A compact and easily manufactured MEMS package with enhanced protective properties.

Abstract

Preferably, the present invention relates to a MEMS package having at least one layer for protecting a MEMS element, the MEMS element having at least one MEMS interaction region on a substrate, and a dielectric layer for conformal surface coating of the MEMS element. Particularly preferably, the present invention relates to a MEMS transducer package, for example, in which a MEMS element having a MEMS membrane and a processor, preferably an integrated circuit, are present on a substrate. For protection, a dielectric surface conformal coating is preferably first applied to the MEMS element, for example, by spray coating, mist coating, and / or vapor coating. Then, preferably, a conductive layer is applied. Depending on the configuration, layers can be removed in some areas above the MEMS interaction region of the MEMS element, for example, for acoustic ports in the MEMS membrane.

Description

Technical Field

[0001] Preferably, the present invention relates to a MEMS package having at least one layer for protecting a MEMS element, the MEMS element having at least one MEMS interaction region on a substrate, and a dielectric layer applying a surface conformal coating to the MEMS element. Particularly preferably, the present invention relates to a MEMS transducer package in which a MEMS element having, for example, a MEMS membrane and a processor, preferably an integrated circuit, are present on a substrate. For protection, a surface conformal coating of a dielectric is preferably first applied to the MEMS element, for example by spray coating, mist coating, and / or vapor coating. And preferably, a conductive layer is applied. Depending on the configuration, for example for an acoustic port of a MEMS membrane, a layer can be removed in a region above the MEMS interaction region of the MEMS element.

Background Art

[0002] Today, microsystem technology is used in many applications for the manufacture of compact mechatronic devices. Microsystems (microelectromechanical systems, abbreviated as MEMS) that can be manufactured in this way are very compact (micrometer range), have excellent functionality, and further have low manufacturing costs.

[0003] Applications of MEMS technology include MEMS-based optical emitters or receivers, filters, electrochemical sensors, gas sensors, or even MEMS acoustic transducers.

[0004] A MEMS transducer is preferably a MEMS acoustic transducer and can be designed, for example, as a MEMS microphone or a MEMS speaker. Both functions can also be realized by one MEMS transducer. Such MEMS transducers are used, for example, in modern smartphones.

[0005] A MEMS transducer preferably includes a MEMS device (e.g., a MEMS chip) having a vibrable film, the vibration of which is generated and / or read out by, for example, a piezoelectric or piezoresistive component on or in the film. Similarly, capacitive methods for generating and / or measuring vibrations of a film are known.

[0006] MEMS transducers are often placed on a substrate together with integrated circuits (ICs) for controlling and / or evaluating vibrations, and contact these via electrical connections formed, for example, by wire bonds and / or applied within the substrate by conductive tracks. The substrate functions particularly as a carrier and can be designed, for example, as a printed circuit board (PCB) or ceramic. In addition to its carrier function, it can preferably also perform electrical functions, for example, by providing electrical connections to individual components.

[0007] An IC is preferably an electronic component in which a control unit or adjustment unit is implemented. In particular, it is an electronic chip. This can be, for example, an application-specific integrated circuit (ASIC) that is particularly well-suited for mass production. However, it may also be a programmable logic device (PLD) for specific applications, such as a field-programmable gate array (FPGA).

[0008] MEMS elements, such as MEMS transducers, are mostly susceptible to external influences and are therefore protected by so-called packaging.

[0009] In this regard, the packaging of MEMS elements fulfills several tasks. These include protecting the components from dust, moisture and liquids, as well as from ESD (electrostatic discharge). However, at the same time, the functional characteristics of the MEMS element, such as the acoustic properties of an acoustic MEMS transducer, should be preserved.

[0010] The package preferably serves as the housing for the MEMS element. On the bottom side of the MEMS element, the substrate itself can perform this function. Furthermore, protection is required above the substrate for components placed on it.

[0011] MEMS devices can be mounted on a substrate in a conventional manner or in a so-called flip-chip assembly, thereby the chip having a downward-facing active contact surface toward the substrate and being mounted without further connecting wires. For this purpose, it is preferable that the substrate itself has contact bumps. This advantageously reduces the dimensions of the housing and shortens the length of the conductor.

[0012] MEMS devices and / or MEMS films can exist on a substrate within a MEMS acoustic transducer in a variety of ways.

[0013] The volume on which sound waves are measured and / or generated, as viewed from the MEMS membrane, is preferably called the front volume. The other side is preferably called the back volume. This is preferably closed and has no direct connection to the front volume except possibly through an opening in the membrane. Depending on the arrangement, the back volume may be located, for example, between the membrane and the substrate. In this case, the front volume is located above the MEMS device and the substrate. The housing component (e.g., cover) located here, which closes the package at the top, preferably has an acoustic port in this area.

[0014] However, a back volume can also be located between the membrane and a housing component positioned above the MEMS device and substrate. This is then preferably completely closed. In this case, a front volume is preferably located between the membrane and an acoustic port in the substrate. The dimensions and geometric shape of these volumes, as well as their size ratio, affect the acoustic properties of the MEMS transducer. The MEMS membrane can be located within both of the described constellations within the height of the MEMS device, preferably positioned toward the substrate at either the upper or lower end.

[0015] In the case of MEMS transducers, the electrical components of the MEMS device itself, such as the electrodes of a capacitive MEMS transducer, are preferably located within the back volume or facing the back volume (e.g., on the side of the membrane oriented toward the back volume) to allow measurement of some liquid by the membrane without short-circuiting or contaminating these components. Preferably, this allows the fluid to come into direct contact with the membrane. General protection against short circuits caused by moisture is also achieved in this way. However, a prerequisite for this is that the package prevents moisture / liquid from entering other areas of the MEMS transducer through the acoustic port. Therefore, the acoustic port in the package must be an opening to the membrane only and not to other areas of the MEMS transducer.

[0016] Conventional packaging for MEMS transducers (see, e.g., Dehe et al. 2013) has a metal cover. These covers enclose a volume significantly larger than the volume theoretically required for the underlying components of the MEMS transducer. The main reason for this is to maintain a distance between the cover and the components (e.g., wire bonds, electrodes in capacitive MEMS transducers) to avoid short circuits. At the same time, metal is desirable as a starting material for these covers because it is mechanically stable and seals particularly well against water and air. Sealing refers, in particular, to impermeability under the normal operating conditions of the transducer, i.e., under pressures considerably higher than atmospheric pressure. Furthermore, sensitive components can be electromagnetically shielded. In this way, negative influences and electrostatic discharge (ESD) can be avoided. However, these covers hinder the compact design of modern MEMS transducers.

[0017] Acoustic openings can be provided in the metal cover. However, even in this case, direct contact between the MEMS film and the material to be measured (solid, gas, liquid) is difficult because the openings are located at a distance above the film (see above), and this distance must be overcome. Furthermore, since the cover and openings are not coplanar with the transducer components, liquid may enter the space between the cover and the MEMS device, which can cause short circuits between their conductive areas and facilitate the entry of contaminants and other harmful substances.

[0018] Acoustic ports passing through a substrate (see also Dehe et al.) have the disadvantage of generating a low-pass filter for acoustic frequencies, particularly due to the dimensions and length of the opening, which are predetermined at least by the thickness of the substrate, thus counteracting the usefulness of ultrasonic transducers.

[0019] The so-called flip-chip package (Feiertag et al., 2010) no longer needs to be designed for wire bonding, allowing for a reduction in cover height. However, even here, the effect of miniaturization is small.

[0020] The use of metallized polymer films as an outer layer is also known from Feiertag et al. For this purpose, a polymer film is laminated on top of the MEMS transducer, and then a metal layer is provided. However, this process is costly. Furthermore, the film must be thermally deformed for this purpose and / or heated by laser ablation during post-processing / structuring to introduce temperature into the MEMS transducer.

[0021] Heating facilitates the formation of thermoplastic materials, which is used in equivalent blow molding or thermoforming of polymers. However, in all of these processes, additional stress is applied to the components. This can introduce stress into the components or cause other damage as well as undesirable gas release. Furthermore, because it is difficult to ensure that the film is perfectly coplanar on all sides of the MEMS transducer, leakage from the package environment can occur, compromising the compact design.

[0022] U.S. Patent No. 6,956,283 discloses a method for protecting components of a MEMS sensor from external influences using a "package first, release later" approach. A matrix array of micromirrors is arranged on a silicon chip, which is then placed on a substrate. In the proposed method, a protective layer is applied to the substantial components of the sensor. Various methods, such as spray or vacuum coating, can be used for the coating. After deposition, the protective layer is removed over the active areas. Finally, a cover is applied as a protective housing.

[0023] U.S. Patent Application Publication No. 2019 / 0148566 relates to a method of manufacturing a semiconductor sensor element that can be a pressure sensor, a gas sensor, or a capacitance sensor. The semiconductor sensor element includes a substrate on which a semiconductor element is disposed and connected to a substrate via bonding wires. A dielectric layer is deposited on the semiconductor sensor element via a deposition process. A laser beam can be used to partially remove the dielectric layer. A cover is used to protect the semiconductor element from external forces.

[0024] U.S. Patent Application Publication No. 2019 / 0311961 discloses a semiconductor sensor including a substrate having a chip thereon. A film layer is deposited on the components of the semiconductor sensor to protect the components of the semiconductor sensor from, for example, external gases, liquids, etc. The film layer is preferably applied by vapor deposition over all the components of the sensor located within the package. A housing includes an opening and is used to protect and support the components of the semiconductor sensor.

[0025] A MEMS package that can function without a rigid lid or package is not known in the prior art.

[0026] Therefore, in light of the drawbacks of the prior art, there is a need for alternative or improved packages and manufacturing methods for MEMS elements, particularly packages for MEMS transducers.

Prior Art Documents

Patent Documents

[0027]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0028] The object of the present invention is to provide a MEMS package that does not have the drawbacks of the prior art and a method for manufacturing such a MEMS package. In particular, one object of the present invention was to provide a MEMS package that is very compact while providing a high level of protection against dust, moisture, liquids and ESD for MEMS elements, such as MEMS transducers, and guaranteeing desired functional characteristics, such as acoustic characteristics in the case of MEMS transducers. The package is also said to be particularly easy and cost-effective to manufacture and suitable for mass production due to fewer simple steps. [Means for solving the problem]

[0029] The objective is resolved by the features of the independent claim. Preferred embodiments of the present invention are described in the dependent claims.

[0030] The present invention relates to a method for manufacturing a MEMS package having at least one layer for protecting a MEMS element, wherein the manufacturing method is: The steps include providing a MEMS element on a substrate that includes at least one MEMS interaction region, The steps include: applying a conformal coating to the surface of a MEMS element using a dielectric layer; Includes.

[0031] Preferably, the MEMS interaction region is an essential functional component of the MEMS element that interacts with the medium in a desired manner.

[0032] Surface conformal coatings are, in particular, coatings that adhere substantially directly and retain their shape to the structure of the substrate.

[0033] "Substantially direct and shape-retaining" preferably means that the majority of the coating is in direct contact, but includes some areas, such as corner areas or volumes not filled by components beneath the wire bond.

[0034] Surface conformal coatings are preferably completely surface conformal. This means that the coating adheres almost perfectly, or the surface is equiangled, allowing even the smallest structures to adhere and be coated. The smallest structures are preferably structures with dimensions of up to 10 nanometers (nm), up to 100 nm, up to 1 micrometer (μm), up to 10 μm, or up to 100 μm.

[0035] The dielectric layer preferably comprises at least one polymer. These are inexpensive and easy to process. It may also be preferable to apply an oxide or nitride layer as the dielectric layer. For surface conformal coatings, physical or chemical vapor deposition (PVD and CVD) is particularly suitable for this purpose.

[0036] In preferred embodiments, the polymer is, for example, a photostructureable polymer with a suitable mixture of photosensitive components. In particular, it is a photoresist.

[0037] Advantageously, the properties of the polymer can be adapted to the functionality of the MEMS device. For example, in the case of a MEMS transducer as a MEMS device, the relative permittivity ε of the polymer r It may be preferable to adapt it to high-frequency applications of MEMS transducers. For example, ε r This can be selected to attenuate the high-frequency electromagnetic field.

[0038] Such dielectric functional coatings are not possible with conventional processes and advantageously provide a very compact protective layer that offers electrical insulation and mechanical protection for MEMS devices.

[0039] In preferred embodiments, the MEMS element is selected from the group consisting of optical MEMS transducers, acoustic MEMS transducers, MEMS sensors, and in particular MEMS gas sensors and / or MEMS filters. The inventors have recognized that the proposed packaging can provide reliable protection for several different MEMS elements, preferably by dielectric coating with polymer.

[0040] On the one hand, an airtight, space-optimized protective layer can be applied very cost-effectively by surface conformal coating, for example, by a polymer-based spray process. On the other hand, surface conformal coating using, for example, photostructureable polymers, allows for a high degree of flexibility with respect to planned openings or recesses in the protective layer within the interaction region of the MEMS device.

[0041] The MEMS interaction region preferably refers to a functional component of the MEMS element that interacts with an external medium in a desired manner. In the case of an acoustic MEMS transducer, for example, this is a MEMS film. In the case of an optical MEMS transducer, for example, this is an optical emitter.

[0042] In both cases, it is preferable that, on the one hand, a protective layer that reduces interaction between the MEMS element and the environment (sound transmission or reception, optical signal transmission or reception) is not directly applied to the interaction area of ​​the MEMS element, while on the other hand, protection of sensitive electronic components is ensured. The method according to the present invention achieves this in a simple and highly efficient manner by coating the surface, preferably by applying a polymer.

[0043] In a preferred embodiment, the MEMS element is an optical MEMS transducer, and the MEMS interaction region includes an optical emitter and / or optical receiver.

[0044] The optical emitter can include, for example, a surface emitter, a VCSEL (vertical cavity surface-emitting laser), or an LED. The optical receiver can be, for example, a photodiode or an image sensor.

[0045] In a preferred embodiment, the optical emitter may be a moduloable MEMS emitter. For example, modulation of the intensity of the optical emitter can be achieved using aperture structures and MEMS actuators such as electrostatic actuators, piezoelectric actuators, electromagnetic actuators, and / or thermal actuators.

[0046] In a preferred embodiment, the MEMS element is a MEMS acoustic transducer, and the MEMS interaction region includes a MEMS film.

[0047] In preferred embodiments, the MEMS transducer is a MEMS speaker, a MEMS microphone, and / or a MEMS ultrasonic transducer. Preferably, the MEMS membrane is vibrable. The membrane is preferably a thin planar structure having, for example, a substantially circular and / or polygonal perimeter. The membrane is preferably at least partially vibrable along one of its perimeters.

[0048] Terms such as substantially, approximately, and about indicate an acceptable range of preferably less than ±20%, preferably less than ±10%, more preferably less than ±5%, and especially less than ±1%. Indications such as substantially, approximately, and about always also disclose and include the exact value mentioned.

[0049] A MEMS speaker or MEMS microphone preferably refers to a speaker or microphone based on MEMS technology, in which the sound-generating or sound-receiving structure has dimensions in the micrometer range (1 μm to 1000 μm) at least partially. Preferably, the vibrating membrane may have dimensions in the range of width, height, and / or thickness of less than 1000 μm.

[0050] The term MEMS transducer refers to both MEMS microphones and MEMS speakers. Generally, a MEMS transducer refers to a transducer for interacting with a volumetric flow of a fluid, and based on MEMS technology, the structure for interacting with a volumetric flow or for receiving or generating fluid pressure waves has dimensions in the micrometer range (1 μm to 1000 μm). The fluid can be a gaseous fluid or a liquid fluid. The structure of a MEMS transducer, in particular a vibrating membrane, is designed to generate or receive fluid pressure waves.

[0051] For example, it may be a sound pressure wave, as in a MEMS speaker or MEMS microphone. However, a MEMS transducer can be equally suitable as an actuator or sensor for other pressure waves. Therefore, a MEMS transducer is preferably a device that converts a pressure wave (e.g., an acoustic signal as a sound pressure wave) to an electrical signal, or vice versa (converts an electrical signal to a pressure wave such as an acoustic signal).

[0052] The MEMS transducer preferably includes a MEMS device (e.g., a MEMS chip) having a vibrable film on or within the film, in which vibrations are generated and / or read out by a piezoelectric or piezoresistive component.

[0053] In a preferred embodiment, the MEMS transducer is a piezoelectric MEMS transducer.

[0054] Similarly, capacitive methods are known for generating and / or measuring membrane vibrations.

[0055] In a preferred embodiment, the MEMS transducer is a capacitive MEMS transducer.

[0056] In a preferred embodiment, the MEMS transducer may also be a MEMS ultrasonic transducer suitable for transmitting and / or receiving ultrasound.

[0057] In particular, these are capacitive micromechanical ultrasonic transducers (CMUTs), piezoelectric micromechanical ultrasonic transducers (PMUTs), or composite ultrasonic transducers (piezoelectric composite ultrasonic transducers, PC-MUTs).

[0058] Ultrasound covers frequencies from 1 kilohertz (kHz), typically mainly around 16 kHz. Applications of miniature ultrasonic transducers include imaging methods in medicine, for example, but also imaging methods for measuring other objects. Possible applications include ultrasonic density measurement, strength measurement of concrete, plaster, and cement, level measurement of liquids and solid media with different viscosities and surface properties, or ultrasonic microscopy. Here, it is often desirable that the transducer membrane (i.e., the MEMS interaction region) is in direct contact with the object / liquid being measured.

[0059] In the method according to the present invention for surface conformal coating of dielectric protective layers, this can be advantageously achieved without impairing the protective function. Alternatively, the dielectric protective layer within the interaction region can be removed in a targeted manner in a simple manner, while the layer remains in close contact with the remaining structure. In particular with respect to acoustic MEMS transducers such as MEMS microphones or MEMS speakers, this method can avoid affecting the acoustic behavior and achieve excellent detection or acoustic results.

[0060] In another preferred embodiment, the MEMS element is a MEMS gas sensor, and the MEMS interaction region includes a MEMS film and / or a MEMS electrochemical detection region.

[0061] For example, it could be a photoacoustic spectrometer equipped with a MEMS sensor.

[0062] In photoacoustic spectroscopy, it is preferable to use intensity-modulated infrared radiation at the frequency of the absorption spectrum of the molecule to be detected in the gas. When this molecule is present in the beam path, modulated absorption occurs, resulting in heating and cooling processes whose timescale reflects the modulation frequency of the radiation. The heating and cooling processes cause expansion and contraction of the gas, generating sound waves at the modulation frequency. These can be measured by sensors such as acoustic detectors or flow sensors.

[0063] Preferably, the power of the sound wave is directly proportional to the concentration of the absorbing gas. Therefore, the photoacoustic spectrometer preferably includes at least one emitter, a detector, and a cell. In a MEMS gas sensor, the detector is preferably implemented as a MEMS sensor.

[0064] For example, a MEMS sensor may include a capacitive or optically readable piezoelectric, piezoresistive, and / or magnetic beam, and / or a capacitive, piezoelectric, piezoresistive, and / or optical microphone or film.

[0065] With respect to the present invention, the MEMS sensor of the photoacoustic spectrometer is preferably in direct contact with the medium and can therefore be preferably understood as its MEMS interaction region.

[0066] In another preferred embodiment, the MEMS element is a MEMS filter, preferably a MEMS frequency filter, particularly a SAW or BAW filter, and the MEMS interaction region includes a MEMS filter structure, particularly a MEMS electrode and / or a MEMS bulk region.

[0067] A SAW filter is preferably an acoustic surface wave filter (similarly an AOW filter), and is in particular a bandpass filter for electrical signals.

[0068] These are preferably based on the interference of signals with different transit times, and preferably utilize the piezoelectric effect. Preferably, each piezoelectric single crystal includes a pair of comb-shaped interlock electrodes that preferably form an interaction region.

[0069] A BAW filter (bulk acoustic wave filter) is preferably a similar electronic filter having bandpass characteristics. However, in contrast to a SAW filter, it is preferable to have a substrate (bulk) where elastic wave propagation occurs. This substrate or bulk region preferably forms a MEMS interaction region.

[0070] In a preferred embodiment of the present invention, the surface conformal coating is carried out by a dielectric coating process, the coating process being selected from the group consisting of spray coating, mist coating, electroplating, and / or vapor coating.

[0071] Spray coating preferably refers to a two-dimensional application of a dielectric layer, where the dielectric is preferably pressurized before spraying (e.g., higher than the general ambient pressure, e.g., preferably above 1 bar, more preferably above 2 bar, particularly 2-6 bar, in the case of atmospheric pressure) so that dielectric and / or foamed fine particles / aerosols are formed. In this way, a particularly fine coating can be achieved that covers all spray areas, even if, for example, a surface has an unfavorable angle with respect to the spraying direction. Thus, even surfaces / areas that are inclined relative to each other can preferably be directly covered. However, when using a film as in known prior art, it is extremely difficult to directly cover such areas without creating uncovered volumes. This is due, for example, to the fact that the film is continuous and under tension.

[0072] Preferably, for the coating process, the liquid dielectric is atomized under a high pressure compared to the environment and applied to the surface.

[0073] The spray coating is preferably a spray paint.

[0074] In particular, when the dielectric layer contains a polymer that can be deposited from the gas phase and / or liquid phase, such as tetraethyl orthosilicate (TEOS) and / or parylene, the spray coating and / or surface conformal coating may be deposited from the gas phase. In this way, particularly tight adhesion or surface conformal coating can be achieved on the transducer components.

[0075] Mist coating preferably involves coating with fine droplets of dielectric material finely dispersed in an atmosphere (preferably a gas). Mist coating preferably allows for the achievement of a complete surface conformal coating.

[0076] Vapor coating is preferably applied by a dielectric in vapor or gaseous form. Vapor coating can include, for example, PVD (physical vapor deposition) or CVD (chemical vapor deposition). Vapor deposition advantageously enables conformal coating of the entire surface of the dielectric.

[0077] In a preferred embodiment, the surface conformal coating is applied by depositing a dielectric layer using a physical vapor deposition (PVD) or chemical vapor deposition (CVD) process.

[0078] In a preferred embodiment, the dielectric layer is an oxide or nitride layer, which is preferably deposited by physical vapor deposition or chemical vapor deposition (CVD).

[0079] The oxide or nitride layer may be, for example, a layer of metal or metalloid oxide or metal or metalloid nitride.

[0080] In preferred embodiments, the dielectric layer is a layer comprising aluminum nitride, silicon nitride, aluminum oxide, silicon dioxide, titanium dioxide, and / or tantalum oxide. Electroplating coatings may also be included in surface conformal coatings. Electroplating preferably refers to the electrochemical deposition of a coating on a substrate (in this case, a MEMS device).

[0081] In a preferred embodiment, the surface conformal coating is provided by a coating that wets the MEMS element in at least some areas.

[0082] Wetting preferably means being completely wet or substantially completely wet. Complete wetting preferably means that the dielectric, applied preferably in liquid form, spreads across the surface in the form of a flat disk. In particular, there is no macroscopic contact angle. Preferably, it is a nearly monolayer with a contact angle of 0.

[0083] Preferably, the expansion parameter S describes the difference between the surface tension of the substrate (GS), the surface tension of the liquid (GL), and the interfacial tension (GSL) between the substrate and the liquid. Preferably, this can be used to distinguish between complete wetting and partial wetting. S=GS-GL-GSL

[0084] If S > 0, the dielectric completely wets the substrate. If S < 0, partial wetting is characteristic.

[0085] "Preferred" means completely wetting the sample, where S > 0.

[0086] In a preferred embodiment, the dielectric, the coating method, and / or the surface of the MEMS element are configured (at least partially) for wet coating.

[0087] Those skilled in the art know how to precisely select the material, dielectric droplet size, surface roughness, etc., in order to obtain the desired wetting. To calculate the relevant variables, one can follow, for example, the method described by Harth et al., 2012.

[0088] In a preferred embodiment, the surface conformal coating is performed by dewetting the MEMS element in at least a number of regions, the regions preferably including MEMS interaction regions.

[0089] Particularly preferably, the surface conformal coating is performed by a coating that wets the MEMS element in at least a specific region, and the wetting coating is applied to the MEMS interaction region.

[0090] Dehydration preferably means that the dielectric shrinks on the surface to form substantially spherical droplets and / or has a contact angle greater than 90°. When the surface is slightly inclined, it is preferable that the droplets slide off without any liquid residue, particularly the liquid (dielectric), peeling off in bead-like manner. Preferably, the dielectric has a contact angle of substantially 180° when applied to a surface, and the droplets contact the solid at substantially only one point. This makes it particularly easy to remove the dielectric from the MEMS interaction region after coating.

[0091] In a preferred embodiment of the present invention, a region on the surface of a dielectric, a coating method, and / or a MEMS element, preferably a MEMS interaction region, is configured for wetting coating.

[0092] Preferably, the same considerations as in wet coating play a role. Those skilled in the art can derive the selection of dielectric droplet size, surface roughness, etc., from well-known methods found in the technical literature (see, in particular, Harth et al., 2012).

[0093] In preferred embodiments, the dielectric layer and / or dielectric comprises a polymer or polymer blend.

[0094] The polymer preferably refers to a chemical compound consisting of chain-like or branched molecules (polymers) composed of identical or similar units (so-called monomers).

[0095] Non-limiting examples of polymers include polymethyl methacrylate (PMMA), poly(methyl methacrylate-co-methacrylic acid) (PMMA co MA), poly(α-methylstyrene-co-chloromethacrylate methyl ester) (PMS co Cl-MMA), polystyrene (PS), polyhydroxystyrene (PSOH), poly(hydroxystyrene-co-methyl methacrylate) (PSOH co MMA), phenolic resins, and especially preferably polyimide (PI) or parylene.

[0096] Polymers are particularly suitable for dielectric coatings due to their ease of processing and shape-conforming coating ability.

[0097] In preferred embodiments, the polymer for coating the MEMS element with a dielectric layer is a photostructureable polymer or a photostructureable polymer blend. Photostructureable means, preferably, that it can be structured by light, electrons, and / or ionic radiation.

[0098] The dielectric layer can be formed particularly easily by a polymer coating, preferably by a photostructureable polymer or a photostructureable polymer blend. The photostructureable polymer or polymer blend preferably refers to a coating that can be modified by exposure (irradiation with electromagnetic radiation) to obtain a structure by dissolving specific regions in response to subsequent irradiation.

[0099] The polymer blend can be made photostructured, for example, by a suitable mixture of photosensitive components. Particularly preferably, the photostructured polymer or photostructured polymer blend is a photoresist.

[0100] This is advantageous because it allows for the subsequent removal of dielectric layers, for example, within MEMS interaction regions, using optical methods. Region-specific removal of dielectric layers is particularly easy when photostructured polymers are involved and lithography is used.

[0101] In a preferred embodiment of the present invention, surface conformal coating of the MEMS element with a dielectric layer is performed by surface conformal coating with a photoresist.

[0102] Photoresists and photoresist compositions are well known to those skilled in the art and are used particularly in photolithography.

[0103] Structuring a photoresist typically involves several steps, including exposing the photoresist to a selected light source via a suitable mask to record the mask's latent image, and then developing and removing selected areas of the photoresist. In "positive" photoresists, the exposed areas are transformed to make them selectively removable, while in "negative" photoresists, the exposed areas are stabilized, but the unexposed areas remain removable.

[0104] The negative-type photoresist can preferably be polymerized by exposure and subsequent baking steps so that its regions become insoluble in the photoresist developer. Therefore, after one development, only the exposed regions remain, while the unexposed regions are dissolved by the photoresist developer.

[0105] In contrast, positive-type photoresists are characterized by the fact that the irradiated area becomes soluble in the photoresist developer. On the other hand, the unexposed areas of the photoresist remain insoluble and therefore persist even after development.

[0106] Positive photoresists may include, for example, a polymer resin (e.g., novolac) along with a photoactive component (e.g., a polymeric diazo compound) and a solvent. The novolac is preferably a phenolic resin with a formaldehyde-phenol ratio of less than 1:1, obtained by acid condensation of methanal and phenol. After coating, the positive photoresist can be pre-baked, preferably as a liquid. During this process, the solvent preferably escapes and the photoresist hardens. When the photoresist is exposed to light, such as UV light, the photoactive component can structure the resist by breaking material bonds within the resist in the irradiated area. The coating becomes soluble in the exposed areas. After exposure, these areas are washed with a suitable photoresist developer, leaving the unexposed portions of the photoresist. The photoresist mask can be further stabilized by another bake (hard bake).

[0107] For example, polymer resin materials that can be activated by irradiation are known as photoresists.

[0108] Polymer resin materials typically contain one or more polymers soluble in aqueous bases (see polymers such as PMMA or PI mentioned above). An example of a polymer resin is novolac.

[0109] To obtain photostructuring properties, it is preferable to add a photosensitive component such as a high-molecular-weight diazo compound, such as naphthoquinone diazide or diazonaphthoquinone (DNQ), to the photoresist.

[0110] The photoresist is processed as a solution, and suitable solvents are known to those skilled in the art, and may include, for example, 1-methoxy-2-propyl acetate (PMA), ethyl lactate, butyrolactone ether, glycol ether, aromatic hydrocarbons, ketones, esters, and other similar solvents.

[0111] Furthermore, photoresists may further contain components such as surfactants, bases, acid-forming agents, or crosslinking agents. In particular, the structuring of negative-type resists is based on the stabilization of the exposure area using a crosslinking agent. Radical initiators such as azo-bis(isobutyronitrile) (AIBN) or dibenzoyl peroxide (DBDO) form reactive radicals upon heating or irradiation (preferably short-wave light less than 300 nm), which cause crosslinking of the polymer matrix as a result of the resulting chain reaction.

[0112] This results in reduced solubility in the organic photoresist developer used (e.g., MIBK developer). Therefore, the exposed areas remain after development. The acid-forming agent can be crosslinked after activation by reaction with the added amine component (Cymel).

[0113] In preferred embodiments, the photoresist may include a polymer and freely selected adjuvants to impart the desired functionality. Examples of optional adjuvants include photochemical acid generators, thermal acid generators, acid enhancers, photochemical base generators, thermal base generators, photodegradable bases, surfactants, organic solvents, base inhibitors, sensitizers, and combinations of the above adjuvants.

[0114] Such photoresists are well known in the prior art. However, according to the present invention, they are recognized to be advantageously suitable as surface conformal coatings as dielectric protective layers for MEMS packages, as described above.

[0115] In preferred embodiments, the dielectric layer and / or dielectric comprises polymethyl methacrylate, polyimide (PI), novolac, polymethylglutarimide, a polymer that can be deposited from the gas phase and / or liquid phase, particularly tetraethyl orthosilicate (TEOS) and / or parylene and / or epoxy resin, particularly SU-8.

[0116] The use of polymers to provide a dielectric protective layer through a coating process is advantageous because it allows for a coating that is particularly conformal to the surface and enables a tight coating of all components. For example, spray deposition or vapor deposition can be used here.

[0117] Advantageously, even the smallest structures of MEMS elements can be reliably enclosed in a hermetically sealed environment. For example, the additional protection of bonding wires required in conventional chip designs can be omitted. Further processes for underfilling flip-chip components are also not required.

[0118] Furthermore, polymer coatings can be used to match the functionality of the dielectric layer to that of the MEMS device.

[0119] For example, the relative permittivity ε of a polymer r It may be preferable to adapt it to high-frequency applications of MEMS transducers. Here, ε r It is preferable to select such a device to reliably attenuate the high-frequency electromagnetic field.

[0120] In particular, when a MEMS device includes or consists of micro-optoelectromechanical (MOEMS) components, it may also be preferable to deposit different polymers on top of each other, for example, to create a dielectric gradient for high-frequency components or to optimize the dielectric layer with respect to its optical properties.

[0121] In particular, surface conformal coating processes using polymers can easily provide highly functional and extremely compact MEMS packages, while simultaneously offering complete protection for the sensitive structure of MEMS elements, such as MEMS transducers.

[0122] In a preferred embodiment, the manufacturing method is: The further step includes applying a conductive layer to a dielectric layer in at least several regions.

[0123] Applying a conductive layer to a dielectric layer in at least a specific region has the advantage of substantially adhering to the resulting layer system, protecting the MEMS transducer from short circuits and electrostatic discharge, and sealing the MEMS transducer from liquids and / or air. Improved mechanical protection is also preferable.

[0124] In particular, the conductive layer is a metal that provides mechanical protection to the MEMS element, preventing air, moisture, liquids, and dust from entering the package. The metal coating is especially airtight.

[0125] By applying a conductive layer, preferably a metal layer, on top of the dielectric layer, it is possible to ensure a mechanically stable seal that can withstand not only the penetration of air, moisture, and liquids but also external forces. Therefore, a layer system consisting of a metal layer on a dielectric layer has a particularly effective housing function, eliminating the need for a separate cover or housing. Advantageously, the layer system also ensures a good acoustic seal, resulting in very good detection or sound results when used with a MEMS speaker or MEMS microphone.

[0126] In a preferred embodiment, the conductive layer comprises a metal, preferably aluminum and / or a precious metal, preferably gold, platinum, iridium, palladium, osmium, silver, rhodium and / or ruthenium.

[0127] A conductive layer is preferably applied or deposited. The conductive layer is preferably a metal layer, more preferably a metal film, and more preferably a thin metal film.

[0128] In a preferred embodiment, the conductive layer is applied by a coating process, particularly PVD, CVD, and / or sputtering.

[0129] Preferably, the dielectric layer overlaps at its outer edge. Such an outer edge is located, for example, on the upper side of the substrate where the dielectric layer terminates. There, the conductive layer preferably covers the edge regions of all sides and extends onto the substrate. Such overlap can improve the opacity of the package.

[0130] The layer system manufactured in this manner is extremely compact and easy to produce, yet provides complete protection for MEMS elements, such as MEMS transducers. Using surface conformal coatings, such as spray coatings, a tight coating can be achieved on all sides, contributing to the compactness and impermeability of the package environment.

[0131] Such a level of adhesion cannot be achieved with films. Furthermore, unlike films, it does not require additional, expensive steps that could affect the MEMS elements.

[0132] Advantageously, the conductive layer can be applied directly to the dielectric layer. The layer system can be visually clearly distinguished from film packaging, for example, by the fineness of the layers (measurable roughness) and direct contact with the underlying components. Also, in contrast to film-based packaging, spray coating can cover the wire bond, as the spray layer simply covers the wire bond advantageously without exerting significant force on the wire bond that could potentially damage it.

[0133] In a preferred embodiment, the MEMS element includes a MEMS device and a processor, preferably an integrated circuit on a substrate, and / or electrical connections between the MEMS device and the processor, preferably the integrated circuit. Here, it is particularly preferable that a dielectric layer and optionally a conductive layer (preferably a metal layer) extend over the MEMS element and the processor, and / or the electrical connections between the MEMS device and the processor. Thus, the layer system can preferably simultaneously achieve complete protection for both sensitive micromechanical components and electronic components or the processor. A separate housing to surround and protect the processor and MEMS device is not required.

[0134] For the purposes of the present invention, the term processor preferably refers to a logic circuit capable of transmitting, receiving, and processing data or electrical signals. Preferred processors include, but are not limited to, integrated circuits (ICs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), microprocessors, microcomputers, programmable logic controllers, and / or other electronic circuits, preferably programmable circuits.

[0135] For example, the substrate may be selected from the group including silicon, single-crystal silicon, polysilicon, silicon dioxide, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, and / or indium phosphide.

[0136] In a preferred embodiment, the MEMS element and / or processor are implemented in a flip-chip design, and preferably, electrical connections are made via a substrate, particularly conductive traces within the substrate.

[0137] The surface conformal coating preferably encapsulates the MEMS element between itself and the substrate in at least a specific area, and thus the MEMS element is preferably electrically insulated and / or chemically protected by the dielectric coating, but preferably at the same time, the gap between the MEMS element (below the MEMS element) and the substrate has a high ε r It can be applied in a way that does not involve filling with a dielectric having [specific properties]. This may be particularly advantageous for high-frequency applications.

[0138] In a preferred embodiment of the present invention, the MEMS element and / or processor, preferably an integrated circuit, is not implemented in a flip-chip design, and preferably, electrical connections are made via at least one wire bond.

[0139] Furthermore, unlike film-based packaging, surface conformal coatings, such as polymer-based spray coatings, can also cover wire bonds because the coating has the advantage of being placed directly on top of the wire bond without exerting significant force on the wire bond that could potentially damage it.

[0140] On the other hand, tensioned films often break wire bonds, and as a result, this type of package can generally only be used for flip-chip packages. In contrast, packages created by the processes described herein are morph-fitted without applying significant tension to the package structure. This is another way in which the packages described herein can be distinguished from other packages when wire bonds are used. For example, wire bonds are surrounded and protected by a layer system, but are still visible from the outside. Generally, in these packages, the structure of the MEMS element is also visible from the outside through the package layers.

[0141] In a preferred embodiment of the present invention, the manufacturing method is: The steps include: providing a MEMS element including a MEMS interaction region on a substrate; The steps include: applying a surface conformal coating, particularly a spray coating of the MEMS element, so that the MEMS element is completely sealed between the dielectric layer and the substrate; Preferably, the step of applying a conductive layer to at least some regions on a dielectric layer, preferably forming a layer system together with the dielectric layer, Includes. A step of locating an opening above an interaction region by optionally removing a dielectric layer and / or layer system above the interaction region in at least several regions.

[0142] In preferred embodiments of the present invention, the arrangement of dielectric layers, MEMS element layer systems, and / or MEMS interaction regions is such that, after removal of the dielectric layer or layer system, the conductive regions do not come into direct contact with the package environment. In particular, they are sealed to air and / or liquids.

[0143] By removing a dielectric layer and / or a layer system containing a dielectric layer and a conductive layer within a specific region, the interaction between the interaction region and the desired medium, particularly with the package environment, can be improved.

[0144] For example, in the case of an acoustic MEMS transducer, the MEMS interaction region is a MEMS film that interacts with the package environment to pick up or generate sound pressure waves.

[0145] In the case of an optical MEMS transducer, the MEMS interaction region may be, for example, an optical emitter or receiver that interacts with the package environment by emitting or receiving electromagnetic radiation.

[0146] In both cases, firstly, it is preferable that the dielectric layer or conductive layer does not directly reduce the interaction between the MEMS element and the environment (sound emission, optical signal) in the interaction region of the MEMS element.

[0147] For example, by using photostructureable polymers to remove layer systems and / or dielectric layers in certain regions, unhindered interaction of MEMS elements in their functional regions can be achieved while ensuring the protection of the entire electronic system.

[0148] The MEMS element preferably includes a MEMS device having a MEMS film for a MEMS transducer. The MEMS package thus manufactured may also preferably be called a MEMS transducer package. Preferred MEMS transducers are acoustic MEMS transducers, particularly PMUTs, CMUTs, and / or PC-MUTs.

[0149] Preferably, the layer system is a surface conformal layer system for coated components of the MEMS element (e.g., MEMS devices, integrated circuits, and preferably electrical interconnects (particularly wire bonds)).

[0150] The spray coating is preferably carried out so that the MEMS element is completely sealed between the dielectric layer and the substrate. In particular, the conductive and / or electrically functional areas of the MEMS element should not be exposed to the package environment, especially to avoid short circuits. All electrical or conductive components should preferably be covered.

[0151] In particular, the electrical functions or conductive areas of the processor, preferably the integrated circuit (IC), exposed wires, and MEMS elements should be covered. Such a dielectric layer advantageously provides a base for subsequent conductive layers. The dielectric layer prevents the conductive layer from causing short circuits on the MEMS elements. The conductive layer then provides electrical shielding for the MEMS elements. Furthermore, if the conductive layer is formed of, for example, metal, it can provide additional mechanical protection, preventing air, moisture, liquids, and dust from entering the package.

[0152] Therefore, the layer system represents a particularly reliable barrier that, in addition to mechanical protection, prevents the penetration of potentially damaging external influences such as water vapor and dust.

[0153] The conductive layer is preferably applied to the dielectric layer in at least a specific region. Preferably, the conductive layer completely covers the dielectric layer. However, the conductive layer can be pre-structured during application so that the region where the acoustic ports will later be formed is already recessed. After that, only the dielectric layer needs to be removed. Removal of the dielectric layer is particularly easy if it contains a photostructureable polymer and a lithography process is used.

[0154] For example, a conductive layer (e.g., a metal layer) can be pre-structured using a shadow mask, which is preferably used as a hard mask for subsequent lithography (e.g., to form acoustic openings).

[0155] Applying a conductive layer to at least some areas on top of a dielectric layer advantageously means that the resulting layer system adheres substantially, protecting the MEMS element from short circuits and electrostatic discharge and sealing the MEMS element to liquids and / or air. A substantially close mating preferably means that the majority of the coating is in direct contact, but includes volumes that are not filled by constituent elements in some areas, such as corner regions or under wire bonds. If the spray coating is vapor deposition, at least the dielectric layer, preferably both layers, adheres completely or their surfaces are conformal.

[0156] Advantageously, spray / or vapor deposition allows for a shape-conformed coating of the component. No further processes for underfilling the flip-chip component and additional protection of, for example, bonding wires are required.

[0157] In a preferred embodiment of the present invention, the removal of the layer system or dielectric layer is performed by a lithography process, particularly by pre-structuring the dielectric layer by appropriate exposure of a photostructureable polymer.

[0158] Preferably, photolithography, electron beam lithography, and / or ion beam lithography can be performed.

[0159] Preferably, such removal is performed layer by layer. In particular, for dielectric layers, this process can be simplified if a photostructureable polymer is included.

[0160] The etching process can be carried out, for example, by dry etching or wet chemical etching.

[0161] Such processes are particularly easy, quick, and cost-effective to implement.

[0162] In a more preferred embodiment of the present invention, the removal of the layer system is carried out by a lift-off process, and in particular, the pre-structuring of the dielectric layer is carried out by appropriate exposure of a photostructureable polymer. In particular, the lift-off method is used to remove the entire layer system within the region of an acoustic port. For example, if the lift-off coating layer (particularly the dielectric layer) is sufficiently thicker than other regions at the location where it is to be removed, it is possible to pre-structure the layers so that both the metal layer and the polymer layer can be removed in a single lift-off step.

[0163] In a preferred embodiment, the thickness of the dielectric layer is 10 nm to 1 mm. Intermediate ranges from the above ranges, such as 10 nm to 100 nm, 100 nm to 200 nm, 200 nm to 500 nm, 500 nm to 1 μm, 1 μm to 5 μm, 5 μm to 10 μm, 10 μm to 50 μm, 50 μm to 100 μm, 100 μm to 500 μm, and even 500 μm to 1 mm, may also be preferred. Those skilled in the art will recognize that other preferred ranges, such as 100 nm to 1 μm, 500 nm to 5 μm, or 200 nm to 10 μm, can also be obtained by combining the above range limits.

[0164] In a preferred embodiment, the thickness of the conductive layer is 10 nm to 20 μm. Intermediate ranges within the above ranges, such as 10 nm to 100 nm, 100 nm to 200 nm, 200 nm to 500 nm, 500 nm to 1 μm, 1 μm to 5 μm, 5 μm to 10 μm, and even 10 μm to 20 μm, may also be preferred. Those skilled in the art will recognize that other preferred ranges, such as 200 nm to 1 μm, 100 nm to 5 μm, or 500 nm to 10 μm, can be obtained by combining the above range limits.

[0165] The preferred thickness of the dielectric and conductive layers provides excellent protection for MEMS devices while maintaining a compact design and high functionality.

[0166] In a preferred embodiment, the present invention relates to a method for manufacturing a MEMS transducer package having a layer system for protecting the MEMS transducer, wherein the manufacturing method is: The steps include: providing a MEMS device including a MEMS film on a substrate, The steps include: providing an integrated circuit having an electrical connection to a MEMS device on a substrate; The steps include spray coating the MEMS device, integrated circuit, and preferably the electrical interconnect with the dielectric layer so that the MEMS device, integrated circuit, and electrical interconnect are completely sealed between the dielectric layer and the substrate, The steps include applying a conductive layer to a dielectric layer in at least several regions, Includes.

[0167] A MEMS device having a MEMS film, and an integrated circuit on a substrate including electrical connections, preferably includes a MEMS transducer. In particular, the MEMS transducer is a PMUT, CMUT, or PC-MUT. Preferably, the electrical connection is at least one wire bond.

[0168] The preferred embodiments of the MEMS package and the advantages described are also applicable to particularly preferred MEMS transducer packages.

[0169] The fabricated layer system, including dielectric and conductive layers, is extremely compact and easy to manufacture, providing complete protection for the MEMS transducer. Particularly advantageous is that the acoustic properties of the MEMS transducer are not degraded during the process.

[0170] In a preferred embodiment of the present invention, the back volume of the MEMS transducer is positioned between the substrate and the MEMS film. The step of positioning an acoustic port above the membrane is to remove at least a specific layer or layer system above the membrane within a particular region.

[0171] Removal can be carried out, for example, by an etching process involving the physical treatment of the layer.

[0172] If a conductive layer has not already been applied to this region initially, only the dielectric layer must be removed. Otherwise, both the dielectric and conductive layers must be removed. In particular, this is done so that the film is not subsequently covered in at least some areas, or so that there is direct contact between the film and the acoustic medium in at least some areas, in order to maintain the acoustic properties of the MEMS transducer. Since the layer system is directly flush with the MEMS transducer, direct contact between the film and the acoustic medium can be established without the acoustic medium reaching other areas of the MEMS transducer. Thus, comprehensive protection from moisture and liquids can be achieved while maintaining the acoustic properties. Flash sealing of the acoustic ports and film also improves the acoustic properties of the MEMS transducer.

[0173] This step is particularly preferably performed between the spray coating and the application of the conductive layer. The spray coating can then be removed, for example, by a lithography process. If the conductive layer, especially the metallic layer, is not applied until the dielectric layer is removed, the conductive layer can be ensured to seal the edge region of the acoustic openings that are coplanar with the MEMS device, which means that the package can be ensured to be impermeable at this point, especially to gases (especially air), moisture, and / or liquids.

[0174] In particular, the CMUT preferably includes two MEMS films. In this embodiment, where the layer system has acoustic ports, it may be advantageously sufficient if the lower film is airtight to the package environment.

[0175] In preferred embodiments of the present invention, the arrangement of dielectric layers, layer systems, MEMS devices, and / or MEMS films is such that conductive regions do not come into direct contact with the package environment after removal of the layers or layer systems. In particular, they are sealed to air and / or liquids.

[0176] In a more preferred embodiment of the present invention, the electrodes of a capacitive MEMS transducer, particularly a capacitive micromechanical ultrasonic transducer, are located within or facing the back volume. For example, they are located within or on the side of a membrane facing the back volume. In this way, short circuits or contamination caused by moisture and liquids can be avoided.

[0177] In a preferred embodiment, the MEMS interaction region may be placed in a mobile state only after the dielectric layer or layer system has been deposited or removed, preferably by a delamination process, particularly by removing a sacrificial layer.

[0178] In particular, this ensures that the packaging method steps do not adversely affect the functionality of mechanically sensitive and finely structured MEMS interaction regions. Instead, the preferred release process for MEMS interaction regions is performed only as one of the final process steps, after the application of a dielectric layer or layer system and, if necessary, targeted removal within the MEMS interaction regions.

[0179] An example of a mechanically sensitive and finely structured MEMS interaction region is a MEMS film in the case of a MEMS transducer as a MEMS element.

[0180] In a preferred embodiment, the MEMS film enters an oscillatory state only after the layer or layer system has been applied or removed, preferably by a delamination process, particularly by removing a sacrificial layer.

[0181] MEMS films are essential components of MEMS transducers. At the same time, such films are particularly finely structured and highly sensitive to achieve desired acoustic properties. Therefore, the process of applying or removing layers or layer systems for acoustic ports can affect or even destroy the film.

[0182] Therefore, the film is preferably brought into vibration only afterward, in particular, by removing a well-structured sacrificial layer intended for this purpose, which is present, for example, between the film and other transducer components and thus blocks and protects the film. This can be done, for example, by an etching process, preferably by removing excess material from the sacrificial layer from the package. Preferably, the sacrificial layer can be located on the opposite side of the film toward the front volume. The material can then be removed through acoustic ports. If the sacrificial layer is located within the back volume, the material is preferably removed through suitable small channels or openings, which can preferably be closed later.

[0183] Such delamination is particularly relevant to CMUTs, PMUTs, and PC-MUTs. The benefits are equally applicable to other MEMS elements.

[0184] In another embodiment, the present invention relates to a MEMS package that can be manufactured or manufactured by the described manufacturing method.

[0185] In particular, the present invention is circuit board and A MEMS element disposed on a substrate including a MEMS interaction region, A dielectric layer for protecting the MEMS element, manufactured by surface conformal coating of the MEMS element using a dielectric coating process, Regarding MEMS packages, including those mentioned.

[0186] Those skilled in the art will recognize that the technical features, definitions, and advantages of preferred embodiments of the described manufacturing methods for MEMS packages are equally applicable to the resulting MEMS packages, and vice versa.

[0187] As explained, a particularly preferred application of the packaging method of the present invention to MEMS transducers.

[0188] In a preferred embodiment, the present invention also relates to a MEMS package including a MEMS transducer package, wherein the MEMS transducer package is circuit board and A MEMS device disposed on a substrate including a MEMS film, wherein the back volume of the MEMS transducer is preferably located between the substrate and the MEMS film. A processor, preferably an integrated circuit, disposed on a substrate and having an electrical connection to a MEMS device, A layer system for protecting MEMS transducers, a. The step of surface conforming coating, preferably spray coating, of the MEMS device, processor, and electrical interconnects with the dielectric layer, preferably a dielectric layer, particularly a photostructureable polymer, so that the MEMS device, processor, preferably an integrated circuit, and electrical interconnects are completely enclosed between the dielectric layer and the substrate. b. The step of applying a conductive layer to at least multiple regions on a dielectric layer, c. The step of optionally placing acoustic ports above a MEMS film by removing a dielectric layer or layer system above the film in several regions, particularly by lithography and / or a lift-off process, and the resulting layer system. Includes.

[0189] Preferably, the arrangement of the layer system, MEMS device and / or MEMS film may be such that, after removal of the dielectric layer or layer system, the conductive region does not come into direct contact with the package environment, and / or the back volume and conductive region of the MEMS transducer are sealed from air and / or liquid, the back volume of the MEMS transducer is positioned between the substrate and the MEMS film, and the MEMS transducer package has an acoustic port above the film. [Modes for carrying out the invention]

[0190] The present invention will be described below with reference to further figures and examples. The examples and figures will be helpful in illustrating preferred embodiments of the present invention without limiting them.

[0191] Figures 1 to 4 show a preferred embodiment of a method for manufacturing a MEMS package using a MEMS transducer package 14 as an example. [Brief explanation of the drawing]

[0192] [Figure 1] Figure 1 shows the MEMS transducer 1 without the completed package 14. A MEMS device 2 (also called a MEMS device) with a MEMS film 3 is located on the substrate 4. Similarly, an IC 5 (in the form of an ASIC here) is placed on the substrate 4. The MEMS device 2 and IC 5 are electrically connected here via wire bonds 6. [Figure 2] Figure 2 schematically illustrates the application of a coating system 16 for protecting the MEMS transducer 1. First, a dielectric is applied to the surface conformal coating (e.g., spray coating) 7, which covers all components present on the substrate with a dielectric layer 8. Thus, this layer surrounds and substantially adheres to these components, namely the MEMS device 2, IC 5, and the wire bond 6 between itself and the substrate 4. Next, a conductive layer 9 is applied to the dielectric layer 8, and the dielectric layer 8 also covers the outer edge region of the dielectric layer 8, preferably being flush with the substrate 4 at the outer edge of the coating to obtain a good seal. [Figure 3] Figure 3 shows a MEMS transducer package 14 that isolates the MEMS transducer 1 from the package environment 17 and thus protects it. The MEMS device 2 is positioned such that the back volume 13 is located between the film 3 and the substrate 4. Thus, the acoustic port 11 is introduced into the layer system 16 above the film, where both layers 8 and 9 are removed above the film 3, for example by a lithography process. Film 3 now exists as an unexfoliated film and is protected for a period of time by the sacrificial layer 12. [Figure 4]In Figure 4, the release film 15 was produced by removing the sacrificial layer 12. [Figure 5] Figure 5 shows a package that is preferably fully surface conformal, and the fully surface conformal coating system 18 is manufactured by vapor deposition of a polymer (e.g., parylene). This shows how the layer system thus manufactured adheres, and even the structure of the wire bond 6 is retained within the package 14 after coating. [Explanation of symbols]

[0193] 1. MEMS element, e.g., MEMS transducer 2 MEMS devices 3. MEMS interaction region, e.g., MEMS membrane 4 circuit boards 5. Processor, preferably an integrated circuit (IC) 6. Electrical connection, preferably wire bond 7. Surface conformal coating (e.g., spray coating) 8. Dielectric layer 9. Conductive layer 10 Outer edge of the coating 11 Anterior opening of the MEMS interaction region, preferably an acoustic port 12 Non-exfoliating interaction regions, e.g., sacrificial layers of non-exposed films 13 Back Volume 14 MEMS packages, e.g., MEMS transducer packages 15. Exfoliated MEMS interaction region, e.g., exfoliated MEMS film 16-layer system 17 Package Environment 18 Surface conformal layer system

[0194] literature Alfons Dehe,Martin Wurzer,Marc Fuldner and Ulrich Krumbein,The Infineon Silicon MEMS Microphone,AMA Conferences 2013-SENSOR 2013,OPTO 2013,IRS 2 2013. Gregor Feiertag,Wolfgang Pahl,Matthias Winter,Anton Leidl,Stefan Seitz,Christian Siegel,Andreas Beer,Flip chip MEMS microphone package with large acoustic reference volume,Proc.Eurosensors XXIV,September 5-8,2010,Linz,Austria. M.Harth,D.W.Schubert,Simple Approach for Spreading Dynamics of Polymeric Fluids.In:Macromol.Chem.Phys.213,no.6,March 2012,pp.654-665.

Claims

1. A method for manufacturing a MEMS package (14) having at least one layer for protecting a MEMS element (1), A step of providing a MEMS element (1) on a substrate (4) including at least one MEMS interaction region (3), wherein the MEMS element (1) comprises a MEMS device (2) and a processor (5) on the substrate (4), and an electrical connection (6) exists between the MEMS device (2) and the processor (5), The steps include: applying a conformal coating to the surface of the MEMS device (1) with a dielectric layer (8); A step of coating a conductive layer (9) on at least the region of the dielectric layer (8), wherein the dielectric layer (8) and the conductive layer (9) extend to cover the MEMS device (2) and the processor (5), A manufacturing method that includes this.

2. The MEMS element (1) is selected from the group consisting of acoustic MEMS transducers, optical MEMS transducers, MEMS sensors, particularly MEMS gas sensors and / or MEMS filters. Characterized by, The manufacturing method according to claim 1.

3. The manufacturing method according to claim 1, wherein the MEMS element (1) is an acoustic MEMS transducer.

4. The surface conformal coating is carried out by a dielectric coating process selected from the group consisting of spray coating, mist coating, vapor coating, and / or electroplating. Characterized by, The manufacturing method according to claim 1.

5. The surface conformal coating is carried out by a coating that wets the MEMS element (1) in at least a number of regions, and it is preferable that the wetting coating is carried out in the MEMS interaction region (3). Characterized by, The manufacturing method according to any one of claims 1 to 4.

6. The dielectric layer (8) comprises a polymer, preferably a photostructureable polymer, polymethyl methacrylate, polyimide, novolac, polymethylglutarimide, a polymer that can be deposited from the gas phase and / or liquid phase, particularly tetraethyl orthosilicate (TEOS), parylene and / or epoxy resin, particularly SU-8. Characterized by, The manufacturing method according to claim 1.

7. The conductive layer (9) comprises a metal, preferably aluminum and / or a precious metal, preferably gold, platinum, iridium, palladium, osmium, silver, rhodium and / or ruthenium, and / or The conductive layer (9) is applied by a coating process, particularly a PVD, CVD and / or sputtering process. Characterized by, The manufacturing method according to claim 1.

8. The MEMS device (2) and / or the processor (5) are mounted in a flip-chip design, preferably the electrical connection (6) is made via the substrate (4), and / or The MEMS device (2) and / or the processor (5) exist in a conventional design rather than a flip-chip design, and preferably the electrical connection (6) is made via at least one wire bond. Characterized by, The manufacturing method according to claim 1.

9. The MEMS element (1) comprises the MEMS device (2) and the processor (5), and the manufacturing method is The steps include providing the MEMS device (2) including the MEMS interaction region (3) on the substrate (4), The step of providing the processor (5) having the electrical connection (6) between it and the MEMS device (2) on the substrate (4), The steps include: applying a surface conformal coating, particularly a spray coating (7), to the MEMS device (2), the processor (5), preferably the electrical connection (6), and the dielectric layer (8), so that the MEMS device (2), the processor (5), and the electrical connection (6) are completely sealed between the dielectric layer (8) and the substrate (4); A step of coating a conductive layer (9) onto the dielectric layer (8) in at least a number of regions, wherein the conductive layer (9) together with the dielectric layer (8) forms a layer system (16), The steps include optionally arranging an opening (11) above the MEMS interaction region (3) by removing the dielectric layer (8) and / or the layer system (16) in at least some regions above the MEMS interaction region (3), including, A method for manufacturing a MEMS package (14) having preferably the layer system (16) for protecting the MEMS element (1), according to any one of claims 1 to 8.

10. The dielectric layer (8) is removed by a lithography process or lift-off, preferably the dielectric layer (8) is formed of a photostructureable polymer, and the pre-structuring of the dielectric layer (8) is performed by corresponding exposure of the photostructureable polymer to light. Characterized by, The manufacturing method according to claim 1.

11. The thickness of the dielectric layer (8) is between 10 nm and 1 mm. The thickness of the conductive layer (9) is between 10 nm and 20 μm. Characterized by, The manufacturing method according to claim 1.

12. The MEMS element (1) is an optical MEMS transducer, and the MEMS interaction region (3) includes an optical emitter and / or optical receiver. The MEMS element (1) is an acoustic MEMS transducer, and the MEMS interaction region (3) includes a MEMS film. The MEMS element (1) is a MEMS gas sensor, and the MEMS interaction region (3) includes a MEMS film and / or an electrochemical MEMS sensor region. The MEMS element (1) is a MEMS filter, preferably a MEMS frequency filter, particularly a SAW or BAW filter, and the MEMS interaction region (3) includes a MEMS filter structure, particularly a MEMS electrode and / or a MEMS bulk region. Characterized by, The manufacturing method according to claim 1.

13. The MEMS element (1) is a MEMS acoustic transducer and includes a MEMS device and a processor (5), and the manufacturing method is The steps include providing the MEMS device (2) including the MEMS film (3) on the substrate (4), The steps include providing the processor (5) having an electrical connection (6) to the MEMS device (2) on the substrate (4), The steps include: applying a surface conformal coating, particularly a spray coating (7), to the MEMS device (2), the processor (5), and preferably the electrical connection (6) to the dielectric layer (8), so that the MEMS device (2), the processor (5), and the electrical connection (6) are completely sealed between the dielectric layer (8) and the substrate (4); A step of optionally applying a conductive layer (9) onto the dielectric layer (8) in at least several regions, wherein the conductive layer (9) together with the dielectric layer (8) forms a layer system (16), The steps include optionally positioning an acoustic port (11) above the MEMS film (3) by removing the dielectric layer (8) or the layer system (16) in at least some regions above the film (3), including Characterized by, The manufacturing method according to claim 1.

14. MEMS package (14), Circuit board (4) and A MEMS element (1) disposed on the substrate (4) including a MEMS interaction region (3), wherein the substrate (4) comprises a MEMS device (2) and a processor (5), A dielectric layer (8) for protecting the MEMS element (1), wherein the dielectric layer (8) is a surface conformal coating, A conductive layer (9) located at least in the region of the dielectric layer (8), wherein the dielectric layer (8) and the conductive layer (9) extend to cover the MEMS device (2) and the processor (5), MEMS package (14), including the above.

Images