WO2019058978A1

WO2019058978A1 - Piezoelectric transducer and piezoelectric module

Info

Publication number: WO2019058978A1
Application number: PCT/JP2018/032951
Authority: WO
Inventors: 健介水原; 庄司岡本
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2017-09-21
Filing date: 2018-09-06
Publication date: 2019-03-28

Abstract

The present invention improves the characteristics of a first piezoelectric region and a second piezoelectric region, said characteristics converting alternating voltage into vibration or converting vibration into alternating voltage. This piezoelectric transducer is provided with: a frame-like supporting part (2) which is internally provided with a cavity (23); and a piezoelectric part (3) which is supported by the supporting part (2). A first piezoelectric layer (40) of the piezoelectric part (3) is in a position that is different from the position of a second piezoelectric layer (50) of the piezoelectric part (3) in the thickness direction of the piezoelectric part (3). A first piezoelectric region (R4) is a region where a first electrode (41), a second electrode (42) and the first piezoelectric layer (40) overlap the cavity (23) in the thickness direction. A second piezoelectric region (R5) is a region where a third electrode (51), a fourth electrode (52) and the second piezoelectric layer (50) overlap the cavity (23) in the thickness direction. The second piezoelectric region (R5) is positioned in a region that surrounds the first piezoelectric region (R4) when viewed from the thickness direction.

Description

Piezoelectric transducer and piezoelectric module

The present disclosure 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.

A piezoelectric device (piezoelectric transducer) described in Patent Document 1 is exemplified as a conventional example. The piezoelectric device described in Patent Document 1 includes a substrate and an upper layer (piezoelectric portion) supported by the substrate. The upper layer includes a vibrating portion, and the vibrating portion includes a lower electrode, an intermediate electrode, and an upper electrode which are spaced apart from each other in the thickness direction. The upper layer is a first piezoelectric layer (first piezoelectric layer) disposed so as to be at least partially sandwiched by the lower electrode and the intermediate electrode, and the intermediate electrode and the upper layer disposed so as to overlap the first piezoelectric layer. And a second piezoelectric layer (second piezoelectric layer) disposed so as to be at least partially sandwiched by the electrodes.

International Publication No. 2016/175013

In the piezoelectric device described in Patent Document 1, there have been cases where it has been required to improve the characteristics in which the upper layer converts an alternating voltage into vibration or the characteristics in which vibration is converted into an alternating voltage.

An object of the present disclosure is to provide a piezoelectric transducer and a piezoelectric module having improved characteristics in which the first piezoelectric region and the second piezoelectric region of the piezoelectric portion convert alternating voltage into vibration or characteristics in which vibration is converted into alternating voltage. Do.

In order to solve the above problems, a piezoelectric transducer according to an aspect of the present disclosure includes a frame-shaped support portion, and a plate-shaped piezoelectric portion supported by the support portion and covering the cavity from one side in the thickness direction. Prepare. The frame-like support has a first surface, a second surface opposite to the first surface, and a cavity provided between and inward of the first surface and the second surface. The piezoelectric portion has a first electrode, a second electrode, a first piezoelectric layer sandwiched between the first electrode and the second electrode in the thickness direction, a third electrode, a fourth electrode, and a thickness. And a second piezoelectric layer sandwiched between the third electrode and the fourth electrode in a direction. The piezoelectric portion includes a first piezoelectric region in which the first electrode, the second electrode, and the first piezoelectric layer overlap the cavity in a direction perpendicular to the first surface, and a third electrode, a fourth electrode, and a second piezoelectric layer. And a second piezoelectric region overlapping the cavity in a direction perpendicular to the first surface. The first piezoelectric layer is not disposed at a position overlapping the second piezoelectric region when viewed from the direction perpendicular to the first surface.

A piezoelectric module according to an aspect of the present disclosure includes a plurality of the piezoelectric transducers.

In the piezoelectric transducer and the piezoelectric module according to each aspect of the present disclosure, it is possible to improve the characteristics in which the first piezoelectric region and the second piezoelectric region convert alternating voltage into vibration or the characteristics in converting vibration into alternating voltage.

FIG. 1 is a plan view of the piezoelectric transducer according to the first embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. FIG. 3 is a cross-sectional view taken along the line III-III of FIG. FIG. 4 is a layout diagram showing the same piezoelectric transducer as above and corresponding to the IV-IV cross section of FIG. FIG. 5 is an end view showing a method of manufacturing the piezoelectric transducer according to the first embodiment. FIG. 6 is an end view showing a method of manufacturing the above piezoelectric transducer. FIG. 7 is a schematic view of the piezoelectric module according to the first embodiment. FIG. 8 is a plan view of a piezoelectric transducer according to a second embodiment. FIG. 9 shows the same piezoelectric transducer as above, and is an end view taken along the line IX-IX of FIG. FIG. 10 shows the same piezoelectric transducer as above, and is an XX end view of FIG. FIG. 11 shows the same piezoelectric transducer as above, and is a layout diagram corresponding to the CC cross section of FIG. FIG. 12 is an end view showing a method of manufacturing a piezoelectric transducer according to the second embodiment. FIG. 13 is an end view showing a method of manufacturing the same piezoelectric transducer as above. FIG. 14 is a schematic view of a piezoelectric module according to the second embodiment.

First Embodiment
Hereinafter, the piezoelectric transducer and the piezoelectric module according to the first embodiment will be described with reference to the drawings. However, the embodiments described below are only some 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 drawing described in the following embodiments is a schematic drawing, and the ratio of the size and thickness of the component in the drawing does not necessarily reflect the actual size ratio.

(Configuration of piezoelectric transducer)
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 is square. The support portion 2 is formed of, for example, a semiconductor substrate. The support portion 2 is formed using 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 opposite to the first surface 21 in the thickness direction of the support portion 2. The cavity 23 is a hole penetrating in the thickness direction of the support portion 2. The cavity 23 is formed in a circular shape when viewed from the thickness direction of the support portion 2. 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. The thickness direction of the support portion 2 refers to a direction perpendicular to the first surface 21.

The piezoelectric portion 3 is formed in a plate shape. The piezoelectric portion 3 is formed in a square shape in 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 in the thickness direction of the piezoelectric portion 3 (the upper side in the drawing of FIG. 2).

In the piezoelectric transducer 1, hereinafter, the thickness direction of the piezoelectric portion 3 is defined as the Z-axis direction unless otherwise noted. The support portion 2 and the piezoelectric portion 3 are arranged 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, in the piezoelectric portion 3, the directions of two adjacent sides in plan view are respectively defined as an X-axis direction and a Y-axis direction. Therefore, the X axis direction, the Y axis direction, and the Z axis direction are orthogonal to one another.

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 on 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 body. 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 unit 3 has a structure in which the second electrode 42, the first piezoelectric layer 40, and the first electrode 41 are stacked in this order from the support 2 side (the negative side of the Z axis). 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 (the negative side of the Z axis).

The fourth electrode 52 is formed on the surface of the protective layer 6 opposite to the support 2 side. The fourth electrode 52 is formed on the entire surface of the protective layer 6 on the opposite side to the support 2 side. The fourth electrode 52 is made of, for example, platinum.

The second piezoelectric layer 50 is formed in a plate shape on the surface of the fourth electrode 52 opposite to the support 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 except for the vicinity of the left end in FIG. The second piezoelectric layer 50 is formed in a rectangular shape. The length of each side of the second piezoelectric layer 50 is larger than the diameter of the cavity 23. The second piezoelectric layer 50 overlaps the entire cavity 23 in the Z-axis direction.

The second electrode 42 and the third electrode 51 are formed on the surface of the second piezoelectric layer 50 opposite to the support 2 side. The second electrode 42 and the third electrode 51 are formed of, for example, platinum. The second electrode 42 and the third electrode 51 are located at the same position in the Z-axis direction. In short, the second electrode 42 and the third electrode 51 are located on the same plane orthogonal to the Z-axis direction.

FIG. 4 is a view of FIG. 2 as viewed from the IV-IV cross section. However, the insulating layer 7 is not shown in FIG. 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 in the Z-axis direction. The piezoelectric transducer 1 further includes a wire 421. The wiring 421 is formed in a linear shape, one end thereof is connected to the second electrode 42, and the other end is located in the vicinity of the peripheral edge of the piezoelectric portion 3. Here, “viewing from the Z-axis direction” means viewing through the piezoelectric transducer 1 from the Z-axis direction. Likewise, in the following description, “viewing from the Z-axis direction” means viewing through the piezoelectric transducer 1 from the Z-axis direction.

The third electrode 51 is formed in an arc shape. The third electrode 51 is formed to surround the second electrode 42. More specifically, the third electrode 51 is formed in an arc shape concentric with the second electrode 42. A wire 421 connected to the second electrode 42 is located between opposing ends 510 of the third electrode 51. The piezoelectric transducer 1 further includes a wire 511. The wiring 511 is formed in a linear shape, one end thereof is connected to the third electrode 51, and the other end is located in the vicinity of the peripheral edge of the piezoelectric portion 3.

As shown in FIG. 2, the surface on the piezoelectric portion 3 side of the frame-shaped support portion 2 is a first surface 21. An inner edge 211 of the first surface 21 on the cavity 23 side is circular. Of the third electrode 51, the outer edge (the outer edge 512: see FIG. 4) 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 512 of the third electrode 51 is formed in an arc shape slightly larger in diameter than the cavity 23. Further, of the third electrode 51, the inner edge (inner edge 515: 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, the third electrode 51 straddles the cavity 23 and the support 2 as viewed in the Z-axis direction.

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 2 side. The first piezoelectric layer 40 is formed on the entire surface of the second electrode 42 on the opposite side to the support 2 side. That is, the first piezoelectric layer 40 is formed in a circular shape.

The insulating layer 7 includes a portion of the surface of the fourth electrode 52, a portion of the surface of the second piezoelectric layer 50, a surface of the wiring 421 opposite to the support portion 2, and a portion of the third electrode 51. It is formed on the surface on the opposite side to the part 2 side and the surface on the side opposite to the support part 2 side of the wiring 511. That is, in the fourth electrode 52, the insulating layer 7 is formed on the surface opposite to the support 2 side and in the portion where the second piezoelectric layer 50 is not formed (near the left end in FIG. 2). Further, in the second piezoelectric layer 50, the insulating layer 7 is formed on the surface opposite to the support 2 side and in the portion where the second electrode 42, the third electrode 51, the wiring 421 and the wiring 511 are not formed. It is done.

The insulating layer 7 has a flat surface 70 on the side opposite to the support 2 side. The surface 70 of the insulating layer 7 is substantially flush with the surface 400 of the first piezoelectric layer 40. 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 each other, They are electrically isolated from each other. The insulating layer 7 reduces the possibility of the occurrence of electrical coupling between the conductors, such as between the first lead wire 413 and the third electrode 51 described later. The insulating layer 7 may be formed of, for example, a resin material.

The first electrode 41 is formed in a disk shape on the surface 400 of the first piezoelectric layer 40. More specifically, the first electrode 41 is formed in a disc shape having a diameter slightly smaller than that of the first piezoelectric layer 40. The first electrode 41 is formed in the vicinity of the center of the piezoelectric portion 3 as viewed in the Z-axis direction. The first electrode 41 is made of, for example, gold.

The second piezoelectric layer 50 is located at a position different from the first piezoelectric layer 40 in the Z-axis direction. More specifically, the second piezoelectric layer 50 is located on the negative side in the Z-axis direction with respect to the first piezoelectric layer 40. That is, the second piezoelectric layer 50 is located between the first piezoelectric layer 40 and the cavity 23 in the Z-axis direction.

The first piezoelectric layer 40 overlaps the second piezoelectric layer 50 in the Z-axis direction. More specifically, when viewed in the Z-axis direction, the first piezoelectric layer 40 is located inside the outer edge of the second piezoelectric layer 50. The first piezoelectric layer 40 has a smaller area than the second piezoelectric layer 50 when viewed in the Z-axis direction.

Below, an example of the dimension of each structure is given. The thickness of the support portion 2 is 200 μm. The thickness of the fourth electrode 52 is 0.4 μm. The thickness of the second piezoelectric layer 50 is 2 μm. The thickness of the second electrode 42 and the third electrode 51 is 0.4 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 is 0.2 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 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 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. 4).

The first piezoelectric region R4 is circular along the first electrode 41 (see FIG. 4), and the second piezoelectric region R5 is circular along the third electrode 51. When viewed in 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 third electrode 51 straddles the cavity 23 and the support 2 as viewed in the Z-axis direction. Therefore, as viewed in 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 512 of the third electrode 51 is along the inner edge 211 of the first surface 21 of the frame-like support 2. Therefore, as viewed in the Z-axis direction, a part of the second piezoelectric region R5 is along the inner edge 211 of the first surface 21.

The first piezoelectric region R4 and the second piezoelectric region R5 generate an AC voltage when receiving ultrasonic waves. In addition, the first piezoelectric region R4 and the second piezoelectric region R5 vibrate when an alternating voltage is applied to transmit ultrasonic waves. 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 made of, for example, aluminum nitride (AlN). Aluminum nitride is a material having a high Young's modulus and a low density as compared to lead zirconate titanate. Therefore, it is preferable that the second piezoelectric layer 50 be disposed so as to cover the entire cavity 23 from one side in the Z-axis direction and be used as part of the configuration of the vibrating film of the piezoelectric transducer 1. The vibrating film of the piezoelectric transducer 1 is configured to perform at least one of receiving and vibrating an ultrasonic wave or the like and transmitting an ultrasonic wave or the like by vibration.

Here, the first piezoelectric layer 40 is not disposed at a position overlapping the second piezoelectric region R5 when viewed in the thickness direction. Therefore, since there are few parts which inhibit the bending movement of the piezoelectric part 3, transmission / reception sensitivity is high.

The first piezoelectric layer 40 does not overlap the second piezoelectric layer 50 in the direction orthogonal to the thickness direction. The second piezoelectric layer 50 can be disposed so as to cover the entire cavity 23 from one side in the Z-axis direction, and can be used as a part of the configuration of the vibrating film of the piezoelectric transducer 1. . The vibrating film of the piezoelectric transducer 1 is configured to perform at least one of receiving and vibrating an ultrasonic wave or the like and transmitting an ultrasonic wave or the like by vibration. Further, since the second piezoelectric layer 50 can be used as part of the configuration of the vibrating film, the process of forming the vibrating film can be omitted, and the cost for manufacturing the element can be reduced.

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 dielectric constant ε _r of the first piezoelectric layer 40 is larger than the relative dielectric constant ε _r of the second piezoelectric layer 50. The relative dielectric constant ε _r of the first piezoelectric layer 40 is, for example, 1200. The relative dielectric constant 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, since the value (d ₃₁ / ε _r ) obtained by dividing the piezoelectric constant d ₃₁ by the relative dielectric constant ε _r is larger than d ₃₁ / ε _r of the first piezoelectric layer 40 The region R5 has better characteristics for converting vibration into an alternating voltage than the first piezoelectric region R4.

As shown in FIG. 1, the piezoelectric transducer 1 has a plurality of (four in FIG. 1) lead wires (first lead wire 413, second lead wire 423, third lead wire 513, and the like) on the surface 70 of the insulating layer 7. A fourth lead 523) and a plurality of (four in FIG. 1) pads (a first pad 414, a second pad 424, a third pad 514 and a fourth pad 524) are further provided. Each lead wire and each pad are formed as a conductor layer.

The plurality of pads are formed at four corners of the surface 70 of the insulating layer 7. Each pad is formed in a rectangular shape. Each pad may be formed in a square shape.

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

The second lead wire 423 electrically connects the wire 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 lead wire 423 and the wire 421 are formed by falling along the inner wall of the opening 72 toward the wire 421 and overlapping a part of the wire 421 in the Z-axis direction. Is connected.

The third lead wire 513 electrically connects the wiring 511 connected to the third electrode 51 and the third pad 514. The insulating layer 7 has an opening 73. One end of the wiring 511 is located at the back of the opening 73 (lower in FIG. 3). The third lead wire 513 falls along the inner wall of the opening 73 toward the wire 511 and is formed to overlap a part of the wire 511 in the Z-axis direction. Is connected.

The fourth lead wire 523 electrically connects the fourth electrode 52 and the fourth pad 524. As shown in FIGS. 1 and 2, the insulating layer 7 has an opening 74 in a region where the second piezoelectric layer 50 is not formed (in the vicinity of the left end in FIG. 1) as viewed in the Z-axis direction. The fourth lead-out wire 523 is formed to fall along the inner wall of the opening 74 toward the fourth electrode 52 and to overlap with a portion of the fourth electrode 52 in the Z-axis direction. And the fourth electrode 52 are connected.

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

First, as shown in A of FIG. 5, the 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 which is the base of the support portion 2 of the piezoelectric transducer 1. In addition, 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 200. However, in FIG. 5A, the illustration of the protective layer formed on the second surface 202 is omitted. The substrate 200 is a disk-shaped wafer.

Next, as shown in FIG. 5B, the fourth electrode 52 is formed on the entire surface 60 of the protective layer 6. The fourth electrode 52 is formed, for example, by sputtering.

Next, as shown in FIG. 5C, the first layer 81 of aluminum nitride is formed on the entire surface 520 of the fourth electrode 52. The first layer 81 is a layer to be the second piezoelectric layer 50 later. The first layer 81 is formed, for example, by sputtering.

Next, as shown in D of FIG. 5, a second layer 82 of platinum is formed on the surface 810 of the first layer 81 opposite to the substrate 200 side. The second layer 82 is a layer to be the second electrode 42, the third electrode 51, the wiring 421, and the wiring 511 later (see FIG. 4). The second layer 82 is formed, for example, by sputtering.

Next, as shown in E of FIG. 5, a third layer 83 of lead zirconate titanate is formed on the surface 820 of the second layer 82 opposite to the substrate 200 side. The third layer 83 is a layer to be the first piezoelectric layer 40 later. The third layer 83 is formed, for example, by sputtering.

Next, as shown in FIG. 5F, the third layer 83 is patterned by photolithography and etching. By this process, the first piezoelectric layer 40 formed of a part of the third layer 83 is formed.

Next, as shown in FIG. 6A, the second layer 82 is patterned by photolithography and etching. By this process, the second electrode 42, the third electrode 51, the wiring 421 (see FIG. 4), and the wiring 511 (see FIG. 4), which are part of the second layer 82, are formed.

Next, as shown in FIG. 6B, the first layer 81 is patterned by photolithography and etching. That is, a portion of the first layer 81 near the left end in A of FIG. 6 is removed. In this step, the second piezoelectric layer 50 formed of a part of the first layer 81 is formed in the region of the surface 520 of the fourth electrode 52 except the vicinity of the left end in A of FIG. That is, the exposed surface 521 on which the second piezoelectric layer 50 is not formed is formed on the surface 520.

Next, as shown in C of FIG. 6, the insulating layer 7 is the exposed surface 521 on the fourth electrode 52 and the surface of the second piezoelectric layer 50, and the second electrode 42, the third electrode 51, and the wiring 421. 4 (see FIG. 4) and the wiring 511 (see FIG. 4) are not formed, the surface of the wiring 421, the surface of the third electrode 51, and the surface of the wiring 511. 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 then polished or etched back from the surface to form the surface 400 of the first piezoelectric layer 40 Be made flush.

Next, as shown in D of FIG. 6, the openings 72 (see FIG. 3), 73 (see FIG. 3), and 74 are formed in the insulating layer 7. The

openings

72, 73, 74 are formed, for example, using photolithography technology and etching technology.

Next, as shown in E of FIG. 6, the first electrode 41 is formed on the surface 400 of the first piezoelectric layer 40, and the first lead wire 413, the second lead wire 423, the third on the surface 70 of the insulating layer 7. The leads 513, the fourth lead 523, the first pad 414, the second pad 424, the third pad 514, and the fourth pad 524 are formed (see FIG. 1). The first electrode 41, each lead wire, and each pad are formed of gold as a material by a vapor deposition method or a sputtering method using a metal mask. In addition, the first electrode 41, the leads, and the pads may be formed using photolithography technology and etching technology. In addition, the first electrode 41, the leads, and the pads may be formed using a photolithography technique, a thin film forming technique, and a lift-off method.

Next, as shown to F of FIG. 6, the cavity 23 is formed in the base material 200. As shown to FIG. Thereby, the support part 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 E of FIG. 6) is patterned using photolithography technology and etching technology. Furthermore, the cavity 23 is formed by etching the central portion of the substrate 200 from the second surface 202 using the patterned remaining protective layer 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 substrate 200 is diced. That is, the substrate 200 is divided into areas occupied by one piezoelectric transducer 1.

Thus, the piezoelectric transducer 1 is manufactured.

(Configuration of piezoelectric module)
As shown in FIG. 7, the piezoelectric module 10 includes a plurality (16 in FIG. 7) of piezoelectric transducers 1. The plurality of piezoelectric transducers 1 are mounted on a substrate. The plurality of piezoelectric transducers 1 are arranged in a two-dimensional array of four vertical rows and four horizontal rows. 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 connected to the external power supply 15 in the first switching unit 11.

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 switch 12. The four piezoelectric transducers 1 arranged in a vertical line share one switch connected to the ground in the second switching unit 12.

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 line share one switch connected to the processing unit 13 in the second switching unit 12.

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 connected to the ground in the first switching unit 11.

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 piezoelectric transducer 1. 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 supply 15, an alternating voltage is applied to the first piezoelectric layer 40 from the external power supply 15. When connected to the processing unit 13, the piezoelectric transducer 1 outputs an alternating voltage generated in the second piezoelectric region R <b> 5 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 central processing unit (CPU) and an AC-DC converter. The AC-DC converter converts an AC voltage input from the piezoelectric transducer 1 into a DC voltage, and outputs the DC voltage to the processor. The processor is electrically connected to the first switching unit 11 and controls opening and closing of the plurality of switches of the first switching unit 11. Furthermore, the processor controls the opening and closing of the plurality of switches of the second switching unit 12.

(Operation)
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 from the external power supply 15 to the first piezoelectric layer 40 of the piezoelectric transducer 1, the first piezoelectric region R4 transmits an ultrasonic wave as the first piezoelectric layer 40 vibrates in the Z-axis direction. To wave. The first electrode 41 and the second electrode 42 are electrodes for applying an alternating 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 to connect 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 alternating voltage. . The third electrode 51 and the fourth electrode 52 are electrodes for extracting AC voltage generated in the second piezoelectric region R5. The third electrode 51 and the fourth electrode 52 take out an alternating voltage generated by the second piezoelectric region R <b> 5 receiving an ultrasonic wave, and output the alternating voltage to the processing unit 13.

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

The piezoelectric module 10 is used, for example, as an ultrasonic sensor mounted on a car and measuring a distance between the car and an object around the car. The piezoelectric module 10 transmits and receives ultrasonic waves. The processing unit 13 measures the time from when the piezoelectric module 10 transmits an ultrasonic wave until the ultrasonic wave is reflected by the object and returns, so that the processing unit 13 measures the time 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 used as a sensor for detecting a human fingerprint. In the piezoelectric module 10, the plurality of piezoelectric transducers 1 are arranged such that the distance between the centers of the adjacent piezoelectric transducers 1 is smaller than the distance between the unevenness of the fingerprints. The plurality of piezoelectric transducers 1 transmit ultrasonic waves and receive ultrasonic waves reflected by human fingers. Since the acoustic impedance is different between the concave and the convex portions of the fingerprint, the processing unit 13 can detect the fingerprint based on the intensity of the ultrasonic wave received by the plurality of piezoelectric transducers 1.

(effect)
If, in the piezoelectric transducer 1, the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the Z-axis direction, 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. In addition, when the second piezoelectric layer 50 vibrates, the second piezoelectric layer 50 may be distorted, which may distort the first piezoelectric layer 40. In particular, when the first piezoelectric layer 40 tends to contract in the direction orthogonal to the Z axis and the second piezoelectric layer 50 tries to extend in the direction orthogonal to the Z axis, the distortion of the first piezoelectric layer 40 and the second piezoelectric layer The strain of the layer 50 may act to cancel out.

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, as compared with the case where the first piezoelectric region R4 and the second piezoelectric region R5 overlap in the Z-axis direction, the extent to which the strain of the first piezoelectric layer 40 and the strain of the second piezoelectric layer 50 affect each other Can be reduced. Thereby, it is possible to improve the characteristics of the first piezoelectric region R4 and the second piezoelectric region R5 (the characteristics of converting an alternating voltage into vibrations or the characteristics of converting vibrations into an alternating voltage).

Also, if the first piezoelectric region R4 is disposed 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, a direction in which the portion of the first piezoelectric region R4 overlapping the region on the center side 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 direction in which the overlapping portion is distorted is opposite to that of the first piezoelectric region R4, the characteristics of the first piezoelectric region R4 (for example, the efficiency of converting AC voltage into vibration) may be reduced.

Similarly, if the second piezoelectric region R5 is disposed so as to overlap the entire area of the cavity 23 in the Z-axis direction, the following problem may occur. That is, when the second piezoelectric layer 50 vibrates, a direction in which the portion of the second piezoelectric region R5 overlapping the region on the center side 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 portion is opposite to the direction of distortion, the characteristics (for example, wave receiving sensitivity) of the second piezoelectric region R5 may be reduced.

Therefore, by arranging the first piezoelectric region R4 at a position overlapping the region on the center side 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 strain in the second piezoelectric region R5 can be aligned. Thereby, the characteristics of the first piezoelectric region R4 and the characteristics of the second piezoelectric region R5 are improved.

Also, 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 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, the electrical interference between the second electrode 42 and the third electrode 51 is suppressed. For example, by suppressing crosstalk (an example of electrical interference) between the second electrode 42 and the third electrode 51, in the piezoelectric transducer 1, the transmission intensity and the reception sensitivity are improved, and Noise and noise in the received signal are reduced. Further, the reduction of the noise of the transmission signal and the noise of the reception signal improves the S / N ratio of the transmission signal and the S / N ratio of the reception signal.

Further, since the second piezoelectric region R5 of the present embodiment is located in the 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. In some cases, the bending rigidity of the second piezoelectric layer 50 can be reduced as compared with the case where For example, when the insulating layer 7 is not provided in the piezoelectric portion 3, when the insulating layer 7 is thinly formed in the Z-axis direction, or when the insulating layer 7 is formed of a soft material, etc. The bending rigidity of the second piezoelectric layer 50 can be reduced as compared with the case where the second piezoelectric region R5 overlaps the Z-axis direction. Thereby, the characteristic (for example, receiving sensitivity) of the second piezoelectric region R5 can be improved.

(Modification of the first embodiment)
Hereinafter, modified examples of the first embodiment will be listed. The following modifications may be implemented in combination as appropriate.

The second piezoelectric layer 50 may be located on the positive side in the Z-axis direction with respect to the first piezoelectric layer 40. For example, the second electrode 42, the first piezoelectric layer 40, and the first electrode 41 are stacked in this order on the protective layer 6 to form a second layer on the upper layer (positive side in the Z-axis direction) than the first electrode 41. The piezoelectric layer 50 may be stacked.

That is, the first piezoelectric layer 40 may be located at a position different from the second piezoelectric layer 50 in the thickness direction (Z-axis direction) of the piezoelectric portion 3. That the first piezoelectric layer 40 is located at a position different from the second piezoelectric layer 50 in the thickness direction of the piezoelectric portion 3 means that part of the first piezoelectric layer 40 or the first piezoelectric layer 40 is viewed from the direction orthogonal to the thickness direction of the piezoelectric portion 3 It means that all and part or all of the second piezoelectric layer 50 do not overlap.

Also, the first piezoelectric layer 40 may not overlap with the second piezoelectric layer 50 in the Z-axis direction. That is, in the second piezoelectric layer 50, a portion overlapping with the first piezoelectric layer 40 in the Z-axis direction may be hollow, and a layer having electrical insulation like the insulating layer 7 is formed in the portion. It may be

Further, although the second piezoelectric region R5 of the embodiment substantially surrounds the first piezoelectric region R4 when viewed from the Z-axis direction, 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 in at least a part of the region surrounding the first piezoelectric region R4 when viewed from the Z-axis direction. In other words, when viewed in the thickness direction (Z-axis direction), the second piezoelectric region R5 may be disposed along a part of the first piezoelectric region R4. Alternatively, when viewed in the thickness direction (Z-axis direction), at least a portion of the first piezoelectric region R4 is located on the center side of the cavity 23, and at least a portion of the second piezoelectric region R5 is located on the outer periphery of the cavity Just do it.

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

Moreover, the support part 2 of embodiment is formed in the frame shape which followed the circumferential direction. In the support portion 2, the frame shape is not limited to the shape continuous in the circumferential direction, and a part of the circumferential direction may be discontinuous. In the support portion, the frame shape may be a shape including the following two parts in the structure which is annular as 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 in between as 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 may be divided into a plurality of members, and the piezoelectric portion 3 may be spanned by the plurality of members. Each of the plurality of members may be formed in, for example, a rectangular parallelepiped shape or a cube shape.

Further, as viewed in the Z-axis direction, the outer edge 512 of the third electrode 51 may overlap a part of the inner edge 211 of the first surface 21 of the frame-like support 2.

Further, the method of 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 deposition (CVD) method such as MOCVD (metal organic chemical vapor deposition) method, or a sol-gel method.

In addition, the second electrode 42, the third electrode 51, the first piezoelectric layer 40, the second piezoelectric layer 50, etc. are formed using a metal mask or the like instead of being formed by photolithography and etching techniques. Alternatively, they may be formed by sputtering.

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). In addition, the first piezoelectric layer 40 may be formed of aluminum nitride, and the second piezoelectric layer 50 may be formed of lead zirconate titanate. Further, as a 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 the ultrasonic waves. For example, the first piezoelectric region R4 and the second piezoelectric region R5 may transmit or receive sound waves in the audible range.

Alternatively, one of the first piezoelectric region R4 and the second piezoelectric region R5 may be used for ultrasonic wave transmission and the other may be used for ultrasonic wave reception, or both for ultrasonic wave transmission. Or both may be used for ultrasonic wave reception. That is, the first electrode 41 and the second electrode 42 are electrodes for extracting the alternating voltage generated in the first piezoelectric region R4, and the third electrode 51 and the fourth electrode 52 are an alternating current 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 alternating voltage to the first piezoelectric layer 40, and the third electrode 51 and the fourth electrode 52 are alternating current 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 extracting alternating voltage generated in the first piezoelectric region R4, and the third electrode 51 and the fourth electrode 52 are alternating current generated in the second piezoelectric region R5. It may be an electrode for taking out a voltage.

Moreover, the application of the piezoelectric transducer 1 is not limited to the application which transmits or receives a sound wave. For example, the application of the piezoelectric transducer 1 may be an actuator.

In addition, in order to electrically connect the second electrode 42 and the second pad 424, the second lead wire 423 does not fall along the inner wall of the opening 72, and the inner surface of the opening 72 is Z The second lead wire 423 may be formed to be inclined with respect to the axial direction, and the second lead wire 423 may fall along the inclined inner surface of the opening 71. That is, the inner surface of the opening 72 is formed to be inclined so as to connect one end of the wiring 421 to the second pad 424, and the wiring 421 is formed by the second lead wire 423 formed along the inclined inner surface of the opening 72. And the second pad 424 may be electrically connected. Similarly, the third lead 513 and the fourth lead 523 may be formed along the inclined inner surface of the opening.

In addition, the second electrode 42 and the third electrode 51 may be electrically connected. For example, an electrode in which the second electrode 42 and the third electrode 51 are integrated may be formed on the entire surface of the second piezoelectric layer 50 on the opposite side to the support 2 side. When the second electrode 42 and the third electrode 51 are electrically connected, the timing at which the current flows to the first electrode 41 and the timing at which the current flows to the fourth electrode 52 differ from each other. Mutual interference between the piezoelectric layer 40 and the second piezoelectric layer 50 may be suppressed.

Further, the number of piezoelectric layers provided 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 have three or more piezoelectric layers. For example, as the piezoelectric layer, two piezoelectric transducers 1 are disposed so as to surround the first piezoelectric layer 40 on both sides of the first piezoelectric layer 40 having the same shape as that of the embodiment and the first piezoelectric layer 40 in the X axis direction. An arc-shaped piezoelectric layer may be provided.

Also, even if a base having a recess formed on one surface of a silicon substrate and having an insulating film formed on one surface so as to close the opening of the recess is used as a base on which the support portion 2 is formed. Good. By forming the piezoelectric portion 3 on the insulating film of the base material, and then etching the silicon substrate of the base material 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.

For example, in the embodiment of FIG. 2, the second piezoelectric layer 50 can function as a vibrating film, which is advantageous for miniaturization without the need for a vibrating film. A vibrating membrane formed of Si) or the like may be separately disposed. Since it is possible to adjust the mechanical constant of the movable part (the part that overlaps with the cavity when viewed from the thickness direction and vibrates during transmission and reception) to a value suitable for use conditions, transmission and The effect of being able to improve the efficiency of a received wave can be acquired.

(Summary)
As described above, the piezoelectric transducer 1 according to the first aspect includes the support portion 2 and the piezoelectric portion 3. The support portion 2 is in the form of a frame 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. The first piezoelectric layer 40 is located at a position different from the second piezoelectric layer 50 in 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 in the thickness direction.

According to the above configuration, the second piezoelectric region R5 is located in the 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 distortion of the first piezoelectric layer 40 of the first piezoelectric region R4 causes the second piezoelectric of the second piezoelectric region R5 to The degree to which the layer 50 is distorted can be reduced. Moreover, the extent to which the first piezoelectric layer 40 is distorted due to the distortion of the second piezoelectric layer 50 can be reduced. As a result, it is possible to improve the characteristics in which the first piezoelectric region R4 and the second piezoelectric region R5 convert an alternating voltage into vibration or the characteristics in which vibration is converted into an alternating voltage.

Further, the first piezoelectric layer 40 is not disposed at a position overlapping the second piezoelectric region R5 when viewed in the thickness direction. Therefore, since there are few parts which inhibit the bending movement of the piezoelectric part 3, transmission / reception sensitivity is high.

In the piezoelectric transducer 1 according to the second aspect, in the first aspect, the first electrode 41 and the second electrode 42 are electrodes for applying an alternating voltage to the first piezoelectric layer 40. The third electrode 51 and the fourth electrode 52 are electrodes for extracting 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 alternating voltage to the first piezoelectric layer 40. That is, the first piezoelectric region R4 converts alternating voltage into vibration. The third electrode 51 and the fourth electrode 52 are electrodes for extracting alternating-current voltage generated in the second piezoelectric region R5. That is, the second piezoelectric region R5 converts the vibration into an alternating voltage. When a force is applied to the piezoelectric portion 3 in the thickness direction (Z-axis direction) by the piezoelectric portion 3 receiving a sound wave or the like, a region surrounding the first piezoelectric region R4 more than the first piezoelectric region R4 There is a high possibility that stress may concentrate on the second piezoelectric region R5 located on the Therefore, in the piezoelectric transducer 1 described above, it is possible to improve the characteristics of the second piezoelectric region R5 for converting vibration into an alternating voltage.

Moreover, in the piezoelectric transducer 1 according to the third aspect, in the first aspect, the first electrode 41 and the second electrode 42 are electrodes for extracting alternating-current voltage generated in the first piezoelectric region R4. The third electrode 51 and the fourth electrode 52 are electrodes for applying an alternating voltage to the second piezoelectric layer 50.

According to the above configuration, the first electrode 41 and the second electrode 42 are electrodes for extracting the AC voltage generated in the first piezoelectric region R4. That is, the first piezoelectric region R4 converts the vibration into an alternating voltage. The third electrode 51 and the fourth electrode 52 are electrodes for applying an alternating voltage to the second piezoelectric layer 50. That is, the second piezoelectric region R5 converts an alternating voltage into vibration. When a force is applied to the piezoelectric portion 3 in the thickness direction (Z-axis direction) by the piezoelectric portion 3 receiving a sound wave or the like, a region surrounding the first piezoelectric region R4 more than the first piezoelectric region R4 There is a high possibility that stress may concentrate on the second piezoelectric region R5 located on the Therefore, in the piezoelectric transducer 1 described above, it is possible to improve the characteristics of the second piezoelectric region R5 for converting an alternating voltage into vibration.

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

According to the above configuration, an alternating 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 alternating 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 alternating voltage into vibration, it is possible to improve the characteristics in which the first piezoelectric region R4 and the second piezoelectric region R5 convert alternating voltage into vibration.

Moreover, in the piezoelectric transducer 1 according to the fifth aspect, in the first aspect, the first electrode 41 and the second electrode 42 are electrodes for extracting alternating-current voltage generated in the first piezoelectric region R4. The third electrode 51 and the fourth electrode 52 are electrodes for extracting AC voltage generated in the second piezoelectric region R5.

According to the above configuration, an alternating voltage is extracted from the first piezoelectric region R4, and an alternating voltage is extracted from the second piezoelectric region R5. That is, the piezoelectric transducer 1 functions as a device for converting the vibration into an alternating 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 alternating voltage, it is possible to improve the characteristics in which the first piezoelectric region R4 and the second piezoelectric region R5 convert vibration into an alternating voltage.

In the piezoelectric transducer 1 according to the sixth aspect, in the second 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, it is possible to improve the characteristics of the first piezoelectric region R4 for converting an alternating voltage into vibration and the characteristics of the second piezoelectric region R5 for converting vibration into an alternating voltage.

In the piezoelectric transducer 1 according to the seventh aspect, in any of the first to sixth aspects, the first electrode 41, the second electrode 42, the third electrode 51, and the fourth electrode 52 are electrically insulated from each other It is done.

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

In the piezoelectric transducer 1 according to the eighth aspect, in any of the first to seventh aspects, the second piezoelectric layer 50 is between the first piezoelectric layer 40 and the cavity 23 in the thickness direction (Z-axis direction). It is located in

According to the above configuration, when a force is applied to the piezoelectric portion 3 in the thickness direction (Z-axis direction) by the piezoelectric portion 3 receiving a sound wave or the like, the piezoelectric portion 3 is supported more than the first piezoelectric layer 40 There is a high possibility that stress may concentrate on the second piezoelectric layer 50 closer to the portion 2. Therefore, in the piezoelectric transducer 1 described above, it is possible to improve the characteristics in which the second piezoelectric region R5 converts an alternating voltage into vibration or the characteristics in which vibration is converted into an alternating voltage.

In the piezoelectric transducer 1 according to the ninth aspect, in any of the first to eighth aspects, the second piezoelectric layer 50 overlaps the entire cavity 23 in the thickness direction (Z-axis direction).

According to the above-described configuration, the portion of the second piezoelectric layer 50 located inside the cavity 23 as viewed from the thickness direction (Z-axis direction) of the second piezoelectric layer 50 than when the second piezoelectric layer 50 does not entirely overlap the cavity 23. The area can be increased.

In the piezoelectric transducer 1 according to the tenth aspect, in any of the first to ninth aspects, at least a part of the second piezoelectric region R5 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) by the piezoelectric portion 3 receiving a sound wave or the like, stress is likely to be concentrated in the vicinity of the inner edge 211 of the support portion 2 . Therefore, in the piezoelectric transducer 1 described above, it is possible to improve the characteristics of the second piezoelectric region R5 (characteristics of converting vibration to alternating voltage or characteristics of converting alternating voltage to vibration).

In the piezoelectric transducer 1 according to the eleventh aspect, in any of the first to tenth aspects, when viewed from the thickness direction (Z-axis direction), the second piezoelectric region R5 Straddle.

The piezoelectric module 10 according to the twelfth aspect includes a plurality of piezoelectric transducers 1 according to any of the first to eleventh aspects.

According to the above configuration, the second piezoelectric region R5 of the piezoelectric transducer 1 is located in the 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 distortion of the first piezoelectric layer 40 of the first piezoelectric region R4 causes the second piezoelectric of the second piezoelectric region R5 to The degree to which the layer 50 is distorted can be reduced. Moreover, the extent to which the first piezoelectric layer 40 is distorted due to the distortion of the second piezoelectric layer 50 can be reduced. As a result, it is possible to improve the characteristics in which the first piezoelectric region R4 and the second piezoelectric region R5 convert an alternating voltage into vibration or the characteristics in which vibration is converted into an alternating voltage. The piezoelectric module 10 also includes a plurality of piezoelectric transducers 1. Thereby, compared with the case where only one piezoelectric transducer 1 is used, the output by converting the AC voltage into the vibration by the first piezoelectric region R4 and the second piezoelectric region R5 can be made larger, or the vibration It is possible to further increase the sensitivity for converting a.

The configurations according to the second to eleventh aspects are not essential to the piezoelectric transducer 1 and can be omitted as appropriate.

Second Embodiment
Hereinafter, a piezoelectric transducer and a piezoelectric module according to a second embodiment will be described using the drawings. However, the embodiments described below are only some 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 drawing described in the following embodiments is a schematic drawing, and the ratio of the size and thickness of the component in the drawing does not necessarily reflect the actual size ratio.

(Configuration of piezoelectric transducer)
As shown in FIGS. 8 to 11, 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 is square. The support portion 2 is formed of, for example, a semiconductor substrate. The support portion 2 is formed using silicon as a main material. As shown in FIGS. 9 and 10, the support portion 2 has a first surface 21 and a second surface 22 opposite to the first surface 21 in the thickness direction of the support portion 2. The cavity 23 is a hole penetrating in the thickness direction of the support portion 2. The cavity 23 is formed in a circular shape when viewed from the thickness direction of the support portion 2. 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. The thickness direction of the support portion 2 refers to a direction perpendicular to the first surface 21.

The piezoelectric portion 3 is formed in a plate shape. The piezoelectric portion 3 is formed in a square shape in 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 in the thickness direction of the piezoelectric portion 3 (the upper side in the drawing of FIG. 9).

The second electrode 42 and the fourth electrode 52 are formed on the surface 60 of the protective layer 6 on the opposite side to the support 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. 11 is a view of FIG. 9 as viewed from the XI-XI cross section. However, the insulating layer 7 is not shown in FIG. 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 in the Z-axis direction. The piezoelectric transducer 1 further includes a wire 421. The wiring 421 is formed in a linear shape, one end thereof is connected to the second electrode 42, and the other end is located in the vicinity of the peripheral edge of the piezoelectric portion 3. Here, “viewing from the Z-axis direction” means viewing through the piezoelectric transducer 1 from the Z-axis direction. Likewise, in the following description, “viewing from the Z-axis direction” means viewing through the piezoelectric transducer 1 from the Z-axis direction.

The fourth electrode 52 is formed in an arc shape. The fourth electrode 52 is formed 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 wire 421 connected to the second electrode 42 is located between opposing ends 520 of the fourth electrode 52. The piezoelectric transducer 1 further includes a wire 521. The wiring 521 is formed in a linear shape, one end thereof is connected to the fourth electrode 52, and the other end is located in the vicinity of the peripheral edge of the piezoelectric portion 3.

As shown in FIG. 9, the surface on the piezoelectric portion 3 side in the frame-shaped support portion 2 is a first surface 21. An inner edge 211 of the first surface 21 on the cavity 23 side is circular. Of the fourth electrode 52, the outer edge (the outer edge 522: see FIG. 11) 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 slightly larger in diameter than the cavity 23. Further, of the fourth electrodes 52, the inner edge (inner edge 525: see FIG. 11) in the radial direction is formed in an arc shape having a diameter smaller than that of the cavity 23. That is, when viewed in the Z-axis direction, the fourth electrode 52 straddles the cavity 23 and the support portion 2.

As shown in FIGS. 9 and 10, the first piezoelectric layer 40 is formed in a plate shape on the surface of the second electrode 42 on the opposite side to the support 2 side. The first piezoelectric layer 40 is formed on the entire surface of the second electrode 42 on the opposite side to the support 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 2 side. The second piezoelectric layer 50 is formed on the entire surface of the fourth electrode 52 on the opposite side to the support 2 side. That is, the second piezoelectric layer 50 is formed in an arc shape. The second piezoelectric layer 50 is formed 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 the direction orthogonal to the Z-axis direction. More specifically, both ends of the second piezoelectric layer 50 coincide with both ends of the first piezoelectric layer 40 in the Z-axis direction.

The first electrode 41 is formed on the surface 400 of the first piezoelectric layer 40 on the opposite side to the support 2 side. The first electrode 41 is formed on 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 slightly smaller in diameter than the first piezoelectric layer 40. The first electrode 41 is formed in the vicinity of the center of the piezoelectric portion 3 as viewed in 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 opposite to the support 2 side. The third electrode 51 is formed on 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 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 lead wire 413, which will be described later, connected to the first electrode 41 is located between opposing ends of the third electrode 51 (see FIG. 8). 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 on the side opposite to the support portion 2 and in the portion 61 where the second electrode 42, the fourth electrode 52, the wiring 421 and the wiring 521 are not formed. There is. The insulating layer 7 has a flat surface 70 on the side opposite to the support 2 side. 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. 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 each other, They are electrically isolated from each other. The insulating layer 7 reduces the possibility of the occurrence of electrical coupling between the conductors, such as between the first lead wire 413 and the wiring 421 described later. The insulating layer 7 may be formed of, for example, a resin material.

Below, an example of the dimension of each structure is given. 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 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 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. 8).

The first piezoelectric region R4 is circular along the first electrode 41 (see FIG. 8), and the second piezoelectric region R5 is circular along the third electrode 51. As viewed from the Z-axis direction, the second piezoelectric region R5 coincides with the region where the third electrode 51 is located (see FIG. 9).

As described above, the fourth electrode 52 straddles the cavity 23 and the support 2 as viewed in the Z-axis direction. Further, the third electrode 51 and the second piezoelectric layer 50 also straddle the cavity 23 and the support portion 2 when viewed from the Z-axis direction. Therefore, as viewed in 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. 11) of the fourth electrode 52 is along the inner edge 211 of the first surface 21 of the frame-like support 2. Therefore, as viewed in the Z-axis direction, a part of the second piezoelectric region R5 is along the inner edge 211 of the first surface 21. Further, of the third electrode 51, the outer edge 512 in the radial direction (see FIG. 8) and the outer edge in the radial direction of the second piezoelectric layer 50 are also along the inner edge 211 of the first surface 21. There is.

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 made of, for example, aluminum nitride (AlN). Aluminum nitride is a material having a high Young's modulus and a low density as compared to lead zirconate titanate.

The first piezoelectric layer 40 is not disposed at a position overlapping the second piezoelectric region R5 when viewed in the thickness direction. Therefore, since there are few parts which inhibit the bending movement of the piezoelectric part 3, transmission / reception sensitivity is high.

The material of the first piezoelectric layer 40 is different from the material of the second piezoelectric layer 50. Therefore, it is possible to obtain an effect that the first piezoelectric region R4 and the second piezoelectric region R5 can have different functions of transmission and reception.

As shown in FIG. 8, the piezoelectric transducer 1 has a plurality of (three in FIG. 8) lead wires (a first lead wire 413, a second lead wire 423, and a fourth lead wire 523) on the surface 70 of the insulating layer 7. And a plurality of (four in FIG. 8) pads (first pad 414, second pad 424, third pad 514 and fourth pad 524). The piezoelectric transducer 1 may further include a third lead. Each lead wire and each pad are formed as a conductor layer.

The plurality of pads are formed near the periphery 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 periphery 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 periphery 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. Each pad may be formed in a square shape.

The second lead wire 423 electrically connects the wire 421 connected to the second electrode 42 and the second pad 424. As shown in FIGS. 8 and 10, 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. 10). The second lead wire 423 and the wire 421 are formed by falling along the inner wall of the opening 72 toward the wire 421 and overlapping a part of the wire 421 in the Z-axis direction. 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 through the third lead formed on the surface 70 of the insulating layer 7.

The fourth lead wire 523 electrically connects the wire 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. 10). The fourth lead-out wire 523 falls along the inner wall of the opening 74 toward the wire 521 and is formed so as to overlap with a part of the wire 521 in the Z-axis direction. Is connected.

(Production method)
Next, an example of a method of manufacturing the piezoelectric transducer 1 will be described with reference to FIGS. 12 (A to F) and 13 (A to D).

First, as shown in A of FIG. 12, the 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 which is the base of the support portion 2 of the piezoelectric transducer 1. In addition, 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 200. However, in FIG. 12A, the illustration of the protective layer formed on the second surface 202 is omitted. The substrate 200 is a disk-shaped wafer.

Next, as shown in B of FIG. 12, a first layer 91 of platinum is formed on the entire surface 60 of the protective layer 6. The first layer 91 is a layer to be the second electrode 42, the fourth electrode 52, the wiring 421, and the wiring 521 later (see FIG. 11). The first layer 91 is formed, for example, by sputtering.

Next, as shown in C of FIG. 12, the second layer 92 of lead zirconate titanate is formed on the entire surface 910 of the first layer 91. The second layer 92 is a layer to be the first piezoelectric layer 40 later. The second layer 92 is formed, for example, by sputtering.

Next, as shown in FIG. 12D, the second layer 92 is patterned by photolithography and etching. By this process, the first piezoelectric layer 40 which is a part of the second layer 92 is formed.

Next, as shown in FIG. 12E, the first layer 91 is patterned by photolithography and etching. By this process, the second electrode 42, the fourth electrode 52, the wiring 421 (see FIG. 11), and the wiring 521 (see FIG. 11), which are part of the first layer 91, are formed.

Next, as shown in F of FIG. 12, the second electrode 42, the fourth electrode 52, the wiring 421 (see FIG. 11) and the wiring 521 (see FIG. 11) are formed on the surface 60 of the protective layer 6. A third layer 93 of aluminum nitride is formed on the non-portion 61 and on the surfaces of the first piezoelectric layer 40, the fourth electrode 52, the wiring 421, and the wiring 521. The third layer 93 is a layer to be the second piezoelectric layer 50 later. The third layer 93 is formed by sputtering, for example. Furthermore, the first piezoelectric layer 40 is exposed by polishing or etching the third layer 93.

Next, as shown in FIG. 13A, the third layer 93 is patterned by photolithography and etching. By this process, the second piezoelectric layer 50 which is a part of the third layer 93 is formed.

Next, as shown to B of FIG. 13, the insulating layer 7 is formed in the part 61 in which the electrode and wiring are not formed among the surfaces 60 of the protective layer 6. As shown in FIG. 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 polished or etched back from the surface to form a first piezoelectric layer. It is flush with the surface 400 of the layer 40 and the surface 500 of the second piezoelectric layer 50.

Next, the openings 72 (see FIG. 10) and 74 (see FIG. 10) are formed in the insulating layer 7. The

openings

72 and 74 are formed, for example, using photolithography technology and etching technology.

Next, as shown in C of FIG. 13, the first electrode 41 is formed on the surface 400 of the first piezoelectric layer 40. The third electrode 51 is formed on the surface 500 of the second piezoelectric layer 50. The first lead wire 413, the second lead wire 423, the fourth lead wire 523, the first pad 414, the second pad 424, the third pad 514, and the fourth pad 524 are formed on the surface 70 of the insulating layer 7. The first electrode 41, the third electrode 51, the leads, and the pads are formed by vapor deposition or sputtering using a metal mask, using gold as a material. In addition, the first electrode 41, the third electrode 51, the leads, and the pads may be formed using photolithography technology and etching technology. In addition, the first electrode 41, the third electrode 51, the leads, and the pads may be formed using a photolithography technique, a thin film forming technique, and a lift-off method.

Next, as shown in D of FIG. 13, a cavity 23 is formed in the base 200. Thereby, the support part 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 C of FIG. 13) is patterned using photolithography technology and etching technology. Furthermore, the cavity 23 is formed by etching the central portion of the substrate 200 from the second surface 202 using the patterned remaining protective layer 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.

Thus, the piezoelectric transducer 1 is manufactured.

At least one region of the first piezoelectric layer 40 overlaps at least one region of the second piezoelectric layer 50 in the direction orthogonal to the thickness direction.

A second layer 92 of lead zirconate titanate is formed for the first piezoelectric layer 40 as shown in C of FIG. 12, and then a second layer of aluminum nitride is used for the second piezoelectric layer 50 as shown in F of FIG. 12. It can be a process of forming the three layers 93. The material of the second piezoelectric layer 50 can be selected without being influenced by the formation temperature of lead zirconate titanate, and it is also possible to use, for example, an organic piezoelectric material. That is, there is an effect that the material selectivity of the second piezoelectric layer 50 is high.

Moreover, although the piezoelectric transducer 1 is mounted on the substrate, the substrates of the first electrode 41 and the third electrode 51 are not provided if the first piezoelectric layer 40 does not overlap the second piezoelectric layer 50 in the direction orthogonal to the thickness direction. There is a large difference in distance to the mounting surface. Although wiring of the wiring is complicated to eliminate the difference in distance, at least one region of the first piezoelectric layer 40 overlaps at least one region of the second piezoelectric layer 50 in the direction orthogonal to the thickness direction, The process of wire routing becomes easy.

(Configuration of piezoelectric module)
As shown in FIG. 14, the piezoelectric module 10 includes a plurality (16 in FIG. 7) of piezoelectric transducers 1. The plurality of piezoelectric transducers 1 are mounted on a substrate. The plurality of piezoelectric transducers 1 are arranged in a two-dimensional array of four vertical rows and four horizontal rows. The piezoelectric module 10 further includes a first switching unit 11, a second switching unit 12, and a processing unit 13.

Further, since the second piezoelectric region R5 of the present embodiment is located in the 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 of FIG. That is, 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 prevents the bending of the second piezoelectric layer 50, or the second piezoelectric layer 50 However, it is difficult to prevent the 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, the transmission intensity and the reception sensitivity) can be improved.

(Modification of the second embodiment)
Hereinafter, modifications of the second embodiment will be listed. The following modifications may be implemented in combination as appropriate.

Both ends of the first piezoelectric layer 40 may not coincide with both ends of the second piezoelectric layer 50 in the Z-axis direction. At least one region of the first piezoelectric layer 40 may overlap at least one region of the second piezoelectric layer 50 in the 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 the ends of the first piezoelectric layer 40 in the Z-axis direction. . Alternatively, the first piezoelectric layer 40 may be thinner than the second piezoelectric layer 50, and both ends of the first piezoelectric layer 40 may be located between the two ends of the second piezoelectric layer 50 in the Z-axis direction. .

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

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

Further, 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-like support 2 as viewed in the Z-axis direction. In the third electrode 51, the outer edge 512 in the radial direction may overlap with a part of the inner edge 211 of the first surface 21. In the second piezoelectric layer 50, the outer edge in the radial direction may overlap with a part of the inner edge 211 of the first surface 21.

In addition, the third electrode 51, the fourth electrode 52, the first piezoelectric layer 40, the second piezoelectric layer 50, etc. are formed by using a metal mask or the like instead of being formed by photolithography technology and etching technology. Alternatively, they may be formed by sputtering.

Further, the first electrode 41 and the third electrode 51 may be electrically connected. For example, an electrode in which the first electrode 41 and the third electrode 51 are integrated is formed on 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. May be 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 process is performed 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 transmission by applying an alternating voltage to the first piezoelectric layer 40 and the timing at which the piezoelectric transducer 1 is used for receiving waves by extracting the alternating voltage generated in the second piezoelectric layer 50 And may be different.

A vibrating film formed of, for example, silicon (Si) or the like may be separately disposed on either the surface on the cavity 23 side of the protective layer 6 or the surface on the first piezoelectric layer 40 side. As a result, the mechanical constant of the movable portion can be adjusted to a value suitable for the use conditions, so that the efficiency of transmitting and receiving waves can be improved.

In addition, the thickness of the insulating layer 7 in a region overlapping with the cavity 23 when viewed in the thickness direction (Z direction) can be, for example, about 0.1 μm. This is because the thickness may be any as long as it functions as a protective layer of the first piezoelectric layer 40 and the second piezoelectric layer 50.

(Summary)
As described above, the piezoelectric transducer 1 according to the thirteenth aspect includes the support portion 2 and the piezoelectric portion 3. The support portion 2 is in the form of a frame 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 the 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 in the thickness direction.

Further, in the piezoelectric transducer 1 according to the fourteenth aspect, in the thirteenth aspect, the material of the first piezoelectric layer 40 is different from the material of the second piezoelectric layer 50. Therefore, it is possible to obtain an effect that the first piezoelectric region R4 and the second piezoelectric region R5 can have different functions of transmission and reception.

In the piezoelectric transducer 1 according to the fifteenth aspect, in the thirteenth or fourteenth aspect, both ends of the second piezoelectric layer 50 are positioned between the ends of the first piezoelectric layer 40 in the thickness direction (Z-axis direction). Do.

According to the above configuration, both ends of the second piezoelectric layer 50 are positioned between the two ends of the first piezoelectric layer 40 in the thickness direction. That is, the thickness of the second piezoelectric layer 50 is smaller than that of the first piezoelectric layer 40. Therefore, it is possible to improve the characteristic of the second piezoelectric region R5 (the characteristic of converting vibration into an alternating voltage or the characteristic of converting alternating voltage into vibration).

In the piezoelectric transducer 1 according to the sixteenth aspect, in the thirteenth to fifteenth aspects, the first electrode 41 and the second electrode 42 are electrodes for applying an alternating voltage to the first piezoelectric layer 40. The third electrode 51 and the fourth electrode 52 are electrodes for extracting AC voltage generated in the second piezoelectric region R5.

Further, in the piezoelectric transducer 1 according to the seventeenth aspect, in the thirteenth to fifteenth aspects, the first electrode 41 and the second electrode 42 are electrodes for extracting alternating-current voltage generated in the first piezoelectric region R4. The third electrode 51 and the fourth electrode 52 are electrodes for applying an alternating voltage to the second piezoelectric layer 50.

In the piezoelectric transducer 1 according to the eighteenth aspect, in the thirteenth to fifteenth aspects, the first electrode 41 and the second electrode 42 are electrodes for applying an alternating voltage to the first piezoelectric layer 40. The third electrode 51 and the fourth electrode 52 are electrodes for applying an alternating voltage to the second piezoelectric layer 50.

Further, in the piezoelectric transducer 1 according to the nineteenth aspect, in the thirteenth to fifteenth aspects, the first electrode 41 and the second electrode 42 are electrodes for extracting alternating-current voltage generated in the first piezoelectric region R4. The third electrode 51 and the fourth electrode 52 are electrodes for extracting AC voltage generated in the second piezoelectric region R5.

Also, the piezoelectric transducer 1 according to the twentieth aspect, in the sixteenth 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.

In the piezoelectric transducer 1 according to the twenty-first aspect, in any of the thirteenth to nineteenth aspects, the first electrode 41, the second electrode 42, the third electrode 51, and the fourth electrode 52 are electrically insulated from each other. It is done.

In the piezoelectric transducer 1 according to the twenty-second aspect, in any of the thirteenth to twentieth aspects, at least a part of the second piezoelectric region R5 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.

In the piezoelectric transducer 1 according to the twenty-third aspect, in any of the thirteenth to twenty-first aspects, when viewed from the thickness direction (Z-axis direction), the second piezoelectric region R5 Straddle.

The piezoelectric module 10 according to the twenty-fourth aspect includes a plurality of piezoelectric transducers 1 according to any of the thirteenth through twenty-second aspects.

According to the above configuration, the second piezoelectric region R5 of the piezoelectric transducer 1 is located in the 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 distortion of the first piezoelectric layer 40 of the first piezoelectric region R4 causes the second piezoelectric of the second piezoelectric region R5 to The degree to which the layer 50 is distorted can be reduced. Moreover, the extent to which the first piezoelectric layer 40 is distorted due to the distortion of the second piezoelectric layer 50 can be reduced. As a result, it is possible to improve the characteristics in which the first piezoelectric region R4 and the second piezoelectric region R5 convert an alternating voltage into vibration or the characteristics in which vibration is converted into an alternating voltage. The piezoelectric module 10 also includes a plurality of piezoelectric transducers 1. Thereby, compared with the case where only one piezoelectric transducer 1 is used, the output by converting the AC voltage into the vibration by the first piezoelectric region R4 and the second piezoelectric region R5 can be made larger, or the vibration It is possible to further increase the sensitivity for converting the voltage into an alternating voltage.

The configurations according to the fourteenth to twenty-third aspects are not essential components of the piezoelectric transducer 1 and can be omitted as appropriate.

In the piezoelectric transducer and the piezoelectric module of the present disclosure, it is possible to improve the characteristics in which the first piezoelectric region and the second piezoelectric region convert alternating voltage into vibration or the characteristics in converting vibration into alternating voltage. Thereby, high performance piezoelectric transducers and piezoelectric modules can be obtained, and thus the piezoelectric transducers and piezoelectric modules of the present disclosure are industrially useful.

Reference Signs List 1 piezoelectric transducer 10 piezoelectric module 2 support portion 21 first surface (surface)
23

cavity

211, 515 inner edge 3 piezoelectric portion 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

A frame-shaped support portion having a first surface, a second surface opposite to the first surface, and a cavity provided between the first surface and the second surface and provided on the inner side; ,
A plate-like piezoelectric portion supported by the support portion and covering the cavity from the first surface side,
The piezoelectric portion is
The first electrode,
A second electrode,
A first piezoelectric layer sandwiched between the first electrode and the second electrode in a direction perpendicular to the first surface;
The third electrode,
The fourth electrode,
A second piezoelectric layer sandwiched between the third electrode and the fourth electrode in a direction perpendicular to the first surface;
The piezoelectric portion is
A first piezoelectric region in which the first electrode, the second electrode, and the first piezoelectric layer overlap the cavity in a direction perpendicular to the first surface;
A second piezoelectric region in which the third electrode, the fourth electrode, and the second piezoelectric layer overlap the cavity in a direction perpendicular to the first surface;
The first piezoelectric layer is not disposed at a position overlapping the second piezoelectric region when viewed from a direction perpendicular to the first surface.
Piezoelectric transducer.
The first piezoelectric layer does not overlap the second piezoelectric layer in the direction orthogonal to the thickness direction.
The piezoelectric transducer according to claim 1.
The first electrode and the second electrode are electrodes for applying an alternating voltage to the first piezoelectric layer,
The third electrode and the fourth electrode are electrodes for extracting AC voltage generated in the second piezoelectric region.
The piezoelectric transducer according to claim 2.
The piezoelectric constant of the first piezoelectric layer is larger than the piezoelectric constant of the second piezoelectric layer,
The piezoelectric transducer according to claim 3.
The first electrode and the second electrode are electrodes for extracting alternating voltage generated in the first piezoelectric region,
The third electrode and the fourth electrode are electrodes for applying an alternating voltage to the second piezoelectric layer,
The piezoelectric transducer according to claim 2.
The first electrode, the second electrode, the third electrode and the fourth electrode are electrically isolated from each other
The piezoelectric transducer according to any one of claims 2 to 5.
The second piezoelectric layer is located between the first piezoelectric layer and the cavity in the thickness direction.
The piezoelectric transducer according to any one of claims 2 to 6.
In the thickness direction, the second piezoelectric layer overlaps the entire cavity.
The piezoelectric transducer according to any one of claims 2 to 7.
Seen from the direction perpendicular to the first surface, at least a portion of the second piezoelectric region is along the edge of the cavity,
A piezoelectric transducer according to any one of claims 2-8.
When viewed from a direction perpendicular to the first surface, the second piezoelectric region straddles the cavity and the support.
The piezoelectric transducer according to any one of claims 2 to 9.
When viewed from a direction perpendicular to the first surface, the second piezoelectric region is disposed along a portion of the first piezoelectric region.
The piezoelectric transducer according to any one of claims 2 to 10.
When viewed from the direction perpendicular to the first surface, at least a portion of the first piezoelectric region is located at the center of the cavity, and at least a portion of the second piezoelectric region is located at the outer periphery of the cavity doing,
The piezoelectric transducer according to any one of claims 2 to 10.
At least a region of the first piezoelectric layer overlaps at least a region of the second piezoelectric layer in a direction perpendicular to a direction perpendicular to the first surface.
The piezoelectric transducer according to claim 1.
The material of the first piezoelectric layer is different from the material of the second piezoelectric layer,
The piezoelectric transducer according to claim 13.
Both ends of the second piezoelectric layer are located between the ends of the first piezoelectric layer in the thickness direction,
A piezoelectric transducer according to claim 13 or 14.
The first electrode and the second electrode are electrodes for applying an alternating voltage to the first piezoelectric layer,
The third electrode and the fourth electrode are electrodes for extracting AC voltage generated in the second piezoelectric region.
The piezoelectric transducer according to any one of claims 13-15.
The first electrode and the second electrode are electrodes for extracting alternating voltage generated in the first piezoelectric region,
The third electrode and the fourth electrode are electrodes for applying an alternating voltage to the second piezoelectric layer,
The piezoelectric transducer according to any one of claims 13-15.
The piezoelectric constant of the first piezoelectric layer is larger than the piezoelectric constant of the second piezoelectric layer,
The piezoelectric transducer according to claim 16.
The first electrode, the second electrode, the third electrode and the fourth electrode are electrically isolated from each other
A piezoelectric transducer according to any of claims 13-18.
When viewed from the thickness direction, at least a portion of the second piezoelectric region is along the inner edge on the cavity side in the surface on the piezoelectric portion side of the support portion.
The piezoelectric transducer according to any one of claims 13-19.
When viewed from a direction perpendicular to the first surface, the second piezoelectric region straddles the cavity and the support.
The piezoelectric transducer according to any one of claims 13 to 20.
When viewed from a direction perpendicular to the first surface, the second piezoelectric region is disposed along a portion of the first piezoelectric region.
The piezoelectric transducer according to any one of claims 13 to 21.
When viewed in the thickness direction, at least a portion of the first piezoelectric region is located on the center side of the cavity, and at least a portion of the second piezoelectric region is located on the outer periphery side of the cavity.
The piezoelectric transducer according to any one of claims 13 to 22.
A plurality of piezoelectric transducers according to any one of the preceding claims,
Piezoelectric module.