SiC single crystal fabrication equipment

Abstract

To provide a SiC single crystal manufacturing apparatus capable of suppressing a temperature fluctuation due to a crucible position even in a case of an enlarged crucible.SOLUTION: A SiC single crystal manufacturing apparatus includes a heat generation source, a soaking plate arranged above the heat generation source, a heating vessel that is positioned inside an outer edge of the soaking plate when seen from a vertical direction and is arranged above the soaking plate, a first cylindrical body arranged so as to cover a side surface positioned at an outer most side of the heating vessel when seen form the vertical direction, and a second cylindrical body arranged so as to cover the first cylindrical body in a state of having a separation part when seen from the vertical direction. A side surface of the first cylindrical body that at least faces the second cylindrical body is composed of a material that partly absorbs infrared and partly reflects infrared. A second surface of the second cylindrical body, which is a side surface facing the first cylindrical body, is composed of a material that at least partly reflects infrared.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a SiC single crystal manufacturing apparatus.

Background Art

[0002] Silicon carbide (SiC) has excellent electrical properties, such as a breakdown electric field strength value that is about one order of magnitude larger than that of silicon (Si) and a bandgap value that is about three times larger. In addition, SiC has excellent thermal properties, such as a thermal conductivity that is about three times higher than that of Si. Due to these excellent properties, SiC is expected to be applied to various devices such as power devices, high-frequency devices, and high-temperature operation devices. These devices are fabricated by forming an epitaxial layer serving as an active region of the device on a SiC single crystal substrate obtained by processing a SiC single crystal ingot using a chemical vapor deposition method (CVD) or the like.

[0003] Currently, the mainstream method for manufacturing SiC single crystals is the sublimation method. In this method, SiC powder as a solid raw material is heated and sublimated at a high temperature exceeding 2000°C in a graphite crucible (heating container), and this sublimated gas is supplied to a seed crystal placed at a relatively low-temperature position, and then recrystallized on the seed crystal to obtain a single crystal ingot.

[0004] Unlike the melt growth method using a liquid phase, the sublimation method utilizes growth by gas, and thus has a fundamental problem that defects are likely to occur when growing at high speed. That is, a certain heating time is required to grow a single single crystal ingot. From this perspective, the applicant has previously proposed a technique of arranging a plurality of crucibles and seed crystals for a furnace unit and growing a plurality of single crystal ingots in parallel (see Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] SiC devices, which are attracting attention as power semiconductors, are beginning to be required to handle even higher currents. To realize SiC devices that can handle high currents, large SiC wafers are required, and to manufacture large SiC wafers, large single-crystal ingots are required. To manufacture large single-crystal ingots, the size of the crucible needs to be increased compared to conventional methods.

[0007] However, when multiple large crucibles are arranged and heated in a single furnace, temperature variations are likely to occur depending on the placement of the crucibles. Such temperature variations can lead to variations in the crystal growth rate of each single-crystal ingot produced in each crucible, and consequently, variations in performance.

[0008] Furthermore, the technology described in Patent Document 1 involves placing separate heat sources on the bottom and sides of the crucible and adjusting the ratio of heating energy supplied from each heat source within a predetermined range. However, as the size of the crucible increases, the device itself also becomes larger, increasing the distance between the heat sources on the sides and the crucible inside the furnace. This makes it more difficult for the heat energy from the side heat sources to reach the crucible. Consequently, a time lag occurs between the timing of adjusting the output of the side heat sources and the timing of the heat energy from the side heat sources reaching the crucible after the output has been adjusted. Due to these circumstances, it becomes difficult to control the ratio of heating energy from the bottom heat source to heating energy from the side heat sources within a predetermined range.

[0009] In view of the above problems, the present invention aims to provide a SiC single crystal manufacturing apparatus that can suppress temperature variations depending on the position of the crucible, even when the crucible is enlarged. [Means for solving the problem]

[0010] The SiC single crystal manufacturing apparatus according to the present invention is Heat source and A heat distribution plate is positioned above the heat source so as to cover the heat source when viewed from the vertical direction, A heating vessel comprising: a raw material storage area for containing a solid raw material made of SiC, located inward from the outer edge of the heat distribution plate when viewed from the vertical direction and positioned above the heat distribution plate; and a seed crystal mounting area for arranging a SiC seed crystal at a position vertically separated from the raw material storage area; A first cylindrical body is positioned to cover the outermost side of the heating container when viewed from the vertical direction, A second cylindrical body is positioned to cover the first cylindrical body and the heat distribution plate and the heat source, with a spaced portion between them when viewed from the vertical direction, The second cylindrical body comprises a lid positioned to close off a portion of its upper surface, The first cylindrical body has at least one first surface, which is a side facing the second cylindrical body, made of a material that partially absorbs and partially reflects infrared rays. The second cylindrical body has a second surface, which is the side surface facing the first cylindrical body, made of a material that reflects at least some infrared rays. The bottom surface of the lid is characterized by being made of a material that reflects at least some infrared rays.

[0011] In this specification, "infrared radiation" refers to electromagnetic waves that have the function of transmitting heat when emitted.

[0012] According to the above configuration, heat generated from a heat source located below the heat equalization plate heats the bottom of the heating container via the heat equalization plate. In addition, infrared rays (radiant heat) emitted from the heat source itself or the heated heat equalization plate travel toward the outer second cylindrical body. The second cylindrical body has a surface (second surface) facing the inner first cylindrical body that is made of a material that reflects at least some infrared rays, so the infrared rays are reflected by this second surface and travel toward the inner first cylindrical body.

[0013] The first cylindrical body has a surface (first surface) facing the second cylindrical body located on its outside, which is made of a material that partially absorbs and partially reflects infrared radiation. As a result, the first cylindrical body heats up by partially reflecting the infrared radiation reflected by the second surface back to the second cylindrical body, and by absorbing some of the infrared radiation. The first cylindrical body is also heated by the heat propagated from the heated uniforming plate. As a result, the heated first cylindrical body functions as a secondary heat source, radiating infrared radiation towards the heating container located inside and the second cylindrical body located outside. Furthermore, the surface of the first cylindrical body facing the second cylindrical body (first surface) also functions as a reflective surface, reflecting some of the infrared radiation incident from the second cylindrical body back to the second cylindrical body.

[0014] Infrared radiation emitted from the first surface of the first cylindrical body is reflected again from the second surface of the second cylindrical body and guided back to the first cylindrical body. Infrared radiation incident on the first cylindrical body is partially absorbed, heating the first cylindrical body, while some of it is re-reflected towards the second cylindrical body. In this way, some of the infrared radiation propagates vertically upward, repeatedly reflecting between the first and second cylindrical bodies. In other words, the separation between the first and second cylindrical bodies forms a propagation path that guides the infrared radiation reflected between the first surface of the first cylindrical body and the second surface of the second cylindrical body vertically upward.

[0015] As a result, the first cylindrical body is easily heated even at a position away from the heat-distributing body towards the lid in the vertical direction (a position vertically above), because infrared radiation emitted from the second surface of the second cylindrical body enters it. Therefore, the first cylindrical body functions as a secondary heat source overall in the height direction, and the infrared radiation emitted inward from this first cylindrical body can heat the heating container placed inside the first cylindrical body regardless of its height.

[0016] Furthermore, according to the above configuration, the bottom surface of the lid is also made of a material that reflects infrared rays. Therefore, when infrared rays that have propagated vertically upward while repeatedly reflecting between the first surface of the first cylindrical body and the second surface of the second cylindrical body are incident on the bottom surface of the lid, they are reflected by this bottom surface and propagate downward. As a result, the heating container can be heated from above.

[0017] According to the SiC single crystal manufacturing apparatus with the above structure, the primary heat source is positioned vertically below the heating plate, yet it is possible to heat the heating container not only from the bottom but also from the sides and top. Furthermore, the thermal energy from the sides and top is not supplied directly from the primary heat source, but rather from infrared rays originating from the first cylindrical body, which functions as a secondary heat source heated by heat transfer and radiation, and from infrared rays reflected from the reflective surface. For this reason, the ratio of thermal energy supplied to the heating container from the sides and top to the thermal energy supplied to the heating container from the bottom is uniquely determined by the material, shape, dimensions, etc., of the first cylindrical body, the second cylindrical body, and the lid.

[0018] In other words, if the materials, shapes, dimensions, etc., of the first cylindrical body, second cylindrical body, and lid are pre-adjusted to achieve the desired thermal balance, then even if the output of the primary heat source located below the heating plate is adjusted for temperature control, it is unlikely that the thermal balance in relation to the heating direction will be significantly disrupted as a result of this output control. Therefore, even when using a large heating container, the occurrence of temperature variations depending on the position of the heating container is suppressed.

[0019] The second surface of the second cylindrical body may have a higher reflectivity to infrared rays than the first surface of the first cylindrical body. More specifically, the second cylindrical body may be made of a main material having heat insulating properties, and a coating material or sheet material with a higher reflectivity to infrared rays than the main material may be formed on the second surface.

[0020] In addition, in this specification, "having heat insulation properties" refers to those with a thermal conductivity of 10 [W / (m·K)] or less.

[0021] As described above, while the first cylindrical body has the function of reflecting a part of infrared rays toward the second cylindrical body, as a secondary heat source, it also has the function of radiating infrared rays inside and heating the heating container arranged inside the first cylindrical body from the side. On the other hand, the second cylindrical body only needs to have the function of reflecting infrared rays toward the first cylindrical body side, and it is not necessarily required to function as a secondary heat source itself. In other words, compared with the first cylindrical body, it is more preferable that the second cylindrical body has higher reflectivity to infrared rays.

[0022] In particular, by configuring the second cylindrical body with a main material having heat insulation properties, the amount of heat exhausted to the outside through the second cylindrical body can be reduced, so that the heat energy generated from the heat source can be efficiently supplied to the heating container. In this specification, the "main material" refers to a material that occupies 50% by mass or more of the constituent materials.

[0023] The second cylindrical body and the lid body may be configured of the same member. Furthermore, the second cylindrical body and the lid body may be an integral member.

[0024] The lid body may have a heat extraction opening in at least a part of the region facing the top of the heating container when viewed from the vertical direction.

[0025] The SiC single crystal manufacturing apparatus includes a plurality of the heating containers. All of the plurality of heating containers are arranged so as to be located inside the outer edge of the heat dissipation plate when viewed from the vertical direction. The first cylindrical body may be arranged so as to cover the plurality of heating containers located on the outermost side when viewed from the vertical direction.

[0026] According to the above configuration, the outermost heating container is heated from the side by infrared radiation emitted from the first cylindrical body, and the heating container located inside it is heated from the side by infrared radiation emitted from the adjacent heating container. Furthermore, as mentioned above, the primary heat source is located below the uniform heating plate, eliminating the need for separate heat sources to the sides and above.

[0027] Therefore, even if the output of the primary heat source, which is positioned below the heating plate for temperature control, is adjusted, it is unlikely that the thermal balance according to the heating direction will be significantly disrupted as a result of this output control. Consequently, even when using multiple heating containers, the occurrence of temperature variations according to the position of the heating containers is suppressed. As a result, it becomes possible to manufacture multiple large SiC ingots in parallel while suppressing variations in performance.

[0028] From the above viewpoint, it is preferable that each of the aforementioned heating containers is not covered with an insulating material and is configured to allow heat to be transferred between adjacent heating containers by radiation. [Effects of the Invention]

[0029] According to the SiC single crystal manufacturing apparatus of the present invention, even when the heating vessel is enlarged, it is possible to suppress temperature variations depending on the position of the heating vessel. [Brief explanation of the drawing]

[0030] [Figure 1] This is a schematic cross-sectional view showing the configuration of one embodiment of the SiC single crystal manufacturing apparatus of the present invention. [Figure 2] This is a schematic plan view of the SiC single crystal manufacturing apparatus shown in Figure 1, with the lid removed. [Figure 3] This is a schematic cross-sectional view showing the structure of the heating container. [Figure 4] This is a schematic plan view of the lid. [Figure 5]This is a magnified view of a portion of Figure 1, with a schematic illustration of infrared propagation. [Figure 6] This is a plan view illustrating the model of the SiC single crystal manufacturing apparatus prepared as Example 1, following the example in Figure 2. [Figure 7A] This is a plan view illustrating a model of a SiC single crystal manufacturing apparatus prepared as Comparative Example 1, following the example in Figure 2. [Figure 7B] This is a cross-sectional view of a SiC single crystal manufacturing apparatus model prepared as Comparative Example 1, illustrated in accordance with Figure 1. [Figure 8A] This is a plan view illustrating a model of a SiC single crystal manufacturing apparatus prepared as Comparative Example 2, following the example in Figure 2. [Figure 8B] This is a cross-sectional view of a SiC single crystal manufacturing apparatus model prepared as Comparative Example 2, illustrated in accordance with Figure 1. [Figure 9A] This is a plan view illustrating a model of a SiC single crystal manufacturing apparatus prepared as Reference Example 1, following the example in Figure 2. [Figure 9B] This is a cross-sectional view of a SiC single crystal manufacturing apparatus model prepared as Reference Example 1, illustrated in accordance with Figure 1. [Figure 10A] This is a 3D cross-sectional view of a 6-inch single-crystal ingot grown under uniform temperature conditions. [Figure 10B] This is a 3D cross-sectional view of a 6-inch single-crystal ingot grown under conditions of non-uniform temperature distribution. [Figure 11] This is a cross-sectional view illustrating the configuration of another embodiment of the SiC single crystal manufacturing apparatus of the present invention, following the example shown in Figure 1. [Modes for carrying out the invention]

[0031] Embodiments of the SiC single crystal manufacturing apparatus according to the present invention will be described below with reference to the drawings as appropriate. Note that the following drawings are schematic illustrations, and the dimensional ratios shown in the drawings do not necessarily match the actual dimensional ratios, nor do the dimensional ratios necessarily match between drawings.

[0032] Figure 1 is a schematic cross-sectional view showing the configuration of one embodiment of a SiC single crystal manufacturing apparatus. In the following description, the XYZ coordinate system appended to Figure 1 will be referred to as appropriate. Here, when expressing direction, positive and negative directions are distinguished, and are indicated with a sign such as "+Z direction" and "-Z direction". When expressing direction without distinguishing between positive and negative directions, it is simply written as "Z direction". In other words, in this specification, when simply written as "Z direction", both "+Z direction" and "-Z direction" are included. In Figure 1, the Z direction corresponds to the vertical direction.

[0033] Figure 2 is a schematic plan view of the SiC single crystal manufacturing apparatus 1 shown in Figure 1 with the lid 50 removed, and corresponds to a plan view when viewed from the +Z side in the -Z direction.

[0034] Figure 3 is a schematic cross-sectional view showing the structure of the heating container 10 of the SiC single crystal manufacturing apparatus 1 shown in Figure 1. Figure 4 is a schematic plan view of the lid 50, and, similar to Figure 2, corresponds to a plan view when viewed from the +Z side in the -Z direction. Figure 5 is a partially enlarged view of Figure 1, with a schematic annotation illustrating the propagation of infrared radiation.

[0035] The structure of the SiC single crystal manufacturing apparatus 1 will be described in detail below with reference to Figures 1 to 5.

[0036] (Heat source 3) As shown in Figure 1, the SiC single crystal manufacturing apparatus 1 is equipped with a heat source 3. This heat source 3 functions as a primary heat source.

[0037] In the SiC single crystal manufacturing apparatus 1 of this embodiment, the type of heat source 3 is not particularly limited, and known heating methods such as resistance heating and induction heating can be used. In view of the controllability of the amount of heat generated from the heat source 3, resistance heating is preferred, and a structure equipped with a three-phase AC power supply mechanism is more preferred.

[0038] (Soaking plate 5) As shown in Figure 1, the SiC single crystal manufacturing apparatus 1 is equipped with a heat equalization plate 5 located on the +Z side relative to the heat source 3.

[0039] The heat equalization plate 5 is provided for the purpose of spreading the heat radiated from the heat source 3 in the XY plane. In view of this, it is preferable that the heat equalization plate 5 exhibits anisotropic heat conduction, where the thermal conductivity in the XY plane is higher than the thermal conductivity in the Z direction. As an example, the heat equalization plate 5 is composed of a C / C composite material or a laminate of multiple carbon members. In Figure 5, the propagation of heat Ea in the XY plane by the heat equalization plate 5 is schematically represented by a dashed line.

[0040] Furthermore, due to radiant heat from the heat source 3, the heat distribution plate 5 reaches a high temperature of over 2000°C. For this reason, the heat distribution plate 5 is made of a material that ensures strength even in a temperature environment of over 2000°C. The material examples listed above can be used even in such a temperature environment. Moreover, not only the heat distribution plate 5, but also each element of the SiC single crystal manufacturing apparatus 1 described later is preferably made of a material that ensures strength even in a temperature environment of over 2000°C.

[0041] In the example shown in Figure 1, the heat distribution plate 5 has a larger area in the XY plane compared to the heat source 3. Therefore, when viewed from the +Z side, the heat source 3 is hidden below the heat distribution plate 5. In this case, the heat distribution plate 5 is positioned to cover the heat source 3 when viewed from the +Z side, and therefore the heat source 3 is not shown in Figure 2.

[0042] However, this does not exclude the case in the SiC single crystal manufacturing apparatus 1 where the area of ​​the heat equalization plate 5 in the XY plane direction is smaller than that of the heat source 3. For example, if the heat source 3 is configured to have resistance heating means arranged in a ring shape on a plate-shaped member, or if it consists of a single ring-shaped arrangement of resistance heating means, the heat generated from the heat source 3 tends to concentrate at the arrangement of the resistance heating means. For these reasons, the heat equalization plate 5 is provided with the aim of spreading the heat in the XY plane direction. In other words, the relative size relationship between the heat equalization plate 5 and the heat source 3 when viewed from the Z direction is arbitrary.

[0043] In Figure 1, the heat source 3 and the heat equalization plate 5 are spaced apart in the Z direction, but the present invention does not exclude the case in which the heat source 3 and the heat equalization plate 5 are in contact.

[0044] (Heating container 10) As shown in Figure 1, the SiC single crystal manufacturing apparatus 1 includes a heating container 10 positioned on the +Z side of the heat distribution plate 5. The SiC single crystal manufacturing apparatus 1 of this embodiment includes a plurality of heating containers 10, 10, ...

[0045] As shown in Figure 2, all of the heating containers 10, 10, ... are located inside the outer edge 5a of the heat distribution plate 5 when viewed in the Z direction.

[0046] As shown in Figure 3, the heating container 10 has a raw material receiving area 13 for containing a solid raw material 11S made of SiC, and a seed crystal mounting area 16 for positioning a SiC seed crystal 12 at a position spaced apart in the Z direction from the solid raw material 11S. The heating container 10 is also called a crucible.

[0047] The raw material storage area 13 is a bottomed cylindrical body having cylindrical sides 14 and a bottom 15, and a solid raw material 11S is stored in a portion of its internal space. In the example shown in Figure 3, an annular seed crystal mounting portion 16 is arranged connected to the side 14 on the +Z side, and a SiC seed crystal 12 is stably held on the upper surface of this seed crystal mounting portion 16. The -Z side of the placed seed crystal 12 is exposed to the internal space of the raw material storage area 13.

[0048] When the heating container 10 is heated, the solid raw material 11S contained in the raw material containment region 13 is heated and sublimes, changing into a gaseous raw material 11G. When this gaseous raw material 11G reaches the -Z side surface of the seed crystal 12, a SiC single crystal grows.

[0049] In the SiC single crystal manufacturing apparatus 1 of this embodiment, the size of the SiC seed crystal 12 attached by the seed crystal mounting section 16 is not particularly limited. However, the SiC single crystal manufacturing apparatus 1 of this embodiment has the effect of suppressing temperature variations depending on the position of the heating container 10, even when growing large SiC single crystals using large crystals, particularly those with a diameter of 6 inches (152.4 mm) or more or 8 inches (203.2 mm) or more. This point will be described later.

[0050] In the present invention, the detailed structure of the seed crystal mounting portion 16 is not particularly limited, but for example, a method can be adopted in which a base protruding from the inner wall of the side portion 14 is provided to hold the outer circumference of the seed crystal 12.

[0051] From the viewpoint of increasing the vapor pressure of the gaseous raw material 11G generated by the sublimation of the solid raw material 11S, it is preferable that the heating container 10 is equipped with a lid 19, as shown in Figure 3.

[0052] The heating container 10 becomes hot when the solid raw material 11S is sublimated to grow a SiC single crystal, so it is desirable that it be made of a material that can withstand high temperatures. Examples of such high-temperature-resistant materials include one or more belonging to the group consisting of graphite, graphite coated with tantalum, and tantalum carbide.

[0053] (First cylindrical body 30) As shown in Figures 1 and 2, the SiC single crystal manufacturing apparatus 1 includes a first cylindrical body 30 that is arranged to cover a plurality of heating containers 10, 10, ... when viewed from the Z direction.

[0054] In this embodiment, as shown in Figure 1, the first cylindrical body 30 is held on the upper surface of the heat equalization plate 5, so that the upper surface of the heat equalization plate 5 functions as the bottom surface, forming a cylindrical space with an open top. However, the first cylindrical body 30 itself may have a bottom. Furthermore, the present invention does not exclude the case in which the first cylindrical body 30 and the heat equalization plate 5 are spaced apart in the Z direction.

[0055] The first cylindrical body 30 has the function of receiving infrared radiation emitted from the heating element, absorbing a portion of it and being heated, while also reflecting a portion of it. More specifically, the first outer surface 31 of the first cylindrical body 30 has the function of reflecting a portion of the infrared radiation while absorbing a portion of it. The inner surface of the first cylindrical body 30 may also have a similar function.

[0056] Examples of the first cylindrical body 30 that achieves such functionality include carbon fiber felt and a structure in which multiple carbon plate-like members are arranged with gaps between them.

[0057] The outer surface (first surface 31) of the first cylindrical body 30 may have a reflectance lower than its absorptance when receiving infrared radiation. On the other hand, the inner surface of the first cylindrical body 30 may function exclusively as a surface that emits infrared radiation from the heated first cylindrical body 30. However, the inner surface of the first cylindrical body 30 may also have the function of reflecting some infrared radiation, similar to the first surface 31.

[0058] (Second cylindrical body 40) As shown in Figures 1 and 2, the SiC single crystal manufacturing apparatus 1 includes a second cylindrical body 40 that is positioned to cover the first cylindrical body 30, with a spaced portion 60.

[0059] More specifically, the second cylindrical body 40 is positioned to cover not only the first cylindrical body 30, but also the heat distribution plate 5 and the heat source 3 from the side.

[0060] The second cylindrical body 40 has a function to reflect at least some of the infrared radiation emitted from the heating element, particularly on its inner surface (second surface 41). The second surface 41 of the second cylindrical body 40 may have a higher infrared reflectivity than the first surface 31 of the first cylindrical body 30.

[0061] Preferably, the second cylindrical body 40 is composed of a main material exhibiting heat insulation properties, and the second surface 41 is formed with a coating material or sheet material that has a higher reflectivity to infrared rays than the main material. An example of such a material is one in which a molded heat insulating material mainly composed of carbon is used as the main material, and a graphite sheet exhibiting metallic luster is formed on the surface, with carbon as the main component. Another example of a coating material is a carbide of a high melting point metal, such as tantalum carbide or niobium carbide.

[0062] (Lid 50) As shown in Figures 1 and 2, the SiC single crystal manufacturing apparatus 1 includes a lid 50 positioned to close off a portion of the upper surface of the second cylindrical body 40. More specifically, as shown in Figures 1 and 4, the lid 50 has a heat dissipation opening 53 in at least a portion of the region facing the top of the heating container 10 in the Z direction.

[0063] The lid 50 has a function to reflect at least some of the infrared radiation emitted from the heating element when it receives infrared radiation, at least on the -Z side (bottom surface 51), similar to the second surface 41 of the second cylindrical body 40.

[0064] The lid 50 may be made of the same material as the second cylindrical body 40. Furthermore, the lid 50 may be made of a single component integrated with the second cylindrical body 40.

[0065] (Heat flow) Next, the heat flow in the SiC single crystal manufacturing apparatus 1 will be explained with reference to Figure 5.

[0066] The heat generated from the heat source 3, which acts as the primary heat source, is received by the heat equalization plate 5 as infrared radiation E0, and heats the heat equalization plate 5. When the heat source 3 is in contact with the heat equalization plate 5, the heat equalization plate 5 is heated by direct heat transfer from the heat source 3. The heated heat equalization plate 5 propagates heat in the XY plane direction (heat Ea).

[0067] The heated uniforming plate 5 functions as a secondary heat source, radiating infrared radiation E1 to the +Z side and heating the heating container 10 from the -Z side. In addition, the first cylindrical body 30 is heated by infrared radiation or heat conduction from the uniforming plate 5.

[0068] When the region on the -Z side of the first cylindrical body 30 is heated, it functions as a secondary heat source and emits infrared radiation E2. The infrared radiation E2 emitted inward from the first cylindrical body 30 heats the heating container 10 from the side. In addition, the infrared radiation E3 emitted outward from the first cylindrical body 30 is incident on the second surface 41 of the second cylindrical body 40. It is also possible that some of the infrared radiation E1 from the heat uniforming plate 5 and some of the infrared radiation E0 from the heat source 3 may be incident on the second cylindrical body 40.

[0069] As described above, the second surface 41 of the second cylindrical body 40 is made of a material that reflects infrared rays. Therefore, infrared rays E3 traveling outward and incident on the second surface 41 of the second cylindrical body 40 are reflected by the second surface 41 of the second cylindrical body 40 and returned to the first cylindrical body 30 located on the inside. Alternatively, the second cylindrical body 40 may be partially heated, causing it to emit infrared rays as a secondary heat source.

[0070] When the infrared radiation E3 emitted from the second cylindrical body 40 is received by the first surface 31 of the first cylindrical body 30, a portion of it is absorbed, causing the first cylindrical body 30 to heat up. As a result, the first cylindrical body 30 functions as a secondary heat source and, similar to the above, emits infrared radiation E2 inward, heating the heating container 10 from the side. In addition, some of the infrared radiation E3 is reflected again by the first surface 31 of the first cylindrical body 30 and returned to the second cylindrical body 40.

[0071] In other words, within the separated portion 60, the infrared radiation E3 propagates in the +Z direction while repeatedly reflecting. As a result, the infrared radiation E3 is incident on the first cylindrical body 30 at different positions in the Z direction, and the first cylindrical body 30 is heated by the infrared radiation E3 even at positions that are farther away from the uniform heating plate 5 in the Z direction.

[0072] Furthermore, when some of the infrared E3 is incident on the bottom surface 51 of the lid 50, it is reflected by the bottom surface 51 of the lid 50 and propagates downward, heating the heating container 10 from above.

[0073] As described above, according to the SiC single crystal manufacturing apparatus 1 of this embodiment, the heat source 3, which serves as the primary heat source, is positioned on the -Z side of the uniform heating plate 5, and the heating container 10 can be heated not only from the bottom side, but also from the side and top side.

[0074] As described above, the heating of the heating container 10 from above originates from infrared radiation E3 reflected from the reflective surface. The heating of the outermost heating container 10 from the side originates from infrared radiation E2 from the first cylindrical body 30, which functions exclusively as a secondary heat source. Furthermore, the heating of the inner heating container 10 from the side originates from infrared radiation E2 from the heated heating container 10 located adjacent to the outermost one. In this case, the heating container 10 itself functions as a secondary heat source.

[0075] Therefore, with the above configuration, heating of the heating container 10 from the side and above is possible without placing primary heat sources on the sides or top. As a result, even if the output of the heat source 3 as the primary heat source is adjusted for temperature control, it is possible to substantially maintain the ratio of thermal energy to the heating container 10 for each heating direction. Thus, in the SiC single crystal manufacturing apparatus 1, by appropriately adjusting the material, shape, dimensions, etc. of the first cylindrical body 30, the second cylindrical body 40, and the lid 50 in advance, it is possible to adjust the temperature of the heating container 10 while maintaining a desirable thermal balance.

[0076] In other words, with the SiC single crystal manufacturing apparatus 1, the heating pattern can be made nearly uniform regardless of the position of each heating container 10, 10, .... By appropriately adjusting the material, shape, dimensions, etc. of the first cylindrical body 30, the second cylindrical body 40, and the lid 50 in advance, the occurrence of temperature variations depending on the position of the heating containers 10, 10, ... is suppressed. This makes it possible to manufacture multiple SiC ingots in parallel while suppressing variations in performance.

[0077] [verification] The aspect of suppressing temperature variations in the SiC single crystal manufacturing apparatus 1 described above will be explained in detail with reference to the examples.

[0078] (Example 1) Figure 6 is a plan view illustrating the model of the SiC single crystal manufacturing apparatus 1 prepared as Example 1, following the example in Figure 2. The model for Example 1 was equipped with 19 heating containers 10, 10, ...

[0079] A cylindrical second cylindrical body 40 was prepared, and a heat source 3, consisting of a resistance heating means with a three-phase AC power supply mechanism, was placed at its bottom. As the second cylindrical body 40, a molded heat insulating material mainly composed of carbon, with a graphite sheet material applied to its surface, was used.

[0080] The heat source 3 employs a heater as a resistance heating means, and its center is aligned with the center of the bottom of the second cylindrical body 40, and it is arranged in an annular shape with a diameter smaller than the inner diameter of the bottom of the second cylindrical body 40.

[0081] A heat-distributing plate 5 made of an anisotropic C / C composite material was placed on the upper surface of the heat source 3. At this time, the position of the heat-distributing plate 5 was adjusted so that its center position aligned with the center position of the annular shape formed by the heat source 3. The material used for the heat-distributing plate 5 had a thermal conductivity of 4 W / (m·K) in the Z direction and a thermal conductivity of 30 W / (m·K) in the XY plane at room temperature.

[0082] Nineteen heating containers 10,10,… were placed at equal intervals on the upper surface of the heat distribution plate 5 in the arrangement shown in Figure 6. More specifically, one heating container 10c was placed in the center, six heating containers 10,10,… were placed concentrically around it (heating container group 10b), and twelve more heating containers 10,10,… were placed concentrically further outside (heating container group 10a). Each heating container 10 has a raw material storage area 13 made of a bottomed cylindrical body (see Figure 3), and contains SiC powder (manufactured by Taiheiyo Random Co., Ltd., model number: GMF-H) as a solid raw material 11S from the bottom 15 up to a predetermined height. Furthermore, a seed crystal 12 with a diameter of 6 inches (approximately 150 mm) was placed by a seed crystal mounting part 16 at a predetermined distance from the upper surface of the solid raw material 11S in the Z direction.

[0083] A cylindrical first cylindrical body 30 was placed on the upper surface of the heat equalization plate 5. The position of the first cylindrical body 30 was adjusted so that its center position aligned with the center position of the heat equalization plate 5. The first cylindrical body 30 was made of carbon fiber felt. As shown in Figure 6, the first cylindrical body 30 was positioned so that its inner surface surrounded the 19 heating containers 10. The distance between the outer surface (first surface 31) of the first cylindrical body 30 and the inner surface (second surface 41) of the second cylindrical body 40 was set to 50 mm.

[0084] A lid 50 was placed so as to cover the upper surface of the second cylindrical body 40. However, the lid 50 used had heat dissipation openings 53 formed in the upper part of the tops of the 19 heating containers 10, 10, ...

[0085] The lid 50 is a disc-shaped component made of the same material as the second cylindrical body 40. Furthermore, the 19 openings 53 in the lid 50 are smaller in size than the diameter of the heating container 10.

[0086] Using the model from Example 1, the heating operation was performed for 120 hours while controlling the output of the heat source 3 so that the upper surface temperature of the uniform heating plate 5 remained constant at 2350°C.

[0087] As a result of the above verification, the upper surface temperature of the uniform heating plate 5 was maintained at 2350°C under control of the output of the heat source 3 within the range of 91kW ± 2kW. At this time, the upper temperature of the innermost heating container 10c was 2113°C, the average upper temperature of the six heating container groups 10b located outside of heating container 10c was 2110°C, and the average upper temperature of the twelve heating container groups 10a located on the outermost side was 2119°C. As a result, the difference between the highest and lowest temperatures of each group was 9°C, and this value was kept below 0.5% of the overall average (the overall average was 2116°C). Note that the temperature values ​​were rounded to one decimal place. Also, the ratio of the temperature difference to the overall average temperature was rounded to three decimal places. The same applies to the following examples.

[0088] In other words, according to the model of Example 1, it was confirmed that 19 heating containers 10,10,... could be heated under homogeneous temperature conditions.

[0089] (Example 2) The heating operation was performed under the same conditions as in Example 1, except that the distance between the outer surface (first surface 31) of the first cylindrical body 30 and the inner surface (second surface 41) of the second cylindrical body 40 was set to 25 mm.

[0090] Verification using the model of Example 2 showed that, similar to Example 1, the upper surface temperature of the uniform heating plate 5 was maintained at 2350°C while the output of the heat source 3 was controlled within the range of 91kW ± 2kW.

[0091] At this time, the upper temperature of the innermost heating container 10c was 2121°C, the average upper temperature of the six heating container groups 10b located outside of heating container 10c was 2122°C, and the average upper temperature of the twelve heating container groups 10a located on the outermost side was 2133°C. As a result, the difference between the highest and lowest temperatures of each group was 12°C, which was less than 0.57% of the overall average.

[0092] In other words, it was confirmed that, even in the model of Example 2, the 19 heating containers 10,10,... could be heated under homogeneous temperature conditions.

[0093] (Example 3) The heating operation was performed under the same conditions as in Example 1, except that the distance between the outer surface (first surface 31) of the first cylindrical body 30 and the inner surface (second surface 41) of the second cylindrical body 40 was set to 15 mm.

[0094] Verification using the model of Example 3 showed that, similar to Example 1, the upper surface temperature of the uniform heating plate 5 was maintained at 2350°C while the output of the heat source 3 was controlled within the range of 91kW ± 2kW.

[0095] At this time, the upper temperature of the innermost heating container 10c was 2115°C, the average upper temperature of the six heating container groups 10b located outside of heating container 10c was 2115°C, and the average upper temperature of the twelve heating container groups 10a located on the outermost side was 2122°C. As a result, the difference between the highest and lowest temperatures of each group was 7°C, which was less than 0.5% of the overall average.

[0096] In other words, it was confirmed that even in the model of Example 3, the 19 heating containers 10,10,... could be heated under homogeneous temperature conditions.

[0097] (Comparative Example 1) Figures 7A and 7B are diagrams illustrating models of the SiC single crystal manufacturing apparatus 1 prepared as Comparative Example 1, following the same diagrams as in Figures 2 and 1.

[0098] The model of Comparative Example 1 differs from the model of Example 1 in that it does not have a first cylindrical body 30. Instead, an annular second heat source 61 is mounted inside the second cylindrical body 40. The surface of the second heat source 61 is positioned to be exposed on the side of the heating containers 10,10,... Other aspects are the same as the model of Example 1.

[0099] Using the model of Comparative Example 1, the output control of the heat source 3 and the second heat source 61 was started so that the upper surface temperature of the heat distribution plate 5 was kept constant at 2350°C and the inner surface temperature (side temperature) of the second cylindrical body 40 was kept constant at 2320°C. Initially, the output of heat source 3 was set to 87kW and the output of the second heat source 61 was set to 25kW. However, after more than 70 hours, while the temperature remained maintained, the output of heat source 3 decreased to 80kW, while the output of the second heat source 61 increased to 32kW. Subsequently, the heating operation was performed for a total of 120 hours while maintaining the target temperature.

[0100] As a result, it was confirmed that the upper temperature of the heating vessels 10,10,... increased by an average of approximately 20°C compared to Example 1. From this result, it is presumed that even with the same set temperature conditions, the temperature distribution changed due to the mutual interference between the heat sources (heat source 3 and the second heat source 61) when the furnace was operated for a long period of 120 hours.

[0101] (Comparative Example 2) Figures 8A and 8B are diagrams illustrating models of the SiC single crystal manufacturing apparatus 1 prepared as Comparative Example 2, following the same diagrams as in Figures 2 and 1.

[0102] The model of Comparative Example 2 corresponds to the model of Example 1 with the first cylindrical body 30 removed, while the rest of the model is the same as that of Example 1.

[0103] Using the model of Comparative Example 2, the heating operation was performed for 120 hours while controlling the output of the heat source 3 so that the upper surface temperature of the uniform heating plate 5 remained constant at 2350°C.

[0104] Verification using the model of Comparative Example 2 showed that the upper surface temperature of the heat distribution plate 5 was maintained at 2350°C while the output of the heat source 3 was controlled within the range of 98kW ± 2kW.

[0105] At this time, the upper temperature of the innermost heating container 10c was 2159°C, the average upper temperature of the six heating container groups 10b located outside of heating container 10c was 2164°C, and the average upper temperature of the twelve heating container groups 10a located on the outermost side was 2192°C. As a result, the difference between the highest and lowest temperatures in each group was 33°C, which is more than 1.5% of the overall average. This value of 33°C is more than twice the value observed in each of Examples 1 to 3.

[0106] In other words, according to the model of Comparative Example 2, it was confirmed that there was variation in the temperature conditions for the 19 heating containers 10,10,... compared to each of Examples 1 to 3.

[0107] (Reference example 1) Figures 9A and 9B are diagrams illustrating models of the SiC single crystal manufacturing apparatus 1 prepared as Reference Example 1, following the same diagrams as Figures 2 and 1.

[0108] The model in Reference Example 1 corresponds to the model in Example 1, but with the first cylindrical body 30 removed, and the outer surfaces of each heating container 10, 10, ... covered with a third cylindrical body 63 made of the same material as the first cylindrical body 30. Other aspects are the same as the model in Example 1.

[0109] Using the model from Reference Example 1, the heating operation was performed for 120 hours while controlling the output of the heat source 3 so that the upper surface temperature of the uniform heating plate 5 remained constant at 2350°C.

[0110] Verification using the model in Reference Example 1 showed that the upper surface temperature of the heat distribution plate 5 was maintained at 2350°C while the output of the heat source 3 was controlled within the range of 95kW ± 2kW.

[0111] At this time, the upper temperature of the innermost heating container 10c was 2107°C, the average upper temperature of the six heating container groups 10b located outside of heating container 10c was 2112°C, and the average upper temperature of the twelve heating container groups 10a located on the outermost side was 2152°C. As a result, the difference between the highest and lowest temperatures of each group was 45°C, which is about 2.1% of the overall average. This value of 45°C is more than four times higher than the values ​​in each of Examples 1 to 3.

[0112] In other words, even in the model of Reference Example 1, it was confirmed that there was variation in the temperature conditions for the 19 heating containers 10,10,... compared to each of Examples 1 to 3. Table 1 summarizes the results of the verification described above.

[0113] [Table 1]

[0114] Furthermore, comparing Reference Example 1 with Examples 1-3, in the model of Reference Example 1, each heating container 10, 10, ... is covered by a third cylindrical body 63 made of carbon fiber felt, so it is assumed that the propagation of radiant heat between adjacent heating containers 10, 10, ... is suppressed. On the other hand, in Examples 1-3, infrared rays E2 (see Figure 5) derived from radiant heat are irradiated from the first cylindrical body 30, which functions as a secondary heat source, onto the outermost group of heating containers 10a, heating the outermost group of heating containers 10a from the side. At the same time, the heated group of heating containers 10a itself functions as a secondary heat source, irradiating the heating container group 10b located inside with infrared rays derived from radiant heat, thus heating the heating container group 10b from the side as well. Similarly, it is presumed that the centrally located heating container 10c was also heated from the side by the heated heating container group 10b itself functioning as a secondary heat source, irradiating the inner heating container 10c with infrared radiation derived from radiant heat.

[0115] Figure 10A is a traced 3D cross-sectional view of a 6-inch single crystal ingot grown with a uniform temperature distribution. Figure 10B is a traced 3D cross-sectional view of a 6-inch single crystal ingot grown with an intentionally non-uniform temperature distribution in the XY plane. In detail, in Figure 10A, the degree of temperature variation depending on the location was suppressed to less than 1% of the average temperature, while in Figure 10B, the degree of temperature variation was 5% of the average temperature. Compared to Figure 10A, it can be seen that the shape of the single crystal ingot in Figure 10B is distorted (asymmetrical left to right in the drawing). This suggests that the temperature conditions of the heating container 10 during growth vary depending on the location, which affects the shape of the single crystal ingot and thus the performance obtained.

[0116] [Alternative Embodiment] Another embodiment of the SiC single crystal manufacturing apparatus according to the present invention will be described below.

[0117] <1> Figure 11 is a cross-sectional view illustrating the configuration of another embodiment of the SiC single crystal manufacturing apparatus 1, following the configuration of Figure 1. Unlike the embodiment described above, the SiC single crystal manufacturing apparatus 1 shown in Figure 11 is equipped with a single heating vessel 10.

[0118] Even with a SiC single crystal manufacturing apparatus 1 equipped with a single heating vessel 10, as shown in Figure 11, the same effects as in the above embodiment can be obtained.

[0119] In other words, even with the SiC single crystal manufacturing apparatus 1 shown in Figure 11, the heat source 3, which serves as the primary heat source, is positioned on the -Z side of the uniform heating plate 5, and the heating container 10 can be heated not only from the bottom but also from the sides and top.

[0120] As described above with reference to Figure 5, the heating of the heating container 10 from above originates from infrared rays E3 reflected from the reflective surface, and the heating from the side originates from infrared rays E2 originating from the first cylindrical body 30 which functions exclusively as a secondary heat source. Therefore, even if the size of the heating container 10 is increased, heating from the side and from above is possible without placing primary heat sources on the sides or top of the heating container 10.

[0121] As a result, even if the output of the heat source 3, which acts as the primary heat source, is adjusted for temperature control, it is possible to substantially maintain the ratio of thermal energy to the heating container 10 for each heating direction. Therefore, in the SiC single crystal manufacturing apparatus 1, by appropriately adjusting the material, shape, dimensions, etc. of the first cylindrical body 30, the second cylindrical body 40, and the lid 50 in advance, it is possible to adjust the temperature of the heating container 10 while maintaining a desirable thermal balance. This makes it possible to manufacture relatively large SiC ingots while suppressing variations in performance.

[0122] <2> In the present invention, the heat source 3 as the primary heat source only needs to be positioned on the -Z side of the heat distribution plate 5, and its number is not limited. However, since the presence of multiple heat sources 3,3,... may cause thermal crosstalk between the heat sources 3,3,... even on the bottom side of the heating container 10, it is more preferable that the heat source 3 be a single unit.

[0123] Furthermore, the effect of thermal crosstalk that occurs when multiple heat sources 3,3,… are placed on the -Z side of the heat distribution plate 5 is significantly smaller compared to when separate heat sources are placed on the sides or top. More specifically, even when multiple heat sources 3,3,… are placed on the -Z side of the heat distribution plate 5, the effect on the ratio of thermal energy for each heating direction to the heating container 10 is small. [Explanation of Symbols]

[0124] 1: SiC single crystal manufacturing equipment 3: Heat source 5: Soaking plate 5a: Outer edge of the heat distribution plate 10: Heating container 10a: Heating container group 10b: Heating container group 10c: Heating container 11G: Gaseous raw material 11S: Solid raw material 12: Seed crystal 13: Raw material storage area 14: Side of the raw material storage area 15: Bottom of the raw material storage area 16: Seed crystal mounting section 19: Lid of the heating container 30: First cylindrical body 31: First surface (of the first cylindrical body) 40:Second cylindrical body 41: (Second surface of the second cylindrical body) 50: Lid 51: Bottom surface of the lid 53: Opening 60: Separation part 61: Second heat source 63:Third cylindrical body E0,E1,E2,E3: Infrared Ea: Heat

Claims

1. Heat source and A heat distribution plate is positioned above the heat source so as to cover the heat source when viewed from the vertical direction, A cylindrical heating container comprising a bottom surface, side surfaces, and top surface, includes a raw material storage area for containing a solid raw material made of SiC, located inward from the outer edge of the heat-sensing plate when viewed from the vertical direction and positioned above the heat-sensing plate, and a seed crystal mounting area for placing a SiC seed crystal at a position vertically separated from the raw material storage area. A first cylindrical body is positioned to cover the outermost side of the heating container when viewed from the vertical direction, A second cylindrical body is positioned to cover the first cylindrical body and the heat distribution plate and the heat source, with a spaced portion between them when viewed from the vertical direction, The second cylindrical body comprises a lid positioned to close off a portion of its upper surface, The first cylindrical body has at least one first surface, which is a side facing the second cylindrical body, made of a material that partially absorbs and partially reflects infrared rays. The second cylindrical body has a second surface, which is the side surface facing the first cylindrical body, made of a material that reflects at least some infrared rays. A SiC single crystal manufacturing apparatus characterized in that the bottom surface of the lid is made of a material that reflects at least some infrared rays.

2. The SiC single crystal manufacturing apparatus according to claim 1, characterized in that the separation portion located between the first cylindrical body and the second cylindrical body forms a propagation path that guides infrared rays reflected between the first surface and the second surface vertically upward.

3. The SiC single crystal manufacturing apparatus according to claim 1, characterized in that the second surface of the second cylindrical body has a higher reflectivity to infrared rays than the first surface of the first cylindrical body.

4. The SiC single crystal manufacturing apparatus according to claim 3, characterized in that the second cylindrical body is made of a main material having heat insulating properties, and a coating material or sheet material with a higher reflectivity to infrared rays than the main material is formed on the second surface.

5. The SiC single crystal manufacturing apparatus according to claim 1, characterized in that the second cylindrical body and the lid are made of the same material.

6. The SiC single crystal manufacturing apparatus according to claim 1, characterized in that the lid has an opening for heat dissipation in at least a portion of the region facing the top of the heating container when viewed from the vertical direction.

7. The heating containers are provided in multiple locations. All of the multiple heating containers are positioned so as to be viewed from the vertical direction, they are located inside the outer edge of the heat distribution plate. The SiC single crystal manufacturing apparatus according to any one of claims 1 to 6, characterized in that the first cylindrical body is arranged to cover the plurality of heating containers located on the outermost side when viewed from the vertical direction.

8. The SiC single crystal manufacturing apparatus according to claim 7, characterized in that each of the heating containers is not covered with an insulating material, and is configured to allow heat to be transferred between adjacent heating containers by radiation.

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