3-axis magnetic field sensor, method for fabricating magnetic field sensing structure and magnetic field sensing circuit

• US 9,069,033 B2
• Filed: 06/02/2013
• Issued: 06/30/2015
• Est. Priority Date: 03/26/2013
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Chen, Young-Shying, Kuo, Keng-Ming, Wang, Ding-Yeong, Chien, Cheng-Wei
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): RIOS RUSSO, RAUL J
• Application Number:
  US13/907,960
• Publication Number:
  US 20140292312A1
• Time in Patent Office: 758 Days
• Field of Search: 324/51, 324/55, 324/200, 324/207.11, 324/207.13, 324/207.21, 324/252
• US Class Current: 1/1
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors

Abstract

A 3-axis magnetic field sensor on a substrate and including, a first tunneling magneto-resistor (TMR) having a first easy-axis for sensing a X-axis magnetic field, a second TMR having a second easy-axis for sensing a Y-axis magnetic field, an out-of-plane magnetic sensor for sensing a Z-axis magnetic field, and a reference unit is provided. The first easy-axis and the second easy-axis are orthogonal and include an angle of 45±5 degrees with a bisection direction, respectively. The out-of-plane magnetic sensor includes a groove or bulge structure having a first incline and a second incline; a third TMR on the first incline having a third easy-axis; a fourth TMR on the second incline having a fourth easy-axis; and a central axis orthogonal to the bisection direction and parallel to the third easy-axis and the fourth easy-axis. The reference unit has a fifth TMR and a fifth easy-axis parallel to the bisection direction.

Claims

1. A 3-axis magnetic field sensor, comprising:

a first in-plane magnetic field sensor, located on a substrate to sense an X-axis magnetic field, and having a first tunneling magneto-resistor (TMR) and a first easy-axis, wherein the first easy-axis is regarded as a Y-axis;

a second in-plane magnetic field sensor, located on the substrate to sense a Y-axis magnetic field, and having a second TMR and a second easy-axis, wherein the second easy-axis is regarded as an X-axis,

an included angle between the first easy-axis and the second easy-axis is 90±

10 degrees, and a bisection direction on the substrate respectively include an angle of 45±

5 degrees with the first easy-axis and the second easy-axis;

an out-of-plane magnetic field sensor, located on the substrate to sense a Z-axis magnetic field, and the out-of-plane magnetic field sensor comprising;

a groove or bulge structure, located on the substrate, and having a first incline, a second incline and a central axis, wherein the first incline and the second incline have a same bevel angle relative to the substrate and are symmetric relative to the central axis, and the central axis is orthogonal to the bisection direction;

a third TMR, formed on the first incline, and having a third easy-axis;

a fourth TMR, formed on the second incline, and having a fourth easy-axis,

wherein the third easy-axis and the fourth easy-axis are parallel to the central axis; and

a tunneling magneto-resistance reference unit, located on the substrate, and having a fifth TMR and a fifth easy-axis, wherein the fifth easy-axis is parallel to the bisection direction.

2. The 3-axis magnetic field sensor as claimed in claim 1, wherein the first TMR has a first pinned direction and comprises:

a first bottom electrode, located on the substrate, and serving as a terminal of circuit connection;

a first magnetic tunneling junction (MTJ) device, comprising;

a first pinned layer of a magnetic material, located on the first bottom electrode, and having a first pinned magnetization parallel to the first pinned direction;

a first tunneling layer of a non-magnetic material, disposed on the first pinned layer; and

a first free layer of a magnetic material, disposed on the first tunneling layer, and having a first free magnetization parallel to the first easy-axis, wherein the first pinned direction and the first easy-axis form a first included angle there between;

a second MTJ device, comprising;

a second pinned layer of a magnetic material, located on the first bottom electrode, and having a second pinned magnetization parallel to the first pinned direction;

a second tunneling layer of a non-magnetic material, disposed on the second pinned layer; and

a second free layer of a magnetic material, disposed on the second tunneling layer, and having a second free magnetization parallel to the first easy-axis; and

a first top electrode, connected to the first free layer and the second free layer, and serving as a terminal of circuit connection,

wherein the first free magnetization and the second free magnetization are parallel to the first easy-axis under an initial state but are anti-parallel to each other, and the first included angle between the first pinned direction and the first easy-axis is substantially 45±

5 degrees or 135±

5 degrees, wherein a first magnetic field sensing direction is orthogonal to the first easy-axis on the substrate.

3. The 3-axis magnetic field sensor as claimed in claim 2, further comprising:

a first metal wire, capable of conducting current to produce a magnetic field, so as to set the initial state of the first free magnetization and the second free magnetization to be parallel to the first easy-axis but anti-parallel to each other.

4. The 3-axis magnetic field sensor as claimed in claim 1, wherein the second TMR has a second pinned direction and comprises:

a second bottom electrode, located on the substrate, and serving as a terminal of circuit connection;

a third MTJ device, comprising;

a third pinned layer of a magnetic material, located on the second bottom electrode, and having a third pinned magnetization parallel to the second pinned direction;

a third tunneling layer of a non-magnetic material, disposed on the third pinned layer; and

a third free layer of a magnetic material, disposed on the third tunneling layer, and having a third free magnetization parallel to the second easy-axis, wherein the second pinned direction and the second easy-axis form a second included angle there between;

a fourth MTJ device, comprising;

a fourth pinned layer of a magnetic material, located on the second bottom electrode, and having a fourth pinned magnetization parallel to the second pinned direction;

a fourth tunneling layer of a non-magnetic material, disposed on the fourth pinned layer; and

a fourth free layer of a magnetic material, disposed on the fourth tunneling layer, and having a fourth free magnetization parallel to the second easy-axis; and

a second top electrode, connected to the third free layer and the fourth free layer, and serving as a terminal of circuit connection,

wherein the third free magnetization and the fourth free magnetization are parallel to the second easy-axis under the initial state but are anti-parallel to each other, and the second included angle between the second pinned direction and the second easy-axis is substantially 45±

5 degrees or 135±

5 degrees, wherein the a second magnetic field sensing direction is orthogonal to the second easy-axis on the substrate.

5. The 3-axis magnetic field sensor as claimed in claim 4, further comprising:

a second metal wire, capable of conducting current to produce a magnetic field, so as to set the initial state of the third free magnetization and the fourth free magnetization to be parallel to the second easy-axis but anti-parallel to each other.

6. The 3-axis magnetic field sensor as claimed in claim 1, wherein the third TMR comprises:

a third bottom electrode, located on the first incline, and serving as a terminal of circuit connection;

a fifth MTJ device, comprising;

a fifth pinned layer of a magnetic material, located on the third bottom electrode, and having a fifth pinned magnetization along the first incline and orthogonal to the third easy-axis;

a fifth tunneling layer of a non-magnetic material, disposed on the fifth pinned layer; and

a fifth free layer of a magnetic material, disposed on the fifth tunneling layer, and having a fifth free magnetization parallel to the third easy-axis; and

a third top electrode, connected to the fifth free layer, and serving as a terminal of circuit connection;

wherein the fourth TMR comprises;

a fourth bottom electrode, located on the second incline, and serving as a terminal of circuit connection;

a sixth MTJ device, comprising;

a sixth pinned layer of a magnetic material, located on the fourth bottom electrode, and having a sixth pinned magnetization along the second incline and orthogonal to the fourth easy-axis;

a sixth tunneling layer of a non-magnetic material, disposed on the sixth pinned layer; and

a sixth free layer of a magnetic material, disposed on the sixth tunneling layer, and having a sixth free magnetization parallel to the fourth easy-axis, wherein the fifth free magnetization and the sixth free magnetization are parallel to each other or anti-parallel to each other; and

a fourth top electrode, connected to the sixth free layer, and serving as a terminal of circuit connection.

7. The 3-axis magnetic field sensor as claimed in claim 1, wherein the fifth TMR has a fifth pinned direction parallel to the fifth easy-axis, and comprises:

a fifth bottom electrode, located on the substrate, and serving as a terminal of circuit connection;

a seventh MTJ device, comprising;

a seventh pinned layer of a magnetic material, located on the fifth bottom electrode, and having a seventh pinned magnetization parallel to the fifth pinned direction;

a seventh tunneling layer of a non-magnetic material, disposed on the seventh pinned layer; and

a seventh free layer of a magnetic material, disposed on the seventh tunneling layer, and having a seventh free magnetization parallel to the fifth easy-axis; and

an eighth MTJ device, comprising;

an eighth pinned layer of a magnetic material, located on the fifth bottom electrode, and having an eighth pinned magnetization parallel to the fifth pinned direction, wherein the seventh pinned magnetization and the eighth pinned magnetization are in a same direction;

an eighth tunneling layer of a non-magnetic material, disposed on the eighth pinned layer; and

an eighth free layer of a magnetic material, disposed on the eighth tunneling layer, and having an eighth free magnetization parallel to the fifth easy-axis; and

a fifth top electrode, connected to the seventh free layer and the eighth free layer, and serving as a terminal of circuit connection,

wherein the seventh free magnetization and the eighth free magnetization are parallel to the fifth easy-axis under the initial state but are anti-parallel to each other.

8. The 3-axis magnetic field sensor as claimed in claim 7, further comprising:

a third metal wire, capable of conducting current to produce a magnetic field, so as to set the initial state of the seventh free magnetization and the eighth free magnetization to be parallel to the fifth easy-axis but anti-parallel to each other.

9. A method for fabricating a magnetic field sensing structure, wherein the magnetic field sensing structure is the 3-axis magnetic field sensor as claimed of claim 1, the method for fabricating the magnetic field sensing structure comprising:

applying a single annealing magnetic field on the 3-axis magnetic field sensor, wherein a direction of the single annealing magnetic field is parallel to an X-Y plane, and respectively include an angle of 45±

5 degrees with the first easy-axis and the second easy-axis, and is orthogonal to the third easy-axis and the fourth easy-axis, and is parallel to the fifth easy-axis.

10. A magnetic field sensing circuit, configured to convert a magnetic field sensed by a magnetic field sensor into an electronic signal, the magnetic field sensing circuit comprising:

a magnetic field sensor, wherein the magnetic field sensor is the out-of-plane magnetic field sensor as claimed in claim 1; and

a voltage clamped signal transfer amplifier, having a positive input terminal, an output terminal, a negative input terminal and a resistor, wherein one end of the third TMR and one end of the fourth TMR are connected to each other and are connected to the negative input terminal, the other end of the third TMR is connected to a power, the other end of the fourth TMR is connected to ground, the positive input terminal is connected to a midpoint voltage source, and the resistor is connected between the output terminal and the negative input terminal.

11. A magnetic field sensing circuit, configured to convert a magnetic field sensed by a magnetic field sensor into an electronic signal, comprising:

a magnetic field sensor, wherein the magnetic field sensor is the first in-plane magnetic field sensor or the second in-plane magnetic field sensor as claimed in claim 1;

a voltage clamped signal transfer amplifier, having a positive input terminal, an output terminal, a negative input terminal and a resistor, wherein the positive input terminal is connected to a midpoint voltage source, and the resistor is connected between the output terminal and the negative input terminal; and

a tunneling magneto-resistance reference unit, having one end connected to the magnetic field sensor and connected to the negative input terminal, and having the other end connected to a power, wherein the other end of the magnetic field sensor that is not connected to the tunneling magneto-resistance reference unit is connected to ground.

12. A magnetic field sensing circuit, configured to convert a magnetic field sensed by a 3-axis magnetic field sensor into an electronic signal, the magnetic field sensing circuit comprising:

a voltage clamped signal transfer amplifier, having a positive input terminal, an output terminal, a negative input terminal and a resistor, wherein the positive input terminal is connected to a midpoint voltage source, and the resistor is connected between the output terminal and the negative input terminal;

a magnetic field sensor, wherein the magnetic field sensor is the out-of-plane magnetic field sensor, the first in-plane magnetic field sensor or the second in-plane magnetic field sensor as claimed in claim 1, wherein one end of the third TMR and one end of the fourth TMR are connected to each other and are connected to the negative input terminal, the other end of the third TMR is connected to a power, and the other end of the fourth TMR is connected to ground; and

a tunneling magneto-resistance reference unit, having one end connected to the first in-plane magnetic field sensor or the second in-plane magnetic field sensor and connected to the negative input terminal, wherein the other end of the first in-plane magnetic field sensor or the second in-plane magnetic field sensor that is not connected to the tunneling magneto-resistance reference unit is connected to ground.

13. A magnetic field sensing circuit, configured to convert a magnetic field sensed by a 3-axis magnetic field sensor into an electronic signal, the magnetic field sensing circuit comprising:

an operational amplifier, having a positive input terminal, an output terminal and a negative input terminal, wherein the positive input terminal is connected to a voltage source;

a magnetic field sensor, wherein the magnetic field sensor is the out-of-plane magnetic field sensor, the first in-plane magnetic field sensor or the second in-plane magnetic field sensor as claimed in claim 1;

a first tunneling magneto-resistance reference unit, having a first terminal and a second terminal, wherein the first terminal is connected to a power;

a second tunneling magneto-resistance reference unit, has a third terminal and a fourth terminal, wherein the fourth terminal is connected to the output terminal, one end of the first in-plane magnetic field sensor or the second in-plane magnetic field sensor is connected to ground, and the other end thereof is connected to the second terminal, the third tell final and the negative input terminal;

a third tunneling magneto-resistance reference unit, having a fifth terminal and a sixth terminal, wherein the fifth terminal is connected to the negative input terminal, and the sixth terminal is connected to the output terminal, one end of the third TMR and one end of the fourth TMR are connected to each other and are connected to the fifth terminal and the negative input terminal, the other end of the third TMR is connected to the power, and the other end of the fourth TMR is connected to the ground.