Method for manufacturing plurality of MEMS converters with enhanced performance

Abstract

The invention preferably relates to a method for manufacturing a MEMS transducer comprising a membrane and a carrier wherein the membrane has a tortuous structure with a vertical portion and a horizontal portion. In this case, first, a shaped part coated with a film layer system is provided. The film layer system includes at least one actuator layer containing an actuator material. By structuring the film layer system, a film that can be attached to the carrier is provided. The shaped part may be completely removed. Furthermore, the invention preferably relates to a MEMS transducer that can be produced according to the method.

Description

Technical Field

[0001] The invention preferably relates to a method for producing a MEMS transducer comprising a membrane and a carrier, wherein the membrane has a meandering structure with vertical sections and horizontal sections. In this case, a shaped part coated with a membrane layer system is first provided. The membrane layer system comprises at least one actuator layer containing an actuator material. By structuring the membrane layer system, a membrane is provided which can be attached to the carrier. The shaped part can be completely removed.

[0002] Furthermore, the invention preferably also relates to a MEMS transducer which can be produced using the method. Background Art

[0003] Microsystem technology is used today in many areas of application to produce compact electromechanical devices. Microsystems produced in this way (microelectromechanical systems, MEMS for short) are very compact (micrometer range) and at the same time have excellent functionality. MEMS transducers, such as MEMS loudspeakers or MEMS microphones, are also known in the prior art. Current MEMS loudspeakers are mostly designed as flat membrane systems with a vibrating membrane that is actuated vertically in the emission direction. Excitation is achieved, for example, using piezoelectric actuators, electromagnetic actuators or electrostatic actuators.

[0004] Shahosseini et al. proposed an electromagnetic MEMS speaker for mobile devices in 2015. The MEMS speaker has a reinforced silicon microstructure as a sound radiator, and its movable part is suspended from a support by a silicon drive spring to achieve a large displacement with the help of an electromagnetic motor.

[0005] Stoppel et al. disclosed in 2017 a two-way loudspeaker based on the concept of concentric piezoelectric actuators. The special feature is that the diaphragm is not closed, but includes eight unimorph actuators, each of which consists of a piezoelectric layer and a passive layer. The outer woofer consists of four trapezoidal actuators sandwiched on one side, while the inner tweeter consists of four triangular actuators connected to a rigid frame by one or more springs. The separation of the membrane will be able to improve the sound image at higher powers.

[0006] The disadvantage of such planar MEMS loudspeakers is their limited acoustic power, especially at low frequencies. One reason for this is that for a given deflection (Auslenkung), the sound pressure level that can be generated is proportional to the square of the frequency. In order to achieve sufficient acoustic power, a diaphragm deflection of at least 100 μm or a large membrane area of ​​several square centimeters is therefore required. These two conditions are difficult to achieve using MEMS technology. In particular, difficulties arise when possible manufacturing steps cannot be implemented efficiently.

[0007] Therefore, in the prior art, a MEMS speaker of the following design is proposed: it does not have a closed membrane for vibrating in the vertical emitting direction, but has a large number of movable elements that can be excited to vibrate laterally or horizontally. The advantage of this is that the volume flow that can be moved in a small area is increased, thereby providing better sound power.

[0008] MEMS speakers based on this principle are disclosed, for example, in US2018 / 0179048 A1 and in the literature of Kaiser et al. (2019). The MEMS speaker includes a plurality of electrostatic bending actuators, which are arranged as vertical sheets between the top wafer and the bottom wafer and can be excited to produce lateral vibrations by corresponding control. The inner sheet forms an actuator electrode opposite to the two outer sheets. In addition to the connection nodes of the electrodes, which are still isolated in the current, there is an air gap between the three bending sheets. If a potential is applied from the inside to the outside, this results in a bidirectional attraction due to the curvature in the preferred direction given by the anchor point by design. The protrusion of the outer sheet facilitates movement. The restoring force is provided by a mechanical spring force. Therefore, pull-push operations are not possible.

[0009] Another disadvantage is that the gap between the bending actuator and the top / bottom wafer, which is necessary for their mobility, leads to a gas flow between the two cavities. This limits the lower frequency. In addition, the lateral movement and the acoustic power of the bending actuator are limited to avoid pull-in effects and acoustic overpressure.

[0010] WO 2021 / 144400 A1 discloses a MEMS transducer that can be used as both a MEMS speaker and a MEMS microphone. The MEMS transducer described therein has a vibrating membrane that is configured such that it includes two or more vertical portions that are substantially parallel to the vertical direction. In addition, the vibrating membrane includes at least one layer of actuator material and is in contact with at least one electrode on the end side. As a result, the vertical portion can be excited to vibrate horizontally by controlling the electrode. Conversely, when the vertical portion is excited to vibrate horizontally, an electrical signal can also be generated at the electrode.

[0011] The MEMS transducer disclosed in WO 2021 / 144400 A1 is a significant improvement over the prior art. The design of the vibrating membrane including the vertical portion advantageously results in higher acoustic power in the case of a MEMS loudspeaker. Even in the case of a MEMS microphone, higher performance and audio quality with a suitable sound image are advantageously achieved. In addition, the MEMS transducer can be manufactured using mature semiconductor processing processes, thereby achieving cost-effective production.

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

[0013] There is a need for optimization of the manufacturing method of the MEMS converter disclosed in WO 2021 / 144400 A1. In particular, it is expensive to provide a carrier for the vibrating membrane by etching a substrate. Preferably, the substrate is etched by DRIE etching, but this method is costly. In addition, DRIE etching has limitations in the choice of sacrificial layer (stop oxide) and the possibility of achieving different depths during etching. The alternative method of providing a carrier by wet chemical KOH (potassium hydroxide) etching requires a larger space area, which will result in a larger installation space and will be accompanied by a loss in the compactness of the MEMS converter. In particular, when producing a large number of MEMS converters, the space required for the carrier frame between the individual MEMS converters is large, resulting in a low effective utilization rate of the wafer and a high cost.

[0014] DE 102017115923 A1 discloses a method for producing a MEMS transducer with a structured membrane. A negative mold is provided by a substrate and an optional sacrificial layer, by which the structure of the membrane can be specified. The substrate or negative mold has grooves corresponding to the crests or troughs of the membrane. Then a conductive layer and a piezoelectric layer are deposited on the negative mold, thereby forming a membrane with sides complementary to the negative mold. In a further process step, the membrane is electrically contacted with electrodes at the crests and troughs. In order to expose the membrane, part of the substrate and part of the sacrificial layer applied in an optional manner are removed by etching on the back. The remaining part of the substrate forms a holder or carrier for the membrane.

[0015] EP 3218303 B1 discloses a method for producing a large number of MEMS packages. The package has a base structure with an embedded chip, a MEMS component and a cover structure. Through holes provide fluid communication between the MEMS component and the environment of the package. The structure of the package is very suitable for mass production. To this end, multiple chips can be embedded in the base main structure and multiple MEMS components can be mounted on the base main structure accordingly. After covering the arrangement structure thus obtained with the main cover structure, a blank for a large number of packages is obtained. By forming separation lines or cutting lines, the arrangement structure is broken down into pieces and a plurality of packages separated from each other are obtained.

[0016] However, neither DE 10 2017 115 923 A1 nor EP 3 218 303 B1 provides any information by which the production process of a MEMS transducer with a corrugated membrane according to WO 2021 / 144400 A1 can be improved in order to avoid complex back-etching processes or to achieve smaller space requirements.

[0017] Therefore, in view of the prior art, there is a need to provide improved or alternative methods for producing MEMS transducers. Summary of the invention

[0018] The object of the present invention is to eliminate the disadvantages of the prior art. In particular, the object of the present invention is to provide a method for producing a MEMS transducer, which method is characterized by high process efficiency and economy, low error rate, easy scalability, and ensures the production of MEMS transducers with excellent acoustic properties and compact size.

[0019] The objects of the invention are achieved 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, the MEMS transducer comprising:

[0021] a carrier; and

[0022] A membrane for generating or receiving pressure waves of a fluid in a vertical direction, the membrane being held by a carrier,

[0023] wherein the membrane has a meandering structure with vertical parts and horizontal parts, wherein the vertical parts are substantially parallel to the vertical direction and the horizontal parts connect the vertical parts 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, so that the vertical parts can be excited to vibrate horizontally by controlling the at least one electrode, or an electrical signal can be generated at the at least one electrode when the vertical parts are excited to vibrate horizontally, and wherein the method comprises the following steps:

[0024] a) providing formed parts,

[0025] b) coating the shaped component with a film layer system comprising at least an actuator layer, wherein after coating on the shaped component the film layer system has a meandering structure with vertical and horizontal sections,

[0026] c) providing a film by structuring the film layer system,

[0027] d) completely remove the formed part,

[0028] e) Attaching the membrane to the carrier such that the membrane is held by the carrier.

[0029] The inventors have realised that a preferred method for producing MEMS transducers achieves significant improvements in many respects. In particular, the complete removal of the shaped part has a very beneficial effect on both the efficiency of the manufacturing method and the MEMS transducers that can be produced.

[0030] On the one hand, it is no longer necessary to use multiple etching processes in order to be able to provide a carrier to which a membrane is attached in order to generate or absorb pressure waves.

[0031] Instead, a (temporary) shaped part is provided which can be completely removed again after coating to form a film layer system. This differs significantly from the method for producing MEMS transducers disclosed, for example, in WO 2021 / 144400 A1. Here, it is proposed to structure the substrate before coating with the film layer system, wherein a frame area of ​​the substrate forms a carrier for the membrane. To this end, an initial substrate is etched starting from the front side, for example by DRIE etching, so as to provide a structure on the substrate that corresponds to the meandering structure of the membrane. A coating process is then carried out to apply the film layer, after which the membrane is partially exposed on the back side by further DRIE etching, the frame of the substrate being retained and forming a carrier. It is not possible to completely remove the substrate from the back side using a simple etching process in the process design, since no carrier would be provided if the substrate was removed.

[0032] According to the invention, it was realized that by attaching the film to a separate carrier, the shaped part can be omitted and can be completely removed (from the back). The supposed disadvantages of providing a separate carrier are offset by a series of advantages, which are particularly accompanied by the possibility of completely removing the shaped part.

[0033] This makes it possible to dispense with expensive DRIE etching processes to expose the back side of the membrane. Instead, for example, a (cost-effective) and highly selective wet chemical etching process can be used. In this regard, a separate grinding process step or polishing step is also advantageously not required before the DRIE etching.

[0034] Since the shaped parts are completely removed and no external carrier needs to be retained, these shaped parts can be positioned very compactly on the wafer when manufacturing a large number of MEMS transducers. The main carrier is to be retained as a frame during the KOH etching (see Figure 1 C, D), there is no need to increase the spacing between the individual chips to meet the increased space requirements. Cutting can also be omitted when manufacturing a large number of MEMS converters on a wafer.

[0035] Therefore, the solution of the present invention advantageously saves time and costs, so that a greater number of MEMS transducers can be produced in a shorter time with less material consumption.

[0036] Preferred method steps a) to e) are not limited to the above order to achieve advantages. Preferably, according to embodiments of aspects of the present invention, steps a) to e) can be performed simultaneously, for example in a temporally overlapping manner, or in a different order.

[0037] For example, it may be preferred that, after applying the film layer system to the shaped part, the film layer system is structured and connected to the support structure so as to achieve stability in order to reliably completely remove the shaped part. Advantageously, by the method step, i.e. the step of completely removing the shaped part, a large number of films are provided, which are first present in a stable manner on the support structure, but from which they can be transported to the carrier and attached to the carrier. Therefore, it may be preferred that after step c) structuring the film layer system to provide the individual films, step d), i.e. completely removing the shaped part, and step e), i.e. attaching the (individual) film to each carrier, respectively, are carried out.

[0038] It may also be preferred to structure the film layer system to provide one or more films (step c) after the film layer system has been connected to the carrier structure (step e). In this case, the film layer system is also preferably attached to the carrier structure before the complete removal of the shaped part (step d), by which the individual films are provided. By attaching the film layer system to the carrier structure before the complete removal of the shaped part, a separate support structure can be omitted. After the removal of the shaped part, the individual films are provided on the individual carriers accordingly by disassembling the carrier structure region by region.

[0039] Therefore, the explanation of the individual process steps given below is applicable to different combinations of the order of the process steps and is not limited to the order selected for the purpose of explanation.

[0040] In a first step, it may be preferred to provide a shaped part. The shaped part is preferably provided (structured) in such a way that a meandering structure corresponding to the desired meandering structure of the film is present on the accessible side, which is preferably the front side. Thus, the structure of the shaped part preferably determines the meandering structure of the film. In other words, the shaped part can also be understood as a template or substrate for shaping the film layer system.

[0041] The shaped structure preferably has the following structure: after the film layer system is applied, a meandering structure including vertical and horizontal parts is present. For this purpose, the shaped component can preferably be present as a comb structure substrate, which includes comb teeth and recessed areas, so that when the film layer system is applied, a film that is wrinkled in accordance with the comb structure can be provided (see Figure 2 A). The shaping structure preferably forms a negative mold for the film layer system and thus in particular forms a negative mold for the film produced from the film layer system. By applying the film layer system to the shaping structure, the film layer system has a geometric configuration that corresponds to the shaping structure.

[0042] The forming structure can be provided by structuring the (semiconductor) substrate, for example, by DRIE etching to form a comb-like teeth portion and a gap area of ​​a comb-like structure substrate for use as a forming structure. After providing the forming part, the film layer system is preferably coated. The comb-like structure substrate preferably includes a main body, a comb-like teeth portion and a gap area. The comb-like teeth portion represents a portion that is substantially orthogonal to the main body portion and is separated from each other by the gap area. Therefore, the main body portion can be regarded as a support for the comb-like teeth portion. The gap area preferably represents a portion where there is no longer any substrate material. The comb-like structure substrate is preferably provided by an etching process. In this process, the (semiconductor) substrate is preferably etched from the front side to leave cavities on the substrate, which in turn form gap areas, while the unetched portions are used as comb-like teeth portions.

[0043] The meandering structure of the membrane can be set in particular by the dimensions of a shaped part, for example as a comb-shaped structure substrate. The length of the comb-shaped teeth of the comb-shaped structure substrate preferably corresponds to the length of the vertical parts of the membrane. The width of the comb-shaped teeth gives the width of the horizontal parts that connect the vertical parts to each other in their (front) upper area. The width of the free-standing area corresponds to the width of the horizontal parts that connect the vertical parts to each other in their lower area. By providing a comb-shaped structure substrate, in which the width of the comb-shaped teeth is equal to the width of the free-standing area or the middle area, it can preferably be ensured that the lengths of the horizontal parts of the membrane are equal.

[0044] For the purposes of the present invention, a membrane layer system preferably denotes one or more layers of a membrane for providing a MEMS transducer. The membrane layer system comprises in particular a layer or interlayer comprising an actuator material, which is referred to as an actuator layer, which is explained in more detail below and which serves in particular to generate or detect vibrations of the membrane. In the context of the present invention, the terms "layer" and "interlayer" may be used synonymously. In addition to the actuator layer, the membrane layer system preferably comprises further layers, in particular a top electrode, a bottom electrode and / or a mechanical support layer. Furthermore, the membrane layer system may preferably comprise a sacrificial layer, which is preferably first applied to the shaped part before the other layers of the membrane layer system are applied.

[0045] By simply structuring the film layer system, interruptions can preferably be provided, which define end regions for the film that can be attached to a carrier. By coating the shaped part, it is therefore advantageously possible to provide the film layer system for a large number of films at the same time, the dimensions of which can be determined on the one hand by the shaped part and on the other hand by the structuring that is performed later. In other words, the structuring of the film layer system preferably includes the formation of interruptions, thereby breaking up the film layer system into pieces or splitting it into individual films. For the purposes of the present invention, the split parts of the film layer system obtained by structuring are preferably already referred to as films before the shaped part is removed and / or the film is attached to the carrier.

[0046] The membrane is thus preferably formed from the membrane layer system by structuring, wherein the membrane is preferably already present when it is still applied to the shaped part or has not yet been exposed. By completely removing the shaped part and attaching the membrane to the carrier, the membrane is exposed and the vibration capability of the membrane is ensured as a functional characteristic for the MEMS transducer. However, in its structural design, the membrane is preferably already present as a blank after structuring the membrane layer system.

[0047] The film system is preferably applied starting from the front side. The front side of the shaped part preferably refers to that side of the shaped part which has a structure (e.g. a comb structure) on which the film system is to be formed by coating. Preferably, the shaped part is provided in such a way that it is present in a correspondingly structured manner from the front side, while the rear side of the shaped part is not structured.

[0048] Preferably, the complete removal of the shaped part is carried out starting from the back side of the shaped part. The back side of the shaped part therefore preferably means the side facing away from the film layer system.

[0049] Preferably, the membrane is also attached to the carrier from the front side, so that the front side of the membrane again faces the sound opening in the carrier and thus preferably represents the direction of the sound emission or sound detection of the finished MEMS transducer.

[0050] Preferably, a wet chemical etching process is used to completely remove the formed part. Advantageously, this allows the use of a thinner sacrificial layer than the sacrificial layer required for the DRIE etching process, thereby advantageously saving material. The use of a wet chemical etching process also means that the material selection of the sacrificial layer is richer, which also has a positive impact on economic efficiency.

[0051] Furthermore, design flexibility is increased in the design of the vertical and / or horizontal parts of the preferred MEMS transducer. In particular, any restrictions associated with exposing the back side of the membrane are eliminated, since a wet chemical etching process can be efficiently performed at any length and / or any width of the vertical and / or horizontal parts to completely remove the formed parts.

[0052] In the context of the present invention, complete removal of a shaped part preferably means a removal such that no functional components (e.g. as carriers) are left behind in the shaped part. A person skilled in the art knows that after complete removal of a shaped part, it cannot be ruled out that small components still remain. However, when a shaped part is completely removed, it is preferred that the shaped part is substantially completely removed.

[0053] The terms "substantially", "approximately" and the like 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 in particular less than ±1%, and in particular include the exact value. "Similar" preferably describes approximately equal dimensions. "Partially" preferably describes at least 5%, particularly preferably at least 10% and in particular at least 20%, in some cases at least 40%.

[0054] Contrary to the disclosure of DE 102017115923 A1 (or WO 2021 / 144400 A1), in the context of the present invention, the shaped part is completely removed. The teaching of DE 102017115923 A1 shows that the negative mold for the film similar to the shaped part is only partially removed, so that a holder or carrier for the film is obtained after partial removal. However, the method according to the present invention is different from the disclosure of DE 102017115923A1, in particular, the shaped part is completely removed. In other words, in the context of the present invention, the structural and functional association between the shaped part and the carrier is released. This preferably means that a separate part is used to carry out the structural design of the film and to provide a holder for the film. As mentioned above, the inventor has recognized that by providing a separate shaped part and a carrier, various advantages are achieved in the manufacturing process, which outweigh the possible disadvantages. On the one hand, the shaped part can be completely removed from the back side more simply and cost-effectively. On the other hand, the wafer can be used particularly effectively, especially in the case of producing a large number of MEMS converters. Within the meaning of the invention, the shaped component is therefore not used as a carrier or holder for the membrane in the finished MEMS transducer, but is preferably a (temporary) aid for geometrically shaping the membrane and for applying the membrane layer system.

[0055] Preferably, the film can be attached to the carrier by transferring the film from the support structure to the carrier. As further explained below, this can be achieved, for example, using a mounting component that is suitable for removing the (individual) film from the support structure and applying the removed film to the carrier, on which there is, for example, a conductive adhesive for contacting.

[0056] It is also possible to attach a support structure to the membrane and the membrane layer system, preferably before removing the shaped part. After removing the shaped part, the support structure is used to stabilize the membrane or the membrane layer system. No additional support structure is required. By separating the support structure (with the applied membrane or membrane layer system) accordingly, a plurality of MEMS converters can be obtained, each of which is held by a carrier. In the finished MEMS converter, the carrier is preferably used both for suspending the membrane and for electrical contacting of the membrane. For this purpose, the carrier can preferably also have through contacts, which can act themselves and / or be used as contact points to apply or detect electrical signals.

[0057] By technologically separating the shaping part, which is provided for shaping the film layer system or the film, and the separate support to which the film is later attached, the freedom in the selection and design of the carrier is increased.

[0058] The preferred method also has a favorable effect on the MEMS transducers themselves which can be produced in this way. The membranes which can be produced can be attached starting from the membrane layer system to a freely selectable carrier, for example after being removed from the support structure or by separating it from the carrier structure. Due to the increased flexibility in the suspension or contacting of the end region of the membrane on the carrier, a particularly compact MEMS transducer can be provided, the acoustic connection of which can also be optimized.

[0059] For example, the membrane can be attached to the carrier preferably by means of an electrically conductive process material, which forms both an electrical contact and an acoustic insulation. Furthermore, the rear volume can be variably designed based on the dimensions of the preferred cover according to the desired purpose. Advantageously, the preferred method can thus provide a MEMS transducer that is particularly suitable in terms of acoustic requirements.

[0060] The MEMS transducers which can be produced using the method are designed in such a way that they advantageously combine the possibility of higher acoustic powers with simplified control.

[0061] Unlike known planar MEMS loudspeakers, for example, the vibrating membrane itself does not have to operate over a large area of ​​several square centimeters or at a deflection of more than 100 μm to generate sufficient sound pressure. Instead, a large vertical portion of the vibrating membrane can increase the total volume moved in the vertical emission direction by a horizontal or lateral movement of a few micrometers.

[0062] At the same time, a simplified control can be achieved. In the prior art, a large number of piezoelectric actuators had to be contacted on the horizontal part, while the MEMS transducer described herein can be operated via at least one electrode, preferably located at the end. This reduces manufacturing costs, minimizes sources of failure, and inherently also results in a synchronous control of the horizontal vibration of the vertical part.

[0063] In this way, the air volume present between the vertical sections can be moved extremely precisely by means of horizontal vibrations in the vertical emission direction.

[0064] In this way, it is also possible to provide a particularly powerful MEMS microphone with high audio quality. The construction of a MEMS microphone is structurally similar to a MEMS loudspeaker, in particular with regard to the design of the vibratable membrane. However, instead of controlling electrodes to generate horizontal vibrations and thus sound pressure waves, a MEMS microphone is designed to receive sound pressure waves in the same vertical direction. Preferably, therefore, there is an air volume between the vertical parts, which moves in the vertical detection direction when a sound wave is received. The sound pressure wave excites the vertical parts to perform horizontal vibrations, so that the actuator material generates a corresponding periodic electrical signal, which can be read out by an electronic circuit.

[0065] The term MEMS transducer can therefore be understood as both a MEMS microphone and a MEMS loudspeaker. In general, a MEMS transducer is a transducer for interacting with a volume flow of a fluid, which is based on MEMS technology and whose structures for interacting with the volume flow or for receiving or generating fluid pressure waves have dimensions in the micrometer range (1 μm to 1,000 μm). The fluid can be both a gaseous fluid and a liquid fluid. The structure of the MEMS transducer, in particular the vibratable membrane, is designed to generate or receive pressure waves of the fluid.

[0066] These can be, for example, sound pressure waves, such as in the case of a MEMS loudspeaker or a MEMS microphone. However, a MEMS transducer can also be used as an actuator or sensor for other pressure waves. A MEMS transducer is therefore preferably a device or apparatus which converts pressure waves (e.g. acoustic signals as alternating sound pressure) into electrical signals or vice versa (converts electrical signals into pressure waves, for example into acoustic signals).

[0067] MEMS transducers can also be used as energy harvesters where pneumatic or hydraulic alternating pressure is used. In these cases, the electrical signal can be extracted, stored or fed to other (consumer) devices as harvested electrical energy.

[0068] A MEMS loudspeaker preferably refers to a loudspeaker which is based on MEMS technology and whose sound-generating structure at least partially has dimensions in the micrometer range (1 μm to 1000 μm). Preferably, for example, the dimensions of the vertical part of the vibrating membrane may be less than 1000 μm in terms of width, height and / or thickness. It may also be preferred that, for example, only the height of the vertical part is dimensioned in the micrometer range, while, for example, the length may have a larger dimension and / or the thickness may have a smaller dimension.

[0069] A MEMS microphone is preferably a microphone which is based on MEMS technology and whose sound receiving structure at least partially has dimensions in the micrometer range (1 μm to 1000 μm). Preferably, for example, the dimensions of the vertical part of the vibrating membrane can be less than 1000 μm in terms of width, height and / or thickness. It can also be preferred here that, for example, only the height of the vertical part is dimensioned in the micrometer range, while, for example, the length can have a larger dimension and / or the thickness can have a smaller dimension.

[0070] The MEMS transducer preferably comprises a vibratable membrane for generating or receiving fluid pressure waves in the vertical direction. Thus, a vibratable membrane refers to a structure that is capable of generating an electrical signal after receiving a pressure wave or generating a pressure wave by applying an electrical signal. For this purpose, it is preferred that the vibratable membrane has at least one actuator layer made of an actuator material. The vibratable membrane is preferably configured to have a meandering structure with vertical and horizontal portions.

[0071] A meandering structure preferably refers to a structure which is formed by a sequence of essentially mutually orthogonal parts in a cross section. The mutually orthogonal parts are preferably vertical and horizontal parts of the vibrating membrane. The meandering structure is particularly preferably rectangular in the cross section. However, it may also be preferred that the meandering structure is sawtooth-shaped (zigzag) or curved or wavy in the cross section. This is particularly the case if the vertical part is oriented not completely parallel to the vertical emission direction or detection direction, but forms an angle of, for example, ±30°, preferably ±20°, particularly preferably ±10° with the vertical direction.

[0072] In a preferred embodiment, the horizontal portion may not be completely at an orthogonal angle of 90° to the vertical emission or detection direction, but may form an angle with this direction, for example, between 60° and 120°, preferably between 70° and 110°, and particularly preferably between 80° and 100°.

[0073] Preferably, the vertical and / or horizontal sections are straight at least in sections or over their entire length, but the vertical and / or horizontal sections may also be curved at least in sections or over their entire length. If the vertical and / or horizontal sections of the vibratable membrane are curved or wavy in cross section, the alignment is preferably referenced to a tangent to the vertical and / or horizontal sections at their respective center points.

[0074] The corresponding shape of the membrane can be ensured by designing the shaped part as described above.

[0075] Although the vibratable membrane is preferably aligned horizontally with the sound emission direction or the sound detection direction, sound waves are generated by actuating the vertical portion, or sound waves are detected by actuating the vertical portion.

[0076] The layer of actuator material in the vertical part is preferably used as a component of a mechanical bimorph, wherein a lateral bending of the vertical part is induced by controlling the actuator layer via electrodes or a corresponding electrical signal is generated by inducing a lateral bending. A bimorph is preferably a structure comprising two layers, wherein a displacement and / or bending can be achieved by the interaction of the two layers.

[0077] The meander structure preferably corresponds to a membrane that is folded along the width. Therefore, in the sense of the present invention, the vibrating membrane can preferably also be referred to as a bellows. The parallel folds of the bellows preferably form vertical sections. The connecting parts between the folds preferably form horizontal sections. The vertical sections are preferably longer than the horizontal sections, for example 1.5, 2, 3, 4 or more times longer than the horizontal sections. The horizontal sections preferably refer to structures that enable a connection between two or more vertical sections.

[0078] The performance of a MEMS transducer, in particular a MEMS loudspeaker or a MEMS microphone, may be significantly determined by the number and / or the dimensions of the vertical parts.

[0079] In preferred embodiments, the vibratable membrane comprises more than 3, 4, 5, 10, 15, 20, 30, 40, 50, 100 or more vertical sections.

[0080] In further preferred embodiments, the vibratable membrane comprises less than 10,000, 5,000, 2,000 or 1,000 or fewer vertical sections.

[0081] The preferred number of vertical sections results in higher acoustic power on a minimal chip surface without affecting the sound image or audio quality.

[0082] The vertical portion is preferably flat, which means in particular that the vertical portion has a greater extension in each of the two dimensions of its surface (height, width) than in the dimension perpendicular to it (thickness). For example, a dimension ratio of at least 2:1, preferably at least 5:1, 10:1 or more may be preferred.

[0083] For the purposes of the present invention, the height of the vertical portion preferably corresponds to the dimension in the direction of sound emission or sound detection, while the thickness of the vertical portion preferably corresponds to the sum of the layer thicknesses of one or more layers forming the vertical portion. The length of the vertical portion preferably corresponds to a dimension orthogonal to the height or thickness. In the cross-sectional views of the figures listed hereinafter, the height and thickness are schematically shown (not necessarily to scale), while the length dimension corresponds to the (invisible) drawing depth of the figures.

[0084] In a preferred embodiment, the height of the vertical portion is between 1 μm and 1000 μm, preferably between 10 μm and 500 μm. Intermediate ranges of the above 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. It is understood by those skilled in the art that the above range limits may also be combined to obtain other preferred ranges, such as 10 μm to 200 μm, 50 μm to 300 μm or even 100 μm to 600 μm.

[0085] In a preferred embodiment, the thickness of the vertical portion is between 100 nm and 10 μm, preferably between 500 nm and 5 μm. Intermediate ranges of the above ranges may also be 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. It is understood by those skilled in the art that the above range limits may also be combined to obtain further preferred ranges, such as 500 nm to 3 μm, 1 μm to 5 μm or even 1500 nm to 6 μm.

[0086] In a preferred embodiment, the length of the vertical portion is between 10 μm and 10 mm, preferably between 100 μm and 1 mm. Intermediate ranges of the above ranges may also be 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. It is understood by those skilled in the art that the above range limits may also be combined to obtain further preferred ranges, such as 10 μm to 500 μm, 500 μm to 5 μm or even 1 mm to 5 mm.

[0087] With the above-mentioned preferred dimensions of the vibratable membrane or the vertical part, a particularly compact MEMS transducer, in particular a MEMS loudspeaker or a MEMS microphone, can be provided, which combines high performance with excellent sound image or audio quality. Advantageously, the dimensions can be achieved particularly easily by designing the shaped part accordingly. Preferably, the structure of the shaped part determines the structure of the vibratable membrane comprising the vertical part and the horizontal part.

[0088] The vertical and horizontal (or lateral) directions preferably refer to the preferred directions in which the vibratable membrane is aligned to generate or receive pressure waves of the fluid. Preferably, the vibratable membrane is suspended horizontally between at least two regions of the carrier, and the vertical direction (interaction direction with the fluid) for generating or receiving pressure waves is orthogonal to the vibratable membrane. In the case of a MEMS speaker, the vertical (interaction) direction corresponds to the vertical sound emission direction of the MEMS speaker. In this case, "vertical" preferably means the direction of sound emission, while "horizontal" means the direction orthogonal thereto. 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 or reception of sound, while "horizontal" means the direction orthogonal to the vertical.

[0089] In another preferred embodiment, the method is characterized in that a plurality of MEMS transducers are produced, wherein, in order to produce a plurality of MEMS transducers, a film layer system on a shaped component is structured to form individual films, wherein, particularly preferably, the individual films are separated by interruptions, which are preferably formed as a whole or layer by layer after coating the film layer system.

[0090] The increased process efficiency of the method is particularly evident in the possibility of efficiently producing a large number of MEMS converters, preferably starting from a shaped part or a substrate as a shaped part. A plurality of MEMS converters preferably means 2, 3, 4, 5, 10, 20, 50, 100, 500, 1000 or more MEMS converters.

[0091] A plurality of MEMS converters can preferably be provided by a shaped part, wherein the membrane layer system is preferably first applied to the structured front side of the shaped part. Subsequently, in order to define a single membrane, the membrane layer system can be (laterally) structured by forming interruptions. The interruptions preferably represent areas where one or more (preferably all) layers of the membrane layer system are removed. Particularly preferably, these are linear interruptions, which are formed on the teeth of the comb when the shaped part is designed as a comb structure. Thus, the interruption is located in the region of the horizontal part of the membrane, which connects the vertical part at the front end. The interruption is preferably substantially linear and is characterized by a very small line width. The interruption preferably has a line width of less than 50 μm, preferably less than 30 μm, less than 20 μm, less than 10 μm, less than 5 μm, less than 2 μm or even less than 1 μm.

[0092] The interruptions can be used to determine the size and / or the number of individual films to be formed from the film layer system.

[0093] It is particularly preferred to define the film array by correspondingly forming the interruptions, the extent of the array being determined by the dimensions of the shaped part. For example, it may be preferred to form a correspondingly dimensioned film array on a structured shaped part having square dimensions in the range of 10 mm to 500 mm. For a film with a width and length of 1 mm, for example, a film array of 10×10 to 500×500 can be formed depending on the dimensions of the shaped part.

[0094] The interruption can be formed using known means of the prior art, for example by an etching process. The interruption can be formed integrally after the coating of the film layer system, so that a plurality of (preferably all) layers of the film layer system are structured in a single step. It can also be preferred to form the interruption layer by layer. This means that after each coating of a layer of the film layer system, lateral structuring is achieved by selectively removing the layer at the interruption to be formed.

[0095] Advantageously, the membrane can be formed on the shaped component in a very space-efficient manner using only thin line-shaped interruptions, so that providing a plurality of membranes and correspondingly a plurality of MEMS transducers requires only a low expenditure of material.

[0096] In another preferred embodiment, the method is characterized in that the shaped part is provided by applying a dry etching method and / or a wet chemical etching method to the substrate, wherein the dry etching method is preferably a physical, chemical and / or physicochemical dry etching method, wherein the dry etching method is particularly preferably selected from reactive ion etching (RIE) and / or deep reactive ion etching (DRIE), wherein KOH etching is preferably used as the wet chemical etching method.

[0097] Dry etching in semiconductor technology and microsystems technology is a group of subtractive processes for microstructuring that are not based on wet chemical reactions (such as wet chemical etching). Material is removed by accelerating particles or by activating gases with the aid of plasma. Depending on the method, chemical, physical or physicochemical effects are used.

[0098] Reactive ion etching (RIE) is an ion-assisted reaction process. Due to the good controllability of the etching characteristics, RIE is a method for producing topographic structures in microsystems technology, semiconductor system technology and nanosystems technology. The method allows isotropic (direction-independent) and anisotropic etching by physicochemical subtraction. Etching is carried out by charged particles (ions) generated in a gas plasma. The corresponding masking of the surface (generated, for example, by photolithography) determines the shape of the structure. For example, cavities and free-standing areas can be formed on the substrate by means of a mask, wherein the unetched parts can represent the comb teeth of a comb structure substrate as a shaped part.

[0099] Deep reactive ion etching (DRIE) is a further development of reactive ion etching (RIE) and is a highly anisotropic dry etching process for producing microstructures in substrates with aspect ratios up to 50:1, where structural depths of several hundred microns can be achieved. The DRIE process is a two-stage alternating dry etching process in which etching and passivation steps are performed alternately. The goal is to etch as anisotropically as possible, i.e., to etch perpendicularly to the substrate surface in a direction-dependent manner. In this way, for example, very narrow cavities or recesses can be etched. Therefore, for example, particularly narrow comb teeth and / or free areas of a comb structure substrate are advantageous as shaped parts, which can transform narrow vertical and / or horizontal portions of the film.

[0100] Wet chemical etching is preferably carried out using liquid reactants. The liquid reactant can be a chemical that dissolves the shaped part to be etched, or a chemical mixture that first oxidizes the shaped part and then dissolves the oxide. Preferably, the reactant can be a stronger acid, such as hydrofluoric acid for silicon substrates, or a weaker acid, such as citric acid for gallium arsenide substrates. In the context of the present invention, KOH etching has been shown to be particularly advantageous for preparing the shaped parts. Advantageously, the wet chemical etching process can be carried out quickly, so that a high etching rate can be achieved and the processing time of the preferred process can be reduced. Advantageously, the wet chemical etching process can also be carried out using simple means, such as using a bath and / or a wet chemical spray to achieve high selectivity.

[0101] The above-mentioned etching method is known to a person skilled in the art and can be advantageously used in a preferred embodiment of the method. In particular, the above-mentioned etching method is suitable for providing a structure that corresponds to the meandering structure of the film in order to form a shaped part on a substrate, wherein the meandering structure is preferably formed after the shaped part is coated with the film layer system.

[0102] Depending on the desired structure of the shaped part, recesses can be introduced into the provided substrate in order to obtain the desired meandering structure of the film. It is advantageously possible to select an etching method which ensures efficient implementation and optimal shaping of the film layer system. For example, potassium hydroxide (KOH etching) has a different <111> Orientation <110> Orientation (expressed as Miller index) A distinct preferred direction of etching. The etching rate can thus be selected so that shaped parts can be produced particularly quickly.

[0103] In another preferred embodiment, the method is characterized in that the shaped part comprises a material selected from monocrystalline silicon, polycrystalline silicon, silicon dioxide, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, indium phosphide and glass. The shaped part is preferably formed by structuring the substrate. Structuring can, for example, cause a comb-shaped structure substrate as a shaped part, wherein the structuring is preferably carried out when an etching process is used. The material of the shaped part is preferably a semiconductor material, so that a semiconductor substrate (wafer) can be used to structure it and thus provide the shaped part. Those of ordinary skill in the art know that the terms "wafer" and "(semiconductor) substrate" can be used as synonyms.

[0104] The above-mentioned materials are particularly easy and cost-effective to process in semiconductor technology and / or microsystem technology and are also very suitable for large-scale production. These materials are also particularly suitable for doping and / or coating in order to obtain the required temporary stable connection with the film layer system and / or to achieve optimal, essentially complete removal. The above-mentioned preferred materials for the shaped parts offer a number of advantages due to the availability of standardized process flows.

[0105] The structuring and dimensions of the shaped part are selected according to the desired number and size of films. The shaped part can have characteristic dimensions (e.g. diameter, length and / or width) in the plane, for example, in the range between 10 mm and 500 mm, while the thickness or height (largest dimension orthogonal to the plane) is in the range of 100 μm to 1000 μm. A comb-like structure with corresponding dimensions as described above is introduced to form the desired film with a meandering structure, wherein a large number of films can be provided on the shaped part in the plane due to the macroscopic dimensions.

[0106] In a further preferred embodiment, the method is characterized in that the shaped component is completely removed by a wet-chemical etching method, wherein the wet-chemical etching method is preferably selected from KOH and / or TMAH etching.

[0107] Advantageously, by using a wet chemical etching method, a thinner sacrificial layer can be used, thereby saving material of the sacrificial layer and thus contributing to the process efficiency of the preferred method. In addition, the wet chemical etching method can be carried out simply and in a controlled manner, thereby ensuring reliable and complete removal of the shaped part. Advantageously, the selectivity of the wet chemical etching method is high, thereby minimizing the risk of unintended etching processes, damage and / or possible contamination.

[0108] Furthermore, multiple executions of dry etching methods and / or physicochemical etching methods, such as DRIE etching, can be advantageously omitted, as these methods are time-consuming and costly. Therefore, by performing a wet chemical etching process once, the process efficiency can be significantly improved.

[0109] In a wet chemical etching process, preferably chemical bonds of the shaped part are broken by the etching medium and converted into soluble components. KOH and / or TMAH etching has proven to be a particularly suitable etching process in the context of the present invention.

[0110] In KOH etching, potassium hydroxide (KOH) in solution is preferably used to substantially completely remove the shaped part. In TMAH etching, a solution containing tetramethylammonium hydroxide (TMAH) is preferably used. Both wet chemical etching processes have good selectivity in terms of material selection of the sacrificial layer and / or the shaped part.

[0111] In a further preferred embodiment, the shaped part is completely removed by a dry etching process, wherein the dry etching process is preferably a physical, chemical and / or physicochemical dry etching process, wherein the dry etching process is particularly preferably selected from reactive ion etching (RIE) and / or deep reactive ion etching (DRIE).

[0112] Can also preferably remove the shaped parts completely by steam etching process (etching by using the etchant as steam or gas).For example, can carry out xenon difluoride vapor etching (XeF2 vapor etching) as steam etching process.Isotropic xenon difluoride vapor etching is advantageously accompanied by the high selectivity of (semiconductor) substrate (particularly silicon).

[0113] The etching processes mentioned for completely removing the shaped parts can be carried out individually or in combination with one another.

[0114] In a preferred embodiment, the method is characterized in that, after structuring the membrane layer system, the plurality of membranes are connected to a support structure by means of a detachable connection.

[0115] By connecting the membrane to the support structure, the stability required for the membrane after the shaped part has been completely removed can advantageously be achieved. In particular, the support structure advantageously ensures that the tortuous structure of the membrane is maintained and the risk of shape loss is reduced. Since the support structure itself is not part of the MEMS transducer, but only serves to temporarily stabilize the membrane, the support structure can be selected in particular from a cost point of view. For example, the support structure can be made of a flat plastic substrate or be designed as a film, preferably as an adhesive film. Basically, various materials and geometries of the support structure are suitable, as long as they ensure sufficient stability of the membrane and are also suitable for forming a connection in a detachable manner.

[0116] The detachable connection of the membrane to the support structure serves for a later transfer of the membrane to a carrier, wherein, as described below, for example mounting components can be used.

[0117] The detachable connector is preferably applied in the manner of an interruption along the film layer system, thus along the end region of the individual films. The detachable connector is preferably a decomposable connector, so that the films can be removed from the film layer system without potential hazards.

[0118] For example, the separable connector can be an adhesive, preferably a UV adhesive. UV adhesive is an adhesive that hardens by being irradiated with UV rays. The UV adhesive can be dissolved, for example, by heating, i.e. by a thermal effect and / or using a corresponding solvent. The UV adhesive preferably comprises epoxy resin and / or acrylate. The separable connector can also be an adhesive that can be dissolved by heat and / or by chemistry. The adhesive that can be dissolved by heat can, for example, be selected from wood glue, elastomer and / or silicone adhesive. The adhesive that can be dissolved by chemistry, i.e. the adhesive whose connection can be dissolved by using a chemical solution, can, for example, comprise polyurethane.

[0119] In a preferred embodiment, the method is characterized in that the membrane is removed from the support structure by means of the mounting component, wherein the membrane is preferably attached to the carrier after the membrane has been removed from the support structure.

[0120] The mounting part preferably refers to a device that can remove the film from the film layer system or from the supporting structure after the forming part is completely removed. The mounting part can be, for example, arranged to apply a low pressure so that the film is removed from the detachable connector or from the supporting structure by a pressure difference. In other embodiments, a vacuum tensioning device (porous suction cup) and / or a pressure needle (Drucknadel) can also be used. Preferably, a porous body, such as a porous ceramic material, is used, wherein the low pressure is applied through the holes of the porous body. The required suction is generated by preferably substantially evenly distributed holes and / or hole sizes, while ensuring that the tortuous structure of the film maintains its shape. It can thus be advantageously achieved that the film is removed from the film layer system in a particularly reliable manner. It may also be preferred to use a pick-and-place tool to mount the parts.

[0121] In particular, the preferred mounting components described above have proven to be particularly reliable so that the shape of the delicate components of the film is not affected during the transport from the support structure to the carrier. In addition, the preferred mounting components, such as pick-and-place tools, can simultaneously support the release process, for example by heating in the case of a heat-detachable adhesive. It should also be understood that it may also be preferred to use a plurality of mounting components to simultaneously transfer a corresponding plurality of films from the support structure to the corresponding carrier. The mounting components can be dimensioned accordingly to reduce the production time, in particular by parallel processing.

[0122] Preferably, the membrane is attached to the carrier after it has been removed from the support structure. This can preferably be done directly using the mounting components so that after the membrane has been removed, the membrane can be attached to the carrier in a continuous process sequence. This advantageously avoids complex processing steps for bringing the membrane into contact with the carrier. Instead, the preferred method provides the option of using the mounting components to ensure an automated sequence of removing the membrane and accurately attaching the membrane to the carrier.

[0123] In a preferred embodiment, the method is characterized in that the membrane is attached to the carrier via an electrically conductive process material, wherein the electrically conductive process material is preferably selected from an electrically conductive adhesive or an electrically conductive soldering material.

[0124] The carrier is preferably a structure with a substantially continuous border so that the membrane can be stably positioned in the end region. The carrier itself is preferably stable and rigid in order to provide sufficient strength.

[0125] The carrier preferably has one or more openings which serve in particular as sound inlet or sound outlet.

[0126] The term "sound inlet" is preferably used in embodiments in which the MEMS transducer is used as a MEMS microphone. The sound reaches the membrane through the sound inlet, causing the membrane to vibrate due to the sound waves. The signal generated in this way, which is indicative of the incoming sound, can preferably be read out by an electronic circuit also located on the carrier.

[0127] Conversely, the term "sound outlet" is preferably used in embodiments in which the MEMS transducer is used as a MEMS loudspeaker. The sound is transmitted from the vibratable membrane into the environment through the sound outlet opening, wherein the vibration of the membrane is preferably generated by an electronic circuit.

[0128] Preferably, a conductive process material is introduced to simultaneously achieve a mechanical connection and an electrical connection between the carrier and the membrane. The conductive process material can preferably be applied to the end region of the membrane before the membrane is positioned on the carrier. The end region of the membrane refers in particular to the lateral region of the membrane, so that the membrane is preferably connected to the carrier along its edge. The conductive process material can also preferably be applied to the carrier first so that the membrane can then be attached to the carrier. Here the membrane is preferably attached to the carrier from the front. This means that the carrier contacts the membrane in particular in the lateral region starting from the front of the membrane, that is, the side of the membrane that is facing away from the formed part in the membrane layer system and points to the direction of sound emission or sound detection in the finished MEMS converter.

[0129] Preferably, the electrically conductive process material is present in the form of a closed loop on the carrier or on the membrane in order to enable optimal fastening of the membrane to the carrier and to enable acoustic insulation of the membrane at the lateral (or horizontal) portions.

[0130] An electrically conductive process material is preferably a process material that is electrically conductive. The process material advantageously ensures a reliable, stable and permanent connection between the membrane and the carrier. In particular, acoustic insulation and electrical contacting of the membrane (or in particular its actuator layer) with the preferably electronic circuit are also advantageously achieved. For example, an electrical connection, such as a bond, can exist between the electronic circuit and the electrically conductive process material.

[0131] The conductive process material is preferably selected from a conductive adhesive, a conductive solder material or a conductive bonding material. The preferred material selection for the conductive process material ensures acoustic isolation and electrical contact. In addition, a flexible connection can be obtained by the conductive adhesive or solder material, which is beneficial to the vibration characteristics of the membrane. In addition, the preferred material is durable and ensures a long service life of the MEMS converter.

[0132] In a further preferred embodiment, the method is characterized in that the carrier part is connected to the cover part, wherein the cover part preferably has a cover part opening.

[0133] The cover preferably refers to a solid and in particular protective housing for the MEMS converter. In particular, the cover serves to protect components of the MEMS converter from foreign bodies and / or from damage. The cover thus extends substantially over preferred components of the MEMS converter, for example over the membrane, the electrical connections and / or the electronic circuit. The cover is preferably located on the back side of the carrier of the membrane.

[0134] Furthermore, the rear volume of the MEMS transducer can be adjusted by appropriately dimensioning the cover, thereby making it possible to easily adapt the acoustic properties of the MEMS transducer to the desired application.

[0135] The cover preferably has a cover opening. Advantageously, since the cover has the cover opening, the acoustic properties of the MEMS transducer can be further optimized. In particular, the introduction of the cover opening leads to an increase in the effective rear volume.

[0136] Preferably, the fastening area is located on the cover so as to connect the carrier to the cover. Conventional methods known in the prior art, such as soldering and / or bonding, can be used. Various fastening schemes and methods for this are known to those skilled in the art and will therefore not be explained in detail.

[0137] In a further preferred embodiment, the method is characterized in that, after structuring the film layer system, a plurality of films are connected to the carrier structure and the shaped part is then completely removed.

[0138] The carrier structure preferably refers to a structural pre-stage for providing one or more carriers. The carrier structure is preferably already characterized by structural components, which the carrier of the membrane preferably has, such as one or more sound inlets or outlets, through-contacts and / or electronic circuits. Therefore, the carrier structure can preferably be understood as an array of carrier elements, which are (still) present in a coherent manner in the carrier structure and form the carrier by being separated.

[0139] The carrier structure preferably has dimensions such that it can be attached to the film layer system in a precisely fitting manner, wherein particularly preferably each carrier element comes into contact with the film to be formed.

[0140] The carrier structure preferably also has sufficient stability to ensure that the tortuous structure of the membrane or membrane layer system is maintained during complete removal of the shaped part. The shaped part is preferably completely removed only after the carrier structure has been connected to the membrane layer system.

[0141] Preferably, the attachment of the carrier structure can be carried out after the structuring of the film layer system and thus after the film layer system has been disassembled to form the film, with the interruptions as described above inserted. Preferably, the carrier structure is connected to the film layer system by means of an electrically conductive process material at the locations of the interruptions in the film layer system, which interruptions correspond to the end regions of the film to be formed.

[0142] In a further preferred embodiment, the method is characterized in that after complete removal of the shaped part, the carrier structure is separated region by region, so that a plurality of carriers is provided starting from the carrier structure, and the membrane is attached to each of the plurality of carriers.

[0143] Separating region by region preferably means spacing or separating the carrier structure in parts. Since the carrier structure is preferably understood as a pre-stage for one or more carriers, the carrier on which the membrane is suspended and in electrical contact is preferably directly provided by separating region by region. For separation region by region, mature techniques in the prior art can be used according to the choice of carrier material to ensure accurate and process-efficient separation region by region. For example, it is preferred to perform cutting, which preferably includes a step selected from the group consisting of scribing, breaking, sawing and / or (laser) cutting.

[0144] In a preferred embodiment, a protective foil is applied to the carrier structure, which is located on the side opposite to the membrane system and preferably extends at least to the area of ​​the sound inlet or the sound outlet, preferably to the entire surface of the carrier structure. The protective foil can provide protection for the carrier structure or the carrier to be formed in different processing steps, for example during the complete removal of the formed part by etching or during the separation of the carrier structure region by region by cutting. Preferably, the protective foil can be used as a so-called dicing foil to indicate the end point of the separation region by region by cutting.

[0145] In a preferred embodiment, the method is characterized in that the carrier structure is connected to a plurality of covers, wherein preferably a plurality of covers have a cover opening.

[0146] Preferably, the attachment of the plurality of covers is carried out in such a way that a precisely fitting cover is provided for each individual film at the interruption of the structured film layer system or at the end region of the film. Preferably, the plurality of covers is attached before the carrier structure is separated region by region, so that parallel processing is achieved and efficiency is increased. Likewise, the covers can also be attached after the carrier structure has been separated region by region to form the individual carriers.

[0147] As mentioned above, the cover is preferably attached to the rear side of the carrier, wherein it may be preferred that the cover has one or more cover openings to increase the rear volume.

[0148] The obtained MEMS transducer comprising a vibratable membrane held by a carrier and preferably protected on the back by a cover can be removed from the protective foil and transported or prepared for further integration into a product, preferably using mounting components.

[0149] In another preferred embodiment, the method is characterized in that the membrane comprises at least two layers, both layers comprise actuator material and each layer is in contact with an electrode, and horizontal vibrations can be generated by a shape change of one layer relative to the other layer, or horizontal vibrations cause a shape change of one layer relative to the other layer and generate an electrical signal.

[0150] In this embodiment, the horizontal vibration is achieved by a relative shape change of the two actuator layers. The actuator layers can consist of the same actuator material and can be controlled differently. The actuator layers can also consist of different actuator materials, for example piezoelectric materials with different deformation coefficients. An actuator layer is to be understood here as a part of a film layer system, which is preferably applied to a shaped part as described above.

[0151] For the purposes of the present invention, a "layer comprising an actuator material" is preferably also referred to as an actuator layer. An actuator material is preferably a material which undergoes a change of shape when a voltage is applied, for example stretching, upsetting or shearing, or conversely a material which generates an electrical voltage when changing shape. Preferably, a material having an electric dipole undergoes a change of shape when a voltage is applied, whereby the orientation of the dipoles and / or the orientation of the electric field can determine the preferred direction of the change of shape. The actuator material is preferably selected from piezoelectric materials, piezoelectric polymer materials and / or electroactive polymers (EAPs).

[0152] In another preferred embodiment, the method is characterized in that the membrane comprises at least two layers, wherein the first layer comprises the actuator material and the second layer comprises the mechanical support material, wherein at least the first layer comprising the actuator material is in contact with the electrode, so that horizontal vibrations can be generated by a shape change of the actuator material relative to the mechanical support material, or so that the horizontal vibrations cause a shape change of the actuator material relative to the mechanical support material and generate an electrical signal.

[0153] In the sense of the present invention, a "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 withstand shape changes of the actuator layer. In contrast to the actuator layer, the mechanical support material preferably does not change shape when a voltage is applied. The mechanical support material is preferably electrically conductive, so that the mechanical support material can also be used directly for contacting the actuator layer. However, in some embodiments, the mechanical support material can also be non-conductive, for example, coated with a conductive layer.

[0154] The mechanical support material is particularly preferably single-crystalline silicon, multicrystalline silicon or doped polycrystalline silicon.

[0155] When the actuator layer is controlled, it can, for example, be subjected to lateral or longitudinal stretching or upsetting. This generates a stress gradient relative to the mechanical support layer, which leads to lateral bending or vibration. This can be achieved, for example, by changing the polarity on the electrodes, preferably by push-pull operation, so that almost the entire air volume between the vertical parts can be moved alternately in the vertical emission direction.

[0156] While the actuator layer changes shape when a voltage is applied, the position of the mechanical support material remains essentially unchanged. The stress gradient generated between the two layers (mechanical bilayer piezoelectric) preferably leads to horizontal bending. For this purpose, the thickness of the support layer should preferably be selected in comparison with the thickness of the actuator layer so that a sufficiently large stress gradient is generated for bending. For doped polysilicon and piezoelectric materials such as PZT or AlN as mechanical support material, essentially equal thicknesses have proven to be particularly suitable, preferably between 0.5 μm and 2 μm.

[0157] Contacting of the actuator layer and / or the layer made of mechanically supporting material and thus application of a voltage can take place directly via the terminal electrodes or can be supported via a layer made of electrically conductive material.

[0158] The end positioning of at least one electrode preferably means that contact with an electronic device, for example contact with a current or voltage source in the case of a MEMS speaker, can be made at one end of the vibrating membrane, preferably at the end where the membrane is suspended on a carrier. The electrode preferably refers to an area made of a conductive material, preferably a metal, which is arranged for contact with an electronic device, for example contact with a current and / or voltage source in the case of a MEMS speaker. Preferably, it can be a conductive adhesive, a welding material or an electrode pad. The electrode is particularly preferably used for contacting an electronic device and is itself connected to a conductive metal layer, which can extend over the entire surface of the vibrating membrane. The conductive layer together with the end contacts realized by the electrode pad or the conductive process material are partially referred to as electrodes below, such as top electrodes or bottom electrodes.

[0159] 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 serves as a top electrode, a middle layer is formed of an actuator material, and a lower layer is formed of a conductive material and serves as a bottom electrode, wherein the conductive material of the upper and / or lower layer is preferably a mechanical support material.

[0160] The top and / or bottom electrode is preferably present as a layer of an electrically conductive material, preferably a metal, and as a continuous or full-surface or coherent layer of the vibratable membrane, which forms a substantially uniform surface and is not structured, in particular, in the region of the respective membrane. In contrast, two or more vertical sections are preferably connected to the end electrodes via an unstructured layer of an electrically conductive material, preferably a metal, so that when the membrane is excited by vibrations emitted by the electronics on the carrier, the actuator layer can be actuated to excite the membrane to vibrate or to read signals generated in the actuator layer.

[0161] The terms "top" and "bottom" preferably refer to the location of the conductive material, so that in cross section one can say that the top electrode includes the conductive material above (or front side) the actuator layer, and the bottom electrode includes the conductive material below (or back side) the actuator layer.

[0162] By means of a layer made of an electrically conductive material, preferably a metal, the two or more vertical sections can advantageously be contacted with a terminal electrode or an electrode pad or an electrically conductive process material.

[0163] In a further preferred embodiment, the layer of electrically conductive material is formed from a support material, so that, for example, the bottom and / or top electrode simultaneously serves as a mechanical support layer.

[0164] In an exemplary embodiment, a sacrificial layer is first applied to the shaped part to form a membrane layer system, then a conductive material for the bottom electrode is applied, which conductive material also serves as a support layer, then an actuator material for providing the actuator layer is applied, and then another conductive material (which is not necessarily a support material) for providing the top electrode is applied (see Figure 2 ).

[0165] 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 to the membrane, wherein the electronic circuit is preferably attached to a carrier.

[0166] Preferably, the electronic circuit is selected without limitation from: 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 other electronic circuits that are preferably programmable.

[0167] Depending on the use of the MEMS transducer, for example as a MEMS microphone or a MEMS loudspeaker, the electronic circuit is designed to excite the membrane to vibrate (thereby generating sound waves) and / or to detect the vibration of the membrane (due to the excitation of incident sound waves).

[0168] In the case of a MEMS microphone, the electronic circuit preferably enables reading out or detection of the electrical signal generated when a sound pressure wave appears on the membrane and thereby excites the vertical portion to vibrate horizontally.

[0169] In the case of a MEMS loudspeaker, the electronic circuit is preferably arranged to generate an electrical signal to excite the vertical portion to vibrate, thereby generating a sound pressure wave in the vertical emission direction.

[0170] The electronic circuit is preferably mounted on a carrier.In embodiments using a carrier structure, one or more electronic circuits may be incorporated into the carrier structure.

[0171] With regard to the choice of the carrier, flexibility in design and electrical properties is advantageously increased. Specifically, the carrier can be used as a circuit carrier in addition to supporting the membrane. In particular, electrical contact between the membrane and the conductive part of the carrier, such as through contacts, can be achieved by conductive process materials. In some embodiments, the producible MEMS converter can adopt a bottom port design.

[0172] In another preferred embodiment, the method is characterized in that the material comprised by the carrier is selected from aluminum, ceramic, copper clad laminate (CCL) and / or fiberglass resin, wherein the fiberglass resin is preferably selected from FR-4 or FR-5. Semiconductor materials can also be used, as disclosed above for the shaped parts. By separately providing the shaped parts for shaping the membrane layer system or the membrane and the separate carrier to which the membrane is subsequently attached, it is advantageously possible to select a carrier material that meets the requirements of mechanical stability, easy electrical contact and ensuring an optimal acoustic sound image, regardless of the requirements for the shaping of the membrane.

[0173] The preferred materials for the carrier described above have proven to be advantageous because they allow a good connection between the membrane and the carrier. In particular, further components such as conductor tracks, solder pads, etc. can advantageously be reliably attached and / or handled. In addition, the materials have proven to be particularly stable and temperature-resistant in various areas of use and processing.

[0174] In another aspect, the invention relates to a MEMS transducer which is or can be produced by a preferred embodiment of the method according to the invention.

[0175] Those skilled in the art will recognize that the technical features, limitations, advantages and preferred embodiments described for the method for manufacturing a MEMS converter according to the present invention are also applicable to the MEMS converter that can be manufactured according to the present invention, and vice versa.

[0176] The manufacturable MEMS transducer advantageously has the following features: for example, a higher degree of design freedom in terms of the carrier design and the attachment of the membrane to the carrier. This is achieved in particular by the fact that, compared with the prior art, the shaped part is completely removed without retaining a substrate or a shaped part as a carrier. As described above, it can thus be positioned individually on any carrier. In addition, the complete removal of the shaped part has the advantageous effect that a particularly compact MEMS transducer can be manufactured.

[0177] The method steps according to the invention for producing a MEMS transducer therefore result not only in a particularly economical and process-efficient production method, but also in an advantageous structural design of the MEMS transducer.

[0178] The method steps according to the invention have a direct influence on the structural properties of the MEMS converter, so that a person skilled in the art can easily and clearly determine whether a manufactured MEMS converter is manufactured by the method according to the invention.

[0179] As defined by the step of completely removing the shaped part, the manufacturable MEMS transducer is characterized by being free of material from the shaped part. In particular, the back side is free of residual structures of the shaped part, which, for example, as proposed in WO 2021 / 144400 A1, serves as a carrier.

[0180] Instead, the membrane is in particular attached to a separate carrier, wherein the contact between the membrane and the carrier occurs on the front side of the vibratable membrane and not on the back side as proposed in WO 2021 / 144400 A1.

[0181] Therefore, it is preferably provided that a separate component is used to ensure the geometry of the membrane and the support for the membrane. In particular, in order to produce a MEMS converter, the shaped component is completely removed. The membrane is attached to a support as a separate component. Since the lateral limiter for holding the membrane in the finished support does not exist for the shaped component that is only partially removed, it can also be determined based on the manufactured MEMS converter itself that the shaped component is completely removed according to the present invention. In particular, a person skilled in the art will clearly recognize that the shaped component for providing the tortuous shape of the membrane is no longer a component of the MEMS converter. In this regard, a person skilled in the art can also clearly distinguish the MEMS converter produced by the method according to the present invention from, for example, the known MEMS converter in DE 10 2017 115923A1, the membrane of which is constructed by providing a negative mold, wherein the side areas of the negative mold form a carrier or holder for the membrane. For example, a person skilled in the art can distinguish whether the film is deposited on the carrier while the carrier is still part of the shaped part or the negative mold, or whether the film is attached to the carrier as a separate part, for example by means of an electrically conductive process material.

[0182] Therefore, in a preferred embodiment, the present invention relates to a MEMS transducer for interacting with a fluid volume flow, the MEMS transducer comprising:

[0183] - a carrier; and

[0184] - a membrane for generating or receiving fluid pressure waves in vertical direction, the membrane being held by a carrier,

[0185] wherein the membrane has a meandering structure with vertical portions and horizontal portions, wherein the vertical portions are substantially parallel to the vertical direction and the horizontal portions connect the vertical portions to each other, wherein the membrane comprises at least one actuator layer made of an actuator material and in contact with at least one electrode, such that the vertical portions can be excited 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 portions are excited to vibrate horizontally,

[0186] It is characterized in that

[0187] The membrane is attached to the carrier at the front side.The front side preferably denotes the side of the membrane facing the fluid, ie the side in which the membrane generates pressure waves or the side from which it can receive pressure waves.

[0188] In a further preferred embodiment, the membrane is attached to a carrier at the front side, wherein the carrier has a substantially continuous edge, so that the membrane can be stably positioned in the end region.

[0189] In a further preferred embodiment, the carrier has one or more openings which serve as sound inlet or sound outlet, depending on whether the MEMS transducer is used as a MEMS microphone or as a MEMS loudspeaker, wherein the front side of the membrane preferably faces the sound inlet or sound outlet. Particularly preferably, an electrically conductive process material, such as an electrically conductive adhesive or an electrically conductive soldering material, is used for the mechanical and electrical connection between the carrier and the membrane, as described above, thereby enabling particularly good acoustic insulation and stable electrical contact. Therefore, not only the position of the carrier relative to the membrane, but also the type of attachment is a feature of the MEMS transducer which can be produced by the method according to the invention.

[0190] The MEMS transducer preferably adopts a bottom port design, that is, there are one or more sound inlet or outlet ports on the carrier, and these openings are preferably located opposite the back side of the membrane. Advantageously, the rear volume of the bottom port design of the MEMS microphone or MEMS speaker is larger than the front volume. The large air volume in the rear volume makes it easier for the membrane to move under the influence of sound waves. This in turn improves the performance of the MEMS speaker or the sensitivity or signal-to-noise ratio of the MEMS microphone.

[0191] Aspects of the invention will be explained in more detail below using examples, but without being restricted to these examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0192] Figure 1 A comparison of the preferred steps for preparing a MEMS transducer with methods previously disclosed in the prior art;

[0193] Figure 2 A schematic diagram of preferred steps for coating a shaped part with a film layer system;

[0194] Figure 3 Schematic diagram of preferred method steps for further processing of a shaped component with a film layer system using a support structure and a mounting component to produce a MEMS transducer;

[0195] Figure 4 Schematic representation of preferred method steps for further processing of a shaped component with a membrane layer system to produce a MEMS transducer by attaching the membrane layer system to a carrier structure. DETAILED DESCRIPTION

[0196] Figure 1 For illustrating a MEMS converter according to WO 2021 / 144400 A1 and its production and for a comparison with a MEMS converter which can be produced using a preferred method.

[0197] Figure 1A of WO 2021 / 144400 A1 shows, by way of example, a MEMS transducer. The membrane 5 is held by a carrier region or a carrier 39, the membrane 5 extending horizontally between the side regions of the carrier region 39. The vertical direction for generating or receiving pressure waves, in particular sound waves, is orthogonal to the horizontal extension of the membrane 5. A housing is provided by a cover 23, and the front side of the membrane 5 is held opposite to the opening on the carrier 39. The membrane 5 has a vertical portion 4, which is substantially parallel to the vertical direction and includes at least one layer 11 made of an actuator material. The membrane 5 is in contact with an electrode at its end region, so that the vertical portion 4 can be excited to vibrate horizontally and a pressure wave can be emitted by controlling at least one electrode. In turn, the vertical portion 4 can be excited to vibrate horizontally by the pressure wave, so that an electrical signal can be generated at the electrode.

[0198] Advantageously, due to the horizontal movement (deflection or fluctuation) of the plurality of vertical sections 4 of the vibratable membrane 5 of only a few micrometers, a larger total volume can be moved in the vertical emission direction and can therefore be used to generate sound. Thus, the design of the vibratable membrane 5 including the vertical sections leads to an increase in the acoustic power in the case of a MEMS loudspeaker. In the case of a MEMS microphone, an increase in performance and audio quality as well as a suitable sound image (Klangbild) are also achieved.

[0199] Figure 1 B and Figure 1 C shows the known process steps for producing such a MEMS converter.

[0200] After coating the film 5 on the structured carrier substrate, the film 5 can be exposed by DRIE etching starting from the back side (see Figure 1 B, right, arrow from below). In this case, the edge region of the carrier substrate is retained as a carrier 39, between which the membrane 5 is suspended. However, the disadvantage of DRIE etching from the back is that it is cumbersome and cost-sensitive. In addition, DRIE etching is also accompanied by restrictions in terms of the choice of the sacrificial layer (stop oxide) and the possibility of achieving different depths during the etching process. In addition, processing steps such as grinding and in particular cutting of the carrier substrate are required to provide a plurality of MEMS transducers.

[0201] exist Figure 1 In C, the back side of the membrane 5 is exposed by KOH etching, and the edge area of ​​the carrier substrate is retained as a carrier 39, between which the membrane 5 is suspended. It can be clearly seen that the size of the carrier 39 is large, which detracts from the compactness of the MEMS converter.

[0202] like Figure 1As shown in D, when a large number of MEMS converters are produced, this will also lead to an increase in the space requirements between the individual MEMS converters, thereby reducing the utilization efficiency of the chip and increasing the cost.

[0203] Figure 1 E schematically shows the intended complete (backside) removal of the shaped part or carrier substrate (bottom), in contrast to the previously shown method in which an edge region of the structured substrate was retained to serve as a carrier 39 for the film 5 (above, crossed out).

[0204] Figure 2 The preferred steps for applying the film system 9 to the shaped part 7 are schematically shown. The film system 9 is applied to the shaped part 7 starting from the front side.

[0205] Figure 2 A shows a shaped part 7, which is first provided before the film layer system 9 is applied. The shaped part 7 is prepared as a comb-shaped structure substrate 7, which includes a comb-shaped tooth portion 43 and a recessed area 45. The meandering structure of the film to be obtained can be set by the structure of the shaped part 7 (for example, by the length and / or width of the comb-shaped tooth portion 43 and / or the recessed area 45). The preparation of the shaped part 7 can be carried out, for example, by a DRIE etching process or KOH etching.

[0206] Figure 2 B shows firstly the application of a sacrificial layer 35 on the shaped part. The sacrificial layer 35 serves in particular to protect the membrane or membrane layer system 9 when the shaped part 7 is removed, preferably by wet chemical etching. The sacrificial layer 35 can be, for example, TEOS or PECVD.

[0207] like Figure 2 As shown in FIG. 3C , a layer of conductive material is coated on the sacrificial layer 35 , and the conductive material layer can be used as the bottom electrode 29 of the membrane. Then, Figure 2 D shows the application of an actuator layer 11, which comprises an actuator material, for example a piezoelectric material. The piezoelectric material may preferably have a c-axis orientation perpendicular to the surface, but other orientations are also possible. Figure 2 FIG. E shows the application of another layer of conductive material to form the top electrode 27 .

[0208] Therefore, the membrane layer system 9 on the shaped part comprises a sacrificial layer 35, a bottom electrode 29, an actuator layer 11 and a top electrode 27. It is understood that the sacrificial layer 35 is preferably removed during the further manufacturing process of the MEMS converter, so that the membrane 5 in the finished MEMS converter has an upper layer as the top electrode 27, an intermediate layer as the actuator layer 11 and a bottom electrode 29. The bottom electrode 29 can preferably be formed from a conductive support material so that the bottom electrode also serves as a passive support layer.

[0209] Figure 3 The use of a support structure 17 and a mounting member 19 for mounting a Figure 2 The shaped component 7 of the film layer system 9 is further processed for the preferred method step of producing a MEMS transducer.

[0210] Figure 3 A shows a film system 9 on a shaped part 7. After coating on the shaped part 7, the film system has a vertical part 4 and a horizontal part 6. In addition, Figure 3 A shows that the film layer system 9 can have interruptions 13, wherein the interruptions 13 are formed by structuring the film layer system 9, in particular by lateral structuring. Thus, a plurality of films 5 can be produced from a single shaped part 7. To this end, the film layer system 9 is first applied to the structured front side of the shaped part 7. In order to define the individual films 5, interruptions 13 are preferably formed by lateral structuring of the film layer system 9. Figure 3 As shown in A, the interruption 13 is preferably formed on the comb teeth 43 and is therefore present in the region of the horizontal portion 6 of the membrane 5 which connects the vertical portions 4 to one another at the upper or front end.

[0211] exist Figure 3 In B, the connection of the film layer system 9 to the support structure 17 after being structured is shown via a detachable connection element 15. The detachable connection element may include an adhesive, such as a UV adhesive.

[0212] By being connected to the support structure 17, it can be advantageously ensured that the membrane 5 has the kind of stability that is required after the shaped part 7 has been completely removed. The support structure 17 thus advantageously ensures that the meandering structure of the membrane 5 is maintained and the risk of deformation is reduced. Since the support structure 17 itself is not part of the MEMS transducer but is only used to temporarily stabilize the membrane 5, the support structure 17 can be selected from a cost point of view. The support structure 17 can, for example, be made of a flat plastic substrate or be designed as a film, preferably as an adhesive film.

[0213] The detachable connector 15 connecting the film 5 to the support structure 17 is used to later transfer the film 5 to the carrier. For this purpose, the detachable connector 15 is preferably present in a manner applied along the interruption 13 of the film layer system 9 and thus along the end region of the individual films 5. The detachable connector is preferably a disintegratable connector so that starting from the film layer system 9, the film 5 can be removed without any damage and thus reliably.

[0214] Figure 3 C shows the complete removal of the shaped part 7. The complete removal of the shaped part can preferably be carried out by means of a wet chemical etching process, in particular by KOH and / or TMAH etching. By using a wet chemical etching process to completely remove the shaped part 7, a thinner sacrificial layer 35 can be advantageously used and material can be saved. In addition, due to the high selectivity of the wet chemical etching process, the material selection of the sacrificial layer 35 is also richer than, for example, a DRIE etching process.

[0215] Figure 3 D schematically shows the removal of the membrane 5 from the support structure 17 by means of the mounting means 19. The mounting means 17 can, for example, be arranged to apply a low pressure so that the membrane 5 is released from the detachable connection 15 or the support structure 17 by a pressure difference. A vacuum tensioner, a pressure pin and / or a pick-and-place tool can also be used as the mounting means 19.

[0216] The above-described options for the mounting element 19 have proven to be particularly reliable in order not to affect the shape of delicate components of the membrane 5 during transport from the support structure 17 to the carrier.

[0217] After the film 5 is removed using the mounting member 19, the film 5 is attached to the carrier 3 by means of the conductive process material 33, such as Figure 3 As shown in E. The carrier 3 is preferably a structure with substantially continuous edges so that the membrane 5 can be stably positioned in the lateral end region. The carrier 3 preferably has one or more openings, which are used as sound inlet or outlet, depending on whether the MEMS transducer is used as a MEMS microphone or as a MEMS speaker. The conductive process material 33 is used to provide a stable connection between the carrier 3 and the membrane 5. In addition, the conductive process material 33 enables acoustic isolation and the possibility of electrical contact with the electronic circuit 31.

[0218] Figure 3 F shows that the electronic circuit 31 (here an "ASIC") is preferably attached to the carrier 3. Depending on the purpose of the MEMS transducer, for example as a MEMS microphone or a MEMS loudspeaker, the electronic circuit 31 is preferably arranged to excite the membrane 5 to vibrate (thereby generating sound waves) and / or detect vibrations of the membrane 5 (generated due to the excitation of incident sound waves).

[0219] The carrier 3 can then be connected to the cover 23, which has a cover opening 25 ( Figure 1 G). By means of the cover 25, a strong protective housing is applied to the MEMS converter, in particular for protecting the components of the MEMS converter 1. Thus, the cover 23 extends substantially over all components of the MEMS converter, for example over the membrane 5, the electrical connections and the electronic circuit 31. Furthermore, the dimensions of the cover 25 provide the possibility of setting the rear volume of the MEMS converter 1 according to the desired acoustic properties.

[0220] Figure 4 The invention shows that the film layer system 9 is attached to the carrier structure 21. Figure 2 The shaped component 7 of the film layer system 9 is further processed to produce a MEMS transducer in a preferred method step.

[0221] Figure 4 A shows the connection of the film 5 or the film layer system 9 to the carrier structure 21. The connection between the film 5 and the carrier structure 21 can be realized by means of an electrically conductive process material 33. The carrier structure 21 is preferably attached after the film layer system 9 has been structured to form the interruption 13.

[0222] The carrier structure 21 preferably represents a structural precursor of one or more carriers and can also be understood as an array of carrier elements, which are (still) present in a coherent manner in the carrier structure 21 and form the carrier by being separated. For this purpose, the carrier structure 21 can already have a series of structural components of the carrier, here for example a plurality of sound inlets or sound outlets. However, it may also be preferred to carry out further processing steps after the carrier structure 21 has been disassembled.

[0223] The carrier structure 21 preferably features sufficient stability to ensure that the meandering structure of the membrane 5 is maintained during the complete removal of the shaped part 7. Therefore, the shaped part is preferably completely removed only after the carrier structure 21 has been connected to the membrane layer system 9.

[0224] The attachment of the carrier structure 21 preferably takes place after structuring the film layer system 9 and thus separating the film layer system 9 to form a film 5 with an intervening interruption 13. The carrier structure 21 is preferably connected to the film layer system 9 by means of an electrically conductive process material 33 at the location of the interruption 13 in the film layer system 9, the interruption 13 corresponding to the end region of the film 5 to be formed.

[0225] It is also shown that a protective foil 37 is preferably attached to the carrier structure 21, wherein the protective foil 37 is present on the side opposite to the film layer system 9 and extends along the entire surface of the carrier structure 21. The protective foil 37 can be a protection for the carrier structure 21 or for the carrier to be formed during different processing steps, for example during the removal of the shaped part 7 or the separation of the carrier structure 21 region by region by cutting. The protective foil 37 can also define the end point of the cutting as a so-called dicing foil.

[0226] Figure 4 B shows the complete removal of the formed part. Figure 4 In C, we can see that Figure 4 B is the same illustration, however with the perspective reversed to illustrate possible further transport and / or positioning for further processing steps.

[0227] Figure 4 D shows the connection of a plurality of covers 23 to the carrier structure 21. The connection is preferably carried out in such a way that the covers 23 are attached at the locations of the interruptions 13 so that there is a precisely fitting cover 23 for each membrane 5.

[0228] Figure 4 E shows the region-by-region separation of the carrier structure 21. The region-by-region separation can be performed, for example, by cutting.

[0229] like Figure 4 After the carrier structure 21 has been separated region by region, the MEMS transducer 1 can be removed from the protective foil and / or further processed, as shown in FIG.

[0230] Reference numerals list

[0231] 1MEMS converter

[0232] 3 Bearings

[0233] 4 Vertical part

[0234] 5. Film

[0235] 6 Horizontal section

[0236] 7 Formed parts

[0237] 9. Membrane system

[0238] 11 Executor Layer

[0239] 13. Interruption

[0240] 15 Separable connector

[0241] 17 Support structure

[0242] 19 Installing Parts

[0243] 21 Load-bearing structure

[0244] 23 Cover

[0245] 25 Cover opening

[0246] 27 Top electrode

[0247] 29 Bottom electrode

[0248] 31 Electronic Circuits

[0249] 33 Conductive process materials

[0250] 35 Sacrificial Layer

[0251] 37 Protective foil

[0252] 39 Prior art rear side carrier or rear side carrier region

[0253] 43 Comb teeth

[0254] 45 Blank Area

[0255] References

[0256] Kaiser B., Sergiu Langa, Lutz Ehrig, Michael Stolz, Hermann Schenk, Holger Conrad, Harald Schenk, Klaus Schimmanz, and David Schuffenhauer, Concept and demonstration of an all-silicon MEMS microspeaker using an air chamber, Microsystems & Nanoengineering, Vol. 5, Article No. 43 (2019).

[0257] Shahosseini I, Elie LEFEUVRE, Johan Moulin, Marion Woytasik, EmileMartincic et al., Electromagnetic MEMS microspeakers for portable electronic devices, Microsystems Technology, Springer Verlag (Germany), 2013, p. 10, <hal-01103612>.

[0258] Stoppel F., C. Eisermann, S. Gu-Stoppel, D. Kaden, T. Giese and B. Wagner, Novel membrane-less bidirectional MEMS loudspeaker based on piezoelectric dual concentric actuators, Transducers2017, Kaohsiung, Taiwan, China, June 18-22, 2017.

Claims

1. A method for producing at least one MEMS transducer (1) for interacting with a volume flow of a fluid and comprising: A carrier (3); as well as a membrane (5) for generating or receiving pressure waves of the fluid in a vertical direction, the membrane (5) being held by the carrier (3), wherein the membrane (5) has a meandering structure with vertical parts (4) and horizontal parts (6), wherein the vertical parts (4) are substantially parallel to the vertical direction and the horizontal parts (6) connect the vertical parts (4) to each other, wherein the membrane (5) comprises at least one actuator layer (11) made of an actuator material and the membrane (5) is in contact with at least one electrode so that the vertical parts (4) can be excited to vibrate horizontally by controlling at least one of the electrodes, or an electrical signal can be generated at at least one of the electrodes when the vertical parts (4) are excited to vibrate horizontally, It is characterized in that The method comprises the following steps: a) providing a shaped part (7), b) coating the shaped component (7) with a film layer system (9), the film layer system (9) comprising at least the actuator layer (11), wherein the film layer system (9) has a meandering structure with vertical parts (4) and horizontal parts (6) after being coated on the shaped component (7), c) providing the film (5) by structuring the film layer system (9), d) completely removing the shaped part (7), e) Attaching the membrane (5) to the carrier (3) such that the membrane (5) is held by the carrier (3).

2. The method according to the preceding claim, It is characterized in that A plurality of MEMS converters (1) are manufactured, wherein, in order to manufacture the plurality of MEMS converters (1), the membrane layer system (9) on the formed part (7) is structured to form individual membranes (5), wherein the individual membranes (5) are preferably present in a manner separated by interruptions (13), and the interruptions are preferably formed as a whole or layer by layer after coating the membrane layer system (9).

3. The method according to one or more of the preceding claims, It is characterized in that The shaped part (7) is provided by applying a dry etching method and / or a wet chemical etching method to the substrate, wherein the dry etching method is preferably a physical dry etching method, a chemical dry etching method and / or a physicochemical dry etching method, wherein the dry etching method is particularly preferably selected from reactive ion etching (RIE) and / or deep reactive ion etching (DRIE), wherein KOH etching is preferably used as the wet chemical etching method.

4. The method according to one or more of the preceding claims, It is characterized in that The shaped part (7) is completely removed by a wet chemical etching method, a dry etching method and / or a steam etching method, wherein the wet chemical etching method is preferably selected from KOH etching and / or TMAH etching.

5. The method according to one or more of the preceding claims, It is characterized in that After structuring the membrane layer system (9), the plurality of membranes (5) are connected to a support structure (17) using detachable connections (15).

6. The method according to one or more of the preceding claims, It is characterized in that The membrane (5) is removed from the support structure (17) by means of a mounting member (19), wherein, preferably, after the membrane (5) has been removed from the support structure (17), the membrane (5) is attached to the carrier (3).

7. The method according to one or more of the preceding claims, It is 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 conductive adhesive or a conductive solder material.

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

9. The method according to one or more of the preceding claims, It is characterized in that After structuring the film layer system (9), a plurality of films (5) are connected to a carrier structure (21) and the shaped part (7) is then completely removed.

10. The method according to one or more of the preceding claims, It is characterized in that After the shaped part (7) has been completely removed, the carrier structure (21) is separated region by region, so that a plurality of carriers (3) are provided from the carrier structure (21) and each membrane (5) is attached to one of the plurality of carriers (3).

11. The method according to one or more of the preceding claims, It is characterized in that The carrier structure (21) is connected to a plurality of covers (23), wherein the plurality of covers (23) preferably have cover openings (25).

12. The method according to one or more of the preceding claims, It is characterized in that The membrane (5) comprises at least two layers, wherein both layers (11) comprise actuator materials and are respectively in contact with electrodes, and are capable of generating horizontal vibrations by a shape change of one layer relative to the other layer, or horizontal vibrations causing a shape change of one layer relative to the other layer and generating electrical signals.

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

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

15. A MEMS transducer (1) which can be manufactured according to the method of one or more of the preceding claims.

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