MICROMACHINED MONOLITHIC 3-AXIS GYROSCOPE WITH SINGLE DRIVE

• US 20130328139A1
• Filed: 09/18/2011
• Published: 12/12/2013
• Est. Priority Date: 09/18/2010
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Acar, Cenk
• Granted Patent: US 9,246,018 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 2203/051 Translation according to an axis parallel to the substrate
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 2203/055 Translation in a plane parallel to the substrate, i.e. enabling movement along any direction in the plane
• CPC Class Codes: B81B 2203/056 Rotation in a plane parallel to the substrate
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 2207/094 Feed-through, via
• CPC Class Codes: B81B 7/04 Networks or arrays of similar microstructural devices
• CPC Class Codes: G01C 19/5755 the devices having a single sensing mass
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0848 using a plurality of mechanically coupled spring-mass systems, the sensitive direction of each system being different
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure

Abstract

This document discusses, among other things, a cap wafer and a via wafer configured to encapsulate a single proof-mass 3-axis gyroscope formed in an x-y plane of a device layer. The single proof-mass 3-axis gyroscope can include 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, and 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.

Claims

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; and

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;

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

3. The system of claim 2, including 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.

4. 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.

5. The system of claim 4, wherein the out-of-plane electrodes are located on the via wafer.

6. 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.

7. 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

wherein 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 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.

9. The system of claim 8, wherein the cap wafer and the via wafer are configured to encapsulate the 3-axis accelerometer and the 3-axis gyroscope in the same cavity.

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

11. The system of claim 10, wherein the in-plane x and y-axis accelerometer sense electrodes are symmetrical about the single, central anchor.

12. The system of claim 11, wherein the 3-axis accelerometer includes out-of-plane z-axis accelerometer sense electrodes.

13. The system of claim 8, wherein the 3-axis accelerometer is rectangular in shape, longer about the y-axis than the x or z-axis.

14. The system of claim 8, wherein the x, y, and z-axis flexure bearings have high out-of-plane stiffness.

15. The system of claim 8, 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.

16. 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; and

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.

17. The apparatus of claim 16, including symmetrical x-axis proof-mass sections configured to move anti-phase along the x-axis in response to z-axis angular motion.

18. The apparatus of claim 16, 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.

19. The apparatus of claim 18, 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.

20. The apparatus of claim 19, 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.