WO2021095311A1 - Transducteur - Google Patents

Transducteur Download PDF

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Publication number
WO2021095311A1
WO2021095311A1 PCT/JP2020/031098 JP2020031098W WO2021095311A1 WO 2021095311 A1 WO2021095311 A1 WO 2021095311A1 JP 2020031098 W JP2020031098 W JP 2020031098W WO 2021095311 A1 WO2021095311 A1 WO 2021095311A1
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WIPO (PCT)
Prior art keywords
beam portions
connecting portion
transducer
electrode layer
layer
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PCT/JP2020/031098
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English (en)
Japanese (ja)
Inventor
伸介 池内
青司 梅澤
勝之 鈴木
文弥 黒川
Original Assignee
株式会社村田製作所
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Publication of WO2021095311A1 publication Critical patent/WO2021095311A1/fr

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • 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

Definitions

  • the present invention can be used as a transmitter for transmitting sound waves and a sound wave receiver (microphone) for receiving sound waves with respect to a transducer, particularly an acoustic transducer.
  • the present invention relates to an ultrasonic transmitter / receiver capable of transmitting and receiving ultrasonic waves.
  • Patent Document 1 is a document that discloses the configuration of the transducer.
  • the transducer described in Patent Document 1 is a microphone, which includes a support frame, a first diaphragm, a second diaphragm, and a coupling body. Both the first diaphragm and one end of the second diaphragm are elastically supported by the support frame. The other end of the first diaphragm and the other end of the second diaphragm are arranged so as to face each other. The other end of the first diaphragm and the other end of the second diaphragm are connected by a connecting body.
  • the connector can be displaced with respect to the other end of the first diaphragm and the other end of the second diaphragm, so that the connector vibrates in parallel or in parallel with the vibration of the first diaphragm or the second diaphragm. It is configured to perform tilt vibration.
  • the present invention has been made in view of the above problems, and provides a transducer capable of suppressing a decrease in electromechanical conversion efficiency while suppressing vibration of a plurality of beam portions in a coupled vibration mode. With the goal.
  • the transducer based on the present invention includes a plurality of beam portions, a base portion, and a connecting portion.
  • the plurality of beam portions have a fixed end portion and a tip portion. The tip is located on the opposite side of the fixed end.
  • Each of the plurality of beams extends from the fixed end toward the tip.
  • Each fixed end of the plurality of beams is located in the same plane.
  • Each of the plurality of beams includes a piezoelectric layer, an upper electrode layer, and a lower electrode layer.
  • the upper electrode layer is arranged above the piezoelectric layer.
  • the lower electrode layer is arranged so as to face at least a part of the upper electrode layer with the piezoelectric layer interposed therebetween.
  • the base is connected to each fixed end of the plurality of beams.
  • the connecting portion connects the tips of the plurality of beam portions to each other.
  • the connecting portion is made of a material having a Young's modulus lower than that of the material constituting the piezo
  • the transducer With respect to the present invention, with respect to the transducer, it is possible to suppress a decrease in electromechanical conversion efficiency while suppressing vibration of a plurality of beam portions in a coupled vibration mode.
  • FIG. 5 is a perspective view showing a state in which the transducer according to the first embodiment of the present invention is vibrating in the basic vibration mode by simulation.
  • FIG. 5 is a cross-sectional view showing a state in which a laminated body is joined to a first support portion in the method for manufacturing a transducer according to the first embodiment of the present invention. It is sectional drawing which shows the state which formed the piezoelectric layer by scraping the piezoelectric single crystal substrate in the manufacturing method of the transducer which concerns on Embodiment 1 of this invention.
  • FIG. 5 is a cross-sectional view showing a state in which a slit is formed from a side opposite to the support layer side of the piezoelectric layer until it reaches the upper surface of the substrate layer in the method for manufacturing a transducer according to the first embodiment of the present invention.
  • FIG. 5 is a cross-sectional view showing a state in which a through hole is formed from a side opposite to the support layer side of the piezoelectric layer to the upper surface of the lower electrode layer in the method for manufacturing a transducer according to the first embodiment of the present invention.
  • FIG. 17 is a cross-sectional view of the transducer of FIG. 17 as viewed from the direction of the arrow along the line XVIII-XVIII.
  • FIG. 1 is a plan view of the transducer according to the first embodiment of the present invention.
  • FIG. 2 is a cross-sectional view of the transducer of FIG. 1 as viewed from the direction of the arrow along line II-II.
  • the transducer 100 according to the first embodiment of the present invention includes a plurality of beam portions 110, a base portion 120, and a connecting portion 130.
  • each of the plurality of beam portions 110 can bend and vibrate, and can be used as an ultrasonic transducer.
  • the plurality of beam portions 110 have a fixed end portion 111 and a tip portion 112.
  • the tip 112 is located on the opposite side of the fixed end 111.
  • Each fixed end 111 of the plurality of beam portions 110 is located in the same plane S.
  • Each of the plurality of beam portions 110 extends from the fixed end portion 111 toward the tip end portion 112.
  • each of the plurality of beam portions 110 extends along the plane S in a state where the transducer 100 is not driven.
  • each of the plurality of beam portions 110 has a tapered outer shape in the extending direction when viewed from the orthogonal direction of the plane S.
  • each of the plurality of beam portions 110 has a triangular outer shape when viewed from the direction orthogonal to the plane S.
  • this triangular shape is an isosceles triangle shape with the fixed end portion 111 as the base and the apex located at the tip portion 112. That is, the extending direction of each of the plurality of beam portions 110 is the direction connecting the midpoint and the apex of the base of the isosceles triangle shape which is the outer shape of each beam portion 110.
  • the length of each of the plurality of beam portions 110 in the extending direction is the dimension of the thickness of each of the plurality of beam portions 110 in the orthogonal direction of the plane S from the viewpoint of facilitating bending vibration. It is preferable that the amount is at least 5 times or more.
  • the transducer 100 includes four beam portions 110. Further, each of the plurality of beam portions 110 is arranged so as to be point-symmetrical with respect to the virtual center point of the transducer 100 when viewed from the direction orthogonal to the plane S. In the present embodiment, each of the four beam portions 110 extends in different directions in the plane S when viewed from the orthogonal direction of the plane S, and the extending directions of the adjacent beam portions 110 are mutually different. They are arranged so that they differ by 90 °.
  • each of the plurality of beam portions 110 has a tip surface 113 at the tip portion 112 along the direction orthogonal to the plane S.
  • "along" in a certain direction means that it may be parallel to the direction or may intersect so as not to be orthogonal to the direction.
  • each tip surface of the plurality of beam portions 110 faces toward the virtual center point of the transducer 100.
  • the gap 114 between the plurality of beam portions 110 is formed in a slit shape extending toward the tip end portion 112 of each of the plurality of beam portions 110.
  • the gap 114 located between the plurality of beam portions 110 extends radially from the virtual center point of the transducer 100 when viewed from the direction orthogonal to the plane S.
  • the width of the gap 114 is substantially constant in the extending direction of the gap 114.
  • the narrower the width of the gap 114 the better the device characteristics of the transducer 100.
  • the narrower the width of the gap 114 the more the force exerted by the plurality of beam portions 110 on the medium located around the plurality of beam portions 110, or the plurality of beam portions.
  • the force that 110 receives from the medium can be prevented from escaping from the gap 114.
  • the slit width is preferably, for example, 10 ⁇ m or less, and more preferably 1 ⁇ m or less.
  • the base portion 120 is connected to each fixed end portion 111 of the plurality of beam portions 110.
  • the base 120 has an annular outer shape when viewed from the direction orthogonal to the plane S, and specifically, has a rectangular annular outer shape.
  • the base portion 120 is connected to each fixed end portion 111 of the plurality of beam portions 110 so as to correspond one-to-one with the plurality of beam portions 110 on a plurality of sides of the inner peripheral surface of the rectangular ring.
  • the base portion 120 has a plurality of recesses 121 communicating with gaps 114 between the plurality of beam portions 110.
  • the recess 121 is formed so as to be continuous with the side of the gap 114 opposite to the tip 112 side.
  • each of the plurality of beam portions 110 is connected on the upper side of the base portion 120 in the orthogonal direction of the plane S. Therefore, in the transducer 100, an opening 101 that opens downward is formed below the plurality of beam portions 110.
  • the transducer 100 includes a piezoelectric layer 10, an upper electrode layer 20, a lower electrode layer 30, and a support layer 40.
  • each of the plurality of beam portions 110 includes a piezoelectric layer 10, an upper electrode layer 20, a lower electrode layer 30, and a support layer 40.
  • the piezoelectric layer 10 constitutes a part of the beam portion 110 and a part of the base portion 120.
  • the piezoelectric layer 10 is made of a single crystal.
  • the cut orientation of the piezoelectric layer 10 is appropriately selected so as to exhibit the desired device characteristics.
  • the piezoelectric layer 10 is a thinned single crystal substrate, and the single crystal substrate is specifically a rotating Y-cut substrate. Further, the cutting direction of the rotating Y-cut substrate is specifically 30 °.
  • the thickness of the piezoelectric layer 10 is, for example, 0.3 ⁇ m or more and 5.0 ⁇ m or less.
  • the piezoelectric layer 10 is made of an inorganic material. Specifically, the piezoelectric layer 10 is composed of an alkaline niobate compound or an alkaline tantalate compound. In the present embodiment, the alkali metal contained in the alkali niobate compound or the alkali tantalate compound comprises at least one of lithium, sodium and potassium. In the present embodiment, the piezoelectric layer 10 is composed of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).
  • each of the upper electrode layer 20 and the lower electrode layer 30 constitutes a part of a plurality of beam portions 110 and a part of a base portion 120.
  • the upper electrode layer 20 is arranged on the upper side of the piezoelectric layer 10, that is, on the side opposite to the support layer 40 side. In other words, the upper electrode layer 20 is arranged on one side of the piezoelectric layer 10 in the orthogonal direction.
  • the lower electrode layer 30 is arranged in each of the plurality of beam portions 110 so as to face at least a part of the upper electrode layer 20 with the piezoelectric layer 10 interposed therebetween.
  • an adhesion layer (not shown) is arranged between the upper electrode layer 20 and the piezoelectric layer 10 and between the lower electrode layer 30 and the piezoelectric layer 10.
  • a plurality of upper electrode layers 20 forming a part of each of the plurality of beam portions 110 are interposed via an upper electrode layer 20 forming a base portion 120. It is provided so as to be electrically connected to each other.
  • the plurality of lower electrode layers 30 forming a part of each of the plurality of beam portions 110 are electrically connected to each other via the lower electrode layer 30 forming the base portion 120. It is provided so that it can be connected as a target. Further, each of the upper electrode layer 20 and the lower electrode layer 30 is provided so as not to face the gap 114.
  • each of the upper electrode layer 20 and the lower electrode layer 30 is composed of Pt.
  • Each of the upper electrode layer 20 and the lower electrode layer 30 may be made of another material such as Al.
  • the adhesion layer is made of Ti.
  • the adhesion layer may be made of another material such as NiCr.
  • Each of the upper electrode layer 20, the lower electrode layer 30, and the adhesion layer may be an epitaxial growth film.
  • the piezoelectric layer 10 is composed of lithium niobate (LiNbO 3 )
  • the adhesion layer is from the viewpoint of suppressing the material constituting the adhesion layer from diffusing into the upper electrode layer 20 or the lower electrode layer 30. Is preferably composed of NiCr. This improves the reliability of the transducer 100.
  • the thickness of each of the upper electrode layer 20 and the lower electrode layer 30 is, for example, 0.05 ⁇ m or more and 0.2 ⁇ m or less.
  • the thickness of the adhesion layer is, for example, 0.005 ⁇ m or more and 0.05 ⁇ m or less.
  • the support layer 40 constitutes a part of the plurality of beam portions 110 and a part of the base portion 120.
  • the support layer 40 is arranged on the side opposite to the upper electrode layer 20 side of the piezoelectric layer 10 and on the side opposite to the piezoelectric layer 10 side of the lower electrode layer 30.
  • the support layer 40 has a first support portion 41 and a second support portion 42 laminated on the side of the first support portion 41 opposite to the piezoelectric layer 10 side.
  • the first support portion 41 is made of SiO 2
  • the second support portion 42 is made of single crystal Si.
  • the thickness of the support layer 40 is preferably thicker than that of the piezoelectric layer 10 from the viewpoint of bending vibration of the beam portion 110. The mechanism of bending vibration of the beam portion 110 will be described later.
  • the transducer 100 further includes a substrate layer 50.
  • the substrate layer 50 constitutes a part of the base 120.
  • the substrate layer 50 is arranged below the support layer 40.
  • the substrate layer 50 has a first substrate 51 and a second substrate 52 laminated on the side opposite to the support layer 40 side of the first substrate 51.
  • the first substrate 51 is made of SiO 2
  • the second substrate 52 is made of single crystal Si.
  • the connecting portion 130 connects the tip portions 112 of each of the plurality of beam portions 110 so that each of the plurality of beam portions 110 can be displaced from the fixed end portion 111 as a starting point. Connected to each other. Each of the plurality of beam portions 110 is connected to the connecting portion 130 at least by the tip surface 113.
  • the slit width of the portion of the gap 114 between the plurality of beam portions 110 facing the tip surface 113 is formed as narrow as possible.
  • the thickness of the connecting portion 130 is thicker than the thickness of each of the plurality of beam portions 110.
  • the thickness is, for example, 5 ⁇ m or more and 20 ⁇ m or less.
  • a portion 131 located on the tip surface 113 from each of the plurality of beam portions 110 projects toward the upper electrode layer 20 of each of the plurality of beam portions 110.
  • the protruding portion 131 further extends toward the upper electrode layer 20 side of the piezoelectric layer 10. That is, as shown in FIG. 1, the diameter dimension of the portion 131 of the connection portion 130 is larger than the slit width dimension of the gap 114 when viewed from the orthogonal direction.
  • the portion 131 of the connecting portion 130 extends from the tip surface 113 to the upper electrode layer 20 when viewed from the orthogonal direction, and has a substantially circular outer shape. Seen from the orthogonal direction, the diameter of the portion 131 of the connecting portion 130 is, for example, 50 ⁇ m or more and 200 ⁇ m or less.
  • the mass of the connecting portion 130 is 5% or less of the total mass of the plurality of beam portions 110. Further, the mass of the connecting portion 130 is preferably 2% or less of the total mass of the plurality of beam portions 110. The mass of the connecting portion 130 is more preferably 1% or less of the total mass of the plurality of beam portions 110.
  • the mass of the connecting portion 130 can be calculated from the density value described in the conventionally known material database for the material constituting the connecting portion 130 and the volume of the connecting portion 130 in the present embodiment.
  • the mass of each of the plurality of beam portions 110 can also be calculated by the same method as that of the connecting portion 130.
  • the mass of the connecting portion 130 is measured by measuring the difference between the total mass of the transducer 100 and the total mass of the transducer after the connecting portion 130 provided on the transducer 100 is removed by local heating or solvent application. It may be calculated by.
  • the connecting portion 130 is made of a material having a Young's modulus lower than that of the material constituting the piezoelectric layer 10.
  • the Young's modulus of the material constituting the connecting portion 130 is 1 GPa or less.
  • the Young's modulus of the material constituting the connecting portion 130 is preferably 100 MPa or less.
  • the Young's modulus of the material constituting the connecting portion 130 is preferably 0.1 MPa or more.
  • the Young's modulus of each of the material constituting the piezoelectric layer 10 and the material constituting the connecting portion 130 the physical property values described in the conventionally known material database can be adopted for each of these materials.
  • the Young's modulus of each of the material constituting the piezoelectric layer 10 and the material constituting the connecting portion 130 is nano-indented with respect to the measurement sample collected from each of the piezoelectric layer 10 and the connecting portion 130 in the transducer 100. It can also be calculated by measuring the deformation rate when pressure is applied by the method. Further, in the present embodiment, it is preferable that the connecting portion 130 is made of a material having reflow resistance and relatively high heat resistance.
  • connection portion 130 is made of an organic material.
  • examples of the material constituting the connecting portion 130 include, for example, a silicone resin or a fluoroelastomer from the viewpoint of the Young's modulus described above.
  • the silicone resin has a lower Young's modulus at low temperatures than the fluoroelastomer. Therefore, the connecting portion 130 is preferably made of a silicone resin. If the connecting portion 130 is made of silicone resin, the transducer 100 can be used in a relatively wide temperature range.
  • polyimide resin and parylene parylene (paraxylylene-based polymer) are hard resins having a relatively high Young's modulus of more than 1 GPa. Therefore, depending on the Young's modulus of the material constituting the piezoelectric layer 10, the polyimide resin and parylene may not be adopted as the material constituting the connecting portion 130.
  • FIG. 3 is a cross-sectional view of the transducer of FIG. 1 as viewed from the direction of the arrow along line III-III.
  • the transducer 100 according to the present embodiment further includes a first connection electrode layer 140 and a second connection electrode layer 150.
  • the first connection electrode layer 140 is arranged on the base portion 120 on the side opposite to the piezoelectric layer 10 side of the upper electrode layer 20.
  • the first connection electrode layer 140 is electrically connected to the upper electrode layer 20 via an adhesion layer (not shown).
  • the second connection electrode layer 150 is arranged in the base portion 120 on the side opposite to the support layer 40 side of the lower electrode layer 30.
  • the second connection electrode layer 150 is electrically connected to the lower electrode layer 30 via an adhesion layer (not shown).
  • each of the first connection electrode layer 140 and the second connection electrode layer 150 is, for example, 0.1 ⁇ m or more and 1.0 ⁇ m or less.
  • the thickness of each of the adhesion layer connected to the first connection electrode layer 140 and the adhesion layer connected to the second connection electrode layer 150 is, for example, 0.005 ⁇ m or more and 0.1 ⁇ m or less.
  • the first connection electrode layer 140 and the second connection electrode layer 150 are composed of Au.
  • the first connection electrode layer 140 and the second connection electrode layer 150 may be made of another conductive material such as Al.
  • the adhesion layer connected to the first connection electrode layer 140 and the adhesion layer connected to the second connection electrode layer 150 are made of, for example, Ti.
  • the adhesion layer may be made of NiCr.
  • each of the plurality of beam portions 110 can flex and vibrate.
  • the mechanism of bending vibration of the plurality of beam portions 110 will be described.
  • FIG. 4 is a cross-sectional view schematically showing a part of a beam portion of the transducer according to the first embodiment of the present invention.
  • FIG. 5 is a cross-sectional view schematically showing a part of a beam portion at the time of driving of the transducer according to the first embodiment of the present invention.
  • the upper electrode layer and the lower electrode layer are not shown in FIGS. 4 and 5.
  • the piezoelectric layer 10 functions as an elastic layer that can be expanded and contracted in the in-plane direction of the plane S, other than the piezoelectric layer 10.
  • the layer functions as a constraint layer.
  • the support layer 40 mainly functions as a restraint layer. In this way, the restraint layer is laminated in the direction orthogonal to the expansion / contraction direction of the expansion / contraction layer with respect to the expansion / contraction layer.
  • the plurality of beam portions 110 are reverse stretchable layers that can be contracted in the in-plane direction when the stretchable layer is stretched in the in-plane direction and can be stretched in the in-plane direction when the stretchable layer is contracted in the in-plane direction. , May be included in place of the restraint layer.
  • the support layer 40 which is a main part of the restraint layer expands and contracts the piezoelectric layer 10 at the joint surface with the piezoelectric layer 10. Restrain. Further, in the present embodiment, in the beam portion 110, the piezoelectric layer 10 which is an expansion / contraction layer is located only on one side of the stress neutral plane N of the beam portion 110. The position of the center of gravity of the support layer 40, which mainly constitutes the restraint layer, is located on the other side of the stress neutral plane N. As a result, as shown in FIGS.
  • the beam portion 110 bends in the direction orthogonal to the plane S.
  • the amount of displacement of the beam portion 110 when the beam portion 110 is bent increases as the distance between the stress neutral plane N and the piezoelectric layer 10 increases. Further, the amount of displacement increases as the stress at which the piezoelectric layer 10 tries to expand and contract increases. In this way, each of the plurality of beam portions 110 bends and vibrates starting from the fixed end portion 111 in the direction orthogonal to the plane S.
  • FIG. 6 is a perspective view showing a state in which the transducer according to the first embodiment of the present invention is vibrating in the basic vibration mode by simulation. Specifically, FIG. 6 shows the transducer 100 in a state in which each of the plurality of beam portions 110 is displaced toward the upper electrode layer 20 side. In FIG. 6, the color becomes lighter as the amount of displacement in which each of the plurality of beam portions 110 is displaced toward the upper electrode layer 20 increases. As shown in FIG. 6, the basic vibration mode is a mode in which the phases when each of the plurality of beam portions 110 bends and vibrates are aligned, and the entire plurality of beam portions 110 are displaced to either the upper or lower side. Is.
  • the coupled vibration mode is a mode in which at least one phase of the plurality of beam portions 110 is not aligned with the phase of the other beam portions 110 when each of the plurality of beam portions 110 bends and vibrates.
  • the occurrence of the coupled vibration mode is suppressed.
  • the transducer 100 according to the present embodiment tends to vibrate in the basic vibration mode and the generation of the coupled vibration mode is suppressed, the device characteristics are particularly improved when used as an ultrasonic transducer.
  • the functional operation of the transducer 100 when the transducer 100 according to the present embodiment is used as an ultrasonic transducer will be described.
  • each of the plurality of beam portions 110 has a unique mechanical resonance frequency. Therefore, when the applied voltage is a sinusoidal voltage and the frequency of the sinusoidal voltage is close to the value of the resonance frequency, the amount of displacement when each of the plurality of beam portions 110 is bent becomes large.
  • the medium around each of the plurality of beam portions 110 is vibrated by the ultrasonic waves, and a force is applied to each of the plurality of beam portions 110 from the peripheral media to form a plurality of beams.
  • Each of the beam portions 110 bends and vibrates.
  • stress is applied to the piezoelectric layer 10.
  • an electric charge is induced in the piezoelectric layer 10.
  • Due to the electric charge induced in the piezoelectric layer 10 a potential difference is generated between the upper electrode layer 20 and the lower electrode layer 30 facing each other via the piezoelectric layer 10.
  • This potential difference is detected by the first connection electrode layer 140 connected to the upper electrode layer 20 and the second connection electrode layer 150 connected to the lower electrode layer 30.
  • the transducer 100 can detect ultrasonic waves.
  • the ultrasonic wave to be detected contains a large amount of a specific frequency component and this frequency component is close to the value of the resonance frequency, the displacement amount when each of the plurality of beam portions 110 bends and vibrates. Becomes larger. As the amount of displacement increases, the potential difference increases.
  • the transducer 100 according to the present embodiment when used as an ultrasonic transducer, it is important to design the resonance frequencies of the plurality of beam portions 110.
  • the resonance frequency changes depending on the density and elastic modulus.
  • each of the plurality of beam portions 110 has the same resonance frequency as each other. For example, when the thicknesses of the plurality of beam portions 110 are different from each other, the lengths of the plurality of beam portions in the extending direction are adjusted so that each of the plurality of beam portions 110 has the same resonance frequency. To have.
  • the transducer 100 As described above, vibration in the basic vibration mode is likely to occur, and the generation of the coupled vibration mode is suppressed. Therefore, when the transducer 100 is used as an ultrasonic transducer, it is suppressed that the phases of vibrations of the plurality of beam portions 110 are different even when detecting ultrasonic waves having the same frequency component as the resonance frequency. To. As a result, the phases of vibrations of the plurality of beam portions 110 are different, so that the charges generated in the piezoelectric layer 10 of each of the plurality of beam portions 110 cancel each other out in the upper electrode layer 20 or the lower electrode layer 30. It is suppressed. That is, in the transducer 100, the device characteristics as an ultrasonic transducer are improved.
  • FIG. 7 is a cross-sectional view showing a state in which a lower electrode layer is provided on a piezoelectric single crystal substrate in the method for manufacturing a transducer according to the first embodiment of the present invention. 7 and 8 to 12 and 4 shown below are shown in the same cross-sectional view as in FIG.
  • an adhesion layer (not shown) is provided on the lower surface of the piezoelectric single crystal substrate 10a, and then a lower electrode layer 30 is provided on the side of the adhesion layer opposite to the piezoelectric single crystal substrate 10a side.
  • the lower electrode layer 30 is formed so as to have a desired pattern by a vapor deposition lift-off method.
  • the lower electrode layer 30 may be formed by laminating over the entire lower surface of the piezoelectric single crystal substrate 10a by sputtering and then forming a desired pattern by an etching method.
  • the lower electrode layer 30 and the close contact layer may be epitaxially grown.
  • FIG. 8 is a cross-sectional view showing a state in which the first support portion is provided in the method for manufacturing a transducer according to the first embodiment of the present invention.
  • a first support portion 41 is provided on the lower surfaces of the piezoelectric single crystal substrate 10a and the lower electrode layer 30 by a CVD (Chemical Vapor Deposition) method, a PVD (Physical Vapor Deposition) method, or the like.
  • CVD Chemical Vapor Deposition
  • PVD Physical Vapor Deposition
  • FIG. 9 is a cross-sectional view showing a state in which a laminated body is joined to a first support portion in the method for manufacturing a transducer according to the first embodiment of the present invention.
  • the laminate 60 composed of the second support portion 42 and the substrate layer 50 is bonded to the lower surface of the first support portion 41 by surface activation bonding or atomic diffusion bonding.
  • the laminate 60 is an SOI (Silicon on Insulator) substrate.
  • FIG. 10 is a cross-sectional view showing a state in which a piezoelectric single crystal substrate is scraped to form a piezoelectric layer in the method for manufacturing a transducer according to the first embodiment of the present invention.
  • the upper surface of the piezoelectric single crystal substrate 10a is thinned by grinding with a grinder.
  • the top surface of the thinned piezoelectric single crystal substrate 10a is further polished by CMP or the like to form the piezoelectric single crystal substrate 10a into the piezoelectric layer 10.
  • the piezoelectric single crystal substrate 10a is formed into the piezoelectric layer 10 by forming a peeling layer by injecting ions into the upper surface side of the piezoelectric single crystal substrate 10a in advance and peeling the peeling layer. Good. Further, the piezoelectric single crystal substrate 10a may be formed into the piezoelectric layer 10 by further polishing the upper surface of the piezoelectric single crystal substrate 10a after the release layer is peeled off by CMP or the like.
  • FIG. 11 is a cross-sectional view showing a state in which an upper electrode layer is provided on the piezoelectric layer in the method for manufacturing a transducer according to the first embodiment of the present invention.
  • an upper electrode layer 20 is provided on the side of the adhesion layer opposite to the piezoelectric layer 10 side.
  • the upper electrode layer 20 is formed so as to have a desired pattern by a vapor deposition lift-off method.
  • the upper electrode layer 20 may be formed by laminating over the entire upper surface of the piezoelectric layer 10 by sputtering and then forming a desired pattern by an etching method.
  • the piezoelectric layer 10 and the close contact layer may be epitaxially grown.
  • FIG. 12 is a cross-sectional view showing a state in which a slit is formed from a side opposite to the support layer side of the piezoelectric layer to reach the upper surface of the substrate layer in the method for manufacturing a transducer according to the first embodiment of the present invention.
  • FIG. 13 is a cross-sectional view showing a state in which a through hole is formed from a side opposite to the support layer side of the piezoelectric layer to the upper surface of the lower electrode layer in the method for manufacturing a transducer according to the first embodiment of the present invention. .. In FIG. 13, it is shown in the same cross-sectional view as in FIG.
  • slits are formed in the piezoelectric layer 10 and the first support portion 41 by dry etching with RIE (Reactive Ion Etching).
  • the slit may be formed by wet etching with fluorine nitric acid or the like.
  • DRIE Deep Reactive Ion Etching
  • the second support portion 42 exposed to the slit is etched so that the slit reaches the upper surface of the substrate layer 50.
  • the gap 114 and the recess 121 shown in FIG. 1 are formed.
  • the piezoelectric layer 10 is etched by the dry etching or the wet etching so that a part of the lower electrode layer 30 is exposed.
  • an adhesion layer (not shown) is provided on each of the upper electrode layer 20 and the lower electrode layer 30, and then an adhesion layer (not shown) is provided on the upper surface of each adhesion layer by a vapor deposition lift-off method.
  • the first connection electrode layer 140 and the second connection electrode layer 150 are provided.
  • the first connection electrode layer 140 and the second connection electrode layer 150 are laminated over the entire surfaces of the piezoelectric layer 10, the upper electrode layer 20 and the exposed lower electrode layer 30 by sputtering, and then a desired pattern is formed by an etching method. May be formed with.
  • FIG. 14 is a cross-sectional view showing a state in which an opening is formed in the method for manufacturing a transducer according to the first embodiment of the present invention. As shown in FIG. 14, a part of the substrate layer 50 is removed by DRIE. As a result, a plurality of beam portions 110, a base portion 120, and an opening portion 101 are formed.
  • connection portion 130 is provided.
  • the connecting portion 130 applies the connecting portion 130 in a liquid state on the tip surface 113 of each of the plurality of beam portions 110 by a dispensing method, a transfer method, or the like.
  • the connecting portion 130 is applied from above on the side opposite to the opening 101 side of the tip surface 113.
  • the connecting portion 130 is applied so as to project at least toward the upper electrode layer 20 side of the beam portion 110 in order to have a sufficient thickness.
  • the liquid connection portion 130 is cured.
  • the connecting portion 130 may be provided before forming the opening 101. As shown in FIG. 12, the substrate layer 50 is located below the gap 114 before the opening 101 is formed. Therefore, even if the width of the gap 114 in the plane S direction is wide, the connecting portion 130 can be provided on the tip surface 113 of each of the plurality of beam portions 110 without the connecting portion 130 falling off.
  • FIG. 15 is a cross-sectional view of a transducer according to a modified example of the first embodiment of the present invention.
  • FIG. 15 it is shown in the same cross-sectional view as in FIG.
  • the gap 114 of the transducer 100a according to the modified example of the first embodiment of the present invention is wider than the gap 114 of the transducer 100 according to the first embodiment of the present invention.
  • the change in the resonance frequency of the plurality of beam portions 110 when the size of the connecting portion 130, that is, the mass of the connecting portion 130 is changed is evaluated. An example will be described.
  • the transducers according to each embodiment used in this experimental example were designed so that the resonance frequency of each of the plurality of beam portions 110 was 43 kHz in a state where the connecting portion 130 was not provided. That is, in the transducer according to each embodiment, the thickness of the piezoelectric layer is 1 ⁇ m, the thickness of each of the upper electrode layer and the lower electrode layer is 0.1 ⁇ m, the thickness of the first support portion is 0.8 ⁇ m, and the first one. 2 The thickness of the support portion is 1.4 ⁇ m, the length of each of the plurality of beam portions in the extending direction is 400 ⁇ m, and the fixed ends of each of the plurality of beam portions when viewed from the orthogonal direction of the plane in which the plurality of beam portions are located.
  • Examples 1 to 6 the connecting portions are provided so that the outer diameter of the upwardly protruding portion of the connecting portion and the overall thickness of the connecting portion are different from each other as shown in Table 1 below. .. Table 1 below shows the results of calculating the resonance frequency of the beam portion by simulation for each of these examples.
  • the resonance frequency was lower than the resonance frequency of 43 kHz of the beam portion before the connection portion was provided. Further, when Examples 1, 3 and 5 are compared and Examples 2, 4 and 6 are compared, it can be seen that the resonance frequency of the beam portion decreases as the outer diameter of the portion protruding upward of the connecting portion increases. .. Further, when Examples 1 and 2 are compared, Examples 3 and 4 are compared, and Examples 5 and 6 are compared, the thicker the connection portion 130 is, the lower the resonance frequency of the beam portion is. You can see that.
  • the absolute value of the difference between the resonance frequency values of the beam portions of Examples 1 and 2 in which the outer diameter of the upwardly protruding portion of the connecting portion is 100 ⁇ m is 2.35 kHz, which is the average of the above values.
  • the value was 39.32 kHz. That is, the absolute value of the difference was 6% with respect to the above average value.
  • the absolute value of the difference is 13.7% of the average value.
  • Example 1 having the highest resonance frequency and Example 5 having the lowest resonance frequency are used.
  • the absolute value of the difference was 13.6% with respect to the average value of the resonance frequencies of Examples 1 and 5.
  • Examples 2, 4 and 6 in which the overall thickness of the connection portion is 20 ⁇ m, the difference between the resonance frequency values of Example 2 having the highest resonance frequency value and Example 6 having the lowest resonance frequency value.
  • the absolute value was 21.3% of the average value of the resonance frequencies of Examples 2 and 6.
  • the thinner the overall thickness of the connecting portion the more the variation in the amount of change in the resonance frequency of the beam portion due to the provision of the connecting portion, which is caused by the variation in the outer diameter of the portion protruding above the connecting portion. It can be seen that can be suppressed.
  • FIG. 16 is a graph showing the rate of decrease in the resonance frequency of the beam portion due to the provision of the connecting portion with respect to the mass of the connecting portion for each embodiment in the experimental example of the present invention.
  • the mass ratio of the connecting portion to the total mass of the plurality of beam portions calculated based on the density of each component in the transducer is plotted as the horizontal axis. ..
  • the vertical axis represents the ratio of the absolute value of the difference between the resonance frequency of the beam portion and 43 kHz with respect to 43 kHz, which is the value of the resonance frequency before the connection portion is provided. It is plotted as.
  • the mass ratio of the connection portion to the plurality of beam portions may be 5% by mass or less.
  • the mass ratio of the connecting portion to the plurality of beam portions should be 2% by mass or less, and in order to keep the reduction rate of the resonance frequency within 5%.
  • the mass ratio of the connecting portion to the plurality of beam portions should be 1% by mass or less.
  • the extending length of the beam portion 110 is shortened or the thickness of the beam portion 110 is increased in advance so that the plurality of beam portions 110 have a resonance frequency having a frequency higher than the desired resonance frequency. Design to keep it.
  • the extending length of each of the plurality of beam portions 110 is shortened or the thickness is increased, it becomes difficult to mechanically bend the beam portion 110, which deteriorates the device performance of the transducer 100.
  • each of the plurality of beam portions 110 is easily bent, and the device characteristics of the transducer 100 are improved.
  • the transducer 100 includes a plurality of beam portions 110, a base portion 120, and a connecting portion 130.
  • the plurality of beam portions 110 have a fixed end portion 111 and a tip end portion 112.
  • the tip 112 is located on the opposite side of the fixed end 111.
  • Each of the plurality of beam portions 110 extends from the fixed end portion 111 toward the tip end portion 112.
  • Each fixed end 111 of the plurality of beam portions 110 is located in the same plane S.
  • Each of the plurality of beam portions 110 includes a piezoelectric layer 10, an upper electrode layer 20, and a lower electrode layer 30.
  • the upper electrode layer 20 is arranged above the piezoelectric layer 10.
  • the lower electrode layer 30 is arranged so as to face at least a part of the upper electrode layer 20 with the piezoelectric layer 10 interposed therebetween.
  • the base 120 is connected to each fixed end 111 of each of the plurality of beams 110.
  • the connecting portion 130 connects the tip portions 112 of each of the plurality of beam portions 110 to each other.
  • the connecting portion 130 is made of a material having a Young's modulus lower than that of the material constituting the piezoelectric layer 10.
  • the connecting portion 130 is made of the material having a Young's modulus as described above, so that the stress of the plurality of beam portions 110 in the in-plane direction of the plane S can be relatively relaxed, so that the plurality of beam portions 110 can be formed. It is possible to suppress the difficulty in displacement and, by extension, the decrease in the electromechanical conversion efficiency of the transducer 100.
  • the thickness of the connecting portion 130 is thicker than the thickness of each of the plurality of beam portions 110 in the direction orthogonal to the plane S of the connecting portion 130.
  • the connecting portion 130 Because of the thickness, the connection 130 can more easily absorb the force. As a result, the reliability of the transducer 100 is improved.
  • the mass of the connecting portion 130 is 5% or less of the total mass of the plurality of beam portions 110.
  • the resonance frequencies of each of the plurality of beam portions 110 of the transducer 100 are a plurality of states before the connecting portion 130 is provided.
  • the difference between each resonance frequency of the beam portion 110 is sufficiently small. Therefore, it is possible to prevent the device characteristics of the transducer 100 from deteriorating by changing the design of the plurality of beam portions 110 in order to adjust the resonance frequency.
  • a portion 131 located on the tip surface 113 from each of the plurality of beam portions 110 projects toward the upper electrode layer 20 of each of the plurality of beam portions 110.
  • the Young's modulus of the material constituting the connecting portion 130 is 1 GPa or less.
  • the Young's modulus is 1 GPa or less, the force that the beam portions 110 restrain each other becomes too strong, and it is suppressed that the resonance frequencies of the plurality of beam portions 110 become high.
  • deterioration of the device characteristics of the transducer 100 can be suppressed.
  • even when external stress such as thermal stress is generated in the plurality of beam portions 110 the influence of the external stress on the device characteristics of the transducer 100 can be reduced.
  • the piezoelectric layer 10 is made of an inorganic material.
  • the connecting portion 130 is made of an organic material. Since most of the organic materials have a Young's modulus lower than that of the inorganic materials, it becomes easy to adopt the materials constituting each of the piezoelectric layer 10 and the connecting portion 130, and the design of the transducer 100 becomes easy.
  • the material constituting the connection portion 130 is a silicone resin or a fluoroelastomer. This makes it easy to design the connecting portion 130 to be made of a material having a Young's modulus lower than that of the material constituting the piezoelectric layer 10.
  • the piezoelectric layer 10 is composed of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ). As a result, the piezoelectric characteristics of the piezoelectric layer 10 can be improved, so that the device characteristics of the transducer 100 can be improved.
  • FIG. 17 is a plan view showing a transducer according to the second embodiment of the present invention.
  • FIG. 18 is a cross-sectional view of the transducer of FIG. 17 as viewed from the direction of the arrow along line XVIII-XVIII.
  • the transducer 200 has a first tip surface 213A as a tip surface along the orthogonal direction of the plane and below the first tip surface 213A in the orthogonal direction. It has a second tip surface 213B located on the side.
  • Each of the plurality of beam portions 110 is connected to the connecting portion 130 at least by the second tip surface 213B.
  • the first tip surface 213A is located along the connecting portion 130 toward the connecting portion 130.
  • FIG. 17 when the connecting portion 130 is arranged on the second tip surface 213B, it is possible to prevent the connecting portion 130 from spreading from the first tip surface 213A to the upper surface of the beam portion 110.
  • the vibration of each of the plurality of beam portions 110 in the orthogonal direction is less likely to be disturbed by the connecting portion 130, and deterioration of the device characteristics of the transducer 100 can be suppressed.
  • the first tip surface 213A of each of the plurality of beam portions 110 is located on the virtual ring when viewed from the orthogonal direction.
  • the first tip surface 213A of each of the plurality of beam portions 110 can be formed by hollowing out a part of each of the plurality of beam portions 110 at a time, so that the configuration of the transducer 100 can be simplified.
  • the diameter of the virtual ring is, for example, 50 ⁇ m or more and 200 ⁇ m or less.
  • the second tip surface 213B of each of the plurality of beam portions 110 is relative to the corresponding first tip surface 213A. It is located on the side opposite to the fixed end 111 side.
  • the first tip surface 213A is the tip surface of the piezoelectric layer 10 and is the second tip.
  • the surface 213B is the tip surface of the support layer 40.
  • the first front end surface 213A may be composed of the respective tip surfaces of the piezoelectric layer 10 and a part of the support layer 40 on the piezoelectric layer 10 side
  • the second front end surface 213B is the support layer 40 and the piezoelectric layer 40. It may be composed of each tip surface of a part of the body layer 10 on the support layer 40 side.
  • the first tip surface 213A may be formed by etching the piezoelectric layer 10.
  • the first front end surface 213A is composed of the respective tip surfaces of the piezoelectric layer 10 and a part of the support layer 40 on the piezoelectric layer 10 side, the piezoelectric layer of the piezoelectric layer 10 and the support layer 40 is formed.
  • the first tip surface 213A may be formed by etching each of the parts on the 10 side.
  • FIG. 19 is a cross-sectional view showing a transducer according to a modified example of the second embodiment of the present invention. In FIG. 19, it is shown in the same cross-sectional view as in FIG. As shown in FIG. 19, in the transducer 200a according to the modified example of the second embodiment of the present invention, the first tip surface 213Aa is separated from the fixed end portion 111 toward the second tip surface 213Ba side in the orthogonal direction. It is inclined to.
  • the connecting portion 130 is provided on the first tip surface 213Aa and the second tip surface 213Ba, the boundary between the upper surface of the beam portion 110 continuous with the second tip surface 213Ba and the first tip surface 213Aa. It is possible to reduce the remaining air bubbles in the portion. As a result, the decrease in the bonding area between the connecting portion 130 and the tip portion 212 is suppressed, and the reliability of the transducer 100 is improved.
  • the tip surface of the piezoelectric layer 10 is inclined as the first tip surface 213Aa so as to be separated from the fixed end portion 111 toward the support layer 40.
  • the resist shape or processing conditions for etching for forming the first tip surface 213A in the transducer 200 according to the second embodiment of the present invention are set.
  • the first tip surface 213Aa in the modified example of the second embodiment of the present invention can be formed.
  • the connecting portion 130 is made of a material having a Young's modulus lower than that of the material constituting the piezoelectric layer 10, as in the transducer according to the first embodiment of the present invention. Therefore, while suppressing the plurality of beam portions 110 from vibrating in the coupled vibration mode, the decrease in the electromechanical conversion efficiency of the transducers 200 and 200a is suppressed.
  • the transducer according to the third embodiment of the present invention is mainly different from the transducer according to the first embodiment of the present invention in the shape of the gap located between the plurality of beam portions. Therefore, the description of the same configuration as that of the transducer according to the first embodiment of the present invention will not be repeated.
  • FIG. 20 is a plan view showing the transducer according to the third embodiment of the present invention.
  • the upper electrode layer, the first connection electrode layer, and the second connection electrode layer are not shown.
  • a connecting portion 330 is further provided along a part of the gap 314.
  • the vent hole 315 penetrating in the orthogonal direction is formed in the gap 314, and the air or the like located in the opening 101 when the transducer 100 is mounted is formed.
  • the medium can pass through the vent hole 315.
  • each of the plurality of beam portions 110 can be more firmly connected to each other in the orthogonal direction while preventing the vibration of the plurality of beam portions 110 from being hindered by the medium located in the opening 101.
  • the connecting portion 330 when the connecting portion 330 is provided on the tip surface 113, the liquid connecting portion 330 is applied by dropping the liquid connecting portion 330 onto the tip surface 113 from the upper electrode layer side. At this time, the connecting portion 330 coated on the tip surface 113 enters the gap 314 due to the capillary phenomenon. As a result, the connection portion 330 can be provided in the gap 314.
  • the slit width of the gap 314 on the side opposite to the tip 112 side is wider than the slit width on the tip 112 side.
  • the vent hole 315 is formed in a portion of the gap 314 where the slit width is wide.
  • FIG. 21 is a plan view showing a transducer according to a modified example of the third embodiment of the present invention.
  • the slit width of the gap 314a becomes wider as the distance from the tip portion 112 side increases.
  • the vent hole 315 can be secured by suppressing the connection portion 330 from reaching the portion of the gap 314 opposite to the tip portion 112 side, and the connection between each of the plurality of beam portions 110 and the connection portion 330. It is possible to suppress the concentration of stress on a part of the interface. As a result, the destruction of the plurality of beam portions 110 is suppressed, and the reliability of the transducer 100 is improved.
  • the connecting portion 330 is made of a material having a Young's modulus lower than that of the material constituting the piezoelectric layer, similarly to the transducer according to the first embodiment of the present invention. While suppressing the plurality of beam portions 110 from vibrating in the coupled vibration mode, the decrease in the electromechanical conversion efficiency of the transducers 300 and 300a is suppressed.
  • Piezoelectric layer 10a Piezoelectric single crystal substrate, 20 Upper electrode layer, 30 Lower electrode layer, 40 Support layer, 41 1st support, 42 2nd support, 50 Substrate layer, 51 1st substrate, 52 2nd substrate , 60 laminated body, 100, 100a, 200, 200a, 300, 300a transducer, 101 opening, 110 beam, 111 fixed end, 112, 212 tip, 113 tip surface, 114, 314, 314a gap, 120 base , 121 recess, 130, 330 connection part, 131 part, 140 first connection electrode layer, 150 second connection electrode layer, 213A, 213Aa first tip surface, 213B, 213Ba second tip surface, 315 vent hole.

Abstract

L'invention concerne un transducteur (100) dans lequel chacune d'une pluralité de parties de faisceau (110) s'étend à partir d'une partie d'extrémité fixe (111) vers une partie d'extrémité distale (112). Les parties d'extrémité fixes (111) de la pluralité de parties de faisceau (110) sont positionnées dans le même plan (S). Chacune de la pluralité de parties de faisceau (110) comprend une couche de corps piézoélectrique (10), une couche d'électrode supérieure (20), et une couche d'électrode inférieure (30). Une partie de base (120) est reliée à la partie d'extrémité fixe (111) de chacune de la pluralité de parties de faisceau (110). Une partie de liaison (130) relie les parties d'extrémité distale (112) de la pluralité de parties de faisceau (110). La partie de liaison (130) est composée d'un matériau ayant un module de Young inférieur à celui du matériau dont la couche de corps piézoélectrique (10) est composée.
PCT/JP2020/031098 2019-11-13 2020-08-18 Transducteur WO2021095311A1 (fr)

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JP2019205354 2019-11-13

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120230524A1 (en) * 2011-03-07 2012-09-13 Ho Hsin Progressive Technology Co., Ltd. Piezoelectric panel speaker
WO2014083998A1 (fr) * 2012-11-30 2014-06-05 京セラ株式会社 Actionneur piézoélectrique, dispositif à vibrations piézoélectriques et terminal portable
JP2015088875A (ja) * 2013-10-30 2015-05-07 理想科学工業株式会社 超音波放射素子
US20180304309A1 (en) * 2015-10-21 2018-10-25 Agency For Science, Technology And Research Ultrasound transducer and method of forming the same
CN208987175U (zh) * 2018-10-11 2019-06-14 东莞希越电子有限公司 压电薄膜麦克风改良结构

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120230524A1 (en) * 2011-03-07 2012-09-13 Ho Hsin Progressive Technology Co., Ltd. Piezoelectric panel speaker
WO2014083998A1 (fr) * 2012-11-30 2014-06-05 京セラ株式会社 Actionneur piézoélectrique, dispositif à vibrations piézoélectriques et terminal portable
JP2015088875A (ja) * 2013-10-30 2015-05-07 理想科学工業株式会社 超音波放射素子
US20180304309A1 (en) * 2015-10-21 2018-10-25 Agency For Science, Technology And Research Ultrasound transducer and method of forming the same
CN208987175U (zh) * 2018-10-11 2019-06-14 东莞希越电子有限公司 压电薄膜麦克风改良结构

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