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

Patent metadata

Field	Value
Publication number	US-10082394-B2
Application number	US-201615169033-A
Country	US
Kind code	B2
Filing date	May 31, 2016
Priority date	Jun 1, 2015
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

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.

First claim

What is claimed is:

1. An apparatus comprising:
a resonant body having a first height dimension value h 1 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 h 2 that is less than the first height dimension value h 1 of the resonant body,
wherein the first height dimension value h 1 and the second height dimension value h 2 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 h 2 is ½ of the first height dimension value h 1 .

3. The apparatus of claim 1 , wherein multiple of the plurality of electrodes are alignment electrodes, each having the second height dimension value h 2 .

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 h 2 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 h 1 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 h 2 that is ½ of the first height dimension h 1 .

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 h 2 .

13. The apparatus of claim 12 , wherein the second height dimension value h 2 is approximately ½ of the first height dimension value h 1 .

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 h 1 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 h 2 that is less than the first height dimension value h 1 of the resonant body,
wherein the first height dimension value h 1 and the second height dimension value h 2 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 h 2 be approximately ½ of the first height dimension value h 1 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 h 2 that is less than the first height dimension value h 1 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 h 1 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 h 1 ;
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 h 2 that is less than the first height dimension value h 1 .

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 h 2 =0.5*h 1 .

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.

Assignees

• Panasonic Corp

Inventors

• Rahafrooz Amir
• Serrano Diego Emilio
• Jafri Ijaz

Classifications

• G01C19/5698 Primary

  using acoustic waves, e.g. surface acoustic wave gyros · CPC title

• G01C19/5684

  the devices involving a micromechanical structure · CPC title