Method and device for cleaning a CVD reactor

Abstract

The invention relates to a device and a method for depositing semiconductor layers in a process chamber (3), wherein cleaning gases are fed into the process chamber (3) in a cleaning method after a depositing step in which a process chamber ceiling (5) bears at least in regions against a gas outlet surface (9) and a layer is deposited on a floor of the process chamber (3). Before a first cleaning step, the process chamber ceiling is brought vertical to the gas outlet surface (9) at a distance from the gas outlet surface (9). The distance between the heated floor (2) and the process chamber ceiling (5) is reduced. Parasitic deposits on the process chamber ceiling (5) are removed by feeding in chlorine. In a second cleaning step, ammonia is introduced into the process chamber. During a third cleaning step, hydrogen is fed into a gap between the gas outlet surface (9) and the process chamber (5) in order to remove parasitic deposits there.

Description

Description of method and device for cleaning a CVD reactor. Field of technology.

[0001] Die Erfindung betrifft ein Verfahren zum Reinigen von Oberflächen in a process chamber of a CVD reactor by means of purification gases introduced into the process chamber, wherein the process chamber is bounded below by a process chamber floor and above by a height-adjustable process chamber ceiling, wherein the floor is heated by a heating device, with a gas inlet device for introducing gases into the process chamber, wherein a gas outlet surface of the gas inlet device facing the process chamber is cooled by means of a cooling element, and a device for carrying out the method. Prior art

[0002] Beim Abscheiden von Schichten auf einem auf dem Boden einer Pro-In the process chamber of a CVD reactor, the substrate is pyrolytically reacted with process gases fed into the chamber via a gas inlet. The resulting solid crystallizes on the substrate. Parasitic growth on the surfaces within the process chamber exposed to the process gas, such as the surface of the process chamber floor surrounding the substrate or on the process chamber ceiling, is unavoidable. The contaminants caused by such parasitic growth form consumption surfaces for the gas fed into the process chamber. This reduces the efficiency of the process and impairs the growth behavior of the layer to be deposited on the substrates. It is therefore necessary to clean the process chamber and, in particular, the surfaces within the process chamber affected by parasitic growth. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0003] Aus der DE 102006018515 A1 ist ein Verfahren und eine VorrichtungA known method for cleaning surfaces within a process chamber of a CVD reactor involves feeding an etching gas, for example HCl, into the process chamber as a cleaning gas. The process chamber is bounded above by a height-adjustable process chamber ceiling and below by a heated process chamber floor designed as a susceptor. During the deposition process, the process chamber ceiling is in contact with a cooled gas outlet surface of the gas inlet device. To raise the surface temperature of the process chamber ceiling to the high level necessary for cleaning, the ceiling is moved away from the cooled gas outlet surface of the gas inlet device by shifting it towards the heated process chamber floor. The surface of the process chamber floor and the surface of the process chamber ceiling are etched together in a single cleaning step.

[0004] Die DE 102011056589 A1 offenbart ebenfalls ein Verfahren und eineDevice for cleaning a process chamber with a vertically and horizontally movable process chamber ceiling that is thermally decoupled from the gas outlet surface. For cleaning, the process chamber ceiling is moved away from the gas outlet surface of the gas inlet. This allows the process chamber ceiling to be heated to temperatures above 500°C. HCl, along with a carrier gas, such as N2 or H2, is fed into the process chamber as the cleaning gas.

[0005] Auch die US 2013 / 005118 A1 beschreibt ein Verfahren zur Reinigung The process chamber of a CVD reactor, in which the process chamber height is changed during a cleaning step. Cl₂ is used as the cleaning gas. In a first cleaning step, the process chamber floor is cleaned. For this purpose, the process chamber floor is moved vertically to a distance of approximately 25 mm from the gas outlet surface. For a da-31281N1PCT drg / gz May 2, 2025 Ai 2024-06 In the second cleaning step, which cleans the gas outlet surface, the process chamber floor is moved towards the gas outlet surface. The distance between the gas outlet surface and the process chamber floor is smaller than during the first cleaning step and is approximately 10 mm. The process chamber pressure during the cleaning steps can range between 6 Torr and 50 Torr, with chloride formation occurring at high process chamber pressures. To improve chlorine sublimation and remove some of the chlorine from the process chamber, a baking step is performed after the chlorine-based cleaning steps, during which H₂ is introduced into the process chamber.

[0006] Die WO 2013 / 033428 A2 beschreibt ebenfalls einen Reinigungsschritt, in which chlorine is fed into the process chamber and a subsequent baking step in which H2 is introduced into the process chamber to remove residual chlorine-containing cleaning gas.

[0007] Die US 2012 / 0000490 A1 offenbart einen mit einem Kühlmittel kühlba-The invention includes a gas inlet device designed as a showerhead. The temperature of the showerhead can be controlled by monitoring the temperature of the coolant. Showerhead temperatures are reported to range from 50°C to 550°C. Cl₂ is disclosed as the cleaning gas. The process chamber pressure during a cleaning step can range from 1 Torr to 100 Torr. Summary of the invention

[0008] Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine To provide a device for cleaning the surfaces of a process chamber of a CVD reactor. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0009] Die Aufgabe wird durch das in den Ansprüchen angegebene Verfahren or the claimed device is solved. 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.

[0010] Den mehreren Reinigungsschritten geht ein Abscheideschritt voraus,in which a layer is deposited onto a substrate arranged on the floor of the process chamber. During the deposition step, the process chamber ceiling is spaced apart from the floor. However, the process chamber ceiling is in direct contact with the gas outlet surface, at least in some areas, so that radiant heat transferred from the heated floor to the process chamber ceiling is dissipated to a cooling element, which cools the gas outlet surface or the gas inlet. Due to the physical contact between the process chamber ceiling and the cooled gas outlet surface, a significant amount of heat transfer occurs from the process chamber ceiling to the gas outlet surface during the deposition step. The temperature of the process chamber ceiling can be less than 350°C. The floor can be spaced between 10 and 13 mm, preferably 11 mm, away from the process chamber ceiling.

[0011] Zum Reinigen der Prozesskammer wird zunächst und im WesentlichenIt is proposed that the cleaning process includes at least two cleaning steps. A cleaning gas, together with a carrier gas, is introduced into the process chamber through gas inlet openings located in the gas outlet surface at a specific bottom temperature, process chamber pressure, and process chamber ceiling temperature. The process chamber ceiling is positioned in a specific location. In this position, the process chamber ceiling can be at a distance from the gas outlet surface. The process chamber ceiling temperature in this position is higher than the process chamber ceiling temperature during the 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 At the end of the separation step, the process chamber ceiling no longer has direct contact with the cooled gas outlet surface. The cleaning gas reacts with parasitic coatings on the process chamber ceiling to form reaction products. Afterwards, and especially immediately afterwards, the floor temperature is increased and, if necessary, the process chamber pressure is reduced. A different cleaning gas is then introduced into the process chamber through the gas inlet openings at a higher process chamber ceiling temperature. The process chamber ceiling can maintain the same distance from the gas outlet surface, preferably between 0.5 mm and 2 mm, and preferably about 1 mm. However, the process chamber ceiling can also have a smaller distance from the gas outlet surface. This other cleaning gas removes parasitic deposits, at least at the gas outlet surface.The process chamber ceiling, positioned a short distance from the gas outlet surface, can act as a flow guide, directing the other cleaning gas along the outlet surface. The reduced overall pressure influences heat transfer between the gas outlet surface and the process chamber ceiling. The distance between the process chamber ceiling and the gas outlet surface is preferably at least large enough to prevent heat transfer via conduction through contact points or surfaces, but not large enough to allow reaction products to flow into the space between the process chamber ceiling and the gas outlet surface during the cleaning step. This cleaning step can be performed with a reduced distance between the process chamber ceiling and the floor. This distance can be in the range of 4 to 10 mm, and preferably between 4 and 6 mm or 5 mm.It is advantageous if the process chamber ceiling can assume two vertical positions. In the first vertical position, the process chamber ceiling rests against the gas outlet surface. In the second vertical position, the process chamber ceiling has the previously described gap. A stop can be provided against which the process chamber ceiling rests in the second vertical position. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 The process chamber ceiling can be repositioned using pins that extend from above through the gas inlet and to which the ceiling is attached. Alternatively, the floor can be vertically repositioned to change the distance between the floor and the ceiling. During the first cleaning step, which can last several minutes, for example, 5 minutes, the process chamber ceiling temperature exceeds 550°C. The floor temperature can range between 850°C and 900°C, with 890°C being a typical value. During this first cleaning step, parasitic coatings are removed from the side of the ceiling panel facing the process chamber and from the floor by a chemical reaction that produces volatile reaction products.

[0012] Gemäß einer bevorzugten Weiterbildung der Erfindung wird vorge-It is proposed that in the first cleaning step, chlorine and nitrogen are introduced into the process chamber, and that in a subsequent cleaning step, ammonia and hydrogen are introduced. This second cleaning step can be carried out at an increased floor temperature. The floor temperature is increased, for example, by 100 to 150 K. A typical value is 1050°C. During the second cleaning step, the distance between the floor and the process chamber ceiling can be increased, for example, to 8 to 10 mm. The process chamber ceiling temperature is greater than 500°C during the second cleaning step. The distance between the process chamber ceiling and the gas outlet surface preferably remains unchanged. Carbon deposits are removed during the second cleaning step. The duration of the second cleaning step can also be several minutes, for example, 2 to 5 minutes, or preferably 3 minutes.

[0013] An diesem zweiten Reinigungsschritt kann sich ein dritter Reinigungs-Follow the next step, in which only hydrogen is fed into the process chamber. The floor temperature, the distance between the floor and the process chamber- 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 The ceiling and the distance between the process chamber ceiling and the gas outlet surface can remain unchanged. They can be selected such that the process chamber ceiling temperature is greater than 400°C. During the third cleaning step, parasitic coatings that were deposited on the back side of the process chamber ceiling facing the gas outlet surface and on the gas outlet surface itself during the first and / or second cleaning steps are removed. The third cleaning step can last several minutes, for example, 3 to 10 minutes, or preferably 5 minutes.

[0014] Gemäß einer alternativen Weiterbildung kann vor dem ersten Reini-In the first cleaning step, a further cleaning step is carried out, which then constitutes a first cleaning step. The previously described further cleaning step, in which the other cleaning gas is fed into the process chamber, can then be a fourth cleaning step. It is thus further intended that the surfaces of a process chamber of a CVD reactor, which is bounded below by a process chamber floor and above by a height-adjustable process chamber ceiling, are to be cleaned in several successive cleaning steps. A first cleaning step is provided in which a first cleaning gas together with a first carrier gas is fed into the process chamber through a gas inlet device located above the process chamber ceiling.

[0015] Das Gaseinlassorgan kann ein Showerhead sein, der eine zur Prozess-The gas outlet surface of the gas inlet device is cooled by a cooling element. This cooling element can, for example, be a cooling chamber through which a liquid coolant flows. It is specifically designed that the temperature of the gas outlet surface of the gas inlet device is controlled by the temperature of the coolant. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0016] Während des ersten Reinigungsschrittes kann insbesondere der alsThe process chamber floor, formed by a susceptor, is cleaned. The first cleaning gas can react with the first decomposition products of a process gas previously introduced into the process chamber, for example, a metal-organic compound and / or a hydride, which are deposited on a parasitic coating on the upper surface of the floor facing the process chamber. These first gaseous reaction products can be transported out of the process chamber, at least partially, by means of the first carrier gas. This requires a specific temperature on the upper surface of the process chamber floor facing the process chamber. The process chamber floor can be heated to the initial floor temperature required for cleaning by means of a heating device.

[0017] Die erste Bodentemperatur kann bevorzugt größer als 900°C betragen.The process chamber pressure during the first cleaning step can be greater than 50 mbar and less than 200 mbar, preferably 100 mbar. The temperature of the coolant introduced into the cooling chamber can preferably be greater than 50°C and less than 100°C. The first cleaning gas can, in particular, be a chlorine-containing gas, for example Cl₂. The first carrier gas can, in particular, be an inert gas, preferably nitrogen (N₂).

[0018] Die parasitäre Beschichtung kann die Elemente der Prozessgase auf- indicate substances that were fed into the process chamber in the previous coating process, for example Ga, Al, C.

[0019] Die Prozesskammerdecke kann während des ersten Reinigungsschrittes It must be arranged in a first position in which the upper surface of the process chamber ceiling is in a heat-transferring functional connection with the cooled gas outlet surface. The process chamber ceiling can be in the first position 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 The cooled gas outlet surface of the gas inlet device must be shielded from the gases fed into the process chamber. Preferably, the upper surface of the process chamber ceiling is in thermally conductive contact with the gas outlet surface. However, it can also be at a slight distance from it.

[0020] Es kann eine Boden- oder Deckenhalterung vorgesehen sein, um die The process chamber ceiling or floor is held within the reactor housing. One or both of these supports can be moved vertically, thus changing the distance between the process chamber ceiling and the floor. During the first cleaning step, the vertical distance between the process chamber ceiling and the process chamber floor can be at its maximum.

[0021] Die Prozesskammerdecke kann im Wesentlichen nur durch die vomThe process chamber floor is heated by the outgoing radiation. Therefore, the temperature of the process chamber ceiling during the first cleaning step can be lower than the temperature of the process chamber floor, particularly lower than 900°C, for example, between 400°C and 600°C. Consequently, parasitic deposits can form on the underside of the process chamber ceiling, which is cooler than the susceptor temperature and faces the process chamber, during the first cleaning step. For example, the first decomposition products can condense on the underside of the process chamber ceiling. If a chlorine-containing cleaning gas is used as the first cleaning gas, the first decomposition products may be chlorides.However, parasitic deposits can also form on other surfaces within the process chamber that are cooler than the top of the susceptor during the first cleaning step. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0022] In einem zweiten Reinigungsschritt wird über das Gaseinlassorgan einA second cleaning gas, together with a second carrier gas, is fed into the process chamber at a second plate temperature and a second process chamber pressure. The second plate temperature can essentially correspond to the first plate temperature. However, the second plate temperature can also be a different value. As in the first cleaning step, the second cleaning gas can preferably be a chlorine-containing gas, for example, Cl₂. The second carrier gas can, for example, be an inert gas, preferably nitrogen (N₂). The mass flow rate of the first cleaning gas and the second cleaning gas, respectively, and the mass flow rate of the first and second carrier gas, respectively, can be selected such that the concentration of the first and second cleaning gas in the first and second carrier gas, respectively, is between 4% and 6%, preferably 5%.

[0023] Die Reinigung der Unterseite der Prozesskammerdecke, insbesondereThe removal of parasitic coatings deposited during a previous coating process requires an increased surface temperature of the process chamber ceiling. To heat the process chamber ceiling to the required temperature, it is moved to a second position for the second cleaning step, where it is spaced further away from the gas outlet surface. This can be achieved by moving the process chamber ceiling towards the process chamber floor. The second floor temperature can preferably be essentially the same as the first floor temperature. To further increase the temperature of the process chamber ceiling, the process chamber floor can also be moved towards the process chamber ceiling.The distance between the process chamber ceiling and the process chamber floor can preferably be smaller in the second cleaning step than the distance between the process chamber ceiling and the process chamber floor in the first cleaning step. The second process chamber ceiling temperature can therefore be higher. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06. be higher than the first process chamber ceiling temperature, especially higher than 700°C.

[0024] In dieser Abstandsstellung zum Gaseinlassorgan entfaltet die bevor- The process chamber ceiling, formed by a perforated thin plate extending over the entire gas outlet surface or susceptor, acts as a flow barrier between an upper region of the space between the gas inlet and the floor and a lower region of this space. The second cleaning gas thus exerts its effect primarily in the upper region of the space.

[0025] Während des zweiten Reinigungsschrittes kann das zweite Reinigungs-The gas reacts with at least one parasitic coating on the process chamber ceiling to form secondary reaction products. These secondary reaction products can be partially removed from the process chamber by means of the second carrier gas. Furthermore, the secondary reaction products can also be deposited as a parasitic coating on surfaces that are cooler than the temperature of the susceptor's top surface. Since the showerhead is no longer shielded by the process chamber ceiling during the second cleaning step, parasitic deposits can also form on the underside of the showerhead, i.e., on the gas outlet surface. For example, parasitic coatings can also form on the back side of the process chamber ceiling facing the gas outlet surface. If the second cleaning gas contains chlorine, the parasitic deposits may contain chlorides.

[0026] In Betracht kommen hier Chloride der Reaktanten des vorangegange-a coating process, for example chlorides containing Ga, N, C or Al. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0027] An den zweiten Reinigungsschritt kann sich direkt ein vierter Reini- connect the next step.

[0028] Um die parasitären Ablagerungen, die während des ersten und / oderTo remove the residues generated during the second cleaning step, particularly at the gas outlet surface, a fourth cleaning step is provided in which a fourth cleaning gas, in particular a hydrogen-containing gas or pure hydrogen, is introduced into the process chamber. The process chamber ceiling can be arranged in a fourth position in which it is spaced a third distance from the gas outlet surface. This third distance can be smaller than the first distance, and preferably smaller than a second distance that the process chamber ceiling assumes in a third position during an optional third cleaning step. The third distance is smaller than the distance during the second or third cleaning step in order to increase the heat input into the gas outlet surface of the gas inlet organ during the fourth cleaning step.The increased heat input into the showerhead raises the temperature of the gas outlet surface, thus facilitating the removal of parasitic deposits. This can, for example, accelerate the evaporation of decomposition products condensed on the gas outlet surface. To support the removal process of parasitic deposits, particularly on the gas outlet surface, process parameters such as pressure and temperature are adjusted to minimize the partial pressure of the gases introduced into the process chamber during the fourth cleaning step. This is achieved by reducing the process chamber pressure and increasing the mass flow rates of the gases (fourth cleaning gas) fed into the process chamber.A high total mass flow rate combined with a low total pressure is crucial for removing parasitic deposits that form at the gas outlet surface during the first and / or second cleaning steps. 31281N1PCT drg / gz 2 May 2025 Ai 2024-06. The pressure in the fourth process chamber can be set to a value lower than the pressure in the third process chamber, in particular lower than 50 mbar and higher than 30 mbar, preferably 35 mbar. The total mass flow rate of the fourth cleaning gas and the fourth carrier gas can in particular preferably be higher than 80 slm.

[0029] Die vierte Bodentemperatur kann höher als die erste und / oder zweite The base temperature should be between 1000°C and 1200°C. At base temperatures higher than 1200°C, the use of hydrogen as a fourth purification gas can etch the surface of the susceptor. Therefore, a base temperature below 1200°C is preferable.

[0030] Die Wärmeleitfähigkeit bei Standardbedingungen der Gase in der Pro-The thermal conductivity of the process chamber during the fourth cleaning gas step can be higher than that of the gases under standard conditions during the optional third cleaning step. This results in a higher heat input into the showerhead during the fourth cleaning step than during the third, which can cause the third process chamber ceiling temperature to be higher than the fourth process chamber ceiling temperature. Specifically, the fourth process chamber ceiling temperature can be greater than 800°C and less than 1200°C.

[0031] Die Erfindung sieht darüber hinaus den optionalen dritten Reinigungs-A third cleaning step is performed as an intermediate step between the second and fourth cleaning steps to remove further parasitic deposits, particularly those containing carbon, from the surfaces of the process chamber. During the third cleaning step, a third cleaning gas, along with a third carrier gas, is introduced into the process chamber at a third bottom temperature and a third reactor pressure. 31281N1PCT drg / gz 2 May 2025 Ai 2024-06 The third cleaning gas can preferably be a gas containing ammonia (NH3). In the first phase of the third cleaning step, the third cleaning gas can be fed into the process chamber together with N2. In a second phase following the first phase, the third cleaning gas can be fed into the process chamber together with hydrogen (H2).

[0032] Die dritte Bodentemperatur kann bevorzugt höher sein als die erste and / or a second soil temperature, in particular greater than 1000°C, preferably greater than 1200°C.

[0033] Die Prozesskammerdecke kann in einer dritten Position angeordnetThe distance between the process chamber ceiling and the gas outlet surface is smaller than the distance between the process chamber ceiling and the gas outlet surface during the second cleaning step. The distance between the process chamber ceiling and the process chamber floor can be larger than in the second cleaning step. Therefore, the temperature of the process chamber ceiling during the third cleaning step can be lower than the temperature of the process chamber ceiling during the second cleaning step. For example, the third process chamber ceiling temperature can be between 400°C and 600°C. The third reactor pressure can be greater than 50 mbar and less than 100 mbar, preferably 50 mbar.

[0034] Während der zuvor genannten Reinigungsschritte wird die TemperaturThe temperature of the coolant flowing through the cooling chamber is selected such that the showerhead temperature reaches a maximum value in order to reduce or prevent parasitic deposits on the gas outlet surface. The coolant temperature is limited by the inlet and outlet temperatures. The inlet temperature can determine the minimum value, and the outlet temperature can determine the maximum value. The maximum value can be 75°C. [The coolant temperature 31281N1PCT drg / gz 2 May 2025 Ai 2024-06] The temperature during the fourth cleaning step may be higher than during the first and / or second cleaning step in order to increase the evaporation rate of the decomposition products condensed on the underside of the gas outlet surface.

[0035] Darüber hinaus ist ein weiteres Ausführungsbeispiel der ErfindungThe system is designed in which, in a growth process preceding the previously described cleaning steps, a layer, in particular a III-V layer, is deposited on a substrate arranged on the susceptor. Process gases, in particular organometallic gallium compounds and / or aluminum compounds and ammonia together with a carrier gas, preferably hydrogen, can be introduced into the process chamber through the gas inlet. Decomposition products of the process gases are deposited as parasitic deposits not only on the one or more substrates arranged on the susceptor, but also, in particular, on the surface of the susceptor surrounding the substrates and on the underside of the process chamber ceiling. During the deposition process, the process chamber ceiling is in heat-transferring contact with an underside of the gas inlet or the gas outlet surface of the gas inlet.Before carrying out the cleaning steps described above, the substrates are removed from the process chamber.

[0036] Die Erfindung betrifft darüber hinaus eine Vorrichtung zum Abschei-The process chamber consists of one or more layers on a substrate, arranged in a reactor housing of a CVD reactor. The process chamber may have a floor, heated by a heating device, on which the substrate rests, and a height-adjustable process chamber ceiling, extending in particular parallel to the floor, as well as a gas inlet device for introducing process gases. The gas inlet device may be in the form of a showerhead and arranged above the process chamber ceiling. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06. The gas inlet device may comprise several gas distribution chambers, in particular arranged vertically one above the other. The gas inlet device may include a cooling unit, for example, a cooling chamber through which a coolant flows. A gas outlet surface, cooled by the cooling unit, may be arranged on the underside of the gas inlet device.Gas outlet openings can be arranged at even distribution points within the gas outlet surface, with a first gas distribution chamber connected to the first gas outlet openings and a second gas distribution chamber connected to the second gas outlet openings. The gas outlet surface can be a flat surface from which projections extend towards the bottom of the process chamber, with the second gas outlet openings located on the front face of these projections. The first gas outlet openings can be located within the gas outlet surface itself. The ceiling of the process chamber can have gas passage channels that are aligned with the gas outlet openings.If the process chamber ceiling is in a position where it is in thermally conductive contact with the gas outlet surface, such as during the previously described growth or initial cleaning process, the areas of the gas outlet surface formed by the projections can fully engage their respective gas passage channels. The end faces of the projections can be arranged in a common plane, with a distance to the underside of the process chamber ceiling that is less than the vertical length of the projections. In this case, the projections only partially extend into their corresponding passage channels in the ceiling panel forming the process chamber ceiling.

[0037] Die Gasaustrittsöffnungen können über Gaseinlasskanäle mit den Gas-distribution chambers. The diameter of the gas inlet channels connected to the first gas inlet openings may be larger than the diameter of the gas inlet channels connected to the second gas inlet openings. In particular, it is provided that the first and second distribution chambers are connected to the first gas inlet openings. 31281N1PCT drg / gz 2 May 2025 Ai 2024-06 The cleaning gas is fed into the process chamber through one of the two gas outlet openings, in particular through the second gas outlet openings, and the third cleaning gas through the other gas outlet opening, in particular through the first gas outlet openings. The carrier gases associated with the cleaning gases can be fed into the process chamber through the other gas outlet openings. In order to achieve the highest possible concentration of the third cleaning gas, the mass flow of the third carrier gas flowing through the second gas outlet openings during the third cleaning step is minimized.

[0038] Um den Gesamtmassenfluss des vierten Reinigungsgases in die Pro- To maximize the process chamber, it is specifically provided that the fourth cleaning gas is fed into the process chamber through both the first and second gas outlet openings. The mass flow rate of the fourth cleaning gas entering through the first gas outlet openings can be greater than the mass flow rate of the fourth cleaning gas flowing through the second gas outlet openings; for example, the mass flow rate through the first gas outlet openings can be 50 slm and through the second gas outlet openings 30 slm.

[0039] In einem weiteren Ausführungsbeispiel der Erfindung kann das Gas-The inlet device has one or more observation channels that intersect the gas distribution chambers of the gas inlet device and open into the gas outlet surface and / or into the end faces of the projections extending from the gas outlet surface. The observation channels may have a larger diameter than the gas inlet channels connected to the gas inlet openings. The observation channel may be aligned with enlarged-diameter passage channels in the process chamber ceiling. The observation channel serves as the passage for an optical path to measure the surface temperature of the process chamber floor from outside the reactor using a pyrometer. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 The diameter of the observation channel, or the associated passage channel in the ceiling plate, can be larger than the gas inlet openings, or the associated passage channels in the ceiling plate. The fourth cleaning gas can be introduced through this observation channel during the fourth cleaning step.

[0040] In einem weiteren Ausführungsbeispiel kann der Beobachtungskanal be formed by an insert tube that can be inserted into a channel crossing the gas inlet device, which opens into the gas outlet surface or the front surface of the projections extending from the gas outlet surface.

[0041] Die Durchmesser der Gaseinlassöffnungen in der die Prozesskammer-The distances between the ceiling panels forming the ceiling are significantly smaller than the distances between adjacent gas inlet openings. In the first position relative to the height-adjustable process chamber ceiling, it is ensured that the entire gas flow through the gas inlet openings enters the process chamber. In one of the spacing positions, where the back of the ceiling panel does not abut the area of ​​the gas outlet surface of the gas inlet extending in a single plane, the gas flow introduced through the gas inlet openings enters at least the space between the gas outlet surface and the back of the ceiling panel. A significant portion of this gas flow bypasses the gas outlet surface and the back of the process chamber ceiling to an edge of the ceiling, where the gas can flow directly into a gas outlet.Only a portion of this gas flow reaches the space between the top of the process chamber floor and the underside of the ceiling panel. In the spaced positions, the cleaning gas supplied through the gas inlet device thus exerts more than 50% of its effect in the space between the gas inlet device and the ceiling panel. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06.

[0042] In den ersten Ausführungsbeispielen gelangt das Reinigungsgas in die-The distance between the process chamber ceiling and the ceiling panel is only reduced by the passage channels in the ceiling. In the embodiment where the passage channels corresponding to the observation channels are enlarged, an increased gas flow can flow into the area between the ceiling and the floor of the process chamber. Here, too, the ceiling acts as a flow barrier between an upper and a lower area of ​​the process chamber during one of the cleaning steps. Brief description of the drawings

[0043] Im Folgenden wird die Erfindung anhand von AusführungsbeispielenThis is explained in more detail below. Figure 1 shows a schematic section of a reactor housing of a CVD reactor 17, with a gas inlet device 1 arranged above a process chamber 3, wherein the process chamber ceiling 5, which bounds the process chamber 3 upwards, is arranged in a first position in which a top surface 5'' of the process chamber ceiling 5 rests against a gas outlet surface 9 of the gas inlet device 1, thus transferring heat; this corresponds to the position in a deposition step. Figure 2 shows a representation according to Figure 1, wherein the process chamber ceiling 5 is arranged in a second position in which the process chamber ceiling 5 is spaced from the gas outlet surface 9 at a first distance H1; the distance H1 is shown enlarged here. It is preferably at 1 mm, it can 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 In some embodiments, however, the distance can also be several millimeters. Fig. 3 shows a representation according to Fig. 1, wherein the process chamber ceiling 5 is arranged at a second distance H2 from the gas outlet surface 9, the distance H2 being between one and several millimeters. It is smaller than the distance H1. Fig. 4 shows a representation according to Fig. 3, wherein the distance H3 between the process chamber ceiling 5 and the gas outlet surface 9 is further reduced. Fig. 5 shows a representation according to Fig. 1 of a second embodiment, wherein an observation channel 19 crossing the gas inlet element 1 is provided, which aligns with a first passage channel 15 running through the process chamber ceiling 5.Figure 6 shows a diagram schematically illustrating the course of various process parameters during successively performed process steps, where curve T represents the temperature profile of a process chamber floor 2 that bounds the process chamber 3 downwards, curve T' represents the temperature profile of the process chamber ceiling 5, and curve P represents the process chamber pressure. Figure 7 shows a schematic representation of a control device 14 that communicates with the CVD reactor 17 and a gas supply device 18. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06. Figure 8 shows a representation according to Figure 6 of a further embodiment. Description of embodiments.

[0044] In den Figuren 1 bis 5 ist grob schematisch der Aufbau eines Abschnitts of the reactor casing of a CVD reactor 17. CVD reactors of this type are described in DE 102006018515 A1 and DE 102011056589 A1, which is why reference is made to the explanations therein, which are fully incorporated into this disclosure.

[0045] Im Gehäuse ist eine Prozesskammer 3 angeordnet, die nach untenThe process chamber is bounded by a base 2 and above by a height-adjustable ceiling 5. The base 2 can be configured as a susceptor and made of graphite or another suitable material. The base 2 and the ceiling 5 can be coated, for example with SiC. A heating device 4 is arranged below the base 2 for heating it. The heating device 4 can be an RF coil or a resistance coil. Substrates can be arranged on the upper surface 2' of the base 2 facing the process chamber ceiling 5 (not shown), which are thermally treated in the process chamber 3, in particular by the deposition of III-V layers on the substrate surface.

[0046] Oberhalb der Prozesskammer 3 ist ein Gaseinlassorgan 1 angeordnet.The gas inlet device 1 comprises several vertically arranged gas distribution chambers 10, 11, separated from each other by boundary walls 20, 20'. At least one gas supply line (not shown) opens into each of the gas distribution chambers 10, 11 to feed gases into them. Gases are discharged into a gas outlet surface 9 facing the process chamber 3 and into the end faces 8' of projections 8 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 A multitude of gas outlet openings 6', 7' open onto the projections. In the front face 8' of the projections 8, first gas outlet openings 6' open, which are connected via first gas inlet channels 6 to a first gas distribution chamber 10. In the gas outlet surface 9 itself, second gas outlet openings 7' open, which are connected via second gas inlet channels 7 to a second gas distribution chamber 11. The diameter of the gas inlet channels 6, 7 can differ, with the diameter of the first gas inlet channels 6 being smaller than the diameter of the second gas inlet channels 7.

[0047] Die Gasaustrittsfläche 9 bildet die Unterseite eines Kühlaggregates 12, which is located below the gas distribution chambers 10, 11 within the gas inlet device 1. The cooling unit 12 is a hollow body through which a cooling fluid flows.

[0048] Die höhenverstellbare Prozesskammerdecke 5 besitzt Durchtrittskanä-le 15, 16, which are aligned with the gas inlet channels 6, 7. In the first position of the process chamber ceiling 5 shown in Figure 1, the projections 8 engage in first passage channels 15, the inner diameter of which corresponds approximately to the outer diameter of the projections 8, so that the projection 8 seals tightly in its respective first passage channel 15. The second gas outlet openings, connected to the second gas inlet channels, are located at the upper opening of the second passage channels 16.

[0049] Die Stirnseiten 8‘ der Vorsprünge 8 liegen in einer Stirnflächenebene 13, which, in the position shown in Figure 1, is spaced from a bottom surface 5' of the process chamber ceiling 5. The distance between the end face plane 13 and the bottom surface 5' of the process chamber ceiling 5 is smaller than the distance between the gas outlet surface 9 and the end face plane 13. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0050] Die Oberseite 5‘‘ der Prozesskammerdecke 5 liegt derartig in der in Fi-The first position of the process chamber ceiling 5 shown in Figure 1 at the gas outlet surface 9 indicates that no gas flowing through the gas inlet channels 6, 7 flows between the gas outlet surface 9 and the top 5'' of the process chamber ceiling 5.

[0051] Der Boden 2 kann eine kreisförmige Gestalt aufweisen. Um den auf ei- A gas outlet extends along the circular arc-shaped edge of the base 2, through which the gas fed into the process chamber 3 can be pumped out by means of a vacuum pump. The process chamber ceiling 5 is arranged between the similarly circular-shaped gas inlet 1 and the base and also has a circular plan.

[0052] Mittels einer Gasversorgungseinrichtung 18 können Prozessgase und Cleaning gases are provided. These gases can be fed into the gas inlet device 1 by means of mass flow controllers and valves.

[0053] Zur Regelung von Temperaturen und Massenflüssen ist eine Steuerein- direction 14 is planned, which follows a predetermined recipe.

[0054] In Figur 2 ist die Prozesskammerdecke 5 in einer zweiten Position an-The process chamber ceiling 5 is arranged in such a way that it is spaced from the gas outlet surface 9 by a first distance H1. The first distance H1 is greater than the distance between the end face 13 and the gas outlet surface 9, so that the projections 8 no longer engage in the first passage channels 15 of the process chamber ceiling 5 to which they are assigned.

[0055] In Figur 3 ist die Prozesskammerdecke 5 in einer dritten Position ange- arranges, in which the process chamber ceiling 5 occupies a second distance H2 to the gas outlet surface 9, which is smaller than the first distance H1. The Ab-31281N1PCT drg / gz 2 May 2025 Ai 2024-06 The level of H2 is greater than the distance between the gas outlet surface 9 and the end face plane 13.

[0056] Die Figur 4 zeigt die Prozesskammerdecke 5 in einer vierten Position, in the process chamber ceiling 5 is spaced from the gas outlet surface 9 by a third distance H3. The third distance H3 is smaller than the second distance H2, and the third distance H3 is smaller than the distance between the gas outlet surface 9 and the end face plane 13.

[0057] Die Figur 5 zeigt ein weiteres Ausführungsbeispiel der Erfindung, wo-An observation channel 19 intersects the gas distribution chambers 10, 11 and the cooling chamber 12. The optical path of a pyrometer can be routed through the observation channel 19. Furthermore, a cleaning gas or purge gas can be fed into the process chamber 3 through the observation channel 19. The inner diameter of the observation channel 19 can be larger than or equal to the inner diameter of the gas inlet channels 6, 7.

[0058] Die Figur 6 zeigt schematisch den Verlauf der Kurve T der Temperaturof the process chamber floor 2, the course of curve T' of the temperature of the process chamber ceiling 5, and the course of curve P of the process chamber pressure during a multi-step cleaning process for cleaning the process chamber 3. The cleaning processes can be preceded by a deposition process, for example, to deposit a III-V layer on a substrate arranged on the process chamber floor 2. During such a deposition process, parasitic deposits can form on the surfaces within the process chamber 3 that are exposed to the process gases. In particular, parasitic deposits form on the upper side 2' of the process chamber floor 2 and the lower side 5' of the process chamber ceiling 5. During the deposition process, the process chamber ceiling 5 is in the position shown in Figure 1. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0059] Während des Abscheideprozesses können metallorganische Verbin-Gallium and / or aluminum compounds, together with a nitrogen hydride, are fed into the process chamber. Simultaneously, hydrogen can be fed into process chamber 3 as a carrier gas.

[0060] Auf Substraten, die auf der Oberseite 2‘ des Suszeptors 2 angeordnet If a GaN layer, an AlN layer or a GaAlN layer is deposited, the material will be precipitated.

[0061] In anderen erfindungsgemäßen Verfahren können andere III-V- Layers, IV-IV layers or II-VI layers are deposited.

[0062] In einem Abscheideschritt liegt die Prozesskammerdecke 5 in einer An- The system is positioned at the gas outlet surface 9. The process chamber ceiling 5 has flat areas that are in contact with flat areas of the gas outlet surface. Due to the contact between the system and the gas outlet surface, heat is transferred via conduction. While the susceptor 2 is heated to a temperature of, for example, 800°C to 1000°C, heat radiation is supplied to the process chamber ceiling 5. Cooling via the coolant in the cooling chamber 12 ensures that the process chamber ceiling temperature is less than 350°C during the separation step.

[0063] Vor einem ersten Reinigungsschritt 100 werden in der Prozesskam-Three substrates stored in process chamber 3 are removed. During a preparatory step 90 preceding the first cleaning step 100, the susceptor 2 is heated to an initial cleaning temperature T1. This also increases the initial temperature T1' of the process chamber ceiling 5. The process chamber pressure P1, the floor temperature T1, and the process chamber ceiling temperature T1' are kept constant during the first cleaning step 100. During the first cleaning step 100, 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 The process chamber ceiling 5 is in the first position shown in Figure 1, in which the process chamber ceiling 5 is in thermally conductive contact with the gas outlet surface 9 of the gas inlet device 1. This results in heat being transferred to the cooled gas outlet surface 9.

[0064] Bei einem bevorzugten Ausführungsbeispiel kann die Prozesskammer-The ceiling 5 can be moved between two positions. In an upper position, the process chamber ceiling 5 is in contact with the gas outlet surface 9. In a lower position, the process chamber ceiling 5 has a defined vertical distance from the gas outlet surface 9. This distance can be 1 mm. The process chamber ceiling 5 can rest against a stop for this purpose.

[0065] Bei dem bevorzugten Ausführungsbeispiel ist der einen Boden der Pro- The susceptor 2 forming the process chamber is vertically displaceable relative to the preferably non-displaceable gas inlet element. In a separation step, the susceptor 2 can assume a lower position and be, for example, 11 mm away from the process chamber ceiling 5. The distance between the process chamber ceiling 5 and the susceptor 2 can be reduced, for example, to 5 mm or 9 mm by raising the susceptor.

[0066] Bei einem bevorzugten Ausführungsbeispiel hat der Abstand der Pro-The chamber ceiling 5 is positioned opposite the susceptor 2 in a first cleaning step 100 at a distance of 5 mm, and in a second cleaning step 101 or a third cleaning step 102 at a distance of 9 mm.

[0067] Während des ersten Reinigungsschrittes 100 wird ein erstes Reini- A cleaning gas, preferably a chlorine-containing gas, is fed into process chamber 3. It is preferably Cl₂. The first cleaning gas is fed into process chamber 3 together with a first carrier gas, preferably N₂. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 The first cleaning gas is preferably fed in together with the first carrier gas through the first gas outlet openings 6', which are arranged in the end faces 8' of the projections 8. However, the first cleaning gas can also be fed into the process chamber 3 additionally or exclusively through one or more of the observation channels 19 shown by way of example in Figure 5. The first carrier gas is additionally fed into the process chamber 3 through the second gas outlet openings 7'. The mass flows of the first cleaning gas and the first carrier gas are selected such that the concentration of the first cleaning gas in the first carrier gas is between 4% and 6%, preferably 5%.

[0068] Das erste Reinigungsgas reagiert mit zumindest einer parasitären Be-Layering occurs on the upper surface 2' of the process chamber floor 2, which faces the process chamber 3, forming the first gaseous reaction products. These first reaction products are at least partially transported out of the process chamber 3 by means of the first carrier gas. However, the first reaction products can also condense, for example, on the lower surface 5' of the process chamber ceiling 5, which is cooler than the upper surface 2' of the process chamber floor 2.

[0069] Bei dem bevorzugten Ausführungsbeispiel beträgt der Abstand zwi-The distance between the process chamber ceiling 5 and the gas outlet surface 9 during the first cleaning step 100 is approximately 1 mm. However, the distance can also be slightly smaller or slightly larger. The distance is chosen such that no heat transfer via conduction occurs between the two contacting surfaces of the process chamber ceiling 5 and the gas outlet surface 9. Furthermore, the distance is chosen such that the mass flow of reaction products into the gap between the process chamber ceiling 5 and the gas outlet surface 9 during cleaning step 100 is minimal. During the first cleaning step 100, the distance of the susceptor 2 to the process chamber ceiling 5 can be reduced to 5 mm, which leads to an increase in the process chamber ceiling temperature.

[0070] In einem auf den ersten Reinigungsschritt 100 folgenden zweiten Reini-In cleaning step 101, a second cleaning gas, together with a second carrier gas, is fed into process chamber 3 at a second bottom temperature T2 and a second process chamber pressure P2. The second cleaning gas, like the cleaning gas in the first cleaning step 100, is preferably a chlorine-containing gas. It is preferably Cl2. The second carrier gas is also preferably N2.

[0071] Das zweite Reinigungsgas wird zusammen mit dem zweiten Trägergas The first gas outlet openings 6' feed the second carrier gas into the process chamber. Additionally, the second carrier gas is fed in through the second gas outlet openings 7'. As during the first cleaning step 100, the concentration of the second cleaning gas in the carrier gas can preferably be between 4% and 6%, preferably 5%.

[0072] Die Temperatur T2 des Prozesskammerbodens 2 während des zweitenThe temperature of the second cleaning step 101 corresponds essentially to the temperature T1 of the process chamber floor 2 during the first cleaning step 100. During the second cleaning step 101, the process chamber ceiling 5 is arranged in the second position shown in Figure 2. In the second position, the process chamber ceiling 5 is shifted towards the process chamber floor 2, resulting in a smaller distance between the process chamber floor 2 and the process chamber ceiling 5 than during the first cleaning step 100. Consequently, the temperature T2' of the process chamber ceiling 5 during the second cleaning step 101 is higher than during the first cleaning step 100. The second process chamber ceiling temperature T2' is higher than the first process chamber ceiling temperature T1' to facilitate the removal of parasitic 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 To simplify the removal of deposits on the underside 5' of the process chamber ceiling 5. During the second cleaning step 101, the second cleaning gas reacts with at least a parasitic coating on the process chamber ceiling to form second reaction products. These are at least partially removed from the process chamber 3 with the second carrier gas. During the second cleaning step, the second process chamber pressure P2 essentially corresponds to the first process chamber pressure P1.

[0073] Dieser zweite Reinigungsschritt ist optional. In dem in der Figur 8 dar-In the embodiment shown, a second cleaning step 101 follows directly after a preparation step 91, after the first cleaning step 100. This second cleaning step is described below. In the embodiment shown in Figure 8, the distance between the susceptor 2 and the process chamber ceiling 5 is increased to 9 mm, which leads to a reduction in the process chamber ceiling temperature. The distance from the process chamber ceiling 5 to the gas outlet surface 9 remains unchanged. However, it is also provided that no change in distance occurs between these cleaning steps.

[0074] Bei dem in der Figur 6 dargestellten Ausführungsbeispiel folgt auf denA second preparation step 91 follows the second cleaning step 101. In the embodiment shown in Figure 8, the preparation step 91 directly follows the first cleaning step 100. During this second preparation step 91, the process parameters for an optional third cleaning step 102 are set. The temperature of the process chamber floor 2 is heated to a third temperature T3, which is higher than the first and second floor temperatures T1, T2, preferably higher than 1100°C. Due to the higher floor temperature T3 during the third cleaning step 102, the temperature of the process chamber ceiling T3' during the third cleaning step 102 is also higher than during the first and / or second cleaning steps. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 tenth cleaning step 100, 101. The third process chamber pressure P3 is set to a value that is lower than the first and / or second process chamber pressure P1, P2.

[0075] Die Prozesskammerdecke 5 kann sich während des dritten Reinigungs- The process chamber ceiling 5 is located in the third position, as exemplified in Figure 4. In the third position, the process chamber ceiling 5 is arranged at a second distance H2 from the gas outlet surface 9, which is smaller than the first distance H1 (see Figure 3). This results in a greater distance between the process chamber ceiling 5 and the process chamber floor 2 than during the second cleaning step 101.

[0076] Bei einem bevorzugten Ausführungsbeispiel, wie es die Figur 8 zeigt, The distance between the process chamber ceiling 5 and the gas outlet surface 9 remains unchanged during all cleaning steps in a range between 0.5 and 2 mm, preferably 1 mm.

[0077] Während des dritten Reinigungsschrittes 102 (Figur 6) oder des zweitenIn cleaning step 101 (Figure 8), a third cleaning gas, preferably NH3, is fed into the process chamber 3 together with a third carrier gas. The third cleaning step 102 is divided into two phases, with the third carrier gas being changed between the two phases. During the first phase, N2 is preferably fed in as the third carrier gas, and during the second phase, H2 is preferably fed in. The third cleaning gas is used to remove decomposition products, particularly those containing carbon, from the process chamber 3. The third cleaning gas is preferably fed in through the second gas outlet openings 7', whereas the third carrier gas is introduced into the process chamber 3 through the first gas outlet openings 6'. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0078] Auf den zweiten Reinigungsschritt 101 bzw. den optionalen drittenCleaning step 102 is followed by a fourth cleaning step 103, in which a fourth cleaning gas, in particular H2, is introduced into the process chamber 3. During the first and second cleaning steps 100 and 102, parasitic deposits can form, at least on the gas outlet surface 9. Since the cooled gas outlet plate 9 is no longer shielded by the process chamber ceiling 9 during the second cleaning step 102, the second decomposition products formed during the second cleaning step can, for example, condense on the cooled gas outlet plate 9. For instance, if a chlorine-containing second cleaning gas is used, these could be chlorides. These are removed by the H2-containing fourth cleaning gas.

[0079] Bei dem in der Figur 8 dargestellten Ausführungsbeispiel schließt sichThis cleaning step 102, in which only hydrogen is fed into the process chamber, directly follows the second cleaning step 101 and, in this embodiment, constitutes a third cleaning step. In this cleaning step, the distance between the process chamber ceiling 5 and the gas outlet surface 9 is again preferably 1 mm, and the distance between susceptor 2 and the process chamber ceiling 5 is preferably 9 mm.

[0080] Um die kondensierten Zerlegungsprodukte beispielsweise abzudamp-In this case, it is advantageous if the partial pressure of the decomposition products is as low as possible. According to the invention, this is achieved by ensuring that the process chamber pressure P4 and the mass flow rate of the fourth cleaning gas are as high as possible during the fourth cleaning step 103. The fourth process chamber pressure is lower than the first, second, and third process chamber pressures P1, P2, P3 and preferably lower than 50 mbar. In order to achieve the highest possible mass flow rate of the fourth cleaning gas during the fourth cleaning step 103, the fourth cleaning gas is supplied both by the first 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 The gas is introduced into the process chamber 3 through the first gas outlet openings 6' as well as through the second gas outlet openings 7'. In a further embodiment of the invention, the fourth cleaning gas is fed into the process chamber 3 exclusively or additionally through one or more observation channels 19.

[0081] Darüber hinaus beschleunigt eine möglichst hohe Temperatur derGas outlet surface 9 represents the fourth purification step, which may involve chemical reactions with the decomposition products, but can also be a purely evaporative process. To increase the heat input from the process chamber ceiling 5, heated by the heated susceptor 2, to the gas outlet surface 9, the distance H3 between the process chamber ceiling 5 and the gas outlet surface 9 is reduced compared to the preceding purification steps (see Figure 4). The process chamber 5 assumes the fourth position shown as an example in Figure 4, whereby the third and fourth positions of the process chamber ceiling 5 can also be the same.

[0082] Mittels einer bevorzugten Ausgestaltung kann im vierten Reinigungs- The distance H3 is minimized in such a way that the end face plane 13 is less than 1 mm away from the top 5'' of the ceiling plate forming the process chamber ceiling 5.

[0083] Bei Ausführungsbeispielen, bei denen keine Vorsprünge 8 vorgesehenSince all gas inlet channels 6, 7 open into a common plane corresponding to the gas outlet surface 9, the third distance H3 can be less than 2 mm.

[0084] Der geringe Abstand H3 bewirkt einen sich zwischen der Gasaustritts- surface 9 and the upper surface 5'' forming a flow channel through which the cleaning gas is introduced in the third and fourth cleaning steps at 31281N1PCT drg / gz 2 May 2025 Ai 2024-06 the upper surface 5'' and the gas outlet surface 9 flows in a horizontal direction. The majority of the cleaning gas fed into the space between the process chamber ceiling 5 and the gas outlet surface 9 leaves this space in a peripheral area not shown in the figures, where the preferably circular edge of the ceiling plate forming the process chamber ceiling 5 abuts the gas outlet device.

[0085] Es wird deshalb als vorteilhaft angesehen, dass die die Prozesskammer-The ceiling 5, forming a ceiling panel, performs a flow-guiding function, concentrating the effective area of ​​the third or fourth cleaning gas onto the gas outlet surface 9. The process chamber ceiling 5 preferably forms a flow barrier between the gas inlet openings 6', 7' and the space between the ceiling panel and the floor 2.

[0086] Wenn im dritten Reinigungsschritt und im vierten Reinigungsschritt When the distance H3 or H2 is equal and, in particular, minimal, a maximum temperature gradient forms between the actively cooled gas outlet surface 9 and the upper surface 5'' of the radiatively heated process chamber ceiling 5. In this embodiment, this is especially the case when, during the third and / or fourth cleaning step, the distance of the upper surface 5'' to the end face 13 is smaller than the distance of the end face 13 to the gas outlet surface 9, i.e., the height of the projections 8.

[0087] Die vierte Bodentemperatur T4 ist kleiner als die dritte Bodentempera-The temperature T3 is higher than the first and second floor temperatures T1 and T2. Therefore, the fourth process chamber ceiling temperature T4' is also higher than the first and second process chamber ceiling temperatures T1' and T2'. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0088] Um die Temperatur der Gasaustrittsfläche 9 zu erhöhen, kann zusätz- The temperature of the coolant flowing through the cooling chamber 12 can be increased.

[0089] In einem anderen Ausführungsbeispiel der Erfindung umfasst das Rei-The cleaning process only includes the cleaning step previously described as the second cleaning step and the cleaning step previously described as the fourth cleaning step, so that after a now first cleaning step, in which a chemical reaction takes place, a second cleaning step is carried out directly, in which only hydrogen is fed into the process chamber. During the now first cleaning step, the process chamber ceiling 5 can be spaced away from the gas outlet surface 9. In the now second cleaning step, the process chamber ceiling 5 assumes a smaller distance position from the gas outlet surface 9.

[0090] Auch hier kann vor dem jetzt zweiten Reinigungsschritt ein Zwischen- The step is carried out as previously described with an optional third cleaning step.

[0091] Figur 7 zeigt schematisch eine Steuereinrichtung 14, die mit einer Gas-The control unit 14 communicates with the supply unit 18 and the CVD reactor 17. For example, the heating unit 4, the cooling element 12, and the mass flow controllers and valves for feeding the gases (not shown) into the process chamber 3 are controlled by means of the control unit 14 in order to carry out the process according to the invention.

[0092] Bei dem in der Figur 8 dargestellten Ausführungsbeispiel werden fol- The cleaning steps already described above are carried out after the deposition of a layer, wherein during the deposition of the layer the distance between susceptor 2 and process chamber ceiling is 511 mm, the31281N1PCT drg / gz 2 May 2025 Ai 2024-06 The process chamber ceiling 5 has no distance to the gas outlet surface 9, and the process chamber ceiling temperature is a maximum of 350°C. By lowering the process chamber ceiling 5, a distance H1 between the gas outlet surface 9 and the process chamber ceiling 5 is established. A first cleaning gas in the form of chlorine, together with nitrogen, is fed into the process chamber 3 at a floor temperature T2 of 890°C. The height of the process chamber 3 is reduced to 5 mm by raising the susceptor 2. The first cleaning step is carried out for several minutes, for example, one to ten minutes or approximately seven minutes. During this time, the process chamber ceiling 5 heats up to a process chamber ceiling temperature of over 550°C. The floor temperature T2 can be in the range between 900°C and 1000°C.

[0093] Nach einem Vorbereitungsschritt 91 folgt ein zweiter Reinigungs-Step 101, in which the distance between the process chamber ceiling 5 and the gas outlet surface 9 remains unchanged, and the distance between the susceptor 2 and the process chamber ceiling 5 is increased to 9 mm. During the second cleaning step 101, ammonia is fed into the process chamber together with hydrogen. The second cleaning step lasts several minutes, for example, one to ten minutes, and preferably about three minutes. The bottom temperature T3 can be 100 K to 150 K higher and, in particular, can reach 1050°C. The process chamber ceiling temperature T3' is more than 500°C.

[0094] An den zweiten Reinigungsschritt 101 schließt sich ein dritter Reini-In cleaning step 102, the floor temperature T4 is 1050°C, the distance of the process chamber ceiling 5 from the gas outlet surface 9 and the distance of the susceptor 2 from the process chamber ceiling 5 remain unchanged, and the process chamber ceiling temperature T4' is at least 400°C. During the third cleaning step 102, only hydrogen is introduced into process chamber 3. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 fed in. The third cleaning step is carried out for several minutes, for example one to ten minutes or about three minutes.

[0095] Der erste Reinigungsschritt 100 kann bei einem ProzesskammerdruckThe cleaning steps 101 and 102 can be carried out at a process chamber pressure of less than 50 mbar. Specifically, it is provided that the process chamber ceiling 5 is heated to a temperature of less than 350°C during the separation step, to a temperature above 550°C during the first cleaning step, to a temperature above 500°C during the second cleaning step, and to more than 400°C during the third cleaning step.

[0096] Die vorstehenden Ausführungen dienen der Erläuterung der von der The application covers all inventions that further develop the prior art, at least through the following combinations of features, each of which can also be independently combined, namely:

[0097] Ein Verfahren zur Reinigung einer Prozesskammer 3 eines CVD-Reactor 17, wherein the process chamber 3 is bounded downwards by a floor 2 and upwards by a height-adjustable process chamber ceiling 5, wherein the floor 2 is heated by a heating device 4, with a gas inlet device 1 for introducing gases into the process chamber 3, wherein a gas outlet surface 9 of the gas inlet device 1 facing the process chamber 3 is cooled by means of a cooling element 12, comprising the following steps: introducing a cleaning gas together with a carrier gas at a floor temperature T2, a process chamber pressure P2 and a process chamber 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 Ceiling temperature T2' through gas inlet openings 6', 7' arranged in the gas outlet surface 9 into the process chamber 3, wherein the process chamber ceiling 5 is arranged in a position in which the process chamber ceiling 5 is preferably spaced at a distance H1 from the gas outlet surface 9, wherein the cleaning gas reacts with at least a parasitic coating on the process chamber ceiling 5 to form reaction products; Introducing another cleaning gas at a higher floor temperature T4, a reduced process chamber pressure P4 and a higher process chamber ceiling temperature T4' through the gas inlet openings 6', 7' into the process chamber 3, wherein the process chamber ceiling 5 is arranged at a smaller distance H3 to the gas outlet surface 9, wherein the other cleaning gas removes parasitic deposits at least on the gas outlet surface 9.

[0098] Ein Verfahren, das gekennzeichnet ist durch die folgenden Schritte:First cleaning step: Introducing a first cleaning gas together with a first carrier gas at a first bottom temperature T1, a first process chamber pressure P1 and a first process chamber ceiling temperature T1' through the gas inlet openings 6', 7' into the process chamber 3, wherein the process chamber ceiling 5 is arranged in a first position in which an upper side 5'' of the process chamber ceiling 5 is in a thermally conductive active connection to the gas outlet surface 9 of the gas inlet device 1, wherein the first cleaning gas reacts at least with a parasitic coating on an upper side 2' of the bottom 2 facing the process chamber 3 to form first gaseous reaction products;Second cleaning step: Introducing the second cleaning gas together with a second carrier gas at a second bottom temperature T2, a second process chamber pressure P231281N1PCT drg / gz May 2, 2025 Ai 2024-06 and the second process chamber ceiling temperature T2', wherein the process chamber ceiling 5 is arranged in the second position in which the process chamber ceiling 5 is spaced at the first distance H1 from the gas outlet surface 9, wherein the second process chamber ceiling temperature T2' is higher than the first process chamber ceiling temperature T1';Fourth cleaning step: Introducing the fourth cleaning gas at the fourth bottom temperature T4, at the fourth process chamber pressure P4 and at the fourth process chamber ceiling temperature T4', wherein the fourth bottom temperature T4 is higher than the first and / or second bottom temperature T1, T2, wherein the fourth process chamber pressure P4 is lower than the first and / or second process chamber pressure P1, P2, wherein the fourth process chamber ceiling temperature T4' is higher than the first and second process chamber ceiling temperatures T1', T2', wherein the process chamber ceiling 5 is arranged in a fourth position in which the process chamber ceiling 5 is arranged at a third distance H3 to the gas outlet surface 9, wherein the third distance H3 is smaller than the first distance H1, wherein the fourth cleaning gas removes at least at the gas outlet surface 9 parasitic deposits that formed at the gas outlet surface 9 during the first and / or second cleaning step.

[0099] Ein Verfahren, das gekennzeichnet ist durch einen zwischen dem zwei-The third cleaning step is performed in the tenth cleaning step and the fourth cleaning step, wherein a third bottom temperature T3 is higher than the first and / or second bottom temperatures T1, T2, wherein a third process chamber pressure P3 is lower than the first and / or second process chamber pressure P1, P2, and wherein a third cleaning gas introduced through the gas inlet openings 6', 7' removes third decomposition products deposited as a parasitic coating on the underside 5' of the process chamber ceiling 5 and the upper side 2' of the process chamber floor 2. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0100] Ein Verfahren, das dadurch gekennzeichnet ist, dass das dritte Reini- The ing gas is ammonia NH3, the third carrier gas in a first phase of the third purification step is nitrogen N2 and in a second phase of the third purification step is hydrogen H2.

[0101] Ein Verfahren, das dadurch gekennzeichnet ist, dass der zweite Ab- The distances H2 and H3 are the same.

[0102] Ein Verfahren, das dadurch gekennzeichnet ist, dass die vierte Boden- temperature T4 is less than 1200°C.

[0103] Ein Verfahren, das dadurch gekennzeichnet ist, dass der erste Prozess-chamber pressure P1 is greater than 50 mbar and the fourth process chamber pressure P4 is less than 50 mbar.

[0104] Ein Verfahren, das dadurch gekennzeichnet ist, dass der Gesamtmas- The mass flow of the gases introduced into process chamber 3 in the fourth cleaning step is higher than the total mass flow of the gases introduced into process chamber 3 in each of the other cleaning steps.

[0105] Ein Verfahren, das dadurch gekennzeichnet ist, dass die Wärmeleitfä- The thermal conductivity (under standard conditions) of the third cleaning gas is lower than the thermal conductivity (under standard conditions) of the fourth cleaning gas.

[0106] Ein Verfahren, das dadurch gekennzeichnet ist, dass das erste und The second cleaning gas contains chlorine, specifically Cl2, and the first and second carrier gases are nitrogen (N2). 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

[0107] Ein Verfahren, das dadurch gekennzeichnet ist, dass das vierte Reini- The gas is hydrogen H2.

[0108] Ein Verfahren, das dadurch gekennzeichnet ist, dass das Gaseinlassor-gan 1 comprises several gas distribution chambers 10, 11, wherein a first gas distribution chamber is connected to first gas outlet openings 6' evenly distributed over the gas outlet surface 9, wherein a second gas distribution chamber is connected to second gas outlet openings 7' evenly distributed over the gas outlet surface 9, wherein the first gas inlet openings 6' are arranged in the gas outlet surface 9 and the second gas outlet openings 7' are located in end faces 8' of projections 8 extending from the gas outlet surface 9, wherein the process chamber ceiling 5 has first gas passage channels 15 and second gas passage channels 16, wherein the projections 8 lie completely in the second gas passage channels 16 during the first cleaning step, wherein the end faces 8' lie in an end face plane 13 which has a distance to the underside 5'' of the process chamber ceiling 5 that is less than the vertical length of the projections 8.

[0109] Ein Verfahren, das dadurch gekennzeichnet ist, dass der DurchmesserThe diameter of the first gas inlet openings 6' is larger than the diameter of the second gas inlet openings 7'.

[0110] Ein Verfahren, das dadurch gekennzeichnet ist, dass das erste und The second cleaning gas is fed into the process chamber 3 only through one of the two gas outlet openings 6', 7' and the third cleaning gas through the other gas outlet opening 6', 7'.

[0111] Ein Verfahren, das dadurch gekennzeichnet ist, dass der Massenfluss of the first and second cleaning gas and the mass flow of the first and second carrier gas are selected such that the concentration of the first 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 The concentration of the second cleaning gas in the first or second carrier gas is between 4% and 6%.

[0112] Ein Verfahren, das dadurch gekennzeichnet ist, dass im vierten Reini-In the next step, the fourth cleaning gas is introduced into the process chamber 3 through both the first gas outlet openings 6' and the second gas outlet openings 7', whereby the mass flow of the fourth cleaning gas flowing in through the first gas outlet openings 6' is greater than the mass flow of the fourth cleaning gas flowing through the second gas outlet openings 7'.

[0113] Ein Verfahren, das dadurch gekennzeichnet ist, dass das Kühlelement a cooling chamber 12 through which a coolant flows, wherein the temperature of the coolant is higher during the fourth cleaning step than during the first and / or second cleaning step.

[0114] Eine Vorrichtung, die dadurch gekennzeichnet ist, dass die Steuerein- direction 14 is programmed for carrying out the procedure according to one of the preceding claims.

[0115] Alle offenbarten Merkmale sind (für sich, aber auch in Kombination(among themselves) essential to the invention. The disclosure of the application hereby also fully incorporates the disclosure content of the associated / attached priority documents (copy of the prior 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 with their features, in particular in order to file divisional applications on the basis of these claims. The invention specified in each claim may additionally include one or more of the 31281N1PCT drg / gz 2 May 2025 Ai 2024-06 The invention includes features described above, in particular those identified by reference numerals and / or listed in the reference numeral list. The invention also relates to designs in which individual features mentioned in the above description are not realized, especially where they are recognizably unnecessary for the respective purpose or can be replaced by other technically equivalent means. 31281N1PCT drg / gz 2 May 2025 Ai 2024-06 List of reference symbols 1 Gas inlet device 10 2 Third cleaning step 2 Bottom / susceptor 10 3 Fourth cleaning step 2' Top 3 Process chamber 4 Heating device 5 Process chamber ceiling 5' Bottom 5'' Top t Time 6 First gas inlet channel 6' First gas inlet opening 7 Second gas inlet channel 7' Second gas inlet opening 8 Projection 8' Front face H1 First clearance 9 Gas outlet surface H2 Second clearance 10 Gas distribution chamber H3 Third clearance 11 Gas distribution chamber P1 First process chamber pressure 12 Cooling chamber P2 Second process chamber pressure 13 Front surface plane P3 Third process chamber pressure 14 Control device P4 Fourth process chamber pressure 15 First through channel T Curve Bottom temperature 16 Second through channel T' Curve Process chamber ceiling 17 CVD reactor temperature 18 Gas supply device T1 First bottom temperature 19 Observation channel T1' First process chamber ceiling 90 Preparation step temperature 91 Preparation step T2 Second bottom temperature 100 First cleaning step T2' SecondProcess chamber ceiling-101 second cleaning step temperature 31281N1PCT drg / gz May 2, 2025 Ai 2024-06T3 third floor temperatureT3' third process chamber ceiling temperatureT4 fourth floor temperatureT4' fourth process chamber ceiling temperature 31281N1PCT drg / gz May 2, 2025 Ai 2024-06

Claims

Claims 1. Method for operating a process chamber (3) of a CVD reactor (17) after a deposition step in which a layer is deposited on a substrate arranged on the bottom (2), wherein the CVD reactor (17) comprises a process chamber (3), a gas inlet element (1) arranged in the process chamber (3) with a gas outlet surface (9) facing the process chamber (3) and cooled by a cooling element (12) and having gas inlet openings (6', 7'), a bottom (2) delimiting the process chamber (3) from below, a heating device (4) for heating the bottom (2) to a bottom temperature (T1, T2, T3, T4) and a process chamber ceiling (5) arranged between the gas outlet surface (9) and the bottom (2), which is cooled by the heating device (4) and a cooling element (12) to a process chamber ceiling temperature (T1', T2', T3', T4') is temperedwherein the process chamber ceiling (5) and the floor (2) are each adjustable relative to the gas outlet surface (9) in a vertical direction, wherein the process chamber (3) is cleaned by at least the following cleaning steps: before a first cleaning step (100): repositioning the process chamber ceiling (5), which during the separation step is at least partially in contact with the gas outlet surface (9) without a gap, vertically relative to the gas outlet surface (9) to a distance (H1) relative to the gas outlet surface (9), reducing the distance of the floor (2) to the process chamber ceiling (5) to a first value, in particular by raising the floor (2); during the first cleaning step (100): introducing a first cleaning gas, in particular chlorine together with a first carrier gas,in particular nitrogen at a first bottom temperature (T1) and a first process chamber ceiling temperature (T1') into the process chamber (3) for a first time; before a second cleaning step (101): optionally increasing the distance of the bottom (2) to the process chamber ceiling (5) to a second value, optionally increasing the bottom temperature to a second bottom temperature (T2); during the second cleaning step (101): introducing a second cleaning gas, in particular ammonia together with a second carrier gas, in particular hydrogen, for a second time; before a third cleaning step (102): optionally increasing the distance of the bottom (2) to the process chamber ceiling (5) to a third value, which is less than the first value; during the third cleaning step (102): introducing a third cleaning gas, in particular hydrogen, for a third time.

2. The method according to claim 1, characterized in that,that reaction products are generated by a chemical reaction of the first cleaning gas or the second cleaning gas with a parasitic coating on the process chamber ceiling (5), which condense in the space between the process chamber ceiling (5) and the gas outlet surface (9) and are removed in the third cleaning step (102), and / or that a first process chamber pressure (P1) is reduced to a second process chamber pressure (P2) during the execution of the first cleaning step (100) before the execution of the second cleaning step (101), and / or that the distance between the process chamber ceiling (5) and the gas outlet surface (9) remains unchanged during the cleaning steps (100, 101, 102, 103). 31281N1PCT drg / gz 2 May 2025 Ai 2024-06, 3. A method according to claim 1 or 2, characterized in that the carrier gas is nitrogen in a first phase of the third purification step (102) and hydrogen in a second phase of the third purification step (102).

4. A method according to claim 1, characterized in that the distance between the process chamber ceiling (5) and the gas outlet surface (9) is changed and, in particular, reduced during the execution of one of the purification steps (100, 101, 102, 103) or between the purification steps (100, 101, 102, 103).

5. Method according to one of the preceding claims, characterized in that the first cleaning step (100) is carried out at a first process chamber pressure (P1) that is greater than 50 mbar and the further cleaning steps (101, 102, 103) are carried out at a process chamber pressure (P2, P3, P4) that is less than 50 mbar.6.A method according to any one of the preceding claims, characterized in that the first cleaning step (100) is carried out at a first bottom temperature (T1) between 900°C and 1000°C and the second bottom temperature (T2) is between 100 and 150 K higher than the first bottom temperature (T1).

7. A method according to any one of the preceding claims, characterized in that the process chamber ceiling (5) is heated to a temperature of less than 305°C during the separation step, is heated to a temperature (T1') above 550°C during the first cleaning step (100), and is heated to a temperature (T2') above 500°C during the second cleaning step (101). 31281N1PCT drg / gz May 2, 2025 Ai 2024-06. and is heated to more than 400°C during the third cleaning step (102).

8. Method according to one of the preceding claims, wherein the cleaning steps (100, 101, 102, 103) are carried out after the separation step, in which the bottom (2) has a distance from the process chamber (5) and after the removal of the substrate.

9. Device for depositing layers, in particular III-V layers, on substrates, comprising a process chamber (3) of a CVD reactor (17) which is bounded downwards by a base (2) and upwards by a height-adjustable process chamber ceiling (5) with passage channels (15, 16), comprising a heating device (4) for heating the base (2), comprising a gas inlet device (1) which has a gas outlet surface (9) facing the process chamber (3) in which gas inlet openings (6', 7') are arranged through which process gases, carrier gases and cleaning gases can be introduced into the process chamber (3),with a cooling element for cooling the gas inlet device (1), and with a control device (14) for controlling the heating device (4), the cooling element, mass flow controllers, and valves for feeding the process gases, carrier gases, and cleaning gases into the process chamber (3) and for moving the process chamber ceiling (5), characterized in that the control device (14) is programmed to carry out the method according to one of the preceding claims.

10. Device according to claim 9, characterized in that the process chamber ceiling (5) is movable between a position in contact with the process chamber ceiling (5) and a position away from the process chamber ceiling (5), and / or that the process chamber ceiling (5) rests against a stop in the position away. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06 11. Method for cleaning a process chamber (3) of a CVD reactor (17), wherein the process chamber (3) is bounded downwards by a bottom (2) and upwards by a height-adjustable process chamber ceiling (5), wherein the bottom (2) is heated by a heating device (4), with a gas inlet device (1) for introducing gases into the process chamber (3), wherein a gas outlet surface (9) of the gas inlet device (1) facing the process chamber (3) is cooled by means of a cooling element (12), comprising the following steps: introducing a cleaning gas together with a carrier gas at a bottom temperature (T2), a process chamber pressure (P2) and a process chamber ceiling temperature (T2') through gas inlet openings (6', 7') arranged in the gas outlet surface (9) into the process chamber (3), wherein the process chamber ceiling (5) is in a position, in particular with a distance (H1) relative to the occupies the gas outlet area (9),wherein the cleaning gas reacts with at least a parasitic coating on the process chamber ceiling (5) to form reaction products; introducing another cleaning gas at a higher bottom temperature (T4), a reduced process chamber pressure (P4) and a higher process chamber ceiling temperature (T4') through the gas inlet openings (6', 7') into the process chamber (3), wherein the process chamber ceiling (5) is arranged at a distance, in particular a smaller distance (H3) to the gas outlet surface (9), wherein the other cleaning gas removes parasitic deposits at least at the gas outlet surface (9).

12. Method according to claim 11, wherein the one cleaning gas is a second cleaning gas, the one carrier gas is a second carrier gas, the one bottom temperature (T2) is a second bottom temperature, the one process chamber 31281N1PCT drg / gz May 2, 2025 Ai 2024-06, pressure (P2) is a second process chamber pressure and the process chamber ceiling temperature (T2') is a second process chamber ceiling temperature, and wherein the other cleaning gas is a fourth cleaning gas, the higher bottom temperature (T4) is a fourth bottom temperature, the reduced process chamber pressure (P4) is a fourth process chamber pressure and the higher process chamber ceiling temperature (T4') is a fourth process chamber ceiling temperature, characterized by the following steps: first cleaning step (100): introducing a first cleaning gas together with a first carrier gas at a first bottom temperature (T1), a first process chamber pressure (P1) and a first process chamber ceiling temperature (T1') through the gas inlet openings (6', 7') into the process chamber (3), wherein the process chamber ceiling (5) is arranged in a first position,in which a top surface (5'') of the process chamber ceiling (5) is in a thermally conductive connection to the gas outlet surface (9) of the gas inlet organ (1), wherein the first cleaning gas reacts with at least a parasitic coating on a top surface (2') of the bottom (2) facing the process chamber (3) to form first gaseous reaction products; second cleaning step (101): introduction of the second cleaning gas together with the second carrier gas at the second bottom temperature (T2), the second process chamber pressure (P2) and the second process chamber ceiling temperature (T2') wherein the process chamber ceiling (5) is arranged in the second position, in which the process chamber ceiling (5) is spaced at the first distance (H1) from the gas outlet surface (9), wherein the second process chamber ceiling temperature (T2') is higher than the first process chamber ceiling temperature (T1'); fourth cleaning step (103): 31281N1PCT drg / gz May 2, 2025 Ai 2024-06, Introducing the fourth cleaning gas at the fourth bottom temperature (T4), the fourth process chamber pressure (P4), and the fourth process chamber ceiling temperature (T4'), wherein the fourth bottom temperature (T4) is higher than the first and / or second bottom temperature (T1, T2), wherein the fourth process chamber pressure (P4) is lower than the first and / or second process chamber pressure (P1, P2), wherein the fourth process chamber ceiling temperature (T4') is higher than the first and second process chamber ceiling temperatures (T1', T2'), wherein the process chamber ceiling (5) is arranged in a fourth position in which the process chamber ceiling (5) is arranged at a smaller distance (H3) from the gas outlet surface (9), wherein the third distance (H3) is smaller than the first distance (H1), wherein the fourth cleaning gas removes at least at the gas outlet surface (9) parasitic deposits that formed at the gas outlet surface (9) during the first and / or second cleaning step. are removed. 13.A method according to claim 11 or 12, characterized by a third cleaning step (102) carried out between the second cleaning step and the fourth cleaning step, wherein a third bottom temperature (T3) is higher than the first and / or second bottom temperature (T1, T2), wherein a third process chamber pressure (P3) is lower than the first and / or second process chamber pressure (P1, P2), and wherein a third cleaning gas introduced through the gas inlet openings (6', 7') removes third decomposition products deposited as a parasitic coating on the underside (5') of the process chamber ceiling (5) and the top (2') of the process chamber floor (2). 31281N1PCT drg / gz May 2, 2025 Ai 2024-06.

14. A method according to any one of claims 11 to 13, characterized in that the third bottom temperature (T3) is higher than the fourth bottom temperature (T4) and / or the third process chamber temperature (T3') is higher than the fourth process chamber temperature (T4').

15. A method according to any one of claims 13 or 14, characterized in that the third purification gas is ammonia (NH3), wherein the third carrier gas is nitrogen (N2) in a first phase of the third purification step (102) and hydrogen (H2) in a second phase of the third purification step (102).

16. A method according to any one of claims 13 to 15, characterized in that the second distance (H2) and the third distance (H3) are equal.

17. A method according to any one of the preceding claims, characterized in that the fourth bottom temperature (T4) is less than 1200°C. 18.A method according to any one of claims 12 to 17, characterized in that the first process chamber pressure (P1) is greater than 50 mbar and the fourth process chamber pressure (P4) is less than 50 mbar.

19. A method according to any one of claims 12 to 18, characterized in that the total mass flow of the gases introduced into the process chamber (3) in the fourth purification step (103) is higher than the total mass flow of the gases introduced into the process chamber (3) in each of the other purification steps (100, 101, 102).

20. A method according to any one of claims 13 to 19, characterized in that the thermal conductivity (at standard conditions) of the third purification chamber is greater than 50 mbar. 31281N1PCT drg / gz May 2, 2025 Ai 2024-06.

21. Method according to any one of the preceding claims, characterized in that the first and second cleaning gases contain chlorine, in particular Cl2, and the first and second carrier gases are nitrogen (N2).

22. Method according to any one of claims 12 to 22, characterized in that the fourth cleaning gas is hydrogen (H2).

23. Method according to any one of the preceding claims, characterized in that the gas inlet device (1) comprises several gas distribution chambers (10, 11), wherein a first gas distribution chamber is connected to first gas outlet openings (6') distributed uniformly over the gas outlet surface (9), and wherein a second gas distribution chamber is connected to second gas outlet openings (7') distributed uniformly over the gas outlet surface (9).wherein the first gas inlet openings (6') are arranged in the gas outlet surface (9) and the second gas outlet openings (7') in end faces (8') of projections (8) extending from the gas outlet surface (9), wherein the process chamber ceiling (5) has first gas passage channels (15) and second gas passage channels (16), wherein the projections (8) lie completely within the second gas passage channels (16) in the first cleaning step (100), wherein the end faces (8') lie in an end face plane (13) which has a distance to the underside (5'') of the process chamber ceiling (5) that is less than the vertical length of the projections (8). 31281N1PCT drg / gz 2 May 2025 Ai 2024-06, 24. A method according to claim 23, characterized in that the diameter of the first gas inlet openings (6') is larger than the diameter of the second gas inlet openings (7').

25. A method according to claim 23 or 24, characterized in that the first and second cleaning gases are each fed into the process chamber (3) only through one of the two gas outlet openings (6', 7') and the third cleaning gas is fed into the process chamber (3) through the other gas outlet opening (6', 7').

26. A method according to any one of claims 23 to 25, characterized in that the mass flow rate of the first and second cleaning gases and the mass flow rate of the first and second carrier gases are selected such that the concentration of the first and second cleaning gases in the first and second carrier gases is between 4% and 6%. 27.A method according to any one of claims 11 to 26, characterized in that in the fourth cleaning step (103) the fourth cleaning gas is introduced into the process chamber (3) through both the first gas outlet openings (6') and the second gas outlet openings (7'), wherein the mass flow of the fourth cleaning gas flowing in through the first gas outlet openings (6') is greater than the mass flow of the fourth cleaning gas flowing through the second gas outlet openings (7').

28. A method according to any one of the preceding claims, characterized in that the cooling element is a cooling chamber (12) through which a coolant flows, wherein the temperature of the coolant during the fourth cleaning step (103) is higher than during the first and / or second cleaning step (100, 101). 31281N1PCT drg / gz May 2, 2025 Ai 2024-06.

29. Device for depositing layers, in particular III-V layers, onto substrates, comprising a process chamber (3) of a CVD reactor (17) which is bounded downwards by a base (2) and upwards by a height-adjustable process chamber ceiling (5) with passage channels (15, 16), comprising a heating device (4) for heating the base (2), comprising a gas inlet element (1) which has a gas outlet surface (9) facing the process chamber (3) in which gas inlet openings (6', 7') are arranged through which process gases, carrier gases and cleaning gases can be introduced into the process chamber (3), comprising a cooling element for cooling the gas inlet element (1), and comprising a control device (14) for controlling the heating device (4), the cooling element, mass flow controllers and valves for feeding in the process gases, carrier gases and cleaning gases. gases into the process chamber (3) and for repositioning the process chamber ceiling (5), characterized in thatthat the control device (14) is programmed to carry out the method according to one of claims 11 to 28.

30. Method or device characterized by one or more of the characterizing features of one of the preceding claims. 31281N1PCT drg / gz 2 May 2025 Ai 2024-06,

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