阅读说明：本技术 组合式波纹状压电麦克风和波纹状压电振动传感器 (Combined corrugated piezoelectric microphone and corrugated piezoelectric vibration sensor ) 是由 C·布雷特豪尔 P·米什拉 D·诺伊迈尔 D·图姆波德 于 2021-06-08 设计创作，主要内容包括：本公开的各实施例涉及组合式波纹状压电麦克风和波纹状压电振动传感器。组合式微机电结构(MEMS)包括具有一个或多个第一电极的第一压电膜,第一压电膜被固定在第一保持件与第二保持件之间；以及具有惯性质量和一个或多个第二电极的第二压电膜,第二压电膜被固定在第二保持件与第三保持件之间。(Embodiments of the present disclosure relate to a combined corrugated piezoelectric microphone and corrugated piezoelectric vibration sensor. A combined microelectromechanical structure (MEMS) includes a first piezoelectric film having one or more first electrodes, the first piezoelectric film being secured between a first holder and a second holder; and a second piezoelectric film having an inertial mass and one or more second electrodes, the second piezoelectric film being fixed between the second holder and the third holder.)

1. A combined MEMS structure comprising:

a first piezoelectric film including one or more first electrodes, the first piezoelectric film being fixed between a first holder and a second holder; and

a second piezoelectric film comprising an inertial mass and one or more second electrodes, the second piezoelectric film being secured between the second holder and a third holder.

2. The combined MEMS structure of claim 1, wherein the first piezoelectric membrane is configured to provide a microphone signal output at the one or more first electrodes, and wherein the second piezoelectric membrane is configured to provide an inertial sensor signal output at the one or more second electrodes.

3. The unitized MEMS structure of claim 1, wherein the first and second piezoelectric films comprise a single film.

4. The unitized MEMS structure of claim 1, wherein at least one of the first and second piezoelectric films comprises a corrugated film.

5. The combined MEMS structure of claim 1, wherein the inertial mass comprises a mass.

6. The unitized MEMS structure of claim 1, wherein the inertial mass comprises a membrane mass.

7. The unitized MEMS structure of claim 1, wherein the inertial mass comprises a mass and a membrane mass.

8. The unitized MEMS structure of claim 1, further comprising a plurality of additional piezoelectric membranes configured to provide additional inertial sensor signal outputs.

9. The combined MEMS structure of claim 8, wherein the plurality of additional piezoelectric films includes individually tuned films each having a different resonant frequency.

10. The unitized MEMS structure of claim 8, wherein at least one of the plurality of additional piezoelectric membranes comprises a corrugated membrane.

11. A packaged MEMS structure comprising:

a substrate including an acoustic port and a contact pad;

a first piezoelectric film including one or more first electrodes, the first piezoelectric film being fixed between a first holder and a second holder;

a second piezoelectric film comprising an inertial mass and one or more second electrodes, the second piezoelectric film being secured between the second holder and a third holder, wherein the first, second, and third holders are secured to the substrate;

an amplifier having first and second inputs coupled to the one or more first electrodes and the one or more second electrodes, and an output coupled to the contact pad; and

a housing secured to the substrate and surrounding the first piezoelectric film, the second piezoelectric film, and the amplifier.

12. The packaged MEMS structure of claim 11, wherein the first piezoelectric film is configured to provide a microphone signal output at the one or more first electrodes, and wherein the second piezoelectric film is configured to provide an inertial sensor signal output at the one or more second electrodes.

13. The packaged MEMS structure of claim 11, wherein the first and second piezoelectric films comprise a single piezoelectric film.

14. The packaged MEMS structure of claim 11, wherein at least one of the first and second piezoelectric films comprises a corrugated film.

15. The packaged MEMS structure of claim 11, further comprising a cover over the second piezoelectric film, the cover secured to the second holder and the third holder.

16. The packaged MEMS structure of claim 11, wherein the amplifier is configured above the second piezoelectric film, the amplifier being secured to the second holder and the third holder.

17. The packaged MEMS structure of claim 11 wherein the amplifier comprises a differential input.

18. The packaged MEMS structure of claim 11, wherein the amplifier comprises a differential output coupled with the contact pad and an additional contact pad.

19. The packaged MEMS structure of claim 11 wherein the inertial mass comprises a mass.

20. The packaged MEMS structure of claim 11 wherein the inertial mass comprises a thin film mass.

21. The packaged MEMS structure of claim 11 wherein the inertial mass comprises a mass and a membrane mass.

22. A MEMS accelerometer, comprising:

a piezoelectric film comprising at least one electrode and an inertial mass, the piezoelectric film being fixed to a holder; and

circuitry configured to evaluate a sum and a difference of signals associated with the at least one electrode to determine a three-dimensional acceleration direction.

23. The MEMS accelerometer of claim 22, wherein the piezoelectric membrane comprises a circular membrane.

24. The MEMS accelerometer of claim 22, wherein the piezoelectric membrane comprises a corrugated membrane.

25. The MEMS accelerometer of claim 22, wherein the at least one electrode comprises a segmented electrode.

26. The MEMS accelerometer of claim 25, wherein the segmented electrode comprises four segmented regions.

27. The MEMS accelerometer of claim 25, wherein the segmented electrode comprises a plurality of high electrode segments and a plurality of low electrode segments.

28. The MEMS accelerometer of claim 22, wherein the piezoelectric membrane comprises a plurality of vent holes.

Technical Field

The present invention generally relates to a combined corrugated piezoelectric microphone and corrugated piezoelectric vibration sensor.

Background

Microelectromechanical transducers function as both sensors and actuators in modern electronics and are used in a variety of different applications, such as microphones, loudspeakers, pressure sensors or acceleration sensors.

The micro-electromechanical transducer may have a membrane that may be displaced in a passive or active manner depending on whether the transducer is formed as a sensor or an actuator. In case the micro-electromechanical transducer is formed as a sensor, the membrane may be moved in a passive manner, e.g. by the sound to be detected or the acceleration to be detected. The properties of the variable to be detected, such as the sound frequency, sound amplitude or time acceleration profile, can be determined from the displacement of the membrane. In case the micro-electromechanical transducer is formed as an actuator, the membrane may be displaced in an active manner, for example to generate sound in a loudspeaker.

The membrane of such a micro-electromechanical transducer may be at least partially formed by a piezoelectric material, wherein in case of passive displacement of the membrane a voltage is induced, which can be read out by a suitable readout circuit to determine the characteristics of the variable to be detected. Alternatively, in the case of an actuator, a voltage may be applied to the membrane to cause a targeted deformation of the membrane, for example to generate sound.

Disclosure of Invention

In one embodiment, a combined MEMS structure comprises: a first piezoelectric film including one or more first electrodes, the first piezoelectric film being fixed between the first holder and the second holder; and a second piezoelectric film comprising an inertial mass and one or more second electrodes, the second piezoelectric film being fixed between the second holder and the third holder.

In another embodiment, a packaged MEMS structure comprises: a substrate including an acoustic port and a contact pad; a first piezoelectric film including one or more first electrodes, the first piezoelectric film being fixed between the first holder and the second holder; a second piezoelectric film comprising an inertial mass and one or more second electrodes, the second piezoelectric film being secured between a second holder and a third holder, wherein the first, second, and third holders are secured to the substrate; an amplifier having first and second inputs coupled to the one or more first electrodes and the one or more second electrodes and an output coupled to the contact pad; and a housing secured to the substrate and enclosing the first piezoelectric film, the second piezoelectric film, and the amplifier.

In another embodiment, a MEMS accelerometer comprises: a piezoelectric film including at least one electrode and an inertial mass, the piezoelectric film being fixed to the holder; and circuitry configured to evaluate a sum and a difference of signals associated with the at least one electrode to determine a three-dimensional acceleration direction.

Drawings

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a plan view of an exemplary piezoelectric film of a micro-electromechanical transducer;

FIG. 2 is a cross-sectional view of a portion of an exemplary piezoelectric film of a micro-electromechanical transducer;

FIG. 3 is a cross-sectional view of a portion of another exemplary piezoelectric film of a micro-electromechanical transducer;

FIG. 4 is a simplified cross-sectional view of a corrugated piezoelectric microphone that may be combined with a corrugated piezoelectric vibration sensor in accordance with an embodiment;

FIG. 5 is a simplified cross-sectional view of a corrugated piezoelectric vibration sensor that may be combined with a corrugated piezoelectric microphone in accordance with one embodiment;

FIG. 6 is a simplified cross-sectional view of a corrugated piezoelectric microphone that may be combined with one or more corrugated piezoelectric vibration sensors in accordance with an embodiment;

FIG. 7 is a simplified cross-sectional view of a packaged combined corrugated piezoelectric microphone and corrugated piezoelectric vibration sensor, according to one embodiment;

FIG. 8 is a simplified cross-sectional view of a packaged combined corrugated piezoelectric microphone and corrugated piezoelectric vibration sensor, according to another embodiment;

FIG. 9 is a plan view and a cross-sectional view of an accelerometer for determining three dimensional acceleration directions according to one embodiment; and

FIG. 10 is a simplified cross-sectional view of a corrugated piezoelectric microphone combined with a plurality of corrugated piezoelectric vibration sensors having separate resonant frequencies in accordance with one embodiment.

Detailed Description

One or more corrugated piezoelectric membranes are used in a combined micro-electromechanical systems (MEMS) device having a corrugated piezoelectric microphone and a corrugated piezoelectric vibration sensor (transducer). The combined MEMS device may be packaged with an amplifier or other processing circuitry. The corrugated piezoelectric film technology described below is used to provide a MEMS device that is robust, stable, manufacturable, and economical. In one embodiment, the combination of a corrugated piezoelectric microphone and a piezoelectric film based vibration sensor with a central mass may advantageously be manufactured in the same technology and thus also on the same wafer. In one embodiment, the central mass of the vibration sensor may be formed from bulk silicon, a thin film structure, or both. Since the readout principle of both transducers is the same, in embodiments both devices may use the same or similar Application Specific Integrated Circuit (ASIC) or analog front end circuit, or even share the latest differential analog microphone ASIC. In the case of using only a single analog differential microphone ASIC, one sensing channel reads the microphone as a single-ended input, and the other channel reads the vibration sensor in parallel also as a single-ended input. The ASIC may therefore be cost effective and may be reused from existing products. These and other aspects of embodiments of the invention are described in further detail below.

Fig. 1 illustrates an exemplary micro-electromechanical transducer 100. The micro-electromechanical transducer 100 may have a holder 102 and a displaceable membrane 104 secured to the holder 102. At least a portion of the membrane 104 may be formed of a piezoelectric material. A voltage that can be measured by a suitable readout circuit can be induced in the piezoelectric material by displacement of the membrane 104. The characteristic of the variable to be detected, such as for example the sound to be detected or the acceleration to be detected, can be determined from the measured voltage. Alternatively, a voltage may be applied to the membrane 104 to displace the membrane 104, for example, to generate sound.

If the transducer 100 is formed as an acceleration sensor or as part of an acceleration sensor, the inertial mass 103 may be provided on the membrane 104, for example on a central portion of the membrane 104, to increase the force exerted on the membrane 104 by the acceleration to be detected. Inertial mass 103 may be formed separately from membrane 104. The inertial mass may be formed, for example, from a semiconductor material such as silicon.

As shown in fig. 1, the membrane 104 may be secured to the holder 102 at its edge region 104R in a circumferential manner. The film 104 may be formed as a closed component such that there is an uninterrupted connection along the film 104 between two arbitrary points of the edge region 104R of the film 104. The membrane 104 may thus be formed without fluid passage openings, which may act as a noise source when a fluid (such as, for example, a gas) flows through such fluid passage openings. The absence of fluid channel openings in the membrane 104 may constitute a considerable advantage compared to piezoelectric membranes having multiple cantilevers that may deflect independently of each other. The closed membrane 104 is also particularly robust, since any cantilever arm reacts in a particularly sensitive manner to extreme mechanical loads, which may lead to damage of the membrane with the cantilever arm, for example in case of a collision. However, this does not preclude the membrane 104 described herein from being able to have one or more openings to minimize drag, which may be caused by gas (e.g., air) collecting on the sides of the membrane 104. This may ensure a high degree of elasticity of the membrane 104.

The membrane 104 shown in fig. 1 may be formed as a planar component. The term "planar" essentially means that the membrane 104 has a substantially greater extension along the first spatial direction X and along a second spatial direction Y orthogonal to the first spatial direction X than along a third spatial direction orthogonal to the first spatial direction X and to the second spatial direction Y and defining an axial direction a of the membrane 104.

The film 104 may have a wave section 106, the wave section 106 including at least one wave peak 108 and at least one wave valley 110, or including a plurality of wave peaks 108 and a plurality of wave valleys 110. The undulation peaks 108 and undulation valleys 110 are continuously arranged in an alternating manner in the radial direction R of the film 104. The undulation peaks 108 or/and undulation valleys 110 may have a circular or circular segment-shaped design and are, for example, arranged concentrically around the center point M of the membrane 104. The circular segment-shaped configuration of the undulation peaks 108 and undulation valleys 110 (not shown) allows, for example, radial laying of feed lines on the membrane 104.

Due to the formation of the rounded or circular segmented shape of the undulation peaks 108 or/and undulation valleys 110, the membrane 104 is mainly arranged to detect deflection in the circumferential direction C.

The above discussed mechanical stress may be compensated by the provision of the wavy segments 106, since the wavy segments 106 may act as elastic elements which may absorb the mechanical stress discussed at the beginning by stretching or compressing, as a result of which the deformation of the membrane 104 caused by the mechanical stress may be limited. This may ensure that the membrane 104 has a well-defined design and thus flexes in a well-defined manner, whereby reproducible behavior may be achieved.

In addition, the undulating sections 106 of the film 104 may be used to reduce or eliminate the compensation of the induced electric field discussed at the outset. This is explained below with reference to fig. 2, which fig. 2 shows a cross section through the membrane 104 along the line III-III shown in fig. 1.

As shown in fig. 2, in each case a piezoelectric unit cell 112 may be provided in a plurality of undulation peaks 108 or/and a plurality of undulation valleys 110, or even in each undulation peak 108 or/and each undulation valley 110, wherein the piezoelectric unit cell has a piezoelectric layer 114 and at least one electrode 116 in electrical contact with the piezoelectric layer 114. In the undulating section 106, the neutral fibers NF of the membrane 104 are located between undulation peaks 108 and undulation valleys 110 in the axial direction a. As a result, the membrane 104 is divided in the axial direction a into two zones by the neutral fibers NF, both zones being subjected to tensile or compressive loads in the event of a deflection of the membrane 104. Thus, for example, in the event that the membrane 104 flexes, the undulation peaks 108 may experience only tensile loads while the undulation valleys 110 may experience only pressure loads, or vice versa. As a result, an electric field with a uniform sign is induced in the undulation peak 108 or the undulation valley 110, so that no compensation of the electric field in the piezoelectric layer 114 takes place compared to the conventional piezoelectric film discussed at the beginning, which will limit the net voltage that can be tapped. As a result, higher voltages U than conventional piezoelectric transducers can eventually be tapped at a predetermined deflection of the membrane 104, which makes it possible to achieve higher sensitivity than conventional micro-electromechanical transducers. Furthermore, a defined deflection of the membrane 104 may be achieved by applying a voltage to the respective electrode 116.

The piezoelectric unit cell 112 shown in fig. 2 may have only a single electrode 116, and the single electrode 116 may be provided on the same side of the respective piezoelectric layer 114. This configuration may make the fabrication of the micro-electromechanical transducer 100 particularly simple, as the electrodes 116 may be simultaneously vapor deposited and/or structured.

Basically, any conductive material may be used as the material of the electrode 116, for example, a metal such as aluminum. The piezoelectric layers 114 of the respective piezoelectric unit cells 112 may be made of, for example, aluminum nitride (AlN), zinc oxide (ZnO), or lead zirconate titanate (PZT).

As shown in fig. 2, the electrodes 116 of the piezoelectric unit cells 112 provided at the fluctuation peaks 108 may be electrically connected in parallel to each other through lines 118, and the electrodes 116 of the piezoelectric unit cells 112 provided in the fluctuation valleys 110 may be electrically connected in parallel to each other through lines 120. In one embodiment, the electrodes 116 of the piezoelectric unit cells 112 may be electrically connected in series. As a result, the electric potential induced in the respective piezoelectric unit cell 112 at the fluctuation peak 108 or in the fluctuation valley 110 can be tapped by means of the respective electrode 116 and subsequently summed, whereby a higher net voltage U can be tapped.

The piezoelectric layers 114 of the respective piezoelectric unit cells 112 may be integrally formed with each other. As shown in fig. 1 and 2, the piezoelectric layers 114 of two adjacent piezoelectric unit cells 112 may be integrally connected to each other by a connecting section 122 extending substantially in the axial direction a. Due to the integral formation of the piezoelectric layer 114, the membrane 104 can be manufactured in a simple manner as a whole, while the piezoelectric layer 114 of the piezoelectric unit cell 112 can also be manufactured when manufacturing the corrugated section 106.

Fig. 3 shows a portion of a corrugated piezoelectric membrane 1021 coupled with a holder 1030, not specifically shown in fig. 1 and 2. The corrugated piezoelectric membrane 1021 includes a conductive layer 1014, a piezoelectric layer 1016, an electrode 1022, contact pads 1026, contact pads 1028, a holder 1030, and an optional inertial mass 1032.

As shown in fig. 3, contact pads 1026 are used to contact conductive layer 1014. Additional contact pads 1028 can also be formed at the electrodes 1022 formed on the piezoelectric layer 1016 to make electrical contact with the piezoelectric layer. In the exemplary illustration according to fig. 3, the inertial mass 1032 is provided on a corrugated section of the membrane 1021. The inertial mass may be provided in a central region of the membrane 1021 that is not corrugated. Fig. 3 shows only a portion of the membrane 1021 having undulating sections and non-undulating regions connected with the holder 1030.

Further description of corrugated piezoelectric films may be found in co-pending U.S. patent application No. 2019/0016588, filed on 2018, 7, 10, the entire contents of which are incorporated herein by reference.

FIG. 4 is a simplified cross-sectional view of a corrugated piezoelectric microphone that may be combined with a corrugated piezoelectric vibration sensor in accordance with one embodiment. In the simplified cross-sectional view of FIG. 4, the corrugations in the corrugated piezoelectric membrane 208 are not actually shown for clarity.

The corrugated piezoelectric microphone 200 includes a first holder or mechanical fixture 202A, a second holder or mechanical fixture 202B, a clamping layer 204, a bulk silicon portion 206, a corrugated piezoelectric membrane 208, vent holes 210, a membrane definition layer 212, and contact pads 214. In one embodiment, the clamping layer 204 may comprise a silicon or dielectric layer. In one embodiment, the film defining layer 212 defines the amount of film exposed and may include a metal, silicon, or dielectric layer. Other such corrugated piezoelectric microphones may also be used in combination with the corrugated piezoelectric vibration sensor shown in fig. 5 and described below.

The corrugated piezoelectric microphone 200 is used to convert changes in air pressure from above or below the corrugated piezoelectric film 208 into a corresponding output voltage at the contact pad 214. In an embodiment, the retainers 202A and 202B may include a bulk silicon portion 206 and a clamping layer 204, the clamping layer 204 being disposed on the bulk silicon portion 206, the clamping layer 204 may include one or more silicon or dielectric thin film layers for securing ends of the corrugated piezoelectric film 208. The vent 210 is designed to minimize flow resistance of the corrugated piezoelectric membrane 208, and in embodiments, may include a pattern of multiple vents 210. For a circular corrugated piezoelectric film 208, a circular pattern of vent holes 210 may be used. In embodiments, the film-defining layer 212 may be positioned between the bulk silicon portion 206 and the clamping layer 204, and may comprise a silicon, dielectric, or metal layer, or a combination of these layers. The purpose of the film-defining layer 212 is to define an acceptable exposed area of the corrugated piezoelectric film 208. In some applications, it may be advantageous to protect the edges of the corrugated piezoelectric membrane 208 from direct exposure to changes in air pressure from below to protect the structural integrity of the membrane 208. The exact lateral extent of the film-defining layer 212 may vary depending on the application of the corrugated piezoelectric microphone 200. In some embodiments, the film-defining layer 212 is optional and may be removed as desired. The contact pads 214 may comprise metal or metal alloy contact pads formed in an upper portion of the clamping layer and in direct contact with the upper surface of the corrugated piezoelectric film 208 as previously described.

FIG. 5 is a simplified cross-sectional view of a corrugated piezoelectric vibration sensor that may be combined with a corrugated piezoelectric microphone in accordance with one embodiment. In the simplified cross-sectional view of FIG. 5, the corrugations in corrugated piezoelectric membrane 308 are not actually shown for clarity.

The corrugated piezoelectric vibration sensor 300 includes a first holder or mechanical fixture 302A, a second holder or mechanical fixture 302B, an inertial mass 302C, a clamping layer 304, a bulk silicon portion or mass 306, a corrugated piezoelectric film 308, vent holes 310, a film defining layer 312, a membrane layer 316, and a membrane mass 318. In one embodiment, the clamping layer 304 may comprise a silicon or dielectric layer. In one embodiment, the film defining layer 312 defines the amount of film exposed and may include a metal, silicon, or dielectric layer. The thin film layer may include a silicon, oxide, dielectric, or metal layer. Other such corrugated vibration sensors may also be used in combination with the corrugated microphone shown in fig. 4 and described above.

As shown in fig. 5, different layer stacks may be used to provide inertial mass (proof mass) to corrugated piezoelectric film 308. The inertial mass may include the mass 306, the film mass 318, or both. Bulk silicon mass 306 provides the greatest mass, which is beneficial for lowering the resonant frequency and increasing the sensitivity of vibration sensor 300. The thin-film mass 318 may include one or more of the film-defining layer 312, the clamping layer 304, and the thin-film layer 316. The film quality 318 may include one or more layers of silicon, oxide, dielectric, and/or metal. The integration of these layers of a thickness of a few microns is directly obtained from the integration of piezoelectric microphones. However, the film quality is less than the bulk silicon quality. Thus, in embodiments, the combined device may need to be larger to achieve the necessary vibration sensitivity. However, in some embodiments, devices with thin film inertial masses may be more robust than devices with bulk silicon inertial masses. By adding an appropriate number of vents 310, the low frequency roll-off for pressure coupling can be adjusted to the kHz range. If it is desired to further suppress the audio sensitivity of the vibration sensor 300, a cover may be used to shield the vibration sensor 300 from sound, as shown in fig. 7 and 8 and described in more detail below.

Fig. 6 is a simplified cross-sectional view of a corrugated piezoelectric microphone 200 that may be combined with one or more corrugated piezoelectric vibration sensors 300D to form a combined MEMS structure 400 according to one embodiment. In the simplified cross-sectional view of FIG. 5, the corrugations in corrugated piezoelectric films 208 and 308 are not actually shown for clarity. Fig. 6 thus includes the corrugated piezoelectric microphone 200 in combination with a selected corrugated piezoelectric vibration sensor 300D, which in turn includes a first corrugated piezoelectric vibration sensor 300A having a bulk inertial mass 306, a second corrugated piezoelectric vibration sensor 300B having a thin-film inertial mass, or a third corrugated piezoelectric vibration sensor 300C having a bulk inertial mass 306 and a thin-film inertial mass 318. More details of the combined MEMS structure 400 will be described in more detail below with reference to fig. 7 and 8.

According to an embodiment, one or more of a selection of corrugated piezoelectric vibration sensors 300D may be combined with corrugated piezoelectric microphone 200 to form a combined MEMS device. Any of the vibration sensors may be used and the application may utilize different vibration response characteristics of each vibration sensor. The first corrugated piezoelectric vibration sensor 300A includes a bulk inertial mass 306 coupled to a bottom surface of a corrugated piezoelectric film 308. Since the mass of the mass inertial mass 306 is relatively high, the corrugated piezoelectric vibration sensor 300A will have a robust vibration response. The second corrugated piezoelectric vibration sensor 300AB includes a thin film inertial mass 318 coupled to the top and bottom surfaces of the corrugated piezoelectric film 308. The corrugated piezoelectric vibration sensor 300B may have a smaller amplitude of vibration response due to the relatively low mass of the thin film inertial mass 318. However, the piezoelectric vibration sensor 300B may have a different frequency response than the corrugated piezoelectric vibration sensor 300A. Finally, the third corrugated piezoelectric vibration sensor 300C includes a bulk inertial mass 306 coupled to the bottom surface of the corrugated piezoelectric film 308 and a thin-film inertial mass 318 coupled to the top and bottom surfaces of the corrugated piezoelectric film 308. The corrugated piezoelectric vibration sensor 300A will have the largest magnitude of vibration response due to the relatively large mass inertial mass 306 in combination with the membrane inertial mass 318.

Fig. 7 is a simplified cross-sectional view of a packaged combined MEMS structure 500, the packaged combined MEMS structure 500 comprising a combined MEMS structure 400, the combined MEMS structure 400 comprising a corrugated piezoelectric microphone 200 and a corrugated piezoelectric vibration sensor 300, according to one embodiment. In the simplified cross-sectional view of FIG. 5, the corrugations in corrugated piezoelectric membranes 208 and 308 are not actually shown for clarity.

In one embodiment, in relevant part, the corrugated piezoelectric microphone 200 and the corrugated piezoelectric vibration sensor 300 share a shared holder or mechanical fixture 524 to form a combined MEMS structure 400. Although separate corrugated membranes 208 and 308 are shown in fig. 7 each secured to a shared retainer 524, in one embodiment, a single combined corrugated membrane may include corrugated membranes 208 and 308 as part of a single combined corrugated membrane extending through a shared retainer 524. Although the vibration sensor 300 is shown as having a thin film inertial mass, a bulk inertial mass or a combination of both inertial masses may be used. Although only one corrugated piezoelectric microphone 200 and one corrugated piezoelectric vibration sensor 300 are combined in fig. 7, other configurations of microphones and vibration sensors are possible. For example, in one embodiment, one corrugated piezoelectric microphone 200 may be combined with a plurality of corrugated piezoelectric vibration sensors.

Fig. 7 thus shows a packaged combined MEMS structure 500 comprising a substrate 506, the substrate 506 having an acoustic port 508. In embodiments, the substrate 506 may comprise a dielectric, plastic, fiberglass, or any other suitable material. The packaged combined MEMS structure also includes a housing 502 attached to the substrate 506, the housing 502 enclosing an internal volume that includes the combined MEMS structure 400, the ASIC 528, and internal wiring between the combined MEMS structure 400 and the ASIC 528. The housing 502 may include a metal or layered metal structure, or a structure having an insulating layer or a dielectric layer and a metal layer. Any other suitable material may also be used in embodiments. In one embodiment, the wafer-bonded cover 504 or other type of cover may be used if the sensitivity of the vibration sensor is too high to cause crosstalk caused by audio signals entering through the sound port 508 and passing through the microphone 200. The corrugated membrane of corrugated piezoelectric vibration sensor 300 includes at least one vent 510. In one embodiment, by introducing a vent in the vibration sensor, the low frequency roll-off for pressure response can be shifted up to the single digit kHz range so that unwanted audio sensitivity below this roll-off frequency can be suppressed as desired without the cover 504. In an embodiment, the vent and the cover may be used together.

In one embodiment, the packaged combined MEMS structure 500 further includes an ASIC 528, the ASIC 528 may be a differential input and differential output ASIC. In embodiments, other custom or commonly available amplifier integrated circuits may be used. The ASIC 528 includes a first input Sens 1512 and a second input Sens 2514 coupled to the output of the corrugated piezoelectric microphone 200. In one embodiment, inputs 512 and 514 may comprise single-ended inputs of a differential input pair. In one embodiment, the ASIC 528 includes a first positive output OutP 516, the first positive output OutP 516 being coupled to a microphone signal pad 520 extending through the substrate 506. In one embodiment, microphone signal pad 520 provides an analog microphone output signal. In one embodiment, the ASIC 528 includes a second negative output, OutN 518, the second negative output, OutN 518, being coupled to the vibration sensor signal pad 522 that extends through 506. In one embodiment, the vibration sensor signal pad 522 provides an analog vibration sensor output signal.

Although a packaged combined MEMS structure 500 of one embodiment is shown in fig. 7, other combinations and placements of the combined MEMS structure, ASIC 528, signal pads 520 and 522, lid 504, and housing 502 are contemplated as would be apparent to one skilled in the art. For example, ASIC 528 may include one or more integrated circuits. The housing 502 may be made to enclose other components, or only certain components shown in fig. 7. Additional signal pads may be used as desired.

Fig. 8 is a simplified cross-sectional view of a packaged combined MEMS structure 600 including a corrugated piezoelectric microphone 200 and a corrugated piezoelectric vibration sensor 300, according to another embodiment. In the simplified cross-sectional view of FIG. 8, the ripples in combined MEMS structure 400 are not actually shown for clarity.

Basically with respect to the packaged combined MEMS structure shown in fig. 7, the packaged combined MEMS structure 600 includes a housing 602, an ASIC 604, a substrate 606, an acoustic port 608, and a vent 610. ASIC 604 includes a microphone signal input 612 coupled to an output of corrugated piezoelectric microphone 200 and a vibration sensor signal input 614 coupled to an output of corrugated piezoelectric vibration sensor 300. The corrugated piezoelectric microphone 200 and the corrugated piezoelectric vibration sensor are incorporated together using a shared retainer 624 as previously described. The ASIC 604 includes a single output signal 616 coupled with a combined MEMS output pad 618. In one embodiment, the combined MEMS output pad 618 provides a multiplexed output signal that combines the amplified signals on inputs 612 and 614. In one embodiment, the combined MEMS structure 400 does not include a lid as previously described, but instead uses the bottom surface of the ASIC 604. In other words, ASIC 604 provides amplification and shielding functions to help isolate corrugated piezoelectric vibration sensor 300 from audio signals input via sound port 608 and piezoelectric microphone 200. In FIG. 8, ASIC 604 is shown mounted on the top surface of corrugated piezoelectric vibration sensor 300.

FIG. 9 is a plan view 700A and a cross-sectional view 700B of a corrugated piezoelectric vibration sensor configured as an accelerometer 700 for determining a three-dimensional acceleration direction according to one embodiment. Although the accelerometer 700 is shown as a separate component in fig. 9, the accelerometer 700 may be combined with the corrugated piezoelectric microphone 200 as a combined MEMS device, as desired, as will be described in further detail below.

In various applications, it may be desirable to pick up vibrations independently of the orientation of the vibration sensor device. The corrugated membrane, in particular in combination with the long bulk silicon inertial mass according to embodiments, will not only react to accelerations perpendicular to its surface (Z-axis), but it will also sense in-plane accelerations (X-axis and Y-axis) due to the torque acting on the mass. These accelerations may even be resolved if a multi-segment electrode design is selected for accelerometer 700 as shown in plan view 700A and cross-sectional view 700B. In the example of accelerometer 700, four membrane sections are used and are described below. While other numbers of membrane segments may be used, the corresponding acceleration equations listed below may have to be updated to reflect the number of membrane segments selected for a particular design.

Accelerometer 700 includes a holder 710. in one embodiment, holder 710 includes a single holder coupled with a single circular corrugated membrane 712. In other embodiments, a plurality of individual holders may be used to support the corrugated membrane 712. In one embodiment, the corrugated film 712 has four sections for generating four corresponding signals: signal 1(s1), signal 2, signal 3(s3), and signal 4(s 4). Each membrane segment includes one or more high electrodes 702 and one or more low electrodes 704. According to one embodiment, the central portion of the corrugated membrane 712 includes a plurality of vent holes 706, which plurality of vent holes 706 may be used to tune the frequency response of the accelerometer 700. The corrugated membrane 712 is coupled to the inertial mass 708, which includes a bulk silicon portion. The longer the inertial mass, the more torque 713 will be generated in the accelerometer for a given acceleration. For thin film layer quality, the output signal for a given acceleration may be much smaller. FIG. 9 defines an acceleration direction 714 on the X-axis, where the Y-axis direction is orthogonal to the X-axis direction in the plane of FIG. 9, and where the Z-axis direction is orthogonal to the X-axis direction extending from the plane of FIG. 9.

By evaluating the sum and difference of the four signals (signal 1, signal 2, signal 3, and signal 4), the acceleration in X, Y and the Z direction can be calculated.

The acceleration in the X-axis direction is determined by the following equation.

Signal 1 to signal 3

Signal 2 to signal 4

Signal 1 ≈ -Signal 2

The acceleration in the Y-axis direction is determined by the following equation.

Signal 1 to signal 2

Signal 3 to signal 4

Signal 1 ≈ -Signal 3

The acceleration in the Z-axis direction is determined by the following equation.

Signal 1, signal 2, signal 3, signal 4

The acceleration signal ratios alpha (α) and beta (β) are design specific sensitivities to the acceleration conditions s1 to s4 (signals from four corrugated membrane segments), described by the following equations.

a_x∝α(s1+s3–s2–s4)

a_y∝α(s1+s2–s3–s4)

a_z∝β(s1+s3+s2+s4)

If desired, the accelerometer 700 may be combined with the corrugated piezoelectric microphone 200 as a combined MEMS device by combining one of the edges of the holder 710 with one of the holders of the corrugated piezoelectric microphone 200 if a single holder 710 is used. If multiple holders 710 are used, the accelerometer 700 may be combined with the corrugated piezoelectric microphone 200 into a combined MEMS device by combining one of the multiple holders 710 with one of the holders of the corrugated piezoelectric microphone 200.

FIG. 10 is a simplified cross-sectional view of a corrugated piezoelectric microphone combined with a plurality of corrugated piezoelectric vibration sensors having separate resonant frequencies in accordance with one embodiment. In the simplified cross-sectional view of FIG. 10, the ripples in the combined MEMS structure 800 are not actually shown for clarity.

In one embodiment, a plurality of corrugated piezoelectric vibration sensor devices having different resonant frequencies may be combined with a corrugated piezoelectric microphone. Although separate devices may be used, both the microphone and the vibration sensor may be coupled together using a shared holder to form a combined MEMS device. In embodiments, a single corrugated membrane may be used, or a single corrugated membrane extending to all devices may be used. To achieve different resonant frequencies, inertial masses of different weights may be used, or by shaping the lateral corrugated membrane and the weight dimensions, or both.

Fig. 10 shows a combined MEMS structure 800, the combined MEMS structure 800 comprising a corrugated piezoelectric microphone 802 and a plurality of tuned corrugated piezoelectric vibration sensors, the plurality of tuned corrugated piezoelectric vibration sensors comprising a corrugated piezoelectric vibration sensor 804A, a corrugated piezoelectric vibration sensor 804B, and a corrugated piezoelectric vibration sensor 804C. Although three vibration sensors are shown, any number may be used in embodiments. Although the corrugated microphone 802 and the corresponding piezoelectric vibration sensor are shown as separate MEMS devices, two or more of these devices may be merged using the merged retainer 824, and the merged retainer 824 may be made as a single retainer, such as the shared retainer 524 shown in fig. 7 or the shared retainer 624 shown in fig. 8. Fig. 10 also shows an audio frequency spectrum that extends from a higher frequency audio signal from the combined MEMS structure 800 to the pressure coupling of the external pressure signal to a lower frequency vibration signal from the structural coupling of the combined MEMS structure to the external environment. Fig. 10 also shows the frequency response of each device in the combined MEMS structure 800, including the frequency response 806 of the corrugated piezoelectric microphone 802, the frequency response 808A of the corrugated vibration sensor 804A, the frequency response 808B of the corrugated vibration sensor 804B, and the frequency response 808C of the corrugated vibration sensor 804C. The ASIC 814 is used to amplify signals associated with the combined MEMS structure 800. The selector circuit 816 of the ASIC 814 includes a corrugated piezoelectric microphone input 810 coupled to the corrugated piezoelectric microphone 802, a corrugated vibration sensor input 812A coupled to the corrugated piezoelectric vibration sensor 804A, a corrugated vibration sensor input 812B coupled to the corrugated piezoelectric vibration sensor 804B, and a corrugated vibration sensor input 812C coupled to the corrugated piezoelectric vibration sensor 804C. In one embodiment, mixer circuit 818 may be used to combine the selector outputs at mixer output 822. The selector circuit 816 also includes a selector input 820 for controlling the channel selection of the selector circuit 816.

In summary, embodiments of a corrugated piezoelectric film microphone in a package combined with one or more corrugated piezoelectric film based vibration sensors using the same corrugated piezoelectric technology have been shown and described, which are suitable for use in a variety of applications including headphone or headset applications.

Example embodiments of the present invention are summarized herein. Other embodiments may be understood from the entire specification and claims as filed herein.

Example 1 according to one embodiment, a combined MEMS structure includes: a first piezoelectric film including one or more first electrodes, the first piezoelectric film being fixed between the first holder and the second holder; and a second piezoelectric film comprising an inertial mass and one or more second electrodes, the second piezoelectric film being fixed between the second holder and the third holder.

Example 2. the combined MEMS structure of example 1, wherein the first piezoelectric film is configured to provide a microphone signal output at the one or more first electrodes, and wherein the second piezoelectric film is configured to provide an inertial sensor signal output at the one or more second electrodes.

Example 3. the combined MEMS structure of any of the preceding examples, wherein the first and second piezoelectric films comprise a single film.

Example 4. the combined MEMS structure of any of the preceding examples, wherein at least one of the first and second piezoelectric films comprises a corrugated film.

Example 5. the combined MEMS structure of any of the preceding examples, wherein the inertial mass comprises a mass.

Example 6. the combined MEMS structure of any of the preceding examples, wherein the inertial mass comprises a membrane mass.

Example 7. the combined MEMS structure of any of the preceding examples, wherein the inertial mass comprises a mass and a membrane mass.

Example 8 the combined MEMS structure of any of the preceding examples, further comprising a plurality of additional piezoelectric films configured to provide additional inertial sensor signal outputs.

Example 9. the combined MEMS structure of any of the preceding examples, wherein the plurality of additional piezoelectric films includes individually tuned films each having a different resonant frequency.

Example 10 the combined MEMS structure of any of the preceding examples, wherein at least one of the plurality of additional piezoelectric membranes comprises a corrugated membrane.

Example 11 according to one embodiment, a packaged MEMS structure includes: a substrate including an acoustic port and a contact pad; a first piezoelectric film including one or more first electrodes, the first piezoelectric film being fixed between the first holder and the second holder; a second piezoelectric film comprising an inertial mass and one or more second electrodes, the second piezoelectric film being secured between a second holder and a third holder, wherein the first, second, and third holders are secured to the substrate; an amplifier having first and second inputs coupled to the one or more first electrodes and the one or more second electrodes, and an output coupled to the contact pad; and a housing secured to the substrate, the housing enclosing the first piezoelectric film, the second piezoelectric film, and the amplifier.

Example 12 the packaged MEMS structure of example 11, wherein the first piezoelectric membrane is configured to provide a microphone signal output at the one or more first electrodes, and wherein the second piezoelectric membrane is configured to provide an inertial sensor signal output at the one or more second electrodes.

Example 13 the packaged MEMS structure of any of the preceding examples, wherein the first and second piezoelectric films comprise a single piezoelectric film.

Example 14 the packaged MEMS structure of any of the preceding examples, wherein at least one of the first and second piezoelectric films comprises a corrugated film.

Example 15 the packaged MEMS structure of any of the preceding examples, further comprising a lid over the second piezoelectric film, the lid secured to the second holder and the third holder.

Example 16 the packaged MEMS structure of any of the preceding examples, wherein an amplifier is configured over the second piezoelectric film, the amplifier being secured to the second holder and the third holder.

Example 17 the packaged MEMS structure of any of the preceding examples, wherein the amplifier includes a differential input.

Example 18 the packaged MEMS structure of any of the preceding examples, wherein the amplifier includes a differential output coupled with the contact pad and the additional contact pad.

Example 19 the packaged MEMS structure of any of the preceding examples, wherein the inertial mass comprises a mass.

Example 20 the packaged MEMS structure of any of the preceding examples, wherein the inertial mass comprises a membrane mass.

Example 21 the packaged MEMS structure of any of the preceding examples, wherein the inertial mass comprises a mass and a membrane mass.

Example 22 according to one embodiment, a MEMS accelerometer includes: a piezoelectric film including at least one electrode and an inertial mass, the piezoelectric film being fixed to the holder; and circuitry configured to evaluate a sum and a difference of signals associated with the at least one electrode to determine a three-dimensional acceleration direction.

Example 23 the MEMS accelerometer of example 22, wherein the piezoelectric membrane comprises a circular membrane.

The MEMS accelerometer of any preceding example, wherein the piezoelectric membrane comprises a corrugated membrane.

Example 25 the MEMS accelerometer of any of the preceding examples, wherein the at least one electrode comprises a segmented electrode.

Example 26 the MEMS accelerometer of any preceding example, wherein the segmented electrode comprises four segmented regions.

The MEMS accelerometer of any of the preceding examples, wherein the segmented electrode comprises a plurality of high electrode segments and a plurality of low electrode segments.

The MEMS accelerometer of any preceding example, wherein the piezoelectric membrane comprises a plurality of vent holes.

While the invention has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.