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DESCRIPTION JP2016066969

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DESCRIPTION JP2016066969
Abstract: The present invention provides an acoustic transducer in which the resistance to
penetration through a slit is larger than that in the past, and the rate of reduction in the
resistance to penetration through the slit is smaller than in the past when warpage or the like of
a vibrating electrode plate occurs. An acoustic transducer includes a fixed electrode plate, and a
vibrating electrode plate facing the fixed electrode via a gap, the vibrating electrode plate
including a slit 17 for transmitting sound. And a high-resistance surface which is a surface
constituting the side surface in the width direction of the slit 17 and which has a high resistance
surface whose thickness exceeds the thickness of the central portion of the vibrating electrode
plate 17 as viewed from the width direction of the slit 17 Have. [Selected figure] Figure 16
Acoustic transducer and microphone
[0001]
The present invention relates to acoustic transducers and microphones.
[0002]
In recent cellular phones and the like, MEMS (Micro Electro-Mechanical Systems) microphones
are often used.
[0003]
The MEMS microphone is a microphone in which an acoustic transducer manufactured using
MEMS technology is housed in a housing together with an application specific integrated circuit
(ASIC) for amplifying the output of the acoustic transducer.
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1
[0004]
As an acoustic transducer for a MEMS microphone, as shown in FIG. 1A, a vibrating electrode
plate (diaphragm) 33 covering the cavity 32a is disposed above the substrate 32 having the
cavity 32a and is opposed to the vibrating electrode plate 33. It is known that the fixed electrode
plate 39 is disposed to do so.
[0005]
The acoustic transducer has a configuration in which the vibration of the portion of the vibrating
electrode plate 33 located on the substrate 32 can propagate to the central portion of the
vibrating electrode plate 33.
Therefore, in the acoustic transducer shown in FIG. 1A, the acoustic resistance in the space
between the substrate 32 and the vibrating electrode plate 33 is high, which may cause acoustic
noise.
[0006]
When the portion of the vibrating electrode plate 33 located on the substrate 32 and the central
portion of the vibrating electrode plate 33 are physically separated, the vibrating electrode plate
33 is positioned on the substrate 32. It is possible to prevent the vibration of the portion that is
being transmitted from being directly transmitted to the central portion of the vibrating electrode
plate 33.
Therefore, as schematically shown in FIG. 1 (B), an acoustic transducer has been developed in
which a plurality of slits 37 are provided on the vibrating electrode plate 33 so as to surround
the central portion of the vibrating electrode plate 33.
[0007]
U.S. Patent No. 5,452,268 Patent specification No. 5,218,432
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[0008]
Even in the acoustic transducer in which the substrate 32, the fixed electrode plate 39, and the
vibrating electrode plate 33 are arranged in order, the central portion of the vibrating electrode
plate 33 is surrounded so as to make the central portion of the vibrating electrode plate 33
easier to vibrate. Providing a plurality of slits 37 is performed.
[0009]
Then, with regard to an acoustic transducer in which a plurality of slits 37 are provided so as to
surround the central portion of the vibrating electrode plate 33, as shown in FIG. 2A, within the
audible range (audio frequency band) when the resistance through the slits 37 decreases. It has
been found that the noise floor of the is pushed to the high frequency side.
The passage resistance of the slit 37 refers to the resistance to which sound (vibration of air) is
received when passing through the slit 37.
[0010]
In addition, if the penetration resistance through the slit 37 is too small, as shown in FIG. 2B, the
sensitivity characteristic at the lower frequency may be lowered, and sufficient sensitivity
characteristic may not be realized at the lower frequency.
[0011]
Therefore, it is preferable that the slits 37 of the acoustic transducer have high penetration
resistance.
[0012]
The penetration resistance through the slit 37 can be increased by narrowing the width of the slit
37 or increasing the thickness of the vibrating electrode plate 33.
However, there are limits to the increase in penetration resistance of the slit 37 due to the
narrowing due to large process limitations.
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In addition, when the thickness of the vibrating electrode plate 33 is increased, the vibrating
electrode plate 33 becomes hard (it becomes difficult to vibrate), so that the sensitivity of the
acoustic transducer is lowered.
Therefore, it is not preferable to increase the thickness of the vibrating electrode plate 33 in
order to increase the penetration resistance through the slits 37.
[0013]
Also, consider the case where the slits 37 are formed in the vibrating electrode plate 33 as
having a penetration resistance as shown by the difference in thickness of the arrows in FIG. 3A.
[0014]
The acoustic transducer is such that a voltage is applied between the vibrating electrode plate 33
and the fixed electrode plate 39 during use.
Therefore, even in the above case, as shown schematically in FIG. 3 (B), the electrostatic
attraction between the vibrating electrode plate 33 and the fixed electrode plate 39 shifts the
inner side surfaces on both sides of the slit 37, As a result, the penetration resistance of the slit
37 may be reduced.
[0015]
Further, as schematically shown in FIG. 3C, the stress in each portion of the vibrating electrode
plate 33 causes the portion in the vicinity of the slit 37 of the vibrating electrode plate 33 to
warp, and as a result, the passing resistance through the slit 37 decreases. There are also times
when
[0016]
As described above, in the case of the acoustic transducer in which the slits 37 are provided in
the vibrating electrode plate 33, the resistance through the slits 37 may be reduced due to the
deformation of the vibrating electrode plate.
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[0017]
Therefore, an object of the present invention is an acoustic transducer of a type in which a slit is
provided in a vibrating electrode plate, and the slit in the slit has a larger resistance than in the
past and a slit or the like occurs in the vibrating electrode plate. It is an object of the present
invention to provide an acoustic transducer in which the rate of decrease in penetration
resistance is smaller than that of the prior art.
[0018]
Another object of the present invention is to provide a higher performance microphone provided
with an acoustic transducer of the type in which the vibrating electrode plate is provided with a
slit.
[0019]
In order to solve the above problems, an acoustic transducer according to the present invention
is a fixed electrode plate, and a vibrating electrode plate facing the fixed electrode plate with a
gap therebetween, the vibrating electrode having a slit for transmitting sound. The vibrating
electrode plate is a surface that constitutes a side surface in the width direction of the slit, and
the high resistance surface whose thickness exceeds the thickness of the central portion of the
vibrating electrode plate is viewed from the width direction of the slit By providing a pair or
more so as to overlap, it has a resistance increasing portion that increases the resistance of the
sound passing through the slit.
[0020]
That is, one or more portions of one side (inside surface; hereinafter, referred to as a first side) of
the slit in the width direction of the slit of the acoustic transducer according to the present
invention have a thickness (length in the thickness direction of the vibrating electrode plate) Is a
high resistance surface which exceeds the thickness of the central portion of the vibrating
electrode plate.
Further, the other side surface in the width direction of the slit (hereinafter, referred to as a
second side surface) has a shape provided with a high resistance surface at a position facing each
high resistance surface of the first side surface.
The slit having the first side surface and the second side surface of such shape is a slit simply
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formed in the vibrating electrode plate having uniform film thickness of each portion (the
thickness (height) of each portion of the side surface is the thickness of the vibrating electrode
plate The average length of the portion in contact with the sound when passing is longer than
that of the same slit (hereinafter referred to as a conventional slit).
That is, the slit having the first side surface and the second side surface has a greater penetration
resistance (passage resistance for sound) than the conventional slit.
In addition, the slit having the above-described configuration also has a rate of reduction in
penetration resistance smaller than that of the conventional slit (see FIG. 16) when warpage or
the like of the vibrating electrode plate occurs.
Therefore, if the configuration of the present invention is adopted, an acoustic transducer in
which the penetration resistance through the slit is larger than in the prior art, and the rate of
decrease in the penetration resistance through the slit is smaller than in the conventional case
You can get
[0021]
Even if the acoustic transducer according to the present invention is realized as “each surface
on the slit side of the resistance increasing portion has a square wave shape” (see FIGS. 9 and
16), “the length direction of the slit The single high-resistance surface extending to each side
constitutes the respective surfaces on the slit side of the resistance increasing portion ”(see FIG.
10).
In general, acoustic transducers having the former configuration can be more easily
manufactured than acoustic transducers having the latter configuration.
Therefore, from the viewpoint of easiness of manufacture, it is preferable to set the shape of each
surface on the slit side of the resistance increasing portion to a square wave shape.
[0022]
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In addition, in the case where a resistance increasing portion having a plurality of pairs of high
resistance surfaces is used, the penetration resistance of the slit is “the length of the high
resistance surface in the lengthwise direction of the slit when the length of the resistance
increasing portion is equal. The larger the value of “×” the “number of high resistance
surfaces”, the larger. Then, if each surface on the slit side of the resistance increasing portion
has a rectangular wave shape (a square wave shape with a duty ratio of 50%), the number of high
resistance surfaces can be easily increased. Therefore, in order to easily increase the number of
high resistance surfaces, the shape of each surface on the slit side of the resistance increasing
portion may be a rectangular wave.
[0023]
In addition, the vibrating electrode plate provided with the slit and the resistance increasing
portion in which each surface on the slit side has a square wave shape can be formed by various
methods. For example, the vibrating electrode plate can be manufactured by the following
procedure. First, a plate-like member provided with a slit structure having a square cross section
in the longitudinal direction is formed. Next, the central portion in the lateral direction of the slit
structure of the formed plate-like member is removed.
[0024]
The resistance increasing portion in the acoustic transducer according to the present invention
protrudes from the vibrating electrode plate, but when the high resistance portion protrudes
toward the fixed electrode plate, the high resistance portion easily sticks to the fixed electrode
plate And the sensitivity of the acoustic transducer may be reduced. Therefore, it is preferable
that the acoustic transducer according to the present invention is configured as "the resistance
increasing portion protrudes from the vibrating electrode plate to the opposite side to the fixed
electrode plate".
[0025]
The acoustic transducer according to the present invention is usually realized as a vibrating
electrode plate provided with a plurality of slits so as to surround a central portion of the
vibrating electrode plate. At that time, even if only some of the slits in the plurality of slits satisfy
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the above condition (the resistance increasing portion is provided side by side), all the slits may
satisfy the above condition. good. In addition, if the fixed electrode plate is not present on the
region outside the slit of the vibrating electrode plate, an acoustic transducer with high
sensitivity can be obtained. Therefore, in the acoustic transducer according to the present
invention, “a plurality of the slits are provided in the vibrating electrode plate so as to surround
a central portion of the vibrating electrode plate, and the fixed electrode plate is a method of the
vibrating electrode plate Those which are contained in the region defined by the plurality of slits
when viewed from the linear direction, and “the slits have a shape surrounding the central
portion of the vibrating electrode plate, and the fixed electrode plate is When viewed from the
normal direction of the vibrating electrode plate, it may be contained in the area defined by the
slit.
[0026]
The acoustic transducer according to the present invention may be realized as “the peripheral
portion of the vibrating electrode plate is fixed to the substrate through one or more support
members”, and the peripheral portion of the vibrating electrode plate is , And may be directly
fixed to the substrate. In the case of realizing the acoustic transducer according to the present
invention as having the former configuration, in order to prevent the slit from expanding due to
the deformation of the portion outside the slit of the vibrating electrode plate, The supporting
member may include a supporting member for fixing the outer portion of the slit of the vibrating
electrode plate to the substrate.
[0027]
In the acoustic transducer according to the present invention, usually, the fixed electrode plate
and the vibrating electrode plate are directly or indirectly attached to a substrate having a cavity
opened on the first surface side. If at least a part is not located on the substrate, the sensitivity
and the signal-to-noise ratio will be improved. Therefore, in the acoustic transducer according to
the present invention, “the fixed electrode plate and the vibrating electrode plate are directly or
indirectly attached to a substrate having a cavity opened on the first surface side, and at least one
of the slits is Are provided at positions shifted inward of the cavity relative to the edge of the
opening on the first surface side of the cavity of the substrate when viewed in the normal
direction of the first surface. You may leave it. The arrangement order of the components of the
acoustic transducer according to the present invention may be the order of the substrate, the
vibrating electrode plate and the fixed electrode plate, or the substrate, the fixed electrode plate
and the vibrating electrode plate.
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[0028]
The acoustic transducer according to the present invention may be realized as “the peripheral
portion of the vibrating electrode plate is fixed to the substrate through one or more support
members”, and the peripheral portion of the vibrating electrode plate is , And may be directly
fixed to the substrate. In the case of realizing the acoustic transducer according to the present
invention as having the former configuration, in order to prevent the slit from expanding due to
the deformation of the portion outside the slit of the vibrating electrode plate, The supporting
member may include a supporting member for fixing the outer portion of the slit of the vibrating
electrode plate to the substrate.
[0029]
The acoustic transducer according to the present invention may be configured to include “a
back plate to which the fixed electrode plate is attached and in which an acoustic hole is not
provided in a portion facing the slit”. By adopting this configuration, the air passing through the
slit does not directly pass through the acoustic hole of the back plate, so the resistance through
the slit can be further increased.
[0030]
An acoustic transducer according to another aspect of the present invention is a back plate, a
fixed electrode plate attached to the back plate, and a vibrating electrode plate opposed to the
fixed electrode plate via a gap, and transmits sound. And a vibrating electrode plate having a slit
for forming a back plate, wherein a portion of the back plate facing the slit is not provided with
an acoustic hole.
[0031]
That is, the acoustic transducer which concerns on this aspect has a structure which the air
which passed the slit does not directly pass through the acoustic hole which penetrates a
backplate (or backplate and fixed electrode plate).
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Therefore, the acoustic transducer of this aspect has a greater resistance to penetration through
the slit than the conventional acoustic transducer in which the acoustic hole penetrating the back
plate (or the back plate and the fixed electrode plate) is provided on the slit. It functions as an
acoustic transducer with a low rate of decrease in resistance through the slit when a board
warpage or the like occurs.
[0032]
A microphone according to the present invention includes the above-described acoustic
transducer according to the present invention, and an integrated circuit that amplifies the output
of the acoustic transducer.
[0033]
That is, as the microphone according to the present invention, an acoustic transducer having a
higher penetration resistance and a smaller reduction rate of the penetration resistance when a
deflection or the like of the vibrating electrode plate occurs than the conventional acoustic
transducer is used.
Therefore, the microphone according to the present invention functions as a microphone with
higher performance than an acoustic transducer in which the vibrating electrode plate is
provided with a simple slit.
[0034]
According to the present invention, in the type in which the vibrating electrode plate is provided
with the slit, the resistance to passing through the slit is greater than in the prior art, and the rate
of reduction of the passing resistance through the slit is It is possible to provide a more
sophisticated microphone with less acoustic transducers than in the prior art and acoustic
transducers of the type in which the vibrating electrode plate is provided with slits.
[0035]
FIG. 1 is an explanatory view of the configuration of an existing acoustic transducer.
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FIG. 2A is an explanatory view of the relationship between a slit passing resistance and noise.
FIG. 2B is an explanatory view of the relationship between the penetration resistance of the slit
and the sensitivity. FIG. 3 is an explanatory view of a problem that may occur in an acoustic
transducer in which a slit is provided in a vibrating electrode plate. FIG. 4 is an exploded
perspective view of an acoustic transducer according to an embodiment of the present invention.
FIG. 5 is a cross-sectional view of an acoustic transducer according to an embodiment. FIG. 6 is a
top view of the acoustic transducer whose back plate and fixed electrode plate are not shown.
FIG. 7 is an explanatory view of a configuration that can be adopted to fix the vibrating electrode
plate to the substrate. FIG. 8 is a top view of the acoustic transducer with the back plate omitted.
FIG. 9 is an explanatory view of a resistance increasing portion. FIG. 10 is an explanatory view of
a resistance increasing portion. FIG. 11A is a process diagram for describing an example of a
manufacturing procedure of a vibrating electrode plate. FIG. 11B is a process diagram for
describing another example of the manufacturing procedure of the vibrating electrode plate. FIG.
12 is a plan view of a member formed on the second sacrificial layer. FIG. 13 is an explanatory
view of a shape example of the resistance increasing portion in which the stress is not
concentrated on the corner portion. FIG. 14 is an explanatory view of a problem that occurs
when a recess with an excessively narrow width is formed on the second sacrificial layer. FIG. 15
is an explanatory view of the function of the slit of the acoustic transducer. FIG. 16 is an
explanatory view of the function of the slit of the acoustic transducer. FIG. 17 is an explanatory
view of an effect obtained by not providing the acoustic hole on the slit. FIG. 18 is a block
diagram of a microphone that can be manufactured using an acoustic transducer. FIG. 19 is an
explanatory view of a modified example of the acoustic transducer according to the embodiment.
FIG. 20 is an explanatory view of a modified example of the acoustic transducer according to the
embodiment. FIG. 21 is an explanatory view of a modified example of the acoustic transducer
according to the embodiment. FIG. 22 is an explanatory view of a modified example of the
acoustic transducer according to the embodiment. FIG. 23 is an explanatory view of a modified
example of the acoustic transducer according to the embodiment.
[0036]
Hereinafter, an embodiment of the present invention will be described with reference to the
attached drawings. However, the present invention is not limited to the following embodiments,
and various design changes can be made without departing from the scope of the present
invention. In particular, although the invention will be described in the following by taking an
acoustic transducer for a microphone as an example, the invention can also be applied to an
acoustic transducer for a speaker.
[0037]
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First, the overall configuration of the acoustic transducer 10 according to an embodiment of the
present invention will be described using FIGS. 4 to 8. FIG. 4 is an exploded perspective view of
the acoustic transducer 10 according to the present embodiment, and FIG. 5 is a cross-sectional
view of the acoustic transducer 10. FIG. 6 is a top view of the acoustic transducer 10 with the
back plate 18 and the fixed electrode plate 19 omitted. FIG. 7 is an explanatory view of a
configuration that can be adopted to fix the vibrating electrode plate 13 to the substrate 12, and
FIG. 8 is a top view of the acoustic transducer 10 with the back plate 18 omitted. Moreover, in
the following description, upper and lower are upper and lower in FIG. 4 and FIG. 5, respectively.
[0038]
The acoustic transducer 10 according to the present embodiment is a capacitive element
manufactured using MEMS technology. As shown in FIGS. 4 and 5, the acoustic transducer 10
includes a substrate 12, a vibrating electrode plate (diaphragm) 13, a back plate 18 and a fixed
electrode plate 19 as main components.
[0039]
The substrate 12 is a silicon substrate provided with a cavity 12 a penetrating from the lower
surface to the upper surface. The substrate 12 shown in FIGS. 4 and 5 has a wall surface of the
cavity 12 a in which a surface equivalent to the (111) surface and the (111) surface of the (100)
surface silicon substrate is the wall surface of the substrate 12. The cavity 12a may have walls of
other shapes (eg, vertical walls).
[0040]
The vibrating electrode plate 13 of the acoustic transducer 10 is a polysilicon thin film. As shown
in FIGS. 4 and 6, the vibrating electrode plate 13 is a substantially rectangular member. However,
at each corner portion of the vibrating electrode plate 13, leg pieces 26 which are portions fixed
to the substrate 12 via the support members 16 are provided. Further, on one side of the
vibrating electrode plate 13, a wiring portion 27 electrically connected to the electrode pad 35
provided on the top surface of the back plate 18 is also provided.
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[0041]
Four slits 17 are formed in the vibrating electrode plate 13 so as to surround a central portion of
the vibrating electrode plate 13. Each slit 17 has a shape in which a portion extending in the
direction of the leg piece 26 is connected to each end of a linear portion substantially parallel to
each side of the outer periphery of the vibrating electrode plate 13. Further, as shown in FIG. 6
(and FIG. 5), each slit 17 is a position where the position of the linear portion is shifted to the
inside of the cavity 12a than the edge of the opening 12b on the upper surface side of the cavity
12a. It is formed to be. Then, the linear portion of each slit 17 is provided with a resistance
increasing portion 20 (details will be described later).
[0042]
As shown in FIG. 6, the central portion of the region outside the slits 17 of the vibrating electrode
plate 13 is also a portion for fixing the vibrating electrode plate 13 to the substrate 12 via the
support member 16. It is used. A configuration different from the configuration shown in FIG. 6
may be adopted for fixing the vibrating electrode plate 13 to the substrate 12. Specifically, as
shown in FIG. 7A, each portion of the vibrating electrode plate 13 outside the slits 17 is a
substrate through a plurality of (two in FIG. 7A) support members 16. It may be fixed to 12.
Further, as shown in FIG. 7B, the vibrating electrode plate 13 may be fixed to the substrate 12 by
one supporting member 16 having a shape surrounding the outer peripheral portion of the
vibrating electrode plate 13. .
[0043]
The portions of the vibrating electrode plate 13 outside the slits 17 may not be fixed to the
substrate 12. However, in such a case, portions outside the slits 17 of the vibrating electrode
plate 13 may be deformed, and the widths of the slits 17 may be increased. Therefore, in order to
fix the vibrating electrode plate 13 to the substrate 12, the configuration as shown in FIG. 6, FIG.
7 (A) and FIG. 7 (B), ie, the outside of the slits 17 of the vibrating electrode plate 13 It is
preferable to adopt a configuration in which each part is fixed to the substrate 12 in any form.
[0044]
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The fixed electrode plate 19 of the acoustic transducer 10 is a polysilicon thin film. As shown in
FIG. 8, the fixed electrode plate 19 has a shape that fits in the central portion of the vibrating
electrode plate 13 surrounded by the four slits 17. Further, on one side of the fixed electrode
plate 19, a wiring portion 28 electrically connected to an electrode pad 36 (see FIG. 4) provided
on the top surface of the back plate 18 is provided.
[0045]
The back plate 18 (see FIGS. 4 and 5) is a member made of SiN, to the lower surface of which the
fixed electrode plate 19 is fixed. The back plate 18 has a shape in which the distance between the
vibrating electrode plate 13 and the fixed electrode plate 19 is a desired value. Further, the fixed
electrode plate 19 is fixed to the back plate 18 so as to be located above the central portion of
the vibrating electrode plate 13 surrounded by the four slits 17.
[0046]
As shown in FIG. 5, a plurality of acoustic holes 24 penetrating the back plate 18 and the fixed
electrode plate 19 are provided in the portion where the back plate 18 and the fixed electrode
plate 19 overlap. Further, in the portion of the back plate 18 where the fixed electrode plates 19
do not overlap and which are not on the slits 17, a plurality of acoustic holes 24 penetrating only
the back plate 18 are provided. That is, the acoustic transducer 10 according to the present
embodiment adopts a configuration in which the acoustic hole 24 is not provided in a portion on
the slit 17 of the back plate 18 (in this portion, the fixed electrode plate 19 is not overlapped). .
[0047]
The portion of the back plate 18 which is not on the slits 17 and the arrangement pattern of the
acoustic holes 24 in the fixed electrode plate 19 are not particularly limited. Therefore, the
arrangement pattern may be a triangular lattice shape, a rectangular lattice shape, a concentric
circular arrangement pattern, or an irregular arrangement pattern.
[0048]
Hereinafter, the configuration of the vibrating electrode plate 13 of the acoustic transducer 10
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will be described more specifically.
[0049]
As already described, the resistance increasing portions 20 are juxtaposed to the slits 17 of the
vibrating electrode plate 13.
[0050]
The resistance increasing portion 20 is a structure provided to increase the passage resistance of
the sound of the slit 17 (more precisely, the linear portion of the slit 17).
The resistance increasing portion 20 is a surface constituting a side surface in the width direction
of the slit 17 and a high resistance surface having a thickness exceeding the thickness of the
central portion of the vibrating electrode plate 13 is a pair or more so as to overlap Any structure
may be provided.
[0051]
The resistance increasing unit 20 will be described in more detail below with reference to FIGS. 9
and 10.
FIG. 9 is an explanatory view of the configuration of the resistance increasing portion 20, and
“d” in FIGS. 9 and 10 indicates the thickness of the central portion of the vibrating electrode
plate 13 It is the film thickness of the part except the vicinity part). FIG. 10A is a top view of an
acoustic transducer provided with a resistance increasing section 20 of another configuration, in
which the back plate 18 and the fixed electrode plate 19 are not shown. FIG. 10C is a crosssectional view taken along line XX 'in FIG. 10A of the resistance increasing portion 20, and FIG.
10B is orthogonal to the cross-sectional view taken along line XX' in the resistance increasing
portion 20. Is an enlarged cross-sectional view in the direction of
[0052]
As already described, the resistance increasing portion 20 is a surface constituting a side surface
in the width direction of the slit 17 and a high resistance surface whose thickness exceeds the
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15
thickness of the central portion of the vibrating electrode plate 13 is viewed from the width
direction of the slit 17 It is sufficient if the structure has a pair or more so as to overlap.
[0053]
Therefore, the resistance increasing portion 20 may have a structure in which a pair of portions
20a having the shape shown in FIG. 9 is opposed to the surface on the slit 17 side (surface to be
the inner surface of the slit 17).
In FIG. 9, the shaded area 21 is a high resistance surface 21 whose thickness (length in the
thickness direction of the vibrating electrode plate 13) exceeds the thickness of the central
portion of the vibrating electrode plate 13. is there. Further, as shown in FIGS. 10A to 10C, the
resistance increasing portion 20 may have a structure including only a pair of high resistance
surfaces 21 extending in the longitudinal direction of the slit 17.
[0054]
The vibrating electrode plate 13 provided with the resistance increasing portion 20 having the
above-mentioned shape can be manufactured by various procedures.
[0055]
Hereinafter, with reference to FIGS. 11A and 12, an example of manufacturing procedure of the
vibrating electrode plate 13 including the resistance increasing portion 20 in which the pair of
portions 20 a having the shape shown in FIG. .
11A is a process diagram for explaining an example of a manufacturing procedure of the
vibrating electrode plate 13, and FIG. 12 is a plan view of a member 13 'formed on the second
sacrificial layer 52.
[0056]
At the time of manufacturing the vibrating electrode plate 13, first, as shown in (a) and (b) of FIG.
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11A, the first sacrificial layer 51 is formed on the substrate 12. As the first sacrificial layer 51,
for example, a polysilicon film, an SiO 2 film, or the like is formed. Thereafter, a plurality of
recesses are arranged along the center line of the planned formation region of the linear portion
of each slit 17 on the surface of the first sacrificial layer 51 by forming a resist pattern, etching,
etc. Are formed (FIG. 11A (c)).
[0057]
Then, a second sacrificial layer 52 having a surface shape corresponding to the surface shape of
the first sacrificial layer 51 is formed by depositing an SiO 2 film or the like on the first sacrificial
layer 51 in which the plurality of recesses are formed. (FIG. 11A (d)). That is, the second
sacrificial layer 52 having a recess slightly smaller than the recess of the first sacrificial layer 51
is formed in a portion above each recess of the first sacrificial layer 51. Incidentally, the concave
portion formed on the second sacrificial layer 52 is a portion shown by hatching in FIG. 12 of the
member 13 ′ corresponding to the vibrating electrode plate 13 before the formation of the slit
17 (after the formation of the slit 17 This is for forming the main portion of the resistance
increasing portion 20).
[0058]
Thereafter, a polysilicon film is formed on the second sacrificial layer 52 to form the member 13
'(FIG. 11A (e)), and then the step of forming the slits 17 in the formed member 13' is performed. .
As a result, it is possible to obtain the vibrating electrode plate 13 provided with the resistance
increasing portion 20 in which the pair of portions 20a having the shape shown in FIG.
[0059]
A sacrificial layer 53 is formed on the substrate 12 as shown in FIG. 11B, and a plurality of
concave portions are formed on the surface of the formed sacrificial layer 53 ((a) to (c). ) Can also
be manufactured. Although this manufacturing procedure is simpler than the manufacturing
procedure described with reference to FIG. 11A, in this manufacturing procedure, the depth of
each recess of the sacrificial layer 53 is determined by the etching time. Therefore, when this
manufacturing procedure is used, the depth of the recess of the sacrificial layer 53 varies
depending on the location of the wafer, and as a result, various acoustic transducers having
different specific shapes of the resistance increasing portion 20 from one wafer. It is possible
17-04-2019
17
that 10 will be obtained. On the other hand, when the manufacturing procedure described with
reference to FIG. 11A is used, the depth of each recess of the sacrificial layer 52 is determined by
the thickness of the sacrificial layer 51. Therefore, by using the manufacturing procedure
described with reference to FIG. 11A, it is possible to manufacture a plurality of acoustic
transducers 10 in which the shapes of the resistance increasing portions 20 match from one
wafer.
[0060]
When a recess (a rectangular recess or the like) having corner portions where two straight lines
(two line segments) intersect is formed on the second sacrificial layer 52 or the sacrificial layer
53, the formed vibrating electrode plate 13 is also formed. , Has a corner where the two straight
lines intersect. And if there is such a corner, stress concentrates on the corner, so that the
acoustic transducer 10 with low drop resistance strength is obtained. On the other hand, if R is
attached to each corner, stress does not concentrate excessively at the corners, so that the
acoustic transducer 10 having high drop resistance strength can be obtained.
[0061]
Therefore, as shown in FIG. 12, the vibrating electrode plate 13 (member 13 ′) may be designed
and manufactured so that R is attached to each corner of the resistance increasing portion 20
which is not the slit 17 side. preferable. Further, by forming the concave portions (see (d) in FIG.
11A and (d) in FIG. 11B) formed on the second sacrificial layer 52 and the sacrificial layer 53
into elliptical concave portions, the slits 17 of the vibrating electrode plate 13 are obtained. The
surface shape in the vicinity may be as shown in FIG.
[0062]
Further, if the width of the concave portion formed on the second sacrificial layer 52 or the
sacrificial layer 53 is excessively narrow, the position of the vibrating electrode plate 13 as
shown in FIG. There is a possibility that the vibrating electrode plate 13 in which the high
resistance surface does not exist on one side surface may be obtained. If one or more pairs of
high resistance surfaces exist on both side surfaces of the slit 17 and the high resistance surfaces
of each pair do not face each other, it is impossible to obtain the vibrating electrode plate 13
capable of sufficiently solving the above-mentioned problems. Therefore, the width of the
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18
concave portion formed on the second sacrificial layer 52 or the sacrificial layer 53 is set to the
resistance increasing portion 20 even if the slit 17 is shifted in consideration of the positional
displacement amount at the time of forming the slit 17 or the like. It is preferable to define it to
be present.
[0063]
As described above, the vibrating electrode plate 13 of the acoustic transducer 10 according to
the present embodiment is a surface that constitutes the side surface in the width direction of the
slit 17 and has a high resistance exceeding the thickness of the central portion of the vibrating
electrode plate 13. A resistance increasing portion 20 is provided which has a pair of surfaces so
as to overlap when viewed from the width direction of the slit 17. Therefore, the acoustic
transducer 10 functions as an acoustic transducer in which the resistance to penetration through
the slit 17 is larger than that in the conventional case, and the rate of reduction in the resistance
to penetration through the slit 17 is smaller than that in the conventional case. .
[0064]
Specifically, an acoustic transducer 10 and an acoustic transducer having a conventional
configuration (see FIG. 1B) including a vibrating electrode plate 33 having the same thickness as
the vibrating electrode plate 13 of the acoustic transducer 10 exist. Think about the case. The
shapes of the inner side surfaces 18a and 18b of the slits 17 of the acoustic transducer 10 are
assumed to be shapes (square waves) as shown in FIGS. 15 (A) and 16 (A).
[0065]
FIG. 15A is a perspective view showing a state of a portion in the vicinity of the slit 17 of the
acoustic transducer 10 in the case where there is no displacement between the inner side
surfaces 18 a and 18 b of the slit 17. FIG. 16A is a perspective view showing the same portion in
the case where there is a shift in height of the slit 17 between the inner side surfaces 18a and
18b. 15 (B) and 16 (B) show the width direction of the slit 17 in the inner side surfaces 18a and
18b of the slit 17 in the states shown in FIGS. 15 (A) and 16 (A), respectively (FIG. 15). It is
explanatory drawing of the overlapping area seen from (A) and the arrow direction in FIG. 16 (A).
FIG. 15C is an explanatory view of the overlapping area in the case where there is no deviation
between the side surfaces 38a and 38b between the inner surfaces 38a and 38b of the slit 37 of
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19
the acoustic transducer of the conventional configuration. FIG. 16C is an explanatory view of the
overlapping area between the side surfaces 38a and 38b of the slit 37 when the height of the slit
37 (= height of the slit 17) deviates between the side surfaces 38a and 38b. .
[0066]
The penetration resistance of the slits (the slits 17 and the slits 37) increases as the overlapping
area of the pair of side surfaces facing each other increases.
[0067]
The resistance increasing portion 20 juxtaposed to the slit 17 is a surface constituting a side
surface in the width direction of the slit 17 and has a pair of high resistance surfaces whose
thickness exceeds the thickness of the central portion of the vibrating electrode plate 13.
Accordingly, the inner side surfaces 18 a and 18 b of the slit 17 are wider than the side surfaces
38 a and 38 b of the slit 37. Moreover, the high resistance surfaces of the resistance increasing
portion 20 overlap as seen in the width direction of the slit 17. Therefore, when no displacement
occurs between the side surfaces, as shown in FIG. 15, the overlapping area between the inner
side surfaces 18a and 18b of the slit 17 (FIG. 15B) is hatched. The area is larger than the
overlapping area (FIG. 15C) between the inner side surfaces 38a and 38b of the slits 37.
[0068]
When the inner side surfaces 38a and 38b of the slit 37 are shifted by the height of the slit 37
due to the warp or the like of the vibrating electrode plate 33, as shown in FIG. 16C, between the
inner side surfaces 38a and 38b. The overlapping area of is "0". Therefore, when the inner side
surfaces 38a and 38b are displaced by the height of the slit 37 (the thickness of the vibrating
electrode plate 33), the penetration resistance of the slit 37 is significantly reduced.
[0069]
On the other hand, when the inner side surfaces 18a and 18b of the slits 17 are shifted by the
same amount, the inner side surfaces 18a and 18b are in a state where the hatched regions
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20
overlap, as shown in FIG. . Therefore, when the inner side surfaces 18a and 18b of the slit 17 are
shifted by the height of the slit 17 (the thickness of the vibrating electrode plate 13), the
reduction rate of the penetration resistance of the slit 17 is through the slit 37 when the same
amount Less than the rate of decrease in resistance.
[0070]
As described above, in the acoustic transducer 10 according to the present embodiment having
the configuration in which the resistance increasing portions 20 are juxtaposed to the slits 17,
the resistance through the slits 17 is larger than that in the related art, and When it occurs, it
functions as an acoustic transducer in which the reduction rate of resistance through the slit 17
is smaller than that in the past.
[0071]
Further, the acoustic hole 24 is not provided in the portion of the acoustic transducer 10 on the
slit 17 of the back plate 18.
That is, as schematically shown in FIG. 17, the acoustic transducer 10 adopts a configuration in
which the sound (air vibration) which has passed through the slit 17 does not directly pass
through the acoustic hole 24 of the back plate 18. ing. Therefore, in the acoustic transducer 10,
the sound passing through the slit 17 does not pass directly through the acoustic hole 24 of the
back plate 18, so that the resistance through the slit 17 is the same as that of the acoustic
transducer of the conventional configuration (FIG. 1 (B) It also functions as a bigger one than).
[0072]
<Microphone Using Acoustic Transducer 10> As described above, in the acoustic transducer 10,
the resistance through the slit 17 is larger than that in the conventional case, and when the
deflection or the like of the vibrating electrode plate 13 occurs, It functions as an acoustic
transducer with a small drop. Therefore, as shown in FIG. 18, if the acoustic transducer 10 and
the ASIC 60 for amplifying the output of the acoustic transducer 10 are accommodated in a
package including the circuit board 61 and the cover 62 to manufacture a microphone, the
existing one can be obtained. It is possible to obtain a microphone with higher performance than
the microphone of. Although the microphone shown in FIG. 18 receives sound from the cover 62
side, it manufactures a microphone to which sound is input from the circuit board 61 side (cavity
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21
12 a side) using the acoustic transducer 10. It is good.
[0073]
<< Modified Form >> The acoustic transducer 10 according to the above-described embodiment
can perform various types of deformation. For example, as shown in FIG. 19, in the acoustic
transducer 10, only the configuration in which the acoustic hole 24 is not provided in the portion
on the slit 17 of the back plate 18 is adopted (a simple slit 17 'in the vibrating electrode plate
13). Can be transformed into
[0074]
The acoustic transducer 10 can also be deformed into one provided with a circular vibrating
electrode plate 13 having an arc-shaped slit 17 and a resistance increasing portion 20. Further,
by providing the conductive film on the substrate 12, the acoustic transducer 10 is deformed into
one that can also output the capacitance between the region of the vibrating electrode plate 13
outside the slit 17 and the substrate 12. It can also be done.
[0075]
As shown in FIG. 20, in the vibrating electrode plate 13 of the acoustic transducer 10, one slit
surrounding the rectangular region at the center of the vibrating electrode plate 13 and the
fixing portions 26 'obliquely extending from the corners of the rectangular region. It is possible
to have 17 provided. Even if the slits 17 have such a shape, the respective fixing portions 26 'and
several locations (four locations in FIG. 20) outside the slits 17 of the vibrating electrode plate 13
are supported via the support members 16. By fixing it to the substrate 12, it is possible to obtain
the acoustic transducer 10 which functions without any problem.
[0076]
In order to suppress the generation of a stick between the vibrating electrode plate 13 and the
fixed electrode plate 19, as shown schematically in FIG. 21, a stopper 30 may be provided on the
back plate 18 of the acoustic transducer 10.
17-04-2019
22
[0077]
In the above-described acoustic transducer 10, the respective components are arranged in the
order of the substrate 12, the vibrating electrode plate 13 and the fixed electrode plate 19.
However, the acoustic transducer 10 comprises the substrate 12, the fixed electrode plate 19 and
the vibrating electrode The components may be modified in the order of the plate 13.
In addition, as a structure for arrange | positioning the fixed electrode plate 19 on the board |
substrate 12, and arrange | positioning the vibrating electrode plate 13 on the fixed electrode
plate 19, the structure shown to (A) of FIG. The configuration shown in) can be adopted. That is,
as the configuration, a portion including the back plate 18 and the fixed electrode plate 19 has a
shape (a shape capable of holding the vibrating electrode plate 13) as shown in FIG. The
configuration in which the vibrating electrode plate 13 is provided can be adopted. Moreover, as
the said structure, as shown to (B) of FIG. 22, the structure by which the vibrating electrode plate
13 is provided on the structure 55 provided on the board | substrate 12 separately from the
backplate 18 is also employable.
[0078]
22A and 22B show a configuration in which the stopper 30 is provided on the back plate 18, but
as shown in FIGS. 23A and 23B, the stoppers are shown. 30 may be provided on the vibrating
electrode plate 13. In the case where the stopper 30 is provided on the vibrating electrode plate
13, as shown in FIGS. 23A and 23B, the resistance increasing portion 20 does not have to be
manufactured separately from the stopper 30. Alternatively, the resistance increasing portion 20
may be protruded to the back plate 18 side.
[0079]
Reference Signs List 10 acoustic transducer 12 substrate 12a cavity 12b opening 13 vibrating
electrode plate 15 chamber 16 support member 17 slit 18 back plate 18a inner side 19 fixed
electrode plate 20 resistance increasing portion 21 high resistance surface 24 acoustic hole 26
legs 27 and 28 wiring portion 35, 36 electrode pad 51 first sacrificial layer 52 second sacrificial
layer 60 ASIC 61 circuit board 62 cover
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23
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