Ferroelectricity in Sub‐3 nm HZO via a Thin Mo Layer: Interface Engineering for Scalable Memory

Stabilizing ferroelectricity in sub‐3 nm HfO 2 ‐based films is a key challenge for next‐generation memory, primarily due to detrimental interfacial effects. This study demonstrates an electrode‐engineering strategy to overcome this issue by employing an ultrathin (5 nm) Mo seed layer on a TiN electrode. In a comparative study with a conventional thick Mo electrode, we show that this engineered 5 nm Mo/TiN stack enables robust ferroelectricity in Hf 0 . 5 Zr 0 . 5 O 2 (HZO) films as thin as 2.9 nm, achieving a high remanent polarization (2 P r ) of ≈45 μC/cm 2 without requiring pretreatments. Structural and chemical analyses, including grazing incidence X‐ray diffraction and angle‐resolved X‐ray photoelectron spectroscopy, reveal the underlying mechanism: the ultrathin Mo layer forms a greater proportion of conductive oxides, such as MoO 2 and MoO x . This unique interfacial structure reduces the effective dead layer, enhances polarization charge compensation, and suppresses the depolarization field. Landau–Khalatnikov (L–K) simulations corroborate these findings, confirming that an improved interfacial capacitance ( C int ) and a higher density of trapped charges ( σ m ) energetically stabilize the ferroelectric state in the ultrathin regime. Engineering electrode thickness and its underlying stack is a powerful method for controlling interfacial properties. This work provides crucial experimental and theoretical insights into stabilizing ferroelectricity under extreme scaling.