Ferroelectricity of Hf0.5Zr0.5O₂ Thin Film Induced at 350°C by Thermally Accelerated Nucleation During Atomic Layer Deposition

(Hf,Zr) <tex-math notation="LaTeX">O_2 </tex-math> -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) <tex-math notation="LaTeX">O_2 </tex-math> -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 <tex-math notation="LaTeX">_0.5 </tex-math> 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 <tex-math notation="LaTeX">26.9~μ C </tex-math> /cm2 and endurance up to <tex-math notation="LaTeX">10^8 </tex-math> 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.