Use of CVD reactors for two-dimensional layers.

Abstract

The present invention relates to a method for depositing a two-dimensional layer on a substrate in a CVD reactor (1), in which a process gas is supplied by means of a supply line (10) to a gas inlet member (2) having gas outlet holes (14, 24) opening into a process chamber (3), in which the process gas or its decomposition products in the process chamber (3) are brought into contact with the surface of a substrate (4), and the substrate (4) is heated to a process temperature (T) by means of a heating device (6), so that a two-dimensional layer is formed on the substrate after chemical reaction of the process gas. P In the present invention, the process temperature (T P During or after heating the substrate to a temperature of 0.15°C, a first gas flow (Q1) of process gas is first supplied into the process chamber (3) at which no layer growth occurs on the surface of the substrate (4), and then, while the substrate surface is being observed, the gas flow of the process gas is increased for a time required to obtain a second gas flow (Q2) at which layer growth begins, and then the gas flow of the process gas is increased by a predetermined value to a third gas flow (Q3) at which a layer is deposited. The onset of phase growth is identified by observing the time progression of the pyrometer measurement curve (26).

Description

[Technical Field]

[0001] The present invention relates to a method for depositing a two-dimensional layer on a substrate in a CVD reactor, in which a process gas is supplied to a gas inlet member by a supply line with gas outlet holes opening into a process chamber, where the process gas or its decomposition products are brought into contact with the surface of the substrate in the process chamber so as to deposit a two-dimensional layer on the surface, and the substrate is raised to a process temperature by a heating device.

[0002] The invention further relates to the use of CVD for carrying out the method.

[0003] CVD reactors are also known from US Pat. No. 5,629,499 and US Pat. No. 5,629,499, as well as other comprehensively described prior art. US Pat. No. 5,629,499 describes a method in which the temperature of the substrate surface can be measured by an optical measurement device. US Pat. No. 5,629,499 describes the deposition of two-dimensional layers using a showerhead. US Pat. No. 5,629,499 describes the deposition of graphene using a reactor equipped with a showerhead. Patent Document 6 discloses a method for depositing layers containing carbon and nitrogen with the use of plasma. Patent Document 7 discloses a method for depositing TiCl in a plasma CVD reactor. 4 A method for depositing TiSi on a silicon substrate by providing [Prior art documents] [Patent documents]

[0004] [Patent Document 1] DE 10 2011 056 589 A1 [Patent Document 2] DE 10 2010 016 471 A1 [Patent Document 3] DE 10 2004 007 984 A1 [Patent Document 4] DE 10 2013 111 791 [Patent Document 5] International Publication No. 2017 / 029470 [Patent Document 6] US Patent Application Publication No. 2016 / 0211265 [Patent Document 7] Patent No. 4319269 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide an improved method for depositing two-dimensional layers in the art and to indicate an apparatus that can be used for this purpose.

[0006] This object is achieved by the invention as set forth in the claims, the dependent claims indicating not only advantageous further developments of the invention set forth therein, but also independent technical solutions to this object.

[0007] Essentially, during or after heating the substrate to a process temperature, a gas flow of a process gas is supplied to the process chamber with a first gas flow value (first gas flow). As a result of the gas flow with the first gas flow value, the partial pressure of one or more process gases is set to be below a threshold at which a solid layer is deposited on the substrate. The start of the supply of the process gas can depend on the temperature being reached. For example, the supply of the first gas flow can be set to start when the heating process is completed and the surface of the substrate reaches the process temperature. However, the supply of the first gas flow of the process gas can also be started in advance. Here, the gas flow of the process gas is set so low that no two-dimensional layer growth is observed on the substrate surface.

[0008] In the present invention, particularly after reaching the process temperature, the gas flow of the process gas is increased incrementally or continuously, linearly or nonlinearly, until layer growth on the substrate is observed. Here, the partial pressure of one or several reactive gases in the process chamber is increased until a threshold value is reached for the second gas flow. The second gas flow of the process gas is then increased by a predetermined value, which may be zero. Consequently, two-dimensional layer deposition occurs during this third gas flow. Here, the partial pressure of one or several reactive gases is set to a value exceeding the threshold value. This value is selected, for example, so that the layer is deposited on the substrate during the third gas flow during which layer growth occurs.

[0009] When depositing two-dimensional layers by the methods of the prior art, particularly those disclosed in the first-mentioned publication, island-like growth is observed. Due to the growth occurring at multiple locations in multiple different areas of the substrate, the layers produced by this method have poor layer quality. Instead of two-dimensional layers such as graphene layers, amorphous carbon layers or multilayers may be formed. This disadvantage is eliminated by the method according to the invention or by using the CVD reactor according to the invention. The objective is to show an optimal growth method for depositing high quality two-dimensional layers. In line with the present invention for controlling the gas flow during the growth phase, a solution is approached in which the partial pressure of the process gas above the substrate is set by a predetermined value above a threshold, where the threshold is defined by the partial pressure at which the state changes between no growth and growth.

[0010] The CVD reactor used in accordance with the present invention comprises an airtight housing capable of being evacuated. The housing incorporates a gas inlet member through which process gases, including one or several reactive gases or alternatively an inert gas, can be supplied by supply lines. The gas inlet member can comprise a gas distribution chamber, e.g., a showerhead shape. The process gas can flow into the process chamber through a gas outlet plate with a planar gas outlet surface. To achieve this goal, the gas outlet plate forms a plurality of uniformly spaced gas outlet holes. The gas outlet holes are formed by the ends of tubes that intersect with a cooling chamber immediately adjacent to the gas outlet plate. The tubes are used to connect one or several gas distribution chambers to the gas outlet surface in terms of flow. Away from the gas outlet surface extends a support surface of the susceptor, which can comprise a coated or uncoated graphite body.

[0011] The susceptor accommodates a substrate on its support surface. A heating device is disposed on one side of the susceptor opposite the support surface. For example, this may be a resistance heater, an infrared heater, or a high-frequency induction heater, capable of heating the susceptor or the substrate to the process temperature. During susceptor heating, an inert gas may be supplied to the process chamber, but a small first gas flow of process gas may also be supplied to the process chamber, while the surface temperature of the substrate is measured by an optical device. The optical device is optically connected to the surface of the substrate via a beam path, allowing the surface to be observed. To this end, the gas inlet member has a window formed by a material transparent to the wavelength used, through which the beam path passes. The beam path may also pass through one of the tubes. In this regard, reference is made to the description in Patent Document 3, the entire contents of which are also incorporated herein by reference. The optical device may be a pyrometer, in which spectra are recorded in two wavelength ranges, for example, between 350 and 1050 nm and between 1050 and 1750 nm. A third spectrum can be calculated from the two spectra and used to determine the surface temperature of the substrate. The spectrum is used to determine the value at which the substrate temperature is known. The latter can be depicted as a measurement curve. Surprisingly, the time progression of the values ​​is not only used to determine the temperature, but also to determine the start of layer growth or the start of multi-layer growth. In addition, the measurement curve can be used to terminate the deposition process.

[0012] It was observed that the measurements used to determine the temperature correspond to a measurement curve that extends along a straight line in time before the layer deposition begins. The measurement curve of values ​​recorded by the optical measuring device over time extends with a constant slope that is essentially negative, among other things. It was observed that the progression of the measurement curve changes with the start of layer deposition. In particular, it was found that the slope of the measurement curve increases slightly at the start of layer growth and then decreases again, thereby resulting in local maxima or minima in the measurement curve. Furthermore, it was found that the value of the slope of the measurement curve, after extending through a peak, again increases or decreases with time. At this point, a complete layer is deposited, or at this point, multilayer growth or deposition of an amorphous carbon layer can be expected.

[0013] The method according to the present invention involves increasing the first gas flow until a first characteristic change is apparent in the progression of the measurement curve, particularly until the slope of the measurement curve measured using an optical measurement device first increases. At this point, the mass flow rate of the process gas supplied into the process chamber is referred to as the second gas flow. This second gas flow is then increased by a predetermined value to a third gas flow, at which the layer is deposited. The predetermined value can be greater than zero. It can be at least 5 percent of the second gas flow, at least 10 percent of the second gas flow, or at least 20 percent of the second gas flow. However, it can also be approximately 20 percent of the second gas flow. It can also be at most 20 percent or at most 25 percent of the second gas flow. The progression of the measurement curve is further observed until another characteristic change in the measurement curve occurs. This characteristic change in the progression of the measurement curve can be an updated increase in the slope of the measurement curve. If this event is detected, the process gas flow is stopped.

[0014] The layer deposited by the method according to the invention or by the use according to the invention may contain transition metals JThe material may be a chalcogenide. In particular, it may be a combination of materials mentioned in Patent Document 4, and the process gases mentioned therein can be used to deposit these materials. For this reason, the entire disclosure of Patent Document 4 is also incorporated herein by reference. It is particularly preferred to deposit graphene, MoS2, MoSe2, WS2, or WSe2, or hBN. To deposit graphene, a hydrocarbon, such as methane, is used as the process gas. W(CO)6 can be used to deposit tungsten compounds. A noble gas, such as argon, can be used as the carrier gas. However, borazine can also be used as a reactive gas during the deposition of hBN. To influence the growth rate, the height of the process chamber, e.g., the distance between the support surface and the gas outlet surface of the susceptor, can be varied during deposition. A sapphire substrate is preferably used as the substrate. However, silicon substrates or other substrates can also be used. In the present invention, it is possible to deposit two-dimensional layers using only one reactive gas, such as graphene or borazine. However, it is also possible to provide that the two-dimensional layer is deposited using two reactive gases, one containing a transition metal and the other containing a chalcogenide. In the case of sulfur, di-tert-butyl-sulfide is preferably included here. [Brief explanation of the drawings]

[0015] In the following, the invention will be explained in more detail with reference to exemplary embodiments. [Figure 1] FIG. 1 is a schematic cross-section through a first exemplary embodiment CVD reactor and a schematic diagram of the components of the gas mixing system necessary to illustrate the present invention. [Figure 2] FIG. 2 is an enlarged view of region II in FIG. [Figure 3] FIG. 3 shows the time progression of the process gas. [Figure 4a] FIG. 4a shows the measurement curve 26 of the two-wave pyrometer during layer deposition. [Figure 4b]FIG. 4b is a diagram of the time progression of the gas flow of reactive gases in the process chamber of FIG. [Figure 5] Similar measurement curve to FIG. 4a, but with reactive gas being supplied to the process chamber for the entire time t. [Figure 6] FIG. 6 is a diagram based on FIG. 1 for a second exemplary embodiment. [Figure 7] FIG. 7 is an enlarged view of region VII in FIG. [Figure 8] FIG. 8 shows the effect of process chamber height on layer growth at various total pressures. DETAILED DESCRIPTION OF THE INVENTION

[0016] The apparatus shown in Figures 1, 6 and 7 is a CVD reactor 1. The CVD reactor 1 has an airtight housing that can be evacuated using a vacuum pump (not shown). The vacuum pump can be connected to a gas outlet member 7.

[0017] A gas inlet member 2 having the shape of a showerhead is located inside the CVD reactor 1. In the exemplary embodiment shown in FIGS. 1 and 2, the gas inlet member 2 comprises two gas distribution chambers 11, 21, into which respective supply lines 10, 20 open, through which gases can be supplied to each gas distribution chamber 11, 21. The supply lines 10, 20 protrude through the wall of the housing. The gas distribution chambers 11, 21 are arranged vertically one above the other. A cooling device 8 is located below the gas distribution chamber 21. Coolant is supplied to the cooling chamber 8 through a supply line 8'. The coolant leaves the cooling chamber 8 through an exhaust line 8'', which supply line 8' and exhaust line 8'' protrude through the wall of the housing of the CVD reactor 1.

[0018] FIG. 1 also shows a schematic of a gas mixing system for supplying process gases. Two reactive gases are generated by evaporating a liquid or solid, respectively. The liquid or powder is fed into an airtight container (bubbler 32, 32'). Mass flow controllers 30, 30' are used to supply inert gas from an inert gas source 39, 39' to each bubbler 32, 32'. The bubblers 32, 32' are maintained at a constant temperature in a temperature bath. Vapors of the reactive gas, carried by the inert gas acting as a carrier gas, exit each bubbler 32, 32'. The concentration of the reactive gas in the output flow is measured by a concentration measuring device 31, 31'. The device sold under the brand name "Epison" is relevant here.

[0019] Two different gas lines for carrying reactive gases are fed using switching valves 33, 33' to either a vent line 35 that bypasses the gases to the reactor 1 or to flow lines 34, 34' that direct the gases to the reactor 1, respectively.

[0020] A control device 29 is provided, which controls the temperature of the heating bath and mass flow controllers 30, 30'. Furthermore, the measurement results of the concentration measuring devices 31, 31' are input to the control device 29.

[0021] 1, a branch of the gas supply, flow line 34, opens into supply line 20. Flow line 34' opens into supply line 10.

[0022] Instead of reactive gases, mass flow controllers 37, 37' and valves 36, 36' can also supply carrier / inert gases to the gas inlet member 2. Reference numerals 40, 40' refer to the source of reactive gases, which can be carbon compounds or, in particular, hydrocarbons such as methane, used in graphene deposition. These reactive gas sources 40, 40' are flow-connected to flow lines 34, 34' via mass flow controllers 41, 41' and valves 38, 38'.

[0023] 1 can optionally be used to simultaneously supply two different reactive gases to two separate gas distribution chambers 11, 21. However, to deposit a sequence of layers comprising, for example, graphene and hBN, it is also possible to supply methane to gas distribution chamber 11 and an inert gas to distribution chamber 21, and then borazine to gas distribution chamber 21 and an inert gas to gas distribution chamber 11. In this way, non-uniform layer structures can be deposited by periodic switching.

[0024] 6 and 7 differs from the exemplary embodiment shown in Figures 1 and 2 essentially only in that it is provided with only one gas distribution chamber 11. The latter is connected to the gas outlet surface 25 by a tube 12, through which the process gas supplied to the gas distribution chamber 11 can flow to the process chamber 3.

[0025] The gas mixing system depicted in Figure 6 comprises only one bubbler 32, to which a carrier gas is supplied using a mass flow controller 30. The concentration of the vapor carried in the carrier gas can be determined by a concentration measuring device 31. A switching valve 33 can be used to supply the mass flow rate of the reactive gas to either the vent line 35 or the flow line 34. The reactive gas can be supplied to the flow line 34 using a mass flow controller 37. To achieve this, valve 36 must be open.

[0026] 1 and 2 additionally comprises tubes 22 connecting the second gas distribution chamber 21 with a gas outlet face 25. In the gas outlet face 25 comprising the gas outlet plate 9, the gas outlet holes 14, 24 connected to the tubes 12, 22 respectively are distributed over the gas outlet face 25. The tubes 12 are connected with an intermediate plate 23 separating the gas distribution chamber 21 from the cooling chamber 8. The tubes 22 are connected with an intermediate plate 13 separating the gas distribution chamber 11 from the gas distribution chamber 21.

[0027] The support surface 15 of the susceptor 5, which may comprise coated or uncoated graphite, extends a distance h from the gas outlet surface 25. Lifting members, not shown, can be used to raise and lower the susceptor 5 and / or the gas inlet member 2 by varying the distance h. Figure 8 shows the effect of varying the height of the process chamber 3 on the growth rate of the deposited layer at different total pressures in the process chamber.

[0028] The susceptor 5 is heated from below using a heating device 6. The heating device can be a resistance heater, an infrared heater, a radio frequency heater, or other power source that supplies thermal energy to the susceptor 5.

[0029] The susceptor 5 is surrounded by a gas outlet member 7 through which gaseous reaction products and carrier gas are discharged.

[0030] One of the tubes 12' serves as a passage channel for the beam path 18 of the optical device. The cover plate 16 of the gas inlet member 2 has a window 17 through which the beam path 18 passes. The beam path 18 extends between a pyrometer 19, which is a dual-wavelength pyrometer, and the surface of the support surface 15 or of the substrate 4 placed on the support surface 15. The pyrometer 19 is used to measure the temperature of the substrate surface. Figures 4a and 5 show measurement curves measured over time t and can be understood as the measured temperature values. The temperature rises to a maximum value during the heating process. The measurement curve then descends slightly along a straight line with an approximately constant slope. Figure 4a shows a first peak 27. Figure 5 additionally shows a second peak 27'.

[0031] FIG. 4a shows a measurement curve in which a first gas flow Q1 of a reactive gas (e.g., methane) or a mixture of several reactive gases is supplied to the process chamber at time t1. The mass flow rate of the process gas steadily increases until time t2, which is marked by an increase in the slope of the measurement curve 26. Observations have shown that this correlates with the event of layer growth initiation on the layer. Thus, the slope of the measurement curve 26 changes continuously during layer deposition, as peak 27 forms, decreasing until it increases again at time t4. Observations have shown that the increase in the measurement curve accompanies the cessation of two-dimensional growth.

[0032] While the mass flow rate of the process gas is stopped at time t4 in the measurement curve in Figure 4a, the process gas is still supplied to the process chamber after peak 27 while recording the measurement curve according to Figure 5. Peak 27' is then formed.

[0033] Based on the findings, the method according to the invention is carried out as follows.

[0034] The method of the present invention begins with providing a CVD reactor of the type described above. A substrate 4 to be coated is placed in the CVD reactor. The substrate is placed on a support surface 15. The temperature of the substrate 4 is increased by a heating device 6 from a point in time indicated as t1 in FIG. 3 . In an exemplary embodiment, a smaller mass flow rate Q1 of a process gas (e.g., methane during graphene deposition) can now be supplied to the process chamber. The mass flow rate Q1 is less than the mass flow rate sufficient to cause layer growth. However, it can also be arranged that the substrate is heated only in the presence of a carrier gas, e.g., argon, and the process gas is switched at a later point in time.

[0035] The substrate surface is over 1000°C to After reaching the process temperature TP, the mass flow rate of the process gas is increased continuously, incrementally, linearly or non-linearly, while the surface of the substrate 4 is observed by a pyrometer 9. The measurement curve initially extends along a straight line until the slope of the measurement curve changes with an increase. At the point in time t2 where an increase is detected in the measurement curve, the value of the gas flow Q2 flowing at this point in time t2 is recorded. A third gas flow Q3 is calculated by adding a predetermined value to the value of the second gas flow Q2. The gas flow is then increased to the third gas flow value Q3. This mass flow rate 28 is maintained during layer growth. The predetermined value added to the second gas flow Q2, or the difference between the third gas flow Q3 and the second gas flow Q2, is 20 percent of the second gas flow Q2.

[0036] Layer deposition continues until a time when a second event is measured during observation of measurement curve 26, where the measurement curve rises again after a previous decrease in the slope of measurement curve 26. This event occurs at time t4 and is caused by turning off the supply of process gas.

[0037] Silicon carbide-coated susceptors can be used during the deposition of hBN. NH3, among others, is used as a reactive gas in the process gas in the prior art. This gas works on uncoated graphite. Monovalent silicon, on the other hand, reacts with hydrogen at substrate temperatures above 1300°C. Borazine (B3N3H6) can be used as the reactive gas. This allows the deposition of hBN at temperatures ranging between 1400°C and 1500°C. A noble gas, e.g., argon, is used as a carrier or inert gas.

[0038] The growth rate at a given rate, which depends on the increase in gas flow from the second to the third gas flow, increases because the growth starts from a very low value to a higher value by the method according to the invention, which makes it possible in particular to control the initial growth of graphene and to reduce the number of nucleation sites, which improves the quality of the two-dimensional graphene layer.

[0039] The method according to the invention relates to all the material combinations mentioned at the beginning and in particular to the deposition of two-dimensional heterostructures.

[0040] The foregoing serves to describe an invention falling within the scope of the present application as a whole, which also advances the relevant art independently through at least the following combinations of features, and which may also combine two, more, or all of said combinations of features.

[0041] The gas flow having a first value Q1 of the process gas is first P a substrate 4 is supplied into the process chamber 3 during or after heating until no layer growth occurs on the surface of the substrate 4, and then the gas flow is increased while observing the substrate surface until layer growth begins at a second value Q2 of gas flow, and then the gas flow is increased to a third value Q3 that corresponds to the sum of the predetermined value and the second value Q2, and a layer is deposited at the gas flow having the third value Q3.

[0042] The gas flow having a first value Q1 of the process gas is first P a substrate 4 is supplied into the process chamber 3 during or after heating until no layer growth occurs on the surface of the substrate 4, and then the gas flow is increased until layer growth begins at a second value Q2 of gas flow while observing the substrate surface, and then the gas flow is increased to a third value Q3 that corresponds to the sum of the predetermined value and the second value Q2, and a layer is deposited at the gas flow having the third value Q3.

[0043] 10. A method or use wherein an optical device is used or provided on a CVD reactor for observing the substrate surface.

[0044] A method or use characterized in that the optical device 19 is a pyrometer and / or a dual wavelength pyrometer.

[0045] A method or use characterized in that the measurement curve 26 of the optical device 19 recorded while observing the substrate surface is evaluated to determine when layer growth begins and / or the onset of layer growth is determined by detecting a change in the slope of the measurement curve 26 of the optical device 19, in particular an increase or decrease.

[0046] 10. A method according to claim 9, wherein the measurement curve is used to determine the number of layers to be deposited and / or the number of layers to be deposited is determined by determining the number of maxima or minima of the measurement curve.

[0047] 10. A method or use, characterized in that the predetermined value is greater than 0 and / or is at least 5 percent of the second gas flow value Q2, or at least 10 percent of the second gas flow value Q2, or at least 20 percent of the second gas flow value Q2.

[0048] 1. A method or use comprising: a gas inlet member (2) having a gas outlet surface (25) extending across the support surface (15) of the susceptor (5) and having a plurality of gas outlet holes (14, 24) connected in flow relation to the gas distribution volumes (11, 21) and uniformly arranged therein.

[0049] 10. A method or use characterized in that the gas outlet face (25) comprises a gas outlet plate (9) of the gas inlet member (2) adjacent to a cooling chamber (8) through which coolant flows.

[0050] A method or use characterized in that the beam path 18 of the optical device 19 passes through a gas inlet member and / or the cover plate 16 of the gas inlet member 2 is provided with a window 17 that is transparent to the wavelength used, and the tube 12' through which the beam path 18 passes opens out onto the gas outlet face 25.

[0051] A method or use characterized in that the distance between the support surface (15) and the gas outlet surface (25) of the susceptor (5) is varied during deposition.

[0052] A method or use characterized in that a process gas is generated by passing a carrier gas through a bubbler 32, 32' containing a solid or liquid starting material.

[0053] A method or use characterized in that a gas concentration measuring device 31, 31' is used downstream of a bubbler 32, 32' to determine the concentration of vapors of the starting material in the carrier gas.

[0054] The method or use is characterized in that during layer deposition the surface is further observed and / or the measurement curve 26 is further evaluated so that the process gas is turned off if an event occurs, and / or the gas flow of the process gas is turned off when a change in the slope of the measurement curve 26, in particular an increase or decrease, is detected.

[0055] All disclosed features are essential to the invention (both by themselves and in combination with one another). The disclosure of the present application includes in its entirety the disclosure content of the relevant / attached priority documents (copies and earlier applications), also for the purpose of incorporating the features of these documents into the claims of the present application. The dependent claims are characterized by an independent, inventive further development of the prior art, even without the features of the claims cited therein, in particular for the purpose of filing a divisional application based on these claims. The invention specified in each claim may additionally have one or more features specified in the preceding description, particularly those given reference signs and / or specified in the sign explanations. The present invention also relates in particular to embodiments in which individual features set forth in the preceding description are not implemented, insofar as they are clearly unnecessary for the respective intended use or can be replaced by other means having the same technical effect. [Explanation of symbols]

[0056] 1 CVD reactor 2 Gas inlet member 3. Process chamber 4 boards 5 Susceptor 6 Heating device 7 Gas outlet member 8 Cooling Chamber 8' supply line 8" discharge line 9 Gas Outlet Plate 10 Supply Line 11 Gas distribution chamber 12 tubes 12' Tube 13 Intermediate plate 14 Gas outlet hole 15 Support surface 16 Cover Plate 17 Windows 18 Beam Path 19 Optical devices, pyrometers 20 Supply Line 21 Gas distribution chamber 22 Gas inlet member 23 Intermediate plate 24 Gas outlet hole 25 Gas outlet surface 26 Measurement curve 27 Peak 27' Peak 28 Mass flow rate 29 Control Device 30 Mass Flow Controller 30' Mass Flow Controller 31 Concentration measuring device 31' Concentration measuring device 32 Bubbler 32' Bubbler 33 Switching valve 33' Switching Valve 34 Flow Line 34' flow line 35 Ventilation line 36 Valves 36' Valve 37 Mass Flow Controller 37' Mass Flow Controller 38 Valve 38' Valve 39 Inert Gas Source 39' Inert gas source 40 Reactive Gas Source 40' Reactive Gas Source 41 Mass Flow Controller 41' Mass Flow Controller Q1 Gas Flow Q2 Gas Flow Q3 Gas Flow T P Process Temperature h Height and distance of the process chamber t1 time t2 time t3 time t4 time

Claims

1. A method for depositing a two-dimensional layer on a substrate in a CVD reactor (1), comprising: A process gas is supplied to the gas inlet member by a supply line (10) having gas outlet holes (14, 24) opening into the process chamber (3); The process gas or its decomposition products are brought into contact with the surface of the substrate (4) in the process chamber (3); The substrate (4) is heated to a process temperature (T Ｐ ) and whereby after chemical reaction of the process gas a two-dimensional layer is deposited on the surface, The process temperature (T Ｐ During or after heating the substrate (4) to a first value (Q １ a first gas flow having a first conductivity type selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, observing the surface of the substrate (4) using an optical device (19) and recording measurements of the temperature of the substrate (4) by the optical device (19); Recording a measurement curve of the measured values; increasing the gas flow of the process gas in the process chamber (3) while observing the surface of the substrate (4) using the optical device (19); A second value (Q) of the flow rate of the process gas in the process chamber (3) at which a change in the slope of the measurement curve occurs between no growth and growth of a layer on the substrate (4) is detected. ２ ) and The second value (Q ２ ) and the second value (Q ２ a third value (Q ３ ), increasing the gas flow of the process gas supplied to the process chamber (3); and The third value (Q ３ ) into the process chamber (3), thereby depositing a layer on a substrate.

2. 2. The method of claim 1, wherein the optical device (19), the pyrometer, and the dual wavelength pyrometer are used to observe the surface of the substrate (4).

3. 3. A method according to claim 1 or 2, characterized in that the distance between the support surface (15) of the susceptor (5) and the gas outlet surface (25) varies during deposition.

4. 4. A method according to any one of claims 1 to 3, characterized in that the process gas is generated by passing a carrier gas through a bubbler (32, 32') containing a solid or liquid starting material.

5. 5. The method of claim 4, wherein a gas concentration measuring device (31, 31') is used downstream of the bubbler (32, 32') to determine the concentration of the vapor of the starting material in the carrier gas.

6. 6. The method according to claim 1, wherein during layer deposition, the surface is further observed and the measurement curve (26) is further evaluated so that the process gas is switched off if an event occurs, and wherein the gas flow of the process gas is switched off when a change in the slope of the measurement curve (26) is detected.

7. 7. The method of claim 6, wherein the change in the measurement curve (26) is an increase.

8. A CVD reactor (1), a gas inlet member (2) having gas outlet holes (14, 24) opening into the process chamber (3); a susceptor (5) for receiving the substrate (4) to be coated; Process temperature (T Ｐ a heating device (6) for heating the substrate (4) to a temperature of 1000 K. A supply line (10) introduces process gases from the gas inlet member (2) through the gas outlet holes (14, 24) into the process chamber (3) where chemical reactions occur in such a way as to deposit a two-dimensional layer on the surface, A CVD reactor, characterized in that it is provided with a control device (29) for controlling mass flow controllers (30, 30') to carry out the method according to any one of claims 1 to 7.

9. 9. The CVD reactor of claim 8, wherein an optical device (19), a pyrometer, or a dual wavelength pyrometer is provided on the CVD reactor (1) for observing the surface of the substrate (4).

10. 10. The CVD reactor according to claim 8 or 9, characterized in that the gas inlet member (2) has a gas outlet surface (25) extending across the support surface (15) of the susceptor (5) and has a plurality of uniformly arranged gas outlet holes (14, 24) connected in flow terms with a gas distribution volume (11, 21), wherein the gas outlet surface (25) comprises a gas outlet plate (9) of the gas inlet member (2) adjacent to a cooling chamber (8) through which a coolant flows.

11. 11. A CVD reactor according to any one of claims 8 to 10, characterized in that the beam path (18) of the optical device (19) passes through the gas inlet member (2) and / or that a cover plate (16) of the gas inlet member (2) is provided with a window (17) that is transparent to the wavelength used, and a tube (12') through which the beam path (18) passes opens into a gas outlet face (25) of the gas inlet member (2).

12. 12. A CVD reactor according to any one of claims 8 to 11, characterized in that it comprises a bubbler (32, 32') containing a solid or liquid starting material, in which case the process gas is generated by passing a carrier gas through the bubbler (32, 32').

13. 13. The CVD reactor of claim 12, characterized by a gas concentration measuring device (31, 31') used downstream of the bubbler (32, 32') to determine the concentration of the vapor of the starting material in the carrier gas.

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