ACOUSTIC TRANSDUCER DEVICE WITH EXTENDED REAR VOLUME

Abstract

An acoustic transducer device comprises: a substrate (102); and a cap (104) arranged on the substrate (102) and defining an acoustic chamber as a volume between the substrate (102) and the cap (102); wherein the acoustic chamber comprises a support structure (106) arranged on the substrate (102); and a membrane (108) arranged on the support structure (106); a seal (110) between the cap (102) and the membrane (108) or the support structure (106); a front volume (112) defined at least by the membrane (108), the seal (110), and the cap (104); and a primary rear volume (114) defined at least by the membrane (108), the support structure (106), and the substrate (102); and a secondary rear volume (116); further comprising a channel (118) in the substrate (102) or the support structure (106), wherein the channel (118) connects the primary back volume (114) and the secondary back volume (116).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from German application 10 2022 113 720.1, filed on May 31, 2022, the entire contents of which are incorporated into the present application by reference. TECHNICAL FIELD

[0002] This disclosure relates generally to an acoustic transducer device and techniques for improving the signal-to-noise ratio (SNR) and / or frequency response thereof. BACKGROUND

[0003] Microphones can use an electroacoustic transducer (e.g., an acoustic transducer) to convert acoustic vibrations into an electrical signal. Microphones are widely used in a variety of electronic devices, including smartphones, smartwatches, tablet computers, laptops, desktop computers, Internet of Things devices, and the like. Market forces may require acoustic transducers to be manufactured with a small form factor and produce high-quality audio signals.

[0004] The acoustic transducer can be implemented using a variety of mechanisms for generating an electrical signal, e.g., capacitive signal generation, optical signal generation, or other means. Particular attention is paid here to an acoustic transducer that generates an electrical signal using an optical sensor—however, nothing in this description is intended to exclude any other method of signal generation. The acoustic transducer may comprise a diaphragm configured to flex or translate in response to changes in sound pressure (e.g., in response to sound waves). The diaphragm may optionally have a reflective surface (e.g.,a reflective surface or a mirror), and the acoustic transducer may comprise a light source configured to direct light onto the membrane (and / or optionally onto the reflective surface) and detect changes in the reflected light to generate a corresponding electrical signal. The acoustic transducer may optionally be configured as a microelectromechanical system (MEMS) microphone.

[0005] The acoustic transducers disclosed herein can generally be understood as having a front volume and a rear volume defined by the diaphragm. The front volume can generally be understood as the volume between (e.g., between and / or between and including) a housing having an acoustic opening (e.g., an opening for the entrance of the sound wave) and the diaphragm. The rear volume can generally be understood as the volume on the opposite side of the diaphragm from the front volume, which contains some or all of the sensor components (e.g., components of the optical sensor).

[0006] As a general concept, it may be desirable to design the acoustic transducer to have a high SNR. One technique for increasing SNR is to reduce (e.g., minimize) the front volume and increase (e.g., maximize) the back volume. Various efforts to improve SNR by reducing the front volume and increasing the back volume have been disclosed, at least as follows.

[0007] Lim et al., US 2020 / 0245078 A1, discloses the hollowing out of the substrate beneath the membrane. This hollowed-out area functionally increases the backside volume.

[0008] Ginnerup et al., US 2018 / 0302725 A1 discloses the use of a gasket to define the front volume and an acoustic path created by creating a gap between an integrated circuit and the substrate to increase the back volume.

[0009] Yang, SU 9,002,040 B2 discloses the arrangement of the membrane on a broad structure and the hollowing out of the adjacent substrate to increase the back volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the present disclosure. The dimensions of various features or elements may be arbitrarily exaggerated or reduced for clarity.

[0011] In the following description, various aspects of the present disclosure are described with reference to the following drawings, in which: Fig. 1 shows an apparatus for an acoustic transducer device 100 according to a first aspect of the disclosure; Fig. 2 shows the acoustic transducer device according to a second aspect of the disclosure; Fig. 3 shows the acoustic transducer device according to a third aspect of the disclosure; Fig. 4 shows the acoustic transducer device according to a fourth aspect of the disclosure; Fig. 5 shows the acoustic transducer device with the photodiode in a cavity of the substrate; Fig. Figure 6 shows the acoustic transducer device with one or more vias (TSVs); Fig. Figure 7 shows a cross-section through the acoustic transducer device; Fig. Figure 8 shows the acoustic transducer device with a channel in the support structure; Fig. 9 shows the acoustic transducer device in which the secondary back volume is incorporated into the cap; and Fig. 10 shows the acoustic transducer device in which the secondary back volume is incorporated into the cap. DETAILED DESCRIPTION

[0012] The following detailed description refers to the accompanying drawings, which, by way of illustration, show exemplary details and embodiments in which aspects of the present disclosure may be practiced.

[0013] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0014] In the drawings, unless otherwise indicated, the same or similar elements, features and structures are designated by the same reference numerals.

[0015] The terms "at least one" and "one or more" may be understood to include a numerical quantity greater than or equal to one (e.g., one, two, three, four, [...], etc.). The phrase "at least one of" with respect to a group of items may be used herein to mean at least one item from the group of items. For example, the phrase "at least one of" with respect to a group of items may be used herein to mean a selection of: one of the listed items, a plurality of one of the listed items, a plurality of individual listed items, or a plurality of a multiple of individual listed items.

[0016] The words "plurality" and "multiple" in the description and claims expressly refer to a set greater than one. Accordingly, all expressions that expressly refer to the above words (e.g., "a plurality of [elements]," "multiple [elements]") refer to a set of elements, expressly referring to more than one of the mentioned elements. For example, the phrase "a plurality of" may be understood to encompass a numerical set greater than or equal to two (e.g., two, three, four, five, [...], etc.).

[0017] The terms "group of," "set of," "collection of," "series of," "sequence of," "grouping of," etc., in the description and claims, if any, refer to a set equal to or greater than one, i.e., one or more. The terms "proper subset," "reduced subset," and "smaller subset" refer to a subset of a set that is not equal to the set, i.e., a subset of a set that contains fewer elements than the set.

[0018] The present disclosure relates to an acoustic device with low acoustic noise, a diaphragm with high compliance (e.g., sensitivity), and a high resonant frequency of the system (e.g., the housing together with the diaphragm). The present disclosure aims to achieve at least a high signal-to-noise ratio (SNR) in an acoustic device (e.g., a front-port microphone) with excellent frequency response, where existing concepts fail. As described above, other acoustic devices attempt to counteract the low SNR by increasing the back volume within the diaphragm matrix. In the present disclosure, instead, the front volume is reduced by an acoustic seal, and the back volume is increased by a channel between a primary back volume and a secondary back volume. In other words, the present disclosure reduces the acoustic noise (e.g.,as in top-ported microphones) by reducing the front volume and thereby creating a high resonant frequency, by increasing the rear volume to reduce acoustic noise dominated by thermal limitations, and by combining the mechanical compliance of the diaphragm (e.g., sensitivity) with the acoustic front volume and rear volume.

[0019] Fig. 1 shows an acoustic transducer device 100 corresponding to a first aspect of the disclosure. The cap 104 defines an acoustic chamber as a volume between the circuit board / substrate 102 and the cap 104. The acoustic chamber includes a membrane substrate (e.g., a support structure) 106 disposed on the circuit board / substrate 102. The acoustic chamber includes a membrane 108 disposed on the support structure 106. The membrane 108 can translate in response to changes in sound pressure. The acoustic chamber further includes a seal 110 disposed between the cap 104 and the membrane 108 or between the cap 104 and the support structure 106. The acoustic chamber includes a front volume 112 defined by at least the membrane 108, the seal 110, and the cap 104.Sound waves penetrate the front volume 112 from an area outside the device and cause a displacement of the diaphragm 108. The acoustic chamber includes a primary back volume 114 defined at least by the diaphragm 108, the support structure 106, and the circuit board / substrate 102. The primary back volume 114 is separated from the front volume 112 by the diaphragm 108. The acoustic chamber further includes a secondary back volume 116 that is distinct from the front volume 112 or the primary back volume 114. The primary back volume 114 and the secondary back volume 116 are connected by a channel 118 in the circuit board / substrate 102 or the support structure 106, with the channel 118 connecting the primary back volume 114 and the secondary back volume 116. The acoustic chamber can define the acoustic compliance of the acoustic transducer.

[0020] The acoustic device may further include an acoustic opening 120, which may be configured as an opening within the cap 104. The acoustic opening 120 may be positioned to create an opening between a space external to the acoustic device 100 and the front volume 112, for example, to allow sound waves to penetrate the front volume 112. The acoustic opening 120 may be any size to meet the requirements of the particular implementation of the acoustic transducer. The acoustic opening 120 may be centered relative to the diaphragm 108. Alternatively, the acoustic opening 120 may be eccentric with respect to the diaphragm 108. In some configurations, it may be desirable to position the acoustic opening 120 off-center relative to the diaphragm, for example, to improve eye safety (e.g.,to prevent the light source laser from emanating from the acoustic aperture, such as in the event of a membrane failure). In one non-limiting example, the acoustic aperture 120 may have a diameter of less than 2 mm; in another non-limiting example, the acoustic aperture 120 may have a diameter of less than 1 mm; in one non-limiting example, the acoustic aperture 120 may have a diameter of less than 0.5 mm; in one non-limiting example, the acoustic aperture 120 may have a diameter of approximately 0.3 mm. Alternatively or additionally, the acoustic transducer device may include a plurality of smaller diameter acoustic apertures. Such apertures may, for example, be 0.3 mm or smaller.

[0021] The acoustic transducer device includes a sensor configured to generate an electrical signal representative of the sound wave in the acoustic chamber. Although various sensor types (e.g., capacitive, optical, etc.) may be used in the acoustic transducer disclosed herein, the acoustic transducer is described below as including a light source and an optical sensor (e.g., a photodiode). As previously mentioned, the acoustic transducer may include a light source 122 configured to generate light (e.g., electromagnetic wavelengths in the visible and / or invisible spectrum, optionally including infrared and / or ultraviolet wavelengths). An exemplary configuration of the light source 122 may be a vertical cavity surface-emitting laser (VCSEL). The light source 122 (e.g., the VCSEL) may be configured to direct light onto the membrane 108.Changes in the bending (e.g., displacement of the diaphragm) of the diaphragm 108 due to changes in sound pressure result in changes in the reflection of light from the diaphragm 108. The acoustic transducer device may include a photodiode / photodiode chip 124, which may be configured to detect light generated by the light source 122 and reflected from the diaphragm 108 and generate an electrical signal based on this detected light. In an optional configuration, the diaphragm may include a mirror 128 or other reflective surface disposed on a second side of the diaphragm (e.g., on a side within the primary back volume), which may increase the amount of light reflected from the surface of the diaphragm. Alternatively, the diaphragm may be configured without a mirror; in this case, the light generated by the light source 122 is simply reflected by the material of the diaphragm.Although the diaphragm itself can be less reflective than a mirror, the acoustic transducer can also operate without a mirror. If a mirror is used, the diameter of the mirror should generally be smaller than the diameter of the diaphragm. In an optional configuration, the diameter of the mirror can range from 10 µm to 120 µm; for example, the diameter is approximately 100 micrometers.

[0022] The acoustic transducer device may include a metallization layer 126.

[0023] The acoustic transducer device may include an integrated circuit 130. The integrated circuit 130 may optionally be attached to the circuit board / substrate 102 with a digital die attachment 132, such as a flip-chip connection or a wire bond.

[0024] The acoustic transducer device may include one or more surface-mounted devices 134. The one or more surface-mounted devices 134 may include one or more electrical components, including, but not limited to, resistors, inductors, capacitors, transistors, or others. The one or more surface-mounted devices 134 may be configured to change a current or voltage of an electrical signal within the acoustic transducer.

[0025] In Fig. 2 shows the acoustic transducer according to a second aspect of the disclosure. In this configuration, each element of the acoustic transducer is Fig. 2 identical to the corresponding elements in Fig. 1, except that a solder ball array 136 may be present, wherein the solder ball array may electrically connect the photodiode / photodiode chip 124 to the metallization layer 126.

[0026] In Fig. 3 shows the acoustic transducer according to a third aspect of the disclosure. In this configuration, each element of the acoustic transducer is Fig. 3 identical to the corresponding elements in Fig. 1, except that the photodiode chip 124 may be configured with an integrated photodiode 138.

[0027] In Fig. Figure 4 illustrates the acoustic transducer according to a fourth aspect of the disclosure. In this configuration, the solder ball array 136 and the integrated photodiode 124 are each present.

[0028] Fig. Figure 5 shows the subject of one of the acoustic transducers of the Fig. 1-4, in which a cavity is formed in the circuit board / substrate 102 and the photodiode / photodiode chip 124 is arranged in the cavity. In this configuration, the light source 122 can be arranged on the circuit board / substrate 102, e.g., above the photodiode / photodiode chip 124.

[0029] Fig. 6 shows the subject of Fig. 1-4, in which one or more silicon vias (TSVs) 140 are used to connect a metallization layer 126 on the top side of the photodiode to a metallization layer (not labeled) on the bottom side of the photodiode.

[0030] Fig. Figure 7 shows a cross section of the acoustic transducer of one of the Fig. 1-6. In this figure, a cap 104 is mounted on the substrate 102 and defines an acoustic chamber. The support structure 106 is disposed on the substrate 102, and a diaphragm 108 is disposed on the support structure 106. A seal 110 is disposed between the support structure and / or the diaphragm 108 and the cap 104, thus defining a front volume as the volume between the cap 104, the diaphragm 108, and the seal 110. On the other side of the diaphragm 108, a primary back volume is defined by the volume between the support structure 106, the diaphragm 108, and the substrate 102. The primary back volume includes a light source 122 and a photodiode / photodiode chip 124. Within the primary back volume, the substrate includes a channel 118 that connects the primary back volume to a secondary back volume.In this figure, the channel 118 is shown running transverse to an axis that lies in the same plane as, but perpendicular to, the primary length of the substrate. Otherwise, the support structure 106 includes four walls forming a closed structure (e.g., defined by the four walls, the substrate, and the membrane). Alternatively, the support structure 106 may have any number of walls, provided that a closed structure is formed between the wall(s) of the support structure, the membrane, and the substrate. The channel may be formed in the substrate beneath one or more walls of the support structure 106. In . Fig. 7, the wall under which the channel is formed is not shown, since Fig. 7 is a cross-section and the wall under which the channel is formed lies on a different plane than the plane forming the basis of this cross-section.

[0031] In an optional configuration, the height of the seal 110 (e.g., a distance along the seal between the cap and the support structure) may be less than 0.5 mm, e.g., less than 0.2 mm. In an optional aspect of the disclosure, the height of the seal may be approximately 0.1 mm.

[0032] In an optional configuration, the height of the support structure 106 may be less than 1 mm, e.g., less than 0.8 mm. In an optional aspect of the disclosure, the height of the support structure may be approximately 0.65 mm. The support structure 106 may optionally consist of multiple layers, e.g., multiple layers of the same material. Such layering of materials may be more cost-effective than etching thicker substrates (e.g., substrates thicker than 0.65 mm).

[0033] In an optional configuration, an outer dimension of the support structure 106 (e.g., a length or width from outer wall surface to outer wall surface) may be less than 2 mm, e.g., less than 1.6 mm. According to an optional aspect of the disclosure, the outer dimension may be about 1.4 mm by 1.4 mm. In these optional aspects, an inner dimension of the support structure 106 (e.g., from inner wall surface to inner wall surface) may be less than 1.5 mm or, e.g., less than 1.3 mm. In an optional aspect, the inner dimension of the support structure may be about 1 mm, about 1.1 mm, or about 1.2 mm.

[0034] According to an optional aspect of the disclosure, the photodiode / photodiode chip 124 and the light source 122 together may be less than 1.0 mm high, e.g., less than 0.7 mm. According to an optional aspect of the disclosure, the combined height of the photodiode / photodiode chip 124 and the light source 122 may be approximately 0.45 mm.

[0035] According to an optional aspect of the disclosure, the channel 118 may be less than 2.0 mm wide, e.g., less than 1.0 mm wide, e.g., a maximum of 0.9 mm wide. According to an optional aspect of the disclosure, the channel 118 may be at least 0.05 mm wide.

[0036] According to an optional aspect of the disclosure, the membrane may be more than 0.5 mm wide, e.g., at least 1.0 mm wide, e.g., in a range of about 1.0 mm to about 1.2 mm wide.

[0037] In Fig. Figure 8 illustrates the acoustic transducer in which the channel is created in the support structure 106 rather than in the substrate 102. In this way, a channel (e.g., the opening) is created in the vertical walls of the support structure 106, allowing air communication between the primary back volume 114 and the secondary back volume 116. The air communication is represented by the arrows along the channel 118. In an optional aspect of the disclosure, the substrate may remain intact (e.g., without a channel) during the fabrication of the channel in the support structure 106.

[0038] Fig. Figure 9 shows an optional, alternative configuration in which the secondary back volume is incorporated into the cap. In this configuration, the acoustic transducer device may include a substrate 102 having a recess 142 (corresponding to the primary back volume 114), a chip 130 disposed over the recess and having a first side facing the recess and a second side opposite the first side, defining an acoustic chamber as a volume between the recess and the chip, and a cap 104 disposed on the substrate 102 and over the chip 130, the acoustic chamber including a support structure 106 disposed in the recess on the first side of the chip and a diaphragm 108 disposed on the support structure 106; and a diaphragm 108 disposed on the support structure 106.a primary back volume 114 defined by at least the membrane, the support structure, and the chip; and a secondary back volume 116 defined by at least the cap, the substrate, and the chip and different from the primary back volume 114; further comprising a channel in the substrate or the support structure, the channel connecting the primary back volume 114 and the secondary back volume 116.

[0039] Fig.10 shows another optional alternative configuration in which the secondary back volume is incorporated into the cap. In this optional alternative configuration, the acoustic transducer device comprises a substrate 1002 having a recess (e.g., the recessed region within 1002); a chip 1030 disposed over the recess and having a first side facing the recess and a second side opposite the first side, defining an acoustic chamber as a volume between the recess and the chip; and a cap 1004 disposed on the substrate 1002 and over the chip 1030, the acoustic chamber comprising a support structure 1006 disposed in the recess on the first side of the chip; and a diaphragm 1008 disposed on the support structure; a seal 1010 disposed in the recess on the diaphragm or the support structure;a front volume 1012 defined by at least the membrane, the seal, and the recess; and a primary back volume 1014 defined by at least the membrane, the support structure, and the chip; and 1016 a secondary back volume defined by at least the cap, the substrate, and the chip and different from the front volume or the primary back volume; further comprising a channel in the substrate or the support structure, the channel connecting the primary back volume and the secondary back volume.

[0040] As described above, the acoustic transducer has a channel between the primary back volume and the secondary back volume. This channel allows air to flow between the primary back volume and the secondary back volume, combining the primary back volume and the secondary back volume into a single back volume that is larger than the primary back volume alone. The opening increases the volume, resulting in a higher SNR and improving the frequency response.

[0041] Various channel configurations are possible. In one aspect, the channel may be a trench in the circuit board / substrate. This channel may, for example, be arranged below the support structure. In another aspect, the channel may be arranged within the support structure and not in the circuit board / substrate. Whether the channel is arranged in the circuit board / substrate or in the support structure can be selected depending on manufacturing requirements, materials used, or otherwise as desired.

[0042] The channel can be manufactured in a variety of shapes. The channel can optionally be manufactured with a rectangular, square, triangular, or a combination of these cross-sections. Alternatively, or additionally, the channel can also be manufactured with an irregular polygonal cross-section. The channel can be manufactured to any desired height, although the channel is preferably at least 50 µm high.

[0043] The acoustic resistance is determined at least in part by the channel opening—by the channel profile and the channel length. The channel height can strongly influence the acoustic resistance, which is why a channel height of at least 50 µm can be specified. The channel width can be selected based on other factors, such as the size of the membrane die. In many cases, it may be desirable to make the channel width as large as possible.

[0044] The acoustic transducer device includes a cap covering the substrate and capable of defining the acoustic chamber, including the front volume, the primary back volume, and the secondary back volume. In some configurations, the cap includes an opening configured to allow sound waves from outside the acoustic chamber to enter the front volume.

[0045] The acoustic transducer comprises a diaphragm configured to translate (e.g., exhibit movement or bending) in response to the sound waves in the front volume. The diaphragm may have a first side and a second side, with the first side facing the cap and the second side facing the substrate. The diaphragm may be disposed on the support structure. The diaphragm may separate the front volume from the primary rear volume. The diaphragm may optionally have a diameter of 100 µm to 2000 µm.

[0046] The acoustic transducer device includes a seal that, in combination with the diaphragm and the support structure, can seal the front volume to prevent or limit the movement of air from the front volume into the primary back volume or the secondary back volume.

[0047] The acoustic transducer device may include a mirror disposed on the second side of the membrane. In an alternative configuration, the mirror may be disposed between the first side and the second side of the membrane. The mirror may be made of or include any reflective material, e.g., gold and / or aluminum. The mirror may be deposited on the second side of the membrane by any deposition method. The mirror may increase the reflectivity of the second side of the membrane so that a greater amount of light is reflected from the membrane to the photodiode / photodiode chip. According to one aspect of the disclosure, the diameter of the mirror (e.g., in case of using the mirror) may be less than 120 µm, e.g., less than 80 µm, e.g., less than 50 µm. The diameter of the mirror may optionally range from about 10 µm to about 120 µm.

[0048] Alternatively, the acoustic transducer can also operate without the mirror on the second side of the diaphragm. When the acoustic transducer is implemented without the mirror, the light source is configured to direct light onto the second surface of the diaphragm, and the photodiode / photodiode chip is configured to detect light reflected from the second surface of the diaphragm without the mirror. Although the non-mirrored surface of the diaphragm is expected to reflect less light than a mirrored surface, the diaphragm surface still exhibits a certain degree of reflectivity, and this degree is often sufficient to detect the reflected light and generate a corresponding electrical signal.

[0049] The membrane may have one or more openings that allow static pressure equalization between the front volume and the rear volume. This opening(s) may allow at least a limited air exchange between the front volume and the primary rear volume. This opening(s) may, for example, be 6 µm or less. In another example, the opening(s) may be 3 µm to 6 µm. If no opening is present, an additional opening for pressure equalization may alternatively be provided in the cap or substrate.

[0050] Various elements of the acoustic transducer can be housed in the back volume, preferably in the primary back volume. These may include the light source, which may be a VCSEL and a photodiode or photodiode chip.

[0051] The light source may be configured to direct light toward the second side of the membrane. The light source may preferably be a VCSEL, although other light sources may be used. VCSELs are well known, so the details of VCSELs or their fabrication will not be discussed here. Because VCSELs emit light perpendicular to the VCSEL, the VCSEL may be positioned or shaped substantially parallel to the circuit board / substrate beneath the membrane so that light emission perpendicular to the circuit board / substrate results in light emission directed toward the membrane. In this way, the VCSEL may have a line of sight to the mirror or the second side of the membrane.

[0052] The acoustic transducer device further comprises an optical sensor configured to detect light reflected from the membrane (e.g., from the second surface of the membrane or from the mirror mounted on the second surface) and generate an electrical signal corresponding to the detected light. The type of optical sensor can be selected for a particular application without limitation. Possible optical sensors include, but are not limited to, photoconductive devices, which can be configured to generate a resistance change in response to incident light; photovoltaic devices, which can be configured to generate a voltage in response to incident light; and photodiodes or phototransistors, which can be used to generate an output current in response to incident light.The terms “photodiode”, “photodiode chip” and “integrated photodiode” are used here as a non-limiting list of types of optical sensors.

[0053] In certain configurations, the acoustic transducer device may have a tertiary back volume, which may be distinct from the front volume, the primary back volume, and the secondary back volume. In this configuration, the channel described above is a first channel, and the acoustic transducer device also includes a second channel configured to connect the primary back volume and the tertiary back volume. In this way, an additional back volume is added to the primary back volume.

[0054] In an optional configuration, the diaphragm may have one or more openings. These openings may be referred to as "vent holes" or "pressure equalization holes" and can equalize pressure at low frequencies and improve robustness. By using these optional openings, the acoustic transducer device can be configured so that the high-pass cutoff frequency is less than 20 Hz. The number and diameter of the openings can be selected to ensure the equivalent acoustic resistance is as high as possible, i.e., greater than 1e15 N / m 3These parameters may depend on the number, position, and diameter of the pressure equalization holes. In various aspects of this disclosure, two or more openings with diameters of 3 µm may be used, which may be located near the larger DRIE opening that forms the primary back volume. Each of the optional one or more openings in the membrane may have a diameter of at least 2 µm. In one non-limiting example, each of the optional openings in the membrane may have a diameter of at most 10 µm. In one non-limiting example, each of the optional one or more openings may have a diameter of about 3 µm. The material of the membrane may be chosen for the particular application without limitation; however, in one non-limiting example, the membrane may comprise or be formed from silicon nitride (SiN) and / or polycrystalline silicon (polySi).The membrane can be fabricated either by plasma-enhanced chemical vapor deposition, low-pressure chemical vapor deposition, a silane-based coating, or by physical vapor deposition (PVD), e.g. by sputtering.

[0055] As previously mentioned, the acoustic transducer device disclosed herein can also be configured as an optical microphone. It should be noted that optical microphones can be configured without a backplane, but instead have a line of sight between the laser (e.g., a VCSEL) and the diaphragm, which can optionally include a mirror. The diaphragm can be flat or corrugated and can have a raised microstructure. In various aspects of this disclosure, the diaphragm has a diameter between 500 and 1500 µm. The diaphragm must be no smaller than, for example, 100 micrometers and no larger than 2000 µm.

[0056] The gasket material can be chosen without limitation for the specific application; however, as a non-limiting example, the gasket may comprise or be formed from silicone, an ultraviolet-curing epoxy resin, a thermally curing epoxy resin, or any of these materials. A material may be selected to provide a good acoustic seal with little leakage toward the edges. Contamination of the membrane by the gasket, thus impairing its performance, should be avoided. The gasket material should ideally be fast-curing.

[0057] In one non-limiting example, the acoustic transducer device of any aspect of the disclosure and / or any aspect disclosed herein may be configured as a micro-electromechanical microphone.

[0058] Further aspects of the revelation are illustrated by examples.

[0059] In Example 1, an acoustic transducer device comprises: a substrate; and a cap disposed on the substrate and defining an acoustic chamber as a volume between the substrate and the cap; wherein the acoustic chamber comprises: a support structure disposed on the substrate; and a diaphragm disposed on the support structure; a seal disposed between the cap and the diaphragm or the support structure; a front volume defined by at least the diaphragm, the seal, and the cap; and a primary back volume defined by at least the diaphragm, the support structure, and the substrate; and a secondary back volume different from the front volume or the primary back volume; further comprising: a channel in the substrate or the support structure, the channel connecting the primary back volume and the secondary back volume.

[0060] Example 1 is the acoustic transducer device of Example 1, wherein the channel is a trench and the trench is in the substrate.

[0061] Example 2 is the acoustic transducer device of Example 2, wherein the channel is a trench and the trench is located in the substrate beneath the support structure.

[0062] Example 3 is the acoustic transducer device of Example 1, wherein the channel is located in the support structure.

[0063] Example 4 is the acoustic transducer device of any one of Examples 1 to 4, wherein the channel is at least 50 µm high.

[0064] Example 5 is the acoustic transducer device of any one of Examples 1 to 5, wherein the cross-section of the channel is rectangular, square, triangular, or a combination thereof.

[0065] Example 6 is the acoustic transducer device of any of Examples 1 to 6, wherein the cap has an opening configured to allow sound waves from outside the acoustic chamber to enter the front volume; and wherein the diaphragm is configured to translate in response to the sound waves in the front volume. In an optional configuration, the cap may have a plurality of such openings, wherein a diameter of each opening is 50 µm to 300 µm.

[0066] Example 7 is the acoustic transducer device of Example 7, wherein the primary back volume includes a transducer configured to generate an electrical signal based on the displacement of the diaphragm.

[0067] Example 8 is the acoustic transducer device of Example 8, wherein the transducer comprises an optical sensor.

[0068] Example 9 is the acoustic transducer device of any one of Examples 1 to 9, wherein the membrane has a first side facing the cap and a second side facing the substrate

[0069] Example 10 is the acoustic transducer device of any one of Examples 1 to 10, wherein the electromechanical microphone further comprises a mirror on the second side of the diaphragm.

[0070] Example 10a is the acoustic transducer device of any one of Examples 1 to 10, wherein the electromechanical microphone further comprises a mirror between the first side of the diaphragm and the second side of the diaphragm.

[0071] Example 11 is the acoustic transducer device of any one of Examples 9 to 11, wherein the transducer comprises a laser.

[0072] Example 12 is the acoustic transducer device of Example 12, in which the laser has a line-of-sight connection to the mirror.

[0073] Example 13 is the acoustic transducer device of any one of Examples 11 to 13, wherein the mirror comprises aluminum or gold.

[0074] Example 14 is the acoustic transducer device of any one of Examples 11 to 14, wherein the diameter of the mirror is between 10 µm and 120 µm.

[0075] Example 15 is the acoustic transducer device of any one of Examples 1 to 15, wherein the membrane has a diameter of 100 µm to 2000 µm.

[0076] Example 16 is the acoustic transducer device of Example 16, wherein the membrane has a diameter of 500 µm to 1500 µm.

[0077] Example 17 is the acoustic transducer device of any one of Examples 1 to 17, wherein the front volume is sealed to prevent the movement of air from the front volume into the primary back volume or the secondary back volume.

[0078] Example 18 is the acoustic transducer device of any one of Examples 1 to 18, wherein the acoustic chamber further comprises a tertiary back volume distinct from the front volume, the primary back volume, and the secondary back volume; wherein the channel is a first channel; further comprising a second channel configured to connect the primary back volume and the tertiary back volume.

[0079] Example 19 is the acoustic transducer device of any one of Examples 1 to 19, wherein the membrane has one or more openings.

[0080] Example 20 is the acoustic transducer device of Example 20, wherein each of the one or more apertures has a diameter of at least 2 µm and at most 10 µm.

[0081] Example 21 is the acoustic transducer device of Example 21, wherein each of the one or more apertures has a diameter of about 3 µm.

[0082] Example 22 is the acoustic transducer device of any one of Examples 1 to 22, wherein the seal comprises silicone, an ultraviolet curable epoxy resin, or a thermally curable epoxy resin.

[0083] Example 23 is the acoustic transducer device of any one of Examples 1 to 23, wherein the membrane comprises silicon nitride (SiN) or polycrystalline silicon (polySi).

[0084] Example 24 is the acoustic transducer device of any one of Examples 1 to 24, wherein the membrane is formed by plasma-enhanced chemical vapor deposition, low pressure chemical vapor deposition, deposition of a silane-based coating, or physical vapor deposition (PVD) such as sputtering.

[0085] Example 25 is the acoustic transducer device of any one of Examples 1 to 25, wherein the acoustic chamber defines the acoustic compliance of the acoustic transducer.

[0086] Example 26 is the acoustic transducer device of any one of Examples 1 to 26, wherein the acoustic transducer is configured as a microelectromechanical microphone.

[0087] Example 27 is an acoustic transducer device comprising: a substrate having a recess; a chip disposed over the recess and having a first side facing the recess and a second side opposite the first side, and defining an acoustic chamber between the recess and the chip as a volume; and a cap disposed on the substrate and over the chip, the acoustic chamber comprising: a support structure disposed in the recess on the first side of the chip; and a diaphragm disposed on the support structure; a seal disposed in the recess on the diaphragm or the support structure; a front volume defined by at least the diaphragm, the seal, and the recess; and a primary back volume defined by at least the diaphragm, the support structure, and the chip.and a secondary back volume defined at least by the cap, the substrate, and the chip and different from the front volume or the primary back volume; further comprising a channel in the substrate or the support structure, the channel connecting the primary back volume and the secondary back volume.

[0088] Example 28 is the acoustic transducer device of Example 28, wherein the channel is a trench and the trench is in the substrate.

[0089] Example 29 is the acoustic transducer device of Example 28 or 29, wherein the channel is at least 50 µm high.

[0090] Example 30 is the acoustic transducer device of any one of Examples 28 to 30, wherein the cross-section of the channel is rectangular, square, triangular, or a combination thereof.

[0091] Example 31 is the acoustic transducer device of any one of examples 28 to 31, wherein the recess includes an opening configured to allow sound waves from outside the acoustic chamber to enter the front volume; and wherein the diaphragm is configured to translate in response to the sound waves in the front volume.

[0092] Example 32 is the acoustic transducer device of Example 32, wherein the primary back volume includes a transducer configured to generate an electrical signal based on the displacement of the diaphragm.

[0093] Example 33 is the acoustic transducer device of Example 33, wherein the transducer comprises an optical sensor.

[0094] Example 34 is the acoustic transducer device of any one of Examples 28 to 34, wherein the membrane has a first side facing the cap and a second side facing the substrate

[0095] Example 35 is the acoustic transducer device of any one of Examples 24 to 31, wherein the electromechanical microphone further comprises a mirror on the second side of the diaphragm.

[0096] Example 36 is the acoustic transducer device of any one of Examples 33 to 35, wherein the transducer comprises a laser.

[0097] Example 37 is the acoustic transducer device of Example 36 in which the laser has a line of sight to the mirror.

[0098] Example 38 is the acoustic transducer device of any one of Examples 35 to 37, wherein the mirror comprises aluminum or gold.

[0099] Example 39 is the acoustic transducer device of any one of Examples 35 to 38, wherein the diameter of the mirror is between 10 µm and 120 µm.

[0100] Example 40 is the acoustic transducer device of any one of Examples 28 to 39, wherein the diaphragm has a diameter of 100 µm to 2000 µm.

[0101] Example 41 is the acoustic transducer device of Example 40, wherein the membrane has a diameter of 500 µm to 1500 µm.

[0102] Example 42 is the acoustic transducer device of any one of Examples 28 to 41, wherein the front volume is sealed to prevent the movement of air from the front volume into the primary back volume or the secondary back volume.

[0103] Example 43 is the acoustic transducer device of any one of Examples 28 to 42, wherein the acoustic chamber further comprises a tertiary back volume distinct from the front volume, the primary back volume, and the secondary back volume; wherein the channel is a first channel; further comprising a second channel configured to connect the primary back volume and the tertiary back volume.

[0104] Example 44 is the acoustic transducer device of any one of Examples 28 to 43, wherein the membrane has one or more apertures.

[0105] Example 45 is the acoustic transducer device of Example 44, wherein each of the one or more apertures has a diameter of about 3 µm.

[0106] Example 46 is the acoustic transducer device of any one of Examples 28 to 45, wherein the seal comprises silicone, an ultraviolet curable epoxy resin, or a thermally curable epoxy resin.

[0107] Example 47 is the acoustic transducer device of any one of Examples 28 to 46, wherein the membrane comprises silicon nitride (SiN) or polycrystalline silicon (polySi).

[0108] Example 48 is the acoustic transducer device of any one of Examples 28 to 47, wherein the membrane is formed by plasma-enhanced chemical vapor deposition, low pressure chemical vapor deposition, a silane-based coating, or physical vapor deposition (PVD) such as sputtering.

[0109] Example 49 is the acoustic transducer device of any one of Examples 28 to 48, wherein the acoustic chamber defines the acoustic compliance of the acoustic transducer.

[0110] Example 50 is the acoustic transducer device of any one of examples 28 to 49, wherein the acoustic transducer is configured as an electromechanical microphone.

[0111] Example 51 is a method of manufacturing an acoustic transducer device, the acoustic chamber comprising: creating a channel in a substrate; disposing a support structure on a substrate, at least a portion of the support structure disposed over the channel; disposing a diaphragm on the support structure; disposing a gasket on one of the diaphragm and the support structure; disposing a cap on the substrate, the cap defining an acoustic chamber as a volume between the substrate and the cap; wherein a front volume is defined by at least one of the diaphragm, the gasket, and the cap; and a primary back volume is defined by at least one of the diaphragm, the support structure, and the substrate; wherein the acoustic chamber further comprises a secondary back volume different from one of the front volume and the primary back volume; and wherein the channel connects the primary back volume to the secondary back volume.

[0112] Example 52 is the method of fabricating an acoustic transducer device of Example 51, wherein the channel is a trench and the trench is in the substrate.

[0113] Example 53 is the method of fabricating an acoustic transducer device of Example 52, wherein the channel is a trench and the trench is located in the substrate beneath the support structure.

[0114] Example 54 is the method of making an acoustic transducer device of any one of Examples 51 to 53, wherein the channel is at least 50 µm high.

[0115] Example 55 is the method of making an acoustic transducer device of any one of Examples 51 to 54, wherein the cross-section of the channel is rectangular, square, triangular, or a combination thereof.

[0116] Example 56 is the method of making an acoustic transducer device of any one of Examples 51 to 55, wherein the cap has an opening configured to allow sound waves from outside the acoustic chamber to enter the front volume; and wherein the diaphragm is configured to translate in response to the sound waves in the front volume.

[0117] In Example 57, the method of manufacturing an acoustic transducer device of Example 56 further comprises disposing a transducer in the primary back volume, the transducer configured to generate an electrical signal based on the displacement of the diaphragm.

[0118] Example 58 is the method of making an acoustic transducer of Example 57, wherein the transducer includes an optical sensor.

[0119] Example 59 is the method of making an acoustic transducer device of any one of Examples 51 to 58, wherein the diaphragm has a first side facing the cap and a second side facing the substrate.

[0120] In Example 60, the method of making an acoustic transducer device of any one of Examples 51 to 59 further comprises attaching a mirror to the second side of the membrane.

[0121] Example 61 is the method of making an acoustic transducer device according to any one of Examples 58 to 60, wherein the transducer comprises a laser.

[0122] Example 62 is the method of making an acoustic transducer device according to Example 61, wherein the laser has a line of sight to the mirror.

[0123] Example 63 is the method of making an acoustic transducer device according to any one of Examples 60 to 62, wherein the mirror comprises aluminum or gold.

[0124] Example 64 is the method of manufacturing an acoustic transducer device of any one of Examples 60 to 63, wherein a diameter of the mirror is between 10 µm and 120 µm.

[0125] Example 65 is the method of making an acoustic transducer device of any one of Examples 51 to 64, wherein the diaphragm has a diameter of 100 µm to 2000 µm.

[0126] Example 66 is the method of making an acoustic transducer device of Example 65, wherein the diaphragm has a diameter of 500 µm to 1500 µm.

[0127] Example 67 is the method of making an acoustic transducer device of any one of Examples 51 to 66, wherein the front volume is sealed so that the movement of air from the front volume into the primary back volume or the secondary back volume is prevented.

[0128] In Example 68, the method of manufacturing an acoustic transducer device comprises: forming a recess in a substrate; disposing a die over the recess, the die having a first side facing the recess and a second side opposite the first side, and having an acoustic chamber defined as a volume between the recess and the die; and disposing a support structure within the recess on the first side of the die; disposing a diaphragm on the support structure; disposing a gasket in the recess on one of the diaphragm and the support structure; disposing a cap on the substrate and over the die, the acoustic chamber comprising: a front volume defined by at least the diaphragm, the gasket, and the recess; and a primary back volume defined by at least the diaphragm, the support structure, and the die;and a secondary back volume defined at least by the cap, the substrate, and the chip and different from the front volume or the primary back volume; further comprising: forming a channel in the substrate or the support structure, the channel connecting the primary back volume and the secondary back volume.

[0129] Example 69 is the method of making an acoustic transducer device of Example 68, wherein the channel is a trench and the trench is in the substrate.

[0130] Example 70 is the method of making an acoustic transducer device of Example 68 or 69, wherein the channel is at least 50 µm high.

[0131] Example 71 is the method of making an acoustic transducer device of any one of Examples 68 to 70, wherein the cross-section of the channel is rectangular, square, triangular, or a combination thereof.

[0132] Example 72 is the method of making an acoustic transducer device of any one of Examples 68 to 71, wherein the recess includes an opening configured to allow sound waves from outside the acoustic chamber to enter the front volume; and wherein the diaphragm is configured to translate in response to the sound waves in the front volume.

[0133] In Example 73, the method of manufacturing an acoustic transducer device of Example 72 further comprises disposing a transducer in the primary back volume, the transducer configured to generate an electrical signal based on the displacement of the diaphragm.

[0134] Example 74 is the method of making an acoustic transducer device according to Example 73, wherein the transducer comprises an optical sensor.

[0135] Example 75 is the method of making an acoustic transducer device of any one of Examples 68 to 74, wherein the diaphragm has a first side facing the cap and a second side facing the substrate.

[0136] Example 76 is the method of making an acoustic transducer device of any one of Examples 68 to 75, wherein the electromechanical microphone further comprises a mirror on the second side of the diaphragm.

[0137] Example 77 is the method of making an acoustic transducer device according to any one of Examples 73 to 75, wherein the transducer comprises a laser.

[0138] Example 78 is the method of making an acoustic transducer device of Example 76, wherein the laser has a line of sight to the mirror. LIST OF REFERENCE SYMBOLS 100 Acoustic Transducer 102 Circuit board / substrate 104 Cap / Housing 106 Support structure / membrane die 108 membrane 110 Seal 112 Anterior volume 114 Primary back volume 116 Secondary back volume 118 channel 120 Acoustic connection 122 light source 124 photodiode / photodiode chip 126 Metallization layer 128 mirrors 130 Integrated Circuit / Chip 132 Digital Die Attachment (e.g. FlipChip or Wire Bonding) 134 Surface-mounted device 136 solder ball array 138 Integrated photodiode 140 Through-Silicon Via (TSV) 142 recess 1002 Substrat 1030 chip 1004 Cap 1006 Support structure 1008 Membran 1010 Seal 1012 Front volume 1014 Primary back volume 1016 Secondary back volume QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 113 720.1

[0001] US 2020 / 0245078 A1

[0007] US 2018 / 0302725 A1

[0008] SU 9,002,040 B2

[0009]

Claims

[1] Acoustic transducer device comprising: a substrate (102); and a cap (104) disposed on the substrate (102) and defining an acoustic chamber as a volume between the substrate (102) and the cap (102); where the acoustic chamber has: a support structure (106) arranged on the substrate (102); and a membrane (108) arranged on the support structure (106); a seal (110) arranged between the cap (102) and the membrane (108) or the support structure (106); a front volume (112) defined at least by the membrane (108), the seal (110) and the cap (104); and a primary back volume (114) defined at least by the membrane (108), the support structure (106) and the substrate (102); and a secondary back volume (116) different from the front volume (112) or the primary back volume (114); further comprising a channel (118) in the substrate (102) or the support structure (106), the channel (118) connecting the primary back volume (114) and the secondary back volume (116). [2] The acoustic transducer device of claim 1, wherein the channel (118) is a trench and the trench is located in the substrate (102). [3] The acoustic transducer device of claim 2, wherein the channel (118) is a trench and the trench is located in the substrate (102) below the support structure (106). [4] The acoustic transducer device of claim 1, wherein the channel (118) is located in the support structure (106). [5] Acoustic transducer device according to one of claims 1 to 4, wherein the channel (118) is at least 50 µm high. [6] The acoustic transducer device of any one of claims 1 to 5, wherein the cap (104) has an opening configured to allow sound waves from outside the acoustic chamber to enter the front volume (112); and wherein the diaphragm (108) is configured to translate in response to the sound waves in the front volume (112). [7] The acoustic transducer device of claim 6, wherein the primary back volume (114) comprises a transducer configured to generate an electrical signal based on the displacement of the diaphragm (108). [8] An acoustic transducer device according to claim 7, wherein the transducer comprises an optical sensor. [9] Acoustic transducer device according to one of claims 1 to 8, wherein the diaphragm (108) has a first side facing the cap and a second side facing the substrate (102). [10] The acoustic transducer device of claim 9, wherein the acoustic transducer device further comprises a mirror (128) on the second side of the diaphragm (108). [11] An acoustic transducer device according to any one of claims 8 to 10, wherein the transducer comprises a laser and the laser has a line of sight to the mirror (128). [12] Acoustic transducer device according to one of claims 8 to 11, wherein the diameter of the mirror (128) is between 10 µm and 120 µm. [13] Acoustic transducer device according to claim 12, wherein the diaphragm (108) has a diameter of 500 µm to 1500 µm. [14] The acoustic transducer device of any one of claims 1 to 13, wherein the acoustic chamber further comprises a tertiary back volume different from the front volume (112), the primary back volume (114) and the secondary back volume (116); wherein the channel (118) is a first channel; further comprising a second channel configured to connect the primary back volume and the tertiary back volume. [15] An acoustic transducer device according to any one of claims 1 to 14, wherein the seal (110) comprises silicone, an ultraviolet curable epoxy or a thermally curable epoxy. [16] Acoustic transducer device according to one of claims 1 to 15, wherein the acoustic transducer is configured as a microelectromechanical microphone. [17] Acoustic transducer device comprising: a substrate (1002) having a recess; a chip (1030) arranged above the recess and having a first side facing the recess, and a second side opposite the first side, has; an acoustic chamber, wherein the acoustic chamber is defined by the first side and the recess as a volume; and a cap (1004) disposed on the substrate (1002) and over the chip (1030); where the acoustic chamber has: a support structure (1006) arranged in the recess on the first side of the chip; a membrane (1008) arranged on the support structure; a seal (1010) disposed in the recess on the membrane or the support structure; a front volume (1012) defined at least by the membrane (1008), the seal (1010) and a portion of the recess; and a primary back volume (1014) defined at least by the membrane (1008), the support structure (1006) and the chip (1030); wherein the acoustic transducer device further comprises a secondary back volume (1016) defined at least by the cap (1004), the substrate (1002) and the chip (1030) and different from the front volume (1012) or the primary back volume (1014); further comprising a channel in the substrate or the support structure, the channel connecting the primary back volume (1014) and the secondary back volume (1016). [18] An acoustic transducer device according to claim 17, wherein the channel is at least 50 µm high. [19] The acoustic transducer device of claim 17, wherein the primary back volume (1014) comprises a transducer configured to generate an electrical signal based on the displacement of the diaphragm (1008). [20] An acoustic transducer device according to any one of claims 17 to 19, wherein the transducer comprises an optical sensor. [21] The acoustic transducer device of claim 20, wherein the optical sensor comprises a vertical cavity surface emitting laser (VCSEL) and a photodiode configured to detect the movement of the diaphragm. [22] The acoustic transducer device of claim 21, wherein the optical sensor further comprises an application-specific integrated circuit configured to generate a digital output signal based on an output signal of the photodiode. [23] An acoustic transducer device according to claim 20, wherein the diaphragm comprises a mirror and the mirror is configured as an aluminum plate or gold plate. [24] Acoustic transducer device, comprising: a membrane (108) having a first side and a second side opposite the first side; a front volume (112) defined by at least the first side of the membrane (108); a primary back volume (114) defined at least by the second side of the membrane (108); and a secondary back volume (116) different from the front volume (112) or the primary back volume (114); further comprising a channel (118) connecting the primary back volume (114) and the secondary back volume (116). [25] The acoustic transducer device of claim 24, further comprising a cap (104) and a substrate (102), wherein the cap is disposed on the substrate (102) and defines an acoustic chamber as a volume between the substrate (102) and the cap (102); wherein the acoustic chamber comprises the front volume or the secondary back volume. [26] The acoustic transducer device of claim 24, further comprising a substrate (102) and a support structure (106) disposed on the substrate (102); wherein the channel is located in the substrate or in the support structure. [27] Acoustic transducer device according to one of claims 24 to 26, wherein the channel is arranged as a trench. [28] Acoustic transducer device according to one of claims 24 to 26, wherein the channel (118) is at least 50 µm high.

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