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JPH1188992

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH1188992
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
integrated capacitive transducer used for a back electret condenser microphone or the like and a
method of manufacturing the same.
[0002]
2. Description of the Related Art Electret condenser microphones, which are easily miniaturized,
are frequently used in mobile phones. There is a back electret system as one of the systems of
this condenser microphone. The conventional structure of a back electret condenser microphone
is shown in FIG.
[0003]
In this type of condenser microphone, the printed circuit board 2, the holding body 3, the back
electrode plate 4, the electret layer 5, the spacer 6, the diaphragm 7, and the ring 8 are
sequentially arranged in the capsule 1 from the rear side to the front side The IC element 9 is
disposed inside the body 3.
[0004]
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The electret layer 5 forms a capacitor portion together with the vibrating film 7. In this method,
the electret layer 5 is located on the rear surface side of the vibrating film 7 via a space formed
by the spacer 6.
For this reason, this system is called a back electret system. Then, the electret layer 5 is formed
by welding a polymer film (usually FEP) of 12.5 to 25 μm to the surface of the back electrode
plate 4.
[0005]
The IC element 9 is an FET for impedance conversion, and its input terminal 9a is connected to
the back electrode plate 4 on the front side, and the output terminal 9b is connected to the
printed circuit board 2 on the rear side. The printed circuit board 2 is connected to an external
circuit such as an amplifier circuit or a noise cancel circuit (not shown).
[0006]
A sound hole 1a is provided in the front of the capsule 1, and a front cross 1 'is attached to the
surface of the sound hole 1a.
[0007]
In such a conventional back electret type condenser microphone, an independent IC element 9
(FET) is used for impedance conversion, and the IC element 9 is Since the circuit is connected to
an external circuit such as an amplifier circuit or a noise cancel circuit, the overall scale including
the external circuit board is considerably large.
[0008]
As described above, this type of electret condenser microphone is widely used in mobile phones.
In this application, as is well known, as much miniaturization as possible is required, but as
described above, the present condition is that the overall scale including external circuits can not
be sufficiently miniaturized. .
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[0009]
The present invention has been made in view of the above circumstances, and it is applied to a
back electret condenser microphone, and the integrated capacitive converter capable of reducing
the overall size significantly compared to the prior art and It aims at providing the manufacturing
method.
[0010]
SUMMARY OF THE INVENTION In order to achieve the above object, an integrated capacitive
converter according to the present invention comprises a semiconductor chip on which an
electronic circuit including an IC element is integrated, and a back electrode on the surface of the
semiconductor chip. The electret film is attached to the surface of the spacer, the electret film
formed by direct film formation on the surface of the conductive film, the spacer formed by
printing on the surface of the outer edge of the electret film, and the spacer And a vibrating
membrane fixed via a space.
[0011]
The integrated capacitive transducer according to the present invention incorporates the
transducer element in which the semiconductor chip, the conductive film, the electret film, the
spacer, and the diaphragm are integrated into a capsule provided with a sound hole in the front
surface portion, By attaching a front cloth to the front surface of the capsule, a back electret
condenser microphone can be configured.
[0012]
The electronic circuit here preferably includes an FET for a microphone, an amplifier circuit and
/ or a noise cancel circuit, and the like.
[0013]
Further, in the method of manufacturing an integrated capacitive converter according to the
present invention, a step of integrating a large number of electronic circuits including an IC
element on a semiconductor wafer to form a large number of chip parts, and a back electrode on
the surface of the semiconductor wafer As a step of forming a conductive film, a step of forming
an electret film by direct film formation on the surface of the conductive film, a step of printing
spacers on the surface of the electret film corresponding to the respective chip parts, and It is
characterized in that it includes a step of attaching a vibrating film, and a step of cutting a
semiconductor wafer into each chip portion after bonding the vibrating film.
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[0014]
In the integrated capacitive converter according to the present invention, a semiconductor chip is
formed by forming a conductive film as a back electrode and an electret film by film formation
on the surface of a semiconductor chip on which electronic circuits including IC elements are
integrated. A transducer element of one chip in which the conductive film, the electret film, the
spacer, and the vibrating film are integrated is formed.
Moreover, in the electronic circuit integrated on the semiconductor chip, an amplifier circuit and
a noise cancel circuit for the microphone can be configured.
[0015]
Therefore, by applying to the back electret condenser microphone, the main components
including the external circuit are integrated into one chip, and the overall scale is greatly
reduced.
[0016]
In addition, since the microphone including the external circuit is configured simply by
incorporating the chip in the capsule, mass productivity is very high.
[0017]
Further, by forming the electret film by film formation, generation of distortion can be avoided
and the film thickness can be reduced to about 1 μm.
Because of these, the performance as a converter is also greatly improved.
[0018]
In the method of manufacturing an integrated capacitive transducer according to the present
invention, the conductive film, the electret film, the spacer and the vibrating film are formed on a
semiconductor wafer and then cut into chips, so that the converter is integrated into one chip.
The element is manufactured with high efficiency.
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[0019]
The semiconductor material in the semiconductor chip and the semiconductor wafer is
preferably Si.
[0020]
The conductive film as the back electrode can be formed of, for example, an Al film having a
thickness of about 0.1 μm.
[0021]
As a material of the electret film, SiO2, FEP or the like can be used.
As the film forming method, a spinner coat is raised, and resistance heating evaporation, EB
evaporation (electron beam evaporation), sputtering (sputtering by high frequency, ion beam,
planar magnetron etc.), CVD (plasma, decompression, etc.) A known film formation method such
as chemical vapor deposition (pressure, light, etc.) can be used.
[0022]
The thickness of the electret film is preferably as thin as possible within the range in which film
formation is possible, and preferably in the range of 1 to 5 μm.
If it is less than 1 μm, it is difficult to form a uniform film thickness.
If it exceeds 10 μm, significant improvement in performance as a converter can not be expected.
[0023]
The thickness of the spacer is usually about 5 to 15 μm.
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[0024]
As the vibrating film, for example, a PPS film having a thickness of about 2 μm in which Ni is
vapor-deposited on one side can be used.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view of an integrated capacitive transducer (electret condenser
microphone) according to an embodiment of the present invention, and FIG. 2 is a semiconductor
wafer showing a method of manufacturing a microphone element used in the integrated
capacitive transducer. It is a top view and a partially enlarged view.
[0026]
The integrated capacitive converter according to the embodiment of the present invention is an
application of the present invention to a back electret condenser microphone.
[0027]
As shown in FIG. 1, this condenser microphone comprises a microphone element 10 as a
transducer element formed into one chip and a ceramic package 20 as a capsule for housing the
microphone element 10.
[0028]
The microphone element 10 has a structure in which a conductive film 12 as a back electrode, an
electret film 13, a spacer 14 and a vibrating film 15 are sequentially stacked on the surface of a
semiconductor chip 11.
[0029]
The semiconductor chip 11 is a Si chip, on which an FET for impedance conversion, an amplifier
circuit and / or a noise cancellation circuit, and the like are further stacked.
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The conductive film 12 is an Al film having a thickness of about 0.1 μm formed on the surface
of the semiconductor chip 11 by vapor deposition or the like.
[0030]
The electret film 13 is formed by spinner coating, resistance heating evaporation, EB evaporation
(electron beam evaporation), sputtering (high frequency, ion beam, sputtering by planar
magnetron etc.), CVD (plasma, reduced pressure, normal pressure, light etc.) It is a thin film
having a thickness of about 2 μm and formed by directly forming SiO 2, FEP, or the like on the
surface of the conductive film 12 using a known film forming method such as chemical vapor
deposition).
The spacer 14 is formed on the peripheral surface of the electret film 13 to a thickness of about
5 to 30 μm by screen printing.
[0031]
The vibrating film 15 is a PPS film having a thickness of about 2 μm, on one side of which Ni is
vapor-deposited, and is adhered to the surface of the spacer 14 to be fixed to the front side of the
electret film 13 via a predetermined space.
[0032]
The ceramic package 20 has a sound hole 21 in the front surface, and a front cloth 30 is
attached to the surface of the front surface.
The terminal portions 11 a and 11 a of the semiconductor chip 11 pass through the rear surface
portion of the ceramic package 20 and are soldered.
[0033]
Next, a method of manufacturing the microphone element 10 will be described with reference to
FIG.
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[0034]
As shown in FIG. 2, a large number of chip portions 41, 41,... Corresponding to the
semiconductor chip 11 are formed on a 6-inch Si wafer 40, for example.
Next, a conductive film is formed on the entire surface of the Si wafer 40 by plating, evaporation,
or the like.
A thin film having a thickness of about 1 μm is formed thereon by directly depositing SiO 2 or
FEP using a known film forming method such as spinner-coat resistance heating evaporation, EB
evaporation, sputtering, or CVD.
Further, the spacer 14 is formed by screen printing with a screen printing agent including an
adhesive corresponding to each chip portion 41 thereon.
Furthermore, the vibrating membrane 15 is adhered thereon.
[0035]
After bonding of the vibrating film 15 is completed, the Si wafer 40 along with the formations on
the surface thereof are cut and separated along the cutting line L shown in FIG. Do.
Thus, the microphone element 10 is manufactured, and the manufactured microphone element
10 is accommodated in the ceramic package 20, whereby the back electret type condenser
microphone is completed.
[0036]
The integrated capacitive converter (condenser microphone) according to an embodiment of the
present invention has the following features as compared to a conventional condenser
microphone.
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[0037]
Since the main components including the external circuit are integrated into one chip on the
microphone element 10, it is extremely compact and easy to assemble.
Further, the microphone element 10 can also be efficiently manufactured by using the Si wafer
40.
[0038]
Since the electret film 13 is formed by directly forming a film on the surface of the conductive
film 12 as a back electrode, no distortion occurs in the electret film 13 and no mechanical stress
occurs.
Therefore, the performance deterioration due to the mechanical stress of the electret film 13 is
avoided, and the performance is improved.
[0039]
Incidentally, in the case of a conventional condenser microphone in which the electret film is
formed by welding a polymer film, the distortion of the electret film can not be avoided, and the
mechanical stress caused by the distortion causes the performance deterioration.
[0040]
The performance of the microphone is also improved because the thickness of the electret film
13 can be reduced to about 2 μm.
The reason is explained as follows.
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[0041]
The output e of the capacitor portion formed by the vibrating film and the electret film is
expressed by Equation 1.
In the equation 1, k is a constant, C1 is the capacity of the space formed between the vibrating
film and the electret film, C2 is the capacity of the electret film, and .DELTA.C1 is the capacity
change of the space when sound pressure is applied.
e = k · [Δ C1 / (C1 + C2)] · sin (ωt + φ) (1)
[0042]
In the case of a conventional condenser microphone using a polymer film as the electret film, the
thickness of the space (the thickness of the spacer) is about 30 μm, and the thickness of the
polymer film is 12.5 to 25 μm.
Assuming that the volume of the space and the volume of the polymer film are roughly equal, the
output e1 of the capacitor section at that time is expressed by the equation 2. e1 k k · (1/2) · (ΔC
1 / C 1) · sin (ωt + φ) (2)
[0043]
On the other hand, when the thickness is reduced to about 1 μm by forming the electret film
directly on the surface of the conductive film, C 2 C0 can be regarded, so the output e 2 of the
capacitor part at that time Is expressed by Equation 3. e2 k k · (ΔC 1 / C 1) · sin (ωt + φ) (3)
[0044]
As can be seen from the comparison of Equations 2 and 3, by forming the film directly on the
surface of the conductive film to thin the electret film, a doubled output is obtained, and the
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sensitivity is improved by 6 dB. That is, a quasi-capacitor type microphone is obtained, and the
sensitivity is greatly improved.
[0045]
By forming the spacer 14 by screen printing, mass productivity is improved. By the way, in the
conventional condenser microphone, a spacer formed by punching out a polymer film was used,
but many errors of punching burrs and the number of inserted sheets occurred, and mass
productivity was low. The use of screen printing to form the spacers 14 solves these problems.
[0046]
In the above embodiment, the integrated capacitive transducer according to the present
invention is applied to an electret condenser microphone, but a semiconductor sensor or the like
that detects pressure, acceleration, etc. by forming a vibrating film of Ti foil or SUS foil The
application to is also possible.
[0047]
As described above, the integrated capacitive converter according to the present invention is
applied to, for example, a back electret type condenser microphone since the main components
including the electronic circuit such as the IC element are integrated into one chip. Thus, the
overall scale of the microphone can be made much smaller than that of the prior art, and it
becomes possible to provide a very small condenser microphone suitable for mobile phones and
the like.
[0048]
Since the electret film is made into a thin film by film formation when the single chip is formed,
the performance can be significantly improved.
[0049]
Since the mass productivity of the chip is high, the manufacturing cost can be reduced.
[0050]
Further, the method of manufacturing an integrated capacitive transducer according to the
present invention can efficiently manufacture the chip using a semiconductor wafer, and thus
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contributes to the reduction of the manufacturing cost.
[0051]
Brief description of the drawings
[0052]
1 is a longitudinal sectional view of an integrated capacitive transducer (electret condenser
microphone) according to an embodiment of the present invention.
[0053]
2 is a plan view and a partially enlarged view of a semiconductor wafer showing a method of
manufacturing a microphone element used in the same integrated capacitive transducer (electret
condenser microphone).
[0054]
3 is a longitudinal sectional view of a conventional electret condenser microphone.
[0055]
Explanation of sign
[0056]
DESCRIPTION OF REFERENCE NUMERALS 10 microphone element (converter element) 11
semiconductor chip 12 conductive film 13 electret film 14 spacer 15 vibrating film 20 ceramic
package (capsule) 21 sound hole 30 front cross 40 Si wafer (semiconductor wafer) 41 chip
portion
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