Seed crystal holding member and single crystal manufacturing apparatus equipped with the same

Abstract

To provide a seed crystal holding member having a lower heat transfer coefficient than a member made of graphite.SOLUTION: A seed crystal holding member 10 is used in a single crystal production apparatus for growing a crystal on a seed crystal to produce a single crystal ingot. The seed crystal holding member for holding a seed crystal is made of a carbon material and has heat transfer coefficient adjusting layers H at different positions from the seed crystal, when viewing from the direction superimposing the seed crystal on the seed crystal holding member when the seed crystal is held by the seed crystal holding member. The heat transfer coefficient adjusting layers H are cavity layers or made of a heat transfer coefficient adjusting material having a different heat transfer coefficient from the carbon material and have a lower heat transfer coefficient than the carbon material in the crystal growth axis direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a seed crystal holding member and a single crystal manufacturing apparatus equipped with the same. [Background technology]

[0002] Silicon carbide (SiC) has a dielectric breakdown field one order of magnitude larger than silicon (Si) and a band gap three times larger. SiC also has properties such as a thermal conductivity that is about three times higher than Si. For this reason, SiC is expected to be used in power devices, high-frequency devices, high-temperature operating devices, and other applications.

[0003] Sublimation is a widely known method for producing SiC single crystals. In this method, the sublimation source material contained in a source material container is heated to 2000°C or higher to sublimate the source material and generate sublimation gas, which is then supplied to a seed crystal made of SiC single crystal that is several tens to several hundreds of degrees Celsius lower than the source material container, whereby the sublimation gas is recrystallized on the seed crystal to grow a SiC single crystal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-5159 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the crucible in which the SiC single crystal is grown, the temperature is controlled so that the SiC seed crystal is at a lower temperature than the raw material surface in order to recrystallize the raw material gas on the surface of the SiC seed crystal. In the SiC single crystal during crystal growth, if the temperature gradient within the crystal is large, the thermal stress within the crystal will be large. If the thermal stress is large, the basal plane dislocation density of the produced SiC single crystal will be high. Furthermore, if the thermal stress exceeds a certain value, cracks may occur. The temperature gradient within a crystal can be considered separately as the temperature gradient in the crystal growth direction and the temperature gradient in the radial direction. Regarding the temperature gradient in the crystal growth direction, if the heat removal from the seed crystal side can be reduced, the temperature gradient in the crystal growth direction can be reduced. If the member to which the seed crystal is fixed can be made of a material with low thermal conductivity, the heat removal from the seed crystal side can be reduced. However, because the temperature of the seed crystal reaches 2000°C or more, graphite has traditionally been used as the member to which the seed crystal is fixed, and materials other than graphite are not normally used.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a seed crystal holding member having a thermal conductivity lower than that of a graphite member, and a single crystal production apparatus including the same. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides the following means.

[0008] A seed crystal holding member according to a first aspect of the present invention is a seed crystal holding member, in a single crystal manufacturing apparatus for manufacturing a single crystal ingot by growing a crystal on a seed crystal, which is made of a carbon material and holds the seed crystal, and has a thermal conductivity adjustment layer at a position overlapping with the seed crystal when viewed from a direction in which the seed crystal and the seed crystal holding member overlap when the seed crystal is held by the seed crystal holding member, and the thermal conductivity adjustment layer is a hollow layer or is made of a thermal conductivity adjustment material that is a material with a thermal conductivity different from that of the carbon material and has a thermal conductivity in the crystal growth axis direction smaller than that of the carbon material.

[0009] The seed crystal holding member according to the above aspect may include a plurality of the thermal conductivity adjustment layers.

[0010] In the seed crystal holding member according to the above aspect, the carbon material may be graphite.

[0011] In the seed crystal holding member according to the above aspect, the thermal conductivity adjusting material may be made of a powder material.

[0012] In the seed crystal holding member according to the above aspect, the powder material may be selected from the group consisting of graphite, tantalum carbide, tungsten carbide, niobium carbide, molybdenum carbide, hafnium carbide, and zirconium carbide.

[0013] In the seed crystal holding member according to the above aspect, the thermal conductivity adjusting material may be made of graphite fibers.

[0014] In the seed crystal holding member according to the above aspect, the thermal conductivity adjustment layer may be a cavity layer, and the length of the cavity layer in the crystal growth axis direction may be 15 mm or less.

[0015] The seed crystal holding member according to the above aspect may include a base for fixing the seed crystal, and the base may be a portion that comes into contact with the seed crystal.

[0016] The seed crystal holding member according to the above aspect may be a lid of a crucible used in a single crystal manufacturing apparatus for manufacturing a SiC single crystal ingot by sublimation.

[0017] A single crystal manufacturing apparatus according to a second aspect of the present invention includes a crucible comprising the lid and crucible body according to the above aspect.

[0018] The seed crystal holder according to the above aspect may be used when producing a SiC single crystal ingot by a solution process.

[0019] The seed crystal holder according to the above aspect may be used when producing a SiC single crystal ingot using a gas method. Effect of the Invention

[0020] The seed crystal holder of the present invention can reduce the temperature gradient in the growth axis direction of a SiC single crystal ingot during crystal growth, thereby preventing the occurrence of cracks and enabling the production of a SiC single crystal ingot with a low basal plane dislocation density. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic cross-sectional view showing a seed crystal holding member according to a first embodiment of the present invention. [Diagram 2] 1A and 1B are schematic cross-sectional views of the pedestal after fabrication; FIG. 1B is a schematic cross-sectional view of the pedestal after fabrication; FIG. [Diagram 3] 1A and 1B are schematic exploded cross-sectional views of the pedestal before fabrication, and FIG. 1B is a schematic cross-sectional view of the pedestal after fabrication, according to another example of a seed crystal holding member having a hollow layer in the pedestal. [Figure 4] 1A and 1B are schematic exploded cross-sectional views of the pedestal before fabrication, and FIG. 1B is a schematic cross-sectional view of the pedestal after fabrication, according to another example of a seed crystal holding member having a hollow layer in the pedestal. [Diagram 5] 5 is a schematic cross-sectional view showing a seed crystal holding member according to a second embodiment of the present invention. FIG. [Figure 6] 1 is a cross-sectional schematic diagram showing a single crystal manufacturing apparatus according to one embodiment of the present invention. [Figure 7] FIG. 7 is an enlarged schematic cross-sectional view of only the cover portion of the single crystal production apparatus shown in FIG. 6. [Figure 8] FIG. 13 is a schematic cross-sectional view showing an example of a lid portion that does not have a base. [Figure 9] 1 shows the results of a simulation of temperature distribution (temperature difference tes in the height direction of the SiC single crystal and temperature difference te1 in the height direction of the pedestal), where (a) shows the results for Example 1, (b) shows the results for Example 2, and (c) shows the results for the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts may be denoted by the same reference numerals in the drawings. In addition, the drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the features easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality. In addition, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. The present invention can be implemented by appropriately changing the materials, dimensions, etc. within the scope of the effects of the present invention. The configuration shown in one embodiment can also be applied to other embodiments.

[0023] (Seed crystal holding member) First Embodiment Fig. 1 is a schematic cross-sectional view showing a seed crystal holding member according to a first embodiment of the present invention. In Fig. 1, a seed crystal S is illustrated to aid in understanding. In the figure, the direction in which the seed crystal S and the seed crystal holding member 10 overlap is the z direction, a plane perpendicular to the z direction is the xy plane, and the x direction and the y direction are perpendicular to each other. The same applies to the subsequent figures.

[0024] The seed crystal holding member 10 shown in Figure 1 has a pedestal 11 as a seed crystal holding portion to which the seed crystal S is fixed, and the pedestal 11 has hollow layers H (H1, H2, H3, H4) as thermal conductivity adjustment layers at a position overlapping with the seed crystal S when viewed in a plane from the z direction, and the thermal conductivity of the seed crystal holding member 10 in the crystal growth direction (z direction) is smaller than the thermal conductivity of the carbon material that constitutes the seed crystal holding member 10. The seed crystal holding member 10 is a member made of a carbon material and used to hold a seed crystal S in a single crystal production apparatus that produces a single crystal ingot by growing a crystal on a seed crystal S. By using a seed crystal S made of silicon carbide (SiC) as the seed crystal S, a SiC single crystal ingot can be produced using the single crystal production apparatus equipped with the seed crystal holding member 10.

[0025] In this specification, the "seed crystal holding member" may or may not have a pedestal. In this specification, the term "pedestal" refers to a part or member to which a seed crystal is fixed, and the fixing surface of the part or member has a diameter approximately equal to that of the seed crystal on the disk.

[0026] In general, "thermal conductivity" indicates how easily heat is transferred from one end of an object to the other, and its unit is W / (m K). In this specification, the "thermal conductivity of the seed crystal holding member" refers to the ease of heat transfer from one end to the other end of the seed crystal holding member in the crystal growth direction (z direction), and the unit is W / (m·K), similar to the general "thermal conductivity". Here, for example, when the seed crystal holding member is a lid part of a crucible having a pedestal, the "one end" is the surface of the pedestal to which the seed crystal is fixed (reference numeral 20a in FIG. 6), and the other end is the surface of the lid part that does not have the pedestal (reference numeral 20b in FIG. 6). The "thermal conductivity of the seed crystal holding member" can be measured by a known method for measuring "thermal conductivity". For example, it can be measured by a laser flash method or the like.

[0027] The seed crystal holding member 10 includes, in addition to the pedestal 11, a support member 12 that is connected to the pedestal 11 and supports the pedestal 11. The pedestal 11 and the support member 12 can be connected to each other by, for example, a carbon adhesive or by screws. The seed crystal holding member 10 includes a base and a support member, but may be configured to consist of only the support member. When the seed crystal holding member 10 is configured to consist of only the support member (in this case, the seed crystal holding member 10 coincides with the support member), the seed crystal is fixed to a predetermined position of the support member.

[0028] The seed crystal holding member 10 has four hollow layers, but there is no limit to the number or size of the hollow layers as long as the thermal conductivity of the seed crystal holding member 10 in the crystal growth direction is smaller than the thermal conductivity of the carbon material that constitutes the seed crystal holding member 10. 2 to 4 show examples of seed crystal holding members in which the thermal conductivity adjustment layer is a hollow layer and how to make them. By filling the hollow layer of the seed crystal holding member shown in each figure with a thermal conductivity adjustment material, it is possible to make a seed crystal holding member in which the thermal conductivity adjustment layer is made of the thermal conductivity adjustment material.

[0029] As an example, the seed crystal holding member shown in Fig. 2 can be made by preparing a pedestal body 111A with a countersunk 111Aa, stacking cylinders 111B and disks 111C alternately on a bottom surface 111Aaa in the countersunk 111Aa to assemble a pedestal 111 having a hollow layer, and connecting the pedestal 111 to a support member 12 (see Fig. 1). In the example shown in Fig. 2, the pedestal 111 can be stably connected to the support member 12 by the umbrella portion 111Ab. Fig. 2(a) is an exploded cross-sectional schematic diagram of the pedestal before fabrication, and (b) is a cross-sectional diagram of the pedestal after fabrication.

[0030] FIG. 2 shows an example in which there are four each of the cylinders 111B and disks 111C (cylinders 111Ba, 111Bb, 111Bc, and 111Bd, and disks 111Ca, 111Cb, 111Cc, and 111Cd), but there may be five or more of each, or three or less of each. The cylinder 111B and the disk 111C may be connected to the inner surface of the countersunk 111Aa with, for example, a carbon adhesive or with screws. Also, the cylinder 111B and the disk 111C may be connected to each other with, for example, a carbon adhesive or with screws.

[0031] In addition, in the seed crystal holding member shown in Figure 2, after placing the cylinder 111Ba, it is filled with a thermal conductivity adjustment material, then a disk 111Ca is placed, the cylinder 111Bb is placed on top of that, it is filled with a thermal conductivity adjustment material, then a disk 111Cb is placed, etc., and by repeating this process, a seed crystal holding member whose thermal conductivity adjustment layer is made of a thermal conductivity adjustment material can be produced.

[0032] As an example, the seed crystal holding member shown in Fig. 3 can be made by preparing a pedestal body 211A with a countersunk 211Aa and a female thread cut on its inner side surface 211Aaa, screwing a disk 211B having a male thread on its side surface so that it can be screwed into the female thread, assembling a pedestal 211 having a hollow layer, and connecting the pedestal 211 to the support member 12 (see Fig. 1). In the example shown in Fig. 3, the pedestal 211 can be stably connected to the support member 12 by the umbrella portion 211Ab. (a) is an exploded cross-sectional schematic diagram of the pedestal before fabrication, and (b) is a cross-sectional diagram of the pedestal after fabrication.

[0033] In the case of the base shown in FIG. 3, the position can be easily adjusted, and adjustments may be made to target a desired thermal conductivity calculated by simulation or the like.

[0034] In the example shown in FIG. 3, an example in which the number of disks 211B is four (disks 211Ba, 211Bb, 211Bc, and 211Bd) is shown, but the number may be five or more, or three or less.

[0035] In addition, in the seed crystal holding member shown in Figure 3, a thermal conductivity adjustment material is laid on the bottom surface of the countersunk 211Aa, then a circular plate 211Ba is placed, a thermal conductivity adjustment material is laid on top of that, then a circular plate 211Bb is placed, etc., and this process is repeated to create a seed crystal holding member whose thermal conductivity adjustment layer is made of a thermal conductivity adjustment material.

[0036] As an example, the seed crystal holding member shown in Fig. 4 can be made by preparing a pedestal body 311A ​​with a countersunk 311Aa, stacking a disk 311B with a support part on its underside on the bottom surface 311Aaa of the countersunk 311Aa to assemble a pedestal 311 having a hollow layer, and connecting the pedestal 311 to the support member 12 (see Fig. 1). In the example shown in Fig. 4, the pedestal 311 can be stably connected to the support member 12 by the umbrella part 311Ab. (a) is an exploded cross-sectional schematic diagram of the pedestal before fabrication, and (b) is a cross-sectional diagram of the pedestal after fabrication.

[0037] In the example shown in FIG. 4, four disks 311B (disks 311Ba, 311Bb, 311Bc, 311Bd) with support portions on their lower surfaces are shown, but the number may be five or more, or may be three. The disks 311Ba, 311Bb, 311Bc, and 311Bd may be connected to the inner surface of the countersunk hole 311Aa by, for example, a carbon adhesive or by screws. Also, the disks 311Ba, 311Bb, 311Bc, and 311Bd may be connected to each other by, for example, a carbon adhesive or by screws.

[0038] In addition, in the seed crystal holding member shown in Figure 4, a thermal conductivity adjustment material is laid on the bottom surface of the countersunk 311Aa, then a circular plate 311Ba with a support portion on its underside is placed, a thermal conductivity adjustment material is laid on top of that, and then a circular plate 311Bb with a support portion on its underside is placed, etc., and by repeating this process, a seed crystal holding member whose thermal conductivity adjustment layer is made of a thermal conductivity adjustment material can be produced.

[0039] Heat transfer occurs by radiation in the cavity layers and by thermal conduction in non-cavity areas (parts made of carbon material). In base 11, in which cavity layers and carbon material layers are alternately arranged, heat transfer occurs by alternating radiation and thermal conduction. Comparing the transfer of heat by conduction and the transfer of heat by radiation, the transfer of heat is thought to be faster in radiation than in conduction because heat transfer occurs by radiation. However, the emissivity of general graphite is 0.7 to 0.9, which is smaller than the 1 of an ideal black body. In other words, this means that when heat transfers through a hollow layer, the amount of radiation from the high-temperature side in the hollow layer is about 10 to 30% smaller than that of an ideal black body, and even in the opposing part, which is the low-temperature side, the amount of absorption is 10 to 30% smaller than that of an ideal black body. Since heat transfer in the pedestal is vertical, a hollow layer with a certain height becomes a resistance to heat transfer due to the above-mentioned influence, and as a result has a heat insulating effect. Specifically, in the case of graphite with an emissivity of 0.8, if the height of the hollow layer is 15 mm or less, the heat transfer in the hollow layer is slower than that by thermal conduction. However, since the emissivity changes depending on the material and surface condition of the graphite, once the carbon material constituting the seed crystal holding member has been determined, it is possible to confirm by conducting a few experiments whether the thermal conductivity of the seed crystal holding member is greater or smaller than that of a seed crystal holding member that does not have a hollow layer.

[0040] The seed crystal holding member 10 is made of a carbon material, but it is acceptable for the material to contain impurities as long as the purity is such that the material can be used in the production of a SiC single crystal ingot. The carbon material constituting the seed crystal holding member 10 is preferably graphite. In the sublimation method, solution method, and gas method used in the production of SiC single crystal ingots, the seed crystal is heated to a high temperature of 2000° C. or more. Graphite has an extremely high sublimation temperature of 3550° C., and can withstand the high temperatures during growth.

[0041] The pedestal 11 has a cavity layer that extends in a direction parallel to the xy plane perpendicular to the z direction in which the pedestal 11 and the seed crystal S overlap. When the seed crystal holding member 10 does not have the pedestal 11, the support member 12 has a hollow layer at a position overlapping with the seed crystal when viewed from the z direction.

[0042] In the case of a graphite seed crystal holder that does not have a hollow layer, its thermal conductivity (i.e., the thermal conductivity of graphite) is about 30 to 40 W / m·K. In contrast, in the case of pedestal 11 that has a hollow layer made of graphite, its thermal conductivity can be made smaller than 30 to 40 W / m·K. At 2000 to 2400°C, which is close to the growth temperature of SiC single crystal, the thermal conductivity of SiC single crystal is about 20 to 25 [W / (m·K)], and the thermal conductivity of graphite used in the crucible is about 30 to 40 [W / (m·K)]. The degree to which the thermal conductivity is reduced can be adjusted by the configuration of the cavity layer.

[0043] The base 11 and the seed crystal S are bonded to each other at a bonding surface 11a and a bonding surface Sa. In this case, the bonding at the bonding surfaces may be performed by fixing the base 11 and the seed crystal S via an adhesive. The pedestal 11 includes parallel portions 11A, 11B1, 11B2, 11B3, and 11C extending substantially parallel to the bonding surface of the seed crystal S, in this order from the bonding surface Sa side of the seed crystal S, and further includes a side wall portion 11AA in a direction substantially perpendicular to the bonding surface of the seed crystal S. The hollow layer H1 is configured by being surrounded by the parallel portion 11A, the parallel portion 11B1, and the side wall portion 11AA, the hollow layer H2 is configured by being surrounded by the parallel portion 11B1, the parallel portion 11B2, and the side wall portion 11AA, the hollow layer H3 is configured by being surrounded by the parallel portion 11B2, the parallel portion 11B3, and the side wall portion 11AA, and the hollow layer H4 is configured by being surrounded by the parallel portion 11B3, the parallel portion 11C, and the side wall portion 11AA.

[0044] The seed crystal can be fixed to the pedestal 11 by, for example, fixing the outer periphery of the seed crystal with graphite claws or by attaching the seed crystal to the pedestal using a carbon adhesive.

[0045] As will be described in detail later, when the seed crystal holding member of the present invention is used as a crucible lid (hereinafter simply referred to as "lid") for a sublimation method, the lid (or base) dissipates less heat than a conventional graphite lid (or graphite base), and thermal stress within a single crystal during crystal growth is reduced more than in the past.

[0046] The seed crystal holding member of the present invention can be used as a member for holding a single crystal when producing a single crystal ingot using a solution method or a gas method in addition to the sublimation method.

[0047] <Second embodiment> FIG. 5 is a schematic cross-sectional view showing a seed crystal holding member according to a second embodiment of the present invention. The seed crystal holding member 10A shown in Figure 5 has a pedestal 111 as a seed crystal holding portion to which the seed crystal S is fixed, and the pedestal 111 has a thermal conductivity adjustment layer 13 (13A, 13B, 13C, 13D) at a position overlapping with the seed crystal S when viewed in a plane from the z direction, and the thermal conductivity of the seed crystal holding member 10A in the crystal growth direction is smaller than the thermal conductivity of the carbon material that constitutes the seed crystal holding member 10A.

[0048] The seed crystal holding member of the first embodiment is provided with a hollow layer serving as a thermal conductivity adjustment layer, whereas the seed crystal holding member of the second embodiment differs from the seed crystal holding member of the first embodiment in that the thermal conductivity adjustment layer is made of a thermal conductivity adjustment material, which is a material with a thermal conductivity different from that of the carbon material constituting the seed crystal holding member. The seed crystal holder 10A shown in FIG. 5 is configured so that the hollow layer is filled with a thermal conductivity adjusting material, but may be configured so that a carbon material layer and a thermal conductivity adjusting layer are laminated in this order.

[0049] As the thermal conductivity adjusting material, various materials can be used as long as the thermal conductivity of the seed crystal holding member 10A in the crystal growth direction is smaller than the thermal conductivity of the carbon material constituting the seed crystal holding member 10A. Examples of the thermal conductivity adjusting material include graphite fiber and high melting point metal carbides (tantalum carbide, tungsten carbide, niobium carbide, molybdenum carbide, hafnium carbide, zirconium carbide).

[0050] The thermal conductivity adjusting material may be a powder material. When the layer made of powder and the layer made of a uniform continuum are made of the same material, the layer made of powder is less likely to conduct heat than the layer made of a uniform continuum. Therefore, the seed crystal holding member 10A has a smaller thermal conductivity than a conventional seed crystal holding member that does not have a thermal conductivity adjusting layer. Examples of the powder material include graphite powder and powder of high melting point metal carbide (tantalum carbide (TaC), tungsten carbide, niobium carbide, molybdenum carbide, hafnium carbide, zirconium carbide). The seed crystal holding member 10A has four thermal conductivity adjustment layers, but there is no limit to the number or size of the thermal conductivity adjustment layers as long as the thermal conductivity of the seed crystal holding member 10A in the crystal growth direction is smaller than the thermal conductivity of the carbon material that constitutes the seed crystal holding member 10A.

[0051] (Single crystal manufacturing equipment) Fig. 6 is a cross-sectional schematic diagram showing a single crystal manufacturing apparatus according to one embodiment of the present invention. In the figure, the direction connecting the crucible lid and the bottom of the crucible body is the z direction, the plane perpendicular to the z direction is the xy plane, and the x direction and the y direction are perpendicular to each other. The single crystal manufacturing apparatus shown in Fig. 6 is used when manufacturing a single crystal ingot by sublimation. Fig. 7 is an enlarged cross-sectional schematic diagram showing only the lid 20 shown in Fig. 6.

[0052] The single crystal manufacturing apparatus 1000 shown in Fig. 6 includes a crucible 100 including a lid 20, which is an example of a seed crystal holding member of the present invention, and a crucible body 30. Around the outer periphery of the crucible body 30, there are provided a heat insulating material (not shown) for keeping the crucible 100 warm, and a heating means 40. In Fig. 6, a raw material M for single crystal growth and a seed crystal S are also shown to aid in understanding. The raw material M for single crystal growth is accommodated in the lower part of the crucible body 30. The seed crystal S is fixed to a pedestal 21 provided on the lid portion 20. Methods for fixing the SiC seed crystal to the pedestal 21 include, for example, a method of fixing the outer periphery of the SiC seed crystal with graphite claws, and a method of attaching the SiC seed crystal to the pedestal using a carbon adhesive.

[0053] The crucible 100 is a crucible for producing a SiC single crystal by a sublimation method, and may be made of, for example, graphite or graphite coated with tantalum carbide. The crucible 100 becomes hot during growth. Therefore, it must be made of a material that can withstand high temperatures. As described above, graphite has an extremely high sublimation temperature of 3550°C and can withstand the high temperatures during growth.

[0054] In the single crystal manufacturing apparatus 1000, a pedestal 21 protruding downward is provided at the center of the inside of the lid part 20, and the lid part 20 is composed of the pedestal 21 and a plate 22. The pedestal 21 corresponds to the pedestal 11 shown in Fig. 1 or the pedestal 1011 shown in Fig. 5, and the plate 22 corresponds to the support member 12 shown in Fig. 1 or Fig. 5. The seed crystal S is fixed to one surface (seed crystal side surface) 21a of the pedestal 21. The pedestal 21 faces the raw material M for single crystal growth contained in the crucible 100 by covering the crucible body 30 with the lid part 20. By facing the raw material M for single crystal growth and the seed crystal S placed on the pedestal 21, the raw material gas can be efficiently supplied to the seed crystal S. The pedestal 21 and the plate 22 may be configured as an integral member or may be separate members.

[0055] The lid 20 (or the base 21) has a thermal conductivity adjustment layer 33 (33A, 33B, 33C, 33D) that extends in the xy direction, and therefore has a smaller thermal conductivity than a conventional graphite lid (or a graphite base) that does not have a thermal conductivity adjustment layer. The thermal conductivity adjustment layer 33 is a cavity layer or a layer made of a thermal conductivity adjustment material that is a material with a thermal conductivity different from that of the carbon material that constitutes the lid 20. The lid portion (or the base which is in contact with the seed crystal), which is an example of a seed crystal holding member of the present invention, dissipates less heat than a conventional graphite lid portion (or a graphite base), and reduces thermal stress in the growing single crystal more than in the conventional method.

[0056] 7, the thermal conductivity adjustment layer 33 has a rectangular shape in cross section, but is not limited to a rectangular shape. In addition, the four thermal conductivity adjustment layers 33A, 33B, 33C, and 33D have the same shape, but may have different shapes.

[0057] In the single crystal production apparatus 1000, the lid part 20 is of a type that includes a pedestal 21 and a seed crystal is fixed onto the pedestal 21, but as shown in Fig. 8, the single crystal production apparatus may be of a type in which the lid part 20A does not include a pedestal and the seed crystal S is fixed to a part of the lid part 20A. In this type, the part 22A corresponding to the plate 22 in Fig. 8 has a thermal conductivity adjustment layer 33. EXAMPLES

[0058] Example 1 Fig. 9(a) shows the results of a simulation of the temperature distribution near the pedestal (the temperature difference in the height direction of the SiC single crystal and the temperature difference in the height direction of the pedestal) for a single crystal manufacturing apparatus of the type shown in Fig. 1, i.e., having a lid with a pedestal. Note that Fig. 9(a) shows the results of Example 1, (b) shows the results of Example 2, and (c) shows the results of a comparative example. The cross-sectional schematic diagrams shown do not show the characteristics of each example and comparative example. This simulation was performed using "Virtual Reactor", a vapor phase crystal growth analysis software made by STR-Group Ltd. This simulation is widely used to simulate temperature distribution inside a furnace, and has been confirmed to have a high correlation with actual experimental results. In order to reduce the calculation load, the simulation was performed only on the structure of half of an arbitrary cross section (half in the radial direction) passing through the central axis of the cylindrical crucible.

[0059] In the model of the single crystal manufacturing equipment used in the simulation, four hollow layers were used as the thermal conductivity adjustment layers. The pedestal was made of graphite, with the height of the pedestal (length in the z direction) being 59 mm, the height of the four hollow layers (length in the z direction) being 2 mm, and the height of the SiC single crystal (length in the z direction) being 53 mm. The thermal conductivity of graphite was set to 40 W / m K.

[0060] As a result of the simulation, the temperature difference in the height direction of the SiC single crystal, t es (i.e., the difference between the temperature of the growing surface of the SiC single crystal and the temperature of the bonding surface with the pedestal), and the temperature difference in the height direction of the pedestal t e1 (i.e., the difference in temperature between the junction surface with the SiC single crystal and the surface on the opposite side) was 75°C and 99°C, respectively (see FIG. 9(a)).

[0061] Example 2 A simulation was performed using a model in which the thermal conductivity adjustment layer was made of a thermal conductivity adjustment material. The difference from Example 1 is that the thermal conductivity adjustment layer was made of one layer of thermal conductivity adjustment material with a height of 5 mm, rather than four hollow layers with a height of 2 mm. The thermal conductivity of the thermal conductivity adjustment material was set to 2 W / m K. As a result of the simulation, the temperature difference in the height direction of the SiC single crystal, tes (i.e., the difference between the temperature of the growing surface of the SiC single crystal and the temperature of the bonding surface with the pedestal), and the temperature difference in the height direction of the pedestal t e1 (i.e., the difference in temperature between the junction surface with the SiC single crystal and the surface on the opposite side) was 60°C and 105°C, respectively (see FIG. 9(b)).

[0062] (Comparative Example) The results of a simulation of the temperature distribution near the pedestal of a conventional single crystal manufacturing apparatus equipped with a lid with a pedestal that does not have a cavity layer are shown below. The only difference from the model in Figure 9(a) is that the pedestal does not have a cavity layer, and the material and dimensions are the same.

[0063] As a result of the simulation, the temperature difference in the height direction of the SiC single crystal, t es (i.e., the difference between the temperature of the growing surface of the SiC single crystal and the temperature of the bonding surface with the pedestal), and the temperature difference in the height direction of the pedestal t e1 (i.e., the difference in temperature between the junction surface with the SiC single crystal and the surface on the opposite side) was 86°C and 69°C, respectively (see FIG. 9(c)).

[0064] In the comparative example, the temperature difference t es The temperature difference in the height direction of the SiC single crystal in Example 1 and Example 2 was 86°C. es were 75° C. and 60° C., respectively. Since the temperature difference in the height direction of the SiC single crystal is smaller in the example than in the comparative example, it is possible to reduce thermal stress during crystal growth and obtain a SiC single crystal ingot with a low basal plane dislocation density and no cracks. [Explanation of symbols]

[0065] 10, 10A Seed crystal holding member 11, 21, 111, 211, 311, 1011 Pedestal 12 Support member 13, 13A, 13B, 13C, 13D, 33, 33A, 33B, 33C, 33D Thermal conductivity adjustment layer 20, 20A lid part 21 Pedestal 22 Plate 30 Crucible body H, H1, H2, H3, H4 cavity layer 100 Crucible 1000 Single crystal manufacturing equipment

Claims

1. A seed crystal holding member for use in a single crystal production apparatus for producing a single crystal ingot by growing a crystal on a seed crystal, the seed crystal holding member being made of a carbon material and holding the seed crystal, a thermal conductivity adjustment layer at a position overlapping with the seed crystal when viewed from a direction in which the seed crystal and the seed crystal holding member overlap when the seed crystal is held by the seed crystal holding member; the thermal conductivity adjustment layer is a layer of a plurality of cavities or is made of a powder material of a thermal conductivity adjustment material having a thermal conductivity different from that of the carbon material; A seed crystal holder having a thermal conductivity in a crystal growth axis direction that is smaller than that of the carbon material.

2. The seed crystal holder according to claim 1 , wherein the carbon material is graphite.

3. 2. The seed holder of claim 1, wherein the powdered material is selected from the group consisting of graphite, tantalum carbide, tungsten carbide, niobium carbide, molybdenum carbide, hafnium carbide, and zirconium carbide.

4. The seed crystal holder according to claim 1 , wherein the thermal conductivity adjusting material is made of graphite fiber.

5. 3. The seed crystal holder according to claim 1, wherein the thermal conductivity adjustment layer is a cavity layer, and the length of the cavity layer in the crystal growth axis direction is 15 mm or less.

6. The seed crystal holder according to claim 1 , further comprising a base for fixing a seed crystal, the base being a portion that comes into contact with the seed crystal.

7. The seed crystal holder according to claim 1 , wherein the seed crystal holder is a lid of a crucible used in a single crystal manufacturing apparatus for manufacturing a SiC single crystal ingot by sublimation.

8. A single crystal manufacturing apparatus comprising a crucible comprising the lid and the crucible body according to claim 7.

9. The seed crystal holder according to claim 1 , which is used when producing a SiC single crystal ingot by a solution process.

10. The seed crystal holder according to claim 1 , which is used when producing a SiC single crystal ingot using a gas method.

Images