Ferroelectric Properties and Polarization Fatigue of La:HfO₂ Thin‐Film Capacitors

Abstract

Recently, doped HfO 2 thin films have attracted considerable attention because of promising applications in complementary metal–oxide–semiconductor (CMOS)‐compatible ferroelectric memories. Herein, the ferroelectric properties and polarization fatigue of La:HfO 2 thin‐film capacitors are reported. By varying the substrate lattice constant and film thickness, a robust remanent polarization of ≈16 μC cm −2 is achieved in a 12 nm‐thick Pt/La:HfO 2 /La 0.67 Sr 0.33 MnO 3 capacitor. Fatigue measurements are conducted using designed pulse sequences, in which the voltage, pulse width, and interval time are changed to observe the evolution of switchable polarization with increasing cycles. Severe fatigue is observed when the La:HfO 2 capacitors are partially switched and the interval between the bipolar switching is elongated. These behaviors may be ascribed to the domain wall pinning scenario, in which domain switching is blocked by the migration and aggregation of charges on non‐electroneutral walls. Further analysis of the fatigue behaviors with a nucleation‐limited‐switching model shows that the mean time and activation field for polarization switching are increased in fatigued La:HfO 2 capacitors because electrical stimuli are required to disperse the aggregated charges before the domains are set free. These results facilitate the design and fabrication of HfO 2 ‐based ferroelectric memories with improved device reliability.