JP2021007118A - Piezoelectric transducer and piezoelectric module - Google Patents

Abstract

To enhance a characteristic in which a first piezoelectric region and a second piezoelectric region convert an AC voltage into vibration or a characteristic in which they convert vibration into an AC voltage.SOLUTION: A frame-shaped support portion 2 having a cavity 23 formed therein and a piezoelectric portion 3 supported by the support portion 2 are provided. At least one region of a first piezoelectric layer 40 of the piezoelectric portion 3 overlaps with at least one region of a second piezoelectric layer 50 of the piezoelectric portion 3 in a direction orthogonal to the thickness direction of the piezoelectric portion 3. A first piezoelectric region R4 is a region in which a first electrode 41, a second electrode 42, and the first piezoelectric layer 40 overlap with the cavity 23 in the thickness direction. A second piezoelectric region R5 is a region in which a third electrode 51, a fourth electrode 52, and the second piezoelectric layer 50 overlap with the cavity 23 in the thickness direction. The second piezoelectric region R5 is located in a region surrounding the first piezoelectric region R4 when viewed from the thickness direction.SELECTED DRAWING: Figure 2

Description

The present invention relates to a piezoelectric transducer and a piezoelectric module, and more particularly to a piezoelectric transducer including a plurality of piezoelectric layers and a piezoelectric module including the piezoelectric transducer.

As a conventional example, the piezoelectric device (piezoelectric transducer) described in Patent Document 1 will be illustrated. The piezoelectric device described in Patent Document 1 includes a base material and an upper layer (piezoelectric portion) supported by the base material. The upper layer includes a vibrating portion, and the vibrating portion includes a lower electrode, an intermediate electrode, and an upper electrode arranged apart from each other in the thickness direction. The upper layer is a first piezoelectric layer (first piezoelectric layer) arranged so that at least a part is sandwiched between the lower electrode and the intermediate electrode, and the intermediate electrode and the upper layer are arranged so as to overlap the first piezoelectric layer. It includes a second piezoelectric layer (second piezoelectric layer) arranged so that at least a part thereof is sandwiched by the electrodes.

International Publication No. 2016/175013

In the piezoelectric device described in Patent Document 1, it may be required to improve the characteristic that the upper layer converts AC voltage into vibration or the characteristic that vibration is converted into AC voltage.

An object of the present invention is to provide a piezoelectric transducer and a piezoelectric module in which the first piezoelectric region and the second piezoelectric region of the piezoelectric portion have improved characteristics of converting an AC voltage into vibration or converting vibration into an AC voltage. To do.

In order to solve the above problems, the piezoelectric transducer according to one aspect of the present invention includes a support portion and a piezoelectric portion. The support portion has a frame shape with a cavity formed inside. The piezoelectric portion is supported by the support portion. The piezoelectric portion has a plate shape that covers the cavity from one side in the thickness direction. The piezoelectric portion includes a first electrode, a second electrode, a first piezoelectric layer, a third electrode, a fourth electrode, and a second piezoelectric layer. The first piezoelectric layer is sandwiched between the first electrode and the second electrode in the thickness direction. The second piezoelectric layer is sandwiched between the third electrode and the fourth electrode in the thickness direction. At least one region of the first piezoelectric layer overlaps with at least one region of the second piezoelectric layer in a direction orthogonal to the thickness direction. The piezoelectric portion includes a first piezoelectric region and a second piezoelectric region. The first piezoelectric region is a region in which the first electrode, the second electrode, and the first piezoelectric layer overlap the cavity in the thickness direction. The second piezoelectric region is a region in which the third electrode, the fourth electrode, and the second piezoelectric layer overlap the cavity in the thickness direction. The second piezoelectric region is located in a region surrounding the first piezoelectric region when viewed from the thickness direction.

The piezoelectric module according to one aspect of the present invention includes a plurality of the piezoelectric transducers.

In the piezoelectric transducer and the piezoelectric module according to each aspect of the present invention, it is possible to improve the characteristic that the first piezoelectric region and the second piezoelectric region convert the AC voltage into the vibration or the characteristic that the vibration is converted into the AC voltage.

FIG. 1 is a plan view of the piezoelectric transducer according to the embodiment. FIG. 2 shows the same piezoelectric transducer as above, and is an end view of AA of FIG. FIG. 3 shows the same piezoelectric transducer as above, and is a BB end view of FIG. FIG. 4 shows the same piezoelectric transducer as above, and is a layout diagram corresponding to the CC cross section of FIG. 5A to 5F are end views showing a method of manufacturing a piezoelectric transducer according to an embodiment. 6A to 6D are end views showing a method of manufacturing the same piezoelectric transducer. FIG. 7 is a schematic view of the piezoelectric module according to the embodiment.

Hereinafter, the piezoelectric transducer and the piezoelectric module according to the embodiment will be described with reference to the drawings. However, the embodiments described below are only part of the various embodiments of the present invention. The following embodiments can be variously modified according to the design and the like as long as the object of the present invention can be achieved. Each figure described in the following embodiment is a schematic view, and the ratio of the size and the thickness of the components in the figure does not necessarily reflect the actual dimensional ratio.

(Piezoelectric transducer configuration)
As shown in FIGS. 1 to 4, the piezoelectric transducer 1 includes a support portion 2 and a piezoelectric portion 3. The piezoelectric portion 3 includes a first piezoelectric layer 40, a second piezoelectric layer 50, a first electrode 41, a second electrode 42, a third electrode 51, and a fourth electrode 52. The piezoelectric portion 3 further includes a protective layer 6 and an insulating layer 7.

The support portion 2 is formed in a frame shape in which a cavity 23 is formed inside. The outer edge of the support portion 2 has a square shape. The support portion 2 is formed of, for example, a semiconductor substrate. The support portion 2 is formed of silicon as a main material. As shown in FIGS. 2 and 3, the support portion 2 has a first surface 21 and a second surface 22 on the side opposite to the first surface 21 in the thickness direction of the support portion 2. The cavity 23 is a hole that penetrates the support portion 2 in the thickness direction. The cavity 23 is formed in a circular shape when viewed from the thickness direction of the support portion 2. The center of the cavity 23 is located near the center of the support portion 2 when viewed from the thickness direction of the support portion 2.

The piezoelectric portion 3 is formed in a plate shape. The piezoelectric portion 3 is formed in a square shape in a plan view. The piezoelectric portion 3 is supported by the support portion 2. The thickness direction of the support portion 2 and the thickness direction of the piezoelectric portion 3 coincide with each other. The piezoelectric portion 3 covers the cavity 23 from one side (upper side of the paper surface in FIG. 2) of the piezoelectric portion 3 in the thickness direction.

In the piezoelectric transducer 1, unless otherwise specified, the thickness direction of the piezoelectric portion 3 is defined as the Z-axis direction. The support portion 2 and the piezoelectric portion 3 are aligned in the Z-axis direction. In the Z-axis direction, the support portion 2 side is defined as the negative side of the Z-axis, and the piezoelectric portion 3 side is defined as the positive side of the Z-axis. Further, the directions of two adjacent sides of the piezoelectric portion 3 in a plan view are defined as the X-axis direction and the Y-axis direction, respectively. Therefore, the X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other.

The protective layer 6 of the piezoelectric portion 3 is formed on the first surface 21 of the support portion 2. The protective layer 6 is formed over the entire area of the first surface 21 so as to cover the cavity 23 from one side (positive side) in the Z-axis direction. The protective layer 6 is formed of, for example, silicon dioxide (SiO ₂ ).

The first piezoelectric layer 40 and the second piezoelectric layer 50 are formed of a piezoelectric material. The first piezoelectric layer 40 and the second piezoelectric layer 50 have a thickness in the Z-axis direction. The polarization directions of the first piezoelectric layer 40 and the second piezoelectric layer 50 are along the Z-axis direction.

The piezoelectric portion 3 has a structure in which the second electrode 42, the first piezoelectric layer 40, and the first electrode 41 are laminated in this order from the support portion 2 side (negative side of the Z axis). Further, the piezoelectric portion 3 has a structure in which the fourth electrode 52, the second piezoelectric layer 50, and the third electrode 51 are laminated in this order from the support portion 2 side (negative side of the Z axis).

The second electrode 42 and the fourth electrode 52 are formed on the surface 60 of the protective layer 6 on the side opposite to the support portion 2 side. The second electrode 42 and the fourth electrode 52 are located at the same position in the Z-axis direction. In short, the second electrode 42 and the fourth electrode 52 are located on the same plane orthogonal to the Z-axis direction. The second electrode 42 and the fourth electrode 52 are formed of, for example, platinum.

FIG. 4 is a view of FIG. 2 as viewed from a CC cross section. However, FIG. 4 does not show the insulating layer 7. The second electrode 42 is formed in a circular shape. The second electrode 42 is formed near the center of the piezoelectric portion 3 when viewed from the Z-axis direction. The piezoelectric transducer 1 further includes wiring 421. The wiring 421 is formed in a straight line, one end thereof is connected to the second electrode 42, and the other end is located near the peripheral edge of the piezoelectric portion 3. Here, "viewed from the Z-axis direction" means to see through the piezoelectric transducer 1 and see it from the Z-axis direction. Similarly in the following description, "viewed from the Z-axis direction" means to see through the piezoelectric transducer 1 and see it from the Z-axis direction.

The fourth electrode 52 is formed in an arc shape. The fourth electrode 52 is formed so as to surround the second electrode 42. More specifically, the fourth electrode 52 is formed in an arc shape concentric with the second electrode 42. A wiring 421 connected to the second electrode 42 is located between both ends of the fourth electrode 52 facing each other. The piezoelectric transducer 1 further includes wiring 521. The wiring 521 is formed in a straight line, one end thereof is connected to the fourth electrode 52, and the other end is located near the peripheral edge of the piezoelectric portion 3.

As shown in FIG. 2, the surface of the frame-shaped support portion 2 on the piezoelectric portion 3 side is the first surface 21. Of the first surface 21, the inner edge 211 on the cavity 23 side is circular. The outer edge (outer edge 522: see FIG. 4) of the fourth electrode 52 in the radial direction is along the inner edge 211 of the first surface 21 when viewed from the Z-axis direction. More specifically, the outer edge 522 of the fourth electrode 52 is formed in an arc shape having a diameter slightly larger than that of the cavity 23. Further, of the fourth electrode 52, the inner edge (inner edge 525: see FIG. 4) in the radial direction is formed in an arc shape having a diameter smaller than that of the cavity 23. That is, when viewed from the Z-axis direction, the fourth electrode 52 straddles the cavity 23 and the support portion 2.

As shown in FIGS. 2 and 3, the first piezoelectric layer 40 is formed in a plate shape on the surface of the second electrode 42 opposite to the support portion 2 side. The first piezoelectric layer 40 is formed on the entire surface of the second electrode 42 on the side opposite to the support portion 2 side. That is, the first piezoelectric layer 40 is formed in a circular shape.

The second piezoelectric layer 50 is formed in a plate shape on the surface of the fourth electrode 52 opposite to the support portion 2 side. The second piezoelectric layer 50 is formed on the entire surface of the fourth electrode 52 on the side opposite to the support portion 2 side. That is, the second piezoelectric layer 50 is formed in an arc shape. The second piezoelectric layer 50 is formed so as to surround the first piezoelectric layer 40. More specifically, the second piezoelectric layer 50 is formed in an arc shape concentric with the first piezoelectric layer 40.

The second piezoelectric layer 50 overlaps the first piezoelectric layer 40 in a direction orthogonal to the Z-axis direction. More specifically, in the Z-axis direction, both ends of the second piezoelectric layer 50 coincide with both ends of the first piezoelectric layer 40.

The first electrode 41 is formed on the surface 400 of the first piezoelectric layer 40 on the side opposite to the support portion 2 side. The first electrode 41 is formed over the entire surface 400 of the first piezoelectric layer 40. That is, the first electrode 41 is formed in a circular shape. More specifically, the first electrode 41 is formed in a circular shape having a diameter slightly smaller than that of the first piezoelectric layer 40. The first electrode 41 is formed near the center of the piezoelectric portion 3 when viewed from the Z-axis direction. The first electrode 41 is made of, for example, gold.

The third electrode 51 is formed on the surface 500 of the second piezoelectric layer 50 on the side opposite to the support portion 2 side. The third electrode 51 is formed over the entire surface 500 of the second piezoelectric layer 50. That is, the third electrode 51 is formed in an arc shape. The third electrode 51 is formed so as to surround the first electrode 41. More specifically, the third electrode 51 is formed in an arc shape concentric with the first electrode 41. A first leader line 413, which will be described later, connected to the first electrode 41 is located between both ends of the third electrode 51 facing each other 510 (see FIG. 1). The third electrode 51 is made of, for example, gold.

The insulating layer 7 is formed on the surface 60 of the protective layer 6 opposite to the support portion 2 side, and is formed on a portion 61 in which the second electrode 42, the fourth electrode 52, the wiring 421 and the wiring 521 are not formed. There is. The surface 70 of the insulating layer 7 on the side opposite to the support portion 2 side is formed flat. The surface 70 of the insulating layer 7, the surface 400 of the first piezoelectric layer 40, and the surface 500 of the second piezoelectric layer 50 are substantially flush with each other. The insulating layer 7 is formed of, for example, silicon dioxide. The insulating layer 7 has electrical insulation. The first electrode 41, the second electrode 42, the third electrode 51, and the fourth electrode 52 sandwich at least one of the insulating layer 7, the first piezoelectric layer 40, and the second piezoelectric layer 50 between them. They are electrically isolated from each other. The insulating layer 7 reduces the possibility of electrical coupling between conductors, such as between the first leader wire 413 and the wiring 421, which will be described later. The insulating layer 7 may be formed of, for example, a resin material.

An example of the dimensions of each configuration is given below. The thickness of the support portion 2 is 200 μm. The thickness of the second electrode 42 and the fourth electrode 52 is 0.4 μm. The thickness of the second piezoelectric layer 50 is 2 μm. The thickness of the first piezoelectric layer 40 is 2 μm. The thickness of the insulating layer 7 is 2 μm. The thickness of the first electrode 41 and the second electrode 42 is 0.2 μm. The thickness of the protective layer 6 is 2 μm. The diameter of the cavity 23 is 30 μm. The length of one side of the support portion 2 is 50 μm.

The first piezoelectric layer 40 is sandwiched between the first electrode 41 and the second electrode 42 in the Z-axis direction. The second piezoelectric layer 50 is sandwiched between the third electrode 51 and the fourth electrode 52 in the Z-axis direction.

The piezoelectric section 3 includes a first piezoelectric region R4 and a second piezoelectric region R5. The first piezoelectric region R4 is a region in which the first piezoelectric layer 40, the first electrode 41, and the second electrode 42 overlap the cavity 23 in the Z-axis direction. The second piezoelectric region R5 is a region in which the second piezoelectric layer 50, the third electrode 51, and the fourth electrode 52 overlap the cavity 23 in the Z-axis direction. The second piezoelectric region R5 is located in a region surrounding the first piezoelectric region R4 when viewed from the Z-axis direction (see FIG. 1).

The first piezoelectric region R4 has a circular shape along the first electrode 41 (see FIG. 1), and the second piezoelectric region R5 has an arc shape along the third electrode 51. When viewed from the Z-axis direction, the second piezoelectric region R5 coincides with the region where the third electrode 51 is located (see FIG. 2).

As described above, the fourth electrode 52 straddles the cavity 23 and the support portion 2 when viewed from the Z-axis direction. Further, when viewed from the Z-axis direction, the third electrode 51 and the second piezoelectric layer 50 also straddle the cavity 23 and the support portion 2. Therefore, when viewed from the Z-axis direction, the second piezoelectric region R5 straddles the cavity 23 and the support portion 2.

Further, as described above, the outer edge 522 (see FIG. 4) of the fourth electrode 52 is along the inner edge 211 of the first surface 21 of the frame-shaped support portion 2. Therefore, when viewed from the Z-axis direction, a part of the second piezoelectric region R5 is along the inner edge 211 of the first surface 21. Further, the outer edge 512 of the third electrode 51 in the radial direction (see FIG. 1) and the outer edge of the second piezoelectric layer 50 in the radial direction are also along the inner edge 211 of the first surface 21. There is.

The first piezoelectric region R4 and the second piezoelectric region R5 generate an AC voltage when receiving ultrasonic waves. Further, the first piezoelectric region R4 and the second piezoelectric region R5 vibrate when an AC voltage is applied to transmit ultrasonic waves. The reception and transmission of ultrasonic waves by the first piezoelectric region R4 and the second piezoelectric region R5 are performed via the protective layer 6.

The first piezoelectric layer 40 of the first piezoelectric region R4 is formed of, for example, lead zirconate titanate (PZT). The second piezoelectric layer 50 of the second piezoelectric region R5 is formed of, for example, aluminum nitride (AlN). Aluminum nitride is a material having a high Young's modulus and a low density as compared with lead zirconate titanate.

The piezoelectric constant d ₃₁ of the first piezoelectric layer 40 is larger than the piezoelectric constant d ₃₁ of the second piezoelectric layer 50. Further, the relative permittivity ε _r of the first piezoelectric layer 40 is larger than the relative permittivity ε _r of the second piezoelectric layer 50. The relative permittivity ε _r of the first piezoelectric layer 40 is, for example, 1200. The relative permittivity ε _r of the second piezoelectric layer 50 is, for example, 10.

Since the piezoelectric constant d ₃₁ of the first piezoelectric layer 40 is larger than the piezoelectric constant d ₃₁ of the second piezoelectric layer 50, a first piezoelectric region R4 is characteristic for converting an AC voltage to the vibration in the Z-axis direction second piezoelectric region Better than R5. On the other hand, in the second piezoelectric layer 50, the value obtained by dividing the piezoelectric constant d ₃₁ by the relative permittivity ε _r (d ₃₁ / ε _r ) is larger than d ₃₁ / ε _r of the first piezoelectric layer 40. The region R5 has a better characteristic of converting vibration into an AC voltage than the first piezoelectric region R4.

As shown in FIG. 1, the piezoelectric transducer 1 has a plurality of (three in FIG. 1) leader lines (first leader line 413, second leader line 423, and fourth leader line 523) on the surface 70 of the insulating layer 7. And a plurality of pads (four in FIG. 1) (first pad 414, second pad 424, third pad 514, and fourth pad 524) are further provided. The piezoelectric transducer 1 may further include a third leader wire. Each leader and each pad is formed as a conductor layer.

The plurality of pads are formed near the peripheral edge of the surface 70 of the insulating layer 7. More specifically, the first pad 414 and the second pad 424 are formed on the surface 70 of the insulating layer 7 near the peripheral edge on the positive side of the Y axis and near the center in the X axis direction. The third pad 514 and the fourth pad 524 are formed on the surface 70 of the insulating layer 7 near the peripheral edge on the negative side of the Y-axis and near the center in the X-axis direction. Each pad is formed in a rectangular shape. In addition, each pad may be formed in a square shape.

The first leader wire 413 electrically connects the first electrode 41 and the first pad 414.

The second leader line 423 electrically connects the wiring 421 connected to the second electrode 42 and the second pad 424. As shown in FIGS. 1 and 3, the insulating layer 7 has an opening 72. One end of the wiring 421 is located at the back of the opening 72 (lower in FIG. 3). The second leader line 423 descends toward the wiring 421 along the inner wall of the opening 72, and is formed so as to overlap a part of the wiring 421 in the Z-axis direction, so that the second leader line 423 and the wiring 421 are formed. Is connected.

The third electrode 51 is electrically connected to the third pad 514 by being directly connected to the third pad 514. The third electrode 51 may be electrically connected to the third pad 514 via a third leader wire formed on the surface 70 of the insulating layer 7.

The fourth leader line 523 electrically connects the wiring 521 connected to the fourth electrode 52 and the fourth pad 524. The insulating layer 7 has an opening 74. One end of the wiring 521 is located at the back of the opening 74 (lower in FIG. 3). The fourth leader line 523 descends toward the wiring 521 along the inner wall of the opening 74, and is formed so as to overlap a part of the wiring 521 in the Z-axis direction, so that the fourth leader line 523 and the wiring 521 are formed. Is connected.

(Production method)
Next, an example of a method for manufacturing the piezoelectric transducer 1 will be described with reference to FIGS. 5A to 5F and FIGS. 6A to 6D.

First, as shown in FIG. 5A, a protective layer 6 made of a thermal oxide film is formed on the first surface 201 of the base material 200, which is a silicon substrate that is the base of the support portion 2 of the piezoelectric transducer 1. Further, a protective layer made of a thermal oxide film is also formed on the second surface 202 opposite to the first surface 201 in the thickness direction of the base material 200. However, in FIG. 5A, the illustration of the protective layer formed on the second surface 202 is omitted. The base material 200 is a disk-shaped wafer.

Next, as shown in FIG. 5B, the first layer 91 of platinum is formed over the entire surface 60 of the protective layer 6. The first layer 91 is a layer that later becomes the second electrode 42, the fourth electrode 52, the wiring 421, and the wiring 521 (see FIG. 4). The first layer 91 is formed by, for example, a sputtering method.

Next, as shown in FIG. 5C, the second layer 92 of lead zirconate titiate is formed over the entire surface 910 of the first layer 91. The second layer 92 is a layer that will later become the first piezoelectric layer 40. The second layer 92 is formed by, for example, a sputtering method.

Next, as shown in FIG. 5D, the second layer 92 is patterned by a photolithography technique and an etching technique. By this step, the first piezoelectric layer 40 composed of a part of the second layer 92 is formed.

Next, as shown in FIG. 5E, the first layer 91 is patterned by a photolithography technique and an etching technique. By this step, the second electrode 42, the fourth electrode 52, the wiring 421 (see FIG. 4) and the wiring 521 (see FIG. 4), which are a part of the first layer 91, are formed.

Next, as shown in FIG. 5F, a portion of the surface 60 of the protective layer 6 on which the second electrode 42, the fourth electrode 52, the wiring 421 (see FIG. 4) and the wiring 521 (see FIG. 4) are not formed. A third layer 93 of aluminum nitride is formed on the surface of 61 and the first piezoelectric layer 40, the fourth electrode 52, the wiring 421, and the wiring 521. The third layer 93 is a layer that will later become the second piezoelectric layer 50. The third layer 93 is formed by, for example, a sputtering method. Further, the first piezoelectric layer 40 is exposed by polishing or etching the third layer 93.

Next, as shown in FIG. 6A, the third layer 93 is patterned by a photolithography technique and an etching technique. By this step, the second piezoelectric layer 50 composed of a part of the third layer 93 is formed.

Next, as shown in FIG. 6B, the insulating layer 7 is formed on the surface 60 of the protective layer 6 on the portion 61 where the electrodes and wiring are not formed. The insulating layer 7 is formed by, for example, a chemical vapor deposition (CVD) method so as to cover the first piezoelectric layer 40 and the second piezoelectric layer 50, and then is polished or etched back from the surface to cause the first piezoelectric layer 7. It is flush with the surface 400 of the layer 40 and the surface 500 of the second piezoelectric layer 50.

Next, openings 72 (see FIG. 3) and 74 (see FIG. 3) are formed in the insulating layer 7. The openings 72 and 74 are formed using, for example, photolithography and etching techniques.

Next, as shown in FIG. 6C, the first electrode 41 is formed on the surface 400 of the first piezoelectric layer 40. A third electrode 51 is formed on the surface 500 of the second piezoelectric layer 50. A first leader wire 413, a second leader wire 423, a fourth leader wire 523, a first pad 414, a second pad 424, a third pad 514, and a fourth pad 524 are formed on the surface 70 of the insulating layer 7. The first electrode 41, the third electrode 51, each leader wire, and each pad are formed of gold as a material by a vapor deposition method or a sputtering method using a metal mask. Further, the first electrode 41, the third electrode 51, each leader wire and each pad may be formed by using a photolithography technique and an etching technique. Further, the first electrode 41, the third electrode 51, each leader wire and each pad may be formed by using a photolithography technique, a thin film forming technique, and a lift-off method.

Next, as shown in FIG. 6D, the cavity 23 is formed in the base material 200. As a result, the support portion 2 is formed. The cavity 23 is formed, for example, by anisotropic etching with an alkaline solution. More specifically, first, the protective layer formed on the second surface 202 (see FIG. 6C) is patterned by using a photolithography technique and an etching technique. Further, the cavity 23 is formed by etching the central portion of the base material 200 from the second surface 202 using the protective layer remaining after patterning as an etching mask. The protective layer 6 functions as an etching stopper. That is, the protective layer 6 is difficult to be etched by the alkaline solution. Therefore, the variation in the thickness of the protective layer 6 is reduced.

Next, the base material 200 is diced. That is, the base material 200 is divided for each region occupied by one piezoelectric transducer 1.

As described above, the piezoelectric transducer 1 is manufactured.

(Piezoelectric module configuration)
As shown in FIG. 7, the piezoelectric module 10 includes a plurality of piezoelectric transducers 1 (16 in FIG. 7). The plurality of piezoelectric transducers 1 are mounted on the substrate. The plurality of piezoelectric transducers 1 are arranged in a two-dimensional array having four rows vertically and four rows horizontally. The piezoelectric module 10 further includes a first switching unit 11, a second switching unit 12, and a processing unit 13.

The first switching unit 11 and the second switching unit 12 each have a plurality of switches. The first electrode 41 of each piezoelectric transducer 1 is connected to the external power supply 15 via the first pad 414 and the switch of the first switching unit 11. The four piezoelectric transducers 1 arranged in a horizontal row share one switch of the first switching unit 11 connected to the external power supply 15.

The second electrode 42 of each piezoelectric transducer 1 is connected to the ground via the second pad 424 and the switch of the second switching unit 12. The four piezoelectric transducers 1 arranged in a vertical row share one switch of the second switching unit 12 connected to the ground.

The third electrode 51 of each piezoelectric transducer 1 is connected to the processing unit 13 via the third pad 514 and the switch of the second switching unit 12. The four piezoelectric transducers 1 arranged in a vertical row share one switch of the second switching unit 12 connected to the processing unit 13.

The fourth electrode 52 of each piezoelectric transducer 1 is connected to the ground via the fourth pad 524 and the switch of the first switching unit 11. The four piezoelectric transducers 1 arranged in a horizontal row share one switch of the first switching unit 11 connected to the ground.

The first switching unit 11 and the second switching unit 12 switch the connection between the piezoelectric transducer 1 and the external power supply 15 for each of the piezoelectric transducers 1. Further, the first switching unit 11 and the second switching unit 12 switch the connection between the piezoelectric transducer 1 and the processing unit 13 for each of the piezoelectric transducers 1. When the piezoelectric transducer 1 is connected to the external power source 15, an AC voltage is applied to the first piezoelectric layer 40 from the external power source 15. When the piezoelectric transducer 1 is connected to the processing unit 13, the AC voltage generated in the second piezoelectric region R5 is output to the processing unit 13. The first switching unit 11 and the second switching unit 12 may have a plurality of relays or a plurality of multiplexers instead of the plurality of switches.

The processing unit 13 includes, for example, a processor such as a CPU (Central Processing Unit) and an AC-DC converter. The AC-DC converter converts the AC voltage input from the piezoelectric transducer 1 into a DC voltage and outputs it to the processor. The processor is electrically connected to the first switching unit 11 and controls the opening and closing of a plurality of switches of the first switching unit 11. Further, the processor controls the opening and closing of a plurality of switches of the second switching unit 12.

(motion)
Next, an operation example of the piezoelectric transducer 1 and the piezoelectric module 10 will be described.

The processing unit 13 controls the opening and closing of the switches of the first switching unit 11 and the second switching unit 12 to connect the piezoelectric transducer 1 to the external power supply 15. When an AC voltage is applied to the first piezoelectric layer 40 of the piezoelectric transducer 1 from the external power source 15, the first piezoelectric layer 40 vibrates in the Z-axis direction, so that the first piezoelectric region R4 sends ultrasonic waves. Wave. The first electrode 41 and the second electrode 42 are electrodes for applying an AC voltage to the first piezoelectric layer 40.

The processing unit 13 controls the opening and closing of the switches of the first switching unit 11 and the second switching unit 12 and connects to the piezoelectric transducer 1. When the second piezoelectric region R5 receives ultrasonic waves, the second piezoelectric layer 50 vibrates in the Z-axis direction, and the second piezoelectric region R5 converts the vibration of the second piezoelectric layer 50 in the Z-axis direction into an AC voltage. .. The third electrode 51 and the fourth electrode 52 are electrodes for taking out the AC voltage generated in the second piezoelectric region R5. The third electrode 51 and the fourth electrode 52 take out the AC voltage generated by the second piezoelectric region R5 receiving ultrasonic waves and output it to the processing unit 13.

The first piezoelectric region R4 mainly transmits ultrasonic waves in the negative direction of the Z axis. The second piezoelectric region R5 mainly receives ultrasonic waves arriving from the negative side of the Z axis. That is, the direction in which the first piezoelectric region R4 and the second piezoelectric region R5 have the maximum transmission intensity and the direction in which the reception sensitivity is maximum are along the negative directions of the Z axis.

The piezoelectric module 10 is mounted on an automobile, for example, and is used as an ultrasonic sensor for measuring a distance between an object around the automobile. The piezoelectric module 10 transmits and receives ultrasonic waves. The processing unit 13 measures the time from when the piezoelectric module 10 sends ultrasonic waves until the ultrasonic waves are reflected by the object and returned, so that the processing unit 13 can move the ultrasonic waves between the object and the piezoelectric module 10. The distance can be calculated.

As another example, the piezoelectric module 10 is mounted on a mobile phone or the like and is used as a sensor for detecting a human fingerprint. In the piezoelectric module 10, the plurality of piezoelectric transducers 1 are arranged so that the distance between the centers of the adjacent piezoelectric transducers 1 is smaller than the distance between the unevenness of the fingerprint. The plurality of piezoelectric transducers 1 transmit ultrasonic waves and receive ultrasonic waves reflected by a human finger. Since the acoustic impedance is different between the concave portion and the convex portion of the fingerprint, the processing unit 13 can detect the fingerprint based on the intensity of the ultrasonic waves received by the plurality of piezoelectric transducers 1.

(effect)
If the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the Z-axis direction in the piezoelectric transducer 1, the first piezoelectric layer 40 is distorted when the first piezoelectric layer 40 vibrates. , The second piezoelectric layer 50 near the first piezoelectric layer 40 may be distorted. Further, when the second piezoelectric layer 50 vibrates, the second piezoelectric layer 50 is distorted, so that the first piezoelectric layer 40 may be distorted. In particular, when the first piezoelectric layer 40 tries to shrink in the direction orthogonal to the Z axis and the second piezoelectric layer 50 tries to expand in the direction orthogonal to the Z axis, the strain of the first piezoelectric layer 40 and the second piezoelectric layer 40 It may act to cancel out the distortion of the layer 50.

In the piezoelectric transducer 1 of the present embodiment, the second piezoelectric region R5 is located in a region surrounding the first piezoelectric region R4 when viewed from the Z-axis direction. Therefore, the degree to which the strain of the first piezoelectric layer 40 and the strain of the second piezoelectric layer 50 affect each other as compared with the case where the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the Z-axis direction. Can be reduced. Thereby, the characteristics of the first piezoelectric region R4 and the second piezoelectric region R5 (characteristics of converting AC voltage into vibration or characteristics of converting vibration into AC voltage) can be improved.

Further, if the first piezoelectric region R4 is arranged so as to overlap the entire area of the cavity 23 in the Z-axis direction, the following problems may occur. That is, when the first piezoelectric layer 40 vibrates, the direction in which the portion of the first piezoelectric region R4 that overlaps the central region of the cavity 23 is distorted, and the region of the first piezoelectric region R4 on the outer peripheral side of the cavity 23. Since the overlapping portion is distorted in the opposite direction, the characteristics of the first piezoelectric region R4 (for example, the efficiency of converting the AC voltage into vibration) may be lowered.

Similarly, if the second piezoelectric region R5 is arranged so as to overlap the entire area of the cavity 23 in the Z-axis direction, the following problems may occur. That is, when the second piezoelectric layer 50 vibrates, the direction in which the portion of the second piezoelectric region R5 that overlaps the central region of the cavity 23 is distorted, and the region of the second piezoelectric region R5 on the outer peripheral side of the cavity 23. Since the overlapping portions are distorted in the opposite direction, the characteristics of the second piezoelectric region R5 (for example, the receiving sensitivity) may be lowered.

Therefore, by arranging the first piezoelectric region R4 at a position overlapping the central region of the cavity 23 as in the present embodiment, the direction of strain in the first piezoelectric region R4 can be aligned. Further, by arranging the second piezoelectric region R5 at a position overlapping the region on the outer peripheral side of the cavity 23, the direction of distortion in the second piezoelectric region R5 can be aligned. As a result, the characteristics of the first piezoelectric region R4 and the characteristics of the second piezoelectric region R5 are improved.

If the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the Z-axis direction, the second electrode 42 and the third electrode 51 face each other in the Z-axis direction. In this case, the second electrode 42 and the third electrode 51 may be capacitively coupled to each other. Therefore, when the piezoelectric portion 3 vibrates, electrical interference may occur between the second electrode 42 and the third electrode 51.

On the other hand, the second piezoelectric region R5 of the present embodiment is located in a region surrounding the first piezoelectric region R4 when viewed from the Z-axis direction, and the first piezoelectric region R4 and the second piezoelectric region R5 do not overlap in the Z-axis direction. Therefore, the occurrence of capacitive coupling between the second electrode 42 and the third electrode 51 is suppressed. Therefore, electrical interference between the second electrode 42 and the third electrode 51 is suppressed. For example, by suppressing the cross talk (an example of electrical interference) between the second electrode 42 and the third electrode 51, the piezoelectric transducer 1 improves the transmission intensity and the reception sensitivity of the transmitted signal. Noise and noise of the received signal are reduced. Further, by reducing the noise of the transmission signal and the noise of the reception signal, the S / N ratio of the transmission signal and the S / N ratio of the reception signal are improved.

Further, since the second piezoelectric region R5 of the present embodiment is located in a region surrounding the first piezoelectric region R4 when viewed from the Z-axis direction, the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the Z-axis direction. The bending rigidity of the first piezoelectric layer 40 and the second piezoelectric layer 50 can be reduced as compared with the case where. That is, as compared with the case where the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the Z-axis direction, the first piezoelectric layer 40 hinders bending of the second piezoelectric layer 50 or the second piezoelectric layer 50. Is less likely to prevent bending of the first piezoelectric layer 40. Thereby, the characteristics of the first piezoelectric region R4 and the characteristics of the second piezoelectric region R5 (for example, transmission intensity and reception sensitivity) can be improved.

(Modified example of embodiment)
Hereinafter, modifications of the embodiment are listed. The following modifications may be realized in appropriate combinations.

In the Z-axis direction, both ends of the first piezoelectric layer 40 do not have to coincide with both ends of the second piezoelectric layer 50. At least one region of the first piezoelectric layer 40 may overlap with at least one region of the second piezoelectric layer 50 in a direction orthogonal to the Z-axis direction.

For example, the thickness of the second piezoelectric layer 50 may be smaller than that of the first piezoelectric layer 40, and both ends of the second piezoelectric layer 50 may be located between both ends of the first piezoelectric layer 40 in the Z-axis direction. .. Alternatively, the thickness of the first piezoelectric layer 40 may be smaller than that of the second piezoelectric layer 50, and both ends of the first piezoelectric layer 40 may be located between both ends of the second piezoelectric layer 50 in the Z-axis direction. ..

Alternatively, even if the vicinity of one end of the first piezoelectric layer 40 on the positive side of the Z axis overlaps the vicinity of one end of the second piezoelectric layer 50 on the negative side of the Z axis in the direction orthogonal to the Z axis direction. Good. Alternatively, even if the vicinity of one end of the first piezoelectric layer 40 on the negative side of the Z axis overlaps the vicinity of one end of the second piezoelectric layer 50 on the positive side of the Z axis in the direction orthogonal to the Z axis direction. Good.

Further, the protective layer 6 may be provided with a convex portion. One of the first piezoelectric layer 40 and the second piezoelectric layer 50 may be formed on the convex portion of the protective layer 6, and the other may be formed around the convex portion of the protective layer 6. According to this configuration, in the first piezoelectric layer 40 and the second piezoelectric layer 50, the ends on the support portion 2 side are located at different positions in the Z-axis direction. The ends of the first piezoelectric layer 40 and the second piezoelectric layer 50 opposite to the support portion 2 side may be located at the same position in the Z-axis direction, or may be located at different positions from each other. The convex portion may be formed only on the protective layer 6, or the convex portion may be formed on the support portion 2, and the convex portion of the protective layer 6 may be formed so as to overlap the convex portion of the support portion 2. ..

Further, the second piezoelectric region R5 of the embodiment substantially surrounds the first piezoelectric region R4 when viewed from the Z-axis direction, but the second piezoelectric region R5 surrounds the first piezoelectric region R4 when viewed from the Z-axis direction. Is not required. The second piezoelectric region R5 may be located at least a part of the region surrounding the first piezoelectric region R4 when viewed from the Z-axis direction.

Further, the shape of the outer edge of the support portion 2 is not limited to a square shape. The outer edge of the support portion 2 may be formed in a rectangular shape or a circular shape, for example. Further, the shape of the cavity 23 is not limited to a circular shape. The cavity 23 may be formed in a square shape or a rectangular shape, for example.

Further, the support portion 2 of the embodiment is formed in a frame shape continuous in the circumferential direction. In the support portion 2, the frame shape is not limited to a shape that is continuous in the circumferential direction, and may be a shape that is partially discontinuous in the circumferential direction. In the support portion, the frame shape may be any shape including the following two portions in the structure which is annular when viewed from the thickness direction (Z-axis direction) of the piezoelectric portion 3. That is, in the support portion, the two portions may face each other with at least one of the first piezoelectric region R4 and the second piezoelectric region R5 sandwiched between them when viewed from the thickness direction of the piezoelectric portion 3. The two parts may be connected or may be formed separately. The support portion may have a shape lacking a part in the circumferential direction, for example, a C-shape or a U-shape. Further, the support portion is formed by being divided into a plurality of members, and the piezoelectric portion 3 may be bridged over the plurality of members. Each of the plurality of members may be formed in a rectangular parallelepiped shape or a cube shape, for example.

Further, when viewed from the Z-axis direction, the outer edge 522 of the fourth electrode 52 may overlap with a part of the inner edge 211 of the first surface 21 of the frame-shaped support portion 2. Further, the outer edge 512 of the third electrode 51 in the radial direction may overlap with a part of the inner edge 211 of the first surface 21. Further, the outer edge of the second piezoelectric layer 50 in the radial direction may overlap with a part of the inner edge 211 of the first surface 21.

Further, the method for forming the first piezoelectric layer 40 and the second piezoelectric layer 50 is not limited to the sputtering method. The first piezoelectric layer 40 and the second piezoelectric layer 50 may be formed by, for example, a chemical vapor phase growth (CVD) method such as a MOCVD (organic metal chemical vapor phase growth) method, or a solgel method.

Further, the third electrode 51, the fourth electrode 52, the first piezoelectric layer 40, the second piezoelectric layer 50 and the like are formed by a vapor deposition method using a metal mask or the like instead of being formed by a photolithographic technique and an etching technique. Alternatively, it may be formed by a sputtering method.

Further, the material of the first piezoelectric layer 40 is not limited to lead zirconate titanate, and the material of the second piezoelectric layer 50 is not limited to aluminum nitride. For example, the first piezoelectric layer 40 and the second piezoelectric layer 50 may be formed of a resin such as polyvinylidene fluoride (PVDF) or zinc oxide (ZnO) as a material. Further, the first piezoelectric layer 40 may be formed of aluminum nitride, or the second piezoelectric layer 50 may be formed of lead zirconate titanate. Further, as the material of the first piezoelectric layer 40 and the second piezoelectric layer 50, a piezoelectric material containing PZTN (: Pb (ZrTiNb) O ₃ ), bismuth (Bi) or an alkali metal as a main component may be used.

Further, the sound waves transmitted or received by the first piezoelectric region R4 and the second piezoelectric region R5 are not limited to ultrasonic waves. For example, the first piezoelectric region R4 and the second piezoelectric region R5 may transmit or receive sound waves in the audible region.

Further, one of the first piezoelectric region R4 and the second piezoelectric region R5 may be used for transmitting ultrasonic waves and the other may be used for receiving ultrasonic waves, or both may be used for transmitting ultrasonic waves. It may be used for receiving ultrasonic waves, or both may be used for receiving ultrasonic waves. That is, the first electrode 41 and the second electrode 42 are electrodes for extracting the AC voltage generated in the first piezoelectric region R4, and the third electrode 51 and the fourth electrode 52 are AC to the second piezoelectric layer 50. It may be an electrode for applying a voltage. Alternatively, the first electrode 41 and the second electrode 42 are electrodes for applying an AC voltage to the first piezoelectric layer 40, and the third electrode 51 and the fourth electrode 52 are AC to the second piezoelectric layer 50. It may be an electrode for applying a voltage. Alternatively, the first electrode 41 and the second electrode 42 are electrodes for taking out the AC voltage generated in the first piezoelectric region R4, and the third electrode 51 and the fourth electrode 52 are AC generated in the second piezoelectric region R5. It may be an electrode for extracting voltage.

Further, the application of the piezoelectric transducer 1 is not limited to the application of transmitting or receiving sound waves. For example, the piezoelectric transducer 1 may be used for an actuator.

Further, the first electrode 41 and the third electrode 51 may be electrically connected to each other. For example, an electrode in which the first electrode 41 and the third electrode 51 are integrated is formed over the entire surface 70 of the insulating layer 7, the surface 400 of the first piezoelectric layer 40, and the surface 500 of the second piezoelectric layer 50. You may. Similarly, the second electrode 42 and the fourth electrode 52 may be electrically connected. When the first electrode 41 and the third electrode 51 are electrically connected, or when the second electrode 42 and the fourth electrode 52 are electrically connected, the first electrode is as follows. Mutual interference between the piezoelectric layer 40 and the second piezoelectric layer 50 may be suppressed. That is, the timing at which the piezoelectric transducer 1 is used for transmitting waves by applying an AC voltage to the first piezoelectric layer 40 and the timing at which the piezoelectric transducer 1 is used for receiving waves by extracting the AC voltage generated at the second piezoelectric layer 50. May be different.

Further, the number of piezoelectric layers included in the piezoelectric transducer 1 is not limited to two, that is, the first piezoelectric layer 40 and the second piezoelectric layer 50. The piezoelectric transducer 1 may include three or more piezoelectric layers. For example, the piezoelectric transducer 1 has two piezoelectric layers, a first piezoelectric layer 40 having the same shape as that of the embodiment, and two piezoelectric layers 40 arranged on both sides of the first piezoelectric layer 40 in the X-axis direction so as to surround the first piezoelectric layer 40. An arcuate piezoelectric layer may be provided.

Further, as the base material on which the support portion 2 is based, a base material in which a recess is formed on one surface of the silicon substrate and an insulating film is formed on one surface so as to close the opening of the recess may be used. Good. After forming the piezoelectric portion 3 on the insulating film of the base material, the silicon substrate of the base material is etched from the side opposite to the piezoelectric portion 3 to form a cavity connected to the recess on one surface. The piezoelectric transducer 1 may be formed.

(Summary)
As described above, the piezoelectric transducer 1 according to the first aspect includes a support portion 2 and a piezoelectric portion 3. The support portion 2 has a frame shape in which a cavity 23 is formed inside. The piezoelectric portion 3 is supported by the support portion 2. The piezoelectric portion 3 has a plate shape that covers the cavity 23 from one side in the thickness direction (Z-axis direction). The piezoelectric portion 3 includes a first electrode 41, a second electrode 42, a first piezoelectric layer 40, a third electrode 51, a fourth electrode 52, and a second piezoelectric layer 50. The first piezoelectric layer 40 is sandwiched between the first electrode 41 and the second electrode 42 in the thickness direction. The second piezoelectric layer 50 is sandwiched between the third electrode 51 and the fourth electrode 52 in the thickness direction. At least one region of the first piezoelectric layer 40 overlaps at least one region of the second piezoelectric layer 50 in a direction orthogonal to the thickness direction. The piezoelectric portion 3 includes a first piezoelectric region R4 and a second piezoelectric region R5. The first piezoelectric region R4 is a region in which the first electrode 41, the second electrode 42, and the first piezoelectric layer 40 overlap the cavity 23 in the thickness direction. The second piezoelectric region R5 is a region in which the third electrode 51, the fourth electrode 52, and the second piezoelectric layer 50 overlap the cavity 23 in the thickness direction. The second piezoelectric region R5 is located in a region surrounding the first piezoelectric region R4 when viewed from the thickness direction.

According to the above configuration, the second piezoelectric region R5 is located in a region surrounding the first piezoelectric region R4 when viewed from the thickness direction (Z-axis direction) of the piezoelectric portion 3. Therefore, as compared with the case where the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the thickness direction, the second piezoelectric region R5 of the second piezoelectric region R5 is distorted due to the distortion of the first piezoelectric layer 40 of the first piezoelectric region R4. The degree to which the layer 50 is distorted can be reduced. Further, the degree to which the first piezoelectric layer 40 is distorted due to the distortion of the second piezoelectric layer 50 can be reduced. Thereby, the characteristic that the first piezoelectric region R4 and the second piezoelectric region R5 convert the AC voltage into the vibration or the characteristic that the vibration is converted into the AC voltage can be improved.

Further, in the piezoelectric transducer 1 according to the second aspect, in the first aspect, both ends of the second piezoelectric layer 50 are located between both ends of the first piezoelectric layer 40 in the thickness direction (Z-axis direction).

According to the above configuration, both ends of the second piezoelectric layer 50 are located between both ends of the first piezoelectric layer 40 in the thickness direction. That is, the second piezoelectric layer 50 is formed to have a smaller thickness than the first piezoelectric layer 40. Therefore, the characteristics of the second piezoelectric region R5 (characteristics of converting vibration into AC voltage or characteristics of converting AC voltage into vibration) can be improved.

Further, in the piezoelectric transducer 1 according to the third aspect, in the first or second aspect, the first electrode 41 and the second electrode 42 are electrodes for applying an AC voltage to the first piezoelectric layer 40. The third electrode 51 and the fourth electrode 52 are electrodes for taking out the AC voltage generated in the second piezoelectric region R5.

According to the above configuration, the first electrode 41 and the second electrode 42 are electrodes for applying an AC voltage to the first piezoelectric layer 40. That is, the first piezoelectric region R4 converts the AC voltage into vibration. Further, the third electrode 51 and the fourth electrode 52 are electrodes for taking out the AC voltage generated in the second piezoelectric region R5. That is, the second piezoelectric region R5 converts the vibration into an AC voltage. When a force is applied to the piezoelectric portion 3 in the thickness direction (Z-axis direction) due to the piezoelectric portion 3 receiving ultrasonic waves or the like, a region surrounding the first piezoelectric region R4 rather than the first piezoelectric region R4. There is a high possibility that stress will be concentrated in the second piezoelectric region R5 located in. Therefore, in the above-mentioned piezoelectric transducer 1, the characteristic that the second piezoelectric region R5 converts the vibration into an AC voltage can be improved.

Further, in the piezoelectric transducer 1 according to the fourth aspect, in the first or second aspect, the first electrode 41 and the second electrode 42 are electrodes for taking out the AC voltage generated in the first piezoelectric region R4. The third electrode 51 and the fourth electrode 52 are electrodes for applying an AC voltage to the second piezoelectric layer 50.

According to the above configuration, the first electrode 41 and the second electrode 42 are electrodes for taking out the AC voltage generated in the first piezoelectric region R4. That is, the first piezoelectric region R4 converts the vibration into an AC voltage. Further, the third electrode 51 and the fourth electrode 52 are electrodes for applying an AC voltage to the second piezoelectric layer 50. That is, the second piezoelectric region R5 converts the AC voltage into vibration. When a force is applied to the piezoelectric portion 3 in the thickness direction (Z-axis direction) due to the piezoelectric portion 3 receiving ultrasonic waves or the like, a region surrounding the first piezoelectric region R4 rather than the first piezoelectric region R4. There is a high possibility that stress will be concentrated in the second piezoelectric region R5 located in. Therefore, in the above-mentioned piezoelectric transducer 1, the characteristic that the second piezoelectric region R5 converts the AC voltage into vibration can be improved.

Further, in the piezoelectric transducer 1 according to the fifth aspect, in the first or second aspect, the first electrode 41 and the second electrode 42 are electrodes for applying an AC voltage to the first piezoelectric layer 40. The third electrode 51 and the fourth electrode 52 are electrodes for applying an AC voltage to the second piezoelectric layer 50.

According to the above configuration, an AC voltage is applied to the first piezoelectric layer 40 and the second piezoelectric layer 50. That is, the piezoelectric transducer 1 functions as a device that converts the AC voltage applied to the first piezoelectric layer 40 and the second piezoelectric layer 50 into vibration. That is, when the piezoelectric transducer 1 functions as a device for converting an AC voltage into vibration, the characteristics of the first piezoelectric region R4 and the second piezoelectric region R5 to convert the AC voltage into vibration can be improved.

Further, in the piezoelectric transducer 1 according to the sixth aspect, in the first or second aspect, the first electrode 41 and the second electrode 42 are electrodes for taking out the AC voltage generated in the first piezoelectric region R4. The third electrode 51 and the fourth electrode 52 are electrodes for taking out the AC voltage generated in the second piezoelectric region R5.

According to the above configuration, the AC voltage is taken out from the first piezoelectric region R4, and the AC voltage is taken out from the second piezoelectric region R5. That is, the piezoelectric transducer 1 functions as a device that converts vibration into an AC voltage in the first piezoelectric region R4 and the second piezoelectric region R5. That is, when the piezoelectric transducer 1 functions as a device for converting vibration into an AC voltage, the characteristics of the first piezoelectric region R4 and the second piezoelectric region R5 to convert the vibration into an AC voltage can be improved.

Further, in the piezoelectric transducer 1 according to the seventh aspect, in the third aspect, the piezoelectric constant d ₃₁ of the first piezoelectric layer 40 is larger than the piezoelectric constant d ₃₁ of the second piezoelectric layer 50.

According to the above configuration, the characteristic that the first piezoelectric region R4 converts the AC voltage into the vibration and the characteristic that the second piezoelectric region R5 converts the vibration into the AC voltage can be improved.

Further, in the piezoelectric transducer 1 according to the eighth aspect, in any one of the first to seventh aspects, the first electrode 41, the second electrode 42, the third electrode 51 and the fourth electrode 52 are electrically insulated from each other. Has been done.

According to the above configuration, the possibility of electrical coupling occurring between the first piezoelectric region R4 and the second piezoelectric region R5 can be reduced.

Further, in the piezoelectric transducer 1 according to the ninth aspect, in any one of the first to eighth aspects, at least a part of the second piezoelectric region R5 is in the support portion 2 when viewed from the thickness direction (Z-axis direction). Of the surface (first surface 21) on the piezoelectric portion 3 side, it is along the inner edge 211 on the cavity 23 side.

When a force is applied to the piezoelectric portion 3 in the thickness direction (Z-axis direction) due to the piezoelectric portion 3 receiving ultrasonic waves or the like, there is a high possibility that stress will be concentrated near the inner edge 211 of the support portion 2. .. Therefore, in the above-mentioned piezoelectric transducer 1, the characteristics of the second piezoelectric region R5 (characteristics of converting vibration into AC voltage or characteristics of converting AC voltage into vibration) can be improved.

Further, in the piezoelectric transducer 1 according to the tenth aspect, in any one of the first to ninth aspects, the second piezoelectric region R5 is formed in the cavity 23 and the support portion 2 when viewed from the thickness direction (Z-axis direction). Straddling.

When a force is applied to the piezoelectric portion 3 in the thickness direction (Z-axis direction) due to the piezoelectric portion 3 receiving ultrasonic waves or the like, there is a high possibility that stress is concentrated near the inner edge 211 of the support portion 2. .. Therefore, in the above-mentioned piezoelectric transducer 1, the characteristics of the second piezoelectric region R5 (characteristics of converting vibration into AC voltage or characteristics of converting AC voltage into vibration) can be improved.

Further, the piezoelectric module 10 according to the eleventh aspect includes a plurality of piezoelectric transducers 1 according to any one of the first to tenth aspects.

According to the above configuration, the second piezoelectric region R5 of the piezoelectric transducer 1 is located in a region surrounding the first piezoelectric region R4 when viewed from the thickness direction (Z-axis direction) of the piezoelectric portion 3. Therefore, as compared with the case where the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the thickness direction, the second piezoelectric region R5 of the second piezoelectric region R5 is distorted due to the distortion of the first piezoelectric layer 40 of the first piezoelectric region R4. The degree to which the layer 50 is distorted can be reduced. Further, the degree to which the first piezoelectric layer 40 is distorted due to the distortion of the second piezoelectric layer 50 can be reduced. Thereby, the characteristic that the first piezoelectric region R4 and the second piezoelectric region R5 convert the AC voltage into the vibration or the characteristic that the vibration is converted into the AC voltage can be improved. Further, the piezoelectric module 10 includes a plurality of piezoelectric transducers 1. As a result, as compared with the case where only one piezoelectric transducer 1 is used, the output of the first piezoelectric region R4 and the second piezoelectric region R5 by converting the AC voltage into vibration can be increased, or the vibration can be increased. Can be made more sensitive to convert to AC voltage.

The configuration according to the second to tenth aspects is not an essential configuration for the piezoelectric transducer 1, and can be omitted as appropriate.

1 Piezoelectric Transducer 10 Piezoelectric Module 2 Support 21 First Surface (Surface)
23 Cavity 211 Inner edge 3 piezoelectric part 40 First piezoelectric layer 41 First electrode 42 Second electrode 50 Second piezoelectric layer 51 Third electrode 52 Fourth electrode R4 First piezoelectric region R5 Second piezoelectric region

Claims (11)

A frame-shaped support with a cavity formed inside,
A plate-shaped piezoelectric portion that is supported by the support portion and covers the cavity from one side in the thickness direction is provided.
The piezoelectric part is
With the first electrode
With the second electrode
A first piezoelectric layer sandwiched between the first electrode and the second electrode in the thickness direction,
With the third electrode
With the 4th electrode
A second piezoelectric layer sandwiched between the third electrode and the fourth electrode in the thickness direction is included.
At least one region of the first piezoelectric layer overlaps with at least one region of the second piezoelectric layer in a direction orthogonal to the thickness direction.
The piezoelectric part is
A first piezoelectric region in which the first electrode, the second electrode, and the first piezoelectric layer overlap the cavity in the thickness direction, and
A second piezoelectric region in which the third electrode, the fourth electrode, and the second piezoelectric layer overlap the cavity in the thickness direction is included.
The second piezoelectric region is a piezoelectric transducer located in a region surrounding the first piezoelectric region when viewed from the thickness direction. The piezoelectric transducer according to claim 1, wherein both ends of the second piezoelectric layer are located between both ends of the first piezoelectric layer in the thickness direction. The first electrode and the second electrode are electrodes for applying an AC voltage to the first piezoelectric layer.
The piezoelectric transducer according to claim 1 or 2, wherein the third electrode and the fourth electrode are electrodes for extracting an AC voltage generated in the second piezoelectric region. The first electrode and the second electrode are electrodes for extracting an AC voltage generated in the first piezoelectric region.
The piezoelectric transducer according to claim 1 or 2, wherein the third electrode and the fourth electrode are electrodes for applying an AC voltage to the second piezoelectric layer. The first electrode and the second electrode are electrodes for applying an AC voltage to the first piezoelectric layer.
The piezoelectric transducer according to claim 1 or 2, wherein the third electrode and the fourth electrode are electrodes for applying an AC voltage to the second piezoelectric layer. The first electrode and the second electrode are electrodes for extracting an AC voltage generated in the first piezoelectric region.
The piezoelectric transducer according to claim 1 or 2, wherein the third electrode and the fourth electrode are electrodes for extracting an AC voltage generated in the second piezoelectric region. The piezoelectric transducer according to claim 3, wherein the piezoelectric constant d ₃₁ of the first piezoelectric layer is larger than the piezoelectric constant d ₃₁ of the second piezoelectric layer. The piezoelectric transducer according to any one of claims 1 to 7, wherein the first electrode, the second electrode, the third electrode, and the fourth electrode are electrically insulated from each other. Any one of claims 1 to 8, wherein at least a part of the second piezoelectric region is along the inner edge of the cavity side of the surface of the support portion on the piezoelectric portion side when viewed from the thickness direction. Piezoelectric transducers described in. The piezoelectric transducer according to any one of claims 1 to 9, wherein the second piezoelectric region straddles the cavity and the support portion when viewed from the thickness direction. A piezoelectric module including a plurality of piezoelectric transducers according to any one of claims 1 to 10.

Images