MRAM sense layer isolation
View Patent ↗A process for forming an MRAM element. The process comprises patterning a globally deposited sense layer and then forming a spacer about the patterned sense layer so as to cover the lateral edges of the patterned sense layer. Subsequently, a globally deposited tunnel layer and fixed layer are patterned so as to define the MRAM element. Preferably, the pinned layer is patterned such that the outer lateral edges of the pinned layer is displaced in a direction parallel to the substrate from the lateral edges of the patterned sensed layer thereby reducing coupling effects between the two layers. Moreover, the use of a spacer during the process further inhibits shorting between the sense layer and the pinned layer during patterning of the pinned layer.
1. A magnetic memory device formed on a substrate comprising:
a pinned layer magnetized in a first direction and patterned to a first width, wherein the pinned layer has a plurality of outer lateral edges;
a sense layer that can be selectively magnetized in the first direction or a second direction that is opposite the first direction so as to change the net resistivity of the magnetic memory device, and wherein the sense layer is patterned to a second width that is at least less than the first width to thereby reduce magnetic coupling between the pinned and sense layers, wherein the sense layer has an upper surface and a plurality of outer lateral edges;
a spacer structure positioned adjacent the outer lateral edges of the sense layer in a manner such that the outer lateral edges of the spacer structure coincide with the outer lateral edges of the pinned layer, wherein the spacer structure does not extend across the upper surface of the sense layer.
2. The device of claim 1 , wherein the substrate comprises a conductor formed therein.
3. The device of claim 2 , wherein the pinned layer is formed above the substrate so as to overlie the conductor.
4. The device of claim 3 , wherein the magnetic memory device further comprises a tunnel layer that is formed so as to overlie the pinned layer and be interposed between the pinned layer and the sense layer.
5. The device of claim 4 , wherein the sense layer is formed so as to overlie the tunnel layer.
6. The device of claim 1 , wherein the sense layer comprises a variable magnetic field that can be varied by the application of an external field to thereby change the combined magnetic characteristic of the pinned and sense magnetic layers.
7. The device of claim 1 , wherein the pinned layer is formed of nickel iron (NiFe), the tunnel layer is formed of aluminum oxide (Al 2 O 3 ) and the sense layer is formed of nickel iron cobalt (NiFeCo).
8. The device of claim 1 , wherein the spacer structure is interposed between the outer lateral edges of the sense layer and the pinned layer.
9. The device of claim 8 , wherein the spacer structure is formed of a non-conducting material.
10. A method of reducing coupling between a pinned layer and a sense layer in an MRAM element, comprising:
forming a first magnetic layer on a substrate, wherein the first magnetic layer is adapted to be a magnetic pinned layer;
forming a tunnel oxide layer on said first magnetic layer; and
forming a second magnetic layer on said tunneling oxide layer, wherein the second magnetic layer is adapted to be a magnetic sense layer;
patterning the second magnetic layer to form a magnetic sense layer having an upper surface and a plurality of lateral edges;
forming a spacer about the lateral edges of the magnetic sense layer, wherein the spacer has a plurality of outer lateral edges, wherein the spacer does not extend across the upper surface of the second magnetic layer; and
patterning the first magnetic layer to form a magnetic pinned layer having a first width and a plurality of outer lateral edges, wherein the outer lateral edges of the magnetic pinned layer coincide with the outer lateral edges of the spacer.
11. The method of claim 10 , wherein said first magnetic layer is magnetized in a first fixed direction.
12. The method of claim 10 , wherein said second magnetic layer is formed of a material that can be magnetized in one of two directions.