X-Y AXIS DUAL-MASS TUNING FORK GYROSCOPE WITH VERTICALLY INTEGRATED ELECTRONICS AND WAFER-SCALE HERMETIC PACKAGING

• US 20100132460A1
• Filed: 11/18/2009
• Published: 06/03/2010
• Est. Priority Date: 11/18/2005
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: CASTRO, Alexander, SEEGER, Joseph, NASIRI, Steven S.
• Granted Patent: US 8,069,726 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion

Abstract

An angular velocity sensor has two masses which are laterally disposed in an X-Y plane and indirectly connected to a frame. The two masses are linked together by a linkage such that they necessarily move in opposite directions along Z. Angular velocity of the sensor about the Y axis can be sensed by driving the two masses into Z-directed antiphase oscillation and measuring the angular oscillation amplitude thereby imparted to the frame. In a preferred embodiment, the angular velocity sensor is fabricated from a bulk MEMS gyroscope wafer, a cap wafer and a reference wafer. In a further preferred embodiment, this assembly of wafers provides a hermetic barrier between the masses and an ambient environment.

Claims

1-16. -16. (canceled)

17. A sensor for measuring angular velocity in a sensor plane, the sensor comprising:

a sensing subassembly comprising;

i) a substantially planar frame parallel to the plane;

ii) a first mass disposed in the plane;

iii) a second mass disposed in the plane laterally to the first mass; and

iv) a linkage within the frame and connected to the frame, wherein the linkage is connected to the first mass and to the second mass and wherein the linkage constrains the first and second masses to move in opposite directions perpendicular to the plane;

wherein the linkage and the substantially planar frame are both anchored to a base;

an actuator for driving a first portion of the subassembly into oscillation at a drive frequency; and

a transducer for sensing motion of a second portion of the subassembly responsive to the angular velocity.

18. The sensor of claim 17, wherein the linkage further comprises:

a center plate connected to the frame and connected to and in between the first and second masses, wherein the center plate is rotatable about a center axis of rotation;

a first edge plate connected to the base via a drive anchor portion of the base and to the first mass, wherein the first edge plate is rotatable about a first axis of rotation; and

a second edge plate connected to the base via a drive anchor portion of the base and to the second mass, wherein the second edge plate is rotatable about a second axis of rotation;

wherein the center, first and second axes of rotation are parallel to each other and are also parallel to the sensor plane.

19. The sensor of claim 17, wherein the actuator is selected from the group consisting of electrostatic actuators, electromagnetic actuators, piezoelectric actuators, and thermal actuators.

20. The sensor of claim 17, wherein the transducer is selected from the group consisting of capacitive sensors, electromagnetic sensors, piezoelectric sensors, and piezoresistive sensors.

21. The sensor of claim 17, wherein the first portion of the subassembly is the linkage and the second portion of the subassembly is the frame.

22. The sensor of claim 17, wherein the actuator comprises an electrostatic actuator connected to the linkage, and wherein the transducer comprises a capacitive sensor connected to the frame.

23. The sensor of claim 17, wherein the first portion of the subassembly is the frame and the second portion of the subassembly is the linkage.

24. The sensor of claim 17, wherein the actuator comprises an electrostatic actuator connected to the frame, and wherein the transducer comprises a capacitive sensor connected to the linkage.

25. The sensor of claim 17, wherein motion of the frame is substantially constrained to rotation about an axis perpendicular to the sensor plane.

26. The sensor of claim 17, wherein the frame is substantially circular.

27. The sensor of claim 17, wherein the frame is substantially rectangular.

28. The sensor of claim 17, wherein the first and second masses are constrained to move only substantially perpendicular to the sensor plane, relative to the frame.

29. The sensor of claim 17, wherein the linkage further comprises a first lever arm connected to the first mass and a second lever arm connected to the second mass, whereby motion of the masses perpendicular to the sensor plane responsive to rotation of the center plate is increased.

30. The sensor of claim 17, wherein the transducer is connected to a base and to the second portion, and wherein the base comprises a reference wafer, wherein the reference wafer includes CMOS electronics connected to the transducer and connected to the actuator, whereby wafer scale integration of the actuator and the transducer is obtained.

31. A sensor for measuring angular velocity in a sensor plane, the sensor comprising:

a sensing subassembly comprising;

i) a substantially planar frame parallel to the plane; and

ii) a linkage within the frame, wherein the linkage is connected to the substantially planar frame and wherein the frame is anchored to a base and the linkage is anchored the base, wherein the linkage comprises a center plate connected to the frame which is rotatable about a center axis of rotation;

an actuator for driving a first portion of the subassembly into oscillation at a drive frequency; and

a transducer for sensing motion of a second portion of the subassembly responsive to the angular velocity.

32. The sensor of claim 31, wherein the actuator is selected from the group consisting of electrostatic actuators, electromagnetic actuators, piezoelectric actuators, and thermal actuators.

33. The sensor of claim 31, wherein the transducer is selected from the group consisting of capacitive sensors, electromagnetic sensors, piezoelectric sensors, and piezoresistive sensors.

34. The sensor of claim 31, wherein the first portion of the subassembly is the linkage and the second portion of the subassembly is the frame.

35. The sensor of claim 31, wherein the actuator comprises an electrostatic actuator connected to the linkage, and wherein the transducer comprises a capacitive sensor connected to the frame.

36. The sensor of claim 31, wherein the first portion of the subassembly is the frame and the second portion of the subassembly is the linkage.

37. The sensor of claim 31, wherein the actuator comprises an electrostatic actuator connected to the frame, and wherein the transducer comprises a capacitive sensor connected to the linkage.

38. The sensor of claim 31, wherein motion of the frame is substantially constrained to rotation about an axis perpendicular to the sensor plane.

39. The sensor of claim 31, wherein the frame is substantially circular.

40. The sensor of claim 31, wherein the frame is substantially rectangular.

41. The sensor of claim 31, which further includes:

i) a first mass disposed in the plane; and

ii) a second mass disposed in the plane laterally to the first mass, wherein the linkage is connected to the first mass and to the second mass and wherein the linkage constrains the first and second masses to move in opposite directions perpendicular to the plane.

42. The sensor of claim 41, wherein the first and second masses are constrained to move only substantially perpendicular to the sensor plane, relative to the frame.

43. The sensor of claim 41, wherein the center plate further comprises a first lever arm connected to the first mass and a second lever arm connected to the second mass, whereby motion of the masses perpendicular to the sensor plane responsive to rotation of the center plate is increased.

44. The sensor of claim 41, wherein the first edge plate further comprises a lever arm connected to the first mass, whereby motion of the first mass perpendicular to the sensor plane responsive to rotation of the first edge plate is increased.

45. The sensor of claim 41, wherein the second edge plate further comprises a lever arm connected to the second mass, whereby motion of the second mass perpendicular to the sensor plane responsive to rotation of the second edge plate is increased.

46. The sensor of claim 31, wherein the transducer is connected to a base and to the second portion, and wherein the base comprises a reference wafer, wherein the reference wafer includes CMOS electronics connected to the transducer and connected to the actuator, whereby wafer scale integration of the actuator and the transducer is obtained.

47. The sensor of claim 33, wherein the frame is coupled to the base via a first anchor and the linkage is coupled to the base via a second anchor.

48. The sensor of claim 33, wherein the frame and the linkage are coupled to the base via the same anchor.