Crystal growth apparatus and crucible

Abstract

A crystal growth apparatus includes a crucible having a main body portion and a low-radiation portion having a lower emissivity than the main body portion, and a heating portion located outside the crucible to heat the crucible by radiation heat, the low-radiation portion being provided to an outer surface of a first point that becomes a heating center in a case where the crucible does not have a low-radiation portion.

Description

TECHNICAL FIELD

[0001] The present application relates to a crystal growth apparatus and a crucible.

[0002] This application claims priority from Japanese Patent Application No. 2018-230182 filed on December 7, 2018, and this application incorporates the content thereof by reference. BACKGROUND

[0003] Silicon carbide (SiC) has an insulating breakdown electric field that is one order of magnitude larger than that of silicon (Si), and a band gap that is three times larger than that of silicon (Si). Silicon carbide (SiC) also has a thermal conductivity that is about three times higher than that of silicon (Si), and other characteristics. Therefore, silicon carbide (SiC) is expected to be applied to power devices, high-frequency devices, high-temperature operation devices, and the like. Thus, in recent years, SiC epitaxial wafers have begun to be used in the above-described semiconductor devices.

[0004] An SiC epitaxial wafer is manufactured by growing an SiC epitaxial film that becomes an active region of an SiC semiconductor device, on an SiC single crystal substrate, using a chemical vapor deposition (CVD) method.

[0005] An SiC single crystal substrate is manufactured by cutting an SiC single crystal. The SiC single crystal can generally be obtained by a sublimation method. The sublimation method is a method in which a seed crystal composed of an SiC single crystal is disposed on a pedestal disposed in a graphite crucible, sublimation gas that is sublimated from a raw material powder in the crucible is supplied to the seed crystal by heating the crucible, and the seed crystal is grown into a larger SiC single crystal.

[0006] In recent years, along with market demands, there is an increasing demand for large-diameter and long-size SiC single crystals. Also, along with the increasing demand for large-diameter and long-size SiC single crystals, there is a demand for high-quality SiC single crystals and an increase in production efficiency.

[0007] Japanese Patent Application Publication No. 2008-290885 describes a partition wall portion provided between the heaters divided in the height direction. The partition wall portion controls heat conduction between the divided heaters and controls radiation heat transferred from the heaters to the crucible, thereby thermally insulating the seed crystal side from the raw material side. The manufacturing apparatus for a silicon carbide single crystal described in Japanese Patent Application Publication No. 2008-290885 controls the seed crystal side and the raw material side of the crucible separately using the partition wall portion.

[0008] Also, Japanese Patent Application Publication No. 2015-212207 describes disposing a thermal insulating member in the crucible, the thermal insulating member blocking the flow of heat from the upper surface of the central portion of the raw material toward the seed crystal side. The thermal insulating member homogenizes the temperature of the entire raw material. SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] However, while the partition wall described in Japanese Patent Application Publication No. 2008-290885 can suppress heat conduction between the separated heaters and thermally separate the seed crystal side from the raw material side, it cannot control the temperature distribution on the raw material side caused by thermal radiation. Furthermore, the insulating element described in Japanese Patent Application Publication No. 2015-212207 is placed inside the crucible, making it impossible to freely design the temperature distribution.

[0011] The present invention was made in view of the above-mentioned problems, and its object is to provide a crystal growth apparatus capable of reducing the temperature distribution generated in the raw material contained in the crucible.

[0012] Technical solutions for solving the problem

[0013] The inventors conducted in-depth research and discovered the following: by making the emissivity of a predetermined portion of the crucible lower than that of other portions, the temperature distribution near the point of highest temperature in the crucible becomes more gradual in the vertical direction, thereby reducing the temperature distribution within the raw material contained in the crucible. In other words, to solve the above-mentioned problems, the present invention provides the following technical solution.

[0014] (1) The crystal growth apparatus of the first embodiment includes: a crucible having a main body and a low-emissivity part having a lower emissivity than the main body; and a heating part located outside the crucible, which heats the crucible by means of radiant heat, wherein the low-emissivity part is disposed on the outer surface of a first point that becomes the heating center of the crucible in the absence of a low-emissivity part.

[0015] (2) In the crystal growth apparatus of the above (1) scheme, the emissivity of the low-emissivity part may be less than 0.6 times that of the emissivity of the main body part.

[0016] (3) In the crystal growth apparatus of the above scheme (1) or (2), the main body may be graphite and the low-emissivity part may be a monomer, carbide, nitride or mixture containing elements selected from Ta, Mo, Nb, Hf, W and Zr.

[0017] (4) In any of the above (1) to (3) crystal growth apparatuses, the outer surface of the main body may be uneven, and the outer surface of the low-radiation part may be flat.

[0018] (5) In any of the above-mentioned (1) to (4) crystal growth apparatus, the height of the low-radiation section may be more than twice the distance of the vertical line drawn from the first point toward the heating section.

[0019] (6) In any of the above-mentioned (1) to (5) crystal growth apparatus, the height of the low-radiation section may be more than 40% of the height of the raw material contained inside the crucible.

[0020] (7) The crucible of the second embodiment has a main body and a low-emissivity part with a lower emissivity than the main body, the low-emissivity part covering a portion of the outer surface below the surface of the raw material contained inside the crucible.

[0021] Invention Effects

[0022] The crystal growth apparatus according to the above scheme can reduce the temperature distribution generated in the raw materials contained in the crucible. Attached Figure Description

[0023] Figure 1 This is a cross-sectional schematic diagram of the crystal growth apparatus according to the first embodiment.

[0024] Figure 2 This is a cross-sectional schematic diagram used to illustrate the function of a crystal growth apparatus that does not have a low-radiation section.

[0025] Figure 3 This is a cross-sectional schematic diagram used to illustrate the function of the crystal growth apparatus of the first embodiment.

[0026] Figure 4 This is a cross-sectional schematic diagram of the crystal growth apparatus according to the second embodiment.

[0027] Figure 5 This is a coordinate graph showing the results of Example 2.

[0028] Figure 6 This is a coordinate graph showing the results of Example 3.

[0029] Label Explanation

[0030] 10, 15 Crucible; 11, 16 Main body; 12, 17 Low radiation part; 13 Crystal setting part; 20 Insulation part; 30 Heating part; 40 Support body; 100, 101 Crystal growth device; S Seed crystal; C Single crystal; K Growth space; G Raw material; P1 First point; P2 Second point; E1 First end; Ts Isothermal surface. Detailed Implementation

[0031] Hereinafter, the crystal growth apparatus and crucible of this embodiment will be described in detail with appropriate reference to the accompanying drawings. In the drawings used in the following description, characteristic parts are sometimes shown enlarged for ease of understanding of the features of the invention, and the size ratios of the constituent elements may differ from the actual figures. The materials, dimensions, etc., illustrated in the following description are merely examples, and the invention is not limited thereto; appropriate modifications can be made without altering its spirit.

[0032] (Crystal growth apparatus)

[0033] Figure 1 This is a cross-sectional schematic diagram of the crystal growth apparatus according to the first embodiment. Figure 1 The crystal growth apparatus 100 shown includes a crucible 10, a heat insulation component 20, a heating element 30, and a support 40. Figure 1 For ease of understanding, the raw material G, the seed crystal S, and the single crystal C grown on the seed crystal S are shown simultaneously.

[0034] In the following figures, the direction perpendicular to the support surface of the crucible 10 supported by the support body 40 is taken as the vertical direction, and the direction perpendicular to the vertical direction is taken as the radial direction. Figure 1 It is a sectional view taken at any section along the central axis of the support 40.

[0035] A crucible 10 surrounds a growth space K for growing single-crystal C. The crucible 10 has a main body 11, a low-emissivity section 12, and a crystal placement section 13. When growing single-crystal C using the sublimation method, a raw material G is filled into the bottom of the crucible 10. The crystal placement section 13 is located opposite the raw material G. When growing single-crystal C using the sublimation method, a seed crystal S is placed in the crystal placement section 13. The raw material gas sublimated from the raw material G recrystallizes on the surface of the seed crystal S, thereby growing single-crystal C.

[0036] The main body 11 is the portion that surrounds the growth space K. The main body 11 is made of a material capable of withstanding the high temperatures required for the growth of single-crystal C. The main body 11 is, for example, graphite. Graphite has an extremely high sublimation temperature of 3550°C and can also withstand the high temperatures during growth.

[0037] The low-emissivity portion 12 is the portion with a lower emissivity than the main body portion 11. Emissivity is also called emissivity. Emissivity is the ratio of the energy radiated by an object in thermal radiation to the energy radiated by a blackbody at the same temperature, which is set to 1. If the emissivity is high, heat is easily absorbed; if the emissivity is low, heat is difficult to absorb. The low-emissivity portion 12 is preferably 0.6 times or less of the emissivity of the main body portion 11, more preferably 0.4 times or less. Furthermore, it is preferable that the low-emissivity portion 12 is 0.1 times or more of the emissivity of the main body portion 11.

[0038] The low-emissivity portion 12 contains, for example, monomers, carbides, nitrides, or mixtures of elements selected from Ta, Mo, Nb, Hf, W, and Zr. Examples of low-emissivity portions 12 include TaC, Ta, Mo, Mo₂C, W, WC, Nb, and NbC. The emissivity of TaC varies depending on the surface shape, roughness, presence or absence of oxidation, measurement temperature, and measurement wavelength, and is, for example, 0.1 to 0.5. Furthermore, the emissivity of W is, for example, 0.1 to 0.4, and the emissivity of Mo is, for example, 0.1 to 0.4. The emissivity of graphite is, for example, 0.7 to 0.95, which is higher than that of the aforementioned materials.

[0039] The low-radiation section 12 covers the outer surface of the first point of the crucible 10. Based on Figure 2 Let's explain the first point, P1. Figure 2 This is a cross-sectional schematic diagram of a crystal growth apparatus without a low-radiation section. Figure 2 The crucible 10' shown does not have a low-radiation section 12, which is consistent with... Figure 1 The crucible 10 shown is different.

[0040] The heating element 30 extends vertically in a manner capable of heating the entire crucible 10'. The crucible 10' is indirectly heated by the heating element 30, which has height in the vertical direction. The heating state of the radial sides of the crucible 10' is uneven, resulting in a temperature distribution in the height direction.

[0041] The first point P1 is the location of the heating center with the highest temperature in the crucible 10'. When the heating section 30 is uniform along its height, for example, sometimes the position opposite to the center of the heating section 30 in the vertical direction is designated as the first point P1. That is, in Figure 1 In the absence of a low-radiation section 12 in the crucible 10 shown, the first point P1 is the location that becomes the heating center.

[0042] The first point P1 is located below the surface of the raw material G contained inside the crucible 10. The sublimation efficiency of the raw material G is improved by positioning the heating center around the raw material. The low-radiation section 12 at least covers a portion of the outer surface below the surface of the raw material G contained inside the crucible 10.

[0043] Figure 3 This is a cross-sectional schematic diagram of the crystal growth apparatus according to the first embodiment. The low-emissivity section 12 covers the outer surface of the crucible 10 at a first point P1, and the surface of the low-emissivity section 12 is exposed to the outer surface of the crucible 10. The outer surface of the crucible 10 is the surface through which electromagnetic waves from the heating section 30 are incident. The state of the outer surface of the crucible 10 is different at the main body section 11 and the low-emissivity section 12, thereby causing a difference in the temperature distribution inside the crucible 10.

[0044] The height h of the low-radiation section 12 is preferably at least twice the distance d of the perpendicular line drawn from the first point P1 toward the heating section 30. More preferably, it is at least twice and less than four times. The intersection of the perpendicular line drawn from the first point P1 toward the heating section 30 and the heating section 30 is designated as the second point P2. One end of the low-radiation section 12 in the vertical direction is designated as the first end E1. The angle formed by the line segment connecting the first point P1 and the second point P2 and the line segment connecting the second point P2 and the first end E1 is designated as θ. When the above relationship is satisfied, tanθ≥1 holds true.

[0045] Furthermore, the height h of the low-radiation section 12 is independent of the distance to the heating section 30, and is preferably 40% or more of the height of the raw material G contained inside the crucible 10, more preferably 60% or more. The height h of the low-radiation section 12 is preferably 80% or less of the height of the raw material G contained inside the crucible 10.

[0046] Insulating component 20 covers the area around crucible 10 and heating element 30 (see reference). Figure 1 The temperature of the crucible 10 is maintained by the heat insulation element 20.

[0047] The insulation component 20 is preferably made of a material with a thermal conductivity of 10 W / mK or less at temperatures above 2000°C. Examples of materials with a thermal conductivity of 10 W / mK or less at temperatures above 2000°C include felt materials with graphite and carbon as the main components. Furthermore, the insulation component 20 is preferably a component with a thermal conductivity of 5 W / mK or less.

[0048] The heating element 30 is located on the outside of the crucible 10. Figure 1 The heating element 30 shown is located radially outside the crucible 10 and radially inside the insulation element 20. The heating element 30 is heated by induction heating generated by a coil (not shown) located on the outer periphery of the insulation element 20. The heated element 30 itself becomes a source of thermal radiation, using radiant heat to heat the crucible 10. The heating element 30 is, for example, a graphite component. The heating element 30 is also referred to as a heater.

[0049] The support body 40 is located below the crucible 10 and supports the crucible 10. The support body 40 is rotatable in the radial direction. If the support body 40 rotates in the radial direction due to the drive device (not shown), the crucible 10 also rotates with the support body 40.

[0050] According to the crystal growth apparatus 100 of the first embodiment, the temperature distribution generated within the raw material G contained in the crucible 10 can be reduced. Based on Figure 2 and Figure 3 Explain the reasons.

[0051] Figure 2The crucible 10' shown does not have a low-radiation section 12, and its heating center coincides with the first point P1. The temperature distribution within the raw material G is generated in a manner that extends from the first point P1. The isothermal surface Ts within the raw material G is formed radially centered on the first point P1, where the highest temperature is reached. A temperature difference ΔT is generated within the raw material G. The temperature difference ΔT is the difference between the highest and lowest temperatures within the raw material G. Figure 2 In this case, the area near the first point P1 of the raw material G becomes the highest temperature, while the area near the center of the bottom of the crucible 10', which is far from the first point P1, becomes the lowest temperature. In addition, depending on the location of the heating center, there are also cases where the upper part of the raw material G becomes the lowest temperature.

[0052] The feed gas from feedstock G flows according to the temperature difference within crucible 10' and recrystallizes at seed crystal S. A portion of the sublimated feed gas also flows towards the vicinity of the bottom center of crucible 10' according to the temperature difference ΔT within feedstock G. The feed gas supplied to the vicinity of the bottom center of crucible 10' is not used for crystal growth. Furthermore, the feedstock recrystallized near the bottom center of crucible 10' does not function as a feedstock. The radial dimension of crucible 10' increases with the increasing diameter of SiC single crystals. The larger the radial dimension of crucible 10', the larger the temperature difference ΔT within feedstock G.

[0053] In contrast, Figure 3 The crucible 10 shown has a low-radiation portion 12 on its outer surface at the first point P1. The low-radiation portion 12 is less susceptible to radiation compared to the main body 11, and therefore less likely to be heated. As a result, the vertical temperature gradient near the heating center of the crucible 10 is mitigated. That is, the temperature distribution gradient extending vertically around the first point P1 becomes gentler, and the temperature near the first point P1 becomes more uniform.

[0054] If the vertical temperature gradient near the heating center is mitigated, the shape of the isothermal surface Ts within the raw material G changes. The isothermal surface Ts forms a radial shape with the heating center as the reference. The area of ​​a temperature region enclosed by two isothermal surfaces Ts increases due to the vertical expansion of the heating center. Figure 2 The situation is amplified. Therefore, the temperature difference ΔT within the raw material G is smaller than in the case without the low-radiation section 12. The smaller the temperature difference ΔT within the raw material, the higher the supply efficiency of the raw material gas to the seed crystal S.

[0055] (Second Implementation)

[0056] Figure 4 This is a cross-sectional schematic diagram of the crystal growth apparatus 101 according to the second embodiment. The crucible 15 of the crystal growth apparatus 101 has a different configuration than the crucible 10 of the crystal growth apparatus 100. Other configurations are the same, and the same reference numerals are used for the same configurations, and descriptions are omitted.

[0057] Figure 4 The crucible 15 shown has a main body 16 and a low-emissivity part 17. Uneven surfaces are formed on the outer surface (outer side) of the main body 16. In contrast, the outer surface of the low-emissivity part 17 is a flat surface.

[0058] Emissivity also varies depending on the surface condition of the object. If the surface of the object has irregularities, the effective emissivity of that part increases. This is because the area absorbing the radiated light (radiative heat) from the heating part 30 increases. In other words, due to the different surface shape, the emissivity of the low-emissivity part 17 is lower than that of the main body part 16.

[0059] The main body 16 and the low-emissivity part 17 can be made of the same material or different materials. The materials used for the main body 16 and the low-emissivity part 17 are the same as those used for the main body 11 and the low-emissivity part 12 in the first embodiment. For example, the main body 16 and the low-emissivity part 17 can both be made of graphite, with only the surface shape being different.

[0060] The low-emissivity section 17 is provided on the outer surface of the heating center in the absence of the low-emissivity section 17. The low-emissivity section 17 is less susceptible to radiation compared to the main body 16, and therefore less prone to heating. As a result, the vertical temperature gradient near the heating center of the crucible 15 is mitigated, and the temperature difference ΔT within the raw material G is smaller than in the case without the low-emissivity section 17. The smaller the temperature difference ΔT within the raw material, the higher the supply efficiency of the raw material gas to the seed crystal S.

[0061] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to specific embodiments. Various modifications and alterations can be made within the scope of the spirit of the present invention as described in the claims.

[0062]

Example

[0063] (Example 1)

[0064] Through simulation reproduction Figure 3 The configuration shown was used to solve for the temperature difference generated within the raw material during the heating of the crucible. The simulation employed heat transfer analysis based on the finite element method using ANSYS Mechanical.

[0065] To reduce computational load, simulations were performed only on half of the structure (radial half) of an arbitrary cross-section passing through the central axis. Furthermore, for simplicity, only the crucible and heating element filled solely with raw material were modeled and simulated. The simulation conditions are as follows.

[0066] Crucible outer radius: 150mm

[0067] Crucible thickness: 10mm

[0068] Raw material section height: 200mm

[0069] The emissivity of the main body of the crucible is 0.8 (equivalent to graphite).

[0070] Crucible thermal conductivity: 40 W / mK

[0071] Thermal conductivity of raw material: 3 W / mK

[0072] Emissivity of the heating element: 0.8

[0073] Inner radius of heating section: 180mm (distance d between heating section and crucible: 30mm)

[0074] The first point (heating center) is located 100mm from the bottom surface (half the height of the raw material), at the same height as the center of the heating element.

[0075] Center temperature of the heating element: 2450℃

[0076] End temperature of heating section: 2250℃

[0077] Height of the low-radiation section: 100mm

[0078] Location of the low-radiating part: The center of the low-radiating part in the height direction is consistent with the height position of the first point.

[0079] Emissivity of the low-radiative region: 0.2 (equivalent to TaC)

[0080] After simulation under the above conditions, the temperature difference ΔT generated in the raw material of the crystal growth apparatus in Example 1 was 147.5°C.

[0081] (Comparative Example 1)

[0082] Reproduced in simulation Figure 2 The configuration shown was used to calculate the temperature difference generated within the raw material during heating of the crucible. Except for the absence of a low-radiation section, the simulation method and conditions were the same as in Example 1.

[0083] After simulation under the above conditions, the temperature difference ΔT generated in the raw material of the crystal growth apparatus in Comparative Example 1 was 155.4°C.

[0084] Compared with the crystal growth apparatus of Comparative Example 1, the temperature difference ΔT within the raw material of the crystal growth apparatus of Example 1 is 7.9 degrees smaller.

[0085] (Example 2)

[0086] In Example 2, the relationship between the emissivity of the main body and the low-emissivity part of the crucible is changed, except that it is the same as in Example 1.

[0087] Figure 5This is a graph showing the results of Example 2. The horizontal axis represents the ratio of the emissivity of the main body to that of the low-emissivity part, and is the value obtained by dividing the emissivity of the low-emissivity part by the emissivity of the main body. The larger the value of the horizontal axis, the greater the difference in emissivity between the main body and the low-emissivity part. The vertical axis shows the reduction in temperature difference ΔT within the raw material compared to the case without the low-emissivity part. The larger the value of the vertical axis, the smaller the temperature difference ΔT within the raw material compared to the case without the low-emissivity part.

[0088] like Figure 5 As shown, the greater the difference in emissivity between the main body and the low-emissivity part of the crucible, the smaller the temperature difference ΔT within the raw material. If the emissivity of the low-emissivity part is less than 0.6 times that of the main body, the temperature difference ΔT within the raw material is about 2°C smaller compared to the case without a low-emissivity part. If the temperature difference ΔT within the raw material is 2°C smaller, the sublimation rate increases by approximately 8-9% when crystal growth continues for more than 150 hours.

[0089] (Example 3)

[0090] In Example 3, the relationship between the distance between the crucible and the heating element and the height of the low-radiation element is changed, except that it is the same as in Example 1.

[0091] The height h of the low-radiation section varies between 0 mm (equivalent to Comparative Example 1) and 160 mm. The distance d between the crucible and the heating section is set to any one of 30 mm, 50 mm, and 70 mm. The intersection of the perpendicular line drawn from the first point P1 toward the heating section 30 and the heating section 30 is designated as the second point P2. One end of the low-radiation section 12 in the vertical direction is designated as the first end E1. The angle formed by the line segment connecting the first point P1 and the second point P2 and the line segment connecting the second point P2 and the first end E1 is designated as θ (refer to...). Figure 3 That is, tanθ = (h / 2) / d.

[0092] Figure 6 This is a graph showing the results of Example 3. The horizontal axis is tanθ as described above. The vertical axis shows the reduction in temperature difference ΔT within the raw material compared to the case without a low-radiation section. The larger the value of the vertical axis, the smaller the temperature difference ΔT within the raw material compared to the case without a low-radiation section.

[0093] If the relationship between the distance between the crucible and the heating element and the height of the low-radiation element satisfies tanθ≥1, then the temperature difference ΔT within the raw material is approximately 2°C smaller than that without a low-radiation element. If the temperature difference ΔT within the raw material is 2°C smaller, then the sublimation rate increases by approximately 8–9% when crystal growth continues for more than 150 hours.

[0094] (Refer to Examples 1-4)

[0095] The relationship between the temperature difference within the feedstock and the sublimation rate of the feedstock gas was determined in the simulation. Crystal growth simulations were performed using STR's Virtual Reactor PVT-SiC. To reduce computational load, simulations were performed only on half (radial half) of an arbitrary cross-section passing through the central axis. The results are shown in Table 1 below.

[0096] Table 1

[0097]

[0098] In Table 1, ΔT difference shows the variation of the temperature difference ΔT within the raw material, based on the temperature difference ΔT within the raw material in Reference Example 1. That is, when the temperature difference ΔT within the raw material in Reference Example 1 is A℃, the temperature difference ΔT within the raw material in Reference Example 2 is A-1.9℃, the temperature difference ΔT within the raw material in Reference Example 3 is A-2.8℃, and the temperature difference ΔT within the raw material in Reference Example 2 is A-3.9℃. The sublimation amount of the raw material gas was calculated at the initial stage of crystal growth (approximately 0 hours), after 20 hours, after 50 hours, after 100 hours, after 150 hours, and after 200 hours. Table 1 is a table showing the increase rate of sublimation amount for each reference example, based on the sublimation amount of Reference Example 1. As shown in Table 1, if the temperature difference ΔT within the raw material decreases, the sublimation efficiency of the raw material gas increases.

Claims

1. A crystal growth apparatus, which utilizes sublimation to grow SiC single crystals, comprising: The crucible has a main body and a low-emissivity part with a lower emissivity than the main body; and A heating element, located on the outside of the crucible, heats the crucible using radiant heat. The low-emissivity section covers the outer surface of the heating center of the crucible, thereby mitigating the vertical temperature gradient near the heating center, which is the location with the highest temperature in the crucible when heated using the heating section without the low-emissivity section. The main body is made of graphite. The low-radiation part is a monomer, carbide, nitride, or mixture containing elements selected from Ta, Mo, Nb, Hf, W, and Zr.

2. A crystal growth apparatus, which utilizes sublimation to grow SiC single crystals, comprising: The crucible has a main body and a low-emissivity part with a lower emissivity than the main body; and A heating element, located on the outside of the crucible, heats the crucible using radiant heat. The low-emissivity section covers the outer surface of the heating center of the crucible, thereby mitigating the vertical temperature gradient near the heating center, which is the location with the highest temperature in the crucible when heated using the heating section without the low-emissivity section. The outer surface of the main body is uneven. The outer surface of the low-radiation part is a flat surface.

3. The crystal growth apparatus according to claim 1 or 2, The emissivity of the low-emissivity portion is less than 0.6 times that of the main body portion.

4. The crystal growth apparatus according to claim 1 or 2, The height of the low-radiation section is more than twice the distance of a perpendicular line drawn from the heating center toward the heating section.

5. The crystal growth apparatus according to claim 1 or 2, The height of the low-radiation section is at least 40% of the height of the raw material contained inside the crucible.

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