PVT method and apparatus for process-safe production of single crystals.

Abstract

PVT method and apparatus for process-safe production of single crystals. To allow reactive gases such as hydrogen to be used as process gases in the PVT process, certain safeguards are required to ensure that the process can be performed reliably. The apparatus for performing the PVT process consists of a highly heatable growth cell placed within a process chamber whose walls are made of a heat-resistant material, typically quartz glass. The process chamber is filled with hydrogen through an inlet valve. The heating device consists of an induction coil that surrounds the process chamber at the level of the growth cell, heating the growth cell to temperatures in excess of 2,000°C and up to 2,400°C. The use of reactive gases poses problems in the event of damage to the chamber walls of the process chamber, which cannot be completely eliminated, and the reactive gases can mix with the ambient air to form ignitable gas mixtures that can quickly ignite in hot parts of the apparatus. The process chamber is therefore surrounded by a safety container filled with an inert gas.

Description

[Technical Field]

[0001] The present invention relates to a PVT method for process-safe production of single crystals and an apparatus comprising a highly heated growth cell, a process chamber in which the growth cell is located, and a heater around the process chamber for heating the growth cell. The growth cell can be introduced with source material and seeds, the process chamber can be filled with process gas, and the growth cell can be heated to cause the source material to sublimate and re-sublimate on the seeds. [Background technology]

[0002] Background and Overview of the Invention In industrial environments, the so-called physical vapor transport (PVT) process is considered the standard method for the production of single-crystal silicon carbide (SiC) crystals. The source material is usually a powder containing many different crystals. Alternatively, bulk crystals can be used. The high-temperature chemical vapor deposition (HT-CVD) process is known as an alternative process. In the PVT process, crystal growth is typically performed in a growth cell made of graphite by sublimation of the SiC feedstock and crystallization on a predefined SiC seed at temperatures above 2,000 °C. The driving force for crystal growth is a temperature gradient applied to the growth cell by a heating device. Common methods for heating PVT devices use resistance or induction heaters. Induction heating is a vacuum-sealed process. The growth cell (hot zone) of the chamber is surrounded by a non-conductive material, usually (quartz) glass. Process gases are contained or introduced into the process chamber and are used to, among other things, influence the crystal growth. The process chamber can be single or double-walled and can be air- or water-cooled. Commonly used process gases are argon, helium, nitrogen, hydrogen, and other gases for target doping. Process pressures range from vacuum to atmospheric pressure. In typical processes for producing doped SiC single crystals, hydrogen is not used or is used only in small concentrations.

[0003] Due to its wide bandgap and high thermal conductivity, SiC single crystals are being produced for a wide range of applications in semiconductor technology. The basic process for producing SiC single crystals has been extensively described, see for example US2011 / 0300323A1. According to this, an inert gas is used as the process gas, which is not problematic from a safety point of view.With regard to the state of the art, reference is also made to EP 0 811 708 A2, US 2012 / 0086011 AA1, GB 772,691, DE 60 2004 001 802T2 and EP 3 760 765 A1.

[0004] The intellectual starting point of the present invention, and one of its objectives, is to enable, inter alia, a process for controlling the introduction of doping into a target or for producing undoped SiC single crystals. With respect to this starting point, within the scope of the present invention, a process is developed that ensures better results than the prior art and / or a safer process that is more cost-effective than known processes. If necessary, this can be carried out using reactive gases, i.e., flammable and / or reactive (possibly toxic) gases, such as hydrogen as process gas, at concentrations greater than 5% and up to 100%.

[0005] In this process, reactive gas molecules, such as hydrogen atoms, attach to the surface of the growing single crystal but are immediately replaced by subsequent sublimable components of the feedstock. In this case, the reactive gas molecules, such as hydrogen atoms, temporarily function as placeholders, resulting in the formation of a crystal lattice with few or no defects. The reactive gas molecules may react with other process gases, source materials, or even hot-zone materials, forming other gas species that enter the process gas atmosphere and attach, at least temporarily, to the crystal. Possible reactive gases, such as silane, methane, and propane, provide elements such as silicon and carbon that are incorporated into the crystal. Overall, adding reactive gases can affect defect density (desirable or undesirable). However, the exact effect depends on numerous parameters and their interactions. The addition of reactive gases is intended to influence crystal growth. Summary of the Invention [Problem to be solved by the invention]

[0006] It is therefore an object of the present invention to provide an apparatus and method that allows for improved or modified crystal growth.

[0007] In one aspect of the present invention or in a further development of the present invention, it can be considered as an aspect of the object to provide an apparatus and method in which reactive gases can be used to improve crystal growth.

[0008] In yet another aspect or further development of the invention, the object is to provide an apparatus and method that can provide improved crystals with less effort or lower(er) cost.

[0009] However, the use of reactive gases, such as those containing hydrogen or other reactive elements, poses potential hazards when carrying out the process. For example, the reactive gas may be flammable or pyrophoric and / or toxic. In the case of hydrogen, for example, an oxyhydrogen reaction may occur with oxygen in the air, which is why hydrogen is referred to as a reactive gas in the context of this specification. Other examples of reactive gases currently under consideration include, in addition to hydrogen, precursors containing carbon and silicon, or hydrocarbons and their derivatives (e.g., silane, methane, propane, etc.).

[0010] Furthermore, in today's equipment, the process chamber is typically made of fused silica, which is inherently brittle and prone to breakage. However, the use of fused silica is particularly preferred because it can withstand the high temperatures of the growth cell and does not block the electromagnetic fields of the induction coils or the radiant heat of the resistance heaters. Similarly, a combination of induction and resistance heaters can be provided. For example, auxiliary heaters in the floor or ceiling can be designed as resistance heaters, and the main heater can be designed as an induction heater. In principle, however, the safety requirements, at least in the case of fused silica, apply to a certain extent to other construction materials for providing the process chamber in a similar manner.

[0011] However, if the process chamber is damaged or leaks, for example if the quartz glass breaks, the hydrogen will mix with the oxygen in the environment, producing oxyhydrogen gas, which will be ignited by the heating device (the high-temperature components of the hot zone, usually graphite parts inside the process chamber) and explode. Therefore, when using reactive gases, known adaptations cannot be used to safely carry out the process.

[0012] The reactive gases (e.g., hydrogen) referred to herein should not be equated with known doping gases, which are typically not used in the concentrations desired herein and / or are not flammable or reactive in the sense used herein. The doping gas purges the crystal's surroundings, so the process takes place entirely within the process chamber. For example, in this context, the process chamber can also be purged with an inert gas such as argon to directly modify the PVT process. Generally, a dopant gas is introduced into a crystal or crystal structure—hence the name "dopant gas"—to affect the crystal's physical and / or chemical properties (such as electrical conductivity). In other words, the molecules or components of the dopant gas subsequently form integral components of the crystal. Such molecules or components of the dopant gas remain within the crystal and can subsequently be detected.

[0013] In contrast, reactive gases such as hydrogen can affect crystal growth and dopant incorporation as reactive components of a gas atmosphere, but dopant gases are not introduced into the crystal to affect its physical and chemical properties. Due to the hazards of reactive gases, such as the potential for fire, combustion, deflagration, and even poisoning, reactive gases have not previously been considered for use in improving crystal growth. In any case, as mentioned above, the safety aspects of handling reactive gases in this environment have not been fully considered. Furthermore, the reactive gases used are not, strictly speaking, sublimable materials. In a typical PVT process, the sublimable material is SiC powder. Variations of the traditional PVT process, such as HT-CVD, use hydrogen as a carrier gas to transport the actual raw material source, typically a gaseous C- or Si-containing precursor. Thus, the gas acts as a carrier gas, i.e., a transport medium for the precursor and dopant. Dopants are solid, liquid, or gaseous elements or compounds, typically containing nitrogen, phosphorus, aluminum, boron, or vanadium.

[0014] In the context of further developments and improvements, this specification describes and identifies various aspects of a containment vessel enclosing a process chamber, developed in-house by applicant PVA TePla. It further contemplates providing a protective atmosphere, e.g., of inert gas, in the region between the process chamber and the vessel wall. One particular purpose of the containment is to prevent or contain an explosive gas mixture in the event of damage, e.g., a rupture, of the process chamber.

[0015] To ensure process reliability, the equipment performing the process can be placed inside a vacuum cell. However, such cells must be completely vacuum-tight and are therefore relatively complex to manufacture, as numerous feedthroughs are required to supply the equipment with electricity, gas, and, if necessary, coolant, each of which must be prepared to be vacuum-tight. Furthermore, vacuum cells are virtually impossible to maintain or repair, or they must first be opened at great expense and then reclosed at great expense after the work or modifications are completed.

[0016] On the other hand, it would be advantageous to present a PVT process for the reliable production of single crystals that can be performed in equipment that can be manufactured with little effort and / or low cost.

[0017] The problem is solved by the invention as defined in the independent claims. The dependent claims show further and preferred embodiments of the invention. [Means for solving the problem]

[0018] To solve one, several, or all of the stated aspects of the problem, a PVT method for process-safe production of single crystals in an apparatus is presented, the apparatus comprising a process chamber containing a highly heatable growth cell and a heating means for heating the growth cell, the growth cell adapted to contain a source material and a seed, the process chamber being fillable with a process gas, and the growth cell being heatable. The apparatus also comprises a containment vessel surrounding the process chamber, the containment vessel preferably enclosing the process chamber in an airtight or substantially airtight manner. The containment vessel thus has a vessel wall in the circumferential direction, and a space is created between the vessel wall of the containment vessel and the process chamber. In other words, the area extending from the inside of the vessel wall to the outside of the process chamber can be referred to as an intermediate space. For example, if the process chamber is circular and the containment vessel is also circular, the clearance space defines a hollow annular segment (considered to be a plane) or hollow cylinder of inner radius r (e.g., corresponding to the process chamber wall), outer radius R (e.g., corresponding to the containment vessel wall), height h (e.g., measured from the base to the lid) and wall thickness b.

[0019] The method presented here includes providing a protective atmosphere to the gap space, thereby filling the gap space with the protective atmosphere, and providing a process gas into the process chamber. The process gas can, for example, include or consist of a reactive gas. In other words, the process first fills the gap space with the protective atmosphere, e.g., to completely replace as much as possible any air that may have previously been present there, and specifies that a further process sequence is initiated only when the containment vessel is ready for use (and this is output, e.g., as a signal) after being filled with the protective atmosphere.

[0020] In principle, the process gas can be introduced into the process chamber before the containment vessel is operational, provided that the process chamber is not yet hot enough to prevent ignition of the process gas in the event of a leak in the process chamber. Similarly, if the process gas or at least the reactive gas has not yet been introduced, the process chamber can be heated, for example, to the operating temperature, before the containment vessel is operational. The transition between providing the containment vessel and starting operation of the process chamber can be smooth. However, it is generally preferred that the provision of the containment atmosphere in the gap space be completed before the process gas is introduced into the process chamber and / or before the growth cell is heated to the deployment temperature. In other words, it is preferred that the provision of the process gas in the process chamber be completed after the gap space has been filled with the protective gas. Therefore, initially filling the gap space with the protective atmosphere—particularly initially filling the gap space with the protective atmosphere or filling the gap space with the first protective atmosphere—preferably also includes replacing the air present in the gap space before the start of sublimation of the source material.

[0021] Therefore, it is particularly advantageous to fill the containment vessel at the latest when sublimation of the source material occurs, since high temperatures are then present that can ignite the highly reactive gas. For safety reasons, it is advantageous to flood the containment vessel before the reactive gas is introduced into the process chamber.

[0022] In the event of damage to the process chamber, such as a rupture, this configuration ensures that the reactive gas in the process chamber will not explode even at high temperatures because it will mix with an inert gas, for example, to form a non-explosive gas mixture within the protective atmosphere of the containment vessel. This safety measure is particularly important when the reactive gas is flammable or prone to deflagration, such as hydrogen.

[0023] The method further includes heating the growth cell with a heating device so that the sublimable material sublimes and re-sublimes into the seeds. Preferably, the heating of the growth cell is performed from all radial sides. To this end, the heating device can surround the process chamber in an annular shape.

[0024] When providing a protective atmosphere in the gap space, it is preferable to set a positive pressure relative to the ambient pressure. For example, the overpressure in the protective vessel (containment vessel) can be set to at least 1 mbar above ambient pressure, preferably 3 mbar or more, and more preferably 5 mbar or more above ambient pressure. When a positive pressure relative to ambient is set in the protective vessel, there is little or no gas from the ambient. This ensures, for example, that no oxygen enters the protective vessel. If process gas were to be discharged into the protective vessel, a reaction could occur there.

[0025] Containment vessels are particularly easy to implement if they are constructed in such a way that gas loss to the outside is particularly small, i.e., they are only approximately gas-tight. This makes the design of the containment vessel more cost-effective, since particularly high requirements for gas-tightness do not have to be considered and undesirable reactions of reactive gases outside the process chamber do not occur. For example, the allowable leakage rate of the containment vessel may exceed 0 l / min. Therefore, particularly due to design choices and geometrical shapes, it may be advantageous and not problematic for cost reasons to allow a leak rate in the range of 0 ≤ leak rate ≤ 5 l / min or 0 ≤ leak rate ≤ 30 l / min. For example, the allowable leak rate could be 2 ml / min, less preferably 5 ml / min, even less preferably 10 ml / min, even less preferably 50 ml / min, or even 100 ml / min. On the other hand, for economic reasons and possibly workplace safety reasons, it does not make sense to allow a containment vessel to have a leak rate that is too high. For example, it may be desirable to limit the leak rate to less than 30 l / min, preferably 10 l / min, more preferably 4 l / min, even more preferably 1 l / min, even more preferably 500 ml / min, and even more preferably less than 150 ml / min. The goal is to achieve a leak rate in the range of 2 ml / min to 50 ml / min, preferably 10 ml / min to 20 ml / min.

[0026] For example, the containment vessel may have a total volume greater than 50 L, preferably greater than 100 L, and / or a total volume less than 500 L, preferably less than 250 L. In other words, the leak rate relative to the total volume may be set to a value in the range of 1% or less, preferably 2% or less, more preferably 5% or less per minute.

[0027] To maintain a protective atmosphere, an overpressure can be increased and / or maintained within the containment vessel, for example by supplying an inert gas to compensate for gas losses. The overpressure prevents atmospheric oxygen from entering the containment vessel from the outside. Therefore, the relative overpressure within the containment vessel can be maintained by a pressure control system, for example, in a range of 1 mbar or more, preferably 3 mbar or more, more preferably 5 mbar or more above ambient pressure, and 50 mbar or less, preferably 30 mbar or less above ambient pressure. However, a completely airtight containment vessel with a leak rate of 0 ml / min or a leak rate that is not measurably low can also be included, and an overpressure can be maintained within the containment vessel.

[0028] To ensure that the air from the containment vessel is displaced as completely as possible, the present disclosure further provides for introducing a first inert gas into the containment vessel to flood the containment vessel. The first inert gas can be more dense than air, so that it flows into the lower region of the containment vessel and displaces the air upward. For this purpose, for example, a closable outlet at the top of the containment vessel can be left open until the air escapes.

[0029] Preferably, the protective atmosphere comprises an inert gas such as argon, which, due to its density, collects at the bottom of the containment vessel and slowly displaces the air upward without mixing with it. Other examples of protective atmospheres currently available in an economically feasible manner include xenon, nitrogen, or carbon dioxide. In principle, a protective atmosphere can include any fluid, individually or in a mixture, that can provide a protective function of neutralizing reactive gases and / or preventing adverse effects such as deflagration in the event of excessive or unacceptable leakage from the process chamber. Protective atmospheres can also exist in liquid or solid states under normal conditions, e.g., at standard atmospheric pressure.

[0030] Once the air has been removed by the first inert gas, it can be replaced with another inert gas, e.g., a cheaper inert gas. Thus, the invention further provides that the containment vessel is flooded one or several times with a first inert gas, after which the latter is replaced with a second inert gas, e.g., nitrogen.

[0031] To prevent further introduction of reactive gas into the apparatus in the event of a process chamber rupture, the containment vessel is provided with a gas sensor capable of detecting the presence of reactive gas within the containment vessel, and if the gas sensor detects reactive gas within the containment vessel, the supply of process gas to the process chamber may be interrupted.

[0032] In a further development, if a pressure drop is detected, such as damage to the quartz glass, the gas supply can be interrupted via an additional pressure sensor or pressure switch that monitors the pressure in the process chamber. For example, a drop below absolute pressure p≦980 mbar (abs), preferably p≦950 mbar (abs), and more preferably p≦920 mbar (abs) can be detected for monitoring purposes. The interruption of the reactive gas supply can therefore also be performed independently of the detection of reactive gas, such as hydrogen, in the space between the process chamber and the cooling jacket.

[0033] The opening of the process chamber, for example in the case of a broken quartz glass, can be detected or indicated by one of the following criteria: Detection of reactive gases such as hydrogen can be achieved by a gas sensor in the containment vessel. In this case, the gas sensor is specifically configured to detect the process gas or process gas content in the containment vessel. Alternatively or additionally, an overpressure (ps) in the containment vessel can be detected, and if the overpressure disappears, a process failure or a leaking seal can be concluded (e.g., an overpressure (ps) of approximately 2 mbar compared to the atmosphere). This is possible if an (even if low) overpressure relative to the atmosphere is established in the containment vessel, which can be easily detected. Such an overpressure in the vessel therefore also constitutes a safety criterion for the operation of the plant. A pressure test can therefore be a step in the plant's safety check.

[0034] The steps of the process presented herein can therefore be defined by a safety check of the containment vessel. Such a safety check can be realized by measuring an adjustable overpressure pS in the containment vessel. In other words, for example, in preparation for the start of crystal production, the leak rate or tightness of the containment can be checked, and if the leak rate is too high, a safety state is assumed or indicated, i.e., for example, operation is disabled or a warning is generated.

[0035] Alternatively or additionally, the pressure pP in the process chamber can be measured. As long as this pressure remains at pP ≦ 950 mbar (absolute), or pP ≦ 920, or, for example, pP ≦ 980, no process fault is detected; however, exceeding a pressure threshold can indicate a process fault. Alternatively or additionally, a sudden pressure surge / pressure increase in the process chamber (a pressure increase rate exceeding the maximum possible or tolerable pressure increase rate due to the introduced gas) can be detected, potentially indicating a process fault such as quartz glass breakage. The aforementioned criteria are effectively independent of each other and can be used individually or in combination with each other to stop the supply of process gas or hydrogen, thus ensuring, for example, the safety standards of the device. In other words, pressure measurement of pP before and / or during the process may enable more rapid detection of whether process gas is entering or is entering the containment vessel.

[0036] The containment vessel may effectively provide a cooling function, which may be designed, for example, so that a cooling medium, such as water, is circulated around or through the containment vessel. For example, the containment vessel may have at least one coolant line through which a coolant flows for this purpose. The at least one coolant line may be attached to the vessel wall of the containment vessel or connected thereto in at least a thermally conductive manner, possibly with the aid of a thermally conductive paste. For example, the coolant line may be soldered to the vessel wall. For example, the coolant line may comprise copper, which is easy to process and / or is designed to have particularly high thermal conductivity.

[0037] Containment vessels can be equipped to provide temperature control of process conditions. For example, a containment vessel designed in this manner can maintain a constant temperature or similar temperature range regardless of ambient conditions, which may vary significantly. For example, the environment may include daily temperature curves, seasonal temperature fluctuations, and may also be affected by thermal processes that may occur nearby; thus, a well-designed containment vessel can keep these environmental conditions separate from the process. Alternatively or additionally, cooling functions may be affected in response to process parameters, such as the temperature within the process chamber, to provide temperature control of the incubation process. For example, the flow rate of the cooling medium through at least one cooling medium conduit may be varied in response to ambient conditions and / or process parameters to alter heat removal. For example, if the ambient and / or process temperatures are higher, more cooling medium may be introduced, a colder cooling medium may be used, and / or an alternative cooling medium may be introduced.

[0038] The cooling medium lines can be arranged outside the vessel wall, preferably thermally conductively connected to the vessel wall or, in either case, adjacent to the vessel wall. The cooling medium lines cool the vessel wall, ensuring that heat is not directly radiated to the environment of the apparatus but is instead removed by the temperature control device. The external arrangement of the cooling medium lines has the advantage that less penetration into the protective atmosphere or containment vessel is required, since the cooling fluid does not penetrate inside. For example, the vessel wall can have a double wall, i.e., an inner wall and an outer wall, so that the cooling medium lines can be arranged between the inner and outer walls of the vessel wall. This allows the cooling medium lines and their fixtures to be hidden from view and protected from mechanical damage. Because the temperature control unit can dissipate a significant portion of the heat output from the process chamber, the outer wall of the vessel wall does not heat up, which places no or few restrictions on the choice of materials and protection against contact.

[0039] The present disclosure also relates to an apparatus for process-safe production of single crystals by the PVT method or the like, comprising a process chamber containing a highly heated growth cell and a heating device for heating the growth cell. The process chamber has a process gas connection for filling with process gas supplied from a process gas source. The growth cell is fabricated to contain source material and seeds.

[0040] The apparatus preferably includes a containment vessel for sealing the process chamber in an airtight or substantially airtight manner. For example, the containment vessel allows process-safe operation using a reactive gas as the process gas. The containment vessel has a vessel wall such that an intermediate space is formed between the vessel wall of the containment vessel and the process chamber, and the intermediate space is arranged to be filled with a protective atmosphere. The process chamber is arranged within the containment vessel. Furthermore, the containment vessel may include a connection to a protective gas source so that the intermediate space between the vessel wall of the containment vessel and the process chamber can be filled with protective gas, for example, before a PVT process is performed.

[0041] The vessel wall may be a segmented vessel wall surrounding the process chamber at least radially on all sides, the vessel wall including at least two wall segments. The segmented vessel wall may form an outer wall of a containment vessel for surrounding the process chamber, preferably in an airtight or essentially airtight manner. The vessel wall may include, as wall segments, for example, a feedthrough segment, a test or inspection segment, a cooling segment, a lid segment, which may be designed, for example, in multiple sections, and / or a bottom segment.

[0042] The vessel walls are preferably designed to surround the process chamber from above and / or below. Preferably, the vessel walls can be designed to completely surround all sides of the process chamber, although this is not necessary in all cases. For example, if the process chamber is recessed in the floor, a portion or section of the process chamber can be designed without a direct protective jacket in the form of a containment vessel, and a portion of the process chamber can be surrounded by a containment vessel located above the floor. In this way, the protective vessel can be designed to reach the floor and, if necessary, be tightly sealed there.

[0043] In further embodiments, the vessel wall can include process chamber adapters to accommodate different sized process chambers on the same vessel wall. Thus, vessel wall components can be provided in a single size or several sizes to cover a variety of different process chambers or process chamber sizes.

[0044] The vessel wall may be of double-wall design. The double-wall construction of the vessel wall may provide design advantages or simply allow for aesthetic aesthetics without the containment vessel components being visible from the outside.

[0045] For example, the cooling device can be located in the middle area of ​​the double-walled vessel wall. This design has many advantages. For example, the cooling device itself is protected from direct heat radiation from the process chamber and is hidden behind the inner wall of the vessel wall. Additionally, in this case, assembly of the cooling device is particularly simple, as it can be attached to the inner wall of the vessel wall by gluing, soldering, or screwing with a connector. An outer screen covers the middle area, protecting it from external interference and unintentional damage, which is particularly effective when the cooling device is located in the middle area.

[0046] The containment vessel may be configured to allow gas to escape to the outside and may include a pressure sensor that is signal-coupled to a controller that is configured to set an overpressure (relative to the environment or atmosphere) within the containment vessel based on the pressure sensor signal.

[0047] The pressure sensor can include or consist of a pressure switch. For example, the pressure sensor can be formed by a differential pressure switch that measures the pressure difference between the inert gas in the containment vessel and the atmosphere or environment. If desired, the pressure sensor can trigger a circuit, such as a safety circuit or a shutoff, when the pressure exceeds or falls below an adjustable pressure differential.

[0048] Advantageously, with respect to the installation orientation of the device, the inert gas connection is located in the lower region of the containment vessel and the closable outlet is located in the upper region of the containment vessel, which allows the air in the containment vessel to be completely replaced by inert gas flowing from the bottom to the top of the outlet, where it is discharged from the containment vessel.

[0049] The containment vessel preferably has two inert gas connections for two different inert gases. After the containment vessel is purged of air with the first inert gas, a second inert gas connection can be filled with a low-cost fluid, such as nitrogen, to replace the first inert gas.

[0050] The containment vessel preferably includes a gas sensor responsive to the reactive gas, so that it can be determined that a reactive gas (e.g., hydrogen) has entered the containment vessel, for example, in the event of a process chamber rupture.

[0051] As already mentioned above, this device can be used, for example, to produce SiC single crystals by the PVT process. For this purpose, the growth cell is equipped with SiC silicon carbide as source material and the process chamber can be filled with hydrogen as reactive gas in addition to other process gases (such as argon).

[0052] In a further embodiment, the apparatus may further comprise a support frame for holding at least two wall segments to the support frame. In this case, the container wall is segmented in this manner and has at least two wall segments. The wall segments together form the container wall. For example, one wall segment may be provided as a fixed wall segment and designed to be removably connected so that another wall segment can be easily removed.

[0053] The support frame thus forms a retaining structure for receiving the wall segments on the support frame, so that the support frame and the wall segments together form the vessel walls of the containment vessel (8) and enclose the process chamber preferably in an airtight or essentially airtight manner.

[0054] At least one sealing element can be disposed on or within the support frame to seal the support frame from the at least two plurality of vessel segments and / or to seal the containment vessel from the environment. In other words, the support frame can be designed to be sealed to reduce gas leakage from the containment vessel to the environment.

[0055] Alternatively or additionally, one or more wall segments may have a correspondingly formed seal receptacle. In other words, a seal element can be disposed on the wall segment. Such a seal receptacle can be formed as a bead or rim of material into which the seal element can be disposed or inserted. Generally, in such a configuration, the seal element is preferably adhered by adhesive. Alternatively, the wall segments can be designed with a greater thickness of material to allow for grooves in the seal element, which may require consideration of potentially increasing the cost of each wall segment. Also, the increased weight due to the increased material thickness can make handling more difficult.

[0056] Combining a multi-part containment with sealing elements is particularly advantageous because it allows for the use of common construction materials such as metal or steel for the wall elements while still achieving sufficient leak-tightness throughout the containment. In environments where core temperatures exceed 2000°C occur, however, such designs pose several challenges that are surprisingly easy to overcome using the embodiments described herein and in the examples.

[0057] The support frame preferably has at least one longitudinal groove on its exterior for receiving the sealing element. In other words, the sealing element is pulled into the longitudinal groove of the support frame. In this case, the longitudinal groove can be formed as a retaining groove. The advantage of a retaining groove is that the sealing element is firmly held in the retaining groove and can only be removed therefrom by applying, for example, a jumping force. In this case, a trapezoidal groove can be used as the retaining groove, since the sealing element can be reused several times and remain in such a retaining groove. The sealing element can be designed in the form of an O-ring or a lip seal.

[0058] Protective mounting of the sealing elements as described herein prevents the sealing elements from burning or rapidly deteriorating in very high temperature environments. For example, the sealing elements are positioned to be protected from radiant heat. This positioning synergistically allows for the use of permanently reusable materials for the sealing elements. Furthermore, because the sealing elements are permanently reusable and not destroyed by operation, they can be advantageously positioned within a retaining groove, ultimately further simplifying containment vessel handling (in this case, when assembling the wall segments to the support frame). In this way, the sealing elements are protected from dirt and damage and remain within the advantageous retaining groove in a protected installation location, where they are protected from radiant heat during operation.

[0059] Alternatively or adaptively to the situation of at least one sealing element on the support frame, at least one wall segment can have a seal receiving portion, i.e., a special shape, for fixing the sealing element to the support frame, as described above. For this purpose, the end of the wall segment can be overlapped from the outside against the end of the support frame, and the sealing element can be attached to the end protrusion. Another embodiment is to provide a longitudinal groove on the narrow side for receiving the sealing element. In this case, the wall segment can have a wall thickness or wall reinforcement that is greater in overall thickness, at least near the end.

[0060] The support frame can be configured to accommodate a segment seal, a cover seal, and / or a bottom seal, or alternatively, the support frame can be designed to accommodate one or more seals for different purposes.

[0061] The support frame can be sealed to the base plate, for example, by a base seal. The support frame can alternatively or superimposedly seal to the adapter, for example, by an adapter seal. The support frame can alternatively or superimposedly seal to the container segment, for example, by a segment seal.

[0062] Each vessel segment can be assigned a separate circumferential segment seal. For example, if four vessel segments are used, four separate segment seals can be provided so that each vessel segment is individually sealed. In practice, it has been shown to be advantageous for the vessel segments not to be electrically connected to each other. However, if they are made of an electrically conductive material—which is also preferable because the vessel segments should be thermally conductive, and inexpensive materials with both thermal and electrical conductivity exist—it can be advantageous to electrically insulate the vessel segments from each other. This is particularly true when induction heating is used. Insulation can be provided by a connection via a support frame, allowing the vessel segments to be mounted at a distance from each other. In this case, it is advantageous to assign each vessel segment its own segment seal, which can perform the insulating function as needed.

[0063] The support frame can be composed of several parts. The support frame can include a plurality of at least two frame elements that can be detachably attached to each other. The support frame can alternatively or overlappingly include at least one of a ceiling element, a plurality of preferably vertically arranged rod elements, and / or a floor element. The multi-part structure of the support frame also helps to simplify the overall setup of the apparatus and further reduce the cost of the apparatus. Furthermore, the multi-part design of the support frame provides advantages over maintenance operations and / or process chamber replacement that may be required when crystal growth is finished and the same containment vessel is used to protect another process chamber or another growth process.

[0064] In other words, the containment vessel is designed to be reusable and can be used to produce a large number of crystals using the PVT process, potentially leading to significant savings, especially in terms of costs. The containment vessel can be modularly assembled around a process chamber before a growth process is performed and can be disassembled again in a simple manner after the crystal growth has been performed. In particularly advantageous embodiments, all parts can be reused, so the containment vessel can be modularly rebuilt around a new process chamber before another growth process is performed. The multi-part design means that the containment vessel can be assembled around other process chambers easily and with low effort, providing a safe atmosphere.

[0065] The support frame elements can also be designed to be sealed to one another so that no or only minimal inert gas leaks into the environment, even between contact or tangent areas between individual support frame elements. Alternatively or additionally, a frame seal can be included to seal one frame member against a second frame member. The frame seal can be, for example, located in a frame seal plane that is not coplanar with the segment seals.

[0066] For example, one embodiment may have each segment seal passing through the cover element, two rod elements, and the bottom element. Alternatively or additionally, a lid seal may be disposed on the top surface of the lid element to seal the lid. Further alternatively or alternatively, a bottom seal may be disposed on the bottom surface of the bottom element to seal the bottom element to the bottom. The bottom may be provided as a manufactured part or as a mounting plate.

[0067] The cover element may have a segmented seal groove on the segment side. Each rod element may have at least one partial seal groove, preferably two partial seal grooves per rod element. The floor element may have a segmented seal groove. For example, at least one of the segmented seal grooves of one of the rod elements may be designed to be aligned with the segmented seal groove of the cover element and the segmented seal groove of the base element, so that a segmented seal can be inserted into the aligned segmented seal grooves for circumferential sealing of the wall segment.

[0068] The apparatus may further include a support frame for holding the at least two wall segments to the support frame, which may be a multi-part structure. Alternatively or additionally, the support frame can comprise a plurality of at least two frame members removably attachable to one another. Alternatively or additionally, the support frame can comprise at least one of a ceiling element, a plurality of, for example, vertical rod elements, and / or a floor element.

[0069] The support frame can have at least one longitudinal groove on its exterior for receiving the sealing element. Alternatively or additionally, the support frame can be designed to accommodate a segment seal, a cover seal, and / or a bottom seal. Alternatively or additionally, the cover element can be integrally formed, for example, for attachment to a rod element. Alternatively or additionally, the cover element can be connected to the bottom element via a rod element. Alternatively or additionally, the elements of the support frame can be detachably connected to each other, for example, by a screw connection, to provide a stable structure on the one hand, and can be disassembled, for example, for maintenance or release purposes on the other hand.

[0070] The floor element can be designed in several parts, comprising a floor fixing section and an intermediate section, and can be manufactured so that the rod element can be placed between the floor fixing sections and in the intermediate section. Alternatively or additionally, the floor element can be designed in one piece, with the rod element being insertable into a recess in the floor element. Alternatively or additionally, the cover element can be formed integrally, with the rod element being insertable into a recess in the cover element. Alternatively or additionally, the cover element can form a laterally protruding collar so that the wall element can fit under the cover element without the wall element protruding laterally beyond the cover element.

[0071] The support frame can be designed as an electrical insulator, ensuring that the wall segments are electrically insulated from one another. Alternatively or additionally, the support frame can be non-magnetic, ensuring that the wall segments do not form ring magnets that could interfere with the heating device. Alternatively or additionally, the support frame can be made of a heat-resistant material. Alternatively or additionally, the support frame can be made of a thermally and / or electrically non-conductive material. Alternatively or additionally, the support frame can include or consist of ceramic, plastic, composite material, or a combination thereof.

[0072] The support frame may preferably form a retaining structure for receiving the wall segments thereon, so that the support frame and the wall segments together form the vessel wall of the containment vessel and can seal the process chamber, preferably in an airtight or essentially airtight manner. An intermediate space may be formed between the vessel wall of the containment vessel and the process chamber, and the intermediate space is arranged to be filled with a protective atmosphere. Alternatively or additionally, the containment vessel may surround the process chamber from all sides.

[0073] The heating device can be designed to surround the process chamber. Alternatively or additionally, the heating device can be formed in an annular shape around the process chamber.

[0074] The present invention will now be described in more detail by way of exemplary embodiments with reference to the drawings, in which identical and similar elements are partly designated by the same reference numerals, and the features of the various exemplary embodiments can be combined with one another. [Brief explanation of the drawings]

[0075] [Figure 1] FIG. 1 is a cross-sectional view of an apparatus according to the invention. [Figure 2] FIG. 2 is a perspective and simplified diagram of a partially assembled containment vessel. [Figure 3] FIG. 3 is a perspective cross-sectional view of one embodiment of the device. [Figure 4] FIG. 4 is an exploded view of one embodiment of the device. [Figure 5] Figure 5 shows the design of the support frame. [Figure 6] FIG. 6 is a detailed cross-sectional view of one embodiment of a support frame. [Figure 7] FIG. 7 shows further details of one embodiment of the support frame. [Figure 8] FIG. 8 is another detailed view of one embodiment of the support frame. [Figure 9] Figure 9 shows a detail of the seal path within the support frame. [Figure 10] FIG. 10 shows details of the seal path within the support frame. [Figure 11] FIG. 11 is a detailed cross-sectional view of the device. [Figure 12] Figure 12 shows the partially assembled containment vessel with the support frame. [Figure 13] FIG. 13 shows an exemplary segment design of a double-walled vessel wall with a temperature control unit. [Figure 14]Figure 14 shows the connection details of the temperature control unit. [Figure 15] FIG. 15 is a design of a cooling segment of the vessel wall with part of the temperature control device. [Figure 16] FIG. 16 is a perspective view of one embodiment of a containment vessel. [Figure 17] FIG. 17 is a partially opened perspective view of one embodiment of an apparatus with a process chamber. [Figure 18] FIG. 18 is a perspective view of the device. DETAILED DESCRIPTION OF THE INVENTION

[0076] Figure 1 shows a cross-sectional view of one embodiment of the apparatus. At the center of the apparatus is a growth cell 1, which consists of a hollow cylinder with a base that stands on a stand and a lid that closes both ends of the hollow cylinder. The growth cell 1 is made of porous graphite. A sublimable material 2 is layered on the bottom. A seed 3 is located on the underside of the lid.

[0077] Growth cell 1 is located within process chamber 4, which consists of a hollow cylinder closed at both ends by a floor or ceiling. The cylindrical walls of process chamber 4 are constructed from heat-resistant quartz glass and can be filled with process gas via a process gas connection to inlet valve 5. Because the graphite in growth cell 1 is porous, process gas from process chamber 4 also flows into growth cell 1.

[0078] The heating device 6 consists of an induction coil 7 that surrounds the process chamber 4 at the level of the growth cell. When an electric current is passed through it, an electromagnetic field is generated that induces a current in the graphite of the growth cell 1, heating it to above 2000°C and up to 2400°C.

[0079] Due to the high temperatures and the required transparency for the electromagnetic field of the induction coil 7, it is necessary to manufacture at least the cylindrical wall of the process chamber 4 from a heat-resistant material suitable for this purpose. Typically, the cylindrical wall of the process chamber 4 is made from quartz glass, which has proven to be particularly suitable and inexpensive to manufacture.

[0080] To produce SiC single crystals, silicon carbide is added to the growth cell 1 and the process chamber 4 is flooded with a process gas. The process gas can contain a reactive gas, such as a percentage of hydrogen, and / or can consist of up to 100% hydrogen. When the growth cell 1 is then heated by the induction coil 7, the silicon carbide sublimes and deposits layer-by-layer on the seed 3, resulting in the growth of a SiC single crystal. The use of hydrogen in the process gas ensures that the crystal does not form crystal defects or deposit foreign atoms at each growth site during the process. Unwanted foreign atom contamination periodically causes electrical conductivity changes, which can occur locally as needed and can be detrimental to quality disturbances and degradation. The process gas composition can also be affected by the use of reactive gases, either through reactions with other process gases or the hot zone (graphite component). Altered process gas composition can affect the crystallinity, structure, crystal defects, and doping of the SiC crystal.

[0081] For example, it has been shown that beneficial effects are achieved from a hydrogen content of 5% or more in the process gas, and that at low concentrations of hydrogen below 5% in the process gas, protective measures, for example for explosion prevention, are usually not required. Particularly advantageous results are obtained at hydrogen contents in the range of 5% to approximately 40%, and crystal purity increases at hydrogen contents in the process gas in the range of 15% (preferably ±5%). In principle, however, the use of the containment vessel according to the invention is effective even at low concentrations.

[0082] However, the use of reactive gases such as hydrogen is problematic as discussed above because if the walls of the process chamber 4 can be breached, the reactive gas can mix with the ambient air without the containment vessels described herein, creating a flammable gas mixture that can quickly ignite, for example, in hot parts of the apparatus.

[0083] The process chamber 4 in the embodiment shown here is surrounded by a containment vessel 8 having a cylindrical vessel wall 9 that surrounds the cylindrical wall of the process chamber 4, the vessel wall 9 standing on a floor 10 and closed at its top by a ceiling 11. The bottom 10 and ceiling 11 of the containment vessel 8 are adjacent to the bottom and ceiling of the process chamber 4.

[0084] The containment vessel 8 can also be part of the cooling concept of the device. In other words, the containment vessel 8 can be integrated into the cooling concept of the device. For this purpose, the cylindrical vessel wall 9 can be provided with cooling channels connected to a cooling system. The cooling concept can therefore result in the containment vessel 8 providing the cooling function for the device. For example, a cooling medium such as water can be circulated inside the containment vessel 8. On the other hand, the containment atmosphere inside the containment vessel 8 can provide the cooling function. For example, the containment atmosphere can be circulated for the purpose of dissipating thermal power. Overall, the containment vessel can be equipped to control the temperature of process conditions using a containment with a cooling function, so that a constant temperature—or a similar temperature range—can always be maintained regardless of ambient conditions, which can vary significantly. For example, the environment can include daily temperature curves, seasonal temperature fluctuations, and can also be influenced by thermal processes occurring nearby.

[0085] Finally, the containment vessel 8 can be constructed to be metallically conductive. A metallically conductive containment vessel 8 can provide shielding for processes taking place therein in the manner of a Faraday cage, so that, for example, alternating electromagnetic fields within the vessel wall 9 of the containment vessel 8 have a defined end point and do not diverge asymptotically, potentially infinitely. This is advantageous when several devices are installed adjacent to one another, where corresponding alternating magnetic fields may affect each other and interfere with each other's process conditions. In other words, a metallically conductive containment vessel 8 can ensure uniform process conditions even under conditions where several devices of different types can be installed adjacent to one another without interfering with each other's processes.

[0086] Overall, it can be seen that the containment vessel 8 can solve several tasks at once in a synergistic way. Not only can it provide the aforementioned protective atmosphere, but it also allows the application of reactive gases within the process chamber. Furthermore, the containment vessel 8 can protect the process chamber from various ambient conditions, such as temperature fluctuations and fluctuating electric and / or magnetic fields, thus ensuring uniform process conditions for the processes taking place within the process chamber.

[0087] At the bottom of the containment vessel 8, a ring line with one or more connections can be arranged in the annular space 12 between the vessel wall 9 of the containment vessel 8 and the cylindrical wall of the process chamber 4 made of quartz glass. The ring line is connected to an argon source 14 and a nitrogen source 15 via a shuttle valve 13.

[0088] A closable outlet valve 16 is arranged in the ceiling 11 of the containment vessel 8. A gas sensor 17 (for example as a hydrogen sensor) and a pressure sensor 18 are also provided therein.

[0089] The entire apparatus may be covered by a hood 20 made of unbreakable plastic or sheet metal that rests on the bottom of the containment vessel 8 .

[0090] Furthermore, a control device 19 is provided which is signal connected to both sensors 17, 18 and controls the shuttle valve 13, the outlet valve 16 and the inlet valve 5 for supplying hydrogen via control lines.

[0091] The control device 19 enables the following procedure to be carried out: the containment vessel 8 is flooded with an inert gas before the process chamber 4 is filled with hydrogen.

[0092] (1) Open the outlet valve 16. (2) The shuttle valve 13 is switched so that argon gas from the argon source 14 slowly flows into the gap 12 from below, filling the gap 12 with argon gas from below, and any air present is displaced by the open outlet valve 16 (or pressure relief valve, etc.). (3) Close the exhaust valve 16 and the shuttle valve 13. (4) A pause in the filling is observed to allow any residual air from the argon gas to settle upward. (5) Repeat steps (1) to (3) one or more times as necessary. (6) Open the exhaust valve 16. (7) Switch shuttle valve 13 to allow nitrogen gas to slowly flow into gap space 12 from below, filling gap space 12 from below with nitrogen gas from nitrogen source 15 and displacing the argon gas present through open outlet valve 16. (8) Close the exhaust valve 16. (9) Establishing and maintaining an overpressure in gap 12 by the controlled opening of shuttle valve 13 so that air cannot enter gap 12 despite any allowable leaks present in the containment vessel.

[0093] A sufficient overpressure is approximately 2 mbar above ambient pressure. In either case, steps (1) to (3) and (9) must be carried out. Steps (4) and (6) to (8) are optional. An additional oxygen sensor can be provided to be able to check whether the interstitial space 12 is free of oxygen to a sufficient extent. What to do if the glass wall breaks during operation:

[0094] (1) Continuously monitor the gas sensor 17. (2) When the gas sensor 17 detects hydrogen in the gap 12, the supply of hydrogen is cut off.

[0095] 2, a perspective view of a simplified embodiment of a partially assembled containment vessel 8 is shown, which for clarity does not show the process chamber 4, as well as various additional components. Furthermore, for completeness, it should be noted that the embodiment shown in FIG. 2 does not include details for sealing the interior region 12, and therefore the leak rate achievable with this embodiment is relatively high. An improved, sealed containment vessel 8 is shown in the further illustrated embodiment.

[0096] In FIG. 2 , the temperature control device 21 is at least partially disposed within the containment vessel 8, whereby a fluid can be supplied to the coolant line 22 through a connection piece 23. The coolant line 22 can be connected to the inner wall 44 of the containment vessel 8, for example, by gluing, soldering, welding, or screwing. From the process chamber 4, the heat power reaches the inner wall 44 primarily as radiant heat, from which it can be efficiently dissipated by the temperature control device 21. For example, liquid water can be used as the coolant. The amount of heat that can be dissipated by the temperature control device 21 is preferably adjustable. For example, the amount of heat that can be dissipated can be influenced by the temperature specification and / or the throughput or rate of the coolant, i.e., temperature control can be performed. Temperature control of the process chamber 4 can then be achieved by a temperature control in response to sensor signals measuring the ambient temperature and / or process temperature, such that a substantially constant temperature is achieved within the process chamber 4 during the process cycle.

[0097] Containment vessel 8 has a sight window 32 that bridges interior region 12 and allows viewing of process chamber 4, for example, for process monitoring purposes. Sight window 32 is designed to be relatively small to keep direct thermal radiation low. Additionally, Figure 14 shows details of refrigerant line 22 with line attachment 22A, connection piece 23, transition piece 23B, and connection piece attachment 23A.

[0098] 3 shows a cross-sectional view of one embodiment of the apparatus 100. The process chamber 4 is partially surrounded by an induction coil 7, which is powered by a heating device 6. The heating device 6 is located partially inside and partially outside the containment vessel 8; for example, the power electronics may be located on the outside with a sealed feedthrough 62 to reduce gas leakage. The induction coil 7 with some of the electronics resides in the interior space 12, i.e., the space that may be occupied by the containment vessel atmosphere.

[0099] The inert gas can be supplied through an inert gas supply 54 below the interior 12 (several inert gas supplies 54 may be provided). An outlet valve 16 is arranged on the upper side 11, by means of which it is possible, for example, to evacuate the protective vessel 8 from the external air (containing oxygen) initially placed in the protective vessel 8, for example by introducing a protective gas that is heavier than air. If a connecting line is subsequently connected to the outlet valve 16 (not shown), it is also possible to provide a circulation of the protective gas, for example to remove heat from the protective vessel 8 or to ensure a regular exchange of the protective gas.

[0100] In the case shown in this embodiment, the coolant lines 22 of the temperature control device 21 are located within the vessel wall 9 of a double-wall design. In the cross-sectional view of the containment vessel 8 with the process chamber 4 shown in Figure 3, the interior 12 of the containment vessel 8 for receiving a protective atmosphere extends from the chamber wall 41, for example, all the way around the process chamber 4 to the vessel wall 9, and the interior 12 is designed to be sealed against the vessel wall 9 in order to keep the leak rate of gas from the interior 12 to the environment 30 low.

[0101] 3 shows a special feature in that the process chamber 4 is equipped with an adapter 46. In the illustrated embodiment, the adapter 46 has two alternative top covers 47, 48, so that either the top cover 47 or the top cover 48, which is further inboard, can be used depending on the desired process height. Thus, the covers 47, 48 can be used alternately as needed.

[0102] Referring to FIG. 4, the apparatus 100 is shown in an exploded view, revealing the components of the containment vessel 8 used therein. Inside, a process chamber 4 is arranged, which in this embodiment is arranged in an empty version for easier understanding. A quartz glass housing 41 (process chamber wall) forms the inner end of an intermediate space 12 that is arranged between the quartz glass housing 41 (as the inner wall of the containment vessel) and the vessel wall 9. An induction coil 7 functions as a heater and is arranged in a ring shape around the process chamber 4.

[0103] The process chamber walls 41 are initially open at the top, and the process chamber 4 is closed or sealed by a chamber closure 42. The top closure is formed by an adapter ring 46, which engages the process chamber walls 41 in a dual function, sealing the upper region of the containment vessel 8 inward and toward the lid 11. The adapter 46 is connected to an upper frame end 64 of the support frame 60 via the lid 11. The support frame 60 forms the "skeleton" of the containment vessel 8, so to speak, in that multiple components of the containment vessel 8, such as vessel segments 91, 92, and 93 and the lid 11, can be attached to the support frame 60. The support frame 60 is then attached to a base 10 via a base element or lower frame end 66, forming an overall stable and rigid structure.

[0104] In the embodiment shown in FIG. 4, an inspection segment 91 equipped with one or more inspection glasses 32 for observing the process chamber 4 or the process performed therein can be mounted on the support frame 60. Furthermore, two cooling segments 92, 93 shown in this embodiment can be arranged on the support frame 60. In the rear area, the electronic unit of the heating device 6 is shown, which can be arranged outside the containment vessel 8, with the connection to the induction coil 7 being made through the vessel wall 9 using a bushing (see, for example, FIG. 7 ). To improve sealing, the support frame has several seals, visually represented here as a segment seal 72, a cover seal 74, and an adapter seal 78. The wall segments 91, 92, 93 shown in FIG. 4 are of double-wall design, each having an inner wall (recognized as the inner wall 923 of the cooling segment 92) and outer screens 919, 939.

[0105] Referring to FIG. 5 , a multi-component support frame 60 is shown, which collectively forms a support frame 60 for supporting wall segments 91, 92, 93, and 94. The support frame 60 has a bottom element or bottom frame end 66, which can be formed in one piece or multiple pieces. In the illustrated case, the lower frame end 66 is composed of multiple pieces, with a plurality of four bottom elements and four intermediate pieces 61 collectively forming the lower frame end 66. A receiving groove 84 is provided on the segment side of the frame bottom end 66 to receive a segmented seal 72. The segmented seal 72 extends through the receiving groove 84 in the base element, the receiving groove 83 in the rod element, and the receiving groove 82 in the cover element, and is designed to provide a circumferential seal around the wall segment. The upper side of the cover element 64 is provided with a cover seal receiving groove 81 to receive the circumferential cover seal 74. All of the illustrated seal elements have in common that they are located on the segment side of the support frame 60 and are therefore protected from thermal radiation from the process chamber 4 by the support frame 60.

[0106] The support frame 60 is preferably made of an electrically and / or thermally non-conductive material. When the segments 91, 92, 93, 94 or the lid 11 are fastened to the support frame 60, for example, with mating fasteners 97A or 69 (threaded holes), the support frame 60 can set the distance between the wall segments 91, 92, 93, 94 and the lid 11 so that the planar components of the containment vessel 8 do not come into contact with each other. Thus, the planar components of the containment vessel 8 can be electrically isolated from each other if they are not in contact and the support frame 60 is not electrically conductive. Nevertheless, the individual segments 11, 91, 92, 93, 94 can seal against the support frame 60, so that good sealing of the containment vessel 8 can be achieved by the provided sealing grooves 81, 82, 83, 84 and sealing elements 72, 74, 76, 78. This provides the advantage of providing planar elements 11, 91, 92, 93, 94 made of relatively inexpensive materials, such as steel or other metals, with excellent thermal conductivity, without forming a sealed metallic or conductive enclosure in which the AC electromagnetic fields of induction heaters 6, 7 could act to disrupt or even disable heating. To further isolate wall segments 91, 92, 93, 94 from lid 11, upper frame terminations 64 have grooves 63 over which the upper frame terminations 64 form overhangs so that they are flush with, for example, the outer panels 99, 919, 929, 939 of wall elements 91, 92, 93, 94 on the outside. This ensures that wall elements 91, 92, 93, 94 do not form an electrical short circuit through lid 11. Furthermore, the overhangs further simplify assembly of lid 11, providing a wider support surface for lid 11, further improving sealing and further increasing the stability of the entire frame 60.

[0107] 6 to 10, detailed cross sections of various embodiments of the support frame 60 are shown. In FIG. 6, the transition from the lower frame end 66 to the floor 10 is more clearly shown, with segment seals 72 inserted into receiving grooves 84 in the floor element and into receiving grooves 83 in the adjacent rod element on the same plane. The lower frame section element 66 has connecting means 68, for example, threaded holes for inserting fixing screws for fixing the lower frame section element 66 to the base 10. A frame seal 77 is provided to seal the rod element 62 to the intermediate piece 61 and, at the same time, to the lower frame section element 66.

[0108] 7 shows a detail of the upper frame element 64 with the rod element 62 and the wall element 92 mounted thereon. The cover element 64 has a recess 67, which in this embodiment has two threaded holes for receiving screws to connect the cover element 64 to the rod element 62. By mounting the screws recessed into the recess 67, the cover 11 can be mounted flush and therefore hermetically on the upper frame element 64. The recess 63 on the cover element 64 can also be seen in shape, and the path of the segment seal 72 extending into the recess 63 is also shown in the cover element receiving groove 82.

[0109] 8 shows further details of a portion of the support frame 60, with a continuous frame portion 66 resting on the floor 10 and sealed to the floor 10 by means of a floor seal 76. The bottom seal 76 extends into a receiving groove 85 and is provided with a plurality of threaded holes 68 for receiving threaded means for connecting the lower frame portion 66 to the floor 10. In this regard, in the embodiment shown, the use of a recess may not be necessary, as no sealing surface is formed on the upper side of the lower frame portion 66.

[0110] 9 and 10 illustrate, for a multi-piece lower frame section 66 with a mid-piece 61, the connection of rod element 62 (not shown in FIG. 9 for clarity; see, e.g., FIG. 8 or 10) to the mid-piece 61 and the sealing of rod element 62 with inner-frame section seal 77 with respect to both the multi-piece lower frame section 66. Grooves 86A are provided along each of the two lower frame sections 66 to accommodate the inner-frame section seals 77, and grooves 86 are provided in the mid-piece 61 to accommodate the frame seals 77 together. Rod element 62 abuts mid-piece 61 and the two lower frame sections 66 at sealed frame section joints 65. Opposing fasteners 97A are provided on rod element 62 to fasten one wall segment 91, 92, 93, 94, respectively.

[0111] Referring to FIG. 11 , a cross-sectional view of one embodiment of the apparatus 100 is shown. The adapter 46 forms an upper closure for the process chamber 4 or 4a. In this embodiment, two process chambers, each of which is different in height, are shown as an example and can be alternately closed by the adapter 46. The adapter 46 can therefore seal the containment chamber 8 via either an adapter seal 78 or an alternative adapter seal 79. An intermediate space 12 is formed between the chamber wall 41 and the vessel wall 9. The lid 11 sealingly connects the adapter 46 to the vessel wall 9 via the upper frame portion 64, thereby forming a sealed enclosure or containment vessel 8 as a whole. In this case, the adapter can be connected to the lid 11 by adapter fastening means 49, e.g., screws, and the lid 11 can be connected to the upper frame portion 64 by fastening means 69, thereby forming a frictional connection from the adapter 46, via the lid 11, to the frame 64, and further to the vessel wall 9. 11, the enclosure wall 9 is a double-walled structure, including an inner wall 98, an outer panel 99, and an intermediate space 122 therebetween. In this embodiment, the outer panel 99 overhangs slightly from the upper frame member 64, filling most of the area of ​​the recess 63. Sealed feedthroughs 26 are provided, for example, for the passage of electrical connections to or from the outside to the environment 30.

[0112] FIG. 12 shows a partially assembled containment vessel 8, with wall segments in the form of connection elements 94 already positioned on a frame 60 secured to a base plate 10. A plurality of hermetic feedthroughs 26 provide a means for connecting electronics and the like located outside the containment vessel 8 to components located inside the containment vessel 8. When these component connections are combined such that multiple or all of the provided connections are made through the connection elements 94, the connection elements 94 may be positioned or configured to remain permanently, or at least exclusively, attached. In contrast, the other wall segments 91, 92, 93 may be configured to be quickly and easily removable to allow rapid access to the process chamber 4. As usual, like reference numerals will refer to like elements throughout this description, and therefore it is not necessary to repeat the description of several elements already described below.

[0113] 13, a further embodiment of a cooling segment 92 having a sandwich structure becomes clearer. The refrigerant lines 22 of the temperature control unit 21 are arranged on the inner wall 98 and can be connected to the outside by means of connections 23. Gap covers 921, 922 circumferentially surround or delimit the segment 92, and an outer screen 99 can be screwed onto the gap cover. The outer cover 99 covers the refrigerant lines 22 and the fixing means 97, thus protecting them from access on the one hand and from inappropriate damage on the other hand. The outer cover 99 thus hides the technical equipment from direct view and access, giving the device 100 an attractive appearance. Furthermore, as can be seen in FIG. 13 , the temperature control device 21 is optimized for quick and easy removal of the entire cooling element 92, for example, by providing connecting pieces 23 that allow the coolant lines to be easily disconnected. For example, the connecting pieces can be designed as quick connectors with bayonet or screw locks, allowing for simple and rapid removal. Thus, the complete cooling element 92 can be easily separated from the coolant source and thereby removed from the vessel assembly as a whole, along with the cooling device (refrigerant lines 22). This further simplifies and speeds up disassembly and / or opening of the containment vessel 8 when maintenance intervention and / or replacement of the process chamber 4 is required. Thus, although the double wall construction of the wall elements 91, 92, 93, 94 is not necessarily required and other arrangements of the refrigerant lines 22 are contemplated, locating the refrigerant lines on the outside of the interior wall 923 has proven particularly advantageous as it also positions the refrigerant lines outside the interior space 12 to be sealed, making disassembly and / or assembly of the wall elements easier as a whole, and the containment assembly 8 as a whole also requires fewer through holes through the vessel wall 9 to seal it.

[0114] 15, a top view of the intermediate region 122 of the double wall of the cooling segment 92 of the vessel wall 9 including the temperature control device 21 is shown, with the coolant lines 22 located in the intermediate region 122 of the vessel wall 9. In the embodiment shown here, the vessel wall 9 includes the inner wall 98, frame parts 92, 94, and the refrigerant lines 22 of the temperature control device 21 located in the intermediate region 122. The frame parts 92, 94 are fastened to the first segment 91 by fastening means 97. Additionally, fastening means 96 (e.g., screw holes) are arranged at regular intervals on the frame parts 92, 94 so that the intermediate region 122 is surrounded by the frame parts 92, 94.

[0115] Finally, FIG. 16 shows the device 100 with a multi-part vessel wall 9 including wall segments 91 and 92 mounted on a base 10. The refrigerant lines 22 (see, e.g., FIG. 15 or FIG. 13) extend protected behind the outer panel 99 and are communicatively connected to one another by means of the compensating bends 24, allowing the refrigerant (e.g., water) to flow through the temperature control device 21. Furthermore, the compensating bends 24 are quickly removable, allowing the refrigerant lines 22, and thus the entire wall segments 91 and 92, to be easily removed from one another. The process chamber 4 (see, e.g., FIG. 1 or 3), is surrounded on all sides by a safe atmosphere in the gap 12, or, in either case, above the bottom 10, depending on the embodiment. In the event of a process gas leak due to a rupture or other failure of the process chamber 4, the process gas mixes with the protective gas held in the interior 12 to form a harmless gas mixture.

[0116] 17, a further embodiment of the device 100 is shown in which the connecting element 94 has been removed and the respective cooling elements 92, 93 have been installed. It is clear that in this embodiment the gas supply and exhaust lines 51, 54 can extend below the bottom 10 and / or differ from the further embodiments in that they extend outside the environment 30 and are therefore not in the area that the containment vessel 8 must protect. Therefore, the lower body 31 can be protected in other ways, or need not be protected by a containment atmosphere at this location. As a result, the process chamber 4 does not extend far enough into the subfloor 31, or even into the subfloor 31 at all, which could lead to significant escape of process gases into the subfloor 31 or potentially hazardous deflagration in the surrounding area 30. Corresponding heating and / or cracking of the chamber wall 41 is not anticipated. This also has the added benefit of reducing the number of feedthroughs that need to be routed through or into the interior 12, further enhancing the airtightness of the containment vessel 8. A further advantage results from the fact that supply and exhaust lines below the floor 10 do not interfere with the environment 30, but rather can be routed concealed.

[0117] Finally, FIG. 18 shows another embodiment of a fully sealed device 100, with the cooling segment 92 inserted on the right and the connecting element 94 inserted on the left. The heating electronics 6 are shown only diagrammatically and are located outside the containment vessel 8. This electronics flange is preferred for the heating device 6, since a further improved gas seal is achieved by flange-like placement directly on the vessel wall 9 without a hose-like intermediate connector. This implies a relatively rigid placement of the connecting element 94, so it would be preferable to remove the cooling element 92, thus providing access to the process chamber and / or induction heater, etc., for the purpose of replacing the process chamber 4 or generally for maintenance access. Alternatively or additionally, it is of course possible to remove the lid 11 or adapter 46 and lift out the process chamber, avoiding the need to remove or modify the hardware and electronics or gas connections, etc., located inside the containment vessel 8.

[0118] The further developments and inventive modular concepts presented herein have been shown to provide significant improvements and increased safety over previous devices while reducing manufacturing costs and simplifying maintainability of system components. Overall, this description has various aspects that, individually or together with others, can define important aspects of the present invention.

[0119] The above-described embodiments should be understood as examples, and it is clear to those skilled in the art that the present invention is not limited thereto and can be modified in various ways without departing from the scope of protection of the claims. Furthermore, it is clear that a feature, even when described together with other features, independently defines an essential component of the present invention, regardless of whether it is disclosed in the specification, claims, drawings, etc. In all figures, the same reference signs represent the same objects, so that the description of an object that is mentioned only once or in any case not mentioned in all figures can be transferred to figures and embodiments in which the object is not explicitly described in the specification. [Explanation of symbols]

[0120] List of reference numbers 1. Growing cells 2 Sauce Ingredients 3 seed 4, 4A process chamber 5 Inlet Valve 6 Heating device 7. Induction Coil 8. Containment Vessel 9 Container wall 10 Floor 11 Lid 12 Intermediate Space 13 Shuttle valve 14 Argon source 15 Nitrogen Source 16 outlets (valves) 17 Gas Sensor 18 pressure sensors 19 Control device 20 Food 21 Refrigeration or temperature control unit 22 Refrigerant line 22A Line Fixture 23 Connecting piece 23A Attachment Holder 23B Curve section 24 Compensation bend 26 Seal bushing 30 Environment 31 Sub-floor 32 Peephole 41 Process chamber walls or inner walls of containment vessels 42 Chamber Rock 46 Adapter 47 Process chamber top cover 48 Process chamber top cover 49 Adapter Fixture 51 Process gas supply unit 52 Process gas exhaust 54 Inert gas supply unit 56 Inert gas outlet 60 Support Frame 61 Intermediate Piece 62 Rod element or frame strut 63 Groove 64 Upper frame edge or cover element 65 Frame joint 66 Lower frame end or floor element 67 Groove for accommodating frame fasteners 68 Connection Methods 69 Fixing the counter of cover 11 72 Segment seal 74 Cover gasket 75 sealing elements 76 Floor seal 77 Inner frame seal 78 Adapter gasket 79 Replacement Adapter Seal 81 Cover gasket accommodation groove 82 Cover element receiving water groove 83 Rod element accommodation groove 84 Floor element receiving groove 85 Storage groove 86 Frame seal receiving groove 86A Front frame seal receiving groove 91 Tank wall section, test segment 92 Tank wall section, cooling segment 93 Tank wall section, further cooling segment 94 Tank wall sections, connecting segments 96 Fastening Elements 97 Fastening Elements 97A Countermount to fastening element 97 98 Inner wall 99 outer panel 100 devices 122 Intermediate Area 919 Test Segment External Panel 921 Top Interspace Cover 922 Horizontal gap cover 923 Inner wall of cooling segment 924 Lower Interspace Cover 929 Cooling Segment Outer Panel 939 Outer panel of further cooling segment

Claims

1. A PVT method for the process-safe production of single crystals in an apparatus (100), comprising a process chamber (4) for accommodating a highly heatable growth cell (1), a heating device (6) for heating the growth cell (1), the growth cell being adapted to accommodate a source material (2) and a seed (3), the process chamber (4) being fillable with a process gas, the growth cell (1) being heatable, the apparatus including a containment vessel (8) for enclosing the process chamber (4) in an airtight or substantially airtight manner, The containment vessel has a circumferentially extending vessel wall (9), and a gap (12) is created between the vessel wall (9) of the containment vessel (8) and the process chamber (4), providing a protective atmosphere in the gap to fill the gap with the protective atmosphere; providing the process gas, including or consisting of a reactive gas, in the process chamber; and heating the growth cell by means of the heating device, wherein the sublimable material sublimes and re-sublimes into the seed.

2. 2. The PVT method according to claim 1, wherein in the step of providing the protective atmosphere in the gap (12), an overpressure relative to the ambient pressure in the environment (30) is adjusted, for example to at least 1 mbar above ambient pressure, preferably to at least 3 mbar above ambient pressure, more preferably to at least 5 mbar above ambient pressure.

3. 3. The PVT method according to claim 1 or 2, wherein heating of the growth cell (1) is exerted from all radial sides by means of the heating device (6) annularly surrounding the process chamber (4), and / or ensuring that the provision of the protective atmosphere in the gap (12) is completed before the process gas is introduced into the process chamber (4), and / or the growth cell (1) is heated to an operating temperature, and / or the gap (12) is filled with the protective atmosphere, further replacing any air present in the gap before sublimation of the source material (2) begins.

4. 4. A PVT method according to any one of claims 1 to 3, wherein the reactive gas comprises or consists of hydrogen and / or the protective atmosphere comprises or consists of an inert gas, preferably comprising argon.

5. 3. The PVT method of claim 2, wherein the containment vessel (8) is configured to allow gas loss to the environment (30), and the inert gas is supplied to compensate for gas loss and, optionally, maintain the overpressure relative to the environment (30) within the containment vessel (8).

6. 6. A PVT method according to any one of claims 1 to 5, wherein a first inert gas heavier than air is introduced into a lower region of the containment vessel (8) to fill it and displace the air to the upper side, for which purpose a closable outlet (16, 56) at the upper end of the containment vessel (8) is kept open until the escape of the air.

7. 7. A PVT method according to any one of claims 4 to 6, wherein the containment vessel (8) is filled once or several times with the first inert gas before the latter is replaced by a second inert gas, such as nitrogen.

8. 8. The PVT method according to any one of claims 1 to 7, wherein the containment vessel (8) is capable of detecting the reactive gas and / or the supply of the process gas to the process chamber (4) is stopped if the reactive gas is detected in the containment vessel (8).

9. 10. An apparatus (100) for the process-safe production of single crystals by the PVT method, e.g. according to any one of claims 1 to 8, comprising a process chamber (4) for accommodating a highly heatable growth cell (1) and a heating device (6, 7) for heating said growth cell (1), said process chamber comprising a process gas connection (51) which can be provided from a process gas source for filling the former with process gas, said growth cell being adapted to accommodate a source material (2) and a seed (3), said apparatus comprising a containment vessel (8) for surrounding said process chamber (4), preferably in an airtight or substantially airtight manner, said containment vessel comprising a vessel wall (9), an intermediate space (12) being created between said vessel wall (9) of said containment vessel (8) and said process chamber (4), which is arranged in such a way that said intermediate space can be filled with a protective atmosphere.

10. 10. The apparatus (100) of claim 9, wherein the vessel wall (9) also completely surrounds the process chamber (4) from top to bottom and on all sides, and / or the vessel wall (9) is designed to include a process chamber adapter (46) for accommodating process chambers of different sizes within the same vessel wall.

11. 11. Apparatus (100) according to claim 9 or 10, wherein the vessel wall is provided in a double-walled manner, e.g. the cooling device (21) is arranged in an intermediate region (122) of the double-walled vessel wall.

12. 12. The device (100) according to any one of claims 9 to 11, wherein the containment vessel (8) allows gas loss to the outside, and / or the containment vessel (8) is provided with a pressure sensor (18) which is in signal connection with a control device (19), and / or the control device (19) is designed to set an overpressure relative to the environment (30) within the containment vessel (8) based on a signal from the pressure sensor.

13. 13. The apparatus according to any one of claims 9 to 12, further comprising a support frame (60) for holding at least two wall segments (11, 91, 92, 93, 94) on a support frame, said support frame forming a holding structure for accommodating said wall segments in said support frame, said support frame and wall segments together forming said vessel wall (9) of said containment vessel (8) such that said vessel wall surrounds said process chamber (4) preferably in an airtight or substantially airtight manner.

14. 14. The apparatus (100) according to any one of claims 9 to 13, wherein at least one sealing element (72, 74, 75, 76, 77, 78, 79) is arranged on or within the support frame (60) for sealing the support frame to at least two of the plurality of container segments (91, 92, 93, 94), and / or the support frame (60) has at least one longitudinally extending groove (81, 82, 83, 84, 85, 86, 86A) on its outer side for accommodating a sealing element (72, 74, 75, 76, 77, 78, 79), and / or the support frame (60) is configured to accommodate a segment seal (72), and / or to accommodate a lid seal (74), and / or to accommodate a bottom seal (76).

15. 15. The apparatus (100) of claim 13 or 14, wherein the support frame (60) is configured to be sealed relative to the base plate (10), and / or the support frame (60) is configured to be sealed relative to the adapter (46), and / or the support frame (60) is configured to be sealed relative to the container segments (91, 92, 93, 94), and / or each container segment (91, 92, 93, 94) is provided with an individual circumferential segment seal (72).

16. 16. The device (100) according to any one of claims 12 to 15, wherein the support frame (60) is designed as a multi-part structure, and / or the support frame (60) has at least two frame elements (61, 62, 64, 66) that can be removably fastened to one another, and / or the support frame (60) has at least one of a cover element (64), a plurality of rod elements (62) and / or a base element (66), which are preferably arranged vertically.

17. 17. The apparatus (100) according to any one of claims 9 to 16, wherein the supporting frame members (61, 62, 64, 66) are designed to be sealed to one another and / or further comprise frame member seals (77) for sealing one frame member to a second frame member, the frame members preferably not being arranged flush with the segment seals (72).

18. 18. The apparatus (100) of any one of claims 12 to 17, wherein each segment seal (72) is positioned to extend through the cover member (64) and through two rod members (62) and the base member (66), and / or a cover seal (74) is disposed on an upper side of the cover member (64) to seal the cover (11) and / or is disposed on a lower side of the base member (66) to seal the base member relative to the base (10).

19. 19. The device (100) according to any one of claims 15 to 18, wherein the cover element (64) has segment side cover elements that accommodate grooves (82), and the rod elements (62) have at least one rod element that each accommodates a groove (83), preferably two rod elements that accommodate multiple grooves per rod element, and the base element or multiple base elements (66) have base elements that accommodate grooves (84), and at least one of the multiple grooves of one of the rod elements is preferably designed to align with the cover element that accommodates the groove and the base element that accommodates the groove, and segment seals (72) can be introduced circumferentially around the wall segments (91, 92, 93, 94) so ​​that the segment seal grooves align with each other for sealing.

20. 20. Apparatus according to any one of claims 9 to 19, further comprising an inert gas port (54) in the lower region of the containment vessel (8) and a closable outlet (16, 56) in its upper region.

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