Spin orbit torque (SOT) memory devices and methods of fabrication

1. A spin orbit torque (SOT) device, comprising:

a fixed magnet;

a first electrode coupled with the fixed magnet;

a free magnet;

a tunnel barrier between the free magnet and the fixed magnet; and

a spin orbit torque (SOT) electrode coupled with the free magnet, the SOT electrode comprising:

a first layer comprising a spin orbit coupling material, wherein the first layer has a first lateral length; and

a second layer comprising the spin orbit coupling material, wherein:

the second layer is between the free magnet and the first layer;

the second layer is in contact with the first layer over a second lateral length that is smaller than the first lateral length; and

at least a portion of the first layer at an interface with the second layer comprises oxygen.

2. The SOT device of claim 1 , wherein the portion of the first layer comprising oxygen is a first portion and has a thickness between 0.1 nm and 0.3 nm.

3. The SOT device of claim 1 , wherein a second portion of the first layer at an interface with the second layer comprises no oxygen.

4. The SOT device of claim 1 , wherein the portion of the first layer at an interface with the second layer comprises a greater concentration of oxygen compared to oxygen at an interface between the second layer and the free magnet.

5. The SOT device of claim 1 , wherein an uppermost surface of the first layer has a surface roughness that is less than a surface roughness of an uppermost surface of the second layer.

6. The SOT device of claim 1 , wherein the first layer is a first width and the second layer is the first width.

7. The SOT device of claim 6 , wherein the free magnet has a diameter equal to the first width and the second lateral length.

8. The SOT device of claim 1 , wherein an uppermost surface of the first layer not covered by the second layer is recessed below a lowermost surface of the second layer, wherein the amount of recess is less than a thickness of the remaining first layer.

9. The SOT device of claim 1 , wherein the SOT device further comprises a conductive layer adjacent to a sidewall of the first layer and between the sidewall of the first layer and a dielectric layer.

10. The SOT device of claim 9 , wherein the first layer extends over an uppermost surface of the conductive layer.

11. The SOT device of claim 10 , wherein at least a portion of the uppermost surface of the conductive layer proximal to the second layer comprises oxygen.

12. A method of fabricating a spin orbit torque (SOT) device, the method comprising:

depositing and planarizing a first layer including a spin orbit coupling material;

depositing a second layer including the spin orbit coupling material on the first layer, wherein at least a portion of the first layer at an interface with the second layer comprises oxygen;

forming a material layer stack for a magnetic tunnel junction (MTJ) memory device, the forming comprising:

depositing a fixed magnetic layer;

depositing a tunnel barrier layer over the fixed magnetic layer; and

depositing a free magnetic layer over the tunnel barrier layer;

etching the material layer stack, wherein the etching forms a magnetic tunnel junction (MTJ) device; and

etching the second layer including the spin orbit coupling material to have a second lateral length that is smaller than a first lateral length of the first layer by using the MTJ device as a mask.

13. The method of claim 12 , wherein the method further comprises:

forming an opening in a dielectric layer;

depositing a conductive layer in the opening prior to depositing the first layer including the spin orbit coupling material;

depositing the first layer including the spin orbit coupling material on the conductive layer; and

planarizing the spin orbit coupling material, portions of the conductive layer and the dielectric layer to form a first spin orbit torque (SOT) electrode in the opening.

14. The method of claim 12 , wherein etching the second layer comprises etching the portion of the first layer comprising oxygen.

15. The method of claim 14 , wherein the etching further comprises recessing an uppermost portion of the first layer by an amount less than a thickness of the second layer.

16. The method of claim 12 , further comprises forming a dielectric spacer layer adjacent to the MTJ device.

17. An apparatus comprising:

a transistor above a substrate, the transistor comprising:

a drain contact coupled to a drain;

a source contact coupled to a source;

a gate contact coupled to a gate; and

a spin orbit torque (SOT) device coupled with the drain contact, the SOT device comprising:

a fixed magnet;

a first electrode coupled with the fixed magnet;

a free magnet;

a tunnel barrier between the free magnet and the fixed magnet; and

a spin orbit torque (SOT) electrode coupled with the free magnet, the SOT electrode comprising:

a first layer comprising a spin orbit coupling material, wherein the first layer has a first lateral length; and

a second layer comprising the spin orbit coupling material,

wherein:

the second layer is between the free magnet and the first layer;

the second layer is in contact with the first layer over a second lateral length that is smaller than the first lateral length; and

at least a portion of the first layer at an interface with the second layer comprises oxygen; and

a conductive interconnect coupled with the SOT electrode, wherein the MTJ device is between the conductive electrode and the drain contact.

18. The apparatus of claim 17 , wherein the portion of the first layer comprising oxygen is a first portion and has a thickness between 0.1 nm and 0.3 nm.

19. The apparatus of claim 17 , wherein a second portion of the first layer at an interface with the second layer comprises no oxygen.

20. The apparatus of claim 17 , wherein the first layer is a first width and the second layer is the first width, and wherein the free magnet has a diameter equal to the first width and the second lateral length.