MEMS with large fluid active surface

Abstract

The present invention relates to a MEMS including a substrate including a cavity. The MEMS includes a movable layer arrangement structure, which is arranged in the cavity, and the cavity includes a first beam, a second beam, and a third beam arranged between the first beam and the second beam and fixed at a discrete area electrically insulated therefrom. The movable layer arrangement structure is configured to move along a moving direction in a substrate plane in response to a potential between a first beam and a third beam, or in response to a potential between the second beam and the third beam. The first, second and third beams are part of a first layer of the movable layer arrangement structure. The movable layer arrangement structure includes a second layer arranged adjacent to the first layer along a direction perpendicular to the substrate plane. The second layer is arranged in a movable manner along the moving direction.

Description

Technical Field

[0001] The present invention relates to micro-electromechanical systems (MEMS) configured to include a large active area for interaction with fluids. In particular, the present invention relates to NEDs (Nanoscopic Electrostatic Drives) having an enlarged lateral surface due to the stacking and / or arrangement of post structures or resistor structures. Background Art

[0002] The principle of NED (Nanoscopic Electrostatic Drive) is described in WO2012 / 095185A1. NED is a novel MEMS (Micro Electro Mechanical System) actuator principle. From a technical point of view, there are basically two types of NED actuators: vertical NED (V-NED) and lateral NED (L-NED). In V-NED, an object such as a silicon (Si beam) moves vertically, i.e. out of the substrate plane, e.g. out of the substrate plane defined by a Si disk or wafer. In L-NED, an object such as a Si beam moves laterally, i.e. in a plane, e.g. in a Si disk.

[0003] In NED gaps, the situation can be described as the smaller the electrode gap, the larger the acting electromotive force and thus the desired deflection of the beam. This means that it is almost always desirable to have a very small gap distance (eg in the nanometer range).

[0004] Technically, such small distances between the electrodes are not always easy to produce. Usually, when producing gaps in silicon, the method used is deep silicon etching (DSi). A widely used DSi method is the so-called Bosch method. With the Bosch method, very small gap distances can be etched, but only when the aspect ratio, i.e. the quotient between the depth and the width of a trench, is not much greater than 30.

[0005] This means that when a gap distance of 300 nm is required, the Bosch method can only etch to a depth of 10 μm with reasonable quality. For many L-NED applications, a depth of only 10 μm is not enough. When a depth of, for example, 100 μm is required, this may result in the trench width also having to be made ten times larger, i.e. about 3 μm wide.

[0006] Fig.11aA schematic cross-sectional view or a cross-section of a known MEMS 1000 assembled as an L-NED is shown. The MEMS 1000 may include a substrate layer 1002, such as a handle wafer of a BSOI (bonded silicon on insulator) wafer. A device layer of the BSOI wafer is stacked thereon, wherein layers 1002 and 1004 are connected via an oxide layer, i.e. via a buried oxide (BOX) of the BSOI wafer. External electrodes 1008a and 1008b consisting of layer 1004 are arranged such that an internal electrode 1008c of layer 1004 is arranged between the external electrodes 1008a and 1008b, wherein NED gaps 10121 and 10122 are arranged between these electrodes, which can be obtained, for example, by means of the DSi method. The outer grooves 10141 and 10142, respectively, between the outer electrodes 1008a and 10008b, and the material of the layer 1004 left as the outer substrate, can define movable beams formed by these electrodes and, for example, can also be formed by DSi. A height 1016 of the L-NED actuator can, for example, be related to the extension of the movable element, possibly by adding a gap between the electrodes 1008a, 1008b and / or 1008c and the layer 1002 and perpendicular to a substrate plane defined, for example, by a main extension direction of the layer 1002.

[0007] Fig.11b A schematic top view of MEMS 1000 is shown. Electrodes 1008a and 1008c, and 1008b and 1008c, may each be firmly mechanically connected to each other via an insulating layer 1022 arranged on discrete areas. The movable element formed by movable electrodes 1008a, 1008b, and 1008c may be movable along a lateral movement direction 1024 arranged in a plane.

[0008] The lateral movement of the L-NED actuator can result in a movement of the medium (e.g. air or liquid) in which the actuator moves. This movement of the medium can be used to produce (micro)speakers or (micro)pumps based on L-NED actuators. The volume of a speaker or the power of a pump depends on the size of the volume (air or liquid) moved. To illustrate with an L-NED actuator, the volume moved is determined by the deflection, i.e. by the amplitude along the movement direction 1024 and the height 1016 of the L-NED actuator. Therefore, it is desirable to produce MEMS speakers and / or MEMS pumps with tall L-NED actuators and with a large deflection.

[0009] As mentioned above, the following general statements apply to L-NED actuators:

[0010] The smaller the gap of the L-NED actuator, the greater the deflection;

[0011] The smaller the gap of the L-NED actuator, the smaller the height of the actuator due to the limited aspect ratio during production (Bosch method).

[0012] This means that the production process makes it difficult to achieve both a small gap (large deflection) and a large height of the stringer.

[0013] DE 10 2015 210 919 A1 describes the principle of a microspeaker or micropump based on L-NED.

[0014] Fig.12 A schematic cross-sectional view of a MEMS 2000 known therefrom is shown, which largely corresponds to the side cross-sectional view of MEMS 1000, wherein layer 1002 may additionally comprise an opening 1026 for allowing a volume flow between a cavity 1028 in which electrodes 1008a, 1008b and 1008c move and an external environment of MEMS 2000. In addition, a further substrate layer 1032 is arranged by means of a further insulating layer 10062, which may, for example, form a cover of MEMS 2000 and also comprises an opening 1034, which may, for example, serve as an inlet opening for cavity 1028 when opening 1026 serves as an acoustic or fluid outlet. A distance 10361 between the layer 1002 and the electrodes 1008a, 1008b and / or 1008c, and / or a distance 10362 between these electrodes and the cover wafer 1032 may typically have a value of about 1 μm (determined by thermal oxidation of Si: 10 nm to 10 μm).

[0015] according to Fig.12 The main principle is to provide a BSOI wafer production, Fig.11a and Fig.11b 1032. The device wafer and the lid wafer may be bonded by a bonding method. Inlet and outlet 1026 and 1034 are provided for acoustic signals or fluids.

[0016] The L-NED beams can move laterally, thereby generating an acoustic effect or a pumping effect. When the ratio of the L-NED height to the L-NED gap is larger, the acoustic effect and the pumping effect become more effective, the larger the better. The ratio of the L-NED height 1016 to the L-NED gap 1012 is about 30. This limitation is caused by the production process of Si technology.

[0017] In addition, according to Fig.12The L-NED stringers are limited by a vertical pull-in effect (pull-in = mechanical and / or electrical contact between the L-NED stringer and the lid wafer or the handle wafer, such as contact due to electrostatic forces). This means that when a voltage is applied to one of the L-NED electrodes 1008a, 1008b or 1008c and the layer 1002 and / or 1032 is connected to ground, an electrical vertical force is generated that pulls the L-NED stringer towards the bottom or towards the top. Since the distances 10361 and 10362 between the L-NED stringer and the lid wafer 1032 or the handle wafer 1002 are small (in the range of 1 bis 2 μm), the movement of the L-NED stringer towards the bottom (vertically, in the z direction) may result in a pull-in effect. Vertical pull-in is undesirable for two reasons:

[0018] Mechanical: Mechanical contact between the L-NED stringers and the cover wafer or handle wafer during operation can lead to mechanical destruction of the device. Among other things, the intended very high motion fidelity (the desired systematic connection between input and output signals) can be limited, resulting in distortion, friction losses and non-linearity;

[0019] Electrical: Electrical contact between the L-NED stringers and the lid wafer or handle wafer during operation can lead to electrical destruction of the device (short circuit).

[0020] DE 10 2017 203 722 A1 states that a large aspect ratio can be achieved by subsequently shifting the electrodes relative to one another. The subsequent shifting of the electrodes is a further process that is difficult to control and is therefore prone to errors.

[0021] Therefore, it would be desirable to have a MEMS with in-plane movable elements that has a large aspect ratio and is easy to produce. Summary of the invention

[0022] Therefore, one object of the present invention is to provide a MEMS which has a large aspect ratio and is easy to produce.

[0023] This purpose is achieved through the content of the subject matter of the independent items of the patent application.

[0024] A core idea of ​​the present invention is to find that the electrode layer of the L-NED device can be supplemented by a second layer providing additional area for interaction with the fluid. This second layer can be produced by means of existing and controllable processes, thus enabling simple production and at the same time increasing the effective aspect ratio.

[0025] According to one embodiment, a MEMS includes a substrate including a cavity. The MEMS includes a movable layer arrangement, the movable layer arrangement being arranged in the cavity, the cavity including a first beam, a second beam, and a third beam arranged between the first beam and the second beam and fixed at a discrete area electrically insulated therefrom, wherein the movable layer arrangement is configured to move in a substrate plane along a movement direction according to a potential between the first beam and the third beam, or in response to a potential between the second beam and the third beam. The first, second and third beams are part of a first layer of the movable layer arrangement. The movable layer arrangement includes a second layer arranged adjacent to the first layer along a direction perpendicular to the substrate plane and arranged movably along the movement direction. Compared to the beam arrangement, the second layer enables additional active area to interact with a fluid, i.e., a gas and / or a liquid.

[0026] According to one embodiment, the second layer is structured into a fourth, fifth and sixth beam. Along a direction perpendicular to the substrate plane, such as z, at least in a rest state of the MEMS, the fourth beam is arranged adjacent to the first beam, the fifth beam is arranged adjacent to the second beam, and the sixth beam is arranged adjacent to the third beam. This enables additional actively controllable areas.

[0027] According to one embodiment, the first stringer is mechanically connected to the fourth beam and / or the second stringer is mechanically connected to the fifth beam and / or the third stringer is mechanically connected to the sixth stringer via an intermediate layer arranged between the first layer and the second layer. This enables small fluid losses between the stringers and mechanical coupling of the movements of the individual stringers.

[0028] According to one embodiment, the third beam and the sixth beam are mechanically connected to each other via an intermediate layer arranged between the first layer and the second layer. The intermediate layer between the first beam and the fourth beam on the one hand and between the second beam and the fifth beam on the other hand is removed so as to space the first beam from the fourth beam and the second beam from the fifth beam. This enables low masses to be moved, since a movement coupling can still be obtained via the mechanical fixings between the fourth, fifth and sixth beams.

[0029] According to one embodiment, the first and fourth beams on the one hand and the second and fifth beams on the other hand are mechanically connected to each other via an intermediate layer arranged between the first layer and the second layer. The intermediate layer between the third and sixth beams is removed to provide a gap between the third and sixth beams. This also achieves low mass.

[0030] According to one embodiment, the first layer and the second layer are connected to each other in a region of the substrate via an intermediate layer, such as an insulating layer, such as silicon oxide, silicon nitride or a polymer. The intermediate layer is removed in a region between the cavity between the first beam and the fourth beam, between the second beam and the fifth beam and between the third beam and the sixth beam. This enables the first, second and third beams to move independently relative to the fourth, fifth and sixth beams.

[0031] According to one embodiment, the first, second and third beams form a first movable element of the movable layer structure. The fourth, fifth and sixth beams form a second movable element of the movable layer structure. The first movable element is arranged movably relative to the second movable element along the movement direction. This enables individual deflection of the movable elements, providing a high degree of freedom in both sensing and actuation.

[0032] According to one embodiment, different potentials may be applied between the first and third beams on the one hand and between the fourth and sixth beams on the other hand. Alternatively or additionally, different potentials may be applied between the second and third beams on the one hand and between the fifth and sixth beams on the other hand. This enables independent evaluation and / or control of the movable elements, for example out-of-phase or phase shift.

[0033] Some of the above embodiments are described such that the second layer is structured as beams and the effective area is enlarged compared to the first layer by means of the additional beam area. A further embodiment, which can alternatively or additionally be combined with an inventive device, is concerned with the fact that the second layer provides a resistor structure for interaction with a fluid in the cavity. For this purpose, it may be sufficient to assemble the resistor structure in an electrically passive manner, which enables a simple implementation. At the same time, pull-in effects between the resistor structure and external areas may be reduced or prevented.

[0034] According to one embodiment, the first beam, the second beam and the third beam form a movable element. The second layer forms a resistor structure for interacting with a fluid in the cavity. The resistor structure is mechanically connected to the movable element and is moved together with the movable element. This enables the actual effective appearance ratio to be enlarged by an additional arrangement of the resistor structure, which can be implemented by means of a simple and precise procedure.

[0035] According to one embodiment, the resistor structure is connected to the first layer via an intermediate layer. This enables a simple configuration by forming the MEMS from a stacked structure.

[0036] According to one embodiment, in addition to the first, second and third beams, the first layer also comprises a piggyback element which is mechanically fixed to the first or second beam on a side facing away from the third beam, i.e. in a plane outside the beam arrangement. The resistor structure is at least partially arranged on the piggyback element. This makes it possible to arrange the resistor structure on an element which is not necessarily actively electrically deformable, so that a low deformation energy is required to deform the resistor structure.

[0037] According to one embodiment, the piggyback element is mechanically fixed to the first, second or third stringer. The resistor structure is at least partially arranged on the piggyback element. This enables a simple production.

[0038] According to one embodiment, the piggyback element is mechanically connected to the first or second stringer via a coupling element, wherein the coupling element is arranged in a region which at most deforms slightly during deformation of the active element in a region of maximum deflection of the movable element, and the movable element is not arranged where a high material strain occurs. This makes it possible to prevent unnecessarily high mechanical energies for deformation of the coupling element and / or resistor structure.

[0039] According to one embodiment, the resistor structure comprises a plurality of partial elements arranged perpendicular to the movement direction and parallel to the substrate plane along an axial extension direction of the movable layer arrangement. This makes it possible to reduce the effective stiffness of the resistor structure, so that low forces are sufficient to affect the deformation of the resistor structure. Alternatively or additionally, this makes it possible to reduce or prevent mechanical interactions between individual partial elements.

[0040] According to one embodiment, the partial elements are at a distance from one another in a projection into a plane perpendicular to the substrate plane and perpendicular to the movement direction. This enables contact freedom during deformation and / or a low mass of the resistor structure.

[0041] According to one embodiment, the distance is at most 100 μm, preferably at most 10 μm and particularly preferably at most 2 μm. Like a wall structure, this achieves low fluid losses or a fluid effect of the resistor structure.

[0042] According to one embodiment, the partial elements are alternatively firmly mechanically connected to the first beam or to the second beam or to the third beam. This achieves low fluid losses by reducing or preventing a diagonal displacement of the fluid point.

[0043] According to one embodiment, the partial elements are arranged on at least two of the first, second and third beams. Although the wall elements effective in the direction of movement can be attenuated by the partial elements arranged offset in the depth direction, the resistor structure still achieves a completely or partially symmetrical mass distribution at the beams. Possibly adverse effects can be compensated by an overlap of the partial areas in a projection into one of the above-mentioned planes perpendicular to the substrate plane.

[0044] According to one embodiment, a first distance between the resistor structure and the substrate is greater than a second distance between the first beam and the third beam along or opposite to the movement direction. Since the resistor structure can be assembled and implemented for fluid interaction in a passive manner, the arrangement of gap structures limited by the aspect ratio can be omitted. Thus, in general, larger gaps are possible, which helps to achieve large effective dimensions along the z direction without complex processing.

[0045] According to one embodiment, the first distance is greater than the second distance by a factor ranging from at least 1 to 20, preferably 3 to 10, particularly preferably 5 to 7.

[0046] According to one embodiment, the second layer comprises a cap perpendicular to the substrate plane, such as along z, which is larger than the first layer by at least a factor in the range of 1 to 20, preferably 3 to 10, particularly preferably 5 to 7. This enables particularly efficient MEMS.

[0047] According to one embodiment, an aspect ratio of the first layer for a layer thickness of the first layer and a distance between the first beam and the third beam or between the second beam and the third beam is less than 40, which enables simple process control.

[0048] According to one embodiment, the resistor structure is a first resistor structure arranged on a first side of the first layer. Furthermore, the MEMS comprises a second resistor structure arranged on a second side of the first layer, the second side being arranged opposite to the first side. This achieves a particularly high effectiveness of the MEMS by enlarging the fluid active area on both sides.

[0049] According to one embodiment, the resistor structure provides a fluid resistance for a fluid disposed in the cavity, which is particularly useful for actuator implementations such as speakers or pumps, but also for sensing implementations such as microphones or other implementations such as MEMS THz waveguides.

[0050] According to one embodiment, the advantages of the resistor structure and an additional beam layer can be combined. To this end, the movable layer arrangement comprises a third layer structured into a fourth, fifth and sixth beam, so that two beam layers and at least one resistor structure are implemented, which enables a further increase in efficiency.

[0051] Here, the first, second and third beams may be mechanically connected to form a first movable element, while the fourth, fifth and sixth beams may be mechanically connected to form a second movable element.

[0052] According to one embodiment, the first movable element is mechanically connected to the second movable element, which enables a higher aspect ratio when considering technical limitations of the aspect ratio and a lower operating voltage since high forces can already be generated by low voltages.

[0053] According to one embodiment, the resistor structure is a first resistor structure, wherein the MEMS comprises a second resistor structure connected to the second movable element. On the one hand, this allows high flexibility by individual control and / or sensing or detection by means of one of the different movable elements, and simple production, the active area of ​​the different movable elements being enlarged on both sides.

[0054] According to one embodiment, the first movable element and the second movable element are arranged adjacent to each other along a direction perpendicular to the substrate plane and between the first resistor structure and the second resistor structure. This enables the possible passive resistor structure to be arranged outside the structure which may be connected to ground, so that low attraction forces and pull-in effects can be prevented.

[0055] According to an alternative embodiment, the first resistor structure and the second resistor structure are arranged adjacent to each other and between the first movable element and the second movable element in a direction perpendicular to the substrate plane. This enables a large distance between the movable elements and thus low electrical cross-effects.

[0056] According to one embodiment, the first resistor structure and the second resistor structure are movable relative to each other, which is particularly advantageous in actuator implementations for being able to control the movable elements independently of each other.

[0057] According to one embodiment, the movable layer structure comprises a flexure beam structure clamped on one side of the substrate. A flexure beam structure clamped on one side enables a large deflection at the free end, which is particularly helpful because according to the above embodiments, the pull-in effect is reduced or prevented, for which clamping can be provided on both sides, where the amplitude reduction can be prevented.

[0058] According to one embodiment, a layer thickness of the first layer and the second layer perpendicular to the substrate plane is at least 50 μm. This realizes ultra-large MEMS.

[0059] According to one embodiment, an axial extension direction of the movable layer arrangement structure parallel to the substrate plane and perpendicular to the movement direction is configured so that a dimension of at least a factor of 0.5 is obtained for the height of the movable structure, which is particularly helpful because this dimension or length affects the efficiency in the same way as the height or thickness.

[0060] According to one embodiment, the cavity is fluidically connected to the external environment of the substrate via at least one opening, wherein the at least one opening is arranged on a plane of the movable layer arrangement. This enables the use of the bottom layer and / or the cover layer for other purposes, since the wafer area can be used for other purposes than an opening.

[0061] According to one embodiment, the MEMS system is configured as a MEMS pump, as a MEMS speaker, as a MEMS microphone or as a MEMS THz waveguide.

[0062] According to one embodiment, the MEMS comprises control means configured to control the movable layer structure.

[0063] According to one embodiment, the first, second and third beams form a first movable element, wherein the MEMS comprises a plurality of movable elements, ie at least two movable elements. The control means are configured to individually control the plurality of movable elements, which enables a high degree of freedom when implementing the MEMS.

[0064] Further advantageous configurations are the subject matter of further appendices to the patent application. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The preferred embodiment of the present invention will be discussed below with reference to the accompanying drawings. It shows:

[0066] Figure 1 A schematic cross-sectional view of a MEMS according to an embodiment;

[0067] Figure 2 A schematic cross-sectional view of a MEMS according to an embodiment, wherein additional actuator thickness is achieved by additional electrodes;

[0068] Figure 3a A schematic cross-sectional view of a MEMS according to an embodiment, wherein the outer electrodes of a first layer and a second layer are connected to each other via an intermediate layer, and in the inner electrode, the intermediate layer is completely removed or not arranged;

[0069] Figure 3bA schematic cross-sectional view of a MEMS according to an embodiment, wherein compared to Figure 3a A MEMS in which the intermediate layer is arranged between the inner electrodes for firmly mechanically connecting the two electrodes to each other but is removed between the outer electrodes;

[0070] Figure 4a A schematic cross-sectional view of a MEMS according to an embodiment, wherein the second layer of the movable layer arrangement comprises a resistor structure, for example consisting of a substrate layer;

[0071] Figure 4b Figure 4a A schematic cross-sectional view of a MEMS, wherein the resistor structure is firmly mechanically connected to an external electrode;

[0072] Figure 4c A schematic cross-sectional view of a MEMS according to an embodiment, wherein the movable element comprises a piggyback element in a plane of the electrodes of the first layer, the resistor structure being firmly mechanically connected thereto via a coupling element;

[0073] Figure 4d A schematic top view of a MEMS according to yet another embodiment, wherein the coupling element is disposed on a freely deflectable end of a movable element clamped on a side of the substrate;

[0074] Figure 4e Figure 4d In the section plane A'A Figure 4d A schematic cross-sectional view of a MEMS;

[0075] Figure 5a A schematic diagram of a MEMS according to an embodiment, wherein the movable element is firmly clamped on two sides;

[0076] Figure 5b Figure 5a A schematic diagram of a MEMS in a deflected state of the movable element;

[0077] Figure 6a A schematic top view of a MEMS according to an embodiment, wherein a portion of the elements of the resistor structure are arranged on one of the electrodes;

[0078] Figure 6b A schematic top view of a MEMS according to an embodiment, wherein a portion of the elements of the resistor structure are arranged on at least two of the electrodes;

[0079] Figure 7a A schematic cross-sectional view of a MEMS according to an embodiment, such as Figure 4a A MEMS that penetrates a cover layer;

[0080] Figure 7b A schematic cross-sectional view of a MEMS according to an embodiment, wherein an opening for connecting the cavity to an external environment is arranged outside the substrate in a plane of the movable layer arrangement;

[0081] Figure 8a A schematic cross-sectional view of a MEMS according to an embodiment, combining features of a dual-group electrode and a back structure or resistor structure;

[0082] Figure 8b A schematic cross-sectional view of a MEMS according to an embodiment, wherein two movable elements are relative to each other Figure 8a The relative positions of the MEMS are exchanged so that the resistor structures are arranged adjacent to each other;

[0083] Fig. 9 A schematic cross-sectional view of a MEMS according to an embodiment, wherein electrodes of different layers are connected to each other and have an offset;

[0084] Fig.10 A schematic cross-sectional view of a MEMS according to an embodiment, wherein electrodes of different layers are not in contact with each other and have an offset;

[0085] Fig.11a A schematic cross-sectional view or a cross-section of a known MEMS configured as an L-NED;

[0086] Fig.11b Fig.11a A schematic top view of a MEMS; and

[0087] Fig.12 A schematic cross-sectional view of yet another known MEMS. DETAILED DESCRIPTION

[0088] Before the embodiments of the present invention are discussed in more detail based on the drawings below, it should be noted that functionally equivalent or equivalent elements, objects and / or structures in different drawings are provided with the same reference numerals, so that the descriptions of these elements shown in different embodiments are interchangeable or mutually applicable.

[0089] Reference is made below to MEMS transducers (MEMS = micro-electromechanical systems). A MEMS transducer may comprise one or more electroactive components which, based on an applied electrical charge (current, voltage, charge or equivalent), cause a change in a mechanical component, i.e. produce a conversion. This change may, for example, be related to a deformation, heating or straining of the mechanical component. Alternatively or in addition, a mechanical impact on the component, such as deformation, heating or straining, may result in an electrical signal or electrical information (voltage, current, charge or equivalent) detectable at the electrical terminals of the component. Some materials or components have a reciprocity, which means that the effects are interchangeable. For example, piezoelectric materials may comprise the inverse piezoelectric effect (deformation based on an applied electrical signal) and the piezoelectric effect (providing an electric charge based on a deformation).

[0090] Some of the embodiments described below are related to the fact that an electrode arrangement forms a movable element. Here, the movement of the movable element can be obtained from a deformation of the electrode arrangement. For the sensing function through a possible reciprocity, an actuator configuration can be assembled so that the electrode arrangement is deformed macroscopically along a lateral movement direction, that is, an element or area can be moved along this lateral movement direction. The element or area can be, for example, a beam end or a central area of ​​a beam structure. From a microscopic point of view, when the deformable element is deformed along the lateral movement direction, the deformable element can undergo a deformation perpendicular to this lateral movement direction. The embodiments described below are related to the macroscopic method.

[0091] Some of the embodiments described below relate to electrodes connected to each other via mechanical fasteners and configured to perform a movement based on a potential. However, the embodiments are not limited thereto and may include any type of beam structure configured to provide a force converted into movement via a mechanical fastener (actuator) in response to an actuation and / or to detect a deformation (sensor), such as by using piezoelectric materials or other actuated materials. The beams may be, for example, electrostatic, piezoelectric, and / or thermomechanical electrodes that provide deformation based on an applied potential.

[0092] Figure 1 A schematic cross-sectional view of a MEMS 10 according to an embodiment is shown. The MEMS 10 comprises a substrate 12, which for example comprises a layer stack 14 of a plurality of individual layers, wherein the substrate 12 comprises a cavity 16 arranged inside the substrate 12 by partially removing individual layers.

[0093] The layer stack 14 may include several layers. For example, the layer stack 14 may include a first substrate layer 181, wherein an active layer or a device layer 241 is arranged thereon by means of an intermediate layer 221, such as by bonding, wherein the layer sequence 181, 221 and 241 may correspond to Fig.11a The layer stack is shown with regard to the materials used and / or the dimensions. A further active layer 242 can form part of the layer stack via a further intermediate layer 222. A further substrate layer 182 can form part of the layer stack 24 via an intermediate layer 223. The layer sequences 182, 223 and 242 can, for example, mirror the layer sequences 181, 221 and 241 at least with regard to the layer type and the layer sequence, and possibly also with regard to the dimensions, so that two half-layer stacks are connected to one another by means of the intermediate layer 222.

[0094] Here, the layer stack is shown only by way of example. Substrate layers 181 and 182 may correspond to layers 1002 and 1032, for example. Here, intermediate layers 221, 222, and / or 223 may be formed as intermediate layer 1006.

[0095] The layer stack 14 may include different layers and / or additional layers and / or may not include one or more of the layers shown. Thus, it is possible that no substrate layer 181 or 182 is arranged, or it is possible to produce, for example, a printed circuit board or the like via a different substrate, where the further layers are arranged. Despite the absence of the layers 181 and / or 182, the cavity 16 is still obtained in the substrate 12.

[0096] By way of example, the MEMS 10 is configured such that two active layers 241 and 242 are connected to each other via the intermediate layer 222. The active layers 241 and / or 242 may, for example, include conductive materials, such as doped semiconductor materials and / or metal materials. The layered arrangement of the conductive layers enables a simple configuration, because the cavity 16 can be obtained by selectively removing it from the layers 241 and 242, and the intermediate layer 222, and the electrode structures 26a to 26e can be retained by appropriate adjustment of one of the procedures. Alternatively, it is also possible to arrange the electrode structures 26a to 26f completely or partially in the cavity 16 by other measures or procedures, such as by generating and / or positioning in the cavity 16. In that case, the electrode structures 26a to 26f can be formed as a structure different from the part of the layers 241 and 242 remaining in the substrate 12, that is, the same ones can include different materials.

[0097] Substrate layers 181 and 182 may include openings 281 or 282 , each of which may provide a fluid inlet and / or a fluid outlet as described for openings 1026 and 1034 .

[0098] Thus, the MEMS 10 may include a MEMS 2000 through at least one additional layer, which is formed as an active layer according to the embodiment shown and forms, for example, the layer 242 .

[0099] The electrodes 26a, 26b and 26c may be fixed to each other at discrete areas in an electrically insulating manner, such as for Fig.11b1000, wherein part of the resistor structure is arranged on at least two of the electrodes. In response to a potential between electrodes 26a and 26c, and / or in response to a potential between electrodes 26b and 26c, a movement of movable element 32 can be obtained by mechanical fixings at discrete points along a movement direction 34, which can, for example, correspond to direction 1024 and can be arranged in an x / y plane of a Cartesian x / y / z coordinate system. The x / y plane can be a claim defining the in-plane movement along which the movement direction 34 occurs.

[0100] Electrodes 26d to 26f may be the remainder of layer 242 and are arranged perpendicular to the substrate plane x / y adjacent to layer 241. Electrodes 26a to 26c at least partially form a first layer of a layer arrangement 36, wherein electrodes 26d to 26f at least partially form a second layer of the layer arrangement 36.

[0101] Although the gap 421 between the electrodes 26a and 26c or 26d and 26f and the gap 422 between the electrodes 26b and 26c or 26e and 26f have the same or comparable dimensions as in the MEMS 2000 because the same procedure can be used, a dimension 38 of the movable layer arrangement 36 along the z direction can be enlarged compared to the dimension 1016. An aspect ratio between the gap dimensions 421 and 422 and the dimensions of the electrodes 26a to 26c or 26d to 26f along the z direction can, for example, be the same or similar as described for the MEMS 2000 and, for example, can have a value less than 40, in particular about 30. However, the actual effective aspect ratio can be higher because the dimension 38 is enlarged, for example doubled, along the z direction by arranging the layers or electrodes 26a to 26f in parallel without enlarging the gaps 421 and 422.

[0102] Here, a partial dimension or partial height 441 and 442 parallel to the z-direction of the MEMS 10 of the respective half-layer stack 14 assembled via the intermediate layer 222 may correspond approximately to a corresponding dimension of the MEMS 1000 along the z-direction.

[0103] Here, a movement of one of the electrodes 26d to 26f can be obtained in different ways. By mechanically combining electrode 26a with electrode 26d, for example electrode 26b with electrode 26e and / or electrode 26c with electrode 26f in pairs, a corresponding movement of one of the other electrodes that is firmly mechanically connected can be obtained directly from the movement of electrode 26a, 26b or 26c of the movable element 32. As a result, mechanical fixings 461 and 462 can be omitted in the layer of electrodes 26d to 26f, which, for example, can correspond to element 1022 of MEMS 1000. Alternatively or in addition, it is also possible to provide corresponding mechanical fixings 46 in the plane of layer 242 so as to mechanically fix electrodes 26d to 26f at discrete positions or regions. As a result, a further movable element can be obtained, which can be firmly mechanically connected to the movable element 32 via the intermediate layer 422, wherein a corresponding connection can also be completely or partially omitted.

[0104] In other words, the ratio of L-NED height to L-NED gap can be doubled, for example, by bonding two device wafers 241 and 242, rather than by bonding a device wafer (layer 22) to a cap wafer (layer 181), as shown in FIG. Figure 1 As shown, Figure 1 Two device wafers are shown bonded so that the L-NED beams are mechanically connected to each other. In this way, the aspect ratio of the L-NED actuator is doubled. This solution has several advantages:

[0105] In micro speakers, for example, doubling the aspect ratio can result in a 6dB increase in sound level;

[0106] Doubling the L-NED height can lead to a higher flexural strength in the z-direction, which in turn leads to a lower sensitivity to vertical (in the z-direction) pull-in effects and enables a high degree of design freedom. This allows, for example, making the L-NED stringers longer, which means that the same can have a high axial extension in the y-direction. Alternatively or additionally, the L-NED stringers can be clamped on one side instead of on two sides, which helps because L-NED stringers clamped on one side achieve greater deflection than, for example, L-NED stringers clamped on two sides.

[0107] • Although still possible, according to the known configuration, a cover is not absolutely necessary, which provides saving potential.

[0108] If, for example, we refer again to Fig.12In a known MEMS, a speaker or a pump is formed by bonding a device wafer of layers 1002, 10061 and 1004 (referred to as technology 1) and a cover wafer 1032 (referred to as technology 2) via layer 10062. Here, two different technologies or production steps are required to produce the cover and the device wafer. In contrast, according to Figure 1 The MEMS 10 can be produced using only one of these technologies (Technology 1) because both components (441 and 442) that are bonded are device wafers and are therefore produced by means of the same Technology 1. This means that the use of Technology 2 can be omitted, which enables simple production. The role of the cover wafer is now fulfilled by 182.

[0109] Here, it should be understood that terms such as lid or bottom are only used to further distinguish the individual components of the MEMS described herein and are neither limited to a specific design nor to an orientation of the layers in space. Furthermore, it should be understood that the doubling of size along the z-direction discussed by way of example is one of the possible configurations. Layers 241 and 242 may have the same or different sizes, both with respect to the area in substrate 12 and also with respect to the area in cavity 16.

[0110] Figure 2 A schematic cross-sectional view of a MEMS 20 according to an embodiment is shown, wherein the intermediate layer 222 is removed between the electrodes 26a, 26b and 26c on the one hand and between the electrodes 26d, 26e and 26f on the other hand.

[0111] As in MEMS 10, the active layer 242 is structured into electrodes 26d, 26e and 26f arranged along the z direction perpendicular to the substrate plane adjacent to the electrodes 26a, 26b or 26c, however, the electrodes 26d and 26f can be mechanically connected to each other firmly at a discrete position via a mechanical fastener 463, and the electrodes 26e and 26f can be mechanically connected to each other via a mechanical fastener 464, so that with respect to the omitted or removed intermediate layer 222, the layer arrangement structure 2 can include movable elements 321 and 322, which result in the same or comparable effective size 38 along the z direction, but enable a different control of the movable elements.

[0112] According to one embodiment, different potentials may be applied between electrodes 26a and 26c on the one hand and between electrodes 26d and 26f on the other hand. Alternatively or additionally, different potentials may be applied between electrodes 26b and 26c on the one hand and between electrodes 26e and 26f on the other hand, which may lead to different movements of movable elements 321 and 322. This means that the respective electrodes are galvanically separated and / or are in contact only in one of the optional control means, such as an application specific integrated circuit (ASIC).

[0113] In other words, the L-NED stringers of the upper device wafer are not directly connected to the L-NED stringers of the bottom device wafer. The two L-NED stringers can be controlled separately.

[0114] Figure 3a A schematic cross-sectional view of a MEMS 301 according to an embodiment is shown, which provides a combined configuration of MEMS 10 and 20, wherein electrodes 26a and 26b and electrodes 26b and 26e are connected to each other via intermediate layer 222, and intermediate layer 222 between electrodes 26c and 26f is completely or partially removed or not arranged so as to separate electrodes 26c and 26f from each other. This causes one of electrodes 26a and 26d and 26b and 26e to move together, so that mechanical fixing member 46 ( Figure 3a ) can be arranged at any position, such as according to Figure 2 The arrangement can be carried out in a configuration in which, for example, it is also possible to omit individual mechanical fastening elements, since a movement transfer can also take place via the intermediate layer 222 between the electrodes.

[0115] Figure 3b A schematic cross-sectional view of a MEMS 302 according to an embodiment is shown, wherein, compared to MEMS 301, the intermediate layer 222 is arranged between electrodes 26c and 26f in order to firmly mechanically connect the two electrodes, but is removed between electrodes 26a and 26b and / or between electrodes 26b and 26e. Figure 2 Some of the mechanical fasteners 46 shown, for example, may omit the mechanical fasteners between electrodes 26a and 26c and between electrodes 26e and 26f, or between electrodes 26b and 26c and between electrodes 26d and 26f. A movement transfer may occur via the mechanical fastening connection between electrodes 26c and 26f.

[0116] In other words, the L-NED stringers of the top device wafer may only partially be directly connected to the L-NED stringers of the bottom device wafer, according to Figure 3b Only the middle electrode and according to Figure 3a External electrodes only.

[0117] Embodiments provide any configuration in which at least one pair of electrodes 26a and 26d, electrodes 26b and 26e, and electrodes 26c and 26f are mechanically firmly connected to each other via an intermediate layer 222 disposed between the layers. Optionally, this layer may also be based on Figure 2 Said completely suffers removal.

[0118] The above-described MEMS 10, 20, 301, and 302 include two actively formed layers arranged or stacked one above the other to increase the aspect ratio of dimension 38 to gap 42. Although these MEMS are described using two active layers connected to each other via an intermediate layer, such as silicon oxide or silicon nitride or polymer or the like, the embodiments are not limited thereto, but any number of additional further layers can be arranged, such as more than three, more than four, more than five, or more.

[0119] In the following, reference is made to further embodiments of the invention, in which the aspect ratio is increased by further layers, which may be passive.

[0120] Figure 4a A schematic cross-sectional view of a MEMS 40 according to an embodiment is shown, wherein the second layer of the movable layer arrangement structure 36 comprises a resistor structure 48, which, for example, is constituted by the base layer 18 remaining, arranged in or not moved away from the area of ​​the cavity 16 and connected to at least one of the electrodes 26a, 26b and / or 26c, in order to provide an additional liquid resistance for the electrodes 26a, 26b and 26c. For example, the resistor structure 48 can be maintained during a selective etching method. Compared to the height 52 of the electrodes 26a, 26b and 26c along the z-direction, which can correspond to the height 1016, for example, an effective height 54 of the movable element 32 can be increased by the resistor structure 48, which is helpful.

[0121] The size 52 may be, for example, between 1 μm and 1 mm, preferably between 50 μm and 400 μm, and particularly preferably between 70 μm and 150 μm. Figure 1 This may result in a dimension 38 that is approximately twice as large due to the addition of the intermediate layer 222, which may have a dimension of a few μm, such as 1 μm, 2 μm or 10 μm. In this way, the dimension 56 may also be at least 50 μm, at least 100 μm or at least 200 μm.

[0122] Here, a height or dimension 56 of the resistor structure 48 can be quite large, especially when considering a selective arrangement of the resistor structure 48 along an x-direction at a position along the y-axis. In this way, an aspect ratio for this is illustrated by the gap or void 581 between the substrate layer 18 and the resistor structure 48, and / or the gap 482 between the substrate layer 18 and the resistor structure 48 relative to the height 56 ​​of the resistor structure 48 can also have a limiting ratio of about less than 40, for example, less than 35 or less than 30 or less, i.e., the dimension 52 can be larger than the gap 421 and / or 422 by this factor. Considering that the gaps 581-582 are much larger than the gaps 421 and / or 422 between the electrodes 26a-26c, this aspect ratio can result in the dimension 56 along the z-direction being much larger than the dimension 52. Dimension 56 in the region of the cavity may also be referred to as the layer thickness of layer 18, so that the resistor structure may be larger than dimension 52 of layer 24 in the region of electrodes 26a to 26c by a factor of at least 2, at least 3, at least 4 or more.

[0123] in other words, Figure 4a An L-NED beam is shown with a rear structure placed below the middle electrode.

[0124] although Figure 4a A resistor structure of one of the intermediate electrodes 26c of the movable element 32 is arranged in the middle, Figure 4b Still shown is a schematic cross-sectional view of a MEMS 40 with a resistor structure 48 firmly mechanically connected to the electrode 26b. Alternatively or additionally, at least a portion of the resistor structure 48 may also be firmly mechanically connected to the electrode 26a, such as via the intermediate layer 22.

[0125] according to Figure 4a and Figure 4b The example may be related to a different MEMS in which the resistor structure 48 is arranged only on one of the electrodes 26b or 26c. Alternatively, the resistor structure 48 may also be structured such that Figure 4a and Figure 4b The illustration shows different positions along the y-axis, as will be shown in more detail below.

[0126] The resistor structure 48 or a portion thereof is firmly mechanically connected to the movable element 32 so that the resistor structure 48 moves together with the movable element 32 .

[0127] in other words, Figure 4b The cross section shows the structure after placement under the external electrodes.

[0128] Figure 4cA schematic cross-sectional view of a MEMS 40' according to an embodiment is shown, wherein the movable element 32 comprises a piggyback element 62 firmly mechanically connected to the resistor structure 48 in a plane of the electrodes 26a to 26c, such as through a portion of the intermediate layer 22. The piggyback element 62 may be made of the same material as the layer 24, i.e. the electrodes 26a to 26c, but may also be made of a different material. For example, a coupling element 64 providing mechanical fixation may be arranged between the electrode 26b firmly mechanically connected to the piggyback element 62 and the piggyback element 62. The coupling element 64 may, for example, provide electrical insulation, which is however optional. It is also possible that the coupling element 64 represents at least a local widening along the x-direction across at least one region along the y-direction, such as represented by the concept of a local thickening, which may, however, lead to asymmetries with respect to the electrostatic forces generated. Preferably, the piggyback element 62 is arranged on a side of the electrode 26b facing away from the electrode 26c. Alternatively, the piggyback element 62 can also be mechanically firmly connected to the electrode 26a, preferably on a side facing away from the electrode 26c. Both embodiments can also be combined and can be combined with the statements about the MEMS 40, which means that the resistor structure 48 can be arranged completely or partially on the piggyback element 62.

[0129] The coupling element 64 and / or the local widening can preferably be arranged along the y-direction in a region that is at most slightly deformed when the active element or movable element 32 is deformed, which region can be a maximum deflection region of the movable element. This means that the coupling element 64 is preferably not arranged where a large material strain of the movable element occurs. The movement amplitude or strain amplitude between the at most slightly deformed region and the actively deformed region can provide, for example, a ratio of 2:1, 3:1 or 4:1.

[0130] Similar to MEMS 40, the distance between resistor structure 48 and substrate, i.e., layer 18, may be greater than the distance between the electrodes illustrated by gaps 421 and 422. This distance may preferably be greater than the second distance by a factor of at least three, preferably at least four or at least 16.

[0131] The resistor structure 48 can provide a fluid resistance for a fluid disposed in the cavity 16. Although the MEMS 40 and MEMS 40' are shown so that the resistor structure 48 is disposed only on one side of the electrode structure 26a-26c along the negative z-direction, these embodiments also relate to the resistor structure being disposed along the positive z-direction. Further embodiments relate to a combination of the two implementations so that a further resistor structure is disposed on both sides along the positive z-direction and the negative z-direction of the layer 24 and the electrodes 26a-26c, respectively.

[0132] In order to control the direction of movement of the fluid out of the cavity 16, for example, Figure 3a and 3b The additional cover layers 181 and / or 182 shown in the figure can be arranged and provided with corresponding openings. Although the openings in the embodiments described herein are shown as part of the outer layers of the layer stack, alternatively or additionally, the openings can also be provided laterally, for example in the layers 241 and / or 242 of the MEMS 10, 20, 301 or 302, and / or in the layers 24 and / or 18 of the MEMS 40 or 40'. This enables the other use of a corresponding cover layer and / or a corresponding silicon area with openings to be omitted.

[0133] You should know that Figure 4a , 4b The mechanical fixing 46 is not shown in FIG. 4c.

[0134] in other words, Figure 4c The structure is shown in cross section laterally after electrode placement.

[0135] Figure 4d A schematic top view of a MEMS 40" according to a further embodiment is shown, wherein a coupling element 64 is arranged on a freely deflectable end of a movable element 32 clamped on a side of a substrate 121, the substrate 121 connecting the movable element or its freely deflectable end to a plurality of resistor structures 481, 482 forming a movable comb structure in a recess 65 of a cavity of the MEMS.

[0136] Figure 4e exhibit Figure 4d MEMS 40” Figure 4d1 , in which it is clearly visible that the movable element 32 moves along the z direction adjacent to a substrate 122 and performs a wiping movement parallel to the movement direction 38, for example, on the substrate. The resistor elements 481 , 482 and 483 can also be moved in the cavity 65 along the movement direction 38 via the coupling element 64 on which the resistor elements 481 , 482 and 483 are arranged, for example by using the intermediate layer 22. The cavity 65 can be laterally limited along the x direction by the substrate 122, so that a corresponding aspect ratio or a dimension of the movable element 32 and / or its electrodes along the z direction can be prevented. The substrate 122, for example, comprises a dimension 67 greater than 75 μm, greater than 150 μm or greater than 300 μm, for example, the same size as the resistor structures 481 , 482 and 483. This means that instead of direct fluid interaction via the movable element 32, indirect actuation or sensing is performed via the comb structure, and due to the large distances 691 and 692 between the resistor structures 481 to 483, the resistor structures 481 to 483 can be respectively configured as large resistor structures while maintaining the corresponding aspect ratio. The coupling element 64 realizes a transfer of the movement of the movable element 32 to the comb structure.

[0137] In other words, the rear structure is mounted on a movable but non-deformed portion of the coupling element 64, which moves at the deformed movable element NED.

[0138] Thus, for the deformed structure, an increase in stiffness in the lateral deflection direction can be inactive, i.e. prevented, so that no reduction in deflection occurs. However, the advantage of the vertical pull-in effect or risk reduction is maintained. Here, the increase in stiffness becomes effective via the resistor structure. The connection of the NED to the rear structure is implemented via a coupling element. Here, the number of resistor structures in the MEMS 40" is an arbitrary number ≥1. A lateral dimension 71 of the comb structure along the movement direction 38 can be greater than 150μm, greater than 300μm or greater than 600μm, for example 725μm.

[0139] Figure 5a A schematic diagram of a MEMS 50 according to an embodiment is shown, for example a top view from a bottom surface. A movable element comprising electrodes 26a, 26b and 26c that can be mechanically connected to each other securely via mechanical fixtures 461 to 468 at discrete locations can be securely clamped on two sides. Electrodes 26a and 26c can be electrically and / or galvanically connected to each other, for example, because they are formed from the same continuous layer 24. However, electrode 26 can be electrically insulated from electrodes 26a and 26b by using insulating regions 661 and 662 so that a different potential from electrodes 26a and 26b can be applied.

[0140] Figure 5b Display and Figure 5a A view of a comparable MEMS 50, wherein the movable element is Figure 5b One of the flexure directions of the movable element, such as along the positive x-direction, can be adjusted via the position of the mechanical fixture 46 .

[0141] If relevant Figure 4a As described above, the resistor structure 48 can be firmly mechanically connected to the electrode 26c and can move together with the same. Figure 5b The view of shows that the deflection of the movable element can also cause the deflection of the resistor structure 48, thereby, as long as the MEMS 50 is an actuator-operated MEMS, a high degree of fluid can be moved. In an operating sensing mode, a low degree of fluid movement, i.e., a small force, can be sufficient to cause the deflection shown.

[0142] An axial extension of the electrodes 26a, 26b and 26c and thus of the movable layer arrangement parallel to the substrate plane and perpendicular to the movement direction 34, for example along y, may be at least a factor of 0.5, preferably at least 0.6 and particularly preferably at least 0.7 compared to a dimension of the movable layer structure along a thickness direction z. Alternatively or additionally, the dimension along y may have a value in the range of at least 10 μm and at most 5000 μm, preferably at least 100 μm and at most 2000 μm, particularly preferably at least 400 μm and at most 1500 μm.

[0143] Although MEMS 50 is shown with the movable element clamped on two sides, clamping on one side is also possible.

[0144] In other words, the use of a resistor structure is an additional or alternative option to increase the efficiency of the NED device. In the illustrated case of an L-NED stringer, a typical aspect ratio of less than 30 or about 30 can be used so that the smallest possible NED gap 42 is achieved. The embodiments are directed to additionally structuring a passive rear structure or resistor structure at the front and / or rear end of the L-NED stringer. The rear structure is partially or completely connected to the L-NED stringer. When the L-NED stringer moves, the rear structure also moves with it, thereby moving more liquid or air with the fluid than through the L-NED stringer alone. Since the rear structure is directly connected to the L-NED electrodes, the shape of the rear structure during deflection of the L-NED stringer is exactly the same as the stringer itself. This means that the deflection or bending of the rear structure can be exactly the same as one of a L-NED stringer.

[0145] Basically the rear structure can be made as high as desired, i.e. the dimension 56 can have any size. The same can, for example, be as large as the thickness of the handle wafer, which means, for example, at least 300 μm, at least 500 μm or at least 600 μm or more, since the structure is no longer subject to the L-NED limitations, i.e. narrow gaps and aspect ratios <30. The rear structure can be structured in a simple way from the rear end of the BSOI wafer via a wider gap (trench). The trench on the rear end is still subject to production specific limitations (e.g. a Bosch limitation with an aspect ratio of <30), since the trench can be made wider, in particular when only one resistor structure is used along the trench direction, or the same can be etched deeper resulting in large dimensions 56. Obviously, the rear structure can also be produced underneath the external L-NED electrode 26a or 26b, or as Figure 4c As shown, even a separate structure parallel to the L-NED stringers is produced. According to a non-limiting example, the L-NED height 52 can be 75 μm and the rear structure height can be 600 μm. Thus, a corresponding structure can move eight times more air than a separate L-NED structure. In the context of a microspeaker, this corresponds to an approximately 18 dB more sound pressure level. This occurs under the assumption that the additional rear structure does not significantly affect the deflection of the L-NED stringers. In order to ensure this, the design of the embodiment aims to keep the stiffness of the rear structure in the lateral direction, that is, in the x-direction or in the direction of movement 34, as low as possible, which can be achieved, for example, by thinning the resistor structure 48 in this direction. An exemplary dimension of the resistor structure 48 along the direction 34 is, for example, at most 100 μm, at most 50 μm or at most 1 μm. In order not to significantly affect the inertia and lateral flexural stiffness of the entire system, the rear structure can be made as thin as possible as long as it is mechanically stable. The lateral deflection losses due to connecting the rear structure to the L-NED stringers may alternatively or additionally be compensated by using a longer dimension along the y-direction, and / or by a softer clamp representing an additional degree of freedom in the system design.

[0146] in other words, Figure 5a and Figure 5b A top view from the bottom is shown, wherein the L-NED stringers (clamped on two sides) are shown in a resting state or a non-deflected state and a deflected state. The rear structure 48 just follows the movement and / or flexure / bending of the L-NED stringers.

[0147] Figure 6a A schematic top view of a MEMS 60 is shown according to an embodiment, wherein the movable element 32 is arranged to be clamped on one side, whereby a free end 68 of the flexure beam structure can have a larger deflection along the movement direction 34 than a central area of ​​the flexure beam of the MEMS 50 clamped on two sides.

[0148] Independently of this, the MEMS 60 comprises means for reducing the stiffness of the resistor structure 48. To this end, the resistor structure can include any number or more of at least two, at least three, at least five or at least ten partial elements 48a to 48j arranged on one or several electrodes 26a, 26b and / or 26c. In this way, for example, the partial elements 48a to 48j are arranged along an axial course along the same y-direction on the central electrode 26c. Due to the structuring of the resistor element 48, the partial elements 48a to 48j are separated from each other by distances 72a to 72i, which allows the stiffness to be reduced, i.e. the stiffness increase caused by the resistor structure is kept low or minimized. The distances 72a to 72j may be equal or different and, for example, may be at most 100 μm, at most 50 μm or at most 5 μm in order to prevent fluid loss or at least keep it low when the partial elements 48a to 48j arranged perpendicular to the moving direction 34 along the axial extension direction y move along the moving direction 34.

[0149] According to an alternative embodiment, partial elements 48 a to 48 j of resistor structure 48 can all be mechanically firmly connected to electrode 26 a or to electrode 26 b or to electrode 26 c .

[0150] Figure 6b A schematic top view of a MEMS 60' according to an embodiment is shown, wherein partial elements 48a to 48i are arranged on at least two of the electrodes 26a, 26b and 26c, in the embodiment shown, partial elements are arranged on each of the electrodes 26a, 26b and 26c. The partial elements are arranged in a distributed manner along the axial extension direction y in order to provide fluid resistance in the cavity. Arranging the same on different electrodes 26a, 26b and / or 26c results in a further degree of freedom, because the projections 48'a to 48'i of the partial elements 48a to 48i overlap in a plane 74 arranged parallel to the axial extension direction and perpendicular to the substrate plane, for example parallel to the y / z plane, i.e. without distance, for example as shown for projections 48'a and 48'b. Although some of the projections 48'a to 48'i may have a distance from adjacent projections, it is still helpful for adjacent projections to have an overlap.

[0151] The fixing members 461 to 468 are symmetrically arranged between the electrodes 26 and 26c on the one hand, and symmetrically arranged between the electrodes 26b and 26c on the other hand. Figure 6a different, Figure 6b The fixing elements 461 to 467 may be asymmetrical, for example, to adjust to one of the movement profiles and / or load profiles of the movable element.

[0152] Although part of the element 48a is arranged on the electrode 26a and part of the element 48b is arranged on the electrode 26b, a fluid resistance is still obtained along the movement direction 34. The stiffness reduction is obtained by the division or segmentation. However, at the same time, the overlap 76 between the projections achieves low fluid losses. The fact that this is an optional feature becomes clear when considering that the projections 48'b and 48'c include, instead of the overlap 76, a distance 78 which is preferably adjusted corresponding to the distances 72a to 72h in order to keep the fluid losses low.

[0153] In other words, it is also possible to divide the rear structure along it in order to significantly reduce the contribution to the stiffening increase in the direction of movement and thus prevent lateral deflection. Here, the divisions are shown as interruptions, the fluid efficiency of which (prevention of a significant acoustic short circuit, possible attenuation adjustment) can be specifically adjusted by a corresponding geometric choice (small gap, i.e. distance 72). Essentially, the choice of sufficiently small gaps helps. Due to the restrictions on the aspect ratio and the resulting given minimum interruption width and the corresponding fluid losses, such as Figure 6b The staggered attachment of the rear structure to the electrodes shown can be helpful, allowing a wall to be built up in a fluidic manner, while still significantly reducing stiffness and maintaining technological boundary conditions due to the fact that the projections overlap.

[0154] in other words, Figure 6a and 6b The structure of a micro speaker or micro pump based on a rear structure is shown. Figures 4a to 4c The structure may then include a cover layer at the top and / or bottom end and may be provided with an inlet and / or an outlet.

[0155] Figure 7a A schematic cross-sectional view of a MEMS 701 according to an embodiment is shown, which is supplemented, for example, by the cover layers 781 and 782 which may be connected to the layer 18 or 24 by means of further intermediate or bonding layers 821 and 822. Figure 4a MEMS 40. Layers 781 and 782 may be formed in the same manner as layer 18. Bonding layers 821 and 822 may be formed in the same or similar manner as intermediate layer 22. A distance 84 between the outer electrodes 26a and 26b of the movable element and substrate 12 may be greater than gaps 421 to 422, so that height 52 is not substantially limited.

[0156] In other words, in a microspeaker and / or micropump, the rear structure provides a further important design advantage. As mentioned above, known microspeakers such as those according to MEMS 2000 suffer from the so-called vertical pull-in effect. This means that the driving voltage may not be so high that the L-NED beams are pulled towards the top or bottom and come into contact with the cover layer, i.e. the vertical pull-in effect occurs. The stiffer the L-NED structure is in the vertical direction z, the higher the driving voltage can be without vertical pull-in occurring. Vertical pull-in is particularly important for L-NED beams clamped on one side. In a normal situation, an L-NED beam clamped on one side will deflect more, at least at the free end, than a beam clamped on the two sides in the center. However, this advantage may be partially lost when a smaller driving voltage is selected due to the vertical pull-in effect than in a comparable L-NED beam clamped on two sides.

[0157] The vertical stiffness of the L-NED structure may be defined primarily by the thickness / height, by the length of the L-NED stringers and by the clamping. The thicker and shorter the stringers and / or the higher the stiffness of the clamping, the less sensitive the stringers are to vertical pull-in. However, as discussed, the thickness of the L-NED stringers cannot be chosen to be of any size, since the production process is accordingly limited, such as by the Bosch process. The length of the stringers cannot also be chosen to be too short, nor can the stiffness of the clamping be too low, since this would limit the lateral deflection. This means that in order to achieve high deflections, long stringers with low-stiffness clamping are desirable with regard to the design, for microspeakers and micropumps. However, this limits the driving voltage due to the vertical pull-in. Thus, the advantage already achieved in terms of deflection by choosing long stringers and low stiffness may again be partially lost by the reduction in driving voltage due to the vertical pull-in effect.

[0158] The discussed rear structure / resistor structure provides a solution to the above-mentioned difficulties. Since the rear structure height can be chosen to be of any size, for example eight times greater than the L-NED stringers, the stiffness of the overall structure is significantly increased in the vertical direction by the rear structure and dominates the overall stiffness. As a result, additional leeway is obtained for designing the length and / or clamping of the L-NED stringers. For example, in order to achieve greater lateral deflection, the stringers can be designed to be longer and the clamping can be designed to be softer. The resulting disadvantages with regard to the vertical pull-in effect are then compensated by the height of the rear structure. This advantage applies both to L-NED stringers clamped on one side and to L-NED stringers clamped on two sides.

[0159] Figure 7bA schematic cross-sectional view of a MEMS 702 according to an embodiment is shown, in which the opening 282 for connecting the cavity 16 to an external environment 88 outside the substrate 12 is arranged in a plane of the movable layer arrangement structure, which means that the same at least partially overlaps with the layer 24 and / or the intermediate layer 22 of the resistor element 48 and / or the electrodes 26a, 26b and 26c. This lateral arrangement of the opening may enable the use of the layer 782 for other purposes than an opening. Alternatively or in addition, the opening 281 may also be arranged laterally. A lateral arrangement of one or several openings is possible in all MEMS described herein without any restrictions. The openings 281 and 282 may also be arranged in the area of ​​the movable layer arrangement structure in the clamped area of ​​a beam clamped on both sides, or in the area of ​​the clamped and freely movable end of a beam clamped on one side of the movable layer arrangement structure.

[0160] Figure 8a A schematic cross-sectional view of a MEMS 801 according to an embodiment is shown, which combines the features of a double electrode and a back structure or resistor structure. This can also be seen, for example, so that the movable structure in the cavity 16 described in the context of the MEMS 701 is also doubled, and / or so that the MEMS 10, 20, 301 or 302 is additionally provided with the resistor structure, or with several resistor structures. In this way, for example, the layers 241 and 242 can be structured in electrodes 26a, 26b and 26c or 26d, 26e and 26f that are completely or partially connected to each other via the intermediate layer 222. Thereby, two movable elements 321 and 322 can be obtained, which can be firmly mechanically connected to each other via the connection to the intermediate layer 222. A respective resistor structure 481 or 482 can be firmly mechanically connected to the respective movable element 321 and 322 or can be part of it. Here, the resistor structures 481 and 482 can be assembled in the same or different ways, for example by structuring into a different number of partial areas, arranging the resistor structures or their partial areas at different electrodes, and / or with different dimensions along the z direction, as this is possible for all layers of the movable elements 321 and 322.

[0161] The MEMS 801 may be configured such that the movable element is arranged adjacent to each other along a direction z perpendicular to the substrate plane between the first resistor structures 481 and 482 relative to the electrode arrangements 26a to 26c and 26d to 26f.

[0162] Figure 8bA schematic cross-sectional view of MEMS 802 is shown, wherein movable elements 321 and 322 are interchanged relative to MEMS 801, so that resistor structures 481 and 482 are adjacent to each other and arranged between movable elements 321 and 322 and electrode arrangement structures 26a to 26c and 26d to 26f along the z direction perpendicular to the substrate plane. Although the intermediate layer 222 between resistor structures 481 and 482 is shown as being removed, the same can also be provided for mechanical fixation between resistor structures 481 and 482. However, in the illustrated variant, resistor structures 481 and 482 can be moved relative to each other, which realizes different controls. Both resistor structures can be connected to an active structure that realizes or controls this movement, such as connecting via movable elements 321 and 322. A control member provided for MEMS 801 and 802 can be assembled to control movable elements 321 and 322 individually or collectively. A control means 86 may be provided for controlling the movable layer structure as for any other MEMS described herein.

[0163] In other words, the idea of ​​stacked electrodes and back structure can be combined to achieve even higher sound pressure levels. Figure 8a and 8b An exemplary combination is shown in . This in turn doubles the movable volume, i.e., in the case of a micro speaker, 6 dB of additional volume can be achieved. This means that the combination of stacking and rear structure can theoretically increase the volume by about 25 dB (2x9), assuming in this example that 20*log(2*9)=25 dB, 2 for doubling the volume and 9 for the total height achieved (600+75) / 75. In accordance with Figure 8a In such a structure, vertical pull-in can even be completely eliminated. When the rear structures 481 and 482 and the covers 781 and 782 are connected to ground, electromotive forces between the rear structures and the cover wafer can be prevented, i.e. vertical pull-in can virtually no longer occur.

[0164] Although Figure 8a and 8b A stack of two L-NED-T actuators is shown, where T indicates the shape of the electrode and resistor structure combination, this concept can be extended in any way so that, for example, further additional electrode structures or L-NED actuators can be added.

[0165] Fig. 9 A schematic side cross-sectional view of a MEMS 100 according to an embodiment is shown, wherein electrodes or beams 26a, 26b and 26c are offset by a possible electrode individual offset 911, 912 and 913, respectively, relative to beams or electrodes 26d, 26e and 26f, respectively, arranged in adjacent layers, wherein the offset may alternatively also have the same amount for two or more elements, or may also point in different directions along the x-direction.

[0166] The layers 241 and 242 and the movable elements 321 and 322 structured from these layers are connected to one another, for example, via intermediate layers 221 and 222. Embodiments include that the distances 911, 912 and 913 do not necessarily assume the same value, but may do so.

[0167] Fig.10 In a cross-sectional view of an embodiment, it is shown that the layers 241 and 242 structured in the form of beams form the movable layer arrangement 36. Fig. 9 Similarly, the distance between the beams 911 , 912 and 913 is at most 100 μm, preferably 50 μm, particularly preferably 5 μm.

[0168] Embodiments of the present invention also make it possible to design inlets and / or outlets laterally in the plane of the rear structure, so that the cover and the bottom plane can be used for electrical signal distribution. Thus, a preferably increased packing density can be obtained.

[0169] Embodiments enable a high amplification of the lateral or cross-area of ​​an L-NED based actuator, for example 16 times. For an inventive microspeaker this can produce a sound level of up to 24 dB, which is a significant amount. Among other things, the effect also helps for the inventive micropump. Since the height of the overall structure is increased by the rear structure, the vertical pull-in voltage is greatly increased. A higher pull-in voltage provides several design freedoms, for example making the L-NED length longer and making the clamps (on one or both sides) softer to obtain a larger NED deflection. Besides pumps, loudspeakers and microphones, other applications are also related to MEMS waveguides for high frequencies, especially in the THz range.

[0170] Although some aspects have been described in the context of an apparatus, it is apparent that these aspects also represent a description of a corresponding method, such that a block or device of an apparatus corresponds to a corresponding method step or a feature of a method step. Similarly, aspects described in the context of a method step also represent a description of a corresponding block or a detail or feature of a corresponding apparatus.

[0171] The above 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 those having ordinary knowledge in the art. Therefore, it is intended that the present invention be limited only to the scope of the appended patent claims and not to the specific details introduced by the description and explanation of the embodiments herein.

Claims

1. A micro-electromechanical system, comprising: a substrate comprising a cavity; a movable layer arrangement structure arranged in the cavity, the cavity comprising a first beam, a second beam, and a third beam arranged between the first beam and the second beam and fixed at a discrete area electrically insulated therefrom; wherein the movable layer arrangement is configured to move along a movement direction in a substrate plane in response to a potential between the first beam and the third beam, or in response to a potential between the second beam and the third beam; wherein the first, second and third beams are part of a first layer of the movable layer arrangement structure, and the movable layer arrangement structure comprises a second layer arranged adjacent to the first layer along a direction z perpendicular to the plane of the substrate, wherein the second layer is arranged in a movable manner along the moving direction; wherein, relative to the first layer, the second layer provides an additional area for interacting with a fluid; and wherein the second layer is structured into a fourth beam, a fifth beam and a sixth beam, wherein the fourth beam is arranged adjacent to the first beam; and the fifth beam is adjacent to the second beam; and the sixth beam is adjacent to the third beam along the direction z perpendicular to the substrate plane; or The first beam, the second beam and the third beam form a movable element, and the second layer forms a resistor structure for interacting with a fluid in the cavity, being mechanically connected to the movable element, and moving and / or deforming together with the movable element.

2. The micro-electromechanical system according to claim 1, wherein the beams are electrostatic, piezoelectric, or thermomechanical electrodes. The micro-electromechanical system according to claim 1 , wherein the beams of adjacent layers are arranged offset from each other. 4 . The micro-electromechanical system according to claim 1 , wherein at least one of the first beam and the fourth beam, the second beam and the fifth beam, and the third beam and the sixth beam is mechanically connected to each other via an intermediate layer disposed between the first layer and the second layer.

5. The micro-electromechanical system according to claim 1 , wherein the third beam and the sixth beam are mechanically connected to each other via an intermediate layer arranged between the first layer and the second layer; and the intermediate layer between the first beam and the fourth beam is removed on the one hand, and the intermediate layer between the second beam and the fifth beam is removed on the other hand, so as to separate the first beam from the fourth beam and the second beam from the fifth beam.

6. The micro-electromechanical system according to claim 1 , wherein the first beam and the fourth beam on the one hand and the second beam and the fifth beam on the other hand are mechanically connected to each other via an intermediate layer arranged between the first layer and the second layer; and the intermediate layer between the third beam and the sixth beam is removed so as to provide a gap between the third beam and the sixth beam.

7. The micro-electromechanical system according to claim 1, wherein the first layer and the second layer are connected to each other via an intermediate layer in a region of the substrate; wherein the intermediate layer in a region of the cavity between the first beam and the fourth beam, between the second beam and the fifth beam, and between the third beam and the sixth beam is removed.

8. The micro-electromechanical system according to claim 7, wherein the first, second and third beams form a first movable element of the movable layer structure, and wherein the fourth, fifth and sixth beams form a second movable element of the movable layer structure, wherein the first movable element is arranged in a movable manner relative to the second movable element along the moving direction.

9. The micro-electromechanical system according to claim 8, wherein Different potentials may be applied between the first beam and the third beam on the one hand and between the fourth beam and the sixth beam on the other hand, and / or Different potentials can be applied therein between the second beam and the third beam on the one hand and between the fifth beam and the sixth beam on the other hand. 10 . The micro-electromechanical system of claim 1 , wherein the resistor structure is connected to the first layer via an intermediate layer. 11 . The micro-electromechanical system according to claim 1 , wherein the first layer further comprises a piggyback element mechanically fixed to the first or second beam on a side facing away from the third beam, wherein the resistor structure is at least partially arranged on the piggyback element. 12 . The micro-electromechanical system of claim 11 , wherein the piggyback element is mechanically firmly connected to the first or second beam via a coupling element, wherein the coupling element is arranged in a region that experiences maximum deflection during a deformation of the movable element. 13 . The micro-electromechanical system according to claim 1 , wherein the resistor structure comprises a plurality of partial elements arranged along an axial extension direction y of the movable layer arrangement structure, perpendicular to the moving direction and parallel to the substrate plane. The micro-electromechanical system according to claim 13 , wherein some components have a distance from each other along the axial extension direction y.

15. The micro-electromechanical system according to claim 14, wherein the distance is at most 100 μm. 16 . The micro-electromechanical system according to claim 13 , wherein a part of the components is firmly mechanically connected to the first beam, to the second beam, or to the third beam. 17 . The micro-electromechanical system according to claim 13 , wherein some components are arranged on at least two of the first beam, the second beam, and the third beam. 18 . The micro-electromechanical system of claim 1 , wherein a first distance between the resistor structure and the substrate along or opposite to the moving direction is greater than a second distance between the first beam and the third beam.

19. The micro-electromechanical system of claim 18, wherein the first distance is greater than the second distance by a factor ranging from at least 1 to 20.

20. The micro-electromechanical system of claim 1, wherein the second layer has a thickness perpendicular to the substrate plane that is greater than the first layer by a factor ranging from at least 1 to 20. 21 . The micro-electromechanical system of claim 1 , wherein an aspect ratio of the first layer is less than 40 for a thickness of the first layer and a distance between the first beam and the third beam.

22. The micro-electromechanical system according to claim 1, wherein the resistor structure is a first resistor structure arranged on a first side of the first layer, and further comprises a second resistor structure arranged on a second side of the first layer, the second side being arranged opposite to the first side.

23. The microelectromechanical system of claim 1, wherein the resistor structure provides a fluid resistance for a fluid disposed in the cavity.

24. The microelectromechanical system of claim 1, wherein the movable layer arrangement structure comprises a third layer structured into a fourth beam, a fifth beam and a sixth beam; wherein the first, second and third beams form a first movable element, and wherein the fourth, fifth and sixth beams form a second movable element of the movable layer arrangement structure. 25 . The micro-electromechanical system of claim 24 , wherein the first movable element is mechanically connected or not connected to the second movable element.

26. The micro-electromechanical system of claim 24, wherein the resistor structure is a first resistor structure and includes a second resistor structure connected to the second movable element. 27 . The micro-electromechanical system according to claim 26 , wherein the first movable element and the second movable element are arranged adjacent to each other and between the first resistor structure and the second resistor structure along a direction z perpendicular to the plane of the substrate. 28 . The micro-electromechanical system according to claim 26 , wherein the first resistor structure and the second resistor structure are arranged adjacent to each other and between the first movable element and the second movable element along a direction z perpendicular to the plane of the substrate.

29. The micro-electromechanical system of claim 28, wherein the first resistor structure and the second resistor structure are movable relative to each other.

30. The micro-electromechanical system of claim 1, wherein the movable layer structure comprises a flexure beam structure clamped on one side at the substrate.

31. The micro-electromechanical system according to claim 1, wherein a thickness of the first layer and the second layer perpendicular to the plane of the substrate is at least 50 μm.

32. The micro-electromechanical system according to claim 1, wherein an axial extension of the movable layer arrangement structure along a direction y parallel to the substrate plane and perpendicular to the movement direction has a dimension of at least a factor of 0.5 compared to a dimension of the movable layer arrangement structure along a thickness direction.

33. The micro-electromechanical system of claim 1, wherein the cavity is fluidically connected to an external environment of the substrate via at least one opening, wherein the at least one opening is arranged in a plane of the movable layer arrangement.

34. The MEMS according to claim 1, configured as a MEMS pump, a MEMS speaker, a MEMS microphone or a MEMS THz waveguide.

35. The micro-electromechanical system according to claim 1, comprising control means configured to control the movable layer structure.

36. The micro-electromechanical system of claim 35, wherein the first, second and third beams form a first movable element, and the micro-electromechanical system comprises a plurality of movable elements, wherein the control means are configured to individually control the plurality of movable elements.

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