Micromachined monolithic 3-axis gyroscope with single drive

1. An inertial measurement system, comprising:

a device layer including a single proof-mass 3-axis gyroscope formed in an x-y plane, the single proof-mass 3-axis gyroscope including:

a main proof-mass section suspended about a single, central anchor, the main proof-mass section including a radial portion extending outward towards an edge of the 3-axis gyroscope sensor;

a central suspension system configured to suspend the 3-axis gyroscope from the single, central anchor;

a drive electrode including a moving portion and a stationary portion, the moving portion coupled to the radial portion, wherein the drive electrode and the central suspension system are configured to oscillate the 3-axis gyroscope about a z-axis normal to the x-y plane at a drive frequency;

symmetrical x-axis proof-mass sections configured to move anti-phase along the x-axis in response to z-axis angular motion; and

a z-axis gyroscope coupling flexure bearing configured to couple the x-axis proof mass sections and to resist in-phase motion between the x-axis proof mass sections;

a cap wafer bonded to a first surface of the device layer; and

a via wafer bonded to a second surface of the device layer, wherein the cap wafer and the via wafer are configured to encapsulate the single proof-mass 3-axis gyroscope.

2. The system of claim 1 , including electrodes out-of-plane with the device layer and configured to detect x-axis angular rotation and y-axis angular rotation.

3. The system of claim 2 , wherein the out-of-plane electrodes are located on the via wafer.

4. The system of claim 1 , wherein the drive electrode includes a plurality of moving fingers interdigitated with a plurality of stationary fingers, and wherein the stationary fingers are anchored to the via wafer.

5. The system of claim 1 , wherein the device layer includes a 3-axis accelerometer formed adjacent the 3-axis gyroscope in the x-y plane; and

wherien the cap wafer and the via wafer are configured to encapsulate the 3-axis accelerometer and the 3-axis gyroscope in the same cavity.

6. The system of claim 1 , wherein the device layer includes a single proof-mass 3-axis accelerometer formed in the x-y plane, the single proof-mass 3-axis accelerometer suspended about a single, central anchor, the single proof-mass 3-axis accelerometer including separate x, y, and z-axis flexure bearings;

wherein the x and y-axis flexure bearings are symmetrical about the single, central anchor and the z-axis flexure is not symmetrical about the single, central anchor.

7. The system of claim 6 , wherien the cap wafer and the via wafer are configured to encapsulate the 3-axis accelerometer and the 3-axis gyroscope in the same cavity.

8. The system of claim 6 , wherein the 3-axis accelerometer includes in-plane x and y-axis accelerometer sense electrodes.

9. The system of claim 8 , wherein the in-plane x and y-axis accelerometer sense electrodes are symmetrical about the single, central anchor.

10. The system of claim 9 , wherein the 3-axis accelerometer includes out-of-plane z-axis accelerometer sense electrodes.

11. The system of claim 6 , wherein the 3-axis accelerometer is rectangular in shape, longer about the y-axis than the x or z-axis.

12. The system of claim 6 , wherein the x, y, and z-axis flexure bearings have high out-of-plane stiffness.

13. The system of claim 6 , wherein the single proof-mass includes an outer portion surrounding in-plane x and y-axis accelerometer sense electrodes and x, y, and z-axis flexure bearings.

14. A micromachined, monolithic inertial sensor apparatus, comprising:

a single proof-mass 3-axis gyroscope formed in an x-y plane of a device layer, the single proof-mass 3-axis gyroscope including:

a main proof-mass section suspended about a single, central anchor, the main proof-mass section including a radial portion extending outward towards an edge of the 3-axis gyroscope;

a central suspension system configured to suspend the 3-axis gyroscope from the single, central anchor;

a drive electrode including a moving portion and a stationary portion, the moving portion coupled to the radial portion, wherein the drive electrode and the central suspension system are configured to oscillate the 3-axis gyroscope about a z-axis normal to the x-y plane at a drive freguency;

symmetrical x-axis proof-mass sections configured to move anti-phase along the x-axis in response to z-axis angular motion; and

a z-axis gyroscope coupling flexure bearing configured to couple the x-axis proof mass sections and to resist in-phase motion between the x-axis proof mass sections.

15. The apparatus of claim 14 , including:

a single proof-mass 3-axis accelerometer formed in the x-y plane of the device layer adjacent the 3-axis gyroscope, suspended about a single, central anchor, the single proof-mass 3-axis accelerometer including separate x, y, and z-axis flexure bearings; and

wherein the x and y-axis flexure bearings are symmetrical about the single, central anchor and the z-axis flexure is not symmetrical about the single, central anchor.

16. The apparatus of claim 15 , wherein the 3-axis accelerometer includes:

in-plane x and y-axis accelerometer sense electrodes symmetrical about the single, central anchor; and

out-of-plane z-axis accelerometer sense electrodes.

17. The apparatus of claim 16 , including:

a cap wafer bonded to a first surface of the device layer; and

a via wafer bonded to a second surface of the device layer, wherein the cap wafer and the via wafer are configured to encapsulate the 3-axis gyroscope and the 3-axis accelerometer in the same cavity.