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JP2016015723

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2016015723
To provide a technology capable of connecting a wiring from a transducer to an external circuit
or the like while suppressing the protrusion of a flexible printed wiring board while securing
electrical insulation at a necessary place. A transducer includes an element (201) provided on a
substrate (200) and having an electrode, and a connection electrode (109) electrically connected
to the electrode of the element. A conductor portion 122 provided on the insulating film of the
flexible printed wiring board 203 is electrically connected to the connection electrode 109. The
conductor portion 122 is partially exposed on the surface side on which the elements of the
substrate are disposed, and the insulating layer 202 is provided on the substrate in a region
facing the flexible printed wiring board on the surface side of the substrate. [Selected figure]
Figure 1
Transducer and measurement device
[0001]
The present invention relates to a transducer for transmitting and receiving an elastic wave such
as an ultrasonic wave (in the present specification, this means at least one of transmission and
reception) and a measurement device using the same.
[0002]
In order to transmit and receive ultrasonic waves, a capacitive ultrasonic transducer (CMUT)
(Capacitive Micromachined Ultrasonic Transducer) has been proposed (see Non-Patent Document
1).
04-05-2019
1
The CMUT is manufactured using a MEMS (Micro Electro Mechanical Systems) process to which
a semiconductor process is applied.
[0003]
FIG. 12 shows a schematic view of a cross section of the CMUT. Here, the first electrode 102 and
the second electrode 103 opposed to each other with the vibrating membrane 101 across the
gap 105 are referred to as a cell as one set. The vibrating film 101 is supported by the support
portion 104 on the substrate 200. A direct current voltage generation means 301 is connected to
the first electrode 102, and a predetermined direct current voltage Va is applied. The second
electrode 103 is connected to the transmission / reception circuit 302 and has a fixed potential
near the GND potential. Thus, a potential difference of Vbias = Va-0 V is generated between the
first and second electrodes. By adjusting the value of Va, the value of Vbias is made to coincide
with the desired potential difference (about several tens V to several hundreds V) determined by
the mechanical characteristics of the cell.
[0004]
By applying an AC drive voltage to the second electrode 103 by the transmission / reception
circuit 302, an electrostatic attraction of AC is generated between the first and second electrodes,
and the diaphragm 101 is vibrated at a certain frequency to Send a sound wave. In addition,
when the vibrating membrane 101 receives ultrasonic waves and vibrates, a minute current is
generated in the second electrode 103 by electrostatic induction. The current value can be
measured by the transmission / reception circuit 302 to take out the received signal. In the
above description, the DC voltage generating means is connected to the first electrode 102, and
the transmitting / receiving circuit is connected to the second electrode 103. However, a
configuration connected reversely can be used similarly.
[0005]
AS Ergun, Y. Huang, X. Zhuang, O. Oralkan, GG Yarahoglu, and BT Khuri-Yakub, "Capacitive
micromachined ultrasonic transducers: fabrication technology," Ultrasonics, Ferroelectrics and
Frequency Control, IEEE Transactions on, vol. 52, no 12, pp. 2242-2258, Dec. 2005.
04-05-2019
2
[0006]
The problem will be described with reference to FIG. FIG. 13A shows a substrate 200 provided
with a CMUT 201. A flexible printed wiring board (hereinafter referred to as a flexible printed
wiring board) is used as an electrical connection means between the connection electrodes 109
and 110 connected to the cell (CMUT) 201 on the chip and the external DC current generation
means 301 and the transmission / reception circuit 302. Note) is used. Flexible is formed by
forming a conductor foil having a pattern on an insulating film such as polyimide (hereinafter
also referred to as a base film). The conductor foil is formed of a metal such as copper and
generally has a thickness of about 10 micrometers to several tens of micrometers. On the
conductor foil of the base film, an insulator (hereinafter also referred to as a cover lay) such as a
polyimide film or a photo solder resist film is covered and protected except for a portion
electrically connected to a connector and other electrodes. The thicknesses of the base film and
the coverlay are each in the range of about 10 micrometers to several tens of micrometers, and
the thickness of the flexible substrate is in the order of several tens of micrometers to one
hundred and several tens of micrometers. The flexible printed circuit has the characteristics of
being flexible and deformable since it is thinner than a normal circuit board or wiring.
[0007]
FIG. 13B is a schematic view of a cross section in which the substrate 200 and the flexible board
203 are connected (a part of a cross section taken along line AB in FIG. 13A). A connection
electrode 109 disposed on a substrate 200 having a CMUT cell and an exposed area (flexure-side
connection electrode) 141 of the conductor foil 122 on the flexible substrate 203 are disposed to
face each other. By electrically connecting the electrodes 109 and 141 with the electrical
connection portion 131, the electrodes connected to the cell 201 can be easily connected to the
external DC current generating means 301, the transmitting / receiving circuit 302, and the like.
As the electrical connection portion 131, a common technique in flip chip mounting of a
semiconductor, such as a solder bump, a gold bump, an anisotropic conductive film (ACF), or an
anisotropic conductive paste (ACP) can be used. Thus, the protrusion of the wiring on the
substrate 200 can be reduced compared to the case where the connection with the electrode
from the substrate 200 is performed by wire bonding.
[0008]
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The substrate 200 is obtained by forming cells on a semiconductor wafer, cutting the wafer with
a dicing saw (hereinafter also referred to as dicing), and separating the chips into individual
chips. Therefore, even if the surface of the substrate 200 is covered with the insulating layer 202
in the wafer state, the semiconductor is exposed on the side surface of the substrate 200 after
dicing. Therefore, when the exposed conductor foil 122 on the flexible substrate 203 and the
side surface of the substrate 200 come in contact with each other, the substrate 200 and the
conductor foil (wiring) 122 on the flexible substrate short-circuit. This can be avoided by
arranging the cover lay 123 of the flexible board 203 on the substrate 200. However, since the
thickness of the cover lay 123 is much thicker than the thickness of the connection electrodes
109 and 141, the flexible substrate on the substrate 200 has a structure in which the thickness
of the base film 121 protrudes from the surface of the chip. . If the flexible film 203 is greatly
projected, the lower limit for thinning the protective film or the distance between the acoustic
lens and the chip when forming the protective film on the substrate 200 or when arranging the
acoustic lens or the like on the substrate 200 The lower limit may be increased. Thus, the
transmission and reception characteristics may be degraded.
[0009]
In view of the above problems, in the transducer according to the present invention, there is
provided a substrate, an element provided on the substrate and an electrode, and a connection
provided on the surface of the substrate on which the element is disposed and electrically
connected to the electrode. A flexible printed wiring board comprising: an electrode; and a
conductor portion electrically connected to the insulating film and the connection electrode and
provided on the insulating film. Then, a part of the conductor portion is exposed on the surface
side of the substrate on which the element is arranged, and an insulating layer is provided on the
substrate in a region facing the flexible printed wiring substrate on the surface side of the
substrate. It is done.
[0010]
According to the present invention, it is possible to connect the wiring from the transducer with
an external circuit or the like while suppressing the protrusion of the flexible, while securing the
electrical insulation at the necessary place.
[0011]
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4
FIG. 2 is a view for explaining a transducer according to the first embodiment.
The figure explaining the transducer concerning 2nd Embodiment. The figure explaining the
transducer concerning 3rd Embodiment. The figure explaining the transducer concerning 4th
Embodiment. The figure explaining the manufacturing method of the transducer concerning 5th
Embodiment. The figure explaining the manufacturing method of the transducer concerning 5th
Embodiment. The figure explaining the manufacturing method of the transducer concerning 5th
Embodiment. A figure explaining a transducer concerning a 6th embodiment. The figure
explaining the manufacturing method of the transducer concerning a 7th embodiment. The
figure explaining the manufacturing method of the transducer concerning a 7th embodiment.
The figure explaining the ultrasonic measuring device concerning 8th Embodiment. The figure
explaining the ultrasonic measuring device concerning 8th Embodiment. A figure explaining a
sensor (measurement device) concerning a 9th embodiment. The figure explaining the ultrasonic
measurement device concerning a 10th embodiment. The figure explaining the conventional
capacitive transducer. The figure explaining the subject of a transducer.
[0012]
The transducer of the present invention has the following two features. First, in the region where
the flexible printed wiring board is on the measurement target side (outside in the thickness
direction of the substrate) from the surface of the substrate on which the CMUT or the like is
disposed, the conductive foil (conductor portion) on the base film No cover lay (insulation film) is
placed on top. Second, an insulating layer is provided on the surface of the substrate on which a
CMUT or the like is disposed, in a region facing the flexible printed wiring substrate. That is, a
transducer having an element provided on a substrate and having an electrode, a connection
electrode provided on the surface of the substrate on which the element is disposed, and
electrically connected to the electrode, and a flexible printed wiring board It is as follows. The
conductor portion of the flexible printed wiring board is partially exposed on the surface side on
which the element of the substrate is disposed, and is insulated on the substrate in a region
facing the conductor portion of the flexible printed wiring board on the surface side of the
substrate Layers are provided. Examples of the element include a cell including a vibrating film
including a first electrode and a second electrode provided on a substrate with a gap from the
first electrode, a piezoelectric element, and the like.
[0013]
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Hereinafter, embodiments of a transducer of the present invention, a measuring device using the
same, and the like will be described in detail using the drawings. (First Embodiment) FIG. 1 is a
schematic view of a capacitive transducer according to the present embodiment. In FIG. 1,
reference numeral 101 denotes a vibrating membrane membrane, 102 denotes a first electrode,
103 denotes a second electrode, 104 denotes a support portion, 105 denotes a gap (cavity), and
106 denotes an insulating film. Reference numerals 107 and 108 are wires, 109 are connection
electrodes, 200 is a substrate, 201 is an electromechanical transducer (hereinafter sometimes
represented by CMUT), 202 is an insulating layer on the substrate surface, and 203 is a flexible
printed wiring substrate is there. Hereinafter, a structure including the substrate 200 and the
insulating layer 202 is referred to as a chip. Further, in this specification, the surface of the chip
on which the CMUT 201 is provided is also referred to as the upper surface, and the surface on
which the CMUT 201 is not formed is also referred to as the lower surface.
[0014]
An insulating layer 202 is formed on the upper surface of the substrate 200, and on the
insulating layer 202, a cell of CMUT consisting of a membrane 101, a first electrode 102, a
second electrode 103, a support portion 104, and a gap 105. It is arranged. The first electrode
102, the wiring 108 connected to the electrode 102, and the wiring 107 connected to the second
electrode 103 are electrically isolated from the substrate 200. The wiring 107 connected to the
second electrode 103 is connected to the flexible connection electrode 109. The chip can be
easily realized by forming the insulating layer 202 on a semiconductor wafer (a thickness of
several hundred micrometers) such as silicon, forming a CMUT, and dicing it into chips.
[0015]
In the flexible film 203, a conductor foil 122 which is a conductor portion having a pattern is
disposed on the base film 121. A cover lay 123, which is an insulating layer, is disposed on a
partial region of the surface of the base film 121 on which the conductor foil 122 is disposed.
Here, the base film 121 is made of an insulating film having a thickness of ten micrometers to
several tens of micrometers, such as polyimide, and the conductive foil 122 is a metal such as
copper having a thickness of ten micrometers to several tens of micrometers. It can be
configured using a foil. The cover lay 123 can be formed using an insulator such as a polyimide
film or a photo solder resist film having a thickness of ten micrometers to several tens of
micrometers.
04-05-2019
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[0016]
In the present embodiment, the fact that the coverlay 123 is not disposed in the area on the
measurement target side (the upper side in FIG. 1 with respect to the thickness direction of the
chip) from the plane coincident with the upper surface of the substrate 200 It is an eye feature.
In other words, the cover lay 123 is arranged in a region facing the side surface (surface
extending from the upper surface through the corner) of the flexible substrate 203 substantially
in parallel. With this configuration, the amount by which the flexible member 203 protrudes
from the upper surface of the substrate 200 to the measurement target can be reduced.
Specifically, the amount of protrusion is substantially equal to the sum of the thickness of the
base film 121 of the flexible film 203, the thickness of the conductor foil 122, the thickness of
the connection electrode 109 on the substrate 200, and the thickness of the electrical connection
portion 141. You can
[0017]
The second feature of the present embodiment is that the insulating layer 202 is disposed in the
region of the surface of the substrate 200 on which the CMUT facing the flexible substrate 203 is
disposed. Thereby, even if the conductor foil 122 exposed on the chip surface side on the flex
203 comes in contact with the chip surface, it is insulated by the insulating layer 202, so the
wiring (conductor foil 122) of the flex 203 and the substrate are electrically There is no contact.
Therefore, electrical insulation can be maintained between the wiring of the flexible substrate
203 and the substrate 200 or between the plurality of wirings in the flexible substrate 203. Here,
the insulating layer 202 has an insulating property, such as one obtained by thermally oxidizing
a base material of a substrate such as silicon, one obtained by forming an oxide, and one
obtained by forming a nitride. If there is no problem in the process of forming the CMUT, it is
used.
[0018]
According to this embodiment, it is possible to connect the wiring with an external circuit or the
like without generating a flexible protrusion while securing electrical insulation between the
substrate and the wiring. Therefore, a thin protective film on the chip and an acoustic lens can be
disposed at a close position, and a capacitive transducer excellent in transmission and reception
characteristics and an apparatus using the same can be provided.
04-05-2019
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[0019]
Although the wiring of the flexible printed circuit 203 is connected to the wiring 107 electrically
connected to the second electrode 103, the present invention is not limited to this structure. A
structure in which the wiring 108 is electrically connected to the first electrode 102 can also be
used, or the flexible wiring 203 has a plurality of electrically separated wirings, each of which
corresponds to the corresponding wiring 107. It can also be used in a configuration connected
with the wiring 108. In this case, since the wiring of the first electrode 102 and the wiring of the
second electrode 103 can be connected together on the circuit side using a single flexible, a small
capacitive transducer or the like can be provided. .
[0020]
Although the insulating layer 202 on the substrate 200 is disposed only on the surface on which
the CMUT or the like is formed, the present invention is not limited to this, and the insulating
layer 202 can also be disposed on the lower surface opposite to the top surface on which the
CMUT is formed. In this case, since the insulating layer 202 is formed on both sides of the
substrate 200, the stress that the substrate 200 receives from the insulating layer 202 is
canceled on both sides, and warpage of the chip can be suppressed.
[0021]
Second Embodiment The second embodiment is different in the configuration of the side surface
of the substrate 200. Other than that, it is the same as the first embodiment. The present
embodiment is characterized in that the insulating layer 200 is disposed on the side surface of
the substrate 200. FIG. 2 is a schematic view of a cross section of the capacitive transducer of the
present embodiment.
[0022]
In FIG. 2A, the insulating layer 202 on the substrate 200 is continuously disposed not only on
the CMUT formation surface but also on part of the end and side surface of the surface on which
the CMUT is formed. Since the side surface of the substrate 200 is partially covered by the
04-05-2019
8
insulating layer 202, the end of the cover lay 123 on the flexible substrate 203 bent along the
edge from the substrate surface to the substrate side matches the upper surface of the substrate
200. Even if not, the insulation between the wiring of the flexible printed circuit 203 and the
substrate 200 is secured. Therefore, even if the position of the chip surface on which the CMUT
is formed and the position of the cover lay 123 of the flex 203 where the conductor portion is
exposed on the side facing the end of the substrate in the bent portion, the wiring of the flex 203
and the board 200 Can ensure electrical insulation between them.
[0023]
The insulating layer can be easily disposed on the side surface of the substrate by a method of
forming the insulating layer. Specifically, a stencil mask or a resist can be used to selectively form
an insulating layer on the side on which the CMUT is formed, whereby the side surface of the
substrate 200 can be selectively formed. According to the present embodiment, the positional
accuracy of arranging the cover lay 123 on the flexible board 203 can be relaxed, and the
insulation can be secured more easily. Therefore, it is possible to use the cheaper flexible
member 203, and in the connection step between the flexible member 203 and the connection
electrode, the positional accuracy between the electrodes can be relaxed, and the process can be
simplified.
[0024]
FIG. 2B is a view for explaining another form of the present embodiment. In FIG. 2B, the
insulating layer 202 is disposed on the entire surface of the side surface of the substrate 200.
Further, with respect to the flexible substrate 203, the cover lay 123 is not disposed in the region
facing the side surface of the substrate 200. Since the insulating layer 202 is disposed on the
side surface of the substrate 200, the electrical insulation between the wiring of the flexible
printed circuit 203 and the substrate 200 is secured even without the cover lay 123. Therefore,
it is not necessary to arrange the cover lay 123 in a region facing the side surface of the flexible
substrate 203 of the flexible substrate 203.
[0025]
According to the present embodiment, since the cover lay 123 is not disposed on the flexible
board 203 on the side surface of the substrate 200, the width of the flexible board extending in
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9
the lateral direction of the substrate 200 can be narrowed by the thickness of the cover lay. In
addition, it is not necessary to arrange the cover lay 123 on the flexible member 203 with high
accuracy, the flexible member 203 can be manufactured with a simpler configuration, and
positioning at the time of mounting the flexible member 203 can be performed with coarser
accuracy. Therefore, a capacitive transducer can be provided at low cost.
[0026]
Third Embodiment The third embodiment is different in that it has a member for supporting the
substrate 200. Other than that, it is the same as the first embodiment. The present embodiment
is characterized in that a support member is provided on the lower surface of the substrate 200,
and an insulating layer is disposed on the side surface of the support member and the substrate
200. FIG. 3 is a schematic view of a cross section of the capacitive transducer of the present
embodiment. In FIG. 3, reference numeral 204 denotes a support member, 205 denotes an
adhesive layer, and 206 denotes an insulating layer. The substrate 200 on which the CMUT 201
is formed is disposed on the support member 204 via the adhesive layer 205. The position of the
side surface of the support member 204 on the side on which the flexible substrate 203 is
disposed substantially coincides with the position of the side surface of the substrate 200, and
the side surface of the support member and the side surface of the substrate 200 form a
substantially continuous flat surface. . In the present embodiment, the insulating layer 206 is
disposed on the continuous plane by adhesion or adhesion.
[0027]
Here, the support member 204 can be made of resin or the like, and the thickness is several
millimeters to several centimeters of a chip several hundred micrometers or more. Since the
thickness of the support member 204 is thicker than the thickness of the substrate 200, the
plane on which the insulating layer 206 is disposed can be wider than when only the side surface
of the substrate 200 is provided. Therefore, the area to which the insulating layer 206 is
attached can be increased, and the insulating layer 206 can be easily and reliably disposed on the
side surface.
[0028]
Here, the insulating layer may be an insulating thin film such as polyester, polyimide, PET, or
04-05-2019
10
PEN, and the thickness may be from ten micrometers to several tens of micrometers. Therefore,
as compared with the case where the insulating layer is formed only on the side surface of the
substrate, the film thickness can be increased, and the insulating layer can have high electrical
insulation since it does not have a pinhole or the like. The adhesive layer 205 between the
substrate 200 and the support member 204 is used as long as it bonds the substrate 200 and the
support member 204, and epoxy adhesive, urethane adhesive, acrylic adhesive, silicone adhesive
An agent etc. can be used.
[0029]
According to this embodiment, since the insulating layer having high insulating performance can
be used, the insulation between the wiring of the flexible printed circuit 203 and the substrate
200 can be enhanced, and a highly reliable capacitive transducer can be provided. it can.
[0030]
Fourth Embodiment In the fourth embodiment, the shape of the side surface of the substrate 200
is different.
Other than that is the same as the second embodiment. The present embodiment is characterized
in that the corner on the side on which the CMUT of the substrate 200 is formed has a recess,
and the surface of the recess is covered with an insulating layer. FIG. 4 is a schematic view of a
cross section of the capacitive transducer of this embodiment. In FIG. 4, reference numeral 210
denotes a recess, and reference numeral 211 denotes an insulating layer in the recess 210.
[0031]
The substrate 200 does not have a corner on the side on which the CMUT is formed on the side
on which the flexible substrate 203 is disposed, and has a recess 210 in that portion. This
depression can be arbitrarily selected from a width and a depth of about several tens of
micrometers to one hundred micrometers. Further, the surface of the depression 210 of the
substrate 200 is covered with the insulating layer 211. The insulating layer 211 may be made of
any material such as one obtained by thermally oxidizing a base material of a substrate such as
silicon, one obtained by forming an oxide, or one obtained by forming a nitride. The depression
210 and the insulating layer 211 covering the depression can be easily formed by using a MEMS
process.
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[0032]
According to the present embodiment, since the corner of the substrate 200 has a recess in the
bent portion of the flexible member 203 where the conductor portion is exposed in the region
facing at least a part of the surface of the recess 210, the flexible member 203 and the substrate
200 is hard to contact physically. Therefore, it is possible to avoid the occurrence of damage to
the wiring of the flexible substrate 203 due to contact and rubbing of the flexible substrate 203
and the substrate 200. Thus, a capacitive transducer with higher wiring reliability can be
provided.
[0033]
Fifth Embodiment In the fifth embodiment, a method of manufacturing a capacitive transducer
according to the fourth embodiment will be described. 5-1 to 5-3 are schematic views of crosssectional views for explaining the manufacturing method. FIG. 5-1 to FIG. 5-3 show a cross
section of a part of the semiconductor wafer.
[0034]
First, a groove 212 is formed by etching on the upper side of the drawing of the semiconductor
wafer 200 (FIG. 5-1 (a)) (FIG. 5-1 (b)). When forming the groove 212, after a resist is applied to
the surface and a part of the resist is removed, the groove can be easily formed by dry etching or
wet etching. The width of the groove 211 needs to be larger than the width of the blade used at
the time of dicing, and is preferably 50 micrometers to several hundreds micrometers. Further,
the depth of the groove 211 can be easily made any depth by controlling the etching time. The
specific thickness is preferably one-third to one-third or less of the thickness of the silicon wafer.
The depth may be set to an appropriate value in consideration of the influence of the grooves
212 on the manufacturing process and the placement accuracy of the cover lay 123 on the
flexible substrate 203.
[0035]
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12
Next, the insulating layer 202 is formed on the surface of the wafer in which the grooves 212 are
formed (FIG. 5-1 (c)). After that, CMUT 201 is formed on the insulating layer 202 formed on the
surface using a normal process (FIG. 5-2 (d)). The schematic diagram which extracted a part of
wafer at this time is shown to FIG. 5-3 (h). In FIG. 5-3 (h), the description of the insulating layer
202 and the like is omitted.
[0036]
Next, approximately the center of the groove 211 is cut and separated by dicing (FIG. 5-2 (e)).
Thus, it is possible to realize a configuration in which the corner of the substrate 200 is not
present and the recess 210 is provided, and the surface of the recess 210 is covered with the
insulating layer 212. Finally, the connection electrode 141, which is the exposed conductor
portion of the flexible printed circuit 203, and the connection electrode 109 on the substrate
200 are connected by the electrical connection portion 131 (FIG. 5-2 (f)). Thereafter, the flexible
member 203 is bent so as to be perpendicular to the substrate 200 (FIG. 5-3 (g)).
[0037]
According to this embodiment, it is possible to form the CMUT or the like and connect the
flexible member 203 only by inserting the groove 212 on the surface of the wafer forming the
CMUT or the like, without changing the process thereafter. Therefore, the wiring can be
connected to an external circuit or the like without causing the flexible protrusion while keeping
the electrical insulation, and a manufacturing method of manufacturing the transducer in a
simple process can be provided.
[0038]
Further, as the insulating layer 202 of the present embodiment, it is possible to use a film formed
of an oxide, a film formed of a nitride, and a film formed by thermally oxidizing a base material of
a wafer. In particular, the thermal oxide film is excellent in the insulating properties, and is
desirable as an insulating layer used as a base for forming a CMUT or the like. In addition, since
the film thickness can be made uniform, the thermal oxide film can be formed without defects
even in the inside of the groove, and the insulation can be surely ensured. In addition, a thermal
oxide film is a particularly desirable material for use in the present embodiment, since film
defects are less likely to occur during dicing.
04-05-2019
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[0039]
The transducer manufactured by the manufacturing method of this embodiment using a material
obtained by thermally oxidizing a wafer for the insulating layer 202 has high reliability because
the insulating properties of the insulating layer are excellent. In addition, since the
manufacturing process is simple, the cost can be reduced.
[0040]
Sixth Embodiment The sixth embodiment is different in the configuration of the substrate 200.
Other than that is the same as the second embodiment. In this embodiment, an SOI (Silicon on
Insulator) substrate is used as the substrate 200, and the side surface of the active layer of the
SOI substrate is covered with an insulating layer. FIG. 6 is a schematic view of a cross section of
the capacitive transducer of this embodiment. In FIG. 6, 221 is an active layer, 222 is a BOX
(Buried Oxide) layer, and 223 is a handle layer.
[0041]
In FIG. 6A, the SOI substrate in which the active layer 221 is disposed on the handle layer 223
via the BOX layer 222 is used as the substrate 200. The CMUT 201 is disposed on the surface of
the active layer 221 via the insulating layer 202. An insulating layer 202 is formed on the side
surface of the substrate 200 on which the flexible substrate 203 is disposed. Further, a cover lay
123 is disposed on the flexible board 203 in the area facing the side surface of the handle layer
223.
[0042]
In this embodiment, since the active layer 221 is surrounded by the BOX layer 222 and the
insulating layer 202, even when the active layer 221 of the substrate 200 is connected to a high
potential, no short circuit with peripheral members occurs. High reliability can be ensured.
Therefore, even if the potential applied to the substrate is made equal to the potential applied to
the second electrode 103 by connecting the potential of the DC voltage generation means to the
04-05-2019
14
active layer 221 of the substrate 200, Electrical insulation can be secured. When the potential of
the active layer 221 and the potential of the second electrode (lower electrode) 103 are common,
the electric field strength between the first electrode (upper electrode) 102 and the second
electrode (lower electrode) 103 The distribution of can be made uniform. In addition, it is also
preferable to fix the potential of the active layer 221 to GND or a bias voltage in order to prevent
external noise. In this case, the number of signal lines disposed on the flexible substrate 203 can
be reduced, and the width of the flexible substrate 203 can be narrowed.
[0043]
FIG. 6 (b) is a view for explaining another form of the present embodiment. In FIG. 6B, a
semiconductor substrate with a small amount of doping is used for the handle layer of the SOI
substrate used for the substrate 200. According to this embodiment, since the semiconductor
substrate with a small amount of doping is used for the handle layer, even if the wiring of the
flexible substrate 203 contacts the handle layer of the substrate 200, the wiring of the handle
layer and the flexible connector 203 is connected with high resistance. As a result, electrical
insulation is maintained. Since the cover lay 123 is not disposed on the flexible board 203 on the
side surface of the substrate 200, the width of the flexible board spreading in the lateral direction
of the substrate 200 can be narrowed by the thickness of the cover lay.
[0044]
In addition, it is not necessary to arrange the cover lay 123 on the flexible member 203 with
high accuracy, the flexible member 203 can be manufactured with a simpler configuration, and
positioning at the time of mounting the flexible member 203 can be performed with coarser
accuracy. Therefore, a low cost capacitive transducer can be provided. 6 (a) and 6 (b), the active
layer 221 can be configured to be made to bear the function of the second electrode 103, as
shown in FIG. 6 (c). . In this case, a wiring 107 connected to the connection electrode 109 on the
substrate 200 is formed through the insulating layer 202 on the surface of the active layer 221.
[0045]
Seventh Embodiment In the seventh embodiment, a method of manufacturing a capacitive
transducer according to the sixth embodiment will be described. 7-1 and 7-2 are schematic views
of cross-sectional views for explaining the manufacturing method. 7-1 and 7-2 show a cross
04-05-2019
15
section of a part of the semiconductor wafer.
[0046]
First, a groove 212 is formed by etching on the upper side toward the drawing of the SOI
substrate (FIG. 7-1 (a)) in which the active layer 221 is disposed on the handle layer 223 via the
BOX layer 222 (FIG. 1 (b). When forming the groove 212, after a resist is applied to the surface
and a part of the resist is removed, the groove can be easily formed by dry etching or wet
etching. The width of the groove 212 needs to be larger than the width of the blade used at the
time of dicing, and is preferably 50 micrometers to several hundred micrometers. Further, the
depth of the groove 212 can be easily determined by the thickness of the active layer 221 by
selecting an etching method in which the etching is stopped at the BOX layer 222 at the time of
etching. The specific thickness is preferably one-third to one-third or less of the thickness of the
silicon wafer. The depth may be set to an appropriate value in consideration of the influence of
the grooves 212 on the manufacturing process and the placement accuracy of the cover lay 123
on the flexible substrate 203.
[0047]
Next, the insulating layer 202 is formed on the surface of the active layer 221 in which the
groove 212 is formed (FIG. 7-1 (c)). After that, CMUT 201 is formed on the insulating layer 202
formed on the surface using a normal process (FIG. 7-2 (d)). Next, approximately the center of the
groove 212 is separated by dicing (FIG. 7-2 (e)). Thus, it is possible to realize a configuration in
which there is no corner of the substrate 200, the recess 210 is provided, and the surface of the
recess 210 is covered with the insulating layer 202. The subsequent steps of connecting the
flexible substrate 203 are the same as those of the fifth embodiment.
[0048]
By using the manufacturing method of the present embodiment, the depth of the recess 210 can
be manufactured with high accuracy. Therefore, in the capacitive transducer manufactured in the
present embodiment, since the depth at which the insulating layer 202 on the side surface of the
substrate 200 is disposed is accurately defined, the positional relationship with the coverlay can
be accurately defined. Thus, it is possible to provide a capacitive transducer with higher
reliability in insulation performance.
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[0049]
Eighth Embodiment Next, the eighth embodiment will be described with reference to FIGS. 8 and
9. FIG. The eighth embodiment relates to an ultrasonic measurement apparatus using the
capacitive transducer according to any one of the first to seventh embodiments.
[0050]
In FIG. 8, reference numeral 401 denotes a capacitive transducer, 402 denotes an object to be
measured, 403 denotes an image information generator, and 404 denotes an image display.
Reference numerals 501 and 502 denote ultrasonic waves, 503 denotes ultrasonic wave
transmission information, 504 denotes ultrasonic wave reception signals, 505 denotes
reproduced image information, and 400 denotes an ultrasonic measurement device. The
ultrasonic wave 501 output from the capacitive transducer 401 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
capacitive transducer 401, and information on the size, shape, and time of the received signal is
sent to the image information generation device 404 as an ultrasonic wave received signal 504.
On the other hand, information on the size, shape, and time of transmission ultrasonic waves is
sent from the capacitive transducer 401 to the image information generation device 403 as
ultrasonic transmission information 503. The image information generation device 403
generates an image signal of the measurement object 402 based on the ultrasonic wave
reception signal 504 and the ultrasonic wave transmission information 503, sends it as the
reproduction image information 505, and displays it on the image display 404.
[0051]
As the capacitive transducer 401 of this embodiment, the CMUT described in any of the above
embodiments is used. This CMUT can reduce the protrusion of the wiring connection portion
connecting the wiring to the external circuit and the CMUT chip to the measurement target side.
Therefore, since the acoustic lens can be disposed close to the surface of the CMUT, it is possible
to provide a capacitive transducer with less deterioration of transmission and reception
characteristics. The capacitance type transducer 401 of the present invention has less
deterioration of transmission / reception characteristics and can obtain more accurate
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information of the ultrasonic wave 502 reflected by the measurement object 402, so that the
image of the measurement object 402 is reproduced more accurately. can do.
[0052]
According to the ultrasonic measurement apparatus of the present embodiment, since a
capacitive transducer having excellent transmission and reception characteristics is used, a
compact ultrasonic measurement apparatus capable of acquiring a high quality image can be
provided.
[0053]
Further, as another configuration of the present embodiment, as shown in FIG. 9, an ultrasonic
wave generated using another transmission sound source 401 can be detected with high
accuracy by the capacitive transducer 403.
Alternatively, the measurement object may be irradiated with light (electromagnetic wave) by a
light source, and an ultrasonic wave generated by the photoacoustic effect may be received by
the capacitive transducer 403. As described above, regardless of the type of transmission sound
source, the capacitive transducer 403 can be used as a receiving element.
[0054]
(Ninth Embodiment) The capacitance type transducer of the present invention can be used not
only for transmission / reception of elastic waves or acoustic waves such as ultrasonic waves, but
also for detection of external force. The ninth embodiment relates to a sensor (measuring device)
using the capacitive transducer according to any one of the first to seventh embodiments. The
ninth embodiment will be described with reference to FIG.
[0055]
FIG. 10 shows a schematic view of a capacitive transducer according to the present embodiment.
A protective film 230 is formed on the surface of the CMUT, and an external force externally
applied to the surface of the CMUT is configured to be transmitted to the vibrating film. A cross
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flow voltage generating means is connected to the first electrode 102 forming a part of the
vibrating membrane. A predetermined DC voltage Va and an AC voltage Vsin of a predetermined
frequency are applied to the first electrode 102 by the cross flow voltage generation means. The
other second electrode 103 is connected to the detection circuit and has a fixed potential near
the GND potential. A potential difference of Vbias = Va-0 V is generated between the first
electrode and the second electrode 103 by the DC voltage Va. By adjusting the value of Va, the
value of Vbias is made to coincide with a desired potential difference (about several tens V to
several hundreds V) which is determined by the mechanical characteristics of the CMUT cell.
[0056]
When there is no external force input to the vibrating membrane 101, a minute current
determined by the AC voltage V sin and the distance between the electrodes is generated in the
second electrode 103, and the detection circuit converts the current value into a voltage and
performs Can be taken out. Here, when the vibrating membrane 101 receives an external force
through the protective film 230 and is deformed, the distance between the electrodes changes,
and the magnitude of the microcurrent generated in the second electrode 103 changes. The
detection circuit can detect the externally applied force by converting the current value at that
time into a voltage and taking it out, and comparing it with the voltage value when there is no
external force input to the vibrating membrane 101. .
[0057]
The capacitive transducer of this embodiment uses the CMUT described in any of the above
embodiments. This CMUT can reduce the protrusion of the wiring connection portion connecting
the wiring to the external circuit and the CMUT chip to the measurement target side. Therefore,
since a thin and uniform protective film can be disposed on the surface of the CMUT, it is
possible to provide a capacitive transducer sensitive to external force. By using the capacitive
transducer of the present embodiment, a sensor sensitive to external force can be provided.
[0058]
Tenth Embodiment The tenth embodiment is different in that another insulating material is
disposed between the conductive foil 122 of the chip 200 and the flexible printed wiring board
203. Other than that is the same as any one of the first to ninth embodiments. Although it
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demonstrates using FIG. 11 based on 1st Embodiment, it can be similarly used for other forms.
[0059]
FIG. 11A is a cross-sectional view when an anisotropic conductive film (ACF) is used for the
electrical connection portion 131 between the electrode 109 on the chip 200 and the electrode
141 on the flexible printed wiring board 203. . The anisotropic conductive film is disposed
between the electrode 109 on the chip 200 and the electrode 141 on the flexible printed wiring
board 203 at the time of production. An anisotropic conductive film (anisotropic conductive
resin) is an insulating thermosetting resin containing fine conductive metal particles. This means
that pressure can be applied between the electrodes to make the distance between the counter
electrodes smaller than the size of the conductive metal particles, thereby electrically connecting
the electrodes and having the function of the electrical connection portion 131. it can. On the
other hand, in the region not sandwiched between the electrodes, since the conductive metal
particles are dispersed in the insulating material, the insulation is maintained. Since the
anisotropic conductive film is produced by heating, the fluidity is increased at the time of
heating, and the film also protrudes to the region other than the region where the electrode is
disposed. As it is cooled as it is and the anisotropic conductive film is cured, the anisotropic
conductive film 161 having insulation property is disposed on the surface of the conductive foil
122 on the flexible printed wiring board 203.
[0060]
In the present embodiment, an anisotropic conductive film 161 having an insulating property is
disposed on the surface of the conductive foil 122 on the flexible printed wiring board 203.
Therefore, the insulation between the side surface of the chip 200 and the conductive foil 122 on
the flexible printed wiring board 203 can be made higher and more reliable, and the reliability of
the insulation can be made higher. In FIG. 11A, the anisotropic conductive film 161 having
insulation property is disposed on the entire surface of the exposed conductive foil 122, but it is
not necessary to be disposed on the entire surface, and a part of Just by being placed, the
reliability of the insulation can be increased as well.
[0061]
Another embodiment will be described with reference to FIG. FIG. 11B is characterized in that
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another insulating material 171 is disposed between the chip 200 and the conductive foil 122 on
the flexible printed wiring board 203. Another insulating material 171 can be easily realized by
filling it with silicone rubber. Compared with the configuration of FIG. 11A, the silicone rubber
can fill the space between the chip 200 and the flexible printed wiring board 203 more securely.
Therefore, the insulation between the side surface of the chip 200 and the conductive foil 122 on
the flexible printed wiring board 203 can be made higher and ensured.
[0062]
Further, another insulating material 171 can also be realized by using a potting material used to
insulate an electrical component. As a material, urethane (urethane resin), epoxy (epoxy resin),
butyl rubber etc. can be used. The potting material used to insulate electrical components can
lower the permeability to water vapor as compared to silicone rubber, and therefore can ensure
high insulation even under high humidity environments.
[0063]
Further, as shown in FIG. 11C, another insulating material can be formed of a plurality of
insulating layers of silicone rubber 181 and potting material 191. The insulating material of the
silicone rubber 181 can be disposed in the area adjacent to the CMUT, and the insulating
material of the potting material 191 can be disposed in the vicinity of the side surface of the chip
200. Since the silicone rubber 181 can be used as a protective layer on the surface of the CMUT,
it can be manufactured to serve as a protective layer and an insulating layer of the CMUT. In
addition, since the silicone rubber 181 is disposed on the CMUT or in the area near the CMUT,
the potting material 191 does not come around at the time of production and adhere to the
surface of the CMUT, thus affecting the characteristics. There is no Thus, in FIG. 11 (c), high
insulation can be secured without affecting the characteristics of the CMUT.
[0064]
Further, as shown in FIG. 11 (d), a configuration in which the forms of FIG. 11 (a) and FIG. 11 (b)
are combined may be employed. Although not shown, a configuration combining the forms of
FIG. 11D and FIG. 11C can also be taken. Thereby, higher insulation can be secured.
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[0065]
In the present embodiment, the insulating materials 171, 181, and 191 are completely filled
between the chip 200 and the flexible printed wiring board 203, but the present invention is not
limited to this. A configuration in which the insulating material is disposed only in part can be
used similarly, as long as no problem occurs in the insulation in use.
[0066]
101 · · Vibrating film, 102 · · First electrode, 103 · · Second electrode, 105 · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · (conductor foil), the conductor portion (conductor foil), 123 · · Insulating film
(cover lay), 200 · · · · · · · · · · · · · · · 203 · · flexible printed wiring board (flexible)
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