JP2003102097

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DESCRIPTION JP2003102097
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound processing apparatus, and more particularly to an apparatus capable of miniaturizing a
sound information input unit.
[0002]
2. Description of the Related Art In the past, sound processing devices such as portable recorders
and portable telephones have been made smaller and lighter as in other electronic devices. The
microphone used in such a small-sized sound processing apparatus is mainly a condenser type,
and is formed of two electrode plates of a diaphragm and a back plate.
[0003]
This type of microphone is excellent in performance such as sensitivity and noise, and is suitable
for miniaturization. For example, a spacer (supporting portion) is interposed between the
diaphragm and the back plate, and the inside of the case is mounted. Are mounted on a circuit
board by being modularized, etc., and mounted on a sound processing apparatus.
[0004]
However, in such a conventional microphone, there are the following problems in order to
assemble and manufacture a plurality of types of parts.
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[0005]
There is a limit to miniaturization due to the limitations of the accuracy of the assembly process
of parts, so the thickness and the occupied area are smaller than other modules such as
semiconductor parts mounted on small electronic devices such as mobile phones. Also, it has
become an obstacle to increasing the mounting density of circuit boards.
[0006]
In addition, when a component made of a resin material is adopted for a diaphragm, spacer
insulating portion, etc., there is a risk that deformation may occur due to thermal shock due to
multiple heat treatments (200 ° C. or more) such as soldering in the mounting process. There is
a possibility that the package can not be processed at once by the mounting process involving
high temperature processing such as bump / reflow, and efficiency can not be improved.
Furthermore, in the mounting process using lead-free solder, resistance to heat treatment at a
high temperature of 240 to 260 ° C. is required.
[0007]
Therefore, in order to solve the above-described problems, the present invention aims to reduce
the size and weight of the sound input unit and to improve the mass productivity, as well as to
reduce the cost of the sound processing apparatus and equalize the characteristics while at the
same time reliability. The purpose is to improve.
[0008]
[Means for Solving the Problems] In order to solve the above problems, the size and weight of the
sound input unit can be reduced by adopting a microphone having a structure that can be
manufactured using micromachine processing technology such as semiconductor manufacturing
technology. To realize a sound input unit that can be mass-produced without the need for an
assembly process, such as LSI in a semiconductor manufacturing process, and along with the
miniaturization of the sound processing device, the assembly efficiency and uniformity of
characteristics To improve reliability.
[0009]
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Here, the sound processing apparatus means one that processes sound information (sound area
of audible area and sound area outside the sound area) of sound wave including human voice,
and transmission of sound information like, for example, mobile phone etc. A device for
processing, a device for recording sound information on a medium such as a cassette tape or a
memory chip, a device for recognizing sound such as a personal computer, a sound for sound
such as a hearing aid or a loudspeaker A device that amplifies information, a device that includes
a microphone, etc., and a device that performs processing to apply feedback to acoustic effects
and sound field effects generated by itself, or a microphone, etc. that includes sound effects and
sounds within a specific range An apparatus etc. which perform measurement processing of field
effect etc. are mentioned.
[0010]
A first invention for solving the above-mentioned problems is a sound processing apparatus for
acquiring sound information by a microphone and processing the sound information, wherein
the microphone is a diaphragm which vibrates by sound pressure, and the vibration. The chip
microphone comprises a chip microphone having a back plate facing the plate and an adhesive
layer for bonding the diaphragm and the back plate to secure a gap, wherein the adhesive layer is
mainly composed of powder silicon oxide, and the diaphragm and back It is characterized in that
the face plate is adhered to the laminated structure.
[0011]
In this invention, the microphone is formed into a chip by forming a laminated structure in which
the diaphragm and the back plate are adhered with the adhesive layer, so that a small-sized
microphone can be manufactured with high accuracy by using micromachine processing
technology.
In addition, since this chip microphone has the adhesive layer formed mainly of powder silicon
oxide, the adhesive layer is deposited on the adhesive surface of the substrate to be the
diaphragm or the substrate to be the back plate. By heat-treating a plurality of substrates
together, the substrates can be easily bonded uniformly in a plane, and formation of an insulating
layer of a desired thickness can be simultaneously realized between these substrates.
At this time, since the adhesive layer is a powder, it is possible to complete the filling of the oxide
and eliminate defects in the oxide film, and to adhere without requiring high process control of
the flatness and cleanliness of the adhesive surface. In addition, the design flexibility of the
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thickness of the substrate, the thickness of the insulating layer, etc. can be made much greater
than direct bonding or conventional SOI (silicon on insulator) technology. Have.
[0012]
Furthermore, since the diaphragm and the back plate are simply formed in a laminated structure
in which they are adhered by the adhesive layer, a step for separating the mutual space is
provided between the electrodes facing each other except the portion directly functioning as the
diaphragm or the back plate. In such a structure, parasitic capacitance generated between the
electrodes can be reduced to improve sensitivity.
[0013]
A second invention for solving the above-mentioned problems is characterized in that, in addition
to the specific matters of the above-mentioned first invention, the chip microphone is
manufactured by a semiconductor manufacturing technology.
[0014]
In this invention, since the chip microphone is manufactured using semiconductor manufacturing
technology of micro machine processing technology, the chip microphone can be manufactured
in a smaller size and with high precision. For example, for a substrate to be a diaphragm or a
back plate In the case of using a silicon-based material, the chip microphone can be subjected to
high-temperature heat treatment by utilizing high heat resistance of the silicon-based material,
and a plurality of times such as reflowing at the time of microphone module production or circuit
board mounting described later. The resistance to thermal shock can be improved.
Therefore, it is possible to produce a chip microphone which is as thin as 1 mm or less like an LSI
chip and which has a small mounting area without using a process of assembling a plurality of
parts, and also using a bump / reflow circuit etc. It is possible to achieve efficiency by adopting a
mounting process involving high temperature processing such as bulk mounting.
Further, the use of the sound information input unit can prevent the usable temperature range
from being narrowed.
The heat resistance of the chip microphone is 300 ° C. or higher even when aluminum generally
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used is used for the electrode, and by having such heat resistance, a high temperature mounting
process using lead-free solder is also applied. be able to.
Further, it goes without saying that this electrode material may be a material having a good
ohmic contact with a substrate material such as silicon.
[0015]
A third invention for solving the above-mentioned problems is characterized in that, in addition
to the above-mentioned specific matters of the first or second invention, the adhesive layer is
formed in a thickness of 1 μm to 20 μm.
[0016]
In the present invention, the diaphragm and the back plate can be adhered by a thin adhesive
layer, and a small chip microphone can be obtained.
The thickness of the adhesive layer is more preferably 2 μm to 5 μm. By this thickness, for
example, a small chip microphone can be manufactured with high precision by semiconductor
manufacturing technology using a silicon-based material and uniform Characteristics can be
obtained.
[0017]
In the fourth invention for solving the above-mentioned problems, in addition to the abovementioned specific matters of any of the first to third inventions, the adhesive layer is an element
of Group IIIB in the periodic table of elements such as boron and indium, or phosphorus And one
or more elements of Group VB in the periodic table of elements such as arsenic and antimony,
which are characterized by containing at high concentration.
[0018]
In this invention, the fluidity of the insulating layer at the time of bonding can be increased by
including an element of group IIIB such as boron and an element of group VB such as
phosphorus in the adhesive layer mainly composed of powder silicon oxide. The uniformity of
adhesion between the substrate as the diaphragm and the substrate as the back plate can be
improved.
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[0019]
According to a fifth invention for solving the above-mentioned problems, in addition to the
above-mentioned specific matters of the first to fourth inventions, the chip microphone is
mounted on a circuit board as it is or as a module in which the chip microphone is packaged. It is
characterized by
[0020]
In the present invention, since the chip microphone is mounted as it is or modularized and
mounted on the circuit board, a high density circuit configuration can be achieved.
[0021]
According to a sixth invention for solving the above-mentioned problems, in addition to the
above-mentioned specific matters of any of the first to fifth inventions, an LC circuit using the
chip microphone as a capacitor, and a change of the capacitor capacity of the chip microphone
And output means for reading out as a change in the transmission frequency.
[0022]
According to the present invention, the vibration of the diaphragm of the chip microphone can be
read as a capacitance change of the capacitor simply by applying a weak voltage in the LC circuit
without applying a bias voltage as in a normal microphone. The LC circuit including the chip
microphone can be formed on the same substrate.
Therefore, even if the adhesive layer is formed thin to a thickness of 1 μm to 20 μm, etc., the
diaphragm and the back plate can be prevented from sticking due to the applied voltage, and the
chip microphone and the entire device can be made smaller. be able to.
[0023]
Furthermore, the connection with the sound input unit can be made wireless by providing a
function of frequency-modulating and transmitting a carrier wave responsive to a change in the
capacitance of the chip microphone.
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[0024]
A seventh invention for solving the above problems is an array microphone in which the chip
microphones are arranged in an array, and outputs of a plurality of chip microphones in the
array microphone, in addition to the above-mentioned specific matters of the first to sixth
inventions. And a synchronous addition circuit for performing synchronous addition.
Further, as an eighth aspect of the present invention for solving the above-mentioned problems,
the array microphones may be arranged such that the chip microphones are arrayed in one
direction and the array arrangement is arranged in parallel.
[0025]
In the present invention, the output of the chip microphone in the array microphone can be
regarded as the same phase and the noise can be reduced by the synchronous addition circuit.
Therefore, it is possible to configure a small-sized, low-noise sound input unit, and by integrally
forming by semiconductor manufacturing technology, a voice input unit having uniform
characteristics for each chip microphone and each device can be manufactured with high
accuracy and small size. can do.
[0026]
The ninth invention for solving the above problems comprises the plurality of array microphones
and the synchronous addition circuit in addition to the specific matters of the seventh or eighth
invention and processes the output from the synchronous addition circuit for each of the array
microphones. A directional control circuit is provided to give directivity to the plurality of array
microphones.
[0027]
In the present invention, it is possible to obtain sound information by providing directivity by a
plurality of array microphones.
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Therefore, for example, in a mobile phone having an imaging function, voice input from a distant
position can be realized.
In addition, by integrally forming the semiconductor manufacturing technology, it is possible to
create a voice input unit with uniform characteristics for each chip microphone and each device
with high accuracy and small size.
[0028]
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described
below based on the drawings.
FIGS. 1 to 3 are views showing an example of an audio recording apparatus to which a first
embodiment of a sound processing apparatus according to the present invention is applied.
[0029]
In FIG. 1, the audio recording device (sound processing device) causes the recording unit 25 to
perform a recording process of recording the sound information after the sound information
such as human voice acquired by the chip microphone 10 is amplified by the amplifier 21. The
chip microphone 10 and the amplifier 21 are integrally formed (fabricated) as an IC chip 20 by a
semiconductor manufacturing technology (micro machine processing technology) described
later, and the IC chip 20 is recorded. It is constructed to be directly connected to the unit 25 and
to be compact as a whole.
[0030]
As shown in FIG. 2, the chip microphone 10 forms a diaphragm 12 that vibrates by sound
pressure at the central portion of the base 11, and around the diaphragm 12 so as to secure the
vibration space (gap layer) S thereof. The adhesive support portion (adhesive insulating layer) 13
supports the back plate 14 to face the diaphragm 12 and forms counter electrodes on the
diaphragm 12 and the back plate 14 to function as a capacitor type microphone. The chip
microphone 10 can be manufactured by the semiconductor manufacturing technology together
with the amplifier 21 by forming a laminated structure in which the adhesive support 13 is
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interposed between the diaphragm 12 and the back plate 14. It is designed to be able to.
Incidentally, reference numeral 14 a in the drawing is a plurality of through holes formed to
connect the front and back of the back plate 14 in order not to disturb the vibration of the
diaphragm 12.
[0031]
Then, as the IC chip 20, when the diaphragm 12 vibrates according to the sound information
input to the chip microphone 10, a change in capacitance generated between the opposing
electrodes to the back plate 14 is an electrode terminal as an analog signal The signals are taken
out at 15 and 16 and amplified by the amplifier 21 and then output.
[0032]
In the chip microphone 10, a cap is attached so as to cover the back plate 14, and a gas flow hole
is formed at the center of the cap, so that the volume of the cap has a role of adjusting the
acoustic characteristics of the microphone. The cap can be used to shield electromagnetic waves,
and the gas flow hole in the center of the cap can control the directivity of the microphone.
[0033]
Next, a manufacturing procedure (method) of the chip microphone 10 according to the
semiconductor manufacturing technology will be described with reference to FIG.
The amplifier 21 may be manufactured by a general semiconductor process, and thus the
description thereof will be omitted.
[0034]
First, as shown in FIG. 3A, for example, a silicon substrate which is a general semiconductor
substrate is prepared as the diaphragm substrate 112 and the back plate substrate 114, and the
back plate substrate 114 of the diaphragm substrate 112 is prepared. On the surface to be
bonded (bonded), an adhesion layer 113 containing powder silicon oxide as a main component
and containing boron or phosphorus in a high concentration by a CVD technique etc. is deposited
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to a desired thickness, for example, 10 μm.
In order to miniaturize the microphone, the adhesive layer 113 is suitably 1 μm to 20 μm in
terms of the manufacturing surface and the bias voltage.
Furthermore, the adhesive layer 113 is more preferably 2 μm to 5 μm in terms of sensitivity
and frequency characteristics, and can be set according to the applied voltage so that the
diaphragm 12 and the back plate 14 do not stick.
Needless to say, the adhesive layer 113 may be formed on the back plate substrate 114 side.
[0035]
Next, as shown in FIG. 3B, the diaphragm substrate 112 and the back plate substrate 114 are
combined and heat-treated to bond the substrates 112 and 114 via the deposited adhesive layer
113. The back plate substrate 114 is polished to form a back plate having a desired thickness,
and thereafter, an oxide film is grown by heat treatment or the like on both surfaces of the
substrates 112 and 114, and the oxide film is The etching mask 117 is formed by processing by
lithography technology.
[0036]
Next, as shown in FIG. 3C, the substrates 112 and 114 are treated by wet etching using an
alkaline etching solution or dry etching using, for example, XeF 2 gas, using the etching mask
117. The base 11 on which the diaphragm 12 is formed and the back plate 14 are formed.
At this time, the back plate 14 has a plurality of through holes 14 a for releasing the pressure of
air generated in the vibration space S due to the vibration of the diaphragm 12 in a mesh
structure by forming plural through holes 14 a except for the portion corresponding to the
bonding support portion 13.
[0037]
Then, as shown in FIG. 3D, the back plate 14 is used as an etching mask, and the adhesive layer
113 is etched with hydrofluoric acid from the network structure of the back plate 14 to form the
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diaphragm 12 and the back plate 14. The adhesive layer 113 is removed leaving a portion
corresponding to the adhesive support portion 13 in the peripheral portion of the substrate to
form a vibrating space S, and thereafter a metal film of, for example, aluminum is vapordeposited from the back plate 14 side to 16 to form a one-piece chip microphone 10.
[0038]
At this time, since the adhesive layer 113 contains powder silicon oxide as a main component, it
is possible to completely fill the oxide and eliminate the occurrence of defects in the oxide film.
Therefore, the planarity of the substrates 112 and 114 can be eliminated. In-plane uniform
adhesion can be performed in a short time without strictly controlling the properties, and
furthermore, the adhesion between the thick substrates 112 and 114 can be carried out without
requiring the extremely high degree of cleanliness management of the adhesion surface. It can be
done simultaneously and easily.
Therefore, the thickness of the substrates 112 and 114, the concentration distribution of
impurities, the layer thickness of the adhesive layer 113 itself, and the like can be freely set as
compared with the case where the substrates 112 and 114 are directly bonded.
Further, since the adhesive layer 113 contains boron or phosphorus at a high concentration, the
fluidity at the time of bonding can be increased, and the uniformity at the time of bonding of the
substrates 112 and 114 can be improved.
[0039]
Then, the IC chip 20 connects the electrode terminals 15 and 16 of the chip microphone 10 and
the input terminal of the amplifier 21 by a method such as wire bonding, and connects the
output terminal of the amplifier 21 and the recording unit 25. , Functions as an audio input unit
of the audio recording device.
[0040]
As described above, in the present embodiment, the chip microphone 10 is made of powder
silicon oxide as a main component and the bonding support portion 13 which is formed between
the diaphragm 12 and the back plate 14 to form a laminated structure as a main component.
Alternatively, by using semiconductor manufacturing technology that does not require an
assembly process so as to contain phosphorus or the like at a high concentration to make it as
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thin as 1 μm to 20 μm, it is possible to inexpensively and easily obtain high precision chip
components. And small-sized microphones having uniform characteristics can be mass-produced
inexpensively.
[0041]
Furthermore, since this chip microphone 10 is integrally formed as an IC chip 20 together with
the amplifier 21, the stability of the quality is high, and downsizing and weight reduction can be
realized more effectively.
[0042]
Further, since the chip microphone 10 is manufactured using a silicon-based material, it has high
heat resistance, and it is possible to reduce limitation of the use range by the use temperature.
[0043]
In the present embodiment, the diaphragm 12, the adhesive support 13, the back plate 14 and
the like are manufactured using the same silicon-based material, but it goes without saying that
the invention is not limited to the silicon-based material.
[0044]
In addition, as a first other mode of the present embodiment, for example, a chip microphone
may be constructed as shown in FIG.
The chip microphone 10 of this embodiment is manufactured by bonding the flat substrates 112
and 114 to each other, so that parasitic capacitance generated by the counter electrode formed
also around the portion functioning as the diaphragm 12 and the back plate 14 However, it
becomes approximately the same as the effective capacity, which causes a sensitivity decrease
when detecting a capacity change due to sound pressure.
From this, the area of the corresponding portion is simply reduced to lower the sensitivity (since
the sensitivity of the microphone is in proportion to the area of the corresponding portion), as
shown in FIG. By forming a step 11a on the base 11 to raise the portion that directly functions as
the base, and forming a thick adhesive support portion 17 also around the adhesive support
portion 13, the distance between opposing electrodes is separated and parasitic The capacity can
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be reduced and the sensitivity can be improved.
[0045]
Furthermore, as a second other mode of the present embodiment, as shown in FIG. 5, in addition
to the step 11a on the base 11 side, the periphery of the portion facing the diaphragm 12 is also
raised on the back plate 14 side. By forming the step 14b to be formed and forming a thick
adhesive support portion 19 also around the adhesive support portion 13, the distance between
opposing electrodes is further separated to further reduce parasitic capacitance and improve
sensitivity. Can.
[0046]
Next, FIG. 6 is a view showing an example of an audio recording and reproducing apparatus to
which a second embodiment of the sound processing apparatus according to the present
invention is applied.
In addition, in this embodiment, since it is comprised in substantially the same manner as the
above-mentioned embodiment, the same code ¦ symbol is attached ¦ subjected to the same
structure and the characteristic part is demonstrated (the same also in the other embodiment
described below) .
[0047]
In FIG. 6, the audio recording / reproducing apparatus (sound processing apparatus) performs
recording / reproducing processing for digitally recording and reproducing the sound
information acquired by the chip microphone 10 of the IC chip 20 and amplified by the amplifier
21. The IC chip 20 encodes an A / D converter 31 for converting an analog signal output from
the amplifier 21 into a digital signal and a digital signal A / D converted by the A / D converter
31. For example, an encoder 32 that compresses sound information, a recording unit 33 that
records sound information encoded by the encoder 32 on a recording medium such as a memory
stick or a magneto-optical disk such as an MO, a recording unit 33 And a D / A converter 35 for
converting the sound information of the digital signal decoded by the decoder 34 into an analog
signal. , An amplifier 36 that amplifies an analog signal D / A converted by the D / A converter
35, and a speaker 37 that outputs voice information and reproduces sound information sent
through the amplifier 36, and a single circuit board It is mounted on 30 (on chip).
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Needless to say, the IC chip 20 may be mounted on the circuit board 30 as a packaged module to
which the cap is attached.
[0048]
Therefore, the microphones can be mounted on a single circuit board 30 instead of being
separately mounted, and the voice recording and reproducing apparatus can be assembled only
by putting in a case.
In the process of mounting on the circuit board 30, since the IC chip 20 is made of a silicon
material, high temperature heat treatment can be performed utilizing high heat resistance, and
bump / reflow accompanied by high temperature treatment is adopted. Then, it can be mounted
on the circuit board 30 in a batch process.
Since the IC chip 20 has an aluminum electrode formed on the chip microphone 10, it can be
applied to a high temperature mounting process using lead-free solder.
[0049]
As described above, in the present embodiment, in addition to the effects of the above-described
embodiment, the IC chip 20 is mounted on the circuit board 30 together with the other
components 31 to 37. Density mounting can be performed, and the assembly process of the
circuit board 30 can be made more efficient by, for example, batch mounting using bumps /
reflows. Therefore, it is possible to contribute to downsizing, cost reduction, and high reliability
of the audio recording and reproducing apparatus.
[0050]
Further, as another aspect of the present embodiment, as shown in FIG. 7, as in the first
embodiment, the IC chip 20 is individually connected to the circuit board 30a on which the
components 31 to 37 are mounted by signal lines. Needless to say, as shown in FIG. 8, the IC chip
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20 and the A / D converter 31 may be mounted on the circuit board 30 b so that the S / N ratio
of the sound information output does not decrease. As shown in FIG. 9, the IC chip 20, the A / D
converter 31, and the encoder 32 can be mounted on the circuit board 30c to unitize the former
stage of the recording unit 33 to facilitate assembly. . These forms may be designed in
accordance with the external shape and function of the apparatus and various processes.
[0051]
Next, FIGS. 10 and 11 are views showing an example of a voice acquisition device to which the
third embodiment of the sound processing device according to the present invention is applied.
[0052]
In FIGS. 10 and 11, the voice acquisition device (sound processing device) includes the adhesive
support 13 between the diaphragm 12 formed in the base 11 and the back plate 14 in which a
plurality of through holes 14a are formed. By mounting, the chip microphone 40 is configured to
function as a condenser microphone.
[0053]
Here, since the chip microphone 40 is a capacitor including the thin and flat diaphragm 12 and
the back plate 14, the displacement of the diaphragm 12 caused by the change in sound pressure
due to the sound wave is detected with high sensitivity as the change in capacitance of the
capacitor. In order to increase the bias voltage, to reduce the distance between the diaphragm 12
and the back plate 14, to increase the electrode area of the diaphragm 12 and the back plate 14,
to make the material of the diaphragm 12 soft. Although there is a measure such as reducing the
stiffness of the diaphragm 12, in the chip microphone 40, it is necessary to prevent the
diaphragm 12 and the back plate 14 from sticking due to electrostatic attraction.
As an index for causing the diaphragm 12 and the back plate 14 to function without sticking to
each other, design for downsizing of a directional capacitor microphone (Akio Mizoguchi
Journal of the Acoustical Society of Japan, vol. 31, No. 10, pp. 593-601 The stability μ obtained
by the following equation (1) is defined in (1975)), and is usually designed to be μ = about 7.
[0054]
From the above equation (1), the measures ˜ for improving the sensitivity of the chip microphone
40 are contrary to the improvement of the stability, and in this chip microphone 40, the distance
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between the diaphragm 12 and the back plate 14 Is extremely small, such as several μm, and
there is a limit to high sensitivity.
[0055]
From this, this voice acquisition device is directly or partly via the signal line as the capacitor
capacity of the transmission / modulation circuit 41 of the LC transmission circuit (without the
amplifier as in the first embodiment described above). By connecting the chip microphone 40, it
is acquired that the capacitance of the capacitor between the opposed electrodes between the
diaphragm 12 and the back plate 14 changes according to the sound information such as voice
as the change of the transmission frequency of the LC circuit. Can be output to an external device
connected to the output terminal of the transmission / modulation circuit 41.
[0056]
Here, the LC oscillation circuit is an oscillation circuit whose oscillation frequency is determined
by the coil and the capacitor, and can detect a change in the capacitance of the capacitor as a
change in the oscillation frequency. According to this method, the capacitor of the chip
microphone 40 Since it is not necessary to apply a bias voltage to the part, it is possible to
increase the degree of freedom in selecting a method for increasing sensitivity.
In this case, only a weak voltage necessary for the transmission circuit of the transmission /
modulation circuit 41 to operate is applied to the capacitor portion of the chip microphone 40,
which is much higher than that of a normal microphone bias voltage. Since only a low voltage is
required, it is possible to increase the stability μ of the above equation (1), and it is possible to
prevent the problem that the diaphragm 12 and the back plate 14 stick to each other.
[0057]
Specifically, the oscillation frequency f of a general LC oscillation circuit is determined by the
following equation (2).
[0058]
Then, assuming that the change in f caused by the sound pressure is Δf, it is expressed as in the
following equation (3), and the above-mentioned measures are effective as a method of
increasing the frequency displacement Δf to improve the sensitivity. It is understood that there
is.
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[0059]
Therefore, while the conventional capacitor type microphone requires a bias voltage Vb of
several volts to obtain practical sensitivity, the chip microphone 40 can be an oscillation circuit
operating at 1 to 2 V. According to the above equation (1), the stability μ can be several times to
several hundreds times as high as that of the conventional microphone, and the degree of
freedom in selecting a measure for high sensitivity can also be greatly increased.
[0060]
The transmission / modulation circuit 41 vibrates with respect to the back plate 14 in response
to changes in the sound pressure of the diaphragm 12 of the chip microphone 40 to change the
capacitance of the capacitor, whereby the oscillation frequency f as the LC oscillation circuit
Changes.
The oscillation frequency f is determined by the above equation (2).
[0061]
The chip microphone 40 and the transmission / modulation circuit (LC circuit) 41 may be
connected and assembled as separate parts, or may be mounted on the same circuit board, and
further, the same semiconductor may be manufactured according to the semiconductor
manufacturing technology. You may produce on a board ¦ substrate.
[0062]
As described above, in this embodiment, in addition to the effects of the above-described
embodiment, the vibration of the diaphragm 12 of the chip microphone 40 is not transmitted by
applying the bias voltage Vb as in a normal microphone, but by a transmission / modulation
circuit. It is possible to read sound information, which is a change in sound pressure, by the
change in the capacitor capacity of the chip microphone 40, only by the application of a weak
voltage 41 in the LC circuit.
[0063]
Therefore, even if the adhesive support portion 13 of the chip microphone 40 is formed as thin
as 2 μm to 5 μm, for example, there is no risk that the diaphragm 12 and the back plate 14 will
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stick due to the applied voltage. The voice input unit including the B. 40 and the entire device
can be further miniaturized.
[0064]
Next, FIG. 12 is a view showing an example of an audio transmission apparatus to which the
fourth embodiment of the sound processing apparatus according to the present invention is
applied.
[0065]
In FIG. 12, in the audio transmission device (sound processing device), the chip microphone 40 is
connected to the transmission / modulation circuit 41, and the transmission / modulation circuit
(LC circuit) 41 allows wireless reception of external devices. An antenna 52 for transmitting
radio waves into the air is attached instead of the output terminal.
[0066]
Since this transmission / modulation circuit 41 detects a change in the capacitance of the chip
microphone 40 as a change in the oscillation frequency, it regards the change in the transmission
frequency as the FM modulation of the carrier frequency and sends it out as a radio wave via the
antenna 52. Thus, wireless transmission can be performed, and demodulation can be performed
on the external device side that receives it to make sound information.
Thus, this audio transmission device can be used as a wireless microphone.
[0067]
Here, the antenna 52 may be connected and assembled as a separate component to the chip
microphone 40 and the transmission / modulation circuit 41, or may be mounted on the same
circuit board, but as the coil antenna, the chip microphone 40 and the transmission / modulation
circuit It is preferable to be able to construct compactly on the same semiconductor substrate by
the semiconductor manufacturing technology together with the step 41.
[0068]
As described above, in the present embodiment, in addition to the operation and effects
according to the above-described embodiment, sound information input from the chip
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microphone 40 can be transmitted to the air wirelessly receivable by an external device, and
used as a compact wireless microphone can do.
[0069]
Next, FIGS. 13 to 18 are views showing an example of an audio transmission apparatus to which
a fifth embodiment of a sound processing apparatus according to the present invention is
applied.
[0070]
13 to 15, the sound transmission apparatus (sound processing apparatus) includes an array
microphone unit 60 in which an array microphone 61 in which a plurality of IC chips 20 are
arrayed in a matrix is further arranged in parallel, and individual IC chips For example, the
cellular phone 100 is mounted so as to process sound information acquired by the twenty chip
microphones 10 and amplified by the amplifier 21 and wirelessly transmit the processed sound
information to an external device.
[0071]
The array microphone unit 60 wirelessly transmits a camera 71 for capturing an image of a
caller and the like and image information acquired by the camera 71 together with sound
information acquired by the array microphone unit 60 to a partner mobile phone via an antenna
(not shown) The transmitting unit 72 for transmission, the receiving unit 73 for receiving sound
information and image information sent from the other party's mobile phone, the speaker 74 for
reproducing the received sound information and outputting the sound, and the received image
information Together with a liquid crystal display 75 for display output, and is housed in the case
of the mobile phone 100.
Note that the layout of each component in FIG. 13 is merely illustrated for the sake of
convenience, and it is needless to say that it is designed according to the form of the apparatus.
[0072]
The array microphone unit 60 forms a low noise microphone by synchronously adding individual
sound information acquired by the chip microphones 10 of n IC chips 20 and output from the
amplifier 21 for each array microphone 61. Thus, the synchronous addition circuit 62 is
connected.
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[0073]
In this array microphone 61, noise is independently acquired (inputted) in each case, but
assuming that the amplitude characteristics of each noise are uniform, superdirective
microphone using a two-dimensional digital filter (Kanamori et al.) Noise calculated by the
following equation (4) by performing synchronous addition with the same weighting for n chip
microphones 10 as described in Japan Acoustical Society of Japan Electroacoustic Research
Material EA 91-84 (1991)) The reduction effect Nr can be obtained.
Nr=10・log(n)[dB] ・・・(4)
[0074]
For example, when the array microphone 61 includes 16 chip microphones 10, the sound
information of the 16 chip microphones 10 is synchronously added to calculate the numerical
value Nr of the above equation (4) shown in FIG. From the results, it can be seen that a large
noise reduction effect of about 12 dB can be obtained.
[0075]
However, in order to perform synchronous addition of sound information by the array
microphone 61, it is necessary for the outputs from the respective chip microphones 10 to be
considered to be in phase, and for that purpose, compared with the wavelength to be collected,
The size must be small enough.
That is, since this array microphone 61 can be regarded as being driven in phase by the sound
wave when the size L of one side is approximately 1/10 or less of the wavelength, noise is
generated by synchronous addition. Using the upper limit frequency fh of the reducible band and
the sound velocity c, the size L of the array microphone 61 is constrained by the following
equation (5).
[0076]
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In the array microphone 61, in order to arrange the 16 chip microphones 10 in a matrix,
assuming that the sound speed c is 340 m / sec in the above equation (5), the size L is allowed as
shown in FIG. The upper limit of the size L is about 4 mm square, assuming that the upper limit
frequency fh of the band in which noise can be reduced is 8 kHz. The size of is at most about 1
mm.
In addition, since this chip microphone 10 is manufactured by the semiconductor manufacturing
technology, it is a size which can be manufactured.
[0077]
Then, since the array microphone unit 60 further arrayed a plurality of array microphones 61 in
parallel, the array microphones 61 are connected to the directivity control circuit 63, and noise is
reduced by performing synchronization addition. Each output (sound information) from the array
microphone 61 is input, and a directivity process which is a known technique is performed to
configure a superdirective microphone.
Note that this directivity processing (known technique) is detailed to the "superdirective
microphone using a two-dimensional digital filter" cited above.
[0078]
Here, the array microphone unit 60 further arranges six sets of array microphones 61 in which
the chip microphones 10 are arranged in a matrix, and connects the synchronous addition
circuits 62 to each of the array microphones 61 and connects them. Manufacturing the
connection circuit configuration for integrating the output from the synchronous addition circuit
62 into the directivity control circuit 63 with high precision on a single substrate 64 using
micromachine processing technology making full use of semiconductor control technology. And
the characteristics of the chip microphone 10 can be processed uniformly.
Reference numeral 64 in FIG. 14 denotes a cover case of the array microphone unit 60.
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[0079]
Therefore, by mounting the small array microphone unit 60, as shown in FIG. 18, the mobile
phone 100 displays on the display 75 the face of the other party to be photographed by the
camera 71 of the other party mobile phone, for example. While confirming, the voice uttered
from the mouth separated from the array microphone unit 60 can be acquired and input by the
superdirectivity of the array microphone unit 60, and can be transmitted to the other party's
mobile phone, and the special microphone A comfortable conversation that does not need to be
worn can be realized.
[0080]
Of course, what is displayed on the display unit 75 does not have to be the other party's face, it
may be characters, figures, or images acquired through means such as broadcasting or the
Internet, or it can be used without displaying anything. It goes without saying that conversations
can also be made with a person who does not have a camera.
[0081]
As described above, in the present embodiment, in addition to the operation and effects
according to the above-described embodiment, the array microphone unit 60 includes the
plurality of chip microphones 10 and the amplifiers 21 and the synchronization addition circuit
62 and the directivity control circuit 63 by semiconductor manufacturing technology. An
excellent directional microphone can be configured by the chip microphone 10 that can be
integrally formed with high precision and small size, and that the individual characteristics are
uniform, and by including the synchronization addition circuit 62 and the directivity control
circuit 63. .
The array microphone unit 60 can also be mass-produced at low cost by semiconductor
manufacturing technology.
[0082]
Although the super-directional microphone has been described in this embodiment, the
directivity can be freely changed from super-directivity to omni-directivity by changing the
processing characteristic of the directivity control circuit 63. Needless to say.
[0083]
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According to the present invention, since the microphone to be mounted is formed into a chip by
forming a laminated structure in which the diaphragm and the back plate are adhered by the
adhesive layer, a compact and lightweight audio input unit can be provided. Since the adhesive
layer is mainly composed of powdered silicon oxide, the diaphragm and the back plate can be
uniformly adhered in the plane by the adhesive layer having a desired thickness without defects.
In addition, by using micromachining technology such as semiconductor manufacturing
technology, it is possible to efficiently produce a smaller and lighter microphone with a wide
operating temperature range, high precision, uniform characteristics, and further, powder
oxidation. By including an element such as Group III boron or Group V phosphorus in the
adhesive layer containing silicon as a main component, the diaphragm and the back plate can be
more uniformly bonded.
Then, by mounting such a chip microphone as it is or modularizing it on a circuit board, it is
possible to mount a circuit board on which the microphones are mounted at high density in the
sound processing apparatus.
Therefore, it is possible to inexpensively provide a small-sized sound processing device with
excellent characteristics and high reliability.
[0084]
Furthermore, by mounting an LC circuit using a chip microphone as a capacitor, the vibration of
the diaphragm of the chip microphone can be output as a change in the oscillation frequency of
the LC circuit due to a change in the capacitance of the chip by applying a weak voltage. Since
the small chip microphone having a thin adhesive layer is formed, sound information can be
acquired without the diaphragm and the back plate being attached due to the application of the
bias voltage.
[0085]
Also, the outputs of chip microphones arranged in an array are synchronously added to reduce
noise, or the outputs of chip microphones arranged in an array for each of a plurality of arrayed
microphones are synchronously added to reduce noise, and then input to sound information. By
performing processing for giving directivity, a compact and directional sound input unit can be
configured, and a sound processing apparatus that does not need to bring the microphone close
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to the mouth can be realized. .
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