Microelectrochemical systems device and method for fabricating same

• US RE42,119 E1
• Filed: 06/02/2005
• Issued: 02/08/2011
• Est. Priority Date: 02/27/2002
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chui, Clarence, Miles, Mark W.
• Primary Examiner(s): Choi; William C
• Application Number:
  US11/144,210
• Time in Patent Office: 2,077 Days
• Field of Search: 359/230, 359/231, 359/247, 359/290, 359/291, 359/302
• 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

One aspect of the invention provides a method for fabricating a microelectromechanical systems device. The method comprises fabricating an array of first elements, each first element conforming to a first geometry; fabricating at least one array of second elements, each second element conforming to a second geometry; wherein fabricating the arrays comprises selecting a defining aspect of each of the first and second geometries based on a defining characteristic of each of the first and second elements; and normalizing differences in an actuation voltage required to actuate each of the first and second elements, wherein the differences are as a result of the selected defining aspect, the defining characteristic of each of the elements being unchanged.

Claims

1. A microelectromechanical systems device comprising:

a plurality of elements each having at least two layers, the layers being disposed in a stacked relationship with a gap therebetween when the element is in an undriven state, the plurality of elements being of at least two different types, defining at least a first region having elements only of a first type and a second region having elements only of a second type, wherein each type differing differs in a height of its gap, wherein the elements within the first region are substantially co-planar, and wherein the elements within the second region are substantially co-planar; and

a driving mechanism circuit configured to drive the plurality of elements to a driven state, wherein one of the layers of each element is configured to electrostatically displaced relative to the other layer to close the gap between the layers, and wherein a minimum voltage required to actuate the driving mechanism electrostatically displace the layer to a driven state is substantially different for each type of element.

2. The microelectromechanical systems device of claim 1, wherein the plurality of elements are arranged in an array structure wherein the plurality of elements are substantially co-planar.

3. The microelectromechanical systems device of claim 2, further comprising a plurality of said array structures each containing only elements of one type.

4. The microelectromechanical systems device of claim 1, wherein the electrostatically displaceable layer is self-supporting comprising es a plurality of spaced apart limbs which rest on a substrate.

5. The microelectromechanical systems device of claim 3 1, wherein the layers of each element in an array are continuous, the electrostatically displaceable layer being supported by a support structure comprising a plurality of supports spaced along a first axis and extending in a direction which is transverse thereto, each support having a support surface to support the electrostatically displaceable layer above the other layer when the elements are in the undriven state.

6. The microelectromechanical systems device of claim 5, wherein the spacing between the supports along the first axis in each array depends on the height of the gap between the layers, the higher the gap, the greater the spacing.

7. The microelectromechanical systems device of claim 5, wherein an area of the support surface of each support in an array is a function of the height of the gap between the layers, the higher the gap, the smaller the area.

8. The microelectromechanical systems device of claim 1, wherein the electrostatically displaceable layer of each element has a Young'"'"'s Modulus which is a function of the height of its gap, the higher the gap, the lower the Young'"'"'s Modulus.

9. The microelectromechanical systems device of claim 1, wherein a thickness of the electrostatically displaceable layer of each element is a function of the height of its gap, the higher the gap, the smaller the thickness.

10. The microelectromechanical systems device of claim 1, wherein the electrostatically displaceable layer of at least those elements having the highest gap have apertures formed therein to reduce a stiffness thereof.

11. The microelectromechanical systems device of claim 1, wherein the electrostatically displaceable layer of each element is under tensile stress to a degree which increases as the height of its gap decreases.

12. The microelectromechanical systems device of claim 1, wherein the driving mechanism circuit comprises an electrode layer to electrostatically displace the electrostatically displaceable layer when energized, wherein the electrode layers which drive at least those elements having the smallest gap have apertures formed therein to increase the minimum voltage required to energize the electrode layers.

13. The microelectromechanical systems device of claim 1, wherein the electrostatically displaceable layer of each element is formed on a dielectric material having a dielectric constant which is a function of the height of the gap of the element, the higher the gap, the greater the dielectric constant.

14. The microelectromechanical systems device of claim 1, wherein the electrostatically displaceable layer of each element is formed on a dielectric material having a thickness which is a function of the height of the gap of the element, the higher the gap, the lower the thickness.

15. The microelectromechanical systems device of claim 11, wherein the minimum voltage is not substantially the same for each kind type of element.

16. The microelectromechanical systems device of claim 1, wherein each of the elements defines an interferometric modulator which configured to modulates light.

17. The microelectromechanical systems device of claim 16, comprising three different kinds types of interferometric modulators, each differing in a height of its gap to reflect red, blue, or green light, respectively when in the undriven state.

18. A method for of fabricating a microelectromechanical systems device comprising:

constructing an array a plurality of elements, each element having a first layer, a second layer spaced from the first layer by a gap when in an undriven state, and an electrode layer configured to electrostatically drive the second layer to contact the first layer corresponding to when in a driven state when energized , the elements being of at least two different types, each type differing in a height of its gap, wherein said constructing includes changing a configuration of each at least one element type to compensate for reduce a differences in between a voltage required to drive each the at least one element type and another voltage required to drive another element type to its their respective driven state.

19. The method of claim 18, wherein the first and second layers of each element in an array are defined by continuous layers which are supported by a support structure comprising a plurality of supports spaced along a first axis and extending in a direction which is transverse thereto, each support having a support surface to support the first layer above the second layer when the elements are in the undriven state, wherein changing the configuration of each element type then comprising comprises changing the spacing between the supports.

20. The method of claim 19, wherein changing the configuration of each element type comprises changing an area of the support surface of each support.

21. The method of claim 18, wherein changing the configuration of each element type comprises using a material having a different Young'"'"'s Modulus for the second layer of each element type.

22. The method of claim 18, wherein changing a configuration of each element type comprises changing a thickness of the second layer of each element type.

23. The method of claim 18, wherein changing a configuration of each element type comprises forming apertures in the second layers of at least those elements having the highest gap.

24. The method of claim 18, wherein changing a configuration of each element type comprises subjecting the second layer of each element to tensile stress to a degree which is inversely proportional to the height of its gap.

25. The method of claim 18, wherein changing a configuration of each element type comprises forming apertures in the electrode layer of at least those element types having the smallest gap.

26. The method of claim 18, wherein the second layer of each element is formed on a dielectric material, wherein changing a configuration of each element type then comprising comprises changing the dielectric constant of the dielectric material on which the second layer of each element is formed.

27. The method of claim 26, wherein changing a configuration of each element type comprises changing a thickness of the dielectric material.

28. The method of claim 18, wherein the elements are interferometric modulators which configured to modulate light.

29. A microelectromechanical systems device comprising:

a plurality of elements, each element having a first layer, a second layer spaced from the first layer by a gap when in an undriven state, and an electrode layer configured to electrostatically drive the second layer to contact the first layer corresponding to a driven state when the electrode layer is energized, the elements being of at least two different kinds, each kind of element differing in at least a height of its gap; and

an element driving mechanism comprising an integrateda drive circuit having multilevel outputs configured to energize the electrode layer of each element to cause the element to change from its undriven state to its driven state.

30. A method for fabricating a microelectromechanical systems device, the method comprising:

fabricating an array a plurality of first elements, each first element conforming to a first geometry;

fabricating at least one array of a plurality of second elements, each second element conforming to a second geometry;

wherein

fabricating the arrays first and second elements comprises

selecting a defining an aspect of each of the first and second geometries based on a defining characteristic of each of the first and second elements ; and

normalizing differences in an actuation voltage required to actuate each of the first and second elements, wherein the differences in the actuation voltages are as a result of the selected defining aspect, the defining characteristic of each of the elements being unchanged of the first and second geometries.

31. The method of claim 30, wherein the normalizing comprises changing an other aspects of the first and second geometries without changing the defining selected aspects of the first and second geometries.

32. The method of claim 30 31, wherein the defining selected aspect comprises a gap between an operatively upper and lower layer of each element, the upper and lower layers being separated by supports.

33. The method of claim 32, wherein each element comprises an electrode to electrostatically drive the upper layer towards the lower layer when actuated by the actuation voltage.

34. The method of claim 33, wherein changing the said other aspects comprises at least a changes selected from the group comprising changing a thickness of the upper layer, and changing a distance between the supports.

35. The method of claim 31 32, wherein the normalizing comprises changing a stiffness of the upper layer of each first and second element.

36. The method of claim 35, wherein changing the stiffness comprises changing the Young'"'"'s modulus of the upper layer of each first and second element.

37. The method of claim 35, wherein changing the stiffness comprises forming apertures in the upper layer to reduce the stiffness thereof.

38. The method of claim 33, wherein the normalizing comprises changing a configuration of the electrode of each first or second element.

39. The method of claim 38, wherein changing a configuration of the electrode comprises forming apertures therein.

40. The method of claim 30, wherein the elements are formed on a dielectric material, the normalization then comprising wherein normalizing the differences comprises changing the dielectric properties of the dielectric material.

41. The method of claim 30, wherein the first and second elements are pixels.

42. A microelectromechanical systems device comprising:

a first element having a first element characteristic and at least two layers with a first gap between the two layers, wherein one layer of the at least two layers of the first element is configured to move relative to another layer and substantially close the first gap upon applying at least a first voltage to the first element; and

a second element having a second element characteristic and at least two layers with a second gap between the two layers, wherein one layer of the at least two layers of the second element is configured to move relative to another layer and substantially close the second gap upon applying at least a second voltage to the second element, wherein the first and second element characteristics are different, wherein a size of the first gap is different than a size of the second gap, wherein the first and second voltages comprise respective mimimum sufficient voltages sufficient to substantially close the gap in the respective element, and wherein the first and second voltages are substantially the same.

43. The microelectromechanical systems device of claim 42, further comprising a circuit configured to apply the first voltage to at least the first element and the second voltage to at least the second element.

44. The microelectromechanical systems device of claim 43, wherein the driving circuit comprises an electrode layer in each of the first and second elements, and wherein the element characteristics of the first and second elements relate to the presence of at least one aperture in the electrode layer of at least one of the first and second elements.

45. The microelectromechanical systems device of claim 42, further comprising a plurality of the first and second elements arranged in a substantially co-planar array.

46. The microelectromechanical systems device of claim 45, further comprising at least two of the substantially co-planar arrays, wherein one of said at least two substantially co-planar arrays comprises only first elements and one of said at least two substantially co-planar arrays comprises only second elements.

47. The microelectromechanical systems device of claim 42, wherein the at least two layers of the respective first and second elements are continuous.

48. The microelectromechanical systems device of claim 42, wherein each movable layer is supported by a support structure comprising a plurality of supports spaced along a first axis and extending in a direction which is transverse to the first axis, and each support having a support surface to support the movable layer above the other of the at least two layers of the respective element.

49. The microelectromechanical systems device of claim 48, wherein the element characteristics of the first and second elements relate to the spacing between the supports along the first axis, wherein the spacing is a function of the size of the gap between the at least two layers of the respective element.

50. The microelectromechanical systems device of claim 48, wherein the element characteristics of the first and second elements relate to an area of the support surface of each support, and wherein the area of the support surface is a function of the height of the gap between the at least two layers.

51. The microelectromechanical systems device of claim 42, wherein the element characteristics of the first and second elements relate to a Young'"'"'s Modulus of the movable layer, wherein the Young'"'"'s Modulus is a function of the size of the gap of the respective element.

52. The microelectromechanical systems device of claim 42, wherein the element characteristics of the first and second elements relate to a thickness of the movable layer, wherein the thickness is a function of the size of the gap of the respective element.

53. The microelectromechanical systems device of claim 42, wherein the element characteristics of the first and second elements relate to the presence of at least an aperture formed on the movable layer of at least one of the first and second elements.

54. The microelectromechanical systems device of claim 42, wherein the element characteristics of the first and second elements relate to a tensile stress of the movable layer, wherein the tensile stress is a function of the size of the gap of the respective element.

55. The microelectromechanical systems device of claim 42, wherein the element characteristics of the first and second element relate to a dielectric material of the first and second elements, wherein the dielectric material comprises a dielectric constant that is a function of the size of the gap of the respective element.

56. The microelectromechanical systems device of claim 42, wherein the element characteristics of the first and second elements relate to a dielectric material of the first and second elements, wherein a thickness of the dielectric material is a function of the size of the gap of the respective element.

57. The microelectromechanical systems device of claim 42, wherein the minimum voltage is the same for the first and second elements.

58. The microelectromechanical systems device of claim 42, wherein each of the first and second elements are interferometric modulators configured to modulate light.

59. The microelectromechanical systems device of claim 58, further comprising a third element, wherein the first, second and third elements each comprise an interferometric modulators, each element differing in a height of its gap to reflect red, blue, or green light, respectively.

60. A microelectromechanical systems device comprising:

a first element comprising a first electrode and at least two layers with a first gap between the two layers, wherein at least one of the at least two layers of the first element is configured to move relative to another layer and substantially close the first gap upon applying a first voltage to at least the first electrode; and

a second element comprising a second electrode and at least two layers with a second gap between the two layers, wherein a size of the first gap is different than a size of the second gap, wherein at least one of the at least two layers of the second element is configured to move relative to another layer and substantially close the second gap upon applying a second voltage to at least the second electrode, wherein the first and second voltages are different;

wherein a plurality of said first and second elements are arranged in a substantially co-planar array.

61. The microelectromechanical systems device of claim 60, further comprising a circuit configured to apply the first voltage to at least the first electrode and the second voltage to at least the second electrode.

62. The microelectromechanical systems device of claim 60, wherein the first electrode is located over one of the at least two layers of the first element, and the second electrode is located over one of the at least two layers of the second element.

63. The microelectromechanical systems device of claim 60, further comprising at least two of the substantially co-planar arrays, wherein one of said at least two substantially co-planar arrays comprises only first elements and one of said at least two substantially co-planar arrays comprises only second elements.

64. The microelectromechanical systems device of claim 60, wherein the at least two layers of the respective first and second elements are continuous.

65. The microelectromechanical systems device of claim 60, wherein in each of the first and second elements the layer configured to move relative to another layer is supported by a support structure comprising a plurality of supports spaced along a first axis and extending in a direction which is transverse to the first axis.

66. The microelectromechanical systems device of claim 65, wherein the spacing between the supports along the first axis is a function of the size of the gap between the at least two layers of the respective element.

67. The microelectromechanical systems device of claim 65, wherein an area of the support surface of each support is a function of the height of the gap between the at least two layers of the respective element.

68. The microelectromechanical systems device of claim 60, wherein in each of the first and second elements the layer configured to move relative to another layer is characterized by a Young'"'"'s Modulus, wherein the Young'"'"'s Modulus is a function of the size of the gap of the respective element.

69. The microelectromechanical systems device of claim 60, wherein in each of the first and second elements the layer configured to move relative to another layer has a thickness that is a function of the size of the gap of the respective element.

70. The microelectromechanical systems device of claim 60, wherein at least the element having the largest gap size has at least one aperture formed in the layer configured to move relative to another layer.

71. The microelectromechanical systems device of claim 60, wherein in each of the first and second elements the layer configured to move relative to another layer is subject to a tensile stress that is a function of the size of the gap of the respective element.

72. The microelectromechanical systems device of claim 60, wherein the element having the smallest gap size has at least one aperture formed in its electrode layer.

73. The microelectromechanical systems device of claim 60, wherein each of the first and second elements further comprises a dielectric material located between the at least two layers, wherein the dielectric material is characterized by a dielectric constant that is a function of the size of the gap of the respective element.

74. The microelectromechanical systems device of claim 60, wherein each of the elements is an interferometric modulator configured to modulate light.

75. The microelectromechanical systems device of claim 74, further comprising a third element, wherein the first, second and third elements each comprise an interferometric modulators, each of the elements differing in a height of its gap to reflect one of red, blue, and green light.