Polarization Switching Kinetics in Thin Ferroelectric HZO Films

Abstract

Ferroelectric polycrystalline HfO2 thin films are the most promising material for the implementation of novel non-volatile ferroelectric memories because of their attractive properties, such as compatibility with modern Si technology, perfect scalability, low power consumption and high endurance. However, for the commercialization of ferroelectric memory, some crucial aspects of its operation should be addressed, including the polarization switching mechanism that determines the switching speed. Although several reports on polarization switching kinetics in HfO2-based layers already exist, the physical origin of retardation behavior of polarization switching at the low and medium switching fields remains unclear. In this work, we examine several models of switching kinetics that can potentially explain or describe retardation behavior observed in experimental switching kinetics for Hf0.5Zr0.5O2 (HZO)-based capacitors and propose a new model. The proposed model is based on a statistical model of switching kinetics, which has been significantly extended to take into account the specific properties of HZO. The model includes contributions of the depolarization field and the built-in internal field originating from the charge injection into the functional HZO layer during the read procedure as well as in-plane inhomogeneity of the total electric field in ferroelectric. The general model of switching kinetics shows excellent agreement with the experimental results.

Effect of Domain Structure and Dielectric Interlayer on Switching Speed of Ferroelectric Hf0.5Zr0.5O2 Film

“…Full dependence of the switched polarization on log t set is similar to the arctan function (solid lines in Figure 2b). Previously, it has been shown in HZO film fitting that parameter Γ is much larger than for perovskite ferroelectrics, while the flat area of time distribution is short [21]. This observation is valid for studied structures of both types.…”

“…For other ferroelectric polycrystalline films, it has been shown that the grain pattern (e.g., grain size and orientation) and grain boundaries affect the polarization switching or domain evolution dynamics in ferroelectric nanofilms [19,20]. Furthermore, the depolarization field of spontaneous polarization, an intrinsic feature of ferroelectrics, has been reported to be the cause of the slowing down of polarization switching [21,22]. Interestingly, the influence of the depolarization field differs for hafnium oxide and perovskites [21,22].…”

“…Furthermore, the depolarization field of spontaneous polarization, an intrinsic feature of ferroelectrics, has been reported to be the cause of the slowing down of polarization switching [21,22]. Interestingly, the influence of the depolarization field differs for hafnium oxide and perovskites [21,22]. This is probably due to the different film thicknesses and different concentrations of charged defects that screen the depolarization field [23].…”