Method and device for depositing sic layers on a substrate

Abstract

A method for depositing a layer on a substrate (9), wherein a homogeneous first gas flow is fed by means of a gas-inlet member (6) into a process chamber (4) brought to a process temperature, flows over the substrate (9) in a flow direction (S) and contains one or more reactive gases, the decomposition products of which form the layer, wherein a second gas flow is fed into the process chamber (4) through a gas-outlet area of a gas-outlet opening (10, 10', 10'') arranged downstream of the gas-inlet member (6) and upstream of the substrate (9), and contains at least one gas that influences a dopant concentration within the layer, wherein the width (B1), extending transversely to the flow direction (S), of the gas-outlet opening (10, 10', 10'') is less than the width (B2), extending transversely to the flow direction (S), of the substrate (9), and a gas that influences the composition of the layer flows through the gas-outlet opening (10, 10', 10'').

Description

Description Method and device for depositing SiC layers on a substrate Field of technology

[0001] The invention relates to a method and a device for depositing a layer on a substrate, wherein a homogeneous gas flow is fed into a process chamber brought to a process temperature by means of a gas inlet device. The gas flow flows evenly and laminarly over the cross-sectional area of ​​the process chamber in a uniform flow direction, wherein the flow lines of the gas flow can run parallel to one another or radially towards a center. The gas flow flowing in one flow direction over the substrate contains one or more reactive gases, the decomposition products of which form the layer to be deposited on the substrate. A second gas flow flows into the process chamber through an additional gas outlet opening arranged downstream of the gas inlet device and upstream of the substrate or a substrate holder carrying the substrate.The second gas flow contains a reactive gas that influences the composition within the layer, for example, a dopant. State of the art.

[0002] DE 102018124957 A1 describes a device for depositing semiconductor layers with a process chamber, in the center of which is a gas inlet element, with which a process gas is fed into the process chamber, which spreads radially in the process chamber and flows over substrates arranged around the gas inlet element. The substrates are carried by substrate holders, which are carried by a purge gas. The purge gas is not only capable of 31039N1PCT – 4.12.2023 By varying the purge gas flow, the heat transfer to the substrate holder can also be influenced. A gas inlet opening is located upstream of the substrate holder, through which a compensating gas is fed into the process chamber, which can be used to compensate for fluctuations in the purge gas.

[0003] US Pat. No. 8,052,794 B2 describes an apparatus and method for depositing SiC. The process is carried out at process temperatures exceeding 1600 degrees Celsius. A silicon-containing and a carbon-containing reactive gas are fed into the process chamber through a gas inlet device. Additionally, a gaseous dopant in the form of nitrogen (N2) is fed through the gas inlet device.

[0004] A similar device is described in US Pat. No. 10,930,492 B2. In both devices, the substrates are supported by substrate holders arranged on a susceptor, which are kept suspended by a purge gas. A gas that influences the dopant concentration within the layer is added to the purge gas in order to influence the dopant incorporation into the layer.

[0005] US 10,858,758 B2 describes a CVD reactor for depositing SiC layers with a gas inlet device arranged upstream of a substrate in the flow direction. The gas inlet device has a gas inlet outlet surface whose width is greater than the width of the substrate. The gas outlet surface is divided into three zones, through each of which a mixture of hydrogen, propane, monosilane, and nitrogen can be fed into the process chamber. The mixtures can differ in the three zones. 31039N1PCT – 4.12.2023

[0006] The last-described method is intended to ensure that the SiC layers deposited on the substrate have the most homogeneous dopant concentration possible. In SiC layers deposited without the additional dopant injection into the purge gas that creates the gas cushion, a dopant concentration increasing toward the edge of the layer was observed. This inhomogeneity of the dopant incorporation is to be reduced with the measures described above. Summary of the Invention

[0007] The invention is based on the object of further improving the homogeneity of the dopant concentration within the layer and, in particular, of providing means by which the layer composition within the layer can be influenced in a locally targeted manner.

[0008] The problem is solved by the invention specified in the claims, wherein the subclaims are not only advantageous developments of the invention specified in the independent claims, but also represent independent solutions to the problem.

[0009] While in the prior art, an additional gas flow is generated containing a gas influencing the dopant concentration within the layer, which exits from a gas exit surface that is wider than the width of the substrate extending transversely to the flow direction, the invention proposes reducing the width of the gas exit surface so that it is smaller than the width of the substrate. As a result, a gas flow is formed flowing along a flow line running in the flow direction, in which the concentration of, for example, a dopant differs from the adjacent gas flow. The gas flow flowing along the flow line can expand due to diffusion effects. 31039N1PCT – 4.12.2023 influences the dopant incorporation into the layer on a locally limited area on the surface of the substrate. The gas inlet element according to the invention has a gas outlet surface on which gas outlet openings are distributed in such a way that the most homogeneous gas flow possible can be fed into the process chamber. The effective width of the gas inlet element is greater than the width of the substrate running transversely to the flow direction, so that a laminar first gas flow emerges from the gas outlet surface of the gas inlet element and flows through the process chamber in a uniform flow direction. The flow lines of the first gas flow, which run straight from the gas inlet element over the substrate, can run parallel to one another or emerge from the gas inlet element in a star shape, i.e. in a radial direction relative to a center of the process chamber.In the first gas flow, the concentration of its components is distributed homogeneously across the entire cross-sectional area. To achieve this, the gas inlet element preferably has a gas outlet surface having a plurality of evenly distributed gas passage openings which have identical areas to one another. It can be provided that the concentration of the first gas flow differs in the vertical direction if, for example, different reactive gases are fed in at different horizontal levels. However, within these horizontal levels the gas flow is homogeneous in each case. According to the invention, a second gas flow is fed into such a homogeneous first gas flow downstream of the gas inlet element and upstream of the substrate. For this purpose, a gas outlet opening is used whose width is less than the width of the substrate.As a result, a local gas flow of the dopant forms, which influences the substrate only on a partial area. The position of this partial area depends on where the at least one gas outlet opening is located on a line running perpendicular to the flow direction. For example, if the gas outlet opening is located on a center line that runs in the flow direction of the gas emerging from the gas inlet, 31039N1PCT – 4.12.2023 If the first gas flow emerging from the outlet element passes through the center of the substrate, the dopant incorporation within the layer in the center of the substrate changes. If, on the other hand, the gas outlet opening is arranged offset from the center line, the dopant incorporation increases in a region of the layer that is spaced from the center of the substrate. The flow line of the second gas flow generated by the gas outlet surface can run over the substrate in a region that runs between the center of the substrate and a point on the edge of the substrate that lies on a line running through the center of the substrate and perpendicular to the flow direction. However, it can also be provided that the flow line runs outside the edge of the substrate, so that the second gas flow flows past the substrate.In this case, the gas influencing the layer composition, in particular the dopant concentration, essentially only influences the edge of the substrate. In a CVD reactor with a central gas inlet, the gas outlet opening can be located on a flow line that is offset by an angle to the center line running through the center of the substrate in the direction of flow. The angle can be selected such that the gas flow flows over a partial surface of the substrate that lies between the center and the edge of the substrate. However, the gas flow can also flow past the substrate. If several substrates are located next to one another, for example in a circumferential line around the center of the process chamber, the second gas flow can also flow through a gap between two substrates, for example, centrally through this gap.In a CVD reactor through which the first gas flow flows linearly rather than in a star pattern, the at least one gas outlet opening can be offset by a certain distance from the center line running through the center of the substrate in the direction of flow. Alternatively, the gas outlet opening can also impart momentum to the second gas flow, so that its direction deviates from the direction of the first gas flow. 31039N1PCT – 4.12.2023 deviates, for example, a bore forming the gas outlet opening can run obliquely to the surface normal of the susceptor surface. In the first case, the angle influences the point of action of the second gas flow, in the second case, the length of the distance influences the position of the point of action of the second gas flow on the substrate. In the third case, the direction of an outlet channel that opens into the outlet opening influences the point of action of the second gas flow. According to a preferred development of the invention, it is proposed that the width of the gas outlet surface of the gas outlet opening running transversely to the flow direction is smaller than half, one third, one quarter, one fifth or one sixth of the width of the substrate running transversely to the flow direction.The smaller the width of the gas outlet area of ​​the gas outlet opening, the more precisely the composition of the layer and in particular the dopant incorporation in the layer can be locally influenced using one or more gas outlet openings. However, the gas outlet area can also be composed of several partial openings with different individual areas. The method described above can be used to locally influence the composition of a layer composed of several components. The dopant incorporation is preferably influenced using the method. The width of the gas outlet opening can also be used as a means of influencing the mass flow of the second gas flow, for example in the manner of a throttle. For this purpose, a combination of different individual openings can be provided, which have the same opening area or different opening areas.This allows the size and shape of the zone in which the substrate is influenced by the second gas flow to be influenced. The method according to the invention is preferably used in the deposition of SiC layers on substrates, for example SiC substrates, as already described in the above-mentioned prior art, i.e., at temperatures greater than, for example, 1500 degrees Celsius. Reactive gases are used. 31039N1PCT – 4.12.2023 At least one carbon-containing gas, for example methane, propane, or the like, and a silicon-containing gas, for example monosilane, disilane, or trichlorosilane, are used. However, it is also possible to use Si(CH3)4). The SiC layer is to be doped with nitrogen. A nitrogen-containing gas such as ammonia or N2 can be used as a gas influencing the dopant concentration within the layer. The method can achieve not only N-doping, but also P-doping. Instead of nitrogen, other dopants can also be used, for example aluminum, boron, for example in the form of TMAl or TEB or another suitable Al or B compound. However, it is also envisaged that a carbon-containing gas such as methane, propane, or the like can be used as the gas influencing the dopant concentration within the layer.While when using a gas containing the dopant, the dopant concentration in the layer increases essentially proportionally with the partial pressure of the gas or of the dopant immediately above the substrate, when using a carbon-containing gas, the dopant incorporation into the layer is reduced essentially in reciprocal fashion with the partial pressure of the gas or of the substance preventing dopant incorporation immediately above the substrate. By using N2, for example, the dopant incorporation can be increased locally. By using methane or propane, for example, the dopant incorporation can be reduced locally. In order to counteract the problem mentioned above of the higher dopant concentration at the edge of the layer, it can therefore be beneficial to position the outlet opening at an angle to the center line oroffset from the centerline by a distance such that the flow line along which the second gas flow flows through the gas outlet opening runs over the substrate between the centerline and the edge of the substrate. This is particularly advantageous when the second gas flow contains N2 and the dopant concentration is 31039N1PCT – 4.12.2023 without the second gas flow, the flow has a W-shaped profile across the diameter of the layer. The dopant concentration in the layer then has a maximum in the area of ​​the center and the edge of the substrate. Between the center and the edge of the substrate, the dopant concentration has a minimum. The angle or distance is selected such that the flow line of the second gas flow passes through this minimum, so that the dopant incorporation is specifically promoted here. With a rotating susceptor, the surfaces exerted on the gas flow by the rotation must also be taken into account.If, on the other hand, the dopant concentration without the second gas flow has a U-shaped curve across the diameter of the layer, i.e. a minimum in the center region and a maximum in the edge region, the second gas flow can contain a reactive gas that suppresses dopant incorporation, for example a carbon-containing gas. It is then advantageous if the second gas flow is limited to the edge of the substrate. For this purpose, it can be beneficial to allow the second gas flow to flow directly past the substrate at the edge of the substrate. It can also be advantageous to allow the second gas flow to flow preferably centrally through a space between two substrates. This specifically reduces dopant incorporation in the edge region of the substrate. The gas outlet opening can be spaced apart from the substrate or by a substrate holder supporting the substrate.The gas outlet opening can be a circular hole in the susceptor that is connected to a supply line. In a rotationally symmetrical arrangement, the hole or holes, each assigned to a substrate, can be arranged in a ring surrounding the gas inlet element. If this ring is movable in an azimuthal direction, the position of the gas outlet opening can be changed. In a process chamber with linear flow, the holes can also be arranged on a movable plate, so that the distance between the holes can be adjusted by moving the plate. 31039N1PCT – 4.12.2023 Gas outlet opening can be adjusted to the center line. The device used to carry out the method can have a susceptor that is driven to rotate about its center. Pockets can be arranged in the susceptor, evenly distributed in the circumferential direction around the center, each containing a substrate holder. Purge gas flows containing exclusively an inert gas, for example hydrogen, can be fed into the bottom of the pockets. This purge gas creates a gas cushion that supports the respective substrate holder and sets it in rotation, whereby the rotation speed of the substrate holder is greater than the rotation speed of the susceptor. Due to the rotation of the substrate holder, a layer that is rotationally symmetrical in terms of its properties is formed on the substrate. By choosing the angle orThe distance and the width of the gas outlet opening measured transversely to the flow direction allow the dopant incorporation to be specifically influenced in radial zones. It can be provided that only an inert gas, for example hydrogen and a carbon-containing and a silicon-containing gas, is fed into the process chamber through the gas inlet element. The dopant is then incorporated into the layer exclusively with reactive gases that exit through one or more gas outlet openings of the type and arrangement described above. For this purpose, it can be advantageous to have several gas outlet openings arranged for one, preferably each, substrate, in particular on a line running transversely to the flow direction, which can be a straight line or a circular arc. The various gas outlet openings allow the dopant incorporation to be specifically influenced locally.However, it can also be provided that different gas flows flow through different gas outlet openings, and in particular through gas outlet openings assigned to different substrates, whereby the flows can differ in terms of mass flow. Preferably, the partial pressure of the reactive gas within the gas flow is the same in all flows. However, it is 31039N1PCT – 4.12.2023 It is also provided that a reactive gas containing the dopant is additionally fed through the gas inlet element, and the dopant incorporation is locally influenced by the second gas flow. For this purpose, it is considered advantageous if the second gas flow inhomogenizes a previously homogeneous gas flow. The device can have a gas outlet element that is arranged downstream of the substrate or the substrate holder in the flow direction of the gas flows. With a rotationally symmetrical arrangement of susceptor and gas inlet element, the gas outlet element can surround the susceptor in a ring, so that an edge of the susceptor running on a circular arc borders the gas outlet element. A gas discharge line can connect the gas outlet element to a pump, with which the total pressure within the process chamber can be adjusted to a negative pressure. The process chamber is preferably heated with a heating device.The heating device can be an RF coil that heats the susceptor, which can be made of graphite, and generates eddy currents in the susceptor. A process chamber ceiling can be heated by thermal radiation from the susceptor. However, the process chamber ceiling can also be actively heated. By feeding the reactive gases into the process chamber, decomposition products, such as Si, C, and N or intermediates containing these elements, are formed due to the elevated temperature. These decomposition products diffuse through an interface of the process gas above the substrate to the substrate surface, where they react with the surface of the substrate or the layer already deposited on it, forming a nitrogen-doped SiC layer. The reactive gas that influences the layer composition can be fed into the process chamber not only through the additional gas outlet opening.It is also intended that this reactive gas be fed into the process chamber through the gas inlet device, so that the supply to the substrate surface is locally modulated by the gas flow emerging from the gas outlet opening. The device for carrying out the process can comprise six uniformly distributed gas streams around the 31039N1PCT – December 4, 2023. Have storage spaces for substrates arranged in the center. The angle by which the flow line is offset from the centerline can range between 5 and 10 degrees. The preferred angle can be 8.5 degrees. In this case, the circular substrate can be positioned at a sector angle of 70 degrees, so that a tangent passing through the center to the edge of the substrate is at an angle of 35 degrees to the centerline.

[0010] The invention further relates to a method for depositing a layer on a substrate having a process chamber that is bounded at the bottom by a susceptor and at the top by a process chamber ceiling. Process gases are fed into the process chamber through a gas inlet element. The process gases flow through the process chamber horizontally. The gas inlet element can have several gas inlet zones arranged vertically one above the other, through which different reactive gases can enter the process chamber separately from one another. The reactive gases can contain silicon and carbon, for example trichlorosilane or H2H4. Ammonia can also be fed into the process chamber as a dopant through one of the gas inlet zones. This can be done through a gas inlet zone arranged at the top.However, the ammonia can also be fed into the process chamber through any other gas inlet zone, for example through a central gas inlet zone that is located away from the process chamber ceiling and the susceptor.

[0011] A further doping gas can be fed into the process chamber through a gas outlet opening in the floor of the process chamber, in particular a gas outlet opening as described above. This gas outlet opening, which can essentially have the same properties as the gas outlet opening described above, is preferably used to introduce a further doping gas into the process chamber. 31039N1PCT – 4.12.2023 Nitrogen (molecular nitrogen N2) is fed in. The nitrogen thus flows through the lowest area of ​​the process chamber.

[0012] NH3 and N2 can be fed in at different positions. The two doping gases can be fed into the process chamber through any of the multiple gas inlet zones arranged one above the other. In particular, it is intended that NH3 or HCN or pyridine (C5H5N), hydrazine (N2H4) or dimethylhydrazine (C2H8N2) or asymmetric dimethylhydrazine be fed into the process chamber through one or more gas inlet zones. Different doping gases can be fed through different gas inlet zones.

[0013] In particular, it is intended that NH3 or another of the above-mentioned doping gases be fed into the process chamber through the gas inlet device. This can occur at various vertical heights, for example, through the topmost gas inlet device, through a central gas inlet device, or through a bottom gas inlet device.

[0014] In addition, NH2 can be fed into the process chamber from the gas outlet opening located in the bottom of the process chamber, i.e. in the susceptor.

[0015] However, it is also possible to feed NH3 through this gas outlet. In particular, it is possible to simultaneously feed NH3 through the lowest gas inlet zone and NH3 through the gas outlet. 31039N1PCT – 4.12.2023 Summary of the invention

[0016] Embodiments of the invention are explained below with reference to the attached drawings. They show: Fig. 1 schematically a cross section through a CVD reactor for carrying out the method, Fig. 2 a plan view approximately along the sectional plane II-II of a susceptor 2, Fig. 3 the section of the first embodiment designated III in Figure 2, Fig. 4 the section of a second embodiment shown in Figure 3, Fig. 5 the section of a third embodiment shown in Figure 3, Fig. 6 schematically the profile of a dopant concentration in a layer on a line d running through the center 12 of the substrate 9, wherein the second gas flow contains a gas that promotes the dopant incorporation, Fig.7 schematically shows the course of a dopant concentration in a layer through a line d running through the center 12 of the substrate 9, wherein the second gas flow contains a gas reducing the dopant incorporation, 31039N1PCT - 4.12.2023. Fig. 8 shows the section of a fourth exemplary embodiment shown in Figure 3, Fig. 9 shows a schematic cross section through a CVD reactor for carrying out the method of a fifth exemplary embodiment, Fig. 10 shows a plan view of the susceptor of the CVD reactor of the fifth exemplary embodiment, Fig. 11 shows a representation according to Figure 10 of a sixth exemplary embodiment, Fig. 12 shows a representation according to Figure 10 of a seventh exemplary embodiment and Fig. 13 shows a representation according to Figure 10 of an eighth exemplary embodiment. Fig. 14 is a view according to Figure 10, wherein the gas outlet opening 10 is arranged on a movable plate 25', Fig. 15 is a view according to Figure 3 of a tenth embodiment, in which two gas inlet openings 11 with different diameters are provided, 31039N1PCT – 4.12.2023 Fig. 16 shows a ninth embodiment in a representation according to Fig. 3, wherein three zones Z1, Z2, Z3 are marked with additional auxiliary lines. Fig. 17 shows the dopant concentration in a layer as a function of the angle α. Fig. 18 shows a representation according to Fig. 9 of an eighth embodiment of the invention. Description of the Embodiments

[0017] The CVD reactor shown in Figures 1 and 9 has a housing 1 and is part of a coating device, which additionally has a control device 24 and a gas supply system.

[0018] The gas supply system has a plurality of supply lines 15, 16, 17, 18, 19 through which reactive gases provided by gas sources 21, 22, 23, together with an inert gas (the source of which is not shown), can be transported to a process chamber 4 arranged in the housing 1. A gas source 21 provides a carbon-containing gas, a gas source 22 provides a silicon-containing gas, and a gas source 23 provides a nitrogen-containing gas. These gases can be methane, propane, silane, disilane, trichlorosilane, nitrogen, ammonia, or the like. Valves (not shown) and mass flow controllers 20, with which the gas flow can be adjusted, are located in the supply lines 15, 16, 17, 18, 19. The gas flows can be adjusted using the control device 24.For this purpose, the control device 24 contains a programmable control computer which can process a recipe stored in the control device 24, in which values ​​for the 31039N1PCT – 4.12.2023. Gas flows are included. The recipe allows several consecutive process steps to be carried out automatically. One or more layers containing SiC and doped with nitrogen can be deposited on a substrate, for example, a SiC substrate. However, the device is also suitable for depositing other material systems.

[0019] The CVD reactor includes a susceptor 2, which extends in a horizontal plane and can be heated to a process temperature of over 1500 degrees Celsius by a heating device 5 arranged below the susceptor 2. A gas inlet element 6 is provided, with which the reactive gases can be fed into the process chamber 4. The supply lines 15, 16, 17 for gases containing carbon, silicon, and nitrogen open into the gas inlet element 6. The gas inlet element 6 has a gas outlet surface that is porous or has a large number of evenly distributed and, in particular, equally sized openings through which a gas mixture of the previously described gases can enter the process chamber 4. In the embodiment, the gas inlet element 6 has a single gas inlet zone through which a homogeneous mixture of gases flows into the process chamber 4, forming a homogeneous laminar flow.In embodiments not shown, several gas inlet zones can be arranged one above the other, through which different mixtures of gases flow into the process chamber 4 as a homogeneous laminar flow.

[0020] The CVD reactor is operated in such a way that a homogeneous, laminar flow profile is formed over at least part of the height of the cross-sectional area, preferably over the entire cross-sectional area of ​​the process chamber 4. In the embodiment shown in Figure 1, the flows of the first gas flow exiting the gas inlet element 6 are star-shaped relative to a center 13, which is arranged within the gas inlet element 31039N1PCT – 4.12.2023 gans 6. The gas outlet surface here extends on a cylindrical surface that extends from a floor of the process chamber 4 formed by the susceptor 2 to a process chamber ceiling 3. In the embodiment shown in Figure 9, the gas outlet surface can be a rectangular surface, wherein the width of the gas outlet surface extending in the flow direction S is greater than a diameter B2 of the substrate 9.

[0021] Downstream of the first gas flow, the susceptor 2 has storage locations, each for a substrate 9. In the exemplary embodiment, the storage locations are each formed by a substrate holder 8, which lies in a pocket of the susceptor 2. Supply lines (not shown) for a purge gas flow consisting of the inert gas, for example, hydrogen, open into the bottom of the pocket. This purge gas flow creates a gas cushion beneath the substrate holder 8, which lifts the substrate holder 8 and causes it to rotate about its axis 8'.

[0022] Radially outside an edge 2' or opposite the gas inlet element 6, a gas outlet element 7 is provided, through which the process gas fed into the process chamber 4 via the gas inlet element 6 or decomposition products of the process gas can be led out of the process chamber 4. This is done with a pump (not shown) that can generate a negative pressure within the process chamber 4.

[0023] In a zone through which the first gas flow preferably flows evenly and homogeneously and which is located downstream of the gas inlet element 6 and upstream of the substrate holder 8 or the substrate 9, a gas outlet opening 10 is arranged, through which a second gas flow can be fed into the process chamber. The position of the gas outlet opening 10 influences the effective point of a gas flow passing through the gas outlet surface of the gas outlet opening 10 in 31039N1PCT – 4.12.2023 A second gas flow flowing through the process chamber 4 contains a gas influencing the layer composition, preferably the dopant concentration within the layer, which gas can be, for example, nitrogen or one of the carbon-containing reactive gases mentioned above. The second gas flow flows through the process chamber 4 along a flow line 14. The position of the flow line 14 with respect to a center line 11, which runs through the center point 12 of the substrate 9 in the flow direction S of the first gas flow, influences the dopant incorporation into the layer at various radial distances relative to the center point 12. The flow line 14 runs along the flow direction S of the first gas flow.

[0024] Supply lines 18, 19 are provided through which the second gas flow can be fed into the process chamber 4. The supply lines 18, 19 are connected to a carbon gas source 21 or a nitrogen gas source 23. The supply lines 18, 19 open into one or more gas outlet openings 10, 10', 10''.

[0025] Figure 2 shows a plan view of the susceptor 2 of the first embodiment, which is surrounded by an annular gas outlet element 7. Six substrates 9 are arranged in a uniform circumferential distribution around the center 13. In other embodiments, the number of substrates 9 can be smaller or larger. Imaginary center lines 11 extend through the centers 12 of the substrates 9, running parallel to the flow direction S of the first gas flow and thus through the center 13. A star-shaped array of flow lines extends symmetrically around the center 13.

[0026] The gas outlet openings 10 are offset in the first embodiment shown in Figure 2, which is shown enlarged in Figure 3. 31039N1PCT – 4.12.2023 to the center line 11. A straight line running through the center 13 and through the center of the gas outlet opening 10 forms a flow line 14 along which the second gas flow emerging from the gas outlet opening 10 flows. The angle α between the center line and the flow line 14 is selected here such that the flow line 14 runs over one of the two halves of the substrate 9 into which the center line 11 divides the substrate surface. Depending on the size of the angle α, the radial position of an effective point of the second gas flow changes relative to the center point 12 of the substrate 9.

[0027] The circular gas outlet opening in the exemplary embodiment has a diameter B1 that is significantly smaller than the diameter B2 of the circular substrate 9. The diameter of the gas outlet surface of the gas outlet opening 10 is preferably smaller than half, one-third, one-quarter, one-fifth, or one-sixth of the diameter of the substrate 9. However, the diameter of the gas outlet opening 10 can also be smaller than one-tenth of the diameter of the substrate. The smaller the width B1 of the gas outlet surface of the gas outlet opening 10, measured transversely to the flow direction S, the smaller the width of the second gas flow emerging from it, which spreads transversely to the flow direction as a result of diffusion or the star-shaped arrangement of the flow lines of the main flow.The smaller the ratio of width B1 of the gas outlet surfaces to a width B2 of the substrate 9 measured transversely to the flow direction S, the more locally targeted the dopant incorporation into the layer can be influenced with the second gas flow.

[0028] In the second embodiment shown in Figure 4, the gas outlet opening 10 is located on the center line 11, so that the second gas flow emerging from it passes through the center of the substrate 9. 31039N1PCT – 4.12.2023

[0029] In the embodiment shown in Figure 5, the gas outlet opening is located approximately on an angle bisector of two center lines 11, which run through the centers 12 of two adjacent substrates 9, so that the flow line 14 runs through the space between two substrates 9. The second gas flow is guided specifically past the substrates 9, so that the gas contained in the second gas flow, which influences the dopant incorporation, acts only in the region of the edge 9' of the substrate.

[0030] Figure 6 shows schematically the effects of the arrangements of the gas outlet openings 10 in the previously described embodiments.

[0031] The W-shaped curve A shows the dopant concentration exhibited by a layer deposited on the substrate 9 without the second gas flow, along a line d through the center 12, with an additional dopant being fed into the process chamber through the gas inlet element 6. Due to the rotation of the substrate 9 during the deposition of the layer, the dopant concentration has a rotational symmetry. However, it has a maximum in the region of the center and in the region of the edges of the substrate 9. There is a minimum in each of these areas.

[0032] Curve B shows the influence of a second gas flow containing a reactive gas that promotes dopant incorporation, such as nitrogen, on the radial dopant concentration. In the area between the center 12 and the edge 9' of the substrate 9, where the active site is in Figure 3, maximum dopant incorporation occurs. This compensates for the minima shown in curve A.

[0033] Curve C shows the influence of a second gas flow containing a reactive gas promoting dopant incorporation, with the gas outlet opening 31039N1PCT – 4.12.2023 The voltage 10 is arranged according to the embodiment shown in Figure 4, i.e., it lies on the center line 11. Here, the active point is in the middle, so that a maximum of the dopant concentration forms in the region of the center point 12.

[0034] Curve D shows the influence of a second gas flow containing a reactive gas that promotes dopant incorporation, with the gas outlet opening 10 being arranged according to the embodiment shown in Figure 5, so that a flow line 14 forms between two substrates 9. Here, only the edge region of the two substrates 9 is influenced by the second gas flow because the effective point lies between the substrates 9. The maxima here are at the edge 9', whereas a minimum 12 is formed in the region of the center point.

[0035] Figure 7 shows schematically the effects of the arrangements of the gas outlet openings 10 in the embodiments described in Figures 3 to 5, whereby now, however, the second gas flow contains a reactive gas that inhibits the incorporation of dopant substances, for example a carbon-containing gas.

[0036] Here, too, the W-shaped curve A shows the dopant concentration of a layer deposited on the substrate 9 without the second gas flow, along line d through the center point 12, with a dopant also being fed in through the gas inlet element 6. Here, too, the dopant concentration is rotationally symmetric due to the rotation of the substrate 9 during the deposition of the layer. 31039N1PCT – December 4, 2023

[0037] Curve B' shows the effect of the second gas flow in an arrangement of the gas outlet opening 10 according to Figure 3. Here, minima form in the area between the center point 12 and the edge 9'.

[0038] Curve C' shows the effect of the second gas flow in an arrangement of the gas outlet opening 10 according to Figure 4. Here, the reactive gas reducing the dopant incorporation causes a minimum in the region of the center and maxima in the region of the edges 9'.

[0039] Curve D' shows the effect of the second gas flow in an arrangement of the gas outlet opening 10 according to Figure 5. Here, the reactive gas reducing the dopant incorporation causes the formation of a maximum in the region of the center 12 and the formation of a minimum in the region of the edges 9'.

[0040] By carefully selecting the angle α or a specific ratio of the gas exiting the gas outlet 10, which influences the dopant incorporation, to the reactive gas exiting the gas inlet 6, which influences the dopant incorporation, the respective curve A can be modified with the second gas flow so that it is as flat as possible. It is thus possible to raise the curve in the area of ​​its minima or lower it in the area of ​​its maxima.

[0041] It is possible to allow a gas stream influencing the dopant concentration within the layer to flow simultaneously through the gas inlet element 6 and through the gas outlet opening 10. However, it is also provided that the gas stream influencing the dopant concentration flows only through the gas outlet opening 10. In the exemplary embodiment shown in Figure 8, several gas outlet openings 10, 10' are provided, which are arranged on mutually 31039N1PCT – 4.12.2023 the different flow lines 14, 14' are arranged and through which the same or different gas flows can emerge. With these two second gas flows, the dopant incorporation can be specifically influenced at two different radial positions on the substrate 9. The angles α, α' can be the same or different.

[0042] Figure 9 shows a second embodiment of a CVD reactor in which the first gas flow flows linearly horizontally through the process chamber 4 arranged in the housing 1. The substrate 9 is located in the center of the susceptor 2 and is equidistant from the two walls of the process chamber 4 in a direction transverse to the flow direction S. A center line 14 runs through a center 13 of the gas inlet element 6 and through the center point 12 of the substrate 9 or a substrate holder 8 supporting the substrate. The center line 14 has the direction of the flow direction S.

[0043] A homogeneous laminar main gas flow emerges from the gas inlet element 6, which may or may not contain a dopant. The gas flow flows through the process chamber 4 such that a SiC layer is deposited on the substrate 9. A further gas flow influencing the dopant concentration is fed into the process chamber through the gas outlet surface of an additional gas outlet opening 10. In the embodiment shown in Figure 10, the gas outlet opening 10 can be at a distance α from the center line 11, so that the flow line 14 extending parallel to the center line 11 runs over one of the two halves of the substrate 9.

[0044] The embodiment shown in Figure 18 corresponds essentially to the embodiment shown in Figure 9. The gas source 23 can contain N2. A gas source 23′ can contain ammonia. 31039N1PCT – 4.12.2023 Mass flow controllers 20 are adjusted such that ammonia flows through the uppermost gas inlet zone through the gas inlet element 6 into the process chamber 4. Ammonia creates a bell-shaped dopant profile in a SiC layer deposited on a substrate 9 resting on a rotating substrate holder 8, sloping toward the edge, as shown by line C in Figure 6.

[0045] N2 is fed into the bottom of the process chamber 4 through the supply line 18, so that it exits the gas outlet opening 10. Ammonia creates a trough-shaped dopant profile that rises toward the edge, as shown by curve A in Figure 6. By appropriately selecting the settings of the mass flow controller 20—i.e., a suitable ratio of the mass flows of N2 and ammonia—a nearly flat dopant profile can be created in the SiC layer deposited on the substrate 9.

[0046] In the embodiment shown in Figure 11, the gas outlet opening 10 is located on the center line 11.

[0047] In the embodiment shown in Figure 12, two gas outlet openings 10, 10' are provided, wherein one gas outlet opening 10 is arranged on the center line 14 and a second gas outlet opening 10' is arranged offset from the center line 14.

[0048] In the embodiment shown in Figure 13, three gas outlet openings 10, 10', 10'' are provided, which, as in the embodiment shown in Figure 12, lie on a line that runs transversely to the flow direction S. The flow lines 14', 14'' running through the gas outlet openings 10', 10'' can extend over the edge 9' of the substrate 9. 31039N1PCT – 4.12.2023

[0049] Here, too, the dopant concentration within the layer can be locally influenced by a targeted selection of the gas influencing the dopant concentration and its mass flow or ratio to a mass flow of a gas influencing the dopant concentration entering through the gas inlet element, wherein the effects of the individual second gas flows with regard to the position of the gas outlet opening 10, 10', 10'' relative to the center line 11 and the quality of the gas are shown in Figures 6 and 7. If several gas outlet openings 10, 10', 10'' are provided, they do not need to run on an exact line transverse to the flow direction S. They can also each have a different distance from the gas inlet element 6, so that the gas flows flowing from the gas outlet openings 10, 10', 10'' are fanned out in a different way at their points of action on the substrate 9.

[0050] The embodiment illustrated in Figure 14 shows a plate 25' that is movable transversely to the flow direction S and that has the gas outlet opening 10. By moving the plate 25, the distance of the flow line 14 from the center line 11 can be individually adjusted.

[0051] Figure 15 shows a tenth embodiment of the invention, wherein a gas outlet opening 10, 10' is arranged on each of two flow lines 14, 14', both of which extend over the surface of the substrate 9, upstream of the substrate 9. The gas outlet opening 10' has a larger diameter than the gas outlet opening 10.

[0052] The eleventh embodiment shown in Figure 16 shows a gas outlet opening 10 that is offset by an angle α of approximately 8 to 10 degrees from the center line 11. The substrate 9 here has a diameter B2 such that the 31039N1PCT – 4.12.2023 Tangents enclose an angle of 70 degrees. With such an arrangement, it is advantageous if the angle α is between 5 and 10 degrees. Preferably, the angle can be 8.5 degrees. Reference numeral 25 represents a ring having a plurality of gas outlet openings 10. The angle α can be adjusted by rotating the ring 25 around the center 13.

[0053] Figure 17 shows the influence of the angle α on the dopant concentration C, which is removed along the radius R of a substrate 9. Zones Z1, Z2, Z3, which are also shown in Figure 16, can be defined in which the dopant incorporation can be specifically influenced. Zone Z1 extends, for example, from the edge 9' of the substrate into a first region of one half of the substrate. Zone Z2 extends over an angular range that runs centrally over one half of the substrate 9. Zone Z3 extends adjacent to this beyond the center of the substrate. The maximum influence on the dopant incorporation lies in zone Z2, which extends over an area that is between 30 mm and 60 mm from the center point 12.

[0054] The minima or maxima of curve A can be specifically neutralized. With the inventive arrangement and size of the gas outlet area of ​​the gas outlet opening, the gas stream exiting the gas outlet opening, which contains a gas that influences the dopant concentration, can be specifically influenced to influence the dopant incorporation in a zone that lies between the center of the substrate and the edge of the substrate.

[0055] The exemplary embodiment describes the local influencing of the dopant incorporation. However, the invention also encompasses methods with which ternary or quaternary semiconductor layers are deposited, wherein the layer composition is locally influenced by the second gas flow. 31039N1PCT – 4.12.2023 In this case, no dopant is fed into the process chamber through the gas outlet opening 10, 10', 10'', but rather one of the starting materials that form the crystal. Such a material system can be the GaInAsP material system.

[0056] The above statements serve to explain the inventions covered by the application as a whole, which each independently develop the state of the art at least by the following combinations of features, whereby two, several or all of these combinations of features can also be combined, namely:

[0057] A method which is characterized in that the width B1 of the gas outlet opening 10, 10', 10'' running transversely to the flow direction S is smaller than the width B2 of the substrate 9 running transversely to the flow direction.

[0058] A method which is characterized in that a flow line 14 running through the gas outlet opening 10, 10', 10'' along the flow direction S is offset by an angle α or by a distance a from a center line 11 running in the flow direction S through the center 12 of the substrate 9.

[0059] A method characterized in that the flow line 14 runs between the center point 12 and the edge 9' of the substrate 9 over the substrate 9, or that the flow line 14 runs past the substrate 9 outside the edge 9' of the substrate 9, or that the flow line 14 runs through a gap between two adjacent substrates 9. 31039N1PCT – 4.12.2023

[0060] A method which is characterized in that the width B1 of the gas outlet opening 10, 10', 10'' running transversely to the flow direction S is smaller than half, one third, one quarter, one fifth or one sixth of the width B2 of the substrate 9 running transversely to the flow direction S.

[0061] A method characterized in that the substrate 9 lies on a substrate holder 8 which is driven in rotation about a rotation axis 8' and / or that the substrate 9 is carried by a susceptor 2 which is brought to a process temperature by a heating device 5 and / or that the gas inlet element 6 forms the center 13 of the susceptor 2 and generates a first gas flow flowing in the radial direction relative to the center 13.

[0062] A method characterized in that the first gas flow flows through the process chamber 4 along parallel or star-shaped flow lines.

[0063] A method characterized in that the first gas flow fed through the gas inlet element 6 contains at least one carbon-containing and silicon-containing gas for depositing a SiC layer and that a carbon-containing or a nitrogen-containing gas flows into the process chamber 4 through the gas outlet opening 10, 10', 10''.

[0064] A method which is characterized in that a plurality of gas outlet openings 10, 10', 10'' are arranged in the flow direction S between the gas inlet element 6 and the substrate 9.

[0065] A device characterized in that the gas outlet opening 10 is connected to a source 23, 21 of the layer composition or 31039N1PCT – 4.12.2023 the dopant concentration within the layer influencing gas.

[0066] A device characterized by a control device 24 having a control program that controls the device according to one of claims 1 to 8.

[0067] 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 characterize, even without the features of a referenced claim, 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 specified in the above description, in particular provided with reference numbers and / or specified 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 to the extent that they are clearly dispensable for the respective intended use or can be replaced by other technically equivalent means. 31039N1PCT – December 4, 2023. List of reference symbols 1 Housing 2 Susceptor d Line through the center point 2' Edge 12 3 Process chamber ceiling B1 Width of the gas outlet opening 4 Process chamber 10, 10', 10'' 5 Heating device B2 Width (diameter) of the substrate 6 Gas inlet device 9 7 Gas outlet device S Flow direction 8 Substrate holder A Dopant concentration 8' Axis of rotation B, B', C, C', D, D' Dopant concentration 9 Substrate concentration 9' Edge S Flow direction of the first gas flow 10 Gas outlet opening 10' Gas outlet opening 10'' Gas outlet opening 11 Center line 12 Center point 13 Center 14, 14', 14'' Flow line 15, 16, 17, 18, 19 Supply line 20 Mass flow controller 21 Gas source, carbon 22 Gas source, silicon 23 Gas source, nitrogen 24 Control device 25 Ring 25' Plate 31039N1PCT – 4.12.2023

Claims

Claims 1.A method for depositing a layer on a substrate (9), wherein a homogeneous first gas flow is fed into a process chamber (4) brought to a process temperature by means of a gas inlet element (6), which gas flow flows in a flow direction (S) over the substrate (9) and contains one or more reactive gases, the decomposition products of which form the layer, wherein a second gas flow is fed into the process chamber (4) through a gas outlet surface of a gas outlet opening (10, 10', 10'') arranged downstream of the gas inlet element (6) and upstream of the substrate (9), which second gas flow contains at least one reactive gas influencing at least the composition of the layer or a dopant concentration within the layer, characterized in that the width (B1) of the gas outlet opening (10, 10', 10'') running transversely to the flow direction (S) is smaller than the width (B2) of the substrate (9) running transversely to the flow direction.

2. The method according to claim 1, characterized in that a flow line (14) running through the gas outlet opening (10, 10', 10'') along the flow direction (S) is offset by an angle (α) or by a distance (a) from a center line (11) running through the center point (12) of the substrate (9) in the flow direction (S).

3. The method according to claim 2, characterized in that the flow line (14) runs over the substrate (9) between the center point (12) and the edge (9') of the substrate (9), or that the flow line (14) runs past the substrate (9) outside the edge (9') of the substrate (9), or that the flow line (14) runs through a gap between two adjacently arranged substrates (9). 31039N1PCT – 4.12.2023.

4. The method according to claim 1, characterized in that the width (B1) of the gas outlet opening (10, 10', 10'') running transversely to the flow direction (S) is smaller than half, one-third, one-quarter, one-fifth, or one-sixth of the width (B2) of the substrate (9) running transversely to the flow direction (S).

5. The method according to claim 1, characterized in that the substrate (9) lies on a substrate holder (8) which is driven in rotation about an axis of rotation (8').

6. The method according to claim 1, characterized in that the substrate (9) is carried by a susceptor (2) which is brought to a process temperature by a heating device (5).

7. The method according to claim 1, characterized in that the gas inlet element (6) forms the center (13) of the susceptor (2) and generates a first gas flow flowing in the radial direction relative to the center (13). 8.The method according to claim 1, characterized in that the first gas flow flows through the process chamber (4) along parallel or star-shaped flow lines.

9. The method according to claim 1, characterized in that the first gas flow fed through the gas inlet element (6) contains at least one carbon-containing and silicon-containing gas for depositing an SiC layer, and that a carbon-containing or nitrogen-containing gas flows into the process chamber (4) through the gas outlet opening (10, 10', 10''). 31039N1PCT - December 4, 2023.

10. The method according to claim 1, characterized in that a plurality of gas outlet openings (10, 10', 10") are arranged in the flow direction (S) between the gas inlet element (6) and the substrate (9).

11. The method according to one of the preceding claims, characterized in that ammonia is fed into the process chamber (4) through the gas inlet element (6) and N2 is fed through the gas outlet opening (10).

12. Device for depositing a layer on a substrate (9), comprising a housing (1) in which a process chamber (4) is arranged, which has a susceptor (2), a gas inlet element (6) for feeding in a first process gas and a gas outlet element (7) for leading the process gas (1) out of the process chamber (4), wherein in a zone downstream of the gas inlet element (6) and upstream of the substrate holder (8) at least one gas outlet opening (10, 10', 10'') is arranged, which has a gas outlet surface,whose width (B1) extending transversely to a flow direction (S) of the first process gas through the process chamber (4) is smaller than the width of the substrate holder (8) or the substrate (9) extending transversely to the flow direction (S), and through which a further gas can be fed into the process chamber (4), characterized in that the gas outlet opening (10) is connected to a source (23, 21) of a gas influencing the layer composition or the dopant concentration within the layer.

13. Device according to claim 12, characterized by a control device (24) having a control program that controls the device according to one of claims 1 to 8.

14. Device or method characterized by one or more of the characterizing features of one of the preceding claims. 31039N1PCT - 4.12.2023,

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