U.S. patent application number 10/643882 was filed with the patent office on 2004-08-12 for electrostatic rf mems switches.
Invention is credited to Hong, Young-tack, Kim, Young-il, Lee, Moon-chul, Nam, Kuang-woo, Park, Sun-hee, Shim, Dong-ha, Song, In-sang.
Application Number | 20040155736 10/643882 |
Document ID | / |
Family ID | 31185828 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040155736 |
Kind Code |
A1 |
Song, In-sang ; et
al. |
August 12, 2004 |
Electrostatic RF MEMS switches
Abstract
A micro switch having a dielectric layer having a movement
region formed on a substrate, a conductive layer formed on a
predetermined portion of the movement region, a dielectric film
formed on the conductive layer, first and second electric
conductors formed a predetermined distance above the dielectric
film, one or two lower electrodes formed on the movement region,
and one or two upper electrodes formed a predetermined distance
above the two lower electrodes, the one or two upper electrodes
moving the conductive layer and the dielectric film upwards when an
electrostatic force occurs between the upper and lower electrodes,
and capacitively coupled with the first and second electric
conductors to allow a current to flow between the first and second
electric conductors. Such a micro switch has a high on/off ratio
and isolation degree and a simple structure, and can be fabricated
in a very easy process.
Inventors: |
Song, In-sang; (Seoul,
KR) ; Kim, Young-il; (Suwon-city, KR) ; Lee,
Moon-chul; (Sungnam-city, KR) ; Shim, Dong-ha;
(Seoul, KR) ; Hong, Young-tack; (Suwon-city,
KR) ; Park, Sun-hee; (Yongin-city, KR) ; Nam,
Kuang-woo; (Yongin-city, KR) |
Correspondence
Address: |
LEE & STERBA, P.C.
SUITE 2000
1101 WILSON BOULEVARD
ARLINGTON
VA
22209
US
|
Family ID: |
31185828 |
Appl. No.: |
10/643882 |
Filed: |
August 20, 2003 |
Current U.S.
Class: |
335/78 |
Current CPC
Class: |
H01H 59/0009 20130101;
H01H 2057/006 20130101; H01H 57/00 20130101; H01P 1/127
20130101 |
Class at
Publication: |
335/078 |
International
Class: |
H01H 051/22 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2002 |
KR |
2002-49319 |
Claims
What is claimed is:
1. A micro switch, comprising: a substrate; a dielectric layer
formed on the substrate, the dielectric layer having a movement
region formed of a predetermined portion of the dielectric layer
that is capable of moving up and down by hinge parts formed on
either side of the movement region; a conductive layer formed on a
predetermined portion of the movement region; a dielectric film
formed on the conductive layer; first and second electric
conductors formed a predetermined distance above the dielectric
film; two lower electrodes formed on the movement region; and two
upper electrodes formed a predetermined distance above the two
lower electrodes, the two upper electrodes moving the conductive
layer and the dielectric film upwards when an electrostatic force
occurs in the lower electrodes, and capacitively coupled with the
first and second electric conductors to allow a current signal to
flow between the first and second electric conductors.
2. The micro switch as claimed in claim 1, wherein a portion of the
substrate positioned under the movement region, a portion of the
dielectric layer surrounding the movement region except where the
hinge parts are formed, and a portion of the substrate positioned
under a portion of the dielectric layer surrounding the movement
region, are selectively etched to provide an etched region for
allowing the movement region to move up and down.
3. The micro switch as claimed in claim 1, wherein the lower
electrodes are respectively formed between the conductive layer and
the hinge parts.
4. The micro switch as claimed in claim 1, further comprising
anchors respectively supporting the electric conductors and the
upper electrodes, and signal terminals applying signals to the
electric conductors.
5. The micro switch as claimed in claim 4, wherein any of the
conductive layer, the electric conductors, the lower electrodes,
the upper electrodes, the anchors and the signal terminals is
formed of one, or a combination of more than one selected from the
group consisting of Au, Ag, Cu, Pt and Rd.
6. A micro switch, comprising: a substrate; a dielectric layer
formed on the substrate, the dielectric layer having a movement
region formed of a predetermined portion of the dielectric layer
that is capable of moving up and down by a hinge part formed on one
side of the movement region; a conductive layer formed on a
predetermined portion of the movement region; a dielectric film
formed on the conductive layer; first and second electric
conductors formed a predetermined distance above the dielectric
film; a lower electrode formed on the movement region; and an upper
electrode formed a predetermined distance above the lower
electrode, the upper electrode causing the conductive layer and the
dielectric film to move upwards when an electrostatic force occurs
in the lower electrode, and capacitively coupled with the first and
second electric conductors to allow a current signal to flow
between the first and second electric conductors.
7. The micro switch as claimed in claim 6, wherein a portion of the
substrate positioned under the movement region, a portion of the
dielectric layer surrounding the movement region except where the
hinge part is formed, and a portion of the substrate positioned
under a portion of the dielectric layer surrounding the movement
region, are selectively etched to provide an etched region for
allowing the movement region to move up and down.
8. The micro switch as claimed in claim 6, wherein the lower
electrode is formed between the conductive layer and the hinge
part.
9. The micro switch as claimed in claim 6, further comprising
anchors respectively supporting the electric conductors and the
upper electrode, and signal terminals applying signals to the
electric conductors.
10. The micro switch as claimed in claim 9, wherein any of the
conductive layer, the electric conductors, the lower electrode, the
upper electrode, the anchors and the signal terminals is formed of
one, or a combination of more than one selected from the group
consisting of Au, Ag, Cu, Pt and Rd.
11. A micro switch, comprising: a substrate; a dielectric layer
formed on the substrate, the dielectric layer having a movement
region formed of a predetermined portion of the dielectric layer
that is capable of moving up and down by a hinge part formed on one
side of the movement region; a conductive layer formed on a
predetermined portion of the movement region; a dielectric film
formed on the conductive layer; first and second electric
conductors formed a predetermined distance above the dielectric
film; and a piezoelectric layer formed on the movement region,
causing the conductive layer to move upwards by the supply of a
predetermined voltage, and resistively coupled with the first and
second electric conductors to allow an electric current to flow
between the first and second electric conductors.
12. The micro switch as claimed in claim 11, wherein a portion of
the substrate positioned under the movement region, a portion of
the dielectric layer surrounding the movement region except where
the hinge part is formed, and a portion of the substrate positioned
under a portion of the dielectric layer surrounding the movement
region, are selectively etched to provide an etched region for
allowing the movement region to move up and down.
13. The micro switch as claimed in claim 11, wherein the
piezoelectric layer is formed between the conductive layer and the
hinge part.
14. The micro switch as claimed in claim 11, further comprising
anchors respectively supporting the electric conductors, signal
terminals applying signals to the electric conductors, and
piezoelectric electrode terminals applying a voltage to the
piezoelectric layer.
15. The micro switch as claimed in claim 14, wherein any of the
conductive layer, the electric conductors, the anchors, the signal
terminals and the piezoelectric electrode terminals is formed of
one, or a combination of more than one selected from the group
consisting of Au, Ag, Cu, Pt and Rd.
16. A micro switch, comprising: a substrate; a dielectric layer
formed on the substrate, the dielectric layer having a movement
region formed of a predetermined portion of the dielectric layer
that is capable of moving up and down by hinge parts formed on
either side of the movement region; a conductive layer formed on a
predetermined portion of the movement region; first and second
electric conductors formed a predetermined distance above the
conductive layer; two lower electrodes formed on the movement
region; and two upper electrodes formed a predetermined distance
above the lower electrodes, the upper electrodes causing the
conductive layer to move upwards when an electrostatic force occurs
between the upper electrodes and the lower electrodes, and
resistively coupled with the first and second electric conductors
to allow a current signal to flow between the first and second
electric conductors.
17. The micro switch as claimed in claim 16, wherein a portion of
the substrate positioned under the movement region, a portion of
the dielectric layer at both sides of the movement region, and a
portion of the substrate positioned under a portion of the
dielectric layer surrounding the movement region, are selectively
etched to provide an etched region for allowing the movement region
to move up and down.
18. The micro switch as claimed in claim 16, wherein the lower
electrodes are respectively formed between the conductive layer and
the hinge parts at both sides of the conductive layer.
19. The micro switch as claimed in claim 16, further comprising
anchors respectively supporting the electric conductors, and signal
terminals applying signals to the electric conductors.
20. The micro switch as claimed in claim 16, wherein any of the
conductive layer, the electric conductors, the lower electrodes,
the upper electrodes, the anchors and the signal terminals is
formed of one, or a combination of more than one selected from the
group consisting of Au, Ag, Cu, Pt and Rd.
21. A micro switch, comprising: a substrate; a dielectric layer
formed on the substrate, the dielectric layer having a movement
region formed of a predetermined portion of the dielectric layer
that is capable of moving up and down by a hinge part formed on one
side of the movement region; a conductive layer formed on a
predetermined portion of the movement region; first and second
electric conductors formed a predetermined distance above the
conductive layer; a lower electrode formed on the movement region;
and an upper electrode formed a predetermined distance above the
movement region, causing the conductive layer to move upwards when
an electrostatic force is occurred between the lower electrode, and
resistively coupled with the first and second electric conductors
to allow a current signal to flow between the first and second
electric conductors.
22. The micro switch as claimed in claim 21, wherein a portion of
the substrate positioned under the movement region, a portion of
the dielectric layer surrounding the movement region except where
the hinge part is formed, and a portion of the substrate positioned
under a portion of the dielectric layer surrounding the movement
region, are selectively etched to provide an etched region for
allowing the movement region to move up and down.
23. The micro switch as claimed in claim 21, wherein the lower
electrode is formed between the conductive layer and the hinge
part.
24. The micro switch as claimed in claim 21, further comprising
anchors respectively supporting the electric conductors and the
upper electrode, and signal terminals applying signals to the
electric conductors.
25. The micro switch as claimed in claim 24, wherein any of the
conductive layer, the electric conductors, the lower electrode, the
upper electrode, the anchors and the signal terminals is formed of
one, or a combination of more than one selected from the group
consisting of Au, Ag, Cu, Pt and Rd.
26. A micro switch, comprising: a substrate; a dielectric layer
formed on the substrate, the dielectric layer having a movement
region formed of a predetermined portion of the dielectric layer
that is capable of moving up and down by a hinge part formed on one
side of the movement region; a conductive layer formed on a
predetermined portion of the movement region; first and second
electric conductors formed a predetermined distance above the
conductive layer; and a piezoelectric layer formed on the movement
region, causing the conductive layer to move upwards by the supply
of a predetermined voltage, and resistively coupled with the first
and second electric conductors to allow a current signal to flow
between the first and second electric conductors.
27. The micro switch as claimed in claim 26, wherein a portion of
the substrate positioned under the movement region, a portion of
the dielectric layer surrounding the movement region except where
the hinge part is formed, and a portion of the substrate positioned
under a portion of the dielectric layer surrounding the movement
region, are selectively etched to provide an etched region for
allowing the movement region to move up and down.
28. The micro switch as claimed in claim 26, wherein the
piezoelectric layer is formed between the conductive layer and the
hinge part.
29. The micro switch as claimed in claim 26, further comprising
anchors respectively supporting the electric conductors, signal
terminals applying signals to the electric conductors, and
piezoelectric electrode terminals applying a voltage to the
piezoelectric layer.
30. The micro switch as claimed in claim 29, wherein any of the
conductive layer, the electric conductors, the anchors, the signal
terminals and the piezoelectric electrode terminals is formed of
one, or a combination of more than one selected from the group
consisting of Au, Ag, Cu, Pt and Rd.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to micro switches. More
particularly, the present invention relates to Radio Frequency
Micro-Electro Mechanical Systems (RF MEMS) micro switches, which
use an electrostatic force for driving thereof.
[0003] 2. Description of the Prior Art
[0004] In general, frequency separators (F/S's), field effect
transistors (FETs), PIN diode switches, and so on, for
high-frequency signal switches are used to control electric
signals, e.g., for closing, restoring, and switching electric
circuits in electronic systems.
[0005] However, drawbacks associated with the devices above include
a low frequency separation degree in the F/S and a high insertion
loss, low isolation, high power consumption, etc., in the
semiconductor switches.
[0006] Currently, micro switches for high frequency signals are
used to make up for such drawbacks.
[0007] Micro switches for high-frequency signals are classified
into resistively coupled (RC) switches and capacitively coupled
(CC) switches based on a switching coupling method.
[0008] The micro switches are further classified into a cantilever
type and a bridge type based on structural features of hinge parts
thereof. The micro switches are also classified into a shunt-type
and a series-type based on a high frequency signal switching
method.
[0009] The operation principle of micro switches is to actuate
hinge parts of a micro switch structure using electrostatic force,
magnetostatic force, oscillation of piezoelectric element, and the
like, as energy sources to turn signal terminal contact portions on
and off. The micro switches are also classified into an
electrostatic actuation type and a piezoelectric actuation type
based on a driving method.
[0010] The conventional shunt-type micro switch described above has
a structure in which signal terminals simultaneously play an
electrode role of generating electrostatic forces, and input signal
terminals and output signal terminals are connected to each other
when the switch is in an off-state. Further, when the switch is in
an on-state, a signal terminal and a ground terminal are
short-circuited so that the output of an input signal is cut off.
The shunt-type micro switch has a simple structure, but the switch
suffers from a low isolation degree and on/off ratio.
[0011] The conventional series-type micro switch described above is
a relay switch that completely separates input and output signal
terminals from upper and lower electrodes generating an
electrostatic force, in which, when the switch is in an off-state,
the input and output signal terminals are completely disconnected
so that an output for an input signal is cut off. Further, when the
switch is in an on-state, the input and output signal terminals are
connected so that an input signal is outputted. The series-type
micro switch has a high isolation degree and on/off ratio, but
drawbacks of the switch include a complex structure, a very
difficult process, and a structure that is easily deformed.
SUMMARY OF THE INVENTION
[0012] In an effort to solve the problems described above, it is a
feature of an embodiment of the present invention to provide a
series-type micro switch which has a high on/off ratio and
isolation degree, a simple structure, and can be easily fabricated
in a very simple process.
[0013] In an effort to provide these and other features, a micro
switch is provided, including a substrate, a dielectric layer
formed on the substrate, the dielectric layer having a movement
region formed of a predetermined portion of the dielectric layer
that is capable of moving up and down by hinge parts formed on
either side of the movement region, a conductive layer formed on a
predetermined portion of the movement region, a dielectric film
formed on the conductive layer, first and second electric
conductors formed a predetermined distance above the dielectric
film, two lower electrodes formed on the movement region, and two
upper electrodes formed a predetermined distance above the two
lower electrodes, the two upper electrodes causing the conductive
layer and the dielectric film to move upwards when an electrostatic
force occurs between the upper electrodes and the lower electrodes,
and capacitively coupled with the first and second electric
conductors to allow a current signal to flow between the first and
second electric conductors.
[0014] Preferably, a portion of the substrate positioned under the
movement region, a portion of the dielectric layer surrounding the
movement region except where the hinge parts are formed, and a
portion of the substrate positioned under a portion of the
dielectric layer surrounding the movement region, are selectively
etched to provide an etched region for allowing the movement region
to move up and down.
[0015] Preferably, the lower electrodes are respectively formed
between the conductive layer and the hinge parts, and anchors
respectively supporting the electric conductors and the upper
electrodes may be further included.
[0016] In an effort to provide another feature of an embodiment of
the present invention, a micro switch is provided, including a
substrate, a dielectric layer formed on the substrate, the
dielectric layer having a movement region formed of a predetermined
portion of the dielectric layer that is capable of moving up and
down by a hinge part formed on one side of the movement region, a
conductive layer formed on a predetermined portion of the movement
region, a dielectric film formed on the conductive layer, first and
second electric conductors formed a predetermined distance above
the dielectric film, a lower electrode formed on the movement
region, and an upper electrode formed a predetermined distance
above the lower electrode, the upper electrode causing the
conductive layer and the dielectric film to move upwards when an
electrostatic force occurs between the upper electrode and the
lower electrode, and capacitively coupled with the first and second
electric conductors to allow a current signal to flow between the
first and second electric conductors
[0017] Preferably, a portion of the substrate positioned under the
movement region, a portion of the dielectric layer surrounding the
movement region except where the hinge part is formed, and a
portion of the substrate positioned under a portion of the
dielectric layer surrounding the movement region, are selectively
etched to provide an etched region for allowing the movement region
to move up and down.
[0018] Preferably, the lower electrode is formed between the
conductive layer and the hinge part, and anchors for respectively
supporting the electric conductors and the upper electrode, and
signal terminals applying signals to the electric conductors may
further be included.
[0019] In still another embodiment of the present invention, a
micro switch is provided, including a substrate, a dielectric layer
formed on the substrate, the dielectric layer having a movement
region formed of a predetermined portion of the dielectric layer
that is capable of moving up and down by a hinge part formed on one
side of the movement region, a conductive layer formed on a
predetermined portion of the movement region, a dielectric film
formed on the conductive layer, first and second electric
conductors formed a predetermined distance above the dielectric
film, and a piezoelectric layer formed on the movement region
causing the conductive layer to move upwards by the supply of a
predetermined voltage, and resistively coupled with the first and
second electric conductors to allow an electric current to flow
between the first and second electric conductors.
[0020] Preferably, a portion of the substrate positioned under the
movement region, a portion of the dielectric layer surrounding the
movement region except where the hinge part is formed, and a
portion of the substrate positioned under a portion of the
dielectric layer surrounding the movement region, are selectively
etched to provide an etched region for allowing the movement region
to move up and down.
[0021] The piezoelectric layer is preferably formed between the
conductive layer and the hinge part, and anchors respectively
supporting the electric conductors, signal terminals applying
signals to the electric conductors, and piezoelectric electrode
terminals applying a voltage to the piezoelectric layer may also be
included.
[0022] Further, in yet another embodiment of the present invention,
a micro switch is provided, including a substrate, a dielectric
layer formed on the substrate, the dielectric layer having a
movement region formed of a predetermined portion of the dielectric
layer that is capable of moving up and down by hinge parts formed
on either side of the movement region, a conductive layer formed on
a predetermined portion of the movement region, first and second
electric conductors formed a predetermined distance above the
conductive layer, two lower electrodes formed on the movement
region, and two upper electrodes formed a predetermined distance
above the lower electrode, the upper electrodes causing the
conductive layer to move upwards when an electrostatic force occurs
between the upper electrodes and the lower electrodes, and
resistively coupled with the first and second electric conductors
to allow an electric current to flow between the first and second
electric conductors.
[0023] Preferably, a portion of the substrate positioned under the
movement region, a portion of the dielectric layer at both sides of
the movement region, and a portion of the substrate positioned
under a portion of the dielectric layer surrounding the movement
region, are selectively etched to provide an etched region for
allowing the movement region to move up and down.
[0024] Preferably, the lower electrodes are respectively formed
between the conductive layer and the hinge parts at both sides of
the conductive layer, and anchors respectively supporting the
electric conductors, and signal terminals applying signals to the
electric conductors may also be included.
[0025] Further, in yet another embodiment of the present invention,
a micro switch is provided, including a substrate, a dielectric
layer formed on the substrate, the dielectric layer having a
movement region formed of a predetermined portion of the dielectric
layer that is capable of moving up and down by a hinge part formed
on one side of the movement region, a conductive layer formed on a
predetermined portion of the movement region, first and second
electric conductors formed a predetermined distance above the
conductive layer, a lower electrode formed on the movement region,
and an upper electrode formed a predetermined distance above the
movement region, causing the conductive layer to move upwards when
an electrostatic force is occurred between the lower electrode, and
resistively coupled with the first and second electric conductors
to allow a current signal to flow between the first and second
electric conductors.
[0026] A portion of the substrate positioned under the movement
region, a portion of the dielectric layer surrounding the movement
region except where the hinge part is formed, and a portion of the
substrate positioned under a portion of the dielectric layer
surrounding the movement region, are selectively etched to provide
an etched region for allowing the movement region to move up and
down.
[0027] The lower electrode is formed between the conductive layer
and the hinge part, and anchors respectively supporting the
electric conductors and the upper electrode, and signal terminals
applying signals to the electric conductors may be further
included.
[0028] Further, in yet another embodiment of the present invention,
a micro switch is provided, including a substrate, a dielectric
layer formed on the substrate, the dielectric layer having a
movement region formed of a predetermined portion of the dielectric
layer that is capable of moving up and down by a hinge part formed
on one side of the movement region, a conductive layer formed on a
predetermined portion of the movement region, first and second
electric conductors formed a predetermined distance above the
conductive layer, and a piezoelectric layer formed on the movement
region, causing the conductive layer to move upwards by the supply
of a predetermined voltage, and resistively coupled with the first
and second electric conductors to allow an electric current to flow
between the first and second electric conductors.
[0029] A portion of the substrate positioned under the movement
region, a portion of the dielectric layer surrounding the movement
region except where the hinge part is formed, and a portion of the
substrate positioned under a portion of the dielectric layer
surrounding the movement region, are selectively etched to provide
an etched region for allowing the movement region to move up and
down.
[0030] The piezoelectric layer is formed between the conductive
layer and the hinge part, and anchors respectively supporting the
electric conductors, signal terminals applying signals to the
electric conductors, and piezoelectric electrode terminals applying
a voltage to the piezoelectric layer may be further included.
[0031] In all of the embodiments of the present invention, any of
the conductive layer, the electric conductors, the lower
electrode(s), the upper electrode(s), the anchor(s), the signal
terminal(s) and the piezoelectric electrode terminal(s) is formed
of one, or a combination of more than one selected from the group
consisting of Au, Ag, Cu, Pt and Rd.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The above and other features and advantages of the present
invention will become more apparent to those of ordinary skill in
the art by describing in detail preferred embodiments thereof with
reference to the attached drawings in which:
[0033] FIG. 1 illustrates a plan view for showing a micro switch
according to a first embodiment of the present invention;
[0034] FIG. 2 illustrates a first side cross-sectional view for
showing the off-state of the micro switch of FIG. 1;
[0035] FIG. 3 illustrates a first side cross-sectional view for
showing the on-state of the micro switch of FIG. 1;
[0036] FIG. 4 illustrates a second side cross-sectional view for
showing the off-state of the micro switch of FIG. 1;
[0037] FIG. 5 illustrates a second side cross-sectional view for
showing the on-state of the micro switch of FIG. 1;
[0038] FIG. 6 illustrates a perspective view for showing the micro
switch of FIG. 1;
[0039] FIG. 7A to FIG. 7E illustrate views for showing a process
for forming a micro switch according to an embodiment of the
present invention;
[0040] FIG. 8 illustrates a perspective view for showing a micro
switch according to another embodiment of the present invention;
and
[0041] FIG. 9 illustrates a perspective view for showing a micro
switch according to yet another embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0042] Korean Patent Application No. 2002-49319, filed on Aug. 20,
2002, and entitled: "Electrostatic RF MEMS Switches," is
incorporated by reference herein in its entirety
[0043] Hereinafter, preferred embodiments of the present invention
will be described with reference to the accompanying drawings.
[0044] FIG. 1 illustrates a plan view for showing a micro switch
according to a first embodiment of the present invention, and FIG.
6 illustrates a perspective view for showing the micro switch of
FIG. 1.
[0045] Further, FIG. 2 and FIG. 4 illustrate cross-sectional views
showing sides perpendicular to each other when the micro switch of
FIG. 1 is in the off-state, and FIG. 3 and FIG. 5 illustrate
cross-sectional views showing sides perpendicular to each other
when the micro switch of FIG. 1 is in the on-state.
[0046] As shown in FIGS. 1 to 5, the micro switch according to a
first embodiment of the present invention is a bridge-type
electrostatic switch of a capacitively coupled structure.
[0047] A dielectric layer 2 is formed on a substrate 1. Either side
of a central portion of the dielectric layer 2 are etched to form
an etched region 11. The etched region 11 on either side of the
central portion of the dielectric layer 2 is mutually communicated
underneath the central portion of the dielectric layer 2, as shown
in FIG. 2. A portion of the substrate 1 positioned under the
central portion of the dielectric layer 2 is selectively etched to
expand the etched region 11, as shown in FIGS. 4 and 5. The central
portion of the dielectric layer 2 forms a movement region 12, which
is capable of easily moving up and down due to the etched region 11
thereunder and on either side thereof. A portion of the dielectric
layer 2 forming a hinge portion is etched to allow smooth upward
and downward movement in the movement region 12.
[0048] A conductive layer 3 is formed on a predetermined central
portion of the surface of the movement region 12 of the dielectric
layer 2, and a dielectric film 3' is formed on the surface of the
conductive layer 3.
[0049] First and second electric conductors 9a and 9b are
separately disposed a predetermined distance above the conductive
layer 3. The first and second electric conductors 9a and 9b are
spaced apart from each other, but are mutually connected by the
dielectric film 3' when the conductive layer 3 moves upwards.
[0050] In the meantime, as shown in FIGS. 4 and 5, lower electrodes
4 are respectively disposed at either end of the movement region 12
of the dielectric layer 2, between hinges formed on either side of
the movement region 12 and the conductive layer 3.
[0051] Further, as shown in FIGS. 4 and 5, upper electrodes 10 are
respectively disposed at positions spaced a predetermined distance
over the lower electrodes 4, so an electrostatic force is generated
if a predetermined dc voltage is applied between the lower
electrodes 4 and the upper electrodes 10, causing the lower
electrodes 4 to move toward the upper electrodes 10.
[0052] As shown in FIG. 2, the first and second electric conductors
9a and 9b are respectively supported by anchors 7a and 7b.
[0053] Further, as shown in FIGS. 4 and 5, the upper electrodes 10
are supported by upper electrode anchors 6, and the upper electrode
anchors 6 are connected to upper electrode terminals 5.
[0054] As shown in FIGS. 3 and 5, in the micro switch having the
above structure, if the lower electrodes 4 fixed at either side of
the movement region 12 move upwards by an electrostatic force
generated between the lower electrodes 4 and the upper electrodes
10, the dielectric film 3' at the central portion of the movement
region 12 becomes connected to the first and second electric
conductors 9a and 9b. At this time, capacitance between the
conductive layer 3 and the first and second electric conductors 9a
and 9b increases so that an electric signal between the first and
second electric conductors 9a and 9b flows.
[0055] A micro switch according to a second embodiment of the
present invention is a cantilever switch of a capacitively coupled
structure, which will be described with reference to FIG. 8.
[0056] As shown in FIG. 8, the electrostatic cantilever switch of a
capacitively coupled structure according to the second embodiment
of the present invention has a single lower electrode 4, a single
upper electrode 10, and a single upper electrode terminal 5 formed
only at one end of the movement region 12, to one side of a
conductive layer 3. There is also not shown in FIG. 8 a single
upper electrode anchor disposed between the upper electrode
terminal 5 and the upper electrode 10 for supporting the upper
electrode 10, which corresponds to one of the upper electrode
anchors 6 of the first embodiment illustrated in FIGS. 4 and 5. The
lower electrode 4, upper electrode 10, upper electrode anchor and
upper electrode terminal 5, which are disposed at only one side of
the conductive layer 3 in the second embodiment, were disposed at
either side of the conductive layer 3 in the first embodiment.
[0057] Further, a hinge part is formed at the side of the
conductive layer 3 opposite the side at which the lower electrode
4, upper electrode 10, upper electrode anchor and upper electrode
terminal 5 are formed, thereby allowing the lower electrode 4 to
move upwards with respect to the hinge part.
[0058] The remaining elements and operations of the micro switch
having the structure of the second embodiment are the same as those
of the first embodiment of the present invention.
[0059] A micro switch according to a third embodiment of the
present invention is a piezoelectric cantilever switch of a
capacitively coupled structure, which will be described with
reference to FIG. 9.
[0060] As shown in FIG. 9, the piezoelectric cantilever switch of a
capacitively coupled structure according to the third embodiment of
the present invention has the structure that can be obtained when
the upper electrode 10, the lower electrode 4, the upper electrode
anchors 6 and the upper electrode terminals 5 are removed from the
structure appearing in the structure according to the second
embodiment, while a piezoelectric film 12 is formed instead of the
lower electrode 4, and piezoelectric electrode terminals 13a, 13b
are formed to the piezoelectric layer 12 to apply voltage to the
piezoelectric layer 12.
[0061] In the micro switch as shown in FIG. 9 according to the
third embodiment of the present invention, as a predetermined
voltage is applied through the piezoelectric electrode terminals
13a, 13b to the piezoelectric layer 12 fixed between the hinge of
the movement region 12 and the conductive layer 3, the dielectric
film 3' moves upward to contact with the first electric conductor
9a and the second electric conductor 9b. Accordingly, capacitance
between the conductive layer 3 and the first and the second
electric conductors 9a, 9b increases, and electric signals flow
between the first and the second electric conductors 9a, 9b.
[0062] A fourth embodiment of the present invention is a
bridge-type switch of a resistively coupled structure, which has a
structure that the dielectric film 3' is removed from the upper
surface of the conductive layer 3 appearing in the structure
according to the first embodiment.
[0063] In the micro switch having the structure of the fourth
embodiment, the conductive layer 3 at the central portion of the
movement region 12 becomes connected to the first and second
electric conductors 9a and 9b if the lower electrodes 4 fixed at
either end of the movement region 12 move upwards by an
electrostatic force between the lower electrodes 4 and the upper
electrodes 10. At this time, electric resistance between the
conductive layer 3 and the first and second electric conductors 9a
and 9b is reduced, so an electric signal between the first and
second electric conductors 9a and 9b flows.
[0064] A fifth embodiment of a micro switch according to the
present invention is a cantilever switch of a resistively coupled
structure, having a structure that the dielectric film 3' on the
conductive layer 3 is removed from the structure of the above
second embodiment of the present invention. The remaining elements
of the micro switch of the fifth embodiment are the same as those
of the third embodiment of the present invention.
[0065] A sixth embodiment of a micro switch according to the
present invention is a piezoelectric cantilever switch of a
resistively coupled structure, having a structure that the
dielectric film 3' is removed from the structure of the above third
embodiment of the present invention.
[0066] Operations of the micro switch having the structure of the
sixth embodiment as described above are the same as those of the
third embodiment of the present invention.
[0067] A process for the micro switch according to the first
embodiment of the present invention will now be described with
reference to FIGS. 7A to 7E.
[0068] As shown in FIG. 7A, a dielectric layer 2 is formed on an
upper surface of the substrate 1. FIG. 7A shows etched regions 11
to aid in understanding a three dimensional structure of the micro
switch according to the present invention, but the etched regions
11 are formed at a final step of the process, at which time a
central portion of the dielectric layer 2 has a densely formed
plurality of via holes (not shown) formed therein.
[0069] As shown in FIG. 7B, a conductive layer 3 is formed on the
central portion of the dielectric layer 2, and a dielectric film 3'
is formed on the conductive layer 3. The conductive layer 3 may be
formed of one, or a proper combination of Au, Ag, Cu, Pt and Rd,
which have excellent electric conductivities.
[0070] Further, electrode terminals 5, lower electrodes 4 and
signal terminals 8a, 8b are formed opposite each other on the
dielectric layer 2 at either side of the conductive layer 3.
[0071] Then, as shown in FIG. 7C, patterns are formed for anchors
7a and 7b for respectively supporting first and second electric
conductors and for upper electrode anchors 6.
[0072] Subsequently, as shown in FIG. 7D, patterns are formed for
first electric conductor 9a, second electric conductor 9b, and
upper electrode 10.
[0073] At the final step, as shown in FIG. 7E, the etched regions
11 are formed by a dry etching method in which the plurality of via
holes are densely formed in the central portion of the dielectric
layer 2. At this time, the etched regions 11 are connected to each
other underneath the central portion of the dielectric layer 2.
[0074] In the above embodiment, the upper electrode 10 has a
rectangular shape, as shown in FIGS. 7D and 7E, and the upper
electrode anchors 6 for supporting the upper electrodes 10 are
positioned at outer ends of the upper electrodes 10, as shown in
FIGS. 4 and 5. However, the shape of the upper electrodes 10 may be
diversely transformed, and the positions of the upper electrode
anchors 6 for supporting the upper electrodes 10 may be
changed.
[0075] The micro switch according to the present invention has a
simple structure, as well as a high on/off ratio and isolation
degree, and may be fabricated in a very easy process.
[0076] Preferred embodiments of the present invention have been
disclosed herein and, although specific terms are employed, they
are used and are to be interpreted in a generic and descriptive
sense only and not for purpose of limitation. Accordingly, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made without departing from the
spirit and scope of the present invention as set forth in the
following claims.
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