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JP2015122736

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DESCRIPTION JP2015122736
The present invention provides a capacitance type transducer capable of reducing the thickness
of a sealing film necessary for sealing a gap and capable of improving performance such as
broadening the bandwidth, and a method of manufacturing the same. A capacitive transducer
comprising a cell (10) including a vibrating membrane (17) including a first electrode (3) and a
second electrode (7) provided at a distance (8) can be manufactured by the following
manufacturing method. it can. A convex portion 19 is formed on the first electrode, a sacrificial
layer 12 thicker than the convex portion is formed on the first electrode and the convex portion,
and a membrane 5 is formed on the sacrificial layer. Further, an etching hole 13 is formed at a
position above the convex portion of the membrane, the sacrificial layer is etched through the
etching hole, and the etching hole is sealed with the sealing layer 6. [Selected figure] Figure 1
Capacitance transducer and method of manufacturing the same
[0001]
The present invention relates to a capacitive transducer used as an ultrasonic transducer or the
like, a method of manufacturing the same, and the like.
[0002]
In recent years, with the development of microfabrication technology, various micromechanical
devices machined with an accuracy on the order of micrometers have been realized.
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Development of a capacitive ultrasonic transducer (CMUT: Capasitive-Micromachined-UltrasonicTransducer) has been promoted using such a technology. CMUT is an ultrasonic device that
vibrates a lightweight diaphragm to transmit and receive acoustic waves (hereinafter sometimes
represented by ultrasonic waves), and it is easy to have excellent broadband characteristics in
liquid and air Obtained. Therefore, when CMUT is used as a medical application, it is possible to
make a diagnosis with higher accuracy than an ultrasonic device consisting of a piezoelectric
element conventionally used, and is attracting attention as a substitute. In the present
specification, acoustic waves include those called sound waves, ultrasonic waves, and
photoacoustic waves. For example, the inside of the subject is irradiated with light
(electromagnetic wave) such as visible light or infrared light, and the photoacoustic wave
generated inside the subject is included.
[0003]
A capacitive transducer comprises a plurality of cell structures. The cell structure is formed, for
example, between a first electrode disposed on a substrate such as Si, a second electrode
disposed opposite to the first electrode, and the first and second electrodes. A vibrating
membrane comprising a second electrode and a membrane formed on the gap and a vibrating
membrane support. The membrane has a structure that seals the gap. A capacitive transducer is
formed by laminating a material on a substrate such as Si as one of the manufacturing methods.
Here, the gap structure is formed by depositing the sacrificial layer material in advance in the
gap and removing the sacrificial layer from the opening (etching hole) provided in a part of the
vibrating film provided thereon. . Capacitance transducers are sometimes used in liquids such as
in water or in oil, and when the liquids infiltrate into the gaps, the vibration characteristics of the
vibrating membrane deteriorate, so they are provided to form the gaps. The etching holes need to
be sealed and used. In the capacitive transducer described in Non-Patent Document 1, sealing is
performed as follows. That is, sealing of the gap is achieved by depositing silicon nitride film
formed by Low-Pressure-Chemical-Vapor-Deposition (LP-CVD) in the flow path connected to the
gap under the vibrating film from the etching hole. Is going. In LP-CVD, due to the nature of the
device, a silicon nitride film is deposited with a substantially uniform thickness from the etching
hole to the gap through the channel, and the gap is sealed by depositing the thickness of the
channel. Ru. However, in this method, the inside of the gap may be deposited through the flow
path, which may affect the vibration characteristics of the vibrating film.
[0004]
On the other hand, in the capacitive transducer described in Patent Document 1, the gap is
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formed by removing the sacrificial layer from the etching hole as in Non-Patent Document 1.
Furthermore, sealing of the gap is performed by depositing a film in the etching hole by plasmaenhanced-chemical-vapor-deposition (PE-CVD). In PE-CVD, as in LP-CVD, the film does not
penetrate into the inside of the gap or the flow path, and the sealing film is formed so as to be
deposited on the etching hole. Therefore, in order to seal the gap, it is necessary to deposit a
sealing film thick enough for the thickness or height of the gap.
[0005]
U.S. Pat. No. 5,982,709
[0006]
ArifSanli Ergun et al.
IEEE Transactions on
Ultrasonics,Vol52,No.12,DECEMBER
2005,2242−2257
[0007]
The thickness of the sealing film for sealing the gap of the capacitive transducer needs to be
about three times the thickness of the gap. Therefore, the larger the thickness of the gap, the
thicker the required sealing film thickness. However, on the other hand, there is a demand for
thinning the membrane to improve performance, and a configuration capable of reducing the
sealing film thickness is required.
[0008]
In view of the above problems, the present invention manufacture of a capacitive transducer
comprising a cell including a first electrode and a diaphragm including a second electrode spaced
apart from the first electrode. The method comprises the following steps. Forming a projection
on the first electrode; Forming a sacrificial layer having a thickness greater than that of the
protrusion on the first electrode and the protrusion; Forming a membrane on the sacrificial layer;
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Forming an etching hole at a position on the convex portion of the membrane; Etching the
sacrificial layer through the etching hole; Sealing the etching hole; Forming the second electrode;
Alternatively, it has the following steps. Forming a sacrificial layer on the first electrode; Forming
a membrane on the sacrificial layer; Forming an etching hole in the membrane; Etching the
sacrificial layer through the etching hole; Forming a projection on the bottom of the etching hole;
Sealing the etching hole; Forming the second electrode;
[0009]
According to the present invention, after the sacrificial layer is etched, the convex portion is
formed at the bottom of the etching hole, so that the convex portion and the etching hole edge
part approach each other. Therefore, in the formation of the sealing film, the film grown from the
bottom surface and the film grown from the etching hole wall quickly contact, and the thickness
of the sealing film can be reduced. That is, even with the structure having the same gap thickness
as the conventional one, the sealing film thickness required for sealing the gap can be made thin.
Therefore, the gap can be sealed with a thinner film thickness than in the past, and the vibrating
film can be thinned to improve performance such as broadening the bandwidth.
[0010]
The figure explaining an example of the electrostatic capacitance type transducer of this
invention. The figure explaining an example of the electrostatic capacitance type transducer of
this invention. Sectional drawing for demonstrating the principle of this invention. FIG. 7 is a
cross-sectional view illustrating an example of a method for manufacturing a capacitive
transducer of the present invention. FIG. 7 is a cross-sectional view illustrating an example of a
method for manufacturing a capacitive transducer of the present invention. FIG. 7 is a crosssectional view illustrating an example of a method for manufacturing a capacitive transducer of
the present invention. FIG. 7 is a cross-sectional view illustrating an example of a method for
manufacturing a capacitive transducer of the present invention. Explanatory drawing of the
example of the information acquisition apparatus using the capacitive transducer of this
invention.
[0011]
In the present invention, the gap is formed by removing the sacrificial layer provided in advance
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in the gap from the etching hole provided in the membrane. Furthermore, the gap is sealed by
the sealing film at the etching hole. At this stage, a convex portion is formed at the bottom of the
etching hole, and when the sealing film is formed after etching the sacrificial layer, the film
grown from the convex portion is in contact with the film grown from the etching hole wall to
seal. Since the film is formed, the thickness of the sealing film can be reduced.
[0012]
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
Fig.1 (a) is AB sectional drawing of the electrostatic capacitance type transducer of this
embodiment, FIG.1 (b) is a top view of Fig.1 (a). 1 (a) and 1 (b) show only one cell structure 10,
but as shown in FIG. 1 (c), the number of cell structures 10 in the capacitive transducer may be
any number. I do not care. Also, the arrangement of the cells may be any arrangement other than
that shown in FIG. 1 (c). As shown in FIGS. 1 (a) to 1 (c), the shape of the vibrating membrane of
this capacitance type transducer is circular, but the shape may be square, hexagonal or the like.
[0013]
The configuration of the present capacitive transducer will be described. The capacitive
transducer has a substrate 1 of Si or the like, an insulating film 2 formed on the substrate 1, a
first electrode 3 formed on the insulating film 2, and an insulating film 4 on the first electrode 3.
. A vibrating membrane 17 consisting of a first membrane 5, a second membrane 6 and a second
electrode 7 is provided on the insulating film 4 via a gap (cavity) 8, and the first membrane 5 It is
supported by the membrane support 16. If the substrate 1 is an insulator such as a glass
substrate, the insulating film 2 may be omitted.
[0014]
In addition, although the second electrode 7 is formed on the second membrane 6 in FIG. 1, the
second electrode 7 is formed of the first membrane 5 and the second membrane 6 as shown in
FIG. 2 (a). It may be placed between With the configuration shown in FIG. 2, the distance between
the first electrode and the second electrode can be reduced, and the capacitance of the capacitive
transducer is further increased to further improve the performance. Can. In addition, a voltage
application means for applying a voltage between the first electrode 3 and the second electrode
7 is provided, and a voltage is applied between the first electrode 3 and the second electrode 7 to
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form a vibrating film. The ultrasonic wave can be transmitted by vibrating 17. Moreover, an
ultrasonic wave can be received by receiving an ultrasonic wave in the state which applied the
bias voltage between electrodes.
[0015]
The gap 8 of the capacitive transducer is formed by a sacrificial layer etching method in which a
sacrificial layer is placed in advance in the gap and etched from etching holes formed in the
membrane to remove the sacrificial layer. . Specifically, a sacrificial layer 12 (see FIG. 4-1
(described later) and the like) is formed in the portion in which the vibration portion gap 8 is
formed and in the portion in which the etching hole portion gap 9 is formed. The sacrificial layer
12 includes a portion of the flow path 18 connecting the etching hole gap 9 and the vibrating
membrane gap 8. Then, after the first membrane 5 and the vibrating membrane support portion
16 are formed on the sacrificial layer 12, an etching hole 13 for removing the sacrificial layer is
formed on the first membrane 5 on the etching hole portion 9. Form. Next, the sacrificial layer 12
is removed from the etching hole 13 by sacrificial layer etching to form a gap 8. After forming
the gap, the sealing film 11 serving as the second membrane 6 is deposited in the etching hole
13 to seal the etching hole 13. Here, the inside of the gap (cavity) 8 is maintained in a reduced
pressure state, and the reduced pressure state of the cavity 8 is maintained by depositing the
sealing film 11 in the etching hole 13 in the depressurizable chamber. . These steps are
performed in a reduced pressure treatment (vacuum treatment) process.
[0016]
The material of the capacitive transducer, in particular, the material forming the gap (such as the
insulating film 4) has a surface roughness so that the vibrating film does not contact the lower
surface of the gap 8 when the vibrating film 17 vibrates. Is desirable. For the first electrode 3,
metal materials such as titanium, aluminum, and molybdenum can be used. In particular,
titanium is desirable because the change in roughness and the like due to the heat applied during
the process is small, and furthermore, the etching selectivity with the material for forming the
sacrificial layer and the vibrating film is high. For the insulating film 4, a silicon oxide film or the
like can be used. In particular, a silicon oxide film formed by a PE-CVD apparatus has a small
surface roughness. Furthermore, since it can be formed at a low temperature of 400 ° C. or less,
it can be formed with less influence of heat to other constituent materials. The first membrane 5
and the second membrane 6 of the vibrating membrane 17 and the vibrating membrane support
16 are insulating films. In particular, since a silicon nitride film formed by a PE-CVD apparatus
can be formed at a low temperature of 400 ° C. or less, the influence of heat on other
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constituent materials can be reduced. In addition, since the film can be formed with a low tensile
stress of 300 MPa or less, large deformation of the vibrating film due to residual stress of the
membrane can be prevented.
[0017]
Furthermore, the second membrane 6 needs to be deposited on the etching hole 13 to seal the
gap, in addition to the function as a vibrating membrane. As a material for sealing the gap, it is
desirable that the coverage be high for sealing by being deposited in the etching hole 13. In
addition to that, it is also desired that the sealing film does not intrude into the vibrating portion
gap 8 from the etching hole 13 through the flow path 18. When the sealing film intrudes into the
vibrating portion gap 8, the thickness of the vibrating portion gap 8 affecting the performance is
changed. For example, in the case of a silicon nitride film formed by LP-CVD, the film may
intrude into the inside of the gap through the flow path, which is not preferable because the
thickness of the gap may change. A silicon nitride film formed by PE-CVD is preferable as a
material that satisfies the desired conditions for the sealing film.
[0018]
It is desirable to select a material of the sacrificial layer 12 for forming the gap, which can be
removed relatively easily in the sacrificial layer etching process, and has a sufficiently high
etching selectivity to other constituent materials. Furthermore, it is desirable to select a material
that has less influence on the roughness and the like even in the heat process when forming the
membrane. As a material that satisfies these requirements, for example, metal materials such as
chromium and molybdenum, amorphous silicon, and the like can be selected. In particular,
chromium can be easily etched with a mixed solution of ceric ammonium nitrate and perchloric
acid. Furthermore, the etching selectivity with respect to titanium of the material of the first
electrode 3 which is a constituent material in the sacrificial layer etching step, silicon oxide of the
material of the insulating film 4 and silicon nitride film of the material of the membrane is
sufficiently high. Therefore, in the sacrificial layer etching step, it is possible to form a gap with
less damage to materials other than the sacrificial layer.
[0019]
In addition, the sacrificial layer is the portion of the vibrating portion gap 8 in the portion where
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the vibrating film vibrates and the portion of the etching hole portion 9 where the solution for
removing the sacrificial layer penetrates when etching the sacrificial layer. It is formed in the
part of the flow path 18 to connect. The thickness of each of the portions of the vibrating portion
gap 8 corresponds to the portion where the vibrating membrane vibrates, and is set according to
the design specification. Since the etching hole portion and the flow path portion need to allow
the solution for removing the sacrificial layer to penetrate into the gap in the sacrificial layer
etching step, the thickness of the etching hole portion can be increased depending on the
thickness at which the sacrificial layer can be etched. The lower limit is determined. The lower
limit value is not determined to one value because the value varies depending on the material of
the sacrificial layer and the solvent for removing the sacrificial layer. If the sacrificial layer is
chromium and the sacrificial layer is etched with a solution of cerium nitrate ammonium and
perchloric acid, the thickness of the sacrificial layer can be 100 nm or less. Further, the width of
the latter is preferably larger than the width of the former for the width of the etching hole and
the width of the etching hole portion. In this case, the etchant is introduced without any problem
through the etching holes, the sacrificial layer etching is performed well, and the subsequent
deposition of the sealing film is performed well. Since the second electrode 7 is a material that
constitutes a part of the vibrating film 17, the second electrode 7 needs to be a material with a
relatively small stress. For example, titanium or aluminum can be used.
[0020]
A process of depositing a sealing film on the etching hole 13 and sealing the gap after forming
the gap by the sacrificial layer etching will be described with reference to FIG. At this stage, the
convex portion 19 is formed at the bottom of the etching hole. FIG. 3 shows a process of
depositing a sealing film made of the second membrane 6 on the etching hole 13 after removing
the sacrificial layer 12 by sacrificial layer etching to seal the gap. When a film is formed on the
etching hole 13 by PE-CVD, the film is deposited on the convex portion 19 at the bottom of the
etching hole and the side and upper surface of the first membrane 5 in which the etching hole 13
is opened. (FIG. 3 (a)-(c)). The etching hole is sealed by connecting the film deposited on the
convex portion 19 at the bottom of the etching hole and the film deposited on the side surface or
wall of the first membrane 5 to form a continuous film (FIG. 3 (d )). At this time, the thickness of
the film required for sealing depends on the distance between the convex portion 19 at the
bottom of the etching hole and the opening side of the membrane 5 in the portion where the
etching hole is formed.
[0021]
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As described above, a cell having a structure including a vibrating film including a second
electrode spaced apart from the first electrode is provided, and a gap is formed by etching the
sacrificial layer through the etching hole. A capacitive transducer is produced. Here, a convex
portion is formed at the bottom of the etching hole, and the etching hole is sealed by forming a
sealing film on the convex portion via the etching hole. The convex portion and the sealing film
may be the same material or different materials. In the capacitive transducer of the present
embodiment, the distance between the convex portion 19 at the bottom of the etching hole and
the side surface of the membrane 5 is appropriately set without changing the thickness of the
vibrating portion gap 8 which affects the performance. There is. This makes it possible to reduce
the thickness of the sealing film required to seal the gap 8 and to improve the reliability of the
sealing.
[0022]
In the present invention, the thickness of the convex portion is selected in consideration of the
thickness of the sacrificial layer 12 corresponding to the thickness of the cavity 8. The thickness
of the sacrificial layer 12 is generally in the range of 50 nm to 200 nm, preferably in the range of
70 nm to 150 nm, in consideration of process controllability and efficiency. The thickness of the
projections needs to be set thinner than the thickness of the sacrificial layer 12, and in general, it
is desirable to be set in the range of 10 nm to 150 nm, preferably in the range of 20 nm to 100
nm.
[0023]
Also, assuming that the thickness direction of the convex portion is the Z direction, the length
(corresponding to the size of the convex portion) of the convex portion in the X direction and Y
direction orthogonal to the Z direction is taken into consideration the size (diameter) of the
etching hole. Will be selected. The size (diameter) of the etching hole is appropriately set in
consideration of the performance of the transducer depending on the thickness of the vibrating
film, the size (diameter) of the vibrating film, the thickness of the cavity, and the like. Among
these, the sizes (diameters) P of the convex portions in the X and Y directions are represented by
the following formula (Equation where E represents the diameter of the etching hole and G
represents the thickness of the sacrificial layer 12 corresponding to It is desirable to be selected
to satisfy 1). P ≦ E-2G (Equation 1)
[0024]
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EXAMPLE 1 Example 1 of the capacitive transducer according to the present invention will be
described below. 4-1 (a)-(f) and FIGS. 4-2 (g)-(k) illustrate the process flow of the capacitive
transducer which has a structure of a present Example. Here, although a capacitive transducer
having only one cell structure 10 is shown, as described above, any number of cell structures 10
may be used. Further, although a figure having one etching hole portion for one cell structure 10
is shown, the number of etching holes for one cell structure 10 may be any number.
[0025]
The capacitance type transducer of this embodiment has a silicon substrate 1 with a thickness of
300 μm, and an insulating film 2 of a thermal oxide film formed on the silicon substrate 1 and
has a cell structure 10 as described below. That is, the cell structure 10 includes the first
electrode 3 made of titanium formed on the insulating film 2, the insulating film 4 of silicon
oxide film formed on the first electrode 3, the first electrode 3 and the second electrode 3. A gap
formed between the electrodes 7, a vibrating membrane 17 formed on the gap, and a vibrating
membrane support portion 16 supporting the vibrating membrane 17. The vibrating membrane
17 includes a first membrane 5 formed on the gap, a second membrane 6 for sealing the gap,
and a second electrode 7, and the first and second electrodes 3, 7 Between the voltage
application means for applying a voltage.
[0026]
The gap portion of the capacitive transducer in the present embodiment is formed by performing
the sacrificial layer etching process shown in FIGS. 4-1 (d) to 4-2 (h). First, an insulating film 2
made of a thermal oxide film, a first electrode 3 made of titanium, and an insulating film 4 made
of a silicon oxide film are formed on a silicon substrate 1. Next, a projection having a thickness of
20 nm to be the projection 19 at the bottom of the etching hole is formed by photolithography
and dry etching using CF 4 gas (FIG. 4-1 (d)). The convex portion 19 can be formed of SiO 2, SiN
or the like. Next, chromium which is a sacrificial layer material having a thickness of 200 nm is
formed on the insulating film 4. The portion in which the etching hole for removing the sacrificial
layer 12 is to be formed is etched by photolithography and dry etching using Cl 2 gas to a
thickness of 80 nm (FIG. 4-1 (e)). Next, patterning is performed by photolithography and dry
etching using a Cl 2 gas, leaving the etching hole sacrificial layer 15 serving as an etching hole
and the vibrating portion sacrificial layer 14 serving as a vibrating portion (FIG. 4-1 (f )). By this
process, it is possible to form a structure in which the thickness of the gap is different between
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the etching hole portion and the vibrating portion. However, the difference in thickness is not
shown in the figure.
[0027]
Next, a silicon nitride film to be the first membrane 5 and the vibrating film supporting portion
16 is formed 400 nm on the sacrificial layer 12 with a PE-CVD apparatus (FIG. 4G). Next,
patterning is performed on the first membrane by photolithography and dry etching using CF 4
gas to form an etching hole 13 (FIG. 4-2 (h)). Next, a solution consisting of ceric ammonium
nitrate and perchloric acid is introduced from the etching hole 13 and the sacrificial layer 12 is
removed to form a gap consisting of the vibrating portion gap 8 and the etching hole portion 9
(see FIG. 4-2 (i). Then, a 300 nm silicon nitride film to be the second membrane 6 is formed on
the etching hole 13 by a PE-CVD apparatus. By this process, the gap is sealed with the etching
hole 13 (FIG. 4-2 (j)). Finally, the second electrode 7 is formed on the second membrane 6 (Fig. 42 (k)).
[0028]
In the present embodiment, the thickness of the sacrificial layer 12 differs between the etching
hole portion and the vibrating portion, and is 80 nm in the etching hole portion and 200 nm in
the vibrating portion. The thickness of the membrane required to seal the gap is about three
times the gap thickness in the conventional configuration. Therefore, in the conventional
configuration, the sealing film thickness required for sealing is three times the thickness 80 nm
of the etching hole gap, and is about 240 nm. On the other hand, in the present configuration,
the thickness of the sealing film necessary for sealing the gap 8 can be reduced by the convex
portion 19 at the bottom of the etching hole, and the sealing performance of the gap is improved.
[0029]
Embodiment 2 A capacitive transducer according to Embodiment 2 of the present invention will
be described with reference to FIGS. 5-1 and 5-2. The present embodiment differs from the first
embodiment in that the convex portion 19 is formed on the bottom of the etching hole after
etching the sacrificial layer. The processes of FIGS. 5-1 (a) to (e) are the same as the processes of
FIGS. 4-1 (a) to (f) except that the convex portions 19 are not formed. In this embodiment, as
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shown in FIG. 5-2 (i), a metal film is formed to a thickness of 20 nm on the bottom of the etching
hole by photolithography after etching the sacrificial layer. Here, an Au film, an Al film or the like
can be employed as the metal film. Thus, after patterning the resist, the convex portion 19 of the
second embodiment forms a metal film by vapor deposition, and lifts off the resist to form the
convex portion of the metal at the bottom of the etching hole. This convex portion can provide
the same effect as that of the first embodiment. In the present embodiment, the second electrode
7 can also be formed when the metal convex portion 19 is formed, and this can be formed
between the first membrane 5 and the second membrane 6. In this case, since the convex portion
19 and the second electrode 7 are formed simultaneously, the process can be simplified.
[0030]
EXAMPLE 3 FIG. 6A shows an example of an object information acquiring apparatus using the
photoacoustic effect. The pulsed light oscillated from the light source 2010 is irradiated to the
subject 2014 via the optical member 2012 such as a lens, a mirror, and an optical fiber. The light
absorber 2016 inside the object 2014 absorbs the energy of the pulsed light and generates a
photoacoustic wave 2018 which is an acoustic wave. The capacitive transducer 2020 of the
present invention in the probe (probe) 2022 receives the photoacoustic wave 2018, converts it
into an electric signal, and outputs the signal to the signal processing unit 2024. The signal
processing unit 2024 performs signal processing such as A / D conversion and amplification on
the input electric signal, and outputs the signal processing to the data processing unit 2026. The
data processing unit 2026 acquires object information (characteristic information reflecting the
optical characteristic value of the object such as a light absorption coefficient) as image data
using the input signal. Here, the signal processing unit 2024 and the data processing unit 2026
are collectively referred to as a processing unit. The display unit 2028 displays an image based
on the image data input from the data processing unit 2026. As described above, the object
information acquiring apparatus of this embodiment includes the capacitance type transducer of
the present invention, and a processing unit that acquires information of the object using the
electrical signal output from the transducer. The transducer receives an acoustic wave from the
subject and outputs an electrical signal.
[0031]
FIG. 6B shows a subject information acquiring apparatus such as an ultrasonic echo diagnostic
apparatus using reflection of acoustic waves. The acoustic wave transmitted from the capacitive
transducer 2120 of the present invention in the probe (probe) 2122 to the subject 2114 is
reflected by the reflector 2116. The transducer 2120 receives the reflected acoustic wave
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(reflected wave) 2118, converts it into an electrical signal, and outputs the electrical signal to the
signal processing unit 2124. The signal processing unit 2124 performs signal processing such as
A / D conversion and amplification on the input electric signal, and outputs the signal processing
to the data processing unit 2126. The data processing unit 2126 acquires object information
(characteristic information reflecting a difference in acoustic impedance) as image data using the
input signal. Here, the signal processing unit 2124 and the data processing unit 2126 are also
referred to as a processing unit. The display unit 2128 displays an image based on the image
data input from the data processing unit 2126. As described above, the subject information
acquisition apparatus of the present example includes the capacitive transducer of the present
invention and a data processing apparatus. Then, the transducer receives the acoustic wave
reflected by the subject and converts the acoustic wave into an electrical signal, and the data
processing apparatus acquires the information of the subject using the electrical signal.
[0032]
The probe may be one that scans mechanically or one that is moved by a user such as a doctor or
an engineer relative to the subject (handheld type). Moreover, in the case of the apparatus using
a reflected wave like FIG.6 (b), you may provide the probe which transmits an acoustic wave
separately from the probe to receive. Furthermore, as an apparatus having both the functions of
the apparatus of FIGS. 6A and 6B, object information reflecting the optical characteristic value of
the object, and object information reflecting the difference in acoustic impedance , And may be
acquired. In this case, the transducer 2020 in FIG. 6A may transmit not only the photoacoustic
wave but also the transmission of the acoustic wave and the reception of the reflected wave.
[0033]
1: Substrate, 3: First electrode, 5: First membrane, 6: Second membrane (sealing layer), 7: Second
electrode, 8: Vibrator gap (gap), 9: Etching hole Portion gap, 10: cell, 12: sacrificial layer, 13:
etching hole, 17: vibrating film, 19: convex portion
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