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JP2007124449

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DESCRIPTION JP2007124449
An object of the present invention is to provide a microphone whose size can be reduced. A
shutter substrate (30) having a conductive electrode (31) and a movable diaphragm electrode
(32) opposed to the conductive electrode (31) with a gap forming a part of a first sound pressure
passage therebetween. It is formed as a so-called MEMS consisting of mechanical parts and
electrical parts formed on a substrate. By applying a voltage between the conductive electrode 31
and the movable diaphragm electrode 32 to generate electrostatic attraction and adsorb the
movable diaphragm electrode 32 to the conductive electrode 31, the first sound pressure
passage is opened or closed. . [Selected figure] Figure 5
マイクロフォンおよびマイクロフォンモジュール
[0001]
The present invention relates to a microphone capable of switching between omnidirectionality
and unidirectionality, and to a microphone module capable of adjusting directivity between
omnidirectionality and unidirectionality.
[0002]
In general, microphones are classified into omnidirectional microphones OM (omni-directional
microphones), uni-directional microphones UM (uni-directional microphones) and the like from
the viewpoint of the directivity thereof.
[0003]
04-05-2019
1
Among them, as shown in FIG. 15A, the nondirectional microphone OM is open to the external
sound field only in front of the diaphragm VF that vibrates according to the sound pressure
transmitted from the external sound source. And its back is closed.
In such a nondirectional microphone OM, regardless of the directions of the sound sources S1
and S2, the sound pressure is transmitted to the diaphragm VF only from the front.
Therefore, the omnidirectional microphone OM can pick up all the sounds gathered at the
installed place regardless of the direction and angle of the diaphragm VF.
[0004]
On the other hand, in the unidirectional microphone UM, as shown in FIG. 15 (b), the sound hole
A, which is a passage for sound, is also formed behind the diaphragm VF. The structure is
different from that of the directional microphone OM. In such a unidirectional microphone UM,
the sound wave generated by the sound source S2 at the rear is transmitted to the vibrating
membrane VF through the sound hole A, and the sound wave wraps around slightly and reaches
the front side of the vibrating membrane VF. Therefore, if an acoustic wave coming from the
front and a sound wave coming from the rear are made to reach simultaneously by devising an
obstacle to delay the sound velocity to the rear side, etc., they can be canceled by the vibrating
membrane VF. . On the other hand, the sound pressure generated by the front sound source S1 is
first transmitted to the diaphragm VF. The sound waves that subsequently travel to the back side
are delayed further by the obstacle.
[0005]
The omnidirectional microphone OM and the unidirectional microphone UM are used properly
depending on the requirements for the directivity of the mounted device. However, depending on
the device to be mounted, it may be desired to change the directivity of the microphone
according to the situation.
[0006]
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2
Heretofore, a microphone module described in Patent Document 1 is known as a technology for
realizing such a request. The microphone module is configured to include two microphones of an
omnidirectional microphone OM and a unidirectional microphone UM. Then, components of
different frequency bands are extracted from the outputs of the respective microphones and then
combined to perform sound collection, and the frequency band components extracted from the
outputs of the respective microphones are changed according to the sound collection
environment, It enables sound collection suitable for the sound collection environment.
[0007]
However, if it is simply to selectively switch between nondirectionality and unidirectionality, it
can be realized by providing the above two microphones and switching between the microphones
used for sound collection as required. . However, in such a case, installation of two types of
microphones becomes essential, and there are problems in terms of installation size and
manufacturing cost.
[0008]
As a microphone that can switch directivity alone, a directivity variable microphone described in
Patent Document 2 is known. The variable directivity microphone opens the front and the rear of
the vibrating membrane to the outside through the sound hole and opens and closes the sound
hole on the rear through the manual operation of the opening / closing mechanism configured
by the packing, the plate spring, the cam and the like. Thus, it is configured to selectively switch
between omnidirectionality and unidirectionality.
[0009]
FIG. 16 shows the structure of this directional microphone mounted on the transmitter. As shown
in the figure, the microphone body 101 is fixed to the housing 100 of the transmitter on which
the directivity variable microphone is mounted in a state of being fixed to the inside of the
mouthpiece 100a. The microphone main body 101 is configured to have a case 102 formed in a
hollow cylindrical shape, and a vibrating film 103 stretched inside the case 102 so as to divide
an internal space into two. Sound holes B1 and B2 communicating the inside and the outside are
formed in the front wall surface (front surface) of the vibrating membrane 103 of the case 102
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and the rear wall surface (rear surface) thereof. The sound hole B1 in front of the vibrating
membrane 103 is in communication with the outside of the case 100 of the transmitter via the
mouthpiece 100a. Further, the sound hole B2 at the rear of the vibrating membrane 103 is
communicated with the outside of the casing 100 through the insertion hole C formed on the
side of the casing 100 of the transmitter.
[0010]
A packing 104 for closing the sound hole B2 on the back side of the case 102 is disposed behind
the microphone main body 101 in a state of being biased toward the back of the microphone
main body 101 by the plate spring 105. Further, an operation knob 106 for opening and closing
the packing 104 is pivotally supported on the side of the microphone main body 101 to the
housing 100 of the transmitter via a pin 107 provided near the center of the microphone main
body 101. It is done. A portion on the microphone front side of the pin 107 of the operation
knob 106 is an operation portion 106 a which is pressed and operated by the user, and
protrudes outside the housing 100 of the transmitter. On the other hand, in the portion on the
microphone rear side of the pin 107 of the operation knob 106, the packing 104 resists the
biasing force of the plate spring 105 through the rotation of the operation knob 106 in response
to the pressing of the operation portion 106a. The cam portion 106b pushes up to the side away
from the rear face of the cam.
[0011]
In the directivity variable microphone configured as described above, when the sound hole B2 in
the rear of the vibrating membrane 103 is closed by the packing 104, the vibrating membrane
103 is opened to the outside only in front of it, and therefore it is a nondirectional microphone
Function. On the other hand, when the packing 104 is pushed up to open the sound hole B2, the
vibrating membrane 103 is opened to the outside not only in front thereof but also in the rear
thereof, so that it functions as a unidirectional microphone. With such a configuration, the
directivity can be switched with only a single microphone. JP-A 5-64284 JP-A 3-68244
[0012]
By the way, in recent years, MEMS (Micro Electro Mechanical Systems), which are extremely
small devices having both mechanical functions and electric functions, which are manufactured
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using a semiconductor manufacturing process, are attracting attention. Then, miniaturization of
microphones is in progress using such MEMS technology, and they are being installed in portable
information devices such as mobile phones, video cameras, voice recorders and the like.
[0013]
If it is intended to switch the directivity by adopting the open / close mechanism of the abovementioned conventional variable directivity microphone consisting of packing, a plate spring, a
cam, etc. to the microphone mounted in such portable information equipment, The occupied
space of the opening and closing mechanism in the case becomes too large. Therefore, under the
present circumstances where it has become possible to miniaturize the microphone itself as
described above, it is advantageous in terms of mountability to mount two microphones of
nondirectionality and unidirectionality. The number of microphones installed will be doubled,
resulting in an increase in manufacturing cost and a deterioration in productivity.
[0014]
A first object of the present invention is to provide a microphone which can be reduced in size. A
second object of the present invention is to further improve the productivity of such a
miniaturized microphone.
[0015]
In the above-mentioned conventional directivity variable microphone, it is only possible to switch
the directivity in binary to either the non-directivity or the uni-directionality, and a structure in
which the directivity can not be finely adjusted. It has become. On the other hand, with the
above-mentioned conventional microphone module, although it is possible to finely adjust the
directivity by adjusting the synthesis ratio of the outputs of both microphones, complex
arithmetic processing is necessary for adjusting the synthesis ratio. It has become.
[0016]
The third object of the present invention made in view of such a situation is to provide a
microphone module capable of facilitating the size reduction and facilitating the fine adjustment
of the directivity.
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[0017]
In order to achieve the first object, in the microphone according to the first aspect of the present
invention, a vibrating membrane vibrated by sound pressure transmitted from the outside and a
transmission path of sound pressure from the outside to one surface of the vibrating membrane
First sound pressure passage, a second sound pressure passage serving as a sound pressure
transmission path from the outside to the other surface of the vibrating membrane, and the first
sound pressure passage selectively opened and closed A movable part formed on the
semiconductor substrate and a shutter mechanism formed of an electrical part related to driving
of the movable part.
[0018]
In such a configuration, when the first sound pressure passage is closed by the shutter
mechanism, the external sound pressure is transmitted only to one surface of the vibrating
membrane through the second sound pressure passage, so that the microphone has no
directivity. Will be
On the other hand, when the first sound pressure passage is opened by the shutter mechanism,
the external sound pressure is transmitted to one surface of the vibrating membrane through the
second sound pressure passage, and the same vibrating membrane through the first sound
pressure passage. Will be transmitted to the other side of the
Since the sound pressure transmitted from the open direction of the first sound pressure passage
at this time is input to both the front and rear of the vibrating membrane and canceled out, the
microphone is single. Becoming directional.
[0019]
In such a microphone, a shutter mechanism for opening and closing the first sound pressure
passage to change directivity is formed by a so-called MEMS consisting of mechanical parts and
electric parts formed on the semiconductor substrate Since miniaturization using a process is
possible, the miniaturization can be easily achieved.
[0020]
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Also, in order to achieve the above first object, in the microphone according to claim 2, a
vibrating membrane vibrated by transmission of sound pressure from the outside and a
conversion unit for converting the vibration of the vibrating membrane into an electric signal are
formed. A microphone substrate made of the semiconductor substrate, a first sound pressure
passage serving as a transmission path of sound pressure from the outside to one surface of the
vibrating film, and sound pressure from the outside to the other surface of the vibrating film A
shutter substrate comprising a semiconductor substrate on which a second sound pressure
passage serving as a transmission path, a movable part selectively opening and closing the first
sound pressure passage, and an electric part related to driving the movable part are formed And
to provide.
[0021]
In such a configuration, when the first sound pressure passage is closed by driving the movable
member provided on the shutter substrate, only the one surface of the diaphragm of the
microphone substrate is transmitted through the second sound pressure passage. Will become
omnidirectional.
On the other hand, when the first sound pressure passage is opened by driving the movable
member formed on the shutter substrate, the external sound pressure is transmitted to one
surface of the diaphragm of the microphone substrate through the second sound pressure
passage. Through the first sound pressure passage to the other side of the vibrating membrane.
Since the sound pressure transmitted from the open direction of the first sound pressure passage
at this time is input to the diaphragm of the microphone substrate from both the front and the
back, the microphone is canceled out. Will be unidirectional.
[0022]
In such a microphone, both the microphone substrate configured to include the diaphragm and
the conversion unit, and the shutter substrate provided with the shutter mechanism that opens
and closes the first sound pressure passage to change the directivity, It is formed as what is
called MEMS which consists of a mechanical component and an electrical component which were
formed in the semiconductor substrate. Therefore, miniaturization can be achieved using a
semiconductor manufacturing process, and the miniaturization can be easily achieved.
04-05-2019
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[0023]
Furthermore, in order to achieve the first object as described above, in the microphone according
to claim 3, a movable diaphragm electrode vibrated by transmission of sound pressure from the
outside and a fixed electrode disposed opposite to the movable electrode with a gap. And a first
sound pressure passage serving as a transmission path of sound pressure from the outside to one
surface of the vibrating film, and the other surface from the outside to the other surface of the
vibrating film. From a semiconductor substrate on which a second sound pressure passage
serving as a sound pressure transmission path, a movable part selectively opening and closing
the first sound pressure passage, and an electric part related to driving the movable part are
formed And a shutter substrate.
[0024]
In such a configuration as well, by switching the opening and closing of the first sound pressure
passage by driving the movable member provided on the shutter substrate, the directivity of the
microphone can be switched to nondirectionality and unidirectionality. .
In such a microphone, a microphone substrate configured to include the movable diaphragm
electrode and the fixed electrode, and a shutter substrate that opens and closes the first sound
pressure passage to change directivity are formed on the semiconductor substrate. It can be
formed by so-called MEMS consisting of mechanical parts and electrical parts. Therefore,
miniaturization can be achieved using a semiconductor manufacturing process, and the
miniaturization can be easily achieved.
[0025]
On the other hand, in the microphone according to the fourth aspect of the present invention, in
order to achieve the first and second objects, the movable diaphragm electrode vibrating due to
the transmission of sound pressure from the outside and the movable diaphragm electrode are
arranged opposite to each other with a gap. A microphone substrate comprising a semiconductor
substrate on which the fixed electrode is formed, a first sound pressure passage forming a sound
pressure transmission path from the outside to one surface of the movable diaphragm electrode,
and the movable diaphragm electrode from the outside A second sound pressure passage
forming a sound pressure transmission path leading to the other surface of the second electrode,
and a conductive electrode and the conductive electrode facing each other with a gap forming a
part of the first sound pressure passage A shahsi consisting of a semiconductor substrate having
04-05-2019
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a movable diaphragm electrode disposed thereon and having a movable diaphragm electrode
attracted to the conductive electrode by electrostatic attraction generated by voltage application
to the conductive electrode. And so it comprises a data substrate.
[0026]
In such a configuration, when a voltage is applied between the conductive electrode of the
shutter substrate and the movable diaphragm electrode, the movable diaphragm electrode is
attracted to the conductive electrode by electrostatic attraction and the first sound pressure
passage formed in the gap between them. A part is blocked.
The external sound pressure at this time is transmitted only to one surface of the movable
diaphragm electrode of the microphone substrate through the second sound pressure passage, so
that the microphone becomes nondirectional.
[0027]
On the other hand, when the application of the voltage between the conductive electrode of the
shutter substrate and the movable diaphragm electrode is released, the adsorbed movable
diaphragm electrode is separated from the conductive electrode and part of the first sound
pressure passage formed in the gap between them. Is released. The external sound pressure at
this time is transmitted to one surface of the movable diaphragm electrode of the microphone
substrate through the second sound pressure passage, and is also transmitted to the other
surface of the movable diaphragm electrode through the first sound pressure passage. become.
Since the sound pressure transmitted from the open direction of the first sound pressure passage
at this time is input from both the front and the rear with respect to the movable diaphragm
electrode of the microphone substrate and is canceled out. The microphone will be unidirectional.
[0028]
In such a microphone, a machine in which a microphone body for converting sound pressure
transmitted from the outside into an electric signal, and a shutter mechanism for opening and
closing the first sound pressure passage to change directivity are formed on a semiconductor
04-05-2019
9
substrate It is formed by what is called MEMS which consists of parts and electric parts.
Therefore, miniaturization of the component using the semiconductor manufacturing process
becomes possible, and the miniaturization can be easily achieved. Further, the microphone
substrate and the shutter substrate constituting such a microphone have a common structure in
that they have a movable diaphragm electrode and an electrode oppositely disposed with a gap
therebetween, and many of the manufacturing process and production equipment of both
substrates. It becomes possible to improve productivity because it is possible to share the
[0029]
It is also possible to integrally form the microphone substrate and the shutter substrate
according to any one of claims 2 to 4 on the same semiconductor substrate as described in claim
5. In such a case, since the number of parts is reduced, productivity can be further improved.
Incidentally, such integration of the microphone substrate and the shutter substrate is, for
example, as described in claim 6, a sound hole which constitutes a part of the first sound
pressure passage in the fixed electrode of the microphone substrate and the shutter substrate.
This can be realized by forming the conductive electrode and arranging the movable diaphragm
electrode of the microphone substrate and the movable diaphragm electrode of the shutter
substrate so as to face each other with the fixed electrode interposed therebetween.
[0030]
On the other hand, in order to achieve the third object, in the microphone module according to
claim 7, a plurality of microphones according to any one of claims 1 to 6 are arranged, and the
first of the microphones is arranged. The open / close control unit is provided to change the ratio
between the number of microphones opening the sound pressure passage and the number of
microphones closing the first sound pressure passage.
[0031]
Also, in order to achieve the above third object, in the microphone module according to claim 9, a
vibrating membrane vibrated by a sound pressure transmitted from the outside, and a sound
pressure reaching the one surface of the vibrating membrane from the outside A first sound
pressure passage which is a transmission path of the second sound pressure passage, a second
sound pressure passage which is a transmission path of a sound pressure from the outside to the
other surface of the vibrating membrane, and the first sound pressure passage A plurality of
microphones each configured to have an opening / closing shutter mechanism, and among the
microphones, the number of microphones opening the first sound pressure passage by the
shutter mechanism; An open / close control unit is provided to change the ratio to the number of
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microphones closing the first sound pressure passage by the shutter mechanism.
[0032]
In the microphone module according to the seventh and ninth aspects of the present invention,
when the first sound pressure passage is closed for all the microphones constituting it to make it
nondirectional, the outputs of the respective microphones are synthesized The microphone
output as a whole of the obtained module is also omnidirectional.
Here, if the ratio of the number of unidirectional microphones is increased by opening the first
sound pressure passage among the microphones of the module, the directivity of the microphone
output as the entire module is unidirectional Become closer to sex.
And if the first sound pressure paths of all the microphones are opened to make them all
unidirectional, the microphone output as a whole module will be completely unidirectional. As
described above, in each of the microphone modules described above, the individual microphone
units constituting the module have a simple configuration in which the directivity is simply
switched in binary to either the nondirectionality or the unidirectionality. The directivity of the
module as a whole can be finely adjusted between omnidirectionality and unidirectionality.
[0033]
In the microphone module according to the ninth aspect, as described in the tenth aspect, the
diaphragms of the microphones arranged in an array are formed on the same semiconductor
substrate, and the shutter mechanism of each microphone is the same. It can also be configured
to be formed on a semiconductor substrate. In this case, the diaphragm and the shutter
mechanism of each of the microphones constituting the module can be simultaneously formed in
the same semiconductor substrate, so that the production can be facilitated.
[0034]
Further, in order to achieve the third object, in the microphone module according to claim 8, a
plurality of microphones according to any one of claims 2 to 6 are arranged, and the first sound
among the microphones is arranged. An open / close control unit is provided to change the ratio
between the number of microphones opening the pressure passage and the number of
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microphones closing the first sound pressure passage, and the microphone substrates of the
microphones arranged in an array are identical to each other. The shutter substrate of each
microphone is formed on the same semiconductor substrate as well as the semiconductor
substrate.
[0035]
In such a configuration, the individual microphone units constituting the module have a simple
configuration in which the directivity is switched in a binary manner to either the
nondirectionality or the unidirectionality, but the above-mentioned ratio is changed. The
directivity of the module as a whole can be finely adjusted between omnidirectionality and
unidirectionality.
In addition, since the microphone substrate and the shutter substrate of the microphones
constituting the module can be simultaneously formed on the same semiconductor substrate, the
production thereof can be facilitated.
[0036]
First Embodiment Hereinafter, a first embodiment in which the directivity variable microphone of
the present invention is embodied will be described in detail with reference to FIGS. 1 to 8. The
directivity variable microphone according to this embodiment is, as described in detail below, a
microphone substrate configured to include a diaphragm and a conversion unit, and a shutter
mechanism that opens and closes a sound pressure passage to switch directivity. By forming both
of the shutter substrates provided in the form of so-called MEMS, the size can be reduced.
[0037]
FIG. 1 shows the side cross-sectional structure of such a variable directivity microphone of this
embodiment. In the variable directivity microphone according to the present embodiment, sound
holes for transmitting the sound pressure outside the case 10 to the inside of the case 10 in the
lower bottom portion 10a and the upper bottom portion 10c of the hollow box type case 10 11a
and 11c are respectively formed. Further, on the upper surfaces of the lower bottom 10a and the
upper bottom 10c in which the sound holes 11a and 11c are formed, crosses 12a and 12c are
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attached to prevent dust and the like from entering the housing 10 through the sound holes 11a
and 11c. It is done. Further, on the upper surface of the cross 12a attached to the lower bottom
10a of the housing 10, a shutter substrate 30 on which a shutter mechanism having a MEMS
structure is formed for opening and closing a sound pressure passage for changing directivity is
mounted. ing. Further, mounted on the upper surface of the shutter substrate 30 is a microphone
substrate 20 in which a vibrating film that vibrates under sound pressure and a conversion unit
that converts the vibration of the vibrating film into an electrical signal are formed as a MEMS
structure. In the variable directivity microphone according to the present embodiment, an IC chip
60 that performs processing of an electrical signal related to sound collection of an external
sound source, variable control of directivity, and the like is mounted on the lower bottom 10a of
the housing 10 together. There is.
[0038]
2 shows the surface structure of the microphone substrate 20, FIG. 3 (a) shows the crosssectional structure along the line YY 'in FIG. 2, and FIG. 3 (b) shows the same. The cross-sectional
structure along a XX 'line is each shown.
[0039]
As shown in FIGS. 3A and 3B, the microphone substrate 20 is formed on the basis of a
semiconductor substrate 40 made of a semiconductor material such as silicon single crystal, for
example.
At a central portion of the plane of the semiconductor substrate 40, an acoustic hole AH2
penetrating the front and back is formed so as to reduce in diameter from the back side to the
front side. A disk-shaped movable diaphragm electrode 21 is stretched on the surface of the
semiconductor substrate 40 on which the etch stopper film 41 is formed so as to cover the
opening on the surface side of the acoustic hole AH2. Above the movable diaphragm electrode
21 having a high elastic modulus and functioning as the vibrating film, a fixed electrode
protective film 22 b made of, for example, silicon nitride (SiN) is spaced apart from the movable
diaphragm electrode 21 by a fixed gap. It is fixed to the upper surface of the semiconductor
substrate 40 in a lifted state. A disk-shaped fixed electrode 22a is formed under the fixed
electrode protective film 22b. A plurality of acoustic holes AH1 that allow sound pressure to pass
through are fixed to the fixed electrode protective film 22b and the fixed electrode 22a. As
shown in FIG. 2, lead wires 24, 26 extend from the movable diaphragm electrode 21 and the
fixed electrode 22a, and bonding wires for electrically connecting them to the IC chip 60 (see
FIG. 1) are provided. It is connected to the lead-out electrodes 25 and 27 to be welded.
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[0040]
In the microphone substrate 20 configured in this way, a parallel two-plate type capacitor is
formed by the movable diaphragm electrode 21 and the fixed electrode 22a which are disposed
opposite to each other with a predetermined gap therebetween. It functions as a conversion unit
that converts the vibration of the movable diaphragm electrode 21 that is a vibrating film into an
electric signal. That is, when the sound pressure from the outside is transmitted to the movable
diaphragm electrode 21 via at least one of the acoustic hole AH1 and the acoustic hole AH2 to
vibrate, the distance between the movable diaphragm electrode 21 and the fixed electrode 22a
changes, The capacitance of the capacitor configured by is changed. The IC chip 60 electrically
connected to the movable diaphragm electrode 21 and the fixed electrode 22a through the lead
wires 24, 26 and the lead electrodes 25, 27 generates an electric signal (sound pressure signal)
according to the change of the electrostatic capacitance. Generate and output.
[0041]
Next, the shutter substrate 30 for switching the directivity of the sound pressure detected by the
movable diaphragm electrode 21 and the fixed electrode 22a of the microphone substrate 20
will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 shows the surface structure of the
shutter substrate 30, and FIGS. 5 (a) and 5 (b) show the sectional structures of the shutter
substrate 30 according to the open and closed states of the sound pressure passage.
[0042]
As shown in FIG. 5A, the shutter substrate 30 is formed with a semiconductor substrate 50
formed of a semiconductor material such as silicon single crystal as its base. At a central portion
of the semiconductor substrate 50, an acoustic hole AH22 penetrating the front and back is
formed so as to decrease in diameter from the back side to the front side. A protective film 51 is
formed on the surface of the semiconductor substrate 50, and a conductive electrode 31 formed
in an annular shape is provided on the upper surface of the protective film 51 so as to surround
an opening on the surface side of the acoustic hole AH22. A protective film 53 is further stacked
on the upper surface of the protective film 51 on which the conductive electrode 31 is formed,
and the conductive electrode 31 is protected.
04-05-2019
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[0043]
A movable diaphragm electrode 32 is disposed above the conductive electrode 31 in a state of
being lifted up with a predetermined gap from the conductive electrode 31. The movable
diaphragm electrode 32 is, for example, a high elastic modulus diaphragm portion 32a made of
silicon nitride (SiN), and an electrode portion 32b made of polycrystalline silicon, for example,
formed at a position facing the conductive electrode 31 on the lower surface thereof. It is
composed of In addition, a plurality of acoustic holes AH21 for transmitting sound pressure are
provided in the outer periphery of the electrode portion 32b of the diaphragm portion 32a.
[0044]
As shown in FIG. 4, conductive lead wires 34 and 36 are extended from the electrode portion
32b of the conductive electrode 31 and the movable diaphragm electrode 32, respectively. The
lead wires 34, 36 are connected to lead electrodes 35, 37 to which bonding wires for electrically
connecting them to the IC chip 60 (see FIG. 1) are welded.
[0045]
In the shutter substrate 30 configured in this manner, the acoustic hole AH22 formed in the
semiconductor substrate 50, the gap between the electrodes 31 and 32, and the acoustic hole
AH21 formed in the movable diaphragm electrode 32 are used. A sound pressure transmission
passage is formed from the back side to the front side.
[0046]
On the other hand, in the shutter substrate 30, a parallel two-plate type capacitor is formed by
the conductive electrode 31 and the movable diaphragm electrode 32 which are disposed
opposite to each other with a predetermined gap therebetween.
The application of a voltage to the conductive electrode 31 and the movable diaphragm electrode
32 (electrode portion 32b) constituting the capacitor is connected to the IC chip 60 electrically
connected thereto via the lead wires 34 and 36 and the lead electrodes 35 and 37 (FIG. It is
controlled by FIG. 1). Here, when a voltage is applied to the conductive electrode 31 and the
04-05-2019
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movable diaphragm electrode 32 (electrode portion 32b), a potential difference is generated, and
both electrodes 31 and 32 come to attract each other by electrostatic attraction. As a result, the
movable diaphragm electrode 32 is largely bent toward the conductive electrode 31 as shown in
FIG. 5B, and as a result, both electrodes 31 and 32 can not maintain the gap and contact each
other. Then, the sound pressure transmission path from the back side to the front side of the
shutter substrate 30 is closed.
[0047]
On the other hand, when the voltage application to the electrode portion 32b of the conductive
electrode 31 and the movable diaphragm electrode 32 is released, the two electrodes 31 and 32
have the same potential and no electrostatic attractive force acts. As shown, the electrodes 31, 32
are spaced apart such that a gap is again formed between them.
[0048]
Here, as shown in FIG. 1, the shutter substrate 30 is disposed such that the acoustic hole AH22
formed in the semiconductor substrate 50 is located above the sound hole 11a formed in the
lower bottom portion 10a of the housing 10. It is done.
The microphone substrate 20 is disposed such that the acoustic hole AH2 formed in the
semiconductor substrate 40 is located above the acoustic hole AH22 of the shutter substrate 30.
Thus, in the directivity variable microphone of the present embodiment in which the microphone
substrate 20 and the shutter substrate 30 are disposed, the sound pressure generated by the
sound source outside the housing 10 is formed in the lower bottom portion 10 a of the housing
10 Sound hole 11a. An acoustic hole AH22 formed in the central portion of the semiconductor
substrate 50. A gap formed between the conductive electrode 31 and the movable diaphragm
electrode 32. An acoustic hole AH21 formed in the movable diaphragm electrode 32. An acoustic
hole AH2 formed in the central portion of the semiconductor substrate 40. In order to be
transmitted to the back surface of the movable diaphragm electrode 21 which is a vibrating film.
In the following, the sound pressure transmission passage leading to the back surface of the
movable diaphragm electrode 21 will be referred to as a first sound pressure passage.
[0049]
On the other hand, in the directivity variable microphone, the sound pressure generated by the
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sound source outside the housing 10 is the sound hole 11 c formed in the upper bottom portion
10 c of the housing 10. An acoustic hole AH1 formed in the center of the fixed electrode
protective film 22b. A gap formed between the movable diaphragm electrode 21 and the fixed
electrode 22a. In order to be transmitted to the surface of the movable diaphragm electrode 21.
In the following, the sound pressure transmission passage leading to the surface of the movable
diaphragm electrode 21 will be referred to as a second sound pressure passage.
[0050]
Now, when a voltage is applied between the movable diaphragm electrode 32 of the shutter
substrate 30 and the conductive electrode 31 so that the gap between the electrodes 31 and 32
constituting a part of the first sound pressure passage is not maintained. , And the first sound
pressure passage is closed. The sound pressure generated by the sound source outside the
housing 10 is transmitted only to the surface of the movable diaphragm electrode 21 of the
microphone substrate 20 which is the diaphragm at this time through the second sound pressure
passage. The directivity variable microphone comes to be omnidirectional.
[0051]
On the other hand, when the application of the voltage between the both electrodes 31, 32a of
the shutter substrate 30 is released and a gap is again formed between the both electrodes 31,
32, the first sound pressure passage is opened. Become. At the movable diaphragm electrode 21
of the microphone substrate 20 at this time, the sound pressure generated by the sound source
outside the housing 10 is transmitted to the surface of the movable diaphragm electrode 21
through the second sound pressure, and the first sound pressure It is also transmitted to the back
surface of the movable diaphragm electrode 21 through the passage. At this time, by designing
the sound pressure coming from the rear to reach simultaneously when passing through the first
sound pressure passage and the second sound pressure passage, the sound coming from the rear
is offset and Only the sound from the diaphragm vibrates, so that the directivity variable
microphone is unidirectional.
[0052]
Subsequently, an example of a manufacturing process of the microphone substrate 20 and the
shutter substrate 30 constituting the directivity variable microphone of the present embodiment
as described above will be described.
04-05-2019
17
[0053]
First, the manufacturing process of the microphone substrate 20 will be described with reference
to FIGS. 6 and 7.
[0054]
In order to manufacture the above-mentioned microphone substrate 20, first, a semiconductor
substrate 40 made of, for example, silicon (Si) single crystal is prepared.
For the semiconductor substrate 40 thus prepared, as an etching stopper formation step, for
example, an etching stopper film 41 made of silicon nitride (SiN) is formed by an LP-CVD (Low
Pressure Chemical Vapor Deposition) method. A film is formed on both the front and back sides
of the same semiconductor substrate 40 by a thickness of 05 to 0.2 μm.
Then, after forming the etch stopper film 41 in the etch stopper formation step, as a first
sacrificial layer formation step, P-CVD (plasma pressure chemical vapor deposition) method, or
atmospheric pressure CVD (normal pressure CVD) Chemical vapor deposition: A sacrificial layer
42 made of, for example, phosphosilicate glass (PSG) 0.5 to 1.0 on the etch stopper film 41 on
the upper surface side of the semiconductor substrate 40 by the Atmospheric Pressure Chemical
Vapor Deposition) method. The film is formed by [μm]. And as shown to Fig.6 (a), pattern
formation is performed through normal photolithography and dry etching.
[0055]
For the semiconductor substrate 40 on which the etch stopper film 41 and the sacrificial layer
42 are formed in this way, high-modulus films 43 and 43a made of, for example, polycrystalline
silicon (Poly-Si) are LP- Only 0.5 to 1.0 [μm] is formed by the CVD method. As shown in FIG. 6B,
even after forming the high elastic modulus films 43 and 43a, pattern formation is performed by
normal photolithography and dry etching, and the right portion of the high elastic modulus film
43 is formed. Is removed leaving a predetermined width.
[0056]
04-05-2019
18
Subsequently, as a second sacrificial layer forming step, a sacrificial layer 44 made of, for
example, PSG is formed on the upper surface of the semiconductor substrate 40 on which the
high elastic modulus films 43 and 43a are formed by P-CVD or atmospheric pressure CVD. To a
thickness of 3.0 μm. After the formation of the sacrificial layer 44, as shown in FIG. 6C, the
upper surface of the high elastic modulus film 43a from the upper surface of the sacrificial layer
44 on the left side in the figure by ordinary photolithography and dry etching. The opening 44a
is formed to the right, and the opening 44b is formed from the upper surface of the sacrificial
layer 44 to the etch stopper film 41 on the right side in the figure.
[0057]
After the openings 44a and 44b are formed in this way, a portion of the upper surface of the
sacrificial layer 44 facing the high elastic modulus film 43 of the conductive film 45 made of, for
example, polycrystalline silicon (Poly-Si) is formed as a fixed electrode forming step. The film
thickness is 1.0 [μm] by the LP-CVD method. On the conductive film 45 thus formed, as shown
in FIG. 6D, a pattern is formed by ordinary photolithography and dry etching.
[0058]
Then, after the fixed electrode forming step, a protective film 46 made of silicon nitride is formed
by P-CVD as a protective film forming step on the upper surface of the semiconductor substrate
40 on which the sacrificial layer 44 and the conductive film 45 are formed. .0 [μm] to form a
film. Then, as shown in FIG. 7A, in a portion of the protective film 46 facing the high elastic
modulus film 43, a through hole 46a from the upper surface of the protective film 46 to the
upper surface of the sacrificial layer 44 is It is formed through normal photolithography and dry
etching. Also, the protective film 46 formed in the opening 44 a formed in the sacrificial layer 44
is removed through the same normal photolithography and dry etching to form the through hole
46 b.
[0059]
As a subsequent substrate processing step, as shown in FIG. 7B, the semiconductor substrate 40
is formed by anisotropic wet etching using a developer such as potassium hydroxide (KOH) or
TMAH (Teramethylammonium Hydroxide), for example. An opening 40 a extending from the
04-05-2019
19
back surface of the semiconductor substrate 40 to the lower surface of the sacrificial layer 42 is
formed in a portion facing the high elastic modulus film 43. As shown in FIG. 7B, the opening
40a formed in the semiconductor substrate 40 has a diameter reduced from the back side to the
front side because of the anisotropy of the wet etching.
[0060]
After the opening 40a is thus formed on the back surface side of the semiconductor substrate 40,
it is formed on the semiconductor substrate 40 by a wet etching method using a chemical such
as hydrofluoric acid (HF) as a subsequent sacrificial layer etching step. Etch the sacrificial layer.
That is, the sacrificial layer 44 located between the lower surface of the protective film 46 and
the upper surface of the semiconductor substrate 40 is removed by the above-mentioned
chemicals using the through holes 46 a formed in the protective film 46. Do. On the other hand,
the portion of the etch stopper film 41 facing the opening 40 a and the sacrificial layer 42 are
removed by the above-mentioned chemicals using the opening 40 a formed in the semiconductor
substrate 40. As a result, as shown in FIG. 7C, a gap AP is formed between the high elastic
modulus film 43 and the protective film 46, and the high elastic modulus film 43 is vibratably
supported by the semiconductor substrate 40. Become. That is, the microphone substrate 20 is
formed.
[0061]
As can be seen from the comparison between FIG. 7C and FIG. 7D which is the same as FIG. 3B,
the opening 40a formed on the back surface side of the semiconductor substrate 40 is acoustic.
As the hole AH2, the high elastic modulus film 43 functions as the movable diaphragm electrode
21, and the protective film 46 and the through hole 46a thereof function as the fixed electrode
protective film 22b and the acoustic hole AH1.
[0062]
Next, a manufacturing process of the shutter substrate 30 will be described with reference to FIG.
[0063]
In order to manufacture the above-mentioned shutter substrate 30, first, a semiconductor
substrate 50 made of, for example, silicon (Si) single crystal is prepared.
04-05-2019
20
In the prepared semiconductor substrate 50, a protective film 51 made of silicon nitride (SiN) is
formed on the front and back sides of the semiconductor substrate 50, for example, by 0.1 μm
by an LP-CVD method as a protective film / conductive electrode forming step. Only form a film.
Then, on the semiconductor substrate 50 on which the protective film 51 is formed on the upper
surface, a conductive film made of, for example, polycrystalline silicon is formed by 0.5 [μm], for
example, through the LP-CVD method. That is, after the protective film 51 is formed on the entire
upper surface of the semiconductor substrate 50, the first conductive film 52 is formed on the
entire upper surface of the protective film 51. Such a semiconductor substrate 50 is patterned
through ordinary photolithography and dry etching to leave the first conductive film 52 only at a
predetermined position on the semiconductor substrate 50. Then, as shown in FIG. 8A, the
protective film 53 made of, for example, silicon nitride is formed only 0.1 [μm] over the entire
upper surface of the semiconductor substrate 50, for example, through the LP-CVD method. Do.
[0064]
Next, as a step of forming a sacrificial layer / electrode portion, the sacrificial layer 54 made of,
for example, PSG is formed on the entire upper surface of the semiconductor substrate 50 on
which the protective film 53 is formed by P-CVD or atmospheric pressure CVD. A film is formed
by 5 to 3.0 μm. After the formation of the sacrificial layer 54, the sacrificial layer 54 is
patterned into a mesa shape in cross section through ordinary photolithography and dry etching
to form a mesa structure in cross section. Then, a conductive film 55 made of, for example,
polycrystalline silicon is formed to a thickness of 0.5 μm on the entire upper surface of the
semiconductor substrate 50, for example, through the LP-CVD method. Thereafter, pattern
formation is performed again through normal photolithography and dry etching, and the second
conductive film 55 is left at a position facing the first conductive film 52 as shown in FIG. 8B.
[0065]
Subsequently, in the shutter film forming step, PE-CVD (plasma enhanced chemical vapor
deposition) is performed on the entire upper surface of the semiconductor substrate 50 on which
the protective film 53, the sacrificial layer 54, and the second conductive film 55 are formed. A
high elastic modulus film 56 made of, for example, silicon nitride is formed by a Plasma
Enhanced Chemical Vapor Deposition) method. Thereafter, patterning is performed through
04-05-2019
21
ordinary photolithography and dry etching to form openings 56a from the upper surface of the
high elastic modulus film 56 to the upper surface of the sacrificial layer 54 as shown in FIG. 8C.
[0066]
As a subsequent substrate processing step, as shown in FIG. 8D, the semiconductor substrate 50
is formed by anisotropic wet etching using a developer such as potassium hydroxide (KOH) or
TMAH (Teramethylammonium Hydroxide), for example. An opening 50 a from the back surface
to the lower surface of the sacrificial layer 54 is formed in the central portion of the
semiconductor substrate 50. As shown in FIG. 8D, the opening 50a formed in the semiconductor
substrate 50 is reduced in diameter from the back surface side to the front surface side due to
the anisotropy of the wet etching.
[0067]
After the opening 50a is thus formed on the back surface side of the semiconductor substrate 50,
it is formed on the semiconductor substrate 50 by a wet etching method using a chemical such
as hydrofluoric acid (HF) as a subsequent sacrificial layer etching step. Etch the sacrificial layer.
That is, for sacrificial layer 54 located between the lower surface of high elastic modulus film 56
and the upper surface of semiconductor substrate 50, opening 56 a formed in high elastic
modulus film 56 and semiconductor substrate 50 are formed. The chemical is used to remove it
using the opening 50a. Thus, as shown in FIG. 8E, a gap is formed between the high elastic
modulus film 56 and the protective film 53, and the high elastic modulus film 56 is supported so
as to be largely bent by the semiconductor substrate 50. It will be done. That is, the shutter
substrate 30 is formed.
[0068]
As can be seen from the comparison between FIG. 8 (e) and FIG. 8 (f) which is the same as FIG. 5
(a), the opening 50a of the semiconductor substrate 50 has high elasticity as the acoustic hole
AH22. The ratio film 56 and the second conductive film 55 function as the movable diaphragm
electrode 32, the opening 56a of the high elastic modulus film 56 functions as the acoustic hole
AH21, and the first conductive film 52 functions as the conductive electrode 31, respectively.
[0069]
As described above, according to the variable directivity microphone according to the first
04-05-2019
22
embodiment, the following excellent effects can be obtained.
[0070]
(1) In the variable directivity microphone according to the present embodiment, the microphone
substrate 20 converts sound pressure transmitted from the outside into an electric signal, and
the shutter substrate opens and closes the first sound pressure passage to change the directivity.
30 was made by so-called MEMS consisting of mechanical parts and electrical parts formed on a
semiconductor substrate.
As a result, it is possible to miniaturize the constituent members using the semiconductor
manufacturing process, and it is possible to easily miniaturize the component.
[0071]
(2) Further, the microphone substrate 20 and the shutter substrate 30 constituting such a
directivity variable microphone are the movable diaphragm electrodes 21 and 32, and the fixed
electrode 22a and the conductive electrode 31 disposed facing each other with a gap
therebetween. The structure is common in many points, such as having a parallel two-plate type
capacitor consisting of
Therefore, it is possible to share many of the manufacturing processes and production facilities
of both the substrates 20 and 30, and to improve the productivity.
[0072]
The directivity variable microphone of the first embodiment can be modified as follows.
[0073]
In the present embodiment, the microphone portion that has a diaphragm and senses the sound
pressure, and the shutter mechanism that opens and closes the sound pressure passage that
switches the directivity of the microphone portion are respectively formed by MEMS. .
04-05-2019
23
However, by adopting a shutter mechanism formed of a MEMS such as the shutter substrate 30
as the microphone having a structure other than the MEMS as the microphone part, the
directivity is switched while suppressing the increase in size. Can be made possible. For example,
FIG. 9 shows an example of a directivity variable microphone in which the directivity is changed
by adopting the shutter substrate 30 as an electret condenser microphone. As shown in the
figure, in this directivity variable microphone, residual polarization is provided inside the hollow
box-shaped housing 10 in which the sound holes 11a and 11c are formed in the lower bottom
portion 10a and the upper bottom portion 10c, respectively. An electret vibrating film 21a made
of a dielectric and a fixed electrode 22a opposed to the electret vibrating film 21a with a gap are
disposed in a state of being supported by the side wall 10b of the housing 10. Here, a large
number of acoustic holes are provided in the fixed electrode 22a, and the sound pressure
generated by the sound source outside the housing 10 can be transmitted to both the front and
back of the electret diaphragm 21a. . On the other hand, in this electret condenser microphone,
the shutter substrate 30 is disposed so as to cover the upper side of the sound hole 11a of the
lower bottom 10a of the case 10, and the sound hole is determined based on the command from
the IC chip 60a. The transmission path of the sound pressure from the outside of the housing 10
to the back surface of the electret vibrating film 21a through the opening 11a is selectively
opened and closed. Even in such a configuration, since the shutter mechanism can be
miniaturized by forming the MEMS, it is possible to preferably suppress the increase in size of
the microphone accompanying the change in directivity.
[0074]
Second Embodiment Next, a second embodiment of the present invention will be described with
reference to FIGS. 10 and 11, focusing on differences from the first embodiment described above.
In this embodiment, the parallel two-plate type capacitor for sound pressure sensing formed on
the microphone substrate 20 of the directivity variable microphone of the first embodiment and
the parallel two-plate type capacitor for the shutter mechanism formed on the shutter substrate
30 are the same. By manufacturing the semiconductor substrate, the number of parts is reduced
and the productivity is further improved.
[0075]
FIG. 10 shows a cross-sectional structure of a microphone / shutter substrate 70 in which the
two parallel double plate capacitors are formed. The microphone / shutter substrate 70 is housed
04-05-2019
24
in a hollow box-like housing having an acoustic hole formed in the upper and lower bottom
portions similar to that of the directional variable microphone of the first embodiment shown in
FIG. There is. In such a case, the microphone / shutter substrate 70 is mounted on the upper
surface of the lower bottom of the case so as to cover the top opening of the acoustic hole in the
lower bottom of the case. The respective electrodes of the two parallel double plate capacitors
formed on the microphone / shutter substrate 70 are electrically connected to an IC chip
disposed in the housing.
[0076]
The semiconductor substrate 40 which is a base of the microphone shutter substrate 70 is
formed of, for example, a semiconductor material such as silicon single crystal, and the acoustic
hole AH2 penetrating the front and back is formed on the front side from the back side It is
formed to be reduced in diameter. An etch stopper film 41 is formed on the upper surface of the
semiconductor substrate 40, and a disk-shaped movable diaphragm electrode 21 functioning as a
vibrating film covers the upper opening of the acoustic hole AH2 on the upper surface. It is
stretched. A sacrificial layer 44 having a predetermined thickness is stacked around the acoustic
hole AH2 in which the movable diaphragm electrode 71 having high elastic modulus is stretched,
and an n-type conductive layer made of polycrystalline silicon is formed on the upper surface
thereof. 72 are provided. The central portion of the n-type conductive layer 72 is supported by
the sacrificial layer 44 so that it is lifted from the movable diaphragm electrode 71 with a certain
gap. Then, this n-type conductive layer 72 formed with a large number of acoustic holes AH11
that allows sound pressure to pass is used as a fixed electrode, along with the movable
diaphragm electrode 71, a parallel two-plate capacitor that constitutes the microphone portion of
the directivity variable microphone. Is formed.
[0077]
On the other hand, a p-type conductive electrode portion 72 b is formed on the upper surface of
the conductive layer 72 so as to surround the acoustic hole AH2 formed in the semiconductor
substrate 40. The n-type conductive layer 72 and the p-type conductive electrode portion 72b
are mutually insulated by the depletion layer Dp formed in the pn junction thereof. A state in
which the etching stopper film 84 is formed on the upper surface of the conductive layer 72 on
which the conductive electrode portion 72b is formed, and the central portion is lifted so as to
form a constant gap with the conductive electrode portion 72b. For example, a diaphragm 73a
made of silicon nitride and having a high elastic modulus is disposed. An electrode portion 73b is
formed on the lower surface of the diaphragm 73a to be located above the conductive electrode
04-05-2019
25
portion 72b, and a plurality of acoustic holes AH12 penetrating the front and back of the
diaphragm 73a are formed around the electrode portion 73b. It is formed. The movable
diaphragm electrode 73 including the diaphragm 73a and the electrode portion 73b and the
conductive electrode portion 72b formed on the upper surface of the conductive layer 72 form a
parallel two-plate capacitor constituting a shutter mechanism.
[0078]
In such a microphone / shutter substrate 70, sound pressure is transmitted from the outside
through an acoustic hole AH2 formed in the semiconductor substrate 40 on the back surface of
the movable diaphragm electrode 71 which is a diaphragm of the microphone portion. In the
present embodiment, the sound pressure transmission path leading to the back surface of the
movable diaphragm electrode 71 corresponds to the first sound pressure path. On the other
hand, on the surface of the movable diaphragm electrode 71, a plurality of acoustic holes AH12
formed in the movable diaphragm electrode 73 of the shutter mechanism portion. A gap formed
between the movable diaphragm electrode 73 of the shutter mechanism portion and the
conductive layer 72.
[0079]
A plurality of acoustic holes AH11 formed in the central portion of the conductive layer 72. A
gap formed between the conductive layer 72 and the movable diaphragm electrode 71. Sound
pressure is transmitted from the outside through. In the present embodiment, the sound pressure
transmission path leading to the surface of the movable diaphragm electrode 71 corresponds to
the first sound pressure path. Then, when the movable diaphragm electrode 71 vibrates due to
the transmitted sound pressure, the gap with the conductive layer 72 serving as the fixed
electrode changes, and the capacity of the capacitor formed by them changes, so that the
electricity corresponding to the vibration It is possible to generate a signal.
[0080]
Now, in such a microphone / shutter substrate 70, when a voltage is applied between the
conductive electrode portion 72b formed on the upper surface of the conductive layer 72 and
the conductive electrode portion 73b of the movable diaphragm electrode 73 provided
thereabove, both electrodes are obtained. A potential difference is generated between the parts to
04-05-2019
26
cause electrostatic attraction. When the movable diaphragm electrodes 73 can not maintain a
gap with the conductive layer 72 due to the electrostatic attraction and bend until they come in
contact with each other, sound pressure from the outside reaching the surface of the movable
diaphragm electrode 71 which is a vibrating film Will be closed. Since the external sound
pressure at this time is transmitted only to the back surface of the movable diaphragm electrode
71, the variable directivity microphone is made nondirectional.
[0081]
On the other hand, when the application of the voltage between the conductive electrode portion
72b and the electrode portion 73b is released, these two electrode portions are at the same
potential and no electrostatic attractive force is generated. Away from the upper surface of 72, a
gap is again formed between them. As a result, the transmission path of the sound pressure from
the outside leading to the surface of the movable diaphragm electrode 71 which is a vibrating
film is opened, and the sound pressure from the outside is transmitted to both the surface and
the back surface of the movable diaphragm electrode 71 . Since the sound pressure generated by
the sound source located in front of the movable diaphragm electrode 71 at this time is input to
both the front and rear of the movable diaphragm electrode 71 and is canceled out, the variable
directivity microphone It will be unidirectional.
[0082]
Next, an example of the manufacturing process of such a microphone shutter substrate 70 will be
described with reference to FIG. In addition, since a part of the manufacturing process of this
microphone shutter substrate 70 overlaps with the manufacturing process of the previous
microphone substrate 20, the overlapping steps (steps corresponding to FIGS. 7A and 7B) I will
omit the detailed explanation about here.
[0083]
In manufacturing the microphone / shutter substrate 70, first, the semiconductor substrate 40
shown in FIG. 11A is prepared. That is, while the etch stopper film 41 is formed on the upper
surface of the semiconductor substrate 40 on the upper and lower surfaces of the semiconductor
substrate 40, the semiconductor substrate 40 in which the sacrificial layer 42, the high elastic
modulus film 43b and the sacrificial layer 81 are sequentially stacked is prepare. Here, the high
04-05-2019
27
elastic modulus film 43 b is, for example, a film having a thickness of 1.0 [μm] formed of
polycrystalline silicon (Poly-Si) by the LP-CVD method. The sacrificial layer 81 is a 3.0 [μm]
thick layer formed of PSG by P-CVD or atmospheric pressure CVD.
[0084]
Next, for the sacrificial layer 81 formed on the upper surface of the semiconductor substrate 40
prepared in this way, as an electrode forming step, for example, as shown in FIG. The conductive
layer 82 is formed to a thickness of 10 .mu.m by, for example, the LP-CVD method. At this time,
phosphorus (P) is diffused into the conductive layer 82 to make the conductive layer 82 n-type.
At the same time, a resist R is applied to the entire upper surface of the conductive layer 82, and
boron (B) is implanted into a part of the conductive layer 82 using the resist R as a mask to make
it p-type. Thus, the p-type conductive film 83 is formed on a part of the n-type conductive layer
82, and the depletion layer Dp is formed at the interface between the n-type conductive layer 82
and the p-type conductive film 83. It will be.
[0085]
Next, as shown in FIG. 11C, first, in the acoustic hole forming step, the resist R remaining on the
upper surfaces of the conductive layers 82 and 83 is peeled off, for example, through oxygen
plasma. Then, after the resist R is removed, an etch stopper film 84 made of silicon nitride is
formed to a thickness of 0.1 μm on the upper surface of the conductive layer 82 by, eg, LP-CVD.
Thereafter, through holes extending from the upper surface of etch stopper film 84 to the upper
surface of sacrificial layer 81 for the portions of conductive layer 82 and etch stopper film 84
opposite to high elastic modulus film 43 b through ordinary photolithography and dry etching. A
plurality of 82a and 84a are formed. Thereafter, P-CVD or atmospheric pressure is applied to the
inside of the etching stopper film 84 by 0.5 to 3.0 [μm] and to the upper surface of the
sacrificial layer 81 for the through holes 82a and 84a. A sacrificial layer 85 made of PSG is
formed by the CVD method. The sacrificial layer 85 thus formed is shaped into a mesa structure
in cross section through planarization and patterning by heat treatment.
[0086]
In the step of forming the movable diaphragm, first, as shown in FIG. 11D, a conductive film 86
made of polycrystalline silicon is formed on the upper surface of the sacrificial layer 85 by 0.5
04-05-2019
28
[μm], for example, through the LP-CVD method. Only form a film. Thus, the conductive film 86
formed on the entire upper surface of the sacrificial layer 85 is removed from the portions other
than the portion facing the conductive film 83 through ordinary photolithography and dry
etching. That is, only the portion facing the conductive film 83 remains. After the conductive film
86 is formed, a high elastic modulus film 87 made of, for example, silicon nitride is formed to a
thickness of 2.0 μm on the entire upper surface of the semiconductor substrate 40 by PE-CVD.
Then, patterning is performed on the formed high elastic modulus film 87 through ordinary
photolithography and dry etching to form through holes 87 a extending from the upper surface
of the same high elastic modulus film 87 to the upper surface of the sacrificial layer 85. Form. On
the other hand, under the etching stopper film 41 from the back surface of the semiconductor
substrate 40 in a portion facing the high elastic modulus film 43 b of the semiconductor
substrate 40 by anisotropic wet etching using a developing solution such as KOH or TMAH. An
opening 40 a reaching the surface is formed. As shown in FIG. 11 (d), the opening 40a formed in
the semiconductor substrate 40 is reduced in diameter from the back surface side to the front
surface side due to the anisotropy of the wet etching.
[0087]
After the opening 40a is thus formed on the back surface side of the semiconductor substrate 40,
the sacrificial layer formed on the semiconductor substrate 40 is etched by wet etching using a
chemical such as hydrofluoric acid (HF), for example. That is, sacrificial layer 85 located between
the lower surface of high modulus film 87 and the upper surface of conductive layer 82, and
sacrificial layer located between the lower surface of conductive layer 82 and the upper surface
of high modulus film 43b. For the layer 81, the above-mentioned medicine is made to permeate
using the through holes 87a formed in the high elastic modulus film 87 and the through holes
82a formed in the conductive layer 82, and this is removed. Further, the agent is made to
penetrate the sacrificial layer 42 located under the high elastic modulus film 43b by using the
opening 40a formed in the semiconductor substrate 40, and the chemical is removed. Thereby, a
gap is formed between the high elastic modulus film 87 and the conductive layer 82, and the
high elastic modulus film 87 can be largely bent. Furthermore, a gap is also formed between the
high elastic modulus film 43 b and the conductive layer 82, and the high elastic modulus film 43
b can also be largely bent.
[0088]
As can be seen from the comparison between FIG. 11D and FIG. 11E which is the same as FIG.
10, the opening 40a formed on the back surface side of the semiconductor substrate 40 serves
04-05-2019
29
as the acoustic hole AH2. The high elastic modulus film 43 b functions as the movable
diaphragm electrode 71. The high elastic modulus film 87 and its through hole 87a function as a
diaphragm 73a and an acoustic hole AH12, and the through hole 82a of the conductive layer 82
functions as an acoustic hole AH11.
[0089]
As described above, according to the directivity variable microphone of the second embodiment,
in addition to the effects of the above (1) and (2) of the first embodiment, the following excellent
effects are newly achieved. be able to. (3) The acoustic hole AH11 and the conductive electrode
portion 72b which constitute a part of the first sound pressure passage are formed in the
conductive layer 72 of the microphone / shutter substrate 70, and the movable diaphragm
electrode 71 and the movable diaphragm electrode 73 are formed. The conductive layer 72 is
disposed so as to face each other. By manufacturing the microphone substrate and the shutter
substrate on the same semiconductor substrate as described above, the number of parts can be
reduced and the productivity can be further improved.
[0090]
The directivity variable microphone of the second embodiment can be modified and implemented
as follows. In the above embodiment, the acoustic hole AH11 and the conductive electrode
portion 72b which constitute a part of the first sound pressure passage are formed in the
conductive layer 72 of the microphone shutter substrate 70, and the movable diaphragm
electrode 71 and the movable diaphragm electrode 73 are formed. Are arranged to face each
other with the conductive layer 72 interposed therebetween. However, the production mode of
the microphone substrate 20 and the shutter substrate 30 on the same semiconductor substrate
is not limited to this and is optional. If the two substrates can be fabricated on the same
semiconductor substrate through so-called MEMS, the effect of the above (3) can be obtained.
[0091]
Third Embodiment Next, a directivity variable microphone module according to a third
embodiment of the present invention will be described with reference to FIGS. 12 to 14. In FIGS.
12 to 14, the same elements as the elements shown in FIGS. 1 to 11 above are denoted by the
same reference numerals, and redundant description of the respective elements is omitted.
04-05-2019
30
[0092]
The directivity variable microphone module according to this embodiment arranges a plurality of
directivity variable microphones in an array, and sets the number of directivity variable
microphones to be set to non-directional among the microphones and the directivity to set to
unidirectivity. By providing an IC chip that controls the ratio to the number of variable
microphones, fine and easy adjustment of directivity is attempted.
[0093]
FIG. 12 shows an exploded perspective view of the circuit board portion of such a directivity
variable microphone module.
FIG. 13 is a side sectional view of the variable directivity microphone module according to this
embodiment.
[0094]
As shown in FIG. 13, on the upper surface of the circuit board 15a having the sound holes 16a
penetrating the front and back, the shutter cells 30b are arrayed on the same substrate so as to
cover the upper opening of the sound holes 16a. The shutter array substrate 30a is mounted, and
the microphone array substrate 20a in which the microphone cells 20b as many as the shutter
cells 30b are arrayed on the same substrate is mounted on the upper surface thereof. Further, on
the side of both the substrates 20a and 30a, among the plurality of microphones arrayed, the
number of directivity variable microphones set as omnidirectional and the number of directivity
variable microphones set as unidirectivity An IC chip 60b (opening / closing control unit) for
controlling the ratio of the two is mounted on the circuit board 15a. Incidentally, the IC chip 60b
also has a function of appropriately combining and outputting the outputs of the microphone
cells 20b of the microphone array substrate 20a. The directivity shown in the output from the IC
chip 60b is approximately equalized to the directivity of each microphone cell 20b.
[0095]
04-05-2019
31
The microphone cells 20b formed on the microphone array substrate 20a have basically the
same structure as the microphone substrate 20 shown in FIG. Each shutter cell 30b formed on
the shutter array substrate 30a has basically the same structure as the shutter substrate 30
shown in FIG.
[0096]
As shown in FIG. 13, a cover 15c formed of a metal material is attached to the upper surface of
the circuit board 15a on which the microphone array substrate 20a, the shutter array substrate
30a, and the IC chip 60b are mounted. A housing 15 is formed to accommodate the main
structure of the sex microphone module. A sound hole 16c is formed on the upper surface of the
cover 15c of the housing 15 to allow sound pressure transmitted from the outside to pass
therethrough, and a cross 17c is provided to prevent the entry of dust etc. through the sound
hole 16c. It is pasted. A similar cross 17a is attached to the upper surface of the circuit board
15a constituting the lower bottom of the housing 10 at the portion where the sound hole 16a is
formed and the periphery thereof.
[0097]
In the directivity variable microphone module configured as described above, a control mode of
directivity by the IC chip 60b is shown in FIG.
[0098]
As shown in FIG. 14, when all the directional variable microphones arranged in an array are set
to the omnidirectional OM, the directivity as the whole directional variable microphone module is
set to omnidirectional.
Here, when the number of same microphones set to unidirectional directivity UM among the
arrayed directional variable microphones is increased, the directivity as the whole directivity
variable microphone module is nondirectional to unidirectional. Become closer to sex. Then,
when all the directional variable microphones arranged in an array are set to single directional
UM, the directivity as the whole directional variable microphone module is set to strong single
directivity.
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[0099]
According to the directivity variable microphone of the third embodiment described above, in
addition to the effects of the above (1) and (2) of the first embodiment, the following excellent
effects can be newly obtained. . (4) A plurality of variable directivity microphones according to
the first embodiment are arrayed, and the ratio between the number of microphones set to
unidirectionality and the number of microphones set to nondirectional among the microphones is
changed The IC chip 60b is provided. As a result, in the individual microphone units constituting
the module, the directivity as a whole of the module is a simple configuration in which the
directivity is simply switched to either the nondirectionality or the unidirectionality in a binary
manner. Can be finely tuned between omnidirectionality and unidirectionality.
[0100]
Such a variable directivity microphone module of the third embodiment can be modified and
implemented as follows.
[0101]
The number and arrangement of the microphone cells 20b and the shutter cells 30b formed on
the microphone array substrate 20a and the shutter array substrate 30a can be arbitrarily
changed.
[0102]
In the present embodiment, the microphone cells 20b are formed on the same substrate
(microphone array substrate 20a). However, the microphone cells 20b may be separately formed
on individual substrates.
Similarly, the shutter cells 30b may be separately formed on individual substrates.
[0103]
FIG. 2 is a cross-sectional view showing a side cross-sectional structure of the microphone
according to the first embodiment of the present invention.
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The top view which shows the surface structure of the microphone board | substrate which
comprises the microphone of the embodiment. (A) And (b) sectional drawing which shows the
side cross-section along the Y-Y 'and X-X' line | wire of a microphone board | substrate. The top
view which shows the surface structure of the shutter board | substrate which comprises the
embodiment. (A) And (b) Sectional drawing which shows the side cross-section of the shutter
board | substrate which comprises the embodiment. (A)-(d) is a figure which shows each of the
manufacturing process of the said microphone board | substrate. (A)-(d) is a figure which each
shows the manufacturing process following FIG. 6 of the said microphone board | substrate. (A)(f) The figure which shows each of the manufacturing process of the said shutter board |
substrate. Sectional drawing which shows the side cross-section structure about one modification
of the embodiment. Sectional drawing which shows the side cross-section of the microphone *
shutter board | substrate of the microphone which concerns on 2nd Embodiment of this
invention. (A)-(d) The figure which shows each of the manufacturing process of the embodiment.
The disassembled perspective view of the circuit board part of the microphone module
concerning 3rd Embodiment of this invention. Sectional drawing which shows the side crosssection of the microphone of the embodiment. The schematic diagram which shows the control
aspect of the directivity of the embodiment. (A) and (b) The schematic diagram which each shows
the structure of a nondirectional microphone and a unidirectional microphone. Sectional drawing
which shows the side cross-section of the conventional microphone and its peripheral part.
Explanation of sign
[0104]
DESCRIPTION OF SYMBOLS 10, 15 ... Housing | casing 10a ... Lower bottom part, 10b ... Side
wall, 10c ... Upper bottom part 11a, 11c, 16a, 16c ... Sound hole, 12a, 17a, 17c ... Cross, 15a ...
Circuit board, 15c ... Cover, 20 ... Microphone board, 20a ... Microphone array board, 20b ...
Microphone cell, 21, 32, 71, 73 ... Movable diaphragm electrode (movable part), 21a ... Electret
diaphragm, 22a ... Fixed electrode, 22b ... Fixed electrode protection film, 24 , 26, 34, 36: lead-out
wiring, 25, 27, 35, 37: lead-out electrode, 30: shutter substrate (shutter mechanism), 30a: shutter
array substrate (shutter mechanism), 30b: shutter cell, 31: conductive electrode, 32a, 73a ...
diaphragm part, 32b, 73b ... electrode part, 40, 50 ... semiconductor substrate, 40a, 44a 44b,
50a, 56a ... opening (portion), 41, 84 ... etch stopper film, 42, 44, 54, 81, 85 ... sacrificial layer,
43, 43a, 43b, 56, 87 ... high elastic modulus film, 45, 47 , 52, 55, 83, 86: conductive film, 46, 51,
53: protective film, 46a, 46b, 82a, 84a, 87a: through hole, 60, 60a, 60b: IC chip (opening /
closing control unit), 70: Microphone shutter substrate 72, 82: conductive layer 72b: conductive
electrode portion.
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