Silicon integrated angular rate sensor

• US 20090188318A1
• Filed: 01/24/2008
• Published: 07/30/2009
• Est. Priority Date: 01/24/2008
• Status: Active Grant

• Current Assignee: Delphi Technologies Ip Limited (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Forestal, Richard G., Johnson, Jack D., Christenson, John C., Chilcott, Dan W., Zarabadi, Seyed R.
• Granted Patent: US 7,908,922 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• CPC Class Codes: G01C 19/5684 the devices involving a micromechanical structure

Abstract

A motion sensor in the form of an angular rate sensor and a method of making a sensor are provided and includes a support substrate and a silicon sensing ring supported by the substrate and having a flexive resonance. Drive electrodes apply electrostatic force on the ring to cause the ring to resonate. Sensing electrodes sense a change in capacitance indicative of vibration modes of resonance of the ring so as to sense motion. A plurality of silicon support rings connect the substrate to the ring. The support rings are located at an angle to substantially match a modulus of elasticity of the silicon, such as about 22.5 degrees and 67.5 degrees, with respect to the crystalline orientation of the silicon.

Claims

1. A motion sensor comprising:

a support substrate;

a silicon sensing ring formed within and supported by the substrate and having a flexural resonance;

at least one drive electrode comprising drive capacitive plates for applying electrostatic force on the ring to cause the ring to resonate;

at least one sense electrode comprising sense capacitive plates for sensing a change in capacitance indicative of the vibration nodes of resonance of the ring so as to sense motion;

a plurality of silicon support springs connecting the substrate to the ring, wherein the support springs are located at an angle to substantially match a modulus of elasticity of the silicon support springs; and

electrical connection comprising at least one external tether in contact with the ring.

2. The sensor as defined in claim 1 further comprising at least one balance electrode comprising balance capacitive plates for applying electrostatic force to the ring to balance vibratory motion of the resonance of the ring.

3. The sensor as defined in claim 1, wherein the sensor is approximately one-eighth symmetric.

4. The sensor as defined in claim 1, wherein the sensor senses changes in capacitance at node locations in response to a Coriolis force.

5. The sensor of claim 1, wherein the sensor is capable of at least four node operation.

6. The sensor as defined in claim 1, wherein the sensor utilizes at least fourth and fifth flexural nodes of said sense element.

7. The sensor as defined in claim 1, wherein the sensor is integrated with on-board electronic compensating circuitry.

8. The sensor as defined in claim 1, wherein the support springs comprise a first spring portion located at an angle in the range of 20°

to 25°

with respect to crystalline orientation of the silicon, and a second spring portion oriented at an angle in the range of 65°

to 70°

with respect to the crystalline orientation of the silicon.

9. The sensor as defined in claim 8, wherein the first spring portion is oriented at an angle of approximately 22.5°

, and the second spring portion is oriented at an angle of approximately 67.5°

.

10. The sensor as defined in claim 8, wherein the first spring portion is oriented at an angle of approximately 22.5°

and the second spring portion is oriented at an angle of approximately 67.5°

from the X and Y-axes of the sensor.

11. The sensor as defined in claim 1, wherein the motion sensor comprises an angular rate sensor.

12. The sensor as defined in claim 1, wherein the motion sensor comprises an angular acceleration sensor.

13. The sensor as defined in claim 1, wherein the motion sensor comprises an angular position sensor.

14. The sensor as defined in claim 1, wherein the substrate is comprised of silicon.

15. The sensor as defined in claim 1, wherein the substrate is comprised of silicon-on-insulator.

16. The sensor as defined in claim 1, wherein the at least one drive electrode comprises at least two drive electrodes, and the at least one sense electrode comprises of at least two sense electrodes.

17. The sensor as defined in claim 2, wherein the at least one balance electrode comprises at least two balance electrodes.

18. The sensor as defined in claim 1 further comprising a compensation mass provided on the ring to compensate for a modulus of elasticity variation around the ring.

19. The sensor as defined in claim 18, wherein the compensation mass is located at locations at approximately 45°

from the X and Y-axes of the sensor.

20. The sensor as defined in claim 19, wherein the compensation mass is located at locations at approximately 45°

with respect to the crystal planes in the substrate.

21. The sensor as defined in claim 1, wherein the silicon sensing ring has a periodically varying width around its circumference.

22. The sensor as defined in claim 1, wherein the springs comprise a first radial portion and a second portion so as to have all spring portions located at an angle to substantially match a modulus of elasticity of the silicon.

23. The sensor as defined in claim 22, wherein the springs comprises at least sixteen springs.

24. The sensor as defined in claim 22, wherein the springs are formed as pairs of springs.

25. The sensor as defined in claim 1, wherein the plurality of support springs are center mounted.

26. The sensor as defined in claim 1, wherein the silicon sensing ring, the at least one drive electrode, the at least one sense electrode, the plurality of silicon support springs, and the at least one external tether, is formed from and within the substrate.

27. The sensor as defined in claim 1, wherein the sensor comprises one or more anti-stiction bumps formed to prevent stiction between a moving component and another component of the sensor.

28. The sensor as defined in claim 1, wherein one or more components of the sensor are perforated.

29. The sensor as defined in claim 18, wherein said ring and the compensating mass are perforated to comprise at least the compensating mass.

30. The sensor as defined in claim 1, wherein one or more components of the sensor have corner compensation.

31. The sensor as defined in claim 2, wherein the at least one drive electrode, the at least one sense electrode and the at least one balance electrode are cantilevered from the ring.

32. The sensor as defined in claim 1, wherein the sensor has symmetric damping.

33. The sensor as defined in claim 1, wherein the at least one drive electrode receives a differential drive signal and the at least one sense electrode generates a differential sense signal.