Patent Publication Number: US-2011075246-A1

Title: Method and apparatus for providing a light absorbing mask in an interferometric modulator display

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     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 
     1. Field of the Invention 
     The present invention relates generally to display devices, and more particularly to interferometric modulator display devices. 
     2. Description of the Related Art 
     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. 
     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 
     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. 
     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. 
     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. 
     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 
         FIG. 1  illustrates a cross-section of a conventional interferometric modulator display including a black matrix layer. 
         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. 
         FIG. 3  is a system block diagram illustrating one embodiment of an electronic device incorporating a 3×3 interferometric modulator display. 
         FIG. 4  is a diagram of movable mirror position versus applied voltage for one exemplary embodiment of an interferometric modulator of  FIG. 1 . 
         FIG. 5  is an illustration of a set of row and column voltages that may be used to drive an interferometric modulator display. 
         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 3×3 interferometric modulator display of  FIG. 2 . 
         FIG. 7A  is a cross-section of an interferometric modulator of  FIG. 2 . 
         FIGS. 7B-7E  illustrate alternative embodiments of an interferometric modulator. 
         FIG. 8  illustrates a cross-sectional view of an interferometric modulator display including light absorbing areas in accordance with one embodiment. 
         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. 
         FIG. 9B  illustrates a cross-section of a support post within the interferometric modulator display of  FIG. 8  in accordance with one embodiment. 
         FIG. 10  illustrates a flow diagram of a process for manufacturing an interferometric modulator display according to one embodiment. 
         FIGS. 11A-11G  illustrate the process of manufacturing an interferometric modulator display according to the process of  FIG. 10 . 
         FIGS. 12A and 12B  are system block diagrams illustrating an embodiment of a visual display device comprising a plurality of interferometric modulators. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     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. 
     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. 
     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. 
       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. 
     The depicted portion of the pixel array in  FIG. 2  includes two adjacent interferometric modulators  12   a  and  12   b.  In the interferometric modulator  12   a  on the left, a movable reflective layer  14   a  is illustrated in a relaxed position at a predetermined distance from an optical stack  16   a,  which includes a partially reflective layer. In the interferometric modulator  12   b  on the right, the movable reflective layer  14   b  is illustrated in an actuated position adjacent to the optical stack  16   b.    
     The optical stacks  16   a  and  16   b  (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. 
     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  14   a,    14   b  may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of  16   a,    16   b ) 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  14   a,    14   b  are separated from the optical stacks  16   a,    16   b  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. 
     With no applied voltage, the gap  19  remains between the movable reflective layer  14   a  and optical stack  16   a,  with the movable reflective layer  14   a  in a mechanically relaxed state, as illustrated by the pixel  12   a  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  12   b  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. 
       FIGS. 3 through 6  illustrate one exemplary process and system for using an array of interferometric modulators in a display application. 
       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®, Pentium II®, Pentium III®, Pentium IV®, Pentium® Pro, an 8051, a MIPS®, a Power PC®, an ALPHA®, 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. 
     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.” 
     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. 
     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. 
     FIGS.  5  and  6 A- 6 B illustrate one possible actuation protocol for creating a display frame on the 3×3 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 bias , and the appropriate row to +ΔV, which may correspond to −5 volts and +5 volts, respectively. Relaxing the pixel is accomplished by setting the appropriate column to +V bias , and the appropriate row to the same +ΔV, 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 bias , or −V 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 bias , and the appropriate row to −ΔV. In this embodiment, releasing the pixel is accomplished by setting the appropriate column to −V bias , and the appropriate row to the same −ΔV, producing a zero volt potential difference across the pixel. 
       FIG. 6B  is a timing diagram showing a series of row and column signals applied to the 3×3 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. 
     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. 
       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. 
       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. 
       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 Å, the dielectric layer  902  has a thickness of approximately 800 Å, and the reflective layer  904  has a thickness of approximately 300 Å (300 Å for aluminum and 500 Å 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 ). 
       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 Å-1000 Å. 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 Å-2100 Å. 
     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 Å-1300 Å. 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 . 
       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. 
     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. 
     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. 
     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. 
     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 . 
     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. 
     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. 
     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. 
     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 . 
     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&#39;s x-y matrix of pixels. 
     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). 
     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 . 
     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. 
     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. 
     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.