SOT MRAM having dielectric interfacial layer and method forming same

1. A device comprising:

a dielectric seed layer having a crystalline structure;

a spin orbit coupling layer over the dielectric seed layer; and

a Magnetic Tunnel Junction (MTJ) stack comprising:

a dielectric layer over the spin orbit coupling layer;

a free layer over the dielectric layer;

a tunnel barrier layer over the free layer; and

a reference layer over the tunnel barrier layer, wherein the spin orbit coupling layer extends beyond edges of the MTJ stack in a first direction and a second direction opposite to the first direction.

2. The device of claim 1 , wherein the dielectric layer comprises a nitride or an oxide.

3. The device of claim 1 , wherein the free layer and the reference layer are formed of ferromagnetic materials.

4. The device of claim 1 , wherein the dielectric layer has a thickness allowing spin polarized carriers in the spin orbit coupling layer to tunnel through and flowing into the free layer.

5. The device of claim 1 , wherein the spin orbit coupling layer further extends laterally beyond edges of the MTJ stack in a third direction perpendicular to the first direction and the second direction.

6. The device of claim 1 , wherein the spin orbit coupling layer extends laterally beyond an edge of the MTJ stack.

7. The device of claim 1 , wherein the dielectric seed layer and the spin orbit coupling layer have edges vertically aligned to each other.

8. The device of claim 7 , wherein the dielectric seed layer comprises magnesium oxide.

9. A device comprising:

a dielectric seed layer having a crystalline structure;

a metal layer over and contacting the dielectric seed layer;

a Magnetic Tunnel Junction (MTJ) over the metal layer, wherein the MTJ comprises:

a dielectric layer over the metal layer;

a free layer over the dielectric layer, wherein the dielectric layer has a thickness configured to allow spin polarized carriers in the metal layer to flow through the dielectric layer into the free layer;

a tunnel barrier layer over the free layer; and

a reference layer over the tunnel barrier layer; and

a dielectric capping layer on sidewalls of the MTJ, wherein the dielectric capping layer contacts edges of the dielectric layer, and extends on a top surface of the metal layer.

10. The device of claim 9 , wherein the dielectric seed layer comprises a material selected from the group consisting of MgO, HfOx, AlOx, AgOx, CuO, SrO, HfN, AlN, AgN, SrN, and combinations thereof.

11. The device of claim 10 , wherein the dielectric seed layer comprises magnesium oxide.

12. The device of claim 10 , wherein edges of the dielectric seed layer are vertically aligned to respective edges of the metal layer.

13. The device of claim 9 , wherein the free layer has an in-plane spin polarization direction.

14. The device of claim 9 , wherein the free layer has a perpendicular spin polarization direction.

15. The device of claim 9 , wherein the metal layer is selected from the group consisting of W, Ta, Pt, AuPt, W 3 Ta, Bi x Se y , BiSeTe, and combinations thereof.

16. A device comprising:

a first dielectric layer having a crystalline structure;

a metal layer over and contacting the first dielectric layer, wherein first edges of the first dielectric layer are vertically aligned to respective second edges of the metal layer;

a second dielectric layer over the metal layer, wherein the second dielectric layer has a thickness thin enough to allow spin polarized carriers to flow through;

a free layer over the second dielectric layer;

a tunnel barrier layer over the free layer; and

a reference layer over the tunnel barrier layer.

17. The device of claim 16 , wherein the second dielectric layer is thin enough to allow electrons to tunnel through.

18. The device of claim 16 , wherein the first dielectric layer comprises MgO.

19. The device of claim 18 , and wherein the first dielectric layer and the metal layer extend laterally beyond the free layer.

20. The device of claim 16 , wherein the free layer comprises a ferromagnetic material.