MEMS structural element

Abstract

The invention relates to a MEMS component, in particular an acoustic transducer or a pressure sensor, comprising a substrate having a cavity and a fastening part, an interaction element arranged above the cavity and connected to the fastening part, the interaction element comprising a bending beam, the bending beam being arranged in the cavity, the bending beam being arranged in the cavity, and the bending beam being arranged in the cavity. The invention relates to a device for manufacturing a back electrode, comprising a curved beam, a limiting layer arranged at a distance from the curved beam via a connecting element, the limiting layer defining a cavity together with the curved beam, and a back plate located within the cavity, the back plate forming a back electrode, the back plate being configured to be harder relative to the limiting layer and the curved beam, the at least one electrode being configured to be electrically connected to the at least one electrode, the at least one electrode being configured to be electrically connected to the at least one electrode, the at least one electrode being configured to be electrically connected to the at least one electrode. The electrode forms a readout capacitance with a back electrode of the back plate in order to capacitively detect an offset of at least one of the bending beam, the connecting element and the limiting layer, at least one stop element, which is designed to be moved into a mechanical stop, the stop element generates at least one fluid flow resistance, in particular a fluid seal, in the stop between a cavity on the side facing the substrate and a volume on the side of the cavity facing away from the substrate.

Description

Technical Field

[0001] The invention relates to a MEMS component, in particular an acoustic transducer or a pressure sensor. Background Art

[0002] Patent document EP 2 664 058 B1 discloses a micromechanical component.

[0003] Patent document EP 3 568 595 B1 discloses a micromechanical device.

[0004] Publication CN 1 14 885 264A1 discloses a microphone.

[0005] Utility model document CN 2 16 852 338U discloses a micro-electromechanical microphone.

[0006] Condenser microphones are particularly efficient in terms of signal-to-noise ratio, energy consumption and further processability. This has led to the widespread replacement of electret microphones by MEMS microphones.

[0007] The development of MEMS microphones with double membranes has again led to a significant increase in the signal-to-noise ratio. In this concept, the fluid damping between the rigid back electrode (back plate) and the movable stagnation pressure membrane is almost completely eliminated. This is achieved by supporting the back electrode in the negative pressure area between the two mutually coupled membranes.

[0008] Two such double-diaphragm microphones are disclosed in documents US Pat. No. 9,181,080 and US Pat. No. 9,986,344. A disadvantage of this arrangement is the high mechanical rigidity of the double-diaphragm structure, which limits its deflectability and thus its sensitivity and signal-to-noise ratio. Summary of the invention

[0009] The object on which the present invention is based should be seen as providing a MEMS component.

[0010] This object is achieved by means of the subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the respective dependent claims.

[0011] According to a first aspect, a MEMS structural element, in particular an acoustic transducer or a pressure sensor, is provided, the MEMS structural element comprising:

[0012] a substrate having a cavity and a fixing portion,

[0013] an interactive element arranged above the cavity and connected to the fixing portion,

[0014] The interactive element comprises a bending beam, a delimiting layer arranged at a distance from the bending beam via a connecting element, the delimiting layer defining a cavity together with the bending beam, and a back plate located in the cavity, the back plate having a back electrode, wherein the back plate is designed to be more rigid than the delimiting layer and the bending beam,

[0015] at least one electrode which forms with the back electrode of the back plate one or more capacitances which can be read out in order to capacitively detect a deflection of at least one of the bending beam, the connecting element and the delimiting layer,

[0016] At least one stop element is designed to be moved into a mechanical stop, wherein the stop element generates at least one fluid flow resistance, in particular a fluid seal, between a cavity on a side facing the substrate in the stop and a volume on a side of the cavity facing away from the substrate.

[0017] The invention is based on and includes the recognition that the above-mentioned object is achieved in the following way: an interaction element is provided, which is arranged above the cavity. In addition, at least one stop element is provided, which can be moved into a mechanical stop. If the stop element is in the mechanical stop, at least one fluid flow resistance, in particular a fluid seal, is generated between the cavity on the side facing the substrate and the volume on the side of the cavity facing away from the substrate. For example, there is a negative pressure in the cavity itself. The stop element is surrounded, for example, by the interaction element or by the fixing part or by the substrate.

[0018] Advantageously, the fluid squeeze film damping effect (fluidische Quetschfilm- ). In particular, gap noises can be advantageously avoided in the case of rapid pressure difference changes. Furthermore, fluid leakage can be advantageously minimized. Furthermore, deflection can advantageously be maximized. Furthermore, the sensitivity of the structural element can advantageously be maximized.

[0019] In particular, a MEMS component is therefore provided which, compared with the above-mentioned prior art, allows a smaller structural size at the same power or a higher power at the same structural size.

[0020] The abbreviation "MEMS" stands for micro-electro-mechanical system.

[0021] In one embodiment, the MEMS component comprises an actuator which is designed to move the stop element into the stop.

[0022] This results in, for example, the technical advantage that the stop element can be moved efficiently.

[0023] In one embodiment, the MEMS component comprises a plurality of electrodes which are formed and / or anchored in regions electrically insulated from one another in and / or on the bending beam and / or in and / or on the delimiting layer and / or in and / or on the connecting element.

[0024] The plurality of electrodes together with the back plate respectively form a capacitance that can be read out in order to capacitively detect a corresponding displacement of at least one of the bending beam and / or the connecting element and / or the delimiting layer relative to the back plate. In other words, the electrodes together with the back plate form a capacitance that can be read out and thus advantageously enable differential capacitive analysis, such as the measurement of a displacement of the interactive element relative to the back plate as a function of an externally applied pressure difference.

[0025] In one embodiment of the MEMS component, it is provided that the electrodes are each designed as planar electrodes or as electrode structures protruding into the cavity.

[0026] This results in the following technical advantages, for example: a high capacitance surface density and thus a higher sensitivity is achieved. In the case of planar electrodes, a smaller gap distance can be achieved, and in the case of a recessed electrode structure, a larger electrode area can be achieved.

[0027] In one embodiment of the MEMS component, it is provided that the bending beam and / or the connecting element and / or the delimiting layer are each formed from a non-conductive material to which the electrode structure projecting into the cavity is anchored.

[0028] This advantageously makes it possible to achieve a higher capacitance density and / or to minimize parasitic capacitances, which allows miniaturization or an increase in the sensitivity of the component.

[0029] In one embodiment of the MEMS component, it is provided that one or more electrode structures form a plurality of sections which are electrically insulated from one another in order to form capacitances with the back plate which can be read out independently of one another.

[0030] This results in the technical advantage, for example, that the capacitances which can be read out independently are formed or shaped such that a differential capacitive evaluation is possible.

[0031] In one embodiment of the MEMS component, it is provided that the delimiting layer is anchored to the bending beam via delimiting walls, or that the delimiting layer is designed as a further bending beam and is directly attached to the fastening via an insulating layer.

[0032] The two aforementioned possibilities advantageously make it possible to achieve complete stress decoupling from the substrate or from the fastening.

[0033] In one embodiment of the MEMS component, it is provided that the connecting element is formed from an electrically insulating material.

[0034] Ideally, evaluation electronics, which may be surrounded by a MEMS component, for example, require the highest possible insulation resistance between all measuring electrodes, which is effectively promoted by providing connecting elements composed of an electrically insulating material.

[0035] In one embodiment of the MEMS component, it is provided that the connecting element has a spring element which is mechanically anchored on one side to the bending beam and / or to the limiting layer, or is designed in two parts, wherein the two parts only come into contact by a movement toward one another.

[0036] The attachment of the connecting element on one side has the advantage in particular that a greater flexibility of the bending beam is possible and no torque is transmitted. A two-part attachment has the technical advantage, for example, that a particularly stable attachment is achieved.

[0037] For example, a plurality of spring elements are provided. The above explanations in the context of one spring element apply analogously to a plurality of spring elements. Thus, for example, the inner spring element can be mechanically anchored on one side to the bending beam and / or the limiting layer, so that the spring element is only in mechanical contact under externally applied gas pressure.

[0038] In one embodiment of the MEMS component, it is provided that a peripheral delimiting wall of the cavity has a transversely corrugated course.

[0039] This results in, for example, the technical advantage that the edges of the interaction element are reinforced against collapse.

[0040] For example, a plurality of boundary walls may also be provided which extend substantially alongside one another, so that explanations given in the context of one boundary wall also apply to a plurality of boundary walls and vice versa.

[0041] In other words, a plurality of delimiting walls may be provided which are, for example, transversely corrugated and extend alongside one another.

[0042] In one embodiment of the MEMS component, it is provided that the back plate is formed at least partially by an electrically conductive layer and / or by a dielectric.

[0043] This results in the technical advantage, for example, that the backplane can be realized in an efficient manner and interfering parasitic capacitances can be minimized.

[0044] For example, the backplane may be formed directly from the conductive layer and / or the dielectric.

[0045] In one embodiment of the MEMS component, it is provided that the back plate comprises an electrically insulating carrier layer, on which one or more electrically conductive regions which are electrically insulated from one another are formed as a back electrode.

[0046] This results in the technical advantage, for example, that the backplane can be realized in an efficient manner and interfering parasitic capacitances can be minimized.

[0047] Thus, the back plate can consist or be formed of an insulating carrier layer, for example a silicon-rich nitride, with a thickness of, for example, 0.5 μm to 5 μm, and, for example, at least one electrode or a plurality of electrodes, which are at least regionally formed in / on the carrier layer and are insulated from one another, which electrodes, for example, can also be arranged in a plurality of layers, which electrodes, for example, consist of polysilicon. Advantageously, leakage currents can be suppressed in this way, and the measuring capacitance can be configured in such a way that it can be maximized and parasitic capacitances can be minimized.

[0048] In one embodiment of the MEMS component, it is provided that the back plate has at least one flexibly flexible region at its edge regions, which is more flexible than a central region of the back plate.

[0049] This results in the technical advantage, for example, that efficient decoupling between the boundary wall and the rear plate can be achieved.

[0050] In particular, the back plate is designed such that, in the event of a deflection of two coupled delimiting layers, ie, the deflection of the back plate is less than half of the deflection of the two coupled delimiting layers.

[0051] The bending of the two coupled delimiting layers (i.e., delimiting layer and bending beam) is transmitted to the back plate via the delimiting walls. Therefore, in order to achieve large signals, i.e., large deflections between the delimiting layers of the back plate, suitable mechanical decoupling at this location is particularly advantageous and therefore particularly provided.

[0052] For example, the back plate has a soft bending region at the edge towards the clamping device on the fastening part, which is softer than the central region of the back plate. This can be achieved, for example, by structuring the back plate at the edge towards the clamping device by structuring a spring into the back plate in this region and / or by using or providing different materials or embodiments of the back plate with different thicknesses between the inner region and the edge.

[0053] In other words, according to one embodiment of the MEMS component, it is provided that the edge regions each have a spring structure in order to form a flexibly soft region.

[0054] As described above, this results in the following technical advantages: efficient mechanical decoupling is achieved.

[0055] Therefore, according to the above-mentioned embodiment, according to one embodiment of the MEMS structural element, the edge region includes a different material compared to the middle region, and / or, wherein the thickness of the corresponding intermediate region between the edge region and the middle region is less than the thickness of the middle region, and / or, wherein a tensile stress layer and / or a tensile stress structure are arranged in the corresponding intermediate region between the edge region and the middle region, and the tensile stress layer and / or the tensile stress structure generate tensile stress relative to the middle region.

[0056] This results in, for example, the technical advantage that a particularly efficient mechanical decoupling is achieved.

[0057] In terms of the above-mentioned tensile stress layer and tensile stress structure, the following contents are supplemented.

[0058] For example, the following layer and / or structure is arranged in the outer region of the back plate: the layer and / or structure generates tensile stress relative to the inner region. The layer or the structure is the tensile stress layer or the tensile stress structure.

[0059] The layer or structure is subjected to tensile stress relative to the inner region.

[0060] In particular, the provision of such a layer or such a structure is advantageous if a thin backing plate having a thickness of less than 5 μm is provided. For example, this means that the backing plate has a thickness of less than 5 μm.

[0061] For example, in the outer region, the backplate is formed completely or partially from tensioned silicon nitride, and in the inner region of the backplate, the backplate is formed from polysilicon. This results, for example, in the polysilicon region being under tensile stress and thus being rigid with respect to bending, which is transmitted to the backplate, for example, by its clamping device.

[0062] In one embodiment of the MEMS component, it is provided that the stop element is formed by one of the delimiting layer, the bending beam and the back plate.

[0063] The use of these layers advantageously reduces process complexity and increases the robustness of the structural element.

[0064] In one embodiment of the MEMS component, it is provided that the stop element has corrugations.

[0065] This results in the technical advantage that, for example, the flexibility of the stop element can be increased by way of the corrugations and / or the fluid seal can be effectively defined.

[0066] In one embodiment of the MEMS component, it is provided that an insulating layer is arranged between the stop element and the stop.

[0067] The insulating layer advantageously serves to electrically insulate an electrode which, according to an exemplary embodiment, is provided for attraction into a stop, which electrode is generally an actuating device.

[0068] In one embodiment of the MEMS component, it is provided that the pressure compensation opening is arranged in the stop element and / or that the pressure compensation opening is arranged as a cylindrical recess passing through the cavity.

[0069] This results in the technical advantage that, for example, quasi-static pressure differences can be compensated and a defined pressure compensation between the fluid volumes on both sides of the interaction element can be achieved. The microphone signal can thus be independent of ambient pressure fluctuations.

[0070] In one embodiment of the MEMS component, it is provided that the bending beam has one or more beam ends which are fastened to a fastening or to a substrate.

[0071] This achieves, for example, the technical advantage that the bending beam can be fastened efficiently to the substrate.

[0072] In other words, the bending beam can have one or also two beam ends fastened to the substrate. The fastening of the beam ends advantageously defines the orientation of the bending beam and, for example, provides the necessary electrical input line(s). In addition, it is advantageous and provided, for example, that the beam ends are anchored as softly as possible to the fixing part via a spring structure in order to be able to achieve a stop in the case of low voltages.

[0073] In one embodiment of the MEMS component, it is provided that the delimiting layer is designed as a further bending beam or as a diaphragm element.

[0074] This achieves, for example, the technical advantage that a stress decoupling of the interaction element from the substrate or from the fastening can be effectively achieved.

[0075] In one embodiment of the MEMS component, it is provided that the further stop is arranged on a side of the stop element which is opposite the stop.

[0076] The following technical advantages are thereby achieved, for example: the interactive element can be brought into a defined deflection / orientation and undesired movements other than the deflection can be limited, so that the robustness of the structural element can be effectively increased.

[0077] In one embodiment of the MEMS component, it is provided that the actuation device comprises at least one actuation electrode which is designed to generate an electrical force in order to move the stop element into the stop.

[0078] This achieves, for example, the technical advantage that the stop element can be efficiently moved into the stop and can subsequently form a fluid seal between adjacent environments.

[0079] The expression "at least one" means "one or more".

[0080] If the singular is used for the stop element in the embodiments, it should always be interpreted as the plural, and vice versa. This means that a plurality of stop elements can be provided.

[0081] The MEMS structural element is, for example, an acoustic transducer or a pressure sensor. The pressure sensor is, for example, a relative pressure sensor. The acoustic transducer is, for example, a microphone.

[0082] If only “structural element” is written, this should always be interpreted as meaning that this is a MEMS structural element.

[0083] The acoustic transducer is, for example, a loudspeaker.

[0084] In one embodiment of the MEMS component, the stop element is surrounded by the interaction element or by the fastening part or by the substrate.

[0085] In the case of a plurality of stop elements, these are, for example, each surrounded by the interaction element or by the fastening or by the substrate.

[0086] The embodiments and examples described here can be combined with one another in any desired manner, even if this is not explicitly described. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Below, the present invention is described in detail according to a preferred embodiment. In this case, it is shown that:

[0088] Figure 1 A schematic cross-sectional view of a first MEMS structural element is shown,

[0089] Figure 2 Show Figure 1 A schematic cross-sectional view of a first MEMS structural element,

[0090] Figure 3 A schematic cross-sectional view of a second MEMS structural element is shown,

[0091] Figure 4 Show Figure 3 A schematic cross-sectional view of a second MEMS structural element,

[0092] Figure 5 A schematic cross-sectional view of a third MEMS structural element is shown,

[0093] Figure 6 Show Figure 5A schematic cross-sectional view of a third MEMS structural element,

[0094] Figure 7 A schematic cross-sectional view showing a fourth MEMS structural element, and

[0095] Figure 8 A schematic cross-sectional view of a fifth MEMS structural element is shown. DETAILED DESCRIPTION

[0096] In the following, the same reference numerals may be used for the same features.

[0097] Figure 1 A schematic cross-sectional view of a first MEMS structural element 101 is shown.

[0098] The first MEMS structure element 101 includes a substrate 103 having a cavity 105 and a fixing portion 107. In addition, the first MEMS structure element 101 includes an interactive element 109 arranged above the cavity 105 and connected to the fixing portion 107. For the sake of clarity, if the interactive element 109 includes a plurality of elements, the elements belonging to the interactive element 109 are surrounded by a dotted line marked with reference numeral 109. In other words, the interactive element 109 includes a plurality of elements, which will be explained below.

[0099] The interaction element 109 comprises a bending beam 111. The interaction element 109 comprises a delimiting layer 115 which is arranged at a distance from the bending beam 111 via a connecting element 113 and which defines a cavity 117 together with the bending beam 111.

[0100] A back plate 119 is arranged in the cavity 117 and is designed as a back electrode, wherein the back plate 119 is designed to be more rigid than the delimiting layer 115 and the bending beam 111 .

[0101] according to Figure 1 As shown in the schematic diagram, the first MEMS element 101 includes a plurality of connection elements 113. Here, the outer connection elements 121, 125 are provided as boundary walls, and the inner connection element 123 is provided as a supporting element.

[0102] This means that the connecting element 123 is arranged between the two outer connecting elements 121, 125. The outer connecting elements 121, 125 are, for example, limiting walls. The inner connecting element 123 is designed as a column here. The outer connecting element 121 is mechanically connected to the back plate 119, while there is no mechanical coupling of the connecting elements 123, 125 to the back plate. Instead, these connecting elements can move freely in the through-opening of the back plate 119.

[0103] A first electrode 126 and a second electrode 127 are schematically drawn in. The first electrode 126 is located on the bending beam 111 on the side of the bending beam facing the back plate 119. The second electrode 127 is located on the delimiting layer 115 on the side of the delimiting layer 115 also facing the back plate 119.

[0104] Therefore, the two electrodes 126, 127 form a capacitance that can be read out with the back plate 119 in order to capacitively detect the deflection of the bending beam 111 and the limiting layer 115 relative to the back plate. For this purpose, the back plate 119 has a first back electrode 129 and a second back electrode 131. The two back electrodes 129, 131 can also be referred to as counter electrodes.

[0105] Here, the first back electrode 129 is disposed on the back plate 119 so as to be opposite to the first electrode 126. The second back electrode 131 is disposed on the back plate 119 so as to be opposite to the second electrode 127.

[0106] The interactive element 109 comprises a stop element 133 which is designed to be moved into a mechanical stop 135, wherein the stop element 133 generates at least one fluid flow resistance, in particular a fluid seal, between the cavity 105 on the side facing the substrate and the volume 137 on the side of the cavity 117 facing away from the substrate in the stop 135.

[0107] Furthermore, the pressure compensation hole 139 is provided as a cylindrical recess penetrating the cavity 117 .

[0108] In addition, a section line II is drawn, where Figure 2 A cross-sectional view according to the section line II is shown in FIG. Figure 2 Draw the section line II-II in Figure 1 A cross section along section line II-II is shown in FIG.

[0109] Figure 3 A schematic cross-sectional view of a second MEMS structural element 301 is shown.

[0110] As Figure 1 In contrast to the first MEMS component 101 , in the second MEMS component 301 the delimiting layer 115 is designed as a further bending beam 303 . In this respect, the elements with the reference numeral 115 are additionally denoted by the reference numeral 303 .

[0111] Furthermore, two spring elements 305 are provided as connecting elements 113 .

[0112] In addition, a first stop element 307 and a second stop element 309 are provided, and the first stop element and the second stop element can stop on the first stop portion 311 and the second stop portion 313 respectively.

[0113] Figure 4 Show Figure 3 FIG. 1 is a schematic cross-sectional view of a second MEMS structure element 301 along line II.

[0114] Figure 5 A schematic cross-sectional view of a third MEMS structural element 501 is shown.

[0115] The third MEMS component 501 has an electrode structure 503 which is suspended centrally on the connecting element 125 and is provided as a back electrode of the back plate 119 .

[0116] Figure 6 Show Figure 5 FIG. 5 is a schematic cross-sectional view of a third MEMS structure element 501 along line II.

[0117] Figure 7 1 shows a schematic cross-sectional view of a fourth MEMS component 701 . Provision is made here for the back plate 119 to have different thicknesses in order to achieve a decoupling between the outer limiting wall 121 and the back plate 119 .

[0118] Reference numeral 703 indicates the location of the clamping device of the back plate. Reference numeral 705 indicates a region of the back plate that is soft to the touch compared to the hard region 707 of the back plate 119 .

[0119] Figure 8 A fifth MEMS structural element 801 is shown, in which the back plate 119 has an outer ring which generates tensile stresses on the inner region and thus reinforces the inner region in order to generate a decoupling between the outer boundary wall 121 and the back plate 119. The prestressed region is marked with reference numeral 803. The tensile stress-generating outer ring is marked with reference numeral 805. The outer ring 805 is the tensile stress structure described above.

[0120] In summary, the concept described here is based in particular on the following: a MEMS structural element has a flexible, suspended interaction element, within which a rigid backplate (referred to in English as "backplate") is present in the low-pressure region. The recess in the substrate serves as a back volume, which reduces the damping effect of the back volume spring or alternatively as a sound inlet opening. The attraction of the stop element to the stop, for example by means of an electrode as an actuating means or actuating device, results in particular in the production of a fluid-tight seal effect, minimization of fluid leakage and maximization of deflection or sensitivity. Advantageously, the sensitivity can thus be adjusted in a targeted manner at low frequencies.

[0121] Electrodes can be constructed or anchored in regions electrically insulated from one another in / on the bending beam, in / on the delimiting layer and / or on the connecting element, wherein the electrodes can be implemented as planar electrodes or as electrode structures extending into the low-pressure region of the cavity. Together with the back plate, the electrodes form a capacitance that can be read out and thus enable differential capacitive evaluation, for example enabling the measurement of a deflection of the interactive element relative to the back plate as a function of an externally applied pressure difference.

[0122] The bending beams and the delimiting layers can be formed from a non-conductive material, to which a conductive, sunken finger-shaped electrode structure pointing into the cavity can be anchored. This measure can, for example, achieve a higher capacitance density than can be achieved with planar electrodes, which can allow miniaturization or increased sensitivity of the structural element.

[0123] The electrode structure anchored on the bending beam, on the delimiting layer and / or on the connecting element can form a plurality of sections which are electrically insulated from one another and thus form independently readable capacitances.

[0124] The delimiting layer can be anchored to the bending beam via delimiting walls or, alternatively, the delimiting layer can itself be designed as a bending beam and attached directly to the fastening via an insulating layer. Both allow complete stress decoupling from the substrate or from the fastening region.

[0125] The connecting elements (external delimiting walls, internal spring elements) can be formed at least partially from insulating material. Ideally, the evaluation electronics require the highest possible insulation resistance between all measuring electrodes, which is facilitated by this.

[0126] The inner spring element can be mechanically anchored on one side to the bending beam and / or the limiting layer, so that the spring element is in mechanical contact only under externally applied gas pressure. Alternatively, the spring element can consist of two parts, which are also in contact only under externally applied gas pressure. The attachment of the support element on one side has the advantage that a greater flexibility of the bending beam is possible and no torque is transmitted.

[0127] The peripheral delimiting wall can in particular be transversely corrugated. This serves primarily to provide an anti-collapse edge.

[0128] The backplate can be formed directly from the conductive layer and / or the dielectric. Alternatively, the backplate can consist of an insulating carrier layer, for example a silicon-rich nitride with a thickness of 0.5 ... 5 μm, and at least one electrode or a plurality of electrodes insulated from one another (for example in a plurality of layers) at least regionally formed on the carrier layer, the insulating carrier layer being, for example, a silicon-rich nitride with a thickness of 0.5 ... 5 μm, the electrodes being, for example, composed of polycrystalline silicon. Advantageously, leakage currents can be suppressed in this way and the measuring capacitance can be configured in such a way that it is maximized and parasitic capacitances are minimized.

[0129] The back plate can have corresponding through-openings for the connecting elements and possible sunken finger electrodes. The through-openings decouple the back plate from the movement of the bending beam. The spring elements prevent the upper and lower limiting layers from collapsing onto the back plate. In addition, the limiting walls and the spring elements connect the bending beam and the limiting layers and enable their synchronous movement.

[0130] The stop element can be formed, for example, by a portion of at least one of the delimiting layer, the bending beam layer or the backing layer and have corrugations. The use of these layers reduces the process complexity and increases the robustness of the structural element. The corrugations can increase the flexibility of the stop element or define a fluid seal.

[0131] There may be an insulating layer between the stop element and the stop, which serves to electrically insulate the actuating means / electrodes required for attraction into the stop.

[0132] For acoustic transducers (microphones, loudspeakers), cylindrical recesses can be provided in the region of the cavity and / or pressure compensation holes and / or pressure compensation gaps can be provided in the region of the bearing seal. This is necessary in order to be able to compensate for quasi-static pressure differences and to enable a defined pressure compensation between the fluid volumes on both sides of the interaction element. As a result, the microphone signal becomes independent of ambient pressure fluctuations.

[0133] One or more bending beams can have one or also two beam ends fastened to the substrate. The fastening of the beam ends defines the orientation and provides the necessary electrical input line(s). It is also advantageous if the beam ends are anchored as softly as possible to the fixing part via a spring structure in order to be able to achieve a stop in the case of low voltages.

[0134] The delimiting layer can be designed as a membrane element or also as a bending beam. Both variants advantageously allow stress decoupling of the interaction element from the substrate / fixture.

[0135] A second stop can be provided on the side of the stop element that is opposite the first stop in order to limit undesired movements other than deflection and to increase the robustness of the component.

Claims

1. A MEMS structural element (101, 301, 501, 701, 801), in particular an acoustic transducer or a pressure sensor, the MEMS structural element comprising: A substrate (103) having a cavity (105) and a fixing portion (107), an interactive element (109) arranged above the cavity (105) and connected to the fixing portion (107), Wherein, the interactive element (109) comprises a bending beam (111), a delimiting layer (115) arranged at a distance from the bending beam (111) via a connecting element, the delimiting layer defining a cavity (113) together with the bending beam (111), and a back plate (119) located in the cavity (113), the back plate having a back electrode, wherein the back plate (119) is designed to be more rigid than the limiting layer (115) and the bending beam (111), at least one electrode, which forms a capacitance that can be read out with a back electrode of the back plate (119) in order to capacitively detect a deflection of at least one of the bending beam (111), the connecting element and the limiting layer (115), At least one stop element (133) is designed to be moved into a mechanical stop portion (135), wherein the stop element (133) generates at least one fluid flow resistance, in particular a fluid seal, between a cavity (105) on the side facing the substrate in the stop portion (135) and a volume on the side of the cavity (113) facing away from the substrate.

2. The MEMS structural element (101, 301, 501, 701, 801) according to claim 1, comprising an actuating device, which is configured to move the stop element (133) into the stop portion (135).

3. The MEMS structural element (101, 301, 501, 701, 801) according to claim 1 or 2, comprising a plurality of electrodes, which are constructed and / or anchored in areas electrically insulated from each other in and / or on the bending beam (111) and / or in and / or on the limiting layer (115) and / or in and / or on the connecting element.

4. The MEMS structural element (101, 301, 501, 701, 801) according to claim 3, wherein: The electrodes are each configured as a planar electrode or as a submerged finger-shaped electrode structure extending into the cavity (113).

5. The MEMS structural element (101, 301, 501, 701, 801) according to claim 4, wherein: The bending beam (111) and / or the limiting layer (115) are each formed of a material that is not electrically conductive, and the electrode structure extending into the cavity (113) is anchored on the material.

6. The MEMS structural element (101, 301, 501, 701, 801) according to any one of claims 3 to 5, wherein: One or more electrode structures form a plurality of sections electrically insulated from one another so as to form capacitances with the back plate (119) that can be read out independently of one another.

7. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The delimiting layer (115) is anchored to the bending beam (111) via delimiting walls, or the delimiting layer (115) is designed as a further bending beam (111) and is directly attached to the fixing part (107) via an insulating layer.

8. The MEMS structural element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The connecting element is formed from an electrically insulating material.

9. The MEMS structural element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The connecting element has a spring element which is mechanically anchored on one side to the bending beam (111) and / or to the limiting layer (115), or which is designed in two parts, wherein the two parts only come into contact by a movement towards one another.

10. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The boundary wall (121) is transversely corrugated.

11. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The back plate (119) is formed by a layer capable of conducting electricity and / or by a dielectric.

12. The MEMS structural element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The back plate (119) comprises an electrically insulating carrier layer on which one or more electrically conductive regions which are electrically insulated from one another are formed as a back electrode.

13. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The back plate (119) has a flexible region at its edge regions, which is more flexible than the central region of the back plate (119).

14. The MEMS structural element (101, 301, 501, 701, 801) according to claim 13, wherein: The edge regions each have a spring structure in order to form the flexibly soft region.

15. The MEMS structure element (101, 301, 501, 701, 801) according to claim 13 or 14, wherein: The edge region comprises a different material than the middle region, and / or the thickness of a corresponding intermediate region between the edge region and the middle region is smaller than the thickness of the middle region, and / or a tensile stress layer and / or a tensile stress structure (805) is provided in the corresponding intermediate region between the edge region and the middle region, and the tensile stress layer and / or the tensile stress structure generate tensile stress relative to the middle region.

16. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The stop element (133) comprises a portion of one of the bounding layer (115), the bending beam (111) and the back plate (119).

17. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The stop element (133) has corrugations.

18. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: An insulating layer is provided between the stop element (133) and the stop portion (135).

19. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The pressure compensation hole is arranged in the stop element (133), and / or, wherein the pressure compensation hole (139) is arranged as a cylindrical recess passing through the cavity (113).

20. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The bending beam (111) has one or more beam ends fastened to the substrate (103).

21. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: The delimiting layer (115) is designed as a further bending beam (111) or as a membrane element.

22. The MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims, wherein: A further stop (135) is arranged on a side of the stop element (133) that is opposite the stop (135).

23. A MEMS structure element (101, 301, 501, 701, 801) according to any one of the preceding claims as referenced to claim 2, wherein: The actuation device comprises at least one actuation electrode, which is configured to generate an electric force in order to move the stop element (133) into the stop portion (135).

Images