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 NiSi 2 and then is used as a bottom electrode (BE) with the right structure for orthorhombic crystallization of Y-doped HfO 2 (YHO) during an additional post deposition annealing (PDA) process. Compared to a standard TiN BE in metal-insulator-metal structures, the use of NiSi 2 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/NiSi 2 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/NiSi 2 interface during PDA.

Reduced fatigue and leakage of ferroelectric TiN/Hf0.5Zr0.5O2/TiN capacitors by thin alumina interlayers at the top or bottom interface

“…Oxygen vacancies have also been identified as the main factor behind the deleterious wake-up effect [28,29], i.e. the increase in remanent polarization with electric field cycling, as well as assisting in fatigue and eventual dielectric breakdown [29,30].…”

“…Pešic´et al suggested that the fastest O vacancy defect generation occurs at the TiO x interface between HfO 2 and TiN where electron trapping creates leakage pathways and eventually results in a breakdown of the device [29]. While the inclusion of oxygen vacancies in small concentration can be favorable for eliciting the ferroelectric phase in HfO 2 , excess vacancy formation from TiN can negatively impact the endurance of HfO 2 ferroelectric devices [30,42].…”