Dielectric isolation for MRAM array
A magnetoresistive random access memory (MRAM) includes a pillar structure having a bottom electrode, a magnetic tunnel junction (MTJ) and a top electrode disposed on the MTJ. The MTJ has a reference layer, a free layer and a tunnel barrier disposed between the reference layer and the free layer. The MTJ is disposed on the bottom electrode. The bottom electrode and the top electrode are recessed within a periphery of the MTJ to form a disrupted sidewall profile.
1 . A magnetoresistive random access memory (MRAM), comprising:
a pillar structure having:
a bottom electrode;
a magnetic tunnel junction (MTJ) having a reference layer, a free layer and a tunnel barrier disposed between the reference layer and the free layer, the MTJ disposed on the bottom electrode; and
a top electrode disposed on the MTJ;
wherein the bottom electrode and the top electrode are recessed within a periphery of the MTJ to form a disrupted sidewall profile, and wherein the top electrode, tunnel barrier and bottom electrode share a same footprint.
2 . The MRAM as recited in claim 1 , further comprising a dielectric ring disposed about a periphery of the tunnel barrier, the dielectric ring extending in a same plane as the tunnel barrier to a periphery of the reference layer and the free layer.
3 . The MRAM as recited in claim 2 , wherein the dielectric ring includes silicon nitride.
4 . The MRAM as recited in claim 2 , wherein the dielectric ring includes aluminum oxide.
5 . The MRAM as recited in claim 2 , wherein the dielectric ring includes tantalum oxide.
6 . The MRAM as recited in claim 1 , further comprising an interlevel dielectric layer adjacent to the pillar structure, the interlevel dielectric layer including at least three sublayers formed by separate processes.
7 . The MRAM as recited in claim 6 , wherein the at least three sublayers includes four sublayers.
8 . The MRAM as recited in claim 6 , wherein the at least three sublayers include at least two different materials.
9 . A method for making a magnetoresistive random access memory (MRAM), comprising:
forming a bottom electrode having a first footprint;
forming a first sublayer of an interlevel dielectric layer corresponding to a level of the bottom electrode;
forming a first ferromagnetic layer on the bottom electrode having a second footprint that is larger than the first footprint;
forming a second sublayer of the interlevel dielectric layer corresponding to a level of the first ferromagnetic layer;
forming a tunnel barrier on the first ferromagnetic layer within the first footprint;
forming a dielectric ring in a plane of the tunnel barrier and extending between the first footprint and the second footprint;
forming a second ferromagnetic layer on the tunnel barrier and the dielectric ring, the second ferromagnetic layer having the second footprint;
forming a third sublayer of the interlevel dielectric layer corresponding to a level of the second ferromagnetic layer; and
forming a top electrode having the first footprint.
10 . The method as recited in claim 9 , further comprising forming a fourth sublayer of the interlevel dielectric layer corresponding to a level of the top electrode.
11 . The method as recited in claim 9 , wherein forming the first ferromagnetic layer includes forming a first portion of a sidewall spacer on sidewalls of the first ferromagnetic layer.
12 . The method as recited in claim 11 , wherein forming the second ferromagnetic layer includes forming a second portion of a sidewall spacer on sidewalls of the second ferromagnetic layer.
13 . The method as recited in claim 12 , wherein the first portion of the sidewall spacer and the second portion of the sidewall spacer intersect at the dielectric ring.
14 . The method as recited in claim 9 , wherein the dielectric ring includes silicon nitride.
15 . The method as recited in claim 9 , wherein the dielectric ring includes aluminum oxide.
16 . The method as recited in claim 9 , wherein the dielectric ring includes tantalum oxide.
17 . A method for making a magnetoresistive random access memory (MRAM), comprising:
forming a bottom electrode having a first footprint;
forming a first sublayer of an interlevel dielectric layer corresponding to a level of the bottom electrode;
forming a first ferromagnetic layer on the bottom electrode having a second footprint that is larger than the first footprint;
forming a first portion of a sidewall spacer on sidewalls of the first ferromagnetic layer;
forming a second sublayer of the interlevel dielectric layer corresponding to a level of the first ferromagnetic layer;
forming a tunnel barrier on the first ferromagnetic layer within the first footprint;
forming a dielectric ring in a plane of the tunnel barrier and extending between the first footprint and the second footprint;
forming a second ferromagnetic layer on the tunnel barrier and the dielectric ring, the second ferromagnetic layer having the second footprint;
forming a second portion of a sidewall spacer on sidewalls of the second ferromagnetic layer, wherein the first portion of the sidewall spacer and the second portion of the sidewall spacer intersect at the dielectric ring;
forming a third sublayer of the interlevel dielectric layer corresponding to a level of the second ferromagnetic layer;
forming a top electrode having the first footprint; and
forming a fourth sublayer of the interlevel dielectric layer corresponding to a level of the top electrode.
18 . The method as recited in claim 17 , wherein the dielectric ring includes aluminum oxide.
19 . The method as recited in claim 17 , wherein the dielectric ring includes tantalum oxide.