Micromachined 3-axis accelerometer with a single proof-mass

• US 9,455,354 B2
• Filed: 09/18/2011
• Issued: 09/27/2016
• 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
• Primary Examiner(s): WILLIAMS, HEZRON
• Assistant Examiner(s): Zhong, Xin
• Application Number:
  US13/821,853
• Publication Number:
  US 20130247666A1
• Time in Patent Office: 1,836 Days
• Field of Search: 735/140.1, 735/140.2, 735/143.2
• US Class Current: 1/1
• 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, an inertial measurement system including a device layer including a single proof-mass 3-axis accelerometer, 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 accelerometer. The single proof-mass 3-axis accelerometer can be suspended about a single, central anchor, and can include 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.

Claims

1. An inertial measurement system, comprising:

a device layer including a single proof-mass 3-axis accelerometer formed in an 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;

wherein the z-axis flexure bearing defines a pivot line offset from the single, central anchor;

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 accelerometer.

2. The system of claim 1, wherein the 3-axis accelerometer includes in-plane x and y-axis accelerometer sense electrodes.

3. The system of claim 2, wherein the in-plane x and y-axis accelerometer sense electrodes are symmetrical about the single, central anchor.

4. The system of claim 2, wherein the 3-axis accelerometer includes out-of-plane z-axis accelerometer sense electrodes.

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

6. The system of claim 5, wherein the cap wafer and the via wafer are configured to encapsulate the single proof-mass 3-axis accelerometer and the 3-axis gyroscope.

7. The system of claim 6, wherein the 3-axis accelerometer and the 3-axis gyroscope are configured to share the same encapsulated cavity.

8. The system of claim 1, wherein the device layer includes a single proof-mass 3-axis gyroscope formed in the x-y plane adjacent the 3-axis accelerometer, 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.

9. The system of claim 8, including symmetrical x-axis proof-mass sections configured to move anti-phase along the x-axis in response to z-axis angular motion.

10. The system of claim 8, including a z-axis gyroscope coupling flexure bearing configured to couple the x-axis proof mass sections and to resist in-phase motion.

11. The system of claim 1, 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 1, wherein the x, y, and z-axis flexure beatings have higher out-of-plane stiffness than in-plane stiffness.

13. The system of claim 1, 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. The system of claim 1, wherein the 3-axis accelerometer includes a micromachined, monolithic, 3-axis accelerometer.

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

a single proof-mass 3-axis accelerometer formed in an x-y plane of a device layer, 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

wherein the z-axis flexure bearing defines a pivot line offset from 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.

17. The apparatus of claim 16, wherein the in-plane x and y-axis accelerometer sense electrodes are symmetrical about the single, central anchor.

18. The apparatus of claim 16, wherein the 3-axis accelerometer includes out-of-plane z-axis accelerometer sense electrodes.

19. The apparatus of claim 15, including:

a single proof-mass 3-axis gyroscope formed in the x-y plane adjacent the 3-axis accelerometer, 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.

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 single proof-mass 3-axis gyroscope and the single proof-mass 3-axis accelerometer in the same cavity.