INTERPOSER FOR DAMPING MEMS MICROPHONES

Description

[0001] In a first aspect, the invention relates to a system comprising a MEMS microphone comprising a sound inlet opening, a vibratable microphone membrane and an electronic circuit, wherein upon excitation of the microphone membrane by sound waves passing through the sound inlet opening, an electrical signal dependent on the sound waves is generated by vibrations of the microphone membrane. A damping element for reducing a sound pressure level of the sound waves acting on the microphone membrane is mounted in front of the sound inlet opening, wherein the damping element comprises an elastic and vibratable damping membrane and wherein the Damping elementIn addition to the microphone membrane, the membrane is excited to vibrate by the sound waves, so that the sound energy of the sound waves is distributed between the damping membrane and the microphone membrane. This makes it possible, in particular, to extend the measurement range of the MEMS microphone to high sound pressure levels without distortion, which were previously unmeasurable with state-of-the-art MEMS microphones.

[0002] In a further aspect, the invention relates to the use of the system according to the invention for aeroacoustic measurements, preferably for measuring sound pressure waves on surfaces of a vehicle component. Background and state of the art

[0003] Microsystems technology is now used in many applications for the production of compact, mechanical-electronic devices. The microsystems produced in this way microelectromechanical system,MEMS for short) are very compact (micrometer range) while offering excellent functionality and ever lower manufacturing costs.

[0004] In particular, microphones based on MEMS technology, so-called MEMS microphones, are known in the prior art. A MEMS microphone comprises a vibrating microphone diaphragm designed to record pressure waves from a fluid. The fluid can be either a gaseous or a liquid, and preferably, it is sound pressure waves. A MEMS microphone preferably converts pressure waves into electrical signals.

[0005] MEMS microphones are characterized by their simple and compact design. This makes them particularly easy to arrange into arrays, which is important for sound measurements with a directional pattern. Furthermore, they can be manufactured using common, highly automated semiconductor processes.

[0006] The majority of MEMS microphones are designed for audio applications, i.e., for telephones and / or hearing aids. These applications are typically characterized by a bandwidth of less than 20 kHz and a sound pressure level of less than approximately 120 dB.

[0007] The state of the art also includes approaches to designing MEMS microphones for aeroacoustic applications. Aeroacoustics deals with the generation and propagation of aerodynamically generated noise and its mitigation. The importance of aeroacoustics has increased significantly in the aviation and automotive industries in recent years. In vehicle acoustics, this is due to customers' growing concern for comfort.

[0008] However, MEMS microphones for audio applications are unsuitable for aeroacoustics because aeroacoustics has different requirements regarding sound quantities.

[0009] The sound pressure level near a jet engine, for example, can be very high. Therefore, an aeroacoustic MEMS microphone should be capable of distortion-free operation up to 160 dB or more. The FAA (Federal Aviation Administration) requires a frequency range above 45 Hz < f ≤ 11.2 kHz for the certification of commercial aircraft. However, aeroacoustic measurements of aircraft and their components are often performed on scale models, so the frequency range of interest is scaled up accordingly. For example, the frequency range for a 1:8 scale model extends up to 89.6 kHz. Therefore, the bandwidth of an aeroacoustic MEMS microphone must be up to 90 kHz to be suitable for model testing (for this information, see David T. et al. (2007) I. Introduction).

[0010] In the state of the art, there are various approaches for a MEMS microphone that can be used for aeroacoustic measurements.

[0011] Martin et al. (2007) propose attaching two additional backplates between the microphone diaphragm. For this purpose, a lower backplate is first coated onto a wafer during the corresponding manufacturing process. The lower backplate is located below the microphone diaphragm. After the microphone diaphragm is attached, an upper backplate is applied above the microphone diaphragm. Both backplates have perforated holes. Sound passes through the holes to the microphone diaphragm, causing it to deflect. They also serve to reduce attenuation in the spaces between the microphone diaphragm and the two backplates. Both the backplates and the microphone diaphragm are made of polysilicon. The MEMS microphone can measure sound pressure levels up to 164 dB (with a reference of 20 µV / Pa). Measurement of higher sound pressure levels is not disclosed.

[0012] Sheplak et al. (1999) discloses a piezoresistive MEMS microphone comprising a thin microphone diaphragm that develops a mechanical bending stress when exposed to sound pressure. The mechanical stress is measured by a change in the electrical resistance of a piezoresistive material structure lying on the diaphragm. The piezoresistors are placed on the microphone diaphragm in a Wheatstone bridge configuration. The MEMS microphone can measure sound pressure levels up to 155 dB.

[0013] Horowitz et al. (2007) disclose a piezoelectric MEMS microphone suitable for aeroacoustic measurements. The mechanical tension of a deflected membrane upon sound excitation generates an electrical voltage across a sandwich structure consisting of two electrodes and a piezoelectric layer. However, the achieved sensitivity is relatively low, and the microphone can only measure a maximum sound pressure level of 169 dB.

[0014] DE 10 2019 124236 A1 discloses a sound measuring device with an acoustic MEMS sensor mounted on a circuit board. In addition to a sound-deflector sensor membrane of the MEMS sensor, a damping membrane spans the hole cross-section of the sound hole behind a sound hole formed in the circuit board and is rigidly supported at the edge. The damping membrane is intended to reduce the sound level of the sound passing through the sound hole in order to enable measurement methods with high maximum sound levels. With a suitable elastic design of the damping membrane, a linear reduction in the sound pressure level is achieved. Specific values regarding the reduction in the sound pressure level are not disclosed.

[0015] Other MEMS microphones are also known in the state of the art, which have an additional membrane, but which is not designed to reduce sound pressure levels.

[0016] For example, US 2019 / 335262 A1 discloses a microphone assembly comprising a MEMS transducer, wherein the MEMS transducer has an elastomeric membrane. The elastomeric membrane serves to protect against contaminants and is intended to have a negligible impact on acoustic performance. In particular, the elastomeric membrane is intended to be acoustically transparent and to lead to a reduction in the SNR (signal-to-noise ratio) of less than 1%.

[0017] US 2020 / 107096 A1 discloses a microphone assembly comprising a port membrane for protection against the ingress of liquids. The port membrane should, in particular, be gas-permeable in order to be permeable or transparent to acoustic energy. Furthermore, the acoustic energy should be able to be transmitted with little or no attenuation. In particular, sound power losses of no more than approximately 3.5 dB should be acceptable in the context of the disclosure of US 2020 / 107096 A1. In addition to the port membrane, the microphone assembly can have an acoustic grid, which is described as a wire mesh. The wire mesh can either be acoustically transparent or achieve frequency-dependent attenuation, which can, however, distort the acoustic signal.

[0018] For certain aeroacoustic measurements, MEMS microphones capable of measuring sound pressure levels up to 180 dB are also required. State-of-the-art MEMS microphones are not designed for such high sound pressure levels.

[0019] Microphones capable of measuring such high sound pressure levels are larger. However, larger designs have the disadvantage that they influence the airflow itself due to their dimensions. However, for accurate measurements, it is important to avoid influencing the flow through the microphone itself. In particular, small lateral resolutions of the flow behavior are no longer possible if the microphone is too large. Furthermore, large microphones are not suitable for attachment to technical surfaces, such as aircraft surfaces or automotive components. Furthermore, microphones capable of measuring such high sound pressure levels, which are important in aeroacoustics, are very expensive to acquire.

[0020] MEMS microphones that can measure very high sound pressure levels, particularly suitable for aeroacoustics, with simultaneously high lateral resolution of the smallest turbulences in the air flow and are also cost-effective to manufacture, are not known from the state of the art. Object of the invention

[0021] The objective of the present invention was to eliminate the disadvantages of the prior art and to provide an improved system capable of measuring very high sound pressure levels, providing high-resolution measurement results, and avoiding any distortion. In particular, the objective was to provide systems suitable for aeroacoustic measurements. Furthermore, the systems should be simple and cost-effective to manufacture. Summary of the invention

[0022] The object of the invention is achieved by the features of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0023] In a preferred embodiment, the invention relates to a system comprising a) a MEMS microphone comprising a sound inlet opening, a vibratable microphone membrane and an electronic circuit, wherein when the microphone membrane is excited to vibrate by sound waves passing through the sound inlet opening, an electrical signal dependent on the sound waves is generated and b) a damping element for reducing a sound pressure level of the sound waves acting on the microphone membrane characterized in that the damping element comprises an elastic and vibratable damping membrane which is mounted in front of the sound inlet opening.

[0024] In addition to the microphone membrane, the damping membrane is excited to vibrate by the sound waves, so that the sound energy of the sound waves is divided between the damping membrane and the microphone membrane.

[0025] The system according to the invention has proven to be advantageous in many aspects, which are explained in more detail below.

[0026] Advantageously, the system according to the invention is capable of measuring particularly high sound pressure levels. In particular, the system can measure sound pressure levels of up to 200 dB, which is not possible with the MEMS microphones known in the prior art.

[0027] Technically, this is due to the fact that the sound energy is distributed between the microphone diaphragm and the damping element, which comprises an elastic and vibrating damping membrane. Sound waves are accompanied by alternating movements of particles in the medium through which the sound propagates. At the same time, parts of the medium alternately condense and rarefy. The energy possessed by the sound can therefore be represented as the sum of kinetic and potential energy. When the sound enters the microphone, it first strikes the damping element, which comprises an elastic and vibrating damping membrane, and transfers part of its energy to it. This energy transfer can be referred to as a first energy transfer in the context of the invention.After the first energy transfer through the sound, the sound passes through the sound inlet opening to the microphone diaphragm, causing the microphone diaphragm to vibrate. The energy transfer of the sound to the microphone diaphragm of the MEMS microphone can be considered a second energy transfer in the context of the invention.

[0028] The vibrations of the microphone diaphragm preferably represent the actual measured signal, which is created by the transmission of the vibrations to an electrical circuit connected to the MEMS microphone.

[0029] In particular, the sound energy is distributed between the damping element and the microphone diaphragm with virtually no loss or distortion. This is due to the elasticity of the damping diaphragm. The elasticity of the damping diaphragm refers to the property that it changes its shape when subjected to force and returns to its original shape when the applied force is removed, similar to a spring. In fact, the vibration of the damping diaphragm occurs because it is elastic, and a sound wave represents the spatial propagation of a mechanical vibration caused by vibrations of a fluid, particularly air, in space. With the propagating vibration, energy is transferred, first to the damping diaphragm and then to the microphone diaphragm. The damping diaphragm is elastic and, in particular, not plastic, i.e.It changes its shape when exposed to a sound wave and returns to its original state.

[0030] Preferably, the damping element and the microphone diaphragm have the same vibration behavior, but the vibrations of the damping element have a lower amplitude than those of the microphone diaphragm. In this context, it is noteworthy that the full bandwidth of the measured sound is retained and, in particular, no portion of the bandwidth is lost. By providing the elastic damping diaphragm, the vibration behavior of the microphone diaphragm is not qualitatively changed. Instead, the division of the sound energy results in a distortion-free reduction in the amplitude of the vibrating microphone diaphragm across the entire frequency spectrum. Frequency-dependent damping, which is, for example, more pronounced at higher frequencies than at lower frequencies, is avoided. In addition, the signal-to-noise ratio (SNR) remains unchanged.signal-to-noise ratio, SNR ratio or SNR ratio) of a measured acoustic signal by dividing the sound energy of the incident sound between the damping element and microphone membrane.

[0031] The operation of the system according to the invention can be explained to a certain extent using an analogy to a level shifter from electrical engineering.

[0032] In electrical engineering, a level shifter (also called a level converter or level converter) is a discrete or integrated electronic circuit that adapts the signal levels – usually voltage levels – of one component to another component, a transmitter and a receiver. Since not all components operate at the same voltage levels, communication between these components requires the signal levels of the information signals to be adapted. This adaptation can be achieved using an active or passive electronic circuit, depending on the requirements. In analog circuits, the signal levels of the transmitter are usually adapted to those of the receiver by amplifiers. For example, the signal from a microphone is adapted to the input signal level range of the AUX input of an amplifier by a microphone preamplifier.

[0033] However, there are applications where simply amplifying or attenuating the information signal is not sufficient, and the signal must also be shifted in the voltage range. For example, if an audio signal with a typical voltage range of -100 mV to 100 mV is to be digitized, it is necessary not only to amplify this signal but also to shift it by adding an offset voltage. For this purpose, the subtraction amplifier circuit is ideal.

[0034] By analogy, the inventors recognized that the microphone diaphragm of a MEMS microphone is unsuitable for detecting the high sound pressure levels that occur particularly in aeroacoustics. By attaching the damping element as an elastic, vibrating diaphragm, the high sound pressure level can be advantageously shifted, allowing the microphone diaphragm to measure the shifted area. This is achieved by recording a portion of the high sound pressure level, making another portion of the sound pressure level detectable for the microphone diaphragm. Signal distortion, for example, due to frequency-dependent attenuation, does not occur.

[0035] A further physical analogy to illustrate the inventive concept can be seen in the mechanical operating principle of a series connection of two springs. With springs connected in series, an applied force is not distributed evenly (as with a parallel connection), but acts equally on both springs. In a series connection, the springs can have different spring constants and different lengths, which has a corresponding effect on the overall change in length. The damping element and the microphone diaphragm are also coupled, so that when a force from incoming sound waves acts on the damping element, the microphone diaphragm is also excited to vibrate as undistorted sound waves propagate beyond the damping element.

[0036] The system according to the invention can be used particularly advantageously as an instrument for performing high-resolution measurements of sound quantities, such as high sound pressure levels, for example, in a wind tunnel. It is also possible for the system according to the invention to be installed on surfaces where high sound pressure levels occur, for example, on the surface of aircraft components. The system according to the invention can also be used to measure the propagation of sound waves on other surfaces or vehicles. A person of ordinary skill in the art is capable of applying the system according to the invention in various fields.

[0037] Another advantage of the system according to the invention is that it has very small dimensions. In particular, the lateral extent of the system according to the invention can be kept small. This is advantageous in that the system according to the invention does not influence the air flowing around it. Thus, measurement results are not distorted and are reproduced with particular accuracy. In particular, the smallest turbulences in the air flowing around it can be detected in order to determine the precise flow behavior of the fluid flowing around it, in particular air, and / or sound parameters in great detail. In particular, it advantageously enables the determination of very low lateral resolutions of the sound pressure level.

[0038] The miniaturization of the system according to the invention is accompanied by further advantages. The small dimensions of the system according to the invention result in a higher density of systems, which can, for example, be arranged along an array. A high number of the system according to the invention or MEMS microphones allows measurement results to be determined particularly precisely. Furthermore, the measurement quality is not compromised by a high number if individual systems in an array fail for any reason.

[0039] By arranging the system according to the invention into an array, applications are also possible that utilize, for example, beamforming to specifically determine measurement values from a specific direction. This allows, for example, a sound pressure level to be determined from a desired position in a targeted manner and with high accuracy. Various array forms are known from the prior art, for example, one-dimensional, two-dimensional, and / or three-dimensional arrays.

[0040] A further advantage is that, according to the invention, the damping element can be installed together with a MEMS microphone, since MEMS microphones are available in very small packages that are, among other things, fully suitable for SMT (surface-mounting technology) assembly. Furthermore, MEMS microphones exhibit excellent temperature properties. The system's temperature stability can be particularly desirable for aeroacoustic applications.

[0041] Preferably, by providing the damping membrane, the system can form a closed system, so that when the system according to the invention is installed on a surface, the entry of unwanted matter, e.g., dirt, soot, and / or dust, into the system is prevented. In particular, internal components of the system according to the invention, for example, internal components of the MEMS microphone, are not damaged. Thus, the damping element not only has the function of shifting the sound pressure level to a range measurable by the microphone membrane without distortion, but also represents a protective and barrier function against the environment. Furthermore, it is possible to prevent the adhesion of dirt via a non-stick coating or to remove adhering dirt from the surface of the system particularly easily.

[0042] Furthermore, the system according to the invention is preferably also suitable for installation on flexible surfaces, for example, by using flexible circuit boards to position the damping element and the MEMS microphone. Thus, the system according to the invention is not limited to fixed surface shapes or structures and advantageously has a wide range of applications. This makes it possible to attach the system to corners, edges, curves, and / or curved and / or bent surfaces.

[0043] Furthermore, the system according to the invention can be manufactured using standardized processes in semiconductor and microsystem technology, so that proven, automated methods of semiconductor processing can be used and cost-effective mass production can be implemented.

[0044] A MEMS microphone preferably refers to a microphone based on MEMS technology, whose sound-receiving structures are at least partially dimensioned in the micrometer range (approximately 1 µm to approximately 1000 µm). The sound-receiving structures are referred to as the microphone diaphragm. The microphone diaphragm can preferably have dimensions in the range of less than 1000 µm in width, height, and / or thickness. In particular, the microphone diaphragm is capable of vibration.

[0045] The microphone diaphragm is designed to pick up pressure waves from the fluid. The fluid can be either gaseous or liquid, but is preferably sound pressure waves. A MEMS microphone therefore preferably converts pressure waves into electrical signals. An electronic circuit can preferably be used to generate and / or read the oscillating diaphragm, for example, using piezoelectric, piezoresistive, or capacitive components on the diaphragm. The microphone diaphragm is preferably sufficiently thin that it bends under the influence of the changes in air pressure caused by the sound waves, thus transitioning to an oscillating behavior. While the microphone diaphragm oscillates, electrical quantities can change, such as the capacitance between the diaphragm and the rear wall.The change in an electrical quantity, such as a change in capacitance, can be converted into an electrical signal by an electrical circuit built into the MEMS microphone, such as an ASIC or a processing unit. The electrical circuit measures changes in such electrical quantities, such as voltage changes, current changes, or capacitance changes, that occur when the microphone diaphragm vibrates under the influence of sound waves.

[0046] The sound inlet opening preferably refers to an opening in the MEMS microphone through which sound waves can pass and impinge on the microphone diaphragm. The sound inlet opening is preferably located in front of the microphone diaphragm in the direction of flow of the fluid, in particular air.

[0047] The electronic circuit preferably converts the vibrations of the microphone diaphragm into electrical signals. This is based on the fact that one or more electrical quantities, such as voltage and / or capacitance, change when the microphone diaphragm vibrates. The electronic circuit preferably comprises electrical connections, such as wires that are in contact with the microphone diaphragm. In addition, the electronic circuit can have an ASIC (application-specific integrated circuit), a processing unit, an integrated circuit (IC), a programmable logic circuit (PLD), a field programmable gate array (FPGA), a microprocessor, a microcomputer, a programmable logic controller and / or other electronic circuit elements.Due to the vibrations of the microphone membrane, the electronic circuit generates an electrical signal that depends on the sound waves and thus also on the amplitudes of the vibrations of the microphone membrane.

[0048] Sound preferably refers to a mechanical deformation in a medium that propagates as a wave. In a fluid, sound is always a longitudinal wave, especially in air. The terms "sound" and "sound wave" can therefore be used synonymously. In gases such as air, sound can be described as a sound pressure wave superimposed on the static air pressure. In sound waves, the fluctuations in the state variables pressure and density are usually small compared to their resting values. When air is discussed below as the fluid of sound waves, the average expert knows that the explanations can also be applied to other fluids.

[0049] The damping element preferably refers to a component of the system according to the invention, which preferably serves to reduce the sound pressure level of the sound waves acting on the microphone diaphragm. Since the microphone diaphragm cannot measure excessively high sound pressure levels, the damping element shifts the sound pressure level of the sound wave undistorted within a range measurable for the microphone diaphragm. In particular, undistorted shifting means that no information and / or values of the actual sound pressure level are lost. Preferably, the bandwidth of the measured signal is retained and the signal-to-noise ratio remains unchanged. For this purpose, the sound energy of the sound wave is distributed between the microphone diaphragm and the damping element in a distortion-free manner as described above. For this purpose, the damping element comprises, in particular, an elastic, oscillatory damping diaphragm.This preferably resonates with a qualitatively similar vibration behavior as the microphone membrane when a sound wave hits the system.

[0050] Attaching the damping element before The sound inlet opening preferably refers to a design of the system according to the invention in which a sound wave first strikes the damping element before reaching the microphone diaphragm. Therefore, from the perspective of an incoming sound wave, the damping element is preferably the first component of the system according to the invention. In particular, the sound wave first causes the damping element to vibrate before the microphone diaphragm is caused to vibrate. The vibrations of the damping element and the microphone diaphragm can therefore be phase-shifted. Although the vibration behavior of the damping element and the damping diaphragm is essentially the same, they differ in amplitude and phase.

[0051] Terms such as substantially, approximately, etc. preferably describe a tolerance range of less than ± 40%, preferably less than ± 20%, particularly preferably less than ± 10%, even more preferably less than ± 5%, and especially less than ± 1%, and particularly include the exact value. Similarly preferably describes quantities that are approximately equal. Partially preferably describes at least 5%, particularly preferably at least 10%, and especially at least 20%, in some cases at least 40%.

[0052] The system according to the invention is characterized in that a distribution of the sound energy of the incident sound waves between the damping membrane and the microphone membrane leads to a reduction of the sound pressure level acting on the microphone membrane by at least 10 dB, preferably by at least 20 dB, particularly preferably by at least 30 dB.

[0053] Advantageously, reducing the sound pressure level acting on the microphone diaphragm by the aforementioned values makes it possible to measure particularly high sound pressure levels, such as those found particularly in aeroacoustics, for example, approximately 175 dB, without distortion. This expands the range of applications of the system according to the invention. In contrast, the MEMS microphones known in the prior art are not capable of measuring such high sound pressure levels, such as up to 170 dB, 175 dB, 180 dB, 185 dB, 190 dB, 195 dB, 200 dB, or higher.

[0054] Such a reduction is not enabled, for example, by the membranes disclosed in US 2019 / 335262 A1 and US 2020 / 107096 A1, and is also not desired in the context of these publications. Rather, the membranes of US 2019 / 335262 A1 and US 2020 / 107096 A1 serve to protect against contamination, whereby a reduction in sound power is to be avoided precisely by designing the membrane as acoustically transparent. The general possibility of reducing sound pressure levels is taught in DE 10 2019 124236 A1. However, there is no disclosure of the above-mentioned particularly preferred values or the associated advantages.

[0055] Another particular advantage is that the system according to the invention can measure the smallest lateral resolutions of the sound pressure level. Lateral resolution preferably refers to a resolution perpendicular to the path of a measurement using sound waves. The opposite of lateral resolution is axial resolution along the longitudinal path of the measurement path, i.e., the path of the sound. In particular, lateral resolution is the distance between two adjacent objects, e.g., two sound sources, which can be imaged as two points. This advantageously makes it possible to create a very precise image of the sound field, despite high sound pressure levels.

[0056] A sound field preferably refers to the area in an elastic medium, particularly air, in which sound waves propagate. The sound pressure level (SPL) is the decimal logarithm of the square ratio between the effective value of the measured sound pressure and its reference value of 20 µPa, commonly used in acoustics. The sound energy preferably refers to the energy contained in a sound field or a sound event, which, as already mentioned above, can be represented as the sum of kinetic and potential energy. The corresponding logarithmic quantity is the sound energy level. According to the invention, the damping element is preferably an elastic body that is excited to mechanical vibrations by the effect of impinging sound waves. As a mechanical wave, sound does not transmit matter, but it does transmit energy.The sound energy of the sound wave is transmitted and divided into vibration energies of the damping element and the microphone membrane.

[0057] Sound pressure is particularly present in the kinetic energy term of the energy balance. Sound pressure refers to the pressure fluctuations in the medium, particularly air, that occur during sound propagation. The effective value is commonly specified here, as this is primarily a harmonic phenomenon. The measured effective value of the sound pressure is included in the sound pressure level specified in dB (decibels). Thus, by distributing the sound energy between the damping element or damping membrane and the microphone membrane, the sound pressure level is also reduced, allowing very high sound pressure levels to be measured. In particular, the sound pressure level is not distorted, and the signal-to-noise ratio remains unchanged.

[0058] In a further preferred embodiment, the system according to the invention is characterized in that the MEMS microphone has a housing in which the sound inlet opening is provided.

[0059] The housing of the MEMS microphone preferably comprises a solid and, in particular, protective casing for the MEMS microphone. In particular, the housing advantageously serves to protect the components of the MEMS microphone, for example, from foreign material and / or damage. However, the housing can also have additional functions. For example, in addition to its protective function, the housing can also serve as a support. Eliminating an additional supporting structure advantageously reduces the weight, the number of components, the assembly effort, and thus also the manufacturing costs.

[0060] The housing preferably includes mounting areas for connecting the MEMS microphone to the housing. Conventional methods known in the prior art, such as soldering and / or gluing, can be used for this purpose. Such mounting options and methods are within the knowledge of the average person skilled in the art and will not be discussed in detail.

[0061] The sound inlet opening on the housing is preferably located above the microphone diaphragm. It may also be preferable for the sound inlet opening not to be located directly above the microphone diaphragm. The sound passes through the sound inlet opening to the microphone diaphragm, which is set into vibration by the sound waves. For this purpose, the electronic circuit generates a signal that can be used to determine various sound parameters, such as sound deflection, sound pressure, sound pressure level, sound energy density, sound energy, sound flux, sound velocity, sound impedance, sound intensity, sound power, sound velocity, sound amplitude, and / or sound radiation pressure.

[0062] In a further preferred embodiment, the system according to the invention is characterized in that the damping membrane is formed from an elastic material, preferably selected from a group comprising monocrystalline silicon, polysilicon, silicon dioxide, silicon nitride, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, indium phosphide, glass, and / or a metal. These are preferably ideally elastic materials that do not undergo plastic deformation when functioning as a damping membrane. In further preferred embodiments, the damping membrane can comprise a material comprising a fiber-plastic composite.

[0063] In a further preferred embodiment, the system according to the invention is characterized in that the damping membrane has a thickness of 50 nm to 500 µm, preferably 100 nm to 200 µm, particularly preferably 1 µm to 50 µm

[0064] The materials and dimensions mentioned have proven particularly advantageous for providing a vibration-capable damping membrane. This is because the materials mentioned, particularly at the thicknesses mentioned, have demonstrated suitable elasticity for the system according to the invention. The damping membrane vibrates when struck by sound waves. In particular, the materials mentioned deform elastically rather than plastically under the influence of sound waves. The damping membrane is therefore deformed in a particularly reversible manner. If a sound wave acts on the damping membrane, the equilibrium position is disturbed and the damping membrane is deformed. Since the sound wave represents a propagation of vibrations, these are transmitted to the damping membrane and thus also set into vibration.

[0065] The vibration behavior of the damping diaphragm preferably essentially corresponds to the vibration behavior of the microphone diaphragm. There is a difference in the vibration behavior in terms of amplitude and phase, but the shape or form of the vibration is preferably essentially the same. Advantageously, the sound pressure level is thus shifted to measurable values, so that even particularly high sound pressure levels can be detected by the system according to the invention. It is particularly advantageous that values of the bandwidth of the measured sound event are not lost. Furthermore, the signal-to-noise ratio remains the same. The measurement signal is advantageously shifted in such an undistorted manner that high sound pressure levels, such as 175 dB, can be measured without distortion.

[0066] Furthermore, the use of these materials as damping membranes is particularly advantageous in that they can be easily processed using proven, state-of-the-art methods. In addition to the aforementioned elasticity, these materials are also robust and stable, preventing them from tearing despite high sound pressure levels. Furthermore, they are advantageously inexpensive to procure and process.

[0067] Furthermore, the materials and values mentioned are advantageous for the manufacturing process of the system according to the invention, as they are suitable for mass production. In particular, standardized manufacturing techniques for coating and / or processing can be used to form the damping membrane.

[0068] In a further preferred embodiment, the system according to the invention is characterized in that the damping membrane extends at least over the sound inlet opening and / or the damping membrane has a lateral extent of 100 µm to 2000 µm, preferably 200 µm to 1000 µm.

[0069] The damping membrane therefore covers at least the sound inlet opening, but can also extend beyond the sound inlet opening or over an entire surface above the sound inlet opening.

[0070] The extension of the damping membrane over the sound inlet of the MEMS microphone provides the aforementioned advantages of shifting high sound pressure levels to a measurable area of the microphone membrane. Furthermore, the damping membrane provides additional protection for the MEMS microphone and its components, such as the electronic circuitry and / or the microphone membrane.

[0071] Preferably, attaching the damping membrane and extending it over the sound inlet opening creates a closed system. This preferably hermetically seals off internal components of the MEMS microphone. A hermetic seal preferably means an absolutely tight seal, in particular one that prevents the exchange of air and / or water. This advantageously protects components of the MEMS microphone and increases its service life.

[0072] Preferably, the lateral extension of the damping membrane is matched to the lateral extension of the sound inlet opening.

[0073] A lateral extension preferably refers to the lateral extension of the damping membrane, in particular extending outward and / or along a surface. The lateral extension preferably refers to a maximum lateral extension of the damping membrane in its plane. In the case of a circle, lateral extension is therefore given by a diameter.

[0074] In a preferred embodiment, the lateral extent of the damping membrane can essentially correspond to the lateral extent of the sound inlet opening of the MEMS microphone. Thus, it may be preferred that the damping membrane extends at least over the sound inlet opening, so that it is completely covered by the damping membrane. However, it may also be preferred that the damping membrane be slightly smaller than the sound inlet opening, so that a smaller vibratable region lies upstream of the sound inlet opening.

[0075] For a sound inlet opening with a diameter of, for example, approximately 500 µm, the damping membrane can preferably have a diameter of at least approximately 500 µm, for example, a diameter of approximately 600 µm, approximately 700 µm, approximately 800 µm, approximately 900 µm, approximately 1000 µm, or more. However, it can also be preferred for the damping membrane to have a smaller diameter than the sound inlet opening, with reference to the above example, for example, a diameter of approximately 400 µm, approximately 300 µm, approximately 200 µm, or less.

[0076] Preferably, the ratio of the lateral extent of the damping membrane to the lateral extent of the sound inlet opening can be more than 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 2, 3 or more and / or less than 10, 9, 8, 7, 6, 5, 4, 3 or less. A person skilled in the art will recognize that intermediate ranges of the aforementioned parameters may be preferred, for example, between 0.8 and 3, between 1.1 and 2, or even between 1.5 and 5.

[0077] The lateral extension—for example, the diameter or radius—of the damping membrane is another parameter that influences its effectiveness. Fig. 9 E shows the dependence of the sound pressure level reduction on the radius of the damping membrane. A smaller radius, and thus a smaller lateral extension of the damping membrane, leads to greater attenuation and increases the potentially measurable sound pressure level range.

[0078] In a further preferred embodiment, the system according to the invention is characterized in that the MEMS microphone is a capacitive, piezoelectric and / or piezoresistive MEMS microphone and / or an electret microphone.

[0079] In a piezoelectric microphone, the microphone diaphragm is mechanically coupled to a piezoelectric element, which is minimally deformed by pressure fluctuations. The piezoelectric effect causes voltage fluctuations due to the deformation of the piezoelectric element. These voltage fluctuations are transmitted to the electronic circuit and read out. Piezoelectric microphones are advantageously mechanically robust and have a simple design. They are particularly advantageous because they do not require an external power supply. They are also insensitive to high temperatures.

[0080] A piezoresistive microphone measures mechanical stress based on a change in electrical resistance of a structure made of piezoresistive material lying on the microphone diaphragm. The piezoresistors can be connected to the microphone diaphragm in a Wheatstone bridge circuit. Due to their simple design, piezoresistive microphones can be monolithically integrated.

[0081] In a capacitive microphone, the microphone diaphragm is mounted electrically insulated from an electrode layer, for example made of a metal or semiconductor, which can in particular form a rear wall. Technically speaking, this arrangement is analogous to a plate capacitor with an air dielectric that possesses an electrical capacitance. This capacitance depends on the plate area and the spacing between the capacitor plates. Incoming sound causes the microphone diaphragm to vibrate, changing the distance between the diaphragm and the counter electrode and thus also the capacitance of the capacitor, which can be detected by the electronic circuit. Capacitive microphones are well known in the art due to their basic design and manufacturing. They advantageously demonstrate high sensitivity and are also insensitive to temperature.

[0082] Electret microphones also use a capacitive measurement principle and feature an electret. Similar to the way a permanent magnet carries a frozen magnetic field, an electret carries a frozen electric field. This takes over the bias voltage otherwise required in condenser microphones, thus allowing for easier operation. Due to the high impedance, an impedance converter is usually necessary.

[0083] There are three types of electret microphones. In the diaphragm type, the diaphragm itself is the electret. In the front-electret type, the electret is applied to the diaphragm. In the back-electret type, the electret is applied to a fixed electrode layer, such as a metal layer or a small metal plate. Electret microphones have the advantage of being very compact, low-cost, and offering good signal quality.

[0084] In a further preferred embodiment, the system according to the invention is characterized in that the MEMS microphone is in a top-port or bottom-port design and / or is integrated within a multilayer substrate, preferably a wafer stack.

[0085] During the development of MEMS microphones, different housing types have emerged. These can be categorized according to the way they are introduced. If the sound reaches the microphone diaphragm via the bottom of the housing, it is called a bottom-port MEMS microphone. Bottom-port microphones also require an opening on the substrate on which the MEMS microphone components are located (also called the carrier substrate), as this is the only way for sound waves to reach the microphone diaphragm. If the sound reaches the sensor via the top of the housing, it is called a top-port MEMS microphone.

[0086] Whether a top-port or bottom-port microphone is preferred usually depends on factors such as the arrangement of the microphone in the product and / or manufacturing considerations.

[0087] The damping membrane according to the invention can advantageously be provided in both a top-port and bottom-port MEMS microphone. Furthermore, a MEMS microphone and a damping element can also be provided within a multilayer substrate, preferably a semiconductor substrate, which is also referred to as a wafer stack.

[0088] In a preferred embodiment, the MEMS microphone is in the bottom-port design, which can also be referred to as a bottom-port microphone.

[0089] Bottom-port designs have a large volume of air in the rear volume of the MEMS microphone, which facilitates the microphone diaphragm's movement under the influence of sound waves. This, in turn, improves the microphone's sensitivity and signal-to-noise ratio. A large rear volume is also beneficial for the inventive system's low-frequency response.

[0090] The damping membrane can preferably be placed upstream of the sound inlet opening such that the housing fits within a cavity of a printed circuit board and the damping membrane extends along the sound inlet opening. In bottom-port microphones, the damping membrane is preferably located on the carrier substrate (see, for example, Fig. 2 AB ). It may also be preferred that the damping membrane in the bottom-port design is located within a cavity of a printed circuit board (see Fig. 4 B) .

[0091] It is particularly preferred that the damping membrane in bottom-port designs be provided by an interposer. The combination of the damping membrane with bottom-port microphones is very advantageous because an interposer can be particularly easily processed to ensure the provision of a damping membrane and its connection to the MEMS microphone. Furthermore, the use of an interposer advantageously makes it possible to simultaneously provide a damping membrane, electrical contact, and acoustic termination.

[0092] Especially with the bottom-port design, different designs can be further subdivided. Common designs include flip-chip assembly and wire bond assembly, which can also be used for the system according to the invention.

[0093] In flip-chip assembly, the connection between the microphone diaphragm, electronic circuitry, and carrier substrate is made using solder. The microphone diaphragm, electronic circuitry, and solder are applied to the carrier substrate and mechanically and electrically connected using a reflow process.

[0094] In the reflow process, a soft solder in the form of solder paste is preferably applied to the components before assembly. This is the main difference from other soldering processes such as soldering iron soldering, dip soldering or wave soldering. There are various ways of applying solder, e.g. using stencil printing, screen printing, dispensers, solder preforms or even galvanically. The components are then assembled. The use of solder paste has the advantage that it is sticky, so the components adhere directly to the paste during assembly. There is no need to glue them on. The assembled carrier substrate (e.g. a circuit board) is heated sufficiently to melt the solder contained in the solder paste. At the same time, the increased temperature activates the flux in the solder paste gel. The heating processes used for this purpose aim to heat the circuit board and the components as evenly as possible.The surface tension of the molten solder pulls the components to the center of the landing pads.

[0095] One advantage of flip-chip assembly is the small and compact component size. With flip-chip assembly, additional bonding wires are not required, as the electrical and mechanical connection is made directly on the carrier substrate. The mechanical connection to the carrier substrate influences the temperature response of the microphone. The different coefficients of linear expansion of the component materials, such as silicon, carrier substrate, solder, and adhesive, influence the mechanical stress of the microphone diaphragm. This leads to a change in deflection and thus to a change in sensitivity.

[0096] In wire bond assembly, the connection between the microphone diaphragm, electronic circuit, and carrier substrate is preferably made using bond wires. For this purpose, the microphone diaphragm and the electronic circuit are first mechanically connected to the carrier substrate, for example, using adhesive, and then electrically connected via bond wires. MEMS microphones constructed using a wire bond assembly advantageously have a large rear volume. Acoustic separation, or the separation of areas of the MEMS microphone, is achieved by dividing the microphone into front and rear volumes. The front volume preferably comprises the volume from the sound inlet opening to the microphone diaphragm, and the rear volume the volume behind the microphone diaphragm.

[0097] In top-port versions of a MEMS microphone, the damping membrane is preferably located planar in front of or above the sound entrance opening. For example, the damping membrane can be provided by the housing itself or an additional microphone cover (see, for example, Fig. 5-6 ).

[0098] The system according to the invention is characterized in that the system comprises an interposer, and the damping membrane is incorporated into the interposer. The installation of an interposer is particularly preferably carried out in a bottom-port version of a MEMS microphone.

[0099] For example, the damping membrane in an interposer can be provided by introducing a cavity into the interposer. The cavity has a boundary layer that separates the cavity from the surroundings of the interposer. This boundary layer serves as a damping membrane, which is preferably located in front of the sound inlet opening (see also Fig. 1As mentioned above, a MEMS microphone in the bottom-port version can also be placed with the housing into a cavity of a circuit carrier, with the interposer with the inserted cavity being located in front of the sound inlet opening (see Fig. 2 B) .

[0100] The inclusion of the damping membrane in the interposer has proven particularly advantageous. In particular, the use of an interposer allows for the simultaneous provision of a damping membrane, an electrical contact, and an acoustic seal. This achieves a synergistic effect that can be achieved in a particularly efficient manufacturing manner—namely, by attaching an interposer. The interposer has also proven useful for the measurement of sound events in the context of the invention, since, particularly with regard to electrical contacts, conduction paths can be shortened, thus achieving optimized signal transfer and simultaneous energy savings per area.

[0101] In a further preferred embodiment, the system according to the invention is characterized in that the MEMS microphone is in contact with a circuit carrier, preferably a printed circuit board, wherein the circuit carrier, preferably a printed circuit board, has a cavity for receiving the MEMS microphone. Preferably, the interposer provides electrical contact between the MEMS microphone and a circuit carrier, preferably a printed circuit board. In this case, the MEMS microphone is preferably placed on the circuit carrier (see Fig. 4 B)The cavity advantageously offers optimal protection for the MEMS microphone, as the MEMS microphone fits perfectly into the cavity and protects the damping element above the cavity in which the MEMS microphone is located from the ingress of unwanted substances. The cavity can be mounted in the circuit carrier and is particularly easy to install. The cavity within the circuit carrier is also advantageous for shortening conduction paths and transmitting electrical signals particularly well and efficiently. The MEMS microphone is also particularly stable, robust, and secure within the cavity, so that stresses, for example due to displacement and / or movement, of the system according to the invention do not result in any displacement of the MEMS microphone. This advantageously increases the overall component quality and the service life of the system according to the invention.The cavity can therefore advantageously be seen as a protective space for the MEMS microphone, whereby electrical signals can be transmitted particularly easily and efficiently from and / or into the cavity in which the MEMS microphone is located.

[0102] A cavity is a hollow space with a volume. The MEMS microphone can be located within this volume. The cavity essentially has the same dimensions as the MEMS microphone, but can be larger or smaller as desired.

[0103] Advantageously, an interposer offers the possibility of providing the damping membrane while simultaneously providing electrical contact. In particular, in addition to the damping function, the interposer also allows for the provision of intermediate circuits, vias, and / or rewiring. Furthermore, the interposer provides an acoustic seal.

[0104] In the prior art, an interposer preferably refers to an intermediate layer or component that provides electrical connections between two or more terminals. The purpose of an interposer is usually to distribute a terminal across a wider grid of terminals or to redirect a terminal to another terminal. One example of an interposer is the provision of a so-called ball grid array, which is a type of integrated circuit package in which the terminals for SMD assembly are located compactly on the underside of the component. The terminals are small solder balls that are arranged next to one another in a grid of columns and rows. These balls are melted during a reflow process in a soldering oven and connect to contact pads on the circuit board.A ball grid array as an interposer thus provides a connection between the terminals of a die with an integrated circuit (on the top side of the interposer) and the terminals or contact pads (on the bottom side of the interposer) of a printed circuit board.

[0105] In the context of the invention, the interposer is preferably a component that provides a connection between first terminals of the MEMS microphone and second terminals of a circuit carrier (preferably a printed circuit board). The component is preferably flat and can therefore be referred to as a layer. For the example of a ball grid array described above, the interposer represents an intermediate layer that provides a connection between terminals on one side (top side) and an opposite side (bottom side).

[0106] In accordance with the invention, it may be preferred that the interposer also provides a connection between terminals for the MEMS microphone and a circuit carrier (preferably a printed circuit board) from one side of the interposer to the other. However, the interposer particularly preferably provides a connection between terminals for the MEMS microphone (particularly in a bottom-port design) and a circuit carrier (preferably a printed circuit board) on the same side of the interposer (cf., among others, Fig. 1-3 ).

[0107] For the purposes of the invention, the interposer can therefore preferably also be referred to as a cover or cover layer. Particularly preferably, the interposer, as a cover or cover layer, closes off the MEMS microphone from one side (where the sound inlet opening is located) and preferably provides a connection to the terminals of a printed circuit board on the side contacting the MEMS microphone.

[0108] The interposer can preferably comprise both flexible and rigid materials. Rigid interposers are particularly preferred because they can create a particularly strong and robust connection to the MEMS microphone and can protect the MEMS microphone in the form of a lid or microphone cover (cf., among others, Fig. 6-7 ).

[0109] Particularly suitable materials for the interposer are silicon, glass, and / or polyimide due to their processing capabilities and low production costs. The interposer can be attached to the MEMS microphone using state-of-the-art adhesive, soldering, and / or bonding techniques.

[0110] The damping membrane is preferably integrated in the interposer, so that the interposer simultaneously serves to contact the MEMS microphone with a circuit carrier and also provides advantageous elastic damping.

[0111] In a preferred embodiment, the damping membrane is formed by introducing a cavity in an interposer, which can preferably be applied as a cover layer or lid on the MEMS microphone. For example, the interposer can be present as a flat lid or layer essentially made of an elastic material, wherein a cavity is introduced such that a damping membrane with the desired thickness remains in the interposer. For the elastic material of the interposer (and thus of the damping membrane), analogous to the above statements, materials are particularly preferably selected from a group comprising monocrystalline silicon, polysilicon, silicon dioxide, silicon nitride, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, indium phosphide, glass and / or a metal.

[0112] The position and lateral extent of the cavity in the interposer can preferably be selected so that, in the connected state, the damping membrane of the interposer is located in front of or above the sound inlet opening of the MEMS microphone.

[0113] In a preferred embodiment, the system according to the invention is characterized in that the damping membrane is formed by introducing a cavity in the interposer, wherein a depth of the cavity is preferably selected such that the damping membrane formed in the interposer has a thickness of 50 nm to 500 µm, preferably 100 nm to 200 µm, particularly preferably 1 µm to 50 µm and / or a lateral extent of 100 µm to 2000 µm, preferably 200 µm to 1000 µm.

[0114] The mentioned values regarding the thickness and lateral extension of the damping membrane by forming a cavity in the interposer - especially in combination with the mentioned materials - have proven to be very advantageous in that they can shift part of the sound pressure level without distortion, so that especially high values of sound pressure levels can be measured through the microphone membrane.

[0115] By selecting the elastic material and the thickness, values of approx. 10 dB, approx. 20 dB, approx. 30 dB, approx. 40 dB, approx. 50 dB or more can be advantageously shifted without distortion.

[0116] The cavity can be preserved using etching processes, which have proven themselves to be efficient, fast, reliable and cost-effective in the state of the art.

[0117] The terms "etching method" and "etching process" can be used synonymously. An etching method preferably refers to the removal of material from a surface. This removal can take the form of depressions that leave cavities, with a boundary layer to the cavity leaving behind the damping element or damping membrane.

[0118] Suitable etching processes for forming a damping membrane with the desired thickness would be, for example, wet-chemical etching processes and / or dry etching processes, preferably physical and / or chemical dry etching processes, particularly preferably by reactive ion etching and / or reactive ion deep etching (Bosch process), or a combination of the aforementioned etching processes.

[0119] In semiconductor technology and microsystems engineering, dry etching refers to a group of abrasive microstructuring processes that are not based on wet chemical reactions (such as wet chemical etching or chemical-mechanical polishing). Material removal occurs either through accelerated particles or with the aid of plasma-activated gases.

[0120] Dry etching processes can be divided into three groups: physical dry etching processes, which are based on material removal by bombardment with particles, chemical dry etching processes, which are based on a chemical reaction of a mostly plasma-activated gas, and physico-chemical dry etching processes, which use both mechanisms of action.

[0121] In wet chemical etching, an etch-resistant mask is transferred into the wafer through a chemical removal process.

[0122] Plasma etching is a plasma-assisted dry etching process that removes material. Plasma etching distinguishes between etching removal due to a chemical reaction and physical removal of the surface due to ion bombardment.

[0123] In chemical plasma etching, material removal occurs through a chemical reaction. Therefore, it is generally isotropic and, due to its chemical nature, also highly material-selective. Physical plasma etching, also called plasma-assisted ion etching, is a physical process. This process can result in a certain preferred direction in the etching attack, which is why the processes may exhibit anisotropy in material removal.

[0124] Of particular note here are reactive ion etching (RIE), an ion-assisted reactivity process with very good controllability of the etching behavior, and deep reactive ion etching (DRIE), a further development of RIE.

[0125] The etching processes mentioned are familiar to a person of ordinary skill in the art. Depending on the desired thickness of the damping membrane and / or the material of the interposer, advantageous methods can be selected to ensure efficient implementation.

[0126] In a preferred embodiment, the interposer has a thickness of up to 1000 µm, preferably up to 700 µm, particularly preferably between 400 and 700 µm.

[0127] Such layer thicknesses ensure that the interposer is particularly stable and robust and, in addition, a damping membrane with preferred thicknesses of 50 nm to 500 µm, preferably 100 nm to 200 µm, particularly preferably 1 µm to 50 µm can be introduced efficiently and safely.

[0128] A circuit carrier is preferably a component comprising an electrically insulating material on which electrically conductive connections (conductor tracks) and / or electronic components or assemblies are present, preferably from semiconductor technology and microsystem technology.

[0129] In particular, a circuit board has metallic conductors that allow electrical connections to be made. These are preferably used for power or voltage supply, signal transmission, and / or temperature dissipation.

[0130] In preferred embodiments, the circuit carrier is a printed circuit board (PCB). printed circuit board),Both conventional (rigid) circuit boards and flexible circuit boards (FPCs) are available. flexible printed circuits) can be used.

[0131] Printed circuit boards consist of electrically insulating material with conductive connections, the conductor tracks, adhered to it. Fiber-reinforced plastic is commonly used as the insulating material, or laminated paper in cheaper devices. The conductor tracks are usually etched from a thin layer of copper. The components are soldered onto pads or solder pads. This simultaneously provides mechanical stability and electrical connection. Larger components can also be attached to the circuit board with cable ties, adhesive, or screws.

[0132] The provision of an interposer with an integrated damping membrane and contact mediation to a circuit carrier (preferably a printed circuit board) allows for an extremely compact and robust system design. The circuit carrier also allows for the implementation of additional electrical and mechanical functions and the design of any desired shape.

[0133] One advantage is the manageability and automation of contacting a circuit board via an interposer.

[0134] In a further preferred embodiment, the system according to the invention is characterized in that a closed electrical connection is formed between the MEMS microphone and the interposer, preferably in the form of a solder ring, around the sound inlet opening, which provides both electrical contact between the MEMS microphone and the interposer and acoustic termination. Particularly preferably, the electrical contact is provided by a solder ring around the sound inlet opening in the bottom-port version of a MEMS microphone.

[0135] Advantageously, this creates a particularly stable and robust electrical and mechanical connection between the MEMS microphone and the interposer. In particular, the connection also acts as an acoustic seal for the MEMS microphone.

[0136] A solder ring preferably refers to a material (preferably solder material) that is essentially ring-shaped, i.e., in particular, closed, and structured on the interposer and serves to attach the MEMS microphone to the interposer, preferably via soldering processes. Other processes such as bonding and / or gluing can also be used.

[0137] An acoustic termination preferably refers to a termination resistor for electrical signals generated by sound waves. Termination resistors are resistors at the ends of cables that match the impedance of the cable or electrical connection and terminate it with the correct impedance. Due to the correct impedance termination, the waves transmitted on the transmission medium extend to infinity and cannot be reflected (even partially).

[0138] In a further preferred embodiment, the system according to the invention is characterized in that a space between the MEMS microphone, an interposer and / or a circuit carrier, preferably a printed circuit board, is filled with a filling material.

[0139] Advantageously, filling the intermediate space with a filler material results in particularly high stabilization and a rear seal. In particular, the filler material largely prevents the interposer and / or the circuit board, which is coupled to the damping membrane, from vibrating in terms of stabilization. In particular, in order to shift the sound to a measurable level, preferably only the damping membrane is set into vibration, i.e. in particular the area above the sound inlet opening, but not lateral areas of the interposer and / or the intermediate circuit. Advantageously, only the damping membrane is mechanically stressed and not the entire interposer and / or circuit board. This results in particularly precise measurement results. In particular, high sound pressure levels are shifted undistorted to a range that is measurable for the microphone membrane.

[0140] A gap preferably refers to one or more gaps between the MEMS microphone, the interposer, and / or the circuit carrier. Without the filler, the gap would only contain air or a vacuum. The gap arises when one or more contacting components have a shape other than a rectangular profile. The gap can be a planned breaking point or separation point between components that are mounted immovably relative to one another or are fixed to one another.

[0141] In a further preferred embodiment, the system according to the invention is characterized in that the filler material comprises one or more polymers, preferably one or more cyclic, linear, branched and / or crosslinked polysiloxanes.

[0142] The materials mentioned are very advantageous as filler materials because of their good durability. For example, the filler material remains stable in its mechanical behavior over a wide temperature range (e.g. from approx. -40 °C to approx. +150 °C), as well as in its optical appearance, i.e., in contrast to other plastics, no yellowing occurs over time. A further advantage is that the materials mentioned have a certain elasticity. This can be relevant, for example, when high mechanical stresses occur, for example due to the effect of very high pressures, as is common in aeroacoustics. As a result, the functionality of the system according to the invention is maintained despite the effect of, for example, high forces.Due to the relatively weak intermolecular bonds of the aforementioned materials, they also exhibit low viscosity, which can be advantageous during production and processing. This relatively low viscosity also offers manufacturing advantages. The processes are easier to handle, short cycle times can be achieved, and production can be carried out within very tight tolerances. Furthermore, the material's flow behavior allows for the molding of very complex geometries.

[0143] In a further preferred embodiment, the system according to the invention is characterized in that the damping membrane is integrated into a microphone cover or is formed by it, wherein the microphone cover optionally comprises an opening for pressure equalization. The microphone cover can preferably be used as a damping membrane in the case of a top-port version of a MEMS microphone (see, for example, Fig. 5-6). In particular, the damping membrane can be provided by the housing or by an additionally attached cover. The microphone cover can, for example, comprise one or more films or a membrane formed from metal, glass, and / or one or more polymers. The microphone cover can also be in the form of a lid. It can also be preferred that the microphone cover is attached to a bottom-port version of a MEMS microphone (see Fig. 7 ). In the bottom-port design, the microphone cover is preferably attached in such a way that it extends laterally along the sound inlet opening and is located on the carrier substrate.

[0144] Advantageously, the attachment of the damping membrane, in particular by etching processes to form the damping membrane, is particularly simple in the case of a microphone cover. At the same time, the microphone membrane provides excellent protection for the MEMS microphone. The microphone cover can be located over an area of the sound inlet opening, over a further area, or along an entire surface above the sound inlet opening. Furthermore, it is advantageous that openings can be made particularly easily in the microphone membrane, which preferably serve to enable pressure equalization between the environment of the system according to the invention and the system according to the invention itself. In particular, the microphone cover can comprise an oscillatory material, for example an oscillatory polymer, so that high sound quantities measured at the microphone membrane, such as e.g.High sound pressure levels can be shifted undistorted to measurable ranges, for example, by at least approximately 10 dB, approximately 20 dB, approximately 30 dB, or more. In particular, there is no loss of bandwidth of the measured signal, and the signal-to-noise ratio remains the same.

[0145] Pressure equalization is preferably referred to as a process in which essentially the same pressure is created between the system according to the invention and its surroundings, which are preferably filled with the same medium. The medium can be either a gas or a liquid, in particular also air. Preferably, pressure equalization is achieved by transporting the medium between the surroundings and the system according to the invention. Advantageously, pressure equalization enables essentially the same vibration behavior of the damping diaphragm and the microphone diaphragm. If no pressure equalization were to take place, this could have a detrimental effect on the sensitivity and overall functional operation. It is therefore preferred that pressure equalization takes place through openings provided on the microphone cover.

[0146] The microphone cover preferably refers to a component of the system according to the invention that has a large areal extent relative to its thickness. In particular, the microphone diaphragm is a biaxially stretched surface that has the ability to separate and / or vibrate. The microphone cover can, for example, comprise films or a diaphragm made of metal, glass, and / or one or more polymers. The microphone cover can also be attached in the form of a lid, the housing, or part of the housing.

[0147] In a further preferred embodiment, the system according to the invention is characterized in that the system comprises at least two wafers forming a wafer stack, wherein the MEMS microphone is formed in a first wafer and the damping membrane is formed in a second wafer. Preferably, the damping membrane can be provided by a cavity within a wafer. Preferably, the wafers are connected to one another in such a way that the damping membrane is located in front of the sound inlet opening (see Fig. 8 AB ).

[0148] The formation of a multilayer substrate, preferably a wafer stack, is formed from at least two wafers, but can also comprise 3, 4, 5, 6, 7, 10, 15, 20, or more wafers. The wafers can be interconnected both horizontally and vertically in two or more layers, forming a three-dimensional configuration. Vertical electrical connections between different wafers are made possible by vias. Additional layers, such as one or more oxide layers, can also be located between the wafers of a wafer stack.

[0149] The advantage of this is a smaller footprint. More functional components fit on a smaller area of the component carrier, e.g. on the circuit board. This enables smaller yet powerful MEMS microphones. In addition, the design is advantageously associated with lower manufacturing costs. Another advantage is that the production of the individual components can be optimized to a much greater degree than if they were manufactured together on a single substrate. In particular, this means that components from different and incompatible manufacturing techniques can be combined in a wafer stack. Furthermore, shorter signal paths and lower power consumption result. The use of an additional dimension enables a higher order in the connectivity of the components and thus opens up new possibilities in construction and design.

[0150] The terms "wafer" and "substrate" can be used synonymously. The wafer can comprise materials selected from the group consisting of monocrystalline silicon, polysilicon, silicon dioxide, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, indium phosphide, and / or glass.

[0151] These materials are particularly easy and cost-effective to process in semiconductor and / or microsystem technology and are also well-suited for mass production. These materials are also particularly suitable for doping and / or coating to achieve the desired electrical, thermal, and / or optical properties in specific areas. The aforementioned materials offer a variety of advantages due to the usability of standardized manufacturing techniques, which are also particularly suitable for the integration of additional components.

[0152] Processing for manufacturing the system according to the invention is particularly simple. In particular, established bonding methods can be used to connect the wafers together.

[0153] It may also be preferable for individual wafers to be thinned, for example, using polishing methods known from microsystems technology. Wafer thinning can be performed before or after bonding. Vertical electrical connections (vias) can also be introduced either before bonding or after the stack has been manufactured.

[0154] Wafer bonding preferably describes a process step in semiconductor and microsystem technology in which two wafers or discs, e.g. made of silicon, quartz, glass and / or the aforementioned preferred materials, are bonded together.

[0155] Various bonding methods can be used. These are also referred to as bonding processes or bonding techniques. Preferred bonding processes include direct bonding, anodic bonding, bonding with interlayers, glass frit bonding, adhesive bonding, and / or selective bonding.

[0156] In direct bonding, particularly of silicon wafers, hydrophilic and hydrophobic surfaces of the wafer are preferably brought into contact at high temperatures. Preferably, one wafer is pressed centrally against the other, advantageously creating a first contact point. This mechanical connection in the contact area is preferably based on hydrogen bonds and / or van der Waals interactions. The contact area thus connected is preferably extended to the remaining wafer surface(s) by successively removing any spacers initially present between these surfaces. Process temperatures are preferably between 1000°C and 1200°C, and a pressure of, for example, 10 megapascals (MPa) to 25 MPa is exerted on the wafers. Direct bonding can preferably be used to join two silicon wafers and / or silicon dioxide wafers.

[0157] In anodic bonding, a glass with an increased Na+ ion concentration (preferably positively charged sodium ions) is used, which is preferably brought into contact with a silicon wafer. An electrical voltage is applied, which is particularly configured to create a negative polarity on the glass. This preferably results, and in particular with the aid of an increased process temperature, in the sodium ions (Na+) diffusing to the electrode, whereby a space charge zone preferably forms at the interface, which increases the electric field and creates Si-O-Si bonds. These bonds preferably expand successively to cover the entire connection area between glass and silicon. This allows glass and silicon wafers, in particular, to be bonded to one another. With appropriate adaptation of the process, bonding two silicon layers and / or a silicon-metal layer to a glass is also possible.Anodic bonding can preferably take place at temperatures of approximately 400°C, but it can also preferably take place at "low temperature" temperatures of approximately 180°C, whereby the materials to be bonded are preferably protected. Preferably, various of the aforementioned materials can also be bonded.

[0158] Bonding processes with so-called intermediate layers between the wafers to be bonded can also be used, such as so-called eutectic bonding, which is preferably based on the connection via a eutectic alloy as an intermediate layer, e.g., Si-Au (silicon-gold) or Ge-Al (germanium-aluminum). A eutectic alloy is preferably an alloy whose components are mixed in such a ratio that the entire alloy becomes liquid or solid at a certain temperature. Eutectic bonding can be used, for example, to join two silicon wafers. However, other of the aforementioned materials can also preferably be joined.

[0159] Glass frit bonding is also preferably based on the use of an intermediate layer between the wafers to be joined, with the bond being formed in particular by melting glass solders / glass frits. Glass solder preferably comprises a glass that has a low softening temperature, e.g., approximately 400°C. Glass frits preferably comprise superficially molten glass powder, the glass grains of which preferably at least partially cake or sinter together. This type of bonding can preferably bond silicon and / or silicon dioxide wafers, but also preferably other aforementioned materials.

[0160] Adhesive bonding preferably describes the formation of a connection through an intermediate layer comprising adhesive. Adhesive bonding can preferably be used to bond various of the aforementioned materials together.

[0161] Preferably, selective bonding can be carried out by photolithography, etching and / or lift-off processes.

[0162] Bonding structures from pre-processed wafers allows for the simple fabrication of complex structures that would be difficult to produce from a single wafer. This allows the semiconductor component to be manufactured without the need for laboriously removing the raw material from the inside to create the damping membrane on a wafer.

[0163] In a further aspect, the invention relates to the use of the system according to the invention for aeroacoustic measurements, preferably for measuring sound pressure waves on surfaces of a vehicle component.

[0164] Particularly in measurements for or in aircraft, aircraft components, vehicles such as automotive systems and / or automotive components, sound quantities can assume very high values, especially with regard to the sound pressure level. Advantageously, the system according to the invention enables the measurement of such high values, especially for measurements with regard to high sound pressure levels.

[0165] The damping element or damping membrane shifts the sound pressure level in particular to a measurable range. This is achieved by causing the damping membrane to vibrate like the microphone membrane. In particular, the shift to a measurable range occurs essentially undistorted and without any loss of signal-to-noise ratio. The damping membrane and the microphone membrane essentially exhibit the same vibration behavior, although they preferably differ in their amplitude and phase. The phase shift occurs because the damping membrane vibrates first before the microphone membrane vibrates. The damping membrane can shift the sound pressure level by at least approximately 10 dB, approximately 20 dB, approximately 30 dB or more via the vibrations, so that the system according to the invention can be used at very high sound pressure levels, such as approximately 180 dB.Such high sound pressure levels are achieved in particular when there is a high relative speed with respect to a flowing fluid, for example high flow and / or wind speeds.

[0166] Due to the small dimensioning of the system according to the invention, the flow of the fluid is advantageously not influenced or only very slightly influenced, so that advantageously small lateral resolutions of high sound quantities such as the sound pressure level are enabled.

[0167] Furthermore, the system according to the invention has a substantially planar design, allowing it to be integrated very easily and efficiently into surfaces. For example, it is conceivable that the system according to the invention could be installed on aircraft components such as the elevator, ailerons, etc.

[0168] The system according to the invention is very simple and efficient in handling, production position and further processing and has proven to be very advantageous.

[0169] The system according to the invention will be explained in more detail below using examples, without being limited to these examples. FIGURES Short description of the characters

[0170] Fig. 1 Representation of a preferred embodiment of the system according to the invention by attaching the damping membrane in an interposer Fig. 2 Representation of a preferred embodiment of the system according to the invention by mounting on a circuit carrier Fig. 3 Representation of a preferred embodiment of the system according to the invention by mounting on a circuit carrier and filling the space with a filling material Fig. 4Representation of a preferred embodiment of the system according to the invention by attaching the damping membrane to a cavity of a circuit carrier Fig. 5 Representation of a preferred embodiment of the system according to the invention by attaching the damping membrane in a microphone cover Fig. 6 Representation of a further preferred embodiment of the system according to the invention by attaching the damping membrane in a microphone cover in a top-port design Fig. 7 Representation of a further preferred embodiment of the system according to the invention by attaching the damping membrane in a microphone cover in a bottom-port design Fig. 8 Representation of a further preferred embodiment of the system according to the invention in a wafer stack Fig. 9 Representation of a model of the damping by the system according to the invention Detailed description of the characters

[0171] Fig. 1is a representation of a preferred system 1. Here, an interposer 15 a damping membrane 11 The damping membrane 11 is formed by forming a cavity 17 into the interposer 15 attached. The cavity 17 can be formed using established and known etching processes, which have been listed and described above. The damping membrane 11 at the interposer 15 is placed in front of a sound inlet 5 a MEMS microphone 3 For aeroacoustic applications or measurements, the sound inlet opening is 5 in the direction of air flow. For mechanical and / or electrical contact, the Interposer 15 and / or on the MEMS microphone 3 a solder ring 19 and a metal pad 31. The MEMS microphone 3 has an electronic circuit 9which can be in the form of an ASIC (identified by the term ASIC), a housing 13 and a vibrating microphone membrane 7. Sound can pass through the sound inlet 5 and to the microphone membrane 7 When sound waves arrive, the microphone membrane 7 stimulated and set into vibration.

[0172] Through the electronic circuit 5 An electrical signal dependent on the sound waves is generated, whereby the sound wave quantities can be measured and / or determined. With the MEMS microphones known in the state of the art, it is not possible to measure high sound pressure levels, for example, at approximately 175 dB. The microphone membrane of the already known MEMS microphones is not designed for such high sound pressure levels. In order to measure such high sound pressure levels, the damping membrane 11which also vibrates when sound waves hit it.

[0173] The damping membrane 11 or the interposer 15 comprises a material which is elastically deformable but not plastically deformable, for example silicon, silicon oxide, silicon nitride, glass, ceramic or other organic material, wherein in the Fig. 1 The blue color is intended to represent silicon. This allows the damping membrane 11 and the microphone membrane 7 have essentially the same vibration behavior. This is a great advantage, as vibrations of the damping membrane 11 the sound pressure level undistorted to a level suitable for the microphone membrane 7 measurable range is shifted.

[0174] In particular, the signal-to-noise ratio of the measured signal is maintained. Sound pressure levels can be reduced by at least 10 dB, at least 20 dB, or at least 30 dB. This is achieved by distributing the sound energy of the sound waves to vibrations of the damping membrane. 11 and the microphone membrane 7. In addition, another major advantage of the system according to the invention is 1, that it has a small dimension. As a result, the flow behavior of the air flowing around it is essentially not affected or only slightly affected, so that accurate and unadulterated measurement results can be obtained. Furthermore, the system according to the invention has 1It has a planar design, allowing it to be integrated particularly easily and efficiently onto surfaces. Furthermore, the system 1 according to the invention forms a closed system, allowing dirt particles to be removed particularly easily and, in particular, preventing them from entering. This advantageously increases the overall component quality.

[0175] C Fig. 2 AB shows a representation of another preferred embodiment of the system according to the invention 1. The system according to the invention 1 on a circuit board 25 attached. The Fig. 2 A shows the system according to the invention 1 before attaching to the circuit board 25. The Fig. 2 B shows the system according to the invention 1, which is now connected to the circuit board 25 is mounted. The circuit carrier can be, for example, a PCB circuit board.

[0176] The inventive system 1 is connected to the circuit board 25 placed so that the MEMS microphone 3 within a cavity 27 of the circuit board, with a gap 29 between the MEMS microphone 3, the interposer 15 and / or the circuit carrier 25 can form. The cavity 27 offers optimal protection for the MEMS microphone. The MEMS microphone is located within the cavity 3 Particularly stable, robust and strong, so that stresses, for example due to displacements that could occur due to high air flow velocities, do not cause damage to the internal components of the MEMS microphone 3Furthermore, this approach allows for a very compact design, which facilitates the integration of MEMS microphones into a surface. Furthermore, cable paths are shortened and efficient transmission of electrical signals is ensured.

[0177] Fig. 3 shows a representation of a preferred embodiment with a filling of the intermediate space 29with a filler material. The filler material can comprise one or more polymers, preferably one or more cyclic, linear, branched, and / or crosslinked polysiloxanes. By filling the intermediate space with a filler material, particularly high stabilization and rear sealing of the system 1 according to the invention are achieved. In addition, the filler material preferably largely prevents any oscillation of the interposer and / or the circuit carrier. To shift the sound pressure level to a measurable range, preferably only the damping membrane is set into vibration, i.e., in particular, the area above the sound inlet opening.

[0178] Fig. 4 AB shows a representation of a preferred embodiment of the system according to the invention by attaching the damping membrane 11 on the cavity 27 of the circuit carrier 25. This is done in Fig. 4 A first the damping membrane11 above the sound inlet opening 5 of the MEMS microphone 3 Attachment can be achieved via bonding, adhesive and / or soldering processes. Fig. 4 B This is inserted into the circuit board 25 placed so that the damping membrane is within the cavity 27 This design is particularly relevant in SMD (surface-mounted device) technology. While the connecting wires of conventional components are routed through mounting holes and must be soldered on the back of the circuit board (or via inner layers), this is eliminated in SMD technology or SMD components. This enables very dense assembly and, above all, assembly on both sides of the circuit board. The electrical properties of the circuits are positively influenced, especially at higher frequencies. Furthermore, the space required for the components is reduced.

[0179] Fig. 5shows a representation of a preferred embodiment of the system according to the invention 1 by attaching the damping membrane 11 on a microphone cover 21. The microphone cover can 21 itself acts as a damping membrane. This means that the microphone cover 21 itself vibrates when sound waves are generated, thus shifting the sound pressure level, for example by approximately 20 dB. It may also be that only an area above the sound inlet 5 is set into vibration, the damping membrane 11, so that the sound pressure level remains undistorted at a level suitable for the microphone membrane 7 measurable range. On the microphone cover 21 openings can 23 which are responsible for pressure equalization between the system according to the invention 1 and its surroundings. In particular, two systems according to the invention1 on a circuit board 25. The inventive system 1 can therefore also be designed as an array to enable high-resolution sound measurements, for example in aeroacoustics.

[0180] Fig. 6 shows a representation of a further preferred embodiment of the system according to the invention by attaching a microphone cover 21 above a MEMS microphone in a top-port design. The sound impinges on the microphone diaphragm via the top of the housing 7. In particular, the rear volume of top-port versions of a MEMS microphone 3 a smaller air volume than the pre-volume. The microphone cover 21 can be in the form of a cover and / or a film made of an elastic material. Preferably, only one area of the microphone cover 21 above the sound inlet opening 5vibrate, or other lateral areas or the entire surface vibrate in order to dampen the sound pressure level from measurable areas of the microphone diaphragm 7.

[0181] Fig. 7 shows a similar representation as in Fig. 6 , However, in Fig. 7 a bottom-port version of the MEMS microphone 3 In bottom-port microphones, the microphone diaphragm is usually positioned directly above the sound inlet 5 arranged, which offers a number of advantages. In particular, the rear volume of bottom-port versions of a MEMS microphone 3 has a larger rear volume than the front volume. A large air volume in the rear volume makes it easier for the microphone diaphragm 7, to move under the influence of sound waves. This in turn improves the sensitivity and signal-to-noise ratio of the MEMS microphone 3. The response of the MEMS microphone also benefits from a back volume 3to low frequencies.

[0182] Fig. 8 shows a representation of another preferred embodiment of the system according to the invention within a wafer stack. The MEMS microphone 3 comprising the microphone membrane 7 in a first wafer 33 and the damping membrane 11 in a second wafer 35. The damping membrane 11 by forming a cavity in the second wafer 35 provided. Fig. 8 A shows the two wafers 33 and 35 before bonding and the Fig. 8 B shows the two wafers 33 and 35 after they are bonded together to form a wafer stack. In particular, this illustration shows that along the first wafer 33 an array of MEMS microphones 3 can be formed and along the second wafer 35 an array of damping membranes 11.The processing for producing the wafer stack is particularly simple. In particular, established bonding processes can be used to bond the wafers 33 and 35 to connect with each other.

[0183] Fig. 9 AD shows a preferred embodiment of the system according to the invention 1 with a modeling within the framework of an equivalent circuit diagram and simulation results regarding some parameters of the damping membrane 11.

[0184] Fig. 9 A shows a preferred embodiment of the system according to the invention 1. At the interposer 15 the cavity 17 attached so that the damping membrane 11 at the interposer 15 The damping membrane can absorb high sound pressure levels while maintaining the bandwidth for the microphone membrane. 7shift measurable ranges, for example by a shift of at least approximately 10 dB, at least approximately 20 dB, or at least approximately 30 dB or more. This is achieved by dividing the sound energy into vibrations of the microphone membrane. 7 and the damping membrane 11. A height h refers to the height or thickness of the damping membrane 11 and a parameter R its radius.

[0185] Fig. 9 B represents the same embodiment in Fig. 9 A but with an additional equivalent circuit diagram, which is used to model the system according to the invention 1At the very top of the circuit diagram, a voltage source for supplying electrical energy is shown, which in the context of the invention corresponds to a sound wave for supplying sound energy. The voltage source supplies current, which is conducted to a capacitor 37, e.g., a plate capacitor. The capacitor 37 corresponds to the damping membrane 11 of the system according to the invention. When sound waves hit, the damping membrane 11 deflected and set into vibration, whereby the damping membrane absorbs sound energy, analogous to the storage of electrical energy in a plate capacitor 37. The cavity 17 and the pre-volume can be modulated by one or more coils connected in series. The air volume in the back volume is also a factor to be considered, which is also controlled by a coil. 39 can be modeled, whereby the microphone membrane7 and a rear panel also through capacitors 37 can be modulated in the circuit diagram.

[0186] As a model of the acoustic system based on the electronic circuit diagram shows, the vibration behavior and thus the ability to reduce the sound pressure levels depends on several parameters. This is explained in the Fig. 9 C and 9 D clearly.

[0187] For the Fig. 9 C For the simulation, the thickness of the damping membrane or the plate thickness h was varied, but the radius R was kept constant. The y-axis represents the sound pressure level in negative dB, and the x-axis represents the frequency in a logarithmic representation. The simulation results demonstrate that a uniform, distortion-free reduction of the sound pressure level is possible over a wide frequency range.

[0188] The results also show that a specific sound pressure level reduction can be achieved by selecting the correct plate thickness. In particular, the sound pressure level reduction increases with the plate thickness h (the thickness of the damping membrane). Compared to the case without a damping membrane, a damping membrane with a plate thickness h of, for example, approximately 6.25 µm can reduce the sound pressure level from approximately -40 dB (without a plate) to approximately -60 dB. A plate thickness of approximately 200 µm achieves a reduction to a sound pressure level of approximately -150 dB across a wide frequency range.

[0189] In Fig. 9 d The same simulation is carried out, but now the plate thickness h kept constant at 400 µm, while the radius R the plate or damping membrane 11 is varied, which corresponds to the lateral extension of the damping membrane 11The desired reduction in sound pressure level can also be achieved by selecting the radius of the damping membrane. In particular, the smaller the radius of the damping membrane, the greater the reduction in sound pressure level.

[0190] At a radius of approximately 500 µm - which almost corresponds to the sound entrance opening - the signal is at approximately -165 dB over a wide frequency range of 100 Hz - 10 kHz, while a radius of approximately 300 µm reduces this to approximately -200 dB. LIST OF REFERENCE SYMBOLS

[0191] 1System 3MEMS microphone 5Sound inlet opening 7Microphone diaphragm 9Electronic circuit (e.g. ASIC) 11Damping diaphragm 13Housing 15Interposer 17Cavity in the interposer 19Solder ring 21Microphone cover 23Opening in the microphone cover 25Circuit carrier 27Cavity in the circuit carrier 29Gap 31Metal pad 33First wafer 35Second wafer 37Capacitor 39Coil hHeight of the damping diaphragm or plate thickness RRadius of the damping diaphragm BIBLIOGRAPHY

[0192] Martin, David T., et al. "A micromachined dual-backplate capacitive microphone for aeroacoustic measurements." Journal of Microelectromechanical Systems 16.6 (2007): 1289-1302.

[0193] Sheplak, Mark, et al. "A MEMS microphone for aeroacoustics measurements." 37th Aerospace Sciences Meeting and Exhibit. 1999.

[0194] Horowitz, Stephen, et al. "Development of a micromachined piezoelectric microphone for aeroacoustics applications." The Journal of the Acoustical Society of America 122.6 (2007): 3428-3436.

Claims

1. System (1) comprising a) a MEMS microphone (3) comprising a sound inlet opening (5), a vibratable microphone membrane (7) and an electronic circuit (9), wherein when the microphone membrane (7) is induced into vibrations by sound waves entering through the sound inlet opening (5), an electrical signal that is dependent on the sound waves is generated, and b) a damping element for reducing a sound pressure level of the sound waves acting on the microphone membrane (7) wherein the damping element comprises an elastic and vibratable damping membrane (11), which is mounted in front of the sound inlet opening (5) and, in addition to the microphone membrane (7), is induced into vibrations by the sound waves, such that sound energy of the sound waves is divided between the damping membrane (11) and the microphone membrane (7), characterized in that the division of the sound energy of the incident sound waves to the damping membrane (11) and the microphone membrane (7) leads to a reduction of the sound pressure level acting on the microphone membrane (7) by at least 10 dB and wherein the system (1) comprises an interposer (15) and the damping membrane (11) is located in the interposer (15).

2. System (1) according to the preceding claim characterized in that dividing the sound energy of the incident sound waves between the damping membrane (11) and the microphone membrane (7) leads to a reduction in the sound pressure level acting on the microphone membrane (7) by at least 20 dB, preferably by at least 30 dB.

3. System (1) according to one or more of the preceding claims characterized in that the damping membrane (11) is formed from an elastic material, preferably selected from a group comprising monocrystalline silicon, polysilicon, silicon dioxide, silicon nitride, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, indium phosphide, glass and / or a metal.

4. System (1) according to one or more of the preceding claims characterized in that the damping membrane (11) exhibits a thickness of 50 nm to 500 µm, preferably 100 nm to 200 µm, particularly preferably 1 µm to 50 µm and / or the damping membrane (11) extends at least over the sound inlet opening (5) and / or the damping membrane (11) exhibits a lateral extension of 100 µm to 2000 µm, preferably 200 µm to 1000 µm.

5. System (1) according to one or more of the preceding claims characterized in that the MEMS microphone (3) is present in a top-port or bottom-port design and / or is integrated within a multilayer substrate, preferably a wafer stack, and / or the MEMS microphone (3) is a capacitive, piezoelectric and / or piezoresistive MEMS microphone (3) and / or an electret microphone.

6. System (1) according to one or more of the preceding claims characterized in that the damping membrane (11) is formed by introducing a cavity (17) in the interposer (15), wherein preferably a depth of the cavity (17) is selected such that the damping membrane (11) formed in the interposer (15) has a thickness of 50 nm to 500 µm, preferably 100 nm to 200 µm, particularly preferably 1 µm to 50 µm and / or has a lateral extension of 100 µm to 2000 µm, preferably 200 µm to 1000 µm.

7. System (1) according to one or more of the preceding claims characterized in that the interposer (15) has a thickness of up to 1000 µm, preferably up to 700 µm, particularly preferably between 400 and 700 µm and / or the interposer (15) provides an electrical contact between the MEMS microphone (3) and a circuit carrier (25), preferably a printed circuit board.

8. System (1) according to one or more of the preceding claims characterized in that a closed electrical connection is formed between the MEMS microphone (3) and the interposer (15), preferably in the form of a solder ring (19), around the sound inlet opening (5), which provides both an electrical contact between the MEMS microphone (3) and the interposer (15) and an acoustic seal.

9. System (1) according to one or more of the preceding claims characterized in that the damping membrane (11) is integrated in or formed by a microphone cover (21), the microphone cover (21) optionally comprising an opening (23) for pressure equalization.

10. System (1) according to one or more of the preceding claims characterized in that the system comprises at least two wafers (33, 35) forming a wafer stack, wherein the MEMS microphone (3) is present in a first wafer (33) and the damping membrane (11) is formed in a second wafer (35).

11. System (1) according to one or more of the preceding claims characterized in that the MEMS microphone (3) is in contact with a circuit carrier (25), preferably a printed circuit board, wherein the circuit carrier (25), preferably a printed circuit board, exhibits a cavity (27) for receiving the MEMS microphone (3).

12. System (1) according to one or more of the preceding claims characterized in that a space (29) between the MEMS microphone (3), an interposer (15) and / or a circuit carrier (25), preferably a printed circuit board, is filled with a filling material.

13. System (1) according to the preceding claim characterized in that the filling material comprises one or more polymers, preferably one or more cyclic, linear, branched and / or cross-linked polysiloxanes.

14. Use of a system (1) according to one or more of the preceding claims for aeroacoustic measurements, preferably for measuring sound pressure waves on surfaces of a vehicle component.