Microelectromechanical device and method utilizing nanoparticles

• US 20070247401A1
• Filed: 04/19/2006
• Published: 10/25/2007
• Est. Priority Date: 04/19/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kogut, Lior, Sasagawa, Teruo
• Granted Patent: US 7,711,239 B2
• Time in Patent Office: Days
• US Class Current: 345/84
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured 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

Abstract

A microelectromechanical device (MEMS) utilizing nanoparticles for reducing stiction is disclosed. In one embodiment, a microelectromechanical device is an interferometric modulator that includes a transparent electrode assembly having a first surface; and a movable reflective electrode assembly with a second surface facing the first surface. The movable reflective electrode assembly is movable between a relaxed and actuated (collapsed) position. Particles are deposited over the transparent electrode assembly or over a sacrificial layer separating the two electrodes. The particles lead to dimples in the reflective surface of the moving electrode. The particles can be removed with the sacrificial layer or remain in final devices.

Claims

1. An interferometric modulator, comprising:

a transparent electrode assembly having a first surface; and

a reflective electrode assembly, the reflective electrode assembly having a second surface facing the first surface, the reflective electrode assembly movable between a first position and a second position, the first position being a first distance from the transparent electrode assembly, the second position being a second distance from the transparent electrode assembly, the second distance being greater than the first distance,

wherein the second surface has a plurality of dimples, each of the dimples having a diameter between about 10 Å and

about 500 Å

.

2. The interferometric modulator of claim 1, wherein the plurality of dimples covers between about 5% and about 75% of the second surface.

3. The interferometric modulator of claim 1, further comprising a plurality of particles, each of the particles being positioned in one of the dimples.

4. The interferometric modulator of claim 3, wherein the reflective electrode assembly comprises a first material, wherein the plurality of particles comprise a second material, and wherein the second material is harder than the first material.

5. The interferometric modulator of claim 4, wherein the first material is a reflector selected from the group consisting of Al, Au, Ag, and alloys of the foregoing.

6. The interferometric modulator of claim 4, wherein the first material comprises Al and the second material comprises Al₂O₃.

7. The interferometric modulator of claim 3, wherein the plurality of particles are formed of at least one selected from the group consisting of cadmium, indium, magnesium, cerium, tin, zinc, cesium oxide, calcium carbonate, gallium, bismuth oxide, barium fluoride, zirconium oxide, zinc oxide, barium sulfate, barium titanate, calcium chloride, or calcium oxide.

8. The interferometric modulator of claim 1, wherein the transparent electrode assembly comprises a plurality of particles on the first surface.

9. The interferometric modulator of claim 8, wherein the plurality of particles are formed of a dielectric material, and wherein the plurality of particles are directly on a conductive layer.

10. The interferometric modulator of claim 8, wherein each of the plurality of particles has a diameter between about 10 Å

and about 500 Å

.

11. The interferometric modulator of claim 8, wherein the plurality of particles are not all aligned with corresponding ones of the dimples when the reflective electrode assembly is in the first position.

12. The interferometric modulator of claim 1, wherein the transparent electrode assembly comprises a dielectric layer defining the first surface.

13. The interferometric modulator of claim 1, wherein the reflective electrode assembly comprises a reflective electrode and a deformable layer, wherein the reflective electrode is attached to the deformable layer.

14. The interferometric modulator of claim 1, wherein the reflective electrode assembly comprises a reflective electrode and a deformable layer, and wherein the reflective electrode is suspended from the deformable layer.

15. The interferometric modulator of claim 1, further comprising a sacrificial layer between the transparent electrode assembly and the reflective electrode assembly.

16. The interferometric modulator of claim 15, further comprising particles on the sacrificial layer.

17. A display system, comprising:

the interferometric modulator of claim 1;

a display;

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

a memory device in electrical communication with the processor.

18. The display system of claim 17, further comprising:

a first controller configured to send at least one signal to the display; and

a second controller configured to send at least a portion of the image data to the first controller.

19. The display system of claim 17, further comprising:

an image source module configured to send the image data to the processor.

20. The display system of claim 19, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

21. The display system of claim 17, further comprising:

an input device configured to receive input data and to communicate the input data to the processor.

22. An electronic device, comprising the display system of claim 17.

23. An interferometric modulator, comprising:

a transparent electrode assembly having a first surface, the transparent electrode assembly having a plurality of particles on the first surface, the particles having an average diameter between about 10 Å and

about 500 Å

; and

a reflective electrode assembly having a second surface facing the first surface, the reflective electrode assembly movable between a first position and a second position, the first position being a first distance from the transparent electrode assembly, the second position being a second distance from the transparent electrode assembly, the second distance being greater than the first distance.

24. The interferometric modulator of claim 23, wherein the first distance is substantially equal to the average diameter of the particles.

25. The interferometric modulator of claim 23, wherein the first surface comprises a conductive surface, wherein the plurality of particles are formed of a dielectric material, and wherein portions of the conductive surface between the particles are exposed to a cavity between the transparent electrode assembly and the reflective electrode assembly.

27. The interferometric modulator of claim 25, wherein the means for increasing roughness increases surface separation between the first and second surfaces by about 5 Å

to about 100 Å

.

28. The interferometric modulator of claim 25, wherein the means for increasing roughness comprises dimples.

29. The interferometric modulator of claim 25, wherein the means for increasing roughness comprises particles on the first surface.

30. The interferometric modulator of claim 25, wherein the transmissive means for at least partially transmitting incident light comprises an indium tin oxide layer.

26. An interferometric modulator, comprising:

transmissive means for at least partially transmitting incident light, the transmissive means having a first surface;

reflective means for substantially reflecting incident light, the reflective means having a second surface facing the first surface; and

means for moving the reflective means relative to the transmissive means between a driven position and an undriven position, the driven position being closer to the transmissive means than is the undriven position,

wherein one of the first and second surfaces has means for increasing roughness by about 5 Å

RMS to about 100 Å

RMS relative to an innate roughness of the one of the first and second surfaces.

31. A microelectromechanical device, comprising:

a first electrode structure having a first surface; and

a second electrode structure having a second surface facing the first surface, the second electrode structure movable between a first position and a second position, the first position being a first distance from the first electrode structure, the second position being a second distance from the first electrode structure, the second distance being greater than the first distance,

wherein the second surface has a plurality of dimples, each of the dimples having a diameter between about 10 Å and

about 500 Å

.

32. The microelectromechanical device of claim 31, wherein the microelectromechanical device is an interferometric modulator.

33. The microelectromechanical device of claim 31, wherein the second electrode structure comprises a conductor selected from the group consisting of Cu, Pt, Ni, Au, Al, and alloys of the foregoing.

34. A method of making a microelectromechanical system (MEMS) device, comprising:

forming a first electrode;

providing a dielectric layer over the first electrode;

providing a sacrificial layer over the dielectric layer;

forming a second electrode over the sacrificial layer; and

depositing a plurality of particles between the dielectric layer and the second electrode after providing the dielectric layer and before forming the second electrode.

35. The method of claim 34, wherein the plurality of particles are deposited provided on the sacrificial layer.

36. The method of claim 34, wherein the plurality of particles are deposited on the dielectric layer.

37. The method of claim 34, wherein the plurality of particles have a diameter between about 10 Å

and about 500 Å

.

38. The method of claim 34, further comprising removing the sacrificial layer.

39. The method of claim 38, wherein removing the sacrificial layer further comprises removing the plurality of particles.

40. The method of claim 38, wherein the plurality of particles are not removed during the step of removing the sacrificial layer.

41. The method of claim 34, wherein depositing the plurality of particles comprises using a spin-on process.

42. The method of claim 34, wherein the second electrode comprises aluminum and wherein the plurality of particles comprise Al₂O₃.

43. The method of claim 34, wherein the sacrificial layer comprises a material selected from the group consisting of molybdenum, silicon, and tungsten and wherein removing the sacrificial layer comprises using an etchant comprising fluorine.

44. The method of claim 43, wherein the plurality of particles are etchable by the etchant.

45. The method of claim 43, wherein the plurality of particles are not etchable by the etchant.

46. A method of making an optical microelectromechanical system (MEMS) device, comprising:

forming a first at least partially transparent electrode;

providing a dielectric layer over the first electrode;

providing a sacrificial layer over the dielectric layer;

forming a second reflective electrode over the sacrificial layer; and

depositing a plurality of particles over the dielectric layer after providing the dielectric layer and before forming the second electrode.

47. The method of claim 46, wherein the plurality of particles are deposited on the sacrificial layer.

48. The method of claim 46, wherein the plurality of particles are deposited on the dielectric layer.

49. The method of claim 46, further comprising removing the sacrificial layer.

50. The method of claim 46, wherein the plurality of particles have an average diameter between about 10 Å

and about 500 Å

.

51. An interferometric modulator made by the method of claim 46.