Investigation of Electrode Materials for Developing Process-Scheme of Transparent ReRAM Cell Fabrication

Influence of electrode materials on the forming voltages (V
f
) is investigated as a basis for process development of a transparent HfO
x
-ReRAM cell fabrication. Metal with higher oxidation activity induced lower V
f
. This indicates that much amount of oxygen vacancies (Vo) are supplied into HfO
x
instead of oxidation of the electrode and then conductive filament (CF) consisting of Vo can be easily formed even under the low voltage bias. Transparent conductive materials of ITO and AZO were found to induce higher V
f
showing low oxidation activity, this is probably because they are oxides even with many oxygen deficiencies. Oxygen incorporation into Ar-sputtering gas showed change of V
f
. This means the oxidation activity is modified by the deposition condition. Thus, the process can be expected to be developed and optimized for a transparent HfO
x
-ReRAM cell fabrication.