Title: Multiple hinge MEMS device
Abstract: A MEMS device is disclosed comprising: a substrate; a movable micromechanical element movable relative to the substrate; a connector and a hinge for allowing movement of the micromechanical element, wherein the connector is made of a material different than the hinge. In another embodiment of the invention, the connector has a conductivity greater than the hinge. In a further embodiment of the invention, the hinge provides at least 90% of the restoring force to the MEMS device, and the connector provides 10% or less of the restoring force. In a further embodiment of the invention, the connector and the hinge have different spring constants. In a still further embodiment of the invention, the connector experiences a lower strain at maximum deflection of the micromechanical element than the hinge.
Patent Number: 6,950,223 Issued on 09/27/2005 to Huibers, et al.
| Inventors:
|
Huibers; Andrew G. (Palo Alto, CA);
Patel; Satyadev R. (Elk Grove, CA)
|
| Assignee:
|
Reflectivity, Inc (Sunnyvale, CA)
|
| Appl. No.:
|
346506 |
| Filed:
|
January 15, 2003 |
| Current U.S. Class: |
359/291; 257/417; 310/36; 310/90; 310/309; 359/214; 359/224; 359/290; 359/298; 359/850 |
| Intern'l Class: |
G02B 026/00; G02B 026/08; G02B 005/08; H01L 029/84 |
| Field of Search: |
359/290,291,298,214,223,224,850,196,198
257/417
310/36,90,309,328
|
References Cited [Referenced By]
U.S. Patent Documents
| 3490056 | Jan., 1970 | Milton et al.
| |
| 4421381 | Dec., 1983 | Ueda et al.
| |
| 5629794 | May., 1997 | Magel et al.
| |
| 5661591 | Aug., 1997 | Lin et al.
| |
| 5739941 | Apr., 1998 | Knipe et al.
| |
| 5808780 | Sep., 1998 | McDonald.
| |
| 5835256 | Nov., 1998 | Huibers.
| |
| 5917647 | Jun., 1999 | Yoon.
| |
| 6046840 | Apr., 2000 | Huibers.
| |
| 6172797 | Jan., 2001 | Huibers.
| |
| 6220561 | Apr., 2001 | Garcia.
| |
| 6275326 | Aug., 2001 | Bhalla et al.
| |
| 6356378 | Mar., 2002 | Huibers.
| |
| 6741383 | May., 2004 | Huibers et al.
| |
| 6876485 | Apr., 2005 | Dunphy.
| |
Primary Examiner: Ben; Loha
Attorney, Agent or Firm: Muir; Gregory R.
Claims
1. A MEMS device comprising:
a substrate;
a movable micromechanical element movable relative to the substrate;
a hinge held on the substrate and connected to the movable micromechanical element
for allowing movement of the micromechanical element, and a connector separate
from the hinge for allowing electrical connection to the movable micromechanical
element, wherein the hinge is made of a material different than the connector.
2. The MEMS device of claim 1, wherein the spring constant of the connector is
different than the spring constant of the hinge.
3. The MEMS device of claim 2, wherein the hinge that is stiffer is insulating
and the connector that is less stiff is conducting.
4. The MEMS device of claim 2, wherein the difference in the spring constants
of the hinge and connector is by at least a factor of one.
5. The MEMS device of claim 3, wherein the hinge comprises a ceramic material.
6. The MEMS device of claim 5, wherein the hinge comprises a nitride or oxide
of silicon.
7. The MEMS device of claim 6, wherein the connector comprises an elemental metal,
conductive intermetallic compound, or a metal alloy.
8. The MEMS device of claim 7, wherein the connector comprises aluminum, titanium,
titanium nitride, titanium tungsten, titanium aluminide, tungsten, copper, and
mixtures thereof.
9. The MEMS device of claim 1, wherein the connector comprises a metal, intermetallic
compound, conductive ceramic or metal alloy layer and the hinge comprises an insulating
ceramic compound layer.
10. The MEMS device of claim 9, wherein the connector is made of aluminum, titanium,
titanium tungsten, titanium nitride, titanium aluminide, tungsten, copper, and
alloys; thereof, and the hinge comprises a metal oxide, metalloid oxide, metalloid
nitride or metal nitride.
11. The MEMS device of claim 1, wherein the hinge supplies at least 99% of the
restoring force to the micromechanical element and the connector supplies 1% of
less or the restoring force.
12. The MEMS device of claim 1, wherein a plurality hinges and connectors are provided.
13. The MEMS device of claim 12, wherein from 1 to 4 hinges and 1 to 2 hinges
are provided.
14. The MEMS device of claim 1, wherein the movable micromechanical element is
a micromirror for a projection display or optical switch.
15. The MEMS device of claim 1, wherein the movable micromechanical element is
a MEMS switch.
16. The MEMS device of claim 1, wherein the connector is thinner than the hinge.
17. The MEMS device of claim 1, wherein the connector experiences lower maximum
strain than the maximum strain of the hinge at maximum deflection.
18. The MEMS device of claim 1, wherein the connector is longer than the hinge.
19. The MEMS device of claim 1, wherein the connector has a circuitous shape
and the hinge is substantially straight and elongated.
20. The MEMS device of claim 1, wherein the connector is a conductive multilayer
laminate and the hinge is an insulator.
21. The MEMS device of claim 1, that is a micromirror.
22. The MEMS device of claim 21, that is a micromirror within a spatial light modulator.
23. A MEMS device comprising:
a substrate;
a movable micromechanical element held on the substrate such that the micromechanical
element is movable relative to the substrate;
a connector and a hinge connecting the movable micromechanical element to the
substrate for allowing movement of the micromechanical element, wherein the connector
has an electrical conductivity greater than the hinge.
24. The MEMS device of claim 23, wherein a spring constant of the connector is
different than a spring constant of the hinge.
25. The MEMS device of claim 24, wherein the hinge has a greater width and/or
thickness than the connector.
26. The MEMS device of claim 25, wherein hinge comprises a ceramic material.
27. The MEMS device of claim 26, wherein the hinge comprises a nitride or oxide
of silicon.
28. The MEMS device of claim 27, wherein the less stiff connector comprises an
elemental metal, intermetallic compound, conductive ceramic or a metal alloy.
29. The MEMS device of claim 28, wherein the connector comprises aluminum, titanium,
titanium tungsten, titanium aluminide, tungsten, copper, and alloys thereof.
30. The MEMS device of claim 24, wherein the difference in the spring constants
of the connector and hinge is by at least a factor of one.
31. The MEMS device of claim 23, wherein the connector comprises a metal, intermetallic
compound, conductive ceramic or metal alloy layer and the hinge comprises a ceramic
compound layer.
32. The MEMS device of claim 31, wherein the connector is made of aluminum, titanium,
titanium tungsten, titanium aluminide, tungsten, copper, and alloys thereof, and
the hinge comprises a metal oxide, metalloid oxide, metalloid nitride or metal nitride.
33. The MEMS device of claim 32, wherein the hinge is a reactively sputtered
metal in nitrogen or oxygen.
34. The MEMS device of claim 23, wherein a plurality of connectors and/or hinges
are provided.
35. The MEMS device of claim 34, wherein from 1 to 4 hinges and 1 to 2 connectors
are provided.
36. The MEMS device of claim 23, wherein the movable micromechanical element
is a micromirror for a projection display or optical switch.
37. The MEMS device of claim 23, wherein the movable micromechanical element
is a MEMS switch.
38. The MEMS device of claim 23, wherein the connector is thinner than the hinge.
39. The MEMS device of claim 23, wherein the connector experiences lower strain
than the hinge at maximum deflection.
40. The MEMS device of claim 23, wherein the connector is longer than the hinge.
41. The MEMS device of claim 23, wherein the connector has a circuitous shape
and the hinge is substantially straight.
42. The MEMS device of claim 23, wherein the connector is a conductive multilayer
laminate and the hinge is an insulator.
43. The MEMS device of claim 23, that is a micromirror.
44. The MEMS device of claim 43, that is a micromirror within a spatial light modulator.
45. A MEMS device comprising:
a substrate;
a movable micromechanical element movable relative to the substrate;
a connector and a hinge held on the substrate by a plurality of posts and arranged
for allowing movement of the micromechanical element, wherein the connector and
hinge have different spring constants;
wherein the connector and hinge extend between the posts across the micromechanical
element; and
wherein the connector and hinge are spaced apart from the micromechanical element
with a gap formed therebetween.
46. The MEMS device of claim 45, further comprising circuitry and an electrode
on the substrate or on a second substrate for electrostatically actuating the micromechanical element.
47. The MEMS device of claim 46, wherein from 1 to 4 hinges and 1 to 2 connectors
are provided.
48. The MEMS device of claim 45, wherein the hinge is stiffer and insulating
and the connector is less stiff and conducting.
49. The MEMS device of claim 48, wherein the hinge comprises a ceramic material.
50. The MEMS device of claim 49, wherein the stiffer insulating hinge comprises
a nitride or oxide of silicon.
51. The MEMS device of claim 50, wherein the less stiff connector comprises an
elemental metal or a metal alloy.
52. The MEMS device of claim 51, wherein the metal or metal alloy is selected
from aluminum, titanium, titanium tungsten, titanium aluminide, tungsten, copper,
and alloys thereof.
53. The MEMS device of claim 45, wherein the difference in the spring constants
of the hinge and connector is by at least a factor of two.
54. The MEMS device of claim 45, wherein the connector comprises a metal or metal
alloy layer and the hinge comprises a ceramic compound layer.
55. The MEMS device of claim 54, where the connector is made of aluminum, titanium,
titanium tungsten, titanium aluminide, tungsten, copper, and alloys thereof, and
the hinge comprises a metal oxide, metalloid oxide, metalloid nitride or metal nitride.
56. The MEMS device of claim 55, wherein the hinge is a reactively sputtered
metal in nitrogen or oxygen.
57. The MEMS device of claim 45, wherein a plurality of connectors and/or hinges
is provided.
58. The MEMS device of claim 45, wherein the movable micromechanical element
is a micromirror for a projection display or optical switch.
59. The MEMS device of claim 45, wherein the movable micromechanical element
is a MEMS switch.
60. The MEMS device of claim 45, wherein the connector is thinner than the hinge.
61. The MEMS device of claim 45, wherein the connector experiences lower strain
than the hinge at maximum deflection.
62. The MEMS device of claim 45, wherein the connector is longer than the hinge.
63. The MEMS device of claim 45, wherein the connector has a circuitous shape
and the hinge is substantially straight.
64. The MEMS device of claim 45, wherein the connector is a conductive multilayer
laminate and the hinge is an insulator.
65. The MEMS device of claim 45, that is a micromirror.
66. A MEMS device comprising:
a substrate;
a movable micromechanical element movable relative to the substrate;
a connector and a hinge held on the substrate by a plurality of posts and arranged
for allowing movement of the micromechanical element, wherein the connector experiences
a lower strain at maximum deflection of the micromechanical element than the hinge;
wherein the connector and hinge extend between the posts across the micromechanical
element; and
wherein the connector and hinge are spaced apart from the micromechanical element
with a gap formed therebetween.
67. The MEMS device of claim 66, wherein a spring constant of the connector is
different than a spring constant of the hinge.
68. The MEMS device of claim 67, wherein the hinge that is stiffer is insulating
and the connector that is less stiff is conducting.
69. The MEMS device of claim 68, wherein the stiffer insulating hinge comprises
a ceramic material.
70. The MEMS device of claim 69, wherein the stiffer insulating hinge comprises
a nitride or oxide of silicon.
71. The MEMS device of claim 70, wherein the less stiff connector comprises an
elemental metal, intermetallic compound, conductive ceramic or a metal alloy.
72. The MEMS device of claim 71, wherein the connector comprises aluminum, titanium,
titanium tungsten, titanium aluminide, tungsten, copper, and alloys thereof.
73. The MEMS device of claim 67, wherein the difference in the spring constants
of the hinges is by at least a factor of two.
74. The MEMS device of claim 66, wherein the connector comprises a metal or metal
alloy layer and the hinge comprises a ceramic compound layer.
75. The MEMS device of claim 74, wherein the connector is made of aluminum, titanium,
titanium tungsten, titanium aluminide, tungsten, copper, and alloys thereof, and
the hinge comprises a metal oxide, metalloid oxide, metalloid nitride or metal nitride.
76. The MEMS device of claim 75, wherein the hinge is a reactively sputtered
metal in nitrogen or oxygen.
77. The MEMS device of claim 66, wherein a plurality of hinges is provided.
78. The MEMS device of claim 77, that is a micromirror in a spatial light modulator.
79. The MEMS device of claim 66, wherein the movable micromechanical element
is a micromirror for a projection display or optical switch.
80. The MEMS device of claim 66, wherein the movable micromechanical element
is a MEMS switch.
81. The MEMS device of claim 66, wherein the connector is thinner than the hinge.
82. The MEMS device of claim 66, wherein the connector is made of a different
material than the hinge.
83. The MEMS device of claim 66, wherein the connector is longer than the hinge.
84. The MEMS device of claim 66, wherein the connector has a circuitous shape
and the hinge is substantially straight.
85. The MEMS device of claim 66, wherein the connector is a conductive multilayer
laminate and the hinge is an insulator.
86. A MEMS device comprising:
a substrate;
a movable micromechanical element movable relative to the substrate;
a connector and a hinge for allowing movement of the micromechanical element,
the hinge being an elongated hinge that connects to one or more posts on the substrate
and to the movable micromechanical element, each hinge having a length in the direction
of the elongation, and a width and depth; and
wherein at least one of the width and depth of the connector is different than
the width or depth of the hinge.
87. The MEMS device of claim 86, wherein a spring constant of the connector is
different than a spring constant of the hinge.
88. The MEMS device of claim 87, wherein the hinge that is stiffer has a greater
width and/or thickness.
89. The MEMS device of claim 88, wherein the stiffer insulating hinge comprises
a ceramic material.
90. The MEMS device of claim 89, wherein the stiffer insulating hinge comprises
a nitride or oxide of silicon.
91. The MEMS device of claim 90, wherein the less stiff connector comprises an
elemental metal, intermetallic compound, conductive ceramic or a metal alloy.
92. The MEMS device of claim 91, wherein the metal or metal alloy is selected
from aluminum, titanium, titanium tungsten, titanium aluminide, tungsten, copper,
and alloys thereof.
93. The MEMS device of claim 87, wherein the difference in the spring constants
of the connector and hinge is by at least a factor of two.
94. The MEMS device of claim 86, wherein the connector comprises a metal or metal
alloy layer and the hinge comprises a ceramic compound layer.
95. The MEMS device of claim 94, wherein the connector is made of aluminum, titanium,
titanium tungsten, titanium aluminide, tungsten, copper, and alloys thereof, and
the hinge comprises a metal oxide, metalloid oxide, metalloid nitride or metal nitride.
96. The MEMS device of claim 95, wherein the hinge is a reactively sputtered
metal in nitrogen or oxygen.
97. A spatial light modulator comprising:
a substrate;
a post connected to the substrate;
a movable micromirror element connected to the post via a hinge such that the
micromirror element is movable relative to the substrate; and
a connector separate from the hinge, wherein the hinge supplies at least 90%
of the restoring force to the micromirror element and the connector supplies 10%
or less of the restoring force.
98. The spatial light modulator of claim 97, wherein the hinge supplies at least
99% of the restoring force to the micromirror element and the connector supplies
1% or less of the restoring force.
Description
BACKGROUND OF THE INVENTION
The present invention is related to MEMS devices and in particular to hinges
and electrical connections for MEMS devices. More particularly, the invention is
related to hinge and electrical connection shapes, characteristics and/or materials
for MEMS device, in particular micromirror or other electrostatically deflectable
micromechanical elements.
There are many MEMS devices in which a movable element is connected to a rigid
substrate through flexible hinges. These hinges allow the movable element to move.
The most commonly used MEMS materials are single crystal silicon, polysilicon,
and silicon nitr. All of these are good MEMS materials because they deform nearly
perfectly elastically, and also the first two conduct electricity, which enables
a variety of electrostatic actuators, fabricated for example in the MUMPS or SUMMIT processes.
These materials do not solve all MEMS device requirements however, because
they are difficult to fabricate. Single crystal silicon must be cut out of a wafer.
Polysilicon requires high temperature deposition, and silicon nitride does not
conduct. A high deposition temperature step is undesirable because it can disturb
other films deposited at lower temperatures, e.g. aluminum. Silicon nitride does
not conduct and thus is not sufficient alone.
A common approach in MEMS devices is to use an insulating mechanical layer in
a
laminate with an additional metal layer provided to conduct electricity. However,
metallic layers often do not deform elastically once their rather low strain limits
are exceeded. As a result, fatigue, fracture and creep sometimes results after
repeated actuation.
What are needed are novel materials and designs for MEMS devices that allow
for electrical conductivity to a MEMS movable element as well as elastic deformation
of such a movable element without fatigue or other damage modes.
SUMMARY OF THE INVENTION
A MEMS device is disclosed comprising: a substrate; a movable micromechanical
element
movable relative to the substrate; a connector and a hinge for allowing movement
of the micromechanical element, wherein the connector is made of a material different
than the hinge.
In another embodiment of the invention, a MEMS device comprises: a substrate;
a movable micromechanical element movable relative to the substrate; a connector
and a hinge for allowing movement of the micromechanical element, wherein the connector
has a conductivity greater than the hinge.
In a further embodiment of the invention, a MEMS device comprises: a substrate;
a movable micromechanical element movable relative to the substrate; a hinge and
a connector separate from the hinge, wherein the hinge provides at least 90% of
the restoring force to the MEMS device, and the connector provides 10% or less
of the restoring force.
In a further embodiment of the invention, a MEMS device comprises: a substrate;
a movable micromechanical element movable relative to the substrate; a hinge and
a connector separate from the hinge, wherein the connector and the hinge have different
spring constants.
In a still further embodiment of the invention, a MEMS device comprises: a substrate;
a movable micromechanical element movable relative to the substrate; a connector
and a hinge for allowing movement of the micromechanical element, wherein the connector
experiences a lower strain at maximum deflection of the micromechanical element
than the hinge.
And in another embodiment of the invention, a MEMS device comprises: a substrate;
a movable micromechanical element movable relative to the substrate; a connector
and a hinge for allowing movement of the micromechanical element, each hinge being
an elongated hinge that connects to one or more posts on the substrate and to the
movable micromechanical element, each hinge having a length in the direction of
the elongation, and a width and depth; wherein at least one of the width and depth
of the connector is different than the width or depth of the hinge.
In a preferred embodiment the MEMS device is a micromirror. Also encompassed
within
the invention are projection systems using the various MEMS devices of the invention.
Such projection systems can comprise a light source for providing a light beam;
a white light color divider for dividing white light temporally or spatially into
different color light beams; a micromirror array comprising the MEMS device of
the invention that is provided in a path of the different color light beams; and
optics for projecting and/or focusing light reflected from the micromirror array.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration of four mirrors from a micromirror array, with one
mirror deflected;
FIGS. 2A and 2B show a micromirror held on a substrate in a deflected state
via hinges and posts;
FIG. 3 shows a top view of an embodiment of a micromirror with two hinges; and
FIG. 4 shows an alternate embodiment of a micromirror with two hinges.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to micro-mechanical devices and more particularly
to systems for physically and electrically connecting micro-mechanical devices
to each other and/or a substrate on which they are formed. The micro-mechanical
device can be any movable device that is held by one or more hinges on a substrate.
As one example, as can be seen in FIG. 1, micromirrors are held on light transmissive
substrate
52 and are actuated by electrodes on a semiconductor substrate
62. General methods for making micromirrors are disclosed in U.S. Pat. No.
5,835,256 issued Nov. 10, 1998 and U.S. Pat. No. 6,172,797 issued Jan. 9, 2001,
both to Huibers et al. and incorporated herein by reference. Other methods for
making micromirrors are disclosed in U.S. patent application Ser. No. 10/005,308
to Patel et al. filed Dec. 3, 2001, U.S. patent application Ser. No. 60/276,222
to Patel et al. filed Mar. 15, 2001, U.S. patent application Ser. No. 09/649,569
to Patel et al. filed Aug. 28, 2000, U.S. patent application Ser. No. 60/298,529
to Reid et al. filed Jun. 15, 2001, and U.S. Pat. No. 6,290,865 to Patel et al.
issued Sep. 18, 2001, each of these being incorporated herein by reference. In
addition, the invention is related to micromirrors for optical switching, such
as disclosed in U.S. Pat. No. 6,337,760 to Huibers et al. issued Jan. 8, 2002,
incorporated herein by reference. Also, the separate hinge and electrical connections
for a MEMS device are disclosed in related U.S. patent application Ser. No. 09/977,603
to Huibers filed Oct. 12, 2001(now abandoned), also incorporated herein by reference.
As can be seen in FIG. 1, four micromirrors are held on a substrate preferably
transmissive to visible light (e.g. glass or quartz). A second substrate
62,
preferably a silicon substrate, comprises circuitry and electrodes for electrostatically
actuating the micromirrors on substrate
52. The micromirrors are microfabricated
separately on substrate
52 and circuitry and electrodes are microfabricated
separately on device substrate
62, followed by bonding of the two substrates
together. Such microfabrication and bonding is disclosed in further detail in the
above-mentioned patents and patent applications.
In FIGS. 2A and 2B, a torsion hinge
80 is shown connecting the mirror
64
to a transparent substrate. In this device the torsion hinge comprises a conducting
component, e.g. it is made of a conducting material or a laminate containing a
conductive material. As such, the hinge
80, whether a single material or
a laminate, is used to both pivotably hold the mirror on the substrate as well
as maintain an electrical connection with the substrate and/or other mirrors.
In one example of the present invention, as can be seen in FIG. 3, a connection
82 is used for electrically connecting to micromechanical (micromirror)
element
64 that is separate from hinge
80. In this way, materials
can be selected and optimized to have the best strength, elasticity, and freedom
from fatigue for the hinge, and different materials can be selected and optimized
for electrical conductivity for the electrical connection
82. The spring
stiffness can thus be different for the hinge
80 and the electrical connection
82—preferably where the hinge is stiffer than the electrical connection.
In many types of MEMS actuators a hinge attaches a movable element to a substrate.
Part of the movable element then moves towards the substrate and touches it or
touches some other limit. At this point it is desirable that the movable element
does not move further. This requirement often results in the engineering situation
that one wants to make hinges short or in tension, and not meandering. The design
of FIG. 3 is a way to get the best of both worlds—a shorter more elastic
hinge doing the mechanical work, and a lightly strained hinge to carry the electrical
charge. The hinge and electrical connection can be provided separately connected
to the substrate and micromirror plate, as can be seen in FIG.
4.
The electrical connection
82 can be any suitable shape, though thin and
or circuitous designs are preferred. Also, the electrical connection
82
can be formed in the same plane or in a different plane, depending upon the exact
deposition method. CVD (chemical vapor deposition) and PVD (physical vapor deposition)
processes can be used for depositing the hinge and electrical connection materials
as known in the art and as set forth in the above noted patents and applications.
In a preferred embodiment, the electrical connection is deposited by sputtering/PVD,
and the hinge is deposited by sputtering or CVD. Also, in a preferred embodiment,
the electrical connection is a metal (e.g. Al, Ti, etc.), intermetallic compound
(e.g. TiAl, TiW, etc.), conductive ceramic (e.g. TiN, WC, RuO, TiO, etc.) or metal
alloy (such as alloys of aluminum, titanium, tungsten, tungsten, copper, etc.)
or a conductive alloy of a metal and a dielectric compound (such as cobalt silicon
nitride, platinum silicon oxide, etc.) such as the compounds set forth in U.S.
patent application Ser. Nos. 09/910,537 filed Jul. 20, 2001 and 60/300,533 filed
Jun. 22, 2001, each incorporated herein by reference. The hinge can be electrically
conductive or a semiconductor, though in a preferred embodiment, the hinge is an
insulating ceramic. By "ceramic" it is meant a compound where a metal (or metalloid)
is bound to a non-metal. Preferred are oxide, nitride and carbide compounds of
metalloids and early transition metals. Particularly preferred are nitrides and
oxides or titanium and silicon, such as silicon nitride, silicon oxynitride, silicon
oxide, titanium oxide, titanium nitride and titanium oxynitride. The ceramic can
be either insulating (such as the silicon nitride) or conductive (such as titanium
nitride). Other hinge materials and methods for deposition are set forth in the
above noted patents and applications.
While the invention has been described in conjunction with specific embodiments,
it is evident to those skilled in the art that many alternatives, modifications,
and variations will be apparent in light of the foregoing description. Accordingly,
the invention is intended to embrace all such alternatives, modifications, and
variations that fall within the spirit and scope of the appended claims.
*
