SINGLE-CHIP TWO-AXIS MAGNETIC FIELD SENSOR

• US 20140035573A1
• Filed: 05/23/2012
• Published: 02/06/2014
• Est. Priority Date: 04/06/2011
• Status: Active Grant

• Current Assignee: Multidimension Technology Co., Ltd
• Original Assignee: Multidimension Technology Co., Ltd
• Inventors: Deak, James Geza, Jin, Insik, Shen, Weifeng, Lei, Xiaofeng, Xue, Songsheng
• Granted Patent: US 9,575,143 B2
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors

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.

Claims

1. A single-chip two-axis magnetic field sensor, comprising:

Two mutually orthogonal sensing axes, the X-axis and the Y-axis;

A referenced bridge sensor that has a sensitive direction along the Y-axis, wherein the referenced bridge comprises reference elements and sense elements;

A push-pull bridge sensor that has a sensitive direction along the X-axis, wherein the push-pull bridge is comprised only of sense elements.

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 the 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 referenced full-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;

additionally, wherein the push-pull full-bridge sensor sense elements have shape anisotropy that control the magnetization directions of the free layers of said 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, additionally 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 the 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 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 the free layers of the sense elements of the push-pull half-bridge 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;

additionally, wherein the push-pull half-bridge sensor sense elements have shape anisotropy that controls the magnetization directions of the free layers of said sense elements.

9. The single-chip two-axis magnetic field sensor of claim 6, further comprising said 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 reference half-bridge sensor causes the sensitivities of the sense elements and the reference elements to be different, additionally 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 the 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, said 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.