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WO2018035486A1 - Structure de couplage de plaques - Google Patents

Structure de couplage de plaques Download PDF

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Publication number
WO2018035486A1
WO2018035486A1 PCT/US2017/047658 US2017047658W WO2018035486A1 WO 2018035486 A1 WO2018035486 A1 WO 2018035486A1 US 2017047658 W US2017047658 W US 2017047658W WO 2018035486 A1 WO2018035486 A1 WO 2018035486A1
Authority
WO
WIPO (PCT)
Prior art keywords
piezoelectric
plates
plate
acoustic device
mismatch reduction
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2017/047658
Other languages
English (en)
Inventor
Robert J. Littrell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Vesper Technologies Inc
Original Assignee
Vesper Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Vesper Technologies Inc filed Critical Vesper Technologies Inc
Publication of WO2018035486A1 publication Critical patent/WO2018035486A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H04R17/02—Microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/003—Mems transducers or their use

Definitions

  • Micro-electro-mechanical systems (MEMS) technology has enabled the development of acoustic transducers such as microphones using silicon-wafer deposition techniques.
  • MEMS capacitive microphones and electret condenser microphones are used in consumer electronics and have an advantage over typical piezoelectric MEMS microphones in that they have historically had greater sensitivity and lower noise floors.
  • ECMs electret condenser microphones
  • MEMS capacitive microphones which are often used in cell phones, have a backplate that is a source of noise in the microphones.
  • MEMS capacitive microphones also have a smaller dynamic range than typical piezoelectric MEMS microphones.
  • a piezoelectric, acoustic device comprises substrate; a plurality of plates, each plate comprising a first electrode layer, a piezoelectric layer and a second electrode layer, wherein the piezoelectric layer is in between the first electrode layer and the second electrode layer, and wherein, for each plate, a base of the plate is affixed to the substrate and a remaining portion of the plate is unaffixed to the substrate; and a plate coupling structure affixed to a first one of the plates and to a second one of the plates, wherein the plate coupling structure at least partly covers a gap between a first edge of the first one of the plates and a second edge of the second one of the plates, wherein the first edge faces the second edge; wherein the plate coupling structure comprises a mismatch reduction element and a stopping element, wherein the mismatch reduction element is configured to reduce an amount of mismatch in deflection of the first one of the plates and the second one of the plates, and wherein the stopping element is configured to enable the
  • the mismatch reduction element comprises a spring.
  • the piezoelectric, acoustic device comprises a microphone.
  • the piezoelectric, acoustic device comprises a
  • a plate comprises a cantilevered beam.
  • the stopping element comprises a plurality of interdigitated fingers.
  • a first portion of the interdigitated fingers are part of the first one of the plates and extend into the second one of the plates.
  • the mismatch reduction element extends from a tip of an interdigitated finger in the first portion to a tip of another one interdigitated finger in the first portion.
  • a second portion of the interdigitated fingers are part of the second one of the plates, and wherein the mismatch reduction element is unconnected to one or more interdigitated fingers included in the second portion.
  • the mismatch reduction element is affixed to an end portion of at least one of the interdigitated fingers.
  • the first one of the plates is adjacent to the second one of the plates.
  • the actions include a vertical gap between at least one of the interdigitated fingers and the mismatch reduction element.
  • the vertical gap is approximately in a range of 0.1 ⁇ to 1.0 ⁇ .
  • the piezoelectric, acoustic device is a transducer.
  • the plurality of plates comprise tapered, transducer beams, with a tapered, transducer beam having a beam base, a beam end, and a beam body, with the beam body tapered from the beam base to the beam end and disposed between the beam base and the beam end, the tapered, transducer beams connected in a cantilever arrangement over the substrate by having beam bases attached to the substrate, beam ends converging towards a common each, and with each beam body free from the substrate and with each beam end free and unattached.
  • the stopping element is comprised of aluminum nitride.
  • the actions include overlapping portions affixed to respective plates, wherein each of the plates comprises openings sized to fit respective stopping elements, and wherein an element of an overlapping portion is affixed to a plate at least partly between two openings, wherein the overlapping portion comprises a strip portion and wherein the strip portion is affixed to the plate between two elements of the overlapping portion and at least partly covers an opening sized to a fit stopping element.
  • FIG. 1 is diagram of a plate.
  • FIG. 2 is a diagram of plates arranged in a gap-controlling geometry.
  • FIG. 3 is a diagram of modeled deflection.
  • FIG. 4 is a diagram of modeled deflection along a gap of two adjacent plates in a gap controlling geometry.
  • FIG. 5 is a diagram of a MEMS die and a magnified view of a center of the MEMS die.
  • FIG. 6 is a diagram of a fabrication process.
  • FIGS. 7, 8 and 10 are each a diagram of a view of a center of a piezoelectric sensor plate with plate coupling structures.
  • FIG. 9A is a diagram of a transducing element with plate coupling structures.
  • FIG. 9B is a diagram of one of the plate coupling structures shown in FIG. 9A.
  • FIG. 11 is a diagram of a portion of a plate coupling structure that includes fingers and overlapping portions.
  • sensor yield is reduced due to manufacturing non-idealities relative to sensor yield without these non-idealities.
  • the tips of the plates can have different amounts of vertical deflection. They could also have different amounts of vertical deflection if they were slightly different lengths. This different deflection of adjacent plates is undesirable because it increases the gap between plates and reduces the acoustic resistance through the sensor as described in U.S. Patent No. 9,055,372.
  • a MEMS microphone transducer design has two 0.5 ⁇ thick layers of aluminum nitride (A1N) stacked on top of each other.
  • the residual film stress in the X-direction (oxx res) for the bottom layer is 400 MPa and that in the Y direction (oyy res) is 435 MPa.
  • the residual film stress in both the X-direction and Y-direction is 400 MPa for the top layer. This difference in X versus Y stress will cause a plate deflection of approximately 15 ⁇ for 380 ⁇ long plates.
  • plate 10 is shown.
  • plate 10 is one of four plates in a gap controlling geometry.
  • Plate 10 includes edges 10a, 10b and base 10c.
  • Base 10c is fixed to a substrate (not shown) and the remaining structure is free to move, creating a fixed-free-free triangular cantilever plate.
  • the substrate not shown
  • length of plate 10 is 380 ⁇ from base to tip and the thickness is 1 ⁇ thick A1N. This includes two 500 nm thick layers which add up to a total of 1 ⁇ .
  • acoustic device 20 includes four plates 22, 24, 26, 28 arranged in a gap-controlling geometry.
  • a gap exists between edges of the plates that face each other.
  • gap 30 exists between edge 34 of plate 22 and edge 32 of plate 28.
  • each triangular plate is a cantilever plate. This is a gap
  • gaps remain relatively small compared to gaps in two facing rectangular cantilevers for example.
  • mismatches in stress in the X and Y directions can still cause these plates 22, 24, 26, 28 to deflect differently and have gaps that are much larger than those created when the stress in X and Y directions is the same.
  • diagram 40 shows modeled deflection of the four plates when the bottom layer stress is 400 MPa in the X-direction and 435 MPa in the Y-direction and the top layer stress is 400 MPa in both the X and Y directions.
  • the two opposing pairs of plates have matched deflection but the difference in X and Y stress causes the adjacent plates to have different vertical deflections, enlarging the gap between plates.
  • diagram 50 shows modeled deflection along the gap of two adjacent plates in the gap controlling geometry. The conditions are the same as those used for FIG 3. The gap between plates is largest at the tip, where it is about 15 ⁇ .
  • cantilever- plate based piezoelectric MEMS microphones In addition to deflection mismatch of adjacent plates, another limitation of cantilever- plate based piezoelectric MEMS microphones is that they do not have a backplate to stop over excursion, as capacitive MEMS microphones do. In some cases, very high pressure levels or very high acceleration levels can cause the piezoelectric microphone diaphragm or plates to bend enough to cause breakage.
  • a capacitive MEMS microphone prevents diaphragms from breaking off the microphone by using a very stiff backplate, which prevents the microphone diaphragm from deflecting too far, thereby limiting the maximum stress in the diaphragm.
  • a capacitive MEMS microphone necessarily includes a backplate to form the capacitor with a diaphragm (e.g., the front plate).
  • a piezoelectric MEMS microphone typically does not have a backplate, which would generate noise in the microphone.
  • a plate coupling structure In order to both reduce mismatch between adjacent plates and prevent breakage due to excessive bending, a plate coupling structure is described here.
  • This structure consists of an interdigitated finger element and a mismatch reduction element.
  • This structure has a non-linear behavior such that it provides two regimes of operation.
  • the first operating regime is called "normal operation.” In this normal operation, an applied acoustic pressure produces a large change in piezoelectric material stress relative to the second regime.
  • the second operating regime is called “overload protection.” In overload protection, an applied pressure or acceleration produces a relatively small change in piezoelectric material stress relative to normal operation.
  • diagram 59 illustrates a MEMS microphone die 60 (e.g., a MEMS transducer) that includes four triangular plates 64, 66, 68 and 70 meeting at a center location 61.
  • each base of plates 64, 66, 68 and 70 is affixed to substrate 62.
  • Diagram 59 also includes magnified view 63 of the center of the MEMS die 60 showing plate coupling structures 71a and 70b-70d connecting adjacent plates.
  • Magnified view 63 illustrates portion 64a of plate 64, portion 66a of plate 66, portion 68a of plate 68, and portion 70a of plate 70.
  • plate coupling structure 71a is affixed to portions 66a, 70a and at least partially covers a gap between an edge of portion 70a and an edge of portion 66a.
  • plate coupling structure 71a includes mismatch reduction elements 72, 74 and stopping elements 76a-76e that are configured to prevent a mismatch reduction elements from stretching too far.
  • each of stopping elements 76a-76e is an interdigitated finger or interdigitated element.
  • the interdigitated fingers are an extension of the plates. These interdigitated fingers extend into the adjacent plates.
  • interdigitated element 76b is an extension of portion 70a of plate 70 and extends into portion 66a of plate 66, which is adjacent to plate 70.
  • a mismatch reduction element (e.g., one of mismatch reduction elements 72, 74) then extends from the tip of one finger to that of the next finger on the same plate, skipping over the finger of the adjacent plate.
  • mismatch reduction element 74 extends from tip 77a of finger 76a to tip 77b of finger 76c to tip 77c of finger 76e, skipping over fingers 76b, 76d of adjacent plate 66.
  • fingers 76a, 76c, 76e all are on the same plate - plate 70.
  • the mismatch reduction element may touch the finger of the neighboring plate, keeping the plates from having excessive mismatch.
  • the microphone is exposed to high pressure or acceleration, however, the plates deflect significantly and the mismatch reduction elements of adjacent plates eventually come into contact with each other.
  • boundary conditions of the plates change and the operating regime changes from “normal operation” to “overload protection.” This change in boundary conditions causes the deflection shape to change and reduces stress in the piezoelectric material caused by an applied pressure or acceleration relative to the stress in the piezoelectric material of a plate without the plate coupling structure.
  • top view 80a and cross-section view 80b illustrate a step in which the plates and interdigitated fingers are defined by a first etch of the plate material or materials.
  • a sacrificial layer is deposited and vias are etched into this sacrificial layer. These vias will become the points where the mismatch reduction element attaches to the tips of the interdigitated fingers.
  • the mismatch reduction element layer is deposited and patterned. The mismatch reduction element material fills the vias, connecting to the fingers of one plate while overlapping but not connecting to the fingers of the adjacent plate. In the end, the device is released by removing the sacrificial material under the mismatch reduction element as well as the sacrificial material under the piezoelectric plates.
  • Some design parameters of this design are the finger length and the nominal vertical gap between the finger and the mismatch reduction element.
  • the length of the fingers will determine the transition point from normal operation to overload protection. The longer the fingers, the larger the range of normal operation. In this embodiment, the finger length increases as the fingers get closer to the plate tip. The length increases such that many of the mismatch reduction elements come into contact at the same time to reduce the peak stress in the mismatch reduction elements.
  • the nominal vertical gap between the finger and the mismatch reduction element is also critical. If this gap is small, fingers on both adjacent plates can come into contact with the mismatch reduction elements before the mismatch reduction elements contact each other.
  • piezoelectric plate sensor 92 includes plate coupling structure 94 with trapezoidal interdigitated fingers 91, 96, 98, 100, 102 and mismatch reduction elements 93, 95, 97, 99, 101.
  • each of mismatch reduction elements 93, 95, 97, 99, 101 is connected to a root (i.e., end portion) of a finger instead of a tip.
  • the majority of the stress induced by contact is in the plate material instead of the mismatch reduction elements 93, 95, 97, 99, 101.
  • the geometry of the trapezoidal fingers can be changed from the base to the tip of the plate in order to allow many of the plates to come into contact at approximately the same level of deflection. This allows the stress to be spread out over many fingers instead of being concentrated on a single finger.
  • piezoelectric sensor plate 124 includes plate coupling structure 124 with T-shaped interdigitated fingers 128.
  • spring 126 is a mismatch reduction element. Similar to the trapezoidal finger, a T-shaped finger directs the maximum stress in the plate material.
  • the T-shaped interdigitated fingers 128 also prevent the spring 126 from overextending and breaking.
  • this structure has a mismatch reduction element (i.e., spring 126) that is nominally in a same vertical plane as the piezoelectric sensor plate 122 and T-shaped interdigitated fingers 128.
  • transducing element 150 includes plates 151, 152, 154, 156, 158, 160 and plate coupling structures 162, 164, 166, 168, 170, 172.
  • FIG. 9B a close-up view of plate coupling structure 162 is shown.
  • plate coupling structure 162 is a same plate coupling structure as each of plate coupling structures 164, 166, 168, 170, 172.
  • plate coupling structure 164 includes spring 164a, fingers 164b-164r, 165a-165b and 165c-165p and overlapping portions 166, 168.
  • each of overlapping portions is represented by the shaded black regions in FIG. 9B that extend horizontally along a length of the plate coupling structure.
  • an overlapping portion is a piece of structural material that is affixed or otherwise connected to a plate.
  • spring 164a acts as the mismatch reduction element and overlapping portions prevent the failure described for FIG 8.
  • one or more of overlapping portions 166, 168 stick to one or more of fingers 164b-164r, 165a-165b and 165c-165p when they touch. Therefore, the microphone sensitivity degrades if one or more of fingers 164b-164r, 165a-165b and 165c-165p touches one or more of overlapping portions 166, 168.
  • spring 164a prevents one or more of fingers 164b-164r, 165a-165b and 165c-165p from touching one or more of overlapping portions 166, 168, e.g., during normal operation.
  • overlapping portions 166, 168 are used to prevent plates 151, 152, 154, 156, 158, 160 (FIG. 9A) from getting out of plane and coming apart, breaking spring 164a.
  • diagram 200 shows a close-up view of a center of a transducing element that includes plates 202, 204, 206, 208.
  • plate coupling structure 210 is attached to plates 202, 206.
  • plate coupling structure 210 includes spring 212, fingers 214, 216, 218, 220 and overlapping portions 222, 224.
  • diagram 250 illustrates a zoomed-in view of fingers
  • a plate coupling structure (attached to plates 252, 254) includes fingers 256, 258, 260, 262, 264, 266, 268.
  • fingers 262, 264, 266, 268 are part of plate 254 (i.e., are extensions of plate 254) and plate 252 includes openings sized to fit each of fingers 262, 264, 266, 268.
  • each of fingers 256, 258, 260 is part of plate 252 and plate 254 includes openings sized to fit each of each of fingers 256, 258, 260.
  • overlapping portion 270 includes elements 270a-270c and is affixed to plate 252 along an edge of a gap (not shown) between plate 252 and plate 254. Each of elements 270a-270c is sized to fit between portions of plate 252 that include the openings for fingers. Overlapping portion 270 also includes strip portion 270d that connects elements 270a, 270b and lies over the opening in plate 252 that is sized for finger 264. In this example, overlapping portion 272 is affixed to plate 254 and includes elements 272a-272b and includes strip portion 272c.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Abstract

L'invention porte sur un dispositif acoustique piézoélectrique comprenant : un substrat ; une pluralité de plaques, chaque plaque comprenant une première couche d'électrode, une couche piézoélectrique et une seconde couche d'électrode, la couche piézoélectrique étant située entre la première couche d'électrode et la seconde couche d'électrode, et pour chaque plaque, une base de la plaque est fixée au substrat et une partie restante de la plaque n'est pas fixée au substrat ; et une structure de couplage de plaque fixée à une première plaque parmi les plaques et à une seconde plaque parmi les plaques, la structure de couplage de plaque recouvrant au moins partiellement un espace entre un premier bord de la première plaque et un second bord de la seconde plaque, le premier bord étant tourné vers le second bord ; la structure de couplage de plaque comprenant un élément de réduction de défaut d'appariement et un élément d'arrêt, l'élément de réduction de défaut d'appariement étant configuré pour réduire une quantité de non-concordance lors de la déviation de la première plaque et de la seconde plaque, et l'élément d'arrêt étant configuré pour permettre à l'élément de réduction de défaut d'appariement de se dilater uniquement jusqu'à une quantité spécifiée.
PCT/US2017/047658 2016-08-18 2017-08-18 Structure de couplage de plaques Ceased WO2018035486A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201662376658P 2016-08-18 2016-08-18
US62/376,658 2016-08-18

Publications (1)

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WO2018035486A1 true WO2018035486A1 (fr) 2018-02-22

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111405442A (zh) * 2020-04-21 2020-07-10 安徽奥飞声学科技有限公司 一种mems结构
EP4037335A4 (fr) * 2019-10-31 2022-11-16 Huawei Technologies Co., Ltd. Capteur mems piézoélectrique et dispositif approprié
SE546765C2 (en) * 2023-11-06 2025-02-18 Myvox Ab A micro-electromechanical-system based sound producing device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002095092A (ja) * 2000-09-18 2002-03-29 Nippon Ceramic Co Ltd マイクロホン
US20070046396A1 (en) * 2005-08-03 2007-03-01 Yongli Huang Mems acoustic filter and fabrication of the same
US20120270352A1 (en) * 2011-04-19 2012-10-25 Huffman James D Fabricating mems composite transducer including compliant membrane
US20140339657A1 (en) * 2008-06-30 2014-11-20 The Regents Of The University Of Michigan Piezoelectric mems microphone
US20150271606A1 (en) * 2011-03-31 2015-09-24 Vesper Technologies Inc. Acoustic Transducer with Gap-Controlling Geometry and Method of Manufacturing an Acoustic Transducer

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002095092A (ja) * 2000-09-18 2002-03-29 Nippon Ceramic Co Ltd マイクロホン
US20070046396A1 (en) * 2005-08-03 2007-03-01 Yongli Huang Mems acoustic filter and fabrication of the same
US20140339657A1 (en) * 2008-06-30 2014-11-20 The Regents Of The University Of Michigan Piezoelectric mems microphone
US20150271606A1 (en) * 2011-03-31 2015-09-24 Vesper Technologies Inc. Acoustic Transducer with Gap-Controlling Geometry and Method of Manufacturing an Acoustic Transducer
US20120270352A1 (en) * 2011-04-19 2012-10-25 Huffman James D Fabricating mems composite transducer including compliant membrane

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4037335A4 (fr) * 2019-10-31 2022-11-16 Huawei Technologies Co., Ltd. Capteur mems piézoélectrique et dispositif approprié
CN111405442A (zh) * 2020-04-21 2020-07-10 安徽奥飞声学科技有限公司 一种mems结构
SE546765C2 (en) * 2023-11-06 2025-02-18 Myvox Ab A micro-electromechanical-system based sound producing device
SE2351266A1 (en) * 2023-11-06 2025-02-18 Myvox Ab A micro-electromechanical-system based sound producing device
WO2025098889A1 (fr) 2023-11-06 2025-05-15 Myvox Ab Dispositif de production de son basé sur un système micro-électromécanique

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