Method and apparatus for electrostatic mode-alignment on planar MEMS gyroscopes

• US 10,082,394 B2
• Filed: 05/31/2016
• Issued: 09/25/2018
• Est. Priority Date: 06/01/2015
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Rahafrooz, Amir, Serrano, Diego Emilio, Jafri, Ijaz
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US15/169,033
• Publication Number:
  US 20160349055A1
• Time in Patent Office: 847 Days
• CPC Class Codes: G01C 19/5684 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5698 using acoustic waves, e.g. surface acoustic wave gyros

Abstract

A MEMS BAW vibratory planar gyroscope having an in-plane electrode configuration for mode-alignment by utilizing alignment electrodes that have a height less than a full height of the gyroscope resonant body. Such alignment electrodes apply a force component that affects modes with both in-plane and out-of-plane movements. The gyroscope includes a resonant body having a height and a perimeter surface and electrodes disposed adjacent the exterior perimeter surface of the resonant body. At least one of the electrodes is an alignment electrode and has a height less than the height of the resonant body.

Claims

1. An apparatus comprising:

a resonant body having a first height dimension value h1 and an exterior perimeter surface; and

a plurality of electrodes disposed adjacent the exterior perimeter surface of the resonant body,

wherein at least one of the plurality of electrodes is an alignment electrode and has a second height dimension value h2 that is less than the first height dimension value h1 of the resonant body,

wherein the first height dimension value h1 and the second height dimension value h2 correspond to heights of top surfaces of the respective structures from a reference base.

2. The apparatus of claim 1, wherein the second height dimension value h2 is ½

of the first height dimension value h1.

3. The apparatus of claim 1, wherein multiple of the plurality of electrodes are alignment electrodes, each having the second height dimension value h2.

4. The apparatus of claim 1, wherein the resonant body has a vibratory mode characterized by in-plane mode anti-node locations and out-of-plane mode anti-node locations on the resonant body and wherein the at least one alignment electrode is disposed at a location about the exterior perimeter of the resonant body where an in-plane mode antinode location and an out-of-plane mode anti-node location coincide.

5. The apparatus of claim 4, wherein multiple of the plurality of electrodes are alignment electrodes, each having the second height dimension value h2 and wherein each of the multiple alignment electrode is disposed at a location about the exterior perimeter of the resonant body where an in-plane mode antinode location and an out-of-plane mode anti-node location coincide.

6. The apparatus of claim 3, wherein the exterior perimeter surface of the resonant body is substantially circular in shape.

7. The apparatus of claim 6, wherein pairs of the multiple alignment electrodes are disposed opposite one another about the circular perimeter of the resonant body.

8. An apparatus comprising:

a resonant body defined by a first height dimension value h1 and an exterior perimeter, the resonant body having a vibratory mode characterized by a plurality of in-plane mode anti-node locations and a plurality of out-of-plane mode anti-node locations on the resonant body; and

at least one electrode disposed at a location about the exterior perimeter of the resonant body where an in-plane mode antinode location and an out-of-plane mode anti-node location coincide,

wherein the at least one electrode is an alignment electrode.

9. The apparatus of claim 8, wherein the at least one alignment electrode has a second height dimension value h2 that is ½

of the first height dimension h1.

10. The apparatus of claim 9, wherein a plurality of electrodes are disposed adjacent the exterior perimeter surface of the resonant body.

11. The apparatus of claim 10, wherein multiple of the plurality of electrodes are alignment electrodes.

12. The apparatus of claim 11, wherein each of the multiple alignment electrodes is of the second height dimension value h2.

13. The apparatus of claim 12, wherein the second height dimension value h2 is approximately ½

of the first height dimension value h1.

14. The apparatus of claim 11, wherein each of the multiple alignment electrode is disposed at a location about the exterior perimeter of the resonant body where an in-plane mode antinode location and an out-of-plane mode anti-node location coincide.

15. A method of making a MEMS apparatus, comprising:

A) forming a resonant body having a first height dimension value h1 and an exterior perimeter surface; and

B) disposing at least one electrode adjacent the exterior perimeter surface of the resonant body,

wherein the at least one of the electrodes is an alignment electrode and has a second height dimension value h2 that is less than the first height dimension value h1 of the resonant body,

wherein the first height dimension value h1 and the second height dimension value h2 correspond to heights of top surfaces of the respective structures from a reference base.

16. The method of claim 15, wherein B) comprises:

B1) forming the at least one electrode to have the second height dimension value h2 be approximately ½

of the first height dimension value h1 of the resonant body.

17. The method of claim 15, wherein B) comprises:

B1) forming a plurality of electrodes disposed adjacent the exterior perimeter surface of the resonant body.

18. The method of claim 17, wherein B1) comprises:

B1a) forming the plurality of electrodes to have a second height dimension value h2 that is less than the first height dimension value h1 of the resonant body.

19. The method of claim 17, wherein the exterior perimeter surface of the resonant body is substantially circular in shape and wherein B1) comprises:

B1a) forming the plurality of electrodes in pairs disposed opposite one another about the circular exterior perimeter surface of the resonant body.

20. A gyroscope, comprising:

a resonant body having a first height dimension value h1 and an exterior perimeter surface, the resonant body having a vibratory mode characterized by a plurality of in-plane mode anti-node locations and a plurality of out-of-plane mode anti-node locations on the resonant body;

an opening defined in the resonant body;

a first plurality of side electrodes disposed adjacent the resonant body, each side electrode having a same height as the first height dimension value h1;

at least one alignment electrode disposed adjacent the resonant body at a location where an in-plane mode antinode location and an out-of-plane mode antinode location coincide,

wherein the at least one alignment electrode has a second height dimension value h2 that is less than the first height dimension value h1.

21. The gyroscope of claim 20, wherein the at least one alignment electrode is disposed adjacent the exterior perimeter surface.

22. The gyroscope of claim 20, wherein the at least one alignment electrode is disposed within the opening of the resonant body.

23. The gyroscope of claim 20, wherein the second height dimension value h2=0.5*h1.

24. The gyroscope of claim 20, wherein the resonant body is a planar resonant body.

25. The gyroscope of claim 20, wherein the plurality of side electrodes are disposed at the exterior perimeter surface of the resonant body.