A CVD reactor with a rising bottom in the pre-processing zone

Abstract

This invention relates to a CVD reactor having a gas inlet member (1) with cooling devices (12, 16, 17) and a gas outlet (14) leading into a process chamber (2). The process chamber (2) has a pre-processing zone (V) directly adjacent to the gas inlet member (1) and a processing zone (P) disposed after the pre-processing zone in the flow direction (S) of the process gas entering the process chamber (2) from the gas outlet (14). One or more mounting sites (4) for placing a substrate (6) are arranged in the processing zone. The pre-processing zone (V) has a first bottom section (10) directly adjacent to the gas inlet member (1) and a second bottom section (11) disposed between the first bottom section (10) and the processing zone (P). In order to prevent the formation of a parasitic coating at the beginning of the pre-processing zone during deposition of, for example, silicon carbide, this invention proposes that the first bottom section (10) rises in the flow direction (S) so that the height of the process chamber initially decreases from the gas inlet member.

Description

Technical Field

[0001] The present invention relates to a CVD reactor having a gas inlet member having a cooling device and a gas outlet for entering a process chamber, wherein the process chamber has a pre-processing zone directly adjacent to the gas inlet member and a processing zone disposed after the pre-processing zone in the flow direction of the process gas entering the process chamber from the gas outlets, and one or more substrate mounting positions are arranged in the processing zone, wherein the pre-processing zone has a first bottom section directly adjacent to the gas inlet member and a second bottom section disposed between the first bottom section and the processing zone.

[0002] The present invention further relates to a ring-shaped body that can be used in a CVD reactor. Prior Technology

[0003] DE 10 2014 104 218 A1 describes a similar CVD reactor. A process chamber is provided within an externally hermetically sealed shell, defined upwards by the bottom surface of the top of the process chamber and downwards by the top surface of a substrate. A process gas is introduced into the process chamber through a gas inlet member that can be arranged at the center of the process chamber. The process gas is preferably a Group IV hydride and / or chloride. However, the process gas may also be a Group V hydride and a Group III organometallic compound, or an element from Groups II and VI. The process gas is introduced into the process chamber by a carrier gas (e.g., hydrogen or nitrogen, or an inert gas) through the gas outlet of the gas inlet member. The gas inlet member is cooled by a coolant, particularly a liquid coolant, to prevent the process gas from decomposing or reacting with each other inside the gas inlet member. For this purpose, the gas outlet wall of the gas inlet member may be provided with a cooling channel for the coolant. The lower section of the gas inlet member may have a coolant distribution chamber for distributing coolant into the cooling channel. The lower section of the gas inlet member may be embedded in a recess in the substrate holder. The recess may also be surrounded by an annular object or formed by an annular element. The annular object or annular element forms a first bottom section of the pretreatment area, and a second bottom section of the pretreatment area is disposed after the first bottom section in the direction in which the process gas flows through the process chamber. The second bottom section is adjacent to the process section in which the substrate to be coated is located. The substrate holder, made of graphite or other conductive and / or thermally conductive material, is heated from below by a heating device. The substrate placed on the substrate carrier is heated to the process temperature by the heat provided by the heating device. A first heat flow is formed from the substrate holder through the process chamber to the top of the process chamber, and a second heat flow is formed from the process zone through the pretreatment area to the cooled gas inlet member. As is known in the prior art, appropriate measures are taken to influence the temperature of the pretreatment area to prevent the reaction products of the process gas from forming a parasitic coating there. Summary of the Invention

[0004] The purpose of this invention is to provide measures that can reduce the formation of parasitic cladding in the upstream region of the pre-treatment area.

[0005] This objective is achieved by the invention defined in the scope of the patent application, wherein the appendix is ​​not only an advantageous improvement to the solution provided in claim 1, but also an independent solution that can achieve this objective.

[0006] In the aforementioned prior art CVD reactor, the section of the gas inlet member having a coolant chamber extends into a recess, which forms a stepped edge. The bottom of the process chamber extends at the same level from the radially innermost region directly adjacent to the gas inlet member into the process area, such that the process chamber height has the same value throughout the entire process chamber.

[0007] According to the invention, the bottom of the process chamber should not have a uniform level in the first bottom section directly adjacent to the gas inlet member, but should rise along the flow direction, particularly from the first level to the second level, such that within the region of the first section, the height of the process chamber decreases with increasing distance from the gas inlet member. The first level can be defined by the height of the plane or step of the bottom of the recess or the lower end face of the gas inlet member. The second level can be defined by the following level: the surface of the substrate seat facing the process chamber, the surface of the cover plate placed on the substrate seat, or the surface of the substrate to be coated extends in this level. In particular, the pre-positioning area extends from the gas inlet member to the mounting position for accommodating the substrate. Therefore, the length of the pre-positioning area can be defined by the distance from at least one mounting position to the gas inlet member. The extension length of the first bottom section rising along the flow direction can be defined by the distance between the starting point of the second level and the gas inlet member. The first bottom section rising along the flow direction can be joined to the second bottom section with the formation of a connecting edge. However, the first bottom section can also be joined smoothly to the second bottom section. The first bottom section can be hollow or spherical. However, the first bottom section can also rise in a stepped manner. Preferably, this bottom section extends smoothly to prevent the process gas flowing above it from forming vortices. In embodiments of the invention, the first bottom section extends in a straight line. The first bottom section can rise linearly from the gas inlet member to the connecting area, such as the connecting edge. If the gas inlet member is located at the center of the process chamber, the first bottom section can be formed by a conical surface surrounding the gas inlet member. In some embodiments of the invention, the first bottom section extends within a range of at least 10%, at least 20%, or 30% + / - 5% of the length of the pre-treatment zone. With the design of the present invention, the area of ​​the first bottom section directly adjacent to the gas inlet member can be cooled less than in the case where the bottom of the process chamber and the bottom of the recess are stepped. Therefore, the beveling treatment of the first bottom section in the present invention reduces the coverage of decomposition products on the first bottom section. The edge of the gas inlet component, particularly extending along an arc, may be separated from the first bottom segment, particularly the inclined first bottom segment, by a certain distance. This edge is defined by a corner angle, at which a preferably cylindrical gas outlet wall abuts the lower end face of the gas inlet component. This edge may be spatially spaced from the edge of the step defining the starting point of the first bottom segment. This distance is the minimum distance between the first bottom segment and the gas inlet component. In a cross-sectional view, the point where the step connects to the first bottom segment may be located below the level defined by the lower end face of the gas inlet component. The first bottom segment rises continuously with increasing distance from the gas inlet component until it reaches its maximum height. This height preferably corresponds to the level where the substrate is mounted. This level is located above the lower end face of the gas inlet component. The angle between the inclined first bottom segment and the second bottom segment it connects to along the flow direction may be between 5 degrees and 20 degrees, preferably between 10 degrees and 25 degrees or between 15 degrees and 20 degrees.

[0008] The bottom surface of the top of the process chamber can extend straight in a plane. This plane can extend parallel to the bottom of the process area of ​​the process chamber and be spaced apart from it by a certain distance. The bottom surface of the top of the process chamber can also extend parallel to the second bottom section radially outward of the pre-processing area. The second bottom section of the pre-processing area can extend at the same level as the bottom of the process chamber in the process area. In these sections of the process chamber, the process chamber has a constant height. In the area of ​​the pre-processing area, particularly in the region of the first bottom section extending at an angle, the height of the process chamber increases continuously or gradually toward the gas inlet member. Therefore, in the flow direction, the height of the process chamber decreases continuously or gradually along the extension length of the first bottom section. The gas inlet member is preferably arranged at the center of a substrate seat that can rotate relative to the gas inlet member. The bottom of the recess can be spaced apart from the bottom surface of the gas inlet member by a certain distance, thereby allowing the substrate seat to rotate freely relative to the gas inlet member. The first bottom section can form an annular surface extending around the gas inlet member, the annular surface extending in a conical shape. The first bottom section can be formed by an annular element placed on the base of the substrate seat. The substrate holder can be supported by a rotatable shaft. A first bottom section can also be formed by a traction disc, by which the substrate holder is fixed to the shaft. This traction disc can be disc-shaped. The traction disc can form a central recess into which a gas inlet member can extend. The edge of the recess forms the first bottom section and can be radially outwardly inclined upward. The first bottom section can connect with a second bottom section extending in a plane. An annular element or a disc-shaped central element can be surrounded by a cover element that covers the radial outer edge of the annular element or the surface of the substrate holder's base extending between the disc-shaped central element and the substrate holder. The substrate holder can be arranged in a recess in the substrate holder or the cover element. A gas outlet can be introduced into the bottom of the recess, from which flushing gas can be discharged to keep the substrate holder suspended or to drive the substrate holder to rotate about its figure axis.

[0009] The gas inlet component can be made of metal, ceramic, quartz, or other suitable materials. The gas inlet component can form a cylindrical gas outlet wall. Several stacked exhaust zones can be provided, each connected to the process chamber surrounding the gas inlet component via a gas outlet on the gas outlet wall, allowing different process gases to enter the process chamber from different exhaust zones at different heights. Coolant channels can be distributed within the gas outlet wall to cool it. A coolant chamber can be provided in the lower region, preferably fully embedded in the recess, for distributing liquid coolant supplied via a delivery line to the cooling channels. The coolant chamber can have an upper wall extending parallel to the bottom of the gas inlet component, separating the coolant chamber from the gas inlet directly above. The partition wall separating the coolant chamber from the gas inlet directly above can be at the same level as the extension level of the second bottom section or the bottom of the process area. The bottom surface of the coolant chamber, the lower wall of the gas inlet component, or the bottom of the recess can define another level. In the first bottom section, the bottom of the process chamber extends upward from the lowest of the two levels to the highest of the two levels. This increases the distance between the lower region of the outer wall of the gas inlet member (i.e., particularly the outer wall of the coolant chamber) and the surface of the first bottom section facing the process chamber.

[0010] The annular body of this invention can be used in the aforementioned CVD reactor. The inner diameter of the annular body is larger than the outer diameter of the gas inlet component. The outer diameter of the annular body is smaller than the inner diameter of the one-piece or multi-piece covering element surrounding the annular body. Preferably, the annular body is placed on a flat surface of the substrate. A hollow conical surface abuts the radial inner edge of the annular body. This hollow conical surface preferably originates from a radial inner wall extending on the inner cylindrical surface. The height of this wall is preferably less than 50% of the material thickness of the annular body. Between the radial inner edge and radial outer edge of the annular body, the hollow conical surface forming an inclined edge in the cross-sectional view connects to a flat surface extending parallel to the bottom surface of the annular body, forming a joint.

[0011] The present invention further relates to the use of such annular structures in CVD reactors to reduce parasitic coatings in the pretreatment zone. Simple Explanation of the Diagram

[0012] Embodiments of the present invention will now be described with reference to the accompanying drawings. Wherein: Figure 1 is a schematic cross-sectional view of the components of the defined process chamber 2 of the CVD reactor in the first embodiment. Figure 2 is a cross-sectional view taken along line II-II in Figure 1. Figure 3 is an enlarged view of part III in Figure 1. Figure 4 is a view similar to Figure 3 of the second embodiment. Implementation

[0013] The CVD reactor shown in the figure essentially corresponds to the CVD reactor disclosed in DE 10 2014 104 218 A1 or the CVD reactor disclosed in the documents cited in this application. Therefore, the contents of such documents are incorporated in their entirety into the disclosure of this application, particularly to include the features of those specifications within the scope of this application. Further embodiments not shown in the figure differ from the embodiments shown in the figure in the aspect ratio of the process chamber or the length ratio of the pre-processing area to the processing area.

[0014] The CVD reactor of the type according to the present invention has an airtight shell, particularly made of stainless steel, into which several gas supply lines extend, and the shell has at least one exhaust line. Process gases such as hydrides, halides, or organometallic compounds of Group IV elements can be fed through the gas supply lines (not shown). However, hydrides of Group III elements and organometallic compounds of Group V elements can also be fed into the gas inlet member 1. The gas inlet member has several stacked gas inlet regions 15, 15', 15'', into which the process gas is always fed along with the carrier gas. The gas inlet regions 15, 15', 15'' are surrounded by a gas outlet wall 13, which has gas outlets 14 through which the process gas flows into the process chamber 2 surrounding the gas inlet member. The process gas flows through the process chamber 2 in the flow direction S until it reaches the gas outlet member (not shown).

[0015] The gas inlet component 1 has a coolant passage 16 connected to a coolant chamber 12 in the lowest region of the gas inlet component 1. A boundary wall 24 below the coolant chamber 12 forms the lower end face of the gas inlet component 1. The coolant chamber 12 forms a coolant distributor to distribute coolant into the coolant passage 17 of the gas outlet wall 13. The liquid coolant flowing through the coolant passages 16 and 17 and the coolant chamber 12 cools the gas inlet component 1 to a temperature that prevents pre-decomposition of the process gas.

[0016] The base plate 18 of the substrate holder 3 is located below the gas inlet member 1. The base plate 18 is shown as a single piece in Figures 1 and 3. However, the base plate can also be multi-piece, and in particular, it has radially nested components. The substrate holder 3 extends around a center Z, which is located at the center of the gas inlet member 1.

[0017] The substrate holder 3 can be driven to rotate about its center Z. For this purpose, the substrate holder 3 can be supported by a shaft that can be driven to rotate about its axis.

[0018] In the central Z region, the substrate base 3, or the one-piece or multi-piece base plate 18, has a recess 9 including a recessed bottom 9'. The recessed bottom 9' is separated from the flat bottom surface or lower wall 24 of the gas inlet member 1 by a distance c.

[0019] Several nested annular bodies 19, 20 are located on the area of ​​the substrate 18 surrounding the gas inlet member. However, the gas inlet member 1 may also be surrounded by only one annular body. At least one annular body 19, 20 extends at a radial distance b around the gas inlet member 1. The radial distance b may be the length of the pre-treatment zone V measured in the flow direction S. The pre-treatment zone V extends at a distance between the gas inlet member 1 and one or more carriers 4 for placing the substrate 6 to be coated. The carriers 4 may be formed by substrate holders 5, which may be conventionally placed on an air cushion and may be rotated by airflow.

[0020] The inner annular body 19 can be a single-piece design, while the outer annular body 20 can be a single-piece or multi-piece design. The outer annular body 20 may have a radially inner dividing line extending along an arc. The radially outer dividing line may deviate from the arc shape and may, for example, at least partially include a groove for accommodating the substrate holder 5. However, it is also possible for the inner annular body 19 to be a multi-piece design, and in particular composed of elements of the same shape, which are arranged circumferentially around the gas inlet member 1.

[0021] The inner ring 19 may, for example, be adjacent to one or more cover elements 20, which in turn are adjacent to the carrier 4 or the substrate carrier 5 forming the carrier 4. Several substrate holders 5 are provided, arranged along a circumferential line around the center.

[0022] According to the invention, the process chamber 2 has a region 10 directly adjacent to the gas inlet member 1, which forms a first bottom section. The radial length a of the first bottom section is at least 10% of the radial length b of the pre-processing zone V. Preferably, the radial length a is at least 20% or at least 30% of the radial length of the pre-processing zone V. In a particularly preferred embodiment of the invention, the radial length is approximately 30% of the radial length of the pre-processing zone V. The surface of the first bottom section 10 may be tilted at an angle of 10 to 25 degrees relative to the horizontal plane. However, smaller or larger tilt angles may also be provided. A preferred tilt angle is 17.5 degrees.

[0023] The region 10 directly adjacent to the gas inlet member 1 differs from the radially outer region 11 of the bottom 3' of the process chamber in that the outer region 11 extends in a plane. The region 10 directly adjacent to the gas inlet member 1 rises along the flow direction S. In embodiments not shown, region 10 may rise in a stepped, hollow arched, or spherical arched shape. In an embodiment, the bottom of the process chamber 2 in the bottom section 10 region extends in cross-section along a line inclined to the plane of rotation of the substrate 3, which is preferably a straight line. Due to this inclined region, the height of the process chamber 2 has a first height H1 immediately adjacent to the gas inlet member 1, which is greater than the second height H2 of the process chamber 2 in the second bottom section 11 region adjacent to the first bottom section 10.

[0024] The bottom 9' of the recess can define a first level, which is further away from the contrast level defined by the extension of the bottom surface 7' of the top 7 of the process chamber than the second level of the bottom of the process chamber. The radially outer region of the pre-processing area V, or the process area P, extends in this second level. The second level can generally extend at the height of the partition wall 23 between the lowest gas inlet area 15 and the coolant chamber 12. The starting point of the rising region of the first bottom section 10 can be formed by a small step, with the bottom 9' of the recess connecting to the rising bottom section 10 via this small step. The angle of the inclined surface of the first bottom section 10 relative to the plane surrounding the first bottom section 10 formed by the second bottom section 11 is chosen such that vortices do not form at the connection edge 22 between the first bottom section 10 and the second bottom section 11. Therefore, the bottom section 10 preferably extends inclined to the second bottom section 11 so that laminar flow is formed on the bottom sections 10 and 11.

[0025] In the embodiment shown in Figure 3, the upward movement of the inclined first bottom section 10 begins at the level of the lower end face of the gas inlet member 1, i.e., generally within the region of the lower wall 24. The inclined bottom section 10 extends to a higher level, which is located below the partition wall 23, i.e., within the region of the coolant chamber 12. However, this level may also be located at the level of the partition wall 23 separating the coolant chamber 12 from the gas inlet region 15''. In a preferred embodiment, the annular body 19 is formed of the same material as the base 18 constructed as the traction plate 21. As shown in Figure 4, the outer section of the traction plate 21 can engage with the cover element 20 from below. The traction element is engaged at the center of the traction plate 21 and applies downward force to the traction plate 21 in the axial direction.

[0026] The apparatus of this invention is particularly suitable for depositing SiC, especially doped SiC. In this process, the pre-deposition zone V has a critical influence on the placement of the dopant. By increasing the distance, particularly the distance from the first bottom section 10 to the gas inlet member 1, the deposition of process gas decomposition products upstream of the process zone is effectively reduced. Although efforts are generally made to maintain a constant height of the process chamber throughout its entire extension when designing reactors, it has been surprisingly shown that reducing the height of the process chamber in the region directly adjacent to the gas inlet member 1 reduces gas phase depletion caused by pre-deposition.

[0027] The foregoing embodiments are used to illustrate the invention encompassed by this application as a whole. These inventions independently constitute improvements over prior art through at least the following combinations of features, wherein two, several, or all of these combinations of features can also be combined with each other, namely:

[0028] A CVD reactor, characterized in that: the first bottom section 10 rises along the flow direction S.

[0029] A CVD reactor, characterized in that: a first bottom section 10 rises from a first level to a second level along an extension length a and / or rises at an angle of 10 to 25 degrees, the extension length being at least 10%, at least 20%, or 30% + / - 5% of the length b of the pre-extension zone V; the bottom 9' of the recess 9 into which the gas inlet member 1 extends is located in the first level, or the lower wall 24 of the gas inlet member 1 is located in the first level; and a second bottom section 11 is located in the second level.

[0030] A CVD reactor, characterized in that: the flat bottom surface 7' of the top 7 of the process chamber has a first spacing height H1 to the starting point of the first bottom section 10 and a second spacing height H2 to the end point of the first bottom section or the starting point of the second bottom section 11 as viewed in the flow direction, and / or extends parallel to the top surface of the substrate carrier 5 facing the process chamber 2, and / or, along the extension length a of the first bottom section 10, as the distance from the gas inlet member 1 increases, the distance between the tops 7 of the process chamber continuously or gradually decreases from the first spacing height H1 to the second spacing height H2.

[0031] A CVD reactor is characterized in that: a gas inlet component 1 is arranged in the center Z of the process chamber 2, a plurality of substrate carriers 5 are arranged in a ring around the gas inlet component 1 in the process zone P, and a first bottom section 10 forms an annular surface surrounding the gas inlet component 1.

[0032] A CVD reactor, characterized in that: the surface of the first bottom section 10 facing the process chamber 2 is smoothly extended and / or is smoothly extended except for a single connecting edge 22.

[0033] A CVD reactor is characterized in that: a first bottom section 10 is formed by an inner ring 19 arranged around a gas inlet member 1, the inner ring being placed on a base 18 of a substrate 3, and / or, the inner ring 19 forming the first bottom section 10 is surrounded by one or more covering elements 20 adjacent to a mounting position 4.

[0034] A CVD reactor, characterized in that: a first bottom section 10 is formed by a disc-shaped central element 21, the central element having a recess 9 formed of the same material, and a gas inlet member 1 extending into the recess.

[0035] A CVD reactor is characterized in that: a gas inlet member 1 has a plurality of stacked gas inlet regions 15, 15', each of which has a gas outlet 14 arranged on a cylindrical surface, and / or, the gas outlet 14 is arranged on a gas outlet wall 13 of the gas inlet member 1 having one or more coolant channels 17, and / or, a coolant chamber 12 is arranged below one or more gas inlet regions 15, 15', 15'' of the gas inlet member 1, wherein the section of the gas inlet member 1 with the coolant chamber 12 is completely or mostly arranged in a recess 9, and / or, the difference between the second level and the first level is greater than the height of the coolant chamber 12 measured in the axial direction relative to the center Z of the process chamber 2.

[0036] A CVD reactor, characterized in that: a substrate holder 3 can be driven to rotate about a center Z, and / or, a disc-shaped substrate carrier 5 can be driven to rotate about its respective center Z.

[0037] A ring-shaped body is characterized in that: a surface segment 10 extending on a hollow conical surface is adjacent to the radial inner edge of the ring-shaped body 19, and the surface segment, when forming a connecting portion 22, is connected to a straight surface 11 extending to the radial outer edge of the ring-shaped body 19.

[0038] A ring-shaped body, characterized in that: the connecting portion 22 is a connecting edge, the distance between the connecting edge and the radial inner edge of the ring-shaped body 19 is equivalent to 40% to 60% of the width of the ring-shaped body 19, and / or, the ring-shaped body 19 has a radial inner wall 25 extending on the inner cylindrical surface, the height of the radial inner wall being less than 50% of the distance between the flat surface 11 and the flat bottom surface 26 of the ring-shaped body 19.

[0039] All disclosed features (as individual features or combinations thereof) are essential to the invention. Therefore, the disclosure of this application also includes all the contents disclosed in the relevant / attached priority files (copies of prior art), and the features described in those files are also included in the scope of this application. The appendices describe the features of the invention in relation to improvements in the prior art, and their purpose is primarily to establish divisional applications based on those claims. The invention defined in each claim may further have one or more of the features given in the foregoing description, particularly those indicated by symbols and / or given in the symbol description. The invention also relates to the following design form: individual features described in the foregoing description are not implemented, particularly features that are not essential for the specific use or can be replaced by other components that are technically equivalent in function.

[0040] 1: Gas inlet components 2: Process Room 3:Substrate base 3': Bottom of the process chamber 4: Load position 5: Substrate carrier 6:Substrate 7: Top of the process room 7': Bottom 8: Heating device 9: Depression 9': Bottom of the recessed area 10: First bottom segment 11: Second bottom segment 12: Coolant Chamber 13: Gas outlet wall 14: Gas outlet 15: Gas Inlet Area 15': Gas inlet area 15'': Gas inlet area 16: Coolant passage 17: Coolant passage 18: Matrix 19: Inner Ring 20: Covering element 21: Central Components 22: Connecting Edges 23: Partition wall 24:Lower wall 25: wall 26: Bottom H1: Process Chamber Height H2: Process Chamber Height P: Process Area S: Flow direction V: Front Area Z: Center a: Extension length of the first bottom segment b: Extension length of the front area c: Distance between the bottom of the recess and the bottom surface of the gas inlet component

Claims

1. A CVD reactor having a gas inlet component (1) having cooling devices (12, 16, 17) and a gas outlet (14) leading into a process chamber (2), wherein, The cooling device (12, 16, 17) includes a coolant chamber (12) separated from the gas inlet area (15”) directly above it by a partition wall (23). The lower partition wall (24) of the coolant chamber (12) forms the lower end face of the gas inlet member (1). A base plate (18) of a substrate (3) is located below the gas inlet member (1). The base plate (18) has a recess (9) including a bottom recess (9'), which is spaced apart from the lower partition wall (24). The bottom recess (9') defines a first horizontal level. The process chamber (2) has a front area (V) directly adjacent to the gas inlet member (1) and a process area (P) disposed after the front area in the flow direction (S) of the process gas entering the process chamber (2) from the gas outlet (14). One or more mounting positions (4) for placing substrates (6) are arranged in the process area. The front area (V) has a first bottom section (10) directly adjacent to the gas inlet member (1) and a second bottom section (11) disposed between the first bottom section (10) and the process area (P). The process area (P) defines a second level, which is generally located at the height of the partition wall (23) or below the partition wall (23). The first bottom section (10) rises along the flow direction (S).

2. The CVD reactor as described in Request 1, wherein, The first bottom segment (10) rises from a first level to a second level along its extension length (a) and / or rises at an angle of 10 to 25 degrees, the extension length being at least 10%, at least 20% or 30% + / - 5% of the length (b) of the front area (V).

3. The CVD reactor as described in request item 1, wherein, The flat bottom surface (7') of the top of the process chamber (7) has a first interval height (H1) to the starting point of the first bottom section (10) as viewed in the flow direction and a second interval height (H2) to the end point of the first bottom section or to the starting point of the second bottom section (11).

4. The CVD reactor as described in Request 1, wherein, The flat bottom surface (7') of the top of the process chamber (7) extends parallel to the top surface of the substrate carrier (5) facing the process chamber (2).

5. The CVD reactor as described in request item 3, wherein, Along the extension length (a) of the first bottom section (10), as the distance from the gas inlet member (1) increases, the distance between the tops (7) of the process chamber continuously or gradually decreases from the first interval height (H1) to the second interval height (H2).

6. The CVD reactor as described in Request 1, wherein, The gas inlet component (1) is arranged at the center (Z) of the process chamber (2), and several substrate carriers (5) are arranged in the process area (P) in a ring around the gas inlet component (1), and the first bottom section (10) forms an annular surface surrounding the gas inlet component (1).

7. The CVD reactor as described in Request 1, wherein, The surface of the first bottom segment (10) facing the process chamber (2) is smoothly extended and / or is smoothly extended except for a single connecting edge (22).

8. The CVD reactor as described in Request 1, wherein, The first bottom section (10) is formed by an inner ring (19) arranged around the gas inlet member (1), which is placed on the base (18) of the substrate seat (3).

9. The CVD reactor as described in Request 1, wherein, The inner ring (19) forming the first bottom segment (10) is surrounded by one or more covering elements (20) adjacent to the mounting position (4).

10. The CVD reactor as described in Request 1, wherein, The first bottom section (10) is formed by a disc-shaped central element (21), which has a recess (9) formed of the same material, into which the gas inlet member (1) extends.

11. The CVD reactor as described in Request 1, wherein, The gas inlet component (1) has several stacked gas inlet areas (15, 15'), each of which has a gas outlet (14) arranged on a cylindrical surface, or the gas outlets (14) are arranged on a gas outlet wall (13) of the gas inlet component (1) having one or more coolant channels (17), or the coolant chamber (12) is arranged below one or more gas inlet areas (15, 15', 15'') of the gas inlet component (1), wherein the section of the gas inlet component (1) in which the coolant chamber (12) is located is completely or mostly located in the recess (9), or the difference between the second level and the first level is greater than the height of the coolant chamber (12) measured in the axial direction relative to the center (Z) of the process chamber (2).

12. The CVD reactor as described in request item 6, wherein, The substrate holder (3) can be driven to rotate about the center (Z), and / or the disk-shaped substrate carriers (5) can be driven to rotate about their respective centers (Z).

13. An annular body (19) for use in any of claims 1 to 12 of a CVD reactor, wherein the inner diameter of the annular body (19) is greater than the outer diameter of the gas inlet member (1), the outer diameter of the annular body is smaller than the inner diameter of a one-piece or multi-piece covering element (20), and the annular body can be placed on a section of a base (18) surrounding the gas inlet member (1), characterized in that a surface section (10) extending on a hollow conical surface is adjacent to the radial inner edge of the annular body (19), and the surface section, in the case of forming a connecting portion (22), is connected to a second bottom section (11) extending to the radial outer edge of the annular body (19).

14. A toroidal body as described in claim 13, wherein, The connecting part (22) is a connecting edge, and the distance between the connecting edge and the radial inner edge of the annular body (19) is equivalent to 40% to 60% of the width of the annular body (19).

15. A toroidal body as described in claim 13, wherein, The annular body (19) has a radial inner wall (25) extending on the inner cylindrical surface, the height of which is less than 50% of the distance between the second bottom segment (11) and the flat bottom surface (26) of the annular body (19).

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