Sic single crystal manufacturing apparatus

Abstract

To provide an apparatus for producing an SiC single crystal capable of increasing the growth rate of the SiC single crystal.SOLUTION: The SiC single crystal manufacturing apparatus includes a chamber, a heating chamber, and a growth chamber. The heating compartment is disposed in the chamber and includes a heat source. The growth chamber is disposed in the chamber and located above the heating chamber. The growth chamber includes a plurality of crucibles and a heat insulator. The plurality of crucibles are provided side by side in a horizontal direction, and a SiC raw material can be charged therein and a SiC seed crystal can be attached thereto. The heat insulating unit has a plurality of through holes corresponding to the plurality of crucibles. Each of the through-holes forms a heat channel for flowing heat supplied from a heat source upward through the corresponding crucible.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a SiC single crystal manufacturing apparatus, and more specifically to a SiC single crystal manufacturing apparatus for manufacturing SiC (Silicon Carbide) single crystals. [Background technology]

[0002] SiC single crystals, which have a wide band gap and high thermal conductivity, are attracting a great deal of attention in the fields of electrical circuits that require high voltage resistance and electronic materials used at high temperatures.

[0003] The main method for producing SiC single crystals is the sublimation recrystallization method, in which raw SiC powder is sublimated at temperatures exceeding 2000°C in a cylindrical graphite crucible, and then recrystallized on a seed crystal at a relatively low temperature to obtain a single crystal ingot.

[0004] To create such a high-temperature environment exceeding 2000°C, a high-frequency induction heating furnace is used, which applies a high-frequency current to a coil surrounding the graphite crucible, thereby directly heating the crucible itself using the induced current generated within the crucible. By controlling the heating area using the induced current, a temperature gradient is established in which the temperature decreases from the SiC raw material placed at the bottom of the crucible to the seed crystal placed at the top, and this temperature gradient promotes the sublimation and recrystallization reactions.

[0005] In this method, since the sidewall of the cylindrical crucible is primarily heated, the temperature tends to decrease toward the center of the cylindrical diameter, making it particularly difficult for the SiC raw material powder located near the center of the cylindrical axis of the crucible to sublimate, resulting in a problem of reduced raw material utilization. For this reason, various efforts have been made to effectively transfer heat to the vicinity of the axial center (see, for example, Japanese Patent No. 5892209 (Patent Document 1)).

[0006] On the other hand, in conventional SiC single crystal manufacturing, it is common to grow one ingot per furnace, as mentioned above, and for mass production, it is necessary to increase the number of furnaces, which makes it difficult to achieve economies of scale when increasing mass production volumes.

[0007] One solution to this problem is to install multiple crucibles in a single furnace, allowing multiple ingots to be grown in parallel simultaneously. However, with the high-frequency induction heating method described above, the heating area depends on the distance from the coil. Therefore, when multiple crucibles are installed in a furnace, only the crucible sidewalls near the coil are heated. Therefore, Japanese Patent Publication No. 6872346 (Patent Document 2) proposes to overcome this problem by installing three sets of compartments in a high-frequency furnace and rotating them on two axes for parallel processing. However, maintaining rotational motion in an ultra-high-temperature environment exceeding 2000°C for a long period of time poses significant challenges.

[0008] On the other hand, in Japanese Patent Laid-Open No. 2022-55282 (Patent Document 3), multiple crucibles are installed horizontally, and heat sources are placed below and to the sides to achieve uniform heating of the multiple crucibles (group of crucibles). When the horizontal cross-sectional area of ​​each crucible is A and the cross-sectional area of ​​the heat source placed below is B, the crucible cross-section is heated from a wider surface so that B / A ≥ 2. Furthermore, to prevent the temperature drop at the periphery due to heat loss toward the periphery of the cylindrical furnace, heat sources are also installed on the sides, and the heating energy C from the bottom and the heating energy D from the side are controlled so that C / D ≥ 1.2. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 5892209 [Patent Document 2] Patent No. 6872346 [Patent Document 3] Japanese Patent Publication No. 2022-55282 [Patent Document 4] Patent No. 3762559 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present disclosure is to provide a SiC single crystal manufacturing apparatus capable of increasing the growth rate of a SiC single crystal. [Means for solving the problem]

[0011] The SiC single crystal manufacturing apparatus according to the present disclosure includes a chamber, a heating chamber, and a growth chamber. The heating chamber is provided within the chamber and includes a heat source. The growth chamber is provided within the chamber and is disposed above the heating chamber. The growth chamber includes multiple crucibles and a heat insulating unit. The multiple crucibles are arranged horizontally side by side, and can be charged with SiC raw material and can have SiC seed crystals attached thereto. The heat insulating unit has multiple through-holes corresponding to the multiple crucibles. Each of the through-holes forms a heat channel for flowing heat supplied from the heat source upward through the corresponding crucible. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing the structure of an SiC single crystal manufacturing apparatus according to the first embodiment. [Figure 2] FIG. 2 is a plan view showing the arrangement of crucibles in the SiC single crystal manufacturing apparatus shown in FIG. [Figure 3] FIG. 3 is a plan view showing a different arrangement of the crucible from that shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing the structure of an SiC single crystal manufacturing apparatus according to the second embodiment. [Figure 5] FIG. 5 is a graph showing growth indexes of Examples 1 to 3 according to the first embodiment shown in FIG. 1 and a comparative example. [Figure 6] FIG. 6 is a graph showing the crucible temperature variation index for Examples 1 to 3 according to the first embodiment shown in FIG. 1 and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Outline of the embodiment> The SiC single crystal manufacturing apparatus according to this embodiment includes a chamber, a heating chamber, and a growth chamber. The heating chamber is provided within the chamber and includes a heat source. The growth chamber is provided within the chamber and is disposed above the heating chamber. The growth chamber includes multiple crucibles and a heat insulating unit. The multiple crucibles are arranged horizontally side by side, and can be charged with SiC raw material and can have SiC seed crystals attached. The heat insulating unit has multiple through-holes corresponding to the multiple crucibles. Each of the through-holes forms a heat channel for flowing heat supplied from the heat source upward through the corresponding crucible.

[0014] According to the above configuration, the growth rate of the SiC single crystal can be increased.

[0015] The heat insulating portion may include a lid portion that covers the through hole.

[0016] In this case, the temperature within the heat channel can be independently controlled by varying the thickness of the lid.

[0017] The heat insulating section may include an outer peripheral side wall, which may be arranged around the outer periphery of the plurality of crucibles and made of a heat insulating material.

[0018] In this case, the presence of a heat insulating material around the outer periphery of the multiple crucibles prevents heat from being transferred from the crucibles to the outside.

[0019] The heat insulating portion may include a protective layer. The protective layer may be provided on an inner circumferential surface of the through hole and may be removable.

[0020] In this case, the protective layer on the inner surface of the through hole prevents sublimation gas leaking from the crucible from penetrating into the insulating material. Furthermore, because the protective layer is removable, even if the sublimation gas recrystallizes within the protective layer and a large amount of SiC polycrystals is produced, the old protective layer can be replaced with a new one.

[0021] The plurality of crucibles may include one central crucible and six first peripheral crucibles arranged on the outer periphery of the central crucible.

[0022] The plurality of crucibles may include six second outer crucibles and six third outer crucibles arranged on the outer periphery of the first outer crucible.

[0023] The heat insulating material may be made of a heat insulating material containing one or more selected from the group consisting of carbon fiber, expanded graphite, and flexible graphite.

[0024] <Details of the embodiment> The present embodiment will be described in detail below with reference to the drawings.

[0025] <Embodiment 1> Referring to FIG. 1 , a SiC single crystal manufacturing apparatus 10 according to the first embodiment includes a chamber 12, a heating chamber 14, and a growth chamber 16. The heating chamber 14 is provided within the chamber 12 and includes a heat source 140. The growth chamber 16 is provided within the chamber 12 and is disposed above the heating chamber 14. The growth chamber 16 includes a plurality of crucibles 160 and a heat insulating section 161. The crucibles 160 are arranged horizontally side by side, and can be charged with SiC raw materials 162 and can have SiC seed crystals 163 attached thereto. The heat insulating section 161 has a plurality of through-holes 164 corresponding to the plurality of crucibles 160. The heat insulating section 161 is made of a heat insulating material. Each of the through-holes 164 forms a heat channel for flowing heat supplied from the heat source 140 upward through the corresponding crucible 160, as indicated by the arrows in FIG. 1 .

[0026] Hereinafter, the plurality of crucibles 160 may be collectively referred to as a crucible group 160. Furthermore, the through-holes 164 may be referred to as heat channels 164.

[0027] Each crucible 160 includes a container having a cylindrical sidewall and a bottom, and a container lid. The crucible 160 is made of graphite. A SiC seed crystal 163 is fixed to the back surface of the lid of the crucible 160. The heat insulating portion 161 extends between the multiple crucibles 160. That is, the heat insulating portion 161 also exists between the multiple crucibles 160.

[0028] The heat insulating section 161 includes a lid 165 that covers the through-hole (heat channel) 164. The lid 165 adjusts the temperature region within the heat channel 164. Specifically, the thicker the lid 165, the less heat flows, resulting in a higher temperature region. On the other hand, the thinner the lid 165, the more heat flows, resulting in a lower temperature region. The lid 165 also prevents radiant light emitted from the high-temperature upper surface of the crucible 160 from directly reaching the chamber 12. Since the chamber 12 is made of stainless steel, it is necessary to avoid direct exposure to radiant light from the crucible 160, which is a heat source exceeding 2000°C. It is desirable to keep the temperature of the upper surface of the lid 165, which is made of a heat insulating material, and the surface facing the chamber 12 at 1000°C or less.

[0029] The heat insulating portion 161 includes an outer peripheral side wall 166. The outer peripheral side wall 166 is disposed on the outer periphery of the plurality of crucibles (crucible group) 160. The outer peripheral side wall 166 is also made of a heat insulating material.

[0030] The heat insulating section 161 includes a plurality of cylindrical sections 167 corresponding to the plurality of crucibles 160. Each cylindrical section 167 has a through-hole (heat channel) 164.

[0031] The heating chamber 14 further includes a heat insulating material 141. The heat insulating material 141 is disposed around and below the heat source 140. The heat insulating material 141 is connected to the heat insulating portion 161.

[0032] The chamber 12 includes a temperature measurement hole 121 for measuring the temperature of the crucible 160 .

[0033] 2, the plurality of crucibles 160 include one central crucible 1600, six first outer crucibles 1601 arranged on the periphery of the central crucible 1600, six second outer crucibles 1602 and six third outer crucibles 1603 arranged on the periphery of the first outer crucible 1601. The distance between the second outer crucible 1602 and the central crucible 1600 is shorter than the distance between the third outer crucible 1603 and the central crucible 1600. In other words, the second outer crucible 1602 is closer to the central crucible 1600 than the third outer crucible 1603.

[0034] 2 shows an example in which a total of 18 outer crucibles 1601, 1602, and 1603 are arranged around the central crucible 1600, but only six first outer crucibles 1601 may be arranged around the central crucible 1600. Also, an additional outer crucible may be arranged around the 12 outer crucibles 1602 and 1603.

[0035] The arrangement shown in FIG. 2 is a closest packed arrangement, but instead of this arrangement, as shown in FIG. 3, three crucibles 1604 may be arranged around the center, nine crucibles 1605 may be arranged around that periphery, and fifteen crucibles 1606 may be arranged around that periphery.

[0036] The insulating material is made of carbon fiber, expanded graphite, or flexible graphite, or a combination of at least two of these. The carbon fiber insulating material may be in the form of, for example, felt or sheet. This type of insulating material has a thermal conductivity of 3.0 W / mK or less at 2000°C. Alternatively, it may be molded carbon fiber insulating material obtained by impregnating carbon fiber insulating material with resin, molding it, and then graphitizing it. This type of insulating material has a thermal conductivity of 1.0 W / mK or less at 2000°C. The expanded graphite insulating material may be in the form of, for example, bulk, flake, or granule. Alternatively, it may be an insulating material made of flexible graphite obtained by compression molding expanded graphite. The flexible graphite insulating material may be in the form of, for example, bulk or sheet. This type of insulating material has a thermal conductivity of 10 W / mK or less in the thickness direction at room temperature (25°C).

[0037] <Chamber> The chamber 12 is airtight and capable of controlling the pressure under reduced pressure while supplying various gases such as argon, helium, and nitrogen. All components (heat source 140, crucible 160, heat insulating section 161, and heat insulating material 141) are housed within the chamber 12. The chamber 12 can be divided into upper and lower halves to allow for easy access to these internal components. The chamber 12 may be opened and closed by raising the upper side of the chamber 12, lowering the lower side, or performing both actions simultaneously. Alternatively, the chamber 12 may be opened and closed by rotating the upper and / or lower sides of the chamber 12. The dividing plane of the chamber 12 may be vertical rather than horizontal. If the dividing plane is vertical, the chamber 12 can be divided horizontally (left and right). The chamber 12 is made of stainless steel such as SUS316, 304, or 430. To prevent the intrusion of foreign matter, the inner surface of the chamber is preferably polished to a mirror finish by mechanical or electrolytic polishing.

[0038] The surface temperature of the heat insulating material in the heating chamber 14 and the growth chamber 16 can reach 300 to 500°C, and the temperature at the top of the heat channel 164 can reach 1000°C. Therefore, it is preferable that the back surface of the inner wall of the chamber 12 is water-cooled, and it is even more preferable that an outer wall of the chamber 12 is provided and the gap between the inner wall and the outer wall is a water-cooled jacket.

[0039] During crystal growth, the surface temperature of the heat source 140 installed in the heating chamber 14, the temperatures of the top, bottom, or side of the crucible 160, and other temperatures are measured as needed. A radiation thermometer is used to measure these temperatures. Therefore, an airtight window made of quartz glass or the like is preferably installed as the temperature measurement hole 121 on the top surface of the chamber 12. Airtight windows are also preferably installed on the bottom and side surfaces of the chamber 12. To suppress external factors during temperature measurement, a graphite pipe with both ends open may be installed penetrating from the temperature measurement hole 121 to the interior of the chamber 12. Furthermore, when crystal growth is continued over a long period of time, accumulation of dirt on the surface of the airtight window can cause a decrease in the reading of the radiation thermometer and lead to temperature measurement errors. Therefore, it is preferable that the airtight window be removable. Alternatively, a wiper for cleaning dirt from the inner surface or a shutter for hiding the inner surface of the airtight window to prevent dirt from accumulating when not measuring the temperature may be installed.

[0040] <Heating chamber> The heating chamber 14 is a space covered with a thermal insulator 141, excluding the heat channel 164 and the inlet of the heat source 140. To promote the flow of heat in the direction of the heat channel 164, it is preferable that the escape of heat toward the periphery of the chamber 12 via the thermal insulator 141 is sufficiently suppressed to maintain heat. There are no particular restrictions on the material, thickness, or shape of the thermal insulator 141 used, but general graphite felt or its molded body can be suitably used, and the required thickness of the thermal insulator 141 on the chamber surface is, for example, 100 mm or more, more preferably 150 mm or more.

[0041] The heat source 140 installed in the heating chamber 14 is not particularly limited as long as it can achieve a surface temperature of 2100 to 2500°C, and high-frequency induction heating, resistance heating, infrared heating, gas heating, arc heating, laser heating, or a combination of these can also be used.

[0042] The surface of the heat insulating material 141 facing the heating chamber 14 is easily worn away by being exposed to high temperatures for a long time. Furthermore, a small amount of sublimation gas containing Si and C leaking from the crucible 160 may reach the interior of the heat insulating material 141 and precipitate as SiC or Si at a temperature where it can be precipitated, thereby reducing the heat insulating performance. Therefore, it is preferable that the surface layer, which is easily worn away, be replaceable. It is even more preferable to cover the surface of the heat insulating material 141 with a flexible graphite sheet or the like to provide resistance to the penetration of sublimation gas. The surface of a graphite sheet has a higher reflectivity to radiant light than graphite felt or the like, and is therefore advantageous in that it can efficiently guide radiant heat from the heat source 140 to the heat channel 164.

[0043] <Growth room> The growth chamber 16 is disposed on a heat flow path (heat channel 164) extending upward from the heating chamber 14. The heat channels 164 are separated by insulating sections 161, which restrict the horizontal transport of heat between the crucibles 160. The thickness of the insulating sections 161 disposed in the vertical direction within the heat channels 164 is thinner than the portions other than the heat channels 164, reducing the resistance to heat transport. As a result, the heat generated in the heating chamber 14 is transported upward from the boundary with the heating chamber 14 through the heat channels 164, ideally evenly, and is absorbed from the top as mainly radiant light by the cooled inner wall of the chamber 12.

[0044] A crucible 160, which is the growth site for the SiC single crystal, is installed within the heat channel 164. The crucible 160 may be suspended from the top of the chamber 12 or may be placed on a pedestal extending from the bottom of the chamber 12. A pedestal may be installed for each heat channel 164, or a single common pedestal may cross all of the heat channels 164. While there are no particular limitations on the material of the pedestal, graphite is preferred, and extruded graphite, which has excellent thermal conductivity in the vertical direction, is more preferred. Furthermore, since the weight on the pedestal increases as the number of crucibles 160 increases, a molded carbon fiber plate (Carbon Fiber Rainforced Carbon Composite Material (CCM)), which has higher bending strength, may be used. This material has thermal conductivity in the horizontal direction (parallel to the pedestal surface) equivalent to that of general graphite, but its thermal conductivity in the vertical direction (perpendicular to the pedestal surface) is approximately 1 / 10 to 1 / 100 of that of general graphite. Therefore, in order to efficiently supply heat from the heating chamber 14 into the crucible 160, a through-hole may be present in the pedestal surface that contacts the crucible 160. A material with excellent vertical thermal conductivity may be disposed in place of a portion of the pedestal surface that contacts the crucible 160. The crucible 160 may be held in such a way that the lower part of the crucible 160 protrudes from the lower surface of the pedestal toward the heating chamber 14.

[0045] The temperatures of the top and bottom surfaces of the crucible 160 and the temperature difference between them are important factors that affect the crystal growth rate. These temperatures and the temperature difference can be controlled by the position and thickness of the heat insulating portion 161 disposed within the heat channel 164. That is, by disposing a heat insulating material between the heating chamber 14 and the bottom surface of the crucible 160, the temperature region at the bottom of the crucible 160 can be lowered. Conversely, by disposing the heat insulating portion 161 between the top surface of the crucible 160 and the top surface of the heat channel 164, the temperature region within the crucible 160 can be raised. Furthermore, by making the heat insulating portion 161 disposed here thinner, the temperature difference between the top and bottom of the crucible 160 increases; conversely, by making the heat insulating portion 161 thicker, the temperature difference between the top and bottom of the crucible 160 decreases. This allows the sublimation rate of the SiC raw material 162 and the growth rate of the SiC single crystal to be adjusted.

[0046] <Effects of the First Embodiment> According to the first embodiment, the heat channel 164 flows heat supplied from the heat source 140 upward through the crucible 160. The temperature difference between the top and bottom of the heat channel 164, including the crucible 160, changes along with the ratio of the heat flowing through the heat channel 164 to the heat from the heat source 140, depending on the ratio of the thermal resistance between the heat channel 164 and the thermal insulation 161. That is, as the thermal resistance of the heat channel 164 becomes smaller than the thermal resistance of the thermal insulation 161, the ratio of the heat flowing through the heat channel 164 increases. Accordingly, the temperature difference between the top and bottom of the crucible 160 in the heat channel 164 also increases, thereby increasing the growth rate of the SiC single crystal. Furthermore, the presence of thermal insulation between the multiple crucibles 160 prevents heat transfer between the multiple crucibles 160. As a result, the temperatures in the multiple crucibles 160 can be controlled independently of each other by utilizing the position and thickness of the thermal insulation 161. Furthermore, since the heat insulating section 161 includes a peripheral sidewall 166 disposed on the outer periphery of the crucible group 160, the insulating material constituting the peripheral sidewall 166 prevents heat from escaping laterally from the crucible group 160. The higher the insulating performance of the peripheral sidewall 166, the less likely heat from the crucible group 160 will escape laterally. Therefore, the lower the thermal conductivity of the insulating material 166 and the thicker the insulating material 166, the more likely heat will flow upward through the heat channel 164. If the insulating performance of the peripheral sidewall 166 is poor, heat from the crucible group 160 will more easily escape laterally, and the peripheral crucibles 1601, 1602, and 1603 will tend to be lower in temperature than the central crucible 1600.

[0047] Furthermore, in a furnace for simultaneously growing multiple SiC single crystals in parallel, the heat flow from heat source 140 is concentrated in heat channel 164 without using a side heat source, thereby achieving both a smaller furnace size and reduced energy consumption, while increasing the temperature difference between the top and bottom of multiple crucibles, which is the driving force for crystal growth.

[0048] <Embodiment 2> 4, in SiC single crystal manufacturing apparatus 10 according to the second embodiment, heat insulating section 161 includes protective layer 168. Protective layer 168 is provided on the inner circumferential surface of through-hole (heat channel) 164 and is detachable.

[0049] Sublimation gas that leaks slightly from the crucible 160 recrystallizes in areas with low temperatures. If the crucible 160 is surrounded by an insulating section 161, a large temperature gradient occurs inside the insulating section 161, and recrystallization begins from areas where the temperature has dropped to a certain level. In other words, the voids inside the insulating section 161 are filled with SiC polycrystals, reducing the insulating performance. The protective layer 168 prevents the sublimation gas from penetrating into the insulating section 161. Flexible graphite sheets made by compressing expanded graphite have poorer gas permeability than the graphite felt used in the insulating section 161, and so can delay the arrival of the sublimation gas inside the insulating section 161, thereby extending the life of the insulating section 161. In addition, the thermal conductivity of graphite sheets in the longitudinal direction (thickness direction) is intermediate between that of ordinary graphite materials such as extruded materials and CIP materials and that of insulating materials such as graphite felt and its molded bodies, so they can also be used as weak insulating materials.

[0050] In this embodiment, the protective layer 168 is provided on a part of the inner circumferential surface of the through-hole 164, that is, above the crucible 160, but it may be provided on the entire inner circumferential surface including the surface facing the crucible 160. [Example]

[0051] To confirm the effects of the above-described embodiment, a simulation of the temperature distribution during steady-state heating was performed using "Femtet" software manufactured by Murata Software Co., Ltd. Here, 19 crucibles with a diameter of 200 mm (corresponding to a grown crystal diameter of 150 mm) were arranged. Specifically, one central crucible was surrounded by six first outer crucibles, and 12 crucibles were arranged around the first outer crucible. Of these, the six closest to the central crucible were designated the second outer crucible, and the six furthest from the central crucible were designated the third outer crucible. The vertical thermal conductivity of the crucibles was set to 85 W / mK and the horizontal thermal conductivity was set to 43 W / mK. Both thermal conductivities were measured at 2000°C, and the same applies to subsequent measurements. The shortest distance between the crucibles was 10 mm, and the distance between the centers of the crucibles was set to 210 mm. The dashed dotted line in FIG. 2 indicates the cross-sectional position where the simulation analysis was performed.

[0052] <Comparative Example> As a comparative example, a model was prepared in which the furnace structure had heat sources below and to the side of the crucible group, no heat insulating material was installed between the crucibles, and no heat channels existed between the crucibles. The vertical inner wall area of ​​the side heat source was 1.6 m 2 The heat supply from the heat source was set to 33 kW. The horizontal area of ​​the lower heat source was set to 0.85 m. 2 The heat supply from the heat source was set to 82 kW. The insulation (thermal conductivity 0.45 W / mK) on the outer side walls installed around each heat source and the crucible group was 150 mm thick at the top and bottom, and 100 mm thick at the side walls. The top lid directly above the crucibles had through holes with a diameter of 160 mm, and a 20 mm thick disk-shaped insulation material was installed at the top of each hole. The crucible group was also placed on a common base (vertical thermal conductivity 9.0 W / mK, horizontal thermal conductivity 1.3 W / mK).

[0053] Example 1 As explained in the first embodiment shown in FIG. 1, the heat source was installed only below the group of crucibles, not to the sides, and the heat supply from the heat source was set to 80 kW. Heat insulation was installed almost everywhere except for the heat channels above the crucibles and the base surface. Compared to the comparative example, the side heat sources were eliminated, and the thickness of the insulation material on the outer peripheral side wall 166 was increased to 200 mm, utilizing the space previously occupied by the heat sources, thereby improving the insulation performance of the heating chamber 14. The other parts were the same as those in the comparative example.

[0054] <Example 2> Compared to Example 1, the portion of the common pedestal where it contacts the underside of the crucible, corresponding to 50% of the thickness of the common pedestal, was replaced with a material with excellent vertical thermal conductivity (vertical thermal conductivity 85 W / mK, horizontal thermal conductivity 43 W / mK). The other portions were the same as in Example 1. For Example 2, the tendency when the heat supply from the heat source was reduced from 80 kW to 70 kW to 60 kW was examined.

[0055] Example 3 Compared to Example 1, all of the common bases were made of the material of Example 2, which has excellent thermal conductivity in the vertical direction. The other parts were the same as in Example 1, and the heat supply from the heat source was set to 60 kW.

[0056] <Result> The simulation results of the above-mentioned Comparative Example and Examples 1 to 3 are summarized in FIGS. 5 and 6 from the viewpoints of "growth index" and "crucible temperature variation index."

[0057] The growth index shown in Figure 5 indicates the difference between the temperature at the center of the source material's bottom surface in the crucible placed in the center of the furnace and the temperature at the center of the pedestal where the seed crystal is placed. These represent the temperature at the site of source material sublimation and recrystallization, and the driving force for crystal growth, respectively. The temperature here is the result of the heat supply setting from the heat source, and is not necessarily a value suitable for SiC crystal growth. A high displayed temperature indicates that there is sufficient heating capacity, meaning that the amount of heat supplied from the heat source can be reduced.

[0058] On the other hand, the crucible temperature variation index shown in Figure 6 is the difference in temperature at the center of the pedestal surface that comes into contact with the seed crystal inside the crucible between the central crucible and the third outer crucible, which are positioned rotationally symmetrically, on the horizontal axis, and the absolute value of the difference between the maximum and minimum temperatures on the pedestal surface that comes into contact with the seed crystal between the central crucible and the first and third outer crucibles, which are positioned rotationally symmetrically. The horizontal axis, which corresponds to the horizontal temperature variation between the crucibles, is an index of the variation in growth rate of the single crystal growing inside the crucible between the crucibles, and the smaller this index, the better the mass production equipment with uniform heating. Furthermore, the smaller the vertical axis representing the horizontal temperature distribution within each crucible, the smaller the horizontal temperature difference that occurs within the growing crystal, which can be said to be an excellent crystal growth environment that can suppress cracks and the introduction of defects due to thermal stress.

[0059] In the comparative example where a combined power of 115 kW was applied to the side and bottom heat sources, the bottom temperature of the central crucible did not reach 2200°C, and the difference with the top temperature, which is the driving force for crystal growth, was 86°C. In addition, a temperature difference of 79°C (higher temperatures at the periphery) was observed between the central crucible and the second peripheral crucible, and a 24°C variation was confirmed in the temperature distribution on the pedestal surface inside the second peripheral crucible.

[0060] As a result of Example 1, the temperature of the bottom surface of the raw material in the central crucible rose to 2691°C. This indicates that the applied heat was reduced by approximately 30% compared to the comparative example, and that there was a large heating reserve. Furthermore, the temperature difference between the bottom and top surfaces increased significantly to 203°C, indicating a significant improvement in the driving force for crystal growth. Furthermore, the temperature difference between the central crucible and the second peripheral crucible was 45°C, significantly lower than in the comparative example, demonstrating improved thermal uniformity between the heat channels. In the comparative example, the heat supply from the sides was also directed toward the center of the furnace, which tended to increase the temperature of the crucible located toward the periphery of the furnace. However, in Example 1, the heat supplied from the lower heat source also escaped slightly to the sides through the crucible, resulting in a tendency for the crucible temperature to decrease toward the periphery.

[0061] In Examples 1 to 3, the thickness of the insulating material installed at the top end of the heat channel was set to 20 mm, but changing this thickness changes the degree of heat removal upward through the heat channel, so for example, by making the insulating material thinner for heat channels closer to the center of the furnace or thicker for heat channels closer to the periphery of the furnace, it is possible to reduce the tendency for the crucible temperature to decrease from the inside to the outside of the furnace. Meanwhile, the temperature distribution variation on the pedestal surface inside the crucible was also reduced to less than half, to less than 10°C, demonstrating an excellent thermal environment for crystal growth inside the crucible.

[0062] In Example 2, by replacing 50% of the pedestal thickness where the common pedestal contacted the bottom surface of the crucible with a material with excellent vertical thermal conductivity, the heat source output was set to 80 kW. While maintaining a large difference between the temperature of the bottom surface of the raw material in the central crucible and the temperature of the pedestal surface holding the seed crystal (196 °C), the temperature of the bottom surface of the raw material further increased to 2775 °C. This indicates that a large vertical temperature gradient occurs within the common pedestal, which has relatively low vertical thermal conductivity. By replacing a portion of the common pedestal contacting the bottom surface of the crucible with a material with high thermal conductivity (or by leaving a gap), the energy consumption for heating can be further reduced. Therefore, similar effects can be achieved by drilling a hole in the pedestal where the common pedestal contacts the bottom surface of the crucible, or by holding the crucible so that its lower part protrudes downward from the pedestal. Furthermore, even when the heat source output was reduced to 60 kW, the temperature of the base of the central crucible remained at 2405°C, with a difference of 159°C from the pedestal surface temperature, demonstrating a reduction in energy consumption of more than 50% compared to the heat source of the comparative example. The temperature difference between the central crucible and the second peripheral crucible also decreased to 19°C, and the temperature distribution variation on the pedestal surface inside the crucible was also very small, comparable to that of Example 1.

[0063] In Example 3, the heat source output was set to 60 kW, and the common pedestals on which the crucibles were mounted were all replaced with materials with excellent vertical thermal conductivity. As a result, the temperature of the raw material bottom surface of the central crucible increased by another 40°C to 2445°C, and the difference with the pedestal surface temperature remained large at 157°C. In addition, the temperature difference between the central crucible and the second peripheral crucible was reduced to 24°C compared to Example 2, and the temperature distribution variation on the pedestal surface inside the crucible was kept to 10°C or less.

[0064] Through the results of the above examples, it was confirmed that a structure with a heat channel can significantly reduce energy consumption in SiC single crystal production, suppress variations in the temperature environment between multiple crucibles, and significantly improve the driving force for single crystal growth within each crucible.

[0065] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified within the scope of the claims. [Explanation of symbols]

[0066] 10: SiC single crystal manufacturing equipment 12: Chamber 14:Heating chamber 16:Growth room 140:Heat source 141: Insulation section 160: Crucible (crucible group) 161: Insulation section 162:SiC raw material 163:SiC seed crystal 164: Through hole (heat channel) 165: Lid 166: Peripheral side wall 167: Cylindrical part 168 :Protective layer 1600: Central crucible 1601: 1st outer crucible 1602:Second outer crucible 1603: Third outer crucible

Claims

1. a chamber; a heating chamber disposed within the chamber and including a heat source; a growth chamber provided within the chamber and positioned above the heating chamber; The growth chamber comprises: a plurality of crucibles arranged side by side in a horizontal direction, into which a SiC raw material can be charged and into which a SiC seed crystal can be attached; and a heat insulating section having a plurality of through holes corresponding to the plurality of crucibles, each of the through holes forming a heat channel for flowing heat supplied from the heat source upward through the corresponding crucible.

2. The SiC single crystal manufacturing apparatus according to claim 1, The heat insulating portion is A SiC single crystal manufacturing apparatus including a lid portion that covers the through hole.

3. The SiC single crystal manufacturing apparatus according to claim 1, The heat insulating portion is The SiC single crystal manufacturing apparatus includes an outer peripheral side wall made of a heat insulating material, the outer peripheral side wall being arranged on the outer periphery of the crucible group consisting of the plurality of crucibles.

4. The SiC single crystal manufacturing apparatus according to claim 1, The heat insulating portion is The SiC single crystal manufacturing apparatus includes a removable protective layer provided on the inner peripheral surface of the through hole.

5. The SiC single crystal manufacturing apparatus according to claim 1, The plurality of crucibles include: one central crucible; and six first outer crucibles arranged around the central crucible.

6. The SiC single crystal manufacturing apparatus according to claim 5, The plurality of crucibles include: A SiC single crystal manufacturing apparatus including six second outer crucibles and six third outer crucibles arranged around the first outer crucible.

7. The SiC single crystal manufacturing apparatus according to claim 1, The SiC single crystal manufacturing apparatus, wherein the heat insulating section is made of a heat insulating material containing one or more selected from the group consisting of carbon fiber, expanded graphite, and flexible graphite.

8. The SiC single crystal manufacturing apparatus according to claim 7, The carbon fiber constituting the heat insulating material has a thermal conductivity of 3.0 W / mK or less at 2000°C.

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