Nucleation limited switching (NLS) model for HfO2-based metal-ferroelectric-metal (MFM) capacitors: Switching kinetics and retention characteristics

Abstract

HfO2-based ferroelectrics (FE-HfO2) have shown promise as an emerging 1-T (single-transistor) non-volatile memory candidate because of its attractive features, such as CMOS compatibility, scalability, fast switching speed, low power, and long retention. The nucleation limited switching (NLS) model, which attributes the polarization switching mainly to the waiting time of nucleation of reversed domains, has been well developed to interpret experimental results for both ferroelectric switching and retention of metal-ferroelectric-metal (MFM) devices based on conventional perovskite ferroelectric materials [such as Pb(Zr, Ti)O3]. However, the applicability of this model to HfO2-based MFM capacitors is not well understood, although some recent experimental evidence has suggested so. In this study, we thoroughly investigated the switching kinetics and the retention characteristics of FE-HfO2 in the context of the NLS model. We show that (1) the NLS model agrees well with the experimental results of switching kinetics over 5 orders of pulse widths, and the extracted modeling parameters are also consistent with those predicted by the density-functional-theory analysis, indicating that the nucleation of reversed domain indeed dominates the switching speed and (2) the NLS model also agrees well with the experimental retention characteristics of HfO2-based MFM devices both at room temperature and at 85 °C.