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DESCRIPTION JP2002209298

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DESCRIPTION JP2002209298
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of manufacturing a condenser microphone, a condenser microphone and an electronic
device.
[0002]
A condenser microphone is known in which a back plate having a plurality of through holes
called acoustic holes formed on a silicon substrate and a diaphragm movable with respect to the
back plate form a capacitor. ing.
[0003]
For example, Japanese Unexamined Patent Publication No. 60-500841 discloses a condenser
microphone in which a glass back plate is formed on a silicon substrate.
[0004]
However, in the condenser microphone, since glass is processed to form a back plate,
productivity is low and processing accuracy is also poor.
[0005]
In particular, it is not easy to form acoustic holes in glass, and the process (work) takes a
relatively long time.
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[0006]
In addition, since the processing accuracy of the back plate is poor, there is a possibility that
desired characteristics can not be obtained.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a method of
manufacturing a condenser microphone, a condenser microphone and a condenser microphone
thereof, which are excellent in productivity and can obtain desired characteristics (mechanical
characteristics and acoustic characteristics). It is to provide the electronic device which it has.
[0008]
Such objects are achieved by the present invention as described in the following (1) to (15).
[0009]
(1) A manufacturing method of a condenser microphone in which a metal back plate having at
least one through hole formed in a semiconductor substrate, and a diaphragm movable with
respect to the back plate form a capacitor. And forming the back plate by plating.
[0010]
(2) The sacrificial layer is formed before forming the back plate, and after the back plate is
formed, the sacrificial layer is removed to form a space between the back plate and the
diaphragm. The manufacturing method of the condenser microphone as described in (1).
[0011]
(3) A manufacturing method of a condenser microphone in which a metal back plate having at
least one through hole formed in a semiconductor substrate, and a diaphragm movable with
respect to the back plate form a capacitor. A step of forming a film to be the diaphragm on the
semiconductor substrate, a step of forming a sacrificial layer, a step of forming the back plate by
plating so as to cover the sacrificial layer, and the step of forming the semiconductor substrate A
method of manufacturing a condenser microphone, comprising the steps of: partially removing a
portion corresponding to a diaphragm; and removing the sacrificial layer to form a space
between the back plate and the diaphragm. .
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[0012]
(4) The method of manufacturing a condenser microphone according to (3), wherein the
sacrificial layer is dissolved and discharged through the through hole in the step of forming the
space.
[0013]
(5) The method for manufacturing a condenser microphone according to any one of (1) to (4),
wherein the back plate is formed by selectively plating a predetermined portion other than the
through hole.
[0014]
(6) In the step of forming the back plate, the step of forming a mask on each of the portion to be
the through hole and the portion not to be plated other than the through hole, the step of plating,
and the step of forming the mask The manufacturing method of the condenser microphone in
any one of said (1) thru | or (4) including the process of removing.
[0015]
(7) The method for manufacturing a condenser microphone according to (6), wherein the portion
other than the through hole that is not plated is a portion outside the portion to be the back
plate.
[0016]
(8) The method of manufacturing a condenser microphone according to any one of (1) to (7),
wherein at least a part of the diaphragm is formed of a part of the semiconductor substrate.
[0017]
(9) The method of manufacturing a condenser microphone according to any one of the above (1)
to (8), wherein the plating method is a wet plating method.
[0018]
(10) The method of manufacturing a condenser microphone according to any one of (1) to (9),
wherein the semiconductor substrate is a single crystal silicon substrate.
[0019]
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(11) A capacitor microphone manufactured by the method of manufacturing a capacitor
microphone according to any one of (1) to (10) above.
[0020]
(12) A condenser microphone provided with a back plate having at least one through hole
formed in a semiconductor substrate and a diaphragm movable with respect to the back plate to
form a capacitor, wherein the back plate is , Condenser microphone characterized in that it is
made of metal.
[0021]
(13) The condenser microphone according to (12), wherein the back plate is formed by plating.
[0022]
(14) The condenser microphone according to (12) or (13), wherein the semiconductor substrate
is a single crystal silicon substrate.
[0023]
(15) An electronic device comprising the condenser microphone according to any one of (11) to
(14).
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION A method of manufacturing a condenser
microphone, a condenser microphone and an electronic device according to the present
invention will be described in detail below based on preferred embodiments shown in the
attached drawings.
[0025]
FIG. 1 is a longitudinal sectional view showing an embodiment of a condenser microphone of the
present invention.
As shown in the figure, a condenser microphone (condenser type microphone) 1 has a substrate
2.
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The substrate 2 is a semiconductor substrate.
[0026]
A metal back plate 7 in which a plurality of acoustic holes (through holes) 73 are formed on the
substrate 2 and a diaphragm 3 movable (displaceable) with respect to the back plate 7 form a
capacitor. It is provided.
[0027]
Further, a recess 23 is formed in a portion corresponding to the diaphragm 3 of the substrate 2.
[0028]
A part of the substrate 2, that is, the film 22 of the upper part of the recess 23 in FIG. 1
constitutes a part (one layer) of the diaphragm 3.
[0029]
A large number of microphones 1 are formed on a semiconductor wafer such as a silicon wafer,
for example, and separated from each other by a predetermined means such as dicing, for
example.
[0030]
The dimensions of the microphone 1 are not particularly limited, but may be, for example, about
2 to 5 mm × 2 to 5 mm, and the thickness may be about 0.2 to 1 mm.
[0031]
Next, a method of manufacturing the condenser microphone 1 will be described.
2, 3, 4, 5, 6, 7, 8, 9 and 10 are views (longitudinal sectional views) for explaining a method of
manufacturing the condenser microphone 1.
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[0032]
First, a semiconductor substrate is prepared as the base material 21 of the substrate 2.
The base material 21 is not particularly limited as long as it is a semiconductor substrate, but is
preferably a single crystal silicon substrate.
[0033]
The thickness of the base material 21 is not particularly limited, but is preferably about 100 to
1000 μm, and more preferably about 200 to 800 μm.
[0034]
<1> First, as shown in FIG. 2, the film 22 is formed on the surface of the base material 21, that is,
on the upper side, the lower side, the right side and the left side of the base material 21 in FIG.
The film 22 constitutes a part of the diaphragm 3 and also functions as a mask for etching the
base material 21.
[0035]
Examples of the constituent material of the film 22 include SiO 2, SiN, and the like. Among these,
SiN is preferable.
[0036]
When the film 22 is composed of a SiO 2 film, the surface (surface layer portion) of the base
material 21 is oxidized (thermally oxidized).
[0037]
When the film 22 is formed of a SiN film, the SiN film is deposited on the surface of the base
material 21 by the CVD (Chemical Vapor Deposition) method.
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[0038]
The thickness of the film 22 is not particularly limited, but is preferably about 0.05 to 2 μm, and
more preferably about 0.5 to 1 μm.
The base material 21 and the film 22 constitute a substrate 2.
[0039]
Next, if necessary, a predetermined circuit (integrated circuit) (not shown) such as an amplifier
circuit and a booster circuit is formed on the upper side of the substrate 2 in FIG.
[0040]
<2> Next, as shown in FIG. 3, the electrode 4 is formed on the upper side of the substrate 2 in
FIG.
The electrode 4 constitutes a part of the diaphragm 3.
[0041]
The electrode 4 has conductivity, and as its constituent material, for example, various metals,
polysilicon (polycrystalline silicon), etc. may be mentioned, and among them, metal is preferable.
[0042]
When the electrode 4 is formed of a metal film, the metal is not particularly limited, and
examples thereof include Cu, a Cu-based alloy, Al, an Al-based alloy, Au, Pt, W, and a W-based
alloy.
[0043]
When the electrode 4 is formed of a polysilicon film, it is preferable to inject a predetermined
dopant into the polysilicon film at a high concentration to improve the conductivity of the
electrode 4.
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[0044]
As a dopant, B, P, As, Al etc. are mentioned, for example.
Moreover, as a method of injecting a dopant, ion implantation etc. are mentioned, for example.
[0045]
The thickness of the electrode 4 is not particularly limited, but is preferably about 0.05 to 0.5
μm, and more preferably about 0.1 to 0.2 μm.
[0046]
Next, the insulating film 5 is formed on the upper side of the electrode 4 in FIG.
The insulating film 5 constitutes a part of the diaphragm 3.
[0047]
In the present embodiment, as shown in FIG. 3, the insulating film 5 is formed so as to cover the
end of the electrode 4 other than the end on the right side in FIG.
The electrode 4 and the back plate 7 are insulated from each other by the insulating film 5.
[0048]
As a constituent material of insulating film 5, SiO2, SiN etc. are mentioned, for example.
The thickness of the insulating film 5 is not particularly limited, but is preferably about 0.03 to 1
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μm, and more preferably about 0.05 to 0.2 μm.
[0049]
The insulating film 5 may be formed only between the electrode 4 and the end 74 of the back
plate 7 (see FIG. 1).
In this case, the insulating film 5 does not become a part of the diaphragm 3.
[0050]
<3> Next, as shown in FIG. 4, the sacrificial layer 6 is formed on the upper side of the substrate 2
and the insulating film 5 in FIG. 4.
[0051]
The sacrificial layer 6 is finally a portion to be removed, and in the present embodiment, as
shown in FIG. 4, the sacrificial layer 6 is formed to cover the insulating film 5 other than the end
on the right side in FIG. The insulating film 5 is also formed on the substrate 2 near the end
portion on the left side in FIG.
[0052]
The sacrificial layer 6 is formed in a predetermined pattern, for example, by photolithography.
[0053]
As a constituent material of the sacrificial layer 6, for example, polyimide, various resist
materials, SiO 2 and the like can be mentioned. Among them, polyimide or a resist is preferable
from the viewpoint that the sacrificial layer 6 can be more easily removed. Materials are
preferred.
[0054]
The thickness of the sacrificial layer 6 is not particularly limited, but the thickness of the
sacrificial layer 6 at the position of the electrode 4 is preferably about 1 to 6 μm, and more
preferably about 3 to 5 μm.
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[0055]
<4> Next, a metal back plate 7 is formed by plating to cover the sacrificial layer 6.
[0056]
The method of forming the back plate 7 is not particularly limited as long as it is a plating
method, and for example, a wet plating method such as electrolytic plating (electroplating) or
electroless plating, sputtering, ion plating, vacuum evaporation, CVD (chemical vapor deposition)
And the like. Among these, the wet plating method is preferable, and the electrolytic plating
method is more preferable.
[0057]
By using the wet plating method, in particular, the electrolytic plating method, it is possible to
form the back plate 7 having a predetermined thickness with high precision easily, quickly and
reliably.
[0058]
Preferably, the back plate 7 is formed by selectively plating a predetermined portion other than
the acoustic holes 73.
That is, it is preferable to use a selective plating method.
[0059]
By using the selective plating method, the number of processes can be reduced as compared with
the case where the acoustic holes 73 are formed later by, for example, etching, and the
productivity is high, which is advantageous for mass production.
[0060]
Hereinafter, representatively, the case of forming the back plate 7 by electrolytic plating and
selectively plating only the necessary portions will be described.
[0061]
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<4-> First, as shown in FIG. 5, for plating on the upper side in FIG. 5 of the laminate, ie, on the
upper side in FIG. 5 of the substrate 2, the electrode 4, the insulating film 5 and the sacrificial
layer 6 A conductive film 71 to be an electrode of
[0062]
The conductorized film 71 is made of metal.
The metal is not particularly limited, and examples thereof include Cu, a Cu-based alloy, Cr / Au,
Cr / Ni and the like.
[0063]
The thickness of the conductorized film 71 is not particularly limited, but is preferably about
0.05 to 1 μm, and more preferably about 0.1 to 0.2 μm.
[0064]
<4-> Next, as shown in FIG. 6, a mask 81 for plating (electroforming) of the back plate 7 is
formed on the upper side of the conductorized film 71 in FIG.
[0065]
The masks 81 are formed in portions to be the plurality of acoustic holes (through holes) 73 of
the back plate 7.
[0066]
In addition, the mask 81 is also formed on the portions other than the acoustic holes 73 which
are not to be plated, that is, the portions outside the portion to be the back plate 7 (for example,
the left side and the right side in FIG.
This prevents (prevents) the formation of the metal layer 72 described later on unnecessary
portions, and can suppress the consumption and deterioration of the plating solution (material).
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Further, by not forming the metal layer 72 in an unnecessary portion, deformation of the
substrate 2 and peeling of the metal layer 72 can be prevented more reliably.
[0067]
The mask 81 is formed in a predetermined pattern, for example, by photolithography.
[0068]
As a constituent material of the mask 81, various resist materials etc. are mentioned, for example.
[0069]
<4-> Next, as shown in FIG. 7, a metal layer 72 is formed on the conductive film 71 by
electrolytic plating (electroplating).
[0070]
It does not specifically limit as a metal which comprises the metal layer 72, For example, Cu, Cu
type alloy, Ni, Ni type alloy, Au etc. are mentioned.
[0071]
The thickness of the metal layer 72 is not particularly limited, but is preferably about 2 to 30
μm, and more preferably about 5 to 20 μm.
[0072]
The compositions of the metal layer 72 and the conductorized film 71 may be the same or
different.
[0073]
<4-> Next, as shown in FIG. 8, the mask 81 is removed.
The removal of the mask 81 can be performed by, for example, a dry etching method, a wet
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etching method, or the like.
[0074]
Next, the conductor film 71 at the portion of each acoustic hole 73 is removed, and each acoustic
hole 73 is penetrated.
[0075]
As a result, a plurality of acoustic holes 73 are formed, and the back plate 7 composed of the
metal layer 72 and the conductorized film 71 is formed.
[0076]
The shape of the acoustic hole 73 in a plan view (shape when viewed from the upper side in FIG.
8) is not particularly limited, and may be, for example, a polygon such as a quadrangle, a circle,
or an ellipse.
[0077]
The conductive film 71 can be removed by, for example, a dry etching method, a wet etching
method, or the like.
[0078]
<5> Next, the portion of the substrate 2 corresponding to the diaphragm 3 is partially removed
to form the diaphragm 3.
[0079]
<5-> First, as shown in FIG. 9, of the film 22 on the lower side of the substrate 2 in FIG. 9, the
portion corresponding to the diaphragm 3, ie, the portion corresponding to the recess 23 shown
in FIG. An opening 24 of a shape corresponding to the diaphragm 3 is formed.
[0080]
The film 22 can be removed by, for example, a dry etching method, a wet etching method, or the
like.
[0081]
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<5-> Next, as shown in FIG. 10, the portion (base material 21) of the opening 24 of the substrate
2 is removed so that the film 22 is exposed.
[0082]
Thereby, the recess 23 is formed in the substrate 2, and the diaphragm 3 formed of the film 22,
the electrode 4 and the insulating film 5 is formed on the upper side of the recess 23 in FIG. 10.
[0083]
The formation of the recess 23 is preferably performed by an etching method.
That is, it is preferable to etch the portion of the opening 24 of the substrate 2 until the film 22
is exposed.
[0084]
As an etching method in this case, for example, a dry etching method, a wet etching method and
the like can be mentioned, and in particular, an alkali anisotropic etching method is preferable.
[0085]
When this process is performed by the alkaline anisotropic etching method, the film 22 is hardly
etched by the etching, and only the base material 21 of the substrate 2 is etched. Stop when
exposed.
Therefore, the portion of the opening 24 of the substrate 2 can be easily and surely removed so
that the film 22 is exposed, and the diaphragm 3 having a predetermined thickness can be
formed with high accuracy.
[0086]
In addition, as an alkaline etching liquid in the case of using an alkali anisotropic etching method,
the aqueous solution of TMAH (tetramethyl ammonium hydroxide) etc. are mentioned, for
example.
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[0087]
Here, the concave portion 23 is formed such that the portion 231 on the back plate 7 side (upper
side in FIG. 10) is positioned inside the end portion 74 of the back plate 7.
That is, the end 74 of the back plate 7 is positioned above the base material 21 of the substrate 2
in FIG.
Thereby, the back plate 7 can be more reliably supported by the substrate 2.
[0088]
<6> Next, as shown in FIG. 1, the sacrificial layer 6 is removed through the acoustic holes 73 of
the back plate 7 using a gas or liquid for removing the sacrificial layer 6.
[0089]
At this time, a gas or liquid for removal of the sacrificial layer 6 enters through the acoustic holes
73, whereby the sacrificial layer 6 is decomposed or dissolved and discharged.
[0090]
Thus, a hollow portion (space) 9 communicating with the acoustic hole 73 is formed between the
back plate 7 and the diaphragm 3.
[0091]
For example, when the sacrificial layer 6 is made of SiO 2, HF (hydrogen fluoride) or the like is
used to remove the sacrificial layer 6, and the sacrificial layer 6 is made of polyimide or a resist
material. If it does, use O2 plasma or the like.
Thereby, only the sacrificial layer 6 can be selectively removed.
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[0092]
Next, the electrodes 4 of the diaphragm 3 and the back plate 7 are electrically connected to
predetermined circuits (not shown) provided on the upper side of the substrate 2 in FIG. 1 by, for
example, lead wires (not shown).
As described above, the condenser microphone 1 shown in FIG. 1 is obtained.
[0093]
Next, the operation of the condenser microphone 1 will be described.
When a voice, that is, a sound wave, enters the condenser microphone 1 while the condenser
microphone 1 is in operation, the diaphragm 3 vibrates by the sound wave (sound pressure).
[0094]
When the diaphragm 3 vibrates, the distance (interval) between the diaphragm 3 and the back
plate 7 changes according to the magnitude of the amplitude, and the capacitance of the
capacitor formed of the diaphragm 3 and the back plate 7 changes. .
[0095]
The change in capacitance is output from the condenser microphone 1 as an electrical signal.
That is, an acoustic signal is converted into an electrical signal by the condenser microphone 1
and output.
[0096]
As described above, according to the condenser microphone 1 and the method of manufacturing
the same, since the back plate 7 is made of metal, its rigidity and strength are high.
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[0097]
Further, the back plate 7 can be formed easily and accurately by the plating method.
[0098]
Thus, the condenser microphone 1 has excellent characteristics (mechanical characteristics and
acoustic characteristics).
[0099]
Also, the microphone 1 can be formed by a semiconductor manufacturing process (in particular,
micromachining).
Therefore, it can be easily and precisely processed, has high productivity, is advantageous for
mass production, and is also advantageous for miniaturization.
[0100]
Further, the microphone 1 and its peripheral circuits can be formed (integrated) on the same
substrate.
[0101]
The condenser microphone 1 described above can be incorporated into various electronic
devices (electronic devices) and used.
[0102]
Next, an embodiment in which the electronic device of the present invention is applied to a
hearing aid will be described.
[0103]
FIG. 11 is a perspective view showing an embodiment in which the electronic device of the
present invention is applied to a hearing aid, that is, an embodiment of a hearing aid provided
with the condenser microphone 1 shown in FIG.
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[0104]
As shown to the same figure, the hearing aid (electronic device) 100 has the casing (exterior
member) 110 in which the opening 120 was formed.
[0105]
In the casing 110, the above-described condenser microphone 1, a not-shown speaker, and a notshown predetermined electric circuit electrically connected to the condenser microphone 1 and
the speaker are respectively installed.
[0106]
The condenser microphone 1 is disposed such that the recess 23 of the substrate 2 is oriented in
the sound source direction, and the recess 23, that is, the diaphragm 3 is located at the position
of the opening 120.
[0107]
Next, the operation of the hearing aid 100 will be described.
As described above, the sound (sound pressure) from the sound source is converted into an
electric signal by the condenser microphone 1.
[0108]
This electrical signal is signal-processed by the electrical circuit, input to the speaker, converted
again to voice by the speaker, and output.
[0109]
Thereby, the user of the hearing aid 100 can easily and reliably hear the sound from the sound
source.
[0110]
As described above, since the hearing aid 100 incorporates the above-described condenser
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microphone 1, it has very good performance.
[0111]
The present invention is not limited to the above-described hearing aids, but any other electronic
devices having a microphone, such as mobile phones (including PHS), video phones, telephones,
voice inputs such as these mobile phones, video phones and phones, etc. It can be applied to
equipment.
[0112]
As mentioned above, although the manufacturing method of the condenser microphone of the
present invention, the condenser microphone and the electronic device have been described
based on the illustrated embodiment, the present invention is not limited to this, and the
configuration of each part has the same function. It can be replaced with one having any
configuration.
[0113]
In the embodiment, the end 74 of the back plate 7 is a spacer for forming a predetermined gap
between the back plate 7 and the diaphragm, but the present invention is not limited to this, for
example, The back plate and the spacer may be configured as separate members, and the back
plate and the spacer may be formed of different constituent materials.
[0114]
In the present invention, the spacer may be formed of a constituent material other than metal.
In addition, as a constituent material of a spacer, polyimide, various resist materials, SiO2, etc. are
mentioned, for example.
[0115]
As described above, according to the present invention, the back plate can be easily and precisely
formed, and since the back plate is made of metal, it has high rigidity and strength. .
[0116]
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Thus, a condenser microphone having high performance, that is, excellent mechanical
characteristics and acoustic characteristics can be obtained.
[0117]
In addition, the condenser microphone can be easily manufactured, has high productivity, is
advantageous for mass production, and is also advantageous for downsizing.
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