Micromachined inertial sensor devices

• US 8,739,626 B2
• Filed: 08/03/2010
• Issued: 06/03/2014
• Est. Priority Date: 08/04/2009
• 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 C
• Application Number:
  US12/849,742
• Publication Number:
  US 20110030473A1
• Time in Patent Office: 1,400 Days
• Field of Search: 735/143.2, 735/142.9, 735/143.6, 735/143.8, 735/10, 735/11, 735/041.4, 735/040.4, 735/041.2
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• 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 2015/0842 the mass being of clover leaf shape
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

A micromachined inertial sensor with a single proof-mass for measuring 6-degree-of-motions. The single proof-mass includes a frame, an x-axis proof mass section attached to the frame by a first flexure, and a y-axis proof mass section attached to the frame by a second flexure. The single proof-mass is formed in a micromachined structural layer and is adapted to measure angular rates about three axes with a single drive motion and linear accelerations about the three axes.

Claims

1. A sensor for measuring a motion thereof, comprising:

a frame;

a first planar proof mass section attached to the frame by a first flexure;

a second planar proof mass section attached to the frame by a second flexure; and

an anchor secured to a wafer disposed beneath the first planar proof mass section and the second planar proof mass section,

wherein the frame, the first planar proof mass section, and the second planar proof mass section are formed in a micromachined layer and are adapted to measure angular rates about three axes and linear accelerations about the three axes, and

wherein the first planar proof mass section and the second planar proof mass section are configured to be driven, in phase, about the anchor.

2. A sensor as recited in claim 1, further comprising:

a comb electrode configured to drive the first and second planar proof mass sections at a drive frequency about an axis normal to a plane, the micromachined layer being substantially disposed on the plane when the sensor is not externally disturbed.

3. A sensor as recited in claim 2, wherein the comb electrode includes a plurality of stationary fingers and a plurality of moving comb fingers.

4. A sensor as recited in claim 3, wherein the plurality of stationary fingers are connected to an anchor that is secured to a wafer disposed beneath the micromachined layer.

5. A sensor as recited in claim 2, wherein the second planar proof mass section includes a pair of wing portions disposed symmetrically about a first axis and the wing portions are adapted to move in opposite directions when the sensor is disturbed at an angular rate along a second axis perpendicular to the first axis.

6. A sensor as recited in claim 5, further comprising:

a pair of gyro electrodes disposed beneath the micromachined layer, wherein the angular rate along the second axis is detected by measuring a variation of capacitance between the pair of gyro electrodes and the pair of wing portions.

7. A sensor as recited in claim 5, further comprising:

a pair of accelerometer electrodes respectively connected to the pair of wing portions and disposed symmetrically about a first axis,

wherein a linear acceleration of the sensor along the second axis is detected by measuring a variation of capacitance of the pair of accelerometer electrodes.

8. A sensor as recited in claim 7, wherein each accelerometer electrode is connected to an anchor that is secured to a wafer disposed beneath the micromachined layer.

9. A sensor as recited in claim 2, wherein the first proof mass section includes a pair of masses disposed symmetrically about a second axis and the pair of masses are adapted to move in opposite directions when the sensor is disturbed at an angular rate along a first axis perpendicular to the second axis.

10. A sensor as recited in claim 9, further comprising:

a pair of gyro electrodes disposed beneath the micromachined layer,

wherein the angular rate along the first axis is detected by measuring a variation of capacitance between the pair of masses and the pair of gyro electrodes.

11. A sensor as recited in claim 10, wherein a linear acceleration of the sensor along the axis normal to the plane is detected by measuring a variation of capacitance between the pair of masses and the pair of gyro electrodes.

12. A sensor as recited in claim 9, wherein the pair of masses are adapted to move in opposite directions when the sensor is disturbed at an angular rate along the axis normal to the plane.

13. A sensor as recited in claim 12, further comprising:

a pair of accelerometer electrodes respectively connected to the pair of masses and disposed symmetrically about the second axis,

wherein the angular rate along the axis normal to the plane is detected by measuring a variation of capacitance in the pair of accelerometer electrodes.

14. A sensor as recited in claim 13, wherein each accelerometer electrode is connected to an anchor that is secured to a wafer disposed beneath the micromachined layer.

15. A sensor as recited in claim 13, wherein a linear acceleration of the sensor along the first axis is detected by measuring a variation of capacitance in the pair of accelerometer electrodes.

16. A sensor as recited in claim 1,

wherein the anchor is located substantially at a center of the sensor.

17. A sensor as recited in claim 16, further comprising:

an inner frame connected to the anchor by a plurality of suspension beams; and

a plurality of flexures connected to the inner frame and the second proof mass section and adapted to provide a restoring force to the second proof mass section.

18. A sensor as recited in claim 17, further comprising:

a pair of gyroscope flexures connected to the second planar proof mass section and to the frame and adapted to provide a restoring torque to the second planar proof mass section.

19. A sensor as recited in claim 1, wherein the first flexure includes two pairs of gyroscope flexures, each said gyroscope flexure having two elongated beams.

20. A sensor as recited in claim 1, further comprising:

a pair of flexures connected to the frame and the second planar proof mass section, each said flexure including a gyro spring configured to provide a restoring torque along a second axis and two accelerometer springs configured to provide a restoring torque along the second axis.

21. A sensor as recited in claim 20, wherein each said flexure includes a linkage, each end of the linkage being connected to a corresponding one of the two accelerometer springs, the gyro spring being connected to a midpoint of the linkage.

22. A device for measuring a motion thereof, comprising:

a first wafer;

a device layer including;

a frame;

a first planar proof mass section attached to the frame by a first flexure;

a second planar proof mass section attached to the frame by a second flexure; and

an anchor secured to a wafer disposed beneath the frame, the first planar proof mass section, and the second planar proof mass section,

wherein the frame, the first planar proof mass section, and the second planar proof mass section are formed in a micromachined layer and are adapted to measure angular rates about three axes and linear accelerations about the three axes, and

wherein the first planar proof mass section and the second planar proof mass section are configured to be driven, in phase, about the anchor; and

a second wafer, the first and second wafer being bonded to the device layer.

23. A device layer as recited in claim 22, wherein the first wafer is a cap wafer.

24. A device layer as recited in claim 23, wherein the second wafer is a via wafer or an ASIC wafer.

25. A device as recited in claim 22, wherein the second wafer includes one or more electrodes configured to measure an angular rate of at least one of the first and second planar proof mass sections.