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JPWO2014077106

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPWO2014077106
The ultrasonic transducer element 20 includes a substrate 11, a lower electrode 12 disposed on
the substrate 11, and a membrane 18 including an upper electrode 16 disposed opposite to the
lower electrode 12 via a cavity 14H. A plurality of columns 14 forming a cavity 14H by
supporting the membrane 18, and a cell group 10Z each including a plurality of cells 10 in which
the respective cavities 14H communicate with each other are provided.
Ultrasonic transducer element and ultrasonic endoscope
[0001]
The present invention relates to an ultrasonic transducer element (hereinafter, also referred to as
an “element”) including a cell group including a plurality of capacitive ultrasonic transducer
cells (hereinafter, also referred to as “cells”) and the ultrasonic wave The present invention
relates to an ultrasonic endoscope including an insertion portion in which a transducer element
is disposed at a distal end.
[0002]
Ultrasonic diagnostic methods are in widespread use in which ultrasonic waves are applied to the
inside of the body, and an internal state of the body is imaged and diagnosed from echo signals.
An ultrasound endoscope is one of the medical devices used for ultrasound diagnosis. In the
ultrasonic endoscope, an element is disposed at the distal end rigid portion of the insertion
04-05-2019
1
portion introduced into the body. The element has a function of converting an electric signal into
an ultrasonic wave and transmitting it to the body, and also receiving an ultrasonic wave
reflected in the body and converting it into an electric signal.
[0003]
In many elements at present, ceramic piezoelectric materials containing lead with high
environmental impact, such as PZT (lead zirconate titanate), are mainly used. On the other hand,
a Capacitive Micro-machined Ultrasonic Transducer (hereinafter referred to as "c-MUT")
manufactured using MEMS (Micro Electro Mechanical Systems) technology and containing no
lead in its material The development of an element having a plurality of cells consisting of
[0004]
For example, element 120 shown in FIGS. 1-3 is disclosed in US Pat. No. 6,854,338. As shown in
FIG. 1 which is a top view, the element 120 has a cell 110 consisting of 25 c-MUTs, which is a
basic unit of ultrasonic wave transmission and reception.
[0005]
FIG. 2 is a cross-sectional view of one cell 110 of element 120, and FIG. 3 is a partially exploded
view of four cells 110 of element 120 shown in FIG. An exclusive area of the cells 110, in other
words, a plan view shape of the cells 110 is shown. Hereinafter, the plan view shape is simply
referred to as the shape. The shape of the cell 110 can be considered as a square.
[0006]
As shown in FIGS. 2 and 3, the cell 110 has a conductive substrate 111 which doubles as the
lower electrode 12, and an upper electrode 116 disposed opposite to each other via the cavity
114 H. The region immediately above the cavity 114 H of the upper electrode 116 constitutes a
membrane 118 that is ultrasonically vibrated. The cavity 114 H is formed by a through hole
formed in the insulating layer 114. The cavity 114H is a sealed space which does not
communicate with the outside.
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[0007]
In the cell 110, when a drive signal is applied between the lower electrode 12 and the upper
electrode 116, the membrane 118 vibrates to generate an ultrasonic wave. When ultrasound is
incident from the outside, the membrane 118 is deformed to change the capacitance between the
electrodes, thereby converting the ultrasound into an electrical signal. The transmission /
reception sensitivity of the element 120 is higher as the aperture ratio indicated by “(area of
membrane 118) / (area of cell 110)” is larger.
[0008]
However, in the element 120 having the square cells 110, the area other than the membrane 118
immediately above the circular cavity 114H is a dead area which does not contribute to the
transmission and reception of ultrasonic waves. For example, the capacitance between the
electrodes in the dead area is a so-called parasitic capacitance which does not change at the time
of ultrasonic wave reception.
[0009]
Since the element 120 has a wide dead zone and a small aperture ratio, it has not been easy to
obtain high transmission / reception sensitivity.
[0010]
An object of the present invention is to provide an ultrasonic transducer element having high
transmission / reception sensitivity and an ultrasonic endoscope equipped with the ultrasonic
transducer element.
[0011]
An ultrasonic transducer element according to an embodiment of the present invention includes
a substrate, a lower electrode disposed on the substrate, a membrane including an upper
electrode disposed opposite to the lower electrode via a cavity, and the membrane. And a
plurality of pillars forming the cavity by supporting the membrane, and a cell group including a
plurality of ultrasonic transducer cells in which the cavities communicate with each other.
04-05-2019
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[0012]
An ultrasonic endoscope according to another embodiment includes a substrate, a lower
electrode disposed on the substrate, and a membrane including an upper electrode disposed
opposite to the lower electrode via a cavity. A plurality of columns forming the cavity by
supporting the membrane; and a cell group comprising a plurality of ultrasonic transducer cells
each having the cavity communicating with each other The ultrasonic transducer element
includes an insertion portion disposed at a distal end portion, an operation portion disposed on
the proximal end side of the insertion portion, and a universal cord extending from the operation
portion.
[0013]
According to the embodiment of the present invention, it is possible to provide an ultrasonic
transducer element having high reception sensitivity and an ultrasonic endoscope equipped with
the ultrasonic transducer element.
[0014]
It is a top view of the conventional element.
It is sectional drawing of the ultrasonic transducer cell of the conventional element.
It is an exploded view of the conventional element.
It is a perspective view of the element of 1st Embodiment.
It is sectional drawing of the ultrasonic transducer cell of the element of 1st Embodiment.
It is an exploded view of the element of a 1st embodiment. It is an upper surface schematic
diagram for demonstrating the cell of the element of 1st Embodiment. It is a figure which shows
the modification of the pillar of the element of 1st Embodiment. It is a figure which shows the
modification of the pillar of the element of 1st Embodiment. It is a figure which shows the
modification of the pillar of the element of 1st Embodiment. It is a figure which shows the
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modification of the pillar of the element of 1st Embodiment. It is an exploded view of the element
of a 2nd embodiment. It is an upper surface schematic diagram for demonstrating the element of
3rd Embodiment. It is an upper surface schematic diagram for demonstrating the element of 4th
Embodiment. It is an upper surface schematic diagram for demonstrating the element of 5th
Embodiment. It is an upper surface schematic diagram for demonstrating the element of 6th
Embodiment. It is an upper surface schematic diagram for demonstrating the element of 7th
Embodiment. It is an upper surface schematic diagram for demonstrating the element of 8th
Embodiment. It is an upper surface schematic diagram for demonstrating the element of 9th
Embodiment. It is an upper surface schematic diagram for demonstrating the element of 10th
Embodiment. It is an exploded view of the element of 11th Embodiment. It is a top view of the
sealing wall of the element of embodiment. It is a perspective view of the array-type ultrasonic
transducer of the ultrasonic endoscope of 12th Embodiment. It is an external view of the
ultrasonic endoscope of 12th Embodiment.
[0015]
First Embodiment As shown in FIG. 4, in the ultrasonic transducer element 20 of the present
embodiment, a cell group 10Z comprising a plurality of ultrasonic transducer cells 10 is disposed
on a substrate 11 . Then, when a drive signal is applied between the lower electrode terminal
12T and the upper electrode terminal 16T, the cell group 10Z transmits an ultrasonic wave, and
the incident ultrasonic wave is between the lower electrode terminal 12T and the upper electrode
terminal 16T. Based on the change in capacitance, it is converted into an electrical signal and
received.
[0016]
As shown in FIG. 5, the cell 10 is supported by the lower electrode 12 connected to the lower
electrode terminal 12T, the lower insulating layer 13 covering the lower electrode 12, the pillar
14 forming the cavity 14H, and the pillar 14 And a membrane 18 including the upper electrode
16 connected to the upper electrode terminal 16T. The membrane 18 in the region directly
above the cavity 14 H includes the upper insulating layer 15, the upper electrode 16, and the
protective layer 17.
[0017]
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The pillars 14 support the membrane 18 to form a cavity 14H. As described later, the cavity 14H
is a space in which a vacuum or a desired gas is contained and sealed at a desired pressure.
[0018]
Although an insulating thin film is formed on the surface of the substrate 11 made of single
crystal silicon or the like, it is not shown. The lower electrode 12 is a single layer film or a
multilayer film made of a conductive metal such as Al, Mo, W, Ti or an alloy of the above metals.
[0019]
In order to reduce the thickness of the membrane 18, graphene, silicene or the like may be used
as the upper electrode 16. Graphene has a two-dimensional network structure of carbon atoms
or a structure in which a plurality of two-dimensional network layers are stacked, and silicene
has a two-dimensional network structure of silicon atoms. Graphene and the like have the same
conductivity, high rigidity and high thermal conductivity as metals, although the thickness is
extremely thin.
[0020]
The lower insulating layer 13, the upper insulating layer 15, and the pillars 14 are made of
silicon nitride, silicon oxide, tantalum oxide, hafnium oxide or the like. The lower insulating layer
13, the upper insulating layer 15, and the pillars 14 may be made of different materials. Note
that at least one of the lower insulating layer 13 and the upper insulating layer 15 is not an
essential component.
[0021]
The lower insulating layer 13 protects the lower electrode 12 during the process and secures the
electrical insulation between the lower electrode 12 and the upper electrode 16. The surface of
the lower insulating layer 13 formed so as to cover the lower electrode 12 is planarized by the
CMP method or the like after the film formation if necessary.
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[0022]
The cavity 14H is formed by sacrificial layer etching. That is, the pillars 14 and the sacrificial
layer are disposed on the lower insulating layer 13, and the upper portion is covered by the
upper insulating layer 15 and the like.
[0023]
Then, an etchant is injected into the sacrificial layer by forming a through hole (VIA hole) in the
upper insulating layer 15 or the like covering the sacrificial layer, and the sacrificial layer is
selectively etched to form the cavity 14H as a cavity. It is formed. The material of the sacrificial
layer is selected from materials having high etching selectivity with the surrounding materials.
For example, when the lower insulating layer 13 and the like are made of silicon nitride,
phosphorus glass or the like is used for the sacrificial layer. Although the via holes are filled after
sacrificial layer etching, the hole filling member may be used as a part of the pillars 14. The
upper electrode 16 is made of the same material as the lower electrode 12. The protective layer
17 covering the upper electrode 16 is made of an insulator made of silicon nitride, silicon oxide,
polyimide, polyparaxylylene or the like.
[0024]
In addition, the material of the component of the element 20, a manufacturing method, etc. are
substantially the same as the conventional element. That is, the element 20 differs from the
conventional element in that the membrane is supported not by the insulating layer 114 but by a
plurality of pillars 14. Therefore, the method of manufacturing the element 20 is not limited to
the above description, and a known method of manufacturing the element can be used.
[0025]
The cell 10 shown in FIG. 5 also appears to be similar to the cell 110 shown in FIG. However, as
shown in FIG. 3, in the conventional element 120, the cavities 114H are spaces in which each is
sealed, in other words, the respective cavities 114H are isolated. On the other hand, as shown in
FIG. 6, in the element 20, the cavity 14H is formed by the plurality of columns 14. For this
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reason, the plurality of cavities 14H of the cell group 10Z are so-called open cavities that
communicate with each other. In other words, the plurality of cavities 14H form one space.
[0026]
In the exploded view of FIG. 6, the lower insulating layer 13 and the protective layer 17 are not
shown. The top view of FIG. 7 shows only the arrangement of the pillars 14, the lower electrode
12 and the upper electrode 16. The regular hexagons shown by broken lines in FIG. 6 and FIG. 7
etc. indicate the exclusive region of one cell 10, in other words, the plan view shape of the cell
10, but the boundaries are not clearly indicated in practice. For example, the boundaries of the
cavities 14 H of the plurality of cells 10 indicated by broken lines are imaginary lines that do not
actually exist.
[0027]
As shown in FIGS. 6 and 7, in the element 20, a plurality of cells 10 having a regular hexagonal
shape in plan view are disposed without a gap. That is, each pillar 14 supports the membranes
18 of three adjacent cells 10 to form a cavity 14H. The area where the upper insulating layer 15
is joined to the column 14 is a dead area which does not contribute to transmission and
reception without vibration, but the area of the membrane 18 which is the vibration area of the
element 20 has an aperture ratio to the cell area of the conventional element. Also much higher.
That is, the shape and area of the cell 10 are approximately equal to the shape and area of the
cavity 14H.
[0028]
Also in the element 20, strictly speaking, although the shape of the cell 10 and the shape of the
cavity 14H not including the region of the pillar 14 are different, hereinafter, the shape of the
cavity 14H may be referred to as the shape of the cell 10.
[0029]
The lower electrodes 12 of the plurality of cells 10 are connected to each other by the lower
electrode wiring 12S, and the upper electrodes 16 are connected to each other by the upper
electrode wiring 16S.
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That is, the plurality of cells 10 of the element 20 constitute a cell group 10Z which is
simultaneously driven.
[0030]
When a potential other than 0 is applied between the lower electrode 12 and the upper electrode
16 via the lower electrode terminal 12T and the upper electrode terminal 16T, the membrane 18
is moved to the lower electrode 12 by the electrostatic attractive force generated by the potential
difference. Pulled and displaced in the direction of From the viewpoint of securing safety, it is
preferable to set the upper electrode 16 to the ground potential.
[0031]
The displacement amount of the membrane 18 is maximum at the center point of the cell 10, and
is maximum at the bisecting point of each side of the regular hexagon at the adjacent cell
boundary. Further, the displacement amount is line symmetrical with respect to the boundary
line of the adjacent cell 10 indicated by the broken line. Furthermore, since the cell 10 is a
regular hexagon, the amount of displacement is six-fold symmetric, which is equivalent to a
rotation of 6 degrees with respect to the center point of the cell 10.
[0032]
When the applied potential is cut off with the membrane 18 displaced, the electrostatic attraction
disappears, the membrane 18 vibrates at a resonant frequency determined by the constituent
materials and structural parameters, and an ultrasonic wave having a frequency equal to the
resonant frequency is transmitted. .
[0033]
When ultrasonic waves are transmitted in a pulse manner, it is preferable to control the
waveform or the like of a drive signal to be applied.
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9
For example, the potential may be increased slowly so that the displacement of the membrane 18
can follow the rise of the applied potential, or the next pulse may be applied after allowing
sufficient time for the membrane 18 to completely stop. Is preferred. Alternatively, after
transmitting the ultrasonic wave, the membrane 18 may be forcibly stopped by attraction due to
the application of the auxiliary pulse or counter vibration generation by the application of the
auxiliary pulse in the reverse phase of the main pulse.
[0034]
On the other hand, when ultrasonic waves are transmitted continuously for Doppler
measurement or the like, a drive signal consisting of, for example, a triangular wave pulse equal
to the resonance frequency of the membrane 18 is applied.
[0035]
The vibration frequency of the membrane 18 at the time of ultrasonic wave generation, that is,
the frequency of the generated ultrasonic wave is slightly lower than the frequency of the
ultrasonic wave generated by a cell having a circular cavity inscribed in the regular hexagonal
cell 10.
In order to achieve the same ultrasound frequency as the cell having the inscribed circular cavity,
the cell 10 may be reduced in a similar shape.
[0036]
When an ultrasonic wave is incident on the cell 10, the membrane 18 vibrates at the frequency
of the incident ultrasonic wave by the sound pressure of the ultrasonic wave, and the thickness of
the cavity 14H, that is, the distance between the electrodes changes according to the vibration.
The capacitance between the electrodes changes accordingly. Therefore, by detecting the
capacitance between the electrodes, the intensity and frequency of the incident ultrasonic waves
are detected.
[0037]
The element 20 can transmit and receive ultrasonic waves of higher frequency by always slightly
deforming the membrane 18 using a DC offset bias method in which a potential difference is
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10
always applied between the electrodes.
[0038]
The drive signal may be supplied from the outside of the element 20, or a drive circuit composed
of an IC or the like may be provided on the back surface of the element 20.
[0039]
Here, as shown in FIG. 7, the diameter R of the cross section of the column 14 which is a column
is preferably 1/20 to 1/5 of the distance D between the column 14 and the column 14.
If it is more than the above range, the membrane 18 can be stably supported, and if it is less than
the above range, the aperture ratio is as large as, for example, 95% or more, so that the feeling of
transmission and reception is high.
[0040]
For example, in a regular hexagonal cell 10, when the distance D is 100 μm and the diameter R
is 10 μm, the area of the cell 10 is 26000 μm 2 and the area of the column 14 is 157 μm 2.
Therefore, the aperture ratio is (26000−157) /26000=99.4%.
[0041]
On the other hand, in the conventional element in which cells having isolated circular cavities are
arranged in a square lattice, the aperture ratio is “(area of circle) / (circle of circle) even in a
form in which the cavities are virtually in contact with each other. Because it is a square area), it
was 78.5%.
[0042]
That is, although the aperture ratio is less than 80% in the element in which the cells having the
conventional isolated circular cavities are arranged in a square lattice, the high aperture ratio of
more than 95% can be easily realized in the element 20.
04-05-2019
11
[0043]
The element 20 achieves an improvement in transmission / reception sensitivity of ultrasonic
waves, and further enables expansion of application development.
Also, the fact that the aperture ratio is large means that the membrane can be driven efficiently,
or the ratio of parasitic capacitance decreases, and the signal-to-noise ratio (SN ratio) also
increases.
[0044]
That is, the element 20 has a large aperture ratio and high transmission / reception sensitivity.
[0045]
Furthermore, in the element 20, the opposing regions of the lower electrode 12 and the upper
electrode 16 all contribute to the reception of the ultrasonic waves, and are therefore not
affected by the parasitic capacitance due to the insensitive region, so the reception sensitivity is
high.
[0046]
The shape of the column 14 is not limited to a cylinder.
For example, in the column 14A shown in FIG. 8A, the cross section is not a circle but a
substantially regular triangle, and the column 14B shown in FIG. 8B is a substantially star shape
with a cross section protruding in three directions.
The column 14C shown in FIG. 8C has an enteric shape in which the center part of the column is
expanded, and the column 14D shown in FIG. 8D has a decorative column shape in which the
upper part of the column is expanded.
04-05-2019
12
[0047]
The column 14 may be in the form of an elliptic cylinder, a polygonal column, a star column, a
cone or a polygonal pyramid, etc. Even if the plurality of columns 14 of the element 20 are
composed of a plurality of columns of different shapes. Good.
In the case of the column 14 other than the column, it is preferable that the column 45 be
designed such that the aperture ratio of the cell is 90% or more, preferably 95% or more.
[0048]
Second Embodiment The element 20A of the second embodiment shown in FIG. 9 is similar to
the element 20, so the same components are denoted by the same reference numerals and the
description thereof will be omitted.
[0049]
In the element 20A, the lower electrode 12A is a common lower electrode of the plurality of
vibrators 10 disposed on the entire surface of the cell group 10ZA formation region.
That is, in FIG. 9, the lower electrodes 12A of the respective vibrators 10 are shown by broken
lines, but the boundary is an imaginary line.
[0050]
In the element 20A, the lower electrode 12A is disposed on the entire surface, but since the
entire area where the upper and lower electrodes face is the membrane 18, the dead area is
increased compared to the element 20 having the patterned lower electrode 12 There is nothing
to do.
[0051]
The element 20A is easy to manufacture because it is not necessary to pattern the lower
electrode 12A.
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13
Further, as described above, since unevenness is formed on the surface of the lower insulating
layer 13 formed on the patterned lower electrode 12, it is preferable to planarize. However, in
the element 20A, since the lower electrode 12 is disposed on the entire surface of the cell group
10ZA formation region, no unevenness is formed on the surface of the lower insulating layer 13,
and planarization is unnecessary.
[0052]
The element 20A has the effect of the element 20 and is easy to manufacture.
[0053]
Even if at least one of the lower electrode 12 and the upper electrode 16 is disposed on the
entire surface of the cell group 10Z formation region of the substrate 11, it goes without saying
that the same effect as that of the element 20A is obtained.
[0054]
Third Embodiment The element 20B of the third embodiment shown in FIG. 10 is similar to the
element 20 and the like, so the same components are denoted by the same reference numerals
and the description thereof will be omitted.
[0055]
In each element 20B, each cell 10 occupies six pillars 14 respectively.
For this reason, useless areas that do not contribute to transmission and reception are formed
between the cells 10.
[0056]
In an element 20 or the like in which adjacent cells 10 share a pillar 14, if one pillar is defective,
three cells 10 sharing the pillar become defective.
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14
On the other hand, the element 20B has a high probability of being usable as a product because
only one cell 10 is defective even if the column is defective.
That is, in many cases, in the element 20, not all the cells 10 need to be non-defective.
[0057]
The element 20B has the effect of the element 20 and the like, and further has a higher
manufacturing yield than the element 20 and the like.
[0058]
Also in the element 20B, the aperture ratio is preferably 90% or more, and particularly preferably
95%.
Also, some of the columns may be shared by adjacent cells, and the remaining columns may be
proprietary.
[0059]
Fourth Embodiment The element 20C of the third embodiment shown in FIG. 11 is similar to the
element 20 and the like, so the same components are denoted by the same reference numerals
and the description thereof will be omitted. In the following drawings, the columns 14 are
indicated by black circles indicating the centers.
[0060]
In the element 20C, three columns 14 are disposed not only at the six apexes of the regular
hexagonal cell 10C but also on two sides of the border with the adjacent cell. That is, the
membrane of the cell 10C is supported by 12 pillars 14.
04-05-2019
15
[0061]
The displacement of the membrane of the cell 10C is not six-fold symmetric with respect to the
cell center, but is two-fold symmetric, and is displaced in a complicated shape. Thus, the cell 10C
has a wide resonant frequency.
[0062]
The element 20C has an effect that the element 20 has, and furthermore, the ultrasonic wave
generated by the membrane 18 is in a wide band, and similarly, can transmit and receive a wide
band ultrasonic wave.
[0063]
Fifth Embodiment The element 20D of the fifth embodiment shown in FIG. 12 is similar to the
element 20 and the like, so the same components are denoted by the same reference numerals
and the description thereof will be omitted.
[0064]
In the element 20D, the pillars 14 are disposed not at the apex of the regular hexagonal cell 10D,
but at a position slightly offset from the apex.
The deviation amount d is set at random, but is set inside a circle of diameter RD.
The diameter RD is preferably, for example, 1/100 or more and 1/10 or less of the distance D. If
it is the said range, an effect will be remarkable. Further, the deviation amount d is set based on,
for example, a random number.
[0065]
In cells 10 in which the distance D between the columns 14 is the same, unnecessary resonance
may occur or unnecessary transverse waves may be emphasized. On the other hand, in the
element 20D, since the pillars 14 of the cell 10D are randomly arranged at minute planar
04-05-2019
16
displacements from the apex of the hexagon, there is no possibility that unnecessary resonance
occurs.
[0066]
That is, the element 20D has the effect that the element 20 has, and further, there is no
possibility that unnecessary resonance occurs.
[0067]
<Sixth and Seventh Embodiments> The element 20E of the sixth embodiment and the element
20F of the seventh embodiment are similar to the element 20 etc., so I omit it.
[0068]
As shown in FIG. 13, in the element 20 </ b> E, the equilateral triangle cells 10 </ b> E are
disposed without a gap.
That is, the membrane 18 of each cell 10E is supported by the common three pillars 14.
In addition, as shown in FIG. 14, in the element 20F, the cell 10F is a regular octagon. The
membrane 18 of the cell 10F is supported by twelve columns 14, eight of which are arranged at
the apex of the regular octagonal cell 10F.
[0069]
Element 20E and element 20F have the same effect as element 20. That is, if the column 14 has
the transducer cell forming the cavity 14H by supporting the membrane 18, the number of
columns supporting the transducer cell is six if it is three or more. It is not limited to The number
of columns supporting the transducer cell is preferably 16 or less. If the number is less than or
equal to the above range, it is easy to increase the aperture ratio.
[0070]
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17
Moreover, the planar view shape of a membrane (cell) is not limited to a specific shape. For
example, it may be a parallelogram, a rectangle, a rhombus, or a trapezoid. In particular, a shape
capable of planar filling a plurality of cells, that is, a shape that can be disposed without a gap is
preferable because it is easy to increase the aperture ratio.
[0071]
Eighth to Eleventh Embodiments The elements 20G to the tenth embodiment of the eighth
embodiment are similar to the elements 20 and the like, so the same reference numerals are
given to the same components, I omit it.
[0072]
As shown in FIG. 15, the cell group 10ZG of the element 20G of the eighth embodiment is
provided with three types of cells 10G1 to 10G3 having the same square shape but different
sizes (dimensions in plan view of the cell 10G). Do.
[0073]
As shown in FIG. 16, in the cell group 10ZH of the element 20H of the ninth embodiment, four
types of cells having the same shape and size of the cavities but having different numbers of
columns 14 supporting the respective cavities 10H1 to 10H4 are provided.
[0074]
As shown in FIG. 17, the cell group 10ZI of the element 20I of the tenth embodiment includes
two types of cells 10I1 to 10I2 having different shapes of cavities (cells).
[0075]
As shown in FIG. 18, the cell group 10ZJ of the element 20J of the eleventh embodiment includes
two types of cells 10J1 to 10J2 having the same cavity shape and the like but different
thicknesses of the membrane 18.
[0076]
The plurality of types of cells different in at least one selected from the shape of the cavity in
plan view, the size of the cavity (plan view), the number of columns, and the thickness of the
membrane have different resonance frequencies.
04-05-2019
18
[0077]
Therefore, the elements 20G to 20J have a wide frequency band of ultrasonic waves that can be
transmitted and received.
For example, in the element 20G shown in FIG. 15, the largest cell 10G1 is disposed at the center
of the element 20G, and the smallest cell 10G3 is disposed at the outermost periphery.
The ultrasonic wave generated by the large cell 10G1 has a low frequency, so the beam spreads
easily, and the ultrasonic wave generated by the small cell 10G3 has a high frequency, so the
beam hardly spreads.
In the element 20G, since the low frequency cell is located at the center, the focusing of the
ultrasonic beam on the entire element is good.
[0078]
On the other hand, in the element 20H shown in FIG. 16, the membrane 18 of the cell 10H1
disposed at the center is supported by the sixteen columns 14, so the resonance frequency is
high.
On the other hand, since the membrane 18 of the cell 10H4 disposed in the peripheral portion is
supported by the five columns 14, the resonance frequency is low.
The membrane 18 of the cell 10H2 disposed between the cell 10H1 and the cell 10H3 is
supported by ten pillars 14, and the membrane 18 of the cell 10H3 is supported by eight pillars
14.
For this reason, the resonant frequencies of the cell 10H2 and the cell 10H3 are between the
resonant frequency of the cell 10H1 and the resonant frequency of the cell 10H4.
04-05-2019
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[0079]
In the element 20H, the near point side of the observation target can be observed with high
resolution. That is, the near point side is high resolution because an image is formed by a high
frequency signal.
[0080]
The shapes of the two types of cells 10I1 and 10I2 of the element 20I shown in FIG. 17 are two
types of rhombuses forming the Penrose tile pattern, and the columns are arranged at the apexes
of the two types of rhombus. In the Penrose tile pattern, two types of rhombuses (a 72-degree
acute angle, a 108-degree obtuse rhombus and a 36-degree acute angle and a 144-degree obtuse
rhombus) are planarly filled. In the case of filling using a regular polygon, a periodic pattern
appears, but Penrose tile patterns do not have a periodic pattern unlike other planar filling.
[0081]
Since the Penrose tile pattern has a specific symmetry of five-fold symmetry, there is no
translational symmetry in plan view. For this reason, unnecessary resonance is extremely
unlikely to occur in the element 20I, and can be particularly preferably used.
[0082]
The element 20I has two types of resonance frequencies because the rhombic cells exhibit the
same resonance frequency as the cells having elliptical cavities of substantially the same size.
Furthermore, an element having a plurality of cells obtained by reducing or expanding a Penrose
tile pattern in one direction is a broadband element having 10 types of resonance frequencies in
principle.
[0083]
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In the element 20J shown in FIG. 18, the resonant frequency of the cell 10J2 with the thick
membrane 18 is higher than the resonant frequency of the cell 10J1 with the thin membrane.
That is, the resonant frequency is proportional to the membrane thickness.
[0084]
In the element having a plurality of types of cells having different resonant frequencies, the cell
arrangement can be changed according to the purpose. In addition, two or more types of cells
may be used.
[0085]
Each of the elements 20G to 20J has an effect of the element 20 and the like, and further has a
wider band characteristic, so that it can be applied and developed to ultrasonic Doppler
measurement and the like. Also, depending on the purpose, it is possible to adopt a cell
arrangement in consideration of the directivity of the sound wave in the element or a cell
arrangement having a high resolution with excellent convergence in the ultrasonic beam.
[0086]
Also, by changing two or more factors selected from the plan view shape of the cavity, the size of
the cavity (plan view size), the number of columns, and the thickness of the membrane, a
broadband element having more resonant frequencies It becomes. In particular, by continuously
and smoothly changing the resonance frequency of the cell to be arranged, it becomes an
element of very wide band.
[0087]
In the element 20J shown in FIG. 18, the lower electrode 12A is formed on the entire surface of
the cell group formation region. On the other hand, the upper electrode 16J is also formed on
substantially the entire surface of the cell group formation region, but a hole 16JH is formed in
the region facing the column 14. Although the membrane immediately above the pillar 14 is a
dead area, in the element 20 J, the reception sensitivity is higher because there is no upper
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21
electrode 16 in the dead area.
[0088]
Here, FIG. 19 shows an example of the end of the cell group 10Z of the element 20 described in
the above embodiment. As already described, the plurality of cavities 14H of the cells 10
constituting the cell group 10Z communicate with each other. However, the outer peripheral side
of the cavity 14H in the outermost peripheral region of the cell group 10Z is a sealed space
which is surrounded by the sealing wall formed of an envelope and the plurality of cavities 14H
of the cell group 10Z do not communicate with the outside. Is preferred. In the elements 20A to
20J, it is preferable that the plurality of cavities 14H be a sealed space not communicating with
the outside.
[0089]
The element which is a sealed space where the plurality of cavities 14H of the cell group 10Z do
not communicate with the outside does not have a possibility of changing the transmission /
reception sensitivity because the internal pressure of the cavity 14H does not change even if the
surrounding environment changes. .
[0090]
<Twelfth Embodiment> The elements 20 to 20J described above can be preferably used in an
ultrasonic endoscope (hereinafter referred to as "endoscope") 2.
[0091]
As shown in FIG. 20, the radial type array type ultrasonic transducer 30 has a plurality of
elements 20, a cylindrical holding member 31 in which the elements 20 are disposed on the
outer surface, and a cable 80.
The lower electrode terminal 12T and the upper electrode terminal 16T of the element 20 are
connected to the conductors 81A and 8B of the cable 80, respectively.
The ultrasound array may be a convex type or a linear type.
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22
[0092]
FIG. 21 shows an ultrasonic endoscope system 1 having the ultrasonic endoscope 2 of the twelfth
embodiment in which the array type ultrasonic transducer 30 (element 20) is disposed at the
distal end portion 47. The endoscope 2 constitutes an ultrasound endoscope system 1 together
with the ultrasound observation apparatus 3 and the monitor 4. The endoscope 2 includes an
elongated insertion portion 41 inserted into the body, an operation portion 42 disposed at a
proximal end of the insertion portion 41, and a universal cord 43 extending from a side portion
of the operation portion 42. .
[0093]
At the proximal end of the universal cord 43, a connector 44A connected to a light source device
(not shown) is disposed. From the connector 44A, a cable 45 detachably connected to the camera
control unit (not shown) via the connector 45A, and a cable 46 detachably connected to the
ultrasonic observation apparatus 3 via the connector 46A It is extended. A monitor 4 is
connected to the ultrasonic observation apparatus 3.
[0094]
The insertion portion 41 has a small diameter and a long length from the tip end side to the tip
end portion 47, the curved portion 48 located at the rear end of the tip portion 47, and the rear
end of the curved portion 48 to the operation portion 42. A flexible tube portion 49 having
flexibility is connected in series. Then, the array type ultrasonic transducer 30 is disposed on the
tip end side of the tip end portion 47. The endoscope 2 acquires an ultrasound image by the
array type ultrasound transducer 30 provided at the distal end portion 47.
[0095]
The endoscope 2 includes an ultrasonic transducer element having high ultrasonic wave
transmission sensitivity and ultrasonic wave reception sensitivity, and thus can obtain a high
resolution image.
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[0096]
The elements 20 to 20 are not only the endoscope 2 shown in FIG. 21, but also various ultrasonic
diagnostic devices that are small and require thinning. For example, IVUS (Intra Vascular
UltraSound), extracorporeal ultrasonic probe It goes without saying that the present invention
can also be arranged in a capsule type ultrasonic endoscope.
[0097]
The present invention is not limited to the above-described embodiment and the like, and various
changes and modifications, for example, combinations of components of the embodiment and the
like are possible without departing from the scope of the present invention.
[0098]
The present invention is not limited to the above-described embodiment and the like, and various
changes, modifications, combinations, and the like can be made without departing from the scope
of the present invention.
[0099]
This application is based on Japanese Patent Application No. 2012-251444 filed on Nov. 15,
2012 as a basis for claiming priority, and the above disclosure is made of the present
specification and claims. It shall be quoted in the drawings.
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