MEMS mass-spring-damper systems using an out-of-plane suspension scheme

• US 8,640,541 B2
• Filed: 05/27/2010
• Issued: 02/04/2014
• Est. Priority Date: 05/27/2009
• Status: Active Grant

• Current Assignee: King Abdullah University of Science and Technology
• Original Assignee: King Abdullah University of Science and Technology
• Inventors: Abdel Aziz, Ahmed Kamal Said, Sharaf, Abdel Hameed, Serry, Mohamed Yousef, Sedky, Sherif Salah
• Primary Examiner(s): Chang, Leonard
• Assistant Examiner(s): HULS, NATALIE F
• Application Number:
  US12/789,051
• Publication Number:
  US 20110030472A1
• Time in Patent Office: 1,349 Days
• Field of Search: 735/041.2, 735/041.4, 735/041, 735/143.26
• US Class Current: 73/504.12
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 3/0062 Devices moving in two or more dimensions, i.e. having special features which allow movement in more than one dimension
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/082 for two degrees of freedom of movement of a single mass

Abstract

MEMS mass-spring-damper systems (including MEMS gyroscopes and accelerometers) using an out-of-plane (or vertical) suspension scheme, wherein the suspensions are normal to the proof mass, are disclosed. Such out-of-plane suspension scheme helps such MEMS mass-spring-damper systems achieve inertial grade performance. Methods of fabricating out-of-plane suspensions in MEMS mass-spring-damper systems (including MEMS gyroscopes and accelerometers) are also disclosed.

Claims

1. A MEMS gyroscope, comprising:

a. a proof mass having a horizontal planar dimension;

b. one or more anchors; and

c. one or more movable combs connected to the proof mass and to the one or more anchors by a plurality of suspensions;

d. wherein said plurality of suspensions are out-of-plane with the horizontal planar dimension of the proof mass and are perpendicular to the proof mass and at least one comb moves parallel to the proof mass.

2. The MEMS gyroscope of claim 1, wherein said MEMS gyroscope is an inertial grade MEMS gyroscope.

3. The MEMS gyroscope of claim 1, wherein said proof mass, together with said one or more movable combs, have a combined mass ranging from 30 μ

g to 3 mg.

4. The MEMS gyroscope of claim 1, wherein said proof mass is positioned below said suspensions.

5. The MEMS gyroscope of claim 1, wherein said suspensions have a cross-section ranging from 5×

5 μ

m² to 100×

100 μ

m².

6. The MEMS gyroscope of claim 1, wherein said suspensions have a length ranging from 150 μ

m to 600 μ

m.

7. The MEMS gyroscope of claim 1, wherein said one or more movable combs rest on said suspensions.

8. The MEMS gyroscope of claim 1, wherein said one or more movable combs are comprised of first and second sense combs and first and second drive combs.

9. The MEMS gyroscope of claim 1, wherein said MEMS gyroscope is a three-fold symmetric gyroscope.

10. The MEMS gyroscope of claim 1, wherein said proof mass, said one or more anchors, said one or more movable combs, and said suspensions are comprised of crystalline Silicon.

11. The MEMS gyroscope of claim 1, wherein said MEMS gyroscope is bulk micromachined.

12. The MEMS gyroscope of claim 1, wherein said proof mass has a length and width ranging from 100 μ

m to 3 mm and a thickness ranging from 10 μ

m to 300 μ

m.

13. The MEMS gyroscope of claim 1, wherein said proof mass is comprised of an upper mass and a lower mass.

14. The MEMS gyroscope of claim 13, wherein said lower mass has a smaller length than said upper mass.

15. The MEMS gyroscope of claim 14, wherein said lower mass is 100 μ

m to 200 μ

m shorter in length than said upper mass.

16. The MEMS gyroscope of claim 1, wherein said proof mass has a weight ranging from 30 μ

g to 3 mg.

17. The MEMS gyroscope of claim 1, wherein said proof mass, said one or more anchors, and said suspensions are comprised of crystalline Silicon.

18. The MEMS gyroscope of claim 1, wherein said proof mass rests on said suspensions.

19. The MEMS gyroscope of claim 1, wherein said suspensions have a cross-section ranging from 5×

5 μ

m² to 100×

100 μ

m².

20. The MEMS gyroscope of claim 1, wherein said suspensions have a length ranging from 250 μ

m to 600 μ

m.

21. The MEMS gyroscope of claim 1, comprising a drive structure and a sense structure, wherein the drive structure comprises at least one movable comb and the sense structure comprises at least one movable comb.

22. A quad-mass MEMS gyroscope, comprising:

a. a plurality of proof masses, each having a horizontal planar dimension;

b. one or more anchors; and

c. one or more movable combs connected to the plurality of proof masses and to the one or more anchors by a plurality of suspensions;

d. wherein said suspensions are out-of-plane with the horizontal planar dimension of said at least one of the proof masses and are perpendicular to the proof masses mass and at least one comb moves parallel to one of the proof masses.

23. The quad-mass MEMS gyroscope of claim 22, comprising a drive structure and a sense structure, wherein the drive structure comprises at least one movable comb and the sense structure comprises at least one movable comb.

24. The quad-mass MEMS gyroscope of claim 22, wherein said one or more movable combs are comprised of a plurality of sense combs and a plurality of drive combs.

25. The quad-mass MEMS gyroscope of claim 24, wherein each proof mass has its own respective drive comb, but said sense combs are shared by said proof masses.

26. A MEMS mass-spring-damper system, comprising:

a. at least one proof mass having a horizontal planar dimension;

b. one or more anchors; and

c. one or more movable structures connected to said at least one proof mass and to the one or more anchors by a plurality of suspensions;

d. wherein said suspensions are out-of-plane with the horizontal planar dimension of at least one of the proof masses and are perpendicular to the proof mass and at least one movable structure moves parallel to the proof mass.

27. The MEMS mass-spring-damper system of claim 26, wherein said MEMS mass-spring-damper system is an inertial grade range MEMS mass-spring-damper system.

28. The MEMS mass-spring-damper system of claim 26, wherein said MEMS mass-spring-damper system is bulk micromachined.