Design Guidelines of Thermally Stable Hafnia Ferroelectrics for the Fabrication of 3D Memory Devices

Abstract

We provide a methodology for designing thermally stable hafnia ferroelectric (FE) materials to be taken into account while fabricating 3D memory devices. We reveal the underlying origins for the thermal instability of hafnia FE materials in terms of kinetics and material science. Furthermore, we suggest adopting dopants whose ionic radius is smaller than Hf in the FE matrix as a feasible option to demonstrate a thermally stable hafnia FE material. Using this approach, robust ferroelectricity is achieved even at a subsequent thermal budget (TB) of 750 °C for 30 min. The improved thermal stability stems from the reduced formation of both the m-phase and oxygen vacancy (VO) in hafnia FE materials at high TB. The in-depth electrical and material analysis in this study serves a framework for further research into the thermal stability of FE. This work contributes to the commercialization of FE devices by filling the gap between the functionality of FE materials and their process applicability for 3D devices.