Insulation for high temperature applications

Abstract

The present invention relates to an insulating material (11) for high temperature applications, in particular for use in an apparatus for producing single crystals, in particular for a system (10) for crystal growth, said insulating material comprising at least partly, preferably entirely, tantalum carbide.

Description

[Background technology]

[0001] The invention relates to insulation for high temperature applications and the manufacture of insulation for high temperature applications, in particular for use in apparatus for producing single crystals, in particular for systems for crystal growth.Furthermore, the invention relates to apparatus for producing single crystals, in particular for systems for crystal growth, and to the use of materials or raw materials that are suitable in insulation for high temperature applications, in particular for apparatus for producing single crystals, in particular for systems for crystal growth.

[0002] Thermal insulation materials of the above-mentioned type are known from the prior art and are typically used in devices for producing single crystals, in particular in systems for crystal growth. Generally, such insulation materials are realized by felts made of graphite, and due to the harsh conditions prevailing in systems for crystal growth in which such insulation materials are used, in particular the effects of high temperatures, the insulation materials typically have a relatively short operating or service life. Thus, the insulation materials or felts known from the prior art typically have to be replaced after each operation of the system for crystal growth in which they are used or after each process of crystal production, which in particular leads to an increase in the operating costs of the system for crystal growth.

[0003] When a felt made of graphite is used as insulation in an apparatus for producing single crystals or in a system for growing crystals, the problem is further complicated by the fact that in the case of an induction heating apparatus for producing single crystals or in the case of a system for growing crystals, the electromagnetic field generated by the coil of such an apparatus or system for growing crystals, provided for heating, not only couples into the crucible of such an apparatus or system for growing crystals, typically made of graphite, but also into the felt, typically located between the coil and the crucible, which leads to additional operating costs for the apparatus or system for growing crystals.

[0004] Furthermore, due to the insulation made of graphite or carbon, there is a risk of carbon being uncontrollably mixed into the running process of crystal production, which may lead to contamination of the crystals to be produced in the process, e.g., crystals made of silicon or silicon carbide.

[0005] Moreover, a drawback of the insulation materials known from the prior art is that they do not maintain their insulating effect during the process of crystal production, which can typically take up to a week, but rather they steadily decrease in terms of insulating effect, thus further increasing the operating costs of the system for crystal growth in which they are used. Summary of the Invention

[0006] The object of the present invention is therefore to propose an insulation for high temperature applications in an apparatus for producing single crystals, in particular for crystal growth, in a system with insulation, a material or raw material suitable for insulation for high temperature applications, and a method for producing insulation for high temperature applications, which overcomes the drawbacks known from the prior art.

[0007] This object is achieved by an insulation material having the features of claim 1, a device having the features of claim 11, a use having the features of claim 13 and a method having the features of claim 14.

[0008] The thermal insulation material for high temperature applications according to the invention, in particular for use in an apparatus for producing single crystals, in particular in a system for crystal growth, consists at least partly, preferably completely, of tantalum carbide.

[0009] The invention is therefore based on the idea that the insulation consists at least partly, preferably entirely, of tantalum carbide, which is substantially more heat-resistant than graphite and is therefore significantly less affected by the harsh conditions prevailing in the crystal growth system in which it is used, in particular by high temperatures. As a result, the service life or operating life of the insulation according to the invention can be significantly increased, so that the insulation according to the invention can be used over several crystal production processes. In this case, it is no longer necessary to replace the insulation after each single crystal production. In addition, the insulation according to the invention maintains its insulating effect during the crystal production process, which can typically take up to one week, and moreover, the insulating effect of the insulation does not change during the process or during a series of processes. Thus, the temperature distribution does not change during the process, which can be controlled more easily and less rejects occur. As a result, an apparatus for producing single crystals, in particular a crystal growth system, having the insulation according to the invention can be operated more cost-effectively. In addition, the insulation material according to the invention itself is so improved in terms of thermal insulation effect that a system for crystal growth having the insulation material according to the invention can be operated in a more energy-efficient manner.

[0010] Moreover, there are two more important advantages if the insulation material consists entirely of tantalum carbide. On the one hand, the operating costs of the crystal growth system can be further reduced, since the electromagnetic field generated by the coil of the crystal growth system, which is provided for induction heating, does not substantially couple with the insulation material according to the invention at the frequency / frequency group of the electromagnetic field at which it couples with the graphite crucible of the crystal growth system. On the other hand, by using the insulation material according to the invention, which consists entirely of tantalum carbide, the uncontrollable mixing of carbon into the running process of crystal production can be prevented, so that crystals consisting of, for example, silicon or silicon carbide can be produced with high purity.

[0011] In one embodiment of the invention, the thermal insulation material may be obtained from a fibrous element having fibers made of carbon, which are at least partially, preferably completely, converted into tantalum carbide by a chemical vapor reaction, so that the thermal insulation material can be produced in a particularly simple and cost-effective manner, since no additional steps are required for its production.

[0012] In an alternative embodiment of the invention, the thermal insulation material may be obtained from a fibrous element having fibers made of carbon, in which case the fibrous element may be infiltrated with pyrolytic carbon, in which case the pyrolytic carbon may be at least partially, preferably completely, converted into tantalum carbide after infiltration by chemical vapor reaction. The fibers may remain in the chemical vapor reaction in which only the pyrolytic carbon may be converted into tantalum carbide, which may then advantageously protect the remaining carbon fibers. Thus, the thermal insulation material may be formed to be particularly stable.

[0013] Advantageously, the infiltration can be carried out by chemical vapor infiltration (CVI). In this case, pyrolytic carbon can infiltrate the fibrous element and at least partially, preferably completely, fill the spaces between the fibers and completely surround the fibers. At the same time, the fibrous element can be intended to be covered on the surface only with pyrolytic carbon by chemical vapor deposition (CVD), thereby forming a surface film formed by pyrolytic carbon. Furthermore, said surface film can be intended to be converted, partially or completely, into tantalum carbide by chemical vapor reaction.

[0014] In addition, it may be intended that the carbon is at least partially, preferably completely, converted to tantalum carbide by a chemical vapor reaction. In other words, the carbon may be partially or completely converted to tantalum carbide along with the pyrolytic carbon, so that the insulating material may consist partially or completely of tantalum carbide.

[0015] Alternatively, the carbon may not be intended to be converted to tantalum carbide by the chemical vapor reaction, in which case the fibers made of carbon remain in the chemical vapor reaction.

[0016] As a result, the carbon can be burned off by temperature treatment after carrying out the chemical vapor reaction. In this case, the insulation can have cavities or hollow fibers, so that the insulating effect of the insulation can be further improved. In this case, the insulation does not contain carbon or graphite that is mixed in an uncontrollable manner in the process of crystal production. In addition, since the insulation does not contain carbon or graphite, the behavior of the insulation in an electromagnetic field changes at different frequencies or different frequency groups of the electromagnetic field, as long as the electromagnetic field is coupled to the insulation completely made of tantalum carbide. If the insulation is then used in a system for crystal growth with a crucible made of graphite, the insulation can then be placed between the crucible and a coil that generates an electromagnetic field, and the frequency can be selected so that the electromagnetic field is coupled to the crucible, whereby eddy currents are formed in the crucible and the crucible can be heated. However, since the electromagnetic field does not substantially couple with the insulation at that frequency, the formation of eddy currents in the insulation or heating of the insulation is strongly suppressed and the system for crystal growth can be operated in a more energy-efficient manner.

[0017] Advantageously, a tantalum halide may be used as a reactant gas for the chemical vapor reaction. For example, tantalum chloride, tantalum iodide, tantalum bromide or tantalum fluoride may be used as the reactant gas. In this case, the fiber member may be placed in a treatment chamber to which a reactant gas may be supplied. By setting the correct process parameters, in particular the temperature in the treatment chamber or the pressure in the treatment chamber and / or the rate at which the reactant gas may be supplied into the treatment chamber, the chemical vapor reaction or reaction process may be controlled and the pyrolytic carbon and / or carbon may be converted into tantalum carbide, partially or completely, according to the selection.

[0018] In an embodiment of the present invention, the fibrous member may consist of a woven fabric, a non-crimped fabric, a non-woven fabric, and / or a felt. The fibers may thus be present in the form of a woven fabric, a non-crimped fabric, a non-woven fabric, and / or a felt.

[0019] Advantageously, the insulation or fibrous element may have a defined geometric shape. In this case, the fibrous element may be treated before or after possible infiltration with pyrolytic carbon or before the chemical vapor reaction. It is also conceivable to form the insulation to have a desired geometric shape after the chemical vapor reaction. For example, the fibrous element or insulation may have a cylindrical shape.

[0020] The device according to the invention for producing single crystals, in particular a system for crystal growth, comprises an insulation according to the invention. For further details on the advantageous effects of the device according to the invention, reference is made to the description of the advantages of the insulation according to the invention. Further advantageous embodiments of the device are evident from the description of the features of the dependent claims with reference to claim 1.

[0021] The device can be realized for the production of single crystals by sublimation of silicon carbide in powder form or by pulling from a crucible made of silicon. For example, single crystals made of silicon carbide can be produced by sublimation by physical vapor transport. Starting from the diameter of a seed crystal, single crystals can be produced with diameters of up to 25 mm (3H-SiC), 50 mm (4H-SiC), 75 mm (6H-SiC), up to 100 mmm, up to 200 mm, up to 300 mm or more. Alternatively, single crystals can be produced by pulling molten silicon from a crucible using the Czochralski method or the zone melting process.

[0022] According to the invention, tantalum carbide is used in insulation for high-temperature applications, in particular in an apparatus for producing single crystals, in particular in a system for crystal growth. In other words, tantalum carbide is proposed as a material or raw material suitable for insulation for high-temperature applications. In general, the porous body made of tantalum carbide may be used for other suitable purposes, for example as a filter body or similar. Thus, the use of the porous material made of tantalum carbide is not necessarily limited to insulation for high-temperature applications. For further details on the advantageous effects of the use according to the invention, please refer to the description of the advantages of the insulator according to the invention. Further advantageous embodiments of the use are evident from the description of the features of the dependent claims with reference to claim 1.

[0023] In the method according to the invention for producing a thermal insulation for high-temperature applications, in particular for use in an apparatus for the production of single crystals, in particular for a system for crystal growth, the thermal insulation consists at least partly, preferably entirely, of tantalum carbide. For further details on the advantageous effects of the method according to the invention, please refer to the description of the advantages of the insulator according to the invention. Further advantageous embodiments of the method are evident from the description of the features of the dependent claims with reference to claim 1. [Brief description of the drawings]

[0024] In the following, preferred embodiments of the invention will be explained in more detail with reference to the accompanying drawings. [Figure 1] 1 shows a system for growing crystals according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The figure shows a system 10 according to the invention for growing crystals, comprising an insulation 11 according to the invention, a crucible 12 made of graphite, which contains powder 13 made of silicon carbide and a coil 14 for inductive heating of the crucible 12. The insulation 11 is arranged between the coil 14 and the crucible 12. Furthermore, the system 10 for growing crystals comprises a crucible lid 15, on whose underside 17 a seed crystal 18 is arranged. The seed crystal 18 serves as a crystal nucleus on which a crystal 16 can form. For this purpose, silicon carbide in the form of a powder is heated in the crucible 12 to 1500°C-3000°C, preferably 2200°C-2500°C, so that it sublimes, i.e. becomes gaseous. The gaseous silicon carbide crystallizes on the seed crystal 18 or on the crystal 16. The crystal 16 grows until the powder 13 is exhausted.

Claims

1. A thermal insulation material (11) for high temperature applications for use in an apparatus for producing single crystals, comprising: A fiber member having an internal space; tantalum carbide filling the spaces in the fibrous member; The insulation material comprises:

2. The space is free of pyrolytic carbon. The insulation material of claim 1.

3. The fiber member is made of a woven fabric, a non-shrink fabric, a non-woven fabric, and / or a felt. The heat insulating material according to claim 1 or 2.

4. The insulation material (11) or the fibrous element is characterized in that it has a defined geometric shape, The heat insulating material according to any one of claims 1 to 3.

5. An apparatus for producing single crystals, said apparatus comprising a thermal insulation material (11) according to any one of claims 1 to 4. Device.

6. Use of tantalum carbide in a thermal insulation material (11) for high temperature applications for use in an apparatus for producing single crystals, comprising: The heat insulating material includes a fibrous member having an internal space, filling the spaces of the fiber member with the tantalum carbide; Use of tantalum carbide.

7. A method for producing an insulating material (11) for high temperature applications for use in an apparatus for producing single crystals, comprising the steps of: A method for manufacturing a fiber member, comprising: permeating a fiber member having fibers made of carbon with pyrolytic carbon; converting the pyrolytic carbon to tantalum carbide by a chemical vapor phase reaction after said infiltration; A method for producing an insulating material (11) comprising:

8. converting the carbon to tantalum carbide by a chemical vapor reaction. A method for manufacturing an insulating material (11) according to claim 7.

9. The infiltrating is performed by chemical vapor infiltration (CVI). A method for manufacturing an insulating material (11) according to claim 7 or 8.

10. Further comprising subjecting the chemical vapor reaction to a temperature treatment to burn off the carbon. A method for manufacturing an insulating material (11) according to any one of claims 7 to 9.

11. further comprising using a tantalum halide as a reactant gas in the chemical vapor reaction. A method for manufacturing an insulating material (11) according to any one of claims 7 to 10.

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