VIBRATION TRANSDUCER AND MANUFACTURING METHOD THEREFOR
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to vibration transducers and in particular
to wave transducers such as miniature condenser microphones serving as MEMS
sensors. The present invention also relates to manufacturing methods of vibration
transducers.
The present application claims priority on Japanese Patent Application
No. 2007-256905 and Japanese Patent Application No. 2007-256906, the contents of
which are incorporated herein by reference.
Description of the Related Art
Various types of vibration transducers have been developed and
disclosed in various documents such as Patent Documents 1, 2, 3 and Non-Patent
Document 1.
Patent Document 1: Japanese Patent Application Publication No. H09-
508777
Patent Document 2: Japanese Patent Application Publication No. 2004-
506394
Patent Document 3: U.S. Patent No. 4,776,019
Non-Patent Document 1: The paper entitled "MSS-01-34" jpublished by the
Japanese Institute of Electrical Engineers
Miniature condenser microphones have been conventionally known as
typical types of vibration transducers and have been produced by way of
semiconductor device manufacturing processes.

Condenser microphones are referred to as MEMS microphones (where
MEMS stands for Micro Electro Mechanical System). A typical example of
condenser microphones is constituted of a substrate, a diaphragm, and a plate. The
diaphragm and plate serving as opposite electrodes, which are distanced from each
other, are composed of films deposed on the substrate and are supported above the
substrate. When the diaphragm vibrates due to sound waves relative to the plate, the
electrostatic capacitance between the diaphragm and the plate varies due to the
displacement of the diaphragm, and then variations of electrostatic capacitance are
converted into electric signals. This condenser microphone (or vibration transducer)
is designed such that the peripheral portion of the plate joins an insulating film.
In the structure in which the plate joins the insulating film, however, a
parasitic capacitance occurs between the diaphragm or the substrate: and the plate
which joins the insulating film serving as a dielectric layer in the peripheral portion,
thus reducing the sensitivity of the vibration transducer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a vibration transducer
having high sensitivity.
It is another object of the present invention to provide a manufacturing
method of the vibration transducer.
In a first aspect of the present invention, a vibration transducer includes
a diaphragm having a conductive property, a plate having a conductive property,
which is positioned opposite to the diaphragm, and a plurality of first spacers having
pillar shapes which are formed using a deposited film having an insulating property
joining the plate and which supports the plate relative to the diaphragm with a gap

therebetween, wherein an electrostatic capacitance formed between the diaphragm
and the plate is varied when the diaphragm vibrates relative to the plate.
In the fixed region of the diaphragm which does not vibrate relative to
the plate, a parasitic capacitance is formed between the diaphragm and the plate,
which are positioned opposite to each other; hence, it is preferable that the first
spacers each having a high dielectric constant (higher than that of the air) be each
reduced in area in plan view. That is. the plate is supported by the first spacers,
which are not formed in ring shapes but are formed in a pillar shape, whereby it is
possible to reduce the electrostatic capacitance between the diaphragm and the plate,
thus improving the sensitivity. The geometric shapes of the first spacers are not
necessarily limited to pillar shapes but can also be formed in flat shapes. The present
invention does not need the support having a structurally closed shape but multiple
supports which are formed in any shape for supporting the plate. It may be possible
to reduce the parasitic capacitance by forming the plate or the diaphragm by use of an
insulating substance in the region in which the diaphragm and the plate is positioned
opposite to each other; however, this causes complexity in film structure with respect
to at least one of the diaphragm and the plate
The aforementioned vibration transducer is manufactured in such a way
that a plurality of holes are formed in the plate; isotropic etching is performed using
the plate as a mask so as to remove a part of the deposited film, thus forming the gap
between the plate and the diaphragm; and the first spacers are formed by use of the
remaining deposited film. Since the plate is used as the etching mask so as to form
the first spacers, it is possible to reduce the total number of masks, thus reducing the
manufacturing cost.
That is, it is preferable that the plate has a plurality of holes which allow

an etchant to transmit therethrough in isotropic etching, thus simultaneously forming
the first spacers and the gap between the plate and the diaphragm
The vibration transducer further includes a substrate and a plurality of
second spacers having pillar shapes which are formed using a deposited film having
an insulating property and which support the plate relative to the substrate with a gap
therebetween, wherein an electrostatic capacitance formed between the diaphragm
and the plate is varied when the diaphragm vibrates relative to the plate.
In consideration of a parasitic capacitance formed in the region in which
the plate and the substrate are positioned opposite to each other via the second
spacers having high dielectric constants (higher than the dielectric constant of the air)
therebetween, it is preferable that the second spacers each be reduced in area in plan
view. That is, the plate is supported by the second spacers which are formed not in
ring shapes but in pillar shapes, whereby it is possible to reduce the electrostatic
capacitance between the substrate and the plate, thus improving the sensitivity of the
vibration transducer. The geometric shapes of the second spacers are not necessarily
limited to pillar shapes but can also be formed in flat shapes. The present invention
does not need the support having a structurally closed shape but multiple supports
which are formed in any shapes for supporting the plate. It may be possible to reduce
the parasitic capacitance in the region in which the plate and the substrate are
positioned opposite to each other with the second spacers therebetween by forming
the prescribed region of the plate joining the second spacers by use of an insulating
substance; however, this causes complexity in the film structure of the plate.
The vibration transducer is manufactured in such a way that a plurality
of holes is formed in the plate; isotropic etching is performed using the plate as a
mask so as to remove a part of the deposited film, thus forming the gap between the

plate and the substrate; and the second spacers are formed using the remaining of the
deposited film. Since the plate is used as an etching mask for use in the formation of
the second spacers, it is possible to reduce the number of masks, thus reducing the
manufacturing cost.
That is, it is preferable that the plate has a plurality of holes allowing an
etchant to transmit therethrough in isotropic etching, thus simultaneously forming the
second spacers and the gap between the plate and the substrate.
In the vibration transducer, the distance between the center and the
external end of the plate is smaller than the distance between the center and the
external end of the diaphragm. In the region in which the diaphragm causes a
relatively small amplitude of vibration or causes substantially no vibration, the
electrostatic capacitance between the diaphragm and the plate varies very little or is
not varied substantially. In the foregoing structure in which the external portion of
the diaphragm is fixed to its upper or lower film, it causes a very small amplitude of
vibration. The vibration transducer is designed such that the distance between the
center and the external end of the plate becomes smaller than the distance between
the center and the external end of the diaphragm, thus inhibiting the external portion
of the diaphragm from being positioned opposite to the plate. When the plate and
the diaphragm are both formed in a circular shape or when they have no recess in the
outlines thereof, it is required that the external end of the plate is positioned inwardly
of the external end of the diaphragm. When the plate and the diaphragm are both
formed in a circular shape or when they have no recess in the outlines thereof, it is
required that the shortest distance between the center and the external end of the
plate be shorter than the shortest distance between the center and the external end of
the diaphragm. Even when the plate is formed in a circular shape or does not have a

recess in the outline thereof and even when the diaphragm has recesses in the outline
thereof, it is required that the shortest distance between the center and the external
end of the plate be shorter than the shortest distance between the center and the
external end of the diaphragm. The aforementioned structure of the vibration
transducer is capable of reducing the parasitic capacitance between the diaphragm
and the plate, thus improving the sensitivity. In this connection, it may be possible to
reduce the parasitic capacitance by forming the external portion of the diaphragm by
use of an insulating substance or by forming the external region of the plate
positioned opposite to the external portion of the diaphragm by use of an insulating
substance, whereas this causes complexity in the film structure of at least one of the
plate and the diaphragm.
Alternatively, the vibration transducer further includes a plurality of
third spacers having pillar shapes which are formed using a deposited film having an
insulating property which joins the substrate and the diaphragm and which supports
the diaphragm relative to the substrate with a gap therebetween. When a parasitic
capacitance is formed between the diaphragm and the substrate in the region in
which they are positioned opposite to each other via the third spacers, it is preferable
that the area of the third spacer (whose dielectric constant is higher than that of the
air) be as small as possible. Each of the third spacers is not formed in a ring shape
but in a pillar shape, whereby the diaphragm is supported by multiple third spacers;
thus, it is possible to reduce the parasitic capacitance between the substrate and the
diaphragm, thus improving the sensitivity. The geometric shapes of the third spacers
are not necessarily limited to pillar shapes but can be formed in flat shapes. It is
required that the third spacer not be formed in a closed wall structure, but a plurality
of third spacers be formed in any shape for supporting the diaphragm. In this

connection, it may be possible to reduce the parasitic capacitance between the
diaphragm and the substrate in the region in which they are positioned opposite to
each other via the third spacers by forming joint portions of the diaphragm joining
the third spacers by use of insulating materials; however, this causes complexity in
the film structure of the diaphragm.
Moreover, the plate is constituted of a center portion and a plurality of
arms which are extended outwardly in a radial direction from the center portion,
whereby the diaphragm is not positioned opposite to the plate at the arms and in the
cutout regions between the arms. Due to the formation of the arms which are
extended outwardly in a radial direction from the center portion of the plate, it is
possible to reduce the parasitic capacitance formed between the diaphragm and the
plate.
In a second aspect of the present invention, a vibration transducer
includes a substrate, a diaphragm having a conductive property which is constituted
of a center portion and a plurality of arms extended outwardly in a radial direction
from the center portion, a plate having a conductive property which is constituted of
a center portion, which is positioned opposite to the center portion of the diaphragm,
and a plurality of arms extended outwardly in a radial direction from the center
portion thereof, a plurality of plate supports for supporting the plate, and a plurality
of diaphragm supports having pillar shapes which are positioned between the cutouts
formed between the arms of the plate and which are positioned outwardly of the plate
supports in the radial direction of the plate so as to support the diaphragm. The
width of each arm of the diaphragm in the circumferential direction of the diaphragm
becomes shortest in the intermediate region between the center portion and the joint
portion at which each arm joins each diaphragm support but becomes longer in

proximity to the joint portion. Herein, an electrostatic capacitance formed between
the diaphragm and the plate is varied when the diaphragm vibrates relative to the
plate.
In the above, the arms of the diaphragm are positioned alternately with
the arms of the plate in plan view, wherein the distance between the plate supports
which are positioned opposite to each other so as to support the plate is shorter than
the distance between the diaphragm supports which are positioned opposite to each
other so as to support the diaphragm. That is, the diaphragm supports which join the
arms of the diaphragm and the substrate are positioned between the plate supports in
the circumferential direction of the plate and are positioned externally of the plate
supports in the radial direction of the plate. This increases the rigidity of the plate to
be relatively higher than the rigidity of the diaphragm. The joint strength between
the arms of the diaphragm and the diaphragm supports increase as the joint areas
therebetween increase; thus, it is possible to increase the durability of the vibration
transducer. When the joint areas are increased by increasing the lengths of the
diaphragm supports in the radial direction of the diaphragm, the rigidity of the
diaphragm is not changed (so that the sensitivity is not increased) irrespective of the
substantial length of the diaphragm between the diaphragm supports, whereas the
vibration transducer may be increased in size. To cope with such a possible
drawback, the widths of the arms of the diaphragm in its circumferential direction are
broadened at the joint areas so as to broaden the joint areas between the arms of the
diaphragm and the diaphragm supports. This makes it possible to increase the
sensitivity and durability of the vibration transducer without increasing its size. The
geometric shapes of the diaphragm supports are not necessarily limited to pillar
shapes but can be formed in flat shapes. That is, it is required for the diaphragm

support to not have a structurally closed-wall structure but should be formed in any
shape for supporting the diaphragm.
The rigidity of the diaphragm decreases as the widths of the arms of the
diaphragm become short; hence, it is preferable that the widths of the arms of the
diaphragm should be mostly broadened at the joint regions joining the diaphragm
supports. That is, it is preferable that the widths of the arms of the diaphragm
become longest at the joint regions joining the diaphragm supports.
It is preferable that the widths of the diaphragm supports be longer than
the shortest width of the arm of the diaphragm at the intermediate position between
the diaphragm support and the center portion of the diaphragm.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects, aspects, and embodiments of the present
invention will be described in more detail with reference to the following drawings.
FIG. 1 is a plan view showing a sensor chip having an MEMS structure
of a condenser microphone in accordance with a first embodiment of the present
invention.
FIG. 2 is a longitudinal sectional view showing the structure of the
condenser microphone.
FIG. 3 is an exploded view showing a lamination structure of films
included in the condenser microphone.
FIG. 4A is a circuit diagram showing an equivalent circuit constituted of
the sensor chip connected with a circuit chip.
FIG. 4B is a circuit diagram showing an equivalent circuit of the sensor
chip having a guard electrode connected with the circuit chip.

FIG. 5 is a sectional view for use in the explanation of a first step of a
manufacturing method of the condenser microphone.
FIG. 6 is a sectional view for use in the explanation of a second step of
the manufacturing method of the condenser microphone
FIG. 7 is a sectional view for use in the explanation of a third step of the
manufacturing method of the condenser microphone.
FIG. 8 is a sectional view for use in the explanation of a fourth step of
the manufacturing method of the condenser microphone.
FIG. 9 is a sectional view for use in the explanation of a fifth step of the
manufacturing method of the condenser microphone.
FIG. 10 is a sectional view for use in the explanation of a sixth step of
the manufacturing method of the condenser microphone.
FIG. 11 is a sectional view for use in the explanation of a seventh step
of the manufacturing method of the condenser microphone.
FIG. 12 is a sectional view for use in the explanation of an eighth step of
the manufacturing method of the condenser microphone.
FIG. 13 is a sectional view for use in the explanation of a ninth step of
the manufacturing method of the condenser microphone.
FIG. 14 is a sectional view for use in the explanation of a tenth step of
the manufacturing method of the condenser microphone.
FIG. 15 is a sectional view for use in the explanation of an eleventh step
of the manufacturing method of the condenser microphone.
FIG. 16 is a sectional view for use in the explanation of a twelfth step of
the manufacturing method of the condenser microphone.
FIG. 17 is a sectional view for use in the explanation of a thirteenth step

of the manufacturing method of the condenser microphone.
FIG. 18 is a sectional view showing a part of the structure of the
condenser microphone.
FIG. 19 is a sectional view showing another part of the structure of the
condenser microphone.
FIG. 20 is a plan view showing a first variation of the diaphragm
included in a condenser microphone in accordance with a second embodiment of the
present invention.
FIG. 21 is a plan view showing a second variation of the diaphragm
included in the condenser microphone of the second embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described in further detail by way of
examples with reference to the accompanying drawings.
1. First Embodiment
(A) Constitution
FIG. 1 shows a sensor chip having an MEMS structure of a condenser
microphone in accordance with a first embodiment of the present invention. FIG. 2
diagrammatically shows the structure of the condenser microphone. FIG. 3 shows
the lamination structure of films included in the condenser microphone 1. FIG. 18
and 19 show prescribed parts of the structure of the condenser microphone I in
detail. The condenser microphone 1 has a package (not shown) encapsulating the
sensor chip and a circuit chip (including a power circuit and an amplification circuit,
not shown).

The sensor chip of the condenser microphone 1 is composed of multiple
films deposited on a substrate 100, i.e., a lower insulating film 110, a lower
conductive film 120, an upper insulating film 130. an upper conductive film 160, and
a surface insulating film 170. The lamination of films included in the MEMS
structure of the condenser microphone 1 will be described below.
The substrate 100 is composed of a P-type monocrystal silicon; but this
is not a restriction. The material of the substrate 100 should be determined to ensure
the adequate rigidity, thickness, and strength in supporting multiple thin films
deposited on a base substrate. A through-hole having an opening 100a is formed in
the substrate 100, wherein the opening 100a corresponds to the opening of a back
cavity CI.
The lower insulating film 110 joining the substrate 100, the lower
conductive film 120, and the upper insulating film 130 is a deposited film composed
of silicon oxide (SiOx). The lower insulating film 110 is used to form a plurality of
third spacers 102 which are aligned in a circular manner with equal spacing
therebetween, a plurality of guard spacers 103 which are aligned in a circular manner
with equal spacing therebetween and are positioned internally of the third spacers
102, and a ring-shaped portion (actually, a rectangular-shaped portion having a
circular opening) 101 which insulates a guard ring 125c and a guard lead 125d from
the substrate 100.
The lower conductive film 120 joining the lower insulating film 110 and
the upper insulating film 130 is a deposited film composed of polycrystal silicon
entirely doped with impurities such as phosphorus (P). The lower conductive film
120 forms the diaphragm 123 and a guard portion 127 which is constituted of guard
electrodes 125a and guard connectors 125b as well as the guard ring 125c and the

guard lead 125d.
The upper insulating film 130 joining the lower conductive film 120, the
upper conductive film 160, and the lower insulating film 110 is a deposited film
composed of silicon oxide. The upper insulating film 130 forms a plurality of first
spacers 131 which are aligned in a circular manner with prescribed distances
therebetween, and a ring-shaped portion (actually a rectangular-shaped portion
having a circular opening) 132 which is positioned outside of the first spacers 131,
which supports an etching ring 161, and which insulates a plate lead 162d from the
guard lead 125d.
The upper conductive film 160 joining the upper insulating film 130 is a
deposited film composed of polycrystal silicon entirely doped with impurities such as
phosphorus (P). The upper conductive film 160 forms the plate 162, the plate lead
162d, and the etching stopper 161.
The surface insulating film 170 joining the upper conductive film 160
and the upper insulating film 130 is a deposited film composed of silicon oxide
having an insulating property.
The MEMS structure of the condenser microphone 1 has four terminals
125e, 162e, 123e, and 100b, which are formed using a pad conductive film 180
(which is a deposited film composed of AlSi having a conductive property), a bump
film 210 (which is a deposited film composed of Ni having a conductive property),
and a bump protection film 220 (which is a deposited film composed of Au having a
superior anti-corrosion property and a conductive property). The side walls of the
terminals 125e, 162e, 123e, and 100b are protected by means of a pad protection film
190 (which is a deposited film composed of SiN having an insulating property) and a
surface protection film 200 (which is a deposited film composed of silicon oxide

having an insulating property).
Next, the mechanical structure of the MEMS structure of the condenser
microphone 1 will be described below.
The diaphragm 123 is formed using a thin single-layered deposited film
having a conductive property and is constituted of a center portion 123a and a
plurality of arms 123c which are extended outwardly in a radial direction from the
center portion 123a. The diaphragm 123 is positioned in parallel with the substrate
100 and is supported by prescribed distances with the substrate 100 and the plate 162
while being insulated from the plate 162 by means of the third spacers 102 having
pillar shapes which join the peripheral portion of the diaphragm 123 at multiple
points. Specifically, the third spacers 102 join the arms 123c of the diaphragm 123
in proximity to their distal ends. Due to the cutouts formed between the arms 123c
adjoining together in the diaphragm 123, the diaphragm 123 is reduced in rigidity
compared with the foregoing diaphragm having no cutout. A plurality of diaphragm
holes 123b is formed in each of the arms 123c, which is thus reduced in rigidity.
Each arm 123c is gradually increased in breadth in a direction towards the center
portion 123a of the diaphragm 123. This reduces concentration of stress at the
boundary between the center portion 123a and each arm 123c. The diaphragm 123 is
designed such that no bent portion is formed in the outline of each arm 123c in
proximity to the boundary with the center portion 123a, thus preventing stress from
being concentrated at the bent portion.
The third spacers 102 are aligned in the circumferential direction with
equal spacing therebetween in the surrounding area of the opening 100a of the back
cavity CI. Each of the third spacers 102 is formed using a deposited film having an
insulating property in a pillar shape. The diaphragm 123 is supported above the

substrate 100 by the third spacers 102 such that the center portion 123a thereof
covers the opening 100a of the back cavity C1 in plan view. A gap C2 whose height
substantially corresponds to the height or thickness of the third spacer 102 is formed
between the substrate 100 and the diaphragm 123. The gap C2 is required to
establish a balance between the internal pressure of the back cavity C1 and the
atmospheric pressure. The gap C2 is reduced in height and is elongated in length in
the radial direction of the diaphragm 123 so as to form a maximum acoustic
resistance in a path which propagate sound waves (for vibrating the diaphragm 123)
to reach the opening 100a of the back cavity C1.
A plurality of diaphragm bumps 123f is formed in the backside of the
diaphragm 123 which is positioned opposite to the substrate 100. The diaphragm
bumps 123f are projections for preventing the diaphragm 123 from being attached
(or stuck) to the substrate 100. They are formed using the waviness of the lower
conductive film 120 forming the diaphragm 123. Thus, dimples (or small recesses)
are formed on the distal ends of the diaphragm bumps 123f.
We claim:
1. A vibration transducer comprising:
a diaphragm composed of a deposited film having a conductive
property;
a plate composed of a deposited film having a conductive property,
which is positioned opposite to the diaphragm; and
a plurality of first spacers having pillar shapes which are formed using a
deposited film having an insulating property joining the plate and which supports the
plate relative to the diaphragm with a gap therebetween.
wherein an electrostatic capacitance formed between the diaphragm and
the plate is varied when the diaphragm vibrates relative to the plate.
2. A manufacturing method for manufacturing a vibration transducer
including a diaphragm having a conductive property, a plate having a conductive
property, and a plurality of first spacers having pillar shapes which are formed using
a deposited film having an insulating property so as to support the plate relative to
the diaphragm with a gap therebetween, said manufacturing method comprising the
steps of:
forming the plate having a plurality of holes;
performing isotropic etching using the plate as a mask so as to remove a
part of the deposited film, thus forming the gap between the plate and the diaphragm;
and
forming the first spacers by use of remaining of the deposited film.

3. A vibration transducer according to claim 1, wherein a plurality of holes
is formed in the plate so as to allow an etchant to transmit therethrough in isotropic
etching, thus simultaneously forming the first spacers and the gap between the plate
and the diaphragm.
4. A vibration transducer comprising:
a substrate;
a diaphragm composed of a deposited film having a conductive
property;
a plate composed of a deposited film having a conductive property,
which is positioned opposite to the diaphragm; and
a plurality of second spacers having pillar shapes which are formed
using a deposited film having an insulating property joining with the substrate and
the plate and which support the plate relative to the substrate with a gap
therebetween,
wherein an electrostatic capacitance formed between the diaphragm and
the plate is varied when the diaphragm vibrates relative to the plate.
5. A manufacturing method for manufacturing a vibration transducer
including a substrate, a diaphragm having a conductive property, a plate having a
conductive property, and a plurality of second spacers having pillar shapes which are
formed using a deposited film having an insulating property and which supports the
plate relative to the substrate with a gap therebetween, said manufacturing method
comprising the steps of:
forming a plurality of holes in the plate;

performing isotropic etching using the plate as a mask so as to remove a
part of the deposited film, thus forming the gap between the plate and the substrate;
and
forming the second spacers by use of remaining of the deposited film.
6. A vibration transducer according to claim 4. wherein a. plurality of holes
is formed in the plate so as to allow an etchant to transmit therethrough in isotropic
etching, thus simultaneously forming the second spacers and the gap between the
plate and the substrate.
7. A vibration transducer comprising:
a diaphragm composed of a deposited film having a conductive
property; and
a plate composed of a deposited film having a conductive property,
which is positioned opposite to the diaphragm,
wherein a distance between a center and an external end of the plate is
smaller than a distance between a center and an external end of the diaphragm, and
wherein an electrostatic capacitance formed between the diaphragm and
the plate is varied when the diaphragm vibrates relative to the plate.
8. A vibration transducer comprising:
a substrate;
a diaphragm composed of a deposited film having a conductive
property;
a plate composed of a deposited film having a conductive property,

which is positioned opposite to the diaphragm; and
a plurality of third spacers having pillar shapes which are formed using
a deposited film having an insulating property joining with the substrate and the
diaphragm and which supports the diaphragm relative to the substrate with a gap
therebetween,
wherein an electrostatic capacitance formed between the diaphragm and
the plate is varied when the diaphragm vibrates relative to the plate.
9. A vibration transducer according to claim 1, wherein the plate is
constituted of a center portion and a plurality of arms which are extended outwardly
in a radial direction from the center portion.
10. A vibration transducer according to claim 3, wherein the plate is
constituted of a center portion and a plurality of arms which are extended outwardly
in a radial direction from the center portion.
11. A vibration transducer according to claim 4, wherein the plate is
constituted of a center portion and a plurality of arms which are extended outwardly
in a radial direction from the center portion.
12. A vibration transducer according to claim 6, wherein the plate is
constituted of a center portion and a plurality of arms which are extended outwardly
in a radial direction from the center portion.
13. A vibration transducer according to claim 7, wherein the plate is

constituted of a center portion and a plurality of arms which are extended outwardly
in a radial direction from the center portion.
14. A vibration transducer according to claim 8, wherein the plate is
constituted of a center portion and a plurality of arms which are extended outwardly
in a radial direction from the center portion.
15. A vibration transducer comprising:
a substrate;
a diaphragm composed of a deposited film having a conductive
property, which is constituted of a center portion and a plurality of arms extended
outwardly in a radial direction from the center portion:
a plate composed of a deposited film having a conductive property,
which is constituted of a center portion, which is positioned opposite to the center
portion of the diaphragm, and a plurality of arms extended outwardly in a radial
direction from the center portion thereof;
a plurality of plate supports for supporting the plate; and
a plurality of diaphragm supports having pillar shapes which are
positioned between cutouts formed between the arms of the plate and which are
positioned outwardly of the plate supports in the radial direction of the plate, thus
supporting the diaphragm,
wherein a width of each arm of the diaphragm in a circumferential
direction of the diaphragm becomes shortest in an intermediate region between the
center portion and a joint portion at which each arm joins each diaphragm support
but becomes longer in proximity to the joint portion, and

wherein an electrostatic capacitance formed between diaphragm and the
plate is varied when the diaphragm vibrates relative to the plate.
16. A vibration transducer according to claim 15, wherein the width of each
arm of the diaphragm becomes longest in the joint portion at which each arm joins
each diaphragm support.
17. A vibration transducer according to claim 15, wherein a width of each
diaphragm support in the circumferential direction of the diaphragm is longer than
the shortest width of each arm at the intermediate portion between the joint portion
and the center portion of the diaphragm.
18. A vibration transducer according to claim 16, wherein a width of each
diaphragm support in the circumferential direction of the diaphragm is longer than
the shortest width of each arm at the intermediate portion between the joint portion
and the center portion of the diaphragm.
19. A vibration transducer according to claim 4 further comprising a plurality of first
spacers having pillar shapes which are formed using a deposited film having an
insulating property joining the plate and which supports the plate relative to the
diaphragm with a gap therebetween.

20. A vibration transducer according to claim 4, wherein the diaphragm is
constituted of a center portion and a plurality of arms extended outwardly in a radial
direction from the center portion, and the plate is constituted of a center portion and a
plurality of arms extended outwardly in a radial direction from the center portion,
said vibration transducer further comprising
a plurality of plate supports for supporting the plate, and
a plurality of diaphragm supports having pillar shapes which are
positioned between cutouts formed between the arms of the plate and which are
positioned outwardly of the plate supports in the radial direction of the plate, thus
supporting the diaphragm,
wherein a width of each arm of the diaphragm in a circumferential direction of the
diaphragm becomes shortest in an intermediate region between the center portion and
a joint portion at which each arm joins each diaphragm support but becomes longer
in proximity to the joint portion.

A vibration transducer is constituted of a substrate, a diaphragm having
a conductive property, a plate having a conductive property, and a plurality of first
spacers having pillar shapes which are formed using a deposited film having an
insulating property joining the plate so as to support the plate relative to the
diaphragm with a gap therebetween. It is possible to introduce a plurality of second
spacers having pillar shapes support the plate relative to the substrate with a gap
therebetween, and/or a plurality of third spacers having pillar shapes which support
the diaphragm relative to the substrate with a gap therebetween. When the
diaphragm vibrates relative to the plate, an electrostatic capacitance formed
therebetween is varied so as to detect vibration with a high sensitivity. The
diaphragm has a plurality of arms whose outlines are curved so that the intermediate
regions thereof are reduced in width.