PROCESS AND STRUCTURE FOR FABRICATION OF MEMS DEVICE HAVING ISOLATED EGDE POSTS

• US 20070279730A1
• 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: Heald, David
• Granted Patent: US 7,321,457 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 method of fabricating an array of MEMS devices includes the formation of support structures located at the edge of upper strip electrodes. A support structure is etched to form a pair of individual support structures located at the edges of a pair of adjacent electrodes. The electrodes themselves may be used as a hard mask during the etching of these support structures. A resultant array of MEMS devices includes support structures having a face located at the edge of an overlying electrode and coincident with the edge of the overlying electrode.

Claims

1. A method of fabricating a microelectromechanical systems (MEMS) device, comprising:

forming an electrode layer over a substrate;

depositing a sacrificial layer over the electrode layer;

forming a plurality of support structures, said support structures extending through the sacrificial layer, wherein at least some of said plurality of support structures comprise edge support structures;

depositing a mechanical layer over the plurality of support structures;

patterning the mechanical layer to form strips, wherein said strips are separated by gaps, and wherein said gaps are located over a central portion of each of said edge support structures; and

after forming the plurality of support structures, etching a portion of each of said edge support structures underlying the gaps, thereby forming isolated edge support structures.

2. The method of claim 1, wherein etching a portion of each of said edge support structures underlying the gaps comprises etching a central portion of each of said edge support structures to form two isolated edge support structures.

3. The method of claim 1, wherein patterning the mechanical layer to form strips comprises using a mask, and wherein etching a portion of each of said edge support structures comprises using the same mask

4. The method of claim 1, wherein the patterned mechanical layer is used as a hard mask during the etching of a portion of each of said edge support structures.

5. The method of claim 1, additionally comprising removing said sacrificial material.

6. The method of claim 1, wherein forming a plurality of support structures comprises:

patterning the layer of sacrificial material to form apertures;

depositing a layer of support structure material over the patterned sacrificial layer and into the apertures; and

patterning the layer of support structure material to form support structures.

7. The method of claim 6, wherein patterning the layer of sacrificial material to form apertures comprises patterning the layer of sacrificial material to form tapered apertures.

8. The method of claim 6, additionally comprising depositing a reflective layer over the sacrificial layer prior to patterning the sacrificial layer.

9. The method of claim 6, additionally comprising depositing a reflective layer over the sacrificial layer after patterning the sacrificial layer.

10. The method of claim 9, wherein etching a portion of each of said edge support structures comprises using a plasma etch.

11. The method of claim 9, wherein patterning the layer of support structure material to form support structures comprises using a plasma etch or wet etch.

12. The method of claim 6, wherein patterning the layer of support structure material to form support structures comprises removing portions of the support structure layer located away from the apertures, thereby forming support structures having wing portions which extend horizontally along the sacrificial layer near the apertures.

13. The method of claim 1, wherein the electrode layer comprises indium tin oxide.

14. The method of claim 1, wherein the sacrificial layer comprises molybdenum, silicon, tungsten, or tantalum.

15. The method of claim 1, wherein the support structures comprise a material selected from the group of:

SiO₂ and SiN_x.

16. The method of claim 1, wherein the mechanical layer comprises a material selected from the group of:

nickel and aluminum.

17. The method of claim 16, wherein the mechanical layer is used as a hard mask during the etching of the portions of the edge support structures.

18. The method of claim 1, additionally comprising depositing a partially reflective layer over the substrate.

19. The method of claim 18, wherein the partially reflective layer is deposited over the electrode layer.

20. The method of claim 18, wherein the partially reflective layer comprises chromium.

21. The method of claim 1, additionally comprising depositing a dielectric layer over the electrode layer.

22. The method of claim 21, wherein the dielectric layer comprises a material selected from the group of:

SiO₂ and SiN_x.

23. The method of claim 1, additionally comprising depositing a reflective layer over the sacrificial layer.

24. The method of claim 23, wherein the reflective layer comprises a material selected from the group of:

aluminum, silver, gold, copper, palladium, platinum, and rhodium.

25. The method of claim 23, additionally comprising etching the reflective layer to remove the portions of the reflective layer located under the gaps in the mechanical layer.

26. A microelectromechanical systems device fabricated by the method of claim 1.

27. An apparatus comprising an array of MEMS devices, the array comprising:

a plurality of lower electrodes located over a substrate;

a plurality of upper strip electrodes spaced apart from the plurality of lower electrodes by a cavity, the upper strip electrodes separated by gaps;

a plurality of isolated edge posts located between the upper strip electrodes and the lower electrodes, wherein the isolated edge posts comprise a face extending along the edge of the isolated edge posts facing an adjacent gap.

28. The apparatus of claim 27, wherein said face is coincident with the edge of the upper strip electrode overlying the isolated edge posts.

29. The apparatus of claim 27, further comprising at least one pair of isolated edge posts, wherein a first isolated edge post is located underneath a first upper strip electrode, and wherein a second isolated edge post is located underneath a second upper strip electrode adjacent to the first upper strip electrode, wherein the pair of isolated edge posts are formed by etching a single support structure.

30. The apparatus of claim 27, wherein the isolated edge posts additionally comprise a substantially horizontal wing portion along the edges of the isolated edge post not facing the adjacent gap between upper strip electrodes, wherein the substantially horizontal wing portion is spaced apart from the substrate by the cavity and extends substantially parallel to the substrate.

31. The apparatus of claim 27, wherein the face extending along the edge of the isolated edge post facing the adjacent gap between upper strip electrodes comprises a substantially vertical face.

32. The apparatus of claim 27, wherein the plurality of upper strip electrodes comprises nickel.

33. The apparatus of claim 27, wherein the plurality of lower electrodes comprises indium tin oxide.

34. The apparatus of claim 27, wherein the isolated edge posts comprise a material selected from the group of:

SiO₂ and SiN_x.

35. The apparatus of claim 27, wherein the isolated edge posts comprise a substantially flat base portion in contact with underlying layers on the substrate, and a sloped side portion extending away from the substrate toward the wing portion.

36. The apparatus of claim 27, additionally comprising a dielectric layer located over the lower electrodes on the same side of the cavity as the electrode.

37. The apparatus of claim 36, wherein the dielectric layer comprises a material selected from the group of:

SiO₂ and SiN_x.

38. The apparatus of claim 27, additionally comprising a partially reflective layer located over the plurality of lower electrodes on the same side of the cavity as the lower electrodes.

39. The apparatus of claim 38, wherein the partially reflective layer comprises chromium.

40. The apparatus of claim 27, additionally comprising a reflective layer located under the plurality of upper strip electrodes on the same side of the cavity as the upper strip electrodes.

41. The apparatus of claim 40, wherein the reflective layer comprises a material selected from the group of:

aluminum, silver, gold, copper, palladium, platinum, and rhodium.

42. The apparatus of claim 40, wherein the reflective layer extends underneath at least a portion of the isolated edge posts.

43. The apparatus of claim 27, additionally comprising

a processor that is configured to communicate with at least one of said upper and lower electrodes, said processor being configured to process image data;

and

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

44. The apparatus of claim 43, further comprising a driver circuit configured to send at least one signal to at least one of said upper and lower electrodes.

45. The apparatus of claim 44, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

46. The apparatus of claim 43, further comprising an image source module configured to send said image data to said processor.

47. The apparatus of claim 46, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

48. The apparatus of claim 43, further comprising an input device configured to receive input data and to communicate said input data to said processor.

49. A method of fabricating a microelectromechanical systems (MEMS) device, comprising:

forming an electrode layer over a substrate;

depositing a sacrificial layer over the electrode layer;

depositing a reflective layer over the sacrificial layer;

forming a plurality of support structures, said support structures extending through the sacrificial layer, wherein at least some of said plurality of support structures comprise edge support structures;

depositing a mechanical layer over the plurality of support structures;

patterning the mechanical layer to form strips, wherein said strips are separated by gaps, and wherein said gaps are located over a central portion of each of said edge support structures; and

etching portions of the reflective layer extending underneath the gaps in the mechanical layer, wherein etching the reflective layer comprises exposing the reflective layer to an etch for a period of time sufficient to electrically isolate portions of the reflective layer located underneath the strips from one another.

50. The method of claim 49, wherein the support structures comprise wing portions extending overlying annular portions of the reflective layer, and wherein etching portions of the reflective layer comprises overetching the reflective layer to etch sections of the annular portions of the layer underlying the gaps in the mechanical layer.

51. A MEMS device, comprising:

first means for electrically conducting;

second means for electrically conducting;

adjacent second means for electrically conducting; and

means for supporting edge portions of and for electrically isolating said second conducting means from said adjacent second conducting means, wherein said second conducting means is electrically isolated from said first conducting means, and wherein said second conducting means is movable relative to said first conducting means in response to generating electrostatic potential between said first and second conducting means.

52. The MEMS device of claim 51, wherein:

said first conducing means comprise a plurality of lower electrodes supported by a substrate;

said second conducting means and said adjacent second conducting means comprise a plurality of upper strip electrodes supported by a substrate, and spaced apart from one another by gaps, wherein the upper strip electrodes are electrically isolated from the lower electrodes; and

said means for supporting edge portions of and for electrically isolating said second conducting means comprise a plurality of isolated edge posts located between the upper strip electrodes and the lower electrodes, wherein the isolated edge posts comprise a face extending along the edge of the isolated edge posts facing an adjacent gap, wherein said face is coincident with the edge of the upper strip electrode overlying the isolated edge posts.

53. The MEMS device of claim 52, wherein said plurality of isolated edge posts comprise at least one pair of isolated edge posts, wherein a first isolated edge post is located underneath a first upper strip electrode, and wherein a second isolated edge post is located underneath a second upper strip electrode adjacent to the first upper strip electrode, wherein the pair of isolated edge posts are formed by etching a single support structure.