MODE-MATCHED SINGLE PROOF-MASS DUAL-AXIS GYROSCOPE AND METHOD OF FABRICATION

• US 20130283911A1
• Filed: 12/05/2011
• Published: 10/31/2013
• Est. Priority Date: 12/07/2010
• 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, Sung, Wang-kyung, Zaman, Mohammad
• Granted Patent: US 9,726,489 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• 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 19/5684 the devices involving a micromechanical structure
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

A single proof-mass, dual-axis gyroscope apparatus comprises a resonating body member and first and second electrodes each capacitively coupled to the resonating body member by a respective lateral capacitive air gap and a vertical capacitive air gap. The width of one of the lateral capacitive air gap of the first electrode is substantially smaller than the vertical capacitive air gap. The width of one of the vertical capacitive air gap of the second electrode is substantially smaller than the lateral capacitive air gap. The apparatus claimed can address the process variation such as vertical and lateral dimension variation by electrostatic tuning method.

Claims

1. A single proof-mass, dual-axis gyroscope apparatus comprising:

a resonating body member;

first and second electrodes each capacitively coupled to the resonating body member by a respective lateral capacitive dielectric gap and a vertical capacitive dielectric gap; and

wherein a width of one of the lateral capacitive dielectric gap and the vertical capacitive dielectric gap of the first electrode is substantially smaller than that of a similar dielectric gap of the second electrode.

2. The apparatus of claim 1, wherein the resonating body member is connected to a central structure.

3. The apparatus of claim 2, wherein the resonating body member is supported by at least one support member connecting the resonating body member to the central structure.

4. The apparatus of claim 1, wherein the resonating body member is an annulus.

5. The apparatus of claim 1, wherein the resonating body member is a polygon.

6. The apparatus of claim 1, wherein the first electrode is capacitively coupled to the resonating body member by a first lateral capacitive dielectric gap substantially smaller than a first vertical capacitive dielectric gap, and wherein the second electrode is capacitively coupled to the resonating body member by a second vertical capacitive dielectric gap substantially smaller than a second lateral capacitive dielectric gap.

7. The apparatus of claim 1, wherein at least one of the lateral capacitive dielectric gap and the vertical capacitive dielectric gap is made from a non-conductive material.

8. The apparatus of claim 1, wherein the first electrode is a drive electrode and the second electrode is a sense electrode.

9. The apparatus of claim 1, wherein the apparatus is configured to utilize an in-plane drive mode, a first orthogonal out-of-plane sense mode orthogonal to the in-plane drive mode, and a second orthogonal out-of-plane sense mode orthogonal to the first orthogonal out-of-plane sense mode and the in-plane drive mode.

10. The apparatus of claim 6, wherein the second electrode comprises four sense electrodes defined on top of anti-nodes of out-of-plane modes.

11. The apparatus of claim 10, wherein the in-plane drive mode has anti-nodes aligned with the anti-nodes of out-of-plane modes.

12. The apparatus of claim 11, wherein the anti-nodes of a first out-of-plane mode are aligned with nodes of a second out-of-plane mode and the anti-nodes of the second out-of-plane mode are aligned with the nodes of the first out-of-plane mode.

13. The apparatus of claim 12, wherein the frequency of the in-plane drive mode, a first orthogonal out-of-plane sense mode, and a second orthogonal out-of-plane sense are mode-matched.

14. The apparatus of claim 13, wherein the resonating body is operated at a mode-matched condition in which the resonance frequencies for an in-plane drive mode and two out-of-plane sense modes are located at a specific frequency.

15. The apparatus of claim 13, wherein the resonating body is operated at a near mode-matched condition in which the resonance frequencies for an in-plane drive mode and two out-of-plane sense modes are located in a bandwidth range of approximately 3 dB within a specific frequency of operation.

16. The apparatus of claim 9, further comprising an in-plane frequency tuning electrode located at an anti-node of the in-plane drive mode.

17. The apparatus of claim 9, further comprising four out-of-plane frequency tuning electrodes separated from one another by approximately 90 degrees.

18. The apparatus of claim 6, wherein the first lateral capacitive dielectric gap is approximately 200 nm.

19. The apparatus of claim 6, wherein the second lateral capacitive dielectric gap is approximately 300 nm.

20. The apparatus of claim 6, wherein the first vertical capacitive dielectric gap and the second lateral capacitive dielectric gap are approximately 5 μ

m.

21. The apparatus of claim 1, further comprising quadrature cancellation electrodes.

22. The apparatus of claim 1, wherein the resonating body member is made from an anisotropic substrate.

23. The apparatus of claim 22, wherein the first electrode is located in at least one of a <

100> and

a <

110>

direction of the anisotropic substrate.

24. The apparatus of claim 1, wherein the resonating body member is made from an isotropic substrate.

25. The apparatus of claim 6, wherein the first electrode configured to actuate the resonating body is located in at least one of a <

100> and

a <

110>

direction of the isotropic substrate when utilized by a (100) silicon substrate.

26. The apparatus of claim 1, wherein the resonating body comprises at least one piezoelectric layer configured to excite and sense resonance modes of the resonating body.

27. The apparatus of claim 26, wherein the at least one piezoelectric layer is attached to a surface of at least one of the resonating body and support structures supporting the resonating body.

28. The apparatus of claim 1, further comprising at least one frequency tuning electrode, the frequency tuning electrode configured to substantially mode-match the resonating body member.

29. The apparatus of claim 28, wherein the frequency tuning electrode is separated from an anti-node of in-plane driving mode of the resonating body member by a capacitive dielectric gap.

30. The apparatus of claim 29, wherein the frequency tuning electrode is separated from an anti-node of out-of-plane mode of the resonating body by a capacitive dielectric gap.

31. The apparatus of claim 1, wherein the capacitive dielectric gaps comprise air.

32. A single proof-mass dual-axis gyroscope apparatus comprising:

a resonating body member;

a plurality of electrodes each capacitively coupled to the resonating body member by a lateral capacitive dielectric gap and a vertical capacitive dielectric gap; and

wherein a width of at least one dielectric gap capacitively coupling a first electrode to the resonating body member is substantially smaller than a width of at least one dielectric gap capacitively coupling a second electrode to the resonating body member.

33. The apparatus of claim 32, wherein a width of the lateral capacitive dielectric gap of one of said plurality of electrodes is substantially smaller than that of another of said plurality of electrodes.

34. The apparatus of claim 32, wherein a width of the vertical capacitive dielectric gap of one of said plurality of electrodes is substantially smaller than that of another of said plurality of electrodes.

35. The apparatus of claim 32, wherein the vertical capacitive dielectric gap of one of said plurality of electrodes has a width that is substantially dissimilar to a width of the lateral capacitive dielectric gap of another of said plurality of electrodes.

36. A method for fabricating a single proof-mass dual-axis gyroscope apparatus comprising:

A) forming a resonating body member having a top surface and a side surface;

B) forming a side electrode separated from the side surface of the resonating body member by a first lateral capacitive dielectric gap substantially smaller than a first vertical capacitive dielectric gap separating the side electrode from the top surface of the resonating body member; and

C) forming a top electrode separated from the top surface of the resonating body member by a second vertical capacitive dielectric gap substantially smaller than a second lateral capacitive dielectric gap separating the top electrode from the side surface of the resonating body member.