Method for providing a process gas for a CVD reactor and related apparatus

Abstract

The invention relates to a device for providing a process gas for a CVD reactor, comprising a first carrier gas supply line and a second carrier gas supply line, each of which is supplied by a carrier gas source, the first carrier gas supply line having a first mass flow regulator with a smaller flow range, and the second carrier gas supply line having a second mass flow regulator with a smaller flow range. The second carrier gas supply line has a second mass flow regulator with a larger flow range, the carrier gas supply line opens into an evaporation device for evaporating the solid or liquid starting material, the process gas supply line leading to the CVD reactor originates from the evaporation device, and in the second carrier gas supply line with the second mass flow regulator, the process gas supply line is connected to the CVD reactor. Downstream of the second mass flow regulator there is provided a valve device having an inlet, a first outlet which is in flow connection with the evaporation device, and a second outlet which is in flow connection with a bypass line which does not open into the evaporation device, the carrier gas mass flow regulated by the second mass flow regulator selectively flows through or bypasses the evaporation device, and to a method for operating such a device.

Description

Technical Field

[0001] This invention relates to a method for providing a process gas for a CVD reactor, comprising a first carrier gas input line and a second carrier gas input line supplied by a carrier gas source, the first carrier gas input line having a first mass flow rate regulator with a narrow flow range, and the second carrier gas input line having a second mass flow rate regulator with a wide flow range. The carrier gas input line leads to an evaporation device for evaporating solid or liquid starting materials, and the process gas input line to the CVD reactor originates from this evaporation device. A valve is provided in the second carrier gas input line with the second mass flow rate regulator, the valve having an inlet and a first outlet in flow connection with the evaporation device. The invention also relates to an apparatus suitable for this application. Background Technology

[0002] DE 10 2021 117457 A1 describes an apparatus for providing a process gas for use in one or more CVD reactors. An evaporation unit is provided with an inlet line through which carrier gas flows from a carrier gas source into the container of the evaporation unit. The carrier gas inlet line is connected to two mass flow regulators arranged in parallel, which may have different flow ranges. In the inlet line leading to the mass flow regulator with the larger flow range, a shut-off valve is provided upstream of the mass flow regulator. This shut-off valve allows selective opening of the mass flow regulator.

[0003] DE 10 2019 117543 A1 discloses a gas mixing system for a substrate processing apparatus (particularly an MOCVD reactor). A carrier gas input line is connected to a mass flow regulator. A valve is located downstream of the mass flow regulator, through which the input line to the evaporation unit can be closed. Another valve allows the mass flow regulator to be connected to a bypass line leading to the reactor gas outlet for calibration.

[0004] US 10,109,483 B2 discloses an MOCVD reactor system in which a liquid precursor is contained in the evaporation vessel of the evaporation unit. A carrier gas mass flow rate, regulated by a mass flow regulator, flows from a gas source into the evaporation vessel via a carrier gas inlet line. A valve is located downstream of the mass flow regulator. When this valve is closed, the carrier gas can flow through a bypass line connected to the process gas inlet line via a three-way valve.

[0005] US 2014 / 0083512 A1 describes an evaporation source with two input lines leading to it, each capable of supplying nitrogen gas into an evaporation chamber. A process gas line originates from the evaporation chamber and can be used to transport vapor from the evaporation chamber to the process chamber of a CVD reactor. The two input lines are connected to the process gas line via bypass lines.

[0006] US 2017 / 0362701 A1 describes an evaporation source having multiple evaporation chambers as part of a central gas supply system. Each evaporation chamber has an input line, and when one of the evaporation chambers needs to be replaced, the input line can be connected to the discharge line via a bypass line.

[0007] DE 10 2020 103822 A1 describes an apparatus for evaporating powder, wherein two inlet lines lead into an evaporation chamber. One of the two inlet lines has a valve device by which the flow rate of carrier gas supplied to the evaporation chamber in a first operating position is directed to bypass the evaporation chamber in a second operating position. Summary of the Invention

[0008] To achieve multiple flow ranges for the carrier gas mass flow rate through the evaporation vessel of a CVD reactor, in the prior art, a second mass flow regulator covering a larger flow range is connected in parallel with a first mass flow regulator covering a smaller flow range. The second mass flow regulator can be accessed via a valve located upstream. To reduce the carrier gas mass flow rate and limit it within the flow range of the first mass flow regulator, the second mass flow regulator is deactivated via the valve. For this purpose, the second mass flow regulator is adjusted to its minimum flow rate. The volume between the mass flow regulator and the shut-off valve remains under overpressure. Due to unavoidable ineffective volume, even after deactivation, a carrier gas mass flow rate that weakens over time may flow into the evaporation vessel of the evaporator, in addition to the carrier gas mass flow rate flowing through the first mass flow regulator. This leads to severe distortion of the gas feed into the evaporation vessel, especially when the carrier gas mass flow rate is low.

[0009] The technical problem to be solved by this invention is to take measures to switch from a high carrier gas mass flow rate to a low carrier gas mass flow rate in a short time with precision. Specifically, the technical problem to be solved by this invention is to provide a method for supplying one or more CVD reactors with a precisely controlled process gas flow rate.

[0010] The technical problem is solved by the invention defined in the claims, wherein the dependent claims are not only advantageous improvements to the technical solution provided in the independent claims, but also independent solutions to the technical problem.

[0011] Firstly, this invention primarily proposes a valve device, preferably a switching valve, located downstream of the second mass flow regulator. In addition to the carrier gas mass flow rate controlled by the first mass flow regulator, this switching valve allows the carrier gas mass flow rate controlled by the second mass flow regulator to selectively flow through the evaporation vessel or bypass the evaporation unit. The switching valve has an inlet through which the carrier gas mass flow rate controlled by the second mass flow regulator flows in. The carrier gas mass flow rate may either exit the switching valve through a first outlet and enter the evaporation unit, or it may exit the switching valve through a second outlet and bypass the evaporation unit. The second outlet can be connected to a bypass line. The bypass line can be connected to the gas outlet of the evaporation vessel of the evaporation unit, or it can be directly connected to one or more processing gas input lines leading to one or more CVD reactors.

[0012] The valve assembly may include two valves. A first valve may be located downstream of the second mass flow regulator, and a second valve may be located in a bypass line. In this case, the bypass line may branch off from the portion of the second carrier gas inlet line located downstream of the second mass flow regulator and upstream of the first valve. The valves can be selectively opened or closed. In the first method step, the first valve is open and the second valve is closed. In the second method step, the first valve is closed and the second valve is open. It is specified that the carrier gas mass flow rate controlled by the second mass flow regulator cannot simultaneously flow through the evaporator and the bypass line.

[0013] To prevent the first and second valves from opening simultaneously, a time delay can be applied to their switching. When switching from the first method step to the second method step, the first valve can be closed first, followed by a time delay before opening the second valve. Conversely, when switching from the second method step to the first method step, the second valve can be closed first, followed by a time delay before opening the first valve.

[0014] To prevent the carrier gas mass flow through the first mass flow regulator from bypassing the evaporator, for example, flowing into the bypass line for a short period during the switching between the two method steps, the valve may have a throttling orifice. The throttling orifice may be designed to maintain a certain pressure difference between the valve's inlet and outlet pressures during the switching between the first and second method steps. This prevents the carrier gas mass flow controlled by the first mass flow regulator from bypassing the evaporator via the bypass line. The cross-sectional narrowing of the throttling orifice can be variable. Cross-sectional narrowing can be achieved using a throttling element, such as a baffle. The throttling valve can be an electrically operated throttling valve. Cross-sectional narrowing can be adjusted by a control device. However, the throttling valve can also be manually controlled. Furthermore, the throttling valve can be pneumatically operated. The throttling valve can be, for example, a screw-in throttling valve or a butterfly valve.

[0015] Preferably, an electronic pressure regulator allows the total pressure within the gas mixing system to remain constant during switching between the first and second method steps of the switching valve. The switching valve continuously and actively maintains the carrier gas mass flow rate through the second mass flow regulator, thus preventing the second mass flow regulator from being deactivated. Therefore, during switching, there is no significant deviation between the actual and rated value of the carrier gas mass flow rate through the evaporation vessel. Because of the device according to the invention, when the total carrier gas mass flow rate through the evaporation vessel changes during switching, the pressure regulator only needs to compensate for small fluctuations, since the total flow rate at the gas outlet does not change by refeeding the carrier gas mass flow rate bypassing the evaporator.

[0016] The mass flow regulator has a regulating loop that controls the mass flow rate according to a specified rated value. The mass flow regulator can operate at different rated values. For example, the rated value can be gradually decreased or increased. This is preferably done under the control of a control device. For example, the rated value can be provided by the recipe. The switching valve can also be controlled by the control device.

[0017] A wide range of flow rates can be covered by selectively switching multiple parallel mass flow rate regulators with different flow ranges to the mass flow rate of the carrier gas flowing through the evaporation vessel.

[0018] One or more mass flow rate regulators connected in parallel form a mass flow rate regulator device. Herein, the mass flow rate regulator device is positioned upstream of the evaporation vessel of the evaporation apparatus, which contains a liquid or solid starting material, such as an organometallic compound for depositing layers of GaN, GaAs, InP, and / or SiC, which is heated and converted into vapor. This vapor is then transported to the CVD reactor along with the carrier gas mass flow rate. The evaporation vessel may be temperature-adjustable. It may be specified that the evaporation vessel is continuously fed by a storage vessel.

[0019] In one variant of the invention, the carrier gas mass flow rate supplied by the carrier gas source is distributed to multiple mass flow regulator devices, each of which is in-flow connected to an evaporation unit. The carrier gas mass flow rate is introduced into the evaporation vessel from each of the mass flow regulator devices. However, the carrier gas mass flow rate may also partially bypass the evaporation vessel. The carrier gas mass flow rate delivers the vapor generated in the evaporation vessel from the gas outlet of the evaporation unit to a process gas inlet line. The process gas inlet line leads to one or more processing chambers of one or more CVD reactors.

[0020] In another variation of the invention, carrier gas mass flow rates from multiple different carrier gas sources flow into one or more different mass flow rate regulator devices, which can be individually connected to the evaporation unit. Therefore, different carrier gases can be used. The carrier gas can be an inert gas, such as nitrogen or hydrogen.

[0021] Using the aforementioned equipment, the carrier gas mass flow rate from the carrier gas source can be switched from a high carrier gas mass flow rate to a low carrier gas mass flow rate via the evaporation unit. In this case, the carrier gas mass flow rate from the carrier gas source flows through a mass flow regulator device. In the mass flow regulator device, the carrier gas mass flow rate is distributed to at least two mass flow regulators, wherein the carrier gas mass flow rate permanently flows through both mass flow regulators. By closing the first valve of the switching valve and opening the second valve, the carrier gas mass flow rate flowing through the second mass flow regulator can flow into a bypass line, thereby bypassing the evaporation unit located downstream of the mass flow regulator device. Thus, the carrier gas mass flow rate through the evaporation vessel of the evaporation unit will be controlled only by the first mass flow regulator, and its flow range can be smaller than the flow range of the second mass flow regulator. The carrier gas mass flow rate is then delivered from the bypass line to the processed gas input line. During the switching process, the opening / closing of the first valve can occur with a delay relative to the opening / closing of the second valve to ensure that the two valves do not open simultaneously. This prevents the mass flow of carrier gas passing through the first mass flow regulator from flowing directly into the process gas input line via the bypass line, instead of flowing through the evaporator first as intended.

[0022] The method according to the invention enables switching between high and low carrier gas flow rates during CVD reactor operation, such as during layer growth. Therefore, the switching time should be minimized to ensure that the layer composition does not undergo uncontrollable changes during the switching process. Attached Figure Description

[0023] The invention is described in detail below with reference to the accompanying drawings. In the drawings:

[0024] Figure 1 A schematic diagram of the first embodiment is shown, wherein the CVD reactor 1 is supplied with gas by the processing gas delivery system 19;

[0025] Figure 2 This is a schematic diagram of the second embodiment of the present invention, wherein the processing gas delivery system 19 supplies gas to multiple CVD reactors;

[0026] Figure 3 This is a schematic diagram of the third embodiment, in which the CVD reactor 1 is supplied with gas by multiple processing gas delivery systems 19, 19', and 19";

[0027] Figure 4 This is a schematic diagram of a fourth embodiment of the processing gas delivery system 19, wherein a central carrier gas input pipeline is connected to multiple processing gas delivery systems that supply gas to the CVD reactor 1. Detailed Implementation

[0028] exist Figures 1 to 4In the shown processing gas delivery systems 19, 19', 19" the carrier gas is introduced into the evaporation container 17 of the evaporation device 6. The carrier gas (e.g., nitrogen, hydrogen or rare gas) is saturated by the vapor of the solid or liquid starting material 24 stored in the evaporation container 17 and leaves the evaporation container 17 through the discharge line.

[0029] The inlet and outlet lines of the evaporator 17 are connected to a switching device 18, which has multiple valves that can be switched so that the mass flow rate of the carrier gas provided by the mass flow regulator device consisting of one or more mass flow regulators 3, 5, 5' either flows through the evaporator or bypasses the evaporator.

[0030] exist Figures 1 to 4 In the illustrated embodiment, one or more processing gas input lines 7 are connected to one or more CVD reactors 1, 1', 1" and the vapor of the starting material 24 is transported by the mass flow rate of the carrier gas from the evaporation unit 6 and fed into the one or more processing gas input lines.

[0031] Processing gas delivery systems 19, 19', 19" are used to provide organometallic starting material 24 to CVD reactors 1, 1', 1" in which one or more substrates 20 are placed on heated substrate holders 21, which form the bottom of processing chamber 22.

[0032] An embodiment illustrates a pressure regulator 16. This pressure regulator is used to maintain a constant total pressure in the process gas delivery systems 19, 19', 19"

[0033] Figure 1The apparatus shown for supplying the processed gas includes two parallel mass flow regulators 3 and 5 with different flow ranges, for example, at least by coefficients 2, 5, or 10. Mass flow regulators 3, 5, and 5' are used to control the mass flow rate of the carrier gas entering the evaporator 6. The flow range of the first mass flow regulator 3 (e.g., 100 standard cubic centimeters) may be smaller than the flow range of the second mass flow regulator 5 (e.g., 1000 standard cubic centimeters). The first mass flow regulator 3 is arranged in the first carrier gas input line 2, and the second mass flow regulator 5 is arranged in the second carrier gas input line 4. The carrier gas input lines 2 and 4 are connected to a central carrier gas source (not shown). The first carrier gas mass flow rate flows from the carrier gas source into the evaporator 6 via the first carrier gas input line 2, and the second carrier gas mass flow rate flows from the carrier gas source into the evaporator 6 via the second carrier gas input line 4. The first carrier gas mass flow rate provided by the first mass flow regulator 3 is continuously fed into the evaporator. The second carrier gas mass flow rate provided by the second mass flow rate regulator 5 can be selectively fed into the evaporator 6 or the bypass line 12 via a valve device 8 (particularly a switching valve) arranged downstream of the second mass flow rate regulator 5. For this purpose, the valve device 8 includes a first valve 13 and a second valve 14. The first valve 13 is arranged in the second carrier gas inlet line 4. The second valve 14 is arranged in the bypass line 12. The bypass line 12 branches upstream of the first valve 13 and connects to the process gas inlet line 7 downstream of the evaporator 17. The mass flow rate regulator 15, located in the process gas inlet line 7, can be used to regulate the mass flow rate of the process gas fed into the CVD reactor 1 through the process gas inlet line 7. This device allows for short-term and precise switching of the carrier gas mass flow rate fed into the evaporator, particularly from a high carrier gas mass flow rate to a low carrier gas mass flow rate, because the total mass flow rate of the gas flowing through the process gas inlet line remains constant. Consequently, the total pressure inside the process gas delivery system 19, measured by the pressure regulator 16, remains constant.

[0034] In another variation of the invention, a switching valve may also be arranged in the first carrier gas input line 2.

[0035] Figure 2 Further embodiments are shown as examples. Figure 1A variation of the illustrated embodiment. Here, an additional second mass flow regulator 5' is arranged in parallel with the first mass flow regulator 3 and the second mass flow regulator 5'. The flow range of this additional second mass flow regulator is greater than that of the first mass flow regulator 3, but different from that of the second mass flow regulator 5. For example, the flow range of the mass flow regulator 5 may be greater than that of the mass flow regulator 3 by at least a factor of 2, and the flow range of the mass flow regulator 5' may be greater than that of the mass flow regulator 5 by at least a factor of 2. This expands the flow range of the carrier gas mass flow rate flowing into the evaporator. Furthermore, the mass flow rate of the process gas is divided into multiple sub-flow rates, which are respectively directed to different CVD reactors 1, 1', 1" wherein each process gas input line 7, 7', 7" leading to one CVD reactor 1, 1', 1" corresponds to a separate mass flow regulator 15, 15', 15".

[0036] Figure 3 The example shown is Figure 1 A variation of the illustrated embodiment. Here, a CVD reactor is connected to multiple different process gas delivery systems 19, 19', 19" . The process gas delivery systems 19, 19', 19" can be supplied by different carrier gas sources or by a central carrier gas source. The mass flow rate of the process gas through the process gas inlet lines 7, 7', 7" can be regulated by mass flow rate regulators 15, 15', 15". The process gas mass flow rate flows into the gas inlet component of the CVD reactor 1, wherein the process gas can be discharged from different inlet openings of the gas inlet component.

[0037] exist Figure 4 In the illustrated embodiment, three processing gas input lines 7, 7', 7" connected to different processing gas delivery systems 19, 19', 19" are respectively connected to the air inlet 23 of a CVD reactor 1, 1', 1". The processing gas delivery systems 19, 19', 19" are supplied with gas from a central carrier gas source.

[0038] The foregoing embodiments are used to illustrate the invention as generally included in this application, which extends the prior art through at least the following combinations of features, each of which independently extends the prior art. Two, more, or all of these combinations of features may also be combined with each other, namely:

[0039] An apparatus characterized in that valve devices 8, 8' are arranged downstream of second mass flow regulators 5, 5' and have second outlets 11, 11' connected to bypass lines 12, 12' which do not flow into evaporator 6, wherein the mass flow rate of carrier gas regulated by the second mass flow regulators 5, 5' selectively flows through or bypasses evaporator 6 by switching valve devices 8, 8'.

[0040] An apparatus characterized in that the valve devices 8 and 8' are switching valves, the switching valves comprising a first valve 13 and 13' arranged in the second carrier gas input lines 4 and 4' and a second valve 14 and 14' arranged in the bypass lines 12 and 12'.

[0041] An apparatus characterized in that a bypass line 12 is connected to a processing gas input line 7.

[0042] An apparatus characterized in that valves 13, 13', 14, and 14' of switching valves 8 and 8' have throttling openings, which are designed such that when switching valves 8 and 8' are switched, a positive pressure difference is maintained between the inlet pressure and the outlet pressure of the first valves 13, 13', 14, and 14', so that the mass flow rate of the carrier gas controlled by the first mass flow rate regulator 3 does not bypass the evaporation device 6, wherein the cross-section of the throttling opening is adjustable.

[0043] An apparatus characterized in that it includes a control device for controlling switching valves 8, 8' and mass flow regulators 3, 5, 5'.

[0044] A CVD reactor apparatus, characterized in that it has means for providing a process gas according to any one of the preceding claims.

[0045] A method for providing a processed gas, wherein a first mass flow regulator 3 provides a first carrier gas mass flow rate, and second mass flow regulators 5, 5' provide a second carrier gas mass flow rate, wherein in a first method step, at least the second carrier gas mass flow rate flows through an evaporator 6, and in a second method step, the first carrier gas mass flow rate flows through the evaporator 6 while the second carrier gas mass flow rate bypasses the evaporator 6, wherein the total carrier gas mass flow rate flowing through the evaporator 6 is greater in the first method position than in the second method position.

[0046] A method characterized in that a first carrier gas flow rate flows through a first carrier gas input line 2, and a second carrier gas flow rate flows through second carrier gas input lines 4 and 4', wherein by closing the first valves 13 and 13' arranged in the second carrier gas input lines 4 and 4' and opening the second valves 14 and 14' arranged in the bypass lines 12 and 12' branching off from the second carrier gas input lines 4 and 4', the carrier gas mass flow rate controlled by the second mass flow regulators 5 and 5' flows through the bypass lines 12 and 12', and by opening the first valves 13 and 13' and closing the second valves 14 and 14', the carrier gas mass flow rate flows into the evaporator 6 through the second carrier gas input lines 4 and 4'.

[0047] A method characterized by a time-delayed switching of first valves 13, 13' and second valves 14, 14', wherein, when switching from a first method step to a second method step, the first valves 13, 13' are closed and then the second valves 14, 14' are opened; and when switching from a second method step to a first method step, the second valves 14, 14' are closed and then the first valves 13, 13' are opened.

[0048] All disclosed features (either individually or in different combinations) are essential to the invention. Therefore, the disclosure of this application also includes the full content of the relevant / attached priority documents (copies of earlier applications), and for this purpose, the features of the priority documents are also incorporated into the claims of this application. Dependent claims, by virtue of their features, characterize unique inventive improvements of the prior art, even when they do not possess the features of the cited claims, and are particularly useful for divisional applications based on such features. The invention given in each claim may additionally have one or more features given in particular by reference numerals and / or in the list of reference numerals in the foregoing description. The invention also relates to various design forms in which individual features mentioned in the foregoing description are not implemented, especially when they are considered irrelevant to the corresponding purpose of use or can be replaced by other means that achieve the same technical effect.

[0049] List of reference numerals

[0050] 1 CVD reactor

[0051] 1' CVD reactor

[0052] 1" CVD reactor

[0053] 2. Carrier gas inlet pipeline

[0054] 3 First mass flow regulator

[0055] 4. Carrier gas inlet pipeline

[0056] 4' Carrier gas inlet line

[0057] 5 Second mass flow regulator

[0058] 5' Second mass flow regulator

[0059] 6. Evaporation apparatus

[0060] 7. Processing gas input lines

[0061] 7' Processing gas input line

[0062] 7" Processing gas input line

[0063] 8 Valve Device

[0064] 8' Valve Device

[0065] 9 entrances

[0066] 9' Entrance

[0067] 10 First Exit

[0068] 10' First Exit

[0069] 11 Second Exit

[0070] 11' Second Exit

[0071] 12 Bypass pipeline

[0072] 12' Bypass line

[0073] 13 First Valve

[0074] 13' First valve

[0075] 14 Second Valve

[0076] 14' Second Valve

[0077] 15. Mass Flow Regulator

[0078] 15' Mass Flow Regulator

[0079] 15" mass flow regulator

[0080] 16 Pressure Regulator

[0081] 17 Evaporation container

[0082] 19. Gas handling and delivery system

[0083] 19' Processing gas delivery system

[0084] 19" Processing Gas Delivery System

[0085] 20 substrates

[0086] 21 substrate base

[0087] 22 Processing Room

[0088] 23. Air intake opening

[0089] 24. Liquid starting materials.

Claims

1. A method for providing a process gas for a CVD reactor (1, 1', 1"), wherein, The first carrier gas input line (2) and the second carrier gas input line (4) are connected to an evaporation device (6) for evaporating solid or liquid starting materials. A processing gas input line (7) leading to the CVD reactor (1, 1', 1") originates from the evaporation device (6). A first mass flow regulator (3) with a smaller flow range is arranged in the first carrier gas input line (2), while a second mass flow regulator (5, 5') with a larger flow range is arranged in the second carrier gas input line (4, 4'). Solid or liquid starting materials are evaporated in the evaporation device (6). In the first method step, the carrier gas supplied from the carrier gas source to the first carrier gas input line (2) is converted by the first carrier gas input line (6). A first mass flow rate regulated by a mass flow rate regulator (3) and a second mass flow rate regulated by the second mass flow rate regulator (5, 5') of the carrier gas fed from the carrier gas source into the second carrier gas input line (4, 4') flow into the processed gas input line (7) via the evaporator (6), wherein, in the second method step, only the first mass flow rate regulated by the first mass flow rate regulator (3) flows into the evaporator (6), and the second mass flow rate bypasses the evaporator (6) via the bypass line (12, 12') and is delivered to the processed gas input line (7), wherein, in the first method step, the total carrier gas mass flow rate flowing through the evaporator (6) is greater than in the second method step.

2. The method according to claim 1, characterized in that, When switching from the first method step to the second method step, the first valve (13, 13') arranged in the second carrier gas input line (4, 4') is closed, and the second valve (14, 14') arranged in the bypass line (12, 12') branching off from the second carrier gas input line (4, 4') is closed.

3. The method according to any one of the preceding claims, characterized in that, The first valve (13, 13') and the second valve (14, 14') are switched with a delay, wherein the first valve (13, 13') is closed first, and then the second valve (14, 14') is opened.

4. The method according to any one of the preceding claims, characterized in that, When switching from the second method step to the first method step, the second valve is closed first, and then the first valve (13, 13') is opened.

5. The method according to any one of the preceding claims, characterized in that, When switching between the first method step and the second method step, the variable cross-section narrowing of the throttling openings in these valves (13, 13', 14, 14') is used to prevent the first mass flow rate regulated by the first mass flow rate regulator (3) from flowing into the bypass line (12, 12').

6. An apparatus for implementing the method according to any one of the preceding claims, comprising a first carrier gas input line (2) and a second carrier gas input line (4, 4'), the first carrier gas input line having a first mass flow regulator (3, 3') with a small flow range, and the second carrier gas input line having a second mass flow regulator (5, 5') with a large flow range, the first carrier gas input line and the second carrier gas input line being supplied with carrier gas by a carrier gas source and controlled by a control device, wherein, These carrier gas input lines (2, 4, 4') lead to an evaporation device (6) for evaporating solid or liquid starting materials, wherein a processing gas input line (7) leading to a CVD reactor (1, 1', 1") originates from the evaporation device (6), wherein a valve device (8, 8') controlled by the control device is provided downstream of the second mass flow regulator (5, 5') in the second carrier gas input line (4, 4'), the valve device having an inlet (9, 9'), a first outlet (10, 10') and a second outlet (11, 11') connected to the evaporation device (6), characterized in that the second outlet (11, 11') is connected to a bypass line (12, 12') that bypasses the evaporation device (6) and leads to the processing gas input line (7).

7. The device according to claim 6, characterized in that, The control device is configured to implement the method according to any one of claims 1 to 5.

8. The device according to claim 6 or 7, characterized in that, The valve device (8, 8') is a switching valve, which includes a first valve (13, 13') arranged in the second carrier gas input line (4, 4') and a second valve (14, 14') arranged in the bypass line (12, 12').

9. The device according to claim 6, 7 or 8, characterized in that, The valves (13, 13', 14, 14') of the switching valve (8, 8') have throttling openings designed to maintain a positive pressure difference between the inlet and outlet pressures at the first valve (13, 13') or the second valve (14, 14') when the switching valve (8, 8') is switched, so that the carrier gas mass flow rate controlled by the first mass flow regulator (3) does not bypass the evaporator (6).

10. An apparatus for implementing the method according to any one of claims 1 to 5, comprising a first carrier gas input line (2) and a second carrier gas input line (4, 4'), the first carrier gas input line having a first mass flow regulator (3, 3') with a small flow range, and the second carrier gas input line having a second mass flow regulator (5, 5') with a large flow range, wherein, These carrier gas input lines (2, 4, 4') lead to an evaporation device (6) for evaporating solid or liquid starting materials, wherein a process gas input line (7) leading to a CVD reactor (1, 1', 1") originates from the evaporation device (6), wherein a valve device (8, 8') controlled by a control device is provided downstream of the second mass flow regulator (5, 5') in the second input line (4, 4'), the valve device having an inlet (9, 9'), a first outlet (10, 10') and a second outlet (11, 11') connected to the evaporation device (6), wherein the second outlet (11, 11') is connected to a bypass line (12, 12') that bypasses the evaporation device (6) and leads to the process gas input line (7), characterized in that these valves (13, 13', 14, 14') of the switching valve (8, 8') have variablely adjustable throttling openings.

11. A method or apparatus, characterized in that, It has one or more distinguishing features as described in any of the preceding claims.

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