Patent Application
20230283963
Embodiments disclosed herein relate to piezoelectric microelectromechanical system microphone packages and to devices including same.
A microelectromechanical system (MEMS) microphone is a micro-machined electromechanical device to convert sound pressure (e.g., voice) into an electrical signal (e.g., voltage). MEMS microphones are widely used in mobile devices such as cellular telephones, headsets, smart speakers, and other voice-interface devices/systems. Capacitive MEMS microphones and piezoelectric MEMS microphones (PMMs) are both available in the market. PMMs requires no bias voltage for operation, therefore, they provide lower power consumption than capacitive MEMS microphones. The single membrane structure of PMMs enable them to generally provide more reliable performance than capacitive MEMS microphones in harsh environments. Existing PMMs are typically based on either cantilever MEMS structures or diaphragm MEMS structures.
Some of the important parameters to consider in the design of a PMM include performance parameters such as SNR (signal to noise ratio), bandwidth (related to frequency response flatness), size, and cost.
The performance of a PMM is largely affected by the size of the PMM, as a larger size may provide for a larger back volume to increase the SNR of the microphone. However, microphone size is becoming a more important design consideration as mobile devices or headsets in which such PMMs are utilized are shrinking and/or including additional functionality and related circuitry and less area is becoming available within the devices for PMMs. Performance of existing PMM designs is typically degraded as designers attempt to reduce the size of the PMMs to meet customer requirements.
In accordance with one aspect, there is provided a piezoelectric microelectromechanical system microphone assembly. The piezoelectric microelectromechanical system microphone assembly comprises a carrier substrate including one of a through-hole or a recess, and a package including a microelectromechanical system die having a piezoelectric microelectromechanical system microphone mounted on a microphone substrate and a lid, at least a portion of the package disposed within the one of the through-hole or recess.
In some embodiments, the lid is a metal lid.
In some embodiments, the lid is at least partially disposed within the one of the through-hole or recess.
In some embodiments, the lid is fully disposed within the one of the through-hole or recess.
In some embodiments, an upper surface of the lid is substantially co-planar with a lower surface of the carrier substrate.
In some embodiments, the lid is formed over the microelectromechanical system die and, together with the microphone substrate, defines a back volume around the piezoelectric microelectromechanical system microphone.
In some embodiments, the package is a bottom-port package.
In some embodiments, a piezoelectric membrane of the piezoelectric microelectromechanical system microphone is disposed proximate the bottom port and between the bottom port and a support substrate for the piezoelectric membrane.
In some embodiments, the lid and microelectromechanical system die are disposed on opposite sides of the microphone substrate.
In some embodiments, the microelectromechanical system die is at least partially disposed within the one of the through-hole or the recess.
In some embodiments, the one of the through-hole or the recess is the recess, and the carrier substrate further includes an opening providing acoustic communication between the microelectromechanical system microphone and an environment outside of the package.
In some embodiments, the lid is at least partially disposed within the one of the through-hole or the recess.
In some embodiments, the one of the through-hole or the recess is the through-hole.
In some embodiments, the package is encapsulated by a conductive material.
In some embodiments, the assembly further comprises a mesh disposed over a piezoelectric membrane of the microelectromechanical system microphone.
In some embodiments, the mesh is conductive.
In some embodiments, the mesh is grounded.
In some embodiments, the assembly further comprises an application specific integrated circuit disposed within the package.
In some embodiments, the assembly is included in an electronics device module.
In some embodiments, the electronics device module is included in an electronic device.
Embodiments of this disclosure will now be described, by way of non-limiting example, with reference to the accompanying drawings.
The following description of certain embodiments presents various descriptions of specific embodiments. However, the innovations described herein can be embodied in a multitude of different ways, for example, as defined and covered by the claims. In this description, reference is made to the drawings where like reference numerals can indicate identical or functionally similar elements. It will be understood that elements illustrated in the figures are not necessarily drawn to scale. Moreover, it will be understood that certain embodiments can include more elements than illustrated in a drawing and/or a subset of the elements illustrated in a drawing. Further, some embodiments can incorporate any suitable combination of features from two or more drawings.
Aspects and embodiments disclosed herein involve engineering of the packaging and assembly of a PMM to reduce the overall assembled package size without compromising performance of the PMM.
One example of a cantilever PMM is illustrated in a plan view in
The cantilevers of a cantilever PMM as disclosed herein may have bases mounted on a support substrate including a SiO2 layer on a Si substrate as illustrated in
In some embodiments, the layer of SiO2 on the surface of the support substrate upon which the cantilevers are formed may have a thickness of from about 1 µm to about 5 µm. As illustrated in
An example of a diaphragm-type piezoelectric microelectromechanical system microphone (PMM) is illustrated in a plan view in
The diaphragm of the PMM may be formed of or include a film of piezoelectric material, for example, aluminum nitride (AlN), zinc oxide (ZnO), or PZT, (also referred to herein as a piezoelectric element) that generates a voltage difference across different portions of the diaphragm when the diaphragm deforms or vibrates due to the impingement of sound waves on the diaphragm. Although illustrated as circular in
The diaphragm PMM of
The inner electrodes and outer electrodes each include top or upper electrodes disposed on top of an upper layer of piezoelectric material of the diaphragm and bottom or lower electrodes disposed on the bottom of the lower layer of piezoelectric material of the diaphragm. In some embodiments, as illustrated in
Diaphragm structures generate maximum stress and piezoelectric charges in the center and near the edge of the diaphragm anchor. The charges in the center and edge have opposite polarities. Additionally, diaphragm structures generate piezoelectric charges at the top and the bottom surfaces and the charge polarities are opposite on the top and bottom surfaces in the same area. Partial sensing electrodes in the diaphragm center and near the anchor may be used for maximum output energy and sensitivity and to minimize parasitic capacitance.
A diaphragm PMM may include one, two, or multiple piezoelectric material film layers in the diaphragm. In embodiments including two piezoelectric material film layers, conductive layers forming sensing/active electrodes may be deposited on the top and the bottom of the diaphragm, as well as between the two piezoelectric material film layers, forming a bimorph diaphragm structure. Partial sensing electrodes may be employed. Inner electrodes may be placed in the center of diaphragm and outer electrodes may be placed near the anchor/perimeter of the diaphragm. Sensing/active electrodes may be placed on the bottom and top, and in the middle of the vertical extent of the multi-layer piezoelectric film forming the diaphragm. The size of the sensing/active electrodes may be selected to collect the maximum output energy (E=0.5*C*V2).
The packaging and assembly methods and structures disclosed herein may be utilized with either cantilever or diaphragm type PMMs.
One form of package for a PMM is a bottom-port package, an example of which is illustrated in
Another form of package for a PMM is a top-port package, an example of which is illustrated in
In many instances PMM packages are assembled on to carrier PCBs for ease of handling and for mechanical support. One example of a PMM assembly including a carrier substrate is illustrated in
In some embodiments, the MEMS die including the PMM can be placed on a different side of the microphone substrate PCB than the lid. The PMM package may be assembled into a carrier PCB having a through-hole or a recess. The PMM package can be mounted to the carrier PCB with the MEMS die fitted into the carrier PCB through-hole as illustrated in
To provide shielding against E-field, EM, or RF interference, the whole microphone package can be encapsulated by conductive materials by metal passing through a PCB via, through a silicon via, by a metal coating the outside of the package, etc., as illustrated in the examples of
A mesh can be added on top of the PMM to provide protection to the PMM membrane. The mesh can also be conductive to provide shielding against E-field, EM, or RF interferences. The conductive mesh can also be grounded to improve the shielding.
In the various embodiments disclosed above, a through-hole is provided in the carrier substrate to house at least a portion of the PMM package. As illustrated in the comparison between the assemblies of
In various embodiments of the assembly structures disclosed herein, as illustrated in
Any of the assembly structures disclosed herein may be modified to include an ASIC within the packaged structure, for example, on the MEMS die, as illustrated in the examples of
Examples of MEMS microphones and assembly structures including same as disclosed herein can be implemented in a variety of packaged modules and devices.
The wireless device 100 can be a cellular phone, smart phone, tablet, modem, communication network or any other portable or non-portable device configured for voice or data communication. The wireless device 100 can receive and transmit signals from the antenna 110.
The wireless device 100 may include one or more microphones as disclosed herein. The one or more microphones may be included in an audio subsystem including, for example, an audio codec. The audio subsystem may be in electrical communication with an application processor and communication subsystem that is in electrical communication with the antenna 110. As would be recognized to one of skill in the art, the wireless device would typically include a number of other circuit elements and features that are not illustrated, for example, a speaker, an RF transceiver, baseband sub-system, user interface, memory, battery, power management system, and other circuit elements.
The principles and advantages of the embodiments can be used for any systems or apparatus, such as any uplink wireless communication device, that could benefit from any of the embodiments described herein. The teachings herein are applicable to a variety of systems. Although this disclosure includes some example embodiments, the teachings described herein can be applied to a variety of structures. Any of the principles and advantages discussed herein can be implemented in association with RF circuits configured to process signals in a range from about 30 kHz to 10 GHz, such as in the X or Ku 5G frequency bands.
Aspects of this disclosure can be implemented in various electronic devices. Examples of the electronic devices can include, but are not limited to, consumer electronic products, parts of the consumer electronic products such as packaged radio frequency modules, uplink wireless communication devices, wireless communication infrastructure, electronic test equipment, etc. Examples of the electronic devices can include, but are not limited to, a mobile phone such as a smart phone, a wearable computing device such as a smart watch or an ear piece, a telephone, a television, a computer monitor, a computer, a modem, a hand-held computer, a laptop computer, a tablet computer, a microwave, a refrigerator, a vehicular electronics system such as an automotive electronics system, a stereo system, a digital music player, a radio, a camera such as a digital camera, a portable memory chip, a washer, a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, a multifunctional peripheral device, a wrist watch, a clock, etc. Further, the electronic devices can include unfinished products.
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” “include,” “including” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The word “coupled”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Likewise, the word “connected”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.
Moreover, conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.
While certain embodiments have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the disclosure. Indeed, the novel apparatus, methods, and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. Any suitable combination of the elements and acts of the various embodiments described above can be combined to provide further embodiments. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Serial No. 63/316,655, titled “MICROPHONE ASSEMBLY AND PACKAGING METHODS FOR SIZE REDUCTION AND BACK VOLUME INCREASE,” filed Mar. 4, 2022, the entire content of which is incorporated herein by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63316655 | Mar 2022 | US |
