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DESCRIPTION JP2007324805

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DESCRIPTION JP2007324805
An object of the present invention is to provide a sensor device capable of suppressing an
increase in the size of the device main body while suppressing the occurrence of bending in a
support. A microphone (sensor device) 30 includes a diaphragm portion 4a provided so as to be
able to vibrate, an electrode plate portion 8a provided to face the diaphragm portion 4a at a
predetermined distance, and an electrode plate portion The support 5 includes a support film 6
supporting the tensile strength 8a and having a tensile internal stress δSt, and a support film 7
stacked on the support film 6 and having a compressive internal stress δSt. [Selected figure]
Figure 1
Sensor device and diaphragm structure
[0001]
The present invention relates to a sensor device and a diaphragm structure, and more
particularly to a sensor device and a diaphragm structure having a support for supporting an
electrode plate.
[0002]
Conventionally, a sensor device such as an acoustic sensor is known that converts sound into an
electrical signal by a change in electrostatic capacitance between a conductive diaphragm
(diaphragm) that vibrates by sound and a fixedly installed electrode plate. (See, for example,
Patent Document 1).
[0003]
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In Patent Document 1 mentioned above, a vibrating plate (diaphragm) capable of vibrating, an
electrode (electrode plate) fixedly disposed to face the vibrating plate, and a member (support)
having a hole for supporting the electrode An acoustic transducer (acoustic sensor) is disclosed,
comprising: a diaphragm and a substrate provided with a member having a hole.
When sound enters the acoustic transducer, the diaphragm vibrates to change the capacitance
between the diaphragm and the electrode to which a constant voltage is applied.
Since the charge amount of the diaphragm and the electrode changes due to the change of the
capacitance, the change amount of the charge is output as an electric signal for the sound.
[0004]
In the acoustic transducer disclosed in Patent Document 1, the rigidity of the holed member
(support) is improved by partially increasing the length of the side portion of the member having
the hole for supporting the electrode. By doing this, it is possible to suppress the bending of the
member having a hole toward the substrate due to the tensile internal stress of the member
having a hole (support).
[0005]
Japanese Patent Publication No. 2004-506394
[0006]
However, in the acoustic transducer disclosed in Patent Document 1 described above, the length
of the side portion of the member having the hole is partially increased in order to prevent the
member having the hole supporting the electrode from bending toward the substrate side. As a
result, there is a problem that the size of the apparatus body is increased.
[0007]
The present invention has been made to solve the problems as described above, and one object of
the present invention is to suppress the increase in size of the device body while suppressing the
occurrence of bending in the support. Providing a sensor device and a diaphragm structure that
can be
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2
Means for Solving the Problems and Effects of the Invention
[0008]
In order to achieve the above object, a sensor device according to a first aspect of the present
invention includes a diaphragm provided in a vibratable manner, an electrode plate provided
opposite to the diaphragm at a predetermined distance, and an electrode plate And a support
including a first support film having a tensile internal stress and a second support film stacked
on the first support film and having a compressive internal stress.
In the present invention, the tensile internal stress is a force acting in the inward direction of the
film constituting the support, and is a force acting to move the outside of the electrode plate on
which the film is laminated to the film side.
The compressive internal stress is a force acting in the outward direction of the film constituting
the support, and is a force acting to move the outside of the electrode plate on which the film is
laminated to the electrode plate side.
[0009]
In the sensor device according to the first aspect, as described above, the first support film
supporting the electrode plate and having a tensile internal stress, and the second support film
stacked on the first support film and having a compressive internal stress And reducing the
overall internal stress of the support, since the second support film having compressive internal
stress can cancel out part of the tensile internal stress of the first support film by providing the
support including Can.
As a result, it is possible to suppress bending of the support toward the substrate due to an
increase in tensile internal stress of the first support film, so it is possible to suppress breakage
of the support.
In addition, since the support can be restrained from bending to the substrate side due to an
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increase in tensile internal stress of the first support film, the range in which the diaphragm can
move without contacting the electrode plate can be enlarged. As a result, the dynamic range of
the sensor device can be improved. In addition, by the second support film being stacked on the
first support film, it is possible to suppress an increase in the size of the apparatus main body.
[0010]
In the sensor device according to the first aspect, preferably, the second support film of the
support is made of the same element as the first support film of the support. According to this
structure, when the first support film and the second support film are dry-etched, the first
support film and the second support film can be etched by the same etching gas, thus simplifying
the manufacturing process. be able to. In addition, when the first support film and the second
support film are formed by the same element, when the first support film and the second support
film are wet-etched, the etching rates of the first support film and the second support film are
equal to each other. Since this becomes the same, it is possible to suppress the occurrence of a
step at the interface between the etched first support film and the second support film.
[0011]
The sensor device according to the first aspect preferably further comprises a substrate provided
with a diaphragm and a support, the first support film of the support being disposed on the
substrate side with respect to the second support film of the support There is. According to this
structure, the sacrificial layer having a tensile internal stress larger than the tensile internal
stress of the first support film and the compressive internal stress of the second support film is
formed between the support and the substrate. Since the first support film can be brought into
contact with the first support film, the force generated at the interface between the support and
the sacrificial layer can be suppressed as compared with the case where the second support film
is in contact with the sacrificial layer. As a result, generation of cracks and the like in the support
can be suppressed at the interface between the support and the sacrificial layer at the time of
manufacture, so that generation of deflection in the support after removing the sacrificial layer
can be further improved. It can be suppressed.
[0012]
In the sensor device according to the first aspect, preferably, the support including the first
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support film and the second support film has a tensile internal stress as a whole. As described
above, when the support composed of the laminated film of the first support film and the second
support film is configured to have a tensile internal stress as a whole, the electrode plate is
formed due to the electrostatic force between the electrode plate and the diaphragm. It has been
confirmed by experiments of the present inventor that the support to be supported can be
suppressed from being moved to the substrate side. As described above, in the present invention,
since the support can be suppressed from moving to the substrate side, a high voltage can be
applied between the electrode plate and the diaphragm. As a result, the sensitivity of the sensor
device can be further improved.
[0013]
The diaphragm structure according to the second aspect of the present invention comprises a
diaphragm provided in a vibratable manner, an electrode plate provided opposite to the
diaphragm at a predetermined distance, and an electrode plate, and the inside of tension. A
support comprising a stressed first support membrane and a second support membrane
laminated to the first support membrane and having a compressive internal stress.
[0014]
In the diaphragm structure according to the second aspect, as described above, the first support
film supporting the electrode plate and having a tensile internal stress, and the second support
having a compressive internal stress and being stacked on the first support film. By providing the
support including the membrane, a part of the tensile internal stress of the first support
membrane can be canceled by the second support membrane having compressive internal stress,
thereby reducing the overall internal stress of the support. be able to.
As a result, it is possible to suppress bending of the support toward the substrate due to an
increase in tensile internal stress of the first support film, so it is possible to suppress breakage
of the support. In addition, since the support can be restrained from bending to the substrate side
due to an increase in tensile internal stress of the first support film, the range in which the
diaphragm can move without contacting the electrode plate can be enlarged. As a result, the
dynamic range of the diaphragm structure can be improved. In addition, by the second support
film being stacked on the first support film, it is possible to suppress an increase in the size of the
apparatus main body.
[0015]
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Hereinafter, embodiments of the present invention will be described based on the drawings.
[0016]
1 and 2 are cross-sectional views showing the structure of a microphone according to an
embodiment of the present invention.
3 and 4 are plan views of the microphone according to the embodiment shown in FIG. 5 to 7 are
schematic diagrams for explaining tensile internal stress and compressive internal stress of the
support of the microphone according to the embodiment shown in FIG. 1 shows a cross section
taken along the line 100-100 in FIG. 3, and FIG. 2 shows a cross section taken along the line
150-150 in FIG. First, the structure of a microphone 30 according to an embodiment of the
present invention will be described with reference to FIGS. 1 to 7. In the present embodiment, a
case where the present invention is applied to a microphone (acoustic sensor) 30 which is an
example of a sensor device and a diaphragm structure will be described.
[0017]
In the microphone 30 according to the present embodiment, as shown in FIGS. 1 and 2, the
etching stopper film 2 made of a silicon nitride film (SiN film) containing hydrogen (H) is formed
on the surface of the silicon substrate 1 There is. The etching stopper film 2 has a thickness of
about 0.05 μm to about 0.2 μm. Then, in a region where a diaphragm portion 4a described
later is formed, a partial quadrangular pyramid (a truncated square pyramid) (see FIGS. 1 and 3)
so as to penetrate the silicon substrate 1 and the etching stopper film 2 An opening 3 is formed.
The opening 3 functions as an air passage when sound enters. The silicon substrate 1 is an
example of the “substrate” in the present invention.
[0018]
A polysilicon film 4 having a thickness of about 0.1 μm to about 2.0 μm is formed on the upper
surfaces of the etching stopper film 2 and the opening 3. The polysilicon film 4 has conductivity
by being doped with an n-type impurity (phosphorus (P)). The sheet resistance of this polysilicon
film 4 is about 10 Ω / □ to about 100 Ω / □, preferably about 30 Ω / □ to about 50 Ω / □.
Also, as shown in FIGS. 3 and 4, the polysilicon film 4 has a disk-shaped diaphragm 4a whose
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center is disposed at the same position as the center of the opening 3 in plan view, and the
diaphragm 4a. 3 extends in the direction of arrow A in FIG. 3 and includes a connection wiring
portion 4b having a contact region 4c. The diaphragm 4 a is configured to be vibrated by the
sound that has entered through the opening 3. The diaphragm portion 4a is an example of the
"diaphragm" in the present invention.
[0019]
Here, in the present embodiment, the support film 6 constituting the support 5 is formed to be in
contact with the upper surfaces of the etching stopper film 2 and the polysilicon film 4. The
support film 6 is made of a silicon nitride film (SiN film) containing hydrogen (H) having a tensile
internal stress δSt6 of about 400 MPa, and has a thickness t6 of about 0.5 μm. Further, on the
upper surface of the support film 6, the support film 7 that constitutes the support 5 together
with the support film 6 is stacked. The support film 7 is made of a silicon nitride film (SiN film)
containing hydrogen (H) having a compressive internal stress δSt7 of about 20 MPa, and has a
thickness t7 of about 1 μm. In the present application, the tensile internal stress δSt6 is a force
acting in the internal direction of the support film 6 as shown in FIG. 5, and the support film is
laminated on the outside of the electrode plate portion 8a described later. It is a force that works
to move to the 6 side. That is, the tensile internal stress δSt6 is a force acting in the direction of
bending the central portion of the electrode plate portion 8a downward. Further, as shown in FIG.
6, the compressive internal stress δSt 7 is a force acting in the outward direction of the support
film 7 so that the outside of the support film 6 on which the support film 7 is laminated is moved
to the support film 6 side. It is a working force. That is, the compressive internal stress δSt7 is a
force acting in a direction to bend the central portion of the support film 6 upward. In the
present embodiment, the support 5 composed of the support films 6 and 7 is in a stressed state
as shown in FIG. The support 5 composed of the support films 6 and 7 is provided to support the
electrode plate portion 8a, as shown in FIG. 1, FIG. 2 and FIG. The internal stress δSt of the
entire support 5 is expressed by the following equation (1) when the compressive internal stress
δSt7 is negative.
[0020]
δSt = (δSt6 · t6 + δSt7 · t7) / (t6 + t7) (1) In this formula (1), the tensile internal stress δSt6 of
the support film 6 = 400 MPa, the thickness t6 of the support film 6 = 0.5 μm, the support film
Substituting the compressive internal stress δSt 7 of 7 = −20 MPa and the thickness t 7 of the
support film 7 = 1 μm, the overall internal stress δSt of the support 5 is δSt = 120 MPa, and in
the present embodiment, the entire support 5 It has a tensile internal stress of about 120 MPa.
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The support films 6 and 7 are examples of the “first support film” and the “second support
film” in the present invention respectively.
[0021]
A polysilicon film 8 having a thickness of about 0.1 μm to about 2 μm is formed on the lower
surface of the support film 6. The polysilicon film 8 has conductivity by being doped with an ntype impurity (phosphorus (P)). The sheet resistance of this polysilicon film 8 is about 10 Ω / □
to about 100 Ω / □, preferably about 30 Ω / □ to about 50 Ω / □. In addition, as shown in
FIG. 3, the polysilicon film 8 is formed of a disk-shaped electrode plate 8a whose center is
disposed at the same position as the center of the diaphragm 4a in plan view, and the electrode
plate 8a. It is formed to extend in the direction of arrow B in FIG. 3 and includes a connection
wiring portion 8b having a contact region 8c. The electrode plate portion 8a is an example of the
"electrode plate" in the present invention. An air gap 9 having a height of about 1 μm to about 5
μm is formed between the diaphragm 4 a and the electrode plate 8 a.
[0022]
A plurality of circular acoustic holes 10 connected to the air gap 9 from the outside are formed
in the electrode plate portion 8 a of the polysilicon film 8 and the support film 6 and the support
film 7 constituting the support 5.
[0023]
As shown in FIG. 1, in the support film 6 and the support film 7 constituting the support 5, the
contact hole 6a and the contact hole 7a in the portion corresponding to the contact region 4c of
the connection wiring portion 4b of the polysilicon film 4 respectively. Is formed.
Further, as shown in FIG. 2, in the support film 6 and the support film 7 constituting the support
5, contact holes 6b and contacts are respectively formed in portions corresponding to the contact
regions 8c of the connection wiring portion 8b of the polysilicon film 8. A hole 7b is formed.
[0024]
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8
Then, as shown in FIG. 1, a thickness of about 500 nm is provided on the contact region 4c of the
connection wiring portion 4b of the polysilicon film 4 via the contact hole 6a of the support film
6 and the contact hole 7a of the support film 7. An electrode 11 made of gold (Au) and chromium
(Cr) having a thickness of about 100 nm is formed. Further, as shown in FIG. 2, a thickness of
about 500 nm is provided on the contact region 8c of the connection wiring portion 8b of the
polysilicon film 8 through the contact hole 6b of the support film 6 and the contact hole 7b of
the support film 7. An electrode 12 made of gold (Au) and chromium (Cr) having a thickness of
about 100 nm is formed.
[0025]
FIG. 8 is a cross-sectional view for explaining the operation of the microphone according to an
embodiment of the present invention. Next, the operation of the microphone 30 according to the
present embodiment will be described with reference to FIGS. 1 and 8. A constant voltage is
applied between the diaphragm 4a and the electrode plate 8a via the electrodes 11 and 12.
[0026]
First, in a state where no sound enters the microphone 30, as shown in FIG. 1, the diaphragm 4a
does not vibrate. Therefore, since the capacitance between the diaphragm 4a and the electrode
plate 8a does not change, the amount of charge accumulated in the capacitor formed of the
diaphragm 4a and the electrode plate 8a does not change.
[0027]
On the other hand, when sound enters the microphone 30, the diaphragm 4a vibrates as shown
in FIG. Therefore, the capacitance between the diaphragm 4a and the electrode plate 8a fixed by
the support 5 changes, so the amount of charge accumulated in the capacitor formed of the
diaphragm 4a and the electrode plate 8a changes. Do. The change in the amount of charge is
output as an electrical signal corresponding to the incoming sound.
[0028]
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In the present embodiment, as described above, the electrode plate portion 8a is supported, and
the support film 6 having a tensile internal stress δSt6 (about 400 MPa) and the support film 6
are laminated, and the compressive internal stress δSt7 (about 20 MPa) By providing the
support 5 including the support film 7, the support film 7 having the compressive internal stress
δSt 7 (about 20 MPa) can cancel part of the tensile internal stress δSt 6 (about 400 MPa) of the
support film 6 Thus, the overall internal stress δSt of the support 5 can be reduced to a tensile
internal stress of about 120 MPa. Thereby, the support 5 can be suppressed from being bent
toward the silicon substrate 1 due to the tensile internal stress δSt 6 (about 400 MPa) of the
support film 6, so that the support 5 is prevented from being damaged. Can. Further, since the
support 5 can be restrained from bending toward the silicon substrate 1 due to the tensile
internal stress δSt6 (about 400 MPa) of the support film 6, the diaphragm 4a is in contact with
the electrode plate 8a. Accordingly, the range of the movable air gap 9 can be enlarged, and as a
result, the dynamic range of the microphone 30 can be improved. In addition, since the support
film 7 is stacked on the support film 6, the apparatus body can be prevented from being
enlarged.
[0029]
Further, in the present embodiment, argon is used when dry etching the support film 6 and the
support film 7 by forming the support film 6 and the support film 7 with a silicon nitride film
(SiN film) containing hydrogen (H). Since the support film 6 and the support film 7 can be etched
with a mixed gas of oxygen and CF 4, the manufacturing process can be simplified.
[0030]
Further, in the present embodiment, the silicon substrate 1 provided with the diaphragm portion
4 a and the support 5 is provided, and the support film 6 is disposed on the silicon substrate 1
side with respect to the support film 7. When a sacrificial layer 22 (see FIG. 16) having a tensile
internal stress larger than the stress δSt6 and the compressive internal stress δSt7 of the
support film 7 is formed between the support 5 and the silicon substrate 1, the sacrificial layer
22 (FIG. Since the support film 6 can be brought into contact with (see), the force generated at
the interface between the support 5 and the sacrificial layer 22 (see FIG. 16) can be suppressed.
As a result, generation of cracks and the like in the support 5 can be suppressed at the interface
between the support 5 and the sacrificial layer 22 (see FIG. 16) at the time of manufacture, so
that the sacrificial layer 22 (see FIG. 16) It is possible to further suppress the occurrence of
bending in the support 5 after removing the
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[0031]
Further, in the present embodiment, the support 5 comprised of a laminated film of the support
film 6 having a tensile internal stress δSt 6 of about 400 MPa and the support film 7 having a
compressive internal stress δSt 7 of about 20 MPa By configuring to have δSt, it is suppressed
that the support 5 supporting the electrode plate portion 8a is moved to the silicon substrate 1
side due to the electrostatic force between the electrode plate portion 8a and the diaphragm
portion 4a. It has been confirmed by the inventor's experiments described below that it can be
done. As described above, in the present embodiment, the movement of the support 5 toward the
silicon substrate 1 can be suppressed, so that a high voltage can be applied between the
electrode plate portion 8a and the diaphragm portion 4a. As a result, the sensitivity of the
microphone 30 can be further improved.
[0032]
Next, an experiment conducted to confirm the effect of the above-described embodiment will be
described. In addition, in this experiment, a total of five types of samples of the sample by
Examples 1-2 corresponding to this embodiment and the sample by Comparative Examples 1-3
were produced 16 each.
[0033]
The sample according to Example 1 has a tensile internal stress of about 400 MPa and a
compressive internal stress of about 20 MPa on a support film having a thickness of about 0.5
μm, as in the above-described embodiment. By laminating a support film having a thickness of 1
μm, a microphone having a support having a tensile internal stress of about 120 MPa as a whole
was formed. In addition, the sample according to Example 2 has a tensile internal stress of about
400 MPa, and has a compressive internal stress of about 20 MPa on a support film having a
thickness of about 0.2 μm, and a support film having a thickness of about 1 μm. To form a
support having an overall tensile internal stress of about 50 MPa. Also, the sample according to
Comparative Example 1 formed a single-layer support composed of a support film having a
tensile internal stress of about 800 MPa and a thickness of about 0.2 μm. In addition, the
sample according to Comparative Example 2 formed a single-layer support composed of a
support film having a tensile internal stress of about 400 MPa and a thickness of about 0.5 μm.
Further, the sample according to Comparative Example 3 formed a single-layer support
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11
composed of a support film having a compressive internal stress of about 20 MPa and a
thickness of about 1 μm. The samples according to Example 2 and Comparative Examples 1 to 3
were produced in the same manner as the sample according to Example 1 except for the above.
[0034]
And about the sample, it measured about the change of the electrostatic capacitance at the time
of applying a voltage from 0V to 12V between a diaphragm part and an electrode plate part. At
this time, if the amount of change in capacitance is within 2 × 10 <−13> F (farad), only the
diaphragm moves, and the support supporting the electrode plate comprises the electrode plate
and the diaphragm. It was judged that they did not move substantially (not flexed) due to the
electrostatic force between them. In addition, if the amount of change in capacitance is larger
than 2 × 10 <−13> F (farad), the diaphragm moves, and the support that supports the electrode
plate has the electrode plate and the diaphragm It was determined that the device was
substantially moving (flexing) due to the electrostatic force between them. The results are shown
in FIG.
[0035]
As shown in FIG. 9, in the sample according to Example 1 consisting of a laminated film of two
support films having a tensile internal stress of about 120 MPa as a whole of the support, in
seven out of the sixteen samples, electrode plates and The movement of the support due to the
electrostatic force between the diaphragm portion did not occur. Further, in the sample
according to Example 2 consisting of a laminated film of two support films having a tensile
internal stress of about 50 MPa as a whole of the support, in two samples out of 16, between the
electrode plate portion and the diaphragm portion There was no movement of the support due to
the electrostatic force of the On the other hand, in the samples according to Comparative
Examples 1 to 3 consisting of single-layer films each having a tensile internal stress of about 800
MPa, a tensile internal stress of about 400 MPa and a compressive internal stress of about 20
MPa, all samples out of 16 The movement of the support due to the electrostatic force between
the electrode plate portion and the diaphragm portion occurred. From the results of FIG. 9, by
laminating the support film having compressive internal stress on the support film having tensile
internal stress, by controlling the overall internal stress of the support to be tensile internal
stress, the microphone It could be confirmed that the withstand voltage can be increased.
[0036]
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10 to 24 are cross-sectional views for explaining a manufacturing process of a microphone
according to an embodiment of the present invention. The manufacturing process of the
microphone 30 according to an embodiment of the present invention will now be described with
reference to FIGS.
[0037]
First, as shown in FIG. 10, LP-CVD (Low Pressure Chemical Vapor Deposition) method using
dichlorosilane gas and ammonia gas or monosilane gas and ammonia gas is applied to the front
and back surfaces of the silicon substrate 1 respectively. An etching stopper film 2 and a mask
layer 20 having a thickness of about 0.05 μm to about 0.2 μm, which are made of a silicon
nitride film (SiN film) containing hydrogen (H), are formed. Thereafter, a polysilicon film 4 having
a thickness of about 0.1 [mu] m to about 2 [mu] m is formed on the entire top surface of the
etching stopper film 2 by LP-CVD using monosilane gas or disilane gas. Thereafter, in order to
make the polysilicon film 4 have a high concentration of n <+> type, solid phase phosphorus
diffusion is performed at about 875 ° C. using phosphorus oxychloride (POCl 3). Then, a resist
film 21 is formed in a predetermined region on the polysilicon film 4 by photolithography.
[0038]
Next, as shown in FIG. 11, the diaphragm 4a and the connection wiring 4b are formed by
patterning the polysilicon film 4 using the resist film 21 as a mask and using a dry etching
technique using a chlorine-based gas. . Thereafter, the resist film 21 is removed.
[0039]
Next, as shown in FIG. 12, a sacrificial layer 22 made of PSG (phosphorus-doped SiO 2) having a
thickness of about 1 μm to about 5 μm is formed by plasma CVD or atmospheric pressure CVD
so as to cover the entire surface. Do. Thereafter, a resist film 23 is formed on a predetermined
region on the sacrificial layer 22 using a photolithography technique.
[0040]
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13
Next, as shown in FIG. 13, using the resist film 23 as a mask, the sacrificial layer 22 for forming
the air gap 9 (see FIG. 1) is patterned using a dry etching technique with a fluorine-based gas.
Thereafter, the resist film 23 is removed.
[0041]
Next, as shown in FIG. 14, an LP-CVD method using a monosilane gas or a disilane gas is used to
form about 0.1 μm to about 2 μm thick on the upper surfaces of the etching stopper film 2, the
polysilicon film 4 and the sacrificial layer 22. A polysilicon film 8 having a thickness is formed.
Thereafter, in order to make the polysilicon film 8 have a high concentration of n <+> type, solid
phase phosphorus diffusion is performed at about 875 ° C. using phosphorus oxychloride (POCl
3). Thereafter, a resist film 24 is formed on a predetermined region of the polysilicon film 8
using a photolithography technique.
[0042]
Next, as shown in FIG. 15, by using the resist film 24 as a mask, the polysilicon film 8 is
patterned using a chlorine gas etching technique to form an electrode plate portion 8a and a
connection wiring portion 8b (FIG. 3). Form a reference). Thereafter, the resist film 24 is
removed.
[0043]
Next, in the present embodiment, as shown in FIG. 16, the upper surfaces of the etching stopper
film 2, the polysilicon film 4, the sacrificial layer 22 and the polysilicon film 8 are formed by LPCVD using dichlorosilane gas and ammonia gas. Then, a support film 6 made of a silicon nitride
film (SiN film) containing hydrogen (H) having a thickness of about 0.5 μm and tensile internal
stress δSt 6 (about 400 MPa) is formed. The conditions for forming the support film 6 having a
tensile internal stress δSt 6 of about 400 MPa are: substrate temperature: about 700 ° C. to
about 850 ° C. (preferably, about 770 ° C. to about 830 ° C.); 60 sccm to about 200 sccm,
ammonia flow rate: about 60 sccm to about 1200 sccm, pressure: about 0.3 Torr to about 0.5
Torr, gas flow ratio (dichlorosilane gas / ammonia gas): about 0.3 to about 10.
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14
[0044]
Next, in the present embodiment, hydrogen (having a thickness of about 1 μm and a
compressive internal stress δSt 7 (about 20 MPa) on the upper surface of the support film 6
using plasma CVD with monosilane gas, ammonia gas and nitrogen gas A support film 7 made of
a silicon nitride film (SiN film) containing H) is formed. The conditions for forming the support
film 7 having a compressive internal stress δSt 7 of about 20 MPa are: substrate temperature:
about 300 ° C. to about 400 ° C. (preferably, about 340 ° C. to about 360 ° C.), monosilane
flow rate: about 140 sccm Ammonia flow rate: about 20 sccm to about 50 sccm, nitrogen flow
rate: about 300 sccm to about 1500 sccm, pressure: about 4 Torr to about 5 Torr. Thus, a
support 5 supporting the electrode plate portion 8a and having a tensile internal stress of about
120 MPa as a whole is formed.
[0045]
Next, as shown in FIG. 17, a resist film 25 is formed in a predetermined region on the support
film 7 using a photolithography technique. Then, as shown in FIG. 18, by using the resist film 25
as a mask, the support film 7 and the support film 6 are etched using an etching technique with a
mixed gas of argon, oxygen and CF 4 to form the contact holes 7a and 6a. And contact holes 7b
and 6b (see FIG. 2).
[0046]
Next, as shown in FIG. 19, a resist film 26 is formed to cover a region other than the regions
where the electrodes 11 and 12 are formed by photolithography, and then a deposition method
is used to a thickness of about 500 nm. An electrode layer 27 is formed of gold (Au) having a
thickness of about 100 nm and chromium (Cr) having a thickness of about 100 nm. Then, the
resist film 26 is removed by using the lift-off method to remove the electrode layer 27 formed on
the upper surface and the side surface of the resist film 26, as shown in FIG. 1 to 3). Thereafter, a
resist film 28 is formed on predetermined regions of the support film 7 and the electrodes 11
and 12 by photolithography.
[0047]
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Next, as shown in FIG. 21, using the resist film 28 as a mask, the support films 7 and 6 are
etched using an etching technique with a mixed gas of argon, oxygen and CF4. Thereafter, using
the same resist film 28 as a mask, the polysilicon film 8 is etched using an etching technique
with a mixed gas of chlorine and oxygen. Thereby, as shown in FIG. 21, the acoustic hole 10 is
formed. Thereafter, the resist film 28 is removed.
[0048]
Next, as shown in FIG. 22, a resist film 29 is formed on a predetermined region on the surface of
the mask layer 20 using a photolithography technique. Thereafter, using the resist film 29 as a
mask, the mask layer 20 is patterned using a fluorine-based gas dry etching technique.
Thereafter, the resist film 29 is removed.
[0049]
Next, as shown in FIG. 23, using the mask layer 20 as a mask, an opening is formed in the silicon
substrate 1 using an anisotropic wet etching technique with an aqueous solution of tetramethyl
ammonium hydroxide (TMAH) or an aqueous solution of potassium hydroxide. Form 3
[0050]
Next, as shown in FIG. 24, the mask layer 20 is removed and the etching stopper film 2 in the
portion exposed from the opening 3 is etched using a dry etching technique using a fluorinebased gas.
Finally, hydrofluoric acid is allowed to flow from the acoustic hole 10 to remove the sacrificial
layer 22, thereby forming the air gap 9, and the microphone 30 of the embodiment shown in FIG.
1 is completed.
[0051]
It should be understood that the embodiments and examples disclosed herein are illustrative and
non-restrictive in every respect. The scope of the present invention is indicated not by the
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description of the embodiments and examples described above but by the claims, and further
includes all modifications within the meaning and scope equivalent to the claims.
[0052]
For example, although the example which applies the present invention to microphone 30 was
shown in the above-mentioned embodiment, the present invention may be applied to sensor
devices, such as not only this but other acoustic sensors, a pressure sensor, and an acceleration
sensor. The present invention may be applied to diaphragm structures such as mechanical
switches other than the sensor device.
[0053]
Further, in the above embodiment, while the support film 6 having the tensile internal stress
δSt6 is formed on the upper surface of the electrode plate portion 8a, the support film 7 having
the compressive internal stress δSt7 is formed on the upper surface of the support film 6
However, the present invention is not limited to this, and like the microphone 30a according to
the modification of the present embodiment shown in FIG. 25, the hole 31b corresponding to the
upper surface of the electrode plate 31a and the acoustic hole 32 of the electrode plate 31a. The
support 33 may be formed to cover the entire side surface of the support.
In addition, the support body 33 is comprised by the support film 34 which has tension internal
stress, and the support film 35 which has compression internal stress so that the support film 34
may be covered. In the microphone 30a according to this modification, since the support
strength of the electrode plate portion 31a by the support body 33 can be improved, the
vibration of the electrode plate portion 31a can be suppressed.
[0054]
In the above embodiment, the etching stopper film 2 and the mask layer 20 made of a silicon
nitride film (SiN film) containing hydrogen (H) are formed. However, the present invention is not
limited to this, and silicon oxide may be used. An etching stopper film and a mask layer made of
metal (SiO.sub.2) may be formed.
[0055]
In the above embodiment, an example of forming the sacrificial layer 22 made of PSG
(phosphorus-doped SiO 2) is shown, but the present invention is not limited to this, and BSG
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(boron-doped SiO 2) etc. if soluble in hydrofluoric acid The sacrificial layer may be formed of
[0056]
In the above embodiment, an example is shown in which the electrodes 11 and 12 made of gold
and chromium are formed. However, the present invention is not limited to this, and an electrode
made of a low resistance metal such as aluminum or copper is formed. It is also good.
[0057]
In the above embodiment, the etching stopper film 2, the support film 6, the support film 7, and
the mask layer 20 made of a silicon nitride film (SiN film) containing hydrogen (H) are formed,
but the etching rate by hydrofluoric acid is It is preferable that X of Si3NX be smaller than 4 so
as to be slower.
[0058]
FIG. 2 is a cross-sectional view of a microphone according to an embodiment of the present
invention;
FIG. 2 is a cross-sectional view of the microphone according to the embodiment shown in FIG. 1;
FIG. 2 is a plan view showing the structure of a microphone according to an embodiment shown
in FIG. 1;
FIG. 2 is a plan view showing the structure of a microphone according to an embodiment shown
in FIG. 1;
It is the schematic for demonstrating the tension internal stress of the support film of the
microphone by one Embodiment shown in FIG. It is the schematic for demonstrating the
compression internal stress of the support film of the microphone by one Embodiment shown in
FIG. FIG. 6 is a schematic view for explaining tensile internal stress and compressive internal
stress of the support of the microphone according to the embodiment shown in FIG. 1; FIG. 6 is a
cross-sectional view for explaining the operation of the microphone according to an embodiment
of the present invention. It is a graph which shows the relationship between the internal stress of
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a support body, and the number of microphones in which movement (deflection) of the support
body did not substantially occur when a voltage is applied between the diaphragm portion and
the electrode plate portion. FIG. 7 is a cross-sectional view for explaining a manufacturing
process of the microphone according to one embodiment of the present invention. FIG. 7 is a
cross-sectional view for explaining a manufacturing process of the microphone according to one
embodiment of the present invention. FIG. 7 is a cross-sectional view for explaining a
manufacturing process of the microphone according to one embodiment of the present invention.
FIG. 7 is a cross-sectional view for explaining a manufacturing process of the microphone
according to one embodiment of the present invention. FIG. 7 is a cross-sectional view for
explaining a manufacturing process of the microphone according to one embodiment of the
present invention. FIG. 7 is a cross-sectional view for explaining a manufacturing process of the
microphone according to one embodiment of the present invention. FIG. 7 is a cross-sectional
view for explaining a manufacturing process of the microphone according to one embodiment of
the present invention. FIG. 7 is a cross-sectional view for explaining a manufacturing process of
the microphone according to one embodiment of the present invention. FIG. 7 is a cross-sectional
view for explaining a manufacturing process of the microphone according to one embodiment of
the present invention. FIG. 7 is a cross-sectional view for explaining a manufacturing process of
the microphone according to one embodiment of the present invention. FIG. 7 is a cross-sectional
view for explaining a manufacturing process of the microphone according to one embodiment of
the present invention. FIG. 7 is a cross-sectional view for explaining a manufacturing process of
the microphone according to one embodiment of the present invention. FIG. 7 is a cross-sectional
view for explaining a manufacturing process of the microphone according to one embodiment of
the present invention. FIG. 7 is a cross-sectional view for explaining a manufacturing process of
the microphone according to one embodiment of the present invention. FIG. 7 is a cross-sectional
view for explaining a manufacturing process of the microphone according to one embodiment of
the present invention. FIG. 7 is a cross-sectional view showing the structure of a microphone
according to a modification of an embodiment of the present invention.
Explanation of sign
[0059]
DESCRIPTION OF SYMBOLS 1 Silicon substrate (substrate) 4a Diaphragm part (diaphragm) 5, 33
Support body 6, 34 Support film (1st support film) 7, 35 Support film (2nd support film) 8a, 31a
Electrode plate part (electrode plate) 30 , 30a Microphone (acoustic sensor, sensor device,
diaphragm structure)
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