MEMS DEVICES WITH PROTECTIVE COATINGS

• US 20090059345A1
• Filed: 11/03/2008
• Published: 03/05/2009
• Est. Priority Date: 03/02/2006
• Status: Abandoned Application

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kogut, Lior, Tung, Ming-Hau
• Application Number:
  US12/263,752
• Publication Number:
  US 20090059345A1
• Time in Patent Office: Days
• US Class Current: 359/290
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: B81C 1/00801 Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer B81C1/00595, B81C1/00468 take precedence
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: B81C 2201/017 Methods for controlling internal stress of deposited layers not provided for in B81C2201/0164 - B81C2201/0169
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: B81C 2201/115 Roughening a surface
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer
• CPC Class Codes: Y10T 428/31678 Of metal
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer

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.

Claims

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 Al₂O₃, Si₃N₄, SiO₂, ZrO₂, PbO₂, 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 Si₃N₄, Al₂O₃, and SiO₂.

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.