WO2021132074A1

WO2021132074A1 - Ultrasound device and ultrasonic diagnostic apparatus

Info

Publication number: WO2021132074A1
Application number: PCT/JP2020/047419
Authority: WO
Inventors: 英章浅尾; 涼上野; 由里子西村; 徳一山地
Original assignee: 京セラ株式会社
Priority date: 2019-12-23
Filing date: 2020-12-18
Publication date: 2021-07-01
Also published as: JPWO2021132074A1

Abstract

An ultrasonic device having a first face and a plurality of elements arranged along the first face. Each of the plurality of elements has a cavity, a lower electrode located on the first face side with respect to the cavity, a piezoelectric substance located on the first face side with respect to the lower electrode, and an upper electrode located on the first face side with respect to the piezoelectric substance. The plurality of elements include two types or more of elements differing in the diameter of the cavity from each other.

Description

Ultrasonic device and ultrasonic diagnostic equipment

The present disclosure relates to an ultrasonic device such as a pMUT (Piezoelectric Micromachined Ultrasonic Transducer), and also relates to an ultrasonic diagnostic apparatus having the ultrasonic device.

There is known an ultrasonic device configured by arranging a plurality of ultrasonic elements for transmitting and / or receiving ultrasonic waves on a plane (for example, Patent Document 1 below). The ultrasonic elements disclosed in Patent Document 1 include a substrate, a common electrode overlapping the lower surface of the substrate, a frustum-shaped piezoelectric film arranged so as to form a gap on the upper surface of the substrate, and an upper surface of the piezoelectric film. It has an electrode that overlaps with. Patent Document 1 proposes to set two or more types of gap diameters in order to widen the bandwidth of ultrasonic waves.

Japanese Unexamined Patent Publication No. 2006-75425

The ultrasonic device according to one aspect of the present disclosure has a first surface and a plurality of elements arranged along the first surface. Each of the plurality of elements includes a cavity, a lower electrode located on the first surface side with respect to the cavity, and a piezoelectric body located on the first surface side with respect to the lower electrode. It has an upper electrode located on the first surface side with respect to the piezoelectric body. The plurality of elements include two or more types of elements in which the diameters of the cavities are different from each other.

The ultrasonic diagnostic apparatus according to one aspect of the present disclosure includes the ultrasonic device and a display device that displays an image based on an electric signal from the ultrasonic device.

It is a perspective view which shows the structure of a part of the ultrasonic device which concerns on 1st Embodiment. FIG. 5 is a cross-sectional view taken along the line II-II of FIG. It is a top view which shows the example of the structure of the cavity in the ultrasonic device of FIG. It is an enlarged view of the region IV of FIG. It is a schematic diagram which shows the example of the vibration of the ultrasonic element which the diameter of a cavity is different from each other. 6 (a) and 6 (b) are diagrams showing the conditions and results of the experiments according to Examples 1 to 4. 7 (a) and 7 (b) are diagrams showing the conditions and results of the experiments according to Examples 5 to 7. It is an enlarged view of the region VIII of FIG. 9 (a) is an enlarged view of the region IXa of FIG. 8, and FIG. 9 (b) is an enlarged view of the region IX b of FIG. It is a plane perspective view which shows a part structure of the ultrasonic device which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the ultrasonic diagnostic apparatus which concerns on embodiment.

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. The drawings below are schematic. Therefore, details may be omitted, and the dimensional ratio and the like do not always match the actual ones. Also, the dimensional ratios of the plurality of drawings do not always match.

For convenience, the drawings may be provided with the Cartesian coordinate system D1-D2-D3. The ultrasonic device may be in any direction upward or downward, but in the description of the embodiment, for convenience, the term upper or lower may be used with the positive side in the D3 axis direction as the upper side. is there. Further, in the following, the term "planar view" or "planar perspective" means viewing in the D3 axis direction unless otherwise specified.

<First Embodiment>
(Device configuration)
FIG. 1 is a perspective view showing a partial configuration of the ultrasonic device 1 according to the first embodiment. Hereinafter, the "ultrasonic device" may be simply referred to as a "device".

The approximate outer shape and dimensions of the device 1 may be appropriately set according to the technical field in which the device 1 is used, the functions required of the device 1, and the like. For example, the device 1 may be made relatively small so that it can be placed in a blood vessel in an intravascular ultrasonography (IVUS: intravascular ultrasonography), or a conventional ultrasonic diagnostic apparatus (for example, to obtain a tomographic image of the abdomen). It may be about the size of a palm so that it can be used for the probe of the device). Further, the device 1 may be configured as MEMS (Micro Electro Mechanical Systems).

In the present embodiment, the device 1 is roughly configured in the form of a substrate, for example. FIG. 1 shows a part of the upper surface 1a of the substrate. The planar shape of the device 1 is arbitrary and may be, for example, a polygon (for example, a rectangle), a circle or an ellipse.

The device 1 has, for example, a plurality of ultrasonic elements 3 (only two are shown in FIG. 1) arranged along the upper surface 1a. Hereinafter, the "ultrasonic element" may be simply referred to as an "element". Each element 3 transmits and / or receives ultrasonic waves. In other words, the element 3 is a transducer that converts ultrasonic waves into electrical signals and / or vice versa.

Specifically, for example, the element 3 is input with an electric signal (drive signal) whose voltage changes in a predetermined waveform (for example, a spike wave, a square wave, or a sine wave). Then, the element 3 converts the electric signal into an ultrasonic wave reflecting the waveform of the electric signal (for example, reflecting the frequency and / or the amplitude), and transmits the ultrasonic wave to the positive side in the D3 axis direction. Further, for example, the element 3 receives an ultrasonic wave from the positive side in the D3 axis direction and converts the ultrasonic wave into an electric signal reflecting the waveform of the ultrasonic wave. The positive side of the ultrasonic wave transmission and reception in the D3 axis direction here is not always parallel to the D3 axis direction.

In the plurality of elements 3, the diameter of some elements 3 (may be one or two or more) in a plan view and some other elements 3 (may be one or two or more). ) Are different from each other in the plan view. That is, the plurality of elements 3 include two or more types of elements 3 having different diameters in a plan view.

This difference in diameter will be described in detail later, and first, the basic configuration of the plurality of elements 3 (matters common to the plurality of elements 3 having different diameters, etc.) will be described.

The plurality of elements 3 may be provided in an arbitrary number and may be arranged in an arbitrary direction. For example, the plurality of elements 3 may be arranged in two or more in the D1 direction and two or more in the D2 direction (see FIGS. 3 and 10 described later). The pitch of the plurality of elements 3 in the D1 direction is constant regardless of, for example, the difference in diameter between the elements 3. The pitch of the plurality of elements 3 in the D2 direction is constant regardless of, for example, the difference in diameter between the elements 3. Further, the former pitch and the latter pitch are, for example, the same.

The pitch is, for example, the distance between the centers of adjacent elements 3 in the plan view of the upper surface 1a. Later, the opening shape and its circumscribed circle when specifying the diameter of the cavity 5c (described later) will be described. The center of the opening shape or the circumscribed circle may be the center of the element 3 when specifying the pitch.

Unlike the illustrated example, for example, the plurality of elements 3 may be arranged one-dimensionally (only one row may be provided), or the rows adjacent to each other may be arranged so as to be offset by half a pitch. You may. Further, the pitch may be set so that the pitch of the element 3 having a relatively large diameter is relatively large.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

The device 1 has, for example, a support substrate 5, a functional layer 7 that overlaps the upper surface 5a of the support substrate 5, and a damping material 9 that overlaps the lower surface 5b of the support substrate 5. Although not particularly shown, the device 1 may have components other than the above. For example, the device 1 may have an electronic element mounted on any surface of the upper surface 5a or the lower surface 5b or the damping material 9.

The support substrate 5 has a plurality of cavities 5c that open to the upper surface 5a. Each element 3 includes a cavity 5c and a portion of the functional layer 7 that substantially overlaps the cavity 5c. The portion of the functional layer 7 that substantially overlaps the cavity 5c is a portion that vibrates to generate ultrasonic waves, and directly bears the transmission and / or reception of ultrasonic waves. The portion may be referred to as an element body 3a. The support substrate 5 contributes to supporting the functional layer 7, and also affects the resonance frequency (natural frequency) of the functional layer 7 (element 3). The damping material 9 contributes to damping unnecessary vibration, for example.

(Support board)
As described above, the support substrate 5 has an upper surface 5a, a lower surface 5b on the back surface thereof, and a plurality of cavities 5c. The support substrate 5 has, for example, a substantially flat plate shape, and the upper surface 5a and the lower surface 5b have a flat shape parallel to each other. The inside of the cavity 5c is, for example, in a vacuum state or is filled with an appropriate gas. The cavity 5c contributes to facilitating the vibration of the portion of the functional layer 7 that constitutes the element 3 (element body 3a), for example. Further, for example, since the element body 3a is in a state of being supported at both ends at both side edges of the cavity 5c in cross-sectional view, the cavity 5c contributes to defining the resonance frequency of the element body 3a (element 3). .. That is, the larger the diameter of the cavity 5c, the lower the resonance frequency of the element 3.

The shape and dimensions of the cavity 5c may be set as appropriate. For example, the shape of the cavity 5c in a plan view (for example, the opening shape on the upper surface 5a) may be circular or polygonal. In the present embodiment, the case where the opening shape of the cavity 5c is circular is taken as an example. Further, in the illustrated example, the shape of the cross section (cross section parallel to the D1-D3 plane) parallel to the depth direction of the cavity 5c is rectangular. From another point of view, the shape of the cross section of the cavity 5c orthogonal to its depth direction (cross section parallel to the D1-D2 plane) is constant regardless of the position in the depth direction (D3 direction). However, the shape of the cross section of the cavity 5c orthogonal to the depth direction may differ depending on the position in the depth direction. For example, in the cross-sectional view as shown in FIG. 2, the shape of the cavity 5c may be a trapezoidal shape in which the diameter is enlarged or reduced toward the upper side. The diameter of the cavity 5c may be appropriately set, and for example, it is 10 μm or more and 100 μm or less.

In an embodiment in which the shape of the cross section of the cavity 5c orthogonal to the depth direction differs depending on the position in the depth direction, the diameter of the cavity 5c refers to the diameter of the opening shape on the upper surface 5a of the cavity 5c unless otherwise specified. To do. This is because the portion of the cavity 5c (support substrate 5) that affects the resonance frequency of the element 3 is mainly the portion that opens to the upper surface 5a. When the opening shape of the cavity 5c is not circular, the diameter of the cavity 5c refers to the diameter of the circumscribed circle of the opening on the upper surface 5a of the cavity 5c unless otherwise specified. This is because the resonance frequency of the element 3 is easily affected by the portion of the opening shape of the cavity 5c having a large diameter. When specifying or setting the circumscribed circle, a specific portion having a small effect on the resonance frequency of the element 3 may be ignored. For example, when an elongated convex portion protruding outward from the cavity 5c is provided in a plan view, such a convex portion may be ignored.

The material of the support substrate 5 is arbitrary. The entire support substrate 5 may be made of one material, or the support substrate 5 may be made of a combination of a plurality of materials. The material of the support substrate 5 is, for example, an inorganic insulating material or an organic insulating material. More specifically, for example, the support substrate 5 may be integrally formed of an insulating material such as silicon (Si). Further, for example, the support substrate 5 may be formed substantially integrally with an insulating material such as silicon, and may have a layer made of another insulating material such as _{SiO 2 on the upper surface and / or the lower surface.} Good.

(Functional layer (element body))
The element body 3a, which is a portion of the functional layer 7 that constitutes the element 3 (generally a portion on the cavity 5c), is, for example, on the cavity 5c side (-D3 side) and the side opposite to the cavity 5c (+ D3 side). Vibration is generated with bending deformation to at least one side. In other words, the vibration is out-of-plane vibration. This vibration causes transmission and / or reception of ultrasonic waves. That is, the element 3 is a flexible vibration type.

Examples of flexible vibration type ultrasonic elements include piezoelectric elements such as pMUT and capacitive elements such as cMUT (Capacitive Micromachined Ultrasonic Transducer). In this embodiment, pMUT is taken as an example. Further, examples of the flexible vibration type piezoelectric element include a bimorph type element and a unimorph type element. In this embodiment, a unimorph type element is taken as an example.

The element body 3a is configured such that the resonance frequency is located in the ultrasonic frequency band with respect to the vibration in the primary mode in which the center thereof is the antinode of the vibration and the outer edge is the node of the vibration. The frequency band of ultrasonic waves is, for example, a frequency band of 20 kHz or higher. There is no particular regulation on the upper limit of the ultrasonic frequency, but it is, for example, 5 GHz. The thickness of the element 3 may be appropriately set, and for example, it is 4 μm or more and 40 μm or less.

The functional layer 7 has, for example, a plurality of membranes 11 located on the plurality of cavities 5c, and a coating layer 13 covering the upper surface 5a from above the plurality of membranes 11. One element 3 (one element body 3a) has one membrane 11 that overlaps one cavity 5c and a region that overlaps one membrane 11 of the coating layer 13. The membrane 11 is a portion directly responsible for transmitting and / or receiving ultrasonic waves. The coating layer 13 contributes, for example, to the protection and / or insulation of the membrane 11.

Among the functional layers 7, a layer containing a plurality of membranes 11 (a layer of the functional layers 7 below the coating layer 13) is referred to as a functional main body layer 8. In addition to the membrane 11, the functional body layer 8 may have wiring or the like that contributes to the electrical connection of the membrane 11. The thickness of the functional body layer 8 may be appropriately set, and for example, it is 2 μm or more and 20 μm or less.

(Membrane)
The membrane 11 has a vibrating portion 15, a lower electrode 17, a piezoelectric body 19, and an upper electrode 21 which are laminated in order from the support substrate 5.

The polarization axis direction of the piezoelectric body 19 (electrical axis and X-axis in a single crystal) is the thickness direction of the piezoelectric body 19. When an electric field is applied to the piezoelectric body 19 by the lower electrode 17 and the upper electrode 21 in the same direction as the polarization direction, the portion of the piezoelectric body 19 sandwiched between the lower electrode 17 and the upper electrode 21 is in the plane direction (D1 direction and Reduce in the D2 direction). This reduction is regulated by the vibrating unit 15. As a result, the membrane 11 bends (displaces) toward the cavity 5c like a bimetal. On the contrary, when an electric field is applied in the direction opposite to the direction of polarization, the membrane 11 bends to the side opposite to the cavity 5c.

Due to the displacement of the element 3 as described above, a pressure wave is formed in the medium (for example, fluid) around the element 3. Then, when an electric signal whose voltage changes with a predetermined waveform is input to the lower electrode 17 and the upper electrode 21, an ultrasonic wave reflecting the waveform (for example, frequency and / or amplitude) of the electric signal is generated.

Although the transmission of ultrasonic waves was described, the reception of ultrasonic waves is realized by the principle opposite to that at the time of transmission. One element 3 may be one that performs only transmission, one that performs only reception, or one that performs both transmission and reception. The element 3 that performs both transmission and reception, for example, intermittently transmits ultrasonic waves and receives ultrasonic waves while the ultrasonic waves are not being transmitted. As a result, for example, the element 3 receives the reflected wave of the ultrasonic wave transmitted by itself.

(Vibration part)
The vibrating portion 15 is a portion of the vibrating layer 16 on the cavity 5c. The vibrating layer 16 extends without gaps over, for example, one region including the plurality of cavities 5c in planar fluoroscopy. In other words, the vibrating layer 16 covers the plurality of cavities 5c and the region between them. However, unlike the illustrated example, the vibrating portion 15 may be provided for each element 3. That is, the plurality of vibrating portions 15 may be separated from each other by forming the non-arranged region of the vibrating layer 16 between the cavities 5c. The vibrating portion 15 is, for example, roughly a layered layer having a constant thickness. The thickness of the vibrating portion 15 may be appropriately set. For example, the thickness of the vibrating portion 15 may be thinner, equal to, or thicker than the thickness of the piezoelectric body 19.

The vibrating portion 15 is formed of, for example, an insulating material. The insulating material may be an organic material in the inorganic material, more specifically, for example, silicon, silicon dioxide (SiO ₂₎ or silicon nitride (SiN _X). The vibrating portion 15 may be integrally formed of, for example, one kind of material, or may be formed by laminating a plurality of layers made of different materials. For example, the vibrating portion 15 may be composed of _{silicon and SiO 2 overlapping the lower surface thereof.} Although not particularly shown, it is also possible to make the lower electrode 17 or the upper electrode 21 function as the vibrating portion without providing the vibrating portion 15.

(Piezoelectric)
The piezoelectric body 19 is, for example, roughly a layer having a constant thickness. The piezoelectric body 19 is provided for each element 3 (every cavity 5c). From another point of view, the plurality of piezoelectric bodies 19 are separated from each other. In planar perspective, the shape and width of the piezoelectric body 19 is, for example, roughly equivalent to that of the cavity 5c. For example, in planar perspective, 90% or more of the piezoelectric body 19 (upper surface or lower surface thereof) and 90% or more of the cavity 5c (opening in the upper surface 5a thereof) overlap. In the present embodiment, as described above, the case where the opening shape of the cavity 5c is circular is taken as an example, and the case where the planar shape of the piezoelectric body 19 is circular is taken as an example. However, the piezoelectric body 19 may have a shape and / or a width completely different from the opening shape of the cavity 5c in plan perspective. The thickness of the piezoelectric body 19 may be appropriately set. As an example, the thickness of the piezoelectric body 19 is 0.5 μm or more and 10 μm or less.

The piezoelectric body 19 is formed in a tapered shape so that the diameter is reduced toward the upper surface side, for example. In other words, the side surface of the piezoelectric body 19 has a slope 19a in which the piezoelectric body 19 is inclined in a direction in which the diameter of the piezoelectric body 19 is increased toward the support substrate 5. As a result, for example, the probability of disconnection of the upper wiring 25 (described later) connected to the upper electrode 21 is reduced. Further, for example, as will be described later, the efficiency of transmitting and / or receiving ultrasonic waves can be improved. The slope 19a may be a part or all of the side surface of the piezoelectric body 19 (illustrated example). The aspect in which the slope 19a is a part of the side surface of the piezoelectric body 19 is the aspect in which a part of the side surface of the piezoelectric body 19 in the vertical direction is the slope 19a and / or the side surface of the piezoelectric body 19 in a plan view. An embodiment in which a part of the circumferential direction is a slope 19a can be mentioned. The tapered surface (side surface) of the piezoelectric body 19 may be flat or curved in the cross section as shown in FIG. Further, the inclination angle of the tapered surface is also arbitrary. Unlike the illustrated example, the piezoelectric body 19 may have a shape in which the upper surface and the lower surface substantially overlap (a shape in which the side surface is a vertical wall).

Unlike the illustrated example, a piezoelectric layer may be provided so as to spread without gaps in the entire one region including the plurality of cavities 5c in planar fluoroscopy. In this case, the piezoelectric body 19 included in one element 3 is composed of a part of the piezoelectric body layer located on the cavity 5c.

The piezoelectric body 19 may be composed of a single crystal or a polycrystal. The material of the piezoelectric body 19 is, for example, aluminum nitride (AlN), barium titanate (BTO: BaTIO ₃ ), sodium potassium niobate (KNN: (K, Na) NbO ₃ ), sodium bismuth titanate (NBT: Na _{0). .5} Bi _0.5 TiO ₃ ) and lead zirconate titanate (PZT: Pb (Zr _x , Ti _1-x ) O ₃ ). As can be understood from the above examples, the piezoelectric body may or may not be a ferroelectric substance, and may or may not be a pyroelectric body. Further, the crystal structure may be an appropriate one such as a perovskite type or a wurtzite type.

(electrode)
The lower electrode 17 is, for example, roughly a layered body having a constant thickness. The lower electrode 17 is provided for each element 3 (every cavity 5c). From another point of view, the plurality of lower electrodes 17 are separated from each other. In planar perspective, the shape and width of the lower electrode 17 are, for example, roughly equivalent to the lower surface of the cavity 5c and / or the piezoelectric body 19. For example, in planar perspective, 90% or more of the lower electrode 17 overlaps with 90% or more of the cavity 5c (the opening in the upper surface 5a thereof) and / or the lower surface of the piezoelectric body 19. In the present embodiment, as described above, the case where the opening shape of the cavity 5c is circular is taken as an example, and the case where the planar shape of the lower electrode 17 is circular is taken as an example. However, the lower electrode 17 may have a shape and / or a width completely different from the opening shape of the cavity 5c in plan perspective.

Unlike the illustrated example, a lower electrode layer that extends without gaps may be provided over the entire region that includes the plurality of cavities 5c in planar fluoroscopy. In this case, the lower electrode 17 included in one element 3 is composed of a part of the lower electrode layer located on the cavity 5c.

The above description of the lower electrode 17 may be incorporated into the upper electrode 21. At this time, the "lower electrode 17" is replaced with the "upper electrode 21", the "lower surface of the piezoelectric body 19" is replaced with the "upper surface of the piezoelectric body 19", and the "lower electrode layer" is replaced with the "upper electrode layer". The lower electrode 17 and the upper electrode 21 may have the same shape and / or size, or may be different from each other. In the illustrated example, the piezoelectric body 19 is tapered. The lower electrode 17 has a shape and size substantially the same as the lower surface of the piezoelectric body 19, and the upper electrode 21 has a shape and size substantially the same as the upper surface of the piezoelectric body 19. As a result, the upper electrode 21 is one size smaller than the lower electrode 17.

The thickness of each electrode may be set appropriately. Usually, the thickness of each electrode is thinner than the thickness of the piezoelectric body 19 and the vibrating layer 16. For example, the thickness of each electrode is 1/10 or less of the thickness of the piezoelectric body 19. The thickness of the lower electrode 17 and the thickness of the upper electrode 21 may be the same as or different from each other.

The material of each electrode may be, for example, a layer of an appropriate metal and / or oxide conductive thin film. The metal is, for example, gold (Au), platinum (Pt), aluminum (Al), copper (Cu), titanium (Ti) or chromium (Cr) or an alloy containing these. The oxide conductive thin film is, for example, a conductive material having a perovskite structure such as strontium ruthenate (SRO) or lanthanum nickelate (LNO). Each electrode may be configured by laminating a plurality of layers made of different materials as shown above. The material of the lower electrode 17 and the material of the upper electrode 21 may be the same as each other or may be different from each other.

The plurality of lower electrodes 17 may be connected to each other or may not be connected to each other. Similarly, the plurality of upper electrodes 21 may be connected to each other or may not be connected to each other. In the description of the present embodiment, a mode in which a plurality of lower electrodes 17 are connected to each other and a plurality of upper electrodes 21 are connected to each other is mainly taken as an example.

(Other configurations included in the functional body layer)
As described above, the functional body layer 8 including the plurality of membranes 11 may include wiring related to the electrical connection of the membrane 11 in addition to the membrane 11. For example, as described above, in the present embodiment, the upper electrodes 21 are connected to each other as an example, and the functional body layer 8 is an upper portion connecting a plurality of upper electrodes 21 arranged in the D1 direction to each other. It has wiring 25 (see also FIG. 10). Other wiring will be described later with reference to FIG. 10 (another embodiment). For various wiring materials, for example, the above description of electrode materials may be incorporated.

The upper wiring 25 is composed of, for example, a conductor layer that overlaps the support substrate 5 from above the membrane 11. The upper wiring 25 extends from one of the upper electrodes 21 adjacent to each other in the D1 direction to the other, and connects the two. The specific shape and dimensions of the upper wiring 25 may be appropriately set.

For example, the upper wiring 25 has a substantially elongated shape extending in the D1 direction with a constant width. Its width is, for example, smaller than the diameter of the upper electrode 21 in the D2 direction. One end of the upper wiring 25 overlaps one of the upper electrodes 21 adjacent to each other, and the other end of the upper wiring 25 overlaps the other of the upper electrodes 21 adjacent to each other. The ends of the two upper wirings 25 located on the same upper electrode 21 face each other in the D1 direction with a gap from each other. The interval is located above the center of the cavity 5c.

Further, for example, the thickness of the upper wiring 25 is thicker than that of the lower electrode 17, the upper electrode 21, and / or the lower wiring 23 described later. As a result, for example, the possibility of disconnection occurring in the portion of the upper wiring 25 that exceeds the step formed by the thickness of the piezoelectric body 19 is reduced. The thickness of the upper wiring 25 may be, for example, 1/20 or more and 1/5 or less of the thickness of the piezoelectric body 19.

An insulating film 27 may be provided that overlaps the lower electrode 17 and / or the lower wiring 23 described later from above and is located below the upper wiring 25 to reduce the probability of a short circuit between the former and the latter. The material, shape, dimensions, etc. of the insulating film 27 are arbitrary. For example, the insulating film 27 is formed thinner than the upper wiring 25, and at least the upper part of the piezoelectric body 19 is exposed. The material of the insulating film 27 may be an inorganic material or an organic material. Unlike the illustrated example, the upper wiring 25 may be insulated from the lower electrode 17 and / or the lower wiring 23 only by the piezoelectric body 19 without providing the insulating film 27.

(Coating layer)
The coating layer 13 constitutes, for example, the upper surface 1a of the device 1. Therefore, the fluid around the device 1 comes into contact with the upper surface of the coating layer 13. However, the coating layer 13 does not have to form the upper surface 1a of the device 1. For example, a layer (not shown) may be superposed on the coating layer 13.

The coating layer 13 extends without gaps over the entire area including a plurality of elements 3 in planar perspective, for example. The coating layer 13 is roughly spread with a constant thickness. Therefore, as shown in FIGS. 1 and 2, the upper surface of the covering layer 13 reflects the unevenness of the upper surface of the functional body layer 8. That is, the covering layer 13 is a so-called conformal layer (translated into Japanese as conformal, conformal, etc.). However, the unevenness of the upper surface of the coating layer 13 is smoother than the unevenness of the upper surface of the functional body layer 8. Further, unlike the illustrated example, the upper surface of the covering layer 13 may be flat regardless of the presence or absence of unevenness on the upper surface of the functional body layer 8. The thickness of the coating layer 13 may be appropriately set.

More specifically, in the present embodiment, a plurality of piezoelectric bodies 19 are provided separately from each other (the piezoelectric layer is not provided so as to spread without gaps over the plurality of cavities 5c). As a result, the upper surface of the functional body layer 8 has a convex portion on the cavity 5c. As a result, the upper surface of the coating layer 13 has a convex portion 13a on the cavity 5c. The shape of the convex portion 13a reflects the shape of the piezoelectric body 19, and in the illustrated example, it is roughly a truncated cone. Further, in the present embodiment, the provision of the relatively thick upper wiring 25 also causes a convex portion on the upper surface of the functional body layer 8. As a result, a convex portion 13b extending in the D1 direction is formed on the surface of the coating layer 13.

The material of the coating layer 13 may be, for example, a material having an insulating property. For example, the volume resistivity of the material of the coating layer 13 is 10 ¹⁴ Ωm or more. The insulating material may be an organic material or an inorganic material. The coating layer 13 may be composed of one material, or may be formed by laminating layers of different materials.

(Attenuating material)
The damping material 9 is made of a material having a damping constant (m ^-1 · Hz ^-1 ) related to acoustics larger than that of the support substrate 5. As a result, for example, the probability that the vibration generated in the element 3 leaks to the outside or, conversely, the vibration from the outside is transmitted to the element 3 is reduced. When the damping material 9 is made of an insulating material, the damping material 9 can function like an insulator of a circuit board. Therefore, for example, an electronic component may be mounted on the surface of the damping material 9 on the + D3 side or the −D3 side, or wiring or an electronic element may be provided inside the damping material 9. The material of the damping material 9 may be any suitable material, for example, resin or ceramic. The damping material 9 may not be provided.

(Cavity diameter)
Differences in diameter of the plurality of cavities 5c will be described.

FIG. 3 is a plan view showing an example of the configuration of the cavity 5c in the device 1. FIG. 4 is an enlarged view of region IV of FIG.

FIG. 3 may be regarded as a diagram showing all cavities 5c of a plurality of elements 3 used for the same purpose, for example. For example, FIG. 3 may be taken to show all the cavities 5c of the plurality of elements 3 that transmit one ultrasonic wave together. Alternatively, FIG. 3 may be regarded as showing all the cavities 5c of the plurality of elements 3 that receive one ultrasonic wave together. Alternatively, FIG. 3 may be regarded as showing all the cavities 5c of the plurality of elements 3 that transmit one ultrasonic wave together and receive the reflected wave together. The above-mentioned one ultrasonic wave is, for example, one of a plurality of ultrasonic signals repeatedly transmitted at a repetition frequency (PRF: Pulse Repetition Frequency). Further, when one ultrasonic wave is transmitted and / or received together, the phases of the plurality of elements 3 may be the same as each other, or the plurality of elements 3 may be displaced from each other due to electron scanning or the like. You may.

The plurality of elements 3 include two or more types of elements 3 in which the diameter DAs of the cavities 5c are different from each other. In FIGS. 3 and 4, four types of cavities 5c are illustrated. Specifically, a cavity 5c0 having a diameter DA0, a cavity 5c1 having a diameter DA1, a cavity 5c2 having a diameter DA2, and a cavity 5c3 having a diameter DA3 are exemplified.

From another point of view, the plurality of elements 3 can be classified into a plurality of element groups 4 having different diameters DA. For example, in the illustrated example, the plurality of elements 3 are an element group 4-0 composed of an element 3 having a diameter DA0, an element group 4-1 composed of an element 3 having a diameter DA1, and an element group 4-consisting of an element 3 having a diameter DA2. It is classified into any of the element group 4-3 consisting of the element 2 and the element 3 having a diameter DA3. In one element group 4, the diameter DAs of the plurality of elements 3 are (omitted) equal to each other.

Of course, if two or more diameter DAs are equivalent to each other, there may be unavoidable manufacturing errors and / or manufacturing tolerances. Further, the difference in diameter DAs (in another viewpoint, the magnitude from the lower limit to the upper limit of the range of diameter DAs in one element group 4) may be larger than the error or the tolerance. In the technical field to which the device 1 is applied, the diameter DA in each element group 4 is set so that the action of the present embodiment described later occurs with a significant magnitude by setting a plurality of element groups 4 having different diameter DAs. The size of the range may be appropriately reduced or increased as appropriate. For example, in a relatively small device 1 used for IVUS or the like, the size of the diameter DA range in each element group 4 may be less than 4 μm or less than 2 μm. However, this may be seen as a matter of thinking about the definition of tolerances. That is, the above 4 μm or 2 μm may be regarded as a kind of tolerance.

As described above, the difference in diameter DA (range of diameter DA in each element group 4) that is equivalent to each other may be larger than the error. In the present disclosure, unless otherwise specified, the term "diameter DA" refers to the value at the center of the range of diameter DAs that are equivalent to each other. For example, when 16 μm is exemplified as the diameter DA, it may be considered that 16 μm ± 2 μm or 16 μ ± 1 μm is exemplified. Further, for example, the explanation of the difference in the diameter DA of the two element groups 4 may be regarded as the explanation of the difference between the values at the center of the range of the diameter DA of the two element groups 4.

The number of element groups 4 (the number of types of diameter DA) may be appropriately set. The number of element groups 4 may be, for example, two, three, or five or more, unlike the illustrated example. Further, the number of elements 3 in one element group 4 (the number of cavities 5c having the same diameter DA from each other) may be appropriately set, and may be, for example, 2 or more (example in the figure), 1 It may be one. However, in the description of the present embodiment, the term of the element group 4 may refer only to those including two or more elements 3. The number of elements 3 in each element group 4 may be different from or the same as the number of elements 3 in any other element group 4.

In the illustrated example, each element group 4 includes two or more elements 3, and all the elements 3 include any element group 4 (the element group 4 here includes two or more elements 3). .) Belongs to. Unlike the illustrated example, for example, the plurality of elements 3 are one or more element groups 4 including two or more elements 3 and an element group 4 including only one element 3 (as described above, in the element group 4). It may be defined as not having). Further, for example, the plurality of elements 3 do not have to be familiar with the concept of the element group 4 because the diameter DAs of all the elements 3 are different from each other (the number of types of the diameter DA and the number of the elements 3 are the same). ..

The difference in diameter DA between the plurality of element groups 4 may be appropriately set. For example, the difference (for example, DA1-DA0) between two element groups 4 whose diameter DAs are adjacent to each other may be 10% or less of the smaller diameter DA, or 10% or more. It may be 50% or more, or 100% or more. And / or, for example, the difference between the two element groups 4 having the largest difference in diameter DA (DA3-DA0 in the illustrated example) may be 10% or less of the smaller diameter DA, or 10%. It may be more than or equal to, 50% or more, or 100% or more.

The ratio and / or difference in the number of elements 3 in the plurality of element groups 4 may be appropriately set. For example, the number of elements 3 having a relatively small diameter DA may be relatively large (example in the figure), and conversely, the number of elements 3 having a relatively large diameter DA may be relatively large. .. Further, although the number of elements 3 (cavities 5c) itself has been focused on in the above, the total area of the cavities 5c for each element group 4 may be focused on. For example, the total area of the cavities 5c in the element group 4 having a relatively small diameter DA may be relatively large (in the illustrated example), and conversely, the cavity 5c in the element group 4 having a relatively large diameter DA may be relatively large. The total area may be relatively large.

The arrangement of a plurality of elements 3 to which the element groups 4 to which they belong is different from each other may be appropriately set. For example, when viewed as an overview, the cavities 5c belonging to the same element group 4 may be densely packed (example in the figure), or may be dispersed so as to be mixed with the elements 3 of the other element group 4. .. Further, the arrangement of the elements 3 having different diameters DA may or may not have regularity. When viewed as an overview, the element 3 having a relatively large diameter DA may be located on the center side of the arrangement area of all the elements 3 (example in the figure), or the element 3 having a relatively small diameter DA may be all. It may be located on the center side of the arrangement area of the element 3.

(Diameter of electrodes, etc.)
In the present embodiment, the lower electrode 17, the piezoelectric body 19, and the upper electrode 21 have a shape and dimensions corresponding to the shape and dimensions of the cavity 5c. Therefore, the above description of the diameter of the cavity 5c may be incorporated into the description of the diameter of the lower electrode 17, the piezoelectric body 19, and / or the upper electrode 21. Further, the diameter of the element 3 may be represented by the diameter of the cavity 5c. Therefore, the above description of the diameter of the cavity 5c may be regarded as a description of the diameter of the element 3 (or the element body 3a).

The diameter of the lower electrode 17, the piezoelectric body 19 and / or the upper electrode 21 may be the size obtained by multiplying the diameter of the cavity 5c by a predetermined magnification. This magnification may be set as appropriate. For example, the diameter of the upper electrode 21 may be 0.5 times or more and 1.1 times or less (for example, 0.9 times) the diameter of the cavity 5c. When it is 0.5 times or more, for example, a sufficient area of the upper electrode 21 is secured, and thus the reception sensitivity is improved. Further, when the value is 1.1 times or less, for example, the probability that the upper electrode 21 collects charges having different codes is reduced, and the reception sensitivity is improved.

(Amplitude of element)
In the following, the correspondence between the diameter DA of the cavity 5c and the amplitude will be described. Unless otherwise specified, the amplitude here may be regarded as either the amplitude when transmitting ultrasonic waves or the amplitude when receiving ultrasonic waves.

The amplitudes of the elements 3 (elements 3 classified in the same element group 4) having the same diameter DA of the cavity 5c may be, for example, the same. For example, elements 3 having the same diameter DA have the same configuration of the element body 3a, and are driven by inputting drive signals having the same waveform (shape and size) to each other, and have the same amplitudes as each other. May occur. However, as described above, the diameters DA that are equivalent to each other do not have to be exactly the same, and there may be a difference in the amplitudes that are equivalent to each other with the corresponding magnitudes. Further, for example, the elements 3 having the same diameter DA generate the same amplitudes as each other when one ultrasonic wave is received together, and thus generate the same electric signals as each other. However, unlike the above description, for example, the elements 3 having the same diameter DA may vibrate with different amplitudes by inputting different drive signals.

The amplitudes of the plurality of elements 3 having different diameters DA of the cavities 5c (the plurality of elements 3 classified into the plurality of element groups 4 different from each other) may be, for example, equal to each other or different from each other. .. In the latter case, the amplitude of the element 3 having a relatively large diameter DA may be larger, equal to, or smaller than the amplitude of the element 3 having a relatively small diameter DA.

FIG. 5 is a schematic diagram showing an example of changes in vibration of a plurality of (two) elements 3 having different diameters of the cavities 5c with time. In this figure, the horizontal axis t represents time. The vertical axis Dis indicates the position in the D3 direction. The waveforms shown by the lines LL and LS indicate the displacement (that is, vibration) of the central portion of the element body 3a in the D3 direction. The element 3 that produces vibration indicated by the line LL has a larger diameter DA than the element 3 that produces vibration indicated by the line LS.

As described above, the larger the diameter DA of the cavity 5c, the lower the resonance frequency of the element 3. As a result, when transmitting or receiving ultrasonic waves, the vibration frequency of the element 3 (wire LL) having a relatively large diameter DA is higher than the vibration frequency of the element 3 (wire LS) having a relatively small diameter DA. It's getting low. Further, in the illustrated example, the amplitude AL of the element 3 having a relatively large diameter DA is larger than the amplitude AS of the element 3 having a relatively small diameter DA.

As in the illustrated example, when the amplitude of the element 3 in which the diameter DA of the cavity 5c is relatively large is relatively large, the method for realizing the amplitude may be appropriate. For example, it may be realized by the configuration of a plurality of elements 3 and / or may be realized by a drive signal. Specifically, for example, it is as follows.

The element body 3a of the element 3 having a relatively large diameter DA generally has a portion having a constant thickness (a portion excluding the tapered surface of the piezoelectric body 19) with respect to the element body 3a of the element 3 having a relatively small diameter DA. It has a shape stretched in the plane direction. In other words, both configurations are equivalent in the thickness direction. Therefore, for example, when a constant load is applied to the element body 3a, the element body 3a of the element 3 having a relatively large diameter DA causes bending deformation more than the element body 3a of the element 3 having a relatively small diameter DA. Cheap.

Therefore, for example, a drive signal having the same waveform (shape and size) of a plurality of elements 3 having different diameters DA may be input. Then, due to the difference in the susceptibility to bending deformation, the amplitude of the element 3 having a relatively large diameter DA may be increased with respect to the amplitude of the element 3 having a relatively small diameter DA. Further, consider a case where a plurality of elements 3 having different diameters DA receive one ultrasonic wave together. At this time, the amplitude of the element 3 having a relatively large diameter DA may be increased with respect to the amplitude of the element 3 having a relatively small diameter DA due to the difference in the susceptibility to bending deformation.

The amplitude is also affected by the difference between the frequency of the drive signal or the received ultrasonic wave and the resonance frequency of the element 3. Therefore, for example, a drive signal close to the resonance frequency of the element 3 having a relatively large diameter DA may be input to the plurality of elements 3. As a result, the amplitude of the element 3 having a relatively large diameter DA may be increased with respect to the amplitude of the element 3 having a relatively small diameter DA. Further, consider a case where ultrasonic waves are transmitted by a plurality of elements 3 having different diameters DA and the reflected waves are received by the above-mentioned plurality of elements 3. At the time of transmission, the amplitude of the element 3 having a relatively large diameter DA may be relatively large. In this case, in the power spectrum of the received ultrasonic wave, the power becomes relatively large at a frequency close to the resonance frequency of the element 3 having a relatively large diameter DA. In other words, the frequency of the received ultrasonic waves approaches the resonance frequency of the element 3 having a relatively large diameter DA. As a result, at the time of reception, the amplitude of the element 3 having a relatively large diameter DA may be increased with respect to the amplitude of the element 3 having a relatively small diameter DA.

In the experiments of the inventors, even if the configurations of a plurality of elements 3 having different diameter DAs in the thickness direction are equivalent to each other, the amplitude of the element 3 having a relatively large diameter DA is relatively small and the diameter DA is relatively small. It was confirmed that the amplitude was not always larger than that of the element 3. The reason is that, for example, when a plurality of elements 3 are arranged at a constant pitch regardless of the diameter of the elements 3, the larger the diameter of the elements 3, the greater the interference between the adjacent elements 3. Can be mentioned. Therefore, for example, by appropriately arranging the elements 3 having different diameter DAs, the amplitude of the element 3 having a relatively large diameter DA is larger than the amplitude of the element 3 having a relatively small diameter DA. It may be enlarged.

Further, for example, a plurality of elements 3 having different diameters DA have different configurations, whereby the amplitude of the element 3 having a relatively large diameter DA is larger than the amplitude of the element 3 having a relatively small diameter DA. May be enlarged. For example, in the element 3 having a relatively large diameter DA, the ratio of the diameter of the upper electrode 21 to the diameter DA may be larger than that of the element 3 having a relatively small diameter DA. In this case, when transmitting ultrasonic waves, a voltage is likely to be applied to the piezoelectric body 19 of the element 3 having a relatively large diameter DA, and by extension, the amplitude of the element 3 having a relatively large diameter DA becomes relatively large. Cheap.

Further, for example, by inputting drive signals different from each other to a plurality of elements 3 having relatively different diameters DA, the amplitude of the element 3 having a relatively large diameter DA and the element having a relatively small diameter DA are relatively small. It may be increased for an amplitude of 3. Specifically, for example, the amplitude of the drive signal input to the element 3 having a relatively large diameter DA is larger than the amplitude of the drive signal input to the element 3 having a relatively small diameter DA. You can do it. At this time, the frequencies of the drive signals having different amplitudes may be the same or different from each other. In the latter case, for example, the frequency of each drive signal may be set to approach the resonance frequency of the element 3 to which each drive signal is input.

(Cavity area ratio)
As described above, the total area of the cavities 5c obtained for each type of diameter DA (for each element group 4) may be appropriately set. However, as a result of diligent studies, the inventor of the present application has found an example of a range in which an advantageous effect can be obtained with respect to this total area. Specifically, it is as follows.

(Examples 1 to 4)
Devices 1 according to Examples 1 to 4 were produced. Each embodiment has four element groups 4 as in FIG. The diameter DA of each element group 4 is the same between Examples 1 to 4. Further, the total number of elements 3 is also the same between Examples 1 to 4. However, in Examples 1 to 4, the number of elements 3 for each element group 4 is different from each other. As a result, in Examples 1 to 4, the total area of the cavities 5c for each element group 4 is different from each other.

In Examples 1 to 4, the sizes of the diameters DA0 to DA3 of the four element groups 4 and the resonance frequencies of the element main body 3a corresponding to the sizes are as follows. Diameter DA0 = 16 μm (62 MHz), diameter DA1 = 20 μm (50 MHz), diameter DA2 = 25 μm (41 MHz), diameter DA3 = 30 μm (35 MHz).

FIG. 6A is a diagram for explaining the conditions relating to the total area of the cavities 5c in Examples 1 to 4.

In FIG. 6A, line C1 shows the conditions of Example 1. Line C2 shows the conditions of Example 2. Line C3 shows the conditions of Example 3. Line C4 shows the conditions of Example 4.

In FIG. 6A, the horizontal axis fr indicates the resonance frequency of the four element groups 4. As described above, the resonance frequencies of the four element groups 4 are set to 62 MHz, 50 MHz, 41 MHz, and 35 MHz due to the difference in diameter DA. To show this, in each of Examples 1 to 4 (lines C1 to C4), points are plotted at the above four frequencies.

In FIG. 6A, the vertical axis Sn / S0 indicates the ratio of the total area of the cavities 5c. Specifically, the total area S0 is the total area of the cavities 5c0 in the element group 4-0 having the smallest diameter DA. The total area Sn is the total area of the cavities 5c in the element groups 4-0, 4-1, 4-2 or 4-3. The vertical axis Sn / S0 indicates the ratio Sn / S0 of the above total area.

Therefore, for example, at the point where fr = 35 MHz and Sn / S0 = 0.6 to 0.7 on the line C1, in the first embodiment, the total area Sn of the cavity 5c3 in the element group 4-3 is the element. It is shown that the total area of the cavities 5c0 in the group 4-0 is 0.6 to 0.7 times the total area S0. Further, for example, since the area ratio Sn / S0 is based on the total area S0 of the element group 4-0, in any embodiment (any line C1 to C4), the element group 4-0 is used. The corresponding point located at fr = 62 MHz is located at Sn / S0 = 1.

As shown in FIG. 6A, in each embodiment, the area ratio Sn / S0 in the element group 4 other than the reference element group 4-0 was set to less than 1. That is, in each of the examples, the element group 4 having the largest total area of the cavities 5c was the element group 4-0 having the smallest diameter DA.

In each example, the area ratio Sn / S0 of the element groups 4-1, 4-2 and 4-3 were almost the same. For example, in Example 1 (wire C1), Sn / S0 is about 0.7 at any of 35 MHz (element group 4-1), 41 Hz (element group 4-2), and 50 Hz (element group 4-3). It was said. However, since the total area of the cavities 5c in each element group 4 changes stepwise (discontinuously) according to the increase or decrease in the number of elements 3, Sn / S0 is slightly deviated between the element groups 4. In the description of the present disclosure, for convenience, this deviation may be ignored and "about" in the value of Sn / S0 (for example, "about 0.7") may be omitted.

In the plurality of examples, the area ratios Sn / S0 of the element groups 4-1, 4-2 and 4-3 were different from each other. Specifically, the value of the area ratio Sn / S0 is as follows. Example 1: 0.7, Example 2: 0.35, Example 3: 0.15, Example 4: 0.05.

The ultrasonic pulse width was measured for each of the above four examples. The pulse width here is the time interval starting from the time when the pressure amplitude first exceeds the reference value and until the pressure amplitude returns to the reference value. The reference value is equal to the sum of 50% of the difference between the maximum pressure amplitude and the minimum pressure amplitude and the minimum pressure amplitude. More specifically, an ultrasonic wave was transmitted by inputting a drive signal composed of a spike wave whose frequency is sufficiently higher than the resonance frequency of the element group 4-0 to the device 1 according to the embodiment. Then, the reflected wave of the transmitted ultrasonic wave was received by the device 1 to obtain a waveform of the received voltage. The pulse width was measured by regarding this waveform as the waveform of the pressure amplitude.

FIG. 6B is a diagram showing the results of measuring the pulse width as described above.

In this figure, the horizontal axis Sn / S0 corresponds to the vertical axis Sn / S0 in FIG. 6A. From another viewpoint, it corresponds to Examples 1 to 4. Therefore, the measurement results corresponding to each example are plotted at Sn / S0 = 0.7, 0.35, 0.15 and 0.05. The vertical axis Wp indicates the pulse width (ns). The line L1 is an approximate straight line connecting the plots according to the first to fourth embodiments.

When the area ratio of the other element group 4 to the element group 4-0 having the minimum diameter DA0 is increased from around 0 (see the range of Sn / S0 = 0.05 to 0.15), the pulse is generated. The width Wp becomes shorter. However, as the area ratio of the other element group 4 is further increased (see the range of Sn / S0 = 0.15 to 0.7), on the contrary, the pulse width Wp becomes longer. From this, it can be seen that there is a range of the area ratio Sn / S0 in which the pulse width Wp can be effectively shortened.

The reasons for the above changes are, for example, the following. As is known, in mathematics, when a delta function (impulse function) is Fourier transformed to obtain a frequency spectrum, a function that takes a constant value regardless of frequency is obtained. As can be understood from this, a short pulse width Wp means that the power is close to a constant value over a wide frequency band. Then, by mixing the element 3 having a low resonance frequency (that is, having a large diameter DA), the power in the low frequency band can be improved and the pulse width Wp can be shortened. However, when the area ratio Sn / S0 is further increased, the power in the low frequency band becomes dominant, and the shape of the frequency spectrum in which the power is close to a constant value over a wide frequency band is destroyed. As a result, the pulse width Wp becomes long.

(Examples 5 to 7)
Devices 1 according to Examples 5 to 7 were produced, and the pulse width Wp was measured in the same manner as described above. In the following, the same items as in Examples 1 to 4 will be appropriately omitted.

FIG. 7 (a) is the same as FIG. 6 (a), and shows the conditions relating to the total area of the cavities 5c according to Examples 5 to 7. Lines C5 to C7 show the conditions of Examples 5 to 7, respectively.

In each of Examples 1 to 4, the number of element groups 4 was 4, whereas in each of Examples 5 to 7, the number of element groups 4 was 3. Specifically, Examples 5 to 7 have the element groups 4-0, 4-1 and 4-2 in Examples 1 to 4, and do not have the element group 4-3. In Examples 5 to 7, the values of the area ratio Sn / S0 are different from each other. Specifically, it is as follows. Example 5: 0.7, Example 6: 0.3, Example 7: 0.05.

FIG. 7 (b) is the same diagram as in FIG. 6 (b), and shows the measurement results of the pulse width Wp according to Examples 5 to 7. Line L2 is an approximate straight line connecting the plots according to Examples 5 to 7.

In Examples 5 to 7, the same tendency as in Examples 1 to 4 was confirmed. That is, when the area ratio of the other element group 4 to the element group 4-0 having the minimum diameter DA0 is increased from the vicinity of 0 (see the range of Sn / S0 = 0.05 to 0.3). , The pulse width Wp becomes shorter. However, as the area ratio of the other element group 4 is further increased (see the range of Sn / S0 = 0.3 to 0.7), on the contrary, the pulse width Wp becomes longer.

(Specific example of area ratio)
Based on the above-mentioned tendency, an example of the range of the area ratio Sn / S0 of the element group 4 other than the element group 4-0 will be given. In the following, for convenience, when the area ratio is simply referred to as Sn / S0, it may refer to the area ratio Sn / S0 of the element group 4 other than the reference element group 4-0.

In FIGS. 6 (b) and 7 (b), Examples 1 and 5 having the smallest area ratio Sn / S0 of the element group 4 other than the element group 4-0 have a pulse width as compared with the other examples. Wp is long. However, the pulse width Wp of Examples 1 and 5 is shorter than the pulse width Wp (not shown) of the comparative example in which the diameter DA of all the elements 3 is the minimum diameter DA0. Therefore, 0.05 can be mentioned as the lower limit of Sn / S0 that can shorten the pulse width Wp.

In FIGS. 6 (b) and 7 (b), the values (30 ns) of the pulse width Wp slightly shorter than the pulse width Wp of Examples 1 and 5 described above are indicated by the lines L5 and L6. The lines L1 and L2 connecting the plots according to the embodiment intersect with L5 and L6 when the area ratio Sn / S0 of the element group 4 other than the element group 4-0 is approximately 1.6. The value of the pulse width Wp on the lines L1 and L2 is smaller than the value of the pulse width Wp indicated by the lines L5 and L6 in the range where Sn / S0 is 1.6 or less. Therefore, 1.6 can be mentioned as the upper limit value of Sn / S0 that can shorten the pulse width Wp.

In summary, from the viewpoint of shortening the pulse width Wp, 0.05 or more and 1.6 or less can be mentioned as an example of the range of the area ratio Sn / S0 of the element group 4 other than the element group 4-0. In FIGS. 6 (b) and 7 (b), the range is shown by hatching.

Examples 1 to 4 and Examples 5 to 7 differ from each other in the number of element groups 4 other than the element group 4-0 having the minimum diameter DA0. Therefore, in Examples 1 to 4 and Examples 5 to 7, for example, even if the area ratio Sn / S0 is the same as each other, for example, the total of the element groups 4 other than the element group 4-0 with respect to the total area S0. The ratio of the sum of the areas Sn is different from each other. For example, the above ratio is (Sn × 3) / S0 in each of Examples 1 to 4, and (Sn × 2) / S0 in each of Examples 5 to 7. However, as can be understood from FIGS. 6 (b) and 7 (b), the above-mentioned range examples of 0.05 or more and 1.6 or less are applicable to both Examples 1 to 4 and Examples 1 to 3. Applicable.

From the above, the above range example of the area ratio Sn / S0 set based on FIGS. 6 (b) and 7 (b) from the viewpoint of shortening the pulse width Wp is the number of element groups 4 (diameter DA). It can be seen that it can be applied regardless of the number of types). Of course, it is expected that this is not the case if the number of element groups 4 is extremely large, but at least when the number of element groups 4 is 4 or less, it is shown by Examples that the number of element groups 4 is arbitrary. ing.

The number of element groups 4 to which the above range example of the area ratio Sn / S0 capable of shortening the pulse width Wp is applied is not the number itself, but all of the total area S0 in the element group 4-0 having the minimum diameter DA0. It may be considered by the ratio S0 / Ss to the total area (referred to as Ss) of the cavity 5c in the element 3. For example, among Examples 1 to 7, the ratio S0 / Ss is the smallest in Example 1. The ratio S0 / Ss in Example 1 is S0 / (S0 × 0.7 × 3 + S0) = 10/31 = about 0.3. Therefore, in an embodiment in which the number of elements 3 for each element group 4 is set so that the total area S0 occupies 30% or more of the total area Ss, the range example of the area ratio Sn / S0 may be applied.

Contrary to the above, it is also possible to consider the upper limit value of the ratio S0 / Ss to which the above range example of the area ratio Sn / S0 that can shorten the pulse width Wp is applied. For example, among Examples 1 to 7, the ratio S0 / Ss is maximized in Example 7. The ratio S0 / Ss in Example 7 is S0 / (S0 × 0.05 × 2 + S0) = 10/11 = about 0.9. Therefore, in an embodiment in which the number of elements 3 for each element group 4 is set so that the total area S0 is 90% or less of the total area Ss, the range example of the area ratio Sn / S0 may be applied.

In each of Examples 1 to 7, the area ratio Sn / S0 was set to be the same among the element groups 4 other than the element group 4-0 having the minimum diameter DA. However, even if the area ratio Sn / S0 is different between the element groups 4 other than the element group 4-0, the area ratio Sn / S0 of all the element groups 4 other than the element group 4-0 is within the above range. If it fits, it is clear that the pulse width Wp can be shortened.

As described above, the area ratio Sn / that can shorten the pulse width Wp in Examples 1 to 4 and Examples 5 to 7 in which the numbers of the element groups 4 other than the element group 4-0 having the minimum diameter DA0 are different from each other. The range of S0 is equivalent. From this, it can be considered that the influence of the area ratio Sn / S0 of some of the element groups 4 among the element groups 4 other than the element group 4-0 on the pulse width Wp is limited. Therefore, when there are a plurality of element groups 4 other than the element group 4-0, the area ratio Sn / S0 in some of the element groups 4 falls within the above range example unless it takes an extremely large value. It does not have to be. From the opposite viewpoint, the area ratio Sn / S0 may fall within the above range example only in a part of the element group 4.

As a range of the area ratio Sn / S0 that can shorten the pulse width Wp, an example of a range narrower than the above range example (0.05 or more and 1.6 or less) can be mentioned. For example, 1 can be mentioned as the upper limit value of the range example. That is, the total area Sn of the element group 4 other than the element group 4-0 may be smaller than the area S0 of the element group 4-0. In other words, 0.05 or more and less than 1 can be mentioned as a range example. As described above, among the element groups 4 other than the element group 4-0 having the minimum diameter DA0, the element group 4 satisfying the area ratio Sn / S0 <1 is, for example, a part of the element group 4. It may be all element groups 4. In other words, among the plurality of element groups 4 (for example, the element group 4 having two or more elements 3), the element group 4 having the largest total area Sn of the cavity 5c is the element group 4- having the smallest diameter DA0. It may be 0.

As described above, in FIGS. 6 (b) and 7 (b), the pulse width Wp is such that the area ratio Sn / S0 of the element group 4 other than the element group 4-0 is larger than 0.35 or 0.3. When the area ratio Sn / S0 reaches about 1.6, the pulse width Wp becomes the length indicated by the line L5 or L6. Therefore, if the upper limit of the area ratio Sn / S0 is reduced to 1 as described above, the effect of shortening the pulse width Wp is expected to be improved.

An example of the range of the area ratio Sn / S0 in which the pulse width Wp can be shortened can be specified from another viewpoint. For example, in FIGS. 6 (b) and 7 (b), the pulse width Wp becomes longer as the area ratio Sn / S0 of the element group 4 other than the element group 4-0 increases from 0.35 or 0.3. This means that the pulse width Wp as the ratio S0 / Ss of the total area S0 of the cavities 5c in the element group 4-0 having the minimum diameter DA0 to the total area Ss of the cavities 5c in all the elements 3 becomes smaller. Is to be longer. Therefore, the pulse width Wp can be further shortened by setting the lower limit value of the ratio S0 / Ss.

For example, in FIG. 6B, when the area ratio Sn / S0 is 0.35 (Example 2), the ratio S0 / Ss is S0 / (S0 × 0.35 × 3 + S0) = 1 / 2.05 = about. It is 0.5. Further, in FIG. 7B, when the area ratio Sn / S0 is 0.3 (Example 6), the ratio S0 / Ss is S0 / (S0 × 0.3 × 2 + S0) = 1 / 1.6 = about. It is 0.6. Therefore, 0.5 can be exemplified as the lower limit of the ratio S0 / Ss. In other words, the pulse width Wp can be further shortened by setting the total area S0 of the element group 4-0 having the minimum diameter DA0 to half or more of the total area Ss of the entire plurality of elements 3.

As described above, the ultrasonic device 1 according to the present embodiment has a first surface (upper surface 1a) and a plurality of elements 3 arranged along the upper surface 1a. Each of the plurality of elements 3 has a cavity 5c, a lower electrode 17 located on the upper surface 1a side with respect to the cavity 5c, a piezoelectric body 19 located on the upper surface 1a side with respect to the lower electrode 17, and a piezoelectric body. It has an upper electrode 21 located on the upper surface 1a side with respect to the body 19. The plurality of elements 3 include two or more types of elements 3 in which the diameter DAs of the cavities 5c are different from each other.

The resonance frequencies of the two or more types of elements 3 are different from each other because the diameter DAs of the cavities 5c are different from each other. As a result, the bandwidth of the transmitted and / or received ultrasonic waves can be widened. By widening the band, for example, the sound pressure of the low frequency component can be increased and the penetrating power can be improved. Further, the pulse width Wp can be shortened by widening the bandwidth. By shortening the pulse width Wp, for example, the probability that reflected waves from reflecting surfaces having different distances from the device 1 will be combined is reduced, and so-called distance resolution is improved.

If the diameters of the plurality of cavities 5c are different from each other, the shapes of the plurality of cavities 5c may be slightly different due to manufacturing errors. In this case, unlike the present embodiment, in the embodiment in which the cavity 5c is interposed between the lower electrode 17 and the piezoelectric body 19, the difference in the shape of the plurality of cavities 5c is caused by the lower electrode 17 and the upper electrode 21. There is a possibility of affecting the electric field applied to the piezoelectric body 19. That is, the difference in the diameter of the cavity 5c may affect properties other than the resonance frequency of the element body 3a. In the present embodiment, since the lower electrode 17, the piezoelectric body 19, and the upper electrode 21 are located on the cavity 5c, the probability that such an inconvenience will occur can be reduced.

Further, in the present embodiment, the plurality of elements 3 have a plurality of element groups 4. Each element group 4 is composed of two or more elements 3 having the same diameter DA of the cavity 5c. The element group 4 having the largest total Sn of the area of the cavity 5c in each element group 4 is the element group 4-0 having the smallest diameter DA of the cavity 5c.

In this case, for example, as described with reference to FIGS. 6 (b) and 7 (b), the area ratio Sn / S0 of each of one or more element groups 4 other than the element group 4-0 is less than 1. Therefore, the pulse width Wp can be effectively shortened.

Further, in the present embodiment, the total area S0 of the cavity 5c in the element group 4-0 having the smallest diameter DA of the cavity 5c is more than half of the total Ss of the area of the cavity 5c in the entire plurality of elements 3.

In this case, for example, as described with reference to FIGS. 6 (b) and 7 (b), the area ratio Sn / S0 of each of one or more element groups 4 other than the element groups 4-0 is relatively small. The effect of shortening the pulse width Wp is improved.

Further, in the present embodiment, the total area S0 of the cavity 5c in the element group 4-0 having the smallest diameter DA of the cavity 5c is 10/11 or less of the total Ss of the total area of the cavity 5c in the entire plurality of elements 3. ..

In this case, for example, as described with reference to FIGS. 6 (b) and 7 (b), the effect of mixing the element group 4 having a relatively large diameter DA with respect to the element group 4-0 is significant. It is easy to appear in size.

The difference in diameter DA of the cavity 5c between the elements 3 belonging to the same element group 4 is less than 4 μm.

From another point of view, the difference between the representative values (for example, the average value or the median value) of the diameter DAs in the plurality of element groups 4 having different diameter DAs is 4 μm or more. Therefore, for example, the effect of providing a plurality of elements 3 having different diameters DA is likely to appear with a significant magnitude.

<Example of detailed membrane shape>
An example of the detailed shape of the membrane 11 will be described below.

(Slope of piezoelectric body)
As described above, the side surface of the piezoelectric body 19 may or may not have a slope 19a, and the shape and inclination angle of the slope 19a are arbitrary. Below, an example of the detailed shape of the slope 19a is shown. In the following description, an embodiment in which the slope 19a is the entire side surface of the piezoelectric body 19 will be taken as an example. Therefore, the slope 19a is synonymous with the side surface of the piezoelectric body 19.

FIG. 8 is an enlarged view of region VIII of FIG.

The side surface (slope 19a) of the piezoelectric body 19 has a first region 19aa and a second region 19ab located above the first region 19aa. The inclination angle θ2 of the second region 19ab is larger than the inclination angle θ1 of the first region 19aa. The inclination angles (θ1 and θ2) referred to here are, for example, angles with respect to the upper surface 5a (FIG. 2) of the support substrate 5, the upper surface of the vibrating layer 16, and / or the lower surface of the piezoelectric body 19. In the following, the upper surface 5a may be used as a representative of the reference surface having such an inclination angle. By providing the first region 19aa and the second region 19ab having different inclination angles from each other, the robustness (robustness) of the device 1 can be improved, for example, as will be described later.

The slope 19a may have three or more slopes having different inclination angles from each other (the shape may be such that it can be grasped as such). In the description of the present embodiment, an embodiment in which the slopes 19a have two slopes having different inclination angles (which can be macroscopically grasped as such) is taken as an example. From another aspect, in the present embodiment, the lower edge of the lower first region 19aa constitutes the lower edge of the slope 19a, the upper edge of the upper second region 19ab constitutes the upper edge of the slope 19a, and the first Take, for example, an embodiment in which the upper edge of the region 19aa and the lower edge of the second region 19ab coincide with each other (which can be macroscopically grasped as such).

The size of the first region 19aa and the inclination angle θ1 may be appropriately set. In the first region 19aa, the length from the lower edge to the upper edge thereof is, for example, relatively short. For example, a cross section as shown in FIG. 8 (for example, a cross section orthogonal to the upper surface 5a of the support substrate 5 and passing through the center of the piezoelectric body 19 and / or a cross section orthogonal to the upper surface 5a and including the normal of the slope 19a). In the above, attention is paid to the length parallel to the upper surface 5a or the length along the slope 19a. At this time, the length of the first region 19aa may be less than 1/2, less than 1/3, or less than 1/4 of the length of the slope 19a (in another viewpoint, the entire side surface of the piezoelectric body 19). The inclination angle θ1 may be, for example, 30 ° or less, 20 ° or less, or 10 ° or less. The first region 19aa may have a linear shape, a concave shape and / or a convex curved shape, or may have unevenness or a step in the cross section as shown in FIG. .. The lower limit of the inclination angle θ1 is not particularly limited. It suffices if it can be confirmed that the first region 19aa is inclined with respect to the upper surface 5a. However, the inclination angle θ1 may be 1 ° or more, 3 ° or more, or 5 ° or more.

The size of the second region 19ab and the inclination angle θ2 may also be set as appropriate. In the present embodiment, the second region 19ab is the remainder of the slope 19a excluding the first region 19aa, so the description of the size is the reverse of the above description of the size of the first region 19aa. As a confirmation, when focusing on the length parallel to the upper surface 5a of the support substrate 5 in the cross section as shown in FIG. 8 or the length along the slope 19a, the length of the second region 19ab is the slope 19a ( From another viewpoint, the length of the entire side surface of the piezoelectric body 19) may be 3/4 or more, 2/3 or more, or 1/2 or more. Further, the inclination angle θ2 may be 10 ° or more, 20 ° or more, 30 ° or more, or 40 ° or more on the assumption that the inclination angle θ2 is larger than, for example, the inclination angle θ1. Similar to the first region 19aa, the second region 19ab may be linear, concave and / or convex curved in the cross section as shown in FIG. 8, and may be uneven or uneven. It may have a step. The upper limit of the inclination angle θ2 is not particularly limited. It suffices if it can be confirmed that the second region 19ab is inclined with respect to the upper surface 5a. However, the inclination angle θ2 may be 80 ° or less, 70 ° or less, or 60 ° or less.

In the cross section as shown in FIG. 8, when either the first region 19aa and the second region 19ab are not linear, the inclination angle (θ1 and / or θ2) may be appropriately specified. For example, a relatively large number of tilt angles at points set at a constant pitch (interval) on each region may be obtained, and the average value thereof may be used as the tilt angle. Further, an approximate straight line for a relatively large number of appropriately distributed points on each region may be obtained, and the inclination angle of this approximate straight line may be used. When specifying the average value or the approximate straight line, the singular portion (for example, near the boundary between the first region 19aa and the second region 19ab) may be excluded from consideration. The number of points on each region when the average value and the approximate straight line are obtained may be appropriately set so that the fluctuation of the inclination angle due to the increase or decrease in the number of the points is sufficiently small.

The upper limit of the length of the first region 19aa described above and / or the lower limit of the length of the second region 19ab described above are when the slope 19a constitutes only a part of the side surface of the piezoelectric body 19. It may be used as an upper limit value and / or a lower limit value with respect to the length of the slope 19a or the length of the entire side surface of the piezoelectric body 19. Further, the above upper limit value and / or lower limit value may be used as an upper limit value and / or a lower limit value when the slope 19a includes a slope other than the first region 19aa and the second region 19ab. The above upper limit value and lower limit value may be appropriately combined as long as there is no contradiction. For example, 1/4 or less of the first region 19aa and 1/2 or more of the second region 19ab may be combined.

The difference between the inclination angle θ1 of the first region 19aa and the inclination angle θ2 of the second region 19ab may be appropriately set. For example, the difference between the two may be 10 ° or more, 20 ° or more, or 30 ° or more. Further, for example, the difference between the two may be 1 time or more, 2 times or more, or 3 times or more the inclination angle θ1. The first region 19aa and the second region 19ab can be clearly distinguished from each other, for example, in the cross section as shown in FIG. 8 from the difference in the inclination angles thereof. However, in the vicinity of the boundary between the two (a relatively narrow range located between the two), the corners of the two may be chamfered and the boundary between the two may be ambiguous.

(Positional relationship between the slope of the piezoelectric body and other components)
When the upper surface 5a of the support substrate 5 is viewed through a plane, most or all of the outer edge (in another viewpoint, the lower edge of the first region 19aa) of the piezoelectric body 19 (for example, 90% or more of the total length) is the cavity 5c (FIG. It may be located outside of 2), may overlap the contour of the cavity 5c, or may be contained within the cavity 5c. In the present embodiment, as shown in FIG. 2, a mode in which most or all of the outer edge of the piezoelectric body 19 is located outside the cavity 5c is taken as an example. In another aspect, this aspect is an aspect in which the slope 19a is located directly above the contour of the cavity 5c.

It may be the first region 19aa or the second region 19ab that is located directly above the contour of the cavity 5c (most (for example, 90% or more of the total length) or all of it; the same applies hereinafter). It is also good. As can be understood from the comparison between FIGS. 2 and 8, in the present embodiment, an embodiment in which the second region 19ab is located directly above the contour of the cavity 5c is taken as an example. When viewed in plan or in cross section, the contour of the cavity 5c may overlap at an appropriate position between the lower edge and the upper edge of the second region 19ab. For example, the contour of the cavity 5c is such that the distance from the lower edge of the second region 19ab is the length of the second region 19ab (the length parallel to the upper surface 5a of the support substrate 5 or the length along the second region 19ab). It may be located in a range of 1/5 or more and 4/5 or less of.

The insulating film 27 extends from the outside of the piezoelectric body 19 in a plan view or a cross-sectional view to the slope 19 a of the piezoelectric body 19. From another point of view, it covers the lower edge of the slope 19a of the piezoelectric body 19. As a result, for example, when the lower electrode 17 is intentionally or due to an error and is exposed from the lower edge of the slope 19a, there is a possibility that the lower electrode 17 and the upper wiring 25 (in another viewpoint, the upper electrode 21) are short-circuited. It will be reduced.

In the cross section as shown in FIG. 8, the width of the insulating film 27 covering the slope 19a may be appropriately set. For example, the insulating film 27 may cover a part or all of the first region 19aa, while the insulating film 27 may not cover the second region 19ab. Further, for example, the insulating film 27 may cover the entire first region 19aa and a part or all of the second region 19ab, while not covering the upper surface of the piezoelectric body 19. Further, for example, the insulating film 27 may cover the entire slope 19a and a part (outer peripheral portion) of the upper surface of the piezoelectric body 19. In the illustrated example, the insulating film 27 covers the entire first region 19aa and a part of the second region 19ab. That is, the insulating film 27 extends from the outside of the piezoelectric body 19 in a plan view or a cross-sectional view to the middle of the second region 19ab.

The insulating film 27 is, for example, a so-called conformal layer, and the unevenness of the piezoelectric body 19 is reflected on the upper surface thereof. For example, the upper surface of the insulating film 27 has a higher region located on the slope 19a of the piezoelectric body 19 than a region located outside the piezoelectric body 19 in plan perspective or cross-sectional view. At this time, the region on the slope 19a of the insulating film 27 has two regions having different inclination angles, reflecting the difference between the inclination angle θ1 of the first region 19aa and the inclination angle θ2 of the second region 19ab. It may or may not have such two regions (illustrated example). Unlike the illustrated example, the insulating film 27 is made relatively thick with respect to the thickness of the piezoelectric body 19 (for example, the thickness is equal to the thickness of the piezoelectric body 19), and the upper surface is the upper surface 5a of the support substrate 5. It may be approximately parallel to.

Since the upper wiring 25 extends from the outside of the piezoelectric body 19 in a plan view or a cross-sectional view to the upper electrode 21 located on the upper surface of the piezoelectric body 19, naturally, it is on the slope 19a of the piezoelectric body 19 (first region). It goes through on 19aa and on the second region 19ab). As described above, the functional body layer 8 may or may not be provided with the insulating film 27, and the size of the insulating film 27 is arbitrary. Therefore, when the upper wiring 25 passes over the first region 19aa and the second region 19ab, a part or all of the upper wiring 25 does not have to directly overlap with these regions, or overlaps with each other. You may. Further, the portion of the upper wiring 25 located outside the piezoelectric body 19 may overlap with an appropriate member, for example, a part or the whole may overlap with the vibrating layer 16, or a part or the whole may overlap. It may overlap with the insulating film 27.

The upper wiring 25 is, for example, a so-called conformal layer, and the unevenness formed by the piezoelectric body 19 and / or the insulating film 27 is reflected on the upper surface thereof. For example, the upper surface of the upper wiring 25 has a higher region located on the upper surface of the piezoelectric body 19 than a region located outside the piezoelectric body 19 in plan perspective or cross-sectional view. Further, the region of the upper surface of the upper wiring 25 on the slope 19a of the piezoelectric body 19 gradually becomes higher as it approaches the upper electrode 21. This gradually increasing region reflects the difference between the inclination angle θ1 of the first region 19aa and the inclination angle θ2 of the second region 19ab, or reflects the shape of the upper surface of the insulating film 27 reflecting the difference. Therefore, it may or may not have two regions having different inclination angles.

(Tapered surface of electrode)
FIG. 9A is an enlarged view of the region IXa of FIG. FIG. 9B is an enlarged view of the area IXb of FIG.

As shown in these figures, the side surface of the upper electrode 21 may have an upper tapered surface 21a that is inclined toward the upper surface side of the upper electrode 21 in a direction in which the upper electrode 21 is reduced in diameter. In the following, an embodiment in which all the side surfaces of the upper electrode 21 are formed by the upper tapered surface 21a (which can be macroscopically grasped as such) will be taken as an example. Similarly, the side surface of the lower electrode 17 may have a lower tapered surface 17a that inclines in a direction that reduces the diameter toward the upper surface side of the lower electrode 17. In the following, an embodiment in which all the side surfaces of the lower electrode 17 are formed by the lower tapered surface 17a (which can be macroscopically grasped as such) will be taken as an example.

The inclination angle θ5 of the upper tapered surface 21a and the inclination angle θ6 of the lower tapered surface 17a may be larger than the other or equal to each other. The inclination angle θ5 is, for example, an angle with respect to the upper surface 5a (FIG. 2) of the support substrate 5 and / or the upper surface of the piezoelectric body 19. The inclination angle θ6 is, for example, an angle with respect to the upper surface 5a and / or the upper surface of the vibrating layer 16 (the lower surface of the piezoelectric body 19). In the following, the upper surface 5a may be used as a representative of the reference surface having such an inclination angle.

In the illustrated example, the tilt angle θ5 is smaller than the tilt angle θ6. The specific size of each inclination angle and the difference between the two inclination angles may be appropriately set. For example, the inclination angle θ5 may be 60 ° or less or 50 ° or less. The inclination angle θ6 may be 50 ° or more or 60 ° or more, provided that it is larger than the inclination angle θ5. The difference between the two may be 10 ° or more or 20 ° or more. Like the slope 19a, the upper tapered surface 21a and the lower tapered surface 17a may have a linear shape, a concave shape, and / or a convex curved shape in a cross section as shown in the drawing. .. The method for specifying the inclination angles θ5 and θ6 when the tapered surface is not straight may be the same as the method for specifying the inclination angles θ1 and θ2 when the slope 19a is not linear.

As described above, the thickness of the lower electrode 17 and the thickness of the upper electrode 21 may be the same as or different from each other, and in FIGS. 8, 9 (a) and 9 (b), , An example of the latter is shown. The length from the lower edge to the upper edge of each tapered surface is determined by the thickness of each electrode and the inclination angle of the tapered surface. With respect to the length, either the upper tapered surface 21a or the lower tapered surface 17a may be longer.

The positional relationship between the upper tapered surface 21a and other components (for example, the cavity 5c) and the positional relationship between the lower tapered surface 17a and other components (for example, the cavity 5c) may be appropriately set. As can be understood from the comparison of FIGS. 2 and 8, in the present embodiment, at least a part (in the present embodiment) of the upper tapered surface 21a overlaps the cavity 5c in the plan perspective of the upper surface 5a of the support substrate 5. Is located. Further, at least a part (in the present embodiment) of the lower tapered surface 17a is located outside the cavity 5c in the plan perspective of the upper surface 5a.

(Manufacturing method of a device in which the piezoelectric material has a slope)
The manufacturing method of the device 1 in which the piezoelectric body 19 has the slope 19a may be roughly an application of a known manufacturing method or a known manufacturing method. For example, the lower electrode 17, the piezoelectric body 19, the upper electrode 21, and the like may be formed by repeating the formation and patterning of a thin film on at least the wafer constituting the support substrate 5. After that, a plurality of devices 1 may be obtained by dicing the wafer.

However, unlike the conventional case, for example, when the piezoelectric layer is etched to form the piezoelectric body 19, the etching conditions may be changed in the middle. For example, the etching rate is lowered in the middle of etching. Examples of the method of lowering the etching rate include a method of lowering the voltage applied to the etching gas and a method of changing the component ratio of the etching gas. In this way, when the etching rate is relatively high, the second region 19ab having a relatively large inclination angle (θ2) is formed, and when the etching rate is relatively low, the inclination angle (θ1) is compared. A small first region 19aa is formed.

Further, the difference between the inclination angle θ5 of the upper electrode 21 and the inclination angle θ6 of the lower electrode 17 may be realized by, for example, the difference in the etching rate as described above. Further, for example, the upper electrode 21 may be patterned by just etching and the lower electrode 17 may be patterned by over-etching to make the inclination angles of the two different. In this case, other etching conditions (including the etching rate) may be the same for both electrodes.

As described above, in the present embodiment, the ultrasonic device 1 has a cavity layer (support substrate 5) and an element main body 3a of the ultrasonic element 3. The support substrate 5 has an upper surface 5a and a cavity 5c that is open to the upper surface 5a. The element body 3a overlaps the upper surface 5a, and the resonance frequency of the out-of-plane vibration on the cavity 5c is within the ultrasonic frequency band. Further, the element body 3a has a piezoelectric body 19. The side surface of the piezoelectric body 19 has a slope 19a that is inclined toward the upper surface 5a side in a direction in which the piezoelectric body 19 increases in diameter. The slope 19a has a first region 19aa and a second region 19ab. The second region 19ab is located on the opposite side of the upper surface 5a with respect to the first region 19aa, and the inclination angle θ2 with respect to the upper surface 5a is larger than the inclination angle θ1 with respect to the upper surface 5a of the first region.

The fact that the piezoelectric body 19 has a slope 19a means that the piezoelectric body 19 has a thin portion on the outer peripheral side from another viewpoint. Therefore, for example, the piezoelectric body 19 is likely to be bent and deformed on the outer peripheral side portion thereof, and thus is likely to cause out-of-plane vibration on the cavity 5c. As a result, the voltage when the received ultrasonic wave is converted into an electric signal is increased with respect to the sound pressure of the ultrasonic wave, and / or the sound pressure when the electric signal is converted into an ultrasonic wave and transmitted is converted into a voltage. On the other hand, it can be made larger. Then, by providing the first region 19aa having a relatively small inclination angle on the lower edge side of the slope 19a, for example, the outer peripheral portion of the piezoelectric body 19 and the outer peripheral portion of the piezoelectric body 19 are maintained while maintaining the above effects. The contact area with the layer immediately below (lower electrode 17 or vibrating layer 16) can be increased. As a result, for example, the stress generated by the flexural vibration can be dispersed. As a result, the robustness of the device 1 can be improved.

In the present embodiment, the inclination angle θ1 of the first region 19aa with respect to the upper surface 5a of the support substrate 5 may be 10 ° or less.

In this case, for example, since the inclination angle θ1 is sufficiently small, the above effect is improved. Further, in the literature disclosing the tapered piezoelectric body, such a relatively small inclination angle is not disclosed. Therefore, it is clear that the specific action expected of the slope and the first region 19aa in the prior art is different.

In the present embodiment, the device 1 is a layered wiring (upper wiring 25) extending in order from the outside of the piezoelectric body 19 in a plan view or a cross-sectional view of the upper surface 5a of the support substrate 5 on the first region 19aa and the second region 19ab. ) Is further possessed.

In this case, for example, the angle at which the upper wiring 25 bends near the lower edge of the slope 19a is reduced as compared with the embodiment in which the first region 19aa is not provided. As a result, for example, stress concentration is less likely to occur in the upper wiring 25. As a result, the robustness of the device 1 is improved.

In the present embodiment, the device 1 extends from the outside of the piezoelectric body 19 in the plan view or the cross-sectional view of the upper surface 5a of the support substrate 5 to the middle of the second region 19ab via the first region 19aa, and is a piezoelectric body. It further has an insulating film 27 interposed between the 19 and the upper wiring 25.

In this case, for example, as described above, the insulation between the lower electrode 17 and the upper wiring 25 can be improved. Further, since the insulating film 27 extends to the middle of the second region 19ab (terminates in the middle), for example, the insulating film 27 extends over the entire slope 19a (this aspect also relates to the present disclosure). Compared with (which may be included in the technique), it is less likely that the above-mentioned effect due to the provision of the slope 19a on the side surface of the piezoelectric body 19 is reduced by the insulating film 27.

In the present embodiment, the second region 19ab is located directly above the edge of the cavity 5c.

Bending deformation of the membrane 11 is easily regulated at the edge of the cavity 5c, which is a theoretical fixed end, and its vicinity. By providing the slope 19a at such a position and lowering the bending rigidity of the piezoelectric body 19, for example, the above-mentioned effect of improving the amount of bending of the membrane 11 by the slope 19a is improved. Further, as compared with an embodiment in which the first region 19aa is located directly above the edge of the cavity 5c (the embodiment may also be included in the technique according to the present disclosure), for example, the volume of the piezoelectric body 19 on the cavity 5c. Is easy to secure. As a result, for example, from the viewpoint of increasing the voltage for converting the received ultrasonic wave into an electric signal and increasing the sound pressure when converting the electric signal into an ultrasonic wave and transmitting it, the volume of the piezoelectric body 19 is secured. , It is easy to balance with the reduction in the thickness of the piezoelectric body 19 just above the edge of the cavity 5c.

In the present embodiment, the element 3 further includes a lower electrode 17 that overlaps the piezoelectric body 19 on the upper surface 5a side of the support substrate 5, and an upper electrode 21 that overlaps the piezoelectric body 19 on the opposite side of the upper surface 5a. Have. The side surface of the upper electrode 21 may have a tapered surface (upper tapered surface 21a) that is inclined in a direction in which the upper electrode 21 expands in diameter toward the upper surface 5a side. Similarly, the side surface of the lower electrode 17 may have a tapered surface (lower tapered surface 17a) that is inclined toward the upper surface 5a side in a direction in which the lower electrode 17 expands in diameter. At this time, the inclination angle θ5 of the upper tapered surface 21a with respect to the upper surface 5a may be smaller than the inclination angle θ6 of the lower tapered surface 17a with respect to the upper surface 5a.

In this case, for example, a layer (for example, upper wiring 25) superimposed on each electrode is compared with a mode in which the side surface of each electrode is perpendicular to the upper surface 5a (the mode may also be included in the technique according to the present disclosure). ) Improves coverage. Here, for example, in the vicinity of the outer edge of the lower surface of the piezoelectric body 19, the first region 19aa having a relatively small inclination angle is provided, so that the upper wiring is higher than that in the vicinity of the outer edge of the upper surface of the piezoelectric body 19. Twenty-five bends have been eased. Therefore, by making the inclination angle θ5 of the upper portion smaller than the inclination angle θ6 of the lower portion, it is expected that the coverage is improved in both the vicinity of the outer edge of the upper surface and the vicinity of the outer edge of the lower surface of the piezoelectric body 19, for example.

In the present embodiment, at least a part of the upper tapered surface 21a overlaps the cavity 5c in the plan perspective of the upper surface 5a of the support substrate 5. At least a part of the lower tapered surface 17a is located outside the cavity 5c in the plan view of the upper surface 5a.

In this case, for example, the upper tapered surface 21a is more likely to cause stress concentration due to the out-of-plane vibration on the cavity 5c of the piezoelectric body 19 as compared with the lower tapered surface 17a. From another point of view, in the layer covering them (for example, the upper wiring 25), the portion on the cavity 5c is more likely to cause stress concentration than the outer portion of the cavity 5c. Therefore, by making the inclination angle on the side where stress concentration is likely to occur relatively small, it is easy to relax the stress concentration as a whole.

<Second Embodiment>
FIG. 10 is a plan perspective view showing a partial configuration of the ultrasonic device 401 according to the second embodiment.

From another point of view, the device 401 is an application example of the device 1 of the first embodiment, and includes all the configurations of the device 1 described above. Therefore, part or all of FIG. 10 may be regarded as a perspective perspective view of the device 1. FIG. 10 shows the lower electrode 17, the upper electrode 21, the lower wiring 23, and the upper wiring 25 in the configuration of the device 401 (1). In FIG. 10, the difference in diameter of the element 3 is not shown.

Further, in FIG. 10, a transmission unit 41 that outputs an electric signal (transmission signal, drive signal) to the plurality of elements 3 and a reception unit 43 that receives an electric signal (reception signal) from the plurality of elements 3 are also schematically shown. It is shown. The device 401 may be defined without including the transmitting unit 41 and the receiving unit 43, or may be defined including these.

As already mentioned, the ultrasonic device may be one that performs only one of transmission and reception of ultrasonic waves, or may be one that performs both. And the device 401 is the latter. Further, in the ultrasonic device that performs such transmission and reception, the transmission and reception of ultrasonic waves may be performed by the same element 3, or may be performed by a plurality of elements 3 that are different from each other. And the device 401 is the latter. In other words, the device 401 has a transmission element 3 (hereinafter, may be referred to as an element 3T) and a reception element 3 (hereinafter, may be referred to as “element 3R”). There is.

The number of transmission element 3T and reception element 3R and their positional relationship may be appropriately set. In the illustrated example, the device 401 has a plurality of elements 3T, and a part (but two or more) or all of the plurality of elements 3T are arranged together to form an element unit 31T for transmission. doing. Similarly, the device 401 has a plurality of elements 3Rs, and a part (but two or more) or all of the plurality of elements 3Rs are arranged together to form a receiving element unit 31R. .. FIG. 3 in the first embodiment may be regarded as a diagram showing the cavity 5c of the entire element portion 31T or the entire element portion 31R (however, the specific number of the elements 3 differs between FIGS. 3 and 10). ing.).

In the element unit 31T for transmission, the number and arrangement mode of the plurality of elements 3T may be appropriately set. In the illustrated example, as mentioned in the description of the first embodiment, the plurality of elements 3T are arranged vertically and horizontally at a constant pitch. Further, in the illustrated example, a 3 × 3 element 3T is shown. This is only an example, and the number of elements 3 may be smaller than this, may be larger, or may be different in length and width. The same applies to the number and arrangement mode of the plurality of elements 3R in the element unit 31R for reception. The number and arrangement of the elements 3 may be the same for the element unit 31T and the element unit 31R (illustrated example), or may be different from each other.

The specific positional relationship between the element unit 31T for transmission and the element unit 31R for reception may be appropriately set. In the illustrated example, the element 3T and the element 3R are arranged in series in the D1 direction (that is, the arrangement direction of the element portion 31T and the element portion 31R). Further, the distance between the element 3T and the element 3R that are adjacent to each other in the D1 direction is the same as the pitch of the element 3T and the pitch of the element 3R. That is, the plurality of elements 3T and the plurality of elements 3R are uniformly arranged as a whole. However, unlike the illustrated example, for example, the distance between the elements 3T and the element 3R adjacent to each other may be different from the pitch of the element 3T and / or the pitch of the element 3R, or the row of the elements 3T. The rows of the elements 3R may not be in series, and the positions of both rows in the D2 direction may be offset from each other.

In the element unit 31T for transmission, as described above, the plurality of lower electrodes 17 may or may not be connected to each other. Here, the former is illustrated. Specifically, in the illustrated example, the lower electrodes 17 adjacent to each other in the D2 direction are connected in series with each other by the lower wiring 23 extending in the D2 direction. These plurality of series lines are connected in parallel to each other by a lower merging wiring 24 extending in the D1 direction outside the region where the element portion 31T for transmission is arranged. The lower wiring 23 and the lower merging wiring 24 are composed of, for example, a conductor layer located on the vibrating layer 16. The same applies to the connection between the plurality of lower electrodes 17 in the receiving element unit 31R.

In the element unit 31T for transmission, as described above, the plurality of upper electrodes 21 may or may not be connected to each other. Here, the former is illustrated. Specifically, in the illustrated example, the upper electrodes 21 adjacent to each other in the D1 direction are connected in series with each other by the upper wiring 25 extending in the D1 direction. These plurality of series lines are connected in parallel to each other by an upper merging wiring 26 extending in the D2 direction outside the region where the element portion 31T for transmission is arranged. The same applies to the connection between the plurality of upper electrodes 21 in the receiving element unit 31R.

The transmission unit 41 is configured to include, for example, a power supply circuit that converts power from a commercial power supply or the like into power of an appropriate mode and outputs it, as indicated by a symbol indicating a power supply for convenience. For example, the power supply circuit generates and outputs a drive signal whose voltage changes with an appropriate waveform. The transmission unit 41 is connected to the lower merging wiring 24 and the upper merging wiring 26 connected to the element unit 31T for transmission. Then, the transmission unit 41 applies an electric signal having a waveform corresponding to the waveform of the ultrasonic wave to be generated to the lower electrode 17 and the upper electrode 21 of the element 3T for transmission via these wirings.

The receiving unit 43 is configured to include, for example, an amplifier that amplifies and outputs an input electric signal, as indicated by a symbol indicating an amplifier for convenience. The amplifier may be, for example, a voltage amplifier or a charge amplifier. The receiving unit 43 is connected to the lower merging wiring 24 and the upper merging wiring 26 connected to the element unit 31R for receiving. When ultrasonic waves are input to the receiving element 3T, the element 3T vibrates to generate an electric signal. This signal is input to the receiving unit 43 via the lower merging wiring 24 and the upper merging wiring 26.

As described above, the device 401 is configured to include the device 1 according to the first embodiment. The device 401 further has a driver (transmission unit 41) that drives the plurality of elements 3 by applying a voltage between the lower electrode 17 and the upper electrode 21 of each of the plurality of elements 3. The plurality of elements 3 include a first element (for example, element 3 of element group 4-0) and a second element (for example, element 3 of element group 4-2) having a larger diameter DA of the cavity 5c than the first element. Includes. As described in the first embodiment, when a plurality of elements 3 are driven by the transmission unit 41, the amplitude of the second element may be larger than the amplitude of the first element.

In this case, for example, it is easy to achieve the effect of mixing the element group 4-0 having a relatively small diameter DA with the element group 4-2 having a relatively large diameter DA. That is, the effect described in the first embodiment is improved.

<Application example>
FIG. 11 is a block diagram schematically showing the configuration of the ultrasonic diagnostic apparatus 101 as an application example of the ultrasonic device. Although the reference numeral of the device 401 is used here, an ultrasonic device having another configuration according to the present disclosure may be used for the ultrasonic diagnostic apparatus 101.

The ultrasonic diagnostic apparatus 101 is, for example, for IVUS. The ultrasonic diagnostic apparatus 101 includes, for example, a catheter 103 inserted into a patient's blood vessel and an apparatus main body 107 connected to the catheter 103.

The catheter 103 has, for example, a substantially tubular catheter body 103a and a device 401 housed in the catheter body 103a. The device 401 transmits ultrasonic waves to the outside of the catheter body 103a in the radial direction via the catheter body 103a, and receives the reflected waves thereof.

The device main body 107 has, for example, a transmission / reception unit 109 connected to the device 401 via a wiring (not shown) in the catheter main body 103a. The transmission / reception unit 109 may include, for example, at least a part of the transmission unit 41 and the reception unit 43 shown in FIG. 10, outputs a transmission signal to the transmission unit 41, and receives a reception signal from the reception unit 43. It may be one. The division of roles between the electrical configuration of the catheter 103 and the transmission / reception unit 109 may be appropriately set.

The apparatus main body 107 includes, for example, an input unit 111 that receives an operation of a user (for example, a doctor or a technician) and a control unit 113 that controls a transmission / reception unit 109 based on a signal from the input unit 111. Further, the apparatus main body 107 includes an image processing unit 115 that performs image processing based on a signal from the transmission / reception unit 109 and a signal from the control unit 113, and a display unit 117 that displays an image based on the signal from the image processing unit 115. (Display device) is provided. On the display unit 117, for example, a tomographic image of a patient (here, a cross-sectional image of a blood vessel) obtained by transmitting and receiving ultrasonic waves is displayed.

Although not particularly shown, the catheter 103 may have a mechanism for flexing the catheter body 103a or changing the orientation of the device 401 in the catheter body 103a. Further, the apparatus main body 107 may have a control unit corresponding to such a mechanism.

In the above embodiment, the upper surface 1a of the device 1 is an example of the first surface. The transmission unit 41 is an example of a driver. The display unit 117 is an example of a display device. The element 3 of the element group 4-0 is an example of the first element. The element 3 of the element group 4 other than the element group 4-0 is an example of the second element. The support substrate 5 is an example of a cavity layer. The upper surface 5a of the support substrate 5 is an example of the second surface. The upper tapered surface 21a is an example of the tapered surface of the upper electrode. The lower tapered surface 17a is an example of the tapered surface of the lower electrode.

The technique according to the present disclosure is not limited to the above embodiments, and may be implemented in various embodiments.

For example, ultrasonic devices are not limited to those used in medical devices. For example, an ultrasonic device may be used as a sensor for measuring a distance to an object, and such a sensor may be used in an imaging device and an automobile.

The ultrasonic device may not transmit ultrasonic waves to the first surface (upper surface 1a) side, but may transmit ultrasonic waves to the opposite side. As mentioned in the description of the embodiment, the element body has a lower electrode layer (common electrode) that extends substantially without gaps over the plurality of cavities 5c on the vibrating layer 16, and substantially extends over the plurality of cavities 5c. It may have a piezoelectric layer that spreads without gaps, and a plurality of upper electrodes 21 (individual electrodes) individually provided in the plurality of cavities 5c.

As already mentioned, the ultrasonic element is not limited to the unimorph type pMUT and may be a bimorph type pMUT. Further, in the embodiment, the vibrating layer is located on the cavity side with respect to the piezoelectric layer, but may be located on the opposite side of the cavity with respect to the piezoelectric layer. The cavity may be formed by a through hole formed in the support substrate instead of the recess formed in the support substrate. A recess may be formed on the lower surface of the support substrate, and a part of the upper surface side of the support member may be used as a vibration layer.

From the technology according to the present disclosure, it is possible to extract various concepts that do not require piezoelectric materials or the like. For example, the following concepts may be extracted.

(Concept 1)
It has a first surface and a plurality of elements arranged along the first surface.
Each of the plurality of elements has a cavity,
The plurality of elements have a plurality of element groups, and each element group is composed of two or more elements having the same cavity diameters.
The element group having the largest total area of the cavities in each element group is an ultrasonic device having the smallest diameter of the cavities.

Piezoelectric is not an essential requirement for the above ultrasonic devices. For example, the ultrasonic device may be a cMUT that does not have a piezoelectric body. Further, when the ultrasonic device has a piezoelectric body, the lower electrode, the piezoelectric body, and the upper electrode do not have to be located on the first surface side with respect to the cavity. For example, the cavity may be located between the lower electrode and the piezoelectric body.

Further, from the technology according to the present disclosure, the following concepts that do not assume that a plurality of elements are provided may be extracted.

(Concept 2)
A cavity layer having a predetermined surface (second surface) and a cavity open to the predetermined surface,
An element body that overlaps the predetermined surface and whose resonance frequency of out-of-plane vibration on the cavity is within the frequency band of ultrasonic waves.
Have and
The element body has a piezoelectric body and has a piezoelectric body.
The side surface of the piezoelectric body has a slope that is inclined toward the predetermined surface side in a direction in which the piezoelectric body expands in diameter.
The slope is
The first area and
It has a second region which is located on the opposite side of the predetermined surface with respect to the first region and whose inclination angle with respect to the predetermined surface is larger than the inclination angle with respect to the predetermined surface of the first region. There is an ultrasonic device.

In the above ultrasonic device, when a plurality of elements are provided, the sizes of the elements (diameters of the cavities) may be the same as each other.

1 ... Ultrasonic device, 1a ... Top surface (first surface), 3 ... Ultrasonic element, 4 (4-0, 4-1, 4-2 and 4-3) ... Element group, 5 ... Support substrate (cavity layer) ), 5c ... Cavity, 7 ... Functional layer, 11 ... Membrane, 13 ... Coating layer, 17 ... Lower electrode, 19 ... Piezoelectric, 21 ... Upper electrode, 41 ... Transmitter (driver), 101 ... Ultrasonic diagnostic device, 117 ... Display unit (display device).

Claims

It has a first surface and a plurality of elements arranged along the first surface.
Each of the plurality of elements
Cavity and
The lower electrode located on the first surface side with respect to the cavity and
A piezoelectric material located on the first surface side with respect to the lower electrode,
It has an upper electrode located on the first surface side with respect to the piezoelectric body, and has.
The plurality of elements are ultrasonic devices including two or more types of elements having different cavity diameters.
The plurality of elements have a plurality of element groups, and each element group is composed of two or more elements having the same cavity diameters.
The ultrasonic device according to claim 1, wherein the element group having the largest total area of the cavities in each element group is the element group having the smallest diameter of the cavity.
The ultrasonic device according to claim 2, wherein the total area of the cavities in the element group having the smallest cavity diameter is at least half the total area of the cavities in the entire plurality of elements.
The ultrasonic device according to claim 2 or 3, wherein the total area of the cavities in the element group having the smallest cavity diameter is 10/11 or less of the total area of the cavities in the entire plurality of elements.
The ultrasonic device according to any one of claims 2 to 4, wherein the difference in the diameters of the cavities between elements belonging to the same element group is less than 4 μm.
It further has a driver for driving the plurality of elements by applying a voltage between the lower electrode and the upper electrode of each of the plurality of elements.
The plurality of elements include a first element and a second element having a larger cavity diameter than the first element.
The ultrasonic device according to any one of claims 1 to 5, wherein the amplitude of the second element is larger than the amplitude of the first element when the plurality of elements are driven by the driver.
The ultrasonic device according to any one of claims 1 to 6, wherein the diameter of the upper electrode is 0.5 times or more and 1.1 times or less the diameter of the cavity.
A cavity layer having a second surface facing the first surface side from the cavity side and the cavity open to the second surface.
An element body that overlaps the second surface, includes the lower electrode, the piezoelectric body, and the upper electrode, and has a resonance frequency of out-of-plane vibration on the cavity within the ultrasonic frequency band.
Have and
The side surface of the piezoelectric body has a slope that is inclined toward the second surface side in a direction in which the piezoelectric body expands in diameter.
The slope is
The first area and
The second region is located on the first surface side with respect to the first region, and the inclination angle with respect to the second surface is larger than the inclination angle with respect to the second surface of the first region. The ultrasonic device according to any one of claims 1 to 7.
The ultrasonic device according to claim 8, wherein the inclination angle of the first region with respect to the second surface is 10 ° or less.
The ultrasonic device according to claim 8 or 9, further comprising a layered wiring extending in order from the outside of the piezoelectric body onto the first region and the second region.
A claim that extends from the outside of the piezoelectric body to the middle of the second region via the first region, and further has an insulating film interposed between the piezoelectric body and the wiring. Item 10. The ultrasonic device according to item 10.
The ultrasonic device according to any one of claims 8 to 11, wherein the second region is located immediately above the edge of the cavity.
The side surface of the upper electrode has a tapered surface that is inclined toward the second surface side in a direction in which the upper electrode expands in diameter.
The side surface of the lower electrode has a tapered surface that is inclined toward the second surface side in a direction in which the lower electrode expands in diameter.
The ultrasonic device according to any one of claims 8 to 12, wherein the inclination angle of the tapered surface of the upper electrode with respect to the second surface is smaller than the inclination angle of the tapered surface of the lower electrode with respect to the second surface. ..
The tapered surface of the upper electrode is located so that at least a part thereof overlaps the cavity.
The ultrasonic device according to claim 13, wherein at least a part of the tapered surface of the lower electrode is located outside the cavity.
The ultrasonic device according to any one of claims 1 to 14, and the ultrasonic device.
A display device that displays an image based on an electric signal from the ultrasonic device, and
Ultrasonic diagnostic equipment that has.