Switching by Ni Filaments in a HfO2 Matrix: A New Pathway to Improved Unipolar Switching RRAM

HfO₂-based resistive RAM (RRAM) devices have received intensive research attention in the recent years. Most of the HfO₂-based RRAM system demonstrates promising performance in bipolar mode. However, HfO₂-based RRAM devices in unipolar mode so far, still suffers from low endurance (<;500 cycles), and non-integratable electrode materials such as Pt or Au. In this work, CMOS-compatible Ni-containing electrodes / HfO₂ / TiN stacks were demonstrated switching in unipolar mode, with promising endurance >;10³ cycles and good retention (stable LRS/HRS baking at 150°C). Ab-initio simulation and physical analysis Tof-SIMS were utilized to study the switching mechanisms in unipolar mode. Excellent bipolar switching in our Ni-containing electrodes / HfO₂ /TiN stacks were also demonstrated, with >;10⁴ endurance and good retention (stable LRS/HRS baking at 150°C). Physical models for both bipolar and unipolar modes were proposed based on electrical and physical characterization. Scaled 90nm devices in contact hole (CT) were also made and switching behavior was presented.