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JP2018007199

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DESCRIPTION JP2018007199
Abstract: To provide a technology capable of obtaining a high signal-to-noise ratio and enhancing
the resistance to input pressure in a capacitive sensor manufactured using MEMS technology. In
a capacitance type sensor that converts displacement of a diaphragm to a change in capacitance
between a diaphragm and a back plate, a part of the outer shape of the diaphragm is a substrate
when viewed from a normal direction. The other part of the outer shape of the diaphragm 5 is
arranged outside the opening of the substrate 3 when viewed from the normal direction.
[Selected figure] Figure 2
MEMS structure, capacitance type sensor having MEMS structure, piezoelectric type sensor,
acoustic sensor
[0001]
The present invention relates to a MEMS structure, a capacitive sensor having the MEMS
structure, a piezoelectric sensor, and an acoustic sensor having the capacitive sensor or the
piezoelectric sensor. More specifically, the present invention relates to a capacitive sensor, a
piezoelectric sensor, and an acoustic sensor having a diaphragm formed using MEMS technology.
[0002]
Heretofore, as a small-sized microphone, one using an acoustic sensor called ECM (Electret
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Condenser Microphone) has been used. However, ECM is weak to heat, and a microphone using a
capacitive sensor manufactured using MEMS (Micro Electro Mechanical Systems) technology is
superior in terms of response to digitization and miniaturization. As a result, in recent years,
MEMS microphones have often been adopted (see, for example, Patent Document 1).
[0003]
Among the above-mentioned capacitance type sensors, there is one that realizes a form in which
a diaphragm that vibrates under pressure is disposed opposite to a back plate to which an
electrode film is fixed via a gap using MEMS technology. . In such a capacitive sensor, for
example, after forming a diaphragm and a sacrificial layer covering the diaphragm on a silicon
substrate, a back plate is formed on the sacrificial layer, and then the sacrificial layer is formed. It
can be realized by the process of removing. Since the MEMS technology applies semiconductor
manufacturing technology in this manner, it is possible to obtain an extremely small capacitive
sensor.
[0004]
FIG. 18A shows a conventional capacitive sensor (hereinafter simply referred to as a MEMS
sensor) manufactured using such a MEMS technology. ) Shows a partial cross section of 100). In
FIG. 18A, a diaphragm 102 and a back plate 103 are formed on a silicon substrate 101. In the
conventional MEMS sensor 100, there is a region A in which the diaphragm 102 and the silicon
substrate 101 overlap as viewed in the normal direction of the diaphragm 102.
[0005]
In this case, since acoustic noise is generated in the region A due to the Brownian motion of air,
there is a possibility that the SN ratio as a capacitive sensor decreases. On the other hand, as
shown in FIG. 18B, when the diaphragm 112 and the silicon substrate 111 do not overlap when
viewed in the normal direction of the diaphragm 112, air is generated from the gap between the
diaphragm 112 and the silicon substrate 101. In some cases, the acoustic resistance is lowered
and the sensitivity as a capacitance sensor is lowered.
[0006]
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On the other hand, as shown in FIG. 19A, a proposal is made to secure the acoustic resistance by
providing the fixed film 124 around the diaphragm 122 so that a narrow slit 122a can be formed
between the fixed film 124 and the diaphragm 122. ing. Thereby, the fall of acoustic resistance is
suppressed and the sensitivity as an electrostatic capacitance sensor is secured, avoiding the fall
of the SN ratio resulting from the Brownian motion of air.
[0007]
FIG. 19B shows an example in which the fixed film 124 is fixed to the back plate 123 for the
same purpose. In the example shown in FIG. 19A, the fixed film 124 is fixed to the substrate 121
via the anchor 125 formed of an oxide film, but when the anchor 125 disappears due to the
variation of the manufacturing process, The fixed film 124 may be peeled off from the substrate
121 and may not perform the function of securing the acoustic resistance. In FIG. 19 (b), the
fixed film 124 is fixed to the back plate 123 in order to avoid such a disadvantage. Thereby, even
if the anchor 125 disappears, the fixed film 124 is fixed to the back plate 123, so it is possible to
perform the function of stably securing the acoustic resistance.
[0008]
By the way, when a large pressure acts on the diaphragm 122 from the silicon substrate 121 side
to the MEMS sensor 120 provided with the fixed film 124 as in the above-mentioned prior art,
the diaphragm 122 is displaced to the back plate 123 side and the back plate By contacting 123,
the displacement of a fixed amount or more can be suppressed. Further, at this time, the slit 122a
between the diaphragm 122 and the fixed film 124 is expanded, so that the pressure that the air
escapes from the slit 122a and acts can be reduced.
[0009]
On the other hand, when a large pressure acts on the diaphragm 122 from the back plate 123
side, the diaphragm 122 and the silicon substrate 121 have no overlapping region when viewed
from the normal direction of the diaphragm 122. The infiltration into the opening (back
chamber) 121a increases the amount of displacement, and stress may concentrate on a beam
(not shown) that supports the diaphragm 122, resulting in breakage.
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[0010]
Such a problem may occur not only when the capacitive sensor is dropped, but also when, for
example, a large acoustic sound pressure is applied to the capacitive sensor or when air is blown
in the mounting process. .
[0011]
U.S. Pat. No. 5,452,268
[0012]
The present invention has been invented in view of the above situation, and an object thereof is
to obtain a high SN ratio in a capacitance type sensor, a piezoelectric type sensor or an acoustic
sensor manufactured using MEMS technology. To provide a technology capable of enhancing the
resistance to input pressure.
[0013]
The present invention for solving the above problems comprises a substrate having an opening, a
diaphragm disposed to face the opening of the substrate, and a plurality of anchors for fixing the
diaphragm to the substrate or another member. A fixed film disposed around the diaphragm via a
slit, wherein the outer shape of the diaphragm includes a shape that protrudes toward an anchor,
and at least one or more of the diaphragms is a portion of the diaphragm It has a predetermined
cross structure in which the outer shape of the diaphragm and the outer shape of the opening of
the substrate when viewed from the normal direction intersect at two intersection points across
the shape projecting toward the anchor, in the cross structure It is characterized in that a
distance between two intersection points is longer than a width of the diaphragm located closer
to the anchor.
[0014]
According to the present invention, at least one or more of the diaphragms, the external shape of
the diaphragm and the external shape of the opening of the substrate, as viewed in the normal
direction of the diaphragm, intersect at two intersection points across the shape projecting
toward the anchor. It has a cross structure.
Therefore, when viewed in the normal direction, the diaphragm and the substrate have a gap at
one portion, and are arranged to overlap at the other portion.
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Then, the region where the diaphragm and the substrate overlap in the normal direction is
limited to a part of the outer shape of the diaphragm, so it is possible to suppress the generation
of noise due to the brown motion of air.
On the other hand, since the area where the diaphragm and the substrate overlap in the normal
direction is left, the diaphragm and the substrate contact each other in the area even when a
large pressure is applied from the back plate side. Excessive displacement can be avoided.
As a result, in the capacitive sensor or the piezoelectric sensor, it is possible to make the high SN
ratio and the resistance to the input pressure compatible with each other.
[0015]
Further, in the present invention, the distance between the two intersection points in the
intersecting structure is made longer than the width of the diaphragm located closer to the
anchor.
Therefore, while the width of the diaphragm near the anchor is narrowed, it is possible to widen
the width of the diaphragm between the intersections where the contour of the diaphragm and
the contour of the opening of the substrate intersect.
[0016]
Then, the sensitivity to the sound pressure can be increased by narrowing the width of the
diaphragm in the vicinity of the anchor. Moreover, stress concentration in the diaphragm can be
alleviated by widening the width of the diaphragm between the intersections.
[0017]
In the present invention, the outer shape of the diaphragm may have an inflection point in the
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vicinity of the intersection. Thereby, more effectively, the width of the diaphragm between the
intersections where the outer shape of the diaphragm and the outer shape of the opening of the
substrate intersect can be widened while the width of the diaphragm near the anchor is
narrowed.
[0018]
Furthermore, in the present invention, the outer shape of the diaphragm is a polygon or a
substantially polygon, and a length of a part of one side of the outer shape of the diaphragm
located outside the outer shape of the opening of the substrate is The length of one side may be
1/20 or more and 1/3 or less. As a result, it is possible to well maintain the balance between the
suppression of noise due to the Brownian motion of air and the avoidance of excessive
displacement of the diaphragm. As a result, in the capacitive sensor or the piezoelectric sensor, it
is possible to make the high SN ratio and the resistance to the input pressure compatible with
each other more reliably.
[0019]
Further, in the present invention, in the portion of the diaphragm where the outer shape is
disposed outside the opening of the substrate, the diaphragm has a convex shape in the direction
of the substrate, and the diaphragm is displaced toward the substrate side A stopper may be
formed in contact with the substrate.
[0020]
According to this, when the diaphragm is displaced to the substrate side, the stopper can be
brought into contact with the substrate, and by making the contact area between the diaphragm
and the substrate small, adhesion of the diaphragm to the substrate can be suppressed.
[0021]
Further, in the present invention, a fixed film may be further provided around the diaphragm via
a slit.
Then, air can be released from the periphery of the diaphragm, so that the pressure applied to
the diaphragm can be suppressed from being inadvertently reduced, and the sensitivity of the
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capacitive sensor can be increased.
Here, the width of the slit may be less than 3 μm, for example, 0.2 μm to 0.6 μm.
[0022]
Further, in the present invention, in the case of further including a fixed film disposed via a slit
around the diaphragm, the fixed film may completely surround the diaphragm and the slit may
form a closed curve.
[0023]
According to this, it is possible to prevent the end of the slit from being opened to the outside of
the fixed film when viewed from the normal direction, and it is possible to suppress the entry of
foreign matter from the open portion.
[0024]
Further, in the present invention, in a region of an angle of 3 degrees or less with respect to the
outer shape of the opening of the nearest one of the outer shapes of the diaphragm, it is
arranged at a distance of 1 μm or more from the outer shape of the opening of the substrate. It
is also good.
[0025]
Here, when the outer shape of the diaphragm and the outer shape of the opening of the substrate
are close to parallel and close to each other, the diaphragm is displaced by pressure and enters
the opening and then returns to the initial position. It is possible that the end of the outer shape
of the is stuck to the end of the opening and the diaphragm can not return to its original position.
[0026]
Therefore, in the present invention, in order to prevent such a disadvantage, in the area of the
angle of 3 degrees or less with respect to the outer shape of the opening of the nearest substrate
in the outer shape of the diaphragm, from the outer shape of the opening of the substrate It was
arranged to be separated by 1 μm or more.
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According to this, of the outer shape of the diaphragm, a portion close to parallel to the opening
of the nearest substrate can be arranged at a certain distance or more away from the outer shape
of the substrate, and the end of the diaphragm is at the end of the opening of the substrate It is
possible to suppress the inconvenience of being caught.
[0027]
Here, the outer shape of the opening of the nearest substrate may be the outer shape of the
opening of the substrate where the actual distance from the predetermined region of the outer
shape of the diaphragm is the smallest.
Alternatively, the outer shape of the opening of the substrate may be such that a perpendicular
line viewed from the normal direction to the region intersects.
Alternatively, it may be a central portion viewed from the normal direction of the diaphragm (in
the case where the diaphragm includes a quadrilateral, an intersection point of quadrilateral
diagonals).
If the diaphragm has a circular shape, it may be centered. And the straight line drawn so as to
pass through the area may be the outline of the opening of the substrate.
[0028]
Further, in the present invention, the crossing angle when the outer shape of the diaphragm
crosses the outer shape of the opening of the substrate may be 30 degrees or more. Then, even if
the position of the outer shape of the opening of the substrate varies due to manufacturing
variation, it is possible to suppress the change in the area of the portion of the outer shape of the
diaphragm which is disposed outside the outer shape of the opening of the substrate. In other
words, it is possible to stabilize the area of the portion of the diaphragm overlapping in plan view
with the substrate outside the opening. Here, the crossing angle means an acute angle side (small
side) of an angle formed by the outline of the opening of the substrate and the outline of the
intersecting diaphragm. When the outer shape of the opening of the substrate and the outer
shape of the diaphragm vertically cross, the crossing angle is 90 degrees.
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[0029]
Further, in the present invention, a portion of the outer shape of the diaphragm, which is
disposed inside the opening of the substrate when viewed in the normal direction, is one side of
the polygon or a central portion of a curve forming the closed curve. The portions disposed and
disposed on the outside of the opening of the substrate when viewed from the normal direction
may be disposed on one side of the polygon or on both sides of the central portion of the curve
forming the closed curve. .
[0030]
According to this, when the diaphragm is displaced to the opening side of the substrate, the
displacement of the diaphragm can be regulated at a portion closer to the support portion in the
diaphragm, and more reliably, with respect to the support portion at the displacement of the
diaphragm It is possible to relieve stress concentration.
[0031]
Furthermore, the present invention may be a capacitance type sensor including any of the abovedescribed MEMS structures and a back plate disposed to face the diaphragm via a gap.
Also, in that case, the anchor may fix the diaphragm to the back plate.
[0032]
Further, in the present invention, the diaphragm in any one of the above MEMS structures may
be a piezoelectric sensor having a piezoelectric effect.
[0033]
Furthermore, the present invention may be an acoustic sensor that has the above-described
capacitance type sensor and converts sound pressure into a change in capacitance between the
diaphragm and the back plate.
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The present invention may also be an acoustic sensor that has the piezoelectric sensor described
above, and converts sound pressure into a change in piezoelectric voltage of the diaphragm to
detect it.
According to this, it is possible to obtain a high S / N ratio for the acoustic sensor, and it is
possible to enhance the resistance to the input pressure.
[0034]
As described above, according to the present invention, the capacitance type sensor which
converts the displacement of the diaphragm into the change of the capacitance between the
diaphragm and the back plate or the change of the piezoelectric voltage by the piezoelectric
effect of the diaphragm In the piezoelectric sensor for converting into, a part of the outer shape
of the diaphragm is disposed inside the opening of the substrate as viewed from the normal
direction, and the other part of the outer shape of the diaphragm is the substrate as viewed from
the normal direction It is arranged outside the opening of the.
[0035]
That is, it comprises: a substrate having an opening; and a diaphragm disposed to face the
opening of the substrate, wherein the diaphragm is fixed to the substrate and supports the
diaphragm, and pressure is applied. A capacitive sensor for converting the displacement of the
vibrating portion in the diaphragm into a change in capacitance between the vibrating portion
and the back plate, or a displacement of the diaphragm In a piezoelectric sensor that converts
into a change in piezoelectric voltage due to a piezoelectric effect of a diaphragm, a part of an
outer shape of the vibrating portion is disposed inside an opening of the substrate when viewed
from a normal direction, and the outer shape of the vibrating portion It can also be said that the
other part of is disposed outside the opening of the substrate as viewed from the normal
direction.
[0036]
The diaphragm has a substantially quadrilateral vibrating portion, and a support portion which
radially extends from four corners of the diaphragm and is fixed to the substrate at an end
portion, and the outer shape of the opening portion of the substrate is It has a substantially
quadrilateral shape, the vibrating portion of the diaphragm is disposed to face the opening of the
substrate, and each side of the vibrating portion has a shape different from a straight line, the
external shape of the vibrating portion One part is disposed inside the opening of the substrate
as viewed from the normal direction, and the other part of the outline of the vibrating part is
disposed outside the opening of the substrate as viewed from the normal direction. You may
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[0037]
In this case, for example, each side of the vibrating portion is made uneven as viewed in the
normal direction, so that the outer shape of the vibrating portion is arranged outside the opening
of the substrate in the convex portion. In the concave portion, the outer shape of the vibrating
portion may be disposed inside the opening of the substrate.
According to this, more easily, a part of the outer shape of the diaphragm is disposed inside the
opening of the substrate as viewed from the normal direction, and the other part of the outer
shape of the diaphragm is viewed from the normal direction It can be arranged outside the
opening of the substrate.
In addition, it is possible to easily change the width of the gap and the width of the overlap
viewed from the normal direction of the outer shape of the diaphragm and the opening of the
substrate.
[0038]
Further, in the present invention, the diaphragm has a substantially quadrilateral vibrating
portion, and a supporting portion which radially extends from four corners of the vibrating
portion and is fixed to the substrate at an end portion. The outer shape of the opening has a
substantially quadrilateral shape, the vibrating portion of the diaphragm is disposed to face the
opening of the substrate, and each side of the opening of the substrate has a shape different from
a straight line. Thus, a part of the outer shape of the vibrating portion is disposed inside the
opening of the substrate when viewed in the normal direction, and the other portion of the outer
shape of the vibrating portion is in the substrate when viewed in the normal direction. It may be
arranged outside the opening.
[0039]
In this case, for example, each side of the opening of the substrate is made uneven as seen in the
normal direction, so that the outer shape of the vibrating portion is arranged inside the opening
of the substrate in the convex portion. In the concave portion, the outer shape of the vibrating
portion may be disposed outside the opening of the substrate.
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Also by this, more easily, a part of the outline of the vibrating part is disposed inside the opening
of the substrate when viewed from the normal direction, and the other part of the outline of the
vibrating part is from the normal direction It may be arranged outside the opening of the
substrate as viewed.
In addition, it is possible to easily change the width of the gap and the width of the overlap
viewed from the normal direction of the outer shape of the vibrating portion and the opening of
the substrate.
[0040]
Note that the means for solving the problems described above can be used in combination as
appropriate.
[0041]
According to the present invention, in a capacitance type sensor, a piezoelectric type sensor or an
acoustic sensor manufactured using MEMS technology, it is possible to obtain a high SN ratio
and to improve the resistance to input pressure. .
[0042]
It is the perspective view which showed an example of the conventional acoustic sensor
manufactured by MEMS technology.
It is the disassembled perspective view which showed an example of the internal structure of the
conventional acoustic sensor.
It is a figure which shows the relationship between the shape of the diaphragm in Example 1 of
this invention, a fixed film | membrane, and the external shape of a back chamber. It is the 1st
figure which expanded both-ends vicinity of the support part of a diaphragm, and a vibration part
in Example 1 of this invention. It is the 2nd figure which expanded both-ends vicinity of the
support part of a diaphragm, and a vibration part in Example 1 of this invention. It is the 3rd
figure which expanded both-ends vicinity of the support part of a diaphragm, and a vibration part
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in Example 1 of this invention. It is a figure which shows stress distribution vicinity of the
support part of the diaphragm in a prior art example and Example 1 of this invention. It is a
figure which shows the variation of a relation with the shape of the diaphragm and fixed
membrane in Example 1 of the present invention, and the outline of a back chamber. It is a figure
which shows the other variation of relationship with the shape of the diaphragm and fixed film |
membrane in Example 1 of this invention, and the external shape of a back chamber. It is a figure
which shows the shape of the slit between the diaphragm in Example 1 of this invention, and a
prior art example, and a fixed film | membrane. It is a figure which shows the shape of the
diaphragm in Example 2 of this invention. It is sectional drawing of diaphragm vicinity in
Example 2 of this invention. It is a figure for demonstrating the malfunction of the diaphragm in
a prior art example. It is a figure which shows the relationship between the shape of the
diaphragm in Example 3 of this invention, a fixed film | membrane, and the external shape of a
back chamber. It is a figure which shows the variation of the shape of the diaphragm in Example
4 of this invention, and a relation with the external shape of a back chamber. It is a figure which
shows the variation of the shape of the diaphragm in Example 5 of this invention, and a
relationship with the external shape of a back chamber. It is a figure which shows the shape of
the diaphragm in Example 6 of this invention. It is a partial sectional view of the acoustic sensor
in a prior art example. FIG. 10 is a partial cross-sectional view of an acoustic sensor in another
conventional example.
[0043]
First Embodiment Hereinafter, an embodiment of the present invention will be described with
reference to the drawings. The embodiment described below is an aspect of the present
invention, and does not limit the technical scope of the present invention. The present invention
can be applied to the entire capacitive sensor, but in the following, the case where the capacitive
sensor is used as an acoustic sensor will be described. However, the capacitive sensor according
to the present invention can also be used as a sensor other than an acoustic sensor as long as it
detects displacement of a diaphragm. For example, in addition to the pressure sensor, it may be
used as an acceleration sensor or an inertia sensor. Moreover, you may utilize as elements other
than a sensor, for example, a speaker etc. which convert an electric signal into a displacement. In
the following, the vibrating portion of the diaphragm is substantially quadrilateral and has four
supporting portions, and the outline of the opening of the substrate is substantially quadrilateral,
but the vibrating portion of the diaphragm is a polygon other than quadrilateral or circular. The
effect is obtained even in the case of a closed curve such as, etc., having a plurality of supporting
portions, and the outline of the opening of the substrate being a closed curve such as a polygon
other than quadrilateral or a circle.
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[0044]
FIG. 1 is a perspective view showing an example of a conventional acoustic sensor 1
manufactured by MEMS technology. FIG. 2 is an exploded perspective view showing an example
of the internal structure of the acoustic sensor 1. The acoustic sensor 1 is a laminated body in
which an insulating film 4, a fixed film 13, a diaphragm (vibrating electrode plate) 5, and a back
plate 7 are stacked on the upper surface of a silicon substrate (substrate) 3 provided with a back
chamber 2 as an opening. It is. The back plate 7 has a structure in which the fixed electrode film
8 is formed on the fixed plate 6, and the fixed electrode film 8 is disposed on the silicon substrate
3 side of the fixed plate 6. The fixed plate 6 of the back plate 7 is provided with a large number
of sound holes as perforations (each meshed point of the fixed plate 6 shown in FIG. 1 and FIG. 2
corresponds to an individual sound hole) . In addition, at one of four corners of the fixed
electrode film 8, a fixed electrode pad 10 for obtaining an output signal is provided.
[0045]
Here, the silicon substrate 3 can be formed of, for example, single crystal silicon. Further, the
diaphragm 5 can be formed of, for example, conductive polycrystalline silicon. The diaphragm 5
has a planar shape in which support portions 12 extending radially (that is, in the direction of the
diagonal of the vibrating portion 11) are disposed at four corners of the vibrating substantially
rectangular vibrating portion 11. The diaphragm 5 is disposed on the upper surface of the silicon
substrate 3 so as to cover the back chamber 2, and is fixed to the silicon substrate 3 via anchors
(not shown) at the tips of the four support portions 12. The vibrating portion 11 of the
diaphragm 5 vibrates up and down in response to the sound pressure. Here, the support 12
corresponds to a shape that protrudes toward the anchor.
[0046]
In addition, the diaphragm 5 is not in contact with the silicon substrate 3 or the back plate 7 at
locations other than the four support portions 12. Therefore, it is possible to vibrate more
smoothly in response to the sound pressure. Further, a diaphragm pad (not shown) is provided
on one of the support portions 12 at the four corners of the vibrating portion 11. The fixed
electrode film 8 provided on the back plate 7 is provided to face the vibrating portion 11
excluding the support portions 12 at the four corners of the diaphragm 5.
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[0047]
A fixed film 13 is provided around the diaphragm 5 so as to form substantially the same plane as
the diaphragm 5 after completion of the acoustic sensor 1 and to surround the diaphragm 5 via
the slit 5a. The fixed film 13 is fixed to the substrate 3 in response to sound pressure and does
not vibrate. The fixed film 13 suppresses the decrease in the sensitivity of the acoustic sensor 1
due to the leakage of the air that displaces the vibrating portion 11 up and down from the
periphery of the diaphragm 5.
[0048]
When the sound reaches the acoustic sensor 1, the sound passes through the sound hole and
applies sound pressure to the diaphragm 5. That is, this sound hole causes sound pressure to be
applied to the diaphragm 5. Further, by providing the sound holes, air in the air gap between the
back plate 7 and the diaphragm 5 can easily escape to the outside, and noise can be reduced.
[0049]
In the acoustic sensor 1, due to the above-described structure, the vibrating portion 11 of the
diaphragm 5 vibrates due to the sound, and the distance between the vibrating portion 11 and
the fixed electrode film 8 changes. When the distance between the vibrating portion 11 and the
fixed electrode film 8 changes, the capacitance between the vibrating portion 11 and the fixed
electrode film 8 changes. Therefore, a DC voltage is applied between the vibrating film electrode
pad 9 electrically connected to the diaphragm 5 and the fixed electrode pad 10 electrically
connected to the fixed electrode film 8 to obtain the above-mentioned capacitance. By extracting
the change as an electrical signal, the sound pressure can be detected as an electrical signal.
[0050]
FIG. 3 is a view of the diaphragm 5 and the fixed film 13 in the present embodiment as viewed
from the normal direction of the diaphragm 5. Further, what is indicated by a broken line in FIG.
3 is an outline of the back chamber 2 as an opening of the silicon substrate 3. As shown in the
drawing, the outer shape of the diaphragm 5 is specified by the slit 5 a formed between the
diaphragm 5 and the fixed film 13. In the drawings after FIG. 3, the slit 5a is expressed by a
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single line for the sake of simplicity.
[0051]
Further, the outer shape of the vibrating portion 11 of the diaphragm 5 in the present
embodiment is formed inside the outer shape of the back chamber 2 at the central portion 11a
on each side, and the back chamber 2 at both end portions 11b of each side. It is formed outside
the outline of. In other words, only the both end portions 11 b of the sides of the outer shape of
the vibrating portion 11 of the diaphragm 5 are made to overlap the silicon substrate 3 outside
the back chamber 2 in plan view.
[0052]
Thus, when a large pressure acts on the diaphragm 5 from the back plate 7 side, the silicon
substrate 3 is located near the outer shape of the back chamber 2 at both ends 11 b of each side
of the vibrating portion 11 displaced in the opposite direction to the back plate 7. , And further
displacement of the vibrating portion 11 is suppressed. As a result, even when a large pressure is
applied from the back chamber 7 side, it is possible to suppress the stress concentration on the
support portion 12 and breakage especially by the displacement of the vibrating portion 11 of
the diaphragm 5 excessively. As a result, it is possible to enhance the resistance to the input
pressure of the acoustic sensor 1.
[0053]
FIG. 4 is an enlarged view of the support portion 12 of the diaphragm 5 and both end portions
11 b of the vibrating portion 11 in the present embodiment. In the present embodiment, the
outer shape of the vibrating portion 11 is formed inside the outer shape of the back chamber 2
at the central portion 11 a on each side, and the outer shape of the back chamber 2 at both end
portions 11 b of each side. It is formed outside. The outer shape of the vibrating portion 11
intersects the outer shape of the back chamber 2 in a region between the central portion 11 a
and the both end portions 11 b. As a result, the outer shape of the diaphragm 5 intersects the
outer shape of the back chamber 2 at two intersections sandwiching the support portion 12, and
this portion corresponds to a predetermined cross structure in the present embodiment. In FIG.
4, the anchor 12 a is hatched at the tip of the support portion 12.
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[0054]
Then, in the present embodiment, the intersection point between the outer shape of the vibrating
portion 11 of the diaphragm 5 and the outer shape of the back chamber 2 and the abovementioned intersection point and another closest point existing on different sides of the vibrating
portion 11 are connected. The length B of the line segment is set to be longer than the width A of
the support portion 12 of the diaphragm 5. As a result, the support portion 12 can suppress the
concentration of stress on the support portion 12 at the time of deformation of the diaphragm 5
while obtaining high sensitivity as a state in which deformation by application of pressure is
likely to occur. Here, the width A of the support portion 12 corresponds to the width of the
diaphragm 5 located closer to the anchor.
[0055]
Further, in the present embodiment, as shown in FIG. 5, an inflection point C is provided in the
vicinity of the point of intersection of the outer shape of the vibrating portion 11 of the
diaphragm 5 and the outer shape of the back chamber 2. Thus, by providing the inflection point
C near the intersection of the outer shape of the diaphragm 5 and the outer shape of the back
chamber 2, geometrically, the outer shape of the vibrating portion 11 of the diaphragm 5 and the
outer shape of the back chamber 2 The length B of the line segment connecting the above
intersection point and the other intersection point closest to the aforementioned intersection
point on the different sides of the vibrating portion 11 is more reliably than the width A of the
support portion 12 of the diaphragm 5 It becomes possible to set for a long time.
[0056]
Here, the inflection point C includes the case of being a point and the case of being an area. That
is, the inflection point C may have a structure in which the bending direction of the curve is
reversed at both ends of the point, or a structure in which the bending direction of the curve is
reversed at both ends of a region having a predetermined size (or length). It may be Here, in the
vicinity, the inflection point may be the same point as the intersection, or may have some
deviation (for example, ± 50 μm or less).
[0057]
11-05-2019
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Further, in the present embodiment, as shown in FIG. 6, in the vibrating portion 11 of the
diaphragm 5, the length D of the both end portions 11 b formed outside the outer shape of the
back chamber 2 is each side of the vibrating portion 11. It is considered to be 1/20 or more and
1/3 or less of the length of. Experimentally, in the vibrating portion 11 of the diaphragm 5, if the
length D of the both end portions 11b formed on the outer side of the outer shape of the back
chamber 2 falls within this range, the suppression of noise due to the brown motion of air and It
has been found that the balance with the avoidance of excessive displacement of the diaphragm
5 can be well maintained. Therefore, according to the present embodiment, in the acoustic
sensor, it is possible to make the high SN ratio and the resistance to the input pressure
compatible with each other more reliably.
[0058]
FIG. 7 shows a stress distribution in the vicinity of the support 12 of the diaphragm 5 when a
large pressure is applied from the back plate 7 side. FIG. 7A shows the both ends of the outer
shape of the vibrating portion 11 of the diaphragm 5 when all of the outer shape of the vibrating
portion 11 of the diaphragm 5 is disposed inside the back chamber 2. FIG. 7 (c) is a diagram in
which the portion 11 b is disposed inside the back chamber 2 and the central portions 11 a of
the sides of the vibrating portion 11 are disposed outside the outline of the back chamber 2.
When the central portion 11a of the outer shape of the vibrating portion 11 of the diaphragm 5
is disposed inside the back chamber 2 and both end portions 11b of each side of the vibrating
portion 11 are disposed outside the outer shape of the back chamber 2 Shows a diagram of
[0059]
As shown in this figure, the stress distribution in the vicinity of the support portion 12 when a
large pressure is applied from the back plate 7 side, both end portions 11 b of the outer shape of
the vibrating portion 11 of the diaphragm 5 are arranged inside the back chamber 2. When the
central portion 11a of each side of the vibrating portion 11 is disposed outside the outer shape
of the back chamber 2, all the outer shapes of the vibrating portion 11 are disposed inside the
outer shape of the back chamber 2. The stress distribution is slightly broadened and the stress
concentration in the support portion 12 is relaxed as compared with the case where it is made.
[0060]
Furthermore, the central portion 11 a of the outer shape of the vibrating portion 11 of the
diaphragm 5 is disposed inside the back chamber 2, and both end portions 11 b of each side of
11-05-2019
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the vibrating portion 11 are disposed outside the outer shape of the back chamber 2. In this case,
both ends 11 b of the outer shape of the vibrating portion 11 of the diaphragm 5 are disposed
inside the back chamber 2, and the central portions 11 a of the sides of the vibrating portion 11
are disposed outside the outer shape of the back chamber 2. The stress distribution is further
broadened and the stress concentration in the support portion 12 is alleviated as compared with
the case where the stress is applied.
[0061]
The central portion 11 a of the outer shape of the vibrating portion 11 of the diaphragm 5 is
disposed inside the back chamber 2, and both end portions 11 b of each side of the vibrating
portion 11 are disposed outside the outer shape of the back chamber 2. In this case, the
maximum value of the stress acting on the support portion 12 is reduced to 60% as compared
with the case where the entire outer shape of the vibrating portion 11 is disposed inside the
outer shape of the back chamber 2.
[0062]
When all of the outer shape of the vibrating portion 11 is disposed inside the outer shape of the
back chamber 2, both end portions 11b of each side in the outer shape of the vibrating portion
11 of the diaphragm 5 are outside of the outer shape of the back chamber 2. There was no
significant difference in the SN ratio between the cases where it was placed at.
[0063]
In the above embodiment, both end portions 11b of each side in the outer shape of the vibrating
portion 11 of the diaphragm 5 are disposed outside the outer shape of the back chamber 2, and
all central portions 11a of each side of the vibrating portion 11 are back chamber. Although the
case where it arrange | positions inside 2 external shapes was demonstrated, the shape of the
vibration part 11 in this invention is not restricted to this.
FIG. 8 shows a variation of the outer shape of the vibrating portion 11 when a part of the outer
shape of the vibrating portion 11 of the diaphragm 5 is disposed outside the outer shape of the
back chamber 2.
8A and 8B show an example in which the outline of the back chamber 2 is a simple quadrilateral,
and each side of the outline of the vibrating portion 11 of the diaphragm 5 is deformed.
11-05-2019
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[0064]
More specifically, as shown in FIG. 8A, in the outer shape of the vibrating portion 11 of the
diaphragm 5, all of the central portions 11a of each side in the outer shape of the vibrating
portion 11 are disposed inside the outer shape of the back chamber 2. Thus, both ends 11 b of
each side in the outer shape of the vibrating portion 11 are disposed outside the outer shape of
the back chamber 2.
On the other hand, FIG. 8B is an example in which a part of the central portion 11 a of each side
in the outer shape of the vibrating portion 11 of the diaphragm 5 is disposed outside the outer
shape of the back chamber 2.
[0065]
As in the variation shown in FIG. 8A and the variation shown in FIG. 8B, both end portions 11b of
each side in the outer shape of the vibrating portion 11 are disposed outside the outer shape of
the back chamber 2. It has been experimentally known that the configuration has a large effect of
suppressing stress concentration on the support portion 12 and improving the resistance to the
input pressure of the acoustic sensor 1.
Based on this result and the analysis result of the stress distribution shown in FIG. 7, it can be
more effectively suppressed the stress concentration on the support 12 if the displacement of the
vibrating portion 11 in the vicinity of the support 12 is suppressed. Conceivable. Therefore, in
the present embodiment, it can be said that in the outer shape of the vibrating portion 11, the
region disposed outside the outer shape of the back chamber 2 is preferably both end portions
11 b closer to the support portion 12.
[0066]
Next, FIG. 9 shows a variation in which the outline of the vibrating portion 11 of the diaphragm 5
is a simple quadrilateral, and each side of the outline of the back chamber 2 is deformed. In FIGS.
9A and 9B, the central portion of each side in the outer shape of the vibrating portion 11 of the
11-05-2019
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diaphragm 5 is relatively back by causing the central portion 2a of each side in the outer shape
of the back chamber 2 to project. It is arranged inside the outline of the chamber 2. Further, both
ends 2b of each side of the outer shape of the back chamber 2 are recessed in comparison with
the central portion 2a, so that both ends of each side in the outer shape of the vibrating portion
11 are relatively outside the outer shape of the back chamber 2. It is made to be arranged.
[0067]
In the present embodiment, as shown in FIG. 10A, the fixed film 13 is provided so as to surround
the entire diaphragm 5 including the support portion 12, and the slit 5a forms a closed curve.
There is. This is because, for example, as shown in FIG. 10 (b), in the state where the slit 5a
between the diaphragm 5 and the fixed film 13 is exposed to the outside of the fixed film 13,
foreign matter is exposed from the exposed portion of the slit 5a in the manufacturing process.
The reason is that there is a possibility of getting into an unintended finish.
[0068]
Example 2 Next, Example 2 of the present invention will be described. In the present
embodiment, in particular, of the outer shape of the vibrating portion 11, the region disposed
outside the outer shape of the back chamber 2 is the both end portions 11b of each side, that is,
the region closer to the support portion 12, An example will be described in which a convex
stopper is provided in the portion 11b so as to abut on the substrate 3 when the vibrating
portion 11 is displaced toward the substrate 3 side.
[0069]
FIG. 11 is a view of the vibration unit 11, the support unit 12, the fixed film 13 and the back
chamber 2 in the present embodiment as viewed from the normal direction. 11 (a) is a plan view
of the whole, and FIG. 11 (b) is an enlarged view of the vicinity of the support 12. FIG. 12 (a)
shows a cross section taken along the line AA 'in FIG. 11 (b), and FIG. 12 (b) shows a cross
section taken along the line B-B' in FIG. 11 (b). As shown in FIGS. 11 (b) and 12 (b), in the present
embodiment, particularly in the vibrating portion 11, in the region where the outer shape is
arranged outside the outer shape of the back chamber 2, the substrate 3 is A convex stopper 5b
is provided. Thereby, when the vibrating portion 11 is displaced to the back chamber 2 side by
the large pressure acting on the vibrating portion 11 from the back plate 7 side, the stopper 5 b
11-05-2019
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can be brought into contact with the surface of the substrate 3. As a result, the contact area when
the vibrating portion 11 abuts on the substrate 3 can be reduced, and the sticking of the
vibrating portion 11 in the state of abutted on the substrate 3 can be suppressed.
[0070]
Example 3 Next, Example 3 of the present invention will be described. In the present
embodiment, the distance between the outer shape of the vibrating portion 11 and the outer
shape of the back chamber 2 is a predetermined distance, particularly in a region where the
angle of the outer shape of the vibrating portion 11 with the nearest outer diameter of the back
chamber 2 is less than a predetermined angle. An example of the above separation will be
described.
[0071]
FIG. 13 is a view showing a disadvantage in the case where the outer shape (that is, the end
surface in the side view, the same applies hereinafter) of the vibration portion 11 excessively
approaches the outer shape (end surface) of the back chamber 2. FIG. 13A is a view showing the
relationship between the outer shape (end surface) of the vibrating portion 11 and the outer
shape (end surface) of the back chamber 2 in a state in which no pressure is applied to the
diaphragm 5. FIG. 13B is a view showing a phenomenon that may occur when pressure is applied
to the diaphragm 5.
[0072]
That is, as shown in FIG. 13A, when the outer shape (end surface) of the vibrating portion 11 and
the outer shape (end surface) of the back chamber 2 come too close, a large pressure is applied
to the vibrating portion 11 from the back plate 7 side. When activated, the vibrating portion 11
is temporarily displaced to the side opposite to the back plate 7 and penetrates into the back
chamber 2. Then, when returning to the initial position, the outer shape (end surface) of the
vibrating portion 11 may be hooked on the outer shape (end surface) of the back chamber 2, and
the return to the initial position may not be possible.
[0073]
11-05-2019
22
On the other hand, in the present embodiment, in particular, in the outer shape (end surface) of
the vibrating portion 11, the angle viewed from the normal direction to the outer shape (end
surface) of the nearest back chamber 2 is a predetermined angle, for example, an area of 3
degrees or less In the above, the outer shape (end surface) of the vibrating portion 11 is disposed
away from the outer shape (end surface) of the back chamber 2 by a predetermined distance, for
example, 1 μm or more, or 3 μm or more.
[0074]
FIG. 14 shows a plan view of the outer shape of the diaphragm 5, the fixed film 13 and the back
chamber 2 in the present embodiment.
As can be seen from FIG. 14, in the present embodiment, in the outer shape of the vibrating
portion 11, regions 11 d and 11 e whose angle with the nearest outer shape of the back chamber
2 is 3 degrees or less The same applies to the other three sides), and it is always separated from
the outer shape of the back chamber 2 by 1 μm or more.
[0075]
According to this, the outer shape of the vibrating portion 11 is the back chamber except for the
area where the outer shape of the vibrating portion 11 intersects the outer shape of the back
chamber 2 or the like with a large angle to the nearest outer shape of the back chamber 2. The
external shape (end surface) of the vibrating portion 11 is caught on the external shape (end
surface) of the back chamber 2 when a large pressure acts on the vibrating portion 11 from the
back plate 7 side. It is possible to prevent the return to the initial position from becoming
impossible. In addition, it is possible to prevent the occurrence of inconveniences such as
bending of the vibrating portion 11 and contact of the region on the center side with the back
plate 7.
[0076]
In the present embodiment, in the outer shape of the vibrating portion 11, a region in which the
outer shape of the vibrating portion 11 is separated from the outer surface of the back chamber
2 by 1 μm or more is an angle viewed from the normal to the outer shape of the nearest back
11-05-2019
23
chamber 2. The reason why the area is 3 degrees or less is as follows. That is, basically, when the
outer shape (end surface) of the vibrating portion 11 intersects the outer shape (end surface) of
the back chamber 2 with the outer shape (end surface) of the back chamber 2 having an angle to
a certain extent And is considered to be difficult to catch on the outer shape (end face) of the
back chamber 2.
[0077]
In the above embodiment, the nearest external shape of the back chamber 2 may be the external
shape of the back chamber 2 in which the distance from the predetermined region of the
external shape of the vibrating portion 11 is the smallest. Alternatively, the outer shape of the
back chamber 2 may be such that vertical lines viewed from the normal direction to the outer
shape intersect. Alternatively, it may be a central portion viewed from the normal direction of the
vibrating portion 11 (in the case where the vibrating portion is a quadrilateral, an intersection of
diagonal lines). If the vibrating portion is circular, it may be the center. And the straight line
drawn so as to pass through the region may cross the outer shape of the back chamber 2.
[0078]
Further, in the present embodiment, as shown in FIG. 14, the crossing angle in the case where
the outer shape of the vibrating portion 11 intersects the outer shape of the back chamber 2 is
approximately 45 degrees. If the crossing angle is 30 degrees or more, even if the outer position
of the back chamber 2 varies due to manufacturing variation, the outer portion of the vibrating
portion 11 of the diaphragm 5 is disposed outside the outer shape of the back chamber 2 It is
possible to suppress the change in the area of the part. In other words, the area of the portion of
the vibrating portion 11 of the diaphragm 5 overlapping in a plan view with the silicon substrate
3 outside the back chamber 2 can be stabilized.
[0079]
Example 4 Next, Example 4 of the present invention will be described. In this embodiment, an
example in which the outer shape of the vibrating portion of the diaphragm is a shape other than
quadrilateral will be described.
11-05-2019
24
[0080]
In FIG. 15, it shows about the variation of the external shape of the diaphragm 5 in a present
Example. FIG. 15A shows an example in which the outer shape of the back chamber 2 and the
outer shape of the vibrating portion 11 of the diaphragm 5 are substantially regular hexagons. In
this case, a total of six radially extending supports 12 are provided at each corner. FIG. 15B
shows an example in which the outer shape of the back chamber 2 and the outer shape of the
vibrating portion 11 of the diaphragm 5 are substantially regular octagonal. In this case, a total
of eight radially extending supports 12 are provided at each corner. FIG. 15C shows an example
in which the outer shape of the back chamber 2 is circular, the outer shape of the vibrating
portion 11 of the diaphragm 5 is substantially quadrilateral, and the central portion 11a is
convex in an arc shape. In this case, a total of four radially extending support portions 12 are
provided at each corner as in the first embodiment.
[0081]
As described above, the shape of the vibrating portion and the number of supporting portions
can be appropriately changed according to the shape of the base and the specifications of the
capacitive sensor. As can be seen from FIG. 15, in the present embodiment, the outer shape of the
vibrating portion 11 is arranged inside the outer shape of the back chamber 2 at the central
portion 11a and is arranged outside the outer shape of the back chamber 2 at both end portions
11b. ing. However, as to which portion of the outer shape of the vibrating portion 11 is disposed
outside the outer shape of the back chamber 2 and which portion is disposed inside the outer
shape of the back chamber 2, the specifications of the capacitive sensor It is natural that it can
change suitably according to it.
[0082]
Example 5 Next, Example 5 of the present invention will be described. In this embodiment, an
example will be described in which an area having a point of intersection with the outline of the
opening of the substrate and an area not having the same exist on the outer shape of the
vibrating portion of the diaphragm.
[0083]
11-05-2019
25
FIG. 16 shows a variation of the outer shape of the diaphragm 5 in the present embodiment. In
FIG. 16A, the vibrating portion 11 is substantially quadrilateral, and the upper and lower two
sides of the quadrilateral are disposed outside the outline of the back chamber 2, and the back
chamber is disposed of the two opposite sides. It is an example arrange | positioned inside the
outline of 2. In FIG. 16B, the vibrating portion 11 is substantially quadrilateral, both ends 11 b
are provided in the vicinity of two opposing diagonals of the quadrilateral, and both ends 11 b
are provided for the remaining two diagonals. This is an example in which is not provided. In FIG.
16C, the outer shape of the back chamber 2 and the outer shape of the vibrating portion 11 of
the diaphragm 5 are substantially octagonal, and the apex angle at which both ends 11b are
provided and the apex at which both ends 11b are not provided. It is an example in which
corners are provided alternately.
[0084]
As described above, the diaphragm 5 in the present invention may have a cross structure in
which the outer shape of the diaphragm 5 and the outer shape of the opening of the substrate
intersect with each other at least at one place when viewed from the normal direction of the
diaphragm 5 The outer shape of the vibrating portion 11 of 5 includes a region in which a region
having an intersection point with the outer shape of the back chamber 2 and a region not having
the same are mixed.
[0085]
Example 6 Next, Example 5 of the present invention will be described.
In this embodiment, an example in which the outer shape of the vibrating portion of the
diaphragm is substantially circular will be described.
[0086]
In FIG. 17, the case where the external shape of the vibration part 11 of the diaphragm 5 in a
present Example is circular is shown. In this example, four support portions 12 are provided to
extend in the radial direction at intervals of 90 degrees. Further, both ends 11 b are provided at
both ends of the curved portion between the support portion 12 and the support portion 12, and
the outer shape of the vibrating portion 11 is disposed outside the outer shape of the circular
11-05-2019
26
back chamber 2 at both ends 11 b. ing. Further, in the central portion 11 a in the curved portion
between the support portion 12 and the support portion 12, the outer shape of the vibrating
portion 11 is disposed inside the outer shape of the circular back chamber 2. The curved portion
between the support portion 12 and the support portion 12 in the diaphragm 5 of FIG. 17
corresponds to the curve constituting the closed curve in the present invention.
[0087]
As described above, the outer shape of the vibrating portion 11 of the diaphragm 5 in the
present invention is not limited to a polygon such as a quadrilateral. Moreover, although the case
where the external shape of the vibration part 11 is circular was demonstrated in the present
Example, the external shape of the vibration part 11 may be formed by closed curved surfaces
other than circular.
[0088]
In the above embodiment, although the example in which the support portion 12 of the
diaphragm 5 is fixed to the substrate 3 by the anchor 12a has been described, in the present
invention, the support portion 12 of the diaphragm 5 is fixed to the back plate 7 by the anchor
12a. It does not matter if it is done. In the above embodiments, although the present invention
has been described as applied to a capacitive sensor, the present invention relates to other
sensors, for example, a diaphragm made of a material having a piezoelectric effect, and
displacement of the diaphragm being piezoelectric. The same applies to a piezoelectric sensor
that detects a change in voltage. In this case, the back plate is unnecessary as a configuration.
[0089]
Reference Signs List 1 acoustic sensor 2 back chamber 3 silicon substrate 5 diaphragm 5 a slit 5
b stopper 7 back plate 8 fixed electrode film 11 · · Vibration portion 11a · · · central portion 11b ·
· · both ends 12 · · · support portion 13 · · · fixed membrane
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