Resistive random access memory cells having metal alloy current limiting layers
View Patent ↗Provided are semiconductor devices, such as resistive random access memory (ReRAM) cells, that include current limiting layers formed from alloys of transition metals. Some examples of such alloys include chromium containing alloys that may also include nickel, aluminum, and/or silicon. Other examples include tantalum and/or titanium containing alloys that may also include a combination of silicon and carbon or a combination of aluminum and nitrogen. These current limiting layers may have resistivities of at least about 1 Ohm-cm. This resistivity level is maintained even when the layers are subjected to strong electrical fields and/or high temperature processing. In some embodiments, the breakdown voltage of a current limiting layer is at least about 8V. The high resistivity of the layers allows scaling down the size of the semiconductor devices including these layers while maintaining their performance.
1. A method for forming a resistive random access memory cell, the method comprising:
forming a resistive switching layer comprising a resistive switching material;
forming a current limiting layer,
the current limiting layer comprising one of chromium, titanium, or tantalum,
the current limiting layer having a breakdown voltage of at least 8V and a resistivity of at least 1 Ohm-cm in a direction normal to the current limiting layer; and
forming an electrode layer.
2. The method of claim 1 , wherein forming the current limiting layer and forming the electrode layer are in a same operation.
3. The method of claim 2 , wherein a flow of a dopant precursor gas is less when the current limiting layer is formed than when the electrode layer is formed.
4. The method of claim 1 , further comprising annealing the resistive random access memory cell by heating at least the current limiting layer of the resistive random access memory cell to at least about 550° C.
5. The method of claim 1 , further comprising forming a current steering element, wherein a resistance of the current steering element and a resistance of the current limiting layer is same.
6. The method of claim 1 , wherein the current limiting layer comprises chromium.
7. The method of claim 6 , wherein the current limiting layer comprises one of NiCr, AlNiCr, SiCr, SiCrO, or SiCrWN.
8. The method of claim 6 , wherein a concentration of chromium in the current limiting layer is between about 25 and 75 atomic percent.
9. The method of claim 1 , wherein the current limiting layer comprises titanium.
10. The method of claim 9 , wherein the current limiting layer comprises one of TiSiC or TiAlN.
11. The method of claim 1 , wherein the current limiting layer comprises tantalum.
12. The method of claim 11 , wherein the current limiting layer comprises one of TaSiC or TaAlN.
13. The method of claim 1 , wherein a resistivity of the current limiting layer in a direction parallel to the current limiting layer is less than the resistivity in the direction normal to the current limiting layer.
14. The method of claim 1 , wherein the current limiting layer has a resistivity of less than 0.001 Ohm-cm in a direction parallel to the current limiting layer.
15. The method of claim 1 , wherein the current limiting layer has a thickness of less than 200 Angstroms.
16. The method of claim 1 , wherein the resistive switching material comprises one of hafnium oxide, aluminum oxide, tantalum oxide, zirconium oxide, or yttrium oxide.
17. The method of claim 1 , wherein the electrode layer comprises one of doped polysilicon, titanium, titanium nitride, platinum, iridium, iridium oxide, ruthenium, or ruthenium oxide.
18. The method of claim 1 , further comprising forming an additional electrode between the current limiting layer and the resistive switching layer.
19. The method of claim 1 , further comprising forming a diffusion barrier layer between the current limiting layer and the resistive switching layer.
20. A method of forming a resistive random access memory cell, the method comprising:
forming a first electrode layer comprising n-doped polysilicon;
forming a second electrode layer comprising titanium nitride;
forming a current limiting layer comprising nickel and chromium,
wherein a concentration of chromium in the current limiting layer is between 25 and 75 atomic percent,
the current limiting layer having a breakdown resistance of at least 8V and a resistivity of at least 1 Ohm-cm in a direction normal to the current limiting layer,
the current limiting layer disposed between the first electrode layer and the second electrode layer and having a thickness of less than 100 Angstroms; and
forming a resistive switching layer comprising hafnium oxide,
the resistive switching layer disposed between the first electrode layer and the second electrode layer.