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

HfO-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 HfO-based ferroelectric films has seldom been reported. This study presents the concept of atomic-level stoichiometry control of ferroelectric HfZrO 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 HfZrO films are determined by the chemical and physical reactions predicted by theoretical simulations. The HfZrO ALM films demonstrate superior crystallinity and ferroelectricity compared to conventional HfZrO ALD films, with large polarization values reaching 2 = 48.8 μC/cm 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.