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JP2013062695

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DESCRIPTION JP2013062695
Abstract: To provide an electromechanical transducer capable of suppressing deterioration of
transmission / reception characteristics due to elastic waves reflected in a support member by
reducing elastic waves entering a support member supporting a substrate on which cells are
arranged. . An electromechanical transducer includes a plurality of cells 200 each having a
vibrating film 101 including a first electrode 102 provided opposite to a second electrode 105
with a gap 104 on a substrate 106. And / or perform at least one of a transmitting operation and
a receiving operation. The substrate 106 is supported by the support member 111 via the spacer
means 111 such that a spacer gap 112 is formed between the substrate 106 and the support
member 110. A spacer gap 112 is formed between the back surface of the substrate 106
opposite to the surface of the substrate 106 provided with cells and the surface of the support
member 110 opposite to the back surface, and a uniform gas or the inside of the spacer gap is
formed. It is kept filled with liquid. [Selected figure] Figure 1
Electromechanical converter
[0001]
The present invention relates to an electromechanical transducer such as a capacitive
electromechanical transducer that performs transmission and reception (in the present
specification, transmission and reception mean at least one of transmission and reception) of
elastic waves such as elastic waves. About.
[0002]
04-05-2019
1
In order to transmit and receive elastic waves, a capacitive micromachined ultrasonic transducer
(CMUT), which is a capacitive elastic wave transducer, has been proposed.
The CMUT is manufactured using a MEMS (Micro Electro Mechanical Systems) process to which
a semiconductor process is applied. FIG. 8 is a schematic view showing a cross section of the
array CMUT and its connection. In FIG. 8, reference numeral 101 denotes a diaphragm, 102
denotes a first electrode (upper electrode), 103 denotes a support portion, 104 denotes a gap,
105 denotes a second electrode (lower electrode), 106 denotes a substrate, 107 denotes an
insulating film, 108 , 109 are wires. Reference numeral 200 denotes a cell, 201 denotes an
element, 301 denotes a DC potential application means, and 302 denotes a drive detection
means. A first electrode 102 is formed on a vibrating membrane 101 (usually about several tens
of microns in size), and the vibrating membrane 101 is supported by a support portion 103
formed on a substrate 106 and disposed on the substrate 106 It is done. A second electrode 105
is disposed on the substrate 106 at a position facing the first electrode 102 formed on the
vibrating film 101 with a gap 104 (usually several tens to several hundreds of nm thick)
interposed therebetween. ing.
[0003]
Hereinafter, the surface of the substrate 106 on which the CMUT is formed (upper surface in FIG.
8) is also referred to as a CMUT forming surface, and the opposite surface (lower surface in FIG.
8) is also referred to as a back surface (CMUT non-forming surface). The first and second
electrodes opposed to the vibrating membrane 101 with the gap 104 therebetween are referred
to as a cell 200 as one set. A plurality of cells in which the first electrode 102 and the second
electrode 105 are electrically connected to each other will be referred to as an element 201 as a
unit by which the CMUT transmits and receives elastic waves. The first and second electrodes in
the element are drawn to the outside of the array CMUT by wires 108 and 109 provided outside
the element, respectively. The wirings 108 and 109 drawn to the outer peripheral portion of the
substrate 106 are connected to the DC potential application unit 301 and the drive detection unit
302, respectively. Since the insulating film 107 is disposed on the substrate 106 to insulate the
wiring from the substrate 106, the wirings of the different elements 201 are also electrically
insulated. The direct current potential application unit 301 can apply a direct current potential to
the first electrode (upper electrode) 102 connected via the wiring 108. By setting the first
electrode 102 to a predetermined potential by the DC potential application unit 301, a
predetermined DC potential difference VB is generated between the first electrode 102 and the
opposing second electrode 105. Due to the predetermined potential difference VB between the
electrodes, when the distance between the electrodes changes due to the elastic wave, an induced
current (charge) is generated in the electrodes. Further, an electrostatic attractive force is
04-05-2019
2
generated between the electrodes by the predetermined potential difference VB between the
electrodes, and the vibrating film 101 is bent to the substrate 106 side. As a result, the distance
between the electrodes becomes narrow, so that the transmission / reception efficiency at the
elastic wave transmission / reception operation of the CMUT is enhanced.
[0004]
The drive detection unit 302 includes at least one of an AC voltage application unit that applies
an AC voltage to the electrode and a current detection unit that detects a current generated in
the electrode. Therefore, the drive detection unit 302 can apply an alternating current potential
to the second electrode (lower electrode) 105 connected through the wiring 109 and detect a
generated current. By applying an alternating voltage, an electrostatic attractive force is
generated between the two electrodes, thereby generating vibration and transmitting an elastic
wave. In addition, it is possible to perform an operation of detecting a change in charge (current)
due to a change in capacitance of the vibrating membrane that has received and vibrated the
elastic wave, and detecting the magnitude of the reached elastic wave. Since the substrate 106
has a thickness of about several hundred μm to about mm, it is supported by the support
member 110 on the CMUT non-formed surface in order to maintain alignment during use and
mechanical strength.
[0005]
Knight J, McLean J, and Degertekin F L, 2004 "Low temperature fabrication of capacitive
micromachined ultrasonic immersion transducers on silicon and dielectric substrates" (IEEE
Trans. Ultrason., Ferroelect., Freq. Contr. 51 10 1324-1333)
[0006]
When transmitting and receiving elastic waves in the array CMUT, the elastic waves that have
reached the CMUT and the elastic waves that are transmitted from the CMUT are generated that
enter the support member 110 that supports the substrate 106. When these elastic waves
entering the support member 110 are reflected in the support member 110 and further reach
the CMUT through the substrate 106, they are detected as noise in the received signal of the
CMUT or unnecessary elastic waves from the CMUT. It is output. As a result, the transmission
and reception characteristics of the array CMUT may be degraded.
04-05-2019
3
[0007]
In view of the above problems, the electromechanical transducer according to the present
invention has the following features. This device comprises a cell having a vibrating film
including a first electrode opposite to a second electrode with a gap on a substrate, and an
operation of transmitting an elastic wave by the vibration of the first electrode and At least one
of the reception operation of the elastic wave is performed by receiving the elastic wave and the
first electrode vibrating. The substrate is supported by the support member via spacer means
(such as a foil) such that a spacer gap is formed between the substrate and the support member.
Thus, the spacer gap is formed between the back surface of the substrate opposite to the surface
of the substrate provided with the cells and the surface of the support member opposite thereto.
And, the inside of the spacer gap is kept filled with uniform gas or liquid (that is, constant state).
[0008]
According to the electromechanical transducer of the present invention, since the spacer gap as
described above is formed, it is possible to reduce the elastic wave entering the support member
for supporting the substrate on which the cell is arranged. Deterioration of transmission and
reception characteristics due to reflected elastic waves is suppressed. In particular, in a
capacitive electromechanical transducer having a wide band characteristic, the transmission and
reception characteristics are greatly affected by the elastic wave (which tends to have a relatively
high frequency) reflected in the support member, so that the transmission and reception
characteristics are degraded. The effect of suppressing
[0009]
The figure explaining the electro-mechanical transducer concerning the 1st-4th embodiment. The
figure explaining the electric machine converter concerning a 5th embodiment. The figure
explaining the electric machine converter concerning a 5th embodiment. The figure explaining
the electric machine converter concerning a 6th embodiment. The figure explaining the electric
machine converter concerning a 7th embodiment. The figure explaining the electric machine
converter concerning an 8th embodiment. In the figure explaining the electro-mechanical
transducer concerning a 9th and 10th embodiment. The figure explaining the measuring device
using the electromechanical transducer of the present invention. The figure explaining the
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4
conventional electrostatic capacitance type electromechanical transducer.
[0010]
Hereinafter, embodiments of the present invention will be described. The important point in the
present invention is that a spacer gap is formed between the back surface of the substrate
opposite to the surface of the substrate on which the cells are disposed and the opposite surface
of the support member supporting the substrate. Keep the fluid (gas or liquid) in a constant state.
Based on this idea, the electromechanical transducer of the present invention has the basic
configuration as described in the section for solving the problems.
[0011]
Hereinafter, an embodiment of an electromechanical transducer according to the present
invention will be described in detail with reference to the drawings. However, the
electromechanical transducer according to the present invention is not limited to the specific
form, dimensions, materials, relative positional relationship between elements, etc. of the
following embodiments, and various changes may be made within the scope of the abovementioned scope of the present invention. , Deformation is possible. Moreover, if structurally
possible, it is also possible to appropriately combine the following embodiments. For example,
the structure of FIG. 4 and the structure of FIG. 5 can be combined, or the structure of FIGS. 2-2
and the structure of FIG. 5 can be combined.
[0012]
First Embodiment FIG. 1A is a schematic perspective view showing a first embodiment, and FIG.
1B is a schematic view of a cross section taken along line X-X '. 200 is a cell, 201 is an element,
106 is a substrate, 110 is a support member, 111 is a spacer (here, a thin plate) which is a
spacer means, and 112 is a spacer gap. In FIG. 1A, the wirings 108 and 109 connected to the
element 201 are not shown. The elements 201 of the CMUT are disposed (formed) on the
substrate 106. The substrate 106 on which the CMUT is formed is supported by the support
member 110 via the spacer 111. By using this spacer 111, a spacer gap 112 is formed between
the back surface of the substrate 106 and the opposite surface of the support member 110
opposite thereto. In the spacer gap 112, the fluid (gas or liquid) in the gap can be kept in a
constant state. In the present specification, the state in which the inside of the spacer gap is filled
04-05-2019
5
with a uniform fluid (gas or liquid) is defined as the state kept constant. As described above, in
the present embodiment, the plurality of cells 200 each including the vibration film including the
second electrode 105 and the first electrode 102 provided opposite to each other with the gap
104 interposed therebetween is provided on the substrate 106 At least one of an operation and a
reception operation can be performed. And, the spacer gap 112 kept in a fixed state is between
the back surface of the substrate opposite to the surface of the substrate 106 provided with cells
or elements and the surface of the support member 110 facing the back surface. It is formed.
[0013]
Here, consider the case where an elastic wave has entered into the substrate 106 from the
vertical direction (CMUT formation surface side) of the substrate 106 on which the CMUT is
disposed. The elastic wave is transmitted in the depth direction of the substrate 106 and reaches
the back surface (the surface on which the CMUT is not formed) of the substrate 106. The elastic
wave that has reached the back surface (the surface on which the CMUT is not formed) of the
substrate 106 is divided into an elastic wave reflected by the surface and an elastic wave
transmitted into the member in contact with the surface. When the difference between the
acoustic impedance Z0 of the back surface (the CMUT non-forming surface) of the substrate 106
and the acoustic impedance Z1 of the member facing it is large, the ratio R of reflection on the
CMUT non-forming surface becomes large. This ratio R can be expressed by the following
equation (1). R = (Z1-Z0) / (Z0 + Z1) .. Formula (1)
[0014]
When the difference between the acoustic impedance Z0 on the back surface of the substrate
and the acoustic impedance Z1 on the member in contact with the back surface is small, the ratio
T of penetration (transmission) into the inside of the member in contact with the back surface
increases. This ratio T can be expressed by the following equation (2). T = 2 × Z1 / (Z0 + Z1) (2)
The elastic wave that has entered the member is reflected inside the member, and a part of the
elastic wave returns in the substrate 106. The elastic wave returned into the substrate 106
reaches the CMUT disposed on the substrate 106 and becomes transmission / reception noise.
Thus, it becomes a factor that degrades the transmission and reception characteristics.
[0015]
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6
In the present embodiment, a silicon or glass substrate is used as the substrate 106 for forming
the CMUT. The acoustic impedance is about 20 [MRayl] for single crystal silicon and about 10 to
20 [MRayl] for glass. On the other hand, the acoustic impedance of the fluid which is a member
in contact with the back surface of the substrate is 2 [MRayl] or less. In the present invention, a
fluid is used as a member in contact with the back surface (the CMUT non-formed surface) of the
substrate 106, and the acoustic impedance has a smaller value than the acoustic impedance of
the substrate 106. Therefore, most of the elastic wave that has entered the substrate 106 is
reflected by the CMUT non-formed surface and is hardly transmitted to the members after the
CMUT back surface (that is, disposed below each part in FIG. 1). Therefore, it is possible to
reduce the elastic wave returned to the CMUT by the reflection in the member after the back
surface (CMUT non-forming surface). That is, deterioration of the transmission and reception
characteristics of the CMUT due to the reflected waves in the members after the back surface can
be reduced.
[0016]
The spacer 111 of the present embodiment can be easily formed of metal, resin or the like. The
spacer 111 is fixed between the back surface of the substrate 106 (the surface on which the
CMUT is not formed) and the support member 110 via an adhesive or the like. The height of the
spacer 111 defines a gap between the back surface (CMUT non-forming surface) and the support
member 110. The height of the gap needs to be at least a certain percentage of the wavelength of
the upper limit frequency to be used (minimum wavelength) from the viewpoint of reliably
reflecting the elastic wave on the back surface (the surface on which the CMUT is not formed). .
Specifically, the height of the spacer 111 is preferably at least one sixteenth of the length of the
wavelength of the upper limit frequency to be used. Further, by using the spacer 111, the area of
the solid in contact with the back surface (the CMUT non-forming surface) of the substrate 106
can be minimized, so the elastic wave transmitted from the back surface (CMUT non-forming
surface) to the support member 110 is It can be reduced. That is, even if elastic waves enter the
support member 110 from the portion of the spacer 111 and reflect within the support member
110, the amount of return to the substrate 106 can be minimized. Further, in the present
embodiment, the spacer gap 112 is formed between the substrate 106 and the support member
110 by using the spacer 111. By using the spacer 111, the spacer gap 112 can be easily formed,
and the height of the spacer gap 112 can be accurately defined. Further, as compared with the
configuration in which the substrate 106 is supported by the support member 110 on the entire
surface, the occurrence of warpage due to the difference in thermal expansion coefficient
between the substrate 106 and the support member 110 can be reduced.
[0017]
04-05-2019
7
In this embodiment, in order to keep the state of the fluid in the spacer gap 112 constant, as
shown in the schematic view of FIG. 1C, the spacer gap 112 is surrounded by the spacer 111 and
the sealing material 113. , And the spacer gap 112 can be sealed. Thus, gas or liquid is enclosed
in the spacer gap. As the sealant 113, an adhesive including an epoxy resin adhesive can be used.
Other than that, metals, rubber, other synthetic resins, and the like can be used as long as they
can maintain the fluid in the spacer gap 112 in a certain state.
[0018]
The thickness of the substrate 106 in the present embodiment can be determined in
consideration of the frequency and the like when the elastic wave that has entered the substrate
106 is reflected by the back surface (the surface without CMUT) of the substrate 106. When the
wavelength λ of the elastic wave in the substrate 106 is an integral multiple of the substrate
thickness t, the transmission and reception characteristics are easily affected. Therefore, the
substrate thickness t is the upper limit wavelength (minimum wavelength) of the used frequency
band. It should be determined in consideration of the length λ. Thus, the higher the frequency
used, the thinner the substrate 106 will be used. For example, when the speed of sound in the
substrate is 6000 (m / sec) and the upper limit of the frequency to be used is 10 MHz, the
thickness t of the substrate 106 needs to be 300 μm or less. Furthermore, in the case of using a
high frequency of 15 MHz, it is necessary to make the thickness t of the substrate 106 thinner
than 200 μm or less.
[0019]
In the present embodiment, the substrate 106 is supported by the support member 110 using
the spacer 111. Therefore, even when the substrate 106 having a thin substrate thickness is
used, the mechanical strength of the substrate 106 can be maintained by the support member
110 and the spacer 111. Therefore, it is possible to provide a capacitive electromechanical
transducer in which mechanical deformation hardly occurs even when an external force is
applied to the portion supporting the substrate 106 by the spacer, and the transmission and
reception characteristics of the CMUT on the substrate hardly change. It can. Further, in the
structure of FIG. 1C, the sealing member 113 is configured to keep the fluid in the spacer gap
112 between the substrate 106 and the support member 110 in a constant state. Therefore, gel,
oil and the like that may be used around the array CMUT will not enter into the spacer gap 112.
Thus, the state of the substance in contact with the back surface (the CMUT non-forming surface)
04-05-2019
8
of the substrate 106 can be kept constant without changing, and an electromechanical
transducer can be provided in which transmission and reception characteristics are less affected
by the environment used. The support member 110 of this embodiment can be used as long as it
can support the substrate 106, such as a printed circuit board (PWB, PCB), a flexible substrate
(FPC), a resin material, a metal material, glass, etc. .
[0020]
Second Embodiment Next, a second embodiment will be described. The second embodiment
relates to the fluid in the spacer gap 112. Other than that, it is the same as the first embodiment.
The present embodiment is characterized in that the fluid in the spacer gap 112 is a gas. First,
the configuration in which the fluid in the spacer gap 112 is decompressed with respect to the
atmospheric pressure will be described. By reducing the pressure with respect to the
atmospheric pressure, the acoustic impedance Zg in the spacer gap 112 can be made smaller
than the acoustic impedance Z0 of the substrate 106 to a value of 5 digits or less (1 / 10th
power or less). it can. The degree of pressure reduction may be any as long as it is below
atmospheric pressure. By reducing the pressure of the entire electromechanical transducer with
a vacuum pump or the like and sealing the spacer gap 112, it can be easily maintained in a fixed
state. Thus, in the present embodiment, the inside of the spacer gap 112 is maintained in a state
of being decompressed with respect to the atmospheric pressure. Therefore, it is possible to
provide an electromechanical transducer which is less in deterioration of transmission /
reception characteristics due to elastic waves reflected in the support member 110 disposed on
the back surface (the surface on which no CMUT is formed) of the substrate 106.
[0021]
As a modification of the present embodiment, there is a configuration in which the spacer gap
112 is filled with a gas. As the gas to be charged, any gas such as nitrogen, argon, carbon dioxide
gas, air or the like can be used, but an inert gas is more preferable. As a method of holding the
gas in the spacer gap 112, by performing sealing using the sealing member 113 in the
atmosphere of gas, it can be easily held in a constant state. By sealing the gas in the spacer gap
112, the acoustic impedance of the gas has a value lower by about five digits as compared to the
acoustic impedance Zg of the substrate 106, so the elastic wave is generated on the back surface
(CMUT non-forming surface) of the substrate 106. Easy to cut Further, sealing can be performed
more easily than in the configuration in which the pressure is reduced, and furthermore, the
configuration to be sealed can be simplified and the configuration can be highly reliable. Further,
since the spacer gap 112 is filled with a gas, even when an external force is applied to the
04-05-2019
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substrate 106, the substrate 106 is unlikely to be bent, and the influence of the bending of the
substrate on the transmission and reception characteristics is not easily produced.
[0022]
Third Embodiment Next, a third embodiment will be described. The third embodiment relates to
the fluid in the spacer gap 112. Other than that, it is the same as the first embodiment. The
present embodiment is characterized in that the fluid in the spacer gap 112 is a liquid. By using a
liquid, the acoustic impedance Zg in the spacer gap 112 can be reduced to about one tenth of the
value of the substrate 106. As the liquid, any liquid such as water or oil can be used. As a holding
method, there is a method in which the inside of the spacer gap 112 is filled with a liquid and
then sealing is performed using the sealing member 113. Alternatively, a mechanism may be
used in which the spacer gap 112 is always filled with liquid.
[0023]
In the present embodiment, the inside of the spacer gap 112 is kept filled with liquid. Therefore,
as compared with the case where the inside of the spacer gap 112 is sealed with gas (the second
embodiment), the volume change of the fluid when the environmental temperature changes is
smaller. Therefore, even when the environmental temperature changes, the fluid is unlikely to
stress the substrate 106. In addition, since the liquid in the spacer gap 112 can move freely, the
difference in thermal expansion coefficient between the substrate 106 or the support member
110 and the resin is greater than the case where the spacer gap 112 is filled with resin or the
like and fixed. It is hard to generate stress. Therefore, there is little degradation of transmission /
reception characteristics due to elastic waves reflected in the support member 110 disposed on
the back surface (the surface without CMUT formation) of the substrate 106, and an
electromechanical transducer is provided that the substrate 106 does not easily deform You can
do it.
[0024]
Fourth Embodiment Next, a fourth embodiment will be described. The fourth embodiment relates
to a region in which the spacer 111 is disposed. Other than that is the same as any of the first to
third embodiments. The present embodiment is characterized in that the spacer 111 is not
disposed on the back side of the substrate (the surface on which the CMUT is not formed) in the
04-05-2019
10
area where the element 201 is disposed. As can be seen from FIG. 1B, as viewed in the thickness
direction of the substrate 106, the region in which the spacer 111 is disposed is disposed so as
not to overlap the region in which the element 201 is disposed. Therefore, the fluid filled in the
spacer gap 112 is always in contact with the back side of the substrate in the area where the
element 201 is disposed. Here, it is assumed that an elastic wave enters the support member 110
via the spacer 111, reflects inside, and returns to the inside of the substrate 106 again via the
spacer 111, and there is an elastic wave. However, as seen from the thickness direction of the
substrate 106, the element 201 is not disposed on the spacer 111, so that the rate at which the
elastic wave returned to the substrate 106 affects the CMUT transmission and reception
characteristics of the element is reduced. it can.
[0025]
As described above, in the present embodiment, the spacer 111 is provided on the back surface
(the surface on which no CMUT is formed) of the area of the substrate 106 where the element
201 is not disposed. Therefore, it is possible to provide an electromechanical transducer which is
less in deterioration of transmission / reception characteristics due to elastic waves reflected in
the support member 110 disposed on the back surface (the surface on which no CMUT is
formed) of the substrate 106.
[0026]
Fifth Embodiment Next, a fifth embodiment will be described with reference to FIGS. 2-1 and 2-2.
The fifth embodiment relates to a region in which the spacer 111 is disposed. Other than that is
the same as the fourth embodiment. The present embodiment is characterized in that the spacer
111 is provided on the back surface of the substrate (the surface on which no CMUT is formed)
in the area where the wirings 108 and 109 provided outside the element 201 are disposed.
[0027]
FIG. 2A is a schematic view of a cross section for explaining the present embodiment. In the array
CMUT, wires 108 and 109 are used to connect the element 201 with the DC potential application
means 301 and the drive detection means 302 (see FIG. 8). In order to arrange these wires 108
and 109, the elements 201 are arranged on the substrate 106 at regular intervals. According to
this embodiment, the spacer 111 is disposed on the back surface (the surface on which the
04-05-2019
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CMUT is not formed) of the region 202 in which the wires 108 and 109 are disposed. That is, as
viewed from the thickness direction of the substrate 106, the region in which the spacer 111 is
disposed is not included in the region in which the element 201 is disposed. Therefore, even if
there is an elastic wave returned from the support member 110 to the substrate 106 via the
spacer 111, the rate of affecting the transmission and reception characteristics of the CMUT can
be reduced. Further, since a plurality of spacers 111 can be dispersedly arranged in the CMUT
array, the strength for supporting the substrate 106 can be enhanced simultaneously, and the
configuration can be made stronger against external force. As described above, in the present
embodiment, a cell connected to the first electrode or the second electrode and used to exchange
electric signals for transmission and reception with the outer peripheral portion of the substrate
106 serves as a unit for performing transmission and reception. Are disposed on the substrate
between the plurality of elements including A spacer 111, which is a spacer means, is disposed in
the area on the back surface of the substrate on the back side of the area of the substrate 106 on
which the wiring is disposed.
[0028]
As a modified example of the present embodiment, a plurality of linear spacers 111 can be
arranged at the same interval as the arrangement interval of the elements 201 or at intervals
(but shifted) of multiple times thereof. FIG. 2B is a schematic view explaining the linear spacer
111, and FIG. 2C is a schematic view of a cross section along the line X-X '. In FIG. 2-1 (b), the
substrate 106 and the support member 110 are separately illustrated so that the structure of the
spacer 111 can be easily confirmed. The elements 201 are two-dimensionally arranged at equal
intervals, and the wires 108 and 109 are drawn out in one direction (not shown in FIG. 2B). The
linear spacers 111 are arranged on the back surface of the substrate in the wiring area arranged
between the elements 201 at the same intervals as the arrangement intervals of the elements. In
this embodiment, by using the linear spacers 111, the spacer gaps 112 are arranged in a line. By
filling the fluid (in particular, liquid) from one direction of the spacer gap 112, it is possible to fill
the entire spacer gap with the fluid to be filled while pushing out the fluid already present in the
gap. In other words, the fluid guiding function of the spacer 114 can easily fill the inside of the
spacer gap with the desired fluid without the other fluid (eg, gas inside the liquid, etc.) remaining
in the spacer gap. Can be combined. Thus, the electric machine has a guide function of filling the
spacer gap 112 with a fluid, and less deterioration in transmission / reception characteristics due
to elastic waves reflected in the support member 110, and the substrate 106 is less likely to be
deformed by external force. A converter can be provided.
[0029]
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Further, as shown in FIGS. 2D and 2E, the linear spacers 111 may be arranged at intervals of
integral multiples of the arrangement intervals of the elements 201. As a result, the function of
supporting and strengthening the substrate 106 and the function of guiding the fluid into the
spacer gap 112 can be compatible while reducing the number of the spacers 111 used.
[0030]
Sixth Embodiment Next, a sixth embodiment will be described with reference to FIG. The sixth
embodiment relates to the spacer 111. Other than that is the same as the fourth or fifth
embodiment. FIG. 3 is a view for explaining the spacer 111 of the present embodiment, and the
substrate 106 and the support member 110 are separated and described so that the structure of
the spacer 111 can be easily confirmed. Although only the two-dimensionally arranged elements
201 are described on the substrate 106 of FIG. 3, wiring from the elements is also provided. The
present embodiment is characterized in that the spacer 111 doubles as the sealing member 113.
The shape of the spacer 111 is along the outer peripheral portion of the back surface (the
surface on which the CMUT is not formed) of the substrate 106. Therefore, the fluid is easily
sealed in the spacer gap 112 by fixing (e.g., bonding) the substrate 106 to the spacer 111
previously fixed (e.g., bonded) to the support member 110 in a certain fluid atmosphere. can do.
Further, by using a resin or the like having an adhesive effect for the spacer 111 itself, the
process of sealing the fluid can be further simplified. This configuration can be easily realized by
using a thermosetting resin, a UV curing resin, or the like as this resin.
[0031]
In this embodiment, since the spacer 111 doubles as the sealing member 113 (see FIG. 1C), the
electromechanical conversion has few components and there is little deterioration in
transmission / reception characteristics due to elastic waves reflected in the support member
110. It can provide the device.
[0032]
Seventh Embodiment Next, a seventh embodiment will be described with reference to FIG.
The seventh embodiment relates to the form of the spacer 111 which is a spacer means. Other
than that is the same as any of the first to sixth embodiments. In FIG. 6, reference numeral 115
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denotes a substrate having a spacer structure or means. The present embodiment is
characterized in that a part of the back surface (CMUT non-forming surface) of the substrate 115
on which the CMUT is disposed has a spacer structure.
[0033]
A groove 116 is formed on the back surface of the substrate 115 (the surface on which the
CMUT is not formed), and the protrusion along the edge of the groove 116 without the groove
116 functions as a spacer means. The groove 116 can be easily formed by dry etching or wet
etching using MEMS technology. It can also be formed using machining techniques. In the
present embodiment, since the substrate 115 doubles as the function of the spacer means, the
number of components can be reduced. Further, since the groove 116 is formed in the substrate
115 to form the spacer gap 112, the height from the CMUT formation surface to the back
surface (CMUT non-formation surface) can be defined with the thickness accuracy of the
substrate 115. Therefore, the heights of the surface of the support member 110 and the surface
of the substrate 115 can be accurately defined, and the height deviation of the surface of the
CMUT with respect to the surface of the support member 110 is less likely to occur. In addition,
when silicon is used for the substrate 115, the substrate 115 easily conducts heat to the support
member 110. Therefore, even when the element portion or the wiring portion generates heat, the
heat is easily dissipated, and the heat generation becomes transmission / reception
characteristics. Hard to affect.
[0034]
As described above, in the present embodiment, the back surface (CMUT non-forming surface) of
the substrate on which the CMUT is disposed has a spacer structure. Therefore, it is possible to
provide an electromechanical transducer in which the height deviation of the CMUT surface with
respect to the support member 110 is small, and the deterioration of the transmission /
reception characteristics due to the elastic wave reflected in the support member 110 is small.
[0035]
Eighth Embodiment Next, an eighth embodiment will be described with reference to FIG. The
eighth embodiment relates to the form of the spacer 111. Other than that is the same as any of
the first to seventh embodiments. In FIG. 5, reference numeral 117 denotes a support member
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having a spacer structure or means. The support member 117 has a groove 118 formed on the
surface, and supports the substrate 106 provided with the CMUT at the surface where the groove
118 is not formed (ie, the protrusion of the support member along the edge of the groove 118).
It has a structure. The groove 118 can be easily manufactured using a mold when the support
member 117 is molded and manufactured. Alternatively, the groove 118 may be formed by
machining the surface of the support member 117.
[0036]
In the present embodiment, since the support member 117 also functions as a spacer, the
number of components can be reduced. Further, since the groove 118 is formed in the support
member 117 to form the spacer gap 112, the height from the CMUT formation surface to the
back surface (CMUT non-formation surface) can be defined with the thickness accuracy of the
substrate 106. Therefore, the heights of the surface of the support member 117 and the surface
of the substrate 106 can be accurately defined, and the height deviation of the surface of the
CMUT with respect to the surface of the support member 117 is less likely to occur. In addition,
when silicon is used for the substrate 106, the substrate 106 easily conducts heat to the support
member 110. Therefore, even if the element portion or the wiring portion generates heat, the
heat is easily dissipated, and the heat generation becomes transmission / reception
characteristics. Hard to affect. In addition, since the groove 118 is formed in the support member
117, the groove can be relatively easily made deeper and the wide spacer gap 112 can be easily
formed compared to the case where the substrate 115 is provided with the spacer function as in
the seventh embodiment. can do. Therefore, filling of the fluid into the spacer gap 112 can be
facilitated, and fabrication can be performed in a simpler process.
[0037]
As described above, in the present embodiment, the support member 117 of the substrate 106
on which the CMUT is disposed has a spacer structure. Therefore, an electromechanical
transducer can be provided in which the height deviation of the CMUT surface with respect to
the support member 117 is small, and the frequency characteristic deterioration due to the
elastic wave reflected in the support member 117 is small.
[0038]
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Ninth Embodiment Next, a ninth embodiment will be described using FIG. 6 (a). The ninth
embodiment relates to the form of sealing. Other than that, it is the same as any of the first to
eighth embodiments. In FIG. 6A, reference numeral 121 denotes a fluid inlet, and reference
numeral 122 denotes a fluid outlet. In the present embodiment, the spacer gap 112 is covered
except for the fluid injection hole 121 and the fluid extraction hole 122. When the fluid is
injected into the spacer gap 112, the fluid is poured from the fluid injection hole 121 into the
spacer gap 112. At this time, the fluid that has already been in the spacer gap 112 is pushed out
of the fluid extraction hole 122 to the outside of the spacer gap 112. After filling the spacer gap
112 with the desired fluid, the injection hole 121 and the withdrawal hole 122 can be sealed to
keep the state of the fluid in the spacer gap 112 constant.
[0039]
In this embodiment, since the inlet (121) for injecting into the spacer gap 112 and the outlet
(122) for coming out of the gap are provided separately, there is no fluid remaining in the spacer
gap 112, Fluid filling can be performed. Further, in the case of sealing, since the area to be sealed
can be small, the spacer gap 112 can be sealed in a simpler process. As described above, the
present embodiment has the injection hole 121 for injecting a gas or liquid into the spacer gap
and the extraction hole 122 for removing the gas or liquid from the spacer gap. Therefore,
reliable filling of the fluid into the spacer gap 112 can be performed in an easy manner, and the
electromechanical transducer can be provided with less deterioration of transmission / reception
characteristics due to elastic waves reflected in the support member 110.
[0040]
Tenth Embodiment Next, a tenth embodiment will be described using FIG. 6 (b). The tenth
embodiment relates to the form of sealing. Other than that is the same as any one of the first to
ninth embodiments. In FIG. 6 (b), 123 is a valve. The present embodiment is characterized in that
a valve 123 is provided between the spacer gap 112 and the outside. The valve 123 has a
function to discharge the fluid in the spacer gap to the outside of the gap when the pressure in
the spacer gap 112 exceeds a certain level, and the pressure in the spacer gap is set by the valve
123. Does not exceed a certain value. The fluid may expand due to a change in ambient
temperature or the like, causing the pressure in the spacer gap 112 to rise too much and
stressing the substrate 106. However, the pressure in the spacer gap is maintained at a
substantially constant value by the presence of the pressure valve 123 for adjusting the pressure
in the spacer gap, and the transmission and reception characteristics of the CMUT can be
prevented from changing.
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[0041]
The valve 123 can be used as long as the pressure within the spacer gap 112 can be reduced
when the pressure in the spacer gap 112 exceeds a certain value, and a pressure valve
manufactured using MEMS technology Or the like may be used. In that case, a MEMS pressure
valve can be integrally formed in the substrate 106 on which the CMUT is formed, in which case
the number of components can be reduced. As described above, since the present embodiment
includes the valve 123 that adjusts the upper limit of the pressure in the spacer gap 112, the
influence of the transmission and reception characteristics on the volume change of the fluid can
be reduced. Therefore, it is possible to provide an electromechanical transducer capable of
reducing the influence of the pressure change in the spacer gap 112 on the transmission and
reception characteristics and the deterioration of the transmission and reception characteristics
due to the elastic wave reflected in the support member 110.
[0042]
Eleventh Embodiment Next, an eleventh embodiment will be described using FIG. 7A. The
eleventh embodiment relates to an ultrasonic measurement apparatus using the
electromechanical transducer according to any of the first to tenth embodiments. In FIG. 7A,
reference numeral 402 denotes an object to be measured, 403 denotes a capacitive type
electromechanical transducer, 404 denotes an image information generating device, and 405
denotes an image display. Reference numerals 501 and 502 denote ultrasonic waves, 503
denotes ultrasonic wave transmission signal information, 504 denotes an ultrasonic wave
reception signal, 505 denotes reproduced image information, and 400 denotes an ultrasonic
measurement device.
[0043]
The ultrasonic wave 501 output from the electromechanical transducer 403 toward the
measurement object 402 is reflected on the surface of the measurement object 402 due to the
difference in specific acoustic impedance at the interface. The reflected ultrasonic wave 502 is
received by the electromechanical transducer 403, and information on the size, shape, and time
of the received signal is sent to the image information generator 404 as information on the
ultrasonic wave received signal 504. On the other hand, information on the size, shape, and time
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of transmission ultrasonic waves is sent from the electromechanical transducer 403 to the image
information generation device 404 as ultrasonic transmission signal information 503. The image
information generation device 404 generates an image signal of the measurement object 402
based on the ultrasonic wave reception signal 504 and the ultrasonic wave transmission signal
information 503, sends it as the reproduction image information 505, and displays it on the
image display 405.
[0044]
The CMUT described in any of the above embodiments is used for the electromechanical
transducer 403 of this embodiment. Accordingly, since the deterioration of the transmission and
reception characteristics due to the ultrasonic wave reflected in the support member 110 is
small, the transmission and reception operation having the good characteristics can be
performed. Therefore, since more accurate information of the ultrasonic wave 502 reflected by
the measurement object 402 can be obtained, the image of the measurement object 402 can be
reproduced more accurately. The present embodiment is not limited to the above-described
configuration, and as shown in FIG. 7B, another ultrasonic wave transmitter (elastic wave
transmitter) 401 and an electromechanical transducer 403 of the present invention. It may be a
combination of both.
[0045]
In this specification, the first electrode (upper electrode) 102 of the element is connected to the
DC potential application means 301 by the wiring 108, and the second electrode (lower
electrode) 105 of the element is detected by the wiring 109. A configuration in which the
connection is made with 302 is described. The present invention is not limited to this
configuration, and the first electrode (upper electrode) 102 is connected to the drive detection
means 302, and the second electrode (lower electrode) 105 is connected to the DC potential
application means 301. Applicable Further, although the configuration in which the insulating
film 107 is disposed over the substrate 106 is described in this specification, the present
invention is not limited to this. The present invention can also be applied to a configuration in
which the insulating film 107 over the substrate 106 is in a partial region or a configuration in
which the substrate 106 has the function of the second electrode 105 by using a low resistance
for the substrate 106.
[0046]
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101 · · Vibrating film, 102 · · First electrode (upper electrode) 104 · · · Gap 105 · · Second
electrode (lower electrode) 106 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · Gap, 200 · · cells
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