PVT method and apparatus for producing single crystals in a safety process

Abstract

In order to allow a reaction gas, such as hydrogen, to be used as a process gas in a PVT process, special protective measures are required to ensure that the process can be carried out in a process-safe manner. An apparatus for carrying out a PVT process consists of a growth unit that can be heated to a high temperature and arranged in a process chamber having walls made of a heat resistant material, such as typically quartz glass. The intake valve is used to fill the process chamber with hydrogen. The heating device consists of an induction coil which surrounds the process chamber at the height of the growth unit and heats the growth unit to 2,000 DEG C to 2400 DEG C. However, the use of the reactant gas brings about the problem that the reactant gas can be mixed with ambient air and thus produce an ignitable gas mixture that will be ignited immediately on the hot components of the apparatus, without completely excluding chamber wall cracks of the process chamber. Thus, the process chamber is surrounded by a safety container filled with an inert gas.

Description

Technical Field

[0001] The present invention relates to a PVT method and apparatus for process-safe manufacturing of single crystals, the apparatus comprising a highly heatable growth unit, a process chamber in which the growth unit is located, and a heater surrounding the process chamber for heating the growth unit. Source material and a seed crystal can be introduced into the growth unit, the process chamber can be filled with a process gas, and the growth unit can be heated so that the source material sublimates and re-sublimates on the seed crystal.

[0002] Background and Summary of the Invention

[0003] In an industrial environment, the so-called physical vapor deposition (PVT) process is considered to be the standard method for producing single-crystalline silicon carbide (SiC) crystals. The source material is usually a powder containing many different crystallites. It is also possible to use bulk crystals. High-temperature chemical vapor deposition (HT-CVD) processes are known as an alternative process. In the PVT process, crystal growth usually takes place in a growth cell consisting of graphite by sublimation of SiC source material at temperatures above 2,000°C and crystallization on a predetermined SiC seed. The driving force for crystal growth is the temperature gradient applied to the growth cell by a heating device. Common methods for heating PVT equipment use resistive heaters or induction heaters. In induction heating, the growth cell (hot zone) of a vacuum-sealed process chamber is surrounded by a non-conductive material, usually (quartz) glass. Process gases are contained or introduced into the process chamber, which process gases are used, in particular, to influence the crystal growth. The process chamber can be single-walled or double-walled and can be air-cooled or water-cooled. Commonly used process gases are argon, helium, nitrogen, hydrogen and possibly other gases for target doping. The process pressure may range from vacuum conditions to atmospheric pressure. In a common process for producing doped SiC single crystals, no hydrogen is used or only a small concentration of hydrogen is used.

[0004] SiC single crystals have a wide range of applications in semiconductor technology due to their large band gap and high thermal conductivity. Therefore, the basic method for producing SiC single crystals has been the subject of many descriptions. As an example, see US2011 / 0300323 A1. As a result, the use of inert gases as process gases is not a problem from a safety point of view. Regarding the prior art, see also EP 0811708A2, US2012 / 0086001A1, GB 772,691, DE 602004001802 T2 and EP 3760765 A1.

[0005] One of the intelligent starting points and the tasks of the present invention is to make possible a method, in particular for the targeted influencing of doping combinations or for the production of undoped SiC single crystals. With regard to this starting point, a process that ensures safety was developed within the scope of the present invention, with better results than in the prior art and / or more cost-effective than known. If necessary, this can even be done using reactive gases (i.e., flammable and / or reactive (and possibly toxic) gases), for example hydrogen with a concentration of more than 5% and up to 100% as process gas.

[0006] In this process, gas molecules (e.g., hydrogen atoms) of the reaction gas attach themselves to the surface of the growing single crystal, but are immediately replaced by the components of the source material that is subsequently sublimated. In this case, the reaction gas molecules (e.g., hydrogen atoms) are briefly used as placeholders, so that a lattice with few defects, if not no defects, can be formed. The reaction gas molecules can also react with other process gases, source materials, or even hot zone materials to form other gas species that can enter the process gas atmosphere and at least temporarily attach to the crystal. Possible reaction gases such as silane, methane, propane, etc. provide elemental silicon and carbon, etc., which are incorporated into the crystal. In general, the addition of reaction gases can affect the defect density (desirable and / or undesirable). However, the exact impact depends on a large number of parameters and their interactions. The addition of reaction gases is intended to affect crystal growth.

[0007] The object of the present invention can therefore be seen in providing an apparatus and a method which enable improved or modified crystal growth.

[0008] In one aspect of the invention or in a further development of the invention, one aspect of the object may be considered to be to provide a device and a method in which a reaction gas can be used to improve crystal growth.

[0009] In a further aspect or further development of the invention, the object may be to provide a device and a method by means of which an improved crystal can be provided with low effort or low (lower) cost.

[0010] However, the use of a reaction gas containing, for example, hydrogen or other reactive elements represents a potential hazard when carrying out the process. For example, the reaction gas may be flammable or combustible and / or toxic. In the case of, for example, hydrogen, the hydroxyl reaction may take place with oxygen in the air, which is why in the context of this specification hydrogen is referred to as the reaction gas. Other examples of reaction gases currently under consideration include, in addition to hydrogen, carbon- and silicon-containing precursors or hydrocarbons and their derivatives (examples: silane or methane, propane, etc.).

[0011] Furthermore, in today's devices, the process chamber is usually formed from fused silicon dioxide, which is inherently brittle and prone to cracking. However, it is particularly preferred to use quartz glass, because it can withstand the high temperatures of the growth unit and because it does not shield the electromagnetic field of the induction coil or the radiation of the resistance heater. Similarly, a combination of induction heaters and resistance heaters can be provided. For example, the bottom plate or top plate auxiliary heater can be designed as a resistance heater, while the main heater is designed as an induction heater. In principle, however, at least in the case of quartz glass, the safety requirements also apply in a similar manner to other construction materials for providing the process chamber.

[0012] However, if the process chamber is damaged or leaking, for example if the quartz glass is broken, the hydrogen can mix with the oxygen in the environment and produce hydroxide gas, which is ignited by the heating device (hot components in the hot zone, usually graphite parts in the process chamber) and explodes. If reactive gases are used, it is not possible to carry out this process safely with the known accessories.

[0013] The reactive gases (e.g. hydrogen) mentioned in this specification are not equivalent to known doping gases. Known general doping gases are not used in the concentrations desired herein and / or are neither flammable nor otherwise reactive in the sense used in this specification. The doping gas is purged around the crystal, 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 change the PVT process. In general, the doping gas is intended to be incorporated into the crystal or crystal structure (from which the name "dopant gas" is derived) to affect the physical and / or chemical properties of the crystal, such as conductivity. In other words, molecules or components of the doping gas form the later integral building material of the crystal. Such molecules or components of the doping gas remain in the crystal and can be detected there subsequently.

[0014] In contrast, reactive gases (e.g., hydrogen) can affect crystal growth and dopant incorporation as a reactive component of the gas atmosphere, but are not incorporated into the crystal-like doping gas to affect the physical and chemical properties of the crystal. Due to the potential hazards of reactive gases, such as ignition, burnout, deflagration or even poisoning, reactive gases have not been considered to date for improving crystal growth, or in any case, the safety aspects of handling reactive gases in this environment as described above have not been fully considered. In addition, the reactive gases used are not expansion materials in the strict sense. In general PVT processes, the expansion material is SiC powder. In variants of the classical PVT process such as HT-CVD, hydrogen can be used as a carrier gas, which transports the actual source material, typically a gaseous C or Si-containing precursor. Thus, the gas is used as a carrier gas, i.e., as a transport medium for precursors and dopants. Dopants can be solid, liquid or gaseous elements or compounds, typically containing nitrogen, phosphorus, aluminum, boron or vanadium.

[0015] In the context of this further development and improvement, the present specification describes and defines various aspects of a safety container surrounding a process chamber, which safety container was developed in-house by the applicant (PVATePla). In addition, the provision of a protective atmosphere (e.g. with an inert gas) in the area between the process chamber and the container wall is investigated. A specific purpose of the safety container is to prevent or suppress an explosive gas mixture in the event of damage (e.g. rupture) to the process chamber.

[0016] In order to achieve process reliability, the equipment for carrying out the process can be arranged in a vacuum unit. However, such a unit would have to be absolutely vacuum-tight and is therefore relatively complex to manufacture, since a large number of feedthroughs are required to supply the equipment with electricity, gas and, if necessary, cooling fluid, each of which must be prepared to be vacuum-tight. Furthermore, the vacuum unit is hardly possible to maintain or repair, or it must first be opened at great expense and then closed again at great expense after the work has been completed or changed.

[0017] On the other hand, it would be advantageous to present a PVT process for the reliable production of single crystals which can be performed in equipment that can be produced with little effort and / or at low cost.

[0018] This problem is solved by the invention defined in the independent claim.The dependent claims present further embodiments and preferred embodiments of the invention.

[0019] In order to solve one, more or all of the aspects of the problem, a PVT method for safely producing a single crystal in a device is proposed, wherein the device includes a process chamber for receiving a highly heatable growth unit and a heating device for heating the growth unit, wherein the growth unit is adapted to receive a source material and a seed, and wherein the process chamber can be filled with a process gas and the growth unit is heatable. The device includes a safety container enclosing the process chamber, which is used to close the process chamber in an airtight or substantially airtight manner. Therefore, the safety container has a circumferential container wall so that a space is formed between the container wall of the safety container and the process chamber. In other words, the area extending from the inside of the container 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 safety container is also circular, the void space defines an annular segment (considered as a plane) or a hollow cylinder with a wall thickness of b, an inner radius r (corresponding to, for example, the wall of the process chamber), an outer radius R (corresponding to, for example, the wall of the safety container) and a height h (measured, for example, from the bottom to the cover).

[0020] The method proposed here comprises the steps of providing a protective atmosphere in the void space and filling the void space with the protective atmosphere and providing a process gas in the process chamber. The process gas can contain, for example, a reactive gas or consist of a reactive gas. In other words, the process provides that first the intermediate space is filled with the protective atmosphere, for example so that any air that may have been present previously has been replaced as completely as possible, and only when the safety container is ready for use by filling with the protective atmosphere (and outputting this, for example, as a signal) does the further process sequence begin.

[0021] In principle, process gases can be introduced into the process chamber before the safety container is ready for use, if the chamber has not yet reached a heat that could ignite the process gases in the event of a leak in the process chamber. Similarly, if no process gas or at least no reactive gas has been introduced, the process chamber can be heated to, for example, operating temperature before the safety container is ready for use. The transition between providing the safety container and starting to operate the process chamber can be smooth. However, it is generally preferred if the supply of the safety container atmosphere in the void space is completed before the process gas is introduced into the process chamber and / or the growth unit is heated to the deployment temperature. In other words, it is preferred if the supply of the process gas in the process chamber is completed after the void space is filled with the protective gas. Therefore, it is also preferred that filling the void space with a protective atmosphere (in particular, initially filling the void space with a first protective atmosphere or filling the void space) also includes replacing the air present in the void space, i.e. before initiating sublimation of the source material.

[0022] Therefore, it is particularly advantageous if the filling of the safety container occurs or is completed at least when sublimation of the source material occurs, because high temperatures are present at this time that can ignite the reactive gases. For safety reasons, it is advantageous if the filling of the safety container occurs before the reactive gases are introduced into the process chamber.

[0023] If the process chamber is damaged (such as rupture) in this arrangement, the reaction gas of the process chamber is mixed with a protective atmosphere in a safety container, for example with an inert gas, to form a non-explosive gas mixture, so that no explosion can occur even in a hot environment. This safety measure is particularly important if the reaction gas is flammable or prone to deflagration, such as hydrogen.

[0024] The method further comprises heating the growth unit by means of a heating device so that the expanded material sublimates or re-sublimates at the seed crystal. Preferably, the heating of the growth unit can be performed from all radial sides. For this purpose, the heating device can annularly surround the process chamber.

[0025] When providing a protective atmosphere in the void space, a positive pressure is preferably set relative to the ambient pressure. For example, the overpressure in the protective container (safety container) can be set, for example, to at least 1 mbar or more above the ambient pressure, preferably 3 mbar or more above the ambient pressure, more preferably 5 mbar or more above the ambient pressure. When a positive pressure is set in the protective container relative to the environment, only trace amounts or no gas from the environment can enter the protective container. This ensures, for example, that no oxygen enters the protective container and avoids possible reactions in the protective container when process gases are discharged into the protective container.

[0026] If the safety container is constructed so that gas leakage to the outside is allowed, in particular to a small extent, i.e. it is only approximately gas-tight, then it is particularly easy to implement. This makes the design of the safety container more cost-effective, because the requirements for particularly high gas tightness do not have to be taken into account, and no undesirable reaction of the reaction gas will occur outside the process chamber. For example, the container can have an allowable leakage rate of more than 0 l / min. Therefore, for cost reasons and unproblematic reasons (especially due to the choice of design and geometry), it can be advantageous to allow a leakage rate in the range of 0≤leakage rate≤5 l / min, or even in the range of 0≤leakage rate≤30 l / min. For example, the allowed leakage rate can be greater than 2 ml / min, less preferably greater than 5 ml / min, even less preferably greater than 10 ml / min, even less preferably greater than 50 ml / min, or even greater than 100 ml / min. On the other hand, it is unreasonable to allow a leakage rate of the container that is too high for economic reasons and possible workplace safety reasons. For example, it may be desirable to limit the leakage rate to less than 30 l / min, preferably less than 10 l / min, further preferably less than 4 l / min, still more preferably less than 1 l / min, further preferably less than 500 ml / min, and still further preferably less than 150 ml / min. The aim is to achieve a leakage rate in the range of from 2 ml / min to 50 ml / min, preferably from 10 ml / min to 20 ml / min.

[0027] For example, the safety container may have a total volume greater than 50 1, preferably greater than 100 1, and / or a total volume less than 500 1, preferably less than 250 1. In other words, the ratio of the leakage rate to the total volume may be set within a range of less than or equal to 1%, preferably less than or equal to 2%, more preferably less than or equal to 5% per minute.

[0028] In order to maintain the protective atmosphere, for example, an inert gas may be supplied to compensate for gas losses and to accumulate and / or maintain an overpressure in the safety container. Overpressure prevents atmospheric oxygen from entering the safety container from the outside. Therefore, the relative overpressure in the safety container may be maintained, for example, in a range of 1 mbar or more above ambient pressure, preferably 3 mbar or more above ambient pressure, more preferably 5 mbar or more above ambient pressure, to 50 mbar or less above ambient pressure, preferably 30 mbar or less above ambient pressure by a pressure control system. However, a completely airtight seal with a leakage rate of 0 ml / min or an immeasurably low leakage rate is also substantially covered by this, wherein an overpressure may also be maintained in the seal.

[0029] In order to ensure that the air is replaced as completely as possible from the safety container, the present description may further provide for allowing a first inert gas to enter the safety container to fill the safety container. The first inert gas may be heavier than air, so that it enters the lower region of the safety container, moving the air upwards. For this purpose, for example, a closable outlet at the upper end of the safety container may remain open until the air has escaped.

[0030] Preferably, the protective atmosphere comprises an inert gas, such as argon. Due to the high density of argon, it collects at the bottom of the safety container and slowly moves the air upward without mixing with it. Other examples of protective atmosphere configurations currently available in an economically feasible manner include xenon, nitrogen or carbon dioxide. In principle, the protective atmosphere can include any fluid, whether a single fluid or a mixture of fluids, which can provide a protective function because it neutralizes the reaction gases and / or prevents negative effects, such as deflagration, in the event of excessive or unacceptable escape from the process chamber. The protective atmosphere can also exist in a liquid or solid state, for example under normal conditions of a standard atmosphere.

[0031] When the air has been removed by the first inert gas, it can be replaced by another inert gas, for example a cheaper inert gas. Therefore, the invention further provides that after the safety container has been filled once or several times with the first inert gas, the first inert gas is replaced by a second inert gas, for example nitrogen.

[0032] In order to ensure that no further reactive gas is introduced into the apparatus in the event of a rupture of the process chamber, provision is made for the safety container to have a gas sensor capable of detecting the presence of reactive gas in the safety container. It can also be provided that the supply of process gas to the process chamber is interrupted when the gas sensor detects reactive gas in the safety container.

[0033] In a further development, if a lower pressure is detected in the event of damage (e.g. a break in the quartz glass), the gas supply can be interrupted by means of a further pressure sensor or pressure switch which monitors the pressure in the process chamber. For example, a drop below an absolute pressure of p≤980 mbar (abs.), preferably p≤950 mbar (abs.), more preferably p≤920 mbar (abs.) can be detected for monitoring. Thus, an interruption of the reactive gas supply can also occur independently of the detection of reactive gas, such as hydrogen, in the space between the process chamber and the cooling jacket.

[0034] For example, in the case of a break in the quartz glass, the opening of the process chamber can be detected or indicated by one of the following criteria, for example. The detection of the reaction gas / hydrogen can be carried out by a gas sensor in the safety container. In this case, the gas sensor is arranged to specifically detect the process gas or the process gas content in the safety container. Alternatively or cumulatively, an overpressure P in the safety container can be detected. S , and if the overpressure disappears, it can be concluded that the process is faulty or the seal is leaking (for example, the overpressure P is greater than that of the atmosphere). S ≤ approx. 2 mbar). This is possible if an (even low) overpressure relative to the atmosphere is set in a safety vessel, which is easily detectable. Such vessel overpressure therefore also represents a safety standard for plant operation. The pressure test can therefore represent a step in the safety inspection of a plant.

[0035] Therefore, the steps in the method presented herein can be defined by a safety check of the safety container. This safety check can be performed by measuring an adjustable overpressure P in the safety container. S In other words, for example before starting the production of crystals, the tightness can be checked with respect to the leakage rate or density, so that if the leakage rate is too high, a safe state is assumed or indicated, i.e., for example, operation is not possible or an alarm is issued.

[0036] Furthermore, alternatively or cumulatively, the pressure Pp in the process chamber can be measured and no process disturbance is detected as long as a pressure Pp≤950 mbar (absolute), or Pp≤920 mbar (absolute), or for example Pp≤980 mbar (absolute) is maintained, while exceeding this pressure threshold can indicate a process disturbance. Furthermore, alternatively or cumulatively, a sudden pressure surge / pressure increase in the process chamber (a pressure increase rate greater than the maximum possible or permissible pressure increase rate due to the gas to be introduced) can be detected and indicate a process disturbance, such as a quartz glass break. The above criteria are advantageously independent of each other and can be used individually or in combination with each other to achieve a shutdown of the process gas or hydrogen supply and thus, for example, ensure the safety standards of the device. In other words, by means of a pressure measurement of Pp before and / or during the process, it can be detected more quickly whether a process gas will enter or enter a safety container.

[0037] The safety container can advantageously provide a cooling function. The cooling function can be designed, for example, so that a cooling medium (such as water) circulates around or through the safety container. For example, for this purpose, the safety container can have at least one cooling medium line through which the cooling medium flows. The at least one cooling medium line can be attached to the container wall of the safety container or at least connected to the container wall in a thermally conductive manner, possibly with the aid of a thermally conductive paste. For example, the cooling medium line is welded to the container wall. For example, the cooling medium line comprises copper, which is easy to process and / or is designed to be particularly thermally conductive.

[0038] Safety containers can be equipped to provide temperature control of process conditions. For example, by the safety container designed in this way, constant temperature (or similar temperature range) can be maintained all the time, and no matter how the environmental conditions are, these environmental conditions can change significantly. For example, the environment can include a daily temperature curve or even seasonal temperature fluctuations, or can also be affected by possible thermal processes occurring nearby, and the safety container designed advantageously can keep these environmental conditions away from the process. Alternatively or cumulatively, the cooling function can also be affected in response to process parameters (such as the temperature in the process chamber) to achieve temperature control of the cultivation process. For example, the cooling medium flow rate through at least one cooling medium conduit can be changed in response to environmental conditions and / or process parameters to change heat dissipation. For example, when the environment and / or process temperature is warmer, more cooling media can be deployed, and / or colder cooling media can be used, and / or alternative cooling media can be introduced.

[0039] The cooling medium line can be arranged outside the container wall, preferably connected to the container wall in a heat-conducting manner or arranged adjacent to the container wall in any case. The cooling medium line can then cool the container wall and ensure that the heat is not radiated into the immediate environment of the device, but is carried away by the temperature control device. The external arrangement of the cooling medium line has the following advantages: since the cooling fluid does not penetrate into the interior, less penetration into the protective atmosphere or the interior of the safety container needs to be provided. For example, the container wall can be double-walled, i.e. with an inner wall and an outer wall, whereby the cooling medium line can be arranged between the inner wall and the outer wall of the container wall. The cooling medium line is then hidden together with the fasteners for the cooling medium line and is protected from mechanical damage. Since the temperature control device is able to dissipate most of the heat output from the process chamber, the outer wall of the container wall does not heat up, and there are no or few restrictions in terms of material selection or protection against contact.

[0040] The present description also relates to an apparatus for process-safe production of single crystals, for example by a PVT method, comprising a process chamber for accommodating a highly heatable growth unit and a heating device for heating the growth unit. The process chamber has a process gas connection for filling the process chamber with a process gas that can be provided from a process gas source. The growth unit is prepared to receive source material and a seed crystal.

[0041] The device comprises a safety container for enclosing a process chamber, preferably enclosing the process chamber in a gas-tight or substantially gas-tight manner. For example, the safety container enables process safety operations with reactive gases as process gases. The safety container has a container wall so that an intermediate space is created between the container wall of the safety container and the process chamber, which intermediate space is arranged so that the intermediate space can be filled with a protective atmosphere. The process chamber is arranged in the safety container. In addition, the safety container can have a connection to a protective gas source so that the intermediate space between the container wall of the safety container and the process chamber can be filled with a protective gas, for example before a PVT process is performed.

[0042] The container wall may be a segmented container wall which radially surrounds the process chamber at least on all sides, the container wall comprising at least two wall segments. By means of the segmented container wall, the outer wall of the protective container may be formed for closing the process chamber, preferably in a gas-tight or substantially gas-tight manner. The container wall may comprise wall segments, such as a feed-through segment, a test or inspection segment, a cooling segment, a cover segment (which may be designed, for example, in multiple parts), and / or a bottom segment.

[0043] The container wall is preferably designed to also close the process chamber from above and / or below. Preferably, the container wall can be designed to completely close the process chamber on all sides. However, this is not necessary in every case. For example, if the process chamber is recessed in the base plate, parts or sections of the process chamber can also be designed without a direct protective covering in the form of a safety container, and parts of the process chamber can be surrounded by a safety container located above the base plate. In this way, the protective container can be designed as far as the base plate and, if necessary, be tightly sealed there.

[0044] In another embodiment, the container wall may include a process chamber adapter for accommodating process chambers of different sizes on the same container wall. Thus, the container wall component may be provided in one size or in a few sizes to cover a variety of different process chambers or process chamber sizes.

[0045] The container wall may have a double wall design. The double wall construction of the container wall may have design advantages or simply achieve a pleasing exterior without components of the secure container being visible from the outside.

[0046] For example, a cooling device can be arranged in the middle region of a double-walled container 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 container wall. Moreover, in this case, the assembly of the cooling device is particularly simple, since it can be attached to the inner wall of the container wall, for example by gluing, soldering or screwing via connectors. The outer cover then covers the middle region so that it is protected from external interference or unintentional damage, which is particularly advantageous if the cooling device is located there.

[0047] The safety container may be configured to allow gas to escape to the outside. It may have a pressure sensor, whereby the pressure sensor is signal-connected to a control device, and the control device is designed so that an overpressure (relative to the environment or atmosphere) is set in the protection container based on these pressure sensor signals.

[0048] The pressure sensor may also include or be formed by a pressure switch. For example, the pressure sensor may be formed by a differential pressure switch that measures the pressure difference between the inert gas in the protective container and the atmosphere or the environment. If necessary, the pressure sensor may trigger a circuit, for example as a safety circuit or a switch-off, when the pressure exceeds or falls below an adjustable pressure difference.

[0049] With regard to the installation orientation of the device, it is advantageous if the inert gas connection is located in the lower region of the protective container and the closable outlet is located in its upper region. This allows the air in the protective container to be completely replaced by the inert gas flowing from the bottom to the top of the outlet before it leaves the protective container.

[0050] The safety container preferably has two inert gas connections for two different inert gases.After the first inert gas has removed the air from the safety container, a low-cost fluid (such as nitrogen) can be filled as a second fluid via the second inert gas connection, thereby replacing the first inert gas.

[0051] Preferably, the safety container has a gas sensor responsive to the reactive gas. In this way, for example in the event of a rupture of the process chamber, it can be determined that the reactive gas (eg, hydrogen) has entered the safety container.

[0052] As described above, the apparatus can be used, for example, to produce SiC single crystals by a PVT process. For this purpose, the growth unit is equipped with Si silicon carbide as source material and the process chamber can be filled with hydrogen as reactive gas in addition to other process gases (eg argon).

[0053] In a further embodiment, the device may further comprise a support frame for holding at least two wall segments on the support frame. In this case, the container wall is thus segmented and has at least two wall segments. These wall segments together form the container wall. For example, one wall segment may be provided as a fixed wall segment, while the other wall segment may be designed to be detachably connected so that it is easily removable.

[0054] The support frame thus forms a holding structure for receiving a wall segment on the support frame, so that the support frame and the wall segment together form a container wall of a safety container (8) for closing the process chamber preferably in a gas-tight or substantially gas-tight manner.

[0055] At least one sealing element may be arranged on or in the support frame for sealing the support frame with at least two container segments and / or for sealing the safety container with the environment. In other words, the support frame may be designed to be sealed to reduce gas leakage from the safety container to the environment.

[0056] Alternatively or cumulatively, one or more wall segments may have a correspondingly formed sealing receptacle. In other words, the sealing element may be arranged on the wall segment. Such a sealing receptacle may be formed as a material curling or edge, against which the sealing element may be placed or inserted. Typically, in such an arrangement, the sealing element will preferably be bonded by an adhesive. Alternatively, the wall segment may be designed to have a greater material thickness, so that a groove may be provided for the sealing element, whereby it may be necessary to take into account that this may increase the cost of the corresponding wall segment. If it is heavier due to the greater material thickness, it may also be more difficult to handle.

[0057] Particular advantages are achieved by combining a multi-part protective shell with a sealing element, as this allows common construction materials such as metal or steel to be used for the wall element and still achieve adequate overall sealing of the protective container. However, in environments with core temperatures exceeding 2000°C, this design presents some challenges that can be addressed with surprising ease using the embodiments explained and exemplified in this specification.

[0058] Preferably, the support frame has at least one longitudinal groove on the outside 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 the retaining groove is that the sealing element is firmly held in the retaining groove and can only be removed in the retaining groove, for example by applying a dislodging force. In the present case, it is possible to use a trapezoidal groove as a retaining groove, because these sealing elements can be reused several times and can remain in such a retaining groove. The sealing element can be designed in the form of an O-ring or a lip seal.

[0059] The protected installation of the sealing elements described herein ensures that the sealing elements will not burn or age rapidly in extremely hot environments. For example, the sealing elements are arranged to be protected from radiation. This arrangement then collaboratively enables the use of permanently reusable materials for these sealing elements. Furthermore, since these sealing elements are permanently reusable and will not be damaged by operation, they can be advantageously arranged in retaining grooves again, which further simplifies the handling of the protective container in the final analysis (in this case, when the wall sections are assembled with the support frame). In this way, these sealing elements are protected from dust and damage and are retained in these advantageous retaining grooves in a protected mounting position, in which these sealing elements are protected from radiant heat during operation.

[0060] Alternatively or adapted to the case of at least one sealing element on the support frame, at least one wall segment may have a sealing receptacle, i.e. a special shape, for fastening the sealing element on the support frame, as described above. For this purpose, the edge of the wall segment may overlap externally relative to the edge of the support frame, and the sealing element may be attached to the edge projection. Another embodiment provides a longitudinal groove for receiving the sealing element on the narrow side. In this case, the wall segment may have a greater overall wall thickness or a wall reinforcement at least near the edge.

[0061] The support frame may be configured to receive a segment seal, and / or to receive a cover seal, and / or to receive a bottom seal. In other words, the support frame may be designed to accommodate one or more seals having different purposes.

[0062] The support frame may be sealed against the base plate, for example by a base seal. The support frame may be alternatively or cumulatively sealed relative to the adapter, for example by an adapter seal. The support frame may be alternatively or cumulatively sealed relative to the container segments, for example by segment seals.

[0063] Each container segment can be assigned a separate circumferential segment seal. For example, if four container segments are used, four separate segment seals can be provided so that these container segments are sealed individually. In practice, it has been shown that it is advantageous if the container segments are not electrically connected to each other. However, if they are made of an electrically conductive material (which is also preferred), because these container segments are heat-conductive and there are cheap, heat-conductive and electrically conductive materials, it may be advantageous to electrically insulate these container segments from each other. This is particularly true if induction heating is used. The insulation can be provided by connecting pieces via a support frame so that these container segments can be installed at a certain distance from each other. In this case, it is advantageous if each container segment is assigned its own segment seal, which, if necessary, takes on the function of heat insulation.

[0064] The support frame may be constructed in several parts. The support frame may include at least two frame elements that are releasably attached to each other. The support frame may alternatively or cumulatively include at least one of a top plate element, a plurality of rod elements, preferably arranged vertically, and / or a bottom plate element. The multi-part structure of the support frame simplifies the overall setup of the device and may also help to further reduce the cost of the device. In addition, the multi-part design of the support frame provides advantages for any maintenance work that may be required and / or replacing the process chamber when the crystal has completed growth and the same container is to be used to protect another process chamber or another growth process.

[0065] In other words, the safety container is designed to be reusable and can be used to produce a large number of crystals using the PVT process, which can result in considerable savings, especially in terms of costs. The safety container can be modularly built up around a process chamber before a growth process is performed and can be disassembled again in a simple manner after crystal growth has been performed. In a particularly advantageous embodiment, all components can be reused, so that the protective container can be modularly built up again around a new process chamber before another growth process is performed. The multi-component design means that the protective container can be easily and effortlessly assembled around a further process chamber and can provide a safe atmosphere.

[0066] The supporting frame elements may also be designed to seal against each other so that even between contact or tangent areas between individual supporting frame elements no or only a small amount of inert gas escapes into the environment. Alternatively or cumulatively, a frame seal may be included for sealing one frame member against a second frame member. The frame seal may, for example, be arranged in a frame seal plane which is not arranged in the same plane as the segment seals.

[0067] For example, one embodiment may be such that each segment seal passes through the cover element, through the two rod elements, and through the bottom element. Alternatively or cumulatively, the cover seal may be arranged on the upper surface of the cover element for sealing the cover. Further alternatively or cumulatively, the bottom seal may be arranged on the bottom side of the bottom element for sealing the bottom element relative to the bottom. The bottom may be provided as a manufactured component or as a mounting plate.

[0068] The cover element may have a segment sealing groove on the segment side. The rod elements may each have at least one segment sealing groove, preferably two segment sealing grooves per rod element. The base element may have a segment sealing groove. For example, at least one of the segment sealing grooves of one of the rod elements may be designed to align with the segment sealing groove of the cover element and the segment sealing groove of the base element, so that a segment seal can be inserted into these mutually aligned segment sealing grooves for circumferential sealing of the wall segment.

[0069] Furthermore, the apparatus may comprise a support frame for holding at least two wall segments thereto. The support frame may be of multi-part construction. Alternatively or cumulatively, the support frame may comprise at least two frame members which are releasably attached to each other. Alternatively or cumulatively, the support frame may comprise at least one of: a top plate element, a plurality of (e.g. vertical) rod elements, and / or a bottom plate element.

[0070] The support frame may have at least one longitudinal groove for receiving the sealing element on the outside. Alternatively or cumulatively, the support frame may be designed to accommodate a section seal, and / or to accommodate a cover seal, and / or to accommodate a bottom seal. Alternatively or cumulatively, the cover element may be formed integrally, for example for mounting on a rod element. Alternatively or cumulatively, the cover element may be connected to the bottom element via a rod element. Alternatively or cumulatively, these elements of the support frame may be detachably connected to each other, for example screwed, so as to provide a stable structure on the one hand and detachable on the other hand, for example for maintenance or opening purposes.

[0071] The base element can be designed in several parts and have a plurality of base fastening sections and intermediate sections and be prepared such that the rod element can be placed between the base fastening sections and on the intermediate sections. Alternatively or cumulatively, the base element can be designed in one part and the rod element can be inserted into a recess of the base element. Alternatively or cumulatively, the cover element can be formed in one piece and the rod element can be inserted into a recess of the cover element. Further alternatively or cumulatively, the cover element can form a laterally projecting collar so that the wall elements can be located below the cover element without the wall elements projecting laterally beyond the cover element.

[0072] The support frame may be designed as an electrical insulator. This ensures that the wall segments are electrically insulated from each other. Alternatively or cumulatively, the support frame may be non-magnetic. This ensures that the wall segments cannot form magnets that could interfere with the heating device. Further alternatively or cumulatively, the support frame may be formed from a temperature-resistant material. Further alternatively or cumulatively, the support frame may be formed from a thermally conductive and / or non-conductive material. Further alternatively or cumulatively, the support frame may comprise or consist of a ceramic, plastic or composite material or a combination thereof.

[0073] Preferably, the support frame may form a holding structure for receiving a wall segment on the support frame, such that the support frame and the wall segment together form a container wall of the safety container, preferably for closing the process chamber in a gas-tight or substantially gas-tight manner. An intermediate space may be created between the container wall of the safety container and the process chamber, which intermediate space is arranged such that the intermediate space can be filled with a protective atmosphere. Alternatively or cumulatively, the safety container may close the process chamber on all sides.

[0074] The heating device may be designed to surround the process chamber.Alternatively or cumulatively, the heating device may be formed annularly around the process chamber.

[0075] In the following, the invention will be described in more detail by means of embodiment examples and with reference to the drawings, wherein identical and similar elements are partly provided with identical reference numerals and features of different embodiment examples may be combined with one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 is a cross-sectional view of a device according to the present invention,

[0077] Figure 2 A perspective view and simplified diagram of a partially assembled safety container.

[0078] Figure 3 is a three-dimensional cross-sectional view of an embodiment of the device,

[0079] Figure 4 is an exploded view of an embodiment of the device,

[0080] Figure 5 For the design of the support frame,

[0081] Figure 6 A detailed cross section of an embodiment of a support frame,

[0082] Figure 7 Further details of embodiments of the support frame;

[0083] Figure 8 Another detail of an embodiment of a support frame;

[0084] Fig. 9 Details of the path of the seal in the support frame,

[0085] Fig.10 For further details of the path of the seal in the support frame,

[0086] Fig.11 For the cross-sectional details of the equipment,

[0087] Fig.12 A partially assembled safety container with a supporting frame,

[0088] Fig.13 Design of an exemplary section of a double-walled container wall with a temperature control device,

[0089] Fig.14 Details for the connection of temperature control devices,

[0090] Fig.15 Design of a cooling section of a container wall as part of a temperature control device,

[0091] Fig.16 is a perspective view of an embodiment of a safety container,

[0092] Fig.17 is a partially opened perspective view of an embodiment of an apparatus having a process chamber,

[0093] Fig.18 A perspective view of the device. Specific embodiments

[0094] Figure 1 A cross-sectional view of an embodiment of the device is shown. In the center of the device, located on a support, is a growth unit 1 consisting of a hollow cylinder with a bottom and a cover that closes both ends of the hollow cylinder. The growth unit 1 is made of porous graphite. An expansion material 2 is layered on the bottom. On the back of the cover is a seed crystal 3.

[0095] The growth unit 1 is arranged in a process chamber 4, which consists of a hollow cylinder closed at both ends by a bottom plate or a top plate. The cylindrical wall of the process chamber 4 consists of heat-resistant quartz glass and can be filled with process gas via a process gas connection with a gas inlet valve 5. Since the graphite of the growth unit 1 is porous, the process gas from the process chamber 4 also enters the growth unit 1.

[0096] The heating device 6 comprises an induction coil 7 which surrounds the process chamber 4 at the level of the growth cell. When current flows through it, it generates an electromagnetic field which induces a current in the graphite of the growth cell 1, heating the growth cell 1 to over 2,000°C up to 2,400°C.

[0097] The high temperature and the required magnetic permeability of the electromagnetic field of the induction coil 7 make it necessary to manufacture at least the cylindrical wall of the process chamber 4 from a temperature-resistant material suitable for this purpose. Typically, the cylindrical wall of the process chamber 4 is made of quartz glass, which has proven to be particularly suitable and inexpensive to manufacture.

[0098] In order to produce a SiC single crystal, silicon carbide is added to the growth unit 1 and the process chamber 4 is filled with a process gas. The process gas may include, for example, a reaction gas containing a certain proportion of hydrogen and / or consisting of up to 100% hydrogen. If the growth unit 1 is now heated by the induction coil 7, the silicon carbide sublimates and accumulates layer by layer on the seed crystal 3, so that the SiC single crystal grows. If hydrogen is used in the process gas, it can be ensured that crystal defects are not formed in the crystal in the process, or that no foreign atoms are deposited at the corresponding growth site. The incorporation of undesired foreign atoms usually leads to a change in conductivity, which may also occur locally if necessary and may be harmful as a disturbance or quality reduction. By using a reactive gas, the process gas composition can also be affected by reactions with other process gases or hot zones (graphite components). The changed process gas composition can then affect the crystallinity, structure, crystal defects and doping of the SiC crystal.

[0099] For example, it can be shown that beneficial effects are achieved with a hydrogen content of 5% or more in the process gas, whereby at such low concentrations of less than 5% hydrogen in the process gas, protective measures, for example for explosion protection, are generally not required. Particularly advantageous results are obtained in the range between a hydrogen content of 5% and a hydrogen content of about 40%, wherein an increased purity of the crystals is obtained in the range of a hydrogen content of 15% in the process gas (preferably ±5%). In principle, however, the use of the safety container according to the invention is also advantageous at low concentrations.

[0100] However, as described above, the use of a reactive gas such as hydrogen is problematic since, in the event of a possible rupture of the walls of the process chamber 4, the reactive gas mixes with the ambient air (no safety container is described here) so that, for example, an ignitable gas mixture can be produced which would immediately ignite on hot parts of the apparatus.

[0101] The process chamber 4 of the embodiment shown here is surrounded by a safety container 8, which includes a cylindrical container wall 9 surrounding the cylindrical wall of the process chamber 4, the container wall 9 being located on a bottom plate 10 and closed at the top by a top plate 11. The bottom 10 and the top plate 11 of the safety container 8 are adjacent to the bottom and the top plate of the process chamber 4.

[0102] The safety container 8 can also be part of the cooling concept of the device. In other words, the safety container 8 can be integrated into the cooling concept of the device. For this purpose, the cylindrical container wall 9 can be provided with cooling channels connected to the cooling system. Therefore, the cooling concept can provide that the safety container 8 provides a cooling function for the device. For example, a cooling medium (such as water) can be circulated through the safety container 8. On the other hand, it can be provided that the safety container atmosphere in the safety container 8 provides a cooling function. For example, for this purpose, the safety container atmosphere can be circulated so as to dissipate the heat output. In general, the safety container can be equipped in such a way that the safety container with its cooling function can be used to control the temperature of these process conditions so that a constant temperature (or a similar temperature range) can always be maintained, regardless of the ambient conditions, which can vary significantly. For example, the environment can include a daily temperature curve or seasonal temperature fluctuations, or can also be affected by any thermal processes occurring nearby.

[0103] Finally, the safety container 8 can be constructed so that it is metallically conductive. The metallically conductive safety container 8 can provide shielding for the processes occurring inside in the manner of a Faraday cage, so that, for example, the electromagnetic alternating field in the container wall 9 of the safety container 8 is given a clear end point and does not extend asymptotically, potentially to infinity. This may be advantageous if several devices are arranged adjacent to each other, in which case the corresponding alternating fields can influence each other and interfere with each other's process conditions. In other words, the metallically conductive safety container 8 can ensure uniform process conditions, even under the conditions of several devices (possibly also of different types), which can be arranged close to each other without the processes interfering with each other.

[0104] Overall, it can be seen that the safety container 8 is able to solve several tasks simultaneously in a synergistic manner. This not only makes it possible to provide the mentioned protective atmosphere, which enables the application of reactive gases in the process chamber. In addition, the safety container 8 is able to shield the process chamber from various environmental conditions, such as temperature fluctuations or fluctuating electric and / or magnetic fields, and thus ensure uniform process conditions for the process taking place in the process chamber.

[0105] At the bottom of the safety container 8, an annular pipeline with one or more connections can be arranged at the annular space 12 between the container wall 9 of the safety container and the cylindrical wall of the process chamber 4 composed of quartz glass. The annular pipeline is connected to an argon source 14 and a nitrogen source 15 via a reversing valve 13.

[0106] A closable exhaust valve 16 is located in the top plate 11 of the safety container 8. A gas sensor 17 (such as, for example, a hydrogen sensor) and a pressure sensor 18 are also provided herein.

[0107] The entire device may be covered by a cover 20 made of unbreakable plastic or metal sheet resting on the bottom of the secure container.

[0108] Furthermore, a control device 19 is provided which is signal-connected to the sensors 17 , 18 and which controls the switchover valve 13 , the exhaust valve 16 and the intake valve 5 via control lines for the hydrogen supply.

[0109] The control device 19 allows the following process to be performed: Filling the safety container 8 with an inert gas before the process chamber 4 is filled with hydrogen:

[0110] (1) Open the exhaust valve 16.

[0111] (2) Switch the reversing valve 13 so that argon gas from the argon gas source 14 slowly flows into the gap 12 from below, so that the gap 12 is filled with argon gas from below, and the existing air is removed through the opened exhaust valve 16 (or pressure reducing valve, etc.).

[0112] (3) Close the exhaust valve 16 and the reversing valve 13.

[0113] (4) Observe the filling pause to allow any residual air to separate upward from the argon.

[0114] (5) If necessary, repeat steps (1) to (3) once or several times.

[0115] (6) Open the exhaust valve 16.

[0116] (7) The reversing valve 13 is switched so that nitrogen slowly flows into the gap 12 from below, the gap 12 is filled with nitrogen from the nitrogen source 15 from below, and the existing argon is removed through the opened exhaust valve 16 .

[0117] (8) Close the exhaust valve 16.

[0118] (9) The overpressure in the space 12 is set and maintained by the controlled opening of the reversing valve 13 so that no air can flow into the space 12 despite the presence and acceptance of leakage in the safety container.

[0119] A sufficient overpressure is approximately 2 mbar above the ambient pressure.

[0120] In any case, steps (1) to (3) and (9) must be performed. Steps (4) and (6) to (8) are optional.

[0121] In order to be able to check whether the interspace 12 is deprived of oxygen to a sufficient extent, an additional oxygen sensor can be provided.

[0122] Behavior in case of glass wall breakage during operation:

[0123] (1) constant monitoring of the gas sensor 17, and

[0124] (2) When the gas sensor 17 detects hydrogen in the gap 12, the hydrogen supply is cut off.

[0125] See also Figure 2 , shows a perspective view of a simplified embodiment of a partially assembled safety container 8, wherein various additional components and the process chamber 4 are not shown for the sake of clarity. In addition, for the sake of completeness, it should be noted that Figure 2 The embodiment shown has no details for sealing the interior region 12, so that the leakage rate achievable with this embodiment will be relatively high. The improved sealed safety container has embodiments of the other figures.

[0126] exist Figure 2 In the embodiment, the temperature control device 21 is at least partially arranged in the safety container 8, whereby the fluid can be supplied to the coolant line 22 through the connection 23. The coolant line 22 can be connected to the inner wall 44 of the safety container 8, for example, glued, brazed, welded or screwed thereto. The heat power reaches the inner wall 44 from the process chamber 4 mainly as radiant heat, and the heat power can be effectively dissipated from the inner wall 44 by the temperature control device 21. For example, liquid water can be used as a coolant. The amount of heat that can be dissipated by the temperature control device 21 can preferably be adjustable. For example, the amount of heat that can be dissipated can be influenced by the temperature specification and / or the throughput or speed of the coolant, that is, temperature control can be provided. Then, in response to the sensor signal measuring the ambient temperature and / or the process temperature, the temperature control of the process chamber 4 can be achieved by a temperature controller, so that there is a substantially constant temperature in the process chamber 4 during the process cycle.

[0127] The safety container 8 has sight glasses 32 which bridge the inner area 12 and allow observation of the process chamber 4, for example for the purpose of process monitoring. In order to keep the direct heat radiation small, the sight glasses 32 are designed to be relatively small. In addition, Fig.14 Details of the refrigerant line 22 with the line attachment 22A, the connector 23, the transition piece 23B and the connector attachment 23A are shown.

[0128] Figure 3 A cross-sectional view of an embodiment of an apparatus 100 is shown. 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 arranged partially inside and outside the safety container 8, and for example the power electronics can be arranged outside, so that a sealed feedthrough 62 is provided to reduce gas leakage. The induction coil 7 with the electronics is located in the inner space 12, i.e. in the space that can be occupied by the safety container atmosphere.

[0129] The inert gas can be supplied via an inert gas supply opening 54 on the lower side of the interior 12 (several inert gas supply openings 54 may be provided). An exhaust valve 16 is arranged on the upper side 11, by means of which, for example, external air (containing oxygen) initially arranged in the protective container 8 can be discharged from the protective container 8, for example by introducing a protective gas that is heavier than air. Subsequently, if a connecting line (not shown) is connected to the exhaust valve 16, a circulation of the protective gas can also be provided, for example to remove heat from the protective container 8, or to ensure a regular replacement of the protective gas.

[0130] In the case shown here, the coolant line 22 of the temperature control device 21 is arranged in the container wall 9, which has a double-walled design. Figure 3 In the cross-section of the safety container 8 with the process chamber 4 shown, the interior 12 of the safety container 8 for receiving the protective atmosphere extends from the chamber wall 41 and, for example, extends all the way around the process chamber 4 to the container wall 9, and the interior 12 is designed to be sealed relative to the container wall 9 to keep the gas leakage rate from the interior 12 to the environment 30 low.

[0131] also, Figure 3 The embodiment shown shows a special feature, in which the process chamber 4 is equipped with an adapter 46. In the embodiment shown, the adapter 46 has two replaceable upper covers 47, 48, so that depending on the desired process height, the upper cover 47 or the upper cover 48 placed further inwards can be used. Thus, if necessary, the covers 47, 48 can be used interchangeably with each other.

[0132] See also Figure 4 , the apparatus 100 is shown in an exploded view, in which the components of the safety container 8 used are visible. In this embodiment, for better illustration, the process chamber 4 is arranged inside it. The quartz glass shell 41 (process chamber wall) forms the inner end of the intermediate space 12, and the intermediate space 12 is arranged between the quartz glass shell 41 (as the inner wall of the safety container) and the container wall 9. The induction coil 7 is used as a heater and is arranged annularly around the process chamber 4.

[0133] The process chamber wall 41 is initially open at the top, the process chamber 4 being closed or sealed by means of a chamber closure 42. The upper closure is formed by an adapter ring 46 which engages in the process chamber wall 41 with a dual function and seals the safety container 8 in the upper region towards the interior and towards the cover 11. The adapter 46 is connected to an upper frame end 64 of a support frame 60 via the cover 11. The support frame 60 forms, so to speak, the “skeleton” of the safety container 8, wherein a plurality of components of the safety container 8 can be attached to the support frame 60, such as the container segments 91, 92, 93 and the cover 11. The support frame 60 is in turn attached to the base 10 via a base element or lower frame end 66, so that the whole forms a stable and rigid structure.

[0134] exist Figure 4 In the embodiment shown, an inspection section 91 can be mounted on the support frame 60, the inspection section 91 comprising one or more inspection glasses 32 for observing the process chamber 4 or the process carried out therein. In addition, the two cooling sections 92, 93 shown here 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 safety container 8 and the connection with the induction coil 7 is via a sleeve passing through the container wall 9 (see Figure 7 ) To improve the sealing, the support frame has a plurality of seals, of which a segment seal 72, a cover seal 74 and an adapter seal 78 are visible here. Figure 4 The wall segments 91 , 92 , 93 shown are of double-walled design and each have an inner wall (inner wall 923 of cooling segment 92 can be seen) and an outer casing 919 , 939 .

[0135] See also Figure 5 , a multi-part support frame 60 is shown, which integrally forms a support frame 60 for supporting wall segments 91, 92, 93, 94. The support frame 60 has a bottom element or bottom frame end 66, which can be formed in one piece or in multiple pieces. In the case shown here, the lower frame end 66 is multi-part, so that four bottom elements together with four intermediate pieces 61 form an integral lower frame end 66. Receiving grooves 84 are provided on the segment side of the lower frame end 66 to receive the segment seal 72. The segment seal 72 extends through the base element receiving groove 84, through the rod element receiving groove 83 and through the cover element receiving groove 82 and is therefore designed to provide a circumferential seal around the wall segment. The cover seal receiving groove 81 is provided on the upper side of the cover element 64 to receive the circumferential cover seal 74. All the sealing elements shown have in common that they are arranged on the segment side of the support frame 60 and are therefore protected by the support frame 60 from the heat radiation of the process chamber 4.

[0136] Preferably, the support frame 60 is made of an electrically non-conductive and / or thermally non-conductive material. If the segments 91, 92, 93, 94 or the cover 11 are fastened to the support frame 60, for example, by mating fasteners 97A or 69 (threaded holes), the distance between the wall segments 91, 92, 93, 94 and the cover 11 can be set by the support frame 60 so that the planar parts of the safety container do not touch each other. Therefore, the planar parts of the safety container can be electrically isolated from each other when they are not in contact and the support frame 60 is not conductive. Nevertheless, by the provided sealing grooves 81, 82, 83, 84 and sealing elements 72, 74, 76, 78, a good seal of the safety container 8 can be achieved because the individual segments 11, 91, 92, 93, 94 can be sealed against the support frame 60. If necessary, this provides the advantage of providing planar elements 11, 91, 92, 93, 94 made of relatively cheap raw materials (such as steel or other metals) that have good thermal conductivity but do not form a closed metal or conductive safety container into which the alternating electromagnetic field of the induction heater 6, 7 can act and interfere with the heating operation or even make it impossible to enter. In order to further separate the wall section 91, 92, 93, 94 from the cover 11, the upper frame end 64 has a recess 63, and the upper frame end 64 forms an overhang on the recess 63, so that the upper frame end 64 is, for example, flush with the outer plate 99, 919, 929, 939 of the wall element 91, 92, 93, 94 on the outside. This ensures that the wall element 91, 92, 93, 94 does not form an electrical short circuit via the cover 11. Furthermore, the overhang further simplifies the assembly of the cover 11 and forms a wider support surface for the cover 11 , further improving the seal and providing greater overall stability for the frame 60 .

[0137] See also Figures 6 to 10 , showing detailed cross-sections of various embodiments of the support frame 60 . Figure 6 The transition from the lower frame end 66 to the base plate 10 is more clearly shown, wherein the section seal 72 is inserted into the base plate element receiving groove 84 and the flush-adjoining rod element receiving groove 83. The lower frame segment element 66 has connecting means 68, for example threaded holes for inserting fastening screws for fastening the lower frame segment element 66 to the base 10. A frame seal 77 is provided for sealing the rod element 62 against the intermediate piece 61 and at the same time against the lower frame segment element 66.

[0138] Figure 7A detail of an upper frame element 64 with a rod element 62 and a wall element 92 mounted thereon is shown. The cover element 64 has recesses 67, in this case two threaded holes, for inserting screws to connect the cover element 64 to the rod element 62. The recessed mounting of the screws in the recesses 67 enables the cover body 11 to be mounted flush and thus in a sealed manner on the upper frame element 64. Also visible in profile is the recess 63 on the cover element 64, wherein the path of the segment seal 72 extending in the recess 63 is also shown in the cover element receiving groove 82.

[0139] See also Figure 8 , shows another detailed view of a section of a support frame 60, wherein a continuous lower frame section 66 rests on the base plate 10 and is sealed against the base plate 10 by a base plate seal 76. The base seal 76 extends in a receiving groove 85 and is provided with a plurality of threaded holes 68 for the passage of threaded means for connecting the lower frame section 66 to the base plate 10. For this purpose, the use of a recess may not be necessary, since no sealing surface is formed on the upper side of the lower frame section 66 in the embodiment shown here.

[0140] Fig. 9 and Fig.10 The rod element 62 (for the sake of clarity, Fig. 9 Not shown, see Figure 8 or Fig.10 ) and the connection of the rod element 62 to the middle piece 61, and the sealing of the rod element 62 relative to the middle piece 61 and the multi-part lower frame section 66 by the inner frame part seal 77. In order to accommodate the inner frame part seal 77, a groove 86A is provided on the side of each of the two lower frame sections 66, and a groove 86 is provided in the middle piece 61 to jointly accommodate the frame seal 77. The rod element 62 adjoins the middle piece 61 and the two lower frame sections 66 at the sealed frame section joint 65. Counter-fasteners 97A for fastening each of the wall sections 91, 92, 93, 94 are provided in the rod element 62.

[0141] See also Fig.11, shows a sectional view of a section through an embodiment of the device 100. The adapter 46 forms a top closure of the process chamber 4 or 4a, and in this embodiment, two process chamber heights of different process chambers 4 or 4a are shown by way of example, which can be closed alternatively by the adapter 46. Therefore, the adapter 46 can be sealed relative to the safety container chamber 8 via an adapter seal 78 or an alternative adapter seal 79. An intermediate space 12 is formed between the chamber wall 41 and the container wall 9. The cover body 11 sealingly connects the adapter 46 to the container wall 9 via the upper frame part 64, so that a sealed housing or safety container 8 is formed as a whole. In this case, the adapter can be connected (for example screwed) to the cover body 11 by means of an adapter fastening device 49, and the cover body 11 can in turn be connected to the upper frame part 64 by means of a fastening device 69, so that a friction connection is also formed from the adapter 46 via the cover body 11 to the frame 64 and further into the container wall 9. In Fig.11 In the example shown, the container wall 9 has a double-walled structure and comprises an inner wall 98, an outer plate 99 and an intermediate space 122 therebetween. In this embodiment, the outer plate 99 slightly overhangs the upper frame member 64 and fills most of the area of ​​the recess 63. A sealed feed-through 26 is provided for bringing electrical connections from or to the external environment 30.

[0142] See also Fig.12 , shows a partially assembled safety container 8, wherein a wall segment in the form of a connecting element 94 has been arranged on a frame 60 fixed to a base plate 10. A plurality of sealed feedthroughs 26 provide means for connecting electronic devices or the like located outside the safety container 8 to components located inside the safety container 8. If these component connections are combined so that several or all of the provided connections are realized by connecting elements 94, the connecting elements 94 can be arranged or configured to remain permanently or at least primarily installed. In contrast, other wall segments 91, 92, 93 can be configured to be quickly and easily removed so as to allow quick access to the process chamber 4. In general, and throughout this specification, the same reference numerals represent the same elements, so that there is no need to repeat the description of multiple elements that have already been described below.

[0143] See also Fig.13, further illustrating another embodiment of a cooling section 92 with a sandwich structure. The coolant line 22 of the temperature control device 21 is arranged on the inner wall 98 and can be connected to the outside via a connection 23. Gap covers 921, 922 circumferentially surround or delimit the section 92, and an outer cover 99 can be screwed onto the gap cover. By means of the outer cover 99, the coolant line 22 and the fastening means 97 are covered and thus protected from access on the one hand and from undue damage on the other hand. The outer cover 99 thus hides these technical facilities from direct viewing and access and gives the device 100 an attractive appearance. In addition, by Fig.13 It can already be shown that the temperature control device 21 is also optimized to enable quick and easy removal of the cooling element 92 as a whole, for example by providing a connection 23 at which the coolant line can be easily disconnected. For example, the connection can be designed as a quick connector with a bayonet lock or a screw lock and can be easily and quickly removed. Thus, the entire cooling element 92 can be easily separated from the coolant supply device and thus removed from the container assembly as a whole together with the cooling device (coolant line 22). This further simplifies and accelerates the disassembly and / or opening of the safety container 8 in the event of a desired maintenance intervention and / or replacement of the process chamber 4. Although a double-walled structure of the wall elements 91, 92, 93, 94 is therefore not absolutely necessary and other arrangements of the coolant line 22 are also conceivable, the arrangement of the coolant line on the outside of the inner wall 923 has proven to be particularly advantageous, since the coolant line is thereby also arranged on the outside of the interior space 12 to be sealed and, overall, in addition to simpler disassembly and / or assembly of the safety container 8 as a whole, fewer penetrations through the container wall 9 to be sealed are required.

[0144] See also Fig.15 , shows a top view of the middle region 122 in the double wall of the cooling section 92 of the container wall 9 with the temperature control device 21, in which the coolant line 22 is arranged in the middle region 122 in the container wall 9. In the case shown here, the container wall 9 comprises an inner wall 98, frame parts 92, 94 and the coolant line 22 of the temperature control device 21 arranged in the middle region 122. The frame parts 92, 94 are fastened to the first section 91 by fastening means 97. Further fastening means 96, for example screw holes, are arranged at regular intervals on the frame parts 92, 94, so that the middle region 122 is thereby closed.

[0145] at last, Fig.16 The apparatus 100 is shown mounted on a base 10, having a multi-part container wall 9 including wall segments 91 and 92. The coolant line 22 (see, e.g., Fig.15 or Fig.13) extend behind the outer plate 99 in a protective manner and are connected to each other in a communicating manner via the compensation bend 24, so that a coolant (e.g. water) can flow through the temperature control device 21. In addition, the compensation bend 24 can be quickly removed, thus making it easy to disassemble the coolant line 22 and the wall segments 91, 92 as a whole from each other. The process chamber 4 (see, for example, Figure 1 or Figure 3 ) is surrounded on all sides by a safe atmosphere in the void 12 or, depending on the embodiment, in any case, is surrounded on all sides by a safe atmosphere above the bottom 10. If the process chamber 4 bursts or fails in another way and process gas escapes, the process gas mixes with the protective gas held in the interior 12 to form a harmless mixed gas.

[0146] See also Fig.17 , shows another embodiment of the device 100, in which the connecting element 94 is removed and corresponding cooling elements 92, 93 are installed. In this embodiment, it is clear and / or different from other embodiments that the gas supply line 51 and the gas exhaust line 54 can be routed below the bottom 10 so that they extend outside the environment 30 and are therefore not in the area that the safety container 8 must protect. Therefore, the lower body 31 can be protected in other ways, or protection by the safety container atmosphere is not required at this place. Therefore, the process chamber 4 does not extend far enough into the underlying floor 31, or does not extend into the underlying floor 31 at all, so that corresponding heating and / or any rupture of the chamber wall 41 is not expected there, which would lead to a large outflow of process gas into the underlying floor 31, or could lead to a deflagration, so that a danger is expected in the surrounding area 30. This also has the additional advantage that fewer feedthroughs are required to pass through or enter the interior 12, thereby further increasing the tightness of the safety container. Further advantages arise from the fact that the supply and exhaust lines below the bottom plate 10 do not interfere with the environment 30, but can be laid hidden.

[0147] at last, Fig.18Another embodiment of a fully enclosed device 100 is shown, in which the cooling section 92 is inserted on the right-hand side and the connecting element 94 is inserted on the left-hand side. The heating electronics 6 are only shown schematically and are arranged outside the safety container 8. A flange-like arrangement directly on the container wall 9 without a hose-like intermediate connector provides a further improved gas seal, making this electronic flange preferred for the heating device 6. Since this may mean a relatively rigid arrangement of the connecting element 94, it may be preferred to better remove the cooling element 92 for the purpose of replacing the process chamber 4 or generally for maintenance access and thus obtain access to the process chamber and / or the induction heater, etc. Of course, alternatively or cumulatively, the cover 11 or the adapter 46 can be removed and the process chamber taken out upwards, so that the hardware and electronics or gas connections, etc. located in the safety container do not need to be removed or modified.

[0148] It has been shown that the modular concept of the further development and invention presented herein provides a huge improvement and safety gain over earlier devices, while reducing manufacturing costs and simplifying the maintainability of system components. In general, the present specification has several aspects which, alone or in combination with other aspects, may define important aspects of the invention.

[0149] It is obvious to a person skilled in the art that the above-described embodiments are to be understood as exemplary and that the invention is not limited to these embodiments but may be varied in various ways without departing from the scope of protection of the claims. Furthermore, it is obvious that the features disclosed, whether in the description, in the claims, in the drawings or otherwise, also individually define essential components of the invention, even if these features are described together with other features. In all figures, the same reference numerals denote the same objects, so that a description of an object mentioned only in one or in any case with respect to all figures may also be transferred to these figures and to embodiments of the object not explicitly described in the description with respect to this figure.

[0150] Reference numerals list

[0151] 1 Growth Unit

[0152] 2 raw materials

[0153] 3 Seed

[0154] 4. 4A process chamber

[0155] 5 Intake valve

[0156] 6 Heating device

[0157] 7 Induction coil

[0158] 8. Secure Container

[0159] 9 container wall

[0160] 10 Bottom Plate

[0161] 11. Lid

[0162] 12 Space

[0163] 13 Directional valve

[0164] 14 Argon source

[0165] 15 Nitrogen source

[0166] 16 outlet (valve)

[0167] 17 Gas Sensor

[0168] 18 Pressure sensor

[0169] 19 Control Device

[0170] 20 hoods

[0171] 21 Cooling or temperature control device

[0172] 22 Coolant lines

[0173] 22A pipeline fasteners

[0174] 23 Connectors

[0175] 23A Attachment Retainer

[0176] 23B bending part

[0177] 24 Compensation bend

[0178] 26 Feedthrough

[0179] 30 Environment

[0180] 31 bottom floor

[0181] 32 sight glass

[0182] 41 Process chamber wall or inner wall of safety container

[0183] 42 Chamber Lock

[0184] 46 Adapter

[0185] 47 Upper cover of process chamber

[0186] 48 Upper cover of process chamber

[0187] 49 Adapter Fastener

[0188] 51 Process gas supply port

[0189] 52 process gas discharge port

[0190] 54 Inert gas supply port

[0191] 56 Inert gas outlet

[0192] 60 Support frame

[0193] 61 Middleware

[0194] 62 rod elements or frame struts

[0195] 63 concavity

[0196] 64 Upper frame end or cover element

[0197] 65 frame component joint

[0198] 66 Lower frame end or floor element

[0199] 67 Recesses for accommodating frame fasteners

[0200] 68 Connectors

[0201] 69 Counter fastener of cover body 11

[0202] 72 Section Seals

[0203] 74 cover gasket

[0204] 75 Sealing element

[0205] 76 bottom plate seal

[0206] 77 Inner frame component seal

[0207] 78 adapter washer

[0208] 79 Replacement Adapter Seal

[0209] 81 Cover gasket receiving groove

[0210] 82 Cover element receiving groove

[0211] 83 Rod element receiving groove

[0212] 84 Bottom plate component receiving groove

[0213] 85 receiving groove

[0214] 86 frame seal receiving groove

[0215] 86A front face frame seal receiving groove

[0216] 91 Section of box wall, test section

[0217] 92 box wall section, cooling section

[0218] 93 Section of the box wall, another cooling section

[0219] 94 box wall section, connecting section

[0220] 96 Fastening elements

[0221] 97 Fastening elements

[0222] 97A to the counter-mounting member of the fastening element 97

[0223] 98 inner wall

[0224] 99 outer panel

[0225] 100 devices

[0226] 122 Middle Area

[0227] 919 test section outer plate

[0228] 921 Top Gap Cover

[0229] 922 Horizontal Gap Cover

[0230] 923 Inner wall of cooling section

[0231] 924 lower gap cover

[0232] 929 outer plate of cooling section

[0233] 939Outer plate of another cooling section

Claims

1. A PVT method for the process-safe production of single crystals in an apparatus (100), wherein: The apparatus comprises a process chamber (4) for receiving a highly heatable growth unit (1) and a heating device (6) for heating the growth unit (1), wherein the growth unit is adapted to receive a source material (2) and a seed crystal (3), and wherein the process chamber (4) can be filled with a process gas and the growth unit (1) can be heated, The device comprises a safety container (8) for enclosing the process chamber so as to enclose the process chamber (4), preferably, the safety container encloses the process chamber (4) in an airtight or substantially airtight manner, and The safety container has a circumferential container wall (9), so that a gap (12) is generated between the container wall (9) of the safety container (8) and the process chamber (4), The following steps are involved: providing a protective atmosphere in the gap and thereby filling the gap with the protective atmosphere, providing a process gas in the process chamber, the process gas comprising or consisting of a reactive gas; and The growth unit is heated by the heating device, causing the source material to sublime and re-sublime at the seed crystal.

2. The PVT method according to the preceding claim, 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, the overpressure being, for example, at least 1 mbar or more above the ambient pressure, preferably 3 mbar or more above the ambient pressure, more preferably 5 mbar or more above the ambient pressure.

3. The PVT method according to any one of the preceding claims, in, The growth unit (1) is heated from all radial sides by means of the heating device (6) which surrounds the process chamber (4) in an annular manner, and / or ensuring that the supply of the protective atmosphere into the gap (12) is completed before the process gas is introduced into the process chamber (4) and / or the growth unit (1) is heated to operating temperature, and / or Wherein, filling the void (12) with the protective atmosphere further comprises removing air present in the void before sublimation of the source material (2) begins.

4. The PVT method according to any one of the preceding claims, characterized in that The reaction gas comprises hydrogen or consists of hydrogen, and / or the protective atmosphere comprises an inert gas or consists of an inert gas, preferably comprising argon or consisting of argon.

5. The PVT method according to any one of the preceding claims, characterized in that The safety container (8) is configured to allow gas leakage into the environment (30), and inert gas is supplied to compensate for gas leakage and, optionally, to maintain an overpressure relative to the environment (30) in the safety container (8) according to claim 2.

6. The PVT method according to any one of the preceding claims, characterized in that In order to fill the safety container (8), a first inert gas heavier than air is admitted into the lower region of the safety container, the air moving upwards, for which purpose a closable outlet (16, 56) at the upper end of the safety container (8) remains open until the air escapes.

7. The PVT method according to any one of claims 4 to 6, characterized in that: After the safety container (8) is filled with the first inert gas once or several times, the first inert gas is replaced with a second inert gas, such as nitrogen.

8. The PVT method according to any one of the preceding claims, characterized in that The safety container (8) comprises a gas sensor (17) capable of detecting the reactive gas, and / or interrupting the supply of the process gas to the process chamber (4) when the reactive gas is detected in the safety container (8).

9. A device (100) for the process-safe production of single crystals, for example by a PVT method according to any one of the preceding claims, comprising: a process chamber (4) for accommodating a highly heatable growth unit (1), a heating device (6, 7) for heating the growth unit (1), The process chamber has a process gas connection (51), and the process gas connection (51) is used to fill the process chamber with a process gas that can be provided from a process gas source. wherein the growth unit is adapted to receive a source material (2) and a seed crystal (3), It is characterized in that The device comprises a safety container (8) for closing the process chamber (4), preferably the safety container closes the process chamber (4) in an airtight or substantially airtight manner, and The safety container has a container wall (9), so that an intermediate space (12) is generated between the container wall (9) of the safety container (8) and the process chamber (4), and the intermediate space (12) is arranged so that it can be filled with a protective atmosphere.

10. The device (100) according to any one of the preceding claims, in, The container wall (9) is also designed to close the process chamber (4) from above and / or from below so as to completely close the process chamber on all sides, and / or Therein, the container wall (9) comprises a process chamber adapter (46) for receiving process chambers with different sizes on the same container wall.

11. The device (100) according to any one of the preceding claims, in, The container wall is arranged in a double-walled manner, In this case, for example, the cooling device (21) is arranged in the middle region (122) of the double-walled container wall.

12. The device (100) according to any one of the preceding claims, characterized in that The safety container (8) is configured to allow gas to leak to the outside, and / or the safety container (8) includes a pressure sensor (18), and the pressure sensor (18) is connected to a control device (19) for signal, and / or Therein, the control device (19) is designed to set the overpressure in the safety container (8) relative to the environment (30) based on the pressure sensor signal.

13. The device (100) according to any one of the preceding claims, further comprising a support frame (60) for holding at least two wall segments (11, 91, 92, 93, 94) on the support frame, The support frame forms a retaining structure for receiving the wall segment on the support frame, so that the support frame and the wall segment as a whole form a container wall (9) of the safety container (8) for closing the process chamber (4), preferably, closing the process chamber (4) in an airtight or substantially airtight manner.

14. The device (100) according to any one of the preceding claims, in, At least one sealing element (72, 74, 75, 76, 77, 78, 79) is arranged on or in the support frame (60) for sealing the support frame with at least two container sections (91, 92, 93, 94) and / or for sealing the safety container (8) with the environment (30), and / or wherein the support frame (60) has on the outer side at least one longitudinal groove (81, 82, 83, 84, 85, 86, 86A) for receiving a sealing element (72, 74, 75, 76, 77, 78, 79), and / or Wherein, the support frame (60) is configured to receive a section seal (72), and / or to receive a cover seal (74), and / or to receive a bottom seal (76).

15. The device (100) according to any one of claims 13 or 14, in, The support frame (60) is configured to be sealed relative to the substrate (10), and / or wherein the support frame (60) is configured to be sealed relative to the adapter (46), and / or wherein the support frame (60) is configured to be sealed relative to the container sections (91, 92, 93, 94), and / or Therein, each container segment (91, 92, 93, 94) is associated with a separate circumferential segment seal (72).

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

17. The device (100) according to any one of the preceding claims, in, The supporting frame members (61, 62, 64, 66) are designed to seal against each other and / or further comprise a frame member seal (77) for sealing one frame member to a second frame member, wherein, preferably, the frame member seal is not arranged in the same plane as the section seal (72).

18. The device (100) according to any one of claims 12 to 17, wherein: Each segment seal (72) is positioned through the cover element (64), through the two rod elements (62) and the base element (66), and / or A cover seal (74) is arranged on the upper side of the cover element (64) for sealing the cover (11), and / or A base seal (76) is arranged on the underside of the base element (66) for sealing the base element relative to the base (10).

19. The device (100) according to any one of claims 15 to 18, in, The cover element (64) has a section side cover element receiving the recess (82), and wherein each of the rod elements (62) has at least one rod element receiving groove (83), preferably each rod element has two rod element receiving grooves, and wherein the base element (66) has a base element receiving groove (84), And wherein, preferably, at least one of the grooves of one of the rod elements is designed to be aligned with the cover element receiving groove and the base element receiving groove, so that a segment seal (72) can be introduced into the mutually aligned segment sealing grooves for circumferential sealing of the wall segments (91, 92, 93, 94).

20. The apparatus (100) according to any of the preceding claims, further comprising an inert gas port (54) located in a lower region of the safety container (8), and a closable outlet (16, 56) located in an upper region of the safety container.

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