Serrated MEMS Resonators

• US 20080150390A1
• Filed: 10/30/2007
• Published: 06/26/2008
• Est. Priority Date: 12/20/2006
• Status: Abandoned Application

• Current Assignee: David Raymond Pedersen, Paul Merritt Hagelin
• Original Assignee: David Raymond Pedersen, Paul Merritt Hagelin
• Inventors: Pedersen, David Raymond, Hagelin, Paul Merritt
• Application Number:
  US11/929,438
• Publication Number:
  US 20080150390A1
• Time in Patent Office: Days
• US Class Current: 310/300
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 9/02275 Comb electrodes
• CPC Class Codes: H03H 9/2468 Tuning fork resonators

Abstract

One embodiment of the present invention sets forth a serrated tooth actuator for driving MEMS resonator structures. The actuator includes a fixed drive electrode having a serrated tooth surface opposing a MEMS resonator arm also having a serrated tooth surface, where the MEMS resonator arm is configured to rotate towards the drive electrode when an AC signal is applied to the drive electrode. Such a configuration permits higher amplitude signals to be applied to the drive electrode without the performance of the actuator being compromised by nonlinear effects. In addition, the serrated tooth configuration enables a sufficiently high actuating force to be maintained even though the distance traversed by the MEMS resonator arm during operation is quite small. Further, the serrated configuration allows a MEMS resonator system to withstand larger fluctuations in voltage and larger substrate stresses without experiencing a substantial shift in resonant frequency.

Claims

1. A microelectromechanical system (MEMS) for generating a timing signal, the system comprising:

a MEMS resonator including a first member having an irregular surface comprised of a first plurality of teeth with an arc-to-point profile; and

a first electrode having an irregular surface comprised of a second plurality of teeth with an arc-to-point profile that opposes the irregular surface of the first member, wherein the teeth in the first plurality are interleaved with the teeth in the second plurality when the first member is stationary, and

wherein the first member is configured to rotate or bend towards the first electrode in response to a drive signal.

2. The system of claim 1, wherein each tooth in the first plurality of teeth is separated from at least one opposing tooth in the second plurality of teeth by a gap when the first member is stationary.

3. The system of claim 2, wherein the gap between each tooth in the first plurality of teeth and the at least one opposing tooth in the second plurality of teeth is substantially the same for each tooth in the first plurality of teeth.

4. The system of claim 3, wherein the gap is approximately 400 nanometers and the first member is approximately 200 microns in length.

5. The system of claim 4, wherein the gaps between the teeth in the first plurality of teeth located proximately to one end of the first member and the opposing teeth in the second plurality of teeth decrease to approximately 200 nanometers when the first member rotates or bends towards the first electrode.

6. The system of claim 1, wherein the MEMS resonator is fixed to an underlying substrate by only one anchor.

7. The system of claim 1, wherein the first electrode is a drive electrode and the first member is configured to rotate or bend towards the drive electrode in response to the drive signal being applied to the drive electrode.

8. The system of claim 7, further comprising a sense electrode having an irregular surface comprised of a third plurality of teeth with an arc-to-point profile, wherein:

the first member further includes an irregular surface comprised of a fourth plurality of teeth with an arc-to-point profile,

the teeth in the third plurality are interleaved with the teeth in the fourth plurality when the first member is stationary, and

the first member is further configured to rotate or bend towards the sense electrode in response to the drive signal being applied to the drive electrode.

9. The system of claim 1, wherein the first electrode is a sense electrode and the first member is configured to rotate or bend towards the sense electrode in response to the drive signal being applied to a drive electrode.

10. The system of claim 1, wherein the MEMS resonator further includes a second member having an irregular surface comprised of a third plurality of teeth with an arc-to-point profile, and further comprising:

a second electrode having an irregular surface comprised of a fourth plurality of teeth with an arc-to-point profile that opposes the irregular surface of the second member, wherein the teeth in the third plurality are interleaved with the teeth in the fourth plurality when the second member is stationary, and

wherein the second member is configured to rotate or bend towards the second electrode in response to the drive signal.

11. The system of claim 10, wherein the rotation or bending of the first member towards the first electrode is substantially equal and opposite to the rotation or bending of the second member towards the second electrode.

12. The system of claim 1, wherein the first plurality of teeth and the second plurality of teeth are configured such that the capacitance between a first portion of the first member and the first electrode is positive and the capacitance between a second portion of the first member and the first electrode is negative when the first member rotates or bends towards the first electrode.

13. The system of claim 1, wherein the first member is configured to rotate and bend towards the first electrode in response to the drive signal.

14. An electronic device, comprising:

application circuitry; and

a microelectromechanical system (MEMS) for generating a timing signal for the application circuitry, the system comprising;

a MEMS resonator including a first member having an irregular surface comprised of a first plurality of teeth with an arc-to-point profile, and

a first electrode having an irregular surface comprised of a second plurality of teeth with an arc-to-point profile that opposes the irregular surface of the first member, wherein the teeth in the first plurality are interleaved with the teeth in the second plurality when the first member is stationary, and

wherein the first member is configured to rotate or bend towards the first electrode in response to a drive signal.

15. The electronic device of claim 14, wherein each tooth in the first plurality of teeth is separated from at least one opposing tooth in the second plurality of teeth by a gap when the first member is stationary.

16. The electronic device of claim 25, wherein the gap between each tooth in the first plurality of teeth and the at least one opposing tooth in the second plurality of teeth is substantially the same for each tooth in the first plurality of teeth.

17. The electronic device of claim 16, wherein the gap is approximately 400 nanometers and the first member is approximately 200 microns in length.

18. The electronic device of claim 17, wherein the gaps between the teeth in the first plurality of teeth located proximately to one end of the first member and the opposing teeth in the second plurality of teeth decrease to approximately 200 nanometers when the first member rotates or bends towards the first electrode.

19. The electronic device of claim 14, wherein the MEMS resonator is fixed to an underlying substrate by only one anchor.

20. The electronic device of claim 14, wherein the first electrode is a drive electrode and the first member is configured to rotate or bend towards the drive electrode in response to the drive signal being applied to the drive electrode.

21. The electronic device of claim 20, further comprising a sense electrode having an irregular surface comprised of a third plurality of teeth with an arc-to-point profile, wherein:

the first member further includes an irregular surface comprised of a fourth plurality of teeth with an arc-to-point profile,

the teeth in the third plurality are interleaved with the teeth in the fourth plurality when the first member is stationary, and

the first member is configured to rotate or bend towards the sense electrode in response to the drive signal being applied to the drive electrode.

22. The electronic device of claim 14, wherein the MEMS resonator further includes a second member having an irregular surface comprised of a third plurality of teeth with an arc-to-point profile, and further comprising:

a second electrode having an irregular surface comprised of a fourth plurality of teeth with an arc-to-point profile that opposes the irregular surface of the second member, wherein the teeth in the third plurality are interleaved with the teeth in the fourth plurality when the second member is stationary, and

wherein the second member is configured to rotate or bend towards the second electrode in response to the drive signal.

23. The electronic device of claim 22, wherein the rotation or bending of the first member towards the first electrode is substantially equal and opposite to the rotation or bending of the second member towards the second electrode.

24. The electronic device of claim 14, wherein the first plurality of teeth and the second plurality of teeth are configured such that the capacitance between a first portion of the first member and the first electrode is positive and the capacitance between a second portion of the first member and the first electrode is negative when the first member rotates or bends towards the first electrode.

25. The electronic device of claim 14, wherein the first member is configured to rotate and bend towards the first electrode in response to the drive signal.

26. A microelectromechanical system (MEMS) for generating a timing signal, the system comprising:

a MEMS resonator including a first member having an irregular surface comprised of a first plurality of teeth; and

a first electrode having an irregular surface comprised of a second plurality of teeth that opposes the irregular surface of the first member,

wherein;

the teeth in the first plurality are interleaved with the teeth in the second plurality when the first member is stationary,

the first member is configured to rotate or bend towards the first electrode in response to a drive signal,

a first portion of the first plurality of teeth has a first profile and a second portion of the first plurality of teeth has a second profile, the first profile being different than the second profile, and

a first portion of the second plurality of teeth has a third profile and a second portion of the second plurality of teeth has a fourth profile, the third profile being different than the fourth profile.

27. The system of claim 26, wherein each of the first, second, third, and fourth profiles comprises an arc-to-point profile, a serrated tooth profile, a rounded serrated tooth profile, or an interlocked tooth profile.

28. The system of claim 26, wherein each tooth in the first plurality of teeth is separated from at least one opposing tooth in the second plurality of teeth by a gap when the first member is stationary.

29. The system of claim 28, wherein the gap between each tooth in the first plurality of teeth and the at least one opposing tooth in the second plurality of teeth is substantially the same for each tooth in the first plurality of teeth.

30. The system of claim 29, wherein the gap is approximately 400 nanometers and the first member is approximately 200 microns in length.

31. The system of claim 30, wherein the gaps between the teeth in the first plurality of teeth located proximately to one end of the first member and the opposing teeth in the second plurality of teeth decrease to approximately 200 nanometers when the first member rotates or bends towards the first electrode.

32. The system of claim 26, wherein the MEMS resonator is fixed to an underlying substrate by only one anchor.

33. The system of claim 26, wherein the first electrode is a sense electrode, and the first member is configured to rotate or bend towards the sense electrode in response to the drive signal being applied to a drive electrode.

34. The system of claim 33, wherein:

the drive electrode has an irregular surface comprised of a third plurality of teeth that opposes the irregular surface of the first member,

the first member further has an irregular surface comprised of a fourth plurality of teeth,

the teeth in the third plurality are interleaved with the teeth in the fourth plurality when the first member is stationary,

a first portion of the third plurality of teeth has a fifth profile and a second portion of the third plurality of teeth has a sixth profile, the fifth profile being different than the sixth profile, and

a first portion of the fourth plurality of teeth has a seventh profile and a second portion of the fourth plurality of teeth has an eighth profile, the seventh profile being different than the eighth profile.

35. The system of claim 26, wherein the MEMS resonator further includes a second member having an irregular surface comprised of a third plurality of teeth, and further comprising a second electrode having an irregular surface comprised of a fourth plurality of teeth that opposes the irregular surface of the second member, and wherein:

the teeth in the third plurality are interleaved with the teeth in the fourth plurality when the second member is stationary,

the second member is configured to rotate or bend towards the second electrode in response to the drive signal,

a first portion of the third plurality of teeth has a fifth profile and a second portion of the third plurality of teeth has a sixth profile, the fifth profile being different than the sixth profile, and

a first portion of the fourth plurality of teeth has a seventh profile and a second portion of the fourth plurality of teeth has an eighth profile, the seventh profile being different than the eighth profile.

36. The system of claim 35, wherein the rotation or bending of the first member towards the first electrode is substantially equal and opposite to the rotation or bending of the second member towards the second electrode.

37. The system of claim 26, wherein the first plurality of teeth and the second plurality of teeth are configured such that the capacitance between a first portion of the first member and the first electrode is positive and the capacitance between a second portion of the first member and the first electrode is negative when the first member rotates or bends towards the first electrode.

38. The system of claim 26, wherein the first member is configured to rotate and bend towards the first electrode in response to the drive signal.

39. An electronic device, comprising:

application circuitry; and

a microelectromechanical system (MEMS) for generating a timing signal for the application circuitry, the system comprising;

a MEMS resonator including a first member having an irregular surface comprised of a first plurality of teeth; and

a first electrode having an irregular surface comprised of a second plurality of teeth that opposes the irregular surface of the first member,

wherein;

the teeth in the first plurality are interleaved with the teeth in the second plurality when the first member is stationary,

the first member is configured to rotate or bend towards the first electrode in response to a drive signal,

a first portion of the first plurality of teeth has a first profile and a second portion of the first plurality of teeth has a second profile, the first profile being different than the second profile, and

a first portion of the second plurality of teeth has a third profile and a second portion of the second plurality of teeth has a fourth profile, the third profile being different than the fourth profile.

40. The electronic device of claim 39, wherein each of the first, second, third, and fourth profiles comprises an arc-to-point profile, a serrated tooth profile, a rounded serrated tooth profile, or an interlocked tooth profile.

41. The electronic device of claim 39, wherein each tooth in the first plurality of teeth is separated from at least one opposing tooth in the second plurality of teeth by a gap when the first member is stationary.

42. The electronic device of claim 41, wherein the gap between each tooth in the first plurality of teeth and the at least one opposing tooth in the second plurality of teeth is substantially the same for each tooth in the first plurality of teeth.

43. The electronic device of claim 42, wherein:

the gap is approximately 400 nanometers;

the first member is approximately 200 microns in length; and

the gaps between the teeth in the first plurality of teeth located proximately to one end of the first member and the opposing teeth in the second plurality of teeth decrease to approximately 200 nanometers when the first member rotates or bends towards the first electrode.

44. The electronic device of claim 39, wherein the MEMS resonator is fixed to an underlying substrate by only one anchor.

45. The electronic device of claim 39, wherein the first electrode is a sense electrode, and the first member is configured to rotate or bend towards the sense electrode in response to the drive signal being applied to a drive electrode.

46. The electronic device of claim 45, wherein:

the drive electrode has an irregular surface comprised of a third plurality of teeth that opposes the irregular surface of the first member,

the first member further has an irregular surface comprised of a fourth plurality of teeth,

the teeth in the third plurality are interleaved with the teeth in the fourth plurality when the first member is stationary,

a first portion of the third plurality of teeth has a fifth profile and a second portion of the third plurality of teeth has a sixth profile, the fifth profile being different than the sixth profile, and

a first portion of the fourth plurality of teeth has a seventh profile and a second portion of the fourth plurality of teeth has an eighth profile, the seventh profile being different than the eighth profile.

47. The electronic device of claim 39, wherein the MEMS resonator further includes a second member having an irregular surface comprised of a third plurality of teeth, and further comprising a second electrode having an irregular surface comprised of a fourth plurality of teeth that opposes the irregular surface of the second member, and wherein:

the teeth in the third plurality are interleaved with the teeth in the fourth plurality when the second member is stationary,

the second member is configured to rotate or bend towards the second electrode in response to the drive signal,

a first portion of the third plurality of teeth has a fifth profile and a second portion of the third plurality of teeth has a sixth profile, the fifth profile being different than the sixth profile, and

a first portion of the fourth plurality of teeth has a seventh profile and a second portion of the fourth plurality of teeth has an eighth profile, the seventh profile being different than the eighth profile.

48. The electronic device of claim 47, wherein the rotation or bending of the first member towards the first electrode is substantially equal and opposite to the rotation or bending of the second member towards the second electrode.

49. The electronic device of claim 39, wherein the first plurality of teeth and the second plurality of teeth are configured such that the capacitance between a first portion of the first member and the first electrode is positive and the capacitance between a second portion of the first member and the first electrode is negative when the first member rotates or bends towards the first electrode.

50. The electronic device of claim 39, wherein the first member is configured to rotate and bend towards the first electrode in response to the drive signal.

51. A microelectromechanical system (MEMS) for generating a timing signal, the system comprising:

a MEMS resonator including a first member having an irregular surface comprised of a first plurality of teeth; and

a first electrode having an irregular surface comprised of a second plurality of teeth that opposes the irregular surface of the first member, wherein the teeth in the first plurality are interlocked with the teeth in the second plurality when the first member is stationary, and

wherein the first member is configured to rotate or bend towards the first electrode in response to a drive signal.

52. The system of claim 51, wherein each tooth in the first plurality of teeth is separated from at least one opposing tooth in the second plurality of teeth by a gap when the first member is stationary.

53. The system of claim 52, wherein the gap between each tooth in the first plurality of teeth and the at least one opposing tooth in the second plurality of teeth is substantially the same for each tooth in the first plurality of teeth.

54. The system of claim 53, wherein the gap is approximately 400 nanometers and the first member is approximately 200 microns in length.

55. The system of claim 54, wherein the gaps between the teeth in the first plurality of teeth located proximately to one end of the first member and the opposing teeth in the second plurality of teeth decrease to approximately 200 nanometers when the first member rotates or bends towards the first electrode.

56. The system of claim 51, wherein the MEMS resonator is fixed to an underlying substrate by only one anchor.

57. The system of claim 51, wherein the first electrode is a drive electrode and the first member is configured to rotate or bend towards the drive electrode in response to the drive signal being applied to the drive electrode.

58. The system of claim 57, further comprising a sense electrode having an irregular surface comprised of a third plurality of teeth, wherein:

the first member further includes an irregular surface comprised of a fourth plurality of teeth,

the teeth in the third plurality are interlocked with the teeth in the fourth plurality when the first member is stationary, and

the first member is further configured to rotate or bend towards the sense electrode in response to the drive signal being applied to the drive electrode.

59. The system of claim 51, wherein the first electrode is a sense electrode and the first member is configured to rotate or bend towards the sense electrode in response to the drive signal being applied to a drive electrode.

60. The system of claim 51, wherein the MEMS resonator further includes a second member having an irregular surface comprised of a third plurality of teeth, and further comprising:

a second electrode having an irregular surface comprised of a fourth plurality of teeth that opposes the irregular surface of the second member, wherein the teeth in the third plurality are interlocked with the teeth in the fourth plurality when the second member is stationary, and

wherein the second member is configured to rotate or bend towards the second electrode in response to the drive signal.

61. The system of claim 60, wherein the rotation or bending of the first member towards the first electrode is substantially equal and opposite to the rotation or bending of the second member towards the second electrode.

62. The system of claim 51, wherein the first plurality of teeth and the second plurality of teeth are configured such that the capacitance between a first portion of the first member and the first electrode is positive and the capacitance between a second portion of the first member and the first electrode is negative when the first member rotates or bends towards the first electrode.

63. The system of claim 51, wherein the first member is configured to rotate and bend towards the first electrode in response to the drive signal.

64. An electronic device, comprising:

application circuitry; and

a microelectromechanical system (MEMS) for generating a timing signal for the application circuitry, the system comprising;

a MEMS resonator including a first member having an irregular surface comprised of a first plurality of teeth, and

a first electrode having an irregular surface comprised of a second plurality of teeth that opposes the irregular surface of the first member, wherein the teeth in the first plurality are interlocked with the teeth in the second plurality when the first member is stationary, and

wherein the first member is configured to rotate or bend towards the first electrode in response to a drive signal.

65. The electronic device of claim 64, wherein each tooth in the first plurality of teeth is separated from at least one opposing tooth in the second plurality of teeth by a gap when the first member is stationary.

66. The electronic device of claim 65, wherein the gap between each tooth in the first plurality of teeth and the at least one opposing tooth in the second plurality of teeth is substantially the same for each tooth in the first plurality of teeth.

67. The electronic device of claim 66, wherein the gap is approximately 400 nanometers and the first member is approximately 200 microns in length.

68. The electronic device of claim 67, wherein the gaps between the teeth in the first plurality of teeth located proximately to one end of the first member and the opposing teeth in the second plurality of teeth decrease to approximately 200 nanometers when the first member rotates or bends towards the first electrode.

69. The electronic device of claim 64, wherein the MEMS resonator is fixed to an underlying substrate by only one anchor.

70. The electronic device of claim 64, wherein the first electrode is a drive electrode and the first member is configured to rotate or bend towards the drive electrode in response to the drive signal being applied to the drive electrode.

71. The electronic device of claim 70, further comprising a sense electrode having an irregular surface comprised of a third plurality of teeth, wherein:

the first member further includes an irregular surface comprised of a fourth plurality of teeth,

the teeth in the third plurality are interlocked with the teeth in the fourth plurality when the first member is stationary, and

the first member is configured to rotate or bend towards the sense electrode in response to the drive signal being applied to the drive electrode.

72. The electronic device of claim 64, wherein the MEMS resonator further includes a second member having an irregular surface comprised of a third plurality of teeth, and further comprising:

a second electrode having an irregular surface comprised of a fourth plurality of teeth that opposes the irregular surface of the second member, wherein the teeth in the third plurality are interlocked with the teeth in the fourth plurality when the second member is stationary, and

wherein the second member is configured to rotate or bend towards the second electrode in response to the drive signal.

73. The electronic device of claim 72, wherein the rotation or bending of the first member towards the first electrode is substantially equal and opposite to the rotation or bending of the second member towards the second electrode.

74. The electronic device of claim 64, wherein the first plurality of teeth and the second plurality of teeth are configured such that the capacitance between a first portion of the first member and the first electrode is positive and the capacitance between a second portion of the first member and the first electrode is negative when the first member rotates or bends towards the first electrode.

75. The electronic device of claim 64, wherein the first member is configured to rotate and bend towards the first electrode in response to the drive signal.