Memory device with active and passive layers
View Patent ↗A memory including memory cells having active and passive layers may store multiple information bits. The active layer may include an organic polymer that has a variable resistance based on the movement of charged species (ions or ions and electrons) between the passive layer and the active layer. The passive layer may be a super-ionic material that has high ion and electron mobility. The active layer may be self-assembled from a monomer in a liquid or gas.
1. A method for forming a memory having a plurality of reversibly programmable memory cells, comprising:
forming a plurality of first electrodes comprising copper on a substrate;
forming a passive layer comprising copper sulfide on each of the plurality of first electrodes;
selectively forming a polymer layer only over the passive layer on each of the plurality of first electrodes to form an active layer thereon by exposing the passive layer to a monomer gas such that material in the monomer gas self-assembles only on the passive layer on each of the plurality of first electrodes to form a polymer in the active layer, the polymer having a reversibly variable electrical conductivity upon the introduction and removal of charged species from the passive layer, and
forming a plurality of second electrodes over the active layer.
2. The method of claim 1 , wherein each of the plurality of reversibly programmable memory cells in the memory includes only two electrodes.
3. The method of claim 1 , wherein forming a passive layer comprises:
exposing the first electrodes of hydrogen sulfide gas suitable to form the passive layer comprising copper sulfide.
4. The method of claim 1 , wherein selectivity forming a polymer layer comprises:
forming the polymer layer having a thickness between about 50 to about 1000 Angstroms.
5. The method of claim 1 , wherein forming a passive layer comprises:
forming the passive layer to have a thickness from about 20 to about 100 Angstroms.
6. The method of claim 1 , further comprising:
forming a barrier layer including a material that impedes spontaneous movement of charged species between the active layer and the passive layer when an electrical potential difference is not applied between the two electrode layers.
7. The method of claim 6 , wherein the barrier layer is positioned between the active layer and the passive layer.
8. The method of claim 1 , wherein the memory cell includes only one active layer and only one passive layer between the first and second electrode layers.
9. The method of claim 1 , further comprising:
applying an electric field to the first and second electrode layers to transfer charged species from the passive layer to polymer material in the active layer, thereby one of doping the polymer material with charged species from the passive layer and forming nanowire features in the polymer material to store information in the memory cell.
10. The method of claim 9 , wherein applying the electric field comprises:
doping the polymer material with charged species from the passive layer to store information in the memory cell.
11. The method of claim 9 , wherein applying the electric field comprises:
forming nanowire features in the polymer material to store information in the memory cell.
12. The method of claim 1 , wherein the two electrode layers are arranged to both program the memory cell to store information and read stored information from the memory cell.
13. A method for forming a memory having a plurality of reversibly programmable memory cells, comprising:
forming a plurality of first electrodes comprising copper on a substrate;
forming a passive layer comprising copper sulfide on each of the plurality of first electrodes;
selectively forming a polymer layer only over the passive layer on each of the plurality of first electrodes to form an active layer thereon by exposing the passive layer to a monomer gas such that material in the monomer gas self-assembles only on the passive layer on each of the plurality of first electrodes to form a polymer in the active layer, the polymer having a reversibly variable electrical conductivity upon the introduction and removal of charged species from the passive layer, selectivity forming a polymer layer comprises: forming a layer of polyphenylacetylene (PPA) or polydiphenylacetylene (PDPA) as the active layer; and
forming a plurality of second electrodes over the active layer.
14. A method for forming a memory having a plurality of reversibly programmable memory cells, comprising:
forming a plurality of first electrodes on a substrate;
forming a passive layer comprising a superionic material on each of the plurality of first electrodes;
selectively forming a polymer layer only over the passive layer on each of the plurality of first electrodes to form an active layer thereon by exposing the passive layer to a gas such that material in the gas self-assembles only on the passive layer on each of the plurality of first electrodes to form the polymer layer, the polymer layer having a reversibly variable electrical conductivity upon the introduction and removal of charged species from the passive layer, and
forming a plurality of second electrodes over the active layer.
15. The method of claim 14 , wherein each of the plurality of reversibly programmable memory cells in the memory cells in the memory includes only two electrodes.
16. The method of claim 14 , wherein forming a passive layer comprises:
exposing the first electrodes to hydrogen sulfide gas suitable to form the passive layer comprising copper sulfide.
17. The method of claim 14 , wherein selectively forming a polymer layer comprises:
forming a layer of polyphenylacetylene (PPA) or polydiphenylacetylene (PDPA) as the active layer.
18. The method of claim 14 , wherein selectively forming a polymer layer comprises:
forming the polymer layer having a thickness from about 50 to about 1000 Angstroms.
19. The method of claim 14 , wherein forming a passive layer comprises:
forming the passive layer to have a thickness from about 20 to about 100 Angstroms.
20. The method of claim 14 , further comprising:
forming a barrier layer comprising a material that impedes spontaneous movement of charged species between the active layer and the passive layer when an electrical potential difference is not applied between the two electrode layers.
21. The method of claim 20 , wherein the barrier layer is positioned between the active layer and the passive layer.
22. The method of claim 14 , wherein the memory cell includes only one active layer and only one passive layer between the first and second electrode layers.
23. The method of claim 14 , further comprising:
applying an electric field to the first and second electrode layers to transfer charged species from the passive layer to polymer material in the active layer, thereby one of doping the polymer material with charged species from the passive layer and forming nanowire features in the polymer material to store information in the memory cell.
24. The method of claim 23 , wherein applying the electric field comprises:
doping the polymer material with charged species from the passive layer to store information in the memory cell.
25. The method of claim 23 , wherein applying the electric field comprises:
forming nanowire features in the polymer material to store information in the memory cell.
26. The method of claim 14 , wherein the two electrode layers are arranged to both program the memory cell to store information and read stored information from the memory cell.