X-ray reflectometry and grazing-incidence X-ray fluorescence characterization of innovative electrodes for tantalum-based resistive random access memories
Résumé
We evaluate the ability of the combination of grazing-incidence X-ray fluorescence (GIXRF) with X-ray reflectometry (XRR) to probe the impact of variations in the deposition process of tantalum oxide on the chemical depth-profiles of Ta2O5/metal structure, titanium nitride and nickel being investigated as bottom electrode material as they are good candidates for the replacement of noble materials by low-cost fab-friendly abundant electrodes for Resistive RAM. TOF-SIMS and GIXRF/XRR both unambiguously demonstrate the significant TiN-Ta intermixing in Ta2O5/TiN stacks, even with optimized Ta2O5 process conditions. On the contrary, TOF-SIMS profiles reveal that the introduction of H* plasma step in PE-ALD Ta2O5 process drastically reduces both the oxidation of nickel electrode material and the Ta2O5/Ni intermixing, therefore confirming that nickel is a good candidate for Ta2O5 based ReRAM. The influence of H* plasma on nickel-based samples was also evidenced by GIXRF/XRR technique, first qualitatively, then quantitatively by the use of model-based multilayer combined analysis, therefore demonstrating the performances of GIXRF/XRR as highly-sensitive, non-destructive chemical depth-profile technique suitable to support process development, either in lab or even in fabs.