Support structure for MEMS device and methods therefor

• US 7,679,812 B2
• Filed: 07/21/2006
• Issued: 03/16/2010
• Est. Priority Date: 07/22/2005
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chui, Clarence, Wang, Chun-Ming, Sampsell, Jeffrey B., Kothari, Manish, Sasagawa, Teruo, Ganti, SuryaPrakash
• Primary Examiner(s): Sugarman; Scott J
• Assistant Examiner(s): PINKNEY, DAWAYNE
• Application Number:
  US11/491,389
• Publication Number:
  US 20070019923A1
• Time in Patent Office: 1,334 Days
• Field of Search: 359290-292, 359/295, 359223-225, 359/245, 359260-263, 359/298, 359/198, 359301-303, 359317-318, 359/237, 359/242
• US Class Current: 359/291
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 2203/0307 Anchors
• CPC Class Codes: B81C 1/00595 Control etch selectivity
• CPC Class Codes: B81C 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal
• 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: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A microelectromechanical systems device having support structures formed of sacrificial material surrounded by a protective material. The microelectromechanical systems device includes a substrate having an electrode formed thereon. Another electrode is separated from the first electrode by a cavity and forms a movable layer, which is supported by support structures formed of a sacrificial material.

Claims

1. A microelectromechanical systems device comprising:

a substrate having a first electrode layer formed thereon;

a second electrode layer spaced apart from the first electrode layer by a cavity;

at least one support structure comprising side surfaces surrounding the support structure;

a protective material surrounding the at least one support structure to laterally isolate the at least one support structure from the cavity, the protective material covering all of the side surfaces and preventing exposure of the side surfaces to the cavity;

a first layer formed over the substrate; and

a second layer formed over the first layer,

wherein the at least one support structure is interposed between the first and second layers,

wherein the protective material, the first layer, and the second layer together encapsulate the at least one support structure, and

wherein the at least one support structure is configured to support the second electrode layer.

2. The microelectromechanical systems device of claim 1, wherein the at least one support structure is formed over the first electrode layer and the protective material is a self-planarizing material.

3. The microelectromechanical systems device of claim 2, wherein the protective material comprises photoresist.

4. The microelectromechanical systems device of claim 2, wherein the protective material comprises spin-on dielectric.

5. The microelectromechanical systems device of claim 1, wherein the second electrode layer is configured to be movable.

6. The microelectromechanical systems device of claim 1, wherein the protective material has a thickness in a range of about 500 Å

to one micron.

7. The microelectromechanical systems device of claim 1, wherein the at least one support structure comprises an inorganic material.

8. The microelectromechanical systems device of claim 1, wherein the at least one support structure comprises molybdenum having straight side surfaces.

9. The microelectromechanical systems device of claim 8, wherein the first layer is a dielectric layer over the first electrode layer, the first layer having a dielectric top surface exposed to the cavity.

10. The microelectromechanical systems device of claim 9, wherein the dielectric top surface comprises silicon dioxide.

11. The microelectromechanical systems device of claim 9, wherein the dielectric top surface comprises Al₂O₃.

12. The microelectromechanical systems device of claim 9, wherein the second layer is the second electrode layer, the second layer comprising an aluminum surface exposed to the cavity.

13. The microelectromechanical systems device of claim 1, wherein the at least one support structure is selectively etchable with respect to the protective material.

14. The microelectromechanical systems device of claim 13, wherein the at least one support structure is etchable by xenon difluoride.

15. The microelectromechanical systems device of claim 1, further comprising:

a display;

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

a memory device in electrical communication with said processor.

16. The microelectromechanical systems device of claim 15, further comprising:

a driver circuit configured to send at least one signal to said display.

17. The microelectromechanical systems device of claim 16, further comprising:

a controller configured to send at least a portion of said image data to said driver circuit.

18. The microelectromechanical systems device of claim 15, further comprising:

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

19. The microelectromechanical systems device of claim 18, wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

20. The microelectromechanical systems device of claim 15, further comprising:

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

21. A method of making an interferometric modulator device, comprising:

providing a substrate having a first electrode layer formed over the substrate;

depositing a sacrificial material over the first electrode layer;

surrounding at least one support structure comprising side surfaces with a protective material after depositing the sacrificial material such that all of the side surfaces are covered and surrounded by the protective material; and

creating a cavity between the first electrode layer and a movable layer after surrounding the at least one support structure, wherein the protective material laterally isolates the at least one support structure from the cavity,

wherein surrounding the at least one support structure comprises;

etching at least one annular opening in the sacrificial material after depositing the sacrificial material; and

filling the at least one annular opening with the protective material to surround the at least one support structure.

22. The method of claim 21, further comprising forming the movable layer after surrounding the at least one support structure, wherein creating the cavity comprises selectively removing the sacrificial material outside of the protective material after forming the movable layer.

23. The method of claim 22, wherein forming the movable layer completes encapsulation of the at least one support structure.

24. The method of claim 22, wherein the sacrificial material comprises a material selected from the group consisting of silicon, molybdenum, tungsten, titanium, and photoresist.

25. The method of claim 22, further comprising removing the protective material after selectively removing the sacrificial material outside of the protective material.

26. The method of claim 25, wherein the protective material is removed by ashing.

27. The method of claim 22, wherein providing the substrate comprises depositing a dielectric material over the first electrode layer before depositing the sacrificial material.

28. The method of claim 22, further comprising forming openings in the movable layer prior to selectively removing the sacrificial material.

29. The method of claim 22, wherein the at least one support structure is formed from the sacrificial material.

30. The method of claim 22, wherein the support structure is formed of a material susceptible to selective removing of the sacrificial material.

31. The method of claim 22, wherein the support structure and selectively removed portions of the sacrificial material are susceptible to removal by a same etchant.

32. The method of claim 31, wherein the etchant is xenon difluoride.

33. The method of claim 22, wherein the protective material has a thickness in a range of ½

to twice a thickness of the sacrificial material.

34. The method of claim 22, wherein selectively removing comprises etching using xenon difluoride.

35. The method of claim 21, further comprising forming the movable layer over the sacrificial material before surrounding the at least one support structure, wherein creating the cavity comprises selectively removing the sacrificial material outside of the protective material.

36. The method of claim 35, further comprising etching the movable layer after depositing the sacrificial material.

37. The method of claim 36, wherein etching the at least one annular opening comprises etching the at least one annular opening after etching the movable layer, wherein etching the at least one annular opening comprises using a timed etch process.

38. The method of claim 36, wherein etching the movable layer comprises etching a plurality of apertures in the movable layer and etching the sacrificial material comprises removing the sacrificial material under the plurality of apertures.

39. The method of claim 36, wherein surrounding the at least one support structure comprises:

depositing a planarization material over the movable layer and into cavity after etching the movable layer and the sacrificial layer; and

etching the planarization material to surround the at least one support structure.

40. The method of claim 39, further comprising removing the planarization material after creating the cavity.

41. The method of claim 22, further comprising:

forming a first layer over the substrate; and

forming a second layer over the first layer such that the at least one support structure is interposed between the first and second layers,

wherein the protective material, the first layer, and the second layer together encapsulate the at least one support structure such that the at least one support structure is protected when selectively removing the sacrificial material.