Ferroelectricity of Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> Thin Film Induced at 350°C by Thermally Accelerated Nucleation During Atomic Layer Deposition
Jaewook Lee, Se Hyun Kim, Hyojun Choi, Hyun Woo Jeong, Kun Yang, Ju Yong Park, Yong Hyeon Cho, Sang‐Youn Park, Young H. Lee, Min Hyuk Park
Abstract
(Hf,Zr) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{O}_{{2}}$ </tex-math></inline-formula> -based ferroelectric thin films have recently received significant interest as next-generation memory device materials. However, the high crystallization temperature of over 500 °C to obtain robust ferroelectricity entails challenges for integrating (Hf,Zr) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{O}_{{2}}$ </tex-math></inline-formula> -based ferroelectrics in back-end-of-line (BEOL) processing, which requires temperatures less than 400 °C. In this study, we suggest an effective yet simple method to reduce the crystallization temperature by thermally accelerating the nucleation on 10-nm-thick Hf <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{0.5}}$ </tex-math></inline-formula> Zr0.5O2 (HZO) film during atomic layer deposition (ALD). Increasing the deposition temperature facilitated seed nuclei of tetragonal/orthorhombic phases, which in turn reduced the crystallization temperature as well as augmented the formation of the ferroelectric orthorhombic phase. Consequently, the HZO film grown at an ALD deposition temperature of 300 °C exhibited switchable polarization (2Pr) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$26.9~\mu \text{C}$ </tex-math></inline-formula> /cm2 and endurance up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{8}}$ </tex-math></inline-formula> cycles after rapid thermal processing (RTP) at 350 °C. This work elucidates that forming seed nuclei of tetragonal/orthorhombic phases by increasing the deposition temperature can be a promising strategy to fabricate the BEOL-compatible HZO thin films.