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JP2012239713

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DESCRIPTION JP2012239713
An ultrasonic transducer element having stable characteristics is provided. An ultrasonic
transducer element includes a silicon substrate, a lower electrode layer, a first insulating layer, a
second insulating layer in which a cavity 14A and a channel 14B are formed, and an upper
electrode layer 16. The first cavity 14A1 and the second cavity 14A2 are different in size, and the
shortest distance d1 from the first opening 15C1 to the center of the first cavity 14A1 via the
first channel 14B1, and the second opening The shortest distance d2 from the portion 15C2 to
the center of the second cavity 14A2 via the second channel 14B2 is the same. [Selected figure]
Figure 6
Ultrasonic transducer element and ultrasonic endoscope
[0001]
The present invention relates to a capacitive ultrasonic transducer element, and an ultrasonic
endoscope equipped with an ultrasonic transducer element.
[0002]
There is known a capacitive ultrasonic transducer cell in which a cavity (air gap) is provided
between a lower electrode and an upper electrode, and a membrane including the upper
electrode vibrates.
When an ultrasonic transducer element in which a plurality of ultrasonic transducer cells are
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two-dimensionally arranged is manufactured using a MEMS technology, a sacrificial layer etching
technology is used for forming a cavity.
[0003]
U.S. Pat. No. 5,870,351 discloses a method of forming a cavity in which an etchant such as a
hydrofluoric acid solution is poured from the opening of the upper insulating layer formed on the
sacrificial layer made of silicon oxide to remove the sacrificial layer. ing. Further, it is disclosed in
the above specification that an ultrasonic transducer element having a plurality of ultrasonic
transducer cells of cavities of different sizes can broaden the frequency of ultrasonic waves to be
transmitted and received.
[0004]
However, due to the etching of the sacrificial layer, it may not be easy to make cavities of
different sizes. That is, when the size of the cavity is different, the time required to complete the
etching of the sacrificial layer is different. To this end, the upper insulating layer of the small
cavity is exposed to the etchant after the etching is completed until the etching of the large cavity
is completed.
[0005]
If the upper insulating layer constituting the membrane is exposed to the etchant for a long time,
it may be eroded and thinned. Then, since the cavity thickness (height) increases, the
transmission / reception sensitivity of the ultrasonic wave may be lowered, or the resonance
frequency may be changed, which may make the characteristics of the ultrasonic transducer
element unstable.
[0006]
U.S. Pat. No. 5,870,351 Japanese Patent Application Publication No. 2008-118632
[0007]
An embodiment of the present invention aims to provide an ultrasonic transducer element having
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stable characteristics and an ultrasonic endoscope having stable characteristics.
[0008]
The ultrasonic transducer element according to an embodiment of the present invention includes
a base, a lower electrode layer, a first insulating layer, a second insulating layer in which a cavity
and a channel are formed, and an upper electrode layer, A first ultrasonic cell and a plurality of
second ultrasonic cells are manufactured, wherein the first cavity of each of the first ultrasonic
cells flows into the second insulating layer through a plurality of first channels. And the second
cavity of each of the second ultrasonic cells is formed by the etching of the sacrificial layer by the
etchant which has flowed in through the plurality of second channels. Furthermore, a first
opening of each of the plurality of first channels and a second opening of each of the plurality of
second channels are formed, and the first cavity is formed of the first cavity. The shortest
distance from the first opening to the center of the first cavity via the first channel, and the
second channel from the second opening to the center of the second cavity, which is larger than
the cavity The shortest distance is the same.
[0009]
An ultrasonic endoscope according to another embodiment of the present invention includes an
insertion portion having a distal end rigid portion provided with the above-mentioned ultrasonic
transducer element, an operation portion located at a proximal end of the insertion portion, and
the operation And a universal cord extending from the side of the part.
[0010]
According to the embodiment of the present invention, it is possible to provide an ultrasonic
transducer element having stable characteristics and an ultrasonic endoscope having stable
characteristics.
[0011]
It is an external view for demonstrating the ultrasound endoscope of 1st Embodiment.
It is a perspective view for demonstrating the front-end ¦ tip part of the ultrasound endoscope of
1st Embodiment.
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It is a perspective view for demonstrating the structure of the ultrasonic transducer part of the
front-end ¦ tip part of the ultrasonic endoscope of 1st Embodiment.
It is an exploded view for demonstrating the structure of the ultrasonic transducer cell of the
ultrasonic transducer element of 1st Embodiment.
It is a top view for demonstrating the pattern of the 2nd insulating layer of the ultrasonic
transducer element of 1st Embodiment.
It is a sectional view for explaining the ultrasonic transducer element of a 1st embodiment. It is a
top view for demonstrating the pattern of the 2nd insulating layer of the ultrasonic transducer
element of 1st Embodiment. It is a top view for demonstrating the etching process of the
sacrificial layer of the ultrasonic transducer element of 1st Embodiment. It is an exploded view
for explaining the pattern of the 2nd insulating layer of the ultrasonic transducer element of a
2nd embodiment. It is a top view for demonstrating the pattern of the 2nd insulating layer of the
ultrasonic transducer element of 2nd Embodiment. It is an exploded view for explaining the
pattern of the 2nd insulating layer of the ultrasonic transducer element of the modification of a
2nd embodiment.
[0012]
First Embodiment Hereinafter, an ultrasonic endoscope (hereinafter referred to as US )
having an ultrasonic transducer element (hereinafter referred to as US element ) 20
according to a first embodiment with reference to the drawings, and US element 20. The
endoscope 2) will be described.
[0013]
<Configuration of Ultrasonic Endoscope> As shown in FIG. 1, the US endoscope 2 constitutes the
ultrasonic endoscope system 1 together with the ultrasonic observation device 3 and the monitor
4.
The US endoscope 2 includes an elongated insertion portion 21 inserted into the body, an
operation portion 22 disposed at a proximal end of the insertion portion 21, and a universal cord
23 extending from the side portion of the operation portion 22. Prepare.
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[0014]
At the proximal end of the universal cord 23, a connector 24A connected to a light source device
(not shown) is disposed. From the connector 24A, a cable 25 detachably connected to the camera
control unit (not shown) via the connector 25A, and a cable 26 detachably connected to the
ultrasonic observation apparatus 3 via the connector 26A It is extended. A monitor 4 is
connected to the ultrasonic observation apparatus 3.
[0015]
The insertion portion 21 has a small diameter and a length extending from the distal end side to
the distal end hard portion 37, the curved portion 38 located at the rear end of the distal end
rigid portion 37, and the rear end of the curved portion 38 to the operation portion 22. And a
flexible tube portion 39 having flexibility and being connected in series. Then, an ultrasonic
transducer unit (hereinafter referred to as "US vibration unit") 9 which is an ultrasonic
transmitting / receiving unit is provided with a plurality of elongated US elements 20 (see FIG. 2
etc.) on the distal end side of the distal end rigid portion 37. Is provided.
[0016]
The operation unit 22 includes an angle knob 22A that performs bending control of the bending
unit 38 in a desired direction, an air / water supply button 22B that performs air supply and
water supply operations, a suction button 22C that performs suction operation, and a treatment
that is introduced into the body A treatment tool insertion port 22D or the like which is an
entrance of the tool is disposed.
[0017]
As shown in FIG. 2, the US transducer unit 9 is a radial transducer in which the long sides of a
plurality of elongated US elements 20 are connected and curved and arranged in a cylindrical
shape.
The distal end rigid portion 37 provided with the US vibrator unit 9 includes an illumination lens
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cover 31 constituting an illumination optical system, an observation lens cover 32 of an
observation optical system, and a forceps port 33 also serving as a suction port. An air / water
nozzle (not shown) is disposed.
[0018]
As shown in FIG. 3, a cable connection board portion 34 provided with a plurality of electrode
pads connected to the electrodes of a plurality of US elements 20 is disposed on the proximal end
side of the US vibrator portion 9. A coaxial cable bundle 35 connected to the cable connection
board portion 34 extends from the US vibrator portion 9. The coaxial cable bundle 35 is inserted
into the distal end rigid portion 37, the bending portion 38, the flexible tube portion 39, the
operation portion 22, the universal cord 23, and the ultrasonic cable 26 through the ultrasonic
connector 26a. Is connected to the ultrasonic observation apparatus 3.
[0019]
Each US element 20 has a signal electrode and a ground electrode. Each signal electrode is
connected to one coaxial cable of the ultrasonic cable 26. That is, the plurality of signal
electrodes of the plurality of US elements 20 are electrically disconnected from each other. On
the other hand, respective ground electrodes of the plurality of US elements 20 are electrically
connected to each other.
[0020]
As described later, each US element 20 may have a signal electrode for each US cell having a
different resonance frequency. Further, although the US vibrator unit 9 is a radial vibrator, the
US vibrator unit may be a convex vibrator curved in a convex shape.
[0021]
<Basic Structure and Basic Manufacturing Method of Ultrasonic Cell> Next, a basic structure and
a basic manufacturing method of an ultrasonic cell (hereinafter referred to as US cell ) 10 of
the US element 20 will be described using FIG. The following figures are schematic diagrams for
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explanation, and the ratio of the thickness of each layer, the size of each pattern, etc. is largely
different from that of the actual US cell.
[0022]
Further, as described later, three types of US cells 10A, 10B, and 10C having different sizes of the
cavity 14A are manufactured in the US element 20, but the basic configuration is the same. Do.
[0023]
As shown in FIG. 4, the US cell 10 includes a lower electrode layer 12 connected to a signal
electrode and a first insulating layer (lower insulating layer) 13 sequentially stacked on a silicon
substrate 11 as a base. A second insulating layer (upper insulating layer) 15 in which the air gap
portion 14 is formed, an upper electrode layer 16 connected to a ground electrode, and a
protective layer 17 are provided.
The air gap portion 14 comprises a cylindrical cavity 14A and four channels 14B. The portion
15B of the second insulating layer 15 directly on the cavity 14A to the protective layer 17
constitute a membrane 18 which is a vibrating film.
[0024]
The silicon substrate 11 is a substrate in which silicon thermal oxide films 11B and 11C are
formed on the surface of silicon 11A. The thickness of the silicon substrate 11 is, for example,
100 to 600 μm, and preferably 200 to 300 μm. The thickness of the silicon thermal oxide films
11B and 11C is, for example, 5 to 25 μm, and preferably 10 to 20 μm.
[0025]
The lower electrode layer 12 formed on one surface of the silicon substrate 11 is made of a metal
such as molybdenum or a conductive material such as silicon. The thickness of the lower
electrode layer 12 is, for example, 0.1 to 0.5 μm, preferably 0.2 to 0.4 μm. The conductive
material is deposited on the entire surface of the silicon substrate 11 by sputtering or the like.
Then, after forming a mask pattern by photolithography, the lower electrode 12A and the
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conductive portion 12B are formed by partially removing it by etching.
[0026]
That is, the lower electrode layer 12 is composed of a circular lower electrode 12A and
conductive portions 12B extending from four sides of the edge of the lower electrode 12A. The
lower electrode 12A is electrically connected to the lower electrode of the US cell of the same US
element 20 by the conductive portion 12B.
[0027]
The resonance frequencies of the three types of US cells 10A, 10B and 10C having different sizes
of the cavity 14A are different. For this reason, the lower electrode of the same type of US cell
may be connected, and the lower electrode of a different type of US cell may not be connected.
[0028]
Next, a first insulating layer 13 made of an insulating material such as SiN is formed on one
surface of the silicon substrate 11 on which the lower electrode layer 12 is formed by a CVD
method (chemical vapor deposition method) or the like. The thickness of the first insulating layer
13 is, for example, 0.10 to 0.20 μm.
[0029]
Then, after depositing the sacrificial layer material on the first insulating layer 13 and partially
removing it, the sacrificial layer in the shape of the cavity 14A and the sacrificial layer in the
shape of the channel 14B are formed. The channel is a flow path for the etchant to flow into the
cavity.
[0030]
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The channel-shaped sacrificial layer extends from four sides of the edge of the cylindrical cavityshaped sacrificial layer. That is, four channels 14B are extended radially from the center of the
cavity 14A in four directions orthogonal to each other.
[0031]
For this reason, as described later, in the sacrificial layer etching step (vacuum portion forming
step), the etchant flows from four directions into the cavity 14A, and the sacrificial layer etching
is completed when the central portion of the cavity 14A dissolves. .
[0032]
The thickness of the sacrificial layer is, for example, 0.05 to 0.3 μm, preferably 0.05 to 0.15
μm, in order to be the height of the cavity 14A.
As a sacrificial layer material, for example, phosphorus glass (PSG: phospho-containing silicon
oxide), silicon dioxide, polysilicon, metal or the like is used.
[0033]
On the upper surface of the first insulating layer 13 on which the sacrificial layer is formed, the
second insulating layer 15 is formed by, for example, the same method and the same material as
the first insulating layer 13. The thickness of the second insulating layer 15 is, for example, 0.20
to 0.50 μm, preferably 0.3 to 0.45 μm. As shown in FIG. 4, the second insulating layer 15 can
also be regarded as consisting of a second insulating layer 15A having the same thickness as the
sacrificial layer, and a second insulating layer 15B formed on the sacrificial layer. . Of course, the
second insulating layer 15A and the second insulating layer 15B are simultaneously formed.
Then, the second insulating layer 15B formed on the sacrificial layer in the shape of the cavity
14A becomes a part of the membrane 18.
[0034]
Then, in order to remove the sacrificial layer, a cylindrical opening 15C into which an etchant
flows is formed at a predetermined position of the second insulating layer 15 by
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photolithography / etching. That is, the opening 15C is a through hole. Then, one opening 15C is
formed on the end side of each of the four channel-shaped sacrificial layers. The opening 15C
may have a quadrangular prism shape or the like.
[0035]
Next, the sacrificial layer is etched to form a void 14 composed of the cavity 14A and the channel
14B.
[0036]
The etchant is a liquid or gas appropriately selected according to the materials of the first
insulating layer, the second insulating layer, and the sacrificial layer.
For example, when phosphorus glass is used as a sacrificial layer and SiN is used as the first
insulating layer 13 and the second insulating layer 15, a hydrofluoric acid solution (buffered HF
solution) is used as an etching agent. HF solution dissolves phosphorus glass, but SiN hardly
dissolves. For this reason, the sacrificial layer is removed, and a void 14 composed of the cavity
14A and the channel 14B is formed between the first insulating layer 13 and the second
insulating layer 15.
[0037]
In the void formation step, the sacrificial layer is removed by the etchant flowing from the
opening 15C through the channel 14B. That is, the etchant flowing from the opening 15C first
dissolves the channel-shaped sacrificial layer, and dissolves the cavity-shaped sacrificial layer
after the channel-shaped sacrificial layer is removed. For this reason, as described later, when the
channel length is long, the time until the dissolution start of the cavity-shaped sacrificial layer
becomes long.
[0038]
Next, the upper electrode layer 16 composed of the upper electrode 16A and the conductive
portion 16B is formed in the same manner as the lower electrode layer 12. Here, a part of the
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upper electrode layer 16 has a function as a sealing portion 16C that seals the opening 15C. The
thickness of the upper electrode layer 16 is, for example, 0.5 to 1.0 μm. The circular upper
electrode 16A and the lower electrode 12A have substantially the same diameter as the cavity
14A.
[0039]
The cavity 14A is not limited to a cylindrical shape, and may be a polygonal cylindrical shape or
the like. When the cavity 14A has a polygonal prism shape, the shapes of the upper electrode
16A and the lower electrode 12A are also preferably polygonal. Also, for example, the upper
electrode layer 16 may be a non-patterned conductive layer.
[0040]
Finally, a protective layer 17 covering the upper electrode layer 16 is formed. The protective
layer 17 is an insulating layer formed by the same method and the same material as the second
insulating layer 15. The protective layer 17 may have a two-layer structure in which a
biocompatible outer film such as polyparaxylylene is further formed on an insulating layer made
of SiN or the like. The thickness of the protective layer 17 is, for example, 0.2 to 1.5 μm,
preferably 0.5 to 1.0 μm.
[0041]
In the US cell 10 having the above structure shown in FIG. 4, the second insulating layer 15B, the
upper electrode layer 16 and the protective layer 17 in the region directly above the cavity 14A
constitute a membrane 18 which is a vibrating portion.
[0042]
The sealing portion of the US cell is not limited to the above. For example, the opening 15C may
be sealed with an insulating film such as SiN formed by a CVD method, and the upper electrode
layer 16 may be formed thereon. The protective layer 17 may have the function of a sealing
portion.
[0043]
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<Configuration of Ultrasonic Transducer Element> As described above, the US element 20
includes three types of US cells 10A, 10B, and 10C having different planar dimensions of the
cavity 14A two-dimensionally arranged in a matrix. It is made.
The basic configuration of each of the three types of US cells 10A, 10B, and 10C is the same as
the configuration described as the US cell 10.
[0044]
That is, as shown in FIG. 5, in the second insulating layer 15A of the second insulating layer 15,
three types of cavities 14A1, 14A2, 14A3 and three types of channels 14B1, 14B2, 14B3 are
formed.
For example, the diameter (2r1) of the cavity 14A1 of the first US cell 10A is 40 μm, the
diameter (2r2) of the cavity 14A2 of the second US cell 10B is 30 μm, and the diameter (2r3) of
the cavity 14A3 of the third US cell 10C is 20 μm It is.
[0045]
Three types of cavities 14A1 to 14A3 of different sizes are arranged in a grid at equal intervals.
That is, the distance d between the centers of the cavities 14A1 to 14A3 of the three types of US
cells is, for example, the same 50 μm. The arrangement of the cavities 14A1, 14A2 and 14A3,
that is, the arrangement of the US cells 10A, 10B and 10C may be regular lattice arrangement,
zigzag arrangement, triangular mesh arrangement or the like, or random arrangement. May be
[0046]
Each of the cavities 14A penetrates the four channels 14B extending radially from the center in
four directions orthogonal to each other. As will be described later, the openings 15C of the US
cells 10 adjacent to each other are configured by the same common opening. That is, the
common openings 15C of adjacent US cells 10 are formed at the intersections of the respective
channels 14B.
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[0047]
Since the three types of cavities 14A1 to 14A3 are arranged at equal intervals, the channels
14B1 to 14B3 extended from the respective cavities 14A1 to 14A3 have different lengths. That
is, the channel 14B1 of the largest cavity 14A1 is the shortest, and the channel 14B3 of the
smallest cavity 14A3 is the longest.
[0048]
The three types of US cells 10A, 10B and 10C are simultaneously fabricated on the same silicon
substrate 11. Here, FIG. 6 shows a cross-sectional structure taken along the line VI-VI of FIG. As
shown in FIG. 6, the US element 20 includes a silicon substrate 11, a lower electrode layer 12, a
first insulating layer 13, a second insulating layer 15 in which a cavity 14A and a channel 14B
are formed, and an upper electrode layer 16 And the protective layer 17.
[0049]
For example, the lower electrode layer 12 includes the respective first lower electrodes 12A1 of
the plurality of first US cells 10A, the respective second lower electrodes 12A2 of the plurality of
second US cells 10B, and the plurality of third US cells 10C. A conductive portion which is a
lower electrode wiring which connects each third lower electrode 12A3, the plurality of first
lower electrodes 12A1, the plurality of second lower electrodes 12A2 and the plurality of third
lower electrodes 12A3 to one another And 12B.
[0050]
Further, three types of cavities 14A1, 14A2, 14A3 and channels 14B1, 14B2, 14B3 different in
length of three types are formed between the first insulating layer 13 and the second insulating
layer 15.
[0051]
That is, in the second insulating layer 15, the first cavity 14A1 of each first US cell 10A is formed
by etching the sacrificial layer by the etchant which has flowed in via the first channel 14B1.
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Further, in the second insulating layer 15, the second cavities 14A2 of the respective second US
cells 10B are formed by etching the sacrificial layer by the etchant that has flowed in via the
second channel 14B2.
Further, in the second insulating layer 15, the third cavities 14A3 of the respective third US cells
10C are formed by etching the sacrificial layer by the etchant which has flowed in via the third
channel 14B3.
[0052]
As shown in FIG. 7, in the second insulating layer 15B, the first openings 15C1 of the plurality of
first channels 14B1, the second openings 15C2 of the plurality of second channels 14B2, and the
plurality of A third opening 15C3 of each of the three channels 14B3 is formed.
[0053]
The shortest distance d1 from the first opening 15C1 to the center CA1 of the first cavity 14A1
via the first channel 14B1 and the second distance 14B from the second opening 15C2 to the
center CA2 of the second cavity 14A2 The shortest distance d2 is the same as the shortest
distance d3 from the third opening 15C3 to the center CA3 of the third cavity 14A3 via the third
channel 14B3.
[0054]
In the US element 20, the first openings 15C1 of the first US cell 10A, the second openings 15C2
of the first US cell 10B, and the third openings 15C3 of the third US cell 10C, which are adjacent
to each other, are arranged in a matrix. And the same common opening.
[0055]
For example, the first opening 15C1 indicated by a lead in FIG. 7 is a common opening of one
first US cell 10A, one second US cell 10B, and two third US cells 10C.
[0056]
Then, as shown in FIG. 8, in the US element 20, for example, the time required for etching of the
cavity 14A1 to be completed by the etchant flowing from the opening 15C1, and etching of the
cavity 14A2 by the etchant flowing from the opening 15C2. And the time required for the
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etching of the cavity 14A3 to be completed by the etchant introduced from the opening 15C3.
[0057]
FIG. 8 shows that the etchant flowing from the opening 15C indicated by a lead line dissolves the
sacrificial layer along the four channels.
That is, the rate at which the etchant dissolves the sacrificial layer in the channel and the rate at
which the sacrificial layer in the cavity dissolves are the same.
This is due to the fact that the sacrificial layer dissolution reaction proceeds with limited reaction
rate.
That is, the reaction rate of dissolution of the sacrificial layer is sufficiently slower than the
penetration rate of the etchant, and only the dissolution reaction of the sacrificial layer and the
etchant determines the progress rate of etching.
[0058]
For this reason, even if the cavities 14A having different sizes are simultaneously manufactured
by the sacrificial layer etching, the lengths of the channels 14B are different, so that only the
second insulating layer 15 (and the first insulating layer 13) of the small cavities is for a long
time There is no exposure to the etchant over time.
That is, in the element 20, the difference in etching time due to the difference in the size
(diameter) of the cavity 14A is adjusted by the length of the channel 14B so that the etching is
simultaneously completed regardless of the size of the cavity 14A. .
[0059]
For this reason, the US element 20 has stable characteristics.
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Also, the US endoscope 2 having the US element 20 has stable characteristics.
[0060]
Further, in the element 20, four channels 14B are extended radially from the centers of the
respective cavities 14A in four directions orthogonal to each other, and an opening 15C is
formed in each of the channels 14B. For this reason, in the element 20, since the etching agent
flows in from four directions, the etching time can be shortened.
[0061]
The above effect can be obtained if there are a plurality of channels 14B inserted into one cavity
14A. The more the etching inflow path, the higher the effect, but the number of channels
increases. For this reason, the number of channels 14B inserted into one cavity 14A is preferably
3 or more and 6 or less, and particularly preferably four.
[0062]
Three types of US cells 10A, 10B, 10C having different sizes of the cavity 14A have different
resonance frequencies. For this reason, the US element 20A has a wide ultrasonic frequency that
can be transmitted and received. The drive signal for driving a plurality of US cells having
different resonance frequencies may be driven at, for example, the center frequency of a wide
frequency band, the frequency of the drive signal may be switched, or three-wave mixing type It
may drive with a special waveform of Of course, when the lower electrodes of the US cells 10A,
10B and 10C are not connected, drive signals of respective resonance frequencies are used.
[0063]
The three types of US cells 10A, 10B, 10C that the US element 20 may have may be substantially
the same, but it is preferable that the number of large US cells in the cavity is smaller than the
number of small US cells in the cavity. This is because the membrane of the large cavity US cell is
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more susceptible to the same voltage drive signal or ultrasonic waves of the same intensity than
the membrane of the small cavity US cell. US elements having different numbers of three types of
US cells can reduce the influence of the frequency of the transmission / reception sensitivity.
[0064]
Also, the two-dimensional arrangement of the three types of US cells 10A, 10B, 10C in the US
element 20 does not have to be uniform. For example, arranging the multiple US cells of the large
cavity for low frequency transmission and reception in the central region of the elongated
element and arranging the multiple US cells of the small cavity for high frequency transmission
and reception in the end region also adjusts the directivity. It is preferable because it can be
done.
[0065]
Although three types of US cells 10 having different sizes of respective cavities 14A are
manufactured in the US element 20A, two types of first US cells 10A and second types having
different sizes of the cavity 14A are manufactured. It is apparent that even if the US cell 10B is
produced, it has the same effect as the US element 20A.
[0066]
Conversely, it is apparent that the US element in which four or more types of US cells 10 having
different sizes of the respective cavities 14A are manufactured has the same effect as the US
element 20A.
That is, the number of types of the US cell 10 of the US element in the embodiment may be two
or more, and the upper limit is, for example, ten types. In other words, in the US element of the
embodiment, at least one ultrasonic cell having the same configuration as the first US cell 10A
and the second US cell 10B and different in the size of the cavity 14A is manufactured.
[0067]
It is also apparent that a US endoscope having a US element in which two or more types of US
cells 10 having different sizes of respective cavities 14A are produced has the same effect as the
US endoscope 2.
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[0068]
Second Embodiment A US endoscope 20A according to a second embodiment and a US
endoscope 2A having the US element 20A will be described below.
Since the US element 20A and the US endoscope 2A are similar to the US element 20 and the US
endoscope 2 respectively, the same components are denoted by the same reference numerals
and the description thereof will be omitted.
[0069]
In the US element 20 of the first embodiment, US cells of cavities having different sizes are twodimensionally arranged at equal intervals (distance d). That is, all other US cells were arranged
based on the US cell 10A of the largest cavity 14A1. For this reason, since the US cells 10 can not
be arranged at high density, miniaturization of the US element 20 is not easy.
[0070]
In addition, since the plurality of cavities 14A share the opening 15C, even if one opening 15C
can not be formed with a predetermined size due to a manufacturing problem, the plurality of US
cells 10 may be used. There was a possibility of becoming bad.
[0071]
On the other hand, as in the second insulating layer pattern 15A1 shown in FIGS. 9A to 9C, in the
US element 20A, three types of US cells 10D, 10E, and 10F having different sizes are
manufactured. It is done.
The cavity 14AD of the US cell 10D has a diameter of 40 μm, the cavity 14AE of the US cell 10E
has a diameter of 30 μm, and the cavity 14AF of the US cell 10F has a diameter of 20 μm.
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[0072]
The four channels 14BD of the US cell 10D, the four channels 14BE of the US cell 10E, and the
four channels 14BF of the US cell 10F have different path shapes. Channel 14BD is straight,
while channel 14BE and channel 14BF are curvilinear with bends.
[0073]
In addition, each channel 14B has a dedicated quadrangular prism-shaped opening 15C. That is,
there is an opening 15CD at each end of the four channels 14BD, and an opening 15CE at each
end of the four channels 14BE, and each end of the four channels 14BF There is an opening
15CF.
[0074]
The three types of US cells 10D, 10E, and 10F differ greatly in the pattern shape of the air gap
portion 14, but the shortest distance from each cavity center CA to the opening portion 15C is
the same. That is, the shortest distance d4 from the cavity center CA4 to the opening 15CD
shown in FIG. 9A, the shortest distance d5 from the cavity center CA5 to the opening 15CE
shown in FIG. 9B, and FIG. The shortest distance d6 from the cavity center CA6 to the opening
15CF shown is the same.
[0075]
Therefore, the US element 20A has the same effect as the US element 20 of the first embodiment,
and the US endoscope 2A having the US element 20A has the same effect as the US endoscope 2
of the first embodiment. .
[0076]
Furthermore, in the US element 20A, the area surrounded by the four first openings 15CD of the
first US cell 10D is larger than the area surrounded by the four second openings 15CE of the
second US cell 10E.
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The area surrounded by the four second openings 15CE of the second US cell 10E is larger than
the area surrounded by the four third openings 15CF of the third US cell 10F. The area occupied
by the US cell 10 can be approximated by the area enclosed by the opening.
[0077]
For this reason, as shown in FIG. 10, the total number of US cells 10 that can be disposed in a
predetermined area is greater than the number of US cells 10D that have the largest cavity 14AD
that can be disposed in the same predetermined area. There are also many.
[0078]
In other words, as shown in FIG. 10, the US element 20A has, for example, distances d7, d8, d9,
d10 from the center CAD of the cavity of the US cell 10D to the centers of the cavities of a
plurality of adjacent US cells. ,not the same.
[0079]
The US element 20A is smaller because the US cell 10 is disposed at a higher density than the US
element 20.
[0080]
Furthermore, even if one of the openings 15C can not be formed to have a predetermined
dimension due to a manufacturing problem, only one US cell 10 is defective.
Therefore, compared to the US element 20, the US element 20A has a high manufacturing yield.
That is, since the US element has many US cells 10, even if some US cells 10 are defective, they
can be used within the range of specifications.
[0081]
In addition, a US element in which only two types of first US cells and a second US cell having
different sizes of the cavity 14A are manufactured is the same as the US element 20A in which
three types of US cells are manufactured. It is clear that it has an effect.
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[0082]
That is, the first channel and the second channel have different path shapes, and one first
opening is formed in each of the first channels, and one second opening is formed in each of the
second channels. A portion is formed, and the area surrounded by the four first openings of the
first ultrasonic cell is larger than the area surrounded by the four second openings of the second
ultrasonic cell. The ultrasonic transducer element has the same effect as the ultrasonic
transducer element 20A.
[0083]
<Modification of Second Embodiment> Next, US elements 20B and 20C of a modification of the
second embodiment will be described using FIGS. 10 (A) and 10 (B).
[0084]
The US cell 10G of the US element 20B and the US cell 10H of the US element 20C each have a
zigzag path shaped channel 14B with a turn back.
However, by designing so that the shortest distance from each opening 15C to the center CA of
each cavity 14A is the same, it can be used similarly to the US cells 10E and 10F of the second
embodiment.
[0085]
And, the US element 20B, 20C having the US cell 10G or the US cell 10H has the same effect as
the cavity of the US element 20A.
Further, the US endoscopes 2B and 2C with the US elements 20B and 20C have the same effect
as the US endoscope 2A.
[0086]
The present invention is not limited to the above-described embodiment, and various changes,
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21
modifications, and the like can be made without departing from the scope of the present
invention.
[0087]
DESCRIPTION OF SYMBOLS 1 ... ultrasonic endoscope system, 2 ... US endoscope, 3 ... ultrasonic
observation apparatus, 9 ... vibrator part, 10 ... US cell, 11 ... silicon substrate, 12 ... lower
electrode layer, 12B ... conduction part, DESCRIPTION OF SYMBOLS 13 ... Insulating layer, 14 ...
Air gap part, 14A ... Cavity, 14B ... Channel, 15 ... Insulating layer, 15A ... Insulating layer, 15B ...
Insulating layer, 15C ... Opening part, 16 ... Upper electrode layer, 16A ... Upper electrode, 16B ...
Conducting part, 16C ... Sealing part, 17 ... Protective layer, 18 ... Membrane, 20 ... US element
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