BULK ACOUSTIC WAVE GYROSCOPE

• US 20090266162A1
• Filed: 05/04/2009
• Published: 10/29/2009
• Est. Priority Date: 03/27/2006
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Ayazi, Farrokh, Johari, Houri
• Granted Patent: US 8,166,816 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• CPC Class Codes: G01C 19/5698 using acoustic waves, e.g. surface acoustic wave gyros

Abstract

Capacitive bulk acoustic wave x, y and z-axes gyroscopes implemented on (100) and (111) silicon substrates are disclosed. Exemplary gyroscopes comprise a handle substrate, a bulk acoustic wave resonator element supported by the handle substrate, and a plurality of electrodes surrounding and separated from the resonator element by very small capacitive gaps. The electrodes can excite and detect at least two degenerate bulk acoustic wave resonant modes in the resonator. Advantages include reduced size; higher Q, which improves noise and bias stability; larger bandwidth, and improved shock resistance. In addition, the high Q is maintained in atmospheric or near-atmospheric pressure which reduces the cost and complexity of the wafer-scale packaging of the gyroscope.

Claims

1. A gyroscope, comprising:

a bulk acoustic resonator;

at least one first electrode coupled to the bulk acoustic resonator, the at least one first electrode being positioned to excite vibration of the bulk acoustic resonator in a first bulk acoustic wave mode; and

at least one second electrode coupled to the bulk acoustic resonator, the at least one second electrode being positioned to detect vibration of the bulk acoustic resonator in a second bulk acoustic wave mode, the first and second bulk acoustic wave modes being degenerate.

2. The gyroscope of claim 1, wherein the bulk acoustic resonator has a disk-shaped structure.

3. The gyroscope of claim 2, wherein the bulk acoustic resonator is supported above a handle substrate by a support element positioned at a center of the bulk acoustic resonator, wherein the support element has a first diameter and the bulk acoustic resonator has a second diameter, wherein the first diameter is at least ten times smaller than the second diameter.

4. The gyroscope of claim 1, wherein the bulk acoustic resonator is solid, or perforated to include release holes.

5. The gyroscope of claim 1, wherein the bulk acoustic resonator is formed of a non-piezoelectric material.

6. The gyroscope of claim 1, wherein the bulk acoustic resonator is formed of a semiconducting, piezoelectric or metallic material.

7. The gyroscope of claim 6, wherein the bulk acoustic resonator is formed of single-crystalline semiconductor.

8. The gyroscope of claim 1, wherein a plurality of electrodes comprises the at least one first electrode and the at least one second electrode, wherein the plurality of electrodes surround the bulk acoustic resonator and are separated from the bulk acoustic resonator by gaps that are small enough to capacitively excite and detect bulk acoustic wave modes of vibration in the bulk acoustic resonator.

9. The gyroscope of claim 8, wherein each of the gaps has a width that is less than about 400 nanometers.

10. The gyroscope of claim 1, wherein the bulk acoustic resonator is disposed in a vacuum having a pressure higher than about 1 ton, and wherein the bulk acoustic resonator has a quality factor of at least 5,000.

11. The gyroscope of claim 1, further comprising:

a handle substrate supporting the bulk acoustic resonator, the handle substrate forming a plane;

wherein the gyroscope is configured to sense rate and/or angle of rotation about an axis perpendicular to the plane.

12. The gyroscope of claim 1, further comprising:

a handle substrate supporting the bulk acoustic resonator, the handle substrate forming a plane;

wherein the gyroscope is configured to sense rate and/or angle of rotation about at least one axis in the plane.

13. The gyroscope of claim 1, configured to sense rate and/or angle of rotation about three orthogonal axes.

14. The gyroscope of claim 1, wherein one or more bulk acoustic resonators, one or more pluralities of electrodes and support electronics are integrated on a single substrate to form an integrated inertial measurement unit.

15. The gyroscope of claim 1, wherein the first and second bulk acoustic wave modes of vibration are separated in orientation by 30°

or 45°

along a circumference of the bulk acoustic resonator.

16. The gyroscope of claim 1, wherein the bulk acoustic resonator comprises a disk-shaped structure comprising a perimeter around a circumference of the disk-shaped structure, a top, and a bottom, and wherein and the gyroscope further comprises:

at least one extended electrode that extends over the top of the disk-shaped structure.

17. The gyroscope of claim 1, wherein the bulk acoustic resonator has a vibration amplitude of no more than about 50 nanometers.

18. The gyroscope of claim 1, further comprising support electronics for excitation, readout and tuning of the bulk acoustic resonator.

19. A gyroscope, comprising:

a microelectromechanical resonator having a resonant frequency of 1 MHz or higher;

at least one first electrode coupled to the microelectromechanical resonator, the at least one first electrode being positioned to excite vibration of the microelectromechanical resonator in a first mode; and

at least one second electrode coupled to the microelectromechanical resonator, the at least one second electrode being positioned to detect vibration of the microelectromechanical resonator in a second mode.

20. The gyroscope of claim 19, wherein the microelectromechanical resonator comprises a disk-shaped structure.

21. The gyroscope of claim 20, wherein the microelectromechanical resonator is supported above a handle substrate by a support element positioned at a center of the microelectromechanical resonator.

22. The gyroscope of claim 19, wherein a plurality of electrodes comprises the at least one first electrode and the at least one second electrode, wherein the plurality of electrodes surround the microelectromechanical resonator and are separated from the microelectromechanical resonator by gaps that are small enough to capacitively excite and detect bulk acoustic wave modes of vibration in the microelectromechanical resonator.

23. The gyroscope of claim 22, wherein each of the gaps has a width that is less than about 400 nanometers.

24. The gyroscope of claim 19, wherein the microelectromechanical resonator is formed of single-crystalline semiconductor.

25. The gyroscope of claim 19, wherein the microelectromechanical resonator is solid, or perforated to include release holes.

26. The gyroscope of claim 19, further comprising:

a handle substrate supporting the microelectromechanical resonator, the handle substrate forming a plane;

wherein the gyroscope is configured to sense rate and/or angle of rotation about an axis perpendicular to the plane.

27. The gyroscope of claim 19, further comprising:

a handle substrate supporting the microelectromechanical resonator, the handle substrate forming a plane;

wherein the gyroscope is configured to sense rate and/or angle of rotation about at least one axis in the plane.

28. The gyroscope of claim 19, configured to sense rate and/or angle of rotation about three orthogonal axes.

29. The gyroscope of claim 19, wherein vibrations in the first and second modes are separated in orientation by 30°

or 45°

along a circumference of the microelectromechanical resonator.

30. The gyroscope of claim 19, wherein the microelectromechanical resonator comprises a disk-shaped structure comprising a perimeter around a circumference of the disk-shaped structure, a top, and a bottom, and wherein and the gyroscope further comprises:

at least one extended electrode that extends over the top of the disk-shaped structure.

31. The gyroscope of claim 19, wherein the microelectromechanical resonator has a vibration amplitude of no more than about 50 nanometers.