Magnetic field sensor with increased SNR

Patent metadata

Field	Value
Publication number	US-10809320-B2
Application number	US-201615141461-A
Country	US
Kind code	B2
Filing date	Apr 28, 2016
Priority date	Apr 29, 2015
Publication date	Oct 20, 2020
Grant date	Oct 20, 2020

Abstract

Various means for improvement in signal-to-noise ratio (SNR) for a magnetic field sensor are disclosed for low power and high resolution magnetic sensing. The improvements may be done by reducing parasitic effects, increasing sense element packing density, interleaving a Z-axis layout to reduce a subtractive effect, and optimizing an alignment between a Z-axis sense element and a flux guide, etc.

First claim

What is claimed is:

1. A magnetic field sensor, comprising:
a plurality of magnetoresistance sense elements coupled together as a first circuit to sense a magnetic field, wherein each magnetoresistance sense element of the plurality of magnetoresistance sense elements includes a first ferromagnetic layer and a second ferromagnetic layer separated by an insulating barrier layer; and
a conductive line coupled to the first ferromagnetic layer of first and second magnetoresistance sense elements of the plurality of magnetoresistance sense elements,
wherein the first magnetoresistance sense element and a third magnetoresistance sense element of the plurality of magnetoresistance sense elements share a common second ferromagnetic layer such that a first portion of the common second ferromagnetic layer is above or below the first ferromagnetic layer of the first magnetoresistance sense element and a second portion of the common second ferromagnetic layer is above or below the first ferromagnetic layer of the third magnetoresistance sense element, and
wherein the common shared ferromagnetic layer is either (1) above both the first ferromagnetic layer of the first magnetoresistance sense element and the first ferromagnetic layer of the third magnetoresistance sense element or (2) below both the first ferromagnetic layer of the first magnetoresistance sense element and the first ferromagnetic layer of the third magnetoresistance sense element.

2. The magnetic field sensor of claim 1 , further comprising:
at least one flux guide located between the first and second magnetoresistance sense elements, wherein the at least one flux guide is located above or below the first and second magnetoresistance sense elements.

3. The magnetic field sensor of claim 2 , wherein the at least one flux guide includes a thin ferromagnetic material layer on both sides of the at least one flux guide.

4. The magnetic field sensor of claim 2 , wherein the at least one flux guide is located symmetrically between the first and second magnetoresistance sense elements, and wherein a width of the at least one flux guide covers a whole width between the first and second magnetoresistance sense elements.

5. The magnetic field sensor of claim 2 , wherein the at least one flux guide is located relatively closer to the first magnetoresistance sense element than to the second magnetoresistance sense element.

6. The magnetic field sensor of claim 2 , wherein the at least one flux guide includes a first flux guide and a second flux guide, wherein the first flux guide is located above the first and second magnetoresistance sense elements, and wherein the second flux guide is located below the first and second magnetoresistance sense elements.

7. The magnetic field sensor of claim 1 , further comprising a plurality of flux guides, and wherein the plurality of flux guides are located above or below the first and second magnetoresistance sense elements.

8. The magnetic field sensor of claim 7 , wherein at least one flux guide of the plurality of flux guides is located symmetrically between the first and second magnetoresistance sense elements.

9. The magnetic field sensor of claim 7 , wherein at least one flux guide of the plurality of flux guides includes a high permeability magnetic material.

10. The magnetic field sensor of claim 1 , wherein, when a magnetic field is sensed by the plurality of magnetoresistance sense elements, a sense current flows through the first ferromagnetic layer, an insulating barrier layer, and the second ferromagnetic layer of a magnetoresistance sense element, and wherein a direction of the sense current flow is perpendicular to the conductive line.

11. The magnetic field sensor of claim 1 , wherein the first ferromagnetic layer of each magnetoresistance sense element includes a magnetization direction free to rotate in a magnetic field, and wherein the second ferromagnetic layer of each magnetoresistance sense element includes a fixed magnetization direction.

12. The magnetic field sensor of claim 1 , wherein the plurality of magnetoresistance sense elements includes one or more tunneling magnetoresistance sense elements, giant magnetoresistance sense elements, and/or anisotropic magnetoresistance sense elements.

13. The magnetic field sensor of claim 1 , further comprising:
a second circuit comprising a plurality of current lines, wherein each current line of the plurality of current lines is adjacent to a corresponding magnetoresistance sense element of the plurality of magnetoresistance sense elements.

14. The magnetic field sensor of claim 13 , wherein at least one current line of the plurality of current lines is positioned above or below a magnetoresistance sense element.

15. The magnetic field sensor of claim 13 , wherein at least one current line of the plurality of current lines is positioned at a 45 degree cross angle relative to a first ferromagnetic layer of a magnetoresistance sense element of the plurality of magnetoresistance sense elements.

16. The magnetic field sensor of claim 13 , wherein at least one current line of the plurality of current lines is positioned at a 90 degree cross angle relative to a first ferromagnetic layer of a magnetoresistance sense element of the plurality of magnetoresistance sense elements.

17. A magnetic field sensor, comprising:
a plurality of magnetoresistance sense elements coupled together as a first circuit to sense a magnetic field, wherein the plurality of magnetoresistance sense elements includes at least a first magnetoresistance sense element and a second magnetoresistance sense element located in a plane; and
a plurality of flux guides, wherein a first flux guide of the plurality of flux guides is located above or below the first magnetoresistance sense element, and wherein the first flux guide is positioned between the first and second magnetoresistance sense elements,
wherein each flux guide of the plurality of flux guides is configured to direct a portion of a magnetic field oriented orthogonally to the plane of first and second magnetoresistance sense elements into the plane of the first and second magnetoresistance sense elements, wherein the first flux guide is configured to direct the magnetic field into the plane in a first direction, and wherein a second flux guide of the plurality of flux guides is configured to direct the magnetic field into the plane in a second direction opposite the first direction, and
wherein two of the magnetoresistance sense elements of the plurality of magnetoresistance sense elements are coupled via a first common ferromagnetic layer that extends between the two magnetoresistance sense elements,
wherein another two of the magnetoresistance sense elements of the plurality of magnetoresistance sense elements are coupled via a second common ferromagnetic layer that extends between the another two magnetoresistance sense elements, and
wherein the first common ferromagnetic layer and the second common ferromagnetic layer are spaced apart.

18. The magnetic field sensor of claim 17 , wherein the first magnetoresistance sense element and a third magnetoresistance sense element of the plurality of magnetoresistance sense elements share the first common ferromagnetic layer, wherein the first common ferromagnetic layer includes first and second portions, wherein the first portion of the common ferromagnetic layer is above or below a ferromagnetic layer of the first magnetoresistance sense element, and wherein the second portion of the common ferromagnetic layer is above or below a ferromagnetic la

Assignees

• Everspin Technologies Inc

Inventors

• Mather Phillip G
• Mohan Anuraag

Classifications

• G01R33/098

  comprising tunnel junctions, e.g. tunnel magnetoresistance sensors · CPC title

• G01R33/093 Primary

  using multilayer structures, e.g. giant magnetoresistance sensors (thin magnetic films H01F10/00) · CPC title