Apparatus and method for providing a mass flow of a vapour of a liquid or solid starting material for a CVD reactor
Patent Information
- Application Number
- PCT/EP2026/054373
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-19
- Filing Date
- 2026-02-18
- Publication Date
- 2026-08-27
Smart Images
Figure EP2026054373_27082026_PF_FP_ABST
Abstract
Description
Description Device and method for providing a mass flow of vapor of a liquid or solid feedstock for a CVD reactor field of technology
[0001] The invention relates to a device and a method for providing vapor of a liquid or solid feedstock transported by a carrier gas, wherein a source mass flow controller feeds a carrier gas flow through a feed line into a container. The feedstock to be vaporized is located in the container. Heat can be supplied to the container, causing the feedstock to vaporize. The vapor thus generated is conveyed as process gas, along with the carrier gas, through a duct from the container to a process chamber of a CVD reactor, in which a chemical reaction takes place with another process gas, resulting in the deposition of a layer on a substrate arranged in the process chamber, which contains components of the two process gases.A total pressure inside the container, in particular in a space of the container above the starting material stored there, is regulated to a constant value by means of a pressure regulator, whereby a gas flow consisting of the carrier gas and the vapor flows through the pressure regulator.
[0002] The invention further relates to a semiconductor component produced using the method. State of the art
[0003] In an embodiment shown in Figure 2 of DE 10 2020 001 894 A1, steam transported by a carrier gas stream is to be selectively directed into an exhaust gas system or into a reactor by switching a RUN-VENT switching device. The carrier gas-steam- 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03 The mixture shall flow through two additional mass flow controllers arranged in two branches of the splitting discharge, with one of the mass flow controllers ending in an exhaust line.
[0004] Figure 3 of DE 10 2021 117 457 A1 describes a device for providing steam transported by a carrier gas, wherein the carrier gas is fed into a container via a feed line and a source mass flow controller. The feedstock stored in the container is vaporized by the addition of heat. The carrier gas transports the steam into a discharge line. A pressure regulator is located in the discharge line to maintain a constant pressure in the container. The discharge line branches into a first branch and a second branch. Both branches contain mass flow controllers. Both branches lead into a process chamber of a CVD reactor.
[0005] WO 2023 / 280715 Al describes various arrangements for providing steam generated by the evaporation of a liquid or solid feedstock. A pressure regulator is used through which a carrier gas flows into the outlet to regulate the total pressure in the vessel to a predetermined value.
[0006] US 2014 / 0299206 Al or EP 2233603 Bl describes a similar arrangement, but the vapor transported from the carrier gas to the process chamber flows through the pressure regulator.
[0007] With a device of this type, a vapor of a first starting material containing a chemical compound with silicon, gallium, aluminum, indium, or the like can be vaporized. The vapor thus generated can then be fed into the process chamber of a CVD reactor via the exhaust. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03. To produce compound semiconductors, a second starting material is required, which may contain a chemical compound with carbon, arsenic, phosphorus, nitrogen, or the like. The first and second starting materials react with each other in the process chamber of the CVD reactor. A substrate is located in the process chamber of the CVD reactor and is heated to an elevated temperature by a heating device. The substrate may, for example, be placed on a susceptor. The two starting materials decompose pyrolytically in the process chamber, so that a compound semiconductor consisting of one element of the first starting material and one element of the second starting material can be deposited on the substrate. The invention relates in particular to a device and a method for producing SiC, GaAs, GaN, GaP, InAs, InP, InN, AIN, AIP, AlAs, and other compounds of the aforementioned elements.The first starting material can be a metal-organic feedstock stored as a liquid or solid in a container. A carrier gas flows through this container. In the prior art, the mass flow of the vapor is determined by the mass flow of the carrier gas. The temperature of the container, or of the first starting material contained within it, also influences the evaporation rate. The second starting material can be a hydride, which is gaseous and can be stored in a gas holder. A mass flow controller is sufficient to supply the second starting material. This mass flow controller directly controls the mass flow of the second starting material. The mass flow of the first starting material is indirectly controlled via the carrier gas flow supplied to the container.A change in the setpoint of the mass flow controller for the second feedstock results in a change in the partial pressure of the second feedstock in the process chamber only after a slight time delay. In contrast, a change in the setpoint of the source mass flow controller, which determines the inflow of the carrier gas into the container, leads to a time-delayed change. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 Change in the partial pressure of the first starting material in the process chamber. This is disadvantageous when, during the processing of a recipe for the deposition of a layer or, in particular, a layer structure consisting of several layers, a ramp must be implemented in which the partial pressure of the two starting materials is intended to either increase or decrease synchronously over time. During this period, in which the partial pressure of the two starting materials is supposed to increase steadily, there is an oversupply of the second starting material, which leads to undesirable compositions of the deposited layer. In particular, if an additional starting material containing a dopant is fed into the process chamber, the dopant concentration within the layer can assume undesirable values. Summary of the invention
[0008] The invention is based on the objective of specifying measures by which the disadvantages described above can be avoided and in particular by which a delayed delivery of the first starting material can be avoided and by which the mass flow of the starting material can be continuously increased or decreased without a prior pause.
[0009] The invention further aims to provide measures for producing a transition zone between two epitaxially deposited layers, in which the layer composition, in particular the concentration of a dopant in a SiC layer, changes continuously. The transition zone should have a thickness that is no greater than, and preferably less than, 100 nm. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0010] The problem is solved by the invention specified in the claims, wherein the dependent claims are not only advantageous further developments of the technical teaching specified in the subordinate claims, but represent independent solutions to the problem.
[0011] The invention essentially proposes that the partial gas flow through the first branch does not enter the process chamber. This partial gas flow can be discarded. Before the second partial gas flow, which enters the process chamber through the second branch, increases, the discarded first partial gas flow is increased. During a layer deposition phase, in which steam with a low mass flow is initially fed into the process chamber, a portion of the steam discharged from the container simultaneously does not enter the process chamber through the first branch. At a predetermined time before the mass flow of steam into the process chamber increases, the mass flow of steam through the first branch is increased, so that the steam delivery rate increases before the mass flow of steam into the process chamber increases.As a result, the mass flow in the discharge can stabilize before the increased mass flow is fed into the process chamber. With the method according to the invention, an increased steam generation rate can stabilize while simultaneously feeding a stable flow of steam into the process chamber. The invention offers the advantages of a vent-run switching system known from the prior art, but without the need for a pause before the reactive gas is fed into the process chamber.
[0012] The gas flows within the duct and its branches are preferably controlled by a pressure regulator and at least two mass flow controllers. A mass flow controller is generally a device with a 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 Measuring unit with which the mass flow of a gas flowing through the device can be measured. A throttle valve allows the volumetric flow rate through the device to be adjusted so that the mass flow is regulated to a predetermined value. A pressure regulator has a similar design. A pressure sensor measures pressure. A throttle valve is adjusted so that the measured pressure is regulated against a setpoint. The pressure sensor can be located upstream of the throttle valve in one direction of flow, so that the pressure regulator maintains a constant pressure upstream of the throttle valve. The pressure sensor can also be located downstream of the throttle valve, so that the pressure regulator can regulate the pressure downstream of the throttle valve. In the first case, the cross-section of the throttle valve is reduced to increase the pressure.In the second case, the cross-section of the throttle valve is enlarged. The downpipe contains at least one pressure regulator, through which, to regulate the pressure in the downpipe or container, either a carrier gas flow can be introduced into the downpipe or container, or a gas flow consisting of a mixture of carrier gas and vapor can flow out of the downpipe or container. In the latter case, this partial gas flow is discarded. Here, the pressure sensor is located upstream of the throttle valve in the direction of flow. The arrangement of the pressure regulator and the at least two mass flow controllers can be implemented in various ways. In one variant, the pressure regulator can be located in a first branch of the downpipe. A mass flow controller is located in a second branch of the downpipe. Another mass flow controller is located in a carrier gas supply line that leads into the downpipe or container.In a second variant, the pressure regulator can be located in the carrier gas supply line. A mass flow controller is then located in each of the two branches of the downstream line. In this arrangement, the pressure sensor is located downstream of the throttle valve. In a third variant, the pressure regulator can be located in the second branch. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 The mass flow controller is then located in the carrier gas supply line and another in the first branch. In this variant, the pressure sensor is located upstream of the throttle valve. In the first and second variants, the mass flow fed into the process chamber is directly determined by the mass flow controller located in the second branch, which in this case is referred to as the feed-in mass flow controller. In the third variant, the mass flow fed into the process chamber is, in a sense, the difference between the carrier gas flow fed into the vessel plus the additional carrier gas flow controlled by the mass flow controller located in the carrier gas supply line and the mass flow through the first branch.
[0013] A device according to the invention has a feed line through which a carrier gas can be fed into a container holding the feedstock to be vaporized. A discharge line allows the vapor carried by the carrier gas to be transported from the container. The discharge line splits into at least two lines, each formed of a pipe. One of these lines does not terminate in the process chamber, but rather such that the gas flowing through it does not enter the process chamber, but instead, for example, flows into a vent line or directly into a gas recycling device. The gas flowing through this line can also be used for other purposes. The other of these lines terminates directly in the process chamber or at a switching valve, with which the other line can be connected to either a run line or a vent line.
[0014] During the deposition of a layer, a partial gas flow of a vapor, transported from the container by the carrier gas, flows through the line that does not open into the process chamber and through the line that opens into the process chamber. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0015] In a first embodiment, it is proposed that the initial gas flow through the pressure regulator, which according to the invention can also be a pressure regulator arrangement, does not flow into the process chamber. The invention proposes a feed-in mass flow controller arranged in the downstream section, with which the mass flow that can be fed into the process chamber can be directly controlled.To carry out the process, in a process step for the deposition of a layer or a sequence of layers that requires a temporal increase in the concentration or partial pressure of at least the first feedstock in the process chamber, the mass flow of the carrier gas flowing through the container, and thus the mass flow of the vapor exiting the container, can be increased by the source mass flow controller before the point at which this process step begins, until a gas flow value is reached that corresponds at least to the gas flow that enters the process chamber at the end of the process step, i.e., after completion of the ramp. According to the invention, the increase in the delivery rate of the first feedstock is thus brought forward in time. During this phase of increasing the delivery rate of the first feedstock, the gas flow fed into the process chamber remains at a low level.The gas flow through the pressure regulator increases. This first gas flow is discarded; it does not enter the process chamber. Only the second gas flow, controlled by the feed mass flow controller, enters the process chamber. A concentration meter installed in the discharge line can be used to verify that the gas flowing through the discharge line has the desired concentration of the first feedstock. This ensures that precisely the desired flow of the first material enters the process chamber. The mass flow is the product of the mass flow set in the mass flow controller and the concentration of the feedstock. Preliminary tests can thus determine a lead time to account for the increase in the carrier gas flow through the source mass flow controller compared to the flow specified in the recipe. 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03 the planned increase in the concentration of the first starting material in the process chamber must be brought forward.
[0016] The device can have a vent line and a run line. The first or second feedstock can be fed directly into an exhaust gas disposal system via the vent line, bypassing the CVD reactor. This is advantageous if the mass flows of the feedstocks need to stabilize before the start of a process step in which the feedstocks are fed into the process chamber. A diverter valve can be provided, allowing the gas flow from the discharge to be directed either into the vent line or the run line. The run line terminates in the process chamber. A gas inlet can be provided, which is fluidically connected to the run line and allows the first feedstock to be fed into the process chamber. The second feedstock can be fed into either the vent line or the run line in the same manner.This can involve a separate run line. When using switching valves, the two gas flows of the two feedstocks can be switched synchronously. The problem described at the beginning essentially arises when, during a process step, the gas flows of the two feedstocks need to be changed from a first value to a second value without interruption, and this change needs to occur simultaneously or within a short timeframe. The ramp can have a steep gradient in this case.
[0017] A carrier gas source, for example a hydrogen source, can supply a carrier gas. This carrier gas is fed into the container holding the starting material via a feed line by means of a source mass flow controller, which can be controlled by a control unit. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 The delivery rate of the steam is determined by the carrier gas flow. The delivery rate of the steam also depends on the temperature of the feedstock, which can be regulated to a constant value by means of a heating device in the vessel. The carrier gas flow supplied by the source mass flow controller flows through the vessel and exits by carrying the steam. The gas flow, consisting of the carrier gas and the steam, leaves the vessel through the outlet. A dilution gas can be introduced into the outlet. For this purpose, a dilution gas mass flow controller is provided, which allows the carrier gas to be introduced into the outlet. This can be done upstream of a concentration meter, which can be used to determine the concentration of the steam or its partial pressure in the carrier gas within the outlet.A control device allows the concentration or partial pressure to be kept at a constant value by varying the dilution gas fed into the discharge using the dilution mass flow controller.
[0018] The line branches into a first branch or strand that does not open into the process chamber and, in particular, opens directly into the vent line or into a gas recycling device. The gas flow through the first branch or strand, consisting of the carrier gas and the vapor, can be used to maintain a constant pressure by means of a throttle valve and a pressure gauge. This pressure is essentially the total pressure within the vessel. According to the invention, this arrangement of throttle valve and pressure gauge is referred to as a pressure regulator. The throttle valve controls the gas flow that does not enter the process chamber.
[0019] The drainage pipe branches into a second branch or strand, which leads into the process chamber. The second branch or strand leads at least... 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 then into the process chamber if it is connected to a run line. A switching valve may be provided for this purpose, with which the second branch or line is connected either to the run line or to the vent line. No such switching valve is provided for the first branch or line. In the second branch or line, there is a feed mass flow controller with which a second gas flow of the vapor-carrier gas mixture can be controlled, which is fed into the process chamber.
[0020] To provide a continuously, and in particular rapidly, increasing second gas flow, in which the mass of the steam fed into the process chamber increases over time along a predetermined ramp, a first, low mass flow of steam should flow into the process chamber through the feed mass flow controller at the beginning of the ramp, and a second, high mass flow of steam should flow into the process chamber at the end of the ramp. At the beginning of the ramp, a mass flow of steam flows through the pressure regulator that corresponds at least to the final value of the mass flow entering the process chamber during the ramp. For this to occur, the carrier gas flow flowing through the source mass flow controller must be increased to a level corresponding to the final value in good time before the start of the ramp. During "normal operation," in which the gas source of the first feedstock is intended to supply a constant second gas flow, the first gas flow can be set to a minimum.The carrier gas flow supplied by the source mass flow controller is only slightly greater than the flow of carrier gas through the feed mass flow controller. The concentration of the vapor in the discharge can be varied using the carrier gas flow supplied by the dilution mass flow controller. The total pressure can be regulated using the initial gas flow through the pressure regulator. This is achieved by means of a control unit that can also execute the recipe. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0021] The device described above can also be used to generate a decreasing mass flow of steam, which can be fed into the process chamber within a process step. While in a process step with a decreasing second gas flow, the first gas flow decreases continuously, in a process step with a decreasing second gas flow, the first gas flow increases continuously. The source mass flow controller allows the carrier gas flow to be reduced with a time delay. In the case of a decreasing second gas flow, the source mass flow controller advances the carrier gas flow in time. According to the invention, it is thus possible to provide a time-varying inflow of a first feedstock that varies synchronously with the supply of a second feedstock, for example, a hydride, and in particular increases or decreases.The ramp can be steep, so that with the method and device described above, it is also possible to raise or lower process gas flows in stages, and this can be done synchronously for all process gases.
[0022] It is possible to give the ramp with which the carrier gas flows into the container a different gradient than the ramp with which the carrier gas vapor mixture flows into the process chamber.
[0023] In the second variant mentioned above, the pressure regulator located in the first branch or line is replaced by the dilution gas mass flow regulator. The carrier gas flow through the pressure regulator, which is then located in the carrier gas supply line, is determined by the setpoints of the mass flow regulators in the first branch or second branch and in the supply line. In the previously described method, where a continuously increasing mass flow is intended to flow through the feed-in mass flow regulator, the mass flow is reduced by the pressure regulator before this increase. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 The mass flow rate of the source mass flow controller and the mass flow controller located in the first branch is increased, resulting in a continuously increasing mass flow in the downstream section. The mass flow exceeding the mass flow fed into the process chamber is discarded until the control unit increases the setpoint of the feed-in mass flow controller.
[0024] The mass flow controllers for a descending ramp are controlled analogously. Therefore, please refer to the above explanations regarding the first variant.
[0025] In the third variant mentioned above, the pressure regulator is not located in the first branch, but in the second branch, which is connected to a process chamber during layer deposition. Here, the mass flow fed into the process chamber is not directly controlled by a feed-in mass flow controller, but indirectly by the setpoints of several mass flow controllers.
[0026] The device according to the invention for providing a mass flow of steam can have a mass flow controller through which a mixture of the steam and the carrier gas can flow. The concentration of the steam in this mixture changes with a deliberately decreasing or increasing mass flow of the steam. The mass flow controller is generally calibrated for a specific gas composition, in particular for a specific specific heat capacity of the gas. This changes with its composition. According to the invention, a setting value for the mass flow controller is therefore corrected according to the following formula. Si-Flow rcorr 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03 where TCSinject is the corrected flow to be set, SiFiow is the target flow of TCS into the reactor that is actually achieved, and Fcorr is the correction factor for the MFC.
[0027] The correction invoice is calculated as follows. P _ _ C TCS _ CORR 273 15 K* F MFC* P * ( £rcs, (2z£rcs ) / T F TCS F H2 > where CTCS is the concentration of vapor in the gas mixture measured by concentration meter 11 (between 0 and 1), FMFC is an MFC conversion factor for 100% calibration gas (typically N2) at 0°C and 1 atm, FTCS is an MFC conversion factor for 100% TCS gas at 0°C and 1 atm, FH2 is an MFC conversion factor for 100% lU gas at 0°C and 1 atm, P is the measured pressure in the gas line in mbar, and T is the gas temperature at the MFC in Kelvin. FMFC, FTCS, and FH2 are well-known conversion factors used for the initial calibration of the mass flow controllers. Cis, P, and T are measured quantities.
[0028] The invention also relates to a semiconductor device produced using the device or method described above. The semiconductor device comprises a sequence of layers and electrical contacts. The semiconductor device can be arranged in a housing. However, the semiconductor device can also be an integrated circuit or a printed circuit board equipped with an integrated circuit or a semiconductor device as described below.
[0029] The semiconductor device consists of several layers deposited on a substrate. The substrate can support a buffer layer or a sequence of buffer layers. One or more [missing information] are located on the buffer layer. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 active layers are deposited. A transition region is essential, situated between the buffer layer or buffer layer sequence and the active layer or active layer sequence. The buffer layer and the active layer are each n- or p-doped. The dopant concentrations of the buffer layer or layer sequence and the active layer or active layer sequence are different. The transition region borders an uppermost section of the buffer layer with a first dopant concentration and a lowermost section of the active layer with a second dopant concentration. Within the transition region, the dopant concentration changes continuously from the first to the second dopant concentration. The maximum thickness of the transition region is 100 nm.According to the invention, the transition region can have a thickness between 40 nm and 100 nm. A thickness of 50 nm + / - 10 nm is preferred.
[0030] The dopant concentration can change by at least a factor of 10, 50, or 100 across the transition region. For example, the doping in the active layer can be lower than the doping in the buffer layer. A highly doped substrate can be used. This is particularly advantageous if one of the electrical contacts is attached to the substrate.
[0031] The component, whether housed in a package, integrated into a circuit, or mounted on a printed circuit board, can be a diode or a transistor. Two of the transistor's contacts can be located on the top side, i.e., above the active layer. However, it is also possible for all three contacts of the transistor to be located on the top side, i.e., above the active layer. In this case, the substrate can be an insulating substrate. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 Brief description of the drawings
[0032] Exemplary embodiments of the invention are explained below with reference to the accompanying drawings. These show: Fig. 1 schematically shows an arrangement for providing steam of a first feedstock for injection into a CVD reactor 1, Fig. 2 shows the time course of gas flows Fl, F2, F3 + F4 during the provision of a mass flow of steam that steadily increases, Fig. 3 shows the time course of gas flows Fl, F2, F3 + F4 during the provision of a mass flow of steam, which steadily decreases, Fig. 4 schematically shows an arrangement according to Figure 1 of a second embodiment, Fig. 5 shows a representation according to Figure 1 of a third embodiment, Fig. 6 shows a representation according to Figure 1 of a fourth embodiment, Fig. 7 shows a representation of a gas mixing system supplemented with further details, wherein the reference numeral 50 denotes an arrangement as shown in Figures 1, 4, 5 and 6 and as outlined with dashed lines in Figure 1. 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03Fig. 8 a half section through a CVD reactor, Fig. 9 shows the section along line IX-IX in Figure 8, Fig. 10 shows a representation according to Figure 2, but supplemented by a third gas flow F5, F5' of a carbon-containing starting material and a fourth gas flow F6, F6', F6" of a fourth gas flow of a dopant carrier, which can be N2 or NH3. Fig. 11 shows a representation of the dopant concentration within a substrate 21, a buffer layer 22 deposited thereon, a transition region 23 and an active drift layer 24. Fig. 12 shows the growth rates during the deposition of the buffer layer 22, the transition zone 23 and the drift layer 24. Fig. 13 shows in a simplified representation the structure of a component 20 manufactured using the method, Fig. 14 schematically shows the structure of a Schottky diode produced using the method and Fig. 15 schematically shows the structure of a field-effect transistor produced using the method. Description of the embodiments
[0033] The arrangement shown in Figures 1 and 4 is part of a gas mixing system of a device for depositing semiconductor layers onto substrates. Reference numeral 1 additionally denotes a CVD reactor. 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03, which has a process chamber 7 in which a substrate can be located for coating. The substrate can be a silicon substrate. However, the substrate can also consist of silicon carbide or another composite semiconductor, so that one of the aforementioned layers can be deposited on it. Reference numeral 15 designates a gas disposal device and reference numeral 15' a gas recycling device.
[0034] The CVD reactor 1 can have a gas inlet (not shown) through which two or more process gases can be fed into the process chamber. One or more substrates can be arranged on a susceptor (also not shown). The susceptor can be heated by a heating device (not shown) so that the substrates or the process chamber can be brought to a process temperature at which the process gases decompose and the decomposition products can form the aforementioned layers. The deposition of the layers takes place in successive process steps. The process steps and the process parameters required for them, such as the timing of changes in flow rates or the flow rates themselves, are stored in a recipe that is executed by a control unit 16.The recipe can include process parameters that, in a process step, cause the flow rate of the two starting materials to increase or decrease synchronously along a predefined ramp. The two flow rates are thus continuously increased or decreased in sync with each other. However, the recipe can also include process parameters that continuously change the flow rate of only one of the starting materials. In other process steps, the flow rates are kept constant over a longer period.
[0035] The gas mixing system has gas sources not shown for the provision of, in particular, hydrides, for example for NH3, PH3 or 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03AsHß. These process gases are fed directly into a vent line 14 or a run line 13 using mass flow controllers (not shown).
[0036] The gas mixing system may also include mass flow controllers with which a dilution gas is fed directly into the vent line 14 or the run line 13.
[0037] Figures 1 and 4 show only the part of the gas mixing system that provides vapor of a first reactant. The reactant can, for example, contain silicon, gallium, indium, or aluminum and be an organometallic compound. The reactant 2' is arranged in a container 2. Above the reactant 2', within the container 2, is a chamber 8 from which a drain 4 emerges. A carrier gas source, for example, a hydrogen source, supplies a carrier gas flow F3, which is controlled by a source mass flow controller 5. The source mass flow controller 5 is located in a supply line 3, through which the carrier gas flow F3 can be introduced into the reactant 2', so that the carrier gas of the carrier gas flow F3 mixes with, or saturates with, the vapor of the reactant 2' formed in the container 2. To vaporize the reactant 2', the container 2 is heated by a heating device (not shown).
[0038] The carrier gas source also supplies a carrier gas flow F4, which can be controlled by a dilution mass flow controller 6 arranged in a dilution gas line 18, the dilution gas line 18 opening into the outlet 4. The carrier gas flow F4 mixes with the carrier gas flow F3 in the direction of gas flow upstream of a concentration measuring device 11, with which the partial pressure or concentration of the vapor in the carrier gas can be measured. By varying the carrier gas flow- 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03ses F4 The concentration or partial pressure of the vapor can be regulated to a predetermined value using the dilution mass flow controller 6. It can be configured that the sum of the carrier gas flows F3 and F4 is kept constant, but the ratio between them is changed. For example, if the concentration is too low, the carrier gas flow F3 is increased and the carrier gas flow F4 is decreased. If the concentration is too high, the carrier gas flow F3 is decreased and the carrier gas flow F4 is increased.
[0039] Downstream of the concentration measuring device 11, the line 4 branches into a first branch or strand 4', in which a pressure regulator 9 is located. The pressure regulator 9 is preferably an arrangement consisting of a pressure gauge and a throttle valve. The pressure gauge allows the total pressure within the line 4 upstream of the pressure regulator 9, i.e., essentially the total pressure within the container 2, to be measured in chamber 8. The throttle valve allows the gas flow Fl, consisting of the carrier gas and the generated vapor, flowing through the pressure regulator 9 to be varied so that the total pressure in the container 2 can be maintained at a predetermined value by means of a control device 16.
[0040] In the embodiment shown in Figure 1, a gas outlet 17 of the pressure regulator 9, through which the vapor transported by the carrier gas flows, opens into the vent line 14. The gas outlet 17 can open directly into the vent line 14. In the embodiment shown in Figure 4, the gas outlet 17 opens into the gas recycling device 15', where the vapor from the gas flow Fl can be frozen, for example, for further use, since it is a pure substance. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0041] Downstream of the concentration measuring device 11, the line 4 branches into a second branch or strand 4", which contains a feed-in mass flow controller 10 that also receives a setpoint from the control unit 16. This feed-in mass flow controller 10 can regulate a second gas flow F2, which can be fed into the process chamber 7. For this purpose, the line 4 can be connected to the process chamber 7 of the CVD reactor 1 via a switching valve 12 and the run line 13, and is connected in a corresponding valve position of the switching valve 12.
[0042] A gas outlet line exiting the feed mass flow controller 10 is directly connected to the switching valve 12, so that the gas outlet line is selectively connected to either the run line 13 or the vent line 14. The run line 13 is flow-connected to the process chamber 7. The latter is in turn flow-connected to the exhaust gas disposal device 15. The vent line 14 is directly flow-connected to the exhaust gas disposal device 15.
[0043] Figures 2 and 3 each show the time course of the aforementioned gas flows F1, F2, F3 and F4, with the gas flows F3 and F4 being represented as sum gas flows.
[0044] In a first phase, shown in Figures 2 and 3, before time t1, a second gas flow F2 is fed into process chamber 7, which remains constant over time. Following time t1, at time t3, another phase begins, in which, according to the curve shown in Figure 2, the second gas flow F2 is expected to increase in the form of a time ramp until time t4. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0045] In the process shown in Figure 2, the carrier gas flow F3 is increased between times t1 and t2, causing the total gas flow F3 + F4 to also rise. During the short time between times t2 and t3, the total gas flow F3 + F4 stabilizes. In the phase between times t1 and t2, the second gas flow F2 is kept constant. The first gas flow F1, flowing through the pressure regulator 9, increases continuously.
[0046] Between times t3 and t4, the initial gas flow F1 decreases again. The increase in the carrier gas flow F3 between times t1 and t2 occurs such that at time t2, a mass flow through the branch 4 is at least equal to the mass flow of the gas flow F2 after time t4.
[0047] In the process shown in Figure 3, the mass flow rate F2 is continuously reduced between times t1 and t2. The total gas flow rate F3 + F4 can be kept constant. The gas flow rate F1 flowing through the pressure regulator 9 increases continuously. After reaching time t2, for example, between times t3 and t4, the total gas flow rate F3 + F4 is reduced primarily by lowering the carrier gas flow rate F3. As a consequence, the initial gas flow rate F1 flowing through the pressure regulator 9 also decreases. Alternatively, the total gas flow rate F3 + F4 can be reduced shortly after time tl, so that the gas flow rate F1 only increases slightly.
[0048] Figures 2 and 3 do not show gas flows of a second starting material, for example a hydride. These can run synchronously with the second gas flow F2, which is fed into process chamber 7. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0049] With the method and device according to the invention, it is also possible to precisely switch process gas flows of a vaporized feedstock, optionally even without the use of a run / vent switching device 12, and in particular to synchronize them with other process gas flows. The mass flow of the vaporized feedstock can thus be changed without the use of a run / vent switching device. Nevertheless, the use of a run / vent switching device is preferred.
[0050] Figure 5 shows a third embodiment of the invention, which differs from the first embodiment shown in Figure 1 essentially only in that the positions of the pressure regulator 9 and the mass flow regulator 6 are reversed. The mass flow regulator 6 is now not a dilution mass flow regulator, but rather regulates the mass flow of the vapor transported by the carrier gas, which is not fed into the process chamber 7. The pressure regulator 9 now carries not a mixture of carrier gas and vapor, but the carrier gas itself, which now flows into the outlet 4 instead of out of the outlet 4. Unlike the embodiment shown in Figures 1 and 4, where the pressure regulator 9 regulates an upstream pressure to a setpoint, here the pressure regulator 9 regulates a downstream pressure to a setpoint.
[0051] In this variant, the partial gas flow Fl through the first branch 4' is determined by the control device. The mass flow controllers 5 and 10 must receive corresponding control values so that a small amount of carrier gas flows continuously through the pressure controller 9. The sum of the two mass flows through the mass flow controllers 9 and 10 therefore only needs to be slightly greater than the mass flow through the source mass flow controller 5 plus the generated steam. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0052] Figure 6 shows a fourth embodiment of the invention, which differs from the first embodiment shown in Figure 1 essentially only in that the positions of the pressure regulator 9 and the mass flow regulator 10 are reversed. The mass flow regulator 10 now controls not the mass flow of the steam fed into the process chamber 7, but rather the mass flow of the steam not fed into the process chamber 7. This mass flow must be set by a suitable combination of the control values of the other mass flow regulators 5, 6, and 10. Here, the pressure regulator 9 is used to regulate an upstream pressure against a setpoint.
[0053] In further embodiments not shown, the gas discharge 17 of the embodiments shown in Figures 5 and 6 can also end directly in a gas recycling device 15', as shown in Figure 4.
[0054] The processes described above, in which a mass flow of steam fed into process chamber 7 steadily increases or decreases along a ramp, can be carried out analogously with the other variants. The gas flow through the first branch 4' is varied before or after this ramp.
[0055] The mass flow controller 10 is permeated by a gas mixture consisting of the carrier gas (carrier gas flow F3, carrier gas flow F4) and the vapor transported from the container 8. The concentration of the vapor is determined in the concentration meter 11. Based on this measured concentration value, the measurement characteristic of the mass flow controller 11 is corrected according to the formula shown above, whereby the formula takes into account the changing specific heat capacity of the gas mixture due to the changing concentration. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0056] Figure 7 shows a gas mixing system with a schematically represented CVD reactor 1, sectional views of which are shown in Figures 8 and 9.
[0057] The CVD reactor 1 has a gas-tight housing, for example, made of stainless steel. Inside the housing is a susceptor 49, which may be made of coated graphite. Below the susceptor 49 is a heating device 47, which heats the susceptor 49 to a process temperature. In the center of the process chamber 7 is a gas inlet 40 with three vertically arranged gas inlet zones 41, 42, 43. Substrates 45 are arranged in a circular pattern around the gas inlet. Reference numeral 44 indicates a pre-zone through which the process gas flowing from the gas inlet zones 41, 42, 43 passes. A deposition zone 46, on which the substrate 45 rests, adjoins the pre-zone 44. The substrate may rest on a substrate holder 48, which is located in a pocket of the susceptor 49. The substrate holder 48 can have a circular disc shape and be driven by a gas cushion.
[0058] Figure 8 shows the gas flows through the gas inlet zones 41, 42, 43. These include a carrier gas, which is H₂, and growth flows Q1, Q2, Q3, Q4, with which a carbon-containing or a silicon-containing starting material is fed into the process chamber 7, where a chemical reaction takes place, so that SiC is deposited on a substrate 45.
[0059] A nitrogen-containing dopant is additionally fed into process chamber 7 through gas inlet zone 42 or 41. The dopant can be a dopant flow Dl containing ammonia. and / or a dopant flux D2 containing molecular nitrogen. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0060] The nitrogen is supplied by a gas source 53. A mass flow controller 57 generates a fourth gas flow F6, which can be directed either into a supply line 55 to the gas inlet device 40 or into a reversing line by means of a switching valve 12.
[0061] Alternatively, or in conjunction with the gas flow F6, a gas flow F6" or F6" can each be provided by a mass flow controller 57, which contains ammonia stored in a gas source 52. The gas flows F6' and F6" can each be selectively directed by means of a switching valve 12 either into a supply line 54 or 56, through which the dopant is transported to the gas inlet 40. The dopant provided by the dopant sources 52 and 53 can be diluted by an additional injection of hydrogen.
[0062] Reference numeral 50 designates a gas source as depicted in Figures 1, 4, 5, and 6. The gas source includes approximately the components contained within the dashed outline in Figure 1, which is designated by reference numeral 50.
[0063] The starting material supplied by the gas source 51 is a gaseous hydrocarbon, in the exemplary embodiment C₂H₄. The mass flow of this starting material is controlled by mass flow controllers 58.
[0064] This starting material is fed into the supply lines 54, 56 as a third gas flow F5, F5' or, depending on the position of a switching valve 12, into the vent line.
[0065] Figure 10 shows a representation according to Figure 2, but additionally includes the third gas flows F5, F5', which represent the gas flow of a second starting material. 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03 concerns a substance that can react with the gas flow fed into process chamber 7 via gas flow F2. In the exemplary embodiment, the starting material supplied by gas source 50 is trichlorosilane. However, it could also be other non-gaseous, but vaporizable, silicon compounds.
[0066] The method shown in Figure 10 allows the fabrication of semiconductor devices that have a buffer layer 22 deposited on a substrate 21, which can consist of several layers. The buffer layer 22 carries an active layer 23. The active layer 23 is deposited directly onto the buffer layer 22 such that a transition region 23 is formed in which the dopant concentration of a p-type or n-type dopant changes continuously.
[0067] Figure 10 shows that the third gas flow F5, F5' is changed simultaneously with the second gas flow F2. In the exemplary embodiment, the gas flows F2, F5, F5' are increased between times t3 and t4. This results in an increase in the growth rate. During the first ramp, not only is the second gas flow changed steadily, continuously, and, in particular, linearly, but also the gas flow F5, F5' of the carbon-containing starting material.
[0068] In a variant of the invention, it is also provided that the C / Si ratio is changed by the continuous change (increase or decrease) of the second gas flow F2, which influences the doping of the produced solid.
[0069] In this process, the buffer layer 22 is initially deposited onto the substrate 21 at a first growth rate r (see Figure 12) and 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03 then in a transition region 23, which is approximately 100 nm thick, but can also be less than 100 nm thick and in particular can be 50 nm or less than 50 nm, the growth rate is increased. The growth rate r increases linearly with time. With the increased growth rate after completion of the deposition of the transition region 23, the active layer 24 is deposited at a constant growth rate r.
[0070] If the fourth gas flow F6, F6 ', F6" transported in the dopant were kept constant during this process, the dopant content n would decrease slightly in the transition region 23.
[0071] As can be seen in Figure 10, the fourth gas flow F6, which transports the dopant, is also reduced between times t3 and t4 of the first ramp, so that the dopant concentration in the transition region 23 decreases from an initial concentration of approximately 10 18 l / cm3 up to a value of approximately 10 16 l / cm 3 sinks (see Figure 11).
[0072] In the exemplary embodiment, the substrate can be 21 n-doped and have a dopant concentration of 10 19 l / cm 3 The substrate can be made of SiC. The buffer layer 22 can have a layer thickness of 2 pm and an n-doping concentration of 10. 18 l / cm 3 exhibit. The buffer layer 22, as well as the transition region 23 and the active layer 24, are made of SiC. The active layer 24 has a layer thickness of approximately 1 mm and is 10 16 l / cm 3 n-doped. The transition region 23, in which the doping changes continuously, can have a layer thickness of approximately 100 nm and is preferably thinner than 100 nm, and in particular can have a thickness of 50 nm.
[0073] Instead of n-doping, p-doping is also possible. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0074] The flow rates and concentrations of the reactants in the gas flows are set such that the time within which the transition zone 23 is deposited, i.e., the time difference between t4 and t3, is approximately 10 to 15 seconds. The time can be approximately 14 seconds.
[0075] Figure 13 shows a layer structure according to the invention, in which a first SiC layer 22 was deposited onto a SiC substrate 21. A transition region 23 of SiC was continuously deposited onto the first layer 22, transitioning into a further SiC layer 24. During the deposition of these layer sequences 22, 23, 24, only the mass flow of the gas fluxes Fl to F6 was varied, but never reduced to zero. However, at least during the deposition of these layer sequences 22, 23, 24, a silicon-containing starting material was continuously fed into the process chamber 7.
[0076] The substrate 21, like the first layer 22, which is a buffer layer, is highly doped. The dopant concentration decreases by at least a factor of 10, preferably a factor of 15 or 100, during the deposition of the transition region 23, so that the second layer 24, which is an active layer and in particular a drift layer, is less densely doped.
[0077] Figure 14 shows an embodiment in the form of a Schottky diode, as illustrated in US 9,704,718 D2, particularly in Figure 7. The device has the same layer structure as shown in Figure 13 and additionally includes p-doped regions 25, a Schottky metal 27 as a contact, and a contact metal 26.
[0078] Figure 15 shows, as a further example, a field-effect transistor, such as that depicted in Figure 2M in US 2004 / 0211980 A1. A structure according to Figure 13 has a drain contact 26 at the bottom and a [missing information] at the top. 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03 a source contact 27. In addition, gate contacts 28 are provided. Beneath each gate contact 28 is an oxide layer 29. Below this is a p-doped region 30, an n-doped region 31 and another p-doped region 25.
[0079] Other components according to the invention include JFETs and BJTs.
[0080] 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:
[0081] A method characterized in that, prior to an increase in the second partial gas flow F2, the first partial gas flow Fl is increased, or, simultaneously with a change in the second partial gas flow F2, the first partial gas flow F1 is changed in the opposite direction.
[0082] A method characterized in that the first mass flow controller 6 is a feed-in mass flow controller arranged in the second branch 4" and a carrier gas flow F4 flows into the outlet 4 through the pressure regulator 9 or the first partial gas flow F1 consisting of the carrier gas and the steam flows through the pressure regulator 9.
[0083] A method characterized in that the carrier gas flow F3 flowing through the supply lines 3 is controlled by a source mass flow controller 5. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03
[0084] A method characterized in that at least one of the mass flow controllers 6, 10 is controlled by a control device 16 such that the mass flow of the steam fed into the process chamber 7 increases over time along a predetermined first ramp, wherein at the beginning t3 of the first ramp a first, low mass flow of steam and at the end t4 of the first ramp a second, high mass flow of steam flows through the second branch 4", wherein before the beginning of the first ramp the mass flow of the steam flowing through the first branch 4' increases over time along a predetermined second ramp, wherein at the beginning tl of the second ramp a third, low mass flow of steam and at the end t2 of the second ramp a fourth, high mass flow of steam flows through the first branch 4'.
[0085] A method characterized in that the end t2 of the second ramp is temporally prior to the start t3 of the first ramp and / or that the fourth mass flow corresponds at least to the difference between the second mass flow and the first mass flow.
[0086] A method characterized in that at least one of the mass flow controllers 6, 10 is controlled by the control device 16 such that the mass flow of the steam fed into the process chamber 7 decreases over time along a predetermined ramp, wherein at the beginning tl of the ramp a first, high mass flow of the steam and at the end t2 of the ramp a second, low mass flow of the steam flows through the second branch 4", wherein simultaneously or afterwards the first partial gas flow Fl is reduced.
[0087] A method characterized in that a concentration measuring device 11 is arranged in the downstream section 4, with which the concentration of the 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 vapor in carrier gas is determined, and / or that the concentration of the vapor in the carrier gas is regulated to a predetermined value by means of the concentration measuring device 11 and a carrier gas flow F4 of the carrier gas fed into the line 4, controlled by a dilution mass flow controller 6.
[0088] A method characterized in that the first gas flow Fl flowing through the first branch 4' is fed directly into a vent line 14 or into a gas recycling device 15' and the second gas flow F2 flowing through the second branch 4" is fed into a switching valve 12 which directs the second gas flow F2 selectively into a run line 13 or the vent line 14.
[0089] A method characterized in that a gas-flowing regulator is arranged in each of the two branches 4', 4" and in a dilution gas line 18 opening into the branch 4, one of which is the pressure regulator 9 formed by a pressure sensor and an adjustable throttle valve and the other two are formed by the first and second mass flow controllers 6, 10.
[0090] A method characterized in that the measuring characteristic of the mass flow controller 10, through which the carrier gas and the vapor flow, is corrected according to a value of the concentration of the vapor in the carrier gas determined by the concentration measuring device 11 during the provision of the vapor.
[0091] A method characterized in that at least a third gas flow F5, F5' and / or a fourth gas flow F6, F6 / F6" is fed into the process chamber 7 simultaneously with the second partial gas flow F2, wherein 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03der drite Gasfluss F5, F5' transports a starting material with which the vapor in the process chamber 7 reacts to form a solid, in particular a crystal, preferably a semiconductor crystal, wherein the fourth gas flow F6, F6', F6" contains a dopant.
[0092] A method characterized in that the third gas flow F5, F5' and / or the fourth gas flow F6, F6, F6" is changed simultaneously, in particular during the first ramp, with the second partial gas flow F2, so that the growth rate of the layer and / or its dopant concentration changes over time.
[0093] A device characterized in that the pressure sensor is part of a pressure regulator 9 which has an adjustable throttle valve.
[0094] A device characterized in that the second branch 4" is connected to a switching valve 12, with which the second gas flow F2 can be selectively fed into a RUN line 13 or into a VENT line 14, wherein the RUN line 13 is flow-connected to the process chamber 7 and the VENT line 14 is flow-connected to an exhaust gas disposal device 15.
[0095] A device characterized in that the first gas flow Fl flowing through the pressure regulator 9 does not flow into the process chamber 7 and a second gas flow F2, consisting of the carrier gas and the steam and controlled by a feed-in mass flow regulator 10 arranged in the downstream 4, flows into the process chamber 7.
[0096] A device characterized in that means are provided with which the second mass flow supplied by the feed-in mass flow controller 10 can be 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 Gas flow F2 is fed into a switching valve 12, with which the second gas flow F2 can be selectively fed into a RUN line 13 or into a VENT line 14, wherein the RUN line 13 is flow-connected to the process chamber 7 and the VENT line 14 is flow-connected to an exhaust gas disposal device 15.
[0097] A method characterized in that the first gas flow through the pressure regulator 9 does not flow into the process chamber 7 and a second gas flow F2, consisting of the carrier gas and the steam and controlled by a feed-in mass flow regulator 10 arranged in the downstream 4, flows into the process chamber 7.
[0098] A method characterized in that the first gas flow Fl flowing through the pressure regulator 9 is fed directly into a vent line 14 or into a gas recycling device 15' and the second gas flow F2 flowing through the feed mass flow regulator 10 is fed into a switching valve 12 which directs the second gas flow either into a run line 13 or the vent line 14.
[0099] A device characterized by a CVD reactor 1 with a process chamber 7 for receiving the substrate to be coated.
[0100] A method characterized in that the first partial gas flow Fl is increased before the second partial gas flow F2 is increased.
[0101] A device characterized in that the first branch 4' terminates in such a way that the second partial gas flow F2 does not flow into the process chamber 7. 31435N2PCT drg / g / gz 02 / 17 / 2026 Ai 2025-03
[0102] A device characterized in that the first branch 4' terminates in the vent line 14 or in a gas recycling plant 15'.
[0103] A device characterized in that a concentration measuring device 11 is arranged in the downpipe 4, with which the concentration of the vapor in the carrier gas can be determined.
[0104] All disclosed features are essential to the invention (individually, but also in combination with one another). The disclosure of this application hereby incorporates in full the disclosure content of the associated / attached priority documents (copy of the earlier application), also for the purpose of including features of these documents in the claims of the present application. The dependent claims, even without the features of a referenced claim, characterize independent inventive developments of the prior art, in particular for the purpose of filing divisional applications based on these claims. The invention specified in each claim may additionally include 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. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03List of reference symbols 1 CVD reactor 25 p-doped area 2 containers 26 drain contact 2' Starting material 27 Source contact 3 Lead 28 Gate contact 4' first branch 29 oxide layer 4" second branch 30 p-doped section 4 derivation 31 n-doped section 5 source mass flow regulator 32 p-doped section 6 dilution mass flow regulator 40 gas inlet ler 41 Gas intake zone 7 Process chamber 42 Gas inlet zone 8 Room 43 Gas Inlet Zone 9 pressure regulators 44 flow zone 10 feed-in mass flow controllers 45 substrate 11 Concentration measuring device 46 Deposition zone 12 Diverter valve 47 Heating unit 13 RUN line 48 Substrate holder 14 VENT line 49 Susceptor 15 Exhaust gas disposal device 50 Gas source 15' gas recycling facility 51 gas source 16 Control unit 52 Gas source 17 Gas discharge 53 Gas source 18 Dilution gas line 54 Supply line 20 Component 55 Supply line 21 Substrate 56 Supply line 22 Buffer layer 57 Mass flow controller 23 Transition region 58 Mass flow controller 24 Drift layer, active layer 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03Fl first gas flow F2 second gas flow F3 carrier gas flow F4 carrier gas flow F5 third gas flow F5' third gas flow F6 fourth gas flow F6" fourth gas flow F6" fourth gas flow tl time t2 Time t3 time t4 time 31435N2PCT drg / g / gz 02 / 17 / 2026 Ai 2025-03
Claims
Claims 1. Method for providing a vapor of a liquid or solid feedstock transported by a carrier gas, wherein a carrier gas flow (F3) of a carrier gas is fed through a supply line (3) into a container (2) which receives the starting material (2') to be vaporized, wherein the carrier gas flow (F3) transports the steam generated in the container (2) through a discharge (4) from the container (2), wherein the branch (4) splits into a first branch (4') and a second branch (4"), wherein a first partial gas flow (Fl) flowing through the first branch (4') does not flow into the process chamber (7) of a CVD reactor (1) and a second partial gas flow (F2) flowing through the second branch (4") flows into the process chamber (7), wherein the total pressure in the container (2) is maintained at a predetermined value by means of a pressure regulator (9), wherein the two partial gas flows are specified by control values of at least one first and one second mass flow controller (6, 10), characterized in that the first partial gas flow (Fl) is increased before an increase in the second partial gas flow (F2) or the first partial gas flow (Fl) is changed in the opposite direction at the same time as a change in the second partial gas flow (F2).
2. Method according to claim 1, characterized in that the first mass flow controller (6) is a feed-in mass flow controller arranged in the second branch (4") and a carrier gas flow (F4) flows into the discharge (4) through the pressure regulator (9) or the first partial gas flow (Fl) consisting of the carrier gas and the steam flows through the pressure regulator (9). 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-033. Method according to one of the preceding claims, characterized in that the carrier gas flow (F3) flowing through the supply lines (3) is controlled by a source mass flow controller (5).
4. Method according to one of the preceding claims, characterized in that at least one of the mass flow controllers (6, 10) is controlled by a control device (16) such that the mass flow of the steam fed into the process chamber (7) increases over time along a predetermined first ramp, wherein at the beginning (t3) of the first ramp a first, low mass flow of steam and at the end (t4) of the first ramp a second, high mass flow of steam flows through the second branch (4"), wherein before the beginning of the first ramp the mass flow of the steam flowing through the first branch (4') increases over time along a predetermined second ramp, wherein at the beginning (t1) of the second ramp a third, low mass flow of steam and at the end (t2) of the second ramp a fourth, high mass flow of steam flows through the first branch (4').
5. Method according to claim 4, characterized in that the end (t2) of the second ramp is prior to the start (t3) of the first ramp and / or that the fourth mass flow corresponds at least to the difference between the second mass flow and the first mass flow.
6. Method according to one of the preceding claims, characterized in that at least one of the mass flow controllers (6, 10) is controlled by a control device (16) such that the mass flow of the steam fed into the process chamber (7) decreases over time along a predetermined ramp, wherein at the beginning (tl) of the ramp a first, high mass flow of the steam and at the end (t2) of the ramp a second, 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03 a small mass flow of steam through the second branch (4"), whereby the first partial gas flow (Fl) is reduced simultaneously or afterwards.
7. Method according to one of the preceding claims, characterized in that a concentration measuring device (11) is arranged in the downpipe (4) with which the concentration of the vapor in the carrier gas is determined, and / or that the concentration of the vapor in the carrier gas is regulated to a predetermined value by means of the concentration measuring device (11) and a carrier gas flow (F4) of the carrier gas fed into the downpipe (4) and controlled by a dilution mass flow controller (6).
8. Method according to one of the preceding claims, characterized in that the first gas flow (Fl) flowing through the first branch (4') is fed directly into a vent line (14) or into a gas recycling device (15') and the second gas flow (F2) flowing through the second branch (4") is fed into a switching valve (12) which directs the second gas flow (F2) selectively into a run line (13) or the vent line (14).
9. Method according to one of the preceding claims, characterized in that a gas-flowing regulator is arranged in each of the two branches (4', 4") and in a dilution gas line (18) opening into the outlet (4), one of which is the pressure regulator (9) formed by a pressure sensor and an adjustable throttle valve and the other two are formed by the first and second mass flow controllers (6, 10). 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-0310. Method according to one of the preceding claims, characterized in that the measuring characteristic of the mass flow controller (10), through which the carrier gas and the vapor flow, is corrected with a value of the concentration of the vapor in the carrier gas determined by the concentration measuring device (11) during the provision of the vapor.
11. Method according to one of the preceding claims, characterized in that at least a third gas flow (F5, F5') and / or a fourth gas flow (F6, F6', F6'') is fed into the process chamber (7) simultaneously with the second partial gas flow (F2), wherein the third gas flow (F5, F5') transports a starting material with which the vapor in the process chamber (7) reacts to form a solid, in particular a crystal, preferably a semiconductor crystal, wherein the fourth gas flow (F6, F6', F6'') contains a dopant.
12. Method according to claim 11, characterized in that the third gas flow (F5, F5´) and / or the fourth gas flow (F6, F6´, F6´´) is changed simultaneously, in particular during the first ramp, with the second partial gas flow (F2), so that the growth rate of the layer and / or its dopant concentration changes over time.
13. Device for providing a mass flow of vapor of a liquid or solid feedstock for feeding into a process chamber (7) of a CVD reactor (1), with a container (2) for receiving and evaporating the starting material (2'), into which an inlet (3) opens and from which an outlet (4) emerges, wherein a carrier gas flow (F3) can be fed into the container (2) through the supply line (3), 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03 where the derivative (4) branches into a first branch (4') and a second branch (4"), wherein the second branch (4") is connected to the CVD reactor (1) in such a way that a second partial gas flow (F2) of the steam transported by the carrier gas through the discharge (4) can be fed into a process chamber (7) of the CVD reactor (1), wherein the first branch (4') ends in such a way that a first partial gas flow (F1) of the vapor transported by the carrier gas through the outlet (4) does not flow into the process chamber (7), wherein the total pressure in the container (2) can be kept at a predetermined value by means of a pressure sensor flow-connected to the drain (4), where the partial gas flows (F1, F2) can be preset by control values of two mass flow controllers (6, 10), characterized in that the pressure sensor is part of a pressure regulator (9) which has an adjustable throttle valve.
14. Device according to claim 13, characterized in that the second branch (4") is connected to a switching valve (12) with which the second gas flow (F2) can be selectively fed into a RUN line (13) or into a VENT line (14), wherein the RUN line (13) is flow-connected to the process chamber (7) and the VENT line (14) is flow-connected to an exhaust gas disposal device (15).
15. Device according to claim 13 or 14, characterized in that the first branch (4') terminates in the vent line (14) or in a gas recycling plant (15'). 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-0316. Device according to one of claims 13 to 15, characterized in that a concentration measuring device (11) is arranged in the downpipe (4) with which the concentration of the vapor in the carrier gas can be determined.
17. Device according to one of claims 13 to 16, characterized in that a gas-flowing regulator is arranged in each of the two branches (4', 4") and in a dilution gas line (18) opening into the outlet (4), one of which is the pressure regulator (9) and the other two are formed by the first and second mass flow controllers (6, 10).
18. Device according to one of claims 13 to 17, characterized by at least two gas sources (50, 51), wherein a first gas source (50) comprises the container (2) and a second gas source (51) supplies a further starting material which reacts with the starting material supplied by the first gas source (50) to form a solid, in particular a crystal, preferably a semiconductor crystal and / or that a third gas source (52, 53) is arranged to provide a dopant.
19. Device according to one of claims 13 to 18, characterized by a control device (16) with which the controllers are controlled according to a method of claims 1 to 9.
20. Semiconductor device with a first buffer layer (22) deposited on a substrate (21) and an active layer (24) deposited thereon, as well as contacts (26, 27, 28), characterized by a transition region (23) arranged between the buffer layer (22) and the active layer (24), in which a dopant concentration in the solid changes continuously, wherein the dopant concentration in the 31435N2PCT drg / g / gz 17,02,2026 Ai 2025-03 solid continuously from a first value corresponding to the dopant concentration of the buffer layer (22) to a second value corresponding to the dopant concentration of the active layer (24) and wherein in particular it is provided that the transition region (23) has a maximum thickness of 100 nm.
21. Component according to claim 20, characterized in that the buffer layer (22), the transition region (23) and the active layer (24) consist of SiC and the dopant concentration changes across the transition region (23) by at least a factor of 10, 50 or 100, wherein in particular it is provided that the doping of the active layer (24) is lower than the doping of the buffer layer (22).
22. Component according to claim 20 or 21, characterized in that the transition region (23) has a thickness that is less than 100 nm and greater than 40 nm and preferably 50 + / - 10 nm.
23. Device or method or component characterized by one or more of the characterizing features of one of the preceding claims. 31435N2PCT drg / g / gz 17.02.2026 Ai 2025-03