Method of manufacturing a magnetorestive random access memeory (MRAM)

1. A method of manufacturing a magnetoresistive random access memory (MRAM) comprising memory cells disposed at intersections of word lines and bit lines, each of the memory cells comprising a transistor connected with one of the word lines and a magnetic tunnel junction (MTJ) device connected with one of the bit lines, the method comprising:

forming a first CoFeB layer of the MTJ devices, the first CoFeB layer being amorphous;

forming a magnesium oxide (MgO) layer of the MTJ devices over the first CoFeB layer;

forming a second CoFeB layer of the MTJ devices, the second CoFeB layer being amorphous over the MgO layer; and

annealing the MTJ devices,

wherein the first and second CoFeB layers are crystallized by the annealing, and

wherein the MgO layer is poly-crystalline in which a (001) crystal plane is preferentially oriented.

2. The method of claim 1 ,

wherein after the annealing, the first and second CoFeB layers are entirely crystallized.

3. The method of claim 1 ,

wherein after the annealing, each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented and each of the first and second CoFeB layers includes a BCC (body-centered cubic) structure.

4. The method of claim 1 , wherein after the annealing,

the first and second CoFeB layers are entirely crystallized, and

each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented and each of the first and second CoFeB layers includes a BCC (body-centered cubic) structure.

5. The method of claim 1 ,

wherein in the forming the MgO layer, the MgO layer is formed as a MgOx (0<x<1) layer.

6. The method of claim 1 ,

wherein in the forming the MgO layer, the MgO layer is formed directly on the first CoFeB layer.

7. The method of claim 1 , wherein:

in the forming the MgO layer, the MgO layer is formed directly on the first CoFeB layer, and

in the forming the second CoFeB layer, the second CoFeB layer is formed directly on the MgO layer.

8. The method of claim 1 ,

wherein after the annealing, the MTJ devices are (001) oriented poly-crystal MTJ devices.

9. A method of manufacturing a magnetoresistive random access memory (MRAM) comprising memory cells, each of the memory cells comprising a transistor and a magnetic tunnel junction (MTJ) device, the method comprising:

forming a first ferromagnetic layer of the MTJ devices, the first ferromagnetic layer including a first CoFeB layer that is amorphous;

forming a barrier layer of the MTJ devices, the barrier layer including a magnesium oxide (MgO) layer to have a poly-crystalline state in which a (001) crystal plane is preferentially oriented over the first ferromagnetic layer;

forming a second ferromagnetic layer of the MTJ devices, the second ferromagnetic layer including a second CoFeB layer that is amorphous over the barrier layer; and

annealing the MTJ devices to crystallize the first and second CoFeB layers.

10. The method of claim 9 ,

wherein after the annealing, the first and second CoFeB layers are entirely crystallized.

11. The method of claim 9 , wherein after the annealing,

the first and second CoFeB layers are entirely crystallized, and

each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented and each of the first and second CoFeB layers includes a BCC (body-centered cubic) structure.

12. The method of claim 9 ,

wherein in the forming the barrier layer, the value of x in MgOx for the MgO layer is greater than 0 and less than 1.

13. The method of claim 9 , wherein:

in the forming the barrier layer, the barrier layer is formed directly on the first ferromagnetic layer, and

in the forming the second ferromagnetic layer, the second ferromagnetic layer is formed directly on the barrier layer.

14. The method of claim 9 ,

wherein after the annealing, the MTJ devices are (001) oriented poly-crystal MTJ devices.

15. A method of manufacturing a magnetoresistive random access memory (MRAM) comprising:

forming transistors on a Si substrate;

forming word lines;

forming a first CoFeB layer of magnetic tunnel junction (MTJ) devices, the first CoFeB layer being amorphous;

forming a magnesium oxide (MgO) layer of the MTJ devices over the first CoFeB layer;

forming a second CoFeB layer of the MTJ devices, the second CoFeB layer being amorphous over the MgO layer;

forming bit lines which intersect with the word lines at intersections, regions of the intersections including one of the transistors and one of the MTJ devices; and

annealing the MTJ devices to form (001) oriented poly-crystal MTJ devices.

16. The method of claim 15 ,

wherein after the annealing, the first and second CoFeB layers are entirely crystallized.

17. The method of claim 15 , wherein after the annealing,

the first and second CoFeB layers are entirely crystallized, and

each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented and each of the first and second CoFeB layers includes a BCC (body-centered cubic) structure.

18. The method of claim 15 ,

wherein in the forming the MgO layer, the MgO layer is formed as a MgOx (0<x<1) layer.

19. The method of claim 15 ,

wherein in the forming the MgO layer, the MgO layer is poly-crystalline in which a (001) crystal plane is preferentially oriented.

20. The method of claim 15 ,

wherein the MgO layer is poly-crystalline in which a (001) crystal plane is preferentially oriented.