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JP2008244627

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2008244627
An object of the present invention is to lower the cutoff frequency of an electrostatic pressure
transducer in the low range without increasing the manufacturing cost. An electrostatic pressure
transducer for achieving the above object comprises a base forming an opening of a back cavity,
and an electrode plate comprising a membrane having a first vent hole deposited on the base. A
spacer comprising a film deposited on the surface of the base and having a through hole, and a
second air vent communicating with the first vent and the back cavity between the base and the
periphery of the opening And a film deposited on the surface of the film bonded to the base and
forming the spacer, forming a counter electrode facing the electrode plate with a gap
therebetween and located in the through hole A diaphragm covering the opening, wherein the
height of the second vent is less than the thickness of the membrane forming the spacer.
[Selected figure] Figure 1
Electrostatic pressure transducer and condenser microphone
[0001]
The present invention relates to an electrostatic pressure transducer and a method of
manufacturing the same, and more particularly to an electrostatic pressure transducer suitable as
a microphone.
[0002]
Conventionally, as a minute electrostatic pressure transducer manufactured by applying a
semiconductor manufacturing process, for example, a so-called silicon microphone is known (see
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Patent Documents 1 and 2).
In the electrostatic pressure transducers described in Patent Documents 1 and 2, a pair of
counter electrodes is formed by the relatively rigid electrode plate and the relatively rigid
diaphragm. The gap between the base forming the opening of the back cavity and the diaphragm
forms an acoustic resistance in the passage for balancing the pressure of the back cavity with the
atmospheric pressure. As the acoustic resistance increases, the cutoff frequency of the low range
decreases. Japanese Patent Application Publication No. 2005-535152 Patent Document 2:
Japanese Patent Application Publication No. 2002-218591
[0003]
However, the electrostatic pressure transducers described in Patent Documents 1 and 2 have the
following problems. That is, narrowing the gap between the diaphragm and the base reduces the
area of the interface between the etchant and the film to be etched, and the etching rate
decreases, resulting in an increase in manufacturing cost. Can not be made narrow enough, and
the acoustic resistance can not be made sufficiently large. Also, instead of narrowing the gap
between the diaphragm and the base, it is necessary to widen the edge of the diaphragm that
overlaps with the base, so that the diaphragm and the base It will contact and sometimes the
diaphragm will stick to the base. Also, if the width of the edge of the diaphragm overlapping with
the base is increased without changing the diameter of the diaphragm, the back cavity narrows
as a result and the sensitivity decreases.
[0004]
The present invention has been made in view of these problems, and it is an object of the present
invention to lower the low frequency cutoff frequency of an electrostatic pressure transducer
without increasing the manufacturing cost.
[0005]
(1) An electrostatic pressure transducer for achieving the above object comprises: a base forming
an opening of a back cavity; a spacer having a through hole and made of a film deposited on the
surface of the base; And a film deposited on the surface of the film forming the spacer, which
communicates with the first vent and the back cavity with the base And a diaphragm which
covers the opening leaving a second vent and is joined to the base around the opening, forming a
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counter electrode facing the electrode plate with a gap therebetween. The height of the second
vent is less than the thickness of the membrane forming the spacer.
In this electrostatic pressure transducer, the back cavity communicates with the atmospheric
pressure space through the second vent located between the base and the diaphragm and the
first vent located in the membrane forming the electrode plate. The film forming the diaphragm
is a film deposited on the surface of the film deposited on the surface of the base, and the spacer
consists of the film deposited on the surface of the base. Therefore, immediately after the film
forming the diaphragm is deposited, the film forming the spacer can be left between the
diaphragm and the base. In this case, the thickness of the film forming the spacer determines the
area of the interface between the etchant of the film forming the spacer and the film to be
etched. When the film forming the spacer is etched, the diaphragm can be moved into the
through hole formed in the film forming the spacer. The height of the second vent remaining
between the diaphragm and the base will then be less than the thickness of the membrane
forming the spacer. This condition can be maintained by bonding the diaphragm to the base
around the opening. That is, since this electrostatic pressure transducer adopts a configuration in
which the diaphragm can be moved to the base side in the manufacturing process and bonded to
the base around the opening, the interface between the etchant and the film to be etched is
narrowed. It is possible to increase the acoustic resistance of the second vent and to lower the
cut-off frequency in the lower region, without increasing the manufacturing cost.
[0006]
(2) In the electrostatic pressure transducer for achieving the above object, the diaphragm has a
convex portion in which the tip is joined to the base and which forms the second vent in the
vicinity of the outer periphery May be In this case, the shape and size of the second vent can be
designed according to the shape and size of the convex portion in the vicinity of the outer
periphery of the diaphragm.
[0007]
(3) In the electrostatic pressure transducer for achieving the above object, the pressure sensor is
made of a film forming the diaphragm, is electrically connected to the counter electrode, and is
connected to the protrusion in the through hole. The base may further include a flat joint joined
to the base on the outer side, and in the base, the base may be conductive and the surface layer
may have a higher electrical resistivity than the base. After applying a voltage to the diaphragm
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and the base layer of the base after etching the film forming the spacer to form the through
holes, electrostatic attraction is exerted between the diaphragm and the base layer of the base. As
a result, the membrane forming the diaphragm is deformed, and the convex portion of the
diaphragm is attracted to the base. When the voltage is further applied, the junction located
outside the convex portion further approaches the base side and is attracted to the base. At this
time, since the opening of the back cavity is formed in the base on the inner side of the convex
portion, the central portion of the diaphragm is hardly drawn to the base side. When the junction
is attracted to the base, a current flows due to the applied voltage, so that it is possible to detect
that the junction and the base are attracted. This current increases as the contact area between
the junction and the base increases, so by setting an appropriate threshold value for this current
magnitude, a diaphragm is formed in the through hole of the membrane forming the spacer. It
can be detected that the membrane is firmly adsorbed to the base. When the membrane forming
the diaphragm is adsorbed to the base, both are joined by van der Waals force. In addition, since
the surface layer of the base has a higher electrical resistivity than the base layer of the base,
when the base is adsorbed to the bonding portion, an overcurrent does not easily flow. The
electrical resistivity of the surface layer of the base is preferably set to a value such that a
resistance on the order of 10 <6> Ω to 10 <9> Ω is formed by the surface layer of the base.
[0008]
(4) In the electrostatic pressure transducer for achieving the above object, the base may have a
recess on the surface that extends outward from the opening and forms the second vent. . In this
case, the shape and size of the second vent can be designed according to the shape and size of
the recess. (5) In the electrostatic pressure transducer for achieving the above object, in the base,
the base layer may be conductive, and the surface layer may have a larger electric resistivity than
the base layer. When a film forming the spacer is etched to form a hole and voltage is applied to
the diaphragm and the base layer of the base, electrostatic attraction is exerted between the
diaphragm and the base, and the diaphragm is attracted to the base. When the diaphragm is
attracted to the base, the two are joined by van der Waals force. In this case, since the surface
layer of the base has a higher electrical resistivity than the base layer of the base, it is difficult for
an overcurrent to flow when the diaphragm is adsorbed to the base. The electrical resistivity of
the surface layer of the base is preferably set to a value such that a resistance on the order of 10
<6> Ω to 10 <9> Ω is formed by the surface layer of the base.
[0009]
(6) In the electrostatic pressure transducer for achieving the above object, the first pressuresensitive conductive film comprises a film deposited between the film forming the diaphragm and
the film forming the electrode plate. A second spacer having a pore and a second through hole
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communicating with the second vent, and a film forming the diaphragm, and a base end portion
thereof is joined to the spacer and the second spacer; A conductive lead projecting toward the
inside of the through hole and continuing to the outer periphery of the diaphragm, wherein the
conductive lead is bent in a direction approaching the base from the proximal end toward the
distal end; You may provide further.
[0010]
(7) The electrostatic pressure transducer to achieve the above object may be a condenser
microphone.
[0011]
(8) A method of manufacturing an electrostatic pressure transducer to achieve the above object
comprises forming a first deposited film for forming a spacer and a diaphragm on a base forming
an opening of a back cavity. The opening and the third deposition film for forming the second
spacer, and the fourth deposition film for forming the electrode plate and the first vent, By
etching the first deposited film and the third deposited film isotropically from the first vent, a
first through hole is formed in the first deposited film in which the back surface of the diaphragm
is exposed, and Forming a second through hole in the third deposition film in which the surface
of the diaphragm is exposed, and then forming a part of the second deposition film in
communication with the first vent and the back cavity with the base; Remaining between In
bonded around the opening of the base, including the.
According to this manufacturing method, the first deposited film and the third deposited film are
etched isotropically after depositing the first deposited film, the second deposited film, the third
deposited film, and the fourth deposited film on the base. And the diaphragm floats in the air.
When the etching of the first deposited film proceeds, the height of the interface between the
etchant of the first deposited film and the first deposited film is equal to the thickness of the first
deposited film. Thereafter, when a portion of the second deposited film is bonded around the
opening of the base with the first vent and the second vent in communication with the back
cavity, the height of the second vent becomes the first It becomes lower than the thickness of the
deposited film. Therefore, according to this manufacturing method, it is possible to lower the
cutoff frequency of the low region of the electrostatic pressure transducer without narrowing the
interface between the etchant of the first deposited film and the first deposited film for forming
the spacer.
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[0012]
(9) In the method of manufacturing an electrostatic pressure transducer to achieve the above
object, a part of the second deposited film is applied to the edge of the opening of the base by
applying a voltage to the base and the diaphragm. It may be joined to the part. In this case, the
second deposited film for forming the diaphragm and the base can be easily joined. For example,
they can be joined without using a special device in the inspection process.
[0013]
(10) In the method of manufacturing an electrostatic pressure transducer to achieve the above
object, in the base, the base layer may be conductive and the surface layer may have a higher
electrical resistivity than the base layer. In this case, by applying a voltage to the base layer of the
base and the diaphragm, overcurrent does not easily flow even if the diaphragm and the base
contact with each other. The electrical resistivity of the surface layer of the base is preferably set
to a value such that an electrical resistance on the order of 10 <6> Ω to 10 <9> Ω is formed by
the surface layer of the base.
[0014]
Hereinafter, embodiments of the present invention will be described in the following order with
reference to the attached drawings. The same reference numerals are given to corresponding
components in the respective drawings, and the overlapping description will be omitted.
*********** 1. Structure 2. Manufacturing method Action effect 4. Other
Embodiments *********
[0015]
1. Structure FIGS. 1A and 1B are schematic cross-sectional views showing the main parts of a
condenser microphone as an embodiment of the electrostatic pressure transducer according to
the present invention. The cross sections of FIGS. 1A and 1B correspond to 1A shown in FIG. 1C
and 1B shown in FIG. 2, respectively. The condenser microphone 1 is a MEMS in which a chip in
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which a plurality of thin films are deposited on a substrate 15 made of a bulk material is
packaged by a wiring base and a cover (not shown).
[0016]
The base portion 16 is composed of a conductive substrate 15 in which the through holes H1 are
formed and a surface insulating film 14 in which the through holes H5 are formed. The electrical
resistivity of the surface insulating film 14 is larger than the electrical resistivity of the substrate
15. The through holes H <b> 1 and H <b> 5 form one through hole forming an opening 141 in
the surface of the base 16. The opening 141 forms an opening of the back cavity BC closed by a
wiring board (not shown) or the like. The substrate 15 forming the base layer of the base 16 is
made of a bulk material such as silicon. The surface insulating film 14 is an insulating film which
can be selectively etched with respect to the first spacer film 13 and the second spacer film 11,
and is made of, for example, Si3N4, in the order of 10 <6> Ω to 10 <9> Ω. The thickness is set
so that the electrical resistance is formed.
[0017]
The first spacer film 13 is formed of an insulating film such as SiO 2 deposited on the surface of
the base 16. In the first spacer film 13, a substantially circular through hole H2 is formed. The
diaphragm electrode film 12 is formed of a conductive film such as polycrystalline Si or the like
doped with an impurity such as P deposited on the surface of the first spacer film 13. The second
spacer film 11 is formed of an insulating film such as SiO 2 deposited on the surface of the
diaphragm electrode film 12. A substantially circular through hole H3 is formed in the second
spacer film 11. The plate electrode film 10 is made of a conductive film such as polycrystalline Si
or the like doped with an impurity such as P deposited on the surface of the second spacer film
11. The plate electrode film 10 is sufficiently thicker than the diaphragm electrode film 12, and
the internal stress in the tensile direction remains.
[0018]
FIG. 1C is a plan view showing the main part of the condenser microphone 1. The electrode plate
101 comprises a plate electrode film 10. The plate electrode film 10 has an outer edge joined to
the second spacer film 11 and is stretched over the second spacer film 11 so as to close the
through hole H3. The electrode plate 101 is formed with a plurality of through holes H4 as first
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vents. The contour of the electrode plate 101 is determined by the contour of the through hole
H3. However, the contour of the electrode plate 101 is not particularly limited as long as the area
of the portion facing the diaphragm 122 is large and sufficiently high deflection rigidity can be
obtained compared to the diaphragm 122. The electrode plate 101 is connected to a pad 103 for
wiring.
[0019]
A gap G2 between the electrode plate 101 forming the pair of opposite electrodes and the
diaphragm 122 appears by the formation of the through hole H3 in the second spacer film 11,
and the junction between the diaphragm 122 and the base 16 It is constant. The gap G2
communicates with the atmospheric pressure space through the through hole H4.
[0020]
FIG. 2 is a plan view showing a pattern of the diaphragm electrode film 12. The diaphragm
electrode film 12 forms a diaphragm 122, a connection portion 123 for bridging the diaphragm
122 to the first spacer film 13, a guard electrode 126, and pads 125 and 127. The guard
electrode 126 is connected to the plate electrode film 10 through the pad 127. The contour of
the diaphragm 122 encloses the opening 141 of the back cavity BC formed in the base 16. That
is, the opening 141 of the back cavity BC is covered by the diaphragm 122.
[0021]
The diaphragm 122 and the guard electrode 126 are separated by a through hole H6. The
through hole H6 functions as a vent connecting the second vent G1 and the gap G2 as shown in
FIG. 1A. The portion functioning as the vent in FIG. 2 is indicated by hatching. As shown in FIG.
1A, the through hole H6 is formed outside the opening 141 of the back cavity BC, and a second
vent G1 is formed between the edge of the diaphragm 122 and the edge of the base 16. The
second vent G1 communicates with the back cavity BC, the through hole H2 and the through
hole H6. Therefore, the back cavity BC communicates with the space of atmospheric pressure
through the second vent G1, the through hole H2, the through hole H6, the gap G2, and the
through hole H4. Of the second vent G1, the through hole H2, the through hole H6, the gap G2,
and the through hole H1, the acoustic resistance of the second vent G1 is the highest. The lower
the height of the second vent G1 (that is, the lower the height of the protrusion 124), and the
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wider the overlap between the edge of the diaphragm 122 and the edge of the base 16, the
acoustic resistance of the second vent G1 Becomes larger, and as the low frequency cutoff
frequency decreases, the low frequency sensitivity improves.
[0022]
As shown in FIGS. 1B and 2, the connection portion 123 extends outward from the outer
periphery of the circular diaphragm 122. Diaphragm 122 is connected to pad 125 by connection
123. The pad 125 is connected to a pad for wire bonding. That is, one of the connection portions
123 functions as a lead. Since the diaphragm electrode film 12 is closer to the base portion 16 as
compared with the state immediately after deposition, the connection portion 123 is bent so as
to be closer to the base portion 16 toward the center of the through hole H2. The tip portions of
two or more connection portions 123 are joined to the first spacer film 13 and the second spacer
film 11 as shown in FIG. 1B. Since the connection portion 123 is in the shape of a band whose
contour is bent, the elastic coefficient in the radial direction of the diaphragm 122 is small.
Therefore, the internal stress of the portion of the diaphragm 122 of the diaphragm electrode
film 12 is released by the connection portion 123. For this reason, the displacement with respect
to the pressure of the diaphragm 122 becomes large, and the sensitivity increases in the entire
region.
[0023]
As shown in FIG. 1B, in the vicinity of the outer periphery of the diaphragm 122, a plurality of
convex portions 124 projecting toward the base 16 are formed at substantially equal intervals.
The convex portion 124 is formed of an insulating deposited film joined to the diaphragm
electrode film 12. In such a convex portion 124, an insulating film is deposited on the surface of
the first spacer film 13 with the concave portion formed in the first spacer film 13, and this
insulating film is ground or polished until the first spacer film 13 is exposed. Then, it can form by
forming diaphragm electrode film 12 later. The tip of the convex portion 124 of the diaphragm
122 is directly bonded to the surface of the base 16. Since the convex portion 124 is smaller
than the thickness of the first spacer film 13, the convex portion 124 keeps the height of the
second vent G 1 between the diaphragm 122 and the base portion 16 lower than the thickness of
the first spacer film 13. And the diaphragm 122 is located in the through hole H2.
[0024]
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2. Manufacturing Method The condenser microphone 1 is manufactured by applying the
process technology of the semiconductor device. Specifically, a thin film is sequentially deposited
on the substrate 15 which is a bulk material, and a gap is formed inside the laminated structure
by etching or lift-off, whereby the structure shown in FIG. 1 is formed.
[0025]
FIGS. 3A and 3B are schematic cross-sectional views showing an intermediate in the
manufacturing process of the condenser microphone 1. Each cross section corresponds to 1A
shown in FIG. 1C. The surface insulating film 14, the first spacer film 13, the diaphragm
electrode film 12, the second spacer film 11, and the plate electrode film 10 are sequentially
stacked on the substrate 15, and the diaphragm electrode film 12 and the plate electrode film 10
are completed. In the state where patterning is performed in the state, through holes H1 are
formed in the substrate 15 by Deep-RIE or the like, and the surface insulating film 14 is
selectively etched to form through holes H5, whereby an intermediate shown in FIG. 3A is
obtained. Be Thereafter, when the first spacer film 13 and the second spacer film 11 are
selectively removed by isotropic etching, through holes H2 and H3 are formed as shown in FIG.
3B. As a result, the back surface of the diaphragm 122 is exposed from the through hole H2, and
the surface of the diaphragm 122 is exposed from the through hole H3. At this time, the etchant
which erodes the first spacer film 13 from the opening 141 of the base 16 gradually forms the
second spacer G1 between the diaphragm 122 and the base 16 shown in FIG. Erode. The area of
the interface between the first spacer film 13 and the etchant is proportional to the height of the
second vent G1. The shape of the through hole H2 of the first spacer film 13 and the shape of the
through hole H3 of the second spacer film 11 are determined by the shape of the opening 141 of
the base 16 and the shape of the through hole H1 of the plate electrode film 10. When the
through hole H2 and the through hole H3 are formed, the connection portion 123 is extended,
and the stress in the tensile direction of the exposed portion of the diaphragm electrode film 12
is released, so that the sensitivity of the condenser microphone 1 is improved in the entire area.
[0026]
Thereafter, when a high voltage is applied to the substrate 15 and the diaphragm electrode film
12, the diaphragm 122 is drawn to the substrate 15 and enters the through holes H2 of the first
spacer film 13 to project the diaphragm 122 as shown in FIG. 1B. The portion 124 is pressed
against the surface insulating film 14 of the base 16. Then, the diaphragm 122 is joined to the
surface insulating film 14 of the base portion 16 by the van der Waals force acting on the
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interface between the convex portion 124 and the surface insulating film 14, and the capacitor
microphone 1 is completed. Since the strength of the direct bonding by the van der Waals force
is sufficiently high, the diaphragm 122 does not peel off from the base 16 even if an impact is
applied to the condenser microphone 1 after completion. As a time of applying a high voltage to
the substrate 15 and the diaphragm electrode film 12, for example, an inspection process is
suitable.
[0027]
3. Operation and Effect According to the present embodiment, when a high voltage is applied
to the substrate 15 and the diaphragm electrode film 12, the gap G2 between the diaphragm 122
and the electrode plate 101 is expanded, and the second between the diaphragm 122 and the
base 16 The vent G1 is narrowed. At this time, in the diaphragm electrode film 12, since the bent
strip-like connection portion 123 extends in the radial direction of the diaphragm 122, the
internal stress of the diaphragm 122 hardly increases in the tensile direction. When the tip end
of the convex portion 124 of the diaphragm 122 is joined to the base portion 16, the gap G2
between the diaphragm 122 and the electrode plate 101 is stabilized in the shape shown in FIG.
1B. As a result, the height of the second vent G1 is smaller than the distance between the
diaphragm 122 and the base 16 in the step of etching the first spacer film 13 (the state shown in
FIG. 3A). The height of the gap G2 between the diaphragm 122 and the electrode plate 101,
which is correlated with the stability against mechanical vibration and the rated pressure, is
larger than the film thickness of the second spacer film 11.
[0028]
As described above, the height of the second vent G1 is determined by the height of the convex
portion 124 of the diaphragm 122. The width (radial length of the diaphragm) of the second vent
G1 is determined by the width of the diaphragm 122 protruding from the opening 141 of the
back cavity BC. Since the second vent G1 is the largest acoustic resistance in the space
connecting the atmospheric pressure space and the back cavity BC, the cutoff frequency and
sensitivity characteristics of the low range of the condenser microphone 1 are the height of the
second vent G1 and Ruled by width. Therefore, it is desirable for the second vent G1 to be low
and wide in the completed state.
[0029]
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On the other hand, the etchant which erodes the first spacer film 13 from the opening 141 of the
base 16 erodes the first spacer film 13 while gradually forming the second vent G1 between the
diaphragm 122 and the base 16 shown in FIG. 3B. Do. At this time, the area of the interface
between the first spacer film 13 and the etchant is proportional to the height of the second vent
G1. The etching rate of the first spacer film 13 increases as the area of the interface between the
first spacer film 13 and the etchant increases. That is, in the step of etching the first spacer film
13 and the second spacer film 11, it is desirable that the height of the second vent G1 be higher.
[0030]
According to the present embodiment, after the step of etching the first spacer film 13 and the
second spacer film 11, the height of the second vent G1 and the gap G2 is changed by voltage
application that is physical energy supply from the outside. In order to make it possible, the
second vent G1 can be narrowed while widening the gap G2 after film deposition. Therefore,
according to the present embodiment, it is possible to lower the cutoff frequency of the low band
and increase the sensitivity of the low band without sacrificing the etching efficiency. Here, for
example, it is assumed that the dimensions of the completed state of the condenser microphone
1 are as follows.
[0031]
Back cavity BC: Cylindrical space with radius 320 μm, height 512 μm Contour of diaphragm
122: circle with radius 325 μm Height of second vent G1 (height of convex portion 124 of
diaphragm 122): 0.7 μm. Length of second vent G1 (width where diaphragm 122 and base 16
overlap): 5 μm Height of gap G2: 4 μm
[0032]
In this case, the cutoff frequency of the low range of the condenser microphone 1 is about 20 Hz.
Here, when the height of the second vent G1 is changed to 1 μm and the height of the gap G2 to
1.3 μm, the cutoff frequency of the low band becomes about 60 Hz.
[0033]
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Further, according to the present embodiment, the cut-off frequency in the low band can be
lowered and the sensitivity in the low band can be increased while the rated pressure can be
increased to improve the stability, and the sensitivity and stability in the low band can be
balanced in high dimensions. The capacitor microphone 1 is realized. Further, according to the
present embodiment, in the step of bonding the diaphragm 122 to the base 16, the contact state
between the convex portion 124 and the surface insulating film 14 is known from the magnitude
of the current flowing by the voltage applied to the diaphragm 122 and the substrate 15. be able
to. In addition, since the surface insulating film 14 is sandwiched between the diaphragm 122
and the substrate 15 in the process, excessive current hardly flows due to the high voltage
applied to the substrate 15 and the diaphragm electrode film 12.
[0034]
4. Other Embodiments FIG. 4, FIG. 5, FIG. 6, FIG. 7, and FIG. 8 are plan views showing other
embodiments of bonding of the diaphragm electrode film 12 and the base 16. In FIG. 4, FIG. 5,
FIG. 6, FIG. 7, and FIG. 8, bonding is a region where the diaphragm electrode film 12 is bonded to
the base 16 in a region farther from the center of the diaphragm 122 than the convex portion
124 of the diaphragm 122 described above. Section 128 is indicated by dotted hatching.
[0035]
When the diaphragm electrode film 12 is bonded to the base portion 16 at the bonding portion
128, it is easy to increase the bonding strength between the diaphragm electrode film 12 and the
base portion 16. The reason is as follows. As the plurality of convex portions 124 closer to the
opening 141 of the base portion 16 than the joint portion 128 is smaller one by one, it may be
considered that the joint strength is insufficient only with the convex portions 124. The larger
the distance from the opening 141, the wider the area for bonding, and the higher the degree of
freedom in the shape and arrangement of the bonding area that affects the acoustic resistance.
On the other hand, the further away the joint area is from the center of the diaphragm 122, the
higher the possibility of contact between the bent diaphragm 122 and the base 16. Therefore, as
shown in FIG. 4, FIG. 5, FIG. 6, FIG. 7, and FIG. 8, when the diaphragm electrode film 12 and the
base 16 are joined in different regions different in distance starting from the center of the
diaphragm 122, these problems are It can be eliminated. When the diaphragm electrode film 12
and the base portion 16 are bonded at the bonding portion 128, the flat portion of the
diaphragm electrode film 12 may be directly bonded to the base portion 16, or the deposition
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may be bonded to the back surface of the diaphragm electrode film 12. The diaphragm electrode
film 12 and the base portion 16 may be joined via a projection made of a film or a projection
provided on the diaphragm electrode film 12 itself. Alternatively, the diaphragm electrode film
12 and the base portion 16 may be bonded only by the bonding portion 128 without providing
the convex portion 124.
[0036]
When the flat portion of the diaphragm electrode film 12 and the base 16 are directly bonded,
the diaphragm electrode film 12 and the base 16 can be bonded while detecting the contact state
of the diaphragm electrode film 12 and the base 16. The reason is as follows. When a high
voltage is applied to the diaphragm electrode film 12 and the substrate 15, the diaphragm
electrode film 12 is attracted to the base 16 by electrostatic attraction, and the convex portion
124 is first attracted to the base 16. When high voltage is further applied, the portion of the
diaphragm electrode film 12 outside the convex portion 124 is bent toward the base 16, and the
junction 128 is attracted to the base 16 from the outside toward the inside. As the junction 128
is attracted to the base 16 from the outside to the inside, the current flowing to the substrate 15
and the diaphragm electrode film 12 increases. Therefore, the contact state between the base 16
and the diaphragm electrode film 12 can be estimated from the magnitude of the current. Then,
by setting an appropriate threshold value for this current and applying a voltage until this
current exceeds the threshold value, the convex portion 124 and the joint portion 128 can be
appropriately joined to the base portion 16.
[0037]
In the example shown in FIG. 4, only one connection portion 123 shown in FIG. 2 is formed in the
diaphragm electrode film 12, but at least one connection portion 123 may be provided. If there is
only one connection portion 123, the diaphragm 122 and the pad 125 can be connected. When
there are two or more connection parts 123, a period from etching of the first spacer film 13 and
the second spacer film 11 as shown in FIG. 3B to bonding of the diaphragm 122 to the base 16
as shown in FIG. 1B. The center of the diaphragm 122 is less likely to deviate from the center of
the opening 141.
[0038]
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9A and 9B are cross sectional views showing another embodiment of the second vent G1. As
shown in FIGS. 9A and 9B, the second vent G1 may be formed by a groove 161 which is a recess
formed in the surface of the base 16. For the groove 161, for example, the surface insulating film
14 is formed so that the outline of the through hole H5 protrudes outward from the outline of
the through hole H1 of the substrate 15, or the groove extending in advance outside the through
hole H1 is The groove 161 may be formed in the base 16 by depositing the surface insulating
film 14 after that. When the former method is adopted, the through holes H5 are formed in the
surface layer insulating film 14 before depositing the first spacer film 13, and the surface of the
first spacer film 13 is planarized after the first spacer film 13 is formed. Good. In the latter
method, a groove is formed in the substrate 15 before the surface insulating film 14 is deposited,
and the surface of the first spacer film 13 is planarized after the surface insulating film 14 and
the first spacer film 13 are deposited. Just do it.
[0039]
In addition, the contour of the electrode plate 101 may be shaped such that the entire periphery
is not joined to the second spacer film 11 as shown in FIG. In this case, an air vent
communicating with the through hole H3 of the second spacer film 11 is formed on the outside
of the plate electrode film 10. Each of the first spacer film 13, the diaphragm electrode film 12,
the second spacer film 11, and the plate electrode film 10 may be a multilayer film. Alternatively,
the diaphragm 122 may be bonded to the base 16 by applying an external force after etching the
first spacer film 13 and the second spacer film 11. In addition, the number of convex portions
124 of the diaphragm 122 may be one or more. In addition, the surface insulating film 14 may
be omitted. Further, the entire circumference of the diaphragm 122 may be joined to the base
16. In this case, in the region inside the opening 141, a fine vent hole serving as an acoustic
resistance may be formed in the diaphragm 122.
[0040]
Furthermore, the technical scope of the present invention is not limited to the above-described
embodiment, and it goes without saying that various modifications can be made without
departing from the scope of the present invention. For example, the materials, dimensions, the
film forming method, and the pattern transfer method described in the above embodiment are
merely examples, and the descriptions of addition, deletion, and replacement of the process order
that are obvious for those skilled in the art are omitted. ing. Moreover, the present invention can
be applied to various electrostatic pressure transducers other than condenser microphones.
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15
[0041]
(1A) and (1B) are typical sectional drawings concerning embodiment of this invention. (1C) is a
top view concerning the embodiment of the present invention. The top view concerning the
embodiment of the present invention. (3A) and (3B) is typical sectional drawing concerning
embodiment of this invention. The top view concerning the embodiment of the present invention.
The top view concerning the embodiment of the present invention. The top view concerning the
embodiment of the present invention. The top view concerning the embodiment of the present
invention. The top view concerning the embodiment of the present invention. (9A) and (9B) is
typical sectional drawing concerning embodiment of this invention.
Explanation of sign
[0042]
1: Condenser microphone, 10: plate electrode film, 11: second spacer film, 12: diaphragm
electrode film, 13: first spacer film, 14: surface insulating film, 15: substrate, 16: base, 101:
electrode plate, 103: Pad, 122: Diaphragm, 123: Connection, 124: Convex, 125: Pad, 126: Guard
electrode, 127: Pad, 128: Junction, 141: Opening, 161: Groove, G1: Second vent , G2: gap
04-05-2019
16
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