WO2018191842A1 - 一种优化电容形状的mems压电换能器 - Google Patents

一种优化电容形状的mems压电换能器 Download PDF

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Publication number
WO2018191842A1
WO2018191842A1 PCT/CN2017/080744 CN2017080744W WO2018191842A1 WO 2018191842 A1 WO2018191842 A1 WO 2018191842A1 CN 2017080744 W CN2017080744 W CN 2017080744W WO 2018191842 A1 WO2018191842 A1 WO 2018191842A1
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Prior art keywords
capacitors
piezoelectric transducer
stress
capacitor
area
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PCT/CN2017/080744
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English (en)
French (fr)
Inventor
冯端
胡念楚
贾斌
Original Assignee
锐迪科微电子（上海）有限公司
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Application filed by 锐迪科微电子（上海）有限公司 filed Critical 锐迪科微电子（上海）有限公司
Priority to US16/605,863 priority Critical patent/US20210367135A1/en
Priority to PCT/CN2017/080744 priority patent/WO2018191842A1/zh
Priority to CN201780089773.3A priority patent/CN110546776B/zh
Publication of WO2018191842A1 publication Critical patent/WO2018191842A1/zh

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/87—Electrodes or interconnections, e.g. leads or terminals
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
    • H10N30/302—Sensors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/101—Piezoelectric or electrostrictive devices with electrical and mechanical input and output, e.g. having combined actuator and sensor parts
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
    • H10N30/304—Beam type
    • H10N30/306—Cantilevers

Definitions

  • the present application relates to a MEMS piezoelectric transducer, and more particularly, but not exclusively, to a piezoelectric transducer that converts vibrational energy, acoustic energy, and the like in the environment into electrical energy.
  • a transducer is a device that converts one form of energy into another, usually a signal in the form of one energy form.
  • These forms of energy include electrical energy, mechanical energy, electromagnetic energy, light energy, chemical energy, acoustic energy, and thermal energy.
  • a piezoelectric transducer is a device that converts mechanical energy and electrical energy by utilizing the piezoelectric effect of a piezoelectric material.
  • piezoelectric effects There are two types of piezoelectric effects: the positive piezoelectric effect is the conversion of mechanical energy into electrical energy, and the inverse piezoelectric effect is the conversion of electrical energy into mechanical energy.
  • a MEMS piezoelectric transducer is a micro-electromechanical transducer that can convert mechanical energy in the environment into electrical energy through a positive piezoelectric effect, and can also convert electrical energy into mechanical energy through an inverse piezoelectric effect.
  • MEMS piezoelectric transducers are commonly used in the following two aspects: (1) Energy harvesting, which converts weak vibrational energy in the environment into electrical energy, thereby driving the electrical device to work; (2) The sensor converts vibration or sound signals in the environment into electrical signals for output. Compared with the traditional capacitive transducing technology, the piezoelectric transducer has higher mechanical reliability, higher electromechanical transducing coefficient, and no need for DC bias.
  • MEMS piezoelectric transducers for converting mechanical energy into electrical energy is: loading a certain load on the piezoelectric transducer, and the piezoelectric material constituting the transducer will be polarized due to the positive piezoelectric effect. And produces positive and negative charges on its two opposite surfaces, and the magnitude of the charge is linearly related to the magnitude of the stress on the structure.
  • FIG. 1A is a side view of the rectangular cantilever beam, the rectangular cantilever beam is uniform in thickness, and the exemplary load is uniformly applied from the top to the bottom on the upper surface of the rectangular cantilever beam.
  • Figure 1B is a top plan view of the rectangular cantilever beam, i.e., the rectangular cantilever beam is viewed along the direction of action of the illustrated load.
  • 1A and 1B show the stress distribution on the rectangular cantilever beam under a fixed load. The darker the color, the greater the stress, and the lighter the color, the smaller the stress. It can be found that the rectangular cantilever beam has zero stress at a fixed support position. At the junction of the fixed support location and the suspended portion, the stress on the surface of the rectangular cantilever is greatest. Along the X-axis direction, as the distance from the fixed support position increases, the stress on the surface of the rectangular cantilever beam becomes smaller and smaller, exhibiting a state of stress gradient distribution. The stress is zero until the end of the rectangular cantilever beam is away from the fixed support position.
  • the magnitude of the charge generated by the positive piezoelectric effect is linearly related to the magnitude of the stress on the structure, so the gradient distribution of the stress causes the corresponding charge of the surface of the piezoelectric material to have corresponding fluctuations, thereby forming a charge in the electrode. Redistribution currents.
  • this is a piezoelectric transducer of uniform thickness rectangular cantilever structure.
  • Fig. 2A is a side view of a rectangular cantilever beam
  • Fig. 2B is a plan view of a rectangular cantilever beam.
  • the rectangular cantilever beam 100 has only one end fixedly supported on the side wall 110, and the remaining portions are suspended.
  • the rectangular cantilever beam 100 includes a piezoelectric film layer 111 and a support layer 112.
  • An upper electrode 113A is provided on the upper surface of the piezoelectric film layer 111.
  • a lower electrode 113B is provided on the lower surface of the piezoelectric film layer 111.
  • the upper electrode 113A and the lower electrode 113B substantially cover the entire areas of the upper surface and the lower surface of the piezoelectric film layer 111, respectively, and constitute the only capacitance of the piezoelectric transducer.
  • the support layer 112 is located below the piezoelectric film layer 111 for supporting the piezoelectric film layer 111 and the electrodes of the upper and lower surfaces thereof.
  • the charge flows from the region where the stress of the rectangular cantilever beam 100 is large to the region where the stress is small, and the flow redistribution of the charge is formed.
  • This flow of charge can adversely affect the output performance of the piezoelectric transducer, such as reducing the output power of the vibration energy harvester, reducing the sensitivity of the sensor, and reducing the signal-to-noise ratio (S NR) of the sensor.
  • FIG. 3A and FIG. 3B is another piezoelectric transducer of uniform thickness rectangular cantilever structure.
  • . 3A is a side view of a rectangular cantilever beam
  • FIG. 3B is a top view of a rectangular cantilever beam.
  • the rectangular cantilever beam 100 has only one end fixedly supported on the side wall 110, and the remaining portions are suspended.
  • the rectangular cantilever beam 100 includes a piezoelectric film layer 111 and a support layer 112.
  • An upper electrode 114A is provided on the upper surface of the piezoelectric film layer 111.
  • a lower electrode 114B is provided on the lower surface of the piezoelectric film layer 111.
  • the upper electrode 114A and the lower electrode 114B cover only a partial region of the upper surface and the lower surface of the piezoelectric film layer 111, and preferably cover a region where the surface stress of the rectangular cantilever beam 100 is large, thereby constituting the only capacitance of the piezoelectric transducer.
  • the support layer 112 is located below the piezoelectric film layer 111 for supporting the piezoelectric film layer 111 and the electrodes of the upper and lower surfaces thereof. Since the coverage area of the effective capacitor is reduced so that it covers only the region of higher stress, the influence of the redistribution of charge flow on the output of the piezoelectric transducer can be reduced.
  • this scheme also has shortcomings, mainly including: (1) wasting the structural area, and directly discarding the transduction of the portion of the structure where the stress is small; (2) Compared with the case where the electrode is completely covered, the electrode partially covers the The capacitance of the capacitor is small. Therefore, this solution is still not the best solution to the stress gradient distribution, and can only partially improve the output performance of the piezoelectric transducer.
  • the technical problem to be solved by the present application is: When a MEMS piezoelectric transducer is loaded with a certain load, a stress distribution unevenness may occur, resulting in a charge generated by a positive piezoelectric effect from a region with a large stress to a stress. Smaller areas flow and redistribute the flow of charge, which adversely affects the output performance of the piezoelectric transducer.
  • the surface of the MEMS piezoelectric transducer that optimizes the capacitance shape of the present application is covered with m sets of capacitances, and m is a natural number of ⁇ 2.
  • Each set of capacitors either contains only one capacitor or consists of multiple capacitors.
  • the same set of capacitors are connected in series and / or in parallel; different sets of capacitors are connected in series.
  • the capacitance is preferentially set in the region where the stress of the MEMS piezoelectric transducer is the largest and the larger, and at least two sets of capacitances cover the two different stress ranges of the surface of the MEMS piezoelectric transducer, and at least two sets of capacitances Performing the series connection helps to reduce the flow redistribution of the charge on the electrodes.
  • the areas of different sets of capacitors are substantially the same, and the capacitors having substantially the same area have substantially the same capacitance value. Since the different sets of capacitors are connected in series, the capacitors participating in the series have a substantially phase The same capacitance value will minimize the output impedance of the piezoelectric transducer.
  • the sum of all the capacitances substantially covers the entire surface of the piezoelectric transducer. If the gap between the capacitors and the small area above the fixed position of the piezoelectric transducer are zero, the surface of the piezoelectric transducer is substantially covered by the capacitor. This makes full use of the stress in almost all areas of the piezoelectric transducer to generate electrical signals.
  • the piezoelectric transducer surface is divided into at least two regions according to the stress of the MEMS piezoelectric transducer under a certain load, and each region corresponds to a different stress range.
  • Each zone contains either one block or multiple blocks.
  • the area of the largest stress range corresponds to the first set of capacitors, the area of the second largest stress range corresponds to the second set of capacitors, and so on.
  • the capacitor has at least two groups. This provides a convenient way to implement a MEMS piezoelectric transducer with how to set the capacitor.
  • the corresponding set of capacitors of the region includes only one capacitor. If a certain area is a discrete plurality of blocks on the MEMS piezoelectric transducer, a corresponding set of capacitors in the area is composed of a plurality of capacitors, one for each block. This is also a convenient way to implement how MEMS piezoelectric transducers can be placed.
  • the MEMS piezoelectric transducer further includes a set of dummy capacitors.
  • the set of dummy capacitors either contains only one dummy capacitor or is composed of a plurality of dummy capacitors.
  • the pseudo capacitance covers the area or the floating electrode is disposed, and the capacitor thus formed does not participate in the electrical signal output; or the electrode is not disposed.
  • the dummy capacitor covers the area to set the electrode, it is advantageous to adopt a uniform manufacturing process on the semiconductor material, and it is not necessary to adopt a special isolation process for the pseudo capacitor coverage area. It is also feasible when the pseudo capacitor coverage area is not provided with an electrode.
  • the sum of all capacitors and all pseudo capacitors covers substantially the entire surface of the piezoelectric transducer. This is in the case where the piezoelectric transducer contains a pseudo capacitor, and if the gap ⁇ between the capacitors is ignored, the surface of the piezoelectric transducer is substantially entirely covered by a capacitor or a pseudo capacitor.
  • This aspect can make full use of piezoelectric transducers The stresses of all regions except the region of the minimum stress range generate electrical signals, and on the other hand, the noise of the region of the minimum stress range is avoided, which adversely affects the output performance of the piezoelectric transducer.
  • the piezoelectric transducer surface is divided into at least three regions, each region corresponding to a different range of stress; each region Or only one block, or consist of multiple blocks; the area of the largest stress range corresponds to the first set of capacitors, the area of the second largest stress range corresponds to the second set of capacitors, and so on; Two groups; the area of the smallest stress range is set to a set of pseudo capacitors. This provides a convenient way to implement a MEMS piezoelectric transducer with how to set the capacitor.
  • the corresponding set of capacitors of the region only includes one capacitor, or the region corresponds to A set of pseudo capacitors only contains one dummy capacitor; if a region is a discrete plurality of blocks on the MEMS piezoelectric transducer, a corresponding set of capacitors in the region is composed of a plurality of capacitors, one for each capacitor a block; or a set of pseudo capacitors corresponding to the area is composed of a plurality of dummy capacitors, each of which corresponds to one block.
  • This is also a convenient way to set the capacitance of a MEMS piezoelectric transducer.
  • the MEMS piezoelectric transducer is either uniform in thickness or non-uniform in thickness; or is regular in shape or irregular in shape; the shape of the MEMS piezoelectric transducer includes at least a rectangular cantilever Beam, fan-shaped cantilever beam, right-angled cantilever beam, square double-sided fixed-support cantilever beam, square suspension film. According to various embodiments disclosed herein and the disclosed technical principles, it is possible to obtain that the scope to which the present application can be applied is not limited by whether the thickness is uniform or whether the shape is regular.
  • the MEMS piezoelectric transducer comprises only one piezoelectric film layer, and an electrode layer is disposed on both upper and lower surfaces of the piezoelectric film layer, and a support layer is provided above or below the entire structure.
  • the ME MS piezoelectric transducer includes two or more piezoelectric thin film layers and the support layer is omitted, and an electrode layer is disposed on the upper and lower surfaces of each of the piezoelectric thin film layers.
  • the MEMS piezoelectric transducer comprises two or more piezoelectric film layers, and an electrode layer is disposed on each of the upper and lower surfaces of each piezoelectric film layer, and is disposed above or below or in the middle of the overall structure.
  • There is a support layer is a different implementation of MEMS piezoelectric transducers, including the number of piezoelectric film layers, the number of electrode layers, and the relative positional relationship of the support layers, all of which can vary.
  • the MEMS piezoelectric transducer forms an electric charge in all electrode layers corresponding to the same region position. Capacitance, or constitute a pseudo capacitor.
  • Capacitance or constitute a pseudo capacitor.
  • the two electrode layers corresponding to the same region position either form a capacitor or constitute a pseudo capacitor.
  • the three electrode layers corresponding to the same region position either form a capacitor or constitute a pseudo capacitor.
  • the capacitance of the capacitor composed of the three electrode layers is approximately twice the capacitance of the capacitor composed of the two electrode layers, which is advantageous for improving the signal output of the piezoelectric transducer.
  • the present application is based on the stress distribution of a MEMS piezoelectric transducer under a certain load, and optimizes the shape, position, and number of the capacitor, and according to the requirements of the device for output impedance, sensitivity, and noise characteristics. Different capacitors are connected in series and / or in parallel. Conventional MEMS piezoelectric transducers typically have only one capacitor and may cause redistribution of charge flow in the electrode layer due to uneven stress distribution.
  • the present application provides at least two regions of the MEMS piezoelectric transducer with at least two sets of capacitances corresponding to different stress ranges, which can significantly reduce the charge flow on the piezoelectric transducer due to uneven stress distribution.
  • the present invention also provides a set of pseudo capacitors that do not participate in the output of the electrical signal, which can enhance the electromechanical transducing coefficient of the piezoelectric transducer as a whole and improve the electrical signal of the transducer.
  • Output For example, increasing the output power of the vibration energy harvester, increasing the sensitivity of the sensor (such as a piezoelectric microphone), increasing the signal-to-noise ratio of the sensor, and the like.
  • FIG. 1A is a side view of a stress distribution of a rectangular cantilever beam.
  • FIG. 1B is a plan view showing the stress distribution of the rectangular cantilever beam shown in FIG. 1A.
  • FIG. 2A is a side view of a piezoelectric transducer of a rectangular cantilever structure.
  • FIG. 2B is a top plan view of the piezoelectric transducer of the rectangular cantilever structure shown in FIG. 2A. [0027] FIG.
  • FIG. 3A is a side view of another piezoelectric transducer of a rectangular cantilever structure.
  • FIG. 3B is a top plan view of the piezoelectric transducer of the rectangular cantilever structure shown in FIG. 3A.
  • FIG. 4A is a top plan view of a first embodiment of a MEMS piezoelectric transducer provided by the present application.
  • 4B is a side view of the first implementation of the first embodiment shown in FIG. 4A.
  • 4C is a side view of a second implementation of the first embodiment shown in FIG. 4A.
  • FIG. 4D is a side view of a third implementation of the first embodiment shown in FIG. 4A.
  • FIG. 5A is a top plan view of a stress distribution of a fan-shaped cantilever beam.
  • 5B is a top plan view of a second embodiment of a MEMS piezoelectric transducer provided by the present application.
  • FIG. 6A is a top plan view of a stress distribution of a right-angled triangular cantilever beam.
  • 6B is a top plan view of a third embodiment of a MEMS piezoelectric transducer provided by the present application.
  • FIG. 7A is a top plan view of a stress distribution of a square bilateral fixed support cantilever beam.
  • FIG. 7B is a top plan view of a fourth embodiment of a MEMS piezoelectric transducer provided by the present application.
  • 8A is a top plan view of a stress distribution of a square suspension film.
  • Embodiment 8B is a top plan view of Embodiment 5 of the MEMS piezoelectric transducer provided by the present application.
  • 100 is a rectangular cantilever beam; 200 is a fan-shaped cantilever beam; 300 is a right-angled triangular cantilever beam; 400 is a square bilateral fixed-support cantilever beam; 500 is a square suspension film; 101 to 104, 201 to 203, 301 to 303, 401 to 404, 501 to 505 are capacitors; 109, 204, 304 to 306, 4 05, 506 are pseudo capacitors; 110, 120, 130 are fixed support sidewalls; 111, 121 are piezoelectric films 1; 31A is the upper piezoelectric film layer; 131B is the lower piezoelectric film layer; 112, 122 is the support layer; 113A, 114A, 115A, 125A, 135A are the upper electrodes of the capacitor; 135B is the middle electrode of the capacitor; 113B, 114B, 1 15B, 125B, 135C are the lower electrodes of the capacitor; 119
  • 4A is a top plan view of a rectangular cantilever beam 100.
  • the rectangular cantilever beam 100 is provided with four effective capacitors 101 to 104, and is also provided with a dummy capacitor 109.
  • the four capacitors 101 to 104 belong to the first group, the second group, the third group, and the fourth group of capacitors, respectively, and each of the four groups of capacitors includes only one capacitor.
  • a set of dummy capacitors only contains dummy capacitors 109. As can be seen from FIG. 1A and FIG.
  • the stress of the rectangular cantilever beam 100 covered by the four capacitors 101 to 104 is successively decreased from large to small, and the capacitor 101 covers the region with the greatest stress on the rectangular cantilever beam 100 (ie, the fixed support portion and The junction of the suspended parts).
  • the dummy capacitor 109 corresponds to the region with the least stress on the rectangular cantilever beam 100 area. As shown in FIG. 1B, there is a partial region where the stress is zero above the fixed support portion, and this portion does not cover the electrode and can be regarded as another pseudo capacitor; alternatively, this portion can also be covered by the extension of the capacitor 101 instead. In the operating state, the four capacitors 101 to 104 are connected in series. The dummy capacitor 109 does not participate in the electrical signal output.
  • the piezoelectric transducer consisting of capacitors 101 to 104 in series has the smallest output impedance.
  • the four different sets of capacitors 101 to 104 can also have different areas, but the output impedance of the piezoelectric transducer is large with the same total area of the effective capacitance.
  • FIG. 4B is a side view of the rectangular cantilever beam 100.
  • the rectangular cantilever beam 100 has only one end fixedly supported on the side wall 110, and the remaining portions are suspended.
  • the rectangular cantilever beam 100 includes a piezoelectric film layer 111 and a support layer 112. On the upper surface of the piezoelectric film layer 111, four upper electrodes 115A and one upper electrode 119A are provided. On the lower surface of the piezoelectric film layer 111, four lower electrodes 11 5B and one lower electrode 119B are provided.
  • the support layer 112 is located below the piezoelectric film layer 111 for supporting the piezoelectric film layer 111 and the electrodes of the upper and lower surfaces thereof.
  • the upper electrode 115A and its corresponding lower electrode 115B constitute a capacitor 101 in Fig. 4A, and the other capacitors 102 to 104 in Fig. 4A are also constituted by the upper electrode 115A and the lower electrode 115B corresponding to the positions of the same region.
  • the lower electrode 119B corresponding to the corresponding position of the upper electrode 119A constitutes the dummy capacitor 109 of Fig. 4A and does not participate in the output of the piezoelectric transducer.
  • the upper electrode 115A and the lower electrode 115B corresponding to the corresponding position have substantially the same shape and area
  • the lower electrode 119B corresponding to the corresponding position of the upper electrode 119A also has substantially the same shape and area.
  • FIG. 4C is a side view of the rectangular cantilever beam 100.
  • the rectangular cantilever beam 100 has only one end fixedly supported on the side wall 120, and the remaining portions are suspended.
  • the rectangular cantilever beam 100 includes a piezoelectric film layer 121 and a support layer 122.
  • On the upper surface of the piezoelectric film layer 111 four upper electrodes 125A and one upper electrode 129A are provided.
  • On the lower surface of the piezoelectric film layer 111 four lower electrodes 12 5B and one lower electrode 129B are provided.
  • the support layer 122 is located above the piezoelectric film layer 121 for supporting the piezoelectric film layer 121 and the electrodes on the upper and lower surfaces thereof.
  • the upper electrode 125A and its corresponding lower electrode 125B constitute a capacitor 101 in FIG. 4A, and the other capacitors 102 to 104 in FIG. 4A are also corresponding to the position of the same region.
  • the upper electrode 125A and the lower electrode 125B are formed.
  • the lower electrode 129B corresponding to the corresponding position of the upper electrode 129A constitutes the dummy capacitor 109 in FIG. 4A and does not participate in the output of the piezoelectric transducer.
  • the upper electrode 125A and the lower electrode 125B corresponding to the corresponding position have substantially the same shape and area
  • the lower electrode 129B corresponding to the corresponding position of the upper electrode 129A also has substantially the same shape and area.
  • FIG. 4D is a side view of the rectangular cantilever beam 100.
  • the rectangular cantilever beam 100 has only one end fixedly supported on the side wall 130, and the remaining portions are suspended.
  • the rectangular cantilever beam 100 includes an upper piezoelectric film layer 131A and a lower piezoelectric film layer 131B.
  • On the upper surface of the upper piezoelectric film layer 131A four upper electrodes 135A and one upper electrode 139A are provided.
  • Four middle electrodes 135B and one middle electrode 139B are provided between the upper piezoelectric film layer 131A and the lower piezoelectric film layer 131B.
  • the upper electrode 135A and its corresponding lower electrode 135C are electrically connected, and the middle electrode 135B corresponding to the corresponding position constitutes a capacitor 101 in Fig. 4A.
  • the other capacitors 102 to 104 in FIG. 4A are also constituted by the upper electrode 13 5A, the middle electrode 135B and the lower electrode 135C corresponding to the positions of the same region, wherein the upper electrode 135A and the lower electrode 135C serve as one plate of the capacitor, and the middle electrode 135B serves as the electrode The other plate of the capacitor.
  • the upper electrode 139A and its corresponding position of the middle electrode 139B and the lower electrode 139C constitute the dummy capacitor 109 of Fig. 4A and do not participate in the output of the piezoelectric transducer.
  • the upper electrode 135A and the corresponding middle electrode 135B and the lower electrode 135C have substantially the same shape and area, and the upper electrode 139A and the corresponding lower middle electrode 139B and the suspended lower electrode 139 C also have a rough The same shape and area.
  • the area of the plate formed by electrically connecting the upper electrode and the lower electrode of the capacitor in FIG. 4D is 2 of any plate area of the capacitor in FIG. 4B or FIG. 4C. This indicates that the capacitance value of the capacitor in Fig. 4D is twice the capacitance value of the capacitor in Fig. 4B or Fig. 4C, which is advantageous for increasing the output of the piezoelectric transducer.
  • the above three implementations may or may not deposit (ie, deposit) an insulating material in a region where the upper and lower surfaces of the piezoelectric film layer 111 do not cover the electrode, for example, an electrode gap between any two capacitors.
  • an insulating material in a region where the upper and lower surfaces of the piezoelectric film layer 111 do not cover the electrode, for example, an electrode gap between any two capacitors.
  • Any material Taking FIG. 4B as an example, when the insulating material ⁇ is deposited, the thickness thereof is preferably substantially equal to the thickness of the electrode, and the upper and lower surfaces of the ⁇ piezoelectric film layer 111 are substantially kept flat. When no material is deposited, since the electrode has a certain thickness, the upper and lower surfaces of the piezoelectric film layer 111 may appear in the region where the electrode is not covered. Stepped depression.
  • the region of the lower surface of the tantalum piezoelectric film layer 111 that does not cover the electrode is in contact with the upper surface of the support layer 112, and the corresponding region of the upper surface of the support layer 112 exhibits, for example, a stepped protrusion.
  • the pseudo capacitors 109 of the above three implementations all have electrode coverage, and the pseudo capacitors do not participate in electrical signal output.
  • the dummy capacitor region may be covered by an electrode or may be covered without an electrode.
  • some of the dummy capacitors may have electrode coverage, and the remaining dummy capacitors may be covered without electrodes.
  • the MEMS piezoelectric transducer of the present application may include only one layer of a piezoelectric film layer on both surfaces of the piezoelectric film layer. An electrode layer is provided, and a support layer is provided above or below the entire structure. Alternatively, the MEMS piezoelectric transducer of the present application may also include two or more piezoelectric thin film layers and omit the support layer, and electrode layers are provided on both surfaces of each piezoelectric thin film layer.
  • the MEMS piezoelectric transducer of the present application may further comprise two or more layers of piezoelectric film layers, and electrode layers are disposed on both surfaces of each layer of the piezoelectric film layer, and The support layer is placed above or below or in the middle of the overall structure, which is still the same principle as the three implementations that have been announced.
  • FIG. 5A is a MEMS piezoelectric transducer of a uniform thickness fan-shaped cantilever structure.
  • Figures 5A and 5B show a fan-shaped cantilever beam structure with only a fixed arc support and the rest being suspended.
  • Figure 5A is a top plan view of the sector-shaped cantilever beam showing the stress distribution on the sector-shaped cantilever beam under a fixed load. The darker the color, the greater the stress, and the lighter the color, the smaller the stress. It can be found that the spherical cantilever beam has zero stress at a fixed support position. At the junction of the fixed support position and the suspended portion, the stress on the surface of the sector cantilever is greatest.
  • FIG. 5B is also a top plan view of the sector cantilever beam 200.
  • the fan-shaped cantilever beam 200 is provided with three effective capacitors 201 to 203, and a dummy capacitor 204 is also disposed.
  • the three capacitors 201 to 203 belong to the first group, the second group, and the third group of capacitors, respectively, and the three groups of capacitors each include only one capacitor.
  • a set of dummy capacitors only contains dummy capacitors 204.
  • the stress of the sector cantilever beam 200 covered by the three capacitors 201 to 203 decreases from large to small, and the capacitor 201 covers the region with the greatest stress on the fan-shaped cantilever beam 200 (ie, the fixed support portion and the suspended portion). Junction) .
  • the dummy capacitor 204 corresponds to the region of the fan-shaped cantilever beam 200 where the stress is minimal.
  • the three capacitors 201 to 203 are connected in series.
  • the dummy capacitor 204 does not participate in the electrical signal output.
  • the different sets of three capacitors 201 to 203 have the same or similar areas such that they have the same or similar capacitance values. This ensures that the piezoelectric transducer consisting of series capacitors 201 to 103 has the smallest output impedance with the total area of the effective capacitance constant.
  • FIG. 6A is a MEMS piezoelectric transducer of a right-angled triangular cantilever structure of uniform thickness.
  • Figures 6A and 6B show a right-angled triangular cantilever beam structure with only oblique beveled support and the rest suspended.
  • Figure 6A is a top plan view of the right-angled cantilever beam showing the stress distribution on the sector-shaped cantilever beam under a fixed load. The darker the color, the greater the stress, and the lighter the color, the smaller the stress. It can be found that the right-angled cantilever beam has zero stress at a fixed support position. At the boundary between the fixed support position and the portion of the suspended portion, the stress of the right-angled cantilever beam surface is the largest.
  • FIG. 1 is a MEMS piezoelectric transducer of a right-angled triangular cantilever structure of uniform thickness.
  • Figures 6A and 6B show a right-angled triangular cantilever beam structure with only oblique beveled support and
  • 6B is also a top plan view of the right triangle cantilever beam 300.
  • the right-angled cantilever beam 300 is provided with three effective capacitors 301 to 303, and three dummy capacitors 304 to 306 are also provided.
  • Capacitor 301 belongs to the first group of capacitors, and the first group of capacitors contains only one capacitor.
  • Capacitors 302 and 303 belong to the second group of capacitors, and the second group of capacitors consist of two capacitors.
  • the pseudo capacitors 3 04 to 306 belong to a set of dummy capacitors, and the set of dummy capacitors are composed of three dummy capacitors. As can be seen from FIG.
  • the stress condition of the region of the right-angled triangular cantilever beam 300 covered by the three capacitors 301 to 303 is: the stress of the area covered by the capacitor 301.
  • the stress of the area covered by the stress capacitor 303 of the capacitor 302 covers the area.
  • the capacitor 301 covers the region of the right-angled cantilever beam 300 where the stress is greatest (i.e., the boundary between the fixed support portion and the suspended portion).
  • the pseudo-capacitors 304 to 306 cover the three blocks with the least stress on the right-angled cantilever beam 300, and the stresses of the three blocks are substantially the same. As shown in FIG.
  • the capacitors 302 and 303 can be connected in series or in parallel, and the capacitors connected in series or in parallel with the capacitor 301 can only be connected in series due to different stress ranges. None of the dummy capacitors 304 to 306 participate in the electrical signal output.
  • the capacitors 301 to 303 have the same or similar areas such that they have the same or similar capacitance values. Thereafter, the three capacitors 301 to 303 are sequentially connected in series to maximize the output electrical signal.
  • the area of the first set of capacitors is substantially equal to the area of the second set of capacitors, i.e., the area of capacitor 301 is approximately the sum of the areas of capacitors 302 and 303.
  • capacitors 302 and 303 are connected in parallel (or combined to the same capacitor without cutting) to form a parallel capacitor having a large capacitance value.
  • the shunt capacitor is then placed in series with capacitor 301.
  • the capacitor 301 belongs to the first group of capacitors, and the parallel capacitor belongs to the second group of capacitors.
  • the capacitances of different groups of capacitors are substantially the same, so that the minimum output impedance of the piezoelectric transducer can be obtained without changing the total area of the effective capacitor.
  • capacitors 302 and 303 have the same or similar area, and capacitor 301 has an area approximately twice the capacitance 302.
  • FIG. 7A is a MEMS piezoelectric transducer of uniform thickness square cantilever structure.
  • Figures 7A and 7B show a square cantilever structure in which only two adjacent sides are fixedly supported and the remainder are suspended.
  • Figure 7A is a top view of the square cantilever beam showing the stress distribution on the square cantilever beam under a fixed load. The darker the color, the greater the stress, and the lighter the color, the smaller the stress. It can be found that the square cantilever beam has zero stress at a fixed support position. At the junction of the fixed support location and the portion of the suspended portion, the stress on the surface of the square cantilever beam is greatest.
  • FIG. 7B is also a top plan view of the square cantilever beam 400.
  • the square cantilever beam 400 is provided with four effective capacitors 401 to 404, and is also provided with a dummy capacitor 405.
  • Capacitors 401 and 402 belong to the first group of capacitors, and capacitors 403 and 404 belong to the second group of capacitors.
  • Each of the two sets of capacitors consists of two capacitors.
  • a set of dummy capacitors only contains dummy capacitors 405.
  • the stress condition of the region of the square cantilever beam 400 covered by the four capacitors 401 to 404 is: the stress of the capacitor 401 covering the region of the stress capacitor 402 covering the region > the capacitance 404 covering the region of the stress capacitor 404 covering the region stress.
  • Capacitors 401 and 402 cover the area of the square cantilever 400 where stress is greatest (i.e., where the fixed support portion meets the portion of the suspended portion).
  • the dummy capacitor 405 covers the area of the square cantilever beam 400 where stress is minimal.
  • capacitors 401 and 402 are connected in series and/or in parallel, and capacitors 403 and 404 are connected in series and/or in parallel, and the two capacitors formed are connected in series.
  • the dummy capacitor 405 does not always participate in the electrical signal output.
  • the four capacitors 401 to 404 have the same or similar areas such that they have the same or similar capacitance values, and the capacitors 401 to 404 are sequentially connected in series to maximize the output electrical signal.
  • the area of the first set of capacitors is substantially equal to the area of the second set of capacitors, i.e., the sum of the areas of capacitors 401 and 402 is substantially equal to the sum of the areas of capacitors 403 and 404.
  • the capacitors 401 and 402 are connected in parallel to obtain a first parallel capacitor having a large capacitance value.
  • the capacitors 403 and 404 are connected in parallel to obtain a second parallel capacitor having a large capacitance value.
  • the first shunt capacitor belongs to the first group of capacitors
  • the second shunt capacitor belongs to the second group of capacitors, and the capacitances of different groups of capacitors are substantially the same, so that the minimum piezoelectric transducer can be obtained without the total area of the effective capacitors being constant.
  • Output impedance Further preferably, the capacitors 401 to 404 have the same or similar areas.
  • FIG. 8A is a MEMS piezoelectric transducer of uniform thickness in a square suspension film structure.
  • Figures 8A and 8B show a square suspension film structure in which only four sides of a square are fixedly supported and the rest are suspended.
  • Figure 8A is a top plan view of the square suspension film showing the stress distribution on the square suspension film under a fixed load. The darker the color, the greater the stress, and the lighter the color, the smaller the stress. It can be found that the stress of the square suspension film at the fixed support position is zero. At the junction of the fixed support location and the portion of the suspended portion, the surface of the square suspension film has the greatest stress.
  • FIG. 8B is also a top plan view of the square suspension film 500.
  • the square suspension film 500 is provided with five effective capacitors 501 to 505, and a dummy capacitor 506 is also provided.
  • Capacitors 501 through 504 belong to the first group of capacitors, and the first group of capacitors consist of four capacitors.
  • Capacitor 505 belongs to the second group of capacitors, and the second group of capacitors contains only one capacitor.
  • the stress condition of the region of the square suspension film 500 covered by the five capacitors 501 to 505 is: the stress of the area covered by the capacitor 501.
  • the stress of the area covered by the capacitor 502. The stress of the area covered by the capacitor 503.
  • the capacitors 501 to 504 cover the region where the stress is the largest on the square suspension film 500 (i.e., the boundary between the fixed support portion and the portion of the suspended portion).
  • the dummy capacitor 506 covers the area of the square suspension film 500 where stress is minimal. As shown in FIG. 8A, there is a partial region where the stress is zero above the fixed support portion, and the portion of the region does not cover the electrode, and another pseudo capacitor can be seen; or, this portion can also be changed from capacitors 501 to 504 and pseudo.
  • Capacitors 506 are respectively extended to cover. In the active state, capacitors 501 through 504 can be connected in series and/or in parallel in any form, and the resulting capacitor is connected in series with capacitor 505.
  • the dummy capacitor 506 does not always participate in the electrical signal output.
  • the five capacitors 501 to 505 have the same or similar areas such that they have the same or similar capacitance values, and the capacitors 501 to 505 are sequentially connected in series to maximize the output electrical signal.
  • the area of the first set of capacitors is substantially equal to the area of the second set of capacitors.
  • the sum of the areas of the capacitors 501 to 504 is approximately equal to the area of the capacitor 505.
  • capacitors 501 through 504 are connected in parallel, and the resulting capacitor is connected in series with capacitor 505.
  • the four capacitors 501 to 504 have the same or similar area, and the area of the capacitor 505 is approximately four times the area of the capacitor 501.
  • the sum of the areas of any two of the capacitors 501 through 504 (referred to as A and B) is approximately equal to the sum of the areas of the other two (referred to as C and D), which is substantially equivalent to the area of the capacitor 505. .
  • capacitors A and B are connected in parallel, and capacitors C and D are connected in parallel, and the two capacitors are connected in series with capacitor 505.
  • the four capacitors 501 to 504 have the same or similar area, and the area of the capacitor 505 is approximately twice the area of the capacitor 501.
  • capacitors 501 through 504 are connected in series and / in parallel, and the resulting capacitor is in series with capacitor 505.
  • Capacitors 501 to 504 are connected to each other to form a capacitor, and capacitor 50 5 belongs to a second group of capacitors. The capacitances of different groups are approximately the same, so that the piezoelectricity can be obtained without changing the total area of the effective capacitor. The minimum output impedance of the transducer.
  • Embodiment 1 may be a layer of a piezoelectric film layer and a support layer above or below it, or may be a pressure of two layers or more.
  • the electric film layer is omitted and the support layer is omitted. It may also be two or more piezoelectric film layers and a support layer may be provided above or below or in the middle of the overall structure.
  • the MEMS piezoelectric transducer provided by the present application optimizes the shape of the capacitor, which is mainly embodied in the following aspects.
  • the present application is to design the position, number, and shape of a capacitor according to the stress distribution of a MEMS piezoelectric transducer under a certain load. Specifically, in areas where the stress of the MEMS piezoelectric transducer is greater, the necessity to set the capacitance is higher; and vice versa. Therefore, the capacitance is preferentially set in the region where the stress of the MEMS piezoelectric transducer is the largest and the larger.
  • the above five embodiments all have dummy capacitors disposed on the MEMS piezoelectric transducer, the dummy capacitors are not necessarily required by the present application. If the MEMS piezoelectric transducer of the present application omits the pseudo capacitance, then the sum of all the effective capacitances substantially covers the entire surface of the piezoelectric transducer. If the MEMS piezoelectric transducer of the present application contains a pseudo capacitor, then the sum of all effective capacitors and pseudo capacitors substantially covers the piezoelectric transducer All surfaces.
  • a pseudo-capacitor is placed on the MEMS piezoelectric transducer, since it covers the region of the piezoelectric transducer with the least stress, this region typically has a noise level higher than the signal level, or at the same level as the signal, pseudo Capacitance does not participate in the signal output in favor of improving the output performance of the piezoelectric transducer. Conversely, if no dummy capacitor is placed on the MEMS piezoelectric transducer, it means that the region with the least stress is also involved in the signal output, which will reduce the output performance of the piezoelectric transducer.
  • the pseudo capacitor is preferentially placed in the region where the stress of the MEMS piezoelectric transducer is the smallest.
  • the capacitance is set in the region where the stress of the MEMS piezoelectric transducer is the largest; the pseudo capacitance is set in the region where the stress of the MEMS piezoelectric transducer is the smallest; in other regions of the MEMS piezoelectric transducer, usually set
  • the capacitor can also be set as a pseudo capacitor.
  • each of the capacitors or dummy capacitors covers a part of the surface of the MEMS piezoelectric transducer, and the surface stress of the covered region is not a specific value but a stress range.
  • the stress ⁇ in the second region actually refers to any stress value within the stress range of the first region> any stress value within the stress region of the second region.
  • the surface of the MEMS piezoelectric transducer is divided into two or more regions according to the magnitude of the stress applied to the MEMS piezoelectric transducer under a certain load, each region corresponding to a different stress range.
  • the area of the largest stress range corresponds to the first set of capacitors
  • the area of the second largest stress range corresponds to the second set of capacitors, and so on.
  • the capacitor has at least two groups. If a region is a continuous block on the surface of the MEMS piezoelectric transducer, the corresponding set of capacitors preferably contains only one capacitor.
  • the corresponding set of capacitors is composed of a plurality of capacitors, each capacitor preferably corresponding to one block.
  • a block of the surface of the MEMS piezoelectric transducer can also be provided as at least two capacitors, which can be connected in series and/or in parallel.
  • the surface of the MEMS piezoelectric transducer is divided into three or more regions according to the stress of the MEMS piezoelectric transducer under a certain load, and each region corresponds to a different stress range .
  • the area of the largest stress range corresponds to the first set of capacitors
  • the area of the second largest stress range corresponds to the second set of capacitors
  • the area of the smallest stress range corresponds to a set of pseudo capacitors.
  • the capacitor has at least two groups. If a region is a continuous block on the surface of the MEMS piezoelectric transducer
  • the corresponding set of capacitors preferably only contains one capacitor, or the corresponding set of dummy capacitors preferably only contains one dummy capacitor.
  • the corresponding set of capacitors is composed of a plurality of capacitors, each of which preferably corresponds to one block; or the corresponding set of pseudo capacitors It consists of a plurality of pseudo capacitors, each of which preferably corresponds to one block.
  • one block of the surface of the MEMS piezoelectric transducer may also be configured as at least two capacitors, which may be connected in series and/or in parallel; or may be configured as at least two pseudo capacitors, all of which are Do not participate in electrical signal output
  • the stress value of the MEMS piezoelectric transducer after loading a certain load is normalized to between 0 and 1, and the region of the stress value between 0.75 and 1 is referred to as a first region, and the stress value is A region between 0.5 and 0.75 is referred to as a second region, a region having a stress value between 0.25 and 0.5 is referred to as a third region, and a region having a stress value between 0 and 0.25 is referred to as a fourth region.
  • Each zone can be a contiguous block or a block of isolated blocks.
  • the fourth region having the smallest stress range is set as a set of pseudo capacitors, and the first region, the second region, and the third region are respectively set to three sets of capacitors. The same set of capacitors are connected in series and / or in parallel; different sets of capacitors are connected in series.
  • a MEMS piezoelectric transducer is provided with at least two sets of effective capacitors.
  • the number, shape, and area of the effective capacitors can be determined based on the actual circuit configuration requirements for output impedance, sensitivity to piezoelectric transducers, and noise.
  • the pseudo capacitor can select the set electrode according to the requirements of the mechanical strength and the resonant frequency of the MEMS piezoelectric transducer in actual conditions, and the set electrode does not participate in the electrical signal output.
  • the dummy capacitor may not be provided with an electrode.
  • the area of the pseudo capacitor can be determined by the output impedance requirements of the circuit configuration, the sensitivity of the transducer, and the noise requirements.
  • the above five embodiments are all cantilever beams or suspended film structures of uniform thickness, the same applies to MEMS piezoelectric transducers having uneven thickness, because the same technical principle is still used.
  • the above five embodiments are regular MEMS piezoelectric transducers, the same is true for the irregularly shaped MEMS piezoelectric transducers because they are still the same technical principle.
  • the present application can be applied to an electronic device for converting mechanical energy into electrical energy (electrical signal) such as a piezoelectric vibration energy harvester, a piezoelectric microphone, or the like.

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Abstract

一种优化电容形状的MEMS压电换能器，表面覆盖有m组电容（101,102,103,104,109），m为≥2的自然数。当所述MEMS压电换能器加载一定载荷时，第一组电容中的任意一个所覆盖区域的应力＞第二组电容中的任意一个所覆盖区域的应力＞......＞第m-1组电容中的任意一个所覆盖区域的应力＞第m组电容中的任意一个所覆盖区域的应力。同一组电容之间进行串联和/或并联；不同组电容之间进行串联。根据MEMS压电换能器在加载一定载荷时的应力分布情况，对电容形状、位置、数量进行了优化设计。这可以显著减少压电换能器上因为应力分布不均而引起的电荷流动，增强压电换能器整体的机电换能系数，提高换能器的电信号输出。

Description

发明名称：一种优化电容形状的 MEMS压电换能器 技术领域
[0001] 本申请涉及一种 MEMS压电换能器， 特别是涉及 （但不局限于） 一种将环境中 的振动能量、 声学能量等转换为电学能量的压电换能器。
背景技术
[0002] 换能器 （transducer) 是将一种形式的能量转换为另一种形式的能量的器件， 通 常是将一种能量形式的信号转换为另一种能量形式的信号。 这些能量形式包括 电能、 机械能、 电磁能、 光能、 化学能、 声能和热能等。
[0003] 压电换能器 （piezoelectric transducer) 是利用压电材料的压电效应将机械能与 电能相互转换的器件。 压电效应包括两类： 正压电效应是将机械能转换为电能 ， 逆压电效应是将电能转换为机械能。
[0004] MEMS压电换能器是一种可以将环境中的机械能通过正压电效应转换为电能， 也可以将电能通过逆压电效应转换为机械能的一种微型机电换能装置。 当用作 机械能转换为电能吋， MEMS压电换能器通常应用于以下两个方面： （1) 能量 采集， 将环境中的微弱的振动能量等转换为电学能量， 从而驱动电学器件进行 工作； （2) 传感器， 将环境中的振动或声音信号等转换为电信号进行输出。 相 比传统的电容式换能技术， 压电换能器具有更高的机械可靠性、 更高的机电换 能系数、 不需要直流偏置的优点， 作为传感器吋其灵敏度更高、 读出电路更为 简单。 近几年， 随着薄膜压电材料制备技术的成熟， 越来越多 MEMS压电换能器 被发明出来， 并应用到我们的生活中， 典型应用如压电式能量采集器、 压电麦 克风、 压电超声指纹识别装置等。
[0005] MEMS压电换能器将机械能转换为电能的物理原理为： 在压电换能器上加载一 定的载荷吋， 构成换能器的压电材料会因正压电效应产生极化现象， 并在它的 两个相对表面上产生正负电荷,电荷量的大小与结构上应力的大小呈现线性相关 的关系。
[0006] 对于特定的机械结构来说， 在其结构上加载一定的载荷吋， 其结构上的应力并 不是均匀分布的， 而是随着结构的受力情况以及结构的几何形状而起伏变化的 。 图 1A和图 1B表示出一端固定支撑、 其余部分均悬空的矩形悬臂梁 （Cantilever ) 结构。 图 1A是该矩形悬臂梁的侧视图， 矩形悬臂梁厚度均匀， 示例的载荷自 上而下均匀地施加在矩形悬臂梁的上表面。 图 1B是该矩形悬臂梁的俯视图， 也 就是沿着示例的载荷的作用方向观察该矩形悬臂梁。 图 1A和图 1B表示出在固定 载荷下该矩形悬臂梁上的应力分布情况， 颜色越深表示应力越大， 颜色越浅表 示应力越小。 可以发现， 该矩形悬臂梁在固定支撑位置的应力为零。 在固定支 撑位置与悬空部分的交界处， 该矩形悬臂梁表面的应力最大。 沿着 X轴方向， 随 着与固定支撑位置距离的增大， 该矩形悬臂梁表面的应力越来越小， 呈现出应 力梯度分布的状态。 直至该矩形悬臂梁远离固定支撑位置的末端， 应力为零。
[0007] 正压电效应产生电荷量的大小与结构上应力的大小呈现线性相关的关系， 所以 应力的梯度分布会导致压电材料表面产生的电荷存在相应的起伏， 进而在电极 中形成电荷的流动再分布 （redistribution currents) 。 请参阅图 2A和图 2B， 这是 一种厚度均匀的矩形悬臂梁结构的压电换能器。 图 2A是矩形悬臂梁的侧视图， 图 2B是矩形悬臂梁的俯视图。 该矩形悬臂梁 100仅有一端固定支撑在侧壁 110上 ， 其余部分均悬空。 该矩形悬臂梁 100包括压电薄膜层 111和支撑层 112。 在压电 薄膜层 111的上表面设有一个上电极 113A。 在压电薄膜层 111的下表面设有一个 下电极 113B。 上电极 113A、 下电极 113B分别基本覆盖压电薄膜层 111的上表面 、 下表面的全部区域， 并构成了压电换能器唯一的电容。 支撑层 112位于压电薄 膜层 111的下方， 用于支撑压电薄膜层 111及其上下表面的电极。 在任一电极的 表面， 电荷从矩形悬臂梁 100应力较大的区域流向应力较小的区域形成电荷的流 动再分布。 这种电荷的流动会对压电换能器的输出性能造成不利的影响， 如降 低振动能量采集器的输出功率、 减小传感器的灵敏度、 降低传感器的信噪比 （S NR) 等。
[0008] 为了减小应力梯度分布对压电换能器的影响， 传统的解决办法如图 3 A和图 3B 所示， 这是另一种厚度均匀的矩形悬臂梁结构的压电换能器。 图 3A是矩形悬臂 梁的侧视图， 图 3B是矩形悬臂梁的俯视图。 该矩形悬臂梁 100仅有一端固定支撑 在侧壁 110上， 其余部分均悬空。 该矩形悬臂梁 100包括压电薄膜层 111和支撑层 112。 在压电薄膜层 111的上表面设有一个上电极 114A。 在压电薄膜层 111的下表 面设有一个下电极 114B。 上电极 114A、 下电极 114B分别仅覆盖压电薄膜层 111 上表面、 下表面的部分区域， 并优选覆盖矩形悬臂梁 100表面应力较大的区域， 由此构成了压电换能器唯一的电容。 支撑层 112位于压电薄膜层 111的下方， 用 于支撑压电薄膜层 111及其上下表面的电极。 由于降低了有效电容的覆盖面积， 使其仅仅覆盖应力较大的区域， 可以减少电荷的流动再分布对压电换能器输出 的影响。 然而， 该方案也存在缺点， 主要包括： （1) 浪费结构面积， 对于结构 上应力较小区域部分的换能直接舍弃； （2) 相比于电极完全覆盖的情况， 电极 部分覆盖所构成的电容的电容值较小。 因此该方案仍不是解决应力梯度分布的 最佳方案， 仅能部分提高压电换能器的输出性能。
技术问题
[0009] 本申请所要解决的技术问题是： 当 MEMS压电换能器加载一定载荷吋， 会出现 应力分布不均匀的情况， 导致因正压电效应产生的电荷从应力较大的区域向应 力较小的区域流动而产生电荷的流动再分布， 这对压电换能器的输出性能带来 了不利影响。
问题的解决方案
技术解决方案
[0010] 为解决上述技术问题， 本申请优化电容形状的 MEMS压电换能器的表面覆盖有 m组电容， m为≥2的自然数。 每一组电容或者仅包含一个电容， 或者由多个电容 组成。 当所述 MEMS压电换能器加载一定载荷吋， 第一组电容中的任意一个所覆 盖区域的应力〉第二组电容中的任意一个所覆盖区域的应力〉 ......〉第!^1组电 容中的任意一个所覆盖区域的应力〉第 m组电容中的任意一个所覆盖区域的应力 。 同一组电容之间进行串联和 /或并联； 不同组电容之间进行串联。 这就表明： 电容优先设置在 MEMS压电换能器的应力最大及较大的区域， 并且至少两组电容 覆盖 MEMS压电换能器表面的两个不同应力范围的区域， 将至少两组电容进行串 联有助于减少电极上电荷的流动再分布。
[0011] 优选地， 不同组电容的面积为大致相同的， 面积大致相同的电容具有大致相同 的电容值。 由于不同组电容之间进行串联， 而参与串联的各组电容具有大致相 同的电容值将使得压电换能器的输出阻抗最小。
[0012] 优选地， 所有电容的总和大致覆盖了压电换能器的全部表面。 如果忽略电容之 间的空隙、 压电换能器的固定位置上方的应力为零的小区域吋， 压电换能器的 表面基本上全部被电容覆盖。 这可以充分利用压电换能器的几乎所有区域的应 力来产生电信号。
[0013] 优选地， 根据 MEMS压电换能器在加载一定载荷吋的应力大小， 将压电换能器 表面划分为至少两个区域， 每个区域对应互不相同的应力范围。 每个区域或者 仅包含一个区块， 或者由多个区块组成。 最大的应力范围的区域对应设置第一 组电容， 第二大的应力范围的区域对应设置第二组电容， 以此类推。 电容至少 具有两组。 这为 MEMS压电换能器如何设置电容提供了便利的实现方式。
[0014] 优选地， 所述至少两个区域中， 某个区域如果在 MEMS压电换能器表面是连续 的一个区块， 则该区域对应的一组电容仅包含一个电容。 某个区域如果在 MEMS 压电换能器上是离散的多个区块， 则该区域对应的一组电容由多个电容组成， 每个电容对应一个区块。 这也是为 MEMS压电换能器如何设置电容提供了便利的 实现方式。
[0015] 进一步地， 所述 MEMS压电换能器还包括一组伪电容 （Dummy Capacitor) 。
该组伪电容或者仅包含一个伪电容， 或者由多个伪电容组成。 当所述 MEMS压电 换能器加载一定载荷吋， 第 m组电容中的任意一个所覆盖区域的应力〉任意一个 伪电容所覆盖区域的应力。 伪电容不参与电信号输出。 这就表明， 伪电容优先 设置在 MEMS压电换能器的应力最小的区域， 将这些区域排除在电信号输出之外 有助于提高压电换能器的输出性能。
[0016] 优选地， 所述伪电容覆盖区域或者设置悬空电极， 并且由此构成的电容不参与 电信号输出； 或者不设置电极。 当伪电容覆盖区域设置电极， 有利于在半导体 材料上采用统一的制造工艺， 不需要为伪电容覆盖区域采用特殊的隔离工艺。 当伪电容覆盖区域不设置电极， 也是可行的。
[0017] 优选地， 所有电容和所有伪电容的总和大致覆盖了压电换能器的全部表面。 这 是在压电换能器包含伪电容的情况下， 如果忽略电容之间的空隙吋， 压电换能 器的表面基本上全部被电容或伪电容覆盖。 这一方面可以充分利用压电换能器 的除了最小应力范围的区域以外的其他所有区域的应力来产生电信号， 另一方 面避免了最小应力范围的区域的噪声等对压电换能器的输出性能的不利影响。
[0018] 优选地， 根据 MEMS压电换能器在加载一定载荷吋的应力大小， 将压电换能器 表面划分为至少三个区域， 每个区域对应互不相同的应力范围； 每个区域或者 仅包含一个区块， 或者由多个区块组成； 最大的应力范围的区域对应设置第一 组电容， 第二大的应力范围的区域对应设置第二组电容， 以此类推； 电容至少 具有两组； 最小的应力范围的区域对应设置为一组伪电容。 这为 MEMS压电换能 器如何设置电容提供了便利的实现方式。
[0019] 优选地， 所述至少三个区域中， 某个区域如果在 MEMS压电换能器表面是连续 的一个区块， 则该区域对应的一组电容仅包含一个电容， 或者该区域对应的一 组伪电容仅包含一个伪电容； 某个区域如果在 MEMS压电换能器上是离散的多个 区块， 则该区域对应的一组电容由多个电容组成， 每个电容对应一个区块； 或 者该区域对应的一组伪电容由多个伪电容组成， 每个伪电容对应一个区块。 这 也是为 MEMS压电换能器如何设置电容提供了便利的实现方式。
[0020] 优选地， 所述 MEMS压电换能器或者为厚度均匀， 或者为厚度不均匀； 或者为 形状规则， 或者为形状不规则； 所述 MEMS压电换能器的形状至少包括矩形悬臂 梁、 扇形悬臂梁、 直角三角形悬臂梁、 正方形双边固定支撑悬臂梁、 正方形悬 浮薄膜。 根据本申请公布的多个实施例及其所揭示的技术原理， 可以得到本申 请所能适用的范围不受厚度是否均匀、 形状是否规则的限制。
[0021] 优选地， 所述 MEMS压电换能器包括仅一层压电薄膜层， 在该压电薄膜层的上 下表面均设置有电极层， 在整体结构的上方或下方具有支撑层。 或者， 所述 ME MS压电换能器包括两层或两层以上的压电薄膜层并省略支撑层， 在每一层压电 薄膜层的上下表面均设置有电极层。 或者， 所述 MEMS压电换能器包括两层或两 层以上的压电薄膜层， 在每一层压电薄膜层的上下表面均设置有电极层， 在整 体结构的上方或下方或中间设置有支撑层。 这是 MEMS压电换能器的不同实现方 式， 包括压电薄膜层的数量、 电极层的数量、 支撑层的相对位置关系， 都可以 变化。
[0022] 优选地， 所述 MEMS压电换能器在同一区域位置对应的全部电极层构成一个电 容， 或构成一个伪电容。 对应于 MEMS压电换能器的不同实现方式， 如果其包含 两层电极层， 那么同一区域位置对应的两层电极层或者构成一个电容， 或者构 成一个伪电容。 如果其包含三层电极层， 那么同一区域位置对应的三层电极层 或者构成一个电容， 或者构成一个伪电容。 针对同一区域位置， 由三层电极层 构成的电容的电容值大致是由两层电极层构成的电容的电容值的两倍， 有利于 提高压电换能器的信号输出。
发明的有益效果
有益效果
[0023] 本申请是根据 MEMS压电换能器在加载一定载荷吋的应力分布情况， 对电容形 状、 位置、 数量进行了优化设计， 并根据器件对输出阻抗、 灵敏度、 以及噪声 特性的要求， 将不同的电容进行串联和 /或并联。 传统的 MEMS压电换能器通常 仅有一个电容， 并可能由于应力分布不均匀而在电极层引起电荷的流动再分布 。 本申请在 MEMS压电换能器上设置了至少两组电容对应应力范围不同的至少两 个区域， 这可以显著减少压电换能器上因为应力分布不均而引起的电荷流动。 本申请在 MEMS压电换能器上应力范围最小的区域还设置一组不参与电信号输出 的伪电容， 这可以增强压电换能器整体的机电换能系数， 提高换能器的电信号 输出。 例如提高振动能量采集器的输出功率， 增大传感器 （如压电麦克风） 的 灵敏度， 增加传感器的信噪比等。
对附图的简要说明
附图说明
[0024] 图 1A是一种矩形悬臂梁的应力分布侧视图。
[0025] 图 1B是图 1 A所示的矩形悬臂梁的应力分布俯视图。
[0026] 图 2A是一种矩形悬臂梁结构的压电换能器的侧视图。
[0027] 图 2B是图 2A所示的矩形悬臂梁结构的压电换能器的俯视图。
[0028] 图 3 A是另一种矩形悬臂梁结构的压电换能器的侧视图。
[0029] 图 3B是图 3 A所示的矩形悬臂梁结构的压电换能器的俯视图。
[0030] 图 4A是本申请提供的 MEMS压电换能器的实施例一的俯视图。
[0031] 图 4B是图 4A所示的实施例一的第一种实现方式的侧视图。 [0032] 图 4C是图 4A所示的实施例一的第二种实现方式的侧视图。
[0033] 图 4D是图 4A所示的实施例一的第三种实现方式的侧视图。
[0034] 图 5A是一种扇形悬臂梁的应力分布俯视图。
[0035] 图 5B是本申请提供的 MEMS压电换能器的实施例二的俯视图。
[0036] 图 6A是一种直角三角形悬臂梁的应力分布俯视图。
[0037] 图 6B是本申请提供的 MEMS压电换能器的实施例三的俯视图。
[0038] 图 7A是一种正方形双边固定支撑悬臂梁的应力分布俯视图。
[0039] 图 7B是本申请提供的 MEMS压电换能器的实施例四的俯视图。
[0040] 图 8A是一种正方形悬浮薄膜的应力分布俯视图。
[0041] 图 8B是本申请提供的 MEMS压电换能器的实施例五的俯视图。
[0042] 图中附图标记说明： 100为矩形悬臂梁； 200为扇形悬臂梁； 300为直角三角形 悬臂梁； 400为正方形双边固定支撑悬臂梁； 500为正方形悬浮薄膜； 101至 104 、 201至 203、 301至 303、 401至 404、 501至 505为电容; 109、 204、 304至 306、 4 05、 506为伪电容； 110、 120、 130为固定支撑侧壁； 111、 121为压电薄膜层； 1 31A为上压电薄膜层； 131B为下压电薄膜层； 112、 122为支撑层； 113A、 114A 、 115A、 125A、 135A为电容的上电极； 135B为电容的中电极； 113B、 114B、 1 15B、 125B、 135C为电容的下电极； 119A、 129A、 139A为伪电容的上电极； 13 9B为伪电容的中电极； 119B、 129B、 139B为伪电容的下电极。
本发明的实施方式
[0043] 实施例一
[0044] 这是一种厚度均匀的矩形悬臂梁结构的 MEMS压电换能器。 图 4A是矩形悬臂梁 100的俯视图。 该矩形悬臂梁 100上设置有四个有效电容 101至 104， 还设置有一 个伪电容 109。 这四个电容 101至 104分别属于第一组、 第二组、 第三组、 第四组 电容， 并且这四组电容每组均仅包含一个电容。 一组伪电容仅包含伪电容 109。 由图 1A和图 1B可知， 这四个电容 101至 104所覆盖的矩形悬臂梁 100区域的应力由 大到小依次递减， 电容 101覆盖矩形悬臂梁 100上应力最大的区域 （即固定支撑 部分与悬空部分的交界处） 。 伪电容 109对应着矩形悬臂梁 100上应力最小的区 域。 如图 IB所示， 在固定支撑部分的上方有部分区域的应力为零， 这部分区域 未覆盖电极， 可视为另一个伪电容； 或者， 这部分区域也可改为由电容 101延伸 覆盖。 在工作状态中， 这四个电容 101至 104进行串联连接。 伪电容 109不参与电 信号输出。
[0045] 优选地， 在有效电容总面积不变的情况下， 如果不同组的电容 101至 104具有相 同或相近的面积， 那么它们具有相同或相近的电容值。 此吋， 由电容 101至 104 串联构成的压电换能器具有最小的输出阻抗。 当然， 这四个不同组的电容 101至 104也可具有不同的面积， 但在有效电容总面积不变的情况下， 压电换能器的输 出阻抗较大。
[0046] 上述实施例一的第一种实现方式如图 4B所示， 图 4B是矩形悬臂梁 100的侧视图 。 该矩形悬臂梁 100仅有一端固定支撑在侧壁 110上， 其余部分均悬空。 该矩形 悬臂梁 100包括压电薄膜层 111和支撑层 112。 在压电薄膜层 111的上表面设有四 个上电极 115A和一个上电极 119A。 在压电薄膜层 111的下表面设有四个下电极 11 5B和一个下电极 119B。 支撑层 112位于压电薄膜层 111的下方， 用于支撑压电薄 膜层 111及其上下表面的电极。 上电极 115A及其相应位置对应的下电极 115B构成 了图 4A中的一个电容 101， 图 4A中的其他电容 102至 104也由同样区域的位置对应 的上电极 115A与下电极 115B构成。 上电极 119A与相应位置对应的下电极 119B构 成图 4A中的伪电容 109， 不参与压电换能器的输出。
[0047] 优选地， 上电极 115A及其相应位置对应的下电极 115B具有大致相同的形状与 面积， 上电极 119A与相应位置对应的下电极 119B也具有大致相同的形状与面积
[0048] 上述实施例一的第二种实现方式如图 4C所示， 图 4C是矩形悬臂梁 100的侧视图 。 该矩形悬臂梁 100仅有一端固定支撑在侧壁 120上， 其余部分均悬空。 该矩形 悬臂梁 100包括压电薄膜层 121和支撑层 122。 在压电薄膜层 111的上表面设有四 个上电极 125A和一个上电极 129A。 在压电薄膜层 111的下表面设有四个下电极 12 5B和一个下电极 129B。 支撑层 122位于压电薄膜层 121的上方， 用于支撑压电薄 膜层 121及其上下表面的电极。 上电极 125A及其相应位置对应的下电极 125B构成 了图 4A中的一个电容 101， 图 4A中的其他电容 102至 104也由同样区域的位置对应 的上电极 125A与下电极 125B构成。 上电极 129A与相应位置对应的下电极 129B构 成图 4A中的伪电容 109， 不参与压电换能器的输出。
[0049] 优选地， 上电极 125A及其相应位置对应的下电极 125B具有大致相同的形状与 面积， 上电极 129A与相应位置对应的下电极 129B也具有大致相同的形状与面积
[0050] 上述实施例一的第三种实现方式如图 4D所示， 图 4D是矩形悬臂梁 100的侧视图 。 该矩形悬臂梁 100仅有一端固定支撑在侧壁 130上， 其余部分均悬空。 该矩形 悬臂梁 100包括上压电薄膜层 131A和下压电薄膜层 131B。 在上压电薄膜层 131A 的上表面设有四个上电极 135A和一个上电极 139A。 在上压电薄膜层 131A和下压 电薄膜层 131B之间设有四个中电极 135B和一个中电极 139B。 在下压电薄膜层 13 1B的下表面设有四个下电极 135C和一个下电极 139C。 上电极 135A及其相应位置 对应的下电极 135C电学导通， 并与相应位置对应的中电极 135B构成了图 4A中的 一个电容 101。 图 4A中的其他电容 102至 104也由同样区域的位置对应的上电极 13 5A、 中电极 135B与下电极 135C构成， 其中上电极 135A与下电极 135C作为电容的 一个极板， 中电极 135B作为电容的另一个极板。 上电极 139A及其相应位置的中 电极 139B与下电极 139C构成图 4A中的伪电容 109， 不参与压电换能器的输出。
[0051] 优选地， 上电极 135A及其相应位置对应的中电极 135B、 下电极 135C具有大致 相同的形状与面积， 上电极 139A与相应位置对应的中电极 139B、 悬空下电极 139 C也具有大致相同的形状与面积。
[0052] 假设以上三种实现方式的电容形状与尺寸相同， 那么图 4D中电容的上电极与下 电极电学导通构成的极板面积是图 4B或图 4C中电容的任意极板面积的 2倍， 这表 明图 4D中电容的电容值是图 4B或图 4C中电容的电容值的 2倍， 有利于提高压电 换能器的输出。
[0053] 以上三种实现方式在压电薄膜层 111的上、 下表面未覆盖电极的区域， 例如任 意两个电容之间的电极间隙， 可以沉积 （即淀积） 绝缘材料， 也可以不沉积任 何材料。 以图 4B为例， 当沉积绝缘材料吋， 其厚度优选大致等同于电极的厚度 ， 此吋压电薄膜层 111的上、 下表面大致保持平整。 当不沉积任何材料吋， 由于 电极具有一定厚度， 压电薄膜层 111的上、 下表面在未覆盖电极的区域会出现台 阶状凹陷。 此吋压电薄膜层 111的下表面未覆盖电极的区域与支撑层 112的上表 面相接触， 支撑层 112的上表面的相应区域例如呈现台阶状凸起。
[0054] 以上三种实现方式的伪电容 109均有电极覆盖， 伪电容不参与电信号输出。 在 其他实现方式中， 伪电容区域可以有电极覆盖， 也可以无电极覆盖。 当一组伪 电容由多个伪电容组成吋， 部分伪电容可以有电极覆盖， 其余伪电容可以无电 极覆盖。
[0055] 以上给出了实施例一的三种实现方式， 可以总结为： 本申请的 MEMS压电换能 器可以包括仅一层的压电薄膜层， 在该压电薄膜层的两个表面均设置有电极层 ， 在整体结构的上方或下方设置有支撑层。 或者， 本申请的 MEMS压电换能器也 可以包括两层或两层以上的压电薄膜层并省略支撑层， 在每一层压电薄膜层的 两个表面均设置有电极层。 进一步地， 可以预见到本申请的 MEMS压电换能器还 可以包括两层或两层以上的压电薄膜层， 在每一层压电薄膜层的两个表面均设 置有电极层， 并在整体结构的上方或下方或中间设置支撑层， 与已公幵的三种 实现方式仍为相同原理。
[0056] 实施例二
[0057] 这是一种厚度均匀的扇形悬臂梁结构的 MEMS压电换能器。 图 5A和图 5B表示 出一种扇形悬臂梁结构， 仅有圆弧固定支撑、 其余部分均悬空。 图 5A是该扇形 悬臂梁的俯视图， 表示出在固定载荷下该扇形悬臂梁上的应力分布情况， 颜色 越深表示应力越大， 颜色越浅表示应力越小。 可以发现， 该扇形悬臂梁在固定 支撑位置的应力为零。 在固定支撑位置与悬空部分的交界处， 该扇形悬臂梁表 面的应力最大。 沿着任意半径方向， 随着与固定支撑位置距离的增大， 该扇形 悬臂梁表面的应力越来越小， 呈现出应力梯度分布的状态。 直至该扇形悬臂梁 远离固定支撑位置的末端即圆心位置， 应力为零。 图 5B也是该扇形悬臂梁 200的 俯视图。 该扇形悬臂梁 200上设置有三个有效电容 201至 203， 还设置有一个伪电 容 204。 这三个电容 201至 203分别属于第一组、 第二组、 第三组电容， 并且这三 组电容均仅包含一个电容。 一组伪电容仅包含伪电容 204。 由图 5A可知， 这三个 电容 201至 203所覆盖的扇形悬臂梁 200区域的应力由大到小依次递减， 电容 201 覆盖扇形悬臂梁 200上应力最大的区域 （即固定支撑部分与悬空部分的交界处） 。 伪电容 204对应着扇形悬臂梁 200上应力最小的区域。 如图 5A所示， 在固定支 撑部分的上方有部分区域的应力为零， 这部分区域未覆盖电极， 可视为另一个 伪电容； 或者， 这部分区域也可改为由电容 201延伸覆盖。 在工作状态中， 这三 个电容 201至 203进行串联连接。 伪电容 204不参与电信号输出。
[0058] 优选地， 不同组的三个电容 201至 203具有相同或相近的面积， 以使它们具有相 同或相近的电容值。 在有效电容的总面积不变的情况下， 这可以保证由电容 201 至 103串联构成的压电换能器具有最小的输出阻抗。
[0059] 实施例三
[0060] 这是一种厚度均匀的直角三角形悬臂梁结构的 MEMS压电换能器。 图 6A和图 6 B表示出一种直角三角形悬臂梁结构， 仅有斜边固定支撑、 其余部分均悬空。 图 6A是该直角三角形悬臂梁的俯视图， 表示出在固定载荷下该扇形悬臂梁上的应 力分布情况， 颜色越深表示应力越大， 颜色越浅表示应力越小。 可以发现， 该 直角三角形悬臂梁在固定支撑位置的应力为零。 在固定支撑位置与悬空部分的 部分交界处， 该直角三角形悬臂梁表面的应力最大。 图 6B也是该直角三角形悬 臂梁 300的俯视图。 该直角三角形悬臂梁 300上设置有三个有效电容 301至 303， 还设置有三个伪电容 304至 306。 电容 301属于第一组电容， 第一组电容仅包含一 个电容。 电容 302和 303属于第二组电容， 第二组电容由两个电容组成。 伪电容 3 04至 306属于一组伪电容， 该组伪电容由三个伪电容组成。 由图 6A可知， 这三个 电容 301至 303所覆盖的直角三角形悬臂梁 300的区域的应力情况是： 电容 301覆 盖区域的应力〉电容 302覆盖区域的应力 电容 303覆盖区域的应力。 电容 301覆 盖直角三角形悬臂梁 300上应力最大的区域 （即固定支撑部分与悬空部分的部分 交界处） 。 伪电容 304至 306覆盖直角三角形悬臂梁 300上应力最小的三个区块， 这三个区块的应力大致相同。 如图 6A所示， 在固定支撑部分的上方有部分区域 的应力为零， 这部分区域未覆盖电极， 可视为另一个伪电容； 或者， 这部分区 域也可改为由电容 301至 303以及伪电容 304至 305分别延伸覆盖。 在工作状态中 ， 电容 302和 303可以进行串联或并联， 该串联或并联后的电容与电容 301之间由 于应力范围不同属于不同组只能进行串联。 伪电容 304至 306均不参与电信号输 出。 [0061] 优选地， 电容 301至 303具有相同或相近的面积， 以使它们具有相同或相近的电 容值。 此吋这三个电容 301至 303依次进行串联连接， 以使输出的电信号最大。
[0062] 优选地， 第一组电容的面积大致等同于第二组电容的面积， 即电容 301的面积 大致是电容 302和 303的面积之和。 此吋， 电容 302与 303并联 （或不进行切割而 合并为同一个电容） ， 以构成一个电容值较大的并联电容。 该并联电容再与电 容 301进行串联。 电容 301属于第一组电容， 该并联电容属于第二组电容， 不同 组的电容的面积大致相同， 因此在有效电容的总面积不变的情况下可以取得压 电换能器的最小的输出阻抗。 此吋进一步优选地， 电容 302和 303具有相同或相 近的面积， 电容 301具有大致两倍于电容 302的面积。
[0063] 实施例四
[0064] 这是一种厚度均匀的正方形悬臂梁结构的 MEMS压电换能器。 图 7A和图 7B表 示出一种正方形悬臂梁结构， 仅有相邻的两条边固定支撑、 其余部分均悬空。 图 7 A是该正方形悬臂梁的俯视图， 表示出在固定载荷下该正方形悬臂梁上的应 力分布情况， 颜色越深表示应力越大， 颜色越浅表示应力越小。 可以发现， 该 正方形悬臂梁在固定支撑位置的应力为零。 在固定支撑位置与悬空部分的部分 交界处， 该正方形悬臂梁表面的应力最大。 图 7B也是该正方形悬臂梁 400的俯视 图。 该正方形悬臂梁 400上设置有四个有效电容 401至 404， 还设置有一个伪电容 405。 电容 401和 402属于第一组电容， 电容 403和 404属于第二组电容， 这两组电 容中的每组均由两个电容组成。 一组伪电容仅包含伪电容 405。 由图 7A可知， 这 四个电容 401至 404所覆盖的正方形悬臂梁 400的区域的应力情况是： 电容 401覆 盖区域的应力 电容 402覆盖区域的应力〉电容 403覆盖区域的应力 电容 404覆盖 区域的应力。 电容 401和 402覆盖正方形悬臂梁 400上应力最大的区域 （即固定支 撑部分与悬空部分的部分交界处） 。 伪电容 405覆盖正方形悬臂梁 400上应力最 小的区域。 如图 7A所示， 在固定支撑部分的上方有部分区域的应力为零， 这部 分区域未覆盖电极， 可视为另一个伪电容； 或者， 这部分区域也可改为由电容 4 01至 404以及伪电容 405分别延伸覆盖。 在工作状态中， 电容 401与 402进行串联 和 /或并联， 电容 403与 404进行串联和 /或并联， 所构成的两个电容再进行串联。 伪电容 405始终不参与电信号输出。 [0065] 优选地， 这四个电容 401至 404具有相同或相近的面积， 以使它们具有相同或相 近的电容值， 将各电容 401至 404依次进行串联， 以使输出的电信号最大。
[0066] 优选地， 第一组电容的面积大致等同于第二组电容的面积， 即电容 401与 402的 面积之和大致等同于电容 403与 404的面积之和。 此吋， 电容 401与 402进行并联 ， 得到电容值较大的第一并联电容。 电容 403与 404进行并联， 得到电容值较大 的第二并联电容。 第一并联电容属于第一组电容， 第二并联电容属于第二组电 容， 不同组的电容的面积大致相同， 因此在有效电容的总面积不变的情况下可 以取得压电换能器的最小的输出阻抗。 此吋进一步优选地， 电容 401至 404具有 相同或相近的面积。
[0067] 实施例五
[0068] 这是一种厚度均匀的正方形悬浮薄膜结构的 MEMS压电换能器。 图 8A和图 8B 表示出一种正方形悬浮薄膜结构， 仅有正方形的四条边固定支撑、 其余部分均 悬空。 图 8A是该正方形悬浮薄膜的俯视图， 表示出在固定载荷下该正方形悬浮 薄膜上的应力分布情况， 颜色越深表示应力越大， 颜色越浅表示应力越小。 可 以发现， 该正方形悬浮薄膜在固定支撑位置的应力为零。 在固定支撑位置与悬 空部分的部分交界处， 该正方形悬浮薄膜表面的应力最大。 图 8B也是该正方形 悬浮薄膜 500的俯视图。 该正方形悬浮薄膜 500上设置有五个有效电容 501至 505 ， 还设置有一个伪电容 506。 电容 501至 504属于第一组电容， 第一组电容由四个 电容组成。 电容 505属于第二组电容， 第二组电容仅包含一个电容。 一组伪电容 仅包含伪电容 506。 这五个电容 501至 505所覆盖的正方形悬浮薄膜 500的区域的 应力情况是： 电容 501覆盖区域的应力《电容 502覆盖区域的应力《电容 503覆盖区 域的应力《电容 504覆盖区域的应力〉电容 505覆盖区域的应力。 电容 501至 504覆 盖正方形悬浮薄膜 500上应力最大的区域 （即固定支撑部分与悬空部分的部分交 界处） 。 伪电容 506覆盖正方形悬浮薄膜 500上应力最小的区域。 如图 8A所示， 在固定支撑部分的上方有部分区域的应力为零， 这部分区域未覆盖电极， 可视 另一个伪电容； 或者， 这部分区域也可改为由电容 501至 504以及伪电容 506分别 延伸覆盖。 在工作状态中， 电容 501至 504可以进行任意形式的串联和 /或并联， 所构成的电容与电容 505进行串联。 伪电容 506始终不参与电信号输出。 [0069] 优选地， 这五个电容 501至 505具有相同或相近的面积， 以使它们具有相同或相 近的电容值， 将各电容 501至 505依次进行串联， 以使输出的电信号最大。
[0070] 优选地， 第一组电容的面积大致等同于第二组电容的面积。 例如， 电容 501至 5 04的面积之和大致等同于电容 505的面积。 此吋， 电容 501至 504进行并联， 所构 成的电容再与电容 505进行串联。 此吋进一步优选地， 四个电容 501至 504具有相 同或相近的面积， 电容 505的面积为电容 501的面积的大致四倍。 又如， 电容 501 至 504中的任意两个 （称为 A和 B) 的面积之和大致等同于另外两个 （称为 C和 D ) 的面积之和， 同吋大致等同于电容 505的面积。 此吋， 电容 A与 B进行并联， 电 容 C与 D进行并联， 所构成的两个电容再与电容 505进行串联。 此吋进一步优选地 ， 四个电容 501至 504具有相同或相近的面积， 电容 505的面积为电容 501的面积 的大致两倍。 归纳起来， 电容 501至 504进行串联和 /并联， 所构成的电容再与电 容 505进行串联。 电容 501至 504任意连接后构成的电容属于第一组电容， 电容 50 5属于第二组电容， 不同组的电容的面积大致相同， 因此在有效电容的总面积不 变的情况下可以取得压电换能器的最小的输出阻抗。
[0071] 上述实施例二至实施例五的实现方式也可以参考实施例一， 可以是一层的压电 薄膜层及其上方或下方的支撑层， 也可以是两层或两层以上的压电薄膜层并省 略支撑层， 还可以是两层或两层以上的压电薄膜层并在整体结构的上方或下方 或中间设置支撑层。
[0072] 根据以上五个实施例可以发现， 本申请提供的 MEMS压电换能器对电容形状进 行了优化设计， 主要体现在以下几个方面。
[0073] 第一， 本申请是根据 MEMS压电换能器在加载一定载荷吋的应力分布情况来设 计电容的位置、 数量与形状。 具体而言， 在 MEMS压电换能器的应力越大的区域 ， 设置电容的必要性就越高； 反之亦然。 因此， 电容优先设置在 MEMS压电换能 器的应力最大及较大的区域。
[0074] 虽然以上五个实施例都在 MEMS压电换能器上设置了伪电容， 然而伪电容并不 是本申请所必须具有的。 如果本申请 MEMS压电换能器省略了伪电容， 那么所有 有效电容的总和大致覆盖了压电换能器的全部表面。 如果本申请 MEMS压电换能 器包含有伪电容， 那么所有有效电容和伪电容的总和大致覆盖了压电换能器的 全部表面。
[0075] 如果在 MEMS压电换能器上设置伪电容， 则由于其覆盖压电换能器上应力最小 的区域， 这一区域通常噪声水平高于信号水平， 或与信号处于同一水平， 伪电 容不参与信号输出有利于提升压电换能器的输出性能。 反之， 如果在 MEMS压电 换能器上不设置伪电容， 就意味着应力最小的区域也参与信号输出， 那么会降 低压电换能器的输出性能。
[0076] 优选地， 在 MEMS压电换能器的应力越小的区域， 设置伪电容的必要性就越高 ； 反之亦然。 因此， 伪电容优先设置在 MEMS压电换能器的应力最小的区域。
[0077] 优选地， 在 MEMS压电换能器的应力最大的区域设置电容； 在 MEMS压电换能 器的应力最小的区域设置伪电容； 在 MEMS压电换能器的其他区域， 通常设置电 容， 也可以设置为伪电容。
[0078] 由以上五个实施例可以发现， 每个电容或伪电容均覆盖了 MEMS压电换能器的 部分表面， 所覆盖区域的表面应力并不是一个具体值而是一个应力范围。 当讨 论到第一个区域的应力〉第二个区域的应力吋， 实际上是指第一个区域的应力 范围内任意应力值〉第二个区域的应力范围内任意应力值。
[0079] 优选地， 根据 MEMS压电换能器在加载一定载荷吋的应力大小将 MEMS压电换 能器的表面划分为两个以上的区域， 每个区域对应互不相同的一个应力范围。 最大的应力范围的区域对应设置第一组电容， 第二大的应力范围的区域对应设 置第二组电容， 以此类推。 电容至少具有两组。 某个区域如果在 MEMS压电换能 器表面是连续的一个区块， 则对应的这一组电容优选仅包含一个电容。 某个区 域如果在 MEMS压电换能器的表面上是离散的多个区块， 则对应的这一组电容由 多个电容组成， 每个电容优选对应一个区块。 可选地， MEMS压电换能器表面的 一个区块也可设置为至少两个电容， 这些电容之间可以串联和 /或并联。
[0080] 进一步优选地， 根据 MEMS压电换能器在加载一定载荷吋的应力大小将 MEMS 压电换能器的表面划分为三个以上的区域， 每个区域对应互不相同的一个应力 范围。 最大的应力范围的区域对应设置第一组电容， 第二大的应力范围的区域 对应设置第二组电容， 以此类推。 最小的应力范围的区域对应设置一组伪电容 。 电容至少具有两组。 某个区域如果在 MEMS压电换能器表面是连续的一个区块 ， 则对应的这一组电容优选仅包含一个电容， 或者对应的这一组伪电容优选仅 包含一个伪电容。 某个区域如果在 MEMS压电换能器上是离散的多个区块， 则对 应的这一组电容由多个电容组成， 每个电容优选对应一个区块； 或者对应的这 一组伪电容由多个伪电容组成， 每个伪电容优选对应一个区块。 可选地， MEMS 压电换能器表面的一个区块也可设置为至少两个电容， 这些电容之间可以串联 和 /或并联； 或者也可设置为至少两个伪电容， 所有伪电容均不参与电信号输出
[0081] 例如将 MEMS压电换能器在加载一定载荷吋的应力值归一化为 0至 1之间， 将应 力值在 0.75至 1之间的区域称为第一区域， 将应力值在 0.5至 0.75之间的区域称为 第二区域， 将应力值在 0.25至 0.5之间的区域称为第三区域， 将应力值在 0至 0.25 之间的区域称为第四区域。 每个区域都可以是一个连续的区块， 也可以由多个 相互隔离的区块组成。 将应力范围最小的第四区域设置为一组伪电容， 第一区 域、 第二区域、 第三区域分别设置为三组电容。 同一组电容之间进行串联和 /或 并联； 不同组电容之间进行串联。
[0082] 第二， 一个 MEMS压电换能器设置至少二组有效电容。 有效电容的数量、 形状 、 面积， 可以根据实际电路配置对输出阻抗的要求、 对压电换能器灵敏度及噪 声的要求来确定。
[0083] 首先， 总的有效电容面积不变的情况下， 电容并联将使得压电换能器的输出阻 抗小， 电容串联将使得压电换能器的输出阻抗大。 串联电容的数量越多， 压电 换能器的输出阻抗就越大、 噪声强度就越大， 但其输出电信号也越大， 器件的 灵敏度就越高； 反之亦然。 对于覆盖区域的应力相同或相近、 或在相同应力范 围内的电容， 即对于同一组电容之间， 可以串联， 也可以并联。 对于覆盖区域 的应力明显不同、 或在不同应力范围内的电容， 即对于不同组电容之间， 只能 串联。 如果将不同组的电容之间进行并联， 电荷的流动再分布还是会在这些电 容覆盖区域的电极上发生， 因而无法实现本申请的发明目的。
[0084] 其次， 总的有效电容面积不变的情况下， 当不同组电容之间进行串联吋， 如果 参与串联的各个电容具有大致相同的电容值， 那么将使得压电换能器的输出阻 抗小； 如果参与串联的各个电容具有明显不同的电容值， 那么将使得压电换能 器的输出阻抗大。 因此不同组的电容的面积优选为相同的。 考虑到每一组电容 可能由多个电容所组成， 这多个电容之间的连接方式可以是串联和 /或并联， 因 此要根据每一组电容实际连接后的电容值以及组内连接方式来确定各个电容的 优选面积以及相互比例。
[0085] 第三， 伪电容可以根据实际情况中对 MEMS压电换能器的机械强度、 谐振频率 的要求来选择设置电极， 所设置的电极不参与电信号输出。 或者， 伪电容也可 以不设置电极。 伪电容的面积可以根据电路配置对输出阻抗的要求、 对换能器 灵敏度及噪声的要求来确定。
[0086] 第四， 虽然以上五个实施例均为厚度均匀的悬臂梁或悬浮薄膜结构， 然而对于 厚度不均匀的 MEMS压电换能器也同样适用， 因为仍为相同的技术原理。 虽然以 上五个实施例均为形状规则的 MEMS压电换能器， 然而对于形状不规则的 MEMS 压电换能器也同样适用， 因为仍为相同的技术原理。
[0087] 以上仅为本申请的优选实施例， 并不用于限定本申请。 对于本领域的技术人员 来说， 本申请可以有各种更改和变化。 凡在本申请的精神和原则之内， 所作的 任何修改、 等同替换、 改进等， 均应包含在本申请的保护范围之内。
工业实用性
[0088] 本申请可以应用在压电式振动能量采集器、 压电式麦克风等用于将机械能转换 为电能 （电信号） 的电子器件中。

Claims

权利要求书
一种优化电容形状的 MEMS压电换能器， 其特征是， 所述 MEMS压电 换能器的表面覆盖有 m组电容， m为≥2的自然数； 每一组电容或者仅 包含一个电容， 或者由多个电容组成； 当所述 MEMS压电换能器加载 一定载荷吋， 第一组电容中的任意一个所覆盖区域的应力〉第二组电 容中的任意一个所覆盖区域的应力〉 ......〉第1^1组电容中的任意一 个所覆盖区域的应力〉第 m电容中的任意一个所覆盖区域的应力； 同 一组电容之间进行串联和 /或并联； 不同组电容之间进行串联。
根据权利要求 1所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 不同组电容的面积为大致相同的， 面积大致相同的电容具有大致相 同的电容值。
根据权利要求 1所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 所有电容的总和大致覆盖了压电换能器的全部表面。
根据权利要求 1所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 根据 MEMS压电换能器在加载一定载荷吋的应力大小， 将压电换能 器表面划分为至少两个区域， 每个区域对应互不相同的应力范围； 每 个区域或者仅包含一个区块， 或者由多个区块组成； 最大的应力范围 的区域对应设置第一组电容， 第二大的应力范围的区域对应设置第二 组电容， 以此类推； 电容至少具有两组。
根据权利要求 4所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 所述至少两个区域中， 某个区域如果在 MEMS压电换能器表面是连 续的一个区块， 则该区域对应的一组电容仅包含一个电容； 某个区域 如果在 MEMS压电换能器上是离散的多个区块， 则该区域对应的一组 电容由多个电容组成， 每个电容对应一个区块。
根据权利要求 1所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 所述 MEMS压电换能器还包括一组伪电容； 该组伪电容或者仅包含 一个伪电容， 或者由多个伪电容组成； 当所述 MEMS压电换能器加载 一定载荷吋， 第 m组电容中的任意一个所覆盖区域的应力〉任意一个 伪电容所覆盖区域的应力； 伪电容不参与电信号输出。
根据权利要求 6所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 所述伪电容覆盖区域或者设置电极， 或者不设置电极。
根据权利要求 6所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 所有电容和所有伪电容的总和大致覆盖了压电换能器的全部表面。 根据权利要求 6所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 根据 MEMS压电换能器在加载一定载荷吋的应力大小， 将压电换能 器表面划分为至少三个区域， 每个区域对应互不相同的应力范围； 每 个区域或者仅包含一个区块， 或者由多个区块组成； 最大的应力范围 的区域对应设置第一组电容， 第二大的应力范围的区域对应设置第二 组电容， 以此类推； 电容至少具有两组； 最小的应力范围的区域对应 设置为一组伪电容。
根据权利要求 9所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 所述至少三个区域中， 某个区域如果在 MEMS压电换能器表面是连 续的一个区块， 则该区域对应的一组电容仅包含一个电容， 或者该区 域对应的一组伪电容仅包含一个伪电容； 某个区域如果在 MEMS压电 换能器上是离散的多个区块， 则该区域对应的一组电容由多个电容组 成， 每个电容对应一个区块； 或者该区域对应的一组伪电容由多个伪 电容组成。
根据权利要求 1所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 所述 MEMS压电换能器或者为厚度均匀， 或者为厚度不均匀； 或者 为形状规则， 或者为形状不规则； 所述 MEMS压电换能器的形状至少 包括矩形悬臂梁、 扇形悬臂梁、 直角三角形悬臂梁、 正方形双边固定 支撑悬臂梁、 正方形悬浮薄膜。
根据权利要求 1所述的优化电容形状的 MEMS压电换能器， 其特征是 所述 MEMS压电换能器包括仅一层压电薄膜层， 在该压电薄膜层的上 下表面均设置有电极层， 在整体结构的上方或下方具有支撑层； 或者， 所述 MEMS压电换能器包括两层或两层以上的压电薄膜层并省 略支撑层， 在每一层压电薄膜层的上下表面均设置有电极层； 或者， 所述 MEMS压电换能器包括两层或两层以上的压电薄膜层， 在 每一层压电薄膜层的上下表面均设置有电极层， 在整体结构的上方或 下方或中间设置有支撑层。
[权利要求 13] 根据权利要求 12所述的优化电容形状的 MEMS压电换能器， 其特征是 ， 所述 MEMS压电换能器在同一区域位置对应的全部电极层构成一个 电容， 或构成一个伪电容。
PCT/CN2017/080744 2017-04-17 2017-04-17 一种优化电容形状的mems压电换能器 WO2018191842A1 (zh)

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