MEMS MASS-SPRING-DAMPER SYSTEMS USING AN OUT-OF-PLANE SUSPENSION SCHEME

• US 20110030472A1
• Filed: 05/27/2010
• Published: 02/10/2011
• 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: Serry, Mohamed Yousef, Sharaf, Abdel Hameed, Sedky, Sherif Salah, Aziz, Ahmed Kamal Said Abdel
• Granted Patent: US 8,640,541 B2
• Time in Patent Office: Days
• 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 shared proof mass;

b. one or more anchors;

c. one or more movable combs; and

d. a plurality of suspensions;

e. wherein said plurality of suspensions are out-of-plane with said shared 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 shared proof mass, together with said one or more movable combs, have a combined weight ranging from 30 μ

g to 3 mg.

4. The MEMS gyroscope of claim 1, wherein said shared 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 shared 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. A MEMS accelerometer, comprising:

a. a proof mass;

b. one or more anchors; and

c. a plurality of suspensions;

d. wherein said plurality of suspensions are out-of-plane with said proof mass.

13. The MEMS accelerometer of claim 12, wherein said MEMS accelerometer is an inertial grade MEMS accelerometer.

14. The MEMS accelerometer of claim 12, 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.

15. The MEMS accelerometer of claim 12, wherein said proof mass is comprised of an upper mass and a lower mass.

16. The MEMS accelerometer of claim 15, wherein said lower mass has a smaller length than said upper mass.

17. The MEMS accelerometer of claim 16, wherein said lower mass is 100 μ

m to 200 μ

m shorter in length than said upper mass.

18. The MEMS accelerometer of claim 12, wherein said proof mass has a weight ranging from 30 μ

g to 3 mg.

19. The MEMS accelerometer of claim 12, wherein said proof mass, said one or more anchors, and said suspensions are comprised of crystalline Silicon.

20. The MEMS accelerometer of claim 12, wherein said proof mass rests on said suspensions.

21. The MEMS accelerometer of claim 12, wherein said suspensions have a cross-section ranging from 5×

5 μ

m² to 100×

100 μ

m².

22. The MEMS accelerometer of claim 12, wherein said suspensions have a length ranging from 250 μ

m to 600 μ

m.

23. The MEMS accelerometer of claim 12, wherein said MEMS accelerometer is bulk micromachined.

24. A quad-mass MEMS gyroscope, comprising:

a. a plurality of proof masses;

b. one or more anchors;

c. one or more movable combs; and

d. a plurality of suspensions;

e. wherein said suspensions are out-of-plane with said proof masses.

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

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

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

a. at least one proof mass; and

b. a plurality of suspensions;

c. wherein said suspensions are out-of-plane with said at least one proof mass.

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

29. The MEMS mass-spring-damper system of claim 27, wherein said MEMS mass-spring-damper system is bulk micromachined.

30. A method for fabricating a vertical suspension in a substrate in a MEMS mass-spring-damper system, said method comprising the steps of:

a. realizing a first side and a second side of said vertical suspension by selectively etching through a top surface of said substrate; and

b. realizing a third side and a fourth side of said vertical suspension by selectively etching through a bottom surface of said substrate.

31. The method of claim 30, wherein said etching in steps (a) and (b) is performed using DRIE.

32. The method of claim 30, wherein said MEMS mass-spring-damper system is an inertial grade MEMS gyroscope.

33. The method of claim 30, wherein said MEMS mass-spring damper system is an inertial grade MEMS accelerometer.