Microelectromechanical apparatus for generating fluid pulses, microelectromechanical speaker, and method for producing a microelectromechanical apparatus

Abstract

The invention relates to a microelectromechanical apparatus (1) for generating fluid pulses, comprising: a carrier structure (2) having a first carrier side (2a) and a second carrier side (2b); a displacing unit (3) which is formed in the carrier structure (2) and has movable displacing elements (4a) which extend between a first environment volume (5) facing the first carrier side (2a) and a second environment volume (6) facing the second carrier side (2b); a drive device for deflecting the displacing elements (4a); and a valve device (7) which is formed in the carrier structure (2) and / or in a circuit carrier structure (2) of the microelectromechanical apparatus (1) and has a fluid channel (8) extending vertically between the first environment volume (5) and the second environment volume (6) and has a movable valve element (9), the movable valve element (9) being designed such that, below a predefined minimum pressure difference between the first environment volume (5) and the second environment volume (6), the movable valve element blocks the fluid channel (8) and, starting from the predefined minimum pressure difference, the movable valve element automatically leaves the fluid channel (8) unblocked. The invention also relates to a microelectromechanical speaker (20) and to a method (100) for producing a microelectromechanical apparatus (1) of this type.

Description

[0001] R. 411678

[0002] - 1 -

[0003] Description

[0004] title

[0005] Microelectromechanical device for generating fluid pulses, microelectromechanical loudspeaker and method for manufacturing a microelectromechanical device

[0006] The invention relates to a microelectromechanical device for generating fluid pulses. The invention further relates to a microelectromechanical loudspeaker and a method for manufacturing a microelectromechanical device for generating fluid pulses.

[0007] State of the art

[0008] Microelectromechanical devices for generating fluid pulses, methods for their production, and microelectromechanical loudspeakers are known from the prior art. Microelectromechanical systems are also abbreviated as MEMS.

[0009] WO 2021 / 144400 A1 relates to a MEMS transducer comprising a vibrating diaphragm for generating or receiving pressure waves of a fluid in a vertical direction. The vibrating diaphragm is held by a support. The vibrating diaphragm has two or more vertical sections, which are parallel to the vertical direction and comprise at least one layer of an actuator material. The vibrating diaphragm is contacted at one end with an electrode, such that by actuating the at least one electrode, the two or more vertical sections can be excited to horizontal vibrations, or such that when the two or more vertical sections are excited to horizontal vibrations, an electrical signal can be generated at the at least one electrode. R. 411678

[0010] - 2 -

[0011] Disclosure of the invention

[0012] According to the features of independent claim 1, a microelectromechanical device for generating fluid pulses is proposed, comprising a microelectromechanical device:

[0013] - a support structure with a first support side and a second support side;

[0014] - a displacement unit formed in the support structure with movable displacement elements that extend between a first ambient volume facing the first side of the support and a second ambient volume facing the second side of the support;

[0015] - a drive device for deflecting the displacement elements; and

[0016] - a valve device formed in the carrier structure and / or in a circuit carrier structure of the microelectromechanical device, comprising a fluid channel extending vertically between the first ambient volume and the second ambient volume and comprising a movable valve element; wherein the movable valve element is configured to block the fluid channel below a predetermined minimum pressure difference between the first ambient volume and the second ambient volume and to automatically release the fluid channel above the predetermined minimum pressure difference.

[0017] In simplified terms, it is proposed to reduce or eliminate excessive overpressure or underpressure present on one side of the microelectromechanical device by enabling pressure equalization via a pressure relief valve of the microelectromechanical device, wherein a movable valve element of the pressure relief valve is at least partially displaced by the applied overpressure and opens a connecting channel between a first and a second ambient volume.

[0018] The microelectromechanical device according to the proposed features has the advantage that, in the case of an existing excessive R. 411678

[0019] - 3 -

[0020] Pressure equalization can be achieved to compensate for the pressure difference between the first and second ambient volumes, thereby protecting the displacement elements of the displacement unit from impairment or damage caused by strong pressure forces. Displacement elements can be sensitive microstructural components that are prone to unintended elastic or plastic deformation under high ambient pressures, so it is advantageous to preserve the structure and functionality of the displacement elements through sufficient pressure relief.

[0021] If the microelectromechanical device is configured to generate sound pressure and is implemented in a microelectromechanical loudspeaker, in particular an in-ear headphone, the microelectromechanical device, according to the proposed features, has the additional advantage of increased user comfort for the wearer of the in-ear headphone. When the in-ear headphone is inserted into or removed from the wearer's ear, an overpressure or underpressure may occur in the wearer's ear canal, which could be perceived as unpleasant and can be advantageously reduced or eliminated by the described valve device.

[0022] The movable valve element is designed to automatically shift when a predetermined pressure difference between the first and second ambient volumes is exceeded, opening the fluid channel to achieve pressure equalization. Therefore, the valve does not require active actuation but is simply actuated directly by existing overpressure. Because the movable valve element is designed to open the fluid channel only after a predetermined minimum pressure difference is reached, a pressure drop at the displacement unit during operation, which would impair performance, can be reliably prevented, unlike with a simple pressure equalization channel without a valve.Accordingly, for example, when implementing the microelectromechanical device in a microelectromechanical loudspeaker, a so-called acoustic short circuit of the displacement unit via an open fluid channel can be avoided. R. 411678.

[0023] - 4 -

[0024] In principle, a microelectromechanical device can be a component, for example, one manufactured using semiconductor technology, with mechanical and electrical microstructures. Due to its fundamentally simple structure, the described microelectromechanical device is suitable for mass production using semiconductor technology. Microelectromechanical devices can be used, for example, as miniaturized sensors or actuators, as described here in connection with fluid pulse generation. Due to its microstructural design, the microelectromechanical device is suitable for implementation as a system-on-a-chip (SoC). In particular, the microelectromechanical device can include a chip. Additionally, the microelectromechanical device can include a circuit carrier structure, such as a printed circuit board, that is mechanically and electrically connected to the chip.The support structure of the microelectromechanical device can, for example, be formed by a silicon wafer chip. The circuit support structure can, for example, be arranged below or above the support structure and connected to the chip, for example, by an adhesive bond. Electrical contact between the chip and the circuit support structure can, for example, be established by wire bonding. At least one electrical circuit, in particular a signal processing unit, can be formed on the circuit support structure, which can, for example, be configured to control the drive mechanism of the microelectromechanical device.

[0025] According to the proposed features, the microelectromechanical device is configured to generate fluid pulses. A fluid pulse can be a moving volume of gas and / or liquid. The fluid of the fluid pulse can, in particular, be a gas mixture, especially air. Accordingly, the fluid pulse can, in particular, be designed as an air pulse and be used, for example, to generate sound pressure. For this purpose, the fluid pulse can, in particular, be a pressurized fluid pulse, so that, in other words, pressure waves can be generated with the microelectromechanical device. It is also fundamentally possible to use the fluid pulses R. 411678

[0026] - 5 - for example, to generate a fluid flow for cooling purposes and to supply it to a target volume.

[0027] The microelectromechanical device comprises a support structure with a first support side and a second support side. The support structure can be a semiconductor element such as a silicon wafer chip. The support structure has a planar shape, meaning that the surface area of ​​both the first and second support sides is larger than the surface area of ​​a connecting surface between the first and second support sides. The first and second support sides are opposite each other and can form a front and a back side of the support structure. Each of the first and second support sides can define a boundary plane of the support structure. The displacement unit and at least the fluid channel of the valve assembly can be located between the boundary planes of the support structure. The fluid channel of the valve assembly can extend vertically through the entire support structure.Alternatively or additionally, the fluid channel of the valve assembly can extend vertically through a circuit support structure of the microelectromechanical device. A vertical extension of a component of the microelectromechanical device can, in principle, mean an extension perpendicular to one of the previously described boundary planes spanned by the first and second support sides. In other words, for simplicity, it is assumed that the first and second support sides of the support structure each extend in a horizontal plane. The horizontal planes of the support sides can extend parallel and spaced apart from each other.

[0028] A displacement unit is integrated into the support structure. The displacement unit can be integral to the support structure or, for example, be created by semiconductor processing techniques that separate it from the support structure. The displacement unit can serve to draw a fluid volume from the first ambient volume and displace it towards the second ambient volume, and vice versa, using deflectable displacement elements. The first ambient volume can therefore be an output volume, while the R. 411678

[0029] - 6 - The second ambient volume can be a target volume into which the generated fluid pulses are conveyed. Conversely, if the fluid conveyance direction is reversed, the second ambient volume can be an output volume and the first ambient volume a target volume. A variable displacement volume can be created using the movable, particularly deflectable, displacement elements, and a fluid pulse can be generated by increasing or decreasing this volume. The displacement elements can, for example, be designed as horizontal displacement membranes. Alternatively, the displacement elements can, for example, be designed as displacement lamellae arranged parallel to each other and extending vertically between the first and second ambient volumes. Such vertically arranged displacement lamellae can be laterally deflected.A displacement lamella can be essentially a planar mechanical structure with a length and width several times greater than its depth. A displacement lamella can also be considered a vibrating membrane, but unlike classic microelectromechanical pressure generator membranes, it is positioned vertically rather than horizontally within the displacement unit.

[0030] The microelectromechanical device further comprises a drive unit for deflecting the displacement elements. For example, the displacement elements can be coated, at least partially, with an actuator material that allows an electrical signal, applied, for example, by means of electrodes, to be converted into a mechanical deflection of the displacement elements. Electromechanical shuttle solutions are also conceivable in principle, in which a connecting element driven by the drive unit and connected to at least one displacement element causes the mechanical deflection of the displacement element. Electrostatic or piezoelectric drive concepts, such as electrostatic bending actuators or piezoelectric coatings, can be used in the microelectromechanical field to convert electrical signals into mechanical movements. R. 411678

[0031] - 7 -

[0032] According to the proposed features, a valve assembly can be formed in the support structure and / or a circuit carrier structure of the microelectromechanical device. This valve assembly comprises a fluid channel extending vertically between the first and second ambient volumes and a movable valve element. When the fluid channel is open, fluid exchange and pressure equalization between the first and second ambient volumes are possible through the fluid channel. The fluid channel can extend through the support structure and / or the circuit carrier structure, forming a through-hole, particularly a slit or slot-shaped opening, although fluid channels with a circular cross-section are also conceivable. If the support structure is designed as a silicon wafer chip, the fluid channel can be configured as a so-called trench through the support structure.The fluid channel can be arranged at a distance from the displacement unit within the support structure and / or the circuit carrier structure. For example, the fluid channel can be located in a lateral boundary region of the support structure and / or the circuit carrier structure. The fluid channel can extend parallel to displacement elements designed as displacement lamellae extending vertically between the first and second surrounding volumes. The fluid channel can be completely confined at its lateral perimeter by the support structure and / or the circuit carrier structure to eliminate fluidic or acoustic leakage paths to the displacement unit.Accordingly, the fluid channel is closed on its circumference and only open in the direction of the first and second ambient volumes, with a channel outlet of the fluid channel to the first and / or second ambient volume being able to be covered by a movable valve element or partially by a closure element, depending on the embodiment, as will be explained in more detail below.

[0033] According to the proposed features, the movable valve element is configured to close the fluid channel below a predetermined minimum pressure differential between the first and second ambient volumes and to automatically open the fluid channel above this predetermined minimum pressure differential. In particular, the movable valve element can be configured to, after opening the fluid channel, [continue to R. 411678].

[0034] - 8 - also to automatically close again if the specified minimum pressure differential is undershot. Depending on the embodiment, the movable valve element, as explained in more detail below, can be arranged at a channel outlet of the fluid channel or extend at least partially through the fluid channel. According to a non-restrictive example value, the specified minimum pressure differential can be, for example, 1 mbar. The specified minimum pressure differential can be specifically set by a corresponding design of the valve assembly, for example, by specific material properties of selected components of the valve assembly, by suitable dimensioning of the fluid channel and the movable valve element, and / or by a specific arrangement of the components of the valve assembly relative to each other.

[0035] According to one embodiment, the movable displacement elements can be designed as displacement lamellae arranged parallel to one another, extending vertically between the first and second ambient volumes and laterally deflectable, with the drive device being configured for the lateral deflection of the displacement lamellae. This provides a particularly compact and efficient displacement unit. The displacement lamellae can be arranged parallel to one another, the parallel arrangement referring in particular to an un-displaced state of the displacement lamellae. The displacement lamellae can be integrally formed and connected to one another by horizontal bridge elements. The displacement lamellae and the horizontal bridge elements can extend alternately in a meandering pattern between two support sections of the support structure.The horizontal bridge elements can each have at least one slot-shaped incision to increase the mobility of the displacement lamellae projecting from the bridge elements. The displacement lamellae can extend vertically between a first surrounding volume facing the first support side and a second surrounding volume facing the second support side. If, as previously simplified, the first and second support sides of the support structure are considered horizontal planes, the displacement lamellae extend R. 411678.

[0036] - 9 - perpendicularly between these horizontal planes. In other words, the displacer lamellae extend along a fluid flow direction of the displacer unit between the first and second ambient volumes. The displacer lamellae are, in particular, laterally deflectable, i.e., essentially transverse to their vertical extent between the first and second ambient volumes. Any two adjacent displacer lamellae can be deflected in opposite lateral directions to form a displacer volume between the two displacer lamellae and, upon returning to their initial position, to reduce this volume again, thereby generating a fluid pulse. In other words, the displacer lamellae can be repeatedly pulled apart and brought back together. This process can, in particular, occur periodically, causing the displacer lamellae to oscillate.

[0037] According to one embodiment, at least two displacement lamellae can be connected to each other by a horizontal bridge element, wherein the horizontal bridge element has at least one slot-shaped incision. Displacement lamellae connected in this way can exhibit high mobility, but at the same time represent particularly sensitive microstructural components that can, for example, deform unintentionally in the area of ​​the horizontal bridge elements, such as through excessive convex bulging of the slot-shaped incision. Furthermore, the slot-shaped incision can create a notch effect on the bridge element, so that there is a risk of damage under high stress.The valve mechanism of the microelectromechanical device reliably prevents excessive deformation, as pressure equalization between the first and second ambient volumes is enabled once a predetermined minimum pressure difference is reached. This prevents critical overpressures that could affect the displacer vanes and bridge elements. Therefore, sufficient pressure relief can be ensured for such interconnected displacer vanes to preserve their structure and functionality. R. 411678.

[0038] - 10 -

[0039] According to one embodiment, the movable valve element can be designed as a cover flap arranged at a channel outlet of the fluid channel. This creates a structurally simple and effective valve device in the form of a flap valve, in which overpressure acting on the cover flap can cause it to be at least partially lifted from the fluid channel, allowing pressure equalization to occur through the resulting opening at the channel outlet. The cover flap can, for example, be attached to the support structure or the circuit support structure laterally to the channel outlet and project beyond it, so that the outlet is covered and closed by a flap surface of the cover flap facing the fluid channel.Depending on the design, the cover flap can be flexible and pliable, meaning it can deform elastically under applied overpressure, or it can be movably mounted, for example, via a spring structure and pivot against the spring force. The cover flap can be a substantially planar mechanical structure designed to cover the duct outlet, but it can be easily lifted by ambient pressure when the predetermined pressure differential is exceeded.

[0040] The channel outlet can be defined as an opening of the fluid channel into the first or second ambient volume, where the cover flap is located, while an opposite opening of the fluid channel into the other ambient volume can be referred to as the channel inlet. The channel inlet can be open, allowing any existing overpressure through the fluid channel to act on the cover flap at the channel outlet. If the microelectromechanical device is implemented in an in-ear headphone, the channel outlet with the cover flap can be located, for example, on the side of the support structure and / or the circuit support structure facing the wearer's ear canal. This allows for pressure equalization between the environment and the ear canal, thus reducing any pressure difference that might occur, for example, when quickly removing the in-ear headphone, and increasing user comfort.

[0041] In principle, the cover flap can be made from a semiconductor material, for example, in particular by means of a substrate structure R. 411678.

[0042] - 11 - a silicon or polysilicon element can be applied, thereby creating a robust cover flap. Alternatively, it is conceivable, for example, to design the cover flap as a film element, in particular a polymer film element. This allows the flexible properties of a film element to be used for the pressure-dependent movement of the cover flap.

[0043] According to one embodiment, the cover flap can be formed by a dry film resist element. This results in an easy-to-manufacture and flexible cover flap that, through suitable design of its mechanical properties, can be adapted to a predetermined minimum pressure differential and, due to its flexibility, can be easily and reversibly lifted from the channel outlet. A dry film resist can be a photoresist that can be applied in solid form to a structured support structure such as a silicon wafer or a circuit carrier structure. A dry film resist element can be a special form of the polymer film element described above. The dry film resist element can, for example, have a thickness of 3 to 50 pm, and in particular a thickness of 5 to 20 pm.The width of the dry film resist element, extending along the substrate and / or circuit carrier structure, can be several times greater than its thickness, for example, up to 100 pm and beyond. Dry film resists enable photolithography processes to be performed on highly structured wafer surfaces, particularly when spin coating with standard photoresists is not feasible. A dry film resist element configured as a cover flap can be considered a mechanical layer element that remains permanently on the substrate and / or circuit carrier structure. Thus, after structuring to form the cover flap, the dry film resist element is not removed but remains as a mechanical structure on the microelectromechanical device. This advantageously utilizes a single process material for the fabrication of a permanent mechanical microstructure.In practice, a variety of dry film resists exist that are suitable for permanent application on a chip. Furthermore, a dry film resist layer applied to produce the dry film resist can advantageously serve as a mechanical and / or chemical protective layer for an underlying microstructure at other locations on the chip. (See R. 411678.)

[0044] - 12 - On a cover flap, which is applied, for example, as a silicon element, a dry film resist can be applied to the structured surface much more easily by lamination, without the need for adhesive or bonding processes. Furthermore, a silicon element would first have to be manufactured more complexly by applying and structuring a silicon layer using a photoresist, whereas the dry film resist element can be structured directly without an additional photoresist layer.

[0045] According to one embodiment, the fluid channel can be slot-shaped with a slot length greater than the slot width, with the cover flap extending transversely across the slot-shaped fluid channel. A slot-shaped fluid channel can be an elongated, narrow opening in cross-section. If the cover flap extends transversely across the slot-shaped fluid channel, its main extent, in the sense of its greatest extent, can run along the slot width of the slot-shaped fluid channel. This allows for a particularly secure connection of the cover flap to the support structure and / or the circuit carrier structure.

[0046] According to one embodiment, the fluid channel can be slot-shaped with a slot length greater than the slot width, with the cover flap extending longitudinally across the slot-shaped fluid channel. If the cover flap extends longitudinally across the slot-shaped fluid channel, its main extent, in the sense of its greatest extent, can run along the slot length of the slot-shaped fluid channel. This allows for the creation of an easily removable cover flap. In particular, the cover flap can be segmented to precisely set the predetermined minimum pressure differential, in the sense of a threshold pressure, for actuating the cover flap. A segmented cover flap can have several cover flap segments that are movable relative to each other. These can be designed differently to enable individually adjustable sequential release of the fluid channel at various minimum pressure differentials.Depending on the level of the applied overpressure, individual, several or all cover flap segments R. 411678 may be affected.

[0047] - 13 - be liftable from the fluid channel. If several slot-shaped fluid channels are provided in the support structure and / or in the circuit support structure, cover flaps extending transversely over a first slot-shaped fluid channel and longitudinally over a second slot-shaped fluid channel can also be combined.

[0048] According to one embodiment, the specified minimum pressure differential can be determined by a predefined mechanical property of the cover flap and / or by a predefined dimensioning of the fluid channel. Accordingly, it is possible to achieve a pressure-dependent automatic displacement of the movable valve element through the design of the valve assembly components, without requiring active control of the valve assembly. For example, by specifically adjusting the mechanical properties of a dry film resist element during the manufacture of the microelectromechanical device, for example with regard to the length, width, and thickness of the dry film resist element, it can be determined with high accuracy whether and to what extent the cover flap is lifted from the channel outlet of the fluid channel at a specific applied overpressure.The mechanical properties of the cover flap can also be influenced by the material used in its manufacture and any optional tempering steps. The dimensions of the fluid channel can affect the pressure exerted on the cover flap by ambient pressure. By specifically designing the fluid channel, for example with regard to its diameter, width, or cross-sectional area, depending on the specified minimum pressure differential, the automatic release of the fluid channel by the cover flap can be precisely controlled. Calculations and simulations can be performed to determine the specific relationship between a particular minimum pressure differential and a mechanical property of the cover flap and / or between a particular minimum pressure differential and a dimension of the fluid channel.

[0049] According to one embodiment, the valve device can have a first fluid channel and a second fluid channel, wherein a first R. 411678 is located at a channel outlet of the first fluid channel facing the first support side.

[0050] - 14 -

[0051] A cover flap is arranged on one side of the support, and a second cover flap is arranged at the outlet of the second fluid channel facing the second support side. This provides a bidirectional valve arrangement that can equalize overpressure in the first ambient volume and overpressure in the second ambient volume by means of their respective movable cover flaps. The outlet of the first fluid channel and the inlet of the second fluid channel can be located on the first support side. Similarly, the inlet of the first fluid channel and the outlet of the second fluid channel can be located on the second support side. The first and second fluid channels can be spaced apart and run parallel to each other.The first and second fluid channels can run directly alongside each other or separated from each other by the displacement unit through the support structure. Alternatively or additionally, the first and second fluid channels can run directly alongside each other or spaced apart from each other through the circuit support structure. Furthermore, it is conceivable that the first fluid channel runs through the support structure and the second fluid channel runs through the circuit support structure, or vice versa. Depending on the embodiment, the first and second fluid channels can be essentially identical in design, in particular identically shaped and dimensioned, or deliberately designed differently to allow the fluid channels to be released at different overpressures.Depending on the embodiment, the first and second cover flaps can be essentially identical in design, in particular identical in shape and dimensions, or deliberately designed differently to open the fluid channels at different overpressures. The first and second cover flaps can be deflected in opposite directions to open the respective channel outlet. In principle, the valve assembly can also have more than two fluid channels equipped with cover flaps. This allows for particularly rapid pressure equalization and / or enables a robust, redundant design of the valve assembly. R. 411678.

[0052] - 15 -

[0053] According to one embodiment, the valve assembly can have a sealing element at the channel outlet for sealing interaction with the cover flap. In other words, a counterpart can be arranged adjacent to the cover flap at the channel outlet, with which the cover flap seals essentially flush in its undisplaced state. The sealing element can be fixed, in particular, essentially immovably to the support structure and / or the circuit support structure. The sealing element reliably ensures that the cover flap is only deflected sufficiently to allow pressure equalization through the resulting opening at the channel outlet once a predetermined minimum pressure differential is reached. Therefore, even a slight lifting of the cover flap from the channel outlet, which does not yet exceed the height of the sealing element, does not lead to any significant fluid exchange.The sealing element can also be considered advantageous with regard to the effects of any mechanical stress on the support structure and / or the circuit carrier structure on the deflection of the cover flap. Accordingly, a mechanical stress gradient along the support structure and / or the circuit carrier structure can lead to a slight deflection of the cover flap, which can be compensated for by the sealing element to such an extent that significant fluid passage is only possible after the specified minimum pressure differential has been reached. The sealing element can be designed, for example, as a silicon element or as a polymer film element, in particular as a dry film resist element.The specified minimum pressure differential can be further influenced by the targeted design of the sealing element's mechanical properties, such as its dimensions or material selection, thus providing an additional parameter for the design-related adjustment of the minimum pressure differential. According to one design option, which is associated with simple manufacturing, the sealing element can be the same height as the cover flap, starting from a surface of the support structure or circuit carrier structure, thereby enabling a uniform layer thickness when applying, for example, a dry film resist layer.

[0054] According to one embodiment, the cover flap can be formed by several adjacent flap elements or several R. 411678

[0055] - 16 - feature movable flap segments. This results in improved mobility of the cover flap. For example, two rectangular cover flap elements can be mounted on opposite sides of the channel outlet and project towards each other in such a way that they are flush with one another. For example, in a fluid channel with a substantially square or circular cross-section, four triangular cover flap elements can be arranged around the channel outlet, each offset from the other at a 90° angle, with one side of each triangle flush with an adjacent cover flap element. Movable flap segments can be formed, for example, by a single continuous cover flap with partial cutouts or by flap segments joined together by connecting sections, the flap segments being designed to be movable relative to one another.

[0056] According to one embodiment, a bearing element can be arranged on the support structure and / or the circuit support structure, by which the cover flap is held essentially cantilevered above the channel outlet and a support structure edge that defines the channel outlet. The partially cantilevered design of the cover flap improves its mobility. It can form a cantilever beam extending from the bearing element. A predefined length of the cantilever beam, which can be adjusted during manufacturing by appropriately designing the bearing element, provides a further parameter for influencing the specified minimum pressure differential.The bearing element can be formed additively or subtractively during the fabrication of the microelectromechanical device, for example, by additively depositing and structuring the bearing element onto the support structure and / or the circuit carrier structure, or by removing support structure material or circuit carrier structure material to form a cavity beneath an extension area of ​​the cover flap adjacent to the channel outlet. Such a cavity can be created, for example, by depositing a sacrificial material layer and subsequently undercutting the deposited cover flap. The cavity can be laterally bounded to prevent fluidic or acoustic leakage paths (see R. 411678).

[0057] - 17 - prevent. The support structure edge can designate an area of ​​the support structure and / or the circuit support structure that adjoins the channel outlet. In other words, a step can be provided between the bearing element and the channel outlet, with the step edge facing the channel outlet forming the support structure edge. If the cover flap is made of a film-like material, in particular a dry film resist, it can also be locally mechanically clamped due to its flexible properties and extend from the clamping point across the channel outlet.One embodiment of the microelectromechanical device, featuring a bearing element that essentially cantilevers the cover flap over the channel outlet and a support structure edge defining the channel outlet, can advantageously be combined with an embodiment in which the valve assembly at the channel outlet has a sealing element for sealing interaction with the cover flap. This ensures high mobility of the cover flap while simultaneously preventing unintentional fluid exchange below the specified minimum pressure differential.

[0058] According to one embodiment, a non-stick layer can be arranged section by section between the support structure and the cover flap and / or between the circuit carrier structure and the cover flap. This improves the mobility of the cover flap. In particular, with a film-like cover flap material, such as a dry film resist element, the flexibility of the cover flap can be better utilized if it can rest non-stickily on the support structure and / or the circuit carrier structure in sections. The cover flap can be firmly attached to the support structure and / or the circuit carrier structure in a mounting section, rest unattached on the support structure and / or the circuit carrier structure in a non-stick layer area located between the mounting section and the channel outlet, and project beyond the channel outlet from the non-stick layer area.A predefined length and width of the non-stick layer between the support structure and the cover flap and / or between the circuit support structure and the cover flap provides a further parameter for influencing the specified R. 411678.

[0059] - 18 -

[0060] A minimum pressure differential is provided. The non-stick coating can, for example, be applied and structured layer by layer onto the support structure and / or the circuit carrier structure in a manufacturing step preceding the production of the cover flap.

[0061] According to one embodiment, the movable valve element can be designed as a laterally deflectable valve blade extending vertically through the fluid channel, wherein the valve assembly includes a closure element that covers at least a portion of the fluid channel. This allows for an efficient valve assembly that can be precisely tuned to a predetermined minimum pressure differential. The valve blade can be flush with an outer edge of the closure element in the region of a channel outlet of the fluid channel where the closure element is located, or the closure element can project beyond the valve blade towards an opposite edge of the support structure.If an overpressure corresponding to a predetermined minimum pressure differential exists in the fluid channel, the valve blade is deflected laterally by this pressure to such an extent that it is displaced, at least partially, beyond an edge of the closure element. This creates an opening between the closure element and the valve blade, allowing pressure equalization. The valve blade can have a similar shape and / or dimensions to a displacer blade of the displacement unit if the displacer elements are designed as displacer blades. It is possible for the valve blade and the displacer blades to be produced in a single manufacturing step during the production of the microelectromechanical device. The valve blade can, for example, be held laterally to the support structure or the circuit carrier structure by a connecting element.

[0062] It is generally possible to combine the embodiment described above with an embodiment in which the movable valve element is designed as a cover flap arranged at a channel outlet of the fluid channel. For this purpose, the valve assembly can, for example, have at least two fluid channels, one of which is equipped with a cover flap and another with a valve blade. This allows for the creation of an R. 411678

[0063] - 19 -

[0064] Pressure equalization can be achieved particularly quickly and / or a robust, redundant design of the valve system is enabled.

[0065] According to one embodiment, a closure element can be arranged at each of two opposite channel outlets of the fluid channel. This allows for a bidirectionally acting valve device to be obtained with only one fluid channel. The fluid channel can have a first channel outlet, which simultaneously forms a first channel inlet, and a second channel outlet, which simultaneously forms a second channel inlet. A closure element can be arranged at each of the first and second channel outlets. The closure elements can project into the respective channel outlets from opposite edges of the support structure. The valve blade can extend between the closure elements such that their outer edges are flush with the valve blade or project beyond the valve blade towards an opposite edge of the support structure.

[0066] According to one embodiment, the specified minimum pressure differential can be determined by a predefined overlap between the valve lamella and the closure element, by a predefined mechanical property of the valve lamella, and / or by a predefined dimensioning of the fluid channel. Accordingly, it is possible, through the design and targeted arrangement of the valve assembly components, to achieve a pressure-dependent, automatic displacement of the movable valve lamella beyond the closure element without requiring active control of the valve assembly.For example, by specifically adjusting the mechanical properties of the valve blade during the manufacture of the microelectromechanical device, for instance with regard to the thickness and stiffness of the valve blade, it can be determined with high accuracy whether and to what extent the valve blade is deflected laterally under a specific applied overpressure. By providing a specific overlap between the valve blade in its un-deflected rest position and the closure element, it can be determined how far the valve blade must be deflected laterally by a specific overpressure in order to achieve a certain degree of deflection (R. 411678).

[0067] - 20 -

[0068] The valve blade is positioned beyond the outer edge of the closure element, thereby creating an opening for pressure equalization. The dimensions of the fluid channel can influence the pressure exerted by the ambient pressure on the valve blade. By specifically designing the fluid channel, for example with regard to its diameter, width, or cross-sectional area, depending on the specified minimum pressure difference, the automatic release of the fluid channel by the valve blade can be precisely controlled. Calculations and simulations can be performed, for example, to determine the specific relationship between a certain minimum pressure difference and an overlap between the valve blade and the closure element, and / or between a certain minimum pressure difference and a mechanical property of the valve blade, and / or between a certain minimum pressure difference and a dimension of the fluid channel.

[0069] In principle, the locking element can be made from a semiconductor material, for example, and in particular formed by a silicon or polysilicon element applied to the support structure, thus producing a robust locking element. Alternatively, it is conceivable, for example, to design the locking element as a film element, in particular a polymer film element.

[0070] According to one embodiment, the closure element can be formed by a dry film resist element. This allows the closure element to be manufactured easily. The dry film resist element can, in particular, be a stationary dry film resist element, i.e., fixed immovably relative to the channel outlet on the support structure and / or on the circuit carrier structure. The dry film resist element can, for example, have a thickness of 3 to 50 pm, particularly a thickness of 10 to 50 pm. A dry film resist element designed as a closure element can be considered a mechanical layer element that remains permanently on the support structure and / or on the circuit carrier structure. Accordingly, the dry film resist element is not removed after its structuring to form the closure element, but remains as a mechanical structure on the microelectromechanical device. This advantageously achieves a R. 411678

[0071] - 21 -

[0072] Process material is used to produce a permanent mechanical microstructure. A dry film resist layer applied to produce the dry film resist can also advantageously serve as a mechanical and / or chemical protective layer for an underlying microstructure at other locations on the chip. Compared to a closure element, such as a silicon element, a dry film resist can be applied to the structured surface much more easily by lamination, without the need for adhesive or bonding processes. Furthermore, a silicon element would first require the more complex process of applying and structuring a silicon layer using a photoresist, whereas the dry film resist element can be structured directly without an additional photoresist layer.

[0073] Regarding the valve mechanism of the microelectromechanical device, it is important to note that, due to the microelectromechanical dimensions and the limited chip area available for implementation, intelligent design solutions must be developed to realize mechanical pressure limiting functions. These solutions must utilize physical principles to function reliably in the smallest possible space and, moreover, be easily and cost-effectively manufactured using semiconductor production methods. For example, the proposed use of a cover flap or valve blade, particularly in conjunction with dry-film resist elements as inexpensive and easy-to-manufacture valve components, allows for the simple and reliable provision of a microstructural valve mechanism with an efficient pressure relief principle.

[0074] According to one embodiment, the microelectromechanical device can be configured to generate sound pressure by means of the displacement unit. This allows the microelectromechanical device to be implemented, for example, in a microelectromechanical loudspeaker. The generated fluid pulses can be designed as air pulses, in particular as pressurized air pulses, so that pressure waves can be generated with the displacement unit. The generated sound pressure can be used, in particular, to transmit sound signals to a human auditory system. R. 411678

[0075] - 22 - perceptible frequency range. In principle, however, the microelectromechanical device can also be designed to be operated, for example, as a pump device for microfluidic applications. It is not excluded that the microelectromechanical device is designed for selective operation as a sound generation unit and as a pump device, for example, to support a loudspeaker and a cooling function in a mobile device.

[0076] The invention also relates to a microelectromechanical loudspeaker for generating sound pressure, comprising a microelectromechanical device according to one of the features described above and a signal processing unit for applying signals to the microelectromechanical device. The proposed microelectromechanical loudspeaker also offers the advantages of pressure relief for protecting its components. In particular, the microelectromechanical loudspeaker can be designed as an in-ear headphone.When inserting or removing in-ear headphones, pressure or pressure can occur in the ear canal, which may be perceived as unpleasant. This pressure or pressure can be advantageously reduced or eliminated by the described valve mechanism of the microelectromechanical device of the microelectromechanical loudspeaker. This significantly increases user comfort. A signal processing unit can be considered a control circuit, which may be designed as an integrated circuit, for example, an ASIC (application-specific integrated circuit). The signal processing unit may be implemented as a circuit on the circuit carrier structure.The signal processing unit is designed to apply signals to the microelectromechanical device and can, in particular, control the drive unit for deflecting the displacement elements. R. 411678.

[0077] - 23 -

[0078] The invention also relates to a method for manufacturing a microelectromechanical device according to one of the features described above, comprising the steps:

[0079] - Providing a support structure;

[0080] - Creating a displacement unit in the support structure with movable displacement elements that extend between a first support side and a second support side of the support structure;

[0081] - Providing a drive device designed to deflect the displacement elements; and

[0082] - Creating a fluid channel through the support structure and creating a movable valve element on or in the fluid channel and / or

[0083] Creating a fluid channel on a circuit support structure, creating a movable valve element on or in the fluid channel, and connecting the circuit support structure to the support structure.

[0084] This allows the microelectromechanical device to be produced easily, particularly using standard semiconductor manufacturing processes. Due to its fundamentally simple design, the described microelectromechanical device is suitable for mass production using semiconductor technology.

[0085] The displacement unit can be structured directly within the support structure, for example, by selective etching processes, particularly using etch stop structures such as silicon oxide layers. The displacement elements can be created from the support structure, for example, by suitable etching steps involving front-side and back-side etching. The fluid channel can be created within the support structure, for example, using a trenching process. In particular, multiple fluid channels can be created within the support structure and / or the circuit carrier structure, for example, to enable bidirectional valve functions or enhanced pressure equalization. Depending on the embodiment, the movable valve element can be additively added, for example, as a dry-film resist element onto the support structure and / or onto the R. 411678.

[0086] - 24 -

[0087] The displacement elements can be applied to the circuit carrier structure or subtractively extracted from the carrier structure and / or the circuit carrier structure, for example, as a valve blade within the carrier structure and / or within the circuit carrier structure. To provide a drive unit, the displacement elements can, for example, be coated with an actuator material and electrically connected to an electrode and a counter electrode, or connected to an electrostatically driven shuttle unit. Providing the drive unit can include establishing electrical contacts between a signal processing unit and the drive unit, as well as between the drive unit and the displacement elements.

[0088] According to one embodiment, the movable displacer elements can be designed as laterally deflectable displacer lamellae extending vertically between the first and second sides of the support structure. This allows for the creation of a very compact and efficient displacer unit. The displacer lamellae can, for example, be formed from the support structure as a meandering structure by suitable etching steps involving front-side and back-side etching.

[0089] According to one embodiment, a cover flap can be designed as a movable valve element. This creates a flap valve that is structurally simple to manufacture, in which an overpressure acting on the cover flap can cause it to be at least partially lifted from the fluid channel, allowing pressure equalization to occur through the opening thus formed at the channel outlet.

[0090] To form the cover flap, a dry film resist layer can be applied and structured, in particular, onto the support structure and / or the circuit carrier structure. For this purpose, the dry film resist layer can first be laminated, especially over the entire surface, onto the support structure and / or the circuit carrier structure, whereby the lamination process can advantageously be supported by the application of pressure and heat. Furthermore, it is conceivable to apply the R. 411678 before the application of the

[0091] - 25 -

[0092] To improve adhesion of the dry film resist layer to the substrate, a surface treatment is applied to the substrate. For example, an oxygen plasma or HMDS process can be used for this surface treatment. The dry film resist layer can be applied to either the first or second substrate side of the substrate. Subsequently, the dry film resist layer can be structured using a photolithography process to create a dry film resist element that forms the cover flap.

[0093] According to one embodiment, a laterally deflectable valve lamella extending vertically through the fluid channel can be designed as a movable valve element, with a closing element additionally being created at a channel outlet of the fluid channel. The valve lamella can, for example, be formed from the support structure in the same process step using the same etching steps as the displacer lamellae, provided the displacer elements are designed as displacer lamellae. Subsequently, an access opening can be created on the first and second sides of the support structure in the area of ​​the valve lamella to form channel outlets of the fluid channel. This process can be analogous to the creation of slot-shaped incisions in bridge elements of the displacer unit, wherein the opening width of the access opening in the area of ​​the valve lamella is increased compared to the slot width of the incisions on the bridge elements.At at least one channel outlet, in particular at both channel outlets of the fluid channel, a closure element can subsequently be created which covers the channel outlet section by section in such a way that it is flush with the valve lamella or has a slight protrusion over the valve lamella, whereby this refers to an undisplaced state of the valve lamella.

[0094] To form the locking element, a dry film resist layer can be applied and structured, in particular, onto the substrate and / or the circuit carrier structure. For this purpose, the dry film resist layer can first be laminated, in particular, over the entire surface of the substrate and / or the circuit carrier structure, whereby the R. 411678

[0095] - 26 -

[0096] The lamination process can be advantageously supported by the application of pressure and heat. Furthermore, it is conceivable to perform a surface treatment on the substrate before applying the dry film resist layer to improve adhesion. For example, an oxygen plasma or HMDS process can be used for surface treatment of the substrate. The dry film resist layer can be applied to either the first or second substrate side of the substrate. Subsequently, the dry film resist layer can be structured using a photolithography process to obtain a dry film resist element that forms the closure element.

[0097] According to one embodiment, during the manufacture of the microelectromechanical device with a cover flap as a movable valve element, a predetermined minimum pressure differential for opening the fluid channel through the cover flap can be set by specifically designing a predefined mechanical property of the cover flap and / or by specifically dimensioning the fluid channel. According to one embodiment, the fluid channel can be designed as a slot-shaped fluid channel. The cover flap can be manufactured such that it extends transversely or longitudinally across the slot-shaped fluid channel.According to one embodiment, a first fluid channel and a second fluid channel can be created in the support structure and / or in the circuit support structure, wherein a first cover flap is created at a channel outlet of the first fluid channel facing the first side of the support, and a second cover flap is created at a channel outlet of the second fluid channel facing the second side of the support. According to one embodiment, a sealing element for sealing interaction with the cover flap can be created at a channel outlet of the fluid channel. According to one embodiment, the cover flap can be manufactured in such a way that it is formed by several adjacent flap elements or has several movable flap segments.According to one embodiment, a bearing element can be formed on the support structure and / or on the circuit support structure, by which the cover flap is essentially cantilevered over the channel outlet and R. 411678.

[0098] - 27 - is held by a support structure edge that delimits the channel outlet. The bearing element can be formed, for example, additively or subtractively during the manufacture of the microelectromechanical device, such as by additively applying and structuring the bearing element onto the support structure and / or onto the circuit carrier structure, or by removing support structure material or circuit carrier structure material to form a cavity below an extension area of ​​the cover flap adjacent to the channel outlet. Such a cavity can be created, for example, by applying a sacrificial material layer and subsequently undercutting the applied cover flap. According to one embodiment, a non-stick layer can be applied and structured between the support structure and the cover flap and / or between the circuit carrier structure and the cover flap.The non-stick coating can, for example, be applied and structured in layers onto the support structure and / or the circuit carrier structure in a manufacturing step preceding the production of the cover flap.

[0099] According to one embodiment, in the manufacture of the microelectromechanical device with a valve lamella, a predetermined minimum pressure difference for releasing the fluid channel through the valve lamella can be set by selectively generating a predefined overlap dimension between the valve lamella and the closure element, by selectively designing a predefined mechanical property of the valve lamella and / or by selectively dimensioning the fluid channel.

[0100] In general, in connection with this application, the words "ein / eine" are not to be understood as numerals, unless expressly defined otherwise, but as indefinite articles with the meaning of "at least one".

[0101] The invention allows for various embodiments and is explained in more detail below with reference to exemplary embodiments and the accompanying drawings. These show, in schematic form: R. 411678

[0102] - 28 -

[0103] Fig. 1a - a schematic diagram of a microelectromechanical device according to a first embodiment in a partial perspective side view;

[0104] Fig. 1b - a schematic diagram of the microelectromechanical device according to the first embodiment in a perspective top view;

[0105] Fig. 2 - a schematic diagram of a valve assembly of the microelectromechanical device according to the first embodiment in a partial perspective side view;

[0106] Fig. 3 - a schematic diagram of a valve assembly of a microelectromechanical device according to a second embodiment in a partial perspective side view;

[0107] Fig. 4 - a schematic diagram of a valve assembly of a microelectromechanical device according to a third embodiment in a partial perspective side view;

[0108] Fig. 5 - a schematic diagram of a valve assembly of a microelectromechanical device according to a fourth embodiment in a partial perspective top view;

[0109] Fig. 6 - a schematic diagram of a valve assembly of a microelectromechanical device according to a fifth embodiment in a partial perspective side view;

[0110] Fig. 7 - a schematic diagram of the valve assembly of the microelectromechanical device according to the fifth embodiment in a top view;

[0111] Fig. 8 - a schematic diagram of a microelectromechanical loudspeaker with a microelectromechanical device and a signal processing unit;

[0112] Fig. 9 - a schematic flowchart of a method for manufacturing a microelectromechanical device. R. 411678

[0113] - 29 -

[0114] Fig. 1a shows a schematic diagram of a section of a microelectromechanical device 1 for generating fluid pulses. The microelectromechanical device 1 can be configured, in particular, to generate sound pressure. The microelectromechanical device 1 comprises a chip 40 with a support structure 2 and a displacement unit 3, as well as a circuit carrier structure 30 designed as a printed circuit board. According to the illustrated embodiment, the chip 40 is attached to the circuit carrier structure 30, which is arranged below the chip 40, by means of an adhesive bond 32. The circuit carrier structure 30 has a circuit board opening 31 to allow interaction between the displacement unit 3 of the chip 40 and the environment, in particular acoustic access to the environment.

[0115] The support structure 2 has a first support side 2a and a second support side 2b. The support structure 2 can, for example, be a chip 40 of a silicon wafer. The first support side 2a can represent a back side and the second support side 2b can represent a front side of the support structure 2. The first support side 2a and the second support side 2b can span parallel horizontal planes.

[0116] The displacement unit 3 is formed within the support structure 2, and is, in particular, integrally formed with the support structure 2. The displacement unit 3 has several displacement elements 4a, which, according to the illustrated embodiment, are designed as displacement lamellae 4 arranged parallel to one another. The displacement lamellae 4 extend vertically between a first ambient volume 5 facing the first support side 2a and a second ambient volume 6 facing the second support side 2b. In other words, the displacement lamellae 4 extend vertically between the horizontal planes spanned by the first support side 2a and the second support side 2b. The displacement lamellae 4 are laterally deflectable.For this purpose, the microelectromechanical device 1 has a drive device (not shown in detail) for the lateral deflection of the displacer lamellae 4, the drive principle of which is based, for example, on a coating of the displacer lamellae 4 with an actuator material and contacting of the displacer lamellae 4 with an electrode and a counter electrode or on R. 411678.

[0117] - 30 - can be based on an electromechanical shuttle drive. Through the laterally deflectable displacement lamellae 4, a fluid volume can be drawn in and displaced by means of each pair of adjacent displacement lamellae 4 enclosing a variable displacement volume, by increasing and decreasing this volume a fluid pulse can be generated.

[0118] The displacement lamellae 4 are connected to each other by horizontal bridge elements 16. As can be seen in Fig. 1a, the displacement lamellae 4 and the horizontal bridge elements 16 can extend alternately in a meandering pattern between two support sections of the support structure 2. The horizontal bridge elements 16 each have a slot-shaped incision 17, which increases the mobility of the displacement lamellae 4.

[0119] As can be seen in Fig. 1a, the microelectromechanical device 1 has a valve assembly 7 formed in the support structure 2 and a valve assembly 7 formed in the circuit support structure 30. The valve assemblies 7 each have two slit-shaped fluid channels 8, 8a, 8b extending vertically between the first ambient volume 5 and the second ambient volume 6. The fluid channels 8, 8a, 8b of the valve assembly 7 formed in the support structure 2 are spaced apart from the displacement unit 3 and extend through the support structure 2 parallel to the displacement vanes 4. The fluid channels 8, 8a, 8b in the support structure 2 and in the circuit support structure 30 each have a channel inlet 8' and a channel outlet 8".

[0120] Furthermore, the valve assemblies 7, as shown in Fig. 2 by way of example for the valve assembly 7 formed in the support structure 2, each have a movable valve element 9 for each fluid channel 8, 8a, 8b. The movable valve element 9 is configured to block the fluid channel 8, 8a, 8b below a predetermined minimum pressure difference between the first ambient volume 5 and the second ambient volume 6 and to automatically release it above the predetermined minimum pressure difference. Accordingly, in the event of an excessive pressure difference between an ambient pressure p of the first ambient volume 5 indicated in Fig. 2 and an R. 411678

[0121] - 31 -

[0122] The ambient pressure p of the second ambient volume 6 is equalized via the valve assembly 7 by the fact that the movable valve element 9 is at least partially displaced by the applied overpressure, thereby forming an opening at a channel outlet 8" to allow fluid exchange. If the specified minimum pressure difference is undershot, the movable valve element 9 can be reset such that the fluid channel 8, 8a, 8b is closed again.

[0123] The valve devices 7 protect the displacement vanes 4 from impairment or damage caused by excessive pressure forces. The valve devices 7 do not require active actuation; instead, they fulfill their valve function through an automatic, pressure-induced displacement of the movable valve element 9.

[0124] Fig. 1b additionally shows a simplified schematic of the microelectromechanical device 1 in a top view to illustrate the connection of the chip 40 to the circuit carrier structure 30. For clarity, the chip 40 is shown without the details of the carrier structure 2, the displacement unit 3, and the valve assembly 7. However, it is evident that the chip 40 is arranged on the circuit carrier structure 30 above the circuit board opening 31 and is attached to it, in particular, by the adhesive bond 32 indicated in Fig. 1a. An electrical connection between the circuit carrier structure 30 and the chip 40 is established by a wire bond 33. Furthermore, Fig. 1b shows the valve assembly 7 formed in the circuit carrier structure 30 with the channel inlets 8' and the movable valve element 9.

[0125] According to the embodiments shown in Figures 1a to 5, the movable valve element 9 is designed as a cover flap 10 arranged at a channel outlet 8" of the fluid channel 8. This forms a flap valve that is structurally simple yet technically effective. As can be seen in Figure 2, the valve assembly 7 has a first fluid channel 8a and a second fluid channel 8b. A first cover flap 10a is arranged at one of the channel outlets 8" of the first fluid channel 8a facing the first support side 2a. Furthermore, a cover flap 10a is arranged at one of the second support sides 2b.

[0126] - 32 - A second cover flap 10b is arranged at the channel outlet 8" of the second fluid channel 8b. The channel inlets 8' of the fluid channels 8a, 8b are designed to be open. The first cover flap 10a and the second cover flap 10b are pivotable in a respective deflection direction A, in particular by elastic bending deformation. For this purpose, the cover flaps 10a, 10b can advantageously be formed by a dry film resist element 11, which is characterized by simple manufacturing and high flexibility, especially compared to, for example, a silicon element as a cover flap. The dry film resist element 11 forms a mechanical layer element that remains permanently on the support structure 2 and / or on the circuit support structure 30.

[0127] If the ambient pressure p of the second ambient volume 6 exceeds the ambient pressure p of the first ambient volume 5 by a predetermined minimum pressure difference, the overpressure present in the first fluid channel 8a acts so strongly on the first cover flap 10a that it is displaced in the deflection direction A and opens the first fluid channel 8a. If the ambient pressure p of the first ambient volume 5 exceeds the ambient pressure p of the second ambient volume 6 by a predetermined minimum pressure difference, the overpressure present in the first fluid channel 8b acts so strongly on the second cover flap 10b that it is displaced in the deflection direction A and opens the second fluid channel 8b. Thus, the arrangement shown, for example, in Fig. 2 provides a bidirectionally acting valve device 7.

[0128] The specified minimum pressure differential can be determined by a predefined mechanical property of the cover flap 10 and / or by a predefined dimensioning of the fluid channel 8. It is therefore possible to adjust the sensitivity of the valve assembly 7 during manufacturing by designing the components of the valve assembly 7.

[0129] According to the embodiments shown in Figures 3 and 4, the valve assembly 7 has a sealing element 12 at each channel outlet 8" for sealing interaction with the cover flap 10. Such a sealing element 12 can be a counterpart of the cover flap 10 at the respective R. 411678

[0130] - 33 -

[0131] The channel outlet 8” is formed, with which the cover flap 10 is flush. Unlike the cover flap 10, the sealing element 12 can be designed to be immovable, i.e., fixed to the support structure 2 and / or the circuit carrier structure 30. The sealing element 12 reliably ensures that pressure equalization, for example, independent of mechanical stress effects, only occurs after the predetermined pressure difference has been reached. The sealing element 12 can also be a dry film resist element 11 and, advantageously, can be structured from the same dry film resist layer applied to the support structure 2 and / or the circuit carrier structure 30 as the cover flap 10.

[0132] Fig. 4 shows an embodiment of a valve assembly 7 according to a specific configuration in which a bearing element 13 is arranged on the support structure 2, by which the cover flap 10 is held essentially cantilevered over the channel outlet 8" and a support structure edge 2' that delimits the channel outlet 8". The partially cantilevered design of the cover flap 10 increases its mobility. According to the embodiment shown in Fig. 4, the bearing element 13 is formed by creating a cavity 19 below the cover flap 10, with the cover flap 10 extending as a cantilever over the cavity 19 and the channel outlet 8". Alternatively, it is conceivable, for example, to provide a non-stick layer below the cover flap 10 instead of the cavity 19, so that the cover flap 10 can rest on the support structure 2 in sections without adhesion, thus increasing its mobility accordingly.The features described above can be applied analogously to a bearing element 13 arranged on the circuit carrier structure 30.

[0133] In the embodiment of a valve assembly 7 shown in Fig. 5, the movable valve element 9 extends longitudinally over a slot-shaped fluid channel 8 along the slot length L, which is greater than the slot width B of the fluid channel 8. The cover flap 10, designed as a segmented cover flap 10c, has several movable flap segments 10' arranged in a row and connected to the support structure 2 via respective fastening elements 12a. [R. 411678]

[0134] - 34 -

[0135] A flap segment 10' abuts a fastening element 12a of an adjacent flap segment 10', i.e., projects an outer edge onto it. The fastening elements 12a can simultaneously serve as sealing elements 12 for a flap segment 10' projecting onto the fastening element 12a, thus creating a sealing interaction between the sealing element 12 and the flap segment 10' projecting onto it. The flap segments 10' and the fastening elements 12a are designed as dry-film resistant elements 11. With a segmented cover flap 10c, a predetermined minimum pressure differential, in the sense of a threshold pressure, above which the flap segments 10' release the fluid channel 8, can be precisely and individually set by means of the selectively designed flap segments 10'.In addition, it is conceivable, for example, to design the flap segments 10' and / or the fastening elements 12a designed as sealing elements 12 differently, so that the individual flap segments 10' release the fluid channel 8 at different minimum pressure differences or more flap segments 10' are raised as the pressure difference increases.

[0136] Figures 6 and 7 show an embodiment of the valve assembly 7 according to a further embodiment. Here, the movable valve element 9 is designed as a valve blade 14 extending vertically through the fluid channel 8. The valve blade 14 is laterally deflectable, as schematically indicated by the dashed lines representing laterally deflected positions of the valve blade 14 in Figures 6 and 7. The valve assembly 7 also has a closure element 15 that partially covers the fluid channel 8, with a closure element 15 being arranged at each of two opposite channel outlets 8" of the fluid channel 8, according to the illustrated embodiment. The closure elements 15 are designed as dry-film resistant elements 11, which makes them particularly easy to manufacture.

[0137] The valve blade 14 can be flush with an outer edge of the closure element 15, as indicated in Fig. 6. Alternatively, it is conceivable that the closure element 15 has a projection beyond the valve blade 14, so that the latter is deflected further laterally by a higher overpressure. R. 411678

[0138] - 35 - must be created to form an opening between the closure element 15 and the valve blade 14, through which pressure equalization can occur along the fluid channel 8. The specified minimum pressure difference can be determined by a predefined overlap dimension between the undisplaced valve blade 14 and the closure element 15, by a predefined mechanical property of the valve blade 14, and / or by a predefined dimensioning of the fluid channel 8.

[0139] Fig. 8 shows a highly schematic and simplified schematic representation of a microelectromechanical loudspeaker 20 for generating sound pressure. The microelectromechanical loudspeaker 20 comprises a microelectromechanical device 1 according to one of the features described above, as well as a signal processing unit 22, for example, designed as an ASIC, for applying signals to the microelectromechanical device 1. The microelectromechanical device 1 and the signal processing unit 21 are connected to each other via a signal connection 22, for example, via an electrical signal connection between the signal processing unit 21 and the drive unit of the microelectromechanical device 1.The valve device 7 provided with the microelectromechanical device 1 advantageously provides pressure relief in the event of overpressure, in order to protect components of the microelectromechanical loudspeaker 20 and to increase user comfort, particularly in the case of a microelectromechanical loudspeaker 20 designed as an in-ear headphone.

[0140] Fig. 9 shows, in a highly schematic and simplified flowchart, a method 100 for manufacturing a microelectromechanical device 1 according to one of the features described above. According to a first step 110, a support structure 2 can be provided. According to a second step 120, a displacement unit 3 is produced in the support structure 2, wherein displacement elements 4a, in particular displacement lamellae 4 arranged parallel to one another, are manufactured, in particular released from the support structure 2, which extend in particular vertically between the first support side 2a and the second support side 2b of the support structure 2. R. 411678

[0141] - 36 -

[0142] According to a third step 130, a drive device is provided which is configured to deflect the displacement elements 4a, in particular to deflect the displacement vanes 4 laterally. According to a fourth step 140, a fluid channel 8 is created through the support structure, for example by means of a trenching process, and a movable valve element 9 is created on or in the fluid channel 8. Alternatively or additionally, the fourth step 140 can include creating a fluid channel 8 on a circuit support structure 30, creating a movable valve element 9 on or in the fluid channel 8, and connecting the circuit support structure 30 to the support structure 2. The movable valve element 9 can be designed as a cover flap 10, in particular by applying and structuring a dry film resist layer onto the support structure 2 and / or onto the circuit support structure 30.The movable valve element 9 can also be designed as a laterally deflectable valve blade 14 extending vertically through the fluid channel 8. Additionally, a corresponding closure element 15 is then created at a channel outlet 8" of the fluid channel 8, for example by applying and structuring a dry film resist layer onto the support structure 2 and / or onto the circuit carrier structure 30. Following the fourth step 140, for example, an electrical contact can be established between a signal processing unit 22 and the drive device.

[0143] The sequence of steps 110 to 140 described above does not equate to a mandatory chronological order. Steps 110 to 140 are intended, in particular, to reflect only one possible process division of procedure 100. Therefore, steps 110 to 140 can be carried out in a different order than described. In particular, it is also conceivable to implement at least two of steps 110 to 140 simultaneously in a single process segment.

Claims

1. R. 411678 - 37 - Claims 1. Microelectromechanical device (1) for generating fluid pulses, comprising: - a support structure (2) with a first support side (2a) and a second support side (2b); - a displacement unit (3) formed in the support structure (2) with movable displacement elements (4a) which extend between a first ambient volume (5) facing the first support side (2a) and a second ambient volume (6) facing the second support side (2b); - a drive device for deflecting the displacement elements (4a); and - a valve device (7) formed in the support structure (2) and / or in a circuit support structure (30) of the microelectromechanical device (1) with a fluid channel (8) extending vertically between the first ambient volume (5) and the second ambient volume (6) and with a movable valve element (9); wherein the movable valve element (9) is configured to block the fluid channel (8) below a predetermined minimum pressure difference between the first ambient volume (5) and the second ambient volume (6) and to automatically release the fluid channel (8) from the predetermined minimum pressure difference.

2. Microelectromechanical device (1) according to claim 1, wherein the movable displacement elements (4a) are designed as displacement lamellae (4) arranged parallel to each other, which extend vertically between the first ambient volume (5) and the second ambient volume (6) and are laterally deflectable, and wherein the drive device is configured for lateral deflection of the displacement lamellae (4). R. 411678 - 38 - 3. Microelectromechanical device (1) according to claim 2, wherein at least two displacement lamellae (4) are connected to each other by a horizontal bridge element (16) and wherein the horizontal bridge element (16) has at least one slot-shaped incision (17).

4. Microelectromechanical device (1) according to one of claims 1 to 3, wherein the movable valve element (9) is designed as a cover flap (10) arranged at a channel outlet (8") of the fluid channel (8).

5. Microelectromechanical device (1) according to claim 4, wherein the fluid channel (8) is slit-shaped with a slit length (L) greater than the slit width (B) and wherein the cover flap (10) extends transversely over the slit-shaped fluid channel (8).

6. Microelectromechanical device (1) according to claim 4 or 5, wherein the fluid channel (8) is slit-shaped with a slit length (L) greater than the slit width (B) and wherein the cover flap (10) extends longitudinally over the slit-shaped fluid channel (8).

7. Microelectromechanical device (1) according to one of claims 4 to 6, wherein the cover flap (10) is formed by a dry film resist element (11).

8. Microelectromechanical device (1) according to one of claims 4 to 7, wherein the predetermined minimum pressure difference is determined by a predefined mechanical property of the cover flap (10) and / or by a predefined dimensioning of the fluid channel (8).

9. Microelectromechanical device (1) according to one of claims 4 to 8, wherein the valve assembly (7) has a first fluid channel (8a) and a second fluid channel (8b) and wherein at one of the first R. 411678 - 39 - A first cover flap (10a) is arranged at the channel outlet (8") of the first fluid channel (8a) facing the support side (2a) and a second cover flap (10b) is arranged at the channel outlet (8") of the second fluid channel (8b) facing the second support side (2b).

10. Microelectromechanical device (1) according to one of claims 4 to 9, wherein the valve device (7) has a sealing element (12) at the channel outlet (8") for sealing interaction with the cover flap (10).

11. Microelectromechanical device (1) according to any one of claims 4 to 10, wherein the cover flap (10) is formed by several adjacent flap elements or has several movable flap segments (10').

12. Microelectromechanical device (1) according to one of claims 4 to 11, wherein a bearing element (13) is arranged on the support structure (2) and / or on the circuit support structure (30), by which the cover flap (10) is held essentially cantilevered over the channel outlet (8") and a support structure edge (2') limiting the channel outlet (8").

13. Microelectromechanical device (1) according to one of claims 4 to 12, wherein a non-stick layer is arranged section by section between the support structure (2) and the cover flap (10) and / or between the circuit support structure (30) and the cover flap (10).

14. Microelectromechanical device (1) according to one of the preceding claims, wherein the movable valve element (9) is designed as a laterally deflectable valve lamella (14, 14') extending vertically through the fluid channel (8) and wherein the valve assembly (7) has a closure element (15) covering the fluid channel (8) at least partially. R. 411678 - 40 - 15. Microelectromechanical device (1) according to claim 14, wherein a closure element (15) is arranged at each of two opposite channel outlets (8") of the fluid channel (8).

16. Microelectromechanical device (1) according to claim 14 or 15, wherein the predetermined minimum pressure difference is determined by a predefined overlap dimension between the valve lamella (14, 14') and the closure element (15), by a predefined mechanical property of the valve lamella (14, 14') and / or by a predefined dimensioning of the fluid channel (8).

17. Microelectromechanical device (1) according to one of claims 14 to 16, wherein the closure element (15) is formed by a dry film resist element (11).

18. Microelectromechanical device (1) according to one of the preceding claims, wherein the microelectromechanical device (1) is configured to generate a sound pressure by means of the displacement unit (3).

19. Microelectromechanical loudspeaker (20) for generating sound pressure, comprising a microelectromechanical device (1) according to one of the preceding claims and a signal processing unit (21) for applying signals to the microelectromechanical device (1).

20. Method (100) for manufacturing a microelectromechanical device (1) according to any one of claims 1 to 18, comprising the steps: - Providing (110) a support structure (2); - Generating (120) a displacement unit (3) in the support structure (2) with movable displacement elements (4a) extending between a first support side (2a) and a second support side (2b) of the support structure (2); R. 411678 - 41 - - Providing (140) a drive device designed to deflect the displacement elements (4a); and - Creating (130) a fluid channel (8) through the support structure (2) and creating a movable valve element (9) on or in the fluid channel (8) and / or Creating (130) a fluid channel (8) on a circuit carrier structure (30), creating a movable valve element (9) on or in the fluid channel (8) and connecting the circuit carrier structure (30) to the carrier structure (20).

21. Method (100) according to claim 20, wherein the movable displacement elements (4a) are designed as laterally deflectable displacement lamellae (4) which extend vertically between the first support side (2a) and the second support side (2b) of the support structure (2).

22. Method (100) according to claim 20 or 21, wherein a cover flap (10) is designed as a movable valve element (9).

23. Method (100) according to claim 22, wherein a dry film resist layer is applied and structured to form the cover flap (10) on the support structure (2) and / or on the circuit support structure (30).

24. Method (100) according to one of claims 20 to 23, wherein a laterally deflectable valve lamella (14, 14') extending vertically through the fluid channel (8) is formed as a movable valve element (9) and wherein a closing element (15) is additionally generated at a channel outlet (8") of the fluid channel (8).

25. Method (100) according to claim 24, wherein a dry film resist layer is applied and structured to form the closure element (15) on the carrier structure (2) and / or on the circuit carrier structure (30).

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