U.S. patent application number 12/719790 was filed with the patent office on 2011-03-31 for method and apparatus for providing a light absorbing mask in an interferometric modulator display.
This patent application is currently assigned to QUALCOMM MEMS Technologies, Inc.. Invention is credited to Chun-Ming Albert Wang.
Application Number | 20110075246 12/719790 |
Document ID | / |
Family ID | 39529866 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110075246 |
Kind Code |
A1 |
Wang; Chun-Ming Albert |
March 31, 2011 |
METHOD AND APPARATUS FOR PROVIDING A LIGHT ABSORBING MASK IN AN
INTERFEROMETRIC MODULATOR DISPLAY
Abstract
A microelectromechanical system (MEMS) device is provided. In
one embodiment, the MEMS device includes a transparent substrate,
and a plurality of interferometric modulators. The plurality of
interferometric modulators includes an optical stack coupled to the
transparent substrate, in which the optical stack includes a first
light absorbing area. The plurality of interferometric modulators
further includes a reflective layer over the optical stack, and one
or more posts to support the reflective layer. Each of the one or
more posts includes a second light absorbing area integrated in the
post.
Inventors: |
Wang; Chun-Ming Albert;
(Fremont, CA) |
Assignee: |
QUALCOMM MEMS Technologies,
Inc.
San Diego
CA
|
Family ID: |
39529866 |
Appl. No.: |
12/719790 |
Filed: |
March 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11683787 |
Mar 8, 2007 |
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12719790 |
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Current U.S.
Class: |
359/291 ;
427/162 |
Current CPC
Class: |
G02B 26/001
20130101 |
Class at
Publication: |
359/291 ;
427/162 |
International
Class: |
G02B 26/00 20060101
G02B026/00; B05D 5/06 20060101 B05D005/06 |
Claims
1. A microelectromechanical system (MEMS) comprising: a transparent
substrate; and a plurality of interferometric modulators
comprising, an optical stack coupled to the transparent substrate,
the optical stack including a first light absorbing area; a
reflective layer over the optical stack; and one or more posts to
support the reflective layer, each of the one or more posts
including a second light absorbing area integrated in the post.
2. The MEMS of claim 1, wherein the second light absorbing area
within each post is separate from the first light absorbing area
within the optical stack.
3. The MEMS of claim 2, wherein: the first light absorbing area
comprises a first black matrix layer; and the second light
absorbing area comprises a second black matrix layer.
4. The MEMS of claim 3, wherein: the first black matrix layer
comprises a first absorber layer, a first dielectric layer, and a
first reflective layer; and the second black matrix layer comprises
a second absorber layer and a second dielectric layer.
5. The MEMS of claim 4, wherein: the first absorber layer has
substantially a same thickness as the second absorber layer; and
the first dielectric layer has substantially a same thickness as
the second dielectric layer.
6. The MEMS of claim 1, wherein a portion of the second light
absorbing area within a given post extends over a portion of the
first light absorbing area within the optical stack such that the
second light absorbing area overlaps the first light absorbing
area.
7. The MEMS of claim 1 as a display system, further comprising: a
display including the MEMS; a processor that is in electrical
communication with the display, the processor being configured to
process image data; and a memory device in electrical communication
with the processor.
8. The display system of claim 7, further comprising: a driver
circuit configured to send at least one signal to the display.
9. The display system of claim 8, further comprising: a controller
configured to send at least a portion of the image data to the
driver circuit.
10. The display system of claim 7, further comprising: an image
source module configured to send the image data to the
processor.
11. The display system of claim 10, wherein the image source module
comprises at least one of a receiver, transceiver, and
transmitter.
12. The display system of claim 7, further comprising: an input
device configured to receive input data and to communicate the
input data to the processor.
13. A micromechanical system (MEMS) comprising: a transparent
substrate means; a plurality of interferometric modulator means
comprising, an optical stack means coupled to the transparent
substrate means, the optical stack means including a first light
absorbing means; a reflective layer means over the optical stack
means; and one or more post means for supporting the reflective
layer means, each of the one or more post means including a second
light absorbing means integrated in the post means.
14. The MEMS of claim 13, wherein the second light absorbing means
within each post means is separate from the first light absorbing
means within the optical stack means.
15. The MEMS of claim 14, wherein: the first light absorbing means
comprises a first black matrix layer means; and the second light
absorbing means comprises a second black matrix layer means.
16. The MEMS of claim 15, wherein: the first black matrix layer
means comprises a first absorber layer means, a first dielectric
layer means, and a first reflective layer means; and the second
black matrix layer means comprises a second absorber layer means
and a second dielectric layer means.
17. The MEMS of claim 16, wherein: the first absorber layer means
has substantially a same thickness as the second absorber layer
means; and the first dielectric layer means has substantially a
same thickness as the second dielectric layer means.
18. The MEMS of claim 13, wherein a portion of the second light
absorbing means within a given post means extends over a portion of
the first light absorbing means within the optical stack means such
that the second light absorbing means overlaps the first light
absorbing means.
19. A method for providing light in an interferometric modulator
device, the method comprising: providing a transparent substrate;
forming a first light absorbing area on the transparent substrate;
forming a conductive layer on the transparent substrate; forming a
reflective layer over the conductive layer; and forming one or more
posts to support the reflective layer, the one or more posts being
formed over portions of the conductive layer that do not overlap
with the first light absorbing area, wherein forming one or more
posts includes integrating a second light absorbing area into the
one or more posts.
20. The method of claim 19, wherein the second light absorbing area
within each post is separate from the first light absorbing
area.
21. The method of claim 20, wherein: forming a first light
absorbing area on the transparent substrate comprises forming a
first black matrix layer on the transparent substrate; and
integrating a second light absorbing area into the one or more
posts comprises integrating a second black matrix layer into the
one or more posts.
22. An interferometric modulator display device manufactured in
accordance with the method of claim 19.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/683,787 filed on Mar. 8, 2007,titled "Method and Apparatus
for Providing a Light Absorbing Mask in an Interferometric
Modulator Display," which is hereby incorporated by reference in
its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to display devices,
and more particularly to interferometric modulator display
devices.
[0004] 2. Description of the Related Art
[0005] Microelectromechanical systems (MEMS) include
micromechanical elements, actuators, and electronics.
Micromechanical elements may be created using deposition, etching,
and or other micromachining processes that etch away parts of
substrates and/or deposited material layers or that add layers to
form electrical and electromechanical devices. One type of MEMS
device is called an interferometric modulator. As used herein, the
term interferometric modulator or interferometric light modulator
refers to a device that selectively absorbs and/or reflects light
using the principles of optical interference. In certain
embodiments, an interferometric modulator may comprise a pair of
conductive plates, one or both of which may be transparent and/or
reflective in whole or part and capable of relative motion upon
application of an appropriate electrical signal. In a particular
embodiment, one plate may comprise a stationary layer deposited on
a substrate and the other plate may comprise a movable reflective
layer (also referred to as a mechanical layer herein) separated
from the stationary layer by a transparent medium (e.g., an air
gap). As described herein in more detail, the position of one plate
in relation to another can change the optical interference of light
incident on the interferometric modulator. Such devices have a wide
range of applications, and it would be beneficial in the art to
utilize and/or modify the characteristics of these types of devices
so that their features can be exploited in improving existing
products and creating new products that have not yet been
developed.
[0006] Interferometric modulator displays typically include light
absorbing areas (or light absorbing masks)--e.g., composed of black
matrix--to improve a display contrast of the interferometric
modulator displays. FIG. 1 illustrates a portion of a conventional
interferometric modulator display 100 including a stationary layer
102 (formed on a substrate 104) and a movable reflective layer 106.
As shown in FIG. 1, the interferometric modulator display 100 also
includes a black matrix layer 108 formed on the substrate 104. The
interferometric modulator display 100 further includes posts
110--formed over of the black matrix layer 108--that support the
movable reflective layer 106. Formation of the posts 110 over the
black matrix layer 108, however, typically causes a "launching" of
the movable reflective layer 106 over the substrate 104 which can
increase the size of an air gap 112 between the stationary layer
102 and the movable reflective layer 106. The increase in size of
the air gap 112 can cause an undesirable shift in an optical
response of an interferometric modulator display. Such a shift in
optical response is noticeable especially in broadband white
interferometric modulator displays which require a tight control
over the size of air gaps.
SUMMARY OF THE INVENTION
[0007] In general, in one aspect, this specification describes a
microelectromechanical system (MEMS) including a transparent
substrate, and a plurality of interferometric modulators. The
plurality of interferometric modulators includes an optical stack
coupled to the transparent substrate. The optical stack includes a
first light absorbing area, a reflective layer over the optical
stack, and one or more posts to support the reflective layer. Each
of the one or more posts includes a second light absorbing area
integrated in the post.
[0008] In general, in another aspect, this specification describes
a method for providing light in an interferometric modulator
device. The method includes providing a transparent substrate;
forming a first light absorbing area on the transparent substrate;
forming a conductive layer on the transparent substrate; forming a
reflective layer over the conductive layer; and forming one or more
posts to support the reflective layer. The one or more posts are
formed over portions of the conductive layer that do not overlap
with the first light absorbing area. Forming one or more posts
includes integrating a second light absorbing area into the one or
more posts.
[0009] Implementations may provide one or more of the following
advantages. In one embodiment, a method of forming black matrix
within an interferometric modulator display is provided that
requires two less masking steps relative to conventional
techniques. Moreover, there are fewer issues with regard to
properly overlaying layers of a black matrix on top of one another
as the method does not require a target mask, as is required in
conventional techniques. In addition, the launching effect of the
metallic membrane layer is reduced as, in one embodiment, an
absorber layer is deposited within the posts so that the posts act
as a black matrix layer.
[0010] The details of one or more embodiments are set forth in the
accompanying drawings and the description below. Other features and
advantages will be apparent from the description and drawings, and
from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 illustrates a cross-section of a conventional
interferometric modulator display including a black matrix
layer.
[0012] FIG. 2 is an isometric view depicting a portion of one
embodiment of an interferometric modulator display in which a
movable reflective layer of a first interferometric modulator is in
a relaxed position and a movable reflective layer of a second
interferometric modulator is in an actuated position.
[0013] FIG. 3 is a system block diagram illustrating one embodiment
of an electronic device incorporating a 3.times.3 interferometric
modulator display.
[0014] FIG. 4 is a diagram of movable mirror position versus
applied voltage for one exemplary embodiment of an interferometric
modulator of FIG. 1.
[0015] FIG. 5 is an illustration of a set of row and column
voltages that may be used to drive an interferometric modulator
display.
[0016] FIGS. 6A and 6B illustrate one exemplary timing diagram for
row and column signals that may be used to write a frame of display
data to the 3.times.3 interferometric modulator display of FIG.
2.
[0017] FIG. 7A is a cross-section of an interferometric modulator
of FIG. 2.
[0018] FIGS. 7B-7E illustrate alternative embodiments of an
interferometric modulator.
[0019] FIG. 8 illustrates a cross-sectional view of an
interferometric modulator display including light absorbing areas
in accordance with one embodiment.
[0020] FIG. 9A illustrates a cross-section of a first black matrix
layer within the interferometric modulator display of FIG. 8 in
accordance with one embodiment.
[0021] FIG. 9B illustrates a cross-section of a support post within
the interferometric modulator display of FIG. 8 in accordance with
one embodiment.
[0022] FIG. 10 illustrates a flow diagram of a process for
manufacturing an interferometric modulator display according to one
embodiment.
[0023] FIGS. 11A-11G illustrate the process of manufacturing an
interferometric modulator display according to the process of FIG.
10.
[0024] FIGS. 12A and 12B are system block diagrams illustrating an
embodiment of a visual display device comprising a plurality of
interferometric modulators.
[0025] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] The following detailed description is directed to certain
specific embodiments of the invention. However, the invention can
be embodied in a multitude of different ways. In this description,
reference is made to the drawings wherein like parts are designated
with like numerals throughout. As will be apparent from the
following description, the embodiments may be implemented in any
device that is configured to display an image, whether in motion
(e.g., video) or stationary (e.g., still image), and whether
textual or pictorial. More particularly, it is contemplated that
the embodiments may be implemented in or associated with a variety
of electronic devices such as, but not limited to, mobile
telephones, wireless devices, personal data assistants (PDAs),
hand-held or portable computers, GPS receivers/navigators, cameras,
MP3 players, camcorders, game consoles, wrist watches, clocks,
calculators, television monitors, flat panel displays, computer
monitors, auto displays (e.g., odometer display, etc.), cockpit
controls and/or displays, display of camera views (e.g., display of
a rear view camera in a vehicle), electronic photographs,
electronic billboards or signs, projectors, architectural
structures, packaging, and aesthetic structures (e.g., display of
images on a piece of jewelry). MEMS devices of similar structure to
those described herein can also be used in non-display applications
such as in electronic switching devices.
[0027] As discussed above, conventional interferometric modulator
displays typically include light absorbing areas--e.g., composed of
black matrix--to improve a display contrast of the interferometric
modulator displays. Black matrix layers within a conventional
interferometric modulator display, however, generally cause a
launching of the movable reflective layer within the
interferometric modulator display, which distorts the optical
response of the interferometric modulator display. Such a
distortion in optical response is visually perceivable, for
example, in broadband white interferometric modulator displays in
that the color white is shifted to another color. Accordingly, this
specification describes an improved method for fabricating an
interferometric display device to reduce the launching of the
moveable reflective layer caused by black matrix layers. In one
embodiment, an interferometric modulator display is provided that
includes black matrix layers that are integrated into one or more
of the posts that support a moveable reflective layer within the
interferometric modulator display.
[0028] One interferometric modulator display embodiment comprising
an interferometric MEMS display element is illustrated in FIG. 2.
In these devices, the pixels are in either a bright or dark state.
In the bright ("on" or "open") state, the display element reflects
a large portion of incident visible light to a user. When in the
dark ("off" or "closed") state, the display element reflects little
incident visible light to the user. Depending on the embodiment,
the light reflectance properties of the "on" and "off" states may
be reversed. MEMS pixels can be configured to reflect predominantly
at selected colors, allowing for a color display in addition to
black and white.
[0029] FIG. 2 is an isometric view depicting two adjacent pixels in
a series of pixels of a visual display, wherein each pixel
comprises a MEMS interferometric modulator. In some embodiments, an
interferometric modulator display comprises a row/column array of
these interferometric modulators. Each interferometric modulator
includes a pair of reflective layers positioned at a variable and
controllable distance from each other to form a resonant optical
gap with at least one variable dimension. In one embodiment, one of
the reflective layers may be moved between two positions. In the
first position, referred to herein as the relaxed position, the
movable reflective layer is positioned at a relatively large
distance from a fixed partially reflective layer. In the second
position, referred to herein as the actuated position, the movable
reflective layer is positioned more closely adjacent to the fixed
partially reflective layer. Incident light that reflects from the
two layers interferes constructively or destructively depending on
the position of the movable reflective layer, producing either an
overall reflective or non-reflective state for each pixel.
[0030] The depicted portion of the pixel array in FIG. 2 includes
two adjacent interferometric modulators 12a and 12b. In the
interferometric modulator 12a on the left, a movable reflective
layer 14a is illustrated in a relaxed position at a predetermined
distance from an optical stack 16a, which includes a partially
reflective layer. In the interferometric modulator 12b on the
right, the movable reflective layer 14b is illustrated in an
actuated position adjacent to the optical stack 16b.
[0031] The optical stacks 16a and 16b (collectively referred to as
optical stack 16), as referenced herein, typically comprise of
several fused layers, which can include an electrode layer, such as
indium tin oxide (ITO), a partially reflective layer, such as
chromium, and a transparent dielectric. The optical stack 16 is
thus electrically conductive, partially transparent and partially
reflective, and may be fabricated, for example, by depositing one
or more of the above layers onto a transparent substrate 20. In one
embodiment, the optical stack further includes a first black matrix
layer, as discussed in greater detail below. The partially
reflective layer can be formed from a variety of materials that are
partially reflective such as various metals, semiconductors, and
dielectrics. The partially reflective layer can be formed of one or
more layers of materials, and each of the layers can be formed of a
single material or a combination of materials.
[0032] In some embodiments, the layers of the optical stack 16 are
patterned into parallel strips, and may form row electrodes in a
display device as described further below. The movable reflective
layers 14a, 14b may be formed as a series of parallel strips of a
deposited metal layer or layers (orthogonal to the row electrodes
of 16a, 16b) deposited on top of posts 18 and an intervening
sacrificial material deposited between the posts 18. When the
sacrificial material is etched away, the movable reflective layers
14a, 14b are separated from the optical stacks 16a, 16b by a
defined gap 19. A highly conductive and reflective material such as
aluminum may be used for the reflective layers 14, and these strips
may form column electrodes in a display device.
[0033] With no applied voltage, the gap 19 remains between the
movable reflective layer 14a and optical stack 16a, with the
movable reflective layer 14a in a mechanically relaxed state, as
illustrated by the pixel 12a in FIG. 2. However, when a potential
difference is applied to a selected row and column, the capacitor
formed at the intersection of the row and column electrodes at the
corresponding pixel becomes charged, and electrostatic forces pull
the electrodes together. If the voltage is high enough, the movable
reflective layer 14 is deformed and is forced against the optical
stack 16. A dielectric layer (not shown) within the optical stack
16 may prevent shorting and control the separation distance between
layers 14 and 16, as illustrated by pixel 12b on the right in FIG.
2. The behavior is the same regardless of the polarity of the
applied potential difference. In this way, row/column actuation
that can control the reflective vs. non-reflective pixel states is
analogous in many ways to that used in conventional LCD and other
display technologies.
[0034] FIGS. 3 through 6 illustrate one exemplary process and
system for using an array of interferometric modulators in a
display application.
[0035] FIG. 3 is a system block diagram illustrating one embodiment
of an electronic device that may incorporate aspects of the
invention. In the exemplary embodiment, the electronic device
includes a processor 21 which may be any general purpose
single-chip or multi-chip microprocessor such as an ARM (Advanced
RISC Machine), Pentium.RTM., Pentium II.RTM., Pentium III.RTM.,
Pentium IV.RTM., Pentium.RTM. Pro, an 8051, a MIPS.RTM., a Power
PC.RTM., an ALPHA.RTM., or any special purpose microprocessor such
as a digital signal processor, microcontroller, or a programmable
gate array. As is conventional in the art, the processor 21 may be
configured to execute one or more software modules. In addition to
executing an operating system, the processor may be configured to
execute one or more software applications, including a web browser,
a telephone application, an email program, or any other software
application.
[0036] In one embodiment, the processor 21 is also configured to
communicate with an array driver 22. In one embodiment, the array
driver 22 includes a row driver circuit 24 and a column driver
circuit 26 that provide signals to a display array or panel 30. The
cross section of the array illustrated in FIG. 2 is shown by the
lines 1-1 in FIG. 3. For MEMS interferometric modulators, the
row/column actuation protocol may take advantage of a hysteresis
property of these devices illustrated in FIG. 4. It may require,
for example, a 10 volt potential difference to cause a movable
layer to deform from the relaxed state to the actuated state.
However, when the voltage is reduced from that value, the movable
layer maintains its state as the voltage drops back below 10 volts.
In the exemplary embodiment of FIG. 4, the movable layer does not
relax completely until the voltage drops below 2 volts. There is
thus a range of voltage, about 3 to 7 V in the example illustrated
in FIG. 4, where there exists a window of applied voltage within
which the device is stable in either the relaxed or actuated state.
This is referred to herein as the "hysteresis window" or "stability
window."
[0037] For a display array having the hysteresis characteristics of
FIG. 4, the row/column actuation protocol can be designed such that
during row strobing, pixels in the strobed row that are to be
actuated are exposed to a voltage difference of about 10 volts, and
pixels that are to be relaxed are exposed to a voltage difference
of close to zero volts. After the strobe, the pixels are exposed to
a steady state voltage difference of about 5 volts such that they
remain in whatever state the row strobe put them in. After being
written, each pixel sees a potential difference within the
"stability window" of 3-7 volts in this example. This feature makes
the pixel design illustrated in FIG. 2 stable under the same
applied voltage conditions in either an actuated or relaxed
pre-existing state. Since each pixel of the interferometric
modulator, whether in the actuated or relaxed state, is essentially
a capacitor formed by the fixed and moving reflective layers, this
stable state can be held at a voltage within the hysteresis window
with almost no power dissipation. Essentially no current flows into
the pixel if the applied potential is fixed.
[0038] In typical applications, a display frame may be created by
asserting the set of column electrodes in accordance with the
desired set of actuated pixels in the first row. A row pulse is
then applied to the row 1 electrode, actuating the pixels
corresponding to the asserted column lines. The asserted set of
column electrodes is then changed to correspond to the desired set
of actuated pixels in the second row. A pulse is then applied to
the row 2 electrode, actuating the appropriate pixels in row 2 in
accordance with the asserted column electrodes. The row 1 pixels
are unaffected by the row 2 pulse, and remain in the state they
were set to during the row 1 pulse. This may be repeated for the
entire series of rows in a sequential fashion to produce the frame.
Generally, the frames are refreshed and/or updated with new display
data by continually repeating this process at some desired number
of frames per second. A wide variety of protocols for driving row
and column electrodes of pixel arrays to produce display frames are
also well known and may be used in conjunction with the present
invention.
[0039] FIGS. 5 and 6A-6B illustrate one possible actuation protocol
for creating a display frame on the 3.times.3 array of FIG. 3. FIG.
5 illustrates a possible set of column and row voltage levels that
may be used for pixels exhibiting the hysteresis curves of FIG. 4.
In the embodiment shown in FIG. 5, actuating a pixel involves
setting the appropriate column to--V.sub.bias, and the appropriate
row to +.DELTA.V, which may correspond to -5 volts and +5 volts,
respectively. Relaxing the pixel is accomplished by setting the
appropriate column to +V.sub.bias, and the appropriate row to the
same +.DELTA.V, producing a zero volt potential difference across
the pixel. In those rows where the row voltage is held at zero
volts, the pixels are stable in whatever state they were originally
in, regardless of whether the column is at +V.sub.bias, or
-V.sub.bias. As is also illustrated in FIG. 5, it will be
appreciated that voltages of opposite polarity than those described
above can be used, e.g., actuating a pixel can involve setting the
appropriate column to +V.sub.bias, and the appropriate row to
-.DELTA.V. In this embodiment, releasing the pixel is accomplished
by setting the appropriate column to -V.sub.bias, and the
appropriate row to the same -.DELTA.V, producing a zero volt
potential difference across the pixel.
[0040] FIG. 6B is a timing diagram showing a series of row and
column signals applied to the 3.times.3 array of FIG. 3 which will
result in the display arrangement illustrated in FIG. 6A, where
actuated pixels are non-reflective. Prior to writing the frame
illustrated in FIG. 6A, the pixels can be in any state, and in this
example, all the rows are at 0 volts, and all the columns are at +5
volts. With these applied voltages, all pixels are stable in their
existing actuated or relaxed states.
[0041] In the frame shown in FIG. 6A, pixels (1,1), (1,2), (2,2),
(3,2) and (3,3) are actuated. To accomplish this, during a "line
time" for row 1, columns 1 and 2 are set to -5 volts, and column 3
is set to +5 volts. This does not change the state of any pixels,
because all the pixels remain in the 3-7 volt stability window. Row
1 is then strobed with a pulse that goes from 0, up to 5 volts, and
back to zero. This actuates the (1,1) and (1,2) pixels and relaxes
the (1,3) pixel. No other pixels in the array are affected. To set
row 2 as desired, column 2 is set to -5 volts, and columns 1 and 3
are set to +5 volts. The same strobe applied to row 2 will then
actuate pixel (2,2) and relax pixels (2,1) and (2,3). Again, no
other pixels of the array are affected. Row 3 is similarly set by
setting columns 2 and 3 to -5 volts, and column 1 to +5 volts. The
row 3 strobe sets the row 3 pixels as shown in FIG. 6A. After
writing the frame, the row potentials are zero, and the column
potentials can remain at either +5 or -5 volts, and the display is
then stable in the arrangement of FIG. 6A. It will be appreciated
that the same procedure can be employed for arrays of dozens or
hundreds of rows and columns. It will also be appreciated that the
timing, sequence, and levels of voltages used to perform row and
column actuation can be varied widely within the general principles
outlined above, and the above example is exemplary only, and any
actuation voltage method can be used with the systems and methods
described herein.
[0042] FIG. 7A is a cross section of the embodiment of FIG. 2,
where a strip of metal material 14 is deposited on orthogonally
extending supports 18. In FIG. 7B, the moveable reflective layer 14
is attached to supports at the corners only, on tethers 32. In FIG.
7C, the moveable reflective layer 14 is suspended from a deformable
layer 34, which may comprise a flexible metal. The deformable layer
34 connects, directly or indirectly, to the substrate 20 around the
perimeter of the deformable layer 34. These connections are
referred to herein as support posts. The embodiment illustrated in
FIG. 7D has support post plugs 42 upon which the deformable layer
34 rests. The movable reflective layer 14 remains suspended over
the gap, as in FIGS. 7A-7C, but the deformable layer 34 does not
form the support posts by filling holes between the deformable
layer 34 and the optical stack 16. Rather, the support posts are
formed of a planarization material, which is used to form support
post plugs 42. The embodiment illustrated in FIG. 7E is based on
the embodiment shown in FIG. 7D, but may also be adapted to work
with any of the embodiments illustrated in FIGS. 7A-7C as well as
additional embodiments not shown. In the embodiment shown in FIG.
7E, an extra layer of metal or other conductive material has been
used to form a bus structure 44. This allows signal routing along
the back of the interferometric modulators, eliminating a number of
electrodes that may otherwise have had to be formed on the
substrate 20. In general, any of the embodiments illustrated in
FIGS. 7A-7E can include a black matrix layer integrated within one
or more support posts, as described in greater detail below.
[0043] FIG. 8 illustrates a cross-section of an interferometric
modulator display 800 including a plurality of interferometric
modulators 802 in accordance with one embodiment. As shown in FIG.
8, the interferometric modulator display 800 includes a substrate
804, a conductive layer--e.g., formed of a dielectric layer 806 and
an electrode layer 808. The interferometric modulator display 800
further includes a mechanical layer 810 and a plurality of support
posts 812 to support the mechanical layer 810. Unlike a
conventional interferometric modulator display that may include a
single black matrix layer formed underneath each support post, the
interferometric modulator display 800 includes black matrix layers
that are separated--i.e., a first black matrix layer 814 is formed
on the substrate 804, and a second black matrix layer integrated
into the support posts 812. Integration of a black matrix layer
into the support posts--rather than placement of a black matrix
layer underneath a support post--reduces a launching of the
mechanical layer and, therefore, a tighter control of an air gap
(e.g., air gap 816) within an interferometric modulator can be
attained. In one embodiment, the separate black matrix layers
include regions that overlap, as indicated by arrows 818. The
overlapping regions of the separate black matrix layers prevent any
reflection issues.
[0044] FIGS. 9A-9B respectively illustrate a cross-sectional view
of a first black matrix layer 814 and a support post 812 (including
a second black matrix layer) of the interferometric modulator
display 800 (FIG. 8) in accordance with one embodiment. As shown in
FIG. 9A, (in one embodiment) the first black matrix layer 814
includes an absorber layer 900, a dielectric layer 902, and a
reflective layer 904. The absorber layer 900 can be composed of
(e.g.) chromium (Cr) or molybdenum-chromium (MoCr), the dielectric
layer 902 can be composed of (e.g.) silicon dioxide (SiO2) or
Aluminum oxide (Al2O3) or SiNx, and the reflective layer 904 can be
composed of (e.g.) aluminum (Al) or nickel (Ni) or a highly
reflective material (e.g. Silver). In one embodiment, the absorber
layer 900 has a thickness (or height) of approximately 80 .ANG.,
the dielectric layer 902 has a thickness of approximately 800
.ANG., and the reflective layer 904 has a thickness of
approximately 300 .ANG. (300 .ANG. for aluminum and 500 .ANG. for
nickel, for example). As shown in FIG. 9B, in one embodiment, the
support post 812 comprises a first dielectric layer 806, an
absorber layer 906, and a second dielectric layer 908. The first
dielectric layer 806 can be composed of silicon dioxide (SiO2) or
silicon nitride (SiNx), and have a suitable thickness that is
sufficient to support the mechanical layer 810 (FIG. 8). The
absorber layer 906 can be composed of (e.g.) chromium (Cr) or
molybdenum-chromium (MoCr). The second dielectric layer 908 can be
composed of (e.g.) silicon dioxide (SiO2) or Aluminum oxide
(Al2O3). In one embodiment, the absorber layer 906 and the second
dielectric layer 908 (of the support post 812) respectively have a
thickness that is substantially the same as that of the absorber
layer 900 and the dielectric layer 902 within the first black
matrix 814 (FIG. 9A).
[0045] FIG. 10 illustrates a process 1000 of fabricating an
interferometric modulator display (e.g., interferometric modulator
display 800) in accordance with one embodiment. The process 1000
begins with providing a substrate (block 1002). Referring to the
example of FIG. 11A, a substrate 1102 is provided. The substrate
1102 can be transparent. Alternatively, the substrate 1102 can be
non-transparent. In one embodiment, the substrate 1102 comprises
glass. A first black matrix layer is deposited and patterned on the
substrate (block 1004). As shown in FIG. 11B, a first black matrix
layer 1104 is deposited over the substrate 1102. In one embodiment,
the first black matrix layer includes an absorber layer, a
dielectric layer, and a reflective layer, as discussed in greater
detail above. In one embodiment, the first black matrix layer has a
thickness of substantially 800 .ANG.-1000 .ANG.. A conductive layer
is formed (block 1006). As shown in FIG. 11C, a conductive
layer--including a dielectric layer 1106 and an electrode layer
1108--is formed over the substrate 1102 and the first black matrix
layer 1104. More generally, the conductive layer comprises one or
more layers and/or films. For example, in one embodiment the
conductive layer comprises a conductive layer (e.g., indium tin
oxide (ITO)) and a partially reflective layer (e.g., chromium). A
sacrificial layer is deposited and patterned (block 1008).
Referring to FIG. 11D, a sacrificial layer 1110 is deposited over
the conductive layer. In one embodiment, the sacrificial layer 1110
comprises molybdenum. In one embodiment, the height of the
sacrificial layer 1110 determines the amount of spacing between the
first conductive layer (or conductive plate) and a second
conductive plate (e.g., a mechanical layer discussed below). In one
embodiment, the height of the sacrificial layer 1110 is
substantially 1800 .ANG.-2100 .ANG..
[0046] A plurality of support posts are formed, in which each
support post includes a second black matrix layer (block 1010). As
shown by FIG. 11E, a support post 1112 is formed within the etched
portion of the sacrificial layer 1110 of the interferometric
modulator display. In one embodiment, the support post 1112
comprises an absorber layer, a dielectric layer, and a reflective
layer, as discussed above. In one embodiment, the support posts are
formed using photolithography and etch techniques to remove
unwanted portions of the material that comprise the support posts.
In one embodiment, the support posts 1112 are formed over portions
of the conductive layer that do not overlap with the first black
matrix layer 1104, as shown in FIG. 11E. A mechanical layer is
deposited (block 1012). Referring to the example of FIG. 11F, a
mechanical layer 1114 is formed over the sacrificial layer 1110 and
the support post 1112. In one embodiment, the mechanical layer 914
comprises a movable reflective layer as discussed above. In one
embodiment, the mechanical layer 1114 comprises aluminum/nickel,
and has a height substantially in the range of 1100 .ANG.-1300
.ANG.. The sacrificial layer is released (block 1014). Referring to
FIG. 11G, the sacrificial layer 1110 is released to form an air gap
1116 between the mechanical layer 1114 and the conductive layer.
The sacrificial layer 1110 can be released through one or more etch
holes formed through the mechanical layer 1114. The one or more
etch holes can be created after deposition of the mechanical layer
1114.
[0047] FIGS. 12A and 12B are system block diagrams illustrating an
embodiment of a display device 40. The display device 40 can be,
for example, a cellular or mobile telephone. However, the same
components of display device 40 or slight variations thereof are
also illustrative of various types of display devices such as
televisions and portable media players.
[0048] The display device 40 includes a housing 41, a display 30,
an antenna 43, a speaker 44, an input device 48, and a microphone
46. The housing 41 is generally formed from any of a variety of
manufacturing processes as are well known to those of skill in the
art, including injection molding, and vacuum forming. In addition,
the housing 41 may be made from any of a variety of materials,
including but not limited to plastic, metal, glass, rubber, and
ceramic, or a combination thereof. In one embodiment the housing 41
includes removable portions (not shown) that may be interchanged
with other removable portions of different color, or containing
different logos, pictures, or symbols.
[0049] The display 30 of exemplary display device 40 may be any of
a variety of displays, including a bi-stable display, as described
herein. In other embodiments, the display 30 includes a flat-panel
display, such as plasma, EL, OLED, STN LCD, or TFT LCD as described
above, or a non-flat-panel display, such as a CRT or other tube
device, as is well known to those of skill in the art. However, for
purposes of describing the present embodiment, the display 30
includes an interferometric modulator display, as described
herein.
[0050] The components of one embodiment of exemplary display device
40 are schematically illustrated in FIG. 12B. The illustrated
exemplary display device 40 includes a housing 41 and can include
additional components at least partially enclosed therein. For
example, in one embodiment, the exemplary display device 40
includes a network interface 27 that includes an antenna 43 which
is coupled to a transceiver 47. The transceiver 47 is connected to
a processor 21, which is connected to conditioning hardware 52. The
conditioning hardware 52 may be configured to condition a signal
(e.g. filter a signal). The conditioning hardware 52 is connected
to a speaker 45 and a microphone 46. The processor 21 is also
connected to an input device 48 and a driver controller 29. The
driver controller 29 is coupled to a frame buffer 28, and to an
array driver 22, which in turn is coupled to a display array 30. A
power supply 50 provides power to all components as required by the
particular exemplary display device 40 design.
[0051] The network interface 27 includes the antenna 43 and the
transceiver 47 so that the exemplary display device 40 can
communicate with one ore more devices over a network. In one
embodiment the network interface 27 may also have some processing
capabilities to relieve requirements of the processor 21. The
antenna 43 is any antenna known to those of skill in the art for
transmitting and receiving signals. In one embodiment, the antenna
transmits and receives RF signals according to the IEEE 802.11
standard, including IEEE 802.11(a), (b), or (g). In another
embodiment, the antenna transmits and receives RF signals according
to the BLUETOOTH standard. In the case of a cellular telephone, the
antenna is designed to receive CDMA, GSM, AMPS or other known
signals that are used to communicate within a wireless cell phone
network. The transceiver 47 pre-processes the signals received from
the antenna 43 so that they may be received by and further
manipulated by the processor 21. The transceiver 47 also processes
signals received from the processor 21 so that they may be
transmitted from the exemplary display device 40 via the antenna
43.
[0052] In an alternative embodiment, the transceiver 47 can be
replaced by a receiver. In yet another alternative embodiment,
network interface 27 can be replaced by an image source, which can
store or generate image data to be sent to the processor 21. For
example, the image source can be a digital video disc (DVD) or a
hard-disc drive that contains image data, or a software module that
generates image data.
[0053] Processor 21 generally controls the overall operation of the
exemplary display device 40. The processor 21 receives data, such
as compressed image data from the network interface 27 or an image
source, and processes the data into raw image data or into a format
that is readily processed into raw image data. The processor 21
then sends the processed data to the driver controller 29 or to
frame buffer 28 for storage. Raw data typically refers to the
information that identifies the image characteristics at each
location within an image. For example, such image characteristics
can include color, saturation, and gray-scale level.
[0054] In one embodiment, the processor 21 includes a
microcontroller, CPU, or logic unit to control operation of the
exemplary display device 40. Conditioning hardware 52 generally
includes amplifiers and filters for transmitting signals to the
speaker 45, and for receiving signals from the microphone 46.
Conditioning hardware 52 may be discrete components within the
exemplary display device 40, or may be incorporated within the
processor 21 or other components.
[0055] The driver controller 29 takes the raw image data generated
by the processor 21 either directly from the processor 21 or from
the frame buffer 28 and reformats the raw image data appropriately
for high speed transmission to the array driver 22. Specifically,
the driver controller 29 reformats the raw image data into a data
flow having a raster-like format, such that it has a time order
suitable for scanning across the display array 30. Then the driver
controller 29 sends the formatted information to the array driver
22. Although a driver controller 29, such as a LCD controller, is
often associated with the system processor 21 as a stand-alone
Integrated Circuit (IC), such controllers may be implemented in
many ways. They may be embedded in the processor 21 as hardware,
embedded in the processor 21 as software, or fully integrated in
hardware with the array driver 22.
[0056] Typically, the array driver 22 receives the formatted
information from the driver controller 29 and reformats the video
data into a parallel set of waveforms that are applied many times
per second to the hundreds and sometimes thousands of leads coming
from the display's x-y matrix of pixels.
[0057] In one embodiment, the driver controller 29, array driver
22, and display array 30 are appropriate for any of the types of
displays described herein. For example, in one embodiment, driver
controller 29 is a conventional display controller or a bi-stable
display controller (e.g., an interferometric modulator controller).
In another embodiment, array driver 22 is a conventional driver or
a bi-stable display driver (e.g., an interferometric modulator
display driver). In one embodiment, a driver controller 29 is
integrated with the array driver 22. Such an embodiment is common
in highly integrated systems such as cellular phones, watches, and
other small area displays. In yet another embodiment, display array
30 is a typical display array or a bi-stable display array (e.g., a
display including an array of interferometric modulators).
[0058] The input device 48 allows a user to control the operation
of the exemplary display device 40. In one embodiment, input device
48 includes a keypad, such as a QWERTY keyboard or a telephone
keypad, a button, a switch, a touch-sensitive screen, a pressure-
or heat-sensitive membrane. In one embodiment, the microphone 46 is
an input device for the exemplary display device 40. When the
microphone 46 is used to input data to the device, voice commands
may be provided by a user for controlling operations of the
exemplary display device 40.
[0059] Power supply 50 can include a variety of energy storage
devices as are well known in the art. For example, in one
embodiment, power supply 50 is a rechargeable battery, such as a
nickel-cadmium battery or a lithium ion battery. In another
embodiment, power supply 50 is a renewable energy source, a
capacitor, or a solar cell, including a plastic solar cell, and
solar-cell paint. In another embodiment, power supply 50 is
configured to receive power from a wall outlet.
[0060] In some embodiments control programmability resides, as
described above, in a driver controller which can be located in
several places in the electronic display system. In some cases
control programmability resides in the array driver 22. Those of
skill in the art will recognize that the above-described
optimization may be implemented in any number of hardware and/or
software components and in various configurations.
[0061] Various implementations of an interferometric modulator
display have been described. Nevertheless, one or ordinary skill in
the art will readily recognize that there that various
modifications may be made to the implementations, and any variation
would be within the spirit and scope of the present invention. For
example, the process steps described above in connection with FIG.
10 may be performed in a different order and still achieve
desirable results. Further, light absorbing layers other than black
matrix layers can be implemented--e.g., light absorbing material
composed of, for example, photo resist, polymer, or multiple layers
consisting of absorber/dielectric layer/reflector. Accordingly,
many modifications may be made by one of ordinary skill in the art
without departing from the scope of the following claims.
* * * * *