Defect gradient to boost nonvolatile memory performance
View Patent ↗Embodiments of the present invention generally relate to a resistive switching nonvolatile memory element that is formed in a resistive switching memory device that may be used in a memory array to store digital data. The memory element is generally constructed as a metal-insulator-metal stack. The resistive switching portion of the memory element includes a getter and/or a defect portion. In general, the getter portion is an area of the memory element that is used to help form, during the resistive switching memory device's fabrication process, a region of the resistive switching layer that has a greater number of vacancies or defects compared to the remainder of resistive switching layer. The defect portion is an area of the memory element that has a greater number of vacancies or defects compared to the remainder of the resistive switching layer, and is formed during the resistive switching memory device's fabrication process.
1. A nonvolatile memory element, comprising:
a first electrode layer;
a first variable resistance layer disposed over the first electrode layer;
a first layer disposed on the first variable resistance layer;
a second variable resistance layer disposed on the first layer; and
a second electrode layer disposed over the second variable resistance layer,
wherein:
the first variable resistance layer and first layer each comprise a first chemical element and a second chemical element; and
the stoichiometry of the first and second chemical elements in the first variable resistance layer is different than the stoichiometry of the first and second chemical elements in the first layer.
2. The nonvolatile memory element of claim 1 , wherein the first variable resistance layer has a first thickness and the second variable resistance layer has a second thickness, and wherein the second thickness is greater than the first thickness.
3. The nonvolatile memory element of claim 1 , wherein the first variable resistance layer and the second variable resistance layer each comprise hafnium oxide, tantalum oxide, aluminum oxide, lanthanum oxide, yttrium oxide, dysprosium oxide, ytterbium oxide or zirconium oxide.
4. The nonvolatile memory element of claim 1 , wherein the first and second chemical elements are selected from a group consisting of hafnium, oxygen and nitrogen.
5. The nonvolatile memory element of claim 1 , wherein:
the second variable resistance layer comprises the first chemical element and the second chemical element; and
the stoichiometry of the first and second chemical elements in the first variable resistance layer is different than the stoichiometry of the first and second chemical elements in the second variable resistance layer.
6. The nonvolatile memory element of claim 5 , wherein the first and second chemical elements are selected from a group consisting of hafnium, oxygen and nitrogen.
7. The nonvolatile memory element of claim 1 , wherein the first electrode layer comprises titanium and the second electrode layer comprises polysilicon, wherein the first variable resistance layer is disposed on the first electrode layer.
8. The nonvolatile memory element of claim 1 , wherein the first layer comprises a metal selected from the group consisting of titanium, aluminum, and combinations thereof.
9. The nonvolatile memory element of claim 1 , further comprising:
a second layer disposed on the second variable resistance layer; and
a third variable resistance layer disposed on the second layer.
10. The nonvolatile memory element of claim 9 , wherein the third variable resistance layer comprises hafnium oxide, tantalum oxide, aluminum oxide, lanthanum oxide, yttrium oxide, dysprosium oxide, ytterbium oxide or zirconium oxide.
11. A nonvolatile memory element, comprising:
a first electrode layer;
a first variable resistance layer disposed over the first electrode layer;
a first layer disposed on the first variable resistance layer;
a second variable resistance layer disposed on the first layer; and
a second electrode layer disposed over the second variable resistance layer,
wherein:
the first and second variable resistance layers each comprise a first material that comprises a first chemical element and a second chemical element; and
the first layer comprises a metal that has a greater affinity for the first chemical element as compared to the first material.
12. The nonvolatile memory element of claim 11 , wherein the first variable resistance layer and the second variable resistance layer each comprise hafnium oxide, tantalum oxide, aluminum oxide, lanthanum oxide, yttrium oxide, dysprosium oxide, ytterbium oxide or zirconium oxide.
13. The nonvolatile memory element of claim 11 , wherein the first layer comprises a metal selected from the group consisting of titanium, aluminum, and combinations thereof.
14. A nonvolatile memory element, comprising:
a first electrode layer;
a first variable resistance layer disposed over the first electrode layer;
a first layer disposed on the first variable resistance layer;
a second variable resistance layer disposed on the first layer; and
a second electrode layer disposed over the second variable resistance layer,
wherein:
the first variable resistance layer, the second variable resistance layer and the first layer each comprise a first chemical element and a second chemical element; and
the stoichiometry of the first and second chemical elements in the first and the second variable resistance layers is different than the stoichiometry of the first and second chemical elements in the first layer.
15. The nonvolatile memory element of claim 14 , wherein the first variable resistance layer and the second variable resistance layer each comprise hafnium oxide, tantalum oxide, aluminum oxide, lanthanum oxide, yttrium oxide, dysprosium oxide, ytterbium oxide or zirconium oxide.
16. A nonvolatile memory element, comprising:
a first electrode layer;
a first variable resistance layer disposed over the first electrode layer;
a first layer disposed on the first variable resistance layer;
a second variable resistance layer disposed on the first layer;
a second electrode layer disposed over the second variable resistance layer; and
a second layer,
wherein the second variable resistance layer is disposed between the first layer and second layer, and the first and second layers each comprise a metal selected from the group consisting of titanium, aluminum, and combinations thereof.
17. The nonvolatile memory element of claim 16 , wherein the first variable resistance layer and the second variable resistance layer each comprise hafnium oxide, tantalum oxide, aluminum oxide, lanthanum oxide, yttrium oxide, dysprosium oxide, ytterbium oxide or zirconium oxide.
18. A nonvolatile memory element, comprising:
a first electrode layer;
a first variable resistance layer disposed over the first electrode layer;
a first layer disposed on the first variable resistance layer;
a second variable resistance layer disposed on the first layer;
a second electrode layer disposed over the second variable resistance layer; and
a second layer that is disposed on the second variable resistance layer, wherein the first layer and the second layer each have a thickness that is substantially equal.
19. The nonvolatile memory element of claim 18 , wherein the first variable resistance layer and the second variable resistance layer each comprise hafnium oxide, tantalum oxide, aluminum oxide, lanthanum oxide, yttrium oxide, dysprosium oxide, ytterbium oxide or zirconium oxide.
20. The nonvolatile memory element of claim 18 , wherein the first and second layers each comprise a metal selected from the group consisting of titanium, aluminum, and combinations thereof.