MEMS with reduced acoustic impedance

Abstract

A MEMS with a fluidic channel in at least one MEMS layer is provided. The fluidic channel is configured to provide a fluidic connection between a first channel side and a second channel side. A sidewall structure of the fluidic channel features a scallop arrangement, whereby the acoustic channel has an effective acoustic channel width due to the scallop structure, which is increased compared to a nominal channel width.

Description

The present invention relates to a MEMS with a fluidic channel which, due to a scalelop arrangement, has an increased effective acoustic channel width and thereby a reduced acoustic impedance. The present invention further relates to a device, in particular a MEMS, for reducing acoustic impedances in a channel through which fluid flows.MEMS can be manufactured and used for various technical purposes. Some of these purposes relate to acoustic transducer systems such as microphones or loudspeakers. In this case, such MEMS sound transducer systems can have a fluid-displacing element, for example a membrane which is generally moved out-of-plane. Other configurations relate to an in-plane movement / a fluid-displacing element, different concepts being known for this purpose. Thus, in addition to actively formed elements which execute a movement in the plane by applying a drive signal, other principles of deflection can also be implemented.From WO 2021 / 223886 A1 a system is known in which a movable structure provided for interaction with the fluid is deflected by a force generated in another MEMS plane.WO 2022 / 117197 A1 discloses a concept in which a deflecting force is generated by means of electrodes which are arranged opposite the movable element in order to generate an out-of-plane directed force which leads to an in-plane deflection of the movable element.These MEMS have in common that an effective surface for interacting with the fluid during production of the MEMS is usually produced by etching along a depth direction in a wafer.CN 111243951 A describes a method for deep etching silicon. The aim is to produce the walls as smooth as possible and to prevent undercutting of the walls.In JP 2007-311584 A, a deep opening having a vertical shape is formed in a semiconductor substrate by the Bosch process. The aim pursued in this publication is, among other things, to produce the walls as smooth as possible.US 2016 / 114365 A1 describes a method for increasing the scaling effect with increasing depth of the opening in order to achieve a negative sidewall angle in a MEMS.US 2020 / 048080 A1 describes a method for producing MEMS microphones by means of the Bosch method. In the method, a void hole which is deeper than 100 μm is formed. The wall of the cavity has a scalelop structure.It would be desirable to have MEMS with a fluidic channel that has a low fluidic impedance.The object of the present invention is therefore to provide a MEMS with a fluidic channel which has a low acoustic impedance.This object is achieved by the subject matter of the independent claims.According to the invention, it has been recognized that it is disadvantageous in the prior art to use smooth walls of a channel through which fluid flows, since these lead to an increase in acoustic impedances.A core idea of the present invention is to have recognized that by using a scalelop arrangement with a scalelop structure, an effective acoustic channel width can be increased compared to a nominal channel width. The increase in the effective acoustic channel width leads to a reduction in the fluidic impedance, which is advantageous in particular for MEMS sound transducers.According to an exemplary embodiment, a MEMS has a fluidic channel in at least one MEMS layer. The fluidic channel is configured to provide a fluidic connection between a first channel side and a second channel side. A side wall structure of the fluidic channel has a scalelop arrangement, wherein the acoustic channel has an effective acoustic channel width through the scalelop structure, which is enlarged compared to a nominal channel width, for example in the case of straight or perpendicular channel walls. The reduced acoustic impedance is advantageous for acoustic quality.According to one exemplary embodiment, a fluidic impedance of the fluidic channel is reduced compared to a fluidic channel of constant channel width with the nominal channel width.According to one exemplary embodiment, the fluidic channel extends along a channel direction. At least one scalelop structure of the scalelop arrangement extends with a scalelop height along the channel direction of at least 200 nm and / or with a scalelop depth perpendicular to the channel direction of at least 100 nm with respect to the nominal channel width in the MEMS layer. These distinct scalelop structures allow precise definition of acoustic impedance.According to an embodiment, the MEMS comprises a movable element arranged parallel to a MEMS plane and configured to interact with a fluid in order to cause a fluidic flow in the fluidic channel, wherein a movement of the movable element is causally related to a movement of the fluid through the fluidic channel. This enables the reduction of the acoustic impedance already at the location of the generation of the fluidic movement.According to one exemplary embodiment, the fluidic channel is formed in part by a side wall structure of the movable element arranged perpendicular to the MEMS plane.According to an embodiment, the fluidic channel is a first fluidic channel and the movable element has a first main side, which is parts of the first fluidic channel, for instance a side wall of the fluidic channel. An opposite second main side of the movable element is part of a second fluidic channel, wherein along a matching direction parallel to the first fluidic channel, a monotonically increasing scalelop height of a first plurality of scalelop structures is arranged on the first main side and a monotonically decreasing scalelop height of a second plurality of scalelop structures is arranged on the second main side. Such a side-specific implementation of scale structures can enable, for example, the reduction of acoustic impedances for a respective fluid flow direction.According to an embodiment, the fluidic channel is configured to provide a fluidic profile at base points of the scalelop structure similar to a plane Poiseuille flow. At apex regions of the scalelop structure, the fluidic channel provides flow with a reversal of a flow direction. This enables local effects for impedance matching, which reduce the overall impedance of the fluidic channel.According to one exemplary embodiment, the nominal channel width is variable over a course of the fluidic channel. The scalelop structure can thus provide modulation of the variable nominal channel width. This makes it possible to maintain an additional degree of freedom for influencing the fluidic damping. For example, in addition to smaller scalelops that may be limited in size (small period) because they are intrinsic generated by, e.g., a Bosch etch, further modulation of the channel width may be performed with a larger period.According to one exemplary embodiment, the nominal channel width is periodically variable over the course of the fluidic channel.According to one exemplary embodiment, the MEMS has a plurality of scale structures, wherein a first pair of adjacent scale structures has a distance from apex regions of the scale structures that is different from a second pair of adjacent scale structures. This allows an advantageous local influencing of the fluidic impedance.According to an embodiment, the plurality of scalelop structures along a course of the fluidic channel has different positions of base points along a channel width of the fluidic channel. This also achieves good local adjustability.According to one exemplary embodiment, the scalelop arrangement has a multiplicity of scalelop structures, wherein the fluidic channel extends along a channel direction and the multiplicity of scalelop structures have a scalelop height which changes monotonically at least in sections along the channel direction. A continuous curve of the impedance can thereby be achieved.According to one exemplary embodiment, the fluidic channel has symmetrically arranged channel sections in a MEMS arrangement. Adjacent channel sections have inverted monotone curves of scale levels. This enables the monotonia to be adapted to a respective fluid flow direction.According to an embodiment, the fluidic channel is a channel element of a serial channel arrangement extending over a plurality of MEMS layer arrangements. A respective channel element is arranged in a MEMS layer arrangement. A monotone variable scale height of a channel element is the same or different as a monotone increase or monotone decrease from an adjacent channel element. This enables an efficient adaptation to a later application of the MEMS.According to an embodiment, a plurality of scale structures have a substantially matching scale depth perpendicular to the channel direction.In an alternative embodiment, a plurality of scale structures is likewise arranged in the fluidic channel. The scale structure is arranged as a first scale structure having a first scale depth and a second scale structure of the plurality of scale structures having a second scale depth different therefrom perpendicular to the channel direction. This enables an adaptation of the fluidic flow within the fluidic channel.According to one exemplary embodiment, the scalelop structure is a first scalelop structure and the scalelop arrangement has at least one second scalelop structure which is arranged alongside the first scalelop structure along a direction perpendicular to a main side normal of the MEMS layer. Geometries of the first scallop structure and the second scallop structure intersect to form at least a portion of a common in-plane scallop arrangement as an additional widening of the fluidic channel at this location. This makes it possible to achieve substantially larger fluidic channels and also to expose movable elements.According to an embodiment, a MEMS described herein is formed as a MEMS loudspeaker.Further advantageous embodiments are the subject matter of further patent claims.Preferred embodiments of the present invention will be explained below with reference to the accompanying drawings: FIG. 1 shows a schematic side sectional view of a MEMS according to an embodiment; FIG. 2 shows a schematic side sectional view of a part of the MEMS from FIG. 1 in an enlarged illustration; FIG. 3 shows a representation of the part of the MEMS comparable to FIG. 2 for the discussion of exemplary embodiments; FIG. 4 is a schematic side sectional view of the portion of FIG. 3 where scalelops of the present invention are defined by the height and radius of the scalelop structures; FIG. 5 shows a schematic side sectional view of a MEMS according to an exemplary embodiment, which has a multiplicity of scale structures in the fluidic channel; FIG. 6 shows a schematic side sectional view of a MEMS according to an exemplary embodiment, in which the MEMS layer has at least two fluidic channels; FIG. 7 shows a schematic plan view of a MEMS according to an exemplary embodiment, in which, inter alia, a bottom layer is illustrated; FIG. 8 ashows a schematic side sectional view of the bottom layer of a MEMS according to an exemplary embodiment with a plurality of scale structures, which have a scale height, which changes monotonically at least in sections, along the channel direction; FIG. 8 b shows a schematic side sectional view of a MEMS according to an embodiment example in which the scalelop height decreases monotonically; FIG. 9 shows a schematic side sectional view of a MEMS according to an embodiment, which may be implemented as a MEMS loudspeaker, for example; FIG. 10 shows a schematic side sectional view of a MEMS according to an exemplary embodiment, in which a movable element has main sides of different configuration from one another; FIG. 11 shows a schematic side sectional view of a further MEMS according to an embodiment; and FIG. 12 shows a schematic flow diagram of a method according to an embodiment, with the aid of which a MEMS can be produced.Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it is pointed out that identical, functionally identical or identically acting elements, objects and / or structures are provided with the same reference numerals in the different figures, with the result that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.Exemplary embodiments described below are described in connection with a multiplicity of details. However, embodiments may also be implemented without these detailed features. Further, embodiments will be described for convenience using block diagrams to replace a detailed diagram. Furthermore, details and / or features of individual exemplary embodiments can be easily combined with one another, provided that it is not explicitly described to the contrary.FIG. 1 shows a schematic side sectional view of a MEMS 10 according to an embodiment. The MEMS 10 comprises a MEMS layer 12 in which a fluidic channel 14 is arranged in order to provide a fluidic connection between a first channel side 16 and a second channel side 18. The MEMS layer 12 is not necessarily a single or integral layer, but alternatively may optionally also comprise a higher number of layers connected to one another. For example, electrically conductive layers and electrically non-conductive layers and / or electrically semiconducting layers may be connected to one another to form a layer arrangement of the MEMS layer 12. One or more layers of the MEMS 10 may comprise semiconductor-based materials, for example a silicon material, which also includes materials derived therefrom, such as silicon oxide and / or silicon nitride.A side wall structure 22 of the fluidic channel 14 has a scalelop arrangement, which has at least one scalelop structure 24 1-24n. The scallop structure or scallop arrangement increases an effective acoustic channel width of the fluidic channel 14 relative to a nominal channel width, as discussed with reference to FIG. 2. An effective acoustic channel width is understood to mean a channel width that is effective for transmitting acoustic waves.A fluid flow 26 can take place through the fluidic channel 14 on account of a pressure difference between the first channel side 16 with a pressure p 1 and the second channel side 18 with a pressure p 2. It is possible, but not necessary, for a pressure p 1 on the first channel side 16 to be present which is increased compared to the pressure p 2. It is thus possible, for example, for at least one substructure of the fluidic channel 14 to be arranged movably, for example in an x / y plane or parallel thereto, which can also be understood as in-plane. As a result, for example, a pressure difference can be generated in the fluidic channel 14 on account of the movement, as a result of which the pressure on one of the two sides 16 or 18 possibly loses relevance.In other words, FIG. 1 illustrates an embodiment of a fluid-throughflow channel 14, for example in a MEMS-based loudspeaker. A wafer stack 12 separates two acoustic domains each having a fluidic pressure p 1 and p 2. This wafer stack contains at least one channel or several channels, which connect the two acoustic domains and simultaneously contain walls structured with scalelops. The pressure difference between the sides 16 and 18 of the wafer stack 12 creates a fluid flow or fluid stream 26 through the channel 14.FIG. 2 shows a schematic side sectional view of a part of the MEMS 10 in an enlarged illustration. FIG. 2 shows a nominal channel width of the fluidic channel 14, which can be obtained, for example, if side walls of the fluidic channel 14 are planar, without scale structures 24. Furthermore, an at least local maximum width 32 of the fluidic channel 14 is shown, which is obtained by an increase of the nominal channel width by a scalelop depth 34 perpendicular to a channel depth z. The scalelop structures 24 increase an effective acoustic channel width 36 compared to the nominal channel width 36. This is illustrated by way of example on the basis of a flow velocity 38 which is zero, 0 or virtually 0 at base points of the scalelop structures 24 at which the nominal channel width 28 is present in the fluidic channel 14. In the region of the scalelop structures, as illustrated with reference to the scalelop structure 24 5 a flow with a reversal of the flow direction can be provided in apex regions of the scalelop structure 24 5 as can be seen with reference to the change in sign of the flow speed 38.This local reduction or reversal of the flow rate can result in a reduction in the overall impedance over the nominal channel width, thus increasing the effective acoustic channel width 36 over the nominal channel width 28.At a root or root portion of a scalelop structure 24 2 due to the scalelop structure, a fluid profile of the fluidic channel 14 similar to a plane Poiseuille flow may be obtained and at the apex portions 42 a flow with a reversal of a flow direction.The scalelop structures 24 can be produced in the MEMS layer 12 using a Bosch process. However, these are not designed as desired, but rather in such a way that the effect according to the invention for increasing the effective acoustic channel width takes place.In other words, an exemplary embodiment is shown in FIG. 2, where a different rapid profile of the fluid is set by the scalelops depending on the position.FIG. 3 shows a representation of the part of the MEMS 10, which is comparable to FIG. 2, for the discussion of exemplary embodiments. Depicted is the scalelop depth 34 along with a scalelop height 46 along the channel direction z. Preferred embodiments relate to MEMS in which the fluidic channel 14 extends along the channel direction z and at least one of the scalelop structures 24 of the scalelop arrangement extends with a scalelop height 46 along the channel direction z of at least 200 nm, at least 300 nm or more, about 350 nm or more. Alternatively or additionally, exemplary embodiments are preferred in which the scalelop depth perpendicular to the channel direction z has a value of at least 100 nm, at least 150 nm or at least 200 nm with respect to the nominal channel width 28 in the MEMS layer 12.In other words, an exemplary embodiment is shown in FIG. 3, where the scalelops are defined by the depth 34 and the height 46. The depth is in a preferred range between 100 nm and 10 μm, while the range of 0.5 μm and 2 μm is particularly preferred. The height 46 lies in a preferred range from 0.2 μm to 20 μm, wherein the range between 1.5 μm and 8 μm is particularly preferred.FIG. 4 shows a schematic side sectional view of the part from FIG. 3, whereas the scalelops 24 are defined by the height 46 and a radius R of the scalelop structures 24. In accordance with FIG. 3, the scalelop height 46 is in a preferred range from 0.2 μm to 20 μm and particularly preferably in a range between 1.5 μm and 8 μm. The radius R is constant over the scale structure according to this embodiment, but can also vary locally, for example in order to provide an elliptical structure. It is preferred if the radius R at the base points and / or the apex regions or at any point is greater than half the height 46. the radius R can lie in a preferred range of at least half the height (h / 2) up to 200 μm, while the range of 3 / 5 h up to 3 h is particularly preferred, wherein h is the value of the height 46.FIG. 5 shows a schematic side sectional view of a MEMS 50 according to an embodiment. The MEMS 50 has a plurality of scalelop structures 24 1-249 in the fluidic channel 14. According to the exemplary embodiment, different pairs of adjacent scalelops can have a distance 48 1 or 48 2 between vertices of the scalelop structures that are different from one another. Although only two different distances 48 1 and 48 2 are shown, additional different distances, i.e., at least three, at least four, or more different distances, may also be implemented. While the scale structures 24 may be formed in 1-249 compared to each other with a matching structure with respect to a scale height, a scale depth and / or a radius, for example, two scale arrangements may be implemented displaced with respect to each other such that a shown paired displacement is obtained. When using an additional, third scalelop arrangement, which may also be periodic along the channel direction z, a third distance can easily be obtained.In the illustration of FIG. 5, for example, the scale structures 24 1, 243, 245, 247 and 24 9 form a first scale arrangement, and scale structures 24 2, 244, 246 and 24 8 form a second scale arrangement. By displacing the second scale-flop arrangement relative to the first scale-flop arrangement along negative z-direction, a first distance 48 1 between two adjacent scale-flop structures 24 4 and 24 5 can be increased and at the same time another adjacent distance between scale-flop structures 24 5 and 24 6 can be decreased. In a particular embodiment of the MEMS 50, a sum of distances 48 1 and 48 2 of any three adjacently arranged scalelop structures may be constant over the channel depth 14, for instance in the case of two scalelop arrangements.The plurality of scale structures of the MEMS 50 may include a first pair 24 4, 245 of scale structures having the first distance 48 1 and a second pair 24 5 / 246 of adjacent scale structures having a different distance 48 2 from vertices of the scale structures.This can likewise result in a position of base points or base regions 44 which differ from one another along a channel width parallel to the x-direction of the fluidic channel when the course of the fluidic channel is viewed along the z-direction. This is illustrated by way of example for a first channel width 28 1 at the foot region 44 2 and a different channel width 28 2 at the foot region 44 3 therefrom.In other words, FIG. 5 shows a further exemplary embodiment, where the scalelops are offset with respect to one another such that at least two different channel widths 28 1 and 28 2 are produced, which are defined by the scalelop peaks. Furthermore, at least two different height distances 48 1 and 48 2 of the Scalop causes are thus produced.FIG. 6 shows a schematic side sectional view of a MEMS 60 according to an embodiment, in which the MEMS layer 12 comprises at least two fluidic channels 14 1 and 14 2 in order to connect the first channel side 16 and the second channel side 18 to one another. It is possible, but not necessary, for the fluidic channels 14 1 and 14 2 to have a matching first channel side 16 and / or a matching second channel side 18.Regardless of the number of fluidic channels, which can also be 1 without further ado, the nominal channel widths of the fluidic channels 14 1 and 14 2 can be varied over a course of the fluidic channels 14 1 and 14 2 along the z-direction. This may result in a nominal channel width 28 that is dependent on the position along the z-direction, such that a nominal channel width 28(z) may be obtained as a function of the position along z. In the embodiment of the MEMS 60, the nominal channel width 28 is periodically variable over the course of the fluidic channel 14 in 1 fashion. Scalelop structures having constant depths and / or heights or also different from one another can be modulated onto this periodic change.In other words, FIG. 6 shows a cross-section of an example fluidic channel. The channel has a tooth-like shape with scalelops on the walls.FIG. 7 shows a schematic plan view of a MEMS 70 according to an exemplary embodiment. Several embodiments may be implemented independently of each other. In addition to the MEMS layer 12, a bottom layer 52 is shown by way of example, which represents a possibly but not necessarily last layer along the negative z direction. This layer may have openings 54 1 to 54 12 for example in order to bend the fluidic channels 14 1 to 14 4 with the first channel side or the second channel side.An advantageous implementation that can be seen in FIG. 7 is the configuration as a MEMS in which the scalelop structure 24 is arranged 1 along a direction perpendicular to a main side normal of the MEMS layer 12, which runs parallel to the z direction, for example, next to a further scalelop structure 24 in 2 fashion. The geometries of the two scale structures 24 1 and 24 2 intersect one another and form at least part of a common in-plane scale arrangement. Whereas, for example, in MEMS 10, adjacent scalelop structures are arranged adjacent to one another along the channel direction z, but a respective scalelop structure 24 can be produced by a single etching process, the scalelop structures 24 1 and 24 2 of the MEMS 70 are arranged in-plane next to one another, which can lead to an increase in the channel cross section. This does not exclude an additional arrangement of further scale structures along the channel direction z, but rather exemplary embodiments explicitly provide this.Independently thereof, at least parts of the MEMS layer 12 can be formed as a movable element 56 1, 562 and / or 56 3 arranged parallel to the MEMS plane. Such a movable element may be configured to interact with a fluid in the adjacent fluidic channel 14 1 to 14 4 to cause a fluidic flow 26 i,j wherein a movement of the movable element 56 1 to 56 3 is causally related to a movement of the fluid through the fluidic channel 14 1 to 14 3. The indices, i and j, of the fluid streams 26 i,j designate the fluidic channel i with i=1,..., 4 and with j a partial fluid stream within the fluidic channel 14 i. This is because, for example, a central region of the respective movable element 56 1, 562 and 56 3 experiences a greater deformation or deflection than an edge region and, for example, a central tapering of the fluidic channel 14 in the x / y plane can lead to a displacement of fluid outwards along the opposite directions.Deflection directions 58 1, 582 and 58 3 of the movable elements 56 1, 562 and 56 3 can extend parallel to one another and the respective movable elements can move in the sense of a back-and-forth movement, wherein an actuation manner can be arbitrary. If the MEMS 70 is configured as a loudspeaker, for example, active forces can be generated by electrostatic, piezoelectric, magnetic and / or thermal forces. It can likewise be provided, for example within the scope of a microphone configuration, that the fluid triggers a movement of the movable element, which is then detected.In the MEMS 70, in both cases a fluidic channel 14 1 to 14 4 is formed at least partially by a side wall structure of the movable element 56 1 to 56 3 arranged perpendicular to the MEMS plane, for example along the z-direction.In other words, FIG. 5 shows a plan view of a MEMS component. The fins 56 have in-plane scales. This results in a reduction in the attenuation of the acoustics along the fins.FIG. 8 ashows a schematic side sectional view of the bottom layer 52 of a MEMS 80 1 according to an embodiment. The bottom layer 52 may include, for example, the MEMS layer 12 of the MEMS 10. At least one additional MEMS layer arrangement 62 having electrically passive and / or electrically active properties and / or mechanically active and / or mechanically active properties may provide a portion of the MEMS 80 1. The scalelop arrangement comprises a multiplicity of scalelop structures per fluidic channel 14 1 and 14 2, wherein, according to exemplary embodiments, already one fluidic channel or else more than two fluidic channels can be provided. The fluidic channel 14 1 and the fluidic channel 14 2 extend along the channel direction z, which, however, does not necessarily have to be arranged perpendicular to the x / y plane. FIG. 8 ashows that the plurality of scale structures 24 1 to 24 n have a scale height 46 1 to 46 n which changes monotonically at least in sections along the channel direction. In the case of the MEMS 80 1 a monotone increase in the scalelop height 46 occurs 1 to 46 n.FIG. 8 bshows a schematic side sectional view of a MEMS 80 2, to which the details of the MEMS 80 1 likewise apply, but here the scalelop height decreases monotonically.In other words, FIGS. 8 aand 8 beach show a cross section of the lid-bottom wafer. The height 46 of the individual scalelops increases with increasing height / depth of the channel. The channel width can remain the same.FIG. 9 shows a schematic side sectional view of a MEMS 90 according to an embodiment, which may be implemented as a MEMS loudspeaker, for example.By way of example, the layer 52 of the MEMS 80 1 from FIG. 8 is illustrated, which can also function here by way of example as a lid wafer. A further MEMS layer or layer arrangement 66 can comprise, for example, a device wafer having one or more layers, wherein movable elements 56 1 and 56 2 can be arranged here, for example. The MEMS 90 can have a further MEMS layer arrangement 68, which can be used, for example, as a bottom wafer, wherein such terms can be interchanged as desired with a changed orientation of the MEMS 90.Movement of the movable members 56 1 and 56 2 may result in sound pressure waves passing alternately through the apertures 54 1 and 54 2 on the one hand and 54 3 on the other hand. For example, a possibly synchronous movement of the movable elements 56 1 and 56 2 away from each other may result in sound pressure waves through the openings 54 1 and 54 2 and a synchronous movement of the movable elements 56 1 and 56 2 towards each other may result in sound pressure waves from the opening 54 3.The fluid stream 26 may have directions locally different from each other. It is shown in FIG. 9 that the scalelop arrangement can be different from one another in different layers. Thus, starting from the MEMS layer arrangement 66 towards the outside along positive z-direction in the MEMS layer 52, an increase in the form of a monotone increase in the scalelop heights 46 1,1 to 46 1,n can be implemented. With respect to the direction z in space, this can be inverted in the MEMS layer arrangement 68, but so an optionally monotone increase in the scalelop heights is also implemented outwards along the negative z direction.Independently of this, a scalelop height in the MEMS layer arrangement 66 can be constant, variable or monotonically variable or strictly monotonically variable along the z direction.In other words, FIG. 9 shows a cross section of the lid, device and bottom wafer. The height of the individual scalelops increases with increasing height in the lid and device wafer. In the bottom wafer, the height h of the scalelops increases with increasing depth.FIG. 10 shows a schematic side sectional view of a MEMS 100 according to an embodiment. The MEMS 100 may be formed in accordance with the MEMS 90, but differing in that, for example, the movable elements 56 1 and 56 2 are formed with main sides different from one another with regard to the arrangement and form of the scalelop structures. In each of the movable members 56 1 and 56 2 a respective main side 56A 1 and 56A 2 respectively, and an opposing second main side 56B 1 and 56B 2 respectively, may be part of a different fluidic channel, as is the case with the MEMS 90. However, for example, while a corresponding monotone increase or decrease in the scalelop heights is arranged on the different main sides of the MEMS 90, the different main sides of a movable element 56 1 and 56 2 have a different arrangement from one another. Thus, for example, an increase in the scale-up levels, in particular a monotone increase, is set up on the main side 56A 1 and the main side 56B 2 along the z-direction, while a monotone decreasing scale-up level is arranged along the z-direction on the respectively opposite main side 56B 1 and 56A 2. This can make it possible to adapt to the respective flow direction of the fluid stream 16. A different configuration on the main sides can be effected, for example, by individual etching of the respective fluidic channel in a MEMS layer 52, 66 and 68, which can each provide a MEMS layer 12 independently and independently of one another.In other words, FIG. 10 shows a cross section of the lid, device and bottom wafer. The height of the individual scalelops increases with increasing height in the lid wafer. In the bottom wafer, the height of the scalelop increases with increasing depth. In the channels of device wafer 66, the height of the scalelop increases in two channels with increasing height and one channel with increasing depth.FIG. 11 shows a schematic side sectional view of a MEMS 110 according to an embodiment. The MEMS 110 may be formed at least partially in correspondence with the MEMS 90 and 100. Deviating from the MEMS 90 and from the MEMS 100, MEMS layer 66, for instance the device wafer, is formed. This channel can comprise channel sections 72 1,1 and 72 1,2 of a first fluidic channel, 72 2,1 and 72 2,2 of a second fluidic channel, and 72 3,1 and 72 3,2 of a third fluidic channel of the MEMS layer 66, respectively, in the fluidic channels. The respective channel sections can be formed symmetrically with respect to a plane of symmetry 74 and, for example, starting from the plane of symmetry 74, provide an increasing scalelop height along positive z-direction and also provide an increasing scalelop height along negative z-direction. This configuration can also be inverted without further ado. Although the channel portions 72 of the three different fluidic channels in the MEMS layer 66 are shown as being the same or identical, the fluidic channels of one or more MEMS layers may also be formed individually and differently from each other, as are the MEMS 90 and 100.Mutually adjacent channel sections 72 1,1 and 72 1,2; 722,1 and 72 2,2 and also 72 3,1 and 72 3,2 can have inverted monotone curves of the scalelop heights.In MEMS 90, 100 and 110, it is shown that a fluidic channel of a MEMS layer 52, 66 and 68 can be a channel element of a series channel arrangement via the different MEMS layers 52, 66 and 68, respectively. The channel arrangement can therefore extend over a plurality of MEMS layer arrangements or MEMS layers. A respective channel element in a MEMS layer arrangement may have a constant or variable, for example monotonically variable, scalelop height of a channel element as a monotonic increase or monotonic decrease, which is the same or different from an adjacent channel element in another MEMS layer.In a possible embodiment, which is illustrated in FIGS. 9, 10 and 11, a plurality of scale structures of a channel section or of a fluidic channel can have a substantially matching scale depth perpendicular to the channel direction z.Alternatively to a matching scalelop depth, scalelop depths different from one another can also be provided in a multiplicity of scalelop structures.In other words, FIG. 11 shows a cross section of the lid, device and bottom wafer. In the device wafer, the height of the individual scalelops increases with increasing height and depth starting from half the channel height.Embodiments of the present invention relate to MEMS, for example as MEMS, which are part of a MEMS loudspeaker. Some embodiments relate to MEMS speakers having a MEMS described herein. In some embodiments, scalelops are marked on the walls of a fluid-flown channel, which have a depth 34 in a range between 0.1 μm and 10 μm, wherein the range between 0.5 to 2 μm may be particularly preferred. Alternatively or additionally, a height 46 of between 0.2 μm and 20 μm is provided, wherein the range of between 1.5 and 8 μm is particularly preferred.Characteristic of some embodiments are scallops with a radius R which is greater than half the height, but at most up to 200 μm, wherein the range 3 / 5 h to 3 h is particularly preferred. The parameter h stands for the scalelop height 46.In some embodiments, scalelops are characteristic that are offset from each other, such that at least two different height distances of the scalelop causes and at least two different channel widths defined by scalelop peaks result, as described in connection with FIG. 5.In some embodiments, scalelops are characteristic that are varied in size over the depth of the channel.In some embodiments, scallops are labeled on the walls of a tooth-shaped fluid-flowed-through channel, as described, for example, in connection with FIG. 6.In some embodiments, fins are labeled with in-plane scales, such as described in FIG. 7.In some embodiments, the height h or the height 46 of the individual scalelops is characteristic, which increases or decreases with increasing height and / or depth of a channel through which fluid flows.In some embodiments, the height h is probably the characteristic of the height 46 of the individual scalelops, which increases with increasing height in the lid and device wafer and increases with increasing depth in the bottom wafer, as is described in connection with FIG. 9.In some exemplary embodiments, the height h or the height 46 of the individual scalelops is characteristic, which increases with increasing height in the lid wafer and increases with increasing depth in the bottom wafer and increases with increasing depth in the channels of the device wafer in at least one channel with increasing height and in at least one other channel with increasing depth, as described in connection with FIG. 10.In some exemplary embodiments, the height h or the height 46 of the individual scalelops is characteristic, which increases or decreases with increasing height and increasing depth starting from half the channel height, for example in the device wafer, as described in connection with FIG. 11.Embodiments of the present invention relate to microelectromechanical systems, MEMS. Using the Bosch method, channels and / or openings may be formed in a semiconductor substrate. In the method, the etching process and the shutdown process are repeated. In this case, wavy side surfaces are formed at the opening which is produced, which is also referred to as scaling, and the structures which are produced in this case are referred to as scalings. While the prior art is aimed at minimizing this scaling effect in order to obtain walls that are as smooth as possible, exemplary embodiments aim to use the scaling effect deliberately, since smooth walls lead to an increase in acoustic impedances in a channel through which fluid flows in a MEMS-based loudspeaker, said acoustic impedances being reduced according to the invention. The goal of MEMS speakers described herein is to reduce acoustic impedances. The same mechanisms may also be used with MEMS microphones or other MEMS for fluid transport.The object of some embodiments is to reduce acoustic impedances in a fluid-flow channel of a MEMS loudspeaker. Such an object is achieved by intentionally increasing the depth and height of the scalelops in a fluid-throughflow channel of a MEMS loudspeaker. At the narrowest point of the channel, the nominal channel width, a fluid profile similar to a flat Poiseuille flow can be produced, while at the widest point of the channel, a channel width with scalelops, a flow with a reversal of the flow direction can be produced in the scalelop base. The flow reversal point lies between the plane of the scalelop tips (nominal channel width) and the plane of the scalelop bases (channel width with scalelops). As a result of this local change in the flow profile, the acoustically effective channel width is greater than the nominal channel width and thus the impedance of the channel with scalelops is reduced compared to a smooth channel with the same nominal channel width, which is advantageous.FIG. 12 shows a schematic flow diagram of a method 1200 according to an embodiment, by means of which a MEMS can be produced, such as a MEMS described herein. A step 1210 includes creating a fluidic channel in at least one MEMS layer to provide fluidic connection between a first channel side and a second channel side such that a sidewall structure of the fluidic channel has a scalelop arrangement, wherein the acoustic channel through the scalelop structure has an effective acoustic channel width that is increased compared to a nominal channel width.Such an enlargement is not achieved by the smallest possible scalelops in the prior art, but is avoided there.Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step. Analogously, aspects described in connection with or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device.The above-described embodiments are merely illustrative of the principles of the present invention. It is to be understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented herein by way of description and explanation of the embodiments.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2021 / 223886 A1

[0003] WO 2022 / 117197 A1

[0004] CN 111243951 A

[0006] JP 2007-311584 A

[0007] US 2016 / 114365 A1

[0008] US 2020 / 048080 A1

[0009]

Claims

A MEMS comprising a fluidic channel (14) in at least one MEMS layer (12; 52, 66, 68) configured to provide fluidic connection between a first channel side (16) and a second channel side (18); wherein a side wall structure (22) of the fluidic channel comprises a scalelop arrangement, wherein the fluidic channel (14) comprises an effective acoustic channel width (36) through the scalelop arrangement, which is enlarged compared to a nominal channel width (28).The MEMS of claim 1, wherein a fluidic impedance of the fluidic channel (14) is reduced compared to a fluidic channel of constant channel width with the nominal channel width (28).The MEMS according to claim 1 or 2, wherein the fluidic channel (14) extends along a channel direction (z) and at least one scalelop structure (24) of the scalelop arrangement extends with a scalelop height (46) along the channel direction (z) of at least 200 nm and / or extends with a scalelop depth (34) perpendicular to the channel direction (z) of at least 100 nm with respect to the nominal channel width (28) in the MEMS layer (12; 52, 66, 68).A MEMS according to any preceding claim, comprising a movable element (56) arranged parallel to a MEMS plane and configured to interact with a fluid to cause a fluidic flow (26) in the fluidic channel (14), wherein a movement of the movable element (56) causally relates to a movement of the fluid through the fluidic channel (14).The MEMS of claim 4, wherein the fluidic channel (14) is formed partly by a sidewall structure (22) of the movable element (56) arranged perpendicular to the MEMS plane.The MEMS of claim 4 or 5, wherein the fluidic channel (14) is a first fluidic channel; and the movable element (56) has a first main side (56A) that is part of the first fluidic channel; and an opposite second main side (56B) that is part of a second fluidic channel; wherein along a matching direction (z) parallel to the first fluidic channel, a monotonically increasing scallop height (46) of a first plurality of scallop structures (24) is arranged on the first main side (56A); and a monotonically decreasing scallop height (46) of a second plurality of scallop structures (24) is arranged on the second main side (56B).A MEMS according to any preceding claim, wherein the fluidic channel (14) is arranged to provide a fluidic profile at root portions (44) of the scalelop structure (24) similar to a planar Poiseuille flow; and at apex portions (42) of the scalelop structure (24) provides a flow with a reversal of a flow direction.MEMS according to one of the preceding claims, in which the nominal channel width (28) is variable over a course of the fluidic channel (14).MEMS according to Claim 8, in which the nominal channel width (28) is periodically variable over the course of the fluidic channel (14).MEMS according to one of the preceding claims, having a plurality of scale structures (24), wherein a first pair of adjacent scale structures (24) has a distance (48 1, 482) from vertices of the scale structures (24) which is different from a second pair of adjacent scale structures (24).The MEMS of claim 10, wherein the plurality of scale structures (24) have different positions of foot points (44) along a channel width of the fluidic channel (14) from one another along a course of the fluidic channel (14).MEMS according to one of the preceding claims, in which the scalelop arrangement has a multiplicity of scalelop structures (24), wherein the fluidic channel (14) extends along a channel direction (z) and the multiplicity of scalelop structures (24) have a scalelop height (46) which changes monotonically at least in sections along the channel direction (z).The MEMS of claim 12, wherein the fluidic channel (14) comprises symmetrically arranged channel sections (72) in a MEMS arrangement; and adjacent channel sections comprise inverted monotone curves of the scalelop heights (46 1, 462).The MEMS of claim 13, wherein the fluidic channel (14) is a channel element of a serial channel array extending across a plurality of MEMS stack layers (52, 66, 68); wherein a respective channel element (72) is disposed in a MEMS stack layer; and a monotonically varying scalelop height (46) of a channel element is the same or different as a monotonic increase or monotonic decrease from an adjacent channel element.The MEMS of any of claims 12 to 14, wherein the plurality of scale structures (24) have a substantially consistent scale depth (34) perpendicular to the channel direction (z).The MEMS according to any one of claims 1 to 14, wherein a plurality of scale structures (24) are arranged in the fluidic channel; and the scale structure (24) is arranged as a first scale structure (24) with a first scale depth (34) and a second scale structure (24) of the plurality of scale structures (24) with a second scale depth (34) different therefrom perpendicular to the channel direction (z).The MEMS according to any one of the preceding claims, wherein the scalelop structure is a first scalelop structure (24 1) and the scalelop arrangement comprises at least one second scalelop structure (24 2) which is arranged along a direction (x, y) perpendicular to a main lateral normal of the MEMS layer (12; 52, 66, 68) next to the first scalelop structure (24 1) ; wherein geometries of the first scalelop structure (24 1) and the second scalelop structure (24 2) intersect and form at least part of a common in-plane scalelop arrangement.MEMS according to one of the preceding claims, which is formed as a MEMS loudspeaker.A method (1200) of manufacturing a MEMS, comprising the steps of: creating (1210) a fluidic channel in at least one MEMS layer to provide a fluidic connection between a first channel side and a second channel side; such that a sidewall structure of the fluidic channel comprises a scalelop arrangement, wherein the fluidic channel through the scalelop arrangement has an effective acoustic channel width that is increased compared to a nominal channel width.

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