Pvt method and apparatus for producing single crystals in a safe process

Abstract

To allow a reactive gas such as hydrogen to be used as a process gas in a PVT method, special safeguards have to be put in place in order that the method can be carried out in a safe process. An apparatus for carrying out the PVT method consists of a growth cell which can be heated to a high temperature and is arranged in a process chamber with a wall made of a heat-resistant material such as typically quartz glass. An inlet valve is used for filling the process chamber with hydrogen. A heating device consists of an induction coil which surrounds the process chamber at the height of the growth cell and heats the growth cell to over 2000°C to 2400°C. The use of a reactive gas entails the problem however that, in the not entirely preventable event of a rupture of the chamber wall of the process chamber, the reactive gas can mix with the ambient air and thereby produce an ignitable gas mixture, which would immediately ignite on the hot parts of the apparatus. The process chamber is therefore surrounded by a safety vessel which is filled with an inert gas.

Description

[0001] PVT process and apparatus for the reliable production of single crystals

[0002] Description

[0003] Field of the invention

[0004] The invention relates to a PVT process for the reliable production of single crystals and an apparatus comprising a highly heatable growth cell, a process chamber in which the growth cell and a heating device surrounding the process chamber for heating the growth cell are located. A source material and a nucleus can be introduced into the growth cell, the process chamber filled with a process gas and the growth cell heated so that the source material sublimates and resublimates at the nucleus.

[0005] Background and general description of the invention

[0006] In the industrial environment, the so-called Physical Vapor Transport (PVT) process is considered the standard method for producing single-crystalline silicon carbide crystals (SiC crystals). The source material is usually a powder that contains many different crystals. The use of bulk crystals is also possible. An alternative process is the High-Temperature Chemical Vapor Deposition (HT-CVD) process. In the PVT process, crystal growth typically takes place within the graphite growth cell by sublimation of a SiC source material and crystallization at a given SiC nucleus at temperatures above 2 000 °C. The driving force for crystal growth is a temperature gradient.which is impressed on the growth cell by a heating device Common methods for heating PVT apparatus use resistance heaters or induction heaters With inductive heating, the growth cell (hot zone) of the vacuum-tight process chamber is surrounded by a non-conductive material, typically (quartz) glass Process gases are located in the process chamber or are introduced there, which are used, among other things, to influence the crystal growth The process chamber can be single- or double-walled and can be fan- or water-cooled Typically, argon, helium, nitrogen, hydrogen and, if necessary, other gases for targeted doping are used as process gases The process pressure can range from vacuum conditions to atmospheric pressure In common processes for producing doped SiC single crystals, no hydrogen or only low concentrations are used,

[0007] SiC single crystals are produced for a variety of applications in semiconductor technology due to their large band gap and high thermal conductivity. The underlying process for producing SiC single crystals has therefore already been the subject of many descriptions. As an example, reference is made to US 2011 / 0300323 A1. According to this document, an inert gas is used as the process gas, which is unproblematic from a safety perspective. Regarding the state of the art, reference is also made to EP 0 811 708 A2, US 2012 / 0086001 A1, GB 772,691, DE 60 2004 001 802 T2 and EP 3 760 765 A1.

[0008] It is a conceptual starting point and one of the objects of the present invention to enable processes, among others for the targeted influencing of the dopant incorporation or for the production of undoped SiC single crystals. With regard to this starting point, the present invention is developed to ensure a process sequence that is safe, with better results than in the prior art and / or more cost-effective than known. If necessary, this can even be carried out using a reactive gas, ie a flammable and / or reactive (possibly also toxic) gas, e.g. hydrogen as the process gas, with concentrations of over 5% and up to 100%.

[0009] In this case, the gas molecules of the reactive gas, such as hydrogen atoms in particular, attach themselves to the surface of the growing single crystal, but are immediately displaced by the following sublimated components of the source material. In this case, the reactive gas molecules, such as hydrogen atoms, serve briefly as placeholders, so that a crystal lattice with few defects, if not completely free of defects, can be created. Reactive gas molecules can also react with other process gases, the source material or even the hot zone material and form further gaseous species that enter the process gas atmosphere and can attach themselves to the crystal, at least temporarily. Possible reactive gases such as silane, methane, propane, etc., supply, among others, the elements silicon and carbon.which are incorporated into the crystal The addition of reactive gases can influence the defect density (desired and / or undesired) The exact influence, however, depends on a variety of parameters and their interaction The addition of reactive gas is intended to influence the crystal growth,

[0010] The object of the present invention can therefore be seen in providing a device and a method with which an improved or modified crystal growth is possible

[0011] In a partial aspect or further development of the invention, it can be considered as an aspect of the task to provide a device and a method in which a reactive gas can be used to improve crystal growth

[0012] In yet another aspect or development of the invention, the object can be to provide a device and a method by means of which improved crystals can be provided with little effort or at lower cost. The use of a reactive gas, comprising, for example, hydrogen or other reactive elements, however, represents a potential hazard when carrying out the method. A reactive gas can, for example, be combustible or flammable and / or toxic. In the case of the example hydrogen, an oxyhydrogen reaction can take place with the oxygen in the air, which is why hydrogen is referred to as a reactive gas in the context of this description. Further examples of reactive 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.).

[0013] Furthermore, in today's common apparatus, the process chamber is typically made of quartz glass, which is naturally brittle and prone to breakage. However, it is particularly preferred to use quartz glass because it can withstand the high temperatures of the growth cell and because it does not shield the electromagnetic field of an induction coil or the radiant heat of a resistance heater. Likewise, a combination of induction and resistance heaters can be provided. For example, an additional floor or ceiling heater can be designed as a resistance heater, while the main heater is designed as an induction heater. In principle, however, the safety requirements are similar for other materials used to provide the process chamber, at least in the case of quartz glass to a particularly high degree.

[0014] However, if the process chamber is damaged or leaks, for example if the quartz glass breaks, the hydrogen can mix with the oxygen in the environment and an oxyhydrogen gas is created, which is ignited by the heating device (hot components of the hot zone, typically graphite parts inside the process chamber) and explodes. As far as a reactive gas is used, a reliable implementation of the process with the known fittings is therefore not possible.

[0015] A reactive gas mentioned in this description - in particular hydrogen - is not to be equated with known doping gases. Known typical doping gases are not used in the concentrations desired here and / or are neither flammable nor otherwise reactive within the meaning used in this description. Doping gases are purged around the crystal, so the processes take place entirely within the process chamber. For example, in this context, the process chamber can also be purged with an inert gas such as argon to directly modify the PVT process. In general, doping gases are intended to be incorporated into the crystal or crystal structure - which is where the term "doping gas" comes from - in order to influence the physical and / or chemical properties of the crystal.for example, the electrical conductivity In other words, molecules or components of a doping gas form a later integral building block of the crystal Such molecules or components of a doping gas remain in the crystal and are detectable there later,

[0016] In contrast, a reactive gas such as hydrogen, as a reactive component of the gas atmosphere, can influence crystal growth and dopant incorporation, but is not incorporated into the crystal like doping gas to influence the physical and chemical properties of the crystal. Due to the hazard potential of reactive gases, in particular ignition, burn-up, deflagration or even poisoning potential, reactive gases have not yet been considered for use in improving crystal growth, or at least the safety aspects when handling a reactive gas in this environment, as described above, have not been sufficiently taken into account. In addition, the reactive gas to be used is not a source material in the true sense of the word. In typical PVT processes, the source material is SiC powder. In variants of the classic PVT process, such as HT-CVD, hydrogen can be used as a carrier gas.which transports the actual source material, usually gaseous C- or Si-containing precursors. The gas serves as a carrier gas, ie as a transport medium for precursors and dopants. Dopants can be solid, liquid or gaseous elements or compounds, which typically contain nitrogen, phosphorus, aluminum, boron or vanadium.

[0017] Within the scope of this further development and improvement, the present description describes and defines various aspects of the safety container surrounding the process chamber, which was developed by the applicant PVA TePla. Furthermore, the provision of a protective atmosphere, in particular with inert gas, in the area between the process chamber and the container wall was investigated. One particular aim of the safety container is to avoid or prevent an explosive gas mixture in the event of damage, in particular rupture, of the process chamber.

[0018] In order to achieve a reliable implementation of the process, an apparatus for carrying out the process could be arranged in a vacuum cell. However, such a cell would have to be absolutely vacuum-tight and is therefore comparatively complex to manufacture because a large number of feedthroughs are required to supply the apparatus with electricity, gas and, if necessary, cooling fluid, each of which must be made vacuum-tight. Furthermore, a vacuum cell is practically impossible to maintain or repair, or it must first be opened at great expense and then closed again after the work or modification has been completed.

[0019] It would be advantageous, however, to present a PVT process for the reliable production of single crystals that can be carried out in an apparatus that is easy to manufacture and / or inexpensive

[0020] The problem is solved by the invention defined in the independent claims. Dependent claims give further developments and preferred embodiments of the invention. To solve one, several or all of the presented aspects of the problem, a PVT method for the reliable production of single crystals in an apparatus is presented, wherein the apparatus comprises a process chamber for accommodating a highly heatable growth cell and a heating device for heating the growth cell, wherein the growth cell is prepared for accommodating a source material and a seed, and wherein the process chamber can be filled with a process gas and the growth cell can be heated. The apparatus has a safety container enclosing the process chamber for enclosing the process chamber, in particular in a gas-tight or substantially gas-tight manner. The safety container has a circumferential container wall,so that a gap is created between the container wall of the containment vessel 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 the gap. For example, if the process chamber is round and the containment vessel is also round, then the gap defines a ring segment (viewed as a plane) or a hollow cylinder of wall thickness b with inner radius r (corresponds, for example, to the wall of the process chamber), outer radius R (corresponds, for example, to the wall of the containment vessel) and height h (measured, for example, from the bottom to the lid),

[0021] The method presented here comprises the steps of providing a protective atmosphere in the intermediate space and, for this purpose, flooding the intermediate space with the protective atmosphere, and providing the process gas in the process chamber. The process gas can, for example, comprise or consist of a reactive gas. In other words, the method defines that firstly the intermediate space is filled with the protective atmosphere, in particular in such a way that any air that may have previously been present there is displaced as completely as possible, and only when the protective container is ready for use by means of the filling with protective atmosphere (and this, for example, outputs as a signal) is the further process sequence initiated.

[0022] In principle, process gas could be introduced into the process chamber before the containment vessel is ready for use, provided that the process chamber is not yet so hot that ignition of the process gas is likely in the event of a leak in the process chamber. Likewise, the process chamber could be heated, for example to operating temperature, before the containment vessel is ready for use, if no process gas or at least no reactive gas has been introduced there. The transition between the readiness of the containment vessel and the start of operation of the process chamber can be fluid. However, it is generally preferred if the provision of the protective atmosphere in the intermediate space is completed before the process gas is introduced into the process chamber and / or the growth cell is heated to operating temperature. In other words, it is preferredif the provision of the process gas in the process chamber only takes place after the intermediate space has been flooded with protective gas. It may therefore also be preferred that the flooding of the intermediate space with the protective atmosphere - in particular the initial flooding of the intermediate space or the flooding of the intermediate space with a first protective atmosphere - also includes the displacement of air located in the intermediate space, before the sublimation of the source material is initiated,

[0023] It is therefore particularly advantageous if the containment vessel is flooded or completed at the latest when the sublimation of the source material takes place, because then high temperatures are present which can ignite the reactive gas. For safety reasons, it is advantageous if the containment vessel is flooded before the reactive gas is introduced into the process chamber.

[0024] Should this arrangement result in damage – in particular a breakage – of the process chamber, the reactive gas of the process chamber mixes in the protective atmosphere in the containment vessel, for example with the inert gas, to form a non-explosive gas mixture, so that even in a hot environment an explosion cannot occur. This safety measure is particularly important if the reactive gas is flammable or prone to deflagration, such as hydrogen.

[0025] The method further comprises heating the growth cell by means of the heating device so that the source material sublimates and resublimates at the nucleus. The heating of the growth cell can preferably be carried out radially from all sides. For this purpose, the heating device can enclose the process chamber in a ring.

[0026] When providing the protective atmosphere in the intermediate space, it is preferable to set an overpressure relative to an ambient pressure. For example, the overpressure in the protective container can be set, further, for example, at least 1 mbar above ambient pressure or more, preferably 3 mbar or more, further preferably 5 mbar or more above ambient pressure. If an overpressure is set in the protective container relative to the environment, only insignificant gas or no gas at all can penetrate from the environment into the protective container. This can ensure that, for example, no oxygen penetrates into the protective container and - in the event of an outlet of process gas into the protective container - a reaction could take place there.

[0027] The containment vessel is particularly easy to realize if it is designed in such a way that it allows gas losses to the outside, especially to a small extent, i.e. is only approximately gas-tight. This makes the design of the containment vessel more cost-effective, since requirements for particularly high hermeticity do not have to be taken into account and yet no undesirable reactions of the reactive gas can occur outside the process chamber. For example, the containment vessel can have a permissible leak rate that is greater than 0 l / min. For cost reasons, it can be advantageous and unproblematic, particularly due to the choice and geometry of the design, to allow a leak rate that is in the range 0 < leak rate < 5 l / min, or even in the range 0 < leak rate < 30 l / min. For example, the permissible leak rate can be greater than 2 ml / min, less preferably 5 ml / min, even less preferably 10 ml / min.even less preferably 50 ml / min or even 100 ml / min On the other hand, it is not sensible, for economic reasons and possibly those of workplace safety, to allow an excessively high leakage rate of the safety container For example, it may be desired to limit the leakage rate to less than 30 l / min, preferably 10 l / min, more preferably 4 l / min, more preferably 1 l / min, more preferably 500 ml / min, and even more preferably 150 ml / min The aim is to achieve leakage rates in a range of 2 ml / min to 50 ml / min, preferably from 10 ml / min to 20 ml / min,

[0028] The safety container can, for example, have a total volume of more than 50 l, preferably more than 100 l and / or a total volume of less than 500 l, preferably less than 250 l. In other words, a ratio of leak rate to total volume can be set in the 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.

[0029] To maintain the protective atmosphere, for example, inert gas can be added to compensate for gas losses and to build up and / or maintain an overpressure in the containment vessel. The overpressure prevents atmospheric oxygen from entering the containment vessel from the outside. Thus, a relative overpressure in the containment vessel can be maintained by means of a pressure regulating system, for example in a range of 1 mbar above ambient pressure or more, preferably 3 mbar or more, more preferably 5 mbar or more, to 50 mbar above ambient pressure or less, preferably 30 mbar or less. However, a completely gas-tight containment vessel with a leak rate of 0 ml / min or a leak rate that is not measurably low is also generally included here, in which an overpressure can also be maintained in the containment vessel.

[0030] In order to ensure the most complete possible displacement of air from the containment vessel, the present description may further provide that a first inert gas is admitted into the containment vessel to flood the containment vessel. The first inert gas may be heavier than air, so that it is admitted into the lower region of the containment vessel, whereby the air is displaced upwards. For this purpose, for example, a closable outlet at the upper end of the containment vessel may remain open until the air has escaped.

[0031] The protective atmosphere preferably comprises an inert gas, such as argon in particular. Due to the high density of argon, it collects at the bottom of the containment vessel and slowly displaces the air upwards without mixing with it. Other examples of the structure of the protective atmosphere that are currently economically viable include xenon, nitrogen or carbon dioxide. In principle, the protective atmosphere can comprise any fluid, whether individually or as a mixture, which is able to provide a protective function in that it can neutralise the reactive gas in the event of excessive or inadmissible escape from the process chamber and / or prevent negative effects such as deflagrations. The protective atmosphere can, for example, also be present in the liquid or solid state under normal conditions of the standard atmosphere.

[0032] If the air has been displaced by the first inert gas, it can be replaced by another, for example a cheaper, inert gas. The invention therefore further provides that after one or more flooding of the safety container with the first inert gas, this is replaced by the second inert gas, in particular nitrogen.

[0033] In order to ensure that in the event of a breach of the process chamber, the reactive gas is no longer fed into the apparatus, it is provided that the containment vessel has a gas sensor that is able to detect the presence of reactive gas in the containment vessel. Furthermore, it can be provided that the process gas supply to the process chamber is interrupted if the gas sensor detects the reactive gas in the containment vessel.

[0034] In a further development, the gas supply can be interrupted via an additional pressure sensor or pressure switch that monitors the pressure within the process chamber if a lower pressure is detected in the event of damage, such as a break in the quartz glass. For example, for monitoring purposes, a drop in the absolute pressure to p < 980 mbarAbs, preferably to p < 950 mbarAbs, more preferably to p < 920 mbarAbs can be detected. The interruption of the reactive gas supply can thus also take place independently of the detection of reactive gas, such as hydrogen, in the space between the process chamber and the cooling jacket.

[0035] An opening of the process chamber, for example in the event of a quartz glass breakage, can be detected or indicated by one of the following criteria: The reactive gas / hydrogen can be detected by a gas sensor in the containment vessel. In this case, the gas sensor is particularly designed to detect the process gas or a process gas content in the containment vessel. Alternatively or cumulatively, the overpressure in the containment vessel ps can be determined and, if the overpressure disappears, a conclusion can be drawn as to a process disturbance or a seal leak (e.g. ps <= approx. 2 mbarg compared to atmosphere). This is possible if an overpressure (even a slight one) compared to atmosphere is set in the containment vessel,which is easy to detect Such a vessel overpressure therefore also represents a safety criterion for the operation of the plant A pressure test can therefore represent a step in a safety check of the plant,

[0036] One step of the method presented here can therefore be defined by a safety check of the containment vessel. Such a safety check can be realized by measuring the adjustable overpressure ps in the containment vessel. In other words, in particular in preparation before starting the production of the crystal, the containment vessel can be checked with regard to the leak rate or tightness, so that if the leak rate is too high, a safety state is assumed or displayed, for example, no operation is possible or a warning is generated.

[0037] Furthermore, the pressure in the process chamber pp can be measured alternatively or cumulatively, and as long as this pressure pp < 950 mbarAbs, or pp < 920 or, for example, pp < 980, is maintained, no process disturbance is detected, whereas exceeding the pressure threshold can indicate a process disturbance. Alternatively or cumulatively, a sudden pressure surge / pressure increase in the process chamber (pressure increase rate greater than the maximum possible or permissible pressure increase rate due to gases to be introduced) can also be detected and indicate a process disturbance - such as a quartz glass breakage. The above criteria are advantageously independent of one another and can be used individually or in conjunction with one another to cause the process gas or hydrogen supply to be switched off.and thus in particular to ensure a safety standard of the equipment In other words, by means of the pressure measurement of pp before and / or during the process execution, it may be possible to detect more quickly whether process gas will or does penetrate into the safety vessel,

[0038] The containment vessel can advantageously provide a cooling function. The cooling function can, for example, be designed such that a cooling medium, such as water in particular, circulates around or through the containment vessel. For example, the containment vessel 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 vessel wall of the containment vessel or at least connected thereto in a heat-conducting manner, if necessary with the aid of a heat-conducting paste. For example, the cooling medium line is soldered to the vessel wall. For example, the cooling medium line comprises copper, which is easy to process and / or is designed to be particularly heat-conductive.

[0039] The containment vessel can be equipped in such a way as to provide temperature control of the process conditions. For example, by means of the containment vessel designed in this way, constant temperatures - or a similar temperature range - can always be maintained, regardless of the potentially strongly fluctuating ambient conditions. For example, the environment can contain a daily temperature curve or seasonal temperature fluctuations, or can also be influenced by thermal processes taking place nearby, whereby the advantageously designed containment vessel can keep these ambient conditions away from the process. Alternatively or cumulatively, the cooling function can also be influenced in response to the process parameters, in particular the temperature in the process chamber.to achieve a temperature control of the growth process For example, the cooling medium flow rate through the at least one cooling medium line can be changed in response to the ambient conditions and / or the process parameters in order to change the heat dissipation In warmer environments and / or process temperatures, for example, more cooling medium can be converted, and / or a colder cooling medium can be used, and / or an alternative cooling medium can be filled,

[0040] The cooling medium line can be arranged on the outside of the container wall, preferably thermally conductively connected to the container wall or in any case arranged adjacent to the container wall The cooling medium line can then cool the container wall and ensure that the heat quantity does not radiate into the immediate vicinity of the apparatus, but is carried away by the temperature control device The external arrangement of the cooling medium line has the advantage that fewer passages into the protective atmosphere or the inside of the protective container that need to be sealed are provided, since the cooling fluid does not penetrate into the interior For example, the container wall can be double-walled, i.e. have an inner wall and an outer wall,where the cooling medium line can be arranged between the inner and outer walls of the container wall. Then the cooling medium line and the fastenings for the cooling medium line are concealed and protected from mechanical damage. Since the temperature control device is able to dissipate a significant part of the heat output from the process chamber, the outer wall of the container wall is subject to few or no restrictions regarding the choice of material or contact protection, since it does not get hot.

[0041] The present description further relates to an apparatus for the reliable production of single crystals, in particular according to the PVT process, which comprises a process chamber for accommodating a highly heatable growth cell, as well as a heating device for heating the growth cell. The process chamber has a process gas connection for filling it with a process gas which can be provided from a process gas source. The growth cell is prepared for accommodating a source material and a nucleus.

[0042] The apparatus comprises a safety container for enclosing the process chamber, in particular in a gas-tight or substantially gas-tight manner. For example, the safety container enables process-safe operation with a reactive gas as the process gas. 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 designed so that the intermediate space can be flooded with a protective atmosphere. The process chamber is arranged within the safety container. Furthermore, 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 flooded with protective gas, in particular before carrying out the PVT process.

[0043] The container wall can be a segmented container wall that surrounds the process chamber radially on all sides, wherein the container wall comprises a plurality of at least two wall segments. By means of the segmented container wall, the outer wall of the containment container can be formed to enclose the process chamber, in particular in a gas-tight or substantially gas-tight manner. The container wall can comprise, as wall segments, for example, a feedthrough segment, a test or inspection segment, a cooling segment, a lid segment, which can in particular be designed in several parts, and / or a base segment.

[0044] The container wall is preferably designed in such a way that it also encloses the process chamber from above and / or below. The container wall can also preferably be designed in such a way that it completely encloses the process chamber on all sides. However, this is not always necessary. For example, if the process chamber is set into a floor, a part or section of the process chamber can be designed without an immediate protective casing in the form of the protective container, and the part of the process chamber that is above the floor can be surrounded by the protective container. In this way, the protective container can be designed to reach the floor and, if necessary, seal tightly there.

[0045] In a further development, the container wall can comprise a process chamber adapter for accommodating process chambers of different sizes on the same container wall. Thus, the components of the container wall can be provided in a standard size or in a few sizes and cover a variety of different process chambers or process chamber sizes.

[0046] The container wall can be double-walled. The double-walled construction of the container wall can have structural advantages or simply enable an attractive exterior without components of the containment vessel being visible from the outside.

[0047] For example, a cooling device can be arranged in an intermediate area of ​​the double-walled container wall. This design has numerous advantages. The cooling device itself is protected from the direct heat radiation of the process chamber and is concealed behind an inner wall of the container wall. In addition, the installation of the cooling device is particularly simple in this case, as it can be attached to the inner wall of the container wall, for example, glued, soldered or screwed there using connectors. An outer cover then covers the intermediate area, so that it is protected from external interference or accidental damage, which is particularly advantageous if the cooling device is arranged there.

[0048] The containment vessel can be designed in such a way that it allows gas losses to the outside. It can have a pressure sensor, wherein the pressure sensor is signal-connected to a control device and the control device is designed in such a way that an overpressure in the containment vessel (compared to the environment or atmosphere) is set on the basis of the pressure sensor signals.

[0049] The pressure sensor can also comprise a pressure switch or be formed from a pressure switch. For example, the pressure sensor can be formed by a differential pressure switch that measures the pressure difference between inerting in the containment vessel and the atmosphere or environment. If necessary, the pressure sensor can then trigger a circuit when an adjustable pressure difference is exceeded or undershot, in particular as a safety circuit or shut-off.

[0050] With regard to the orientation of the equipment, it can be advantageous if an inert gas connection is located in the lower area of ​​the containment vessel and a closable outlet in its upper area. This allows the air in the containment vessel to be completely displaced upwards to the outlet by the protective gas flowing in at the lower area, where it leaves the containment vessel.

[0051] The safety vessel preferably has two protective gas connections for two different protective gases. After the first inert gas has displaced the air from the safety vessel, a more cost-effective fluid, such as nitrogen, can be filled as a second fluid via the second protective gas connection, thus replacing the first protective gas.

[0052] The containment vessel preferably comprises a gas sensor which responds to a reactive gas. In this way, it can be determined that reactive gas (e.g. hydrogen) has penetrated into the containment vessel, for example in the event of a rupture of the process chamber.

[0053] As already explained above, the apparatus can be used, in particular, to produce a SiC single crystal using the PVT process. For this purpose, the growth cell is equipped with silicon carbide as the source material, and the process chamber can be flooded with hydrogen as a reactive gas in addition to other process gases (e.g., argon). In a further embodiment, the apparatus can further comprise a support frame for holding at least two wall segments on the support frame. In this case, the container wall is therefore segmented and has at least two wall segments. The wall segments together form the container wall. For example, one wall segment can be provided as a permanently installed wall segment, and another wall segment can be detachably connected so that it can be easily removed.

[0054] The support frame thus forms a holding structure for receiving the wall segments on the support frame, so that the support frame and wall segments as a whole form the container wall of the safety container (8), in particular for gas-tight or essentially gas-tight enclosing of the process chamber

[0055] At least one sealing element can be arranged on or in the support frame for sealing the support frame against the plurality of at least two container segments and / or for sealing the protective container against the environment. In other words, the support frame can be designed to be sealed in order to reduce gas leakage from the containment container into the environment.

[0056] Alternatively or cumulatively, one or a plurality of wall segments can have a correspondingly designed sealing receptacle. In other words, the sealing element can be arranged on the wall segment. Such a sealing receptacle can be designed as a material bead or edge, to which the sealing element can be applied or inserted. Typically, in such an arrangement, the sealing element would preferably be glued using an adhesive. Alternatively, the wall segment could be designed with a greater material thickness so that a groove for the sealing element could be provided, although it may be taken into account that this may increase the costs for a respective wall segment. It may also be more difficult to handle if it is heavier due to a greater material thickness.

[0057] The combination of the multi-part safety container with the sealing elements achieves particular advantages, as this allows the use of common construction materials, such as metal or steel for the wall elements, while still achieving sufficient tightness of the safety container as a whole. In an environment in which core temperatures of over 2000 °C occur, such a construction presents some challenges, which could be solved with astonishing ease using the designs explained in the present description and the exemplary embodiments.

[0058] The support frame preferably has at least one longitudinal groove on an outer side for receiving a sealing element. In other words, the sealing element is drawn into the longitudinal groove of the support frame. The longitudinal groove can be designed as a holding groove. The advantage of a holding groove is that the sealing element is securely held in the holding groove and can only be removed from there, for example, against the application of an over-thrust force. In the present case, the use of a trapezoidal groove as a holding groove is possible, since the sealing elements can be reused several times and can remain in such a holding groove. The sealing elements can be designed as O-rings or in the form of lip seals.

[0059] The protected installation of the sealing elements as described here ensures that the sealing elements do not burn or age quickly in the extremely thermally hot environment. In particular, the sealing elements are arranged in a way that is protected from radiant heat. This arrangement, in turn, synergistically enables the use of permanently reusable materials for the sealing elements. Since the sealing elements are permanently reusable and are not destroyed during operation, they can be advantageously arranged in a retaining groove, which ultimately further simplifies the handling of the containment vessel (here when assembling the wall segments with the support frame). In this way, the sealing elements are protected from contamination and damage and remain in the advantageous retaining grooves in the protected installation position, in which they are protected from radiant heat during operation.

[0060] Alternatively, or depending on the situation of the at least one sealing element on the support frame, as described above, at least one wall segment can have the sealing receptacle, i.e. a special shape, for fastening a sealing element against the support frame. For this purpose, an edge of a wall segment opposite the edge of the support frame can be covered on the outside and a sealing element can be attached to the edge projection. Another embodiment provides a longitudinal groove on the narrow side for receiving a sealing element. The wall segment can have a greater wall thickness overall or a wall reinforcement at least near the edge.

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

[0062] The support frame can be designed to be sealed against a base plate, in particular by means of a base seal. The support frame can be designed to be sealed alternatively or cumulatively against the adapter, in particular by means of an adapter seal. The support frame can be designed to be sealed alternatively or cumulatively against the container segments, in particular by means of a segment seal. Each container segment can be assigned its own circumferential segment seal. Thus, when using four container segments, it can be provided to provide four separate segment seals so that the container segments are individually sealed. It has been shown that it is advantageous if the container segments are not electrically connected to one another. However, if these are made of electrically conductive material - which is also preferred since the container segments should be thermally conductive and inexpensive materials exist,which are thermally and electrically conductive - then it may be appropriate to electrically insulate the container segments from each other This is particularly the case when an inductive heating is used The insulation can be achieved by means of the connection via the support frame, so that the container segments can be mounted at a distance from each other In this case, it is advantageous if each container segment is assigned its own segment seal, which takes over the insulating function if necessary,

[0063] The support frame can be constructed in several parts. The support frame can have a plurality of at least two frame elements that can be detachably fastened to one another. The support frame can alternatively or cumulatively comprise at least one of a cover element, a plurality of in particular vertical rod elements, and / or a base element. The multi-part construction of the support frame simplifies the installation of the apparatus as a whole and can also contribute to further reducing the costs of the apparatus. In addition, the multi-part construction of the support frame offers advantages for any maintenance work that may be required and / or when replacing the process chamber when a crystal has been fully grown and another process chamber or another growth process is to be protected with the same safety container.

[0064] In other words, the containment vessel is designed to be reusable and can be used to produce a large number of crystals using the PVT process, which can lead to considerable savings, particularly on the cost side. The containment vessel can be modularly constructed around the process chamber before a growth process is carried out and can be easily dismantled again after the crystal growth has been carried out. In a particularly advantageous embodiment, all parts are reusable, so that the containment vessel can be modularly constructed around the new process chamber before a further growth process is carried out. Due to the multi-part construction, the containment vessel can be easily and without great effort built up around another process chamber and a safety atmosphere can be provided.

[0065] The support frame elements can also be designed to be sealed against each other, so that no or only a small amount of protective gas escapes into the environment between the contact areas between individual support frame elements. Alternatively or cumulatively, a frame seal can be included to seal one frame part against a second frame part. The frame seal can, for example, be arranged in a frame seal plane that is not arranged in the same plane as the segment seal.

[0066] For example, an embodiment can be designed such that each segment seal is guided through the cover element, through two rod elements and the base element. Alternatively or cumulatively, a cover seal can be arranged on an upper side of the cover element to seal the cover. Furthermore, alternatively or cumulatively, a base seal can be arranged on an underside of the base element to seal the base element against the base. The base can be provided as a manufacturing part or as a mounting plate.

[0067] The cover element can have a segment-side segment sealing groove. The rod elements can each have at least one segment sealing groove, preferably two segment sealing grooves per rod element. The base element(s) can have a segment sealing groove. In particular, at least one of the segment sealing grooves of one of the rod elements can be aligned 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 the mutually aligned segment sealing grooves for the circumferential sealing of the wall segment.

[0068] Furthermore, the apparatus can comprise a support frame for holding at least two wall segments on the support frame. The support frame can be constructed in several parts. Alternatively or cumulatively, the support frame can have a plurality of at least two frame elements that can be releasably fastened to one another. Alternatively or cumulatively, the support frame can comprise at least one of a cover element, a plurality of in particular vertical rod elements, and / or a base element.

[0069] The support frame can have at least one longitudinal groove on an outer side for receiving a sealing element. Alternatively or cumulatively, the support frame can be designed to receive a segment seal, and / or a cover seal, and / or a base seal. Alternatively or cumulatively, the cover element can be designed in one piece, in particular for placement on the rod elements. The cover element can alternatively or cumulatively be connected to the base element via the rod elements. The elements of the support frame can alternatively or cumulatively be detachably connected to one another, for example screwably, in order to provide a stable construction on the one hand, which on the other hand is designed to be removable for purposes, in particular for maintenance or opening.

[0070] The floor element can be designed in several parts and have floor fastening sections and intermediate sections and can be prepared in such a way that the rod elements can be placed between the floor fastening sections and on the intermediate sections. Alternatively or cumulatively, the floor element can be designed in one piece and the rod elements can be inserted into recesses in the floor element. Alternatively or cumulatively, the cover element can be designed in one piece and the rod elements can be inserted into recesses in the cover element. Further alternatively or cumulatively, the cover element can form a laterally projecting collar so that the wall elements can be placed below the cover element without the wall elements projecting laterally beyond the cover element.

[0071] The support frame can be designed as an electrical insulator This ensures that the wall segments are electrically insulated from one another Alternatively or cumulatively, the support frame can be designed to be non-magnetic This can ensure that the wall segments cannot form a ring magnet, which could possibly have a disruptive effect on the heating device Further alternatively or cumulatively, the support frame can be made of temperature-resistant material Further alternatively or cumulatively, the support frame can be made of thermally and / or electrically non-conductive material Further alternatively or cumulatively, the support frame can comprise or consist of ceramic, plastic or a composite material or a combination thereof

[0072] The support frame can preferably form a holding structure for receiving the wall segments on the support frame, so that the support frame and wall segments as a whole form the container wall of a safety container, in particular for enclosing the process chamber in a gas-tight or substantially gas-tight manner. Between the container wall of the safety container and the process chamber, an intermediate space can be created which is designed in such a way that the intermediate space can be flooded with a protective atmosphere. Alternatively or cumulatively, the safety container can enclose the process chamber on all sides.

[0073] The heating device can be designed to surround the process chamber. Alternatively or cumulatively, the heating device can be designed in a ring shape around the process chamber.

[0074] In the following, the invention is described in more detail using exemplary embodiments and with reference to the figures, wherein identical and similar elements are partly provided with the same reference numerals and the features of the various exemplary embodiments can be combined with one another.

[0075] Short description of the characters

[0076] It shows:

[0077] Fig. 1 Cross-sectional view of an apparatus according to the invention,

[0078] Fig 2 perspective and simplified representation of a partially assembled safety container,

[0079] Fig 3 perspective sectional view of an embodiment of an apparatus,

[0080] Fig 4 Exploded view of an embodiment of an apparatus,

[0081] Fig 5 Embodiment of a supporting frame,

[0082] Fig 6 Detail of an embodiment of a supporting frame,

[0083] Fig 7 further detail of an embodiment of a support frame,

[0084] Fig 8 another detail of an embodiment of a support frame,

[0085] Fig 9 Detail of the course of seals in the supporting frame,

[0086] Fig 10 further detail on the course of seals in the supporting frame,

[0087] Fig 11 Cross-sectional detail of an apparatus,

[0088] Fig 12 partially assembled safety container with supporting frame,

[0089] Fig 13 Structure of an exemplary segment of a double-walled container wall with temperature control device,

[0090] Fig 14 Detail of a connection of the temperature control device,

[0091] Fig 15 Embodiment of a cooling segment of the container wall with part of the temperature control device,

[0092] Fig 16 perspective view of an embodiment of a safety container,

[0093] Fig 17 perspective partially opened view of an embodiment of an apparatus with process chamber,

[0094] Fig 18 perspective view of an apparatus

[0095] Detailed description of the invention

[0096] Fig. 1 shows a cross-sectional view of an embodiment of the apparatus. In the center of the apparatus, standing on a stand, there is a growth cell 1 consisting of a hollow cylinder with a base and a lid that closes the two ends of the hollow cylinder. The growth cell 1 consists of a porous graphite. A source material 2 is layered on the base. On the underside of the lid there is a nucleus 3. are to be set up, whereby corresponding alternating fields can influence each other and mutually disturb the process conditions In other words, the metallically conductive safety vessel 8 can ensure uniform process conditions even under the condition that several, possibly even different, devices can be set up close to each other without the processes interfering with each other

[0097] Overall, it can be seen that the containment vessel 8 is capable of solving several tasks in a synergistic manner. Not only is it capable of providing the protective atmosphere mentioned, which enables the use of a reactive gas in the process chamber, but the containment vessel 8 is also capable of shielding the process chamber from various environmental conditions such as temperature fluctuations or fluctuating electrical and / or magnetic fields, thus ensuring uniform process conditions for the process taking place in the process chamber.

[0098] In the bottom of the containment vessel 8, a ring line with one or more connections can be arranged at an annular space 12 between the vessel wall 9 of the containment vessel 8 and the cylindrical wall of the process chamber 4 made of quartz glass. The ring line is connected to an argon source 14 and a nitrogen source 15 via a shuttle valve 13.

[0099] In the ceiling 11 of the containment vessel 8 there is a closable outlet valve 16. In addition, a gas sensor 17 (in particular as a hydrogen sensor) and a pressure sensor 18 are provided there.

[0100] A hood 20 made of a shatter-proof plastic or sheet metal can be placed over the entire apparatus and rests on the bottom of the safety container 8

[0101] Furthermore, a control device 19 is provided, which is signal-connected to both sensors 17, 18 and controls the changeover valve 13, the outlet valve 16 and the inlet valve 5 for the hydrogen supply via control lines.

[0102] The control device 19 allows the following processes to be carried out: Filling the safety container 8 with an inert gas before the process chamber 4 is filled with hydrogen:

[0103] (1) The outlet valve 16 is opened

[0104] (2) The shuttle valve 13 is switched so that argon gas from the argon source 14 flows slowly into the space 12 from below, so that the space 12 is filled with the argon gas from below, whereby the existing air is displaced through the open outlet valve 16 (or pressure relief valve or the like).

[0105] (3) Closing the outlet valve 16 and the shuttle valve 13

[0106] (4) Observe a filling pause so that any remaining air residues from the argon gas can settle upwards

[0107] (5) If necessary, repeat steps (1) to (3) once or several times

[0108] (6) Opening the exhaust valve 16

[0109] (7) Switching the shuttle valve 13 so that nitrogen gas flows slowly into the space 12 from below, whereby the space 12 is filled from below with the nitrogen gas from the nitrogen source 15 and the existing argon gas is displaced through the open outlet valve 16

[0110] (8) Closing the exhaust valve 16

[0111] (9) Setting and maintaining an overpressure in the intermediate space 12 by controlled opening of the shuttle valve 13, so that despite existing and accepted leaks in the containment vessel, no air can flow into the intermediate space 12

[0112] A sufficient overpressure is approximately 2 mbar above ambient

[0113] In any case, steps (1) to (3) and (9) must be carried out. Steps (4) and (6) to (8) are optional.

[0114] In order to check whether the space 12 is sufficiently free of oxygen, an oxygen sensor can also be provided

[0115] Behavior in case of a glass wall breakage during operation:

[0116] (1) Continuous monitoring of the gas sensor 17 and

[0117] (2) Closing the hydrogen supply when the gas sensor 17 detects hydrogen in the space 12

[0118] Referring to Fig. 2, a perspective view of a simplified embodiment of a partially assembled safety container 8 is shown, wherein for reasons of clarity, various attachments as well as the process chamber 4 are not shown. Furthermore, for the sake of completeness, it should be noted that the embodiment shown in Fig. 2 does not have any details for sealing the interior area 12, so that the leak rates achievable with this embodiment would be comparatively high. Improved sealed safety containers 8 are presented with embodiments of the other figures.

[0119] In Fig. 2, a temperature control device 21 is arranged, at least partially, in the containment vessel 8, wherein a fluid can be fed into a coolant line 22 through connecting pieces 23. The coolant line 22 can be connected to the inner wall 44 of the containment vessel 8, for example glued, soldered, welded or screwed thereon. From the process chamber 4, heat output reaches the inner wall 44 predominantly as radiant heat, from where the heat output can be efficiently dissipated by means of the temperature control device 21. For example, liquid water can be used as the coolant. The amount of heat that can be dissipated by means of the temperature control device 21 can preferably be adjustable. For example, the amount of heat that can be dissipated can be influenced by means of the temperature setting for the coolant and / or the flow rate or speed.a temperature control is then provided. In response to sensor signals measuring the ambient temperature and / or the process temperature, a temperature control of the process chamber 4 can be achieved with the temperature control, so that a substantially constant temperature is present in the process chamber 4 during the process sequence,

[0120] The safety vessel 8 has sight glasses 32, which bridge the interior area 12 and allow a view of the process chamber 4, for example for the purpose of process monitoring. In order to keep the direct heat radiation low, the sight glasses 32 are designed to be relatively small. Furthermore, Fig. 14 shows a detail of the refrigerant line 22 with line fastening 22A, connection piece 23, transition piece 23B and connection piece fastening 23A.

[0121] Fig. 3 shows a sectional view of an embodiment of an apparatus 100. A process chamber 4 is partially surrounded by an induction coil 7, which is supplied with electrical power by a heating device 6. The heating device 6 is arranged partially inside and outside the containment vessel 8, wherein, for example, the power electronics can be arranged outside, so that a sealed feedthrough 62 is provided to reduce gas leaks. The induction coil 7 with parts of the electronics is arranged in the interior 12, i.e. in the space occupied by the safety atmosphere.

[0122] The protective gas can be supplied through the protective gas supply 54 on the underside of the interior 12 (if necessary, several protective gas supplies 54 are provided). The outlet valve 16 is arranged on the top side 11, by means of which, for example, the outside air (containing oxygen) initially arranged in the protective container 8 can be let out of the protective container 8, for example by admitting a protective gas which is heavier than air. Subsequently, if a connecting line is connected to the outlet valve 16 (not shown), a circulation of the protective gas can also be provided, for example in order to dissipate heat from the protective container 8, or to ensure a regular exchange of the protective gas.

[0123] The coolant line 22 of the temperature control device 21 is arranged in the container wall 9 in the case shown here, which is designed as a double-walled container. In the cross section of the containment vessel 8 with process chamber 4 shown in Fig. 3, the interior space 12 of the containment vessel 8 for receiving the protective atmosphere extends from the chamber wall 41 and, for example, around the process chamber 4 to the container wall 9, wherein the interior space 12 is sealed against the container wall 9 in order to keep the gas leakage rate from the interior space 12 into the environment 30 low.

[0124] Furthermore, the embodiment shown in Fig. 3 shows a special feature in that the process chamber 4 is equipped with an adapter 46. In the embodiment shown, the adapter 46 has two alternative upper covers 47, 48, so that depending on the desired process height, the upper cover 47 or the further inner upper cover 48 can be used. The covers 47, 48 can thus be used alternatively to each other if necessary.

[0125] Referring to Fig. 4, an apparatus 100 is shown in an exploded view so that the components of the containment vessel 8 used there are visible. The process chamber 4 is arranged inside, in this embodiment in an empty version for better illustration. The quartz glass wall 41 (process chamber wall) forms the inner closure of an intermediate space 12 which is arranged between the quartz glass wall 41 (as the inner wall of the containment vessel) and the vessel wall 9. The induction coil 7 serves as a heater and is arranged in a ring around the process chamber 4.

[0126] The process chamber wall 41 is initially open at the top, with the process chamber 4 closing off or being sealed by means of a chamber closure 42. The upper closure is formed by the adapter ring 46, which engages in the process chamber wall 41 in a dual function and seals the safety container 8 in the upper area towards the inside and towards the lid 11. The adapter 46 is connected to the upper frame closure 64 of the support frame 60 via the lid 11. The support frame 60 forms, so to speak, the "skeleton" of the safety container 8, in that numerous components of the safety container 8 can be fastened to the support frame 60, such as in particular the container segments 91, 92, 93 and the lid 11. The support frame 60 is in turn fastened to the base 10 via a base element or lower frame closure 66, so that overall a stable and rigid construction is formed. In the embodiment shown in Fig.4, a test segment 91 can be mounted, comprising one or more sight glasses 32 for viewing the process chamber 4 or the process taking place therein. Furthermore, the two cooling segments 92, 93 shown here can be arranged on the support frame 60. In the rear area, the electronics unit of the heating device 6 is shown, which can be arranged outside the safety container 8 and the connections to the induction coil are led through the container wall 9 by means of feedthroughs (cf. e.g. Fig. 7). To improve the sealing, the support frame has a plurality of seals, visible here are segment seals 72, a cover seal 74 and an adapter seal 78. The wall segments 91, 92, 93 shown in Fig. 4 are double-walled and each have an inner wall (the inner wall 923 of the cooling segment 92 can be seen) and an outer cover 919, 939.

[0127] Referring to Fig. 5, a multi-part support frame 60 is shown, which as a whole forms the support frame 60 for holding the wall segments 91, 92, 93, 94. The support frame 60 has a base element or a lower frame end 66, which can be formed in one piece or in several parts. In the case shown here, the lower frame end 66 is multi-part, so that a plurality of four base elements together with four intermediate pieces 61 form the lower frame end 66. On the lower frame end 66, a receiving groove 84 is provided on the segment side for receiving the segment seal 72. The segment seal 72 runs through the base element receiving groove 84, through the rod element receiving groove 83 and through the cover element receiving groove 82 and is designed such thatto seal a wall segment all around. On the top side of the cover element 64, a cover seal receiving groove 81 is provided for receiving the circumferential cover seal 74. All sealing elements shown have in common that they are arranged on the segment side of the support frame 60 and are thus protected by the support frame 60 from the heat radiation of the process chamber 4,

[0128] The support frame 60 is preferably made of electrically and / or thermally non-conductive material. If the segments 91, 92, 93, 94 or the lid 11 are fastened to the support frame 60, in particular in the counter-fasteners 97A or 69 (screw holes), then a distance between the wall segments 91, 92, 93, 94 and the lid 11 can be set by means of the support frame 60, so that the flat components of the container 8 do not touch each other. This means that the flat components of the container 8 can be electrically insulated from each other if they do not touch each other and the support frame 60 is not electrically conductive. Nevertheless, a good seal of the safety container 8 can be achieved by means of the provided sealing grooves 81, 82, 83, 84 and the sealing elements 72, 74, 76, 78, because the individual segments 11, 91, 92, 93, 94 can be sealed against the supporting frame 60. This offers the advantage of sealing the flat elements 11, 91, 92, 93,94 made of comparatively inexpensive raw materials such as steel or other metals which have excellent thermal conductivity, but without forming a closed metallic or conductive wall into which the alternating electromagnetic fields of the induction heater 6, 7 can penetrate and disrupt the heating operation or even make it impossible. In order to separate the wall segments 91, 92, 93, 94 even better from the cover 11, the upper frame end 64 has a bezel 63, over which the upper frame end 64 forms a projection, so that the upper frame end 64, for example, is flush with the outer panels 99, 919, 929, 939 of the wall elements 91, 92, 93, 94. This ensures that the wall elements 91, 92, 93,94 do not form an electrical short circuit via the cover 11. In addition, the overhang further simplifies the assembly of the cover 11 and creates a wider support surface for the cover 11, so that the seal is further improved and a further increased overall stability is achieved for the frame 60,

[0129] Referring to Figures 6 to 10, detailed sections of various embodiments of the support frame 60 are shown. Figure 6 shows the transition from the lower frame end 66 to the floor 10 more clearly, wherein the segment seal 72 is inserted into the floor element receiving groove 84 and the flush adjoining rod element receiving groove 83. The lower frame end 66 has connecting means 68, for example screw holes for inserting fastening screws for fastening the lower frame end 66 to the floor 10. A frame seal 77 is provided to seal the rod element 62 against the intermediate piece 61 and at the same time against the lower frame section elements 66.

[0130] Fig. 7 shows a detail of the upper frame end 64 with a rod element 62 and the wall element 92 mounted thereon. The cover element 64 has recesses 67, here two screw holes for inserting screws for connecting the cover element 64 to the rod element 62. The recessed mounting of the screws in the recesses 67 enables a flush and thus sealed mounting of the cover 11 on the upper frame element 64. The bezel 63 on the cover element 64 is also visible in profile, whereby the course of the segment seal 72 running in the bezel 63 in the cover element receiving groove 82 is also shown.

[0131] Fig. 8 shows a further detailed view of a section of a support frame 60, wherein a continuous lower frame section 66 rests on the floor 10 and is sealed against the floor 10 by means of the floor seal 76. The floor seal 76 runs in the receiving groove 85. A plurality of screw holes 68 are provided for the passage of screw means for connecting the lower frame section 66 to the floor 10. In this case, the use of recesses may not be necessary, since in the embodiment shown here no sealing surface is formed on the upper side of the lower frame section 66. Figures 9 and 10 illustrate the connection of a rod element 62 (not shown in Fig. 9 for the sake of clarity) in a multi-part lower frame section 66 with intermediate piece 61.see e.g. Fig. 8 or 10) with the intermediate piece 61 and the sealing of the rod element 62 by means of the inner frame part seal 77 with respect to both the intermediate piece 61 and the multi-part lower frame section 66. To accommodate the inner frame part seal 77, a groove 86A is provided along the length of two lower frame sections 66 and a groove 86 is provided in the intermediate piece 61 for the joint accommodation of the frame seal 77. The rod element 62 abuts the intermediate piece 61 at the sealed frame part joint 65 and two of the lower frame sections 66. To fasten one wall segment 91, 92, 93, 94 in each case, counter fasteners 97A are provided in the rod element 62,

[0132] Referring to Fig. 11, a detail view of a cross section through an embodiment of the apparatus 100 is shown. The adapter 46 forms the upper closure of the process chamber 4 or 4a, wherein in this embodiment, two process chamber heights of different process chambers 4 or 4a are shown as examples, which can be closed off alternatively from one another by the adapter 46. The adapter 46 can therefore be sealed against the safety container 8 either via the adapter seal 78 or the alternative adapter seal 79. The intermediate space 12 is formed between the chamber wall 41 and the container wall 9. The lid 11 sealingly connects the adapter 46 via the upper frame part 64 to the container wall 9, so that overall a sealed shell or container 8 is formed. The adapter can be connected to the lid 11 by means of adapter fastening means 49, for example screwed,and the lid 11 in turn by means of fastening means 69 to the upper frame part 64, so that a force-fitting connection from the adapter 46 via the lid 11 to the frame 64 and further into the container wall 9 is formed. The container wall is double-walled in the example shown in Fig. 11 and has an inner wall 98, an outer panel 99 and the intermediate space 122 located therebetween. In this embodiment, the outer panel 99 projects slightly over the upper frame part 64 and fills the area of ​​the casing 63 to a greater extent. A sealed leadthrough 26 is provided for the leadthrough of, for example, electrical connections from or to the outside to the environment 30,

[0133] Fig. 12 shows a partially assembled container 8, wherein a wall segment in the form of the connection element 94 is already arranged on the frame 60 fixed to the base plate 10. A plurality of sealed feedthroughs 26 provide a possibility of connecting electronics or the like located outside the container 8 with components arranged inside the container 8. If these component connections are combined in such a way that a majority of the or all of the intended connections are made through the connection element 94, then the connection element 94 can be arranged or designed such that it remains permanently or at least predominantly mounted. In contrast, other wall segments 91, 92, 93 can be designed such that they can be quickly and easily removed.so that rapid access to the process chamber 4 is possible. As usual and throughout the present description, like reference numerals represent like elements, so that the description of the multitude of elements already described need not be repeated below,

[0134] Referring to Fig. 13, a further embodiment of the cooling segment 92 with a sandwich structure is further illustrated. The coolant line 22 of the temperature control device 21 is arranged on the inner wall 98 and can be connected to the outside by means of connections 23. An intermediate space cover 921, 922 surrounds or delimits the segment 92 all the way around, wherein an outer panel 99 can be screwed onto the intermediate space cover. The coolant line 22 and the fastening means 97 are covered by the outer panel 99 and are thus protected from access on the one hand and from improper damage on the other. The outer panel 99 thus conceals the technical installations from direct view and access and gives the apparatus 100 an attractive appearance. Furthermore, it can already be illustrated with Fig. 13 that the temperature control device 21 is also optimized in such a way that the cooling element 92 as a whole can be removed quickly and easily.for example, by providing connecting pieces 23 at which the coolant line can be easily separated. For example, the connecting pieces can be designed as quick connectors which have a bayonet or screw closure and can be removed easily and quickly. Thus, the complete cooling element 92 can be easily separated from the coolant supply and thereby detached from the container assembly together with the cooling device (coolant line 22). This further simplifies and accelerates the disassembly and / or opening of the container 8 in the event that maintenance work and / or a change of the process chamber 4 is desired. Thus, the double-walled construction of the wall elements 91, 92, 93, 94 is not absolutely necessary, but other arrangements of the coolant line 22 are also conceivable, but the arrangement of the coolant line outside the inner wall 923 has proven to be particularly advantageous.since the coolant line is thereby also arranged outside the interior 12 to be sealed and, in addition to the easier disassembly and assembly of the safety container 8, fewer passages through the container wall 9 that need to be sealed are required,

[0135] Referring to Fig. 15, a plan view of the intermediate region 122 in the double wall of the cooling segment 92 of the container wall 9 is shown with the temperature control device 21, wherein the coolant line 22 is arranged in the intermediate 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, which is arranged in an intermediate region 122. Frame parts 92, 94 are fastened to the first segment 91 by means of fastening means 97. Further fastening means 96 (e.g. screw holes) are arranged at regular intervals on the frame parts 92, 94, so that the intermediate region 122 is enclosed thereby.

[0136] Fig. 16 finally shows an apparatus 100 constructed on the base 10 with a multi-part container wall 9, which comprises wall segments 91 and 92. The coolant lines 22 (cf. e.g. Fig. 15 or 13) run protected behind the outer panel 99 and are connected to each other by means of compensating bends 24, so that a coolant - e.g. water - can flow through the temperature control device 21. In addition, the compensating bends 24 are quickly removable, so that the coolant lines 22 and thus the wall segments 91, 92 as a whole can be easily detached from each other. The process chamber 4 (cf. e.g. Fig. 1 or 3) is surrounded on all sides by the safety atmosphere in the intermediate space 12 - or, depending on the embodiment, at least surrounded on all sides by the safety atmosphere above the base 10. Should the process chamber 4 burst or otherwise fail and process gas escape,the process gas mixes with the protective gas stored in the interior 12 to form a harmless mixed gas,

[0137] Referring to Fig. 17, a further embodiment of an apparatus 100 is shown, wherein the connection element 94 is removed and a cooling element 92, 93 is mounted. In this embodiment, it is clear and / or differs from the other embodiments that gas supply and discharge lines 51, 54 can be routed beneath the base 10, so that they run outside the environment 30 and are therefore not in the area against which the containment vessel 8 would have to protect. Thus, the underbody 31 can be protected in a different way, or it is not necessary there for protection to be provided by the safety atmosphere. Consequently, the process chamber 4 does not extend far enough into the underbody 31 or not at all into the underbody 31, so that no corresponding heating and / or a crack in the chamber wall 41 is to be expected there, which would lead to a significant outflow of process gas into the underbody 31.or which could lead to such an explosion that a hazard in the surrounding area 30 would be expected. This also has the further advantage that fewer penetrations have to be made through or into the interior 12 and thus the tightness of the protective container 8 can be further increased. A further advantage is that the supply and discharge lines below the floor 10 do not interfere with the surrounding area 30, but can rather be laid concealed,

[0138] Finally, Fig. 18 shows a further embodiment of a fully closed apparatus 100, wherein in the illustration a cooling segment 92 is inserted on the right side and a connection element 94 on the left side. The heating electronics 6 is only indicated schematically and is arranged outside the protective container 8. The flange-like arrangement directly on the container wall 9 without hose-like intermediate connectors ensures a further improved gas seal, so that this electronics flange is preferred for the heating device 6. Since this can mean a comparatively rigid arrangement of the connection element 94, it can therefore be preferredFor the purpose of replacing the process chamber 4 or generally for maintenance access, it is better to remove the cooling element 92 and thus gain access to the process chamber and / or the induction heater etc. Alternatively or cumulatively, the cover 11 or the adapter 46 can of course also be removed and the process chamber can be removed upwards, so that the hardware and electronics or gas connections etc. located in the containment vessel 8 do not have to be removed or modified,

[0139] It has been shown that the modular concept of the developments and inventions presented here brings about a huge improvement and a gain in safety compared to previous devices, while reducing manufacturing costs and simplifying the maintainability of the system components. The present description has a large number of aspects which, individually or together with others, can define essential aspects of the invention(s).

[0140] It is clear to the person skilled in the art that the embodiments described above are to be understood as examples and that the invention is not limited to these, but can be varied in many ways without departing from the scope of the claims. Furthermore, it is clear that the features, regardless of whether they are disclosed in the description, the claims, the figures or otherwise, also individually define essential components of the invention, even if they are described together with other features. In all figures, the same reference symbols represent the same objects, so that descriptions of objects that may only be mentioned in one or at least not with regard to all figures, can also be transferred to these figures and embodiments with regard to which the object is not explicitly described in the description. List of reference symbols

[0141] 1 growth cell

[0142] 2 Source material

[0143] 3 germ

[0144] 4, 4A Process Chamber

[0145] 5 Inlet valve

[0146] 6 Heating device

[0147] 7 Induction coil

[0148] 8 safety containers

[0149] 9 Container wall

[0150] 10 Floor

[0151] 11 Ceiling

[0152] 12 space

[0153] 13 shuttle valve

[0154] 14 Argon source

[0155] 15 Nitrogen source

[0156] 16 Exhaust valve

[0157] 17 Gas sensor

[0158] 18 Pressure sensor

[0159] 19 Control device

[0160] 20 hood

[0161] 21 Cooling or tempering device

[0162] 22 coolant line

[0163] 22A cable fastening

[0164] 23 Connector

[0165] 23A connection holder

[0166] 23B curved section

[0167] 24 compensation sheets

[0168] 26 sealed bushings

[0169] 30 Surroundings

[0170] 31 Underbody

[0171] 32 sight glass

[0172] 41 Process chamber wall or inner wall of the containment vessel

[0173] 42 bolt action

[0174] 46 adapters

[0175] 47 upper cover of the process chamber

[0176] 48 upper cover of the process chamber

[0177] 49 adapter fasteners

[0178] 51 Process gas supply

[0179] 52 Process gas discharge

[0180] 54 Shielding gas supply

[0181] 56 Shielding gas outlet

[0182] 60 supporting frames

[0183] 61 intermediate piece

[0184] 62 Bar element or frame strut

[0185] 63 Bezel

[0186] 64 upper frame end or cover element

[0187] 65 frame part joint

[0188] 66 lower frame end or base element recesses for receiving frame connecting means connecting means counter-fastening for cover 11 segment seal cover seal sealing element base seal internal frame part seal adapter seal alternative adapter seal cover seal receiving groove cover element receiving groove rod element receiving groove base element receiving groove receiving groove frame seal receiving groove A front frame seal receiving groove section of the vessel wall, test segment section of the vessel wall, cooling segment section of the vessel wall, further cooling segment section of the vessel wall,Connecting segment Fastening element Fastening element A Counter fastening to the fastening element 97 Inner wall Outer panel 0 Apparatus 2 Intermediate area 9 Outer panel of the test segment 1 Upper intermediate space cover 2 Side intermediate space cover 3 Inner wall of the cooling segment 4 Lower intermediate space cover 9 Outer panel of the cooling segment 9 Outer panel of the further cooling segment,

Claims

Patent claims 1 PVT method for the reliable production of single crystals in an apparatus (100), wherein the apparatus comprises a process chamber (4) for accommodating a highly heatable growth cell (1) and a heating device (6) for heating the growth cell (1), wherein the growth cell is prepared for accommodating a source material (2) and a seed (3), and wherein the process chamber (4) can be filled with a process gas and the growth cell (1) can be heated, wherein the apparatus comprises a safety container (8) enclosing the process chamber for enclosing the process chamber (4), in particular in a gas-tight or substantially gas-tight manner, and wherein the safety container has a circumferential container wall (9), so that an intermediate space (12) is created between the container wall (9) of the safety container (8) and the process chamber (4), comprising the steps Providing a protective atmosphere in the space and flooding the space with the protective atmosphere, Providing the process gas in the process chamber, wherein the process gas comprises or consists of a reactive gas, and Heating the growth cell using the heating device so that the source material sublimates and resublimates at the nucleus 2 PVT method according to the preceding claim, in which the protective atmosphere is provided in the intermediate space (12) by setting an overpressure relative to a pressure in the environment (30), in particular of at least 1 mbar above ambient pressure or more, preferably 3 mbar or more, more preferably 5 mbar or more above ambient pressure 3 PVT method according to one of the preceding claims, wherein the heating of the growth cell (1) is carried out radially from all sides by means of the heating device (6) annularly enclosing the process chamber (4), and / or wherein it is ensured that the provision of the protective atmosphere in the intermediate space (12) is completed before the process gas is introduced into the process chamber (4) and / or the growth cell (1) is heated to the operating temperature, and / or wherein the flooding of the intermediate space (12) with the protective atmosphere further comprises the displacement of air located in the intermediate space before the sublimation of the source material (2) is initiated 4 PVT process according to one of the preceding claims, characterized in that the reactive gas comprises or consists of hydrogen, and / or that the protective atmosphere comprises or consists of an inert gas, wherein the inert gas preferably comprises or consists of argon 5 PVT method according to one of the preceding claims, characterized in that the containment vessel (8) is constructed in such a way that it allows gas losses into the environment (30), and that protective gas is supplied in order to compensate for gas losses, and in particular to maintain the overpressure relative to the environment (30) in the containment vessel (8) according to claim 2 6 PVT process according to one of the preceding claims, characterized in that for flooding the containment vessel (8), a first inert gas which is heavier than air is admitted into its lower region, whereby the air is displaced upwards, for which purpose a closable outlet (16, 56) at the upper end of the containment vessel (8) remains open until the air has escaped 7 PVT process according to one of claims 4 to 6, characterized in that after one or more floodings of the containment vessel (8) with the first inert gas, this is replaced by a second inert gas, in particular nitrogen 8 PVT method according to one of the preceding claims, characterized in that the safety container (8) has a gas sensor (17) which is able to detect the reactive gas, and / or that the process gas supply to the Process chamber (4) is interrupted when the reactive gas in the containment vessel (8) is detected. Apparatus (100) for the process-reliable production of single crystals, in particular according to the PVT method according to one of the preceding claims, comprising a process chamber (4) for accommodating a highly heatable growth cell (1), a heating device (6, 7) for heating the growth cell (1), wherein the process chamber has a process gas connection (51) for filling it with a process gas which can be provided from a process gas source, wherein the growth cell is prepared for accommodating a source material (2) and a nucleus (3), characterized in that the apparatus comprises a containment vessel (8) for enclosing the process chamber (4), in particular in a gas-tight or substantially gas-tight manner, and the containment vessel has a vessel wall (9),so that an intermediate space (12) is created between the container wall (9) of the safety container (8) and the process chamber (4), which is designed such that the intermediate space can be flooded with a protective atmosphere. Apparatus (100) according to one of the preceding claims, wherein the container wall (9) is designed to enclose the process chamber (4) from above and / or below, in particular to completely enclose it on all sides, and / or wherein the container wall (9) comprises a process chamber adapter (46) for accommodating process chambers of different sizes on the same container wall. Apparatus (100) according to one of the preceding claims, wherein the container wall is double-walled, wherein in an intermediate region (122) of the double-walled container wall, in particular a cooling device (21) is arranged. Apparatus (100) according to one of the preceding claims, characterized in that the safety container (8) is constructed such thatthat it allows gas losses to the outside, and / or that the containment vessel (8) has a pressure sensor (18) and the pressure sensor (18) is signal-connected to a control device (19), and / or wherein the control device (19) is designed such that, on the basis of the pressure sensor signals, an overpressure relative to the environment (30) in the containment vessel (8) is set. Apparatus (100) according to 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, wherein the support frame forms a holding structure for receiving the wall segments on the support frame, so that the support frame and wall segments as a whole form the vessel wall (9) of the containment vessel (8), in particular for enclosing the process chamber (4) in a gas-tight or substantially gas-tight manner. Apparatus (100) according to the preceding claim, wherein at least one sealing element is arranged on or in the support frame (60). (72, 74, 75,76, 77, 78, 79) is arranged to seal the support frame against the plurality of at least two container segments (91, 92, 93, 94) and / or to seal the protective container (8) against the environment (30), and / or wherein the support frame (60) has at least one longitudinal groove (81, 82, 83, 84, 85, 86, 86A) on an outer side for receiving a sealing element (72, 74, 75, 76, 77, 78, 79), and / or wherein the support frame (60) is designed to receive a segment seal (72), and / or a lid seal (74), and / or a bottom seal (76), Apparatus (100) according to one of claims 13 or 14, wherein the support frame (60) is designed to be sealed against a base plate (10), and / or wherein the support frame (60) is designed to be sealed against the adapter (46), and / or wherein the support frame (60) is designed to be sealed against the container segments (91, 92, 93, 94), and / or wherein each container segment (91, 92, 93, 94) is assigned its own circumferential segment seal (72). Apparatus (100) according to one of claims 12 to 15, wherein the support frame (60) is constructed in several parts, and / or wherein the support frame (60) has a plurality of at least two frame elements (61, 62, 64, 66) that can be releasably fastened to one another, and / or wherein the support frame (60) comprises at least one of a cover element (64), a plurality of in particular vertical rod elements (62), and / or a floor element (66) Apparatus (100) according to the preceding claim, wherein the support frame elements (61, 62, 64,66) are sealed against each other, and / or further comprising a frame part seal (77) for sealing one frame part against a second frame part, wherein the frame seal is in particular not arranged in the same plane as the segment seal (72). Apparatus (100) according to one of claims 12 to 17, wherein each segment seal (72) is guided through the cover element (64), through two rod elements (62) and the base element (66), and / or a cover seal (74) is arranged on an upper side of the cover element (64) for sealing the cover (11), and / or a base seal (76) is arranged on an underside of the base element (66) for sealing the base element against the base (10). Apparatus (100) according to one of claims 15 to 18, wherein the cover element (64) has a segment-side cover element receiving groove (82), and wherein the rod elements (62) each have at least one rod element receiving groove (83)preferably two rod element receiving grooves per rod element, and wherein the base element(s) (66) has a base element receiving groove (84), and wherein in particular at least one of the grooves of one of the rod elements is aligned with the cover element receiving groove and the base element receiving groove, so that a segment seal (72) can be inserted into the mutually aligned segment seal grooves for circumferential sealing of the wall segment (91, 92, 93, 94). Apparatus (100) according to one of the preceding claims, further comprising a protective gas connection (54) in the lower region of the safety container (8) and a closable outlet (16, 56) in its upper region,

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