MEMS devices having support structures with substantially vertical sidewalls and methods for fabricating the same

• US 20070042524A1
• Filed: 08/18/2006
• Published: 02/22/2007
• Est. Priority Date: 08/19/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Zee, Stephen, Wang, Chun-Ming, Kogut, Lior, Zhong, Fan, Qiu, Chengbin
• Granted Patent: US 7,704,773 B2
• Time in Patent Office: Days
• US Class Current: 438/52
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0163 Spring holders
• CPC Class Codes: B81B 2203/019 characterized by their profile
• 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 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: B81C 1/00142 Bridges deformable micromirrors G02B26/0841
• CPC Class Codes: B81C 1/00666 Treatments for controlling internal stress or strain in MEMS structures
• CPC Class Codes: B81C 2201/0167 by adding further layers of materials having complementary strains, i.e. compressive or tensile strain
• 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
• CPC Class Codes: Y10S 359/90 Methods

Abstract

Embodiments of MEMS devices include support structures having substantially vertical sidewalls. Certain support structures are formed through deposition of self-planarizing materials or via a plating process. Other support structures are formed via a spacer etch. Other MEMS devices include support structures at least partially underlying a movable layer, where the portions of the support structures underlying the movable layer include a convex sidewall. In further embodiments, a portion of the support structure extends through an aperture in the movable layer and over at least a portion of the movable layer.

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 an aperture;

depositing a layer of inorganic self-planarizing material over the sacrificial layer, such that it fills the aperture;

etching back the layer of self-planarizing material to a level at or below the upper surface of the sacrificial layer to form a support structure; and

depositing a movable layer over the support structure.

2. The method of claim 1, additionally comprising perfoming a release etch to remove the sacrificial layer, forming an air gap located between the movable layer and the electrode layer.

3. The method of claim 1, wherein the aperture comprises substantially vertical sidewalls.

4. The method of claim 1, wherein patterning the layer of self-planarizing material to form a support structure comprises etching back the layer of self-planarizing material to a level at or below the upper surface of the sacrificial layer.

5. The method of claim 1, wherein depositing a movable layer over the support structure comprises depositing a reflective sublayer over the support structures and depositing a mechanical sublayer over the reflective sublayer.

6. The method of claim 1, wherein depositing a movable layer over the support structure comprises:

depositing an upper electrode layer over the sacrificial layer;

patterning the upper electrode layer layer to form isolated electrode members; and

depositing an upper sacrificial layer over the isolated electrode members, wherein the upper sacrificial layer is deposited prior to patterning the sacrificial layer to form the aperture, and wherein patterning the sacrificial layer to form the aperture comprises patterning both the upper sacrificial layer and the lower sacrificial layer.

7. The method of claim 6, wherein the upper electrode layer comprises a reflective layer.

8. The method of claim 6, additionally comprising

patterning the upper sacrificial layer to form an aperture exposing a portion of the isolated electrode member;

and

forming a mechanical layer over the support structure and the patterned upper sacrificial layer, wherein a portion of the mechanical layer is in contact with the exposed portion of the isolated electrode member.

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

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

11. 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 define an aperture;

forming a metallic seed layer, wherein the metallic seed layer does not extend over unpatterned portions of the sacrificial layer;

forming a support structure within the aperture via a plating process; and

depositing a movable layer over the support structure.

12. The method of claim 11, additionally comprising perfoming a release etch to remove the sacrificial layer, forming an air gap located between the movable layer and the electrode layer.

13. The method of claim 11, wherein the aperture comprises substantially vertical sidewalls.

14. The method of claim 11, wherein the sacrificial layer comprises a conductive material, and wherein the metallic seed layer can be selectively plated relative to the sacrificial layer.

15. The method of claim 14, wherein forming the metallic seed layer comprises:

depositing the metallic seed layer after depositing of the sacrificial layer; and

patterning the metallic seed layer to remove portions of the metallic seed layer extending over unpatterned portions of the sacrificial layer.

16. The method of claim 14, wherein the metallic seed layer is deposited prior to deposition of the sacrificial layer, additionally comprising patterning the metallic seed layer prior to deposition of the sacrificial layer to form remove a portion of the metallic seed layer which will not underlie the aperture in the sacrificial layer.

17. The method of claim 11, wherein depositing a movable layer over the support structure comprises depositing a reflective sublayer over the support structures and depositing a mechanical sublayer over the reflective sublayer.

18. The method of claim 11, wherein the MEMS device is an interferometric modulator.

19. A MEMS device formed by the method of claim 11.

20. 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 define an aperture having a substantially vertical sidewall;

depositing a layer of conformal support material over the vertical sidewall and over an upper surface of the sacrificial layer;

performing a directional etch to form a spacer structure located within the aperture and against the substantially vertical sidewall, wherein the directional etch removes the support material overlying the upper surface of the sacrificial layer, and

depositing a movable layer over the support structure.

21. The method of claim 20, additionally comprising perfoming a release etch to remove the sacrificial layer, forming an air gap located between the movable layer and the electrode layer.

22. The method of claim 20, wherein performing a directional etch comprises removing the portions of the layer of support material located away from the aperture.

23. The method of claim 20, wherein performing a directional etch comprises removing a portion of the support layer located within the aperture, thereby exposing a portion of an underlying layer.

24. The method of claim 20, wherein the movable layer is conformal over the spacers and wherein a portion of the movable layer is located within the aperture.

25. The method of claim 20, wherein depositing a movable layer over the support structure comprises depositing a reflective sublayer over the support structures and depositing a mechanical sublayer over the reflective sublayer.

26. The method of claim 20, wherein the MEMS device is an interferometric modulator.

27. A MEMS device formed by the method of claim 20.

28. 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;

depositing a movable layer over the sacrificial layer;

patterning the movable layer to form an aperture extending through the movable layer, thereby exposing a portion of the sacrifical layer;

etching the exposed portion of the sacrificial layer to form a cavity extending through the sacrificial layer and undercutting a portion of the movable layer; and

depositing a layer of self-planarizing support material to fill the cavity.

29. The method of claim 28, wherein the layer of self-planarizing material extends over the movable layer, additionally comprising patterning the layer of support material to form a support structure, wherein the support structure comprises a convex outer surface corresponding to a re-entrant profile of the cavity.

30. The method of claim 29 additionally comprising patterning the layer of support material, leaving a portion overlying at least a portion of the aperture in the movable layer and extending over at least a portion of the movable layer.

31. The method of claim 30, wherein patterning the layer of support material to form a support structure additionally comprises removing a portion of the support material extending though the aperture in the mechanical layer, forming an aperture extending through the support structure.

32. The method of claim 28, additionally comprising perfoming a release etch to remove the sacrificial layer, forming an air gap located between the movable layer and the electrode layer.

33. The method of claim 28, wherein depositing the layer of support material comprises exposing the partially fabricated MEMS device to a liquid precursor.

34. The method of claim 33, wherein the liquid precursor comprises a spin-on precursor.

35. The method of claim 28, wherein the layer of support material comprises a polymeric material.

36. The method of claim 28, wherein etching the exposed portion of the sacrificial layer to form a cavity comprises performing an isotropic etch.

37. The method of claim 28, wherein depositing a movable layer over the support structure comprises depositing a reflective sublayer over the support structures and depositing a mechanical sublayer over the reflective sublayer.

38. The method of claim 28, wherein the MEMS device comprises an interferometric modulator.

39. A MEMS device formed by the method of claim 28.

40. 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 an air gap; and

an inorganic support structure underlying the movable layer, wherein the inorganic support structure comprises a substantially vertical sidewall, and wherein the inorganic support structure is spaced apart from the substrate by at least one intermediate layer.

41. The MEMS device of claim 40, wherein the support structure comprises a metallic material and is formed by an electroplating process.

42. The MEMS device of claim 40, wherein the support structure comprises an annular spacer having a tapered interior surface.

43. The MEMS device of claim 42, wherein the movable layer is conformal over the tapered interior surface of the annular spacer.

44. The MEMS device of claim 40, wherein the support structure comprises a self-planarizing material.

45. The MEMS device of claim 40, wherein the at least one intermediate layer comprises a dielectric layer located over the electrode layer.

46. The MEMS device of claim 40, wherein the movable layer comprises a mechanical sublayer and a reflective sublayer located on the side of the mechanical sublayer facing the air gap.

47. The MEMS device of claim 46, additionally comprising a partially reflective layer located on the opposite side of the air gap from the reflective sublayer.

48. The MEMS device of claim 40, wherein the movable layer comprises an isolated electrode member spaced apart from the electrode layer by the air gap and a mechanical layer overlying the support structure, wherein the mechanical layer supports the isolated electrode member and is partially detached from the isolated electrode member.

49. The MEMS device of claim 40, 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.

50. The MEMS device of claim 49, further comprising a driver circuit configured to send at least one signal to at least one of said electrode layer and said movable layer.

51. The MEMS device of claim 50, further comprising a controller configured to send at least a portion of the image data to the driver circuit

52. The MEMS device of claim 49, further comprising an image source module configured to send said image data to said processor.

53. The MEMS device of claim 52, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

54. The MEMS device of claim 49, further comprising an input device configured to receive input data and to communicate said input data to said processor.

55. 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 an air gap, said movable layer comprising an aperture extending through the movable layer; and

a support structure located at least partially beneath the aperture in the movable layer, said support structure comprising a convex sidewall portion located underneath the movable layer.

56. The MEMS device of claim 55, wherein the support structure comprises a self-planarizing material.

57. The MEMS device of claim 56, wherein the support structure comprises a spin-on material.

58. The MEMS device of claim 56, wherein the support structure comprises a polymeric material.

59. The MEMS device of claim 55, wherein a portion of the support structure extends through the aperture in the movable layer, and wherein said support structure encloses at least a portion of the movable layer located adjacent the aperture in the movable layer.

60. The MEMS device of claim 59, wherein the support structure comprises an aperture extending through support structure to an underlying layer, and wherein said aperture extending though the support structure extends through the aperture in the movable layer.

61. The MEMS device of claim 55, wherein the movable layer comprises a mechanical sublayer and a reflective sublayer located on the side of the mechanical sublayer facing the air gap.

62. The MEMS device of claim 61, additionally comprising a partially reflective layer located on the opposite side of the air gap from the reflective sublayer.

63. 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 is movable relative to said first conducting means in response to generating electrostatic potential between said first and second conducting means, and wherein said supporting means extend through an aperture in said second conducting means and enclose at least a portion of said second conducting means.

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

65. The MEMS device of claim 63, wherein the second conducting means comprises a movable layer, portions of which are spaced apart from said first conducting means by an interferometric gap.

66. The MEMS device of claim 63, wherein the supporting means comprises a support structure which extends through an aperture in the second conducting means and encloses at least a portion of the second conducting means, wherein the support structure is formed from a self-planarizing material.

67. A method of manufacturing a MEMS device, comprising:

forming a lower sacrificial layer over a substrate;

forming a movable layer over the first sacrificial layer;

forming an upper sacrificial layer over the movable layer, wherein the thickness of the second sacrificial layer is between 30 and 500 angstroms;

forming a rigid ceiling layer over the second sacrificial layer; and

forming a support structure which provides support to both the movable layer and the rigid ceiling layer.

68. The method of claim 67, additionally comprising removing the upper and lower sacrificial layers via a release etch.

69. The method of claim 67, wherein forming a support structure comprises forming a lower support segment underlying the movable layer and forming an upper support segment overlying the movable layer.

70. The method of claim 69, wherein forming the upper support segment comprises:

patterning the second sacrificial layer to form an aperture extending through the second sacrificial layer; and

depositing a support layer over the patterned second sacrificial layer.

71. The method of claim 70, wherein the support material comprises a self-planarizing material.

72. The method of claim 71, additionally comprising etching back the support layer to a height below the upper surface of the patterned second sacrificial layer.

73. The method of claim 70, wherein the support layer overlying substantially flat portions of the upper sacrificial layer remains in the finished MEMS device and serves as the rigid ceiling layer.

74. The method of claim 73, wherein patterning the second sacrificial layer to form apertures comprises forming tapered apertures, and wherein the support layer is conformal over the patterned second sacrificial layer.

75. The method of claim 67, wherein forming the support structure comprises:

removing portions of the upper sacrificial layer, the movable layer, and the lower sacrificial layer to form a via; and

depositing a layer of self-planarizing material to fill the via, thereby forming a support structure which extends through an aperture in the movable layer and encloses at least a portion of the movable layer.

76. The method of claim 71, wherein the rigid ceiling layer is formed prior to forming the via, additionally comprising patterning the rigid ceiling layer to remove a portion of the rigid ceiling layer overlying the via.

77. The method of claim 67, wherein the thickness of the upper sacrificial material is between 50 and 200 angstroms.

78. The method of claim 67, wherein forming the movable layer comprises:

forming a reflective sublayer over the first sacrificial layer; and

forming a mechanical sublayer over the reflective sublayer.

79. The method of claim 67, wherein forming the movable layer comprises:

depositing a layer of reflective material over the lower sacrificial layer;

patterning the layer of reflective material to form independent electrode members;

depositing an intermediate layer of sacrificial material over the isolated electrode members;

patterning the intermediate layer of sacrificial material to expose a portion of the isolated electrode members; and

depositing a mechanical layer over the patterned sacrificial layer.

80. The method of claim 67, wherein the MEMS device comprises an interferometric modulator.

81. A MEMS device formed by the method of claim 67.

82. A MEMS device, comprising:

a movable layer spaced apart from a substrate by a lower air gap;

a rigid ceiling layer spaced apart from the movable layer by an upper air gap, wherein the height of the upper air gap is between 30 and 500 angstroms; and

a support structure which provides support to both the movable layer and the rigid ceiling layer.

83. The MEMS device of claim 82, wherein the support structure comprises an upper support segment overlying the movable layer and a lower support segment underlying the movable layer.

84. The MEMS device of claim 83, wherein the upper support segment comprises a self-planarizing material.

85. The MEMS device of claim 83, wherein the rigid ceiling layer and the upper support segment comprise a single structure spaced apart from the movable layer in the upper air gap in a ceiling region and in contact with the movable layer in a support region.

86. The MEMS device of claim 85, wherein the single support structure comprises a depression having a tapered sidewall in the support region.

87. The MEMS device of claim 82, wherein the support structure comprises a unitary support structure extending through an aperture in the movable layer and enclosing at least a portion of the movable layer.

88. The MEMS device of claim 87, wherein the unitary support structure extends through an aperture in the rigid ceiling layer and encloses at least a portion of the rigid ceiling layer.

89. The MEMS device of claim 82, wherein the height of the upper air gap is between 50 and 200 angstroms.

90. The MEMS device of claim 82, wherein the movable layer comprises a reflective sublayer facing the electrode layer and a mechanical sublayer overlying the reflective sublayer.

91. The MEMS device of claim 82, wherein the MEMS device comprises an interferometric modulator.