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JPWO2017081806

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DESCRIPTION JPWO2017081806
Abstract: One aspect of the present invention is to connect a substrate, a vibrating portion
vibrating in a direction perpendicular to the substrate, a facing portion facing the vibrating
portion via one or a plurality of cavities, and connecting the vibrating portion and the facing
portion The vibrating portion, the opposing portion, and the supporting portion constitute a
vibrating element having a structure in which the vibrating portion, the opposing portion, and
the supporting portion are continuously and integrally formed of the same base material.
MEMS device and method of manufacturing the same
[0001]
The present invention relates to a MEMS device, and more particularly to a technology effectively
applied to a MEMS device having a vibration device as a component.
[0002]
Some MEMS elements have a vibration element as a component.
The MEMS element having a vibration element as a constituent element further includes a type
formed by deep etching such as a silicon substrate and a type formed repeatedly by film
formation and etching on the surface such as a silicon substrate.
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[0003]
As an example of the latter, Capacitive Micro-machined Ultrasonic Transducers (CMUT) are
described in Patent Document 1 and Patent Document 2. CMUT has a function to transmit
ultrasonic waves to a subject and receive reflected echo signals from the subject, diagnoses a
tumor in the body, etc., nondestructive testing of a structure, velocity detection of fluid, etc. Used
in
[0004]
In Patent Document 1 and Patent Document 2, a cell constituting a CMUT is provided with an
upper electrode and a lower electrode forming a capacitance. A bias voltage is applied between
these upper and lower electrodes during operation. And at the time of transmission of an
ultrasonic wave, a membrane is vibrated by applying a drive voltage signal of an appropriate
waveform (AC) between upper and lower electrodes by a drive voltage signal source, and an
ultrasonic wave corresponding to the drive voltage signal is generated. Conversely, when
ultrasonic waves are received, the membrane vibrates due to the ultrasonic waves reaching the
CMUT, whereby the capacitance between the upper and lower electrodes changes, and a current
signal corresponding to the ultrasonic waves is generated. By detecting this current signal, the
received ultrasonic waves can be detected.
[0005]
In addition, pp. An example of a method for forming a three-dimensional MEMS element on the
surface of a substrate is introduced in 1734-1735. In the method introduced here, film
formation, photolithography, etching, and surface polishing are repeated a plurality of times to
fabricate a MEMS element.
[0006]
JP 2014-510489 gazette WO 2012 /050172
[0007]
The International Journal of Advanced
Manufacturing Technology July 2013、Volume 67、
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Issue 5、pp.1721−1754
[0008]
The vibration type MEMS element including the CMUT has a larger vibration as the bias voltage
or the alternating voltage becomes larger, and therefore, the transmission and reception signals
can be made larger.
However, if the voltage is increased too much, there is a problem that the MEMS element is
broken.
In addition, there is a problem that the element characteristics deteriorate while the vibration is
repeated.
[0009]
Furthermore, the MEMS element of the type formed on the substrate surface needs to form a
cavity portion necessary for vibration at an internal location which can not be directly accessed
from the upper surface of the substrate. Therefore, the manufacturing requires a huge number of
processes, and there is a problem that it is difficult to reduce the manufacturing cost.
[0010]
One cause of these problems is the structure formed by laminating a plurality of films formed by
chemical vapor deposition (CVD) or sputtering. That is, the vibrating portion and its supporting
portion and the opposing portion facing the vibrating portion are made of films separately
formed, and further, the amount of impurities contained in these films is large, or the density of
the film is low. This is because it is difficult to further enhance the voltage resistance and the
long-term reliability. In addition, it is necessary to repeat the procedure of film formation,
photolithography, and etching a plurality of times, which makes it difficult to reduce the number
of steps.
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[0011]
Based on the above, it is an object of the present invention to improve voltage resistance and
long-term reliability in a MEMS element having a vibration element as a component and formed
on the surface of a substrate. In addition, the number of steps in the manufacturing process is to
be reduced.
[0012]
The above and other objects and novel features of the present invention will be apparent from
the description of the present specification and the accompanying drawings.
[0013]
One aspect of the present invention for solving the above problems is a substrate, a vibrating
portion that vibrates in a direction perpendicular to the substrate, and a facing portion that faces
the vibrating portion via one or more cavities, and a vibrating portion. It is a MEMS element
which has a support part which connects with a part, and a vibration part, a countering part, and
a support part constitute a vibration element of a structure continuously constituted integrally
from the same base material.
[0014]
Another aspect of the present invention includes a vibrator forming step of forming a vibrator by
processing a member manufacturing substrate, and a vibrator constructing step of implanting a
vibrator on a device construction substrate by micromanipulation. A method of manufacturing a
MEMS device characterized by
[0015]
More specifically, the substrate for producing a member includes a substrate for a base, a base
disposed opposite to the substrate for a base, an adhesive layer for bonding the substrate for a
base and the base, and an adhesive layer. It comprises a sacrificial layer which is only present in
part between the substrates.
The vibrator also includes a vibrating portion, a facing portion facing the vibrating portion via a
gap, and a supporting portion connecting the vibrating portion and the facing portion.
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Then, in the vibrator forming step, a part of the base material is removed until it reaches the
surface of the adhesive layer or the sacrificial layer, whereby the vibrating part, the opposing
part, the supporting part, the vibrating part, the opposing part, and the supporting part Forming
a connected extension, removing the sacrificial layer, vibrating the vibrating part, the opposing
part, holding the supporting part with a probe, separating the vibrating part, the opposing part,
the supporting part and the extending part, Prepare.
[0016]
As a more specific example, a step of forming the lower electrode on the device construction
substrate is provided, and in the vibrator construction step, the vibrating portion, the opposing
portion, and the support portion held by the probe are placed on the device construction
substrate The method includes the steps of conveying, disposing the vibrating portion, the facing
portion, and the support portion such that the facing portion contacts the lower electrode, and
separating the probe from the vibrating portion, the facing portion, and the support portion.
[0017]
As a more specific example, the area of the lower electrode is formed larger than the area of the
facing portion.
[0018]
Another aspect of the present invention includes a substrate, a vibrating portion including a
vibrating surface parallel to the substrate, a facing portion facing the vibrating portion via a gap,
and a supporting portion connecting the vibrating portion and the facing portion. The vibrating
portion, the facing portion, and the supporting portion have a microscopically continuous
structure, and have no bonding surface or interface, and a lower electrode is provided between
the substrate and the facing portion, and an electrode is provided on the vibrating surface. It is a
MEMS element which vibrates the oscillating portion by applying a voltage between the lower
electrode and the upper electrode.
[0019]
The outline of typical ones of the inventions disclosed in the present application will be briefly
described as follows.
[0020]
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A vibrating portion that vibrates in a direction perpendicular to the substrate, one or more hollow
portions present in the lower portion of the vibrating portion, an opposing portion facing the
vibrating portion via the hollow portion, and a connecting portion between the vibrating portion
and the opposing portion A MEMS device having a vibrating element having a structure in which
a vibrating portion, a facing portion, and a supporting portion are continuously and integrally
formed of the same base material.
[0021]
The effects obtained by typical ones of the inventions disclosed in the present application will be
briefly described as follows.
[0022]
In the device, voltage resistance and long-term reliability can be improved in a MEMS element
having a vibration element as a component and formed on the substrate surface.
Furthermore, in the manufacturing method, the number of steps can be reduced in the
manufacturing process of the MEMS element having a cavity.
[0023]
It is an overhead view which shows the structure of the MEMS element in Example 1 of this
invention.
It is an overhead view which shows the middle stage of manufacture of the MEMS element in
Example 1 of this invention.
It is an overhead view which shows the middle stage of manufacture of the MEMS element in
Example 1 of this invention.
It is an overhead view which shows the middle stage of manufacture of the MEMS element in
Example 1 of this invention.
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It is an overhead view which shows the middle stage of manufacture of the MEMS element in
Example 1 of this invention.
It is an overhead view which shows the middle stage of manufacture of the MEMS element in
Example 1 of this invention.
It is an overhead view which shows the middle stage of manufacture of the MEMS element in
Example 1 of this invention. It is an overhead view which shows the middle stage of manufacture
of the MEMS element in Example 1 of this invention. It is an overhead view which shows the
middle stage of manufacture of the MEMS element in Example 1 of this invention. It is an
overhead view which shows the middle stage of manufacture of the MEMS element in Example 1
of this invention. It is an overhead view which shows the middle stage of manufacture of the
MEMS element in Example 1 of this invention. It is an overhead view which shows another
structural example of the MEMS element in Example 1 of this invention. It is an overhead view
which shows another structural example of the MEMS element in Example 1 of this invention. It
is an overhead view which shows another structural example of the MEMS element in Example 1
of this invention. It is an overhead view which shows the structure of the MEMS element in
Example 2 of this invention.
[0024]
In the following embodiments, when it is necessary for the sake of convenience, it will be
described divided into a plurality of sections or embodiments, but unless otherwise specified,
they are not unrelated to each other, one is one other Part or all of the variations, details,
supplementary explanations, etc.
[0025]
Further, in the following embodiments, when referring to the number of elements (including the
number, numerical value, amount, range, etc.), unless otherwise specified or in principle when
clearly limited to a specific number, etc. The number is not limited to the specific number, and
may be more or less than the specific number.
Furthermore, in the following embodiments, it is needless to say that the constituent elements
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(including element steps and the like) are not necessarily essential unless specifically stated or
considered to be obviously essential in principle. Yes. Similarly, in the following embodiments,
when referring to the shapes, positional relationships and the like of components etc., the shapes
and the like of the components etc. are substantially excluded unless specifically stated otherwise
and where it is apparently clearly not so in principle. It includes those that are similar or similar
to The same applies to the above numerical values and ranges.
[0026]
In the present specification and the like, the expressions “first”, “second”, “third” and the
like are used to identify components, and are not necessarily limited in number or order. In
addition, the identification numbers of components are used for each context, and the numbers
used in one context do not necessarily indicate the same configuration in other contexts. In
addition, it does not prevent that a component identified by a certain number doubles as a
feature of a component identified by another number.
[0027]
The positions, sizes, shapes, ranges, and the like of the respective components shown in the
drawings and the like may not represent actual positions, sizes, shapes, ranges, and the like in
order to facilitate understanding of the invention. For this reason, the present invention is not
necessarily limited to the position, size, shape, range, etc. disclosed in the drawings and the like.
[0028]
Further, in all the drawings for explaining the following embodiments, components having the
same function are basically given the same reference numerals, and repeated description thereof
will be omitted. Hereinafter, embodiments of the present invention will be described in detail
based on the drawings.
[0029]
A MEMS device according to a first embodiment of the present invention will be described with
reference to FIGS.
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[0030]
First, the configuration and operation principle of the MEMS element MD according to the first
embodiment of the present invention will be described with reference to FIG.
The vibrating element constituting the MEMS element MD according to the first embodiment is
configured on the main surface of the device construction substrate DS, as shown in FIG. The
lower electrode LE is disposed on the device construction substrate DS, and the facing portion
FM, the support portion SM, and the vibration portion OM, which are integrally and continuously
formed of the same base material, are disposed thereon. A cavity CAV is present between the
facing part FM and the vibrating part OM. The facing portion FM, the support portion SM, the
vibrating portion OM, and the hollow portion CAV together constitute a vibrating element OD.
The upper electrode UE is disposed on the vibrating portion OM, and a capacitance is formed by
the upper electrode UE and the lower electrode LE.
[0031]
The device construction substrate DS is made of, for example, silicon. The lower electrode LE is
made of, for example, a metal material such as tungsten. The facing portion FM, the support
portion SM, and the vibrating portion OM are made of an insulating material such as quartz, for
example, and are continuously and integrally formed. The continuous integral structure is, for
example, a structure formed by processing a single quartz substrate. Microscopically, the
structure is continuous, and there is no bonding surface or interface between the facing portion
FM, the support portion SM, and the vibrating portion OM. With respect to the cavity CAV, it is
desirable to seal only the cavity CAV or the whole of the vibrating element OD separately to be as
close to vacuum as possible, but it may be filled with a gas such as air. The upper electrode UE is
made of, for example, a metal material such as tungsten.
[0032]
In the vibration operation of the MEMS element MD, a bias voltage and an AC drive voltage
superimposed on the bias voltage are applied between the upper electrode UE and the lower
electrode LE, and the vibrating portion OM and the upper electrode UE thereon are arranged
above and below in FIG. Swing in the direction. In addition, when operating as a signal receiver, it
04-05-2019
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is used that the vibration state changes due to vibration signals including an acoustic wave
received from the outside, an ultrasonic wave, adhesion of fine particles to the vibration part OM,
and the like. As a result, the capacitance between the upper electrode UE and the lower electrode
LE changes, and a current signal corresponding to the vibration is generated.
[0033]
The dimensions of the MEMS element MD vary depending on the application and characteristics,
but one example is: thickness of lower electrode LE: 100 nm thickness of upper electrode UE:
100 nm thickness of vibrating portion OM: 300 nm height of cavity CAV: 300 nm Thickness of
opposing portion FM: 300 nm Width of vibrating element OD: 50 μm Depth of vibrating element
OD: 500 μm. Processing with such dimensions can be realized by the existing semiconductor
manufacturing technology. In particular, the width of the vibrating element OD and the depth of
the vibrating element OD largely change depending on the application.
[0034]
Next, a method of manufacturing the MEMS element MD according to the first embodiment of
the present invention will be described with reference to FIGS.
[0035]
FIG. 2 shows a substrate for member preparation MS, which comprises a substrate for base
material BS, a substrate BM, an adhesive layer AL, and a sacrificial layer SL.
The base substrate BS is made of, for example, silicon. The base material BM is made of, for
example, an insulating material such as quartz. The adhesive layer AL is made of, for example, an
insulating material such as a resin. The sacrificial layer SL is made of a material having a wet
etching rate larger than that of the substrate BM, for example, a metal material such as tungsten.
For example, a metal film is formed on a base material BM made of a quartz substrate, a
sacrificial layer SL is formed by performing photolithography, dry etching, and ashing, and a
silicon substrate is formed using an adhesive layer AL. It forms by adhere | attaching with the
board | substrate BS for base materials which consists of.
[0036]
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FIG. 3 is a view showing an intermediate stage of the manufacture of the MEMS element obtained
by processing the member production substrate MS of FIG. The structure of FIG. 3 is formed by
performing photolithography, dry etching, and ashing on the member forming substrate MS of
FIG. The cavity CAV penetrates the base material BM and reaches the sacrificial layer SL.
[0037]
FIG. 4 is a structure obtained by removing the sacrificial layer SL by wet etching following the
state of FIG. The base substrate BS is processed into a portion BM (A) that will later become the
facing portion FM, the support portion SM, and the vibrating portion OM, and a portion BM (B)
that supports this. As a result of removing the sacrificial layer SL, the part BM (A) is held in the
air by the part BM (B).
[0038]
FIG. 5 shows how a part of the portion BM (A) of the base substrate BS is held. As shown in FIG.
5, a part of the base material BM is held by the micro manipulation probe PR. As the method of
holding, an appropriate method is selected as needed from electrostatic force, van der Waals
force, adhesion with resin, carbon, metal, insulating material, grip with scissors structure, and the
like.
[0039]
FIG. 6 shows how the part BM (A) and the part BM (B) are cut. As shown in FIG. 6, a portion BM
(A) of the substrate BM held by the probe is separated from the other portion BM (B) by local
etching with Focused Ion Beam (FIB) or the like.
[0040]
FIG. 7 shows a separately prepared substrate DS for device construction, which is made of, for
example, silicon.
04-05-2019
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[0041]
FIG. 8 shows a state in which the lower electrode LE is formed by depositing a metal material on
the device construction substrate DS of FIG. 7 and performing photolithography, dry etching and
ashing.
[0042]
A portion BM (A) of the base material BM separated in FIG. 6 is moved by micromanipulation on
the structure shown in FIG.
[0043]
FIG. 9 shows a state in which a part of BM (A) is transported onto the lower electrode LE by the
probe PR.
As shown in FIG. 9, if the area of the lower electrode LE is formed to be larger than the area of
the part BM (A) opposed to it, positioning is easy.
In this case, the area of the lower electrode LE is larger than the area of the upper electrode UE.
[0044]
FIG. 10 shows a state in which the portion BM (A) is disposed on the lower electrode LE from the
state of FIG.
The lower electrode LE and the base material BM (A) disposed are joined by room temperature
bonding, anodic bonding, local film formation using FIB, or the like according to the material to
be used if necessary. These bonding methods may employ known techniques.
[0045]
FIG. 11 shows a state in which an electrode is formed on the vibrating element. By depositing a
04-05-2019
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metal material on the base material BM (A), and applying photolithography, dry etching, and
ashing, as shown in FIG. 11, the upper electrode UE is formed on the vibrating portion OM. The
MEMS element MD is completed through the above steps. Thereafter, if necessary, a protective
film may be formed thereon by CVD or the like, or may be embedded with a resin.
[0046]
In the MEMS element MD according to the first embodiment, since the facing portion FM, the
supporting portion SM, and the vibrating portion OM that constitute the vibrating element OD
are configured as a continuous integral structure from the same base material, each of them is
separately deposited. The voltage resistance and the long-term reliability can be enhanced as
compared with the structure formed by the insulating film. Further, since the vibration element
OD of the continuous integral structure is formed of the base material BM made of a quartz
substrate or the like, the amount of impurities contained in the film is smaller than that of the
film formed by CVD or sputtering. Have a high density. Therefore, the voltage resistance and the
long-term reliability can be enhanced as compared with the case where the film is formed of a
film formed by CVD, sputtering or the like.
[0047]
Furthermore, as compared with a structure in which the opposing part FM, the support part SM,
and the vibrating part OM, which constitute the vibration element OD, are constituted by
insulating films separately formed, the steps required for manufacturing photolithography,
etching The number can be reduced. In the case of a structure in which the opposing part FM,
the support part SM, and the vibrating part OM, which constitute the vibrating element OD, are
constituted by the insulating film separately formed, the film formation at least three times and 1
A cycle of photolithography, dry etching, ashing and wet etching are required. Non-Patent
Document 1 pp. The number of these steps is further increased when producing by the method
described in 1734-1735. When a plurality of transducer elements OD having cavities CAV of
different heights are produced on the device construction substrate DS, the number of film
formation, photolithography, etching and ashing described above increase.
[0048]
12 to 14 show a variant comprising a cavity CAV having a complex shape. In the conventional
04-05-2019
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manufacturing method, for example, in the case of forming the cavity CAV having a shape as
shown in FIGS. 12 to 14, the number of film formation, photolithography, etching and ashing
increase similarly. On the other hand, in the method as in the first embodiment, film formation is
not necessary in the preparation of the vibration element OD, and in any of the above cases, the
necessary steps are one photolithography, dry etching, ashing, wet etching , FIB etching is
sufficient. In the embodiment of the present invention, it is also easy to provide a complicated
uneven structure on the substrate side of the vibrating portion and the upper surface of the
opposing portion.
[0049]
As mentioned above, although the invention made by the present inventor was concretely
explained based on an example, the present invention is not limited to the above-mentioned
example, and can be variously changed in the range which does not deviate from the gist.
[0050]
A MEMS device according to a second embodiment of the present invention will be described
with reference to FIG.
[0051]
The vibrating element constituting the MEMS element MD according to the second embodiment
is configured on the main surface of the device construction substrate DS, as shown in FIG.
The lower electrode LE is disposed on the device construction substrate DS, and the opposing
portion FM, the support portion SM, and the vibration portion OM, which are integrally and
continuously configured from the same base material, are disposed thereon.
A space OS exists between the facing part FM and the vibrating part OM. The facing portion FM,
the support portion SM, the vibrating portion OM, and the space portion OS are combined to
constitute a vibrating element OD. The upper electrode UE is disposed on the vibrating portion
OM, and a capacitance is formed by the upper electrode UE and the lower electrode LE.
[0052]
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The device construction substrate DS is made of, for example, silicon. The lower electrode LE is
made of, for example, a metal material such as tungsten. The facing portion FM, the support
portion SM, and the vibrating portion OM are made of an insulating material such as quartz, for
example, and are configured to be continuously integrated. In the space portion OS, it is desirable
that the entire vibration element OD be sealed separately and be in a state as close to vacuum as
possible, but a gas such as air may be filled. The upper electrode UE is made of, for example, a
metal material such as tungsten.
[0053]
In the vibration operation of the MEMS element MD, a bias voltage and an AC drive voltage
superimposed on the bias voltage are applied between the upper electrode UE and the lower
electrode LE, and the vibrating portion OM and the upper electrode UE thereon are the upper
and lower portions in FIG. Swing in the direction. In addition, when operating as a signal receiver,
it is used that the vibration state changes due to vibration signals including an acoustic wave
received from the outside, an ultrasonic wave, adhesion of fine particles to the vibration part OM,
and the like. As a result, the capacitance between the upper electrode UE and the lower electrode
LE changes, and a current signal corresponding to the vibration is generated. As a variation, it is
also possible to use a material forming the vibration element OD as a piezoelectric material, or to
detect a change in vibration state by an optical method.
[0054]
As shown in FIG. 15, it is also possible to make the vibrating part have a cantilever structure and
to measure the mass of the fine particles attached to the vibrating part by the change of the
vibration state such as the resonance frequency.
[0055]
The manufacturing method of the MEMS device MD according to the second embodiment of the
present invention and the effects obtained by the MEMS device MD according to the second
embodiment of the present invention are the manufacturing method of the MEMS device MD
according to the first embodiment and the MEMS according to the first embodiment. It conforms
to the effect obtained by the element MD.
[0056]
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The present invention is not limited to the embodiments described above, but includes various
modifications.
For example, part of the configuration of one embodiment can be replaced with the configuration
of another embodiment, and the configuration of another embodiment can be added to the
configuration of one embodiment.
In addition, with respect to a part of the configuration of each embodiment, it is possible to add,
delete, and replace the configuration of another embodiment.
[0057]
In the present embodiment, the vibrating element is formed by processing a single substrate, and
therefore, when a plurality of vibrating elements are connected, a minute step difference is
generated at the contact portion between the plurality of vibrating elements. And discontinuities
in the crystal plane may occur.
[0058]
The present invention can be applied to a vibration type MEMS device including an ultrasonic
probe and a cantilever.
[0059]
AL: adhesive layer BM: base material BS: base substrate CAV: hollow part DS: device construction
base board FM: facing part LE: lower electrode MD: MEMS element MS: Substrate for
manufacturing a member OD: Vibrating element OM: Vibrating portion OS: Space portion PR:
Probe SM: Support portion SL: Sacrifice layer UE: Upper portion electrode
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