WO2024149163A1 - 压电微机械超声换能器、制作方法以及电气产品 - Google Patents

压电微机械超声换能器、制作方法以及电气产品 Download PDF

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WO2024149163A1
WO2024149163A1 PCT/CN2024/070757 CN2024070757W WO2024149163A1 WO 2024149163 A1 WO2024149163 A1 WO 2024149163A1 CN 2024070757 W CN2024070757 W CN 2024070757W WO 2024149163 A1 WO2024149163 A1 WO 2024149163A1
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electrode
layer
substrate
electrostatic force
piezoelectric
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PCT/CN2024/070757
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English (en)
French (fr)
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庞慰
牛鹏飞
张孟伦
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天津大学
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Publication of WO2024149163A1 publication Critical patent/WO2024149163A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • 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
    • 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]

Definitions

  • the present application relates to the field of electronic technology, and in particular to a piezoelectric micromechanical ultrasonic transducer, a manufacturing method and an electrical product.
  • PMUT Piezoelectric Micromachined Ultrasonic Transducer
  • PMUT is a micro-motor system that uses the forward and reverse piezoelectric effects of piezoelectric materials to make the piezoelectric film vibrate, thereby transmitting or receiving ultrasonic signals.
  • PMUT can be used as an actuator to transmit sound waves and as a sensor to receive sound waves.
  • the mass production process and wafer-level packaging process based on MEMS standard process make PMUT production cost low, which is very suitable for large-scale commercial applications.
  • PMUT in the prior art usually includes a bottom electrode, a piezoelectric layer, a top electrode, a support layer, a substrate and a cavity.
  • PMUT diaphragm layer the membrane layer that bends when the PMUT is working, including the piezoelectric film layer and the electrode layers on both sides thereof) is a planar structure.
  • the radius of curvature of the PMUT diaphragm layer with a curved surface becomes a fixed value and cannot be changed once the product is formed.
  • the ultrasonic emission performance of the obtained PMUT will be improved, its performance cannot be adjusted, which limits the application of PMUT.
  • the embodiments of the present application provide a piezoelectric micromechanical ultrasonic transducer, a manufacturing method, and an electrical product.
  • a PMUT with a large curvature can be formed to obtain good ultrasonic performance.
  • the piezoelectric micromechanical ultrasonic transducer provided by the embodiments of the present invention can adjust the curvature of the PMUT diaphragm layer as needed, so that the PMUT has a better application range.
  • a piezoelectric micromechanical ultrasonic transducer comprising:
  • At least one piezoelectric film layer wherein electrode layers are disposed on both sides of the piezoelectric film layer, and the electrode layer below the piezoelectric film layer closest to the substrate is located above the substrate;
  • the piezoelectric film layer and the electrode layers on both sides thereof are curved surfaces, and the curved surfaces are formed by the electrostatic force between the electrode layers and the substrate.
  • a ratio of a minimum width of the curved surface on a horizontal cross-section of the piezoelectric micromechanical ultrasonic transducer to a depth of the curved surface is greater than 1/40.
  • the piezoelectric micromechanical ultrasonic transducer further includes:
  • an insulating layer located between the electrode layer below the piezoelectric film layer closest to the substrate and the substrate;
  • a DC voltage is applied between the electrode layer below the piezoelectric film layer closest to the substrate and the substrate;
  • the electrostatic force is generated by the DC voltage.
  • the piezoelectric micromechanical ultrasonic transducer further includes:
  • the support layer is located at at least one of the following positions: between the electrode layer below the piezoelectric film layer closest to the substrate and the insulating layer, and on the electrode layer above the piezoelectric film layer farthest from the substrate.
  • the insulating layer is laid along the substrate surface and the cavity surface between the electrode layer below the piezoelectric film layer closest to the substrate and the substrate.
  • the piezoelectric micromechanical ultrasonic transducer further includes:
  • a first electrostatic force electrode is located on the insulating layer at the bottom of the cavity, and a DC voltage is applied between the first electrostatic force electrode and an electrode layer below the piezoelectric film layer closest to the substrate;
  • the dielectric layer is located at at least one of the following positions: between the electrode layer and the insulating layer below the piezoelectric film layer closest to the substrate, and on the top of the first electrostatic force electrode.
  • the piezoelectric micromechanical ultrasonic transducer further includes:
  • the insulating column is arranged on the first electrostatic force electrode.
  • the piezoelectric micromechanical ultrasonic transducer further includes:
  • a dielectric layer located between the electrode layer below the piezoelectric film layer closest to the substrate and the insulating layer;
  • the second electrostatic force electrode is located below the dielectric layer, and a DC voltage is applied between the second electrostatic force electrode and the substrate.
  • the method when the dielectric layer is located between the electrode layer below the piezoelectric film layer closest to the substrate and the insulating layer, the method further includes:
  • the third electrostatic force electrode is located between the dielectric layer and the insulating layer, and a DC voltage is applied to the third electrostatic force electrode and at least one of the first electrostatic force electrode and the substrate.
  • the substrate includes at least one of the following materials: single crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, high conductivity doped silicon and diamond.
  • the electrode layer, the first electrostatic force electrode, the second electrostatic force electrode and the third electrostatic force electrode include at least one of the following materials: highly conductive silicon, molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above materials.
  • the piezoelectric film layer includes at least one of the following materials:
  • the support layer includes at least one of the following materials: silicon nitride, silicon dioxide and silicon.
  • a fourteenth aspect of the embodiments of the present application there is provided a method for manufacturing a piezoelectric micromechanical ultrasonic transducer as described in any one of the first to thirteenth aspects above, comprising:
  • the first electrostatic force electrode is located on the insulating layer at the bottom of the cavity, the second electrostatic force electrode is located under the dielectric layer; the third electrostatic force electrode is located between the dielectric layer and the insulating layer; the dielectric layer is located at at least one of the following positions: between the electrode layer below the piezoelectric film layer closest to the substrate and the insulating layer, and covering the first electrostatic force electrode;
  • the first electrostatic force electrode exists, there is a dielectric layer and/or an insulating layer and/or an insulating column between the first electrostatic force electrode and the electrode layer below the piezoelectric film layer closest to the substrate, the second electrostatic force electrode, and the third electrostatic force electrode;
  • the electrostatic force generated by the DC voltage causes the electrode layer, the piezoelectric film layer, the first electrostatic force electrode, the second electrostatic force electrode and the third electrostatic force electrode to present a curved surface.
  • an electrical product wherein the electrical product has a piezoelectric micromechanical ultrasonic transducer as described in any one of the first to thirteenth aspects above.
  • the piezoelectric micromechanical ultrasonic transducer, manufacturing method and electrical product proposed in the present application in the process of manufacturing the piezoelectric micromechanical ultrasonic transducer, the diaphragm layer of the piezoelectric micromechanical ultrasonic transducer is made curved through the electrostatic force between the electrode layers and between the electrode layer and the substrate, so that a PMUT diaphragm layer with a high degree of curvature can be obtained.
  • FIG1 is a schematic diagram of a piezoelectric micromechanical ultrasonic transducer in the prior art
  • FIG2 is a schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application
  • FIG3 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG4 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG5 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG6 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG7 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG8 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG9 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG10 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG11 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG12 is another schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application.
  • FIG13 is a schematic flow chart of a method for manufacturing a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present application
  • Figure Number 100 substrate; 101 cavity; 110 insulation layer; 200 bottom electrode; 300, 500 piezoelectric film layer; 400, 600 top electrode 800, 120 dielectric layer; 900 second electrostatic force electrode; 1000 first electrostatic force electrode; 1100 A third electrostatic force electrode.
  • the term “and/or” includes any one and all combinations of one or more of the associated listed terms.
  • the terms “include”, “comprises”, “has”, etc. refer to the existence of the stated features, elements, components or components, but do not exclude the existence or addition of one or more other features, elements, components or components.
  • one side of the substrate also referred to as base plate or substrate
  • the supporting layer, the bottom electrode, the piezoelectric film layer, and the bonding layer is referred to as the upper side
  • the other side of the top electrode, the supporting layer, the bottom electrode, the piezoelectric film layer, and the bonding layer is referred to as the lower side.
  • FIG1 is a cross-sectional view of a typical PMUT.
  • the PMUT includes: a substrate 100, a bottom electrode 200, a piezoelectric film layer 300, and a top electrode 400.
  • the substrate 100 contains a cavity 101, which is used to provide space for the PMUT diaphragm layer to bend and vibrate.
  • the pressure inside the cavity 101 is the same or equivalent to the external environmental pressure of the PMUT, that is, the pressure on both sides of the PMUT diaphragm layer is equivalent, thereby making it basically flat. Even when the PMUT product is formed and its diaphragm layer is bent, due to the relatively large rigidity of the diaphragm layer, the degree of its upward or downward bending is limited and not easy to control.
  • the piezoelectric micromechanical ultrasonic transducer provided in some embodiments of the present application includes:
  • a substrate 100 is provided with a cavity 101;
  • At least one piezoelectric film layer 300 electrode layers are arranged on both sides of the piezoelectric film layer 300 (for ease of description, the electrode layer 500 above the piezoelectric film layer 400 farthest from the substrate 100 is referred to as the top electrode, and the remaining electrode layers 300 are referred to as the bottom electrode), and the electrode layer 200 below the piezoelectric film layer 300 closest to the substrate 100 is located on the substrate 100;
  • the piezoelectric film layer 300 and the electrode layers ( 200 and 400 ) on both sides thereof are curved surfaces, which are formed by the electrostatic force between the electrode layer ( 400 ) and the substrate 100 .
  • the above-mentioned electrostatic force can be realized in the following manner: a DC voltage is applied to the bottom electrode 200 and the substrate 100, thereby forming an electrostatic force through the DC voltage.
  • the curved surface mentioned above refers to the state of the PMUT when it is working, that is, when there is an electrostatic force between the top electrode 400, the bottom electrode 200 and the substrate 100, and when there is no such electrostatic force, the piezoelectric film layer 300 and the electrode layers (200, 400) on both sides thereof are in a planar state. It should be noted that when the PMUT is working, an AC voltage needs to be applied to the top electrode 400 and the bottom electrode 200 to drive the vibration of the diaphragm layer of the PMUT.
  • the substrate 100 needs to have high conductivity, for example, be made of highly conductive doped silicon.
  • a ratio of a minimum width of the curved surface in a horizontal cross-section of the piezoelectric micromechanical ultrasonic transducer to a depth of the curved surface is greater than 1/40.
  • the above-mentioned minimum width refers to that, on the horizontal section of the piezoelectric micromechanical ultrasonic transducer, a straight line passing through the center (or approximate center) of the curved surface intersects the curved surface at two points, and the minimum distance between these two points is the minimum width.
  • the ratio of the minimum width of the curved surface to its depth is greater than 1/20 or 1/10.
  • the value of the DC voltage V applied between the bottom electrode 200 and the substrate 100 can be adjustable, that is, its value can be set according to the degree of bending to be achieved by the PMUT diaphragm layer, so that a PMUT with adjustable frequency and acoustic performance and a curved structure can be obtained.
  • the cavity 101 in the substrate 100 there is no limitation on the position of the cavity 101 in the substrate 100 , and the cavity 101 may be located at the center of the substrate 100 , or on the left side, or on the right side of the substrate 100 .
  • the piezoelectric micromechanical ultrasonic transducer provided in some embodiments of the present application makes the diaphragm layer of the piezoelectric micromechanical ultrasonic transducer curved through the electrostatic force between the electrode layers and between the electrode layers and the substrate, so as to obtain a PMUT diaphragm layer with a high degree of curvature.
  • the piezoelectric micromechanical ultrasonic transducer makes the diaphragm layer of the piezoelectric micromechanical ultrasonic transducer curved through the electrostatic force between the electrode layers and between the electrode layers and the substrate, so as to obtain a PMUT diaphragm layer with a high degree of curvature.
  • the DC voltage applied to the electrode different electrostatic forces can be obtained, and then the degree of curvature of the PMUT diaphragm layer can be controlled, which greatly expands the application scope of the piezoelectric micromechanical ultrasonic transducer.
  • the piezoelectric micromechanical ultrasonic transducer in order to ensure electrical isolation between the bottom electrode 200 and the substrate 100 , the piezoelectric micromechanical ultrasonic transducer further includes:
  • the insulating layer 110 is located between the electrode layer 200 below the piezoelectric film layer 300 closest to the substrate 100 and the substrate 100;
  • an alternating voltage is applied between the electrode layers (200, 400), and a direct current voltage is applied between the electrode layer 200 below the piezoelectric film layer closest to the substrate and the substrate 100;
  • Electrostatic forces are generated by alternating voltage as well as direct voltage.
  • the insulating layer 110 is located between the bottom electrode 200 and the substrate 100 ; similarly, an AC voltage is applied between the top electrode 400 and the bottom electrode 200 , and a DC voltage is applied between the bottom electrode 200 and the substrate 100 .
  • the piezoelectric micromachined ultrasonic transducer further comprises:
  • the support layer is located at at least one of the following positions: between the electrode layer 200 below the piezoelectric film layer 300 closest to the substrate 100 and the insulating layer 110, and above the electrode layer 400 above the piezoelectric film layer 300 farthest from the substrate 100.
  • the function of the support layer is to make the neutral layer of the diaphragm layer of the piezoelectric micromechanical ultrasonic transducer deviate from the mass center plane of the piezoelectric film layer 300.
  • the diaphragm layer includes the support layer, the piezoelectric film layer 300, and the electrode layers (200 and 400) on both sides thereof.
  • the neutral layer of the diaphragm layer composed of the piezoelectric film layer 300 and the electrode layers (200 and 400) on both sides thereof is the mass center plane of the piezoelectric film layer 300, that is, its mid-axis plane (the position shown by the dotted line in Figure 5), but after adding a supporting surface, the neutral layer of the diaphragm layer can deviate from this surface.
  • a support layer is not necessary; for example, in FIG2 , the bottom electrode 200 is thicker than the top electrode 400, so the bottom electrode 200 serves as both a support layer and an electrode layer. Even if the bottom electrode 200 and the top electrode 400 are of the same thickness, the diaphragm layer of the piezoelectric micromechanical ultrasonic transducer provided in some embodiments of the present application has a curved surface structure, and it can still be used to excite and receive ultrasonic waves.
  • the insulating layer 110 is laid between the bottom electrode 200 and the substrate 100 along the surface of the substrate 100 and the surface of the cavity 101 , that is, the insulating layer 110 is substantially in a “concave” shape in cross section.
  • the piezoelectric micromechanical ultrasonic transducer further includes:
  • the first electrostatic force electrode 1000 is located on the insulating layer 110 at the bottom of the cavity 101 , and a DC voltage is applied between the first electrostatic force electrode 1000 and the electrode layer 200 below the piezoelectric film layer 300 closest to the substrate.
  • the dielectric layer 800 is located at at least one of the following positions: between the electrode layer 200 and the insulating layer 110 below the piezoelectric film layer 300 closest to the substrate 100 , and covering the first electrostatic force electrode 1000 .
  • the dielectric layer 800 is located at at least one of the following positions: between the bottom electrode 200 and the insulating layer 110, and only covers the first electrostatic force electrode 1000 (this situation is not shown in the figure).
  • the role of the dielectric layer 800 is to prevent the bottom electrode 200 from contacting the first electrostatic force electrode 1000. Its role is similar to that of the insulating column. Of course, the insulating column and the dielectric layer can be provided in the piezoelectric micromechanical ultrasonic transducer at the same time. It should be noted that when the dielectric layer 800 is located between the bottom electrode 200 and the insulating layer 110, it bends with the PMUT diaphragm layer (when the PMUT is working). When the dielectric layer 800 covers the first electrostatic force electrode 1000, its shape does not change.
  • the first electrostatic force electrode 1000 can be eliminated and disposed in the substrate 100, that is, a DC voltage is applied between the substrate 100 and the bottom electrode 200.
  • the first electrostatic force electrode 1000 is located on the insulating layer 110 at the bottom of the cavity 101, and a DC voltage is applied between the first electrostatic force electrode 1000 and the bottom electrode 200.
  • the DC voltage is applied between the bottom electrode 200 and the substrate 100 in FIG3 , but is replaced by the first electrostatic force electrode 1000 and the bottom electrode 200.
  • an insulating layer 110 is disposed between the bottom electrode 200 and the substrate 100.
  • the insulating layer 110 may not be added, and the present invention is not limited thereto.
  • the piezoelectric micromachined ultrasonic transducer further comprises:
  • the insulating column is arranged on the first electrostatic force electrode 1000 and is used to prevent the electrode layer 200 from contacting the first electrostatic force electrode 1000 when the PMUT diaphragm layer bends during the operation of the PMUT, thereby preventing the device from failing.
  • the method further includes:
  • the second electrostatic force electrode 900 is located below the dielectric layer 800 , wherein an AC voltage is applied between the electrode layers ( 200 , 400 ), and a DC voltage is applied between the second electrostatic force electrode 900 and the substrate 100 .
  • the piezoelectric micromechanical ultrasonic transducer when the dielectric layer 800 is located between the bottom electrode 200 and the insulating layer 110, the piezoelectric micromechanical ultrasonic transducer further includes: a second electrostatic force electrode 900, located below the dielectric layer 800 (the two are connected), wherein an AC voltage is applied to the top electrode 400 and the bottom electrode 200, and a DC voltage is applied between the second electrostatic force electrode 900 and the substrate 100.
  • the insulating layer 110 in FIG. 9 may not exist.
  • the first electrostatic force electrode 1000 cannot be set on the insulating layer 110 at the bottom of the cavity 101, because if the first electrostatic force electrode 1000 and the second electrostatic force electrode 900 exist at the same time, there is a greater risk of contact between the two when the PMUT is working.
  • the method further includes:
  • the third electrostatic force electrode 1100 is located between the dielectric layer 800 and the insulating layer 110, wherein an AC voltage is applied between the electrode layers (200, 400), and a DC voltage is applied between the third electrostatic force electrode 1100 and at least one of the first electrostatic force electrode 1000 or the substrate 100 (as shown in Figures 10 and 11).
  • the piezoelectric micromechanical ultrasonic transducer when the dielectric layer 800 is located between the bottom electrode 200 and the insulating layer 110, the piezoelectric micromechanical ultrasonic transducer also includes: a third electrostatic force electrode 1100, located between the dielectric layer 800 and the insulating layer 110, wherein an AC voltage is applied to the top electrode 400 and the bottom electrode 200, and a DC voltage is applied to the third electrostatic force electrode 1100 and at least one of the electrostatic force electrode 1000 or the substrate 100.
  • the component of the electrostatic attraction force in the piezoelectric ultrasonic transducer in FIG11 contains a first electrostatic force electrode 1000 and a second electrostatic force electrode 900 for applying a DC voltage signal.
  • a DC voltage By applying a DC voltage to the electrode pair and applying an AC voltage to the top electrode 400 and the bottom electrode 200, an electrostatic attraction force is generated, causing the PMUT diaphragm layer to bend toward the cavity 101, forming a PMUT with a curved surface structure.
  • there is a dielectric layer 800 between the bottom electrode 200 and the second electrostatic force electrode 900 of the PMUT so that the two electrode pairs work independently, there is no common electrode, and the influence between them is reduced.
  • the insulating layer 110 in the figure is not necessary and may not exist.
  • a dielectric layer 120 is added between the second electrostatic force electrode 900 and the first electrostatic force electrode 1000, thereby preventing the two electrodes from
  • the film layer can cover the first electrostatic force electrode 1000 instead of just being next to the dielectric layer 800, or a certain amount of insulating pillars can be added between the dielectric layer 800 and the first electrostatic force electrode 1000 to prevent the bottom electrode 200 from contacting the first electrostatic force electrode 1000 during the operation of the PMUT, thereby preventing the device from failing.
  • the above embodiments can all be applied to this type of design.
  • FIG. 12 is an embodiment in which there are multiple piezoelectric film layers (two are used as an example in FIG. 12, but the present application is not limited thereto), wherein 300 and 500 are piezoelectric film layers, 200 and 400 are bottom electrodes, and 600 is a top electrode, which is located on both sides of the piezoelectric film layers 300 and 500.
  • the PMUT contains two piezoelectric film layers, and the simultaneous vibration of the two piezoelectric film layers can generate a stronger ultrasonic signal.
  • a DC voltage V is applied between the electrode pair substrate 100 and the bottom electrode 200, causing the PMUT diaphragm layer to bend under the action of electrostatic attraction, and an AC voltage is applied between the bottom electrode 400 and the top electrode 600, and an electrostatic force is generated between the bottom electrode 200 and the substrate 100, thereby stimulating the piezoelectric film layer to vibrate and excite ultrasonic waves.
  • the DC voltage V values applied can be different, thereby controlling the bending degree of the PMUT diaphragm layer to be different, and obtaining a PMUT with adjustable frequency and acoustic performance and a curved surface structure. It can be understood that the ultrasonic emission performance of the PMUT is greatly improved due to the double-layer piezoelectric film layer and the curved surface structure.
  • 400 and 200 are two bottom electrodes, which can be the same or different.
  • 300 and 500 are two piezoelectric film layers, which can be the same or different.
  • the simultaneous vibration of the two piezoelectric film layers 300 and 500 can generate a stronger ultrasonic signal.
  • the first electrostatic force electrode 1000 cannot be set on the insulating layer 110 at the bottom of the cavity 101 at this time, because if the first electrostatic force electrode 1000 and the bottom electrode 200 exist at the same time (without an insulating layer or dielectric layer between the two), there is a greater risk of contact between the two when the PMUT is working.
  • the substrate includes at least one of the following materials: single crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, high conductivity doped silicon (silicon on insulator (SOI)) and diamond.
  • the electrode layer, the first electrostatic force electrode, the second electrostatic force electrode and the third electrostatic force electrode include at least one of the following materials: highly conductive silicon, molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above materials.
  • the piezoelectric film layer includes at least one of the following materials: the optional materials are polycrystalline aluminum nitride (AlN), polycrystalline zinc oxide, polycrystalline lead zirconate titanate (PZT), polycrystalline lithium niobate (LiNbO3), polycrystalline lithium tantalate (LiTaO3), polycrystalline potassium niobate (KNbO3) and the like, or single crystal aluminum nitride, single crystal gallium nitride, single crystal Lithium niobate, single crystal lead zirconate titanate, single crystal potassium niobate, single crystal quartz film, or single crystal lithium tantalate, rare earth elements with a preset atomic ratio (such as scandium-doped aluminum nitride).
  • AlN polycrystalline aluminum nitride
  • PZT polycrystalline lead zirconate titanate
  • LiNbO3 polycrystalline lithium niobate
  • LiTaO3 polycrystalline lithium tantalate
  • the support layer includes at least one of the following materials: silicon nitride, silicon dioxide, and silicon.
  • the cross-sectional area of the top electrode 500 in Figures 1 to 12 is smaller than the cross-sectional area of the piezoelectric film layer 400, the bottom electrode 300, the support layer 200 and the insulating layer 800.
  • the cross-sectional area of the top electrode 500 may be the same as or different from the cross-sectional area of the piezoelectric film layer 400, the bottom electrode 300, the support layer 200 and the bonding layer 800, and may also be other shapes, such as circular, triangular, annular, and the like.
  • the piezoelectric micromechanical ultrasonic transducer provided in some embodiments of the present application can, under a certain cavity radius D, first obtain a higher degree of bending h through the stretching effect of the electrostatic force, thereby meeting the requirement of a larger degree of bending of the PMUT diaphragm layer, such as h/D ⁇ 0.5%, especially h/D ⁇ 1%; in addition, by regulating the DC voltage V applied to the electrode, different electrostatic forces can be obtained, thereby obtaining the desired degree of bending of the PMUT diaphragm layer.
  • a method for manufacturing the above-mentioned piezoelectric micromechanical ultrasonic transducer is also provided according to the present application, and the method includes:
  • Step 100 applying a DC voltage between the substrate or/and the first electrostatic force electrode and at least one of the following film layers: an electrode layer below the piezoelectric film layer closest to the substrate, a second static electrode, and a third electrostatic force electrode;
  • the first electrostatic force electrode is located on the insulating layer at the bottom of the cavity, the second electrostatic force electrode is located under the dielectric layer; the third electrostatic force electrode is located between the dielectric layer and the insulating layer; the dielectric layer is located at at least one of the following positions: between the electrode layer below the piezoelectric film layer closest to the substrate and the insulating layer, and covering the first electrostatic force electrode;
  • the first electrostatic force electrode exists, there is a dielectric layer and/or an insulating layer and/or an insulating column between the first electrostatic force electrode and the electrode layer below the piezoelectric film layer closest to the substrate, the second electrostatic force electrode, and the third electrostatic force electrode.
  • Step 200 The electrode layer, the piezoelectric film layer, the first electrostatic force electrode, the second electrostatic force electrode and the third electrostatic force electrode are curved by the electrostatic force generated by the DC voltage.
  • step 200 when observed from a direction parallel to the substrate, the electrode layer, the piezoelectric film layer, the first electrostatic force electrode, the second electrostatic force electrode and the third electrostatic force electrode are curved surfaces;
  • the method for manufacturing the piezoelectric micromechanical ultrasonic transducer also includes:
  • Step 300 Apply an alternating voltage between the electrode layers on both sides of the piezoelectric film layer to vibrate the diaphragm layer of the PMUT.
  • Some embodiments of the present application also provide an electrical product having the piezoelectric micromechanical ultrasonic transducer as described above.
  • the electrical product includes, for example, an ultrasonic imager, an ultrasonic radar, a sonar detection, a sweeping robot, an ultrasonic smoke alarm, etc., but the present application is not limited thereto.

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Abstract

一种压电微机械超声换能器、制作方法以及电气产品。压电微机械超声换能器包括：衬底（100），设置有空腔（101）；至少一个压电薄膜层（300），压电薄膜层（300）两侧均设置有电极层（200,400），距离衬底（100）最近的压电薄膜层（300）下方的电极层（200）位于衬底（100）之上；其中，从平行于衬底（100）的方向观察，压电薄膜层（300）以及其两侧的电极层（200,400）呈曲面，曲面通过顶电极（400）、底电极（200）以及衬底（100）之间的静电力而形成。通过电极层之间以及电极层与衬底之间的静电力使压电微机械超声换能器的振膜层呈曲面，从而获得具有较高弯曲程度的PMUT振膜层。另外，通过调整施加在电极上的直流电压，可以获得不同的静电力，进而可以调控PMUT振膜层的弯曲程度，极大的扩展了压电微机械超声换能器应用范围。

Description

压电微机械超声换能器、制作方法以及电气产品
相关申请
本申请要求于2023年01月12日递交的申请号为202310041814.9的中国发明专利申请的优先权，并引用上述专利申请公开的全部内容作为本申请的一部分。
技术领域
本申请涉及电子技术领域，特别涉及一种压电微机械超声换能器、制作方法以及电气产品。
背景技术
压电微机械超声换能器(Piezoelectric Micromachined Ultrasonic Transducer，PMUT)是一种微电机系统，其利用压电材料的正逆压电效应使压电薄膜振动，从而发射或者接收超声波信号，PMUT既可以做执行器发射声波，又可以做传感器接收声波，另外，基于MEMS标准工艺的批量化生产工艺和晶圆级封装工艺使PMUT生产成本较低，非常适合大规模商业应用。
PMUT的发射和接收性能是其关键指标，决定了产品的优劣。现有技术中的PMUT通常包括底电极、压电层、顶电极、支撑层以及衬底和空腔组成。一般情况下，PMUT振膜层(PMUT工作时发生弯曲的膜层，包括压电薄膜层以及其两侧的电极层)呈平面结构，其工作原理为，当在电极上施加交变信号时，因逆压电效应，空腔上方PMUT振膜层中的压电薄膜层产生d31模式的伸张和收缩振动，导致PMUT振膜层呈弯曲模式振动，进而激发超声波。
发明内容
研究发现，现有技术中的PMUT的发射性能不足，产生的超声波传播距离太短，限制PMUT的大规模商业应用，因此需要提高PMUT的发射性能。
研究发现，当PMUT振膜层呈曲面形式时，其发射性能呈数量级的提升。然而曲面形式PMUT的制造难度巨大，很难应用于规模化PMUT的研发。
另一方面，具有曲面的PMUT振膜层的曲率半径一经产品成型后，便成为固定值，不能改变，在这种情况下，虽所得PMUT的超声发射性能会得到提升，但是其性能不可调控，从而限制了PMUT的应用。
为了解决上述问题中的至少之一或其他类似问题，本申请实施例提供了一种压电微机械超声换能器、制作方法以及电气产品，一方面，能够形成较大弯曲程度的PMUT，进而获得良好的超声性能。另一方面，本发明实施例所提供的压电微机械超声换能器可以依据需要调整的PMUT振膜层的弯曲程度，从而使PMUT具有更好的应用范围。
根据本申请实施例的第一方面，提供一种压电微机械超声换能器，包括：
衬底，设置有空腔；
至少一个压电薄膜层，所述压电薄膜层两侧均设置有电极层，距离所述衬底最近的压电薄膜层下方的电极层位于所述衬底之上；
其中，从平行于所述衬底的方向观察，所述压电薄膜层以及其两侧的电极层呈曲面，所述曲面通过所述电极层与所述衬底之间的静电力而形成。
根据本申请实施例的第二方面，所述曲面在所述压电微机械超声换能器的水平剖面上的最小宽度与所述曲面的深度之比大于1/40。
根据本申请实施例的第三方面，压电微机械超声换能器还包括：
绝缘层，位于距离所述衬底最近的压电薄膜层下方的电极层与所述衬底之间；
其中，距离所述衬底最近的压电薄膜层下方的电极层与所述衬底之间施加直流电压；
所述静电力通过所述直流电压而形成。
根据本申请实施例的第四方面，压电微机械超声换能器还包括：
支撑层，位于如下至少之一的位置：距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间以及离所述衬底最远的压电薄膜层上方的电极层之上。
根据本申请实施例的第五方面，所述绝缘层沿所述衬底表面以及所述空腔表面铺设于所述距离所述衬底最近的压电薄膜层下方的电极层与所述衬底之间。
根据本申请实施例的第六方面，压电微机械超声换能器还包括：
第一静电力电极，位于所述空腔底部的绝缘层之上，所述第一静电力电极与距离所述衬底最近的压电薄膜层下方的电极层之间施加直流电压；
介质层，位于如下至少之一的位置：距离衬底最近的压电薄膜层下方的电极层与绝缘层之间，以及覆盖第一静电力电极之上。
根据本申请实施例的第七方面，压电微机械超声换能器还包括：
绝缘柱，设置与所述第一静电力电极之上。
根据本申请实施例的第八方面，压电微机械超声换能器还包括：
介质层，位于距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间；
第二静电力电极，位于所述介质层之下，所述第二静电力电极与所述衬底之间施加直流电压。
根据本申请实施例的第九方面，当所述介质层位于距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间时，还包括：
第三静电力电极，位于所述介质层与所述绝缘层之间，所述第三静电力电极与所述第一静电力电极或所述衬底中的至少之一施加直流电压。
根据本申请实施例的第十方面，所述衬底包括如下至少之一的材料：单晶硅、氮化镓、砷化镓、蓝宝石、石英、碳化硅、高导电性掺杂硅以及金刚石。
根据本申请实施例的第十一方面，所述电极层、第一静电力电极、第二静电力电极以及第三静电力电极包括如下至少之一的材料：高导电硅、钼、钌、金、铝、镁、钨、铜，钛、铱、锇、铬或以上材料的复合体或合金。
根据本申请实施例的第十二方面，所述压电薄膜层包括如下至少之一的材料：
多晶氮化铝、多晶氧化锌、多晶锆钛酸铅、多晶铌酸锂、多晶钽酸锂、多晶铌酸钾、单晶氮化铝、单晶氮化镓、单晶铌酸锂、单晶锆钛酸铅、单晶铌酸钾、单晶石英薄膜、单晶钽酸锂、预设原子比的稀土元素。
根据本申请实施例的第十三方面，所述支撑层包括如下至少之一的材料：氮化硅、二氧化硅以及硅。
根据本申请实施例的第十四方面，提供一种具有如上第一方面至第十三方面任一项所述的压电微机械超声换能器的制作方法，包括：
在衬底或/及第一静电力电极与下述膜层的至少之一之间施加直流电压：距离所述衬底最近的压电薄膜层下方的电极层、第二静电极以及第三静电力电极；
其中：第一静电力电极位于所述空腔底部的绝缘层之上，第二静电力电极，位于介质层之下；第三静电力电极，位于所述介质层与所述绝缘层之间；所述介质层位于如下至少之一的位置：距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间，以及覆盖所述第一静电力电极之上；
当存在所述第一静电力电极时，其与距离所述衬底最近的压电薄膜层下方的电极层、第二静电力电极以及所述第三静电力电极之间存在介质层及/或绝缘层及/或绝缘柱；
通过所述直流电压所形成静电力使所述电极层、压电薄膜层、所述第一静电力电极、第二静电力电极以及第三静电力电极呈曲面。
根据本申请实施例的第十五方面，提供一种电气产品，所述电气产品具有如上第一方面至第十三方面任一项所述的压电微机械超声换能器。
本申请实施例的有益效果之一在于：本申请所提出的压电微机械超声换能器、制作方法以及电气产品，在制作压电微机械超声换能器的过程中，通过电极层之间以及电极层与衬底之间的静电力使压电微机械超声换能器的振膜层呈曲面，可以获得具有较高弯曲程度的PMUT振膜层，另外，通过调整施加在电极上的直流电压，可以获得不同的静电力，进而可以调控PMUT振膜层的弯曲程度，极大的扩展了压电微机械超声换能器应用范围。
参照后文的说明和附图，详细公开了本申请的实施方式。应该理解，本申请的实施方式在范围上并不因此而受到限制。在所附权利要求的精神和条款的范围内，本申请的实施方式包括许多改变、修改和等同。
针对一种实施方式描述和/或示出的特征可以以相同或类似的方式在一个或更多个其他实施方式中使用，与其他实施方式中的特征相组合，或替代其他实施方式中的特征。
应该强调，术语“包括/包含/具有”在本文使用时指特征、整件、或组件的存在，但并不排除一个或更多个其他特征、整件或组件的存在或附加。
附图说明
从以下结合附图的详细描述中，本申请实施例的上述以及其他目的、特征和优点将变得更加明显，在附图中：
图1是现有技术中的压电微机械超声换能器的一意图；
图2是本申请实施例的压电微机械超声换能器的一示意图；
图3是本申请实施例的压电微机械超声换能器的另一示意图；
图4是本申请实施例的压电微机械超声换能器的另一示意图；
图5是本申请实施例的压电微机械超声换能器的另一示意图；
图6是本申请实施例的压电微机械超声换能器的另一示意图；
图7是本申请实施例的压电微机械超声换能器的另一示意图；
图8是本申请实施例的压电微机械超声换能器的另一示意图；
图9是本申请实施例的压电微机械超声换能器的另一示意图；
图10是本申请实施例的压电微机械超声换能器的另一示意图；
图11是本申请实施例的压电微机械超声换能器的另一示意图；
图12是本申请实施例的压电微机械超声换能器的另一示意图；
图13是本申请实施例的压电微机械超声换能器的制作方法的流程示意图；
附图标号：
100衬底；
101空腔；
110绝缘层；
200底电极；
300、500压电薄膜层；
400、600顶电极
800、120介质层；
900第二静电力电极；
1000第一静电力电极；
1100第三静电力电极。
具体实施方式
参照附图，通过下面的说明书，本申请的前述以及其它特征将变得明显。在说明书和附图中，具体公开了本申请的特定实施方式，其表明了其中可以采用本申请的原则的部分实施方式，应了解的是，本申请不限于所描述的实施方式，相反，本申请包括落入所附权利要求的范围内的全部修改、变型以及等同物。
在本申请实施例中，术语“和/或”包括相关联列出的术语的一种或多个中的任何一个和所有组合。术语“包含”、“包括”、“具有”等是指所陈述的特征、元素、元件或组件的存在，但并不排除存在或添加一个或多个其他特征、元素、元件或组件。
在本申请实施例中，单数形式“一”、“该”等可以包括复数形式，应广义地理解为“一种”或“一类”而并不是限定为“一个”的含义；此外术语“所述”应理解为既包括单数形式也包括复数形式，除非上下文另外明确指出。此外术语“根据”应理解为“至少部分根据……”，术语“基于”应理解为“至少部分基于……”，除非上下文另外明确指出。此外， 本申请中“靠近”“远离”等术语仅用于说明各部件的相对位置关系，并不表示距离大小或具体程度。例如，“远离”也可以称为“背离”等。
另外，在本申请的下述说明中，为了说明的方便，将衬底(也可称为基板或基底)、支撑层、底电极、压电薄膜层、键合层的一侧称为上方或上侧，顶电极、支撑层、底电极、压电薄膜层、键合层的另一侧称为下方或下侧。但值得注意的是，这些只是为了说明的方便，并不限定本申请一些实施例的压电微机械超声换能器在制造和使用时的朝向。
图1是典型的PMUT的截面图。如图1所示，PMUT包括：衬底100，底电极200，压电薄膜层300，顶电极400。衬底100上含有空腔101，用于向PMUT振膜层弯曲振动时提供空间。在现有技术中，空腔101内部的压力与PMUT外部环境压力相同或者相当，即PMUT振膜层两侧受到的压力相当，进而使其基本呈现平面状态。即使PMUT产品成型时，其振膜层呈弯曲时，由于振膜层相对较大的刚性，其向上或向下弯曲的程度受限，且不容易控制。
下面参照附图对本申请一些实施例的实施方式进行说明。
如图2所示，本申请一些实施例所提供的压电微机械超声换能器包括：
衬底100，设置有空腔101；
至少一个压电薄膜层300，压电薄膜层300两侧均设置有电极层(为了便于描述，这里将距离衬底100最远的压电薄膜层400上方的电极层500称为顶电极，其余电极层300称为底电极)，距离衬底100最近的压电薄膜层300下方的电极层200位于衬底100之上；
参见图3，其中，从平行于衬底100的方向观察，压电薄膜层300以及其两侧的电极层(200以及400)呈曲面，曲面通过电极层(400)与衬底100之间的静电力而形成。
上述静电力可通过以下方式实现，底电极200与衬底100施加直流电压，从而通过直流电压形成静电力。另外，上面说的曲面是指PMUT在工作时的状态，即顶电极400、底电极200以及衬底100之间存在静电力的情况下，而不存在该静电力时，压电薄膜层300以及其两侧的电极层(200、400)为平面状态。需要说明的是，当PMUT在工作时，还需要在顶电极400与底电极200施加交流电压，以驱动PMUT的振膜层振动。
另外，可以理解的是，当底电极200与衬底100施加直流电压时，此时衬底100需要有高导电性，例如采用高导电性掺杂硅制成。
在本申请一些实施例中，所述曲面在所述压电微机械超声换能器的水平剖面上的最小宽度与所述曲面的深度之比大于1/40。
因为本申请曲面的形状不限制，上述的最小宽度是指，在压电微机械超声换能器的水平剖面上，过曲面中心(或者大致中心)的一条直线与曲面相交于两点，这两点的最小距离为最小宽度，在一更为优选的实施方式中，曲面的最小宽度与其深度之比大于1/20或者1/10。
在本申请一些实施例所提供的压电微机械超声换能器中，底电极200与衬底100施加直流电压V数值可以是可以调控的，即其数值可以根据PMUT振膜层所欲实现的弯曲程度进行设置，从而可以获得频率和声学性能可调且具有曲面结构的PMUT。
需要说明的是，在本申请一些实施例中，对于空腔101处于衬底100的位置不做限制，其可以位于衬底100的中心位置，也可以位于衬底100的靠左一侧，或者靠右一侧。
综上，本申请一些实施例所提供的压电微机械超声换能器，通过电极层之间以及电极层与衬底之间的静电力使压电微机械超声换能器的振膜层呈曲面，可以获得具有较高弯曲程度的PMUT振膜层，另外，通过调整施加在电极上的直流电压，可以获得不同的静电力，进而可以调控PMUT振膜层的弯曲程度，极大的扩展了压电微机械超声换能器应用范围。
在一些实施例中，参见图4，为了确保底电极200与衬底100之间的电隔绝，压电微机械超声换能器还包括：
绝缘层110，位于距离衬底100最近的压电薄膜层300下方的电极层200与衬底100之间；
其中，电极层(200、400)之间施加交流电压，距离衬底最近的压电薄膜层下方的电极层200与衬底100之间施加直流电压；
静电力通过交流电压以及直流电压而形成。
特别的，在上述一些实施例中，当压电薄膜层300数量为1时，参见图4，绝缘层110位于底电极200与衬底100之间；同样地，在顶电极400与底电极200施加交流电压，底电极200与衬底100施加直流电压。
在一些实施例中，压电微机械超声换能器还包括：
支撑层，位于如下至少之一的位置：距离所述衬底100最近的压电薄膜层300下方的电极层200与所述绝缘层110之间以及离所述衬底100最远的压电薄膜层300上方的电极层400之上。该支撑层的作用在于，使得压电微机械超声换能器的振膜层的中性层偏离压电薄膜层300的质量中心面，振膜层包括支撑层、压电薄膜层300以及其两侧的电极层(200以及400)。
可以理解的是，当各层材料均匀时，且压电薄膜层300两侧的电极层厚度相等其材料一致时，由压电薄膜层300以及其两侧的电极层(200以及400)所组成的振膜层的中性层为压电薄膜层300的质量中心面，即其中轴面(图5中虚线所示位置)，但在加入支撑面以后，可以使振膜层的中性层偏离该面。
需要说明的是，在本申请一些实施例所提供的压电微机械超声换能器中，支撑层不是必须的；例如图2中，底电极200相对于顶电极400要厚，因此底电极200既充当支撑层，又充当电极层。即使底电极200与顶电极400厚度一直，因本申请一些实施例所提供的压电微机械超声换能器的振膜层具有曲面结构，其仍能够用于激发和接收超声波。
在一些实施例中，参见图4以及图6，绝缘层110沿衬底100表面以及空腔101表面铺设于底电极200与衬底100之间，即绝缘层110在剖面上大致呈一“凹”字形。
在一些实施例中，参见图7，压电微机械超声换能器还包括：
第一静电力电极1000，位于空腔101底部的绝缘层110之上，第一静电力电极1000与距离衬底最近的压电薄膜层300下方的电极层200之间施加直流电压。
介质层800，位于如下至少之一的位置：距离衬底100最近的压电薄膜层300下方的电极层200与绝缘层110之间，以及覆盖第一静电力电极1000之上。
具体地，介质层800，位于如下至少之一的位置：底电极200与绝缘层110之间，以及仅覆盖第一静电力电极1000之上(此种情况图中未出示)。
介质层800的作用在于防止底电极200与第一静电力电极1000接触，其作用与绝缘柱类似，当然可以同时在压电微机械超声换能器中设置绝缘柱以及介质层。需要说明的是，当介质层800位于底电极200与绝缘层110之间时，其随着PMUT振膜层一起弯曲(当PMUT工作时)，当介质层800覆盖第一静电力电极1000之上时，其形状不发生改变。
参见图8，与图3类似的，可以将第一静电力电极1000取消，并设置在衬底100中，即在衬底100与底电极200之间施加直流电压，具体地，第一静电力电极1000位于空腔101底部的绝缘层110之上，第一静电力电极1000与底电极200施加直流电压。一些实施例本质上是图3中的底电极200与衬底100施加直流电压，更换为第一静电力电极1000与底电极200施加直流电压，另外为了确保底电极200与第一静电力电极1000之间的绝缘性，在底电极200与衬底100之间设置有绝缘层110，当然也可以不加该绝缘层110，本发明不以此为限。
在一些实施例中，压电微机械超声换能器还包括：
绝缘柱，设置与第一静电力电极1000之上，其用于阻止PMUT工作过程中，PMUT振膜层发生弯曲时电极层200和第一静电力电极1000接触，导致器件失效。
在一些实施例中，参见图9，当介质层800位于距离衬底100最近的压电薄膜层300下方的电极层200与绝缘层110之间时，还包括：
第二静电力电极900，位于介质层800之下，其中，电极层(200、400)之间施加交流电压，第二静电力电极900与衬底100中之间施加直流电压。
上述一些实施例具体为，当介质层800位于底电极200与绝缘层110之间时，压电微机械超声换能器还包括：第二静电力电极900，位于介质层800之下(两者相接)，其中，顶电极400与底电极200施加交流电压，第二静电力电极900与衬底100之间施加直流电压。另外，需要说明的是，图9中的绝缘层110可以不存在。另外，此时不可以空腔101底部的绝缘层110之上设置第一静电力电极1000，因为如果同时存在第一静电力电极1000以及第二静电力电极900，在PMUT工作时，两者存在较大的接触风险。
在一些实施例中，参见图10，当介质层800位于距离衬底100最近的压电薄膜层300下方的电极层200与绝缘层110之间时，还包括：
第三静电力电极1100，位于介质层800与绝缘层110之间，其中，电极层(200、400)之间施加交流电压，第三静电力电极1100与第一静电力电极1000或衬底100中的至少之一施加直流电压(图10以及图11所示)。
具体地，当介质层800位于底电极200与绝缘层110之间时，压电微机械超声换能器还包括：第三静电力电极1100，位于介质层800与绝缘层110之间，其中，顶电极400与底电极200施加交流电压，第三静电力电极1100与静电力电极1000或衬底100中的至少之一施加直流电压。
图11中的压电超声换能器中的静电吸引力的组件，含有用于施加直流电压信号的第一静电力电极1000和第二静电力电极900。通过在该电极对上施加直流电压以及在顶电极400与底电极200施加交流电压，产生静电吸引力，引起PMUT振膜层向空腔101方向弯曲，形成具有曲面结构的PMUT。其中，PMUT的底电极200和第二静电力电极900之间存在介质层800，使两个电极对各自独立工作，不存在共用的电极，减少互相之间的影响。另外，图中的绝缘层110不是必须的，可以不存在。
工作过程中，当需要较大的弯曲程度时，为了避免PMUT振膜层较大的弯曲导致PMUT振膜层中的第二静电力电极900与第一静电力电极1000接触短路，造成器件损坏，在第二静电力电极900和第一静电力电极1000之间添加介质层120，从而避免两个电极 的直接接触的可能。当然，该膜层可以覆盖第一静电力电极1000，而不是仅挨着介质层800，或者在介质层800和第一静电力电极1000之间添加一定量的绝缘柱子，阻止PMUT工作过程中，底电极200和第一静电力电极1000接触，导致器件失效。以上的实施例均可以施加此类的设计。
在一些实施例中，图12是压电薄膜层为多个的实施例(图12中以2个为例，本申请不以此为限)，其中300和500为压电薄膜层，200以及400为底电极，600为顶电极，位于压电薄膜层300和500的两侧。与图1至图11中的一些实施例相比，该PMUT中含有双压电薄膜层，其同时振动能产生更加强的超声信号。
工作时，在电极对衬底100和底电极200之间施加直流电压V，引起PMUT振膜层在静电吸引力作用下弯曲，同时在底电极400和顶电极600之间施加交流电压，在底电极200以及衬底100之间，进而产生静电力，从而激励压电薄膜层振动，激发超声波。其中所施加的直流电压V数值可以是不同的，进而控制PMUT振膜层弯曲程度不同，获得频率和声学性能可调且具有曲面结构的PMUT。可以理解的是，因为双层压电薄膜层以及曲面结构，PMUT的超声发射性能大大提高。
图中400以及200是两个底电极，这两个底电极可以相同，也可以不同，300以及500为两个压电薄膜层，同样地，这两个压电薄膜层可以相同，也可以不同。在图12中，由于采用了双压电薄膜层，这两个压电薄膜层300以及500同时振动能产生更加强的超声信号。另外，同图9类似的，此时不可以空腔101底部的绝缘层110之上设置第一静电力电极1000，因为如果同时存在第一静电力电极1000以及底电极200(两者之间没有绝缘层或者介质层的情况下)，在PMUT工作时，两者存在较大的接触风险。
在本申请一些实施例中，衬底包括如下至少之一的材料：单晶硅、氮化镓、砷化镓、蓝宝石、石英、碳化硅、高导电性掺杂硅(绝缘层上的硅，即Silicon on Insulator(SOI))以及金刚石。
在本申请一些实施例中，电极层、第一静电力电极、第二静电力电极以及第三静电力电极包括如下至少之一的材料：高导电硅、钼、钌、金、铝、镁、钨、铜，钛、铱、锇、铬或以上材料的复合体或合金。
在本申请一些实施例中，压电薄膜层包括如下至少之一的材料：可选材料为多晶氮化铝(AlN)、多晶氧化锌、多晶锆钛酸铅(PZT)、多晶铌酸锂(LiNbO3)、多晶钽酸锂(LiTaO3)、多晶铌酸钾(KNbO3)等材料，或者单晶氮化铝、单晶氮化镓、单晶 铌酸锂、单晶锆钛酸铅、单晶铌酸钾、单晶石英薄膜、或者单晶钽酸锂、预设原子比的稀土元素(例如掺钪氮化铝)。
在本申请一些实施例中，支撑层包括如下至少之一的材料：氮化硅、二氧化硅以及硅。
另外，需要说明的是，图1至图12中的顶电极500截面积小于压电薄膜层400、底电极300、支撑层200以及绝缘层800的横截面积，这里仅仅是示意，不做限定，即顶电极500的横截面积可以与压电薄膜层400、底电极300、支撑层200以及键合层800的横截面积相同或者不同，也可以为其他形状，例如圆形、三角形以及环形等等。
以图3为例，本申请一些实施例所提供的压电微机械超声换能器，在一定空腔半径D的情况下，首先通过静电作用力的拉伸作用，可以获得较高的弯曲程度h，满足较大的PMUT振膜层弯曲程度的需求，比如h/D≥0.5％，尤其是h/D≥1％；另外，通过调控施加在电极上的直流电压V，可以获得不同的静电力，进而获得所欲获取的PMUT振膜层的弯曲程度。
以上对本申请一些实施例的结构进行了说明，但本申请不限于此，各个装置或部件的具体内容还可以参考相关技术；此外还可以增加图1至图12中没有示出的装置或部件，或者减少图1至图12中的一个或多个装置或部件。
以上各个实施例仅对本申请实施例进行了示例性说明，但本申请不限于此，还可以在以上各个实施例的基础上进行适当的变型。例如，可以单独使用上述各个实施例，也可以将以上各个实施例中的一种或多种结合起来。
在一些实施例中，参见图13，根据本申请还提供一种上述压电微机械超声换能器的制作方法，该方法包括：
步骤100：在衬底或/及第一静电力电极与下述膜层的至少之一之间施加直流电压：距离所述衬底最近的压电薄膜层下方的电极层、第二静电极以及第三静电力电极；
其中：第一静电力电极位于所述空腔底部的绝缘层之上，第二静电力电极，位于介质层之下；第三静电力电极，位于所述介质层与所述绝缘层之间；所述介质层位于如下至少之一的位置：距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间，以及覆盖所述第一静电力电极之上；
当存在所述第一静电力电极时，其与距离所述衬底最近的压电薄膜层下方的电极层、第二静电力电极以及所述第三静电力电极之间存在介质层及/或绝缘层及/或绝缘柱。
步骤200：通过所述直流电压所形成静电力使所述电极层、压电薄膜层、所述第一静电力电极、第二静电力电极以及第三静电力电极呈曲面。
在步骤200中，从平行于衬底的方向观察，电极层、压电薄膜层、所述第一静电力电极、第二静电力电极以及第三静电力电极呈曲面；
需要说明的是，压电微机械超声换能器的制作方法还包括：
步骤300：在压电薄膜层两侧的电极层之间施加交流电压；以使驱动PMUT的振膜层振动。
本申请一些实施例还提供一种电气产品，该电气产品具有如上所述的压电微机械超声换能器。该电气产品例如包括超声成像仪、超声雷达、声呐探测、扫地机器人、超声烟雾报警器等等，本申请不限于此。
值得注意的是，以上仅对本申请实施例进行了示例性说明，但本申请实施例不限于此，还可以在以上各个实施方式的基础上进行适当的变型。此外，以上仅对各个部件进行了示例性说明，但本申请实施例不限于此，各个部件的具体内容还可以参考相关技术；此外还可以增加图中没有示出的部件，或者减少图中的一个或多个部件。
本说明书中的各个实施例均采用递进的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。尤其，对于设备实现方法的实施例而言，由于其基本相似于方法实施例，所以描述的比较简单，相关之处参见方法实施例的部分说明即可。
上述对本说明书特定实施例进行了描述。其它实施例在所附权利要求书的范围内。在一些情况下，在权利要求书中记载的动作或步骤可以按照不同于实施例中的顺序来执行并且仍然可以实现期望的结果。另外，在附图中描绘的过程不一定要求示出的特定顺序或者连续顺序才能实现期望的结果。在某些实施方式中，多任务处理和并行处理也是可以的或者可能是有利的。
虽然本说明书实施例提供了如实施例或流程图的方法操作步骤，但基于常规或者无创造性的手段可以包括更多或者更少的操作步骤。实施例中列举的步骤顺序仅仅为众多步骤执行顺序中的一种方式，不代表唯一的执行顺序。术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、产品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、产品或者设备所固有的要素。在没有更多限制的情况下，并不排除在包括要素的过程、方法、产品或者设备中还存在另外的相同或等同要素。
本说明书中的各个实施例均采用递进的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。尤其，对于系统实施例而言，由于其基本相似于方法实施例，所以描述的比较简单，相关之处参见方法实施例的部分说明即可。在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本说明书实施例的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不必须针对的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任一个或多个实施例或示例中以合适的方式结合。此外，在不相互矛盾的情况下，本领域的技术人员可以将本说明书中描述的不同实施例或示例以及不同实施例或示例的特征进行结合和组合。
以上仅为本说明书实施例的实施例而已，并不用于限制本说明书实施例。对于本领域技术人员来说，本说明书实施例可以有各种更改和变化。凡在本说明书实施例的精神和原理之内所作的任何修改、等同替换、改进等，均应包含在本说明书实施例的权利要求范围之内。
以上结合具体的实施方式对本申请实施例进行了描述，但本领域技术人员应该清楚，这些描述都是示例性的，并不是对本申请实施例保护范围的限制。本领域技术人员可以根据本申请实施例的精神和原理对本申请实施例做出各种变型和修改，这些变型和修改也在本申请实施例的范围内。
以上参照附图描述了本申请实施例的优选实施方式。这些实施方式的许多特征和优点根据该详细的说明书是清楚的，因此所附权利要求旨在覆盖这些实施方式的落入其真实精神和范围内的所有这些特征和优点。此外，由于本领域的技术人员容易想到很多修改和改变，因此不是要将本申请实施例的实施方式限于所例示和描述的精确结构和操作，而是可以涵盖落入其范围内的所有合适修改和等同物。

Claims (15)

  1. 一种压电微机械超声换能器，其特征在于，包括：
    衬底，设置有空腔；
    至少一个压电薄膜层，所述压电薄膜层两侧均设置有电极层，距离所述衬底最近的压电薄膜层下方的电极层位于所述衬底之上；
    其中，从平行于所述衬底的方向观察，所述压电薄膜层以及其两侧的电极层呈曲面，所述曲面通过所述电极层与所述衬底之间的静电力而形成。
  2. 根据权利要求1所述的压电微机械超声换能器，其特征在于，所述曲面在所述压电微机械超声换能器的水平剖面上的最小宽度与所述曲面的深度之比大于1/40。
  3. 根据权利要求1所述的压电微机械超声换能器，其特征在于，还包括：
    绝缘层，位于距离所述衬底最近的压电薄膜层下方的电极层与所述衬底之间；
    其中，距离所述衬底最近的压电薄膜层下方的电极层与所述衬底之间施加直流电压；
    所述静电力通过所述直流电压而形成。
  4. 根据权利要求3所述的压电微机械超声换能器，其特征在于，还包括：
    支撑层，位于如下至少之一的位置：距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间以及离所述衬底最远的压电薄膜层上方的电极层之上。
  5. 根据权利要求3所述的压电微机械超声换能器，其特征在于，所述绝缘层沿所述衬底表面以及所述空腔表面铺设于所述距离所述衬底最近的压电薄膜层下方的电极层与所述衬底之间。
  6. 根据权利要求3所述的压电微机械超声换能器，其特征在于，还包括：
    第一静电力电极，位于所述空腔底部的绝缘层之上，所述第一静电力电极与距离所述衬底最近的压电薄膜层下方的电极层之间施加直流电压；
    介质层，位于如下至少之一的位置：距离衬底最近的压电薄膜层下方的电极层与绝缘层之间，以及覆盖第一静电力电极之上。
  7. 根据权利要求6所述的压电微机械超声换能器，其特征在于，还包括：
    绝缘柱，设置与所述第一静电力电极之上。
  8. 根据权利要求3所述的压电微机械超声换能器，其特征在于，还包括：
    介质层，位于距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间；
    第二静电力电极，位于所述介质层之下，所述第二静电力电极与所述衬底之间施加直流电压。
  9. 根据权利要求6所述的压电微机械超声换能器，其特征在于，当所述介质层位于距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间时，还包括：
    第三静电力电极，位于所述介质层与所述绝缘层之间，所述第三静电力电极与所述第一静电力电极或所述衬底中的至少之一施加直流电压。
  10. 根据权利要求1所述的压电微机械超声换能器，其特征在于，所述衬底包括如下至少之一的材料：单晶硅、氮化镓、砷化镓、蓝宝石、石英、碳化硅、高导电性掺杂硅以及金刚石。
  11. 根据权利要求9所述的压电微机械超声换能器，其特征在于，所述电极层、第一静电力电极、第二静电力电极以及第三静电力电极包括如下至少之一的材料：高导电硅、钼、钌、金、铝、镁、钨、铜，钛、铱、锇、铬或以上材料的复合体或合金。
  12. 根据权利要求1所述的压电微机械超声换能器，其特征在于，所述压电薄膜层包括如下至少之一的材料：
    多晶氮化铝、多晶氧化锌、多晶锆钛酸铅、多晶铌酸锂、多晶钽酸锂、多晶铌酸钾、单晶氮化铝、单晶氮化镓、单晶铌酸锂、单晶锆钛酸铅、单晶铌酸钾、单晶石英薄膜、单晶钽酸锂、预设原子比的稀土元素。
  13. 根据权利要求4所述的压电微机械超声换能器，其特征在于，所述支撑层包括如下至少之一的材料：氮化硅、二氧化硅以及硅。
  14. 一种如权利要求1至13任一项所述的压电微机械超声换能器的制作方法，其特征在于，包括：
    在衬底或/及第一静电力电极与下述膜层的至少之一之间施加直流电压：距离所述衬底最近的压电薄膜层下方的电极层、第二静电极以及第三静电力电极；
    其中：第一静电力电极位于所述空腔底部的绝缘层之上，第二静电力电极，位于介质层之下；第三静电力电极，位于所述介质层与所述绝缘层之间；所述介质层位于如下至少之一的位置：距离所述衬底最近的压电薄膜层下方的电极层与所述绝缘层之间，以及覆盖所述第一静电力电极之上；
    当存在所述第一静电力电极时，其与距离所述衬底最近的压电薄膜层下方的电极层、第二静电力电极以及所述第三静电力电极之间存在介质层及/或绝缘层及/或绝缘柱；
    通过所述直流电压所形成静电力使所述电极层、压电薄膜层、所述第一静电力电极、第二静电力电极以及第三静电力电极呈曲面。
  15. 一种电气产品，其特征在于，所述电气产品具有如权利要求1至13中任一项所述的压电微机械超声换能器。
PCT/CN2024/070757 2023-01-12 2024-01-05 压电微机械超声换能器、制作方法以及电气产品 WO2024149163A1 (zh)

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CN101712028A (zh) * 2009-11-13 2010-05-26 中国科学院声学研究所 一种薄膜超声换能器及其制备方法
CN103284756A (zh) * 2012-02-24 2013-09-11 精工爱普生株式会社 探头单元、超声波探测器、电子设备及诊断装置
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