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JP2006319712

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DESCRIPTION JP2006319712
PROBLEM TO BE SOLVED: To construct an area which is unlikely to be elastically deformed in
the vicinity of the central portion of a membrane, to form a region which is easily elastically
deformed around the membrane, and in the vicinity of the center, an electrostatic capacitive
ultrasonic wave Provide a transducer. A silicon substrate, a first electrode disposed on the upper
surface of the silicon substrate, a second electrode disposed opposite to the first electrode and
separated by a predetermined gap, and A capacitive ultrasonic transducer comprising a
transducer element comprising a transducer cell comprising a membrane for supporting two
electrodes and a membrane support for supporting the membrane, the capacitive ultrasonic
transducer comprising: The above problems are solved by a capacitive ultrasonic transducer
having a structure in which the end portion is more easily deformed than the central portion of
the membrane. [Selected figure] Figure 1
Capacitive ultrasonic transducer and method of manufacturing the same
[0001]
The present invention relates to a capacitive ultrasonic transducer.
[0002]
Ultrasonic diagnostic methods are in widespread use in which ultrasonic waves are emitted
toward the wall of a body cavity, and an internal state of the body is imaged and diagnosed from
the echo signals.
04-05-2019
1
An ultrasound endoscope scope is one of the equipment used for this ultrasound diagnostic
method.
[0003]
In an ultrasonic endoscope, an ultrasonic probe is attached to the tip of an insertion portion to be
inserted into a body cavity, and this ultrasonic probe converts an electric signal into an ultrasonic
wave and emits it into a body cavity, or in a body cavity It receives the reflected ultrasonic waves
and converts them into electrical signals.
[0004]
Conventionally, ceramic piezoelectric material PZT (lead zirconate titanate) has been used as a
piezoelectric element for converting an electric signal to ultrasonic waves in an ultrasonic probe,
but a silicon semiconductor substrate is processed using silicon micromachining technology.
Capacitive micromachined ultrasonic transducers (hereinafter referred to as c-MUTs) have
attracted attention.
This is one of the elements collectively referred to as a micromachine (MEMS: Micro ElectroMechanical System).
[0005]
On the other hand, in the field of ultrasound diagnosis, recently, diagnostic modalities of
harmonic imaging have been in the spotlight because of the possibility of unprecedented highprecision ultrasound diagnosis. Therefore, a body cavity insertion type ultrasound diagnostic
apparatus The standard equipment of this diagnostic modality is becoming essential. Therefore,
for this purpose, the frequency band of the conventional piezoelectric transducer is insufficient,
and it is desired to further broaden the ultrasonic transducer.
[0006]
As described above, in recent years, a capacitive ultrasonic transducer (cMUT) using a
04-05-2019
2
micromachine process is attracting attention. It goes without saying that this cMUT does not
contain heavy metals such as lead, is not only environmentally friendly, but can easily obtain
wide band characteristics, and is therefore suitable for the above-described harmonic imaging.
[0007]
FIG. 23 shows an example of a conventional cMUT. This figure is the cMUT disclosed in Patent
Document 1. The ultrasound transducer is formed by a plurality of capacitive micromachined
ultrasound transducers (cMUTs). Each cell constituting the cMUT has a charged vibration plate
301. The charged vibration plate 301 capacitively faces the oppositely charged substrate 302.
[0008]
The diaphragm 301 is bent toward the substrate 302 by the bias charge. In addition, the
substrate 302 has a central portion 303 which is raised with respect to the center of the
diaphragm 301 so that the charge of the cell has the maximum density at the center of the
vibration of the diaphragm 301. The drive pulse waveform fed to the cell is pre-distorted for
harmonic operation. This is done in view of the non-linear operation of the device in order to
reduce the distortion of the transmitted ultrasound signal in the harmonic band.
[0009]
The cMUT cell may be integrated with an auxiliary transducer circuit such as bias charge
regulator 201 as it is fabricated by conventional semiconductor processing. cMUT cells can also
be processed by microstereolithography. As such, cells are formed using a variety of polymers
and other materials.
[0010]
The ultrasonic observation apparatus is provided with a high breakdown voltage switch in the
ultrasonic probe in order to operate by the harmonics. In the ultrasonic observation apparatus,
pulse generation means and control means are provided. The pulse generation means can output
a pulse having an arbitrary waveform and an arbitrary voltage value. The control means controls
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3
the outputs of the high withstand voltage switch and the pulse generation means based on the
scanning timing of the ultrasonic transducer.
[0011]
Further, in recent years, a capsule type endoscope for obtaining an image in a body cavity by
sending a capsule unit configured for medical use into a body cavity is being put to practical use
(for example, Patent Document 1 and Patent Document 2). The ultrasound diagnostic medical
capsule enables ultrasound diagnosis of a site where diagnosis is difficult with an ultrasound
probe. JP-A-2004-503313 JP-A-2004-350705 JP-A-2004-350704 Minoru Murakami et al.,
"Study on Photolithography of Curved Surface by Gray Scale Mask Exposure", 11th Design
Engineering System Division Lecture, The Japan Society of Mechanical Engineers Proceedings of
the Meeting, Takamatsu, November 5, 2001, pp. 39-pp. 42 Yasuhiro Sato et al., "High-precision
microlens fabrication technology and its application to beam shaping elements", Richoh
Technical Report No. 29, December 2003, pp. 13-pp. 20
[0012]
However, as shown in FIG. 23, the membrane has a curved shape due to the electrostatic force
between the electrodes, and the charge on the upper electrode facing the lower electrode is
biased. That is, the central portion of the curved membrane is more bent and becomes closer to
the lower electrode, and a large amount of charge is collected, and the electric flux density is
high. Further, since the entire membrane is curved, the electric flux is not uniform on the upper
electrode side facing the lower electrode, and the direction of the electric flux is also bent along
with the bending of the upper electrode.
[0013]
From such a thing, non-linearity arises between a drive voltage and a bending displacement, and
a high frequency component will be included in a vibration source from the beginning. Therefore,
it has been difficult to generate transmission ultrasonic waves having large transmission sound
pressure and no harmonic component as transducer characteristics.
[0014]
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4
On the other hand, the term harmonic component may be used not to mean non-linear
harmonics but to mean high-order standing waves. Since these harmonics are transmitted from
the sound source, if these harmonics are not suppressed, imaging using nonlinear harmonics is
adversely affected (the harmonic components generated from the living body or the high-order
waves originally contained in the sound source). It becomes impossible to distinguish between
standing waves, which causes a large S / N reduction in the case of harmonic (harmonic)
imaging. ).
[0015]
The high-order standing wave component is generated at a frequency that is an integral multiple
of the fundamental wave, but the vibration source (sound source) is of uniform length and
thickness, and is made of homogeneous material, and vibration and non-vibration parts, For
example, it is premised that the boundary with the membrane support is acoustically clear. If this
is not the case (if it is composed of a region susceptible to elastic deformation and a region not
so, etc.), high-order standing waves will be dispersed and suppressed, or they will be generated at
non-integer multiples, and harmonics (harmonics) There is no negative impact on imaging.
[0016]
In view of the above problems, in the present invention, a region that is not easily elastically
deformed is formed in the vicinity of the central portion of the membrane, a region that is easily
elastically deformed is formed around the membrane, and the electric flux between the
electrodes is perpendicular to the electrodes in the vicinity of the center. Provided are a
capacitive ultrasonic transducer and a method of manufacturing the same.
[0017]
According to the invention described in claim 1 of the present invention, a silicon substrate, a
first electrode disposed on the upper surface of the silicon substrate, and a predetermined
electrode facing the first electrode are provided. A vibrator element composed of a vibrator cell
consisting of a second electrode arranged with a gap, a membrane for supporting the second
electrode, and a membrane supporting portion for supporting the membrane is integrated. In the
capacitive ultrasonic transducer, the end portion of the membrane has a structure that makes it
relatively easier to deform than the central portion of the membrane. Can be achieved by
providing
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[0018]
According to the invention as set forth in claim 2, the above-mentioned problem is characterized
in that the displacement of the end of the membrane, which is deformed relatively more than the
central part of the membrane, is a bending displacement. This can be achieved by providing the
capacitive ultrasonic transducer according to Item 1.
[0019]
According to the third aspect of the present invention, in the above object, the structure which is
relatively more deformable than the central portion of the membrane is at least one row of
grooves provided at the end of the membrane. This can be achieved by providing the capacitive
ultrasonic transducer according to claim 1.
[0020]
According to the invention described in claim 4 of the above-mentioned subject, the membrane
has a substantially circular shape, and the groove row is a groove row provided substantially
concentrically in the vicinity of the membrane peripheral portion. This can be achieved by
providing the capacitive ultrasonic transducer according to claim 3 which is characterized in that.
[0021]
According to the invention set forth in claim 5 of the invention, a plurality of the grooves are
formed substantially in the shape of a circular arc. This can be achieved by providing a
transducer.
[0022]
According to the sixth aspect of the present invention, the groove is formed in at least one of the
upper surface and the lower surface of the membrane. This can be achieved by providing the
described capacitive ultrasonic transducer.
[0023]
According to the seventh aspect of the present invention, the second electrode is formed on the
inner side of the groove in the membrane according to the seventh aspect of the present
invention. This can be achieved by providing a capacitive ultrasonic transducer.
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[0024]
According to the invention as set forth in claim 8, the upper electrode is a substantially circular
central portion represented by the innermost one of the concentric grooves in the membrane. It
can be achieved by providing a capacitive ultrasonic transducer according to claim 4,
characterized in that it has a diameter approximately equal to.
[0025]
According to the invention as set forth in claim 9, the above object is achieved by the invention
as set forth in claim 9 in which the space between the membrane, the membrane support portion
and the silicon substrate and the void portion surrounded by the membrane support portion is
provided. The present invention can be achieved by providing a capacitive ultrasonic transducer
according to claim 1, wherein a sacrificial layer removing hole for removing the sacrificial layer
is penetrated.
[0026]
According to the invention set forth in claim 10, the above object is that an elastic structure is
formed on the upper surface of the membrane, and the elastic structure is inclined with respect
to the surface of the membrane. This can be achieved by providing the capacitive ultrasonic
transducer according to claim 1.
[0027]
According to the invention described in claim 11 of the above object, the elastic structure is
formed on the upper surface of the membrane, and the elastic structure has a curved surface.
This can be achieved by providing a capacitive ultrasonic transducer.
[0028]
According to the invention as set forth in claim 12, the above object is achieved by a capacitive
ultrasonic transducer and a housing for incorporating the same, wherein a window for ultrasonic
radiation is formed in the housing This can be achieved by providing a capacitive ultrasonic
transducer characterized in that the window part is provided with an acoustic lens.
[0029]
According to the invention as set forth in claim 13, the above object is characterized in that the
housing has a flow hole for filling the ultrasonic wave propagation medium therein. This can be
achieved by providing a capacitive ultrasonic transducer.
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[0030]
According to the invention set forth in claim 14, the above-mentioned problem is that, among all
the elements arranged in the housing, all the elements electrically conducting to the electrode
terminals of the cMUT are insulated. This can be achieved by providing a capacitive ultrasonic
transducer according to claim 12 having a structure to be coated.
[0031]
According to the invention as set forth in the claim 15 of the present invention, the abovementioned object is characterized in that the ultrasonic transducers are provided with a plurality
of the transducer elements in the form of an array. This can be achieved by providing the
capacitive ultrasonic transducer according to any of the above.
[0032]
According to the invention as set forth in claim 16 of the appended claims, the above-mentioned
problem is an intracorporeal insertion type ultrasonic endoscope apparatus having the ultrasonic
transducer according to any one of claims 1 to 15 mounted thereon. It can be achieved by
providing.
[0033]
According to the invention described in claim 17, the above-mentioned problem is provided by
providing an ultrasonic capsule endoscope equipped with the ultrasonic transducer according to
any one of claims 1 to 15. Can be achieved.
[0034]
According to the invention as set forth in claim 18, the above object is achieved by a silicon
substrate, a first electrode disposed on the upper surface of the silicon substrate, and a
predetermined electrode facing the first electrode. A vibrator element composed of a vibrator cell
consisting of a second electrode arranged with a gap, a membrane for supporting the second
electrode, and a membrane supporting portion for supporting the membrane is integrated. In the
method of manufacturing a capacitive ultrasonic transducer, the method of providing a groove at
the end of the membrane is either chemical etching or reactive ion etching. This can be achieved
by providing a method of manufacturing the transducer.
[0035]
According to the invention as set forth in the nineteenth aspect of the present invention, in the
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above-mentioned subject, the groove is formed by removing the sacrificial layer formed at a
predetermined position by etching processing, thereby making it possible to obtain This can be
achieved by providing a method of manufacturing a capacitive ultrasonic transducer according to
claim 18, characterized in that it is formed on at least one surface.
[0036]
According to the invention as set forth in the claim 20, the above-mentioned subject is
characterized in that the groove is formed to provide a gap between the first electrode and the
second electrode. Forming a second sacrificial layer made of the same material as the first
sacrificial layer on the upper surface of the sacrificial layer, forming the membrane on the upper
surface of the second sacrificial layer, and then etching the first sacrificial layer; 19. The method
for manufacturing a capacitive ultrasonic transducer according to claim 18, wherein the method
is formed on the lower surface of the membrane by removing the sacrificial layer and the second
sacrificial layer. it can.
[0037]
According to the invention set forth in claim 21, the above-mentioned subject is an electrostatic
capacitance type in which an elastic structure is formed on the upper surface of the membrane,
which is inclined with respect to the ultrasonic radiation surface of the membrane. 21. A method
of manufacturing an ultrasonic transducer can be achieved by providing a method of
manufacturing a capacitive ultrasonic transducer according to claim 19 or 20, characterized in
that a gray scale mask process is included.
[0038]
According to the invention as set forth in the appended claims, in the above object, according to
the invention as set forth in claim 22, the method of manufacturing a capacitive ultrasonic
transducer including a gray scale mask process is characterized in that the elastics having a
curved surface on the upper surface of the membrane. This can be achieved by providing a
method of manufacturing a capacitive ultrasonic transducer according to claim 19 or 20,
characterized by forming a structure.
[0039]
By forming a region that is less likely to be elastically deformed near the center of the membrane
and a region that is more likely to be resiliently deformed near the periphery of the membrane,
the electric flux between the electrodes near the center becomes perpendicular to the electrode
surface, and the applied voltage and displacement There is no non-linearity between them, and
furthermore, a large displacement can be made as a whole of the membrane.
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[0040]
First Embodiment In the present embodiment, a region that is less likely to be elastically
deformed is formed in the vicinity of the central portion of the membrane, a region that is more
likely to be elastically deformed is configured in the periphery of the membrane, Vertically, the
entire membrane has a large displacement structure, and cMUT suitable for harmonic imaging
that does not cause non-linearity in the relationship between drive voltage and displacement, that
is, does not include harmonic components. Will be explained.
[0041]
FIG. 1 shows a conceptual diagram of a cMUT cell in the present embodiment.
The membrane 201 of the cMUT cell 200 is curved (curved part 202) in the vicinity of the
membrane support part 204, and has a planar shape at the membrane central part 203.
The curved portion 202 is formed in such a manner that the membrane is easily elastically
deformed by forming concentric groove rows in the vicinity of the circumference of the
membrane.
[0042]
As described above, by forming a region that is not easily elastically deformed in the vicinity of
the central portion of the membrane and a region that is easily deformed in the vicinity of the
membrane end, the electric flux between the electrodes is perpendicular to the electrode surface
in the vicinity of the central portion. Furthermore, the entire membrane can be subjected to large
flexural vibration displacement.
[0043]
Now, embodiments of the present invention will be described below.
FIG. 2 is a view for explaining an ultrasonic endoscope apparatus.
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As shown in FIG. 2, the ultrasonic endoscope apparatus 1 of the present embodiment includes an
ultrasonic endoscope (hereinafter abbreviated as an endoscope) 2, an endoscope observation
apparatus 3, and an ultrasonic observation apparatus 4. And a monitor 5.
[0044]
An ultrasound endoscope (hereinafter, abbreviated as an endoscope) 2 includes an electrostatic
ultrasound transducer described later.
The endoscope observation apparatus 3 performs a variety of signal processing of a light source
unit (not shown) for supplying illumination light and driving of an image pickup device (not
shown) and electric signals transmitted from the image pickup device to perform endoscopic
observation images. A signal processing unit that generates a video signal is provided.
[0045]
The ultrasonic observation device 4 performs driving of the electrostatic ultrasonic transducer
and various signal processing of electric signals transmitted from the electrostatic ultrasonic
transducer to generate a video signal for ultrasonic tomographic image Equipped with
The monitor 5 displays an observation image based on the ultrasonic observation device 4 and
the image signal generated by the endoscope observation device 3.
[0046]
The endoscope 2 includes an insertion unit 11, an operation unit 12, and a universal cord 13.
The insertion portion 11 is an elongated portion to be inserted into a body cavity.
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The operation unit 12 is located on the proximal end side of the insertion unit 11.
The universal cord extends from the side of the operation unit 12.
[0047]
An endoscope connector 14 connected to the endoscope observation device 3 is provided at a
proximal end of the universal cord 13.
A lighting connector 14 a connected to the light source of the endoscope observation device 3 is
provided at the tip of the endoscope connector 14.
On the side of the endoscope connector 14 is provided an electrical connector 14a to which an
electrical cord (not shown) electrically connected to the signal processing unit is detachably
connected.
[0048]
In addition, an ultrasonic cable 15 having an ultrasonic connector 15a electrically connected to
the ultrasonic observation device 4 extends from the proximal end of the endoscope connector
14.
The insertion portion 11 is composed of a distal end portion 6, a bending portion 7, and a
flexible tube portion 8 in order from the distal end side.
The tip 6 is formed of a hard member.
The bending portion 7 is a bendable portion connected to the proximal end side of the distal end
portion 6.
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The flexible tube portion 8 is a portion having a small diameter and a long length extending
continuously to the proximal end side of the curved portion 7 and reaching the distal end side of
the operation portion 12 and having flexibility.
[0049]
The distal end portion 6 is provided with an endoscope observation unit 20 and an ultrasonic
observation unit 21.
The endoscope observation unit 20 is provided with an observation optical unit and an
illumination optical unit that perform endoscopic observation by direct vision.
The ultrasonic observation unit 31 has a plurality of ultrasonic transducer elements that transmit
and receive ultrasonic waves arranged to form an ultrasonic scan surface.
[0050]
The operation unit 12 is provided with an angle knob 16, an air supply / water supply button
17a, a suction button 17b, a treatment instrument insertion port 18, various operation switches
19 and the like.
The angle knob 16 controls the bending of the bending portion 7.
The air supply / water supply button 17 a is a button for performing air supply and water supply
operations.
[0051]
The suction button 17 b is a button for performing a suction operation.
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The treatment instrument insertion port 18 is a portion serving as an entrance of the treatment
instrument to be introduced into the body cavity.
The various operation switches 19 are switches for various operations for switching a display
image to be displayed on the monitor 5 and giving instructions such as freeze and release.
Reference numeral 9 is a mouthpiece disposed in the oral cavity of the patient.
[0052]
An ultrasonic observation unit 21 for performing ultrasonic observation is disposed on the distal
end side of the distal end portion 6.
Further, an inclined surface portion is formed in the endoscope observation portion 20 of the
distal end portion 6.
An illumination lens cover that forms an illumination optical unit that irradiates the observation
site with illumination light, an observation lens cover that forms an observation optical unit that
captures an optical image of the observation site, and the treatment instrument insertion port 18
A forceps outlet which is an opening from which the treatment instrument protrudes is provided.
[0053]
The ultrasonic observation unit 21 mainly includes a capacitive ultrasonic transducer (cMUT) for
transmitting and receiving ultrasonic waves, and a housing portion in which the ultrasonic
transducer is accommodated and fixed to the distal end portion 6. It is done.
[0054]
The capacitive ultrasonic transducer cMUT is obtained by processing a silicon semiconductor
substrate using silicon micromachining technology.
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Capacitive ultrasonic transducers are manufactured automatically and faithfully according to the
operation sequence in a completely clean environment by a silicon process.
[0055]
The capacitive ultrasonic transducer is composed of a plurality of ultrasonic transducer elements
(or simply referred to as “elements”), which is the minimum unit for inputting and outputting
drive control signals.
This element is composed of an oscillator of a unit called an oscillator cell (or simply called
"cell").
A cell refers to a group of elements constituting one cavity (air gap) as described later.
[0056]
Hereinafter, a capacitive ultrasonic transducer in which a groove row is formed on one or both of
the upper surface and the lower surface of the membrane will be described. FIG. 3 shows a cross
section of a cMUT transducer element in which a groove row in the present embodiment is
arranged on the upper surface of a membrane. In the figure, the capacitive ultrasonic transducer
element 31 includes a silicon substrate 32, a lower electrode 33, a dielectric film 34, a membrane
support portion 35, a membrane 36, a cavity (air gap) 40, an upper electrode 39, and a ground
side. The electrode pad 37, the diffusion layer 38, the signal input / output terminal electrode
pad 41, the substrate through hole 42, the substrate through hole wiring 42a, the conduction
hole (via hole) 43, the via hole wiring 44, and the groove row 45.
[0057]
The membrane 36 is a vibrating membrane whose end is fixed by the membrane support 35. One
of the components of the membrane 36 includes an upper electrode 39. A lower electrode 33 is
formed on the upper surface of the silicon substrate 32, and a dielectric film 39 (for example,
SiO2) is formed thereon. A groove row 45 is provided on the upper surface side of the membrane
04-05-2019
15
36.
[0058]
The signal input / output terminal electrode pad 43 provided on the bottom surface of the silicon
substrate 32 is electrically conducted to the lower electrode 33 by the substrate through hole
wiring 42 a provided on the surface of the substrate through hole 42. The bottom surface of the
silicon substrate 42 is coated with a silicon oxide film 42a.
[0059]
Upper electrode 39 is electrically connected to via hole interconnection 44 of via hole 43. The
ground side electrode pad 37 is a pad for electrically connecting the via hole interconnection 44
formed in the via hole 43 to the bottom surface of the silicon substrate 32 in order to connect
the upper electrode 39 to GND.
[0060]
The dielectric film 34 is for increasing the capacitance between the upper electrode 39 and the
lower electrode 33 sandwiching the cavity 40. The diffusion layer 38 is a layer in which almost
no electrons or holes exist.
[0061]
The cavity (air gap) 40 refers to a space surrounded by the membrane 36, the membrane
support 35, the lower electrode 33, and the dielectric film 34. Further, as described above, a
portion 60 surrounded by a broken line in the figure is called a cell. The membrane 36 is
composed of a plurality of membrane membranes in the manufacturing process, as described
later with reference to FIG.
[0062]
Further, the silicon substrate 32 realizes an ohmic contact between the electrode and the silicon
04-05-2019
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substrate by the formation of the diffusion layer 38, and the upper electrode 39 is electrically
connected to the ground electrode pad 37.
[0063]
The operation of the capacitive ultrasonic transducer 31 will be described below.
By applying a voltage to the pair of electrodes of the upper electrode 39 and the lower electrode
33, the electrodes are pulled apart, and when the voltage is set to 0, the electrodes return to the
original state. As a result of vibrating the membrane 36 by this vibration operation, ultrasonic
waves are generated, and the ultrasonic waves are irradiated in the upper direction of the
membrane.
[0064]
FIG. 4 shows a cross section of a cMUT transducer element in which the groove row in the
present embodiment is disposed on the lower surface of the membrane. In the same drawing, the
groove row 46 is provided on the lower surface side of the membrane 36. The other structure is
the same as that of FIG.
[0065]
FIG. 5 shows a cross section of a cMUT transducer element in which the groove rows in this
embodiment are arranged on the upper and lower surfaces of the membrane. In the figure,
groove rows 45 and 46 are provided on the upper surface side and the lower surface side of the
membrane 36, respectively. The other structure is the same as that of FIG.
[0066]
In FIG. 3 to FIG. 5, two groove rows are respectively formed at both ends of the membrane, but
the invention is not limited to this, and any number may be used. Moreover, in FIG. 5, although
the position of the groove rows 45 and 46 is aligned up and down, it is not limited to this, You
04-05-2019
17
may shift | deviate relatively. The same applies to cMUT described below.
[0067]
FIG. 6 shows a cross section of a cMUT transducer element in which the groove row in the
present embodiment is disposed on the upper surface of the membrane and the sacrificial layer
removing hole is provided in a part of the membrane. The sacrificial layer removal hole 47 is a
hole provided when forming the cavity 40 in the manufacturing process.
[0068]
FIG. 7 shows a cMUT vibrator element in which the groove row in this embodiment is disposed
on the upper surface of the membrane, one opening of the sacrificial layer removing hole is
provided on the cavity sidewall, and the other opening is provided on the surface of the
membrane support. Shows a cross section of In the same figure, a sacrificial layer removal hole
48 is provided which is inclined from the upper portion 49 of the membrane support 35 toward
the side surface 50 of the cavity 40.
[0069]
In such a structure, since the sacrificial layer removal hole 48 is not provided in the membrane
region, it is difficult to affect the vibration of the membrane. Also, in order to close the sacrificial
layer removal hole, the sacrificial layer removal hole closing member (SiN) or the like is formed
from the upper surface. At this time, the sacrificial layer removal hole closing member enters the
cavity 40 from the sacrificial layer removal hole. There is a risk of deposition in the cavity 40.
However, when the sacrificial layer removal hole is inclined as shown in FIG. 7, it is possible to
prevent the sacrificial layer removal hole closing member from being directly volumed inside the
cavity 40.
[0070]
FIG. 8 shows a cross section of a cMUT transducer element in which the groove row in the
present embodiment is disposed on the lower surface of the membrane and the sacrificial layer
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removing hole is provided on the surface of the membrane support. A groove array 46 and a
sacrificial layer removal hole 47 are provided on the lower surface of the membrane.
[0071]
In FIG. 9, the groove row in the present embodiment is disposed on the upper surface of the
membrane, one opening of the sacrificial layer removal hole is provided on the cavity sidewall,
the other opening is provided on the surface of the membrane support, and further on the lower
surface of the membrane. Fig. 6 shows a cross section of a cMUT transducer element in which a
row of grooves is formed. In FIG. 9, as described in 3, the groove row 46 is formed on the lower
surface of the membrane 36. Further, as described in FIG. 7, a sacrificial layer removal hole 48 is
provided which is inclined from the upper portion 49 of the membrane support 35 toward the
side surface 50 of the cavity 40.
[0072]
6-9, the number of sacrificial layer removal holes 47 and 48 is not limited to this embodiment,
but may be any number. FIG. 10 shows a top view of the cMUT cell of FIG. FIG. 10 shows the top
surface of the cell 70 in the portion enclosed by the broken line in FIG. The upper electrode film
39 constitutes an upper electrode 39a and an upper electrode connection wiring 39b. As shown
in the figure, the groove row 45 is formed in an arc shape of a concentric circle at the peripheral
portion of the membrane. Therefore, the accumulated portion of the groove array is easily
deformed and is therefore easily bent. In addition, the sacrificial layer removal hole 47 is formed
on the membrane.
[0073]
An area 71 at the center of the membrane of the cell 70 indicates an area which is relatively
difficult to elastically deform in the area of the membrane where the groove row is not formed.
The diameter of the upper electrode that actually functions as the upper electrode corresponding
to the lower electrode is approximately equal to the diameter of this region 71.
[0074]
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FIG. 11 shows a top view of the cMUT cell of FIG. FIG. 11 shows the top surface of the cell 70 in
the portion enclosed by the broken line in FIG. Reference numeral 48 a denotes a sacrificial layer
removal hole opening of the sacrificial layer removal hole 48.
[0075]
An area 81 at the center of the membrane of the cell 80 indicates an area which is relatively
difficult to elastically deform in the area of the membrane where the groove row is not formed.
The diameter of the upper electrode which actually functions as the upper electrode
corresponding to the lower electrode is approximately equal to the diameter of this region 81.
[0076]
As shown in the drawing, the groove row 45 is formed in an arc shape of a concentric circle on
the end side of the membrane. Therefore, the accumulated portion of the groove array is easily
deformed and is therefore easily bent. Also, an opening 48 a at one end of the sacrificial layer
removal hole 48 is formed on the membrane support 35.
[0077]
As shown in FIGS. 10 and 11, the shape of the membrane is a disk, and a region (a groove row
portion) which is easily deformed is disposed at the peripheral portion of the disk, and a region
which is relatively difficult to be deformed is a central portion of the disk. It is arranged. In
addition, the easily deformed area (the groove row portion) disposed at the peripheral portion is
easily deformed in the radial direction and hardly deformed in the circumferential direction.
[0078]
A groove row portion that is easily deformed in the radial direction and hard to be deformed in
the circumferential direction is at least one groove row formed concentrically. And, when viewed
from above the membrane, the concentrically arranged groove rows are shaped like a broken line
circle. That is, a plurality of arcs are formed concentrically.
04-05-2019
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[0079]
In the present embodiment, there are a plurality of arcs having the same diameter and a plurality
of arcs, each forming a circle on a broken line and forming a circle on the broken line and having
different diameters in a concentric manner. Although the row is formed, the present invention is
not limited to this, and any shape may be used as long as a groove row is formed near the end of
the membrane. For example, when the membrane is viewed from above, a plurality of circular
groove rows having different diameters may be provided concentrically. Further, the shape of the
cross section of the groove row is not limited to the concave shape, and may be, for example, a Vshape or a U-shape. That is, it may be relatively easy to deform relative to the central portion of
the membrane.
[0080]
12 to 14 show the manufacturing process of the cMUT vibrator of FIG. First, an upper surface of
a low resistance N-type silicon substrate 90 (about 100 to 500 μm in thickness) is masked with
an oxide film (SiO 2). In the mask formation, an oxide film having a thickness of about 3000 to
4000 Å is formed by the wet oxidation method. Then, patterning for forming the lower electrode
through hole electrode portion 91 is performed in the photolithography step, and the oxide film
patterned in the etching step is removed.
[0081]
Next, by performing ICP-RIE (Inductively Coupled Plasma Reactive Ion Etching: inductively
coupled plasma reactive ion etching), the through holes 91 are opened in the unmasked portion.
[0082]
Next, diffusion layers 92 are formed on both sides of the silicon substrate 90 (S1).
The portions other than the portion where the diffusion layer 92 is to be formed are masked with
SiO 2 by the mask formation step, the photolithography step, and the etching step. Then, N-type
ions are implanted into the unmasked portion and heat treatment is performed to form an N-type
04-05-2019
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diffusion layer. This is performed at predetermined positions on both sides of the silicon
substrate 90.
[0083]
Next, the insulating film 93 is formed on the entire surface of the silicon substrate 90 (including
the wall surface in the through hole 91) (S2). Next, a part of the insulating film 93 covering the
diffusion layer 92 is removed to form a substrate back side contact via hole 94. Thereafter, a
metal film is provided on the hole wall surface of the substrate back side contact via hole 94 and
the periphery thereof to form a contact electrode pad 95.
[0084]
Next, an electrode film (Pt / Ti) 96 is formed around the insulating film 93 (upper surface side),
the inner wall of the through hole 91, and the lower opening of the through hole (S3). The
material of the electrode is not limited to Pt / Ti, and may be Au / Cr, Mo, W, phosphor bronze, Al
or the like.
[0085]
Next, a dielectric film 97 (SrTiO3) is formed on the electrode film 96 by sputtering, CVD or the
like (S3). The dielectric film 97 is not limited to SrTiO 3, and may have a high dielectric constant
such as SiN, barium titanate BaTiO 3, barium strontium strontium titanate, tantalum pentoxide,
niobium oxide stabilized tantalum pentoxide, aluminum oxide, or titanium oxide TiO 2. You may
use the material which it has. Any film can be formed by sputtering or CVD.
[0086]
Next, the membrane support layer 98 is formed (S4). After masking portions other than the
portion for forming the membrane supporting portion, a SiN layer is formed by CVD, and the
mask is removed. Then, a membrane support 98 is formed.
04-05-2019
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[0087]
Next, polysilicon is filled on the upper surfaces of the membrane support 98 and the insulating
film 97 as a sacrificial layer 99 (S4). Although polysilicon is used for the sacrificial layer in this
embodiment, it is not particularly limited as long as it is a member that can be etched, for
example, SiO2.
[0088]
Next, in order to align the sacrificial layer 99 to the height of the membrane support 98, a
surface flattening process is performed (S5). The surface planarization process removes excess
sacrificial layer, for example, by polishing or ion etching.
[0089]
Next, a SiN film is formed as the sacrificial layer sealing film 100 on the planarized surface (S6).
The sacrificial layer sealing film 100 is a film to be the lowermost layer of the membrane later.
Next, a sacrificial layer removal hole 101 is formed (S7). Here, the sacrificial layer removal holes
101 are formed from the portion of the sacrificial layer sealing film 100 corresponding to the
upper portion of the membrane supporting portion 98 toward the portion filled with the
sacrificial layer 99 (the portion to be a cavity later). For example, the silicon substrate 90 after
the process of S6 is inclined, and ion etching is performed from the upper surface of the
membrane support 98 toward the portion filled with the sacrificial layer 99 (the portion to be a
cavity later).
[0090]
Next, the sacrificial layer 99 is removed by etching (S8). In the present embodiment, since poly-Si
is used for the sacrificial layer, the sacrificial layer 99 is removed from the sacrificial layer
removal hole 101 by etching using XeF 2 as an etcher. Then, the cavity 102 is formed.
[0091]
04-05-2019
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Next, a sacrificial layer removal hole blocking film (SiN film) 103 is formed to close the sacrificial
layer removal hole 101 (S9). Further, the groove 104 is formed by etching to expose the
diffusion layer 92. Next, an electrode film (upper electrode) 105 is formed on the upper surface
of the element and the inner wall and bottom of the groove 104 (S10). Next, a groove forming
resist 106 is formed on the membrane. The groove forming resist 106 is provided on both ends
(membrane support side) of the membrane (S11).
[0092]
Next, the space between the groove forming resists 106 is filled with an electrode protection film
107. Then, planarization processing is performed to make the height of the electrode protection
film 107 the same height as the groove forming resist (S12). Then, the groove forming resist 106
is removed (S13). Then, a groove row 108 is formed.
[0093]
In the present embodiment, in the process of forming the electrode film (and the contact layer),
that is, the process of forming the electrode in the groove (conductorization process), ion
implantation or CVD (Chemical Vapor Deposition: chemical vapor deposition method) and It is
performed by diffusion processing or PVD (Physical Vapor Deposition).
[0094]
FIG. 15 shows a manufacturing process of the cMUT vibrator of FIG.
First, the steps S1 to S5 described above are performed. Next, a groove row formation sacrificial
layer pattern 110 is formed at a predetermined position on the upper surface of the sacrificial
layer 99 (S5-2). The trench layer forming sacrificial layer pattern 110 is the same material as the
sacrificial layer 99. Next, the space between the groove row formation sacrificial layer patterns
110 is filled with the membrane groove formation layer 111 (SiN film). Then, planarization is
performed to make the height of the membrane groove forming layer 111 the same height as the
groove row forming sacrificial layer pattern 110 (S5-3).
[0095]
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Next, the SiN layer 112 is formed (S6-1). Then, as in S7, the sacrificial layer etching holes 114
are formed, and the sacrificial layer 99 and the trench layer forming sacrificial layer pattern 110
are removed by etching (S8-1). Then, the cavity 113 is formed. After that, the process after S9 is
performed.
[0096]
Although the method of manufacturing the cMUT of FIGS. 7 and 8 has been described as an
example in this embodiment, cMUTs of other drawings can be manufactured in the same manner.
In addition, when providing a groove row in the upper and lower surface of a membrane, what is
necessary is just to combine FIG. 12-FIG.
[0097]
As described above, by forming the region that is not easily elastically deformed near the center
of the membrane and the region that is easily elastically deformed near the membrane end, the
electric flux between the electrodes in the vicinity of the center becomes perpendicular to the
electrode surface. Furthermore, a large displacement can be made for the entire membrane.
Therefore, in ultrasonic wave transmission, the transmission pressure increases and does not
include harmonic components.
[0098]
In addition, the sacrificial layer removal hole does not affect the vibration of the membrane by
providing the cavity at one end and the sacrificial layer removal hole opened at the membrane
support at the other end, and the material for closing the sacrificial layer removal hole is in the
cavity. Can be prevented from being deposited.
[0099]
Although the present embodiment has been described using the ultrasonic endoscope apparatus
shown in FIG. 2, the present invention is not limited to this, and the cMUT according to the
present embodiment can be used for a capsule type ultrasonic endoscope. .
04-05-2019
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Further, in the present embodiment, the membrane has a substantially circular shape when
viewed from the top, but is not limited to this. For example, the membrane may have a shape
such as a polygon or an ellipse.
[0100]
Second Embodiment In this embodiment, a cMUT in which an elastic body including at least one
surface inclined with respect to a membrane is formed on the upper surface of the membrane
will be described. The cMUT in the present embodiment is not limited to the ultrasound
endoscope apparatus as in the first embodiment, and may be mounted on a capsule-type
ultrasound endoscope.
[0101]
FIG. 16 shows the cMUT (1) in the present embodiment. FIG. 16 shows a cMUT in which a domeshaped elastic body 120 including at least one surface inclined with respect to the membrane is
formed on the upper surface of the membrane.
[0102]
This cMUT is obtained by forming a dome-shaped deposit (elastic body 120) in the central
portion of the circle (inside of the groove row 45) of the membrane 36 of the cMUT of FIG. The
elastic body 120 is formed of, for example, SiO, SiN, or polysilicon, but is not limited thereto. The
sacrificial layer removal hole is omitted.
[0103]
The elastic body 120 is formed on the inner side (the central portion of the membrane) than the
groove row in consideration of the first embodiment. This is because forming an elastic body
outside the groove row or groove row (on the membrane end side) prevents the groove row
portion from being elastically deformed. Furthermore, by forming an elastic body inside the
04-05-2019
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groove row (membrane central portion), it is possible to make elastic deformation less likely to
occur in the region near the membrane central portion in the first embodiment.
[0104]
By using the cMUT of FIG. 16, the membrane surface on which the ultrasonic beam is emitted
can be a point sound source instead of a plane sound source. The synthesized wavefront of the
ultrasonic waves from the point source can be a clean plane wave because the phases at the
synthesized wavefront are aligned. However, since the synthetic wave of ultrasonic waves from
the surface sound source may not have the same phase in the synthetic wave front, it is a
distorted synthetic wave front. When distortion of the combined wavefront is converged by the
acoustic lens or the like, distortion occurs in the obtained ultrasonic image, resulting in an image
with a poor S / N.
[0105]
FIG. 17 shows the cMUT (part 2) in the present embodiment. In FIG. 17, elastic bodies 131 and
132 are formed on the upper surface of the membrane 36 in a plane inclined with respect to the
membrane. The elastic bodies 131 and 132 are formed of, for example, SiO, SiN, or polysilicon,
but are not limited thereto.
[0106]
In the figure, the upper surfaces of the elastic bodies 131 and 132 have slopes inclined by θ1
and θ2 with respect to the vertical direction, respectively. In this case, when a voltage is applied
between the upper electrode and the lower electrode, the membrane 36 vibrates and an
ultrasonic beam is emitted from the membrane surface (in this case, the surface of the slopes of
the elastic members 131 and 132). At this time, the ultrasonic beam is emitted in a direction
perpendicular to the inclined surfaces of the elastic bodies 131 and 132. The inclination angles
θ1 and θ2 of the elastic bodies are adjusted so that the ultrasonic beams emitted from the
elastic bodies 131 and 132 converge at one point.
[0107]
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As a result, when the ultrasonic beam is focused, the beam width at the acoustic focus is
narrowed and the sensitivity is also increased. The cMUT of FIG. 16 leads to the improvement of
the spatial resolution of the ultrasound image, and the cMUT of FIG. 17 leads to the improvement
of the brightness of the image.
[0108]
18 and 19 show the manufacturing process of the cMUT of FIG. In the present embodiment, a
cMUT in which hemispheres are formed on the upper surface of the membrane is manufactured
by a method using a gray scale mask (for example, Non-Patent Document 1 and Non-Patent
Document 2). In this method, the shape of the resist can be controlled by the transmittance
distribution given to the mask.
[0109]
This method consists of two major processes: resist patterning by photolithography using a gray
scale mask, and transfer of the resist pattern to the substrate by anisotropic dry etching.
[0110]
First, the design data of the dome-like structure is converted into the shape of the photoresist
pattern.
In this process, the shape of the dome-like structure to be manufactured is corrected in
consideration of the shape change at the time of etching, and the shape of the resist is set so that
the desired shape can be obtained after the etching.
[0111]
The change in shape at the time of etching depends on the type of etching apparatus, etching
gas, the material of the substrate, etc. Here, an etching model for estimating the change in shape
at the time of etching is set and used.
[0112]
04-05-2019
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Next, the transmittance distribution of the gray scale mask is determined according to the design
data of the resist pattern, and a mask is manufactured.
This gray scale mask is an area gradation type mask in which a large number of minute opening
patterns are arranged, and the transmittance is adjusted by the area ratio of the opening portion
to the light shielding portion. On the other hand, it is of course possible to form a gray scale
mask formed by changing the concentration of the light shielding particles in the mask so as to
change the transmittance stepwise in the mask.
[0113]
In the photolithography process, the transmittance distribution on the mask and the intensity
distribution of light irradiated to the resist are deviated depending on the exposure apparatus, so
photolithography is set to estimate the influence of the exposure apparatus. It is used for
transmission distribution determination. Although a detailed description of the photolithography
model is omitted in this specification, a model based on a response function when light irradiated
to the mask pattern is exposed onto the resist through the optical system of the exposure
apparatus. Is used. A resist pattern is exposed using the produced photomask, and the resist
shape is transferred to the substrate by anisotropic dry etching to complete a dome-like
structure.
[0114]
In the present embodiment, through the steps described in the first embodiment, the groove row
is filled with the photoresist 145, and the dome-shaped elastic body precursor layer (for example,
SiO, SiN, or polysilicon, etc.) is formed thereon. C) Create cMUT in which 144 is formed. A
photoresist layer 143 is formed on the dome-shaped elastic body precursor layer 144.
[0115]
The parallel ultraviolet light 141 is irradiated to the photoresist layer 143 through the gray scale
mask 142 described above (S21). As described above, the transmittance distributions 142 a and
04-05-2019
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142 b are set in the grayscale mask 142. The gray scale mask 142 sets this transmittance
distribution by adding silver. The transmittance of the parallel ultraviolet light 141 changes
according to the density of silver.
[0116]
Then, based on the gray scale mask 142, the resist pattern is exposed on the photoresist 143
(S22). At this time, a dome-shaped portion 143 a and a flat portion 143 b are formed in the
photoresist 143.
[0117]
Thereafter, the shape of the resist pattern 143 is transferred to the dome-shaped elastic body
precursor layer 144 by anisotropic dry etching (S23). Then, the dome-shaped elastic body
precursor layer 144 is gradually etched through the resist pattern 143. 144a shows the etched
part. Reference numeral 144 b denotes a portion formed by etching.
[0118]
At this time, in fact, the resist pattern 143 itself is also etched gradually and simultaneously, but
the appearance thereof is omitted in FIG. 18 and FIG. Then, when the shape of the target domeshaped elastic body is formed, the etching of the dome-shaped elastic body precursor layer 144
is completed (S24).
[0119]
Finally, the photoresist 143 and the resist 145 buried in the groove are removed to complete the
cMUT of FIG. 16 (S25). The cMUT of FIG. 17 can also be formed by the method of FIGS. 18 and
19 in the same manner.
[0120]
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As described above, in the cMUT having a portion that is not easily bent and deformed at the
central portion of the membrane and has a portion that is easily bent at the peripheral portion,
the elastic structure is disposed to be in contact with the membrane upward. An elastic structure
having at least one inclined surface can be provided on a cell basis. Further, the surface of the
elastic structure may be formed into a semi-curved surface. The shape of the structure to be
disposed in contact with the membrane is not limited to the above-described structure, and the
shape can be appropriately determined as needed.
[0121]
In addition, the cMUT according to the present embodiment can be manufactured by using a
gray scale mask. Third Embodiment The present embodiment is an implementation of the cMUT
according to the second embodiment. In this embodiment, a cMUT in which an acoustic lens for
focusing an ultrasonic beam is provided above the membrane will be described. In the present
embodiment, the ultrasonic beam can be focused by an acoustic lens or the like to the same
effect as the cMUT in FIG. The cMUT in the present embodiment is not limited to the ultrasound
endoscope apparatus as in the first embodiment, and may be mounted on a capsule-type
ultrasound endoscope.
[0122]
FIG. 20 shows an appearance structure of a packaged cMUT in the present embodiment. In this
package, a cMUT chip in which all cMUT cells are connected in parallel is mounted, and an
example of the cMUT cell structure is the cMUT shown in the first or second embodiment, for
example.
[0123]
In FIG. 20, the exterior structure of the packaged cMUT comprises an acoustic lens 150, an
epoxy seal 151, a metal package 152, a terminal watertight seal cover cylinder 153, and a
coaxial cable 154.
[0124]
04-05-2019
31
The acoustic lens 150 is for focusing the ultrasonic beam.
The metal package 152 is a housing member for storing the cMUT. Hereinafter, the metal
package 152 is referred to as a housing member. The epoxy seal 151 and the terminal watertight
seal cover cylinder 153 are for supporting the terminal portion, covering the terminal portion,
waterproofing and the like. The coaxial cable 154 is for transmitting an ultrasonic signal from
the ultrasonic observation device 4 to the cMUT, and transmitting an ultrasonic signal from the
cMUT to the ultrasonic observation device 4.
[0125]
Hereinafter, a cMUT in which the acoustic lens 150 has a convex shape or a concave shape will
be described. FIG. 21 shows a cMUT in which a convex acoustic lens is provided above the
membrane in the present embodiment. The cMUT 155 is composed of multiple elements or
arrays. The cMUT 155 is housed in a housing member 152, and a convex acoustic lens 150a
(made of, for example, a silicone resin or the like) is provided at a portion of the ceiling portion of
the housing member above the ultrasonic radiation surface of the membrane. It is provided.
[0126]
When a voltage is applied to the cMUT 155, the membranes of the individual cells vibrate and an
ultrasonic beam is emitted perpendicularly to the membrane surface. That is, an ultrasonic beam
is emitted parallel to the upper direction of the figure from the membrane of each cell which is
an ultrasonic radiation surface. When passing through the acoustic lens 150a, these ultrasonic
beams are focused at one point as shown in the figure.
[0127]
FIG. 22 shows a cMUT in which a concave-shaped acoustic lens is provided above the membrane
in the present embodiment. The cMUT 155 is composed of multiple elements or arrays. The
cMUT 155 is housed in the housing member 152, and a portion of a ceiling portion of the
housing member 152 which is located above the ultrasonic radiation surface of the membrane is
a concave acoustic lens 150b (for example, made of epoxy resin or the like) ) Is provided.
04-05-2019
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[0128]
When a voltage is applied to the cMUT 155, the membranes of the individual cells vibrate and an
ultrasonic beam is emitted perpendicularly to the membrane surface. That is, an ultrasonic beam
is emitted parallel to the upper direction of the figure from the membrane of each cell which is
an ultrasonic radiation surface. When these ultrasonic beams pass through the acoustic lens
150b, they converge at one point as shown in the figure.
[0129]
When the speed of sound passing through the material of the acoustic lens is smaller than the
speed of sound passing through the water, a convex acoustic lens is used. If the speed of sound
passing through the material of the acoustic lens is greater than the speed of sound passing
through the water, a concave-shaped acoustic lens is used.
[0130]
In the first to third embodiments, an ultrasonic probe provided with a plurality of capacitive
ultrasonic transducer elements arranged in an array is included in an ultrasonic endoscope
apparatus or a capsule ultrasonic wave. It may be mounted on a scope.
[0131]
As described above, the spatial resolution can be improved by focusing the ultrasonic beam.
In addition, the shape of the acoustic lens can be made concave or convex depending on the
difference in material. Note that the inside of the housing member 152 needs to be filled with the
acoustic propagation medium, and for this purpose, it is necessary to provide the housing cap
portion with a hole for promoting the inflow and outflow of the acoustic propagation medium.
[0132]
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33
The conceptual diagram of the cMUT cell in 1st Embodiment is shown. It is a figure explaining
the ultrasonic endoscope apparatus in a 1st embodiment. The cross section of the cMUT
transducer element in which the groove row in the first embodiment is arranged on the upper
surface of the membrane is shown. 5 shows a cross section of a cMUT transducer element in
which a groove row in the first embodiment is arranged on the lower surface of a membrane. The
cross section of the cMUT vibrator | oscillator element which arrange | positioned the groove
row | line in 1st Embodiment on the membrane up-down surface is shown. Fig. 6 shows a cross
section of a cMUT transducer element in which the row of grooves in the first embodiment is
arranged on the upper surface of the membrane and the sacrificial layer removing hole is
provided on a part of the membrane. The cross section of the cMUT transducer element in which
the groove row in the first embodiment is disposed on the upper surface of the membrane, one
opening of the sacrificial layer removal hole is provided on the cavity sidewall, and the other
opening is provided on the surface of the membrane support Indicates The cross section of the
cMUT transducer element in which the groove row in the first embodiment is disposed on the
lower surface of the membrane and the sacrificial layer removing hole is provided on the surface
of the membrane support portion is shown. The groove row in the first embodiment is disposed
on the upper surface of the membrane, one opening of the sacrificial layer removal hole is
provided on the side wall of the cavity, the other opening is provided on the surface of the
membrane support, and the groove row is further formed on the lower surface of the membrane.
Fig. 6 shows a cross section of a cMUT transducer element in which Figure 7 shows a top view of
the cMUT cell of Figure 6; Figure 8 shows a top view of the cMUT cell of Figure 7; The
manufacturing process (the 1) of the cMUT vibrator of FIG. 7 is shown. The manufacturing
process (the 2) of the cMUT vibrator of FIG. 7 is shown. The manufacturing process (the 3) of the
cMUT vibrator of FIG. 7 is shown. FIG. 9 shows a manufacturing process of the cMUT vibrator of
FIG. 8. The cMUT (1) in 2nd Embodiment is shown. The cMUT (the 2) in 2nd Embodiment is
shown. The manufacturing process (the 1) of cMUT of FIG. 16 is shown. The manufacturing
process (the 2) of cMUT of FIG. 16 is shown. FIG. 7 shows an appearance structure of a packaged
cMUT in a third embodiment. The cMUT which provided the convex-shaped acoustic lens above
the membrane in 3rd Embodiment is shown. The cMUT which provided the concave-shaped
acoustic lens above the membrane in 3rd Embodiment is shown. An example of cMUT in the past
is shown.
Explanation of sign
[0133]
200 cMUT cell 201 Membrane 202 Curved part 203 Membrane central part 204 Membrane
support part 1 Ultrasonic endoscope apparatus 2 Ultrasonic endoscope 3 Endoscope observation
apparatus 4 Ultrasonic observation apparatus 5 Monitor 31 Capacitance type ultrasonic
vibration Child element 32 silicon substrate 33 lower electrode 34 dielectric film 35 membrane
04-05-2019
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support portion 36 membrane 37 ground side electrode pad 38 diffusion layer 39 upper
electrode 40 cavity 41 signal input / output terminal electrode pad 42 substrate through hole 42
a substrate through hole wiring 43 conduction hole (Via hole) 44 Via hole wiring 45, 46 Groove
row 47, 48 Sacrifice layer removing hole 120, 131, 132 Elastic body 150 (150a, 150b) Acoustic
lens 152 Metal package (housing member) 155 cMUT
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