Micromachined monolithic 6-axis inertial sensor

• US 9,278,846 B2
• Filed: 09/18/2011
• Issued: 03/08/2016
• 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): Kwok, Helen
• Application Number:
  US13/821,793
• Publication Number:
  US 20130270657A1
• Time in Patent Office: 1,633 Days
• Field of Search: 735/041.2, 735/041.4, 735/040.3, 735/040.4, 735/10, 735/11, 735/143.2, 735/143.8
• US Class Current: 1/1
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• 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 2015/082 for two degrees of freedom of movement of a single mass
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

The device layer of a 6-degrees-of-freedom (6-DOF) inertial measurement system can include a single proof-mass 6-axis inertial sensor formed in an x-y plane, the inertial sensor including: a main proof-mass section suspended about a single, central anchor; a central suspension system configured to suspend the 6-axis inertial sensor 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. The drive electrode and the central suspension system are configured to oscillate the 6-axis inertial sensor about a z-axis normal to the x-y plane.

Claims

1. A 6-degrees-of-freedom (6-DOF) inertial measurement system, comprising:

a device layer including a single proof-mass 6-axis inertial sensor formed in an x-y plane, the single proof-mass 6-axis inertial sensor 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 6-axis inertial sensor;

a pair of x-axis proof-mass sections coupled to the main proof-mass section using multi-function flexure bearings and coupled to each other using an anti-phase flexure bearing;

a central suspension system configured to suspend the 6-axis inertial sensor 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 6-axis inertial sensor 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 6-axis inertial sensor.

2. The system of claim 1, wherein the multi-function flexure bearings are configured to allow the first and second x-axis proof-mass sections to move in-phase or anti-phase along an x-axis of the x-y plane.

3. The system of claim 2, wherein the multi-function flexure bearings are configured to allow the first and second x-axis proof-mass sections to move in-phase along the x-axis in response to an x-axis acceleration.

4. The system of claim 2, wherein the multi-function flexure bearings are configured to allow the first and second x-axis proof-mass sections to move anti-phase along the x-axis in response to a z-axis rotation.

5. The system of claim 1, wherein the multi-function flexure bearings are configured to allow each of the first and second x-axis proof-mass sections to rotate about a y-axis of the x-y plane in response to a z-axis acceleration.

6. The system of claim 1, wherein at least one of the multi-function flexure bearings is elongate, extending between the main proof-mass section and the first x-axis proof-mass section along a y-axis of the x-y plane.

7. The system of claim 6, wherein the at least one multi-function flexure bearing is configured to be flexed under torsion about an axis parallel to the y-axis.

8. The system of claim 7, wherein four multi-function flexure bearings couple the single proof-mass to the first and second x-axis proof-mass sections, wherein for each multi-function flexure bearing there is an opposing multi-function bearing mirrored about an x-z plane, and another multi-function bearing mirrored about an y-z plane.

9. The system of claim 1, wherein the anti-phase flexure bearing that is elongate extending along a y-axis of the x-y plane.

10. The system of claim 9, wherein two anti-phase flexure bearings couple the first x-axis proof-mass section to the second x-axis proof-mass section on opposing sides of an x-z plane.

11. The system of claim 10, wherein each of the two anti-phase flexure bearings zigzag as they extend along an x-axis between the first and second x-axis proof-mass sections.

12. The system of claim 1, wherein the single proof-mass inertial sensor is quadrilateral in shape, wherein the single, central anchor is centered in the quadrilateral, and wherein the main proof-mass section includes four radial portions extending outward towards the four corners of the 6-axis inertial sensor.

13. 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.

14. The system of claim 1, including:

first electrodes in-plane with the device layer and configured to detect z-axis angular rotation, x-axis acceleration, and y-axis acceleration; and

second electrodes out-of-plane with the device layer and configured to detect z-axis acceleration, x-axis angular rotation, and y-axis angular rotation.

15. A single proof-mass, micromachined, monolithic, 6-axis inertial sensor apparatus, comprising:

a main proof-mass section forming an x-y plane suspended about a single, central anchor, the main proof-mass section including radial portions extending outward towards an edge of the 6-axis inertial sensor;

a pair of x-axis proof-mass sections coupled to the main proof-mass section using multi-function flexure bearings and coupled to each other using an anti-phase flexure bearing;

a pair of y-axis proof-mass sections coupled to multiple radial portions of the main proof-mass section using elongated flexure bearings;

a central suspension system configured to suspend the 6-axis inertial sensor from the single, central anchor; and

a drive electrode including a moving portion and a stationary portion, the moving portion coupled to the radial portions, wherein the drive electrode and the central suspension system are configured to oscillate the 6-axis inertial sensor about a z-axis normal to the x-y plane at a drive frequency.

16. The apparatus of claim 15, wherein the multi-function flexure bearings are configured to allow the pair of x-axis proof-mass sections to move in-phase or anti-phase along an x-axis of the x-y plane.

17. The apparatus of claim 16, wherein the multi-function flexure bearings are configured to allow the pair of x-axis proof-mass sections to move in-phase along the x-axis in response to an x-axis acceleration, and anti-phase along the x-axis in response to a z-axis rotation.

18. The apparatus of claim 15, wherein the multi-function flexure bearings are configured to allow each of the pair of x-axis proof-mass sections to rotate about a y-axis of the x-y plane in response to a z-axis acceleration.

19. A method, comprising:

suspending a single proof-mass of a 6-axis inertial sensor about a single, central anchor coupled to a stationary layer using a central suspension, the single proof-mass including a main proof-mass section including a radial portion extending outward towards an edge of the 6-axis inertial sensor;

suspending first and second x-axis proof-mass sections from the main proof-mass section using multi-function flexure bearings;

coupling the first and second x-axis proof-mass sections to each other using an anti-phase flexure bearing;

anchoring a stationary drive electrode to the stationary layer;

coupling a moveable electrode to the stationary electrode; and

oscillating the single proof-mass at a drive frequency using the stationary drive electrode, the moveable electrode, and the central suspension.

20. The method of claim 19, wherein the multi-function flexure bearings are configured to allow the first and second x-axis proof-mass sections to move in-phase along the x-axis in response to an x-axis acceleration, anti-phase along the x-axis in response to a z-axis rotation, and to rotate about the y-axis in response to a z-axis acceleration.