Enhanced Reliability, Switching Speed and Uniformity for Ferroelectric HfZrO x on Epitaxial Ge Film by Post Deposition Annealing for Oxygen Vacancy Control

Abstract

Instead of employing post metal annealing (PMA), post deposition annealing (PDA) was proposed to crystalize HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> (HZO) into the ferroelectric phase on an epitaxial Ge film with higher reliability. Due to the absence of top electrode/HZO reaction during annealing, PDA-processed HZO intrinsically possesses a better capability to control the amount of oxygen vacancies ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{o}$ </tex-math></inline-formula> ). It is physically and electrically confirmed that the amount of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{o}$ </tex-math></inline-formula> for the PDA-HZO is suppressed by 10.3%. Due to fewer <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{o}$ </tex-math></inline-formula> , the PDA-based device shows a higher switching speed than the counterpart by a factor of 12. By integration with an AlON interfacial layer, the PDA-based device reveals superior reliability performance to that by PMA in terms of robust endurance of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> cycles, stable retention up to ten years, and smaller imprint. In addition, the PDA process also leads to enhanced remanent polarization ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{r}$ </tex-math></inline-formula> ) uniformity among devices by 61.3% due to reduced grain size. Furthermore, additional thermal annealing after metal deposition hardly affects the devices’ performance, implying that the PDA process can be integrated with a subsequent dopant activation annealing to implement ferroelectric field-effect transistors (FeFETs) and pave a viable way to advance the development of high-reliability Ge-based FeFET memory.