CRUCIBLE FOR PRODUCING SiC VOLUME MONO CRYSTAL AND METHOD FOR GROWING SiC VOLUME MONO CRYSTAL

Abstract

To provide a crucible for producing a SiC volume mono crystal, and a method for growing the SiC volume mono crystal.SOLUTION: Provided is a crucible having a cavity for growing a SiC volume mono crystal in a growth direction (Y) by sublimation growth. The crucible comprises: an end wall (110) with a seed holder (112) for holding a SiC seed crystal in the cavity, the end wall (110) extending in a direction (r) perpendicular to the growth direction (Y); a side wall (140) extending in the growth direction (Y), the side wall (140) preventing permeation of a doping gas from the outside into the cavity, with the doping gas for doping the SiC volume mono crystal during the sublimation growth; and a diffusion region (114) allowing permeation of the doping gas from the outside into the cavity, the diffusion region (114) being located between the seed holder (112) and an edge (142) of the side wall (140).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001]

Background Art

[0002] Silicon carbide (SiC), a semiconductor material, is used in high-frequency components and special light-emitting semiconductor components due to its excellent physical, chemical, electrical, and optical properties, and is also used as a starting material for power electronics semiconductor components. For example, as described in U.S. Patent No. 8,747,982, a large substrate diameter (200 mm or more) and high-quality SiC substrates are required for such components. A large-diameter and high-quality SiC bulk single crystal is the object of this specification.

[0003] At least this object is achieved by the independent claims. Advantageous embodiments are achieved by the dependent claims.

[0004] More specifically, a single crystal is a substance without grain boundaries, where the crystal lattice throughout the sample is continuous up to the ends of the sample without interruption. The absence of defects associated with grain boundaries can endow the single crystal with its inherent properties, particularly mechanical, optical, and electrical properties. These properties are industrially utilized in various technical applications, particularly in optics and electronics.

[0005] Using appropriate raw materials, for example, by the physical vapor transport (PVT) method, a SiC bulk single crystal can be grown. The PVT method represents a vacuum deposition method that can be used to produce single crystals. PVT is characterized by the process in which the material transitions from the condensed phase to the vapor phase (i.e., the sublimation phase) and then returns to the condensed phase of the thin film. The material is transported in the vapor phase from the source region to the seed region. The most common PVT methods are sputtering and evaporation. Further details of the PVT method can be obtained, for example, from U.S. Patent No. 8,747,982.

[0006] A disk-shaped single-crystalline SiC substrate is cut out from a SiC volume single crystal and provided especially during the manufacture of a component having at least one epitaxial layer also made of SiC. In a subsequent epitaxial process, a thin single-crystalline layer (e.g., SiC, GaN) can first be deposited on the SiC substrate. The quality of this epitaxial layer depends critically on the local orientation of the single-crystalline substrate, or rather, on the SiC substrate cut out from the SiC volume single crystal. If a local deviation from the optimal orientation occurs in the crystal structure of the SiC substrate, there is a possibility that it will propagate into the epitaxial layer. Then, the epitaxial layer will also contain local defects, which may ultimately lead to poor properties of the end product, or rather, the semiconductor component.

[0007] As shown in FIG. 9, the growth of the PVT crystal is carried out in a crucible 1100. The crucible is a container that can be exposed to a very high temperature (above 2000 °C), for example, a temperature at which sublimation of materials such as SiC is possible. Specifically, the crucible is made of a material that can withstand a high temperature sufficient to melt and / or sublime its contents.

[0008] As shown in FIG. 10, the crucible 1100 is arranged in a cylindrical container 1200, which may be designed as quartz glass (suitable for induction heating described later) or stainless steel (suitable for resistance heating described later), and forms a reactor that is the core of the plant 2000. For example, the crucible is held by a stand 1210 arranged in the cylindrical container 1200. The cylindrical container 1200 is a machine used to carry out processes that require elevated temperatures and pressures with respect to the ambient pressure and / or temperature.

[0009] The actual crystal growth is carried out in the reactor. The growth structure includes a heat insulator 1300 arranged around the crucible.

[0010] The wall of the crucible can contain materials such as graphite or carbon. These materials enable the crucible to heat SiC up to a growth temperature above 2000 °C.

[0011] Specifically, to grow a SiC bulk single crystal, a SiC seed crystal 1114 is placed on a seed holder 1112, and the seed holder 1112 is placed on the end wall 1110 of the crucible before the start of growth. More specifically, the SiC seed crystal 1114 is placed in the crystal growth region 1124 of the growth crucible 1100, and the crucible is preferably completely closed, especially during at least growth.

[0012] Powdery SiC raw material is introduced into the SiC storage region 1120 of the growth crucible. The boundary of the SiC storage region 1120 at the start of the growth process is indicated by the thick dashed line 1122. This boundary is, for example, a wall made of porous graphite. During growth, sublimation of the powdery SiC raw material and transfer of the sublimated gaseous components into the crystal growth region 1124, i.e., along the Y-axis, generate a SiC growth gas phase there, and deposition from the SiC growth gas phase onto the SiC seed crystal 1114 causes a SiC bulk single crystal having a central longitudinal axis along the Y-axis to grow.

[0013] To grow a SiC bulk single crystal, a temperature distribution along the Y-axis as shown in FIG. 11 is realized within the crucible. Specifically, the dashed line 1130 indicates the highest temperature in FIGS. 10 and 11. Specifically, the highest temperature is located at the center of the SiC storage region 1120.

[0014] As shown in FIG. 10, heating can be provided by any of the induction coils 1400 arranged outside the cylindrical container 1200. Specifically, the induction coil 1400 is arranged along the radial axis R with a radius R coil and arranged circumferentially. Alternatively, according to a solution not shown, a resistance heater can be arranged inside the reactor 1200.

[0015] Induction heating is a method of heating a conductive substance by electromagnetic induction. A current passing through the inductor 1400 creates an electromagnetic field within the coil to directly heat the material within the SiC storage region 1120 and / or to heat the sidewall 1140 of the crucible to indirectly heat the SiC in the storage region. The sidewall 1140 of the crucible extends circumferentially along a radius R along the growth direction, i.e., the Y-axis. sidewall The heat insulator 1300 insulates the crucible and the cavity formed inside the crucible.

[0016] The temperature can be measured by one or more (not shown) pyrometers or by one or more thermocouples. Specifically, the temperature is measured inside the chamber formed by the reactor 1200, but outside the crucible. The vacuum-sealed reactor 1200 may be evacuated by one or more (not shown) vacuum pumps via the outlet 1500. Further, an inert gas and / or a doping gas (e.g., nitrogen) can be supplied to the system via one or more gas supply lines 1600, and the pressure within the system can be measured and controlled by a (not shown) pressure sensor.

[0017] Process parameters such as pressure, temperature, and gas flow rate can be set, controlled, and recorded by a computerized system control device. The plant control system communicates with all relevant components (e.g., converters, pyrometers, vacuum control valves, mass flow controllers (MFCs) for supplying doping gases, and pressure sensors).

[0018] As described above, the SiC single crystal or the substrate manufactured therefrom must be of high quality for the subsequent epitaxial process. For this purpose, doping gas such as nitrogen must be present in the growth space as a doping gas in a controlled form throughout the growth period and be guaranteed to be incorporated into the crystal lattice of the growing SiC single crystal. Non-uniform doping gas concentration during the growth period, and thus non-uniform incorporation into the single crystal, leads to an increase in waste during the processing of the SiC substrate. More specifically, doping gas such as nitrogen affects the brittleness of the SiC single crystal. Non-uniform incorporation of doping gas, especially nitrogen, into the crystal lattice causes the bow value and warp value of the SiC substrate to become too high, leading to cracking during crystal processing and wafer rejection. As used herein, the bow and warp of semiconductor wafers and substrates are measures of the flatness of the wafer.

[0019] The doping gas can be introduced into the system in two different ways: the use of a gas-permeable growth crucible or the use of a gas-impermeable growth crucible. Generally, the gas-permeable crucible is more frequently used.

[0020] When using a gas-permeable growth mechanism, the gas supply lines of the inert gas and the dopant gas controlled by the MFC usually lead into the reactor chamber, and there is a concentration balance between the amount of nitrogen in the reactor chamber and the amount of nitrogen inside the growth crucible. There are the following problems with this method. That is, the gas permeability of the crucible and the diffusion of nitrogen change with temperature. For example, due to the pore expansion of graphite that depends on temperature, the concentration inside the crucible changes over the duration of growing the SiC volume single crystal. This is because the growth is usually carried out with a temperature gradient to compensate for the effects such as powder depletion. Growing the SiC volume single crystal with a temperature gradient also leads to fluctuations in the incorporation of nitrogen into the crystal lattice because the incorporation of nitrogen into the crystal lattice also occurs as a function of temperature.

[0021] This has the effect that the changing nitrogen concentration during the growth period leads to crystal cracking and poor shape values (bow and / or warp) that are factors reducing the utilization described above.

[0022] In view of the above, there is a problem of uniformly and controllably supplying nitrogen to the crystal growth space of the crucible. As the crystal diameter increases (200 mm or more) and the size of the growth mechanism increases accordingly, new solution methods are required in view of these problems. At the same time, the PVT method requires a vacuum-tight framework condition for the process conditions and the materials used.

[0023] Existing solutions propose providing a gas-permeable crucible, for example a graphite crucible. The amount of nitrogen in the reactor is controlled, for example, by an MFC and selectively introduced into the reactor. In this solution, the growth crucible located in the reactor has a certain permeability so that nitrogen can diffuse from the reactor into the growth crucible. However, usually there is no means to control the amount of nitrogen in the crucible, and the amount of nitrogen follows the law of diffusion depending on temperature. Similarly, the incorporation of nitrogen (in the growth space of the crucible) into the SiC crystal lattice follows a law depending on temperature, and it is not possible to affect the nitrogen incorporation mechanism in other ways. Due to the permeability of the crucible, the gaseous components of the raw material (compounds containing Si and C) can also enter the reactor by diffusion along the radial temperature gradient from the crucible. Therefore, they deposit in the low-temperature regions, for example on the insulator or the wall of the reactor, causing aging and wear.

[0024] Alternatively, a gas-impermeable crucible, for example a crucible made entirely of TaC, can be used. In this design, nitrogen has to be supplied directly to the gas-impermeable crucible through a pipe, which leads to, for example, significantly increased process labor and significantly higher manufacturing costs. Without dopant nitrogen being supplied internally via an additional gas feed, it is not possible to produce N-doped SiC crystals for use in power electronics. In addition, it is disadvantageous that pre-process related impurities present in the crucible (e.g., water, Na, Ca...) (e.g., the impurities enter the crucible while preparing the raw materials and seeds in the crucible before placing the crucible in the reactor) cannot be removed from the system at the start of the process by a bake-out step under vacuum by diffusion through the crucible walls. However, the advantage of this design is that the gaseous components of the raw materials enter the reactor by diffusion along the radial temperature gradient from the crucible, without causing aging of the insulator and wear of the reactor. SUMMARY OF THE INVENTION

[0025] The object of the present invention is to provide, in particular, a solution for a crucible that enables the supply of doping gas at a constant concentration. Specifically, the temperature effect caused by the temperature gradient should be avoided. A further object is to minimize the complexity of the process, for example, by providing a pipe for directly supplying nitrogen into a cavity formed in the crucible. Furthermore, the influence of interfering materials in the crucible should be avoided.

[0026] According to a general example, a specially configured diffusion region that allows the doping gas to permeate from the outside into the cavity solves this problem. More specifically, the diffusion region according to this general example is located between an impermeable seed holder in the end wall and the edge of the impermeable side wall.

[0027] Specifically, the diffusion region defined above is arranged only in the region that receives the smallest temperature gradient during the growth cycle. Considering that the diffusion region has a substantially constant temperature during the growth cycle, the amount of doping gas in the cavity of the crucible is constant, and thus the control of the incorporation of the doping gas into the crystal lattice is improved.

[0028] The permeability of the growth crucible with respect to the doping gas is changed by coating and / or impregnation such that the side walls of the growth crucible within the areas of the source region and the growth space, i.e., the radial boundaries, are substantially impermeable to the doping gas. At the same time, the seed holder arranged on the end wall of the growth crucible provides a barrier against the ingress of nitrogen throughout that area.

[0029] This leads to the design of the growth crucible in which the diameter of the crucible into which the SiC seed is inserted is larger than the diameter of the SiC seed, and / or a diffusion gap is formed between the edge of the end wall and the side wall. As a result, the doping gas ring formed between the outer SiC seed diameter and the inner crucible diameter, and / or the resulting diffusion gap of the doping gas, serves as the doping gas diffusion surface and / or the doping gas diffusion gap within the growth apparatus according to the present invention.

[0030] More specifically, the first aspect relates to a crucible having a cavity for growing a SiC volume single crystal in a growth direction by sublimation growth.

[0031] Regarding the description of the crucible, the above description is referred to. Specifically, the crucible forms a cavity inside which the SiC volume single crystal grows. The inner surface of the crucible faces the cavity. The outer surface of the crucible faces the above-mentioned reactor, i.e., is surrounded by the chamber formed by the reactor.

[0032] Advantageously, the crucible has a prismatic shape. A prism is a polyhedron having a base that is an n-sided polygon, a second base that is a translational copy (fixed movement without rotation) of the first base, and side walls, and n other faces that connect corresponding sides of the two bases. Thus, a closed cavity is realized. This prismatic shape enables the easy removal of the SiC volume single crystal from the cavity, i.e., parallel to the faces forming the side walls. In many cases, the crucible has a cylindrical shape, i.e., the base has a circular cross-section.

[0033] It should be noted that since the cost of processing / coating the side walls, which will be described later, is high, a shape that can be used several times is advantageous. Thus, the SiC volume single crystal can be pulled out along the growth direction, and the dead space in the cavity can be reduced. Therefore, in particular, the prismatic shape, especially the cylindrical shape, is advantageous.

[0034] Regarding the description of the SiC volume single crystal, the above description is referred to. Regarding the description of sublimation growth, the above description is referred to. Specifically, in the case of a cylinder having a prismatic shape, the growth direction is perpendicular to the extending direction of the base, i.e., parallel to the direction of the faces forming the side walls.

[0035] According to a first aspect, the crucible comprises an end wall, for example, a first base having a prismatic shape. The end wall comprises a seed holder for holding the SiC seed crystal in the cavity. The seed holder and the SiC seed crystal are hereinafter referred to as the holder-seed unit. The holder-seed unit reduces the permeability of the end wall to the doping gas. Specifically, in view of the growing SiC volume single crystal, the permeability is reduced with increasing thickness. In other words, at least a part or only a part of the end wall is impermeable to at least the doping gas.

[0036] The seed holder can be formed, for example, from polycrystalline SiC. In that case, the thermal expansion coefficients of the two components of the holder-seed unit, namely the seed holder and the SiC seed crystal, become very close to each other, so that the force effect caused by the temperature of the seed holder relative to the SiC seed crystal is particularly small. However, other holder materials, such as graphite materials, are also basically possible.

[0037] The end wall extends perpendicular to the growth direction. This enables the easy extraction of the SiC volume single crystal after growth is completed, i.e., it allows the end wall to be translated along the growth direction together with the holder-seed unit. Specifically, in the case of a crucible having a cylindrical shape, the end wall extends radially.

[0038] Furthermore, according to a first aspect, the crucible comprises side walls extending in the growth direction. For example, in the case of a crucible having a cylindrical shape, the side walls form a cylindrical surface extending circumferentially around the growth direction and in the growth direction. In this case, the crucible may additionally have a bottom wall facing the end wall, so that the cavity is closed. However, the bottom wall can have any shape for closing the cavity of the crucible.

[0039] Furthermore, the side walls are designed to prevent the permeation of doping gas from an external source into the cavity. Permeation (also called imbuing) is the intrusion of a permeant (a fluid such as a doping gas) through parts such as the walls of the crucible and contact regions. This is directly related to the concentration gradient of the permeant, the intrinsic permeability of the material, and the mass diffusivity of the material. The process of permeation involves the diffusion of molecules called permeants through an interface such as the side wall. Permeation acts through diffusion, and the permeant moves from a higher concentration to a lower concentration across the interface. Preventing permeation means that the amount of permeant passing through this part of the side wall is negligible (or at least less) compared to another part, namely the diffusion region described later.

[0040] The doping gas enables doping of the material. Doping is the intentional introduction of impurities into an intrinsic semiconductor, i.e., a SiC volume single crystal, for the purpose of changing its electrical, optical, and structural properties. The material after doping is referred to as an extrinsic semiconductor.

[0041] According to a first aspect, the doping gas is used to dope a SiC volume single crystal during sublimation growth. More specifically, the doping substance is supplied in the SiC growth gas phase. The doping gas (also referred to as the doping substance) is, for example, nitrogen (N), aluminum (Al), vanadium (V), and / or boron (B). The doping substance is supplied in gaseous form or solid form. For example, doping metals or non-metals such as Al, V, and B are supplied in solid form, for example, together with the raw material to the crucible. Additionally or alternatively, the metal and / or non-metal may be supplied in gaseous form and can enter by diffusion through the crucible. Advantageously, the SiC volume single crystal is an n-doped SiC crystal with nitrogen. However, other doping is basically possible. Advantageously, the polytype of SiC is 4H. 4H is particularly advantageous for use in power electronics. However, other SiC polytypes are basically possible.

[0042] To supply the doping gas, according to a first aspect, a diffusion region is provided that allows the doping gas to permeate from the outside into the cavity. More specifically, the diffusion region is located between the seed holder and the edge of the side wall. More specifically, the edge of the side wall abuts the end wall. Thus, during the growth phase, the diffusion region is arranged in a place that undergoes a smaller temperature change than, for example, the side wall close to the heated SiC storage region. For further details of the temperature distribution, reference is made to the above description with reference to FIGS. 10 and 11. Examples of the realization of the diffusion region are described in the following further aspects.

[0043] According to a second aspect, in addition to the first aspect, the side wall comprises or is composed of a material for preventing the permeation of the doping gas, and the material has a density of 1.8 g / cm 3It contains at least one of the above graphite, vitreous carbon, and refractory metal carbide. As used herein, a refractory metal carbide that can withstand high temperatures during the PVT process. According to an advantageous aspect, the material has a density of 1.85 g / cm 3 It contains the above graphite. Additionally or alternatively, the material has a density of 1.95 g / cm 3 It contains graphite below this value. The density of graphite is controlled by using methods such as isostatic pressing. Thus, graphite with a lower density than natural graphite can be achieved. Advantageously, the sidewall comprises or is composed of the above-described combination of materials. Thus, the material of the sidewall can prevent the permeation of gas. This avoids the process step of coating the sidewall. Thus, the transmittance of the crucible can be adapted by an impregnation process.

[0044] As used herein, graphite is elemental carbon in crystalline form.

[0045] As used herein, glassy carbon or vitreous carbon, often referred to as glass-like carbon, is a non-graphitizing or non-graphitizable carbon that combines glass-like properties and ceramic properties with those of graphite. The most important properties are high temperature resistance, hardness, low density, low electrical resistance, low friction, low thermal resistance, extremely high resistance to chemical erosion, and impermeability to gases and liquids.

[0046] As used herein, carbide or refractory metal carbide typically refers to a compound composed of carbon and a refractory metal.

[0047] According to a third aspect, in addition to any of the preceding aspects, the sidewall has a layer on at least one of the inner surface and the opposite outer surface, and this layer is for preventing the permeation of doping gas, and the inner surface faces the cavity. Thus, the transmittance of the crucible can be adapted by a coating process.

[0048] It should be noted that, as described with reference to the prismatic shape that can be used several times, since the cost of processing / coating the side walls is lower than using a crucible made of or containing graphite, it is advantageous to provide a layer on the crucible. Therefore, in combination with the layer, a shape of a prism, particularly a shape of a cylinder, is advantageous.

[0049] Advantageously, according to a fourth aspect in addition to the third aspect, the layer comprises at least one of a photoresist, a graphitized sugar layer, TaC, WC, and Ta4HfC5. These materials can be applied as thin films from a solution or from a gas phase. These layers are more stable in terms of temperature and chemical properties and are more airtight than graphite.

[0050] Advantageously, according to a fifth aspect in addition to the third or fourth aspect, the layer has a thickness of 0.5 μm or more, preferably the thickness is 1 μm or more, and more preferably the thickness is 2 μm or more. Optionally, the maximum thickness is 5 μm or less.

[0051] According to a sixth aspect, in addition to any of the preceding aspects, the side wall has a layered structure for preventing the permeation of doping gas, and the layered structure comprises alternating first and second layers. In the case of a cylindrical shape, each layer forms a cylindrical surface. At least two layers of a first material and two layers of a second material are provided. Advantageously, the first layer contains graphite and the second layer contains a refractory metal carbide.

[0052] According to a seventh aspect, in addition to any of the preceding aspects, the end wall has a diffusion region. For example, in the case of a circular end wall, the diffusion region forms an annulus around the seed holder.

[0053] According to this example, the diameter of the crucible is larger than the diameter of the inserted seed holder. The resulting doping gas permeation diameter between the outer seed holder diameter and the inner crucible diameter serves as the doping gas diffusion surface in the growth apparatus according to the first example.

[0054] As the diameter of the seed holder used increases, the size of the diffusion region can also be adjusted by adjusting the growth crucible so that the amount of doping gas corresponding to the growing crystal volume and the required doping level becomes available.

[0055] According to an eighth aspect in addition to the seventh aspect, the area of the diffusion region with respect to the inner surface of the end wall is 20% or more and 40% or less, and the inner surface of the end wall faces the cavity. This particularly applies to SiC volume single crystals having a diameter greater than 200 mm perpendicular to the growth direction. The inventors have found that these ratios are sufficient to provide the required transmittance.

[0056] According to a ninth aspect, in addition to any of the preceding aspects, the crucible further comprises a sealing element, which seals the contact region between the end wall and the edge of the side wall, thereby controlling, for example, reducing the permeation of doping gas through the contact region.

[0057] The sealing of the end wall and the side wall, and in the case where the side wall is not designed as a "pot", the sealing of the bottom wall and the side wall can be optimized by introducing a sealing element containing or composed of graphite so that the influence of the doping gas diffusion channel in the contact region is eliminated. In that case, the influence of the channel in the end wall and / or the end wall and the bottom wall can be ignored, and the diffusion of the doping gas only needs to be considered through the diffusion region next to the seed holder.

[0058] According to a tenth aspect, in addition to any of the preceding aspects, the crucible further comprises a fastening element, which fastens the end wall to the side wall, thereby adjusting the transmittance of doping gas through the contact region between the end wall and the edge of the side wall. Thus, the thickness of the diffusion gap arranged in the contact region can be defined, for example, by fixing a fastening element, for example a screw, with a defined torque.

[0059] According to the 11th aspect, in addition to the 10th aspect, during the growth of the SiC volume single crystal, a gap is formed between the edge of the end wall and the side wall, and this gap allows the doping gas to pass through. This makes it possible for the diameter of the seed holder to be the same as the inner diameter of the crucible. The diffusion region is realized by this gap that forms the doping gas diffusion channel. The channel width can be defined by the gap remaining between the end wall and the side wall when fastening the fastening element, for example, when screwing with a specified torque, and possibly between the base wall and the side wall if the side wall is not designed as a "pot".

[0060] Advantageously, the gap is 0.1 mm or more and 0.5 mm or less. The gap width is measured along the radial axis and / or the longitudinal axis of the crucible. The gap surrounds the crucible in the circumferential direction, thereby forming an annulus that connects the outer surface of the crucible and the inner surface of the crucible. This particularly applies to SiC volume single crystals having a diameter greater than 200 mm perpendicular to the growth direction.

[0061] According to the 12th aspect, in addition to any of the preceding aspects, the crucible further comprises a bottom wall, and the bottom wall extends perpendicular to the growth direction such that the bottom wall, together with the end wall and the side wall, surrounds a cavity. This is one possible solution for closing the cavity.

[0062] Specifically, according to the first example of the 12th aspect, the bottom wall comprises a second seed holder for holding a second SiC seed crystal within the cavity, the crucible comprises a second diffusion region for allowing the doping gas to permeate, and the second diffusion region is located between the second seed holder and the second edge of the side wall. For the description of the second seed holder, the second SiC seed crystal, and the second diffusion region, reference is made to the above description of the seed holder, the SiC seed crystal, and the diffusion region. This solution enables a two-crystal design. For example, when a stand is connected to the bottom wall, a gas-permeable heat-insulating material is introduced between the stand and the growth crucible, so that the second doping diffusion region can also be realized at this location. Alternatively, a perforated or porous stand can be used.

[0063] Instead, according to a second example of the twelfth aspect, the bottom wall is removably connected to the side wall, thereby forming a pot that prevents the permeation of doping gas from the outside into the cavity. Optionally, the outer surface of the bottom wall is connected to a stand that holds the crucible within the growth apparatus, thereby preventing the doping gas from permeating from the outside through the bottom wall into the cavity, and the outer surface faces outward. The impermeable stand obviates the need to process the bottom wall to be impermeable.

[0064] The thirteenth aspect relates to a growth apparatus. The growth apparatus includes a crucible according to any of the preceding aspects, a reactor that forms a chamber, wherein the crucible is disposed within the chamber, and a gas inlet for supplying doping gas to the chamber. For the description of the reactor, the above description is referred to. The gas inlet may be, for example, a valve, a permeable membrane, or the like.

[0065] Advantageously, the growth apparatus of the thirteenth aspect further includes at least one heating device surrounding the side wall for inductively heating the side wall. For the description of inductive heating, the above is referred to. Additionally or alternatively, the growth apparatus further includes a gas outlet for connecting to a vacuum pump for reducing the pressure within the chamber. For the description of the gas outlet, the description of the gas inlet is referred to. Specifically, the gas outlet can be used to control the low pressure, i.e., vacuum, within the reactor chamber. Further, through this outlet, outgassing can be removed to reduce the contamination of the reactor.

[0066] The fourteenth aspect relates to a method for growing a SiC volume single crystal in a growth direction by sublimation growth within a cavity, the method comprising supplying at least one SiC seed crystal into the cavity, wherein the SiC seed crystal is disposed on an end wall comprising a seed holder for holding the SiC seed crystal, and the end wall extends perpendicular to the growth direction, Closing the cavity with sidewalls extending in the growth direction, wherein the sidewalls prevent the permeation of doping gas from the outside into the cavity, and the doping gas is for doping the SiC volume single crystal during sublimation growth; Doping the SiC volume single crystal with doping gas, wherein the doping gas diffuses through a diffusion region that allows the doping gas to permeate from the outside into the cavity, and the diffusion region is located between the seed holder and the edge of the sidewall; comprising.

[0067] For the description of the parts referred to in the 14th aspect, the descriptions of the 1st to 13th aspects described above are referred to. Specifically, for example, two SiC seed crystals can be supplied into the cavity. For the description of the two SiC seed crystals, the above description is referred to.

[0068] The 15th aspect relates to a method, which comprises: providing a crucible according to any one of the 1st to 12th aspects or a growth apparatus according to the 13th aspect; growing a SiC volume single crystal by the method of the 14th aspect. comprising.

[0069] Next, the present invention will be described in more detail and exemplarily with reference to the drawings, using advantageous aspects. However, the described aspects are only possible configurations, and the individual features described above can be provided independently of each other or omitted.

[0070] The accompanying drawings are incorporated herein to illustrate several embodiments of the present invention and form a part of this specification. These drawings serve to explain the principles of the present invention in conjunction with the description. The drawings are for the sole purpose of illustrating preferred and alternative examples of how the present invention can be implemented and used, and should not be construed as limiting the present invention to only the illustrated and described embodiments. Furthermore, some aspects of the embodiments can, individually or in various combinations, form solutions according to the present invention. Therefore, the embodiments described below may be considered alone or in any combination thereof.

[0071] The described embodiments are merely possible configurations, and it should be borne in mind that the individual features described above can be provided independently of each other or omitted entirely when implementing the present invention. Further features and advantages will become apparent from the following detailed description of various embodiments of the present invention illustrated in the accompanying drawings. In the accompanying drawings, like reference numerals indicate like elements.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0073] Next, the present invention will be described with reference to the drawings. First, refer to FIG. 1 which is similar to FIG. 10 described above. More specifically, FIG. 1 shows a growth apparatus 10 having a crucible and a reactor 200 forming a chamber, and the crucible is disposed in the chamber.

[0074] The crucible includes a cavity for growing a SiC volume single crystal (not shown) in the growth direction Y by sublimation growth. The crucible includes an end wall 110 having a seed holder 112 for holding a SiC seed crystal (not shown) in the cavity. The end wall 110 extends perpendicular to the growth direction Y. In other words, the end wall 110 extends in the radial direction R. More specifically, a SiC seed crystal (not shown) is disposed in the crystal growth region 124 of the growth crucible. Further, the crucible includes a side wall 140 extending in the growth direction Y and a bottom wall 150. The end wall 110, the side wall 140, and the bottom wall 150 surround a cavity for growing a SiC volume single crystal.

[0075] Powdery SiC raw material is disposed in the SiC storage region 120 of the crucible. The boundary of the SiC storage region 120 at the start of the growth process is indicated by a thick broken line 122. As described above, during growth, a SiC growth gas phase is generated there by sublimation of the powdery SiC raw material and transfer of the sublimated gas component to the crystal growth region 124, that is, along the Y-axis, and a SiC volume single crystal having a central longitudinal axis along the Y-axis grows by deposition from the SiC growth gas phase onto the SiC seed crystal.

[0076] The crucible is held in the reactor 200 by a stand 210. Further, an isolator 300 surrounds the crucible. The growth apparatus further includes induction heating 400, a gas outlet 500, and a gas inlet 600.

[0077] Furthermore, the end wall 110 includes a diffusion region 114 that allows doping gas to permeate from the outside into the cavity. The diffusion region 114 is located between the seed holder 112 and the edge 142 of the side wall 140. The edge 142 of the side wall 140 abuts against the end wall 110. More specifically, the diffusion region forms an annulus around the seed holder 112. According to this example, the area of the diffusion region with respect to the inner surface of the end wall 110 is 20% or more and 40% or less, and the inner surface of the end wall 110 faces the cavity. According to a further example, the area of the diffusion region with respect to the inner surface of the end wall 110 is 25% or more and 35% or less, and the inner surface of the end wall 110 faces the cavity.

[0078] Therefore, the arrangement of the diffusion region 114 on the end wall 110 improves the control of the amount of doping supplied to the cavity. Specifically, the heater 400 heats particularly the SiC storage region 120, and during the growth cycle, the SiC storage region 120 undergoes large temperature changes, while the diffusion region 114 undergoes small temperature changes. Therefore, the influence caused by the transmittance of the end wall 110 that depends on temperature can be reduced.

[0079] Furthermore, the side wall 140 is designed to prevent the permeation of doping gas from the outside into the cavity, and the doping gas is for doping the SiC volume single crystal during sublimation growth. According to the example shown in FIG. 1, the side wall 140 contains a material for preventing the permeation of doping gas. Specifically, the side wall 140 is impregnated with a material for preventing the permeation of doping gas. The material includes, for example, at least one of graphite with a density of 1.8 g / cm 3 or more, vitreous carbon, and metal carbide. Advantageously, the material includes graphite with a density of 1.85 g / cm 3 or more. Additionally or alternatively, the material includes graphite with a density of 1.95 g / cm 3 or less. For example, the material includes graphite with a density of 1.95 g / cm 3 or less and 1.8 g / cm 3 or more, and advantageously 1.85 g / cm 3 or more.

[0080] An alternative to sidewall 140 including a material for blocking the permeation of doping gas is shown in FIG. 2. FIG. 2 is substantially the same as FIG. 1. FIG. 2 is different from FIG. 1 in the illustration of sidewall 140. According to the example of FIG. 2, sidewall 140 can include a heat insulation layer 146 on the inner surface and a heat insulation layer 144 on the outer surface on the opposite side. Each of layers 144 and 146 blocks the permeation of doping gas. The inner surface faces the cavity. For example, the layer includes at least one of photoresist, graphitized sugar layer, TaC, WC, and Ta4HfC5, or other refractory metal carbides, and / or combinations thereof. According to one example, the layer has a thickness of 0.5 μm or more, preferably the thickness is 1 μm or more, and more preferably the thickness is 2 μm or more. Additionally or alternatively, the maximum thickness is 5 μm or less.

[0081] A further alternative for adjusting the transmittance of sidewall 140 of FIG. 1 is shown in FIG. 3. According to the example of FIG. 3, sidewall 140 made of an impermeable material further includes heat insulation layers 144 and 146. For the description of the heat insulation layer, the above description of FIG. 2 is referred to.

[0082] In the examples disclosed with reference to FIGS. 1-3, bottom wall 150 extends in a direction R perpendicular to the growth direction such that bottom wall 150 surrounds the cavity together with end wall 110 and sidewall 140.

[0083] According to the examples disclosed with reference to FIGS. 1-3, bottom wall 150 is impermeable to doping gas. For example, bottom wall 150 includes a material or layer similar to sidewall 140.

[0084] Additionally or alternatively, stand 210 is made of an impermeable material. More specifically, the outer surface of bottom wall 150 is connected to stand 210. The stand holds the crucible within growth apparatus 10. Thus, stand 210 can prevent doping gas from permeating from the outside into the cavity through bottom wall 150.

[0085] In addition, the bottom wall 150 can be non-removably connected to the side wall 140, thereby forming a pot. The pot prevents the permeation of doping gas from the outside into the cavity. Non-removably means that the bottom wall 150 and the side wall 140 are designed such that they cannot be removed without damage.

[0086] An alternative example of the bottom wall 150 of FIGS. 1 to 3 is shown in FIG. 4. FIG. 4 is substantially the same as FIG. 3. FIG. 4 differs from FIG. 3 in the illustration of the bottom wall 151 and the SiC storage region 121. Specifically, in addition to the first crystal growth region 124 of FIGS. 1 to 3, FIG. 4 provides a second crystal growth region 126. The first crystal growth region 124 is disposed at the first end of the crucible along the growth direction, and the second crystal growth region 126 is disposed at the opposite end of the crucible in the growth direction. Thus, two crystals can be grown during one cycle.

[0087] Furthermore, the bottom wall 151 includes a second seed holder 152 for holding a second SiC seed crystal (not shown) inside the cavity, the crucible includes a second diffusion region 154 for allowing the doping gas to permeate, and the second diffusion region is located between the second seed holder 152 and the second edge of the side wall 148. In other words, the bottom wall 151 shown in FIG. 4 is similar to the end wall 110 described above with respect to FIGS. 1 to 3.

[0088] A further aspect of the crucible is shown in FIG. 5. Specifically, FIG. 5 is the same as FIGS. 1 to 3 and, in addition, includes at least one fastening element 170. The fastening element 170 fastens the end wall 110 to the side wall 140. For example, the fastening element 170 is a screw. By adjusting the torque, the permeation rate of the doping gas through the contact region 172 formed between the end wall 110 and the edge 142 of the side wall 142 can be adjusted. The example of FIG. 5 may be adapted to the example shown in FIG. 4. Specifically, the bottom wall 151 can be fastened to the side wall 140 with a fastening element.

[0089] Details of FIG. 5 are shown in FIGS. 6 and 7. Specifically, FIG. 6 shows the crucible of FIG. 5, where in addition a sealing element 180 is provided. The sealing element seals the contact area 172 between the edge of the end wall 110 and the side wall 140. Thereby, the sealing element 180 reduces the permeation of the doping gas through the contact area 172. Alternatively, as shown in FIG. 7, a gap 190 is formed between the edge of the end wall 110 and the side wall 140. The gap allows the doping gas to pass from the outside into the cavity. This can be advantageous when the diameter of the seed holder 113 is the same (or approximately the same) as the inner diameter of the crucible. For example, the gap is 0.1 mm or more and 0.5 mm or less.

[0090] Although not described above with reference to FIGS. 1 to 6, the side wall can be provided with a layered structure for preventing the permeation of the doping gas. The layered structure includes alternating first and second layers. For example, the first layer contains graphite and the second layer contains a refractory metal carbide.

[0091] A method for growing such a SiC bulk single crystal in the growth direction by sublimation growth is illustrated in FIG. 8. According to this method, first in step S10, a SiC seed crystal is supplied into the cavity. The SiC seed crystal is disposed on an end wall provided with a seed holder for holding the SiC seed crystal. The end wall extends perpendicular to the growth direction. Also, the SiC material is supplied to a storage area formed in the cavity.

[0092] Then, the method subsequently closes the cavity in step S12. Specifically, a side wall extending in the growth direction surrounds the cavity. The side wall prevents the permeation of the doping gas from the outside into the cavity, and the doping gas is for doping the SiC bulk single crystal during sublimation growth.

[0093] Then, the method subsequently grows a SiC volume single crystal in the cavity in step S14. During the growth, a doping gas is supplied to dope the SiC volume single crystal with the doping gas. The doping gas is diffused through a diffusion region that allows the doping gas to permeate from the outside into the cavity, and the diffusion region is located between the seed holder and the edge of the side wall.

[0094] Specifically, for example, the crucible described in FIGS. 1 to 7 above is used as the method for growing a SiC volume single crystal in the cavity in the growth direction by sublimation growth. Advantageously, the growth apparatus described in FIGS. 1 to 7 above is used to grow the SiC volume single crystal.

Explanation of Reference Numerals

[0095] 10 Growth apparatus 200 Reactor 110 End wall 112, 113, 152 Seed holder 114 Diffusion region 120 SiC storage region 124 Crystal growth region 140 Side wall 142 Edge 144, 146 Heat insulation layer 148 Side wall 150, 151 Bottom wall 152 Second seed holder 154 Second diffusion region 170 Fastening element 172 Contact region 180 Sealing element 190 Gap 210 Stand 300 Isolator 400 Induction heating, heater 500 Gas outlet 600 Gas inlet 1100 Crucible 1200 Container, reactor 1210 Stand 1112 Seed holder 1114 SiC seed crystal 1124 Crystal growth region 1120 SiC storage region 1400 Induction coil, inductor 1140 Side wall 1300 Heat insulator 1500 Outlet 1600 Gas supply line 2000 Plant

Claims

1. A crucible having a cavity for growing a volume SiC single crystal in a growth direction (Y) by sublimation growth, an end wall (110) having a seed holder (112) for holding a SiC seed crystal within the cavity, the end wall (110) extending in a direction (r) perpendicular to the growth direction (Y); a sidewall (140) extending in the growth direction (Y), the sidewall (140) preventing permeation of a doping gas from the outside into the cavity, the doping gas being for doping the SiC volume single crystal during the sublimation growth; a diffusion region (114) for transmitting the doping gas from the outside into the cavity, the diffusion region (114) being located between the seed holder (112) and an edge (142) of the sidewall (140); A crucible.

2. The sidewall (140) comprises a material for preventing permeation of a doping gas, the material having a density of 1.8 g / cm ３ and optionally the material comprises at least one of graphite, glassy carbon, and refractory metal carbide having a density of 1.85 g / cm ３ and / or the material has a density of 1.9 g / cm ３ 2. The crucible of claim 1 comprising a graphite having a melting point of 1000 nm or less and a melting point of 1000 nm or less.

3. 3. The crucible of claim 1 or 2, wherein the side wall (140) comprises a layer (144, 146) on at least one of an inner surface and an opposite outer surface, the layer being for preventing permeation of the doping gas, the inner surface facing the cavity.

4. The crucible of claim 3, wherein the layers (144, 146) include at least one of photoresist, a graphitized sugar layer, TaC, WC, and Ta4HfC5.

5. 6. The crucible of any one of claims 4 to 5, wherein the layers (144, 146) have a thickness of 0.5 μm or more, preferably the thickness is 1 μm or more, more preferably the thickness is 2 μm or more, and optionally a maximum thickness of 5 μm or less.

6. 6. The crucible of claim 1, wherein the sidewall (140) comprises a layered structure for preventing permeation of a doping gas, the layered structure comprising alternating first and second layers, and optionally, the first layers comprise graphite and the second layers comprise a metal carbide.

7. 7. The crucible of claim 1, wherein the end wall (110) comprises the diffusion region (114), optionally forming an annular ring around the seed holder.

8. 8. A crucible according to claim 7, wherein the area of ​​the diffusion zone (114) relative to the inner surface of the end wall (110) is greater than or equal to 20% and less than or equal to 40%, the inner surface of the end wall (110) facing towards the cavity, and advantageously the area of ​​the diffusion zone (114) relative to the inner surface of the end wall (110) is greater than or equal to 25% and less than or equal to 35%.

9. 9. The crucible of claim 1, further comprising a sealing element (180) for sealing a contact area (172) between the end wall (110) and the edge (142) of the side wall (140) to thereby reduce permeation of the doping gas through the contact area (172).

10. 10. The crucible of claim 1, further comprising a fastening element (170) for fastening the end wall (110) to the side wall (140) and thereby adjusting the permeability of the doping gas through a contact area (172) between the end wall (119) and the edge (142) of the side wall (140).

11. 11. The crucible of claim 10, wherein a gap (190) is formed between the end wall (110) and the edge (142) of the side wall (140) during growth of the SiC volume single crystal, the gap (190) being for passing a doping gas, and preferably the gap is 0.1 mm or more and 0.5 mm or less.

12. a bottom wall (150, 151) extending in a direction (r) perpendicular to the growth direction (Y) such that said bottom wall (150, 151) encloses said cavity together with said end wall (110) and said side wall (140); the bottom wall (151) comprises a second seed holder (152) for holding a second SiC seed crystal in the cavity, the crucible comprises a second diffusion region (154) permeable to the doping gas, the second diffusion region (154) being located between the second seed holder (152) and a second edge (148) of the side wall (140); or 12. The crucible according to any one of claims 1 to 11, wherein the bottom wall (150) is non-detachably connected to the side wall (140) thereby forming a pot, which prevents permeation of doping gas from the outside into the cavity, and optionally an outer surface of the bottom wall is connected to a stand (210) for holding the crucible in a growth apparatus (10) thereby preventing permeation of the doping gas from the outside into the cavity through the bottom wall (150), and wherein the outer surface faces towards the outside.

13. A growth apparatus (10), comprising: A crucible according to any one of claims 1 to 12, A reactor (200) forming a chamber, said crucible being placed in said chamber; a gas inlet (600) for supplying a doping gas to the chamber; and optionally said growth apparatus (10) further comprising at least one of a heating device (400) surrounding said sidewall (140) for inductively heating said sidewall (140) and a gas outlet (500) for connection to a vacuum pump for reducing pressure within said chamber.

14. 1. A method for growing at least one volumetric single crystal of SiC in a cavity by sublimation growth in a growth direction (Y), comprising: providing a SiC seed crystal in the cavity, the SiC seed crystal being arranged on an end wall (110) having a seed holder (112) for holding the SiC seed crystal, the end wall (110) extending in a direction (r) perpendicular to the growth direction (Y); - closing the cavity with a sidewall (140) extending in the growth direction (Y), the sidewall (140) preventing the permeation of a doping gas from the outside into the cavity, the doping gas being for doping the SiC volume single crystal during the sublimation growth; doping the volume of SiC single crystal with the doping gas, the doping gas being diffused through a diffusion region (114) that transmits the doping gas from the outside into the cavity, the diffusion region (114) being located between the seed holder (112) and an edge (142) of the sidewall (110); The method includes:

15. 1. A method for growing at least one volumetric single crystal of SiC in a cavity by sublimation growth in a growth direction, comprising: Providing a crucible according to any one of claims 1 to 12 or a growth apparatus (10) according to claim 13; 15. The method of claim 14, further comprising growing the volume single crystal of SiC. The method includes:

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