Atomic-Level Stoichiometry Control of Ferroelectric Hf_xZr_yO_z Thin Films by Understanding Molecular-Level Chemical Physical Reactions

HfO₂-based thin films have garnered significant interest for integrating robust ferroelectricity into next-generation memory and logic chips, owing to their applicability with modern Si device technology. While numerous studies have focused on enhancing ferroelectric properties and understanding their fundamentals, the fabrication of ultrathin HfO₂-based ferroelectric films has seldom been reported. This study presents the concept of atomic-level stoichiometry control of ferroelectric Hf_xZr_yO_z films by examining the molecular-level interactions of precursor molecules in the atomic layer deposition (ALD) process through theoretical calculations. Atomic layer modulation (ALM) employs sequential precursor pulses, and the stoichiometries of Hf_xZr_yO_z films are determined by the chemical and physical reactions predicted by theoretical simulations. The Hf_xZr_yO_z ALM films demonstrate superior crystallinity and ferroelectricity compared to conventional Hf_xZr_yO_z ALD films, with large polarization values reaching 2P_r = 48.8 μC/cm² at a thickness of 4.5 nm. Because the ALM concept combines experimental and theoretical approaches, it can be applied to other applications that require multicomponent thin films with atomic-level stoichiometry control.