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JP2009055474

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2009055474
Abstract: [Problem] A capacitive ultrasonic transducer, an ultrasonic diagnostic device, and an
ultrasonic transducer capable of transmitting and receiving ultrasonic waves at a wide frequency
without reducing the transmission intensity and reception sensitivity of ultrasonic waves. Provide
an acoustic microscope. An ultrasonic wave comprising a first electrode, a vibrating membrane
disposed on the first electrode with a cavity in the cavity, and a second electrode supported by
the vibrating membrane. In the transducer, the holes are formed by connecting a plurality of air
gaps having different cross-sectional areas when viewed from the second electrode side in a
direction from the first electrode toward the second electrode. . [Selected figure] Figure 5
Ultrasonic transducer, ultrasonic diagnostic apparatus and ultrasonic microscope
[0001]
According to the present invention, there is provided an electrostatic capacitance type device
comprising a first electrode, a vibrating membrane disposed on the first electrode via a gap, and
a second electrode supported by the vibrating membrane. The present invention relates to an
ultrasonic transducer, an ultrasonic diagnostic apparatus, and an ultrasonic microscope.
[0002]
2. Description of the Related Art Ultrasonic diagnostic methods for irradiating a subject with
ultrasonic waves and diagnosing the state of the subject from echo signals thereof are in
widespread use.
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An ultrasonic endoscope used in the medical field is one of the ultrasonic diagnostic apparatuses
used for the ultrasonic diagnostic method.
[0003]
The ultrasonic diagnostic apparatus is used not only in the medical field but also in the industrial
field to diagnose the presence or absence of a defect such as a flaw, a crack, or a cavity generated
in a subject (sample), and these are nondestructive It is known as an inspection device or a
nondestructive testing device.
[0004]
In addition, so-called V (z) curve for quantifying the elastic property of the subject or evaluating
the structure of the thin film by irradiating the subject (sample) with ultrasonic waves and
evaluating the acoustic characteristics of the subject The analysis method by is known.
An ultrasonic microscope is known as an apparatus for analyzing the property of an object from
such a V (z) curve.
[0005]
These ultrasonic diagnostic apparatuses and ultrasonic microscopes are provided with ultrasonic
transducers for converting electric signals into ultrasonic waves and transmitting the ultrasonic
waves, and for receiving ultrasonic waves and converting them into electric signals.
[0006]
Conventionally, a piezoelectric element such as ceramic piezoelectric material PZT (lead zirconate
titanate) has been mainly used as an ultrasonic transducer, but as disclosed in Japanese Patent
Application Publication No. 2005-510264 in recent years Capacitive micromachined ultrasonic
transducers (hereinafter referred to as c-MUTs) manufactured using micromachining technology
have attracted attention.
[0007]
The c-MUT has a cell configured by including a pair of flat plate-like electrodes (parallel flat plate
electrodes) facing each other across a gap and a membrane (membrane) supporting one of the
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electrodes. The ultrasonic waves are transmitted and received by vibration of the membrane.
[0008]
In such a c-MUT, in order to expand the frequency band of transmittable / receivable ultrasonic
waves, a technology for arranging cells having different characteristics with different diameters
and thicknesses of the membrane is disclosed in US Pat. No. 351 is disclosed.
Japanese Patent Application Publication No. 2005-510264 US Patent No. 5,870, 351
[0009]
As disclosed in U.S. Pat. No. 5,870,351, in the case of a c-MUT in which the frequency of
ultrasonic waves to be transmitted and received is broadened by providing a plurality of types of
cells having characteristics matched to different frequency bands. When focusing on a particular
frequency, the number of cells corresponding to that particular frequency decreases, so the
transmission intensity and reception sensitivity of c-MUT ultrasonic waves at each frequency
decrease. There is a problem of
[0010]
To address this problem, c-MUT has been realized that enables transmission and reception of
ultrasound at a wide-band frequency without reducing the transmission intensity and reception
sensitivity of ultrasound by increasing the number of cells with characteristics corresponding to
each frequency. In this case, there is a problem that the c-MUT is enlarged.
[0011]
The present invention has been made in view of the above problems, and is small in size and
capable of transmitting and receiving ultrasonic waves at a wide frequency without reducing the
transmission intensity and reception sensitivity of the ultrasonic waves. It is an object of the
present invention to provide a type of ultrasonic transducer, an ultrasonic diagnostic apparatus
and an ultrasonic microscope.
[0012]
An ultrasonic transducer according to the present invention comprises: a first electrode; a
vibrating membrane disposed above the first electrode with a cavity in the cavity; and a second
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electrode supported by the vibrating membrane. And the plurality of air gaps having different
cross-sectional areas when viewed from the second electrode side are directed from the first
electrode to the second electrode. It is characterized in that it is arranged continuously in the
direction.
[0013]
First Embodiment Hereinafter, a first embodiment of the present invention will be described with
reference to FIGS. 1 to 12.
In each of the drawings used in the following description, the scale of each member is made
different in order to make each member have a size that can be recognized in the drawings.
FIG. 1 is an explanatory view showing a schematic configuration of an ultrasonic endoscope.
FIG. 2 is a perspective view showing the structure of the distal end portion of the ultrasonic
endoscope.
FIG. 3 is a perspective view of the transducer array.
[0014]
In this embodiment, an example in which the present invention is applied to an ultrasonic
endoscope as an ultrasonic diagnostic apparatus will be described.
As shown in FIG. 1, the ultrasonic endoscope 1 according to the present embodiment includes an
elongated insertion portion 2 introduced into a body cavity, an operation portion 3 positioned at
a proximal end of the insertion portion 2, and the operation portion 3. And a universal cord 4
extending from the side of the main body.
[0015]
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The proximal end of the universal cord 4 is provided with an endoscope connector 4a connected
to a light source device (not shown).
The endoscope connector 4a is detachably connected to the electric cable 5 detachably
connected to the camera control unit (not shown) via the electric connector 5a and the ultrasonic
observation apparatus (not shown) via the ultrasonic connector 6a. The ultrasonic cable 6 is
extended.
[0016]
The insertion portion 2 is positioned at a distal end rigid portion 20 formed of a hard resin
member in order from the distal end side, a bendable curved portion 8 positioned at the rear end
of the distal end rigid portion 20, and a rear end of the curved portion 8 A flexible tube portion 9
having a small diameter and a long length and extending to the tip end portion of the operation
portion 3 is continuously provided. Further, an ultrasonic wave transmitting / receiving unit 30
for transmitting / receiving an ultrasonic wave described later in detail is provided on the distal
end side of the distal end rigid portion 20.
[0017]
The operation unit 3 has an angle knob 11 for controlling the bending of the bending portion 8
in a desired direction, an air supply / water supply button 12 for performing air supply and
water supply operations, a suction button 13 for performing suction operation, a body cavity The
treatment tool insertion port 14 etc. which become an entrance of the treatment tool to introduce
to are provided.
[0018]
As shown in FIG. 2, the distal end rigid portion 20 includes an illumination lens (not shown) that
constitutes an illumination optical unit that emits illumination light to the observation site, and
an objective that constitutes an observation optical unit that captures an optical image of the
observation site A lens 21, a suction and forceps port 22, which is an opening through which a
portion to be removed is suctioned or a treatment tool protrudes, and an air / water supply port
(not shown) for supplying air and water are provided.
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[0019]
As shown in FIG. 3, the ultrasonic transmitting / receiving unit 30 provided at the tip of the distal
end rigid portion 20 is configured to include the transducer array 31, a drive circuit 34 as a drive
unit, and an FPC 35.
The FPC 35 is a wiring board (flexible wiring board) having flexibility and mounting surfaces
formed on both sides, and in the ultrasonic wave transmitting / receiving unit 30, the FPC 35 is
an axis substantially parallel to the insertion axis of the distal end rigid portion 20. Is wound in a
substantially cylindrical shape with the central axis as a center axis.
[0020]
On the outer peripheral surface of the cylindrical FPC 35, a transducer array 31 which is an
ultrasonic transducer array is provided.
The transducer array 31 includes a plurality of transducer units 32 arranged in the
circumferential direction on the outer peripheral surface of the FPC 35. The transducer units 32
have a substantially rectangular shape as viewed from the normal direction of the outer
peripheral surface of the FPC 35, and are arranged at equal intervals on the outer peripheral
surface of the cylindrical FPC 35, with the short direction as the circumferential direction. The
transducer array 31 includes, for example, several tens to several hundreds of transducer units
32. The transducer array 31 according to the present embodiment includes 128 transducer units
32. Each transducer unit 32 is provided with sixteen transducer elements 33.
[0021]
As will be described in detail later, the transducer unit 32 of the present embodiment is a
capacitive ultrasonic transducer formed by micromachining technology on a silicon substrate
made of a silicon semiconductor with low resistance, and so-called MEMS (Micro Electro) It
belongs to the technical scope of Mechanical Systems. A capacitive ultrasonic transducer formed
by such micromachining technology is generally called c-MUT (Capacitive Micromachined
Ultrasonic Transducer).
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[0022]
In the transducer array 31 of the present embodiment, a plurality of transducer elements 33
arranged in one transducer unit 32 constitute a minimum drive unit for transmitting and
receiving ultrasonic waves. The transducer elements 33 transmit ultrasonic waves in the normal
direction of the mounting surface of the FPC 35, that is, outward in the radial direction of the
cylindrical FPC 35.
[0023]
On the other hand, a plurality of drive circuits 34 are mounted on the inner peripheral surface of
the cylindrical FPC 35, that is, on the mounting surface opposite to the mounting surface on
which the transducer array 31 is mounted. The drive circuit 34 has an electric circuit such as a
pulser for driving the transducer element 33 or a selection circuit, and is electrically connected
to each transducer element 33.
[0024]
The drive circuit 34 is also electrically connected to the plurality of signal electrodes 36 and the
ground electrode 37 formed on the outer peripheral surface of the cylindrical FPC 35. The signal
electrode 36 and the ground electrode 37 are inserted in the ultrasonic cable 6 and one end is
electrically connected to the ultrasonic connector 6a. The other end of the coaxial cable is
electrically connected. Thus, the drive circuit 34 is electrically connected to the ultrasonic
observation apparatus.
[0025]
The ultrasonic transmitting and receiving unit 30 having the above-described configuration is
formed on a plane substantially orthogonal to the insertion axis of the distal end rigid portion 20
by the two-dimensional transducer array 31 disposed on the outer peripheral surface of the
cylindrical FPC 35 It is possible to perform electronic radial scanning capable of sector scanning,
which transmits and receives radially based on the above.
[0026]
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Next, the detailed configuration of the transducer cell 100 which is the capacitive ultrasonic
transducer of the present embodiment will be described below with reference to FIGS. 4 to 6.
FIG. 4 is a top view of the transducer unit 32 as viewed from the ultrasonic wave transmitting
and receiving side. That is, in FIG. 4, ultrasonic waves are transmitted in the direction orthogonal
to the paper surface and away from the paper surface. FIG. 5 is a cross-sectional view taken
along the line V-V of FIG. FIG. 6 is a cross-sectional view of the transducer cell in the case where
the second void portion is a cavity.
[0027]
As shown in FIG. 4, the transducer unit 32 of the present embodiment is configured by arranging
a plurality of transducer cells 100 in a matrix. All the transducer cells 100 in a single transducer
unit 32 are all electrically connected in parallel, and a drive signal from the ultrasonic
observation apparatus is input through the signal electrode pad 38, At the same time, ultrasonic
waves of the same phase are transmitted.
[0028]
As shown in FIG. 5, the transducer cell 100 of the present embodiment is a capacitive type
having a laminated structure formed on a silicon substrate 101 made of a silicon semiconductor
with low resistance by a micromachining technology using a semiconductor process or the like.
Ultrasonic transducer.
[0029]
In the following description of the laminated structure, the vertical direction of each layer is such
that the direction of moving away from the surface of the silicon substrate 101 in the normal
direction is the upper direction.
For example, in the cross-sectional view of FIG. 5, the upper electrode 120 is referred to as being
disposed above the lower electrode 110. The thickness of each layer refers to the dimension of
each layer in the direction normal to the surface of the silicon substrate 101. In the following
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description, for convenience, the surface of the silicon substrate 101 on which the transducer cell
100 is to be formed is referred to as the cell formation surface, and the surface opposite to the
surface on which the transducer cell 100 is to be formed is referred to It is called the back side.
[0030]
The silicon substrate 101 is made of low resistance silicon having conductivity, and a first
insulating film 102 and a back surface insulating film 109 which are silicon oxide films having
electric insulating properties are formed on both surfaces. The first insulating film 102 and the
back surface insulating film 109 are high temperature oxide films formed by thermally oxidizing
the silicon substrate 101. The first insulating film 102 and the back surface insulating film 109
may be silicon nitride films.
[0031]
The transducer cell 100 is a pair of parallel flat plate electrodes facing each other via a cavity
130 which is a hole of a substantially cylindrical cavity, a lower electrode 110 (first electrode)
and an upper electrode 120 (second electrode) It is configured to have The vibrator unit 32
configured to include the vibrator cell 100 is vibrated by the membrane 100 a (diaphragm film),
which is an elastic membrane structure including the upper electrode 120 of the vibrator cell
100. It transmits and receives ultrasonic waves.
[0032]
A lower electrode 110 which is a conductive layer is formed on the first insulating film 102 in a
substantially circular shape as viewed from above. The lower electrode 110 is formed by
depositing Mo (molybdenum) by sputtering and patterning.
[0033]
The material constituting the lower electrode 110 which is the lower layer portion of the
laminated structure and is formed on the silicon oxide film is, besides Mo, a high melting point
metal such as W (tungsten), Ti (titanium), Ta (tantalum), etc. And their alloys, but if the heat
04-05-2019
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treatment at high temperature can be avoided in the subsequent manufacturing process, the
material is not limited to this, and is Al (aluminum), Cu (copper), etc. May be The lower electrode
110 may have a multilayer structure in which two or more conductive materials are stacked.
[0034]
Although not shown, all the lower electrodes 110 in the same vibrator unit 32 are electrically
connected to the signal electrode pads formed on the back surface of the silicon substrate 101
through the wafer penetration electrodes.
[0035]
On the lower electrode 110, an upper electrode 120 which is spaced apart from the lower
electrode 110 by a predetermined distance and substantially parallel to the lower electrode 110
is formed.
The upper electrode 120 is a conductive layer patterned in a substantially circular shape when
viewed from above, and provided approximately concentric with the lower electrode 110 when
viewed from above. In the present embodiment, the upper electrode 120 is formed by depositing
and patterning Al by sputtering.
[0036]
The material constituting the upper electrode 120 may be any material other than Al, for
example, one having conductivity such as Cu, W, Ti, or Ta. The upper electrode 120 may have a
multilayer structure in which two or more conductive materials are stacked.
[0037]
Although not shown, all upper electrodes 120 in the same vibrator unit 32 are electrically
connected to the ground electrode pad formed on the back surface of silicon substrate 101 via
conductive silicon substrate 101. There is.
[0038]
Between the lower electrode 110 and the upper electrode 120 which are the pair of parallel flat
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plate electrodes, the second insulating film 103, the third insulating film 104, the fourth
insulating film 105 and the fifth insulating film 106 having electrical insulation are formed. It is
done.
[0039]
The second insulating film 103, the third insulating film 104, the fourth insulating film 105, and
the fifth insulating film 106 are silicon nitride films in the present embodiment, and are formed
by plasma CVD or the like.
These insulating films may be insulating films formed by other processes such as silicon oxide
film, hafnium nitride (HfN), hafnium oxynitride (HfON), and other processes.
[0040]
Here, although the details will be described later, the third insulating film 104 and the fourth
insulating film 105 have a thickness in a region sandwiched by the lower electrode 110 and the
upper electrode 120 of the third insulating film 104 and the fourth insulating film 105. A cavity
130 is formed which is a sealed void layer in an atmospheric pressure, pressurized or
depressurized state penetrating in the direction.
Here, the reduced pressure state refers to a state in which the pressure is lower than the
atmospheric pressure, and also includes a so-called vacuum state. The cavity 130 has a
substantially cylindrical shape and is provided substantially concentrically with the lower
electrode 110 as viewed from above.
[0041]
That is, the lower electrode 110 and the upper electrode 120 opposed to each other through the
cavity 130, which is a void, are formed on the lower surface side of the second insulating film
103 formed on the lower electrode 110 and the lower electrode of the upper electrode 120. It is
electrically isolated by the insulating film 106. In other words, the upper electrode 120 opposed
to the lower electrode 110 via the cavity 130 is supported by the fifth insulating film 106.
04-05-2019
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[0042]
Further, the upper electrode 120 is made of a paraxylylene resin or the like having water
resistance, chemical resistance, etc. and excellent in biocompatibility and electrical insulation so
as to cover the entire upper surface portion of the transducer unit 32. A protective film 107 is
formed.
[0043]
Here, in the transducer cell 100 having the above-described configuration, of the fifth insulating
film 106, the upper electrode 120, and the protective film 107, the portion corresponding to the
region on the cavity 130 constitutes the membrane 100a which is a vibrating film. And the cavity
130 constitutes an air gap layer for the membrane 100a to vibrate.
[0044]
The transducer unit 32 configured by including a plurality of the transducer cells 100 described
above is mounted on the FPC 35 by a known method such as solder bonding, anisotropic
conductive film bonding, ultrasonic bonding, or the like.
Thereby, the transducer cell 100 of the transducer element 33 described above is electrically
connected to the drive circuit 34 mounted on the opposite side of the FPC 35 through the signal
electrode pad 38 and the ground electrode pad 39.
[0045]
And, at the time of transmission of the transducer cell 100, a change in electrostatic attractive
force between both electrodes generated by applying a voltage signal of a predetermined
frequency between the lower electrode 110 and the upper electrode 120 which are a pair of
electrodes. Causes the membrane 100a to vibrate and transmit an ultrasonic wave.
On the other hand, at the time of reception of the transducer cell 100, an ultrasonic signal is
converted into an electric signal from a change in capacitance between the lower electrode 110
and the upper electrode 120 due to the vibration of the membrane 100a by the receiving
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ultrasonic wave.
[0046]
The ultrasonic endoscope 1 which is the ultrasonic diagnostic apparatus of the present
embodiment is configured to transmit a DC bias voltage of an arbitrary value to the lower
electrode 110 of the transducer cell 100 at the time of transmitting and receiving ultrasonic
waves by the transducer cell 100. And a configuration that can be applied between the upper
electrodes 120.
[0047]
Next, the detailed configuration of the cavity 130 of the transducer cell 100 of the present
embodiment will be described below.
[0048]
In the present embodiment, the cavity 130 is formed by etching the sacrificial layer, which is a
known technique, and connects the inside of the cavity 130 used at the time of etching the
sacrificial layer with the upper layer side of the fifth insulating film 106. The sacrificial layer
removal holes are sealed by plugs (not shown).
The cavity 130 may be formed by a different method, for example, a method of bonding wafers
after mechanical or chemical micromachining, as long as it has the shape described below.
[0049]
The cavity 130 of the present embodiment has a first void portion 131 which is a substantially
cylindrical hole having a diameter D1 and a depth t1 when viewed from the upper side, that is,
the transmission side of ultrasonic waves, and the first void portion. In the bottom surface
portion 131a of the base member 131, a diameter D2 formed concentrically with the first gap
portion 131 and a second gap portion 132 which is a substantially cylindrical hole portion
having a depth t2 are continuously provided in the vertical direction. It is configured by
Here, the diameter D1 of the first void portion 131 is larger than the diameter D2 of the second
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void portion 132, that is, the cavity 130 has a so-called stepped shape in which the aperture
diameter decreases stepwise as it goes downward. It is a void of cylindrical shape.
[0050]
In addition, about the formation method of the cavity 130 which has the said shape, since it is a
well-known thing performed by a semiconductor process, the description shall be abbreviate |
omitted and shall be demonstrated easily below. In the present embodiment, first, the third
insulating film 104 is formed with a thickness t 2 on the second insulating film 103, and a region
to be on the lower electrode 110 of the third insulating film 104 by patterning by
photolithography. A through hole having a diameter D2 which penetrates the third insulating
film 104 is formed.
[0051]
Then, the fourth insulating film 105 is formed with a thickness t1 on the third insulating film
104, and the fourth insulating film is formed in a region on the lower electrode 110 of the fourth
insulating film 105 by patterning by photolithography. A through hole with a diameter D1
passing through 105 is formed. Thus, a stepped hole having two diameters of diameter D1 and
diameter D2 is formed in a region which is to be on the lower electrode 110 of the fourth
insulating film 105 and the third insulating film 104.
[0052]
Next, a sacrificial layer made of PSG (phosphorus glass) is formed so as to fill the stepped holes,
and the upper surfaces of the fourth insulating film 105 and the sacrificial layer are planarized.
Then, the fifth insulating film 106 and the upper electrode 120 are formed on the upper surfaces
of the fourth insulating film 105 and the sacrificial layer, and then the sacrificial layer is removed
by etching through the sacrificial layer removing hole to form the stepped hole. The part
becomes a cavity 130.
[0053]
In the present embodiment, the third insulating film 104 of thickness t2 and the fourth insulating
film of thickness t1 are formed in order to form a stepped hole having two cylindrical portions of
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diameter D1 and diameter D2. A step having through holes each having a diameter D1 and a
diameter D2 but having two cylindrical shapes with a diameter D1 and a diameter D2 in a single
insulating film of thickness t1 + t2 by controlling the etching depth It is needless to say that a
method of forming the attached holes may also be used.
[0054]
Here, although the details will be described later, the values of the diameter D1 and the diameter
D2 are set so that the fundamental frequency of the vibration of the membrane 100a becomes a
value suitable for transmitting and receiving ultrasonic waves of two predetermined frequencies.
.
Since the frequency of ultrasonic waves transmitted and received by vibrating the membrane
100a which is a vibrating membrane is determined by the diameter, density, elastic constant, etc.,
calculation of the values of the diameter D1 and the diameter D2 is a known technique. Is
possible. Hereinafter, the ultrasonic waves of two types of frequencies transmitted and received
by the transducer cell 100 are referred to as an ultrasonic wave of a first frequency f1 and an
ultrasonic wave of a second frequency f2 higher than the first frequency.
[0055]
The ultrasound endoscope 1 according to the present embodiment is configured to transmit the
lower electrode 110 and the upper portion of the transducer cell 100 to a DC bias voltage which
is a DC voltage of a predetermined value at the time of transmission and reception of ultrasound
by the transducer cell 100. The voltage is applied between the electrodes 120. The value of the
DC bias voltage applied between the lower electrode 100 and the upper electrode 120 which are
a pair of electrodes is changed according to the frequency of the ultrasonic wave transmitted by
the transducer cell 100 or the frequency of the ultrasonic wave received. .
[0056]
In the present embodiment, the value of the DC bias voltage is either one of a first voltage value
V1 and a second voltage value V2 which are two predetermined voltage values. The absolute
value of the first voltage value V1 of the DC bias voltage has a value lower than the absolute
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value of the second voltage value V2.
[0057]
Specifically, in the first voltage value V1 of the DC bias voltage, the surface on the cavity 130
side of the membrane 100a vibrating at the time of transmission and reception of ultrasonic
waves contacts the bottom portion 131a of the first void portion 131 of the cavity 130 Not set in
the condition.
[0058]
On the other hand, the second voltage value V2 of the DC bias voltage is the bottom surface
portion of the first void portion 131 of the cavity 130, as shown in FIG. It is set on the condition
which does not separate and contact on the smallest diameter part of 131a.
Here, the portion with the smallest diameter of the bottom surface portion 131 a of the first gap
portion 131 refers to the corner portion 131 b where the bottom surface portion 131 a and the
side surface portion of the second gap portion 132 intersect.
[0059]
The transducer cell 100 which is the ultrasonic transducer of the present embodiment having the
above-mentioned configuration transmits ultrasonic waves of the first frequency f1 and the
second frequency f2 which are ultrasonic waves of two predetermined frequencies. At least one
of the receptions is configured to be possible. The operation of this transducer cell 100 will be
described below.
[0060]
First, the basic operation of the transducer cell 100 which is a capacitive ultrasonic transducer
called c-MUT will be described. When ultrasonic waves are transmitted by the transducer cell
100, a voltage is applied between the lower electrode 110 and the upper electrode 120 to
generate electrostatic attraction between the lower electrode 110 and the upper electrode 120,
and the membrane 100a It is pulled in the direction of and elastically deformed. Then, when the
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voltage between the lower electrode 110 and the upper electrode 120 is reduced, the membrane
100a is restored in a direction away from the lower electrode 110 by an elastic force. That is,
when a pulse-like voltage signal is applied between the lower electrode 110 and the upper
electrode 120, the membrane 100a vibrates, and ultrasonic waves are transmitted in the upper
direction of the membrane 100a.
[0061]
On the other hand, when ultrasonic waves are received by the transducer cell 100, a DC bias
voltage of a predetermined value is applied in advance between the lower electrode 110 and the
upper electrode 120. Then, the ultrasonic waves are received by converting the vibration of the
membrane 100a due to the ultrasonic waves reaching the membrane 100a into an electrical
signal based on the change in capacitance between the lower electrode 110 and the upper
electrode 120. .
[0062]
Next, details of the operation of the transducer cell 100 in the present embodiment will be
described. As described above, the ultrasonic endoscope 1 according to the present embodiment
transmits the DC bias voltage of a predetermined value to the lower electrode 110 of the
transducer cell 100 at the time of transmission and reception of the ultrasonic wave by the
transducer cell 100. The voltage is applied between the upper electrodes 120. When the
transducer cell 100 performs at least one of transmission and reception of ultrasonic waves of
the first frequency f 1, the DC bias voltage is set to the first voltage value V 1, and the transducer
cell 100 generates the second frequency. When at least one of transmission and reception of the
ultrasonic wave of f2 is performed, the DC bias voltage is set to the second voltage value V2.
[0063]
That is, in the present embodiment, when at least one of transmission and reception of the
ultrasonic wave of the first frequency f1 is performed, the diameter of the region in which the
membrane 100a vibrates is D1.
[0064]
On the other hand, when at least one of transmission and reception of the ultrasonic wave of the
second frequency f2 is performed, a DC bias voltage of the second voltage value V2 is applied
04-05-2019
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between the lower electrode 110 and the upper electrode 120, as shown in FIG. Thus, the
membrane 100a is always in contact with the bottom portion 131a of the first void portion 131,
and the diameter of the area where the membrane 100a vibrates is D2.
[0065]
In other words, the transducer cell 100 according to the present embodiment includes the cavity
130 including the plurality of different types of air gaps (the first air gap 131 and the second air
gap 132) arranged in the transmission direction of the ultrasonic wave. And the membrane 100a
is vibrated in the void portion of at least one kind of the plurality of void portions selected
according to the change of the DC bias voltage value.
[0066]
Below, the effect of the transducer cell 100 which is an ultrasonic transducer of this embodiment
is demonstrated.
[0067]
In the transducer cell 100 according to the present embodiment, when performing at least one of
transmission and reception of ultrasonic waves, the membrane 100a is configured by setting the
value of the DC bias voltage to the first voltage value V1 or the second voltage value V2. It is
possible to change the diameter of the vibrating area of D to D1 or D2.
Here, the values of the diameters D1 and D2 are values suitable for transmitting and receiving
the ultrasonic wave of the first frequency f1 and the ultrasonic wave of the second frequency f2
when the membrane 100a having the diameter of the value vibrates. It is done.
[0068]
Therefore, when the value of the DC bias voltage is the first voltage value V1, the transducer cell
100 according to the present embodiment can transmit and receive ultrasonic waves of the first
frequency f1, and the DC bias can be transmitted. When the voltage value is the second voltage
value V2, it is possible to transmit and receive the ultrasonic wave of the second frequency f2.
[0069]
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Conventionally, in order to transmit and receive ultrasonic waves of a plurality of different
frequencies, it has been necessary to provide a plurality of transducer cells having different
characteristics such as the diameter of the membrane corresponding to the respective
frequencies.
However, according to the present embodiment, it is possible to transmit and receive ultrasonic
waves of a plurality of different frequencies by a single transducer cell 100.
[0070]
For this reason, according to the present embodiment, at least one of transmission and reception
of ultrasonic waves in a wider band is possible, but there is no need to provide transducer cells of
a plurality of types of characteristics, so the size and transmission strength and reception are
small. It is possible to provide an ultrasonic transducer with high sensitivity.
[0071]
In addition, the ultrasonic endoscope 1 which is a diagnostic apparatus configured to include the
above-described transducer cell 100 does not increase the diameter of the ultrasonic wave
transmitting / receiving unit 30, and the ultrasonic waves of a plurality of different frequencies
are It becomes possible to diagnose the subject with sufficient transmission strength and
reception sensitivity.
[0072]
For this reason, the ultrasound endoscope 1 of the present embodiment, for example, in the case
where it is desired to inspect a wide range in the subject, that is, in the case where an echo signal
from a region farther from the ultrasound transmission / reception unit 30 is desired. If you want
to make a diagnosis by transmitting and receiving low frequency ultrasonic waves that reach far,
and if you want to test with high resolution in the subject, high frequency ultrasonic waves that
can obtain high resolution It is possible to realize a more flexible and highly responsive diagnosis
such as switching to transmit and receive and performing diagnosis.
[0073]
In the above-described embodiment, the first frequency f1, which is the frequency of ultrasonic
waves that can be transmitted and received by the transducer cell 100, and the second frequency
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f2, which is a frequency higher than the first frequency. Although the relationship is not
specified, as a first modification of this embodiment, the values of the diameters D1 and D2 are
such that the value of the second frequency f2 approximates to an integral multiple of the value
of the first frequency f1. Can be listed.
That is, in the first modification, the ultrasonic wave of the second frequency f2 is an overtone of
the ultrasonic wave of the first frequency f1.
[0074]
Then, when ultrasonic waves are transmitted by the transducer cell 100, ultrasonic waves of the
first frequency f1 are transmitted into the subject in a state in which the DC bias voltage of the
first voltage value V1 is applied, and when ultrasonic waves are received The ultrasonic wave of
the second frequency f2 is received in a state in which the DC bias voltage of the voltage value
V2 is applied.
[0075]
According to the ultrasonic diagnostic apparatus of the present modification having such a
configuration, it is possible to detect with high sensitivity harmonic components having a
frequency that is an integral multiple of the frequency of the ultrasonic wave (fundamental wave)
transmitted into the object. It is possible to realize so-called harmonic imaging by imaging the
harmonic components.
[0076]
Further, in the above-described embodiment, the cavity 130 of the transducer cell 100 is
described as a stepped hole having one step constituted by the first void portion 131 and the
second void portion 132 having different diameters. However, the present invention is not
limited to this form.
[0077]
A second modified example in which the configuration of the cavity 130 of the present
embodiment described above is different is shown in FIG.
As shown in FIG. 7, the cavity 140 of the transducer cell 100 of this modification may be a
04-05-2019
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stepped hole having two or more steps whose diameter decreases with distance from the
membrane 100a.
In other words, the cavity 140 of the present modification is a stepped hole which is expanded in
the transmission direction of the ultrasonic wave.
[0078]
More specifically, the cavity 140 is a hole formed in the insulating film 108 formed on the lower
electrode 110 and supporting the membrane 100 a including the upper electrode 120.
The cavity 140 has a first void 131 which is a substantially circular hole having a diameter D1
and a depth t1 when viewed from the upper side, that is, the transmission side of ultrasonic
waves, and a bottom 131a of the first void 131. A second air gap 132 which is a substantially
circular hole having a diameter D2 and a depth t2 formed, and a substantially circular shape
having a diameter D3 and a depth t3 formed on the bottom 132a of the second air gap 132. It is
comprised by the 3rd space | gap part 133 which is a hole of this.
[0079]
Here, the first void portion 131, the second void portion 132, and the third void portion 133 are
formed substantially concentrically as viewed from above.
Further, the diameter D1 of the first void portion 131 is larger than the diameter D2 of the
second void portion 132, and the diameter D2 of the second void portion 132 is larger than the
diameter D3 of the third void portion 133.
That is, the cavity 140 is a so-called stepped hole-shaped gap portion in which the opening
diameter decreases stepwise as it goes downward.
Further, the diameter D3 of the third air gap portion 133 transmits and receives an ultrasonic
wave of the third frequency f3, which is a frequency higher than the second frequency f2, when
04-05-2019
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the membrane 100a vibrates in the area of the diameter D3. It corresponds to the value of
[0080]
In the transducer cell 100 according to the present modification configured as described above,
the DC bias voltage is transmitted by the transducer cell 100 when at least one of ultrasonic
wave transmission and reception is performed as in the above-described embodiment. The value
is changed according to the frequency of the ultrasonic wave to be received or the frequency of
the ultrasonic wave to be received.
Then, in accordance with the value of the DC bias voltage, a gap for vibrating the membrane
100a is selected from among the plurality of gaps forming the cavity.
[0081]
Specifically, in the present modification, any one of the voltage value V1, the voltage value V2,
and the voltage value V3 is selected as the value of the DC bias voltage.
Here, the voltage value V1 is a voltage value at which the membrane 100a is not in contact with
the bottom surface portion 131a of the first gap portion 131, and the voltage value V2 is that of
the membrane 100a at the bottom surface portion 131a of the first gap portion 131. It is a
voltage value which does not separate on contact with the smallest diameter portion and does
not contact the membrane 100 a on the bottom portion 132 a of the second air gap 132. The
voltage value V3 is a voltage value that does not separate the membrane 100a from being in
contact with the smallest diameter portion of the bottom portion 132a of the second gap portion
132.
[0082]
That is, in this modification, the diameter of the area where the membrane 100a vibrates is
changed by changing the DC bias voltage applied between the lower electrode 110 and the upper
electrode 120 to the voltage value V1, voltage value V2 and voltage value V3 described above. ,
Diameter D1, diameter D2, and diameter D3 become smaller stepwise.
04-05-2019
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[0083]
Therefore, according to the present modification, at least one of transmission and reception of
ultrasonic waves of three different frequencies can be performed by the single transducer cell
100, and the ultrasonic wave can be It becomes possible to transmit and receive sound waves.
[0084]
In the present modification, the cavity 140 is a two-step stepped hole constituted by three air gap
portions different in diameter, but the cavity 140 has three or more steps, and the DC bias
voltage is The membrane 100a may be configured to be in contact with the step.
[0085]
Also, based on such a technical idea, when the number of steps of the cavity is further increased,
that is, the cavity 150 as shown in FIG. 8 as a third modification of the present embodiment is an
ultrasonic wave. An embodiment configured as a tapered hole expanding in the transmission
direction (upward direction) is also included in the present invention.
Such a tapered cavity 150 can be formed, for example, by photolithography using a known gray
mask.
[0086]
In the present modification shown in FIG. 8, the value of the DC bias voltage applied between the
lower electrode 110 and the upper electrode 120 is changed to change the electrostatic
attractive force between the lower electrode 110 and the upper electrode 120. By controlling the
distance between H.sub.2 and the membrane 100a, it is possible to arbitrarily select the diameter
of the area in which the membrane 100a vibrates.
[0087]
Therefore, according to this modification, at least one of transmission and reception of ultrasonic
waves of an arbitrary frequency can be performed by a single transducer cell 100, and ultrasonic
waves can be transmitted at a wider frequency band than the embodiment described above. It
becomes possible to transmit and receive.
[0088]
04-05-2019
23
In each of the embodiments described above, the cavity, which is a hollow portion interposed
between the lower electrode and the upper electrode, is formed on the upper side (upper
electrode side by making the side surface portion stepped or tapered). The cross-sectional area of
the hollow portion as viewed from the top is configured to increase as it goes upward.
[0089]
Then, the membrane supporting the upper electrode elastically deforms in the direction
approaching the lower electrode in accordance with the value of the DC bias voltage applied to
the lower electrode and the upper electrode, whereby the peripheral portion of the membrane is
stepped of the cavity Contact with the top or tapered side of the shape results in a change in the
area of the area over which the membrane can vibrate.
[0090]
That is, in the vibrator cell according to the present invention, when the membrane is attracted to
the lower electrode by electrostatic attraction and elastically deformed by a predetermined
amount, the cross-sectional area of the vibrating region of the membrane changes by a
predetermined amount. It is not limited to the above-described embodiment.
Another modification is described as a fourth modification and a fifth modification with reference
to FIGS. 9 and 10, respectively.
[0091]
First, in the fourth modified example of the present embodiment, as shown in FIG. 9, a cylinder
having a diameter D1 and a depth t1 + t2 is formed on the insulating film 108 formed on the
lower electrode 110 and supporting the membrane 100a including the upper electrode 120. A
hole 163 having a shape is formed, and a substantially annular convex portion 164 having an
inner diameter D1 and a height t2 is provided on the upper surface 163a of the second insulating
film 103 which is the bottom of the hole 163.
[0092]
The cavity 160 of this modification having such a configuration is formed below the first void
161, which is a hole having a diameter D1 and a depth t1 when viewed from above, and the first
void. It is comprised by the diameter D2 which is an area | region enclosed by the substantially
cyclic | annular convex part 164, and the 2nd space | gap part 162 which is a hole of depth t2.
04-05-2019
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[0093]
That is, in the present modification, the top surface portion 164a of the substantially annular
convex portion 164 corresponds to the bottom surface portion 131a of the first void portion 131
in the embodiment shown in FIG. The child cells have the same effect as the above-described
embodiment.
[0094]
If a plurality of substantially annular convex portions having different diameters and heights are
concentrically provided on the upper surface 163a of the second insulating film 103 as viewed
from above, the second deformation shown in FIG. 7 is obtained. Needless to say, the same effect
as in the example can be obtained.
[0095]
Further, in the fifth modification of the present embodiment, as shown in FIG. 10, the insulating
film 108 formed on the lower electrode 110 and supporting the membrane 100a including the
upper electrode 120 has a cylinder with a diameter D1 and a depth t1 + t2. A shaped hole 173 is
formed.
A substantially annular convex portion 174 having an inner diameter D2 and a height t2 is
formed on the lower surface of the membrane 100a, that is, the surface of the membrane 100a
facing the lower electrode 110 so as to protrude downward.
[0096]
The cavity 170 of this modification having such a configuration is formed above the first void
171, which is a hole having a diameter D1 and a depth t1 when viewed from above, and the first
void. It is comprised by the diameter D2 which is an area | region enclosed by the substantially
cyclic | annular convex part 174, and the 2nd space | gap part 172 which is a hole of the depth
t2.
That is, the cavity 170 in this modification is configured by laminating a plurality of air gaps
04-05-2019
25
having different cross-sectional areas when viewed from above, and the cross-sectional areas of
the plurality of air gaps are closer to the upper electrode 120 It is considered small.
[0097]
Then, in the transducer cell of this modification, as in the above-described embodiment, when at
least one of transmission and reception of ultrasonic waves is performed, the DC bias voltage is
the frequency of the ultrasonic waves transmitted by the transducer cell 100. Alternatively, the
value is changed according to the frequency of the received ultrasonic wave.
[0098]
Specifically, in the present modification, either the voltage value V1 or the voltage value V2 is
selected as the value of the DC bias voltage.
Here, the voltage value V1 is a voltage value at which the substantially annular convex portion
174 provided so as to project downward from the membrane 100a does not contact the bottom
surface of the hole portion 173, and the voltage value V2 is a substantially annular convex
portion 174 It is a voltage value which does not separate while in contact with the bottom of the
hole 173.
[0099]
Therefore, in this modification, when the DC bias voltage is voltage value V1, the diameter of the
area where membrane 100a vibrates is D1, and when the DC bias voltage is voltage value V2,
membrane 100a vibrates. The diameter of the area is D2.
Therefore, the transducer cell of this modification has the same operation and effect as the
embodiment described above.
[0100]
In the embodiment described above, when a DC bias voltage of the second voltage value V2 is
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applied as shown in FIG. 6, the membrane 100a does not contact the entire surface of the bottom
portion 131a, but the outer periphery of the membrane 100a. A gap 139 is created between the
side and the outer peripheral side of the bottom portion 131a.
If such a gap 139 exists, when vibrating the membrane 100 a to transmit ultrasonic waves, the
region of the membrane 100 a facing the gap 139 also vibrates.
For this reason, it is possible that the ultrasonic wave of the unnecessary frequency different
from the transmitted ultrasonic wave will be generated.
[0101]
In order to prevent the gap 139 from being formed between the outer peripheral portion of the
membrane 100a and the bottom surface portion 131a, for example, as shown in FIG. 11, the side
surface portion of the first void portion 131 is tapered. When a DC bias voltage having a voltage
value V2 of 2 is applied, the membrane 100a may be in contact with the side surface portion and
the bottom surface portion 131a of the first void portion 131 without any gap.
For example, as shown in FIG. 12, the DC bias voltage of the second voltage value V2 is applied
by forming the outer peripheral portion of the membrane 100a thin and making the deformation
amount of the membrane 100a large at the outer peripheral portion. In this case, the membrane
100a may be in contact with the side surface and the bottom surface 131a of the first void
portion 131 without any gap.
[0102]
As described above, when the DC bias voltage of the second voltage value V2 is applied to the
transducer cell 100 according to the present embodiment, the membrane 100a does not have a
gap between the side surface portion and the bottom surface portion 131a of the first gap
portion 131. By being configured to be in contact, it is possible to prevent generation of
ultrasonic waves of unnecessary frequencies and to transmit ultrasonic waves without noise.
[0103]
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In the configuration described above, the lower electrode 110, the upper electrode 120, and the
cavity 130 have a substantially circular shape as viewed from above, but the shape thereof is not
limited to this embodiment, for example, a regular octagon, It may be a polygonal shape such as
a regular hexagon or a parallelogram, or any other shape.
Further, the dimensions of the membrane 100a and the cavity 130 are determined by the
wavelength and output of ultrasonic waves used at the time of observation.
[0104]
The vibrator unit of the present embodiment is configured using the conductive silicon substrate
101 as a base, but the vibrator unit is made of electrically insulating quartz, sapphire, quartz,
alumina, zirconia, or the like. You may form on the base material comprised with insulating
materials, such as glass and resin.
[0105]
In addition, although the ultrasonic endoscope of the present embodiment is described as
performing electronic radial scanning, the scanning method is not limited to this, and linear
scanning, convex scanning, mechanical scanning, etc. It may be adopted.
The transducer array may be a two-dimensional array in which a plurality of transducer elements
are two-dimensionally arrayed, and not only a form in which the transducer elements are
arrayed, but a single transducer element It may be a form using.
[0106]
Further, the ultrasonic diagnostic apparatus of the present embodiment may be an ultrasonic
probe type without an optical observation window, or may be a capsule type ultrasonic
endoscope.
The ultrasound diagnostic apparatus may be a so-called extracorporeal ultrasound diagnostic
apparatus that performs ultrasound scanning from above the body surface of the subject into the
body cavity.
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The ultrasonic diagnostic apparatus may be a nondestructive inspection apparatus or a
nondestructive testing apparatus used in the industrial field.
[0107]
Second Embodiment Hereinafter, a second embodiment of the present invention will be described
with reference to FIGS. 13 and 14.
FIG. 13 is a top view of a transducer cell according to the second embodiment. FIG. 14 is a crosssectional view taken along line XIV-XIV of FIG.
[0108]
The second embodiment is different from the configuration of the first embodiment only in the
configuration of the cavity of the transducer cell. Therefore, only the difference will be described
below, and the same components as those of the first embodiment are denoted by the same
reference numerals, and the description thereof will be appropriately omitted.
[0109]
As shown in FIG. 13, the transducer cell 200 of the present embodiment is substantially circular
as viewed from the upper side, that is, the transmission side of the ultrasonic waves. Then, as
shown in FIG. 14, as in the first embodiment, the lower electrode 110, which is a pair of parallel
flat plate electrodes facing each other via the cavity 230 which is a hole, as in the first
embodiment. (First electrode) and upper electrode 120 (second electrode) are configured. The
upper electrode 120 is supported by a membrane 100a which is a vibrating membrane, and the
cavity 230 is a void formed in the insulating film 108 interposed between the lower electrode
110 and the membrane 100a.
[0110]
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The cavity 230 of the present embodiment has a first void portion 231 which is a substantially
cylindrical hole with a diameter D4 and a depth t4 formed in contact with the membrane 100a,
and a bottom portion 231a of the first void portion 231. And a plurality of second air gaps 232
which are substantially cylindrical holes with a diameter D5 and a depth t5. In the present
embodiment, four second air gaps 232 are equally formed in the circumferential direction on the
bottom surface 231 a of the circular first air gap 231 as viewed from above.
[0111]
That is, the cavity 230 of the present embodiment is configured by laminating the first void
portion 231 and the second void portion 232 having different cross-sectional areas when viewed
from above in the thickness direction. The plurality of second void portions are formed in the
bottom surface portion 231 a of the first void portion 231.
[0112]
Then, as in the first embodiment, in the present embodiment, the DC bias voltage applied
between the lower electrode 100 and the upper electrode 120 which are a pair of electrodes is
the frequency of the ultrasonic wave transmitted by the transducer cell 200 or The value is
changed according to the frequency of the received ultrasound.
[0113]
In the present embodiment, the value of the DC bias voltage is one of the first voltage value V4
and the second voltage value V5, which are two predetermined voltage values.
The absolute value of the first voltage value V4 of the DC bias voltage has a value lower than the
absolute value of the second voltage value V5.
[0114]
Specifically, in the first voltage value V4 of the DC bias voltage, the surface on the cavity 230
side of the membrane 100a vibrating at the time of transmission and reception of ultrasonic
waves contacts the bottom surface portion 231a of the first void portion 231 of the cavity 230
Not set in the condition.
04-05-2019
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[0115]
On the other hand, the second voltage value V5 of the DC bias voltage is the first air gap 231 of
the membrane 100a in a region inside the circle circumscribing at least all of the plurality of
second air gaps 232 when viewed from above. It is set on the conditions which do not separate,
contacting on the bottom face part 231a of.
[0116]
In the transducer cell 200 which is the ultrasonic transducer of the present embodiment having
the above configuration, when the DC bias voltage of the first voltage value V4 is applied, in the
region where the membrane 100a vibrates. The diameter is D4.
[0117]
On the other hand, when a DC bias voltage of the second voltage value V5 is applied, the
diameter of the region in which the membrane 100a vibrates is D5.
Then, in the case where the DC bias voltage of the second voltage value V5 is applied, the region
of the diameter D5 in which the membrane 100a vibrates is present at four places per single
transducer cell 200.
[0118]
Therefore, the transducer cell 200 which is the ultrasonic transducer of this embodiment having
such a configuration can transmit or receive at least one of ultrasonic waves of two different
frequencies according to the voltage value of the DC bias voltage. is there.
[0119]
Specifically, when a DC bias voltage of the first voltage value V4 is applied, at least transmission
and reception of ultrasonic waves of the first frequency f4 corresponding to the vibration of the
membrane 100a in the area of the diameter D4. One becomes possible.
When a DC bias voltage of the second voltage value V5 is applied, at least one of transmission
and reception of ultrasonic waves of the second frequency f5 corresponding to the vibration of
04-05-2019
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the membrane 100a in the area of the diameter D5 is possible. It becomes.
[0120]
Therefore, according to the transducer cell 200 which is the ultrasonic transducer of the present
embodiment configured as described above, it is possible to transmit and receive ultrasonic
waves of a plurality of different frequencies with a single transducer cell 200. .
[0121]
For this reason, according to the present embodiment, at least one of transmission and reception
of ultrasonic waves in a wider band is possible, but there is no need to provide transducer cells of
a plurality of types of characteristics, so the size and transmission strength and It is possible to
provide an ultrasonic transducer with high sensitivity.
[0122]
Further, in the present embodiment, since the plurality of second air gaps 232 are formed in the
bottom surface 231 a of the first air gap 231, the second frequency can be obtained by focusing
on a single transducer cell 200 In the case of at least one of transmission and reception of
ultrasonic waves of f5, there are a plurality of regions in which the membrane 100a vibrates.
[0123]
For this reason, according to the present embodiment, it is possible to improve the transmission
intensity and the reception sensitivity of ultrasonic waves having a high frequency at which
attenuation easily occurs, as compared with the first embodiment.
[0124]
The second air gap 232 formed on the bottom surface 231 a of the first air gap 231 has a
plurality of different diameters and is applied with a DC bias voltage of the second voltage value
V5. May have a configuration capable of simultaneously performing transmission and reception
of ultrasonic waves of a plurality of different frequencies.
[0125]
Further, also in the present embodiment, similarly to the first embodiment, a gap having a
diameter smaller than that of the second gap is formed at the bottom of the second gap 232, and
the DC bias voltage is divided into three stages. It may be possible to transmit and receive
ultrasonic waves of a plurality of types of different frequencies by changing.
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[0126]
Third Embodiment Hereinafter, a third embodiment of the present invention will be described
with reference to FIG.
The third embodiment is an application of the above-described ultrasonic transducer of the
present invention to an ultrasonic microscope.
FIG. 15 is a view for explaining the configuration of the ultrasonic microscope of the present
embodiment.
[0127]
The ultrasound microscope 300 applies a high frequency signal generated by the high frequency
oscillator 301 to the ultrasound transducer 303 according to the present invention via the
circulator 302 to convert it into ultrasound.
The ultrasonic waves are converged by the acoustic lens 304, and the sample 305 is placed at
the convergence point.
The sample 305 is held by a sample holder 306, and a coupler 307 such as water is filled
between the sample 305 and the lens surface of the acoustic lens 304.
The reflected wave from the sample 305 is received by the transducer 303 via the acoustic lens
304 and converted into an electrical reflected signal.
An electrical signal corresponding to the received ultrasound output from the ultrasound
transducer 303 is input to the display device 308 via the circulator 302.
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The sample holder 306 is driven by the scanning device 310 controlled by the scanning circuit
309 in two horizontal directions of XY in the horizontal plane.
[0128]
The ultrasonic microscope 300 configured as described above quantifies the elastic property of
the sample 305 or evaluates the structure of the thin film by irradiating the sample 305 with
ultrasonic waves to evaluate the acoustic characteristics of the sample 305. It is possible.
[0129]
The following configuration can be proposed based on the embodiment described above.
That is, (Appendix 1) In the capacitive ultrasonic transducer, the ultrasonic transducer is
composed of a large number of transducer cells, and the transducer cells are a diaphragm
(membrane) comprising at least a dielectric film and an upper electrode A gap portion in contact
with the vibrating membrane, and a lower electrode at a position facing the vibrating membrane
with the gap portion interposed therebetween, and the electrostatic gap determined by the void
portion is narrowed near the periphery of the cavity. Ultrasonic transducer.
[0130]
(Supplementary Note 2) The ultrasonic transducer described in the supplementary note 1 is a
capacitive ultrasonic transducer (c-MUT) using a micromachine process.
[0131]
(Supplementary Note 3) The ultrasonic transducer according to supplementary note 1 or 2 is
characterized in that a step is provided in the vicinity of the outer periphery of the cavity.
[0132]
(Supplementary Note 4) The ultrasonic transducer according to any one of supplementary notes
1 to 3 is characterized in that an inclination is provided in the vicinity of the outer periphery of
the cavity.
[0133]
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(Supplementary Note 5) The ultrasonic transducer according to any one of supplementary notes
1 to 4 is characterized in that the drive voltage (DC bias voltage) is variable.
[0134]
(Supplementary Note 6) The ultrasonic transducer according to supplementary note 3 is
characterized in that a step is formed on the outer periphery of the cavity by laminating a
plurality of films.
[0135]
(Supplementary Note 7) The ultrasonic transducer according to supplementary note 4 is
characterized in that a slope of the outer periphery of the cavity is formed by a gray mask.
[0136]
(Supplementary Note 8) The ultrasonic transducer according to any one of supplementary notes
1 to 7 is characterized in that a plurality of air gaps having different cross-sectional areas are
stacked when viewed from above the cavity. I assume.
[0137]
(Supplementary Note 9) The plurality of void portions described in supplementary note 8 have a
larger cross-sectional area toward the upper electrode side.
[0138]
(Supplementary Note 10) The plurality of void portions described in supplementary note 8 have
a smaller cross-sectional area toward the upper electrode side.
[0139]
(Supplementary note 11) The ultrasonic transducer according to any one of supplementary notes
1 to 10 is characterized in that a vibrating region of the vibrating membrane is changed
according to the driving voltage. .
[0140]
(Supplementary Note 12) In the ultrasonic transducer described in supplementary note 11, the
area of the vibrating region of the vibrating membrane decreases as the absolute value of the DC
bias voltage supplied between the upper electrode and the lower electrode increases. It is
04-05-2019
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characterized in that it is constructed.
[0141]
(Supplementary Note 13) An ultrasonic endoscope and an ultrasonic endoscopic system
equipped with the ultrasonic transducer according to any one of supplementary notes 1 to 12.
[0142]
The present invention is not limited to the above-described embodiment, and can be
appropriately modified without departing from the scope or spirit of the invention as can be read
from the claims and the entire specification, and an ultrasonic wave accompanied by such a
modification. Transducers, ultrasound systems and ultrasound microscopes are also within the
scope of the present invention.
[0143]
It is explanatory drawing which shows schematic structure of an ultrasonic endoscope.
It is a perspective view which shows the structure of the front-end | tip part of an ultrasonic
endoscope.
It is a perspective view of a vibrator array.
It is the top view which looked at a transducer unit from the transmission direction of an
ultrasonic wave.
FIG. 5 is a cross-sectional view taken along the line V-V of FIG. 4;
It is sectional drawing of a vibrator | oscillator cell when the 2nd space | gap part is made into a
cavity.
It is sectional drawing of the vibrator | oscillator cell of the 2nd modification of 1st Embodiment.
04-05-2019
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It is sectional drawing of the vibrator | oscillator cell of the 3rd modification of 1st Embodiment.
It is sectional drawing of the vibrator | oscillator cell of the 4th modification of 1st Embodiment.
It is sectional drawing of the vibrator | oscillator cell of the 5th modification of 1st Embodiment.
It is sectional drawing of the vibrator | oscillator cell of the other modification of 1st
Embodiment.
It is sectional drawing of the vibrator | oscillator cell of the other modification of 1st
Embodiment.
It is a top view of the vibrator | oscillator cell of 2nd Embodiment.
It is XIV-XIV sectional drawing of FIG.
It is an explanatory view showing a schematic structure of an ultrasonic microscope.
Explanation of sign
[0144]
DESCRIPTION OF SYMBOLS 100 vibrator cell, 100a membrane, 101 silicon substrate, 102 1st
insulating film, 103 2nd insulating film, 104 3rd insulating film, 105 4th insulating film, 106 5th
insulating film, 107 protective film, 109 back surface insulating film , 110 lower electrode, 111
lower electrode wire, 114 lower conductive layer, 120 upper electrode, 121 upper electrode
wire, 124 upper conductive layer, 130 cavity, 131 first void portion, 132 second void portion
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