Dynamic imprint recovery as an origin of the pulse width dependence of retention in Hf0.5Zr0.5O2-based capacitors

Abstract

Retention of the storing polarization state at elevated temperatures (typically 85-105 °C) as well as the ability to rewrite and subsequently read it are an essential property of usable HfO2-based ferroelectrics for ferroelectric random access memory implementation. This work shows that retention loss in TiN/Hf0.5Zr0.5O2 (HZO)/TiN capacitors is highly dependent on the duration of pulses that are used for measurements, i.e., there is better retention of the same state (SS), new same state (NSS), and opposite state (OS) for longer pulses. The root cause of this phenomenon is the dynamic recovery of the imprint, which happens during the first long SS measurement. This may be due to the fast re-injection of charges injected from the electrode and trapped in the HZO during storage at elevated temperatures. Such dynamic imprint recovery underlies the best NSS behavior compared to other states and may affect the worst retention loss of the OS.