Superior and stable ferroelectric properties of hafnium-zirconium-oxide thin films deposited via atomic layer deposition using cyclopentadienyl-based precursors without annealing

Abstract

HfO₂-based ferroelectric thin films deposited via atomic layer deposition have been extensively studied as promising candidates for next-generation ferroelectric devices. The conversion of an amorphous Hf_1−xZr_xO₂ film to the ferroelectric phase (non-centrosymmetric orthorhombic phase) has been achieved through annealing using a post-thermal process. However, in this study, we present the first report of ferroelectricity of hafnium-zirconium-oxide (HZO) thin films deposited via atomic layer deposition using cyclopentadienyl-based precursors without additional post-thermal processing. By increasing the deposition temperature using a cyclopentadienyl-based cocktail precursor, the conditions of the as-deposited HZO thin film to crystallize well with an orthorhombic phase were secured, and excellent ferroelectric properties with a large remanent polarization (2P_r ∼ 47.6 μC cm⁻²) were implemented without crystallization annealing. The as-deposited HZO thin film possessed very stable ferroelectric properties without a wake-up effect or significant fatigue up to 10⁶ cycles. Futhermore, we demonstrated the applicability to devices using negative capacitance and non-volatile memory characteristics. This result suggests that a new strategy can be applied to ferroelectric devices where subsequent processing temperature constraints are required, such as back-end-of-line processes and ferroelectric-based flexible device applications.