METHOD FOR PRODUCING A MULTIPLE OF HIGH-PERFORMANCE MEMS CONVERTERS

Description

[0001] The invention preferably relates to a method for manufacturing a MEMS transducer comprising a membrane and a support, wherein the membrane has a meandering structure comprising vertical and horizontal sections. First, a forming component is provided which is coated with a membrane layer system. The membrane layer system comprises at least one actuator layer comprising an actuator material. By structuring the membrane layer system, membranes are provided which can be attached to a support. The forming component can be completely removed.

[0002] Furthermore, the invention preferably relates to a MEMS converter that can be manufactured using the method. Background and state of the art

[0003] Microsystems technology is now used in many application areas for the production of compact, mechanical-electronic devices. The microsystems (microelectromechanical systems, or MEMS) produced in this way are extremely compact (micrometer range) while offering excellent functionality. MEMS transducers, such as MEMS loudspeakers or MEMS microphones, are also known from the state of the art. Current MEMS loudspeakers are mostly designed as planar diaphragm systems with vertical actuation of a vibrating diaphragm in the emission direction. Excitation is achieved, for example, by means of piezoelectric, electromagnetic, or electrostatic actuators.

[0004] An electromagnetic MEMS loudspeaker for mobile devices is described in Shahosseini et al. 2015. The MEMS loudspeaker features a stiffening silicon microstructure as a sound radiator, with the moving part suspended on a support via silicon drive springs to allow large out-of-plane displacements by means of an electromagnetic motor.

[0005] Stoppel et al. (2017) describe a two-way loudspeaker whose concept is based on concentric piezoelectric actuators. A unique feature is that the diaphragm is not a closed system, but rather comprises eight piezoelectric unimorphic actuators, each consisting of a piezoelectric and a passive layer. The outer woofers consist of four trapezoidal actuators mounted on one side, while the inner tweeters are formed by four triangular actuators connected to a rigid frame by one or more springs. This diaphragm separation is intended to allow for improved sound reproduction at higher power levels.

[0006] A disadvantage of such planar MEMS loudspeakers is their limitation in terms of sound power, especially at low frequencies. One reason for this is that the achievable sound pressure level is proportional to the square of the frequency for a given excursion. Therefore, sufficient sound power requires either excursions of at least 100 µm for the vibrating diaphragms or large-area diaphragms in the square centimeter range. Both conditions are difficult to achieve using MEMS technology. The difficulties become particularly apparent in the manufacturing processes, which do not allow for efficient implementation.

[0007] Therefore, prior art has proposed designing MEMS loudspeakers that do not have a closed diaphragm vibrating in the vertical emission direction, but rather a multitude of movable elements that can be excited to lateral or horizontal vibrations. The advantage of this is that a larger volume flow can be moved within a smaller area, thus providing increased sound power.

[0008] A MEMS loudspeaker based on this principle is disclosed, for example, in US 2018 / 0179048 A1 and Kaiser et al. (2019). The MEMS loudspeaker comprises a plurality of electrostatic bending actuators arranged as vertical lamellae between a top and bottom wafer and can be excited to lateral vibrations by appropriate control. Here, an inner lamella forms an actuator electrode opposite two outer lamellae. Except for a connection point of galvanically isolated electrodes, there is an air gap between the three bent lamellae. If a potential is applied from the inside to the outside, this leads to a bilateral attraction due to the curvature of the design in the direction of a preferred direction, which is defined by an armature. The bulges of the outer lamellae provide mobility. The restoring force is provided by a mechanical spring force. A pull-push operation is therefore not possible.

[0009] A further disadvantage is that gaps between the bending actuators and the top / bottom wafers, which are necessary for their movement, lead to ventilation between the two chambers. This limits the lower cutoff frequency. Furthermore, the lateral movement of the bending actuators, and thus the sound power, is restricted to prevent a pull-in effect and acoustic penetration.

[0010] WO 2021 / 144400 A1 discloses a MEMS transducer that can be used as both a MEMS loudspeaker and a MEMS microphone. The MEMS transducer described therein has a vibrating diaphragm constructed such that it comprises two or more vertical sections, which are essentially parallel to the vertical direction. Furthermore, the vibrating diaphragm includes at least one layer of an actuator material and is end-contacted with at least one electrode. This allows the vertical sections to be excited to horizontal vibrations by driving the electrode. Conversely, an electrical signal can also be generated at the electrode when the vertical sections are excited to horizontal vibrations.

[0011] The MEMS transducer disclosed in WO 2021 / 144400 A1 exhibits significant improvements over the prior art. The design of the vibrating diaphragm, encompassing the vertical sections, advantageously results in higher sound power in the case of a MEMS loudspeaker. Similarly, in the case of a MEMS microphone, it advantageously achieves higher performance and audio quality with a suitable sound signature. Furthermore, the MEMS transducer can be manufactured using established semiconductor processing methods, thus enabling cost-effective production.

[0012] The MEMS transducer disclosed in WO 2021 / 144400 A1 is preferably manufactured by etching a substrate, preferably from a front side, to form a meandering structure. At least two layers are then applied, wherein at least one first layer comprises an actuator material and a second layer a mechanical support material, or wherein at least two layers are coated with an actuator material. Subsequently, the first and / or the second layer is contacted with an electrode.

[0013] There is a need for optimization regarding the manufacturing process of the MEMS transducer disclosed in WO 2021 / 144400 A1. In particular, the etching of the substrate, which provides a support for the vibrating membrane, is complex. Etching of the substrate is preferably carried out by DRIE etching, which, however, is costly. Furthermore, DRIE etching has limitations regarding the selection of sacrificial layers (stop oxides) and the ability to achieve different etching depths. An alternative method for providing a support by wet-chemical KOH (potassium hydroxide) etching requires a larger spatial area, resulting in a larger build volume and a loss of compactness in the MEMS transducer.Especially when manufacturing a large number of MEMS transducers, the larger space requirement for the support frame between the individual MEMS transducers leads to less efficient use of the wafer and higher costs.

[0014] German patent DE 102017115923 A1 discloses a method for manufacturing a MEMS transducer with a structured membrane. In this process, a negative mold is provided by a substrate and, optionally, a sacrificial layer, which defines the membrane's structure. The substrate or negative mold has recesses that correspond to the wave crests and troughs of the membrane. Subsequently, an electrically conductive layer and a piezoelectric layer are deposited onto the negative mold, forming a membrane with a side complementary to the negative mold. In further process steps, electrodes are electrically connected to the membrane at the wave crests and troughs. To expose the membrane, a portion of the substrate and the optionally applied sacrificial layer is removed by back-side etching. The remaining portion of the substrate forms a holder or support for the membrane.

[0015] EP 3218303 B1 discloses a method for manufacturing a large number of MEMS packages. The package comprises a base structure with an embedded chip, a MEMS component, and a cover structure. A through-hole provides a fluid connection between the MEMS component and the package's surroundings. The package's design is well-suited for batch manufacturing. For this purpose, multiple chips can be embedded in a base master structure, and correspondingly, multiple MEMS components can be mounted on the base master structure. After covering the resulting assembly with a cover master structure, a preform for a large number of packages is obtained. By creating separation or cutting lines, the assembly is individualized, resulting in several separate packages.

[0016] However, neither DE 102017115923 A1 nor EP 3218303 B1 offer suggestions for improving the manufacturing process of a folded membrane MEMS transducer according to WO 2021 / 144400 A1 in order to avoid a complex back-side etching process or to achieve a smaller space requirement.

[0017] In light of the current state of the art, there is therefore a need to offer improved or alternative methods for manufacturing a MEMS transducer. Object of the invention

[0018] The object of the invention was to eliminate the disadvantages of the prior art. In particular, it was an object of the invention to provide a method for manufacturing MEMS transducers that is characterized by high process efficiency and cost-effectiveness, low susceptibility to errors, is easily scalable, and ensures the production of MEMS transducers that are characterized by excellent acoustic properties and compact dimensions. Summary of the invention

[0019] The object of the invention is solved by the independent claims. Advantageous embodiments of the invention are disclosed in the dependent claims.

[0020] In a first aspect, the invention relates to a method for manufacturing at least one MEMS transducer for interacting with a volume flow of a fluid comprising a support and a membrane for generating or receiving pressure waves of the fluid in a vertical direction, which is held by the support, wherein the membrane has a meandering structure with vertical sections and horizontal sections, wherein the vertical sections are essentially parallel to the vertical direction and the horizontal sections connect the vertical sections together, wherein the membrane comprises at least one actuator layer made of an actuator material and is in contact with at least one electrode, such that by actuating the at least one electrode the vertical sections can be excited to horizontal vibrations or such that when the vertical sections are excited to horizontal vibrations an electrical signal can be generated at the at least one electrode, characterized in that the method comprises the following steps: a) Provision of a shaping component, b) Coating of the shaping component with a membrane layer system comprising at least the actuator layer, wherein the membrane layer system, after coating on the shaping component, has the meander structure comprising vertical sections and horizontal sections, c) Provision of the membrane by structuring the membrane layer system, d) Complete removal of the shaping component, e) Attachment of the membrane to the support so that the membrane is held by the support.

[0021] The inventors recognized that the preferred method for manufacturing a MEMS transducer achieves significant improvements in many aspects. In particular, the complete elimination of the shaping component has a highly beneficial effect on both the efficiency of the manufacturing process and the MEMS transducer that can be produced.

[0022] Firstly, it eliminates the need to use multiple etching processes to provide a substrate to which the membrane for generating or receiving pressure waves is attached.

[0023] Instead, a (temporary) shaping component is provided, which can be completely removed after coating to form a membrane layer system. This represents a significant difference compared to, for example, the method disclosed in WO 2021 / 144400 A1 for the fabrication of a MEMS transducer. In that method, it is proposed to structure a substrate prior to coating it with a membrane layer system, with frame regions of the substrate forming a support for the membrane. For this purpose, a starting substrate is etched from a front side, e.g., by DRIE etching, to provide a structure on the substrate congruent with the meandering structure of the membrane.Subsequently, coating processes are carried out to apply the membrane layers, and then the membrane is exposed again section by section through further DRIE etching, leaving a frame of the substrate intact to form the support. Complete removal of the substrate from the back using a simple etching process is not possible in this process design, as otherwise no support could be provided.

[0024] According to the invention, it was discovered that by attaching the membrane to a separate carrier, the shaping component can be dispensed with and complete (rear) removal is possible. The apparent disadvantage of providing a separate carrier is offset by a number of advantages, which are particularly associated with the possible complete removal of the shaping component.

[0025] This eliminates the need for complex DRIE etching to expose the membrane from the back. Instead, a (cost-effective) and highly selective wet chemical etching process can be used. In this respect, separate grinding steps prior to DRIE etching are also advantageously unnecessary.

[0026] Because the shaping component is completely removed and no external support is required, a large number of MEMS transducers can be positioned extremely compactly on the wafer during manufacturing. Increased spacing of the individual chips is necessary to accommodate the increased space requirements if a support is to remain as a frame during KOH etching (see...). Fig. 1C , D Dicing is not necessary. Similarly, dicing can be omitted when manufacturing a large number of MEMS migrates on a wafer.

[0027] The solution according to the invention thus advantageously saves time and costs, so that a higher number of MEMS transducers can be produced with less material in a shorter time.

[0028] The preferred process steps a) - e) are not limited to the above sequence to achieve the advantages. Preferably, depending on the embodiment and the aspects of the invention, steps a) - e) can be carried out, for example, overlapping in time, simultaneously, or in another sequence.

[0029] For example, it may be preferable, after coating the membrane layer system onto the shaping component, to structure it and connect it to a support structure, thereby enabling stabilization to reliably and completely remove the shaping component. Advantageously, a single process step—namely, the complete removal of the shaping component—provides a large number of membranes that are initially stabilized on a support structure but can then be transported from it to a carrier and attached. Therefore, it may be preferable that step d), the complete removal of the shaping component, and step e), the attachment of the (individual) membranes to individual carriers, are carried out after step c), the structuring of the membrane layer system to provide individual membranes.

[0030] It may also be preferred that the membrane layer system is structured to provide one or more membranes (step c) after the membrane layer system has been connected to a support structure (step e). In this case, the membrane layer system is preferably attached to a support structure before the complete removal of the forming components (step d), which provide the individual membranes. By attaching the membrane layer system to a support structure before the complete removal of the forming component, a separate support structure can be dispensed with. After the removal of the forming component, individual membranes are provided on individual supports by selectively separating the support structure.

[0031] The following explanations of the individual process steps therefore apply to different combinations of the sequence of process steps and are not limited to the sequence chosen for illustrative purposes.

[0032] As a first step, it may be preferable to provide the shaping component. Preferably, the shaping component is provided (structured) such that a meander structure congruent with the desired meander structure of the membrane is present on an accessible side, preferably a front side. The structure of the shaping component thus preferably defines the meander structure of the membrane. In other words, the shaping component can also be described as a template or matrix for shaping the membrane layer system.

[0033] Preferably, the shaping structure has such a structure that, after coating the membrane layer system, a meandering structure comprising vertical and horizontal sections is present. Preferably, the shaping component can be configured as a comb-like substrate comprising comb fingers and empty areas, so that a membrane folded congruent with the comb structure can be provided during coating of the membrane layer system (see Fig. 2A Preferably, the shaping structure forms a negative mold for the membrane layer system and thus, in particular, for the membrane resulting from the membrane layer system. By coating the membrane layer system onto the shaping structure, the membrane layer system exhibits a geometric configuration congruent with the shaping structure.

[0034] The shaping structure can be provided by structuring a (semiconductor) substrate, for example, by DRIE etching of a substrate to create the comb fingers and voids for the comb structure substrate as the shaping structure. After providing the shaping component, the membrane layer system is preferably coated. The comb structure substrate preferably comprises a main strand, comb fingers, and voids. The comb fingers are sections that are essentially orthogonal to the main strand and are separated from each other by the voids. The main strand can thus be considered a support for the comb fingers. The voids preferably are sections in which no substrate material is present. The comb structure substrate is preferably provided by an etching process.In this process, a (semiconductor) substrate is preferably etched starting from a front side, leaving cavities on the substrate, with the cavities in turn forming the empty areas, while the unetched sections act as comb fingers.

[0035] The meandering structure of the membrane can be adjusted, in particular, by the dimensions of the shaping component, e.g., as a comb-like substrate. The length of the comb fingers of a comb-like substrate preferably corresponds to the length of the vertical sections of the membrane. The width of the comb fingers determines the width of the horizontal sections that connect the vertical sections at their (front) upper region. The width of the gaps corresponds to the width of the horizontal sections that connect the vertical sections at their lower region. By providing a comb-like substrate in which the width of the comb fingers is equal to the width of the gaps or intermediate sections, horizontal sections of equal length can preferably be ensured for the membrane.

[0036] In the context of the invention, the membrane layer system preferably refers to one or more layers that serve to provide the membrane of the MEMS transducer. The membrane layer system particularly comprises a layer or layer containing an actuator material, which is referred to as the actuator layer. This layer will be explained in more detail below and is used in particular for generating or detecting vibrations of the membrane. The terms "layer" and "layer" can be used synonymously in the context of the invention. Preferably, in addition to the actuator layer, the membrane layer system comprises further layers, in particular a top electrode, a bottom electrode, and / or a mechanical support layer. Furthermore, the membrane layer system may preferably include a sacrificial layer, which is preferably applied to the shaping component before the application of further layers of the membrane layer system.

[0037] By simply structuring the membrane layer system, breaks can preferably be provided that define end regions for the membranes that can be attached to the support. By coating the shaping component, a membrane layer system for a multitude of membranes can thus advantageously be provided simultaneously, the dimensions of which can be determined by the shaping component on the one hand and the subsequent structuring on the other. In other words, the structuring of the membrane layer system preferably comprises the formation of breaks, thereby singulating or separating the membrane layer system into membranes. For the purposes of the invention, the singulated sections of the membrane layer system obtained by structuring are preferably already referred to as membranes before a shaping component is removed and / or the membranes are attached to a support.

[0038] A membrane is preferably formed from the membrane layer system by structuring, whereby the membrane is preferably already present when it is still applied to the forming component or has not yet been released. By completely removing the forming component and attaching the membrane to a support, the membrane is released, and its ability to vibrate is ensured as a functional property of the membrane for the MEMS transducer. In its structural configuration, however, the membrane as a preform is preferably already present after the structuring of the membrane layer system.

[0039] Preferably, the membrane layer system is coated starting from a front side. The front side of the forming component preferably refers to the side on which the forming component has a structure (for example, a comb structure) onto which the membrane layer system is to be formed by coating. Preferably, the forming component is provided such that it has a correspondingly structured front side, while the back side of the forming component is unstructured.

[0040] The complete removal of the shaping component preferably begins from the back side of the shaping component. The back side of the shaping component preferably refers to the side facing away from the membrane layer system.

[0041] The membrane is preferably attached to a carrier from the front, so that the front of the membrane again faces a sound opening in the carrier and thus preferably indicates a direction of sound emission or sound detection of the finished MEMS transducer.

[0042] Preferably, the complete removal of the shaping component is achieved using a wet chemical etching process. This advantageously allows for the use of thinner sacrificial layers than would be necessary with a DRIE etching process, resulting in significant material savings. Furthermore, the use of wet chemical etching processes offers a wider selection of materials for the sacrificial layer, which has an additional positive impact on cost-effectiveness.

[0043] Furthermore, there is increased design flexibility with regard to the configuration of the vertical and / or horizontal sections of the preferred MEMS transducer. In particular, any limitations associated with a rear-side cutout of the membrane are eliminated, since wet chemical etching processes for the complete removal of the shaping component can be efficiently carried out for any length and / or width of the vertical and / or horizontal sections.

[0044] In the context of the invention, the complete removal of the forming component preferably means a removal in which no functional components of the forming component (for example, as a support) remain. The average person skilled in the art knows that after complete removal of the forming component, it cannot be ruled out that minor components may still remain. However, it is preferred that the forming component is substantially completely removed during its complete removal.

[0045] Terms such as "essentially", "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 particularly less than ± 1%, and especially include the exact value. "Similarly" preferably describes quantities that are approximately equal. "Partially" preferably describes at least 5%, particularly preferably at least 10%, and particularly at least 20%, and in some cases at least 40%.

[0046] In contrast to the disclosure of DE 102017115923 A1 (or WO 2021 / 144400 A1), the forming component is completely removed in the context of the invention. DE 102017115923 A1 describes the partial removal of a negative mold for the membrane, which would be comparable to the forming component, so that a holder or support for the membrane is obtained after the partial removal. However, the method according to the invention differs from the disclosure of DE 102017115923 A1, particularly in that the forming component is completely removed. In other words, the invention provides for a structural and functional decoupling of a forming component and a support. This preferably means that separate components are used to carry out the structural shaping of the membrane and to provide a holder for the membrane.As described above, the inventors recognized that providing a separate shaping component and a carrier offers several advantages in the manufacturing process, which outweigh any potential disadvantages. Firstly, the shaping component can be removed more easily and cost-effectively from the back. Secondly, a wafer can be used particularly efficiently, especially when manufacturing a large number of MEMS transducers. Therefore, in accordance with the invention, the shaping component is not used as a carrier or holder for the membrane in the finished MEMS transducer, but rather serves primarily as a (temporary) aid for the geometric shaping of the membrane and for applying the membrane layer system.

[0047] The membrane can preferably be attached to the substrate by transferring the membrane from a support structure to a substrate. As explained below, a component suitable for removing (individual) membranes from the support structure and applying them to a substrate on which, for example, a conductive adhesive is present for contacting.

[0048] It may also be preferred that a support structure is attached to the membranes and the membrane layer system before the forming component is removed. After the forming component is removed, the support structure serves to stabilize the membrane(s) or the membrane layer system. An additional support structure is not necessary. By appropriately separating the support structure (with the attached membranes or the membrane layer system), several MEMS transducers can thus be obtained, with each support holding one membrane. In the finished MEMS transducer, the support preferably serves both to suspend the membrane and to provide electrical contacts for it. For this purpose, the support may preferably also have vias that can be used as such and / or as re-contacts to apply or acquire electrical signals.

[0049] By separating the process-related provision of a shaping component for forming the membrane layer system or the membrane from a separate support onto which the membrane is later attached, there is increased freedom with regard to the selection or design of the support.

[0050] The preferred method also has a beneficial effect on the MEMS transducer itself. Membranes can be fabricated from the membrane layer system onto a freely selectable substrate, for example, after removal from a support structure or by cutting them out of a substrate. The increased flexibility with regard to suspending or contacting the end-face areas of the membrane on the substrate allows for the production of particularly compact MEMS transducers, whose acoustic coupling can also be optimized.

[0051] For example, it may be preferable to mount the membrane onto a support using a conductive process material that allows both electrical contact and provides an acoustic seal. Furthermore, the back volume can be varied depending on the dimensions of a preferred cover, depending on the desired application. Advantageously, the preferred method thus provides a MEMS transducer that is particularly suitable with regard to acoustic requirements.

[0052] The design of the MEMS transducer that can be manufactured using this method advantageously combines the possibility of high sound power with simplified control.

[0053] Unlike conventional planar MEMS loudspeakers, the vibrating diaphragm itself does not need to cover a large area of ​​several square centimeters or be operated with displacements exceeding 100 µm to generate sufficient sound pressure. Instead, the majority of the vertical sections of the vibrating diaphragm can move an increased total volume in the vertical emission direction with small horizontal or lateral movements of just a few micrometers.

[0054] Simultaneously, simplified control can be achieved. While prior art technology requires contacting numerous piezoelectric actuators on the horizontal sections, the MEMS transducer described here can be operated using at least one electrode, preferably at the end. This reduces manufacturing effort, minimizes potential sources of error, and inherently results in synchronous control of the vertical sections relative to the horizontal oscillations.

[0055] In this way, the air volumes located between the vertical sections can be moved with extreme precision by the horizontal vibrations along the vertical emission direction.

[0056] This approach also enables the provision of a particularly powerful MEMS microphone with high audio quality. The MEMS microphone's structure is similar to that of the MEMS loudspeaker, especially regarding the design of the vibrating diaphragm. However, instead of driving the electrodes to generate horizontal vibrations and thus sound pressure waves, the MEMS microphone is designed to detect sound pressure waves in the same vertical direction. Preferably, air volumes are located between the vertical sections, which are moved along a vertical detection direction when sound waves are detected. The sound pressure waves excite the vertical sections to horizontal vibrations, causing the actuator material to generate a corresponding periodic electrical signal that can be read out by an electronic circuit.

[0057] The term MEMS transducer encompasses both MEMS microphones and MEMS loudspeakers. Generally, a MEMS transducer is a transducer for interacting with a fluid flow, based on MEMS technology, whose structures for interacting with the fluid flow or for capturing or generating pressure waves from the fluid have dimensions in the micrometer range (1 µm to 1,000 µm). The fluid can be either gaseous or liquid. The structures of the MEMS transducer, particularly the vibrating diaphragm, are designed to generate or capture pressure waves from the fluid.

[0058] For example, as in the case of a MEMS loudspeaker or MEMS microphone, the pressure waves can be sound pressure waves. However, the MEMS transducer can also function as an actuator or sensor for other pressure waves. Thus, the MEMS transducer is preferably a device or instrument that converts pressure waves (e.g., acoustic signals as alternating sound pressures) into electrical signals or vice versa (conversion of electrical signals into pressure waves, for example, acoustic signals).

[0059] MEMS transducers can also be used as energy harvesters, utilizing pneumatic or hydraulic pressure changes. In these cases, the electrical signal can be extracted as recovered electrical energy, stored, or supplied to other (consumer) devices.

[0060] A MEMS loudspeaker preferably refers to a loudspeaker based on MEMS technology whose sound-generating structures have dimensions in the micrometer range (1 µm to 1000 µm), at least partially. Preferably, for example, the vertical sections of the vibrating diaphragm can have dimensions of less than 1000 µm in width, height, and / or thickness. It may also be preferred that, for example, only the height of the vertical sections is dimensioned in the micrometer range, while the length can be larger and / or the thickness smaller.

[0061] A MEMS microphone preferably refers to a microphone based on MEMS technology whose sound-receiving structures have dimensions in the micrometer range (1 µm to 1000 µm), at least partially. Preferably, for example, the vertical sections of the vibrating diaphragm can have dimensions of less than 1000 µm in width, height, and / or thickness. It may also be preferred that, for example, only the height of the vertical sections is dimensioned in the micrometer range, while the length can be larger and / or the thickness smaller.

[0062] Preferably, the MEMS transducer comprises a vibrating diaphragm for generating or receiving pressure waves of the fluid in a vertical direction. The vibrating diaphragm is thus defined as the structure that enables the generation of an electrical signal after the reception of pressure waves or the generation of pressure waves by applying an electrical signal. It is preferred that the vibrating diaphragm has at least one actuator layer made of an actuator material. Preferably, the vibrating diaphragm is structured such that it has a meandering structure comprising vertical and horizontal sections.

[0063] A meandering structure preferably refers to a structure formed from a sequence of essentially orthogonal sections in cross-section. These orthogonal sections are preferably vertical and horizontal sections of the vibrating membrane. A rectangular cross-section of the meandering structure is particularly preferred. However, it may also be preferred that the meandering structure has a sawtooth (zigzag) cross-section or is curved or wave-shaped. This is particularly the case if the vertical sections are not aligned exactly parallel to the vertical emission or detection direction, but rather form an angle, for example, of ± 30°, preferably ± 20°, and particularly preferably ± 10° with the vertical direction.

[0064] In preferred embodiments, the horizontal sections may also not be positioned exactly at an orthogonal angle of 90° to the vertical emission or detection direction, but may, for example, form an angle between 60° and 120°, preferably between 70° and 110°, and particularly preferably between 80° and 100° with the vertical direction.

[0065] Preferably, the vertical and / or horizontal sections are straight at least partially or along their entire length; however, the vertical and / or horizontal sections may also be curved at least partially or along their entire length. In the case of a curved or wavy shape of the vertical and / or horizontal sections of the vibrating membrane in cross-section, the orientation preferably refers to a tangent to the vertical and / or horizontal sections at their respective midpoints.

[0066] The appropriate shape of the membrane(s) can be ensured by designing the shaping component as described above.

[0067] While the vibrating membrane is preferably oriented horizontally to the direction of sound emission or sound detection, the sound waves are generated by an actuation of the vertical sections or, conversely, detected.

[0068] Preferably, the layer of actuator material in the vertical sections serves as a component of a mechanical bimorph, wherein lateral curvature of the vertical sections is caused by controlling the actuator layer via the electrode, or wherein a corresponding electrical signal is generated by an induced lateral curvature. A bimorph preferably refers to a structure comprising two layers, wherein a displacement and / or curvature is enabled by the interaction of the two layers.

[0069] The meandering structure preferably corresponds to a membrane folded along its width. In accordance with the invention, a vibrating membrane can therefore preferably also be referred to as a bellows. The parallel folds of the bellows preferably form the vertical sections. The connecting sections between the folds preferably form the horizontal sections. Preferably, the vertical sections are longer than the horizontal sections, for example by a factor of 1.5, 2, 3, 4 or more. The horizontal sections preferably denote those structures that enable a connection between two or more vertical sections.

[0070] The performance of the MEMS transducer, especially of a MEMS loudspeaker or MEMS microphone, can be significantly determined by the number and / or dimensions of the vertical sections.

[0071] In preferred embodiments, the vibrating membrane comprises more than 3, 4, 5, 10, 15, 20, 30, 40, 50, 100 or more vertical sections.

[0072] In further preferred embodiments, the vibrating membrane comprises fewer than 10000, 5000, 2000 or 1000 or fewer vertical sections.

[0073] The preferred number of vertical sections results in high sound power on the smallest chip surfaces, without compromising the sound image or audio quality.

[0074] Preferably, the vertical sections are planar, meaning in particular that their extent in each of the two dimensions (height, width) of their surface is greater than in a dimension perpendicular to these (thickness). For example, size ratios of at least 2:1, preferably at least 5:1, 10:1 or more, may be preferred.

[0075] In accordance with the invention, the height of the vertical sections preferably corresponds to the dimension along the direction of sound emission or sound detection, while the thickness of the vertical sections preferably corresponds to the sum of the layer thicknesses of the one or more layers that form the vertical sections. The length of the vertical sections preferably corresponds to a dimension orthogonal to the height or thickness. In the cross-sectional views of the figures shown below, the height and thickness are represented schematically (not necessarily to scale), while the length dimension corresponds to a (non-visible) drawing depth of the figures.

[0076] In a preferred embodiment, the height of the vertical sections is between 1 µm and 1000 µm, preferably between 10 µm and 500 µm. Intermediate ranges from the aforementioned ranges may also be preferred, such as 1 µm to 10 µm, 10 µm to 50 µm, 50 µm to 100 µm, 100 µm to 200 µm, 200 µm to 300 µm, 300 µm to 400 µm, 400 µm to 500 µm, 600 µm to 700 µm, 700 µm to 800 µm, 800 µm to 900 µm or even 900 µm to 1000 µm. A person skilled in the art will recognize that the aforementioned range limits can also be combined to obtain further preferred ranges, such as 10 µm to 200 µm, 50 µm to 300 µm or 100 µm to 600 µm.

[0077] In a preferred embodiment, the thickness of the vertical sections is between 100 nm and 10 µm, preferably between 500 nm and 5 µm. Intermediate ranges from the aforementioned ranges are also preferred, such as 100 nm to 500 nm, 500 nm to 1 µm, 1 µm to 1.5 µm, 1.5 µm to 2 µm, 2 µm to 3 µm, 3 µm to 4 µm, 4 µm to 5 µm, 5 µm to 6 µm, 6 µm to 7 µm, 7 µm to 8 µm, 8 µm to 9 µm, or even 9 µm to 10 µm. A person skilled in the art will recognize that the aforementioned range limits can also be combined to obtain further preferred ranges, such as 500 nm to 3 µm, 1 µm to 5 µm or 1500 nm to 6 µm.

[0078] In a preferred embodiment, the length of the vertical sections is between 10 µm and 10 mm, preferably between 100 µm and 1 mm. Intermediate ranges from the aforementioned ranges are also preferred, such as 10 µm to 100 µm, 100 µm to 200 µm, 200 µm to 300 µm, 300 µm to 400 µm, 400 µm to 500 µm, 500 µm to 1000 µm, 1 mm to 2 mm, 3 mm to 4 mm, 4 mm to 5 mm, 5 mm to 8 mm, or even 8 mm to 10 mm. A person skilled in the art will recognize that the aforementioned range limits can also be combined to obtain further preferred ranges, such as 10 µm to 500 µm, 500 µm to 5 µm or 1 mm to 5 mm.

[0079] With the aforementioned preferred dimensions of the vibrating diaphragm or the vertical sections, a particularly compact MEMS transducer, especially a MEMS loudspeaker or MEMS microphone, can be provided, which simultaneously combines high performance with excellent sound image or audio quality. Advantageously, the aforementioned dimensions can be achieved particularly easily through a corresponding design of the shaping component. Preferably, the structure of the shaping component determines the structure of the vibrating diaphragm comprising vertical and horizontal sections.

[0080] The directional terms vertical and horizontal (or lateral) preferably refer to a preferred direction in which the vibrating membrane is oriented to generate or receive pressure waves from the fluid. Preferably, the vibrating membrane is suspended horizontally between at least two areas of a support, while the vertical direction (interaction direction with the fluid) for generating or receiving pressure waves is orthogonal to this. In the case of a MEMS loudspeaker, the vertical (interaction) direction corresponds to the vertical sound emission direction of the MEMS loudspeaker. In this case, vertical preferably means the direction of sound emission, while horizontal means a direction orthogonal to it. In the case of a MEMS microphone, the vertical (interaction) direction corresponds to the vertical sound detection direction of the MEMS microphone. In this case, vertical preferably means the direction of sound detection.Intake, while horizontal refers to a direction orthogonal to it.

[0081] In a further preferred embodiment, the method is characterized in that a plurality of MEMS transducers are produced, wherein, for the production of the plurality of MEMS transducers, the membrane layer system is structured on the forming component to form individual membranes, wherein the individual membranes are particularly preferably separated by interruptions, which are preferably formed entirely after the coating of the membrane layer system or layer by layer.

[0082] The increased process efficiency of the method is particularly evident in the ability to efficiently produce a large number of MEMS transducers, preferably starting from a forming component or a substrate as the forming component. A plurality of MEMS transducers preferably means 2, 3, 4, 5, 10, 20, 50, 100, 500, 1000 or more MEMS transducers.

[0083] The majority of MEMS transducers can preferably be provided by means of a forming component, wherein a membrane layer system is preferably first applied to the structured front surface of the forming component. Subsequently, to define the individual membrane, the membrane layer system can be (laterally) structured by creating discontinuities. A discontinuity preferably refers to an area in which one or more (preferably all) layers of the membrane layer system are removed. Particularly preferably, these are linear discontinuities, which, in the case of the forming component being designed as a comb structure, are created on the comb fingers. The discontinuities are thus located in the area of ​​horizontal sections of the membrane that connect the vertical sections at the front end.The interruptions are preferably essentially line-shaped and characterized by a small line width. Preferably, the interruptions have line widths of less than 50 µm, more preferably less than 30 µm, 20 µm, 10 µm, 5 µm, 2 µm or even less than 1 µm.

[0084] The interruptions allow the dimensioning and / or number of individual membranes to be formed from the membrane layer system to be determined.

[0085] Particularly preferably, an array of membranes can be defined by appropriately forming interruptions, the extent of which is determined by the dimensions of the forming component. For example, it may be preferred to form a suitably dimensioned array of membranes on a structured forming component with square dimensions in a range of 10 mm to 500 mm. For a membrane width and length of 1 mm each, for example, an array of 10x10 to 500x500 membranes can be formed, depending on the size of the forming component.

[0086] The formation of the discontinuities can be achieved using known methods of the prior art, for example, by etching processes. In this case, the discontinuities can be created all at once after the membrane layer system has been coated, whereby several (preferably all) layers of the membrane layer system are structured in a single step. It may also be preferable to form the discontinuities layer by layer. That is, after each layer of the membrane layer system has been coated, lateral structuring is immediately carried out by selectively removing the layer at the discontinuities to be formed.

[0087] Advantageously, the membranes can be formed extremely efficiently on the shaping component using only thin, linear interruptions, so that the provision of the majority of membranes and corresponding majority of MEMS transducers is associated with very low material costs.

[0088] In a further preferred embodiment, the method is characterized in that the shaping component is provided by applying a dry etching process and / or a wet chemical etching process to a substrate, wherein the dry etching process is preferably a physical, a chemical and / or a physicochemical dry etching process, wherein the dry etching process is particularly preferably selected from a group comprising reactive ion etching (RIE) and / or reactive ion deep etching (DRIE), wherein a KOH etching process is preferably used as the wet chemical etching process.

[0089] In semiconductor and microsystems technology, dry etching encompasses a group of subtractive microstructuring processes that are not based on wet chemical reactions (such as wet chemical etching). Material removal is achieved either through accelerated particles or using plasma-activated gases. Thus, depending on the specific process, chemical, physical, or physicochemical effects are utilized.

[0090] Reactive ion etching (RIE) is an ion-assisted reactivity process. Due to the precise controllability of the etching behavior, RIE is a method for fabricating topographic structures in micro-, semiconductor, and nanosystem technology. The process allows for both isotropic (direction-independent) and anisotropic etching through physicochemical ablation. Etching is achieved using charged particles (ions) generated in a gas plasma. Appropriate masking of the surface (e.g., created by photolithography) determines the shape of the structures. For example, masks can be used to create cavities and thus voids on a substrate, with the unetched areas representing the comb-like fingers of a comb-like substrate as a shaping element.

[0091] Deep reactive ion etching (DRIE) is an advancement of reactive ion etching (RIE) and a highly anisotropic dry etching process for fabricating microstructures in substrates with an aspect ratio of up to 50:1, achieving structure depths of several hundred micrometers. The DRIE process is a two-stage, alternating dry etching process in which etching and passivation steps alternate. The goal is to etch as anisotropically as possible, meaning directionally dependent, perpendicular to the substrate surface. In this way, for example, very narrow cavities or depressions can be etched. Advantageously, particularly narrow comb fingers and / or empty areas of the comb-structure substrate can be used as shaping components, which can be translated into narrow vertical and / or horizontal sections of the membrane(s).

[0092] Wet chemical etching is preferably carried out using a liquid reactant. This can be a chemical that dissolves the shaping component to be etched or a chemical mixture that first oxidizes the shaping component and then dissolves the oxide. Preferably, the reactant can be a stronger acid, e.g., hydrofluoric acid for a silicon substrate, or a weaker acid, e.g., citric acid for a gallium arsenide substrate. In the context of the invention, KOH etching has proven particularly advantageous for providing the shaping component. Wet chemical etching processes are advantageously fast, allowing high etch rates to be achieved and reducing the process time of the preferred method. High selectivity can also be advantageously achieved with simple means for carrying out the wet chemical etching process, e.g., with baths and / or wet chemical sprays.

[0093] The aforementioned etching processes are known to those skilled in the art and can be advantageously applied in preferred embodiments of the process. In particular, the aforementioned etching processes are suitable for providing a structure on a substrate for the formation of the shaping component that is congruent to the meandering structure of the membrane, wherein the meandering structure preferably results after coating the shaping component with the membrane layer system.

[0094] Depending on the desired structure of the shaping component, depressions can be created in a provided substrate to achieve the desired meandering membrane structure. Etching processes can advantageously be selected that ensure efficient execution and optimal shaping of the membrane layer system. For example, potassium hydroxide (KOH etching) exhibits a clear preference for etching along a specific direction. <110> Orientation (notation for Miller indices) of a silicon crystal versus a <111> Orientation is key. This allows etching rates to be selected to enable particularly fast provision of the shaping component.

[0095] In a further preferred embodiment, the method is characterized in that the shaping component comprises a material selected from the group consisting of monosilicon, polysilicon, silicon dioxide, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, indium phosphide, and glass. Preferably, the shaping component is formed by structuring a substrate. The structuring can, for example, result in a comb-structured substrate as the shaping component, the structuring preferably being carried out by etching. Preferably, the material of the shaping component is a semiconductor material, so that a semiconductor substrate (wafer) can be used to structure it and thus provide the shaping component. The average person skilled in the art knows that the terms "wafer" and "(semiconductor) substrate" can be used synonymously.

[0096] The aforementioned materials are particularly easy and cost-effective to process in semiconductor and / or microsystems technology and are also well-suited for mass production. Likewise, these materials are especially well-suited for doping and / or coating to achieve a desired temporary stable bond with the membrane layer system and / or to enable optimal, essentially complete removal. The preferred aforementioned materials for the shaping component offer numerous advantages due to the applicability of standardized process techniques.

[0097] The structure and dimensions of the forming component are selected according to the desired number and dimensions of the membranes. For example, the forming component can have a characteristic surface area (e.g., diameter, length, and / or width) ranging from 10 mm to 500 mm, while its thickness or height (greatest dimension perpendicular to the surface) ranges from 100 µm to 1000 µm. A comb-like structure, as described above, is incorporated with appropriate dimensions to form the desired membrane with a meandering pattern. Due to the macroscopic surface area, a large number of membranes can be accommodated on a single forming component.

[0098] In a further preferred embodiment, the method is characterized in that the shaping component is completely removed by a wet chemical etching process, wherein the wet chemical etching process is preferably selected from a group comprising KOH and / or TMAH etching.

[0099] Advantageously, the use of a wet chemical etching process allows for the application of thinner sacrificial layers, thus saving material for the sacrificial layers and thereby improving the process efficiency of the preferred method. Furthermore, the wet chemical etching process is simple and controllable, ensuring reliable and complete removal of the shaping component. The high selectivity of the wet chemical etching process is also advantageous, minimizing the risk of unwanted etching, damage, and / or potential contamination.

[0100] Furthermore, it is advantageous to avoid multiple runs of dry etching processes and / or physicochemical etching processes, such as DRIE etching, which are time-consuming and costly. A single wet chemical etching process thus achieves significantly increased process efficiency.

[0101] In wet chemical etching processes, the chemical bonds of the shaping component are preferably broken by etching media and converted into soluble components. KOH and / or TMAH etching has proven to be particularly suitable etching processes in the context of the invention.

[0102] In KOH etching, potassium hydroxide (KOH) in solution is preferably used to remove the shaping component almost completely. In TMAH etching, a solution comprising tetramethylammonium hydroxide (TMAH) is preferably used. Both wet-chemical etching processes advantageously exhibit excellent selectivity with respect to the material selection for the sacrificial layer and / or shaping component.

[0103] In further preferred embodiments, the complete removal of the shaping component is carried out by a dry etching process, wherein the dry etching process is preferably a physical, a chemical and / or a physicochemical dry etching process, wherein the dry etching process is particularly preferably selected from a group comprising reactive ion etching (RIE) and / or reactive ion deep etching (DRIE).

[0104] It may also be preferable to completely remove the shaping component by a vapor etching process (etching using an etchant as a vapor or gas). For example, xenon difluoride vapor etching (XeF₂ vapor etching) can be used as a vapor etching process. Isotropic xenon difluoride vapor etching is advantageously associated with high selectivity for (semiconductor) substrates, especially silicon.

[0105] The aforementioned etching processes for the complete removal of the shaping component can be carried out individually or in combination with each other.

[0106] In a preferred embodiment, the method is characterized in that, after structuring the membrane layer system, several membranes are connected to a support structure using a detachable connection.

[0107] By connecting the support structure, the necessary stability for the membrane(s) can be advantageously achieved after the complete removal of the shaping component. In particular, the support structure advantageously ensures the maintenance of the membrane's meandering structure and reduces the risk of shape loss. Since the support structure itself is not part of the MEMS transducer but merely serves to temporarily stabilize the membranes, it can be selected primarily with cost considerations in mind. For example, the support structure can be made of a flat plastic substrate or as a film, preferably an adhesive film. Essentially, a wide variety of materials and geometric shapes are suitable for the support structures, provided they can guarantee sufficient stability for the membranes and are also suitable for a detachable connection.

[0108] The detachable connection of the membranes to the support structure serves for the subsequent transfer of the membrane(s) to the carriers, whereby, as explained below, for example a mounting component can be used.

[0109] Preferably, the releasable bond is applied along the discontinuities of the membrane layer system and thus at the end regions of the individual membranes. The releasable bond is preferably decomposable, allowing the membranes to be removed from the membrane layer system without any damage.

[0110] For example, the releasable bond can be an adhesive, preferably a UV adhesive. A UV adhesive is an adhesive that cures upon exposure to UV radiation. UV adhesives can be dissolved, for example, by the application of heat, i.e., a thermal effect, and / or by using appropriate solvents. Preferably, a UV adhesive comprises epoxy resin and / or acrylate. The releasable bond can also be a thermally and / or chemically releasable adhesive. Thermally releasable adhesives can, for example, be selected from a group comprising wood glues, elastomers, and / or silicone adhesives. Chemically releasable adhesives, i.e., adhesives whose bond can be dissolved by the use of a chemical solution, can, for example, include polyurethane.

[0111] In a preferred embodiment, the method is characterized in that the membrane is removed from a support structure by a mounting component, wherein preferably after removal of the membrane from the support structure the membrane is attached to the carrier.

[0112] The assembly component preferably refers to a device that enables the membrane to be removed from the membrane layer system or from the support structure after the forming component has been completely removed. The assembly component can, for example, be configured to apply low pressure so that a pressure differential releases the membrane from the detachable connection or the support structure. In further embodiments, a vacuum clamping device (English: porous chucks) and / or a printing pin (English: (push needle)A porous body, such as a porous ceramic material, is preferably used, with the low pressure being applied through the pores of the porous body. A desired suction force is generated by a preferably essentially uniform distribution of the pores and / or pore size, while simultaneously ensuring the preservation of the meandering structure of the membrane. Advantageously, this allows for particularly reliable removal of the membrane from the membrane layer system. It may also be advantageous to use a pick-and-place tool for the assembly component.

[0113] In particular, the aforementioned preferred assembly components have proven to be especially reliable in ensuring that the shape of the delicate membrane components is not compromised during transport from the support structure to the substrate. Furthermore, these preferred assembly components, such as a pick-and-place tool, can simultaneously facilitate the removal process, for example, by heating in the case of a thermally releasable adhesive. It is also understood that it can be advantageous to simultaneously transport a corresponding number of membranes from a support structure to their respective substrates using a plurality of assembly components. The assembly components can be dimensioned accordingly to reduce manufacturing time, particularly through parallel processing.

[0114] Preferably, after the membrane is removed from the support structure, it is attached to the substrate. This can preferably be done directly using the placement component, enabling the membrane to be attached to the substrate in a continuous process. Advantageously, this avoids complex processing steps required to contact the membrane with the substrate. Instead, the preferred method offers the option of using the placement component to ensure an automated sequence of membrane removal and precise attachment to the substrate.

[0115] In a preferred embodiment, the method is characterized in that the membrane is attached to the support via a conductive process material, wherein the conductive process material is preferably selected from a group comprising a conductive adhesive or a conductive solder material.

[0116] The support structure preferably has a substantially continuous perimeter, allowing the membrane to be stably positioned at its ends. The support structure itself is preferably stable and rigid, ensuring sufficient strength.

[0117] Preferably, the carrier has one or more openings, which function in particular as sound inlet or sound outlet openings.

[0118] The term "sound inlet aperture" is preferably used in embodiments where the MEMS transducer is used as a MEMS microphone. Sound enters the diaphragm through the sound inlet aperture, causing it to vibrate. A signal generated in this way, indicating the incoming sound, can preferably be read out by means of an electronic circuit, which is also located on the substrate.

[0119] The term "sound outlet" is preferably used in embodiments where the MEMS transducer is used as a MEMS loudspeaker. Sound from a vibrating diaphragm passes through the sound outlet into the surrounding environment, with the diaphragm vibrations preferably being generated by an electronic circuit.

[0120] Preferably, a conductive process material is incorporated to simultaneously enable a mechanical and electrical connection between the support and the membrane. The conductive process material can preferably be applied to the membrane's end regions before the membrane is positioned on the support. The membrane's end regions refer in particular to its lateral areas, so that the membrane is preferably connected to the support along its perimeter. The conductive process material can also preferably be applied to the support first, followed by the application of the membrane to the support. The membrane is preferably attached to the support from the front. That is, the support contacts the membrane at its lateral areas, particularly starting from a front surface of the membrane.that side of the membrane which, in the membrane layer system, was facing away from the shaping component and which, in the manufactured MEMS transducer, points in the direction of sound emission or sound detection.

[0121] Preferably, the conductive process material is present on the support or the membrane as a closed ring to enable optimal attachment of the membrane to the support and acoustic sealing of the membrane at lateral (or horizontal) sections.

[0122] A conductive process material preferably refers to an electrically conductive process material. The process material advantageously ensures a reliable, stable, and long-lasting connection between the membrane and the support. In particular, it also advantageously enables both acoustic sealing and electrical contact between the membrane (or, more specifically, its actuator layer) and a preferred electronic circuit. For example, electrical connections, such as wire bonds, can be established between an electronic circuit and the conductive process material.

[0123] Preferably, the conductive process material is selected from a group comprising a conductive adhesive, a conductive solder material, or a conductive bonding material. The preferred material options for the conductive process material ensure both acoustic termination and electrical contact. Furthermore, a flexible connection can be achieved using a conductive adhesive or solder material, which promotes the vibration behavior of the diaphragm. In addition, the preferred materials are durable and ensure a long service life for the MEMS transducer.

[0124] In a further preferred embodiment, the method is characterized in that the carrier is connected to a cover, the cover preferably having a cover opening.

[0125] The cover preferably refers to a rigid and, in particular, protective enclosure for the MEMS transducer. Specifically, the cover serves to protect the components of the MEMS transducer from foreign material and / or damage. Thus, the cover essentially extends over preferred components of the MEMS transducer, for example, the diaphragm, electrical connections, and / or an electronic circuit. The cover is preferably positioned on the back of the diaphragm carrier.

[0126] Furthermore, the rear volume of the MEMS transducer can be adjusted by appropriately dimensioning the cover. This allows the acoustic performance of the MEMS transducer to be easily adapted to desired applications.

[0127] Preferably, the cover has a cover opening. Advantageously, the acoustic properties of the MEMS transducer can be further optimized by including the cover opening. In particular, the introduction of a cover opening leads to an increase in the effective rear volume.

[0128] Preferably, the cover has fastening areas for connecting the carrier to the cover. Common methods known in the prior art, such as soldering and / or gluing, can be used for this purpose. Various fastening options and methods are within the knowledge of those skilled in the art and will not be described in detail here.

[0129] In a further preferred embodiment, the method is characterized in that, after structuring the membrane layer system, several membranes are connected to a support structure and the shaping component is then completely removed.

[0130] The term "support structure" preferably refers to a structural precursor for providing one or more carriers. The support structure is preferably already characterized by structural components that a carrier for the membrane preferably has, e.g., one or more sound inlet or outlet openings, vias, and / or electronic circuits. The support structure can therefore preferably be understood as an array of support elements that are (still) interconnected within the support structure and form the carriers through separation.

[0131] Preferably, the support structure has dimensions that allow for a precise fit to the membrane layer system, and it is particularly preferred that a support element is contacted to each membrane to be formed.

[0132] Preferably, the support structure also possesses sufficient stability to ensure the preservation of the meandering structure of the membranes or the membrane layer system during the complete removal of the shaping component. Preferably, the shaping component is only completely removed after the support structure is bonded to the membrane layer system.

[0133] The support structure can preferably be attached after structuring the membrane layer system and thus separating the membrane layer system to form membranes by inserting interruptions as explained above. Preferably, the support structure is connected to the membrane layer system at the positions of the interruptions, which correspond to the end regions of the membranes to be formed, via a conductive process material.

[0134] In a further preferred embodiment, the method is characterized in that, after the complete removal of the shaping component, a support structure is partially separated, so that several supports are provided starting from the support structure and a membrane is attached to each of the several supports.

[0135] Sectional separation preferably means that the support structure is separated or cleaved section by section. Since the support structure is preferably considered a precursor to one or more carriers, sectional separation preferably results in the direct provision of the carriers on which the membranes are already suspended and electrically connected. For sectional separation, proven technologies from the prior art can be used, depending on the choice of carrier material, which ensure precise and process-efficient execution of the sectional separation. For example, dicing may be preferred, preferably comprising steps selected from scoring, breaking, sawing, and / or (laser) cutting.

[0136] In preferred embodiments, a protective film is applied to the support structure, the protective film being located on the side opposite the membrane layer system and preferably extending at least over the area of ​​the sound inlet or outlet openings, and preferably over the entire surface of the support structure. The protective film can provide protection for the support structure or the carriers to be formed during various processing steps, such as the complete removal of the shaping components by etching or the section-by-section separation of the support structure by dicing. Preferably, the protective film can act as a so-called dicing foil, forming an endpoint of section-by-section separation by dicing.

[0137] In a preferred embodiment, the method is characterized in that a support structure is connected to several covers, the several covers preferably having a cover opening.

[0138] Preferably, the multiple covers are applied such that a precisely fitting cover is provided for each individual membrane at the breaks in the structured membrane layer system or at the membrane end regions. Preferably, the multiple covers are applied before the section-by-section separation of the support structure is carried out, thereby achieving parallel processing and increased efficiency. Likewise, the covers can also be applied after the section-by-section separation of the support structure to form the individual carriers.

[0139] As explained above, the covers are preferably attached to the back of the carrier, and it may be preferred that the covers have one or more openings to increase the back volume.

[0140] The resulting MEMS transducer, comprising a vibrating membrane held by a carrier and preferably protected at the rear by a cover, can be removed from the protective film and transported or prepared for further integration into a product by the preferred use of a component.

[0141] In a further preferred embodiment, the method is characterized in that the membrane comprises at least two layers, wherein both layers comprise an actuator material and are each contacted with an electrode, and the horizontal vibrations can be generated by a change in shape of one layer relative to the other layer, or the horizontal vibrations lead to a change in shape of one layer relative to the other layer and generate an electrical signal.

[0142] In this embodiment, the horizontal vibrations are enabled by a relative change in shape of the two actuator layers. The actuator layers can be made of the same actuator material and controlled differently. Alternatively, the actuator layers can be made of different actuator materials, for example, piezoelectric materials with different deformation coefficients. The actuator layers are considered part of the membrane layer system, which is preferably coated onto the shaping component as described.

[0143] For the purposes of the invention, the "layer comprising an actuator material" is preferably also referred to as the actuator layer. An actuator material preferably means a material that undergoes a deformation, for example, elongation, compression, or shearing, when an electrical voltage is applied, or conversely, generates an electrical voltage when its shape changes. Materials with electric dipoles that undergo a deformation when an electrical voltage is applied are preferred, wherein the orientation of the dipoles and / or the electric field can determine the preferred direction of the deformation. Preferably, the actuator material can be selected from the group comprising a piezoelectric material, a piezoelectric polymer material, and / or an electroactive polymer (EAP).

[0144] In a further preferred embodiment, the method is characterized in that the membrane comprises at least two layers, wherein a first layer comprises an actuator material and a second layer comprises a mechanical support material, wherein at least the first layer comprising the actuator material is in contact with the electrode, such that horizontal vibrations can be generated by a change in shape of the actuator material relative to the mechanical support material, or such that horizontal vibrations lead to a change in shape of the actuator material relative to the mechanical support material and generate an electrical signal.

[0145] For the purposes of the invention, the "layer comprising a mechanical support material" is preferably also referred to as a support layer or support layer. The mechanical support material or support layer preferably serves as a passive layer that can resist deformation of the actuator layer. In contrast to an actuator layer, the mechanical support material preferably does not change its shape when an electrical voltage is applied. Preferably, the mechanical support material is electrically conductive so that it can also be used directly for contacting the actuator layer. However, in some embodiments, it can also be non-conductive and, for example, coated with an electrically conductive layer.

[0146] The mechanical support material is preferably monocrystalline silicon, polysilicon or doped polysilicon.

[0147] When the actuator position is controlled, it can, for example, undergo transverse or longitudinal stretching or compression. This creates a stress gradient relative to the mechanical support layer, leading to lateral bulging or vibration. This can be achieved, for example, by alternating the polarity at the electrodes, preferably through a push-pull operation, which allows almost the entire air volume between the vertical sections to be moved alternately in the vertical emission direction.

[0148] While the actuator layer undergoes a deformation under electrical voltage, the position of the mechanical support material remains essentially unchanged. The resulting stress gradient between the two layers (mechanical bimorphism) preferably causes a horizontal warping. For this purpose, the thickness of the support layer is preferably selected relative to the thickness of the actuator layer such that a sufficiently large stress gradient is generated for the warping to occur. For example, for doped polysilicon as the mechanical support material and a piezoelectric material such as PZT or AIN, essentially equal thicknesses, preferably between 0.5 µm and 2 µm, have proven particularly suitable.

[0149] Contacting the actuator layer and / or the layer made of a mechanical support material, and thus applying an electrical voltage, can be done directly via end-side electrodes or supported by a layer made of a conductive material.

[0150] An end-side positioning of the at least one electrode preferably means that contact with electronics, e.g., a current or voltage source in the case of a MEMS loudspeaker, can be made at one end of the vibrating diaphragm, preferably at the end where the diaphragm is suspended from the support. Electrode preferably means an area made of a conductive material (preferably a metal) that is designed for such contact with electronics, e.g., a current and / or voltage source in the case of a MEMS loudspeaker. Preferably, this can be a conductive adhesive, solder, or electrode pad. Particularly preferably, the electrode serves for contact with electronics and is itself connected to a conductive metal layer that can extend over the entire surface of the vibrating diaphragm.In some cases, the conductive layer together with the end-side contact by an electrode pad or a conductive process material is referred to as the electrode, for example as the top electrode or bottom electrode.

[0151] In a preferred embodiment, the method is characterized in that the membrane comprises three layers, wherein an upper layer is formed of a conductive material and acts as a top electrode, a middle layer is formed of an actuator material, and a lower layer is formed of a conductive material and acts as a bottom electrode, wherein the conductive material of the upper and / or lower layer is preferably a mechanical support material.

[0152] Preferably, the top and / or bottom electrode is a layer of conductive material, preferably metal, forming a continuous or entire or continuous layer of the vibrating membrane, which constitutes a substantially homogeneous surface and is not structured, particularly in the area of ​​the individual membranes. Instead, the two or more vertical sections are preferably connected to end electrodes by means of an unstructured layer of conductive material, preferably metal, so that the actuator layer can be actuated to excite the membrane to vibrate, or a signal generated in the actuator layer can be read out in the event of excitation of the membrane by vibrations originating from electronics on the substrate.

[0153] The terms "top" and "bottom" primarily refer to the position of the conductive material, so that in a cross-section, it can be said that the top electrode comprises a conductive material above (or on the front) of the actuator layer, and the bottom electrode comprises a conductive material below (or on the back) of the actuator layer.

[0154] By means of a layer of conductive material, preferably metal, the two or more vertical sections can advantageously be contacted with an end electrode or electrode pad or conductive process material.

[0155] In further preferred embodiments, a layer of the conductive material is formed from a support material, so that, for example, a bottom and / or top electrode simultaneously functions as a mechanical support layer.

[0156] In an exemplary embodiment, a sacrificial layer is first applied to a shaping component for forming a membrane layer system, followed by a conductive material for the bottom electrode, which also serves as a support layer, then an actuator material to provide the actuator layer, and finally another conductive material (which is not necessarily a support material) to provide the top electrode (see figure). Fig. 2 ).

[0157] In a further preferred embodiment, the method is characterized in that the MEMS transducer has an electronic circuit, wherein the electronic circuit has an electrical connection with the membrane, and preferably the electronic circuit is mounted on the carrier.

[0158] Preferably, the electronic circuit is selected without restriction from a group comprising an integrated circuit (IC), an application-specific integrated circuit (ASIC), a programmable logic circuit (PLC), a field programmable gate array (FPGA), a microprocessor, a microcomputer, a programmable logic controller and / or another electronic circuit, preferably programmable.

[0159] Depending on the use of the MEMS transducer, for example as a MEMS microphone or MEMS loudspeaker, the electronic circuitry is designed to excite the diaphragm to vibrate (and thus to generate sound waves) and / or to detect vibrations of the diaphragm (due to excitation by incident sound waves).

[0160] In the case of a MEMS microphone, the electronic circuit preferably makes it possible to read out or detect an electrical signal which is generated when sound pressure waves occur on the diaphragm and the associated excitation of the vertical sections to horizontal vibrations.

[0161] In the case of a MEMS loudspeaker, the electronic circuit will preferably be configured to generate an electrical signal to excite the vertical sections to vibrate, so that sound pressure waves are generated along a vertical emission direction.

[0162] Preferably, the electronic circuit is mounted on the carrier. In embodiments where a carrier structure is used, one or more electronic circuits can be integrated onto the carrier structure.

[0163] Advantages include increased flexibility in terms of substrate design and electrical properties. In particular, the substrate can function not only as a support for the membrane but also as a circuit carrier. Specifically, the conductive process material enables electrical contact between the membrane and conductive sections of the substrate, for example, vias. In some embodiments, the resulting MEMS transducer can be manufactured as a bottom-port design.

[0164] In a further preferred embodiment, the method is characterized in that the support comprises a material selected from the group consisting of aluminum, ceramic, copper-clad laminate (CCL), and / or glass fiber resin, wherein the glass fiber resin is preferably selected from the group comprising FR-4 or FR-5. Semiconductor materials, as disclosed above for the forming component, can also be used. By separately providing a forming component for shaping the membrane layer system or the membrane and a separate support onto which the membrane is subsequently mounted, support materials can advantageously be selected, independent of the requirements for the membrane's shape, that meet the requirements for mechanical stability, simple electrical contacting, and ensuring optimal acoustic sound.

[0165] The aforementioned preferred materials for the substrate have proven advantageous in that they enable a good bond between the membrane and the substrate. In particular, additional components, such as conductive traces, solder pads, etc., can be reliably attached and / or processed. Furthermore, the aforementioned materials have proven to be particularly stable and temperature-resistant in various applications and processing environments.

[0166] In another aspect, the invention relates to a MEMS converter that can be manufactured or produced by a preferred embodiment of the method according to the invention.

[0167] The average person skilled in the art recognizes that technical features, definitions, advantages and preferred embodiments described for the inventive method for manufacturing a MEMS transducer apply equally to the MEMS transducer that can be manufactured according to the invention, and vice versa.

[0168] The producible MEMS transducer is characterized, for example, by increased design freedom with regard to the design of the substrate and the attachment of the diaphragm to it. This is achieved in particular by completely removing the shaping component, instead of retaining a substrate or the shaping component as a carrier, as is the case with prior art. This allows for separate positioning on any substrate, as explained above. Furthermore, the complete removal of the shaping component has the advantage of enabling the production of particularly compact MEMS transducers.

[0169] The inventive process steps for manufacturing the MEMS transducer thus not only lead to a particularly economical and process-efficient manufacturing process, but also result in an advantageous structural design of the MEMS transducer.

[0170] The process steps according to the invention directly affect the structural properties of the MEMS transducer, so that a person skilled in the art can clearly determine, without much effort, whether a manufactured MEMS transducer was produced using the method according to the invention.

[0171] As defined by the step of completely removing the forming component, the producible MEMS transducer is characterized by the absence of any material from the forming component. In particular, there are no residual structures of a forming component on the back side that could function as a support, as proposed, for example, in WO 2021 / 144400 A1.

[0172] Instead, in particular, the membrane is attached to a separate support, with the contacting of the membrane and support taking place on a front side of the vibrating membrane, instead of on the back side as proposed in WO 2021 / 144400 A1.

[0173] Therefore, it is preferably provided that separate components are used to ensure the geometry and support of the membrane. In particular, the forming component is completely removed to manufacture the MEMS transducer. The membrane is attached to a support carrier as a separate component. Since there is no lateral limitation of a partially removed forming component for supporting the membrane in the finished carrier, the complete removal of the forming component according to the invention is also evident in the manufactured MEMS transducer itself. The person skilled in the art will clearly recognize that the forming component used to provide the membrane in a meandering shape is no longer part of the MEMS transducer.Therefore, the MEMS transducer produced by the method according to the invention can be clearly distinguished by a person skilled in the art from MEMS transducers known, for example, from DE 10 2017 115923 A1, whose membranes were structured by providing a negative mold, wherein side regions of the negative mold form the support or holder of the membrane. For example, a person skilled in the art can distinguish whether a membrane was deposited on a support when the support was still part of a shaping component or negative mold, or whether the membrane was attached to a support as a separate component, for example by means of a conductive process material.

[0174] In preferred embodiments, the invention therefore relates to a MEMS transducer for interacting with a volume flow of a fluid comprising a support and a membrane for generating or receiving pressure waves of the fluid in a vertical direction, which is held by the support, wherein the membrane has a meandering structure with vertical and horizontal sections, the vertical sections being substantially parallel to the vertical direction and the horizontal sections connecting the vertical sections to each other, wherein the membrane comprises at least one actuator layer made of an actuator material and is in contact with at least one electrode, such that by actuating the at least one electrode the vertical sections can be excited to horizontal vibrations or such that an electrical signal can be generated at the at least one electrode when the vertical sections are excited to horizontal vibrations, characterized in that the membrane is attached to the support at a front side. The front side preferably means the side of the membrane facing the fluid, i.e.the side in whose direction pressure waves are generated by the membrane or from whose direction pressure waves can be received.

[0175] In further preferred embodiments, the membrane is attached to a support at the front, wherein the support has a substantially continuous border so that the membrane can be stably positioned at the end regions.

[0176] In further preferred embodiments, the carrier has one or more openings that function as sound inlet or outlet openings, depending on the application of the MEMS transducer as a MEMS microphone or as a MEMS loudspeaker, wherein a front face of the diaphragm preferably faces the sound inlet or outlet opening. A conductive process material, for example a conductive adhesive or conductive solder, is particularly preferred for providing a mechanical and electrical connection between the carrier and the diaphragm, thereby enabling, as explained above, a particularly good acoustic seal and stable electrical contact. Thus, not only the position of the carrier relative to the diaphragm, but also the method of attachment is characteristic of a MEMS transducer that can be produced using the method according to the invention.

[0177] Preferably, the MEMS transducer is configured as a bottom-port design, meaning that one or more sound inlet or outlet openings are located on the substrate, preferably positioned opposite the rear of the diaphragm. Advantageously, the rear volume of bottom-port MEMS microphones or MEMS loudspeakers is larger than the front volume. A large air volume in the rear volume facilitates the movement of the diaphragm under the influence of sound waves. This, in turn, improves the performance of a MEMS loudspeaker or the sensitivity and signal-to-noise ratio of a MEMS microphone.

[0178] The aspects of the invention will be explained in more detail below using examples, without being limited to these examples. FIGURES Brief description of the characters

[0179] Fig. 1Comparison of preferred steps for providing a MEMS converter with previously disclosed methods in the prior art Fig. 2 Schematic representation of preferred steps for coating the forming component with a membrane layer system Fig. 3 Schematic representation of preferred process steps for further processing of a shaping component with a membrane layer system for the production of a MEMS transducer using a support structure and assembly component Fig. 4 Schematic representation of preferred process steps for further processing of a shaping component with a membrane layer system for the production of a MEMS transducer by attaching the membrane layer system to a support structure Detailed description of the figures

[0180] Fig. 1This serves to illustrate a MEMS transducer and its manufacture according to WO 2021 / 144400 A1 and to compare a MEMS transducer that can be manufactured using the preferred method.

[0181] Fig. 1A This shows an example of a MEMS transducer from WO 2021 / 144400 A1. The membrane is used in this process. 5 from a carrier area or carrier 39 held, whereby the membrane 5 horizontally between side areas of the support area 39 The vertical direction for generating or receiving pressure waves, especially sound waves, is orthogonal to the horizontal extent of the membrane. 5 before. Through a cover 23 A housing is provided, with the front of the membrane 5 opposite an opening on the carrier 39 is held. The membrane 5 has vertical sections 4on, which are essentially parallel to the vertical direction and have at least one layer made of an actuator material 11 include the membrane 5 It is contacted at its end regions with an electrode, so that by activating at least one electrode, the vertical sections 4 They can be excited to horizontal vibrations and emit pressure waves. Conversely, the vertical sections can 4 They are excited to horizontal vibrations by pressure waves, so that an electrical signal can be generated at the electrode.

[0182] The majority of vertical sections can be advantageous. 4 the vibrating membrane 5 With small horizontal movements (displacements or bulges) of just a few micrometers, an enlarged total volume is moved in the vertical emission direction and thus used to generate sound. The design of the vibrating membrane5 Extensive vertical sections thus lead to increased sound power in the case of a MEMS loudspeaker. Similarly, in the case of a MEMS microphone, increased performance and audio quality with a suitable sound signature are achieved.

[0183] In Fig. 1B and Fig. 1C Known process steps for the manufacture of such MEMS transducers are illustrated.

[0184] After the membrane 5 When coated onto a structured carrier substrate, the membrane is exposed. 5 can be provided by DRIE etching starting from a reverse side (see Fig. 1B (right image, arrows from below). Here, the edge areas of the support substrate remain as supports. 39, between which the membrane 5The device is suspended. However, backside DRIE etching is complex and cost-sensitive. Furthermore, DRIE etching has limitations regarding the selection of sacrificial layers (stop oxides) and the ability to achieve different etching depths. Additionally, process steps such as grinding, and especially dicing of the substrate, are required to produce multiple MEMS transducers.

[0185] In Fig. 1C A rearward release of the membrane occurs. 5 by means of KOH etching, whereby edge areas of the support substrate serve as the support 39 remain, between which the membrane 5 It is suspended. The increased size of the support is clearly visible. 39, which compromises the compactness of the MEMS converter.

[0186] As in the Fig. 1DAs illustrated, this also leads to an increased space requirement between the individual MEMS converters when manufacturing a large number of MEMS converters, and thus to a less efficient use of the wafer and increased costs.

[0187] Fig. 1E The figure schematically illustrates the intended complete (rear) removal of a shaping component or support substrate (below), which contrasts with the previously illustrated methods in which edge areas of a structured substrate are left in place to serve as a support. 39 for the membrane 5 to function (above, crossed out).

[0188] Fig. 2 schematically shows preferred steps for coating the forming component 7 with a membrane layer system 9. The coating of the membrane layer system 9 on the shaping component 7 It starts from a front side.

[0189] In Fig. 2A is the shaping component 7 shown, which is initially provided before the coating of the membrane layer system 9 This is done. The shaping component 7 is used here as a comb-like structure substrate 7 comprehensive comb finger 43 and empty spaces 45 Provided. Through the structure of the shaping component 7 (e.g., by the length and / or width of the comb fingers) 43 and / or empty spaces 45) The meandering structure of the resulting membrane can be adjusted. The provision of the shaping component 7 This can be done, for example, using a DRIE etching process or KOH etching.

[0190] In Fig. 2B First, a sacrificial layer is coated. 35 depicted on the shaping component. The sacrificial layer 35 It serves in particular to protect the membrane or the membrane layer system. 9during the removal of the shaping component 7, preferably by means of wet chemical etching. In the sacrificial layer 35 It could be, for example, TEOS or PECVD.

[0191] On the victim class 35 will be, as in Fig. 2C shown, a layer coated with a conductive material, which serves as the bottom electrode for the membrane. 29 can function. Following this, in Fig. 2D the coating of an actuator layer 11 comprising an actuator material, for example a piezoelectric material. Preferably the piezoelectric material can have a c-axis orientation perpendicular to the surface, although other orientations are also possible. Fig. 2E The coatings are applied to a further layer of an electrically conductive material to form a top electrode. 27 shown.

[0192] This includes the membrane layer system 9a sacrificial layer on the shaping component 35, a bottom electrode 29, an actuator position 11 and a top electrode 27. It goes without saying that the victim class 35 in the further manufacturing process of the MEMS transducer, it is preferably removed so that the membrane 5 In the completed MEMS converter, an upper layer serves as the top electrode. 27, a middle position as actuator position 11 and a bottom electrode 29 exhibits. The bottom electrode 29 It can preferably be formed from a conductive support material, so that it simultaneously functions as a passive support layer.

[0193] Fig. 3 shows preferred process steps for further processing of the shaping component 7 with membrane layer system 9 according to Fig. 2 for the production of a MEMS transducer using a support structure 17 and assembly component 19.

[0194] In Fig. 3A will the membrane layer system 9 on the shaping component 7 The membrane layer system is shown after coating on the shaping component. 7 vertical sections 4 and horizontal sections 6 on. Furthermore, in Fig. 3A shown that the membrane layer system 9 Interruptions 13 may exhibit interruptions 13 by structuring the membrane layer system 9, in particular, through lateral structuring. Therefore, a single shaping component can be used. 7 a plurality of membranes 5 to be provided. This will first involve the application of a membrane layer system. 9 on the structured front side of the shaping component 7. To define the individual membrane 5are achieved through a lateral structuring of the membrane layer system 9 preferably interruptions 13 educated. As in the Fig. 3A The interruptions are illustrated. 13 preferably on the comb fingers 43 formed and therefore lie within the area of ​​the horizontal sections 6 the membrane 5 before, which the vertical sections 4 Connect them at the top or front end.

[0195] In Fig. 3B A connection of the membrane layer system will be formed 9 after its structuring by means of a detachable connection 15 on a support structure 17 illustrated. The releasable bond can include an adhesive, for example a UV adhesive.

[0196] Through a connection with the supporting structure 17 This can advantageously provide stability for the membranes. 5to ensure which, after the complete removal of the shaping component, 7 is required. Therefore, the supporting structure 17 Advantageously, the meandering structure of the membranes is maintained. 5 This ensures stability and reduces the risk of deformation. Because the support structure 17 The support structure is not itself part of the MEMS transducer, but merely serves to temporarily stabilize the membranes 5. 17 The support structure is selected based on cost considerations. 17 It can be made, for example, from a flat plastic substrate or as a film, preferably as an adhesive film.

[0197] A detachable connection 15 the membranes 5 with the support structure 17 serves for the later transfer of the membranes 5 to the carriers. The detachable connection 15For this purpose, it is preferably arranged in such a way that it runs along the interruptions. 13 of the membrane layer system 9 and thus the end regions of the individual membranes 5 The releasable compound is preferably a decomposable compound, so that, starting from the membrane layer system, 9 the membranes 5 free from any damage and therefore able to be reliably removed.

[0198] Fig. 3C shows the complete removal of the shaping component 7. The complete removal of the shaping component can preferably be achieved using a wet chemical etching process, in particular by KOH and / or TMAH etching. Advantageously, the use of wet chemical etching processes for the complete removal of the shaping component allows for the formation of seven thin sacrificial layers. 35This allows for the use of more materials and saves material. Furthermore, the high selectivity of wet chemical etching processes also allows for a wider range of materials to be used for sacrificial layers. 35 such as in a DRIE etching process.

[0199] In Fig. 3D schematically, a removal of the membrane is shown. 5 from the supporting structure 17 through a component 19 illustrated. The assembly component 17 It can, for example, be set to apply low pressure so that a pressure difference causes the membrane to... 5 from the detachable connection 15 or the supporting structure 17 is solved. It can also be used as a component for assembly. 19 A vacuum clamping device, a pressure needle and / or a pick-and-place tool may be used.

[0200] The aforementioned options of the assembly component 19have proven to be particularly reliable in transporting the support structure 17 The shape of the delicate components of the membrane forms the carrier 5 not to be affected.

[0201] After removing the membrane 5 using the assembly component 19 will the membrane 5 on a carrier 3 via a conductive process material 33 appropriate as in Fig. 3E is shown. In the case of the carrier 3 It is a structure which preferably has a substantially continuous border, so that the membrane 5 It can be stably positioned at its lateral end regions. Preferably, the carrier has 3 one or more openings that function as sound inlet or outlet openings, depending on whether the MEMS transducer is used as a MEMS microphone or a MEMS loudspeaker. The conductive process material 33serves to create a stable connection between the support 3 and the membrane 5. Furthermore, the conductive process material 33 an acoustic termination and an electrical contact option with an electronic circuit 31 made possible.

[0202] In Fig. 3F It is shown that an electronic circuit 31 (here: "ASIC") preferably on the carrier 3 is attached. Depending on the use of the MEMS converter, for example as a MEMS microphone or MEMS speaker, the electronic circuit is 31 preferably designed for the membrane 5 to excite vibrations (and thus to generate sound waves) and / or vibrations of the membrane 5 (due to excitation by incident sound waves) to detect.

[0203] The carrier can then 3 with a cover 23to be connected, with the cover 23 a cover opening 25 exhibits (Fig. 1 G). By means of the cover 25 A solid and protective casing is applied to the MEMS converter, especially to protect components of the MEMS converter. 1 to protect. Thus, the cover extends 23 essentially via all components of the MEMS transducer, for example via the membrane 5, electrical connections and the electronic circuit 31. Furthermore, the dimensions of the cover offer 25 the possibility to adjust the rear volume of the MEMS transducer 1 with regard to desired acoustic properties.

[0204] Fig. 4 shows preferred process steps for further processing of the shaping component 7 with membrane layer system 9 according to Fig. 2 for the production of a MEMS transducer by attaching the membrane layer system 9to a support structure 21.

[0205] In Fig. 4A The connection of the membranes will be 5 or of the membrane layer system 9 with a support structure 21 The connection between the membranes is shown. 5 and the supporting structure 21 can be achieved through a conductive process material 33 to be realized. Preferably, the support structure is attached. 21 after the structuring of the membrane layer system 9 to avoid interruptions 13 to form.

[0206] The support structure 21 preferably denotes a structural precursor for the provision of one or more carriers and can also be understood as an array of carrier elements which are in the carrier structure 21 (still) exist in a coherent manner and will form the supporting structures through separation. The supporting structure 21For this purpose, a support structure can already have a number of structural components, for example, several sound inlet or outlet openings. However, it may also be preferred that, after the support structure has been separated, 21 Further processing steps will follow.

[0207] Preferably the support structure 21 characterized by sufficient stability to withstand the complete removal of the shaping component 7 the preservation of the meandering structure of the membranes 5 to ensure this. The shaping component is therefore preferably only completely removed after the support structure. 21 with the membrane layer system 9 is connected.

[0208] The installation of the support structure 21 preferably occurs after structuring the membrane layer system 9 and thus a separation of the membrane layer system 9for the formation of membranes 5 including interruptions 13. The support structure 21 preferably at the location of the interruptions 13 of the membrane layer system 9, which correspond to the end regions of the membranes to be formed 5 correspond to a conductive process material 33 with the membrane layer system 9 tied together.

[0209] It is also shown that on the support structure 21 preferably a protective film 37 is attached, with the protective film 37 on the membrane layer system 9 is located on the opposite side and extends along the entire surface of the support structure 21 extends. The protective film 37 can provide protection for the supporting structure 21or represent the carriers to be formed during different processing steps, such as the removal of the shaping components 7 or a section-by-section separation of the supporting structure 21 through a dicing. The protective film 37 Here, an endpoint for dicing can also be defined as a so-called dicing foil.

[0210] Fig. 4B illustrates the complete removal of the shaping component. In Fig. 4C is the same representation as in the Fig. 4B to be seen, but in an inverted view to illustrate possible further transport and / or positioning for the subsequent processing steps.

[0211] In Fig. 4D The connection of multiple covers will 23 with the support structure 21 shown. The connection is preferably made such that the covers 23 to the position of the interruptions 13to be attached so that each membrane 5 a perfectly fitting cover 23 is available.

[0212] Fig. 4E shows the area-by-area separation of the support structure 21. The separation of areas can be achieved, for example, by dicing.

[0213] As in Fig. 4F Illustrated, after the area-by-area separation of the support structure 21 the MEMS converters 1 The protective film must be removed and / or the component subjected to further processing. A component assembly, as described above, can be used for this purpose. REFERENCE SIGN LIST

[0214] 1 MEMS transducer 3 Carrier 4 Vertical section 5 Membrane 6 Horizontal section 7 Shaping component 9 Membrane layer system 11 Actuator layer 13 Interruption 15 Detachable connection 17 Support structure 19 Component placement 21 Carrier structure 23 Cover 25 Cover opening 27 Top electrode 29 Bottom electrode 31 Electronic circuit 33 Conductive process material 35 Sacrificial layer 37 Protective film 39 Backside carrier or carrier area from the prior art 43 Comb finger 45 Empty area BIBLIOGRAPHY

[0215] Kaiser B., Sergiu Langa, Lutz Ehrig, Michael Stolz, Hermann Schenk, Holger Conrad, Harald Schenk, Klaus Schimmanz und David Schuffenhauer, Concept and proof for an all-silicon MEMS microspeaker utilizing air chambers Microsystems & Nanoengineering volume 5, Article number: 43 (2019). Shahosseini I., Elie LEFEUVRE, Johan Moulin, Marion Woytasik, Emile Martincic, et al. Electromagnetic MEMS Microspeaker for Portable Electronic Devices. Microsystem Technologies, Springer Verlag (Germany), 2013, pp.10. <hal-01103612> . Stoppel F., C. Eisermann, S. Gu-Stoppel, D. Kaden, T. Giese and B. Wagner, NOVEL MEMBRANE-LESS TWO-WAY MEMS LOUDSPEAKER BASED ON PIEZOELECTRIC DUAL-CONCENTRIC ACTUATORS, Transducers 2017, Kaohsiung, TAIWAN, June 18-22, 2017.< / hal-01103612>

Claims

1. Method for producing at least one MEMS transducer (1) for interacting with a volume flow of a fluid comprising - a carrier (3) and - a membrane (5) for generating or receiving pressure waves of the fluid in a vertical direction, which is held by the carrier (3), wherein the membrane (5) exhibits a meander structure with vertical sections (4) and horizontal sections (6), wherein the vertical sections (4) are configured substantially parallel to the vertical direction and the horizontal sections (6) connect the vertical sections (4) to one another, wherein the membrane (5) comprises at least one actuator layer (11) made of an actuator material and is in contact with at least one electrode, such that the vertical sections (4) can be induced to vibrate horizontally by controlling the at least one electrode or such that an electrical signal can be generated at the at least one electrode when the vertical sections (4) are induced to vibrate horizontally, characterized in that the method comprises the following steps: a) provision of a shaping component (7), b) coating of the shaping component (7) with a membrane layer system (9) comprising at least the actuator layer (11), wherein the membrane layer system (9), after coating on the shaping component (7), exhibits the meander structure comprising vertical sections (4) and horizontal sections (6), c) provision of the membrane (5) by structuring the membrane layer system (9), wherein by forming interruptions (13) the membrane layer system (9) is separated to provide the membrane (5), d) complete removal of the shaping component (7), e) attachment of the membrane (5) to the carrier (3) such that the membrane (5) is held by the carrier (3).

2. Method according to the preceding claim characterized in that a plurality of MEMS transducers (1) are produced, wherein the membrane layer system (9) is structured on the shaping component (7) to form individual membranes (5) in order to produce the plurality of MEMS transducers (1), wherein the individual membranes are preferably separated by interruptions (13) which are preferably formed as a whole after the coating of the membrane layer system (9) or layer by layer.

3. Method according to one or more of the preceding claims characterized in that the shaping component (7) is provided by an application of a dry etching process and / or a wet chemical etching process to a substrate, wherein preferably the dry etching process is a physical, a chemical and / or a physico-chemical dry etching process, wherein particularly preferably the dry etching process is selected from a group comprising reactive ion etching (RIE) and / or deep reactive ion etching (DRIE), wherein preferably KOH etching is used as the wet chemical etching process.

4. Method according to one or more of the preceding claims characterized in that the shaping component (7) is completely removed by a wet chemical etching process, a dry etching process and / or a vapor etching process, wherein preferably the wet chemical etching process is selected from a group comprising KOH etching and / or TMAH etching.

5. Method according to one or more of the preceding claims characterized in that after the structuring of the membrane layer system (9), a plurality of membranes (5) are connected to a support structure (17) by means of a detachable connection (15).

6. Method according to one or more of the preceding claims characterized in that the membrane (5) is removed from a support structure (17) by a mounting component (19), wherein preferably after removal of the membrane (5) from the support structure (17), the membrane (5) is attached to the carrier (3).

7. Method according to one or more of the preceding claims characterized in that the membrane (5) is attached to the carrier (4) via a conductive process material (33), wherein preferably the conductive process material (33) is selected from a group comprising a conductive adhesive or a conductive solder material.

8. Method according to one or more of the preceding claims characterized in that the carrier (3) is connected to a cover (23), wherein the cover (23) preferably exhibits a cover opening (25).

9. Method according to one or more of the preceding claims characterized in that after the structuring of the membrane layer system (9), a plurality of membranes (5) are connected to a support structure (21) and the shaping component (7) is then completely removed.

10. Method according to one or more of the preceding claims characterized in that after the complete removal of the shaping component (7), a carrier structure (21) is regionally separated such that, starting from the carrier structure (21), a plurality of carriers (3) are provided and a membrane (5) is attached to one of the plurality of carriers (3) in each case.

11. Method according to one or more of the preceding claims characterized in that a carrier structure (21) is connected to a plurality of covers (23), wherein the plurality of covers (23) preferably exhibit a cover opening (25).

12. Method according to one or more of the preceding claims characterized in that the membrane (5) comprises at least two layers, wherein both layers (11) comprise an actuator material and are respectively in contact with an electrode, and the horizontal vibrations can be generated by a change in shape of one layer relative to the other, or the horizontal vibrations lead to a change in shape of one layer relative to the other layer and generate an electrical signal.

13. Method according to one or more of the preceding claims characterized in that the membrane comprises at least two layers, wherein a first layer (11) comprises an actuator material and a second layer comprises a mechanical support material, wherein at least the first layer (11) comprising the actuator material is in contact with the electrode, such that horizontal vibrations can be generated by a change in shape of the actuator material relative to the mechanical support material or such that horizontal vibrations lead to a change in shape of the actuator material in relation to the mechanical support material and generate an electrical signal.

14. Method according to one or more of the preceding claims characterized in that the membrane (5) comprises three layers, wherein an upper layer is formed by a conductive material and functions as a top electrode (27), a middle layer (11) is formed by an actuator material and a lower layer is formed by a conductive material and functions as a bottom electrode (29), wherein the conductive material of the upper and / or lower layer is preferably a mechanical support material.

15. MEMS transducer (1) producible by a method according to one or more of the preceding claims.