NiSi2 as a bottom electrode for enhanced endurance of ferroelectric Y-doped HfO2 thin films

Abstract

We exploit the uniform silicidation of an ultra-thin Ni film deposited on crystalline silicon that upon rapid thermal annealing transforms into NiSi2 and then is used as a bottom electrode (BE) with the right structure for orthorhombic crystallization of Y-doped HfO2 (YHO) during an additional post deposition annealing (PDA) process. Compared to a standard TiN BE in metal–insulator–metal structures, the use of NiSi2 and PDA promotes a more reproducible and stable ferroelectric behavior of YHO thin films. In contrast to YHO/TiN, high reproducibility in the current–voltage characteristics as well as lower leakage currents for the YHO/NiSi2 structures (after PDA below 600 °C) enable these devices to withstand up to 10e9 stressing cycles without significantly changing the magnitude of its original remanent polarization (Pr), thus ensuring small wake-up and/or fatigue behavior. All this is possible by the seemingly passivation effect of an interfacial layer developed at the YHO/NiSi2 interface during PDA.