Impact of Al-doping on Al:HfO₂Dielectric Reliability in MIM Capacitors

The impact of Al-doping in Al:HfO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>on the reliability and dielectric properties of metal-insulator-metal (MIM) capacitors is investigated. Dielectric constant and breakdown field were found to strongly depend on the Al-doping concentration, correlating with phase transitions from monoclinic to tetragonal/cubic phases at low doping levels (< 4 % Al) and to an amorphous phase at higher concentrations (> 17% Al). The crystallization behavior in lower-doped samples was further confirmed by pronounced current fluctuations observed during leakage measurements under constant voltage stress. Lifetime predictions based on a power law (PL) extrapolation model highlighted the improved reliability of MIM devices with enhanced Al-doping. It was shown that higher doping concentrations exhibited increased activation energies for time-dependent dielectric breakdown (TDDB), consistent with an Arrhenius behavior. Additionally, reversible degradation under bipolar stressing, resembling resistive switching mechanisms, was observed across all studied samples. This behavior suggests the potential for mitigating leakage path formation, offering pathways to improve device performance and reliability.