MEMS device having a layer movable at asymmetric rates

• US 20070194630A1
• Filed: 02/23/2006
• Published: 08/23/2007
• Est. Priority Date: 02/23/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Mignard, Marc, Kogut, Lior
• Granted Patent: US 7,550,810 B2
• Time in Patent Office: Days
• US Class Current: 310/10
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2201/054 Microvalves
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 3/0078 Constitution or structural means for improving mechanical properties not provided for in B81B3/007 - B81B3/0075
• 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: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

A microelectromechanical (MEMS) device includes a substrate and a movable layer mechanically coupled to the substrate. The movable layer moves from a first position to a second position at a first rate and from the second position to the first position at a second rate faster than the first rate. The MEMS device further includes an adjustable cavity defined between the substrate and the movable layer and containing a fluid. The MEMS device further includes a fluid conductive element through which the fluid flows at a first flowrate from inside the cavity to outside the cavity upon movement of the movable layer from the second position to the first position and through which the fluid flows at a second flowrate slower than the first flowrate from outside the cavity to inside the cavity upon movement of the movable layer from the first position to the second position.

Claims

1. A microelectromechanical (MEMS) device comprising:

a substrate;

a movable layer mechanically coupled to the substrate, the movable layer movable between a first position and a second position, wherein the movable layer moves from the first position to the second position at a first rate and wherein the movable layer moves from the second position to the first position at a second rate that is faster than the first rate;

an adjustable cavity defined between the substrate and the movable layer, the adjustable cavity containing a fluid; and

a fluid conductive element through which the fluid flows at a first flowrate from inside the adjustable cavity to outside the adjustable cavity upon movement of the movable layer from the second position to the first position and through which the fluid flows at a second flowrate from outside the adjustable cavity to inside the adjustable cavity upon movement of the movable layer from the first position to the second position, the second flowrate slower than the first flowrate.

2. The MEMS device of claim 1, wherein the second rate is about 100 times faster than the first rate.

3. The MEMS device of claim 1, wherein the second position is further from the substrate than is the first position.

4. The MEMS device of claim 1, wherein the MEMS device is substantially reflective to incident light when the movable layer is in the first position and wherein the MEMS device is substantially non-reflective to incident light when the movable layer is in the second position.

5. The MEMS device of claim 1, further comprising a partially reflective layer between the substrate and the movable layer.

6. The MEMS device of claim 1, wherein the fluid comprises one or more gases, one or more liquids, or a combination of one or more gases and liquids.

7. The MEMS device of claim 6, wherein the one or more gases comprises air.

8. The MEMS device of claim 6, wherein the one or more liquids comprises water.

9. The MEMS device of claim 1, wherein the fluid conductive element comprises at least one aperture through the movable layer.

10. The MEMS device of claim 9, wherein the at least one aperture comprises a first opening area on a surface of the movable layer facing towards the substrate and a second opening area on a surface of the movable layer facing away from the substrate, the second opening area smaller than the first opening area.

11. The MEMS device of claim 9, wherein the fluid conductive element further comprises at least one stopple that at least partially restricts fluid flow through the aperture.

12. The MEMS device of claim 11, wherein the at least one stopple comprises a flap at least partially covering the aperture.

13. The MEMS device of claim 11, wherein the at least one stopple comprises flexible material.

14. The MEMS device of claim 9, further comprising at least one plug on the substrate, wherein the plug restricts fluid flow through the aperture when the movable layer is in the first position, wherein the first position is closer to the substrate than is the second position.

15. The MEMS device of claim 14, wherein the plug and the substrate comprise the same material.

16. The MEMS device of claim 14, wherein the plug is coupled to the aperture when the movable layer is in the first position.

17. The MEMS device of claim 1, further comprising a support structure between the movable layer and the substrate.

18. The MEMS device of claim 17, wherein the support structure includes at least one wall surrounding the adjustable cavity, the at least one wall inhibiting fluid flow between inside the adjustable cavity and outside the adjustable cavity.

19. The MEMS device of claim 17, wherein the fluid conductive element comprises at least one aperture through the support structure.

20. The MEMS device of claim 19, wherein the at least one aperture comprises a first opening area on a surface of the support structure layer facing towards the adjustable cavity and a second opening area on a surface of the support structure facing away from the adjustable cavity, the second opening area smaller than the first opening area.

21. The MEMS device of claim 19, wherein the fluid conductive element comprises at least one stopple that at least partially restricts fluid flow through the aperture.

22. The MEMS device of claim 21, wherein the at least one stopple comprises a flap at least partially covering the aperture.

23. The MEMS device of claim 21, wherein the at least one stopple comprises flexible material.

24. The MEMS device of claim 17, wherein the fluid conductive element comprises at least one aperture through the movable layer and at least one corresponding plug on the support structure, wherein the plug restricts fluid flow through the aperture when the movable layer is in the first position, wherein the first position is closer to the substrate than is the second position.

25. The MEMS device of claim 24, wherein the plug and the support structure comprise the same material.

26. The MEMS device of claim 17, wherein the fluid conductive element comprises at least one aperture through the support structure and at least one corresponding plug on the movable layer, wherein the plug restricts fluid flow through the aperture when the movable layer is in the first position, wherein the first position is closer to the substrate than is the second position.

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

a display;

a processor in electrical communication with the display, the processor configured to process image data; and

a memory device in electrical communication with the processor.

28. The MEMS device of claim 27, further comprising a driver circuit configured to send at least one signal to the display.

29. The MEMS device of claim 28, wherein the driver circuit is compatible with a super twisted nematic (STN) display.

30. The MEMS device of claim 28, wherein the driver circuit is configured to refresh the display at a frequency greater than about once per 30 milliseconds.

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

providing a substrate;

forming a sacrificial layer on the substrate;

forming a movable layer on the sacrificial layer;

removing the sacrificial layer, wherein the movable layer is movable between a first position and a second position, wherein the movable layer moves from the first position to the second position at a first rate and wherein the movable layer moves from the second position to the first position at a second rate that is faster than the first rate; and

forming a fluid conductive element through which fluid flows at a first flowrate from a region between the substrate and the movable layer upon movement of the movable layer towards the substrate and through which fluid flows at a second flowrate into the region upon movement of the movable layer away from the substrate, the second flowrate slower than the first flowrate.

32. The method of claim 31, wherein the second position is further from the substrate than is the first position.

33. The method of claim 31, wherein forming the fluid conductive element comprises forming an aperture through the movable layer.

34. The method of claim 33, wherein forming the aperture comprises forming a first opening area on a surface of the movable layer facing towards the substrate and forming a second opening area on a surface of the movable layer facing away from the substrate, the second opening area being smaller than the first opening area.

35. The method of claim 33, wherein forming the fluid conductive element further comprises forming at least one stopple which at least partially restricts fluid flow through the aperture.

36. The method of claim 35, wherein forming the at least one stopple comprises forming at least one flap, the at least one flap at least partially covering the aperture.

37. The method of claim 33, further comprising forming at least one plug on the substrate which at least partially restricts fluid flow through the aperture when the movable layer is in the first position, wherein the first position is closer to the substrate than is the second position.

38. The method of claim 33, wherein forming the aperture comprises etching the movable layer.

39. The method of claim 33, wherein removing the sacrificial layer comprises introducing etchant to the sacrificial layer through the aperture in the movable layer.

40. The method of claim 31, further comprising forming a support structure between the substrate and the movable layer.

41. The method of claim 40, wherein forming the fluid conductive element comprises forming an aperture through the support structure.

42. The method of claim 41, wherein forming the aperture comprises forming a first opening area on a surface of the support structure facing towards the region and forming a second opening area on a surface of the support structure facing away from the region, the second opening area smaller than the first opening area.

43. The method of claim 41, wherein forming the fluid conductive element further comprises forming at least one stopple which at least partially restricts fluid flow through the aperture.

44. The method of claim 43, wherein forming the at least one stopple comprises forming at least one flap, the at least one flap at least partially covering the aperture.

45. The method of claim 41, wherein forming the aperture comprises etching the support structure.

46. The method of claim 41, wherein removing the sacrificial layer comprises introducing etchant to the sacrificial layer through the aperture in the support structure.

47. A microelectromechanical (MEMS) device fabricated by the method of claim 31.

48. A microelectromechanical (MEMS) device comprising:

means for supporting a MEMS device;

means for reflecting light;

means for moving the reflecting means between a first position and a second position, wherein the reflecting means moves from the first position to the second position at a first rate and wherein the reflecting means moves from the second position to the first position at a second rate faster than the first rate; and

means for conducting fluid from inside an adjustable cavity between the supporting means and the moving means to outside the adjustable cavity upon movement of the moving means from the second position to the first position at a first flowrate and wherein the fluid can flow through the fluid conducting means from outside the adjustable cavity to inside the adjustable cavity upon movement of the moving means from the first position to the second position at a second flowrate slower than the first flowrate.

49. The MEMS device of claim 48, wherein the second position is further from the supporting means than is the first position.

50. The MEMS device of claim 48, wherein the supporting means comprises a substrate.

51. The MEMS device of claim 48, wherein the reflecting means comprises a reflective layer.

52. The MEMS device of claim 48, wherein the fluid conducting means comprises an element having at least one aperture through which fluid can flow between inside the adjustable cavity and outside the adjustable cavity.

53. A microelectromechanical (MEMS) device comprising:

a substrate;

a movable layer mechanically coupled to the substrate, the movable layer movable between a first position and a second position, wherein the movable layer moves from the first position to the second position at a first rate and wherein the movable layer moves from the second position to the first position at a second rate that is faster than the first rate; and

an adhesive layer on at least a portion of the substrate or the movable layer, the layer increasing adhesion between the movable layer and the substrate when the movable layer is in the position closer to the substrate.

54. A microelectromechanical (MEMS) device comprising:

a substrate; and

a movable layer mechanically coupled to the substrate, the movable layer movable between a first position and a second position in response to a voltage applied between a first electrode and a second electrode, the first electrode configured to communicate with a diode, wherein the diode is configured to allow a charge to flow from the first electrode to a capacitor between the first electrode and the second electrode and a leakage resistor in parallel with the capacitor and wherein the diode is configured to block the charge from flowing from the capacitor to the first electrode, wherein the movable layer moves from the first position to the second position at a first rate and wherein the movable layer moves from the second position to the first position at a second rate that is faster than the first rate.