Apparatus and method for anchoring electrodes in MEMS devices

• US 8,919,199 B2
• Filed: 12/01/2011
• Issued: 12/30/2014
• Est. Priority Date: 12/01/2010
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Judy, Michael W., Geen, John A., Johari-Galle, Houri
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US13/308,687
• Publication Number:
  US 20120137773A1
• Time in Patent Office: 1,125 Days
• Field of Search: 735/041.2, 735/041.3, 735/040.4, 735/143.2, 735/143.6, 735/243.8
• US Class Current: 73/504.12
• 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
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

One or more electrodes that interact with a movable mass in a MEMS device are anchored or otherwise supported from both the top and bottom and optionally also from one or more of the lateral sides other than the transduction side (i.e., the side of the electrode facing the mass) in order to severely restrict movement of the electrodes such as from interaction with the mass and/or external forces.

Claims

1. A MEMS device comprising:

a movable mass having a top surface, a bottom surface, and at least one side surface; and

at least one electrode configured to interact with the mass, wherein the at least one electrode is adjacent to a side surface of the mass, and wherein a top surface of the electrode is anchored to an overlying support structure and wherein a bottom surface of the electrode is anchored to an underlying support structure in order to constrain movement of the electrode, wherein the electrode is anchored to the overlying support structure via a plurality of top anchors and is anchored to the underlying support structure via a plurality of bottom anchors.

2. A MEMS device according to claim 1, wherein the at least one electrode is configured to interact with the mass electrostatically.

3. A MEMS device according to claim 1, wherein the electrode is anchored to the overlying support structure via a plurality of top anchors that protrude at least partially into the electrode and the overlying support structure and is anchored to the underlying support structure via a plurality of bottom anchors that protrude at least partially into the electrode and the underlying support structure.

4. A MEMS device according to claim 1, wherein the electrode is further anchored by at least one surface other than the top surface and the bottom surface to at least one side support structure.

5. A MEMS device according to claim 1, wherein the electrode is formed on an electrode support structure, and wherein the electrode includes at least one side anchor through at least a portion of the electrode support structure.

6. A MEMS device according to claim 5, wherein the electrode support structure and the mass are fabricated from a common layer of material or from a different layer of material.

7. A MEMS device according to claim 1, wherein the at least one electrode is configured for at least one of driving and sensing movement of the mass.

8. A MEMS device according to claim 1, wherein the overlying support structure is a device cap.

9. A MEMS device according to claim 1, wherein the underlying support structure is a device substrate.

10. A MEMS gyroscope comprising:

a resonant mass having a top surface, a bottom surface, and at least one side surface; and

at least one electrode configured to interact with the mass, wherein the at least one electrode is adjacent to a side surface of the mass, and wherein a top surface of the electrode is anchored to an overlying support structure and wherein a bottom surface of the electrode is anchored to an underlying support structure in order to constrain movement of the electrode, wherein the electrode is anchored to the overlying support structure via a plurality of top anchors and is anchored to the underlying support structure via a plurality of bottom anchors.

11. A MEMS gyroscope according to claim 10, wherein the at least one electrode is configured to interact with the mass electrostatically.

12. A MEMS gyroscope according to claim 10, wherein the electrode is anchored to the overlying support structure via a plurality of top anchors that protrude at least partially into the electrode and the overlying support structure and is anchored to the underlying support structure via a plurality of bottom anchors that protrude at least partially into the electrode and the underlying support structure.

13. A MEMS gyroscope according to claim 10, wherein the electrode is further anchored by at least one surface other than the top surface and the bottom surface to at least one side support structure.

14. A MEMS gyroscope according to claim 10, wherein the electrode is formed on an electrode support structure, and wherein the electrode includes at least one anchor through at least a portion of the electrode support structure.

15. A MEMS gyroscope according to claim 14, wherein the anchor through at least a portion of the electrode support structure is formed by trench refilling with a conductive or non-conductive material.

16. A MEMS gyroscope according to claim 14, wherein the electrode support structure and the mass are fabricated from a common layer of material or from a different layer of material.

17. A MEMS device according to claim 10, wherein the overlying support structure is a device cap.

18. A MEMS device according to claim 10, wherein the underlying support structure is a device substrate or a cap.

19. A MEMS gyroscope according to claim 10, wherein the gyroscope is a shell-type gyroscope in which the resonant mass is configured to resonate in a flexure mode or bulk mode in response to receipt of an electrostatic signal, and wherein the at least one electrode is configured for at least one of driving and sensing movement of the resonant mass.

20. A MEMS gyroscope according to claim 10, wherein the top surface of the resonant mass is anchored to an overlying support structure and wherein the bottom surface of the resonant mass is anchored to an underlying support structure in order to constrain movement of the resonant mass.

21. A MEMS gyroscope according to claim 10, wherein at least one of:

the top surface of the electrode and the top surface of the resonant mass are anchored to the same overlying support structure;

the top surface of the electrode and the top surface of the resonant mass are anchored to different overlying support structures;

the bottom surface of the electrode and the bottom surface of the resonant mass are anchored to the same underlying support structure; and

the bottom surface of the electrode and the bottom surface of the resonant mass are anchored to different underlying support structures.

22. A method for forming a MEMS device having a movable mass and at least one electrode configured to interact with the mass, the movable mass having a top surface, a bottom surface, and at least one side surface, wherein the at least one electrode is adjacent to a side surface of the mass, the method comprising:

anchoring a top surface of the electrode to an overlying support structure; and

anchoring a bottom surface of the electrode to an underlying support structure in order to constrain movement of the electrode, wherein the electrode is anchored to the overlying support structure via a plurality of top anchors and is anchored to the underlying support structure via a plurality of bottom anchors.

23. A method according to claim 22, further comprising:

anchoring the electrode by at least one surface other than the top surface and the bottom surface to at least one side support structure.