Micromachined monolithic 3-axis gyroscope with single drive
View Patent ↗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.
1. An inertial measurement system, comprising:
a device layer including:
a 3-axis gyroscope including a single proof mass formed in an x-y plane of a device layer, the single proof mass of the 3-axis gyroscope including:
symmetrical x-axis proof mass sections; and
a z-axis gyroscope coupling flexure coupled to the symmetric x-axis proof mass sections;
a sense electrode included within the single proof mass of the 3-axis gyroscope; and
a 3-axis accelerometer including a single proof mass formed in the x-y plane of the device layer adjacent the 3-axis gyroscope,
the 3-axis gyroscope including a central suspension configured to suspend the single proof mass of the 3-axis gyroscope about a single, central gyroscope anchor, and
the 3-axis accelerometer including separate x, y, and z-axis flexure bearings configured to suspend a single proof mass of the 3-axis accelerometer about a single, central accelerometer anchor.
2. The system of claim 1 , 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 accelerometer and the 3-axis gyroscope in the same cavity.
3. The system of claim 1 , including a via wafer bonded to a perimeter of a surface of the device layer, and
wherein the single proof masses of the 3-axis gyroscope and the 3-axis accelerometer are anchored to the via wafer using the single, central gyroscope anchor and the single, central accelerometer anchor.
4. The system of claim 1 , wherein the 3-axis gyroscope includes:
a drive electrode including a moving portion and a stationary portion, the moving portion coupled to the single proof mass of the 3-axis gyroscope, wherein the drive electrode and the central suspension are configured to oscillate the 3-axis gyroscope about a z-axis normal to the x-y plane at a drive frequency.
5. The system of claim 1 , wherein the x and y-axis flexure bearings are symmetrical about the single, central accelerometer anchor and the z-axis flexure is not symmetrical about the single, central accelerometer anchor.
6. The system of claim 1 , wherein the symmetrical x-axis proof mass sections are configured to move anti-phase along an x-axis of the x-y plane in response to a z-axis angular motion.
7. The system of claim 6 , wherein the z-axis gyroscope coupling flexure bearing is configured to couple the symmetric x-axis proof mass sections and to resist in-phase motion between the x-axis proof mass sections.
8. The system of claim 1 , including:
a via wafer bonded to a surface of the device layer, the via wafer including:
x-axis and y-axis gyroscope sense electrodes out-of-plane with the device layer configured to detect x-axis and y-axis angular rotation of the single proof mass of the 3-axis gyroscope; and
z-axis accelerometer sense electrodes out-of-plane with the device layer configured to detect z-axis acceleration of the single proof mass of the 3-axis accelerometer; and
wherein the sense electrode includes a z-axis gyroscope sense electrode, the device layer includes:
x-axis and y-axis accelerometer sense electrodes in-plane with the device layer and configured to detect x-axis and y-axis acceleration of the single proof mass of the 3-axis accelerometer; and
the z-axis gyroscope sense electrodes in-plane with the device layer and configured to detect z-axis angular rotation of the single proof mass of the 3-axis gyroscope.
9. An inertial measurement system, comprising:
a device layer including:
a 3-axis gyroscope including a single proof mass formed in an x-y plane of a device layer, the single proof mass of the 3-axis gyroscope including:
symmetrical x-axis proof mass sections; and
a z-axis gyroscope coupling flexure coupled to the symmetric x-axis proof sections;
a drive electrode included in the single proof mass of the 3-axis gyroscope; and
a 3-axis accelerometer including a single proof mass formed in the x-y plane of the device layer adjacent the 3-axis gyroscope;
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,
the 3-axis gyroscope including a central suspension configured to suspend the single proof mass of the 3-axis gyroscope about a single, central gyroscope anchor,
the 3-axis accelerometer including separate x, y, and z-axis flexure bearings configured to suspend a single proof mass of the 3-axis accelerometer about a single, central accelerometer anchor, and
the cap wafer and the via wafer being configured to encapsulate the 3-axis accelerometer and the 3-axis gyroscope in the same cavity.
10. The system of claim 9 , wherein the via wafer is bonded to a perimeter of the second surface of the device layer, and
wherein the single proof masses of the 3-axis gyroscope and the 3-axis accelerometer are anchored to the via wafer using the single, central gyroscope anchor and the single, central accelerometer anchor.
11. The system of claim 9 , wherein the symmetrical x-axis proof mass sections are configured to move anti-phase along an x-axis of the x-y plane in response to a z-axis angular motion.
12. The system of claim 11 , wherein the z-axis gyroscope coupling flexure bearing is configured to couple the x-axis proof mass sections and to resist in-phase motion between the x-axis proof mass sections.
13. The system of claim 9 , including:
a via wafer bonded to a surface of the device layer, the via wafer including:
x-axis and y-axis gyroscope sense electrodes out-of-plane with the device layer configured to detect x-axis and y-axis angular rotation of the single proof mass of the 3-axis gyroscope; and
z-axis accelerometer sense electrodes out-of-plane with the device layer configured to detect z-axis acceleration of the single proof mass of the 3-axis accelerometer; and
wherein the device layer includes:
x-axis and y-axis accelerometer sense electrodes in-plane with the device layer and configured to detect x-axis and y-axis acceleration of the single proof mass of the 3-axis accelerometer; and
a z-axis gyroscope sense electrode in-plane with the device layer and configured to detect z-axis angular rotation of the single proof mass of the 3-axis gyroscope.
14. The system of claim 9 , wherein the drive electrode includes a moving portion and a stationary portion, the moving portion is coupled to the single proof mass of the 3-axis gyroscope, the drive electrode and the central suspension are configured to oscillate the 3-axis gyroscope about a z-axis normal to the x-y plane at a drive frequency.
15. The system of claim 9 , wherein the x- and y-axis flexure bearings are symmetrical about the single, central accelerometer anchor and the z-axis flexure is not symmetrical about the single, central accelerometer anchor.
16. The system of claim 9 , wherein the single proof mass of the 3-axis gyroscope includes symmetrical x-axis proof mass sections configured to move anti-phase along an x-axis of the x-y plane in response to a z-axis angular motion.
17. An inertial measurement system, comprising:
a device layer including:
a 3-axis gyroscope including a single proof mass formed in an x-y plane of a device layer, the single proof mass of the 3-axis gyroscope including:
symmetrical x-axis proof mass sections; and
a z-axis gyroscope coupling flexure coupled to the symmetric x-axis proof sections;
a drive electrode included in the single proof mass of the 3-axis gyroscope; and
a 3-axis accelerometer including a single proof mass formed in the x-y plane of the device layer adjacent the 3-axis gyroscope;
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,
the cap wafer and the via wafer being configured to encapsulate the 3-axis accelerometer and the 3-axis gyroscope in the same cavity.
18. The system of claim 17 , wherein the 3-axis gyroscope includes a central suspension configured to suspend the single proof mass of the 3-axis gyroscope about a single, central gyroscope anchor, and
wherein the 3-axis accelerometer including separate x-, y-, and z-axis flexure bearings is configured to suspend a single proof mass of the 3-axis accelerometer about a single, central accelerometer anchor.
19. The system of claim 18 , wherein the via wafer is bonded to a perimeter of the second surface of the device layer, and
wherein the single proof masses of the 3-axis gyroscope and the 3-axis accelerometer are anchored to the via wafer using the single, central gyroscope anchor and the single, central accelerometer anchor.
20. The system of claim 17 , wherein:
the symmetrical x-axis proof mass sections are configured to move anti-phase along an x-axis of the x-y plane in response to a z-axis angular motion; and
the z-axis gyroscope coupling flexure bearing is configured to couple the x-axis proof mass sections and to resist in-phase motion between the x-axis proof mass sections.