Method and apparatus for depositing n-doped SiC

Abstract

The invention relates to a method for depositing a SiC layer, wherein a first doping gas flow (D1) containing NH3, a second doping gas flow (D2) containing N2, a first growth gas flow (Q1) containing C2H4, and a second growth gas flow (Q2) containing HCl3Si flow in a horizontal direction over a heated substrate. The two doping gas flows (D1, D2) are fed into a process chamber (2) in a separately controlled manner 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 curved in opposite directions to each other, so that a homogeneous dopant profile in the deposited layer can be achieved by a favorable choice of the ratio of the doping gas flows (D1, D2) and an additional argon feed.

Description

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 walls of the process chamber, 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 preferably nitrogen. State of the art

[0002] In another prior art method, described in DE 10 2011 054 566 A1, namely the deposition of GaN layers, the process gas exiting the cold gas inlet device initially heats up in a pre-flow zone. During this phase, parasitic growth occurs on the surface of the pre-flow zone. As the 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 flow direction of the process gas. As a result, the growth rate of the layer or the transport of the dopant from the gas phase toward the substrate surface steadily decreases in the flow direction. If the substrate is rotated about a vertical axis during deposition, this effect can be compensated.If the depletion curve above the substrate runs on a straight line descending 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 one. The above-mentioned DE 10 2011 054 566 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-linear depletion curves. A suitable mixture of the reactive gases flowing through different gas inlet zones can influence the lateral profile of the layer thickness.

[0004] US 2020 / 0043725 A1 describes an apparatus and a method for depositing n-doped SiC using NH3 and N2 as dopants.

[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 around a rotating axis using NH3 as the 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 NH3 under 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.

[0008] The depletion described above does not occur when N2 is used as a dopant carrier. However, N2 reacts catalytically on the surface of the process chamber, particularly in the immediate vicinity of the substrate or on the surface of a pre-flow zone located between the gas inlet element and the substrate. HCN can form here. The amount of HCN that reaches the substrate depends essentially on the geometry of the pre-flow zone and, in particular, on the cover plate arranged there and its surface. As a result, when depositing nitrogen-doped SiC, an increase in dopant incorporation can be observed in the region of the edge of the substrate, which rotates during deposition. The dopant distribution in the deposited SiC layer thus depends on the concentration of N2, HCN, and the carbon-containing reactive gas in the gas phase.

[0009] US 7,118,781 B1 and JP 6424384 B2 disclose the deposition of SiC layers using argon as the carrier gas for feeding growth gases into the process chamber. Due to its high molecular weight, argon is said to reduce parasitic deposits on the process chamber ceiling and improve the layer thickness homogeneity of a layer deposited on a substrate. Summary of the invention

[0010] 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.

[0011] The problem is solved by the method and the claimed device specified in the claims. The subclaims not only represent advantageous developments of the technical teachings specified in the subordinate claims, but also represent independent solutions to the problem.

[0012] The invention relates to a method for depositing a SiC layer on a substrate, in which, in addition to the growth gases described above and at least one of the doping gas flows described above, a further gas or gas mixture is fed into the process chamber, wherein this further gas has a molar mass that is greater than the molar mass of the hydrogen used as carrier gas and preferably greater than the molar mass of the dopant. Argon or a mixture of argon and hydrogen is particularly suitable for this purpose. This additional gas effects a modification of the flow profile of the process gas in the process chamber. The additional heavier gas further effects a change in the transport mechanism of the decomposition products vertical to the flow direction, i.e., the diffusion of the reaction products to the substrate or to the floor of the process chamber. The diffusion coefficient depends on the molar mass of the gas molecules.Increasing the molecular weight inhibits diffusion. The introduction of a gas, referred to below as a barrier gas, whose molecular weight is at least heavier than hydrogen, thus influences the diffusion of the reaction products or reactants. The barrier gas flow is preferably pure argon or a mixture of hydrogen and argon. This mixture is used instead of the carrier gas in the previously described embodiments.

[0013] The mass-increased carrier gas is fed through a gas inlet device. This can occur in one or more sub-flows, for example, through stacked gas inlet zones. At least one of these A sub-flows has a molar mass that is increased by the addition of a heavier gas.

[0014] According to a preferred development of the invention, argon, optionally together with hydrogen, is fed into the uppermost gas inlet zone. This reduces the diffusion of the decomposition products to the process chamber ceiling and also influences the doping profile in the deposited layer. The barrier gas can also be fed into the lowest gas inlet zone. It can be fed into several gas inlet zones simultaneously, i.e., also into the middle gas inlet zone. In one variant of the invention, a 15% argon / hydrogen mixture is fed into the uppermost gas inlet zone as a carrier gas. Another barrier gas flow can be fed into the lowest gas inlet zone. In this case, it can be provided that the argon proportion of the barrier gas fed into the lower gas inlet zone is lower than the argon proportion of the barrier gas flow fed into the uppermost gas inlet opening.For example, the mass flow fed through the lower gas inlet zone may have 50%, 20%, or only 10% of the argon content of the barrier gas flow fed at the top.

[0015] By additionally feeding in a barrier gas, whose molar mass is preferably greater than the molar mass of the doping gas, the doping profile is influenced in such a way that a relative maximum deviation from the mean value of the dopant concentration in the layer can be minimized. A doping profile that, for example, has a tub shape can be modified by feeding in the argon flow in such a way that the edge enhancement of the doping profile is reduced. Similarly, a doping profile that is bell-shaped can be influenced by additionally feeding in argon in such a way that the center enhancement is reduced. This results in a further possibility, in particular by combining ammonia and molecular nitrogen as dopant carriers, of depositing a layer with a doping profile with improved homogeneity.The introduction of additional argon through one or more of the gas inlet openings thus offers the possibility of fine-tuning the doping profile. It is therefore particularly advantageous if at least ammonia or at least N2 is used as the dopant. Particularly preferably, ammonia and molecular nitrogen are used simultaneously, whereby these two dopant carriers can be fed into the process chamber at different vertical levels. One of these doping gas flows generates a first availability curve that reflects the availability of the dopant immediately above the substrate surface. This can have a first curvature. The curvature of a second availability curve of the second doping gas flow is opposite to this curvature. Both curvature profiles can be influenced by the barrier gas, which in particular contains argon.Ammonia can be fed through the topmost, but preferably through the bottommost gas inlet. Nitrogen is preferably fed through a middle gas inlet zone.

[0016] It is further 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 different 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, in particular, it can be provided 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 along a diametrical line through the substrate that is A-, U-, V-, or W-shaped. The other of the doping gas flows can generate a dopant profile that is opposite to this dopant profile and, 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, generate a doping profile that is curved upwards in the middle. The dopant carrier of a second doping gas flow can, for example, generate a doping profile that is curved downwards in the middle. An effective doping profile can be achieved by appropriately mixing the two doping gas flows.

[0017] The dopant carriers are preferably gases containing nitrogen. For example, the first dopant carrier can be NH3 and the second dopant carrier can be 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 different bonding 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. In particular, it is provided that the dopant carriers used react at different reaction rates on the surface of the substrate, on the surface of the precursor zone, and / or with the growth gases.

[0018] It can also 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 can contain carbon, for example, methane or ethene. However, the growth gas flow can also contain dichlorosilane. In this case, HCl can also be fed into the process chamber.

[0019] The following nitrogen compounds are particularly suitable as dopant carriers: N2, NH3 HCN, pyridine (C5H5N), hydrazine (N2H4), dimethylhydrazine (C2H8N2) or asymmetric dimethylhydrazine.

[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 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. A further variant provides that the first doping gas flow flows through the same gas inlet zone together with a first growth gas flow. NH3 can flow through the same gas inlet zone together with C2H4. In a further variation, the second doping gas flow, for example N2, can be fed into the process chamber together with a second growth gas flow, for example a silicon-containing growth gas flow, for example HCl3Si. A further variant provides that a third growth gas flow, which contains, in particular, carbon, flows through a bottommost gas inlet zone.It can be provided that a carbon-containing growth gas flow flows through all gas inlet zones, and a silicon-containing, and in particular 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 influences 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 in between.

[0022] The device according to the invention comprises a CVD reactor and a gas mixing device, as well as a control device. The gas mixing device comprises storage containers for the reactive gases containing silicon and carbon. It further comprises storage containers for the at least one dopant carrier, but preferably storage containers for at least two dopant carriers. The gas mixing device further comprises mass flow controllers and valves for appropriately distributing the reactive gases and the dopant carriers as growth gas flows and doping gas flows to the vertically stacked gas inlet zones of the gas inlet element. The mass flow controllers and the valves are controlled by the control device according to a control program.The reactive gases are fed into the gas inlet zones together with H2, wherein preferably a gas whose molecular mass is greater than 20 g / mol or 30 g / mol or 35 g / mol or argon is also fed into at least one gas inlet zone.

[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 these graphite parts is coated, in particular with SiC or TaC. 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 or TaC, or of SiC or TaC. 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. Short description of the drawings

[0024] The invention is explained in more detail below using exemplary embodiments. They show: Fig. 1 schematically in the form of a half-section along the line II in Fig. 2 a CVD reactor 1, Fig. 2 the section along line II in Fig. 1, Fig. 3 schematically shows a device for depositing SiC layers with a gas mixing system and a CVD reactor, Fig. 4 a diagram showing two dopant profiles through a SiC layer at the top and two dopant profiles each produced by different dopant carriers at the bottom, Fig. 5 a schematic representation of a second embodiment with regard to the composition and distribution of the process gas flow, Fig. 6 a representation according to Fig. 5 of a third embodiment, Fig. 7 a representation according to Fig. 5 of a fourth embodiment, Fig. 8 a representation according to Fig. 5 of a fifth embodiment, Fig. 9 a representation according to Fig. 5 a sixth embodiment, Fig. 10 an embodiment in which argon is additionally fed into the uppermost and lowermost gas inlet zones 4, 6, Fig. 11 the embodiment according to Fig. 6, whereby additional argon is also fed in through the lowest gas inlet zone 4, Fig. 12 the embodiment according to Fig. 11, with argon being fed through all gas inlet zones, Fig. 13 a representation of the embodiment according to Fig. 6, with argon additionally being fed through all gas inlet zones. Description of the embodiments

[0025] The Fig. 1 and Fig. 2 schematically show the structure of a CVD reactor 1. In a housing of the CVD reactor 1, which can be made of stainless steel, there is a susceptor 10, which can be made of graphite and whose surface can be coated with SiC. The susceptor can be driven in rotation about a central axis. The susceptor has the Fig. 2 shown circular disc shape.

[0026] 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 support 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 SiC-coated graphite. The gas outlet element 9 can also be made of this material. However, it can also be made of a ceramic material.

[0027] The susceptor 10 is covered with cover plates 15, 16, which can also be made of SiC-coated graphite. However, they can also be made of SiC. 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-coated or uncoated graphite, and drives the substrate holder 11 around a rotational axis.

[0028] A heating device 14 is provided below the susceptor 10. This heating device 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. However, the ceiling plate 19 is preferably 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.

[0029] In the center of the process chamber 2 is a gas inlet element 3, which can be made of a ceramic material, stainless steel, quartz, or SiC-coated graphite. The gas inlet element 3 forms three (see Fig. 3) comprises stacked gas inlet zones 4, 5, 6, each connected to a supply 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 comprising a gas source 27 for nitrogen, a gas source 28 for ammonia, a gas source 29 for trichlorosilane, a gas source 31 for argon, a gas source 32 for hydrogen, and a gas source 30 for ethene (C2H4). A gas source for HCl may also be provided.

[0030] 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. Both a growth gas flow and a doping gas flow can flow through each of these gas inlet zones 4, 5, 6. In addition, a carrier gas can be fed into the process chamber 2 through one or more, through each or through all of the gas inlet zones, wherein the carrier gas can be hydrogen. Preferably, however, the carrier gas is a mixture of a gas with a high molecular weight, for example argon, and hydrogen, wherein the proportion of argon in this gas mixture can be in the range between 0% and 100%. Preferably, however, the proportion of argon in the carrier gas flow is in a range between 10% and 90%.

[0031] Argon, as well as the dopant carriers, are provided in the gas mixing system.

[0032] Each of the gas sources 27 to 31 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 further usable nitrogen compounds. Furthermore, the gas mixing system 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 can also contain chlorine, for example trichlorosilicon, dichlorosilicon, or HCl. The gas sources 31, 32 provide a carrier gas containing argon and / or hydrogen. The mass flow controllers 21 can be used to feed any desired mixture of argon and hydrogen into each of the supply lines 24, 25, 26.

[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. Furthermore, the components of the doping gas flows and the growth gas flows can react catalytically on the surfaces of the cover plates 15 or the ceiling plate 19. Intermediate products and, in particular, decomposition products are formed. The intermediate or decomposition products and, if present, 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.

[0036] Due to this consumption of Si, C and N on 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 is reduced. Fig. 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] The doping profile a is generated in a SiC layer deposited on the substrate 11 when the substrate 11 is rotated during deposition and only the first doping gas flow D1 is fed into the process chamber 2 through the gas inlet zone 6. The dopant profile b is generated in a SiC layer deposited on the substrate 11 when the substrate 11 is rotated during deposition and only the second doping gas flow D2 is fed into the process chamber 2 through the gas inlet zone 5.

[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 choice of dopant carriers and the choice of 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. For example, one doping profile can be U-shaped. The other doping profile can be in the shape of an inverted U.

[0040] In the Fig. In the first exemplary embodiment shown in Figure 1, hydrogen and a fourth growth gas flow Q4, which is C2H4, are fed into the lowest-lying gas inlet zone 4. The mass flow of the fourth growth gas flow Q4 corresponds 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 growth gas flow Q1, which contains C2H4, are fed through the topmost gas inlet zone 6. The mass flow of this growth gas flow Q1 corresponds approximately 10% of the sum of all carbon-containing growth gas flows.In addition, a first doping gas flow D1 containing NH3 is fed through the uppermost gas inlet zone 6. Argon can also be fed in through a gas inlet zone, preferably the uppermost one.

[0041] The Fig. Figure 4 describes the effect that the introduction 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 within the layer, which is almost uniform. Only in the region near the edge of the layer of the circular disk-shaped substrate 12 is a slight reduction in the dopant concentration observed.

[0042] The two lower curves show the dopant incorporation that would be achieved by only one of the two different dopant carriers. The open and closed squares represent the dopant incorporation that would be achieved by only N2. When using only N2 as the dopant carrier, a strong edge enhancement of the dopant incorporation is observed. The open and closed circles show the dopant incorporation that would be achieved by only NH3. When using only NH3 as the dopant carrier, a strong center enhancement of the dopant incorporation is observed.By a suitable choice of the ratio of the mass flows of N2 and NH3 or by a suitable choice of 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 elevation or edge elevation.

[0043] In the Fig. The embodiment shown in Figure 5 is different from the one shown in Fig. In the embodiment shown in Figure 1, a third doping gas flow D3, which is NH3, is additionally fed through the lowest gas inlet zone 4. Argon can also be fed into the topmost gas inlet zone 6.

[0044] In the Fig. In the embodiment shown in Figure 6, no doping gas flow is fed into the process chamber 2 through the uppermost gas inlet zone 6. Here, only a first doping gas flow D1 (NH3) is fed through the lowest gas inlet zone 4, and a second doping gas flow D2 (N2) is fed through the middle or immediately above gas inlet zone. Argon can also be fed into the uppermost gas inlet zone 6.

[0045] In the Fig. In the embodiment shown in Figure 7, two doping gas flows D1 and D2 are fed into the process chamber 2, each containing NH3 as the dopant carrier. The two doping gas flows D1 and D2 are fed into the process chamber 2 through the lowest gas inlet zone 4 and the uppermost gas inlet zone 6, respectively. The shape of the depletion curves a, b can be adjusted simply by selecting the vertically different or spaced-apart gas inlet zones 4, 6. Argon can also be fed into the uppermost gas inlet zone 6.

[0046] In the Fig. In the exemplary embodiment shown in Figure 8, two doping gas flows D1, D2 are fed simultaneously through the uppermost gas inlet zone 6 into the process chamber 2. In this exemplary 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 are fed through the remaining gas inlet zones 5, 4, but rather at most a carrier gas or growth gas flows. 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. Argon can also be fed into the uppermost gas inlet zone 6.

[0047] In the Fig. In the embodiment shown in Figure 9, two different doping gas flows D1, D2, D3, D4 are 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 Fig. In the embodiment shown in Figure 8, a gas mixture comprising two different dopant carriers can flow 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 from the NH3 flow through the gas inlet zone 6. The two N2 flows can also be different. Argon can also be fed into the uppermost gas inlet zone 6.

[0048] By feeding the doping gases across different feed levels, it is possible to specifically adjust the doping profile. The following procedure can be used for this, 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 tests, until an acceptable "flat" doping profile is achieved.

[0049] When using NH3, it is considered essential that a gas inlet zone 4 or 6 is used through which no chlorine-containing gas mixture flows. Thus, it is specifically intended that a chlorine-containing growth gas flow be fed into the process chamber exclusively through a central gas inlet zone 5.

[0050] It can be provided that a gas flow of a carbon-containing growth gas flows through all gas inlet zones 4, 5, 6.

[0051] When selecting dopant carrier pairings, it can be advantageous if the dopant carriers have different nitrogen bonds (single, double, or triple bonds), or if the dopants of the dopant carriers are bound with different chemical bond strengths within the dopant carrier molecule. It can be assumed that these dopant carriers decompose differently and thus exhibit different depletion curves, allowing the dopant profile to be adjusted within the layer to be cut off.

[0052] It may be advantageous if NH3 is fed in through the top and bottom gas inlet zones 4 and 6, respectively, and N2 is fed in through the middle gas inlet zone 5.

[0053] 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 middle gas inlet zone 5.

[0054] The Fig. Figure 10 shows a further embodiment of the invention, in which hydrogen is not fed as the carrier gas through the uppermost gas inlet zone 6, but rather a mixture of argon and hydrogen. The argon content can vary between 0% and 100%. An argon content of this carrier gas flow between 10% and 40% is preferred; the argon content is preferably between 15% and 30%. Here, argon can also be fed into the lowermost gas inlet zone 4.

[0055] The Fig. 11 shows a further embodiment of a modification of the Fig. 6, wherein, instead of hydrogen, a mixture of argon and hydrogen is fed into the process chamber through the uppermost gas inlet zone 6. Argon can also be fed through the lowermost gas inlet zone 4.

[0056] The Fig. 12 and Fig. 13 show further embodiments as modifications of the Fig. 1 and Fig. 6, wherein, instead of a carrier gas flow consisting of hydrogen, a carrier gas flow consisting of argon and hydrogen is fed through the lowest gas inlet zone 4. The argon content of the barrier gas fed through the lowest gas inlet zone 4 is preferably lower than the argon content of the barrier gas flow fed through the uppermost gas inlet zone 6. Argon can also be fed through the middle gas inlet zone 5.

[0057] The doping gas flow D1, D2, D3, D4 from the one or more dopants and growth gas flows Q1, Q2, Q3, Q4, Q5 of the growth gases each flow together with hydrogen as carrier gas or admixed argon from the associated gas inlet zones 4, 5, 6 of the gas inlet device 3 into a pre-flow zone of the process chamber 2, where the gases heat up. The doping gas and the growth gases reach temperatures at which they decompose into their components. The decomposition products diffuse in a direction perpendicular to the horizontal flow in a vertical direction to the process chamber floor. The process parameters are set such that the deposition rate of the decomposition products of the growth gases reaches a peak immediately upstream of a growth zone adjoining the pre-flow zone in the flow direction.A silicon and carbon availability curve at the surface, which is reflected in the growth rate, then decreases in the direction of flow in the growth zone where the substrate to be coated is located. The decrease should be as linear as possible, i.e., straight, so that a layer with a high degree of layer thickness homogeneity is deposited on a rotating substrate. This layer homogeneity can also be influenced by the introduction of argon.

[0058] Just like the growth gases, the doping gases also decompose. However, due to different binding energies and pre-decomposition reactions in the gas phase, the availability curves of the various dopants immediately above the surface have different profiles. For ammonia, the availability curve is downwardly curved, resulting in a doping profile with a centrally elevated doping level on a layer deposited on a rotating substrate. This central elevation can be reduced by introducing argon, particularly by introducing argon into the uppermost gas inlet zone 6.

[0059] For nitrogen as a dopant carrier, the availability curve curves downwards, resulting in a dopant profile with increased edge height. The edge height is reduced by the introduction of argon. The introduction of argon into the uppermost gas inlet zone 6 leads to reduced diffusion of the dopant carriers toward the process chamber ceiling. The introduction of argon through a lowermost gas inlet zone 4 stabilizes the flow, as the heavier gas increases the dynamic pressure in the gas flow. At the same time, the introduction of argon fundamentally inhibits the diffusion of the reactive gases or their decomposition products in the direction perpendicular to the flow, as the diffusion coefficient depends on the molar mass of the gas.Although feeding argon through the lowest gas inlet zone 4 can lead to a reduced growth rate, it also leads to a reduction in the depletion in the gas phase, so that the growth curve or the availability curve of the growth gases is flatter than with the same process parameters without the additional feeding of argon into the process chamber.

[0060] By a suitable choice of the carrier gas composition, i.e. the molar mass of the carrier gas and the vertical level at which heavier carrier gas is fed into the process chamber, the Fig.4, the result of increasing the homogeneity of the dopant concentration in the layer can be further improved to achieve a doping profile that is as smooth as possible, in which a relative deviation of a maximum value of the dopant concentration or a minimum value of the dopant concentration from an average value measured over the entire layer is kept below, for example, 10%.

[0061] The above statements serve to explain the inventions covered by the application as a whole, which each independently develop the state of the art by at least the following combinations of features, whereby two, several or all of these combinations of features can also be combined, namely:

[0062] A method which is characterized in that the carrier gas of at least one of the partial flows has a molecular mass which is greater than the molecular mass of the dopant carrier and is in particular argon or a mixture of argon and hydrogen.

[0063] A method which is characterized in that the process gas flow contains a second doping gas flow D2 containing a second gaseous dopant carrier, wherein the two doping gas flows D1, D2 are fed into the process chamber 2 in a separately controlled manner as a partial flow through gas inlet zones 4, 5, 6 arranged vertically one above the other, and each of the two doping gas flows D1, D2 generates a lateral profile a, b of its dopant with a characteristic surface curvature in a SiC layer.

[0064] A method which is characterized in that the mass flows of the first and second doping gas flows D1, D2 and / or the molar mass of the carrier gas, the vertical position of the gas inlet zones 4, 5, 6 through which the two doping gas flows D1, D2 and / or the carrier gas flows having the increased molar mass flow, are selected such that the lateral profiles (a, b) have surface curvature profiles which are different from one another.

[0065] A method characterized in that the first dopant carrier is a nitrogen-containing gas, in particular NH3, and the second dopant carrier is a nitrogen-containing gas, in particular N2.

[0066] A method characterized in that the binding forces of a nitrogen atom to other atoms of the second dopant carrier are greater than the binding forces of a nitrogen atom to other atoms of the first dopant carrier.

[0067] 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.

[0068] A method characterized in that the first and second dopant carriers and the mass flows of the dopant gas flows D1, D2 carrying them or the mass flows or molar masses of the carrier gas are selected such that a sum of the two profiles a, b weighted by the ratio of the mass flows approaches a plane.

[0069] A process characterized in that the dopant carriers are selected from the following nitrogen compounds: N2, NH3, HCN, pyridine (C5H5N), hydrazine (N2H4), dimethylhydrazine (C2H8N2) or unsymmetrical dimethylhydrazine.

[0070] 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 carried by a gas cushion and driven in rotation.

[0071] A method 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 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 an overlying gas inlet zone 5 and / or that the first doping gas flow D1 and the secondDoping gas flow D2 contain the same dopant carrier, 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 toply 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.

[0072] A device characterized in that the control device 20 is configured to carry out a method according to one of the preceding claims.

[0073] A method or a device which is characterized in that a gas with a high molecular mass, in particular argon, is fed through at least one, preferably the upper or the lower gas inlet zone 4, 5, 6, wherein preferably a mixture of argon and hydrogen is used, wherein the argon content of the gas mixture can be between 15 and 30%.

[0074] A method or a device which is characterized in that ammonia and nitrogen are fed into the process chamber 2 as dopant carriers simultaneously and in particular through different gas inlet zones 4, 5, 6 and additionally argon or another gas with a molecular mass which is greater than the molecular mass of one of the dopant carriers is fed into the process chamber 2 through at least one gas inlet zone 4, 5, 6, preferably through the uppermost gas inlet zone 6.

[0075] All disclosed features are essential to the invention (individually, but also in combination with one another). The disclosure of the application hereby fully incorporates the disclosure content of the associated / attached priority documents (copy of the prior application), also for the purpose of incorporating features of these documents into claims of the present application. The subclaims, even without the features of a referenced claim, characterize independent inventive developments of the prior art with their features, in particular for filing divisional applications based on these claims. The invention specified in each claim may additionally comprise one or more of the features provided in the above description, in particular with reference numerals, and / or specified in the list of reference numerals.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 unnecessary for the respective intended use or can be replaced by other technically equivalent means. List of reference symbols 1 CVD reactor 2 process chambers 3 Gas inlet organ 4 Gas inlet zone 5 Gas inlet zone 6 Gas inlet zone 7 Lead zone 8 Deposition zone 9 Gas outlet device 10 Susceptor 11 substrate holder 12 Substrat 13 Gas supply line 14 Heating device 15 Cover plate 16 Cover plate 17 bag 18 Holding element 19 Ceiling panel 20 Control device 21 Mass flow controller 22 Valve 24 supply line 25 supply line 26 supply line 27 Gas source, nitrogen 28 Gas source, ammonia 29 Gas source, trichlorosilane 30 Gas source, ethene 31 Gas source, argon 32 Gas source, hydrogen D1 Doping gas flow D2 doping gas flow D3 Doping gas flow D4 Doping gas flow Q1 Growth gas flow Q2 Growth gas flow Q3 Growth gas flow Q4 Growth gas flow Q5 Growth gas flow S Flow direction a doping profile b Doping profile QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2011 054 566 A1 [0002, 0003] US 2020 / 0043725 A1

[0004] JP 2015-143168 A

[0005] WO 2022 / 053963 A1

[0007] US 7,118,781 B1

[0009] JP 6424384 B2

[0009] Cited non-patent literature

[0000] Experimental Study of the Pyrolysis of NH3 under Flow Reactor Conditions, Mario Benés, et al, 2021 American Chemical Society, p 7193

[0006]

Claims

[1] Method for depositing a SiC layer on a substrate (12) in a process chamber (2) of a CVD reactor (1) heated to a process temperature by a heating device (14), wherein a process gas flow is fed into the process chamber (2) through a gas inlet element (3) in one or more partial flows together with a carrier gas and flows in a horizontal direction in a flow direction (S) over the rotationally driven substrate (12), wherein the process gas flow consists of at least one first doping gas flow (D1) containing a first gaseous dopant carrier, a carbon-containing first growth gas flow (Q1) and a silicon-containing second growth gas flow (Q2), wherein the one or more dopant carriers decompose as they flow through the process chamber (2), Decomposition products of one or more dopant carriers on the surface of the SiC layer growing on the substrate are incorporated into the SiC layer as dopant, characterized by that the carrier gas of at least one of the partial flows has a molecular mass which is greater than the molecular mass of the dopant carrier and is in particular argon or a mixture of argon and hydrogen. [2] Method according to claim 1, characterized by in that the process gas flow contains a second doping gas flow (D2) containing a second gaseous dopant carrier, wherein the two doping gas flows (D1, D2) are controlled separately from one another and are each fed into the process chamber (2) as a partial flow through gas inlet zones (4, 5, 6) arranged vertically one above the other, and each of the two doping gas flows (D1, D2) produces a lateral profile (a, b) of its dopant with a characteristic surface curvature in a SiC layer. [3] Method according to one of the preceding claims, characterized by that the mass flows of the first and second doping gas flows (D1, D2) and / or the molar mass of the carrier gas, the vertical position of the gas inlet zones (4, 5, 6) through which the two doping gas flows (D1, D2) and / or the carrier gas flows having the increased molar mass flow, are selected such that the lateral profiles (a, b) have different surface curvature profiles. [4] Method according to one of the preceding claims, characterized by that the first dopant carrier is a nitrogen-containing gas and in particular NH3 and the second dopant carrier is a nitrogen-containing gas and in particular N2 and / or that the binding forces of a nitrogen atom to other atoms of the second dopant carrier are greater than the binding forces of a nitrogen atom to other atoms of the first dopant carrier. [5] Method according to one of the preceding claims, characterized bythat 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 first doping gas flow (D1) containing NH3. [6] Method according to one of the preceding claims, characterized by that the first and second dopant carriers and the mass flows of the dopant gas flows (D1, D2) carrying them or the mass flows or molar masses of the carrier gas are selected such that a sum of the two profiles (a, b) weighted by the ratio of the mass flows approaches a plane. [7] Method according to one of the preceding claims, characterized bythat the dopant carriers are selected from the following nitrogen compounds: N2, NH3, HCN, pyridine (C5H5N), hydrazine (N2H4), dimethylhydrazine (C2H8N2) or asymmetrical dimethylhydrazine and / or 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 carried by a gas cushion and driven in rotation. [8] Method according to one of the preceding claims, characterized bythat 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 overlying gas inlet zone (5) and / or that the first doping gas flow (D1) and the secondDoping gas flow (D2) contain the same dopant carrier, 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 toply 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, and / or that a gas with a high molecular mass, in particular argon, is fed through at least one, preferably the upper or the lower gas inlet zone (4, 5, 6), wherein preferably a mixture of argon and hydrogen, with the argon content of the gas mixture being between 15 and30%, and / or, simultaneously and in particular through different gas inlet zones (4, 5, 6), ammonia and nitrogen are fed into the process chamber (2) as dopant carriers and, in addition, through at least one gas inlet zone (4, 5, 6), preferably through the uppermost gas inlet zone (6), argon or another gas with a molecular mass which is greater than the molecular mass of one of the dopant carriers is fed into the process chamber (2). [9] 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 by means of supply lines (24, 25, 26) and mass flow controllers (21) and valves (22) arranged in the supply lines to gas sources (27, 28, 29, 30) 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 by that the control device (20) is designed to carry out a method according to one of the preceding claims. [10] Method or device, characterized byone or more of the characterizing features of any of the preceding claims.

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