U.S. patent application number 14/098630 was filed with the patent office on 2015-06-11 for piezoelectric device.
This patent application is currently assigned to MURATA MANUFACTURING CO., LTD.. The applicant listed for this patent is MURATA MANUFACTURING CO., LTD.. Invention is credited to Toshio Imanishi, Ville Kaajakari, Keiichi Umeda.
Application Number | 20150162523 14/098630 |
Document ID | / |
Family ID | 53272057 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150162523 |
Kind Code |
A1 |
Umeda; Keiichi ; et
al. |
June 11, 2015 |
PIEZOELECTRIC DEVICE
Abstract
A piezoelectric device that includes: a diaphragm; a supporting
part configured to support at least a portion of an end of the
diaphragm; a piezoelectric film disposed along a portion supported
by the supporting part on the diaphragm, a width of the film along
the supported portion being narrower than a width of the portion; a
lower electrode disposed at a face of the piezoelectric film on a
diaphragm side; and an upper electrode disposed on a face of the
piezoelectric film on an opposite side to the diaphragm.
Inventors: |
Umeda; Keiichi;
(Nagaokakyo-shi, JP) ; Imanishi; Toshio;
(Nagaokakyo-shi, JP) ; Kaajakari; Ville;
(Altadena, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MURATA MANUFACTURING CO., LTD. |
Nagaokakyo-shi |
|
JP |
|
|
Assignee: |
MURATA MANUFACTURING CO.,
LTD.
Nagaokakyo-shi
JP
|
Family ID: |
53272057 |
Appl. No.: |
14/098630 |
Filed: |
December 6, 2013 |
Current U.S.
Class: |
310/331 |
Current CPC
Class: |
H04R 17/025 20130101;
H04R 2201/003 20130101; H01L 41/0478 20130101; H01L 41/1138
20130101; H04R 19/016 20130101; H01L 41/187 20130101; H04R 17/02
20130101 |
International
Class: |
H01L 41/113 20060101
H01L041/113; H01L 41/047 20060101 H01L041/047 |
Claims
1. A piezoelectric device comprising: a diaphragm having a first
surface and a second surface; a supporting part adjacent the second
surface of the diaphragm and configured to support at least a
portion of an end of the diaphragm; a piezoelectric film adjacent
the first surface of the diaphragm and disposed along the portion
of the end of the diaphragm supported by the supporting part, a
width of the piezoelectric film along the supported portion being
narrower than a width of the supported portion; and an electrode
disposed on a surface of the piezoelectric film opposite to the
diaphragm.
2. The piezoelectric device according to claim 1, wherein the
diaphragm is formed of a degenerate semiconductor.
3. The piezoelectric device according to claim 2, wherein the
electrode is an upper electrode and the diaphragm is configured to
function as a lower electrode for the piezoelectric film.
4. The piezoelectric device according to claim 1, wherein the
electrode is an upper electrode and the piezoelectric device
includes a lower electrode disposed on a surface of the
diaphragm.
5. The piezoelectric device according to claim 1, wherein the
diaphragm has a substantially rectangular shape.
6. The piezoelectric device according to claim 5, wherein the
supporting part is configured to support a pair of opposing sides
of the diaphragm.
7. The piezoelectric device according to claim 6, further
comprising a plurality of piezoelectric films disposed along each
side of the pair of sides of the diaphragm.
8. The piezoelectric device according to claim 7, wherein the
diaphragm is divided along a first substantial center line
substantially parallel to the pair of opposing sides.
9. The piezoelectric device according to claim 8, wherein the
diaphragm is further divided along a second substantial center line
substantially perpendicular to the pair of opposing sides.
10. The piezoelectric device according to claim 5, wherein the
supporting part is configured to support all sides of the
diaphragm, and a plurality of piezoelectric films are disposed
along each side of all the sides of the diaphragm.
11. The piezoelectric device according to claim 1, wherein the
diaphragm is thinner at a center region thereof than a region
thereof where the piezoelectric film is disposed.
12. The piezoelectric device according to claim 1, wherein the
piezoelectric film has a compressive stress, and the upper
electrode has a tensile stress.
13. The piezoelectric device according to claim 1, wherein the
supporting part includes a supporting part and an insulating
layer.
14. The piezoelectric device according to claim 13, wherein the
insulating layer is adjacent the diaphragm.
15. The piezoelectric device according to claim 14, wherein the
insulating layer is silicon oxide.
16. The piezoelectric device according to claim 1, further
comprising a plurality of piezoelectric films adjacent the first
surface of the diaphragm, the plurality of piezoelectric films
being electrically coupled in parallel.
17. The piezoelectric device according to claim 1, wherein the
diaphragm has a substantially circular shape.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to piezoelectric devices.
[0002] Electronic apparatuses such as cellular phones may be
mounted with a plurality of microphones. For instance, a cellular
phone may be provided with a microphone for detecting ambient sound
(environmental sound) for a purpose of noise canceling in addition
to a microphone for detecting a transmission voice during a call.
As more and more electronic apparatuses are mounted with a
plurality of microphones, downsizing of microphones is increasingly
demanded.
[0003] Against a background like this, in recent years, a
microphone manufactured using a micro electro mechanical systems
(MEMS) technology (hereinafter, referred to as a MEMS microphone)
has been drawing an attention (for instance, Patent Publication JP
2004-506394 A).
[0004] In mounting a microphone onto an electronic apparatus, not
only downsizing of a microphone but also sensitivity enhancement of
the microphone is required. Sensitivity enhancement is required
also for a MEMS microphone.
SUMMARY OF THE INVENTION
[0005] The present invention has been made in consideration of such
circumstances, and an object thereof is to enhance the sensitivity
of a MEMS microphone.
[0006] A piezoelectric device related to one aspect of the present
invention includes: a diaphragm; a supporting part configured to
support at least a part of an end of the diaphragm; a piezoelectric
film disposed on the diaphragm along a portion supported by the
supporting part, a width of the film along the supported portion
being narrower than a width of the portion; a lower electrode
disposed on a surface of a diaphragm side of the piezoelectric
film; and an upper electrode disposed on a face of the
piezoelectric film on an opposite side to the diaphragm.
[0007] According to the present invention, the sensitivity of a
MEMS microphone can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a view showing an appearance of a piezoelectric
device of one embodiment of the present invention;
[0009] FIG. 2 is a cross-sectional view showing the piezoelectric
device;
[0010] FIG. 3 is a view showing one example of a wiring of an
electrode of the piezoelectric device;
[0011] FIG. 4 is a graph showing one example of a relation between
a width of a piezoelectric part and voltage sensitivity;
[0012] FIG. 5 is a graph showing one example of a relation between
a width of the piezoelectric part and generated energy;
[0013] FIG. 6 is a graph showing one example of a relation between
temperature and Young's modulus;
[0014] FIG. 7 is a view showing another configuration example of
the piezoelectric device;
[0015] FIG. 8 is a view showing another configuration example of
the piezoelectric device;
[0016] FIG. 9 is a view showing one configuration example of a
diaphragm in which a vicinity of a center thereof is made thin;
[0017] FIG. 10 is a view showing another configuration example of
the piezoelectric device;
[0018] FIG. 11 is a view showing another configuration example of
the piezoelectric device; and
[0019] FIG. 12 is a view showing another configuration example of
the piezoelectric device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] One embodiment of the present invention is described below
with reference to the drawings. FIG. 1 is a view showing an
appearance of a piezoelectric device of one embodiment of the
present invention. A piezoelectric device 100 is a device for
configuring a MEMS microphone that converts sound pressure into an
electrical signal, and includes a diaphragm 110, a supporting part
111, and piezoelectric parts 112. The piezoelectric device 100 is
divided into two by a minute slit 113 of about 1 .mu.m or less wide
for instance.
[0021] The diaphragm 110 is a thin film that vibrates due to sound
pressure and can be formed of silicon (Si). The diaphragm 110 has a
substantially rectangular shape, wherein lower parts of a facing
set of sides 114 and 115 are supported by the supporting part 111.
In other words, the diaphragm 110 has a both-end supported beam
structure. It is beneficial that the diaphragm 110 is degenerate
silicon, and has a function as a lower electrode of the
piezoelectric part 112 as described later. What is called a
degenerate silicon or degenerate semiconductor doped with a dopant
in high concentration (1.times.10.sup.19 cm.sup.-3 or over). To be
more precise, by doping phosphorus (P), arsenic (As), or antimony
(Sb) at a concentration of 1.times.10.sup.19 cm.sup.-3 or over into
Si as an n-type dopant (a donor), a degenerate semiconductor can be
formed. A degenerate semiconductor may also be formed by doping a
p-type dopant (an acceptor) into Si.
[0022] The piezoelectric parts 112 are disposed along the portion
supported by the supporting part 111 on the diaphragm 110. As shown
in FIG. 1, a width (A) of the piezoelectric part 112 (a width of a
piezoelectric film 210 as described later) is narrower than a width
(B) of the portion supported by the supporting part 111 on the
diaphragm 110 (in other words, a width of the side 114). For
instance, the width (A) of the piezoelectric part 112 may be about
100 .mu.m, and the width (B) of the portion supported by the
supporting part 111 on the diaphragm 110 may be about 300 .mu.m.
Although four piezoelectric parts 112 are disposed on the diaphragm
110 in the configuration shown in FIG. 1, the number of
piezoelectric parts 112 is not limited to this. In the
configuration shown in FIG. 1, although ends of the piezoelectric
parts 112 are disposed on the sides 114 and 115, ends may be
disposed separately from the sides 114 and 115.
[0023] FIG. 2 is a cross-sectional view of the piezoelectric device
100 at a line X-Y shown in FIG. 1. The supporting part 111 includes
a substrate 200 and an insulating layer 201.
[0024] The substrate 200 is formed of silicon (Si) for instance.
The insulating layer 201 is formed of silicon oxide (SiO.sub.2) for
instance. The diaphragm 110 is formed on the supporting part 111
formed in this manner.
[0025] Each of the piezoelectric parts 112 disposed along the
portion supported by the supporting part 111 on the diaphragm 110
includes a piezoelectric film 210, an upper electrode 211, and
wirings 212 and 213.
[0026] The piezoelectric film 210 is disposed on the diaphragm 110
so as to be vibrated in association with vibration of the diaphragm
110. The piezoelectric film 210 is a thin film of a piezoelectric
body that converts force applied by the vibration to voltage, and
is formed of scandium doped aluminum nitride (ScAlN) for instance.
ScAlN is formed by substituting a part of aluminum (Al) in aluminum
nitride (AlN) with scandium (Sc). For instance, ScAlN used for the
piezoelectric film 210 may be formed by substituting Al with Sc so
that Sc becomes about 40 atom % when atomic concentration that is a
sum of the number of Al atoms and the number of Sc atoms is assumed
to be 100 atom %. The thickness of the piezoelectric film 210 may
be about 500 nm for instance. A ratio of a width (D) of a vibration
portion of the piezoelectric film 210 to a width (C) from a center
of the diaphragm 110 to the supporting part 111 may be about 40%
for instance. The width (C) may be about 300 .mu.m and the width
(D) may be about 120 .mu.m for instance.
[0027] The upper electrode 211 is disposed on an upper side of the
piezoelectric film 210. The upper electrode 211 is a metal
electrode and may be formed of aluminum (Al) for instance, and may
have a thickness of about 50 nm. The upper electrode 211 may have
tensile stress. Since the piezoelectric film 210 formed of ScAlN
has a compressive stress, by allowing the upper electrode 211 to
have a tensile stress, a stress at the piezoelectric part 112 is
corrected and a deformation of the diaphragm 110 can be
suppressed.
[0028] The wiring 212 is electrically coupled to the upper
electrode 211. The wiring 213 is electrically coupled to the lower
electrode (the diaphragm 110). The wirings 212 and 213 are formed
by using gold (Au), platinum (Pt), titanium (Ti), aluminum (Al), or
the like for instance.
[0029] In the piezoelectric device 100 of the configuration
described above, the piezoelectric film 210 vibrates in association
with a vibration of the diaphragm 110 caused by sound pressure.
Voltage corresponding to the vibration of the piezoelectric film
210 is output through the wirings 212 and 213 of the piezoelectric
body 112. As shown in FIG. 1, four piezoelectric bodies 112 are
provided in the piezoelectric device 100. The four piezoelectric
bodies 112 can be electrically coupled in parallel as shown in FIG.
3 for instance. The coupling shown in FIG. 3 is just an example and
a form of coupling of the piezoelectric bodies 112 is not limited
to this.
[0030] In the piezoelectric device 100, as shown in FIG. 1, the
width (A) of the piezoelectric part 112 (the width of the
piezoelectric film 210) is narrower than the width (B) of the
portion supported by the supporting part 111 of the diaphragm 110
(in other words, the width of the side 114). Such a structure
increases the stress applied to the piezoelectric part 112 by the
vibration of the diaphragm 110 caused by sound pressure compared to
the case where the piezoelectric part 112 has the same width as the
diaphragm 110 (in other words, the width (A) of the piezoelectric
part 112=the width (B) of the diaphragm 110). Consequently, the
stress applied to a unit area of the piezoelectric part 112 becomes
large, and the voltage sensitivity and the generated energy of the
piezoelectric part 112 can be increased. In other words,
sensitivity of the MEMS microphone configured by using the
piezoelectric device 100 can be improved.
[0031] FIG. 4 is a graph showing one example of a relation between
the width of the piezoelectric part 112 and the voltage sensitivity
at the piezoelectric device 100. In FIG. 4, the horizontal axis
represents a ratio (%) of the width (A) of the piezoelectric part
112 to the width (B) of the diaphragm 110, and the vertical axis
represents the voltage sensitivity (mV/Pa) showing output voltage
(mV) per sound pressure (Pa) at the piezoelectric part 112. As
shown in FIG. 4, the voltage sensitivity increases as the ratio of
the width of the piezoelectric part 112 to that of the diaphragm
110 decreases. Accordingly, at the piezoelectric device 100 of the
embodiment, the voltage sensitivity can be improved.
[0032] FIG. 5 is a graph showing one example of a relation between
the width of the piezoelectric part 112 and the generated energy.
In FIG. 5, the horizontal axis represents the ratio (%) of the
width (A) of the piezoelectric part 112 to the width (B) of the
diaphragm 110, and the vertical axis represents the generated
energy (fJ/Pa) per sound pressure at the piezoelectric part 112. As
shown in FIG. 5, the generated energy increases as the ratio of the
width of the piezoelectric part 112 to that of the diaphragm 110
decreases. Accordingly, at the piezoelectric device 100 of the
embodiment, the generated energy can be enlarged.
[0033] When the width of the piezoelectric part 112 becomes narrow,
a capacitance value of the piezoelectric part 112 becomes small.
When the capacitance value becomes small, impedance mismatching
with an amplifier circuit may be likely to occur due to an
impedance increase, or an influence of parasitic capacitance may be
likely to become large. Therefore, the width (A) of the
piezoelectric part 112 is determined by taking account of a
trade-off between improvement of the voltage sensitivity and an
increase in the impedance and such.
[0034] When Young's modulus of the diaphragm 110 changes with
temperature, the voltage sensitivity of the piezoelectric device
100 also changes. In this respect, in the embodiment, since the
diaphragm 110 is formed of a degenerate semiconductor, a change of
Young's modulus of the diaphragm 110 with temperature can be
suppressed. In other words, a change of the voltage sensitivity of
the piezoelectric device 100 can be suppressed.
[0035] FIG. 6 is a graph showing one example of a relation between
temperature and Young's modulus. In FIG. 6, the horizontal axis
represents temperature (.degree. C.) and the vertical axis
represents Young's modulus (GPa). In FIG. 6, four temperature
characteristics (P1) to (P4) of the diaphragm 110 with different
doping concentrations are shown. P1 in FIG. 6 shows a temperature
characteristic when nothing is doped into Si. P2 in FIG. 6 shows a
temperature characteristic when an n-type dopant is doped into Si
at a concentration of 1.times.10.sup.19 cm.sup.-3. P3 in FIG. 6
shows a temperature characteristic when the n-type dopant is doped
into Si at a concentration of 5.times.10.sup.19 cm.sup.-3. P4 in
FIG. 6 shows a temperature characteristic when the n-type dopant is
doped into Si at a concentration of 8.times.10.sup.19 cm.sup.-3. As
shown in FIG. 6, in comparison with Young's modulus in a case P1
where nothing is doped into Si, by making the doping concentration
in Si 1.times.10.sup.19 cm.sup.-3 or more, in other words, by
making Si into a degenerate semiconductor, the change in Young's
modulus due to temperature change can be suppressed. With the
diaphragm 110 being formed of a degenerate semiconductor, the
change of the voltage sensitivity of the piezoelectric device 100
can be suppressed.
[0036] FIG. 7 is a view showing another configuration example of
the piezoelectric device. As for the same components as those of
the piezoelectric device 100 shown in FIG. 1, the same reference
numerals are given and descriptions are omitted. As shown in FIG.
7, in the piezoelectric device 700, lower parts of all sides 710 to
713 of the diaphragm 110 are supported by the supporting part 111.
In other words, the diaphragm 110 has an entire circumference
supported beam structure. A configuration of a cross-section at an
X-Y line shown in FIG. 7 is equivalent to the configuration shown
in FIG. 2.
[0037] The piezoelectric device 100 shown in FIG. 1 has the
both-end supported beam structure, wherein the diaphragm 110 is
provided with the slit 113. For that reason, in the piezoelectric
device 100, while the diaphragm 110 is easily bendable and the
voltage sensitivity can be improved, the diaphragm 110 may be
deformed due to stresses of the piezoelectric films 210 and the
upper electrodes 211, which may change an amount of sound leakage
from the slit 113 and may cause variations in the voltage
sensitivity. On the contrary, as shown in FIG. 7, the piezoelectric
device 700 is not provided with the slit 113 of the piezoelectric
device 100. Therefore, in the piezoelectric device 700, no sound
leakage from the slit occurs and the variations in the voltage
sensitivity can be suppressed.
[0038] FIG. 8 is a view showing another configuration example of
the piezoelectric device. As for the same components as those of
the piezoelectric device 100 shown in FIG. 1, the same reference
numerals are given and descriptions are omitted. As shown in FIG.
8, in a piezoelectric device 800, a slit 810 is provided along a
substantial center line 810 substantially parallel to the sides 114
and 115 supported by the supporting part 111 in addition to the
slit 113. The diaphragm 110 is divided into four by the slits 113
and 810. In other words, the diaphragm 110 has a cantilever
structure. By making the diaphragm 110 the cantilever structure,
the diaphragm 110 becomes more flexible than in the case of the
piezoelectric device 100 shown in FIG. 1, and the voltage
sensitivity can be improved.
[0039] FIG. 9 is a view showing one configuration example in which
a vicinity of a center of the diaphragm 110 is made thin in the
piezoelectric device 100 shown in FIG. 1. As shown in FIG. 9, a
thickness of a region 901 in the vicinity of the center of the
diaphragm 110 can be formed thinner than a thickness of a region
900 of the diaphragm 110, where the piezoelectric film 210 is
disposed. In this manner, by thinning the thickness of the region
901 in the vicinity of the center of the diaphragm 110, the
diaphragm 110 is made to be easily bendable, and the voltage
sensitivity can be improved. Since the piezoelectric device 800
shown in the FIG. 8 is not provided with the slit 810, the
deformation of the diaphragm 110 is suppressed, and the variations
in the voltage sensitivity are suppressed.
[0040] Changing the thickness of the region 900 in the diaphragm
110, where the piezoelectric film 210 is disposed, changes a state
of expansion and contraction of the piezoelectric film 210
resulting from the vibration of the diaphragm 110 and changes
voltage output characteristics of the piezoelectric part 112. More
specifically, thinning the thickness of the region 900 in the
diaphragm 110, where the piezoelectric film 210 is disposed, when
the piezoelectric film 210 bends downwardly for instance, may
increase an amount of contraction of an under side of the
piezoelectric film 210, may cancel out voltage output resulting
from expansion of an upper side of the piezoelectric film 210, and
may reduce the output voltage from the piezoelectric part 112. For
this reason, thinning only the region 901 in a vicinity of a center
without changing the thickness of the region 900 can improve the
voltage sensitivity without influencing the voltage output
characteristics of the piezoelectric part 112.
[0041] Not only in the configuration shown in FIG. 1 but also in
the configurations shown in FIG. 7 and FIG. 8, a region in the
vicinity of the center of the diaphragm 110 may be thinned.
[0042] FIG. 10 is a view showing another configuration example of
the piezoelectric device. As for the same components as those of
the piezoelectric device 100 shown in FIG. 1, the same reference
numerals are given and descriptions are omitted. As shown in FIG.
10, the diaphragm 110 has a substantially circular shape in a
piezoelectric device 1000. In this case also, the width (A) of the
piezoelectric part 112 is made narrower than the width (B) of the
portion supported by supporting part 111 in the diaphragm 110 of
the piezoelectric part 112. In this manner, the diaphragm 110 may
have not only a substantially rectangular shape but also an
arbitrary shape. Although four piezoelectric parts 112 are disposed
on the diaphragm 110 in FIG. 10, the number of the piezoelectric
parts 112 is not limited to this but may be any number. For
instance, as shown in FIG. 11 three piezoelectric parts 112 may be
disposed on the diaphragm 110 having a substantially circular
shape.
[0043] FIG. 12 is a view showing another configuration example of
the piezoelectric device. As for the same components as those of
the piezoelectric device 100 shown in FIG. 2, the same reference
numerals are given and descriptions are omitted. As shown in FIG.
2, the diaphragm 110 is used as a lower electrode of the
piezoelectric part 112 in the piezoelectric device 100. On the
other hand, in a piezoelectric device shown in FIG. 12, a lower
electrode 1210 is provided separately from the diaphragm 110. The
lower electrode 1210 is a metal electrode and may be formed of
aluminum (Al) for instance, and may have a thickness of about 50
nm.
[0044] The embodiments of the present invention have been described
above. According to the embodiments, the piezoelectric device is
formed so that the width (A) of the piezoelectric part 112 is
narrower than the width (B) of the portion supported by the
supporting part 111 in the diaphragm 110. This increases a stress
applied to a unit area of the piezoelectric part 112, and enables
enhancement of the voltage sensitivity and the generated energy in
the piezoelectric part 112. In other words, the sensitivity of a
MEMS microphone configured by using the piezoelectric device 100
can be improved.
[0045] According to the embodiment, the diaphragm 110 can be formed
of a degenerate semiconductor. Thereby, variations in the Young's
modulus of the diaphragm 110 with temperature can be suppressed,
and variations in the voltage sensitivity of the piezoelectric
device with temperature can be suppressed.
[0046] According to the embodiment, the diaphragm 110 formed of a
degenerate semiconductor can be used as a lower electrode of the
piezoelectric part 112. Thereby, the piezoelectric device 100 can
be downsized as compared with a case where the lower electrode is
formed separately from the diaphragm 110.
[0047] According to the embodiment, as shown in FIG. 1, making the
diaphragm 110 have the both-end supported beam structure makes it
possible to make the diaphragm 110 easily bendable and to improve
the voltage sensitivity of the piezoelectric device.
[0048] According to the embodiment, as shown in FIG. 8, when making
the diaphragm 110 have the both-end supported beam structure, the
substantial center line 810 substantially parallel to the sides 114
and 115 of the supporting part 111 makes the diaphragm 110 have a
separate configuration, thereby, making the diaphragm 110 more
bendable and being able to improve the voltage sensitivity of the
piezoelectric device.
[0049] According to the embodiment, as shown in FIG. 7, making the
diaphragm 110 have the entire circumference supported beam
structure makes it possible to suppress the deformation of the
diaphragm 110 and to suppress the variations in the voltage
sensitivity caused by the deformation of the diaphragm 110.
[0050] According to the embodiment, as shown in FIG. 9, making the
region 901 in the vicinity of the center of the diaphragm 110 thin
makes it possible to make the diaphragm 110 more bendable and to
improve the voltage sensitivity of the piezoelectric device.
[0051] According to the embodiment, it is possible to make the
upper electrode 211 formed at an upper side of the piezoelectric
film 210 having a compressive stress have a tensile stress.
Thereby, the stress at the piezoelectric part 112 is corrected, and
the deformation of the diaphragm 110 is suppressed.
[0052] The embodiment is for facilitating comprehension of the
present invention, and not for comprehending by limiting the
present invention. The present invention can be changed and/or
improved without being deviated from the gist thereof. The present
invention includes also equivalents thereof.
[0053] For instance, in the embodiment, although an example is
described in which the piezoelectric device is used as a MEMS
microphone by vibrating the diaphragm by sound pressure, uses of
the piezoelectric device is not limited to this, and is usable for
a sensor that detects vibration of a medium in the surrounding of
the piezoelectric device.
* * * * *