Atomic layer deposition of metal oxide materials for memory applications
Embodiments of the invention generally relate to nonvolatile memory devices, such as a ReRAM cells, and methods for manufacturing such memory devices, which includes optimized, atomic layer deposition (ALD) processes for forming metal oxide film stacks. The metal oxide film stacks contain a metal oxide coupling layer disposed on a metal oxide host layer, each layer having different grain structures/sizes. The interface disposed between the metal oxide layers facilitates oxygen vacancy movement. In many examples, the interface is a misaligned grain interface containing numerous grain boundaries extending parallel to the electrode interfaces, in contrast to the grains in the bulk film extending perpendicular to the electrode interfaces. As a result, oxygen vacancies are trapped and released during switching without significant loss of vacancies. Therefore, the metal oxide film stacks have improved switching performance and reliability during memory cell applications compared to traditional hafnium oxide based stacks of previous memory cells.
1. A resistive random access memory cell comprising:
a first electrode;
a second electrode;
a coupling layer comprising a first metal oxide,
the coupling layer being disposed between the first electrode and the second electrode,
the coupling layer forming a first interface with the first electrode; and a host layer comprising a second metal oxide,
the host layer being disposed between the first electrode and the second electrode,
the host layer forming a second interface with the second electrode,
wherein at least one of the coupling layer or the host layer is crystalline and forms a grain boundary interface with a remaining one of the coupling layer or the host layer,
the grain boundary interface comprising grain boundaries extending parallel to the first interface and the second interface.
2. The resistive random access memory cell of claim 1 , wherein the coupling layer is amorphous.
3. The resistive random access memory cell of claim 2 , wherein the host layer is crystalline.
4. The resistive random access memory cell of claim 1 , wherein the coupling layer and the host layer are crystalline, and wherein the coupling layer and the host layer differ in at least one of a grain structure or a grain size thereby forming a misaligned grain interface between the coupling layer and the host layer.
5. The resistive random access memory cell of claim 4 , wherein the grain size of the host layer is greater on average than the grain the grain size of the coupling layer.
6. The resistive random access memory cell of claim 1 , wherein the second metal oxide has a generic chemical formula of MO x , where M is one of hafnium, zirconium, or titanium and x is within a range from about 1.65 to about 1.95.
7. The resistive random access memory cell of claim 1 , wherein the second metal oxide has a generic chemical formula of HfO x , where x is within a range from about 1.70 to about 1.90.
8. The resistive random access memory cell of claim 1 , wherein the second metal oxide has a generic chemical formula of HfO x , where x is within a range from about 1.75 to about 1.85.
9. The resistive random access memory cell of claim 1 , wherein the first metal oxide has a generic chemical formula of MM′ y O z , where M is the same type of metal selected for the first metal oxide host material, M′ is one of aluminum, yttrium, and lanthanum, y is within a range from about 0.05 to about 0.50, and z is within a range from about 1.50 to about 2.50.
10. The resistive random access memory cell of claim 1 , wherein the first metal oxide has a generic chemical formula of HfAl y O z , where y is within a range from about 0.05 to about 0.50, and z is within a range from about 1.50 to about 2.50.
11. The resistive random access memory cell of claim 1 , wherein the first metal oxide has a generic chemical formula of HfAl y O z , where y is within a range from about 0.05 to about 0.15 and z is within a range from about 1.50 to about 2.10.
12. The resistive random access memory cell of claim 1 , wherein the first metal oxide has a generic chemical formula of HfAl y O z , where y is within a range from about 0.40 to about 0.50 and z is within a range from about 2.10 to about 2.50.
13. The resistive random access memory cell of claim 1 , wherein the host layer has a thickness within a range from about 5 Å to about 100 Å.
14. The resistive random access memory cell of claim 1 , wherein the host layer has a thickness within a range from about 10 Å to about 80 Å.
15. The resistive random access memory cell of claim 1 , wherein the host layer has a thickness within a range from about 15 Å to about 50 Å.
16. The resistive random access memory cell of claim 1 , wherein the coupling layer has a thickness within a range from about 3 Å to about 80 Å.
17. The resistive random access memory cell of claim 1 , wherein the coupling layer has a thickness within a range from about 5 Å to about 50 Å.
18. The resistive random access memory cell of claim 1 , wherein the coupling layer has a thickness within a range from about 5 Å to about 30 Å.
19. The resistive random access memory cell of claim 1 , further comprising a layer comprising silicon oxide, the layer being disposed between the first electrode and the coupling layer.
20. A resistive random access memory cell comprising:
a first electrode comprising titanium nitride;
a second electrode comprising an n-type polysilicon;
a coupling layer comprising a first metal oxide having a generic chemical formula of HfAl y O z , where y is within a range from about 0.05 to about 0.15 and z is within a range from about 1.50 to about 2.10,
the coupling layer having a thickness within a range from about 5 Å to about 30 Å,
the coupling layer being disposed between the first electrode and the second electrode,
the coupling layer forming a first interface with the first electrode; and
a host layer comprising a second metal oxide having a generic chemical formula of HfO x , where x is within a range from about 1.75 to about 1.85,
the host layer having a thickness within a range from about 15 Å to about 50 Å,
the host layer being disposed between the first electrode and the second electrode,
the host layer forming a second interface with the second electrode,
wherein the host layer forms a grain boundary interface with the coupling layer,
the grain boundary interface comprising grain boundaries extending parallel to the first interface and the second interface.