U.S. patent application number 09/497270 was filed with the patent office on 2002-06-13 for micro-electro-mechanical-system (mems) mirror device.
Invention is credited to Bowers, John Edward, Corbalis, Charles, Helkey, Roger Jonathan, Lee, Seung Bok, MacDonald, Noel, Sink, Robert Kehl.
Application Number | 20020071169 09/497270 |
Document ID | / |
Family ID | 23976147 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020071169 |
Kind Code |
A1 |
Bowers, John Edward ; et
al. |
June 13, 2002 |
Micro-electro-mechanical-system (MEMS) mirror device
Abstract
A micro-electro-mechanical-system (MEMS) mirror device and
methods for fabricating the same allow for a large range of angular
motion for a center mirror component. The large range of angular
motion for a center mirror component is dictated simply by a
thickness of a substrate used or a thickness of a thick film used
in making a support structure to support the center mirror
component. The MEMS mirror device and methods for fabricating the
same allow a large number mirror devices to be fabricated on a
substrate. The MEMS mirror device includes a substrate. Electrodes
are formed supported by the substrate. A support structure is
formed adjacent to the electrodes. A hinge pattern and a mirror
pattern having a center mirror component are formed such that the
support structure supports the hinge pattern and mirror pattern.
The support structure also supports the hinge pattern and mirror
pattern such that a bottom surface of the center mirror component
in a stationary non-rotating position is capable of exceeding a
height of 50 .mu.m above the electrodes.
Inventors: |
Bowers, John Edward; (Santa
Barbara, CA) ; Helkey, Roger Jonathan; (Montecito,
CA) ; Corbalis, Charles; (Saratoga, CA) ;
Sink, Robert Kehl; (Santa Barbara, CA) ; Lee, Seung
Bok; (Ithaca, NY) ; MacDonald, Noel; (Santa
Barbara, CA) |
Correspondence
Address: |
Lester J Vincent
Blakely Sokoloff Taylor & Zafman LLP
7th Floor
12400 Wilshire Boulevard
Los Angeles
CA
90025
US
|
Family ID: |
23976147 |
Appl. No.: |
09/497270 |
Filed: |
February 1, 2000 |
Current U.S.
Class: |
359/291 ;
359/292; 359/295 |
Current CPC
Class: |
G02B 26/0841 20130101;
B81B 3/004 20130101; B81B 2201/042 20130101 |
Class at
Publication: |
359/291 ;
359/295; 359/292 |
International
Class: |
G02B 026/00 |
Claims
What is claimed is:
1. A micro-electro-mechanical-system (MEMS) mirror device,
comprising: a substrate; electrodes supported by the substrate; a
support structure formed adjacent to the electrodes; a hinge
pattern and a mirror pattern having a center mirror component such
that the support structure supports the hinge pattern and mirror
pattern; and wherein the support structure supports the hinge
pattern and mirror pattern such that a bottom surface of the center
mirror component in a stationary non-rotating position is capable
of exceeding a height of 50 .mu.m above the electrodes.
2. The MEMS mirror device of claim 1, wherein the center mirror
component is capable of having an angular range of motion exceeding
20 degrees with respect to an axis.
3. The MEMS mirror device of claim 1, wherein the support structure
is photosensitive glass, silicon, or plated metal.
4. The MEMS mirror device of claim 1, wherein the plated metal is
nickel Ni, Copper Cu, or gold Au.
5. The MEMS mirror device of claim 1, wherein the support structure
defines holes such that the holes are approximately centered below
the center mirror component.
6. The MEMS mirror device of claim 1, further comprising: a wiring
pattern coupled with the electrodes; and an insulation layer
insulating the wiring pattern and electrodes.
7. The MEMS mirror device of claim 1, wherein the mirror pattern
includes a frame pattern such that the hinge pattern supports the
frame pattern.
8. The MEMS mirror device of claim 1, wherein the mirror pattern
includes a frame pattern and a mirror component such that the hinge
pattern supports the frame pattern and mirror component.
9. The MEMS mirror device of claim 1, wherein the mirror pattern
includes at least one layer.
10. The MEMS mirror device of claim 9, wherein the mirror pattern
includes a gold Au metal layer, an aluminum Al metal layer, or a
copper Cu layer.
11. The MEMS mirror device of claim 9, wherein the mirror pattern
includes: a first metal layer; a support layer formed on the first
metal layer; and a second metal layer formed on the support
layer.
12. The MEMS mirror device of claim 11, wherein the first and
second metal layers are a gold Au metal layer, aluminum Al metal
layer, or copper Cu metal layer.
13. The MEMS mirror device of claim 11, wherein the support layer
is a silicon dioxide SiO.sub.2 layer, silicon nitride
Si.sub.xN.sub.y layer, polysilicon layer, silicon oxynitride
Si.sub.xO.sub.yN.sub.z layer, or polymer layer.
14. The MEMS mirror device of claim 1, wherein the center mirror
component is used for optical switching.
15. The MEMS mirror device of claim 1, wherein the center mirror
component is a component for scanning systems, printing systems,
and display systems.
16. A micro-electro-mechanical-system (MEMS) mirror device
fabrication method, comprising: exposing selectively a substrate to
form exposed regions and unexposed regions; forming electrodes
supported by the substrate; forming a mirror pattern having a
center mirror component and a hinge pattern supported by the
substrate; and removing portions of the substrate in the exposed
regions to form a support structure from the unexposed regions such
that the support structure supports the mirror pattern and hinge
pattern.
17. The fabrication method of claim 16, wherein the substrate is a
photosensitive glass substrate.
18. The fabrication method of claim 17, wherein exposing
selectively a substrate exposes selectively the photosensitive
glass substrate to form exposed regions such that the center mirror
component is approximately centered of the exposed regions.
19. The fabrication method of claim 18, further comprising:
polishing the photo sensitive glass substrate after exposing
selectively the photo sensitive glass substrate to retain planarity
and remove any materials formed thereon.
20. The fabrication method of claim 18, wherein removing portions
of the substrate includes: etching selectively using an etching
solution the exposed regions of the photosensitive glass
substrate.
21. The fabrication method of claim 20, wherein the etching
solution is hydro-fluoric HF acid and wherein the HF acid etches
more rapidly in the exposed regions than in the unexposed
regions.
22. The fabrication method of claim 20, wherein etching selectively
includes: forming a protection layer over the mirror pattern and
hinge pattern such that portions of the photosensitive glass
substrate are exposed to allow the etching solution to reach the
exposed regions of the photosensitive glass substrate; and
depositing the etching solution over the photosensitive glass such
that the etching solution reaches the exposed regions of the
photosensitive glass to form the support structure from the
unexposed regions of the photosensitive glass.
23. The fabrication method of claim 22, further including: removing
the protection layer.
24. The fabrication method of claim 16, wherein forming the mirror
pattern forms a frame pattern such that the hinge pattern supports
the frame pattern.
25. The fabrication method of claim 16, wherein forming the mirror
pattern forms a frame pattern and a mirror component such that the
hinge pattern supports the frame pattern and mirror component.
26. The fabrication method of claim 16, wherein a thickness of the
support structure is capable of exceeding a thickness of 50
.mu.m.
27. The fabrication method of claim 16, wherein the mirror pattern
includes at least one layer.
28. The fabrication method of claim 27, wherein the mirror pattern
includes a gold Au metal layer, an aluminum Al metal layer, or a
copper cu metal layer.
29. The fabrication method of 27, wherein forming a mirror pattern
includes: forming a first metal layer; forming a support layer on
the first metal layer; and forming a second metal layer on the
support layer.
30. The fabrication method of claim 29, wherein the first and
second metal layers are a gold Au metal layer, aluminum Al metal
layer, or copper Cu metal layer.
31. The fabrication method of claim 29, wherein the support layer
is a silicon dioxide SiO.sub.2 layer, silicon nitride
Si.sub.xN.sub.y layer, polysilicon layer, silicon oxynitride
Si.sub.xO.sub.yN.sub.z layer, or polymer layer.
32. The fabrication method of claim 16, further comprising: forming
a wiring pattern such that the wiring pattern is coupled with the
electrodes; forming an insulation layer such that the insulation
layer insulates the wiring pattern and electrodes.
33. A micro-electro-mechanical-system (MEMS) mirror device
fabrication method, comprising: forming a release layer on a first
substrate; forming a mirror pattern having a center mirror
component and a hinge pattern supported by the release layer;
forming electrodes supported by a second substrate; forming a
support structure; attaching the first substrate with the second
substrate using the support structure; removing the first substrate
and the release layer such that the support structure supports the
hinge pattern and mirror pattern.
34. The fabrication method of claim 33, wherein forming a support
structure forms the support structure such that the support
structure is supported by the second substrate.
35. The fabrication method of claim 34, wherein forming a support
structure includes: forming a bond with a topside of the support
structure with the hinge pattern supported by the first substrate
such that the first substrate is attached with the second
substrate.
36. The fabrication method of claim 33, wherein forming a support
structure forms the support structure such that the support
structure is supported by the first substrate.
37. The fabrication method of claim 36, wherein forming a support
structure includes: forming a bond with a topside of the support
structure with the second substrate such that first substrate is
attached with the second substrate.
38. The fabrication method of claim 33, wherein forming the support
structure uses a thick patterned film.
39. The fabrication method of claim 38, wherein forming the support
structure uses an electroless, electro-plating, or a sputtering
process with the thick patterned film to form the support
structure.
40. The fabrication method of claim 39, wherein the thickness of
the thick patterned film dictates the thickness of the support
structure.
41. The fabrication method of claim 40, wherein forming the support
structure uses nickel Ni, copper Cu, gold Au, or aluminum Al.
42. The fabrication method of claim 33, wherein the release layer
is a polymer layer, oxide layer, or a nitride layer.
43. The fabrication method of claim 42, wherein removing the first
substrate and release layer includes: etching away the first
substrate using an etching solution; and applying oxygen plasma to
react with the release layer such that the release layer is removed
from the mirror pattern.
44. The fabrication method of claim 42, wherein removing the
release layer includes: etching away the release layer such that
the release layer is removed from the mirror pattern.
45. The fabrication method of claim 33, wherein the first substrate
is a silicon substrate, glass substrate, or borosilicate glass
substrate.
46. The fabrication method of claim 33, wherein forming a mirror
pattern forms a frame pattern supported by the release layer.
47. The fabrication method of claim 33, wherein forming a mirror
pattern forms a frame pattern and a mirror component supported by
the release layer.
48. The fabrication method of claim 33, wherein the mirror pattern
includes at least one layer.
49. The fabrication method of claim 48, wherein the mirror pattern
includes a gold Au metal layer, an aluminum Al metal layer, or a
copper Cu metal layer.
50. The fabrication method of claim 48, wherein forming a mirror
pattern includes: forming a first metal layer on the release layer;
forming a support layer on the first metal layer; and forming a
second metal layer on the support layer.
51. The fabrication method of claim 50, wherein the first and
second metal layers are a gold Au metal layer, aluminum Al metal
layer, or copper Cu metal layer.
52. The fabrication method of claim 51, wherein the support layer
is silicon dioxide SiO.sub.2 layer, silicon nitride Si.sub.xN.sub.y
layer, polysilicon layer, silicon oxynitride Si.sub.xO.sub.yN.sub.z
layer, or polymer layer.
53. The fabrication method of claim 33, further comprising: forming
a wiring pattern such that the wiring pattern is coupled with the
electrodes; and forming an insulation layer insulating the wiring
pattern and electrodes.
54. A micro-electro-mechanical-system (MEMS) mirror device
fabrication method, comprising: forming a release layer on a first
substrate; forming a mirror pattern having a center mirror
component and a hinge pattern supported by the release layer;
forming electrodes supported by a second substrate; forming a
support structure using a third substrate; attaching the first
substrate with the second substrate using the support structure;
removing the first substrate and release layer.
55. The fabrication method of claim 54, wherein the release layer
is a polymer layer, oxide layer, or a nitride layer.
56. The fabrication method of claim 55, wherein removing the first
substrate and release layer includes: etching away the first
substrate using an etching solution; and applying oxygen plasma to
react with the release layer such that the release layer is removed
from the mirror pattern.
57. The fabrication method of claim 55, wherein removing the
release layer includes: etching away the release layer such that
the release layer is removed from the mirror pattern.
58. The fabrication method of claim 54, wherein forming a mirror
pattern forms a frame pattern supported by the release layer.
59. The fabrication method of claim 54, wherein forming a mirror
pattern forms a frame pattern and a mirror component supported by
the release layer.
60. The fabrication method of claim 54, wherein the mirror pattern
includes at least one layer.
61. The fabrication method of claim 60, wherein the mirror pattern
includes a gold Au metal layer, an aluminum Al metal layer, or a
copper Cu metal layer.
62. The fabrication method of claim 60, wherein forming a mirror
pattern includes: forming a first metal layer; forming a support
layer on the first metal layer; and forming a second metal layer on
the support layer.
63. The fabrication method of claim 62, wherein the first and
second metal layers are a gold Au metal layer, aluminum Al metal
layer, or copper Cu metal layer.
64. The fabrication method of claim 62, wherein the support layer
is silicon dioxide SiO.sub.2 layer, silicon nitride Si.sub.xN.sub.y
layer, polysilicon layer, silicon oxynitride Si.sub.xO.sub.yN.sub.z
layer, or polymer layer.
65. The fabrication method of claim 54, wherein the third substrate
is a silicon substrate or a photosensitive glass substrate.
66. The fabrication method of claim 65, wherein forming a support
structure includes: exposing selectively the photosensitive glass
substrate to form exposed regions and unexposed regions in the
photosensitive glass substrate; and removing portions of the
photosensitive glass substrate in the exposed regions to form the
support structure from the unexposed regions such that the support
structure supports the hinge pattern and mirror pattern.
67. The fabrication method of claim 65, wherein forming a support
structure includes: etching deep holes in the silicon substrate
such that the remaining portions of the silicon substrate form the
support structure.
68. The fabrication method of claim 54, wherein a thickness of the
third substrate dictates the thickness of the support structure,
and wherein the thickness of the support structure is capable of
exceeding a thickness of 50 .mu.m.
69. The fabrication method of claim 54, further comprising: forming
a wiring pattern such that the wiring pattern is coupled with the
electrodes; and forming an insulation layer insulating the wiring
pattern and electrodes.
70. A micro-electro-mechanical-system (MEMS) mirror device
fabrication method, comprising: forming electrodes supported by a
first substrate; removing selectively portions of a second
substrate on a bottom side; removing selectively portions of the
second substrate on a topside to form a mirror pattern, frame
pattern, hinge pattern, and support structure; and attaching the
first substrate with the second substrate.
71. The fabrication method of claim 70, wherein the second
substrate is a silicon substrate or a single-crystal silicon
substrate.
72. The fabrication method of claim 70, wherein removing
selectively portions of a second substrate on a bottom side
includes: etching selectively the bottom side of the second
substrate using an reactive ion etching RIE process, wet etch
process, or a laser ablation process.
73. The fabrication method of claim 70, further comprising: forming
at least one layer on the mirror.
74. The fabrication method of claim 73, wherein the at least one
layer is a gold Au metal layer, aluminum Al metal layer, or a
copper Cu metal layer.
75. The fabrication method of claim 70, further comprising: forming
at least one layer on the mirror and frame pattern.
76. The fabrication method of claim 75, wherein the at least one
layer is a gold Au metal layer, aluminum Al metal layer, or a
copper Cu metal layer.
77. The fabrication method of claim 70, wherein the hinge pattern
is formed such that the hinge pattern has a smaller thickness than
the mirror and frame pattern.
78. The fabrication method of claim 77, wherein removing
selectively portions of the second substrate on a topside to form
the hinge pattern includes: releasing the hinge pattern from the
second substrate such that the hinge pattern is supported by the
support structure.
79. The fabrication method of claim 78, wherein removing
selectively portions of the second substrate on a topside to form
the mirror and the frame pattern includes: releasing the mirror and
the frame pattern from the second substrate such that frame pattern
is supported by the hinge pattern and the mirror is supported by
the frame pattern.
80. The fabrication method of claim 70, wherein the hinge pattern,
the mirror, and frame pattern have the same thickness.
81. The fabrication method of claim 80, wherein removing
selectively portions of the second substrate on a topside to form
the hinge pattern, mirror, and frame pattern include: releasing the
hinge pattern, mirror, and frame pattern from the second substrate
such that the hinge pattern is supported by the support structure,
the frame pattern is supported by the hinge pattern, and the mirror
is supported by the frame pattern.
82. The fabrication method of claim 70, wherein a thickness of the
support structure is capable of exceeding a thickness of 50
.mu.m.
83. The fabrication method of claim 70, further comprising: forming
a wiring pattern such that the wiring pattern is coupled with the
electrodes; and forming an insulation layer insulating the wiring
pattern and electrodes.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains to the field of
micro-electro-mechanical-system (MEMS) devices. More particularly,
the present invention relates to a MEMS mirror devices and methods
for fabricating the same.
BACKGROUND OF THE INVENTION
[0002] A MEMS device is a micro-sized mechanical structure having
electrical circuitry fabricated using conventional integrated
circuit (IC) fabrication methods. A well-known MEMS device is a
microscopic gimbaled mirror mounted on a substrate. A gimbaled
mirror is a device that may pivot on a hinge about an axis. By
pivoting about an axis, a gimbaled mirror can redirect light beams
to varying positions. Typically, MEMS gimbaled mirrors are arranged
in an array on single silicon wafer substrate.
[0003] A prior process for fabricating MEMS gimbaled mirrors on a
substrate is a surface micro-machining process. A surface
micro-machining process utilizes thin layers to mount the MEMS
mirrors off the substrate. A disadvantage with using the
micro-machining process is that the gimbaled mirrors are mounted by
only at a few .mu.m ("micro-meters") off the substrate. At such a
small height, the gimbaled mirror is inhibited from pivoting at
large angles with respect to an axis thereby limiting the number of
positions for redirecting light.
[0004] One kind of micro-machining process to make gimbaled mirrors
is the stress curling method. The stress curling method applies a
stress gradient on a thin cantilever layer. The stress gradient
causes the end of the cantilever layer to curl that is used to lift
a gimbaled mirror off the substrate. A disadvantage with using the
stress curling method is that it is process dependent and it is
difficult to control the stress gradient. Another disadvantage with
the stress curling method is that cantilever layer requires a large
area on the substrate that reduces the number of gimbaled mirrors
that can be arranged on the substrate.
[0005] Another kind of micro-machining process to make gimbaled
mirrors utilizes hinges and scratch motors. A scratch motor uses
electrostatic force to move a mass that raises a gimbaled mirror
off the substrate by rotating the mass around a hinge. A
disadvantage with using scratch motors and hinges is that it
requires a large area of space on the substrate to make the scratch
motors and hinges thereby limiting the number of gimbaled mirrors
to be arranged on the substrate. Furthermore, scratch motors are
difficult to make at a microscopic level.
SUMMARY OF THE INVENTION
[0006] A micro-electro-mechanical-system (MEMS) mirror device is
disclosed. The MEMS mirror device includes a substrate. Electrodes
are formed supported by the substrate. A support structure is
formed adjacent to the electrodes. A hinge pattern and a mirror
pattern having a center mirror component are formed such that
support structure supports the hinge pattern and mirror pattern.
The support structure also supports the hinge pattern and mirror
pattern such that a bottom surface of the center mirror component
in a stationary non-rotating position is capable of exceeding a
height of 50 .mu.m above the electrodes.
[0007] A MEMS mirror device fabrication method is disclosed. A
substrate is exposed selectively to form exposed regions and
unexposed regions in the substrate. Electrodes are formed supported
by the substrate. A mirror pattern having a center mirror component
and a hinge pattern are formed supported by the substrate. Portions
of the substrate are removed in the exposed regions to form a
support structure from the unexposed regions such that the support
structure supports the mirror pattern and hinge pattern.
[0008] Another method for fabricating a MEMS mirror device is
disclosed. A release layer is formed on a first substrate. A mirror
pattern having a center mirror component and a hinge pattern are
formed supported by the release layer. Electrodes are formed
supported by a second substrate. A support structure is formed. The
first substrate is attached with the second substrate using the
support structure. The first substrate and the release layer are
removed such that the support structure supports the mirror pattern
and hinge pattern.
[0009] Another method for fabricating a MEMS mirror device is
disclosed. A release layer is formed on a first substrate. A mirror
pattern having a center mirror component and a hinge pattern are
formed supported by the release layer. Electrodes are formed
supported by a second substrate. A support structure is formed
using a third substrate. The first substrate is attached with the
second substrate using the support structure. The first substrate
and release layer are removed.
[0010] Another method for fabricating a MEM gimbaled mirror device
is disclosed. Electrodes are formed supported by a first substrate.
Portions of a second substrate on a bottom side are removed
selectively. Portions of the second substrate on a topside are
removed selectively to form a mirror, frame pattern, and hinge
pattern. The first substrate is attached with the second
substrate.
[0011] Other features and advantages of the present invention will
be apparent from the accompanying drawings, and from the detailed
description, which follows below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention is illustrated by way of example and
not limited in the figures of the accompanying drawings in which
like references indicate similar elements and in which:
[0013] FIG. 1 is a top view of a MEMS mirror device according to
one embodiment without electrodes and a wiring pattern;
[0014] FIG. 2 is a top view of a MEMS mirror device according to
one embodiment illustrating electrodes and a wiring pattern;
[0015] FIG. 3 is a cross-sectional side view of one embodiment
along the line A-A' such as that shown in FIG. 2;
[0016] FIGS. 4a through 4f are cross-sectional side views
illustrating process steps of a method for fabricating the MEMS
mirror device according to a first embodiment;
[0017] FIGS. 5a through 5f are cross-sectional side views
illustrating process steps of a method for fabricating the MEMS
mirror device according to a second embodiment;
[0018] FIGS. 6a through 6f are cross-sectional side views
illustrating process steps of a method for fabricating the MEMS
mirror device according to a third embodiment;
[0019] FIG. 7a is a top view of a MEMS mirror device according to
another embodiment without electrodes and a wiring pattern;
[0020] FIG. 7b is an illustration showing the cross-sectional side
views along the lines B-B', C-C', D-D', and E-E' such as that shown
in FIG. 7a to show the thickness and width for the hinge pattern,
frame pattern, mirror, and support structure; and
[0021] FIGS. 8a-8f are cross-sectional side views illustrating
process steps of a method for fabricating the MEMS mirror device
according to a fourth embodiment.
DETAILED DESCRIPTION
[0022] A micro-electro-mechanical-system (MEMS) mirror device is
described that includes a substrate. Electrodes are formed
supported by the substrate. A support structure is formed adjacent
to the electrodes. A hinge pattern is formed on the support
structure. A hinge pattern and a mirror pattern having a center
mirror component are formed such that support structure supports
the hinge pattern and mirror pattern. The support structure also
supports the hinge pattern and mirror pattern such that a bottom
surface of the center mirror component in a stationary non-rotating
position is capable of exceeding a height of 50 .mu.m above the
electrodes. For example, the support structure may support the
hinge pattern and mirror pattern such that the bottom surface of
the center mirror component in a stationary non-rotating position
has a height of about 100 .mu.m above the electrodes.
[0023] By having a center mirror component capable of exceeding a
height of 50 .mu.m above the electrodes, the center mirror
component may have a larger angular range of motion that can pivot
about an axis. For example, the center mirror component is capable
of having an angular range of motion exceeding 20 degrees with
respect to an axis. Because the center mirror component may have
such a large range of angular motion, the center mirror component
may redirect light beams at a larger number of positions. Thus,
such a MEMS mirror device having a large angular motion can provide
increased flexibility for optical switching systems, scanning
systems, printing systems, and display systems that require
redirecting beams of light.
[0024] The methods for fabricating a MEMS mirror device as
described herein allow for a large number of mirror devices to be
arranged on a single substrate. The methods for fabricating a MEMS
mirror device also allow the center mirror component to be at a
desired height above the electrodes or substrate dictated simply by
a thickness of a substrate or a thickness of a formed support
structure.
[0025] For a first embodiment, a MEMS mirror device fabrication
method exposes selectively a substrate to form exposed regions and
unexposed regions. Electrodes are formed supported by the
substrate. A mirror pattern having a center mirror component and a
hinge pattern are formed supported by the substrate. Portions of
the substrate are removed in the exposed regions to form a support
structure from the unexposed regions such that the support
structure supports the mirror pattern and hinge pattern.
[0026] For the first embodiment, a single substrate is used to
fabricate a MEMS mirror device. The single substrate is used to
form the electrodes, mirror pattern, hinge pattern, and support
structure. The height at which a center mirror component is above
the electrodes is dictated by the thickness of the substrate.
[0027] For a second embodiment, a MEMS mirror device fabrication
method forms a release layer on a first substrate. A mirror pattern
having a center mirror component and a hinge pattern are formed
supported by the release layer. Electrodes are formed supported by
a second substrate. A support structure is formed. The first
substrate and the second substrate are attached using the support
structure. The first substrate and the release layer are removed
such that the support structure supports the mirror pattern and
hinge pattern.
[0028] For the second embodiment, two substrates are used to
fabricate a MEMS mirror device. The height at which the center
mirror component is above the electrodes is dictated by a thickness
of the formed support structure. Thus, to increase the height of
the of the center mirror component above the electrodes, a thicker
support structure is formed. As such, the thickness of the support
structure formed dictates the height at which a center component is
above the electrodes.
[0029] For a third embodiment, a MEMS mirror device fabrication
method forms a release layer on a first substrate. A mirror pattern
having a center mirror component and a hinge pattern are formed
supported by the release layer. Electrodes are formed supported by
a second substrate. A support structure is formed using a third
substrate. The first substrate is attached with the second
substrate using the support structure. The first substrate and
release layer are removed.
[0030] For the third embodiment, three substrates are used to
fabricate a MEMS mirror device. A first substrate is used to form
the hinge pattern and mirror pattern. A second substrate is used to
form the electrodes. A third substrate is used to form the support
structure. The thickness of the third substrate used dictates the
thickness of the support structure. Thus, the height at which the
center mirror component is above the electrodes is simply dictated
by the thickness of the third substrate. Thus, to increase the
height of the of the center mirror component above the electrodes,
a thicker third substrate is simply used.
[0031] For a fourth embodiment, a MEMS mirror device fabrication
method forms electrodes supported by a first substrate. Portions of
a second substrate are removed selectively on a bottom side.
Portions of the second substrate are removed selectively on a
topside to form a mirror pattern, frame pattern, hinge pattern, and
support structure. The first substrate is attached with the second
substrate.
[0032] For the fourth embodiment, two substrates are used to
fabricate a MEMS mirror device. The height at which the center
mirror component is above the electrodes is dictated by the
thickness of the second substrate used. Furthermore, the mirror
pattern, frame pattern, hinge pattern, and support structure can be
formed from a single substrate.
[0033] For all the embodiments, a layer can be selectively
patterned on a substrate using any combination of a
photolithography and dry or wet etching process or a liftoff
process. A liftoff process involves depositing a photosensitive
film over a substrate that is then exposed and developed to pattern
the photosensitive film. Material is then deposited over the entire
surface the substrate and on the patterned photosensitive film.
After the material is deposited over the substrate and on the
patterned photosensitive film, the patterned photosensitive film is
dissolved and any material formed thereon is removed. As a result
of this process, the material deposited is selectively patterned.
Furthermore, a layer may also be removed or released by using
oxygen plasma that reacts with the layer to release or remove the
layer from an attached material.
[0034] FIG. 1 is top view of one embodiment of a MEMS mirror device
without electrodes and a wiring pattern illustrating a first mirror
device 9A and a second mirror device 9B having a support structure
5, hinge pattern 6, and mirror pattern 7. Mirror pattern 7 may
include a center mirror component 7a, frame pattern 7b, and mirror
component 7c. Center mirror component 7a is capable of having an
angular range of motion with respect to an axis. Frame pattern 7b
provides support for center mirror component 7a. Mirror component
7c may be used for alignment or bonding purposes. Alternatively,
mirror component 7c may be omitted from mirror pattern 7.
[0035] FIG. 2 is a complete top view of one embodiment of a MEMS
mirror device such as that shown in FIG. 1 further illustrating
electrodes 4 and wiring pattern 2 for the first mirror device 9A
and second mirror device 9B.
[0036] FIG. 3 is a cross sectional side view showing the structure
of one embodiment of a MEMS mirror device taken along the line A-A'
such as that shown in FIG. 2. As shown in FIG. 3, a MEMS mirror
device includes a substrate 1 having wiring pattern 2 formed
thereon. Electrodes 4 are formed such that electrodes are coupled
with wiring pattern 2. An insulation layer 3 is formed to provide
insulation for wiring pattern 2 and electrodes 4.
[0037] Support structure 5 is formed on insulation layer 3 adjacent
from electrodes 4. Support structure 5 may include a post structure
to provide support for layers formed thereon or attached therewith.
Support structure 5 may define a honeycombed shape. Support
structure 5 may also define holes such that the holes are centered
approximately below the center mirror component. Support structure
5 provides support for hinge pattern 6 and mirror pattern 7.
[0038] Mirror pattern 7 includes a center mirror component 7a,
frame pattern 7b, and mirror component 7c. Alternatively, mirror
pattern may include center mirror component 7a and frame pattern
7b. Hinge pattern 6 is attached with mirror pattern 7 and support
structure 5. Hinge pattern 6 may be a thin and flexible material.
Hinge pattern 6 provides support for mirror pattern 7. Frame
pattern 7b provides support for center mirror component 7a. Mirror
component 7c is supported by hinge pattern 6 and may be used for
alignment or bonding purposes. Alternatively, mirror component 7c
may be omitted from mirror pattern 7.
[0039] The center mirror component 7a is formed such that it is
disposed above electrodes 4. Center mirror component 7a includes a
reflective surface to reflect beams of light. Electrodes 4 are
located below at opposing edges of center mirror component 7a.
Center mirror component 7a may also be connected with a ground line
(not shown) in substrate 1 for electrical shielding purposes.
Electrodes 4 are coupled with a respective wiring pattern 2 located
on substrate 1. Alternatively, a ground line may be disposed
between electrodes 4 and wiring pattern 2 for purposes of
electrical shielding.
[0040] Center mirror component 7a may move about an axis to have an
angular range of motion caused by electrostatic actuation from
electrodes 4. Electrostatic actuation is caused by a voltage being
applied to electrodes 4 through wiring pattern 2. A voltage applied
to electrodes 4 creates an electric field between, for example,
electrodes 4 and center mirror component 7a. Typically, the
electric field is created near the edges of center mirror component
7a. The electric field causes center mirror component 7a to have an
angular range of motion with respect to an axis such as, for
example, an axis parallel to hinge pattern 7. The edges of center
mirror component 7a towards electrodes 4 at which the voltage is
applied moves towards such electrodes 4.
[0041] By increasing the angular range of motion for center mirror
component 7a, center mirror component 7a can redirect beams of
light to a larger number of positions thereby increasing
flexibility for optical switching. Increasing the thickness for
support structure 5 can increases the angular range of motion for
center mirror component 7a. Support structure 5 having an increased
thickness provides a larger height for center mirror component 7a
to be off of substrate 1. Because center mirror component 7a may
have a large height off substrate 1, center mirror component 7a is
provided with a larger angular range of motion.
[0042] For the following embodiments, the support structure can be
fabricated to support the hinge pattern and mirror pattern such
that a bottom surface of the center mirror component in a
stationary non-rotating position is capable of exceeding a height
of 50 .mu.m above the electrodes. Also, in the following
embodiments, the support structure may support the hinge pattern
and mirror pattern such that the bottom surface of the center
mirror component in a stationary non-rotating position is capable
of having a height about 100 .mu.m above the electrodes. At such
heights, the following embodiments provide a center mirror
component that is capable of having an angular range of motion
exceeding 20 degrees with respect to an axis.
[0043] FIGS. 4a through 4f are cross-sectional side views
illustrating process steps of a method for fabricating the MEMS
mirror device according to a first embodiment.
[0044] Referring to FIG. 4a, substrate 10 is exposed selectively on
a first side to form exposed regions 11a and unexposed regions 11b
in substrate 10. A honeycombed mask may be used to expose
selectively substrate 10. Alternatively, other masks may be used to
form exposed regions on a substrate such that mirror components are
centered approximately over the exposed regions. For purposes of
illustration, the first side is a topside of substrate 10.
[0045] Substrate 10 is a substrate that can be etched more rapidly
in the exposed regions than in the unexposed regions. For example,
substrate 10 may be a photosensitive glass substrate that can be
exposed selectively and etched more rapidly in the exposed regions
than in the unexposed regions. After being exposed selectively,
substrate 10 may be polished to retain planarity and remove any
materials that may have formed on substrate 10 during this
process.
[0046] Referring to FIG. 4b, a first metal layer is formed on a
second side of substrate 10 and is selectively patterned and etched
to form electrodes 14. For purposes of explanation, the second side
is a bottom side of substrate 10. The first metal layer may be a
metallic layer such as, for example, an aluminum Al layer. After
forming electrodes 14, an oxide layer is then formed over
electrodes 14 and substrate 10 on the bottom side and selectively
patterned to form insulation layer 13, such that insulation layer
13 exposes portions of electrodes 14. Alternatively, other
dielectric layers may be used such as, for example, silicon dioxide
SiO.sub.2 layer, silicon nitride Si.sub.xN.sub.y layer, or silicon
oxynitride Si.sub.xO.sub.yN.sub.z layer, that can be selectively
patterned and etched to form insulation layer 13.
[0047] After forming insulation layer 13, a second metal layer is
formed on insulation layer 13 and on exposed portions of electrodes
14 and is selectively patterned and etched to form wiring pattern
12. The second metal layer may also be a metallic layer such as,
for example, an Al layer. Wiring pattern 12 is formed such that it
is coupled with electrodes 14. Insulation layer 13 provides
insulation for wiring pattern 12 and electrodes 14.
[0048] Referring to FIG. 4c, a polysilicon layer is formed on the
topside of substrate 10. The polysilicon layer is selectively
patterned and etched to form hinge pattern 16. Alternatively, a
polymer layer, oxide layer, nitride layer, silicon nitride
Si.sub.xN.sub.y layer, silicon dioxide SiO.sub.2, layer, or silicon
oxynitride Si.sub.xO.sub.yN.sub.z layer may be used that is
selectively patterned and etched to form hinge pattern 16. Hinge
pattern 16 is formed to be thin and flexible. Hinge pattern 16 is
also formed such that portions of substrate 11 are exposed above an
area near electrodes 14.
[0049] Referring to FIG. 4d, at least one layer having light
reflective properties is formed on hinge pattern 16 and on the
exposed portions of the topside of substrate 11. For example, a
metal layer having light reflective properties may be formed on
hinge pattern 16 and portions of the exposed substrate 11 and
selectively pattern and etched to form mirror pattern 17. The metal
layer may be a gold Au metal layer, aluminum Al metal layer, or a
copper Cu metal layer. Mirror pattern 17 includes a center mirror
component 17a, frame pattern 17b, and mirror component 17c. Frame
pattern 17b is supported by hinge pattern 16. Frame pattern 17b
provides support for center mirror component 17a. Mirror component
17c is supported by hinge pattern 16. Alternatively, mirror
component 17c may be omitted from mirror pattern 17.
[0050] Multiple layers may also be used to form mirror pattern 17.
For example, a first metal layer is formed on hinge pattern 17 and
on portions of the exposed substrate 11. A support layer is formed
on the first metal layer. A second metal layer is formed on the
support layer. The three layers are selectively patterned and
etched to form mirror pattern 17.
[0051] The first and second metal layers are layers having light
reflective properties. For example, a gold Au metal layer, an
aluminum Al metal layer, or a copper Cu metal layer may be used for
the first and second metal layers. The support layer is a layer
that provides a flat surface and structural support. For example, a
silicon dioxide SiO.sub.2 layer, silicon nitride Si.sub.xN.sub.y
layer, polysilicon layer, silicon oxynitride Si.sub.xO.sub.yN.sub.z
layer, or a polymer layer may be used for the support layer.
Alternatively, the support layer may include the same material as
the first and second metal layers.
[0052] Referring to FIG. 4e, a polymer layer is formed over mirror
pattern 17 and hinge pattern 16 and is patterned selectively and
etched to form protection layer 18. Alternatively, a polysilicon
layer, oxide layer, or nitride layer may be used to form protection
layer 18. Protection layer 18 is patterned to protect mirror
pattern 17 and hinge pattern 16. Protection layer 18 is also
patterned such that an etching solution can reach substrate 11. For
example, a hydrofluoric (HF) acid etching solution is used to etch
substrate 11. Alternatively, forming protection layer 18 may be
optional if mirror pattern 17 and hinge pattern 16 are resistant to
the etching solution. If, for example, HF acid is used and hinge
pattern 16 is made from an oxide material, which etches easily in
HF acid, protection layer 18 (not made of an oxide) is then
required.
[0053] Referring to FIG. 4f, the etching solution is deposited over
substrate 11 to etch substrate 11. For example, HF acid is used
that etches away the exposed regions 11a more rapidly than the
unexposed regions 11b such that remaining portions of the unexposed
regions 11b of substrate 11 form support structure 15. If a
protection layer is used, then the protection layer is removed
using an oxygen plasma, wet, or dry etch process.
[0054] The thusly-fabricated MEMS mirror device serves to provide a
support structure using a single substrate. The single substrate is
a photosensitive substrate. For example, the photosensitive
substrate is a photosensitive glass substrate that is exposed
selectively. Because the photosensitive substrate is exposed
selectively, the photosensitive substrate can be etched to form the
support structure after forming the hinge pattern and mirror
pattern. Thus, mounting a mirror pattern and a hinge pattern on a
support structure is avoided. Furthermore, the thickness of the
photosensitive substrate dictates the height at which a center
mirror component is above the electrodes.
[0055] FIGS. 5a through 5f are cross-sectional side views
illustrating process steps of a method for fabricating the MEMS
mirror device according to a second embodiment.
[0056] Referring to FIG. 5a, a polymer layer is formed on a first
substrate 20 to form a release layer 21. Release layer 21 may also
be a layer that can be etched easily away or is removed easily from
first substrate 20. For example, release layer 21 may be a
polysilicon layer, oxide layer, or a nitride layer. First substrate
20 may be a silicon substrate, glass substrate, or a borosilicate
glass substrate.
[0057] Referring to FIG. 5b, at least one layer having light
reflective properties is formed on release layer 21. For example, a
metal layer having light reflective properties may be formed on
release layer and selectively pattern and etched to form mirror
pattern 27. The metal layer may be a gold Au metal layer, aluminum
Al metal layer, or a copper Cu metal layer. Mirror pattern 27
includes a center mirror component 27a, frame pattern 27b, and
mirror component 27c formed on release layer 21. Alternatively,
mirror component 27c may be omitted from mirror pattern 27.
[0058] Multiple layers may also be used to form mirror pattern 27.
For example, a first metal layer is formed on release layer 21. A
support layer is formed on the first metal layer. A second metal
layer is formed on the support layer. The three layers are
selectively patterned and etched to form mirror pattern 27.
[0059] The first and second metal layers are layers having light
reflective properties. For example, a gold Au metal layer, an
aluminum Al metal layer, or a copper Cu metal layer may be used for
the first and second metal layers. The support layer is a layer
that provides a flat surface and structural support. For example, a
silicon dioxide SiO.sub.2 layer, silicon nitride Si.sub.xN.sub.y
layer, polysilicon layer, silicon oxynitride Si.sub.xO.sub.yN.sub.z
layer, or a polymer layer may be used for the support layer.
Alternatively, the support layer may include the same material as
the first and second metal layers.
[0060] After mirror pattern 27 is formed on release layer 21, a
polysilicon layer is formed over mirror pattern 27 and is
selectively patterned and etched to form hinge pattern 26.
Alternatively, a polymer layer, oxide layer, nitride layer, silicon
nitride Si.sub.xN.sub.y layer, silicon dioxide SiO.sub.2, layer, or
silicon oxynitride Si.sub.xO.sub.yN.sub.z layer may be used that is
selectively patterned and etched to form hinge pattern 26. Hinge
pattern 26 is formed on portions of mirror pattern 27. Hinge
pattern 26, however, is not formed on center mirror component 27a.
Hinge pattern 26 is formed to be thin and flexible.
[0061] Referring to FIG. 5c, a first metal layer is formed on a
second substrate 30 and is selectively patterned and etched to form
wiring pattern 32. Second substrate 30 may be may be a silicon
substrate, glass substrate, or borosilicate glass substrate. The
first metal layer may be a metallic layer such as, for example, an
aluminum Al layer. After forming wiring pattern 32, an oxide layer
is then formed over wiring pattern 32 and second substrate 30 and
is selectively patterned and etched to form insulation layer 33.
Insulation 33 is formed such that portions of wiring pattern 32 are
exposed. Alternatively, other dielectric layers may be used such
as, for example, silicon dioxide SiO.sub.2 layer, silicon nitride
Si.sub.xN.sub.y layer, or silicon oxynitride Si.sub.xO.sub.yN.sub.z
layer, that can be selectively patterned and etched to form
insulation layer 33.
[0062] After forming insulation layer 33, a second metal layer is
formed over insulation layer 33 and wiring pattern 32 and is
selectively patterned and etched to form electrodes 34. The second
metal layer may also be a metallic layer such as, for example, an
Al layer. Electrodes 34 are formed such that they are coupled with
wiring pattern 32. Insulation 33 provides insulation for wiring
pattern 32 and electrodes 34.
[0063] Referring to FIG. 5d, a thick patterned film is used to form
support structure 35. A metal plating process is used with the
thick patterned film to form support structure 35. For example, an
electroless metal deposition process may be used to form support
structure 25.
[0064] Initially, for the electroless metal deposition process, a
thick photo resist film is formed on insulation layer 33 and
selectively patterned to allow support structure 35 to be formed
therein on insulation layer 33. Alternatively, a thick photo resist
film may be formed on hinge pattern 26 and selectively patterned to
allow support structure 35 to be formed on hinge pattern 26.
[0065] Subsequently, an aqueous solution having nickel Ni is
deposited over the patterned photo resist film such that nickel Ni
is formed in the patterned thick photo resist film. After Ni is
formed, the remaining photo resist film is removed to form support
structure 35 made of Ni. Alternatively, an aqueous solution having
copper Cu or gold Au may be used to form support structure 35 using
the electroless metal deposition process. The remaining photo
resist film is then removed.
[0066] Alternatively, an electroplating process or a metal
sputtering process may be used. For the electroplating process, a
thick photo resist film is formed on insulation layer 33 and
selectively patterned to allow support structure 35 to be formed
therein on insulation layer 33. Alternatively, a thick photo resist
film is formed on hinge pattern 26 and selectively patterned to
allow support structure 35 to be formed therein on hinge pattern
26.
[0067] Subsequently, an electroplating solution having nickel Ni is
deposited over the patterned photo resist film and an electric
current is passed through the solution such that Ni is formed in
the patterned thick photo resist film. After Ni is formed, the
remaining photo resist film is removed to form support structure 35
made of Ni. Alternatively, an electroplating solution having copper
Cu or gold Au may be used to form support structure 35 using the
electroplating process. Depending on where the patterned photo
resist film is formed, a thin conductive layer (not shown) may be
formed selectively on insulation layer 33 or hinge pattern 26 to
assist in the electroplating process. The photo resist film is then
removed.
[0068] For the sputtering process, a thick photo resist film is
formed on insulation layer 33 and selectively patterned to allow
support structure 35 to be formed therein on insulation layer 33.
Alternatively, a thick photo resist film is formed on hinge pattern
26 and selectively patterned to allow support structure 35 to be
formed therein on hinge pattern 26.
[0069] Subsequently, metal is sputtered on the patterned thick
photo resist film such that the metal is formed therein. For
example, nickel Ni, copper Cu, or gold Au may be sputtered on the
patterned thick photo resist film such that metal is formed
therein. Subsequently, the remaining patterned thick photo resist
film and metal formed thereon are removed to form support structure
35. The thick photo resist film is then removed.
[0070] Referring to FIG. 5e, first substrate 20 is attached with
second substrate 30. If support structure 35 is formed on
insulation layer 33, first substrate 20 may be attached with second
substrate 30 by flipping first substrate 20 and bonding hinge
pattern 26 with a top side of support structure 35. Alternatively,
if support structure 35 is formed on hinge pattern 26, first
substrate 20 may be attached with second substrate 30 by flipping
first substrate 20 and bonding support structure 35 with insulation
layer 33.
[0071] Support structure 35 can be bonded to insulation layer 33 or
hinge pattern 26 using a soldering bond technique that forms a
bonding layer. For example, if support structure 35 is formed on
insulation layer 33, a bonding layer 38 may be formed to bond
support structure 35 with hinge pattern 26. Alternatively, if
support structure 35 is formed on hinge pattern 26, a bonding layer
may be formed near insulation layer 33 to bond support structure 35
with hinge pattern 26. The bonding layer may include a lead-tin
PbSn mixture. Alternatively, a thin metal layer may be formed on
hinge pattern 26 or insulation layer 33 to assist in the bonding
process.
[0072] Referring to FIG. 5f, after first substrate 20 is attached
with second substrate 30, first substrate 20 and release layer 21
are removed such that support structure 35 supports hinge pattern
26. Hinge pattern 26 supports mirror pattern 27. First substrate 20
may be removed using an etching or polishing process. For example,
first substrate 20 may be etched away using hydro-fluoric (HF) acid
or first substrate 20 may be polished away. Release layer 21 may be
removed using oxygen plasma, wet etch, or a dry etch process.
[0073] The thusly fabricated MEMS mirror device serves to provide a
support structure using a thick film process. In the above process,
the thickness of the thick photo resist film used dictates the
thickness of support structure 35. Furthermore, the thickness of
support structure 35 dictates the height in which a center mirror
component is above the electrodes that determines angular range of
motion for the center mirror component.
[0074] FIGS. 6a through 6e are cross-sectional side views
illustrating process steps of a method for fabricating the MEMS
mirror device according to a third embodiment. Initially, the
fabrication steps illustrated by FIG. 6a to form release layer 41,
mirror pattern 47, and hinge pattern 46 are identical to the
fabrication steps illustrated by FIGS. 5a and 5b for a first
substrate 40 and accordingly descriptions to FIG. 6a will be
omitted. Also, the fabrication steps illustrated by FIG. 6b to form
wiring pattern 52, electrodes 54, and insulation layer 53 using a
second substrate 50 are identical to the fabrication steps
illustrated by FIG. 5c and accordingly descriptions to FIG. 6b will
be omitted.
[0075] Referring to FIGS. 6c and 6d, a third substrate 60 is used
to form support structure 65. Third substrate 60 may be etched
selectively to form support structure 65. Third substrate may be a
silicon substrate, glass substrate, or a borosilicate glass
substrate. Third substrate 60 may be etched selectively in areas
61a of third substrate 60 using a reactive ion etching (RIE)
process. The RIE etching process forms deep holes in third
substrate 60 such that areas 61b of third substrate 60 remain to
form support structure 65. Alternatively, deep holes may be formed
in third substrate 60 using a wet etch or a laser ablation process
such that areas 61a are removed from third substrate 60.
[0076] Third substrate 60 may also be a photosensitive substrate
that is exposed selectively to form exposed regions 61a and
unexposed regions 61b in third substrate 60. Third substrate 60 is
a substrate that can be etched more rapidly in the exposed regions
than in the unexposed regions. After being exposed selectively,
third substrate 60 may be polished to retain planarity and remove
any materials that may have formed on third substrate 60 during
this process.
[0077] Subsequently, an etching solution is used to etch third
substrate 60. For example, HF acid etching solution is deposited
selectively over third substrate 60 to etch third substrate 60. The
HF acid etches away the exposed regions 61a more rapidly than the
unexposed regions 61b such that the remaining portions of the
unexposed regions 61b of third substrate 60 form support structure
65. Support structure 65 may define a honeycombed shape or define
holes approximately centered with respect to center mirror
components.
[0078] Referring to FIG. 6e, first substrate 40 is attached with
second substrate 50 using support structure 65. For example,
support structure 65 is bonded with insulation layer 53 using a
solder bond process thus forming a bonding layer 69. Subsequently,
hinge pattern 46 is bonded with support structure 65 using a solder
bond process thus forming a bonding layer 68. Alternatively,
support structure 65 is bonded with hinge pattern 46 using a solder
bond process thus forming a bonding layer 68. Subsequently,
insulation layer is bonded with support structure 65 thus forming
bonding layer 69. Bonding layers 68 and 69 may include a lead-tin
PbSn mixture. A thin metal layer may also be formed on insulation
layer 53 and hinge pattern 46 to assist in the bonding process.
[0079] Referring to FIG. 6f, after first substrate 40 is attached
with second substrate 50 using support structure 65. First
substrate 40 and release layer 41 are removed such that support
structure 65 supports hinge pattern 46. Hinge pattern 46 supports
mirror pattern 47. First substrate 40 may be removed using an
etching or polishing process. For example, first substrate 40 may
be etched away using HF acid or first substrate 40 may be polished
away. Release layer may be removed using an oxygen plasma, wet
etch, or a dry etch process.
[0080] The thusly fabricated MEMS mirror device uses three
substrates. One substrate is used to form mirror pattern 47 and
hinge pattern 46. A second substrate is used to form electrodes 54,
and a third substrate 50 is used to form a support structure 65.
The height at which the center mirror component is above the
electrodes is simply dictated by the thickness of the third
substrate used. Thus, to increase the height of the center mirror
component above the electrodes, a thicker substrate may be
used.
[0081] FIG. 7a is a top view of a MEMS mirror device according to
another embodiment without electrodes and a wiring pattern. FIG. 7a
shows a first mirror device 101a and a second mirror device 101b
having a support structure 95, hinge pattern 96, frame pattern 97,
and mirror 97a.
[0082] Support structure 95, hinge pattern 96, frame pattern 97,
and mirror 97a are all formed from a single substrate. Hinge
pattern 96 provides support for frame 97b and mirror 97a. Frame 97b
provides support for mirror 97a. Support structure 95 provides
support for hinge pattern 96, frame pattern 97b, and mirror 97a.
Mirror 97a is capable of having an angular range of motion with
respect to an axis.
[0083] FIG. 7b is an illustration showing the cross-sectional side
views along the lines B-B', C-C', D-D', and E-E' such as that shown
in FIG. 7a to show the different thickness and width for the hinge
pattern 96, frame pattern 97b, mirror 97a, and support structure
95, respectively, for first mirror 101a and second mirror 101b.
Referring to FIG. 7b, along the lines B-B', C-C', and D-D', hinge
pattern 96 is formed to have a smaller thickness than frame pattern
97b and mirror 97a. Alternatively, hinge pattern 96 may be formed
to have the same thickness as frame pattern 97b and mirror 97a.
Frame pattern 97b and mirror 97a are formed to have the same
thickness.
[0084] FIGS. 8a-8f are cross-sectional side views illustrating
process steps of a method for fabricating the MEMS mirror device
according to the fourth embodiment. FIG. 8a illustrates the
processing steps to form a wiring pattern, electrodes, insulation
layer using a first substrate. Referring to FIG. 8a, the
fabrication steps illustrated by FIG. 8a to form wiring pattern 82,
electrodes 84, insulation layer 83 using a first substrate 80 are
identical to the fabrication steps illustrated by FIGS. 5c and 6b
and accordingly descriptions to FIG. 8a will be omitted.
[0085] FIGS. 8b, 8c, and 8d illustrate the processing steps to form
the hinge pattern, frame pattern, mirror, and support structure
individually from a single substrate such as that shown in FIG. 7b.
The processing steps are illustrated along the lines B-B', C-C',
D-D', E-E' such as that shown in FIG. 7a for mirror device 101a and
mirror device 101b.
[0086] Referring to FIG. 8b, a second substrate 90 is etched
selectively on a first side to remove large portions of second
substrate 90 to define open areas ("windows") 100 such that the
open areas 100 are located below where hinge pattern 96, mirror
97a, and frame pattern 97b will be formed. For purposes of
illustration, the first side of second substrate 90 refers to a
bottom side of second substrate 90. To form open areas 100, a
silicon etching process is used to etch selectively the bottom side
of second substrate 90. For example, a reactive ion etching (RIE)
process may be used to etch selectively a bottom side of second
substrate 90 to form open areas 100. Alternatively, a wet etch or a
laser ablation process may be used to etch the bottom side of
second substrate 90 to form open areas 100.
[0087] An oxide layer is deposited on a second side of second
substrate 90 to form a mask layer 91. Alternatively, a polymer
layer, silicon nitride Si.sub.xN.sub.y layer, silicon oxynitride
Si.sub.xO.sub.yN.sub.z layer, or a metal layer may be used to form
mask layer 91. Mask layer 91 may also be formed prior to forming
open areas 100. For purposes of illustration, the second side
refers to the topside of second substrate 90. Mask layer 91 is
patterned to define hinge pattern 96, frame pattern 97b, mirror
97a, and support structure 95 from second substrate 90.
[0088] FIGS. 8c and 8d illustrate the processing steps for forming
hinge pattern 96, frame pattern 97b, mirror 97a, and support
structure 95. The following process steps describe forming hinge
pattern 96 such that it has a smaller thickness than frame pattern
97b and mirror 97a. Alternatively, the following processing steps
may be modified to form hinge pattern 96 having the same thickness
as frame pattern 97b and mirror 97a.
[0089] Referring to FIG. 8c, mask layer 91 is patterned selectively
on second substrate 90 to expose portions of second substrate 90.
The patterned mask layer 91 defines hinge pattern 96, frame pattern
97b, mirror 97a, and support structure 95. The exposed portions of
second substrate 90 are etched using a silicon etching process. For
example, a RIE etching process may be used to etch exposed portions
of second substrate 90 to a first depth such that a thin portion
("floor") of second substrate 90 remains above open areas 100.
Alternatively, a wet etch or a laser ablation process may be used
to etch the exposed portions of second substrate 90 to the first
depth.
[0090] At this depth, an oxide layer is deposited over second
substrate 90 and etched selectively to form sidewalls 94.
Alternatively, a polymer layer, silicon nitride Si.sub.xN.sub.y
layer, silicon oxynitride Si.sub.xO.sub.yN.sub.z layer, or a metal
layer may be used to form sidewalls 94. Sidewalls 94 provide
protection to selective portions of the topside of second substrate
90 that define hinge pattern 96, frame pattern 97b, mirror 97a, and
support structure 95. Layers that have formed on the floor in
making sidewalls 94 are the etched to expose the floor.
[0091] Subsequently, exposed portions of the floor of second
substrate 90 are etched using a silicon etching processes. For
example, a RIE etching process may be used to etch exposed portions
of the floor such that the floor falls below the sidewalls.
Alternatively, a wet etch process or a laser ablation process may
be used to etch the exposed portions of the floor to fall below the
sidewalls. Next, a release process is performed to form hinge
pattern 96, frame pattern 97b, and mirror 97a. The release process
is an etching process that undercuts selectively the exposed
portions of topside of second substrate 90 that defines hinge
pattern 96, frame pattern 97b, and mirror 97a underneath sidewalls
94 such that the floor is separated. If hinge pattern 96 is to have
the same thickness as frame pattern 97b and mirror 97a, hinge
pattern 96, frame 97b, and mirror 97a are released at the same
time. Alternatively, if hinge pattern 96 is to have a smaller
thickness than frame pattern 97b and mirror 97a, frame pattern 97b
and mirror 97a are released after hinge pattern 96 at a lower
depth.
[0092] The following step describes the release process. To release
frame pattern 97b and mirror 97a at a larger depth than hinge
pattern 96, the above steps are repeated such that exposed portions
of the topside of second substrate 90 that define frame pattern 97b
and mirror 97a underneath sidewalls 94 fall below hinge pattern
96.
[0093] A RIE etching process may be used to release the exposed
portions of the topside of second substrate that defines hinge
pattern 96, frame pattern 97b, and mirror 97a underneath sidewalls
94 to form hinge pattern 96, frame pattern 97b, and mirror 97a from
second substrate 90. Alternatively, a time controlled profile
etching process may be used to release hinge pattern 96, frame
pattern 97b, and mirror 97a from second substrate 96. The release
process may undercut frame pattern 97b and mirror 97a underneath
sidewalls 94 such that non-straight edge surfaces are formed.
Alternatively, the release process may undercut hinge pattern 96
such that non-straight edge surfaces are also formed. Hinge pattern
96, frame pattern 97b, and mirror 97a are thus formed after it has
been released from second substrate 90, and the remaining mask
layer 91 and sidewalls 94 are removed. Alternatively, mask layer 91
and sidewalls 94 may remain in forming the MEMS mirror device.
[0094] Referring to FIG. 8d, the next step in the process is to
remove the floor ("clear the floor"). The floor is etched away to
clear the floor such that hinge pattern 96, frame pattern 97b, and
mirror 97a are suspended about support structure 95 and second
substrate 90. For example, the floor of second substrate 90 may be
etched away using an RIE etching process. Alternatively, a wet etch
or a laser ablation process may be used to etch the exposed
portions of the floor to clear the floor. Second substrate 90 may
also be flipped and the floor may be cleared from the back side
using the same etching processes. After the floor has been cleared,
support structure 95 is thusly formed. For purposes of
illustration, support structure 95, hinge pattern 96, frame pattern
97b, and mirror 97a are illustrated with straight surfaces, but may
have non-straight edge surfaces.
[0095] FIG. 8e is a cross-sectional side of the thusly formed hinge
pattern 96, frame pattern 97b, mirror 97a, and support structure 95
taken along the line A-A' such as that shown in FIG. 7a with
showing electrodes. Referring to FIG. 8e, support structure 95
provides support for hinge pattern 96, frame pattern 97b, and
mirror 97a. Hinge pattern 96b provides support for frame pattern
97b. Frame pattern 97b provides support for mirror 97a.
[0096] A reflective material 97a' may then be formed on a top
surface of mirror 97a. Reflective material 97a' provides a
reflective surface for mirror 97a, which is used to redirect beams
of light. Alternatively, reflective material 97a' may be formed on
frame pattern 97b and hinge pattern 96. Reflective material 97a'
includes at least one layer. For example, reflective material 97a'
may include a metal layer such as, for example, a gold Au metal
layer, an aluminum metal layer, or a copper Cu metal layer.
Alternatively, reflective material 97a' may be formed after the
processing steps as illustrated in FIG. 8e or after first substrate
80 is attached with second substrate 90.
[0097] FIG. 8f illustrate attaching first substrate 80 with second
substrate 90 to form the MEMS mirror device according to the fourth
embodiment. Referring to FIG. 8f, first substrate 80 is attached
with second substrate 90 using support structure 95. For example,
support structure 95 is bonded with insulation layer 83 using a
solder bond process thus forming a bonding layer 98. Bonding layer
98 may include a lead-tin PbSn mixture. A thin metal layer may also
be formed on insulation layer 83 and a bottom side of support
structure 95 to assist in the bonding process.
[0098] Referring to FIG. 8f, the MEMS mirror device according to
the fourth embodiment includes first substrate 80, wiring pattern
82, insulation layer 83, and electrodes 84. First substrate 80,
wiring pattern 82, insulation layer 83, and electrodes 84 are
constructed and operate in a similar manner as substrate 1, wiring
pattern 2, insulation layer 3, and electrodes 4, respectively, of
FIG. 3.
[0099] The MEMS mirror device according to the fourth embodiment
also includes a support structure 95, hinge pattern 96, frame
pattern 97b, and mirror 97a. Support structure 95, hinge pattern
96, frame pattern 97b, and mirror 97a are made from a second
substrate, which is separate from first substrate 80. The substrate
to form support structure 95, hinge pattern 96, frame pattern 97b,
and mirror 97a may be a single crystal silicon (SCS) substrate or a
substrate in which deep holes may be formed. Support structure 95,
hinge pattern 96, frame pattern 97b, and mirror 97a are formed as a
single unit. Support structure 95, mirror 97a, frame pattern 97b,
and hinge pattern 96 operate in a similar manner as support
structure 5, center mirror component 7a, frame pattern 7b, and
hinge pattern 6, respectively, of FIG. 3.
[0100] The thusly fabricated MEMS mirror device uses two
substrates. One substrate is used to form electrodes 84, wiring
pattern 82, and insulation layer 83. A second substrate is used to
form support structure 95, mirror 97a, hinge pattern 96, and frame
pattern 97b. The height at which the mirror is above the electrodes
is simply dictated by the thickness of the second substrate used.
Thus, to increase the height of the of the center mirror component
above the electrodes, a thicker second substrate may be used. Also,
the mirror, frame pattern, and hinge pattern are formed without
using thin film layering, which reduces the number of processing
steps.
[0101] In the foregoing specification, the invention has been
described with reference to specific exemplary embodiments thereof.
It will, however, be evident that various modifications and changes
may be made thereto without departing from the broader spirit and
scope of the invention as set forth in the appended claims. The
specification and drawings are, accordingly, to be regarded in an
illustrative rather than a restrictive sense.
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