DE102022208829A1 - MEMS, MEMS speakers and method of making the same - Google Patents

Abstract

A MEMS comprises a layer stack comprising a plurality of MEMS layers and a cavity arranged in the layer stack, which is at least partially delimited by a boundary structure comprising at least part of a MEMS layer of the layer stack. The MEMS comprises an actuator device which is designed to move a structural element of the MEMS arranged in the cavity, the structural element being mechanically coupled to the limiting structure and the actuator device being designed to move the limiting structure to the structural element.

Description

The present invention relates to MEMS, in particular MEMS with a layer stack and a cavity arranged therein, which has a structural element which is designed to interact with a fluid. The present invention relates to using additional masses and moving them by means of an actuator device. The present invention relates in particular to a compact MEMS device.

A mechanical resonator is an elastic or acoustic spring-mass oscillator. Such an oscillator has a natural frequency. If a resonator is excited with a harmonic signal very close to or exactly at the natural frequency, large oscillation amplitudes are created, which is also called resonance. This means that an application of small energies can cause very large amplitudes, which in turn can be used specifically to adjust the frequency responses of acoustic or elastic systems. Below the natural frequency, the behavior of the resonator is dominated by static stiffness (potential energy) and the deflection is always in phase with the excitation. Above the natural frequency, the vibration behavior is determined by the mass (kinetic energy) and the deflection is in anti-phase to the excitation. The natural frequency is calculated as the square root of the effective stiffness divided by the effective mass.

The difficulty with MEMS, especially with MEMS loudspeakers, is to construct resonators with low natural frequencies and to couple them into the sound guidance. A low-frequency Helmholtz resonator (purely acoustic spring-mass system) would couple very well into the sound field, but requires too much space so that implementation as MEMS is not economical. However, a passive elastic low-frequency resonator can be designed to be accommodated in MEMS. Nevertheless, such a design is much more complex than is known from general technical mechanics. If springs are manufactured with very small dimensions that are typical for MEMS, this leads to high stiffness and at the same time the oscillating masses are very small. This in turn means that the natural frequencies of such small oscillators are generally much higher and can only be implemented to a limited extent in the area of low natural frequencies. Furthermore, the coupling of purely mechanical vibrations into the acoustic region is also non-trivial and very complex in terms of construction.

Compact, resonantly operated MEMS with low frequencies would be desirable.

An object of the present invention is therefore to provide MEMS, MEMS loudspeakers and methods for producing the same, which enable resonant operation with low frequencies and at the same time require little installation space.

This task is solved by the subject matter of the independent patent claims.

A core idea of the present invention is to use as a vibrating mass at least part of a boundary structure surrounding a cavity of the MEMS, i.e. a structure that is already required for the definition of the cavity in order to synergistically use this part of the MEMS as a vibrating mass of the spring To be able to use the mass system of a resonator. As a result, a low frequency can be obtained by means of high masses and since the corresponding structural parts are already present in the MEMS layer stack, the effect can be achieved without any significant additional components, so that the installation space requirement remains low and the manufacturing effort is also low.

According to one embodiment, a MEMS comprises a layer stack comprising a plurality of MEMS layers. A cavity is arranged in the layer stack and is at least partially delimited by a boundary structure comprising at least part of a MEMS layer of the layer stack. The MEMS includes an actuator device that is designed to move a structural element of the MEMS arranged in the cavity. The structural element is mechanically coupled to the limiting structure and the actuator device is designed to move the limiting structure with the structural element. By moving the limiting structure with the structural element, the vibration behavior of a corresponding oscillator can be adjusted by the additional mass of the limiting structure and, in particular, shifted to low frequencies, which is possible using the limiting structure already present for limiting the cavity.

According to one exemplary embodiment, a MEMS comprises a layer stack comprising a plurality of MEMS layers and a cavity arranged in the layer stack, which is at least partially delimited by a boundary structure comprising at least part of a MEMS layer of the layer stack. A structural element is arranged in the cavity. The MEMS further comprises an actuator device which is designed to move the confining structure with respect to the structural element of the MEMS to provide interaction of the structural element with a fluid disposed in the cavity. Here too, by moving the boundary structure and using its mass, the vibration behavior can be adjusted using existing structural elements and, in particular, lower vibration frequencies can be stimulated.

According to one embodiment, a MEMS speaker comprises a layer stack comprising a plurality of MEMS layers and a cavity arranged in the layer stack for receiving a fluid. The cavity is at least partially delimited by a boundary structure comprising at least part of a MEMS layer of the layer stack. The MEMS speaker includes an actuator device that is designed to move a structural element of the MEMS arranged in the cavity to interact with the fluid in order to generate an acoustic signal in the cavity. The structural element is mechanically coupled to the limiting structure and the actuator device is designed to move the limiting structure with the structural element. Such a MEMS speaker can be adapted for resonant behavior, especially at low frequencies, and at the same time can be designed using a small installation space.

Further embodiments relate to methods for producing MEMS and a MEMS speaker.

Further advantageous embodiments of the present invention are the subject of the dependent claims.

• 1 eine schematische perspektivische Ansicht eines MEMS gemäß einem Ausführungsbeispiel;
• 2 eine schematische Draufsicht auf ein MEMS gemäß einem Ausführungsbeispiel;
• 3a-b korrespondierend zur 2 eine Darstellung von Schichten eines MEMS gemäß einem Ausführungsbeispiel;
• 4a zeigt eine schematische Draufsicht auf einen Teil des MEMS aus 2 mit einer Schnittlinie,
• 4b-c schematische Seitenschnittansichten des aus 4a in einem unausgelenkten und einem ausgelenkten Zustand;
• 5a eine schematische Seitenschnittansicht durch ein MEMS in einem unausgelenkten Zustand gemäß einem Ausführungsbeispiel analog zur 4b, wobei ein zusätzlicher beweglicher Bereich vorgesehen ist;
• 5b einen ausgelenkten Zustand des MEMS aus 5a;
• 6 eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeilspiel, bei dem eine Aktuatoreinrichtung ausgebildet ist, um eine laterale Schicht gegenüber einem Strukturelement auszulenken;
• 7 eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel, bei dem eine Mehrzahl von in der Kavität angeordneten Strukturelementen vorgesehen ist;
• 8a eine schematische Draufsicht auf ein MEMS gemäß einem Ausführungsbeispiel, bei dem die bewegliche Begrenzungsstruktur in Segmente unterteilt ist;
• 8b eine schematische Seitenschnittansicht durch eine Schnittlinie der 8a;
• 9 eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel zur Implementierung eines beispielhaften Zwei-Wege-Ansatzes eines Lautsprechers;
• 10a eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel, bei dem die die Begrenzungsstruktur als beweglicher Bereich einer Deckelschicht gebildet ist; und
• 10b eine schematische Seitenschnittansicht eines MEMS gemäß einem Ausführungsbeispiel, das gegenüber dem MEMS aus 10a dahingehend modifiziert ist, dass das Strukturelement die beweglichen Bereiche gegenüberliegender Schichten miteinander verbindet, wie es im Zusammenhang mit dem MEMS aus 5a und 5b beschrieben ist.

Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. Show:

• 1 a schematic perspective view of a MEMS according to an embodiment;
• 2 a schematic top view of a MEMS according to an exemplary embodiment;
• 3a -b corresponding to 2 a representation of layers of a MEMS according to an exemplary embodiment;
• 4a shows a schematic top view of part of the MEMS 2 with a cutting line,
• 4b -c schematic side section views of the from 4a in an undeflected and a deflected state;
• 5a a schematic side sectional view through a MEMS in an undeflected state according to an exemplary embodiment analogous to 4b , with an additional movable area being provided;
• 5b a deflected state of the MEMS 5a ;
• 6 a schematic side sectional view of a MEMS according to an exemplary embodiment, in which an actuator device is designed to deflect a lateral layer relative to a structural element;
• 7 a schematic side sectional view of a MEMS according to an exemplary embodiment, in which a plurality of structural elements arranged in the cavity are provided;
• 8a a schematic top view of a MEMS according to an embodiment in which the movable boundary structure is divided into segments;
• 8b a schematic side section view through a section line of the 8a ;
• 9 a schematic side sectional view of a MEMS according to an embodiment for implementing an example two-way approach to a speaker;
• 10a a schematic side sectional view of a MEMS according to an exemplary embodiment, in which the boundary structure is formed as a movable region of a cover layer; and
• 10b a schematic side sectional view of a MEMS according to an embodiment, which is opposite the MEMS 10a is modified in such a way that the structural element connects the movable areas of opposite layers to one another, as is the case with MEMS 5a and 5b is described.

Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it should be noted that identical, functionally identical or equivalent elements, objects and/or structures are provided with the same reference numerals in the different figures, so that those shown in different exemplary embodiments Description of these elements is interchangeable or can be applied to one another.

Embodiments described below are described in connection with a large number of details. Examples of embodiments can However, they can also be implemented without these detailed features. Furthermore, for the sake of clarity, exemplary embodiments are described using block diagrams as a replacement for a detailed representation. Furthermore, details and/or features of individual exemplary embodiments can easily be combined with one another, as long as it is not explicitly described to the contrary.

The following exemplary embodiments relate to micromechanical components (MEMS components). The MEMS devices described herein may be multilayer layer structures. Such MEMS can be obtained, for example, by processing semiconductor materials at wafer level, which can also include a combination of multiple wafers and/or the deposition of layers at wafer levels. Some of the embodiments described herein address MEMS levels. A MEMS plane is understood to be a not necessarily two-dimensional or non-curved plane that extends essentially parallel to a processed wafer, for example parallel to a main side of the wafer or the later MEMS. A plane direction of such a plane or layer plane can be understood as a direction within this plane, which can also be referred to with the English term “in-plane”. A direction perpendicular to this, that is, perpendicular to a plane direction, can be simply referred to as the thickness direction or stacking direction, whereby the term thickness does not have any limitation in the sense of an orientation of this direction in space. It is understood that terms used herein such as “length,” “width,” “height,” “top,” “bottom,” “left,” “right,” and the like are used solely to illustrate embodiments described herein because of their location can be changed as desired in space and the exemplary embodiments are not limited to this.

Some of the embodiments described herein are described in the context of a speaker configuration or speaker function of a corresponding MEMS device. It is understood that, with the exception of the alternatives or additional function of a sensory evaluation of the MEMS component or the movement or position of movable elements thereof, these statements can be transferred to a microphone configuration or microphone function of the MEMS audio element, so that such Microphones represent further embodiments of the present invention without limitation.

Some of the MEMS described herein refer to MEMS with resonators, which can be understood as meaning spring-mass systems that can be excited to a resonant oscillation, for example by means of an actuator, in order to oscillate at least in the vicinity of the resonance range using comparatively low energies to achieve large vibration amplitudes. For this purpose, the present MEMS describe a structural element that is excited to oscillate, which is additionally coupled to a mass element that increases the oscillatable mass of the spring-mass system, thereby reducing the resonance frequency. This mass element can limit the cavity in which the oscillatable structural element is excited to oscillate, laterally, in the plane and/or out of the plane.

1 shows a schematic perspective view of a MEMS 10 according to an exemplary embodiment. The MEMS 10 comprises a layer stack 12 with a plurality of layers 12 ₁ , 12 ₂ and/or 12 ₃ . A number of layers is not necessarily three, but can be any other number of at least 2, for example, 2, 4, 5, 6 or more. A layer can be understood as a functional layer, which can consist of or include at least one but also several material layers. For example, a layer 12 ₁ may include a bottom layer. A layer 12 ₃ shown transparently can, for example, provide a top layer of the layer stack 12, whereby neither the bottom layer 12 ₁ nor the top layer 12 ₃ have to be a final layer in the layer stack 12, but can, for example, represent layers that form a cavity 14 along a stacking direction 16 , along which the layers 12 ₁ -12 ₃ are stacked on top of one another in the layer stack 12. For example, the layer 12 ₂ can have a recess between the layers 12 ₁ and 12 ₃ in order to at least partially form the cavity 14, for example in that the layer 12 ₂ or parts thereof move the cavity laterally along an x-direction and/or y-direction limit. Instead of a single layer 12 _2, several layers of the MEMS stack 12 can also be arranged and form the cavity 14. The cavity 14 can in this respect be delimited by further layers and can be completely or partially delimited along the stacking direction 16 by at least one delimiting structure, for which, for example, the layers 12 ₁ and/or 12 ₃ can be used, and additional structural elements can also be arranged in order to to provide a boundary of the cavity 14. A remaining material of the layer 12 ₂ and possible further layers can provide a lateral boundary structure for the cavity 14.

To simplify reference, an exemplary Cartesian coordinate system with the directions x, y and z is used, whereby, for example, an x/y plane can be understood as a plane parallel to the layer plane and both the x direction and the y direction can be understood as in-plane. The z-direction can be arranged in space parallel to the stacking direction 16.

The MEMS 10 includes an actuator device 18 which, according to one embodiment, is designed to move a structural element 22 arranged in the cavity 14. The structural element can be designed to interact indirectly by means of further mechanically coupled elements or directly with a fluid arranged in the cavity.

The structural element 22 can, for example, form an actuator of the actuator device 18 in whole or in part, but can alternatively also be formed passively. For example, the structural element 22 may include a so-called Nanoscopic Electrostatic Drive (NED) actuator. NED describes a form of actuator that can be formed, for example, as an elongated beam structure, which can deform in-plane and can therefore be used both as an element for displacing fluid and as an actuator. Alternatively or additionally, the actuator device 18 can also include, for example, piezoelectric and/or electrostatic drives, such as a comb drive or the like, which is coupled to the structural element 22. This means that the structural element 22 can at least partially form the actuator or include an element connected thereto, such as a fin or the like. The structural element 22 can interact with a fluid arranged in the cavity 14.

According to an embodiment of the present invention, the structural element 22 is mechanically coupled to the limiting structure and the actuator device 18 is designed to move the limiting structure with the structural element 22. For this purpose, the actuator device 18 can, for example, send a control signal 24 to an active element or convert such a signal to generate a force. In the case of operation of the MEMS 10 as a sensor, such as a microphone, the actuator device 18 can be formed as a sensor device in order to convert the movement of the structural element 22 and the limiting structure into a sensor signal, which can be formed, for example, optically and / or electrically.

According to the invention, the limiting structure is moved together with the structural element 22, which means for resonant operation or a resonant oscillation that the mass of both parts, the structural element 22 and the limiting structure, can form a vibrating mass and influences the vibration behavior.

According to a possible embodiment, the structural element 22 can, for example, be mechanically coupled to at least one of the bottom layer 12 ₁ and the cover layer 12 ₃ in order to move this layer and to include its mass in the vibration behavior. Alternatively or additionally, it is also possible to move the lateral layer 12 ₂ with it. For this purpose, for example, the layer 12 ₂ can be connected to one of the layers 12 ₁ or 12 ₃ and can also be moved.

Compared to a movement of the structural element 22 alone, a higher mass can therefore be used for vibration. The MEMS 10, like the other MEMS described herein, may be designed for operation in which the structural element 22 together with the boundary structure is excited into a resonant oscillation, such as due to external forces and/or the actuator device. The structural element 22, together with the boundary structure, can form part of a resonator that can generate sound waves in an energy-efficient manner.

According to one exemplary embodiment, the MEMS layers 12 ₁ -12 ₃ are arranged adjacent to one another in the layer stack 12 along the stacking direction 16, which can be arranged perpendicular to the layer plane x/y. The actuator device 18 can be designed to provide a movement of the boundary structure parallel thereto, that is, in-plane and parallel to the layer plane.

In an advantageous embodiment of the present invention, the boundary structure comprises a part of at least one MEMS layer and, for example, a part of a MEMS layer that provides a bottom or a lid of the cavity 14. Such adjacent layers can be easily connected to one another or partially separated, for example by bonding, growing or etching.

Alternatively or additionally, the layer 12 ₂ can also be moved at least in part only or in combination with other elements in order to provide an additional mass in relation to the structural element. The delimitation structure can therefore, for example, comprise a part of a MEMS layer that laterally delimits the cavity, as is described, for example, for the layer 12 ₂ .

Both the use of a top cover and a lateral layer enable the use of several substructures in one Boundary structure. For example, the base or the lid can be connected together with the laterally delimiting layer 12 ₂ or several such layers, or, for example, both the lid and the base 12 ₁ and 12 ₃ can each form a partial structure of the delimiting structure. For example, the layers 12 ₁ and 12 ₃ may be mechanically coupled to one another by means of the structural element 22 or otherwise.

In some embodiments, it is preferred if a mass of the boundary structure is greater than a mass of the structural element, which enables the mass of the boundary structure to have a significant influence on the resonance frequency.

2 shows a schematic top view of a MEMS 20 according to an exemplary embodiment. In the illustration shown, layer 12 ₃ is shown shifted compared to a combination of layers 12 ₁ and 12 ₂ to show additional details. In fact, the layer 12 ₃ can be analogous to the illustration 1 form a layer stack with layers 12 ₁ and 12 ₂ .

The layer 12 ₁ can, for example, have an opening 26 ₁ , which can serve as an inlet into the cavity ₁₄ or an outlet from the cavity 14 for an air flow 28 1. The structural element can be arranged in the plane of the layer 12 ₂ . According to a non-limiting embodiment, the structural element may comprise a region 22A, which comprises, for example, a flexible actively or passively formed structure. An active structure of the region 22A may, for example, include a beam actuator, for example formed as an NED. A passive structure of region 22A may include, for example, an elastic beam or a membrane. The region 22A can be firmly clamped laterally, for example at an edge region of the region 22A and with the layer 12 ₂ , whereby neither the presence of the restraint nor its location is restrictive. The element 22A could also be rigid or clamped to the layers 12 ₁ and or 12 ₃ .

According to an exemplary embodiment, the structural element 22 can be mechanically coupled to the limiting structure 34 at a discrete area, by which it can be understood that the limiting structure 34 is not in full contact with the structural element, but only partially. Such a discrete area or fastening area can be arranged at a location of maximum deflection of the structural element 22, which means that the location of the contact can define a maximum deflection of the structural element and/or the boundary structure. Embodiments also refer, for example, to the fact that a mechanical contact of the structural element with the surrounding solid substrate implements a device for limiting movement in order to prevent a mechanical overload when a maximum deflection is exceeded. For example, a mechanical contact with the layer 12 ₁ when the movement 36 ₁ and/or 36 ₂ is carried out can limit further movement, the mechanical connection between the structural element and the movement structure being preferably designed for such a mechanical load.

According to an exemplary embodiment, the structural element 22 comprises a beam structure clamped on both sides, which is designed to deform in-plane with respect to a MEMS layer. Like it in 2 is shown, the limiting structure can be arranged out-of-plane, that is, in a different plane than the structural element 22 itself. However, the limiting structure can also be partially arranged in the same plane, as is the case, for example 6 is shown.

According to an exemplary embodiment, the structural element 22 is part of the actuator device and has beam elements that are firmly connected to one another and can be deformed in-plane at discrete areas and are designed to provide an in-plane deformation of the structural element with respect to the layer stack. For example, the beams that are firmly connected to each other in discrete areas can be used to create a back and forth movement in-plane.

An optional region 22B of the structural element 22 can be used, for example, to mechanically couple the structural element 22 to at least one of the layers 12 ₁ and/or 12 ₃ , for example in order to move a part of such a layer as a delimiting structure. The area 22B can serve as a coupling point.

The actuator device 18 can, for example, be supported on the structural element 22 or form part of it and can be used, for example, as a so-called asymmetric nanoscopic electrostatic drive, Asymmetric Nanoscopic Electrostatic Drive (ANED), as a lateral nanoscopic electrostatic drive, Lateral Electrostatic Drive (LNED) or as a balanced nanoscopic Electrostatic drive, Balanced Electrostatic Drive (BNED) can be implemented here. Bar structures arranged next to one another can be designed to be deformable and can be selectively coupled to one another in discrete areas in order to achieve a deformation of the overall structure when actuated. Actuation can be achieved, for example, electrostatically or electrodynamically, due to thermally induced deformation or based on piezoelectric effects. Alternatively or additionally, the actuator device 18 can be formed differently and region 22A includes or provides an externally driven fin. For this purpose, the power can be generated at another location and transferred accordingly.

The structural element 22 can be used to divide the cavity 14 into a first partial cavity 14a and a second partial cavity 14b. An increase in the size of one partial cavity can lead to a corresponding reduction in the size of the other partial cavity.

For the layer 12 ₃ it is shown that it can have a stationary region 42, possibly used as a substrate, and a movable region 34. The movable area 34 can be movable relative to the fixed area 32 along a positive and/or negative direction of movement 36 ₁ , 36 ₂ , whereby the stationary area 32 can also be omitted. By means of the actuator structure, for example, the structural element 22 can be supported on the layer 12 ₂ , so that, for example, the movable region 34 is moved along with the structural element 22 by the actuator device. A deformation of the structural element 22 can take place in the plane of the layer 12 ₂ in that the structural element 22 can be spaced apart from the layers 12 ₁ and 12 ₃ in areas of deformation or can be mounted so that it can slide, without causing an acoustic short circuit between the partial cavities 14a and 14b to create.

The ones in the 2 The structure shown can also be arranged multiple times in a MEMS, which means that a MEMS can also have several cavities, several actuators and/or several openings 26 ₁ and/or 26 ₂ . Also for the structure shown, the number of actuators and openings 26 ₁ , 26 ₂ as well as structural elements is chosen only as an example and can also be chosen differently for each of the elements, depending or independently of other elements, for example 2, 3, 4, 5 or more.

An opening 26 ₂ in the cover plane 12 ₃ can connect the partial cavity 14b with the environment in order to lead an air flow 28 ₂ out of the cavity 14 into the environment or into the cavity 14 or the partial cavity 14b. For example, when the structural element 22 and the movable region 34 serving as a limiting structure move along the direction 36 ₁ , the air flow 28 ₁ can be guided into the sub-cavity 14a and the air flow 28 ₂ out of the sub-cavity 14b. When the movement is reversed in the direction 36 ₂ , the directions of the air flows 28 ₁ and 28 ₂ can also be reversed.

Like it in 2 As shown, the actuator device can be designed to provide an in-plane movement of the boundary structure, such as the movable region 34, with respect to a layer arrangement. The boundary structure can comprise a part of a MEMS layer 12 ₃ , whereby alternatively or additionally a corresponding part of the layer 12 ₁ can also be moved. The structural element 22 can interact with a fluid arranged in the cavity based on an actuation by the actuator device indirectly, ie in direct contact, or directly, for example by coupling with corresponding plate elements or displacement elements. The boundary structure may have an opening, such as the opening 26 ₁ and/or 26 ₂ , which is designed to conduct sound in the fluid or the fluid itself out of the cavity 14 or into the cavity 14.

As it is in the 2 As can be seen, the structural element 22 and the limiting structure, for example the movable region 34, can together form a mass structure of a spring-mass system and can be set up for a resonant vibration excited by the actuator device 18. For example, a stiffness of the region 22A and/or another coupled element may provide a corresponding spring stiffness for the spring-mass system.

In other words shows 2 in one embodiment, a micromechanical transducer with a resonating, movable cover of the cover level as a resonator in a first basic principle of the present invention. Here, the cover resonator is coupled to an actively deflectable element, a coupling point of the structural element 22. The cover resonator follows the movements of the actively deflectable elements via the coupling point. In this exemplary embodiment, the cover resonator is detached from the surrounding substrate and is movable, for example not connected or elastically connected. In a first time interval, the active elements of the actuator deflect in a first direction 36 ₁ or 36 ₂ , parallel to the substrate plane, and transport fluid out of the lid wafer via the oscillating openings 26 ₂ . At the same time interval, fluid is conveyed into the cavities via the openings 26 ₁ in the bottom wafer. In a second time interval, the active elements of the actuator deflect in a second direction, which is opposite to the first direction. Fluid is thus conveyed out of the cavities via the openings in the base wafer and into the cavities via the oscillating openings in the cover wafer.

The 3a and 3b show corresponding to 2 a representation of layers 12 ₁ and 12 ₂ ( 3a) or the layer 12 ₃ ( 3b) a MEMS 30. Compared to the MEMS 20, the MEMS 30 has several arranged adjacent to one another nete cavities 14 ₁ -14 ₃ , whereby the number of such cavities can have any value of ≥ 2, for example 3, 4, 5, 8, 10 or more.

A position of the coupling element 22B can be arranged at a location of maximum deflection of the structural element 22 or the region 22A, which can occur, for example, in the middle of a double-sided clamped configuration of a beam structure or at the deflectable end of a one-sided clamped beam structure.

A partition 38 ₁ or 38 ₂ can be arranged between adjacent cavities 14 ₁ and 14 ₂ or 14 ₂ and 14 ₃ , which can be formed, for example, from material of the layer 12 ₂ and, depending on the embodiment, can also be referred to as a solid fin. In embodiments where layer 12 ₂ is moved relative to other elements, a movable fin may be implemented.

The 3b correspondingly shows a movable area 34, which has a plurality of openings 26 ₂ , of which each opening 26 ₂ is assigned to one of the cavities 14 ₁ -14 ₃ , an assignment preferably being made to a respective partial cavity of the cavity 14 ₁ -14 ₃ .

In other words, it shows 3a an embodiment analogous to 2 with several actively deflectable elements, each of which has a coupling point or a coupling element 22B. 3b shows an exemplary embodiment analogous to 2 with a cover resonator that is connected to several actively deflectable elements via the coupling points.

4a shows a schematic top view of the MEMS 20 with a section line 42, where the 4b and 4c show schematic side sectional views of the MEMS 20 through the section line 42 to different deflection states of the MEMS 20.

In 4b An exemplary undeflected state of an embodiment is shown in which the layers 12 ₁ and 12 ₂ are firmly connected to one another and are possibly, but not necessarily, formed from the same material. Additional layers can easily be arranged, for example to implement different material stiffness, at least partially provided electrical conductivity or other functions.

4b shows a side sectional view in a first state of the MEMS 20, for example a reference state or undeflected state. In contrast, this shows 4c a deflected state of the MEMS 20, in which the structural element 22 and the delimitation structure formed by the movable region 34 for delimiting the cavity 34 along the z-direction are deflected along the direction 36 ₂ . This creates the respective air flow 28 ₁ and 28 ₂ , with a resonance frequency of a corresponding spring-mass system being influenced not only by the structural element 22, but also by the mass of the movable area 34.

In other words, they show 4b and 4c a sectional view through the middle of the component 20, wherein the structural element 22 or coupling element is connected to the top layer, but not to the bottom layer.

In other words shows 4b an actively deflected element connected to a lid resonator in a non-deflected position. 4c is analogous to 4b a deflection in a first direction. A first fluid stream is conveyed through the resonating opening in the cover resonator into a first cavity. At the same moment, a second fluid stream is conveyed outwards from a second cavity through a non-movable opening in the bottom wafer.

5a shows a schematic side sectional view through a MEMS 20' analogous to 4b , whereby, unlike in MEMS 20, a movable region 34 ₁ of layer 12 ₁ is also movable relative to layer 12 ₂ . For this purpose, the region 22A of the structural element 22 can be active and formed as part of the actuator device and further mechanically firmly connected via a coupling point 22B ₁ to the region 34 ₁ and with a coupling point 22B ₂ to a movable region 34 ₂ of the layer 12 ₃ , the latter in accordance with the MEMS 20. Compared to the MEMS 20, a further increased mass is used, which can lead to lower-frequency resonances of the spring-mass oscillator. This means that compared to the MEMS 20, not only one of the layers 12 ₁ or 12 ₃ , but both the bottom wafer and the top wafer are partially movable.

While the 5a one to 4b shows a comparable reference state 5b a deflected state of the MEMS 20`. As a result, the limiting devices 34 ₁ and 34 ₂ coupled to the structural element 22 are moved relative to the layer 12 ₂ . As with other MEMS described herein, this may include movement and/or deformation of the structural element.

6 shows a schematic side sectional view of a MEMS 60 according to an exemplary embodiment, in which the actuator device 18 is designed to, for example, the layer 12 ₂ to deflect relative to the structural element 22. For example, the structural element 22 can be formed passively, with an active configuration also providing an interaction of the structural element 22 with a fluid arranged in the cavity. The limiting structure is formed, for example, by the side walls of the layer 12 ₂ , which laterally delimit the cavity 14. By moving the boundary structure, the layer 12 ₂ , with respect to the structural element 22 of the MEMS 60, a comparable effect and an interaction of the structural element 22 with the fluid arranged in the cavity 14 can be obtained. An additional mass is provided by the moving mass of the one or more layers 12 ₂ .

Just like in the 5a and 5b will be in the 6 a cross section through a MEMS layer structure with a resonating lid or lid wafer, bottom wafer on the one hand or a chip frame on the other hand is shown. In the 5a and 5b All air outlet openings are movable. The 6 shows opposite the 2 a supplementary embodiment of the present invention.

7 shows a schematic side sectional view of a MEMS 70 according to an exemplary embodiment, in which a plurality of structural elements 22 ₁ -22 ₃ arranged in the cavity 14 are provided, which are coupled to the actuator device and are arranged to be movable along different relative directions. For example, the structural element 22 ₁ and the structural element 22 ₂ are movable along the direction of movement 36 ₂ and at the same time the structural element 22 ₂ is movable along the direction of movement 36 ₁ . Adjacent structural elements are preferably movable along complementary directions 36 ₁ /36 ₂ .

A respective partial cavity 14b and 14c can be arranged between adjacent structural elements 22 ₁ -22 ₃ , which has a variable volume under the influence of a movement of the adjacent structural elements. A respective partial cavity 14b and 14c can be fluidically connected to an environment of the layer stack through an opening in the MEMS layer stack. An analogous configuration also applies to partial cavities 14a and 14d, at least in some embodiments, in which case a structural element can only be provided on one side of the respective partial cavity. The arrangement of three structural elements for the exemplary definition of four partial cavities 14a-14d is merely an example. Fewer or more structural elements can also be arranged in the cavity. A first subset of structural elements, preferably those which are arranged to be movable along a same direction, as is shown, for example, for the structural elements 22 ₁ and 22 ₃ on the one hand and the structural element 22 ₂ on the other hand, are provided with a respective boundary structure 34 ₂ and 34 _1, respectively mechanically coupled, with the limiting structures 34 ₁ and 34 ₂ being arranged opposite one another. A corresponding concept can also be easily transferred to the MEMS 60, in which the chip frame or the layer 12 ₁ is arranged to be movable. Here, for example, different sides could be moved relative to one another or a first subset of structural elements could be arranged in a stationary manner and a second subset could be movable.

The corresponding actuators can be arranged individually or in groups and include, for example, actuators arranged on the layers 12 ₁ and 12 ₃ or groups of actuators which are each arranged on the layer 12 ₁ or the layer 12 ₃ .

In other words shows 7 a cross section through a MEMS layer structure with two groups of actively deflected elements and two lid resonators, each in the lid wafer and in the bottom wafer. The actuator groups differ in the direction of movement, that is, if a first group is deflected in a first direction, a second group is deflected in a second direction. Furthermore, the actuator groups differ in the coupling to the lid resonators, ie a first group is coupled to the lid resonator in the lid wafer, while a second group is coupled to the lid resonator in the bottom wafer. The lid resonator in the lid wafer thus deflects in a first direction and the lid resonator in the base wafer deflects in a second direction.

8a shows a schematic top view of a MEMS 80 according to an exemplary embodiment, in which the boundary structure, for example the layer 12 ₁ and / or 12 ₂ , is divided into segments 34 _2,1 and 34 _2,2 , including any other and in particular higher Number of segments is possible.

In 8a It can also be seen that with respect to a partial cavity, several openings can be provided in the lid and / or base, for example 2, although any other, higher number can also be provided.

In other words shows 8a a MEMS layer system with two cap resonators in a cap wafer. A first cover resonator is deflected in a first direction, with the second cover resonator being deflected in a second direction. The first and second cover resonators both have openings through which an air flow can be guided orthogonally to the first and second deflection directions.

8b shows a schematic side sectional view through the cutting line 42. The segments 34 _2.1 and 34 _2.2 on the one hand and optionally the segments 34 _1.1 and 34 _1.2 on the other hand can each be movable in opposite directions to one another and be mechanically coupled to different structural elements. For example, the segment 34 _1,1 of the layer 12 ₁ can be coupled to the structural element 22 ₂ for actuation, the boundary structure 34 _1,2 to the structural element 22 ₃ , the boundary structure 34 _2,1 to the structural element 22 ₁ and the boundary structure 34 _2,2 with the structural element 22 ₄ . A configuration is preferred in which adjacent structural elements 22 ₁ -22 ₄ are each moved in opposite directions to one another, so that the actuator paths have an additive effect.

The movable areas 34 _1,2 and 34 _2,1 and/or the movable areas 34 _1,1 and 34 _2,2 can be mechanically coupled with a mechanical coupling, not shown, in order to ensure a synchronous and equal deflection of the movable areas or boundary structures to enable. Alternatively, the movable areas can also vibrate independently of one another and possibly be equipped with different masses, for example in order to provide resonance frequencies that differ from one another, wherein the actuator device can be set up to excite the resonance frequencies that differ from one another.

Referring to the MEMS 70 and 80, some embodiments refer to the fact that different structural elements may be coupled to different boundary structures and may provide more than a single spring-mass system in the MEMS. This means that different structural elements can be coupled to different boundary structures to provide different spring-mass systems. The actuator device can be designed to stimulate the respective spring-mass systems, for example by moving the respective structural element together with the limiting structure. Resonance frequencies of the different spring-mass systems can be the same or different from one another, with resonant frequencies that differ from one another enabling a broader emission spectrum or a broader reception spectrum, and matching resonant frequencies can have a higher amplitude or higher sensitivity at a targeted frequency.

In accordance with the present invention, several spring-mass systems can also have the same resonance frequency and several spring-mass systems can have different resonance frequencies at the same time. According to one embodiment, a MEMS is designed to generate a sound pressure based on the resonant movement with a frequency based on a resonant frequency of the resonant vibration.

Different frequencies can also be obtained differently according to embodiments of the present invention, such as via a multi-path approach.

In other words shows 8b a cross section derived from 8a and points in addition to the cover resonators 8a additional lid resonators in the bottom wafer. For example, there are four actuator groups, each with at least one deflectable element. Each deflectable element deflects in a first or second direction and is coupled to a first or second air-flowing lid resonator in the lid wafer or in the bottom wafer.

9 shows a schematic side sectional view of a MEMS 90 according to an embodiment for implementing an exemplary two-way approach. For example, structural elements 22 ₁ and 22 ₂ can be arranged with respective boundary structures implemented by movable regions 34 ₂ and 34 ₁ , as described for example in connection with the MEMS 70, with the movable regions 34 ₁ and/or 34 ₂ also being segmented can be and/or several structural elements can be arranged on a respective segment or the structure 34 ₁ or 34 ₂ .

In the cavity 14 or another cavity, which can be acoustically separated from the cavity 14, additional actuators or elements for sound generation 44 ₁ -44 ₄ can be arranged. These can, for example, be designed in the same or similar way as the actuators for moving the structural elements 22 ₁ and 22 ₂ , but due to their lower mass they can be designed for vibrations in higher frequency ranges f ₂ and in this respect one in comparison to those through the openings 26 ₁ and 26 ₂ Emerging low-frequency sound and having a frequency or frequency range f ₁ output higher-frequency sound or sound range through the corresponding opening 46 ₁ -46 ₅ . A position of the openings 46 ₁ -46 ₅ can possibly be coordinated with a movement amplitude of the movable areas 34 ₁ and 34 ₂ , so that corresponding partial cavities between adjacent sound generators 44 ₁ -44 ₄ with a respective opening 46 ₁ -46 ₅ with an environment of the MEMS 90 can be connected. The frequencies f ₁ and/or f ₂ can be in the range audible to humans, although this is not necessary. It With the structures described here, any application-specific frequencies can be excited, for example alternatively or additionally in the ultrasonic range.

For example, a two-way loudspeaker can be implemented that includes both a subwoofer, in particular a comparatively small µSubwoofer, together with a tweeter, in particular a comparatively small µTweeter. A movement of the structural elements 22 ₁ and 22 ₂ can be used as a woofer/subwoofer and a movement of the sound generators 44 ₁ -44 ₄ can be used as a tweeter. According to exemplary embodiments, at least one movable element is arranged in the cavity 14, which is set up to generate sound in a fluid arranged in the cavity.

In other words shows 9 a MEMS layer system with a multi-way approach. Analogous to 7 There are several actuator groups, with at least one further group that can be characterized by the oscillation with a second frequency. In addition to the version in 7 There are openings in both cover resonators through which an air flow with a second frequency f2 is conveyed perpendicular to the deflection of the cover resonator with a first frequency f1.

10a shows a schematic side sectional view of a MEMS 100 ₁ according to an exemplary embodiment. There, the boundary structure is formed, for example, as a movable region 34 of the layer 12 ₃ and is movable together with the structural element 22 relative to the layer 12 ₁ and the layer 12 ₂ , whereby another configuration can easily be implemented, such as an additional movement of the layer 12 ₁ and/or a movement of the layer 12 ₂ together with the layer 12 ₃ or the movable area 34.

The boundary structure or the movable region 34 can be mechanically coupled via a mechanical suspension 48 to a substrate of the MEMS 100 ₁ , for example a remaining region of the layer 12 ₃ , such as the region 32. The mechanical suspension 48 can be designed to provide a mechanical To provide damping 52 and/or a mechanical stiffness 54, which at least partially determines a resonance frequency of a spring-mass system comprising the structural element 22 and the limiting structure 34. An appropriate suspension can be used to adjust and adapt the vibration behavior. According to exemplary embodiments, the mechanical suspension 48 can also be designed adaptively in order to enable the frequency response to be adjusted during operation or for adjustment purposes.

In the execution of the 10a For example, the lid wafer is connected to the surrounding substrate with additional rigidity and/or damping.

The MEMS 100 ₁ , like other MEMS described herein, may have or be connectable to a control device 58. The control device 58 can be designed to control the actuator device for moving the structural element 22 in order to set a resonant movement of the structural element 22. A resonance frequency of the resonant movement can be influenced by a mass of the structural element 22 and the mass of the limiting structure 34. Possibly, but not necessarily, such a MEMS is formed as a MEMS speaker, which is designed to generate sound in the fluid based on a joint movement of the structural element 22 and the boundary structure 34 in the cavity.

According to one exemplary embodiment, the mechanical suspension 48 can also be designed in such a way that it has a preferred direction along which the deflection of the structural element 34 is influenced at most insignificantly. For example, an out-of-plane movement along the z direction can be limited or prevented, while the mechanical suspension 48 allows the freest possible in-plane movement, for example along x and/or y. Alternatively, movement along x can be restricted and along y, ie along positive or negative movement direction 36 ₂ , only insignificantly influenced. This can enable a high quality of airborne sound contained in the air stream 28 ₁ and/or 28 ₂ .

In other words shows 10a an embodiment analogous to 2 , where the lid resonator in the lid wafer is connected to the substrate by a connecting element. The connecting element is fluidic or mechanical and has stiffness and/or damping properties.

10b shows a schematic side sectional view of a MEMS 100 ₂ according to an exemplary embodiment, which is modified compared to the MEMS 100 ₁ in that the structural element 22 connects the movable regions 34 ₁ and 34 ₂ to one another, as described in connection with the MEMS 20 '. Although in some embodiments it may be sufficient to have the mechanical suspension 48 ₁ or 48 ₂ with only one of the movable portions 34 ₁ or 34 ₂ , respectively to mechanically couple and suspend it from the surrounding substrate 32 ₁ or 32 ₂ , it may be advantageous to suspend the respective region 34 ₁ via a mechanical suspension 48 ₁ on the fixed region, substrate 32 ₁ , and the movable region 34 ₂ as a further Boundary structure via the mechanical suspension 48 ₂ on the fixed area, substrate 32 ₂ .

Regardless of this, the MEMS 100 _2, like other MEMS described herein, may have a motion limiting device 56. The device 56 can be designed to limit a maximum deflection of the movable structure along one or more directions and to prevent mechanical overload occurring on the MEMS by exceeding such a maximum deflection. For example, the device 56 can be a mechanical stop and/or implement another form of overload prevention. The mechanical device 56 can be arranged on any element of the MEMS and therefore not necessarily on the region 34 ₁ and/or 34 ₂ .

Embodiments of the present invention relate to a MEMS speaker with a layer stack comprising a plurality of MEMS layers 12 ₁ -12 ₃ , a cavity arranged in the layer stack for receiving a fluid, the cavity being composed of at least a part of a MEMS layer. Layer of the layer stack comprising boundary structure, is at least partially limited laterally, in-plane and / or along the stacking direction out-of-plane. An actuator device is designed to move a structural element of the MEMS arranged in the cavity to interact with the fluid in order to generate an acoustic signal, preferably by means of a resonant vibration. The structural element 22 is mechanically coupled to the limiting structure 34 and the actuator device is designed to move the limiting structure with the structural element.

In other words shows 10b an embodiment analogous to 10a , where a lid resonator in the lid wafer and in the bottom wafer are connected to the substrate by connecting elements, a mechanical suspension.

Embodiments of the present invention relate to a structure which is designed in multiple layers with at least three layers, one layer being coupled to another layer in such a way that the stiffness from the first layer and the mass from the second layer are decisive for the resonance frequency of a vibration is influenced, with reference to the 6 can also be carried out in the same shift. The second layer or a second component is simultaneously used as a sound guide and therefore has openings. Furthermore, a layer can be completely moved in relation to the other layers.

Embodiments relate to a large chip entity as a mass body with integrated sound guidance, as described for example for the movable areas 34. For this purpose, the cover wafer and/or the base wafer can be used in parts as a mass body. Alternatively or additionally, the chip frame, the layer 12 ₂ , can also be used as a mass body, in addition to or as a reversal to the principle of the top/bottom mass body. When using multiple structural elements, corresponding fins or elements can be alternately coupled to the bottom wafer and to the top wafer.

The chip entity can be coupled via springs and/or dampers. Alternatively or additionally, the device can be designed in such a way that the deflection is not limited, for example by duffing, rotation or the like. This is described in connection with the preferred direction. Alternatively or additionally, the device can be designed such that the chip entity has mechanical shock protection, for example to achieve shock resistance. This is described in connection with the movement limitation device. As is the case, for example, in connection with the 8a is described, symmetrical chip areas can be formed to be movable in order to enable inertial compensation. Multiple chip areas, ie multiple moving elements or resonators, can be used to generate different frequencies.

MEMS components described herein have layer stacks that consist of at least one substrate layer in which the electrodes and the passive elements are arranged. Further layers relate to a base, which can also be referred to as a handling wafer, and a lid, which can also be referred to as a lid wafer. Both cover wafers and handling wafers can be connected to the substrate plane via cohesive processes, preferably bonding, which can create acoustically sealed gaps in a component. In this space, which corresponds to the device level, the deformable components can deform; in other words, the deformation can take place in-plane. The layers can, for example, comprise electrically conductive materials, e.g. B. doped semiconductor materials and / or metal materials. The layered arrangement of electrically conductive layers enables a simple design Electrodes, for example for deflectable elements and passive elements, can be formed selectively from the layer. If electrically non-conductive materials are to be arranged, these materials can be applied in layers, for example by deposition processes.

Some of the MEMS described herein can be used, for example, as loudspeakers and in particular in in-ear applications. When used in the ear, the space between the eardrum and the hearable can represent a pressure chamber that can be considered tight. For low frequencies, the so-called Harman curve for in-ear headphones shows a preference for higher sound pressure levels. The frequency response can be designed using resonator elements or a combination of different actuators with different resonator elements. A different picture emerges with near-field loudspeakers. The transmission range is limited at the bottom by the position of the resonance; below resonance the level decreases. By increasing the actuator mass, the resonance frequency of the actuator can be reduced and the transmission range can be increased downwards. Further possibilities arise from coupling additional resonators, whose resonance can be below the actual actuator resonance. In known embodiments, additional resonators require additional chip area in both cases and the usable area for actuators is therefore limited or the total area of the chip is thereby increased. The design of the layer system can be carried out in such a way that the mass of passive layers, for example if there are no actuators, are coupled to the actuators in the active layer; the acoustic air guidance is directly through openings in the coupled and moving areas of the passive Layer realizes what is implemented in embodiments discussed herein.

Embodiments of the present invention make it possible to expand the transmission range of the sound sources compared to known solutions and to additionally amplify certain frequency ranges through resonance. Sound sources within the meaning of this application are, for example, loudspeakers, in particular for in-ear applications and near-field applications, for example in cell phones or tablets. Both use cases can be distinguished.

The object according to the invention is achieved by a MEMS layer system. In a plane with one or more layers of the layer system, cavities are formed in which deflectable elements are arranged, which can be arranged laterally spaced apart from one another. A vibrating mass is arranged in a further level of the MEMS layer system, which is either not connected to the substrate or is coupled to the surrounding substrate by means of connecting elements. The mass and the deflectable elements and possibly the connecting elements can together form a resonator. The mass can alternatively or additionally also be arranged in the same plane. In some embodiments, this resonator is arranged at a vertical distance from the deflectable elements and at the same time forms the sound guide (the cover) with air outlet openings designed for sound generation and emission. The coupling elements to the deflectable elements and the connecting elements can be designed in such a way that lateral deformation in the plane is possible. Deformation perpendicular to the plane can be reduced, hindered or prevented by the geometry of the deflectable elements or the connecting elements. The deflectable element can be an actively deflectable element, which represents the preferred embodiment. In exemplary embodiments, the deflectable element can be passive. It can then be connected to an actively deflectable element via coupling elements. In some areas of application, it may be preferred to arrange the actively deflectable elements in a different plane than the passively deflectable elements. This offers the advantage that a higher number of these deflectable elements, referred to as actuators, can be arranged in the plane of the actively deflectable elements. This can increase the force that can be applied within the actuator level and also increase the fill factor. This means, according to one exemplary embodiment, a MEMS or MEMS speaker is designed in such a way that the structural element is designed to be passive and an actuator of the actuator structure is arranged in a plane or layer of the MEMS that is different from the structural element.

The distance between the resonator and the surrounding substrate perpendicular to the plane can be small to minimal, so that an acoustic short circuit is prevented. The resonator contains openings for sound guidance, which can be moved by the oscillating movement of the resonator. In such a case, the sound energy can emerge from the MEMS layer system perpendicular to the layer plane, while the openings vibrate laterally. The oscillation frequency and the sound frequency can be different and can be generated by different actively deflectable elements.

Although some aspects have been described in connection with a device, it is understood that these aspects also constitute a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding process step or as a feature of a process step. Analogously, aspects that have been described in connection with or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device.

The embodiments described above are merely illustrative of the principles of the present invention. It will be understood that modifications and variations of the arrangements and details described herein will occur to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented from the description and explanation of the exemplary embodiments herein.

Claims (28)

MEMS with: a layer stack (12) comprising a plurality of MEMS layers (12 ₁ -12 ₃ ) of a cavity (14) arranged in the layer stack (12), which is surrounded by at least a part of a MEMS layer (12 ₂ ) of the Layer stack (12) comprising boundary structure (34; 12 ₂ ) is at least partially limited; an actuator device (18) which is designed to move a structural element (12) of the MEMS arranged in the cavity (14); wherein the structural element (22) is mechanically coupled to the limiting structure (34; 12 ₂ ) and the actuator device (18) is designed to move the limiting structure (34; 12 ₂ ) with the structural element (22). MEMS in accordance Claim 1 , in which the MEMS layers (12 ₁ -12 ₃ ) are arranged adjacent to one another in the layer stack (12) along a stacking direction (16) arranged perpendicular to a layer plane and the actuator device (18) is designed to enable movement of the limiting structure (34 ; 12 ₂ ) to provide in-plane parallel to the layer plane. MEMS in accordance Claim 1 or 2 , in which the boundary structure (34) comprises part of a MEMS layer (12 ₁ , 12 ₃ ) which provides a bottom or a lid of the cavity (14). MEMS according to one of the preceding claims, in which the delimiting structure comprises part of a MEMS layer (12 ₂ ) which laterally delimits the cavity (14). MEMS according to one of the preceding claims, in which the boundary structure (34) comprises a first substructure (34 ₁ ) and a second substructure (34 ₂ ), wherein the structural element (22) between the first substructure (34 ₁ ) and the second substructure ( 34 ₂ ) is arranged. MEMS according to one of the preceding claims, in which a mass of the boundary structure (34; 12 ₂ ) is greater than a mass of the structural element (22). MEMS according to one of the preceding claims, in which the actuator device (18) is designed to provide an in-plane movement of the boundary structure (34; 12 ₂ ) with respect to a layer arrangement; and the boundary structure (34) comprises a portion of a MEMS layer (12 ₁ , 12 ₃ ) that provides a bottom or a lid of the cavity (14). MEMS according to one of the preceding claims, in which the structural element (22) is designed to interact directly or indirectly with a fluid arranged in the cavity (14) based on an actuation; wherein the boundary structure (34; 12 ₂ ) has an opening (26) which is designed to conduct sound in the fluid out of the cavity (14) or into the cavity (14). MEMS according to one of the preceding claims, in which the structural element (22) and the limiting structure (34; 12 ₂ ) together form a mass structure of a spring-mass system and are set up for a resonant vibration excited by the actuator device (18). MEMS in accordance Claim 9 , in which the structural element (22) is a first structural element (22 ₁ ), in which the limiting structure (34) is a first limiting structure (34 _1,1 ) and in which the spring-mass system is a first spring-mass system is; wherein the MEMS has a second structural element (22 ₂ ) which is mechanically coupled to a second limiting structure (34 _1,2 ) and forms a mass structure of a second spring-mass system, the actuator device (18) being designed to provide the second to move the limiting structure (34 _1,2 ) with the second structural element (22 ₂ ); wherein a first resonance frequency of the first spring-mass system is different from a second resonance frequency of the second spring-mass system. MEMS in accordance Claim 9 or 10 , which further has at least one movable element (44) in the cavity (14), which is used to produce a Sound is set up in a fluid arranged in the cavity (14). MEMS according to one of the Claims 9 until 11 , which is designed to generate a sound pressure based on the resonant movement with a frequency based on a resonance frequency of the resonant vibration. MEMS according to one of the preceding claims, with a plurality of structural elements (22 ₁ -22 ₃ ) arranged in the cavity (14) which are coupled to the actuator device (18) and are arranged movably along different directions (36 ₁ , 36 ₂ ); wherein a first subset of the plurality of structural elements (22 ₂ ) is mechanically coupled to the delimitation structure (34 ₁ ) as the first delimitation structure and a second subset of the plurality of structural elements (22 ₁ , 22 ₃ ) is coupled to an oppositely arranged second delimitation structure (34 ₂ ) is mechanically coupled. MEMS in accordance Claim 13 , in which the first limiting structure (34 ₁ ) and/or the second limiting structure (34 ₂ ) is segmented into segments (34 _1.1 -34 _2.2 ), which are arranged to move in opposite directions to one another and with different structural elements (22) mechanically are coupled. MEMS in accordance Claim 13 or 14 , in which a partial cavity (14b-d) of the cavity (14) is arranged between adjacent structural elements (22), which has a variable volume under the influence of a movement of the adjacent structural elements (22), and the partial cavity (14b-d). an opening (26) in the layer stack (12) is fluidly connected to an environment of the layer stack (12). MEMS according to one of the preceding claims, in which the boundary structure (34; 12 ₂ ) is mechanically coupled to a substrate of the MEMS via a mechanical suspension (48); wherein the suspension (48) is designed to provide a mechanical damping (52) and/or a mechanical stiffness (54) which has a resonance frequency of a spring-mass element comprising the structural element (22) and the limiting structure (34; 12 ₂ ). system is at least partially determined. MEMS in accordance Claim 16 , in which the mechanical suspension (48) has a preferred direction along which the deflection of the structural element (22) is at most insignificantly influenced MEMS according to one of the preceding claims, which has a device (56) for limiting movement, which is designed to limit a maximum deflection of the limiting structure (22) and to prevent a mechanical overload occurring on the MEMS by exceeding the maximum deflection. MEMS according to one of the preceding claims, comprising a control device (58) which is designed to control the actuator device (18) in order to set a resonant movement of the structural element (22); wherein a resonance frequency of the resonant movement is influenced by a mass of the structural element (22) and a mass of the limiting structure (34; 12 ₂ ). MEMS according to one of the preceding claims, in which the structural element (22) is mechanically coupled to the boundary structure (34; 12 ₂ ) at a discrete region and the discrete region is arranged at a location of maximum deflection of the structural element (22). MEMS according to one of the preceding claims, wherein the structural element (22) comprises a bilaterally clamped beam structure which is designed to deform in-plane with respect to a MEMS layer (12 ₁ -12 ₃ ) and the boundary structure (34; 12 ₂ ) is arranged out-of-plane to the structural element (22). MEMS according to one of the preceding claims, which is formed as a MEMS speaker which is designed to generate sound based on a joint movement of the structural element (22) and the boundary structure (34; 12 ₂ ) in the cavity (14). MEMS according to one of the preceding claims, in which the structural element (22) is part of the actuator device (18) and has adjacent beam elements which are firmly connected to one another in discrete areas and can be deformed in-plane and which are designed to prevent deformation of the structural element (22 ) in-plane relative to the layer stack (12). MEMS with: a layer stack (12) comprising a plurality of MEMS layers (12 ₁ -12 ₃ ); a cavity (14) arranged in the layer stack (12), which is at least partially delimited by a boundary structure (34; 12 ₂ ) comprising at least part of a MEMS layer (12 ₁ -12 ₃ ) of the layer stack (12); a structural element (22) arranged in the cavity (14); an actuator device (18) which is designed to move the limiting structure (34; 12 ₂ ) with respect to the structural element (22) of the MEMS, in order to provide an interaction of the structural element (22) with a fluid arranged in the cavity (14). MEMS speaker with: a layer stack (12) comprising a plurality of MEMS layers (12 ₁ -12 ₃ ); a cavity (14) arranged in the layer stack (12) for receiving a fluid, which is at least partially delimited by a boundary structure (34; 12 ₂ ) comprising at least part of a MEMS layer (12 ₁ -12 ₃ ) of the layer stack (12). is; an actuator device (18) which is designed to move a structural element (22) of the MEMS arranged in the cavity (14) to interact with the fluid in order to generate an acoustic signal in the cavity (14); wherein the structural element (22) is mechanically coupled to the limiting structure (34; 12 ₂ ) and the actuator device (18) is designed to move the limiting structure (34; 12 ₂ ) with the structural element (22). Method for producing a MEMS with the following steps: Providing a layer stack (12) comprising a plurality of MEMS layers (12 ₁ -12 ₃ ), with a cavity (14) arranged in the layer stack (12), which is composed of at least one part a boundary structure (34; 12 ₂ ) comprising a MEMS layer (12 ₁ -12 ₃ ) of the layer stack (12) is at least partially limited; Providing an actuator device (18) which is designed to move a structural element (22) of the MEMS arranged in the cavity (14); so that the structural element (22) is mechanically coupled to the limiting structure (34; 12 ₂ ) and the actuator device (18) is designed to move the limiting structure (34; 12 ₂ ) with the structural element (22). Method for producing a MEMS with the following steps: Providing a layer stack (12) comprising a plurality of MEMS layers (12 ₁ -12 ₃ ), with a cavity (14) arranged in the layer stack (12), which is composed of at least one part a boundary structure (34; 12 ₂ ) comprising a MEMS layer (12 ₁ -12 ₃ ) of the layer stack (12) is at least partially limited; Arranging a structural element (22) in the cavity (14); Providing an actuator device (18) which is designed to move the limiting structure (34; 12 ₂ ) with respect to the structural element (22) of the MEMS in order to ensure interaction of the structural element (22) with a fluid arranged in the cavity (14). to provide. Method for producing a MEMS speaker with the following steps: providing a layer stack (12) comprising a plurality of MEMS layers (12 ₁ -12 ₃ ); and a cavity (14) arranged in the layer stack (12) for receiving a fluid, so that the cavity (14) is surrounded by a boundary structure (34) comprising at least part of a MEMS layer (12 ₁ -12 ₃ ) of the layer stack (12). ; 12 ₂ ) is at least partially limited; Providing an actuator device (18) designed to move a structural element (22) of the MEMS arranged in the cavity (14) to interact with the fluid in order to generate an acoustic signal in the cavity (14); so that the structural element (22) is mechanically coupled to the limiting structure (34; 12 ₂ ) and the actuator device (18) is designed to move the limiting structure (34; 12 ₂ ) with the structural element (22).

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