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JP2009272824

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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 JP2009272824
An ultrasonic transducer cell 10 having a capacitance type capable of reducing applied DC bias,
an ultrasonic transducer 2 having an ultrasonic transducer cell 10, and an ultrasonic endoscope
1 are provided. An ultrasonic transducer cell includes a lower electrode, a first insulating film
disposed above or below the lower electrode, and an air gap formed on the first insulating film.
And the vibrating film 9 disposed on the air gap 18 and including at least the second insulating
film 15, and the first insulating film 12 and / or the second insulating film 15 includes the
floating electrodes 13 and 13 B. . [Selected figure] Figure 2
Ultrasonic transducer cell, ultrasonic transducer and ultrasonic endoscope
[0001]
The present invention relates to an ultrasonic transducer cell, an ultrasonic transducer having the
ultrasonic transducer cell, and an ultrasonic endoscope. In particular, components of the
capacitive ultrasonic transducer cell and arrangement positions of the components About.
[0002]
Ultrasonic diagnostic methods are in widespread use in which ultrasonic waves are applied to the
inside of the body, and the state of the inside of the body is imaged and diagnosed from the echo
signals.
An ultrasound endoscope is one of the equipment used for this ultrasound diagnosis method. In
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the ultrasonic endoscope, an ultrasonic transducer is attached to the tip of the insertion portion
to be inserted into the body, and this ultrasonic transducer converts an electric signal into an
ultrasonic wave and irradiates it into the body, and it is also reflected in the body. It receives
sound waves and converts them into electrical signals.
[0003]
Generally, an ultrasonic transducer includes a structure for transmitting and receiving ultrasonic
waves called an ultrasonic transducer cell. For example, as shown in FIG. 12, the structure of the
ultrasonic transducer cell 210 disclosed in Patent Document 1 uses the insulating support
portion 214 on the other surface of the conductive silicon substrate 211B having the electrode
211A formed on one side. The vibrating plate 215 and the upper electrode 216 are provided via
the hollow portion 218 which has been formed. That is, the conductive substrate 211B, which is
a planar electrode, and the upper electrode 216 face each other via the hollow portion 218, and
the upper electrode 216 is configured to be able to vibrate in a so-called membrane structure.
[0004]
Then, when ultrasonic vibration is generated in the ultrasonic transducer cell 210, as shown in
FIG. 13, an RF (Radio Frequency: high frequency) signal is applied between the two flat
electrodes to form the upper electrode 216 of the membrane structure. Then, the diaphragm 215
is repeatedly attracted and released to the conductive silicon substrate 211B by the Coulomb
force. In FIG. 13, a DC (Direct Current) bias voltage VB is applied to the bias terminal 224, and is
connected to the upper electrode 216 by a path having a high impedance Z to an AC signal such
as an inductive impedance, The RF signal from the signal terminal 226 is electrostatically
coupled to the upper electrode 216.
[0005]
Then, in the ultrasonic transducer cell 210, when ultrasonic waves are received, the diaphragm
215 and the upper electrode 216 of the membrane structure are vibrated by the ultrasonic
waves reflected by the inspection object, and two planar electrodes are used. Since the distance
between a certain upper electrode 216 and the conductive silicon substrate 211B changes, the
change in capacitance between the electrodes is detected and converted into an electrical signal.
In addition, at the time of transmission and reception of an ultrasonic wave, if the DC bias voltage
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VB is not applied between the electrodes, driving the ultrasonic transducer cell 210, that is,
efficient vibration of the electrodes of the membrane structure and interelectrodes The detection
of the change in capacitance of was difficult.
[0006]
On the other hand, Patent Document 2 discloses an electrostatic capacitive ultrasonic transducer
310 that can be driven without applying a DC bias voltage between the opposing electrodes by
using the electret film 340. . Here, the electret film 340 is a film in which the surface is charged
by irradiating the surface of the insulating thin film with an electron beam or the like. As shown
in FIG. 14, in the capacitive ultrasonic transducer 310, the lower electrode 311 is formed on the
thermally oxidized silicon layer 330C of the silicon substrate 330A in which the air reservoir hole
318 is formed, and the electret film 340 is further formed. As a result, a CVD silicon oxide film
into which charges are injected is formed, and a polyester film 317 in which an aluminum layer
to be the upper electrode 316 is vapor-deposited is stretched on the electret film 340.
[0007]
The electret film 340 of the capacitive ultrasonic transducer 310 has the effect of raising the
surface potential by injecting a charge from one side of the CVD silicon oxide film to polarize it,
thereby equivalently giving a DC bias, ie, a self bias Is realized. Therefore, a DC bias power supply
is not required when driving the capacitive ultrasonic transducer 310.
[0008]
In the nonvolatile semiconductor memory, a floating electrode surrounded by an insulating film,
that is, a storage MOS transistor having a so-called floating gate and a data input / output wiring,
etc. is used to store charge by storing charge in the floating electrode. Semiconductor memory to
hold is known. JP-A-2004-503313 JP-A-2-52599
[0009]
However, the capacitive ultrasonic transducer, which obtains the effect of making the DC bias
voltage unnecessary by the electret film, is biased by the change of the distribution of the
electrons charged in the electret film, and the disappearance of the electrons out of the film. Due
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to fluctuations, the effect of making the DC bias voltage unnecessary may change over time.
[0010]
The semiconductor memory is not only different from the ultrasonic transducer cell of the
present invention in the technical field, but the purpose of charge storage on the floating
electrode in the semiconductor memory is to hold the memory, and It is completely different
from the purpose of a sound transducer cell or the like.
[0011]
An object of the present invention is to provide a capacitive ultrasonic transducer cell capable of
continuously reducing applied DC bias, an ultrasonic transducer having the ultrasonic transducer
cell, and an ultrasonic endoscope. I assume.
[0012]
The present inventors have found that the problem can be solved by using a floating electrode in
place of the electret film in the ultrasonic transducer cell.
[0013]
That is, in the ultrasonic transducer cell of the present invention, a lower electrode, a first
insulating film disposed on the lower electrode or under the lower electrode, and a gap portion
disposed on the first insulating film And a vibrating film disposed on the gap and made of at least
a second insulating film, wherein the first insulating film and / or the second insulating film
includes a floating electrode.
[0014]
The present invention provides a capacitive ultrasonic transducer cell capable of continuously
reducing applied DC bias, an ultrasonic transducer having the ultrasonic transducer cell, and an
ultrasonic endoscope. .
[0015]
First Embodiment An ultrasonic transducer cell 10 of a capacitive ultrasonic transducer (c-MUT)
according to a first embodiment of the present invention will be described below with reference
to the drawings.
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In each of the drawings used in the following description, the scale of each member is made
different in order to make each member have a size that can be recognized in the drawings.
[0016]
FIG. 1 exemplifies a part of an ultrasonic transducer 2 according to the present embodiment, and
is a top view of a part having four ultrasonic transducer cells 10.
FIG. 2 is a cross-sectional view of the ultrasonic transducer cell 10 of FIG. 1 taken along line II-II.
[0017]
In the following description of the laminated structure, the direction from the lower electrode to
the void portion is referred to as the upper direction in the vertical relationship between the
layers.
For example, in the cross-sectional view of FIG. 2, the second insulating film 15 is referred to as
being disposed above the first insulating film 12.
[0018]
As shown in FIG. 2, the basic structure of the ultrasonic transducer cell 10 is the lower electrode
11 and the vibrating film 9 which face each other with the gap 18 therebetween.
In the ultrasonic transducer cell 10, the vibrating film 9 is constituted by at least the second
insulating film 15.
The ultrasonic transducer cell 10 transmits and receives ultrasonic waves by the vibration of the
vibrating membrane 9 which is a membrane-like structure having elasticity.
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In FIGS. 1 and 2, the shape of the void 18 is a cylindrical shape, but the present invention is not
limited to this and the shape can be appropriately determined according to the purpose.
[0019]
Then, as shown in FIG. 1, the electrode wiring 21 of the lower electrode 11 of each ultrasonic
transducer cell 10 is a common wiring of the plurality of ultrasonic transducer cells 10. The
electrode wiring 21 is a conductive line for inputting and outputting an electric signal drawn to
the outside of the ultrasonic transducer cell group constituting the ultrasonic transducer array.
The plurality of ultrasonic transducer cells 10 connected to each other by common wiring are
simultaneously driven as an ultrasonic transducer array. The void 18 indicated by a broken line
in FIG. 1 indicates that the void 18 is formed inside.
[0020]
Next, the structure of the ultrasonic transducer cell 10 according to the present embodiment will
be described with reference to FIG. The ultrasonic transducer cell 10 is disposed with a gap 18
between the lower electrode 11, the first insulating film 12 disposed on the lower electrode 11,
and the lower electrode 11 so as to face the lower electrode 11. And the second insulating film
15. The first insulating film 12 includes the floating electrode 13.
[0021]
The ultrasonic transducer cell 10 according to the present embodiment includes the floating
electrode 13 inside the first insulating film 12 and therefore can be driven even if the DC bias
applied to the lower electrode 11 is reduced or zero. , The effect can last longer.
[0022]
The above-described vibrating membrane 9 has a membrane structure in which the end is fixed
by the vibrating membrane support portion 14, and in the ultrasonic transducer cell 10
according to the present embodiment, as shown in FIG. It comprises the second insulating film
15 which faces.
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That is, the vibrating membrane 9 of the ultrasonic transducer cell 10 is made of a
nonconductive material.
[0023]
Here, the void portion 18 refers to a space surrounded by the vibrating membrane 9, the
vibrating membrane support portion 14 and the first insulating film 12, and the inside thereof
may be at atmospheric pressure or higher than atmospheric pressure. It may be at low pressure,
for example vacuum.
[0024]
The material of the lower electrode 11 is not particularly limited. For example, it is preferable to
use a known conductive material such as Au, Al, Mo, Al, Ti, W, Cu, SnO2, ITO, polysilicon, or
amorphous silicon.
[0025]
The material of the first insulating film 12 or the second insulating film 15 is not particularly
limited, but it is preferable to use an insulating material such as silicon nitride such as Si3N4 or
SiN, SiO2, TiO2, Al2O3, ZrO2, or HfO2.
[0026]
Although the material of the floating electrode 13 is not limited, it is preferable to use, for
example, a conductive material such as Au, Al, Mo, Al, Ti, W, Cu, SnO 2, ITO, polysilicon, or
amorphous silicon.
These materials can form a floating electrode regardless of a special film forming method, and
can suppress an increase in cost.
Moreover, the compatibility with the MEMS (Micro Electro-Mechanical System) technology,
which is one of the preferred manufacturing methods of the present invention, is also excellent.
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[0027]
The floating electrode 13 is preferably charged, and the amount of charge accumulated in the
floating electrode 13 is not particularly limited, but the electron density is 1 × 10 <−10> to 1 ×
10 <−14> electron / cm < 2>, that is, in the charge density, 1.6 × 10 <−9> to 1.6 × 10 <−5>
C / cm <2> is preferable, and more preferably 1.6 × 10 <− 7> to 1.6 × 10 <-5> C / cm <2>.
When the floating electrode is charged, the DC bias reduction effect can be improved.
[0028]
Although the material of the vibrating membrane support 14 is not limited, it is preferable to use,
for example, an insulating material such as Si3N4.
[0029]
Hereinafter, the manufacturing process of the ultrasonic transducer cell 10 will be described.
Although the manufacturing method of the ultrasonic transducer cell of the present invention is
not particularly limited, it is preferable to use the MEMS technology. If MEMS technology is used,
it is also possible to create an ultrasound transducer cell without using lead.
[0030]
Prepare the substrate first. As the substrate, for example, a silicon substrate, a glass substrate, a
ceramic substrate, a flexible polyimide film, or the like can be used. Alternatively, the substrate
may be shared with the substrate of the drive circuit for driving the ultrasonic transducer cell 10,
or after the ultrasonic transducer cell 10 is formed, the ultrasonic transducer cell 10 is separated
from the substrate and the substrate is You may reuse it. That is, although the substrate is
essential when the ultrasonic transducer cell 10 is formed, the substrate may not be present after
the ultrasonic transducer cell 10 is formed. In the following description, for convenience, the
surface of the substrate on which the ultrasonic transducer cell 10 is formed is referred to as a
cell formation surface.
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[0031]
Next, the lower electrode 11 is formed on the cell formation surface of the substrate. The lower
electrode 11 is formed of, for example, a known conductive material such as Au, Al, Mo, Al, Ti, W,
Cu, SnO2, ITO, polysilicon, or amorphous silicon by a sputtering method, a vapor deposition
method, a CVD method, or a plating method. It is preferable to form a film by a known method
such as, and process it into a desired lower electrode 11 pattern by photolithography or the like.
A conductive silicon substrate or the like is used as the substrate, and the portion other than the
pattern of the lower electrode 11 of the substrate is made nonconductive, or an insulating film is
formed on the substrate and the portion other than the pattern of the lower electrode 11 May be
made nonconductive. Also, the electrode wiring 21 may be formed simultaneously with the
formation of the lower electrode 11.
[0032]
Next, a first insulating film lower portion 12A covering the lower electrode 11 is formed. The
insulating film is formed by depositing silicon nitride such as Si 3 N 4 or SiN, or an insulating
material such as SiO 2, TiO 2, Al 2 O 3, ZrO 2 or HfO 2 by a known method such as sputtering,
vapor deposition, CVD or sol-gel method. It is preferable to process into a desired pattern using a
lithography method or the like.
[0033]
Then, the floating electrode 13 is formed on the first insulating film lower portion 12A. The
floating electrode 13 is made of a known conductive material such as Au, Al, Mo, Al, Ti, W, Cu,
SnO2, ITO, polysilicon, or amorphous silicon by sputtering, vapor deposition, CVD or plating. It is
preferable that the film is formed by a method and processed into a desired pattern of the
floating electrode 13 by using a photolithography method or the like.
[0034]
Furthermore, the first insulating film upper portion 12 B is formed on the floating electrode 13.
That is, the first insulating film 12 is constituted by the first insulating film lower portion 12A
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and the first insulating film upper portion 12B. For forming the first insulating film upper portion
12B, the same insulating material as the first insulating film lower portion 12A may be used in
the same formation method, or different insulating materials may be used in different formation
methods. Further, the first upper insulating film portion 12B and the first lower insulating film
portion 12A may be simultaneously processed into a desired pattern.
[0035]
Here, the floating electrode 13 is covered and sealed by the first lower insulating film portion
12A and the first upper insulating film portion 12B, as well as the entire peripheral surface
thereof, that is, the four side surfaces as well as the upper and lower surfaces.
[0036]
Next, the vibrating film support portion 14 is formed of an insulator, for example, a Si3N4 film.
Then, a sacrificial layer (not shown) is formed in the portion to be the void 18. The sacrificial
layer is a temporary one that is removed in a later step, and is preferably formed of a material
that is easily removed by etching or the like, such as polysilicon.
[0037]
Then, the second insulating film 15 is formed on the vibrating film support 14 and the sacrificial
layer by a known material and method as the first insulating film 12 is.
[0038]
After the formation of the vibrating film 9, that is, the second insulating film 15, the sacrificial
layer is removed by etching or the like to form the void portion 18, whereby the ultrasonic
transducer cell 10 is manufactured.
[0039]
Although it has been described above that the floating electrode 13 is more preferably charged, it
is also preferable that the floating electrode 13 store an electric charge during manufacture.
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That is, after forming the upper portion of the first insulating film, it is preferable to store
charges in the floating electrode 13 by a known method.
Known methods include, for example, electron beam irradiation or corona discharge.
[0040]
Here, the difference between the effect of reducing the DC bias voltage by the conventional
electret film and the effect of reducing the DC bias voltage by the floating electrode of the
present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of a film
having an effect of reducing a DC bias voltage, in which (A) shows an electret film and (B) shows
an insulating film including a floating electrode. In the electret film 140 shown in FIG. 3A, for
example, when charges, ie, electrons 100, are injected on one side A, holes 101 are formed on
the opposite side B and are polarized. That is, the electret film 140 has different charges on both
sides. Then, in the vicinity of the electron injection surface A of the electret film 140, positive
holes 101 are attracted and act as a DC bias, whereas in the vicinity of the surface B opposite to
the electron injection surface A of the electret film 140. , Negatively charged electrons 100 are
attracted.
[0041]
On the other hand, in the insulating film 112 including the floating electrode 113 inside, since
the electrons 100 which are negative charges are uniformly stored in the floating electrode 113,
the electrons of the negative charge repel on both surfaces of the insulating film 112 Since the
positive charge hole 101 is attracted away, it acts as a DC bias.
[0042]
That is, if only the phenomenon on one side of the insulating film, for example, the upper side in
FIG. 3, is observed, the effects of the electret film 140 and the floating electrode 113 on the
periphery are very similar, but both are totally different physical phenomena. is there.
[0043]
And since the ultrasonic transducer cell 10 of this embodiment includes the floating electrode 13
in the first insulating film 12, the DC bias applied to the electrode at the time of driving can be
reduced or eliminated.
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[0044]
And since the floating electrode 13 is covered with the first insulating film 12 around it, unlike
the electret film, the accumulated charge hardly changes or disappears in its distribution, and DC
is stable for a long period of time The effect of reducing the bias voltage can be maintained.
Furthermore, when the charge accumulated in the floating electrode 13 decreases while the
ultrasonic transducer cell 10 is in use, the first insulating film is applied by applying a higher
voltage to the external electrode than during normal driving. It is possible to inject charges into
the floating electrode 13 by a known principle such as leakage current, hot electrons or
tunneling current via 12.
By recharging the floating electrode 13, the ultrasonic transducer cell 10 can maintain the effect
of reducing the desired DC bias voltage for a longer period of time.
[0045]
In addition, the structure of the first insulating film 12 including the floating electrode 13 has
good compatibility with the MEMS process, can be produced by a device of a normal MEMS
process, and does not require a special device etc. It is easy and less likely to contaminate other
devices in the process.
[0046]
Next, the operation of the capacitive ultrasonic transducer cell 10 will be described with
reference to FIG.
FIG. 4 is a cross-sectional view for explaining the operation of the ultrasonic transducer cell 10.
[0047]
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12
The ultrasonic transducer cell 10 is driven by being combined with the conductor 31 of the
ground potential.
That is, an RF signal is applied to the lower electrode 11 by the RF signal generating means 32 in
a state where the vibrating film 9 composed of the second insulating film 15 is in close contact
with the electrically grounded conductor 31. Then, the vibrating membrane 9 is pulled by the
lower electrode 11 and returns to its original state when the voltage is made zero. As a result of
vibrating the vibrating membrane 9 by this vibration operation, an ultrasonic wave is generated,
and the ultrasonic wave is irradiated in the upper direction of the vibrating membrane 9. At the
time of reception of the ultrasonic wave, the vibrating film 9 vibrates by the ultrasonic wave, that
is, the distance between the lower electrode 11 and the interface where the conductor 31 of the
ground potential is in close contact with the vibrating film 9 changes. The ultrasonic wave can be
received by detecting a change in capacitance with the conductor 31.
[0048]
The conductor 31 may be a solid or liquid having flexibility or deformability capable of being in
close contact with the vibrating membrane 9, and a living tissue, physiological saline, or the like
can be preferably used. In order to electrically ground the conductor 31, the electrode plate etc.
electrically connected to the conductor 31 are grounded.
[0049]
The ultrasonic transducer cell 10 of the present invention can operate without forming the upper
electrode film and the upper electrode wiring, and in this case, the manufacturing process is
simple. Further, in this case, since the ultrasonic transducer cell 10 does not have the upper
electrode wiring formed on the uneven surface, the failure due to the disconnection of the upper
electrode wiring does not occur. Furthermore, since the vibrating membrane 9 does not have the
upper electrode film, the vibrating membrane 9 is light and easily vibrated, so that efficient
transmission of ultrasonic waves and improvement of ultrasonic wave reception sensitivity can
be achieved.
[0050]
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13
The ultrasonic transducer cell 10 may have a conductive film of an isolated pattern on the top of
the vibrating film 9. The conductive film of this isolated pattern is a film electrically insulated
from the other members constituting the ultrasonic transducer cell 10, and is, for example, a film
of a circular pattern concentric with the gap portion 18. In particular, as the conductive film in
the isolated pattern, a biocompatible biocompatible oxide conductive material or conductive
polymer material can be preferably used. The ultrasonic transducer cell 10 having a conductive
film of an isolated pattern formed on the top of the vibrating film 9 electrically isolated from
other members constituting the ultrasonic transducer cell 10 is electrically Good contact. For
example, even if the conductor 31 is constituted by a plurality of portions having different
conductivity, the potential in the conductive film of the isolated pattern is stable at a uniform
ground potential.
[0051]
Second Embodiment Hereinafter, an ultrasonic transducer cell 10B, which is a capacitive
ultrasonic transducer according to a second embodiment of the present invention, will be
described with reference to the drawings. FIG. 5 is a cross-sectional view for explaining the
structure of the ultrasonic transducer cell 10B of the present embodiment. The same components
as those of the ultrasonic transducer cell 10 according to the first embodiment are denoted by
the same reference numerals, and descriptions thereof will be omitted. Only differences from the
ultrasonic transducer cell 10 will be described.
[0052]
As shown in FIG. 5, the ultrasonic transducer cell 10B of the present embodiment is a capacitive
ultrasonic transducer including the floating electrode 13B inside the second insulating film 15.
[0053]
The material of the lower electrode, the first insulating film, the second insulating film, the
vibrating film instruction portion, or the floating electrode in the second embodiment is not
particularly limited, but is described in the first embodiment described above. It is preferable to
use one of
[0054]
The method of manufacturing the ultrasonic transducer cell according to the second embodiment
is not particularly limited. However, the second insulating film 15 including the floating electrode
13 B is a first insulation including the floating electrode 13 in the ultrasonic transducer cell 10. It
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14
is preferable to form the film 12 in the same manner as the film 12, that is, in the order of the
lower part of the second insulating film, the floating electrode 13, and the lower part of the
second insulating film.
[0055]
In addition to the effects of the ultrasonic transducer cell 10 of the first embodiment, the
ultrasonic transducer cell 10B of the present embodiment further includes a step of forming the
floating electrode 13B in the ultrasonic transducer cell 10B. Since it is in the latter half of the
manufacturing process, the charges accumulated in the floating electrode 13B during
manufacturing are less likely to disappear, and the effect of reducing the DC bias voltage
compared to the ultrasonic transducer cell 10 is strong.
[0056]
Third Embodiment Hereinafter, an ultrasonic transducer cell 10C which is a capacitive ultrasonic
transducer according to a third embodiment of the present invention will be described with
reference to the drawings.
FIG. 6 is a cross-sectional view for explaining the structure of the ultrasonic transducer cell 10C
of the present embodiment.
The same components as those of the ultrasonic transducer cell 10 according to the first
embodiment are denoted by the same reference numerals, and descriptions thereof will be
omitted. Only differences from the ultrasonic transducer cell 10 will be described.
[0057]
The ultrasonic transducer cell 10C is disposed on the lower electrode 11, the first insulating film
12 on the lower electrode 11, and the lower electrode 11 so as to face the lower electrode 11
and to be separated by the gap 18 by the diaphragm supporting portion 14. The upper electrode
16 on the second insulating film 15 and the protective film 17 on the upper electrode 16 are
formed.
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That is, in the ultrasonic transducer cell 10 </ b> C, the vibrating film 9 includes the second
insulating film 15, the upper electrode 16, and the protective film 17.
The first insulating film 12 includes the floating electrode 13 therein.
[0058]
The material of the lower electrode, the first insulating film, the second insulating film, the
vibrating film instruction portion, or the floating electrode in the third embodiment is not
particularly limited, but it is described in the first embodiment described above. It is preferable to
use one of
[0059]
As the protective film 17, a known insulating material can be used, and preferably an insulating
organic film, particularly preferably parylene is used.
Parylene is a general term for organic substances consisting of polyparaxylylene, but it is
possible to deposit a film in which the occurrence of defects such as pinholes is suppressed by
vapor deposition or CVD, etc., and on an uneven surface. Also, film formation with a uniform film
thickness is possible. However, the formation method of the protective film 17 is not limited to
these, The formation method conventionally known can be used. Since the ultrasonic transducer
cell 10C has the upper electrode 16, unlike the ultrasonic transducer cell 10, it can be driven
without being combined with the conductor 31 of the ground potential. That is, the ultrasonic
transducer cell 10C can transmit and receive ultrasonic waves even in the air or in the insulating
liquid.
[0060]
Furthermore, since the ultrasonic transducer cell 10C has the protective film 17, in addition to
the effects of the ultrasonic transducer cell 10 of the first embodiment, even though the upper
electrode 16 is included, It is hard to cause problems such as corrosion.
[0061]
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16
Fourth Embodiment Hereinafter, an ultrasonic transducer cell 10D, which is a capacitive
ultrasonic transducer according to a fourth embodiment of the present invention, will be
described with reference to the drawings.
FIG. 7 is a cross-sectional view for explaining the structure of the ultrasonic transducer cell 10D
of the present embodiment. The same components as those of the ultrasonic transducer cell 10C
of the third embodiment are denoted by the same reference numerals, and descriptions thereof
will be omitted. Only differences from the ultrasonic transducer cell 10C will be described.
[0062]
The ultrasonic transducer cell 10D is disposed on the lower electrode 11, the first insulating film
12 on the lower electrode 11, and the lower electrode 11 so as to face the lower electrode 11
and to be separated by the gap 18 by the vibrating film support portion 14. The upper electrode
16 on the second insulating film 15 and the protective film 17 on the upper electrode 16 are
formed. The second insulating film 15 includes the floating electrode 13B inside.
[0063]
In addition to the effects of the ultrasonic transducer cell 10 of the first embodiment, the
ultrasonic transducer cell 10D of the present embodiment further includes a step of forming the
floating electrode 13B in the ultrasonic transducer cell 10D. Since it is in the latter half of the
manufacturing process, the charge accumulated in the floating electrode 13B during
manufacturing is less likely to disappear, and the effect of reducing the DC bias voltage is strong.
[0064]
Fifth Embodiment Hereinafter, an ultrasonic transducer cell 10E which is a capacitive ultrasonic
transducer according to a fifth embodiment of the present invention will be described with
reference to the drawings.
FIG. 8 is a cross-sectional view for explaining the structure of the ultrasonic transducer cell 10E
of the present embodiment. The same components as those of the ultrasonic transducer cell 10C
of the third embodiment are denoted by the same reference numerals, and descriptions thereof
will be omitted. Only differences from the ultrasonic transducer cell 10C will be described.
04-05-2019
17
[0065]
The ultrasonic transducer cell 10E is disposed so as to face the lower electrode 11, the first
insulating film 12 disposed under the lower electrode 11, and the lower electrode 11 with the
vibrating film supporting portion 14 and the air gap 18 therebetween. And the upper electrode
16. The first insulating film 12 has the floating electrode 13 therein.
[0066]
The ultrasonic transducer cell 10D of the present embodiment has the same function and effect
as the ultrasonic transducer cell 10C of the third embodiment, and the distance between the
opposing electrodes is further reduced. It can be driven at a lower voltage than the cell 10C.
[0067]
In the above description, the ultrasonic transducer cell according to the embodiment in which
either the first insulating film 12 or the second insulating film 15 includes the floating electrode
13 or 13B has been described. The film 12 may include the floating electrode 13 and the second
insulating film 15 may include the floating electrode 13B.
The ultrasonic transducer cell in which the first insulating film and the second insulating film
include the floating electrode has a strong effect of reducing the DC bias voltage.
[0068]
Next, the ultrasonic transducer 2 and the ultrasonic endoscope 1 to which the ultrasonic
transducer cell of the present invention can be applied will be described. FIG. 9 is an explanatory
view showing a schematic configuration of the ultrasonic endoscope 1, FIG. 10 is a perspective
view showing a distal end portion 4A of the ultrasonic endoscope 1, and FIG. It is the partial top
view which looked at from the transmission / reception direction of an ultrasonic wave.
[0069]
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The ultrasonic endoscope 1 shown in FIG. 9 includes an elongated insertion portion 4 introduced
into the body, an operation portion 5 positioned at a proximal end of the insertion portion 4, and
a universal extending from the side portion of the operation portion 5. Although mainly
configured with the code 6, the present invention is not limited to this.
[0070]
An endoscope connector 7 is provided at the proximal end of the universal cord 6.
The endoscope connector 7 is detachably connected to the camera control unit (not shown) via
the electrical connector 8 via the electric connector 8 and the ultrasonic observation apparatus
(not shown) via the ultrasonic connector 3. The ultrasonic cable 3a is extended. An ultrasonic
transducer 2 for transmitting and receiving an ultrasonic wave is disposed at the distal end 4A of
the insertion portion 4.
[0071]
The ultrasonic transducer 2 shown in FIG. 11 is composed of a plurality of ultrasonic transducer
cells 10 arranged at substantially equal intervals in the plane. The number of ultrasonic
transducer cells used for the ultrasonic transducer is not particularly limited, and can be
appropriately determined according to the purpose. The ultrasonic transducer 2 has flexibility as
a whole, and as shown in FIG. 10, is wound around the tip 4A in a substantially cylindrical shape
with an axis substantially parallel to the insertion axis of the insertion portion 4 as a central axis.
It is preferable to be disposed in a rotated manner.
[0072]
The ultrasonic transducer 2 transmits an ultrasonic wave outward in the radial direction of the
distal end portion 4A of the insertion portion 4 having a cylindrical shape. Therefore, the
ultrasonic transducer 2 configured by arranging the ultrasonic transducer cells 10 has a function
as a two-dimensional ultrasonic transducer array.
[0073]
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A plurality of ultrasonic transducer cells 10 (not shown) are formed on the inner peripheral
surface of the cylindrical ultrasonic transducer 2, that is, on the mounting surface opposite to the
mounting surface on which the ultrasonic transducer cell 10 is mounted. The drive circuit of is
mounted. The drive circuit has an electric circuit such as a pulser for driving the ultrasonic
transducer cell 10 and a selection circuit, and is electrically connected to the ultrasonic
transducer cell 10.
[0074]
The ultrasonic transducer 2 having the above-described configuration is a two-dimensional
ultrasonic transducer array disposed on the outer peripheral surface of the distal end portion 4A
of the cylindrical insertion portion 4, substantially orthogonal to the insertion axis of the distal
end portion 4A. The ultrasonic waves are transmitted and received radially on the same plane.
[0075]
The ultrasound endoscope 1 and the ultrasound transducer 2 according to the present
embodiment can reduce or eliminate the DC bias applied to the ultrasound transducer cell 10, so
that the burden on the living body can be reduced. it can.
[0076]
Moreover, instead of the ultrasonic transducer cell 10C, an ultrasonic endoscope and an
ultrasonic transducer using the ultrasonic transducer cell 10, 10B, 10D or 10D are also the
ultrasonic endoscope 1 and the ultrasonic transducer. The same effect as that of 2 is exerted.
[0077]
In particular, the ultrasonic endoscope and the ultrasonic transducer having the ultrasonic
transducer cell 10 or 10B have the ultrasonic transducer cell 10C because the ultrasonic
transducer cell does not have the upper electrode and the upper electrode wiring. The
manufacturing process is simpler and more reliable than ultrasound endoscopes and ultrasound
transducers that have etc.
[0078]
In addition, although the ultrasonic endoscope 1 inserted into a test subject's body via the
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insertion part 4 as the ultrasonic endoscope 1 of embodiment of this invention was
demonstrated, the ultrasonic transducer cell of this embodiment 10 to 10E and the ultrasonic
transducer 2 can be similarly used for a so-called capsule type medical device.
Here, a capsule-type medical device is a device for acquiring information in the body of a subject,
and refers to a non-wired device sealed by an exterior.
[0079]
The present invention is not limited to the above-described embodiment, and various changes,
modifications, and the like can be made without departing from the scope of the present
invention.
[0080]
It is a top view of a part of ultrasonic transducer of a 1st embodiment.
It is sectional drawing of the ultrasonic transducer cell of 1st Embodiment.
It is sectional drawing of a film | membrane which has an effect which reduces DC bias voltage,
(A) shows an electret film | membrane, (B) has shown the insulating film which has a floating
electrode.
It is sectional drawing for demonstrating the operation | movement of the ultrasonic transducer
cell of 1st Embodiment.
It is sectional drawing for demonstrating the structure of the ultrasonic transducer cell of 2nd
Embodiment. It is sectional drawing for demonstrating the structure of the ultrasonic transducer
cell of 3rd Embodiment. It is sectional drawing for demonstrating the structure of the ultrasonic
transducer cell of 4th Embodiment. It is sectional drawing for demonstrating the structure of the
ultrasonic transducer cell of 5th Embodiment. It is explanatory drawing which shows schematic
structure of an ultrasonic endoscope. It is a perspective view which shows the front-end | tip part
of an ultrasonic endoscope. FIG. 6 is a partial view of a part of the ultrasonic transducer in the
transmission / reception direction of ultrasonic waves. It is sectional drawing which shows the
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structure of the cell of a well-known electrostatic capacitance type ultrasonic transducer. It is a
cross-sectional schematic diagram for demonstrating the drive of the cell of a well-known
electrostatic capacitance type ultrasonic transducer. It is sectional drawing which shows the
structure of the cell of an electrostatic capacitive type ultrasonic transducer using a well-known
electret film.
Explanation of sign
[0081]
Reference Signs List 1 ultrasonic endoscope, 2 ultrasonic transducers, 3 ultrasonic connectors,
3a ultrasonic cables, 4 insertion parts, 4A tip parts, 5 operation parts, 6 universal cords, 7
endoscope connectors, 8 electrical connectors, 8a Electric cable, 9 diaphragms, 10 ultrasonic
transducer cells, 10B ultrasonic transducer cells, 10C ultrasonic transducer cells, 10D ultrasonic
transducer cells, 10E ultrasonic transducer cells, 11 lower electrodes, 12 first Insulating film,
12A first insulating film lower portion, 12B first insulating film upper portion, 13 floating
electrode, 13B floating electrode, 14 vibrating film support portion, 15 second insulating film, 16
upper electrode, 17 protective film, 18 air gap Parts, 21 electrode wiring, 31 conductors, 32
signal generating means, 100 electrons, 101 holes, 112 insulating films, 113 floating electrodes,
140 electret films, 210 cells LE, 211A electrode, 211B conductive silicon substrate, 214
insulating support, 215 diaphragm, 216 upper electrode, 218 cavity, 224 bias terminal, 226
signal terminal, 310 capacitive ultrasonic transducer, 311 lower electrode, 316 upper electrode,
317 polyester film, hole for 318 air reservoir, 330A silicon substrate, 330C thermal silicon oxide
layer, 340 electret film.
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