Mechanical resonator device having phenomena-dependent electrical stiffness

• US 6,958,566 B2
• Filed: 08/13/2002
• Issued: 10/25/2005
• Est. Priority Date: 08/16/2001
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Hsu, Wan-Thai, Nguyen, Clark T.-C.
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US10/217,877
• Publication Number:
  US 20030051550A1
• Time in Patent Office: 1,169 Days
• Field of Search: 310/306, 310/309, 310/321, 310/365, 333154-156, 333/158, 333160-164
• US Class Current: 310/321
• CPC Class Codes: H03H 2009/02511 Vertical, i.e. perpendicular to the substrate plane
• CPC Class Codes: H03H 9/02448 of temperature influence
• CPC Class Codes: H03H 9/24 Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators

Abstract

A mechanical resonator device which has a phenomena-dependent electrical stiffness is provided. The phenomena may be temperature or acceleration, for example. The device includes a substrate and a resonator supported above the substrate by supports. The device further includes an electrode supported above the substrate adjacent the resonator by supports to obtain an electrode-to-resonator gap wherein electrical stiffness generated across the gap is phenomena-dependent to take instability of resonant frequency of the device caused by the phenomena into consideration.

Claims

1. A mechanical resonator device having a resonant frequency, the device comprising:

a micromechanical resonator; and

an electrode adjacent the micromechanical resonator to obtain an electrode-to-resonator gap wherein electrical stiffness generated across the gap is phenomena-dependent and wherein a control voltage between the electrode and the micromechanical resonator is applied to take instability of the resonant frequency caused by the phenomena into consideration rather than for excitation of the micromechanical resonator.

2. The device as claimed in claim 1, wherein the phenomena is temperature.

3. The device as claimed in claim 1, wherein the phenomena is acceleration.

4. The device as claimed in claim 1, wherein distance across the gap between the electrode and the resonator varies as a function of temperature.

5. The device as claimed in claim 4, further comprising supports for supporting the resonator and the electrode and wherein a material of the resonator and its supports expands at a different rate than a material of the electrode and its supports due to temperature.

6. The device as claimed in claim 1, wherein the device is substantially temperature-insensitive without the need for additional power consumption.

7. The device as claimed in claim 1, wherein the resonator is a polysilicon resonator.

8. The device as claimed in claim 7, wherein the resonator is a polysilicon resonator beam.

9. The device as claimed in claim 1, further comprising a substrate and supports for supporting the resonator and the electrode above the substrate.

10. The device as claimed in claim 9, wherein the substrate is a semiconductor substrate.

11. The device as claimed in claim 1, wherein the device has a frequency-versus-phenomena curve and wherein the frequency-versus-phenomena curve is specifically tailored.

12. The device as claimed in claim 1, wherein the device has a substantially zero temperature coefficient temperature at which the device may be biased.

13. The device as claimed in claim 1, wherein the device is a two-port, vertical, micromechanical resonator device.

14. The device as claimed in claim 1, wherein the electrode is supported above the resonator.

15. The device as claimed in claim 1, wherein distance across the gap and operating voltage of the electrode substantially cancel resonant frequency shifts caused by temperature.

16. The device as claimed in claim 1, further comprising a drive electrode structure formed at a position to allow electrostatic excitation of the resonator wherein the resonator and the drive electrode structure define a gap therebetween.

17. The device as claimed in claim 1, wherein the resonator is a single resonator beam.

18. The device as claimed in claim 1, wherein the electrode is metal electrode.

19. The device as claimed in claim 18, wherein the metal electrode is a plated metal electrode.

20. The device as claimed in claim 1, wherein the device is a phenomena sensor.

21. The device as claimed in claim 2, wherein the device is a temperature sensor.

22. The device as claimed in claim 3, wherein the device is an acceleration sensor.

23. The device as claimed in claim 1, wherein the supports for the electrode include at least one pair of off-axis anchors.

24. The device as claimed in claim 1, wherein the electrode is cut to reduce lateral expansion-induced stress in the electrode.

25. The device as claimed in claim 1, wherein the gap is a capacitive gap.

26. The device as claimed in claim 1, wherein the resonator is a flexural mode resonator.

27. The device as claimed in claim 1, wherein the control voltage is a bias voltage.

28. The device as claimed in claim 27, wherein the resonator is supported by a first structure, the electrode is supported by a second structure, the first and second structures comprise first and second materials, respectively, and the first and second materials have differing thermal expansion coefficients such that the gap varies during operation based on the differing thermal expansion coefficients.

29. A micromechanical resonator device, the device comprising:

a resonator supported by a first structure; and

an electrode supported by a second structure and adjacent the resonator to obtain an electrode-to-resonator gap spacing;

wherein the first and second structure comprise first and second materials, respectively,

the first and second materials have differing thermal expansion coefficients; and

the gap spacing varies during operation based on the differing thermal expansion coefficients.

30. The device as claimed in claim 29, wherein a bias voltage is applied between the resonator and the electrode.