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DESCRIPTION JP2004200766

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DESCRIPTION JP2004200766
A thin condenser microphone having a simple structure and manufacturing process and a
method of manufacturing the same. A microphone chip (5), a field effect transistor (6), and a
casing (4). The casing (4) has a bottom wall (41) formed with a concave groove (411) whose
opening is covered by the microphone chip (5). The microphone chip 5 includes an electrode
layer 51, a vibrating film 52 formed under the electrode layer 51, and a spacer 53 formed on the
outer peripheral edge of the lower surface of the vibrating film 52. The microphone chip 5 is
attached to the top surface of the bottom wall 41 so as to shield the recessed groove 411 so as to
form a vibrating space 55 together with the vibrating film 52 and the spacer 53, and a field
effect transistor 6 is mounted in the casing 4 and electrically connected to a predetermined
portion of the electrode layer 51 of the microphone chip 5 and the casing 4. . [Selected figure]
Figure 1
Condenser microphone and method of manufacturing the same
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
condenser microphone and a method of manufacturing the same, and more particularly to a
condenser microphone which converts an acoustic signal into an electric signal and outputs the
signal and a method of manufacturing the same. [0002] A conventional condenser microphone
generally comprises a microphone chip, a field effect transistor (FET), and a casing for housing
the microphone chip and the field effect transistor. This condenser microphone vibrates a
diaphragm in the microphone chip when an acoustic sound signal from the outside enters the
microphone chip, thereby changing a space (vibration space) between a pair of electrodes
serving as a capacitor to generate electricity. Produce changes in capacity. And the change of the
said electrical capacitance is converted into an electric signal via the said field effect transistor,
and it outputs. As prior art literature information related to the air conditioning system for
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vehicles of the present invention, there are the following. Patent Document 1: US Pat. No.
5,870,482 Patent Document 2: US Pat. No. 6,243,474 FIG. 4 shows a part of a method of
manufacturing a microphone chip disclosed in Patent Document 1. It is a flowchart. In this
manufacturing method, first, the SiO 2 layer 12 is formed on the upper surface of the silicon
substrate 11 as a sacrificial layer. Then, the SiO 2 layer 12 is dug down by an etching method to
expose a part of the upper surface of the silicon substrate 11 therebelow to form a reverse
trapezoidal concave groove 13. Thereafter, a Si3 O4 layer 14 as a vibrating film is formed to
cover the exposed portion of the silicon substrate 11 and the upper surface of the SiO2 layer 12
by vapor deposition or sputtering. Finally, the remaining SiO 2 layer 12 is completely removed
by hydrofluoric acid (HF) to form a vibration space 15. Then, other necessary layers are
sequentially formed on the upper surface of the vibrating membrane 14. All the layers of the
microphone chip are formed by several steps belonging to a photolithography method
(semiconductor process) such as coating, exposure, development, etching, vapor deposition, and
sputtering. Therefore, at least four steps are required to form only the vibration film and the
vibration space as described above. Therefore, there is an inherent problem that the number of
processes at the time of manufacturing is large and it takes much time and effort. Therefore, in
order to reduce the number of steps in manufacturing, Patent Document 2 discloses microelectromechanical systems configuration technology (micro-electromechanical systems), which
includes the photolithography method and microtechniques in other fields. Hereinafter, MEMS
technology is proposed).
FIG. 5 is a cross-sectional view of the microphone chip 2 formed by this MEMS technology. As
shown in FIG. 5, in the method of manufacturing the microphone chip 2 of Patent Document 2,
first, a pair of chips 21 and 22 having different configurations are respectively formed by
photolithography. Then, the vibration space 23 is formed to align the microphone chip 2 while
overlapping and coupling the pair of chips 21 and 22 formed by the MEMS technology. In the
figure, reference numeral 211 denotes a vibrating film. However, although the manufacturing
method of the microphone chip 2 by the MEMS technology as disclosed in this patent document
2 can certainly reduce the number of steps compared to the conventional manufacturing method,
a pair of silicon substrates is used. In order to form a pair of chips 21 and 22 by respectively
laminating on each other, there is a disadvantage that the microphone chip 2 is too thick and not
suitable for thinning. Further, since the vibrating film 211 is made of an organic material, there is
a possibility that the vibrating film 211 may be deformed when the temperature is 240 ° C. or
higher. It can not be used for surface mount technology (SMT) of C or higher. Therefore, there is
also a disadvantage that the method of automation can not be combined with, for example, the
substrate of a mobile phone. The present invention has been made in view of the above
problems, and has a first object to provide a thin condenser microphone having a simple
structure and a simple manufacturing process, and a method of manufacturing the same. Another
object of the present invention is to provide a condenser microphone applicable to surface
mounting technology (SMT) and a method of manufacturing the same. SUMMARY OF THE
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INVENTION In order to solve the above-mentioned problems, a condenser microphone according
to the present invention comprises a microphone chip for receiving an acoustic signal from the
outside and causing a change in electric capacity; A field effect transistor that converts a change
into an electrical signal and outputs the same, and a casing that accommodates the microphone
chip and the field effect transistor, and the casing is a recessed groove whose opening is
completely covered by the bottom surface of the microphone chip And an outer peripheral wall
extending upward from a peripheral portion of the bottom wall, the microphone chip being
under an electrode layer and an electrode layer so that at least a part is in contact with the
electrode layer. A vibrating membrane formed on the side, a spacer formed on the outer
peripheral edge of the lower surface of the vibrating membrane, the vibrating membrane and the
space And a perforated bottom plate coupled to the spacer so as to form a vibration space
together with the microphone chip, the microphone chip facing the perforated bottom plate
facing downward so as to shield the recess of the casing. Mounted on the top surface, the field
effect transistor is mounted in the casing and electrically connected to the electrode layer of the
microphone chip and a predetermined place of the casing, and an acoustic sound signal is
transmitted from the open end of the casing When entering the casing, the vibrating membrane
is vibrated to cause a change in electric capacitance in the microphone chip, and the change in
electric capacitance is converted into an electric signal and output through the field effect
transistor. .
The microphone chip in the condenser microphone according to this configuration is simple in
construction, and since the bottom plate with holes is joined to the spacer by MEMS technology,
it can be manufactured from a chip formed only by the conventional photolithography method.
The number of steps can be reduced. In addition, since the microphone chip can be
manufactured by being stacked on one silicon substrate, the thickness is thinner than that
obtained by using at least a pair of conventional silicon substrates. That is, according to the
present invention, it is possible to provide a thin condenser microphone which has a simple
structure and can further simplify the manufacturing process. In the condenser microphone, the
vibrating membrane is preferably a layer of a predetermined pattern made of an inorganic
material that can withstand a temperature of 450 ° C. or more. Thereby, the condenser
microphone of the present invention can be applied to the surface mount technology (SMT) and
coupled with the substrate by the method of automation. Preferably, the vibrating film is formed
by vertically laminating a first inorganic material layer of a predetermined pattern and a second
inorganic material layer of a predetermined pattern. Furthermore, the casing is further provided
with a perforated lid portion provided above the outer peripheral wall and provided with a hole
so as to coincide with the upper portion of the microphone chip, and shielding an open end of
the casing. Is preferred. Furthermore, the bottom plate is preferably a flat body having a
thickness of 20 to 100 μm and at least the outer surface of which is made of a metal material.
Further, in the present invention, the method of manufacturing the condenser microphone has a
bottom wall formed with a concave groove whose opening is completely covered by the bottom
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surface of the microphone chip, and an outer periphery extending upward from a peripheral
portion of the bottom wall. A casing having a wall, a microphone chip mounted in the casing and
receiving an acoustic signal from the outside to generate a change in electrical capacity, and
mounted in the casing to convert the change in electrical capacity into an electrical signal
Method of manufacturing a condenser microphone including a field effect transistor for
outputting the signal, the steps of forming the casing, forming the microphone chip, preparing
the field effect transistor, and the microphone chip Assemble the field effect transistor in the
casing The step of forming the microphone chip comprises the steps of: forming a vibrating film
on the lower surface of the silicon substrate by photolithography after preparing the silicon
substrate; and forming the lower surface of the vibrating film by photolithography Step of
forming a spacer on the outer periphery of the diaphragm, a vibrating membrane charging step
of charging the vibrating membrane, and a vibrating membrane for digging the silicon substrate
by an etching method and exposing a part of the upper surface of the vibrating membrane
therebelow An exposing step, an electrode layer forming step of forming an electrode layer on
the exposed portion of the vibrating film and the upper surface of the silicon substrate, a
perforated bottom plate at least the outer surface of which is a metal material, the vibrating film
and the spacer A perforated bottom plate coupling step coupled thermally with said spacer to
form a vibrating space together The assembling step includes a first assembling step of mounting
the field effect transistor in the casing so as to electrically connect the field effect transistor to a
predetermined portion of the casing; and the microphone chip with the bottom plate with holes
facing downward. A second assembling step is mounted on the upper surface of the bottom wall
of the casing to shield the recess of the casing and to electrically connect with the field effect
transistor.
Since the manufacturing method adopts the MEMS technology to form the respective layers of
the microphone chip, the number of steps in manufacturing can be reduced compared to the
method of forming only by the conventional photolithography method. In addition, since only
one silicon substrate is used, it is easier to make the microphone chip thinner than the
conventional method using at least one pair of silicon substrates. That is, according to the
manufacturing method of the present invention, a thin condenser microphone can be
manufactured by a simpler manufacturing process. In the manufacturing method, in the vibrating
film forming step, a first inorganic material layer forming step of forming a first inorganic
material layer having a predetermined pattern on the lower surface of the silicon substrate, and
the first inorganic material layer And forming a second inorganic material layer having a
predetermined pattern on the lower surface of the second inorganic material layer. DETAILED
DESCRIPTION OF THE INVENTION Preferred embodiments of a condenser microphone and a
method of manufacturing the same according to the present invention will be described in detail
with reference to the drawings. The condenser microphone 3 according to the embodiment of the
present invention is attached to a ceramic casing 4 and the casing 4 as shown in FIG. 1, and
receives an acoustic signal from the outside to change the electric capacity. And a field effect
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transistor 6 attached to the inside of the casing 4 for converting a change in the electric capacity
into an electric signal and outputting the electric signal. Specifically, the casing 4 extends upward
from the peripheral portion of the bottom wall 41, and the bottom wall 41 is formed with a
recessed groove 411 whose opening is completely covered by the bottom surface of the
microphone chip 5. An outer peripheral wall 42, a hole 431 provided above the outer peripheral
wall 42 and matching the upper side of the microphone chip 5, a perforated cover 43 for
shielding the open end of the casing 4, and the bottom It comprises a plurality of terminals 44
provided on the lower surface of the wall 41 and coupled to a substrate such as a mobile phone.
The recessed groove 411 of the bottom wall 41 is formed with a stepped portion 412 having a
plurality of steps on the inner peripheral wall thereof. The microphone chip 5 mainly has a flat
plate-like metal electrode layer 51 in which only the central portion is recessed downward, and
the electrode layer 51 so as to be in contact with the lower surface of the recessed portion of the
electrode layer 51. A vibrating film 52 made of an inorganic material that can withstand a
temperature of 450 ° C. or higher formed on the lower side of the substrate, and a silicon
substrate described later sandwiched between non-contacting portions of the electrode layer 51
and the vibrating film 52 7 so as to form a vibration space 55 together with the remaining
portion after processing, the annular spacer 53 formed on the outer peripheral edge of the lower
surface of the vibrating film 52, and the vibrating film 52 and the spacer 53. And a metal
perforated bottom plate 54 coupled to the lower surface of the
More specifically, the vibrating film 52 is formed by laminating an SiO 2 layer 521 of a
predetermined pattern and an Si 3 O 4 layer 522 of a predetermined pattern in the upper and
lower direction. The spacer 53 is formed by laminating an annular SiO 2 layer 531 made of an
inorganic material and an annular metal layer 532 made of a metal material up and down.
Furthermore, the thickness of the bottom plate 54 is 20 to 100 μm. The microphone chip 5
configured as described above shields the recessed groove 411 by attaching the holed bottom
plate 54 downward to the stepped portion 412 of the casing 4, and the lower surface of the
diaphragm 52 is the bottom wall 41. Contact the top of the The field effect transistor 6 is
mounted on the bottom wall 41 and is electrically connected to the electrode layer 51 of the
microphone chip 5 and a predetermined terminal 44 of the casing 4. Thus, in the condenser
microphone 3, in the state where a voltage is applied, the sound wave signal of the sound is
transmitted from the open end of the casing 4, that is, from the hole 431 in the perforated lid
portion 43 into the casing 4. The vibration film 52 is vibrated to make the microphone chip 5
change in capacitance. Then, the change of the electric capacitance can be converted into an
electric signal and output through the field effect transistor 6. The vibration space 55
communicates with the recessed groove 411 via a hole 541 formed in the bottom plate 54.
Therefore, the air in the vibration space 55 can escape from the hole 541 according to the
vibration, and the pressure applied to the bottom plate 54 can be relieved, so that the temporal
deformation due to the use of the bottom plate 54 is substantially prevented. be able to. Next, a
method of manufacturing the condenser microphone 3 will be specifically described. As shown in
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FIG. 2, in the manufacturing method of this embodiment, a step 70 of forming the casing 4, a
step 71 of forming the microphone chip 5, and the field effect transistor 6 are prepared by
MEMS technology. And the step 73 of assembling the microphone chip 5 and the field effect
transistor 6 in the casing 4 in order. Specifically, in the casing forming step 70 in the
manufacture of the condenser microphone 3, a casing having the bottom wall 41, the outer
peripheral wall 42, the perforated lid 43 and the terminal 44 made of a ceramic material
Manufacture 4
In the microphone chip forming step 71 in the manufacture of the condenser microphone 3, as
shown in FIG. 3, after preparing the silicon substrate 7, a vibrating membrane forming step, a
spacer forming step, a vibrating membrane charging step, The vibrating film exposing step, the
electrode layer forming step, and the holed bottom plate coupling step are sequentially
performed. In the vibrating film forming step, the respective layers are formed on the silicon
substrate 7 by several processes belonging to photolithography such as coating, exposure,
development, etching, vapor deposition, and sputtering. That is, after forming a SiO2 layer 521 of
a predetermined pattern as a first inorganic material layer on the lower surface of the silicon
substrate 7, an Si3O4 layer 522 of a predetermined pattern is formed on a lower surface of the
SiO2 layer 521 as a second inorganic material layer. The vibrating film 52 is formed by the SiO 2
layer 521 and the Si 3 O 4 layer 522. In the spacer formation step, an annular SiO 2 layer 531 is
formed on the outer peripheral edge of the lower surface of the vibrating film 52 by
photolithography, and then a metal layer 532 is formed on the lower surface of the annular SiO 2
layer 531. The SiO 2 layer 531 and the metal layer 532 form a spacer 53. In the vibrating
membrane charging step, the vibrating membrane 52 is charged by charging or the like. In the
vibrating film exposing step, the silicon substrate 7 is dug down by an etching method to expose
a part of the upper surface of the vibrating film 52 therebelow. In the electrode layer forming
step, an electrode layer 51 is formed on the exposed portion of the vibrating film 52 and the
upper surface of the silicon substrate 7 by photolithography. In the holed bottom plate coupling
step, a nickel holed bottom plate 54 having a thickness of 20 to 100 μm and in which a plurality
of holes are formed by etching is combined with the vibrating film 52 and the spacer 53 as a
vibrating space 55. To the lower surface of the spacer 53 by heat welding. Thereby, the
microphone chip 5 of the above-mentioned configuration is manufactured. In the field effect
transistor preparing step 72 in the manufacture of the condenser microphone 3, the field effect
transistor 6 is prepared. In the assembling step 73 in the manufacture of the condenser
microphone 3, as shown in FIG. 3, first, the casing 4 is electrically connected to the field effect
transistor 6 with the predetermined terminal 44 of the casing 4. Perform the first assembly step
of attaching to the bottom wall 41 of the
Then, the microphone chip 5 is attached to the stepped portion 412 of the casing 4 with the
holed bottom plate 54 facing downward, thereby shielding the recessed groove 411 and
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electrically connecting to the field effect transistor 6. Subsequently, the open end of the casing 4
is shielded by the perforated lid portion 43 of the casing 4, whereby the assembly of the
condenser microphone 3 is completed. The condenser microphone and the method of
manufacturing the same according to the present invention are not limited to the configuration
of the above embodiment. That is, the above embodiments are made with the intention of
clarifying the technical contents of the present invention to the last, and the present invention is
not to be interpreted in a narrow sense as being limited to such specific examples. Various
modifications may be made within the spirit and scope of the claims. For example, in the above
embodiment, the spacer 53 is composed of the annular SiO 2 layer 531 made of an inorganic
material and the annular metal layer 532 made of a metal material. The spacer 53 may be
formed by applying a photoresist material such as benzocyclobutene), SINR, polyimide, or SU-8.
In this way, it is not necessary to form the metal layer 532, and the bottom plate 54 can be
coupled to the spacer 53 by heating and pressing. The spacer 53 is not limited to an annular
shape, and may be configured by arranging a plurality of island-shaped blocks along the outer
peripheral edge of the vibrating film 52. Furthermore, in the above embodiment, the perforated
bottom plate 54 is formed of a metal material, but it may be used that only the outer surface
thereof is formed of a metal material. As is apparent from the above description, the condenser
microphone manufactured by the MEMS technology of the present invention has a simple
structure and can further simplify the manufacturing process, and the vibrating film is Since it is
made of an inorganic material that can withstand 450 ° C. or more, it can be applied to surface
mounting technology (SMT) and the terminal can be coupled to the substrate by an automated
method. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a
condenser microphone according to an embodiment of the present invention. FIG. 2 is a
flowchart showing a method of manufacturing a condenser microphone. FIG. 3 is a block diagram
showing a method of manufacturing a condenser microphone.
FIG. 4 is a flowchart showing a part of a method of manufacturing a microphone chip in a
conventional condenser microphone. FIG. 5 is a cross-sectional view of the microphone chip in a
conventional condenser microphone. Explanation of symbols 3 Condenser microphone 4 Casing
41 Bottom wall 411 Concave groove 412 Stair portion 42 Outer circumferential wall 43
Perforated lid 431 Hole 44 Terminal 5 Microphone chip 51 Electrode layer 52 ... Vibrating film
521 ... first inorganic material layer 522 ... second inorganic material layer 53 ... spacer 531 ...
inorganic material layer 532 ... metal layer 54 ... bottom plate with holes 541 ... hole 55 ...
vibration space 6 ... field effect transistor 7 ... Silicon substrate
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