Vertically integrated 3-axis MEMS angular accelerometer with integrated electronics

• US 7,934,423 B2
• Filed: 12/10/2007
• Issued: 05/03/2011
• Est. Priority Date: 12/10/2007
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Taheri, Babak, Nasiri, Steven S., Seeger, Joseph, Yaralioglu, Goksen G.
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US11/953,762
• Publication Number:
  US 20090145225A1
• Time in Patent Office: 1,240 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 accelerometer comprising:

a cover substrate,

a sense substrate; and

an actuator layer;

the actuator layer comprising at least two proof masses constrained to rotate about at least one axis, the at least two proof masses being anchored to the cover and to the sense substrate via at least one flexure, and a plurality of electrodes that can sense rotation about the at least one axis, capacitively, wherein at least one of the 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 a X-direction to measure rotational acceleration about the X-direction and the other of the two proof masses is constrained to rotate about substantially Z-direction to measure rotational acceleration about the Z-direction, and is constrained to rotate about substantially a Y-direction to measure rotational acceleration about the Y-direction.

2. The accelerometer of claim 1 wherein the cover substrate and the sense substrate provide for a hermetically sealed controlled enclosure for the accelerometer.

3. The accelerometer of claim 1 wherein the at least one proof mass is constrained to rotate substantially about a Z-direction to measure rotational acceleration about the Z-direction, and is constrained to rotate about substantially for X-direction to measure rotational acceleration about the X-direction.

4. The accelerometer of claim 1 wherein the at least one proof mass is constrained to rotate substantially about a Z-direction to measure rotational acceleration about the Z-direction, and is constrained to rotate about substantially a Y-direction to measure rotational acceleration about the Y-direction.

5. The accelerometer of claim 1 wherein the plurality of electrodes form a parallel plate capacitance.

6. The accelerometer of claim 1 wherein a full bridge configuration is utilized for capacitive measurement of the at least two proof masses.

7. The accelerometer of claim 1, wherein a full bridge configuration is utilized for capacitance measurement of the at least two proof masses constrained to rotate about a Z-direction.

8. The accelerometer of claim 1, wherein a full bridge configuration is utilized for capacitance measurement of the at least two proof masses constrained to rotate about a Y-direction.

9. The accelerometer of claim 1, wherein a full bridge configuration is utilized for capacitance measurement of the at least two proof masses constrained to rotate about a X-direction.

10. The accelerometer of claim 1 which includes a self-test electrode to actuate the at least one proof mass for test purposes.

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

12. The accelerometer of claim 1 wherein the at least one proof mass is connected electrically to the sense substrate at an anchor.

13. The accelerometer of claim 1 wherein the at least one proof mass is connected electrically to the sense substrate through the at least one flexure.

14. The accelerometer of claim 1 wherein the sense substrate comprises a single crystal silicon wafer.

15. The accelerometer of claim 1 wherein the sense substrate comprises a CMOS integrated circuit.

16. The accelerometer of claim 15 wherein a measurement is provided utilizing a half bridge configuration with a capacitance being in series with a constant capacitance.

17. The accelerometer of claim 15 wherein a measurement is provided utilizing a full bridge configuration with a capacitance being with three other capacitances.

18. The accelerometer of claim 16 wherein a capacitance measurement for the half bridge configuration is proof mass driven.

19. The accelerometer of claim 16 wherein a capacitance measurement for the half bridge configuration is electrode driven.

20. The accelerometer of claim 17 wherein a capacitance measurement for the full bridge configuration is proof mass driven.

21. The accelerometer of claim 17 wherein a capacitance measurement for the full bridge configuration is electrode driven.