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DESCRIPTION JP2016002352

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DESCRIPTION JP2016002352
The present invention provides a small acoustic sensor and ultrasonic probe capable of efficiently
transmitting and receiving ultrasonic waves. SOLUTION: A transmission / reception element of
ultrasonic waves in which a plurality of piezoelectric thin film portions are arranged in a plane, a
wiring for electrically connecting a plurality of piezoelectric thin film portions to input / output
electric signals, and transmission of ultrasonic waves And a switching unit configured to switch
at least a part of the wiring between time and reception to change the electrical impedance.
[Selected figure] Figure 4
Acoustic sensor and ultrasonic probe
[0001]
The present invention relates to an acoustic sensor and an ultrasonic probe.
[0002]
2. Description of the Related Art Conventionally, there is an ultrasonic diagnostic apparatus that
inspects an internal structure by irradiating ultrasonic waves into the inside of a subject and
receiving and analyzing the reflected waves.
In ultrasound diagnosis, since a subject can be nondestructively and noninvasively examined, it is
widely used in various applications such as examination for medical purposes and examination of
the inside of a building structure.
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1
[0003]
In an ultrasonic diagnostic apparatus, a piezoelectric body is used as a transducer. The
piezoelectric body is expanded and deformed by application of a predetermined voltage pulse to
emit an ultrasonic wave, and is expanded and deformed by incidence of a reflected wave (echo)
of the ultrasonic wave, and both ends of the piezoelectric body Charge (voltage) corresponding to
the intensity of the echo is generated and acquired as an electrical signal. The piezoelectric body
is made to function as an active acoustic sensor by transmitting and receiving ultrasonic waves at
appropriate timing. In recent years, miniaturization and high precision of an acoustic sensor of
ultrasonic waves in which such transducers are arranged in a plurality of predetermined patterns
are in progress. In Patent Document 1, piezoelectric elements and diaphragms related to
transmission and reception of ultrasonic waves are stacked and arranged in a two-dimensional
matrix using a piezoelectric material such as PVDF (polyvinylidene fluoride) and a manufacturing
technique such as an IC chip. A technique for generating compact image sensing arrays is
disclosed.
[0004]
However, in this acoustic sensor using ultrasonic waves, particularly when the reflectance of the
object is low, the reception intensity of the echo is very small compared to the transmission
intensity of the ultrasonic waves. Therefore, in order to obtain diagnostic data efficiently with
such an acoustic sensor, a transmission wave is generated with a low electrical impedance so that
high sound pressure can be obtained with a low voltage, and a weak input can be acquired as a
large voltage change. Preferably, an electrical signal relating to echo is obtained with high
electrical impedance. However, in order to obtain a configuration that covers a very large
difference in electrical impedance corresponding to such a very large difference in transmission /
reception strength, it has conventionally been necessary to use a special material or member,
which increases cost and manufacturing efficiency. There was a problem that it led to a fall.
[0005]
Therefore, in Patent Document 2, a piezoelectric element for transmitting an ultrasonic wave and
a piezoelectric element for receiving an echo are separately prepared and arranged in parallel,
and the numbers of piezoelectric bodies to be laminated are made different. A technique is
disclosed that responds to the difference in electrical impedance between reception and
transmission.
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[0006]
No. 5,160,870 U.S. Pat. No. 5,744,898
[0007]
However, when the piezoelectric body is laminated, the volume, in particular, the thickness is
increased correspondingly, which makes it difficult to use the thin film technology related to the
processing of the IC chip, and there is a problem that the fine processing becomes complicated
and difficult.
Moreover, since the area | region where the thickness of a piezoelectric element differs is
arranged, a three-dimensional structure arises, and the subject that wiring becomes complicated
and processing becomes difficult occurs.
[0008]
An object of the present invention is to provide a compact acoustic sensor and an ultrasonic
probe capable of efficiently transmitting and receiving ultrasonic waves.
[0009]
In order to achieve the above object, according to the first aspect of the present invention, the
plurality of piezoelectric thin film portions are electrically connected to each other by electrically
connecting the plurality of ultrasonic thin film portions with ultrasonic wave transmitting /
receiving elements arranged flat. An acoustic sensor comprising: a wire for inputting and
outputting a signal; and a switching unit for switching at least a part of the wire at the time of
transmission and reception of an ultrasonic wave to change an electrical impedance.
[0010]
The invention according to claim 2 is the acoustic sensor according to claim 1, wherein the
wiring does not change the sound axis of the ultrasonic wave transmitted and received by the
piezoelectric thin film portion connected by the wiring due to the switching. It is characterized by
being done.
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[0011]
The invention according to claim 3 is the acoustic sensor according to claim 1 or 2, wherein the
wiring is connected in series and in parallel with the connection of the plurality of piezoelectric
thin film portions at the time of transmission and reception of ultrasonic waves. It is
characterized by switching between connections.
[0012]
The invention according to claim 4 relates to the acoustic sensor according to any one of claims
1 to 3, in which the wiring changes the electric impedance by changing the number of the
piezoelectric thin film portions to be connected. It is characterized by
[0013]
The invention according to claim 5 relates to the acoustic sensor according to any one of claims
1 to 3, wherein the wiring includes all of the plurality of piezoelectric thin film portions when
transmitting and receiving ultrasonic waves. It is characterized by connecting.
[0014]
The invention according to claim 6 is characterized in that, in the acoustic sensor according to
any one of claims 1 to 5, the diaphragm includes a diaphragm joined to one of the planes formed
by the transmitting and receiving elements. There is.
[0015]
The invention according to claim 7 is the acoustic sensor according to any one of claims 1 to 6,
wherein the plurality of piezoelectric thin film portions are formed of a ferroelectric and the
plurality of piezoelectric thin film portions And a voltage supply unit for supplying a
predetermined voltage for setting the polarization characteristic.
[0016]
According to an eighth aspect of the present invention, in the acoustic sensor according to the
sixth aspect, the plurality of piezoelectric thin film portions are formed of a ferroelectric
substance, and a node and a belly of a vibration mode related to ultrasonic vibration of the
diaphragm. And at least one of the polarization characteristics of the piezoelectric thin film
portion and the connection order of the wires.
[0017]
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The invention according to claim 9 is the acoustic sensor according to any one of claims 1 to 8,
wherein the plurality of piezoelectric thin film portions are respectively stacked directly or
indirectly on a semiconductor substrate. The conduction state of a predetermined region of the
semiconductor substrate changes based on the amount of charge induced in the piezoelectric
thin film portion according to the sound pressure incident on the piezoelectric thin film, and a
signal according to the conduction state Is output to the wiring.
[0018]
The invention according to claim 10 is characterized in that, in the acoustic sensor according to
any one of claims 1 to 9, the switching unit switches the connection of the wiring by a transistor.
[0019]
The invention according to claim 11 is an ultrasonic probe comprising the acoustic sensor
according to any one of claims 1 to 10 arranged in a plurality of patterns in a predetermined
pattern.
[0020]
The invention according to claim 12 is the ultrasonic probe according to claim 11, wherein the
wiring connects the plurality of piezoelectric thin film portions so as to have a plurality of levels
of electrical impedance by switching by the switching means. The wiring switching control means
performs setting of apodization relating to transmission and reception of ultrasonic waves by
switching the electrical impedance of the acoustic sensor according to the arrangement of the
acoustic sensor.
[0021]
According to the present invention, there is an effect that ultrasonic waves can be efficiently
transmitted and received in a small acoustic sensor and an ultrasonic probe.
[0022]
FIG. 1 is an overall view showing an ultrasonic diagnostic apparatus according to an embodiment
of the present invention.
It is a block diagram which shows the internal structure of an ultrasound diagnosing device.
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It is a figure explaining an example of transducer arrangement in an ultrasonic probe.
In the ultrasonic diagnostic apparatus of this embodiment, it is a top view which shows the
wiring between each area | region at the time of (a) ultrasonic wave transmission, and (b)
ultrasonic wave reception.
It is a top view which shows the other example of the wiring between each area | region at the
time of ultrasonic wave reception.
It is a figure which shows the cross-section of one area | region among the transducers which
concern on transmission / reception of the ultrasonic wave in the ultrasound diagnosing device
of 2nd Embodiment.
It is a figure which shows arrangement | positioning of each area | region of one vibrator |
oscillator in the ultrasound diagnosing device of 2nd Embodiment, and the utilization pattern of
the said area | region at the time of transmission / reception of an ultrasonic wave.
It is a figure which shows the example of the utilization pattern of each area | region of the
vibrator | oscillator at the time of transmission / reception of the ultrasonic wave by the
ultrasound diagnosing device of 3rd Embodiment.
It is a figure which shows the example of the polarization state of each area | region of a vibrator.
It is a block diagram which shows the example of an internal structure of an ultrasound probe.
[0023]
Hereinafter, embodiments of the present invention will be described based on the drawings.
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First Embodiment FIG. 1 is an overall view of an ultrasonic diagnostic apparatus U provided with
an ultrasonic probe using the acoustic sensor of the present embodiment.
FIG. 2 is a block diagram showing an internal configuration of the ultrasonic diagnostic
apparatus U.
[0024]
As shown in FIG. 1, the ultrasonic diagnostic apparatus U comprises an ultrasonic diagnostic
apparatus main body 1 and an ultrasonic probe 2 (ultrasonic probe) connected to the ultrasonic
diagnostic apparatus main body 1 via a cable 22. Equipped with
[0025]
The ultrasonic diagnostic apparatus main body 1 is provided with an operation input unit 18 and
an output display unit 19.
Further, as shown in FIG. 2, in addition to the above, the ultrasonic diagnostic apparatus main
body 1 includes a control unit 11, a transmission unit 12, a reception unit 13, a transmission /
reception switching unit 14 (switching unit), and a voltage supply unit , An image processing unit
16, a storage unit 17, and the like.
[0026]
The control unit 11 outputs a drive signal to the ultrasonic probe 2 to output an ultrasonic wave
based on an input operation from the outside to an input device such as a keyboard or a mouse
of the operation input unit 18, and outputs an ultrasonic wave. The reception signal relating to
the ultrasonic wave reception is acquired from the child 2 and various processing is performed,
and the result etc. are displayed on the display screen of the output display unit 19 as necessary.
[0027]
The control unit 11 includes a central processing unit (CPU), a hard disk drive (HDD), a random
access memory (RAM), and the like.
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The CPU reads out various programs stored in the HDD, loads them into the RAM, and generally
controls the operation of each part of the ultrasonic diagnostic apparatus U according to the read
program.
The HDD stores a control program and various processing programs for operating the ultrasonic
diagnostic apparatus U, various setting data, and the like.
These programs and setting data may be stored in an auxiliary storage device using a nonvolatile memory such as a flash memory other than the HDD, for example, so as to be readable
and writable.
The RAM is volatile memory such as SRAM or DRAM, provides a working memory space to the
CPU, and stores temporary data.
[0028]
The transmitter 12 outputs a pulse signal to be supplied to the ultrasound probe 2 in accordance
with a control signal input from the controller 11, and causes the ultrasound probe 2 to generate
ultrasound.
The transmission unit 12 includes, for example, a clock generation circuit, a pulse generation
circuit, a pulse width setting unit, and a delay circuit. The clock generation circuit is a circuit that
generates a clock signal that determines the transmission timing and transmission frequency of
the pulse signal. The pulse generation circuit is a circuit that generates a bipolar rectangular
wave pulse of a preset voltage amplitude at a predetermined cycle. The pulse width setting unit
sets the pulse width of the rectangular wave pulse output from the pulse generation circuit.
Before or after the input to the pulse width setting unit, the rectangular wave pulse generated by
the pulse generation circuit is separated into different wiring paths for each transducer 21 of the
ultrasonic probe 2. The delay circuit is a circuit that delays and outputs the delay time set for
each of these wiring paths in accordance with the timing of transmitting the generated
rectangular wave pulse to each of the transducers 21.
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[0029]
The receiving unit 13 is a circuit that acquires the reception signal input from the ultrasound
probe 2 according to the control of the control unit 11. The receiving unit 13 includes, for
example, an amplifier, an A / D conversion circuit, and a phasing addition circuit. The amplifier is
a circuit that amplifies the received signal corresponding to the ultrasonic wave received by each
transducer 21 of the ultrasonic probe 2 at a predetermined amplification factor set in advance.
The A / D conversion circuit is a circuit that converts the amplified reception signal into digital
data at a predetermined sampling frequency. The phasing addition circuit gives a delay time to
the A / D converted received signal for each wiring path corresponding to each vibrator 21 to
adjust the time phase, and adds them (phasing addition) to obtain a sound. It is a circuit that
generates line data.
[0030]
The transmission / reception switching unit 14 transmits a drive signal from the transmission
unit 12 to the vibrator 21 when the ultrasonic wave is oscillated from the vibrator 21 based on
the control of the control unit 11, and the ultrasonic wave transmitted from the vibrator 21. In
the case of receiving the reflected wave (echo), the switching operation for outputting the
reception signal to the reception unit 13 is performed. Further, the transmission / reception
switching unit 14 outputs a switching signal related to switching of the wiring of each transducer
21 to be described later according to either transmission or reception, and changes the electrical
impedance of the transducer 21.
[0031]
The voltage supply unit 15 supplies power supplied from an external power supply or a battery
to each unit such as the control unit 11 or the ultrasonic probe 2 at a predetermined voltage. The
power supplied to the ultrasonic probe 2 is not only the pulse voltage related to the transmission
of the ultrasonic wave, but also the change setting of the polarization characteristic of the
ferroelectric thin film and the switching of the wiring in each transducer 21 as described later. It
is used for such an operation. Depending on the circuit configuration of the ultrasound probe 2, a
part or all of these voltages may be output via the transmission unit 12.
[0032]
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The image processing unit 16 includes a control unit including a CPU and a RAM that perform
control calculations separately from the CPU of the control unit 11, and performs calculation
processing for generating a diagnostic image based on reception data of ultrasonic waves. . The
diagnostic image may include image data to be displayed on the output display unit 19 in
substantially real time, a series of moving image data, still image data of a snapshot, and the like.
The image processing unit 16 may be configured such that the arithmetic processing is
performed by the CPU of the control unit 11. In addition to software processing according to a
program by the CPU, processing may be performed using a dedicated processing chip or the like
related to a DSP (Digital Signal Processor).
[0033]
The storage unit 17 is, for example, a volatile memory such as a dynamic random access memory
(DRAM). Alternatively, various non-volatile memories that can be rewritten at high speed, or a
combination thereof may be used. The storage unit 17 stores diagnostic image data for real-time
display processed by the image processing unit 16 in frame units. The ultrasonic diagnostic
image data stored in the storage unit 17 is read according to the control of the control unit 11
and transmitted to the output display unit 19 or to the outside of the ultrasonic diagnostic
apparatus U via a communication unit (not shown). It is output. At this time, if the display mode
of the output display unit 19 is a television system, a DSC (Digital Signal Converter) is provided
between the storage unit 17 and the output display unit 19 and the scan format is converted and
then output. It should be done.
[0034]
The operation input unit 18 includes a push button switch, a keyboard, a mouse, or a trackball,
or a combination of these, converts a user's input operation into an operation signal, and inputs
the operation signal to the ultrasonic diagnostic apparatus main body 1. Alternatively, a touch
sensor may be provided as the operation input unit 18, and a touch operation on the display
screen of the output display unit 19 may be detected to output a scanning signal related to the
operation type or the position.
[0035]
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The output display unit 19 is a display using any of various display methods such as a liquid
crystal display (LCD), an organic electro-luminescent (EL) display, an inorganic EL display, a
plasma display, and a cathode ray tube (CRT) display. It has a screen and its drive unit. The
output display unit 19 generates a drive signal of the display screen (each display pixel)
according to the control signal output from the control unit 11 or the image data generated by
the image processing unit 16 and performs ultrasonic diagnosis on the display screen. Display of
the menu, the status, and measurement data based on the received ultrasound. In addition, one or
more lamps (such as an LED lamp) can be provided to perform display such as on / off of the
power source depending on the lighting state.
[0036]
The operation input unit 18 and the output display unit 19 may be integrally provided in the
case of the ultrasonic diagnostic apparatus main body 1, or may be a USB cable, an HDMI cable
(registered trademark: HDMI), or the like. It may be attached to the outside via Further, as long as
the ultrasonic diagnostic apparatus main body 1 is provided with an operation input terminal and
a display output terminal, peripheral devices for conventional operation and display may be
connected to these terminals for use.
[0037]
The ultrasound probe 2 oscillates an ultrasonic wave (here, about 1 to 30 MHz) and emits it to a
subject such as a living body, and a reflected wave (a reflected wave reflected by the subject
among the emitted ultrasonic waves) Functions as an acoustic sensor that receives echoes and
converts them into electrical signals. The ultrasonic probe 2 includes a transducer array 210
which is an array of a plurality of transducers 21 for transmitting and receiving ultrasonic waves,
and a cable 22. The cable 22 has a connector (not shown) with the ultrasonic diagnostic
apparatus main body 1 at one end thereof, and the ultrasonic probe 2 is configured to be
detachable from the ultrasonic diagnostic apparatus main body 1 by the cable 22. ing.
[0038]
The transducer array 210 has a thin film-like (usually less than 10 μm thick, more preferably
less than 1 μm) piezoelectric body, and is configured to be able to apply a voltage between both
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sides of the piezoelectric thin film (eg, It is an arrangement of a plurality of transducers 21
provided with piezoelectric elements (by electrodes), and these transducers 21 are, for example,
on a semiconductor substrate (silicon substrate) along the surface where the ultrasonic probe 2
contacts the object. Etc. are arranged two-dimensionally. By applying a pulse voltage (pulse
signal) between both surfaces of the piezoelectric thin film, the piezoelectric is deformed
according to the electric field generated in each piezoelectric, and an ultrasonic wave is emitted
(sent). Further, when an ultrasonic wave of a predetermined frequency band is incident on the
vibrator 21, the thickness of the piezoelectric body fluctuates (oscillates) due to the sound
pressure, and an electric charge corresponding to the amount of fluctuation appears in the
piezoelectric thin film. A corresponding amount of charge is output and acquired (measured).
[0039]
Here, as a piezoelectric material used for the vibrator 21, for example, a ferroelectric material
such as PZT (lead zirconate titanate) is used. As the ferroelectric material, in addition to PZT,
ferroelectrics having various perovskite-type structures, ferroelectrics having a tungsten-bronzetype structure, ferroelectrics having a bismuth layer structure, PVDF (polyvinylidene fluoride) or
PVDF-based copolymer Organic ferroelectrics as described above, or composite materials using
these in combination may be used. These ferroelectrics usually have a multi-domain and / or
polycrystalline structure. The electric field generated in the ferroelectric during transmission and
reception of ultrasonic waves is smaller than the coercive electric field strength of the
ferroelectric.
[0040]
Here, the piezoelectric thin film of the vibrator 21 is dominated by a thickness direction vibration
mode which fluctuates (oscillates) in the direction of the electric field according to the
piezoelectric constant d33. In the vibrator 21, ultrasonic waves are mainly emitted in the
expansion and contraction direction along with the expansion and contraction of the
piezoelectric thin film related to the vibration in the thickness direction vibration mode, and the
echo is incident in the same direction. In addition to this, depending on the shape of the
piezoelectric thin film, etc., a radial vibration mode or the like that fluctuates in a plane
perpendicular to the direction of the electric field (that is, the length in the width direction of the
piezoelectric thin film) according to the piezoelectric constant d31 It may be considered.
[0041]
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FIG. 3 is a view for explaining an example of the transducer array 210 in the ultrasound probe 2.
In the ultrasound probe 2 of the present embodiment, the transducer array 210 includes 192
transducers 21 arranged in a predetermined pattern, for example, a two-dimensional array.
Alternatively, the plurality of transducers 21 may be arranged in a one-dimensional array
provided along a predetermined scanning direction. In addition, the number of transducers 21
can be set arbitrarily. The ultrasound probe 2 may employ either an electronic scanning method
or a mechanical scanning method, and may adopt any of a linear scanning method, a sector
scanning method or a convex scanning method as a scanning method. It may be Moreover, the
bandwidth of the reception frequency of the ultrasonic wave in the ultrasonic probe 2 can be set
arbitrarily. In addition, the ultrasonic diagnostic apparatus U can be configured to be able to
connect and use any one of a plurality of different ultrasonic probes 2 according to an object of
diagnosis to the ultrasonic diagnostic apparatus main body 1.
[0042]
Next, the vibrator 21 of the present embodiment will be described. The piezoelectric body
according to each vibrator 21 of the present embodiment is divided into smaller areas
(piezoelectric thin film portions) in a two-dimensional matrix, and voltages are individually
applied to the respective areas, Further, charges are acquired according to the incident ultrasonic
waves and converted into voltages. The respective regions are electrically connected to each
other in a predetermined pattern using a wire, and here, as the wire pattern, two types for
ultrasonic wave transmission and ultrasonic wave reception are provided. These two types of
wiring are used by switching between transmission and reception of ultrasonic waves. Control of
application of voltage to each region may be performed individually or collectively. In addition,
each region may be completely divided through an insulating layer, an air gap or the like, or each
region may be simply defined in one piezoelectric thin film.
[0043]
FIG. 4 is a plan view showing the wiring between the regions at the time of (a) ultrasonic wave
transmission and at (b) ultrasonic wave reception in the ultrasonic diagnostic apparatus U of the
present embodiment.
[0044]
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Here, the piezoelectric body of the vibrator 21 is divided into 64 regions in an 8 × 8 matrix.
As shown in FIG. 4A, at the time of transmission of ultrasonic waves, the piezoelectric thin films
in each region are electrically connected in parallel to the voltage application circuit (not shown)
in a common centroid arrangement, respectively, The output voltage is equally applied to each
region. That is, the circuit related to the wiring has a low electrical impedance. At this time, one
surface of the piezoelectric thin film in each region may simply be grounded.
[0045]
On the other hand, as shown in FIG. 4B, at the time of reception of the ultrasonic wave, the wire
indicated by the solid line among the two wires connected to the nodes related to each region is
connected to one surface of the piezoelectric thin film, The wiring indicated by the broken line is
connected to the other surface of the piezoelectric thin film. Then, the wiring connected to the
one surface at one end is connected to the other surface of the piezoelectric thin film of the other
region at the other end, thereby connecting the respective regions in series There is. By this
series connection, charges (electric fields) generated in the respective regions are serially added
and output. That is, the circuit related to the wiring has a high electrical impedance. At this time,
one end of the wires arranged in series is connected to the receiver 13, and the output charge or
voltage is amplified by the receiver 13 and processed as an ultrasonic reception signal.
[0046]
At this time, as described above, the respective surfaces of the piezoelectric thin films in the
respective regions in the case of parallel connection are wired so as to be symmetrical with
respect to the center of the piezoelectric element by the common centroid arrangement. On the
other hand, when the respective regions are connected in series, one surface and the other
surface of eight regions among the sixteen regions divided into four with respect to the center of
the piezoelectric body are connected in order. , The order of connection is designed not to be
biased significantly. Therefore, the influence of parasitic capacitance or wiring resistance
generated between wires or wires appears equally, and the axis (sound axis) of the ultrasonic
beam to be transmitted and received is aligned substantially at the center of the ultrasonic wave
transmitting / receiving surface of the transducer 21; The switching between transmission and
reception does not change beyond the range of errors or slight deviations related to the order of
serial connection. The electrical impedance changes 4096 times between the parallel connection
and the parallel connection of the 64 regions provided in this manner.
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[0047]
FIG. 5 is a plan view showing another example of the wiring between the respective regions at
the time of ultrasonic wave reception.
[0048]
In this example, when transmitting ultrasonic waves, all 64 areas are connected in parallel and
ultrasonic waves are transmitted with low impedance as in the example shown in FIG. By
connecting only a part of the 64 areas, for example, only 8 areas in parallel (sparse connection)
and using it for reception, the impedance is not lowered compared to when transmitting the
ultrasonic waves.
[0049]
In this wiring, the same wiring can be used at the time of transmission and at the time of
reception, and at the time of reception, the wiring between the area shared by transmission and
reception and the area used only at the time of transmission should be switched to disconnection.
Thus, the electric impedance is switched without changing the sound axis at the time of
transmission and the sound axis at the time of reception.
Also, by using only parallel connection, it is sufficient to connect only the same surface of each
region.
Therefore, the wiring becomes easy as compared with the above-mentioned example. The
conduction state of the wiring to the area used only at the time of transmission can be switched
by the switching signal from the transmission / reception switching unit 14 based on the control
of the control unit 11 using a switching element such as a FET (transistor) . These switching
elements may be disposed between the piezoelectric elements in each region as shown by the
positions indicated by “x” symbols in FIG. 5 or provided outside the piezoelectric element
arrangement range related to the vibrator 21. It is good.
[0050]
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In order not to change the sound axis, it is most preferable that the wires be provided
symmetrically with respect to the center of the ultrasonic wave transmitting / receiving surface
of the transducer 21 as described above. In the case of parallel connection, it is also possible to
wire radially from the center as long as ultrasonic transmission and reception in each area is not
impeded. As a result, the ultrasonic transmission / reception positions from the respective
transducers 21 can be easily identified, and can be easily arranged at equal intervals. In addition,
symmetrical wiring patterns may be determined using conventionally known circuit wiring
patterns. In the case where it is difficult to provide the order of wiring symmetrically with respect
to the center of the vibrator 21, the sound axis may be a wiring that is slightly shifted with
respect to the center of the vibrator 21. Also in such a case, the wiring can be biased from the
center of the transducer 21 so that the sound axis does not shift between transmission and
reception of the ultrasonic wave in consideration of the shift. The acoustic sensor is configured
by the configuration of the vibrator 21 and the wiring and switching according to one vibrator
21.
[0051]
As described above, the electrical impedance is changed by switching the wiring. Here, since the
electrical impedance also affects the transmission and reception efficiency, the apodization can
be set by making the electrical impedance different for each transducer 21 at the time of
transmission or reception of the ultrasonic wave. Arrows shown in FIG. 3 schematically indicate
the polarization amount at each position related to apodization. That is, by increasing the
transmission / reception efficiency near the center of the transducer array 210 and setting the
transmission / reception efficiency low at the end, apodization is realized. As described above, in
order to set the reception efficiency of each transducer 21 in multiple stages, not only two types
of wiring for connecting the respective areas, but also three or more types of multistage (multiple
It can be provided corresponding to the setting of step).
[0052]
As described above, in the ultrasonic probe 2 according to the ultrasonic diagnostic apparatus U
of the first embodiment, a plurality of regions are arranged in a planar manner on the
semiconductor substrate 100, and the plurality of regions are electrically connected. A wire for
inputting and outputting an electrical signal is provided, and at least a part of the wire is
switched to change the electrical impedance at the time of transmission and reception of
ultrasonic waves. Therefore, using the manufacturing technology of a semiconductor chip using a
ferroelectric thin film such as a ferroelectric memory structure, electricity corresponding to the
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large difference between the electric requirements at the time of transmission and reception of
ultrasonic waves It is possible to easily obtain a small acoustic sensor and an ultrasonic probe
capable of efficiently transmitting and receiving ultrasonic waves by setting the impedance.
[0053]
Further, in the wiring connecting the respective regions, the sound axis of the ultrasonic waves
transmitted and received by the respective regions connected by the wiring is not changed by
switching at the time of transmission and reception of the ultrasonic waves. Therefore,
transmission of ultrasonic waves can be performed at an appropriate interval from a desired
position, and echoes of the transmitted ultrasonic waves can be received with high accuracy.
[0054]
In addition, these lines connect each area in parallel at the time of transmission of ultrasonic
waves, and connect each area in series at the time of reception. As a result, the difference in
electrical impedance can be determined to be very large as the number of regions increases, so
efficient matching with completely different electrical impedance can be achieved.
[0055]
Also, these wires increase the electrical impedance by reducing the number of parallel connected
regions during reception. Therefore, the electrical impedance is matched only by disconnecting
the wiring portion connected only at the time of transmission by the switching element, so that
the transmission / reception sensitivity can be efficiently raised together with a very easy circuit
configuration.
[0056]
In addition, since these wires are connected so as to connect all of the areas when transmitting
and receiving ultrasonic waves, it is possible to increase the transmission and reception
sensitivity of ultrasonic waves without wasting the set areas. It can.
[0057]
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In addition, since these wirings can be switched by a transistor such as an FET, the
manufacturing technology of the semiconductor element can be used as it is, and can be easily
formed integrally with the structure relating to ultrasonic transmission / reception.
[0058]
Further, by using the ultrasound probe 2 in which the transducers 21 in which a plurality of
regions are thus defined and the electrical impedance is variably formed are arrayed in a
predetermined pattern, for example, a plurality of two-dimensional arrays, It is possible to
acquire an accurate ultrasound image with a small size and low power consumption.
[0059]
Moreover, the wiring connecting the plurality of regions can be connected in a plurality of ways
so as to have a plurality of levels of electrical impedance, and the electrical connection according
to the position of each transducer 21 in the transducer array 210 of the ultrasonic probe 2 The
impedance can be switched.
That is, since each transducer 21 can be set to the transmission / reception sensitivity according
to the respectively set electrical impedance, the reception sensitivity at the end portion of the
transducer array 210 is lowered thereby, and the side lobe at the time of reception etc. Can be
realized to reduce apodization.
[0060]
Second Embodiment Next, an ultrasonic diagnostic apparatus according to a second embodiment
will be described.
The configuration of the ultrasonic diagnostic apparatus U of the second embodiment is the same
as the configuration of the ultrasonic diagnostic apparatus U of the first embodiment, and the
explanation will be omitted as the same reference numerals are used.
[0061]
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In FIG. 6, the cross-section of one area | region is shown among the transducers 21 which
concern on transmission / reception of the ultrasonic wave in the ultrasound diagnosing device U
of this embodiment.
Each region according to the vibrator 21 of the present embodiment is formed on the
semiconductor substrate 100 as a stacked structure in which the ferroelectric thin film layer 112
and the gate electrode 113 are stacked with the gate insulating film 111 interposed
therebetween. Side walls 114 and 115 are provided on both sides of the ferroelectric thin film
layer 112. A source region 101, a drain region 102, and an extension region (not shown) are
formed on the upper surface of the semiconductor substrate 100 with a region under the gate
electrode 113 (portion to be a channel region) interposed therebetween. Source region 101 and
drain region 102 are connected to metal interconnections 103 and 104, respectively. The side
walls 114 and 115 need to be formed so as not to prevent the expansion and contraction of the
ferroelectric thin film layer 112, or may not be formed.
[0062]
The semiconductor substrate 100 is, for example, a p-type silicon substrate. By implanting n-type
ions such as phosphorus or arsenic into the semiconductor substrate 100, an extension region is
formed, and further, a source region 101 and a drain region 102 are formed. In the
semiconductor substrate 100, a plurality of stacked structures of the above-described respective
regions with respect to one vibrator 21 are arrayed and provided. The semiconductor substrate
100 in the portion where the layered structure related to the vibrators 21 is provided is scraped
from the opposite surface of the structure, that is, from the lower side in FIG. 6 to form a
common hole 100a. The bottom surface of (i.e., the top surface in FIG. 6) is a thin plate structure
100b having a thickness necessary to form a channel region in the laminated structure. The thin
plate structure 100 b is a diaphragm that vibrates according to the expansion and contraction of
the vibrator 21 (ferroelectric thin film layer 112). That is, the thin plate structure 100 b forms a
diaphragm structure which is displaced according to the stress related to the expansion and
contraction of the ferroelectric thin film layer 112 in each stacked region. The thin plate
structure 100 b may be separately formed according to each vibrator 21.
[0063]
Source region 101 is grounded via metal wire 103. The drain region 102 is connected to the
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signal output via the metal wire 104. The gate electrode 113 can be connected to the voltage
supply unit 15 via a voltage application circuit (not shown) provided on the semiconductor
substrate 100, and supplies a gate-source bias voltage to the gate electrode 113. By applying a
pulsed bias voltage to the ferroelectric thin film layer 112, the ferroelectric thin film layer 112 is
deformed according to the bias voltage to emit an ultrasonic wave. When a higher voltage is
applied for a predetermined time to generate an electric field higher than the coercive electric
field in the ferroelectric thin film layer 112, the polarization state of the ferroelectric thin film
layer 112 is changed.
[0064]
On the other hand, when the ultrasonic wave is incident on the ferroelectric thin film layer 112
while the gate electrode 113 is kept in the floating state or the ground state, charges
corresponding to the ultrasonic intensity (sound pressure) and the polarization state Occurs on
both sides of the ferroelectric thin film layer 112. As a result, the conduction state in the channel
region between the source region 101 and the drain region 102 of each region changes in
accordance with the charge generated on the side of the gate insulating film 111 of the
ferroelectric thin film layer 112, and the source-drain is changed. The charge that has flowed is
output as a signal from the drain region 102.
[0065]
The ferroelectric thin film layer 112 is, for example, a thin film (generally less than 10 μm, more
preferably less than 1 μm) using the above-mentioned various ferroelectric members such as
PZT (lead zirconate titanate). The surface area and the thickness are set to values corresponding
to the reception frequency of ultrasonic waves while maintaining the channel length between the
drain region 102 appropriately.
[0066]
The ferroelectric thin film layer 112 and the gate electrode 113 are formed on the
semiconductor substrate 100 by sputtering (PVD (physical vapor deposition)), sol-gel method,
CVD (chemical vapor deposition), etc. Then, it is formed by etching back using a mask (such as a
photoresist pattern) in accordance with the structure of the structure.
Next, sidewalls 114 and 115 are also formed by etching after forming an insulating film (for
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example, silicon dioxide SiO 2) on semiconductor substrate 100, ferroelectric thin film layer 112,
and gate electrode 113 using the CVD method or the like. Ru. The source region 101 and the
drain region 102 are formed by performing ion implantation by self alignment using the gate
electrode 113 and the sidewalls 114 and 115 as a mask. Then, metal wires 103 and 104
connected to the gate electrode 113, the source region 101 and the drain region 102 are
provided. The plurality of transducers 21 and the ferroelectric thin film layers 112
corresponding to the respective regions can be formed individually, but by forming a plurality of
them on one or a small number of wafers, The transducer array 210 can be formed easily and at
low cost while arranging the plurality of transducers 21 with high accuracy.
[0067]
As described above, by using the ferroelectric thin film layer 112 for the transducer 21 of the
ultrasonic probe 2, the ferroelectric layer is uniformly formed, and the polarization with high
accuracy corresponding to the incident ultrasonic intensity occurs. . Further, in such a thin film,
since the voltage (coercive field voltage) for generating a coercive electric field necessary for
polarization inversion is sufficiently small, the ferroelectric thin film can be easily formed even
after the circuit of the vibrator 21 is formed. A voltage can be applied to layer 112 to change the
polarization state. At this time, in the vibrator 21, the withstand voltage of each part, for example,
the dielectric breakdown voltage of the gate insulating film, the withstand voltage between the
drain and the source, the withstand voltage between the P and N wells, the withstand voltage
between the well and the semiconductor substrate, etc. The film thickness of the ferroelectric
thin film layer 112 needs to be determined so as to be equal to or higher than the maximum
applied voltage for causing the ferroelectric thin film layer 112 to generate a coercive electric
field. In general, the withstand voltage is 10 to several tens of volts or less, and the coercive field
voltage may be smaller than this. The coercive electric field is, for example, of the order of 1 MV
/ m depending on the ferroelectric part material, composition ratio, crystal system, etc., and the
thickness of the gate insulating film 111 to make the coercive electric field voltage less than the
withstand voltage. The thickness of the ferroelectric thin film layer 112 is on the order of 1 μm
or less including the influence.
[0068]
FIG. 7 is a view showing the arrangement of each region of one transducer 21 in the ultrasonic
diagnostic apparatus U of the present embodiment and the usage pattern of the region at the
time of transmission and reception of ultrasonic waves.
[0069]
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21
In the ultrasonic diagnostic apparatus U of the present embodiment, the region related to the
vibrator 21 is two-dimensionally arranged in a substantially circular shape as a whole, and at
least a part of the laminated structure overlaps the thin plate structure 100 b.
As described above, the thin plate structure 100b can be provided commonly to a plurality of
vibrators 21. However, in the following, for simplification of the description, each of the thin
plate structures 100b may be provided according to the size of one vibrator 21. The case where
it is provided will be described as an example.
[0070]
As shown in FIG. 7A, at the time of transmission of ultrasonic waves, all the regions are
connected in parallel and the same voltage is applied to the ferroelectric thin film layer 112 as in
the ultrasonic diagnostic apparatus U of the first embodiment. It is applied and an ultrasonic
wave is emitted. At this time, as described above, the thin plate structure 100b is displaced in
response to the deformation and vibration of the ferroelectric thin film layer 112, and vibrates at
the same frequency, and an ultrasonic wave is transmitted together with the ferroelectric thin
film layer 112 in accordance with the vibration. So, the transmission efficiency of ultrasonic
waves is increased.
[0071]
As shown in FIG. 7B, at the time of reception of ultrasonic waves, only a partial region along the
peripheral portion among regions forming the transducers 21 arranged in a circle is connected in
parallel (sparse connection), The electrical impedance is set high. As a result, as in the other
examples in the first embodiment, the charge related to the expansion and contraction of the
corresponding ferroelectric thin film layer 112 is acquired from the channel region of the
connected region, and is efficiently converted into a voltage signal, It can be output.
[0072]
Here, also in the ultrasound probe 2 according to the present embodiment, as in the first
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embodiment, not only the number of areas to be energized by switching on and off at
transmission and reception is switched, but the wiring is switched in series and in parallel It can
be done. Further, parallel connection and series connection may be combined and set to an
appropriate electrical impedance between the respective regions.
[0073]
As described above, in the ultrasonic probe 2 of the second embodiment, one of the planes
formed by the respective regions of the vibrator 21 is joined to the bottom of the hole of the
semiconductor substrate 100, and the portion of the semiconductor substrate 100 is a thin plate.
It has a structure 100b. Therefore, the ultrasonic wave transmission / reception efficiency can be
further increased by ultrasonically vibrating the thin plate structure 100b as a diaphragm in
accordance with the vibration related to the ultrasonic wave transmission / reception of each
transducer 21.
[0074]
In addition, the plurality of regions are stacked and arranged indirectly on the semiconductor
substrate 100 with the gate insulating film 111 interposed therebetween, and the respective
regions are respectively arranged according to the sound pressure incident on each region of the
ferroelectric thin film layer 112. The conduction state of the channel region in the semiconductor
substrate 100 is changed based on the amount of induced charges, and a signal corresponding to
the conduction state is output to the wiring through the channel region. Therefore, it is possible
to easily and efficiently perform efficient ultrasonic transmission and reception without major
design changes by the configuration similar to that of the 1T ferroelectric memory.
[0075]
Third Embodiment Next, an ultrasonic diagnostic apparatus U including the ultrasonic probe 2 of
the third embodiment will be described. The ultrasonic diagnostic apparatus U has the same
configuration as the ultrasonic diagnostic apparatus U of the second embodiment, and the same
reference numerals are given and the description is omitted.
[0076]
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FIG. 8 is a view showing an example of a usage pattern of each region of the transducer 21 at the
time of transmission and reception of ultrasonic waves by the ultrasonic diagnostic apparatus U
of the present embodiment.
[0077]
In this example, as shown in FIG. 8A, a rectangular wave for ultrasonic wave transmission is
provided in a region provided in the vicinity of the peripheral portion of the ferroelectric thin
film layer 112 related to the vibrator 21 at the time of ultrasonic wave transmission. Wires are
supplied so as to supply a pulse, and as shown in FIG. 8B, charges are received from a region
provided in contact with the vicinity of the center of the ferroelectric thin film layer 112 related
to the vibrator 21 at the time of receiving ultrasonic waves. It is wired so that (voltage) is output
and detected.
[0078]
Here, for example, bending vibration is generated in the thin plate structure 100b indirectly
bonded to the ferroelectric thin film layer 112 against expansion and contraction according to
the piezoelectric constant d31 of the ferroelectric thin film layer 112 at the time of ultrasonic
wave transmission. Ultrasonic waves can be efficiently emitted in a desired direction.
On the other hand, at the time of ultrasonic wave reception, the expansion and contraction
according to the piezoelectric constant d33 of the ferroelectric thin film layer 112 accompanying
the echo can be reinforced by the vibration of the thin plate structure 100b in the vicinity of the
center to efficiently receive.
[0079]
Conversely, the excitation state of each vibration mode may be changed by changing the
thickness distribution of the thin plate structure 100b for each position.
[0080]
FIG. 9 is a view showing an example of the polarization state of each region of the vibrator 21. As
shown in FIG.
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The polarization state can be determined by supplying a voltage equal to or higher than the
coercive field voltage to each region.
In the ultrasound probe 2 of the present embodiment, the transmission / reception efficiency of
ultrasound can be increased by appropriately setting this polarization state in each region. The
polarization characteristic of the ferroelectric thin film layer 112 is changed by setting the
absolute value of the bias voltage supplied from the voltage supply circuit to the gate electrode
113 or more while setting the source region 101 and the drain region 102 to ground. Ru.
[0081]
In the ultrasonic probe 2 of the present embodiment, the ultrasonic intensity transmitted /
received from each region is increased by vibrating the circular thin plate structure 100b as a
diaphragm. However, in the thin plate structure 100b, since the vibration whose end is a fixed
end (node) is excited, the amplitude is different between the end and the center which is the
antinode of the natural vibration mode.
[0082]
In addition, when vibration of a frequency outside the ultrasonic frequency to be acquired can be
received by the vibrator 21 according to the resonant frequency or anti-resonant frequency of
the thin plate structure 100b, the amplitude related to the vibration is In the case where a large
place is localized in the thin plate structure 100b, the polarization amount of the region
corresponding to the portion can be set small.
[0083]
In the case where a second or higher harmonic appears largely in the vibration of the thin plate
structure 100b, the polarization characteristic is reversed in the region where the phase of the
vibration is reversed based on the harmonic, and the amplitude of the same direction is You may
set so that an ultrasonic wave may be output.
[0084]
Based on these, here, for example, at the end of the thin plate structure 100b where the
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amplitude decreases, the amount of polarization is set large to increase the amplitude (○ symbol,
× symbol) while aligning the amplitude phase, and the amplitude is large. In the region near the
central portion, the amount of polarization is set small (no symbol).
As a result, it is possible to transmit and receive ultrasonic waves having substantially uniform
amplitude and in phase in the entire vibrator 21.
[0085]
As described above, the ferroelectric thin film layer 112 is used for the ultrasonic probe 2 of the
third embodiment, and the coercive electric field voltage from the voltage supply unit 15 is
applied to each region of the ferroelectric thin film layer 112. The polarization characteristics
can be set by supplying the above voltages.
Therefore, by setting the polarization characteristics of each region according to the vibration
mode of the thin plate structure 100b which is the bottom of the hole of the semiconductor
substrate 100 in which ultrasonic vibration occurs according to the vibration mode as one
diaphragm, more uniform and efficient It is possible to transmit and receive ultrasonic waves
with high sensitivity.
[0086]
In addition, by determining at least one of the polarization characteristics of each region of the
vibrator 21 and the connection order of wiring according to the position of the node and the
antinode of the vibration mode related to the ultrasonic vibration of the thin plate structure
100b, each vibration mode Can appropriately transmit and receive ultrasonic waves by
appropriately using the
[0087]
The present invention is not limited to the above embodiment, and various modifications are
possible.
For example, although the above embodiments have been described as using various ferroelectric
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materials as the piezoelectric thin film, a piezoelectric material not having ferroelectricity may be
used.
[0088]
In the above embodiment, setting control of transmission / reception of the ultrasonic wave in
the ultrasonic probe 2 is performed based on the control in the ultrasonic diagnostic apparatus
main body 1. The setting control may be performed.
[0089]
FIG. 10 is a block diagram showing an example of the internal configuration of the ultrasound
probe 2.
The ultrasound probe 2 includes a receiving unit 23, a transmitting unit 24, a transmission /
reception switching unit 28, a drive control unit 25 and a communication unit 26 in addition to
the transducer array 210, and the communication unit 26 via the cable 22. The drive control unit
25 autonomously switches the transmission and reception of the ultrasonic wave from the
vibrator 21 based on the setting acquired from the external ultrasonic diagnostic apparatus main
body 1 by using the ultrasonic wave from the appropriate vibrator 21 at an appropriate timing.
Can be sent or received. Then, only the reception data subjected to various processing in the
reception unit 23 is transmitted to the ultrasonic diagnostic apparatus main body 1 via the cable
22 by the communication unit 26. The communication unit 26 may be a communication
interface related to wireless communication, and in this case, wireless communication without
using the cable 22, for example, wireless LAN (such as IEEE 802.11n), Bluetooth communication
(registered trademark: Bluetooth) The communication system of each frequency band based on
(1) and body area network (IEEE802.15.6) is used.
[0090]
Therefore, in the ultrasonic probe 2, the drive control unit 25 sets the polarization state of each
transducer 21 of the transducer array 210 to realize apodization at the time of transmission and
reception of the ultrasonic wave, and each region It is possible to change the setting of the
electrical impedance at the time of reception and at the time of transmission by switching the
wiring of.
[0091]
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The setting of the apodization can also be made by changing the polarization characteristic of the
ferroelectric for each of the transducers 21, and may be performed by combining the switching
of the wiring and the change of the polarization characteristic of the ferroelectric.
[0092]
Further, in the above embodiment, the case is described in which wiring between areas is made
so that the sound axis becomes equal at transmission and reception. However, transmission and
reception can be performed within the range where measurement and display data can be
obtained with the required accuracy. The sound axis may not be equal (or change) at reception.
For example, the piezoelectric thin film may be simply divided into two regions, one for reception
and the other for transmission.
Even with such an arrangement, the configuration relating to the transmission and reception of
ultrasonic waves can be easily formed in a planar manner on a semiconductor substrate using
thin film technology.
[0093]
Further, even in the case where the wiring is made such that the sound axes become equal (do
not change), the present invention makes the case where the sound axis becomes equal to the
central axis of the vibrator 21 or the wiring is symmetrical with respect to the central axis. It is
not limited to the case where it is provided. In the range where measurement and display data
can be obtained with the required accuracy, the wiring for ultrasonic wave reception and the
wiring for ultrasonic wave transmission are intermingled, preventing the formation process from
becoming complicated and unnecessary parasitic capacitance from being generated. In order to
reduce the distance, the wiring may be somewhat asymmetrical, and the sound axis may be offset
from the central axis of the vibrator 21.
[0094]
In the above embodiment, the ferroelectric thin film layer is indirectly stacked on the
semiconductor substrate via the gate oxide film, but the ferroelectric thin film layer is not
sandwiched between the gate oxide films as in the MFSFET structure. It may be stacked directly
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on the semiconductor substrate.
[0095]
In the second embodiment, the ferroelectric thin film layer is provided in the laminated structure
of the gate electrode, and the charge according to the intensity of the ultrasonic wave (the
amount of deformation of the ferroelectric thin film layer) incident on the ferroelectric thin film
layer. Although the 1T-type configuration that directly reads out is described as an example, the
present invention is not limited to this.
For example, a capacitor having a ferroelectric thin film layer interposed therebetween is
provided, one of the electrodes of the capacitor is connected to the source region of the FET, and
the source is formed at the timing when the channel region is formed according to voltage
application to the gate electrode. A 1T1C type configuration in which charge is read out from the
region through the channel region may be used. In this case, a diaphragm or a piezoelectric
member can be separately provided in contact with one electrode surface of the ferroelectric
capacitor. For the diaphragm, various materials that can vibrate in the ultrasonic frequency band
can be used. In this case, a space can be provided between the diaphragm and the semiconductor
substrate. In addition, as in the third embodiment, each of the ferroelectric thin film layers in the
ferroelectric capacitor according to the vibration mode of the diaphragm or the piezoelectric
member, the position of the node or antinode of the vibration in the vibration mode, etc. The
wiring connection state of the area can be switched and set.
[0096]
Further, the transistor used for switching the conduction state is not limited to the FET type, and
may be a bipolar type transistor.
[0097]
In the above embodiment, the ultrasonic probe according to the medical ultrasonic diagnostic
apparatus has been described as an example, but the ultrasonic diagnostic apparatus may be
used for diagnosis of the inside of the building structure, etc. .
In this case, the acoustic sensor portion for transmitting and receiving the ultrasonic wave does
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not have to be provided outside the ultrasonic diagnostic apparatus main body as an ultrasonic
probe, and may be integrally provided in the ultrasonic diagnostic apparatus main body.
[0098]
Further, the acoustic sensor of the present invention does not have to be used in an ultrasonic
diagnostic apparatus, and may be used in a measurement apparatus that simply measures the
reception intensity of ultrasonic waves. In such a case, only a single acoustic sensor may be
provided without providing a plurality of acoustic sensors. In addition, the specific configuration,
structure, arrangement, and the like described in the above embodiment can be appropriately
changed without departing from the scope of the present invention.
[0099]
DESCRIPTION OF SYMBOLS 1 ultrasound diagnostic apparatus main body 2 ultrasound probe 11
control unit 12 transmission unit 13 reception unit 14 transmission / reception switching unit
15 voltage supply unit 16 image processing unit 17 storage unit 18 operation input unit 19
output display unit 21 vibrator 22 cable 23 Reception unit 24 Transmission unit 25 Drive
control unit 26 Communication unit 28 Transmission / reception switching unit 100
Semiconductor substrate 100a Hole 100b Thin plate structure 101 Source region 102 Drain
region 103 Metal wiring 104 Metal wiring 111 Gate insulating film 112 Ferroelectric thin film
layer 113 Gate electrode 114, 115 Side Wall 210 Transducer Array U Ultrasonic Diagnostic
Device
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