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JP2009130297

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DESCRIPTION JP2009130297
The present invention provides a method of manufacturing a substrate for a transducer capable
of enhancing the dimensional accuracy of a diaphragm, the substrate for a transducer, and a
transducer. A frame layer 11a is formed on one surface side of a semiconductor substrate 10,
surrounding a region to be formed of a diaphragm 12a (FIG. 1 (j)) formed on one surface side of
the semiconductor substrate 10 (FIG. 1 (b)). ), A thin film 12 serving as a base of the diaphragm
12a is formed on one surface side of the semiconductor substrate 10 (FIG. 1 (c)), and a pattern is
designed on the other surface side of the semiconductor substrate 10 according to the planar
shape of the diaphragm 12a. A mask layer 15 having a portion is formed, and the mask layer 15
is used as an etching mask, and the portion of the thin film 12 formed inside the frame layer 11a
and the frame layer 11a are used as an etching stopper layer. By etching to a depth reaching the
thin film 12 from the side, a diaphragm 12a consisting of a part of the thin film 12 is formed
(FIG. 1 (h)). [Selected figure] Figure 1
Method of manufacturing substrate for transducer, substrate for transducer, and transducer
[0001]
The present invention relates to a method of manufacturing a substrate for a transducer, a
substrate for a transducer, and a transducer.
[0002]
2. Description of the Related Art A microphone, an ultrasonic sensor, a pressure sensor, a
speaker, an infrared sensor, etc. are conventionally known as a transducer provided with a
transducer substrate having a diaphragm formed on one surface side of a semiconductor
substrate using micromachining technology. However, since the dimensional accuracy of the
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1
diaphragm greatly affects the characteristics of the transducer, various methods of
manufacturing a substrate for a transducer capable of forming the diaphragm with high
thickness accuracy have been proposed (for example, Patent Documents 1 to 3).
[0003]
Here, in the above-mentioned Patent Documents 1 to 3, the transducer for the transducer in the
transducer substrate including the transducer substrate on which the diaphragm also serving as
the movable electrode is formed on one surface side of the semiconductor substrate and the fixed
electrode disposed opposite to the movable electrode. A method of manufacturing a substrate is
described.
[0004]
Here, as shown in FIG. 4A, in the Patent Document 1, after the high concentration impurity
doping layer 104 is formed on one surface side of the semiconductor substrate 10 made of a
silicon substrate, the other surface side of the semiconductor substrate 10 is formed. Forming a
mask layer 15 having an opening 15a patterned in accordance with the desired planar shape of
the diaphragm 20, and subsequently, using the mask layer 15 as an etching mask and the high
concentration impurity doping layer 104 as an etching stopper layer The semiconductor
substrate 10 is etched from the other surface side to a depth reaching the high concentration
impurity doping layer 104 to form a recess 17, thereby forming the diaphragm 20 consisting of
a part of the high concentration impurity doping layer 104 The method is described.
[0005]
Further, as shown in FIG. 5, in the patent document 2, as shown in FIG. 5, an SOI substrate
having a silicon layer 10c on an insulating layer (buried oxide film) 10b made of a silicon oxide
film on a support substrate 10a A mask layer 15 having openings 15a designed as a substrate 10
'and patterned in accordance with the planar shape of the diaphragm 20 formed on one surface
side of the semiconductor substrate 10' is formed on the other surface side of the semiconductor
substrate 10 '; Subsequently, using the mask layer 15 as an etching mask, the support substrate
10a and the insulating layer 10b are sequentially etched to form the recess 17, thereby forming
the diaphragm 20 made of a part of the silicon layer 10c. Have been described.
In this manufacturing method, when etching the support substrate 10a, the insulating layer 10b
is used as an etching stopper layer, and when the insulating layer 10b is etched, the silicon layer
10c is used as an etching stopper layer.
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2
[0006]
Further, in Patent Document 3 described above, a microphone unit in which a plurality of
microphones are disposed on the same plane and the outputs of the microphones are
synchronously added to reduce noise is manufactured using micromachining technology or the
like. It has been described that.
JP, 2002-345089, A JP, 2004-356707, A JP, 2002-152873, A
[0007]
However, in the method of manufacturing the transducer substrate described in the abovementioned Patent Document 1, the opening size of the opening 15a of the mask layer 15, the
thickness of the semiconductor substrate 10, and the recess 17 are formed as factors
determining the planar size of the diaphragm 20. When the opening size of the opening 15a of
the mask layer 15 is the same, the planar size of the diaphragm 20 varies due to the variation of
the thickness of the semiconductor substrate 10 and the variation of the side etching quantity. It
will occur.
For example, when the thickness of the semiconductor substrate 10 in FIG. 4A is d, and the
thickness of the semiconductor substrate 10 in FIG. 4B is d ′ (<d), FIGS. 4A and 4B and Then,
the dimensions H1 and H2 of the diaphragm 20 in the left-right direction are different, and H1
<H2.
Further, in the method of manufacturing a transducer substrate described in Patent Document 1,
even if the thickness of the semiconductor substrate 10 is the same, for example, side etching as
shown in FIG. 4C with respect to FIG. 4A. As the amount increases, the horizontal dimension H3
of the diaphragm 20 becomes larger than H1.
[0008]
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3
Also in the method of manufacturing a transducer substrate described in Patent Document 2, as
in the case of the manufacturing method described in Patent Document 1, even if the opening
size of the opening 15a of the mask layer 15 is the same, The variation in thickness of the
semiconductor substrate 10 'and the variation in amount of side etching cause a problem in that
variation occurs in the planar size of the diaphragm 20. Further, in the method of manufacturing
the transducer substrate described in Patent Document 2 above, when etching the support
substrate 10a, anisotropic etching is performed using an alkali-based solution, utilizing the
crystal plane orientation dependency of the etching rate. Even if the etching of the supporting
substrate 10a is performed by dry etching such as RIE, the dimension H4 of the diaphragm 20 is
dispersed by side etching of the insulating layer 10b as shown in FIG. 6, and batch processing
can not be performed. It gets higher.
[0009]
In addition, as another method of manufacturing a substrate for a transducer, as shown in FIG.
7A, an etching stopper layer 105 is formed in a region corresponding to the diaphragm 20 on
one surface side of the semiconductor substrate 10 made of a silicon substrate. A thin film 14 to
be a base of the diaphragm 20 is formed on the entire surface of the substrate 10, and then the
opening 15a is patterned on the other surface of the semiconductor substrate 10 according to
the desired planar shape of the diaphragm 20. Then, the through hole 16 is formed by etching
the semiconductor substrate 10 so as to reach the etching stopper layer 105 from the other
surface side using the mask layer 15 as an etching mask, and then, as shown in FIG. As shown in
(b), the thin film 14 is removed by etching away the etching stopper layer 105. Manufacturing
method so as to form a diaphragm 20 made of a part is considered.
[0010]
However, in such a manufacturing method, a step is formed on the diaphragm 20, and there is a
possibility that the diaphragm 20 may be broken due to stress concentration at a portion where
the step is formed.
[0011]
In addition, in order to synchronously add the outputs of the microphones as in Patent Document
3 described above, the outputs of the microphones need to be regarded as the same phase, but
for this purpose, the size of the arrayed microphone units is collected. It needs to be sufficiently
small compared to the wavelength of sound waves, and miniaturization is also important from
the viewpoint of manufacturing cost.
[0012]
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4
However, as shown in FIG. 8, a plurality of diaphragms 20 consisting of a part of thin film 14 is
formed on semiconductor substrate 10 by anisotropic etching using an alkaline solution on one
surface side of semiconductor substrate 10 consisting of a silicon substrate. When the tapered
through holes 16 are formed, the opening size of each opening 15a of the mask layer 15 on the
other surface side of the semiconductor substrate 10 becomes larger than the planar size of the
diaphragm 20. There is a problem that it is difficult to narrow the gap between the two, and as a
result, it is difficult to miniaturize the microphone unit, and there is a problem that the planar
size of the diaphragm 20 varies as described above.
[0013]
In addition, as shown in FIG. 9, an SOI substrate having a silicon layer 10c on an insulating layer
(buried oxide film) 10b formed of a silicon oxide film on a supporting substrate 10a formed of a
silicon substrate is used as a semiconductor substrate 10 '. Using the mask layer (not shown) on
the other surface side of the substrate 10 ′ as an etching mask, the support substrate 10a and
the insulating layer 10b are sequentially etched to form a recess 17, thereby forming a
diaphragm 20 consisting of a part of the silicon layer 10c. If the support substrate 10a is etched
by dry etching such as RIE, the distance between the adjacent diaphragms 20 can be narrowed.
However, due to the variation of the side etching amount, the diaphragms 20 are formed.
Problem that the flat size of the device is dispersed, batch processing can not be performed, and
the manufacturing cost is There is a problem that Kuna' to become.
[0014]
The present invention has been made in view of the above, and it is an object of the present
invention to provide a method of manufacturing a substrate for a transducer, a substrate for the
transducer, and a transducer capable of enhancing the dimensional accuracy of a diaphragm.
[0015]
The invention according to claim 1 is a method of manufacturing a transducer substrate in which
a semiconductor substrate is processed to form a diaphragm on one surface side of the
semiconductor substrate, wherein the diaphragm is to be formed on the one surface side of the
semiconductor substrate. Forming a frame layer surrounding the region on the one surface side
of the semiconductor substrate, and forming a thin film as a basis of the diaphragm on the one
surface side of the semiconductor substrate after the frame layer forming process After the thin
film forming step of covering at least the region to be formed and the frame layer, and after the
thin film forming step, the other surface side of the semiconductor substrate has an opening
portion patterned according to the planar shape of the diaphragm. After the mask layer forming
step of forming the mask layer and the mask layer forming step, the mask layer is used as an
etching mask and is formed on the inner side of the frame layer of the thin film Providing a
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diaphragm forming etching step of forming the diaphragm made of a part of the thin film by
etching the semiconductor substrate from the other surface side to a depth reaching the thin film
by using the base and frame layers as an etching stopper layer; It features.
[0016]
According to this invention, the planar size of the diaphragm can be determined by the frame
layer formed in the frame layer forming step, and the thickness dimension of the diaphragm can
be determined by the thickness of the thin film formed in the thin film forming step. Therefore,
the dimensional accuracy of the diaphragm can be enhanced, and a transducer substrate with
high dimensional accuracy of the diaphragm can be provided at low cost.
[0017]
The invention of claim 2 is characterized in that, in the invention of claim 1, the semiconductor
substrate is wet-etched in the diaphragm forming etching step.
[0018]
According to the present invention, batch processing can be performed in the diaphragm forming
etching step, so that the manufacturing cost can be reduced.
[0019]
The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, the
semiconductor substrate is a single crystal silicon substrate, and the frame layer is formed of SiO
2 in the frame layer forming step. Do.
[0020]
According to this invention, the frame layer can be easily formed.
[0021]
The invention of claim 4 is the invention according to claims 1 to 3, wherein the transducer
substrate is provided with a plurality of the diaphragms in an array, and in the frame layer
forming step, a plurality of the planned formation regions are formed. The frame layer is formed
to surround the frame.
[0022]
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6
According to the present invention, the dimensional accuracy of each of the diaphragms of the
transducer substrate provided with a plurality of the diaphragms can be enhanced, and the entire
transducer substrate can be miniaturized.
[0023]
The invention according to claim 5 is the invention according to claim 4, wherein, in the mask
layer forming step, when the semiconductor substrate is etched to a depth reaching the thin film
in the diaphragm forming etching step, the adjacent ones of the frame layers The mask layer is
formed so as to expose a portion between planned formation regions.
[0024]
According to the present invention, the entire transducer substrate can be miniaturized.
[0025]
The invention of claim 6 is characterized by being manufactured by the manufacturing method
according to any one of claims 1 to 5.
[0026]
According to the present invention, it is possible to provide a transducer substrate with high
dimensional accuracy of the diaphragm.
[0027]
The invention of claim 7 is characterized by comprising the transducer substrate according to
claim 6, a movable electrode provided on a diaphragm of the transducer substrate, and a fixed
electrode disposed opposite to the movable electrode.
[0028]
According to the present invention, it is possible to provide an electrostatic transducer with high
dimensional accuracy of the diaphragm.
[0029]
According to the first aspect of the present invention, the dimensional accuracy of the diaphragm
can be enhanced, and a transducer substrate with high dimensional accuracy of the diaphragm
can be provided at low cost.
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[0030]
According to the invention of claim 6, there is an effect that it is possible to provide a transducer
substrate with high dimensional accuracy of the diaphragm.
[0031]
According to the seventh aspect of the present invention, there is an effect that it is possible to
provide an electrostatic transducer with a dimensional accuracy of the diaphragm.
[0032]
Embodiment 1 In this embodiment, the electrostatic type shown in FIG. 1 (j) is applied by
applying a method of manufacturing a transducer substrate in which a semiconductor substrate
is processed to form a diaphragm on one surface side of the semiconductor substrate. A method
of manufacturing the transducer will be described with reference to FIG. 1, but before describing
the manufacturing method, a brief description will be given of the electrostatic transducer shown
in FIG. 1 (j).
[0033]
The electrostatic transducer of the configuration shown in FIG. 1 (j) is a transducer substrate 1
having a diaphragm 12a formed on one surface side of a semiconductor substrate 10 consisting
of a single crystal silicon substrate of which one surface is a (100) plane; A movable electrode
13a formed on the diaphragm 12a of the transducer substrate 1, a fixed plate portion 21a made
of a silicon nitride film disposed opposite to the movable electrode 13a, and a fixed electrode 22a
stacked on the fixed plate portion 21a. In the fixed electrode portion formed of a laminate of the
fixed plate portion 21a and the fixed electrode 22a, the space 26 between the fixed electrode
portion and the movable electrode 13a and the external space on the opposite side to the space
26 side in the fixed electrode portion A plurality of acoustic holes 25 are provided to
communicate with each other.
The diaphragm 12a has a rectangular planar shape (in the present embodiment, a square shape),
and is surrounded by the frame layer 11a having a rectangular planar shape over the entire
circumference.
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[0034]
In the above-described electrostatic transducer, since the capacitor is formed by the movable
electrode 13a provided on the diaphragm 12a and the fixed electrode 22a provided on the fixed
plate portion 21a, the diaphragm 12a is moved by receiving the pressure of the sound wave. The
distance between the electrode 13a and the fixed electrode 22a changes, and the capacitance of
the capacitor changes.
Therefore, if a DC bias voltage is applied between the pad 13b electrically connected to the
movable electrode 13a and the pad 22b electrically connected to the fixed electrode 22a, an
acoustic wave is generated between the two pads 13b and 22b. Because a minute voltage change
occurs according to the pressure of the sound wave, the sound wave can be converted into an
electrical signal.
Further, the above-mentioned electrostatic transducer is not excessively damped by air which is
the medium of the space 26 when the diaphragm 12a vibrates under the pressure of the sound
wave, for example, because the acoustic hole 25 is formed. It is possible to obtain flat frequency
characteristics and a wide dynamic range over a wide frequency band.
[0035]
Hereinafter, a method of manufacturing the transducer of the present embodiment will be
described.
[0036]
First, a frame material layer 11 made of a silicon oxide film to be a base of the frame layer 11a is
formed by the CVD method or the like on the one surface side of the semiconductor substrate 10
made of a single crystal silicon substrate whose one surface is a (100) plane. By performing the
frame material layer forming step, the structure shown in FIG. 1 (a) is obtained.
The material of the frame material layer 11 is not limited to SiO 2, and may be a material having
a sufficiently low etching rate as compared to Si which is a material of the semiconductor
substrate 10 in the diaphragm forming etching process described later. It may be Si3N4.
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Further, the thickness of the frame material layer 11 may be appropriately set, for example, in a
range of about 1 μm to 5 μm.
[0037]
Next, by patterning the frame material layer 11 on the one surface side of the semiconductor
substrate 10 using photolithography technology and etching technology, a rectangular frameshaped frame layer made of a part of the frame material layer 11 By performing a frame material
layer patterning step of forming 11a, the structure shown in FIG. 1 (b) is obtained.
In the present embodiment, in the frame material layer forming step and the frame material layer
patterning step, the frame layer 11a surrounding the formation planned region of the diaphragm
12a formed on the one surface side of the semiconductor substrate 10 is used as the
semiconductor substrate 10 The frame layer forming step is formed on the one surface side of
the above.
[0038]
After the above-mentioned frame material layer patterning step, a thin film forming step of
forming a thin film 12 made of a silicon nitride film as a base of the diaphragm 12a on the entire
surface of the one surface of the semiconductor substrate 10 by the CVD method etc. The
structure shown in FIG. 1 (c) is obtained.
In the thin film forming step, the thin film 12 may be formed so as to cover at least the region to
be formed and the frame layer 11 a on the one surface side of the semiconductor substrate 10.
In addition, in the thin film forming process, it is necessary to form the thin film 12 in
consideration of the thickness of the diaphragm 12 a and the residual stress.
Further, in the present embodiment, the film thickness of the thin film 12 is set to 1 μm, but the
film thickness of the thin film 12 is not particularly limited, and may be appropriately set, for
example, in the range of about 0.1 μm to 2 μm. .
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10
Further, the material of the thin film 12 is not limited to Si 3 N 4, and it may be a material having
a sufficiently low etching rate as compared to Si which is a material of the semiconductor
substrate 10 in the diaphragm forming etching process described later. Good.
[0039]
Next, a first conductive layer (for example, an Al layer or the like) 13 serving as a base of the
movable electrode 13a is formed on the entire surface (that is, on the thin film 12) of the first
surface of the semiconductor substrate 10 by evaporation or sputtering. By performing a first
conductive layer forming step to be formed and then performing a first conductive layer
patterning step of patterning the first conductive layer 13 using photolithography technology
and etching technology, as shown in FIG. The structure shown in) is obtained.
In the present embodiment, the movable electrode formation step of forming the movable
electrode 13a is configured by the first conductive layer formation step and the first conductive
layer patterning step.
Further, in the present embodiment, Al is adopted as a material of the first conductive layer 13,
and a part of the first conductive layer 13 constitutes the pad 13 b (FIG. 1 (j)).
Further, the material of the first conductive layer 13 is not limited to Al, and may be, for example,
Cr from the viewpoint of corrosion resistance, thermal stability, etc. A stacked structure of an Au
layer and an upper Cr layer may be used.
When polysilicon is used as the material of the thin film 12 described above, the first conductive
layer 13 may be formed by doping the thin film 12 with an impurity to impart conductivity. .
[0040]
After the above-described first conductive layer patterning step, the sacrificial layer 14 made of a
polyimide film whose film thickness is set according to the gap length of the above-described
space 26 is spin-coated on the entire surface of the semiconductor substrate 10 on the one
surface side. The film shown in FIG. 1 (e) is obtained by forming a film by the like.
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[0041]
Thereafter, a silicon nitride film 21 as a base of the fixing plate portion 21a is formed on the
entire surface of the semiconductor substrate 10 by, for example, a CVD method to obtain a
structure shown in FIG.
In forming the silicon nitride film 21 as the basis of the fixed plate portion 21a, it is necessary to
form the film in consideration of the rigidity and the residual stress of the fixed plate portion
21a.
[0042]
Subsequently, a second conductive layer (for example, an Al layer or the like) 22 serving as a
base of the fixed electrode 22a is formed on the entire surface of the one surface of the
semiconductor substrate 10 by a deposition method or a sputtering method. A structure shown
in FIG. 1G is obtained by performing a forming step and subsequently performing a second
conductive layer patterning step of patterning the second conductive layer 22 using
photolithography technology and etching technology.
In the present embodiment, the fixed electrode forming step of forming the fixed electrode 22a is
configured in the second conductive layer forming step and the second conductive layer
patterning step.
Further, in the present embodiment, Al is adopted as a material of the second conductive layer
22, and a part of the second conductive layer 22 constitutes the pad 22b (FIG. 1 (j)).
Further, the material of the second conductive layer 22 is not limited to Al, and may be, for
example, Cr from the viewpoint of corrosion resistance, thermal stability, etc. A stacked structure
of an Au layer and an upper Cr layer may be used.
[0043]
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12
After the second conductive layer patterning step described above, a mask material layer made of
a silicon oxide film to be a basis of the mask layer 15 described later is formed on the entire
surface of the other surface of the semiconductor substrate 10. Are patterned on the other
surface side of the semiconductor substrate 10 according to the planar shape of the diaphragm
12a by patterning using a photolithographic technique and an etching technique. The mask layer
forming step of forming the mask layer 15 having the above is then performed, and then the
semiconductor substrate 10 is used from the other surface side with the mask layer 15 as an
etching mask and the thin film 12 and the frame layer 11a as an etching stopper layer. The thin
film 1 is formed by etching to a depth reaching the frame layer 11 a to form a tapered through
hole 16. By performing the diaphragm forming etching process for forming a diaphragm 12a
made of a portion of the structure shown in FIG. 1 (h).
Here, in the diaphragm forming etching step, the thin film 12 and the frame layer 11a are etched
by performing anisotropic etching using an alkaline solution such as, for example, a KOH
solution, a TMAH solution, or an EPW (ethylenediamine pyrocatechol) solution. It can be used as
a stopper layer, and the thickness accuracy of the diaphragm 12a can be enhanced.
In the mask layer forming step described above, the edge of the (111) plane constituting the
inner peripheral surface of the through hole 16 on the one surface side of the semiconductor
substrate 10 is the inner peripheral line and the outer periphery of the frame layer 11a in plan
view. It is necessary to pattern design the openings of the mask layer 15 in consideration of the
side etching amount in the diaphragm forming etching process and the thickness of the
semiconductor substrate 10 so as to be between the lines.
Further, in the present embodiment, it is necessary to form a protective layer such as a resist
layer on the one surface side of the semiconductor substrate 10 before the diaphragm forming
etching process.
[0044]
After the diaphragm forming etching step, an acoustic hole forming step of forming a plurality of
acoustic holes (through holes) 25 in the fixed electrode portion constituted by the fixed plate
portion 21a and the fixed electrode 22a using photolithography technology and etching
technology To obtain the structure shown in FIG. 1 (i).
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In the acoustic hole forming step, after the fixed electrode 22a is etched with an etching solution
capable of etching only the fixed electrode 22a, the fixed plate portion 21a may be dry etched
using, for example, CF4 gas.
Further, the size and number of openings of the acoustic holes 25 may be designed so as to
satisfy the design as the acoustic holes and enable the etching of the sacrificial layer 14 in the
sacrificial layer etching process described later.
[0045]
A sacrificial layer forming a space 26 by etching away a part of the sacrificial layer 14 from the
one surface side of the semiconductor substrate 10 through the respective acoustic holes 25 by a
dry process such as oxygen plasma after the above-mentioned acoustic hole forming step By
performing the etching process, an electrostatic transducer of the structure shown in FIG. 1 (j) is
obtained.
Here, the diaphragm 12a and the movable electrode 13a on the diaphragm 12a become a
movable portion.
[0046]
In the present embodiment, an electrostatic transducer is illustrated as a device including the
transducer substrate 1, but as the transducer substrate 1, a diaphragm formed of the
semiconductor substrate 10, the frame layer 11 a, and part of the thin film 12 12a may be
provided.
[0047]
Therefore, in the method of manufacturing the transducer substrate 1 which is the basis of the
method of manufacturing the transducer according to the present embodiment, the frame layer
11a surrounding the formation planned region of the diaphragm 12a formed on the one surface
side of the semiconductor substrate 10 Of the thin film 12 to be the basis of the diaphragm 12a
on the one surface side of the semiconductor substrate 10 after the frame layer forming step
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14
formed on the one surface side of the substrate and the frame layer forming step A mask is
formed on the other surface side of the semiconductor substrate 10 after the thin film forming
process to form 11a and the thin film forming process, and a mask layer 15 having an opening
portion patterned according to the planar shape of the diaphragm 12a is formed. After the layer
forming step and the mask layer forming step, the mask layer 15 is used as an etching mask and
the frame layer 1 of the thin film 12 is formed. A diaphragm forming a diaphragm 12a made of a
part of the thin film 12 by etching the semiconductor substrate 10 from the other surface side to
the depth reaching the thin film 12 with the portion formed inside the frame layer 11a as an
etching stopper layer The planar size of the diaphragm 12a can be determined (defined) by the
frame layer 11a formed in the frame layer forming process, and the thickness dimension of the
diaphragm 12a is formed in the thin film forming process. Therefore, the dimensional accuracy
of the diaphragm 12a can be improved, and the transducer substrate 1 with high dimensional
accuracy of the diaphragm 12a can be provided at low cost.
Therefore, even if the thicknesses d and d 'of the semiconductor substrate 10 vary as shown in
FIGS. 2 (a) and 2 (b) or the side etching amounts vary as shown in FIGS. 2 (a) and 2 (c), It is
possible to form the diaphragms 12a having the same planar size (the dimensions H1 of the
diaphragms 12a become the same as in FIGS. 2 (a), (b) and (c)).
[0048]
Further, according to the method of manufacturing the transducer substrate 1 of the present
embodiment, the semiconductor substrate 10 is wet-etched using the above-mentioned alkaline
solution in the diaphragm-forming etching step, so batch processing becomes possible in the
diaphragm-forming etching step. The cost of manufacturing can be reduced.
Further, according to the method of manufacturing the transducer substrate 1 of the present
embodiment, the semiconductor substrate 10 is a single crystal silicon substrate, and in the
frame layer forming step, the frame layer 11a is formed of SiO 2. Can be easily formed.
[0049]
Further, according to the above-described transducer manufacturing method, the planar size of
the diaphragm 12a can be determined by the size surrounded by the frame layer 11a formed in
the frame layer forming step, and the thickness dimension of the diaphragm 12a is a thin film
Since the thickness can be determined by the thickness of the thin film 12 formed in the forming
step, the dimensional accuracy of the diaphragm 12a can be enhanced, and an electrostatic
04-05-2019
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transducer with high dimensional accuracy of the diaphragm 12a can be manufactured.
[0050]
The use example of the electrostatic transducer described above is not limited to the microphone,
but may be used as a speaker by driving so as to change the voltage applied between the
movable electrode 12a and the fixed electrode 22a. .
[0051]
Second Embodiment The basic configuration of the electrostatic transducer exemplified in this
embodiment is substantially the same as that of the first embodiment, and a plurality of
diaphragms 12a are arrayed (two-dimensional arrayed) as shown in FIG. 3 (j). And the through
hole 16 penetrating in the thickness direction of the semiconductor substrate 10 is formed so as
to straddle all the diaphragms 12a. The difference is that a capacitor including the movable
electrode 13a and the fixed electrode 22a is formed in each region corresponding to each
diaphragm 12a.
[0052]
Thereafter, the manufacturing method of the transducer substrate 1 in which the semiconductor
substrate 10 is processed to form the diaphragm 12a on the one surface side of the
semiconductor substrate 10 is applied to manufacture the electrostatic transducer shown in FIG.
Although the manufacturing method will be described, the description of the same steps as in
Embodiment 1 will be omitted as appropriate.
[0053]
First, a frame material layer 11 made of a silicon oxide film to be a base of the frame layer 11a is
formed by the CVD method or the like on the one surface side of the semiconductor substrate 10
made of a single crystal silicon substrate having one surface is (100). By performing the frame
material layer forming step, the structure shown in FIG. 3A is obtained.
[0054]
Next, by patterning the frame material layer 11 on the above-described one surface side of the
semiconductor substrate 10 using photolithography technology and etching technology, a lattice
frame-like frame layer consisting of a part of the frame material layer 11 By performing the
frame material layer patterning step of forming 11a, the structure shown in FIG. 3 (b) is obtained.
04-05-2019
16
In the present embodiment, in the frame material layer forming step and the frame material layer
patterning step, the frame layer 11a surrounding the formation planned region of each
diaphragm 12a formed on the one surface side of the semiconductor substrate 10 is used as a
semiconductor substrate. A frame layer forming step is to be formed on the one surface side of
the above 10.
[0055]
After the above-described frame material layer patterning step, a thin film forming step of
forming a thin film 12 made of a silicon nitride film as a basis of each diaphragm 12a on the
entire surface of the one surface of the semiconductor substrate 10 is performed by CVD. , The
structure shown in FIG. 3 (c) is obtained.
[0056]
Next, a first conductive layer (for example, an Al layer or the like) 13 serving as a base of each
movable electrode 13a is deposited or sputtered on the entire surface (that is, on the thin film
12) of the first surface of the semiconductor substrate 10 By performing a first conductive layer
forming step of forming the first conductive layer, and then performing a first conductive layer
patterning step of patterning the first conductive layer 13 using photolithography technology
and etching technology, as shown in FIG. The structure shown in d) is obtained.
[0057]
Thereafter, a sacrificial layer 14 made of a polyimide film whose film thickness is set in
accordance with the gap length of each space 26 is formed on the entire surface of the
semiconductor substrate 10 by the spin coating method, for example. The structure shown in e)
is obtained.
[0058]
Thereafter, a silicon nitride film 21 serving as a base of each fixing plate portion 21a is formed
on the entire surface of the semiconductor substrate 10 by, for example, a CVD method to obtain
a structure shown in FIG.
[0059]
Subsequently, a second conductive layer (for example, an Al layer or the like) 22 serving as a
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base of each fixed electrode 22a is formed on the entire surface of the one surface of the
semiconductor substrate 10 by evaporation or sputtering. By performing a layer forming step
and then performing a second conductive layer patterning step of patterning the second
conductive layer 22 using photolithography technology and etching technology, the structure
shown in FIG. 3 (g) is obtained. .
[0060]
Thereafter, a mask material layer made of a silicon oxide film to be a basis of the mask layer 15
described later is formed on the entire surface of the other surface of the semiconductor
substrate 10, and then the mask material layer is subjected to photolithography and etching
techniques. Forming a mask layer 15 having one rectangular (in the present embodiment, a
square) opening portion patterned in accordance with the planar shape of each diaphragm 12a
on the other surface side of the semiconductor substrate 10 by patterning Mask layer 15 is used
as an etching mask and the thin film 12 and the frame layer 11a are used as an etching stopper
layer to reach the thin film 12 and the frame layer 11a from the other surface side. Each part is
made of a part of the thin film 12 by etching so as to form tapered through holes 16 By
performing the diaphragm forming etching process for forming a number of diaphragm 12a, to
obtain a structure shown in FIG. 3 (h).
Here, in the mask layer formation step, when the semiconductor substrate 10 is etched to a
depth reaching the thin film 12 in the diaphragm formation etching step, the above-mentioned
formation scheduled region (the diaphragm 12a is scheduled to be formed) of the lattice frame
layer 11a. The mask layer 15 is formed so as to expose the portion between the regions).
[0061]
After the diaphragm forming etching step, a plurality of acoustic holes (through holes) are
formed in each of the regions overlapping the diaphragm 12 a in the laminate of the silicon
nitride film 21 and the second conductive layer 22 using photolithography technology and
etching technology. The structure shown in FIG. 3I is obtained by performing the acoustic hole
forming step of forming 25).
[0062]
After the above-described acoustic hole forming step, a portion of the sacrificial layer 14 is
etched away by a dry process such as oxygen plasma from the one surface side of the
semiconductor substrate 10 through the respective acoustic holes 25 to form each space 26 By
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performing the layer etching step, an electrostatic transducer of the structure shown in FIG. 3 (j)
is obtained.
[0063]
By the way, in the present embodiment, an electrostatic transducer is illustrated as a device
provided with the transducer substrate 1, but the transducer substrate 1 is made of the
semiconductor substrate 10, the frame layer 11 a and part of the thin film 12. A plurality of
diaphragms 12a may be provided.
[0064]
Therefore, in the method of manufacturing the transducer substrate 1 which is the basis of the
method of manufacturing the transducer of the present embodiment, the frame layer 11a
surrounding the formation planned region of each diaphragm 12a formed on the one surface
side of the semiconductor substrate 10 A thin film 12 to be a base of each diaphragm 12a is
formed on at least the above-mentioned formation scheduled region and frame on the one
surface side of the semiconductor substrate 10 after the frame layer forming step formed on the
one surface side of 10 and the frame layer forming step. In the thin film forming step to cover
body layer 11a, and after the thin film forming step, mask layer 15 having openings designed in
a pattern according to the planar shape of each diaphragm 12a on the other surface side of
semiconductor substrate 10 is After the mask layer forming step to be formed and the mask
layer forming step, the mask layer 15 is used as an etching mask and a frame of the thin film 12
is formed. A plurality of diaphragms 12a formed of a part of the thin film 12 by etching the
semiconductor substrate 10 from the other surface side to the depth reaching the thin film 12
with the portion formed inside the layer 11a and the frame layer 11a as an etching stopper layer.
The planar size of each diaphragm 12a can be determined (defined) by the frame layer 11a
formed in the frame layer forming process, and the thickness dimension of each diaphragm 12a
can be determined. Since it can be determined by the thickness of the thin film 12 formed in the
thin film forming step, the dimensional accuracy of each diaphragm 12a can be enhanced, and
the transducer substrate 1 with high dimensional accuracy of each diaphragm 12a can be
provided at low cost. It becomes possible.
[0065]
Further, according to the method of manufacturing the transducer substrate 1 of the present
embodiment, in the frame layer forming step, the frame layer 11a is formed so as to surround
the formation planned regions of the plurality of diaphragms 12a. While being able to raise the
dimensional accuracy of each diaphragm 12a of substrate 1 for a transducer, miniaturization of
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the substrate 1 for a whole of a transducer can be attained.
Further, according to the method of manufacturing the transducer substrate 1 of the present
embodiment, in the mask layer forming step, when the semiconductor substrate 10 is etched to a
depth reaching the thin film 12 in the diaphragm forming etching step, the frame layers 11a are
adjacent. Since the mask layer 15 is formed so as to expose the portion between the abovedescribed formation planned regions, the entire transducer substrate 1 can be miniaturized.
[0066]
Further, according to the electrostatic transducer of the present embodiment, directional acoustic
detection, high sensitivity by increasing the signal of the sensor, high S / N, etc. can be realized.
[0067]
The application device of the transducer substrate 1 described in each of the first and second
embodiments is not limited to a microphone or a speaker, but may be applied as a piezoelectric
sensor or a piezoelectric actuator by providing a piezoelectric material layer on the diaphragm
12a. A piezoresistive element provided on the diaphragm 12a for application as a strain sensor
or a pressure sensor, or a combination of a light source for irradiating the diaphragm 12a with
light and a photodetector for detecting reflected light or diffracted light from the diaphragm 12a;
The sensor system may be applied as a sensor system for detecting the position or operation, or
may be applied as an infrared sensor by providing an infrared detection element on the
diaphragm 12a.
[0068]
FIG. 7 is a main process cross-sectional view for illustrating the method of manufacturing the
transducer in the first embodiment.
It is explanatory drawing of the manufacturing method of the board | substrate for transducers in
said same.
FIG. 14 is a main process cross-sectional view for illustrating the method of manufacturing the
transducer in the second embodiment.
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It is explanatory drawing of the manufacturing method of the board | substrate for transducers in
a prior art example.
It is explanatory drawing of the manufacturing method of the board | substrate for transducers in
the other prior art example.
FIG. 16 is an explanatory view of a method of manufacturing a transducer substrate in still
another conventional example.
It is explanatory drawing of the manufacturing method of the board | substrate for transducers in
another prior art example.
FIG. 14 is an explanatory view of a method of manufacturing a transducer substrate in still
another conventional example.
FIG. 14 is an explanatory view of a manufacturing method of a transducer substrate in another
conventional example.
Explanation of sign
[0069]
1 Transducer Substrate 10 Semiconductor Substrate (Single Crystal Silicon Substrate) 11a Frame
Layer 12 Thin Film 12a Diaphragm 15 Mask Layer 15a Opening 16 Through Hole
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