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DESCRIPTION JP2017163330

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DESCRIPTION JP2017163330
Abstract: An ultrasonic device, an ultrasonic module, and an ultrasonic measurement device
capable of improving distance resolution are provided. An ultrasonic device (22) has a vibrating
membrane (412) and is provided on an ultrasonic transducer (45) transmitting ultrasonic waves
from the first surface (412A) of the vibrating membrane (412), and provided on the first surface
(412A) of the vibrating membrane (412). The acoustic matching layer 43 includes the first layer
431, the first layer 413, and the acoustic matching layer 43, and the acoustic lens 44 provided
on the opposite side of the vibrating film 412 of the acoustic matching layer 43. The first layer
431 and the second layer 432 are disposed in order from the vibrating membrane 413 toward
the acoustic lens 44, and the first layer 431 is composed of an even layer including the second
layer 432 having an acoustic impedance smaller than that of the lens 44. The second layer 432
has a thickness that is an odd multiple of λ / 4 where λ is the wavelength of ultrasonic waves.
[Selected figure] Figure 4
Ultrasonic device, ultrasonic module, and ultrasonic measurement apparatus
[0001]
The present invention relates to an ultrasonic device, an ultrasonic module, and an ultrasonic
measurement apparatus.
[0002]
Conventionally, a piezoelectric device is known that includes a vibrating membrane and a
piezoelectric element provided on the vibrating membrane as a vibrator that vibrates the
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vibrating membrane (for example, Patent Document 1).
The piezoelectric device transmits an ultrasonic wave by driving the piezoelectric element to
vibrate the vibrating film, and receives the ultrasonic wave by detecting the vibration of the
vibrating film by the ultrasonic wave using the piezoelectric element.
[0003]
The piezoelectric device described in Patent Document 1 further includes an acoustic matching
layer provided on the vibrating film, and an acoustic lens provided on the acoustic matching
layer and having an acoustic impedance close to that of the living body to be measured. . The
piezoelectric device transmits and receives ultrasonic waves in a state where the acoustic lens is
in contact with a measurement target such as a living body. For example, ultrasonic waves
transmitted by driving of the piezoelectric element are output from the surface of the acoustic
lens into the living body after propagating through the acoustic matching layer and the acoustic
lens.
[0004]
JP, 2015-195351, A
[0005]
Here, as described above, in the configuration in which the acoustic matching layer and the
acoustic lens are laminated, a part of the ultrasonic waves transmitted from the vibrator
(hereinafter also referred to as a first wave) is measured from the acoustic lens The other part
may be reflected at the interface between the acoustic matching layer and the acoustic lens.
In this case, the interface reflection wave reflected at the interface is reflected to the acoustic lens
side by the vibrator and is output from the acoustic lens to the living body, so that the distance
resolution may be reduced.
[0006]
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That is, the interface reflected wave is emitted to the object to be measured with a delay
corresponding to the thickness of the acoustic matching layer with respect to the first wave.
Therefore, the first wave reflected by the measuring object and the interface reflected wave
reflected by the measuring object are detected at different timings. In this case, the reception
signal output when the ultrasonic device is received by the piezoelectric device has a so-called
tailing in which a peak corresponding to the interface reflected wave is detected in addition to
the peak corresponding to the first wave. There is a problem that the distance resolution
decreases.
[0007]
An object of the present invention is to provide an ultrasonic device, an ultrasonic module, and
an ultrasonic measurement apparatus as the following modes or applications that can improve
distance resolution.
[0008]
An ultrasonic device according to an application example includes an ultrasonic transducer that
has a vibrating film and transmits ultrasonic waves from the first surface side of the vibrating
film, and an acoustic wave provided on the first surface side of the vibrating film. A matching
layer, and an acoustic lens provided on the side of the acoustic matching layer opposite to the
vibrating film, wherein the acoustic matching layer includes a first layer, an acoustic impedance
more than the first layer, and the acoustic lens. And the first layer and the second layer are
disposed in order from the vibrating film toward the acoustic lens, and the first layer and the
second layer are The thickness of the ultrasonic wave is an odd multiple of λ / 4 where λ is the
wavelength of the ultrasonic wave.
[0009]
In this application example, the acoustic matching layer is formed by an even number of layers,
in which the first layer and the second layer are arranged in order from the vibrating film side.
Each of the first and second layers has a thickness that is an odd multiple of λ / 4 where λ is
the ultrasonic wave transmitted from the ultrasonic transducer.
Also, the second layer has lower acoustic impedance than the first layer and the acoustic lens.
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That is, in the present application example, the acoustic matching layer is composed of even
layers, and the relationship of the acoustic impedance with respect to the adjacent layers in each
layer is in the order from high to low from the diaphragm to the acoustic lens. In such a
configuration, even if an interface reflected wave is generated at the interface between the
acoustic matching layer and the acoustic lens or at the interface between the acoustic matching
layers, the interface reflected wave is delayed to the first wave as described above, and thus the
acoustic It is possible to suppress emission from the lens to the object to be measured, and to
improve the distance resolution. That is, when the ultrasonic wave propagating toward the
second medium having a small acoustic impedance from the first medium having a large acoustic
impedance is reflected at the interface between the first medium and the second medium, the
phase of the ultrasonic wave is reversed. . Therefore, when the ultrasonic wave from the acoustic
matching layer (first layer) is reflected at the interface with the ultrasonic transducer (vibration
film), and the ultrasonic wave from the first layer is reflected at the interface with the second
layer When it is done, the phase of the ultrasonic wave is reversed. At this time, in this
application example, since the thickness of each acoustic matching layer is an odd multiple of λ
/ 4, the ultrasonic wave whose phase is inverted as described above and the ultrasonic wave
whose phase is not inverted mutually cancel each other. Fit. Therefore, the interface reflection
wave at each interface located between the ultrasonic transducer and the acoustic lens can be
prevented from being emitted from the acoustic lens to the object to be measured, and the
distance resolution can be improved.
[0010]
In the ultrasonic device of this application example, the acoustic matching layer preferably
includes one each of the first layer and the second layer. In this application example, the acoustic
matching layer is composed of two layers. In such a configuration, for example, the thickness of
the entire acoustic matching layer can be reduced as compared to the case where the acoustic
matching layer includes four or more layers, and the attenuation of ultrasonic waves emitted
from the acoustic lens can be suppressed. .
[0011]
An ultrasonic device according to an application example includes an ultrasonic transducer that
has a vibrating film and transmits ultrasonic waves from the first surface side of the vibrating
film, and an acoustic wave provided on the first surface side of the vibrating film. A matching
layer, and an acoustic lens provided on the side of the acoustic matching layer opposite to the
vibrating film, wherein the acoustic matching layer has an acoustic impedance smaller than that
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of the acoustic lens, and the wavelength of the ultrasonic wave is λ And have a thickness that is
an integral multiple of λ / 2. In this application example, the acoustic matching layer has a
thickness that is an integral multiple of λ / 2, where λ is an ultrasonic wave transmitted from
the ultrasonic transducer. Also, the acoustic matching layer has lower acoustic impedance than
the acoustic lens. In such a configuration, even if an interface reflected wave is generated at the
interface between the acoustic matching layer and the acoustic lens, the interface reflected wave
is prevented from being delayed to the first wave and emitted from the acoustic lens to the
measurement target And the distance resolution can be improved. That is, as in the application
example, the phase of the interface reflected wave can be made opposite to the phase of the first
wave, and the interface reflected wave can be canceled by the first wave.
[0012]
The ultrasonic device according to the application example includes an intermediate layer
disposed between the acoustic matching layer and the acoustic lens, wherein the intermediate
layer is a first intermediate layer having an acoustic impedance larger than that of the acoustic
matching layer. And an even layer including the first intermediate layer and a second
intermediate layer having an acoustic impedance smaller than that of the acoustic lens, wherein
the first intermediate layer and the second intermediate layer are directed from the diaphragm
toward the acoustic lens. It is preferable that the first intermediate layer and the second
intermediate layer have a thickness that is an odd multiple of λ / 4. In the present application,
the intermediate layer is disposed between the acoustic matching layer and the acoustic lens. In
this intermediate layer, the first intermediate layer and the second intermediate layer are
disposed in order from the acoustic matching layer side, and are constituted by an even number
of layers. Also, the first intermediate layer has a larger acoustic impedance than the acoustic
matching layer, and the second intermediate layer has a smaller acoustic impedance than the
first intermediate layer and the acoustic lens. In addition, the first intermediate layer and the
second intermediate layer have a thickness that is an odd multiple of λ / 4, where λ is an
ultrasonic wave transmitted from the ultrasonic transducer. In such a configuration, an interface
reflection wave is generated at the interface between the acoustic matching layer and the
intermediate layer, the interface between the first intermediate layer and the second intermediate
layer, and the interface between the intermediate layer and the acoustic lens, as in the above
application example. Even if the above occurs, the interface reflection wave can be prevented
from being delayed to the first wave and emitted from the acoustic lens to the object to be
measured, and the distance resolution can be improved.
[0013]
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In the ultrasonic device of this application example, the intermediate layer preferably includes
one each of the first intermediate layer and the second intermediate layer. In the present
application example, the intermediate layer is composed of two layers. In such a configuration,
for example, the thickness of the entire intermediate layer can be reduced as compared with the
case where the intermediate layer includes four or more layers, and the attenuation of the first
wave can be suppressed.
[0014]
In the ultrasonic device according to the application example, the vibrating film has the planar
first surface, and the surface of the acoustic matching layer on the vibrating film side and the
surface on the acoustic lens side, and the surface of the acoustic lens It is preferable that the
surface on the side of the acoustic matching layer is parallel to the first surface. In this
application example, the vibrating membrane has a planar first surface, and each interface is
planar and parallel to the first surface. Thus, for example, the interface reflection wave can be
more reliably canceled regardless of the reflection position of the interface reflection wave in the
plane direction of each interface, as compared with the case where the interface is not planar,
and the distance resolution is improved. be able to. That is, when the interface is planar and not
parallel, the interface reflection wave is reflected in the direction according to the reflection
position, and the propagation distance changes according to the reflection position. As a result,
the phase of the interface reflected wave when it reenters the interface does not have an opposite
phase to the first wave, and the interface reflected wave may not be canceled out. In this
application example, since the interface reflection wave is reflected in the normal direction of the
interface regardless of the reflection position, the occurrence of the above-mentioned failure can
be suppressed, and the interface reflection wave can be canceled more reliably by the first wave.
[0015]
In the ultrasonic device according to the application example, the ultrasonic transducer
preferably includes a piezoelectric element provided on a second surface side opposite to the
first surface of the vibrating membrane. In this application example, the ultrasonic transducer is
provided with the piezoelectric element on the second surface of the vibrating film opposite to
the first surface provided with the acoustic matching layer. By driving this piezoelectric element,
it is possible to vibrate the vibrating film and transmit an ultrasonic wave from the first surface
side. In such a configuration, the interface between the acoustic matching layer and the
ultrasonic transducer is formed by the planar first surface, thereby improving the flatness of the
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interface between the acoustic matching layer and the ultrasonic transducer. it can. Therefore,
the inter-interface distance can be made more uniform, and interface reflected waves can be
canceled more reliably.
[0016]
In the ultrasonic device according to this application example, the ultrasonic transducer has a
substrate supporting the vibrating film, and the substrate is closed by the vibrating film and has
an opening that opens on the opposite side to the vibrating film. Preferably, at least a portion of
the acoustic matching layer is disposed in the opening. In this application example, the ultrasonic
transducer has an opening closed by the vibrating membrane and has a substrate that closes the
vibrating membrane. Then, at least a part of the acoustic matching layer adjacent to the vibrating
membrane is disposed in the opening. In such a configuration, for example, when the acoustic
matching layer is formed in one layer, the entire acoustic matching layer is disposed in the
opening, and in the case where the acoustic matching layer is formed in a plurality of layers, one
layer on the vibrating film side The thickness of the acoustic matching layer can be adjusted
according to the thickness of the opening, and it is easy to dispose the opening in the opening.
[0017]
An ultrasonic device according to this application example, comprising: an adjusting member
disposed on the acoustic lens side of the substrate and adjusting a thickness of the acoustic
matching layer. In this application example, an adjustment member for adjusting the thickness of
the acoustic matching layer is provided. In such a configuration, for example, the thickness of the
acoustic matching layer can be easily adjusted by adjusting the thickness of the adjustment
member. In addition, it is easy to set the thickness of the acoustic matching layer to an
appropriate value.
[0018]
An ultrasonic module according to an application example includes a vibrating film, and an
ultrasonic transducer that transmits ultrasonic waves from the first surface side of the vibrating
film, and an acoustic wave provided on the first surface side of the vibrating film. And a circuit
board on which the ultrasonic device is provided, the acoustic matching layer comprising: a
matching layer; and an acoustic lens provided on an opposite side of the acoustic matching layer
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to the vibrating film. And an even layer including a first layer, and a second layer having a
smaller acoustic impedance than the first layer and the acoustic lens, and the first layer and the
second layer facing the acoustic lens from the vibrating membrane The two layers are disposed
in order, and the first layer and the second layer have a thickness which is an odd multiple of λ /
4 where λ is a wavelength of the ultrasonic wave. In this application example, the acoustic
matching layer is formed of even layers, in which the first layer and the second layer are
disposed in order from the vibrating film side. Each of the first and second layers has a thickness
that is an odd multiple of λ / 4 where λ is the ultrasonic wave transmitted from the ultrasonic
transducer. Also, the second layer has lower acoustic impedance than the first layer and the
acoustic lens. In such a configuration, as in the application example according to the above
ultrasonic device, even if an interface reflected wave is generated at the interface between the
acoustic matching layer and the acoustic lens or at the interface between the acoustic matching
layers, the interface reflected wave is As described above, it is possible to suppress the delay to
the first wave and to be emitted from the acoustic lens to the object to be measured, and to
improve the distance resolution.
[0019]
An ultrasonic module according to an application example includes a vibrating film, and an
ultrasonic transducer that transmits ultrasonic waves from the first surface side of the vibrating
film, and an acoustic wave provided on the first surface side of the vibrating film. And a circuit
board on which the ultrasonic device is provided, the acoustic matching layer comprising: a
matching layer; and an acoustic lens provided on an opposite side of the acoustic matching layer
to the vibrating film. An acoustic impedance is smaller than that of the acoustic lens, and a
wavelength of the ultrasonic wave is λ, which has a thickness that is an integral multiple of λ /
2. In this application example, the acoustic matching layer has a thickness that is an integral
multiple of λ / 2, where λ is an ultrasonic wave transmitted from the ultrasonic transducer.
Also, the acoustic matching layer has lower acoustic impedance than the acoustic lens. In such a
configuration, even if an interface reflected wave is generated at the interface between the
acoustic matching layer and the acoustic lens, as in the application example according to the
ultrasonic device, the interface reflected wave is delayed to the first wave. It is possible to
suppress emission from the acoustic lens to the object to be measured, and to improve the
distance resolution.
[0020]
An ultrasonic measurement device according to one application example includes an ultrasonic
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transducer that has a vibrating film and transmits ultrasonic waves from the first surface side of
the vibrating film, and is provided on the first surface side of the vibrating film. An ultrasonic
device comprising: an acoustic matching layer; and an acoustic lens provided on the opposite
side of the acoustic matching layer to the vibrating film, and a control unit for controlling the
ultrasonic device, the acoustic matching layer Is composed of an even layer including a first
layer, a second layer having a smaller acoustic impedance than the first layer and the acoustic
lens, and the first layer and the first layer facing the acoustic lens from the vibrating membrane
The second layer is disposed in order, and the first layer and the second layer have a thickness
which is an odd multiple of λ / 4 where λ is a wavelength of the ultrasonic wave. In this
application example, the acoustic matching layer is formed of even layers, in which the first layer
and the second layer are disposed in order from the vibrating film side. Each of the first and
second layers has a thickness that is an odd multiple of λ / 4 where λ is the ultrasonic wave
transmitted from the ultrasonic transducer. Also, the second layer has lower acoustic impedance
than the first layer and the acoustic lens. In such a configuration, as in the application example
according to the above ultrasonic device, even if an interface reflected wave is generated at the
interface between the acoustic matching layer and the acoustic lens or at the interface between
the acoustic matching layers, the interface reflected wave is As described above, it is possible to
suppress the delay to the first wave and to be emitted from the acoustic lens to the object to be
measured, and to improve the distance resolution.
[0021]
An ultrasonic measurement device according to one application example includes an ultrasonic
transducer that has a vibrating film and transmits ultrasonic waves from the first surface side of
the vibrating film, and is provided on the first surface side of the vibrating film. An ultrasonic
device comprising: an acoustic matching layer; and an acoustic lens provided on the opposite
side of the acoustic matching layer to the vibrating film, and a control unit for controlling the
ultrasonic device, the acoustic matching layer Is characterized in that the acoustic impedance is
smaller than that of the acoustic lens, and the wavelength of the ultrasonic wave is λ, which has
a thickness that is an integral multiple of λ / 2. In this application example, the acoustic
matching layer has a thickness that is an integral multiple of λ / 2, where λ is an ultrasonic
wave transmitted from the ultrasonic transducer. Also, the acoustic matching layer has lower
acoustic impedance than the acoustic lens. In such a configuration, even if an interface reflected
wave is generated at the interface between the acoustic matching layer and the acoustic lens, as
in the application example according to the ultrasonic device, the interface reflected wave is
delayed to the first wave. It is possible to suppress emission from the acoustic lens to the object
to be measured, and to improve the distance resolution.
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[0022]
BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows schematic structure of the
ultrasound apparatus of 1st embodiment. BRIEF DESCRIPTION OF THE DRAWINGS The top view
which shows schematic structure of the ultrasonic sensor in 1st embodiment. The top view which
looked at the element substrate of the ultrasonic device in a first embodiment from the sealing
plate side. Sectional drawing at the time of cut | disconnecting an ultrasonic device by the AA line
of FIG. BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows schematic
structure of the ultrasonic device in 1st embodiment. The figure which shows the sound pressure
fluctuation by the ultrasonic wave transmitted from the ultrasonic device of 1st embodiment, and
the ultrasonic device of a comparative example. The figure which shows the sound pressure
fluctuation by the ultrasonic wave transmitted from the ultrasonic device of 1st embodiment, and
the ultrasonic device of a comparative example. 6 is a flowchart showing an example of a method
of manufacturing the ultrasonic device according to the first embodiment. FIG. 7 is a view
showing the manufacturing process of the ultrasonic device of the first embodiment. FIG. 7 is a
view showing the manufacturing process of the ultrasonic device of the first embodiment. FIG. 7
is a view showing the manufacturing process of the ultrasonic device of the first embodiment.
Sectional drawing which shows schematic structure of the ultrasonic device of 2nd embodiment.
The figure which shows the sound pressure fluctuation | variation by the ultrasonic wave
transmitted from the ultrasonic device of 2nd embodiment, and the ultrasonic device of a
comparative example. Sectional drawing which shows schematic structure of the ultrasonic
device of 3rd embodiment.
[0023]
First Embodiment An ultrasonic apparatus according to a first embodiment will be described
below with reference to the drawings. [Configuration of Ultrasonic Measurement Apparatus] FIG.
1 is a perspective view showing a schematic configuration of the ultrasonic measurement
apparatus 1 of the present embodiment. The ultrasonic measurement apparatus 1 of the present
embodiment corresponds to an electronic device, and as shown in FIG. 1, an ultrasonic probe 2
and a control apparatus 10 electrically connected to the ultrasonic probe 2 via a cable 3. And.
The ultrasonic measurement apparatus 1 brings an ultrasonic probe 2 into contact with the
surface of a living body (for example, a human body), and transmits ultrasonic waves from the
ultrasonic probe 2 into the living body. In addition, the ultrasound probe 2 receives the
ultrasonic wave reflected by the organ in the living body, and based on the received signal, for
example, acquires an internal tomographic image in the living body, the state of the organ in the
living body (for example, Measure blood flow etc.)
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[0024]
[Configuration of Control Device] As shown in FIG. 1, the control device 10 includes, for example,
an operation unit 11 and a display unit 12. Further, although not shown, the control device 10
includes a storage unit configured by a memory or the like, and an operation unit configured by a
CPU (Central Processing Unit) or the like. Then, the control device 10 causes the operation unit
to read and execute various programs stored in the storage unit, for example, to output a
command for controlling the drive of the ultrasound probe 2 or to input from the ultrasound
probe 2 Based on the received signal, the image of the internal structure of the living body is
formed and displayed on the display unit 12 or biological information such as blood flow is
measured and displayed on the display unit 12. That is, the control device 10 corresponds to a
control unit. As such a control device 10, for example, a terminal device such as a tablet terminal,
a smartphone, or a personal computer can be used, and a dedicated terminal device for operating
the ultrasonic probe 2 may be used.
[0025]
[Configuration of Ultrasonic Probe] FIG. 2 is a plan view showing a schematic configuration of
the ultrasonic sensor 24 in the ultrasonic probe 2. The ultrasonic probe 2 includes a housing 21
(see FIG. 1), an ultrasonic device 22 provided inside the housing 21, and a wiring board 23
provided with a driver circuit for controlling the ultrasonic device 22 and the like. And. An
ultrasonic sensor 24 (corresponding to an ultrasonic module) is configured by the ultrasonic
device 22 and the wiring substrate 23.
[0026]
[Configuration of Housing] As shown in FIG. 1, the housing 21 is formed in, for example, a box
shape having a rectangular shape in a plan view, and a sensor window 21B is provided on one
surface (sensor surface 21A) orthogonal to the thickness direction. And part of the ultrasound
device 22 is exposed. Further, a passage hole 21C for the cable 3 is provided in a part of the case
21 (a side surface in the example shown in FIG. 1), and the cable 3 is inserted into the case 21
from the passage hole 21C. Are connected to the connector portion 231 (see FIG. 2). Further, the
gap between the cable 3 and the passage hole 21C is, for example, filled with a resin material or
the like to ensure waterproofness. In addition, in this embodiment, although the structural
example to which the ultrasonic probe 2 and the control apparatus 10 are connected using the
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cable 3 is shown, it is not limited to this, For example, the ultrasonic probe 2 and the control
apparatus 10 are wireless. It may be connected by communication, and various configurations of
the control device 10 may be provided in the ultrasonic probe 2.
[0027]
[Structure of Wiring Board] The wiring board 23 corresponds to a circuit board, and has a
terminal portion electrically connected to the electrode pads 414P and 416P (see FIG. 3)
provided in the ultrasonic device 22. The wiring board 23 is provided with a driver circuit or the
like for driving the ultrasonic device 22. Specifically, the wiring board is provided with a
transmission circuit for transmitting an ultrasonic wave from the ultrasonic device 22 and a
receiving circuit for processing a reception signal when the ultrasonic device 22 receives an
ultrasonic wave. . The wiring board is connected to the control device 10 by the cable 3 or the
like, and drives the ultrasonic device 22 based on a command from the control device 10.
[0028]
[Configuration of Ultrasonic Device] FIG. 3 is a plan view of the element substrate 41 in the
ultrasonic device 22 as viewed from the sealing plate 42 side. FIG. 4 is a cross-sectional view of
the ultrasonic device 22 taken along the line A-A in FIG. As shown in FIG. 4, the ultrasonic device
22 includes an element substrate 41, a sealing plate 42, an acoustic matching layer 43, and an
acoustic lens 44.
[0029]
(Structure of Element Substrate) The element substrate 41 is, as shown in FIG. 4, a substrate
body 411, a vibrating film 412 provided on the sealing plate 42 side of the substrate body 411,
and a piezoelectric provided on the vibrating film 412. An element 413 and an adjusting member
417 for adjusting the thickness of a second layer 432 of the acoustic matching layer 43
described later are provided. Here, in the following description, the surface of the element
substrate 41 facing the sealing plate 42 is referred to as a back surface 41A. The surface (first
surface) of the vibrating film 412 opposite to the sealing plate 42 is referred to as an ultrasonic
transmission / reception surface 412A, and the surface (second surface) on the sealing plate 42
side is referred to as an operation surface 412B. In a plan view of the element substrate 41
viewed from the thickness direction of the substrate, the central region of the element substrate
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41 is an array region Ar1, and a plurality of ultrasonic transducers 45 are arranged in a matrix in
the array region Ar1. .
[0030]
The substrate body 411 is a substrate for supporting the vibrating film 412, and is made of, for
example, a semiconductor substrate of Si or the like. In the array area Ar1 of the substrate body
411, an opening 411A corresponding to each ultrasonic transducer 45 is provided. Each opening
411A is closed by a vibrating film 412 provided on the back surface 41A side of the substrate
body 411. Although described later, the inside of the opening 411A is filled with the first layer
431 of the acoustic matching layer 43, and the depth dimension of the opening 411A matches
the thickness dimension of the first layer 431. Therefore, the thickness dimension of the first
layer 431 can be adjusted by the depth dimension of the opening 411A.
[0031]
The vibrating film 412 is made of, for example, SiO 2, a laminate of SiO 2 and ZrO 2, and the like,
and is provided so as to cover the entire back surface 41 A of the substrate body 411. The
thickness dimension of the vibration film 412 is sufficiently smaller than that of the substrate
body 411. When the substrate body 411 is made of Si and the vibrating film 412 is made of SiO
2, for example, by oxidizing the back surface 41A side of the substrate body 411, the vibrating
film 412 having a desired thickness can be easily formed. It becomes possible. Further, in this
case, the opening 411A can be easily formed by etching the substrate body 411 using the
vibrating film 412 of SiO 2 as an etching stopper.
[0032]
In addition, as shown in FIG. 4, on the vibrating film 412 closing the openings 411A (on the back
surface 41A side), there is a piezoelectric element 413 which is a laminate of the lower electrode
414, the piezoelectric film 415, and the upper electrode 416. It is provided. Here, one ultrasonic
transducer 45 is configured by the vibrating film 412 and the piezoelectric element 413 which
close the opening 411A.
[0033]
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In such an ultrasonic transducer 45, a rectangular wave voltage of a predetermined frequency is
applied between the lower electrode 414 and the upper electrode 416 to vibrate the vibrating
film 412 in the opening region of the opening 411A, Ultrasonic waves can be transmitted from
the sound wave transmitting / receiving surface 412A side. In addition, when the vibrating film
412 is vibrated by the ultrasonic wave that is reflected from the object and is incident from the
ultrasonic transmission / reception surface 412A side, a potential difference is generated above
and below the piezoelectric film 415. Therefore, by detecting the potential difference generated
between the lower electrode 414 and the upper electrode 416, it is possible to detect the
received ultrasonic waves.
[0034]
Further, in the present embodiment, as shown in FIG. 3, the ultrasonic transducers 45 as
described above cross in the X direction (slice direction) and the X direction in a predetermined
array region Ar1 of the element substrate 41 ( In the present embodiment, a plurality of
ultrasonic transducer arrays 46 are configured by arranging a plurality in the Y direction
(scanning direction) orthogonal to each other. The ultrasonic transducer array 46 corresponds to
an ultrasonic transmitting and receiving unit. Here, the lower electrode 414 is formed in a
straight line along the X direction. That is, the lower electrode 414 is provided across the
plurality of ultrasonic transducers 45 arranged along the X direction, and the lower electrode
main body 414A located between the piezoelectric film 415 and the vibrating film 412 and the
adjacent lower portion A lower electrode line 414B connecting the electrode main body 414A
and a lower terminal electrode line 414C drawn out to a terminal area Ar2 outside the array area
Ar1 are formed. Therefore, in the ultrasonic transducers 45 aligned in the X direction, the lower
electrodes 414 have the same potential. The lower terminal electrode line 414C extends to a
terminal area Ar2 outside the array area Ar1, and constitutes a first electrode pad 414P in the
terminal area Ar2. The first electrode pad 414P is connected to a terminal portion provided on
the wiring substrate.
[0035]
On the other hand, as shown in FIG. 3, in the upper electrode 416, the end portions of the
element electrode portion 416A provided across the plurality of ultrasonic transducers 45
arranged along the Y direction and the end portions of the plurality of element electrode portions
416A are And a common electrode portion 416B to be connected. The element electrode portion
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416A includes an upper electrode main body 416C stacked on the piezoelectric film 415, an
upper electrode wire 416D connecting the adjacent upper electrode main body 416C, and
ultrasonic transducers 45 arranged at both ends in the Y direction. And an upper terminal
electrode 416E extending outward along the Y direction. The common electrode portion 416B is
provided at each of the + Y side end and the −Y side end of the array region Ar1. The common
electrode section 416B on the + Y side is the upper terminal electrode 416E extended to the + Y
side from the ultrasonic transducer 45 provided on the + Y side end of the ultrasonic transducers
45 provided along the Y direction. Connect with each other. The common electrode portion 416B
at the -Y side end connects the upper terminal electrodes 416E extended to the -Y side.
Accordingly, in each of the ultrasonic transducers 45 in the array region Ar1, the upper
electrodes 416 have the same potential. The pair of common electrode portions 416B are
provided along the X direction, and the end portions thereof are drawn from the array region Ar1
to the terminal region Ar2. The common electrode portion 416B constitutes a second electrode
pad 416P connected to the terminal portion of the wiring substrate in the terminal region Ar2.
[0036]
In the ultrasonic transducer array 46 as described above, the ultrasonic transducers 45 aligned
in the X direction connected by the lower electrode 414 constitute one ultrasonic transducer
group 45A, and the ultrasonic transducer groups 45A are A plurality of one-dimensional array
structures are arranged along the Y direction.
[0037]
The adjusting member 417 is a member for adjusting the thickness of the second layer 432 of
the acoustic matching layer 43 described later, and is arranged on the + Z side of the substrate
body 411 so as to surround the array region Ar1 in which the opening 411A is formed. Ru.
The region surrounded by the adjusting member 417 is filled with the second layer 432, and the
thickness dimension of the adjusting member 417 matches the thickness dimension of the
second layer 432. Therefore, the thickness of the second layer 432 can be adjusted by the
thickness of the adjustment member 417.
[0038]
(Structure of Sealing Plate) The sealing plate 42 is formed to have, for example, the same shape
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as the element substrate 41 when viewed in the thickness direction, and is made of a
semiconductor substrate such as Si or an insulator substrate. In addition, since the material and
thickness of the sealing plate 42 affect the frequency characteristics of the ultrasonic transducer
45, it is preferable to set based on the central frequency of the ultrasonic wave transmitted and
received by the ultrasonic transducer 45.
[0039]
The sealing plate 42 has a plurality of recessed grooves 421 corresponding to the openings 411
A of the element substrate 41 in the array facing area facing the array area Ar 1 of the element
substrate 41. As a result, in the region (in the opening 411A) of the vibrating film 412 which is
vibrated by the ultrasonic transducer 45, a gap 421A of a predetermined size with the element
substrate 41 is provided. Vibration is not disturbed. In addition, it is possible to suppress the
disadvantage (cross talk) that the back waves from one ultrasonic transducer 45 are incident on
the other adjacent ultrasonic transducers 45.
[0040]
In addition, when the vibrating film 412 vibrates, ultrasonic waves are emitted as back waves to
the sealing plate 42 side (rear surface 41A side) as well as the opening 411A side (ultrasonic
transmission / reception surface 412A side). The back wave is reflected by the sealing plate 42
and emitted again to the vibrating film 412 through the gap 421A. At this time, if the phase of
the reflection back surface wave and the ultrasonic wave emitted from the vibrating film 412 to
the ultrasonic wave transmitting / receiving surface 412A are shifted, the ultrasonic wave is
attenuated. Therefore, in the present embodiment, the groove depth of each concave groove 421
is set such that the acoustic distance in the gap 421A is an odd multiple of λ / 4 where λ is the
wavelength of the ultrasonic wave. In other words, in consideration of the wavelength λ of the
ultrasonic wave emitted from the ultrasonic transducer 45, the thickness dimension of each part
of the element substrate 41 and the sealing plate 42 is set.
[0041]
Further, the sealing plate 42 is provided with an opening (not shown) at a position facing the
terminal area Ar2 of the element substrate 41 corresponding to each of the electrode pads 414P
and 416P provided in the terminal area Ar2, etc. It may be In this case, by providing a through
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16
electrode (TSV; Through-Sillicon Via) penetrating the sealing plate 42 in the thickness direction
in the opening portion, each electrode pad 414P, 416P is a terminal on the wiring substrate
through the through electrode. Connected to the department. Alternatively, flexible printed
circuits (FPC), cable wires, wires, and the like may be inserted into the openings to connect the
electrode pads 414P and 416P to the wiring substrate.
[0042]
(Configuration of Acoustic Lens) The acoustic lens 44 is provided on the acoustic matching layer
43 (+ Z side) described in detail later. The acoustic lens 44 is exposed to the outside from the
sensor window 21B of the housing 21 as shown in FIG. The acoustic impedance Z3 of the
acoustic lens 44 is set to an acoustic impedance close to the acoustic impedance of the living
body. The acoustic lens 44 is brought into close contact with the surface of the living body,
thereby efficiently focusing the ultrasonic wave transmitted from the ultrasonic transducer 45 in
the living body via the acoustic matching layer 43, and super reflected in the living body. The
sound wave is efficiently propagated to the ultrasonic transducer 45. In the present embodiment,
the acoustic impedance Z3 is, for example, 1.5 MRayls.
[0043]
As a material for forming such an acoustic lens 44, for example, a millable silicone rubber can be
exemplified. The millable silicone rubber contains, for example, silicone rubber having a
dimethylpolysiloxane structure containing a vinyl group, silica, and a vulcanizing agent.
Specifically, silica is mixed with silicone rubber as a silica particle having a weight average
particle diameter of 15 μm to 30 μm and a mass ratio of 40% by mass to 50% by mass with
respect to the silicone rubber. As a vulcanizing agent, for example, 2,5-dimethyl-2,5-di-tertbutylperoxycyclohexane can be used.
[0044]
(Structure of Acoustic Matching Layer) The acoustic matching layer 43 is provided on the side of
the ultrasonic transmitting / receiving surface 412A of the vibrating membrane 412 as shown in
FIG. And a second layer 432 provided on the The acoustic matching layer 43 efficiently
propagates the ultrasonic wave transmitted from the ultrasonic transducer 45 to the living body
to be measured together with the acoustic lens 44, and efficiently transmits the ultrasonic wave
14-04-2019
17
reflected in the living body. Propagate to 45 Therefore, the acoustic matching layer 43 is set to
an acoustic impedance close to the acoustic impedance of the living body. As a material which
has such an acoustic impedance, silicone resin materials, such as RTV silicone rubber, can be
used, for example.
[0045]
The first layer 431 is filled in the opening 411 A of the element substrate 41 and provided on the
vibrating film 412 (+ Z side). That is, the first layer 431 has a thickness L1 corresponding to the
depth of the opening 411A. The surface of the first layer 431 opposite to the vibrating
membrane 412, that is, the interface with the second layer 432 (hereinafter also referred to as a
first interface F1) is substantially parallel to the ultrasonic wave transmission / reception surface
412A. The surface 43A on the vibrating film 412 side of the acoustic matching layer 43 is a
surface in contact with the ultrasonic transmission / reception surface 412A, and is parallel to
the ultrasonic transmission / reception surface 412A. Also, the acoustic impedance Z1 of the first
layer 431 is larger than the acoustic impedance Z2 of the second layer 432. In the present
embodiment, the acoustic impedance Z1 is, for example, 1.5 MRayls, and the acoustic impedance
Z2 is, for example, 1 MRayls. Further, the difference between the acoustic impedance Z1 and the
acoustic impedance Z2 is preferably set to a value at which the reflection of the ultrasonic wave
is appropriately generated between the first layer and the second layer, preferably about 0.1
MRayls to about 1 MRayls, 0 .3 MRayls to about 0.7 MRayls are more preferable.
[0046]
The second layer 432 is provided on the first layer 431 (+ Z side), and has the same thickness L1
as the first layer 431. The thickness of the second layer 432 is adjusted by setting the thickness
dimension of the adjusting member 417 to L1. The surface on the first layer 431 side of the
second layer 432 of the first layer 431 (that is, the first interface F1) and the interface on the
acoustic lens 44 side (hereinafter also referred to as the second interface F2) Approximately
parallel. The acoustic impedance Z2 of the second layer 432 is smaller than the acoustic
impedance Z1 of the first layer 431 and the acoustic impedance Z3 of the acoustic lens 44. The
value of the acoustic impedance can be obtained by the product of the density of the medium and
the velocity of sound in the medium. For example, by forming the second layer 432 using a
material having a density smaller than that of the first layer 431, the acoustic impedance Z2 of
the second layer 432 may be smaller than the acoustic impedance Z1 of the first layer 431. it
can. In the present embodiment, the acoustic impedance Z1 is, for example, 1.5 MRayls.
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[0047]
The thickness dimension L1 of the first layer 431 and the second layer 432, that is, the distance
between the ultrasonic transmission / reception surface 412A and the first interface F1, and the
distance between the first interface F1 and the second interface F2 is an ultrasonic transformer.
Assuming that the wavelength of the ultrasonic wave transmitted from the reducer 45 is λ, and
an integer of 1 or more is n, the following formula (1) is satisfied. That is, the first layer 431 and
the second layer 432 are formed such that the dimension L1 is an odd multiple of λ / 4. In
addition, the effect by L1 satisfy | filling a following formula (1) is mentioned later.
[0048]
[Equation 1] L1 = (λ / 4) × (2 n-1) (1)
[0049]
[Reduction of Tailing by Acoustic Matching Layer] Here, the ultrasonic device 22 is transmitted
from the ultrasonic transducer 45, propagates through the acoustic matching layer 43 and the
acoustic lens 44, and is emitted into the living body (hereinafter referred to as The ultrasonic
measurement is carried out by receiving the reflected wave (also referred to as the first wave).
In the configuration in which the acoustic matching layer 43 and the acoustic lens 44 are stacked
on the ultrasound transmitting / receiving surface 412A when performing this ultrasonic
measurement, interface reflection that occurs at the interface between the acoustic matching
layer 43 and the acoustic lens 44 An ultrasonic wave caused by a wave (hereinafter also referred
to as a second wave) may be delayed to the first wave and emitted into the living body, and
tailing may occur in the ultrasonic wave emitted from the ultrasonic device 22. When this tailing
occurs, the pulse width of the ultrasonic wave may be increased, and the distance resolution may
be reduced.
[0050]
On the other hand, in the ultrasonic device 22 of the present embodiment, as described in detail
later, the thickness dimensions of the first layer 431 and the second layer 432 of the acoustic
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matching layer 43 (the ultrasonic transmitting / receiving surface 412A and the first interface F1
And the distance between the first interface F1 and the second interface F2) satisfy the abovementioned equation (1). In addition, the acoustic impedance Z1 of the second layer 432 is
smaller than the acoustic impedance Z1 of the first layer 431 and smaller than the acoustic
impedance Z3 of the acoustic lens 44. With such a configuration, emission of the second wave
into the living body can be suppressed, and distance resolution can be improved.
[0051]
FIG. 5 is a view for explaining the suppression effect of the tailing due to the interface reflection
wave in the ultrasonic device 22 of the present embodiment, which is a main part (acoustic
matching layer 43 and acoustic lens 44) of the ultrasonic device 22. The cross section is shown
schematically. In addition, in FIG. 5, the structure of the ultrasonic device 22 is simplified and
shown in figure. As shown in FIG. 5, an ultrasonic wave U0 transmitted from the ultrasonic
transducer 45 in the normal direction and transmitted through the first interface F1 and the
second interface F2 is emitted from the acoustic lens 44 into the object to be measured. The
ultrasonic measurement is performed by detecting the reflected wave of the ultrasonic wave U0
by the ultrasonic transducer 45.
[0052]
Here, as shown in FIG. 5, the interface reflected wave U1 may be generated by reflecting a part of
the ultrasonic wave U0 incident on the first interface F1 at the first interface F1. When the
interface reflected wave U1 is reflected by the ultrasonic wave transmitting / receiving surface
412A and reaches the first interface F1 again, it has an antiphase with the ultrasonic wave U0.
For this reason, at least a part of the interface reflected wave U1 is canceled by the ultrasonic
wave U0. More specifically, when the ultrasonic wave incident on the first interface F1 from the
side of the first layer 431 whose acoustic impedance is smaller than that of the second layer 432
is reflected by the first interface F1, the phase of the ultrasonic wave is reversed. Also, when
propagating through the first layer 431 and being reflected by the ultrasonic transmission /
reception surface 412A, the phase of the ultrasonic wave is reversed. For this reason, by setting
the thickness of the first layer 431 (the distance between the ultrasonic transmission / reception
surface 412A and the first interface F1) to an odd multiple of λ / 4, interface reflected wave U1
at the time of re-incident on the first interface F1. The phase of can be antiphase to the ultrasonic
wave U0. From the above, at least a part of the interface reflected wave U2 that is reflected by
the first interface F1 and reflected by the ultrasonic transmission / reception surface 412A and
then enters the first interface F1 again is canceled by the ultrasonic wave U0.
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[0053]
Further, a part of the ultrasonic wave U0 incident on the second interface F2 is reflected by the
second interface F2 to generate an interface reflected wave U2, and further, a part of the
interface reflected wave U2 is a first interface. An interface reflected wave U21 may be generated
by reflection at F1. When the interface reflected wave U21 is reflected by the first interface F1
and reaches the second interface F2 again, the interface reflected wave U21 has an opposite
phase to the ultrasonic wave U0. For this reason, at least a part of the interface reflected wave
U21 is canceled by the ultrasonic wave U0. Specifically, by setting the thickness of the second
layer 432 (the distance between the first interface F1 and the second interface F2) to an odd
multiple of λ / 4, an interface reflected wave when re-incident on the second interface F2 The
phase of U21 can be antiphase to the ultrasonic wave U0. Therefore, at the second interface F2,
at least a part of the interface reflected wave U21 is canceled by the ultrasonic wave U0.
[0054]
The interface reflected wave U22 of the interface reflected wave U2 transmitted through the first
interface F1 passes through the first layer 431 and is then reflected by the ultrasonic wave
transmitting / receiving surface 412A and reaches the interface F2 again. The phase is opposite
to the sound wave U0. At least a part of the interface reflected wave U22 is canceled by the
ultrasonic wave U0. That is, when the interface reflected wave U22 is reflected by the ultrasonic
transmitting / receiving surface 412A, the phase is reversed. Therefore, by setting the thickness
of the first layer 431 and the second layer 432 to an odd multiple of λ / 4 (ie, the distance
between the interface F2 and the ultrasonic transmission / reception surface 412A is an even
multiple of λ / 4, in other words, By setting the integral multiple of λ / 2), the phase of the
interface reflected wave U22 when reincident on the second interface F2 can be made opposite
to the ultrasonic wave U0. Therefore, at the second interface F2, at least a part of the interface
reflected wave U22 is canceled by the ultrasonic wave U0.
[0055]
As described above, by canceling at least a part of the interface reflection wave generated at each
of the interfaces F1 and F2, emission of the interface reflection wave into the living body can be
suppressed, and the distance resolution can be improved. Further, in the present embodiment,
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since the surface 43A on the vibrating film 412 side of the acoustic matching layer 43 and the
interfaces F1 and F2 are substantially parallel to the ultrasonic transmitting / receiving surface
412A, the interface reflected wave is the ultrasonic transmitting / receiving surface 412A and It
can be propagated in the normal direction (Z direction) of each of the interfaces F1 and F2. For
this reason, the propagation distance of the interface reflected wave can be set to the abovementioned distance, and the interface reflected wave can be canceled more reliably.
[0056]
6 and 7 are diagrams showing an example of the time change of the ultrasonic wave transmitted
from the ultrasonic device. Here, the time change of the ultrasonic wave emitted from the
ultrasonic device 22 of the present embodiment is indicated by a solid line. On the other hand, an
alternate long and short dash line indicates an example of a time change of ultrasonic waves
transmitted from the ultrasonic device of the comparative example including a single acoustic
matching layer whose thickness is not an integral multiple of λ / 2. 6 and 7, the value of the
acoustic impedance of the first layer 431 and the acoustic lens 44 is 1.5 MRayls, and the value of
the acoustic impedance of the second layer 432 is 1 MRayls.
[0057]
In the example shown in FIGS. 6 and 7, a driving voltage having a burst wave waveform of 5
MHz, for example, is applied to the ultrasonic transducer 45 to drive the ultrasonic transducer
45. As shown in FIG. 6, when the Q value of the ultrasonic device 22 is 2, in the comparative
example indicated by the alternate long and short dash line, fluctuation of the sound pressure is
detected after approximately 3.00 × 10 <-7> sec. Tailing has occurred. On the other hand, in the
ultrasonic device 22 of the present embodiment shown by the solid line, it can be seen that the
change in sound pressure is suppressed and the tailing is suppressed. Further, as shown in FIG. 7,
even when the Q value of the ultrasonic device 22 is 4, by using the ultrasonic device 22 of the
present embodiment compared to the comparative example, the sound pressure change of the
tailing portion is suppressed. ing.
[0058]
Further, as shown in FIG. 5, when passing through the first interface F1, the ultrasonic wave U0
propagates from the first layer 431 having high acoustic impedance to the second layer 432
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having low acoustic impedance, and the sound pressure is small. However, when passing through
the second interface F2, conversely, the sound is propagated from the second layer 432 having
low acoustic impedance to the acoustic lens 44, and the sound pressure becomes large.
Therefore, compared with the ultrasonic device of the comparative example in which the acoustic
matching layer is a single-layer structure, the ultrasonic device 22 provided with the acoustic
matching layer 43 having a two-layer structure can suppress the reduction in sound pressure
while suppressing tailing. .
[0059]
As shown in FIG. 6 and FIG. 7, even in the case of the comparative example, the sound pressure
change of the tailing portion can be suppressed by reducing the Q value of the ultrasonic device.
However, the output of the ultrasonic wave U0 also decreases. On the other hand, by using the
ultrasonic device 22 of the present embodiment, it is possible to suppress the change in sound
pressure of the tailing portion without reducing the Q value. Therefore, according to the
ultrasonic device 22, it is possible to suppress a decrease in the output of the ultrasonic wave U0
and to suppress the influence of tailing, and ultrasonic measurement with high accuracy can be
performed.
[0060]
Method of Manufacturing Ultrasonic Device Next, a method of manufacturing the ultrasonic
device 22 as described above will be described. FIG. 8 is a flow chart showing each step in the
manufacture of the ultrasonic sensor 24 of the present embodiment. 9 to 11 schematically show
the ultrasonic sensor 24 in each step. In order to manufacture the ultrasonic sensor 24, as shown
in FIG. 8, a device body forming step S1, a first layer forming step S2, a second layer forming
step S3 and an acoustic lens disposing step S4 are performed.
[0061]
In the device body forming step S1, a device body 40 (see FIG. 9) including the element substrate
41 and the sealing plate 42 is formed. In this step S 1, after the vibrating film 412 is formed on
the substrate body 411, the piezoelectric element 413 is formed on the vibrating film 412, and
the opening 411 A is formed on the substrate body 411. At this time, the opening 411A is
formed to have the same depth as the thickness of the first layer 431. Thereafter, the sealing
14-04-2019
23
plate 42 is formed, and the device body 40 and the sealing plate 42 are joined.
[0062]
Next, the first layer forming step S2 is performed. In step S2, as shown in FIG. 10, the first layer
431 of the acoustic matching layer 43 is formed in the opening 411A of the device body 40.
Specifically, the forming material of the first layer 431 is filled in the opening 411A. The excess
forming material protruding from the opening 411A is removed so that the surfaces on the + Z
side of the opening 411A and the first layer 431 are on the same plane.
[0063]
Next, the second layer formation step S3 is performed. In step S3, as shown in FIG. 11, the
adjustment member 417 is disposed on the substrate body 411. The thickness of the adjustment
member 417 is formed to be the same as the thickness of the second layer 432. Thereafter, the
forming material of the second layer 432 is filled in the area surrounded by the adjusting
member 417. In addition, the excess formation material which overflows is removed so that the
surface by the side of + Z of the adjustment member 417 and the 2nd layer 432 may become the
same plane. Next, an acoustic lens disposing step S4 is performed to dispose the acoustic lens 44
on the + Z side of the second layer 432. Thus, the ultrasonic device 22 is formed.
[0064]
In the method of forming the ultrasonic device 22 described above, after the element substrate
41 and the sealing plate 42 are joined, the acoustic matching layer 43 is formed and the acoustic
lens 44 is disposed. However, the present invention is not limited thereto. That is, the acoustic
matching layer 43 may be formed on the element substrate 41 before bonding to the sealing
plate 42, and the acoustic lens 44 may be disposed. Further, although the second layer 432 is
formed after the adjustment member 417 is disposed on the element substrate 41, the present
invention is not limited to this. The second layer 432 may be formed without providing the
adjustment member 417. In addition, the second layer 432 may be formed on the acoustic lens
44 side without forming the second layer 432 on the element substrate 41 side. In this case, for
example, a recess is provided in the acoustic lens 44, the second layer 432 is formed inside the
recess, and the acoustic lens 44 on which the second layer 432 is formed is formed on the
element substrate 41 on which the first layer 431 is formed. It may be joined.
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[0065]
[Operation and Effect of First Embodiment] The ultrasonic device 22 of the present embodiment
includes an acoustic matching layer 43 provided on the ultrasonic transmission / reception
surface 412A of the vibrating film 412, and an acoustic lens 44 provided on the acoustic
matching layer 43. And. The acoustic matching layer 43 includes a first layer 431 on the
ultrasonic transmission / reception surface 412A side and a second layer 432 on the acoustic
lens 44 side, and each layer is an odd multiple of λ / 4 where λ is the wavelength of ultrasonic
waves. It has a thickness. The second layer 432 has an acoustic impedance smaller than that of
the first layer 431 and the acoustic lens 44. In the ultrasonic device 22 configured in this way,
even if interface reflection waves are generated at the interfaces F1 and F2 in the acoustic
matching layer 43 and the acoustic lens 44 (see interface reflection waves U1 and S2 in FIG. 5),
Thus, when the interface reflection wave reenters the interface, the phase of the interface
reflection wave can be made opposite to the phase of the ultrasonic wave U 0 transmitted from
the ultrasonic transducer 45. Therefore, by canceling at least a part of the interface reflected
wave, it is possible to suppress that the interface reflected wave is delayed to the ultrasonic wave
U0 and emitted from the acoustic lens 44 to the object to be measured, and the distance
resolution can be improved.
[0066]
Further, in the present embodiment, the acoustic matching layer 43 is composed of two layers.
Here, even if the acoustic matching layer 43 is an even layer and the first layer 431 and the
second layer 432 are alternately arranged, generation of tailing due to interface reflection waves
can be similarly suppressed. On the other hand, if the acoustic matching layer 43 is thickened,
the attenuation of the ultrasonic wave may be increased, and the transmission output of the
ultrasonic wave and hence the reception sensitivity may be reduced. Although it is possible to
thin the entire acoustic matching layer 43 by thinning each layer, there is a limit to thinning each
layer. On the other hand, by forming the acoustic matching layer 43 with two layers, the
thickness of the acoustic matching layer 43 can be reduced, and the thickness can be easily
reduced.
[0067]
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The vibrating film 412 has a planar ultrasonic transmission / reception surface 412A, and the
interfaces F1 and F2 are parallel to the ultrasonic transmission / reception surface 412A. Here,
when the interfaces F1 and F2 are not planar and not parallel to the ultrasonic transmission /
reception surface 412A, the interface reflected wave is reflected in the direction according to the
reflection position. For this reason, the propagation distance changes according to the reflection
position of the interface reflection wave, and the phase of the interface reflection wave when reincident on the interface may not be in reverse phase to the ultrasonic wave U0. On the other
hand, in the present embodiment, regardless of the reflection position, the interface reflection
wave is reflected along the Z direction which is the normal direction of the interfaces F1 and F2,
so that the occurrence of the above-mentioned problems can be suppressed. The waves can be
canceled more reliably.
[0068]
Further, in the present embodiment, the piezoelectric element 413 is provided on the actuating
surface 412B side of the vibrating film 412, and the ultrasonic wave is transmitted from the
ultrasonic wave transmitting / receiving surface 412A side. In such a configuration, for example,
as compared with the configuration in which the piezoelectric element 413 is formed on the
ultrasonic transmission / reception surface 412A side, the flatness of the ultrasonic transmission
/ reception surface 412A which is the interface between the acoustic matching layer 43 and the
ultrasonic transducer 45. It is possible to improve the quality. Therefore, the distance between
the ultrasonic transmission / reception surface 412A and each of the interfaces F1 and F2 can be
made more uniform, and interface reflected waves can be canceled more reliably.
[0069]
In the present embodiment, the first layer 431 of the acoustic matching layer 43 is filled in the
opening 411A formed in the substrate body 411. In such a configuration, the first layer 431 can
be formed according to the depth of the opening 411A. In addition, by appropriately adjusting
the thickness of the opening 411A, the thickness of the first layer 431 can be adjusted to an
appropriate value, and it is easy to form the first layer 431 having a desired thickness.
[0070]
Further, in the present embodiment, the adjusting member 417 for adjusting the thickness of the
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26
second layer 432 in the acoustic matching layer 43 is provided. The adjustment member 417 is a
frame-shaped member disposed on the + Z side of the substrate body 411. By forming the second
layer 432 in the recess surrounded by the adjusting member 417, the second layer 432 can be
formed in accordance with the thickness of the adjusting member 417. Therefore, by adjusting
the thickness of the adjustment member 417, the thickness of the second layer 432 can be
adjusted to an appropriate value, and it is easy to form the second layer 432 having a desired
thickness.
[0071]
Second Embodiment Next, a second embodiment of the ultrasonic device will be described. The
above-described first embodiment exemplifies a configuration in which the ultrasonic device 22
includes the acoustic matching layer 43 including the first layer 431 and the second layer 432.
On the other hand, the ultrasonic device of the second embodiment is different from the first
embodiment in that a single acoustic matching layer 47 is provided instead of the acoustic
matching layer 43.
[0072]
FIG. 12 is a cross-sectional view schematically showing a cross section of the ultrasonic device
25 of the second embodiment. As shown in FIG. 12, the ultrasonic device 25 includes an element
substrate 41, a sealing plate 42, an acoustic matching layer 47, and an acoustic lens 44. The
element substrate 41 of the present embodiment is the first embodiment except that the depth
dimension of the opening 411A is an integral multiple of λ / 2, where λ is the wavelength of
the ultrasonic wave transmitted by the ultrasonic transducer 45. It is configured substantially the
same as the form. The acoustic matching layer 47 is formed of a material whose acoustic
impedance is smaller than that of the acoustic lens 44, similarly to the second layer 432 of the
first embodiment. The acoustic matching layer 47 is filled in the opening 411A. An acoustic lens
44 is disposed on the + Z side of the acoustic matching layer 47.
[0073]
The thickness dimension L2 of the acoustic matching layer 47, that is, the distance L2 between
the interface F3 of the acoustic matching layer 47 and the acoustic lens 44, and the ultrasonic
transmission / reception surface 412A determines the wavelength of the ultrasonic wave
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transmitted from the ultrasonic transducer 45 The following formula (2) is satisfied, where n is
an integer of 1 or more. That is, the first layer 431 and the second layer 432 are formed such
that the dimension L2 is an integral multiple of λ / 2. Also in the present embodiment, the
thickness of the acoustic matching layer 47 can be adjusted by the depth of the opening 411A.
[0074]
[Equation 2] L 2 = (λ / 2) × n (2)
[0075]
[Reduction of Tailing by Acoustic Matching Layer] Also in the present embodiment, it is possible
to suppress the occurrence of tailing due to the interface reflection wave generated at the
interface F3, and it is possible to improve the distance resolution.
That is, the interface reflected wave propagating in the −Z direction generated at the interface
F3 reverses in phase when it is reflected by the ultrasonic wave transmitting / receiving surface
412A. Therefore, by setting the thickness of the acoustic matching layer 47 (the distance
between the ultrasonic transmitting / receiving surface 412A and the interface F3) to an integral
multiple of λ / 2, the phase of the interface reflected wave at the time of re-incident on the
interface F3 can be The phase can be reversed with respect to the ultrasonic wave U0 (see FIG. 5)
transmitted from the acoustic wave transducer 45. From the above, at least a part of the interface
reflected wave that is reflected by the interface F3 and is reflected by the ultrasonic transmitting
/ receiving surface 412A and then enters the interface F3 again is canceled by the ultrasonic
wave U0. Therefore, it is possible to suppress that the interface reflection wave is delayed to the
ultrasonic wave U0 and emitted into the living body, and the distance resolution can be
improved.
[0076]
FIG. 13 is a diagram showing an example of time change of the ultrasonic wave transmitted from
the ultrasonic device 25. As shown in FIG. In FIG. 13, as in FIG. 6, the time change of the
ultrasonic wave emitted from the ultrasonic device 25 of the present embodiment is indicated by
a solid line. On the other hand, an alternate long and short dash line indicates an example of a
time change of ultrasonic waves transmitted from the ultrasonic device of the comparative
example including a single acoustic matching layer whose thickness is not an integral multiple of
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λ / 2. Further, in FIG. 13, the value of the acoustic impedance of the acoustic lens 44 is 1.5
MRayls, the value of the acoustic impedance of the acoustic matching layer 47 is 1 MRayls, and
the Q value of the ultrasonic device 25 is 2. Further, the case where a driving voltage having a
waveform of a burst wave of 5 MHz, for example, is applied to the ultrasonic transducer 45 is
illustrated. As shown in FIG. 13, in the ultrasonic device 25 of the present embodiment indicated
by the solid line, the change in sound pressure after approximately 3.00 × 10 <-7> sec is
suppressed as compared with the comparative example indicated by the one-dot chain line. You
can see that the tailing is suppressed.
[0077]
[Operation and Effect of Second Embodiment] In the ultrasonic device 25 of the present
embodiment, the acoustic matching layer 47 is formed of a single layer, and has a thickness that
is an integral multiple of λ / 2 where λ is the wavelength of the ultrasonic wave. The acoustic
matching layer 47 has an acoustic impedance smaller than that of the acoustic lens 44. In the
ultrasonic device 25 configured as described above, even if the interface reflected wave is
generated at the interface F3 between the acoustic matching layer 47 and the acoustic lens 44,
the interface reflected wave reenters the interface as described above. The phase of the interface
reflection wave can be made opposite to the phase of the ultrasonic wave U0 transmitted from
the ultrasonic transducer 45. Therefore, by canceling at least a part of the interface reflected
wave, it is possible to suppress that the interface reflected wave is delayed to the ultrasonic wave
U0 and emitted from the acoustic lens 44 to the object to be measured, and the distance
resolution can be improved.
[0078]
Third Embodiment Next, a third embodiment of the ultrasonic device will be described. The
above-described second embodiment exemplifies the configuration in which the ultrasonic lens
25 is disposed on the acoustic matching layer 47 in the ultrasonic device 25. On the other hand,
the ultrasonic device according to the third embodiment is different from the ultrasonic device
according to the first embodiment in that the intermediate layer 48 is provided between the
acoustic matching layer 47 and the acoustic lens 44.
[0079]
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FIG. 14 is a cross sectional view schematically showing a cross section of the ultrasonic device 26
of the third embodiment. As shown in FIG. 14, the ultrasonic device 26 includes an element
substrate 41, a sealing plate 42, an acoustic matching layer 47, an intermediate layer 48, and an
acoustic lens 44. In the third embodiment, the intermediate layer 48 includes a first intermediate
layer 481 and a second intermediate layer 482, a first adjusting member 418 for adjusting the
thickness of the first intermediate layer 481, and a second intermediate layer 482 The second
adjusting member 419 is configured substantially the same as the second embodiment, except
that a second adjusting member 419 for adjusting the thickness of The first adjustment member
418 is configured in the same manner as the adjustment member 417 in the first embodiment,
and is provided on the + Z side of the substrate body 411. The recess surrounded by the first
adjustment member 418 is filled with the first intermediate layer 481 of the intermediate layer
48. Therefore, the thickness of the first intermediate layer 481 can be adjusted by appropriately
adjusting the thickness of the first adjusting member 418. The second adjustment member 419
is provided on the + Z side of the first adjustment member 418. The second intermediate layer
482 is filled in the recess surrounded by the second adjustment member 419. Therefore, the
thickness of the second intermediate layer 482 can be adjusted by appropriately adjusting the
thickness of the second adjusting member 419. An acoustic lens 44 is disposed on the + Z side of
the second adjustment member 419 and the second intermediate layer 482.
[0080]
The intermediate layer 48 has a first intermediate layer 481 provided on the acoustic matching
layer 47 and a second intermediate layer 482 provided on the first intermediate layer 481, as
shown in FIG. Among these, the first intermediate layer 481 corresponds to the first layer 431 of
the first embodiment, and the second intermediate layer 482 corresponds to the second layer
432 of the first embodiment. That is, the acoustic impedance of the first intermediate layer 481
is larger than the acoustic impedance of the second intermediate layer 482 and larger than the
acoustic impedance of the acoustic matching layer 47. Also, the acoustic impedance of the
second intermediate layer 482 is smaller than the acoustic impedance of the acoustic lens 44.
[0081]
Further, an interface between the acoustic matching layer 47 and the first intermediate layer 481
(hereinafter also referred to as a first interface F4), an interface between the first intermediate
layer 481 and the second intermediate layer 482 (hereinafter also referred to as a second
interface F5) The interface between the second intermediate layer 482 and the acoustic lens 44
(hereinafter also referred to as a third interface F6) is substantially parallel to the ultrasonic wave
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transmission / reception surface 412A. Furthermore, the thickness dimension L3 of the first
intermediate layer 481 and the second intermediate layer 482 (ie, the distance between the first
interface F4 and the second interface F5, and the distance between the second interface F5 and
the third interface F6) is Assuming that the wavelength of the ultrasonic wave transmitted from
the ultrasonic transducer 45 is λ, and the integer of 1 or more is n, the following formula (3) is
satisfied.
[0082]
[Equation 3] L 3 = (λ / 4) × (2 n −1) (3)
[0083]
The intermediate layer 48 configured in this manner functions in the same manner as the
acoustic matching layer 43 of the first embodiment.
That is, the first interface F4, the second interface F5, and the third interface F6 of the present
embodiment correspond to the ultrasonic transmission / reception surface 412A, the first
interface F1, and the second interface F2 of the first embodiment, respectively. The first interface
F4 of the present embodiment corresponds to the interface F3 of the second embodiment.
Therefore, even in the ultrasonic device 22 configured as described above, even if interface
reflection waves are generated at the interfaces F4, F5, and F6 as in the first embodiment and the
second embodiment, the interface reflection waves are used. The occurrence of tailing can be
suppressed, and distance resolution can be improved.
[0084]
[Operation and Effect of Third Embodiment] The ultrasonic device 26 of the present embodiment
includes an acoustic matching layer 47 provided on the ultrasonic transmission / reception
surface 412A of the vibrating film 412, and an intermediate layer 48 provided on the acoustic
matching layer 47. , And an acoustic lens 44 provided in the intermediate layer 48. The
intermediate layer 48 includes a first intermediate layer 481 on the acoustic matching layer 47
side and a second intermediate layer 482 on the acoustic lens 44 side, and each layer is an odd
multiple of λ / 4 where λ is the wavelength of ultrasonic waves. It has a thickness. The second
intermediate layer 482 has an acoustic impedance smaller than that of the first intermediate
layer 481 and the acoustic lens 44. In the ultrasonic device 26 configured as described above,
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even if interface reflection waves are generated at the interfaces F3, F4, and F5 in the acoustic
matching layer 43, the intermediate layer 48, and the acoustic lens 44, as described above, the
interface reflection When the wave reenters the interface, the phase of the interface reflected
wave can be made opposite to the phase of the ultrasonic wave U0 transmitted from the
ultrasonic transducer 45. Therefore, by canceling at least a part of the interface reflected wave, it
is possible to suppress that the interface reflected wave is delayed to the ultrasonic wave U0 and
emitted from the acoustic lens 44 to the object to be measured, and the distance resolution can
be improved.
[0085]
Further, in the present embodiment, the intermediate layer 48 is configured of two layers. Here,
even if the intermediate layer 48 is an even number of four or more layers, and the first
intermediate layer 481 and the second intermediate layer 482 are alternately arranged,
generation of tailing due to interface reflection waves is similarly performed. It can be
suppressed. On the other hand, if the intermediate layer 48 is thickened, the attenuation of the
ultrasonic wave may increase, and the transmission output of the ultrasonic wave and hence the
reception sensitivity may be reduced. Although it is possible to thin the entire intermediate layer
48 by thinning each layer, there is a limit to thinning each layer. On the other hand, by forming
the intermediate layer 48 with two layers, the intermediate layer 48 can be thinned, and the
thickness can be easily reduced.
[0086]
[Modification] The above-described embodiments are not limited to the configurations described
in the description of the embodiments, and modifications, improvements, and combinations of
the embodiments may be appropriately performed.
[0087]
For example, although the case where the acoustic matching layer 43 has a two-layer
configuration is exemplified in the first embodiment, the invention is not limited thereto, and the
acoustic matching layer 43 may be configured by four or more even layers.
In this case, the first layer 431 and the second layer 432 may be alternately arranged. Moreover,
although the case where the intermediate | middle layer 48 was 2 layer structure was illustrated
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in the said 3rd embodiment, it is not limited to this, You may be comprised by the even layer of
four or more layers. In this case, the first intermediate layer 481 and the second intermediate
layer 482 may be alternately arranged.
[0088]
In the first embodiment, although the configuration in which the first layer 431 and the second
layer 432 have the same thickness is illustrated, the present invention is not limited thereto, and
the first layer 431 and the second layer 432 have different thicknesses. It is also good. Similarly,
in the third embodiment, the configuration in which the first intermediate layer 481 and the
second intermediate layer 482 have the same thickness is exemplified, but the present invention
is not limited thereto, and the first intermediate layer 481 and the second intermediate layer The
layer 482 may have a different thickness.
[0089]
In the first embodiment, the adjustment member 417 for adjusting the thickness of the second
layer 432 is provided on the element substrate 41. However, the adjustment member 417 may
be integrally formed on the element substrate 41. The adjustment member 417 may not be
provided. For example, a recess may be provided in the acoustic lens 44 as an adjustment unit
for adjusting the thickness of the second layer 432. Even in this case, the thickness of the second
layer 432 can be adjusted by adjusting the depth of the recess of the acoustic lens 44. Further,
the adjustment member 417 may not be provided. For example, the thickness may be adjusted
after the second layer 432 is formed on the first layer 431, or the second layer 432 formed to
have an appropriate thickness may be disposed on the first layer 431. Good. Further, in the third
embodiment as well, the configuration in which the adjustment members 418 and 419 are
provided on the element substrate 41 is exemplified, but the configuration is not limited to this,
and the adjustment members 418 and 419 are integrally formed on the element substrate 41.
Alternatively, the adjustment members 418 and 419 may not be provided.
[0090]
In the first embodiment, the thickness of the first layer 431 is exemplified to be the same as the
depth of the opening 411A, and the thickness of the first layer 431 is adjusted by the depth of
the opening 411A. It is not limited. For example, the depth of the opening 411A and the
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thickness of the first layer 431 may be different. In the second and third embodiments, the
thickness of the acoustic matching layer 47 may be different from that of the opening 411A.
[0091]
In each of the above embodiments, as shown in FIG. 4, the substrate body 411 having the
opening 411A is provided on the side of the ultrasonic wave transmission / reception surface
412A of the diaphragm 412, and piezoelectric on the side of the operation surface 412B of the
diaphragm 412. Although the element 413 is provided and the structure which transmits /
receives an ultrasonic wave from the ultrasonic transmission / reception surface 412A side was
illustrated, it is not limited to this. For example, the substrate main body 411 may be provided on
the side of the ultrasonic wave transmitting / receiving surface 412A of the vibrating film 412,
and the piezoelectric element 413 may be provided on the side of the ultrasonic transmitting /
receiving surface 412A. In addition, the substrate main body 411 may be provided on the
working surface 412B side of the vibrating film 412, and the piezoelectric element 413 may be
provided on the ultrasonic wave transmitting / receiving surface 412A side. Further, the
substrate main body 411 may be provided on the actuating surface 412B side of the vibrating
film 412, and the piezoelectric element 413 may be provided in the opening 411A on the
actuating surface 412B side.
[0092]
In each of the above embodiments, as the piezoelectric element 413 included in the ultrasonic
transducer 45, the lower electrode 414, the piezoelectric film 415, and the upper electrode 416
are illustrated as an example configured by a laminated body stacked in the thickness direction.
It is not limited. For example, a pair of electrodes may be arranged to be opposed to each other
on one surface side orthogonal to the thickness direction of the piezoelectric film 415.
Alternatively, the electrodes may be disposed so as to sandwich the piezoelectric film on the side
surface along the thickness direction of the piezoelectric film. Moreover, although the structure
which the ultrasonic transducer 45 transmits / receives was illustrated in said each embodiment,
the structure which the ultrasonic transducer 45 only transmits may be sufficient.
[0093]
In the above-mentioned embodiment, although the ultrasonic measuring device which makes a
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living body measurement object was illustrated, the present invention is not limited to this. For
example, the present invention can be applied to an electronic device which performs detection
of defects of a structure or inspection of deterioration with various structures as objects to be
measured. In addition, for example, the present invention can be applied to an electronic device
that detects a defect of the measurement target with a semiconductor package, a wafer, or the
like as the measurement target.
[0094]
In addition, the specific structure in the practice of the present invention may be configured by
appropriately combining the above-described embodiments and modifications within the range in
which the object of the present invention can be achieved. You may
[0095]
DESCRIPTION OF SYMBOLS 1 ... ultrasonic measurement apparatus, 2 ... ultrasonic probe, 10 ...
control apparatus (control part), 22 ... ultrasonic device, 23 ... wiring board (circuit board), 24 ...
ultrasonic sensor (ultrasonic module), 41 ... Element substrate, 41A: back surface, 42: sealing
plate, 43: acoustic matching layer, 44: acoustic lens, 45: ultrasonic transducer, 46: ultrasonic
transducer array, 47: acoustic matching layer, 48: intermediate layer, 411: Substrate body
portion 411A: Opening portion 412: Vibrating film 412A: Ultrasonic wave transmission /
reception surface (first surface) 412B: Operating surface (second surface) 413: Piezoelectric
element 414: Lower electrode 414A: Lower electrode main body, 414B: lower electrode wire,
414C: lower terminal electrode wire, 415: piezoelectric film, 416: upper electrode, 416C, upper
electrode main body, 421: concave groove, 421A: gap, 431: fourth Layer 432 second layer 481
first intermediate layer 482 second intermediate layer F1 first interface F2 second interface F3
interface F4 first interface F5 second interface F6: third interface, L1: thickness dimension of first
layer and second layer, L2: thickness dimension of acoustic matching layer, L3: thickness
dimension of first intermediate layer and second intermediate layer.
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