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JP2015035730

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DESCRIPTION JP2015035730
An object of the present invention is to improve the strength of a substrate, shorten the etching
time for forming a cavity, and improve the low frequency characteristics in a microphone in
which a cavity inside the substrate is a front chamber. An acoustic sensor (41) is housed in a
package. The acoustic sensor 41 has a plurality of front chambers 43 formed in a substrate 42,
and has a capacitor structure including a diaphragm 46 and a fixed electrode plate 50 above the
substrate. The front chambers 43 are separated from one another by the partition wall 44 of the
substrate 42. Under a portion of the partition wall 44, an acoustic space 45 communicating with
each of the front chambers 43 and opened on the lower surface side of the substrate 42 is
formed. The height of the acoustic space 45 measured from the lower surface of the substrate is
equal to or less than 0.5 times the height of the front chamber 43. The package has a package
sound hole 33 opened at a position in communication with the acoustic space 45. [Selected
figure] Figure 3
Microphone, acoustic sensor and method of manufacturing acoustic sensor
[0001]
The present invention relates to a microphone, an acoustic sensor, and a method of
manufacturing the acoustic sensor. Specifically, the present invention relates to a capacitive
acoustic sensor having a plurality of sensing units (capacitor structures) and a microphone in
which the acoustic sensor is housed in a package. The invention also relates to a method of
manufacturing the acoustic sensor.
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1
[0002]
The capacitance-type acoustic sensor has a structure in which a diaphragm (movable electrode
plate) and a fixed electrode plate are provided on the upper surface of a cavity (through hole)
provided in a substrate. Further, the microphone is provided with an acoustic sensor and a
processing circuit on the bottom of the package, and a package sound hole for introducing
acoustic vibration is provided in the package. In order to improve the acoustic characteristics
such as the sensitivity and frequency characteristics of the microphone, a space on the side
opposite to the side where the acoustic vibration enters with reference to the diaphragm (this
space is called a back chamber. It is known that it is sufficient to increase the volume of
[0003]
As said microphone, what provided the package sound hole in the upper surface of the package
is common. In this type of microphone, the acoustic vibration that has entered the package
through the package sound hole passes through the fixed electrode plate and the diaphragm and
escapes into the cavity, causing the diaphragm to vibrate and the static charge between the
diaphragm and the fixed electrode plate Change the capacitance. Therefore, with this
microphone, the cavity in the substrate becomes the back chamber, so the back chamber volume
can not be made very large.
[0004]
Therefore, as a practical method of improving acoustic characteristics such as microphone
sensitivity and frequency characteristics, a method is proposed in which the package sound hole
is directly connected to the cavity of the substrate, that is, a method of opening in the package
directly under the cavity (see FIG. 1 (A)).
[0005]
Further, as another method for improving the acoustic characteristics such as the S / N ratio
(signal-to-noise ratio) and the sound pressure band of the microphone, there is a method of
incorporating two acoustic sensors in the microphone.
If two acoustic sensors are built in one package, the sensitivity of the microphone can be
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2
improved or noise canceling can be performed by adding the outputs of the two acoustic sensors,
as a result. The S / N ratio can be improved. Alternatively, if two acoustic sensors having different
sensitivities, sound pressure bands, frequency bands, etc. are built in each other, one acoustic
sensor can be used by switching the outputs of these acoustic sensors in the circuit at the later
stage. The characteristic which can not be realized can be obtained. For example, by using an
acoustic sensor compatible with high sensitivity but small sound pressure and an acoustic sensor
compatible with low sensitivity but large sound pressure, and switching each acoustic sensor
according to the sound pressure band, pseudo high-sensitivity large sound It is possible to realize
a wide band microphone that can handle pressure.
[0006]
As a microphone incorporating a plurality of acoustic sensors, there is, for example, one
disclosed in Patent Document 1. However, in the microphone shown in Patent Document 1 (FIG.
3A), a plurality of acoustic sensors are disposed on the bottom surface of the package, and the
package sound hole is opened on the top surface of the package. It can not be directly connected
to the cavity.
[0007]
Therefore, as an improvement example of the microphone shown in Patent Document 1 (FIG. 3A),
as shown in FIG. 1, a plurality of mutually independent acoustic sensors 13a, 13b,. It is
conceivable to provide a package sound hole 14 directly connected to the cavity 17 on the
bottom of the plate 12. In this microphone 11, since the diaphragm 15 and the fixed electrode
plate 16 are provided on the upper surfaces of the acoustic sensors 13a, 13b, ..., the cavity 17
inside the acoustic sensor becomes a front chamber and the package space 18 inside the package
becomes a back chamber. . Thus, the volume of the back chamber can be increased, and the
characteristics of the microphone can be improved.
[0008]
However, in the microphone of such a structure, since each sound sensor is provided with a
package sound hole, each sound sensor may detect slightly different sound vibrations entering
from different sound holes of the package. . When the output signals of the acoustic vibration
detecting the slightly different acoustic vibration are superimposed as described above, for
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example, the output signals may interfere with each other to generate a beat. In addition, when a
plurality of independent acoustic sensors as shown in FIG. 1 are used, manufacturing variations
among the acoustic sensors may be a problem.
[0009]
On the other hand, in the acoustic sensor shown in Patent Document 1 (FIG. 4), as shown in FIG.
2, the fixed electrode plate 16 is provided on the upper surface of the substrate 22, and a
plurality of diaphragms 15 are provided above it. A plurality of sensing portions 21a, 21b,... In
each of the sensing portions 21a, 21b, ..., an acoustic hole 23 is opened in the fixed electrode
plate 16. In the acoustic sensor 13 as shown in FIG. 2, since a plurality of sensing units 21a,
21b,... Are formed on a single substrate, manufacturing variations for each of the sensing units
are reduced. Therefore, it is conceivable to provide one package sound hole in the package so as
to be directly connected to the lower surface of the cavity 17 using the acoustic sensor 13 as
shown in FIG.
[0010]
Furthermore, in the acoustic sensor 13 of FIG. 2, it is convenient that the sensing portions 21a,
21b,... Share the cavity 17. Therefore, the cavity 17 is spread over the entire space below the
sensing portions 21a, 21b,. There is. On the other hand, inside the cavity 17, a stiffening rib 24 is
provided by the substrate 22 above the cavity 17.
[0011]
However, the reinforcing material 24 is an etching residue when the cavity 17 is formed in the
substrate 22 by etching, and since the reinforcing material 24 is a member whose thickness is
considerably thinner than the thickness of the substrate 22, it is sufficient for the acoustic sensor
13 by itself. It is not possible to give strength. Therefore, the substrate 22 is distorted by an
impact when the microphone is dropped, and the diaphragm 15 is easily broken.
[0012]
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Further, in the acoustic sensor 13 of FIG. 2, since the etching volume when forming the cavity 17
in the substrate 22 is large, the etching time becomes long, and the productivity of the acoustic
sensor is deteriorated. Furthermore, in this acoustic sensor 13, since the cavities 17 under the
respective sensing portions 21a, 21b,... Are connected, the acoustic vibration entering the cavities
17 is easily extracted from the entire sensing portion, and the low frequency characteristics of
the acoustic sensor 13 are Deteriorate.
[0013]
Further, in the acoustic sensor 13 of FIG. 2, the position where the package sound hole is
provided is limited to the opening area of the lower surface of the cavity 17, so the degree of
freedom in position design of the package sound hole is low. Dust and other foreign matter are
likely to invade inside.
[0014]
In the acoustic sensor of Patent Document 1 (FIG. 4), the reinforcing material 24 is extended to
the lower surface of the substrate 22 to form the partition wall 25, and the cavities 17 can be
partitioned by the partition wall 25.
Then, a through hole 26 is provided at the height of the middle of the partition wall 25 to
connect the adjacent cavities 17 (shown by a broken line in FIG. 2). However, in such a
modification, the through hole 26 has to be formed in the middle of the partition wall 25 so as to
penetrate the partition wall 25 sideways, and the process of opening the through hole 26
becomes extremely difficult. . Furthermore, if only the partition wall 25 is provided and the
through hole 26 is not provided, it is necessary to provide a package sound hole for each of the
cavities 17, and the same problem as in the case of FIG. 1 occurs.
[0015]
U.S. Patent Application Publication No. 2007-47746
[0016]
An object of the present invention is to improve the strength of a substrate and to form a cavity
in an acoustic sensor and a microphone for directly connecting a package sound hole to a cavity
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provided in a substrate and using the cavity as a front chamber. The etching time is shortened
and the low frequency characteristics are improved.
Another object of the present invention is to improve the productivity of the acoustic sensor.
[0017]
The microphone according to the present invention is a microphone in which the lower surface
of an acoustic sensor is fixed to the inner surface of a package, wherein the acoustic sensor is
disposed above each of a substrate having a plurality of cavities penetrating from the upper
surface to the lower surface. A package sound hole is opened at a position facing the lower
surface of the acoustic sensor, and the package communicates with each of the cavities in the
lower surface of the substrate And the hollow formed on the lower surface side of the substrate
is formed, and the height of the hollow measured from the lower surface of the substrate is not
more than 0.5 times the height of the hollow.
[0018]
Since the microphone of the present invention is structured to capture acoustic vibration from
the package sound hole into the cavity of the acoustic sensor, the space in the package becomes
a back chamber and has a large back chamber space.
In addition, a plurality of capacitor structures (sensing units) are provided on one substrate.
Therefore, in this microphone, acoustic characteristics such as sensitivity and frequency
characteristics are improved. Moreover, in the microphone according to the present invention,
the lower surface of the substrate communicates with each of the cavities, and a recess opened
on the lower surface side of the substrate is formed, and the height of the recess measured from
the lower surface of the substrate is Since the height of the cavity is 0.5 times or less, the rigidity
of the substrate is increased. As a result, even if a shock is applied to the microphone due to a
drop or the like, the substrate is not easily distorted, and the movable electrode plate is less likely
to be damaged by the shock. In addition, since the etching volume of the substrate can be small,
the etching time of the substrate can be shortened, and the productivity of the acoustic sensor
can be improved. Furthermore, since the cavities are substantially independent, the acoustic
vibration entering the cavities is less likely to escape, and the low frequency characteristics of the
acoustic sensor become better.
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[0019]
In an embodiment of the microphone according to the present invention, the cavities are
mutually separated by a partition wall of the substrate, and the recess is formed in at least a part
of the lower surface of the partition wall of the lower surface of the substrate; A recess is in
communication with the lower end side of each of the cavities. The recess is provided in at least a
part of the lower surface of the partition wall, but may be provided in an area other than the
lower surface of the partition wall. According to this embodiment, the space between the cavities
of the substrate is held by the partition wall, and the recess below the partition wall is 0.5 times
or less the height of the cavity, so the rigidity of the substrate is increased. As a result, even if a
shock is applied to the microphone due to a drop or the like, the substrate is not easily distorted,
and the movable electrode plate is less likely to be damaged by the shock. In addition, since the
height of the depression is half or less of the height of the cavity, the etching volume of the
substrate can be small, the etching time of the substrate can be shortened, and the productivity
of the acoustic sensor can be improved. Furthermore, since the cavities are separated by the
partition walls and the cavities are substantially independent, it is difficult for acoustic vibration
entering the cavities to escape and the low frequency characteristics of the acoustic sensor
become good. In addition, since the package sound hole can be provided at any position as long
as there is a recess or cavity on the lower surface of the substrate, the design freedom of the
microphone is improved.
[0020]
Another embodiment of the microphone according to the present invention is characterized in
that the package sound hole is opposed to the lower surface of the partition wall. According to
this aspect, since the lower surface of the partition wall exists above the package sound hole,
foreign matter, disturbance, and the like are less likely to intrude into the acoustic sensor from
the package sound hole.
[0021]
A still further embodiment of the microphone according to the present invention is characterized
in that a support column is provided in a projecting manner on a part of the lower surface of the
partition wall. According to such an embodiment, the rigidity of the substrate is higher and the
strength of the acoustic sensor is increased. In addition, since the etching volume of the substrate
is further reduced, the etching time of the substrate is further shortened. In particular, it is
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desirable that the lower surface of the support column be located on the same plane as the lower
surface of the substrate.
[0022]
The package sound hole may be opposed to the lower surface of any one of the plurality of
cavities.
[0023]
In still another embodiment of the microphone according to the present invention, the cavities
are mutually separated by a partition wall of the substrate, and the recess is a lower surface of
the lower surface of the substrate in a region other than at least the cavity and the partition wall.
It is characterized in that the depressions are in communication with respective lower end side
surfaces of the cavities.
According to this embodiment, the degree of freedom in the position of the package sound hole is
higher. At this time, the package sound hole may be opposed to the lower surface of the region
other than the cavity and the partition wall.
[0024]
A further embodiment of the microphone according to the invention is characterized in that the
recess is surrounded by the substrate all around its periphery. According to such an embodiment,
it is possible to prevent acoustic vibration entering the recess from leaking from the package
sound hole, and the sensitivity of the acoustic sensor is improved.
[0025]
An acoustic sensor according to the present invention comprises a substrate having a plurality of
cavities penetrating from the upper surface to the lower surface, and a capacitor structure
comprising a movable electrode plate and a fixed electrode plate disposed above each of the
cavities. In the sensor, a recess which is in communication with each of the cavities and is opened
on the lower surface side of the substrate is formed in the lower surface of the substrate, and the
height of the recess measured from the lower surface of the substrate is It is characterized in that
the height is 0.5 times or less.
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[0026]
The acoustic sensor according to the present invention has a structure in which acoustic
vibration is taken into the cavity of the acoustic sensor from the package sound hole, so a wide
back chamber space can be secured.
In addition, a plurality of capacitor structures (sensing units) are provided on one substrate.
Therefore, in this acoustic sensor, acoustic characteristics such as sensitivity and frequency
characteristics are improved. Moreover, in the acoustic sensor according to the present
invention, the lower surface of the substrate communicates with each of the cavities, and a recess
opened on the lower surface side of the substrate is formed, and the height of the recess
measured from the lower surface of the substrate is Since the height of the cavity is 0.5 times or
less, the rigidity of the substrate is increased. As a result, even if an impact due to drop or the like
is applied to the acoustic sensor, the substrate is not easily distorted, and the movable electrode
plate is less likely to be damaged by the impact. In addition, since the etching volume of the
substrate can be small, the etching time of the substrate can be shortened and the productivity of
the acoustic sensor can be improved. Furthermore, since the cavities are substantially
independent, the acoustic vibration entering the cavities is less likely to escape, and the low
frequency characteristics of the acoustic sensor become better.
[0027]
A first method of manufacturing an acoustic sensor according to the present invention is a
method of manufacturing an acoustic sensor for manufacturing an acoustic sensor according to
the present invention, wherein a movable electrode plate or a fixed electrode plate is formed on
the upper surface of a flat substrate material. A second step of forming a structure for forming a
second layer on a lower surface of the substrate material, and forming a first mask opened in a
region to be a lower surface of the cavity and the recess; Forming a second mask on the lower
surface of the substrate material and the first mask, covering the region to be the lower surface
of the recess and opening at least the region to be the lower surface of the cavity; A depth equal
to a value obtained by subtracting the height of the recess from the height of the cavity in a
region to be the cavity of the substrate material by dry etching the substrate material from the
lower surface side through the mask and the first mask The depression Forming the cavity and
the recess of the substrate material by dry etching the substrate material from the lower surface
side through the first mask in the absence of the second mask and a fourth step of forming
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Removing the substrate material by the same depth as the height of the recess to produce the
substrate having the cavity and the recess; and the movable electrode plate and the fixed
electrode on the upper surface of the substrate by the structure And a sixth step of forming a
plate. According to the first method of manufacturing an acoustic sensor of the present invention,
the acoustic sensor of the present invention can be manufactured.
[0028]
In one embodiment of the first method of manufacturing an acoustic sensor according to the
present invention, in the third step, the thickness of the substrate is A, the height of the recess is
H, and the etching of the second mask with respect to the substrate material When the ratio of
rates is R2, the thickness T of the second mask is defined as T = (A−H) × R2. According to this
embodiment, since the fourth and fifth steps can be processed continuously in the dry etching
apparatus, the productivity of the acoustic sensor is improved.
[0029]
Furthermore, in the third step, the dry etching may be stopped leaving the second mask, and the
remaining second mask may be removed by ashing. According to this embodiment, the height of
the recess is less susceptible to the variation in the thickness of the second mask.
[0030]
In another embodiment of the first method of manufacturing an acoustic sensor according to the
present invention, in the second step, the height of the recess is H, and the ratio of the etching
rate of the first mask to the substrate material is R1. In this case, the thickness t of the first mask
is defined as t ≧ H × R1. According to this embodiment, according to this embodiment, the first
mask can be prevented from being consumed by dry etching before the cavity is formed in the
substrate. In particular, if the thickness of the first mask is t = H × R1, the first mask is
consumed by dry etching when a cavity is formed in the substrate, so the step of peeling the first
mask Become unnecessary.
[0031]
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A second method of manufacturing an acoustic sensor according to the present invention is the
method of manufacturing an acoustic sensor for manufacturing an acoustic sensor according to
claim 11, wherein the movable electrode plate and the fixing are fixed on the upper surface of a
flat substrate material. A first step of producing a structure for forming an electrode plate, and a
second step of forming a third mask opened in a region to be the lower surface of the cavity and
the recess on the lower surface of the substrate material Third, a recess having the same depth as
the height of the recess is formed in the area to be the cavity and the recess of the substrate
material by etching the substrate material from the lower surface side through the third mask.
The substrate through a process, a fourth process of covering a region of the upper surface of
the recess, which becomes the recess, and a side wall surface of the recess with a fourth mask,
the third mask and the fourth mask The lower side of the hollow area of the material Etching to
form the substrate having the cavity and the recess, and a sixth step of forming the movable
electrode plate and the fixed electrode plate on the upper surface of the substrate by the
structure. , Is characterized by. The acoustic sensor according to the present invention can also
be produced by the second method of producing the acoustic sensor according to the present
invention.
[0032]
In addition, the means for solving the above-mentioned subject in the present invention has the
feature which combined suitably the component explained above, and the present invention
enables many variations by the combination of such a component. .
[0033]
FIG. 1 is a cross-sectional view showing the structure of a microphone of a reference example
incorporating a plurality of acoustic sensors.
FIG. 2 is a cross-sectional view of the acoustic sensor described in Patent Document 1. As shown
in FIG. FIG. 3A is a partially omitted plan view showing the acoustic sensor according to the first
embodiment of the present invention. FIG. 3B is a cross-sectional view showing a state in which
the acoustic sensor according to the first embodiment of the present invention is mounted on a
package substrate. FIG. 4A and FIG. 4B are a plan view showing a substrate used for the acoustic
sensor of FIG. 3A and a perspective view seen from the back side. FIG. 5 is a cross-sectional view
of a microphone incorporating the acoustic sensor of FIG. 3 (B). FIGS. 6A to 6C are crosssectional views for describing a first manufacturing method for manufacturing the acoustic
sensor of FIG. 3B. FIGS. 7A to 7C are cross-sectional views for describing a first manufacturing
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method for manufacturing the acoustic sensor of FIG. 3B, and are continued from FIG. 6C. It is. 8
(A) -8 (C) are cross-sectional views for explaining a first manufacturing method for
manufacturing the acoustic sensor of FIG. 3 (B), and are continued drawings of FIG. 7 (C). It is. 9
(A) -9 (C) are cross-sectional views for explaining a first manufacturing method for
manufacturing the acoustic sensor of FIG. 3 (B), and are continued drawings of FIG. 8 (C). It is.
FIGS. 10A to 10C are cross-sectional views for describing a second manufacturing method for
manufacturing the acoustic sensor of FIG. 3B. 11 (A) -11 (C) are cross-sectional views for
explaining a second manufacturing method for manufacturing the acoustic sensor of FIG. 3 (B),
and are continued drawings of FIG. 10 (C). It is. 12 (A) to 12 (C) are cross-sectional views for
explaining a second manufacturing method for manufacturing the acoustic sensor of FIG. 3 (B),
and are continued drawings of FIG. 11 (C). It is. 13 (A) to 13 (C) are cross-sectional views for
explaining a second manufacturing method for manufacturing the acoustic sensor of FIG. 3 (B),
and are continued from FIG. 12 (C). It is. 14 (A) and 14 (B) are cross-sectional views for
describing a second manufacturing method for manufacturing the acoustic sensor of FIG. 3 (B),
and are continued drawings of FIG. 13 (C). It is. FIG. 15 (A) is a partially omitted plan view
showing an acoustic sensor according to a modification of Embodiment 1 of the present
invention. FIG. 15 (B) is a perspective view from the back side showing a substrate used for the
acoustic sensor of FIG. 15 (A). FIG. 16 is a partially omitted plan view showing an acoustic sensor
according to another modification of the first embodiment of the present invention. FIG. 17A is a
partially omitted plan view showing an acoustic sensor according to a second embodiment of the
present invention.
FIG. 17B is a cross-sectional view showing a state in which the acoustic sensor according to the
second embodiment of the present invention is mounted on a package substrate. FIG. 18A and
FIG. 18B are a plan view showing a substrate used for the acoustic sensor of FIG. 17A and a
perspective view seen from the back side. FIG. 19 is a cross-sectional view of a microphone
incorporating the acoustic sensor of FIG. 17 (B). FIG. 20A is a partially omitted plan view showing
an acoustic sensor according to a third embodiment of the present invention. FIG. 20B is a crosssectional view showing a state in which the acoustic sensor of Embodiment 3 according to the
present invention is mounted on a package substrate. FIG. 21 is a perspective view from the back
side showing a substrate used in the acoustic sensor of FIG. 20 (A). FIG. 22A is a partially omitted
plan view showing an acoustic sensor according to a fourth embodiment of the present invention.
FIG. 22B is a cross-sectional view showing a state in which the acoustic sensor according to the
fourth embodiment of the present invention is mounted on a package substrate. FIG. 23 is a
perspective view from the back side showing a substrate used in the acoustic sensor of FIG. 22
(A). FIG. 24A and FIG. 24B are a perspective view and a plan view from the back side showing
substrates of different shapes. FIGS. 25A and 25B are plan views showing substrates of different
shapes. 26 (A) and 26 (B) are plan views showing substrates of different shapes. FIG. 27 is a
cross-sectional view showing the acoustic sensor of the fifth embodiment according to the
present invention mounted on a package substrate. FIG. 28A is a partially omitted plan view
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showing an acoustic sensor according to a sixth embodiment of the present invention. FIG. 28 (B)
is a perspective view from the back side showing a substrate used for the acoustic sensor of FIG.
28 (A).
[0034]
31, 82 microphone 32 package 32 a package substrate 32 b cover 33 package sound hole 41,
81, 91, 101, 111, 121 acoustic sensor 42 substrate 43 front chamber 44 partition 45 acoustic
space 46 diaphragm 49 back plate 50 fixed electrode plate 51 acoustic Holes 52a, 52b, 52c, 52d
Sensing part 62, 63 SiO 2 layer 64, 65, 67, 70, 71 Photoresist 69 P-SiO 2 film 92 Support
column
[0035]
Hereinafter, preferred embodiments of the present invention will be described with reference to
the accompanying 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.
[0036]
The structure of the acoustic sensor 41 and the microphone 31 according to the first
embodiment of the present invention will be described below with reference to FIGS. FIG. 3A is a
plan view showing the acoustic sensor 41 according to the first embodiment of the present
invention. However, in FIG. 3A, the back plate 49 of the acoustic sensor 41 and the fixed
electrode plate 50 are omitted. FIG. 3B is a cross-sectional view showing the acoustic sensor 41
mounted on the package substrate 32a. In FIG. 3B, the acoustic sensor 41 represents a cross
section along line XX in FIG. 3A, and the package substrate 32 a represents a cross section
passing through the package sound hole 33. FIG. 4A and FIG. 4B are a plan view of the substrate
42 used for the acoustic sensor 41 and a perspective view seen from the back side. FIG. 5 is a
cross-sectional view of the microphone 31 in which the acoustic sensor 41 is incorporated.
[0037]
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As shown in FIGS. 3A and 3B, the acoustic sensor 41 is provided with a plurality of sensing units
on the top surface of a semiconductor substrate 42 such as a silicon substrate. In the illustrated
example, four sensing units 52a, 52b, 52c and 52d are provided. As shown in FIG. 4A, in the
substrate 42, four prismatic hollows, ie, a front chamber 43, are opened so as to penetrate from
the upper surface to the lower surface. Between the front chambers 43, there is a cross-shaped
partition wall 44 seen from above, and the front chambers 43 are separated from each other by
the partition wall 44. Furthermore, as shown in FIG. 4B, a part of the lower surface of the
partition wall 44 is recessed upward, and a recess, that is, an acoustic space 45 is formed below
the partition wall 44. The height of the acoustic space 45 is equal to or less than half the height
of the front chamber 43 (ie, the thickness of the substrate 42). In this embodiment, an acoustic
space 45 is provided on the lower surface of the partition wall 44 closer to the central portion
(intersection portion of the flat wall) than the substantially central portion of the flat wall portion
located between the pair of front chambers 43, The acoustic space 45 is recessed in a cross
shape on the lower surface of the substrate 42. Thus, the acoustic spaces 45 communicate with
the lower end side surface of each front chamber 43, and the front chambers 43 communicate
with each other through the acoustic spaces 45.
[0038]
The sensing portions 52 a to 52 d of the acoustic sensor 41 have a capacitor structure mainly
including a conductive diaphragm 46 (movable electrode plate) and a fixed electrode plate 50
provided on the lower surface of the back plate 49. The diaphragm 46 is a thin film structure
having a substantially rectangular shape, and is positioned on the upper surface of the substrate
42 so as to cover the upper surface of the front chamber 43. Support pieces 47 extend from the
four corners of the diaphragm 46 in the diagonal direction, and each support piece 47 is
supported by anchors 48 provided on the upper surface of the substrate 42. Therefore, the
diaphragm 46 is separated from the upper surface of the substrate 42, and a passage (vent hole)
of acoustic vibration is generated between the edge of the diaphragm 46 and the upper surface
of the substrate 42.
[0039]
A back plate 49 made of an insulating material is provided above the diaphragm 46. The back
plate 49 covers the diaphragm 46 in a dome shape. Further, the outer peripheral portion of the
back plate 49 and the portion located between the diaphragms are fixed to the upper surface of
the substrate 42. A conductive fixed electrode plate 50 is provided on the lower surface of the
01-05-2019
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back plate 49 so as to face the diaphragm 46 with an air gap therebetween. The back plate 49
and the fixed electrode plate 50 have a large number of small acoustic holes 51 penetrating
vertically.
[0040]
The microphone 31 (MEMS microphone) according to the first embodiment of the present
invention incorporates the acoustic sensor 41 having the above-described structure. That is, as
shown in FIG. 5, the package 32 of the microphone 31 includes a package substrate 32a and a
cover 32b, and a package space 34 is formed inside the package 32. Wires and an electric circuit
are provided on the upper surface, lower surface, or the inside of the package substrate 32a as
needed, and a processing circuit 53 such as an acoustic sensor 41 or ASIC is mounted on the
upper surface of the package substrate 32a. The processing circuit 53 is configured by an
amplification circuit, a power supply circuit, an output circuit, and the like. Further, the acoustic
sensor 41 and the processing circuit 53 are connected by the bonding wire 54, and the
processing circuit 53 is connected by the bonding wire 55 to the wiring and electric circuit of the
package substrate 32a.
[0041]
The package 32 is configured by adhering the lower surface of the cover 32 b to the upper
surface of the package substrate 32 a, and the acoustic sensor 41 and the processing circuit 53
are accommodated in the package space 34. Further, as shown in FIG. 3B, the package sound
hole 33 is opened in the package substrate 32a at a position facing the central portion of the
acoustic space 45. The package sound hole 33 vertically penetrates the package substrate 32 a,
and the upper surface opening of the package sound hole 33 communicates with the acoustic
space 45. The package sound hole 33 may have any shape, for example, may have an opening
shape such as a circular shape, an elliptical shape, or a rectangular shape.
[0042]
Thus, in this microphone 31, acoustic vibration entering the acoustic space 45 from the package
sound hole 33 propagates through the acoustic space 45 to the respective front chambers 43,
and the diaphragms of the respective sensing portions 52a to 52d. Vibrate 46. As a result, in
each of the sensing units 52a to 52d, the acoustic vibration is converted into a capacitance
01-05-2019
15
between the diaphragm 46 and the fixed electrode plate 50, and an electric signal is output to
the processing circuit 53.
[0043]
Since the package sound holes 33 are directly connected to the front chambers 43 in this
manner, the acoustic vibration that has entered the acoustic sensor 41 from the package sound
holes 33 passes through the sound space 45 and enters the front chamber 43 to Vibrate. The
package space 34 in the package 32 (outside of the acoustic sensor 41) serves as a back
chamber. Therefore, the volume of the back chamber in the microphone 31 can be increased, and
acoustic characteristics such as the sensitivity and frequency characteristics of the microphone
31 can be improved.
[0044]
Moreover, since the plurality of sensing units 52a to 52d are provided, the processing circuit 53
adds the outputs of the sensing units 52a to 52d to improve the sensitivity, or switches the
outputs of the sensing units 52a to 52d. The sensitivity, frequency band, sound pressure band,
etc. can be expanded.
[0045]
Moreover, since each sensing part 52a-52d is produced on the same board | substrate using a
MEMS manufacturing technique, the manufacture variation of sensing part 52a-52d can be made
small.
Furthermore, since one package sound hole 33 is directly connected to each front chamber 43 by
the acoustic space 45, acoustic vibration entering from the same package sound hole 33
propagates to each sensing portion 52a to 52d, and each sensing portion The same acoustic
vibration can be detected at 52a-52d.
[0046]
Furthermore, in the microphone 31 or the acoustic sensor 41 according to the present
01-05-2019
16
embodiment, the front chamber 43 is partitioned by the partition wall 44, and the partition wall
44 is provided in a region of 1/2 or more of the height of the front chamber 43. Therefore, the
rigidity of the substrate 42 can be increased by the partition wall 44. Therefore, even if an
impact is applied to the acoustic sensor 41 due to a drop or the like of a device incorporating the
microphone 31, the diaphragm 46 can be prevented from being bent excessively, and the
diaphragm 46 is less likely to be damaged by the impact.
[0047]
Further, compared to the acoustic sensor shown in FIG. 2, in the acoustic sensor 41 of the
present embodiment, since the etching volume of the substrate 42 is smaller, the etching time in
the manufacturing process of the acoustic sensor 41 can be shortened. Productivity of the sensor
41 is improved.
[0048]
Further, in the acoustic sensor 41 of the present embodiment, since each front chamber 43 is
partitioned by the partition wall 44, the acoustic vibration entering the front chamber 43 from
the package sound hole 33 is less likely to come out, and the low frequency of the acoustic
sensor 41 The characteristics are good.
[0049]
Further, in the microphone 31 of the present embodiment, the lower surface of the partition wall
44 is opposed to the package sound hole 33. Therefore, the microphone 31 becomes more
resistant to disturbance entering from the package sound hole 33, and the function of the
microphone 31 is less likely to deteriorate .
That is, foreign substances such as dust and liquid from the package sound hole 33 and other
factors causing damage such as compressed air and excessive sound pressure are less likely to
intrude, so the resistance of the acoustic sensor 41 to disturbance is high. can do.
In particular, for this purpose, the diameter of the package sound hole 33 is preferably smaller
than the wall thickness of the partition wall 44 so that the package sound hole 33 does not
overlap with the front chamber 43 when viewed from above.
01-05-2019
17
[0050]
Furthermore, since the acoustic space 45 is provided on the lower surface of the substrate 42,
the size of the package sound hole 33 can be reduced, and alignment at the time of mounting the
acoustic sensor 41 on the package 32 becomes easy.
[0051]
Also, the package sound hole 33 is not limited to the center of the acoustic space 45.
If it is a position facing the lower surface of the partition wall 44, it is possible to prevent the
entry of disturbance, and it may be a position facing the front chamber 43 as long as the entry of
the disturbance is not a problem as described later. Therefore, if the package sound hole 33 is
made smaller, alignment with the package sound hole 33 when mounting the acoustic sensor 41
on the package 32 is facilitated.
[0052]
Manufacturing Method 1 Next, manufacturing steps for manufacturing the acoustic sensor 41 of
the first embodiment will be described with reference to FIGS. FIG. 6A shows a state in which a
SiO 2 layer 62 (sacrificial layer) and a plurality of polysilicon layers are laminated on the upper
surface of a silicon substrate 42 (substrate material such as Si wafer) using a film forming
technique such as CVD. Show. The polysilicon layer is patterned, and an anchor layer 61 is
formed at the position where the anchor 48 is to be provided, the layer thereon is patterned to be
the diaphragm 46, and the layer above is the fixed electrode plate 50. It is patterned. In the step
shown in FIG. 6B, after the SiO 2 layer 62 is etched so as to have the inner surface shape of the
back plate 49, an SiN film is formed on the surface thereof to produce the back plate 49. In the
process of FIG. 6C, the back plate 49 and the fixed electrode plate 50 are sequentially etched to
open a large number of acoustic holes 51 penetrating from the back plate 49 to the fixed
electrode plate 50. Thereafter, the back surface of the silicon substrate 42 is polished to reduce
the substrate thickness to, for example, 725 μm to 400 μm.
[0053]
Thereafter, as shown in FIG. 7A, a SiO 2 layer 63 (first mask) is formed on the entire back surface
01-05-2019
18
of the substrate 42. In the step of FIG. 7B, a photoresist 64 is formed on the lower surface of the
SiO 2 layer 63, and then the photoresist 64 is patterned by photolithography to form the front
chamber 43 and the acoustic space 45 on the lower surface. The photoresist 64 is opened. In the
step of FIG. 7C, the exposed portion of the SiO 2 layer 63 is removed by etching through the
opening of the photoresist 64. As a result, the SiO 2 layer 63 becomes an SiO 2 hard mask
opened at the lower surface of the area to be the front chamber 43 and the acoustic space 45.
[0054]
After removing the photoresist 64 as shown in FIG. 8A, the photoresist 65 is applied again to the
entire lower surface of the substrate 42 and the SiO 2 layer 63. Next, the photoresist 65 is
patterned by photolithography, and the photoresist 65 is opened on the lower surface of the area
to be the front chamber 43 as shown in FIG. 8B. The photoresist 65 may not be present in the
region where the SiO 2 layer 63 is present.
[0055]
Thereafter, the substrate 42 is dry etched from the back side using the photoresist 65 as a
second mask. The dry etching proceeds with a large etching rate in the exposed portion of the
substrate 42, while the etching rate of the photoresist 65 is much lower than that of the
substrate 42, so the consumption of the photoresist 65 by dry etching is small. As a result, as
shown in FIG. 8C, a recess 66 having a depth equal to A-H is formed in a region of the lower
surface of the substrate 42 which is to be the front chamber 43. Here, A is the thickness (after
polishing) of the substrate 42, and H is the height of the acoustic space 45 (see FIG. 3B).
[0056]
Next, as shown in FIG. 9A, the substrate 42 is dry etched from the back surface side using the SiO
2 layer 63 as a first mask. As a result, the front chamber 43 penetrates the substrate 42 in the
region where the recess 66 exists, and the acoustic space 45 is formed on the lower surface of
the substrate 42 in the region where the photoresist 65 is directly provided on the lower surface
of the substrate 42. A partition 44 is formed by the remaining portion that is not etched.
[0057]
01-05-2019
19
The film thickness t of the SiO 2 layer 63 needs to have a thickness enough to resist the
substrate etching in the process of FIG. 9A after the photoresist 65 is eliminated. That is, the
etching of the front chamber portion must reach the upper surface of the substrate 42 before the
SiO 2 layer 63 is consumed by etching. For that purpose, the film thickness t of the SiO 2 layer
63 needs to satisfy t ≧ H × (the etching rate ratio of the SiO 2 layer to the substrate). Here, H is
the height of the acoustic space 45. For example, assuming that the height H of the acoustic
space 45 is 20 μm and the etching rate of the SiO 2 layer 63 is 1/250 times the etching rate of
the substrate 42, the thickness t of the SiO 2 layer 63 is H It may be equal to or larger than x
(1/250) = 20/250 = 0.08 [μm]. In particular, if it is equal to 0.08 μm, the SiO 2 layer 63
disappears when the etching of the front chamber 43 reaches the upper surface of the substrate
42 and the front chamber 43 is opened. Therefore, it is not necessary to remove the SiO 2 layer
63 after the etching of the front chamber 43.
[0058]
Here, it is preferable to set the film thickness T of the photoresist 65 manufactured in the step of
FIG. 8B to (A−H) × (etching rate ratio of the photoresist to the substrate) (A is the substrate 42
Thickness H, the height of the acoustic space 45). For example, assuming that the thickness A of
the substrate 42 is 400 μm, the height H of the acoustic space 45 is 20 μm, and the etching
rate of the photoresist 65 is 1/80 times the etching rate of the substrate 42. The film thickness T
may be set to T = (A−H) × (1/80) = (400−20) /80=4.75 [μm]. Thus, if the film thickness T of
the photoresist 65 is prepared, as shown in FIG. 8C, when the photoresist 65 is completely
etched and the SiO 2 layer 63 and the substrate 42 are exposed, the recess of the substrate 42 is
obtained. The depth D of 66 equals A-H. Then, if the dry etching is continued as it is, the
substrate 42 is etched using the SiO 2 layer 63 as a first mask, and the region (the region to be
the acoustic space 45) of the substrate 42 where the direct photoresist 65 is provided The top
surface 66 (the area to be the front chamber 43) is etched. The process after the photoresist 65
disappears is the process of FIG. Therefore, if the film thickness T of the photoresist 65 is
prepared as described above, the process of FIG. 8C and the process of FIG. 9A can be
continuously performed without taking it out from the dry etching apparatus. Thus, the time for
etching the substrate is shortened, and the productivity of the acoustic sensor is improved.
[0059]
Alternatively, as indicated by a two-dot chain line in FIG. 8C, the dry etching in the process of
01-05-2019
20
FIG. The remaining photoresist 65 is removed by ashing. Thereafter, dry etching is performed
again in the process of FIG. 9A to penetrate the front chamber 43 to the upper surface of the
substrate 42 and provide an acoustic space 45. Even in such a method, the steps of FIG. 8C to the
steps of FIG. 9A can be continuously performed without removing the substrate 42 from the dry
etching apparatus.
[0060]
Moreover, in the case of the method of completely removing the photoresist 65 by dry etching,
the height of the acoustic space 45 varies due to the variation of the film thickness of the
photoresist 65 or the variation during the dry etching. On the other hand, if the photoresist 65 is
removed by ashing while leaving a small amount of the photoresist 65, the height of the acoustic
space 45 is not affected by the film thickness variation of the photoresist 65. As a result, the
height of the acoustic space 45 is only affected by the variation during dry etching, and the
height accuracy of the acoustic space 45 is improved.
[0061]
In the step of FIG. 9B, an etchant such as BHF is applied to the upper surface and the lower
surface of the silicon substrate 42. The etchant penetrates from the acoustic holes 51 and the
front chamber 43 into the back plate 49 and etches away the SiO 2 layer 62. Then, the etching is
stopped when the SiO 2 layer 62 remains on the upper and lower surfaces of the anchor layer
61, and the substrate 42 is cleaned. The SiO 2 layer 63 on the lower surface of the substrate 42
is also removed in this step.
[0062]
Thus, as shown in FIG. 9C, an anchor 48 is formed by the anchor layer 61 and the upper and
lower SiO 2 layers 62, and each diaphragm 46 is supported at its four corners by the anchor 48,
and between the diaphragm 46 and the fixed electrode plate 50. An air gap is formed.
[0063]
According to the manufacturing method 1 as described above, the thickness of the photoresist
65 is determined according to the ratio of the etching rate of the photoresist 65 to the etching
01-05-2019
21
rate of the substrate 42, whereby the etching of the front chamber 43 and the acoustic space 45
are performed. Can be performed by one dry etching process, and the manufacturing process of
the acoustic sensor 41 can be streamlined.
Further, by determining the film thickness of the SiO 2 layer 63 in accordance with the ratio of
the etching rate of the SiO 2 layer 63 to the etching rate of the substrate 42, the SiO 2 layer 63
disappears when the front chamber 43 is formed. Therefore, after the process of forming the
front chamber 43, the process of removing the SiO 2 layer 63 becomes unnecessary, and the
manufacturing process of the acoustic sensor 41 can be streamlined.
[0064]
(Manufacturing method 2) The acoustic sensor 41 can also be manufactured by methods other
than the above manufacturing method. Another manufacturing process for manufacturing the
acoustic sensor 41 will be described with reference to FIGS. 10 and 11. 10A shows the anchor
layer 61, the SiO 2 layer 62, the diaphragm 46, the back plate 49, and the like on the upper
surface of the silicon substrate 42 (Si wafer) by the same steps as in FIG. 6A to FIG. The fixed
electrode plate 50 is formed. After the back surface of the substrate 42 is polished to reduce the
thickness of the substrate 42 from, for example, 725 μm to 400 μm, a photoresist 67 is formed
on the lower surface of the substrate 42 as shown in FIG. The photoresist 67 is patterned to open
the photoresist 67 in the area to be the front chamber 43 and the acoustic space 45. Next, in the
step of FIG. 10C, the lower surface of the substrate 42 is dry etched using the photoresist 67 as a
third mask. At this time, a recess 68 having the same depth as the height H (for example, 20 μm)
of the acoustic space 45 is formed on the lower surface of the substrate 42 by etching time
control (for example, DRIE time fixing).
[0065]
Thereafter, a photoresist is applied again by a spray coater, and a photoresist 67 is formed on the
upper surface and the side wall surface of the recess 68 as well. Then, as shown in FIG. 11A, the
photoresist 67 is patterned, and an opening is provided in the photoresist 67 in a region to be
the front chamber 43. At this time, it is desirable to stop the amount of the photoresist 67
sticking out in the recess 68 to such an extent that the photoresist 67 recedes to the back surface
of the substrate 42 in the process of etching of FIG.
01-05-2019
22
[0066]
Next, as shown in FIG. 11B, using the photoresist 67 as a fourth mask, the substrate 42 is dry
etched from the lower surface side, and the front chamber 43 penetrates the substrate 42. At this
time, since the portion to be the acoustic space 45 is covered with the photoresist 67, the depth
does not become deeper. Incidentally, in this step, because of the photoresist 67 formed on the
side wall surface of the recess 68, there is a possibility that a level difference may occur on the
side wall surface of the front chamber 43 as shown by a broken line in FIG. However, when the
photoresist 67 on the side wall surface recedes to the back surface of the substrate 42 due to the
progress of the dry etching, the step on the side wall surface of the front chamber 43 also
becomes inconspicuous. In addition, if such a level difference is not a problem (the function of
the acoustic sensor is hardly affected), the amount of the photoresist 67 that protrudes in the
recess 68 may not be optimized.
[0067]
In the above description, it is suggested that the photoresist to be the third mask and the
photoresist to be the fourth mask use the same symbol (67) and be photoresists of the same
material. . However, the photoresist to be the third mask and the photoresist to be the fourth
mask may be photoresist materials of different materials. In the above description, while the third
mask is left, the photoresist 67 is applied to form the fourth mask. However, after the third mask
is once removed, the photoresist 67 is applied to newly form the fourth mask. A fourth mask may
be formed. Further, in the process of FIG. 11A, the photoresist 67 may not be formed on the
sidewall surface of the recess 68, and the sidewall surface of the recess 68 may be exposed from
the photoresist 67.
[0068]
Thereafter, an etchant such as BHF is applied to the upper and lower surfaces of the silicon
substrate 42, the SiO 2 layer 62 is removed leaving the upper and lower portions of the anchor
layer 61, and the photoresist 67 on the lower surface of the substrate 42 is etched away. The
acoustic sensor 41 is obtained as shown in FIG.
[0069]
(Manufacturing Method 3) Another manufacturing process for manufacturing the acoustic sensor
01-05-2019
23
41 will be described with reference to FIGS.
In FIG. 12A, the anchor layer 61, the SiO 2 layer 62, the diaphragm 46, the back plate 49, and
the fixed electrode plate 50 are formed on the upper surface of a silicon substrate 42 (Si wafer).
After the back surface of the substrate 42 is polished to reduce the thickness of the substrate 42
from, for example, 725 μm to 400 μm, a P-SiO 2 film 69 (first mask) is formed on the lower
surface of the substrate 42 as shown in FIG. For example, the film thickness is 10,000 Å).
[0070]
Thereafter, in the step of FIG. 12C, a photoresist 70 is applied to the entire lower surface of the
P-SiO 2 film 69, and the photoresist 70 is patterned by photolithography to form the front
chamber 43 and the acoustic space 45. The photoresist 70 is opened at the bottom of the Next,
as shown in FIG. 13A, an etchant such as BHF is applied to the exposed portion of the P-SiO 2
film 69 through the opening of the photoresist 70 to selectively etch the exposed portion of the
P-SiO 2 film 69. Do. As a result, the P-SiO 2 film 69 is formed with an opening at the lower
surface of the area to be the front chamber 43 and the acoustic space 45. Thereafter, the
photoresist 70 is peeled off.
[0071]
In the step of FIG. 13B, a photoresist 71 is applied again to the entire lower surface of the
substrate 42 and the P-SiO 2 film 69. Next, the photoresist 71 is patterned by photolithography,
and the photoresist 71 is opened on the lower surface of the region to be the front chamber 43.
Here, assuming that the thickness S of the substrate 42 is A and the height of the acoustic space
45 is H, the film thickness S of the photoresist 71 to be the second mask is S = (A−H) ×
(photoresist for the substrate The etching rate ratio of For example, assuming that the thickness
A of the substrate 42 is 400 μm, the height H of the acoustic space 45 is 20 μm, and the
etching rate of the photoresist 71 is 1/80 times the etching rate of the substrate 42. The film
thickness S may be S = (A−H) × (1/80) = (400−20) /80=4.75 [μm]. Thus, if the film thickness
S of the photoresist 71 is prepared, when all the photoresist 71 is dry-etched as shown in FIG. AH recess 72 is formed. Furthermore, even if the dry etching is continued as it is, since the etching
rate of the P-SiO 2 film 69 is 1 / 250-1 / 300 of the etching rate of the substrate 42, the P-SiO 2
film 69 is hardly etched. Therefore, as shown in FIG. 14A, when the recess 72 reaches the upper
surface of the substrate 42 by dry etching, an acoustic space 45 of height H is formed on the
lower surface of the partition wall 44. Therefore, even with this manufacturing method, the
01-05-2019
24
process of FIG. 13C and the process of FIG. 14A can be continuously performed without taking
out the substrate 42 from the dry etching apparatus, and the time of the substrate etching
process is shortened. The productivity of the acoustic sensor is improved. In addition, since the PSiO 2 film 69 having a small etching rate is used as the first mask, the film thickness of the P-SiO
2 film 69 can be reduced, and the formation of the first mask (P-SiO 2 film 69) The film time can
be shortened to improve the productivity of the acoustic sensor.
[0072]
Thereafter, an etchant such as BHF is applied to the upper and lower surfaces of the silicon
substrate 42 to remove the SiO 2 layer 62 leaving the top and bottom of the anchor layer 61, and
the P-SiO 2 film 69 on the lower surface of the substrate 42 removed. For example, the acoustic
sensor 41 as shown in FIG. 14 (B) is manufactured.
[0073]
In this manufacturing method 3 as well as the manufacturing method 1, the manufacturing
process of the acoustic sensor 41 can be made efficient, and the productivity of the acoustic
sensor 41 can be improved.
[0074]
(Modification of Embodiment 1) In the present embodiment, the shape and arrangement of the
partition wall 44, the acoustic space 45, the front chamber 43 and the like can be freely changed.
For example, in the modification shown in FIGS. 15A and 15B, the acoustic space 45 is formed on
the entire lower surface of the partition wall 44.
[0075]
Further, in another modification shown in FIG. 16, a cylindrical front chamber 43 is provided on
the substrate 42, and a substantially cross-shaped acoustic space 45 is recessed on the lower
surface of the partition wall 44.
01-05-2019
25
The acoustic space 45 has a substantially cross shape excluding a portion of the front chamber
43 from a circular area centered on the center of the partition wall 44 when viewed from above.
[0076]
Second Embodiment FIG. 17A is a plan view showing an acoustic sensor 81 according to a
second embodiment of the present invention, in which the back plate 49 and the fixed electrode
plate 50 are omitted. FIG. 17B is a cross-sectional view in which the acoustic sensor 81 is
mounted on the package substrate 32a. 18A and 18B are a plan view of the substrate 42 used in
the acoustic sensor 81 and a perspective view from the back side.
[0077]
The substrate 42 used for the acoustic sensor 81 according to the second embodiment has a
structure as shown in FIGS. 18 (A) and 18 (B). When viewed from above, in the three-direction
partition wall 44 (flat wall portion), the acoustic space 45 extends from the center of the
partition wall 44 to approximately the center of the flat wall portion located between the front
chambers 43. Further, in the one-direction partition wall 44, the acoustic space 45 extends from
the center of the partition wall 44 beyond the end of the flat wall portion between the front
chambers 43 to the outside of the partition wall 44 (that is, the outer peripheral portion of the
substrate 42). ing. Therefore, the acoustic space 45 has a larger area than that of the first
embodiment.
[0078]
FIG. 19 is a cross-sectional view showing a microphone 82 in which the acoustic sensor 81 and
the processing circuit 53 are housed. In the microphone 82, as shown in FIGS. 17A and 17B, the
package sound hole 33 is opened in the package substrate 32a so as to face the area of the
acoustic space 45 extending outward beyond the partition wall 44. doing.
[0079]
According to such an embodiment, since the area of the acoustic space 45 is wide, the package
01-05-2019
26
communicates with the acoustic space 45 not only in the region facing the lower surface of the
partition wall 44 but also in the outer peripheral portion of the lower surface of the substrate. A
sound hole 33 can be provided. Therefore, the degree of freedom in the position where the
package sound hole 33 is provided is increased. In particular, as shown in FIG. 9, it becomes
possible to position the package sound hole 33 at the end of the acoustic sensor 41. In that case,
as shown in FIGS. 17B and 18A, the area of the region of the acoustic space 45 located on the
lower surface of the outer peripheral portion of the substrate 42 is increased, and the package
sound hole 33 is opposed thereto. If this is done, the tolerance for misalignment of the package
sound hole 33 is increased.
[0080]
The other points are the same as in the first embodiment, and thus the same reference numerals
are given to the same components, and the description will be omitted (the same applies to the
following embodiments).
[0081]
Third Embodiment FIG. 20A is a partially omitted plan view showing an acoustic sensor 91
according to a third embodiment of the present invention.
FIG. 20B is a cross-sectional view in which the acoustic sensor 91 is mounted on the package
substrate 32a. FIG. 21 is a perspective view from the back side showing a substrate 42 used for
the acoustic sensor 91. As shown in FIG.
[0082]
The substrate 42 used for the acoustic sensor 91 has a structure as shown in FIG. In this
embodiment, an acoustic space 45 is provided in an area of the lower surface of the partition
wall 44 except an intersection portion located in the central portion thereof. Therefore, a support
post 92 is formed on the lower surface of the partition wall 44 at the lower surface central
portion (intersection portion) of the partition wall 44. The lower surface of the support column
92 is located in the same plane as the lower surface of the substrate 42, and the support column
92 is surrounded in four directions by the acoustic space 45.
01-05-2019
27
[0083]
In the illustrated example, the support post 92 is located above the package sound hole 33, but
may be located outside the package sound hole 33. Further, a plurality of support posts 92 may
be provided. When the support pillar 92 is provided on the package sound hole 33, the area of
the support pillar 92 should be smaller than the opening area of the package sound hole 33 so
that the package sound hole 33 is not closed by the support pillar 92. There is a need.
[0084]
In this acoustic sensor 91, since the support column 92 is made to project from the lower surface
of the partition wall 44, the rigidity of the substrate 42 becomes higher, the strength against the
impact of the acoustic sensor 91 increases, and the diaphragm 46 becomes particularly difficult
to break. . Further, since the processing volume at the time of etching the acoustic space 45 etc.
on the substrate 42 is reduced, the etching time is further shortened, and the productivity of the
acoustic sensor 91 is improved.
[0085]
In the acoustic sensor 91 according to such an embodiment as well, in the process of forming the
acoustic space 45 by etching, if a region to be the convex portion 92 is covered with a mask, the
manufacturing method 1-3 of the first embodiment is performed. It can be manufactured by the
same manufacturing method.
[0086]
(Embodiment 4) FIG. 22 (A) is a partially omitted plan view showing an acoustic sensor 101
according to Embodiment 4 of the present invention.
FIG. 22B is a cross-sectional view in which the acoustic sensor 101 is mounted on the package
substrate 32a. FIG. 23 is a perspective view from the back side showing a substrate 42 used for
the acoustic sensor 101.
[0087]
01-05-2019
28
The substrate 42 used for the acoustic sensor 101 has a structure as shown in FIG. In this
embodiment, an acoustic space 45 is provided in the lower surface of the partition wall 44 in the
region excluding the intersection portion located in the central portion, and further, a region
surrounding the front chamber 43 and the partition wall 44 (a lower surface of the substrate 42
An acoustic space 45 is provided also in the outer peripheral area of Further, a support post 92
is provided on the lower surface of the partition wall 44.
[0088]
In this acoustic sensor 91, since the acoustic space 45 becomes wide, the degree of freedom in
the position where the package sound hole 33 is provided becomes high. In particular, as shown
in FIG. 9, it becomes possible to position the package sound hole 33 at the end of the acoustic
sensor 41. Further, since the support column 92 is protruded from the lower surface of the
partition wall 44, the rigidity of the substrate 42 is further increased, the strength against the
impact of the acoustic sensor 91 is increased, and the diaphragm 46 is particularly difficult to be
damaged.
[0089]
(Other Substrate Shapes) Various substrate shapes (or acoustic space structures) are possible
other than the above-mentioned substrate shapes. For example, in the substrate 42 shown in
FIGS. 24A and 24B, the acoustic space 45 extending in the diagonal direction is provided on the
lower surface of the partition wall 44. The package sound hole 33 is disposed to face the central
portion (intersection portion) of the acoustic space 45.
[0090]
In the substrate 42 shown in FIG. 25A, an acoustic space 45 extending in the wall thickness
direction is provided on the lower surface of the partition wall 44 so as to connect the adjacent
front chambers 43. The package sound hole 33 is disposed to face the lower surface opening of
any one front chamber 43. Even in such a configuration, the front chambers 43 communicate
with each other through the acoustic space 45 or through the acoustic space 45 and the
intermediate front chamber 43. The package sound hole 33 can also be provided at a position
01-05-2019
29
facing the front chamber 43 unless the possibility of dust or the like entering the front chamber
43 from the package sound hole 33 becomes a problem.
[0091]
In the substrate 42 shown in FIG. 25B, the front chamber 43 is not provided in one of the
substrates 42 in FIG. 25A, the number of front chambers 43 is reduced, and the number of the
front chambers 43 is reduced. An acoustic space 45 is provided on the lower surface of the
housing 42.
[0092]
In the substrate shown in FIG. 26A, an acoustic space 45 is provided on the lower surface of the
partition wall 44 so as to connect the adjacent front chambers 43, and the acoustic space 45
between the front chambers 43 is opposed to the package. A sound hole 33 is disposed.
In the substrate shown in FIG. 26A, the width of the acoustic space 45 in which the package
sound holes 33 are disposed opposite to each other is made wider than the other.
[0093]
Further, the number of front chambers 43 provided on the substrate 42 may be four or more. For
example, as shown in FIG. 26B, a large number of front chambers 43 may be arranged in a
rectangular shape, and an acoustic space 45 may be provided on the lower surface of the
partition wall 44 so as to connect the adjacent front chambers 43. In this case, the package
sound hole 33 may be disposed to face the lower surface opening of any one of the front
chambers 43, or may be disposed to face the acoustic space 45.
[0094]
(Fifth Embodiment) FIG. 27 is a cross-sectional view of an acoustic sensor 111 according to a
fifth embodiment of the present invention mounted on a package substrate 32a. Although the
fixed electrode plate 50 is provided above the diaphragm 46 in each of the embodiments and the
modifications described above, the arrangement may be reversed. That is, in the acoustic sensor
01-05-2019
30
111 shown in FIG. 27, the back plate 49 is installed on the upper surface of the substrate 42, and
the fixed electrode plate 50 is provided on the upper surface of the back plate 49 above the front
chamber 43. A large number of acoustic holes 51 are formed in the back plate 49 and the fixed
electrode plate 50. A diaphragm 46 is disposed above each fixed electrode plate 50 so as to face
the fixed electrode plate 50, and each corner of the diaphragm 46 is supported on the upper
surface of the back plate 49 by an anchor 48.
[0095]
In this acoustic sensor 111, the acoustic vibration that enters from the package sound hole 33
and enters the front chamber 43 through the acoustic space 45 further passes through the
acoustic hole 51 to vibrate the diaphragm 46, and the diaphragm 46 and the fixed electrode
plate Change the capacitance between 50.
[0096]
Sixth Embodiment FIG. 28A is a partially omitted plan view showing an acoustic sensor 121
according to a sixth embodiment of the present invention.
FIG. 28B is a perspective view from the back side showing the substrate 42 used for the acoustic
sensor 121. FIG.
[0097]
The substrate 42 used for the acoustic sensor 121 has a structure as shown in FIGS. 28 (A) and
28 (B). In this embodiment, an acoustic space 45 is provided on the lower surface of the
substrate 42 in the area outside the front chamber 43 and the partition wall 44. In the illustrated
example, a frame-shaped acoustic space 45 is provided to surround lower portions of the front
chamber 43 and the partition wall 44. The acoustic space 45 has a rectangular groove crosssectional shape, and communicates with the front chamber 43 on the inner peripheral side
surface thereof. The lower surface of the partition wall 44 is located on the same plane as the
lower surface of the substrate 42. In this embodiment, since the height of the partition wall 44 is
increased, the rigidity of the substrate 42 is further increased.
[0098]
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31
The acoustic sensor may be fixed to the inner surface of the cover of the package in a state of
being turned upside down. In this case, the package sound hole is opened in the cover at a
position facing the acoustic space of the acoustic sensor.
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32
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