Processes and CVD reactors for the purification of process gases

Abstract

The invention relates to a method for processing waste gas generated during the operation of a CVD reactor 4, including all auxiliary gas flows, which is first purified in a processing unit 40 or disposed of in a gas scrubber 25. The processed waste gas is qualitatively and quantitatively analyzed for impurities in an analysis unit 19. Based on the analysis results obtained here and the knowledge from the process step in which the gas was used, a sorting unit 17 sorts the purified waste gas as recycled gas into different containers 12, 13, 14, wherein each container 12, 13, 14 is assigned an application class that indicates in which process step in a CVD reactor this recycled gas can be reused as a carrier gas.The reuse of the gas is characterized by the fact that any residual impurities present in the used gas do not negatively affect the process.

Description

field of technology

[0001] The invention relates to a method in which a process gas, consisting of one or more reactive gases and an inert carrier gas, is fed into a process chamber, in which a used gas, e.g. an exhaust gas removed from the process chamber or another auxiliary gas, in particular used in the operation of a CVD reactor, is analyzed for reusability according to analytical criteria and is processed and stored as recycled gas in a storage device and is used as a component of a process gas. State of the art

[0002] Methods for depositing a layer onto a substrate in a process chamber of a CVD reactor, in which different process gases are fed into the process chamber together with a carrier gas in separate process steps, are known from the prior art. The process gases enter the process chamber through a gas inlet device. In this chamber, at least one substrate to be coated is located on a heated susceptor. The gases fed into the process chamber decompose, particularly pyrolytically, and form an exhaust gas. The exhaust gas is routed from the process chamber through an exhaust line and treated in purification units before being released into the ambient air, depending on the type and degree of contamination. A significant portion of this exhaust gas thus remains unused.Given the comparatively high costs of the process gases used for the deposition of semiconductor layers in particular, there is a need to reuse the used gases.

[0003] Various methods for processing gases are known from the state of the art.

[0004] US Patent 8,444,766 B2 discloses a method in which unused gas fed into a CVD reactor for the deposition of a semiconductor layer on a substrate is extracted from the process chamber and transferred to a storage unit. The gas stored in the storage unit is analyzed by a first analytical unit to determine the type and degree of contamination. If the contamination level is below a predetermined threshold, the gas is transferred from the storage unit to a purification unit where the used gas is mixed with clean gas. A second analytical unit determines the type and degree of contamination of the mixed gas. The mixed gas is then fed back into the process chamber for the deposition of the same or a different layer only if the degree of contamination is below a predetermined threshold.the concentration of the species used for deposition is above a predetermined threshold.

[0005] US Patent 8,454,728 B2 also discloses a method for processing hydrogen gas used in a process chamber. In a first step, the gas is extracted from the process chamber and subsequently purified by passing through several purification units, each filtering out different species. In a second step, the composition of the purified gas is determined using an analytical unit. The purified gas is then stored in a storage unit. Depending on its composition, in a fourth step, pure gas, such as hydrogen, is added to the purified gas stored in the storage unit until the purified gas in the storage unit has the same composition as the gas originally fed into the process chamber.

[0006] US Patent 10,329,668 B2 discloses a process in which, during an ongoing separation process in a CVD reactor, waste gas containing process gases, carrier gases, and process gas decomposition products is extracted from the process chamber and routed to a particle filter. The purified gas is then fed into a first gas scrubber. After the separation process, the waste gas remaining in the process chamber is fed into a cold trap. The purified gas is then fed into a second gas scrubber.

[0007] German patent DE 10 2020 214 063 A1 discloses a method for treating exhaust gases, wherein at least two different gas scrubbers are provided for treating exhaust gases from several process chambers. Depending on the type of gas, it is treated in different gas scrubbers, and the exhaust gases can also pass through several gas scrubbers sequentially. If the treatment in the gas scrubbers is sufficient, the gases treated can be released into the environment or recycled. Summary of the invention

[0008] The invention is based on the objective of specifying a method by which the reusability of waste gases in semiconductor technology is increased and of providing a corresponding device.

[0009] The problem is solved by the invention specified in the claims. The dependent claims not only represent advantageous further developments of the invention specified in the dependent claims, but also independent solutions to the problem.

[0010] According to the invention, it is proposed that the used gas, after being analyzed using analytical criteria and processed, be assigned to an application class. The process can include two sequential analyses. A first analytical criterion can be a quantitative and qualitative material composition of the used gas. For example, in a first analysis, the concentration of impurities in a carrier gas is measured. Alternatively, a recipe can be used according to which a semiconductor layer is deposited in a CVD reactor in a process step. The semiconductor layer can consist of several components, for example, a III-V semiconductor layer. In this example, the process gas can contain hydrogen as a carrier gas, as well as a hydride of an element from group V and a metal-organic compound of an element from group III.Additionally, the process gas may contain a dopant. In the initial analysis, the used gas can be analyzed for chemical compounds containing the element from Group 13, the element from Group 15, and the element of the dopant. The initial analysis determines the concentration of these chemical compounds in the used gas. In processes where ternary or quaternary layers are deposited, the analysis can also be performed for multiple elements from Group 13 or multiple elements from Group 15, respectively. If a dopant is used, the analysis also includes elements of the dopant. Information taken from the recipe can be used to specify which gas should undergo quantitative analysis. The quantitative analysis determines the concentration of one of these gases in the used gas.The initial analysis can also determine the concentration of impurities from other waste gases used within the CVD reactor, such as purge gases from pumps or other components, particularly those located outside the reactor chamber. Analyzing the concentration of impurities in these waste gases can also evaluate information on expected impurities from recipes used for growth and / or treatment processes. For example, the recipes may contain information about the gas composition, or the concentration of impurities may be determined based on the gas flow rates specified in the recipe.

[0011] The initial analysis allows for a preliminary decision as to whether the waste gas is fundamentally reprocessable, i.e., purified, or whether it must be disposed of. Following this initial analysis, the results are used by a first sorting unit to determine the further processing of the waste gas. This might involve temporarily storing waste gas with a specific composition, such as a concentration of a compound from Group 13 or Group 15, in a container. Several different containers can be provided, each temporarily storing waste gas with varying concentrations of a primary impurity. For example, there might be a first container for waste gas where the concentration of chemical compounds containing an element from Group 15 is below a predefined threshold.A second container may be provided for the temporary storage of used gas in which the concentration of chemical compounds containing an element of Group 5 is below a higher, second threshold. Further containers may be provided, each for the temporary storage of used gases in which the concentration of chemical compounds containing a specific element is below a given threshold.

[0012] It is essential that one or more of the analyses include an application class. According to the invention, an application class is defined as a criterion that specifies for which of a multitude of coating or treatment steps, as well as purging steps of pumps or other components carried out in a CVD reactor, a recycled gas can be used, for example, as a carrier gas or purge gas. Assigning an application class ensures that residual impurities present in a recycled used gas do not negatively affect the processes covered by the assigned application class. For example, an application class can specify the criterion for a gas that can be used as a carrier gas when heating a process chamber containing III-V substrates that have an arsenic component or an arsenic-containing layer.A recycled gas assigned to this application class may, for example, have a high arsenic concentration. Another application class may specify the suitability of the recycled gas as a carrier gas for depositing arsenic-containing layers. A further application criterion might specify, for example, the suitability of the recycled gas for a cleaning process. Such a recycled gas may, for example, be contaminated with chlorine or hydrochloric acid (HCl). Another application criterion might specify, for example, the suitability of a recycled gas for depositing phosphorus-containing layers or for heating a process chamber containing a substrate with a phosphorus component.An application class could, for example, be the usability of the recycling gas as a carrier gas in the deposition of doped semiconductor layers, for example if the recycling gas assigned to the application class contains a concentration of the dopant.

[0013] It is considered particularly advantageous that the reactive gas assigned to an application class according to the invention can not only be used as a replacement for a carrier gas, for example hydrogen, argon, helium or nitrogen, but that a major impurity can also be used specifically as a reactive gas, so that not only an inert gas but also a reactive gas is reused with the method according to the invention.

[0014] After analyzing the potential technological applications for which the processed used gas is suitable—that is, assigning an application criterion—the recycled gas can be stored in a container corresponding to the assigned application class. Alternatively, it can be used directly as a component of a process gas in a CVD process, for example, in the same CVD reactor from which the used gas originates or in another CVD reactor within a cluster of multiple CVD reactors. The containers holding recycled gases corresponding to specific application criteria can be connected to a central gas supply, allowing these recycled gases to supply multiple CVD reactors with a carrier gas containing not only pure inert gas but also reactive gases.

[0015] According to a preferred embodiment of the invention, the containers each contain recycling gases with a standardized composition. The composition can be stabilized by deliberately adding foreign gases, for example an inert gas or a reactive gas.

[0016] For purifying the used gas, methods known from the prior art can be used, for example, by means of cold traps to remove certain components of the used gas. The analysis of the used gas or a purified used gas can be performed spectrally, in particular mass spectrometrically. A control device can be provided that automatically evaluates the analysis results and controls valves of a sorting device to direct the purified used gas into designated containers. Compressors can be provided that compress the purified used gas for storage in containers.

[0017] The application class can include one or more parameters that can be used to assess in which process in a process chamber, in particular a CVD reactor, the recycling gas can be reused.

[0018] The parameters can include, in particular, values ​​and / or value ranges defining the type and degree of impurities contained in the recycled gas. These values ​​and / or value ranges can be defined based on data obtained through analysis of the recycled gas. For example, an analytical instrument can be used to determine the composition and / or the type and degree of impurities in the recycled gas after processing. This data can then be used to assign an application class to the recycled gas. For example, the concentration of different types of impurities contained in the recycled gas can be determined before storage. The data generated during the analysis can parameterize the application class. A primary impurity type and one or more secondary impurities can be identified.Information, for example in the form of numerical values, about the concentration of these different types of impurities can be included in the application class. The application class can preferably be a matrix comprising one or more parameters. The main type of impurity and the secondary types of impurities can be parameters of this matrix. Minimum and maximum values ​​for the concentration of the impurity types can be specified. The application class can be a type of label, particularly an electronic one, by which it can be assessed whether a recycled gas can be reused in specific processes within the process chamber. Parameters of the application class can also include specific information on particular processes in which the recycled gas can be reused. The recycled gases stored in the storage containers can also have a standardized composition.

[0019] This enables the reuse of recycled gas in various processes. Different processes, such as heating / warming the reactor chamber and deposition processes, require different purity levels. Specific ranges can be defined within which the concentration of an impurity, such as arsenic or phosphorus, in a recycled gas must lie to ensure its suitability for a process involving the deposition of arsenic or phosphorus layers of a III-V semiconductor. A gas with a standardized composition can meet the purity requirements of several different processes.

[0020] The recycled gases can be stored in different storage containers of the storage system, depending on their application class, using a sorting device. One or more storage systems may be provided. The used gases extracted from the process chamber can be pre-sorted, with the used gases being sorted into one or more storage containers of the storage system depending on the type and degree of contamination. After gas processing, which may involve cleaning the gases, the recycled gas, which may be a processed gas, can be re-analyzed and sorted into another storage container of the same storage system or a different storage system, according to its application class.

[0021] The recycled gas can be mixed with a pure gas, for example from a high-purity gas source, from which the process gas containing one or more reactive gases and a carrier gas is initially fed into the process chamber, which is then discharged from the process chamber as used gas after the process gas has been used.

[0022] Depending on their type, processing residues generated during the treatment or purification of used gas can be stored in a further storage facility. Alternatively, these residues can be fed into a disposal facility, which may include a gas scrubber.

[0023] Multiple recycled gases with the same or different application classes can be fed into the process chamber during a single process. If the application class of a recycled gas does not match the application class of the process, the recycled gas can be mixed with a pure gas, with the resulting mixed gas having an application class that matches that of the process.

[0024] The method according to the invention provides, in particular, that the processed gases are assigned an application class depending, in particular, on the type and degree of the respective impurity. Based on the application class, it can be determined for which types of processes the processed gases can be reused. The application class can provide information on the composition of the processed gas and / or specify particular processes. The gases classified in this way are then stored in separate containers of a storage device, depending on their respective application class. The classified gases can then be fed from the containers into the process chamber as needed. The classified gases can be used for separation processes that have the same application class as the respective classified gas.In this way, the treated gases can be selectively reused in process steps where the impurity contained in the treated gases has no or only minor negative effects. For example, treated gases containing a phosphorus (P) impurity can be used in processes where P impurities are not critical, such as in the deposition of P-containing layers.

[0025] One embodiment of the process according to the invention comprises several steps carried out successively in the direction of flow of the waste gas. A first step involves feeding a first process gas together with a first carrier gas into a process chamber of a CVD reactor. The process gas can contain elements of groups V and III, or elements of groups II and VI, or elements of group IV. Additionally, dopants can be present in the process gas. The process gas can consist of individual gases reacting with one another. For example, the first process gas for depositing III-V layers can contain components of groups III and V. The chemical reaction products form a preferably single-crystal layer on the substrate resting on a heated susceptor in the process chamber.Gaseous decomposition products, as well as undiluted process gases and carrier gases, are discharged from the process chamber as waste gas via a gas outlet in a second step. This gas outlet can be connected to a first analytical unit, where the composition of the waste gas is determined. The first analytical unit can then provide an initial analysis result. This unit can be configured to measure both the composition and purity of the waste gas.

[0026] In a third step, the used gas is sorted according to the type and degree of contamination using a first sorting device. Depending on the initial analysis results, the used gas can then be either sent to a storage facility for recycling or to a gas scrubber for disposal. The gas scrubber can be, for example, a combustion-type gas destroyer or a gas scrubber that uses a liquid to neutralize, cool, and / or filter gases. If the gas treatment by the gas scrubber was sufficient, the used gas can be released into the environment. If, on the other hand, the used gas is sent to the first storage facility, it is stored in a storage tank, depending on the type and degree of contamination.The selection of the used gas can be automated, for example by processing a recipe in which predefined threshold values ​​are stored and compared with the analysis results. For example, species-dependent threshold values ​​can be defined.

[0027] In a fourth step, the gases stored in the first storage unit are purified or treated. This purification / treatment can take place within the storage units themselves or in a purification unit connected to the first storage unit. For example, the purification unit can include a particle filter that removes particles present in the waste gas stream. Alternatively, the purification unit can include a cold trap to freeze the waste gas. A diffusion cell can also be used to purify the waste gas. The waste gas can also be diluted by adding pure gas, creating a mixture of the waste gas and the pure gas. Preferably, the pure gas is a gas used for depositing a layer in the process chamber but which was not introduced into the process chamber.Mixing the gases produces a purified used gas with a lower impurity concentration than the unpurified used gas. For example, pure hydrogen can be added to used gas containing hydrogen (H2), thereby reducing the impurity concentration.

[0028] Several different waste gases can be cleaned simultaneously in different cleaning units. For example, a first waste gas can be cleaned in a first cleaning unit that includes a particle filter, and a second waste gas can be treated in a second cleaning unit that includes a cold trap. The waste gas can also be treated sequentially in different cleaning units.

[0029] In a fifth process step, the composition of the purified used gases is determined using a second analytical unit. This second unit can provide a second analytical result, which, among other things, determines the type and degree of contamination in the purified used gas. Following the analysis, the purified used gas is sorted using a second sorting unit. The second analytical result can preferably serve as the selection criterion. The sorting unit can reject those purified used gases whose contamination level exceeds a predetermined threshold. The rejected used gas can be transferred to a disposal facility, which, for example, may contain a gas scrubber. Further treatment of the rejected used gas can take place in the disposal facility.If the treatment is sufficient, the treated, sorted gases can, for example, be released into the environment.

[0030] The purified used gas, whose impurity level is below the threshold, can be assigned an application class depending on the type and degree of its impurities. The application class can, for example, include information about the composition of the purified used gas, as well as the type and degree of impurities. In particular, the application class can include information about the deposition processes for which the purified used gas can be reused. For example, the purified used gas can be classified as hydrogen gas containing less than 1% arsenic impurities, suitable for process steps in which arsenic-containing layers are deposited, where such an impurity concentration is not critical. The hydrogen gas can also be used (additionally) as a purge gas, for example, in pumps or similar equipment.In general, the recycled waste gases can also be reused in other processes outside the process chamber of the CVD reactor or outside the CVD reactor itself. For example, in other systems that use gases, especially purge gases, for cleaning components or measuring instruments. The application class can contain all the information that is crucial for assessing whether a waste gas can be reused for a specific process within the process chamber of a CVD reactor or outside the process chamber in other system components, such as for cleaning pumps, or is suitable for another application outside the CVD reactor, such as for fuel cells or building heating.

[0031] In a sixth step, the classified, purified used gases are stored in different storage containers of a second storage facility according to their application class. The assignment of the application class links the storage location to the future application of the recycled gas.

[0032] In an optional intermediate step, a clean gas or a carrier gas with a lower impurity level than the cleaned used gas can be added to the cleaned used gas in order to assign a specific application class to the used gas. For example, cleaned used gas with a 10% impurity level after purification can be mixed with a specific quantity of a clean gas, thereby reducing the impurity concentration of the mixed cleaned used gas to less than 5%. This mixed cleaned used gas can then be assigned a different application class than the unmixed cleaned used gas. Accordingly, the mixed cleaned used gas is stored in a different storage tank of the second storage facility than the unmixed cleaned used gas.

[0033] Purification products generated during the cleaning of the used gas, such as filtered-out species, can be stored in containers of a further storage facility, sorted, for example, according to species type. The filtered-out species can also be recycled. Alternatively, the purification products can be sent directly to the disposal facility.

[0034] Furthermore, a method is provided in which the classified, purified waste gases stored in the second storage unit are selected by means of a selection device, wherein the classified, purified waste gases selected by means of the selection device have an application class that corresponds to the application class of one or more process gases and carrier gases fed into the process chamber. The selected waste gases can be fed into the process chamber via different gas supply lines according to their application class.

[0035] The second storage unit can be connected to the gas inlet of the CVD reactor via supply lines. For example, one or more containers of the second storage unit can each be connected to the gas inlet of the CVD reactor via a supply line, with each supply line leading into a gas inlet zone of the gas inlet. In addition to the recycled waste gases, clean gases can also be fed into the process chamber. For example, the clean gases can be fed in via the same supply lines as the recycled gases or via different supply lines. For example, recycled waste gases can be fed into the process chamber of the CVD reactor via primary supply lines to heat or cool it. In a subsequent growth process, clean gases from a separate gas source can be fed into the process chamber via secondary supply lines.The stored gases can also be used for other processes with lower purity requirements, such as pump purging. For example, supply lines can be provided to connect the storage tanks to other plant components, such as pumps. Supply lines can also be provided to provide recycled used gas to external systems, particularly those located outside the CVD reactor.

[0036] However, classified purified waste gases with different application classes can also be fed into the process chamber, whereby a new waste gas is created by mixing the waste gases, which has an application class corresponding to the application class of the process carried out in the process chamber. For example, a first classified purified waste gas with a first application class can be fed into the process chamber together with a second classified purified waste gas with a second application class through the same feed line or different feed lines.By mixing the first classified purified waste gas and the second classified purified waste gas, a third classified purified waste gas can be produced, which has a third application class that differs from the first and second application classes. The third application class can correspond to the application class of a carrier gas or process gas fed into the process chamber.

[0037] Furthermore, a device is provided comprising one or more process chambers of a CVD reactor, as well as a first and a second analysis unit. Additional analysis units may also be provided, which can determine the composition of the gases in optional intermediate steps. The device also includes a first and a second sorting unit for sorting the exhaust gases according to the type and degree of contamination. More than two sorting units may also be provided. In addition, several storage units may be provided, in which the sorted exhaust gases are stored in multiple storage containers. A control unit may be provided, which is configured to carry out the process according to the invention. For example, the control unit can execute a recipe in which the individual process steps according to the invention are carried out sequentially.Gases used in successive process steps can be recycled successively using the method according to the invention. Additional system components, such as pumps for gas supply and gas disposal, can also be provided, whose purge gases can be recycled and / or which can reuse recycled used gases as purge gases.

[0038] The recycled gases can also be fed into the process chamber immediately after the second sorting if the application class of the ongoing process matches the application class of the recycled gas.

[0039] The recycled gases are preferably carrier gases containing hydrogen, silane, nitrogen, or argon. When depositing, in particular, III-V layers, the recycled gases contain phosphorus, arsenic, silicon, or carbon impurities. These impurities may also include elements from Group II or VI that serve as dopants. When depositing, in particular, IV-IV layers such as SiC, the recycled gases contain silicon and carbon impurities. Purification steps may contain Group VII elements such as chlorine or bromine. The recycled gases may also be purge gases from other plant components, such as pumps, containing various impurities. For example, these purge gases may be inert gases containing corrosive materials. Brief description of the drawings

[0040] The invention will now be explained in more detail using exemplary embodiments. The figures shown are: Fig. 1. Schematic representation of a process for treating process gases according to the state of the art, Fig. 2 schematically a first embodiment, Fig. 3 schematically a second embodiment, Fig. 4 schematically a third embodiment, Fig. Figure 5 shows a schematic cross-section of a CVD reactor 4, a first and a second analysis unit 26, 19, a first and a second sorting unit 24, 17, a first and a second storage unit 27, 28, a cleaning unit 20, and two gas scrubbers 18, 25; Fig. 6 a flowchart of the process steps according to the invention, in which gases led from a process chamber 2 of the CVD reactor 4 are recycled. Description of the embodiments

[0041] The method according to the invention is carried out in a device such as is schematically illustrated by way of example in the Fig. Figure 5 shows a process chamber 2 of a CVD reactor 4, which is depicted as an example of a planetary reactor. However, other gas phase deposition systems can also be used.

[0042] The CVD reactor 4 has a gas-tight housing, for example made of stainless steel, in which the process chamber 2 is located. The bottom of the process chamber 2 is formed by a susceptor 8, which can be made of graphite and is preferably coated with SiC. The susceptor 8 can be rotated about a rotary axis 34 by means of a shaft 10 and a rotary drive (not shown). The susceptor 8 is heated by a heating device 6 arranged on a downward-facing rear side of the susceptor 8. The heating device 6 can, for example, be an RF coil that generates an RF field which induces eddy currents in the susceptor 8, heating it to a process temperature. One or more substrates 1 are rotatably mounted on the susceptor 8. It can be a substrate 1 made of Si, GaAs or a substrate made of sapphire or another material particularly suitable for the deposition of III-V semiconductors.This also works for SiC substrates and for multi-layered substrates such as Si on insulator or layered GaN substrates with an AlN core.

[0043] In the central region of the susceptor 8 is a recess into which a lower section of a gas inlet element 5 can be immersed. The gas inlet element 5 is fixedly attached to the housing of the CVD reactor 4. The gas inlet element preferably has three or more vertically arranged gas inlet zones 9, 9', 9", each connected to a flow line 11, 11', 11", 35, 35', 35", 35". However, fewer or more gas inlet zones may also be provided.

[0044] The Fig. Figure 1 shows a process as disclosed in the aforementioned prior art. A gas supply 39 provides a process gas containing a carrier gas and several reactive gases. The process gas is fed into a process chamber of a CVD reactor 4. The waste gas removed from the CVD reactor 4 is analyzed for reusability in a processing unit 40. If the waste gas is deemed unusable, it is disposed of in a first gas scrubber 25. Otherwise, the waste gas is purified and stored in a container 12 for later use.

[0045] The one in Fig. The first embodiment of the invention, as illustrated in Figure 2, provides an additional analysis unit 19 in which the purified process gas is analyzed for its potential for later reuse. In this analysis unit 19, the purified process gas is analyzed for the presence of certain impurities. In addition to a qualitative analysis, which checks whether a specific species is present in the purified process gas, a quantitative analysis is performed to determine the concentration of minor impurities and at least one major impurity. Furthermore, information stored in recipes used for carrying out growth or treatment processes can also be used in the analysis.For example, the type and concentration of the gases can be determined based on information stored in the recipes, such as the precursor organs used and their flow rates. Using a table or comparative data stored in a control unit, the purified process gas is then assigned to an application class, for example, whether the analyzed recycling gas can be used as a carrier gas for a tempering process, as a carrier gas for a specific separation process, or as a purge gas for other system components, such as pumps. According to the invention, the impurities still present in the recycling gas can be used specifically as a reactive gas. In the case of the... Fig. In the embodiment shown in Figure 2, the classified recycling gas is fed directly into a gas supply 39.

[0046] The information regarding which contaminants the used gas is analyzed for can be obtained from a recipe, after a control unit has directed the treatment process within the process chamber. For each of the contaminants under consideration, a concentration or partial pressure in the used gas is determined. The qualitative analysis then proceeds as the analysis of this recipe.

[0047] The subsequent quantitative analysis can also be part of a qualitative analysis, because it can determine a lower limit value that must be reached for the species tested for to be relevant as a contaminant.

[0048] In the Fig. In the second embodiment shown in Figure 3, the recycling gas sorted in the second sorting device 17 is stored in containers 12, 13, 14, each container being assigned to a defined application class, for example containing reactive gases whose concentrations are within a specified range.

[0049] In the Fig. In the embodiment shown in Figure 4, additional containers 21, 22, 23 are provided in which used gas, pre-sorted by a first analysis unit 26 and a first sorting unit 24, is temporarily stored. This can occur after or before cleaning the used gas. In this embodiment, the temporary storage takes place before cleaning in a cleaning unit 20. After cleaning in the cleaning unit 20, the cleaned used gas is analyzed again, assigned an application class in a second analysis unit 19, and then in a second sorting unit 17.

[0050] The Fig. Figure 5 shows a further embodiment with several details. The second sorting unit 17 is shown here as a unit with the second analysis unit 19. Likewise, the first sorting unit 24 is shown together with the first analysis unit 26 as a unit. The cleaning unit 20 can be a single cleaning unit for all the used gases stored in the containers 21, 22, and 23. However, the cleaning unit 20 can also comprise several different individual cleaning units, each particularly suitable for removing the respective impurities from the carrier gas.

[0051] In a first process step, process gases are fed into process chamber 2 through the supply lines 35, 35', 35" . III-V layers, for example, gallium arsenide, indium arsenide, indium phosphide, or gallium nitride layers, or SiC, are deposited on the substrates 1. More generally, layers containing preferably gallium, indium, aluminum, phosphorus, arsenic, silicon, carbon, and / or nitrogen are deposited within process chamber 2. However, SiC layers or layers consisting of 2D materials, such as graphene or transition metal dichalcogenides, or other materials, can also be deposited. Organic materials can also be used. Furthermore, the layers can be doped with dopants. Process gases in the form of organometallic compounds or hydrides, such as NH3, are used, for example.The process gases, along with a carrier gas, are introduced into the process chamber through the gas inlet device. Hydrogen, nitrogen, or a noble gas, for example, can be used as the carrier gas.

[0052] The process gases and their decomposition products are brought to a surface of the heated substrate 1, so that a layer forms on the surface.

[0053] In a second process step, waste gas containing the carrier gas and the decomposition products of the process gases and / or the process gases themselves is discharged from the process chamber 2 via a gas outlet 3. The waste gas is analyzed using a first analysis device 26, whereby the composition of the waste gas is determined.

[0054] In a third process step, the used gas is stored in a container 21, 22, 23 of a first storage unit 27, depending on the type and degree of contamination. Alternatively, the used gas can be fed into a first gas scrubber 25, where it is treated and subsequently disposed of by means of a disposal unit (not shown). For example, the treated used gas can be released from the disposal unit into the environment. The disposal unit can also include at least one storage container in which the treated used gas is temporarily stored (not shown).

[0055] In a fourth step, the used gas stored in one of the containers 21, 22, 23 of the first storage unit 27 is purified. This can take place in a separate purification unit 20 or in the container 21, 22, 23 within the first storage unit 27. The purification unit 20 can, for example, comprise one or more purification elements, such as a particle filter. Particles present in the used gas stream are filtered out in the particle filter. The purification element can also be, for example, a cold trap to freeze out impurities in the used gas. Alternatively, a diffusion cell or elements with similar purification objectives, such as a palladium diffusion cell, can be used as the purification element. Undissue gas can be directed to a further gas scrubber (not shown) after purification.

[0056] In a fifth step, the composition of the purified used gas is determined using a second analytical unit. Subsequently, the purified used gas is sorted according to the type and degree of its impurities using a sorting unit. If the impurity level exceeds a predetermined threshold, the purified used gas is rejected and directed to a further gas scrubber 18. If, however, the impurity level is below the predetermined threshold, the purified used gas is assigned an application class depending on the type and degree of its impurities.

[0057] In a sixth step, the classified purified used gas is stored in a container 12, 13, 14 of a second storage unit 28, depending on its application class. The gas stored in the second storage unit 28 can be fed into process chamber 2 via the supply lines 11, 11', 11' opening into the gas inlet zones 9, 9', 9" if the application class of the classified purified used gas matches one of the process gases or carrier gases fed into process chamber 2. For example, the classified purified used gas can be fed into process chamber 2 together with one of the pure process gases or pure carrier gases fed into process chamber 2 from the gas source via the supply lines 35, 35', 35" if the application class of the gas produced by mixing the purified and recycled gases matches the application class of the process running in the process chamber.The process running in process chamber 2 need not be the same process from which the waste gases were originally extracted from process chamber 2. The classified waste gases can be stored in the second storage unit 28 until a process is carried out whose application class matches that of the respective classified waste gas. For example, a classified waste gas containing primarily hydrogen and containing arsenic impurities can be used as a carrier gas for the deposition of arsenic-containing layers in a different process than the one from which the unpurified waste gas was originally extracted.

[0058] The Fig.Figure 6 shows a further embodiment of the invention. The cleaning unit 20 has three different cleaning chambers 31, 32, 33 in which different waste gases can be processed simultaneously. The composition of the cleaned waste gases is then analyzed separately in the second analysis unit 19 in the fifth step of the process according to the invention. Before the cleaned waste gases are stored in different storage containers 12, 13, 14 of the second storage unit 28 by means of the second sorting unit 17, depending on the type and degree of their respective contamination, pure gas from the gas source 29 is added to the cleaned waste gases in an optional intermediate step. This further reduces the concentration of the contamination. Pure process gases are also fed directly into the process chamber 2 from the gas source 29.The used gas can also be supplied with pure gas at another defined time within the process according to the invention.

[0059] The control unit 30 communicates with the process chamber 2, the first analysis unit 26, the first sorting unit 24, the first storage unit 27, the cleaning unit 20, as well as the second analysis unit 19, the gas source 29, the second sorting unit, and the second storage unit 28. The control unit 30 also controls mass flow controllers and valves (not shown) that control the gas flows within the device according to the invention. The method according to the invention is preferably carried out automatically, for example, by following a recipe.

[0060] The foregoing statements serve to explain the inventions covered by the application as a whole, which each independently further develop the prior art at least through the following combinations of features, whereby two, several or all of these combinations of features may also be combined, namely:

[0061] All disclosed features are essential to the invention (individually, but also in combination with one another). The disclosure of this application hereby incorporates in full the disclosure content of the associated / attached priority documents (copy of the earlier application), also for the purpose of including features of these documents in the claims of the present application. The dependent claims, even without the features of a referenced claim, characterize independent inventive developments of the prior art, in particular for the purpose of filing divisional applications based on these claims. The invention specified in each claim may additionally comprise one or more of the features described above, in particular those identified by reference numerals and / or listed in the reference numeral list.The invention also relates to design forms in which individual features mentioned in the preceding description are not realized, in particular insofar as they are recognizably unnecessary for the respective purpose or can be replaced by other technically equivalent means. List of reference symbols 1 substrate 2nd Trial Chamber 3 Gas outlet 4 CVD reactor 5 Gas inlet device 6 Heating system 7 Process chamber ceiling 8 Susceptor 9, 9', 9" Gas Intake Zone 10 shaft 11, 11', 11" supply line 12 containers 13 containers 14 containers 15 mass flow controllers 16 valve 17 second sorting unit 18 second gas scrubber 19 second analysis facility 20 Cleaning equipment 21 containers 22 containers 23 containers 24 first sorting facility 25 first gas scrubber 26 first analysis facility 27 first storage device 28 second storage device 29 Gas source 30 Control unit 31 Cleaning chamber 32 cleaning chamber 33 Cleaning chamber 34 Rotation axis 35, 35', 35" supply line 36 Derivative 39 Gas supply 40 Processing unit QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 8,444,766 B2

[0004] US 8, 454, 728 B2

[0005] US 10,329,668 B2

[0006] DE 10 2020 214 063 A1

[0007]

Claims

[1] Method for the treatment of used gases, in particular a waste gas produced during the operation of a CVD reactor (4), wherein the gases are process gases consisting in particular of an inert carrier gas and one or more reactive gases, the used gas is analyzed and processed according to initial analysis criteria, subsequently stored as recycling gas in a container (12) of a storage facility and the recycling gas is later reused as a component of a process gas, characterized by , that the recycled gas is assigned an application class before its reuse, particularly after further analysis. [2] Method according to claim 1, characterized by , that the storage facility has several containers (12, 13, 14) in which recycling gases with different application classes are stored. [3] Method according to any one of the preceding claims, characterized by, that the first analytical criterion includes both a quantitative and a qualitative material composition of the used gas, wherein the qualitative composition includes the presence of a component, for example a chemical compound, in the used gas above a threshold value and the quantitative composition includes defined value ranges of the individual components of the used gas. [4] Method according to any one of the preceding claims, characterized by , that the application class is the usability of the recycling gas for the deposition of a semiconductor layer with a defined layer composition in a CVD reactor, wherein the layer composition includes value ranges with respect to the layer components in the case of ternary or quaternary semiconductor layers or doped semiconductor layers. [5] Method according to any one of the preceding claims, characterized by, that a first analytical unit (26) analyzes the used gas using the first analytical criteria and provides a first analytical result, which is used by a first sorting unit (24) in a sorting process in which the used gas is temporarily stored as pre-sorted used gas in first containers (21, 22, 23), wherein the pre-sorted used gas is taken from the first containers (21, 22, 23) and cleaned, and the cleaned used gas is assigned to an application class in a second analytical unit according to second analytical criteria. [6] Method according to any one of the preceding claims, characterized by, that the purified used gas assigned to an application class is stored as recycling gas in a second container (12, 13, 14) assigned to the application class or is used directly in a CVD reactor, wherein the CVD reactor is the same CVD reactor whose used gas has been processed or another CVD reactor of a cluster of several CVD reactors. [7] Method according to any one of the preceding claims, characterized by , that the second analysis result is compared by a second sorting facility (24) with information on the requirements of the application class with regard to the quantitative and qualitative material composition of the recycling gas to be used. [8] Method according to any one of the preceding claims, characterized by, that in the first and / or second analytical unit a major contaminant type and / or one or more minor contaminants are identified and that the first or second sorting unit uses the analytical result obtained in this process, and / or that the analysis criterion includes values ​​for a minimum and maximum concentration of the main type of impurity, and / or that the analysis criterion includes values ​​for a maximum concentration of a minor contaminant type, and / or that during processing only or also components of the used gas of a minor contaminant type are removed from the used gas, and / or that during processing essentially no or also components of the main contaminant type are removed from the used gas. [9] Method according to any one of the preceding claims, characterized by, that processing residues are generated during the cleaning of the used gas and that these processing residues are processed separately. [10] Apparatus for carrying out the method according to one of the preceding claims, with several first containers (21, 22, 23) and several second containers (12, 13, 14), with a first analytical device (26) which is set up to determine the material composition of a used gas both quantitatively and qualitatively in order to provide a first analytical result, with a first sorting device (24) which is set up to use the first analytical result and to sort the used gas into one of the first containers (21, 22, 23), with a cleaning device (20) configured to clean the used gas contained in each of the first containers (21, 22, 23), or with several cleaning devices (20) configured to each clean the used gas contained in one of the first containers (21, 22, 23), with a second analytical device (26) which is configured to provide a second analytical result with which an application class is assigned to the purified used gas, and with a second sorting device (24) which is set up to use the second analysis result to store the purified used gas as recycling gas in one of the second containers (12, 13, 14) or to introduce it into a feed line (11, 11', 11") to a CVD reactor (4). [11] Method for depositing semiconductor layers in a CVD reactor, characterized by, that the process gas is at least partially taken from one of the second containers (12, 13, 14), whereby it is provided that an inert gas or a reactive gas is added to the recycling gas taken from the second container (12, 13, 14). [12] Method and apparatus, characterized by one or more of the characterizing features of any of the preceding claims.

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