Mems devices with protective coatings

Abstract

A microelectromechanical devices with protective coatings on one or more surfaces of the micromechanical device is disclosed. The micromechanical device includes a substrate. The micromechanical device further includes a mirror positioned over the substrate. The mirror can be at least partially reflective to incident light. The micromechanical device further includes an optical layer positioned over the substrate and spaced from the mirror. The optical layer can be at least partially transmissive to incident light. The micromechanical device can further include a protective coating. The optical layer and the mirror define a cavity and the protective coating overlies surfaces of the microelectromechanical device exposed to the cavity.

1 . A microelectromechanical device comprising:
 a substrate;   a mirror positioned over the substrate, the mirror being at least partially reflective to incident light;   a partially transparent layer positioned over the substrate and spaced from the mirror, the partially transparent layer being at least partially transmissive to incident light; and   a protective coating comprising a protective material, wherein the partially transparent layer and the mirror define a cavity and the protective coating overlies a plurality of surfaces of the microelectromechanical device exposed to the cavity.   
   
   
       2 . The apparatus of  claim 1 , further comprising:
 a display;   a processor that is configured to communicate with the display, the processor being configured to process image data; and   a memory device that is configured to communicate with the processor.   
   
   
       3 . The apparatus of  claim 2 , comprising a driver circuit configured to send at least one signal to the display. 
   
   
       4 . The apparatus of  claim 3 , further comprising a controller configured to send at least a portion of the data image to said driver circuit. 
   
   
       5 . The apparatus of  claim 4 , further said image source module comprises at least one of a receiver, transceiver, and transmitter. 
   
   
       6 . The apparatus of  claim 1 , wherein the plurality of surfaces comprise a lower surface of a movable reflective layer and an upper surface of an optical stack of the interferometric modulator. 
   
   
       7 . The apparatus of  claim 1 , wherein the apparatus is an interferometric modulator. 
   
   
       8 . The apparatus of  claim 7 , wherein the protective coating is configured to modulate an optical property of an optically active surface inside the cavity. 
   
   
       9 . The apparatus of  claim 8 , wherein the optically active surface is the partially transparent layer of the interferometric modulator. 
   
   
       10 . The apparatus of  claim 8 , wherein the optically active surface is the mirror of the interferometric modulator. 
   
   
       11 . The apparatus of  claim 8 , wherein the optical property being modulated comprises an ability of the optically active surface to reflect, absorb, scatter, and/or transmit a particular wavelength of light. 
   
   
       12 . The apparatus of  claim 8 , wherein the protective material comprises a composition selected from the group consisting of Al 2 O 3 , Si 3 N 4 , SiO 2 , ZrO 2 , PbO 2 , tantalum pentoxide, diamond, and a diamond-like material. 
   
   
       13 . The apparatus of  claim 12 , wherein the protective material comprises the diamond-like material, the diamond-like material selected from the group of diamond-like carbon (DLC), amorphous carbon (α-C), cubic boron nitride (CBN), and combinations thereof. 
   
   
       14 . The apparatus of  claim 7 , wherein the protective coating is configured to reduce or prevent stiction. 
   
   
       15 . The apparatus of  claim 14 , wherein the protective material comprises a composition selected from the group consisting of a polymer, diamond, a diamond-like material, and polymethylmethacrylate (PMMA). 
   
   
       16 . The apparatus of  claim 15 , wherein the protective material comprises the polymer, the polymer being a hydrophobic polymer. 
   
   
       17 . The apparatus of  claim 15 , wherein the protective material comprises the diamond-like material, the diamond-like material selected from the group of diamond-like carbon (DLC), amorphous carbon (α-C), cubic boron nitride (CBN), and combinations thereof. 
   
   
       18 . The apparatus of  claim 15 , wherein a surface energy of the protective coating is lower than a surface energy of the at least one of the surfaces. 
   
   
       19 . The apparatus of  claim 7 , wherein the protective coating is configured to dissipate a charge build-up. 
   
   
       20 . The apparatus of  claim 19 , wherein the protective material comprises a composition selected from the group consisting of Si 3 N 4 , Al 2 O 3 , and SiO 2 . 
   
   
       21 . The apparatus of  claim 19 , wherein the protective coating comprises a metal film. 
   
   
       22 . The apparatus of  claim 21 , wherein the metal film comprises a composition selected from the group consisting of Cr, W, and Au. 
   
   
       23 . A microelectromechanical device comprising:
 a substrate;   an optical stack having one or more surfaces formed over the substrate;   a reflective layer having one or more surfaces formed over the optical stack,   wherein the surfaces of the optical stack and the reflective layer include one or more surfaces within an optical path and one or more surfaces outside the optical path;   a protective coating overlying at least one of the surfaces within the optical path; and   a protective coating overlying at least one of the surfaces outside the optical path.   
   
   
       24 . The apparatus of  claim 23 , further comprising a deformable layer having the one or more surfaces outside the optical path, wherein the deformable layer is formed over the reflective layer, and the reflective layer is a movable reflective layer. 
   
   
       25 . The apparatus of  claim 24 , wherein at least one of the protective coatings overlies a lower surface of the movable reflective layer. 
   
   
       26 . The apparatus of  claim 24 , wherein at least one of the protective coatings overlies an upper surface of the movable reflective layer. 
   
   
       27 . The apparatus of  claim 24 , further comprising one or more support posts having one or more surfaces, wherein at least one of the protective coatings overlies one of the surfaces of the one or more support posts. 
   
   
       28 . The apparatus of  claim 24 , wherein at least one of the protective coatings overlies a surface of the deformable layer. 
   
   
       29 . The apparatus of  claim 23 , wherein at least one of the protective coatings overlies a surface exposed to an optical cavity defined by the optical stack and the reflective layer. 
   
   
       30 . The apparatus of  claim 23 , wherein at least one of the protective coatings overlies a surface not exposed to an optical cavity defined by the optical stack and the reflective layer. 
   
   
       31 . The apparatus of  claim 23 , wherein at least one of the protective coatings has a non-uniform thickness across one or more underlying surfaces. 
   
   
       32 . The apparatus of  claim 31 , wherein the at least one of the protective coatings has a greater thickness on or near a surface of interest. 
   
   
       33 . The apparatus of  claim 23 , wherein at least one of the protective coatings has a non-uniform density across one or more underlying surfaces. 
   
   
       34 . The apparatus of  claim 33 , wherein the at least one of the protective coatings has a higher density on or near a surface of interest. 
   
   
       35 . The apparatus of  claim 23 , wherein at least one of the protective coatings has a non-uniform composition across one or more underlying surfaces. 
   
   
       36 . The apparatus of  claim 35 , wherein the protective coating overlying the at least one of the surfaces within the optical path is of a different composition from the protective coating overlying the at least one of the surfaces outside the optical path.