In-plane sensing Lorentz force magnetometer

• US 9,664,750 B2
• Filed: 12/31/2012
• Issued: 05/30/2017
• Est. Priority Date: 01/11/2011
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Thompson, Matthew Julian, Seeger, Joseph
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): RHODES-VIVOUR, TEMILADE S
• Application Number:
  US13/731,301
• Publication Number:
  US 20140184213A1
• Time in Patent Office: 1,611 Days
• Field of Search: 3242441
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B
• CPC Class Codes: G03F 1/00 Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
• CPC Class Codes: H01H 1/00 Contacts liquid contacts H01H29/04
• CPC Class Codes: H02K 1/00 Details of the magnetic circuit magnetic circuits for relays H01H50/16

Abstract

A magnetic field sensor includes a driving element through which an electric current circumnavigates the driving element. A Lorentz force acts on the driving element resulting in a torque about a first axis in response to a magnetic field along a second axis substantially parallel to a plane of a substrate. The driving element is coiled-shaped. A sensing element of the magnetic field sensor is configured to rotate about the first axis substantially parallel to the plane of the substrate in response to the magnetic field and a coupling element mechanically couples the driving element to the sensing element. The driving element, the sensing element, and the coupling element are disposed in the plane, substantially parallel to the substrate. At least two anchors are configured to connect the driving element, the sensing element, and the coupling element to the substrate.

Claims

1. A device comprising:

a magnetic field sensor including,

a driving element onto which a Lorentz force acts resulting in a torque about a first axis in response to a magnetic field along a second axis, the direction of the magnetic field being substantially parallel to a plane of a substrate onto which the driving element resides, the driving element being a coil through which an electric current flows;

a sensing element configured to rotate about the first axis substantially parallel to the plane of the substrate and in response to the magnetic field,

wherein the sensing element and the driving element have a symmetric structure relative to each other about the first axis;

a coupling element mechanically coupling the driving element to the sensing element, the sensing element and the coupling element being disposed in the plane, substantially parallel to the substrate; and

at least two anchors configured to connect the driving element, the sensing element, and the coupling element to the substrate.

2. The magnetic field sensor of claim 1, further comprising at least one electrode disposed between the sensing element and the substrate to form a capacitive sensor, where in capacitance of the capacitive sensor changes in response to magnetic field.

3. The magnetic field sensor of claim 1, further comprising at least one optical interferometry sensor, where the interferometer signal changes in response to magnetic field.

4. The magnetic field sensor of claim 1, further comprising a piezoresistive sensor, where in resistivity of the piezoresistor sensor changes in response to magnetic field.

5. The magnetic field sensor of claim 1, wherein the electric current is AC modulated.

6. The magnetic field sensor of claim 1, wherein the driving element is balanced about the first axis.

7. The magnetic field sensor of claim 1, wherein the driving element, the sensing element, and the coupling element are made from the same material.

8. The magnetic field sensor of claim 1, wherein the coupling element is made from a first material, and the driving element and the sense element are each made from a second material, the first material being different than the second material.

9. The magnetic field sensor of claim 1, wherein the driving element is made from a first material and the coupling element and the sense element are each made from a second material, the first material being different than the second material.

10. The magnetic field sensor of claim 1, wherein the driving element is comprising highly doped silicon of with resistivity less than 5 milli Ohm cm.

11. The magnetic field sensor of claim 1, wherein the driving element comprises metal.

12. The magnetic field sensor of claim 1, wherein the coiled-shape is a half-turn coil, single-turn or multi-turn.

13. The magnetic field sensor of claim 1, further comprising at least one electrode between the sense element and the substrate to form a capacitive sensor, wherein capacitance of the capacitive sensor changes in response to magnetic field.

14. The magnetic field sensor of claim 1, further comprising a piezoelectric sensor, wherein an output of the piezoelectric sensor changes in response to the magnetic field.

15. The magnetic field sensor of claim 1, wherein the second coupling element further comprises a first rotational lever that rotates about the first axis, a second rotational lever that rotates about a second axis and a flexible element connecting the first rotational lever to the second rotational lever.

16. The magnetic field sensor of claim 1, wherein the first electric current and the second electric current are AC modulated.

17. The magnetic field sensor of claim 1, wherein the first driving element is coiled-shaped.

18. The magnetic field sensor of claim 1, wherein the second driving element is coiled-shaped.

19. The magnetic field sensor of claim 1, wherein the coiled-shape is a half coil or a single-turn coil or a multi-turn coil.

20. The magnetic field sensor of claim 1, wherein the first driving element is balanced about the first axis.

21. The magnetic field sensor of claim 1, wherein the second driving element is balanced about the second axis.

22. The magnetic field sensor of claim 1, wherein the first driving element, the second driving element, the sensing element, the first coupling element and the second coupling element are constructed from a same material.

23. The magnetic field sensor of claim 1, wherein the first coupling element and the second coupling element is constructed from a first material, the first driving element, the second driving element and the sense element are constructed from a second material.

24. The magnetic field sensor of claim 1, wherein the first driving element and the second driving element is constructed from a first material, the first coupling element, the second coupling element and the sense element are constructed from a second material.

25. The magnetic field sensor of claim 1, wherein the first driving element and the second driving element is constructed from a low resistance material.

26. The magnetic field sensor of claim 1, wherein the low resistance material is highly doped silicon with resistivity less than 5 milli Ohm cm.

27. The magnetic field sensor of claim 1, wherein the low resistance material is metal deposited on silicon.

28. The magnetic field sensor of claim 1, wherein the low resistance material is metal.

29. A method of measuring a magnetic field along 2-axes comprising:

driving inner drive current through an inner drive coil causing displacement of the sense element related to the magnetic field;

driving outer drive current through an outer coil at a phase that is substantially ninety degrees phase shifted relative to that of the inner drive current, causing displacement of the sense element related to the magnetic field;

measuring the displacement of the sense element, in phase, using the outer drive current;

determining the magnetic field of the sense element along a first-axis;

measuring the displacement of the sense element, in phase, using the inner drive current;

determining the magnetic field of the sense element along an second-axis;

terminating the inner drive current and the outer drive current.

30. A device comprising:

a magnetic field sensor including,

a first driving element where in, a first electric current flows through the first driving element, a Lorentz force acts on the first driving element resulting in a torque about a first axis in response to a first magnetic field along a second axis substantially parallel to a plane of a substrate;

a second driving element where in, a second electric current flows through the second driving element, a Lorentz force acts on the second driving element resulting in a torque about the second axis in response to a second magnetic field along the first axis substantially parallel to a plane of a substrate;

a sensing element configured to rotate about the first axis substantially parallel to the plane of the substrate in response to the first or the second magnetic field;

a first coupling element that mechanically couples the first driving element to the second driving element;

a second coupling element mechanically couples the first driving element to the sensing element and the first driving element, the second driving element, the sensing element, the first coupling element and the second coupling element are disposed in the plane; and

at least two anchor configured to connect the first driving element to the substrate and at least two anchor configured to connect the second driving element to the substrate.

31. The magnetic field sensor of claim 30, further comprising at least one optical sensor for detecting motion of the sense element, wherein output of the optical sensor changes in response to the magnetic field.

32. The magnetic field sensor of claim 30, further comprising a piezoresistive sensor, wherein resistivity of the piezoresistor sensor changes in response to the magnetic field.

33. The magnetic field sensor of claim 30, wherein the coiled-shape is a half coil or a single-turn coil or a multi-turn coil.