Method and device for separating n-doped sic

Abstract

The invention relates to a method for separating an SiC layer, wherein an NH3-containing first doping gas flow (D1), a second N2-containing doping gas flow (D2), a C2H4-containing first growth gas flow (Q1) and an HCl3Si-containing second growth gas flow (Q2) flow in a horizontal direction over a heated substrate. The two doping gas flows (D1, D2) are fed separately from one another into a process chamber (2) in a manner controlled through gas inlet zones (4, 5, 6) arranged vertically one above the other. The mass flows of the doping gas flows (D1, D2) or the vertical position of the gas inlet zones (4, 5, 6) through which the two doping gas flows (D1, D2) flow are selected such that they generate first and second doping profiles (a, b) which are oppositely curved with respect to one another such that by favourably choosing the ratio of the doping gas flows (D1, D2), a homogeneous doping substance profile can be achieved in the separated layer.

Description

Description Method and device for depositing n-doped SiC Field of technology

[0001] The invention relates to a method for depositing a SiC layer on a substrate in a process chamber of a CVD reactor, wherein walls of the process chamber are heated to a process temperature using a heating device. A process gas flow is fed into the process chamber through a gas inlet element. The process gas flow flows through the process chamber and over the substrates arranged therein in a horizontal direction. The process gas flow contains growth gas flows that contain a silicon-containing and a carbon-containing reactive gas. The process gas flow also contains doping gas flows that contain gaseous dopant carriers. The carbon- and nitrogen-containing reactive gases decompose at the process temperature in the process chamber or on surfaces of the heated walls of the process chamber and on the substrate surface.The decomposition products of the reactive gases deposit as a single-crystalline layer on the substrate. The dopant carriers also decompose in the process chamber, on the surfaces of the process chamber walls, or on the substrate surface. The decomposition products of the dopant carriers are incorporated into the SiC layer as dopants. The dopant preferably leads to an n-doped layer. The dopant is, for example, nitrogen. State of the art.

[0002] In another prior art method, which is described in DE 102011054566 A1, namely the deposition of GaN layers, the process gas emerging from the cold gas inlet element heats up. 31222N1PCT – 11 / 8 / 2024 Ai 2023-13 The gas initially accumulates in a pre-flow zone. During this phase, parasitic growth occurs on the surface of the pre-flow zone. As the carrier gas flows over the substrate, the concentration or partial pressure of the reactive gases in the carrier gas flow through the process chamber decreases. This leads to a progressive depletion in the direction of flow of the process gas. As a result, the growth rate of the layer or the transport of the dopant from the gas phase towards the substrate surface steadily decreases in the direction of flow. If the substrate is rotated about a vertical axis during deposition, this effect can be compensated for. If the depletion curve above the substrate runs on a straight line that decreases in the direction of flow, a layer with a homogeneous layer thickness can still be deposited.

[0003] In reality, however, the depletion curve does not follow an ideal straight line, but rather a curved curve. The above-mentioned DE 102011054566 A1 describes a process in which various reactive gases are fed into the process chamber through a gas inlet device located in the center of the process chamber and through gas inlet zones arranged vertically one above the other. Due to the depletion effect described above, the partial pressures of the reactive gases used decrease along non-rectilinear depletion curves. A lateral profile of the layer thickness can be influenced by a suitable mixture of the reactive gases flowing through different gas inlet zones.

[0004] US 2020 / 0043725 A1 describes an apparatus and a method for depositing n-doped SiC using NH3 and N2 as dopants. 31222N1PCT – 11 / 8 / 2024 Ai 2023-13

[0005] JP 2015-143168 A describes a process in which a process gas containing a silicon compound, a carbon compound, and NH3 is fed into a fully heated process chamber. The surfaces of the process chamber walls are coated with SiC. N-doped SiC is deposited on a substrate rotating about a rotation axis using NH3 as a dopant carrier. The partial pressure of the process gas components decreases steadily in the direction of flow.

[0006] From the publication “Experimental Study of the Pyrolysis of NH3under Flow Reactor Conditions, Mario Benés, et al, 2021 American Chemical Society, p 7193” it is known that at high temperatures on SiC surfaces, intermediates containing nitrogen, for example HCN or Si3N, are formed from ammonia, methane or ethane, trichlorosilane and hydrogen.

[0007] WO 2022 / 053963 A1 describes a similar process for depositing n-doped SiC, in which decomposition products of the dopant carriers are said to play a role.

[0008] DE 112017006965 T5 describes a method for depositing N-doped SiC layers, using either ammonia or gaseous nitrogen as the dopant. Summary of the Invention

[0009] The invention is based on the object of improving the dopant homogeneity during the deposition of n-doped SiC and in particular in a CVD reactor in which a gas inlet element is surrounded by substrates to be coated, which are simultaneously coated with a SiC layer. 31222N1PCT – 11 / 8 / 2024 Ai 2023-13

[0010] The problem is solved by the method and device specified in the claims. The subclaims not only represent advantageous developments of the technical teachings specified in the subordinate claims, but are also independent solutions to the problem.

[0011] Model calculations and experiments confirming their results have shown that dopant incorporation using both molecular nitrogen as the dopant carrier and another nitrogen-containing dopant carrier leads to a non-flat doping profile in a layer deposited on the substrate. The other dopant carrier can be ammonia or another molecule of a nitrogen compound in which the nitrogen is not triple-bonded. The model calculations and experiments show that when using nitrogen compounds with a non-triple-bonded nitrogen atom, such as ammonia, as the dopant carrier, the nitrogen incorporation into the SiC layer depends on the Si / C ratio. A particularly important criterion is the Si availability in the gas phase directly above the substrate.It has been shown that the Si availability or the Si / C ratio increases in a region of the process chamber downstream of the pre-deposition zone, particularly at the beginning of the deposition zone where the substrate is located. The Si availability or the Si / C ratio then reaches a maximum above the substrate. On the side of the substrate facing the gas inlet element, there is therefore a reduced dopant incorporation into the deposited layer. The substrate is rotated about its center during layer deposition, resulting in a rotationally symmetric doping profile. The doping profile is characterized by a flat central profile and decreases towards the edge of the substrate, so that the doping profile can be described as bell-shaped. 31222N1PCT – 11 / 8 / 2024 Ai 2023-13 The reaction mechanism relating to the other dopant carrier, which in particular has a non-triple-bonded nitrogen atom, is described below using ammonia as an example. In order to incorporate the nitrogen atom of the ammonia as a dopant into the SiC layer, the ammonia must first be decomposed into the radical NH2 or NH. According to the findings obtained from experiments and model calculations, this is achieved with the help of H radicals, which must be formed in the pre-run zone from the carrier gas H2. One finding underlying the invention is that, for this purpose, a conditioning layer deposited in the pre-run zone should have dangling bonds on its surface. The conditioning layer consists of Si-C compounds, whereby these compounds can have polycrystalline structures in which the Si atoms are located on the surface.The unsaturated bonds formed during the deposition of the conditioning layer are saturated by the hydrogen used as a carrier gas during deposition. One hydrogen atom of a hydrogen molecule remains on the Si surface, while the other hydrogen atom enters the gas phase as a radical. Radical formation is therefore not catalytic, since a reaction product, namely the hydrogen atom, remains on the surface. The H radical can then react with NH3 in the gas phase, forming an NH2 radical and H2. Analogously, it can also react with the NH2 radical there, forming NH and H2. A prerequisite for ammonia decomposition in the gas phase is therefore the continuous creation of unsaturated bonds on the surface. This, in turn, means that the conditioning layer must grow continuously, since each incorporation of a SiC pair creates an unsaturated bond on the surface.The growth of the SiC layer is preferably carried out by means of a carbon-containing first growth gas flow and a silicon-containing second growth gas flow, wherein the first growth gas flow contains a carbon compound. 31222N1PCT – 11 / 8 / 2024 Ai 2023-13 which is particularly ethene. Ethene (C2H4) can hydrogenate to ethane (C2H6) at process temperatures. Ethane can decompose into two CH3 radicals in a homolytic bond cleavage in the gas phase or in a heterolytic bond cleavage at the surface. CH3 can react with a silicon-containing molecule, such as silicon trichloride (SIHCl3), at the surface with hydrogen bound to the surface, incorporating a SiC pair into the surface of the conditioning layer and leaving one bond of the silicon atom unsaturated. The continuous growth of the conditioning layer thus generates the H radicals required to decompose the ammonia.

[0012] Experiments and model calculations have also led to the discovery that the decomposition of N2 also requires the presence of unsaturated bonds at the surface. Furthermore, a decomposition reaction of N2 taking place at the surface also requires the simultaneous presence of CH3 radicals for a CN bond to form. During the surface reaction, a bond forms between the unsaturated bond and one of the two nitrogen atoms of N2. The other nitrogen atom combines with the C atom of CH3 and one of the hydrogen atoms to form gaseous HCN, which, like the NH formed in parallel, is transported into the gas phase above the substrate via the carrier gas flow or by diffusion.

[0013] The decomposition of N2 or the formation of H radicals for the decomposition of ammonia depends on the size of the surface over which N2 or ammonia flows before reaching the substrate. The flow path, which is directed from the gas inlet directly towards the center of the substrate, is the shortest path. 31222N1PCT – 8.11.2024 Ai 2023-13 the smallest amount of N2 is decomposed. The flow path, however, which is directed laterally past the substrate and, to a certain extent, laterally touches the substrate, is the largest path along which the greatest amount of N2 is decomposed. The availability of the decomposition product HCN is thus greatest to the side of the substrate, which is consistent with the finding that the use of N2 as a dopant leads to an edge effect, namely to an edge-exaggerated doping profile. The simultaneous use of N2 and NH3 as dopant carriers thus creates the possibility of compensating for the reduced dopant incorporation observed at the edge when using NH3 as a dopant with the increased dopant incorporation observed at the edge when using N2 as a dopant.

[0014] To generate as many radicals as possible, it is necessary to deposit a conditioning layer with the largest possible effective surface area. The conditioning layer should therefore be as porous or fissured as possible. Preferably, the conditioning layer is deposited on a non-monocrystalline surface, so that the conditioning layer consists of a multitude of small columnar structures or dendrites. The process parameters are preferably set so that the effective surface area of the conditioning layer increases in the direction of flow. The height or diameter of the columnar structures or dendrites thus increases in the direction of flow of the process gas through the process chamber.The effective area of the conditioning layer, i.e., the free SiC surface of the conditioning layer, is significantly larger than its surface area on the susceptor, particularly in the deposition zone. It can be at least 1.5 times or twice as large. The conditioning layer is preferably deposited on a polycrystalline or quasi-amorphous SiC coating or on a TaC coating on the surface of the susceptor facing the process chamber. The coating can also consist of SiTaC solid solutions. The ratio of the free SiC surface to the. 31222N1PCT – 11 / 8 / 2024 Ai 2023-13 The surface area of the susceptor used can increase in the direction of flow and reach a maximum in the area of the deposition zone between the substrates.

[0015] According to a preferred variant of the method, the conditioning layer is deposited in a conditioning step before the actual deposition of an N-doped SiC layer on a SiC substrate in the process chamber. This occurs before the process chamber is loaded with the substrate to be coated and, in particular, using a dummy substrate that is located in a storage location, for example, a substrate holder, in the process chamber instead of the substrate to be coated. After the conditioning layer has been deposited, the dummy substrate is removed from the process chamber and replaced with a SiC substrate to be coated.

[0016] After loading the process chamber with the substrate to be coated, the process chamber is purged with hydrogen and heated. The substrate temperature is increased to such an extent that the native oxides on the SiC surface of the substrate are removed and the surface is terminated with H. A process gas flow is then fed into the process chamber. This contains a first growth gas flow containing carbon, with the first growth gas flow preferably consisting of ethene (C2H4). The process gas flow contains a second growth gas flow containing silicon, with the second growth gas flow preferably consisting of silicon tetrachloride (SiHCl3). The process gas flow also contains a first doping gas flow containing ammonia and a second doping gas flow containing molecular nitrogen. The process gas flow is fed into the process chamber together with a carrier gas flow of H2.This occurs in such a way that hydrogen radicals and HCN are continuously generated at the conditioning layer, whereby this requires that the conditioning layer. 31222N1PCT – 11 / 8 / 2024 Ai 2023-13 through continuous growth, surface areas have unsaturated bonds (dangling bonds) that are required for the generation of hydrogen radicals and HCN.

[0017] In a further development of the invention, it is proposed to divide the process gas flow into several gas inlet zones arranged vertically one above the other and to select the pairing of the various dopant carriers such that the dopant carrier of the first doping gas flow generates a lateral doping profile in a SiC layer that has a different profile, particularly at the edge of the substrate, than a lateral doping profile generated in the SiC layer by the dopant carrier of the second doping gas flow. Thus, it can be provided, in particular, that the lateral doping profile generated by the first doping gas flow has a dopant concentration that decreases toward the edge of the substrate, and the second lateral doping profile has a dopant concentration that increases toward the edge of the substrate.By appropriately selecting the doping gas flows, i.e. the mass flows of the dopant carriers into the process chamber, a superimposed doping profile can be generated, which is generated by both the first dopant carrier and the second dopant carrier. A cumulative profile is formed. The edge enhancement generated by one doping gas flow can be compensated for by an edge reduction of the cumulative profile by the other doping gas flow. For example, one of the doping gas flows can generate a dopant profile measured on a diametrical line through the substrate, which is A-, U-, V-, or W-shaped. The other of the doping gas flows can generate a dopant profile opposite to this dopant profile, which, for example, corresponds to the shape of an upside-down A, U, V, or W.The different dopant carriers are fed into the process chamber, in particular, through different gas inlet zones located at different vertical levels. The dopant carrier of a first doping gas flow can, for example, be a 31222N1PCT – November 8, 2024 Ai 2023-13 Create a doping profile that is curved upwards in the center. The dopant carrier of a second doping gas flow, for example, can create a doping profile that is curved downwards in the center. By appropriately mixing the two doping gas flows, an effective doping profile can be achieved. However, the two doping profiles can also be flat in the center and only decrease or increase in the edge region, so that edge inhomogeneities can be compensated.

[0018] It may further be provided that a doping gas flow containing NH3 does not flow through the same gas inlet zone as a growth gas flow containing chlorine, for example, trichlorosilane. Another growth gas flow may contain carbon, for example, methane, ethane, or ethene. However, the growth gas flow may also contain dichlorosilane. In this case, HCl may additionally be fed into the process chamber. It is also possible for the growth gas flow to contain silane or disilane.

[0019] The following nitrogen compounds are particularly suitable as dopant carriers: N2, NH3HCN, pyridine (C5H5N), hydrazine (N2H4), dimethylhydrazine (C2H8N2), or asymmetric dimethylhydrazine. The reaction and decomposition mechanism of ammonia described above applies, for example, to the aforementioned nitrogen compounds, in which the nitrogen is bound with weaker bonding forces than in N2. It is particularly preferred that the nitrogen atoms in the molecules of the dopant carriers are bonded to the other atoms of the molecules with bonding forces of different strengths. Thus, it can be provided that in one dopant carrier, the nitrogen is bonded to the other molecules with a single bond, and in another dopant carrier, the nitrogen is bonded to the other molecules with a double or triple bond. Es31222N1PCT – 11 / 8 / 2024 Ai 2023-13 In particular, it is provided that the dopant carriers used react with different reaction rates on the surface of the substrate, on the surface of the pre-run zone and / or with the growth gases.

[0020] According to a preferred variant of the method, the process gas flow fed into the process chamber through at least three gas inlet zones arranged vertically one above the other contains two different doping gas flows, which are fed through different gas inlet zones. The doping gas flows can each be fed into the process chamber through the same gas inlet zone together with a growth gas flow, i.e., a carbon-containing or a silicon-containing gas. In particular, exactly three gas inlet zones arranged vertically one above the other are provided, namely one gas inlet zone arranged at the top, one gas inlet zone arranged at the bottom, and one gas inlet zone arranged in the middle. However, additional gas inlet zones can also be provided.

[0021] According to one variant of the invention, a first doping gas flow is fed through a topmost gas inlet zone, and a second doping gas flow is fed into a lower-lying gas inlet zone. Another variant provides that the first doping gas flow flows through the same gas inlet zone together with a first growth gas flow. It can be provided that NH3 flows through the same gas inlet zone together with C2H4. In a further variation, it can be provided that the second doping gas flow, for example N2, is fed into the process chamber together with a second growth gas flow, for example a silicon-containing growth gas flow, for example HCl3Si. Another variant provides that a third growth gas flow, which in particular contains carbon, flows through a bottommost gas inlet zone. It can be provided that 31222N1PCT – 8.11.2024 Ai 2023-13 A carbon-containing growth gas flow flows through all gas inlet zones, and a silicon-containing, and in particular a chlorine-containing, growth gas flow flows only through a middle gas inlet zone. It can also be provided that no doping gas flow flows through the lowest gas inlet zone or through the topmost gas inlet zone. It can also be provided that the dopant carriers of the various doping gas flows do not differ. In this case, the various doping gas flows are fed through different gas inlet zones. The vertical height of the gas inlet zone can influence the shape of the doping profile, so that the doping profile can be influenced solely by the choice of the gas inlet zone.In particular, it is provided that the two doping gas flows are fed into the process chamber through the gas inlet zones that are vertically furthest apart from each other. For example, NH3 can be fed into the process chamber through a topmost gas inlet zone, and NH3 can be fed into the process chamber through a bottommost gas inlet zone. Preferably, no doping gas flow flows through the gas inlet zones located between them. It can also be provided that NH3 is fed into the process chamber through a topmost gas inlet zone and N2 is fed into the process chamber through a bottommost gas inlet zone.

[0022] The device according to the invention has a CVD reactor and a gas mixing device, as well as a control device. The gas mixing device has storage containers for the reactive gases containing silicon and carbon. It also has storage containers for the at least one dopant carrier, but preferably storage containers for at least two dopant carriers. The gas mixing device also has mass flow controllers and valves to distribute the reactive gases and the dopant carriers in a suitable manner as growth gas flows and doping gas flows to the vertically stacked gas inlet zones of the gas inlet element. The mass- 31222N1PCT – 8.11.2024 Ai 2023-13 The flow controller and the valves are controlled by the control unit according to a control program. The reactive gases are fed into the gas inlet zones together with H2.

[0023] The CVD reactor has a gas inlet device. The latter is located in the center of a process chamber. The gas inlet device is surrounded by a susceptor, which has substrate supports arranged on a circular arc around the center of the gas inlet device. The substrate supports can be circular disk-shaped bodies, each located in a pocket on an upward-facing surface of the susceptor. A gas supply line opens into the bottom of each pocket, through which a purge gas is fed into the pocket, so that the substrate support is lifted and rotated on a gas cushion. At least one substrate can be arranged on the substrate support, which is rotated about a vertical axis during the deposition of the SiC layer. The susceptor can rotate about a central axis. The susceptor and a process chamber ceiling opposite the susceptor can be made of graphite.The surface of this graphite is coated, in particular with SiC, TaC, or SiTaC. The gas inlet element can also be made of graphite. However, the gas inlet element is preferably made of quartz, steel (stainless steel), or a ceramic material. The surface of the susceptor can also be covered with cover plates made of graphite, in particular graphite coated with SiC, TaC, or SiTaC, or of SiC, TaC, or SiTaC. The substrate supports can be made of the same coated or uncoated graphite material. The process chamber ceiling can be supported by a support. This support can be made of a different material. 31222N1PCT – 8.11.2024 Ai 2023-13.

[0024] The method according to the invention thus consists of providing a CVD reactor with a process chamber and a susceptor arranged therein, which is heated to a process temperature by a heating device. A process gas is fed into the process chamber through a gas inlet element and flows through the process chamber in one flow direction. A pre-flow zone initially adjoins the gas inlet element, and a deposition zone adjoins the pre-flow zone. The substrate lies in the deposition zone. According to the invention, a conditioning layer is deposited in the pre-flow zone simultaneously with the deposition of the SiC layer. This occurs in such a way that the surface of the conditioning layer has unsaturated bonds. Hydrogen is fed into the process chamber together with the process gas. The hydrogen molecules react with the unsaturated bonds, whereby the bonds are saturated.The bonds are saturated using two mechanisms that can occur in parallel. According to a first mechanism, a hydrogen radical is formed, which can react with a molecule of the first doping gas, in particular ammonia, or a decomposition product of the first doping gas. The molecule releases a hydrogen atom, allowing a hydrogen molecule to form in the gas phase. According to a second mechanism, the unsaturated bonds react with a molecule of the second doping gas, in particular gaseous nitrogen, to form HCN. The carbon atom can be removed from the conditioning layer. Brief description of the drawings.

[0025] The invention is explained in more detail below using exemplary embodiments. They show: Fig. 1 schematically, in the form of a half-section along line II in Figure 2, a CVD reactor 1, 31222N1PCT – 8.11.2024 Ai 2023-13 Fig. 2 the section along line II in Figure 1, Fig. 3 enlarged section III in Figure 2 to illustrate the position of a conditioning layer K, Fig. 4 the profile of the availability of Si or the availability ratio of Si / C along the reference line 31 shown in Figure 3, Fig. 5 the profile of the generation rate of H radicals or of HCN or the effective surface of the conditioning layer K, Fig. 6 schematically a device for depositing SiC layers with a gas mixing system and a CVD reactor, Fig. 7 a diagram showing two dopant profiles through a SiC layer at the top and two dopant profiles generated by different dopant carriers at the bottom,Fig.Fig. 8 is a schematic representation of a second exemplary embodiment with regard to the composition and distribution of the process gas flow. Fig. 9 is a representation according to Fig. 8 of a third exemplary embodiment. Fig. 10 is a representation according to Fig. 8 of a fourth exemplary embodiment. Fig. 11 is a representation according to Fig. 8 of a fifth exemplary embodiment. Fig. 12 is a representation according to Fig. 8 of a sixth exemplary embodiment. Fig. 13 is a schematic representation of the temperature profile of the susceptor in the radial direction. Fig. 14 is a schematic representation of the temperature profile of the process chamber ceiling in the radial direction. Description of the embodiments.

[0026] Figures 1 and 2 schematically show the structure of a CVD reactor 1. A housing of the CVD reactor 1, which may be made of stainless steel, contains a susceptor 10, which may be made of graphite and whose surface may be coated with SiC, TaC, or SiTaC. The susceptor can be driven to rotate around a central axis. The susceptor has the circular disk shape shown in Figure 2.

[0027] Above the susceptor 10 is a process chamber 2, which is bounded at the top by a process chamber ceiling. The process chamber ceiling is formed by a ceiling plate 19, which can be supported on a holding element 18. The ceiling plate 19 can also be supported on a gas outlet element 9 arranged around the susceptor 10. The ceiling plate 19 can be made of graphite coated with SiC, TaC, or SiTaC. The gas outlet element 9 can also be made of this material. However, it can also be made of a ceramic material. 31222N1PCT – 8.11.2024 Ai 2023-13

[0028] The susceptor 10 is covered with cover plates 15, 16, which can also be made of graphite coated in this way. However, they can also be made of SiC, TaC, or SiTaC. Pockets 17 are formed, each having a pocket bottom into which a gas supply line 13 opens. The purge gas, for example, hydrogen, flowing from the gas supply line 13 can generate a rotating gas cushion that suspends a substrate holder 11, which can also be made of SiC, TaC, or SiTaC-coated or uncoated graphite, and drives the substrate holder 11 to rotate about a rotational axis.

[0029] A heating device 14 is provided below the susceptor 10. This can be an RF heater, which is used to heat the susceptor 10. Furthermore, a further heating device (not shown) can be provided to heat the process chamber ceiling, i.e., the ceiling plate 19, so that the process chamber 2 is heated from all sides. Preferably, however, the ceiling plate 19 is not actively heated. The ceiling plate 19 is passively heated via thermal radiation from the susceptor 10 or from the cover plates 15, 16, so that the surface temperature of the ceiling plate 19 is significantly lower than the surface temperature of the cover plates 15, 16. This results in different surface reactions taking place on the ceiling plate 19 than on the cover plates 15, 16 or on the susceptor 10.The intermediate products mentioned above, which arise during the decomposition of NH3 or N2, can thus be formed to a reduced extent in the upper area of process chamber 2. This can also influence the doping profile.

[0030] In the center of the process chamber 2 there is a gas inlet element 3, which is made of a ceramic material, stainless steel, quartz or a 31222N1PCT – 8.11.2024 Ai 2023-13 The gas inlet element 3 forms three (see Figure 3) superimposed gas inlet zones 4, 5, 6, each connected to a feed line 24, 25, 26 through which portions of a process gas flow can be fed into the respective gas inlet zone 4, 5, 6. The process gas flow is provided in a gas mixing system that has a gas source 27 for nitrogen, a gas source 28 for ammonia, a gas source 29 for trichlorosilane, and a gas source 30 for ethene (C2H4). A gas source for HCl can also be provided.

[0031] In an embodiment not shown, the gas inlet element 3 has, for example, four or five or more gas inlet zones arranged one above the other.

[0032] Each of the gas sources 27 to 30 is connected to at least one of the supply lines 24, 25, 26 via valves 22 and mass flow controllers 21. The mass flow controllers 21 and the valves 20 are controlled according to a program of the control device 20.

[0033] The gas mixing system provides at least two doping gas flows D1, D2, each containing a dopant carrier, for example, N2 or NH3 or one of the above-mentioned nitrogen compounds that can still be used. The gas mixing system also provides at least two growth gas flows Q1, Q2, but preferably several growth gas flows Q1, Q2, Q3, Q4, Q5. The growth gas flows contain carbon and silicon. One of these gases may also contain chlorine, for example, trichlorosilicon, dichlorosilicon, or HCl. However, the growth gas flows may also contain other carbon-containing or silicon-containing gases. For example, all hydrocarbons, in particular alkenes, alkanes, or alkynes, are suitable as carbon-containing gases. 31222N1PCT – 8.11.2024 Ai 2023-13 Silane, disilane or silicon chlorides, especially silicon tetrachloride, can also be considered as silicon-containing gases.

[0034] The doping gas flows D1, D2, and optionally D3 or D4 are fed into the process chamber 2 through the different and vertically stacked gas inlet zones 4, 5, 6, together with the multiple growth gas flows Q1 to Q5. The resulting process gas flow first flows through a pre-flow zone 7 of the process chamber 2, which is heated by the heating device 14 or another heating device arranged above and not shown. In this pre-flow zone 7, the process gas, which may in particular contain hydrogen as a carrier gas, is heated to a process temperature.

[0035] At the end of the pre-flow zone 7, the doping gas flows D1, D2, D3, D4 and the growth gas flows Q1 to Q5 reach a temperature at which the components of the doping gas flows and the growth gas flows can decompose or react with each other. The components of the doping gas flows and the growth gas flows can also react on the surfaces of the cover plates 15 or the ceiling plate 19. In the process, intermediate products and, in particular, decomposition products are formed. The intermediate or decomposition products and, if applicable, undecomposed dopant carriers (e.g., N2) migrate from the gas phase above the substrate holder 11 in a deposition zone 8 toward the surface of a rotating substrate 12 resting on the substrate holder 11. This occurs essentially by diffusion due to a depletion of the gas phase caused by the condensation or consumption of the intermediate or decomposition products on the substrate surface 12.31222N1PCT – 11 / 8 / 2024 Ai 2023-13.

[0036] Due to this consumption of Si, C, and N at the surface of the substrate 12 or the n-doped SiC layer deposited there, the partial pressure of the growth gas and the dopant carrier in the gas phase above the substrate 12 decreases. Figure 1 schematically shows two doping profiles a and b measured across a diameter of the substrate 2. The linear doping profiles a and b, shown as curved lines, are rotationally symmetric and represent a section through the lateral doping profile in the layer deposited on the substrate 12.

[0037] Doping profile a is generated in a SiC layer deposited on substrate 11 when substrate 11 is rotated during deposition and only the first doping gas flow D1 is fed into process chamber 2 through gas inlet zone 6 or another gas inlet zone. Dopant profile b is generated in a SiC layer deposited on substrate 11 when substrate 11 is rotated during deposition and only the second doping gas flow D2 is fed into process chamber 2 through gas inlet zone 5 or another gas inlet zone. Dopant profiles a, b in Figure 1 are essentially symbolic. The actual dopant profiles may deviate from this and may be flat, particularly in the central region.

[0038] In the exemplary embodiment, the dopant carrier of the first doping gas flow D1 is NH3, and the dopant carrier of the second doping gas flow D2 is N2. It can be seen that the two doping profiles are not straight, but curved. The selection of the dopant carriers or the selection of the gas inlet zones 4, 5, 6 through which the respective doping gas flow D1, D2 flows is carried out in such a way that two doping profiles a, b are formed that are curved in opposite directions. For example, in the exemplary embodiment, doping profile a is curved upwards and doping profile b is curved downwards. By varying the mass flows of the two doping gas flows D1, D2, a doping profile that is almost straight can be set.A rectilinear doping profile in a rotationally driven substrate 12 results in a nearly homogeneous dopant distribution being formed in the SiC layer deposited on the substrate 12.

[0039] The selection of the dopant carriers and the gas inlet zones 4, 5, 6 through which the dopant carriers are fed into the process chamber can be made such that the inhomogeneous, rotationally symmetric doping profile generated by one dopant carrier is compensated by the equally inhomogeneous, rotationally symmetric doping profile generated by another dopant carrier, toward a homogeneous, rotationally symmetric total profile. One doping profile can, for example, be U-shaped or trough-shaped. The other doping profile can be in the shape of an inverted U or bell-shaped.

[0040] In the first embodiment shown in Figure 1, hydrogen and a fourth growth gas flow Q4, which is C2H4, are fed into the lowest gas inlet zone 4. The mass flow of the fourth growth gas flow Q4 corresponds to approximately 10% of the sum of all carbon-containing growth gas flows Q1 + Q3 + Q4. In the middle gas inlet zone 5, in addition to hydrogen, a third growth gas flow Q3, which contains C2H4, and a second growth gas flow Q2, which contains HCl3Si, are fed in. The third growth gas flow Q3 contains approximately 80% of the sum of all carbon-containing growth gas flows. In addition, a second doping gas flow D2, which is nitrogen, is fed through the middle gas inlet zone 5. Nitrogen and a first 31222N1PCT – 8.11.2024 Ai 2023-13 Growth gas flow Q1, containing C2H4, is fed in. The mass flow of this growth gas flow Q1 corresponds to approximately 10% of the sum of all carbon-containing growth gas flows. Additionally, a first doping gas flow D1, containing NH3, is fed in through the topmost gas inlet zone 6.

[0041] Before depositing a SiC layer on a SiC substrate, a conditioning layer K is first deposited in the feed zone 7 and in a secondary zone 7' adjoining the feed zone 7 in the flow direction S. This occurs without the presence of the SiC substrate. Instead, a dummy substrate lies on the substrate storage location, which is removed again after the conditioning layer K has been deposited. It is essential that the conditioning layer K also extends at least as far as a line bordering the center Z of the substrate 12 or a storage location for the substrate 12, which is shown in dashed lines in Figure 3.The process parameters for depositing the conditioning layer K are set such that a surface element of the conditioning layer does not have an effective free surface that is larger (at least 1.5 times or at least 2 times) than the area of the susceptor covered by the surface element. The effective free surface of the conditioning layer should be as large as possible, i.e. the ratio of the free surface to the covered surface of the susceptor 10 should be >1.5 or greater than 2 if possible. The process parameters are set such that the conditioning layer K consists of a SiC compound and in particular of polycrystalline SiC. The conditioning layer K should be as porous and in particular fissured as possible. The process parameters are preferably set such that columnar structures or dendrites 33 are deposited on the susceptor surface in the region of the advance zone 7 and the secondary zone 7'.The layer thickness, or the ratio of the effective surface to the covered surface of the conditioning layer, should increase in the flow direction S, as shown in Figure 5 31222N1PCT – 8.11.2024 Ai 2023-13, so that this ratio is greatest in the area of the secondary zone 7', which separates two adjacent substrates 12 from each other. The dendrites 33 are, as shown in Figure 3, irregularly distributed over the surface. The distance between adjacent dendrites 33 can approximately correspond to the diameter of the dendrites 33. The height of the dendrites 33 can be greater than the diameter of the dendrites 33. The height of the dendrites can increase in the flow direction, as shown in Figure 5. However, it is also intended that the diameters of the dendrites 33 increase in the flow direction or that the distance between neighboring dendrites 33 becomes smaller in the flow direction.The peripheral surfaces of the dendrites 33 form reaction surfaces where chemical reactions can take place.

[0042] For this purpose, suitable silicon compounds and carbon compounds are fed into the process chamber, with the susceptor temperature being an essential process parameter.

[0043] After the conditioning layer K has been deposited, the dummy substrate(s) are removed from the process chamber. Monocrystalline Si substrates with a smooth surface are placed on the storage locations. One or more layers are deposited onto these substrates, with at least one of these multiple layers being an n-doped SiC layer, with nitrogen being used as the dopant. The deposition process is carried out as previously described.

[0044] Before the layer is deposited, the surfaces of the substrates are cleaned of adhering oxides. This takes place in a hydrogen atmosphere at elevated temperatures, so that the silicon atoms lying on top, according to the model underlying the invention, are each 31222N1PCT – 8.11.2024 Ai 2023-13 are bonded to a hydrogen atom. The silicon atoms thus have saturated surface bonds in the initial state of the coating process. During this thermal treatment, the Si atoms of the conditioning layer K are also freed from any oxides and terminated with H.

[0045] The deposition of a SiC layer is carried out according to the model underlying the invention according to the following reaction Here, {H(s)-Si(b)} denotes a hydrogen-terminated silicon compound; SiHCl^(^^) denotes silicon trichloride adsorbed on the surface, CH^(^^) denotes CH3 adsorbed on the surface, {Si(^) − C(^)} denotes a SiC pair deposited on the layer surface, where Si has an unsaturated bond.

[0046] SiHCl3 adsorbs directly on the surface. C2H4 hydrogenates beforehand according to the following reaction to ethane and subsequently decomposes according to the reaction CH ^g^ →C ∗ 2 ^ H ^(^) to a radical CH^ ∗ ( ^) . 31222N1PCT – 11 / 8 / 2024 Ai 2023-13

[0047] As a result of the growth of the SiC conditioning layer, unsaturated bonds are constantly forming on the free surface of the conditioning layer K.

[0048] According to the following reaction, the unsaturated bonds are saturated by the absorption of an H atom from an H 2 atom that is adsorbed on the surface or forms a strong bond with Si. Si(s) + H 2^g^ → {H(^) − Si(^)} + H* The H formed in this process ∗ enters the gas phase and can react with NH3 in the gas phase according to the following mechanism. N H + H∗ → ∗ ^ NH^ + H2^g^NH ∗^ + H∗ → NH + H2^g^

[0049] In a first step, NH∗^ is formed. In a second step, NH is formed. Both NH∗^ and NH are transported to the substrate. This occurs on the one hand with the carrier gas in the flow direction and on the other hand perpendicular to it by diffusion. A surface reaction then takes place on the substrate, in which hydrogen is released and N is incorporated into the layer.

[0050] Gaseous nitrogen can be adsorbed on the surface of the conditioning layer K. This occurs at an unsaturated bond of the silicon according to the following reaction 31222N1PCT – 8.11.2024 Ai 2023-13where {CH^(^^) − Si(^)} is a cation adsorbed on a neighboring silicon atom Si(s) a nitrogen atom incorporated into the surface and bonded to a silicon atom.

[0051] The gaseous HCN produced is transported to the substrate and can then be deposited on the surface of the substrate according to react, whereby nitrogen is incorporated into the layer.

[0052] Since the decomposition reaction of NH3 is considerably faster than the decomposition reaction of N2, an N2 flow is used that is approximately 20 times as large as the NH3 flow.

[0053] Figure 7 describes the effect that the injection of different doping gas flows D1, D2 through gas inlet zones 5, 6 arranged at different levels has on the dopant distribution within the deposited layer. The upper curve, represented as open and closed triangles, shows a section through the center of a layer deposited on the substrate 12 and the dopant distribution in the layer, which is almost uniform. A slight reduction in the dopant concentration can be observed only in the region near the edge of the layer of the circular disk-shaped substrate 12.

[0054] The two lower curves show the dopant incorporation that would be generated by only one of the two different dopant carriers. The open and closed squares represent the dopant incorporation, 31222N1PCT – 8.11.2024 Ai 2023-13. which only N2 would cause. When using only N2 as the dopant carrier, a strong edge enhancement of the dopant incorporation is observed. The open and closed circles represent the dopant incorporation that only NH3 would cause. When using only NH3 as the dopant carrier, a strong center enhancement of the dopant incorporation is observed. By appropriately selecting the ratio of the mass flows of N2 and NH3 or by appropriately selecting the vertical height of the gas inlet zones through which the different dopant carriers are fed into the process chamber, a doping profile can be generated that leads to a compensation of the center enhancement or edge enhancement.

[0055] In the embodiment shown in Figure 8, unlike the embodiment shown in Figure 1, a third doping gas flow D3, which is NH3, is additionally fed through the gas inlet zone 4 arranged at the bottom.

[0056] In the embodiment shown in Figure 9, no doping gas flow is fed into the process chamber 2 through the gas inlet zone 6 arranged at the top. Here, only a first doping gas flow D1 (NH3) is fed through the gas inlet zone 4 located at the bottom, and a second doping gas flow D2 (N2) is fed through the gas inlet zone located in the middle or directly above it.

[0057] In a first embodiment of a process chamber, the susceptor 10 can have a diameter in the range between 400 and 420 mm.On the susceptor 10, six substrates, each having a diameter of 200 mm, can be arranged on a circular line around the center of the susceptor 10, with the centers of the circular substrates being approximately 240 to 260 mm from the center. The gas inlet element 6 can have an outer diameter of between 50 and 60 mm, so that the pre-flow zone 7 extends between a circular line with a radius in the range between 25 and 30 mm and a circular line with a radius between 140 and 150 mm. The secondary zone 7' then extends to a radial distance of 240 to 260 mm. The height of the process chamber can be 20 to 30 mm. The pressure in the process chamber can be in a range between 50 and 100 mbar (preferably 80 mbar). The minimum distance between two adjacent substrates can be in a range between 50 and 7 mm.

[0058] In a second embodiment of the process chamber, the susceptor 10 can have the same diameter. Nine substrates, each with a diameter of 150 mm, lie on the susceptor 10, with the minimum distance between two adjacent substrates now being 20 to 30 mm.

[0059] When using these susceptors, the average flow velocity of the gas flow in the area of the beginning of the pre-flow zone 7 can be in the range of 15 to 25 m / s, but it can also be in a range between 18 and 20 m / s. This is a parabolic flow profile. As the gas flow heats up, its volume increases, so the flow velocity increases.

[0060] In a third embodiment of the process chamber, the susceptor 10 can have a diameter in the range between 350 and 370 mm.Eight substrates with a diameter of 150 mm can be arranged on a circular arc with a radius of 210 to 230 mm around the center of the susceptor 10. The outer diameter of the gas inlet element 6 can be in the range between 60 and 70 mm. The minimum distance between two directly adjacent substrates can be 20 to 30 mm.

[0061] When using this susceptor, the average flow velocity of the gas flow in the region of the beginning of the pre-flow zone 7 can be in the range between 10 and 20 m / s.

[0062] In the embodiment shown in Figure 11, two doping gas flows D1, D2 are fed simultaneously through the uppermost gas inlet zone 6 into the process chamber 2. In this embodiment, N2 and NH3 are fed into the process chamber 2 through the same gas inlet zone 6.It can be provided that the doping gas flows D1, D2 are fed into the process chamber exclusively through the uppermost gas inlet zone 6, and that no doping gas flows, but at most a carrier gas or growth gas flows, flow through the remaining gas inlet zones 5, 4. In particular, it is provided that a gas mixture comprising two different dopant carriers flows through a gas inlet zone 6, wherein the gas mixture consists of NH3 and N2.

[0063] In the embodiment shown in Figure 12, two different doping gas flows D1, D2, D3, D4 are each fed into the process chamber 2 through two different gas inlet zones 5, 6, which are preferably upper gas inlet zones. The mass flows of the doping gas flows D1, D2, D3, D4 fed through the different gas inlet zones 5, 6 then differ.As in the embodiment shown in Figure 8, it can be provided that a gas mixture comprising two different dopant carriers flows through a gas inlet zone 5, 6. The gas mixture can consist of NH3 and N2, respectively. The NH3 flow through the gas inlet zone 5 can be different. 31222N1PCT – 8.11.2024 Ai 2023-13. be from the NH3 flow through the gas inlet zone 6. The two N2 flows can also differ.

[0064] By feeding the doping gases distributed over different feed levels, it is possible to specifically adjust the doping profile. For this purpose, the following method can be used, for example: First, a doped layer is deposited using only an NH3 flow. The dopant profile is determined for this layer. A second layer is deposited on a second substrate using only an N2 flow as the dopant. Alternatively, the second layer can also be deposited by simultaneously feeding an NH3 flow and an N2 flow into the process chamber. The dopant profile is then measured for these layers.The NH3 flow or N2 flow is then adjusted / varied, i.e., increased or decreased, for example in model calculations or in further experiments, until an acceptable "flat" doping profile is achieved.

[0065] It is considered essential that, when using NH3, a gas inlet zone 4 or 6 is used through which no chlorine-containing gas mixture flows. Thus, it is particularly provided that a chlorine-containing growth gas flow is fed into the process chamber exclusively through a central gas inlet zone 5.

[0066] It can be provided that a gas flow of a carbon-containing growth gas flows through all gas inlet zones 4, 5, 6.

[0067] When selecting the pairings of the dopant carriers, it can be advantageous if the dopant carriers have different nitrogen bonds (intakes).2024 Ai 2023-13 (multiple, double, or triple bonds), or if the dopants of the dopant carriers are bound with chemical bonds of varying strength within the molecule of the dopant carrier. It can be assumed that these dopant carriers decompose differently and thus exhibit different depletion curves, so that the dopant profile within the layer to be cut off can be adjusted.

[0068] It can be advantageous if NH3 is fed through the topmost and bottommost gas inlet zones 4 and 6, respectively, and N2 is fed through the central gas inlet zone 5.

[0069] The carbon-containing reaction gas, for example C2H4, is preferably fed into the process chamber 2 in the following mass distribution: 10% each through the lowest and the uppermost gas inlet zones 4, 6 and 80% through the middle gas inlet zone 5.The silicon-containing reactive gas, in particular trichlorosilane or dichlorosilane, is preferably fed into the process chamber 2 exclusively through the central gas inlet zone 5.

[0070] Figure 13 shows, by way of example, the temperature profile on the surface of the susceptor in a susceptor according to the first or second exemplary embodiment. It can be seen that the temperature in the advance zone 7 is lower than in the region of the deposition zone or the secondary zone 7'. The surface temperature of the susceptor (technically referring here to the surface temperature of a cover plate 15) can be between 1650 and 1800°C.

[0071] Figure 14 shows, by way of example, the temperature profile on the underside of the process chamber ceiling 19. It can be seen that this temperature is at least 100°C lower than the temperature of the susceptor. The temperature 31222N1PCT – 11 / 8 / 2024 Ai 2023-13. The temperature of the process chamber ceiling (where technically the surface temperature of the underside of the ceiling panels 19 is meant here) can be between 1401 and 1600°C.

[0072] If the above statements refer to a coating of the susceptor, these statements also include a coating of a cover plate 15, 16, which covers a base body previously described as susceptor 15. The statements refer to a surface that delimits the process chamber 2 at the bottom.

[0073] The above statements serve to explain the inventions covered by the application as a whole, which also independently develop the prior art at least by the following combinations of features, whereby two, several or all of these combinations of features can also be combined, namely:

[0074] A method for depositing a SiC layer on a substrate with the following steps:- Providing a CVD reactor 1 with a process chamber 2,a susceptor 10 arranged therein, which can be heated to a process temperature TS by a heating device 14, and with a gas inlet element 3 for feeding a process gas flow into the process chamber 2 - providing a first growth gas which has carbon-containing molecules, a second growth gas which has silicon-containing molecules, a first doping gas which contains a non-triply bonded nitrogen compound, a second doping gas which contains molecular nitrogen, and a carrier gas which contains hydrogen; 31222N1PCT – 8.11.2024 Ai 2023-13- Arranging a substrate 12 in a deposition zone 8 on the susceptor 10, wherein the deposition zone 8 is arranged downstream of a pre-flow zone 7 adjacent to the gas inlet element 3 with respect to a process gas flow through the process chamber 2;- Depositing the SiC layer on the substrate 12 by feeding the process gas flow, which has a first growth gas flow Q1,containing the first growth gas, a second growth gas flow Q2 containing the second growth gas, a first doping gas flow D1 containing the first doping gas, and a second doping gas flow D2 containing the second doping gas together with the carrier gas, through the gas inlet element 3 into the process chamber 2 heated to the process temperature TS;- During the deposition of the SiC layer:- Deposition of a conditioning layer K in the pre-run zone 7, the surface of which has unsaturated bonds;- Saturation of the unsaturated bonds by absorbing one hydrogen atom of a hydrogen molecule of the carrier gas and releasing a hydrogen radical and forming a reaction product from the hydrogen radical and a molecule of the first doping gas or a molecule of a decomposition product of the first doping gas,wherein the molecule or the decomposition product releases a hydrogen atom; and / or- saturation of the unsaturated bonds by absorption of a nitrogen atom of a molecule of the second doping gas and formation of gaseous HCN.

[0075] A method for depositing a SiC layer on a substrate 12, comprising the following steps: wherein a susceptor 10 is heated to a susceptor temperature TS with a heating device 14,31222N1PCT - 8.11.2024 Ai 2023-13, wherein a process gas flow is fed into a process chamber 2 delimited downwards by the susceptor 10 by means of a gas inlet element 3 together with a carrier gas flow, wherein a process chamber ceiling 19' delimiting the process chamber 2 upwards has a process chamber ceiling temperature TD, wherein the process gas flow contains a carbon-containing first growth gas flow Q1, a silicon-containing second growth gas flow Q2, a first doping gas flow D1 containing ammonia or another, in particular non-triply bonded nitrogen compound, and a second doping gas flow D2 containing molecular nitrogen, wherein the carrier gas flow contains hydrogen, wherein the substrate 12 is arranged in a deposition zone 8 which, with respect to the process gas flow, is arranged downstream of a pre-run zone 7 adjacent to the gas inlet element 3 and the deposition zone 8, characterized in that process parameters, namely in particularthe susceptor temperature TS and the process chamber ceiling temperature TD as well as the mass flows of the first and second doping gas flows D1, D2 and the first and second growth gas flows Q1, Q2 and a total pressure in the process chamber 2 are selected such that a conditioning layer K grows in the pre-run zone 7 during the deposition of the SiC layer, wherein during the deposition of the conditioning layer K, unsaturated bonds form on its surface,- which are saturated by absorbing a hydrogen atom of a hydrogen molecule of the carrier gas, wherein at least one hydrogen radical is released, with which ammonia or a reaction product of the ammonia reacts to release a hydrogen atom, and / or 31222N1PCT – 8.11.2024 Ai 2023-13- which are saturated by absorbing a nitrogen atom of a nitrogen molecule of the second doping gas flow D2, wherein gaseous HCN.

[0076] A process thatcharacterized in that process parameters, namely in particular the susceptor temperature TS and the process chamber ceiling temperature TD as well as the mass flows of the first and second doping gas flows D1, D2 and the first and second growth gas flows Q1, Q2 and a total pressure in the process chamber 2, are selected such that a conditioning layer K grows in the pre-run zone 7 during the deposition of the SiC layer, wherein during the deposition of the conditioning layer K, unsaturated bonds are formed on its surface, which are saturated by absorbing a hydrogen atom of a hydrogen molecule of the carrier gas, wherein at least one hydrogen radical is released, with which ammonia or a reaction product of the ammonia reacts to release a hydrogen atom, and / or which are saturated by absorbing a nitrogen atom of a nitrogen molecule of the second doping gas flow D2, wherein gaseous HCN

[0077] A method characterized in that the carrier gas flow, the growth gas flows Q1, Q2, and the doping gas flows D1, D2 are fed into the process chamber 2 in a controlled manner through vertically stacked gas inlet zones 4, 5, 6, and a further method parameter is the vertical position of the gas inlet zones 4, 5, 6 through which the two doping gas flows D1, D2 and the two growth gas flows Q1, Q2 flow. 31222N1PCT – 8.11.2024 Ai 2023-13

[0078] A method characterized in that the method parameters are selected such that the conditioning layer has an upper side facing the process chamber 2, which has a maximized free surface and, in particular, dendrites.

[0079] A method which is characterized in that the conditioning layer K extends beyond the pre-run zone 7 into a secondary layer 7' located in the deposition zone 8 next to the substrate 12.

[0080] AA method characterized in that the roughness of the conditioning layer K increases in the flow direction and / or that, in particular in a secondary zone 7' located in the deposition zone 8, the ratio of the free surface of the conditioning layer K is at least 1.5 times the area occupied by the conditioning layer K on the susceptor 10 or a cover plate 15, 16 arranged thereon.

[0081] A method characterized in that a base layer of the conditioning layer K is deposited before the deposition of the SiC layer, wherein the base layer has a ratio between free surface and occupied surface that increases in the flow direction S.

[0082] A method characterized in that the thickness of the conditioning layer K consisting of SiC and N, the density of dendrites 33 forming the conditioning layer K, their diameters or their surfaces during depositionthe SiC layer becomes larger.

[0083] A method characterized in that the first doping gas flow D1 is fed into the process chamber 2 through a gas inlet zone 6 furthest from the pre-flow zone 7.31222N1PCT – 8.11.2024 Ai 2023-13

[0084] A method characterized in that the susceptor temperature TS is higher than the process chamber ceiling temperature TD, wherein the process chamber ceiling temperature TD is selected in particular such that no reactions of the ammonia take place at the process chamber ceiling 19'.

[0085] A method which is characterized in that the substrate is rotationally driven and the mass flows of the first and second doping gas flows D1, D2 and the vertical position of the gas inlet zones 4, 5, 6, through which the two doping gas flows D1, D2 flow, are selected such that the lateral doping profile generated by the first doping gas flow D1 decreases towards the edge and the lateral profile a, b generated by the second doping gas flow D2 decreases towards the edgeis increasing.

[0086] A method characterized in that the first and second dopant carriers and the mass flows of the doping gas flows D1, D2 carrying them are selected such that a sum of the two profiles a, b weighted by the ratio of the mass flows approximates a plane.

[0087] A method characterized in that the second growth gas flow Q2 contains chlorine and the first growth gas flow Q1 does not flow through the same gas inlet zone 4, 5, 6 together with the NH3-containing first doping gas flow D1.

[0088] A method characterized in that the process gas flow is fed into a central gas inlet element 3, which is surrounded by substrate holders 11 arranged in a circle around the gas inlet element 3 and lying in pockets 17 of a susceptor 10, wherein the substrate holders 11 are supported by a gas cushion and driven in rotation. 31222N1PCT – 8.11.2024 Ai 2023-13

[0089] A method characterized in thatcharacterized in that the first doping gas flow D1 flows through a topmost gas inlet zone 6 and the second doping gas flow D2 flows through a lower-lying gas inlet zone 5 and / or that the first doping gas flow D1 flows together with the first growth gas flow Q1 through the same gas inlet zone 6 and / or that the second doping gas flow D2 flows together with the second growth gas flow Q2 through the same gas inlet zone 5 and / or that a third growth gas flow Q3 flows through a bottommost gas inlet zone 4 and no doping gas flow flows through the bottommost gas inlet zone 4 and / or that a third doping gas flow D3 flows through a bottommost gas inlet zone 4 and / or that the first doping gas flow D1 flows through a bottommost gas inlet zone 4 and the second doping gas flow D2 flows through a gas inlet zone 5 above it and / or that the first doping gas flow D1 and the second doping gas flow D2 have the sameDopant carriers, wherein the first doping gas flow D1 flows through a topmost gas inlet zone 6 and the second doping gas flow D2 flows through a bottommost gas inlet zone 4 and / or that two mutually different doping gas flows D1, D2; D3, D4 are fed into the process chamber 2 through a gas inlet zone 6, in particular the topmost gas inlet zone, or through two gas inlet zones 5, 6, in particular through top-arranged gas inlet zones 5, 6, wherein the doping gas flows D1, D2; D3, D4 flowing through a common gas inlet zone 5, 6 have mutually different dopant carriers.

[0090] A device which is characterized in that the control device 20 is set up to carry out a method according to one of the preceding claims and / or that the surface of the susceptor 10 or cover plates 15, 16 resting on the susceptor 10 are coated with a conditioning layer K whichconsists of SiC, wherein the ratio of a free surface of the conditioning layer K to the claimed area increases in a direction away from the gas inlet element 3.

[0091] All disclosed features are (individually, but also in combination with one another) essential to the invention. The disclosure content of the associated / attached priority documents (copy of the prior application) is hereby fully incorporated into the disclosure of the application, also for the purpose of incorporating features of these documents into claims of the present application. The subclaims characterize, even without the features of a referenced claim, with their features, independent inventive developments of the prior art, in particular in order to make divisional applications based on these claims. The invention stated in each claim may additionally include one or more of the features described in the above description, in particularhave features provided with reference numbers and / or indicated in the list of reference numbers. The invention also relates to designs in which individual features mentioned in the above description are not implemented, in particular insofar as they are clearly dispensable for the respective intended use or can be replaced by other technically equivalent means. 31222N1PCT – 8.11.2024 Ai 2023-13 List of reference symbols1 CVD reactor 28 Gas source, ammonia2 Process chamber 29 Gas source, trichlorosilane3 Gas inlet device 30 Gas source, ethene4 Gas inlet zone 31 Reference line5 Gas inlet zone 32 Reference line6 Gas inlet zone 33 Dendrite7 Pre-flow zone7' Secondary zone D1 Doping gas flow8 Deposition zone D2 Doping gas flow9 Gas outlet device D3 Doping gas flow10 Susceptor D4 Doping gas flow11 Substrate holder K Conditioning layer12 Substrate Q1 Growth gas flow13 Gas supply line Q2 Growth gas flow14 Heating device Q3 Growth gas flow15 Cover plate Q4 Growth gas flow16 Cover plate Q5 Growth gas flow17 Pocket S Flow direction18 Holding element Z Center19 Cover plate20 Control device21 Mass flow controller a Doping profile22 Valve b Doping profile24 Supply line25 Supply line26 Supply line27 Gas source, Nitrogen31222N1PCT – 11 / 8 / 2024 Ai 2023-13

Claims

Claims 1. A method for depositing a SiC layer on a substrate (12), comprising the following steps: - Providing a CVD reactor (1) with a process chamber (2), a susceptor (10) arranged therein, which can be heated to a process temperature (TS) by a heating device (14), and a gas inlet element (3) for feeding a process gas flow into the process chamber (2); - Providing a first growth gas comprising carbon-containing molecules, a second growth gas comprising silicon-containing molecules, a first doping gas comprising a non-triply bonded nitrogen compound, a second doping gas comprising molecular nitrogen, and a carrier gas comprising hydrogen; - Arranging a substrate (12) in a deposition zone (8) on the susceptor (10),wherein the deposition zone (8) is arranged downstream of a pre-flow zone (7) adjacent to the gas inlet element (3) with respect to a process gas flow through the process chamber (2); -Deposition of the SiC layer on the substrate (12) by feeding the process gas flow, which comprises a first growth gas flow (Q1) containing the first growth gas, a second growth gas flow (Q2) containing the second growth gas, a first doping gas flow (D1) containing the first doping gas, and a second doping gas flow (D2) containing the second doping gas together with the carrier gas, through the gas inlet element (3) into the process chamber (2) heated to the process temperature (TS);- During and / or before the deposition of the SiC layer:31222N1PCT – 8.11.2024 Ai 2023-13- Depositing a conditioning layer (K) in the pre-run zone (7),whose surface has unsaturated bonds; -saturation of the unsaturated bonds by absorbing a hydrogen atom from a hydrogen molecule of the carrier gas and releasing a hydrogen radical and forming a reaction product from the hydrogen radical and a molecule of the first doping gas or a molecule of a decomposition product of the first doping gas, wherein the molecule or the decomposition product releases a hydrogen atom; and / or -saturation of the unsaturated bonds by absorbing a nitrogen atom from a molecule of the second doping gas and forming gaseous HCN.

2. Method for depositing a SiC layer on a substrate (12) in a CVD reactor (1), in particular according to claim 1, wherein a process chamber ceiling (19') delimiting the process chamber (2) upwards has a process chamber ceiling temperature (TD), wherein the process gas flow comprises the carbon-containing first growth gas flow (Q1),characterized in that process parameters, namely in particular the susceptor temperature (TS) and the process chamber ceiling temperature (TD) as well as the mass flows of the first and second doping gas flows (D1, D2) and the first and second growth gas flows (Q1, Q2) and a total pressure in the process chamber (2), are selected such that the conditioning layer (K) grows in the pre-run zone (7) during the deposition of the SiC layer, wherein the saturated bonds form on the surface of the conditioning layer (K) during the deposition of the conditioning layer (K).31222N1PCT – 8.11.2024 Ai 2023-13, 3. Method according to one of the preceding claims, characterized in that the conditioning layer consists of a Si-C compound deposited in the pre-run zone (2), which has polycrystalline structures in which the Si atoms are located on the surface.

4. Method according to one of the preceding claims, characterized in that the carrier gas flow, the growth gas flows (Q1, Q2), and the doping gas flows (D1, D2) are fed into the process chamber (2) in a separately controlled manner through gas inlet zones (4, 5, 6) arranged vertically one above the other, and a further method parameter is the vertical position of the gas inlet zones (4, 5, 6) through which the two doping gas flows (D1, D2) and the two growth gas flows (Q1, Q2) flow.Method according to one of the preceding claims, characterized in that the conditioning layer has an upper side facing the process chamber (2), which upper side has a maximized free surface and in particular dendrites.

6. Method according to one of the preceding claims, characterized in that the conditioning layer (K) extends beyond the advance zone (7) into a secondary layer (7') located in the deposition zone (8) next to the substrate (12).

7. Method according to one of the preceding claims, characterized in that the roughness of the conditioning layer (K) increases in the flow direction and / or that in particular in a secondary zone (7') located in the deposition zone (8), the ratio of the free surface of the conditioning layer (K) is at least 1.5 times that of the 31222N1PCT - 8.11.2024 Ai 2023-13. Conditioning layer (K) on the susceptor (10) or a cover plate (15, 16) arranged thereon.

8. Method according to one of the preceding claims, characterized in that a base layer of the conditioning layer (K) is deposited before the deposition of the SiC layer, wherein the base layer has a ratio between free surface and occupied surface that increases in the flow direction (S).

9. Method according to one of the preceding claims, characterized in that the thickness of the conditioning layer (K) consisting of SiC and N, the density of dendrites (33) forming the conditioning layer (K), their diameter or their surfaces increases during the deposition of the SiC layer.10.Method according to one of the preceding claims, characterized in that the first doping gas flow (D1) is fed into the process chamber (2) through a gas inlet zone (6) furthest from the pre-flow zone (7).

11. Method according to one of the preceding claims, characterized in that the susceptor temperature (TS) is higher than the process chamber ceiling temperature (TD), wherein the process chamber ceiling temperature (TD) is selected in particular such that no reactions of the ammonia take place at the process chamber ceiling (19').

12. Method according to one of the preceding claims, characterized in that the substrate is rotationally driven and the mass flows of the first and second doping gas flows (D1, D2) and the vertical position of the gas inlet zones (4, 5, 6) through which the two doping gas flows (D1, D2) 31222N1PCT – 8.11.2024 Ai 2023-13. flow are selected such that the lateral doping profile generated by the first doping gas flow (D1) decreases towards the edge and the lateral profile (a, b) generated by the second doping gas flow (D2) increases towards the edge.

13. Method according to one of the preceding claims, characterized in that the first and second dopant carriers and the mass flows of the doping gas flows (D1, D2) carrying them are selected such that a sum of the two profiles (a, b) weighted by the ratio of the mass flows approaches a plane.

14. Method according to one of the preceding claims, characterized in that the second growth gas flow (Q2) contains chlorine and the first growth gas flow (Q1) does not flow through the same gas inlet zone (4, 5, 6) together with the NH3-containing first doping gas flow (D1).15.Method according to one of the preceding claims, characterized in that the process gas flow is fed into a central gas inlet element (3) which is surrounded by substrate holders (11) arranged in a circle around the gas inlet element (3) and lying in pockets (17) of a susceptor (10), wherein the substrate holders (11) are supported by a gas cushion and driven in rotation.

16. Method according to one of the preceding claims, characterized in that the first doping gas flow (D1) flows through a topmost gas inlet zone (6) and the second doping gas flow (D2) flows through a lower-lying gas inlet zone (5). 31222N1PCT - 8.11.2024 Ai 2023-13.

17. Method according to one of the preceding claims, characterized in that the first doping gas flow (D1) flows together with the first growth gas flow (Q1) through the same gas inlet zone (6).

18. Method according to one of the preceding claims, characterized in that the second doping gas flow (D2) flows together with the second growth gas flow (Q2) through the same gas inlet zone (5).

19. Method according to one of the preceding claims, characterized in that a third growth gas flow (Q3) flows through a gas inlet zone (4) arranged at the bottom and no doping gas flow flows through the gas inlet zone (4) arranged at the bottom.

20. Method according to one of the preceding claims, characterized in that a third doping gas flow (D3) flows through a gas inlet zone (4) arranged at the bottom. 21.Method according to one of the preceding claims, characterized in that the first doping gas flow (D1) flows through a gas inlet zone (4) arranged at the bottom, and the second doping gas flow (D2) flows through a gas inlet zone (5) arranged above it.

22. Method according to one of the preceding claims, characterized in that the first doping gas flow (D1) and the second doping gas flow (D2) contain the same dopant carrier, wherein the first doping gas flow (D1) flows through a gas inlet zone (6) arranged at the top, and the second doping gas flow (D2) flows through a gas inlet zone (4) arranged at the bottom. 31222N1PCT – 8.11.2024 Ai 2023-13.

23. Method according to one of the preceding claims, characterized in that two different doping gas flows (D1, D2; D3, D4) are fed into the process chamber (2) through a gas inlet zone (6), in particular the uppermost gas inlet zone, or through two gas inlet zones (5, 6), in particular through gas inlet zones (5, 6) arranged at the top, wherein the doping gas flows (D1, D2; D3, D4) flowing through a common gas inlet zone (5, 6) have different dopant carriers.

24. Device with a CVD reactor (1) which has a susceptor (10) extending in a horizontal plane for receiving substrates (12) and a gas inlet element (3) having a plurality of gas inlet zones (4, 5, 6) arranged vertically one above the other, wherein the gas inlet zones (4, 5, 6) are connected to gas sources (27, 28, 29, 30) by means of supply lines (24, 25, 26) and mass flow controllers (21) and valves (22) arranged in the supply lines,in which first and second dopant carriers as well as a carbon-containing reactive gas and a silicon-containing reactive gas are stored separately from one another, and with a control device (20) for controlling the mass flow controllers (21) and valves (22), characterized in that the control device (20) is set up to carry out a method according to one of the preceding claims and / or that the surface of the susceptor (10) or cover plates (15, 16) resting on the susceptor (10) are coated with a conditioning layer (K) consisting of SiC, wherein the ratio of a free surface of the conditioning layer (K) to the claimed area increases in a direction away from the gas inlet element (3).

25. Method, characterized by one or more of the characterizing features of one of the preceding claims. 31222N1PCT – November 8, 2024 Ai 2023-13,

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