High force MEMS device

• US 7,692,521 B1
• Filed: 05/12/2006
• Issued: 04/06/2010
• Est. Priority Date: 05/12/2005
• Status: Expired due to Fees

• Current Assignee: Microassembly Technologies Incorporated
• Original Assignee: Microassembly Technologies Incorporated
• Inventors: Cohn, Michael B.
• Primary Examiner(s): Mai; Anh T
• Assistant Examiner(s): Rojas; Bernard
• Application Number:
  US11/433,044
• Time in Patent Office: 1,425 Days
• Field of Search: 335/78, 335/75, 200/181, 333/101
• US Class Current: 335/78
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

Problems with the short lifetime of MEMS devices, low actuation forces, contaminant build-up on contacts, etc. are minimized by a MEMS device with an improved cantilever design that enables high force while maintaining large gaps. The improved cantilever design both allows for high force and fast switching while minimizing damage to contacts. The improved design can be fabricated on one or two substrates, which are bonded together with a seal ring to provide a packaged MEMS device.

Claims

1. A MEMS device with a cantilever design, the device comprising:

a substrate with a stationary contact affixed thereto;

an anchor affixed to the substrate;

a torsion arm affixed to the anchor by a first torsion hinge with a first axis; and

a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, the moveable contact positioned at an end of the cantilever plate adjacent to the second torsion hinge, wherein the first torsion hinge is adapted to rotate the cantilever plate in a first direction about the first axis toward or away from the substrate in response to an actuating force and the second torsion hinge is adapted to rotate the cantilever plate in a second direction opposite the first direction about the second axis toward or away from the substrate in response to the actuating force moving the moveable contact into contact with the stationary contact or separating the moveable contact from the stationary contact.

2. The device of claim 1, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward the substrate in response to an increase in electric potential of the cantilever plate relative to the substrate and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward the substrate in response to a further increase in the electric potential moving the moveable contact into contact with the stationary contact.

3. The device of claim 1, wherein the second torsion hinge is adapted to rotate the cantilever plate about the second axis away from the substrate in response to an decrease in electric potential of the cantilever plate relative to the substrate and the first torsion hinge is adapted to rotate the cantilever plate about the first axis away from the substrate in response to a further decrease in the electric potential separating the moveable contact from the stationary contact.

4. The device of claim 1, further comprising a second substrate in aligned confronting relation with the substrate, wherein the anchor, torsion arm, first and second torsion hinges, and cantilever plate with moveable contact are formed on the second substrate instead of the substrate.

5. The device of claim 4, wherein the substrate and the second substrate are bonded together and the first and second torsion hinges are adapted move the cantilever plate on the second substrate toward or away from the stationary contact on the substrate.

6. The device of claim 4, wherein the substrate and the second substrate are bonded together and wherein the device further comprises a seal ring around the bonded substrates to hermetically seal the substrates together.

7. The device of claim 6, further comprising a signal path that enters and exits a cavity formed between the bonded substrates using feedthroughs selected from a group consisting of:

vias, lateral feedthroughs, and combinations thereof.

8. The device of claim 1, wherein one or more of the anchor, torsion arm and cantilever plate are fabricated out of a material selected from a group consisting of:

silicon, a top single crystalline silicon layer of a silicon on insulator substrate, polysilicon, doped silicon, silicon geranium, gold, nickel, dielectrics, ceramic, and combinations thereof.

9. The device of claim 1, wherein the actuating force is selected from a group consisting of:

electrostatic, electromagnetic, thermal, electrothermal, shape memory alloy, piezo, and combinations thereof.

10. The device of claim 1, wherein at least one of the stationary and the moveable contact are fabricated out of a material selected from a group consisting of:

gold, gold nickel alloy, platinum, ruthenium, iridium, rhodium, ruthenium oxide, tungsten, rhenium, carbon, and combinations thereof.

11. A method for actuating a MEMS device including a substrate with a stationary contact affixed thereto, an anchor affixed to the substrate, a torsion arm affixed to the anchor by a first torsion hinge with a first axis, and a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, the method comprising:

applying an actuating force to the MEMS device;

responsive to the actuating force, rotating the cantilever plate in a first direction about the first axis of the first torsion hinge toward the substrate to move the moveable contact into contact with the stationary contact in a state of initial closure; and

responsive to the actuating force, rotating the cantilever plate in a second direction opposite the first direction about the second axis of the second torsion hinge toward the substrate, wherein the rotation of the cantilever plate about the first and second axes moves the moveable contact into a state of full contact with the stationary contact.

12. The method of claim 11, wherein the MEMS device is a micro-switch.

13. The method of claim 11, wherein the state of initial closure further comprises a state in which the moveable contact is in contact with and positioned at an angle relative to the stationary contact.

14. The method of claim 11, wherein rotating the cantilever plate in a second direction further comprises rotating the cantilever plate into a position in which the cantilever plate is parallel to the substrate.

15. The method of claim 11, wherein rotation of the cantilever plate about the first and second axes brings the moveable contact into contact with the stationary contact in such a manner that a surface of the moveable contact moves across at least a portion of a surface of the stationary contact.

16. The method of claim 15, wherein movement of the surface of the moveable contact across at least a portion of the surface of the stationary contact creates a scrubbing motion that removes at least some contaminants on the surfaces of one or both of the contacts.

17. The method of claim 11, wherein a gap between the moveable and stationary contacts during an open state is at least 2 microns.

18. The method of claim 11, wherein applying an actuating force comprises raising the electric potential of the cantilever plate relative to the substrate.

19. The method of claim 18, wherein rotating the cantilever plate about a first axis occurs in response to a raising of the electric potential and rotating the cantilever plate about the second axis occurs in response to a raising of the electric potential.

20. A method for separating contacts on a MEMS device including a substrate with a stationary contact affixed thereto, an anchor affixed to the substrate, a torsion arm affixed to the anchor by a first torsion hinge with a first axis, and a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contact, the moveable contact being in contact with the stationary contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, the method comprising:

reducing application of an actuating force applied to the MEMS device;

responsive to the reduced actuating force, rotating the cantilever plate in a first direction about the second axis of the second torsion hinge away from the substrate to move the moveable contact into only partial contact with the stationary contact; and

responsive to the reduced actuating force, rotating the cantilever plate in a second direction opposite the first direction about the first axis of the first torsion hinge away from the substrate, wherein the rotation of the cantilever plate about the first and second axes fully separates the moveable contact from the stationary contact into an open state.

21. The method of claim 20, wherein a gap between the moveable and stationary contacts after being separated is at least 2 microns.

22. The method of claim 20, wherein the state of partial contact further comprises a state in which the moveable contact is in contact with and positioned at an angle relative to the stationary contact.

23. The method of claim 20, wherein before reducing the application of the actuation force, the cantilever plate is a position in which the cantilever plate is parallel to the substrate.

24. The method of claim 20, wherein rotation of the cantilever plate about the first and second axes initially separates the moveable contact from the stationary contact in such a manner that only a portion of a surface of the moveable contact is in contact with the stationary contact.

25. The method of claim 24, wherein initial separation creates an unzipping motion that peels apart the moveable and stationary contacts.

26. The method of claim 20, wherein reducing application of an actuating force comprises removing the actuating force.

27. The method of claim 20, wherein reducing application of an actuating force comprises lowering an electric potential of the cantilever plate relative to the substrate.

28. The method of claim 27, wherein rotating the cantilever plate about a second axis occurs in response to a lowering of the electric potential and rotating the cantilever plate about the first axis occurs in response to a lowering of the electric potential.

29. A MEMS device with a cantilever design, the device comprising:

a first substrate with a stationary contact affixed thereto;

a second substrate with an anchor affixed thereto, wherein the second substrate is in aligned confronting relation with the first substrate, the first and second substrates being bonded together;

a seal ring surrounding the bonded first and second substrates to hermetically seal the bonded substrates together to form a cavity between the bonded substrates;

a signal path that enters and exits the cavity using feedthroughs selected from a group consisting of;

vias, lateral feedthroughs, and combinations thereof,

a torsion arm affixed to the anchor by a first torsion hinge with a first axis; and

a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, the moveable contact positioned at an end of the cantilever plate adjacent to the second torsion hinge, the cantilever plate being substantially formed from silicon, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward or away from the substrate in response to an actuating force and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward or away from the substrate in response to the actuating force moving the moveable contact into contact with the stationary contact or separating the moveable contact from the stationary contact.

30. The device of claim 29, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward the first substrate in response to an increase in electric potential of the cantilever plate relative to the first substrate and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward the first substrate in response to a increase in the electric potential moving the moveable contact into contact with the stationary contact.

31. The device of claim 29, wherein the second torsion hinge is adapted to rotate the cantilever plate about the second axis away from the first substrate in response to an decrease in electric potential of the cantilever plate relative to the first substrate and the first torsion hinge is adapted to rotate the cantilever plate about the first axis away from the first substrate in response to a decrease in the electric potential separating the moveable contact from the stationary contact.

32. The device of claim 29, further comprising a horn contact affixed to the cantilever plate at an edge adjacent to the moveable contact, wherein the horn contact provides stabilization of the device as the cantilever plate is moved toward or away from the first substrate.

33. A MEMS device with a cantilever design, the device comprising:

a substrate with a stationary contact affixed thereto;

an anchor affixed to the substrate;

a torsion arm affixed to the anchor by a first torsion hinge with a first axis; and

a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contacts and a horn contact affixed to the cantilever plate at an edge adjacent to the moveable contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward or away from the substrate in response to an actuating force and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward or away from the substrate in response to the actuating force moving the moveable contact into contact with the stationary contact or separating the moveable contact from the stationary contact, wherein the horn contact is adapted to contact the substrate upon actuation before the moveable contact comes into contact with the stationary contact.

34. The device of claim 33, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward the substrate in response to an increase in electric potential of the cantilever plate relative to the substrate and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward the substrate in response to a further increase in the electric potential moving the moveable contact into contact with the stationary contact.

35. The device of claim 33, wherein the second torsion hinge is adapted to rotate the cantilever plate about the second axis away from the substrate in response to an decrease in electric potential of the cantilever plate relative to the substrate and the first torsion hinge is adapted to rotate the cantilever plate about the first axis away from the substrate in response to a further decrease in the electric potential separating the moveable contact from the stationary contact.

36. The device of claim 33, further comprising a second substrate in aligned confronting relation with the substrate, wherein the anchor, torsion arm, first and second torsion hinges, and cantilever plate with moveable contact are formed on the second substrate instead of the substrate.

37. The device of claim 36, wherein the substrate and the second substrate are bonded together and the first and second torsion hinges are adapted move the cantilever plate on the second substrate toward or away from the stationary contact on the substrate.

38. The device of claim 36, wherein the substrate and the second substrate are bonded together and wherein the device further comprises a seal ring around the bonded substrates to hermetically seal the substrates together.

39. The device of claim 38, further comprising a signal path that enters and exits a cavity formed between the bonded substrates using feedthroughs selected from a group consisting of:

vias, lateral feedthroughs, and combinations thereof.

40. The device of claim 33, wherein one or more of the anchor, torsion arm and cantilever plate are fabricated out of a material selected from a group consisting of:

silicon, a top single crystalline silicon layer of a silicon on insulator substrate, polysilicon, doped silicon, silicon geranium, gold, nickel, dielectrics, ceramic, and combinations thereof.

41. The device of claim 33, wherein the actuating force is selected from a group consisting of:

electrostatic, electromagnetic, thermal, electrothermal, shape memory alloy, piezo, and combinations thereof.

42. The device of claim 33, wherein at least one of the stationary and the moveable contact are fabricated out of a material selected from a group consisting of:

gold, gold nickel alloy, platinum, ruthenium, iridium, rhodium, ruthenium oxide, tungsten, rhenium, carbon, and combinations thereof.

43. The device of claim 33, wherein the cantilever plate is adapted to rotate about an axis of the horn contact and the second axis simultaneously when the moveable contact is moved toward or away from the stationary contact.

44. A MEMS device with a cantilever design, the device comprising:

a substrate with a stationary contact affixed thereto;

an anchor affixed to the substrate;

a torsion arm affixed to the anchor by a first torsion hinge with a first axis; and

a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contacts and a second moveable contact affixed to the cantilever plate adjacent to the moveable contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward or away from the substrate in response to an actuating force and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward or away from the substrate in response to the actuating force moving the moveable contact into contact with the stationary contact or separating the moveable contact from the stationary contact, wherein the second moveable contact is adapted to maintain a parallel gap between and to prevent direct contact between the cantilever plate and the substrate upon actuation.

45. The device of claim 44, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward the substrate in response to an increase in electric potential of the cantilever plate relative to the substrate and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward the substrate in response to a further increase in the electric potential moving the moveable contact into contact with the stationary contact.

46. The device of claim 44, wherein the second torsion hinge is adapted to rotate the cantilever plate about the second axis away from the substrate in response to an decrease in electric potential of the cantilever plate relative to the substrate and the first torsion hinge is adapted to rotate the cantilever plate about the first axis away from the substrate in response to a further decrease in the electric potential separating the moveable contact from the stationary contact.

47. The device of claim 44, further comprising a second substrate in aligned confronting relation with the substrate, wherein the anchor, torsion arm, first and second torsion hinges, and cantilever plate with moveable contact are formed on the second substrate instead of the substrate.

48. The device of claim 47, wherein the substrate and the second substrate are bonded together and the first and second torsion hinges are adapted move the cantilever plate on the second substrate toward or away from the stationary contact on the substrate.

49. The device of claim 47, wherein the substrate and the second substrate are bonded together and wherein the device further comprises a seal ring around the bonded substrates to hermetically seal the substrates together.

50. The device of claim 49, further comprising a signal path that enters and exits a cavity formed between the bonded substrates using feedthroughs selected from a group consisting of:

vias, lateral feedthroughs, and combinations thereof.

51. The device of claim 44, wherein one or more of the anchor, torsion arm and cantilever plate are fabricated out of a material selected from a group consisting of:

silicon, a top single crystalline silicon layer of a silicon on insulator substrate, polysilicon, doped silicon, silicon geranium, gold, nickel, dielectrics, ceramic, and combinations thereof.

52. The device of claim 44, wherein the actuating force is selected from a group consisting of:

electrostatic, electromagnetic, thermal, electrothermal, shape memory alloy, piezo, and combinations thereof.

53. The device of claim 44, wherein at least one of the stationary and the moveable contact are fabricated out of a material selected from a group consisting of:

gold, gold nickel alloy, platinum, ruthenium, iridium, rhodium, ruthenium oxide, tungsten, rhenium, carbon, and combinations thereof.

54. A method for actuating a MEMS device including a substrate with a stationary contact affixed thereto, an anchor affixed to the substrate, a torsion arm affixed to the anchor by a first torsion hinge with a first axis, and a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contacts and a second moveable contact affixed to the cantilever plate adjacent to the moveable contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, the method comprising:

applying an actuating force to the MEMS device;

responsive to the actuating force, rotating the cantilever plate about the first axis of the first torsion hinge toward the substrate; and

responsive to the actuating force, rotating the cantilever plate about the second axis of the second torsion hinge toward the substrate, wherein the rotation of the cantilever plate about the first and second axes first moves the second moveable contact into contact with the substrate and then moves the moveable contact into contact with the stationary contact.

55. The method of claim 54, wherein the MEMS device is a micro-switch.

56. The method of claim 54, wherein the rotation about the first axis moves the moveable contact into a state of initial closure with the stationary contact.

57. The method of claim 54, wherein the rotation about the second axis moves the moveable contact into a state of full contact with the stationary contact.

58. The method of claim 54, wherein rotation of the cantilever plate about the first and second axes brings the moveable contact into contact with the stationary contact in such a manner that a surface of the moveable contact moves across at least a portion of a surface of the stationary contact.

59. The method of claim 58, wherein movement of the surface of the moveable contact across at least a portion of the surface of the stationary contact creates a scrubbing motion that removes at least some contaminants on the surfaces of one or both of the contacts.

60. The method of claim 54, wherein a gap between the moveable and stationary contacts during an open state is at least 2 microns.

61. The method of claim 54, wherein applying an actuating force comprises raising the electric potential of the cantilever plate relative to the substrate.

62. The method of claim 61, wherein rotating the cantilever plate about a first axis occurs in response to a raising of the electric potential and rotating the cantilever plate about the second axis occurs in response to a raising of the electric potential.

63. A method for separating contacts on a MEMS device including a substrate with a stationary contact affixed thereto, an anchor affixed to the substrate, a torsion arm affixed to the anchor by a first torsion hinge with a first axis, and a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contact and a second moveable contact affixed to the cantilever plate adjacent to the moveable contact, the moveable contact being in contact with the stationary contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, the method comprising:

reducing application of an actuating force applied to the MEMS device;

responsive to the reduced actuating force, rotating the cantilever plate about the second axis of the second torsion hinge away from the substrate; and

responsive to the reduced actuating force, rotating the cantilever plate about the first axis of the first torsion hinge away from the substrate, wherein the rotation of the cantilever plate about the first and second axes first moves the second moveable contact to no longer be in contact with the substrate and then separates the moveable contact from the stationary contact.

64. The method of claim 63, wherein a gap between the moveable and stationary contacts after being separated is at least 2 microns.

65. The method of claim 63, wherein the rotation about the second axis moves the moveable contact into a state of initial separation from the stationary contact.

66. The method of claim 63, wherein the rotation about the second axis moves the device into an open state of full separation of the moveable contact from the stationary contact.

67. The method of claim 63, wherein rotation of the cantilever plate about the first and second axes initially separates the moveable contact from the stationary contact in such a manner that only a portion of a surface of the moveable contact is in contact with the stationary contact.

68. The method of claim 67, wherein initial separation creates an unzipping motion that peels apart the moveable and stationary contacts.

69. The method of claim 63, wherein reducing application of an actuating force comprises removing the actuating force.

70. The method of claim 63, wherein reducing application of an actuating force comprises lowering an electric potential of the cantilever plate relative to the substrate.

71. The method of claim 70, wherein rotating the cantilever plate about a second axis occurs in response to a lowering of the electric potential and rotating the cantilever plate about the first axis occurs in response to a lowering of the electric potential.

72. A MEMS device with a cantilever design, the device comprising:

a first substrate with a stationary contact affixed thereto;

a second substrate with an anchor affixed thereto, wherein the second substrate is in aligned confronting relation with the first substrate, the first and second substrates being bonded together;

a seal ring surrounding the bonded first and second substrates to hermetically seal the bonded substrates together to form a cavity between the bonded substrates;

a signal path that enters and exits the cavity using feedthroughs selected from a group consisting of;

vias, lateral feedthroughs, and combinations thereof;

a torsion arm affixed to the anchor by a first torsion hinge with a first axis; and

a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contacts and a horn contact affixed to the cantilever plate at an edge adjacent to the moveable contact, the cantilever plate connected to the torsion arm by a second torsion hinge with a second axis, the cantilever plate being substantially formed from silicon, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward or away from the substrate in response to an actuating force and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward or away from the substrate in response to the actuating force moving the moveable contact into contact with the stationary contact or separating the moveable contact from the stationary contact, wherein the horn contact is adapted to contact the first substrate upon actuation before the moveable contact comes into contact with the stationary contact.

73. The device of claim 72, wherein the first torsion hinge is adapted to rotate the cantilever plate about the first axis toward the first substrate in response to an increase in electric potential of the cantilever plate relative to the first substrate and the second torsion hinge is adapted to rotate the cantilever plate about the second axis toward the first substrate in response to a increase in the electric potential moving the moveable contact into contact with the stationary contact.

74. The device of claim 72, wherein the second torsion hinge is adapted to rotate the cantilever plate about the second axis away from the first substrate in response to an decrease in electric potential of the cantilever plate relative to the first substrate and the first torsion hinge is adapted to rotate the cantilever plate about the first axis away from the first substrate in response to a decrease in the electric potential separating the moveable contact from the stationary contact.

75. The device of claim 72, wherein the horn contact provides stabilization of the device as the cantilever plate is moved toward or away from the first substrate.

76. A MEMS device with a cantilever design, the device comprising:

a substrate with a stationary contact affixed thereto;

an anchor affixed to the substrate;

a torsion arm moveably affixed to the anchor by a first hinge; and

a cantilever plate with a moveable contact affixed thereto in aligned confronting relation to the stationary contact, the cantilever plate moveably connected to the torsion arm by a second hinge wherein the first hinge is configured for a first stage of rotation about a first axis toward or away from the substrate and the second hinge is configured to be stiffer than the first hinge for a second stage of rotation about a second axis toward or away from the substrate, the rotation about the axes occurring in response to the actuating force for moving the moveable contact.