Resistive random access memory device with switching multi-layer stack and methods of fabrication
A memory device includes a bottom electrode above a substrate, a first switching layer on the bottom electrode, a second switching layer including aluminum on the first switching layer, an oxygen exchange layer on the second switching layer and a top electrode on the oxygen exchange layer. The presence of the second switching layer including aluminum on the first switching layer enables a reduction in electro-forming voltage of the memory device.
1. A memory device, comprising:
a substrate;
a bottom electrode above the substrate;
a first switchable layer on the bottom electrode;
a second switchable layer comprising aluminum on the first switchable layer;
an oxygen exchange layer on the second switchable layer; and
a top electrode on the oxygen exchange layer;
wherein the bottom electrode, the first switchable layer, the second switchable layer, the oxygen exchange layer and the top electrode form a stack having a sidewall, and wherein the memory device further comprises a dielectric spacer film surrounding the sidewall of the stack and extending from a lowermost portion of the bottom electrode to an uppermost portion of the top electrode, and
wherein the first switchable layer has a thickness between 2 nm and 4 nm, wherein the second switchable layer has a thickness between 1 nm and 2 nm, and wherein the first switchable layer and the second switchable layer have a total combined thickness between 3 nm and 5 nm.
2. The memory device of claim 1 , wherein the first switchable layer comprises a metal and oxygen.
3. The memory device of claim 2 , wherein the first switchable layer comprises hafnium oxide, tantalum oxide, zirconium oxide, titanium oxide, or tungsten oxide.
4. The memory device of claim 3 , wherein the first switchable layer is sub-stoichiometric.
5. The memory device of claim 1 , wherein the second switchable layer comprises aluminum and oxygen.
6. The memory device claim 1 , wherein the first switchable layer and the oxygen exchange layer comprise a same metal.
7. A memory device, comprising:
a substrate;
a bottom electrode above the substrate, wherein the bottom electrode comprises one or more of titanium, tantalum, tungsten, ruthenium, and nitrogen;
a first switchable layer on the bottom electrode, wherein at least a portion of an interface between the bottom electrode and the first switchable layer is oxidized;
a second switchable layer comprising aluminum on the first switchable layer;
an oxygen exchange layer on the second switchable layer;
a top electrode on the oxygen exchange layer, wherein the second switchable layer, the oxygen exchange layer, and the top electrode form a stack having a sidewall; and
a dielectric spacer film on the sidewall of the stack and extending at least from a lowermost portion of the second switchable layer to an uppermost portion of the top electrode,
wherein the first switchable layer has a thickness between 2 nm and 4 nm, wherein the second switchable layer has a thickness between 1 nm and 2 nm, and wherein the first switchable layer and the second switchable layer have a total combined thickness between 3 nm and 5 nm.
8. The memory device of claim 1 , wherein the top electrode comprises titanium nitride, tantalum nitride, tungsten, or ruthenium.
9. The memory device of claim 1 , wherein the bottom electrode and the top electrode are a same material, the material comprising titanium nitride, tantalum nitride, tungsten, or ruthenium.
10. A IT-IR memory cell, comprising:
a resistive random access memory (RRAM) device including
a bottom electrode comprising a metal layer;
a first switchable layer on the bottom electrode, wherein at least a portion of an interface between the bottom electrode metal layer and the first switchable layer is oxidized;
a second switchable layer comprising Al 2 O 3 (aluminum oxide) on the first switchable layer;
an oxygen exchange layer on the second switchable layer; and
a top electrode on the oxygen exchange layer,
wherein the first switchable layer has a thickness of at least 2 nm, and wherein the second switchable layer has a thickness of at least 1 nm.
11. The IT-IR memory cell of claim 10 , wherein the first switchable layer comprises a metal and oxygen.
12. The IT-IR memory cell of claim 10 , wherein the first switchable layer comprises hafnium oxide, tantalum oxide, zirconium oxide, titanium oxide, or tungsten oxide.
13. The IT-IR memory cell of claim 10 , wherein the first switchable layer has a thickness between 2 nm and 4 nm, wherein the second switchable layer has a thickness between 1 nm and 2 nm, and wherein the first switchable layer and the second switchable layer have a total combined thickness between 3 nm and 5 nm.
14. The memory device of claim 7 , wherein the stack further includes the bottom electrode and the first switchable layer, and wherein the dielectric spacer film extends from a lowermost portion of the bottom electrode to the uppermost portion of the top electrode.
15. The memory device of claim 7 , wherein the first switchable layer comprises a metal and oxygen, and wherein the second switchable layer comprises aluminum and oxygen.
16. The memory device of claim 7 , wherein the first switchable layer and the oxygen exchange layer comprise a same metal.
17. The memory device of claim 7 , wherein one or both of the bottom electrode and the top electrode comprises titanium, tantalum, tungsten, or ruthenium.
18. The IT-IR memory cell of claim 10 , wherein the second switchable layer comprises graded concentration of oxygen, with a first concentration of oxygen within the second switchable layer near the first switchable layer, and a second concentration of oxygen within the second switchable layer near the oxygen exchange layer, wherein the first concentration is different from the second concentration.
19. The IT-IR memory cell of claim 18 , wherein the first concentration is higher than the second concentration.
20. The IT-IR memory cell of claim 10 , comprising a dielectric spacer film on a sidewall of the second switchable layer, on a sidewall of the oxygen exchange layer, and on a sidewall of the top electrode.