Continuous plane of thin-film materials for a two-terminal cross-point memory
View Patent ↗A structure for a memory device including a plurality of substantially planar thin-film layers or a plurality of conformal thin-film layers is disclosed. The thin-film layers form a memory element that is electrically in series with first and second cladded conductors and operative to store data as a plurality of conductivity profiles. A select voltage applied across the first and second cladded conductors is operative to perform data operations on the memory device. The memory device may optionally include a non-ohmic device electrically in series with the memory element and the first and second cladded conductors. Fabrication of the memory device does not require the plurality of thin-film layers be etched in order to form the memory element. The memory element can include a CMO layer having a selectively crystallized polycrystalline portion and an amorphous portion. The cladded conductors can include a core material made from copper.
1. A memory device, comprising:
a first cladded conductor including a first core conductor and a first outer cladding in contact with and completely surrounding the first core conductor;
a first electrode in contact with a portion of the first outer cladding and including a substantially planar surface;
a second cladded conductor including a second core conductor and a second outer cladding in contact with and partially surrounding the second core conductor;
a memory element operative to store data as a plurality of conductivity profiles and including a plurality of substantially planar thin-film layers, the thin-film layers including,
a layer of a conductive metal oxide (CMO) including a selectively crystallized portion in contact with the substantially planar surface of the first electrode and having a polycrystalline structure and an amorphous portion having an amorphous structure, and
a layer of a first electrically insulating material including a first tunnel barrier in contact with the selectively crystallized portion; and
a non-ohmic device including,
a second electrode in contact with the first tunnel barrier,
a second tunnel barrier made from a second electrically insulating material and in contact with the second electrode, and
a third electrode in contact with the second tunnel barrier and a portion of the second outer cladding,
wherein the memory element and the non-ohmic device are electrically in series with the first and second cladded conductors.
2. The memory device of claim 1 , wherein the plurality of substantially planar thin-film layers further comprises:
an ion barrier layer positioned between and in contact with the first electrically insulating material and the CMO.
3. The memory device of claim 2 , wherein the ion barrier layer comprises strontium titinate (STO).
4. The memory device of claim 1 , wherein the amorphous portion of the CMO includes implanted ions operative to decrease a conductivity of the amorphous portion.
5. The memory device of claim 1 , wherein the first electrode comprises platinum.
6. The memory device of claim 5 , wherein the platinum includes a substantially <111> crystal orientation and the polycrystalline structure of the selectively crystallized portion has a crystal orientation that is substantially identical to the <111> crystal orientation of the platinum.
7. A memory device, comprising:
a first cladded conductor including a first core conductor and a first composite cladding that completely surrounds the first core conductor, the first composite cladding including a first material and a second material;
a first electrically conductive adhesion layer in contact with the second material;
a first electrode in contact with the first electrically conductive adhesion layer and including a substantially planar surface;
a second cladded conductor including a second core conductor and a second composite cladding that completely surrounds the second core conductor, the second composite cladding including a first material and a second material;
a memory element operative to store data as a plurality of conductivity profiles and including a plurality of conformal thin-film layers, the conformal thin-film layers including,
a conformal layer of a conductive metal oxide (CMO) including a selectively crystallized portion in contact with the substantially planar surface of the first electrode and having a polycrystalline structure and an amorphous portion having an amorphous structure, and
a conformal layer of a first electrically insulating material including a first tunnel barrier in contact with the selectively crystallized portion; and
a second electrode in contact with the first tunnel barrier and a portion of the first material of the second composite cladding, wherein the memory element is electrically in series with the first and second cladded conductors.
8. The memory device of claim 7 , wherein the second material for the first and second composite claddings comprises cobalt tungsten phosphide.
9. The memory device of claim 7 , wherein the plurality of conformal thin-film layers further comprises:
a conformal ion barrier layer positioned between and in contact with the first electrically insulating material and the CMO.
10. The memory device of claim 9 , wherein the ion barrier layer comprises strontium titinate (STO).
11. The memory device of claim 7 , wherein the amorphous portion of the CMO includes implanted ions operative to decrease a conductivity of the amorphous portion.
12. The memory device of claim 11 , wherein the implanted ions comprises argon.
13. The memory device of claim 7 , wherein the CMO comprises a perovskite.
14. The memory device of claim 13 , wherein the perovskite is selected from the group consisting of PCMO, LCMO, LSMO, and LNO.
15. The memory device of claim 7 , wherein the first electrically insulating material has a thickness of less than approximately 50 Angstroms.
16. The memory device of claim 7 , wherein the first electrically insulating material comprises yttria-stabilized zirconia (YSZ).
17. The memory device of claim 7 , wherein the first electrode comprises platinum.
18. The memory device of claim 17 , wherein the platinum includes a substantially <111> crystal orientation and the polycrystalline structure of the selectively crystallized portion has a crystal orientation that is substantially identical to the <111> crystal orientation of the platinum.
19. The memory device of claim 7 and further comprising:
a non-ohmic device including,
a second tunnel barrier made from a second electrically insulating material, the second tunnel barrier in contact with the second electrode,
a third electrode in contact with the second tunnel barrier, and
an electrically conductive hard mask in contact with the third electrode and a portion of the first material of the second composite cladding,
wherein the memory element and the non-ohmic device are electrically in series with the first and second cladded conductors.
20. A memory device, comprising:
a first cladded conductor including a first core conductor and a first composite cladding that completely surrounds the first core conductor, the first composite cladding including a first material and a second material;
a first electrically conductive adhesion layer in contact with the second material;
a first electrode in contact with the first electrically conductive adhesion layer and including a substantially planar surface;
a second cladded conductor including a second core conductor and a second composite cladding that completely surrounds the second core conductor, the second composite cladding including a first material and a second material;
a memory element operative to store data as a plurality of conductivity profiles and including a plurality of substantially planar thin-film layers, the thin-film layers including,
a layer of a conductive metal oxide (CMO) including a selectively crystallized portion in contact with the substantially planar surface of the first electrode and having a polycrystalline structure and an amorphous portion having an amorphous structure, and
a layer of a first electrically insulating material including a first tunnel barrier in contact with the selectively crystallized portion of the CMO; and
a second electrode in contact with the first tunnel barrier and a portion of the first material of the second composite cladding, wherein the memory element is electrically in series with the first and second cladded conductors.
21. The memory device of claim 20 , wherein the second material for the first and second composite claddings comprises cobalt tungsten phosphate.
22. The memory device of claim 20 wherein the plurality of thin-film layers further comprises:
an ion barrier layer positioned between and in contact with the first electrically insulating material and the CMO.
23. The memory device of claim 22 , wherein the ion barrier layer comprises strontium titinate (STO).
24. The memory device of claim 20 , wherein the amorphous portion of the CMO includes implanted ions operative to decrease a conductivity of the amorphous portion.
25. The memory device of claim 20 , wherein the CMO comprises a perovskite.
26. The memory device of claim 25 , wherein the perovskite is selected from the group consisting of PCMO, LCMO, LSMO, and LNO.
27. The memory device of claim 20 , wherein the first electrically insulating material has a thickness of less than approximately 50 Angstroms.
28. The memory device of claim 20 , wherein the first electrically insulating material comprises yttria-stabilized zirconia (YSZ).
29. The memory device of claim 20 , wherein the first electrode comprises platinum.
30. The memory device of claim 29 , wherein the platinum includes a substantially <111> crystal orientation and the polycrystalline structure of the selectively crystallized portion has a crystal orientation that is substantially identical to the <111> crystal orientation of the platinum.
31. The memory device of claim 20 and further comprising:
a non-ohmic device including,
a substantially planar layer of a second electrically insulating material including a second tunnel barrier, the second electrically insulating material positioned between the second electrode and the first material of the second composite cladding, the second tunnel barrier in contact with the second electrode and a portion of the first material of the second composite cladding, and
wherein the memory element and the non-ohmic device are electrically in series with the first and second cladded conductors.