Microelectromechanical system dies and microelectromechanical system devices

Abstract

The present application relates to microelectromechanical system dies and microelectromechanical system devices. A microelectromechanical system (MEMS) device includes a MEMS die including a first diaphragm and a second diaphragm, a first plurality of electrodes each disposed on the first diaphragm, and a second plurality of electrodes each disposed on the second diaphragm. A fixed dielectric element is disposed between the first diaphragm and the second diaphragm and includes a plurality of apertures. The MEMS die further includes a third plurality of electrodes, wherein each of the third plurality of electrodes includes a first conductive layer disposed on the first diaphragm adjacent to at least one of the first plurality of electrodes, a second conductive layer disposed on the second diaphragm adjacent to at least one of the second plurality of electrodes, and a conductive pin extending through one of the plurality of apertures and electrically connecting the first conductive layer to the second conductive layer.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to microelectromechanical system (MEMS) dies, and more particularly to MEMS dies having dual diaphragm dielectric sensors. BACKGROUND

[0002] It is well known that in the manufacture of MEMS devices, multiple devices are typically manufactured in a single batch process, in the form of a wafer. The individual portions of a batch processed wafer that represent individual MEMS devices are referred to as dies. Thus, multiple MEMS dies can be manufactured in a single batch processed wafer, and then singulated or otherwise separated for further manufacturing steps or for their end use, such as but not limited to including use as an acoustic transducer or microphone.

[0003] In existing MEMS capacitive sensors, two conductive electrodes are defined, including a movable element identified as a diaphragm and a fixed element identified as a backplate. In response to an acoustic input, movement of the movable element relative to the backplate produces a modulated capacitance. SUMMARY

[0004] One aspect of the present application relates to a microelectromechanical system (MEMS) die comprising: a first diaphragm; a second diaphragm; a first plurality of electrodes, each of the first plurality of electrodes disposed on the first diaphragm; a second plurality of electrodes, each of the second plurality of electrodes disposed on the second diaphragm; a fixed dielectric element disposed between the first diaphragm and the second diaphragm and comprising a plurality of apertures; and a third plurality of electrodes, each of the third plurality of electrodes comprising: a first conductive layer disposed on the first diaphragm adjacent to at least one of the first plurality of electrodes; a second conductive layer disposed on the second diaphragm adjacent to at least one of the second plurality of electrodes, and a conductive pin extending through one of the plurality of apertures and electrically connecting the first conductive layer to the second conductive layer, wherein the MEMS die generates one or more signals based on changes in capacitance caused by movement of the first diaphragm and the second diaphragm relative to the fixed dielectric element.

[0005] The fixed dielectric element is free of conductive layers.

[0006] At least a subset of the first plurality of electrodes are electrically connected to each other, at least a subset of the second plurality of electrodes are electrically connected to each other, and at least a subset of the third plurality of electrodes are electrically connected to each other.

[0007] The first diaphragm has a first face and a second face opposite the first face; the second diaphragm has a first face and a second face opposite the first face; the first face of the first diaphragm faces the first face of the second diaphragm; and the microelectromechanical system (MEMS) die further includes: a first connector pad disposed on the second face of the first diaphragm and electrically connected to at least a first subset of the first plurality of electrodes; a second connector pad disposed on the second face of the first diaphragm and electrically connected to at least a first subset of the second plurality of electrodes; and a third connector pad disposed on the second face of the first diaphragm and electrically connected to at least a first subset of the third plurality of electrodes.

[0008] A low pressure region is defined relative to atmospheric pressure between the first diaphragm and the second diaphragm.

[0009] The first diaphragm has a first face and a second face opposite the first face; the second diaphragm has a first face and a second face opposite the first face; the first face of the first diaphragm faces the first face of the second diaphragm; the low pressure region is defined by the first face of the first diaphragm and the first face of the second diaphragm; the microelectromechanical system (MEMS) device further includes: a sealed channel extending through the first diaphragm and the second diaphragm; wherein the sealed channel provides fluid communication between the second face of the first diaphragm and the second face of the second diaphragm; and wherein the sealed channel is configured to maintain the low pressure region.

[0010] Each of the first plurality of electrodes and the second plurality of electrodes and each of the first conductive layer and the second conductive layer of the third plurality of electrodes includes a strip having an aspect ratio of at least 5 to 1.

[0011] The strips are parallel, and wherein the strips of the first plurality of electrodes and the third plurality of electrodes are arranged side-by-side and alternating on the first diaphragm, and the strips of the second plurality of electrodes and the third plurality of electrodes are arranged side-by-side and alternating on the second diaphragm.

[0012] Another aspect of the present application relates to a microelectromechanical system, MEMS, apparatus comprising: a microelectromechanical system, MEMS, die as described above; the microelectromechanical system, MEMS, apparatus further comprising: a voltage source electrically connected to at least a first subset of the third plurality of electrodes to provide a voltage bias relative to ground to at least the first subset of the third plurality of electrodes; a differential amplifier; a first electrical connection between at least a first subset of the first plurality of electrodes and a first input of the differential amplifier; and a second electrical connection between at least a first subset of the second plurality of electrodes and a second input of the differential amplifier.

[0013] Another aspect of the present application relates to a microelectromechanical system, MEMS, apparatus comprising: a microelectromechanical system, MEMS, die as described above; an integrated circuit, IC; and a housing comprising: a base having a first surface and an opposite second surface; a cover attached to the first surface of the base, wherein the cover and the base define an interior of the housing; and a port allowing pressure waves to enter the interior, wherein the microelectromechanical system, MEMS, die is disposed within the interior of the housing; and wherein the integrated circuit, IC, is disposed within the interior of the housing and electrically connected to the microelectromechanical system, MEMS, die.

[0014] The port extends through the base and the microelectromechanical system, MEMS, die is disposed above the port.

[0015] Another aspect of the present application relates to a microelectromechanical system, MEMS, die comprising: a first diaphragm; a second diaphragm, wherein a low pressure region is defined between the first diaphragm and the second diaphragm; a first plurality of electrodes, each of the first plurality of electrodes disposed on the first diaphragm; a second plurality of electrodes, each of the second plurality of electrodes disposed on the second diaphragm; a fixed dielectric element without a conductive layer, the fixed dielectric element disposed between the first diaphragm and the second diaphragm and comprising a plurality of holes; and a third plurality of electrodes, each of the third plurality of electrodes comprising: a first conductive layer disposed on the first diaphragm adjacent to at least one of the first plurality of electrodes; a second conductive layer disposed on the second diaphragm adjacent to at least one of the second plurality of electrodes; and a conductive pin extending through one of the plurality of holes and electrically connecting the first conductive layer to the second conductive layer; the conductive pin providing structural integrity to prevent the first diaphragm and the second diaphragm from collapsing onto the fixed dielectric element; the microelectromechanical system, MEMS, die further comprising: a sealed channel extending through the first diaphragm and the second diaphragm; wherein the microelectromechanical system, MEMS, die generates one or more signals based on a change in capacitance caused by movement of the first diaphragm and the second diaphragm relative to the fixed dielectric element.

[0016] the first diaphragm has a first face and a second face opposite the first face; the second diaphragm has a first face and a second face opposite the first face; the first face of the first diaphragm faces the first face of the second diaphragm; and the microelectromechanical system, MEMS, die further comprises: a first connector pad disposed on the second face of the first diaphragm and electrically connected to at least a first subset of the first plurality of electrodes; a second connector pad disposed on the second face of the first diaphragm and electrically connected to at least a first subset of the second plurality of electrodes; and a third connector pad disposed on the second face of the first diaphragm and electrically connected to at least a first subset of the third plurality of electrodes.

[0017] the first diaphragm has a first face and a second face opposite the first face; the second diaphragm has a first face and a second face opposite the first face; and the first face of the first diaphragm faces the first face of the second diaphragm; wherein the sealed channel provides fluid communication between the second face of the first diaphragm and the second face of the second diaphragm; and wherein the sealed channel is configured to maintain the low pressure region.

[0018] Each of the first plurality of electrodes and the second plurality of electrodes and each of the first conductive layer and the second conductive layer of the third plurality of electrodes comprises a strip having an aspect ratio of at least 5 to 1, wherein the strips are parallel, and wherein the strips of the first plurality of electrodes and the third plurality of electrodes are arranged side-by-side alternately on the first diaphragm, and the strips of the second plurality of electrodes and the third plurality of electrodes are arranged side-by-side alternately on the second diaphragm.

[0019] Another aspect of the present application relates to a microelectromechanical system, MEMS, apparatus comprising: a microelectromechanical system, MEMS, die as described above; a voltage source electrically connected to at least a first subset of the third plurality of electrodes to provide a voltage bias relative to ground to the first subset of the third plurality of electrodes; a differential amplifier; a first electrical connection between at least a first subset of the first plurality of electrodes and a first input of the differential amplifier; and a second electrical connection between at least a first subset of the second plurality of electrodes and a second input of the differential amplifier.

[0020] Another aspect of the present application relates to a microelectromechanical system, MEMS, apparatus comprising: a microelectromechanical system, MEMS, die as described above; an integrated circuit, IC; and a housing comprising: a base having a first surface and an opposite second surface; a cover attached to the first surface of the base, wherein the cover and the base define an interior of the housing; and a port allowing pressure waves to enter the interior, wherein the microelectromechanical system, MEMS, die is disposed within the interior of the housing; wherein the integrated circuit, IC, is disposed in the interior of the housing and electrically connected to the microelectromechanical system, MEMS, die; and wherein the port extends through the base and the microelectromechanical system, MEMS, die is disposed above the port.

[0021] Another aspect of the present application relates to a microelectromechanical system, MEMS, die comprising: a first diaphragm; a second diaphragm; a first electrode disposed on the first diaphragm; a second electrode disposed on the second diaphragm; a fixed dielectric element disposed between the first diaphragm and the second diaphragm and comprising an aperture, wherein the fixed dielectric element is isolated from any electrode; and a third electrode comprising: a first conductive layer disposed on the first diaphragm; a second conductive layer disposed on the second diaphragm; and a conductive pin extending through the aperture and electrically connecting the first conductive layer to the second conductive layer; the conductive pin providing structural integrity to prevent the first diaphragm and the second diaphragm from collapsing onto the fixed dielectric element; wherein the MEMS die generates one or more signals based on a change in capacitance caused by movement of the first diaphragm and the second diaphragm relative to the fixed dielectric element.

[0022] A low pressure region relative to atmospheric pressure is defined between the first diaphragm and the second diaphragm.

[0023] Yet another aspect of the present application relates to a microelectromechanical system, MEMS, device comprising: a microelectromechanical system, MEMS, die as described above; a voltage source electrically connected to the third electrode, the voltage source providing a voltage bias relative to ground to the third electrode; and a differential amplifier comprising a first input electrically connected to the first electrode and a second input electrically connected to the second electrode; the first input and the second input of the differential amplifier each having an input impedance greater than 1 giga-ohm and establishing a DC bias level at each input that is less than the supply level relative to ground potential.

[0024] The DC bias level is less than half of the supply level relative to ground. BRIEF DESCRIPTION OF DRAWINGS

[0025] 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. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are not to be considered limiting thereof, the following description has benefit of specifically pointing out and describing the several embodiments, one by one. As such, the inclusion of specific detail is not intended to be construed as limiting the scope of the disclosure.

[0026] Figure 1 is a cross-sectional schematic view of the MEMS die of Figure 2 taken generally along line 1-1 of Figure 2 the MEMS die of

[0027] Figure 2is a cross-sectional perspective schematic view of a MEMS die according to an embodiment, and includes partially transparent portions for better illustration of internal components.

[0028] Figure 3 is a top view of an exemplary geometric arrangement of electrodes on a diaphragm of a MEMS die according to an embodiment.

[0029] Figure 4 is a top view of an exemplary geometric arrangement of electrodes on a diaphragm of a MEMS die according to another embodiment.

[0030] Figure 5 is a simplified perspective view of a portion of a MEMS die according to an embodiment.

[0031] Figure 6 is an exemplary electrical schematic of a circuit defined by a MEMS die according to an embodiment.

[0032] Figure 7 is a cross-sectional schematic view of a MEMS die according to another embodiment.

[0033] Figure 8 is a cross-sectional schematic view of a MEMS die according to another embodiment.

[0034] Figure 9 is a cross-sectional view of a sensor assembly according to an embodiment.

[0035] In the following detailed description, various embodiments are described with reference to the accompanying drawings. Those skilled in the art will appreciate that the drawings are illustrative and are simplified for the sake of clarity. The same reference numbers in different drawings identify the same elements or components. Thus, the same elements or components will not be described with respect to every drawing. DETAILED DESCRIPTION

[0036] According to various embodiments described herein, a MEMS die includes a first diaphragm and a second diaphragm, a first plurality of electrodes, each of the first plurality of electrodes disposed on the first diaphragm, and a second plurality of electrodes, each of the second plurality of electrodes disposed on the second diaphragm. A fixed dielectric element is disposed between the first diaphragm and the second diaphragm and includes a plurality of apertures. The MEMS die further includes a third plurality of electrodes, wherein each of the third plurality of electrodes includes a first conductive layer disposed on the first diaphragm adjacent to at least one of the first plurality of electrodes, a second conductive layer disposed on the second diaphragm adjacent to at least one of the second plurality of electrodes, and a conductive pin extending through one of the plurality of apertures and electrically connecting the first conductive layer to the second conductive layer. The MEMS die generates one or more signals based on changes in capacitance caused by movement of the first diaphragm and the second diaphragm relative to the fixed dielectric element. According to one embodiment, the fixed dielectric element is free of conductive layers.

[0037] In one embodiment, at least a subset of the first plurality of electrodes is electrically connected to each other, at least a subset of the second plurality of electrodes is electrically connected to each other, and at least a subset of the third plurality of electrodes is electrically connected to each other. In one embodiment, the first diaphragm has a first face and a second face opposite the first face, and the second diaphragm has a first face and a second face opposite the first face, wherein the first face of the first diaphragm faces the first face of the second diaphragm, wherein the MEMS die further comprises: a first connector pad disposed on the second face of the first diaphragm in electrical connection with at least a first subset of the first plurality of electrodes; a second connector pad disposed on the second face of the first diaphragm in electrical connection with at least a first subset of the second plurality of electrodes; and a third connector pad disposed on the second face of the first diaphragm in electrical connection with at least a first subset of the third plurality of electrodes. According to one embodiment, the MEMS device further comprises: a voltage source electrically connected to at least the first subset of the third plurality of electrodes to provide a voltage bias to the first subset of the third plurality of electrodes relative to ground; a differential amplifier; a first electrical connection between at least the first subset of the first plurality of electrodes and a first input of the differential amplifier; and a second electrical connection between at least the first subset of the second plurality of electrodes and a second input of the differential amplifier.

[0038] According to embodiments, a low pressure region is defined between the first diaphragm and the second diaphragm. In one embodiment, the low pressure region is defined by the first faces of the first diaphragm and the second diaphragm. In one embodiment, the MEMS die further comprises a sealed channel extending through the first diaphragm and the second diaphragm, wherein the channel provides fluid communication between the second faces of the first diaphragm and the second diaphragm, and wherein the channel is configured to maintain the low pressure region.

[0039] In one embodiment, the MEMS device further comprises an integrated circuit (IC) and a housing, the housing comprising: a base having a first surface and an opposite second surface; a cover connected to the first surface of the base, wherein the cover and the base define an interior of the housing; and a port allowing pressure waves to enter the interior, wherein the MEMS die is disposed within the interior of the housing, and wherein the IC is disposed within the interior of the housing and electrically connected to the MEMS die. In one embodiment, the port extends through the base and the MEMS die is disposed above the port. In one embodiment, each of the first plurality of electrodes and the second plurality of electrodes and each of the first conductive layer and the second conductive layer of the third plurality of electrodes comprises a strip having a length to width ratio of at least about 5 to 1. In one embodiment, the strips are substantially parallel, wherein the strips of the first plurality of electrodes and the third plurality of electrodes are arranged side by side alternately on the first diaphragm, and the strips of the second plurality of electrodes and the third plurality of electrodes are arranged side by side alternately on the second diaphragm.

[0040] In the present disclosure, two or more electrodes are fixed relative to each other to define a capacitor having a capacitance, but move together relative to a fixed dielectric element that is not an electrode and does not have an electrically conductive portion. Thus, motion of the two or more electrodes relative to the fixed dielectric element caused by an input comprising acoustic pressure, vibration, or acceleration causes a change in the effective dielectric constant of the capacitor, and thus a change in the capacitance value between the two or more electrodes, which capacitance value represents the input.

[0041] Turning to Figure 1 and Figure 2 , a MEMS die 100 according to an embodiment is schematically illustrated. In Figure 2 a top cross-sectional perspective view of an exemplary MEMS die 100 is shown, where a portion of the first diaphragm 102 and the fixed dielectric element 110 are both shown as transparent to better illustrate the internal structure, as further described below. Figure 1 A cross-sectional view illustrating the exemplary MEMS die 100 taken generally along line 1-1 of Figure 2 is shown.

[0042] In one embodiment, the MEMS die 100 includes a base 111 having an outer boundary 113, as shown in Figure 1 In one embodiment, the base 111 has a generally rectangular perimeter, but in other embodiments it can be any shape. The base 111 in embodiments includes an opening 123 formed therethrough.

[0043] Referring to Figure 1 , in one embodiment, the MEMS die 100 includes a first diaphragm 102 and a second diaphragm 104. One half or side of the MEMS die 100 is shown in Figure 1 , with the centerline of the MEMS die identified by centerline 101 on the left side. A fixed dielectric element 110 is disposed between the first diaphragm 102 and the second diaphragm 104, and includes a plurality of holes 112 disposed therethrough. The fixed dielectric element 110 is relatively thick and / or stiff compared to the first diaphragm 102 and the second diaphragm 104, for example by using a thicker material or being fabricated using a thin, very high tensile stress film to maintain sufficient rigidity. The fixed dielectric element 110 remains relatively immobile when the first diaphragm 102 and the second diaphragm 104 are deflected.

[0044] In one embodiment, the second diaphragm 104 is attached to the base 111 over the opening 123 via a spacer layer 125, as can be seen in Figure 2 However, in embodiments of the MEMS die 100 (see Figure 1), at least a portion of the second diaphragm 104 is directly attached to the base 111. In some embodiments, the spacer layer 125 can be an integral part of the base 111 or added to the base 111 as an additional sacrificial layer (i.e., the spacer layer 125). The spacer layer 125 can be made of, for example, any insulating material as described below. In one embodiment, the base 111 is made of silicon.

[0045] In one embodiment, each of the first diaphragm 102 and the second diaphragm 104 extends radially to the outer boundary 113 of the base 111, as shown in Figure 2 In other embodiments, the first diaphragm 102 and the second diaphragm 104 extend over the opening 123, but one or both of the first diaphragm 102 and the second diaphragm 104 do not extend radially to the outer boundary 113, as shown in Figure 1 In one embodiment, the fixed dielectric element 110 extends radially to the outer boundary 113 of the base 111, as shown in Figure 2 and Figure 8 In other embodiments, the fixed dielectric element 110 extends over the opening 123, but does not extend radially to the outer boundary 113, as shown in Figure 1 and Figure 7 The radially outer portion of each of the first diaphragm 102 and the second diaphragm 104 is rigidly connected to the radially outer portion of the fixed dielectric element 110. In one embodiment, a material 117 (see Figure 1 and Figure 2 ) is disposed between the fixed dielectric element 110 and each of the first diaphragm 102 and the second diaphragm 104. The material 117 can be a sacrificial material, which can be made of, for example, any insulating material as described below.

[0046] Referring to Figure 1 and Figure 2 , a first plurality of electrodes 106 is disposed on the first diaphragm 102 and a second plurality of electrodes 108 is disposed on the second diaphragm 104. The third plurality of electrodes 114 each includes a first conductive layer 116 disposed on the first diaphragm 102 adjacent to at least one of the first plurality of electrodes 106 and a second conductive layer 118 disposed on the second diaphragm 104 adjacent to at least one of the second plurality of electrodes 108. In one embodiment, the adjacent arrangement of any pair of electrodes as described above means that the pair of electrodes is separated by a finite gap or spacing. In one embodiment, the gap or spacing is narrower than the width of the pair of narrower electrodes. In one embodiment, the gap or spacing is narrower than half the width of the pair of narrower electrodes, while in another embodiment, the gap or spacing is narrower than one quarter the width of the pair of narrower electrodes.

[0047] The conductive pin 120 extends through the hole 112 and electrically connects the first and second conductive layers 116, 118. The conductive pin also provides structural integrity to prevent the first and second diaphragms 102, 104 from collapsing onto the fixed dielectric element 110 due to ambient pressure loads.

[0048] Reference is now made to Figure 1 The first diaphragm 102 has a first face 20 and a second face 22 opposite the first face 20. Similarly, the second diaphragm 104 has a first face 24 and a second face 26 opposite the first face 24. In this embodiment, the first face 20 of the first diaphragm 102 faces the first face 24 of the second diaphragm 104.

[0049] The geometric arrangement of the first plurality of electrodes 106, the second plurality of electrodes 108, and the third plurality of electrodes 114 varies in different embodiments and, for example and without limitation, can be curved arcs or strips of conductive material arranged in a spiral or partially concentric pattern, wherein the members of the first plurality of electrodes 106 are disposed on the first diaphragm 102 adjacent to the members of the third plurality of electrodes 114, and wherein the members of the second plurality of electrodes 108 are disposed on the second diaphragm 104 adjacent to the members of the third plurality of electrodes 114. In one embodiment, the first plurality of electrodes 106, the second plurality of electrodes 108, and the third plurality of electrodes 114 comprise strips of conductive material distributed or arranged in a side-by-side arrangement.

[0050] For example, with reference to the exemplary MEMS die 100 shown in Figure 2 In an embodiment, each of the first and second plurality of electrodes 106, 108 and each of the first and second conductive layers 116, 118 of the third plurality of electrodes 114 comprises a strip of conductive material S1, S2, S3, respectively, wherein each of the strips S1, S2, S3 has an aspect ratio of at least 5 to 1. In one embodiment, each strip S1, S2, S3 is divided into segments arranged side-by-side or end-to-end and electrically connected, for example, by conductive traces, wherein each segment has the aspect ratio required or demanded by the overall geometry.

[0051] Still with reference to Figure 2 In this embodiment, the strips S1, S2, S3 are substantially parallel. The strips S1 of the first plurality of electrodes 106 are arranged on the first face 20 of the first diaphragm 102 in a side-by-side alternating arrangement with the strips S3 of the third plurality of electrodes 114. Similarly, the strips S2 of the second plurality of electrodes 108 are arranged on the first face 24 of the second diaphragm 104 in a side-by-side alternating arrangement with the strips S3 of the third plurality of electrodes 114.

[0052] In other embodiments, the geometric arrangement of the first plurality of electrodes 106, the second plurality of electrodes 108, and the third plurality of electrodes 114 varies from Figure 2are shown. For example, in one implementation, each of the first plurality of electrodes 106 and the second plurality of electrodes 108 is a curvilinear electrode arranged in a spiral pattern on the respective first face 20, 24 adjacent to the curvilinear first plurality of conductive layers 116 and the second plurality of conductive layers 118. Figure 3 An example of a spiral configuration of the first plurality of electrodes 106 (or the second plurality of electrodes 108) and the first plurality of conductive layers 116 (or the second plurality of conductive layers 118) arranged on the first face 20 of the first diaphragm 102 (or the first face 24 of the second diaphragm 104) is shown in FIG. 2.

[0053] In another implementation, each of the first plurality of electrodes 106 and the second plurality of electrodes 108 is a curvilinear electrode arranged in a generally concentric pattern proximate to the curvilinear first plurality of conductive layers 116 and the second plurality of conductive layers 118. Figure 4 An example of a generally concentric configuration of the first plurality of electrodes 106 (or the second plurality of electrodes 108) and the first plurality of conductive layers 116 (or the second plurality of conductive layers 118) arranged on the first face 20 of the first diaphragm 102 (or the first face 24 of the second diaphragm 104) is shown in FIG. 3. In other implementations, each of the first plurality of electrodes 106 and the second plurality of electrodes 108 is an electrode having a shape comprising linear and / or curvilinear elements arranged in any pattern proximate to the linear and / or curvilinear first plurality of conductive layers 116 and the second plurality of conductive layers 118 on the respective first face 20, 24.

[0054] Referring again to FIG. 1 Figure 2 In one implementation, at least a subset of the first plurality of electrodes 106 are electrically connected to one another, for example, by one or more conductive traces 30. Similarly, in an implementation, at least a subset of the second plurality of electrodes 108 are electrically connected to one another, for example, by one or more conductive traces 32. Further, in an implementation, at least a subset of the third plurality of electrodes are electrically connected to one another, for example, by one or more conductive traces 34.

[0055] In one implementation, each of the one or more conductive traces 30, 32, 34 is electrically connected to a connector pad disposed on the second face 22 of the first diaphragm 102. For example, as shown in FIG. 4, a first connector pad 40, a second connector pad 44, and a third connector pad 48 are disposed on the second face 22 of the first diaphragm 102. The first connector pad 40 is electrically connected to a first pad trace 42, which is electrically connected to the one or more conductive traces 30. As shown in FIG. 4, the second connector pad 44 is electrically connected to a second pad trace 46, which is electrically connected to the one or more conductive traces 32. The third connector pad 48 is electrically connected to a third pad trace 50, which is electrically connected to the one or more conductive traces 34. Figure 2 In one implementation, at least a subset of the first plurality of electrodes 106 are electrically connected to one another, for example, by one or more conductive traces 30. Similarly, in an implementation, at least a subset of the second plurality of electrodes 108 are electrically connected to one another, for example, by one or more conductive traces 32. Further, in an implementation, at least a subset of the third plurality of electrodes are electrically connected to one another, for example, by one or more conductive traces 34. Figure 1 As shown schematically in FIG. 4, the second connector pad 44 (for ease of illustration, only the first and third connector pads 40, 48 are shown in FIG. 4) is electrically connected to the second pad trace 46, which is electrically connected to the one or more conductive traces 32. Figure 1(As shown on the right) is electrically connected to the second pad trace 46, which is electrically connected to one or more conductive traces 32. For example... Figure 2 As shown, the third connector pad 48 is electrically connected to the third pad trace 50, and the third pad trace 50 is electrically connected to one or more conductive traces 34.

[0056] refer to Figure 5 The perspective view schematically illustrates a simplified exemplary structure of some common components, in which exemplary electric field lines 122 are added. Figure 5 In the illustration, for clarity, only a single universal diaphragm 160 is shown, and a universal electrode pair including electrodes 162 and 163 is shown on the surface of the single universal diaphragm 160 facing the universal fixed dielectric element 164. Electrode 162 is a universal common electrode, described above as one of a third plurality of electrodes 114 having a first conductive layer 116 and a second conductive layer 118. Therefore, electrode 162 is structurally equivalent to Figures 1 to 4 Either the first conductive layer 116 or the second conductive layer 118 shown. Similarly, electrode 163 is a general electrode described above as one of the first plurality of electrodes 106 or the second plurality of electrodes 108, and is structurally equivalent to Figures 1 to 4 One of the first plurality of electrodes 106 or the second plurality of electrodes 108 described herein.

[0057] A common electrode 162 is electrically biased by a DC voltage relative to electrode 163. In this configuration, the common electrode pair including electrodes 162 and 163 defines a capacitor having a capacitance as indicated by reference numeral 124, wherein the capacitor has an effective dielectric constant depending on the relative geometry of the illustrated components, which include a spacing 126 between a single common diaphragm 160 and a common fixed dielectric element 164. Variations in the spacing 126, together with the dielectric constant of the fixed dielectric element 164, cause compression or expansion of the electric field lines 122 and a corresponding change in the effective dielectric constant, which in turn causes a change in the capacitance 124.

[0058] Now for reference Figure 1 ,about Figure 5The described structure exists on both sides of the fixed dielectric element 110. In this implementation, each pair of adjacent electrodes defined by the first plurality of electrodes 106 adjacent to the first conductive layer 116 disposed on the first face 20 of the first diaphragm 102 defines a capacitor having an effective dielectric constant that depends on the geometry including the spacing 172 between the first diaphragm 102 and the fixed dielectric element 110. Similarly, each pair of adjacent electrodes defined by the second plurality of electrodes 108 adjacent to the second conductive layer 118 disposed on the first face 24 of the second diaphragm 104 defines a capacitor having an effective dielectric constant that depends on the geometry including the spacing 174 between the second diaphragm 104 and the fixed dielectric element 110.

[0059] Each of the first diaphragm 102 and the second diaphragm 104 can move in response to an input including, for example, but not limited to, a sound pressure, a vibration, or an acceleration. Both the first diaphragm 102 and the second diaphragm 104 move relative to the fixed dielectric element 110 to change the spacing 172, 174 therebetween, respectively. As discussed with respect to Figure 5 The changes in the spacing 172, 174 cause changes in the effective dielectric constant of the capacitors defined by at least a subset of each of the first plurality of electrodes 106 and the second plurality of electrodes 108. The changes in the dielectric constant cause changes in the capacitance measured across at least a subset of each of the first plurality of electrodes 106 and the second plurality of electrodes 108.

[0060] Figure 1 And Figure 2 The symmetry of the MEMS die of

[0061] Referring now to Figure 2 And Figure 6 In one implementation, the voltage source 60 is electrically connected to at least a subset of the third plurality of electrodes 114. For example, the voltage source 60 is connected to at least a subset of the third plurality of electrodes 114 via the third connector pad 48. The voltage source provides a voltage bias to at least the subset of the third plurality of electrodes 114 relative to ground.

[0062] In Figure 6In the electrical schematic diagram, the differential amplifier 70 includes a first input 72 and a second input 74 corresponding to the exemplary embodiment of the MEMS die 100. A first electrical connection 76 connects at least a subset of the first plurality of electrodes 106 to the first input 72 of the differential amplifier 70, for example, through a physical connection between the first connector pad 40 and the first input 72 of the differential amplifier 70. Reference C1 represents the capacitance of at least a subset of the first plurality of electrodes 106 and the first conductive layer 116 disposed on the first diaphragm 102.

[0063] A second electrical connection 78 connects at least a subset of the second plurality of electrodes 108 to the second input 74 of the differential amplifier 70, for example, through a physical connection between the second connector pad 44 and the second input 74 of the differential amplifier 70. Reference C2 represents the capacitance of at least a subset of the second plurality of electrodes 108 and the second conductive layer 118 disposed on the second diaphragm 104. Thus, the MEMS die 100 generates one or more signals based on changes in capacitance caused by movement of the first diaphragm 102 and the second diaphragm 104 relative to the fixed dielectric element 110, and the one or more signals are electrically connected to the first input 72 and the second input 74 of the differential amplifier 70.

[0064] In one embodiment, each of the first input 72 and the second input 74 of the differential amplifier 70 has an input impedance greater than about 1 giga-ohm. The input impedance of the first input 72 and the second input 74 establishes a DC bias level at each input that is less than the power supply DC bias level relative to ground potential, and preferably less than half of the power supply DC bias level relative to ground potential.

[0065] Referring to Figure 7 A vacuum region, near or partial vacuum region, or low pressure region 200 (hereinafter referred to as "low pressure region") is defined between the first diaphragm 102 and the second diaphragm 104. In some embodiments, the low pressure region 200 has a pressure lower than atmospheric pressure. In one embodiment, the low pressure region 200 has an internal pressure of, for example, less than 100,000 Pa. In another embodiment, the low pressure region 200 has an internal pressure of less than 10,000 Pa. In another embodiment, the low pressure region 200 has an internal pressure of less than 1,000 Pa, and in yet another embodiment, the low pressure region 200 has an internal pressure of less than 100 Pa.

[0066] In one embodiment, the low pressure region 200 is defined by the first face 20, 24 of the first diaphragm 102 and the second diaphragm 104, respectively. In one embodiment, a sealed channel 210 extends through the first diaphragm 102 and the second diaphragm 104 without extending through the fixed dielectric element 110, for example, as illustrated inFigure 7 is shown. In other embodiments, the sealing channel 210 also extends through the fixed dielectric element 110, as Figure 8 is shown. Figure 7 The sealing channel 210 is shown adjacent to the outer edge of the MEMS die 100; however, in other embodiments, the sealing channel 210 is disposed along the centerline 101, or at any location along the radius of the MEMS die 100, as is desired or advantageous for the embodiment. In one embodiment, the opening 123 of the base 111 at least partially vertically overlaps the sealing channel 210.

[0067] In one embodiment, the sealing channel 210 is sealed by a boundary wall 212 shown in cross-section in Figure 7 and Figure 8 In one embodiment, the geometry of the boundary wall 212 can be chosen such that the cross-sectional shape of the sealing channel 210 as seen from a plan view above can be any regular or irregular shape as is desired or advantageous for the embodiment. In one embodiment, at least a portion of the boundary wall 212 is surrounded by a material 117. The material 117 can be a sacrificial material, and the material 117 and the boundary wall 212 can be made of any insulating material, for example, as described below. In one embodiment, the boundary wall 212 can be made of the same material as the conductive pin 120, as described below.

[0068] A first perforation 214 is disposed through the first diaphragm 102, and a second perforation 216 is disposed through the second diaphragm 104. Thus, the sealing channel 210 provides fluid communication between the second faces 22, 26 of the first diaphragm 102 and the second diaphragm 104, respectively, while maintaining the low pressure region 200 between the first diaphragm 102 and the second diaphragm 104.

[0069] In one embodiment, the fixed dielectric element 110 is free of conductive layers. In one embodiment, the fixed dielectric element 110, as well as the first diaphragm 102 and the second diaphragm 104, are each made of any insulating material that will not be damaged during a sacrificial layer removal process. For example, but not limited to, the insulating material can be silicon nitride, silicon oxynitride, metal oxide, a polymer, a material that is not damaged by a sacrificial layer removal process, and combinations thereof. Similarly, the material of any of the first plurality of electrodes 106, the second plurality of electrodes 108, and the third plurality of electrodes 114, the conductive pin 120, the boundary wall 212, and the first connector pad 40, the second connector pad 44, the third connector pad 48 can be any conductive material that will not be damaged during a sacrificial layer removal process. For example, but not limited to, the conductive material can be polysilicon, one or more metals, a metal alloy, carbon, a material that is not damaged by a sacrificial layer removal process, and combinations thereof.

[0070] Referring toFigure 1 、 Figure 2 and Figure 7 The fixed dielectric element 110 is disposed between the first diaphragm 102 and the second diaphragm 104. In one embodiment, the first diaphragm 102 and the second diaphragm 104 extend across the entirety of the base 111. In other embodiments, the first diaphragm 102 and the second diaphragm 104 extend across a portion of the base 111, but not the entirety. The mechanically active area of each of the first diaphragm 102 and the second diaphragm 104 is defined by the innermost radial boundary of the material 117 disposed between the fixed dielectric element 110 and each of the first diaphragm 102 and the second diaphragm 104 (the release front). As shown in Figure 1 and Figure 2 , in one embodiment, portions of the first diaphragm 102 and the second diaphragm 104 extend radially beyond the release front.

[0071] During operation of the above-described MEMS die 100, e.g., as an acoustic transducer 1000 that is part of a device, e.g., a sensor assembly 900 (see Figure 9 ), a charge in the form of a DC voltage bias with respect to ground is applied to at least a subset of the third plurality of electrodes 114, where the third plurality of electrodes 114 includes the first plurality of electrically conductive layers 116 and the second plurality of electrically conductive layers 118 disposed on the first diaphragm 102 and the second diaphragm 104, respectively, and connected by the electrically conductive lead 120. The first input 72, the second input 74 of the differential amplifier 70 provide a DC bias to at least a subset of the first plurality of electrodes 106 and the second plurality of electrodes 108 that is close to ground potential. An electric field is induced between each pair of electrodes disposed on the first face 20 of the first diaphragm 102 and the first face 24 of the second diaphragm 104.

[0072] Thus, as described above with reference to Figure 1 and Figure 5 , at least the paired first plurality of electrodes 106 and the first plurality of electrically conductive layers 116 disposed on the first diaphragm 102 define a first capacitor having a first capacitance, and at least the paired second plurality of electrodes 108 and the second plurality of electrically conductive layers 118 disposed on the second diaphragm 104 define a second capacitor having a second capacitance. Motion of the first diaphragm 102 and the second diaphragm 104 with respect to the fixed dielectric element 110 caused by an input comprising, for example, but not limited to, acoustic pressure, vibration, or acceleration, causes a change in the separation 172, 174 between each of the first diaphragm 102 and the second diaphragm 104 and the fixed dielectric element 110, respectively. The change in separation causes a change in the effective dielectric constant of each of the first capacitor and the second capacitor, thereby modulating the first capacitance and the second capacitance, which can be detected as a change in the output voltage level, which can be amplified, as described with respect to Figure 6 .

[0073] Turning to Figure 9 A MEMS die 100 used as a sound transducer 1000 is configured to fit within a sensor assembly 900. The sensor assembly 900 includes a housing that includes a base 902 having a first surface 905 and an opposite second surface 907. The housing also includes a cover 904 (e.g., a housing cover) and a sound port 906. In one implementation, the sound port 906 extends between the first surface 905 and the second surface 907. In one implementation, the base 902 is a printed circuit board. The cover 904 is connected to the base 902 (e.g., the cover 904 can be mounted on a peripheral edge of the base 902). Together, the cover 904 and the base 902 form an enclosed volume 908 of the sensor assembly 900.

[0074] As Figure 9 shown, the sound port 906 is disposed on the base 902 and is configured to transmit sound waves to the MEMS die 100 used as a sound transducer 1000 located within the enclosed volume 908. In other implementations, the sound port 906 is disposed on the cover 904 and / or a sidewall of the cover 904. In some implementations, the sensor assembly 900 forms part of a compact computing device (e.g., a portable communication device, a smart phone, a smart speaker, an Internet of Things (IoT) device, etc.) in which one, two, three, or more assemblies can be integrated for picking up and processing various types of sound signals, such as speech and music.

[0075] The sensor assembly 900 includes circuitry disposed within the enclosed volume 908. In one implementation, the circuitry includes an integrated circuit (IC) 910. In one implementation, the IC 910 is disposed on the first surface 905 of the base 902 and is electrically connected to the MEMS die 100 (as the sound transducer 1000). The IC 910 can be an application specific integrated circuit (ASIC). Alternatively, the IC 910 can include a semiconductor die that integrates various analog, analog-to-digital, and / or digital circuitry. In one implementation, the cover 904 is disposed on the first surface 905 of the base 902 covering the MEMS sound transducer 1000 and the IC 910.

[0076] In Figure 9 the sensor assembly 900, the MEMS sound transducer 1000 is shown disposed on the first surface 905 of the base 902. The MEMS sound transducer 1000 converts sound waves, and / or vibrations, and / or sensed accelerations received through the sound port 906 into corresponding electrical sensor signals and generates electrical signals (e.g., voltages) at a transducer output in response to sound activity, vibrations, and / or sensed accelerations incident on the sound port 906. As Figure 9As shown, the transducer output includes pads or terminals of the MEMS acoustic transducer 1000 that are electrically connected via one or more bond wires 912 to circuitry disposed within the enclosed volume 908. Figure 9 The sensor assembly 900 also includes electrical contacts, illustratively represented as contacts 914, that are typically disposed on the bottom face of the base 902. The contacts 914 are electrically coupled to circuitry disposed within the enclosed volume 908. The contacts 914 are configured to electrically connect the sensor assembly 900 to one of a variety of host devices.

[0077] As noted above, multiple MEMS devices can be fabricated in a single batch. A single portion of a batch that represents a single MEMS device is referred to as a die. Thus, multiple MEMS dies can be fabricated in a single batch and then singulated or otherwise separated for further manufacturing steps or for their end use, which for example but is not limited to includes other portions as acoustic transducers or microphones.

[0078] Steps in the manufacturing process for fabricating the MEMS die 100 as described above include etching, masking, patterning, dicing, drilling, and / or releasing steps performed on a workpiece. All steps are not described in detail here. However, typically the workpiece portions that will eventually end as structures of the MEMS die 100 are layered onto the workpiece using sacrificial materials, or otherwise drilled out or etched out of a block of solid material.

[0079] With respect to the use of plural and / or singular terms herein, those having skill in the art can provide appropriate conversions from plural to singular and / or from singular to plural as appropriate in context and / or application. Various singular / plural permutations can be expressly set forth herein for clarity.

[0080] The use of the words "approximately," "about," "substantially," and the like, means plus or minus ten percent, unless otherwise stated.

[0081] The above description of illustrative implementations has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the precise form disclosed, and modifications and variations are possible in light of the above teachings or can be acquired from practice of the disclosed implementations. The scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A microelectromechanical system (MEMS) die, the MEMS die comprising: First diaphragm; Second diaphragm; A plurality of electrodes, each of which is disposed on the first diaphragm; A second plurality of electrodes, each of which is disposed on the second diaphragm; A fixed dielectric element is disposed between the first diaphragm and the second diaphragm and includes a plurality of holes; as well as A third plurality of electrodes, each of which includes: A first conductive layer is disposed on the first diaphragm adjacent to at least one of the first plurality of electrodes; A second conductive layer, wherein the second conductive layer is disposed on the second diaphragm adjacent to at least one of the second plurality of electrodes, and A conductive pin extends through one of the plurality of holes and electrically connects the first conductive layer to the second conductive layer. The movement of the first and second diaphragms relative to the fixed dielectric element alters the capacitance of the microelectromechanical system (MEMS) die. The fixed dielectric element has no conductive layer.

2. The microelectromechanical system (MEMS) die according to claim 1, wherein, At least a subset of the first plurality of electrodes are electrically connected to each other. At least a subset of the second plurality of electrodes are electrically connected to each other, and At least a subset of the third plurality of electrodes are electrically connected to each other.

3. The microelectromechanical system (MEMS) die according to claim 2, wherein: The first diaphragm has a first surface and a second surface opposite to the first surface; The second diaphragm has a first surface and a second surface opposite to the first surface; The first surface of the first diaphragm faces the first surface of the second diaphragm; and, The microelectromechanical system (MEMS) die also includes: The first connector pad is disposed on the second surface of the first diaphragm and electrically connected to at least the first subset of the first plurality of electrodes; The second connector pad is disposed on the second surface of the first diaphragm and electrically connected to at least the first subset of the second plurality of electrodes; and The third connector pad is disposed on the second surface of the first diaphragm and is electrically connected to at least the first subset of the third plurality of electrodes.

4. The microelectromechanical system (MEMS) die according to claim 1, wherein, A low-pressure region relative to atmospheric pressure is defined between the first diaphragm and the second diaphragm.

5. The microelectromechanical system (MEMS) die according to claim 4, wherein, The first diaphragm has a first surface and a second surface opposite to the first surface; The second diaphragm has a first surface and a second surface opposite to the first surface; The first surface of the first diaphragm faces the first surface of the second diaphragm; The low-pressure region is defined by the first surface of the first diaphragm and the first surface of the second diaphragm; The microelectromechanical system (MEMS) device further includes a sealed channel that extends through the first diaphragm and the second diaphragm; The sealed channel provides fluid communication between the second surface of the first diaphragm and the second surface of the second diaphragm; and The sealed channel is configured to maintain the low-pressure area.

6. The microelectromechanical system (MEMS) die according to claim 1, wherein, Each of the first plurality of electrodes and the second plurality of electrodes, as well as each of the first conductive layer and the second conductive layer of the third plurality of electrodes, includes a strip with an aspect ratio of at least 5:

1.

7. The microelectromechanical system (MEMS) die according to claim 6, wherein, The strips are parallel, and wherein the strips of the first plurality of electrodes and the strips of the third plurality of electrodes are arranged alternately side by side on the first diaphragm, and the strips of the second plurality of electrodes and the strips of the third plurality of electrodes are arranged alternately side by side on the second diaphragm.

8. A microelectromechanical system (MEMS) device, the MEMS device comprising: The microelectromechanical system (MEMS) die according to claim 2; The microelectromechanical system (MEMS) device also includes: A voltage source electrically connected to at least a first subset of the third plurality of electrodes to provide a voltage bias relative to ground potential to at least the first subset of the third plurality of electrodes; Differential amplifier; A first electrical connection is established between at least a first subset of the first plurality of electrodes and a first input terminal of the differential amplifier; and A second electrical connection is made between at least a first subset of the second plurality of electrodes and a second input terminal of the differential amplifier.

9. A microelectromechanical system (MEMS) device, the MEMS device comprising: The microelectromechanical system (MEMS) die according to claim 1; Integrated circuit (IC); as well as Housing, the housing comprising: A base having a first surface and an opposite second surface; A cover, attached to the first surface of the base, wherein the cover and the base define the interior of the housing; and The port allows pressure waves to enter the interior. The microelectromechanical system (MEMS) die is disposed within the interior of the housing; and The integrated circuit (IC) is disposed inside the housing and electrically connected to the microelectromechanical system (MEMS) die.

10. The microelectromechanical system (MEMS) device according to claim 9, wherein, The port extends through the base, and the microelectromechanical system (MEMS) die is disposed above the port.

11. A microelectromechanical system (MEMS) die, the MEMS die comprising: First diaphragm; A second diaphragm, wherein a low-pressure region is defined between the first diaphragm and the second diaphragm; A plurality of electrodes, each of which is disposed on the first diaphragm; A second plurality of electrodes, each of which is disposed on the second diaphragm; A fixed dielectric element without a conductive layer, the fixed dielectric element being disposed between the first diaphragm and the second diaphragm, and including a plurality of holes; and A third plurality of electrodes, each of which includes: A first conductive layer is disposed on the first diaphragm adjacent to at least one of the first plurality of electrodes; A second conductive layer, wherein the second conductive layer is disposed on the second diaphragm adjacent to at least one of the second plurality of electrodes; and A conductive pin extends through one of the plurality of holes and electrically connects the first conductive layer to the second conductive layer; The conductive pins provide structural integrity to prevent the first and second diaphragms from collapsing onto the fixed dielectric element. The microelectromechanical system (MEMS) die further includes a sealed channel that extends through the first diaphragm and the second diaphragm; The movement of the first diaphragm and the second diaphragm relative to the fixed dielectric element changes the capacitance of the microelectromechanical system (MEMS) die.

12. The microelectromechanical system (MEMS) die according to claim 11, wherein: The first diaphragm has a first surface and a second surface opposite to the first surface; The second diaphragm has a first surface and a second surface opposite to the first surface; The first surface of the first diaphragm faces the first surface of the second diaphragm; and The microelectromechanical system (MEMS) die also includes: The first connector pad is disposed on the second surface of the first diaphragm and electrically connected to at least the first subset of the first plurality of electrodes; The second connector pad is disposed on the second surface of the first diaphragm and electrically connected to at least the first subset of the second plurality of electrodes; and The third connector pad is disposed on the second surface of the first diaphragm and is electrically connected to at least the first subset of the third plurality of electrodes.

13. The microelectromechanical system (MEMS) die according to claim 11, wherein... The first diaphragm has a first surface and a second surface opposite to the first surface; The second diaphragm has a first surface and a second surface opposite to the first surface; and The first surface of the first diaphragm faces the first surface of the second diaphragm; in, The sealed channel provides fluid communication between the second surface of the first diaphragm and the second surface of the second diaphragm; and The sealed channel is configured to maintain the low-pressure area.

14. The microelectromechanical system (MEMS) die according to claim 11, wherein, Each of the first plurality of electrodes and the second plurality of electrodes, and each of the first conductive layer and the second conductive layer of the third plurality of electrodes, includes a strip with an aspect ratio of at least 5:1, wherein the strips are parallel, and wherein the strips of the first plurality of electrodes and the strips of the third plurality of electrodes are arranged alternately side-by-side on the first diaphragm, and the strips of the second plurality of electrodes and the strips of the third plurality of electrodes are arranged alternately side-by-side on the second diaphragm.

15. A microelectromechanical system (MEMS) device, the MEMS device comprising: The microelectromechanical system (MEMS) die according to claim 12; A voltage source electrically connected to at least a first subset of the third plurality of electrodes to provide a voltage bias relative to ground potential to the first subset of the third plurality of electrodes; Differential amplifier; A first electrical connection is made between at least a first subset of the first plurality of electrodes and a first input terminal of the differential amplifier; as well as A second electrical connection is made between at least a first subset of the second plurality of electrodes and a second input terminal of the differential amplifier.

16. A microelectromechanical system (MEMS) device, the MEMS device comprising: The microelectromechanical system (MEMS) die according to claim 11; Integrated circuit (IC); as well as Housing, the housing comprising: A base having a first surface and an opposite second surface; A cover, attached to the first surface of the base, wherein the cover and the base define the interior of the housing; and The port allows pressure waves to enter the interior. The microelectromechanical system (MEMS) die is disposed inside the housing. The integrated circuit (IC) is disposed inside the housing and electrically connected to the microelectromechanical system (MEMS) die; and The port extends through the base, and the microelectromechanical system (MEMS) die is disposed above the port.

17. A microelectromechanical system (MEMS) device, the MEMS device comprising: MEMS die, the MEMS die comprising: First diaphragm; Second diaphragm; The first electrode is disposed on the first diaphragm; The second electrode is disposed on the second diaphragm; A fixed dielectric element, disposed between the first diaphragm and the second diaphragm and including a hole, wherein the fixed dielectric element is isolated from any electrode; and The third electrode includes: A first conductive layer is disposed on the first diaphragm; A second conductive layer, wherein the second conductive layer is disposed on the second diaphragm; and A conductive pin extends through the hole and electrically connects the first conductive layer to the second conductive layer; The conductive pins provide structural integrity to prevent the first and second diaphragms from collapsing onto the fixed dielectric element. The movement of the first diaphragm and the second diaphragm relative to the fixed dielectric element changes the capacitance of the microelectromechanical system (MEMS) die. A voltage source electrically connected to the third electrode provides a voltage bias relative to ground potential to the third electrode; and A differential amplifier, the differential amplifier including a first input terminal electrically connected to the first electrode and a second input terminal electrically connected to the second electrode; The first and second input terminals of the differential amplifier each have an input impedance greater than 1 gigahertz, and a DC bias level is established at each input terminal, which is less than the power supply level relative to ground potential.

18. The microelectromechanical system (MEMS) device according to claim 17, wherein, A low-pressure region relative to atmospheric pressure is defined between the first diaphragm and the second diaphragm.

19. The microelectromechanical system (MEMS) device according to claim 17, wherein, The DC bias level is less than half of the power supply level relative to ground potential.

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