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JP2001296310

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2001296310
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
optical sensor and a method of manufacturing the same, and more particularly, to the
configuration of an optical sensor for optically detecting the displacement of a vibrating film
vibrating with external energy and the manufacturing technology thereof. It is a thing.
[0002]
2. Description of the Related Art An optical sensor including a vibrating membrane as a part of a
component is applied to an acceleration sensor, a pressure sensor, an optical microphone and the
like. With regard to the optical microphones among them, an optical microphone as shown in
FIG. 10 is proposed in the AES academic paper: OPTICAL MICROPHONES BREAK-THROUGH
(Author: Alexander Paritsky et al., 1999, Sep. 24, 27).
[0003]
The optical microphone includes a base substrate 1 on which the light emitting element 1a and
the light receiving element 1b are mounted, an optical head 3 and a diaphragm 4 and an optical
fiber between the light emitting element 1a and the light receiving element 1b and the optical
head 3 It is connected by 2a and 2b.
[0004]
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That is, the light from the light emitting element 1 a is guided to the optical head 3 through the
optical fiber 2 a and is irradiated toward the diaphragm 4 from there.
The reflected light of the diaphragm 4 is guided from the optical head 3 to the light receiving
element 1b via the optical fiber 2b. Although not shown, these components are provided in a
light shielding optical cavity.
[0005]
However, the above-described prior art has the following problems. First, since the optical head 3
and the optical fibers 2a and 2b are provided between the elements 1a and 1b and the
diaphragm 4, many parts are required. In addition, in order to optically couple these parts with
each other, high assembly accuracy is required, and productivity is not good.
[0006]
Even if the reflected light from the diaphragm 4 is received by the optical fiber 2b, the light
incident on the optical fiber 2b is a part of the totally reflected light because the diameter of the
fiber is small, and therefore the light utilization efficiency is not good. Furthermore, the sway of
the optical fiber changes the optical path of light, resulting in non-uniform characteristics.
[0007]
In addition, metal foils such as aluminum, titanium, gold, etc. or mylar or plastic films are used
for the diaphragm 4. However, if the thickness is reduced to improve the frequency
characteristics, the workability when stretched on a mount frame As a vibrating membrane, it
becomes difficult to stretch with a predetermined tension (tension).
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve such problems,
and its first object is to provide an optical sensor having a simple structure and excellent
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detection capability. It is.
A second object of the present invention is to provide a method of manufacturing an optical
sensor which has high productivity and can therefore manufacture the optical sensor at low cost.
A third object of the present invention is to provide a method of manufacturing a diaphragm for
an optical sensor in which a thin film thickness and a wide frequency characteristic can be
obtained.
[0009]
In order to achieve the first object, according to the present invention, there is provided a lightreflecting diaphragm capable of vibrating with external energy such as a sound wave or
acceleration, a light emitting portion for irradiating light to the same, and reflection thereof An
optical sensor including a light receiving unit for receiving light and detecting the external
energy according to an output signal from the light receiving unit, the substrate having the light
emitting unit and the light receiving unit, the diaphragm, and the substrate And a mount frame
for providing an optical cavity of a predetermined volume, wherein the light emitting unit is
disposed substantially at the center of the optical cavity, and a plurality of the light receiving
units are disposed around the light emitting unit. And
[0010]
As described above, by disposing the plurality of light receiving units around the light emitting
unit, the reflected light from the diaphragm is received by a wider surface, so the light utilization
efficiency is improved, and the detection capability is correspondingly increased. Is enhanced.
[0011]
In the present invention, each light receiving portion is preferably arranged concentrically with
the light emitting portion as a center, but the arrangement pattern may be, for example, a
concentric ring-like pattern, and each light receiving portion is identical. As a thing which has a
light receiving surface of an area, you may provide in the shape of a division around a light
emission part.
[0012]
When a concentric ring-like pattern is employed, the second light receiving unit disposed outside
the first light receiving unit closer to the light emitting unit side has a light receiving area than
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that of the first light receiving unit. It is preferable to have a large light receiving area.
Then, by adding the output of each light receiving unit to the input terminal of the differential
amplifier, it is possible to cancel noise components due to electromagnetic noise or leaked light
input in the same phase.
[0013]
The manufacturing method of the present invention comprises a first step of attaching the light
emitting portion on the first substrate, a second step of concentrically forming the plurality of
light receiving portions on the second substrate, and a predetermined space capable of
containing the light receiving portions. A third step of providing a mount frame having an optical
cavity of a volume on the second substrate, and a fourth step of opening a hole through which
the light emitting portion can be inserted into the second substrate at a central position with
respect to the light receiving portions; A fifth step of combining the first substrate and the
second substrate so that the light emitting unit passes through the hole, and disposing the light
emitting unit at a central position of each light receiving unit; and light on the mount frame And
a sixth step of providing a reflective diaphragm, thereby achieving the second object.
[0014]
In addition, the ordinal number attached to each process does not mean the execution order of
the processes.
That is, the first process may be performed independently of the process of the second substrate.
As an example, the third and fourth steps may be interchanged.
Further, the fifth and sixth steps can be interchanged.
[0015]
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In the manufacturing method of the present invention, the mount frame in the third step is
preferably formed by metal plating after forming a resist along the mount frame forming pattern
on the second substrate. In addition, it is preferable to use the first substrate and the second
substrate as a mother substrate and to cut out the individual photosensors with a dicing saw, for
example, in the final step in order to achieve mass production.
[0016]
Further, according to the present invention, when manufacturing a diaphragm for an optical
sensor that vibrates by external energy such as a sound wave or acceleration, a metal film to be a
light reflection film is formed on one surface of a base film made of a polymer material. An
optical sensor having a wide frequency characteristic by forming a film and mounting the base
film on a mount frame with a predetermined tension applied, and then reducing the thickness of
at least a region necessary as a diaphragm of the base film by etching. A diaphragm is obtained.
[0017]
The etching amount of the base film may be half etching in which a part of the base film is left, or
may be full thickness etching in which only the metal film is formed by removing all the base
film.
In addition, when attaching to the mount frame, the base film side may be an attachment surface
to the mount frame, but if light is directly applied to the metal film, the metal film side is an
attachment surface to the mount frame Is preferred.
[0018]
In the method of manufacturing a diaphragm for an optical sensor according to the present
invention, after a metal foil of a predetermined thickness is mounted on a mount frame in a state
where a predetermined tension is applied, the metal foil is etched by at least a region necessary
as a diaphragm of the metal foil. Also included is an aspect of reducing the thickness.
[0019]
DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention
will be specifically described with reference to the drawings.
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Referring to the exploded perspective view including the cross section in a part of FIG. 1 and the
cross sectional view of FIG. 2, this optical sensor 10 provides a substrate 20 having a light
emitting portion 21 and a light receiving portion 22 and an optical cavity on the substrate 20
And a light-reflecting diaphragm 40 supported by the mounting frame 30.
[0020]
Referring also to the plan view of the substrate 20 shown in FIG. 3, the light emitting portion 21
is disposed at a central position in the optical cavity, and the light receiving portion 22 is
provided therearound as the first and second light receiving portions. Two light receiving units
221 and 222 are arranged concentrically.
[0021]
The light emitting unit 21 may be a light emitting diode.
Further, although photodiodes or phototransistors are used for the respective light receiving
portions 221 and 222, they have light receiving surfaces of predetermined areas respectively. In
this embodiment, each of the light receiving sections 221 and 222 is formed in a circular shape,
but may be a polygonal pattern on the condition that it is concentric.
[0022]
The light emitted from the light emitting unit 21 is diffused with a light intensity distribution as
generally shown in FIG. 4. The light emitted from the light emitting portion 21 at the emission
angle θ is reflected by the light reflecting film of the diaphragm 40 at the angle θ and returns
to the light receiving surface of each of the light receiving portions 221 and 222. In this case, as
the angle θ increases, the light intensity at the light receiving surface decreases.
[0023]
Further, the optical path length until the light reflected by the diaphragm 40 reaches the light
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receiving surface becomes longer as the angle θ becomes larger, and the light intensity also
becomes weaker. That is, the light reaching the light receiving surface becomes weaker as it gets
farther from the light emitting unit 21.
[0024]
On the other hand, the relationship between the distance between the substrate 20 and the
diaphragm 40 and the light intensity at the light receiving surface at a specific point is that the
light intensity increases and peaks with increasing distance from several microns. After that, it
will decrease gradually.
[0025]
Then, as shown in FIG. 5, this peak point quickly arrives at the side closer to the light emitting
portion 21 in the first light receiving portion 221 side in this embodiment, and its peak light
intensity is also strong.
On the other hand, on the second light receiving unit 222 side far from the light emitting unit 21,
the peak is late and the peak light intensity is also weak.
[0026]
As described above, although there is a difference in light intensity between the first light
receiving unit 221 and the second light receiving unit 222, the total detection output thereof can
be made equal by adjusting the respective light receiving areas. it can.
[0027]
FIG. 5 is a graph in which the vertical axis is the light intensity and the horizontal axis is the
distance between the substrate 20 and the diaphragm 40, and a point with a radius of 40 μm is
taken from the light emitting portion 21 as a light receiving point of the first light receiving
portion 221 A point with a radius of 100 μm is taken from the light emitting portion 21 as the
light receiving point 222, but the peak value of the light intensity appears when the distance is
30 μm at the point with a radius of 40 μm and the distance is 100 μm It appears at 70 μm.
[0028]
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From this graph, the peak value of the light intensity is about 2.4 times larger at a radius of 40
μm than at a radius of 100 μm.
Therefore, in this example, the distance between the substrate 20 and the diaphragm 40 is set to
45 μm, and the ring width of the light receiving surface of the second light receiving portion
222 is 2.4 times the ring width of the first light receiving portion 221, As shown in FIG. 6, by
adding the outputs of the light receiving sections 221 and 222 to the input terminals of the
differential amplifier 23, it is possible to cancel noise components due to electromagnetic noise
and leaked light input in phase.
[0029]
As a modification, as shown in FIG. 7A, for example, four light receiving portions 22 may be
dividedly arranged around the light emitting portion 21, and as shown in FIG. 7B. A
predetermined number (five in this example) of light emitting units 21 may be arranged in a line,
and a predetermined number (six in this example) of light receiving units 22 may be arranged on
both sides thereof.
[0030]
For example, the diaphragm of the microphone causes partially different vibrations (divided
vibrations) due to high and low frequencies, but according to this modification, the outputs of the
respective light receiving units 22 are combined in a predetermined manner and electrically
processed. By this, it is possible to detect the local change distribution of the diaphragm, the
change distribution of the entire surface, and the like.
[0031]
Since light is incident on each light receiving element in the normal state and appears as an
output as a DC component, it is difficult to detect the change amount (AC component) of the
diaphragm. Preferably, only an amount of change is taken out using an AC amplifier.
Alternatively, the DC component may be returned to the light receiving unit to cancel the offset.
[0032]
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This optical sensor 10 is applicable also as sensors, such as a pressure gauge and an
accelerometer, including a microphone.
[0033]
Next, an example of a method of manufacturing the optical sensor 10 will be described with
reference to FIGS. 8A to 8G. This manufacturing method is for the case where a plurality of
optical sensors 10 are taken from the mother substrate. is there.
[0034]
First, as shown in FIG. 8A, in order to form a mount frame (optical cavity) by plating on a silicon
substrate 201, a resist 203 is applied, exposed and developed to pattern the shape of the mount
frame. .
[0035]
In this case, the film thickness of the resist 203 is set to be thicker than the required plating
thickness.
As described above, if the distance between the substrate 20 and the diaphragm 40 is set to 45
μm, the film thickness of the resist 203 needs to be about 50 μm or more.
The first light receiving unit 221 and the second light receiving unit 222 are formed in advance
on the silicon substrate 201.
In this example, a silicon substrate is used, but another substrate may be used as long as the light
receiving portion can be formed.
[0036]
Next, as shown in FIG. 8B, a metal material 301 such as CU or Ni, which serves as a mount frame,
is formed to a predetermined thickness by plating.
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Then, as shown in FIG. 8C, the resist 203 is peeled off to form the mount frame 30 on the silicon
substrate 201.
[0037]
Next, as shown in FIG. 8D, holes 204 are formed in the silicon substrate 201 by, for example,
laser or switching.
The hole 204 is for inserting the light emitting portion 21 and is provided in the central portion
of each optical cavity by the mount frame 30.
[0038]
On the other hand, as shown in FIG. 8E, the light emitting diode as the light emitting unit 21 is
provided in a state of being mounted on the ceramic substrate 202 as another substrate.
Although not shown, a predetermined wiring pattern is formed on the ceramic substrate 202,
and terminals are provided by wires or the like.
[0039]
Then, as shown in FIG. 8F, the ceramic substrate 202 and the silicon substrate 201 are combined,
and the light emitting unit 21 is disposed through the hole 204 at the center of the optical cavity,
ie, at the center position of each light receiving unit 221, 222.
[0040]
Thereafter, as shown in FIG. 8G, the diaphragm 40 is stretched on each mount frame 30 while
applying a predetermined tension.
In this case, it is preferable to attach the vibration plate 40 to the mount frames 30 at the same
size as each of the substrates 201 and 202 in order to enhance productivity. Finally, each optical
sensor 10 is cut out by dicing to obtain a finished product.
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[0041]
In the above embodiment, after the ceramic substrate 202 and the silicon substrate 201 are
combined, the vibrating film is stretched. However, the vibrating film is stretched first, and then
the ceramic substrate 202 and the silicon substrate 201 are combined. May be Further, although
the silicon substrate 201 and the ceramic substrate 202 are used as the two substrates
constituting the substrate 20, the material of the substrate is not limited to this.
[0042]
By the way, the diaphragm 40 for microphone is required to have a frequency band from several
kHz only for voice to about 20 KHz which is a human audible band like music. In order to realize
this frequency response, it is required that the thickness be extremely thin, for example, a thin
film thickness of about 1 μm to several μm be stably made, and that the film be stretched with
a predetermined tension.
[0043]
According to the present invention, a vibrating membrane satisfying such a requirement can be
obtained by the method described below. First, as shown in FIG. 9A, for example, a metal such as
titanium or aluminum is deposited on one surface of a polymer film 401 having a thickness of
several micrometers, such as polyethylene terephthalate (PET), by evaporation or sputtering. A
light reflecting film 402 having a thickness of about 0.1 to 1 μm is formed to obtain a base
material 40a.
[0044]
Then, as shown in FIG. 9 (b), the base material 40a is attached to the mount frame 30 while
applying a predetermined tension so as not to be wrinkled. At that time, it is preferable that the
light reflection film 402 side be the attachment surface side to the mount frame 30. In addition,
the sticking method may be adhesion | attachment, welding, etc.
05-05-2019
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[0045]
Next, as shown in FIG. 9C, a resist 403 is applied to the other surface of the polymer film 401,
exposed through a photomask, and developed to form a predetermined resist pattern. In this
example, the resist pattern is formed only on the supporting portion for the mount frame 30, but
in some cases, the resist pattern may be formed on the portion functioning as a diaphragm.
[0046]
Next, as shown in FIG. 9D, the polymer film 401 is etched and thinned by wet etching or dry
etching in which gasification is performed with oxygen plasma using a plasma etching apparatus,
for example. At this time, it is possible to adjust whether to stop by half etching or to etch only
the metal film (light reflection film 402) according to the required frequency characteristics.
[0047]
Finally, as shown in FIG. 9 (e), by removing the resist 403, the objective thin plate 40 reflects
light well and the diaphragm 40 excellent in frequency response has already been mounted on
the mount frame 30. It is obtained in a stretched state.
[0048]
As another manufacturing method, a metal foil having a thickness of about several μm is
attached to a mount frame while applying a predetermined tension, and after forming a resist
coating / resist pattern as described above, the metal foil It is also possible to obtain a diaphragm
by half etching.
[0049]
As described above, according to the present invention, the following effects can be obtained.
(1) Since components such as an optical fiber and an optical head are not required, the
configuration is simple and the size can be reduced, and the production is also suitable for mass
production, so that a low cost optical sensor can be provided.
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(2) Since the light emitting portion and the light receiving portion are provided on the same
substrate, and the light receiving portion includes the light receiving surface pattern in
consideration of the light intensity distribution of the reflected light, the light utilization
efficiency is high, and hence the detection sensitivity is good. An optical sensor is obtained. (3) It
is possible to form a chip which can be surface-mounted structurally. (4) By inputting the output
of each light receiving unit to the differential amplifier, it is possible to cancel noise components
due to electromagnetic noise or leaked light input in the same phase. (5) Despite being thin, it is
stretched with a predetermined tension on the mount frame, and a vibrating film having excellent
frequency response characteristics can be obtained.
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