High Performance Sensors and Methods for Forming the Same

• US 20100005884A1
• Filed: 07/09/2008
• Published: 01/14/2010
• Est. Priority Date: 07/09/2008
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Elliott, Richard, Bancu, Mirela G., Bickford, James A., Bernstein, Jonathan J., Weinberg, Marc S.
• Granted Patent: US 8,187,902 B2
• Time in Patent Office: Days
• US Class Current: 73/504.150
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion
• CPC Class Codes: Y10T 156/1039 Surface deformation only of sandwich or lamina [e.g., embossed panels]
• CPC Class Codes: Y10T 428/2495 Thickness [relative or absolute]

Abstract

A sensor includes a proof mass suspended by a suspension beam, the suspension beam having a thickness less than a thickness of the proof mass.

Claims

1. A sensor comprising:

a proof mass suspended over a substrate by a suspension beam,

wherein a thickness of the suspension beam is less than a thickness of the proof mass.

2. The sensor of claim 1, wherein the thickness of the proof mass is greater than approximately 23 μ

m.

3. The sensor of claim 1, wherein the thickness of the proof mass is between approximately 50 μ

m and approximately 1000 μ

m.

4. The sensor of claim 1, wherein a difference between the thickness of the suspension beam and the thickness of the proof mass is between approximately 10 μ

m and approximately 50 μ

m.

5. The sensor of claim 1, wherein the proof mass and the suspension beam comprise silicon.

6. The sensor of claim 1, wherein the substrate comprises glass.

7. The sensor of claim 1, wherein the substrate comprises a semiconductor material substantially coated with a dielectric material on at least one surface thereof.

8. The sensor of claim 1, further comprising a stationary comb disposed over the substrate, the stationary comb having stationary comb fingers interleaved with mobile comb fingers disposed on an edge of the proof mass.

9. The sensor of claim 8, wherein a thickness of the stationary comb fingers is less than a thickness of the mobile comb fingers.

10. The sensor of claim 9, wherein the thickness of the mobile comb fingers is approximately equal to the thickness of the proof mass.

11. The sensor of claim 9, wherein the thickness of the stationary comb fingers is between approximately 30 μ

m and approximately 40 μ

m.

12. A method of fabricating a sensor, the method comprising:

forming a first recess in a first surface of a first substrate;

bonding a portion of the first surface of the first substrate to a second substrate; and

forming a second recess in a second surface of the first substrate, the second recess being disposed over the first recess, thereby forming a suspension beam suspending a proof mass over the second substrate.

13. The method of claim 12, wherein a thickness of the suspension beam is less than a thickness of the proof mass.

14. The method of claim 13, wherein a difference between the thickness of the proof mass and the thickness of the suspension beam is approximately equal to an aggregate depth of the first and second recesses.

15. The method of claim 12, wherein a depth of the first recess is approximately equal to a depth of the second recess.

16. The method of claim 12, further comprising:

forming a third recess in the first surface of the first substrate; and

forming a fourth recess in the second surface of the first substrate, thereby forming a stationary comb finger disposed over the second substrate.

17. The method of claim 16, wherein a thickness of the stationary comb finger is less than a thickness of a mobile comb finger disposed on an edge of the proof mass.

18. The method of claim 16, wherein a depth of the third recess is approximately equal to a depth of the fourth recess.

19. The method of claim 16, wherein the first and third recesses are formed substantially simultaneously and the second and fourth recesses are formed substantially simultaneously.

20. A method of sensing angular rate, the method comprising:

providing a sensor comprising;

two proof masses, each proof mass (i) being suspended over a substrate by a suspension beam having a thickness less than a thickness of the proof mass it suspends and (ii) including a plurality of mobile comb fingers on at least one edge thereof, and

a plurality of stationary comb fingers proximate the two proof masses and interleaved with the mobile comb fingers;

applying a voltage between the stationary comb fingers and the proof masses such that the proof masses vibrate approximately parallel to a surface of the substrate;

detecting a differential displacement of the two proof masses in a plane approximately perpendicular to the surface of the substrate; and

outputting a signal based on the differential displacement, the signal representing an angular rate experienced by the sensor.

21. The method of claim 20, wherein a thickness of the stationary comb fingers is less than a thickness of the mobile comb fingers.

22. The method of claim 20, wherein a thickness of each of the two proof masses is between approximately 50 μ

m and approximately 60 μ

m.

23. The method of claim 20, wherein a wide-bandwidth rate noise of the sensor is less than approximately 0.01 °

/h^1/2.

24. The method of claim 20, wherein a bias error over temperature of the sensor is less than approximately 1 °

/h.