example, while the above embodiments describe a vertical Bridgman single crystal growth apparatus, the present invention can also be applied to other single crystal growth apparatuses using unidirectional solidification crystal growth methods, such as vertical gradient temperature solidification single crystal growth apparatuses, that are equipped with the same crucible, susceptor, heating element, and the like as the above-described vertical Bridgman single crystal growth apparatus. Vertical gradient temperature solidification differs from the vertical Bridgman method in that the temperature distribution within the apparatus (furnace) is changed instead of moving the crucible. However, the same crucible, susceptor, heating element, and the like as the above-described vertical Bridgman single crystal growth apparatus can be used. Furthermore, the components of the above-described embodiments and examples can be combined in any way without departing from the spirit and scope of the invention.

[0068] Furthermore, the above-described embodiments and examples do not limit the scope of the invention as claimed, and it should be noted that not all of the combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention. [Explanation of symbols]

[0069] 1...single crystal growth apparatus, 10...crucible, 101...seed crystal section, 102...growth crystal section, 11...susceptor, 111...thick section, 13...molybdenum disilicide heating element, 20...seed crystal, 21...raw material melt, 22...single crystal

Claims

1. A single crystal growth apparatus for growing a single crystal of a gallium oxide-based semiconductor, a crucible having a seed crystal portion for accommodating a seed crystal and a growing crystal portion located above the seed crystal portion for crystallizing the contained raw material melt to grow the single crystal; a tubular susceptor that surrounds the seed crystal portion and supports the crucible from below; a molybdenum disilicide heating element for melting the raw material in the growing crystal portion to obtain the raw material melt; Equipped with the susceptor has a thick-walled portion in a part of its height direction that is thicker than other parts and has a short horizontal distance from the seed crystal portion; the thick-walled portion surrounds at least a portion of the seed crystal portion in a height direction, an upper end of the thick portion is located lower than an upper end of the seed crystal portion; Single crystal growth equipment.

2. a ratio of an inner diameter of the thick-walled portion to an outer diameter of the seed crystal portion is 2.5 or less; 2. The single crystal growth apparatus according to claim 1.

3. a lower end of the thick portion is located higher than a lower end of the seed crystal portion; 3. The single crystal growth apparatus according to claim 1 or 2.

4. The width of the thick portion in the height direction is 16 mm or more. The single crystal growth apparatus according to any one of claims 1 to 3.

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