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JP2018110282

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DESCRIPTION JP2018110282
Abstract: PROBLEM TO BE SOLVED: To provide a manufacturing method of a capacitance
transducer in which a decrease in sensitivity and variation are reduced by accurately confirming
that etching of a sacrificial layer is completed. A method of manufacturing a capacitive
transducer in which a gap is formed by removing a sacrificial layer, and etching is performed
until it is accurately confirmed that etching has been completed. [Selected figure] Figure 3
Capacitance transducer and method of manufacturing the same
[0001]
The present invention relates to a capacitive transducer and a method of manufacturing the
same.
[0002]
Heretofore, micromachine components manufactured by micromachining technology can be
processed on the order of micrometers, and various microfunctional devices are realized using
these.
Capacitive micromachined ultrasonic transducers (CMUTs), which are capacitive transducers
using micromachining technology, are being investigated as alternatives to piezoelectric
elements. The CMUT makes it possible to transmit or receive ultrasound using the vibration of
the vibrating membrane, and in particular to obtain excellent broadband characteristics in liquid.
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1
[0003]
One example of a CMUT is configured to include a plurality of elements, and each element is
configured to include a plurality of cells. Each cell includes a gap that allows vibration, which can
be formed by etching the sacrificial layer through the etch holes. After etching, sealing is
performed by filling the etching holes. In order to suppress cell-to-cell variations, it is desirable to
sufficiently seal the etching holes in any cell.
[0004]
Patent Document 1 discloses a configuration of a CMUT having a sensor cell and a dummy cell
used for transmission and reception of ultrasonic waves on a substrate, and a method of
manufacturing a CMUT by forming a gap by etching a sacrificial layer. Further, Patent Document
1 discloses that a dummy cell is used to confirm that the etching of the sacrificial layer is
completed. That is, although the sensor cell has the upper electrode above the gap (cavity) and
the lower electrode below, the dummy cell has only the lower electrode, so the end of etching of
the sacrificial layer when forming the gap is confirmed from the side without the upper
electrode. Can.
[0005]
JP, 2008-085246, A
[0006]
However, in the method of Patent Document 1, it may be difficult to accurately determine
whether the etching of the sensor cell is completed.
That is, when the conditions relating to the etching speed are different between the dummy cell
and the sensor cell, it may occur that the etching of the sensor cell is not completed even though
the etching of the dummy cell is completed.
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[0007]
If the completion of etching can not be confirmed accurately, the surface roughness inside the
cell may increase due to overetching, or the size of the cell diameter, membrane thickness, gap
thickness, etc. may change, and the transmission / reception sensitivity (performance) may
change. Sometimes.
[0008]
Therefore, an object of the present invention is to provide a method of manufacturing a
capacitance transducer in which the decrease in sensitivity and the variation are reduced by
accurately confirming that the etching of the sacrificial layer is completed.
[0009]
A method of manufacturing a capacitive transducer according to the present invention comprises
the steps of: providing a sacrificial layer in a stacking direction on a first electrode; providing an
insulating film in the stacking direction on the sacrificial layer; Providing a second electrode on
the surface in a direction smaller than the region where the sacrificial layer is provided in the inplane direction orthogonal to the stacking direction, and etching the sacrificial layer; A method of
manufacturing a capacitive transducer, comprising the step of: etching the first portion of the
sacrificial layer provided outside the region where the second electrode is provided in the inplane direction. Etching is started from the position, and the etching is performed until etching of
the second position of the sacrificial layer farthest from the first position is completed.
[0010]
Another method of manufacturing a capacitive transducer according to the present invention is a
method of manufacturing a capacitive transducer including an element configured to include a
plurality of cell structures, in a stacking direction on a first electrode. Providing a plurality of
sacrificial layer regions so as to form an independent cavity for each cell structure, providing an
insulating film in the stacking direction on the sacrificial layer region, and stacking the stacking
direction on the insulating film. Providing the second electrode in a region smaller than the
region where the insulating film is provided in the in-plane direction orthogonal to the stacking
direction, removing the sacrificial layer region, and Providing the independent cavity for each
structure, and the etching step is performed by setting the number of the sacrificial layer
provided outside the region where the second electrode is provided in the in-plane direction. One
Start the laid et etching until said second position of the etching of the first farthest the sacrificial
layer from the position is completed, it is a step of etching, characterized by.
[0011]
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In still another method of manufacturing a capacitive transducer according to the present
invention, a step of providing a sacrificial layer on a first electrode, a step of providing an
insulating film on the sacrificial layer, and a step of providing on the insulating film A step of
providing a second electrode, a step of providing an etching hole for etching the sacrificial layer
in the insulating film, and a step of forming a gap by etching the sacrificial layer through the
etching hole; A method of manufacturing a capacitive transducer, comprising an etching
confirmation portion for confirming etching in addition to the etching hole.
[0012]
Further, in the electrostatic capacitance type transducer according to the present invention, there
is provided an electrostatic sensor having a cell on which a vibrating membrane including one of
a pair of electrodes provided so as to sandwich a gap on a substrate is vibratably supported. In
the capacitive transducer, the gap has at least one or more etching confirmation parts, and from
the distance between the end of the etching hole and the end of the cell to the end of the etching
hole and the end of the etching confirmation part Is longer than at least a part of the etching
confirmation part is not sandwiched between the pair of electrodes.
[0013]
According to the method of manufacturing a capacitive transducer according to the present
invention, it can be accurately confirmed that the etching of the sacrificial layer is completed.
[0014]
It is a top perspective view of CMUT which concerns on Embodiment 1 of this invention, and is
an AB sectional view of FIG.
It is sectional drawing of CMUT which concerns on Embodiment 1 of this invention.
It is a figure for demonstrating the manufacturing method of CMUT which concerns on
Embodiment 1 of this invention.
It is CMUT (AB sectional drawing of FIG. 1) which concerns on Embodiment 2 of this invention.
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It is a top perspective view of CMUT which concerns on Embodiment 3 of this invention.
It is a figure explaining a mode that the etching which removes the sacrificial layer of CMUT
which concerns on Embodiment 1 of this invention advances.
It is a figure of another form of protrusion shape of the etching confirmation part of CMUT which
concerns on Embodiment 1 of this invention.
It is a figure of another form of CMUT which concerns on Embodiment 1 of this invention. It is a
figure of another form of CMUT which concerns on Embodiment 1 of this invention. It is a figure
of another form of CMUT which concerns on Embodiment 1 of this invention. It is a figure of
another form of CMUT which concerns on Embodiment 1 of this invention. It is a figure of
another form of CMUT which concerns on Embodiment 1 of this invention.
[0015]
Hereinafter, although a capacitive transducer (CMUT) concerning an embodiment of the present
invention is explained, the present invention is not limited to these.
[0016]
The manufacturing method of CMUT which concerns on this embodiment has at least each
following process.
It demonstrates using FIG. 1, 3. FIG. (1) A step of providing a sacrificial layer in the stacking
direction on the first electrode. (2) A step of providing an insulating film in the stacking direction
on the sacrificial layer. (3) A step of providing the second electrode on the insulating film so as to
be smaller than the region where the sacrificial layer is provided in the in-plane direction
orthogonal to the stacking direction. (4) Step of etching the sacrificial layer.
[0017]
In FIGS. 1 and 3, the first electrode is 6, the sacrificial layer is 15, the insulating film is 9, the
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second electrode is 10, the stacking direction is the vertical direction of the paper surface, and
the in-plane direction is the horizontal direction of the paper surface. The insulating film 9 can be
reworded as a membrane (the same applies hereinafter).
[0018]
Then, in the etching step, etching is started from the first position of the sacrificial layer provided
outside the region where the second electrode is provided in the in-plane direction. Then, the
etching is performed until the etching of the second position of the sacrificial layer farthest from
the first position is completed.
[0019]
Here, the first position is a position in the sacrificial layer which appears by forming 16 etching
holes, and is a position where etching is started. The second position is the position farthest from
the first position among the 14 etching confirmation parts.
[0020]
Since the second position is the farthest from the first position, once the etching of the second
position is completed, the etching of the other sacrificial layer regions is also completed, so that
the etching timing of the sacrificial layer can be accurately grasped. it can. As a result, it is
possible to reduce the decrease in sensitivity and the variation in each cell.
[0021]
In addition, a step of providing a first insulating film may be provided between the step of
providing the first electrode and the step of providing the sacrificial layer.
[0022]
Further, the first insulating film preferably has a silicon oxide film, and the insulating film
preferably has a silicon nitride film.
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The first electrode can be provided on a substrate, and a silicon substrate can be used as the
substrate.
[0023]
Furthermore, the method may further include the step of providing a third insulating film on the
substrate, and the step of providing the first electrode may be a step of providing the first
electrode on the third insulating film. The third insulating film preferably includes a silicon oxide
film.
[0024]
The shape in the in-plane direction of the sacrificial layer may be configured to have the same
shape as that of the second electrode and a shape in which a protrusion is added. In addition, the
shape in the in-plane direction of the sacrificial layer may be configured to have the same shape
as that of the second electrode and a shape in which a protrusion is added. The shape of the
projection in the in-plane direction may be a configuration having at least one shape of a
rectangle, a circle, and a triangle.
[0025]
The method of manufacturing a capacitive transducer according to this embodiment is a method
of manufacturing a capacitive transducer including an element configured to include a plurality
of cell structures, and includes at least the following steps. (1) A step of providing a plurality of
sacrificial layer regions so as to be independent cavities for each cell structure in the stacking
direction on the first electrode. (2) A step of providing an insulating film in the stacking direction
on the sacrificial layer region. (3) A step of providing the second electrode in the stacking
direction on the insulating film so as to be smaller than the region where the insulating film is
provided in the in-plane direction orthogonal to the stacking direction. (4) removing the
sacrificial layer region and providing an independent cavity for each cell structure.
[0026]
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And the process to etch starts etching from the 1st position of the said sacrificial layer provided
in the outer side of the area ¦ region in which the said 2nd electrode is provided regarding the
said in-plane direction. Then, the etching is performed until the etching of the second position of
the sacrificial layer farthest from the first position is completed.
[0027]
The first position is preferably configured to be shared by a plurality of cells.
[0028]
First Embodiment (Configuration of CMUT) The configuration of a CMUT according to the
present embodiment will be described using FIGS. 1 and 2.
[0029]
FIG. 2 shows a cross-sectional view of the CMUT.
The cell 2 includes a substrate 4, a third insulating film 5 provided on the substrate 4, a first
electrode 6 formed on the third insulating film 5, and a first insulating film 7 on the first
electrode 6. Have.
Furthermore, a vibrating film 12 is formed of the second insulating film 9, the second electrode
10, and the sealing film 11, and the vibrating film support 13, the gap 8, and the etching check
14 have. The vibrating membrane support 13 has a portion including the second electrode 10
and a portion not including the second electrode 10 for wiring extraction. When the substrate 4
is an insulating substrate such as a glass substrate, the third insulating film 5 may be omitted.
The shape of the gap 8 viewed from the top is circular, and the shape of the vibrating part is
circular, but may be square, rectangular or the like.
[0030]
FIG. 2 is a cross-sectional view taken along line A-B of FIG. For the sake of clarity, only the main
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part is clearly stated. One element 3 is provided on a substrate 4, and the elements 3 are formed
by arranging a plurality of cells 2 in an array (cell group). The cell 2 is composed of a film (s) to
be described later and an electrode (pair), and has an etching confirmation portion 14 and a gap
8. Each gap 8 in the cell 2 is formed by etching through one etching hole 16 for etching a
sacrificial layer described later. Each etching confirmation portion 14 is arranged such that the
distance D between the end of etching hole 16 and the end of etching confirmation portion 14 is
longer than the distance C between the end of etching hole 16 and the end of gap 8. . In addition
to the etching holes, an etching confirmation portion for confirming etching is provided by
providing a region in which a gap is not sandwiched between the first electrode and the second
electrode.
[0031]
Further, the etching confirmation portion 14 has a projecting shape with respect to the gap 8 in
the in-plane direction of the substrate 4. The protrusion shape is easier to visually recognize
etching as described later. The portion of the etching confirmation portion 14 which
communicates with the cell 2 is preferably elongated or tapered. If this is not the case, the
strength of the diaphragm supporting portion 13 described later is affected, and the vibration
characteristics of the diaphragm may be changed, which may lead to a decrease in transmission /
reception sensitivity. The shape of the projections of the etching confirmation portion 14 may be,
for example, shapes as shown in FIGS. 7 (a) to 7 (d). If visibility is to be improved, FIGS. 7B and
7C are desirable. The size of the etching confirmation portion 14 is desirably about 1/100 or less
of the size of the cell 2. Therefore, the size of the etching confirmation unit 14 is desirably a size
that does not lead to a decrease in transmission / reception sensitivity.
[0032]
In FIG. 1, the etching holes are respectively provided at positions equidistant from the center of
the gap of the cell, and the etching holes are formed in the gap so that the etching holes for
individual etching are not provided.
[0033]
In addition, a gap is formed between the first electrode and the first electrode so that the area of
the first electrode is larger than the area of the gap in FIG.
[0034]
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(Driving Principle of CMUT) Here, the driving principle of the CMUT 1 will be described with
reference to FIG.
When the ultrasonic wave is received by the CMUT 1, the DC voltage (bias voltage) from the first
voltage application unit 17 is the first electrode 6 so that a potential difference is generated
between the first electrode 6 and the second electrode 10. Is applied to the
When an ultrasonic wave is received in that state, the vibrating film 12 having the second
electrode 10 vibrates, so the distance between the second electrode 10 and the first electrode 6
changes, and the capacitance changes. Due to the change in capacitance, a signal (current) is
output from the second electrode 10, and a current flows in a lead wire (not shown). This current
is converted into a voltage by a current-voltage conversion element (not shown) to obtain an
ultrasonic reception signal. As described above, the DC voltage may be applied to the second
electrode 10 and the signal may be extracted from the first electrode 6 by changing the
configuration of the lead wiring.
[0035]
Further, in the case of transmitting an ultrasonic wave, an alternating voltage is applied to the
second electrode 10 by the second voltage application unit 18 in a state in which a direct current
voltage is applied to the first electrode 6. Alternatively, a voltage obtained by superimposing a DC
voltage and an AC voltage (that is, an AC voltage whose positive and negative are not reversed) is
applied to the second electrode 10 by the second voltage application means 18, and the vibrating
film 12 is vibrated by electrostatic force. An ultrasonic wave can be transmitted by this vibration.
Also in the case of transmitting ultrasonic waves, an alternating voltage may be applied to the
first electrode 6 to vibrate the vibrating film 12 by changing the configuration of the lead-out
wiring. Thus, the CMUT 1 of the present embodiment can perform at least one of transmission
and reception of an ultrasonic wave (acoustic wave).
[0036]
(Method of Manufacturing CMUT) A method of manufacturing CMUT 1 according to the first
embodiment of the present invention will be described with reference to FIG. FIG. 3 shows the
processes that are taken to produce the CMUT according to the embodiment of FIG. As shown in
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FIG. 3A, the third insulating film 5 is formed on the substrate 4. The substrate 4 is a silicon
substrate, and the third insulating film 5 is provided to electrically insulate the first electrode 6
from the substrate 4. When the substrate 4 is an insulating substrate such as a glass substrate,
the third insulating film 5 may not be formed. The substrate 4 is preferably a substrate having a
small surface roughness. When the surface roughness is large, the surface roughness is
transferred also in the film forming step after the present step, and the distance between the first
electrode 6 and the second electrode 10 due to the surface roughness is , Every 2 cells. Since this
variation is a variation of conversion efficiency, it is a variation of sensitivity and band. Therefore,
the substrate 4 is preferably a substrate having a small surface roughness.
[0037]
Furthermore, the first electrode 6 is formed on the third insulating film 5. The first electrode 6 is
desirably a conductive material having a small surface roughness, and a material containing
titanium, tungsten, aluminum or the like can be used as the first electrode 6. As in the case of the
substrate 4, when the surface roughness of the first electrode 6 is large, the distance between the
first electrode 6 and the second electrode 10 for each cell 2 is an element due to the surface
roughness. Since it varies every three, a conductive material with a small surface roughness is
desirable.
[0038]
Next, the first insulating film 7 is formed on the first electrode 6. The first insulating film 7 is
desirably an insulating material having a small surface roughness, and when a voltage is applied
between the first electrode 6 and a second electrode 10 described later, the first electrode 6 and
the It forms in order to make an electrical short between the two electrodes 10 or a dielectric
breakdown hard to occur. In addition, it is formed in order to suppress the etching of the first
electrode 6 at the time of removal of the sacrificial layer 15 performed in a step subsequent to
the present step. As in the case of the substrate 4, when the surface roughness of the first
insulating film 7 is large, the distance between the first electrode 6 and the second electrode 10
due to the surface roughness varies among the cells 2. It is desirable to use an insulating film
having a small surface roughness. A material including a silicon nitride film, a silicon oxide film,
or the like can be used as a material of the first insulating film 7. The surface roughness of the
first insulating film 7, the second insulating film 9 described later, and the third insulating film 5
increases as the thickness increases, so the thickness must be at least the minimum required to
maintain insulation.
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[0039]
Next, as shown in FIG. 3B, a sacrificial layer 15 is formed in two stages on the first insulating film
7. For example, patterning of the sacrificial layer 15 is performed by the manufactured mask (not
shown), and etching of the sacrificial layer 15 is performed by the mask slimmed by side etching.
As another method, a method of controlling the etching direction or a method of using a two-step
guide may be used. The thickness of the sacrificial layer 15 to be the gap 8 later is indicated by
the gap 19, and the thickness of the sacrificial layer 15 to be the etching confirmation portion 14
is indicated by the gap 20. The sacrificial layer 15 is desirably a material having a small surface
roughness. Similar to the substrate 4, when the surface roughness of the sacrificial layer 15 is
large, the distance between the first electrode 6 and the second electrode 10 due to the surface
roughness varies among the cells 2, so the surface roughness A sacrificial layer 15 with a small
size is desirable. Also, in order to shorten the etching time of etching for removing the sacrificial
layer 15, a material having a high etching rate is desirable. In addition, it is required to use a
material of the sacrificial layer 15 such that the insulating film and the vibrating film 12 are not
substantially etched with respect to the etchant or etching gas for removing the sacrificial layer
15. When the insulating film and the vibrating film 12 are etched with respect to the etching
solution or etching gas for removing the sacrificial layer 15, the thickness variation of the
vibrating film 12, the distance between the first electrode 6 and the second electrode 10
Variations are likely to occur. Variations in the thickness of the vibrating film 12 and variations
in the distance between the first electrode 6 and the second electrode 10 result in variations in
sensitivity and bandwidth among the cells 2. When the insulating film and the vibrating film 12
are a silicon nitride film or a silicon oxide film, the material of the sacrificial layer 15 which can
use an etching solution or etching gas which has a small surface roughness and is difficult to etch
the insulating film and the vibrating film 12 desirable. For example, amorphous silicon,
polyimide, chromium or the like. In particular, when the insulating film and the vibrating film 12
are a silicon nitride film or a silicon oxide film, a chromium etching solution is desirable. This is
because the chromium etching solution hardly etches the silicon nitride film or the silicon oxide
film.
[0040]
Next, as shown in FIG. 3C, a second insulating film 9 is formed. The second insulating film 9
desirably has low tensile stress. For example, a tensile stress of 500 MPa or less is good. The
silicon nitride film can be stress controlled and can have a low tensile stress of 500 MPa or less.
When the vibrating membrane 12 has a compressive stress, the vibrating membrane 12 causes
sticking or buckling and is largely deformed. Also, in the case of a large tensile stress, the second
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insulating film 9 may be broken. Therefore, the second insulating film 9 desirably has low tensile
stress. For example, it is a silicon nitride film capable of stress control and low tensile stress. In
addition, since the thickness of the second insulating film 9 is formed on the sacrificial layer 15,
it is preferable that the thickness can ensure the coverage of the sacrificial layer 15.
[0041]
Next, as shown in FIG. 3D, the second electrode 10 is formed. Therefore, the sacrificial layer 15
to be the gap 8 is sandwiched between the pair of electrodes (the first electrode 6 and the second
electrode 10), and the sacrificial layer 15 to be the etching confirmation portion 14 is not
sandwiched. The second electrode 10 is desirably a material having a small residual stress, such
as aluminum. When the removal process or sealing process of the sacrificial layer 15 is
performed after the formation of the second electrode 10, the second electrode 10 is desirably a
material having etching resistance to the etching of the sacrificial layer 15 and heat resistance.
For example, aluminum silicon alloy or titanium.
[0042]
Next, as shown in FIG. 3E, etching holes 16 are formed in the second insulating film 9. The
etching holes 16 are holes for introducing an etching solution or etching gas to etch away the
sacrificial layer 15. After etching, the sacrificial layer 15 is removed to form a gap 8. Therefore,
by using the portion of the sacrificial layer 15 where the etching confirmation portion 14 is used,
it is possible to confirm completion of removal of the sacrificial layer 15 to be the gap 8. The
portion of the etching confirmation portion 14 in the sacrificial layer 15 has a projection shape
in the in-plane direction of the substrate 4, so that the etching in the projection direction
proceeds fast and the etching visual recognition is easy. Furthermore, over-etching can be
minimized. Note that the progress of etching will be described later. The method of removing the
sacrificial layer 15 is preferably wet etching, dry etching or the like. When chromium is used as
the material of the sacrificial layer 15, wet etching is preferred. When chromium is used as the
material of the sacrificial layer 15, the second electrode 10 is preferably made of titanium in
order to prevent the second electrode 10 from being etched when the sacrificial layer 15 is
etched. When the second electrode 10 is made of aluminum silicon alloy or the like, after
forming the second electrode 10, an insulating film is formed on the second electrode 10 with
the same material as the second insulating film 9 and then etched Preferably, the holes 16 are
formed to remove the sacrificial layer 15.
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[0043]
Next, as shown in FIG. 3F, in order to seal the etching holes 16, the sealing film 11 is formed. The
vibrating film 12 is formed of the second insulating film 9, the second electrode 10, and the
sealing film 11. The sealing film 11 is required to prevent the liquid and the outside air from
entering the gap 8. When the gap 8 is at the atmospheric pressure, the temperature change
causes the gas in the gap 8 to expand and contract. In addition, since a high electric field is
applied to the gap 8, it causes a decrease in the reliability of the element 3 due to the ionization
of molecules. Therefore, sealing is required to be performed in a reduced pressure environment.
By reducing the pressure in the gap 8, the air resistance in the gap 8 can be reduced. As a result,
the vibrating membrane 12 easily vibrates, and the sensitivity of the CMUT 1 can be increased.
Moreover, CMUT1 can be used in a liquid by sealing. As a sealing material, the same material as
the second insulating film 9 is preferable because of high adhesion. When the second insulating
film 9 is silicon nitride, the sealing film 11 is also preferably silicon nitride.
[0044]
In FIG. 3, the configuration in which the second electrode 10 is sandwiched between the second
insulating film 9 and the sealing film 11 is shown as an example. However, the etching hole 16
may be formed after the second insulating film 9 is formed, and the sacrificial layer 15 may be
etched after forming the sealing film 11, and then the second electrode 10 may be provided.
However, if the second electrode 10 is exposed to the outermost surface, the possibility of the
element 3 shorting due to foreign matter or the like is high, so the second electrode 10 is
preferably provided on the insulating film.
[0045]
The progress of the etching for removing the sacrificial layer 15 will be described with reference
to FIG. FIG. 6A shows a state before the etching through the etching hole 16 is started. 6 (b) to 6
(e) show the state after the start of etching. Before the etching of the sacrificial layer 15 is
started, as shown in FIG. 6A, all the sacrificial layer 15 remains, and the gap 8 and the etching
confirmation portion 14 have not been formed yet. After the etching is started, as shown in FIGS.
6B to 6C, the area of the gap 8 gradually expands from the area near the etching hole 16.
Therefore, as described above, since the sacrificial layer 15 to be the gap 8 is sandwiched
between the pair of electrodes, the formation of the gap 8 can not be confirmed. And as shown in
FIG.6 (d), the clearance gap 8 is formed in a perfect state and the etching confirmation part 14 is
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formed. Finally, as shown in FIG. 6 (e), all the sacrificial layer 15 is etched and completely
removed, whereby the etching confirmation portion 14 is completely formed. Then, since the
etching confirmation part 14 is made into protrusion shape, it is easy to visually recognize. Since
the formation of the gap 8 is completed when the etching confirmation portion 14 is formed, the
completion of the etching of the region of the gap 8 can be confirmed by visually recognizing the
formation of the etching confirmation portion 14. In addition, it may be considered that the
etching of the region of the gap 8 is completed when it is possible to visually recognize the
partial formation of the etching confirmation unit 14 without waiting for the completion of the
formation of the etching confirmation unit 14.
[0046]
In FIG. 1, one gap 8 leads to one etching hole 16, but as shown in FIG. 9, three gaps 8 may lead
to one etching hole 16, and as shown in FIG. The gap 8 may lead to one etching hole 16. Further,
as shown in FIG. 10, one gap 8 may lead to three etching holes 16, and as shown in FIG. 11, one
gap 8 may lead to two etching holes 16. Furthermore, different patterns may be used in
combination of the gap 8 and the etching hole 16. For example, as shown in FIG. 12, two gaps 8
combine a pattern leading to one etching hole 16, and three gaps 8 combine a pattern leading to
one etching hole 16.
[0047]
Although one element 3 is shown in FIG. 1, the number of elements 3 may be any number.
Further, the element 3 is configured of 18 cells 2. However, as shown in FIG. 8 and FIG. 11, for
example, 24 elements may be used, and any number may be used. Further, the arrangement of
the cells 2 may be a lattice arrangement, a zigzag arrangement, or any arrangement.
Furthermore, the outline of the element 3 may be rectangular, square or hexagonal as shown in
FIG.
[0048]
Through the above steps, the CMUT 1 as shown in FIGS. 1 and 2 can be manufactured. Since the
etching of each cell 2 can be confirmed at the time of manufacturing the CMUT 1 as in this
embodiment, appropriate etching can be performed.
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[0049]
Second Embodiment Case where Thickness of Etching Confirmation Portion is Same as Thickness
of Gap Next, the configuration of the CMUT 1 according to a second embodiment will be
described with reference to FIG. FIG. 4 is a cross-sectional view taken along a line AB in FIG. The
configuration of the CMUT 1 of the second embodiment is different from that of the first
embodiment in the thickness of the etching confirmation unit 14.
[0050]
In the CMUT 1 of the present invention, the thickness of the etching confirmation portion 14 is
the same as the thickness of the gap 8. The other configuration and manufacturing method are
substantially the same as those of the first embodiment, and thus the description thereof is
omitted.
[0051]
Although the thickness of the sacrificial layer 15 is two in the first embodiment, the thickness of
the sacrificial layer 15 can be reduced to one as in this configuration, so the process of forming
the sacrificial layer 15 can be reduced. Further, by making the thickness of the sacrificial layer
15 to be the gap 8 and the thickness of the sacrificial layer 15 to be the etching confirmation
portion 14 the same, etching confirmation of the sacrificial layer 15 of the gap 8 in the thickness
direction can be performed. Etching can be realized.
[0052]
(Embodiment 3) (Case where Multiple Etching Confirmation Portions exist in One Cell) Next, the
configuration of the CMUT 1 according to Embodiment 3 will be described with reference to FIG.
FIG. 5 is a top perspective view of the CMUT 1 of the present invention. The configuration of the
CMUT 1 of the third embodiment differs from that of the first embodiment in the arrangement
and the number of etching holes 16 and the arrangement and the number of etching
confirmation portions 14 provided in each gap 8.
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[0053]
The CMUT 1 of the present invention is configured such that the element is a combination of
cells 2 in which etching holes 16 are individually provided in each gap 8, and four etching
confirmation portions 14 are provided in each gap 8. Although four etching confirmation parts
14 are provided in each cell 2 in FIG. 5, one to three etching confirmation parts 14 may be
provided. The other configuration and manufacturing method are substantially the same as those
of the first embodiment, and thus the description thereof is omitted.
[0054]
As in the present configuration, since each cell 2 has four etching confirmation parts 14, etching
confirmation of the sacrificial layer 15 to be the gap 8 can be performed at four ends of the gap
8. Therefore, since etching confirmation can be performed more reliably, more appropriate
etching can be realized.
[0055]
1 Capacitance Transducer (CMUT) 2 Cell 3 Elements (Element) 4 Substrate 5 Third Insulating
Film 6 First Electrode 7 First Insulating Film 8 Gap (Cavity) 9 Second Insulating Film 10 Second
Electrode 11 Sealing film 12 Vibrating film 13 Vibrating film support 14 Etching confirmation
part 15 Sacrifice layer 16 Etching hole 17 First voltage application means 18 Second voltage
application means 19 Gap of gap 20 Gap of etching confirmation part
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