CVD reactor and method of use thereof and device

Abstract

The CVD reactor (1) according to the invention has a process chamber (2) having a process chamber height (H1, H2, H3, H4) that varies stepwise in flow direction (S). The position of the steps or inert gas flows (Q1, Q2, Q3) which are fed into the process chamber (2) at different positions (d1, d2, d3) and the molar mass of which is greater than 20 g / mol leads to a reduction of inhomogeneities in a layer that are otherwise observed at the edge of a substrate.

Description

Description CVD reactor and methods for its use and setup field of technology

[0001] The invention relates to a CVD reactor with a process chamber comprising a process chamber floor and a process chamber ceiling. One or more substrates are located on the process chamber floor. A process gas can be fed into the process chamber via a gas inlet device. The process gas contains a carrier gas, in particular hydrogen, and reactive gases that chemically decompose in the process chamber, with decomposition products being deposited on the walls of the process chamber and on the substrate. In particular, a SiC layer, and especially a nitrogen-doped SiC layer or a GaN layer, is deposited on the substrate.The invention relates to a method for depositing such layers and a method for optimizing the process chamber design and in particular the flow channel formed by the process chamber as well as process parameters, in particular mass flows of inert gases and compositions of inert gases, which are fed into the process chamber at one or more positions in addition to the process gas in order to dynamically influence the effective cross-sectional area for the process gas flow. State of the art

[0002] TW 1721514 B describes the effect of a changing cross-section of a process chamber on the growth rate of a layer and the layer thickness homogeneity of a layer deposited on a rotating substrate.

[0003] JP 2020-64978 A describes the effect of an inert gas flow introduced through a gas inlet opening in the process chamber ceiling on the The growth rate of a layer and the layer thickness homogeneity of a layer deposited on a rotating substrate are described. Also described is a calculated influence of the vertical position and height of gas inlet zones of a gas inlet device on the layer thickness homogeneity, where a sloping ceiling extending beyond an edge of the substrate adjoins an uppermost gas inlet zone.

[0004] From US 8,927,302 B2 and EP 2253 734 Bl, it is known to introduce inert gas flows, particularly at various positions, into the process chamber through gas inlet openings in the process chamber ceiling in order to suppress parasitic growth on the process chamber ceiling.

[0005] JP 6424384 B2 describes the influence of the molar mass of the carrier gas on the growth rate of a SiC layer on a substrate. US 7,118,781 Bl describes the influence that a process chamber height changing in the direction of flow and the injection of argon into the process chamber have on the growth rate of a SiC layer deposited on a substrate. Summary of the invention

[0006] The invention is based on the objective of providing, based on the knowledge of the aforementioned prior art, measures for increasing the layer thickness homogeneity of a layer deposited in a CVD reactor. The invention is further based on the objective of developing a method for depositing SiC or GaN layers to improve the quality of the deposited layers and of providing a suitable device for this purpose.

[0007] The problem is solved by the invention specified in the claims. The dependent claims not only represent advantageous further developments of the invention specified in the dependent claims, but also independent solutions to the problem.

[0008] The invention further pursues the approach described in the aforementioned TW 121514 B and JP 2020-64978 A, namely, modifying the design of a process chamber using model calculations or experiments, with the aim of improving the quality of a layer on a substrate. According to the invention, it is particularly intended to deposit layers with uniform thickness (high layer thickness homogeneity) and / or composition (layer homogeneity) across their entire surface. While design and process parameters can be optimized using the known method, the resulting outcome is not of the desired quality. Therefore, the invention provides for supplementing the parameters considered for optimizing the process chamber design or the process with further parameters that influence layer thickness homogeneity, or for limiting the range of values ​​of parameters.

[0009] First and essentially, it is proposed that, to optimize the CVD reactor or a process for depositing layers on a substrate, particularly SiC or GaN layers, one or more positions where the height of the process chamber changes or where a gas inlet opening is located to introduce gas into the process chamber are varied. Furthermore, it is proposed that not only the position of a first gas inlet opening and the initial inert gas flow entering the process chamber through this opening, but also the position of a The second gas inlet opening into the process chamber and the resulting second inert gas flow are considered during parameter optimization. The second gas inlet opening should be located downstream of the first gas inlet opening and spaced apart from it in the flow direction. The first position can be between the gas inlet element and the substrate. Alternatively, the first gas inlet opening can be located within the gas inlet element, i.e., at its position. The first gas inlet opening can, for example, be formed by a gas inlet zone, particularly an uppermost one. It is specifically intended that an inert gas flow of a gas with a high molar mass is introduced into the process chamber through the two gas inlet openings. Argon or a mixture of argon and another gas is preferably used for this purpose. The molar mass should preferably be greater than 20 g / mol.As a result, not only is the effect described in the prior art achieved, namely preventing parasitic growth on the process chamber ceiling, but the larger molar mass of the inert gas compared to the process gas also leads to a reduction in the effective cross-sectional area through which the process gas flows. Alternatively, or in combination with this, a change in the process chamber height in the flow direction can be considered as a further parameter during optimization. Thus, at least one additional optimization parameter is available: the position of the change in process chamber height, for example, a step in the process chamber floor or ceiling, which is particularly inclined, and / or the position of at least one gas inlet opening for introducing a molar-mass-sized inert gas.An additional optimization parameter is also available: a dynamic property, namely the mass flow rate of an inert gas and its molar mass.

[0010] The process chamber height can change at various positions, each with different distances from the gas inlet. The process chamber height preferably increases in a pre-combustion zone, which corresponds to the area of ​​the process chamber extending between the gas inlet and the upstream edge of a substrate storage area. The change in process chamber height can be between 5% and 15%, preferably between 5% and 10% of the reactor height immediately upstream of the gas inlet. Hereinafter, the term "storage area" refers to the area provided for receiving a substrate during layer deposition, in particular the area occupied by the substrate. The edges of a storage area thus also correspond to the edges of a substrate. The area of ​​the storage area or the substrate extending in the direction of flow is also referred to as the growth zone.The growth zone can be directly connected to the feed zone. The feed zone can have two or more gas inlet openings through which different mass flows of the inert gas are fed into the process chamber.

[0011] The design parameters used for variation include not only the positions of vertical step flanks in the process chamber ceiling or floor, but also the positions of slopes, for example, the position of an upstream edge of a step flank running obliquely to a vertical surface, hereinafter referred to as a slope, and the position of a downstream edge of such a slope, whereby the slope can decrease or increase the process chamber height. A slope that decreases the process chamber height can be located in the area between the gas inlet and the substrate storage area. A slope that increases the process chamber height can be located between the gas inlet and the downstream edge of the storage area. The slope should be located in the center of the storage area. Preferably, the slope can be positioned within a distance of one-third of the diameter of the storage area from the upstream edge of the storage area. The upstream edge of this slope can also lie between the gas inlet and the upstream edge of the storage area. Alternatively, the upstream edge of this slope can lie between the upstream edge of the storage area and the downstream edge of the storage area, or the center of the storage area.

[0012] According to a preferred embodiment of the invention, a gas inlet opening and / or a step, preferably designed as a slope, is located in a region downstream of an upstream edge of the storage area or of a substrate lying on the storage area, where the process chamber height changes. The step or the gas inlet opening is associated with the process chamber ceiling. Preferably, the position of the gas inlet opening or the step is located upstream of the center of the storage area or the substrate. It can thus be provided that a first gas flow is fed into the process chamber in the upstream zone and a second gas flow downstream of the upstream zone. It can further be provided that a first elevation of the process chamber ceiling is provided in the upstream zone and a second elevation of the process chamber ceiling is provided downstream of the upstream zone.The second elevation of the process chamber ceiling can be provided in the growth zone, which extends between the upstream and downstream edges of a storage area. It can also be provided that each of the two gas inlet openings is assigned to a stage. The gas inlet openings can be slot-shaped—as is generally known from the prior art—and extend across the entire width of the upstream zone. An inert gas flow can then enter the process chamber from the gas inlet openings, distributed evenly across the width of the process chamber. The process chamber extends. in a horizontal direction and can have a constant width. The distances between the stages, or the distance of the first stage from the gas inlet, are preferably greater than 10 mm.

[0013] According to a preferred embodiment, the CVD reactor has a gas inlet element located in its center with a gas outlet surface extending along a cylindrical shell, which features several vertically stacked gas outlet zones. Various reactive gases, each accompanied by a carrier gas such as hydrogen or another inert gas, can be fed into the process chamber through these gas outlet zones. A circular process chamber with a susceptor forming the chamber floor surrounds the gas inlet element. The susceptor can be heated. Around the center of the susceptor are ring-shaped storage positions for individual substrates. These storage positions can be formed by substrate holders, which are circular and disc-shaped and are driven by a gas cushion to rotate the substrates during layer deposition.To achieve a homogeneous layer on the rotating substrates during deposition, it is therefore necessary that the availability of the layer-forming reactants decreases as linearly as possible in the flow direction immediately above the process chamber floor in the growth zone. The profile of this availability in the flow direction corresponds to the growth rate of a layer deposited on a stationary, i.e., non-rotating, substrate. Only if this availability above the substrate exhibits sufficient linearity will the averaging achieved by the substrate's rotation result in a layer of uniform thickness extending across the entire substrate surface. The optimization method according to the invention is therefore designed to vary at least the parameters described above such that the growth rate of a layer on a stationary substrate exhibits maximum linearity in the flow direction. It therefore has no curvature there. Deviations from linearity lead to undesirable edge effects. The layer thickness of a layer deposited on the substrate is then either greater or lesser at the edge than in the middle. The inventive method aims to optimize the parameters so that the edge effects disappear as far as possible.

[0014] Optimization parameters include not only the positions of additional gas inlet openings in the process chamber ceiling, but also the positions of steps in the process chamber floor (here in the feed zone) and in the process chamber ceiling (in the feed zone and in the growth zone). Furthermore, the mass flows and molar masses of the inert gas flows are varied, with the molar mass being primarily adjusted by the ratio of argon to hydrogen.

[0015] The result of the previously described optimization process, which also considers further optimization parameters such as additional positions of steps in the process chamber ceiling or floor, gas inlet openings, or gas flows, is a method for depositing layers onto substrates, wherein the layers are preferably SiC layers or III-V layers, such as GaN layers. Furthermore, the result of the process is a device that incorporates the optimized design parameters, multiple gas sources, and a control unit in which the process parameters are programmed and which controls mass flow controllers and valves to feed the carrier gases, inert gases, and reactive gases stored in the gas sources into the process chamber.

[0016] During optimization, certain constructive parameters are preferably kept constant, such as the height of the steps at which the steps meet.The process chamber height changes, as does the step flank extending in the flow direction. In the simplest case, the latter can be a vertical wall. Preferably, however, the step flank has a slope inclined at an angle of between 30° and 80° to a horizontal plane. The slope can also have a smaller angle of inclination. It is particularly desirable that the slope extends over a maximum of twice the distance in the flow direction corresponding to the height offset caused by the step. This offset can be in the range of 3 to 5 mm, but can also be up to 10 mm. It is therefore advantageous if at least some, and especially all, areas of the process chamber ceiling in the area of ​​the inlet zone and the growth zone are horizontal planes running parallel to the horizontal plane of the process chamber floor.It is advantageous if the steps extend a maximum of 5 or 10 mm in the direction of flow and if the process chamber ceiling runs parallel to the process chamber floor between the steps. A minimum process chamber height can be 20 mm.

[0017] The results underlying this patent application, based on extensive model calculations and verified by experiments, show that the homogeneity of the layer thickness or the dopant incorporation can be specifically improved by the arrangement of additional gas inlet openings and the resulting injection of an inert gas with an increased molar mass, or by the special arrangement of steps or slopes to modify the process chamber.

[0018] The gas outlet openings can generate a gas flow that flows parallel to the process chamber ceiling. However, it is also possible for the gas outlet openings to be nozzles that direct the gas flow obliquely to the process chamber ceiling, particularly towards the process chamber floor. Preferably, the gas outlet openings generate a wide, shallow flow. The process chamber features a flat gas flow extending across its entire width. A homogeneous, linear flow profile should develop. If the process chamber surrounds a central gas inlet, the gas outlet openings are preferably arranged along a circular arc around the inlet, so that the resulting gas flow exits the outlet openings continuously along a circular arc. A laminar flow preferably develops within the process chamber.

[0019] The inventive process can have the following features: A first inert gas flow, which is fed into the feed zone, is at least five times larger than the sum of all further inert gas flows fed downstream of the first inert gas flow. Downstream of the first position where the first inert gas flow is fed, several further positions can be provided, at each of which a further inert gas flow is fed into the process chamber. At least some of these positions can be located in the growth zone. However, it is preferred that these positions are located in the upstream half of the growth zone, namely in a region between an upstream edge of the storage area and a center of the storage area.A second inert gas flow can thus be provided, which is fed into the downstream half of the feed zone, a third inert gas flow, which is fed into the growth zone, and a fourth inert gas flow, which is also fed into the growth zone. The gas inlet openings can each be configured with the steps described above, so that the process chamber height also changes at the positions where the inert gas flows are fed into the process chamber.

[0020] The ratio of the initial inert gas flow to the process gas flow can be between 0.1 and 0.3. For example, the process gas flow fed into the process chamber can be 200–300 slm. The initial inert gas flow can be between 50 and 80 slm. The initial inert gas flow is preferably significantly larger than the sum of all subsequent inert gas flows fed into the process chamber downstream. The ratio between the initial inert gas flow and the sum of the subsequent inert gas flows can be between 6 and 600, with the flow values ​​given in standard liters per minute.

[0021] According to a variant of the invention, it is proposed that the height of the process chamber in the feed zone changes at least twice. This can be achieved by a step in the process chamber ceiling and / or by a step in the process chamber floor. According to a preferred embodiment, a first gas inlet opening is formed in a first stage located downstream of the gas inlet device in the flow direction, through which the first inert gas flow is fed into the process chamber. It is possible that no further inert gas flows are fed into the process chamber. However, it is provided that the process chamber height changes and, in particular, increases at at least one point downstream of the first gas inlet opening. A first stage can be provided in the feed zone. A second stage can be provided in the growth zone. The two stages are preferably formed by inclined surfaces.Downstream of the first gas inlet opening, a step may be provided in the bottom of the process chamber. Two, three, or more closely adjacent positions may be provided. The positions are spaced a maximum of 50 mm apart. A gas inlet opening and / or a step may be provided at each of these positions. The distance along which the two, three, or more closely adjacent positions are located extends over the upstream edge of the bearing. space, so that the area in which the two, three or more closely adjacent positions are located is assigned to both the lead-out zone and the growth zone.

[0022] The positions of the stages and / or the gas inlet openings, or the gas flows through the gas inlet openings and their composition, are selected to minimize the curvature of the growth curve. The total pressure in the process chamber can range from 80 mbar to 1000 mbar. The temperature of the susceptor can range from 1530°C to 1620°C.

[0023] Using the optimization method described above, a further process chamber design was determined in which a pre-zone, in which the process chamber height remains constant, is initially connected to a gas inlet element, preferably comprising three gas inlet zones arranged one above the other. The pre-zone ends at the upstream edge of the substrate storage area. Approximately at this position, the process chamber ceiling has a slope that increases the process chamber height. The angle of this slope can be between 20° and 80°, preferably between 30° and 60°. The upstream edge of the slope can be located either upstream of or downstream of the upstream edge of the storage area in the direction of process gas flow. Preferably, the upstream edge of this slope is approximately the same distance from the gas inlet element as the upstream edge of the storage area.The position of the upstream edge of the slope can deviate by + / -15 mm, preferably + / -10 mm, and particularly preferably + / - 5 mm from this preferred position. This results in at least a partial section of the slope, but preferably a substantial partial section or the entire slope, being located above the bearing area. and extends downstream of the upstream edge of a substrate in a process for depositing a SiC layer onto a substrate. The height of the slope can be in the range of 2.5 to 5.5 mm. Preferably, it is between 3 and 5 mm. According to a further development of the invention, this slope, arranged in the process chamber ceiling, has a gas inlet opening through which an inert gas flow, which can be a mixture of argon and hydrogen, is fed into the process chamber. In this process, C₂H₄ is ​​fed in through a lowest gas inlet zone, C₂H₄ and trichlorosilane through a middle gas inlet zone, and C₂H₄ together with a hydrogen flow, each through an uppermost gas inlet zone. For the deposition of N-doped SiC, ammonia can additionally be fed into the process chamber through the lowest gas inlet zone and / or through the uppermost gas inlet zone.It is specifically intended that only ammonia will be used as the dopant. The gas supplied through the gas inlet opening, which has an increased molar mass, and the arrangement of the slope ensure that the availability of the silicon- or carbon-containing decomposition products of the process gases at the surface of the downstream edge of the bearing area is influenced in such a way that the layer thickness profile exhibits neither edge nor center contouring.

[0024] Using the optimization method described above, a further process chamber design was determined in which a pre-zone, in which the process chamber height decreases, is initially connected to a gas inlet element, which preferably has five gas inlet zones arranged one above the other. For this purpose, the bottom of the process chamber forms a slope, wherein an upstream edge of this slope is a maximum of 15 mm, preferably a maximum of 10 or a maximum of 5 mm, from the gas inlet element, and wherein a downstream edge of this slope is a maximum of 15 mm, preferably at least 10 mm, away from the gas inlet element. The process chamber height changes between the gas inlet and the storage area, with the slope extending in the flow direction over more than half the distance between the storage area and the gas inlet. Preferably, the process chamber height does not change between the upstream edge of the slope and the upstream edge of the storage area. This embodiment can also have a process chamber ceiling with a slope as described above. However, in this embodiment, the slope cannot have an additional gas inlet opening. The process chamber configured in this way is preferably used for a GaN deposition process in which ammonia is fed into the lowest gas inlet zone along with an inert gas, which can be nitrogen and / or hydrogen.The slope formed by the process chamber floor imparts a momentum to the ammonia flow that has a vertical component. This upwardly directed momentum of the relatively high-molecular-weight ammonia influences the flow profile in the process chamber in such a way that the layer thickness profile on a rotating substrate during deposition becomes more uniform. The height of the slope formed by the process chamber floor preferably corresponds to the height of the lowest gas inlet zone, so that the lowest level of the gas inlet zone above it is flush with the surface of the storage area. The aforementioned inert gas (hydrogen and / or nitrogen) and trimethylgallium can flow through this gas inlet zone. The aforementioned inert gas, along with ammonia, can then flow through the gas inlet above it. Trimethylgallium, along with the aforementioned inert gas, can then flow through the fourth gas inlet.Ammonia can flow into the process chamber through the uppermost gas inlet zone along with the inert gas. A second slope, which in this embodiment can be formed by the process chamber ceiling, further improves the homogeneity of the layer thickness profile. The height of this slope can also be varied. The thickness of the layer lies between 2.5 and 5.5 mm, and preferably between 3 and 5 mm. The two slopes influence, in particular, the availability of the gallium- and nitrogen-containing decomposition products of the process gases at the surface in the region of the downstream and upstream edges of the storage area, such that the layer thickness profile has neither an edge nor a center elevation.

[0025] According to a further development of the invention, the growth rate of a layer deposited on the substrate is to be locally influenced by steps / slopes arranged in the process chamber ceiling. The invention is based on model calculations that show that a step or slope in the process chamber ceiling influences the growth rate of a layer deposited on the substrate in the previously described CVD reactor, in particular a SiC layer.

[0026] The process parameters are set such that the deposition rate of the growth gas decomposition products reaches a maximum immediately upstream of the growth zone, which follows the feed zone in the direction of flow. An availability curve of, for example, silicon and carbon, or of III-V elements, but also of II-V elements at the surface, which is reflected in the growth rate, then decreases in the direction of flow within the growth zone where the substrate to be coated is located. This decrease should be as linear as possible, i.e., straight, so that a layer with high thickness homogeneity is deposited on a rotating substrate.

[0027] The model calculations show that by positioning the step / slope between the gas inlet device and upstream of the upstream edge of the storage area, the maximum of the growth curve can be achieved. The depletion zone is shifted downstream and its maximum height is reduced. With a rotating substrate, this results in an increased growth rate in the center of the deposition zone or storage area, while the growth rate at the periphery of the storage area is lower compared to the growth rate generated when no step / slope is present in the process chamber ceiling. Conversely, if the step / slope is positioned downstream of the upstream edge and upstream of the center of the storage area, the depletion zone is not shifted downstream, but rather the maximum of the depletion curve located immediately downstream of the upstream edge of the storage area is reduced.

[0028] A similar effect is achieved when a gas with a high molar mass, such as argon, is introduced via the uppermost gas inlet zone of the gas inlet device. This also leads to a reduction in the height of the maximum of the growth curve and a shift of the maximum in the flow direction.

[0029] The placement of the step / slope in a region downstream of the upstream edge of the storage area and upstream of the storage area's center also influences the homogeneity of the growth rate. The model calculations show that, unlike positioning the step / slope within the upstream zone (i.e., upstream of the storage area), positioning it downstream of the upstream edge and upstream of the storage area's center does not shift the growth rate maximum in the flow direction, but merely reduces its height. Thus, a step / slope positioned in the process chamber ceiling between the upstream edge and center of the storage area increases the homogeneity of the growth rate on the substrate. deposited layer. The model calculations show that the height of the maximum is greatest for a step / slope positioned at a distance of 4% to 15%, preferably 5%, of the bearing diameter downstream of the upstream edge of the bearing, i.e., the highest homogeneity of the growth rate of the layer is achieved.

[0030] The vertical height of the slope can preferably be between 5 and 10 mm, and the height of the step between 2 and 5 mm. The length of the slope can preferably also be less than half the diameter of the bearing surface.

[0031] In a further embodiment of the invention, a further step / slope can be arranged downstream of a step / slope located within the upstream zone and upstream of the downstream edge of the storage area. The model calculations show that positioning the second step / slope within the upstream zone has a similar effect on the growth rate profile as introducing a gas with a higher molar mass through the uppermost zone of the gas inlet element, namely, in addition to reducing the height of the growth rate maximum, it also shifts the growth rate maximum in the flow direction. Conversely, if the further step / slope is positioned above the storage area in the deposition zone, preferably between the upstream edge of the storage area and the center of the storage area, this leads to a local reduction in the growth rate in the area where the step / slope is located.in the area of ​​the layer that is deposited below the step / slope. The model calculations show that the greatest reduction in the height of the maximum is achieved by a second step / slope located downstream of the upstream edge of the storage area at a distance of 1% to 14% from the upstream edge of the storage area, or by a second step / slope. Step / slope that is located downstream of the first step / slope and upstream of the upstream edge of the storage area.

[0032] According to a further embodiment of the invention, a gas inlet opening can be arranged in the area of ​​the step / slope, through which a gas with a higher molar mass, in particular argon, is fed into the process chamber. The feeding of an inert gas through a gas inlet opening arranged downstream of the gas inlet element in the process chamber ceiling is fundamentally known from EP 2253 734 B1. There, the feeding takes place through a gas inlet opening arranged directly downstream of the gas inlet element. The feeding also occurs in the area of ​​a step. The inert gas flow is intended to suppress parasitic growth on the process chamber ceiling.

[0033] The invention proposes, in contrast, to arrange at least one gas inlet opening at a sufficiently downstream distance from the gas inlet device in the upstream zone. Unlike the design disclosed in EP 2253 734 B1, the gas outlet opening is not located directly upstream of the gas inlet device in the process chamber ceiling, but rather at a distance of at least 10% or 15%, preferably greater, and in particular at least 20% or 25%, of the length of the upstream zone extending between the gas inlet device and the upstream edge of the storage area. This has the effect of lowering the depletion or growth curve in the upstream half above the storage area and raising it in the downstream half of the storage area.

[0034] The invention is based on the finding that by introducing a gas or a gas mixture having a molar mass greater than Since the molar mass of the hydrogen used as the carrier gas is preferably greater than the molar mass of the dopant, a gas inlet opening located downstream of the upstream zone at a significant distance from the gas inlet device in the process chamber ceiling can influence not only parasitic depositions, for example on the process chamber ceiling, but also the growth rate and dopant concentration in a layer deposited on the substrate in the deposition zone. The additional heavier gas causes a change in the transport mechanism of the decomposition products perpendicular to the flow direction. The diffusion coefficient depends on the molar mass of the gas molecules. Increasing the molar mass inhibits diffusion.The injection of a gas, subsequently referred to as a barrier gas, whose molar mass is at least heavier than hydrogen, thus results in an influence on the diffusion of the reaction products or reactants.

[0035] The growth gas and doping gas flows, each accompanied by hydrogen as a carrier gas, flow from their respective gas inlet zones of the gas inlet device into a pre-flow zone of the process chamber, where the gases heat up. The doping gas and the growth gas reach temperatures at which they decompose into their constituent parts. These decomposition products diffuse vertically towards the bottom of the process chamber, perpendicular to the horizontal flow direction.

[0036] Model calculations show that the diffusion of the decomposition products vertically to the flow direction can be locally influenced by a barrier gas injected through a gas inlet opening located in the process chamber ceiling. By injecting the barrier gas through gas inlet openings located in the process chamber ceiling, the diffusion of the gas injected through the gas inlet element is reduced in the area below the gas inlet opening. The growth gas flow towards the substrate is increased. The gases fed in via the gas inlet are thus forced towards the bottom of the process chamber. This leads to an increase in the concentration of the growth gas above the bottom of the process chamber in this area. The model calculations show that if the gas inlet opening is located upstream of the maximum deposition rate of the decomposition products within the pre-flow zone, the maximum is reduced. This results in an increased linearity of the decline in the growth rate in the flow direction. Thus, by means of a barrier gas fed in via a gas inlet opening located in the process chamber ceiling within the pre-flow zone, the growth rate can be locally influenced in such a way that the layer thickness homogeneity of a layer deposited on a substrate in the deposition zone adjacent to the pre-flow zone is increased.

[0037] The gas inlet opening can preferably be arranged in the area of ​​a step or slope of the process chamber ceiling, wherein the gas inlet opening is preferably arranged within the pre-flow zone at a distance of at least 10%, preferably greater, in particular at least 20%, of the length of the pre-flow zone extending between the gas inlet device and the upstream edge of the storage area.

[0038] The extent of the reduction in the maximum growth rate depends on the mass flow rate of the barrier gas introduced through the gas inlet. The model calculations show that the higher the mass flow rate, the greater the reduction in the maximum growth rate. However, a high mass flow rate through the first gas outlet can also lead to an unstable overall flow rate.

[0039] In a further embodiment of the invention, in addition to the first gas inlet opening located in the upstream zone, a further gas inlet opening can be provided downstream of the first gas inlet opening within the upstream zone. A barrier gas can also be introduced into the process chamber through this second gas inlet opening. The mass flow through the first gas inlet opening can be reduced by the second gas inlet opening, which leads to a stabilization of the overall flow. Preferably, the mass flow of the barrier gas flowing through the second gas outlet opening can be higher than the mass flow of the barrier gas flowing through the first gas outlet opening. The further gas inlet opening can preferably be located within the upstream zone downstream of the first gas outlet opening.The model calculations show that using two gas outlet openings located in the upstream zone has a greater impact on the growth rate than using only one gas inlet opening. The model calculations demonstrate that the maximum of the growth curve is significantly reduced when both gas inlet openings are located within the upstream zone. Conversely, if the first gas inlet opening is located within the upstream zone and the second gas inlet opening is located downstream of the upstream edge of the storage area, this only results in a shift in the position of the maximum, either in or against the flow direction, but does not reduce the growth rate in the region of the maximum.

[0040] In a further embodiment of the invention, in addition to at least one gas inlet opening arranged in the upstream zone, one or more steps or one or more slopes can be arranged downstream of the upstream edge of the storage area and upstream of the center point of the storage area. The additional steps or slopes result in a further reduction of the growth rate in the region of the layer that is deposited below the steps / slopes. This leads to the fact that the The layer thickness profile of a layer deposited on a rotating substrate has neither an edge nor a center elevation. The vertical height of the steps / slopes can be between 3 mm and 10 mm. In model calculations, values ​​of 3 mm, 5 mm, and 6 mm were used. A preferred height is 6 mm, but 5 mm is also acceptable. Downstream of the steps / slopes arranged in the deposition zone, another slope can be arranged in the process chamber ceiling, where the height of the process chamber decreases. This slope can be located, at least partially, downstream of the downstream edge of the storage area. Instead of discrete steps or slopes arranged in the process chamber ceiling between the upstream and downstream edges of the storage area, a slope extending continuously across the diameter of the storage area can also be provided, where the height of the process chamber increases.In a preferred embodiment of the invention, this continuous slope can be followed by a slope where the process chamber narrows and extends at least partially downstream of the downstream edge and / or upstream of the downstream edge of the storage area. Model calculations show that a slope extending continuously across the diameter of the storage area produces a higher homogeneity of the growth rate than one or more discrete steps / slopes. To achieve a higher homogeneity of the growth rate with a continuous slope, it may be necessary to reduce the mass flow of the hydrogen supplied through the gas inlet. The model calculations show that a reduction of 15% compared to the mass flow supplied when using discrete steps / slopes is optimal.

[0041] Another aspect of the invention relates to influencing the doping profile by the additional injection of the barrier gas, whose molar- The mass is preferably greater than the molar mass of the dopant gas. The doping profile is thereby influenced in such a way that the relative maximum deviation from the mean dopant concentration in a layer can be minimized. A doping profile of a layer deposited on a rotating substrate, which, for example, has a bell shape for ammonia as the dopant carrier, can be modified by introducing the barrier flow from a gas inlet opening located in the process chamber ceiling, such that the midpoint is reduced. This makes it possible to deposit a layer with a doping profile exhibiting improved homogeneity. Introducing the barrier gas through one or more of the gas inlet openings thus offers the possibility of "fine-tuning" the doping profile.

[0042] The invention relates to a method for depositing a SiC layer or N-doped SiC onto a substrate, or to the optimization of such a method, or to an apparatus for carrying out the method, in which, in addition to the growth gases and dopant gas flows described above, which are fed in via the vertically arranged gas inlet surfaces of the gas inlet device, a further gas or a gas mixture is fed into the process chamber, wherein this further gas has a molar mass that is greater than the molar mass of the hydrogen used as the carrier gas and preferably greater than the molar mass of the dopant. Argon or a mixture of argon and hydrogen is particularly suitable for this purpose. This additional gas modifies the flow profile of the process gas in the process chamber.The barrier gas is fed into the process chamber through at least one gas inlet opening located in the process chamber ceiling at a distance of at least 25% of the length of the upstream zone extending between the gas inlet device and the upstream edge of the storage area from the gas inlet device. The gas inlet opening can be... preferably arranged in the area of ​​a step and / or slope where the height of the process chamber increases.

[0043] The invention is based primarily on model calculations and experiments demonstrating that the doping profile in a deposited SiC layer can be influenced by introducing a gas with a high molar mass, particularly argon, through gas inlet openings located downstream of the gas inlet element in the process chamber ceiling. Ammonia is preferably used as the dopant. The dopant is introduced into the process chamber through different gas inlet surfaces of the gas inlet element, i.e., at different levels. Preferably, 85% of the total ammonia flow is introduced through the uppermost gas inlet surface and 15% through the lowermost gas inlet surface. However, it is also possible, for example, for 50% of the total ammonia flow to be introduced through the uppermost and lowermost gas inlet surfaces respectively, or for 100% of the total dopant flow to be introduced through the uppermost gas inlet surface.The fluxes flowing through the gas inlet surfaces are stabilized by injecting hydrogen to achieve a total mass flux.

[0044] The results obtained from the model calculations also apply, at least in principle, to devices and methods for depositing other, in particular semiconductor, layers such as III-V layers or II-VI layers, but also other IV-IV layers.

[0045] In the model calculation results described below, a first growth gas, trichlorosilane SiHCh, is fed into the process chamber through a middle gas inlet surface located at a mid-level. This is followed by a lowest gas inlet surface located at the lowest level, and then by a gas inlet surface located at the highest level. A second growth gas, a hydrocarbon specifically ethene (C₂H₄), is introduced into the process chamber through the uppermost gas inlet and the middle gas inlet. The mass flow rate of this second growth gas through the lowermost gas inlet was 10 slm, through the middle gas inlet 75 slm, and through the uppermost gas inlet 15 slm. Additionally, hydrogen is introduced into the process chamber through each of the gas inlet surfaces. Furthermore, ammonia is used as a dopant, with 85% of the total ammonia flow being introduced through the uppermost gas inlet and 15% through the lowermost gas inlet.

[0046] To feed the barrier gas into the process chamber, a first gas inlet opening is provided at a distance of at least 10%, preferably larger than 20%, of the upstream zone extending between the gas inlet device and the upstream edge of the storage area. At least one further gas inlet opening may be provided downstream of the first gas inlet opening and upstream of the upstream edge of the storage area. Feeding the barrier gas through a further gas inlet opening located downstream of the first gas inlet opening can reduce recirculation, thereby achieving greater flow stability.

[0047] The gas inlet openings can preferably be arranged in the region of a step. The step height is preferably between 2 and 6 mm, with the results of model calculations and experiments showing an optimal step height of 3 mm. The horizontal distance between the two steps can be between 2% and 15%, preferably between 10% and 13%, of the distance between the gas inlet and gas outlet for the deposition of SiC layers. The mass flow rate of the barrier gas injected through the first gas inlet opening can preferably be lower than the mass flow rate of the barrier gas injected through the second gas inlet opening. The highest homogeneity of the doping profile of an N-doped SiC layer was achieved by injecting a mass flow rate of 20 slm through the first gas inlet opening and 30 slm through the second gas inlet opening.

[0048] The second gas inlet opening can also be arranged between the upstream edge of the storage area and the center of the storage area. Preferably, the gas inlet openings are arranged within the upstream zone.

[0049] In a further embodiment of the invention, in addition to at least one gas inlet opening arranged in the upstream zone, one or more steps or one or more slopes can be arranged downstream of the upstream edge of the bearing area and upstream of the center point of the bearing area. The additional steps or slope further reduce the dopant concentration, in particular the central peak in dopant concentration, and thus increase the homogeneity of the doping profile.

[0050] In a further embodiment of the invention, a slope can be arranged downstream of the gas inlet element and upstream of the center of the bearing area. The slope reduces the central height of the bell-shaped doping profile of the SiC layer. The upstream edge of the slope can preferably be arranged at a distance of more than 10%, and preferably at least 20%, of the length of the upstream zone extending between the gas inlet element and the upstream edge of the bearing area. The model calculations show that a A slope arranged at a distance of at least 25% of the length of the lead-in zone most effectively reduces the central elevation. For the deposition of SiC layers, the horizontal length of the slope can be between 2% and 15%, preferably between 10% and 13%, of the distance between the gas inlet and outlet.

[0051] The slope influences the doping profile of the SiC layer in a similar way to an argon flow introduced through the uppermost gas inlet zone of the gas inlet device. An argon flow introduced through the uppermost gas inlet zone also reduces the dopant concentration above the substrate, in particular reducing the peak in the dopant concentration profile.

[0052] The results of these model calculations and experiments led to the technical conclusion that by introducing a barrier gas with a greater molar mass than the doping gas, through at least one gas inlet opening located between the gas inlet device and the upstream edge of the storage area in the process chamber ceiling, the doping profile can be influenced in such a way as to minimize the relative maximum deviation from the mean doping concentration. The curvature of an availability curve generated by at least one doping gas flow introduced through the gas inlet device can be influenced by the barrier gas.

[0053] Another embodiment of the invention provides a horizontal reactor with a process chamber through which process gases can flow linearly. One or more substrates can be arranged downstream of the gas inlet element. The gas outlet surface of the gas inlet- The gas inlet device can be a flat surface. Within the gas outlet surface, several gas inlet zones arranged horizontally side by side can be located. As previously explained using the example of a planetary reactor, where the gas inlet device is located in the center of the process chamber, steps and / or slopes and / or gas inlet openings can be arranged in the process chamber ceiling downstream of the gas inlet device. An additional gas, in particular an inert gas, such as nitrogen, is introduced into the process chamber through these gas inlet openings. The additional gas can also be a barrier gas with a molar mass greater than that of the doping gas, such as argon. A gas mixture can also be introduced through the gas inlet openings.Furthermore, the process chamber is designed to have steps and / or ramps and / or gas inlet openings in its side walls, through which an inert gas can be introduced. Introducing this inert gas prevents parasitic deposits from forming on the side walls. Reactive gases can also flow through the gas inlet openings in the side walls. The side walls of the process chamber can be cleaned by introducing gases through the gas outlet openings in the side walls before, after, and / or during a coating process carried out in the process chamber. For example, deposition processes for SiC layers on suitable substrates can be performed within the horizontal reactor, whereby inert gases can be introduced through the gas inlet openings in the side walls of the process chamber during the deposition process.The gas inlet openings can preferably be arranged upstream of the center of the substrate. For example, the gas inlet openings can be arranged within the upstream half of the substrate, preferably within the upstream first quarter of the substrate.

[0054] The one or more steps in the side walls of the process chamber can preferably be arranged upstream of the center of the substrate, for example, within the upstream zone between the gas inlet and the substrate. In addition to or instead of the steps, one or more inclined surfaces can be arranged in the side walls. The flow profile within the process chamber can be influenced by means of the steps or inclined surfaces.

[0055] The width of the process chamber can increase or decrease at the steps or inclines. The diameter of the substrate storage area can be larger or smaller than the smallest width of the process chamber. Preferably, the steps or inclines can be arranged at the same level as the substrate storage area, or at least partially at that level. The steps or inclines can also extend over the entire length of the feed zone and / or the entire length of the substrate storage area. Brief description of the drawings

[0056] Exemplary embodiments of the invention and results of the model calculations are explained below with reference to the accompanying drawings. These show: Fig. 1 shows a schematic top view of a susceptor of a CVD reactor 1, as described in this application with various configurations of the process chamber, Fig. 2 is a schematic representation according to the section line II-II in Figure 1 of a first embodiment, Fig. 3 shows the growth rate of a layer deposited in a process chamber according to Figure 2 in the direction of flow with different parameters, Fig. 4 shows a representation according to Figure 2 of a second embodiment, Fig. 5 shows the growth rate of a layer deposited in a process chamber according to Figure 4 in the direction of flow with different parameters, where the substrate does not rotate, so that the growth rate reflects the availability of the reaction products above the substrate. Fig. 6 shows the progression of layer thicknesses on substrates rotating during layer deposition with the parameters according to Figures 3 and 5. Fig. 7 shows a representation according to Figure 2 of a third embodiment, Fig. 8 shows the growth rate in a process chamber of the layer deposited according to Figure 7 in the direction of flow with different parameters, Fig. 9 shows the progression of layer thicknesses on substrates rotating during layer deposition with the parameters according to Figure 8. Fig. 10 shows a representation according to Figure 2 of a fourth embodiment, Fig. 11 shows the progression of layer thicknesses on substrates rotating during layer deposition with different parameters in a device according to Figure 10. Fig. 12 shows a schematic top view of a susceptor 17 of a CVD reactor 1 of a fifth embodiment, Fig. 13 schematically shows a cross-section through a CVD reactor with a gas inlet device 5 arranged in the center of a process chamber 2, Fig. 14 shows a representation according to Figure 2 of a sixth embodiment of a process chamber 2 of a CVD reactor 1 for depositing, in particular, nitrogen-doped SiC layers, wherein the gas inlet openings 7, 8 in the flanks of the slopes 24, 32 are optional, Fig. 15 shows a representation according to Figure 2 of a seventh embodiment of a process chamber 2 of a CVD reactor 1 for depositing, in particular, nitrogen-doped SiC layers, wherein the gas inlet opening 8 in the slope 24 is optional. Fig. 16 shows the progression of the layer thickness of a SiC layer in the flow direction S, whereby the substrate was not rotated during the deposition of the layer, with curve a being a reference point. The limit curve is where no additional inert gas has been supplied through a gas inlet opening 8 according to Figure 15, and curves b and c indicate the layer thickness where argon has been supplied through the gas inlet opening 8, with curve b indicating the layer thickness profile at a height el of 3 mm and curve c indicating the layer thickness profile at a height el of 5 mm. Fig. 17 shows the thickness profile of a silicon layer on a substrate that was rotated during layer deposition, where curve a is a reference curve where no additional inert gas was introduced through a gas inlet opening 8 according to Figure 15 and the total flow through the process chamber is 309 slm, and curve b is another reference curve where, likewise, no additional inert gas was introduced through a gas inlet opening 8 according to Figure 15, but the total flow through the process chamber is 2288 slm, where curve c shows the thickness profile when the height el is 5 mm and argon is introduced through a gas inlet opening 8 according to Figure 15. Fig. 18 shows a representation according to Figure 2 of an eighth embodiment of a process chamber 2 of a CVD reactor 1 for depositing GaN layers, Fig. 19 shows the profile of the layer thickness of a GaN layer (no rotation of the substrate during deposition) deposited in a device according to Figure 18, where curve a is a reference curve in which neither the Slope 24, nor slope 25 was present, curve b indicates the layer thickness profile when both slopes 24, 25 are present and nitrogen has been additionally supplied through a gas inlet opening in slope 24 (not shown in Figure 18), and curve c indicates the layer thickness profile when both slopes 24, 25 are present but no additional nitrogen has been supplied. Fig. 20 shows the layer thickness profiles according to Figure 19 when the substrate is rotated during deposition. Fig. 21 shows a representation of the carbon incorporation into the GaN layer when (curve a) none of the slopes 24, 25 are present or (curve b) when the slopes 24, 25 shown in Figure 18 are present, Fig. 22 shows a representation of a ninth embodiment according to Figure 2, wherein a slope 24 is arranged in the process chamber ceiling 4 within the pre-run zone 31, Fig. 23 schematically shows the profile of a layer thickness r of a SiC layer in the flow direction S, where curve a is a reference curve in which no slope 24 was arranged in the feed zone and no argon was fed into the process chamber 2, curve b indicates the layer thickness profile when no slope 24 is arranged in the feed zone 31 and argon is fed into the process chamber 2 via the uppermost inlet zone 21 of the gas inlet device 5 with a mass flow of 14 slm, and curve c indicates the layer thickness profile. if, as shown in Figure 22, a slope 24 70 mm downstream of the gas inlet device 5 is arranged in a pre-flow zone 31 approximately 135 mm long, Fig. 24 schematically shows the layer thickness profiles according to Figure 23 when the substrate 6 is rotated during deposition. Fig. 25 shows a representation of a tenth embodiment according to Figure 22, wherein the inclined plane 24 is arranged in the deposition zone 30, wherein in Figure 25a the inclined plane 24 is 10 mm downstream of the edge 9' and in Figure 25b the inclined plane 24 is 28 mm downstream of the edge 9', Fig. 26 schematically shows the profile of a layer thickness r of a SiC layer in the flow direction S, where curve a is a reference curve indicating the layer thickness profile when argon is fed into the process chamber 2 via the uppermost inlet zone 21 of the gas inlet device 5 with a mass flow of 14 slm and no slope 24 is arranged in the process chamber ceiling 4, curve b is also a reference curve for the case where no slope 24 is arranged in the feed zone and no argon is fed into the process chamber 2, curve c shows the layer thickness profile when the slope 24 is arranged in the position shown in Fig. 25b, and curve d shows the layer thickness profile when the slope 24 is arranged in the position shown in Fig. 25a. Fig. 27 schematically shows the layer thickness profiles according to Figure 26 when the substrate 6 is rotated during deposition. Fig. 28 shows an eleventh embodiment according to Figure 2, wherein two stages 13, 14 are arranged in the pre-zone 31, Fig. 29 schematically shows the layer thickness profiles of a SiC layer in the flow direction S, where curve a shows the layer thickness profile when two stages 13, 14 are arranged in the upstream zone 31 at the positions shown in the illustration of the embodiment according to Figure 28, where curve b shows the layer thickness profile when the second stage 14 is arranged 50 mm downstream of the position shown in Figure 28, where curve c is a reference curve when only a single stage 13 is arranged in the upstream zone 31, where curve d indicates the layer thickness profile when the second stage 14 is arranged 75 mm downstream of the position shown in Figure 28, where curve e shows the layer thickness profile in the case that the second stage 14 is arranged 100 mm downstream of the position shown in Figure 28 in the deposition zone 30. Fig. 30 schematically shows the layer thickness profiles according to Figure 29 when the substrate 6 is rotated during deposition. Fig. 31 shows another embodiment, similar to the embodiment shown in Figure 2, to illustrate the layer thickness profile. Fig. 32 schematically shows the layer thickness profiles of a SiC layer in the flow direction S, where curve a is a reference curve. if no argon is fed into the process chamber 2 according to Figure 31 through the first and second gas outlet openings 7, 8 arranged in the area of ​​a stage 13, 14 within the pre-zone 31, where curve b shows the layer thickness profile when only argon with a mass flow of 20 slm is fed in through the first gas outlet opening 7, and curve c shows the layer thickness profile when argon with a mass flow of 30 slm is additionally fed in through the second gas outlet opening 8, Fig. 33 shows a representation of a twelfth embodiment according to Figure 2, wherein in the upstream zone 31 only a gas inlet opening 7 is arranged in the area of ​​a step 13, which is located approximately 30 mm downstream of the gas inlet element 5, Fig. 34 schematically shows the layer thickness profiles of a SiC layer in the flow direction S, where curve a shows the layer thickness profile when no argon is fed into the process chamber 2 through the gas inlet opening 7 according to figure 33, curve b shows the layer thickness profile when argon is fed through the gas inlet opening 7 with a mass flow rate of 20 slm according to figure 33, and curve c shows the layer thickness profile when argon is fed through the gas inlet opening 7 with a mass flow rate of 30 slm according to figure 33. Fig. 35 shows a representation of a thirteenth embodiment according to Figure 2, wherein the second gas inlet opening 8 is arranged in the area of ​​a step 14 50 mm downstream of the position shown in Figure 31 within the deposition zone 30, Fig. 36 schematically shows the layer thickness profiles of a SiC layer in the flow direction S, where curve a shows the layer thickness profile when no argon is fed into the process chamber 2 according to figure 35 through the two gas inlet openings 7, 8, curve b shows the layer thickness profile when argon with a mass flow of 20 slm is fed through the first gas inlet opening 7 according to figure 35, and curve c shows the layer thickness profile when argon with a mass flow of 30 slm is additionally fed through the second gas inlet opening 8 according to figure 35. Fig. 37 shows a representation of a fourteenth embodiment according to Figure 2, wherein the second gas inlet opening 8 is arranged in the area of ​​a step 14 75 mm downstream of the position shown in Figure 31 within the deposition zone 30, Fig. 38 schematically shows the layer thickness profiles of a SiC layer in the flow direction S, where curve a shows the layer thickness profile when no argon is fed into the process chamber 2 according to figure 37 through the two gas inlet openings 7, 8, curve b shows the layer thickness profile when argon with a mass flow of 20 slm is fed through the first gas inlet opening 7 according to figure 37, and curve c shows the layer thickness profile when argon with a mass flow of 30 slm is additionally fed through the second gas inlet opening 8 according to figure 37. Fig. 39 shows a representation of a fifteenth embodiment according to Figure 2, wherein the second gas inlet opening 8 is located in the area a stage 14 100 mm downstream of the position shown in Figure 31 within the deposition zone 30, Fig. 40 schematically shows the layer thickness profiles of a SiC layer in the flow direction S, where curve a shows the layer thickness profile when no argon is fed into the process chamber 2 according to Figure 39 through the two gas inlet openings 7, 8, curve b shows the layer thickness profile when argon with a mass flow rate of 20 slm is fed through the first gas inlet opening 7 according to Figure 39, and curve c shows the layer thickness profile when argon with a mass flow rate of 30 slm is additionally fed through the second gas inlet opening 8 according to Figure 39. Fig. 41 shows a representation of a sixteenth embodiment according to Figure 2, wherein two additional stages 13, 14 are arranged within the deposition zone 30 in the process chamber ceiling 4, Fig. 42 schematically shows the layer thickness profiles of a SiC layer in the flow direction S, which was deposited on a rotating substrate 6, where curve a is a reference curve when no argon is fed in through the two gas inlet openings 7, 8 arranged in the feed zone 31 according to Figure 41 and no steps are arranged within the deposition zone 30 in the process chamber ceiling 4, curve b shows the layer thickness profile when gas is fed in through the two gas inlet openings 7, 8 arranged in the feed zone 31 according to Figure 41 and no steps are arranged within the Deposition zone 30 is arranged in the process chamber ceiling 4 and curve c shows the layer thickness profile when, additionally, as shown in Figure 41, two steps 13, 14 are arranged within the deposition zone 30 in the process chamber ceiling 4, Fig. 43 shows a representation according to Figure 2 of a seventeenth embodiment of a process chamber 2 of a CVD reactor 1 for depositing, in particular, nitrogen-doped SiC layers, wherein a slope 32 is arranged in the feed zone 31 in the process chamber ceiling 4, Fig. 44 schematically shows the profile of the dopant concentration C across the diameter of a SiC layer deposited on a rotating substrate 6, a first doping profile a, which forms in a SiC layer when no additional argon is fed into the process chamber 2, a second doping profile b, which forms in a SiC layer when, as shown in Figure 43, a slope 32 is arranged within the feed zone 31, a third doping profile c, which forms in a SiC layer when a slope 32 is arranged within the deposition zone 30 in the region of the upstream edge 9' of the bearing area 9, a fourth doping profile d, which forms in a SiC layer when a slope 32 is arranged within a distance of one quarter of the diameter of the bearing area 9 from the upstream edge 9' of the bearing area 9, and a fifth doping profile, which is in a SiC layer is formed when argon is fed into the process chamber 2 via the uppermost gas inlet zone 21 of the gas inlet device 5, Fig. 45 schematically shows the dopant concentration C in the flow direction S of a SiC layer deposited on a rotating substrate 6, where curve a shows a doping profile when, as shown in Figure 31, 20 slm of argon are fed into the process chamber 4 via a first gas inlet opening 7 and 30 slm of argon are fed into a second gas inlet opening 8, curve b shows a doping profile when the second gas inlet opening 8 is located 100 mm downstream of the position shown in Figure 31, curve c shows a doping profile when the second gas inlet opening 8 is located 75 mm downstream of the position shown in Figure 31, curve d shows a doping profile when the second gas inlet opening 8 is located 50 mm downstream of the position shown in Figure 31, and curve e shows a doping profile when the second gas inlet opening 8 is located at the position shown in Figure 31. Fig. 46 schematically shows the course of the dopant concentration C across the diameter of a SiC layer deposited on a rotating substrate 6, a first doping profile a, which is formed in a SiC layer when no argon is fed into the process chamber 2, and a second doping profile b, which is formed in a SiC layer when, as shown in Figure 31, gas is introduced through two gas inlet openings arranged in the feed zone 31. Argon is supplied to the first gas inlet opening 7, 8, with a mass flow rate of 20 slm through the first gas inlet opening 7 and 30 slm through the second gas inlet opening 8, and a third doping profile c, which is formed in a SiC layer when, in addition to the gas inlet openings 7, 8 through which argon is supplied, as shown in Figure 45, two stages 13, 14 are arranged in the deposition zone 30, Fig. 47 shows a representation according to Figure 28 of a nineteenth embodiment, wherein a slope 24, where the height H2 of the process chamber ceiling 4 increases, is arranged in the process chamber ceiling 4 within the deposition zone 30, and a further slope 32, where the height H3 of the process chamber ceiling 4 decreases, is arranged in the process chamber ceiling 4 at least partially within the deposition zone 30. Fig. 48 shows a representation according to Figure 47, wherein the slope 24, on which the height H2 of the process chamber ceiling 4 increases, extends continuously over the storage area 9, Fig. 49 schematically shows the layer thickness profiles of a SiC layer in the flow direction S, which was deposited on a rotating substrate 6, where curve a shows the layer thickness profile of a layer deposited in a CVD reactor 1 according to Figure 47 and curve v shows the layer thickness profile of a layer deposited in a CVD reactor 1 according to Figure 48. Fig. 50 schematically shows a top view of a susceptor 17 of a CVD reactor 1 designed as a horizontal reactor of a twentieth embodiment, wherein the side walls of the process chamber 2 each form two steps 13, 14 enlarging the process chamber 2, Fig. 51 schematically shows a top view of a susceptor 17 of a CVD reactor 1 designed as a horizontal reactor of a twenty-first embodiment, wherein the side walls of the process chamber 2 each form a slope 24 enlarging the process chamber 2, wherein a gas outlet opening 7 is arranged in the area of ​​the slopes 24, through which a gas can be fed into the process chamber 2, Fig. 52 schematically shows a top view of a susceptor 17 of a CVD reactor 1 designed as a horizontal reactor of a twenty-first embodiment, wherein the side walls of the process chamber 2 each form a slope 24 reducing the size of the process chamber 2. Description of the embodiments

[0057] In the drawings of the exemplary embodiments, the CVD reactor is shown only schematically. Figure 13 schematically shows a CVD reactor with a housing, which is made primarily of stainless steel and is gas-tight and evacuatable. The housing contains a gas inlet device 5, which is supplied with reactive gases via at least one supply line 16. These gases, together with a carrier gas, are fed into the process chamber 2. The gas inlet device 5 has a substantially cylindrical shape and The gas inlet element 5 has several vertically arranged gas inlet zones. One of the supply lines opens into each gas inlet zone to introduce the carrier gas and one of the reactive gases. The cylindrical surface of the gas inlet element 5 forms a gas outlet surface for each gas inlet zone. Each gas outlet surface has a multitude of evenly distributed gas outlet openings for the passage of the process gas. The gas inlet element is surrounded by a circular susceptor 17, which forms the bottom of the process chamber 2. The process chamber 2 is bounded at the top by a process chamber ceiling 4. The process chamber is surrounded by a gas outlet element 18, which removes the carrier gas introduced into the process chamber through the gas inlet element, as well as decomposition products of the reactive gases. A heating device 10 is located below the susceptor, which heats the susceptor and / or the process chamber 2.The process chamber ceiling 4 can also be heated. In this case, however, the process chamber ceiling 4 is not heated. It may be provided that a temperature control device is located above the process chamber ceiling 4, with which the process chamber ceiling can either be cooled or heated. Storage positions 9 are arranged on an annular surface around the center of the gas inlet device 5, each for storing a substrate 6. The storage positions are formed by circular substrate supports, each of which holds a substrate. The substrate supports can float on a gas cushion and be set into rotation by it.

[0058] Figure 13 shows a gas supply system 33 with a plurality of gas sources 28, which provide inert gases such as hydrogen and argon. The gas sources 28 also supply process gases, such as ammonia, trichlorosilane, ethane, trimethylgallium, and nitrogen. A control device 27 is provided, which can control control elements such as mass flow controllers 29 and valves, with which the The gas flows required to carry out the procedures can be provided.

[0059] Figures 1 and 12 each show a top view of a susceptor 17 of a CVD reactor 1. In the embodiment shown in Figure 1, the susceptor 17 has a circular disk shape and forms the bottom 3 of a process chamber 2. A gas inlet 5 is located in the center of the process chamber 2, through which process gases, such as silane, disilane, methane, ethane, or organometallic compounds of an element of group III or hydrides of an element of group V, together with an inert gas, in particular hydrogen or helium, can be fed into the process chamber 2. The gas inlet 5 can form several vertically arranged gas inlet zones 19, 20, 21, through which different reactive gases, each together with a carrier gas, can be fed into the process chamber 2 separately.

[0060] The embodiment shown in Figure 12 differs from the embodiment shown in Figure 1 essentially in that the process chamber is traversed linearly by the process gas. The gas outlet surface of the gas inlet element 5 can be a flat surface.

[0061] In both embodiments, the CVD reactor has a heating device shown in Figure 13, with which the susceptor 17, coated with graphite and in particular with SiC graphite, can be heated to a process temperature. A process chamber ceiling 4 opposite the process chamber floor 3 can also be actively heated. However, it is specifically provided that the process chamber ceiling 4 is heated passively, namely by heat transfer from the process chamber floor 3. Furthermore, a gas outlet device, shown in Figure 13, is provided, with which reaction products from The process chamber 2 can be removed. The gas outlet device is connected, in particular, to a vacuum pump. In the embodiment shown in Figure 1, the susceptor is surrounded by an annular gas outlet device. In the embodiment shown in Figure 12, the gas outlet device (not shown there) is located directly opposite the gas inlet device 5. Pockets are arranged in the bottom of the process chamber 3. Gas supply lines open into the bottom of the pockets, through which a purge gas can be fed into the pockets. Each pocket contains a circular substrate carrier, which is supported by a gas cushion generated by the purge gas. The gas cushion is able to rotate this substrate carrier, which forms a storage area 9 for a substrate 6, during the deposition of a layer onto the substrate 6, so that the substrate 6 rotates during the deposition of the layer.

[0062] Figures 2, 4, 7, and 10 each schematically show a longitudinal section in the direction of flow along section line II-II in Figure 1. On the left in each figure, the gas outlet surface of the gas inlet device 5 is shown at position dO. At this position, the process chamber 2 has a process chamber height HO, which corresponds to the distance between the process chamber floor 3 and the process chamber ceiling 4, and can be between 20 and 30 mm. Downstream of the first position dO are further positions dl, d2, d3, and d4. At these positions, the flow profile of the gas flow through the process chamber 2 is influenced. The flow control devices provided at these positions dl, d2, d3, and d4 can be gas inlet openings 7, 8, 11, and 12 and / or steps 13, 14, and 15, each of which can be formed by slopes along which the process chamber height HO changes up to H4.An inert gas flow is fed into the process chamber through each of the gas inlet openings 7, 8, 11, 12, wherein the inert gas flow can have a molar mass greater than the molar mass of the carrier gas, for example hydrogen, and in particular greater than 20 g per mole. The inert gas is preferably argon or a mixture of hydrogen and argon.

[0063] The process chamber 2 forms a pre-zone 31, which extends from the first position dO, i.e., the gas outlet surface of the gas inlet device 5, to an upstream edge 9' of the storage space 9. Adjoining this, in the direction of flow, is a growth zone 30, which extends over the entire substrate 6 or the storage space 9 supporting the substrate.

[0064] Furthermore, a gas mixing system 33, shown in Figure 13, is provided, which includes gas lines, valves, and mass flow controllers for supplying the reactive gases. The gas mixing system is also capable of supplying inert gas flows, in particular a mixture of argon and hydrogen, via gas lines, valves, and mass flow controllers. The mixing ratio of the inert gas flows and their total flow can be individually adjusted by a control unit. For depositing a layer onto a substrate, the control unit can execute a recipe stored in a control unit 27 and, for this purpose, control / regulate valves and mass flow controllers.

[0065] A method according to the invention for setting up a CVD reactor is preferably carried out on a high-performance computer by performing a model calculation. In this model calculation, the temperature profile, gas flow, and chemical reactions are calculated. Selected design parameters and selected process parameters are varied to calculate the growth rate of a layer and, if applicable, its doping on a stationary substrate in the flow direction. Optimal conditions exist when the curve representing the growth rate is linear in the growth zone. The curve should exhibit a constant negative slope in this region.

[0066] In a first embodiment of the invention, shown in Figures 2 and 3, the gas outlet surface of the gas inlet element 5 is located at position dO, which is approximately 30 mm from an origin, for example, the center of the process chamber 2. The process chamber 2 has a process chamber height HO of, for example, 20 mm. It can be in the range of 20 to 30 mm. At a first position dl, a first slot-shaped gas inlet opening 7 is formed by a step in the process chamber ceiling 4, through which a first inert gas flow Q1 is fed into the process chamber 2, flowing horizontally directly below the process chamber 4. At a second position d2, which is located downstream of the first position dl, a second inert gas flow Q2 is fed into the process chamber 2. The second position d2 is located upstream of the growth zone, i.e., like the first position dl, in the feed zone.At the second position d2, there is a second gas inlet opening 8 through which a second inert gas flow Q2 is fed into the process chamber. This second inert gas flow Q2 flows between the first inert gas flow Q1 and the process chamber ceiling 4. At the second position dl, the process chamber ceiling 4 has a step that forms the second gas inlet opening 8, which is also slot-shaped. The edge 9' of the storage position 9 is approximately 140 mm from the origin. In the model, the length of the feed zone is approximately 110 mm. The edge 9" of the storage position 9 is approximately 340 mm from the origin. The first position dl is located here at a distance of 63 mm and the second position d2 at a distance of 100 mm from the origin. The second gas inlet opening 8 is located here in the feed zone 31. At positions dl and d2, the process chamber height H increases by 3 to 5 mm in each case.

[0067] Here and in the other embodiments, the step is shown with a vertically extending step flank. Other embodiments of the invention have a step that runs at an angle, i.e., rises obliquely in the direction of flow. The step can extend over a length approximately equal to the The step height corresponds to the length. However, the length can also be two to five times the step height. Between the individual steps and downstream of the last step in the flow direction, the process chamber ceiling 4 can run on planes that are parallel to the process chamber floor 3, which runs in a plane. The process chamber floor 3 can also have steps, for example, step-like elevations or depressions formed by steps. At least in the area of ​​storage space 9, however, the process chamber floor 3 runs on a horizontal plane.

[0068] Figure 3 shows calculated growth curves (growth rate versus distance from the origin) in the growth zone. Curve a shows the growth rate r in the flow direction S of a reference where the process chamber ceiling 4 has no steps and no gas inlet openings. Curve b shows the growth rate r in the flow direction S where the first inert gas flow Ql is 60 slm argon and the second inert gas flow Ql is 20.1 slm argon. Curve c shows the growth rate r in the flow direction S where the first inert gas flow Ql is 60 slm argon and the second inert gas flow Ql is 230 slm argon.

[0069] In a second embodiment of the invention, shown in Figures 4 and 5, the second position d2 is located at 200 mm, unlike in the embodiment shown in Figures 2 and 3. The second gas inlet opening 8 is located in the growth zone. All other parameters remain unchanged.

[0070] Figure 5 shows calculated growth curves in the growth zone. Curve a again shows the reference curve. Curve d shows the growth rate r in the flow direction S, where the first inert gas flow Q1 is 60 slm argon and the second inert gas flow Q2 The curve e shows the growth rate r in the flow direction S, where the first inert gas flow Q1 is 60 slm argon and the second inert gas flow Q230 slm argon.

[0071] Figure 6 shows the calculated layer thickness of a layer deposited on a rotating substrate. Curves a, b, c, d, and e were calculated using the parameters mentioned above.

[0072] It is evident that with the additional parameters used, a finer tuning of the calculated layer thicknesses is possible, by achieving a linear growth curve and a horizontal layer thickness curve through further optimization.

[0073] In a third embodiment of the invention, shown in Figures 7 to 9, the second position d2, where the second inert gas flow Q2 is fed into the process chamber 2, is located immediately upstream of the upstream edge 9' of the storage area 9. At a third position d3, a third, also slot-shaped, gas inlet opening 11 is located, forming a step, through which a third inert gas flow Q3 is fed into the process chamber 2. Crucially, the third position d3 is arranged downstream of the upstream edge 9' of the storage area 9. Furthermore, the third position d3 is located upstream of a center M of the substrate 6 (which is circular in this embodiment) or the center M of the storage area 9.

[0074] In the third embodiment, an optional fourth gas inlet opening 12 is provided at a fourth position d4, which is also slot-shaped and is arranged downstream of the third position d3. Through the A fourth inert gas flow Q4 can be introduced into the process chamber 2 above the substrate 6 via the fourth gas inlet opening 12. At positions d2, d3, and d4, the process chamber height H increases to process chamber heights H2, H3, and H4, respectively. Here, too, the step height is 3 to 5 mm. The step length extending in the flow direction S of a step 7 to 12, for example, one with an inclined step flank, can be 3 to 10 mm. The fourth gas inlet opening 12 can also be located downstream of the center point M.

[0075] Figure 8 shows calculated growth curves on a stationary substrate in the growth zone. Curve a again shows the curve of a reference where the process chamber ceiling 4 has no steps and no gas inlet openings. Curve b was calculated with the following parameters: Q1: 60 slm argon, Q2, Q3, Q4: 0.1 slm argon each. Curve c was calculated with the following parameters: Q1: 60 slm argon, Q2, Q3, Q4: 3 slm argon each. Curve d was calculated with the following parameters: Q1: 60 slm argon, Q2, Q3, Q4: 10 slm argon each. The total flow Q0 through the gas inlet 5 was 276 slm. The height of the process chamber was 25 mm. The positions were: dl 63.5 mm, d2100 mm, d3 175 mm and d3200 mm. The step height in the process chamber ceiling was 3 mm in each case.

[0076] Figure 9 shows the layer thickness calculated using the parameters mentioned above for a layer deposited on a rotating substrate during deposition. Here, too, it is evident that the layer thickness profile can be optimized by appropriately optimizing the positions d2, d3, d4 and the inert gas or argon fluxes Q2, Q3, Q4.

[0077] In the fourth embodiment of the invention, shown in Figures 10 and 11, a first inert gas flow, namely Q1 60 slm argon, is fed into the process chamber only at the first position dl. At the second position d2, a step 13 is provided in this embodiment, behind which the process chamber floor 3 runs at a lower level. The process chamber height rises here from process chamber height H1 to process chamber height H2. The height of step 13 can be between 3 and 10 mm. At the third position d3, a further step 14 is provided. Here, the step is arranged in the process chamber ceiling and is located above the substrate, i.e., downstream of the upstream edge of storage location 9 and upstream of the center M of storage location 9. The process chamber ceiling rises here from process chamber height H2 to process chamber height H3. The height of step 14 can be between 3 and 7 mm.In this embodiment, the mixing ratio of the first inert gas flow Q1 is varied as a parameter. The total inert gas flow Q1 is 60 slm. Here, D1 was 63.5 mm, d298.5 mm, and d3175 mm. The step height in the process chamber ceiling was 3 mm. The height of step 13 in the process chamber floor was 55 mm. The process chamber height at the gas inlet was 25 mm.

[0078] Here too, the steps and in particular the sloping step flanks extend only over a short area of ​​the process chamber ceiling or the process chamber floor, which corresponds at most to twice or three times the step height, so that the upstream zone extends downstream of the step or upstream of the step on one plane, with the two planes running parallel to each other.

[0079] Figure 11 shows the calculated layer thicknesses of a layer deposited on a rotating substrate during deposition. For curve a the ratio H2 / Ar is zero, for curve b the ratio is 3, for curve c the ratio is 2, for curve d the ratio is 1 and for curve e the ratio is 4, 5.

[0080] Figure 13 shows a process chamber 2 for depositing SiC layers and in particular for depositing nitrogen-doped SiC layers, which formed the basis of the model calculations, and how it is used in experiments to verify the results of the model calculations.

[0081] The gas inlet device 5 has three gas inlet zones 19, 20, and 21 arranged one above the other. Ammonia and C₂H₄ together with hydrogen are fed into the process chamber 2 through the lowest gas inlet zone 19, C₂H₄ and trichlorosilane together with hydrogen through the middle gas inlet zone 20, and ammonia and C₂H₄ together with hydrogen through the uppermost gas inlet zone 21. This process gas flow Q₀ passes through a pre-flow zone 31, followed in the direction of flow by a growth zone 30, in which a storage area 9 for a substrate 6 is located. A gas outlet surface of the gas inlet device 5, extending over a cylindrical surface, is located 195 mm from the center. In one variant, the distance is 215 mm.

[0082] In the pre-zone, process chamber 2 initially has a constant process chamber height HO of approximately 20 mm. Within the pre-zone, the process chamber ceiling 4 forms a first slope with a gas inlet opening 7 through which a mixture of argon and hydrogen can be fed into the process chamber. The slope increases the process chamber height by an amount el of 3 to 5 mm. At the end of the pre-zone, the process chamber height rises in a ramp-like fashion. For this purpose, the process- The chamber ceiling 4 has a slope 24. The angle α at which the slope 24 is inclined relative to the section of the process chamber ceiling 4 running in a plane can be between 20° and 80°, preferably between 30° and 60°. The height μ of the slope can be between 2.5 and 5 mm. The upstream edge 24' of the slope 24 is located approximately at the same position μ as the upstream edge 9' of the bearing position 9. However, the upstream edge 24' can also be located slightly downstream of the upstream edge 9'. Preferably, the majority of the slope 24 extends over the bearing position 9. In both variants, the upstream edge 9' of the bearing position 9 can be 255 mm from the center. The radial length of the growth zone is 200 mm.

[0083] In the area of ​​the slope, a gas inlet opening 8 is provided, which can have a design as described in the previously discussed embodiments.

[0084] In this embodiment, the gas inlet element 5 is located at the center of a process chamber 2 surrounding the gas inlet element 5, such that the process gas flow Q0 is a gas flow extending in a radial direction. The inclined plane 24 thus runs along a circular arc around the center of the process chamber 2, with a downstream edge 24" of the inclined plane 24 extending over the substrates 3 arranged circularly around the gas inlet element 5.

[0085] Figure 15 shows a variant of the embodiment depicted in Figure 14, in which only the inclined plane 24 is provided. Here, the process chamber 2 has a constant process chamber height HO of 20 mm in the feed zone.

[0086] Figure 16 shows the calculated profile of the layer thickness or growth rate in the flow direction when the substrate on which the SiC layer has been deposited is not rotated during deposition. Curve a represents a reference curve calculated using a process chamber design with a constant process chamber height. Curves b and c were calculated when an argon flow of 50 slm was introduced into the feed zone at the top of a device according to Figures 14 and 15, respectively, and a total of 6 slm of argon was introduced through the gas inlet opening 8. The curves differ essentially only in that the height el of the slope 24 is 3 mm in the calculation of curve a, and 5 mm in the calculation of curve b.

[0087] Figure 17 shows the profile of the layer thickness or growth rate across the diameter of a substrate that rotated during the deposition of the SiC layer. Curves a and b are reference curves showing the influence of the total flow rate through the process chamber. Curve a was calculated with a total flow rate of 309 slm and curve b with a total flow rate of 288 slm. Curve c represents the growth rate or layer thickness when a total of 6 slm of argon is fed through the gas inlet opening 8 into a device according to Figures 14 and 15, and an additional 60 slm of argon is fed into the feed zone.

[0088] The embodiment shown in Figure 18 depicts a process chamber 2 for depositing GaN layers.

[0089] The gas inlet device 5 has five gas inlet zones 19, 20, 21, 22, 23 arranged one above the other, through which an inert gas, which can be hydrogen and / or nitrogen, flows. Ammonia additionally flows through the lowest gas inlet zone 19. Trimethylgallium additionally flows through the gas inlet zone 20 located above it. Ammonia additionally flows through the gas inlet zone 21 located above it. Trimethylgallium additionally flows through the gas inlet zone 22 located above it. Ammonia additionally flows through the uppermost gas inlet zone 23.

[0090] Unlike the embodiment shown in Figures 14 or 15, the process chamber height HO is reduced in the upstream zone between the gas inlet element 5 and the upstream edge 9' of the storage space 9. For this purpose, the area of ​​the process chamber floor 3 immediately adjacent to the gas inlet element 5 extends along a slope 25. The angle of inclination β, at which the slope 25 is inclined relative to the level of the top of the storage space 9, can be between 20° and 80°, preferably between 30° and 60°. The upstream edge 25' of the slope 25 is preferably located directly next to the gas inlet element 5. However, the downstream edge 25" of the slope 25 is preferably spaced apart from the upstream edge 9' of the storage space 9. In this area, the process chamber 2 has a constant height Hl. The flow Q0 can stabilize in this area.The distance dl of the downstream edge 25" is therefore smaller than the distance of the upstream edge 9' from the gas inlet organ 5.

[0091] Downstream of the downstream edge 25", the process chamber ceiling 4 forms a slope 24 which has essentially the same geometric properties as the embodiment shown in Figure 14 or 15, for which reference is made to the descriptions therein. Unlike there, however, the slope 24 here cannot have an additional gas inlet opening.

[0092] In this embodiment as well, the gas inlet element 5 is located in the center of a process chamber 2 surrounding the gas inlet element 5.

[0093] Figure 19 shows the profile of the layer thickness and growth rate in the flow direction S, calculated when the substrate on which a GaN layer is deposited is not rotated during growth. Curve a is a reference curve calculated without considering the influence of slopes 24 and 25. Curves b and c were calculated taking both slopes 24 and 25 into account, with curve b additionally considering the injection of nitrogen (N₂) through an opening in slope 24 (not shown in Figure 18). It is evident that this additional nitrogen flow has a negligible effect on the growth curve.

[0094] Figure 20 shows the profile of the layer thickness or growth rate across the diameter of a substrate when the substrate rotates during deposition. Otherwise, the calculations were performed using the same parameters as those shown in Figure 19. It is evident that the slopes 24 or 25 are able to largely compensate for any edge effect.

[0095] Figure 21 shows the carbon incorporation into a GaN layer, calculated using the same parameters as Figures 19 and 20. It is evident that the inclined planes 24 or 25 are able to reduce the carbon incorporation, which has a direct influence on the doping.

[0096] Figure 22 shows another embodiment in which a slope 24 is arranged in the pre-zone 31 in the process chamber ceiling 4, where the height HO, Hl of the process chamber ceiling 4 increases. The vertical height of the slope 24 shown here and also in the following figures is, for example, between 3 and 10 mm. The calculations were performed with a height of 5 mm.

[0097] Figure 23 shows calculated growth curves (growth rate r versus distance from the origin) in the area of ​​the feed zone 31 and the growth zone 30. Curve a shows the growth rate r in the flow direction S of a SiC layer deposited on a substrate 6 located in storage position 9, when a slope 24 is arranged at the location shown in Figure 22 in the feed zone 31. Curve b shows the growth rate r in the flow direction S of a reference where no slope is arranged in the feed zone 31 and the first inert gas flow Ql 14 slm argon is fed into the process chamber 2 through the uppermost gas inlet zone 21 of the gas inlet device 5. Curve c shows the growth rate r in the flow direction S of another reference where neither a slope is arranged in the process chamber ceiling 4 nor an inert gas flow is fed into the process chamber 2.It is evident that both the injection of the inert gas flow and a slope 24 arranged in the feed zone 31 in the process chamber ceiling 4 shift the maximum of the growth curve in the flow direction S. Furthermore, the height of the maximum of the growth curves decreases. Thus, the injection of an inert gas flow via the uppermost gas inlet zone 21 of the gas inlet device 5 has a similar effect on the growth rate as a slope 24 arranged in the feed zone 31 in the process chamber ceiling 4. In both cases, a more linear growth curve is achieved in the region of the growth zone 30. This leads, as shown in Figure 24, to an almost horizontal layer thickness curve in the region of the deposition zone 30 for a layer deposited on a rotating substrate 6.

[0098] Figure 24 shows calculated growth curves in the growth zone 30 for a SiC layer deposited on a rotating substrate 6. Curves a, b, and c were calculated using the parameters mentioned above. It is evident that with just one slope 24 arranged in the pre-zone 31 in the process chamber ceiling 4, the layer thickness profile can be optimized towards a more horizontal profile even without argon injection. The steps / slopes 24 should maintain a minimum distance from the gas inlet 5.

[0099] Figures 25a and 25b each show a further embodiment of the invention in which the slope 24 is arranged at least partially within the deposition zone 30, i.e., above the storage area 9 in the process chamber ceiling 4. If the slope 24 is located downstream of the upstream edge 9' of the substrate 9 in the flow direction, a slightly different effect is observed, which can be achieved by injecting argon there. The growth curve is not forced downstream. The arrangement of a slope 24 in the process chamber ceiling 4 leads here to a local reduction in the growth rate, and in particular to a local reduction of the maximum growth rate in the upstream region of the deposited layer. This effect improves the layer thickness homogeneity. The results show that it is optimal if the slope is located directly adjacent to the upstream edge 9'.At least a major section of length 1 of slope 24 should be located downstream of edge 9'. Edge 9' can therefore also be located downstream of an upstream edge 24' of slope 24.

[0100] Figure 26 shows calculated growth curves on a stationary substrate in the area of ​​the pre-zone 31 and the growth zone 30. Curve a again shows the course of a reference where there is no slope 24 in The first inert gas flow Ql 14 slm of argon is located in the upstream zone 31 and is fed into the process chamber 2 through the uppermost gas inlet zone 21 of the gas inlet device 5. Curve b shows another reference in which neither a slope 24 is arranged in the process chamber ceiling 4 nor is argon fed into the process chamber. Curve c shows the layer thickness profile when the slope 24, as shown in Figure 25b, is arranged within the deposition zone 30 in the area above the upstream edge 9' of the storage area 9 in the process chamber ceiling 4. Curve d shows the layer thickness profile when the slope 24 is arranged in the position shown in Figure 25a in the deposition zone 30, where the position of the slope 24 in Figure 24a is downstream of the position shown in Figure 24b.It is evident that a slope 24 arranged within the deposition zone 30, unlike a slope 24 arranged within the upstream zone 31, does not lead to a shift of the maximum of the growth curve in the direction of flow, but merely reduces the height of the maximum of the growth curve locally, with a slope 24 arranged in the region of the upstream edge 9' of the storage area 9 within the deposition zone 30 leading to a greater reduction in the height of the maximum (see curve c) than a slope 24 arranged further downstream (see curve d).

[0101] Figure 27 shows the layer thickness of a SiC layer calculated using the parameters mentioned above, which is deposited on a rotating substrate 6 during deposition. Here, too, it is evident that an optimization of the layer thickness profile can be achieved by a slope 24 arranged within the deposition zone 30, in particular between the upstream edge 9' of the bearing area 9 and the center of the bearing area 9. The most homogeneous layer thickness profile is achieved by a slope 24 arranged in the upstream edge region of the bearing area 9 within the deposition zone 30 (see curve c).

[0102] Instead of a slope 24, one or more steps 13, 14 can also be arranged in the process chamber ceiling 4, which in the simplest case can each be a vertical wall.

[0103] In the model calculations, whose parameters and results are shown in Figures 22 to 27, the process chamber height hO was 20 mm, the distance of the gas outlet surface of the gas inlet device 5 from the origin was 30 mm, the edge 24' of the slope 24 was 100 mm in Figure 22, 175 mm in Figure 25a, and 157 mm in Figure 25b. The distance of the edge 9' from the origin was 147 mm.

[0104] Figure 28 shows a further embodiment of the invention, in which two stages 13, 14 are arranged within the pre-zone 31 in the process chamber ceiling 4, at which the height HO, Hl, H2 of the process chamber 2 increases.

[0105] Figure 29 shows calculated layer thickness profiles of a SiC layer deposited on a stationary substrate in the region of the pre-zone 31 and the growth zone 30. Curve a shows the growth rate r in the flow direction S when the first and second stages 13, 14 are located within the pre-zone 31.

[0106] Curve b shows the growth rate r in the flow direction S when the first stage 13 is located at the position shown in Figure 28 within the upstream zone 31 and the second stage 14 is located within the deposition zone 30. For the calculation of curve a, the first stage 14 is located at a position 63 mm downstream of the origin, and the second stage 14 is located 100 mm downstream of the origin. For the calculation of curve b, the second stage 14 is located 50 mm downstream of the position shown in Figure 28. as it was used as the basis for calculating curve a. The distance from the origin is 150 mm.

[0107] Curve c shows the growth rate r in the flow direction S of a reference where only a first stage 13 is located within the inlet zone 31 at the position shown in Figure 28. The distance of the single stage 13 is 63 mm from the origin.

[0108] Curve d shows the growth rate r in the flow direction S when the second stage 14 is displaced 75 mm downstream from its position shown in Figure 28. In the model, the distance of the second stage 14 from the origin is 175 mm.

[0109] Curve e shows the growth rate r in the flow direction S when the second stage 14 is located 100 mm downstream of the position of the second stage 14 shown in Figure 28. In the model, the second stage 14 was located 200 mm from the origin.

[0110] It is evident that when the second stage 14 is arranged downstream of the upstream edge 9' of the storage space 9 in the process chamber 2, the height of the maximum of the growth curve is locally reduced and, unlike with a single slope 24 or stage 13 arranged in the upstream zone 31, the maximum of the growth curve is not shifted in the flow direction S.

[0111] The results show that optimizing layer thickness homogeneity is beneficial if the process chamber height changes both upstream of and downstream of the edge 9' of the storage area. The height of the process chamber ceiling 4 above the storage area should change accordingly. of storage location 9, but downstream of this process chamber elevation change no longer changes significantly.

[0112] Instead of several steps 13, 14, the process chamber ceiling 4 in this area can also change in the form of a slope 24.

[0113] Figure 30 shows the profile of the layer thickness or growth rate r across the diameter D (200 mm) of a substrate 6 on which a SiC layer with the previously described parameters is deposited, with the substrate 6 rotating during deposition. It is also evident here that the growth curves can be optimized by appropriately selecting the number and position of the steps 13, 14 and the inclined planes 24 arranged in the process chamber ceiling 4.

[0114] Figure 31 shows a further embodiment of the invention, which essentially corresponds to Figure 2. In the area of ​​two stages arranged in the feed zone 31, a gas outlet opening 7, 8 is arranged in each case, through which a molar mass-increased inert gas flow Q1, Q2 can be fed into the process chamber 2.

[0115] Figure 32 shows calculated layer thickness profiles of a SiC layer deposited on a stationary substrate in the region of the feed zone 31 and the growth zone 30. Curve a shows the growth rate r in the flow direction S of a reference in which only two stages 13, 14 are arranged in the feed zone 31, through which no inert gas flow Q1, Q2 is fed into the process chamber 2. Curve b shows the growth rate r in the flow direction S when a first inert gas flow Q1 containing argon with a mass flow of 20 slm is fed into the process chamber 2 through the first gas outlet opening 7. Curve c Figure 1 shows the growth rate r in the flow direction S when an additional inert gas flow Q2, also containing argon, is fed into the process chamber 2 through the second gas inlet opening 8 with a mass flow rate of 30 slm. In the model calculation, the distances of the two stages 13 from the origin were 63 mm and 100 mm, respectively, with a stage height of 3 mm each.

[0116] It is evident that an argon flow introduced through the first gas inlet opening 7 reduces the height of the maximum of the growth curve, while the second gas inlet opening 8, located downstream of the first gas inlet opening 7, reduces the height of the maximum to such an extent that the decrease in the growth rate r across the growth zone 30 is almost linear. The second gas inlet opening 8 thus has a significant influence on the homogeneity of the layer thickness within the growth zone 30. It is also essential that at least one of the two gas inlet openings 7, 8 has a minimum distance from the gas outlet surface of the gas inlet device 5, which should be 10% or 32% of the length of the upstream zone 31.

[0117] Figure 33 shows a further embodiment of the invention in which a gas inlet opening 7 is arranged in the area of ​​a stage 13 arranged in the feed zone 31, through which an inert gas flow Ql can be fed into the process chamber 2.

[0118] Figure 34 shows calculated growth curves of a SiC layer deposited on a stationary substrate 6, where curve a is a reference curve indicating the growth rate r in the flow direction S when no argon is injected through the gas inlet opening 7. Curve b shows the growth rate r in the flow direction S when 20 slm of argon is injected through this gas inlet opening 7. Figure c shows the The growth rate r in the flow direction S is shown when 30 slm of argon are injected through this gas inlet opening 7. It is evident that the height of the maximum of the growth curve is influenced by the mass flow rate through a single gas inlet opening 7 located in the upstream zone 31, thus optimizing the growth rate profile. Here too, the position of the gas inlet opening 7, which can also coincide with a step, should have a minimum distance from the gas outlet surface of the gas inlet device 5, with the minimum distance being at least 10%, preferably at least 25%, of the length of the upstream zone 31. In the model calculations, the position of the gas outlet surface is approximately 30 mm from the origin, the position of the gas inlet opening 7 is 63 mm from the origin, and the position of the edge 9' is 147 mm from the origin.

[0119] Figure 35 shows a further embodiment of the invention, wherein a first gas inlet opening 7, arranged in the region of a stage, is located in the pre-zone 31 and a second gas inlet opening 8, also arranged in the region of a stage, is located in the deposition zone 30, through which an inert gas flow Q1, Q2 can be introduced into the process chamber 2. At each of the two stages, the height HO, H1, H2 of the process chamber ceiling 4 increases.

[0120] Figure 36 shows calculated growth curves of a SiC layer deposited on a stationary substrate 6 in the region of the pre-zone 31 and growth zone 30. The two gas inlet openings 7, 8 were positioned 63 mm and 150 mm apart, respectively. Figure 35 shows a change in the process chamber height at these locations. However, this is optional. The effects achieved by introducing an inert gas are of primary importance here.

[0121] Curve a shows the growth rate r in the flow direction S of a reference when no inert gas flow Q1, Q2 is introduced into the process chamber 2 through the first and second gas inlet openings 7, 8, with the gas inlet openings 7, 8 arranged in the position shown in Figure 35. Curve b shows the growth rate r in the flow direction S when only argon with a mass flow of 20 slm is introduced through the first gas inlet opening 7. Curve c shows the growth curve for the case where argon with a mass flow of 30 slm is additionally introduced through the second gas inlet opening 8. It can be seen that the maximum of the growth curve is influenced by the introduction of argon through the second gas inlet opening 8, particularly in the region of its maximum.

[0122] Figure 37 shows a further embodiment, in which, unlike the embodiment shown in Figure 35, the second gas inlet opening 8 is arranged 25 mm further downstream within the deposition zone 30. In the model calculation, the position of the second gas inlet opening 8 was 175 mm from the origin.

[0123] Figure 38 shows growth curves calculated analogously to those in Figure 36. Curve a shows the growth rate r in the flow direction S of a reference when no inert gas flow Q1, Q2 is introduced into the process chamber 2 through the first and second gas inlet openings 7, 8, with the gas inlet openings 7, 8 arranged in the position shown in Figure 37. Curve b shows the growth rate r in the flow direction S when only argon with a mass flow of 20 slm is introduced through the first gas inlet opening. Curve c shows the growth curve for the case where argon with a mass flow of 30 slm is also introduced through the second gas inlet opening 8.

[0124] Figure 39 shows a further embodiment, wherein the second gas inlet opening 8 is arranged in a position that is 50 mm further in the flow direction S than the position of the second gas inlet opening in Figure 35, and 25 mm further downstream in the deposition zone 30 than the position of the second gas inlet opening in Figure 37. The position of the second gas inlet opening 8 relative to the origin was 200 mm in this case.

[0125] Figure 40 shows growth curves calculated analogously to Figures 36 and 38. Curve a shows the growth rate r in the flow direction S of a reference when no inert gas flow Q1, Q2 is fed into the process chamber 2 through the first and second gas inlet openings 7, 8, with the gas inlet openings 7, 8 arranged in the position shown in Figure 37. Curve b shows the growth rate r in the flow direction S when only argon with a mass flow of 20 slm is fed in through the first gas inlet opening. Curve c shows the growth curve for the case where argon with a mass flow of 30 slm is additionally fed in through the second gas inlet opening 8.

[0126] Comparing the growth curve c in Figures 36, 38, and 40 with the growth curve c in Figure 32, it is evident that the position of the second gas inlet openings influences the height of the maximum of the growth curve. If the second gas inlet opening 8 is located within the pre-zone 31 in the process chamber ceiling 4 (see Figure 31), this leads to a local reduction in the height of the maximum of the growth rate r (see curve c in Figure 32). However, if the second gas inlet opening is located within the growth zone 30 in the process chamber ceiling 4, as shown in Figures 35, 37, and 39, this leads to a shift in the maximum of the growth rate r. either in the flow direction S (see Figures 38 and 40) or upstream (see Figure 36). Here too, it is evident that an optimization of the layer thickness profile can be achieved through suitable optimization of the position of the second gas inlet opening. The calculations show that positioning the second gas inlet opening 8 within the upstream zone 31 is optimal.

[0127] In the further embodiment of the invention shown in Figure 41, in addition to two gas inlet openings 7, 8 arranged in the area of ​​a stage within the feed zone 31, through which an inert gas flow Q1, Q2 can be fed into the process chamber 2, two stages 13, 14 without gas inlet openings are arranged in the growth zone 30 between the upstream edge 9' of the storage area 9 and the center of the storage area 9 in the process chamber ceiling 4. At the stages 13, 14, the height HO, H1, H2, H3, H4 of the process chamber 2 increases. Alternatively, the process chamber height can also change continuously there in the form of a slope 24.

[0128] In the model calculations, the first gas inlet opening 7 was located 63 mm from the origin, and the second gas inlet opening 8 was located 100 mm from the origin. At both inlets 7 and 8, the process chamber height increased by 3 mm. The two stages 13 and 14 were located 175 mm and 200 mm from the origin, respectively, and each had a stage height of 3 mm. A relative slope 24 can have a length of 25 mm and a height of 6 mm.

[0129] Figure 42 shows calculated growth curves for a SiC layer deposited on a rotating substrate 6. Curve a shows the progression The growth rate r in the flow direction S of a reference is shown, where no argon is fed into the process chamber 2 through the gas inlet openings 7, 8 arranged in the upstream zone 31, as shown in Figure 41, and no stages 13, 14 are arranged in the process chamber ceiling 4 within the deposition zone 30. Curve b shows the course of the growth rate r in the flow direction S when argon with a mass flow rate of 20 slm is fed into the process chamber 2 through the first gas inlet opening 7 and argon with a mass flow rate of 30 slm is fed into the process chamber 2 through the second gas inlet opening 8, and no stages 13, 14 are arranged in the process chamber ceiling 4 within the deposition zone 30.Curve c shows the growth rate r in the flow direction S when argon with a mass flow rate of 20 slm is fed into the process chamber 2 through the first gas inlet opening 7 and argon with a mass flow rate of 30 slm is fed into the second gas inlet opening 8, and two stages 13, 14, as shown in Figure 41, are arranged in the process chamber ceiling 4 within the deposition zone 30. It is evident that if, in addition to the gas inlet openings arranged in the upstream zone 31 through which argon is fed into the process chamber, stages 13, 14 are arranged in the deposition zone 30, the growth curve is further optimized. The stages 13, 14 lead to a significant reduction in the midpoint of the bell-shaped growth curve.Instead of the two steps 13, 14, in a further embodiment not shown, the aforementioned slope can be arranged in the process chamber ceiling 4 within the growth zone 30, in particular between the upstream edge 9' of the storage area 9 and the center of the storage area 9. The horizontal length of the slope is preferably 6 mm. The vertical height of the steps shown in Figures 31, 33, 35, 37, 39 and 41 is preferably 3 mm.

[0130] The previously described embodiments show that by adding the parameters selected according to the invention, such as steps, slopes, a finer adjustment of the growth rate r in the growth zone 30 is possible.

[0131] The embodiment shown in Figure 43 depicts a process chamber 2 for depositing SiC layers. A slope 32 is arranged within the pre-zone 31.

[0132] Figure 44 illustrates the effect that the slope 32 in the process chamber ceiling 4 has on the dopant distribution within a SiC layer deposited on a rotating substrate 6 within a process chamber 2 according to Figure 22. The dopant gas flow contains ammonia as the dopant carrier. The ammonia flow is introduced via the uppermost gas inlet zone 21 and the lowermost gas inlet zone 19.

[0133] Curves a, b, c, and d show the calculated dopant concentration C across the diameter of the SiC layer in the flow direction S. Curve a serves as a reference, showing the dopant concentration C when no slope 32 is located in the process chamber ceiling 4. The dopant gas flow creates a lateral profile of its dopant with a characteristic, here bell-shaped, curvature pattern in the layer. Curve b shows the dopant concentration C when the slope 32 is located above the substrate 6 stored at bearing position 9, i.e., within the upstream first quarter of the deposition zone 30 at position 175 mm. The center point M of the substrate 6 is located at position 247 mm. The midpoint of curve b is less than that of curve a. The midpoint of the doping profile is further reduced as the position of the slope 32 shifts towards the gas inlet device 5. This is evident from the Curves c and d are visible. Curve c shows the dopant concentration C when the slope 32 is located in the region of the upstream edge 9' of the substrate 6 at position 157 mm, i.e., still within the deposition zone 30. Curve d, on the other hand, shows the doping profile of the SiC layer when the slope 32 is located within the upstream zone 31, i.e., upstream of storage location 9 or substrate 6. The reduction of the midpoint peak correlates with the Si / C ratio. The corresponding curves (not shown), which represent the Si / C ratio, are also flatter when a slope 32 is provided in the process chamber ceiling 4. Curves a to d in Figure 44 show that the midpoint peak of the doping profile is reduced most significantly when the slope 32 is positioned within the upstream zone 31.

[0134] Curve e shows, for comparison, the influence of an argon flow injected via the uppermost gas inlet zone 21 of the gas inlet device 5. Compared to curves a to d, curve e is noticeably at a lower level. It is evident that an argon flow injected via the uppermost gas inlet zone 21 also reduces the midpoint of the doping profile, thereby reducing the dopant concentration within the entire deposition zone 30 by injecting an argon flow.

[0135] A slope 32 arranged in the process chamber ceiling 4 thus influences the central elevation of the bell-shaped doping profile produced by the ammonia flow in a similar way to an argon flow fed in through the uppermost gas inlet zone 21.

[0136] Figure 45 shows the effect of the argon flow on the dopant distribution within a SiC layer deposited on a substrate 6 in a process chamber 2 according to Figure 2, when argon does not pass over the uppermost gas inlet zone 21, but is supplied through gas inlet openings 7, 8 arranged in the process chamber ceiling 4. The graph shows the dopant concentration C across the diameter of the substrate 6, which rotated during deposition. Curve a is a reference curve showing the influence of the argon flow on the doping profile when argon is supplied to the process chamber 2 only via a first gas outlet opening 7 located at position 63 mm with a mass flow of 20 slm.

[0137] Curves b, c, d, and e show the effect of introducing argon with a mass flow rate of 30 slm, i.e., a higher mass flow rate than that introduced through the first gas outlet 7, via an additional gas outlet 8 located downstream of the first gas outlet 7. Introducing argon through a second gas outlet 8 located downstream of the first gas outlet 7 further reduces the midpoint of the doping profile (see curves b, c, d, and e). Curve b shows the doping profile when the second gas outlet is located at a position 200 mm, i.e., within the deposition zone 30 at a distance of approximately D / 2 from the upstream edge 9' of the storage area 9, where D is the diameter of the storage area 9. Curve c shows the doping profile when the second gas outlet opening 8 is at position 175 mm, i.e. also within the deposition zone 30.Curve d is significantly flatter than curve b. Curve d represents the dopant concentration C when the second gas outlet 8 is located in the marginal region of the upstream edge 9' of storage area 9 within the deposition zone 30. Curve d is again flatter than curve c. The flattest curve is curve e, which indicates the dopant concentration C when the second gas outlet is located within the upstream zone 31 at position 100 mm. The greatest reduction in the midpoint of the doping profile, and thus the most homogeneous doping profile, is achieved when argon is not only introduced by a first gas outlet in the storage area 9. The argon flow is not only fed into the gas outlet 7 located in the upstream zone 31, but is also fed in through a second gas outlet 8, which is located downstream of the first gas outlet 8 within the upstream zone 31. The argon flow fed in through the second gas outlet 8 reduces the risk of recirculation caused by the argon flow fed in through the first gas outlet 7, and thus increases the flow stability.

[0138] Figure 46 shows the influence of the stages 13, 14 arranged in the deposition zone 30, as depicted in Figure 41, on the dopant distribution within a SiC layer deposited on a rotating substrate 6. The graph shows the dopant concentration C as a function of the diameter of the substrate 6. Curve a shows, as a reference, the doping profile of a SiC layer deposited without the injection of argon. Curve b corresponds to curve e in Figure 45 and shows the influence of argon injected through the gas inlet openings 7, 8 arranged in the upstream zone 30. Curve c shows the dopant concentration C when, in addition, two stages 13, 14 are arranged within the process chamber ceiling 4 in the upstream half of the storage area 9, where, as shown in Figure 41, the process chamber height increases HO, H1, H2, H3, H4.Curve b shows that the injection of argon has the strongest influence on the dopant distribution. If, in addition to the injection of argon, the two stages 13 and 14 are provided within the deposition zone 30 (see curve c), fine-tuning of the dopant distribution is possible, with the midpoint rise being slightly reduced compared to curve b. Instead of the two stages 13 and 14, a slope 32 can also be arranged in the deposition zone 30 (not shown). The slope 32 can also be used to influence the dopant concentration. The curve representing the dopant concentration C is flattened.

[0139] From the findings discussed above, it is evident that the dopant concentration profile in the deposition zone 30 is influenced by the injection of gas through inlet openings, particularly those located in the feed zone 31. Furthermore, the dopant concentration profile in the deposition zone 30 can also be influenced by a slope 32 located within the feed zone 31 in the process chamber ceiling 4. Fine-tuning of the dopant concentration profile is also possible by steps 13, 14, or slopes 32 located in the deposition zone 30, in addition to the gas inlet openings, steps, or slopes located in the feed zone 31. The curves were plotted on linear axes.

[0140] Figures 50 to 52 each show an embodiment according to the invention of a CVD reactor 1 designed as a horizontal reactor.

[0141] The horizontal reactor 1 shown in Figure 50 has steps 13, 14 formed by the side walls that laterally delimit the process chamber 2. Each of the two side walls forms two steps 13, 14, at which the width of the process chamber 2 increases. More or fewer steps 13, 14 may also be provided. The width of the process chamber 2 corresponds to the distance between the side walls of the process chamber 2. The steps 13, 14 extend at least partially within the feed zone 31, which is located between the gas inlet device 5 and the substrate storage area 9. However, the length and / or number of the steps 13, 14 can also be greater, so that the steps 13, 14 extend at least partially into the deposition zone 32. The steps 13, 14 can also be located entirely within the deposition zone 32. Instead of steps 13, 14, one or more inclined planes 24 can be arranged, as shown in the example dashed line.

[0142] Figure 51 shows another embodiment of a horizontal reactor 1 according to the invention. The side walls of the process chamber 2 each form a slope 24, at which the width of the process chamber 2 increases. The slope 24 is arranged between an upstream edge of the storage area 9 and the center of the storage area 9. In the region of the slope 24, there is a gas outlet opening 7 through which a gas, in particular an inert gas, can be fed into the process chamber 2. The gas outlet opening 7 is, by way of example, arranged at the upstream end of the slope 32. The gas outlet opening 7 can also be arranged between the upstream end and the downstream end of the slope 32 or at the downstream end of the slope 32.By introducing the inert gas through the gas outlet openings 7 in the side walls of the process chamber 2, parasitic deposits on the side walls can be removed or their formation prevented.

[0143] Figure 52 shows a horizontal reactor 1, wherein the side walls laterally delimiting the process chamber 2 of the horizontal reactor 1 each form a slope 24, at which the width of the process chamber 2 decreases. The slope 24 is located within the feed zone 31. However, the slope 24 can also be located at least partially or completely within the deposition zone 32. The smallest width of the process chamber 2 corresponds approximately to the diameter D of the substrate storage area 9. However, the diameter D of the substrate storage area 9 can also be smaller.

[0144] The foregoing statements serve to explain the inventions covered by the application as a whole, which each independently further develop the prior art at least through the following combinations of features, whereby two, several or all of these combinations of features may also be combined, namely:

[0145] A device characterized in that the upstream edge 24' of the flank 24 is spaced away from the gas outlet surface.

[0146] A device characterized in that the flank 24 lies downstream of the upstream edge 9' of the storage location 9 and upstream of a center point M of the storage location 9.

[0147] A device characterized in that the flank 24 is located at a distance of at most one third of the diameter of the bearing position 9 from the upstream edge 9' of the bearing position 9.

[0148] A device characterized in that the change in the process chamber height HO to H4 is between 5% and 15%, preferably between 5% and 10% of the process chamber height HO immediately downstream of the gas inlet device 5.

[0149] A device characterized in that the process chamber ceiling 4 has a further flank 32 increasing the process chamber height HO to H4, which lies in front of the first flank 24 in the flow direction S.

[0150] A device characterized in that the process chamber floor 3 forms a flank 25 reducing the process chamber height HO to H4, wherein an upstream edge 25' is spaced a maximum of 15 mm from the gas inlet device 5 and an upstream edge 25" is spaced a maximum of 15 mm from the upstream edge 9' of the storage place 9.

[0151] A device characterized in that the height e2 of the flank 25 formed by the process chamber floor 3 corresponds to the height of a lowest gas outlet zone 19 of the gas inlet device 5, and / or the vertical The level of a lower edge of a gas outlet zone 20 arranged immediately above the lowest gas outlet zone 19 is aligned with the level of the surface of the storage area 9.

[0152] A device characterized in that the gas inlet opening 7 is located at a distance of at least 10% of the length of the pre-zone 31 from the gas inlet element 5.

[0153] A device characterized in that at least one further gas inlet opening 8, 11, 12 is arranged downstream of the first gas inlet opening 7 and upstream of a center point M of the storage place 9 and / or upstream of an upstream edge 9' of the storage place 9.

[0154] A device characterized in that the gas inlet opening 7, 8, 11, 12 is arranged in the area of ​​a step 13, 14, 15 and / or slope 24, 32, where the process chamber height HO to H4 increases.

[0155] A device characterized in that the horizontal distance between two steps 13, 14, 15 and / or the horizontal length of the slope 24, 32 lies in the range between 3% and 8% of a diameter of the process chamber ceiling 4.

[0156] A device characterized in that at least one step 13, 14, 15 or slope 24, 32 is arranged downstream of the upstream edge 9' and the center point M of the storage place.

[0157] A device characterized in that the side walls of the process chamber 2 have at least one flank 24 or step 13, 14 extending at least partially upstream of a center of the storage place 9, at which the width of the process chamber 2 increases or decreases.

[0158] A device characterized by one or more gas inlet openings 7, 8 arranged in the area of ​​the flank 24 or stage 13, 14, through which a gas can be fed into the process chamber 2.

[0159] A method for depositing a layer on a substrate 6 in a CVD reactor 1, which has a process chamber 2 with a process chamber floor 3 formed by a susceptor 17 and a process chamber ceiling 4 spaced from the process chamber floor 3 by a process chamber height HO to H4, wherein a gas supply device 33 provides a process gas flow Q0 which can be fed into the process chamber 2 through a gas inlet device 5 and flows through the process chamber 2 in a horizontal flow direction S, wherein the process gas flow Q0, which includes a carrier gas, in particular hydrogen and reactive gases, which decompose in the process chamber 2 or on the surface of the substrate 6 arranged on a storage location 9 of the process chamber floor 3 into decomposition products which are deposited on the substrate 6 with a growth rate r,wherein the growth rate r in the flow direction S above the substrate 6 is determined in a model calculation or by experiments and the design parameters of the process chamber 2 and the process parameters are varied such that the growth rate r above the substrate 6 is as linear as possible, wherein the design parameters changed during the variation are at least the following: one or more positions dl, d2, d3, d4 at which the height HO, Hl, H2, H3, H4 of the process chamber 2 changes or at which a gas inlet opening 7, 8, 11, 12 is arranged.

[0160] A method characterized in that, during the variation, the values ​​of gas flows through the one or more gas inlet openings 7, 8, 11, 12 are changed and / or that the molar mass of at least one inert gas flow Q1, Q2, Q3 flowing through the gas inlet openings 7, 8, 11, 12 is changed, wherein the molar mass is adjusted in particular by a mixture of argon and hydrogen.

[0161] A method characterized in that at least one position d2, d3 is located downstream of an upstream edge 9' of storage location 9 and upstream of a midpoint M of storage location 9.

[0162] A method characterized in that a first position dl is located downstream of the gas inlet device 5 and upstream of the upstream edge 9' of the storage location 9 in the flow direction S, and a second position d2 is located downstream of the first position dl and upstream of the upstream edge 9' of the storage location 9, and / or a third position d3 is located downstream of the upstream edge 9' of the storage location 9 and upstream of a center point M or a downstream edge 9" of the storage location 9, and / or the change in height HO to H4 of the process chamber 2 is a change in the course of the process chamber ceiling 4 and / or the process chamber floor 3.

[0163] A process characterized in that the second inert gas flow Q2 is less than the first inert gas flow Q1 and the molar mass of the two inert gas flows Q1, Q2 is greater than the molar mass of hydrogen and the two inert gas flows contain, in particular, argon.

[0164] A method characterized in that a third gas inlet opening 11 downstream of the second gas inlet opening 8 provides access to a third Inert gas flow Q3 is fed into the process chamber 2, wherein the third gas inlet opening 11 is arranged at a third position d3, which is located downstream of an upstream edge 9' of the storage space 9 and upstream of a midpoint M or a downstream edge 9" of the storage space 9, wherein the third inert gas flow Q3 is less than the first inert gas flow Q1 and the molar mass of the third inert gas flow Q3 is greater than the molar mass of hydrogen and, in particular, contains argon or predominantly argon, and / or that the first inert gas flow Q1 is at least five times greater than the sum of all further inert gas flows Q2, Q3, which are fed into the process chamber 2 at the second and / or third position d2, d3 downstream of the first position, and / or that a fourth inert gas flow Q4 is fed into the process chamber 2 through a fourth gas inlet opening 12 downstream of the third gas inlet opening 11. is fed inwherein the fourth gas inlet opening 12 is arranged at a fourth position d3, which is located downstream of the third position d3 and upstream of the downstream edge 9" of the storage location 9 and / or that the ratio of the first inert gas flow Q1 to the process gas flow QO is in the range between 0.1 and 0.3 and / or that the ratio of the first inert gas flow Q1 to the sum of further inert gas flows Q2, Q3, Q4 fed in downstream of the first position dl is in the range between 6 and 600.

[0165] A method characterized in that the first position dl is located at a distance of at least 10% or at least 25% of the distance between the gas inlet device 5 and the upstream edge 9' of the storage location 9 and the second position d2 is located downstream of the first position dl and the upstream edge 9' of the storage location 9, wherein the inert gas flow Q1, which is fed in at the first position dl, is less than the inert gas flow Q2, which is fed in at the second position d2.

[0166] A method characterized in that the at least one change is located at a second position d2 and / or at a third position d3, wherein the second position d2 is located downstream of the first position dl and upstream of an upstream edge of the storage location 9, and the third position d3 is located downstream of the upstream edge 9' of the storage location 9 and upstream of a center point M or a downstream edge 9" of the storage location 9, or that the first position dl is spaced at a distance of at least 10% or at least 25% of the distance between the gas inlet device 5 and the upstream edge 9' of the storage location 9, and the process chamber ceiling 4 forms a slope 24 at the first position dl that increases the process chamber height HO to H4, or the process chamber floor 3 forms a slope between the gas inlet device 5 and the first position dl that decreases the process chamber height HO to H4. 25 are trained.

[0167] A method characterized in that the process chamber height HO to H4 increases in the flow direction S at a third position d3, wherein the third position d3 is located downstream of the upstream edge 9' of the storage location 9 and upstream of the center point M or the downstream edge 9" of the storage location 9.

[0168] A CVD reactor characterized in that the control device 10 is configured to carry out a method according to one of claims 13 to 21.

[0169] A CVD reactor characterized in that a third gas inlet opening 11 is arranged downstream of the second gas inlet opening 8 at a third position d3 downstream of an upstream edge 9' of the storage space 9 and upstream of a center M or a downstream edge 9" of the storage space 9.

[0170] A CVD reactor characterized in that the process chamber 2 has a process chamber height HO in the range between 20 and 30 mm immediately downstream of the gas inlet device 5, wherein the process chamber height HO increases at each of the first, second or third or fourth position dl, d2, d3, d4 by 5% to 15% of the process chamber height HO immediately downstream of the gas inlet device 5.

[0171] A CVD reactor characterized in that downstream of a downstream edge 9" of storage space 9 the process chamber height is reduced to a fourth process chamber height H4.

[0172] A CVD reactor characterized in that changes in the process chamber height HO to H4 are formed by stages 13, 14, 15 and / or that the stages 13, 14, 15 have stage flanks 24, 32 extending vertically or obliquely thereto and / or that the process chamber ceiling 4 extends in a plane parallel to the process chamber floor 3 between some of the first, second or third positions dl, d2, d3, d4, in particular between all of the positions dl to d4 and / or that the stage flanks 24, 32 extend in the flow direction S over a maximum distance corresponding to 3% to 9% of the diameter of the process chamber ceiling 4.

[0173] A CVD reactor characterized in that the process chamber floor 3 forms a second slope 25 reducing the process chamber height HO, Hl, H2, wherein an upstream edge 25' has a distance to the gas inlet device 5 and a downstream edge 25" has a distance to the upstream edge 9' of the storage place 9.

[0174] A CVD reactor characterized in that the height el of the first slope 24 is between 3% and 9% of the process chamber height HO immediately in front of the gas inlet device 5, preferably between 3 and 5 mm.

[0175] A CVD reactor characterized in that the height e2 of the second slope 25 corresponds to the height of a lowest gas outlet zone 19 of the gas inlet device 5, and / or that the vertical level of a lower edge of a gas outlet zone 20 arranged immediately above the lowest gas outlet zone 19 is aligned with the level of the surface of the storage place 9.

[0176] All disclosed features are essential to the invention (individually, but also in combination with one another). The disclosure of this application hereby incorporates in full the disclosure content of the associated / attached priority documents (copy of the earlier application), also for the purpose of including features of these documents in the claims of the present application. The dependent claims characterize, even without the features of a referenced claim, independent inventive developments of the prior art, in particular for the purpose of filing divisional applications based on these claims. The invention specified in each claim may additionally comprise one or more of the features described above, in particular those identified by reference numerals and / or listed in the reference numeral list.The invention also relates to design forms in which individual features mentioned in the preceding description are not realized, in particular insofar as they are recognizably unnecessary for the respective purpose or can be replaced by other technically equivalent means. List of reference symbols 1 CVD reactor 25 inclined 2 Process chamber 25' Edge of the slope 25 3 Process chamber floor 25" Edge of the slope 25 4 Process chamber ceiling 26 Gas inlet 5 Gas inlet device 27 Control unit 6 Substrate 28 Gas source 7 first gas inlet opening 29 mass flow regulator 8 second gas inlet opening 30 deposition zone 9 Storage space 31 Pre-sale zone 9' upstream edge 32 slope 9" downstream edge 33 Gas supply unit 10 Control unit 11 third gas inlet opening 12 fourth gas inlet opening 13th level 14 stage a curve 15 stage b curve 16 Supply line c Curve 17 Susceptor of the curve 18 Gas outlet device e Curve 19 Gas inlet zone el height 20 Gas inlet zone e2 height 21 Gas inlet zone dl first position 22 Gas inlet zone d2 second position 23 Gas inlet zone d3 third position 24 Slant d4 fourth position 24' Edge of the slope 24 r Growth rate 24" edge of the slope 24 1 length C Dopant concentration Diameter Holy first trial chamber height H2 second process chamber height H3 third chamber level M Center of the substrate 7 QO Process gas flow Ql first inert gas flow Q2 second inert gas flow Q3 third inert gas flow Q4 fourth inert gas flow S Flow direction

Claims

Claims 1. Device for depositing a layer on a substrate (6) in a CVD reactor (1) comprising a process chamber (2) with a process chamber floor (3) formed by a susceptor (17) and a process chamber ceiling (4) spaced from the process chamber floor (3) by a process chamber height (HO to H4), wherein a gas supply device (33) provides a process gas flow (QO) which can be fed into the process chamber (2) through a gas inlet device (5) and flows through the process chamber (2) in a horizontal flow direction (S), wherein the process gas flow (QO) contains reactive gases which decompose in the process chamber (2) into decomposition products which are deposited on the surface of the substrate (6) arranged on a storage area (9) of the process chamber floor (3) at a growth rate (r), wherein a gas outlet surface of the gas inlet device (18) and the storage area (9) are located between a gas outlet surface of the gas inlet device (18) and the storage area (9). The pre-season zone (31) extendswherein the process chamber ceiling (4) extends at least partially downstream of an upstream edge (9') of the storage area (9), flank (24) has a slope at which the process chamber height (HO to H4) increases, wherein the length of the flank (24) measured in the flow direction (S) is less than half the diameter of the bearing space (9), characterized in that the upstream edge (24') of the flank (24) is spaced away from the gas outlet surface.

2. Device according to claim 1, characterized in that the flank (24) downstream of the upstream edge (9 Z ) of the storage site (9) and upstream of a midpoint (M) of the storage site (9) lies- 3. Device according to one of the preceding claims, characterized in that the flank (24) is located at a distance of at most one third of the diameter of the bearing space (9) from the upstream edge (9). Z) of the storage area (9).

4. Device according to one of the preceding claims, characterized in that the change in the process chamber height (HO to H4) is between 5% and 15%, preferably between 5% and 10% of the process chamber height (HO) directly downstream of the gas inlet device (5).

5. Device for depositing a layer on a substrate (6) in a CVD reactor (1) comprising a process chamber (2) with a process chamber floor (3) formed by a susceptor and a process chamber ceiling (4) spaced from the process chamber floor (3) by a process chamber height (HO to H4), wherein a gas supply device (33) provides a process gas flow (Q0) which can be fed into the process chamber (2) through a gas inlet device (5) and flows through the process chamber (2) in a horizontal flow direction (S), wherein the process gas flow (Q0) contains reactive gases which decompose in the process chamber (2) into decomposition products which are deposited on the surface of the substrate (6) arranged on a storage area (9) of the process chamber floor (3) with a growth rate (r),wherein the process chamber ceiling (4) has a flank (24) extending at least partially downstream of an upstream edge (9') of the storage area (9), at which the process chamber height (H1 to H4) increases, characterized in that the process chamber ceiling (4) has a further, the process chamber height (HO to H4) has a flank (32) that increases in height and is located in the direction of flow (S) in front of the first flank (24).

6. Device according to one of the preceding claims, characterized in that the process chamber floor (3) forms a flank (25) reducing the process chamber height (HO to H4), wherein an upstream edge (25') is spaced a maximum of 15 mm from the gas inlet element (5) and an upstream edge (25") is spaced a maximum of 15 mm from the upstream edge (9). Z ) of the storage area (9) is spaced apart.

7. Device according to claim 6, characterized in that the height (e2) of the flank (25) formed by the process chamber floor (3) corresponds to the height of a lowest gas outlet zone (19) of the gas inlet element (5), and / or the vertical level of a lower edge of a gas outlet zone (20) arranged directly above the lowest gas outlet zone (19) is aligned with the level of the surface of the storage place (9).

8. Device for depositing a layer on a substrate in a CVD reactor (1) comprising a process chamber (2) with a process chamber floor (3) formed by a susceptor and a process chamber ceiling (4) spaced from the process chamber floor (3) by a process chamber height (HO to H4), wherein a gas supply device provides a process gas flow (Q0) which can be fed into the process chamber (2) through a gas inlet device (5) and flows through the process chamber (2) in a horizontal flow direction (S), wherein the process gas flow (Q0) includes reactive gases which are deposited in the process chamber (2) on the surface of the substrate on a storage area (9) of the decompose the substrate (6) arranged in the process chamber floor (3) into decomposition products which are deposited on the substrate (6) with a growth rate (r), wherein the process chamber ceiling (4) has a gas inlet opening (7) arranged downstream of the gas inlet element (5), which is located in a pre-flow zone (31) extending between the gas inlet element (5) and the storage area (9) and which is connected to an inert gas source which provides an inert gas flow (Ql) whose molar mass is greater than that of hydrogen and which contains in particular argon, characterized in that the gas inlet opening (7) is located at a distance of at least 10% of the length of the pre-flow zone (31) from the gas inlet element (5).

9. Device according to claim 8, characterized in that downstream of the first gas inlet opening (7) and upstream of a center point (M) of the bearing space (9) and / or upstream of an upstream edge (9 Z) of the storage area (9) at least one further gas inlet opening (8, 11, 12) is arranged.

10. Device according to claim 8 or 9, characterized in that the gas inlet opening (7, 8, 11, 12) is arranged in the area of ​​a step (13, 14, 15) and / or the slope (24, 32) where the process chamber height (HO to H4) increases.

11. Device according to one of the preceding claims, characterized in that the horizontal distance between two steps (13, 14, 15) and / or the horizontal length of the slope (24, 32) is in the range between 3% and 8% of a diameter of the process chamber ceiling (4).

12. Device according to one of claims 9 to 11, characterized in that downstream of the upstream edge (9 Z ) and the center point (M) of the storage area at least one step (13, 14, 15) or slope (24, 32) is arranged.

13. Device for depositing a layer on a substrate (6) in a CVD reactor (1) comprising a process chamber (2) with a process chamber floor (3) formed by a susceptor (17) and a process chamber ceiling (4) spaced from the process chamber floor (3) by a process chamber height (HO to H4), and with side walls laterally bounding the process chamber (2), wherein a gas supply device (33) is configured to provide a process gas flow (QO) which can be fed into the process chamber (2) through a gas inlet device (5) and flows through the process chamber (2) in a horizontal flow direction (S), wherein the process gas flow (QO) includes reactive gases which decompose in the process chamber (2) into decomposition products which are deposited on the surface of the substrate (6) arranged on a storage area (9) of the process chamber floor (3) with a growth rate (r).wherein a pre-flow zone (31) extends between a gas outlet surface of the gas inlet device (18) and the storage area (9), characterized in that the side walls of the process chamber (2) have at least one flank (24) or step (13, 14) extending at least partially upstream of a center of the storage area (9), at which the width of the process chamber (2) increases or decreases.

14. Device according to claim 13, characterized by one or more gas inlet openings (7, 8) arranged in the region of the flank (24) or step (13, 14), through which a gas can be fed into the process chamber (2).

15. Method for depositing a layer on a substrate (6) in a CVD reactor (1) comprising a process chamber (2) with a process chamber floor (3) formed by a susceptor (17) and a process chamber ceiling (4) spaced from the process chamber floor (3) by a process chamber height (HO to H4), wherein a gas supply device (33) provides a process gas flow (Q0) which can be fed into the process chamber (2) through a gas inlet device (5) and flows through the process chamber (2) in a horizontal flow direction (S), wherein the process gas flow (Q0), which includes a carrier gas, in particular hydrogen and reactive gases, which decompose in the process chamber (2) or on the surface of the substrate (6) arranged on a storage area (9) of the process chamber floor (3) into decomposition products which are deposited on the substrate (6) with a growth rate (r),wherein the growth rate (r) in the flow direction (S) above the substrate (6) is determined in a model calculation or by experiments and the design parameters of the process chamber (2) and process parameters are varied such that the growth rate (r) above the substrate (6) is as linear as possible, wherein the design parameters changed during the variation are at least the following: one or more positions (dl, d2, d3, d4) at which the height (HO, Hl, H2, H3, H4) of the process chamber (2) changes or at which a gas inlet opening (7, 8, 11, 12) is arranged.

16. Method according to claim 15, characterized in that, during the variation, the values ​​of gas flows through the one or more gas inlet openings (7, 8, 11, 12) are changed and / or that the molar mass of at least one of the gases flowing through the gas inlet openings (7, 8, 11, 12) is changed. inert gas flow (Q1, Q2, Q3) is changed, whereby the molar mass is adjusted in particular by a mixture of argon and hydrogen.

17. Method according to claim 15 or 16, characterized in that at least one position (d2, d3) is downstream of an upstream edge (9 Z ) of the storage site (9) and upstream of a midpoint (M) of the storage site (9).

18. Method according to one of claims 15 to 17, characterized in that a first position (dl) is located downstream of the gas inlet device (5) and upstream of the upstream edge (9') of the storage space (9) in the flow direction (S), and a second position (d2) is located downstream of the first position (dl) and upstream of the upstream edge (9') of the storage space (9), and / or a third position (d3) is located downstream of the upstream edge (9') of the storage space (9) and upstream of a midpoint (M) or a downstream edge (9") of the storage space (9), and / or the change in height (HO to H4) of the process chamber (2) is a change in the profile of the process chamber ceiling (4) and / or the process chamber floor (3).

19. Method for depositing a layer on a substrate (6) in a CVD reactor (1) comprising a process chamber (2) with a process chamber floor (3) formed by a susceptor (17) and a process chamber ceiling (4) spaced apart from the process chamber floor (3) by a process chamber height (HO to H4), wherein a process gas flow (QO) is fed into the process chamber (2) through a gas inlet device (5), which flows through the process chamber (2) in a horizontal flow direction (S), wherein the process gas flow (QO) comprises a carrier gas, in particular hydrogen and reactive gases, which decompose in the process chamber (2) or on the surface of the substrate (6) arranged on a storage location (9) of the process chamber floor (3) into decomposition products which are deposited on the substrate (6) with a growth rate (r), wherein a first inert gas flow (Ql) is fed into the process chamber (2) at a first position (dl) downstream of the gas inlet element (5) or at the position of the gas inlet element (5) and upstream of the storage location (9), wherein a second inert gas flow is fed into the process chamber (2) at a second position (d2) through a second gas inlet opening (8) downstream of the first gas inlet opening (7) in the process chamber ceiling (4), characterized in that the second inert gas flow (Q2) is less than the first inert gas flow (Ql) and the molar mass of the two inert gas flows (Ql,Q2) is larger than the molar mass of hydrogen and the two inert gas fluxes contain, in particular, argon.

20. Method according to claim 19, characterized in that a third inert gas flow (Q3) is fed into the process chamber (2) through a third gas inlet opening (11) downstream of the second gas inlet opening (8), wherein the third gas inlet opening (11) is arranged at a third position (d3) which is arranged downstream of an upstream edge (9') of the storage space (9) and upstream of a midpoint (M) or a downstream edge (9") of the storage space (9), wherein the third inert gas flow (Q3) is less than the first inert gas flow (Q1) and the molar mass of the third inert gas flow (Q3) is greater than the molar mass of hydrogen and in particular contains argon or predominantly argon and / or that the first inert gas flow (Q1) min- is at least five times greater than the sum of all other inert gas flows (Q2, Q3) that are fed into the process chamber (2) at the second and / or third position (d2, d3) downstream of the first position, and / or that a fourth inert gas flow (Q4) is fed into the process chamber (2) through a fourth gas inlet opening (12) downstream of the third gas inlet opening (11), wherein the fourth gas inlet opening (12) is located at a fourth position (d3) that is located downstream of the third position (d3) and upstream of the downstream edge (9") of the storage area (9), and / or that the ratio of the first inert gas flow (Q1) to the process gas flow (QO) is in the range between 0.1 and 0.3, and / or that the ratio of the first inert gas flow (Q1) to the sum of other inert gas flows fed downstream of the first position (dl) (Q2, Q3, Q4) lies in the range between 6 and 600.

21. Method according to one of claims 18 to 20, characterized in that the first position (dl) is located at a distance of at least 10% or at least 25% of the distance between the gas inlet element (5) and the upstream edge (9). Z ) of the storage site (9) and the second position (d2) downstream of the first position (dl) and the upstream edge (9 Z ) of the storage location (9), wherein the inert gas flow (Q1) injected at the first position (dl) is smaller than the inert gas flow (Q2) injected at the second position (d2).

22. Method for depositing a layer on a substrate in a CVD reactor (1) comprising a process chamber (2) with a process chamber floor (3) formed by a susceptor and a process chamber ceiling (4) spaced apart from the process chamber floor (3) by a process chamber height (HO to H4), wherein a process gas flow (QO) is fed into the process chamber (2) through a gas inlet device (5), which flows through the process chamber (2) in a horizontal flow direction (S), wherein the process gas flow (QO) includes a carrier gas, in particular hydrogen and reactive gases, which decompose in the process chamber (2) on the surface of the substrate (6) arranged on a storage location (9) of the process chamber floor (3) into decomposition products, which are deposited on the substrate (6) with a growth rate (r), wherein a first inert gas flow (Ql) is fed into the process chamber (2) at a first position (dl) downstream of the gas inlet device (5) or at the position of the gas inlet device (5) and upstream of the storage location (9), and the profile of the process chamber height (HO to H4) has at least one change in the flow direction, characterized in thatthat the at least one change is located at a second position (d2) and / or at a third position (d3), wherein the second position (d2) is downstream of the first position (dl) and upstream of an upstream edge of the storage space (9) and the third position (d3) is downstream of the upstream edge (9') of the storage space (9) and upstream of a midpoint (M) or a downstream edge (9") of the storage space (9), or that the first position (dl) is at a distance of at least 10% or at least 25% of the distance between the gas inlet device (5) and the upstream edge (9). Z ) of the storage place (9) is spaced apart and the process chamber ceiling (4) at the first position (dl) forms a slope (24) increasing the process chamber height (HO to H4) or the process chamber floor (3) between gas inlet device (5) and the first position (dl) forms a slope (25) decreasing the process chamber height (HO to H4).

23. Method according to one of claims 18 or 22, characterized in that the process chamber height (HO to H4) increases in the flow direction (S) at a third position (d3), wherein the third position (d3) is located downstream of the upstream edge (9') of the bearing place (9) and upstream of the center point (M) or the downstream edge (9") of the bearing place (9).

24. CVD reactor (1) for depositing a layer on a substrate (6), comprising a process chamber (2) with a process chamber floor (3) formed by a susceptor (17) and a process chamber ceiling (4) spaced from the process chamber floor (3) by a process chamber height (HO to H4), a gas inlet device (5) for feeding a process gas flow (QO) into the process chamber (2), which includes a carrier gas, in particular hydrogen and reactive gases, which decompose in the process chamber (2) or on the surface of the substrate (6) arranged on the process chamber floor (3) into decomposition products that are deposited on the substrate (6), a first gas inlet opening (7) arranged at a first position (dl) downstream of the gas inlet device (5) or at the position of the gas inlet device (5) and upstream of a storage location (9) of the substrate (6) in the process chamber ceiling (4) for Injecting an initial inert gas flow (Ql) into the process chamber (2),a second position (d2) downstream of the first gas inlet opening (7) and upstream of the storage location (9), where a second gas inlet opening (8) is located for feeding a second inert gas flow (Q2) into the process chamber (2), or where the course of the process chamber height (HO to H4) in the flow direction (S) has a first change, and one or more gas sources (28) a control device (27) for controlling control elements (29) for regulating the composition of gas flows (QO, Q1, Q2) by at least the gas inlet element (5) and the first gas inlet opening (7), characterized in that the control device (10) is configured to carry out a method according to one of claims 15 to 23.

25. CVD reactor (1) according to claim 24, characterized in that downstream of the second gas inlet opening (8) at a third position (d3) a third gas inlet opening (11) is arranged downstream of an upstream edge (9') of the storage space (9) and upstream of a center (M) or a downstream edge (9") of the storage space (9).

26. CVD reactor (1) according to claim 24 or 25, characterized in that the process chamber (2) has a process chamber height (HO) in the range between 20 and 50 immediately downstream of the gas inlet device (5). 30 mm, wherein the process chamber height (HO) increases by 5% to 15% of the process chamber height (HO) immediately downstream of the gas inlet device (5) at each of the first, second or third or fourth position (dl, d2, d3, d4).

27. CVD reactor according to one of claims 24 to 26, characterized in that downstream of a downstream edge (9") of the storage space (9) the process chamber height is reduced to a fourth process chamber height (H4).

28. CVD reactor according to one of claims 24 to 27, characterized in that changes in the process chamber height (HO to H4) of stages (13, 14, 15) are formed and / or that the stages (13, 14, 15) extend vertically or have step flanks (24, 32) extending obliquely to it and / or that the process chamber ceiling (4) extends in a plane parallel to the process chamber floor (3) between some of the first, second or third positions (dl, d2, d3, d4), in particular between all of the positions (dl to d4) and / or that the step flanks (24, 32) extend in the flow direction (S) over a maximum distance corresponding to 3% to 9% of the diameter of the process chamber ceiling (4).

29. CVD reactor (1) for depositing a layer on a substrate (6), comprising a process chamber (2) comprising a process chamber floor (3), a process chamber ceiling (4) spaced apart from the process chamber floor (3) by a process chamber height (HO, Hl, H2), a gas inlet element (5) for feeding a process gas flow (QO) into the process chamber (2), and a storage area (9) arranged in the process chamber floor (3) for storing the substrate, wherein the process chamber height (HO, Hl, H2) changes downstream of the gas inlet element (5), characterized in that the process chamber floor (3) forms a second slope (25) reducing the process chamber height (HO, Hl, H2), wherein an upstream edge (25') has a distance to the gas inlet element (5) and a downstream edge (25") has a distance to the upstream edge (9) Z ) of the storage area (9).

30. CVD reactor according to claim 29, characterized in that the height (el) of the first slope (24) is between 3% and 9% of the process chamber height (HO) immediately in front of the gas inlet device (5), preferably between 3 and 5 mm.

31. CVD reactor according to one of claims 29 or 30, characterized in that the height (e2) of the second slope (25) is the height of a lowest Gas outlet zone (19) of the gas inlet device (5) corresponds, and / or that the vertical level of a lower edge of a gas outlet zone (20) arranged directly above the lowest gas outlet zone (19) is aligned with the level of the surface of the storage area (9).

32. Method or CVD reactor, characterized by one or more of the characterizing features of one of the preceding claims.

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