U.S. patent application number 11/004354 was filed with the patent office on 2005-06-23 for meso-microelectromechanical system having a glass beam and method for its fabrication.
Invention is credited to Eliacin, Manes, Liu, Junhua, Savic, Jovica, Tungare, Aroon V..
Application Number | 20050134141 11/004354 |
Document ID | / |
Family ID | 34680797 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050134141 |
Kind Code |
A1 |
Savic, Jovica ; et
al. |
June 23, 2005 |
Meso-microelectromechanical system having a glass beam and method
for its fabrication
Abstract
A meso-electromechanical system (900, 1100) includes a substrate
(215), a standoff (405, 1160) disposed on a surface of the
substrate, a first electrostatic pattern (205, 1105, 1110, 1115,
1120) disposed on the surface of the substrate, and a glass beam
(810). The glass beam (810) has a fixed region (820) attached to
the standoff and has a second electrostatic pattern (815, 1205,
1210, 1215, 1220) on a cantilevered location of the glass beam. The
second electrostatic pattern is substantially co-extensive with and
parallel to the first electrostatic pattern. The second
electrostatic pattern has a relaxed separation (925) from the first
electrostatic pattern when the first and second electrostatic
patterns are in a non-energized state. In some embodiments, a
mirror is formed by the electrostatic materials that form the
second electrostatic pattern. The glass beam may be patterned using
sandblasting (140).
Inventors: |
Savic, Jovica; (Downers
Groved, IL) ; Eliacin, Manes; (Buffalo Grove, IL)
; Liu, Junhua; (Roselle, IL) ; Tungare, Aroon
V.; (Winfield, IL) |
Correspondence
Address: |
MOTOROLA, INC.
1303 EAST ALGONQUIN ROAD
IL01/3RD
SCHAUMBURG
IL
60196
|
Family ID: |
34680797 |
Appl. No.: |
11/004354 |
Filed: |
December 3, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60531961 |
Dec 23, 2003 |
|
|
|
Current U.S.
Class: |
310/309 ;
359/225.1 |
Current CPC
Class: |
H02N 1/006 20130101;
G02B 26/0841 20130101 |
Class at
Publication: |
310/309 ;
359/225; 359/226 |
International
Class: |
G02B 026/08; H02N
001/00 |
Claims
What is claimed is:
1. A meso-electromechanical system comprising: a substrate; at
least one standoff disposed on a surface of the substrate; a first
electrostatic pattern disposed on the surface of the substrate; and
a glass beam having a fixed region attached to the at least one
standoff that has a second electrostatic pattern on a cantilevered
location of the glass beam, wherein the second electrostatic
pattern is substantially co-extensive with and parallel to the
first electrostatic pattern, and wherein the second electrostatic
pattern has a relaxed separation from the first electrostatic
pattern when the first and second electrostatic patterns are in a
non-energized state.
2. The meso-electromechanical system according to claim 1, wherein
the glass beam is between 10 and 75 microns thick.
3. The meso-electromechanical system according to claim 1, wherein
the relaxed separation is between 5 and 200 microns.
4. The meso-electromechanical system according to claim 1, wherein
at least one standoff is between 7 and 200 microns thick.
5. The method according to claim 1, wherein the first electrostatic
pattern comprises a conductive metal layer having a thickness
between 2 microns and 70 microns.
6. The meso-electromechanical system according to claim 1, wherein
the second electrostatic pattern is a conductive metal that is
patterned to include an electrical termination area at the fixed
region of the glass beam.
7. The meso-electromechanical system according to claim 1, wherein
the glass beam further comprises a mirror that is near the
cantilevered location.
8. The meso-electromechanical system according to claim 7, wherein
the mirror is substantially parallel to the electrostatic
pattern.
9. The meso-electromechanical system according to claim 7, wherein
a light directing device is affixed to the glass beam near the
cantilevered location.
10. The meso-electromechanical system according to claim 1, wherein
the mirror is formed by the second electrostatic pattern.
11. The meso-electromechanical system according to claim 1, further
comprising: a first electrical contact attached to the surface of
the glass beam; and a second electrical contact that is stationary
relative to the glass beam.
12. The meso-electromechanical system according to claim 1, wherein
the first and second electrostatic patterns comprise a first pair
of electrostatic patterns, further comprising at least one
additional pair of electrostatic patterns, wherein each of the at
least one additional pair comprises: a first electrostatic pattern
disposed on the surface of the substrate; a second electrostatic
pattern on a cantilevered location of the glass beam, wherein the
second electrostatic pattern is substantially co-extensive with and
parallel to the first electrostatic pattern when the
meso-electromechanical system is non-energized.
13. The meso-electromechanical system according to claim 12,
wherein the first pair and one of the at least one additional pair
(a second pair) are on a first common axis of the glass beam.
14. The meso-electromechanical system according to claim 13,
wherein a third pair and a fourth pair of the at least one
additional pair are on a second common axis of the glass beam that
is perpendicular to the first common axis.
15. The meso-electromechanical system according to claim 14,
wherein the meso-electromechanical system is coupled to a
controller that is configured to control the meso-electromechanical
system to generate a scanned image using a light beam that reflects
off a mirror on the glass beam.
16. A method for fabricating a meso-electromechanical system,
comprising: forming a first electrostatic pattern within a device
region of a substrate from a metal layer on the substrate;
disposing a sacrificial photodielectric layer over the device
region; exposing the sacrificial photodielectric layer to form at
least one latent standoff region; coating top and bottom surfaces
of a glass dielectric with an electrostatic material; laminating
the coated glass dielectric to the sacrificial photodielectric
layer; forming a patterned protective layer on the coated glass
dielectric having a pattern of a glass beam that includes a second
electrostatic pattern substantially co-extensive with the first
electrostatic pattern; removing glass and electrostatic material
not within the pattern of the glass beam; and removing portions of
the sacrificial photodielectric layer other than the at least one
latent standoff region, thereby forming at least one standoff.
17. The method according to claim 16, wherein forming the patterned
protective layer comprises applying a photosensitive etch resist at
least 50 microns thick on the top surface of the glass dielectric,
and exposing the photosensitive etch resist using a pattern; and
wherein removing the glass and electrostatic material not within
the pattern of the glass beam comprises sandblasting.
18. The method according to claim 16, wherein forming the patterned
protective layer comprises applying a photosensitive etch resist,
and exposing the photosensitive etch resist using a pattern; and
wherein removing the glass and electrostatic material not within
the pattern of the glass beam comprises applying a glass
etchant.
19. The method according to claim 16, wherein removing portions of
the sacrificial photodielectric layer further comprises solvent
developing using ultrasonic agitation.
20. The method according to claim 16, further comprising: forming
an electrical connection to the second electrostatic pattern at a
portion of the glass beam laminated to the at least one
standoff.
21. An electronic equipment, comprising: a meso-electromechanical
system comprising a substrate, at least one standoff disposed on a
surface of the substrate, a first electrostatic pattern disposed on
the surface of the substrate, and a glass beam having a fixed
region attached to the at least one standoff that has a second
electrostatic pattern on a cantilevered location of the glass beam,
wherein the second electrostatic pattern is substantially
co-extensive with and parallel to the first electrostatic pattern,
and wherein the second electrostatic pattern has a first relaxed
separation from the first electrostatic pattern when the first and
second electrostatic patterns are in a non-energized state; and a
controller coupled to the first and second electrostatic patterns
that controls movement of the glass beam by energizing the
electrostatic patterns.
Description
BACKGROUND
[0001] Optical switches based on opto-electromechanical,
electro-optic, or liquid crystal technologies are commercially
available. The commercial opto-electromechanical switches are
typically fabricated in silicon using silicon-processing
techniques, and comprise micron dimension mirrors that can be
electrostatically actuated. They are classified as
micro-electromechanical systems (MEMS). Cost, reliability of
operation, and power drain are the primary drawbacks of these
commercially available optical switches. In order to improve
reliability, elaborate processes are used to hermetically seal the
MEMS structures--further adding to the cost.
[0002] In another MEMS technology, called the meso-MEMS technology,
low cost switches are fabricated on a polymer structure with a
mechanical cantilever member that is at least partially made of
metal--typically copper. These have been shown to provide useful
electrical switching functions, such as for RF signal
switching.
[0003] What is needed is a more reliable and lower cost switch
technology that can be used for optical switching.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The present invention is illustrated by way of example and
not limitation in the accompanying figures, in which like
references indicate similar elements, and in which:
[0005] FIG. 1 is a flow chart that shows steps of a method of
fabricating a meso-microelectromechanical system (meso-MEMS) in
accordance with embodiments of the present invention;
[0006] FIGS. 2-9 are mechanical drawings showing perspective views
of a meso-MEMS structure at various stages of fabrication, in
accordance with embodiments of the present invention;
[0007] FIG. 10 is a mechanical drawing showing a side view of a
meso-MEMS structure at an advanced stage of fabrication, in
accordance with embodiments of the present invention;
[0008] FIGS. 11 and 12 are mechanical drawings showing perspective
views of a meso-MEMS structure, in accordance with embodiments of
the present invention; and
[0009] FIG. 13 is a schematic representation of an electrical
equipment that includes meso-MEMS.
[0010] Skilled artisans will appreciate that elements in the
figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions of
some of the elements in the figures may be exaggerated relative to
other elements to help to improve understanding of embodiments of
the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0011] Before describing in detail the particular
meso-microelectromechani- cal system (meso-MEMS) in accordance with
the present invention, it should be observed that the present
invention resides primarily in combinations of method steps and
apparatus components related to micromechanical switching.
Accordingly, the apparatus components and method steps have been
represented where appropriate by conventional symbols in the
drawings, showing only those specific details that are pertinent to
understanding the present invention so as not to obscure the
disclosure with details that will be. readily apparent to those of
ordinary skill in the art having the benefit of the description
herein.
[0012] Referring to FIG. 1, a flow chart of a method for
fabricating a meso-MEMS is shown, in accordance with embodiments of
the present invention. FIGS. 2-9 are isometric views of the
meso-MEMS in various stages of fabrication in accordance with
embodiments of the present invention.
[0013] At step 105 (FIG. 1), a first electrostatic pattern 205 (see
FIG. 2) is formed within a device region 210 of a substrate 215
from an inner metal layer on the substrate 215, in accordance with
embodiments of the present invention. In some instances, the
substrate 215 may be larger than the device 210. In the example
being described with reference to FIG. 2, the device region 210 and
substrate 215 are shown as being the same size. The substrate 215
may be made of any organic printed wiring board (PWB) material, of
which one example is FR-4, or may be made of materials that are
more expensive (e.g., Teflon) or less expensive (e.g., epoxy
without glass fill). The substrate may be a multilayer PWB. The
metal layer may be copper having a thickness between 2 and 70, and
more typically between 5 microns and 35 microns, but could be of
other materials such as nickel or gold or multilayers of metal, or
alloys of metal. The metal need only be capable of holding and
releasing an electrostatic charge. Copper is useful since it is
relatively inexpensive and commonly used. The first electrostatic
pattern 205 may be fabricated using conventional photo-lithographic
patterning and etching techniques or applying a conductive paste by
screen-printing, pad printing or other conventional thick film
paste application method.
[0014] At step 110 (FIG. 1), a sacrificial photodielectric layer
305 (see FIG. 3) that is photosensitive is disposed over the device
region 210 (FIG. 2), in accordance with embodiments of the present
invention. The sacrificial photodielectric layer 305 is preferably
a photo-sensitive (positive or negative) epoxy resin that may be
deposited via roller coating or curtain coating to a thickness that
is between 50 and 200 microns. An example of material that can be
used for the sacrificial photodielectric layer 305 is the
Probimer.RTM. 7081/82 photo-polymer resin material distributed by
Huntsman of Basel, Switzerland. For this example, the resin
material may be dried in an air assist infra-red horizontal drying
oven for 30-60 minutes at a temperature of 60-80C. The sacrificial
photodielectric layer 305 may have a thickness between 7 microns
and 200 microns, and more typically between 50 microns and 125
microns
[0015] At step 115 (FIG. 1), the sacrificial photodielectric layer
305 is exposed to form a latent standoff region 405 (see FIG. 4),
in accordance with embodiments of the present invention. As one
example, once the sacrificial photodielectric layer 305 is dry, an
artwork (film) is used to expose a pattern onto the photo-polymer
using 1500-1700 millijoules of ultraviolet irradiation, creating
one or more "latent" imaged regions which include the latent
standoff region 405. The latent standoff region 405 is defined by
its differentially polymerized state as compared to the surrounding
bulk material of the sacrificial photodielectric layer 305. The one
or more latent imaged regions will act as anchoring points for the
meso-MEMS of the present invention upon completion of its
fabrication. Under conventional PWB fabrication circumstances, a
PWB would undergo a thermal "bump" and then solvent developing
immediately after UV exposure. In the present invention, the
unimaged areas are not thermally bumped or developed until a later
step. At this point the device region 210 is essentially still
fully coated by the sacrificial photodielectric layer 305,
presenting an essentially planar surface.
[0016] At step 120 (FIG. 1) a first side (top side) of a glass
dielectric 505 (see FIG. 5) is coated with an electrostatic
material 510, forming a coated glass dielectric 500, in accordance
with embodiments of the present invention. Note that this step may
occur before or after any of steps 105, 110, and 115. In
embodiments for which a light reflecting surface (mirror) is needed
(for example, for embodiments that are for optical light beam
switching), and for which the reflective surface (mirror) is to be
on a surface of the glass dielectric 505 (as opposed, for instance,
to an embodiment in which a reflective surface is needed that is at
some angle to the surface of the glass dielectric 505), materials
are used in this coating step 120 that are both electrostatic and
light reflecting. The glass dielectric 505 may be formed in the
shape of the device region 210 (or smaller), and has a thickness
that is typically between 30 and 50 microns, but which may be as
small as 10 microns and as large as 75 microns. The coating of the
top side of the glass dielectric 505 comprises applying one or more
metal layers having a total thickness less than 25 microns. The
second side (bottom side) of the glass dielectric 505 may also be
coated with electrostatic material 515 during the coating of the
first side, or as an independent step, or not at all. A first
example of an electrostatic and light reflecting coating is
sputtering approximately 500 Angstroms of titanium tungsten (Ti/W)
on both sides of the glass dielectric 505, followed by sputtering
approximately 1000 Angstroms of copper on both sides of the glass
dielectric 505. A second example of coating is depositing by
evaporation approximately 500 Angstroms of chrome followed by 5000
Angstroms of copper onto both surfaces of the glass dielectric 505.
These electrostatic materials 510, 515 have very good light
reflecting properties and are very compatible with conventional PWB
processing techniques. Other metal layers may be used for
electrostatic and light reflecting surfaces, for example chrome,
chrome/gold, Ti/W, and Ti/W with copper, and tantalum, while a
broader range of materials may be used for electrostatic only
characteristics. Electrostatic only characteristics are useful for
electronic switches, such as radio frequency (RF) switches. Other
electrostatic materials 510 that may be used are other conductive
metals, such as pure copper, nickel, silver, gold, or conductive
metals alloys in combination with other materials. An electrostatic
material 510 that is susceptible to conventional PWB etching
techniques may be more useful if it is compatible with additional
fabrication steps described herein below, but may still be usable
to form the unique apparatus described herein even if not
compatible with conventional PWB techniques.
[0017] As stated above, electrostatic materials may be formed on
the top and bottom surfaces in the same step or steps. Thus,
mirrored surfaces may also be formed on the top and bottom surfaces
in the same steps. In some embodiments, the electrostatic materials
are not formed on the top surface of the glass, but the
electrostatic material is formed as a mirror material on the bottom
surface.
[0018] It will be appreciated that in other embodiments of the
present invention, a mirror may be formed on the top surface of the
coated glass dielectric at a location other than the first
electrostatic pattern 205, which may require a different shape of
the glass beam than those described herein below.
[0019] At step 125 (FIG. 1), the coated glass dielectric 500 is
laminated to the sacrificial photodielectric layer 305 (see FIG.
6), forming a laminated glass dielectric 600, in accordance with
embodiments of the present invention. The sacrificial
photodielectric layer 305 is still "tacky", particularly under heat
and pressure, and acts as a "glue" for the metallized glass
dielectric. Lamination of the coated glass dielectric 500 to the
sacrificial dielectric layer 305 has been demonstrated in both a
conventional PWB laminator (a Wabash laminating press made by
Wabash MPI of Wabash, Indiana) and a conventional vacuum dry-film
laminator. It is important to note that lamination temperature must
not exceed 80 degrees C. in the embodiment of the present invention
that uses the Probimer.RTM. sacrificial photodielectric layer 305.
The process in the embodiment using the Probimer.RTM. sacrificial
dielectric layer 305 is to laminate the coated glass dielectric 500
to the sacrificial photodielectric layer 305 in a vacuum laminator
for approximately 10 minutes at 65-75 C.
[0020] At step 130 (FIG. 1), a patterned protective layer is formed
on the laminated glass dielectric 600 having a protective pattern
710 (FIG. 7) of a glass beam in a desired geometry that includes a
second electrostatic pattern 715 substantially co-extensive with
the first electrostatic pattern 205, in accordance with embodiments
of the present invention . This pattern comprises a standard
temporary etch resist material, formed by conventional techniques,
some examples of which are: photo-imaged and developed dry-film or
liquid photo-resist; screen printing; and stenciling
[0021] At step 135 (FIG. 1) a portion of the electrostatic material
510 on top of the coated glass dielectric 500 that is not within
the second electrostatic pattern 715 is removed in accordance with
embodiments of the present invention. Removing the portion of the
electrostatic material 510 comprises applying an electrostatic
material etchant. When the electrostatic material 510 comprises a
top layer of copper, conventional copper etching chemistry
(peroxide/sulfuric, cupric chloride, ammonium chloride, etc.) is
used. This step may include etching with additional solutions when
the electrostatic material 510 comprises multiple layers. In the
example of a Ti/W layer under copper, the Ti/W layer outside the
desired pattern that was located directly beneath the copper layer
may be conveniently etched away by a warm (50 degrees Centigrade)
hydrogen peroxide solution. In an alternative embodiment, a
commercially available material distributed by the Shipley Company,
L.L.C., of Marlborough, Mass. that is identified as 746 W etchant,
which is commonly used for PWB copper etching, has also been
demonstrated to effectively remove the Ti/W layer. When chrome is
used as a part of the electrostatic material 510, then the chrome
may be etched in cerric ammonium nitrate solution (available as a
conventional chrome etchant "Chrome Etchant 1020" distributed by
Transene Company, Inc. of Danvers, Mass.), followed by conventional
copper etching as described above.
[0022] At step 140 (FIG. 1) glass not within the pattern of the
glass beam is removed. The patterned protective layer 710 that had
been applied to protect during the metal/mirror etch step 135 and
the remaining patterned electrostatic material 510 that remains all
act as inherent etch resists during the glass removal process. In
one embodiment, the glass is etched in 25% hydrogen floride (HF)
solution for approximately 25 minutes. The glass can alternatively
be etched in ammonium bifloride solution, a buffered oxide etch
solution (BOE) or fluorosilicic acid solution. In another
embodiment, the glass can be removed by mechanical means, namely
sandblasting. For example, horizontal sandblasting may be performed
using 27 micron aluminum oxide particles at 80 pounds per square
inch (552 kilopascals) ejected from a nozzle having a nozzle
diameter of 0.035" (0.88 mm) at a distance from the substrate 215
of 2" (5.08 cm), and a conveyor speed of 4" (10.16 cm) per minute.
When sandblasting is used, the patterned protective layer 710 may
be applied to a greater thickness than usual, such as 50 to 100
microns.
[0023] At step 145 (FIG. 1), a portion of the electrostatic
material 515 that was on the bottom of the coated glass dielectric
505 is removed from the surface of the sacrificial photodielectric
layer 305, in accordance with embodiments of the present invention.
The electrostatic material 510 (e.g., Ti/W-copper or chrome/copper)
that was on the bottom of the removed glass needs to be removed
from the exposed surface of the sacrificial photodielectric layer
305. The electrostatic material 515 (e.g., Ti/W-copper or
chrome/copper) is removed by exposing the meso-MEMS structure 800
once again to appropriate etching solutions such as warm peroxide
(or chrome etch) and standard copper etch solutions. It can be
important to have this second layer of Ti/W-copper or chrome-copper
during glass removal because it protects the epoxy resin from the
glass removal agent, specifically during chemical etching. The
resin is inherently resistant to HF but long term exposure may
impair the photo-sensitive properties of the material. When
sandblasting is used to remove glass, it may also be used to remove
the portion of the electrostatic material 515 instead of etching
the electrostatic material.
[0024] At step 150, after the portion of the electrostatic material
515 that was on the bottom of the coated glass dielectric 505 is
removed, the remaining portion of the patterned protective layer
710 is removed from the top surface of the coated glass, leaving a
glass beam having the electrostatic material 510 on the top surface
of the glass beam, and exposing the reflective surface of the
second electrostatic pattern 815 (FIG. 8). This step can be
performed either before or after step 155. A solvent such as a
water based solution of sodium hydroxide, which will dissolve the
protective layer 705 essentially without harming other parts of the
meso-MEMS structure 800 (FIG. 8) is used.
[0025] Referring to FIG. 8, a perspective view of the meso-MEMS
structure 800 at this point of the fabrication is shown, in
accordance with embodiments of the present invention. The remaining
coated glass is now in a pattern having the shape of a glass beam
that was determined by the protective pattern 710. The meso-MEMS
structure 800 has a glass beam 810 with a second electrostatic
pattern 815 that is essentially co-extensive with the first
electrostatic pattern 205, that is on a cantilevered portion of the
glass beam 810, and that is also a mirrored surface in this
embodiment. When the electrostatic material is formed on both the
top and bottom of the glass material 505, then the electrostatic
pattern 815 is on both the top and bottom of the glass beam 810,
and there may be a mirror surface on both sides, depending on the
materials used for the electrostatic patterns 815. On the other
hand, the electrostatic material may be formed on only the top or
only the bottom of the glass beam 810.
[0026] At step 155 (FIG. 1), the sacrificial photodielectric layer
305, other than the lateral standoff region, is removed. In a first
sub step, the sacrificial photodielectric layer 305 is thermally
bumped for 60 minutes at 110-130 degrees Celsius in either a batch
air convection oven or a horizontal air-assist IR oven to complete
the photo-reaction initiated in the first stage of the meso-MEMS
structure build-up, at steps 110, 115. After thermal bumping the
sacrificial photodielectric layer is solvent developed, for example
using gamma-butyrolactone (GBL) for 20 minutes with ultrasonic
agitation, in a second sub-step. The GBL will penetrate under the
glass beam 810, removing all un-polymerized material. The material
which was latent imaged--the latent standoff region 405--remains as
a standoff 905 while all the other sacrificial dielectric material
will have been removed. Once all this sacrificial dielectric
material has been removed, the glass beam 810 will have an air
space underneath it allowing it freedom to change position
according to electrostatic actuation. It will be appreciated that
in some embodiments there are a plurality of standoffs, and the
glass beam may be substantially more complex than the one shown in
FIGS. 2-10. It will be further appreciated that more than one glass
beam could be simultaneously fabricated in a meso-MEMS structure by
the methods described herein.
[0027] Referring to FIGS. 9 and 10, a perspective and a side view
of a meso-MEMS structure 900 are shown, in accordance with
embodiments of the present invention. The meso-MEMS structure 900
has been fabricated by the steps 105-155. The glass beam 810 has a
fixed region 920 that is affixed to the standoff region 405, and
has a relaxed separation 925 between the first and second
electrostatic patterns 205, 815 that may be between 5 and 200
microns when no electrical potential exists between them (i.e.,
they are in a non-energized state). (The relaxed separation is
largely determined by the thickness of the sacrificial
photodielectric layer 305.) The second electrostatic pattern 815 is
essentially parallel to the first electrostatic pattern when they
are in a non-energized state. The approximate size of a meso-MEMS
structure that has been fabricated using steps of the above
described process is 3.5 mm long with an electrostatic pattern
width of approximately 1.5 mm. Meso-MEMS structures such as
meso-MEMS 900 can be used, for example, as an optical switch and
can be fabricated more economically than, for example, a silicon
based electro-optical-mechanical switch.
[0028] At step 160, an electrical connection is formed to the
second electrostatic pattern 815 at or near a portion of the glass
beam 810 laminated to the standoff region 405. This may be done in
any reliable manner, such as soldering or wire bonding a wire to
the electrostatic material 510 on the top and/or bottom surfaces
(depending on whether the electrostatic pattern is on the top or
bottom, or both) of the fixed region 920 of the glass beam 810, or
by pressing a conductive material against the electrostatic
material 510 near the fixed region 920 of the glass beam 810.
Electrical connection to the first electrostatic pattern 205 may be
conveniently provided by patterning a conventional printed wire
that connects to the first electrostatic pattern 205 and to a
connection pad on the substrate 215 that is for an electrical
connector or that is connected to an electronic component, such as
an integrated circuit terminal. It will be appreciated that by
applying the electrostatic material onto only one surface of the
glass material 505, and by using electrostatic materials that form
a good mirror, the resulting mirror can be a front surface or back
surface mirror for light that is incident on the top surface of the
glass beam 810, which offers a design choice that may be
beneficial. Also, it will be appreciated that in embodiments of the
present invention, the electrostatic force can be applied to the
electrostatic pattern 815 on either the top surface, the bottom
surface, or both surfaces of the glass beam 810, offering other
design choices that may be beneficial.
[0029] It will be appreciated that the examples described with
reference to FIGS. 1-10 are related to a meso-MEMS structure having
a glass beam with a straight flexible arm that allows movement
along essentially one axis from the relaxed position, having a
mirror that is moved by the movement of the arm. In this example,
the second electrostatic pattern 205 and the mirror (reflective
surface) are at the same location on the glass beam 810, a
cantilevered location (i.e., a location near the end of the glass
beam 810 that is farthest from the fixed region 920 of the glass
beam 810). This is a simple and highly useful MEMS that can provide
optical switching or modulation functions, but there are many
variations of the present invention that can provide other useful
functions. For example, the mirror may be located near, but not at,
the cantilevered location of the second electrostatic pattern 205.
As another example, an opposing pair of electrical contacts could
be fabricated, one at the end 1005 of the glass beam 810 and
another one on the substrate 215 at an opposing location 1010, and
there may be no mirror. This example of an electrical switch
meso-MEMS may not need to have multiple metals forming the
electrostatic patterns 205, 815, and may operate as an RF switch.
Such electrical contacts may alternatively be located nearer to the
standoff region 405 than is the second electrostatic pattern 205.
As another example, there may be a light directing device affixed
to the glass beam 810 near or at the cantilevered location, instead
of (or possibly in addition to) a mirror on the top or bottom
surface of the glass beam 810. The light directing device could be
a flat mirror or shutter (a non-reflecting, opaque plane) mounted
at some planar angle with reference to the top surface of the glass
beam 810, or an object of some other shape, such as a bar that is
triangular in cross section with two mirrored surfaces, mounted on
the glass beam 810 near the cantilevered location.
[0030] Referring now to FIGS. 11 and 12, perspective drawings of
another example of an optical meso-MEMS structure 1100 are shown,
in accordance with an embodiment of the present invention. The
meso-MEMS structure 1100 is fabricated using essentially the same
steps described above for the meso-MEMS structure 900. FIG. 12
shows the meso-MEMS structure 900 after the completion of steps
105-155, while FIG. 11 exposes the bottom portion of the meso-MEMS
structure 900 (and does not relate to a specific fabrication step).
It can be seen in FIGS. 11 and 12 that there are four pairs of
electrostatic patterns comprising electrostatic patterns 1105,
1205, electrostatic patterns 1110, 1210, electrostatic patterns
1115, 1215 and electrostatic patterns 1120, 1220. Electrostatic
patterns 1105, 1110, 1115, 1120 are formed on a substrate 1150. The
electrostatic patterns 1215, 1220 are located at the cantilevered
locations for flexible beam portions 1240, 1245, and electrostatic
patterns 1205, 1210 are located at the cantilevered locations for
flexible beam portions 1250, 1255 of the glass beam comprising the
flexible portions 1205, 1210, 1240, 1245 and the electrostatic
patterns 1205, 1210, 1215, 1220. For each electrostatic pair (1105,
1205), (1110, 1210), (1115, 1215), and (1120, 1220), the
electrostatic patterns are substantially co-extensive and parallel
to each other when the meso-MEMS is non-energized. The
electrostatic patterns 1205, 1210 are conductively joined and also
form a mirror that is used to move a light beam that is aimed onto
the mirror, but the electrostatic patterns 1205, 1210 may be
considered, for electrostatic energizing purposes, as two patterns
split by the (imaginary) line 1208. The electrostatic patterns
1205, 1210 are conductively joined to each other (and to
electrostatic patterns 1215, 1220, but may be considered, for
electrostatic energizing purposes, as two electrostatic patterns. A
common electrical potential can be applied to the four
electrostatic patterns 1205, 1210, 1215, 1220 and the movement of
the mirror is determined essentially by independent electrical
potentials that can be applied to the electrostatic patterns 1105,
1110, 1115, 1120. It can be seen that the two pairs of
electrostatic patterns (1105, 1205) and (1110, 1210) are at
cantilevered locations along a first axis of freedom of movement of
the mirror that is afforded by flexible glass beam arms 1240, 1245
and that the other two pairs of electrostatic patterns (1105, 1205)
and (1110, 1210) are at cantilevered locations on a second axis of
freedom of movement of the mirror afforded by flexible glass beam
arms 1250, 1255 that is perpendicular to the first axis. Thus, by
appropriate application of potential differences, the mirror can be
moved in two axes, within angular displacement limits imposed at
least by the dimensions of the meso-MEMS 1100. A device such as
meso-MEMS 1100 could be used, for example, to scan a light beam to
create an image. In a related embodiment, a single axis meso-MEMS
may be constructed using only two pairs of electrostatic patterns
on a common axis, such as electrostatic patterns (1115, 1215) and
(1120, 1220) of FIG. 12 in an embodiment similar to that shown in
FIG. 12, but with the entire area that includes electrostatic
patterns 1215, 1220, beams 1250, 1255, and electrostatic patterns
1210, 1205 being a single, solid plate. A device of this type could
be used, for example, to displace a light beam along an axis, under
which a photosensitive paper is moved, to record voltages, as for
an electrocardiogram.
[0031] Referring to FIG. 13, a schematic and block diagram of an
example of an electronic equipment which includes at least one
meso-MEMS structure is shown, in accordance with an embodiment of
the present invention. An optical switching network includes a bank
of optical fiber switches 1305, 1306 each of which has a single
optical fiber input 1350 and two optical fiber outputs 1365, 1367.
The single optical fiber input 1350 can be switched to either one
of the two optical fiber outputs 1365, 1367 as determined by a
controller 1320 that is coupled to an electrostatic interface 1310.
Each switch 1305 comprises a guide 1353 for the optical fiber input
1350 that directs an optical input signal to a mirror surface 1385
on a glass beam of the present invention. When the controller 1320
determines that a meso-MEMS device is not to be switched, as in the
case of optical fiber switch 1305, the electrostatic interface 1310
removes essentially all electrostatic charge difference between the
electrostatic patterns 1385, 1383, the glass beam assumes a relaxed
position. As a consequence, the optical input signal reflects 1357
off the mirror 1385 to a first optical fiber output guide and
amplifier 1359 and is guided out the optical fiber 1365 coupled to
switch 1305, and optical fiber 1367 couple to switch 1305 has no
signal. When the controller 1320 determines that a meso-MEMS device
is to be switched, as in the case of optical fiber switch 1306, the
electrostatic interface 1310 places an electrostatic charge
difference onto the electrostatic patterns 1385, 1383. As a
consequence, the glass beam assumes an energized, deflected
position, and the optical input signal reflects 1393 off the mirror
1385 to a second optical fiber output guide and amplifier 1367 and
is guided out the optical fiber 1367 coupled to switch 1306, and
optical fiber 1365 coupled to switch 1306 has no signal.
[0032] The meso-MEMS structures formed in accordance with the
present invention can be combined with silicon devices and other
electronic components using PWB technology. Optoelectronic circuits
thus formed (i.e., those including either electronic or photonic
circuits, or both) can be complicated systems that include, for
example, an essentially complete optical receiver, transmitter, or
transceiver, and can be included in any of a very wide variety of
optoelectronic assemblies (i.e., those including either electronic
or photonic circuits, or both), including passive optical networks
and consumer products such as projection displays and optical
fiber-to-home set top boxes.
[0033] In the foregoing specification, the invention and its
benefits and advantages have been described with reference to
specific embodiments. However, one of ordinary skill in the art
appreciates that various modifications and changes can be made
without departing from the scope of the present invention as set
forth in the claims below. Accordingly, the specification and
figures are to be regarded in an illustrative rather than a
restrictive sense, and all such modifications are intended to be
included within the scope of present invention. The benefits,
advantages, solutions to problems, and any element(s) that may
cause any benefit, advantage, or solution to occur or become more
pronounced are not to be construed as a critical, required, or
essential features or elements of any or all the claims.
[0034] As used herein, the terms "comprises, " "comprising, " or
any other variation thereof, are intended to cover a non-exclusive
inclusion, such that a process, method, article, or apparatus that
comprises a list of elements does not include only those elements
but may include other elements not expressly listed or inherent to
such process, method, article, or apparatus.
[0035] The term "another", as used herein, is defined as at least a
second or more. The construction "either . . . . or" is equivalent
to a Boolean exclusive or statement. The terms "including" and/or
"having", as used herein, are defined as comprising. The term
"coupled", as used herein with reference to electro-optical
technology, is defined as connected, although not necessarily
directly, and not necessarily mechanically.
* * * * *