MEMS devices having support structures and methods of fabricating the same

• US 20070047900A1
• Filed: 07/21/2006
• Published: 03/01/2007
• Est. Priority Date: 07/22/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chung, Wonsuk, Chui, Clarence, Kothari, Manish, Sasagawa, Teruo, Tung, Ming-Hau, Miles, Mark, Sampsell, Jeffrey
• Granted Patent: US 7,936,031 B2
• Time in Patent Office: Days
• US Class Current: 385/147
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0307 Anchors
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 3/007 For controlling stiffness, e.g. ribs
• 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

Embodiments of MEMS devices comprise a conductive movable layer spaced apart from a conductive fixed layer by a gap, and supported by rigid support structures, or rivets, overlying depressions in the conductive movable layer, or by posts underlying depressions in the conductive movable layer. In certain embodiments, both rivets and posts may be used. In certain embodiments, these support structures are formed from rigid inorganic materials, such as metals or oxides. In certain embodiments, etch barriers may also be deposited to facilitate the use of materials in the formation of support structures which are not selectively etchable with respect to other components within the MEMS device.

Claims

1. A method of fabricating a MEMS device, comprising:

providing a substrate;

depositing an electrode layer over the substrate;

depositing a sacrificial layer over the electrode layer;

patterning the sacrificial layer to form apertures;

forming support structures over the sacrificial layer, wherein the support structures are formed at least partially within the apertures in the sacrificial material and wherein the support structures comprise a substantially horizontal wing portion extending over a substantially flat portion of the sacrificial material; and

depositing a movable layer over the sacrificial layer and the support structures.

2. The method of claim 1, additionally comprising etching the sacrificial layer to remove the sacrificial layer, thereby forming a gap between the movable layer and the electrode layer.

3. The method of claim 1, wherein the support structures comprise an inorganic material.

4. The method of claim 1, wherein the movable layer includes a mechanical sublayer and a reflective sublayer.

5. The method of claim 4, wherein the mechanical sublayer is formed directly over the reflective sublayer.

6. The method of claim 4, wherein depositing a movable layer over the sacrificial layer comprises:

depositing a reflective sublayer over the sacrificial layer;

patterning the reflective sublayer;

depositing a second sacrificial layer after and over the reflective sublayer; and

depositing a mechanical sublayer after and over the reflective sublayer.

7. The method of claim 4, wherein the reflective sublayer comprises aluminum.

8. The method of claim 4, wherein the mechanical sublayer comprises at least one material selected from the group of:

nickel and chromium.

9. The method of claim 4, additionally comprising:

patterning the second sacrificial layer to form at least one additional aperture, exposing at least a portion of the reflective sublayer; and

depositing a layer of support material over the second sacrificial layer to form a stiffening structure within the at least one additional aperture.

10. The method of claim 1, wherein the support structure comprises at least one material selected from the group of:

aluminum, AlO_x, silicon oxide, SiN_x, nickel, and chromium.

11. The method of claim 1, additionally comprising depositing an etch barrier layer over the sacrificial layer.

12. The method of claim 11, wherein the etch barrier layer comprises a reflective material.

13. The method of claim 11, wherein the etch barrier layer is deposited prior to the patterning of the sacrificial layer.

14. The method of claim 11, wherein the etch barrier layer is deposited after the patterning of the sacrificial layer.

15. The method of claim 14, additionally comprising removing the portions of the etch barrier layer located away from the support structures.

16. The method of claim 15, wherein the support structures are used as a hard mask during etching of the etch barrier layer.

17. The method of claim 1, wherein the support structures have a substantially planar upper surface.

18. The method of claim 1, wherein forming the support structures comprises:

depositing a layer of support material over the sacrificial layer; and

patterning the layer of support material to form support structures overlying at least a portion of the apertures in the sacrificial material.

19. The method of claim 18, wherein the layer of support material comprises depressions corresponding to the underlying apertures in the sacrificial layer.

20. The method of claim 19, additionally comprising:

depositing a layer of planarization material after deposition of the layer of support material so as to at least partially fill the depressions in the layer of support material; and

etching back the layer of planarization material to approximately an upper surface of the support structure, wherein the movable layer is formed over a remainder of the planarization material.

21. The method of claim 20, wherein the planarization material comprises photoresist material used to pattern the support structures.

22. The method of claim 18, additionally comprising depositing an adhesion enhancement layer after deposition of the support layer and prior to deposition of the movable layer.

23. The method of claim 1, wherein forming the support structures comprises:

depositing a layer of support material over the sacrificial layer; and

anodizing at least a portion of the layer of support material to form at least one support structure.

24. The method of claim 23, wherein the layer of support material comprises aluminum or tantalum.

25. The method of claim 1, wherein forming the support structures comprises:

depositing a seed layer over the patterned sacrificial layer;

forming a mask over the seed layer, wherein the mask comprises at least one aperture; and

forming a support structure within the aperture in the mask via a plating process.

26. The method of claim 25, wherein the aperture in the mask defines the shape of a support structure.

27. The method of claim 1, additionally comprising:

depositing a layer of rivet material over the movable layer; and

patterning the layer of rivet material to form additional support structures at least partially overlying the support structures underlying the movable layer.

28. The method of claim 1, additionally comprising depositing a partially reflective layer prior to deposition of the sacrificial layer.

29. The method of claim 28, wherein the partially reflective layer comprises chromium.

30. The method of claim 1, additionally comprising depositing a partially reflective layer prior to deposition of the sacrificial layer, wherein depositing the movable layer over the sacrificial layer comprises depositing a reflective sublayer over the sacrificial material.

31. The method of claim 1, wherein the MEMS device comprises an interferometric modulator.

32. The method of claim 1, wherein the electrode layer comprises ITO.

33. The method of claim 1, additionally comprising patterning the electrode layer to form electrode apertures, wherein said electrode apertures are located underneath the apertures in the sacrificial layer.

34. The method of claim 1, additionally comprising depositing a dielectric layer between the electrode layer and the sacrificial material.

35. The method of claim 1, wherein the support structures have a thickness which is thinner than that of the layer of sacrificial material.

36. The method of claim 1, wherein the support structures are conformal over the sacrificial material, the support structures comprising a depression corresponding to the apertures in the sacrificial layer.

37. A MEMS device formed by the method of claim 1.

38. A MEMS device, comprising:

a substrate;

an electrode layer located over the substrate;

a movable layer located over the electrode layer, wherein the movable layer is generally spaced apart from the electrode layer by a gap; and

support structures underlying at least a portion of the movable layer, wherein the support structures comprise a substantially horizontal wing portion, said substantially horizontal wing portion being spaced apart from the electrode layer by the gap.

39. The MEMS device of claim 38, wherein the support structures comprise an inorganic material.

40. The MEMS device of claim 38, wherein the movable layer comprises a reflective sublayer facing the electrode layer, and a mechanical sublayer located over the reflective sublayer.

41. The MEMS device of claim 40, wherein the mechanical sublayer is at least partially spaced apart from the reflective sublayer.

42. The MEMS device of claim 40, wherein the reflective sublayer comprises aluminum.

43. The MEMS device of claim 40, wherein the mechanical sublayer comprises at least one material selected from the group of:

nickel and chromium.

44. The MEMS device of claim 40, wherein the reflective sublayer extends underneath at least a portion of the support structure.

45. The MEMS device of claim 40, additionally comprising a partially reflective layer located on the opposite side of the gap as the reflective sublayer.

46. The MEMS device of claim 40, additionally comprising at least one stiffening structure formed on the opposite side of the reflective sublayer from the electrode layer.

47. The MEMS device of claim 46, wherein the stiffening structure comprises the same material as the support structure.

48. The MEMS device of claim 38, wherein a protective layer is located between at least a portion of the support structure and the air gap.

49. The MEMS device of claim 38, additionally comprising at least one support structure located over the movable layer, wherein the at least one overlying support structure at least partially overlies at least one support structure underlying the substrate.

50. The MEMS device of claim 38, additionally comprising an adhesion enhancement layer located between the support structures and the movable layer.

51. The MEMS device of claim 38, additionally comprising a partially reflective layer located over the substrate, wherein the partially reflective layer is located on the same side of the air gap as the electrode layer.

52. The MEMS device of claim 38, wherein the support structure comprises a depression, and wherein said depression is at least partially filled by a planarization material.

53. The MEMS device of claim 38, wherein the support structure comprises a metallic material.

54. The MEMS device of claim 38, wherein the support structure comprises an anodized material.

55. The MEMS device of claim 38, wherein the MEMS device comprises an interferometric modulator.

56. The MEMS device of claim 38, additionally comprising:

a processor that is configured to communicate with at least one of said electrode layer and said movable layer, said processor being configured to process image data; and

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

57. The MEMS device of claim 56, further comprising a driver circuit configured to send at least one signal to at least one of said electrode layer and said movable layer.

58. The MEMS device of claim 57, further comprising a controller configured to send at least a portion of the image data to the driver circuit

59. The MEMS device of claim 56, further comprising an image source module configured to send said image data to said processor.

60. The MEMS device of claim 59, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

61. The MEMS device of claim 56, further comprising an input device configured to receive input data and to communicate said input data to said processor.

62. A MEMS device, comprising:

first means for electrically conducting;

second means for electrically conducting; and

means for supporting said second conducting means over said first conducting means, wherein said second conducting means overlie the supporting 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, wherein said supporting means comprise a substantially horizontal wing portion spaced apart from said first conducting means.

63. The device of claim 62, wherein the first conducting means comprises an electrode layer supported by a substrate.

64. The device of claim 62, wherein the second conducting means comprises a movable layer, portions of which are spaced apart from said first conducting means by an interferometric gap.

65. The device of claim 62, wherein the supporting means comprise at least one support structure formed over said first conducting means and underlying said second conducting means.