Steric Hindrance and Film Quality in HfO2 Atomic Layer Deposition: Comparative Kinetic Monte Carlo Simulation of TEMA-Hf and HfCp(NMe2)3 Precursors

Abstract

Hafnia (HfO₂)-based ferroelectrics have attracted considerable attention for next-generation memory devices due to their robust ferroelectricity at ultrathin scales. Achieving desired ferroelectric properties relies on the precise control of film quality, which is strongly influenced by deposition conditions, precursor chemistry, and the presence of impurities. Here, we combine density functional theory and kinetic Monte Carlo simulations to investigate the atomic layer deposition of HfO₂ films from TEMA–Hf and HfCp(NMe₂)₃ precursors using O₃ as the oxidant. Our results show that both precursors decompose preferentially at 2-coordinate O sites on the HfO₂ surface, while 3-coordinate O sites present much higher energy barriers. Kinetic Monte Carlo simulations reveal that growth rates per cycle (GPC) of TEMA-Hf and HfCp(NMe₂)₃ with O₃ are 0.094–0.109 nm/cycle and 0.081–0.096 nm/cycle from 150 to 350 °C, aligning closely with experiments. The slower GPC observed for HfCp(NMe₂)₃ is attributed to the greater steric hindrance of the cyclopentadienyl ligand (Cp) compared to the dimethylamide(NMe₂) groups. Film morphology analysis suggests TEMA-Hf leads to smoother HfO₂ films. Nitrogen incorporation remains at about 1% for TEMA–Hf and HfCp(NMe₂)₃, consistent with experimental observations, while the concentration of O vacancies slightly decreases with the increase of deposition temperature. These findings provide insights into how precursor selection and atomic-level reaction pathways influence film growth and composition, thereby affecting the ferroelectric performance in HfO₂-based devices.