Single-chip two-axis magnetic field sensor

Patent metadata

Field	Value
Publication number	US-9575143-B2
Application number	US-201214110106-A
Country	US
Kind code	B2
Filing date	May 23, 2012
Priority date	Apr 6, 2011
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

The present invention discloses a design for a single-chip dual-axis magnetic field sensor, based on magnetic tunnel junction (MTJ) elements and permanent magnets integrated on a semiconductor substrate to produce two types of sensor bridges that detect orthogonal magnetic field components. The orthogonal magnetic field component detection capability results from the different types of sensor bridges that can be produced by varying the shape of the MTJ elements and the bias fields that can be created by permanent magnets. Because the permanent magnets can create orthogonal bias fields on the different sensor bridges, it is possible to use a single pinned layer to set direction for both sensor bridges. This is advantageous because it permits the two-axis sensor to be fabricated on a single semiconductor chip without the need for specialized processing technology such as local heating, or deposition of multiple magnetoresistive films with different pinned layers setting directions.

First claim

The invention claimed is:

1. A single-chip two-axis magnetic field sensor, comprising:
a semiconductor substrate;
two mutually orthogonal sensing axes, the X-axis and the Y-axis;
a referenced bridge sensor integrated on the semiconductor substrate, the referenced bridge sensor having a sensitive direction along the Y-axis, wherein the referenced bridge comprises reference elements and sense elements, wherein the sense elements have a magnetoresistive transfer curve strongly dependent on applied magnetic fields and the reference elements have a magnetoresistive transfer curve weakly dependent on an applied magnetic field;
a push-pull bridge sensor integrated on the semiconductor substrate, the push-pull bridge sensor having a sensitive direction along the X-axis, wherein the push-pull bridge is comprised only of sense elements; and
each of the reference elements and each of the sense elements including a magnetic sensor element, the magnetic sensor element being either a tunneling magnetoresistance (TMR) element or a giant magnetoresistance (GMR) element, wherein the magnetic sensor elements in the referenced bridge sensor and the magnetic sensor elements in the push-pull bridge sensor have a common pinning direction, and wherein a technique is implemented to reduce sensitivity of the reference elements to applied magnetic fields such that the reference elements have the magnetoresistive transfer curve weakly dependent on the applied magnetic field, the technique being selected from the group of techniques consisting of: shielding, shape anistropy stabilization, exchange bias, and magnetic field bias.

2. The single-chip two-axis magnetic field sensor of claim 1 , wherein the referenced bridge sensor is a full-bridge sensor and the push-pull bridge sensor is a full bridge sensor.

3. The single-chip two-axis magnetic field sensor of claim 2 , further comprising permanent magnets used to create different bias magnetic fields on the reference elements and sense elements of the referenced bridge in order to make the sensitivity of the reference elements and sense elements of the referenced full-bridge sensor different, and also to bias the magnetization directions of free layers of the sense elements of the push-pull full-bridge sensor.

4. The single-chip two-axis magnetic field sensor of claim 2 , wherein the sense elements and the reference elements of the referenced full bridge sensor have different shape anisotropy such that the sensitivity of the sense elements and the reference elements is different, and wherein the sense elements of the push-pull full bridge sensor have shape anisotropy that control the magnetization directions of the free layers of the sense elements.

5. The single-chip two-axis magnetic field sensor of claim 2 , further comprising the permanent magnets to create bias fields, wherein the combined effect of the permanent magnet bias fields and the shape anisotropy of the sense elements and the reference elements in the referenced full-bridge sensor causes the sensitivities of the sense elements and the reference elements to be different, wherein the combined effect of the permanent magnet bias field and the shape anisotropy of the sense elements of the push-pull full-bridge sensor sets the magnetization directions of free layers of the sense elements of the push-pull full-bridge sensor.

6. The single-chip two-axis magnetic field sensor of claim 1 , wherein the referenced bridge sensor is a half-bridge sensor and the push-pull bridge sensor is a half-bridge sensor.

7. The single-chip two-axis magnetic field sensor of claim 6 , further comprising permanent magnets used to create different bias magnetic fields on the reference elements and the sense elements of the referenced half-bridge in order to make the sensitivity of the reference elements and sense elements of the referenced half-bridge sensor different, and also to bias the magnetization directions of free layers of the sense elements of the push-pull halfbridge sensor.

8. The single-chip two-axis magnetic field sensor of claim 6 , wherein the referenced half-bridge sensor sense elements and reference elements have different shape anisotropy such that the sensitivity of the sense elements and the reference elements is different, wherein the push-pull half-bridge sensor sense elements have shape anisotropy that controls the magnetization directions of free layers of the sense elements.

9. The single-chip two-axis magnetic field sensor of claim 6 , further comprising permanent magnets to create bias fields, wherein the combined effect of the bias fields and the shape anisotropy of the sense elements and the reference elements in the referenced half-bridge sensor causes the sensitivities of the sense elements and the reference elements to be different, wherein the combined effect of the permanent magnet bias fields and the shape anisotropy of the sense elements of the push-pull half-bridge sensor sets the magnetization directions of free layers of the sense elements of the push-pull half-bridge sensor.

10. The single-chip two-axis magnetic field sensor of claim 1 , further comprising a shield covering the reference elements of the referenced bridge sensor in order to lower the sensitivity of the reference elements, wherein the shield is comprised of a soft ferromagnetic material with high magnetic permeability.

11. The single-chip two-axis magnetic field sensor of claim 1 , further comprising soft ferromagnetic structures in the regions around and between the sense elements of the referenced bridge-type sensor in order to increase the sensitivity of the sensing elements.

12. The single-chip two-axis magnetic field sensor of claim 1 , wherein of the magnetic sensor elements in both the referenced bridge sensor and the push-pull bridge sensor have pinning layers with magnetization initialized in a same direction.

13. A sensor, comprising:
a substrate; and
magnetic sensor elements fabricated on the substrate, the magnetic sensor elements being either tunneling magnetoresistance (TMR) elements or giant magnetoresistance (GMR) elements, the magnetic sensor elements fabricated on the substrate forming a referenced bridge sensor and forming a push-pull bridge sensor,
wherein the referenced bridge sensor has a sensitive direction along a first axis and the push-pull bridge sensor has a sensitive direction along a second axis, the second axis being orthogonal to the first axis,
wherein the magnetic sensing elements forming the referenced bridge sensor including reference elements and sense elements, and the magnetic sensing elements forming the push-pull bridge sensor including only sense elements, wherein the sense elements have a magnetoresistive transfer curve strongly dependent on applied magnetic fields and the reference elements have a magnetoresistive transfer curve weakly dependent on an applied magnetic field, and
wherein the magnetic sensor elements have a common pinning direction for all of the magnetic sensor elements in both of the referenced bridge sensor and the push-pull bridge sensor, and wherein a technique is implemented to reduce sensitivity of the reference elements to applied magnetic fields such that the reference elements have the magnetoresistive transfer curve weakly dependent on the applied magnetic field, the technique being selected from the group of techniques consisting of: shielding, shape anistropy stabilization, exchange bias, and magnetic field bias.

14. The sensor of claim 13 , wherein the magnetic sensor elements are TMR elements.

15. The sensor of claim 13 , wherein the magnetic sensor elements are GMR elements.

Assignees

• Deak James Geza
• Jin Insik
• Shen Weifeng
• Lei Xiaofeng
• Xue Songsheng
• Multidimension Technology Co Ltd

Inventors

• Deak James Geza
• Jin Insik
• Shen Weifeng
• Lei Xiaofeng
• Xue Songsheng

Classifications

• G01R33/098 Primary

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