Microelectromechanical gyroscopes and related apparatus and methods

• US 9,651,376 B2
• Filed: 01/28/2014
• Issued: 05/16/2017
• Est. Priority Date: 03/01/2010
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Zolfagharkhani, Guiti, Chen, David M., Mohanty, Pritiraj, Kuypers, Jan H., Gaidarzhy, Alexei
• Primary Examiner(s): Chapman, Jr., John
• Application Number:
  US14/166,138
• Publication Number:
  US 20140137648A1
• Time in Patent Office: 1,204 Days
• Field of Search: 7350412
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure

Abstract

In one embodiment, an apparatus comprises a micromechanical gyroscope and a circuit. The micromechanical gyroscope is configured to be excited in a first mode by a drive signal, and configured to be excited in a second mode by a gyroscopic effect. The circuit is coupled to the micromechanical gyroscope and configured to detect the gyroscopic effect when the micromechanical gyroscope is in the second mode.

Claims

1. An apparatus, comprising:

a substrate;

a plate, comprising a piezoelectric material, suspended from the substrate and excitable by a gyroscopic effect, the plate having a thickness and including a temperature compensation structure including at least one layer that has a stiffness that increases with increasing temperature over a temperature range and at least one layer that has a stiffness that decreases with increasing temperature over the temperature range;

a first electrode coupled to the plate and configured to excite a first mode of vibration in the plate; and

a second electrode coupled to the plate and configured to sense a second mode of vibration in the plate.

2. The apparatus of claim 1, wherein the plate has a fundamental mode, and wherein first electrode is configured to excite a mode of higher order than the fundamental mode.

3. The apparatus of claim 1, wherein the first mode of vibration has a first frequency and the second mode of vibration has a second frequency lower than the first frequency.

4. The apparatus of claim 1, wherein the plate is made of at least one of silicon or silicon oxide.

5. The apparatus of claim 1, wherein the first electrode is configured to excite an extensional mode of vibration in the plate.

6. The apparatus of claim 1, wherein the piezoelectric material of the plate is a piezoelectric thin film, and wherein the plate further comprises a support on which the piezoelectric thin film is disposed, the support being formed of a material that is not piezoelectric.

7. The apparatus of claim 1, wherein the first electrode is one electrode of a first pair of electrodes configured to excite the first mode of vibration, and wherein the second electrode is one electrode of a second pair of electrodes configured to sense the second mode of vibration, and wherein the electrodes of the first pair of electrodes are disposed on a same side of the plate as each other, and wherein the electrodes of the second pair of electrodes are disposed on opposite sides of the plate from each other.

8. An apparatus, comprising:

a substrate;

a member, comprising a support and a piezoelectric material layer on the support, the member being moveably coupled to the substrate at a first anchor and a second anchor, the member being excitable by a gyroscopic effect and including a temperature compensation structure including at least one layer that has a stiffness that increases with increasing temperature over a temperature range and at least one layer that has a stiffness that decreases with increasing temperature over the temperature range; and

a circuit coupled to the member and configured to detect a gyroscopically-induced mode of vibration in the member.

9. The apparatus of claim 8, wherein the temperature compensation structure comprises at least three layers.

10. The apparatus of claim 8, wherein the support of the member is made of at least one of silicon or silicon oxide.

11. The apparatus of claim 8, further comprising a first pair of electrodes disposed on the member and configured to drive vibration of the member, and a second pair of electrodes coupled to the circuit and configured to sense the gyroscopically-induced mode of vibration.

12. The apparatus of claim 8, wherein the member includes a first piezoelectric thin film, a second piezoelectric thin film, and an electrode layer disposed between the first piezoelectric thin film and the second piezoelectric thin film.

13. An apparatus, comprising:

a micromechanical gyroscope configured to be excited by a gyroscopic effect, wherein the micromechanical gyroscope includes a multi-layer temperature-compensated stack having at least two different layers of different materials, the micromechanical gyroscope including a first electrode positioned to excite a first mode of vibration in the micromechanical gyroscope and a second electrode configured to generate a detection signal in response to a second mode of vibration of the micromechanical gyroscope; and

a circuit coupled to the micromechanical gyroscope and configured to detect the gyroscopic effect.

14. The apparatus of claim 13, wherein the multi-layer temperature-compensated stack includes a first layer of a first material and a second layer of a second material having a lower acoustical loss than the first material.

15. The apparatus of claim 14, wherein the first material comprises silicon dioxide.

16. The apparatus of claim 13, wherein the circuit provides a positive gain feedback loop when a drive signal is applied to the first electrode of the micromechanical gyroscope.

17. The apparatus of claim 13, wherein the first electrode is part of a first differential electrode pair disposed on a common surface of the micromechanical gyroscope, and wherein the second electrode is part of a second differential electrode pair, the second differential electrode pair including the second electrode and a third electrode positioned on a different layer of the micromechanical gyroscope than the second electrode.

18. The apparatus of claim 13, wherein the micromechanical gyroscope has a fundamental mode, and wherein the first mode of vibration is a higher order mode.

19. The apparatus of claim 18, further comprising a low-pass filter coupled to a mixer, the low-pass filter configured to output an output voltage responsive to a drive signal being applied to the first electrode of the micromechanical gyroscope.

20. The apparatus of claim 13, further comprising a first piezoelectric thin film, a second piezoelectric thin film, and an electrode layer disposed between the first piezoelectric thin film and the second piezoelectric thin film.