METHOD AND SYSTEM FOR PROVIDING DUAL MAGNETIC TUNNELING JUNCTIONS USABLE IN SPIN TRANSFER TORQUE MAGNETIC MEMORIES

• US 20110102948A1
• Filed: 10/30/2009
• Published: 05/05/2011
• Est. Priority Date: 10/30/2009
• Status: Active Grant

• Current Assignee: Samsung Semiconductor Incorporated (Samsung Electronics Co. Ltd.)
• Original Assignee: Grandis, Inc. (Samsung Electronics Co. Ltd.)
• Inventors: Nikitin, Vladimir, Druist, David, Watts, Steven M., Apalkov, Dmytro
• Granted Patent: US 8,159,866 B2
• Time in Patent Office: Days
• US Class Current: 360/324.2
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: G11C 11/1659 Cell access
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods
• CPC Class Codes: G11C 11/5607 using magnetic storage elements
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

A method and system for providing a magnetic junction usable in a magnetic memory are described. The magnetic junction includes first and second pinned layers, first and second nonmagnetic spacer layers, and a free layer. The first pinned layer has a first pinned layer magnetic moment and is nonmagnetic layer-free. The first nonmagnetic spacer layer resides between the first pinned and free layers. The free layer resides between the first and second nonmagnetic spacer layers. The second pinned layer has a second pinned layer magnetic moment and is nonmagnetic layer-free. The second nonmagnetic spacer layer resides between the free and second pinned layers. The first and second pinned layer magnetic moments are antiferromagnetically coupled and self-pinned. The magnetic junction is configured to allow the free layer to be switched between stable magnetic states when a write current is passed through the magnetic junction.

Claims

1. A magnetic junction for use in a magnetic memory device comprising:

a first pinned layer having a first pinned layer magnetic moment and being nonmagnetic layer-free;

a first nonmagnetic spacer layer;

a free layer, the first nonmagnetic spacer layer residing between the first pinned layer and the free layer;

a second nonmagnetic spacer layer, the free layer residing between the first nonmagnetic spacer layer and the second nonmagnetic spacer layer; and

a second pinned layer having a second pinned layer magnetic moment and being nonmagnetic layer-free, the second nonmagnetic spacer layer residing between the free layer and the second pinned layer, the first pinned layer magnetic moment and the second pinned layer magnetic moment being antiferromagnetically coupled and self-pinned;

wherein the magnetic junction is configured to allow the free layer to be switched between a plurality of stable magnetic states when a write current is passed through the magnetic junction.

2. The magnetic junction of claim 1 wherein at least one of the first nonmagnetic spacer layer and the second nonmagnetic spacer layer is a tunneling barrier layer.

3. The magnetic junction of claim 2 wherein the tunneling barrier layer is a crystalline MgO layer.

4. The magnetic junction of claim 1 wherein the magnetic junction further includes:

at least one nonmagnetic seed layer.

5. The magnetic junction of claim 1 wherein the magnetic junction has a thickness of not more than twenty nanometers.

6. The magnetic junction of claim 5 wherein the thickness is not more than fifteen nanometers.

7. The magnetic junction of claim 1 wherein the first pinned layer has a first thickness such that the first pinned layer magnetic moment is stable at room temperature and wherein second pinned layer has a second thickness such that the second pinned layer magnetic moment is stable at the room temperature.

8. The magnetic junction of claim 1 wherein the first pinned layer has a first easy axis, the second pinned layer has a second easy axis, the first pinned layer magnetic moment being at a first angle from the first easy axis, the first angle being greater than zero and not more than ten degrees, the second pinned layer magnetic moment being at a second angle from the second easy axis, the second angle being greater than zero and not more than ten degrees.

9. The magnetic junction of claim 1 wherein the free layer has a free layer magnetic moment and a free layer easy axis, the free layer magnetic moment being at an angle greater than zero degrees and not more than twenty degrees from the free layer easy axis.

10. The magnetic junction of claim 9 wherein the free layer magnetic moment is at least five degrees from the free layer easy axis.

11. A magnetic junction for use in a magnetic memory device comprising:

a first pinned layer having a first pinned layer magnetic moment, having a first easy axis, and being nonmagnetic layer-free, the first pinned layer magnetic moment being greater than zero degrees and not more than two degrees from the first easy axis;

a first crystalline MgO tunneling barrier layer;

a free layer having a free layer magnetic moment and a free layer easy axis, the first tunneling barrier layer residing between the first pinned layer and the free layer, the free layer magnetic moment being at least five and not more than twenty degrees from the free layer easy axis;

a second crystalline MgO tunneling barrier layer, the free layer residing between the first tunneling barrier layer and the second tunneling barrier layer; and

a second pinned layer having a second pinned layer magnetic moment, having a second easy axis, and being nonmagnetic layer-free, the second tunneling barrier layer residing between the free layer and the second pinned layer, the second pinned layer magnetic moment being greater than zero degrees and not more than two degrees from the second easy axis, the first pinned layer magnetic moment and the second pinned layer magnetic moment being antiferromagnetically coupled and self-pinned;

wherein the magnetic junction has a thickness of not more than fifteen nanometers and is configured to allow the free layer to be switched between a plurality of stable magnetic states when a write current is passed through the magnetic junction.

12. A magnetic memory comprising:

a plurality of magnetic storage cells, each of the plurality of magnetic storage cells including at least one selection device and at least one magnetic junction, the at least one magnetic junction including a first pinned layer, a first nonmagnetic spacer layer, a free layer, a second nonmagnetic spacer layer, and a second pinned layer, the first pinned layer having a first pinned layer magnetic moment and being nonmagnetic layer-free, the first nonmagnetic spacer layer residing between the first pinned layer and the free layer, the free layer residing between the first nonmagnetic spacer layer and the second nonmagnetic spacer layer, the second pinned layer having a second pinned layer magnetic moment and being nonmagnetic layer-free, the second nonmagnetic spacer layer residing between the free layer and the second pinned layer, the first pinned layer magnetic moment and the second pinned layer magnetic moment being antiferromagnetically coupled and self-pinned, the magnetic junction being configured to allow the free layer to be switched between a plurality of stable magnetic states when a write current is passed through the magnetic junction;

a plurality of bit lines coupled with the plurality of magnetic storage cells; and

a plurality of word lines coupled with the plurality of magnetic storage cells.

13. A method for providing a magnetic junction for use in a magnetic memory device comprising:

providing a magnetic junction stack, the magnetic junction stack including a first pinned layer film, a first nonmagnetic spacer layer film, a free layer film, a second nonmagnetic spacer film, and a second pinned layer film, the first pinned layer film being nonmagnetic layer-free, the first nonmagnetic spacer layer film residing between the first pinned layer film and the free layer film, the free film layer residing between the first nonmagnetic spacer layer film and the second nonmagnetic spacer layer film, the second pinned layer film being nonmagnetic layer-free, the second nonmagnetic spacer layer film residing between the free layer film and the second pinned layer film;

defining the magnetic junction such that the magnetic junction includes a first pinned layer defined from the first pinned layer film, a first nonmagnetic spacer layer defined from the first nonmagnetic spacer layer film, a free layer defined from the free layer film, a second nonmagnetic spacer layer defined from the second nonmagnetic spacer layer film, and a second pinned layer defined from the second nonmagnetic spacer layer film, the first pinned layer having a first pinned layer magnetic moment, the second pinned layer having a second pinned layer magnetic moment;

setting the first pinned layer magnetic moment and the second pinned layer magnetic moment such that the first pinned layer magnetic moment and the second pinned layer magnetic moment are antiferromagnetically coupled and self-pinned;

wherein the magnetic junction is configured to allow the free layer to be switched between a plurality of stable magnetic states when a write current is passed through the magnetic junction.

14. The method of claim 13 wherein at least one the first nonmagnetic spacer layer film and the second nonmagnetic spacer layer film further includes a tunneling barrier layer film.

15. The method of claim 13 wherein the step of providing the magnetic junction stack further includes:

providing at least one nonmagnetic seed layer film.

16. The method of claim 13 further comprising:

annealing the magnetic junction stack at a temperature greater than three hundred fifty degrees Celsius.

17. The method of claim 16 wherein the temperature is at least four hundred degrees Celsius.

18. The method of claim 13 wherein the first pinned layer has a first easy axis and the second pinned layer has a second easy axis substantially parallel to the first easy axis and wherein the step of setting the first pinned layer magnetic moment and the second pinned layer magnetic moment further includes:

applying a magnetic field in a direction substantially perpendicular to the first easy axis and the second easy axis until each of the first pinned layer magnetic moment and the second pinned layer magnetic moment has a component parallel to the applied field, the first pinned layer magnetic moment has a first projection on the first easy axis, the second pinned layer magnetic moment has a second projection onto the second easy axis, the first projection and the second projection being substantially antiparallel; and

reducing the magnetic field to zero, thereby allowing the first pinned layer magnetic moment and the second pinned layer magnetic moment to fall into the equilibrium directions such that the substantially antiparallel orientation of the first pinned layer magnetic moment and the second pinned layer magnetic moment is provided.

19. The method of claim 18 wherein the step of applying the magnetic field further includes:

monotonically increasing the magnetic field until the first pinned layer magnetic moment and the second pinned layer magnetic moment are substantially parallel.

20. The method of claim 18 wherein the step of decreasing the magnetic field further includes:

monotonically decreasing the magnetic field to zero.