Angular speed measurement system for substrates used in epitaxial deposition reactors

Abstract

To provide a method for accurately measuring and controlling angular speed of a substrate in an epitaxial reactor for semiconductor film deposition and an assembly suitable to execute the method.SOLUTION: The present invention discloses a method for measuring and controlling angular speed of a substrate in an epitaxial reactor for semiconductor film deposition. The present invention further discloses an assembly suitable to execute the method, as well as a reaction chamber and a reactor comprising the assembly. In particular, though not exclusively, the above assembly, reaction chamber, and method may be used in a hot-wall, crossflow reactor for epitaxial deposition of silicon, silicon carbide, or gallium nitride.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the field of epitaxial deposition of semiconductor films on substrates, and in particular to a method for measuring and controlling the rotation speed of a substrate in a reaction chamber of an epitaxial deposition reactor, as well as an assembly suitable for carrying out said method. [Background technology]

[0002] Semiconductor films made by epitaxial growth, also known as epilayers, are formed by deposition in a reaction chamber of a reactor. The deposited material may be the same as the substrate or may contain a different semiconductor with certain desired qualities. Epitaxial techniques control the crystal structure formed on the substrate and improve the characteristics of the epilayer surface, making it suitable for the fabrication of highly complex microprocessors and memory devices.

[0003] To ensure the uniformity of the epilayer deposited in the reaction chamber, both in terms of thickness and doping concentration, the semiconductor substrate is placed on a support system that rotates during film deposition. It is important that the rotation speed of the substrate is predetermined and constant during the deposition process to reduce both thickness deviation and non-uniformity of the doping concentration.

[0004] In hot-wall reaction chambers, where the walls are actively heated and temperatures can reach 1800° C., controlling the rotational speed of the substrate support system becomes a particularly challenging task due to the high temperature of the reaction chamber in which the rotating substrate is located.

[0005] Indeed, hot-wall reaction chambers can be used, for example, for epitaxial deposition of silicon (Si), silicon carbide (SiC), or gallium nitride (GaN) on substrates made of the same or different materials. In the non-limiting examples above, the chambers typically operate at temperatures of 800-1800° C. depending on the chemistry.

[0006] The available techniques for measuring and controlling the rotational speed of a support system are influenced by its actuation mechanism.

[0007] For example, the substrate support system may be set in rotation via mechanical actuation means that allow precise control of its rotational speed, however this solution adversely affects the manufacturing, maintenance and assembly operations of the reactor due to the number of interconnected mechanical parts involved and their arrangement, and increases the overall complexity of the system.

[0008] Alternatively, the substrate support system may be set to rotate via a gas flow, typically an inert gas, which lifts and engages the device and allows its unhindered rotation in the reaction chamber. To this effect, the bottom surface of the support system may be provided with a set of grooves extending towards its outer edge and / or spiraling out, as described in WO2007010568, WO2004053188A1, WO2004053189A1, WO2005121417A1. The grooves provide a preferential path flow for the inert gas. As a result, the support system experiences a torque that causes it to rotate.

[0009] The gas flow rate and velocity may be read and controlled via a suitable gas flow control device (GFCD), such as a mass flow controller (MFC), but these values ​​do not clearly correlate with the rotational speed of the support system. Therefore, this quantity cannot be used to determine rounds per minute (rpm) with the required precision, as it is also affected by other factors (such as the placement of the support system and / or sediment buildup).

[0010] US Patent Application Publication No. 2022411961 describes an apparatus and method for measuring and adjusting the angular velocity of a support system in a hot-wall reactor, the system comprising a disk-shaped element set in rotation via an argon gas flow. The disk-shaped element comprises a shaft extending below the base of the reaction chamber and features a protrusion whose rotation is adapted to be detected by a pyrometer or a thermographic camera. This method for measuring the rotation speed has proven to be accurate and allows maintaining a constant rotation speed with a variation of less than 1 rpm. However, the presence and arrangement of the shaft and other structural elements described in the cited art may hinder maintenance operations and increase the downtime of the reactor.

[0011] It would therefore be desirable to provide a system that allows for accurate measurement and control of the angular velocity of a substrate inside a hot-wall reaction chamber of an epitaxial reactor without substantially interfering with maintenance operations and ensuring uniformity of film deposition. Summary of the Invention

[0012] The object of the present invention is to overcome the drawbacks of the prior art. In particular, it is an object of the present invention to provide a method for accurate measurement and control of the angular velocity of a substrate in an epitaxial reactor for semiconductor film deposition and an assembly suitable for carrying out said method. A further object of the present invention is to provide an assembly and method that ensures uniformity of film deposition (particularly, but not exclusively, inside the hot-wall reaction chamber of an epitaxial reactor) without substantially interfering with maintenance operations of the reactor.

[0013] The above main objects of the present specification are achieved through the invention as recited in the appended claims, which form an integral part of this specification.

[0014] This Summary is provided to introduce selected concepts in a simplified form. These concepts are described in more detail in the Detailed Description of Example Embodiments of the Disclosure below. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 provides a schematic diagram of a hot wall reactor. [Diagram 2] FIG. 2 shows a detail of the lifting element in panel (a) and a portion of the base of the reaction chamber of an assembly according to the invention in panel (b). [Diagram 3] FIG. 3 illustrates a support system according to one embodiment of the present invention.

[0016] It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale, for example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of the illustrated embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Although certain specific embodiments and examples are disclosed below, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments and / or uses of the invention, and obvious modifications and equivalents thereof, and therefore it is not intended that the scope of the disclosed invention should be limited by the specific disclosed embodiments described below.

[0018] In one aspect, the invention relates to an assembly for a reactor suitable for epitaxial deposition of semiconductor films, the assembly comprising a reaction chamber having a base provided with a receiving area characterized by a plurality of gas outlets, the outlets being connected to at least one gas conduit suitable for delivering a gas flow into the interior of the reaction chamber when the assembly is in use.

[0019] The assembly further comprises a support system accommodated in the aforementioned receiving area and suitable for supporting a substrate to be subjected to epitaxial deposition, the support system being rotatable about an axis of rotation and comprising a lifting element.

[0020] The lifting element has a bottom surface facing the receiving area and a top surface opposite the bottom surface. It may support at least one substrate for epitaxial deposition on its top surface. The substrate may be disposed directly on the top surface of the lifting element or on other additional components disposed therebetween, as discussed further below.

[0021] As used herein, the term "substrate" may refer to any underlying material or materials, including any underlying material or materials, on which a device, circuit, or film may be formed, that may be modified or on which a device, circuit, or film may be formed. A "substrate" may be continuous or non-continuous, rigid or flexible, solid or porous, and combinations thereof. A substrate may be in any form, such as a powder, a plate, or a workpiece. Substrates in the form of plates may include wafers of various shapes and sizes. Substrates may be made of semiconductor materials, including, for example, silicon, silicon germanium, silicon oxide, gallium arsenide, gallium nitride, and silicon carbide.

[0022] The lifting element is adapted to receive a gas flow from a gas outlet on its bottom surface. The gas flow causes the lifting element to (1) lift the support system from the receiving area and / or (2) rotate about an axis of rotation perpendicular to the base of the reaction chamber. The first effect is achieved via the pressure exerted by the gas flow on the bottom surface. The second effect is obtained by the interaction of the gas flow with at least two grooves or ridges located on the bottom surface of the lifting element. The grooves or ridges are designed to provide a preferential path for the gas flow and to induce continuous rotation of the support system by exerting a small torque thereon.

[0023] The assembly according to the invention further comprises at least one pressure sensor adapted to measure and record the variations in the pressure signal in the gas conduit as the lifting element rotates. The pressure sensor may be located outside the reaction chamber, which is advantageous for reducing the complexity of maintenance operations and manufacturing.

[0024] The assembly may further include at least one GFCD, such as an MFC, that can be used to measure and maintain a substantially constant gas flow in the gas conduit.

[0025] Those skilled in the art will appreciate how the assembly according to the invention makes it possible to accurately calculate and control the rotation speed of the substrate in the reaction chamber, thereby ensuring uniform epitaxial deposition. Compared to the prior art, this objective is achieved by reducing the number of mechanical elements connected to the support system, thereby facilitating maintenance operations. Furthermore, the speed measurement and control operations may be performed outside the reaction chamber, thereby increasing the reliability of the entire assembly. This is particularly important in hot-wall reactors, such as those designed for Si, SiC, and GaN deposition, which present a unique set of challenges due to the extremely high temperatures that reach inside the reaction chamber.

[0026] Indeed, assuming an approximately constant gas flow rate in the gas conduit, the change in flow resistance is mainly associated with the pressure change in the gas conduit. When the lifting element rotates during deposition, the resistance to gas flow presented by the bottom surface of the lifting element depends on the mutual positioning of the gas outlet and the grooves / ridges formed on the bottom surface.

[0027] In particular, as the lifting element rotates, when the receding surface is closer to (or aligned with) the gas outlet, gas flow resistance within the gas conduit is reduced, whereas when the protruding surface approaches (or is aligned with) the gas outlet, gas flow resistance increases.

[0028] Thus, in the case of constant rotation of the lifting element, the pressure inside the gas conduit varies in an essentially periodic manner and can be inferred by monitoring the pattern and duration of the fluctuations of the pressure signal inside the gas conduit relative to the rotational speed of the lifting element (which correlates with the angular velocity of the support system and, consequently, the pattern and duration of the one or more substrates contained therein), by using a pressure sensor located outside the reaction chamber, by using a pressure sensor located outside the reaction chamber, by using a pressure sensor located outside the reaction chamber,

[0029] Typically, the GFCD is also placed outside the reaction chamber and further upstream of the pressure sensor with respect to the gas flow direction. To prevent the positioning of the GFCD from affecting the pressure signal measured by the pressure sensor, such as the intensity of the fluctuations of the pressure signal, an orifice may be placed on the gas line to locally reduce its cross section. The orifice should be located between the GFCD and the pressure sensor, preferably closer to the latter. As a result, the signal fluctuations measured by the pressure sensor are mainly driven by the changes in flow resistance occurring downstream of the orifice in the gas conduit connected to the gas outlet as a result of the interaction between the gas flow and the bottom surface of the lifting element.

[0030] It should be noted that the substrate or substrates may be placed in a suitably designed recess on the upper surface of the lifting element. Alternatively, they may be placed on a substrate holder located on the upper surface of the lifting element. The holder may be integral with the lifting element or may be connected or connectable to the lifting element. The substrate holder may advantageously be a removable part that allows the transfer of substrates in and out of the reaction chamber without direct contact, thereby maintaining their integrity and facilitating an automated process.

[0031] The lifting element and substrate holder preferably have a disk-like shape, with their centres approximately coinciding with the axis of rotation of the support system when the assembly is in use.

[0032] The substrate holder may advantageously be designed with suitable annular ridges and protrusions to avoid extensive planar contact with the substrate, which may prevent mechanical instability due to loss of adhesion with the substrate holder if the substrate bends / flexes towards its center during deposition.

[0033] Additionally, an annular ledge may be placed on top of the substrate holder to cradle the substrate and prevent it from displacing. Alternatively, the annular ledge may be used to elevate the substrate relative to the substrate holder or clamp it onto it.

[0034] The lifting elements, as well as the optional substrate holder and optional annular ledge, may advantageously be made of one or more materials having high sensitivity, such as graphite, to efficiently reach temperatures of up to 1800° C. when subjected to an appropriate electromagnetic field. The same materials may also be advantageously used for the walls of the reaction chamber (including the base) and other suitable elements of the reactor to achieve the same effect.

[0035] Some or all parts of the reaction chamber, such as those corresponding to or above the receiving area, may be optionally coated with a TaC layer to protect the graphite surface during cleaning. Other coatings (such as thin layers of SiC) may be used to achieve the same or different purposes, for example to prevent accumulation of deposits or to seal the porous graphite surface to avoid contamination. For example, the lifting elements and support holders may be advantageously provided with a TaC coating, while the annular ledge may be coated with a SiC layer.

[0036] It is noted that for the gas flow in the assembly according to the invention, it is desirable to use an inert gas such as nitrogen, argon, neon, helium, xenon, or a combination thereof. Alternatively, hydrogen may be used. To reach multiple gas outlets, the gas flow coming from the gas conduit may be split into multiple gas channels. The lifting element may rotate more efficiently if one or more channels reach the base at an angle α<90°, preferably α<80°. A similar approach may be used when multiple gas conduits are used to reach multiple gas outlets, by having at least one of the individual conduits impinge on the base at an angle α<90°, preferably α<80°. Additional outlets or conduits impinging at the same or different angles may be used to lift the lifting element more efficiently without departing from the scope of the invention.

[0037] According to one embodiment, each groove or ridge of the lifting element is a continuous segment connecting an inner end and an outer end, the outer end extending outward (linearly, arcuately, or spirally) towards the outer circumference of the lifting element. The inner end is thus positioned closer to the axis of rotation of the support system relative to the outer end. This design helps to direct the flow from the gas outlet so that the lifting element rotates more efficiently. The grooves or ridges may all be of the same length or different lengths.

[0038] According to one embodiment, in the assembly according to the invention, the bottom surface of the lifting element is provided with several N grooves, which may advantageously differ in shape and arrangement from the grooves and ridges mentioned above. i The support system further comprises ≥ 2 indentations or protrusions, which may be disposed relative to one another such that at least two of the indentations or protrusions align with the location of the at least two gas outlets at least once during a 360° rotation of the support system about its axis, thereby generating a pulsation in the pressure signal that can be correlated to a rotational speed of the lifting element.

[0039] Advantageously, all indentations or protrusions may be made to align with the position of the entire plurality of gas outlets at least once during a 360° rotation, thereby maximizing the strength of the measured signal fluctuations.

[0040] It should be noted that the grooves / ridges of the support system have two main contributions: (i) they induce fluctuations in the pressure signal in the gas conduit as the gas flow leaves the multiple outlets, and (ii) they ensure a constant rotation of the lifting element upon reception of the gas flow. On the other hand, the main effect of the indentations / protrusions is to intensify the changes in the pressure signal in the gas conduit during operation. Thus, each indentation / protrusion may advantageously occupy a smaller area on the bottom surface of the lifting element relative to the individual grooves / ridges. Preferably, but not exclusively, the indentations / protrusions may present an area equal to 0.3 to 3 times the area of ​​the induced gas outlets on the reception area.

[0041] In general, the depth, thickness and size of the grooves, ridges, indentations or protrusions may be adapted by one skilled in the art based on the size, weight and nominal angular velocity of the lifting element, as well as the instrument sensitivity of the pressure sensor.

[0042] Using the same approach, we find the appropriate number of recesses or protrusions, N i and the number of grooves or ridges N g In most cases, N i and N gmay be less than or equal to 20 to avoid signal blurring. To ensure the stability of the lifting element during lifting and rotation, the number of outlets and the number of grooves / ridges is preferably greater than or equal to 3. The number of indentations / protrusions may also advantageously be greater than or equal to three and equal to the number of gas outlets.

[0043] In certain embodiments, the number of grooves or ridges N g may be an integer multiple of the number of gas outlets. In this case, amplification of the fluctuations in the pressure signal may occur. This effect may be further enhanced by optimizing the placement of the inner edge of one or more grooves or ridges so that the gas outlets are aligned or in close proximity to the gas outlets at least once during a 360° rotation of the support system when the assembly is in use. This is particularly useful when no recesses or protrusions are used. N g Note that if N is not an integer multiple of the number of gas outlets, the strength of the signal may be reduced, but the signal resolution may be increased.

[0044] In a further embodiment, in the assembly according to the invention, the distance of the recesses or protrusions from the axis of rotation of the support system does not exceed the distance of the inner end of each groove or ridge from the axis of rotation. This means that the recesses or protrusions are arranged in an area around the axis of rotation without grooves / ridges. Advantageously, if the gas outlet is positioned correspondingly to this surface, the lifting element can more easily raise the support system to ensure unhindered rotation.

[0045] In another embodiment, the assembly may further comprise (i) at least one GFCD for controlling gas flow in the one or more gas conduits, and (ii) at least one feedback loop circuit connecting the GFCD to the pressure sensor. The feedback loop circuit may be advantageously configured to adjust the gas flow via the GFCD based on real-time input of the pressure signal to maintain a constant rotational speed of the support system.

[0046] Alternatively, the above-described assembly may further include an electronic device programmed to convert fluctuations in the pressure signal into a rotational speed of the support system, in which case a feedback loop circuit connects the gas flow controller to the electronic device and is configured to adjust the gas flow through the GFCD based on real-time input of the rotational speed signal to maintain a constant speed.

[0047] In any of the above embodiments, the GFCD may be an MFC or any other device suitable for achieving the same effect.

[0048] In a second aspect, the present invention relates to a reaction chamber for a reactor (preferably, but not exclusively, a hot-wall, cross-flow reactor) suitable for epitaxial deposition of semiconductor films, comprising any embodiment of the assembly described above, as well as any combination or equivalent thereof.

[0049] In a third aspect, the present invention relates to a reactor comprising a reaction chamber as described above.

[0050] In a fourth aspect, the present invention relates to a method for controlling the rotational speed of the support system of the above-described assembly during operation, in order to maintain a constant rotational speed of a substrate supported therein.

[0051] The method is executed upon activation by a user and includes the following steps: (i) delivering a gas flow into at least one gas conduit via a GFCD; (ii) recording the pressure signal measured by the pressure sensor; (iii) converting the pressure signal via an electronic device to a real-time speed of the rotation of the support system and calculating the difference relative to a predetermined nominal value; (iv) adjusting the gas flow via the GFCD to minimize the difference between the converted real-time rotational speed of the support system and the predetermined nominal value; and (v) sequentially repeating steps (i)-(iv) until an interrupt signal is provided by the user.

[0052] In a fifth aspect, the invention relates to the use of a pressure sensor of the assembly described above for measuring and controlling the rotational speed of a support system contained therein. Description of the drawings The illustrations presented herein are not meant to be actual representations of any particular materials, structures, or devices, but merely idealized representations used to describe embodiments of the present disclosure. Moreover, the connecting lines shown in the various figures are intended to represent example functional relationships and / or physical couplings between the various elements. Many alternative or additional functional relationships or physical connections may be present in an actual system and / or may not be present in some embodiments.

[0053] FIG. 1 shows a schematic example of a hot-wall cross-flow reactor (1) for SiC deposition, with a cylindrical shape that extends uniformly along its longitudinal axis. This type of reactor may advantageously implement the assembly and the method according to the invention. The reactor is characterized by a reaction chamber (10) in which the epitaxial deposition takes place, which is defined by the assembly of several susceptor elements (11, 12, 13, 14) contained in an insulating cover (15) and a quartz tube (16) for the flow of a cooling fluid, such as water. The susceptor elements may advantageously be made of a material with high sensitivity, such as graphite, to ensure that temperatures of up to 1800° C. can be reached when subjected to a suitable electromagnetic field. The latter may be generated by an inductor coil, not shown, wound around the quartz tube.

[0054] Some or all parts of the reaction chamber may be coated with one or more TaC coating layers to protect the susceptor elements during cleaning. Other coatings may be used to achieve the same or different effects, for example to prevent deposition build-up or to seal selected areas of the porous graphite surface and avoid contamination resulting therefrom.

[0055] The reaction chamber is characterized by a base (100) that may provide an area suitable for receiving a support system for a substrate to be epitaxially deposited. Of course, the assemblies and methods according to the invention may be advantageously implemented in other types of reactors, which may differ in geometry, materials, operating conditions, and chemistry from the reactors depicted and discussed herein.

[0056] FIG. 2(a) provides a schematic bottom view of the lifting element (210). FIG. 2(b) provides an illustration of some features of the reaction chamber base (100) from a top side view according to a particular embodiment of the invention. In FIG. 2(a), the lifting element (210), which may form an integral part of a substrate support system rotatable about a rotation axis (z), has a bottom surface (250) characterized by four grooves (261, 262, 263, 264) designed to induce continuous rotation when subjected to a gas flow. To this effect, the grooves extend towards the outer edge of the lifting element. The bottom surface of the lifting element also comprises two indentations (281, 282) designed to align with two gas outlets (161, 162) located in the receiving area of ​​the base (100) shown in FIG. 2(b). The base (100) is part of the reactor susceptor element (11), which is traversed by a gas conduit (150) that is divided into two gas channels that eventually reach the outlets (161, 162). In operation, the lifting element (210) is positioned with its bottom surface above the receiving area. During rotation of the lifting element around the z-axis (dashed line), the indentations on the bottom align with the gas outlets on the receiving area twice during each 360° rotation cycle, thereby creating alternating pressure fluctuations in the gas conduit that can be measured by a pressure sensor (not shown). Pressure fluctuations are also induced by the individual grooves approaching / leaving the gas outlets as the support system rotates. It should be noted that gas from the gas outlets also allows the lifting element to rise above the receiving area. It is understood that the number of grooves, indentations, and gas outlets may vary without departing from the scope of the invention. In particular, the use of at least three gas outlets and at least three grooves / ridges may improve the stability of the support system as it is lifted and rotated during operation of the assembly. The use of a number of indentations or protrusions equal to the number of outlets may amplify the pressure fluctuations measured by the sensor, therefore these may also advantageously be chosen to be more than three.

[0057] Figure 3 shows a top view of a section of a support system (200) having a disk-like shape according to an embodiment of the invention. The support system comprises a lifting element (210) having a support holder (300) on its upper surface. The support holder features a peripheral ridge (310) to prevent the planar substrate (not shown) from adhering to its exposed surface. This allows the substrate to be better held in place even if the latter undergoes slight deformations (typically curvature) during epitaxial deposition. An annular ledge (400) is used to further secure the substrate against lateral displacements in a plane perpendicular to the rotation axis z.

[0058] The particular implementations shown and described above are illustrative of the present invention and its best mode, and are not intended to otherwise limit the scope of the aspects and implementations in any manner. Indeed, for the sake of brevity, conventional manufacturing, association, preparation, and other functional aspects of the system may not be described in detail. [Explanation of symbols]

[0059] 1. Hot-wall cross-flow reactor 10 Reaction chamber 11 Susceptor element 12 Susceptor element 13 Susceptor element 14 Susceptor element 15 Insulation cover 16 Quartz tube 100 Reaction chamber base 110 Receptive Area 150 Gas Pipe 161 Gas outlet 162 Gas outlet 200 Support System 210 Elements 250 bottom 261-264 Groove or ridge 281 Protrusion 282 Protrusion 300 Support holder, substrate holder 310 Surrounding Ridge 400 Circular Ledge

Claims

1. An assembly for a reactor (1) suitable for epitaxial deposition of semiconductor films, comprising: a reaction chamber (10) having a base (100) provided with a receiving area (110), said receiving area (110) being provided with a number of gas outlets (161, 162) connected to at least one gas conduit (150) suitable for delivering a gas flow when said assembly is in use; a support system (200) rotatable about an axis of rotation (z) and adapted to support at least one substrate, the support system comprising a lifting element (210) having a bottom surface (250) facing said receiving area and a top surface opposite said bottom surface; Equipped with The support system is housed within the receiving area (110), and the lifting element is adapted to (i) receive the gas flow from the gas outlet on its bottom surface and (ii) lift the support system during rotation, the bottom surface comprising at least two grooves or ridges (261, 262, 263, 264) designed to induce continuous rotation of the support system, and the assembly further comprises at least one pressure sensor adapted to measure and record pressure signal variations in the gas conduit when the gas flow impinges on the bottom surface of the lifting element.

2. 2. The assembly of claim 1, wherein the support system further comprises at least one removable substrate holder (300) disposed on the upper surface of the lifting element, the substrate holder being integral with the lifting element and connected or connectable to the lifting element.

3. The assembly of claim 2 , wherein the support system further comprises at least one annular ledge (400) disposed on the at least one substrate holder.

4. 4. The assembly of claim 1, wherein each groove or ridge of the lifting element is a continuous segment having an inner end and an outer end, the inner end being positioned closer to the axis of rotation of the support system than the outer end.

5. 5. The assembly according to claim 4, wherein the bottom surface of the lifting element further comprises a number Ni≧2 of indentations or protrusions (281, 282), the indentations or protrusions being mutually arranged such that at least two indentations or protrusions are aligned with the positions of at least two gas outlets at least once during a 360° rotation of the support system.

6. 6. The assembly of claim 5, wherein the indentations or protrusions are positioned such that all of the indentations or protrusions are aligned with the locations of the plurality of gas outlets at least once during a 360 degree rotation of the support system.

7. 7. An assembly according to claim 5 or 6, wherein the number of said at least two grooves or ridges is Ng, which is an integer multiple of the number of said gas outlets.

8. An assembly according to any one of claims 5 to 7, wherein the distance of the recesses or protrusions from the axis of rotation of the support system does not exceed the distance of the inner end of each groove or ridge from the axis of rotation.

9. 9. The assembly of claim 1, comprising: (i) at least one gas flow controller for controlling the gas flow in the at least one gas conduit; and (ii) at least one feedback loop circuit connecting the gas flow controller to the pressure sensor, the feedback loop circuit configured to adjust the gas flow via the gas flow controller based on the pressure signal measured by the pressure sensor to maintain a constant rotational speed of the support system.

10. 9. The assembly of claim 1, further comprising electronics for converting the variations in the pressure signal measured by the pressure sensor into the rotational speed of the support system.

11. 11. The assembly of claim 10, further comprising at least one gas flow controller for controlling the gas flow in the at least one gas conduit, and at least one feedback loop circuit connecting the gas flow controller to the electronic device, the feedback loop circuit configured to adjust the gas flow via the gas flow controller based on the rotational speed measured by the electronic device, to maintain a constant rotational speed of the support system, the feedback loop circuit comprising: a step of: adjusting the gas flow via the gas flow controller based on the rotational speed measured by the electronic device;

12. 12. The assembly of claim 9 or 11, wherein the gas flow control device is a mass flow controller.

13. Assembly according to any one of the preceding claims, further comprising a gas flow control device, preferably a mass flow controller.

14. A reaction chamber (10) for a reactor (1) suitable for epitaxial deposition of semiconductor films, comprising an assembly according to any of the claims 1 to 11.

15. A reactor (1) suitable for epitaxial deposition of semiconductor films, comprising a reaction chamber (10) according to claim 14.

16. 13. A method for controlling the rotational speed of the support system of the assembly of claim 1 when the assembly is in use upon activation by a user, comprising: (i) delivering a gas flow into the at least one gas conduit via a gas flow control device; (ii) recording the pressure signal measured by the pressure sensor; and (iii) converting said pressure signal via an electronic device into said rotational speed of said support system and calculating the difference against a predetermined nominal value; (iv) adjusting the gas flow via the gas flow control device to minimize a difference between the converted rotational speed of the support system and the predetermined nominal value; (v) sequentially repeating steps (i)-(iv) until an interrupt signal is provided by the user.

17. Use of the pressure sensor of the assembly of claim 1 for measuring and controlling the rotational speed of the support system.

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