Chamfered MRAM device structure
View Patent ↗Embodiments of present invention provide a method of forming a MRAM structure. The method includes forming a blanket first ferromagnetic layer on top of a bottom electrode; etching the blanket first ferromagnetic layer to form a first ferromagnetic layer, the first ferromagnetic layer having an upper portion that has an angled edge and a lower portion that has a vertical edge; forming a blanket tunnel barrier layer on top of the first ferromagnetic layer and a blanket second ferromagnetic layer on top of the blanket tunnel barrier layer; patterning the blanket tunnel barrier layer and the blanket second ferromagnetic layer to form a tunnel barrier layer and a second ferromagnetic layer; and forming a top electrode on top of the second ferromagnetic layer. A MRAM structure formed thereby is also provided.
1 . A MRAM structure comprising:
a magnetic tunnel junction (MTJ) stack, the MTJ stack, vertically from a bottom to a top thereof, comprising a bottom electrode, a first ferromagnetic layer, a tunnel barrier layer, a second ferromagnetic layer, and a top electrode,
wherein at least one of the first ferromagnetic layer and the second ferromagnetic layer has a chamfered edge and a vertical edge that intersects with the chamfered edge, and the chamfered edge of the at least one of the first ferromagnetic layer and the second ferromagnetic layer, the vertical edge of the at least one of the first ferromagnetic layer and the second ferromagnetic layer, and sidewall surfaces of the tunnel barrier layer are each covered by a dielectric liner.
2 . The MRAM structure of claim 1 , wherein the first ferromagnetic layer has the chamfered edge, and a bottom surface of the second ferromagnetic layer is larger than a top surface of the first ferromagnetic layer.
3 . The MRAM structure of claim 2 , wherein the first ferromagnetic layer has a vertical edge, and the chamfered edge intersects with the vertical edge.
4 . The MRAM structure of claim 3 , wherein the chamfered edge forms an angle, between about 120 degrees and about 150 degrees, with the top surface of the first ferromagnetic layer.
5 . The MRAM structure of claim 1 , wherein both the first ferromagnetic layer and the second ferromagnetic layer have chamfered edges intersecting with respective vertical edges.
6 . The MRAM structure of claim 1 , wherein the first ferromagnetic layer is a reference layer and the second ferromagnetic layer is a free layer.
7 . The MRAM structure of claim 1 , wherein the MTJ stack is a first MTJ stack, further comprising a second MTJ stack, and wherein the first and second MTJ stacks have a height of about 260 nm and are separated by a distance less than about 80 nm.
8 . A MRAM structure comprising:
a magnetic tunnel junction (MTJ) stack, the MTJ stack, vertically from a bottom to a top thereof, comprising a bottom electrode, a reference layer, a tunnel barrier layer, a free layer, and a top electrode,
wherein the reference layer and the free layer have chamfered edges, the reference layer and the free layer have vertical edges, the chamfered edge of the reference layer intersects with the vertical edge of the reference layer, and the chamfered edge of the free layer intersects with the vertical edge of the free layer, the chamfered edge and the vertical edge of the reference layer is covered by a first dielectric liner, the chamfered edge and the vertical edge of the free layer is covered by a second dielectric liner, the first dielectric liner is materially different from the second dielectric liner.
9 . The MRAM structure of claim 8 , wherein a bottom surface of the free layer is larger than a top surface of the reference layer.
10 . The MRAM structure of claim 8 , wherein a bottom surface of the top electrode is larger than a top surface of the free layer, a bottom surface of the free layer is larger than a top surface of the reference layer, and a bottom surface of the reference layer is larger than a top surface of the bottom electrode.
11 . The MRAM structure of claim 8 , wherein the first dielectric liner comprises silicon-nitride-carbide (SINC) and the second dielectric liner comprises silicon-nitride (SiN).