Short bridge phase change memory cells
Random access memory cells having a short phase change bridge structure and methods of making the bridge structure via shadow deposition. The short bridge structure reduces the heating efficiency needed to switch the logic state of the memory cell. In one particular embodiment, the memory cell has a first electrode and a second electrode with a gap therebetween. The first electrode has an end at least partially non-orthogonal to the substrate and the second electrode has an end at least partially non-orthogonal to the substrate. A phase change material bridge extends over at least a portion of the first electrode, over at least a portion of the second electrode, and within the gap. An insulative material encompasses at least a portion of the phase change material bridge.
1. A phase change memory unit comprising:
a first electrode proximate a substrate surface, the first electrode comprising a first layer comprising a first conductive material and a second layer comprising a second conductive material, the first electrode having a first end and an opposite second end, the second end at least partially non-orthogonal to the substrate;
a second electrode proximate the substrate surface spaced from the first electrode, the second electrode comprising the second conductive material and having a first end and a second end, the second end at least partially non-orthogonal to the substrate surface;
a gap of no more than 100 nm between the first electrode and the second electrode, the gap defined by the second ends of the electrodes;
a bridge comprising a phase change material contacting the first electrode, the second electrode, and present within the gap; and
an insulative material adjacent at least a portion of the phase change material.
2. The memory unit of claim 1 wherein the gap is no more than 60 nm.
3. The memory unit of claim 1 wherein the second layer of the first electrode has an end non-orthogonal to the substrate surface.
4. The memory unit of claim 3 wherein the end of the second layer of the first electrode has an angle of about 5 to 60 degrees to the substrate surface.
5. The memory unit of claim 4 wherein the end of the second layer of the first electrode has an angle of about 10 to 25 degrees to the substrate surface.
6. The memory unit of claim 1 wherein the first layer of the first electrode has an end at least approximately orthogonal to the substrate surface.
7. The memory unit of claim 1 wherein the phase change material comprises a binary or ternary compound comprising Ge, Sb and Te.
8. The memory unit of claim 1 wherein substrate proximate the first layer of the first electrode and substrate proximate the second electrode are planar.
9. The memory unit of claim 1 wherein substrate proximate the first layer of the first electrode and substrate proximate the second electrode are not planar.
10. A phase change memory unit comprising:
a first electrode proximate a substrate surface, the first electrode comprising:
a first layer comprising a first conductive material and having a first end and an opposite second end; and
a second layer comprising a second conductive material and having a first end and an opposite second end, the second end non-orthogonal to the substrate surface;
a second electrode proximate the substrate surface spaced from the first electrode, the second electrode comprising the second conductive material and having a first end and a second end, the second end non-orthogonal to the substrate surface;
a gap of no more than about 100 nm between the first electrode and the second electrode, the gap defined by the second end of the first layer of the first electrode and the second end of the second electrode;
a bridge comprising a phase change material contacting the first electrode, the second electrode, and present within the gap; and
an insulative material adjacent at least a portion of the phase change material.
11. The memory unit of claim 10 wherein the gap is no more than about 60 nm.
12. The memory unit of claim 11 wherein the gap is no more than about 25 nm.
13. The memory unit of claim 10 wherein the second end of the second layer of the first electrode has an angle of about 5 to 60 degrees to the substrate surface.
14. The memory unit of claim 13 wherein the second end of the second layer of the first electrode has an angle of about 10 to 25 degrees to the substrate surface.
15. The memory unit of claim 10 wherein the phase change material comprises a binary or ternary compound comprising Ge, Sb and Te.
16. The memory unit of claim 10 wherein substrate proximate the first layer of the first electrode and substrate proximate the second electrode are planar.
17. The memory unit of claim 10 wherein substrate proximate the first layer of the first electrode and substrate proximate the second electrode are not planar.