Analog interferometric modulator device with electrostatic actuation and release

• US 20070279729A1
• Filed: 06/01/2006
• Published: 12/06/2007
• Est. Priority Date: 06/01/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kothari, Manish, Kogut, Lior, Sampsell, Jeffrey B.
• Granted Patent: US 7,649,671 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• 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

Abstract

A microelectromechanical system (MEMS) device includes a first electrode, a second electrode electrically insulated from the first electrode, and a third electrode electrically insulated from the first electrode and the second electrode. The MEMS device also includes a support structure which separates the first electrode from the second electrode and a reflective element located and movable between a first position and a second position. The reflective element is in contact with a portion of the device when in the first position and is not in contact with the portion of the device when in the second position. An adhesive force is generated between the reflective element and the portion when the reflective element is in the first position. Voltages applied to the first electrode, the second electrode, and the third electrode at least partially reduce or counteract the adhesive force.

Claims

1. A microelectromechanical system (MEMS) device comprising:

a first electrode;

a second electrode electrically insulated from the first electrode;

a third electrode electrically insulated from the first electrode and the second electrode;

a support structure which separates the first electrode from the second electrode;

a reflective element located and movable between a first position and a second position, the reflective element in contact with a portion of the device when in the first position and not in contact with the portion of the device when in the second position;

wherein an adhesive force is generated between the reflective element and the portion when the reflective element is in the first position, and wherein voltages applied to the first electrode, the second electrode, and the third electrode at least partially reduce or counteract the adhesive force.

2. The MEMS device of claim 1, wherein the third electrode comprises a conductive portion of the reflective element.

3. The MEMS device of claim 1, wherein the third electrode comprises a conductive portion of the support structure.

4. The MEMS device of claim 1, wherein at least a portion of the third electrode is higher than the reflective element when the reflective element is in the first position.

5. The MEMS device of claim 4, wherein at least a portion of the third electrode is directly above at least a portion of the reflective element when the reflective element is in the first position.

6. The MEMS device of claim 1, wherein the third electrode is supported by the support structure.

7. The MEMS device of claim 1, wherein the support structure comprises one or more posts and the third electrode comprises a conductive portion of at least one of the posts.

8. The MEMS device of claim 7, wherein the support structure comprises a plurality of posts, each post having a conductive portion, and the third electrode comprises the conductive portions.

9. The MEMS device of claim 8, wherein the plurality of posts are positioned substantially symmetrically relative to the reflective element.

10. The MEMS device of claim 1, wherein the reflective element comprises a first layer and a second layer over the first layer.

11. The MEMS device of claim 10, wherein the first layer is more flexible than the second layer.

12. The MEMS device of claim 10, wherein the first layer is thinner than the second layer.

13. The MEMS device of claim 10, wherein the second layer covers a central portion of the first layer and does not cover one or more edge portions of the first layer.

14. The MEMS device of claim 10, wherein at least one of the first layer and the second layer is conductive.

15. The MEMS device of claim 1, wherein the reflective element comprises end portions that are thinner than a center portion.

16. The MEMS device of claim 15, wherein at least a portion of the reflective element is conductive.

17. The MEMS device of claim 1, wherein the reflective element comprises one or more extensions above an upper surface of the reflective element and extending toward the second electrode.

18. The MEMS device of claim 17, wherein the one or more extensions are on or near one or more edge portions of the reflective element and have a height above the upper surface of the reflective element that is about ⅓

to about ½

of a thickness of a central portion of the reflective element.

19. The MEMS device of claim 1, wherein the second electrode comprises one or more portions extending toward the reflective element.

20. The MEMS device of claim 1, wherein the third electrode comprises one or more portions extending toward the reflective element.

21. The MEMS device of claim 1, further comprising:

a display;

a processor that is configured to communicate with said display, said processor being configured to process image data; and

a memory device that is configured to communicate with said processor.

22. The MEMS device of claim 21, further comprising a driver circuit configured to send at least one signal to said display.

23. The MEMS device of claim 22, further comprising a controller configured to send at least a portion of said image data to said driver circuit.

24. The MEMS device of claim 21, further comprising an image source module configured to send said image data to said processor.

25. The MEMS device of claim 24 wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

26. The MEMS device of claim 21, further comprising an input device configured to receive input data and to communicate said input data to said processor.

27. A microelectromechanical system (MEMS) device comprising:

a first means for conducting electricity;

a second means for conducting electricity, the second conducting means electrically insulated from the first conducting means;

a third means for conducting electricity, the third conducting means electrically insulated from the first conducting means and the second conducting means;

means for separating the first conducting means from the second conducting means;

means for reflecting light, the reflecting means located and movable between a first position and a second position, the reflecting means in contact with a portion of the device when in the first position and not in contact with the portion of the device when in the second position;

wherein an adhesive force is generated between the reflecting means and the portion when the reflecting means is in the first position, and wherein voltages applied to the first conducting means, the second conducting means, and the third conducting means at least partially reduce or counteract the adhesive force while the reflecting means is in the first position.

28. The MEMS device of claim 27, wherein the first conducting means comprises an electrode.

29. The MEMS device of claim 27, wherein the second conducting means comprises an electrode.

30. The MEMS device of claim 27, wherein the third conducting means comprises an electrode.

31. The MEMS device of claim 30, wherein at least a portion of the electrode is higher than the reflecting means when the reflecting means is in the first position.

32. The MEMS device of claim 31, wherein at least a portion of the electrode is directly above at least a portion of the reflecting means when the reflecting means is in the first position.

33. The MEMS device of claim 30, wherein the electrode is supported by the separating means.

34. The MEMS device of claim 27, wherein the separating means comprises a mechanical layer and one or more support posts.

35. The MEMS device of claim 27, wherein the reflecting means comprises a reflective element disposed between the first conducting means and the second conducting means.

36. A method of operating a microelectromechanical system (MEMS) device, the method comprising:

providing a MEMS device comprising;

a first electrode;

a second electrode electrically insulated from the first electrode;

a third electrode electrically insulated from the first electrode and the second electrode;

a support structure which separates the first electrode from the second electrode; and

a reflective element located and movable between a first position and a second position, the reflective element in contact with a portion of the device when in the first position and not in contact with the portion of the device when in the second position, wherein an adhesive force is generated between the reflective element and the portion when the reflective element is in the first position; and

applying voltages to the first electrode, the second electrode, and the third electrode to at least partially reduce or counteract the adhesive force.

37. The method of claim 36, wherein the voltages have magnitudes between about 10 Volts and about 50 Volts.

38. The method of claim 36, wherein the voltages applied to the first, second, and third electrodes causes a portion of the reflective element to undergo an elastic deformation.

39. The method of claim 36, wherein at least one of the voltages applied to the first, second, and third electrodes comprises a time-varying voltage having a frequency.

40. The method of claim 39, wherein the frequency is in a range from about 100 Hz to about 50 MHz.

41. The method of claim 39, wherein the frequency is substantially equal to a mechanical resonant frequency of the reflective element.

42. The method of claim 39, wherein the time-varying voltage causes a portion of the reflective element to undergo an elastic oscillation.

43. The method of claim 42, wherein the frequency is selected to provide an increased amplitude of the elastic oscillation.

44. The method of claim 36, wherein the voltages applied to the first, second, and third electrodes decrease an area of the reflective element in contact with the portion of the device when in the first position by elastically deforming the reflective element.

45. The method of claim 36, wherein at least one of the voltages applied to the first, second, and third electrodes comprises a time-varying voltage which applies an impulse to the reflective element.

46. A method of manufacturing a microelectromechanical system (MEMS) device comprising:

forming a first reflective layer on a substrate;

forming a sacrificial layer over the first reflective layer;

removing a portion of the sacrificial layer to form an opening;

filling the opening with a dielectric material to form a post;

forming a second reflective layer over the sacrificial layer;

removing a portion of the second reflective layer and a portion of the post to form a hole;

filling the hole with a conductive material to form an electrode; and

removing the sacrificial layer.

47. The method of claim 46, wherein the second reflective layer is located and movable between a first position and a second position, the second reflective layer in contact with a portion of the device when in the first position and not in contact with the portion of the device when in the second position, wherein at least a portion of the electrode is higher than the second reflective layer when the second reflective layer is in the first position.

48. The method of claim 47, wherein at least a portion of the electrode is directly above at least a portion of the second reflective layer when the second reflective layer is in the first position.

49. The method of claim 46, wherein the electrode is at least partially supported by the post.

50. A MEMS device manufactured with the method of claim 46.