MEMS with reduced acoustic impedance of a channel

Abstract

A MEMS is provided with a fluidic channel in at least one MEMS layer. The fluidic channel is designed to provide a fluidic connection between a first channel side and a second channel side. A lateral wall structure of the fluidic channel has a scallop-shaped assembly, wherein by virtue of the scallop-shaped structure, the acoustic channel has an effective acoustic channel width which is enlarged in comparison to a nominal channel width.

Description

[0001] MEMS WITH REDUCED ACOUSTIC IMPEDANCE OF ONE CHANNEL

[0002] Description

[0003] The present invention relates to a MEMS with a fluidic channel, which, due to a scallop arrangement, has an increased effective acoustic channel width and thus a reduced acoustic impedance. The present invention further relates to a device, in particular a MEMS, for reducing acoustic impedances in a fluid-flow channel.

[0004] MEMS can be manufactured and used for a variety of technical purposes. Some of these purposes relate to sound transducer systems such as microphones or loudspeakers. Such MEMS sound transducer systems can incorporate a fluid-displacing element, such as a membrane, which is typically moved out-of-plane. Other configurations involve in-plane movement / a fluid-displacing element, although different concepts are known for this. Thus, in addition to actively formed elements that execute in-plane movement upon application of a control signal, other displacement principles can also be implemented.

[0005] From WO 2021 / 223886 A1, a system is known in which a movable structure intended for interaction with the fluid is deflected by a force generated in another MEMS plane.

[0006] From WO 2022 / 117197 A1, a concept is known in which a deflecting force is generated by means of electrodes 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.

[0007] What these MEMS have in common is that an effective surface for interacting with the fluid is usually created by etching along a depth direction in a wafer during MEMS fabrication.

[0008] CN 11 1243951 A describes a process for deep etching silicon. The goal is to produce the walls as smooth as possible and prevent undercutting. In JP 2007-311584 A, a deep, vertical opening is formed in a semiconductor substrate using the Bosch process. One of the goals pursued in this document is to produce the walls as smooth as possible.

[0009] US 2016 / 114365 A1 describes a method for increasing the scalloping effect with increasing depth of the opening in order to achieve a negative sidewall angle in a MEMS.

[0010] US 2020 / 048080 A1 describes a method for manufacturing MEMS microphones using the Bosch process. This process involves forming a cavity hole that is deeper than 100 pm. The cavity wall has a scallop structure.

[0011] MEMS with a fluidic channel that has a low fluidic impedance would be desirable.

[0012] The object of the present invention is therefore to provide a MEMS with a fluidic channel that has a low acoustic impedance.

[0013] This problem is solved by the subject matter of the independent patent claims.

[0014] According to the invention, it was recognized that it is disadvantageous in the prior art to use smooth walls of a fluid-flowing channel, since these lead to an increase in acoustic impedances.

[0015] A core idea of ​​the present invention is the recognition that by using a scallop arrangement with a scallop structure, an effective acoustic channel width can be increased compared to a nominal channel width. Increasing the effective acoustic channel width leads to a reduction in fluidic impedance, which is particularly advantageous for MEMS sound transducers.

[0016] According to one 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 sidewall structure of the fluidic channel has a scallop arrangement, wherein the scallop structure provides the acoustic channel with an effective acoustic channel width that is increased compared to a nominal channel width, for example, with straight or vertical channel walls. The reduced acoustic impedance is advantageous for the acoustic quality.

[0017] According to one embodiment, a fluidic impedance of the fluidic channel is reduced compared to a fluidic channel of constant channel width with the nominal channel width.

[0018] According to one embodiment, the fluidic channel extends along a channel direction. At least one scallop structure of the scallop arrangement extends with a scallop height along the channel direction of at least 200 nm and / or with a scallop depth perpendicular to the channel direction of at least 100 nm compared to the nominal channel width in the MEMS layer. These distinct scallop structures enable a precise definition of the acoustic impedance.

[0019] According to one embodiment, the MEMS comprises a movable element arranged parallel to a MEMS plane, which is configured to interact with a fluid to effect 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 acoustic impedance to be reduced already at the location where the fluidic movement occurs.

[0020] According to one embodiment, the fluidic channel is partially formed by a sidewall structure of the movable element arranged perpendicular to the MEMS plane.

[0021] According to one embodiment, the fluidic channel is a first fluidic channel, and the movable element has a first main side that is part of the first fluidic channel, such as a side wall of the fluidic channel. An opposite second main side of the movable element is part of a second fluidic channel, wherein a monotonically increasing scallop height of a first plurality of scallop structures is arranged along a corresponding direction parallel to the first fluidic channel on the first main side, and a monotonically decreasing scallop height of a second plurality of scallop structures is arranged on the second main side. Such a side-specific implementation of scallop structures can, for example, enable the reduction of acoustic impedances for a respective fluid flow direction.According to one embodiment, the fluidic channel is configured to provide a fluid profile at the base points of the scallop structure similar to a plane Poiseuille flow. At the apex regions of the scallop structure, the fluidic channel provides a flow with a reversal of flow direction. This enables local impedance matching effects that reduce the overall impedance of the fluidic channel.

[0022] According to one embodiment, the nominal channel width is variable along the length of the fluidic channel. The scallop structure can thus provide a modulation of the variable nominal channel width. This allows for an additional degree of freedom to influence the fluidic damping. For example, in addition to smaller scallops, which may be limited in size (small period) because they are intrinsically generated, for example, by a Bosch etch, a further modulation of the channel width with a larger period is possible.

[0023] According to one embodiment, the nominal channel width is periodically variable over the course of the fluidic channel.

[0024] According to one embodiment, the MEMS comprises a plurality of scallop structures, wherein a first pair of adjacent scallop structures has a different distance from the apex regions of the scallop structures than a second pair of adjacent scallop structures. This enables advantageous local influencing of the fluidic impedance.

[0025] According to one embodiment, the plurality of scallop structures along a course of the fluidic channel have mutually different positions of base points along a channel width of the fluidic channel. This also achieves good local adjustability.

[0026] According to one embodiment, the scallop arrangement comprises a plurality of scallop structures, wherein the fluidic channel extends along a channel direction, and the plurality of scallop structures have a scallop height that varies monotonically, at least in sections, along the channel direction. This allows a continuous impedance profile to be achieved. According to one embodiment, the fluidic channel comprises symmetrically arranged channel sections in a MEMS arrangement. Adjacent channel sections have inverted monotonic profiles of scallop heights. This enables adaptation of the monotony to a respective fluid flow direction.

[0027] According to one embodiment, the fluidic channel is a channel element of a serial channel arrangement extending across multiple MEMS layer arrangements. Each channel element is arranged in a MEMS layer arrangement. A monotonically varying scallop height of a channel element is the same or different from that of a neighboring channel element, either as a monotonous increase or monotonous decrease. This enables efficient adaptation to a later application of the MEMS.

[0028] According to one embodiment, a plurality of scallop structures have a substantially identical scallop depth perpendicular to the channel direction.

[0029] In an alternative embodiment, a plurality of scallop structures are also arranged in the fluidic channel. The scallop structure is arranged perpendicular to the channel direction as a first scallop structure with a first scallop depth and a second scallop structure of the plurality of scallop structures with a different second scallop depth. This enables adaptation of the fluidic flow within the fluidic channel.

[0030] According to one embodiment, the scallop structure is a first scallop structure, and the scallop arrangement comprises at least a second scallop structure arranged adjacent to the first scallop 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 part of a common in-plane scallop arrangement, further widening the fluidic channel at this location. This allows for significantly larger fluidic channels and also exposes movable elements.

[0031] According to one embodiment, a MEMS described herein is formed as a MEMS loudspeaker.

[0032] Further advantageous embodiments are the subject of further patent claims. Preferred embodiments of the present invention are explained below with reference to the accompanying drawings: They show:

[0033] Fig. 1 is a schematic side sectional view of a MEMS according to an embodiment;

[0034] Fig. 2 is a schematic side sectional view of a portion of the MEMS of Fig. 1 in an enlarged view;

[0035] Fig. 3 is a representation of the part of the MEMS comparable to Fig. 2 for discussing embodiments;

[0036] Fig. 4 is a schematic side sectional view of the part of Fig. 3, where scallops according to the invention are defined by the height and a radius of the scallop structures;

[0037] Fig. 5 is a schematic side sectional view of a MEMS according to an embodiment having a plurality of scallop structures in the fluidic channel;

[0038] Fig. 6 is a schematic side sectional view of a MEMS according to an embodiment in which the MEMS layer has at least two fluidic channels;

[0039] Fig. 7 is a schematic plan view of a MEMS according to an embodiment, showing, among other things, a bottom layer;

[0040] Fig. 8a is a schematic side sectional view of the bottom layer of a MEMS according to an embodiment with a plurality of scallop structures having a scallop height that varies monotonically at least in sections along the channel direction;

[0041] Fig. 8b is a schematic side sectional view of a MEMS according to an embodiment in which the scallop height is monotonically decreasing; Fig. 9 is a schematic side sectional view of a MEMS according to an embodiment that can be implemented, for example, as a MEMS loudspeaker;

[0042] Fig. 10 is a schematic side sectional view of a MEMS according to an embodiment in which a movable element has main sides that are designed differently from one another;

[0043] Fig. 11 is a schematic side sectional view of another MEMS according to an embodiment; and

[0044] Fig. 12 is a schematic flow diagram of a method according to an embodiment by means of which a MEMS can be manufactured.

[0045] 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 equivalent or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.

[0046] The embodiments described below are described in conjunction with numerous details. However, embodiments may also be implemented without these detailed features. Furthermore, for clarity, embodiments are described using block diagrams instead of detailed illustrations. Furthermore, details and / or features of individual embodiments may be readily combined with one another, unless explicitly described otherwise.

[0047] Fig. 1 shows a schematic side sectional view of a MEMS 10 according to an embodiment. The MEMS 10 has a MEMS layer 12 in which a fluidic channel 14 is arranged 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 can alternatively optionally also comprise a larger number of interconnected layers. For example, electrically conductive layers and electrically non-conductive layers and / or electrically semiconductive layers can be interconnected to form a layer arrangement of the MEMS layer 12. One or more layers of the MEMS 10 can comprise semiconductor-based materials, for example a silicon material, including materials derived therefrom, such as silicon oxide and / or silicon nitride.

[0048] A side wall structure 22 of the fluidic channel 14 has a scallop arrangement, which has at least one scallop structure 24i-24 n The scallop structure or scallop arrangement increases the effective acoustic channel width of the fluidic channel 14 compared to a nominal channel width, as discussed with reference to Fig. 2. An effective acoustic channel width is understood to be a channel width effective for transmitting sound waves.

[0049] A fluid flow 26 can occur through the fluidic channel 14 due to a pressure difference between the first channel side 16 with a pressure p1 and the second channel side 18 with a pressure p2. It is possible, but not necessary, for a pressure p1 that is higher than the pressure p2 to be present on the first channel side 16. For example, it is possible for at least one substructure of the fluidic channel 14 to be arranged so as to be movable, 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 due to the movement, whereby the pressure on one of the two sides 16 or 18 may become irrelevant.

[0050] In other words, Fig. 1 shows an embodiment of a fluid-flow channel 14, for example, in a MEMS-based loudspeaker. A wafer stack 12 separates two acoustic domains, each with a fluid pressure p1 and p2. This wafer stack contains at least one channel or several channels that connect the two acoustic domains and simultaneously contain scallop-structured walls. 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.

[0051] Fig. 2 shows a schematic side sectional view of a portion 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 the side walls of the fluidic channel 14 are flat, without scallop structures 24. Furthermore, an at least local maximum width 32 of the fluidic channel 14 is shown, which is obtained by increasing the nominal channel width by a scallop depth 34 perpendicular to a channel depth z. The scallop structures 24 increase an effective acoustic channel width 36 compared to the nominal channel width 36. This is illustrated by way of example using a flow velocity 38, which is zero, 0, or almost 0 at the channel walls at the base points of the scallop structures 24, where the nominal channel width 28 is present in the fluidic channel 14.In the area of ​​the scallop structures, as shown by the scallop structure 245, a flow with a reversal of the flow direction can be provided in the apex regions of the scallop structure 245, as can be seen from the change in sign of the flow velocity 38.

[0052] This local reduction or reversal of the flow velocity can lead to a reduction in the total impedance compared to the nominal channel width, thus increasing the effective acoustic channel width 36 compared to the nominal channel width 28.

[0053] At a base point or base region of a scallop structure 242, a fluid profile of the fluidic channel 14 similar to a plane Poiseuille flow can be obtained due to the scallop structure, and at the apex regions 42, a flow with a reversal of a flow direction can be obtained.

[0054] The scallop structures 24 can be created in the MEMS layer 12 using a Bosch process. However, these are not designed arbitrarily, but rather in such a way that the inventive effect of increasing the effective acoustic channel width occurs.

[0055] In other words, Fig. 2 shows an embodiment in which the scallops set a different velocity profile of the fluid depending on the position.

[0056] Fig. 3 shows a representation of the part of the MEMS 10, comparable to Fig. 2, for discussing exemplary embodiments. The scallop depth 34 is shown together with a scallop 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 scallop structures 24 of the scallop arrangement extends with a scallop height 46 along the channel direction z of at least 200 nm, at least 300 nm or more, approximately 350 nm or more. Alternatively or additionally, exemplary embodiments are preferred in which the scallop depth perpendicular to the channel direction z has a value of at least 100 nm, at least 150 nm, or at least 200 nm compared to the nominal channel width 28 in the MEMS layer 12.

[0057] In other words, Fig. 3 shows an embodiment where the scallops are defined by the depth 34 and the height 46. The depth lies in a preferred range between 100 nm and 10 pm, while the range between 0.5 pm and 2 pm is particularly preferred. The height 46 lies in a preferred range between 0.2 pm and 20 pm, with the range between 1.5 pm and 8 pm being particularly preferred.

[0058] Fig. 4 shows a schematic side sectional view of the part from Fig. 3, whereas the scallops 24 are defined by the height 46 and a radius R of the scallop structures 24. In accordance with Fig. 3, the scallop height 46 lies in a preferred range from 0.2 pm to 20 pm and particularly preferably in a range between 1.5 pm and 8 pm. According to this embodiment, the radius R is constant across the scallop structure, but can also vary locally, for example to provide an elliptical structure. It is preferred if the radius R is greater than half the height 46 at the base points and / or the apex regions or at any point. The radius R can lie in a preferred range from at least half the height (h / 2) up to 200 pm, while the range from 3 / 5 h up to 3 h is particularly preferred, where h is the value of the height 46.

[0059] Fig. 5 shows a schematic side sectional view of a MEMS 50 according to an embodiment. The MEMS 50 has a plurality of scallop structures 24i-24g in the fluidic channel 14. According to the embodiment, different pairs of adjacent scallops can have a different distance 48i or 482 between vertices of the scallop structures. Although only two different distances 48i and 482 are shown, additional different distances, i.e., at least three, at least four, or more different distances, can also be implemented. While the scallop structures 24i-24g can be formed with a matching structure with respect to a scallop height, a scallop depth, and / or a radius, for example, two scallop arrangements can be implemented shifted relative to one another to obtain a pairwise shift shown.By using an additional, third scallop arrangement, which may also be periodic along the channel direction z, a third spacing can easily be achieved. In the illustration of Fig. 5, for example, the scallop structures 24i, 243, 245, 247, and 249 form a first scallop arrangement, and the scallop structures 242, 244, 246, and 24s form a second scallop arrangement. By shifting the second scallop arrangement relative to the first scallop arrangement along the negative z-direction, a first spacing 48i between two adjacent scallop structures 244 and 24s can be increased and, at the same time, another adjacent spacing between the scallop structures 245 and 246 can be decreased. In a particular embodiment of the MEMS 50, a sum of distances 48i and 482 of any three adjacently arranged scallop structures may be constant over the channel depth 14, for example in the case of two scallop arrangements.

[0060] The plurality of scallop structures of the MEMS 50 may include a first pair 244, 24s of scallop structures having the first pitch 48i and a second pair 245 / 246 of adjacent scallop structures having a different pitch 482 from vertices of the scallop structures.

[0061] This can also result in a different position of foot points or foot regions 44 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 28i at foot region 442 and a different channel width 282 at foot region 443.

[0062] In other words, Fig. 5 shows a further embodiment where the scallops are offset from each other such that at least two different channel widths 28i and 282 are created, defined by the scallop tips. Furthermore, at least two different height distances 48i and 482 of the scallop bases are created.

[0063] Fig. 6 shows a schematic side sectional view of a MEMS 60 according to an embodiment in which the MEMS layer 12 has at least two fluidic channels 14i and 142 to interconnect the first channel side 16 and the second channel side 18. It is possible, but not necessary, for the fluidic channels 14i and 142 to have a matching first channel side 16 and / or a matching second channel side 18.

[0064] Regardless of the number of fluidic channels, which can easily be 1, the nominal channel widths of the fluidic channels 14i and 142 are variable along the course of the fluidic channels 14i and 142 along the z-direction. This can result in a nominal channel width 28 that depends on the position along the z-direction, so that a nominal channel width 28(z) can 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 along the course of the fluidic channel 14i. Scallop structures that are constant or have different depths and / or heights can be modulated onto this periodic change.

[0065] In other words, Fig. 6 shows a cross-section of an exemplary fluidic channel. The channel has a serrated shape with scallops on the walls.

[0066] Fig. 7 shows a schematic top view of a MEMS 70 according to one embodiment. Several independently implementable configurations can be seen therein. In addition to the MEMS layer 12, a base layer 52 is shown as an example, which may, but is not necessarily, the last layer along the negative z-direction. This layer can have openings 54i to 54i2, for example, to bend the fluidic channels 14i to 14i with the first channel side or the second channel side.

[0067] An advantageous implementation, which can be seen in Fig. 7, is the configuration as a MEMS, in which the scallop structure 24i is arranged next to another scallop structure 242 along a direction perpendicular to a main side normal of the MEMS layer 12, which runs, for example, parallel to the z-direction. The geometries of the two scallop structures 24i and 242 intersect each other and form at least part of a common in-plane scallop arrangement. While, for example, in MEMS 10, adjacent scallop structures are arranged adjacent to each other along the channel direction z, but a respective scallop structure 24 can be produced by a single etching process, the scallop structures 24i and 242 of the MEMS 70 are arranged in-plane next to each other, which can lead to an enlargement of the channel cross-section.This does not exclude an additional arrangement of further scallop structures along the channel direction z, but embodiments explicitly provide for this.

[0068] Independently of this, at least parts of the MEMS layer 12 can be formed as a movable element 56i, 562, and / or 56s arranged parallel to the MEMS plane. Such a movable element can be configured to interact with a fluidic channel 14i to 144 in the adjacent fluidic channel to effect a fluidic flow 26ij, wherein a movement of the movable element 56i to 56s is causally related to a movement of the fluid through the fluidic channel 14i to 14s. The indices i and j of the fluid flows 26i,j denote the fluidic channel i with i = 1,...,4, and j denotes a partial fluid flow within the fluidic channel 14j.The reason for this is that, for example, a central region of the respective movable element 56i, 562 and 56s 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.

[0069] Deflection directions 58i, 582, and 58s of the movable elements 56i, 562, and 563, respectively, can run parallel to one another, and the respective movable elements can move in a back-and-forth motion, whereby the actuation method 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 also be provided, for example in the context of a microphone configuration, that the fluid triggers a movement of the movable element, which is then detected.

[0070] In the MEMS 70, in both cases, a fluidic channel 14i to 144 is formed at least partially by a side wall structure of the movable element 56i to 563 arranged perpendicular to the MEMS plane, approximately along the z-direction.

[0071] In other words, Fig. 5 shows a top view of a MEMS component. The fins 56 have in-plane scallops. This leads to a reduction in acoustic attenuation along the fins.

[0072] Fig. 8a shows a schematic side sectional view of the bottom layer 52 of a MEMS 801 according to an embodiment. The bottom layer 52 can, for example, comprise the MEMS layer 12 of the MEMS 10. At least one additional MEMS layer arrangement 62 with electrically passive and / or electrically active properties and / or mechanically active and / or mechanically active properties can provide a part of the MEMS 801. The scallop arrangement comprises a plurality of scallop structures per fluidic channel 14i and 142, wherein, according to embodiments, one fluidic channel or more than two fluidic channels can already be provided. The fluidic channel 14i and the fluidic channel 142 extend along the channel direction z, which, however, does not necessarily have to be arranged perpendicular to the x / y plane. Fig. 8a shows that the plurality of scallop structures 24i to 24 na scallop height 46i to 46, which at least in sections changes monotonously n along the channel direction. In the case of the MEMS 8O1, there is a monotonic increase in the scallop height 46i to 46 n .

[0073] Fig. 8b shows a schematic side sectional view of a MEMS 802, to which the details of the MEMS 801 also apply, but here the scallop height is monotonically decreasing.

[0074] In other words, Figures 8a and 8b each show a cross-section of the cap-bottom wafer. The height 46 of the individual scallops increases with increasing channel height / depth. The channel width can remain the same.

[0075] Fig. 9 shows a schematic side sectional view of a MEMS 90 according to an embodiment, which can be implemented, for example, as a MEMS loudspeaker.

[0076] By way of example, layer 52 of the MEMS 801 from Fig. 8 is shown, which can also function as a cover wafer here. A further MEMS layer or layer arrangement 66 can, for example, comprise a device wafer with one or more layers, wherein, for example, movable elements 56i and 562 can be arranged. The MEMS 90 can have a further MEMS layer arrangement 68, which can, for example, be used as a base wafer, wherein such terms can be interchanged arbitrarily with a changed orientation of the MEMS 90.

[0077] Movement of the movable elements 56i and 562 can lead to sound pressure waves that alternately pass through the openings 54i and 542 on the one hand and 54s on the other. For example, a possibly synchronous movement of the movable elements 56i and 562 away from each other can lead to sound pressure waves through the openings 54i and 542, and a synchronous movement of the movable elements 56i and 562 toward each other can lead to sound pressure waves from the opening 54s.

[0078] The fluid flow 26 can have locally different directions. Figure 9 illustrates that the scallop arrangement can be different in different layers. Thus, starting from the MEMS layer arrangement 66 outward along the positive z-direction in the MEMS layer 52, an increase in the form of a monotonic increase in the scallop heights 46i,i to 46i , nbe implemented. With respect to the z direction in space, this can be inverted in the MEMS layer arrangement 68, so that an optionally monotonic increase in the scallop heights is also implemented outwardly along the negative z direction.

[0079] Independently of this, a scallop height in the MEMS layer arrangement 66 along the z-direction can be constant, variable, or monotonically variable or strictly monotonically variable.

[0080] In other words, Fig. 9 shows a cross-section of the lid, device, and bottom wafers. The height of the individual scallops increases with increasing depth in the lid and device wafers. In the bottom wafer, the height h of the scallops increases with increasing depth.

[0081] Fig. 10 shows a schematic side sectional view of a MEMS 100 according to an embodiment. The MEMS 100 can be formed in accordance with the MEMS 90, but differs in that, for example, the movable elements 56i and 562 are formed with different main sides with respect to the arrangement and configuration of the scallop structures. For each of the movable elements 56i and 562, a respective main side 56Ai or 56A2 and an opposite second main side 56Bi or 56B2 can be part of a different fluidic channel, as is also the case with the MEMS 90. However, while, for example, a consistent monotonic increase or decrease in the scallop heights is arranged on the different main sides of the MEMS 90, the different main sides of a movable element 56i and 562 have a different arrangement.For example, an increase in the scallop heights, in particular a monotonic increase, is arranged on the main side 56Ai and the main side 56B2 along the z-direction, while a monotonically decreasing scallop height is arranged along the z-direction on the respective opposite main side 56Bi and 56A2. This can enable adaptation to the respective flow direction of the fluid stream 16. A different configuration on the main sides can be achieved, for example, by individually etching the respective fluidic channel in a MEMS layer 52, 66, and 68, each of which can independently and independently provide a MEMS layer 12.

[0082] In other words, Figure 10 shows a cross-section of the lid, device, and bottom wafers. The height of the individual scallops increases with increasing height in the lid wafer. In the bottom wafer, the height of the scallops increases with increasing depth. In the channels of the device wafer 66, the height of the scallops increases in two channels with increasing height and one channel with increasing depth.

[0083] Fig. 11 shows a schematic side sectional view of a MEMS 110 according to an embodiment. The MEMS 110 can be formed at least partially in accordance with the MEMS 90 and 100. Deviating from the MEMS 90 and the MEMS 100, the MEMS layer 66, for example, is formed as a device wafer. This wafer can comprise, in the fluidic channels, channel sections 72i,i and 72i,2 of a first fluidic channel, 72i,i and 72i,2 of a second fluidic channel, and 72i,i and 72i,2 of a third fluidic channel of the MEMS layer 66. The respective channel sections can be formed symmetrically with respect to a plane of symmetry 74 and, for example, provide an increasing scallop height starting from the plane of symmetry 74 along the positive z-direction and likewise provide an increasing scallop height along the negative z-direction. This configuration can easily be inverted.Although the channel sections 72 of the three different fluidic channels in the MEMS layer 66 are shown as being formed the same or identically, the fluidic channels of one or more MEMS layers may also be formed individually and differently from one another, which also applies to the MEMS 90 and 100.

[0084] Adjacent channel sections 72i,i and 72I,2; 722,I and 722,2 as well as 723,I and 723,2 may have inverted monotonic curves of the scallop heights.

[0085] In the MEMS 90, 100, and 110, it is shown that a fluidic channel can be a MEMS layer 52, 66, and 68, each channel element of a series channel arrangement across the different MEMS layers 52, 66, and 68. The channel arrangement can therefore extend across multiple MEMS layer arrangements or MEMS layers. A respective channel element in a MEMS layer arrangement can have a constant or variable, for example, monotonically variable, scallop 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.

[0086] In one possible embodiment, illustrated in Figs. 9, 10, and 11, a plurality of scallop structures of a channel section or a fluidic channel can have a substantially identical scallop depth perpendicular to the channel direction z. As an alternative to a consistent scallop depth, different scallop depths can also be provided in a plurality of scallop structures.

[0087] In other words, Fig. 11 shows a cross-section of the lid, device, and bottom wafers. In the device wafer, the height of the individual scallops increases with increasing height and depth, starting at half the channel height.

[0088] Embodiments of the present invention relate to MEMS, for example, as MEMS that are part of a MEMS loudspeaker. Some embodiments relate to MEMS loudspeakers with a MEMS described herein. In some embodiments, scallops on the walls of a fluid-flow channel are characteristic, having a depth 34 in a range between 0.1 pm and 10 pm, with the range between 0.5 to 2 pm being particularly preferred. Alternatively or additionally, a height 46 between 0.2 pm and 20 pm is provided, with the range between 1.5 to 8 pm being particularly preferred.

[0089] Some embodiments feature scallops with a radius R greater than half the height, but up to a maximum of 200 pm, with the range of 3 / 5 h to 3 h being particularly preferred. The parameter h represents the scallop height 46.

[0090] Some embodiments feature scallops that are offset from one another to create at least two different heights of the scallop bases and at least two different channel widths defined by scallop tips, as described in connection with Fig. 5.

[0091] Some embodiments feature scallops that vary in size across the depth of the channel.

[0092] In some embodiments, scallops are characteristic of the walls of a serrated fluid-flow channel, as described, for example, in connection with Fig. 6.

[0093] In some embodiments, fins with in-plane scallops are characteristic, as described, for example, in Fig. 7. In some embodiments, the height h or the height 46 of the individual scallops is characteristic, which increases or decreases with increasing height and / or depth of a fluid-flowing channel.

[0094] In some embodiments, the height h is likely to characterize the height 46 of the individual scallops, which increases with increasing height in the lid and device wafers and increases with increasing depth in the bottom wafer, as described in connection with Fig. 9.

[0095] In some embodiments, the height h or the height 46 of the individual scallops is characteristic, which increases with increasing height in the lid wafer and increases with increasing depth in the bottom wafer and increases 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.

[0096] In some embodiments, the height h or the height 46 of the individual scallops is characteristic, which increases or decreases starting from half the channel height, for example in the device wafer with increasing height and increasing depth, as described in connection with Fig. 11.

[0097] Embodiments of the present invention relate to microelectromechanical systems (MEMS). Using the Bosch method, channels and / or openings can be formed in a semiconductor substrate. The etching and shutdown processes are repeated in the method. Wave-shaped side surfaces form at the resulting opening, which is also referred to as scalloping. The resulting structures are referred to as scallops. While the prior art aims to minimize this scalloping effect in order to obtain the smoothest possible walls, embodiments aim to deliberately utilize the scalloping effect, since smooth walls in a fluid-flowing channel in a MEMS-based loudspeaker lead to an increase in acoustic impedances, which are reduced according to the invention. The goal of the MEMS loudspeakers described herein is to reduce the acoustic impedances.The same mechanisms can also be used in MEMS microphones or other MEMS for fluid transport.

[0098] The objective of some embodiments is to reduce the acoustic impedances in a fluid-flow channel of a MEMS loudspeaker. This objective is achieved by deliberately increasing the depth and height of the scallops in a fluid-flow 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 arise, while at the widest point of the channel, a channel width with scallops, a flow with a reversal of the flow direction in the scallop base can arise. The flow inflection point lies between the plane of the scallop tips (nominal channel width) and the plane of the scallop bases (channel width with scallops).Due to this local change in the flow profile, the acoustically effective channel width is larger than the nominal channel width and thus the impedance of the channel with scallops is reduced compared to a smooth channel with the same nominal channel width, which is advantageous.

[0099] Fig. 12 shows a schematic flow diagram of a method 1200 according to an embodiment, by means of which a MEMS can be manufactured, such as a MEMS described herein. A step 1210 comprises creating 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 has a scallop arrangement, wherein the acoustic channel has an effective acoustic channel width that is increased compared to a nominal channel width due to the scallop structure.

[0100] Such an enlargement is not achieved by the smallest possible scallops in the state of the art, but is avoided there.

[0101] 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 component of a device can also be understood as a corresponding method step or as a feature of a method step. Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device.

[0102] The above-described embodiments are merely illustrative of the principles of the present invention. It is 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 in the description and explanation of the embodiments herein.

Claims

Patent claims 1. A MEMS comprising a fluidic channel (14) in at least one MEMS layer (12; 52, 66, 68) configured to provide a fluidic connection between a first channel side (16) and a second channel side (18); wherein a sidewall structure (22) of the fluidic channel has a scallop arrangement, wherein the fluidic channel (14) has an effective acoustic channel width (36) that is increased compared to a nominal channel width (28) due to the scallop arrangement.

2. MEMS according to 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).

3. MEMS according to claim 1 or 2, wherein the fluidic channel (14) extends along a channel direction (z) and at least one scallop structure (24) of the scallop arrangement extends with a scallop height (46) along the channel direction (z) of at least 200 nm and / or extends with a scallop depth (34) perpendicular to the channel direction (z) of at least 100 nm compared to the nominal channel width (28) in the MEMS layer (12; 52, 66, 68).

4. MEMS according to one of the preceding claims, comprising a movable element (56) arranged parallel to a MEMS plane, which is designed to interact with a fluid to cause a fluidic flow (26) in the fluidic channel (14), wherein a movement of the movable element (56) is causally related to a movement of the fluid through the fluidic channel (14).

5. MEMS according to claim 4, wherein the fluidic channel (14) is partially formed by a sidewall structure (22) of the movable element (56) arranged perpendicular to the MEMS plane.

6. MEMS according to 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) which is part of the first fluidic channel; and an opposite second Main side (56B) which is part of a second fluidic channel; wherein a monotonically increasing scallop height (46) of a first plurality of scallop structures (24) is arranged on the first main side (56A) along a matching direction (z) parallel to the first fluidic channel; and a monotonically decreasing scallop height (46) of a second plurality of scallop structures (24) is arranged on the second main side (56B).

7. MEMS according to one of the preceding claims, wherein the fluidic channel (14) is configured to provide a fluid profile at base regions (44) of the scallop structure (24) similar to a plane Poiseuille flow; and at apex regions (42) of the scallop structure (24) provides a flow with a reversal of a flow direction.

8. MEMS according to one of the preceding claims, wherein the nominal channel width (28) is variable over a course of the fluidic channel (14).

9. MEMS according to claim 8, wherein the nominal channel width (28) is periodically variable over the course of the fluidic channel (14).

10. MEMS according to one of the preceding claims, comprising a plurality of scallop structures (24), wherein a first pair of adjacent scallop structures (24) has a different distance (48i, 482) from vertices of the scallop structures (24) than a second pair of adjacent scallop structures (24). 1 1. MEMS according to claim 10, wherein the plurality of scallop structures (24) along a course of the fluidic channel (14) have mutually different positions of foot points (44) along a channel width of the fluidic channel (14).

12. MEMS according to one of the preceding claims, wherein the scallop arrangement has a plurality of scallop structures (24), wherein the fluidic channel (14) extends along a channel direction (z) and the plurality of scallop structures (24) have a scallop height (46) that changes monotonically at least in sections along the channel direction (z).

13. MEMS according to claim 12, wherein the fluidic channel (14) has symmetrically arranged channel sections (72) in a MEMS arrangement; and adjacent channel sections have inverted monotonic progressions of the scallop heights (46i, 462).

14. MEMS according to claim 13, wherein the fluidic channel (14) is a channel element of a serial channel arrangement extending across multiple MEMS layer arrangements (52, 66, 68); wherein a respective channel element (72) is arranged in a MEMS layer arrangement; and a monotonically varying scallop height (46) of a channel element is the same or different from an adjacent channel element as a monotonous increase or monotonous decrease.

15. MEMS according to one of claims 12 to 14, wherein the plurality of scallop structures (24) have a substantially identical scallop depth (34) perpendicular to the channel direction (z).

16. MEMS according to one of claims 1 to 14, wherein a plurality of scallop structures (24) are arranged in the fluidic channel; and the scallop structure (24) is arranged as a first scallop structure (24) with a first scallop depth (34) and a second scallop structure (24) of the plurality of scallop structures (24) with a different second scallop depth (34) is arranged perpendicular to the channel direction (z).

17. MEMS according to one of the preceding claims, wherein the scallop structure is a first scallop structure (24i) and the scallop arrangement comprises at least a second scallop structure (242) arranged along a direction (x, y) perpendicular to a main side normal of the MEMS layer (12; 52, 66, 68) adjacent to the first scallop structure (24i); wherein geometries of the first scallop structure (24i) and the second scallop structure (242) intersect and form at least part of a common in-plane scallop arrangement.

18. MEMS according to one of the preceding claims, which is formed as a MEMS loudspeaker.

19. A method (1200) for manufacturing a MEMS comprising the following steps: 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 has a scallop arrangement, wherein the fluidic channel has an effective acoustic channel width that is increased compared to a nominal channel width due to the scallop arrangement.

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