MEMS ACCELEROMETER WITH PROOF MASSES MOVING IN AN ANTI-PHASE DIRECTION

• US 20150192603A1
• Filed: 03/09/2015
• Published: 07/09/2015
• Est. Priority Date: 12/23/2013
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: BALDASARRE, Leonardo, THOMPSON, Matthew Julian
• Granted Patent: US 10,371,715 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0837 the mass being suspended so as to only allow movement perpendicular to the plane of the substrate, i.e. z-axis sensor
• CPC Class Codes: G01P 2015/086 using a torsional suspension spring

Abstract

A sensor is disclosed. The sensor includes a substrate and a mechanical structure. The mechanical structure includes at least two proof masses including a first proof mass and a second proof mass. The mechanical structure also includes a flexible coupling between the at least two proof masses and the substrate. The at least two proof masses move in an anti-phase direction normal to the plane of the substrate in response to acceleration of the sensor normal to the plane and move in anti-phase in a direction parallel to the plane of the substrate in response to an acceleration of the sensor parallel to the plane. The at least two proof masses move in a direction parallel to the plane of the substrate in response to an acceleration of the sensor parallel to the plane.

Claims

1. A sensor comprising:

a substrate; and

a mechanical structure, wherein the mechanical structure includes

at least two proof masses including a first proof mass and a second proof mass,

a flexible coupling between the at least two proof masses and the substrate;

wherein the at least two proof masses move in an anti-phase direction normal to the plane of the substrate in response to acceleration of the sensor normal to the plane and move in anti-phase in a direction parallel to the plane of the substrate in response to an acceleration of the sensor parallel to the plane

2. The sensor of claim 1, wherein the first and second proof masse have unbalancing torque.

3. The sensor of claim 1, wherein the flexible coupling further comprises:

at least one anchor; and

a rotational and torsional system;

the rotational and torsional system further including an anchoring spring connecting the at least one anchor and a first rotational lever;

a first rotational and torsional spring connects the first proof mass to the rotational lever with a first lever length; and

a second rotational and torsional spring connects the second proof mass to the first rotational lever with a second lever length.

4. The sensor of claim 3, wherein the first lever length and the second lever length are different.

5. The sensor of claim 4, wherein the flexible coupling further includes a second anchoring rotational and torsional spring connecting the at least one anchor and a second rotational and torsional lever;

a third rotational and torsional spring connects the first proof mass to the second rotational lever with a third lever length; and

a fourth rotational and torsional spring connects the second proof mass to the second rotational lever with a fourth lever length;

wherein the first and second rotational levers rotates antiphase in a direction normal to the substrate in response to acceleration of the sensor normal to the substrate;

wherein the first and second rotational levers rotates antiphase in a plane parallel to the substrate in response to acceleration of the sensor parallel to the substrate

6. The sensor of claim 5, wherein the third lever length and the fourth lever length are different.

7. The sensor of claim 1, further comprising a magnetic material wherein the magnetic material is on any of the at least two proof masses, on the first rotational lever, and the second rotational levers;

wherein the mechanical structure rotates in a plane parallel to the plane in response to the magnetic field in a direction parallel to the plane.

8. The sensor of claim 1, further comprising a magnetic material wherein the magnetic material is on any of the at least two proof masses, on the first rotational lever, and the second rotational levers;

wherein the mechanical structure rotates in a directional normal to the plane in response to the magnetic field in a direction normal to the plane.

9. The sensor of claim 1, further comprising a transducer for measuring motion in a direction either normal and parallel to the plane of the substrate of the mechanical structure relative to the substrate

10. The sensor of claim 9, wherein the transducer is on any of the two proof masses, or the mechanical structure or the lever arms,

11. The sensor of claim 9, wherein the transducer is a capacitive sensor.

12. A sensor comprising:

a substrate; and

a mechanical structure, wherein the mechanical structure includes

at least two proof masses including a first proof mass and a second proof mass,

a flexible coupling between the at least two proof masses and the substrate;

wherein the at least two proof masses move in an anti-phase direction normal to the plane of the substrate in response to acceleration of the sensor normal to the plane and move in a direction parallel to the plane of the substrate in response to an acceleration of the sensor parallel to the plane.

13. The sensor of claim 12, wherein the first and second proof masse have unbalancing torque along a direction normal to the substrate.

14. The sensor of claim 12, wherein the flexible coupling further comprises:

at least one anchor; and

a translational and torsional system;

the translational and torsional system further including an anchoring spring connecting the at least one anchor and a first rotational lever;

a first translational and torsional spring connects the first proof mass to the rotational lever with a first lever length; and

a second translational and torsional spring connects the second proof mass to the first rotational lever with a second lever length.

15. The sensor of claim 14, wherein the first lever length and the second lever length are different.

16. The sensor of claim 15, wherein the flexible coupling further includes a second anchoring translational and torsional spring connecting the at least one anchor and a second translational and torsional lever;

a third translational and torsional spring connects the first proof mass to the second translational and torsional lever with a third lever length; and

a fourth translational and torsional spring connects the second proof mass to the second translational and torsional lever with a fourth lever length;

wherein the first and second translational and torsional levers rotates antiphase in a direction normal to the substrate in response to acceleration of the sensor normal to the substrate;

wherein the first and second translational and torsional levers translates in a plane parallel to the substrate in response to acceleration of the sensor parallel to the substrate

17. The sensor of claim 16, wherein the third lever length and the fourth lever length are different.

18. The sensor of claim 12, further comprising a magnetic material wherein the magnetic material is on any of the at least two proof masses, on the first rotational lever, and the second rotational levers;

wherein the mechanical structure rotates in a plane parallel to the plane in response to the magnetic field in a direction parallel to the plane.

19. The sensor of claim 12, further comprising a magnetic material wherein the magnetic material is on any of the at least two proof masses, on the first rotational lever, and the second rotational levers;

wherein the mechanical structure rotates in a directional normal to the plane in response to the magnetic field in a direction normal to the plane.

20. The sensor of claim 12, further comprising a transducer for measuring motion in a direction either normal and parallel to the plane of the substrate of the mechanical structure relative to the substrate.

21. The sensor of claim 20, wherein the transducer is on any of the two proof masses, or the mechanical structure or the lever arms.

22. The sensor of claim 20, wherein the transducer is a capacitive sensor.

23. A sensor comprising:

a substrate; and

a mechanical structure, wherein the mechanical structure includes

at least two proof masses including a first proof mass and a second proof mass,

a flexible coupling between the at least two proof masses and the substrate;

wherein the at least two proof masses move in an anti-phase direction normal to the plane of the substrate in response to acceleration of the sensor normal to the plane and wherein move in anti-phase in a direction parallel to the plane of the substrate in response to an acceleration of the sensor parallel to the plane,

wherein the at least two proof masses move in a direction parallel to the plane of the substrate in response to an acceleration of the sensor parallel to the plane.

24. The sensor of claim 23, wherein the first and second proof masses have unbalancing torque.

25. The sensor of claim 23, wherein the flexible coupling further comprises:

at least one anchor; and

a rotational, translational and torsional system;

the rotational, translational and torsional system further including an anchoring spring connecting the at least one anchor and a first rotational lever;

a first rotational, translational and torsional spring connects the first proof mass to the rotational, translational and torsional lever with a first lever length; and

a second rotational, translational and torsional spring connects the second proof mass to the first rotational, translational and torsional lever with a second lever length.

26. The sensor of claim 25, wherein the first lever length and the second lever length are different.

27. The sensor of claim 26, wherein the flexible coupling further includes a second anchoring rotational, translational and torsional spring connecting the at least one anchor and a second rotational, translational and torsional lever;

a third rotational, translational and torsional spring connects the first proof mass to the second rotational, translational and torsional lever with a third lever length; and

a fourth rotational, translational and torsional spring connects the second proof mass to the second rotational, translational and torsional lever with a fourth lever length;

wherein the first and second rotational, translational and torsional levers rotates antiphase in a direction normal to the substrate in response to acceleration of the sensor normal to the substrate;

wherein the first and second rotational, translational and torsional levers rotates in a plane parallel to the substrate in response to acceleration of the sensor parallel to the substrate;

wherein the first and second rotational, translational and torsional levers translates in a plane parallel to the substrate in response to acceleration of the sensor parallel to the substrate.

28. The sensor of claim 27, wherein the third lever length and the fourth lever length are different.

29. The sensor of claim 27, further comprising magnetic material, wherein the magnetic material is on any of the at least two proof masses, on the first rotational lever, and the second rotational levers.

30. The sensor of claim 23, further comprising a magnetic material wherein the magnetic material is on any of the at least two proof masses, on the first rotational lever, and the second rotational levers;

wherein the mechanical structure rotates in a plane parallel to the plane in response to the magnetic field in a direction parallel to the plane.

31. The sensor of claim 23, further comprising a magnetic material wherein the magnetic material is on any of the at least two proof masses, on the first rotational lever, and the second rotational levers;

wherein the mechanical structure rotates in a directional normal to the plane in response to the magnetic field in a direction normal to the plane.

32. The sensor of claim 23, further comprising a transducer for measuring motion in a direction either normal and parallel to the plane of the substrate of the mechanical structure relative to the substrate

33. The sensor of claim 32, wherein the transducer is on any of the two proof masses, or the mechanical structure or the lever arms,

34. The sensor of claim 32, wherein the transducer is a capacitive sensor.

35. A sensor comprising:

a substrate; and

a mechanical structure, wherein the mechanical structure includes

at least two proof masses including a first proof mass and a second proof mass,

a flexible coupling between the at least two proof masses and the substrate;

wherein the at least two proof masses move in anti-phase in a direction parallel to the plane of the substrate in response to an acceleration in the same direction of the sensor via an unbalancing torque.

36. The sensor of claim 35, wherein the flexible coupling further comprises:

at least one anchor; and

a rotational system;

the rotational system further including an anchoring spring connecting the at least one anchor and a first rotational lever;

a first rotational spring connects the first proof mass to the rotational lever with a first lever length; and

a second rotational spring connects the second proof mass to the first rotational lever with a second lever length.

37. The sensor of claim 36, wherein the first lever length and the second lever length of the first rotational lever are different.

38. The sensor of claim 37, wherein the flexible coupling further includes a second anchoring rotational spring connecting the at least one anchor and a second rotational lever;

a third rotational spring connects the first proof mass to the second rotational lever with a third lever length; and

a fourth rotational spring connects the second proof mass to the second rotational lever with a fourth lever length;

wherein the second rotational lever rotates in a plane parallel to the substrate counter to the rotation of the first rotational lever in response to acceleration of the sensor on the same direction.

39. The sensor of claim 38, wherein the third lever length and the fourth lever length of the second rotational lever are different.

40. The sensor of claim 35, further comprising a transducer for measuring motion of the mechanical structure relative to the substrate.

41. The sensor of claim 40, wherein the motion of the at least two proof masses relative to the substrate is measured by the transducer via capacitive sensing.

42. The sensor of claim 35, wherein motion of the at least two proof masses relative to each other are measured by a transducer.

43. The sensor of claim 42, where in the transducer is a capacitive sensor.

44. The sensor of claim 40, wherein the displacement of the coupling springs is measured by the transducer via capacitive sensing.

45. The sensor of claim 36, wherein a displacement of the first rotational lever is measured by the transducer via capacitive sensing.

46. The sensor of claim 41, wherein the one or more electrodes are located on the substrate.

47. The sensor of claim 41, further comprising a cap, wherein the mechanical structure is located between the cap and the substrate, wherein the one or more electrodes are located on the cap facing the mechanical structure.