WO2023010247A1 - 压电mems扬声器及其设计方法、电子设备 - Google Patents

压电mems扬声器及其设计方法、电子设备 Download PDF

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Publication number
WO2023010247A1
WO2023010247A1 PCT/CN2021/110104 CN2021110104W WO2023010247A1 WO 2023010247 A1 WO2023010247 A1 WO 2023010247A1 CN 2021110104 W CN2021110104 W CN 2021110104W WO 2023010247 A1 WO2023010247 A1 WO 2023010247A1
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diaphragm
gap
diaphragms
piezoelectric mems
adjacent
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PCT/CN2021/110104
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English (en)
French (fr)
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张孟伦
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天津大学
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Priority to PCT/CN2021/110104 priority Critical patent/WO2023010247A1/zh
Publication of WO2023010247A1 publication Critical patent/WO2023010247A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
    • 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

Definitions

  • the invention relates to the technical field of MEMS, in particular to a piezoelectric MEMS speaker, a design method thereof, and electronic equipment.
  • MEMS speakers typically produce sound by vibrating air through one or more actuator diaphragms.
  • the displacement of the traditional MEMS speaker reaches the maximum at the resonant frequency, which leads to an unacceptably high-amplitude peak in the sound pressure level of the speaker at the resonant frequency, and the frequency domain bandwidth is small, and the frequency response curve deteriorates.
  • the present invention proposes a piezoelectric MEMS speaker, its design method, and electronic equipment, which can adaptively generate an acoustic short circuit, reduce the peak of the sound pressure level at the resonance, and increase the bandwidth.
  • the first aspect of the present invention proposes a piezoelectric MEMS speaker.
  • the piezoelectric MEMS speaker includes N diaphragms adjacent to each other.
  • the structures of the N diaphragms adjacent to each other are asymmetrical, and N is a positive integer greater than 1.
  • the piezoelectric MEMS speaker includes at least one diaphragm and at least one boundary element adjacent to the diaphragm, the height of the border element is not higher than the height of the diaphragm, and the diaphragm
  • the boundary element There is a second gap with the boundary element, wherein the size of the first gap and/or the second gap satisfies a preset condition, so that the acoustic short circuit phenomenon occurs when the diaphragm vibrates at the mechanical resonance point, and does not occur when the diaphragm is stationary Acoustic short circuit occurs.
  • the height of the boundary element is lower than the height of the diaphragm.
  • the preset condition includes: when the diaphragm vibrates at the mechanical resonance point, the gap size of the first gap and/or the second gap is greater than 20 ⁇ m, or the gap area of the first gap and/or the second gap is larger than that of the speaker 5% of the area; and when the diaphragm is at rest, the gap size of the first gap and/or the second gap is less than 20 ⁇ m, or the gap area of the first gap and/or the second gap is less than 5% of the loudspeaker area.
  • the structural asymmetry of the N adjacent diaphragms includes that one or more of the N adjacent diaphragms are different in shape, size, and thickness of the diaphragm.
  • the piezoelectric MEMS speaker includes N diaphragms adjacent to each other, the structure of the N diaphragms adjacent to each other is asymmetrical, and the design of the diaphragm meets the following characteristics: the N diaphragms adjacent to each other are spliced into a polygon In the diaphragm area, the fixed end of each diaphragm is located on the contour of the polygonal diaphragm area, and the free ends of each diaphragm have the same common point, which is an eccentric point inside the polygonal diaphragm area; and/or, N The vibrating membranes adjacent to each other are N-level nested design, wherein the fixed ends of the vibrating membranes of each level are collinear.
  • N adjacent vibrating membranes are designed in N-level nesting, and at least two of the vibrating membranes have different shapes.
  • the piezoelectric MEMS speaker includes at least one diaphragm and at least one border element adjacent to the diaphragm, the height of the border element is not higher than the height of the diaphragm, and the edge of the border element is in contact with the free end of the diaphragm. At least one side is parallel.
  • the size of the fixed end of the diaphragm is smaller than the size of the free end.
  • the diaphragm includes: a vertically stacked structural layer, a bottom electrode layer, a piezoelectric layer, and a top electrode layer; or, a vertically stacked bottom electrode layer, alternately arranged N piezoelectric layers and N-1 middle The electrode layer, and the top electrode layer, wherein N is a positive integer greater than 1.
  • a base is also included, and the boundary element is composed of a part of the base, and the material of the boundary element is silicon.
  • the fixed end of the diaphragm is connected to the supporting layer of the diaphragm, and the material of the supporting layer of the diaphragm is silicon.
  • the second aspect of the present invention proposes a design method for a piezoelectric MEMS speaker, which is characterized in that it includes: setting N diaphragms adjacent to each other, the structures of N diaphragms adjacent to each other are asymmetrical, and N is greater than 1 A positive integer, there is a first gap between adjacent diaphragms; and/or, at least one diaphragm and at least one boundary element adjacent to the diaphragm are provided, the height of the boundary element is not higher than the height of the diaphragm, and the diaphragm There is a second gap between the membrane and the boundary element; the size of the first gap and/or the second gap is set to meet the preset conditions, so that when the diaphragm vibrates at the mechanical resonance point, an acoustic short circuit occurs, and when the diaphragm is stationary, no Acoustic short circuit occurs.
  • the height of the boundary element is lower than the height of the diaphragm.
  • the preset condition includes: when the diaphragm vibrates at the mechanical resonance point, the pitch of the first gap and/or the second gap is greater than 20 ⁇ m, or the area of the first gap and/or the second gap is larger than the speaker area 5%; and when the diaphragm is stationary, the pitch of the first gap and/or the second gap is less than 20 ⁇ m, or to, the area of the first gap and/or the second gap is less than 5% of the speaker area.
  • the structural asymmetry of the N adjacent diaphragms includes that one or more of the N adjacent diaphragms are different in shape, size, and thickness of the diaphragm.
  • the diaphragm design process includes the following steps: determine the polygonal diaphragm area and the The eccentric point inside the polygonal diaphragm area connects the vertex angle of the polygonal diaphragm area with the eccentric point, thereby dividing the polygonal diaphragm area into N diaphragms adjacent to each other, and setting the fixed end of each diaphragm on the polygonal diaphragm area on the contour of the membrane area, and use the eccentric point as the free end of N diaphragms at the same time; and/or, determine the total area of the nested diaphragm, and then divide the total area of the nested diaphragm into N-level nested design For the N adjacent diaphragms, at least one edge on the outline of the total area of
  • At least two diaphragms have different shapes.
  • the device layout design process includes the following steps: The edge of the boundary element is designed to be parallel to at least one side of the free end of the diaphragm.
  • the size of the fixed end of the diaphragm is smaller than the size of the free end.
  • the diaphragm includes: a vertically stacked structural layer, a bottom electrode layer, a piezoelectric layer, and a top electrode layer; or, a vertically stacked bottom electrode layer, alternately arranged N piezoelectric layers and N-1 middle The electrode layer, and the top electrode layer, wherein N is a positive integer greater than 1.
  • it further includes: setting the boundary element to be composed of a part of the substrate of the piezoelectric MEMS speaker, and the material of the boundary element is silicon.
  • it further includes: setting a diaphragm support layer to provide support for the fixed end of the diaphragm, and the material of the diaphragm support layer is silicon.
  • the third aspect of the present invention provides an electronic device, which is characterized by comprising the piezoelectric MEMS speaker according to any one of claims 1-11.
  • the adaptive acoustic short-circuit structure is realized through the asymmetric design of the loudspeaker diaphragm structure, or the adaptive acoustic short-circuit structure is realized through the height of the boundary element being lower than or equal to the height of the diaphragm, which can reduce the sound pressure level at the resonance spikes and increase bandwidth.
  • Fig. 1 is the top view of the piezoelectric MEMS speaker of the first embodiment of the present invention
  • FIG. 2 to 5 are cross-sectional schematic diagrams of different vibration modes of two adjacent diaphragms at the resonance frequency of the embodiment shown in FIG. 1;
  • Fig. 6 is the top view of the piezoelectric MEMS loudspeaker of traditional structure
  • Fig. 7 is a comparison diagram of the frequency response curves of the piezoelectric MEMS speaker shown in Fig. 1 and the piezoelectric MEMS speaker shown in Fig. 6;
  • Fig. 8 to Fig. 10 have respectively shown the vibrating membrane situation of the piezoelectric MEMS loudspeaker shown in Fig. 1 at three different frequency points;
  • FIG. 11 is a top view of a piezoelectric MEMS speaker according to a second embodiment of the present invention.
  • FIG. 12 is a top view of a piezoelectric MEMS speaker according to a third embodiment of the present invention.
  • FIG. 13 is a top view of a piezoelectric MEMS speaker according to a fourth embodiment of the present invention.
  • FIG. 14 is a top view of a piezoelectric MEMS speaker according to a fifth embodiment of the present invention.
  • FIG. 15 is a top view of a piezoelectric MEMS speaker according to a sixth embodiment of the present invention.
  • FIG. 16 is a top view of a piezoelectric MEMS speaker according to a seventh embodiment of the present invention.
  • Fig. 17 to Fig. 19 have respectively shown the cross-sectional schematic diagrams of different vibration modes of the diaphragm in the piezoelectric MEMS speaker shown in Fig. 16;
  • FIG. 20 is a top view of a piezoelectric MEMS speaker according to an eighth embodiment of the present invention.
  • FIG. 21 is a top view of a piezoelectric MEMS speaker according to a ninth embodiment of the present invention.
  • FIG. 22 is a top view of a piezoelectric MEMS speaker according to a tenth embodiment of the present invention.
  • FIG. 23 is a top view of a piezoelectric MEMS speaker according to an eleventh embodiment of the present invention.
  • FIG. 24 is a top view of a piezoelectric MEMS speaker according to a twelfth embodiment of the present invention.
  • 25 is a top view of a piezoelectric MEMS speaker according to a thirteenth embodiment of the present invention.
  • 26 is a top view of a piezoelectric MEMS speaker according to a fourteenth embodiment of the present invention.
  • FIG. 27 is a schematic cross-sectional diagram of a diaphragm of a piezoelectric MEMS speaker according to an embodiment of the present invention.
  • FIG. 28 is a schematic cross-sectional diagram of a diaphragm of a piezoelectric MEMS speaker according to another embodiment of the present invention.
  • the present invention proposes the design of adaptive acoustic short circuit, its basic principle is: there is a gap between the diaphragm and other adjacent structures (which can be another diaphragm or boundary element), at the mechanical resonance frequency due to The gap is large, causing the acoustic cavity on both sides of the speaker diaphragm to produce an acoustic short circuit, thereby greatly reducing the sound pressure level peak at the resonant frequency; sound pressure levels in these frequency bands.
  • This situation is collectively referred to as an adaptive acoustic short circuit.
  • the height of the boundary element is lower than or equal to the height of the diaphragm, and the gap between the diaphragm and the boundary element becomes larger during the vibration process near the resonance point, resulting in an acoustic short circuit, thereby reducing the frequency sound pressure level at .
  • the piezoelectric MEMS loudspeaker includes N diaphragms adjacent to each other, the structures of the N diaphragms adjacent to each other are asymmetrical, N is a positive integer greater than 1, and there is a gap between the adjacent diaphragms.
  • the size of the first gap and/or the second gap satisfies a preset condition so that the acoustic short circuit phenomenon occurs when the diaphragm vibrates, and the acoustic short circuit phenomenon does not occur when the diaphragm is stationary.
  • the height of the boundary element is lower than the height of the diaphragm. Due to the existence of the height difference, it can be guaranteed that the distance d between the boundary element and the diaphragm must be greater than zero.
  • the structural asymmetry of the N adjacent diaphragms specifically means that one or more of the N adjacent diaphragms are different in diaphragm shape, diaphragm size, and diaphragm thickness.
  • the preset condition may include: when the diaphragm vibrates near the resonance point, the pitch of the first gap and/or the second gap is larger than 20 ⁇ m, or the area of the first gap and/or the second gap is larger than 5% of the speaker area.
  • the distance between the first gap and/or the second gap is less than 20 ⁇ m, or, the first gap and/or The area of the second gap is less than 5% of the area of the loudspeaker, so that the sound pressure of the loudspeaker at the non-resonant point will not deteriorate.
  • the gap area refers to the gap width d multiplied by the gap length, and the speaker area refers to the area of the speaker as a whole (including the diaphragm and the gap) on the horizontal plane.
  • FIG. 1 is a layout of a piezoelectric MEMS speaker according to a first embodiment of the present invention. It should be noted that the revised figure only shows the diaphragm and surrounding structures, and other parts have been omitted. Similar processing is also done for the subsequent drawings, so no more details will be given.
  • the piezoelectric MEMS loudspeaker shown in Fig. 1 comprises four asymmetric diaphragms of 10, 11, 12 and 13, 14 is the gap between adjacent diaphragms, and 23 is a diaphragm supporting layer (for mechanical support or fixing diaphragm edge). Since the shapes of the four diaphragms 10 to 13 are different, the piezoelectric MEMS speaker generates four resonance frequencies.
  • each diaphragm Since the vibration mode or direction of each diaphragm is different, at a frequency point, one diaphragm will have a larger vibration amplitude and the other diaphragm will have a smaller vibration amplitude, or the two diaphragms will vibrate in opposite directions. In both cases, the gap spacing becomes larger, creating an acoustic short circuit that reduces the sound pressure level at that frequency.
  • FIG. 2 to 5 are schematic diagrams of different vibration modes of two adjacent diaphragms at the resonance frequency of the embodiment shown in Fig. 1, wherein 11 and 13 are two opposite diaphragms, 23 is a diaphragm support layer, d is the gap distance between the tips of the two diaphragms.
  • Figure 2 corresponds to the case where the vibration directions of the two diaphragms are opposite
  • Figure 3 corresponds to the case where one diaphragm has a large amplitude and the other diaphragm does not vibrate
  • Figure 4 corresponds to the case where the two diaphragms vibrate in the same direction, but the amplitude difference is relatively large Large case
  • Figure 5 corresponds to the case of single-ended diaphragm vibration.
  • the condition of the adaptive acoustic short circuit is satisfied between the diaphragms, so the sound pressure peak can be reduced; when the frequency is far below the resonance frequency, the condition of the adaptive acoustic short circuit is not satisfied between the diaphragms, so it can prevent Acoustic short circuit, sound pressure does not deteriorate.
  • N is a positive integer greater than or equal to 1
  • adjacent diaphragms are spliced into a polygonal diaphragm area, and the fixed end of each diaphragm is located on the contour of the polygonal diaphragm area, and The free ends of the individual diaphragms have a common point, which is an eccentric point inside the polygonal diaphragm area.
  • N adjacent and asymmetric diaphragms can be designed in the following way: first determine the N-gon diaphragm area and the internal eccentric point, and then provide N polygonal vertexes to the eccentric point The gap, which can divide the diaphragm area into N asymmetric diaphragms.
  • Fig. 6 is a layout of a piezoelectric MEMS speaker with a traditional structure, which has four symmetrically arranged diaphragms with the same shape, size and thickness.
  • FIG. 7 is a graph comparing the frequency response curves of the piezoelectric MEMS speaker according to the embodiment of the present invention shown in FIG. 1 and the traditional piezoelectric MEMS speaker shown in FIG. 6 . It can be clearly seen from the results that the traditional loudspeaker shown in Figure 6 has a strong symmetry of the four diaphragms, and its sound pressure level frequency response curve is shown by the dotted line in Figure 7. It can be seen that there is an unacceptable 155dB at 7kHz Sound pressure level spikes. However, the high-amplitude peak of the piezoelectric MEMS speaker of the embodiment of the present invention shown in FIG. 1 is obviously reduced, and the bandwidth is also increased.
  • Fig. 8 to Fig. 10 have respectively shown the diaphragm vibration situation of the piezoelectric MEMS loudspeaker of the adaptive acoustic short-circuit structure of the embodiment of the present invention shown in Fig. 1 at three different frequency points.
  • the distance between the membranes becomes larger, resulting in an acoustic short circuit phenomenon.
  • the displacement of adjacent diaphragms near the resonance frequency is the same, resulting in too small spacing between the diaphragms, no acoustic short circuit, and therefore a sound pressure peak.
  • FIG. 11 is a layout of a piezoelectric MEMS speaker according to a second embodiment of the present invention, in which a nested cantilever beam structure design is adopted.
  • 10_1 , 10_2 , and 10_3 are three sequentially nested diaphragms fixed at the same end, 22 is a boundary element, 23 is a diaphragm supporting layer, and 14 is a gap between the diaphragms.
  • the three diaphragms are of different sizes and therefore have different resonant frequencies for adaptive acoustic short-circuiting.
  • the height of the boundary element 22 is not higher than the height of the diaphragms 10_1 , 10_2 , 10_3 .
  • the layout of the piezoelectric MEMS speaker of the third embodiment of the present invention is obtained as shown in FIG. 12 .
  • 10i, 11i, 12i, and 13i are inner diaphragms, which are used for high-frequency parts;
  • 10a, 11a, 12a, and 13a are outer diaphragms, which are used for low-frequency parts;
  • 22 is boundary elements,
  • 23 is diaphragm supporting layers, and 14 is The gap between the diaphragms.
  • FIG. 13 is a layout of a piezoelectric MEMS speaker according to a fourth embodiment of the present invention
  • FIG. 14 is a layout of a piezoelectric MEMS speaker according to a fifth embodiment of the present invention.
  • the resonant frequency of the diaphragm will also change. For example, comparing the fourth embodiment shown in FIG. 13 with the fifth embodiment shown in FIG. 14 , the resonant frequencies are different due to the different shapes of the diaphragm 10_1 and the diaphragm 10_2 .
  • FIG. 15 is a layout of a piezoelectric MEMS speaker according to a sixth embodiment of the present invention. This embodiment is based on the traditional symmetrical four-diaphragm piezoelectric MEMS speaker, adding a nested design of diaphragm structures with different shapes, which will also cause different resonance frequencies for each diaphragm, so as to meet the requirements of adaptive acoustics. Shorted hardware condition.
  • FIG. 16 is a layout diagram of a piezoelectric MEMS speaker according to a seventh embodiment of the present invention.
  • 10 and 11 are two triangular diaphragms
  • 14 is the gap between the diaphragm and the diaphragm and the boundary element
  • 22 is the boundary element
  • 23 is the diaphragm support layer.
  • This embodiment demonstrates the structure of using the height difference between the boundary element and the diaphragm to realize an adaptive acoustic short circuit, which can make the gap between the diaphragm and the boundary element larger at and near the resonance frequency, resulting in the phenomenon of acoustic short circuit , thereby reducing the sound pressure level at that frequency.
  • the vibration mode of the diaphragm is shown in Figures 17 to 19, where 13 is the diaphragm, 22 is the boundary element, 23 is the supporting layer of the diaphragm, and d is the distance between the diaphragm and the boundary element. distance between.
  • Figure 17 corresponds to the case where the height of the boundary element is the same as the height of the diaphragm
  • Figure 18 corresponds to the case where the boundary element is lower than the diaphragm by d0
  • Figure 19 corresponds to the case where a part of the diaphragm is above the boundary element.
  • the distance d When the diaphragm is stationary, the distance d is small, and the acoustic short circuit condition is not reached; when the diaphragm vibrates upward or downward, the distance d becomes larger to achieve the acoustic short circuit condition, realizing an adaptive acoustic short circuit.
  • the present invention also proposes other piezoelectric MEMS speakers with adaptive acoustic short-circuit structure, as shown in FIGS. 20 to 22 .
  • FIG. 20 is a layout of a piezoelectric MEMS speaker according to an eighth embodiment of the present invention.
  • the height difference between the diaphragms 10 , 11 , 13 and between the diaphragm and the boundary element 22 is used to realize the acoustic short circuit structure.
  • FIG. 21 is a layout of a piezoelectric MEMS speaker according to a ninth embodiment of the present invention.
  • the height difference between the diaphragms 10, 11 and the boundary elements 22 on both sides may cause an acoustic short circuit, and the difference between the two diaphragms may also cause an acoustic short circuit due to different resonance frequencies.
  • FIG. 22 is a layout diagram of a piezoelectric MEMS speaker according to a tenth embodiment of the present invention.
  • the four diaphragms are only fixed in the middle, and the height difference between the periphery of the diaphragm and the boundary element 22 can realize an acoustic short circuit.
  • the size of the fixed end is larger than that of the free end.
  • the size of the free end of the diaphragm can be set to be larger than the fixed end, so that more air can be pushed to achieve the purpose of increasing the sound pressure level.
  • 10, 11, 12, and 13 are diaphragms
  • 14 is a gap
  • 22 is a boundary element
  • 23 is a diaphragm support layer.
  • FIG. 23 is a layout of a piezoelectric MEMS speaker according to an eleventh embodiment of the present invention.
  • the two diaphragms 10 and 11 have the fixed end on the short side and the free end on the long side. There is a height difference between the diaphragm and the surrounding boundary elements, which may cause an acoustic short circuit.
  • FIG. 24 is a layout of a piezoelectric MEMS speaker according to a twelfth embodiment of the present invention.
  • the loudspeaker in Figure 24 contains three diaphragms, and the working principle is the same as that in Figure 27.
  • FIG. 25 is a layout of a piezoelectric MEMS speaker according to a thirteenth embodiment of the present invention.
  • the traditional planar structure diaphragm is fixed around the periphery and fixed in the middle.
  • FIG. 26 is a layout of a piezoelectric MEMS speaker according to a fourteenth embodiment of the present invention.
  • Figure 26 adopts the asymmetric structure of the diaphragm, and the difference in resonance frequency and the height difference between the diaphragm and the boundary elements will cause acoustic short circuit at the same time.
  • a diaphragm in a piezoelectric MEMS speaker may include longitudinally stacked structural layers, a bottom electrode layer, a piezoelectric layer, and a top electrode layer.
  • 1 is the structural layer, and the material can be silicon, etc.
  • 2 is the piezoelectric layer, and the material can be AlN, PZT, ZnO, etc.
  • 3 is the top electrode layer and the bottom electrode layer, the material Metals such as molybdenum, platinum, and gold may be used.
  • the diaphragm in the piezoelectric MEMS speaker of the embodiment of the present invention may also include vertically stacked bottom electrode layers, N piezoelectric layers and N-1 middle electrode layers alternately arranged, and a top electrode layer, wherein N is greater than 1 positive integer of .
  • the piezoelectric layer 2 has two layers, and the electrode layer 3 (including the top electrode layer, the middle electrode layer, and the top electrode layer) has three layers. In this case the structural layer can be omitted.
  • the material of the boundary element and the diaphragm supporting layer is preferably silicon. Silicon materials have good mechanical properties and are readily available at low cost.
  • the design method of the piezoelectric MEMS speaker includes: setting N diaphragms adjacent to each other, the structures of the N diaphragms adjacent to each other are asymmetrical, N is a positive integer greater than 1, and they are adjacent to each other There is a first gap between the diaphragms; and/or, at least one diaphragm and at least one boundary element adjacent to the diaphragm are arranged, the height of the boundary element is not higher than the height of the diaphragm, and the distance between the diaphragm and the boundary element There is a second gap; the size of the first gap and/or the second gap is set to meet a preset condition, so that the acoustic short circuit phenomenon occurs when the diaphragm vibrates, and the acoustic short circuit phenomenon does not occur when the diaphragm is stationary.
  • the height of the boundary element is lower than the height of the diaphragm.
  • the preset conditions may include: when the diaphragm vibrates, the pitch of the first gap and/or the second gap is greater than 20 ⁇ m, or the area of the first gap and/or the second gap is greater than 5% of the area of the speaker; and, when the vibrating When the membrane is at rest, the pitch of the first gap and/or the second gap is less than 20 ⁇ m, or at least, the area of the first gap and/or the second gap is less than 5% of the loudspeaker area.
  • the structural asymmetry of the N adjacent diaphragms may include that one or more of the N adjacent diaphragms are different in shape, size, and thickness of the diaphragm.
  • the diaphragm design process may include the following steps: determine the polygonal diaphragm area and locate the polygonal diaphragm The eccentric point inside the area connects the vertex angle of the polygonal diaphragm area with the eccentric point, thereby dividing the polygonal diaphragm area into N diaphragms adjacent to each other, and setting the fixed end of each diaphragm at the center of the polygonal diaphragm area contour, and use the eccentric point as the free end of N diaphragms at the same time; and/or, determine the total area of the nested diaphragm, and then divide the total area of the nested diaphragm into N in N-level nested design For the diaphragms adjacent to each other, at least one side on the
  • At least two diaphragms have different shapes.
  • the device layout design process includes the following steps: designing the boundary element The edge is parallel to at least one side of the free end of the diaphragm.
  • the size of the fixed end of the diaphragm can be smaller than the size of the free end.
  • the diaphragm may include longitudinally stacked structural layers, a bottom electrode, a piezoelectric layer, and a top electrode.
  • the design method of the piezoelectric MEMS speaker may further include: setting the boundary element to be composed of a part of the substrate of the piezoelectric MEMS speaker, and the material of the boundary element is silicon.
  • the design method of the piezoelectric MEMS loudspeaker may further include: setting a diaphragm support layer to provide support for the fixed end of the diaphragm, and the material of the diaphragm support layer is silicon.
  • An electronic device may include any one of the piezoelectric MEMS speakers disclosed above.
  • the adaptive acoustic short-circuit structure is realized through the asymmetrical design of the speaker diaphragm structure, or the adaptive acoustic short-circuit structure is realized through the height of the boundary element being lower than or equal to the height of the diaphragm, which can reduce the acoustic resonance at the resonance. Voltage spikes are reduced and bandwidth is increased.

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Abstract

一种压电MEMS扬声器及其设计方法和电子设备。压电MEMS扬声器包括N个彼此相邻的振膜（10、11、12、13），N个彼此相邻的振膜（10、11、12、13）的结构不对称，N为大于1的正整数，彼此相邻的振膜（10、11、12、13）之间具有第一间隙（14），并且/或者，压电MEMS扬声器包括至少一个振膜（10-1、10-2、10-3）和至少一个临近振膜（10-1、10-2、10-3）的边界元件（22），边界元件（22）的高度不高于振膜（10-1、10-2、10-3）的高度，振膜（10-1、10-2、10-3）与边界元件（22）之间具有第二间隙（14），其中，第一间隙（14）和/或第二间隙（14）的尺寸满足预设条件，使得当振膜在机械谐振点振动时发生声短路现象，并且当振膜静止时不发生声短路现象。通过扬声器振膜结构不对称设计实现自适应声短路结构，或通过边界元件（22）的高度低于或等于振膜高度实现自适应声短路结构，能够降低谐振处的声压级尖峰，并且增大带宽。

Description

压电MEMS扬声器及其设计方法、电子设备 技术领域
本发明涉及MEMS技术领域，具体涉及一种压电MEMS扬声器及其设计方法，和电子设备。
背景技术
MEMS扬声器通常靠一个或多个执行器振膜带动空气振动，从而发出声音。传统的MEMS扬声器在谐振频率处的位移达到最大，这就导致扬声器在谐振频率处的声压级出现一个不可接受的高幅值尖峰，并且频域带宽较小，频响曲线恶化。
发明内容
有鉴于此，本发明提出一种压电MEMS扬声器及其设计方法、电子设备，能够自适应地发生声短路，降低谐振处的声压级尖峰并且增大带宽。
本发明第一方面提出一种压电MEMS扬声器，压电MEMS扬声器包括N个彼此相邻的振膜，N个彼此相邻的振膜的结构不对称，N为大于1的正整数，彼此相邻的振膜之间具有第一间隙，并且/或者，压电MEMS扬声器包括至少一个振膜和至少一个临近该振膜的边界元件，边界元件的高度不高于该振膜的高度，振膜与边界元件之间具有第二间隙，其中，第一间隙和/或第二间隙的尺寸满足预设条件，使得当振膜在机械谐振点振动时发生声短路现象，并且当振膜静止时不发生声短路现象。
可选地，边界元件的高度低于振膜的高度。
可选地，预设条件包括：当振膜在机械谐振点振动时，第一间隙和/或第二间隙的间隙尺寸大于20μm，或者，第一间隙和/或第二间隙的间隙 面积大于扬声器面积的5％；并且当振膜静止时，第一间隙和/或第二间隙的间隙尺寸小于20μm，或者，第一间隙和/或第二间隙的间隙面积小于扬声器面积的5％。
可选地，N个彼此相邻的振膜的结构不对称包括：N个彼此相邻的振膜的振膜形状、振膜尺寸、振膜厚度中一者或多者不相同。
可选地，压电MEMS扬声器包括N个彼此相邻的振膜，N个彼此相邻的振膜的结构不对称，并且振膜设计满足如下特征：N个彼此相邻的振膜拼接成多边形振膜区域，各个振膜的固定端位于多边形振膜区域的轮廓上，并且各个振膜的自由端具有同一个共同点，该共同点是多边形振膜区域内部的偏心点；并且/或者，N个彼此相邻的振膜呈N级嵌套式设计，其中，各级振膜的固定端共线。
可选地，N个彼此相邻的振膜呈N级嵌套式设计，并且其中至少两个振膜的形状不同。
可选地，在压电MEMS扬声器中包括至少一个振膜和至少一个临近该振膜的边界元件，边界元件的高度不高于该振膜的高度，并且边界元件的边缘与振膜的自由端的至少一条边平行。
可选地，振膜的固定端尺寸小于自由端的尺寸。
可选地，振膜包括：纵向堆叠的结构层、底电极层、一个压电层和顶电极层；或者，纵向堆叠的底电极层、交替设置的N个压电层与N-1个中间电极层、以及顶电极层，其中N为大于1的正整数。
可选地，还包括：基底，并且边界元件由基底的一部分组成，边界元件的材料为硅。
可选地，振膜的固定端与振膜支撑层连接，振膜支撑层的材料为硅。
本发明第二方面提出一种压电MEMS扬声器的设计方法，其特征在于，包括：设置N个彼此相邻的振膜，N个彼此相邻的振膜的结构不对称，N为大于1的正整数，彼此相邻的振膜之间具有第一间隙；并且/或者，设置至少一个振膜和至少一个临近该振膜的边界元件，边界元件的高度不高于该振膜的高度，振膜与边界元件之间具有第二间隙；设置第一间隙和/或第二间隙的尺寸满足预设条件，使得当振膜在机械谐振点振动时发生声短路现象，并且当振膜静止时不发生声短路现象。
可选地，边界元件的高度低于振膜的高度。
可选地，预设条件包括：当振膜在机械谐振点振动时，第一间隙和/或第二间隙的间距大于20μm，或者，第一间隙和/或第二间隙的面积大于扬声器面积的5％；并且当振膜静止时，第一间隙和/或第二间隙的间距小于20μm，或至，第一间隙和/或第二间隙的面积小于扬声器面积的5％。
可选地，N个彼此相邻的振膜的结构不对称包括：N个彼此相邻的振膜的振膜形状、振膜尺寸、振膜厚度中一者或多者不相同。
可选地，在压电MEMS扬声器包括N个彼此相邻的振膜，N个彼此相邻的振膜的结构不对称的情况下振膜设计过程包括如下步骤：确定多边形振膜区域以及位于该多边形振膜区域内部的偏心点，将多边形振膜区域的顶角与偏心点相连，从而将多边形振膜区域划分为N个彼此相邻的振膜，将各个振膜的固定端设置在多边形振膜区域的轮廓上，并且将该偏心点同时作为N个振膜的自由端；并且/或者，确定嵌套振膜总区域，然后将嵌套振膜总区域划分为呈N级嵌套式设计的N个彼此相邻的振膜，将嵌套振膜总区域的轮廓上的至少一条边作为N个彼此相邻的振膜的固定端。
可选地，N级嵌套式设计的N个彼此相邻的振膜当中，至少两个振膜的形状不同。
可选地，在压电MEMS扬声器中包括至少一个振膜和至少一个临近该振膜的边界元件，边界元件的高度不高于该振膜的高度的情况下，器件版图设计过程包括如下步骤：设计边界元件的边缘与振膜的自由端的至少一条边平行。
可选地，振膜的固定端尺寸小于自由端的尺寸。
可选地，振膜包括：纵向堆叠的结构层、底电极层、一个压电层和顶电极层；或者，纵向堆叠的底电极层、交替设置的N个压电层与N-1个中间电极层、以及顶电极层，其中N为大于1的正整数。
可选地，还包括：设置边界元件由压电MEMS扬声器的基底的一部分组成，边界元件的材料为硅。
可选地，还包括：设置振膜支撑层为振膜的固定端提供支撑，振膜支撑层的材料为硅。
本发明第三方面提出一种电子设备，其特征在于，包括权利要求1至11中任一项的压电MEMS扬声器。
根据本发明的技术方案，通过扬声器振膜结构不对称设计实现自适应声短路结构，或通过边界元件的高度低于或等于振膜高度实现自适应声短路结构，能够降低谐振处的声压级尖峰，并且增大带宽。
附图说明
为了说明而非限制的目的，现在将根据本发明的优选实施例、特别是参考附图来描述本发明，其中：
图1为本发明第一实施例的压电MEMS扬声器的俯视图；
图2至图5为图1所示实施例的两个相邻振膜在谐振频率处的不同振动模式截面示意图；
图6为传统结构的压电MEMS扬声器的俯视图；
图7为图1所示压电MEMS扬声器与图6所示压电MEMS扬声器的频响曲线对比图；
图8至图10分别展示了图1所示的压电MEMS扬声器在三个不同频率点处的振膜振动情况；
图11为本发明第二实施例的压电MEMS扬声器的俯视图；
图12为本发明第三实施例的压电MEMS扬声器的俯视图；
图13为本发明第四实施例的压电MEMS扬声器的俯视图；
图14为本发明第五实施例的压电MEMS扬声器的俯视图；
图15为本发明第六实施例的压电MEMS扬声器的俯视图；
图16为本发明第七实施例的压电MEMS扬声器的俯视图；
图17至图19分别展示了图16所示的压电MEMS扬声器中振膜的不同振动模式截面示意图；
图20为本发明第八实施例的压电MEMS扬声器的俯视图；
图21为本发明第九实施例的压电MEMS扬声器的俯视图；
图22为本发明第十实施例的压电MEMS扬声器的俯视图；
图23为本发明第十一实施例的压电MEMS扬声器的俯视图；
图24为本发明第十二实施例的压电MEMS扬声器的俯视图；
图25为本发明第十三实施例的压电MEMS扬声器的俯视图；
图26为本发明第十四实施例的压电MEMS扬声器的俯视图；
图27为本发明实施方式的压电MEMS扬声器的振膜截面示意图；
图28为本发明另一实施方式的压电MEMS扬声器的振膜截面示意图。
具体实施方式
为了解决这个问题，本发明提出了自适应声短路的设计，其基本原理是：振膜与其他相邻结构(可以是另一振膜或者边界元件)之间具有间隙， 在机械谐振频率时由于该间隙较大，引起扬声器振膜两侧的声腔产生声短路，从而大幅降低谐振频率处的声压级尖峰；在激励频率远离谐振频率时，由于间隙较小未达到声短路的条件，因此保证了这些频段的声压级。将这种情况综合地称为自适应声短路。
实现自适应声短路的手段主要包括两种：一，利用不对称振膜结构(如尺寸或形状不同)，使至少有两个振膜的机械谐振频率不同，振膜会在不同的频率点起振，这就导致振膜在振动的过程中，相邻振膜之间的间隙变大，导致声短路现象，从而降低谐振频率处的声压级；同时扬声器存在多个谐振频率，这也会将传统平面MEMS扬声器在一个谐振频率处的能量分到这几个谐振频率处，从而实现了带宽的增加。二，利用边界元件的高度低于或等于振膜的高度，也可以使得振膜在谐振点附近的振动过程中，与边界元件之间的间隙变大，导致声短路的现象，从而降低该频率处的声压级。
下面结合实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明的一部分实施例，而并不是全部的实施例。基于本发明中的实施例，本领域普通技术人员所获得的所有其他实施例，都属于本发明保护的范围。
根据本发明实施方式的压电MEMS扬声器包括N个彼此相邻的振膜，N个彼此相邻的振膜的结构不对称，N为大于1的正整数，彼此相邻的振膜之间具有第一间隙；并且/或者，包括至少一个振膜和至少一个临近该振膜的边界元件，边界元件的高度不高于该振膜的高度，振膜与边界元件之间具有第二间隙。其中第一间隙和/或第二间隙的尺寸满足预设条件使得当振膜振动时发生声短路现象，并且当振膜静止时不发生声短路现象。
优选地，边界元件的高度低于振膜的高度。由于存在高度差，可以保证边界元件与振膜之间的间距d必然大于零。
其中，N个彼此相邻的振膜的结构不对称具体是指：N个彼此相邻的振膜的振膜形状、振膜尺寸、振膜厚度中一者或多者不相同。其中，预设条件可以包括：当振膜在谐振点附近振动时，第一间隙和/或第二间隙的间距大于20μm，或者，第一间隙和/或第二间隙的面积大于扬声器面积的5％，这样能够使扬声器在谐振点附近振动时发生声短路，降低声压尖峰；并且当振膜静止时，第一间隙和/或第二间隙的间距小于20μm，或者，第一间隙和/或第二间隙的面积小于扬声器面积的5％，这样能够使扬声器在非谐振点处的声压不发生恶化。其中间隙面积指间隙宽度d乘间隙长度，扬声器面积指扬声器整体(包括振膜和间隙)在水平面的面积。
图1为本发明第一实施例的压电MEMS扬声器的版图。需要说明的是改图仅显示振膜及周边结构，其他部分已省略。后面多幅附图也做类似处理，不再赘述。图1所示的压电MEMS扬声器包括10、11、12和13四个不对称振膜，14为相邻振膜之间的间隙，23为振膜支撑层(用于机械支撑或固定振膜边缘)。由于四个振膜10至13的形状各不不同，该压电MEMS扬声器会产生四个谐振频率。由于每个振膜的振动模式或方向不同，在一个频率点会产生一个振膜振幅较大、另一个振膜振幅较小，或者产生两个振膜振动方向相反的情况。这两种情况都会使间隙间距变大，产生声短路现象，从而降低该频率处的声压级。
图2至图5为图1所示实施例的两个相邻振膜在谐振频率处的不同振动模式示意图，其中11与13为两个位置相对的振膜，23为振膜支撑层，d为两个振膜尖端的间隙间距。具体地：图2对应两个振膜振动方向相反的情况；图3对应一个振膜振幅较大，另一个振膜不振动的情况；图4对应两个振膜振动方向相同，但振幅相差较大的情况；图5对应单端振膜振动的情况。当接近谐振频率时，振膜之间满足自适应声短路的条件，因此能够降低声压尖峰；当频率远低于谐振频率时，振膜之间不满足自适应声短路的条件，因此能够防止声短路，声压不发生恶化。
需要之处的是，四振膜中只要至少有其中的两个谐振频率不同，即可 发生自适应声短路。谐振频率不同的实现方式有多种，如振膜之间的形状不同、尺寸不同、厚度不同等。这里仅展示了四个振膜的情况，还可以根据需要灵活设计两个振膜、三个振膜以及更多个振膜。这类实施例中，可以视作N个(N为大于等于1的正整数)彼此相邻的振膜拼接成多边形振膜区域，各个振膜的固定端位于多边形振膜区域的轮廓上，并且各个振膜的自由端具有同一个共同点，该共同点是多边形振膜区域内部的偏心点。换成设计方法的角度理解，可以通过以下方式设计出N个相邻且非对称的振膜：首先确定N边形的振膜区域以及内部的偏心点，然后提供N个从多边形顶点到偏心点的间隙，这样可以将振膜区域分割成了N个不对称的振膜。
图6为传统结构的压电MEMS扬声器的版图，它具有四个对称设置形状、尺寸以及厚度均相同的振膜。
图7为图1所示本发明实施方式的压电MEMS扬声器与图6所示传统的压电MEMS扬声器的频响曲线对比图。从结果中可以明显的看出，图6所示的传统的扬声器由于四个振膜对称性强，其声压级频响曲线如图7中虚线所示，可见在7kHz处出现不可接受的155dB声压级尖峰。而图1所示的本发明实施例的压电MEMS扬声器高幅值尖峰明显降低，带宽也有所增大。
图8至图10分别展示了图1所示的本发明实施方式的自适应声短路结构的压电MEMS扬声器在三个不同频率点处的振膜振动情况，相邻振膜振动方向相反造成振膜之间间距变大，导致声短路现象。而传统结构扬声器振膜由于不同振膜的形状或尺寸相同，在谐振频率附近相邻振膜位移相同，导致振膜之间的间距过小，并未出现声短路，因此出现声压尖峰。
图11为本发明第二实施例的压电MEMS扬声器的版图，该实施例中采用了嵌套式悬臂梁结构设计。如图11所示，其中10_1、10_2、10_3为同一端固定的三个依次嵌套的振膜，22为边界元件，23为振膜支撑层， 14为振膜之间的间隙。三个振膜的尺寸不同，因此谐振频率各不相同，以实现自适应声短路。边界元件22的高度不高于振膜10_1、10_2、10_3的高度。
将图1和图11两个实施例的设计思路综合，即将嵌套式设计加入到不对称振膜中，得到如图12所示的本发明第三实施例的压电MEMS扬声器的版图。其中10i、11i、12i、13i为内振膜，用于高频部分；10a、11a、12a、13a为外振膜，用于低频部分；22为边界元件，23为振膜支撑层，14为振膜之间的间隙。
图13为本发明第四实施例的压电MEMS扬声器的版图，图14为本发明第五实施例的压电MEMS扬声器的版图。改变嵌套式设计中振膜的形状，振膜的谐振频率也会发生改变。例如，图13所示的第四实施例和图14所示的第五实施例两者进行对比，由于振膜10_1以及振膜10_2的形状不同，导致谐振频率不同。
图15为本发明第六实施例的压电MEMS扬声器的版图。该实施例是在传统的对称四振膜的压电MEMS扬声器的基础上加入形状各异的嵌套式设计的振膜结构，也会使各个振膜出现不同的谐振频率，从而满足自适应声短路的硬件条件。
图16为本发明第七实施例的压电MEMS扬声器的版图。图16所示，其中，10和11为两个三角形振膜，14为振膜与振膜之间以及振膜与边界元件之间的间隙，22为边界元件，23为振膜支撑层。该实施例展示了利用边界元件与振膜的高度差实现自适应声短路的结构，可以使得振膜在谐振频率处以及谐振频率附近，与边界元件之间的间隙变大，导致声短路的现象，从而降低该频率处的声压级。
在图16所示的实施例中，振膜的振动模式如图17至图19所示，其中13为振膜，22为边界元件，23为振膜支撑层，d为振膜与边界元件之 间的距离。具体地：图17对应边界元件的高度和振膜高度相同的情况；图18对应边界元件比振膜低d0的情况；图19对应振膜一部分位于边界元件上方的情况。当振膜静止时，间距d较小，未达到声短路条件；当振膜向上或向下振动时，间距d变大以达到声短路条件，实现自适应声短路。
基于与图16所示的实施例的发明原理，本发明还提出了其他结构的自适应声短路结构的压电MEMS扬声器，具体如图20至图22所示。
图20为本发明第八实施例的压电MEMS扬声器的版图。该实施例中利用振膜10,11,13之间，以及振膜和边界元件22之间的高度差实现声短路结构。
图21为本发明第九实施例的压电MEMS扬声器的版图。图21中振膜10,11与两侧的边界元件22之间的高度差可以导致声短路，两个振膜中间因为谐振频率不同也会导致声短路。
图22为本发明第十实施例的压电MEMS扬声器的版图。图22中四个振膜仅中间固定，振膜的四周和边界元件22之间的高度差可以实现声短路。
上述几个实施例都是固定端的尺寸大于自由端的尺寸，为了提高声压级，可以设置振膜自由端的尺寸比固定端大，这样可以推动更多的空气，达到提高声压级的目的，具体如图23至图26所示，其中10,11,12,13为振膜，14为间隙，22为边界元件，23为振膜支撑层。
图23为本发明第十一实施例的压电MEMS扬声器的版图。图23中两个振膜10,11由短边为固定端，长边为自由端，振膜与四周的边界元件之间存在高度差，可以导致声短路。
图24为本发明第十二实施例的压电MEMS扬声器的版图。图24中 扬声器包含三个振膜，工作原理和图27相同。
图25为本发明第十三实施例的压电MEMS扬声器的版图。图25中将传统平面结构振膜在四周固定改为中间固定。
图26为本发明第十四实施例的压电MEMS扬声器的版图。图26采用振膜的不对称结构，谐振频率不同以及振膜与边界元件之间存在高度差同时都会导致声短路。
本发明实施方式的压电MEMS扬声器中的振膜可以包括纵向堆叠的结构层、底电极层、一个压电层和顶电极层。如图27所示的振膜截面示意图中，1为结构层，材料可以为硅等；2为压电层，材料可以为AlN、PZT、ZnO等；3为顶电极层和底电极层，材料可以为钼、铂、金等金属。
本发明实施方式的压电MEMS扬声器中的振膜也可以包括纵向堆叠的底电极层、交替设置的N个压电层与N-1个中间电极层，以及顶电极层，其中N为大于1的正整数。如图28所示的另一个实施例的振膜截面示意图中，压电层2有两层，电极层3(含顶电极层、中间电极层、顶电极层)有三层。这种情况下可以省略结构层。
本发明实施方式的压电MEMS扬声器中，边界元件和振膜支撑层的材料优选硅。硅材料具有良好的机械性能，且易于获得，成本较低。
根据本发明实施方式的压电MEMS扬声器的设计方法，包括：设置N个彼此相邻的振膜，N个彼此相邻的振膜的结构不对称，N为大于1的正整数，彼此相邻的振膜之间具有第一间隙；并且/或者，设置至少一个振膜和至少一个临近该振膜的边界元件，边界元件的高度不高于该振膜的高度，振膜与边界元件之间具有第二间隙；设置第一间隙和/或第二间隙的尺寸满足预设条件，使得当振膜振动时发生声短路现象，并且当振膜静止时不发生声短路现象。优选地，边界元件的高度低于振膜的高度。
预设条件可以包括：当振膜振动时，第一间隙和/或第二间隙的间距大于20μm，或者，第一间隙和/或第二间隙的面积大于扬声器面积的5％；并且，当振膜静止时，第一间隙和/或第二间隙的间距小于20μm，或至，第一间隙和/或第二间隙的面积小于扬声器面积的5％。
N个彼此相邻的振膜的结构不对称可以包括：N个彼此相邻的振膜的振膜形状、振膜尺寸、振膜厚度中一者或多者不相同。
在压电MEMS扬声器包括N个彼此相邻的振膜，N个彼此相邻的振膜的结构不对称的情况下振膜设计过程可以包括如下步骤：确定多边形振膜区域以及位于该多边形振膜区域内部的偏心点，将多边形振膜区域的顶角与偏心点相连，从而将多边形振膜区域划分为N个彼此相邻的振膜，将各个振膜的固定端设置在多边形振膜区域的轮廓上，并且将该偏心点同时作为N个振膜的自由端；并且/或者，确定嵌套振膜总区域，然后将嵌套振膜总区域划分为呈N级嵌套式设计的N个彼此相邻的振膜，将嵌套振膜总区域的轮廓上的至少一条边作为N个彼此相邻的振膜的固定端。
N级嵌套式设计的N个彼此相邻的振膜当中，至少两个振膜的形状不同。
在压电MEMS扬声器中包括至少一个振膜和至少一个临近该振膜的边界元件，边界元件的高度不高于该振膜的高度的情况下，器件版图设计过程包括如下步骤：设计边界元件的边缘与振膜的自由端的至少一条边平行。采用这样的设计时，器件处于静态时，狭缝各处宽度(即间距)是一致，易于加工实现；器件出于工作状态时，狭缝各处工作情况相同，易于实现声短路现象。
振膜的固定端尺寸可以小于自由端的尺寸。
振膜可以包括纵向堆叠的结构层、底电极、压电层和顶电极。
压电MEMS扬声器的设计方法，还可以包括：设置边界元件由压电MEMS扬声器的基底的一部分组成，边界元件的材料为硅。
压电MEMS扬声器的设计方法，还可以包括：设置振膜支撑层为振膜的固定端提供支撑，振膜支撑层的材料为硅。
根据本发明实施方式的电子设备，可以包括上文公开的任一项压电MEMS扬声器。
根据本发明实施方式的技术方案，通过扬声器振膜结构不对称设计实现自适应声短路结构，或通过边界元件的高度低于或等于振膜高度实现自适应声短路结构，能够降低谐振处的声压级尖峰，并且增大带宽。
上述具体实施方式，并不构成对本发明保护范围的限制。本领域技术人员应该明白的是，取决于设计要求和其他因素，可以发生各种各样的修改、组合、子组合和替代。任何在本发明的精神和原则之内所作的修改、等同替换和改进等，均应包含在本发明保护范围之内。

Claims (23)

  1. 一种压电MEMS扬声器，其特征在于，
    所述压电MEMS扬声器包括N个彼此相邻的振膜，所述N个彼此相邻的振膜的结构不对称，N为大于1的正整数，所述彼此相邻的振膜之间具有第一间隙，并且/或者，
    所述压电MEMS扬声器包括至少一个振膜和至少一个临近该振膜的边界元件，所述边界元件的高度不高于该振膜的高度，所述振膜与所述边界元件之间具有第二间隙，
    其中，所述第一间隙和/或所述第二间隙的尺寸满足预设条件，使得当所述振膜在机械谐振点振动时发生声短路现象，并且当所述振膜静止时不发生声短路现象。
  2. 根据权利要求1所述的压电MEMS扬声器，其特征在于，所述边界元件的高度低于所述振膜的高度。
  3. 根据权利要求1所述的压电MEMS扬声器，其特征在于，所述预设条件包括：
    当所述振膜在机械谐振点振动时，所述第一间隙和/或所述第二间隙的间隙尺寸大于20μm，或者，所述第一间隙和/或所述第二间隙的间隙面积大于扬声器面积的5％；并且
    当所述振膜静止时，所述第一间隙和/或所述第二间隙的间隙尺寸小于20μm，或者，所述第一间隙和/或所述第二间隙的间隙面积小于扬声器面积的5％。
  4. 根据权利要求1所述的压电MEMS扬声器，其特征在于，所述N个彼此相邻的振膜的结构不对称包括：所述N个彼此相邻的振膜的振膜形状、振膜尺寸、振膜厚度中一者或多者不相同。
  5. 根据权利要求1所述的压电MEMS扬声器，其特征在于，所述压电 MEMS扬声器包括N个彼此相邻的振膜，所述N个彼此相邻的振膜的结构不对称，并且振膜设计满足如下特征：
    所述N个彼此相邻的振膜拼接成多边形振膜区域，各个振膜的固定端位于所述多边形振膜区域的轮廓上，并且各个振膜的自由端具有同一个共同点，该共同点是所述多边形振膜区域内部的偏心点；并且/或者，
    所述N个彼此相邻的振膜呈N级嵌套式设计，其中，各级振膜的固定端共线。
  6. 根据权利要求5所述的压电MEMS扬声器，其特征在于，所述N个彼此相邻的振膜呈N级嵌套式设计，并且其中至少两个振膜的形状不同。
  7. 根据权利要求1所述的压电MEMS扬声器，其特征在于，在所述压电MEMS扬声器中包括至少一个振膜和至少一个临近该振膜的边界元件，所述边界元件的高度不高于该振膜的高度，并且所述边界元件的边缘与所述振膜的自由端的至少一条边平行。
  8. 根据权利要求7所述的压电MEMS扬声器，其特征在于，所述振膜的固定端尺寸小于自由端的尺寸。
  9. 根据权利要求1至8中任一项所述的压电MEMS扬声器，其特征在于，所述振膜包括：
    纵向堆叠的结构层、底电极层、一个压电层和顶电极层；或者，
    纵向堆叠的底电极层、交替设置的N个压电层与N-1个中间电极层、以及顶电极层，其中N为大于1的正整数。
  10. 根据权利要求1至8中任一项所述的压电MEMS扬声器，其特征在于，还包括：基底，并且所述边界元件由所述基底的一部分组成，所述边界元件的材料为硅。
  11. 根据权利要求1至8中任一项所述的压电MEMS扬声器，其特征在于，所述振膜的固定端与振膜支撑层连接，所述振膜支撑层的材料为硅。
  12. 一种压电MEMS扬声器的设计方法，其特征在于，包括：
    设置N个彼此相邻的振膜，所述N个彼此相邻的振膜的结构不对称，N为大于1的正整数，所述彼此相邻的振膜之间具有第一间隙；并且/或者，设置至少一个振膜和至少一个临近该振膜的边界元件，所述边界元件的高度不高于该振膜的高度，所述振膜与所述边界元件之间具有第二间隙；
    设置所述第一间隙和/或所述第二间隙的尺寸满足预设条件，使得当所述振膜在机械谐振点振动时发生声短路现象，并且当所述振膜静止时不发生声短路现象。
  13. 根据权利要求12所述的压电MEMS扬声器的设计方法，其特征在于，所述边界元件的高度低于所述振膜的高度。
  14. 根据权利要求12所述的压电MEMS扬声器的设计方法，其特征在于，所述预设条件包括：
    当所述振膜在机械谐振点振动时，所述第一间隙和/或所述第二间隙的间距大于20μm，或者，所述第一间隙和/或所述第二间隙的面积大于扬声器面积的5％；并且
    当所述振膜静止时，所述第一间隙和/或所述第二间隙的间距小于20μm，或至，所述第一间隙和/或所述第二间隙的面积小于扬声器面积的5％。
  15. 根据权利要求12所述的压电MEMS扬声器的设计方法，其特征在于，所述N个彼此相邻的振膜的结构不对称包括：所述N个彼此相邻的振膜的振膜形状、振膜尺寸、振膜厚度中一者或多者不相同。
  16. 根据权利要求12所述的压电MEMS扬声器的设计方法，其特征在 于，在所述压电MEMS扬声器包括N个彼此相邻的振膜，所述N个彼此相邻的振膜的结构不对称的情况下振膜设计过程包括如下步骤：
    确定多边形振膜区域以及位于该多边形振膜区域内部的偏心点，将所述多边形振膜区域的顶角与偏心点相连，从而将多边形振膜区域划分为N个彼此相邻的振膜，将各个振膜的固定端设置在所述多边形振膜区域的轮廓上，并且将该偏心点同时作为N个振膜的自由端；并且/或者，
    确定嵌套振膜总区域，然后将嵌套振膜总区域划分为呈N级嵌套式设计的N个彼此相邻的振膜，将所述嵌套振膜总区域的轮廓上的至少一条边作为所述N个彼此相邻的振膜的固定端。
  17. 根据权利要求16所述的压电MEMS扬声器的设计方法，其特征在于，所述N级嵌套式设计的N个彼此相邻的振膜当中，至少两个振膜的形状不同。
  18. 根据权利要求12所述的压电MEMS扬声器的设计方法，其特征在于，在所述压电MEMS扬声器中包括至少一个振膜和至少一个临近该振膜的边界元件，所述边界元件的高度不高于该振膜的高度的情况下，器件版图设计过程包括如下步骤：
    设计所述边界元件的边缘与所述振膜的自由端的至少一条边平行。
  19. 根据权利要求18所述的压电MEMS扬声器的设计方法，其特征在于，所述振膜的固定端尺寸小于自由端的尺寸。
  20. 根据权利要求12至19中任一项所述的压电MEMS扬声器的设计方法，其特征在于，所述振膜包括：
    纵向堆叠的结构层、底电极层、一个压电层和顶电极层；或者，
    纵向堆叠的底电极层、交替设置的N个压电层与N-1个中间电极层、以及顶电极层，其中N为大于1的正整数。
  21. 根据权利要求12至19中任一项所述的压电MEMS扬声器的设计 方法，其特征在于，还包括：设置所述边界元件由压电MEMS扬声器的基底的一部分组成，所述边界元件的材料为硅。
  22. 根据权利要求12至19中任一项所述的压电MEMS扬声器的设计方法，其特征在于，还包括：设置振膜支撑层为所述振膜的固定端提供支撑，所述振膜支撑层的材料为硅。
  23. 一种电子设备，其特征在于，包括权利要求1至11中任一项所述的压电MEMS扬声器。
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