Apparatus and method for feeding a gas into a process chamber of a CVD reactor

Abstract

The invention relates to a CVD reactor (1) having a housing and a gas inlet element (21) which is contained therein and has an uppermost gas inlet zone (Z1) and at least one further gas inlet zone (Z2, Z3) which is arranged therebelow, each of which has a gas outlet surface (6, 6', 6'') with first gas outlet openings (15) each for feeding a gas into a process chamber (19), and having an extension plate (4) which is arranged in the process chamber (19) and directly adjoins the gas inlet element (21) between the upper gas inlet zone (Z1) and the further gas inlet zone (Z2) arranged therebelow, for spatially separating the gases flowing through the upper gas inlet zone (Z1) and through the further gas inlet zone (Z2) arranged therebelow. In order to simplify the mounting of the extension plate (4), it is proposed that the extension plate (4) is connected by means of a connection element (20) to a holding device (18) which is fastened to the housing (2) or to a component of the CVD reactor (1) which is fixed to the housing.

Description

Description Device and method for injecting a gas into a process chamber of a CVD reactor field of technology

[0001] The invention relates to a CVD reactor with a housing and a gas inlet element contained therein, which has an uppermost gas inlet zone and at least one further gas inlet zone arranged below it, each having a gas outlet surface with first gas outlet openings for feeding a gas into a process chamber, and with an extension plate arranged in the process chamber between the upper gas inlet zone and the further gas inlet zone arranged below it, directly adjacent to the gas inlet element for spatially separating the gases flowing through the upper gas inlet zone and through the further gas inlet zone arranged below it.

[0002] The invention further relates to a method for depositing a layer in a CVD reactor, wherein an inert gas is fed in through the gas inlet zone of the gas inlet device located at the top.

[0003] The invention further relates to a CVD reactor with a housing and a gas inlet element arranged therein, wherein the gas inlet element has one or more vertically arranged gas distribution chambers, which are separated from one another by means of partition plates, wherein the one or more gas distribution chambers each have a gas outlet wall, wherein a plurality of gas outlet openings are arranged in the gas outlet wall, through which a process gas fed into the one or more gas distribution chambers by means of a supply line can flow into a process chamber, which flows into the process chamber in a flow direction towards 31323N1PCT November 3, 2025 Ai 2024-10 a storage space arranged at a distance from the gas outlet wall for receiving a substrate, and with a gas flow stabilization element arranged immediately downstream of the gas inlet device in the direction of flow, comprising one or more vertically stacked gas separation plates.

[0004] The invention also relates to a method for depositing a layer, in particular a SiC layer, in such a CVD reactor.

[0005] Furthermore, the invention relates to a method for operating or manufacturing a CVD reactor comprising at least the following components: a susceptor with a storage space for a substrate, a process chamber arranged between the susceptor and a process chamber ceiling, and a gas inlet element with a first gas outlet surface, wherein an upstream edge of the storage space is spaced a distance equal to the substrate from the first gas outlet surface of the gas inlet element or an edge of the susceptor in a flow direction, wherein process gases are fed into the process chamber through several vertically arranged gas outlet zones, separated from one another, and mixing with each other in a gas mixing zone beginning at the gas outlet zones and extending in the flow direction, and flowing to the substrate through a feed zone beginning at a beginning of the gas mixing zone and ending at the upstream edge of the storage space.as well as a device for carrying out the procedure. State of the art

[0006] CVD reactors with a gas inlet device having several vertically arranged gas inlet zones, through which different process gases can be introduced into a process chamber through which flow is in a horizontal direction, are described, among other things, in DE 102011 002145 B4. 31323N1PCT November 3, 2025 Ai 2024-10 DE 10 2008 055 582 Al, DE 102014 104 218 Al and the DE 102019 133 023 Al is known. The process chamber is bounded above by a process chamber ceiling and below by a substrate-supporting susceptor.

[0007] US Patent 8,927,302 B2 also describes a gas inlet device that has several vertically stacked gas inlet zones. Extension plates are attached to the outer wall of the gas inlet device, separating the different process gases flowing out of the gas inlet zones. The extension plates are designed as ring-shaped plates that surround the gas inlet device when assembled. The diameter of the extension plates increases vertically from the susceptor to the process chamber ceiling. In this stepped arrangement, only the downstream end of the lowest extension plate projects into the area between the gas outlet surface of the gas inlet device and the upstream edge of the storage area. The upstream end of the extension plates arranged above it is positioned between the upstream and downstream edges of the substrate storage area.This allows the different gases flowing from the different gas outlet zones to be fed into the process chamber at specific horizontal positions.

[0008] The process gases flowing into the process chamber from the gas inlet zones of the previously described gas inlet devices typically contain a carrier gas and reactive gases, which decompose at the process temperature in the process chamber or on the substrate surface. The decomposition products diffuse vertically, perpendicular to the horizontal flow direction, and precipitate as a single-crystal layer on the substrates, but also on other heated surfaces within the process chamber, such as... 31323N1PCT November 3, 2025 Ai 2024-10 for example, on the process chamber ceiling. These parasitic deposits on the process chamber ceiling necessitate frequent replacement of the process chamber ceiling.

[0009] EP 2253 734 Bl discloses the injection of an inert gas through a gas inlet opening located immediately downstream of the gas inlet device in the process chamber ceiling. The inert gas flow is intended to suppress parasitic growth on the process chamber ceiling.

[0010] It is also known from US patent 8,927,302 B2 to introduce inert gas flows, particularly at various positions, through gas inlet openings in the process chamber ceiling into the process chamber of a CVD reactor in order to prevent parasitic growth on the process chamber ceiling.

[0011] The invention relates, for example, to a CVD reactor with a gas inlet element having several vertically arranged gas inlet zones, as described, for example, in DE 102011 002145 B4, DE 102008 055582 Al, DE 10 2014 104 218 Al and DE 10 2019133 023 Al discloses the process. The gas inlet zones each have a gas outlet surface. Different process gases are fed into the gas inlet zones. The process gases flow from the gas outlet surfaces, each of which has a plurality of gas outlet openings, into the process chamber. The process gases flow through the process chamber and over the substrates arranged therein in a horizontal direction. The process gases contain a carrier gas and reactive gases, which decompose at the process temperature in the process chamber or on the substrate surface. The decomposition products diffuse vertically in a direction perpendicular to the horizontal flow direction and precipitate as a single-crystal layer on the substrates, but also on other heated surfaces. 31323N1PCT November 3, 2025 Ai 2024-10 within the process chamber, such as on the process chamber ceiling. These parasitic deposits on the process chamber ceiling necessitate frequent replacement of the process chamber ceiling.

[0012] US Patent 8,927,302 B2 describes a series of gas flow baffles that are individually mounted on the outer wall of a gas inlet of a CVD reactor. The gas flow baffles are horizontally connected to adjacent gas distribution chambers, from which different process gases are fed into the process chamber. The baffles are ring-shaped and, when mounted, surround the gas inlet. The outer diameter of the baffles increases vertically from the susceptor to the top of the process chamber. This stepped arrangement ensures that the different gases flowing from the various gas outlet zones are fed into the process chamber at specific positions relative to the substrate.

[0013] KR 101651880 Bl, KR 102572371 Bl, and KR 10-2022-0135320 A disclose a gas inlet device with several vertically arranged gas inlet zones. Individual gas flow baffles are detachably attached to the gas inlet device. These baffles connect to the separating plates that divide the adjacent gas distribution chambers. The baffles can be fixed obliquely to the gas inlet device using wedges. The length of the baffles can vary, but it corresponds approximately to the distance between the gas outlet surface of the gas inlet device and the upstream edge of the substrate storage area, so that the process gas is fed into the process chamber directly in front of or above the substrate. 31323N1PCT November 3, 2025 Ai 2024-10

[0014] German patent DE 10 2019139 794 A1 describes a gas inlet device in which cooling channels run vertically through a gas outlet wall. These cooling channels separate the gas openings arranged in the gas outlet wall into individual gas outlet fields. Adjacent gas outlet fields are separated from each other by horizontally adjacent free spaces, within which the cooling channels run. If process gases for the deposition of SiC are fed into the process chamber using such a gas inlet device, and in particular if argon is additionally fed into the process chamber through an uppermost gas outlet zone, parasitic depositions form on the underside of the process chamber ceiling facing the process chamber. These depositions have a symmetry that corresponds to the symmetry of the horizontal free spaces.Between the two free spaces, in the immediate vicinity of the gas inlet on the process chamber ceiling, i.e., near the upstream edge of the process chamber ceiling, a greater thickness of the parasitic coating is deposited than in the area of ​​the free spaces. This leads to unwanted stresses in the process chamber ceiling, which can cause cracks in the ceiling when the process chamber cools down or is subsequently reheated.

[0015] DE 10 2011 002 145 B4 describes a device or method for depositing II-VI or III-V semiconductor layers onto one or more substrates arranged on a susceptor within a housing of a CVD reactor. The device has a gas inlet element with at least three vertically arranged gas outlet zones, forming a gas outlet surface through which different process gases can be introduced into a process chamber through which the gas flows horizontally. Each gas outlet zone is associated with a gas distribution chamber into which the process gas can be fed via a gas supply line. Adjacent gas distribution chambers are separated from each other by partitions. The gas inlet element 31323N1PCT November 3, 2025 Ai 2024-10 The susceptor is located at the center of a rotationally symmetrical planetary reactor. It forms a multitude of substrate storage sites surrounding the gas inlet in a planetary-like arrangement. An upstream edge of these storage sites is positioned at a distance from the gas outlet of the gas inlet. This distance corresponds to the length of a pre-flow zone through which the process gases flowing from the gas inlet pass and where they mix.

[0016] DE 10 2008 055 582 Al, DE 102014 104218 Al and DE 102019 133 023 Al also disclose gas inlet devices with several vertically arranged gas outlet zones, each of which is connected to a gas source via a supply line.

[0017] The length of the pre-flow zone is optimized for the specific reactor design. However, if different susceptors with varying substrate distances are used for different processes, the length of the pre-flow zone changes. This affects, among other things, the flow profile of the process gases flowing over the substrates and thus the homogeneity of the layers deposited on the substrates. One way to keep the length of the pre-flow zone constant even when the susceptor configuration changes is to adjust the diameter of the gas inlet such that the length of the pre-flow zone remains constant, i.e., it does not change. However, this requires having several gas inlet components on hand and a time-consuming and costly replacement of the gas inlet component every time the susceptor configuration is changed.

[0018] US Patent 8,927,302 B2 describes a variety of extension plates that are individually inserted into the outer wall of a gas inlet device of a CVD reactor. 31323N1PCT November 3, 2025 Ai 2024-10 The extension plates are pluggable. They connect horizontally to a partition. The extension plates are designed as ring-shaped plates that, when assembled, surround the gas inlet element. The diameter of the extension plates increases vertically from the susceptor to the process chamber ceiling. In this stepped arrangement, only the downstream end of the lowest extension plate projects into the area between the gas outlet surface of the gas inlet element and the upstream edge of the storage area. The upstream end of the extension plates above it is positioned between the upstream and downstream edges of the substrate storage area. This ensures that the different gases flowing from the various gas outlet zones are fed into the process chamber at specific horizontal positions.

[0019] KR 101651880 Bl, KR 102572371 Bl, and KR 10-2022-0135320 A each disclose individual extension plates detachably attached to the gas inlet device. The extension plates can be fixed obliquely to the gas inlet device using wedges. The length of the extension plates can vary, but the length corresponds approximately to the distance between the gas outlet surface of the gas inlet device and the upstream edge of the substrate storage area, so that the process gas is fed into the process chamber directly in front of or above the substrate. Summary of the invention

[0020] The invention is based on the objective of providing a device and a method with which parasitic deposits on the process chamber ceiling of a process chamber of a CVD reactor can be suppressed. 31323N1PCT November 3, 2025 Ai 2024-10

[0021] The problem is solved by the device or method specified in the claims. The dependent claims not only represent advantageous further developments of the technical teachings specified in the dependent claims, but are also independent solutions to the problem.

[0022] First and foremost, the design provides a spatial separation between the process gas flowing from the uppermost gas inlet zone of the gas inlet element into the process chamber and the process gases flowing through the lower gas inlet zones. For this purpose, the invention provides an extension plate adjoining the gas outlet wall of the gas inlet element, located in the area between the uppermost gas inlet zone and the lower gas inlet zone. According to the invention, the extension plate is connected by a connecting element to a holding device, which is attached to the housing of a CVD reactor or to a housing-fixed component of the CVD reactor. The holding device can, for example, be attached to the gas inlet element itself.

[0023] Preferably, the retaining device is detachably attached to the housing or to a housing-fixed component of the CVD reactor. For example, an external thread formed by the gas inlet element itself can be provided, into which an internal thread formed by the retaining device engages. Alternatively, a bayonet fitting can be provided, for example, with which the retaining device is attached to the gas inlet element. The retaining device can also be attached directly to the inner wall of the CVD reactor housing.

[0024] Furthermore, the holding device is designed to support the process chamber ceiling. For example, the holding device can form a support flank. 31323N1PCT November 3, 2025 Ai 2024-10 form, on which an upstream edge of the process chamber ceiling is supported.

[0025] The connecting element linking the extension plate to the holding device can be formed by one or more vertically extending webs. The webs can be arranged at a fixed angle to each other in a common horizontal plane.

[0026] The process gas flowing from the gas outlet surface of the uppermost gas inlet zone can flow into the process chamber through one or more flow channels bounded upwards by the retaining device and downwards by the extension plate. Adjacent flow channels can be separated from each other by a bridge. The flow channels can have a second gas outlet opening at a downstream end. The second gas outlet opening preferably has a larger opening area than the first gas outlet openings arranged in the gas outlet surfaces of the gas inlet element.

[0027] The gas flowing from the uppermost gas inlet zone can be fed into the process chamber through the second gas outlet openings. In particular, one or more inert gases can be fed into the process chamber through the uppermost gas inlet zone. The gas fed into the process chamber through the uppermost gas inlet zone is preferably a gas with a high molar mass, especially a higher molar mass than hydrogen. Argon or, for example, a mixture of argon and hydrogen are particularly suitable for this purpose. 31323N1PCT November 3, 2025 Ai 2024-10

[0028] The invention is based on the understanding that introducing a gas or gas mixture with a high molar mass, such as argon, through the uppermost gas inlet zone can suppress the undesired convection of the gas flows towards the process chamber ceiling and the resulting parasitic deposits. The additionally heavier gas alters the transport mechanism of the decomposition products vertically to the flow direction. The diffusion coefficient depends on the molar mass of the gas molecules. Increasing the molar mass inhibits diffusion. Therefore, introducing a gas, subsequently referred to as a barrier gas, whose molar mass is at least higher than that of the carrier gases introduced into the process chamber, influences the diffusion of the reaction products or reactants.

[0029] By separating the process gas flowing into the process chamber through the uppermost gas inlet zone from the process gases flowing into the process chamber through the lower gas inlet zones, in the area immediately downstream of the gas inlet element, the injection point of the process gas injected through the uppermost gas inlet zone can be shifted further downstream horizontally from the gas outlet surfaces of the other gas inlet zones of the gas inlet element. This results in the process gas flowing through the uppermost gas inlet zone being injected deeper into the process chamber. Furthermore, by injecting an intermediate gas through the uppermost gas inlet zone, the process chamber ceiling can be purged, thereby reducing parasitic deposits that form there, particularly in the area immediately surrounding the gas inlet element on the process chamber ceiling. 31323N1PCT 3. November 2025 Ai 2024-10

[0030] According to a first embodiment of the invention, the extension plate connected to the connecting element and the holding device can be formed from a common annular body, optionally a flat body, arranged rotationally symmetrically around a center of the gas inlet element. The body can, for example, be formed from two vertically stacked annular plates connected to each other by one or more vertically extending webs, one of which is the extension plate and the other forming the holding device. The height of the body preferably corresponds to the height of the uppermost gas inlet zone. The webs preferably extend vertically over the entire height of the uppermost gas inlet zone. The body can be detachably attached to the process chamber ceiling, for example, by means of the holding device.For example, the holding device can have a shaft projecting from the ring-shaped body, which can be detachably attached to the housing of the process chamber. Alternatively, the flow guide element can be attached to the gas inlet.

[0031] The retaining device can also form a thread that engages with an external thread formed by the gas inlet element. For example, a retaining device formed as an annular plate can have a thread on its inner wall. Alternatively, the retaining device can be detachably attached to the housing of the CVD reactor or to a component connected to or attached to the housing.

[0032] The process chamber ceiling can be horizontally oriented and have a circular disc shape. It can have a central opening through which the gas inlet device protrudes. The inner diameter of the central opening can be larger than the outer diameter of the gas inlet device. 31323N1PCT November 3, 2025 Ai 2024-10

[0033] The extension plate and the mounting device can also have a central opening through which the gas inlet element can be inserted when the extension plate is mounted. The inner diameter of the extension plate can be larger than the outer diameter of the gas inlet element. The difference between the outer diameter of the gas inlet element and the inner diameter of the extension plate can be selected such that the process gas flowing from the uppermost gas inlet zone can flow slightly or only slightly through a gap created by the difference in diameter between the gas inlet element and the flow guide element.

[0034] The radial length of the extension plate can correspond to the distance between the edge surrounding the central opening of the process chamber ceiling and the outer wall of the gas inlet device. However, the length of the extension plate can also be greater or less than this distance.

[0035] The webs can extend radially over the entire length of the extension plate or only over a portion of its length. For example, the webs can fan out from the upstream end of the extension plate, surrounding the opening that houses the gas inlet, to a downstream end. Alternatively, a gas distribution volume, bounded above and below by the annular plates, can be arranged at the upstream end of the webs. The gas flowing from the uppermost gas inlet zone enters this volume before being guided through the flow channels into the process chamber. 31323N1PCT November 3, 2025 Ai 2024-10

[0036] Downstream of the gas inlet, storage areas for substrates can be provided on a susceptor that defines the bottom boundary of the process chamber. These storage areas can be arranged in a ring around the center of the susceptor. The edges of a storage area thus correspond to the edges of a substrate. The portion of the storage area extending in the direction of flow is referred to as the growth zone. The growth zone can directly adjoin a feed zone located between the gas inlet and the storage area. The extension plate can extend over part or all of the length of the feed zone located upstream of the growth zone.Preferably, a second gas outlet opening can be arranged at a downstream end of the extension plate within the feed zone, so that the process gas flowing through the uppermost gas inlet zone mixes within the feed zone with the process gases flowing from the other gas inlet zones below it. Alternatively, the extension plate can extend into the growth zone, so that the gas flowing from the uppermost gas inlet zone is fed into the growth zone, i.e., above the substrate. The opening area of ​​a second gas outlet opening adjoining a flow volume formed between an annular plate formed by the holding device and the extension plate can preferably be larger than the opening area of ​​the first gas outlet opening.Due to the different flow cross-sections, the dynamic pressure of the process gas flowing in through the uppermost gas inlet zone can be higher when flowing through the first gas outlet openings than when flowing through the second gas outlet openings.

[0037] The invention further aims to provide measures to suppress parasitic deposits on the process chamber ceiling of a CVD reactor. 31323N1PCT November 3, 2025 Ai 2024-10

[0038] The problem is solved by the device or method specified in the claims. The dependent claims not only represent advantageous further developments of the technical teachings specified in the dependent claims, but are also independent solutions to the problem.

[0039] First and essentially, a gas flow stabilization element or gas separation element is provided on a gas inlet element having several vertically arranged gas inlet zones, which is particularly detachably mounted. This element comprises several vertically arranged separation plates that can be selectively attached to the gas outlet wall at various vertical heights, for example, by means of one or more fastening means. The fastening means can preferably be pins that can be inserted into gas outlet openings arranged in the gas outlet wall and that support the gas flow separation plates. Adjacent gas flow separation plates can be connected to each other by connecting pieces, for example, webs. The connecting webs can preferably run along cooling channels arranged in the gas outlet wall, through which a coolant flows to cool the gas outlet wall.

[0040] The invention is based on the understanding that by introducing different gases or gas mixtures through the various vertically arranged gas inlet zones of the gas inlet device, significant differences in flow velocities and dynamic pressures result between the process gases flowing from the different gas inlet zones. The dynamic pressure 31323N1PCT November 3, 2025 Ai 2024-10 For example, the dynamic pressure is significantly different immediately downstream of the gas outlet surface of the gas inlet device in the area of ​​an uppermost gas outlet zone. For example, directly downstream of the gas outlet surface in the area of ​​a lower gas outlet zone. This can lead to undesirable turbulence and thus to undesirable convective gas transport. If, for example, a gas with a higher molar mass, such as argon, is fed into the process chamber through the uppermost gas inlet zone, increased convection of the process gases fed in through the lower gas inlet zones can occur towards the process chamber ceiling. Due to the comparatively high molar mass of the gas flowing into the process chamber through the uppermost gas inlet zone, the dynamic pressure in the area of ​​the uppermost gas inlet zone is higher and thus the static pressure is lower than in the area of ​​the lower gas inlet zones, through which reactive gases with a lower molar mass are preferably fed. For example, reactive gases of an element of the III.- Elements of the main group, of group IV or V, are fed into the process chamber through the lower gas inlet zones, for example, to deposit a III-V layer or an IV-IV layer on a substrate. The resulting negative pressure in the area immediately in front of the uppermost gas inlet zone draws the process gases fed in through the lower gas inlet zones towards the process chamber ceiling. Decomposition products of these process gases are deposited on the process chamber ceiling, for example, as a crystalline layer. Preferably, however, reactive gases containing carbon and silicon are fed into the process chamber, for example, ethene and trichlorosilane. 31323N1PCT November 3, 2025 Ai 2024-10 The gas inlet device has three gas inlet zones, in particular spaced equally apart and lying one above the other, whereby ethene is fed in through all three gas inlet zones and trichlorosilane only through the middle gas inlet zone.

[0041] An effect that intensifies the flow of process gases towards the process chamber ceiling occurs when vertically oriented cooling channels are arranged in the gas outlet wall of the gas inlet device, through which a coolant flows to cool the gas outlet wall. No gas outlet openings are arranged in the area of ​​the cooling channels through which a process gas could flow into the process chamber. This results in the process gases flowing from the lower gas inlet zones being able to flow "freely" towards the process chamber ceiling in the area of ​​the cooling channels without a diffusion barrier in the form of other gases flowing from the gas outlet openings.

[0042] Gas flow baffles positioned between the stacked gas inlet zones and connected to the gas outlet wall can suppress these vertical gas flows towards the process chamber ceiling. Each gas baffle has a length extending in the flow direction (here, the horizontal direction) that corresponds to the distance between an end of the gas flow baffle adjacent to the gas outlet wall and an end downstream of the gas flow baffle. The length of the gas flow baffles is chosen such that the process gases flowing through the lower gas inlet zones, which have a lower molar mass, are not drawn towards the process chamber ceiling. Flow simulations show that the length of the gas flow baffles must be greater than the length of "dead water zones" between the gas inlet zones, where backflow of the process gases towards the gas chamber ceiling would occur. 31323N1PCT 3. November 2025 Ai 2024-10 The term "dead water zones" refers to the horizontal free spaces described above. Furthermore, it is necessary that the downstream end of the gas flow separation plates lies within the upstream zone, which extends between the gas outlet wall of the gas inlet device and the upstream edge of the substrate storage area. Preferably, the gas flow separation plates extend over the upstream half of the upstream zone, particularly over one-third of the upstream zone. This ensures that the diffusion of the different process gases occurs upstream of the growth zone, which extends over the entire length of the substrate storage area.It is particularly advantageous if the radial extent of the separating plates corresponds to at least 200% of the distance of this "dead water zone," i.e., the distance from the lowest gas outlet opening of an upper gas outlet opening to the uppermost gas outlet opening of a gas outlet zone immediately below it. In exemplary embodiments, the vertical height of the dead water zone can be approximately 2.65 mm.

[0043] The optimal radial length of the partition plate can also be related to the vertical height of a gas outlet zone, for example, the vertical distance between the uppermost and lowest gas outlet openings of a gas outlet zone, which might be 8.33 mm. In this case, it is advantageous if the length of the partition plate is at least 75% of this height, but no more than 300%.

[0044] Another criterion for optimizing the length of the partition plate can be its relation to the outer diameter of the gas inlet. The length should be at least 20% of the radius of the gas inlet and at most 100% of this radius. 31323N1PCT November 3, 2025 Ai 2024-10

[0045] The length of the distance between the gas inlet device and the substrate, or a storage location for a substrate, can also serve as a reference point for optimizing the length. This distance could, for example, be 117.5 mm. The radial length should be at least 5% of this distance, but no more than 20%.

[0046] Preferably, all four of the aforementioned conditions must be met. This is the case, for example, if the radial length is 10 mm + / - 10%.

[0047] The flow velocity of the gases exiting the gas outlet zones in the downstream end of the gas flow dividers is lower than at the upstream end. This results in lower dynamic pressure differences between two adjacent gas inlet zones at the downstream end of the gas flow dividers than at the upstream end.

[0048] One criterion for determining the radial length of the partition plates can also be the difference in dynamic pressure between the flow channels separated by the partition plate. Preferably, the difference between the two dynamic pressures should not exceed a threshold value.

[0049] The dimensioning rule can also be based on a quotient of the two mean dynamic pressures in the two flow channels separated by the partition plate. With the larger of the two values ​​in the numerator of the quotient, the latter should be smaller than a threshold value.

[0050] The threshold value is preferably less than 2 and particularly preferably less than 3 / 2, 4 / 3, 5 / 4 or 6 / 5, where in the formula shown above the larger of the two velocities is in the denominator. 31323N1PCT November 3, 2025 Ai 2024-10

[0051] The partition plates define flow channels, with an uppermost partition plate and the process chamber ceiling defining an uppermost flow channel, a lowermost partition plate and the susceptor defining a lowermost flow channel, and partition plates in between defining a flow channel among themselves.

[0052] The radial length L of the separating plates extending in the direction of flow is chosen such that, under standard process parameters, dynamic pressures are established at the downstream end of the flow channels that differ from each other by a maximum of the threshold value.

[0053] The standard process parameters, each with a tolerance of + / -10%, can have the following values: a vertical distance of the process chamber ceiling from the susceptor of 25 mm, a total pressure in process chamber 6 of 100 mbar, a hydrogen flow of 100 slm through each flow channel, a C Hi gas flow of 40 sccm through a top flow channel, a C Hi gas flow of 250 sccm through a middle flow channel, a trichlorosilane gas flow of 780 sccm through the middle flow channel, a nitrogen flow of 7.5 sccm through the middle flow channel, a C2H4 gas flow of 90 sccm through a bottom flow channel, and an ammonia gas flow of 90 sccm through a bottom flow channel.

[0054] The standard process parameters, each with a tolerance of + / -10%, can also have the following values: a vertical distance of 25 mm between the process chamber ceiling and the susceptor, a total pressure of 100 mbar in process chamber 6, a hydrogen flow of 11 slm through the uppermost flow channel, and a G EL gas flow of 60 sccm through an uppermost flow channel. 31323N1PCT November 3, 2025 Ai 2024-10 an argon gas flow of 20 slm through the uppermost flow channel, a hydrogen flow of 94 slm through the middle flow channel, a C2H4 gas flow of 445 sccm through a middle flow channel, a trichlorosilane gas flow of 480 sccm through the middle flow channel, a nitrogen flow of 7.5 sccm through the middle flow channel, a hydrogen flow of 110 slm through the lower flow channel, a CHi gas flow of 90 sccm through a lower flow channel and an ammonia gas flow of 90 sccm through a lower flow channel, wherein, with this set of parameters, the total flows through the individual vertically stacked flow channels lie within a narrow window.

[0055] The standard process parameters, each with a tolerance of + / -10%, can also have the following values: a vertical distance of 25 mm between the process chamber ceiling and the susceptor, a total pressure of 100 mbar in process chamber 6, a hydrogen flow of 80 slm through the uppermost flow channel, a C₆H₆ gas flow of 60 sccm through an uppermost flow channel, an argon gas flow of 20 slm through the uppermost flow channel, a hydrogen flow of 100 slm through the middle flow channel, a C₂H₄ gas flow of 445 sccm through a middle flow channel, a trichlorosilane gas flow of 480 sccm through the middle flow channel, a nitrogen flow of 7.5 sccm through the middle flow channel, a hydrogen flow of 100 slm through the lower flow channel, a C₂H₄ gas flow of 90 sccm through a lower flow channel, and a Ammonia gas flow of 90 sccm through a lower flow channel,where, with this parameter set, the total flows through the individual vertically stacked flow channels differ more significantly from one another, and in particular the total flow through the uppermost flow channel should be reduced. 31323N1PCT November 3, 2025 Ai 2024-10

[0056] The invention also relates to a gas separation element for carrying out a method according to the invention or as a component of a device according to the invention, wherein two or more separation plates are connected to each other by connecting webs, wherein the angular division of the connecting webs can correspond to the angular division of the cooling channels of the gas inlet device.

[0057] Another aspect of the invention relates to the problem of specifying suitable means by which one or more separating plates can be attached in a CVD reactor.

[0058] The gas separation element according to the invention is attached to the gas outlet surface of the gas inlet device by fastening elements. The fastening elements preferably have a shaft with a diameter slightly smaller than the diameter of a gas outlet opening in the gas outlet wall of the gas inlet device. The fastening elements can have a head with a diameter slightly larger than the diameter of the gas outlet opening, so that the fastening element, forming a pin, can be inserted into a gas outlet opening, with the head protruding from the gas outlet wall. Two or three such fastening elements can be used to detachably attach the gas separation element to the gas inlet device.

[0059] The gas separator has several separating plates. It can have a lower separating plate and an upper separating plate. Preferably, either the lower or the upper separating plate can be supported by the mounting elements. The supported separating plate can have a recess on its underside into which the head is received. The recess can be formed by a rib or a projection. 31323N1PCT November 3, 2025 Ai 2024-10

[0060] According to a further embodiment, the fastening element is a wire. The wire preferably has a diameter slightly smaller than the diameter of the gas outlet opening. A first section of the wire can be inserted into the gas outlet opening. A subsequent section of the wire runs in a recess or beneath a partition plate. A middle section of the wire can protrude through an opening. A third section of the wire can run perpendicular to the middle section. The wire can be bent into a Z-shape.

[0061] Furthermore, the invention is based on the objective of simplifying the operation of a CVD reactor with different susceptor configurations and simplifying the manufacture of CVD reactors with different susceptor configurations.

[0062] The problem is solved by the method or device specified in the claims. The dependent claims not only represent advantageous developments of the technical teachings specified in the dependent claims, but are also independent solutions to the problem.

[0063] First and foremost, a gas inlet element with a first gas outlet surface is provided in a CVD reactor. This element has several vertically stacked gas inlet zones, from which different process gases flow into a process chamber of the CVD reactor. The process gases flowing from the gas inlet element mix with each other within a gas mixing zone that begins at the gas outlet zones and extends in the direction of flow. Downstream of the gas inlet- 31323N1PCT November 3, 2025 Ai 2024-10 In the organs, a storage area for a substrate is arranged at a substrate distance. A pre-flow zone extends between an upstream edge of the storage area and the beginning of the gas mixing zone. The length of this pre-flow zone can be adjusted using the method according to the invention. For this purpose, an extension element is provided, which can be detachably attached to the gas inlet organ or another stationary component of the CVD reactor. If the susceptor is exchanged for another susceptor, which, for example, has a larger or smaller substrate distance, or if another susceptor with a larger or smaller substrate distance is used, the distance from the beginning of the gas mixing zone to the first gas outlet surface can be changed by means of the extension element.

[0064] During the operation of a CVD reactor, the susceptor configuration can be easily changed. For example, a gas inlet fitting attached to the reactor lid does not need to be replaced. It is only necessary to attach an extension fitting to the gas inlet fitting, which is secured to the gas inlet fitting using fasteners. In the manufacture of CVD reactors, different requirements regarding the susceptor configuration can be addressed in a similar way. Only one type of gas inlet fitting needs to be provided. Adaptation to the various susceptors, where the bearing positions have different radial distances, can be achieved by using an extension fitting matched to the susceptor configuration.

[0065] The extension element can have several extension plates which, when the extension element is assembled, surround the gas inlet element. The gas inlet element preferably has a substantially cylindrical base body that can be inserted into a central opening of the extension element. The extension plates can be 31323N1PCT November 3, 2025 Ai 2024-10 The extension plates extend in the direction of flow, with an upstream end adjacent to the gas outlet surface of the gas inlet device. The extension plates are preferably of equal length, with the extension length preferably being less than the substrate distance.

[0066] The gas inlet element can have vertically arranged gas distribution volumes, each assigned to one of the gas outlet zones. Each gas distribution volume can be connected to a supply line through which process gas is fed into the distribution volume. Adjacent gas distribution volumes can be separated from each other by partitions. Preferably, when the extension element is connected to the gas inlet element, the extensions can be horizontally connected to each partition.

[0067] The gas inlet element can be a substantially cylindrical body located in the center of the process chamber. One surface of the cylindrical body can serve as the gas outlet, preferably with a plurality of gas outlet openings. The process gases can flow from these gas outlet openings into the extension element within their respective zones. A further gas outlet can be arranged at the downstream end of the extension plates, allowing the process gases to flow from the extension element into the feed zone. The extension element can also be a substantially cylindrical body with a cylindrical surface that forms a further gas outlet, arranged coaxially with the gas outlet of the gas inlet element.The gas outlet surface of the extension element can also have a wall with a plurality of gas outlet openings, wherein the number of gas outlet openings in a first gas outlet surface of the gas inlet element and the. 31323N1PCT November 3, 2025 Ai 2024-10 The number of gas outlet openings in a second gas outlet surface of the extension element can be the same or different. The opening area of ​​the gas outlet openings of the first and second gas outlet surfaces can also be the same or different.

[0068] Depending on the susceptor configuration used, and in particular on the substrate distance, different extension elements can be employed, with varying horizontal lengths of the extension plates. The length of the extension plates can be adapted to the substrate length, thus keeping the pre-zone length constant for a given reactor design. The length of the pre-zone can be adjusted based on the length of the extension plates.

[0069] According to the invention, a method for operating or manufacturing a CVD reactor is provided in which, by means of the extension device for the gas inlet device, when replacing one susceptor with another or when using a different susceptor that has a larger substrate distance, the distance between the beginning of the gas mixing zone, in which the process gases flowing out of the gas inlet device mix, and the storage area on which the substrate is stored can be adjusted.

[0070] The extension element can be detachably connected to the gas inlet element or another stationary component of the CVD reactor by means of a fastening device. Several extension elements can be provided, each with extension plates of different lengths. The extension plates can be detachably or permanently connected to the extension element. 31323N1PCT November 3, 2025 Ai 2024-10 The length of the pre-flow zone can be adjusted by replacing the extension element with extension plates of varying lengths in the direction of flow. Alternatively, only the individual extension plates can be replaced, whereby the base body of the extension element, to which the extension plates are detachably attached, remains detachably connected to the gas inlet element during the replacement.

[0071] For example, several sets of extension plates of the same or different lengths can be provided, which can be attached to the main body of the extension element as needed. Alternatively, several sets of extension elements can be provided, each with extension plates permanently attached to the respective extension element. In this case, adjusting the length of the inlet zone requires replacing the main body and the permanently attached extension plates.

[0072] The extension element can be attached to the gas inlet element, for example, using a bayonet fitting. Alternatively, the extension element can be attached to the gas inlet element using a thread or one or more screws. For example, the extension element can be screwed onto the gas inlet element.

[0073] The gas inlet element can, for example, be located in the center of a first susceptor in a process chamber of a CVD reactor. The gas inlet element can, for example, comprise a cylindrical base body in which the multiple gas distribution chambers are arranged vertically one above the other. Each gas distribution chamber can be connected to a supply line through which a process gas can be fed into the gas distribution chamber. The gas distribution chambers can have a first gas outlet surface with a plurality of 31323N1PCT November 3, 2025 Ai 2024-10 The gas inlet element has gas outlet openings, the gas outlet surface extending onto a cylindrical surface of the cylindrical base body. The extension plates can be annular plates whose inner diameter is slightly larger than the diameter of the cylindrical surface, allowing them to be slid onto the gas inlet element during assembly. For example, in the assembled state of the extension element, an upstream end of the extension plates can be positioned less than 1 millimeter from the first gas outlet surface. The process gases flowing from the gas outlet openings of the first gas outlet surface are directed into the extension element without mixing.The distance between the upstream end of the extension plates and the first gas outlet surface is chosen such that no mixing of the process gases flowing from the first gas outlet surface occurs in the area immediately downstream of the first gas outlet surface.

[0074] The first susceptor can be equipped with initial storage positions for substrates. These storage positions can be arranged, for example, along a circular arc around the gas inlet. An upstream edge of the first storage positions can be positioned at a distance from the first gas outlet. Extension plates can project horizontally from the gas inlet to a point upstream of the upstream edge of the storage positions. A pre-flow zone extends between a downstream end of the extension plates and the upstream edge of the storage positions. In this pre-flow zone, the process gases flowing out of the extension and into the process chamber mix. The length of the pre-flow zone thus depends on the length of the extension plates, the position of the substrates on the susceptor relative to the first gas outlet, and the diameter of the substrates.Are the substrates being replaced? 31323N1PCT November 3, 2025 Ai 2024-10 When used with a larger or smaller diameter, the length of the extension plates can be adjusted so that the length of the inlet zone remains constant. The length of the extension plates can be changed by replacing individual extension plates or the entire extension assembly.

[0075] The process gases flowing from the first gas outlet of the gas inlet device can enter the process chamber through flow volumes arranged between adjacent extension plates. Gas distribution can occur within these flow volumes. A flow volume extending circumferentially around the first gas outlet can be arranged between each pair of adjacent extension plates. This flow volume can be bounded above and below by one of the extension plates, thus extending in a ring shape around the first gas outlet. The flow volume can be bounded upstream by the first gas outlet and downstream by a second gas outlet. The second gas outlet can be directly adjacent to the downstream end of the extension plates.The second gas outlet surface can be arranged coaxially to the first gas outlet surface. Like the first gas outlet surface, the second gas outlet surface can be a gas outlet wall with gas outlet openings.

[0076] The first gas outlet surface can preferably extend parallel to the second gas outlet surface. However, the gas outlet surfaces can also be configured differently. For example, the first gas outlet surface can have different outer diameters in certain sections, or it can be stepped. 31323N1PCT November 3, 2025 Ai 2024-10 the second gas outlet surface extends onto a cylindrical shell surface of the extension element with a constant outer diameter.

[0077] The first gas outlet surface can extend across a cylindrical surface. The extension plates can be ring-shaped plates that can be individually and detachably attached to the first gas outlet surface of the gas inlet device. The inner diameter of the ring-shaped plates can be slightly larger than the diameter of the cylindrical surface. This allows the ring-shaped extension plates to be slid onto the gas inlet device for assembly.

[0078] The extension element can also comprise a cylindrical base body with a cavity into which the gas inlet element can be inserted. Support elements can be provided with which the extension plates can be detachably attached to the base body at a predetermined distance from one another. For example, the extension plates, designed as ring-shaped plates, can have a thread on an inner wall that can be screwed onto a corresponding mating thread on the outer wall of the gas inlet element.

[0079] Sealing elements can be provided between the extension element and the gas outlet surface to prevent a vertical gas flow from forming in the space between the outer wall of the gas inlet element and the inner wall of the extension element, thus preventing the process gases from mixing in this area. For example, sealing rings can be provided that extend along the inner wall of the extension plates and block vertical gas flow. 31323N1PCT November 3, 2025 Ai 2024-10

[0080] In the assembled state, an underside of the extension element formed by an extension plate can preferably be spaced apart from an upper side of the susceptor.

[0081] The extension plates of a set of extension plates are preferably of equal length. The extension plates preferably extend horizontally parallel to the surface of the susceptor.

[0082] The extension plates are preferably made of a material inert to the gases fed into the process chamber, for example quartz or metal, or another heat-resistant material. The extension plates are preferably made of the same material as the first gas outlet wall of the gas inlet device. The extension plates can also be made of an electrically conductive material to influence the gas flow.

[0083] The extension element can also have a base body that can be detachably attached to the gas inlet element and which has a number of extension plates permanently connected to the base body. In order to adjust the supply zone length, it is necessary in this case to replace the base body together with the extension plates permanently attached to it.

[0084] The extension element can have a cup-shaped opening with a base. The base is an integral part of the main body. The gas inlet element can be accommodated in the cup-shaped opening. The extension element can be secured with a fastening device that connects the base of the extension element to the base of the gas inlet element. 31323N1PCT November 3, 2025 Ai 2024-10 The gas is connected, for example with a screw, a bayonet fitting, or another force-fit connection. For example, the base body of the extension element can have an internal thread that can be screwed onto an external thread formed by the gas inlet element.

[0085] Furthermore, the invention comprises a system consisting of a CVD reactor as previously described by way of example and a second susceptor having second storage positions for substrates. The second susceptor can be exchanged for the first susceptor. For example, the second storage positions can have a larger diameter than the first storage positions. An upstream edge of the second storage position can be arranged at a second distance from the first gas outlet surface, which is smaller than the first distance. A first and a second extension element can be provided, which can be interchanged. The extension length of the extension plates of the first extension element, measured in the direction of flow, can differ from the extension length of the extension plates of the second extension element, also measured in the direction of flow.

[0086] The method according to the invention can, for example, be carried out with a system comprising a first susceptor and a second susceptor, each having at least one storage location for a substrate. An upstream edge of the storage location of the first susceptor can be spaced a first substrate distance from the gas outlet surface of the gas inlet element. An upstream edge of the storage location of the second susceptor can be spaced a second substrate distance from the gas outlet surface of the gas inlet element. The first substrate distance and the second substrate distance can preferably be different. 31323N1PCT November 3, 2025 Ai 2024-10 For example, the first substrate distance can be smaller than the second substrate distance. The first susceptor can be exchanged for the second susceptor. With the extension element according to the invention, the distance from the beginning of the gas mixing zone to the gas outlet surface can be changed, in this example, lengthened. For this purpose, the extension element can be mounted on the gas inlet element.

[0087] Furthermore, the invention relates to a CVD reactor as described in DE 102019 104433 Al, DE 102008 055582 Al, or DE 10043 600 B4. Such a CVD reactor has a gas-tight housing, to the top of which a holder is attached, which supports a process chamber ceiling. The housing can be made of stainless steel, for example. However, the housing can also be made of another material. The process chamber ceiling defines the upper boundary of the process chamber. The process chamber is bounded at the bottom by a susceptor, for example made of graphite, which may have a central recess. A gas inlet element, as described above by way of example, can be arranged in the center of the process chamber. The gas inlet element can project into the process chamber through a central opening in the process chamber ceiling.A lower section of the gas inlet element can extend into the central recess of the susceptor, so that the gas outlet openings of the lowermost gas inlet zone open directly above the top of the susceptor. The susceptor can have one or more storage positions surrounding the gas inlet element, each for storing a substrate. The substrates can be arranged on substrate holders that are supported on a gas cushion and rotated by the gas cushion. A heating device can be provided below the susceptor to heat it. A gas mixing system can be provided to supply the gas inlet element with process gases, such as organometallic compounds of group III and hydrides of group V, as well as hydrogen or an inert gas as a carrier gas. 31323N1PCT November 3, 2025 Ai 2024-10 The device is connected to gas sources. Several sets of susceptors, each with different substrate distances, may be provided. Furthermore, at least one extension element is provided. Multiple extension elements, each with different diameters (i.e., with extension plates of different lengths), may also be provided. The extension plates can preferably be arranged between the gas inlet zones in order to separate the process gases exiting from the gas outlet surface of the gas inlet device. Brief description of the drawings

[0088] Exemplary embodiments of the invention are explained with reference to the accompanying drawings. The reference numerals in Figures 1 to 7 are defined in List I of Reference Numerals, the reference numerals in Figures 8 to 22 are defined in List II of Reference Numerals, and the reference numerals in Figures 23 to 32 are defined in List III of Reference Numerals. The figures show: Fig. 1 shows in schematic half-section the essential elements of the process chamber 19 of a CVD reactor 1 with an extension plate 24 separating the process gas flowing from a gas inlet zone ZI arranged at the top from the process gases flowing through the gas inlet zones Z2, Z3 arranged below, which is connected by means of a connecting element 20 to a holding device 18 which is detachably attached to the housing 2 of the CVD reactor 1, Fig. 2 is a representation according to Figure 1, wherein a gas outlet opening 17, into which a flow limited upwards by the holding device 18 and downwards by the extension plate, flows 31323N1PCT November 3, 2025 Ai 2024-10 The channel 5 opens into a growth zone 23, which extends downstream in the flow direction S of an upstream edge of the storage area 25. Fig. 3 shows a section along line III-III in Figure 2, Fig. 4 shows a representation according to Figure 2, wherein the inner radius of a process chamber ceiling 3 of the process chamber 19 of the CVD reactor 1 is enlarged, Fig. 5 shows a representation according to Figure 1, wherein the holding device 18 forms an internal thread 27 which engages in an external thread 28 formed by the gas inlet element 21, Fig. 6 shows a representation according to Figure 1, wherein the extension plate 4 lies within the first gas outlet zone ZI, Fig. 7 shows a further embodiment, wherein the CVD reactor is a horizontal reactor, with a gas inlet device 21 arranged at one end of the process chamber 19, wherein the ceiling which limits the flow channel 5 upwards is attached to the process chamber ceiling 3, Fig. 8 schematically shows a cross-sectional view of a CVD reactor, Fig. 9 shows a side view of a first embodiment of a gas inlet device 30 with a gas separation element 20 attached to it. 31323N1PCT November 3, 2025 Ai 2024-10 Fig. 10 shows the view in the direction of arrow III in Figure 9, Fig. 11 shows a partial section of section XX in Figure 9, Fig. 12 shows the gas inlet element 30 shown in Figure 9 partially broken open, Fig. 13 shows an exploded view of the gas inlet element 30 together with the gas separating element 20, Fig. 14 shows a detailed representation of a second embodiment, Fig. 15 shows the section along line XV-XV in Figure 14, Fig. 16 shows a fastening element 27 in detail, Fig. 17 shows a schematic representation of a cross-section through a process chamber 6 of a CVD reactor, Fig. 18 is a representation similar to Figure 17, where the lines represent locations with the same flow velocity, without the use of a gas separating element 20; Fig. 19 is a representation according to Figure 18 but with a gas separating element 20. Fig. 20 enlarges a section of an outer wall of a gas inlet device 30 to illustrate the horizontal distances b between two adjacent gas outlet fields 31 and a 31323N1PCT November 3, 2025 Ai 2024-10 vertical distance a between two stacked Gas outlet fields 31, Fig. 21 shows a representation approximately according to Figure 19, except that the two broad surfaces of the separating plates 21, 22 are not parallel to each other. Fig. 22 shows a representation approximately according to Figure 11, except that the two broad surfaces of the connecting web 23 are not parallel to each other. Fig. 23 schematically shows a process chamber 3 of a CVD reactor 1 in a half-section view. Fig. 24 shows a half-section according to Figure 23 of a first embodiment of the invention, wherein extension plates 15 of an extension element 17, separating the process gases flowing from the gas outlet zones ZI, Z2, Z3, connect to the first gas outlet surface 12, Fig. 25 shows a half-section according to Figure 24 of a second embodiment, wherein an upstream edge of a storage place 11 arranged from a susceptor 5" for storing a substrate 4 is spaced at a substrate distance A2 from the first gas outlet surface 12 of the gas inlet element, which is greater than the substrate distance Al of the susceptor 5' shown in Figure 24, 31323N1PCT November 3, 2025 Ai 2024-10 Fig. 26 schematically shows a sectional view of the CVD reactor 1 of a third embodiment, in which several extension plates 15 are detachably attached to a first gas outlet surface 12 of a gas inlet device 2. Fig. 27 shows the section along line XXVII-XXVII in Figure 26, Fig. 28 schematically shows a sectional view of a CVD reactor 1 of a fourth embodiment, Fig. 29 schematically shows a sectional view of a CVD reactor 1 of a fifth embodiment, Fig. 30 schematically shows a sectional view of a CVD reactor 1 of a sixth embodiment, Fig. 31 is an enlarged view of the gas inlet organ 2 from Figure 30, Fig. 32 shows a schematic, enlarged sectional view of a gas inlet element 2 of a seventh embodiment. Description of the embodiments

[0089] The following description refers to the embodiments shown in Figures 1 to 7, the reference numerals corresponding to those in List I of reference numerals. 31323N1PCT November 3, 2025 Ai 2024-10

[0090] The device according to the invention is located in a housing 2 of a CVD reactor 1, as shown in Figures 1, 2 and 4. The housing 2, which is made primarily of stainless steel and is gas-tight and evacuatable, contains a gas inlet element 21 into which reactive gases, together with an inert gas, can be fed via supply lines 8, 8', 8". The gas inlet element 21 is essentially cylindrical and is located in the center of a process chamber 19 arranged in the housing 2.

[0091] The gas inlet element 21 has several vertically arranged gas inlet zones ZI, Z2, Z3, each connected to a gas distribution chamber 14, 14', 14" above the other. One of the supply lines opens into each of the gas distribution chambers 14, 14', 14" through which a predetermined mass flow of gas is fed into the gas distribution chambers 14, 14', 14" above the other. The cylindrical surface of the gas inlet element 21 forms a gas outlet wall 7, which has a plurality of uniformly distributed first gas outlet openings 15. The gas outlet zones ZI, Z2, Z3 have a height, which may be the same or different.

[0092] The gas inlet element 21 is surrounded by a circular disk-shaped susceptor 12, which is supported by a shaft 16 that can be rotaryally driven. The susceptor 12 defines the lower boundary of the process chamber 19 of the CVD reactor 1, which is arranged circularly around the gas inlet element 21. The process chamber 19 is surrounded by a gas outlet element 9, which allows the gases fed into the process chamber 19, as well as decomposition products of the reactive gases, to be removed.

[0093] Below the susceptor 12 is a heating device 10, which heats the susceptor 12 or the process chamber 19, but also a process chamber ceiling 3 that limits the process chamber 19 upwards. 31323N1PCT November 3, 2025 Ai 2024-10 Optionally, an additional heating device (not shown) can be provided above the process chamber ceiling 3 to heat the process chamber ceiling 3 separately. A cooling device can also be provided above the process chamber ceiling 3 for active cooling of the process chamber ceiling 3.

[0094] On an annular surface surrounding the gas inlet element 21 located in the center of the housing 2, several substrates 11 are arranged on the upper surface of the susceptor 12 facing the process chamber ceiling 3. Each substrate 11 rests on a storage position 25, supported by a substrate holder 13. The substrate holder 13 is a circular disk that can be supported by a gas cushion. The gas cushion can cause the substrate holder 13 to rotate around a center point of the storage position 25.

[0095] The area of ​​the susceptor 12, which forms the bottom of the process chamber and is immediately adjacent to the gas inlet element 21, forms a pre-zone 22. A growth zone 23 adjoins the pre-zone 22, in which the substrates 11 or the storage locations 25 are arranged. The length of the growth zone depends on the diameter of the storage location 25 and essentially corresponds to the diameter of the substrates 11 stored in the storage locations 25.

[0096] Figure 1 schematically shows the inlet area of ​​the process chamber 19, which is bounded above by the process chamber ceiling 3 and below by the susceptor 12. Three vertically arranged gas inlet zones ZI, Z2, Z3 are shown as an example, all having a uniform height for clarity. However, fewer or more than three gas inlet zones ZI, Z2, Z3, for example five gas inlet zones, are also possible. 31323N1PCT November 3, 2025 Ai 2024-10 Various process gas flows enter the process chamber 19 through the first gas outlet openings 15 arranged in the gas outlet wall 7 of the gas inlet device 21.

[0097] According to the invention, an extension plate 4 is provided which, in an area of ​​the process chamber 19 adjacent to the gas inlet element 21, separates the process gas flowing from the uppermost gas inlet zone ZI from the process gases flowing from the gas inlet zones Z2 and Z3 arranged below it. This shifts the mixing zone, in which all process gases flowing into the process chamber 19 mix, away from the gas outlet wall 7 of the gas inlet element 21 in the direction of flow.

[0098] The extension plate 4 is designed as an annular plate surrounding the gas inlet element 21, which is connected to a holding device 18 by means of a connecting element 20, which in turn is attached to the housing 2 of the CVD reactor 1 or to a housing-fixed component of the CVD reactor 1.

[0099] The holding device 18 comprises an annular plate, which can have the same inner and outer diameters as the extension plate 4 arranged below it. However, the outer diameter can also be smaller. The underside of the annular plate of the holding device 18 is flush with the underside of the process chamber ceiling 3 facing the process chamber 19. In Figures 2 and 5, the underside of the process chamber ceiling 3 is arranged vertically offset from the underside of the annular plate of the holding device 18. However, the underside of the process chamber ceiling 3 can also be flush with the underside of the annular plate of the holding device 18, as shown in Figure 1. 31323N1PCT November 3, 2025 Ai 2024-10

[0100] The connecting element linking the extension plate 4 to the holding device 18 is formed by several webs. The webs 20 are arranged in a fan shape between the extension plate 4 and the holding device 18 (see Figure 3).

[0101] In the embodiments shown in Figures 1, 2, and 4, the retaining device 18 comprises a shaft projecting upwards from an annular plate, which is attached to the inner wall of the housing 2 of the CVD reactor 1. In the embodiments of the invention shown in Figures 1 to 5, the extension plate 4, the connecting element 20, and the retaining device 18 are designed as an annular body made of a single material and arranged rotationally symmetrically around the center of the gas inlet element 21. The height of the body corresponds to the height of the uppermost gas inlet zone ZI. Within the body, webs 20 are arranged in a fan shape around the center of the body. The webs 20 function as connecting elements and as partitions between adjacent flow channels 5, which are bounded upwards by the retaining device 18 and downwards by the extension plate 4. The flow channels 5 are fluidically connected to the first gas inlet zone ZI.The process gas flowing from the first gas outlet openings 15 within the uppermost gas inlet zone ZI, which is the first gas inlet zone, flows into the flow channels 5 and out into the process chamber 19 through a second gas outlet opening 17 located at the downstream end of each flow channel 5. The area of ​​the second gas outlet opening 17 is larger than the area of ​​the first gas outlet openings 15 located in the gas outlet wall 7 of the gas inlet element 21. 31323N1PCT November 3, 2025 Ai 2024-10

[0102] A downstream end of the annular plate of the holding device 18 forms a support step 26 on which an upstream end of the process chamber ceiling 3 is supported. The holding device 18 thus functions as a fastening means for the process chamber ceiling 3.

[0103] In the first embodiment of the invention shown in Figure 1, the inner radius of the process chamber ceiling 3 corresponds approximately to the outer radius of the extension plate 4. In the second embodiment of the invention shown in Figure 2, the inner radius of the process chamber ceiling 3 is smaller than the outer radius of the extension plate 4, so that an upstream end section of the process chamber ceiling 3 rests on the upper surface of the plate of the holding device 18. The second gas outlet opening 17, which adjoins each of the flow channels 5, is arranged within the growth zone 23. This allows the process gas flowing from the uppermost gas inlet zone ZI to be fed into the process chamber 19 downstream of the process gas flowing through the other gas inlet zones Z2 and Z3.Within the upstream zone 22, the extension plate 4 5 prevents the diffusion of decomposition products from the process gases flowing from the lower gas inlet zones Z2 and Z3 towards the process chamber ceiling 3. Within the growth zone 23, the gas flowing from the uppermost gas inlet zone ZI prevents the diffusion of decomposition products from the process gases flowing from the other gas outlet zones Z2 and Z3 located below it. The process gas flowing out of the uppermost gas inlet zone ZI acts as a barrier gas and prevents the decomposition products of the other process gases from depositing on the process chamber ceiling 3.

[0104] As can be seen in Figure 3, the substrates 11 stored on the storage positions 25 are arranged in a ring around the gas inlet element 21. The flow channels 5 open into the second gas outlet openings 17, which are located above 31323N1PCT November 3, 2025 Ai 2024-10 The substrates 11 are arranged within the growth zone 23. Due to the increasing flow cross-section, the process gas flowing from the second gas outlet openings 17 has a lower flow velocity than the process gas flowing from the first gas outlet openings 15 within the uppermost gas inlet zone ZI.

[0105] The partition walls 20 separating the adjacent flow channels 5 preferably extend over the entire length in the flow direction of the extension plate 4. The distance between the upstream ends of two adjacent webs 20 is preferably larger than the area of ​​one of the first gas outlet openings 15, so that several first gas outlet openings 15 each feed a flow channel 5.

[0106] Figure 4 shows a third embodiment of the invention. Unlike the embodiment shown in Figure 3, the inner radius of the process chamber ceiling 3 essentially corresponds to the outer radius of the extension plate 4 or the holding device 18, so that only an upstream edge of the process chamber ceiling 3 rests on the support step 26 formed by the upper plate of the flow guide element 4.

[0107] The shaft formed by the holding device 18, with which the holding device 18 is attached to the housing 2, is arranged at any position on the top of the annular plate of the holding device 18.

[0108] Figure 5 shows a fourth embodiment of the invention. Unlike the embodiment shown in Figure 1, the retaining device 18 is not attached to the housing 2 of the CVD reactor 1, but to the gas inlet element 21. The retaining device 18 forms an internal thread 27 that engages in an external thread 28 formed by the gas inlet element 21. 31323N1PCT November 3, 2025 Ai 2024-10 This means that the retaining device 18 and thus the extension plate 4 are detachably attached to the gas inlet device 21.

[0109] Figure 6 shows a fifth embodiment of the invention. Unlike the embodiment shown in Figure 1, the extension plate 4 is arranged within the first gas outlet zone ZI. By way of example, two of the three first gas outlet openings 15 leading into the first gas outlet zone ZI are arranged above the extension plate 4. The lowest first gas outlet opening 15 in the first gas outlet zone ZI is arranged below the extension plate 4. More or fewer first gas outlet openings can also be arranged above the extension plate 4. Alternatively, the extension plate 4 can also be arranged within the second gas outlet zone Z2 or the third gas outlet zone Z3 (not shown).

[0110] Figure 7 schematically shows a horizontal reactor with a gas inlet 21 arranged at a first end of the process chamber 19 and a gas outlet 9 (not shown) arranged at a second end of the process chamber 19 opposite the first end. Process gases flowing out of the gas inlet 21 horizontally through the process chamber 19. The flow channel 5 extends vertically over the entire first gas outlet zone ZI, with the extension plate 4, which limits the flow channel downwards, lying in a horizontal plane with the bottom of the uppermost gas distribution chamber 14. The flow channel 5 is bounded upwards by a ceiling, which here, by way of example, directly adjoins the process chamber ceiling 3. However, the flow channel 5, or rather the ceiling that limits it upwards, can also be fastened to the process chamber ceiling 3. 31323N1PCT November 3, 2025 Ai 2024-10 the ceiling may be directly adjacent to the process chamber ceiling 3 or may be spaced away from it.

[0111] The following description refers to the embodiments shown in Figures 8 to 22, the reference numerals corresponding to those in List II of reference numerals.

[0112] Figure 8 schematically shows a CVD reactor, such as that used for depositing SiC layers. A susceptor 2, which can be made of graphite, particularly coated graphite, is located in a stainless steel housing 1. The susceptor has a circular disk shape and is supported by a shaft 8, which can be rotated about an axis by a rotary drive (not shown).

[0113] Below the susceptor 2 is a heating device 7, which can be used to heat the susceptor 2 to a process temperature. The heating device 7 can be an induction heater. It can also be an infrared heater.

[0114] Above the susceptor 2 is a process chamber 6. In the upper surface of the susceptor 2, facing the process chamber 6, is a pocket containing a substrate holder 3, which provides a storage area for a substrate 4 to be coated. A gas stream can be introduced into the pocket to cause the substrate holder 3 to rotate.

[0115] A gas inlet element 30, shown in detail in Figures 9 to 15, extends symmetrically to the axis between susceptor 2 and a process chamber ceiling 5. The gas inlet element 30 has three superimposed 31323N1PCT November 3, 2025 Ai 2024-10 The drawings show chambers (not shown) separated from each other by partitions (also not shown). Each chamber has a feed line (also not shown) through which a process gas can be introduced. For example, to deposit SiC, C₂H₄ and trichlorosilane are fed into a chamber of a middle gas distribution volume 15. Nitrogen can also be introduced into the middle zone. Hydrogen is additionally introduced there as a carrier gas. C₂H₄ and ammonia can be introduced into a chamber of a lower gas distribution volume 16. Hydrogen is also used as the carrier gas here. Argon is introduced into the chamber of an uppermost gas distribution volume 14. C₂H₄ and hydrogen can also be introduced here. Reference is made to the previously described standard process parameters.

[0116] The gas inlet element 30 has a gas outlet wall 32 extending across a cylindrical surface. Cooling channels 34 extend vertically at regular intervals along this gas outlet wall 32, through which a coolant can flow. Several rows of gas outlet openings 33 extend between the cooling channels 34, through which the aforementioned process gases can flow into the process chamber 6. The gas outlet openings 33 form gas outlet fields 31, spaced apart horizontally by horizontal gaps 36. The gas outlet openings 33 located at the edges of two adjacent gas outlet fields 31 are spaced apart by a distance b, which can be between 5 and 10 mm. The gas outlet fields 31 are also spaced apart by vertical gaps 35.The vertical free spaces 35 are located at the points where the different gas distribution volumes are separated from each other by walls (not shown). The distance a from the gas outlet openings 33 located at the edge of two vertically arranged openings is shown. 31323N1PCT November 3, 2025 Ai 2024-10 The dimensions of the gas outlet fields 31 can be between 2 and 5 mm. The vertical height of a gas outlet field 31, i.e., the distance from the uppermost gas outlet opening 33 to the lowermost gas outlet opening 33, can be between 5 and 10 mm. Preferably, it is approximately 8 mm to 8.5 mm.

[0117] A gas separation element 20 is provided, which can be made of metal, steel, a precious metal, a ceramic material, or another suitable material. In the exemplary embodiment, the gas separation element 20 is a single-piece body forming two vertically arranged separation plates 21, 22. The two separation plates 21, 22 have an annular shape. Their inner diameter is slightly larger than the outer diameter of the gas outlet wall 32. The distance L of an inner edge 21', 22' to a radially outer edge 21", 22" is selected according to criteria described below such that crossflows, eddies, and backflows are largely avoided during operation of the CVD reactor.

[0118] The radial extension length L can, for example, be 10 mm. Preferably, several design conditions are to be met simultaneously. The length L should lie within a range of 10% to 50% of the outer diameter of the gas inlet element 30. The length L should lie within a range of 75% to 300% of the vertical height of a gas outlet field 31. The length L should lie within a range of 200% to 1000% of the vertical distance a between two gas outlet fields 31. The length L should lie within a range of 5% to 20% of the distance A between the gas inlet element 30 and the storage location 3.

[0119] An upper partition plate 21 is connected to a lower partition plate 22 by means of connecting webs 23. The connecting webs 23 have the same angular spacing as the cooling channels 34. In the assembled state, they extend 31323N1PCT November 3, 2025 Ai 2024-10 The connecting webs 23 extend along the horizontal free spaces 36, which lie circumferentially between two gas outlet fields 31. The separating plates 21, 22 lie at the vertical height of the walls (not shown) arranged in the gas inlet device, which separate two adjacent gas distribution volumes 14, 15, 16 from each other.

[0120] In the embodiment shown in Figures 10 to 13, fastening elements 25 in the form of pins, for example ceramic or metal pins, are provided, which have a shaft 25' that connects to a head 25". The shaft 25' has the same diameter as the gas outlet opening 33, so that it can be inserted into a gas outlet opening 33. The diameter of the head 25" is slightly larger. It protrudes from the outside of the gas outlet wall 32.

[0121] The partition plate 22 has recesses 26 on its underside into which the head 25" can be received. In the exemplary embodiment, the recesses 26 are formed by ribs 26' or projections.

[0122] In the embodiment shown in Figures 15 and 16, the fastening element 27 is a Z-shaped bent wire with a first section 27' that can be inserted into a gas outlet opening 33 and that can partially lie in a recess 29' of a rib 29. A second section 27" adjoins the first section 27' at a right angle to it and penetrates an opening 28 of the rib 29. A third section 27'' adjoins the second section 27" and can run parallel to the first section 27' and can rest against an upper surface of the rib 29. 31323N1PCT November 3, 2025 Ai 2024-10

[0123] Figure 17 schematically shows a longitudinal section through the process chamber 6. On the left is the gas inlet device 20 with partitions arranged within the gas outlet wall 35, which separate adjacent gas distribution volumes 14, 15, 16 from one another. Supply lines (not shown) are provided, which are connected to a gas mixing system to feed process gases into the gas distribution volumes 14, 15, 16 in the manner described above.

[0124] The partition plates 21, 22 define an upper flow channel 17, a middle flow channel 18, and a lower flow channel 19. At the beginning of each flow channel, the gas streams exiting the gas outlet openings 33 in a jet-like manner have an average flow velocity ul, u2, u3. Thus, a dynamic pressure pl, p2, p3 is generated in each of the flow channels 17, 18, 19. Since the radius of the flow channels 17, 18, 19 in the region of the upstream ends 21', 22' is smaller than the radius in the region of the downstream ends 21", 22", the passage areas through which the gas flow flows on the upstream and downstream sides are also different from each other, therefore the mean flow velocities v1, v2, v3 are lower than the flow velocities ul, u2, u3 in the region of the downstream ends 21", 22".

[0125] The length L of the preferably parallel separating plates 21, 22 is selected such that the mean dynamic pressures in the region of the uppermost gas outlet zone 11, the middle gas outlet zone 12, and the lower gas outlet zone 13 of the three superimposed flow channels 17, 18, 19 do not differ by more than a factor of between 2 and 1 / 2. The difference in dynamic pressures depends on the length L of the separating plates 21, 22. The longer the separating plates 21, 22 are, the smaller the difference in dynamic pressures in the region of the gas outlet zones 11, 12 separated by the separating plates 21, 22, because the flow velocity of the 31323N1PCT November 3, 2025 Ai 2024-10 The gas flowing through the respective outlet zones decreases with increasing distance to the gas outlet wall 32.

[0126] The separating plates 21, 22 preferably have the same length L. The length L is also significantly shorter than the distance A between the storage location 3 and the gas outlet wall 32. A pre-zone V, which adjoins the downstream end 21", 22" and extends to the storage location 3, therefore has a length greater than the length L of the separating plates 21, 22.

[0127] Figures 18 and 19 illustrate the effect of the previously described separating plates 21, 22.

[0128] Figure 18 shows the flow pattern when no partition plates 21, 22 are present within process chamber 6. The lines indicate locations with the same flow velocity. Argon, along with hydrogen and C2H4, is fed into process chamber 6 through the uppermost gas distribution volume 14. A downward movement of zone Bl, representing the argon flow, can be observed.

[0129] Zone B2 shows the gas flow out of the middle gas distribution volume 15, where the arrow Gl indicates a suction effect caused by a large difference in dynamic pressures between the area immediately downstream of the uppermost gas distribution volume 14 and the middle gas distribution volume 15. Similarly, a suction effect is also created, represented by arrow C2.

[0130] In the areas marked A, a backflow occurs due to the vortices represented by the arrows Cl, C2. 31323N1PCT November 3, 2025 Ai 2024-10

[0131] D denotes an area below the process chamber ceiling 5 where parasitic deposits form.

[0132] Both the areas of backflow between two gas outlet fields 31 and in the area between gas inlet device 30 and the storage location 3 or the area of ​​backflow extending over the storage location 3 are to be avoided by means of the separating plates 21, 22.

[0133] During the deposition of SiC, the suction effect designated Gl and C2 causes reactive gases to be transported to the process chamber ceiling 5. This results in the formation of a thick parasitic coating there. The horizontal spaces 36, arranged at a uniform angular interval around the center of the process chamber, also lead to the formation of a structured parasitic coating, particularly in the radially inner edge region of the underside of the process chamber ceiling 5. Circumferentially, the parasitic coating has areas of low thickness, namely in the zones vertically above the horizontal spaces 36, and areas of high parasitic coating thickness, in the region between adjacent horizontal spaces 36. This star-shaped structuring of the parasitic coating leads to mechanical stress within the process chamber ceiling when it is heated and cooled during the deposition processes.These stresses can lead to fractures in the process chamber ceiling 5.

[0134] Figures 21 and 22 show alternative embodiments in which the two broad surfaces of the partition plates 21, 22 or of the connecting webs 23 between the partition plates 21, 22 are not parallel to each other. Instead, the broad surfaces are inclined to each other in such a way that the webs 23 or the partition plates 21, 22 31323N1PCT November 3, 2025 Ai 2024-10 The separating plates 21, 22 and the connecting webs 23 taper towards their downstream ends 21", 22", 23". The separating plates 21, 22 and the connecting webs 23 can have their greatest material thickness in the region of the upstream ends 2T, 22', 23'. In the embodiments shown in the drawings, the separating plates 21, 22 and the connecting webs 23 taper in a wedge shape in the direction of flow. However, the tapered section of the separating plates 21, 22 and the connecting webs 23 can also be limited to a section adjacent to the downstream ends 21', 22', 23'.

[0135] In an embodiment not shown, the downstream ends 21", 22", 23" are merely rounded.

[0136] These measures can ensure that vortices form in the area of ​​the ends 21", 22", 23", which each form a downflow edge.

[0137] One object of the invention is therefore also to take measures to increase the service life of the process chamber ceiling 5.

[0138] The invention described above solves this problem.

[0139] Figure 19 shows the effect when, under the same process parameters, separating plates 21, 22 are used whose radial length meets the conditions described above. The backflows observed under the conditions of Figure 18 are completely suppressed. The zone labeled D, in which the parasitic deposits form, is also significantly reduced. The otherwise described structured parasitic coatings on the radially inner edge of the underside of the process chamber ceiling 5 have a completely different appearance. In the area adjacent to the radially inner 31323N1PCT November 3, 2025 Ai 2024-10 Adjacent to the edge, a parasitic coating does form, but it has a smaller layer thickness and only minimal differences in layer thickness in the circumferential direction. A star-shaped structured coating can only be observed further away from the radially inner edge. It also does not exhibit the large differences in layer thickness in the circumferential direction observed without the use of the separating plates 21, 22.

[0140] The following description refers to the embodiments shown in Figures 23 to 32, the reference numerals being defined in List III of Reference Numerals.

[0141] The figures schematically show a CVD reactor known per se, or details of such a CVD reactor, in which the details are limited to the elements essential for explaining the invention.

[0142] A CVD reactor 1 has a housing 22 containing a process chamber 3, which is bounded above by a process chamber ceiling 7 and below by a susceptor 5, 5', 5". The process chamber ceiling 7 and the susceptor 5, 5', 5" can, for example, be made of coated graphite.

[0143] A heating device 6 is arranged below the susceptor 5, 5', 5" for heating the susceptor 5, 5', 5" and the process chamber 3 above it. The heating device 6 can be an RF coil that generates eddy currents within the susceptor 5, 5', 5" to heat it. A shaft 8 supporting the susceptor 5, 5', 5" can be driven by a rotary drive (not shown). A gas outlet device (not shown) is attached around the circumferential edge of the susceptor 5, 5', 5" which forms a circle. 31323N1PCT November 3, 2025 Ai 2024-10 The system is arranged so that gases or decomposition products fed into process chamber 3 can be pumped out of process chamber 3 by means of a vacuum pump (also not shown). A plurality of substrate 4-bearing substrate storage positions 11 are arranged on the susceptor 5, 5', 5".

[0144] The substrate storage locations 11 are arranged in a circular configuration around a gas inlet element 2 located in the center of the process chamber 3. The gas inlet element 2 is preferably made of a material inert to the gases fed into the process chamber 3, for example, quartz. Several gas distribution chambers 18, 18', 18", 18'", 18"" are arranged vertically one above the other in the gas inlet element 2. The gas distribution chambers 18, 18', 18", 18'", 18"" are separated from each other by partitions 20. A gas supply line 10, 10", 10'", 10"" opens into each of the gas distribution chambers 18, 18', 18", 18'", 18"" to introduce a process gas into the gas distribution chamber 18, 18', 18", 18'", 18""". The gas inlet device 2 has a first gas outlet surface 12 extending on the outer surface of a circular cylinder. The first gas outlet surface 12 has a plurality of gas outlet openings 16 through which the process gases can flow into the process chamber 3.At a distance A0, Al, A2 from the first gas outlet surface 12, an upstream edge of the storage areas 11 is arranged.

[0145] Figure 23 shows a first susceptor 5 having a first substrate distance A0. Process gases flowing from the gas outlet zones ZI, Z2, Z3 of the gas inlet device 2 mix in a gas mixing zone 27 that begins at the gas outlet zones ZI, Z2, Z3 and extends in the flow direction S. In the susceptor configuration shown in Figure 23, the upstream zone V0 extends from the first gas outlet surface 12 to the upstream edge of the storage area 11. 31323N1PCT November 3, 2025 Ai 2024-10

[0146] Figure 24 shows a second susceptor 5' having a second substrate distance Al that is greater than the first substrate distance AO of the first susceptor 5 shown in Figure 23. To keep the length of the inlet zone VI, VI constant when exchanging the first susceptor 5 for the second susceptor 5', an extension element 17 is provided according to the invention, which increases the diameter of the gas inlet element 2. This extension element 17 comprises extension plates 15 that connect to the first gas outlet surface 12 of the gas inlet element 2 and thus shift the beginning 27' of the gas mixing zone 27 away from the gas outlet surface 12 in the flow direction S, increasing the distance between the beginning 27' of the gas mixing zone 27 and the gas outlet surface 12.In the susceptor configuration shown in Figure 24, the feed zone VI extends from a downstream end 15", which corresponds to the beginning 27' of the gas mixing zone 27, to the upstream edge of the storage area 11. The diameter of the extension element 17 or the length of the extension plates 15 of the extension element is chosen such that the length of the feed zone V0, VI, V2 does not change when the substrate distance A0, Al, A2 is changed, for example by replacing the susceptor 5, 5', 5".

[0147] Figure 25 shows a further embodiment of the invention. A third susceptor 5" with a third substrate distance A2 is provided. The length of the extension plates 15 of the extension element 17 is longer than in the embodiment shown in Figure 24, since the third substrate distance A2 is greater than the second substrate distance A1. Thus, by means of the extension element 17, the distance from the beginning 27' of the gas mixing zone 27 to the gas outlet surface 12 is increased when the second susceptor 5' shown in Figure 24 is replaced by the third susceptor 5" shown in Figure 25. The use of the extension element 17 keeps the length of the pre-zones V0, VI, V2 shown in Figures 23 to 25 constant. 31323N1PCT November 3, 2025 Ai 2024-10

[0148] The extension plates 15, extending in a horizontal direction, each connect to the separating plates 20 that separate the adjacent gas distribution chambers 18, 18', 18", 18'", 18"". The extension plates 15 assigned to each extension element 15 are preferably of the same length. The extension plates 15 are detachably or permanently connected to the extension element 17. The outer diameter of the gas inlet element 2 is slightly smaller than the inner diameter of the extension element 17, so that the extension plates 15, which are formed as ring-shaped plates, can be slipped onto the gas inlet element 2 for assembly. In the assembled state, an upstream end 15' of the extension plates 15 is arranged slightly spaced from the first gas outlet surface 12. The distance can be, for example, less than 1 mm.

[0149] The process gas flowing from the gas outlet openings 16 arranged in the first gas outlet surface 12 flows through a flow volume arranged between two adjacent extension plates 15. The flow volume can also be arranged between an uppermost extension plate 15 and the process chamber ceiling 7.

[0150] Figure 26 shows a further embodiment of the invention. The extension plates 15 are shown by way of example as ring-shaped plates which are detachably attached to the gas inlet element 2 by means of a bayonet fitting 14 (see Figure 27). However, other fastening means not shown can also be used to attach the extension element 15 to the gas inlet element 2. The substrates 4 arranged on the susceptor 5 have a diameter Dl. An upstream edge of the bearing area 11 is arranged at a distance Al from the first gas outlet surface 12. The extension plates 15 can be detachably attached individually to the gas inlet element 2 or to the first gas outlet surface 12 of the gas inlet element 2. For example 31323N1PCT November 3, 2025 Ai 2024-10 Several extension plates 15 can be attached to the gas inlet device 2 one after the other, with the extension plate 15 located at the top being mounted first.

[0151] The detachable fastening of the extension plates 15 to the gas inlet element 2 allows for easy replacement. The length of the pre-flow zone V0, VI, V2 is optimized for the respective reactor design used. To maintain this optimized pre-flow zone length VI, V2 constant, different extension elements 17 with extension plates 15 of varying lengths can be used. Comparing the fourth embodiment of the invention shown in Figure 28 with the third embodiment shown in Figure 26, the diameter D1 of the substrates 4 in Figure 26 is schematically shown as larger than the diameter D2 of the substrates 4 in Figure 28. Consequently, the distance Al, A2 between the upstream edge of the associated storage positions 11 and the first gas outlet surface 12 differs between these two embodiments.In order to keep the length of the pre-zone VI, V2 constant when replacing the susceptor 5, 5', 5", but otherwise maintaining the same CVD reactor 1, the embodiment of the extension element 17 according to the invention shown in Figure 28 has longer extension plates 15 than the embodiment of the extension element 17 shown in Figure 26. The length VI, V2 can therefore be adjusted by replacing the extension element 17 with extension plates 15 of different lengths in the flow direction S of the process gas.

[0152] Figure 29 shows a further embodiment of the invention. The extension element 17 is depicted as a cylindrical body having a cavity into which the gas inlet element 2 can be inserted. The extension element 17 is attached by fastening means (not shown). 31323N1PCT November 3, 2025 Ai 2024-10 The extension element 17 is attached to the gas inlet device 2. The cylindrical surface of the extension element 17 forms a second gas outlet surface 13, which is arranged coaxially to the first gas outlet surface 12 of the gas inlet device 2. The second gas outlet surface 13 also has gas outlet openings 16' through which the process gases flowing through the extension element 17 are fed into the process chamber 3. The second gas outlet surface 13 is preferably arranged upstream of the upstream edge of the storage area 11.

[0153] The extension plates 15 are preferably rigidly connected to the cylindrical surface 13 of the extension element 17. The height of the cylindrical extension element 17 is slightly less than the distance between the process chamber ceiling 7 and the top of the susceptor 5, so that the cylindrical surface 13 is spaced at one top from the underside of the process chamber ceiling 7 and at one bottom from the top of the susceptor 5. In this way, the process gases do not flow past the gas outlet surface 13 into the process chamber 3.

[0154] The number of gas outlet openings 16 in the first gas outlet surface 12 can differ from the number of gas outlet openings 16' in the second gas outlet surface 13, as illustrated by way of example in Figure 29. The opening area of ​​the gas outlet openings 16 of the first gas outlet surface 12 can also differ from or be the same size as the opening area of ​​the gas outlet openings 16' of the second gas outlet surface 13. The gas outlet openings 16, 16' are arranged on the gas outlet surfaces 12, 13 such that a gas flow that is as homogeneous as possible emerges radially from the respective gas outlet surface 12, 13.

[0155] Figures 30 and 31 show a further embodiment of the invention. The extension organ 17 also has a cylindrical shape. 31323N1PCT November 3, 2025 Ai 2024-10 The body has a cylindrical surface that forms the second gas outlet surface 13. The second gas outlet surface 13 is fixedly connected to the extension plates 15. The extension element 17 has a cavity into which the gas inlet element 2 is inserted, the base of the cylindrical extension element 17 forming a bottom with a base surface 24 on which an end face 23 of the gas inlet element 2 rests. The base surface 24 and the end face 23 are detachably connected by a screw 21 when the extension element 17 is assembled. However, several screws 21 can also be used for fastening. The top surface of the cylindrical extension element 17 forms an opening, with the rim surrounding the opening resting on the underside of the process chamber ceiling 7. The top surface can also be formed by an extension base 15, so that the extension element 17 is gas-tight at the top and bottom.

[0156] The embodiment of the invention shown in Figure 32 differs essentially from the embodiment shown in Figures 30 and 31 in that the gas distribution chambers 18, 18', 18", 18'" each have different heights. Furthermore, the outer diameter of the extension element 17 corresponds approximately to the recess 25 arranged in the surface of the susceptor 5, into which the end face 23 of the gas inlet element 2 projects, so that the underside of the extension element 17 facing the susceptor 5, which forms a step in its edge region, has a greater distance from the bottom of the recess 25 in its edge region than the central region of the extension element 17, which rests against the end face 23 of the gas inlet element. To prevent process gases from the process chamber 3 from entering the recess 25, a sealing ring 19 is provided, which is located in the recess 25.The thickness of the sealing ring 19 corresponds approximately to the distance between the edge area of ​​the base surface 24 of the extension element and the bottom of the recess 25. 31323N1PCT November 3, 2025 Ai 2024-10

[0157] 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:

[0158] A CVD reactor characterized in that the extension plate 4 is connected by a connecting element 20 to a holding device 18 which is attached to the housing 2 or to a housing-fixed component of the CVD reactor 1.

[0159] A CVD reactor characterized in that the holding device 18 supports a process chamber ceiling 3 which limits the process chamber 19 upwards.

[0160] A CVD reactor characterized in that the connecting element 20 is formed by one or more webs extending in a vertical direction.

[0161] A CVD reactor characterized in that the webs 20 are arranged in a common horizontal plane at a fixed division angle to each other and / or that the length of the webs 20 in the horizontal direction corresponds to the length of the extension plate 4 in the horizontal direction.

[0162] A CVD reactor characterized in that each web 20 and / or the extension plate 4 has an upstream end 24 and a downstream end 24', wherein the upstream end 24 is immediately adjacent to the gas outlet wall 7 of the gas inlet device 21, wherein 31323N1PCT November 3, 2025 Ai 2024-10 the downstream end 24' is arranged within a pre-flow zone 22 extending between the gas outlet wall 7 and an upstream edge of a storage space 25 arranged downstream of the gas inlet device 21 and / or that two adjacent webs 20 flank a flow channel which opens into a second gas outlet opening 17, the opening area of ​​which is larger than the opening area of ​​the first gas outlet openings 15 formed by the gas outlet wall 7 of the gas inlet device 21.

[0163] A CVD reactor characterized in that the holding device 18 is detachably attached to the housing 2 or to the housing-fixed component of the CVD reactor 1.

[0164] A CVD reactor characterized in that the extension plate 4, the connecting element 20 and the holding device 18 are formed from a common annular body arranged rotationally symmetrically around the gas inlet element 21.

[0165] A CVD reactor characterized in that the extension plate 4 and the holding device 18 have a central opening through which the gas inlet element can be inserted during assembly, wherein the inner diameter of the extension plate 4 and the holding device 18 is larger than the outer diameter of the gas inlet element 21.

[0166] A method for depositing a layer on a substrate in a process chamber of a CVD reactor 1 according to one of the preceding claims, wherein an inert gas, in particular argon, is fed into the process chamber 21 through the uppermost gas inlet zone ZI and an inert gas and a reactive gas are fed into the process chamber 21 through the further gas inlet zones Z2, Z3 arranged below it. 31323N1PCT November 3, 2025 Ai 2024-10

[0167] A device characterized in that the radial extent L is at least 5% of the horizontal distance AV and at most 20% of the horizontal distance AV, or that the radial extent L is at least 200% of the vertical distance aA and at most 1000% of the vertical distance aal.

[0168] A device characterized in that the molar mass of the gas fed into a topmost flow channel 17 is greater than the molar mass of the gas fed into a lower flow channel 18, 19.

[0169] A device characterized in that the separating plates 21, 22 are attached to the gas inlet element 30 by means of fastening elements 25, 27 engaging in the gas outlet openings 33.

[0170] A device characterized in that the separating plates 21, 22 are connected to each other by one or more vertically extending connecting webs 23 to form a gas separating element 20 which has a central opening in which the gas inlet element 30 is located.

[0171] A device characterized in that the gas inlet element 30 forms several gas outlet fields 31, each separated from one another by vertical free spaces 35 and horizontal free spaces 36, wherein a vertical cooling channel 34 runs in a gas outlet wall 32 between two horizontally spaced gas outlet fields 31 and wherein the separating plates 21, 22 are located at the level of the vertical free spaces 35.

[0172] A device characterized in that the gas inlet element 30 extends in a vertical direction in a gas outlet wall 32 31323N1PCT November 3, 2025 Ai 2024-10 The cooling channels 34 have and the separating plates 21, 22 connecting connecting webs 23 run directly along the cooling channels 34.

[0173] Gas separation element as part of a device, characterized in that two annular separating plates 21, 22 are connected to each other by means of connecting webs 23.

[0174] A device characterized in that the outwardly facing broad surfaces of the separating plates 21, 22 taper or round at least in the area adjacent to the downstream end 21", 22" and / or that connecting webs 23, which connect two superimposed separating plates 21, 22, have an area adjacent to a downstream end 23" which has outwardly facing broad surfaces that taper to a point or are rounded towards the downstream end 23".

[0175] A method characterized in that, when the susceptor 5 is replaced by another susceptor 5' or when another susceptor 5' with a larger substrate distance Al, A2 is used, the distance of the beginning 27' of the gas mixing zone 27 to the first gas outlet surface 12 is changed by means of an extension device 17.

[0176] A system comprising a first susceptor 5 and a second susceptor 5', each having at least one storage location 11 for storing a substrate 4, for use in a method according to claim 1, wherein an upstream edge of the storage location 11 of the first susceptor 5 is spaced at a first substrate distance A0 from the first gas outlet surface 12, and an upstream edge of the storage location 11 of the second susceptor 5' is spaced at a second larger substrate distance A2 from the 31323N1PCT November 3, 2025 Ai 2024-10 first gas outlet surface 12 is spaced apart, and an extension device 17 with which the distance of the beginning 27' of the gas mixing zone 27 to the first gas outlet surface 12 can be changed.

[0177] A system characterized by a second susceptor 5', which has a second larger substrate distance Al, A2 and an extension organ 17, with which a distance of the beginning 27' of the mixing zone 27 to the first gas outlet surface 12 can be changed.

[0178] A method or system characterized in that the extension element 17 has extension plates 15 extending in the direction of flow S, which have an upstream end 15' and a downstream end 15", wherein the upstream end 15' is immediately adjacent to the first gas outlet surface 12.

[0179] A method or system characterized in that the extension element 17 can be detachably attached to the gas inlet element 2 or to another stationary component of the CVD reactor 1.

[0180] A method or system characterized in that the extension plates 15 are connected to each other by connecting elements and / or are components of an extension element 17 that can be detachably attached to the gas inlet element 2 and / or that the extension element 17 has a cylindrical base body with a central opening into which the gas inlet element 2, formed by a substantially cylindrical body, can be inserted. 31323N1PCT November 3, 2025 Ai 2024-10

[0181] A method or system characterized in that a cylindrical shell surface of the extension element 17 forms a second gas outlet surface 13 with a plurality of gas outlet openings 16' through which the process gas can be fed from the extension element 17 into the process chamber 2.

[0182] An extension element characterized in that several superimposed circular disk-shaped extension plates 15 are connected to each other and can be detachably connected to the gas inlet element 2 or to another component fixedly connected to a housing 22 of the CVD reactor 1 by means of fastening elements.

[0183] An extension element characterized in that the extension plates 15 have a common opening for receiving the substantially cylindrical gas inlet element 2.

[0184] 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 characterize, even without the features of a referenced claim, 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- 31323N1PCT November 3, 2025 Ai 2024-10 This also applies to design forms in which individual features mentioned in the above 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. 31323N1PCT November 3, 2025 Ai 2024-10 List I of reference symbols 1 CVD reactor 22 pre-charge zone 2 housings 23 growth zones 3 Process chamber ceiling 24 upstream end 4 V extension plate 24' downstream end 5 flow channel 25 storage space 6 Gas outlet area 26 Support step 6' Gas outlet area 27 Internal thread 6" gas outlet area, 28 external thread 7 Gas outlet wall 8 Gas supply line 8' Gas supply line 8" gas supply line 9 Gas outlet 10 Heating unit ZI Gas outlet zone 11 substrate Z2 gas exit zone 12 Susceptor Z3 Gas outlet zone 13 substrate holders 14 Gas distribution chamber 14' Gas distribution chamber 14" gas distribution chamber 15 first gas outlet 16 shaft 17 second gas outlet opening 18 Holding device 19th Tribunal 20 V connecting element 21 Gas inlet device 31323N1PCT November 3, 2025 Ai 2024-10 List II of reference symbols 1 case 2 Susceptor 3 substrate holders, storage space 4 Substrat 5 Process chamber ceiling 6th Trial Chamber 7 Heating system 8 shaft 11 uppermost gas outlet zone 12 medium gas outlet zone 13 lower gas outlet zone 14 upper gas distribution volume 15 average gas distribution volume 16 lower gas distribution volume 17 upper flow channel 18 middle flow channel 19 lower flow channel 20 Gas separator 21 upper partition plate 21' upstream end 21" downstream end 22 lower partition plate 22' upstream end 22" downstream end 23 Connecting bridge 23' upstream end 31323N1PCT November 3, 2025 Ai 2024-10 23" downstream end 24 Gas passage zone 25 Fastening element, pin 25' shaft 25" head 26 Niche 26' rib 27 wire, fastening element 27' first section 27" second section 27'" third section 28 Opening 29th rib 29' niche 30 Gas inlet device 31 Gas outlet field 32 Gas outlet wall 33 Gas outlet opening 34 Cooling channel 35 vertical free space 36 horizontal free space A distance Zone B Bl Zone B2 Zone Cl Arrow 31323N1PCT November 3, 2025 Ai 2024-10 C2 arrow L radial extent V Inlet zone, distance a, distance b, distance pl, pressure p2, pressure p3, pressure ul, flow velocity u2, flow velocity u3, flow velocity vl, flow velocity v2, flow velocity v3, flow velocity 31323N1PCT November 3, 2025 Ai 2024-10 List III of reference symbols 1 CVD reactor 18'" gas distribution volume 2 Gas inlet device 18"" Gas distribution volume 3 Process chamber 19 Buffer element 4 substrate 20 separating layer 5 Susceptor 21 Screw 5' Susceptor 22 housing 5" Susceptor 23 Front surface 6 Heating system 24 Floor area 7 Process chamber ceiling 25 Recess 8 shaft 26 rim 9 substrate holders 27 gas mixing zone 10 Gas supply line 27' Start of gas mixing zone 10' Gas supply line VI Flow zone 10" Gas supply line V2 Flow zone 11 Storage space AO Substrate spacing 12 First gas outlet surface Al substrate distance 13 second gas outlet surface A2 substrate distance 14 Support element D Axis of rotation 15 Extension plate DO diameter substrate 15' upstream end DL diameter substrate 15" downstream end D2 diameter substrate 16 Gas outlet opening S Flow direction 16' Gas outlet opening ZI Gas outlet zone 17 Extension organ Z2 Gas outlet zone 18 Gas distribution volume Z3 Gas outlet zone 18' Gas distribution volume Z4 Gas outlet zone 18" gas distribution volume Z5 gas outlet zone 31323N1PCT November 3, 2025 Ai 2024-10

Claims

73 Claims 1. CVD reactor (1) with a housing and a gas inlet element (21) contained therein, the gas inlet element having an uppermost gas inlet zone (ZI) and at least one further gas inlet zone (Z2, Z3) arranged below it, each having a gas outlet surface (6, 6', 6") with first gas outlet openings (15) for feeding a gas into a process chamber (19), and with an extension plate (4) arranged in the process chamber (19) between the upper gas inlet zone (ZI) and the further gas inlet zone (Z2) arranged below it, directly adjacent to the gas inlet element (21) for spatially separating the gases flowing through the upper gas inlet zone (ZI) and through the further gas inlet zone (Z2) arranged below it, characterized in that the extension plate (4) is connected by a connecting element (20) to a holding device (18) which is attached to the housing (2) or to a housing-fixed component of the is attached to the CVD reactor (1).

2. CVD reactor (1) according to claim 1, characterized in that the holding device (18) supports a process chamber ceiling (3) which limits the process chamber (19) upwards.

3. CVD reactor (1) according to one of the preceding claims, characterized in that the connecting element (20) is formed by one or more webs extending in a vertical direction.

4. CVD reactor (1) according to claim 3, characterized in that the webs (20) are arranged in a common horizontal plane at a fixed division angle to each other and / or that the length of the 31323N1PCT November 3, 2025 Ai 2024-10 74 The length of the extension plate (4) in the horizontal direction corresponds to the length of the webs (20) in the horizontal direction.

5. CVD reactor (1) according to one of claims 3 to 5, characterized in that each web (20) and / or the extension plate (4) has an upstream end (24) and a downstream end (24'), wherein the upstream end (24) is immediately adjacent to the gas outlet wall (7) of the gas inlet device (21), wherein the downstream end (24') is arranged within a pre-flow zone (22) extending between the gas outlet wall (7) and an upstream edge of a storage space (25) arranged downstream of the gas inlet device (21), and / or that two adjacent webs (20) flank a flow channel which opens into a second gas outlet opening (17) whose opening area is larger than the opening area provided by the gas outlet wall (7) of the gas inlet device. (21) formed first gas outlet openings (15).

6. CVD reactor (1) according to one of the preceding claims, characterized in that the holding device (18) is detachably attached to the housing (2) or to the housing-fixed component of the CVD reactor (1).

7. CVD reactor (1) according to one of the preceding claims, characterized in that the extension plate (4), the connecting element (20) and the holding device (18) are formed from a common annular body arranged rotationally symmetrically around the gas inlet element (21). 31323N1PCT November 3, 2025 Ai 2024-10 75 8. CVD reactor (1) according to one of the preceding claims, characterized in that the extension plate (4) and the holding device (18) have a central opening through which the gas inlet element can be inserted during assembly, wherein the inner diameter of the extension plate (4) and the holding device (18) is larger than the outer diameter of the gas inlet element (21).

9. Method for depositing a layer on a substrate in a process chamber of a CVD reactor (1) according to one of the preceding claims, wherein an inert gas, in particular argon, is fed into the process chamber (21) through the uppermost gas inlet zone (ZI) and an inert gas and a reactive gas are fed into the process chamber (21) through the further gas inlet zones (Z2, Z3) arranged below it.

10. Device comprising a housing (1) comprising a process chamber (6) arranged between a process chamber ceiling (5) and a susceptor (2) with a storage space (3) for receiving the substrate (4), a gas inlet element (30) arranged in a center of the process chamber (6) for feeding a process gas into the process chamber (6), and a heating device (7) for heating the process chamber (6), wherein the gas inlet element (30) has several vertically arranged gas distribution volumes (14, 15, 16) through whose gas outlet openings (33) leading into the process chamber (6) different reactive gases and / or inert gases can be fed into the process chamber (6), wherein the gas outlet openings (33) extend in a gas outlet wall (32) adjacent to the process chamber (6), each with a location where the gas outlet openings (33) The gas distribution volumes (14, 15, 16) of different sizes are adjacent to each other, with separating plates (21,22), which have a radial extent (L) and, 31323N1PCT November 3, 2025 Ai 2024-10 76 between each other or between themselves and the process chamber ceiling (5) and the susceptor (2) each form a flow channel (17, 18, 19), the respective upstream end (21', 22') of which is immediately adjacent to the gas outlet wall (32) of the gas inlet device (30) and the respective upstream end (21'', 22'') of which lies within a pre-flow zone extending between the gas outlet wall (32) and an upstream edge of the storage space (3), wherein the upstream end (21', 22') has a horizontal distance (A) from the upstream edge of the storage space (3), wherein a lowest gas outlet opening (33) of a gas outlet field (31) of a gas outlet zone (11, 12) arranged immediately above the partition plate (21, 22) has a vertical distance (a) from an uppermost gas outlet opening (33) of a gas outlet field (31) of a gas outlet zone (12, 13) arranged directly below the separating plate (21, 22),characterized in that the radial extent (L) is at least 5% of the horizontal distance (A) and at most 20% of the horizontal distance (A) or that the radial extent (L) is at least 200% of the vertical distance (a) and at most 1000% of the vertical distance (a).

11. Device according to claim 10, characterized in that the molar mass of the gas fed into a flow channel (17) arranged at the top is greater than the molar mass of the gas fed into a flow channel (18, 19) below.

12. Device with a housing (1) comprising a process chamber (6) arranged between a process chamber ceiling (5) and a susceptor (2) with a storage space (3) for receiving the substrate (4), and a gas inlet device (30) for supplying a process gas into the process chamber (6) 31323N1PCT November 3, 2025 Ai 2024-10 77 and a heating device (7) for heating the process chamber (6), wherein the gas inlet element (30) has several vertically arranged gas distribution volumes (14, 15, 16) through whose gas outlet openings (33) leading into the process chamber (6) different reactive gases and / or inert gases can be fed into the process chamber (6), with separating plates (21, 22) arranged at a point where the gas outlet openings (33) of different gas distribution volumes (14, 15, 16) adjoin each other, which have a radial extension (L) and form a flow channel (17, 18, 19) between each other and between themselves and the process chamber ceiling (5) and the susceptor (2), the respective upstream end (21', 22') of which is directly adjacent to the gas inlet element (30). is and whose respective downstream end (21", 22") has a distance (V) from the storage place (3), characterized by,that the separating plates (21, 22) are attached to the gas inlet element (30) by means of fastening elements (25, 27) engaging in the gas outlet openings (33).

13. Device according to one of claims 10 to 12, characterized in that the separating plates (21, 22) are connected to each other by one or more connecting webs (23) extending in a vertical direction to form a gas separation element (20) which has a central opening in which the gas inlet element (30) is located.

14. Device according to one of claims 11 or 13, characterized in that the gas inlet element (30) forms several gas outlet fields (31) separated from each other by vertical free spaces (35) and horizontal free spaces (36), wherein between two horizontally separated 31323N1PCT November 3, 2025 Ai 2024-10 78 spaced gas outlet fields (31) each have a vertical cooling channel (34) running in a gas outlet wall (32) and the separating plates (21, 22) are located at the level of the vertical free spaces (35).

15. Device according to one of claims 10 or 14, characterized in that the gas inlet element (30) has cooling channels (34) extending vertically in a gas outlet wall (32) and connecting webs (23) connecting the partition plates (21, 22) run directly along the cooling channels (34).

16. Gas separation element (20) as part of a device according to one of claims 10 to 15 characterized in that two annular separating plates (21, 22) are connected to each other by means of connecting webs (23).

17. Device according to one of the preceding claims 10 or 14 to 16, characterized in that the outwardly facing broad surfaces of the separating plates (21, 22) taper or round at least in the area adjacent to the downstream end (21", 22") and / or that connecting webs (23) connecting two separating plates (21, 22) arranged one above the other have an area adjacent to a downstream end (23") which has outwardly facing broad surfaces that taper to a point or are rounded towards the downstream end (23").

18. Method for operating or manufacturing a CVD reactor (1) comprising at least the following components: a susceptor (5) with a storage space (11) for a substrate (4), a process chamber (3) arranged between the susceptor (5) and a process chamber ceiling (7), and a 31323N1PCT November 3, 2025 Ai 2024-10 Gas inlet device (2) with a first gas outlet surface (12), wherein an upstream edge of the storage area (11) is spaced a substrate distance (AO) from the first gas outlet surface (12) of the gas inlet device (2) or an edge (26) of the susceptor (5) in a flow direction (S), wherein process gases are fed into the process chamber (3) separately from one another by several vertically arranged gas outlet zones (ZI, Z2, Z3, Z4, Z5), which mix with one another in a gas mixing zone (27) beginning at the gas outlet zones (ZI, Z2, Z3, Z4, Z5) and extending in the flow direction (S) and flow to the substrate (4) through a pre-flow zone (VI, V2) beginning at a beginning (27') of the gas mixing zone (27) and ending at the upstream edge of the storage area (11), characterized in that that if the susceptor (5) is replaced with another susceptor (5 Z ) or when using a different susceptor (5 Z) with a larger substrate distance (Al, A2) the distance of the beginning (27') of the gas mixing zone (27) to the first gas outlet surface (12) is changed by means of an extension device (17).

19. System consisting of a first susceptor (5) and a second susceptor (5 Z ), each having at least one storage location (11) for storing a substrate (4) for use in a method according to claim 18, wherein an upstream edge of the storage location (11) of the first susceptor (5) is spaced at a first substrate distance (AO) from the first gas outlet surface (12) and an upstream edge of the storage location (11) of the second susceptor (5) Z ) is spaced at a second larger substrate distance (A2) from the first gas outlet surface (12), and an extension device (17) with which the distance of the beginning (27') of the gas mixing zone (27) to the first gas outlet surface (12) can be changed. 31323N1PCT 3. November 2025 Ai 2024-10 20. System comprising a CVD reactor (1) comprising at least the following components: a first susceptor (5) with a storage space (11) for a substrate (4), a process chamber (3) arranged between the first susceptor (5) and a process chamber ceiling (7), and a gas inlet device (2) with a first gas outlet surface (12), wherein in a flow direction (S) an upstream edge of the storage space (11) is spaced at a first substrate distance (A0) from the first gas outlet surface (12) of the gas inlet device (2) or an edge (26) of the first susceptor (5), wherein process gases can be fed separately into the process chamber (3) through several vertically arranged gas outlet zones (ZI, Z2, Z3, Z4, Z5), which are located at the gas outlet zones (ZI, Z2, Z3, Z4,gas mixing zone (27) beginning at Z5) and extending in the flow direction (S) mix with each other and flow through a pre-flow zone (VI, V2) beginning at a beginning (27') of the gas mixing zone (27) and ending at the upstream edge of the storage area (11) to the substrate (4), characterized by a second susceptor (5, Z ), which has a second larger substrate distance (Al, A2) and an extension organ (17) with which the distance of the beginning (27') of the mixing zone (27) to the first gas outlet surface (12) can be changed.

21. Method according to claim 18 or system according to one of claims 19 or 20, characterized in that the extension element (17) has extension plates (15) extending in the direction of flow (S), which have an upstream end (15') and a downstream end (15"), wherein the upstream end (15') is immediately adjacent to the first gas outlet surface (12). 31323N1PCT November 3, 2025 Ai 2024-10 22. Method or system according to one of claims 18 to 21, characterized in that the extension organ (17) can be detachably attached to the gas inlet organ (2) or to another stationary component of the CVD reactor (1).

23. Method or system according to one of claims 21 or 22, characterized in that the extension plates (15) are connected to each other by connecting elements and / or are components of an extension element (17) that can be detachably attached to the gas inlet element (2) and / or that the extension element (17) has a cylindrical base body with a central opening into which the gas inlet element (2) formed by a substantially cylindrical body can be inserted.

24. Method or system according to claim 23, characterized in that a cylindrical shell surface of the extension element (17) forms a second gas outlet surface (13) with a plurality of gas outlet openings (16') through which the process gas can be fed from the extension element (17) into the process chamber (3).

25. Extension element for carrying out a method according to claim 23 or 24, characterized in that several circular disc-shaped extension plates (15) arranged one above the other are connected to each other and can be detachably connected to the gas inlet element (2) or to another component fixedly connected to a housing (22) of the CVD reactor (1) by means of fastening elements. 31323N1PCT November 3, 2025 Ai 2024-10 26. Extension element according to claim 25, characterized in that the extension plates (15) have a common opening for receiving the substantially cylindrical gas inlet element 2.

27. Device or method characterized by one or more of the characterizing features of one of the preceding claims. 31323N1PCT November 3, 2025 Ai 2024-10

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