DE102022123747A1 - PVT process and apparatus for the reliable production of single crystals - Google Patents

Abstract

In order to be able to use a reactive gas such as hydrogen as a process gas in a PVT process, special security is required in order to be able to carry out the process reliably. An apparatus for carrying out the PVT process consists of a highly heatable growth cell which is arranged in a process chamber whose wall consists of a heat-resistant material such as typically quartz glass. The process chamber is filled with hydrogen via an inlet valve. A heating device consists of an induction coil that surrounds the process chamber at the level of the growth cell and heats the growth cell to over 2,000 °C up to 2,400 °C. However, the use of a reactive gas brings with it the problem that if the chamber wall of the process chamber breaks, which cannot be completely ruled out, the reactive gas can mix with the ambient air, so that an ignitable gas mixture is created, which would immediately ignite on the hot parts of the apparatus. The process chamber is therefore surrounded by a safety container which is filled with an inert gas.

Description

Field of invention

The invention relates to a PVT method for the reliable production of single crystals and an apparatus which comprises a highly heatable growth cell, a process chamber in which the growth cell is located and a heating device surrounding the process chamber for heating the growth cell. A source material and a germ 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 on the germ.

Background and general description of the invention

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 containing many different crystallites. The use of volume crystals is also possible. The High-Temperature Chemical Vapor Deposition (HT-CVD) process is known as an alternative process. In the PVT process, crystal growth typically takes place within the growth cell made of graphite through sublimation of a SiC source material and crystallization on a specified SiC seed at temperatures of over 2,000 °C. The driving force for crystal growth is a temperature gradient that is imposed on the growth cell by a heating device. Common methods for heating PVT devices 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 crystal growth. The process chamber can be single- or double-walled and air- or water-cooled. Argon, helium, nitrogen, hydrogen and possibly other gases are typically used as process gases for targeted doping. 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.

SiC single crystals are manufactured for a variety of applications in semiconductor technology because of 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. Accordingly, an inert gas is used as the process gas, which is not problematic from a safety perspective. Regarding the state of the art, please also refer 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 referred.

It is an intellectual starting point and one of the tasks of the present invention to enable processes, among other things, to specifically influence the incorporation of dopant or to produce undoped SiC single crystals. With regard to this starting point, the present invention develops to ensure a process flow 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, i.e. a flammable and/or reactive (possibly also toxic) gas, e.g. hydrogen as a process gas, with concentrations of over 5% and up to 100%.

The gas molecules of the reactive gas, especially hydrogen atoms, attach 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 as placeholders for a short time, so that a crystal lattice with few errors, if not no errors at all, can be created. Reactive gas molecules can also enter into reactions with other process gases, the source material or even the HotZone material and form further gaseous species that enter the process gas atmosphere and can, at least temporarily, attach to the crystal. Possible reactive gases such as silane, methane, propane, etc. provide, among other things, the elements silicon and carbon, which are incorporated into the crystal. The addition of reactive gases can overall influence the defect density (desired and/or undesirable). However, the exact influence depends on a large number of parameters and their interaction. The addition of reactive gas is intended to influence crystal growth.

The object of the present invention can therefore be seen as providing a device and a method with which improved or modified crystal growth is possible.

In a partial aspect or development of the invention, the provision of a device and a method can be viewed as an aspect of the task places in which a reactive gas can be used to improve crystal growth.

In yet another partial aspect or development of the invention, the task may be to provide a device and a method by means of which improved crystals can be provided with little effort or cost-effectively.

However, the use of a reactive gas, comprising, for example, hydrogen or other reactive elements, represents a potential danger when carrying out the method. A reactive gas can, for example, be flammable or flammable and/or toxic. In the case of hydrogen as an example, an oxyhydrogen reaction can take place with the oxygen in the air, which is why hydrogen is referred to as a reactive gas in this description. In addition to hydrogen, other examples of currently possible reactive gases include carbon and silicon-containing precursors or hydrocarbons and their derivatives (examples: silane or methane, propane, etc.).

In addition, in today's common apparatus, the process chamber is typically formed from quartz glass, which is inherently brittle and prone to breaking. 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. A combination of induction and resistance heaters can also 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, the safety requirements also apply in a similar way to other building materials for providing the process chamber, at least in the case of quartz glass to a particular extent.

However, if the process chamber becomes 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 produced by the heating device (hot components of the hot zone, typically graphite parts inside the Process chamber) is ignited and explodes. If a reactive gas is used, it is therefore not possible to carry out the process reliably with the known fittings.

A reactive gas mentioned in the present 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 reactive in any other way within the meaning used in this description. Doping gases are flushed around the crystal, so the processes take place entirely in the process chamber. For example, in this context, the process chamber can also be flushed with an inert gas such as argon in order to directly modify the PVT process. In general, doping gases are intended to be incorporated into the crystal or the crystal structure - which is where the term “doping gas” comes from - in order to influence physical and/or chemical properties of the crystal, such as electrical conductivity. In other words, molecules or components of a doping gas form a later integral building material of the crystal. Such molecules or components of a doping gas remain in the crystal and can be detected there later.

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 dopant gas in order to influence the physical and chemical properties of the crystal. Due to the danger potential of reactive gases, i.e. in particular ignition, combustion, deflagration or poisoning potential, reactive gases have not yet been considered for use to improve crystal growth, or at least the safety aspects described above when dealing with a reactive gas in this environment have not been considered sufficiently taken into account. In addition, the reactive gas to be used is not a source material in the true sense. 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 precursors containing C or Si. The gas serves there 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.

As part of this further development and improvement, the present description describes and defines various aspects of the safety container that surrounds the process chamber and 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 determined. A goal particularly sought with the security container is the avoidance or prevention of an explosive gas mixture in the event of damage, especially breakage, to the process chamber.

In order to carry out the process reliably, 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 produce 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 rather it has to be laboriously opened and then laboriously closed again after the work or changes have been made.

On the other hand, it would be advantageous to present a PVT process for the reliable production of single crystals that can be carried out in an apparatus that can be produced with little effort and/or is inexpensive.

The problem is solved by the invention defined in the independent claims. Dependent claims reflect further developments and preferred embodiments of the invention.

To solve one, several or all aspects of the problem presented, a PVT method for the reliable production of single crystals in an apparatus is presented, the apparatus comprising a process chamber for accommodating a highly heatable growth cell and a heating device for heating the growth cell, the growth cell is prepared to hold a source material and a germ, 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 a particularly gas-tight or essentially gas-tight manner. The security container has a circumferential container wall, so that a space is created between the container wall of the security 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 the intermediate space. For example, the process chamber is round and the safety container 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 to the wall of the process chamber, for example), outer radius R (corresponds to the wall, for example of the security container) and height h (measured, for example, from the floor to the lid).

The method presented here has 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 the intermediate space is first filled with the protective atmosphere, in particular in such a way that the air that may have previously been present there has been displaced as completely as possible, and only when the protective container is ready for use by filling it with the protective atmosphere (and this, for example, as a signal outputs) the further process is initiated.

In principle, process gas could be introduced into the process chamber before the safety container is ready for use if it 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 before the safety container is ready for use, for example up to operating temperature, if no process gas or at least no reactive gas has been introduced there. The transition between the deployment of the safety container and the start of operation of the process chamber can be fluid. However, it is preferred overall 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 the operating temperature. In other words, it is preferred if the process gas is provided in the process chamber only after the intermediate space has been flooded with protective gas. It can therefore also be preferred that the flooding of the intermediate space with the protective atmosphere - particularly namely the first-time 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.

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

If damage to the process chamber - in particular a break - occurs with this arrangement, the reactive gas of the process chamber mixes in the protective atmosphere in the safety container, for example with the inert gas, to form a non-explosive gas mixture, so that it An explosion cannot occur even in a hot environment. This safety measure is particularly important if the reactive gas is flammable or prone to deflagration, such as hydrogen.

The method further includes heating the growth cell using the heating device so that the source material sublimes and resublimes at the germ. The growth cell can preferably be heated from radially on all sides. For this purpose, the heating device can enclose the process chamber in a ring.

When providing the protective atmosphere in the intermediate space, it is preferred to set an excess pressure compared to an ambient pressure. For example, the excess pressure in the protective container can be set, for example, at least 1 mBar above ambient pressure or more, preferably 3 mBar or more, more preferably 5 mBar or more above ambient pressure. If an excess pressure is set in the protective container relative to the environment, only insignificant or no gas from the environment can penetrate into the protective container. In this way it can be ensured 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.

The safety container is particularly easy to implement if it is constructed in such a way that it allows gas losses to the outside, particularly to a small extent, and is therefore only approximately gas-tight. This makes the construction of the safety container more cost-effective, since requirements for a 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 safety container can have a permissible leak rate that is greater than 0 l/min. For cost reasons, it can be advantageous and unproblematic, especially due to the choice and geometry of the construction, to allow a leak rate that is in the range 0 ≤ leak rate ≤ 5 l/min, or also in the range 0 ≤ leak rate ≤ 30 l/min. For example, the leak rate to be permitted 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 does not make sense to allow the containment leakage rate to be too high for economic reasons and possibly those related to workplace safety. For example, it may be desirable to limit the leak rate to less than 30 l/min, preferably 10 l/min, more preferably 4 l/min, more preferably 1 l/min, more preferably 500 ml/min, and even more preferably 150 ml /min. The aim is to achieve leak rates in a range from 2 ml/min to 50 ml/min, preferably from 10 ml/min to 20 ml/min.

To maintain the protective atmosphere, inert gas can, for example, be supplied to compensate for gas losses and to build up and/or maintain an excess pressure in the safety container. The excess pressure prevents atmospheric oxygen from entering the safety container from outside. A pressure control system can be used to maintain a relative overpressure in the safety container, for example in a range from 1 mBar above ambient pressure or more, preferably 3 mBar or more, more preferably from 5 mBar or more, to 50 mBar above ambient pressure or less, preferably 30 mBar or less. But this also basically includes a completely gas-tight security container with a leak rate of 0 ml/min or a leak rate that is not measurably low, in which an excess pressure can also be maintained in the security container.

In order to ensure that air is displaced as completely as possible from the security container, the present description can further provide that a first inert gas is admitted into the security container to flood the security container. The first inert gas can be heavier than air so that it is admitted into the lower region of the containment, displacing the air upwards. For this purpose, for example, a lockable outlet at the upper end of the security container can remain open until the air has escaped.

The protective atmosphere preferably comprises an inert gas such as, in particular, argon. Because of the high density of argon, it collects at the bottom of the containment and slowly pushes 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 include any fluid, whether individually or as a mixture, which is able to provide a protective function to neutralize the reactive gas in the event of excessive or impermissible escape from the process chamber and/or to prevent negative effects such as deflagrations. For example, the protective atmosphere can also be the standard under normal conditions atmosphere in a liquid or solid state.

When the air has been displaced by the first inert gas, it can be replaced by another, for example a less expensive, inert gas. The invention therefore further provides that after the safety container has been flooded once or several times with the first inert gas, it is replaced by the second inert gas, in particular nitrogen.

In order to ensure that the reactive gas is not fed into the apparatus in the event of a rupture of the process chamber, it is provided that the safety container has a gas sensor that is capable of detecting the presence of reactive gas in the safety container. Furthermore, it can be provided that the process gas supply to the process chamber is interrupted when the gas sensor detects the reactive gas in the safety container.

In a further development, the gas supply can be interrupted via a further pressure sensor or pressure switch, which 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, a fall below 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 therefore also take place independently of the detection of reactive gas, such as hydrogen, in the space between the process chamber and the cooling jacket.

An opening of the process chamber, for example in the event of the quartz glass breaking, can be detected or indicated, for example, by one of the following criteria. The reactive gas/hydrogen can be detected by a gas sensor in the safety container. Alternatively or cumulatively, the excess pressure in the containment can be determined and, when the excess pressure disappears, a process malfunction can be concluded (e.g. p <= approx. 2 mbarg compared to the atmosphere).

Furthermore, the pressure in the process chamber can be measured alternatively or cumulatively, and as long as this pressure is maintained at ≤ 950 mbarAbs (or 920 or 980), no process malfunction is detected, whereas exceeding the pressure threshold can indicate a process malfunction. Alternatively or cumulatively, a sudden pressure shock/pressure increase in the process chamber (pressure increase rate greater than the maximum possible pressure increase rate due to gases to be introduced) can be detected and indicate a process malfunction - such as a quartz glass breakage. The aforementioned criteria are advantageously independent of one another and can be used individually or in conjunction with one another to switch off the process gas or hydrogen supply.

The security container 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 safety container. For example, the safety container can have a 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 in any case connected to it in a heat-conducting manner, if necessary with the help of a thermal paste. For example, the cooling medium line is soldered 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.

The safety container can be equipped to provide temperature control of the process conditions. For example, by means of the safety container designed in this way, constant temperatures - or a similar temperature range - can always be maintained, regardless of the environmental conditions, which may fluctuate greatly. For example, the environment can contain a daily temperature curve or seasonal temperature fluctuations, or can also be influenced by thermal processes that may take place nearby, with the advantageously designed safety container being able to keep these environmental conditions from affecting the process. Alternatively or cumulatively, the cooling function can also be influenced in response to the process parameters, i.e. in particular the temperature in the process chamber, in order to achieve temperature control of the cultivation process. For example, the cooling medium throughput 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 removal. If the environment and/or process temperature is warmer, for example, more cooling medium can be implemented, and/or a colder cooling medium can be used, and/or an alternative cooling medium can be filled.

The cooling medium line can be arranged on the outside of the container wall, preferably connected to the container wall in a thermally conductive manner or in any case arranged adjacent to the container wall. The cooling medium line can then cool the container wall and ensure that the amount of heat does not escape into the immediate surroundings radiates from the apparatus, but is continued by the temperature control device. Arranging the coolant line on the outside has the advantage that fewer passages need to be sealed into the protective atmosphere or the inside of the protective container, since the cooling fluid does not penetrate into the interior. For example, the container wall can be designed to be double-walled, i.e. have an inner wall and an outer wall, wherein the cooling medium line can be arranged between the inner wall and outer wall of the container wall. Then the coolant line and the fasteners for the coolant line are hidden from view and protected from mechanical damage. Since the temperature control device is able to dissipate a significant portion of the heat output from the process chamber, the outer wall of the container wall is subject to little or no restrictions with regard to the choice of material or protection against contact, since it does not get hot.

The present description also relates to an apparatus for the reliable production of single crystals, in particular using the PVT process, which comprises a process chamber for accommodating a highly heatable growth cell and 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 to receive a source material and a germ.

The apparatus comprises a safety container for enclosing the process chamber, in particular in a gas-tight or essentially gas-tight manner. For example, the safety container enables process-reliable operation with a reactive gas as the process gas. The security container has a container wall, so that a gap is created between the container wall of the security container and the process chamber, which is set up so that the gap can be flooded with a protective atmosphere. The process chamber is arranged within the security container. Furthermore, the safety container can have a connection to a protective gas source, so that the 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.

The container wall can be a segmented container wall that surrounds the process chamber at least radially on all sides, the container wall comprising a plurality of at least two wall segments. By means of the segmented container wall, the outer wall of the safety container can be formed to enclose the process chamber, in particular in a gas-tight or essentially gas-tight manner. The container wall can comprise, as wall segments, for example a lead-through segment, a testing or inspection segment, a cooling segment, a lid segment, which can in particular be designed in several parts, and/or a base segment.

The container wall is preferably designed in such a way that it also encloses the process chamber from the top and/or bottom. More preferably, the container wall can be designed to completely enclose the process chamber on all sides. However, this is not necessary in every case. For example, if the process chamber is embedded in a floor, a part or section of the process chamber can also be designed without an immediate protective jacket in the form of the protective container, and the portion of the process chamber can be surrounded by the protective container, which lies above the floor. The protective container can be designed all the way to the floor and, if necessary, close tightly there.

In a further development, the container wall can include a process chamber adapter for accommodating process chambers of different sizes on the same container wall. The components of the container wall can therefore be provided in a standard size or in a few dimensions and cover a large number of different process chambers or process chamber sizes.

The container wall can be double-walled. The double-walled structure of the container wall can have structural advantages or simply enable a pleasing appearance without components of the security container being visible from the outside.

For example, a cooling device can be arranged in an intermediate region of the double-walled container wall. This structure has numerous advantages. The cooling device itself is protected from direct heat radiation from the process chamber and is hidden behind an inner wall of the container wall. In addition, the assembly of the cooling device is particularly simple in this case, since 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.

The safety container can be constructed in such a way that it allows gas losses to the outside. He may have a pressure sensor, wherein the pressure sensor is signal-connected to a control device and the control device is designed such that an overpressure in the safety container (relative to the environment or atmosphere) is set based on the pressure sensor signals.

The pressure sensor can also include a pressure switch or be formed from a pressure switch. For example, the pressure sensor can be formed by a differential pressure switch which measures the pressure difference between inerting in the safety container and the atmosphere or environment. If necessary, the pressure sensor can then trigger a circuit if an adjustable pressure difference is exceeded or fallen below, in particular as a safety circuit or shut-off.

With regard to the orientation of the installation of the apparatus, it can be advantageous if there is an inert gas connection in the lower area of the safety container and a closable outlet in its upper area. As a result, the air in the safety container can be completely displaced upwards to the outlet by the protective gas flowing in in the lower area, where it leaves the safety container.

The safety container preferably has two protective gas connections for two different protective gases. After the first inert gas has displaced the air from the safety container, a less expensive fluid, such as nitrogen, can be filled in as a second fluid using the second protective gas connection and thus the first protective gas can be replaced.

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

As already stated above, the apparatus can be used to produce, in particular, a SiC single crystal using the PVT process. For this purpose, the growth cell is equipped with a silicon carbide as 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 designed to be 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 designed to be detachably connected so that it can be easily removed.

The support frame therefore 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 enclosing the process chamber in a gas-tight or essentially gas-tight manner.

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

The combination of the multi-part security container with the sealing elements achieves particular advantages, as this makes it possible to use common construction materials, such as metal or steel for the wall elements, and yet a sufficient sealing of the security container as a whole can be achieved. However, in an environment in which core temperatures of over 2000 ° C occur, such a construction poses some challenges that could be solved surprisingly easily with the configurations explained in the present description and the exemplary embodiments.

The support frame preferably has at least one longitudinal groove on an outside for receiving a sealing element. In other words, the sealing element is drawn into the longitudinal groove of the support frame.

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

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 alternatively or cumulatively be designed to be sealed against the adapter, in particular by means of an adapter seal. The support frame can alternatively or cumulatively be designed to be sealed against the container segments, in particular by means of a segment seal.

Each container segment can be assigned its own circumferential segment seal. 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 cheap materials exist that are thermally and electrically conductive - then the container segments must be electrically insulated from each other. This can be done by means of the connection via the support frame, so that the container segments can be mounted at a distance from one another. In this case, it is advantageous if each container segment is assigned its own segment seal.

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 releasably attached 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 structure of the support frame simplifies the overall installation of the apparatus and can also help to further reduce the costs of the apparatus. In addition, the multi-part structure of the support frame offers advantages for any maintenance work and/or when replacing the process chamber when a crystal has been grown and another process chamber or another growth process is to be protected with the same safety container.

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 lead to significant savings, particularly on the cost side. However, due to the multi-part structure, the safety container can be easily and easily assembled around another process chamber and a safety atmosphere can be provided.

The support frame elements can also be designed to be sealed against one another, so that little or no protective gas escapes into the environment even between the contact or touching areas between individual support frame elements. Alternatively or cumulatively, a frame seal for sealing a frame part against a second frame part can be included. The frame seal can, for example, be arranged in a frame sealing plane that is not arranged in the same plane as the segment seal.

For example, one embodiment can be designed in such a way that each segment seal is guided through the cover element, through two rod elements and the base element. Alternatively or cumulatively, a lid seal can be arranged on an upper side of the cover element to seal the lid. Furthermore, alternatively or cumulatively, a floor seal can be arranged on an underside of the floor element to seal the floor element from the floor. The floor can be provided as a production part or as a mounting plate.

The cover element can have a segment sealing groove on the segment side. The rod elements can each have at least one segment sealing groove, preferably two segment sealing grooves per rod element. The floor element or elements can have a segment sealing groove. In particular, at least one of the segment sealing grooves of one of the rod elements can be designed to 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 circumferential sealing of the wall segment.

Furthermore, the apparatus can include 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 attached 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.

The support frame can have at least one longitudinal groove on an outside to accommodate a sealing element. Alternatively or cumulatively, the support frame can be designed to accommodate a segment seal, and/or to accommodate a cover seal, and/or to accommodate a base seal. Alternatively or cumulatively, the cover element can be formed in one piece, in particular for placement on the rod elements. The cover element can alternatively or cumulatively be connected to the floor element via the rod elements. The elements of the support frame can alternatively or cumulatively be releasably connectable to one another, for example screwed, in order on the one hand to provide a stable construction, which on the other hand is designed to be removable for purposes in particular of maintenance or opening.

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 bar elements can be inserted into recesses in the floor element. Alternatively or cumulatively, the cover element can be made 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 protruding laterally over the cover element.

The support frame can be designed as an electrical insulator. This ensures that the wall segments are electrically insulated from each other. 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 may comprise or consist of ceramic, plastic or a composite material or a combination thereof.

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 security container, in particular for enclosing the process chamber in a gas-tight or essentially gas-tight manner. An intermediate space can be created between the container wall of the safety container and the process chamber, which is set up so 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.

The heating device can be designed so that it surrounds the process chamber. Alternatively or cumulatively, the heating device can be designed in a ring shape around the process chamber.

The invention is presented in more detail below using exemplary embodiments and with reference to the figures, whereby the same and similar elements are partly provided with the same reference numerals and the features of the different exemplary embodiments can be combined with one another.

Short description of the characters

• 1 Querschnittsdarstellung einer erfindungsgemäßen Apparatur,
• 2 perspektivische und vereinfachte Darstellung eines teilmontierten Sicherheitsbehälters,
• 3 perspektivische Schnittansicht einer Ausführungsform einer Apparatur,
• 4 Explosionsdarstellung einer Ausführungsform einer Apparatur,
• 5 Ausführungsform eines Tragrahmens,
• 6 Detailausschnitt einer Ausführungsform eines Tragrahmens,
• 7 weiteres Detail einer Ausführungsform eines Tragrahmens,
• 8 noch ein Detail einer Ausführungsform eines Tragrahmens,
• 9 Detail des Verlaufs von Dichtungen im Tragrahmen,
• 10 weiteres Detail zum Verlauf von Dichtungen im Tragrahmen,
• 11 Querschnitt-Detail einer Apparatur,
• 12 teilmontierter Sicherheitsbehälter mit Tragrahmen,
• 13 Aufbau eines beispielhaften Segments einer doppelwandigen Behälterwandung mit Temperierungseinrichtung,
• 14 Detail eines Anschlusses der Temperierungseinrichtung,
• 15 Ausführungsform eines Kühlsegments der Behälterwandung mit Teil der Temperierungseinrichtung,
• 16 perspektivische Ansicht einer Ausführungsform eines Sicherheitsbehälters,
• 17 perspektivische teilgeöffnete Darstellung einer Ausführungsform einer Apparatur mit Prozesskammer,
• 18 perspektivische Darstellung einer Apparatur.

It shows:

• 1 Cross-sectional representation of an apparatus according to the invention,
• 2 perspective and simplified representation of a partially assembled security container,
• 3 perspective sectional view of an embodiment of an apparatus,
• 4 Exploded view of an embodiment of an apparatus,
• 5 Embodiment of a support frame,
• 6 Detail of an embodiment of a support frame,
• 7 further detail of an embodiment of a support frame,
• 8th another detail of an embodiment of a support frame,
• 9 Detail of the course of seals in the support frame,
• 10 further detail on the course of seals in the support frame,
• 11 Cross-sectional detail of an apparatus,
• 12 partially assembled security container with supporting frame,
• 13 Construction of an exemplary segment of a double-walled container wall with a temperature control device,
• 14 Detail of a connection of the temperature control device,
• 15 Embodiment of a cooling segment of the container wall with part of the temperature control device,
• 16 perspective view of an embodiment of a security container,
• 17 perspective, partially opened view of an embodiment of an apparatus with a process chamber,
• 18 perspective view of an apparatus.

Detailed description of the invention

The 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, which close the two ends of the hollow cylinder. The growth cell 1 consists of a porous graphite. There will be a quelmate on the floor rial 2 layered. There is a germ 3 on the underside of the lid.

The growth cell 1 is arranged in a process chamber 4, which consists of a hollow cylinder closed at both ends by a floor or a ceiling. The cylindrical wall of the process chamber 4 consists of a heat-resistant quartz glass and can be filled with a process gas via a process gas connection with an inlet valve 5. Since the graphite of the growth cell 1 is porous, the process gas from the process chamber 4 also reaches the growth cell 1.

A heating device 6 consists of an induction coil 7 which surrounds the process chamber 4 at the level of the growth cell. When an electric current flows through it, it generates an electromagnetic field that induces an electric current in the graphite of the growth cell 1, which heats the growth cell 1 to over 2,000 ° C and up to 2,400 ° C.

The high temperatures and the required permeability for the electromagnetic field of the induction coil 7 make it necessary to produce at least the cylindrical wall of the process chamber 4 from a suitable temperature-resistant material. The cylindrical wall of the process chamber 4 is usually made of quartz glass, which has proven to be particularly suitable and is inexpensive to produce.

To produce a SiC single crystal, silicon carbide is added to the growth cell 1 and the process chamber 4 is flooded with a process gas. The process gas may comprise a reactive gas, such as containing a portion of hydrogen, and/or consist of up to 100% hydrogen. If the growth cell 1 is now heated using the induction coil 7, the silicon carbide sublimes and deposits itself layer by layer on the seed 3, so that a SiC single crystal grows. If hydrogen is used in the process gas, it can ensure that no crystal defects form in the crystal or that foreign atoms cannot be deposited at the respective growth point. The incorporation of undesirable foreign atoms regularly leads to a change in the electrical conductivity, which can also occur locally and can be disadvantageous as a disruption or reduction in quality. The process gas composition can also be influenced by reactions with other process gases or the HotZone (graphite components) through the use of the reactive gas. The changed process gas composition can in turn have an influence on the crystallinity, structure, crystal defects and doping of the SiC crystal.

For example, it has been shown that advantageous effects can be achieved from a hydrogen content of 5% or more in the process gas, although at such low concentrations of less than 5% hydrogen in the process gas, protective measures, for example for explosion protection, are typically not necessary. Particularly advantageous results could be obtained in the range between 5% hydrogen content to approximately 40% hydrogen content, with an increased degree of purity of the crystal being able to be obtained in the range of 15% hydrogen content in the process gas (in particular ±5%). In principle, the use of a safety container according to the invention is advantageous even at low concentrations.

However, as described in the introduction, the use of a reactive gas such as hydrogen is problematic because in the event of a potential break in the wall of the process chamber 4, the reactive gas mixes with the ambient air - without the safety container described here - so that, for example, an ignitable gas mixture is created that would immediately ignite on the hot parts of the apparatus.

The process chamber 4 of the exemplary 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, which stands on a floor 10 and is closed at the top by a ceiling 11. The floor 10 and ceiling 11 of the safety container 8 adjoin the floor and ceiling of the process chamber 4.

The safety container 8 can at the same time be part of the cooling concept of the apparatus. In other words, the safety container 8 can be integrated into the cooling concept of the apparatus. For this purpose, the cylindrical container wall 9 can be provided with cooling channels which are connected to a cooling system. The cooling concept can therefore provide that the safety container 8 provides a cooling function for the apparatus. For example, a cooling medium, such as water in particular, can circulate through the safety container 8. On the other hand, it can be provided that the safety atmosphere in the safety container 8 provides the cooling function. For example, the safety atmosphere can be circulated to dissipate heat. Overall, the safety container can be equipped in such a way that the safety container with its cooling function can be used to regulate the temperature of the process conditions, so that constant temperatures - or a similar temperature range - can always be maintained, regardless of the environmental conditions that may fluctuate greatly. For example, the environment may have a daytime temperature ture curve or seasonal temperature fluctuations, or can also be influenced by thermal processes that may take place nearby.

Finally, the security container 8 can be constructed in such a way that it is equipped with metal conductivity. The metallic conductive security container 8 can provide a shield for the process taking place inside in the manner of a Faraday cage, so that, for example, alternating electromagnetic fields in the container wall 9 of the security container 8 have a defined end point and do not expire asymptotically, potentially to infinity . This can be advantageous if several devices are to be set up next to each other, whereby corresponding alternating fields influence each other and can disrupt the process conditions. In other words, the metallically conductive safety container 8 can ensure uniform process conditions even under the condition that several, possibly different types of apparatus can be set up close to one another without the processes interfering with one another.

Overall, it can be seen that the security container 8 is able to solve several tasks in a synergistic manner. Not only that it can provide the protective atmosphere mentioned, which enables the use of a reactive gas 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 electrical and/or magnetic fields and thus ensure uniform process conditions for the process taking place in the process chamber.

In the bottom of the security container 8, a ring line with one or more connections can be arranged at an annular space 12 between the container wall 9 of the security container 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.

A lockable outlet valve 16 is located in the ceiling 11 of the security container 8. A gas sensor 17 (in particular as a hydrogen sensor) and a pressure sensor 18 are also provided there.

A hood 20 made of unbreakable plastic or sheet metal can be placed over the entire apparatus and rests on the bottom of the safety container 8.

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

1. (1) Das Auslassventil 16 wird geöffnet.
2. (2) Das Wechselventil 13 wird so geschaltet, dass Argongas aus der Argonquelle 14 von unten langsam in den Zwischenraum 12 einströmt, so dass sich der Zwischenraum 12 von unten mit dem Argongas füllt, wobei die vorhandene Luft durch das offene Auslassventil 16 (oder Überdruckventil oder dgl.) verdrängt wird.
3. (3) Schließen des Auslassventils 16 und des Wechselventils 13.
4. (4) Einhalten einer Füllpause, damit sich noch vorhandene Luftreste vom Argongas nach oben absetzen können.
5. (5) Ggf. einfache oder mehrfache Wiederholung der Schritte (1) bis (3).
6. (6) Öffnen des Auslassventils 16.
7. (7) Schalten des Wechselventils 13, so dass Stickstoffgas von unten langsam in den Zwischenraum 12 einströmt, wobei sich der Zwischenraum 12 von unten mit dem Stickstoffgas aus der Stickstoffquelle 15 füllt und das vorhandene Argongas durch das offene Auslassventil 16 verdrängt wird.
8. (8) Schließen des Auslassventils 16.
9. (9) Einstellung und Einhaltung eines Überdrucks im Zwischenraum 12 durch gesteuertes Öffnen des Wechselventils 13, so dass trotz vorhandener und akzeptierter Undichtigkeiten des Sicherheitsbehälters keine Luft in den Zwischenraum 12 einströmen kann.

The control device 19 allows the following procedures to be carried out: filling the safety container 8 with an inert gas before the process chamber 4 is filled with hydrogen:

1. (1) The exhaust valve 16 is opened.
2. (2) The shuttle valve 13 is switched so that argon gas from the argon source 14 slowly flows into the gap 12 from below, so that the gap 12 fills with the argon gas from below, with the existing air flowing through the open outlet valve 16 (or pressure relief valve or the like) is displaced.
3. (3) Closing the exhaust valve 16 and the shuttle valve 13.
4. (4) Allow a filling pause so that any remaining air from the argon gas can settle upwards.
5. (5) If necessary, repeat steps (1) to (3) one or more times.
6. (6) Opening the exhaust valve 16.
7. (7) Switching the shuttle valve 13 so that nitrogen gas slowly flows into the gap 12 from below, the gap 12 filling from below with the nitrogen gas from the nitrogen source 15 and the argon gas present is displaced through the open outlet valve 16.
8. (8) Closing the exhaust valve 16.
9. (9) Setting and maintaining an overpressure in the intermediate space 12 by controlled opening of the shuttle valve 13, so that no air can flow into the intermediate space 12 despite existing and accepted leaks in the safety container.

A sufficient overpressure is approx. 2 mbar above ambient.

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

In order to be able to check whether the gap 12 is sufficiently free of oxygen, an oxygen sensor can also be provided.

1. (1) Ständige Überwachung des Gassensors 17 und
2. (2) Verschließen der Wasserstoffzufuhr, wenn der Gassensor 17 Wasserstoff im Zwischenraum 12 detektiert.

What to do if the glass wall breaks during operation:

1. (1) Constant monitoring of the gas sensor 17 and
2. (2) Closing the hydrogen supply when the gas sensor 17 detects hydrogen in the gap 12.

Referring to the 2 a perspective view of a simplified embodiment of a partially assembled security container 8 is shown, with various attachments and the process chamber 4 not being shown for reasons of clarity. Furthermore, for the sake of completeness, it should be noted that the 2 Embodiment shown has no details for sealing the interior area 12, so that the leak rates that can be achieved with this embodiment would be comparatively high. Improved sealed security containers 8 are presented with versions of the other figures.

In 2 a temperature control device 21 is arranged, at least partially, in the safety container 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 safety container 8, for example glued, soldered, welded or screwed there. From the process chamber 4, heat output predominantly reaches the inner wall 44 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 a coolant. The amount of heat that can be dissipated with the temperature control device 21 can preferably be adjustable. For example, the amount of heat that can be dissipated can be influenced via the temperature specification for the coolant and/or flow rate or speed, i.e. a temperature control can be provided. Then, in response to sensor signals, measuring the ambient temperature and/or the process temperature with the temperature control, temperature control of the process chamber 4 can be achieved, so that a substantially constant temperature is present in the process chamber 4 during the process sequence.

The safety container 8 has sight glasses 32 which bridge the interior area 12 and enable a view 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. Furthermore, with 14 a detail of the refrigerant line 22 with line fastening 22A, connecting piece 23, transition piece 23B and connecting piece fastening 23A can be seen.

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 partially arranged inside and outside the safety container 8, 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 in the interior 12, i.e. in the space that can be occupied by the safety atmosphere.

The protective gas can be supplied through the protective gas supply 54 on the underside of the interior 12 (if necessary, several protective gas supply lines 54 are provided). The outlet valve 16 is arranged on the top 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 letting in a protective gas that is heavier than air. Subsequently, if a connection line is connected to the outlet valve 16 (not shown), circulation of the protective gas can also be provided, for example to remove the amount of heat from the protective container 8, or to ensure a regular exchange of the protective gas.

In the case shown here, the coolant line 22 of the temperature control device 21 is arranged in the container wall 9, which is double-walled. With that one 3 In the cross section shown of the safety container 8 with process chamber 4, the interior 12 of the safety container 8 extends to accommodate the protective atmosphere from the chamber wall 41 and, for example, around the process chamber 4 to the container wall 9, the interior 12 being designed to be sealed against the container wall 9 to keep the gas leak rate from the interior 12 into the environment 30 low.

Furthermore, it shows 3 Embodiment shown has 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 upper cover 48 located further inside can be used. The covers 47, 48 can therefore possibly be used alternatively to one another.

Referring to 4 an apparatus 100 is shown in an exploded view to the extent that the components of the security container 8 used there can be seen. Inside is the Pro cess chamber 4 arranged, in this embodiment in an empty version for better illustration. The quartz glass wall 41 (process chamber wall) forms the inner end of an intermediate space 12, which is arranged between the quartz glass wall 41 (as the inner wall of the safety container) and the container wall 9. The induction coil 7 serves as a heater and is arranged in a ring around the process chamber 4.

The process chamber wall 41 is initially designed to be open at the top, with the process chamber 4 being closed or sealed by means of a chamber closure 42. The upper end 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 inwards in the upper area and towards the lid 11. The adapter 46 is connected to the upper frame end 64 of the support frame 60 via the cover 11. The support frame 60 forms, so to speak, the “skeleton” of the security container 8, in that numerous components of the security container 8 can be attached 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 via a base element or lower Frame end 66 is attached to the floor 10, so that overall a stable and rigid construction is formed.

On the support frame 60 is in the in 4 In the embodiment shown, a test segment 91 can be mounted, having 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 7 with bushings (cf. e.g 7 ) can be carried out through the container wall 9. 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 in 4 Wall segments 91, 92, 93 shown are double-walled and each have an inner wall (the inner wall 923 of the cooling segment 92 can be seen) and an outer panel 919, 939.

Referring to 5 a multi-part support frame 60 is shown, which overall 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 designed in one piece or in several parts. In the case shown here, the lower frame end 66 is made up of several parts, so that a plurality of four floor 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 to seal a wall segment all around. A cover seal receiving groove 81 is provided on the top side of the cover element 64 to accommodate the circumferential cover seal 74. What all of the sealing elements shown have in common is that they are arranged on the segment side of the support frame 60 and are therefore protected from the heat radiation of the process chamber 4 by the support frame 60.

The support frame 60 is preferably made of non-conductive material. If the segments 91, 92, 93, 94 or the cover 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 can be created by means of the support frame 60 and the lid 11 can be adjusted so that the flat components of the container 8 do not touch each other. This allows the flat components of the container 8 to be electrically insulated from one another if they do not touch each other and the support frame 60 is not electrically conductive. Nevertheless, a good sealing of the security 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 pressed against the support frame 60 be sealed. This offers the advantage of providing the flat elements 11, 91, 92, 93, 94 from comparatively cheap 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 and could 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 bevel 63, over which the upper frame end 64 forms a projection, so that the upper frame end 64, for example, is flush with the outside Outer panels 99, 919, 929, 939 complete 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 projection further simplifies the assembly of the lid 11 and forms a wider support surface for the lid 11, so that the seal is further improved a further increased stability overall for the frame 60 is achieved.

Referring to 6 to 10 Detailed sections of various embodiments of the support frame 60 are shown. With 6 the transition from the lower frame end 66 to the floor 10 is shown more clearly, with the segment seal 72 being inserted into the floor element receiving groove 84 and the bar element receiving groove 83 that is flush with it. 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.

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 to connect the cover element 64 to the rod element 62. Due to the recessed mounting of the screws in The recesses 67 enable the cover 11 to be mounted flush and thus sealingly on the upper frame element 64. The bevel 63 on the cover element 64 is also visible in profile, with the course of the segment seal 72 running in the bevel 63 also being shown in the cover element receiving groove 82.

With 8th a further detailed representation of a section of a support frame 60 is shown, with a continuous lower frame section 66 resting on the floor 10 and being sealed against the floor 10 by means of the floor seal 76. The base seal 76 runs in the receiving groove 85. A large number of screw holes 68 are provided for the passage of screw means for connecting the lower frame section 66 to the base 10. The use of recesses may not be necessary here, as in the embodiment shown here no sealing surface is formed on the top of the lower frame section 66.

9 and 10 illustrate the connection of a rod element 62 (in 9 Not shown for the sake of clarity, see e.g 8th or 10 ) with the intermediate piece 61 and the sealing of the rod element 62 by means of the internal frame part seal 77 against both the intermediate piece 61 and the multi-part lower frame section 66. To accommodate the internal frame part seal 77, a groove 86A is provided along the side of each of two lower frame sections 66 and in the intermediate piece 61 a groove 86 is provided for jointly receiving the frame seal 77. The rod element 62 abuts on the sealed frame part joint 65 on the intermediate piece 61 and on two of the lower frame sections 66. To fasten one wall segment 91, 92, 93, 94, counter fasteners 97A are provided in the rod element 62.

Referring to the 11 is a detail view of a cross section through an embodiment of the apparatus 100. The adapter 46 forms the upper end of the process chamber 4 or 4a, with two process chamber heights of different process chambers 4 or 4a being shown as an example in this embodiment, which can be closed off by the adapter 46 as an alternative to one another. The adapter 46 can therefore be sealed against the security container 8 either via the adapter seal 78 or the alternative adapter seal 79. The gap 12 is formed between the chamber wall 41 and the container wall 9. The lid 11 sealingly connects the adapter 46 to the container wall 9 via the upper frame part 64, so that overall a sealed cover or container 8 is formed. The adapter can be connected to the cover 11 by means of adapter fastening means 49, for example screwed, and the cover 11 can in turn be connected to the upper frame part 64 by means of fastening means 69, so that there is also a non-positive connection from the adapter 46 via the cover 11 to the frame 64 and further into the container wall 9 is formed. The container wall is in the example shown 11 double-walled and has an inner wall 98, an outer panel 99 and the space 122 between them. In this embodiment, the outer loin 99 projects slightly beyond the upper frame part 64 and fills the area of the bevel 63 to a greater extent. A sealed feedthrough 26 is provided for the implementation, for example, of electrical connections from or to the outside to the environment 30.

With 12 a partially assembled container 8 is shown, with a wall segment in the form of the connecting element 94 already being arranged on the frame 60 fixed to the base plate 10. A plurality of sealed feedthroughs 26 provide a means of connecting electronics or the like located outside of the container 8 to components located within the container 8. When these component connections are combined in such a way that a majority or all of the intended connections are carried out through the connection element 94 the, then the connecting element 94 can be arranged or designed so that it remains permanently or at least predominantly mounted. In contrast, other wall segments 91, 92, 93 can be designed so that they can be removed quickly and easily, so that rapid access to the process chamber 4 is possible. As usual and throughout the present description, the same reference numbers represent the same elements, so that the description of the large number of elements already described does not have to be repeated below.

Referring to 13 A further embodiment of the cooling segment 92 with a sandwich structure is further clarified. 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. A space cover 921, 922 surrounds or delimits the segment 92 all around, with an outer cover 99 being screwable onto the space cover. The coolant line 22 and the fastening means 97 are covered by the outer cover 99 and are therefore protected from access on the one hand and from improper damage on the other. The outer cover 99 hides the technical installations from direct view and access and gives the apparatus 100 an attractive appearance. Furthermore, you can already do so 13 It can be illustrated 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 on which the coolant line can be easily separated. For example, the connecting pieces can be designed as quick connectors that have a bayonet or screw connection and can be removed quickly and easily. 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 interventions and/or a change of the process chamber 4 is desired. The double-walled structure 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 on the outside of the inner wall 923 has proven to be particularly advantageous, since this means that the coolant line is also outside of the interior 12 to be sealed and, in addition to the easier disassembly and assembly of the security container 8, fewer passages through the container wall 9 to be sealed are also required.

Referring to 15 is a top view of the intermediate area 122 in the double wall of the cooling segment 92 of the container wall 9 shown with temperature control device 21, the coolant line 22 being arranged in the intermediate area 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 attached to the first segment 91 with fasteners 97. Further fastening means 96 (eg screw holes) are arranged at regular intervals on the frame parts 92, 94 so that the intermediate region 122 is surrounded by them.

16 finally shows an apparatus 100 built on the floor 10 with a multi-part container wall 9, which includes wall segments 91 and 92. The coolant lines 22 (see e.g 15 or 13 ) run protected behind the outer panel 99 and are connected to one another in a communicating manner by means of compensating bends 24, so that a coolant - for example water - can flow through the temperature control device 21. In addition, the compensating bends 24 can be quickly removed, so that the coolant lines 22 and thus the wall segments 91, 92 as a whole can be easily detached from one another. The trial chamber 4 (see e.g 1 or 3 ) is surrounded on all sides by the safety atmosphere in the intermediate space 12 - or, depending on the embodiment, at least above the floor 10, surrounded on all sides by the safety atmosphere. Should the process chamber 4 burst or otherwise fail and process gas escapes, the process gas mixes with the protective gas held in the interior 12 to form a harmless mixed gas.

Referring to 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. This embodiment makes it clear and/or differs from the other embodiments that gas supply and discharge lines 51, 54 can be guided below the floor 10, so that they run outside the environment 30 and are therefore not in the area against which the security container 8 would have to protect. So the underbody 31 can be protected in another way or it is not necessary for protection to be provided by the safety atmosphere. The process chamber 4 therefore 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 would lead, or which would lead to such a deflagration ren could mean that a danger could be expected in the area 30. This also has the further advantage that fewer bushings have to be guided 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 surroundings 30, but rather can be laid concealed.

With 18 Finally, a further embodiment of a fully closed apparatus 100 is shown, with a cooling segment 92 being inserted on the right side and a connecting element 94 being inserted on the left side in the illustration. 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 may therefore be preferable to remove the cooling element 92 for the purpose of replacing the process chamber 4 or generally for maintenance access and thus to gain access to the process chamber and/or to the induction heater etc. Alternatively or cumulatively, the cover 11 or the adapter 46 can of course also be removed and the process chamber removed upwards, so that the hardware and electronics or gas connections etc. located in the safety container 8 do not have to be removed or changed.

It could be shown that the modular concept of the further developments and inventions presented here brings with it an enormous improvement and a safety gain compared to previous devices, whereby the manufacturing costs can be reduced and the maintainability of the system components can be simplified. The present description as a whole has a number of aspects which, individually or together with others, may define essential aspects of the invention(s).

It will be apparent to those skilled in the art that the embodiments described above are to be understood as examples and the invention is not limited to these, but can be varied in many ways without departing from the scope of protection of the claims. Furthermore, it can be seen 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 numerals 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 exemplary embodiments, in relation to which the object is not explicitly described in the description is.

Reference symbol list

1

growth cell

2

Source material

3

Germ

4, 4A

Trial Chamber

5

Inlet valve

6

Heating device

7

induction coil

8th

Security container

9

container wall

10

Floor

11

Ceiling

12

space

13

Shuttle valve

14

Argon source

15

Nitrogen source

16

Outlet valve)

17

Gas sensor

18

Pressure sensor

19

Control device

20

Hood

21

Cooling or temperature control device

22

Coolant line

22A

Cable attachment

23

Connector

23A

Connection holder

23B

Arch piece

24

Compensating arch

26

sealed bushing

30

Vicinity

31

subfloor

32

sight glass

41

Process chamber wall or inner wall of the containment

42

Bolt lock

46

adapter

47

top cover of the process chamber

48

top cover of the process chamber

49

Adapter fasteners

51

Process gas supply

52

Process gas removal

54

Inert gas supply

56

Shielding gas outlet

60

Support frame

61

Intermediate piece

62

Bar element or frame strut

63

Bezel

64

upper frame finish or cover element

65

Frame part joint

66

lower frame end or floor element

67

Recesses to accommodate frame fasteners

68

lanyard

69

Counter fastening for cover 11

72

Segment seal

74

Lid seal

75

Sealing element

76

Bottom seal

77

internal frame part seal

78

Adapter seal

79

alternative adapter seal

81

Lid gasket receiving groove

82

Cover element receiving groove

83

Bar element receiving groove

84

Floor element receiving groove

85

receiving groove

86

Frame seal receiving groove

86A

Front frame seal receiving groove

91

Section of the container wall, test segment

92

Section of the container wall, cooling segment

93

Section of the container wall, further cooling segment

94

Section of the container wall, connection segment

96

fastener

97

fastener

97A

Counter-fastening to fastening element 97

98

Interior wall

99

External panel

100

apparatus

122

Intermediate area

919

Outer panel of the test segment

921

upper space cover

922

lateral space cover

923

Inner wall of the cooling segment

924

lower space cover

929

External cover of the cooling segment

939

Outer panel of the further cooling segment

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0811708 A2 [0003]
• US 2012/0086001 A1 [0003]
• GB 772691 [0003]
• DE 602004001802 T2 [0003]
• EP 3760765 A1 [0003]

Claims (20)

PVT method for the reliable production of single crystals in an apparatus (100), the apparatus comprising a process chamber (4) for accommodating a highly heatable growth cell (1) and a heating device (6) for heating the growth cell (1), the growth cell is prepared to hold a source material (2) and a germ (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, in particular, gas-tight or substantially gas-tight, enclosing the process chamber (4), and wherein the security container has a circumferential container wall (9), so that a gap (12) is created between the container wall (9) of the security container (8) and the process chamber (4), with the steps Providing a protective atmosphere in the intermediate space and for this purpose flooding the intermediate space with the protective atmosphere, Providing the process gas in the process chamber, the process gas comprising or consisting of a reactive gas, and Heating the growth cell using the heating device so that the source material sublimates and resublimates on the germ. PVT method according to the preceding claim, in which providing the protective atmosphere in the intermediate space (12) sets an excess pressure compared 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 of 5 mBar or more above ambient pressure. PVT method according to one of the preceding claims, wherein the growth cell (1) is heated from radially on all sides by means of the heating device (6) which surrounds the process chamber (4) in a ring shape, 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 flooding the gap (12) with the protective atmosphere further includes displacing air in the gap before the sublimation of the source material (2) is initiated. PVT method 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. PVT method according to one of the preceding claims, characterized in that the safety container (8) is constructed in such a way that it allows gas losses into the environment (30), and that protective gas is replenished in order to compensate for gas losses, and in particular to reduce the excess pressure compared to the Environment (30) in the safety container (8). Claim 2 to maintain. PVT method according to one of the preceding claims, characterized in that in order to flood the safety container (8), a first inert gas, which is heavier than air, is admitted into its lower region, the air being displaced upwards, for which purpose a closable outlet ( 16, 56) at the upper end of the safety container (8) remains open until the air has escaped. PVT method according to one of the Claims 4 until 6 , characterized in that after the safety container (8) has been flooded once or several times with the first inert gas, it is replaced by a second inert gas, in particular nitrogen. 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 is detected in the safety container (8). Apparatus (100) for the 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, the growth cell being prepared to receive a source material (2) and a germ (3), characterized in that the apparatus comprises a security container (8). for, in particular gas-tight or essentially gas-tight, enclosing the process chamber (4), and the safety container has a container wall (9), so that a gap (12) between the container wall (9) of the safety container (8) and the process chamber (4) is created, which is set up so 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 the top and/or bottom, 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, whereby the container wall is double-walled, wherein in particular a cooling device (21) is arranged in an intermediate region (122) of the double-walled container wall. Apparatus (100) according to one of the preceding claims, characterized in that the safety container (8) is constructed in such a way that it allows gas losses to the outside, and/or that the safety container (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 an excess pressure relative to the environment (30) in the security container (8) is set based on the pressure sensor signals. 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 container wall (9) of the safety container (8), in particular for gas-tight or essentially gas-tight enclosing of the process chamber (4). Apparatus (100) according to the preceding claim, wherein 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 from the plurality of at least two container segments (91, 92, 93, 94 (and /or for sealing the protective container (8) from 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 outside for receiving a sealing element (72, 74, 75, 76, 77, 78, 79), and / or wherein the support frame (60) is designed to accommodate a segment seal (72), and/or to accommodate a cover seal (74), and/or to accommodate a base seal (76). Apparatus (100) according to one of the Claims 13 or 14 , wherein the support frame (60) is designed to be sealed relative to a base plate (10), and/or wherein the support frame (60) is designed to be sealed relative to the adapter (46), and/or wherein the support frame (60) is designed to be sealed relative to the container segments (91 , 92, 93, 94) is designed to be sealed, and / or each container segment (91, 92, 93, 94) is assigned its own circumferential segment seal (72). Apparatus (100) according to one of the Claims 12 until 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 attached to one another, and / or wherein the support frame (60) at least one comprises a cover element (64), a plurality of, in particular, vertical rod elements (62), and/or a base element (66). Apparatus (100) according to the preceding claim, wherein the support frame elements (61, 62, 64, 66) are designed to be sealed against one another, and/or further comprising a frame part seal (77) for sealing a frame part against a second frame part, the frame seal in particular not being arranged in the same plane as the segment seal (72). Apparatus (100) according to one of the Claims 12 until 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) to seal the Lid (11), and / or a base seal (76) is arranged on an underside of the base element (66) to seal the base element from the base (10). Apparatus (100) according to one of the Claims 15 until 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 or elements (66) has a base element receiving groove (84), and in particular 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 inserted into the aligned segment sealing grooves for all-round 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 security container (8) and a closable outlet (16, 56) in the upper region thereof.

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