The present disclosure relates generally to a microelectromechanical systems (MEMS) diaphragm assembly, and more particularly to a MEMS diaphragm assembly having a non-uniform pillar distribution.
It is known that in the fabrication of MEMS devices often a plurality of devices are manufactured in a single batch process wherein individual portions of the batch process representative of individual MEMS devices are known as dies. Accordingly, a number of MEMS dies can be manufactured in a single batch process and then cut apart or otherwise separated for further fabrication steps or for their ultimate use, which for example without limitation includes use as an acoustic transducer or other portion of a microphone.
The vibrational response to acoustic stimuli of a dual-diaphragm assembly includes a distribution of velocity over the assembly. Integrating the velocity distribution of the assembly over the entire assembly for a given acoustic stimuli provides a measure of performance known as an acoustic effective area for the assembly. Similarly, integrating the velocity distribution of the assembly over the electrode area of the assembly for a given acoustic stimuli provides a measure of performance known as an electric effective area for the assembly. It has been observed that increasing the acoustic effective area for the assembly decreases the acoustic damping for the assembly, and that increasing the electric effective area for the assembly increases the sensitivity and active capacitance for the assembly, all of which is desirable. A need therefore exists for a dual-diaphragm assembly having a structure that results in increased acoustic and electrical effective areas.
The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. These drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope.
In the following detailed description, various embodiments are described with reference to the appended drawings. The skilled person will understand that the accompanying drawings are schematic and simplified for clarity. Like reference numerals refer to like elements or components throughout. Like elements or components will therefore not necessarily be described in detail with respect to each figure.
According to various embodiments described herein, a MEMS diaphragm assembly comprises a first diaphragm and a second diaphragm, wherein a plurality of pillars connect the first and second diaphragms, and wherein the plurality of pillars has a higher distribution density at a geometric center of the MEMS diaphragm assembly than at an outer periphery thereof.
According to other embodiments, the MEMS diaphragm assembly comprises a geometric central region surrounding the geometric center, and an outer region between an outer edge of the geometric central region to the outer periphery of the MEMS diaphragm assembly. In an embodiment, the distribution density of the plurality of pillars is constant within the geometric central region and decreases from the outer edge of the geometric central region to the outer periphery of the MEMS diaphragm assembly. In another embodiment the region between the outer edge of the geometric central region and the outer periphery comprises a plurality of concentric annular regions, and the distribution density of the plurality of pillars is constant within each of the plurality of concentric annular regions.
In an embodiment the distribution density of the plurality of pillars decreases from the geometric center to the outer edge of the geometric central region and remains constant from the outer edge of the geometric central region to the outer periphery of the MEMS diaphragm assembly. In another embodiment the distribution density of the plurality of pillars is constant within the geometric central region, and the distribution density of the plurality of pillars is constant from the outer edge of the geometric central region to the outer periphery of the MEMS diaphragm assembly. In a further embodiment the geometric central region comprises a central core region surrounded by a plurality of concentric annular regions, and the distribution density of the plurality of pillars is constant within each of the central core region and the plurality of concentric annular regions.
In an embodiment the outer edge of the geometric central region is disposed in a range of about 30% to 70% of the distance between the geometric center and the outer periphery of the MEMS diaphragm assembly. In some embodiments the distribution density of the pillars disposed within a region of the MEMS diaphragm assembly is defined by the number of pillars disposed within the region. In other embodiments the distribution density of the pillars disposed within a region of the MEMS diaphragm assembly is defined by the cross-sectional area of the pillars disposed within the region, and in other embodiments the distribution density of the pillars disposed within a region of the MEMS diaphragm assembly is defined by the cross-sectional area of the pillars disposed within the region and by the number of pillars disposed within the region.
Turning to
In an embodiment, a stationary electrode assembly 150 is disposed between the first diaphragm 130 and the second diaphragm 140. The first diaphragm 130 and the second diaphragm 140 are connected to the stationary electrode assembly 150 around their outer peripheries 120 by spacer layers 160. In an embodiment the stationary electrode assembly 150 includes an insulative layer 150A, a first conductive layer 150B, and a second conductive layer 150C. The insulative layer 150A is sandwiched between the first conductive layer 150B and the second conductive layer 150C. In one embodiment, the first conductive layer 150B and the second conductive layer 150C are shorted together so as to form a single electrode (also referred to herein as a stationary electrode), which faces the first movable electrode and also faces the second movable electrode. In another embodiment, the first conductive layer 150B and the second conductive layer 150C are electrically isolated from one another, and may be respectively referred to as a first stationary electrode (which faces the first movable electrode) and a second stationary electrode (which faces the second movable electrode). In an embodiment, the stationary electrode assembly 150 is relatively thick and stiff compared to the first and second diaphragms 130 and 140 and remains relatively motionless when the first and second diaphragms 130 and 140 are deflected.
The material of any of the insulative layers 130A, 140A, and 150A can be any insulative material that would not be damaged during a sacrificial layer removal process. For example, without limitation, the insulative material can be silicon nitride, silicon oxynitride, metal oxides, polymers, materials that are not damaged by a sacrificial layer removal process, and combinations thereof. Similarly, the material of any of the conductive layers 130B, 140B, 150B, and 150C can be any conductive material that would not be damaged during a sacrificial layer removal process. For example, without limitation, the conductive material can be polycrystalline silicon, one or more metals, alloys of metals, carbon, materials that are not damaged by a sacrificial layer removal process, and combinations thereof. The structural geometry of materials comprising the first and second diaphragms 130 and 140 and the stationary electrode assembly 150 can be other than those described hereinabove in other embodiments.
Still referring to
Referring again to
As will be fully described in regard to
Referring now to
Referring in particular to
Referring to
Regardless of their actual shape, the boundaries 310A, 310B and 410A, 410B separate the region between the outer edge 210A, 210B of the geometric central region 200 and the outer periphery 120 into the plurality of generally concentric annular regions 300, 400, 500 in this embodiment. The distribution density of the plurality of pillars 180 is constant within each of the plurality of concentric annular regions 300, 400, 500.
Referring to
Referring to
Regardless of their actual shape, the boundaries 205A, 205B and 305A, 305B separate the geometric central region 200 into the central core region 200A and the plurality of generally concentric annular regions, 200B and 200C in this embodiment. The distribution density of the plurality of pillars 180 is constant within the central core region 200A and within each of the plurality of generally concentric annular regions, 200B and 200C.
Referring to
Referring to any of
As noted hereinabove, the distribution density of the plurality of pillars 180 can be increased or decreased by spacing the plurality of pillars 180 closer together or further apart relative to one another, respectively. The distribution density can also be increased by increasing the cross-sectional areas of some or all of the plurality of pillars 180. For example,
In addition to variations in the size and spacing of the plurality of pillars 180, the plurality of pillars 180 need not be circular and may be of any cross-sectional shape. For example, without limitation, referring to
Referring to
In an embodiment the second diaphragm 140 is attached around the outer periphery 120 thereof to the substrate 118 over the opening 122 via a spacer layer 124. In other embodiments at least a portion of the second diaphragm 140 is attached directly to the substrate 118. In some embodiments the spacer layer 124 can be an integral part of the substrate 118 or added onto the substrate 118 as an additional sacrificial layer 124. The spacer layer 124 can, for example, be made of any insulative material as described hereinabove. In an embodiment the substrate 118 is made of silicon.
Referring to
As shown in
As shown in
In a further embodiment the MEMS die 1000 is disposed on the first surface 905 of the base 902 as illustrated but further includes openings or cutouts 909 disposed through the substrate portion 118 (see
In some embodiments, the microphone device 900, 901 forms part of a compact computing device (e.g., a portable communication device, a smartphone, a smart speaker, an internet of things (IoT) device, etc.), where one, two, three or more microphone devices 900, 901 may be integrated for picking-up and processing various types of acoustic signals such as speech and music. The MEMS die 1000, used as an acoustic transducer 1000, converts sound waves, received through acoustic port 906, 906A, into a corresponding electrical microphone signal, and generates an electrical signal (e.g., a voltage) at a transducer output in response to acoustic activity incident on the port 906, 906A.
As shown in
During operation of the MEMS diaphragm assembly 100 described hereinabove, for example as part of the acoustic transducer 1000 shown in
As noted hereinabove, a plurality of MEMS devices can be manufactured in a single batch process. Individual portions of the batch process representative of individual MEMS devices are known as dies. Accordingly, a number of MEMS dies can be manufactured in a single batch process and then cut apart or otherwise separated for further fabrication steps or for their ultimate use, which for example without limitation includes as an acoustic transducer or other portion of a microphone.
Steps in a production process utilized to produce the MEMS diaphragm assembly 100 as described hereinabove include etching, masking, patterning, cutting, boring, and/or release steps executed on a workpiece. All of the steps are not described in detail herein. However, generally the portions of the MEMS diaphragm assembly 100 (and the larger MEMS die 1000 of which it can be a part) that ultimately end up as the structures of the first and second diaphragms 130, 140, the stationary electrode assembly 150, and the plurality of pillars 180 are applied onto a workpiece in particular layers or patterns and the spaces between the structures are created utilizing sacrificial material, or are otherwise bored or etched out of a solid block of material.
With respect to the use of plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
Unless otherwise noted, the use of the words “approximate,” “about,” “around,” “substantially,” etc., mean plus or minus ten percent.
The foregoing description of illustrative embodiments has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
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