MEMS CAVITY-COATING LAYERS AND METHODS

• US 20080231931A1
• Filed: 03/21/2007
• Published: 09/25/2008
• Est. Priority Date: 03/21/2007
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm, Inc.
• Inventors: Gousev, Evgeni, Heald, David, Webster, James Randolph, Londergan, Ana R., Natarajan, Bangalore R.
• Granted Patent: US 7,733,552 B2
• Time in Patent Office: Days
• US Class Current: 359/237
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• 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

Devices, methods, and systems comprising a MEMS device, for example, an interferometric modulator, that comprises a cavity in which a layer coats multiple surfaces. The layer is conformal or non-conformal. In some embodiments, the layer is formed by atomic layer deposition (ALD). Preferably, the layer comprises a dielectric material. In some embodiments, the MEMS device also exhibits improved characteristics, such as improved electrical insulation between moving electrodes, reduced stiction, and/or improved mechanical properties.

Claims

1. A method for forming an interferometric modulator, the method comprising:

forming a cavity in an interferometric modulator, wherein

the cavity is defined by a first layer and a second layer, and

the second layer is movable relative to the first layer; and

forming at least part of the optical dielectric layer within the cavity after forming the cavity.

2. The method of claim 1, wherein forming at least part of the optical dielectric layer comprises forming at least part of an optical oxide layer by atomic layer deposition.

3. The method of claim 2, wherein forming at least part of the optical dielectric layer comprises forming at least one of Al₂O₃ and SiO₂.

4. The method of claim 2, wherein forming at least part of the optical dielectric layer comprises forming a plurality of sub-layers.

5. The method of claim 1, wherein forming at least part of the optical dielectric layer comprises forming at least part of the optical oxide layer at a temperature of less than about 350°

C.

6. The method of claim 1, wherein forming at least part of the optical dielectric layer by atomic layer deposition comprises forming a first conformal layer of an optical oxide material within the cavity.

7. The method of claim 6, wherein a thickness of the first conformal layer formed over a portion of the first layer defining the cavity is substantially equal to a thickness of the first conformal layer formed over a portion of the second layer defining the cavity.

8. The method of claim 7, wherein a thickness of the first conformal layer formed over a portion of the first layer defining the cavity is from about 50 Å

to about 400 Å

.

9. The method of claim 1, wherein forming at least part of the optical dielectric layer by atomic layer deposition comprises forming a non-conformal layer of an optical oxide material over at least a portion of the first layer.

10. The method of claim 1, further comprising forming a layer of an optical dielectric material on a surface of the second layer after forming the cavity, wherein the surface of the second layer is outside of the cavity.

11. The method of claim 1, wherein the first layer defining the cavity comprises a dielectric material.

12. The method of claim 11, wherein forming at least part of dielectric layer by atomic layer deposition comprises sealing at least one pinhole in the dielectric material.

13. The method of claim 11, wherein a total thicknesses of an optical dielectric system, which includes two layers of the at least part of dielectric layer and the dielectric material, is less than about 100 nm.

14. The method of claim 1, wherein forming at least part of dielectric layer by atomic layer deposition comprises forming at least part of an optical oxide layer over a manufacturing residue disposed on the first layer.

15. The method of claim 1, further comprising packaging the interferometric modulator before forming at least part of the optical dielectric layer by a method comprising:

forming a seal circumscribing the interferometric modulator, wherein the seal comprises at least one opening; and

securing a backplate to the seal, thereby packaging the interferometric modulator.

16. The method of claim 15, further comprising filling the at least one opening in the seal after forming at least part of an optical dielectric layer.

17. An interferometric modulator formed by the method of claim 1.

18. An interferometric modulator comprising:

a first layer comprising a partial reflector;

a reflective layer movable relative to the first layer;

a cavity defined by the first layer and the reflective layer; and

a conformal dielectric layer formed within the cavity over the first layer and the reflective layer.

19. The interferometric modulator of claim 18, further comprising a deformable layer coupled to the reflective layer.

20. The interferometric modulator of claim 18, wherein the conformal dielectric layer comprises at least one of SiO₂ and Al₂O₃.

21. The interferometric modulator of claim 18, wherein thickness of the conformal dielectric layer is at least about 10 Å

.

22. The interferometric modulator of claim 21, wherein thickness of the conformal dielectric layer is from about 50 Å

to about 400 Å

.

23. The interferometric modulator of claim 18, further comprising a primary dielectric layer formed over the first layer.

24. A display comprising an array of the interferometric modulator of claim 18, further comprising:

a seal circumscribing the interferometric modulator; and

a backplate secured to the seal.

25. An apparatus comprising:

a display comprising the microelectromechanical systems device of claim 24;

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.

26. The apparatus of claim 25, further comprising a driver circuit configured to send at least one signal to the display.

27. The apparatus of claim 26, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

28. The apparatus of claim 25, further comprising an image source module configured to send said image data to said processor.

29. The apparatus of claim 28, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

30. The apparatus of claim 25, further comprising an input device configured to receive input data and to communicate said input data to said processor.

31. An interferometric modulator comprising:

a means for partially reflecting light;

a movable means for actuating the interferometric modulator and for reflecting light; and

a dielectric means for covering the means for partially reflecting light and the movable means.

32. A microelectromechanical systems device comprising:

a substrate comprising a first face;

a deformable layer comprising a first face and a second face;

a variably-sized cavity comprising opposite faces defined by the first face of the substrate and the first face of the deformable layer;

a plurality of openings in the deformable layer;

a plurality of locations on the first face of the substrate opposite from the openings in the deformable layer; and

a dielectric layer in the cavity formed over the first face of the substrate and the first face of the deformable layer, and at least a portion of the second face of the deformable layer.

33. The microelectromechanical systems device of claim 32, wherein the dielectric layer is thicker over the plurality of locations on the first face of the substrate opposite from the openings in the deformable layer than over another location on the first face of the substrate.

34. The microelectromechanical systems device of claim 32, wherein the dielectric layer is substantially conformal over all surfaces within the cavity.

35. The microelectromechanical systems device of claim 32, further comprising a movable conductor disposed in the cavity and secured to the deformable layer, wherein

the movable conductor comprises a surface proximal to the substrate, and

a portion of the dielectric layer is formed over the surface of the movable conductor proximal to the substrate.

36. A method for manufacturing a microelectromechanical systems device comprising:

forming a sacrificial layer over a first electrode;

forming a deformable layer over the sacrificial layer;

forming a plurality of openings in the deformable layer;

removing the sacrificial layer through at least some of the plurality of openings in the deformable layer, thereby forming a cavity between the first electrode and the deformable layer; and

depositing a layer in the cavity by atomic layer deposition after removing the sacrificial layer.

37. The method of claim 36, wherein depositing a layer in the cavity by atomic layer deposition comprises depositing a layer comprising at least one of Al₂O₃ and SiO₂.

38. The method of claim 36, wherein depositing a layer in the cavity by atomic layer deposition comprises depositing a conformal layer.

39. The method of claim 36, wherein depositing a layer in the cavity by atomic layer deposition comprises depositing a non-conformal layer.

40. A microelectromechanical systems device manufactured by the method of claim 36.

41. A method for manufacturing an interferometric modulator comprising:

forming a sacrificial layer over a first layer comprising a partial reflector;

forming a movable reflective layer over the sacrificial layer;

etching away the sacrificial layer, thereby forming an optical interference cavity comprising opposite sides defined by the first layer and the movable mirror; and

depositing a layer in the cavity by atomic layer deposition.

42. The method of claim 41, wherein etching away the sacrificial layer comprises contacting the sacrificial layer with XeF₂.

43. The method of claim 41, wherein forming a sacrificial layer comprises forming a layer comprising at least one of molybdenum, germanium, amorphous silicon.

44. The method of claim 41, wherein forming a sacrificial layer comprises forming a layer comprising a plurality of sublayers.

45. The method of claim 41, further comprising:

forming a seal comprising at least one opening on the first layer circumscribing the movable reflective layer; and

securing a backplate to the seal,

wherein the forming a seal and securing a backplate are performed before depositing a layer in the cavity.

46. An interferometric modulator manufactured by the method of claim 41.

47. A method for reducing stiction in a microelectromechanical systems device comprising:

defining a cavity in a microelectromechanical systems device between a first layer and a second layer, wherein the second layer is movable relative to the first layer; and

forming by atomic layer deposition a stiction-reducing layer within the cavity after defining the cavity.

48. The method of claim 47, wherein forming by atomic layer deposition a stiction-reducing layer comprises forming by atomic layer deposition a stiction-reducing layer comprising at least one of Al₂O₃ and SiO₂.

49. The method of claim 47, wherein forming by atomic layer deposition a stiction-reducing layer comprises forming by atomic layer deposition a conformal layer.

50. A microelectromechanical systems device formed by the method of claim 47.

51. A method for forming a microelectromechanical systems device comprising:

defining a cavity for the microelectromechanical systems device between a first layer and a second layer, wherein the second layer is movable relative to the first layer; and

forming a layer by atomic layer deposition within the cavity after defining the cavity.

52. The method of claim 51, wherein the microelectromechanical systems device is an element of an array of microelectromechanical systems devices.

53. The method of claim 51, further comprising forming a plurality of openings in the second layer.

54. A microelectromechanical systems device manufactured by the method of claim 51.