Patent Application
20240035153
The present invention relates according to claims 1 and 3 respectively to a method for producing a preferably elongated SiC solid, in particular of polytype 3C, according to claims 12 and 13 respectively to a device for producing a preferably elongated SiC solid, in particular of polytype 3C, in particular for carrying out a method mentioned above, according to claim 14 to SiC solid-state material, in particular 3C-SiC solid-state material, and according to claim 15 to a use of the SiC solid-state material in a PVT reactor for producing monocrystalline SiC.
DE1184738 (B) discloses a method for producing silicon carbide crystals in monocrystalline and polycrystalline form by reacting silicon halides with carbon tetrachloride in a molar ratio of 1:1 in the presence of hydrogen on heated graphite bodies. In this process, a mixture of 1 volume percent silicon chloroform, 1 volume percent carbon tetrachloride and hydrogen is first passed over the graphite body at a flow rate of 400 to 600 I/h until a compact silicon carbide layer is formed on the graphite body, and then at a flow rate of 250 to 350 I/h over the deposition body at 1500 to 1600° C.
This state of the art is disadvantageous because it does not meet today's requirements for cheaply available and high-purity SiC. SiC is used in many areas of technology, in particular power applications and/or electromobility, to increase efficiency. In order for the products requiring SiC to be accessible to a mass market, the manufacturing costs must decrease and/or the quality must increase.
It is therefore the object of the present invention to provide a low-cost supply of silicon carbide (SiC). Additionally or alternatively, high purity SiC shall be provided. Additionally or alternatively SiC shall be provided very fast. Additionally or alternatively SiC shall be producible very effectively. Additionally or alternatively, monocrystalline SiC having advantageous properties shall be produced.
The aforementioned object is solved according to the invention by a method for producing a preferably elongated SiC solid, in particular of polytype 3C, according to claim 1. The method according to the invention preferably comprises at least the steps:
This solution is advantageous because, due to the chosen parameters, a very fast growth of the deposition element is possible. This rapid growth has a significant impact on the overall cost, allowing SiC to be produced at a significantly lower cost compared to the state of the art.
According to a preferred embodiment of the present invention, the method according to the invention comprises the step of introducing at least one carrier gas into the process chamber, wherein the carrier gas preferably comprises H.
This embodiment is advantageous because the carrier gas can be used to generate an advantageous gas flow in the process chamber.
The above-mentioned object is also solved according to the invention by a method for producing a preferably elongated SiC solid, in particular of polytype 3C, according to claim 3. This method according to the invention preferably comprises the following steps:
This solution is advantageous because, due to the chosen parameters, a very fast growth of the deposition element is possible. This rapid growth has a significant impact on the overall cost, allowing SiC to be produced at a significantly lower cost compared to the state of the art.
According to a preferred embodiment of the present invention, the method previously described also comprises the step of introducing at least a second source gas into the process chamber, wherein the second source gas comprises C.
Further preferred embodiments of the present invention are the subject of the following description parts and/or sub-claims.
According to a further preferred embodiment of the present invention, the introduction of the first source gas and/or the second source gas generates a pressure in the process chamber of between 2 bar and 10 bar, preferably the introduction of the first source gas and/or the second source gas generates a pressure in the process chamber of between 4 bar and 8 bar, particularly preferably the introduction of the first source gas and/or the second source gas generates a pressure in the process chamber of between 5 bar and 7 bar, particularly of 6 bar.
This embodiment is advantageous, since the increase in pressure provides more starting material, which is arranged in the form of SiC on the deposition element or through which the deposition element grows.
According to another preferred embodiment of the present invention, the surface of the deposition element is heated to a temperature in the range between 1450° C. and 1700° C., in particular to a temperature in the range between 1500° C. and 1600° C. or between 1490° C. and 1680° C.
This embodiment is advantageously an environment is created in which very pure SiC is deposited on the deposition element. In particular, it has been recognized that at too low temperatures the proportion of Si deposited on the deposition element increases and at too high temperatures the proportion of C deposited on the deposition element increases. In the temperature range mentioned, however, the SiC is at its purest.
According to another preferred embodiment of the present invention, the first source gas is introduced into the process chamber via a first supply means and the second source gas is introduced into the process chamber via a second supply means, or the first source gas and the second source gas are mixed prior to introduction into the process chamber and are introduced into the process chamber via a supply means, wherein the source gases are mixed in a molar ratio Si:C of Si=1 and C=0.8 to 1.1 and/or an atomic ratio Si:C of Si=1 and C=0.8 to 1.1 are introduced into the process chamber. This is further advantageous because it allows the Si:C=1:1 ratio in the SiC solid material to be adjusted very precisely via the molar ratio of the two gases.
This embodiment is advantageous a gas composition is created in the processor chamber in which very pure SiC is deposited at the deposition element.
According to another preferred embodiment of the present invention, the carrier gas comprises H, wherein the source gases and the carrier gas are present in a molar ratio Si:C:H of Si=1 and C=0.8 to 1.1 and H=2-10, in particular in a molar ratio Si:C:H of Si=1 and C=0.9 to 1 and H=3-5, and/or an atomic ratio Si:C:H of Si=1 and C=0.8 to 1.1 and H=2-10, in particular in an atomic ratio Si:C:H of Si=1 and C=0.9 to 1 and H=3-5, are introduced into the process chamber.
During deposition, the atomic ratio or molar ratio shown below is preferably present: H2:SiCl4:CH4=5:1:1 alternatively H2:SiCl4:CH4=6:1:1 alternatively H2:SiCl4:CH4=7:1:1 alternatively H2:SiCl4:CH4=8:1:1 alternatively H2:SiCl4:CH4=9:1:1 alternatively H2:SiCl4:CH4=10:1:1.
Thus, the atomic ratio or molar ratio between H2:SiCl4:CH4 during deposition is preferably between 5:1:1 and 10:1:1.
Preferably, a set atomic ratio or molar ratio is kept constant during deposition, this can preferably also apply in the case of changing flow rates. Particularly preferably, the total pressure or the pressure in the process chamber is also kept constant during the deposition.
This embodiment is advantageous as a gas composition is created in the processor chamber and an advantageous gas transport is created in the process chamber, where thereby very pure SiC is deposited very fast at the deposition element.
According to another preferred embodiment of the present invention, the deposition rate is set in the range between 300 μm/h and 2500 μm/h, more particularly in the range between 350 μm/h and 1200 μm/h, more particularly in the range between 400 μm/h and 1000 μm/h, more particularly in the range between 420 μm/h and 800 μm/h.
This embodiment is advantageous, since the production of SiC material is much more favorably convertible.
According to another preferred embodiment of the present invention, the first source gas is SiCl4, SiHCl3 or SiCl4 and the second source gas is CH4 or C3H8, wherein preferably the first source gas is SiCl4 and the second source gas is CH4 or wherein preferably the first source gas is SiHCl3 and the second source gas is CH4 or wherein preferably the first source gas is SiCl4 and the second source gas is C3H8.
This embodiment is advantageous because these source gases enable optimal Si and C provision for deposition.
Preferably, the source gas or the source gases and/or the carrier gas have a purity which excludes at least 99.9999% (ppm wt) of impurities, in particular of the substances B, Al, P, Ti, V, Fe, Ni.
Thus, preferably less than 1 ppm wt of impurities, in particular of the substances B, Al, P, Ti, V, Fe, Ni, is a component of the swelling gas or gases and/or of the carrier gas or less than 0.1 ppm wt of impurities, in particular of the substances B, Al, P, Ti, V, Fe, Ni, is a component of the swelling gas or gases and/or of the carrier gas. of the swelling gases and/or of the carrier gas or less than 0.01 ppm wt of foreign substances, in particular of the substances B, Al, P, Ti, V, Fe, Ni, constituent of the swelling gas or of the swelling gases and/or of the carrier gas.
Particularly preferably, less than 1 ppm wt of substance B is a constituent of the swelling gas or gases and/or of the carrier gas. Particularly preferably, less than 1 ppm wt of substance Al is a constituent of the swelling gas or gases and/or of the carrier gas. Particularly preferably, less than 1 ppm wt of substance P is a constituent of the swelling gas or gases and/or of the carrier gas. Particularly preferably, less than 1 ppm wt of the substance Ti is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 1 ppm wt of substance V is a constituent of the swelling gas or gases and/or of the carrier gas. Particularly preferably, less than 1 ppm wt of the substance Fe is a constituent of the swelling gas or gases and/or of the carrier gas. Particularly preferably, less than 1 ppm wt of the substance Ni is a constituent of the swelling gas or gases and/or of the carrier gas.
Particularly preferably, less than 0.1 ppm wt of substance B is a constituent of the swelling gas or gases and/or of the carrier gas. Particularly preferably, less than 0.1 ppm wt of substance Al is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.1 ppm wt of substance P is a constituent of the swelling gas or gases and/or of the carrier gas. Particularly preferably, less than 0.1 ppm wt of the substance Ti is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.1 ppm wt of substance V is a constituent of the swelling gas or gases and/or of the carrier gas. Particularly preferably, less than 0.1 ppm wt of the substance Fe is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.1 ppm wt of the substance Ni is a constituent of the source gas or gases and/or of the carrier gas.
Particularly preferably, less than 0.01 ppm wt of substance B is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.01 ppm wt of substance Al is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.01 ppm wt of substance P is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.01 ppm wt of the substance Ti is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.01 ppm wt of substance V is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.01 ppm wt of the substance Fe is a constituent of the source gas or gases and/or of the carrier gas. Particularly preferably, less than 0.01 ppm wt of the substance Ni is a constituent of the source gas or gases and/or of the carrier gas.
According to a further preferred embodiment of the present invention, a temperature measuring device, in particular a pyrometer, is used to measure the surface temperature of the deposition element. Preferably, the temperature measuring device outputs a temperature signal and/or temperature data. Particularly preferably, a control device modifies, in particular increases, the electrical loading of the separator element as a function of the temperature signal and/or the temperature data.
This embodiment is advantageous, since disadvantageous effects resulting from the growth can be compensated. In particular, as a result of the SiC formation or deposition, the mass of the deposition element increases, as a result of which the temperature of the deposition element changes, in particular decreases, with the same electrical loading. This would lead to an increase in the Si content. By modifying, in particular increasing, the electrical application, in particular increasing the current flow, the change in temperature can be compensated or reversed.
According to a further preferred embodiment of the present invention, the temperature measuring device performs temperature measurements and outputs temperature signal and/or temperature data at time intervals of less than 5 minutes, in particular less than 3 minutes or less than 2 minutes or less than 1 minute or less than 30 seconds. Preferably, a target temperature or a target temperature range is defined. The control device preferably controls an increase of the electrical application as soon as the temperature signal and/or the temperature data represents a surface temperature which is lower than a defined threshold temperature, whereby the threshold temperature is a temperature which is lower by a defined value than the set temperature or the lower limit of the set temperature range. The defined value is preferably less than 10° C. or less than 5° C. or less than 3° C. or less than 2° C. or less than 1.5° C. or less than 1° C.
This embodiment is advantageous because very accurate temperature changes can be detected and compensated or reversed. Very high purity can be achieved as a result. The current flow or the current intensity can thereby preferably increase over the period of the deposition by a factor of up to 1.1 or 1.5 or 1.8 or 2 or 2.3 or 2.5 or 2, 8 or 3 or 3.5 or 5 or 10. The current flow or the current intensity can thereby preferably increase over the period of deposition by at least a factor of 1.1 or 1.5 or 1.8 or 2 or 2.3 or 2.5 or 2, 8 or 3 or 3.5 or 5 or 10.
According to a further preferred embodiment of the present invention, more per unit time is introduced into the process chamber from the source gas, in particular the first source gas and/or the second source gas, continuously or stepwise, in particular in a defined ratio. Preferably, more of the source gas, in particular the first source gas and/or the second source gas, is introduced into the process chamber as a function of time, and/or more of the source gas, in particular the first source gas and/or the second source gas, is introduced into the process chamber as a function of the electrical loading.
This embodiment is advantageous since the source gas mass can be adapted to the surface increase of the deposition element. As a result, an optimum amount (mass) of Si and C can preferably be maintained in the process chamber throughout the entire production process.
The above-mentioned object is also solved by a device for producing a preferably elongated SiC solid, in particular of polytype 3C, in particular for carrying out a previously mentioned method according to claim 12. This device according to the invention preferably comprises at least one process chamber for receiving an electrically chargeable deposition element, a first source gas, wherein the first source gas comprises Si, a second source gas, wherein the second source gas comprises C, a first feed device and/or a second feed device, a first supply means and/or a second supply means for introducing the first source gas and/or the second source gas with a pressure of more than 1 bar into the process chamber, a temperature measuring means for measuring the surface temperature of the deposition element, and a control means for setting a deposition rate of more than 200 μm/h. Preferably, the control device is able to adjust the electrical application to the separator element, the electrical application being adjustable from 1300° C. and 1700° C. to generate a surface temperature.
The above-mentioned object is also solved by a device for producing a preferably elongated SiC solid, in particular of polytype 3C, in particular for carrying out a previously mentioned method according to claim 13. This device according to the invention preferably comprises at least one process chamber for receiving an electrically chargeable deposition element, at least one source gas, in particular SiCl3(CH3), wherein the source gas comprises Si and C, and a carrier gas, wherein the carrier gas preferably comprises H, a first supply means and/or a second supply means for introducing the source gas and/or the carrier gas with a pressure of more than 1 bar into the process chamber, a temperature measuring means for measuring the surface temperature of the deposition element, and a control means for setting a deposition rate of more than 200 μm/h. Preferably, the control means is capable of adjusting the electrical application to the separator element, the electrical application being adjustable from 1300° C. and 1700° C. to produce a surface temperature.
The separating element described within the scope of the present invention, in particular preferably in all embodiments, is preferably an elongated body, which preferably consists of graphite or carbon or SiC or which has graphite or carbon and/or SiC. It is also possible that the separating element is made of graphite or carbon and SiC plates, in particular with a thickness of less than 5 mm or less than 2 mm or less than 1 mm or less than 0.1 mm, are arranged thereon or are covered therewith. Alternatively, it is also possible that an SiC layer is grown on the graphite. The SiC plates and/or the grown SiC layer can be e.g. mono-crystalline or poly-crystalline. The deposition element is preferably coupled to a first electrical contact in the region of a first end in its longitudinal extension, in particular closer to the first end of the longitudinal extension than to the second end of its longitudinal extension. In addition, the deposition element is preferably coupled to a second electrical contact in the region of a second end in its longitudinal extension, in particular closer to the second end than to the first end of its longitudinal extension. Preferably, for heating the separator element, an electric current is introduced into the separator element via one of the two contacts and is discharged from the separator element via the other contact.
Furthermore, the above object is solved by a SiC solid state material, in particular 3C-SiC solid state material, having a purity excluding at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni and/or a density of less than 3.21 g/cm3 according to claim 14.
The SiC solid material or the deposition element (after termination of the deposition process) preferably has a diameter of at least or exactly 4 inches or at least or exactly or up to 6 inches or at least or exactly or up to 8 inches or at least or exactly or up to 10 inches.
Preferably, the SiC solid state material according to the invention is produced by a method according to any one of claims 1 to 11. Preferably, the SiC solid-state material has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni. Thus, preferably less than 1 ppm wt of the substances B, Al, P, Ti, V, Fe, Ni is part of the SiC solid material or less than 0.1 ppm wt of the substances B, Al, P, Ti, V, Fe, Ni is part of the SiC solid material or less than 0.01 ppm wt of the substances B, Al, P, Ti, V, Fe, Ni is part of the SiC solid material.
Especially preferred is less than 1 ppm wt of substance B component of the SiC material. Especially preferred is less than 1 ppm wt of the substance Al component of the SiC material. Especially preferred is less than 1 ppm wt of the substance P component of the SiC material. Especially preferred is less than 1 ppm wt of the substance Ti component of the SiC material. Especially preferred is less than 1 ppm wt of the substance V component of the SiC material. Especially preferred is less than 1 ppm wt of the substance Fe component of the SiC material. Especially preferred is less than 1 ppm wt of the substance Ni component of the SiC material.
Especially preferred is less than 1 ppm wt of the substance B component of the SiC material. Especially preferred is less than 1 ppm wt of the substance Al component of the SiC material. Especially preferred is less than 1 ppm wt of the substance P component of the SiC material. Especially preferred is less than 1 ppm wt of the substance Ti component of the SiC material. Especially preferred is less than 1 ppm wt of the substance V component of the SiC material. Especially preferred is less than 1 ppm wt of the substance Fe component of the SiC material. Especially preferred is less than 1 ppm wt of the substance Ni component of the SiC material.
Particularly preferred is less than 0.1 ppm wt of the substance B component of the SiC material. Particularly preferred is less than 0.1 ppm wt of substance Al component of the SiC material. Particularly preferably, less than 0.1 ppm wt of substance P is a constituent of the SiC material. Particularly preferred is less than 0.1 ppm wt of the substance Ti component of the SiC material. Particularly preferably, less than 0.1 ppm wt of substance V is a constituent of the SiC material. Particularly preferred is less than 0.1 ppm wt of the substance Fe component of the SiC material. Particularly preferred is less than 0.1 ppm wt of the substance Ni component of the SiC material.
Particularly preferred is less than 0.01 ppm wt of the substance B component of the SiC material. Particularly preferred is less than 0.01 ppm wt of substance Al component of the SiC material. Particularly preferably, less than 0.01 ppm wt of substance P is a constituent of the SiC material. Particularly preferred is less than 0.01 ppm wt of the substance Ti component of the SiC material. Particularly preferably, less than 0.01 ppm wt of substance V is a constituent of the SiC material. Particularly preferred is less than 0.01 ppm wt of the substance Fe component of the SiC material. Particularly preferably, less than 0.01 ppm wt of the substance Ni is a constituent of the SiC material.
In the context of the present patent specification, ppm wt is preferably to be understood as wt ppm.
Furthermore, the above-mentioned object is solved by using the SiC solid-state material according to claim 14 in a PVT reactor for producing monocrystalline SiC.
Furthermore, the above-mentioned object is solved by using the aforementioned SiC solid-state material or the SiC solid-state material according to claim 14 in a PVT reactor (PVT=Physical Vapor Transport) for the production of monocrystalline SiC.
This solution is advantageous because the pure SiC solid-state material provides a very advantageous starting material for a PVT process. On the one hand, this material is advantageous because it is available as a solid-state block. This solid block can then be crushed, for example, into fragments with a defined minimum size or mass or volume. Preferably, at least 50% (by weight) or at least 70% (by weight) or at least 80% (by weight) or at least 90% (by weight) or at least 950% (by weight) of the SiC solid material is thereby broken into fragments whose volume is greater than 0.5 cm3 or greater than 1 cm3 or greater than 1.5 cm3 or 2 cm3 or 5 cm3.
Alternatively, the solid block may be divided, in particular split or sawed, into a plurality of preferably at least substantially homogeneous pieces, in particular orthogonal to its longitudinal axis or direction of extension. Preferably, the divided pieces are slices with a minimum thickness of 0.5 cm or 1 cm or 3 cm or 5 cm, in particular a thickness of up to 20 cm or 30 cm or 50 cm. In both cases (crushing or dividing) solids with a minimum size can be provided. This is advantageous because when heating the SiC solid material (starting material) compared to very fine-grained starting material for the PVT process, a significantly more homogeneous temperature distribution in the starting material is possible, resulting in a significantly more homogeneous vaporization of the starting material. In addition, in the case of very fine-grained starting material, relative movements between the individual material fragments occur due to the rising vapor and the material removal at the individual material fragments, resulting in turbulence that negatively affects the crystal growth process. These disadvantages are eliminated by using the larger fragments or parts.
This solution is further advantageous because, due to the larger fragments or parts, the total surface area is significantly smaller than when very fine-grained material is used. Thus, the total surface area is easier to determine and to use as a parameter for adjustment in the PVT process.
This solution is further advantageous because, due to the low density of the SiC solid-state material produced according to the invention, the transformation of the boundary layer forming the surface of the solid-state material can take place more quickly.
The SiC solid-state material produced according to the invention, in particular 3C-SiC solid-state material, is preferably introduced into a reactor or furnace device or PVT reactor described below, which has at least the following features: Such a novel reactor is preferably a reactor or PVT reactor for crystal growth, in particular for SiC crystal growth. Said reactor or furnace device also comprises at least one or more or exactly one crucible or crucible unit, wherein the at least one crucible or crucible unit is arranged within the furnace volume. The crucible or crucible unit comprises, and has or forms, a crucible housing, the crucible housing forming a housing, the housing having an outer surface and an inner surface, the inner surface at least partially defining a crucible volume. A receiving space for receiving a starting material is arranged or formed within the crucible volume. Preferably, a seed holder unit for receiving a defined seed wafer 18 is also provided, which is arranged in particular within the crucible volume, or such a seed holder unit is arrangeable within the crucible volume. The reactor or oven device also has at least one heating unit, in particular for heating the starting material and/or the crucible housing of the crucible unit. If a seed holder unit is provided, the receiving space for receiving the starting material is preferably arranged at least partially between the heating unit and the seed holder unit.
This oven device is advantageous in that it can be modified in one or more ways to release at least one of the above-mentioned objects, or several or all of the above-mentioned objects.
Further preferred embodiments are the subject of the further specification parts and/or the dependent claims.
According to a preferred embodiment of the present invention, the furnace apparatus further comprises at least one leak prevention device for preventing leakage of gaseous silicon during operation from the interior of the crucible or crucible unit into a portion of the furnace volume surrounding the crucible unit. This design is advantageous as the disadvantages of leaky Si vapor are eliminated.
According to another preferred embodiment of the present invention, the leak prevention agent is selected from a group of leak prevention agents. The group of leak prevention means preferably comprises at least (a) a covering element for covering surface parts and/or a density increasing element for increasing the density of a volume section of the crucible housing of the crucible unit, (b) a filter unit for collecting gaseous Si and/or (c) a pressure unit for building up a first pressure inside the crucible unit and a second pressure inside the furnace but outside the crucible unit, the second pressure being higher than the first pressure, (d) seals arranged between housing parts of the crucible unit. This embodiment is advantageous as several features are provided to provide an improved furnace device. It is possible to provide such an oven apparatus with one or more or all of the features of said group of leak prevention means. Thus, the present invention also provides solutions for different needs, in particular for different products, especially crystals with different properties.
According to another preferred embodiment of the present invention, the leak prevention agent reduces the leakage from the crucible volume through the crucible housing into the furnace volume of sublimation vapors, in particular of Si vapor, generated during a run, in particular by at least 50% (mass) or by at least 80% (mass) or by at least 90% (mass) or by more than 99% (mass) or by at least 99.9% (mass). This embodiment is advantageous because, due to the significant reduction in leaky Si-steam furnaces, components such as the crucible housing and the heating unit can be reused multiple times, in particular more than 10 times or more than 20 times or more than 50 times or more than 100 times. Thus, the crucible unit or the crucible housing or sections of the crucible unit or sections of the crucible housing have a permeability of less than 10-2 cm2/s or of less than 10-5 cm2/s or of less than 10-10 cm2/s, in particular with respect to Si vapor.
According to a further preferred embodiment of the present invention, the crucible housing comprises carbon, in particular at least 50% (by mass) of the crucible housing consists of carbon and preferably at least 80% (by mass) of the crucible housing consists of carbon and most preferably at least 90% (by mass) of the crucible housing consists of carbon or the crucible housing consists entirely of carbon, in particular the crucible housing comprises at least 90% (by mass) graphite or consists of graphite to withstand temperatures above 2. 000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The crucible housing is preferably impermeable to silicon gas (Si vapor). This design is advantageous because it prevents Si vapor from penetrating through the crucible housing and damaging the crucible housing and components outside the crucible housing. Additionally or alternatively, the crucible unit or the crucible housing structure or the crucible housing have glassy carbon coated graphite and/or solid glassy carbon and/or pyrocarbon coated graphite and/or tantalum carbide coated graphite and/or solid tantalum carbide.
According to another preferred embodiment of the present invention, the leak protection means is a covering element for covering the surface of the housing, in particular the inner surface and/or the outer surface, or for covering surface parts of the housing, in particular surface parts of the inner surface of the housing and/or surface parts of the outer surface of the housing. This embodiment is advantageous because the covering element can be generated on a surface of the housing or can be attached to a surface of the housing. However, either of the two steps (generating/attaching) can be performed in a cost effective and reliable manner.
According to another preferred embodiment of the present invention, the cover element is a sealing element, wherein the sealing element is a coating. The coating preferably consists of a material or a combination of materials which reduces the leakage of sublimation vapors, in particular Si vapor, generated during a run, from the crucible volume through the crucible housing into the furnace volume, in particular by at least 50% (mass) or by at least 80% (mass) or by at least 90% (mass) or by more than 99% (mass) or by at least 99.9% (mass).
The coating preferably withstands temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. This embodiment is advantageous because a modified crucible unit has at least two layers of material, one layer forming a crucible shell and the other layer reducing the permeability of Si vapor. The coating most preferably comprises one or more materials selected from a group of materials comprising at least carbon, in particular pyrocarbon and vitreous carbon. Thus, the crucible unit, in particular the crucible housing or the housing of the crucible unit, is preferably coated with pyro-carbon and/or glassy carbon. The layer of pyrocarbon preferably has a thickness of more than or up to 10 μm, in particular of more than or up to 20 μm or of more than or up to 50 μm or of more than or up to 100 μm or of more than or up to 200 μm or of more than or up to 500 μm. The glassy carbon layer preferably has a thickness of more than or up to 10 μm, in particular of more than or up to 20 μm or of more than or up to 50 μm or of more than or up to 100 μm or of more than or up to 100 μm or of more than or up to 200 μm or of more than or up to 500 μm.
According to a further preferred embodiment, the coating is produced by chemical vapor deposition or wherein the coating is produced by painting, in particular on a precursor material, in particular phenol formaldehyde, and pyrolysis after painting. This embodiment is advantageous because the coating can be generated in a reliable manner.
According to another preferred embodiment of the present invention, the leak protection agent is a density-increasing element or a sealing element for increasing the density of a volume portion of the crucible housing of the crucible unit, wherein the density-increasing element is arranged or created in the internal structure of the crucible housing, wherein the density-increasing element is a sealing element, wherein the sealing element prevents leakage of sublimation vapors, in particular Si-vapor generated during a run, from the crucible volume through the crucible housing into the furnace volume, in particular by at least 50% (mass) or by at least 80% (mass) or by at least 90% (mass) or by more than 99% (mass) or by at least 99.9% (mass). This embodiment is advantageous because the dimensions of the crucible unit remain the same or similar or are not affected by the modification. The sealing element is preferably created inside the crucible housing by impregnation or deposition.
According to another preferred embodiment of the present invention, the leak prevention means is a filter unit for collecting gaseous Si. The filter unit comprises a filter body, the filter body having a filter input surface or input section for introducing gas containing SiC species vapor, Si vapor and process gases into the filter body and an output section or filter output surface for outputting filtered process gases. A filter element is disposed between the filter input surface and the filter output surface, the filter element forming a trapping section for adsorbing and condensing SiC species vapor and Si vapor in particular. Therefore, the filter material is preferably adapted to cause absorption and condensation of Si vapor on a filter material surface. This design is advantageous because the total amount of Si vapor inside the crucible unit can be significantly reduced with the help of the filter unit. This also significantly reduces the amount of Si vapor that can escape. Most and preferably all of the Si vapor is preferably collected as a condensed liquid film on the inner surfaces of the filter. Additionally or alternatively, a section is defined in the uppermost portions of the filter where the temperature is below the melting point of Si and the condensed vapors actually solidify. Preferably, the Si vapors do not solidify into particles, and preferably a solid film is produced on the inner surfaces of the filter. This film can be amorphous or polycrystalline. Excess Si2C and SiC2 vapors preferably also reach the lower region of the filter and are deposited there preferably as solid polycrystalline deposits on the inner surfaces.
According to a preferred embodiment of the present invention, the filter element forms or defines a gas flow path from the filter inlet surface to the outlet surface. The filter element has a height S1 and wherein the gas flow path through the filter element has a length S2, wherein S2 is preferably at least 10 times longer than S1, in particular S2 is at least 100 times longer than S1 or S2 is at least or up to 1,000 times longer than S1 or S2 is at least or up to 10,000 times longer than S1. This embodiment is advantageous because the filter unit has the ability to absorb or trap more than or up to 50% (mass), in particular more than or up to 50% (mass) or more than or up to 70% (mass) or more than or up to 90% (mass) or more than or up to 95% (mass) or more than or up to 99% (mass) of the Si vapor generated by vaporization of the feedstock, in particular the feedstock used or required during a run. By “one run” is preferably meant the generation or production of a crystal, in particular SiC crystal or SiC block or SiC boule.
According to another preferred embodiment of the present invention, the filter unit is arranged between a first part of the crucible unit housing and a second part, in particular crucible lid or filter lid, of the crucible unit housing. At least 50% (vol.), in particular at least 80% (vol.) or at least 90% (vol.), of the first part of the housing of the crucible unit are arranged in vertical direction below the seed holder unit, wherein a first crucible volume is present between the first part of the housing of the crucible unit and the seed holder, wherein the first crucible volume can be operated in such a way that at least 80% or preferably 90% or even more preferably 100% of the first crucible volume is above the condensation temperature Tc of silicon at the prevailing pressure. Additionally, up to 50% (vol.) or up to 20% (vol.) or up to 10% (vol.) of the first part of the crucible unit housing is arranged vertically above the seed holder unit. Alternatively, at least 50% (vol.), in particular at least 80% (vol.) or 90% (vol.), of the second housing part of the crucible unit is arranged in vertical direction above the seed holder unit. A second crucible volume is preferably present between the second part of the housing of the crucible unit and the seed holder unit. At least 60%, or preferably 80%, or more preferably 90% of the filter element is below the condensation temperature Tc. Thus, the thermal conditions within the filter element of the filter unit allow condensation of Si vapor. Thus, the filter element can condense or trap Si very effectively.
According to another preferred embodiment of the present invention, the filter unit is arranged between a first wall portion of the first part of the housing and a further wall portion of the second part of the housing, the filter body forming a filter outer surface, the filter outer surface connecting the first wall portion of the first part of the housing and the further wall portion of the second part of the housing, the filter outer surface forming part of the outer surface of the cross unit. This embodiment is advantageous because a large-sized filter unit can be used without increasing the amount of material of the crucible housing of the crucible unit.
According to another preferred embodiment of the present invention, the filter outer surface comprises a filter surface cover element. The filter surface covering element is preferably a sealing element, wherein the sealing element is preferably a coating, wherein the coating is preferably produced on the filter surface or attached to the filter surface or forms the filter surface. The coating preferably consists of a material or a combination of materials which reduces the leakage of sublimation vapors, in particular Si vapor, generated during a run, from the crucible volume through the crucible housing into the furnace volume, in particular by at least 50% (mass) or by at least 80% (mass) or by at least 90% (mass) or by more than 99% (mass) or by at least 99.9% (mass), the coating withstanding temperatures above 2. 000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C.
The coating has one or more materials selected from a group of materials comprising at least carbon, in particular pyrocarbon and glassy carbon. Therefore, the coating is preferably a glass-carbon coating or a pyrocarbon coating or a glass-carbon undercoat and a pyrocarbon topcoat or a pyrocarbon undercoat and a glass-carbon topcoat. Thus, the filter unit, in particular the outer surface of the filter unit, is preferably coated with pyrocarbon and/or glassy carbon. The pyrocarbon layer preferably has a thickness of more than or up to 10 μm, in particular of more than or up to 20 μm or of more than or up to 50 μm or of more than or up to 100 μm or of more than or up to 200 μm or of more than or up to 500 μm. The glassy carbon layer preferably has a thickness of more than or of up to 10 μm, in particular of more than or of up to 20 μm or of more than or of up to 50 μm or of more than or of up to 100 μm or of more than or of up to 200 μm or of more than or of up to 500 μm.
According to another preferred embodiment of the present invention, the filter body forms an inner filter surface. The filter inner surface or filter inner surface is preferably arranged coaxially with the filter outer surface. The filter body is preferably annular in shape. The outer filter surface preferably has a cylindrical shape and/or wherein the inner filter surface preferably has a cylindrical shape. The filter outer surface and the filter inner surface extend in vertical direction. This embodiment is advantageous because the filter unit can be used in a circular crucible unit and/or in a crucible unit having a circular crucible volume. Thus, the filter unit or the furnace apparatus in which the filter unit is located does not require any substantial modifications, so that the furnace apparatus according to the present invention can be manufactured at low cost.
According to a further preferred embodiment of the present invention, the filter inner surface comprises a further filter inner surface cover element. The further filter inner surface covering element is preferably a sealing element, wherein the sealing element is preferably a coating. The coating is preferably created on the filter surface, or attached to the filter surface, or forms the filter surface. The coating preferably has a material or combination of materials that reduces the leakage of sublimation vapors, in particular Si vapor, generated during a run, from the crucible volume through the crucible housing to the furnace volume, in particular by at least 50% (mass) or by at least 80% (mass) or by at least 90% (mass) or by more than 99% (mass) or by at least 99.9% (mass).
The coating preferably resists temperatures above 2,000° C., in particular above 2,200° C. or above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The coating preferably has one or more materials selected from a group of materials containing at least carbon, in particular pyrocarbon and glassy carbon. Thus, the filter unit, in particular the inner surface of the filter unit, is preferably coated with pyrocarbon and/or glassy carbon. The pyrocarbon layer preferably has a thickness of more than or up to 10 μm, in particular of more than or up to 20 μm or of more than or up to 50 μm or of more than or up to 100 μm or of more than or up to 200 μm or of more than or up to 500 μm. The glassy carbon layer preferably has a thickness of more than or of up to 10 μm, in particular of more than or of up to 20 μm or of more than or of up to 50 μm or of more than or of up to 100 μm or of more than or of up to 200 μm or of more than or of up to 500 μm.
According to another preferred embodiment of the present invention, the filter element comprises a filter element member, wherein the filter element member comprises filter particles and a binder. The filter particles comprise carbon or consist of carbon, wherein the binder holds the filter particles in fixed relative positions to each other. The filter particles wi-resist temperatures above 2,000° C., in particular above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The binder withstands temperatures above 2,000° C., in particular 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. This embodiment is advantageous because a filter unit is provided that can withstand conditions within a crucible unit during operation of the furnace apparatus. In addition, the combination of filter particles and binder forms a surface area that is substantially larger compared to the outer surface area of the filter unit, particularly up to or at least 10 times larger or up to or at least 100 times larger or up to or at least 1,000 times larger or up to or at least 10,000 times larger. This embodiment is further advantageous because the filter unit has a capacity to absorb or capture more than or up to 50% (mass), in particular more than or up to 50% (mass) or more than or up to 70% (mass) or more than or up to 90% (mass) or more than or up to 95% (mass) or more than or up to 99% (mass) of the Si vapor generated by vaporization of the starting material, in particular the starting material required in each case in one pass.
According to another preferred embodiment of the present invention, the binder comprises starch or wherein the binder comprises modified starch.
This embodiment is advantageous because the binder resists temperatures above 2,000° C., in particular above or up to 2,000°, in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The binder co-resists temperatures above 2,000° C., in particular 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C.
According to a further preferred embodiment of the present invention, the gas inlet is arranged between the receiving space and the holder seed unit, the gas inlet preferably being arranged closer to the receiving space in the vertical direction than the seed holder unit, in particular the vertical distance between the seed holder unit and the gas inlet is preferably more than twice the vertical distance between the receiving space and the gas inlet, in particular more than five times the vertical distance between the receiving space and the gas inlet or more than eight times the vertical distance between the receiving space and the gas inlet or more than ten times the vertical distance between the receiving space and the gas inlet or more than twenty times the vertical distance between the receiving space and the gas inlet. This embodiment is advantageous because a gas flow can be established that causes the vaporized starting material to homogeneously reach the seed wafer 18 or the growth front of the crystal.
According to a further preferred embodiment of the present invention, the gas inlet is covered by a gas guiding element or a gas distributing element. The gas distribution element preferably extends parallel to a bottom surface of the crucible unit, in particular the inner bottom surface of the crucible unit. Additionally or alternatively, the gas distribution element extends in a horizontal plane. This embodiment is advantageous because the introduced gas can be homogeneously distributed to the annular receiving space and thus to the starting material presented in the receiving space or to the vaporized starting material flowing out of the receiving space. The vaporized feedstock material moves by thermally driven diffusion. Additionally or alternatively, the vaporized feedstock material moves by convection of injected gas, in particular Ar and/or N2.
According to a further preferred embodiment of the present invention, the gas distribution element is arranged at a defined distance from the bottom surface of the crucible unit, in particular the inner bottom surface of the crucible unit. The defined distance in vertical direction between the bottom side of the gas distribution element and the bottom surface of the crucible unit is preferably smaller than 0.5× vertical distance between the receiving space and the gas inlet (i.e. less than half the vertical distance between the receiving space and the gas inlet) or less than 0.3× vertical distance between the receiving space and the gas inlet or less than 0.1× vertical distance between the receiving space and the gas inlet or less than 0.05× vertical distance between the receiving space and the gas inlet.
According to another preferred embodiment of the present invention, the gas distribution element is a gas baffle. The gas baffle preferably forms a lower surface and an upper surface. The lower surface and the upper surface preferably extend parallel to each other at least in sections. The distance between the lower surface and the upper surface is preferably less than 0.5× distance between the receiving space and the gas inlet, or less than 0.3× distance between the receiving space and the gas inlet, or less than 0.1× distance between the receiving space and the gas inlet, or less than 0.05× distance between the receiving space and the gas inlet. This embodiment is advantageous because a truly thin gas distribution plate can be used. This is advantageous because the gas distribution plate does not require a significant amount of material. In addition, the gas distribution plate does not affect heat radiation radiated from a lower portion covered by the gas distribution plate.
According to another preferred embodiment form of the present invention, the means for preventing leakage is a pressure unit for building up a first pressure inside the crucible unit and a second pressure inside the furnace but outside the crucible unit, wherein the second pressure is higher than the first pressure and wherein the second pressure is below 200 Torr, in particular below 100 Torr or below 50 Torr, in particular between 0.01 Torr and 30 Torr. The second pressure is preferably up to 10 Torr or up to 20 Torr or up to 50 Torr or up to 100 Torr or up to 180 Torr higher than the first pressure. This embodiment is advantageous because leakage of Si vapor is prevented due to the higher pressure around the crucible unit.
A pipe system is part of the furnace apparatus according to another preferred embodiment of the present invention. The pipe system preferably comprises a first pipe or crucible pipe connecting the crucible volume to a vacuum unit, and a second pipe or furnace pipe connecting the part of the furnace surrounding the crucible unit to the vacuum unit. The vacuum unit preferably has a control element for controlling the pressure inside the crucible volume and the pressure in the part of the furnace surrounding the crucible unit. The vacuum unit preferably reduces the pressure inside the crucible volume via the crucible tube or inside the part of the furnace surrounding the crucible unit via the furnace tube if the control element determines that the pressure inside the crucible volume is above a first threshold and/or if the control element determines that the pressure inside the part of the furnace surrounding the crucible unit is above a second threshold. This embodiment is advantageous because the pressure difference between the pressure inside the crucible volume and the pressure inside the furnace and around the crucible volume can be reliably maintained.
According to another preferred embodiment of the present invention, the furnace system comprises two or more than two leak prevention means selected from the group consisting of leak prevention means. This embodiment is advantageous because the furnace apparatus comprises at least the cover element and/or the density increasing element and the filter unit for collecting gaseous Si, or because the furnace apparatus comprises at least the cover element and/or the density increasing element and the pressure unit for building up the first pressure inside the crucible unit and the second pressure inside the furnace, but outside the crucible unit or since the furnace device comprises at least the pressure unit for building up the first pressure inside the crucible unit and the second pressure inside the furnace but outside the crucible unit and the filter unit.
However, it is also possible that the furnace device comprises at least the cover element and/or the density increasing element and the filter unit for collecting gaseous Si and the pressure unit for setting the first pressure inside the crucible unit and the second pressure inside the furnace but outside the crucible unit.
This embodiment is advantageous because the leakage of Si vapor can be prevented in various ways, so that it is possible to set up the furnace unit according to the present invention to meet the requirements depending on various needs.
According to a further preferred embodiment of the present invention, the heating unit comprises at least one, in particular horizontal, heating element, wherein the heating element is arranged in vertical direction below the receiving space. Thus, the heating element preferably overlaps the receiving space at least partially and preferably predominantly or completely. This design is advantageous because the receiving space and the part of the crucible volume or crucible housing enclosed by the receiving space can be heated from below the crucible volume. This is advantageous because the height of the receiving space and the height of the part of the crucible volume or crucible housing surrounded by the receiving space are the same for seed wafers 18 with a small diameter or with a larger diameter. This allows the starting material to be homogeneously heated. The heating unit preferably also has at least one further, in particular vertical, heating element, the further heating element preferably being arranged next to the crucible unit, in particular next to a side wall of the crucible unit surrounding the crucible unit. The heating element and/or the further heating element is preferably arranged inside the furnace insert outside the crucible unit, in particular outside the crucible volume.
According to a further preferred embodiment of the present invention, the receiving space is formed in a wall part of the crucible unit or is arranged on a wall or bottom part inside the crucible unit. The receiving space preferably extends about a central axis, the central axis preferably being coaxial with a central axis of the seed holder unit. The receiving space is preferably arranged at a defined distance from the central axis.
According to a further preferred embodiment of the present invention, a gas tube or gas guiding device is provided for introducing gas into the crucible unit. The gas tube or gas guiding means, or a portion of the gas tube or gas guiding means, or a gas inlet attached to the gas tube or gas guiding means, or a part of the gas tube or gas guiding means is at least partially, and preferably predominantly or completely, surrounded by the receiving space. The gas tube or gas guiding means preferably extends at least partially in the direction of the center axis. The gas tube or gas conducting means preferably enters the crucible volume through a bottom part of the crucible unit or through a bottom part of the crucible housing of the crucible unit. This embodiment is advantageous because gas can be provided into the crucible volume via a gas line or gas guiding device. Furthermore, since the gas inlet is surrounded by the receiving volume, the gas introduced via the gas inlet can be distributed to the different parts of the receiving volume, in particular homogeneously. In this way, a mixture of injected gas and vaporized feedstock can be generated, in particular in a homogeneous manner.
According to another preferred embodiment of the present invention, the receiving space has an annular shape. The receiving space is preferably shaped or formed as a trench, in particular a circular trench, or by multiple recesses, in particular circular recesses. These multiple recesses are preferably arranged along a predetermined contour, the predetermined contour preferably being circular in shape. This embodiment is advantageous because the seed wafer 18 is preferably circular in shape. Thus, the evaporated starting material advantageously approaches the growth surface of the seed wafer 18 or a growth surface of the growing crystal.
According to a further preferred embodiment of the present invention, the defined distance between the receiving space and the center axis is up to 30% or up to 20% or up to 10% or up to 5% or up to 1% shorter than the diameter of the defined seed wafer 18. Alternatively, the defined distance between the receiving space and the center axis is up to 1% or up to 5% or up to 10% or up to 20% or up to 30% longer than the diameter of the defined seed wafer 18. Alternatively, the defined distance between the receiving space and the center axis coincides with the diameter of the defined seed wafer 18. This embodiment is advantageous as it further supports homogeneous distribution of the vaporized starting material over the growth surface of the seed wafer 18 or over a growth surface of the growing crystal.
According to another preferred embodiment of the present invention, the receiving space encloses a housing bottom portion or a portion above the housing bottom. The bottom section is a solid material section. The solid material section or a crucible massive bottom section preferably has a height (in vertical direction) or a wall thickness which is greater than 0.3× the smallest distance of the receiving space from the center axis, or is greater than 0.5× the smallest distance of the receiving space from the center axis, or is 0.7× the smallest distance between the receiving space and the center axis, or is greater than 0.9× the smallest distance between the receiving space and the center axis, or is 1.1× the smallest distance between the receiving space and the center axis, or is greater than 1.5× the smallest distance between the receiving space and the center axis. This design is advantageous because the lower part or the surrounding lower part can be heated by the heating unit. If the lower part is heated, it heats the space between the seed wafer 18 and also the seed wafer 18. If the lower part is heated, it heats the space between the seed wafer 18 and also the seed wafer 18. Since the lower part is preferably a solid block of material and/or a crucible-shaped solid bottom section, the heating of the space between the seed wafer 18 and the bottom section and the heating of the seed wafer 18 or the wax-tum surface of the growing crystal is performed in a homogeneous manner. The bottom portion preferably has an outer surface portion, which is preferably a surface portion of the crucible body, and an inner surface portion, the inner surface portion preferably being parallel to the outer surface portion. This is advantageous because the bottom portion can be homogeneously heated. The inner surface portion of the bottom portion is preferably a flat surface, wherein the flat surface is preferably arranged in a horizontal plane. The inner surface portion is preferably arranged parallel to the surface of the seed wafer 18. This embodiment is advantageous because the space between the seed wafer 18 and the bottom portion and the seed wafer 18 and/or the growth surface of the growing crystal can be homogeneously heated.
The bottom portion thus has an inner surface, the inner surface of the bottom portion being disposed within the crucible volume and preferably parallel to the seed holder unit. The center of the inner surface and the center of the seed holder unit are preferably arranged on the same vertical axis, wherein a distance between the inner surface of the bottom section is preferably arranged at a predefined distance from the seed holder unit. The distance is preferably greater than 0.5× the smallest distance between the receiving space and the center axis or greater than 0.7× the smallest distance between the receiving space and the center axis or greater than 0.8× the smallest distance between the receiving space and the center axis or greater than 1× the smallest distance between the receiving space and the center axis or greater than 1, 2× the smallest distance between the receiving space and the center axis, or greater than 1.5× the smallest distance between the receiving space and the center axis, or greater than 2× the smallest distance between the receiving space and the center axis, or greater than 2.5× the smallest distance between the receiving space and the center axis. This embodiment is advantageous because large (wide and/or long) crystals can be grown.
The filter unit is arranged vertically above the receiving chamber. This embodiment is advantageous because the evaporated feedstock and/or the injected gas flows from a lower crucible section to an upper crucible section, so the filter unit is preferably arranged in the gas flow path.
According to another preferred embodiment of the present invention, the filter unit and the receiving space are preferably arranged coaxially. This embodiment is advantageous, since vaporized starting material and/or introduced gas or a mixture of vaporized starting material and introduced gas can pass homogeneously through the preferably cylindrical sei-den wall. In this way, accumulations of vaporized starting material and/or introduced gas can be pre-aerated. This is advantageous because it allows the crystal to grow homogeneously. Homogeneous growth preferably means that the growth rate on all surface parts of the growth area of the crystal is within a defined range and/or the accumulation of defects and/or doping is uniformly distributed, the term “uniformly distributed” defining a permissible range of deviations.
According to a further preferred embodiment of the present invention, an outer diameter of the filter unit corresponds to an outer diameter of the receiving space and/or wherein an inner diameter of the filter unit preferably corresponds to an inner diameter of the receiving space. This embodiment is advantageous because the housing shape does not cause any notable complexity and thus allows for low-cost manufacturing. The outer diameter of the filter unit is preferably at least or up to 1.05× larger compared to the outer diameter of the receiving space, or wherein the outer diameter of the filter unit is preferably at least or up to 1.1× larger compared to the outer diameter of the receiving space, or wherein the outer diameter of the filter unit is preferably at least or up to 1.3× larger compared to the outer diameter of the receiving space, or wherein the outer diameter of the filter unit is preferably at least or up to 1.5× larger compared to the outer diameter of the receiving space. Alternatively, the outer diameter of the receiving space is preferably at least or up to 1.05× larger compared to the outer diameter of the filter unit or wherein the outer diameter of the receiving space is preferably at least or up to 1, 1× larger compared to the outer diameter of the filter unit or wherein the outer diameter of the receiving space is preferably at least or up to 1.3× larger compared to the outer diameter of the filter unit or wherein the outer diameter of the receiving space is preferably at least or up to 1.5× larger compared to the outer diameter of the filter unit. Additionally or alternatively, the inner diameter of the receiving space is preferably at least or up to 1.05× larger compared to the inner diameter of the filter unit, or wherein the inner diameter of the receiving space is preferably at least or up to 1, 1× larger, or wherein the inner diameter of the receiving space is preferably at least or up to 1.3× larger compared to the inner diameter of the filter unit, or wherein the inner diameter of the receiving space is preferably at least or up to 1.5× larger compared to the inner diameter of the filter unit. Alternatively, the inner diameter of the filter unit is preferably at least or up to 1.05× larger compared to the inner diameter of the receiving space or wherein the inner diameter of the filter unit is preferably at least or up to 1, 1× larger compared to the inner diameter of the receiving space or wherein the inner diameter of the filter unit is preferably at least or up to 1.3× larger compared to the inner diameter of the receiving space or wherein the inner diameter of the filter unit is preferably at least or up to 1.5× larger compared to the inner diameter of the receiving space.
According to another preferred embodiment of the present invention, a growth guiding element is arranged or provided in a vertical direction above the receiving space for guiding vaporized starting material and/or introduced gas into a space between the seed holder unit and the inner bottom surface of the crucible unit. This embodiment is advantageous because the growth guiding element preferably performs several functions. On the one hand, the growth guide element guides the vaporized starting material to the seed wafer 18 or to the growing crystal. On the other hand, the growth guide element influences the shape of the growing crystal by limiting its radial expansion.
According to another preferred embodiment of the present invention, the growth guide element comprises a first wall section or a first growth guide section and a second wall section or a second growth guide section. The first growth guide section is preferably shaped to match a corresponding wall section of the crucible housing. Matching in this context preferably means that the wall portion of the crucible housing and the growth guide member are preferably coupled by a form-fit and/or press-fit connection. The second portion of the growth guide is preferably shaped to manipulate the shape of a growing crystal. The first portion of the growth guide and the second portion of the growth guide are coaxially arranged according to another preferred embodiment of the present invention. The first section of the growth guide is arranged at a first diameter with respect to the central axis, and wherein the second section of the growth guide is arranged at a second diameter with respect to the central axis, the first diameter being larger compared to the second diameter. The first growth guide section and the second growth guide section are interconnected by a third wall section and a third growth guide section, respectively, the third growth guide section extending at least partially in a horizontal direction.
The first growth guide section and the third growth guide section form an arcuate section and a fourth growth guide section, respectively, and/or wherein the second growth guide section and the third growth guide section are arranged at an angle between 60° and 120°, in particular at an angle between 70° and 110°, in particular at an angle of 90°. The fourth growth leader section may have, for example, a convex or concave or conical shape. The first wall section, the second section of the growth aid and the third section of the growth aid are preferably integral parts of the growth aid. Preferably, the growth aid is made of graphite. This embodiment is advantageous because the growth guide element has a simple but effective shape. Thus, the growth guide element can be manufactured in a cost-effective manner.
According to another preferred embodiment of the present invention, the outer diameter of the filter unit is at least or up to 1.05× larger than the first diameter of the growth guide element, or wherein the outer diameter of the filter unit is preferably at least or up to 1.1× larger than the first diameter of the growth guide element, or wherein the outer diameter of the filter unit is preferably at least or up to 1, 3× larger than the first diameter of the growth guide or wherein the outer diameter of the filter unit is preferably at least or up to 1.3× larger than the first diameter of the growth guide or wherein the outer diameter of the filter unit is preferably at least or up to 1, 5× larger compared to the first diameter of the growth guide and/or wherein the second diameter of the growth guide is preferably at least or up to 1.05× larger compared to the inner diameter of the filter unit or wherein the second diameter of the growth guide is preferably at least or up to 1, 1× larger compared to the inner diameter of the filter unit or wherein the second diameter of the growth guide is preferably at least or up to 1.3× larger compared to the inner diameter of the filter unit or wherein the second diameter of the growth guide is preferably at least or up to 1.5× larger compared to the inner diameter of the filter unit.
wherein the upper vertical end of the growth guide of the second section of the growth guide and the seed holding unit form a gas flow channel, wherein the smallest distance between the upper vertical end of the growth guide of the second section of the growth guide and the seed holding unit is smaller than 0, 3× second diameter of the growth guide or smaller than 0.1× second diameter of the growth guide or smaller than 0.08× second diameter of the growth guide or smaller than 0.05× second diameter of the growth guide or smaller than 0.03× second diameter of the growth guide or smaller than 0.01× second diameter of the growth guide.
According to a further preferred embodiment of the present invention, the coating is preferably applied to the receiving space, in particular the surface of the receiving space within the crucible volume and/or to the growth guide element or the growth guide plate or gas distribution plate. The coating preferably has a material or combination of materials that reduces the permeability of Si vapor through the wall portions bounding the receiving space and/or through the wall portions bounding the growth guide element to 10-3 m2/s, or preferably 10-11 m2/s, or more preferably 10-12 m2/s.
The coating preferably withstands temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. This embodiment is advantageous because a modified containment and/or growth guide element has at least two layers of material, one layer forming the structure of the containment and/or growth guide element, and the other layer reducing or avoiding permeability of Si-vapor. Most preferably, the coating has one or more materials selected from a group of materials comprising at least carbon, in particular pyrocarbon and glassy carbon. Thus, the receiving space and/or the growth directing element is preferably coated with pyrocarbon and/or glassy carbon. The layer of pyrocarbon preferably has a thickness of more than or up to 10 μm, in particular of more than or up to 20 μm or of more than or up to 50 μm or of more than or up to 100 μm or of more than or up to 200 μm or of more than or up to 500 μm. The glassy carbon layer preferably has a thickness of more than or of up to 10 μm, in particular of more than or of up to 20 μm or of more than or of up to 50 μm or of more than or of up to 100 μm or of more than or of up to 200 μm or of more than or of up to 500 μm. According to a further preferred embodiment, the coating is produced by chemical vapor deposition or wherein the coating is produced by painting, in particular on a precursor material, in particular phenol formaldehyde, and pyrolysis after painting. This embodiment is advantageous because the coating can be generated in a reliable manner.
According to another preferred embodiment of the present invention, the heating unit comprises at least one heating element. The heating element is preferably arranged vertically below the receiving space and/or below a bottom part of the crucible unit, the bottom part of the crucible unit being surrounded by the receiving space. This design is advantageous because the receiving space and/or the bottom section surrounded by the receiving space can be heated by the heating element. The heating element preferably overlaps the receiving space and/or the bottom section surrounded by the receiving space at least partially and preferably to more than 50% or to more than 70% or up to 90% or completely. This design is advantageous because a homogeneous temperature distribution can be set, in particular homogeneous temperature levels can be generated.
According to a further preferred embodiment of the present invention, the furnace apparatus comprises a gas flow unit. The gas flow unit preferably has a gas inlet for conducting gas into the crucible unit or into the crucible volume and a gas outlet for withdrawing gas from the crucible unit or from the crucible volume. The gas inlet is preferably arranged closer to the bottom of the crucible unit than the gas outlet. Both the gas inlet and the gas outlet are preferably arranged within the crucible volume. This design is advantageous because the conditions within the crucible volume and/or the vapor composition and/or the liquid flow (direction and/or velocity) within the crucible can be influenced or controlled.
According to another preferred embodiment of the present invention, the gas outlet comprises a gas carrying means, in particular a tube. The gas outlet preferably has a sensor, in particular a temperature and/or pressure sensor, the sensor preferably being arranged inside the conducting means, in particular tube, or as part of the conducting means, in particular tube, or being attached to an outer wall of the conducting means, in particular tube. This embodiment is advantageous because the temperature and/or pressure conditions can be monitored.
Additionally or alternatively, the gas inlet according to a further preferred embodiment of the present invention comprises a gas conducting means, in particular a pipe. The gas inlet preferably has a sensor, in particular a temperature and/or pressure sensor, the sensor preferably being arranged inside the conduit means, in particular tube, or as part of the conduit means, in particular tube, or being attached to an outer wall of the conduit means, in particular tube. This embodiment is advantageous because the temperature and/or pressure conditions can be monitored.
According to a further preferred embodiment of the present invention, the sensor in the gas inlet and/or gas outlet is a pyrometer. This embodiment is advantageous because the pyrometer can withstand high temperatures. This embodiment is also advantageous because the pyrometer can be used multiple times, making it a very cost-effective solution.
According to another preferred embodiment of the present invention, the sensor in the gas inlet and/or gas outlet is in connection with a control unit. This embodiment is advantageous because the control unit receives sensor signals or sensor data. Thus, the control unit can output conditions within the crucible unit, in particular as a function of a time stamp, to an operator for monitoring the production or growth process. Additionally or alternatively, the control unit may be provided with control rules to control the oven apparatus depending on the control rules, the time and/or the sensor output.
According to another preferred embodiment of the present invention, the receiving space is formed by one or at least one continuous trench or a plurality of recesses. The trench or the recesses preferably at least partially and preferably substantially or preferably completely enclose a surface arranged or provided or materialized inside the crucible unit, in particular an inner surface of a wall and/or bottom section of the crucible unit, wherein the receiving space preferably has an annular shape. The heating element preferably covers at least 30% or at least 40% or at least 50% or at least 60% or at least 70% or at least 70% or at least 80% or at least 90% or at least 90% or at least 95% of a bottom surface of the receiving space and at least 20% or at least 30% or at least 40% or at least 50% or at least 60% or at least 70% or at least 70% or at least 80% or at least 90% or at least 95% of the surface at least partially surrounded by the receiving space. The area at least partially surrounded by the receiving space preferably belongs to a solid wall or a crucible bottom wall or a crucible bottom section, respectively, which extend at least over a distance V1 in vertical direction, wherein in the receiving space a distance V2 extends in vertical direction between a receiving space bottom surface and a top surface of the lowermost side wall part of the receiving space, wherein V2>V1 (i.e.: distance V2 is greater in the vertical direction). i.e.: distance V2 is greater compared to distance V1), in particular V2>1.1×V1 or V2>1.2×V1 or V2>1.5×V1 or V2>2×V1, or V2=V1 or V2<V1, in particular V2<1.1×V1 or V2<1.2×V1 or V2<1.5×V1 or V2<2×V1.
The receiving space thus preferably encloses a lower part of the housing and, in particular, has the surface surrounded by the receiving space. The bottom portion is preferably a solid material portion. The solid crucible bottom portion preferably has a height (in the vertical direction) greater than 0.3× the smallest distance between the receiving space and the center axis, or greater than 0.5× the smallest distance between the receiving space and the center axis, or 0, 7× the smallest distance between the receiving space and the center axis or which is greater than 0.9× the smallest distance between the receiving space and the center axis or 1.1× the smallest distance between the receiving space and the center axis or which is greater than 1.5× the smallest distance between the receiving space and the center axis.
According to another preferred embodiment of the present invention, the bottom portion has an inner surface or the surface surrounded by the receiving space. The inner surface of the bottom part is arranged within the crucible volume and preferably parallel to the seed holder unit. The center of the inner surface and the center of the seed holder and/or the center of a seed wafer 18 held by the seed holder unit are preferably arranged on the same vertical axis. The inner surface of the lower part is preferably arranged at a predefined distance from the seed holder unit. The distance is preferably greater than 0.5× the smallest distance between the receiving space and the center axis or greater than 0.7× the smallest distance between the receiving space and the center axis or greater than 0.8× the smallest distance between the receiving space and the center axis or greater than 1× the smallest distance between the receiving space and the center axis or greater than 1, 2× the smallest distance between the receiving space and the center axis or greater than 1.5× the smallest distance between the receiving space and the center axis or greater than 2× the smallest distance between the receiving space and the center axis or greater than 2.5× the smallest distance between the receiving space and the center axis. This embodiment is advantageous because the crucible volume has, at least in sections and preferably predominantly or completely, a rotationally symmetrical shape that supports homogeneous distribution of the vaporized starting material on the seed wafer 18 or the growing crystal.
According to a further preferred embodiment of the present invention, the area surrounded by the receiving space has at least a size of 0.5× the size of the top surface of the defined seed wafer 18 or has at least a size of 0.8× the size of the top surface of the defined seed wafer 18 or has at least a size of 0, 9× the size of the top surface of the defined seed wafer 18 or has at least a size of 1× the size of the top surface of the defined seed wafer 18 or has at least a size of 1.1× the size of the top surface of the defined seed wafer 18. Additionally or alternatively, the center of the surface surrounded by the receiving space and the center of the top surface of the defined seed wafer 18 are preferably disposed on the same vertical axis. Additionally or alternatively, the surface surrounded by the receiving space and the upper surface of the defined seed wafer 18 are preferably arranged parallel to each other. This embodiment is advantageous because a heat distribution can be homogeneously performed over the surface surrounded by the receiving space.
According to another preferred embodiment of the present invention, a control unit is provided for controlling the pressure level within the crucible unit and/or the furnace and/or for controlling the gas flow into the crucible unit and/or for controlling the heating unit. Preferably, the heating unit is controlled to generate an isothermal temperature profile parallel to the support unit or orthogonal to the vertical direction or horizon-tally. This embodiment is advantageous because the control unit could use predefined rules and/or sensor data or sensor signals to monitor the growth process and change operating parameters of one or more of the aforementioned units to control crystal growth.
A filter unit is provided according to another preferred embodiment of the present invention. The filter unit preferably surrounds the seed crystal holder unit and/or wherein the filter unit is preferably arranged at least partially above the seed crystal holder unit, in particular at least 60% (vol.) of the filter unit is arranged above the seed crystal holder unit. The filter unit comprises a filter body, wherein the filter body comprises a filter input surface for introducing gas containing Si-vapor into the filter body and an output surface for discharging filtered gas, wherein the filter input surface is preferably arranged in vertical direction at a level below the level of the output surface. At least one or exactly one filter element is arranged between the filter input surface and the output surface. It is possible that the filter element forms the filter input surface and/or the output surface. Preferably, the filter element forms a separation area for adsorption and condensation of Si vapor. This design is advantageous because Si vapor can be trapped inside the filter element, thus reducing defects caused by Si vapor. Preferably, the separation area has at least or up to 50% (vol.) of the filter element volume or at least or up to 80% (vol.) of the filter element volume or at least or up to 90% (vol.) of the filter element volume. Thus, it is possible that 1%-50% (vol.) or 10%-50% (vol.) or 1%-30% (vol.) of the filter element volume is a vapor section or a section in which the vaporized feedstock is in a vapor configuration.
In accordance with another preferred embodiment of the present invention, the filter element forms a gas flow path from the filter input surface to the output surface. The filter element preferably has a height S1 and the gas flow path through the filter element has a length S2, wherein S2 is at least 10 times longer than S1, in particular S2 is 100 times longer than S1 or S2 is 1,000 times longer than S1. This design is advantageous because the filter element has sufficient capacity to absorb all the Si vapor generated during a flow or during the growth of a crystal, in particular a SiC crystal. Therefore, the filter element preferably forms a porous, large surface area for capturing Si sublimation vapor during PVT growth, in particular SiC single crystals. The filter element preferably has a material with a surface area of at least 100 m2/g or of at least 1000 m2/g.
According to another preferred embodiment of the present invention, the filter unit is arranged between a first part of the crucible unit housing and a second part of the crucible unit housing. At least 50% (vol.), in particular at least 80% (vol.) or 90% (vol.) of the first housing part of the crucible unit are arranged in vertical direction below the seed holder unit. A first crucible volume is provided between the first housing part of the crucible unit and the seed holder, wherein the first crucible volume can be operated such that at least 80% or preferably 90% or more preferably 100% of the first crucible volume is above the condensation temperature Tc of silicon at the prevailing pressure. Additionally, up to 50% (vol.) or up to 20% (vol.) or up to 10% (vol.) of the first part of the crucible unit housing is arranged vertically above the seed holder unit. Alternatively, at least 50% (vol.), in particular at least 80% (vol.) or 90% (vol.), of the second housing part of the crucible unit is arranged in vertical direction above the seed holder unit. A second crucible volume is preferably provided between the second housing part of the crucible unit and the seed holder. At least 60%, or preferably 80%, or more preferably 90% of the filter element is below the condensation temperature Tc. This embodiment is advantageous because the output material vaporizes or is vaporized at Tc or above and condenses or condenses at Tc or below. Therefore, the fact that Si vapor condenses below a certain temperature can be used to trap condensed Si in the filter element. Therefore, the filter element is very effective.
According to another preferred embodiment of the present invention, the filter unit is arranged between a first wall part of the first housing part and a further wall part of the second housing part. The filter body preferably forms a filter outer surface. The filter outer surface preferably connects the first wall part of the first housing part and the further wall part of the second housing part. The filter outer surface preferably forms a part of the outer surface of the crucible unit. This embodiment is advantageous because the filter unit can be arranged to increase the volume of the crucible unit without the need for one or more additional crucible housing parts.
According to another preferred embodiment of the present invention, the filter outer surface comprises a filter outer surface cover element. The filter outer surface cover element is preferably a sealing element. The sealing element is preferably a coating. The coating is preferably created on the filter surface, or attached to the filter surface, or forms the filter surface. The coating preferably has a material or combination of materials that reduces leakage of sublimation vapors, in particular Si vapor, generated during a run, from the crucible volume through the crucible housing into the furnace volume, in particular by at least 50% (mass) or by at least 80% (mass) or by at least 90% (mass) or by more than 99% (mass) or by at least 99.9% (mass).
The coating preferably withstands temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The coating preferably comprises one or more materials selected from a group of materials comprising at least carbon, in particular pyrocarbon and vitreous carbon. This embodiment is advantageous because the filter unit can also form an outer barrier of the crucible unit. Thus, the filter unit preferably absorbs or traps Si and preferably also prevents Si vapor from escaping. The ash content of the filter element is preferably below 5% (mass) or below 1% (mass). This means that the less than 5% or less than 1% of the mass of the filter element is ash.
According to another preferred embodiment of the present invention, the filter body forms an inner filter surface. The filter inner surface is preferably coaxial with the filter outer surface. The filter body is preferably annular in shape. The filter outer surface preferably has a cylindrical shape and/or the filter inner surface preferably has a cylindrical shape. The filter outer surface and/or the filter inner surface has the longest extension in vertical direction or in circumferential direction. This embodiment is advantageous because the filter unit can be positioned in a simple manner due to its shape. Additionally or alternatively, the filter inner surface encloses a space above the seed holder unit. The space surrounded by the seed holder unit may serve as a cooling space for cooling the filter element and/or for cooling the seed holder unit. A cooling unit may be provided, wherein the cooling unit preferably comprises at least one cooling tube for guiding a cooling liquid. This cooling tube may be arranged to at least partially or at least mainly (more than 50% in circumferential direction) surround or completely surround the crucible unit. Additionally or alternatively, the cooling tube can be arranged inside the crucible volume, in particular in the space surrounded by the filter inner surface. However, it is also possible that the cooling tube extends from the outside of the crucible unit through a wall of the crucible unit and/or a wall of the filter unit into the crucible volume, in particular into the space surrounded by the filter inner surface. It is additionally possible that the cooling tube extends to the outside of the furnace. This embodiment is advantageous because the temperature inside the crucible unit can be advantageously controlled. In addition, it is possible to set a temperature distribution profile in the crucible volume with a much steeper gradient compared to a situation without a cooling unit.
According to a further preferred embodiment of the present invention, the filter inner surface has a further filter inner surface cover element. The further filter inner surface covering element is preferably a sealing element. The sealing element is preferably a coating, wherein the coating is preferably created on the filter surface or attached to the filter surface or forms the filter surface. The coating preferably has a material or combination of materials that resists leakage of sublimation vapors, in particular Si vapor, generated during a run, in particular at least 50% (mass) or at least 80% (mass) or at least 90% (mass) or more than 99% (mass) or at least 99.9% (mass), from the crucible volume through the crucible housing back into the furnace volume.
The coating preferably withstands temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The coating preferably has one or more materials selected from a group of materials comprising at least carbon, in particular pyrocarbon and vitreous carbon. This solution is advantageous because the leakage of Si vapor into the space surrounded by the inner surface of the filter is prevented.
The filter element preferably consists of an activated carbon block and/or one or more, in particular different, graphite foams, including those made of carbonized bread and/or rigid graphite insulation and/or flexible graphite insulation.
According to another preferred embodiment of the present invention, the filter element comprises a filter element member. The filter element preferably comprises filter particles and a binder. The filter particles preferably comprise carbon or consist of carbon material. The binder preferably holds the filter particles in fixed relative positions to each other. The filter particles preferably withstand temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The filter particles preferably resist temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 4,000° C. The filter particles preferably withstands temperatures above 1700° C., in particular above 2,000° C., in particular up to or above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. This solution is advantageous because the solid filter element has no toxic materials. In addition, the solid filter element can be manufactured at low cost. The filter unit, in particular the filter element, is preferably a disposable unit or element.
According to a further preferred embodiment of the present invention, the binder comprises starch or wherein the binder comprises starch.
According to a further preferred embodiment of the present invention, the furnace system comprises a gas flow unit. The gas flow unit preferably has a gas inlet for conducting gas into the crucible unit and a gas outlet for discharging gas from the crucible unit into the furnace or through the furnace to the outside of the furnace. The gas inlet is preferably arranged upstream of the filter unit in the gas flow direction, in particular upstream of the receiving space in the gas flow direction, and wherein the gas outlet is arranged downstream of the filter unit in the gas flow direction. Thus, a gas inlet is preferably arranged in a transformation zone within the crucible unit. The transformation zone preferably also comprises the seed holder unit and the receiving space. A starting material may be transformed from a solid configuration to a vapor configuration, and from the vapor configuration to a solid target body. The starting material may be disposed within the receiving space, and the solid target body may be held by the seed holder unit. The solid target body is a crystal, in particular a SiC crystal. The gas introduced via the gas inlet preferably mixes with and/or reacts with the starting material in the vapor configuration and/or during solidification. The gas outlet is preferably arranged in a trapping zone, wherein the trapping zone also comprises the outlet surface of the filter unit, wherein the gas composition in the trapping zone is preferably free of Si vapor or has no Si vapor. The temperature in the capture zone is preferably below the solidification temperature of gaseous Si or Si vapor. This embodiment is advantageous because the crystal growth process can be manipulated. For example, it is possible to add one or more gases to dope the crystal. Additionally or alternatively, it is possible to modify, in particular to accelerate, the vapor transport from the receiving space to the seed wafer 18 or crystal. Homogeneous growth preferably means that the growth rate on all surface parts of the growth area of the crystal is within a defined range and/or the accumulation of defects and/or doping is uniformly distributed, the term “uniformly distributed” defining a permissible range of deviations.
According to a further preferred embodiment of the present invention, an outer diameter of the filter unit corresponds to an outer diameter of the receiving space and/or wherein an inner diameter of the filter unit preferably corresponds to an inner diameter of the receiving space. This embodiment is advantageous because the housing shape does not cause any notable complexity and thus allows for low-cost manufacturing. The outer diameter of the filter unit is preferably at least or up to 1.05× larger compared to the outer diameter of the receiving chamber or wherein the outer diameter of the filter unit is preferably at least or up to 1, 1× larger compared to the outer diameter of the receiving space or wherein the outer diameter of the filter unit is preferably at least or up to 1.3× larger compared to the outer diameter of the receiving space or wherein the outer diameter of the filter unit is preferably at least or up to 1.5× larger compared to the outer diameter of the receiving space. Alternatively, the outer diameter of the receiving space is preferably at least or up to 1.05× larger compared to the outer diameter of the filter unit or wherein the outer diameter of the receiving space is preferably at least or up to 1, 1× larger compared to the outer diameter of the filter unit or wherein the outer diameter of the receiving space is preferably at least or up to 1.3× larger compared to the outer diameter of the filter unit or wherein the outer diameter of the receiving space is preferably at least or up to 1.5× larger compared to the outer diameter of the filter unit. Additionally or alternatively, the inner diameter of the receiving space is preferably at least or up to 1.05× larger compared to the inner diameter of the filter unit, or wherein the inner diameter of the receiving space is preferably at least or up to 1, 1× larger, or wherein the inner diameter of the receiving space is preferably at least or up to 1.3× larger compared to the inner diameter of the filter unit, or wherein the inner diameter of the receiving space is preferably at least or up to 1.5× larger compared to the inner diameter of the filter unit. Alternatively, the inner diameter of the filter unit is preferably at least or up to 1.05× larger compared to the inner diameter of the receiving space or wherein the inner diameter of the filter unit is preferably at least or up to 1, 1× larger compared to the inner diameter of the receiving space or wherein the inner diameter of the filter unit is preferably at least or up to 1.3× larger compared to the inner diameter of the receiving space or wherein the inner diameter of the filter unit is preferably at least or up to 1.5× larger compared to the inner diameter of the receiving space.
According to another preferred embodiment of the present invention, a growth guiding member is arranged or provided vertically above the receiving space for guiding vaporized starting material and/or introduced gas into a space between the seed holder unit and the inner bottom surface of the crucible unit. This embodiment is advantageous because the growth guide element preferably performs several functions. On the one hand, the growth guide element guides the vaporized starting material to the seed wafer 18 or to the growing crystal. On the other hand, the growth guiding element influences the shape of the growing crystal by limiting its radial extent.
According to another preferred embodiment of the present invention, the growth guide element comprises a first wall section or a first growth guide section and a second wall section or a second growth guide section. The first growth guide section is preferably shaped to match a corresponding wall section of the crucible housing. Matching in this context preferably means that the wall portion of the crucible housing and the growth guide member are preferably coupled by a form-fit and/or press-fit connection. The second portion of the growth guide is preferably shaped to manipulate the shape of a growing crystal. The first portion of the growth guide and the second portion of the growth guide are coaxially arranged according to another preferred embodiment of the present invention. The first section of the growth guide is arranged at a first diameter with respect to the central axis, and wherein the second section of the growth guide is arranged at a second diameter with respect to the central axis, the first diameter being larger compared to the second diameter. The first growth guide section and the second growth guide section are interconnected by a third wall section and a third growth guide section, respectively, the third growth guide section extending at least partially in a horizontal direction. The first growth guide section and the third growth guide section form an arcuate section and a fourth growth guide section, respectively, and/or wherein the second growth guide section and the third growth guide section are arranged at an angle between 60° and 120°, in particular at an angle between 70° and 110°, in particular at an angle of 90°. The fourth growth leader section may have, for example, a convex or concave or conical shape. The first wall section, the second section of the growth aid and the third section of the growth aid are preferably integral parts of the growth aid. Preferably, the growth aid is made of graphite. This embodiment is advantageous because the growth guide element has a simple but effective shape. Thus, the growth guide element can be manufactured in a cost-effective manner.
According to another preferred embodiment of the present invention, the outer diameter of the filter unit is at least or up to 1.05× larger than the first diameter of the growth guide element, or wherein the outer diameter of the filter unit is preferably at least or up to 1.1× larger than the first diameter of the growth guide element, or wherein the outer diameter of the filter unit is preferably at least or up to 1, 3× larger than the first diameter of the growth guide or wherein the outer diameter of the filter unit is preferably at least or up to 1.3× larger than the first diameter of the growth guide or wherein the outer diameter of the filter unit is preferably at least or up to 1, 5× larger compared to the first diameter of the growth guide and/or wherein the second diameter of the growth guide is preferably at least or up to 1.05× larger compared to the inner diameter of the filter unit or wherein the second diameter of the growth guide is preferably at least or up to 1, 1× larger compared to the inner diameter of the filter unit or wherein the second diameter of the growth guide is preferably at least or up to 1.3× larger compared to the inner diameter of the filter unit or wherein the second diameter of the growth guide is preferably at least or up to 1.5× larger compared to the inner diameter of the filter unit.
wherein the upper vertical end of the growth guide of the second section of the growth guide and the seed holder unit form a gas flow channel, wherein the smallest distance between the upper vertical end of the growth guide of the second section of the growth guide and the seed holder unit is smaller than 0, 3× second diameter of the growth guide or smaller than 0.1× second diameter of the growth guide or smaller than 0.08× second diameter of the growth guide or smaller than 0.05× second diameter of the growth guide or smaller than 0.03× second diameter of the growth guide or smaller than 0.01× second diameter of the growth guide.
According to a further preferred embodiment of the present invention, the coating is preferably applied to the receiving space, in particular the surface of the receiving space within the crucible volume and/or to the growth guide element or the growth guide plate or gas distribution plate. The coating preferably has a material or combination of materials that reduces the permeability of Si vapor through the wall portions bounding the receiving space and/or through the wall portions bounding the growth guide element to 10-3 m2/s, or preferably 10-11 m2/s, or more preferably 10-12 m2/s.
The coating preferably withstands temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. This embodiment is advantageous because a modified containment and/or growth guide element has at least two layers of material, one layer forming the structure of the containment and/or growth guide element, and the other layer reducing or avoiding permeability of Si-vapor. Most preferably, the coating has one or more materials selected from a group of materials comprising at least carbon, in particular pyrocarbon and glassy carbon. Thus, the receiving space and/or the growth directing element is preferably coated with pyrocarbon and/or glassy carbon. The layer of pyrocarbon preferably has a thickness of more than or up to 10 μm, in particular of more than or up to 20 μm or of more than or up to 50 μm or of more than or up to 100 μm or of more than or up to 200 μm or of more than or up to 500 μm. The glassy carbon layer preferably has a thickness of more than or of up to 10 μm, in particular of more than or of up to 20 μm or of more than or of up to 50 μm or of more than or of up to 100 μm or of more than or of up to 200 μm or of more than or of up to 500 μm. According to a further preferred embodiment, the coating is produced by chemical vapor deposition or wherein the coating is produced by painting, in particular on a precursor material, in particular phenol formaldehyde, and pyrolysis after painting. This embodiment is advantageous because the coating can be generated in a reliable manner.
According to another preferred embodiment of the present invention, the heating unit comprises at least one heating element. The heating element is preferably arranged vertically below the receiving space and/or below a bottom part of the crucible unit, the bottom part of the crucible unit being surrounded by the receiving space. This design is advantageous because the receiving space and/or the bottom section surrounded by the receiving space can be heated by the heating element. The heating element preferably overlaps the receiving space and/or the bottom section surrounded by the receiving space at least partially and preferably to more than 50% or to more than 70% or up to 90% or completely. This design is advantageous because a homogeneous temperature distribution can be set, in particular homogeneous temperature levels can be generated.
According to a further preferred embodiment of the present invention, the furnace apparatus comprises a gas flow unit. The gas flow unit preferably has a gas inlet for conducting gas into the crucible unit or into the crucible volume and a gas outlet for withdrawing gas from the crucible unit or from the crucible volume. The gas inlet is preferably arranged closer to the bottom of the crucible unit than the gas outlet. Both the gas inlet and the gas outlet are preferably arranged within the crucible volume. This design is advantageous because the conditions within the crucible volume and/or the vapor composition and/or the liquid flow (direction and/or velocity) within the crucible can be influenced or controlled.
According to another preferred embodiment of the present invention, the gas outlet comprises a gas carrying means, in particular a tube. The gas outlet preferably has a sensor, in particular a temperature and/or pressure sensor, the sensor preferably being arranged inside the conducting means, in particular tube, or as part of the conducting means, in particular tube, or being attached to an outer wall of the conducting means, in particular tube. This embodiment is advantageous because the temperature and/or pressure conditions can be monitored.
Additionally or alternatively, the gas inlet according to a further preferred embodiment of the present invention comprises a gas conducting means, in particular a pipe. The gas inlet preferably has a sensor, in particular a temperature and/or pressure sensor, the sensor preferably being arranged inside the conduit means, in particular tube, or as part of the conduit means, in particular tube, or being attached to an outer wall of the conduit means, in particular tube. This embodiment is advantageous because the temperature and/or pressure conditions can be monitored.
According to a further preferred embodiment of the present invention, the sensor in the gas inlet and/or gas outlet is a pyrometer. This embodiment is advantageous because the pyrometer can withstand high temperatures. This embodiment is also advantageous because the pyrometer can be used multiple times, making it a very cost-effective solution.
According to another preferred embodiment of the present invention, the sensor in the gas inlet and/or gas outlet is in connection with a control unit. This embodiment is advantageous because the control unit receives sensor signals or sensor data. Thus, the control unit can output conditions within the crucible unit, in particular as a function of a time stamp, to an operator for monitoring the production or growth process. Additionally or alternatively, the control unit may be provided with control rules to control the oven apparatus depending on the control rules, the time and/or the sensor output.
According to another preferred embodiment of the present invention, the receiving space is formed by one or at least one continuous trench or a plurality of recesses. The trench or the recesses preferably at least partially and preferably substantially or preferably completely enclose a surface arranged or provided or materialized inside the crucible unit, in particular an inner surface of a wall and/or bottom section of the crucible unit, wherein the receiving space preferably has an annular shape. The heating element preferably covers at least 30% or at least 40% or at least 50% or at least 60% or at least 70% or at least 70% or at least 80% or at least 90% or at least 90% or at least 95% of a bottom surface of the receiving space and at least 20% or at least 30% or at least 40% or at least 50% or at least 60% or at least 70% or at least 70% or at least 80% or at least 90% or at least 95% of the surface at least partially surrounded by the receiving space. The area at least partially surrounded by the receiving space preferably belongs to a solid wall or a crucible bottom wall or a crucible bottom section, respectively, which extend at least over a distance V1 in vertical direction, wherein in the receiving space a distance V2 extends in vertical direction between a receiving space bottom surface and a top surface of the lowermost side wall part of the receiving space, wherein V2>V1 (i.e.: distance V2 is greater in the vertical direction). i.e.: distance V2 is greater compared to distance V1), in particular V2>1.1×V1 or V2>1.2×V1 or V2>1.5×V1 or V2>2×V1, or V2=V1 or V2<V1, in particular V2<1.1×V1 or V2<1.2×V1 or V2<1.5×V1 or V2<2×V1.
The receiving space thus preferably encloses a lower part of the housing and, in particular, has the surface surrounded by the receiving space. The bottom portion is preferably a solid material portion. The solid crucible bottom portion preferably has a height (in the vertical direction) greater than 0.3× the smallest distance between the receiving space and the center axis, or greater than 0.5× the smallest distance between the receiving space and the center axis, or 0, 7× the smallest distance between the receiving space and the center axis or which is greater than 0.9× the smallest distance between the receiving space and the center axis or 1.1× the smallest distance between the receiving space and the center axis or which is greater than 1.5× the smallest distance between the receiving space and the center axis.
According to another preferred embodiment of the present invention, the bottom portion has an inner surface or the surface surrounded by the receiving space. The inner surface of the bottom part is arranged within the crucible volume and preferably parallel to the seed holder unit. The center of the inner surface and the center of the seed holder and/or the center of a seed wafer 18 held by the seed holder unit are preferably arranged on the same vertical axis. The inner surface of the lower part is preferably arranged at a predefined distance from the seed holder unit. The distance is preferably greater than 0.5× the smallest distance between the receiving space and the center axis, or greater than 0.7× the smallest distance between the receiving space and the center axis, or greater than 0.8× the smallest distance between the receiving space and the center axis, or greater than 1× the smallest distance between the receiving space and the center axis, or greater than 1, 2× the smallest distance between the receiving space and the center axis or greater than 1.5× the smallest distance between the receiving space and the center axis or greater than 2× the smallest distance between the receiving space and the center axis or greater than 2.5× the smallest distance between the receiving space and the center axis. This embodiment shape is advantageous because the crucible volume has, at least in sections and preferably predominantly or completely, a rotationally symmetrical shape that supports a homogeneous distribution of the evaporated starting material on the seed wafer 18 or the growing crystal.
According to another preferred embodiment of the present invention, the area surrounded by the receiving space has at least a size of 0.5× the size of the top surface of the defined seed wafer 18 or has at least a size of 0.8× the size of the top surface of the defined seed wafer 18 or has at least a size of 0, 9× the size of the top surface of the defined seed wafer 18 or has at least a size of 1× the size of the top surface of the defined seed wafer 18 or has at least a size of 1.1× the size of the top surface of the defined seed wafer 18. Additionally or alternatively, the center of the surface surrounded by the receiving space and the center of the top surface of the defined seed wafer 18 are preferably disposed on the same vertical axis. Additionally or alternatively, the surface surrounded by the receiving space and the upper surface of the defined seed wafer 18 are preferably arranged parallel to each other. This embodiment is advantageous because a heat distribution can be homogeneously performed over the surface surrounded by the receiving space.
According to another preferred embodiment of the present invention, a control unit is provided for controlling the pressure level within the crucible unit and/or the furnace and/or for controlling the gas flow into the crucible unit and/or for controlling the heating unit. Preferably, the heating unit is controlled to generate an isothermal temperature profile parallel to the support unit or orthogonal to the vertical direction or horizon-tally. This embodiment is advantageous because the control unit could use predefined rules and/or sensor data or sensor signals to monitor the growth process and change operating parameters of one or more of the aforementioned units to control crystal growth.
A filter unit is provided according to another preferred embodiment of the present invention. The filter unit preferably surrounds the seed holder unit and/or wherein the filter unit is preferably arranged at least partially above the seed holder unit, in particular at least 60% (vol.) of the filter unit is arranged above the seed holder unit. The filter unit comprises a filter body, wherein the filter body comprises a filter input surface for introducing gas containing Si-vapor into the filter body and an output surface for discharging filtered gas, wherein the filter input surface is preferably arranged in vertical direction at a level below the level of the output surface. At least one or exactly one filter element is arranged between the filter input surface and the output surface. It is possible that the filter element forms the filter input surface and/or the output surface. Preferably, the filter element forms a separation region for adsorption and condensation of Si-vapor. This design is advantageous because Si vapor can be trapped inside the filter element, thus reducing defects caused by Si vapor. The capture area preferably has at least or up to 50% (vol.) of the filter element volume or at least or up to 80% (vol.) of the filter element volume or at least or up to 90% (vol.) of the filter element volume. Thus, it is possible that 1%-50% (vol.) or 10%-50% (vol.) or 1%-30% (vol.) of the filter element volume is a vapor section or a section in which the vaporized starting material is in a vapor configuration.
In accordance with another preferred embodiment of the present invention, the filter element forms a gas flow path from the filter input surface to the output surface. The filter element preferably has a height S1 and the gas flow path through the filter element has a length S2, wherein S2 is at least 10 times longer than S1, in particular S2 is 100 times longer than S1 or S2 is 1,000 times longer than S1. This design is advantageous because the filter element has sufficient capacity to absorb all the Si vapor generated during a flow or during the growth of a crystal, in particular a SiC crystal. Therefore, the filter element preferably forms a porous, large surface area for capturing Si sublimation vapor during PVT growth, in particular SiC single crystals. The filter element preferably has a material with a surface area of at least 100 m2/g or of at least 1000 m2/g.
According to another preferred embodiment of the present invention, the filter unit is arranged between a first part of the crucible unit housing and a second part of the crucible unit housing. At least 50% (vol.), in particular at least 80% (vol.) or 90% (vol.) of the first housing part of the crucible unit are arranged in vertical direction below the seed holder unit. A first crucible volume is provided between the first housing part of the crucible unit and the seed holder unit, wherein the first crucible volume can be operated such that at least 80% or preferably 90% or even more preferably 100% of the first crucible volume is above the condensation temperature Tc of silicon at the prevailing pressure. Additionally, up to 50% (vol.) or up to 20% (vol.) or up to 10% (vol.) of the first part of the crucible unit housing is vertically disposed above the seed holder unit. Alternatively, at least 50% (vol.), in particular at least 80% (vol.) or 90% (vol.), of the second housing part of the crucible unit is arranged in vertical direction above the seed holder unit. A second crucible volume is preferably provided between the second housing part of the crucible unit and the seed holder unit. At least 60%, or preferably 80%, or even more preferably 90% of the filter element is below the condensation temperature Tc. This embodiment is advantageous because the starting material vaporizes or is vaporized at Tc or above and condenses or condenses at Tc or below. Therefore, the fact that Si vapor condenses below a certain temperature can be used to trap condensed Si in the filter element. Therefore, the filter element is very effective.
According to another preferred embodiment of the present invention, the filter unit is arranged between a first wall part of the first housing part and a further wall part of the second housing part. The filter body preferably forms a filter outer surface. The filter outer surface preferably connects the first wall part of the first housing part and the further wall part of the second housing part. The filter outer surface preferably forms a part of the outer surface of the crucible unit. This embodiment is advantageous because the filter unit can be arranged to increase the volume of the crucible unit without the need for one or more additional crucible housing parts.
According to another preferred embodiment of the present invention, the filter outer surface comprises a filter outer surface cover element. The filter outer surface cover element is preferably a sealing element. The sealing element is preferably a coating. The coating is preferably created on the filter surface, or attached to the filter surface, or forms the filter surface. The coating preferably has a material or combination of materials that reduces leakage of sublimation vapors, in particular Si vapor, generated during a run, from the crucible volume through the crucible housing into the furnace volume, in particular by at least 50% (mass) or by at least 80% (mass) or by at least 90% (mass) or by more than 99% (mass) or by at least 99.9% (mass).
The coating preferably withstands temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The coating preferably comprises one or more materials selected from a group of materials comprising at least carbon, in particular pyrocarbon and vitreous carbon. This embodiment is advantageous because the filter unit can also form an outer barrier of the crucible unit. Thus, the filter unit preferably absorbs or traps Si and preferably also prevents Si vapor from escaping. The ash content of the filter element is preferably below 5% (mass) or below 1% (mass). This means that the less than 5% or less than 1% of the mass of the filter element is ash.
According to another preferred embodiment of the present invention, the filter body forms an inner filter surface. The filter inner surface is preferably coaxial with the filter outer surface. The filter body is preferably annular in shape. The filter outer surface preferably has a cylindrical shape and/or the filter inner surface preferably has a cylindrical shape. The filter outer surface and/or the filter inner surface has the longest extension in vertical direction or in circumferential direction. This embodiment is advantageous because the filter unit can be positioned in a simple manner due to its shape. Additionally or alternatively, the filter inner surface encloses a space above the seed holder unit. The space surrounded by the seed holder unit may serve as a cooling space for cooling the filter element and/or for cooling the seed holder unit. A cooling unit may be provided, wherein the cooling unit preferably comprises at least one cooling tube for guiding a cooling liquid. This cooling tube may be arranged to at least partially or at least mainly (more than 50% in circumferential direction) surround or completely surround the crucible unit. Additionally or alternatively, the cooling tube can be arranged within the crucible volume, in particular in the space surrounded by the filter inner surface. However, it is also possible that the cooling tube extends from the outside of the crucible unit through a wall of the crucible unit and/or a wall of the filter unit into the crucible volume, in particular into the space surrounded by the filter inner surface. It is additionally possible for the cooling tube to extend to the outside of the furnace. This embodiment is advantageous because the temperature inside the crucible unit can be advantageously controlled. In addition, it is possible to set a temperature distribution profile in the crucible volume with a much steeper gradient compared to a situation without a cooling unit.
According to a further preferred embodiment of the present invention, the filter inner surface has a further filter inner surface cover element. The further filter inner surface covering element is preferably a sealing element. The sealing element is preferably a coating, wherein the coating is preferably created on the filter surface or attached to the filter surface or forms the filter surface. The coating preferably has a material or combination of materials that resists leakage of sublimation vapors, in particular Si vapor, generated during a run, in particular at least 50% (mass) or at least 80% (mass) or at least 90% (mass) or more than 99% (mass) or at least 99.9% (mass), from the crucible volume through the crucible housing back into the furnace volume.
The coating preferably withstands temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The coating preferably has one or more materials selected from a group of materials containing at least carbon, in particular pyrocarbon and vitreous carbon. This solution is advantageous as it prevents the leakage of Si vapor into the space surrounded by the inner surface of the filter.
The filter element preferably comprises an activated carbon block and/or one or more, in particular different, graphite foams, including those made of carbonized bread and/or rigid graphite insulation and/or flexible graphite insulation.
According to another preferred embodiment of the present invention, the filter element comprises a filter element member. The filter element preferably comprises filter particles and a binder. The filter particles preferably comprise carbon or consist of carbon material. The binder preferably holds the filter particles in fixed relative positions to each other. The filter particles preferably withstand temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. The filter particles preferably resist temperatures above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 4,000° C. The filter particles preferably withstands temperatures above 1700° C., in particular above 2,000° C., in particular up to or above 2,000° C., in particular at least or up to 3,000° C. or at least up to 3,000° C. or up to 3,500° C. or at least up to 3,500° C. or up to 4,000° C. or at least up to 4,000° C. This solution is advantageous because the solid filter element has no toxic materials. In addition, the solid filter element can be manufactured at low cost. The filter unit, in particular the filter element, is preferably a disposable unit or element.
According to a further preferred embodiment of the present invention, the binder comprises starch or wherein the binder comprises starch.
According to a further preferred embodiment of the present invention, the furnace system comprises a gas flow unit. The gas flow unit preferably has a gas inlet for conducting gas into the crucible unit and a gas outlet for discharging gas from the crucible unit into the furnace or through the furnace to the outside of the furnace. The gas inlet is preferably arranged upstream of the filter unit in the gas flow direction, in particular upstream of the receiving space in the gas flow direction, and wherein the gas outlet is arranged downstream of the filter unit in the gas flow direction. Thus, a gas inlet is preferably arranged in a transformation zone within the crucible unit. The transformation zone preferably also comprises the seed holder unit and the receiving space. A starting material may be transformed from a solid configuration to a vapor configuration, and from the vapor configuration to a solid target body. The starting material may be disposed within the receiving space and wherein the solid target body may be held by the seed holder unit. The solid target body is a crystal, in particular a SiC crystal. The gas introduced via the gas inlet preferably mixes with and/or reacts with the starting material in the vapor configuration and/or during solidification. The gas outlet is preferably located in a capture zone, comprising also the exit surface of the filter unit, wherein the gas composition in the capture zone is preferably free of Si vapor or has no Si vapor. The temperature in the capture zone is preferably below the solidification temperature of gaseous Si or Si vapor. This embodiment is advantageous because the crystal growth process can be manipulated. For example, it is possible to add one or more gases to dope the crystal. Additionally or alternatively, it is possible to modify, in particular accelerate, the vapor transport from the receiving space to the seed wafer 18 or crystal. Additionally or alternatively, the gas can be provided in a defined temperature or temperature range.
An inert gas, in particular argon, or a gas mixture, in particular argon and nitrogen, can be or is introduced into the crucible unit or into the crucible volume or into the conversion zone via the gas inlet.
The size of the crucible housing is configurable or changeable according to another preferred embodiment of the present invention. The crucible housing surrounds a first vo-lumen VI in a crystal growth configuration and the crucible housing surrounds a second vo-lumen VII in a coating regeneration configuration. The crystal growth configuration represents a configuration or setting that is present during growth of a crystal or during solidification of evaporated starting material on a seed wafer 18 or at a growth front of a crystal growing on the seed wafer 18. The regeneration configuration represents a setting that is present in the event that a seed holder unit is removed and no crystal growth is possible because no seed wafer 18 is present. In the regeneration configuration, the filter unit is preferably not part of the crucible unit and a lid disposed on top of the filter unit in the crystal growth configuration is preferably in contact with a sidewall portion of the crucible housing that is in contact with the lower end of the filter unit during the crystal growth configuration. The volume VI is preferably larger compared to the volume VII, wherein the volume VI is at least 10% or at least or up to 20% or at least or up to 30% or at least or up to 40% or at least or up to 50% or at least or up to 60% or at least or up to 70% or at least or up to 80% or at least or up to 100% or at least or up to 100% or at least or up to 120% or at least or up to 150% or at least or up to 200% or at least or up to 250% larger than the volume VII. This embodiment is advantageous because the crucible unit can be reconditioned after use, in particular after one run or after several runs, in particular up to or at least three, up to or at least five or up to or at least ten runs. Thus, the overall service life of the crucible unit is very long. Since the heating unit can also be used multiple times, a very cost-effective furnace apparatus is thus provided.
The housing preferably has at least one further wall element in the crystal growth configuration compared to the layer regeneration configuration. The further wall element is preferably a filter unit or the filter unit. In the layer regeneration configuration, the filter unit is removed. A lower housing wall member of the housing, which is in contact with the filter unit in the crystal growth configuration, and an upper housing wall member of the housing, which is in contact with the filter unit in the crystal growth configuration, are in contact with each other in the coating regeneration configuration. At least one seal is preferably disposed between the lower housing wall member and the upper housing wall member in the coating regeneration configuration. In the crystal growth configuration, at least one seal is preferably arranged between the filter unit and the upper housing wall element, and wherein at least one seal is preferably arranged between the filter unit and the lower housing wall element. This embodiment is advantageous, since in any configuration the leakage of gas or steam is prevented.
According to another preferred embodiment of the present invention, the crucible unit comprises one or at least one receiving space gas guide element in the coating regeneration configuration. The receiving space gas guiding element extends into the receiving space to guide gas into the receiving space. This embodiment is advantageous because the gas introduced during the coating regeneration configuration better contacts the surface of the receiving space.
According to another preferred embodiment of the present invention, the gas inlet is arranged in a conversion zone within the crucible unit. The conversion zone preferably comprises the seed holder unit and/or the receiving space. This embodiment form is advantageous because the flow of the vaporized starting material and/or the composition of the liquid flowing upward from the receiving space to the seed wafer 18 and/or the growing crystal can be modified.
The receiving space gas guiding element preferably rests at least partially on the respective gas distributing element, wherein the gas distributing element preferably holds the receiving space gas guiding element, in particular by means of a form-fit connection. This embodiment is advantageous because the installation can be carried out quickly and easily.
The receiving space gas guide element preferably has an annular or circular shape. This embodiment is advantageous because the amount of vaporized starting material better matches the amount of vaporized material that solidifies on the seed wafer 18 of the crystal, compared to another shape, such as a rectangular receiving space shape. The receiving space gas guide member preferably has carbon or is made of carbon and/or graphite.
According to a further preferred embodiment of the present invention, the first section of the growth conductor and the third section of the growth conductor form, in particular on the underside, a fourth section of the growth conductor and/or wherein the second section of the growth conductor and the third section of the growth conductor are arranged at an angle between 60° and 120°, in particular at an angle between 70° and 110°, in particular at an angle of 90°.
A growth plate gas guide member is preferably provided to guide gas to a surface on top of the third section of the growth guide member. The growth plate gas guide member preferably has an annular or circular shape. The growth plate gas guide member is preferably disposed on the upper or top wall portion of the housing. The growth plate gas guide element preferably has carbon or is made of carbon and/or graphite.
Thus, a method and a reactor or furnace apparatus or apparatus for PVT growth of SiC single crystals preferably comprises the following: providing a furnace volume capable of accommodating a crucible unit and heaters, and insulating and/or providing a crucible unit with a lid inside the vacuum chamber and/or with a seed holder seed holder integrated into or attached to the lid and/or with a SiC single crystal seed attached to the seed holder and/or with an axial heater positioned below the crucible unit, so that radially flat temperature isotherms can be generated in the growing crystal and/or placing source material in the crucible unit so that there is no source material between the axial heat source and the seed and/or generating a vacuum in the crucible unit, heating and sublimating the source material resp. of the SiC solid material (originating from the method according to the invention) and growing the crystal, in particular the SiC single crystal).
Further advantages, objectives and features of the present invention are explained with reference to the following description of accompanying drawings, in which the device(s) according to the invention are shown by way of example. Components or elements of the device according to the invention, which at least substantially correspond in the figures with respect to their function, can be marked with the same reference signs, whereby these components or elements do not have to be numbered or explained in all figures.
Individual or all representations of the figures described in the following are preferably to be regarded as construction drawings, i.e. the dimensions, proportions, functional relationships and/or arrangements resulting from the figure or figures preferably correspond exactly or preferably substantially to those of the device according to the invention or the product according to the invention or the method according to the invention.
The reference sign 854 indicates a mixing device or a mixer by which the source fluids and/or the carrier fluid can be mixed with one another, in particular in predetermined ratios. The reference sign 855 indicates an evaporator device or an evaporator by which the fluid mixture which can be supplied from the mixing device 854 to the evaporator device 855 can be evaporated.
The evaporated fluid mixture is then fed to a process chamber 856 or a separator vessel, which is designed as a pressure vessel. At least one deposition element 857 and preferably several deposition elements 857 are arranged in the process chamber 856, wherein Si and C are deposited from the vaporized fluid mixture at the deposition element 857 and SiC is formed.
The reference sign 858 indicates a temperature measuring device, which is preferably provided for determining the surface temperature of the deposition element 857 and is preferably connected to a control device (not shown) by data and/or signal technology.
The reference sign 859 indicates an energy source, in particular for introducing electrical energy into the separating element 857 for heating the separating element. The energy source 859 is thereby preferably also connected to the control device in terms of signals and/or data. Preferably, the control device controls the energy supply, in particular power supply, through the deposition element 857 depending on the measurement signals and/or measurement data output by the temperature measurement device 858.
Furthermore, a pressure holding device is indicated by the reference sign 860. The pressure holding device 860 can preferably be implemented by a pressure-regulated valve or the working pressure of a downstream exhaust gas treatment system.
The crucible lower housing 152 also includes a growth directing element 230 used to tune the heat field and vapor flow around the sides of the crystal 17. The crystal 17 grows on a seed wafer 18 that is attached to a seed holder 122. The seed holder 122 seals against the lower inner edge of a thick-walled tubular filter or filter unit 130. The lower crucible housing 152 seals against the lower outer edge of this filter 130. The filter includes filter grooves 22 to increase surface area for removal of excess SiC2 and Si2C sublimation vapors. The filter 130 also includes a filter outer surface coating 158, 164 on its inner and outer walls to minimize permeability to Si vapor.
The upper outer edge of the filter 130 seals against a crucible lid or filter cover 107 or a crucible upper housing 154, which in turn seals against a crucible vacuum outlet tube 174. The crucible vacuum outlet tube 174 is connected to an adjustable crucible vacuum outlet 26 which extends through the furnace upper housing 3. All sealing surfaces are provided with seals 20.
The crucible gas inlet tube 172, the crucible unit, the seed holder unit 122, the filter 130, the filter cover 107, and the crucible vacuum outlet tube 174 define a crucible volume 116. The temperature of the bottom of the gas distribution plate 190 is measured by a pyrometer along the lower pyrometer sight line 7. The temperature of the top of the seed holder 122 is measured with a pyrometer along the upper pyrometer sight line 28.
The oven 100 is operated under conditions of high temperature and low pressure. First, the oven volume 104 and crucible volume 116 are purged of air with an inert gas such as argon to prevent oxidation. Then, axial heating element 214 and radial heating element 212 are used to create a thermal field inside crucible volume 116 such that the temperature of the bottom of gas distribution plate 190 is typically in the range of 2,200-2,400° C. and the temperature of the crystal growth surface is typically in the range of 2,000-2. 200° C., with flat radial isotherms throughout crystal 17. The lower temperature of crystal 17 is achieved by having little or no insulation above seed crystal holder 122, allowing heat to pass through crystal 17 and seed crystal holder 122 and radiate to the water-cooled inner wall of upper furnace housing 3.
The pressure inside the crucible volume 116 during crystal growth is typically in the range of 0.1-50 Torr and is slightly lower than the pressure inside the furnace volume 104. This negative relative pressure inside the crucible volume 116 minimizes the leakage of sublimation vapors into the furnace volume 104.
Under the temperature and pressure conditions described, the starting material sublimates, releasing Si, SiC2, and Si2C vapors. The temperature gradient between the starting material 50 and the cooler crystal 17 drives these sublimation vapors toward the crystal 17, where the SiC2 and Si2C vapors become incorporated into the crystal 17 and lead to its growth. Excess SiC2 and Si2C vapors form polycrystalline deposits on the sides of the seed holder unit 122, the lower surfaces of the filter 130, and the upper inner walls of the crucible unit. In one embodiment, a low flow rate of Argon and/or nitrogen convectively assists in the thermally driven diffusion of the sublimation vapors to the crystal 17. In another embodiment, a low flow rate of nitrogen is added to dope the crystal 17 and modify its electrical properties. The gas flows radially outward from the gas distribution plate 190 and mixes with the sublimation vapors rising from the starting material 50.
All components within the furnace volume 104 are made of materials that are compatible with the operating temperatures and pressures and that do not contaminate the crystal 17. In one embodiment, the bottom insulation 8 and side insulation 9 may be made of graphite felt or graphite foam. The axial heating element 214 and the radial heating element 212 may be made of graphite, as may the crucible legs 13 and the crucible gas inlet tube 172.
The crucible base 152, the gas distribution plate or gas distribution plate 190, the wax-tumor conducting element 230, and the seed holder or seed holder 122 can be made of materials that also minimize permeation of the Si vapor. These materials include glassy infiltrated graphite, glassy carbon, pyrocarbon coated graphite, and tan-talkarbide ceramics and coatings. While graphite has a permeability of 10-1 cm/s, glassy infiltrated graphite has a permeability of 10-3 cm/s, glassy carbon has a permeability of 10-11 cm/s, and pyrocarbon coated graphite has a permeability of 10-12 cm/s. The Si vapor generated from the sublimating feedstock 50, which does not significantly permeate these components or is embedded in the crystal 17, passes between the growth guide element 230 and the crystal 17 or the growing crystal and enters the filter 130.
The filter 130 comprises a porous material having a large surface area. In one embodiment, this material is activated carbon powder with a unit surface area of about 2,000 m2/g bonded with a high temperature binder such as carbonized starch. The inner and outer walls of the filter 130 have filter outer surface coatings 158, 164 made of a material that minimizes permeation of Si vapor. In one embodiment, this material is a glassy carbon coating. Since the Si vapor does not substantially permeate the outer surface coatings 158, 164 of the filter, the Si vapor rises further into the filter 130 and eventually condenses in the upper portion of the filter 130 due to the lower temperatures.
Thus, the present invention may relate to a method or furnace device or apparatus for PVT growth of single crystals, particularly SiC single crystals, having multiples or all of the features or steps listed below:
Providing a furnace housing capable of housing a crucible unit, heating elements and insulation, the furnace housing also having an adjustable lower crucible gas inlet tube and an adjustable upper crucible vacuum outlet tube. Providing a crucible unit and a growth guide, both of which are substantially impermeable to Si vapor. Loading the crucible unit with SiC source material.
Providing a lid assembly for the crucible unit, comprising: A large surface area annular porous filter for trapping Si sublimation vapors, having outer and inner vertical tubular surfaces coated with a coating that is substantially impermeable to Si vapor and having upper and lower outer circumferential sealing shoulders; a seed holder. A filter comprising: a plurality of filter elements coated with a coating that is substantially impermeable to Si-vapor and that has upper and lower outer circumferential sealing shoulders; a seed holder that is also substantially impermeable to Si-vapor and that is attached to and seals the lower inner opening of the filter; a SiC single crystal seed attached to the seed holder; a filter cap that seals against the upper outer circumferential sealing shoulder of the filter and that also seals against the vacuum outlet tube of the crucible.
Raising the crucible gas inlet tube and lowering the crucible vacuum outlet tube so that the crucible gas inlet tube presses and seals against the crucible unit, the crucible unit presses and seals against the lower outer circumferential sealing shoulder of the filter, the upper outer circumferential sealing shoulder of the filter presses and seals against the filter cap, and the filter cap presses and seals against the crucible vacuum outlet tube. Providing seals at all seal interfaces to improve the gas tightness of the seal interfaces.
Creating an inert vacuum in the crucible volume defined by the crucible unit and filter assembly. Creating an inert vacuum in the furnace volume via a separate furnace gas inlet and a separate furnace vacuum outlet.
Maintaining the crucible volume at a lower pressure than the furnace volume. Heating and sublimation of the starting material.
Activating the flow of carrier and dopant gases, if required, into the crucible unit. Grow the crystal while confining the Si vapor in the filter, preventing the Si vapor from penetrating and coating the crucible unit, heating elements, insulation, and any other components in the furnace volume.
Therefore, a PVT furnace is preferably provided for the production of SiC single crystals in which the sublimating Si vapors are prevented from penetrating the crucible housing wall, heating elements, and insulation. First, the penetration of Si vapor into these components changes their thermal properties, making it difficult to grow a good crystal because the thermal field is not stable. Second, the physical structure of these components is eventually destroyed by the Si. Therefore, the present PVT furnace avoids such infiltration.
This is preferably achieved by making the walls, in particular the inner walls of the crucible housing, impermeable to Si vapor and/or by removing the Si vapor from the gas mixture inside the crucible volume, in particular by adsorption and condensation or by deposition on a surface, which surface may be a fil-ter. This surface may be located, for example, inside the crucible unit or outside the crucible unit, but inside the furnace or even outside the entire furnace unit. In case this surface is located outside the crucible unit, fluid communication is preferably provided by means of at least one pipe or pipe system to functionally connect this surface to the crucible volume.
In this way, heating elements can be introduced into the furnace volume and generate the thermal field necessary for the growth of large diameter boules without worrying about the heating elements being destroyed by the Si vapor. In this way, the life of the insulation and the crucible housing can be drastically extended. In addition, since all of these materials have stable thermal properties, a higher yield of boules meeting specifications is possible.
In principle, the present invention also relates to the introduction of SiC solid-state material produced in accordance with the invention, in particular 3C-SiC, into a furnace apparatus 100, in particular a furnace apparatus 100 for growing crystals, in particular for growing SiC crystals, in particular monocrystalline crystals. The furnace apparatus comprises a furnace unit 104, wherein the furnace unit 102 comprises a furnace housing 108, at least one crucible unit, wherein the crucible unit is arranged within the furnace housing 108, wherein the crucible unit comprises a crucible housing 110, wherein the housing 110 comprises an outer surface 112 and an inner surface 114, wherein the inner surface 114 at least partially defines a crucible volume 116, wherein a receiving space 118 for receiving a starting material 50 is disposed or formed within the crucible volume 116, wherein a seed holder unit 122 for holding a defined seed wafer 18 is disposed within the crucible volume 116, and at least one heating unit 124 for heating the starting material 50, wherein the receiving space 118 for receiving the starting material 50 is disposed at least partially between the heating unit 124 and the seed holder unit 122.
Further, the present invention relates to a reactor 100, and more particularly to a reactor 100 for crystal growth, and more particularly for SiC crystal growth. The reactor comprises a furnace 102, the furnace 102 comprising a furnace chamber 104, at least one crucible, the crucible being arranged within the furnace chamber 104, the crucible comprising a frame structure 108, the frame structure 108 comprising a housing 110, the housing 110 comprising an outer surface 112 and an inner surface 114, the inner surface 114 at least partially forming a crucible chamber 116, wherein a receiving space 118 for receiving a source material 50 is disposed or formed within the crucible chamber 116, wherein a seed holder unit 122 for holding a defined seed wafer is disposed within the crucible chamber 116, and at least one heating unit 124 for heating the source material 50, wherein the receiving space 118 for receiving the source material 50 is disposed at least partially between the heating unit 124 and the seed holder unit 122.
Thus, the present invention relates to a method for producing a preferably elongated SiC solid, in particular of poly-type 3C. The method according to the invention preferably comprises at least the following steps:
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 215 755.3 | Dec 2020 | DE | national |
This application is a U.S. national phase of International Application No. PCT/EP2021/085393 filed Dec. 13, 2021, which claims priority to German Application No. 10 2020 215 755.3 filed Dec. 11, 2020, both of which are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/085393 | 12/13/2021 | WO |
