Fast Thermal Quenching on the Ferroelectric Al:HfO2 Thin Film with Record Polarization Density and Flash Memory Application

Abstract

We have investigated the effects of post cooling process with chamber cooling, air cooling and fast quenching in DI water on the ferroelectric (FE) characteristics of Al-doped Hf02 (Al:HfO2) thin films and demonstrated their potential flash memory applications. Compared with other cooling processes, using fast quenching after annealing we achieved the drastic increase of remnant polarization $(\mathrm{P}_{\mathrm{r}})$ and coercive electric field $(\mathrm{E}_{\mathrm{c}})$. The highest $2\mathrm{P}_{\mathrm{r}}$ and $2\mathrm{E}_{\mathrm{c}}$ are $\sim 100\mu\mathrm{C}/\mathrm{cm}^{2}$ and ~9.5 MV/cm, respectively, the highest records among HfO2-based FE reported so far. These improvements are attributed to induce higher stress/strain within A1:HfO2 thin film, leading to stable orthorhombic phase (o-phase). Program/erase up to 106 cycles and 10 years retention characteristics are also evaluated for the potential flash memory application. Our simulation with experimental data indicates that Pr and Ec significantly can influence on the memory window and multi-bit states, which can be tuned by our proposed quenching process.