Device with particle protection for a microelectromechanical system

Abstract

The present invention relates to a device comprising: a microelectromechanical system (hereinafter referred to as MEMS for short), which interacts with ambient air (20), a protective element (30) and a wiring carrier (40), wherein the MEMS (10) is arranged on the wiring carrier (40) and is electrically contacted therewith, and wherein the protective element (30) is mounted on the MEMS (10) and / or on the wiring carrier (40) and is designed to protect respective interfaces (12) of the MEMS (10) in relation to the ambient air (20) against ingress of particles (25).

Description

[0001] R.415739

[0002] - 1 -

[0003] Description

[0004] title

[0005] Device with particle protection for a microelectromechanical system

[0006] State of the art

[0007] The present invention relates to a device with particle protection for a microelectromechanical system.

[0008] Microelectromechanical systems (MEMS for short) are miniaturized devices that can consist of mechanical elements, sensors and actuators and are manufactured using semiconductor manufacturing methods.

[0009] MEMS include, among others, MEMS that interact with ambient air, such as microphones, pressure sensors, gas sensors, ultrasonic transmitters and / or receivers, or micro loudspeakers.

[0010] Specifically, earphones are known from the prior art which have a particle protection in the form of a mesh and / or fleece in an outer housing (also called "2nd-level package"), which is inserted into an open end part of the earphone that is in contact with the ear canal when worn.

[0011] Due to their small size, particle contamination of such MEMS poses a major challenge, as it can limit the reliability and / or performance of environmentally exposed MEMS.

[0012] Particles that lead to such contamination can originate from various sources, such as from a manufacturing process of R.415739

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[0014] MEMS, a packaging and interconnection technology, and an environment in which the MEMS is subsequently used (e.g., air pollution such as fine dust).

[0015] Disclosure of the invention

[0016] The device according to the invention comprises a microelectromechanical system (hereinafter referred to as MEMS) which interacts with ambient air, a protective element, and a wiring carrier. The wiring carrier is, for example, configured as a printed circuit board or in a different configuration.

[0017] The MEMS is mounted on the wiring carrier and preferably electrically connected to it. This electrical connection can be established, for example, by means of a soldered or wire-bonded connection, without being limited to such a connection method. Other electrical components and / or circuit units, such as driver circuits, wireless communication interfaces (e.g., for a Bluetooth connection), etc., can be mounted on the wiring carrier. Furthermore, it is conceivable that additional MEMS devices could be mounted on the wiring carrier.

[0018] The protective element is mounted on the MEMS itself and / or on the wiring carrier and is designed to protect the respective interfaces of the MEMS to the ambient air from ingress of particles. The interfaces of the MEMS can include, for example, acoustic inlet and / or outlet openings, or other differently designed transitions between the MEMS and the ambient air.

[0019] Furthermore, it is possible that the interfaces of the MEMS are provided on a single side or on different sides (e.g. on a front volume side and on a back volume side) of the MEMS.

[0020] It should be noted generally that the particles which are to be prevented from entering the MEMS by the protective element can in principle include any type of contaminant and may, for example, also include water droplets or other liquid particles. R.415739

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[0022] can obtain. Accordingly, it is also conceivable to provide moisture protection for the MEMS based on the device according to the invention.

[0023] Preferably, in addition, the size and / or shape and / or material of the protective element are specified depending on predefined acoustic properties of the device, which are to be achieved by means of the device.

[0024] The device according to the invention offers the particular advantage that particle and / or moisture protection is provided as part of the so-called "1st-level package", i.e., at the level of the MEMS and / or the wiring carrier. This reduces and / or prevents contamination and the resulting defects and / or deterioration of the device's technical properties, since protection is already provided during the device's manufacture.

[0025] This means that the risk of defects can be minimized in subsequent production process steps such as assembly, testing, shipping, and / or integration of the device at a customer's site. Furthermore, this makes it possible to save costs, as less critical requirements for cleanroom conditions, etc., may be necessary since the MEMS has already been protected at the "1st-level package" level according to the invention.

[0026] Furthermore, according to the invention it is advantageously possible to realize the protection of the MEMS through cost-effective, highly scalable manufacturing in a wafer composite or in the “1st-Level-Package” setup.

[0027] Furthermore, high precision in the protective design is possible using microsystems technology, which ensures defined properties (e.g., acoustic damping in electroacoustic MEMS) while simultaneously guaranteeing defined barrier properties against particles and moisture.

[0028] The dependent claims describe preferred embodiments of the invention. R.415739

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[0030] In a preferred embodiment of the present invention, the MEMS is a microphone and / or a pressure sensor and / or a gas sensor and / or an ultrasonic sensor and / or a loudspeaker, without thereby limiting it to the aforementioned possible embodiments of the MEMS.

[0031] In a further preferred embodiment of the present invention, the protective element is designed as a structured thin film formed over the interfaces of the MEMS with the ambient air and having openings whose dimensions are each smaller than the minimum expected size of particles occurring in the vicinity of the MEMS. The thin film is, for example, a lateral thin film produced using conventional methods, structured laterally as a mesh, and exposed by sacrificial etching. The mesh size of such a mesh is, for example, in the range of 2 pm to 30 pm.

[0032] Preferably, the protective element is designed as a porous layer formed over the interfaces of the MEMS with the ambient air, and containing cavities whose dimensions are each smaller than the minimum expected size of particles occurring in the vicinity of the MEMS. The porous layer can be formed, for example, from a powder containing defined, micrometer-sized particles (e.g., by aerosol deposition, pulsed laser deposition, or other methods). The powder is fixed, for example, by depositing a nanometer-thick fixative layer using highly conformal atomic layer deposition (ALD), wherein the fixative layer consists, for example, of silicon dioxide (SiO2) or aluminum oxide (Al2O3) approximately 60 nm thick.

[0033] The porous layer is particularly advantageously formed from a powder whose grain size is larger than the interfaces (e.g., openings in a bottom layer of the MEMS) of the MEMS to the ambient air. Alternatively or additionally, the porous layer is arranged above the interfaces of the MEMS and / or in a cavity of the MEMS, into which the powder is introduced before fixation. In a further advantageous embodiment, the porous layer is arranged in an opening of the wiring carrier, while the interfaces of the MEMS face the opening of the wiring carrier. Alternatively or additionally, the porous layer fills a housing at least R.415739.

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[0035] The housing is partially enclosed, mounted on the wiring carrier, and surrounds the MEMS and / or other components arranged on the wiring carrier. The housing can advantageously be open in a direction corresponding to a main entry and / or exit direction of sound waves generated by and / or received by the MEMS. Since the porous layer within the housing is preferably fixed as described above, it is sufficient in such a case for the housing to at least partially enclose it to ensure the porous layer is secured within the housing.

[0036] Alternatively or additionally, the porous layer can also be mounted on the MEMS and / or the wiring carrier. Furthermore, it is advantageous to arrange the porous layer within a separate wafer, which is mounted over the interfaces of the MEMS (e.g., by chip and / or wafer bonding, adhesive bonding, etc.). The separate wafer can also have structured openings in which the porous layer is arranged and fixed.

[0037] Alternatively or additionally, the protective element is formed from a multitude of bond wires arranged across the interfaces of the MEMS to the ambient air. The multitude of bond wires are arranged parallel to each other, for example, in one or more bond wire planes and / or within each bond wire plane. Alternatively or additionally, the multitude of bond wires between adjacent bond wire planes may have different orientations relative to each other, and in particular an angle of 90°. Furthermore, alternatively or additionally, it is possible for the multitude of bond wires within a bond wire plane and / or between respective bond wire planes to be subjected to different electrical potentials in order to form an electrostatic particle filter.

[0038] In a further advantageous embodiment of the present invention, the protective element is designed as a channel within a housing mounted on the wiring carrier (which may be the housing described above or a different housing), wherein the channel is formed by overlapping and spaced-apart surfaces of the housing. By providing such a channel, which is as long as possible and advantageously tubular, through the housing, sound waves are directed into the R.415739

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[0040] Since particles can enter and / or exit the housing, the probability of particles from the environment penetrating to the MEMS to be protected is reduced, which can lead to an increase in robustness and an extension of the service life of the device according to the invention.

[0041] Preferably, the housing has a plurality of overlapping and spaced-apart surfaces that are nested within each other to further reduce the probability of particles from the environment penetrating to the MEMS due to the resulting increased channel length. Furthermore, the nested arrangement necessitates changing directions of movement for the particles to reach the MEMS, thus further reducing the probability of this occurring.

[0042] The device is preferably configured to provide different electrical potentials between at least two overlapping surfaces of the housing that form the channel, in order to form an electrostatic particle filter and thereby at least largely prevent particles from penetrating to the MEMS.

[0043] Alternatively or additionally, the protective element is designed as a channel within the MEMS and / or overlapping and spaced-apart surfaces of the MEMS forming the channel can be subjected to different electrical potentials in order to form an electrostatic particle filter and thereby at least largely prevent particles from penetrating to the MEMS.

[0044] In a further advantageous embodiment of the present invention, the device further comprises an outer housing (e.g. an earphone housing, a microphone housing, etc.) which is referred to as a so-called "2nd-level package" and which surrounds the MEMS, the wiring carrier and the protective element and, if applicable, other components of the device according to the invention.

[0045] Brief description of the drawings R.415739

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[0047] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. The drawing shows:

[0048] Figure 1 shows a schematic view of a first embodiment of a device according to the invention;

[0049] Figure 2 shows a schematic view of a second embodiment of a device according to the invention;

[0050] Figure 3 shows a schematic view of a third embodiment of a device according to the invention;

[0051] Figure 4 shows a schematic view of a fourth embodiment of a device according to the invention;

[0052] Figure 5 shows a schematic view of a fifth embodiment of a device according to the invention;

[0053] Figure 6 shows a schematic view of a sixth embodiment of a device according to the invention;

[0054] Figure 7 shows a schematic view of a seventh embodiment of a device according to the invention;

[0055] Figure 8 shows a schematic view of an eighth embodiment of a device according to the invention;

[0056] Figure 9 shows a schematic view of a ninth embodiment of a device according to the invention;

[0057] Figure 10 shows a schematic view of a tenth embodiment of a device according to the invention;

[0058] Figure 11 shows a schematic view of an eleventh embodiment of a device according to the invention; and R.415739

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[0060] Figure 12 shows a schematic view of a twelfth embodiment of a device according to the invention.

[0061] Embodiments of the invention

[0062] Figure 1 shows a schematic view of a first embodiment of a device according to the invention.

[0063] The device comprises a MEMS 10, which is configured here as a micro-speaker and has a plurality of outlet slots 12, which represent interfaces between the MEMS 10 and the ambient air 20. The outlet slots 12 are provided here on both a top and a bottom surface of the MEMS 10, whereby in this case only the top surface is exposed in such a way that particles 25 from the ambient air 20 can strike it.

[0064] To protect the MEMS 10 from such particles 25, the device has a protective element 30, which is designed here as a structured thin film with a plurality of openings for sound emission and which is arranged above the outlet slots 12 on the top of the MEMS 10.

[0065] An electrical potential can be applied between the MEMS 10 and the protective element 30 in order to attract particles 25 via an electric field thereby formed and to prevent their penetration into the outlet slots 12.

[0066] A wiring carrier 40 (see e.g. Fig. 3) of the device on which the MEMS 10 is mounted is not shown here.

[0067] Figure 2 shows a schematic view of a second embodiment of a device according to the invention.

[0068] In this embodiment, the MEMS 10 has a cavity 14 located above outlet slots 12 of the MEMS 10, the outlet slots 12 representing an interface between the MEMS 10 and the ambient air 20. R.415739

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[0070] A protective element 30 is arranged in the cavity 14, which is formed here as a bound porous layer and which has cavities 34, the extent of which is each smaller than a minimum expected size of particles 25 occurring in the vicinity of the MEMS 10.

[0071] A wiring carrier 40 (see e.g. Fig. 3) of the device on which the MEMS 10 is mounted is not shown here.

[0072] Figure 3 shows a schematic view of a third embodiment of a device according to the invention.

[0073] Figure 3 shows a MEMS 10 of the device, which is arranged on a printed circuit board 40. The respective interfaces of the MEMS 10 to the ambient air 20 face an opening 42 in the printed circuit board 40.

[0074] The opening 42 is filled with a protective element 30 designed as a porous layer, so that particles 25 appearing below the circuit board 40 in Figure 3 are prevented from penetrating through the opening 42 of the circuit board 40 to the interfaces 12 of the MEMS 10, which could restrict the functionality of the MEMS 10.

[0075] The device shown in Figure 3 also includes an electrical circuit 60 (e.g., a driver circuit) which is configured to control the MEMS 10. The MEMS 10 and the electrical circuit 60 are electrically connected to each other by means of bond wires 85.

[0076] In addition, the circuit board 40 is enclosed by a housing 50, which provides additional protection for the device.

[0077] Figure 4 shows a schematic view of a fourth embodiment of a device according to the invention.

[0078] It should be noted that, due to numerous similarities between the device shown in Figure 3 and the device shown in Figure 4, to avoid repetition, only the differences between the two figures are described below, and otherwise reference is made to the description of Figure 3. R.415739

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[0080] In Figure 4, a space formed between the circuit board 40 and the housing 50 is completely filled by means of a protective element 30 designed as a bonded porous layer, so that no particles 25 from the ambient air 20 can penetrate to the interfaces of the MEMS 10 and restrict a functionality of the MEMS 10.

[0081] There is no exposure of the back side of the MEMS 10 to particles 25, which is why the opening 42 of the circuit board 40 is not provided with a protective element 30.

[0082] Figure 5 shows a schematic view of a fifth embodiment of a device according to the invention.

[0083] It should be noted that, due to numerous similarities between the device shown in Figure 4 and the device shown in Figure 5, to avoid repetition, only the differences between the two figures are described below, and otherwise reference is made to the description of Figure 4.

[0084] In Figure 5, the opening 42 of the circuit board 40 is additionally filled with a further protective element 30 (similar to Figure 3), so that in this embodiment protection against particles 25 from the ambient air 20 is provided for the interfaces 12 of the MEMS 10 on both sides of the MEMS 10.

[0085] Figure 6 shows a schematic view of a sixth embodiment of a device according to the invention.

[0086] In this embodiment, the protective element 30 (a bonded porous layer) is formed within a separate wafer 70, which is connected to the MEMS 10 via respective connecting surfaces 75 of the MEMS 10 and the separate wafer 70.

[0087] In this way, the MEMS 10 is also protected from particles 25 from the ambient air 20.

[0088] Figure 7 shows a schematic view of a seventh embodiment of a device according to the invention. R.415739

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[0090] In this embodiment, the protective element 30 is formed similarly to Figure 6 in a separate wafer 70, which is connected to the MEMS 10 during the manufacture of the device according to the invention. The mounting direction of the separate wafer 70 is indicated here by an arrow.

[0091] In contrast to Figure 6, the protective element 30 (a bonded porous layer) is not fully integrated into the separate wafer 70, but rather into a multitude of recesses in the separate wafer 70.

[0092] Figure 8 shows a schematic view of an eighth embodiment of a device according to the invention.

[0093] It should be noted that, due to numerous similarities between the device shown in Figure 3 and the device shown in Figure 8, to avoid repetition, only the differences between the two figures are described below, and otherwise reference is made to the description of Figure 3.

[0094] In this embodiment, the housing 50 has overlapping upper surfaces of the housing 50, which form a channel 55 that here acts as a protective element 30 to protect against particles 25 in the ambient air.

[0095] Due to the length of the channel 55 and the covering of the MEMS 10 by the upper surfaces of the housing 50, the penetration of the particles 25 to the MEMS 10 is at least made more difficult.

[0096] Figure 9 shows a schematic view of a ninth embodiment of a device according to the invention.

[0097] It should be noted that, due to numerous similarities between the device shown in Figure 8 and the device shown in Figure 9, to avoid repetition, only the differences between the two figures will be described below, and otherwise reference is made to the description of Figure 8.

[0098] In this embodiment, the housing 50 has a plurality of overlapping surfaces which are nested within one another and thus form a correspondingly long channel 55 which allows for penetration. R.415739

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[0100] the transmission of particles 25 to the MEMS 10 is further made more difficult compared to the embodiment shown in Figure 8.

[0101] Figure 10 shows a schematic view of a tenth embodiment of a device according to the invention.

[0102] It should be noted that, due to numerous similarities between the device shown in Figure 8 and the device shown in Figure 10, to avoid repetition, only the differences between the two figures will be described below, and otherwise reference is made to the description of Figure 8.

[0103] In this embodiment, the device is additionally configured to apply different electrical potentials P1, P2 between the two overlapping surfaces of the housing 50, so that an electrostatic field is formed between these surfaces, which acts as a particle trap and can thus make it difficult or prevent particles 25 from penetrating to the MEMS 10.

[0104] Figure 11 shows a schematic view of an eleventh embodiment of a device according to the invention.

[0105] In this embodiment, the protective element 30 is designed as a channel 55 in a separate wafer 70, which is connected to the MEMS 10 to be protected during the manufacture of the device.

[0106] The device is also designed to apply 70 different potentials P1, P2 between two overlapping surfaces of the separate wafer in order to form a particle trap on the basis of an electrostatic field thereby created.

[0107] Figure 12 shows a schematic view of a twelfth embodiment of a device according to the invention.

[0108] It should be noted that, due to numerous similarities between the device shown in Figure 10 and the device shown in Figure 12, to avoid repetition, only the differences between the two figures are described below, and otherwise reference is made to the description of Figure 10. R.415739

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[0110] In contrast to the embodiment of the device according to the invention shown in Figure 10, the device here has a protective element 30, which is composed of a plurality of bond wires, each arranged in a first bond wire plane 80 and a second bond wire plane 80', and covering the MEMS 10. Within each bond wire plane 80, 80', several bond wires are arranged parallel to one another. The bond wires between the bond wire planes 80, 80' are arranged at an angle of 90° to each other, so that, in a top view of the bond wire planes 80, 80', the bond wires of the two bond wire planes 80, 80' form a wire mesh which is designed to keep larger particles 25 away from the MEMS 10.

[0111] Furthermore, in this embodiment, the device is configured to apply different electrical potentials P1, P2 to the two bond wire planes 80, 80' in order to form a particle trap as described in the preceding figures, which additionally provides protection against very small particles 25 that may penetrate to the MEMS 10 without the application of the electrical potentials P1, P2.

Claims

R.415739 - 14 - Claims 1. Device comprising: - a microelectromechanical system (10) (hereinafter referred to as MEMS) which interacts with ambient air (20), - a protective element (30), and - a wiring carrier (40), where - the MEMS (10) is arranged on the wiring carrier (40) and electrically contacted with it, and - the protective element (30) on which the MEMS (10) and / or on the wiring carrier (40) is mounted and is designed to protect the respective interfaces (12) of the MEMS (10) to the ambient air (20) from incoming particles (25).

2. Device according to claim 1, wherein the MEMS (10) - a microphone, and / or - a pressure sensor, and / or - a gas sensor, and / or - an ultrasonic sensor, and / or - a loudspeaker is.

3. Device according to one of the preceding claims, wherein the protective element (30) is designed as a structured thin film, which is formed over the interfaces (12) of the MEMS (10) to the ambient air (20), and - has openings (32) whose dimensions are each smaller than a minimum expected size of particles (25) occurring in the vicinity of the MEMS (10).

4. Device according to one of the preceding claims, wherein the protective element is designed as a porous layer (30) which - is formed over the interfaces (12) of the MEMS (10) to the ambient air (20), and R.415739 - 15 - - has cavities (34) whose extent is each smaller than a minimum expected size of particles (25) occurring in the vicinity of the MEMS (10).

5. Device according to claim 4, wherein the porous layer - is formed from a powder whose grain size is larger than the interfaces of the MEMS (10) to the ambient air (20), and / or - is located above the interfaces of the MEMS (10), and / or - is located in a cavity (14) of the MEMS (10), and / or - is arranged in an opening (42) of the wiring carrier (20), and / or - a housing (50) at least partially fills which is mounted on the wiring carrier (40) and surrounds the MEMS (10) and / or other components (60) arranged on the wiring carrier (40), and / or - is arranged within a separate wafer (70) which is mounted over the interfaces (12) of the MEMS (10) 6. Device according to one of the preceding claims, wherein the protective element (30) is formed from a plurality of bond wires which - are arranged above the interfaces (12) of the MEMS (10) to the ambient air (20), and / or - are arranged in one or more bond wire planes (80), and / or - are arranged parallel within a bond wire plane (80), and / or - have different orientations to each other between adjacent bond wire planes (80), and in particular an angle of 90°, and / or - can be subjected to different electrical potentials (P1 , P2) within a bond wire plane (80) and / or between respective bond wire planes (80).

7. Device according to one of the preceding claims, wherein the protective element (30) is designed as a channel (55) within a housing (50) mounted on the wiring carrier (40), the housing (50) being formed by overlapping and spaced-apart surfaces. R.415739 - 16 - 8. Device according to claim 7, wherein the housing (50) has a plurality of overlapping and spaced-apart surfaces which are nested within each other.

9. Device according to one of claims 7 or 8, wherein the device is configured to provide different electrical potentials (P1 , P2) between at least two overlapping surfaces of the housing (50) which form the channel (55).

10. Device according to one of the preceding claims, wherein - the protective element (30) is designed as a channel (55) within the MEMS (10), and / or - the overlapping and spaced surfaces of the MEMS (10) forming the channel (55) can be subjected to different electrical potentials (P1, P2).

11. Device according to one of the preceding claims further comprising an outer housing which surrounds the MEMS, the wiring carrier and the protective element.

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