U.S. patent application number 10/407353 was filed with the patent office on 2003-10-09 for micro-electro mechanical system.
Invention is credited to Chason, Marc, Gamota, Daniel, Ghaem, Sanjar, Skipor, Andrew, Tungare, Aroon.
Application Number | 20030188958 10/407353 |
Document ID | / |
Family ID | 25458390 |
Filed Date | 2003-10-09 |
United States Patent
Application |
20030188958 |
Kind Code |
A1 |
Chason, Marc ; et
al. |
October 9, 2003 |
Micro-electro mechanical system
Abstract
The organic MEMS according to the present invention comprises a
polymeric substrate comprising a substrate surface including a
first region and a second region. A polymer coating is applied to
the first region to provide a coating surface that is spaced apart
from the substrate surface. A terminal is disposed on the second
region. A metallic trace is affixed to the coating surface such
that the metallic trace forms a flexible extension over the second
region. The extension has a rest position where the extension is
spaced apart from the terminal, and a flexed position where the
extension is disposed towards the terminal. An actuator is used to
provide an electric field to deflect the extension from the rest
position to the flexed position. By changing the spacing between
the extension and the terminal, it is possible to change the
electrical condition provided by the MEMS.
Inventors: |
Chason, Marc; (Schaumburg,
IL) ; Skipor, Andrew; (West Chicago, IL) ;
Tungare, Aroon; (Winfiled, IL) ; Gamota, Daniel;
(Palatine, IL) ; Ghaem, Sanjar; (Chesapeak,
VA) |
Correspondence
Address: |
MOTOROLA, INC.
1303 EAST ALGONQUIN ROAD
IL01/3RD
SCHAUMBURG
IL
60196
|
Family ID: |
25458390 |
Appl. No.: |
10/407353 |
Filed: |
April 4, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10407353 |
Apr 4, 2003 |
|
|
|
09929750 |
Aug 14, 2001 |
|
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Current U.S.
Class: |
200/181 |
Current CPC
Class: |
H01H 2001/0073 20130101;
H05K 3/4092 20130101; H01H 59/0009 20130101 |
Class at
Publication: |
200/181 |
International
Class: |
H01H 057/00 |
Claims
We claim:
1. A method for manufacturing an electronic circuit element
comprising: providing a substrate comprising a surface including a
first region and a second region, fabricating an electrode on the
second region; applying a film of a photosensitive polymeric
material on the first region, the second region and the electrode,
the photosensitive polymeric material having a soluble state prior
to irradiation and an insoluble state after irradiation;
selectively irradiating the film to form an insoluble coating on
the first region, and a soluble coating on the second region and
the electrode; fabricating a metallic trace on the film, the
metallic trace affixed to the insoluble coating and forming an
extension on the soluble coating that overlaps the electrode; and
removing the soluble coating from the second region to expose the
terminal, such that the electrode is spaced apart from the
extension.
2. The method of claim 1 wherein the substrate is selected from the
group consisting of polymer, ceramic, silicon, gallium arsenide,
semiconductor, metal, and glass.
3. The method of claim 1 wherein the film is formed of a
photoimageable polymer.
4. The method of claim 1 wherein the film is selected from the
group consisting of a photoimageable polyimide, epoxy, and
acrylate.
5. The method of claim 1 wherein a second electrode is formed on
the second region prior to applying the film.
6. The method of claim 1 wherein the electrode is formed by plating
a metal layer on the substrate and pattern etching the metal layer
to define the electrode.
7. The method of claim 6 wherein the plating method is selected
from the group consisting of electroplating and electroless
plating.
8. The method of claim 6 wherein the metal layer is formed of a
metal selected from the group consisting of copper, aluminum,
platinum, gold, nickel, silver, chrome, palladium, tin, bismuth,
indium, lead, gold-palladium, and alloys thereof.
9. The method of claim 6 wherein a second electrode is defined by
pattern etching the metal layer.
10. The method of claim 1 wherein the electrode is formed by
laminating a metal layer on the substrate and pattern etching the
metal layer to define the electrode.
11. The method of claim 10 wherein the metal layer is formed of a
metal selected from the group consisting of copper, aluminum,
platinum, gold, nickel, silver, chrome, palladium, tin, bismuth,
indium, lead, gold-palladium, and alloys thereof.
12. The method of claim 10 wherein a second electrode is defined by
pattern etching the metal layer.
13. The method of claim 1 wherein the insoluble coating is cured
after the soluble coating is removed.
14. The method of claim 1 wherein the metallic trace is fabricated
by laminating a metal layer on the film and pattern etching the
metal layer to define the metallic trace.
15. The method of claim 14 wherein the metallic trace is formed of
metal selected from the group consisting of copper, aluminum,
platinum, gold, nickel, silver, chrome, palladium, tin, bismuth,
indium, lead, gold-palladium, and alloys thereof.
16. The method of claim 1 wherein the metallic trace is fabricated
by plating a metal layer on the film and pattern etching the metal
layer to define the metallic trace.
17. The method of claim 16 wherein the plating method is selected
from the group consisting of electroplating and electroless
plating.
18. The method of claim 16 wherein the metal layer is formed of a
metal selected from the group consisting of copper, aluminum,
platinum, gold, nickel, silver, chrome, palladium, tin, bismuth,
indium, lead, gold-palladium, and alloys thereof.
19. The method of claim 1 wherein a metal layer is formed in the
first region as the electrode is formed on the second region, and
the film is applied over the metal layer.
20. An electronic circuit element comprising: a substrate
comprising a substrate surface including a first region and a
second region; a polymer coating applied to the first region, the
polymer coating including a coating surface spaced apart from the
substrate surface; a terminal disposed on the second region; a
metallic trace affixed to the coating surface such that the
metallic trace forms an extension over the second region, whereby
the extension has a rest position where the extension is spaced
apart from the terminal, and a flexed position where the extension
is disposed towards the terminal; and an actuator disposed on the
second region capable of creating an electric field effective to
flex the extension from the rest position to the flexed
position.
21. The electronic circuit element of claim 20 wherein the
substrate is selected from the group consisting of polymer,
ceramic, silicon, gallium arsenide, semiconductor, metal, and
glass.
22. The electronic circuit element of claim 20 wherein the polymer
coating is formed of a photopolymer.
23. The electronic circuit element of claim 20 wherein the polymer
coating is formed of a material selected from the group consisting
of polyimide and epoxy.
24. The electronic circuit element of claim 20 wherein the polymer
coating is formed of photoimageable polymer.
25. The electronic circuit element of claim 20 wherein the
substrate is a reinforced polymer composite.
26. The electronic circuit element of claim 20 wherein a metal
layer is interposed between the substrate and the polymer
coating.
27. The electronic circuit element of claim 20 wherein the
extension has a free end that is remote from a fixed end on the
polymer coating.
28. The electronic circuit element of claim 20 wherein the
extension has a free end that is remote from a fixed end on the
polymer coating and is simply supported.
29. The electronic circuit element of claim 20 wherein the polymer
coating further comprises fixed first and second edges disposed
about the second region, and the extension bridges the second
region between the fixed first and second edges.
30. The electronic circuit element of claim 29 wherein the first
and second edges surround the second region, and the extension
forms a diaphragm over the second region.
31. The electronic circuit element of claim 29 wherein the first
and second edges surround the second region, and the extension
forms a plate over the second region.
32. The electronic circuit element of claim 20 wherein the polymer
coating further comprises a fixed first edge and a simply supported
second edge disposed about the second region, and the extension
bridges the second region between the fixed first edge and the
simply supported second edge.
33. The electronic circuit element of claim 20 wherein the terminal
is also the actuator.
34. The electronic circuit element of claim 20 wherein the terminal
is distinct from the actuator.
35. The electronic circuit element of claim 20 wherein the
extension in the flexed position makes contact with the
terminal.
36. The electronic circuit element of claim 20 wherein there is a
gap between the extension and the terminal when the extension is in
the flexed position.
37. The electronic circuit element of claim 20 wherein the
extension forms a plate over the second region.
38. The electronic circuit element of claim 20 wherein the
extension forms a diaphragm over the second region.
39. The electronic circuit element of claim 20 wherein the
extension forms a cantilever having a free end over the second
region.
40. A printed wiring board having a switch, the switch comprising:
a substrate comprising a substrate surface including a first region
and a second region; a polymer coating applied to the first region,
the polymer coating including a coating surface spaced apart from
the substrate surface; a terminal disposed on the second region; a
metallic trace affixed to the coating surface such that the
metallic trace forms a extension over the second region, the
extension having a rest position wherein the extension is spaced
apart from the terminal and a flexed position wherein the extension
is disposed towards the terminal; and an actuator disposed on the
second region capable of creating an electric field effective to
flex the extension from the rest position to the flexed
position.
41. The printed wiring board of claim 40 wherein the extension
contacts the terminal in the flexed position.
42. The printed wiring board of claim 40 wherein there is a gap
between the extension and the terminal when the extension is in the
flexed position.
43. The printed wiring board of claim 40 wherein the extension
forms a plate over the second region.
44. The printed wiring board of claim 40 wherein the extension
forms a diaphragm over the second region.
45. The printed wiring board of claim 40 wherein the extension
forms a cantilever having a free end over the second region.
45. The printed wiring board of claim 40 wherein the terminal is an
electrode having a first gap from the extension in the resting
position and the actuator is a second electrode having a second gap
from the extension in the resting position, such that when the
extension is in the flexed position, the extension makes contact
with the terminal and there is a gap between the terminal and the
actuator.
46. The printed wiring board of claim 40 wherein the extension is
supported by an organic polymer backing.
47. A printed wiring board having a variable capacitor, the
variable capacitor comprising: a substrate comprising a substrate
surface including a first region and a second region; a polymer
coating applied to the first region, the polymer coating including
a coating surface spaced apart from the substrate surface; a
terminal disposed on the second region; a metallic trace affixed to
the coating surface such that the metallic trace forms a extension
over the second region, the extension having a rest position
wherein the extension is spaced apart from the terminal and a
flexed position wherein the extension is disposed towards the
terminal; and an actuator disposed on the second region capable of
creating an electric field effective to flex the extension from the
rest position to the flexed position.
48. The printed wiring board of claim 47 wherein the extension is
spaced apart from the terminal by a first gap in the rest position
and the extension is spaced apart from the terminal by a second gap
less than the first gap in the flexed position.
49. The printed wiring board of claim 47 further comprising a
dielectric layer disposed between the terminal and the extension,
such that there is a gap between the extension and the dielectric
layer when the extension is in the rest position and the extension
contacts the dielectric layer when the extension is in the flexed
position.
50. The printed wiring board of claim 49 wherein the dielectric
layer is selected from the group consisting of ceramic, polymer,
oxide, and a polymer-inorganic material
51. The printed wiring board of claim 47 wherein the substrate is
selected from the group consisting of polymer, ceramic, silicon,
gallium arsenide, semiconductor, metal, and glass.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an organic micro-electro
mechanical system that can be fabricated within or on the surface
of an organic Printed Wiring Board (PWB) utilizing high density
interconnect (HDI) substrate technology.
BACKGROUND OF THE INVENTION
[0002] Smaller and more complex electronic devices require smaller
switches. Current solid-state switches are not ideal, because they
exhibit a finite leakage that precludes a complete "off" state. On
the other hand, current mechanical and electromechanical switches
are bulky and consume a large amount of power. Micro
electromechanical systems (MEMS) have been reported to address the
drawbacks of the prior art. See U.S. Pat. No. 5,051,643 to Dworsky
and Chason, 1991; and U.S. Pat. No. 5,578,976 to Yao, 1996.
However, the above-referenced MEMS are fabricated from crystalline
silicon or ceramic silicon dioxide that require fabrication methods
(e.g., reactive ion etching, vapor deposition, etc.) that are not
compatible with printed wiring board (PWB) fabrication. Therefore,
MEMS made by this technology must be made separately, then
incorporated into printed wiring boards.
[0003] Moreover, crystalline silicon or silicon dioxide ceramic
tends to be stiff. Accordingly, these materials are only useful for
making switches that have relatively small gaps (e.g., .ltoreq.1
micron), not switches having relatively large gaps (e.g., >1
micron), and these switches require a higher activation voltage
than switches having a lower elastic modulus. It would be desirable
to form MEMS switches that are not based on crystalline silicon or
ceramic silicon dioxide.
[0004] The organic MEMS according to the present invention can be
fabricated during fabrication of the printed wiring board (PWB),
and are useful for switches having a wide range of gaps (about 1-25
microns). The organic MEMS comprises a polymeric substrate
comprising a substrate surface including a first region and a
second region. A polymer coating is applied to the first region to
provide a coating surface that is spaced apart from the substrate
surface. A terminal is disposed on the second region. A metallic
trace is affixed to the coating such that the metallic trace forms
a flexible extension over the second region. The extension has a
rest position where the extension is spaced apart from the
terminal, and a flexed position where the extension is disposed
towards the terminal. An actuator is used to provide an electric
field to deflect the extension from the rest position to the flexed
position. By changing the spacing between the extension and the
terminal, it is possible to change the electrical condition
provided by the organic MEMS. Because, the extension is not
supported by a material such as crystalline silicon or silicon
dioxide ceramic, the organic MEMS is compatible with PWB
fabrication, and provides a wider range of deflection gaps at a
lower activation voltage.
[0005] The extension and the terminal need not contact each other
to change the electrical condition provided by the organic MEMS. By
changing the distance between the extension and the terminal, a
variable capacitor is formed, wherein in the rest position, the
MEMS has one capacitance, while in the flexed position, the MEMS
has another capacitance. The organic MEMS and the method of
fabrication are compatible with PWB fabrication and are used to
make PWB embedded switches and capacitors.
[0006] The present invention is also directed to a method of
forming the organic MEMS comprising depositing an electrode at the
second region of a polymeric substrate comprising a substrate
surface including a first region and a second region, then applying
a photopolymer coating over both regions and the electrode. The
photopolymer is selectively irradiated in the first region to form
an insoluble coating in the first region, while a soluble coating
remains in the second region. A metal trace is fixed to the coating
such that a flexible extension overlaps the electrode. The soluble
coating is removed to expose the electrode such that the electrode
is spaced apart from the extension.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIGS. 1A-J show cross-sectional views that illustrate the
steps for making two MEMS embodiments having a cantilever
extension;
[0008] FIG. 2A shows an organic MEMS in which the metal trace
defines a diaphragm extension;
[0009] FIG. 2B shows a top view the MEMS of FIG. 2A in which the
diaphragm extension has been removed to expose the dielectric
surface; and
[0010] FIGS. 2C-D show cross-sectional views of the MEMS of FIGS.
2A and 2B across line S-S.
DETAILED DESCRIPTION OF THE DRAWINGS
[0011] In FIG. 1, a polymer substrate 12 with a metal layer 14 on
substrate surface 16 (FIG. 1A) is treated to form electrodes 18 and
20 in second region 24, such that metal layer 14 remains in first
region 22 (FIG. 1B). Formation of electrodes 18 and 20 can be
accomplished using metal print and etch processes widely known in
the printed wiring board industry. Photopolymer 26 is applied over
both regions of the substrate, including metal layer 14 and
electrodes 18 and 20, and selectively irradiated in region 22 with
radiation so that the photopolymer becomes insoluble in that region
(FIG. 1C). A metal trace 28 is fabricated on photopolymer 26 over
both first and second regions 22 and 24, respectively (FIG. 1D).
The metal trace 28 can be formed, for example, by first laminating
a metal foil (such as copper) to the photopolymer layer using low
temperature lamination, and then printing and etching the metal to
form the metal trace 28. To form MEMS 36, photopolymer 26 in region
24 that was not exposed to the radiation is removed by dissolving
in a suitable solvent. An insoluble coating 30 over first region 22
on which metal trace 28 is fixed on coating surface 32, and an
extension 34 over second region 24, set apart from electrodes 18
and 20 (FIG. 1E), is thus formed.
[0012] For MEMS 36, electrode 18 is shown to be thicker than
electrode 20. In one embodiment, the shorter height of electrode 20
can be achieved, for example, by selectively thinning the electrode
metal using controlled depth etching processes known in the printed
wiring board industry. Accordingly, when MEMS 36 is a switch,
electrode 20 is the actuator and electrode 18 is the terminal. As
an electric field is created at electrode 20, extension 34 is drawn
towards electrode 20 until extension 34 makes contact with
electrode 18 in order to complete a circuit. Alternatively, when
MEMS 36 is a variable capacitor, electrode 18 is an actuator. As an
electric field is created at electrode 18, extension 34 is drawn
towards electrode 18 until extension 34 makes contact with
electrode 18. As the extension 34 is deflected from a rest state to
a flexed state, the gap between extension 34 and electrode 20
changes. The different gaps produce different capacitance states
between extension 34 and electrode 20. Those skilled in the art
would recognize alternative embodiments, such as, for example,
having a thicker electrode 20 than electrode 18 (not shown).
[0013] In FIG. 1F, only electrode 18 is formed in the second region
24 on surface 16. As described above, photopolymer 26 is applied,
then selectively irradiated in first region 22 (FIG. 1G). Metal
trace 28 is fabricated on photopolymer 26 over both the first and
second regions 22 and 24, respectively (FIG. 1H). A polymer backing
38 can be formed over metal trace 28 (FIG. 11). MEMS 40 is formed
when soluble photopolymer 26 is selectively removed to form
insoluble coating 30, on which metal trace 28 is fixed on coating
surface 32 and forms an extension 34 over second region 24, set
apart from electrode 18 (FIG. 1J) In this embodiment, electrode 18
is both the actuator and the terminal.
[0014] Examples of polymer substrate encompass any PWB material,
such as polymers and reinforced polymer composites. Common resin
vary from epoxy to Teflon. Common reinforcing materials include
woven or non-woven glass fabrics or organic fibers (e.g., aromatic
polyamide polymer-aramid paper). Particular materials include
epoxy, polyamide, polyimide, modified epoxy, BT epoxy, cyanate
ester, PTFE, E-glass, S-glass, aramid paper, FR-4, modified
epoxy-aramid, modified epoxy-SI-glass, CE-E-glass and PTFE
(Gore).
[0015] Any polymer can form the coating for the MEMS according to
the present invention, including photopolymers. In one embodiment,
the polymer can be a photopolymer such as an HDI photoimageable
dielectric. Examples of such photopolymers, included for example
only and not as limitations on the scope of the present invention,
can be Probelec.TM. 7081 (Ciba Specialty Chemicals) or ViaLux.TM.
81 (DuPont) HDI photoimageable dielectric. After the soluble
polymer is selectively removed, the insoluble coating may be
cured.
[0016] The conductive components of the MEMS, such as the
electrodes and metal trace are fabricated by known methods.
Examples include electroless or electroplate deposition of copper,
gold, aluminum, platinum, nickel, silver, chrome, palladium, tin,
bismuth, indium, lead, and alloys thereof, such as gold-palladium.
The metal can also be laminated on the polymer substrate. Examples
include electroless or electroplate deposition of copper, gold,
aluminum, platinum, nickel, silver, chrome, palladium, tin,
bismuth, indium, lead, and alloys thereof, such as gold-palladium.
To define the conductive components, the plated or laminated metals
are pattern etched by wet or dry etch methods.
[0017] As shown in FIG. 11, in addition to the metal trace, the
extension described herein has an optional backing that is not made
from crystalline silicon or ceramic silicon dioxide. Such backings
are made from organic dielectric materials, such as, for example,
epoxies, polyacrylates or polyimides. For example, in one
embodiment presented as an example and not to limit the scope of
the present invention, the backing material can be epoxy
polyacrylate. Photoimageable dielectrics may also be used as
backing materials. Extensions can be made from Cu-clad polyimide,
epoxy resin coated foil (RCF), or copper, for example. Use of just
the metal or a metal with a polymer backing, provides a switch that
requires less activation voltage, and can be used to close larger
gaps. The extension described herein may take many forms, such as a
simply supported beam, a cantilever beam, plate or diaphragm.
[0018] FIG. 2A shows MEMS 42 with a metal trace 28 that forms a
diaphragm on coating 30 and over polymer substrate 12. FIG. 2B
shows a top view of MEMS 42 in which the metal trace is removed to
reveal substrate surface 16 in second region 24, with electrode 20
forming a concentric ring around dielectric layer 46. FIGS. 2C-D
are cross-sectional views of MEMS 42 across line S-S, showing
polymeric substrate 12 with surface 16 having first region 22 and
second region 24. Metal trace 28 is fixed on the insoluble coating
30, and forms an extension 34 over second region 24. Electrode 20
and electrode 18 are disposed in second region 24, on surface 16.
As shown in MEMS 42, electrode 18 could have a dielectric layer 46
on an electrode surface 44. The dielectric layer could be ceramic,
polymer, oxide or a polymer-inorganic material. FIG. 2C shows MEMS
42 in a rest position where extension 34 is set apart from
electrode 18. FIG. 2D shows MEMS 42 in a flexed position where
electrode 20, as the actuator, has deflected extension 34 to
contact dielectric ceramic layer 46 on electrode 18.
[0019] One advantage of the organic MEMS and process for forming
the organic MEMS according to the present invention, is the
compatibility of the MEMS and PWB fabrication process. Such MEMS
can be embedded in an HDI layer, fabricated on the PWB surface, or
over a metal or dielectric layer on the PWB or any substrate
surface. As part of the HDI fabrication, the organic MEMS is used
as an electronic circuit element in connecting resistors,
capacitors and inductors embedded in the substrate, or placed on
the substrate providing for optimal circuit performance, reducing
inductance by reducing the length of the signal path between an IC
I/O and the electronic circuit element, and minimizing assembly
costs.
[0020] While the present invention has been described in terms of
particular embodiments, it is apparent that one skilled in the art
can adopt other forms without departing from the scope and spirit
of this invention. Accordingly, the scope of the invention is
limited only by the literal and equivalent scope of the claims that
follow. In addition, any art cited herein is incorporated by
reference.
* * * * *