Vertically integrated 3-axis MEMS angular accelerometer with integrated electronics

• US 8,960,002 B2
• Filed: 04/28/2011
• Issued: 02/24/2015
• Est. Priority Date: 12/10/2007
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Nasiri, Steven S., Yaralioglu, Goksen G., Seeger, Joseph, Taheri, Babak
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US13/096,732
• Publication Number:
  US 20110197677A1
• Time in Patent Office: 1,398 Days
• Field of Search: 735/140.2, 735/140.1, 735/143.2
• US Class Current: 73/514.02
• CPC Class Codes: B60R 2021/01327 Angular velocity or angular acceleration
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

Sensors for measuring angular acceleration about three mutually orthogonal axes, X, Y, Z or about the combination of these axes are disclosed. The sensor comprises a sensor subassembly. The sensor subassembly further comprises a base which is substantially parallel to the X-Y sensing plane; a proof mass disposed in the X-Y sensing plane and constrained to rotate substantially about the X, and/or Y, and/or Z, by at least one linkage and is responsive to angular accelerations about the X, and/or Y, and/or Z directions. Finally, the sensor includes at least one electrode at the base plate or perpendicular to the base plate and at least one transducer for each sensing direction of the sensor subassembly responsive to the angular acceleration. Multi-axis detection is enabled by adjusting a configuration of flexures and electrodes.

Claims

1. A rotational sensor comprising:

a sense substrate;

an actuator layer;

the actuator layer comprising at least two proof masses capable of rotating about a Z-axis normal to plane of the sense substrate wherein each of the at least two proof masses being anchored to the sense substrate via at least one flexure;

at least two transducers that can sense rotation of the at least two proof masses about Z-axis; and

a circuit coupled to the at least two transducers to provide an output related to the rotation of the rotational sensor.

2. The rotational sensor of claim 1 further comprising a cover substrate, wherein the cover substrate and the sense substrate provide for a hermetically sealed controlled enclosure for the rotational sensor.

3. The rotational sensor of claim 1 wherein at least one of the at least two proof masses is operable to rotate about substantially an X-axis in the plane parallel to the sense substrate;

a transducer that can sense rotation of the at least one of the two proof masses about the X-axis.

4. The rotational sensor of claim 1 wherein at least one of the at least two proof masses is constrained to rotate about substantially a Z-direction to measure rotational acceleration about the Z-direction, and is constrained to rotate about substantially for a X-direction to measure rotational acceleration about the X-direction and the other of the at least two proof masses is constrained to rotate about substantially a Z-direction to measure rotational acceleration about the Z-direction, and is constrained to rotate about substantially for a Y-direction to measure rotational acceleration about the Y-direction.

5. The rotational sensor of claim 1 which includes a self-test electrode to actuate at least one of the at least two proof masses for test purposes.

6. The rotational sensor of claim 1 which includes travel stoppers in at least one of an X or a Y or a Z direction.

7. The rotational sensor of claim 1 wherein at least one of the at least two proof masses is connected electrically to the sense substrate at an anchor.

8. The rotational sensor of claim 1 wherein at least one of the at least two proof masses is connected electrically to the sense substrate through the at least one flexure.

9. The rotational sensor of claim 1 wherein the sense substrate comprises a single crystal silicon wafer.

10. The rotational sensor of claim 1 wherein the sense substrate comprises a CMOS integrated circuit.

11. The rotational sensor of claim 3 wherein a capacitance measurement is provided utilizing a half bridge configuration.

12. The rotational sensor of claim 11 wherein the capacitance measurement for the half bridge configuration is proof mass driven.

13. The rotational sensor of claim 11 wherein the capacitance measurement for the half bridge configuration is electrode driven.

14. The rotational sensor of claim 1, wherein the rotation of the two-proof masses is capacitively sensed.

15. The rotational sensor of claim 14 wherein at least one of the two transducers forms a parallel plate capacitance.

16. The rotational sensor of claim 14, wherein the at least two transducers comprise capacitors formed by a plurality of fixed electrodes on the sense substrate and a plurality of moveable electrodes coupled to the at least two proof masses, wherein capacitance of the capacitors changes in response to rotation of the sensor.

17. The rotational sensor of claim 16 wherein a full bridge configuration is utilized for capacitive measurement of the at least two proof masses.

18. The rotational sensor of claim 17 wherein the capacitance measurement for the full bridge configuration is proof mass driven.

19. The rotational sensor of claim 17 wherein the capacitance measurement for the full bridge configuration is electrode driven.

20. The rotational sensor of claim 1, wherein the at least two proof masses are electrically isolated.