Role of Oxygen Source on Buried Interfaces in Atomic-Layer-Deposited Ferroelectric Hafnia-Zirconia Thin Films

Hafnia-zirconia (HfO₂-ZrO₂) solid solution thin films have emerged as viable candidates for electronic applications due to their compatibility with Si technology and demonstrated ferroelectricity at the nanoscale. The oxygen source in atomic layer deposition (ALD) plays a crucial role in determining the impurity concentration and phase composition of HfO₂-ZrO₂ within metal-ferroelectric-metal devices, notably at the Hf_0.5Zr_0.5O₂ /TiN interface. The interface characteristics of HZO/TiN are fabricated via sequential no-atmosphere processing (SNAP) with either H₂O or O₂-plasma to study the influence of oxygen source on buried interfaces. Time-of-flight secondary ion mass spectrometry reveals that HZO films grown via O₂-plasma promote the development of an interfacial TiO layer at the bottom HZO/TiN interface. The presence of the TiO layer leads to the development of 111-fiber texture in HZO as confirmed by two-dimensional X-ray diffraction (2D-XRD). Structural and chemical differences between HZO films grown via H₂O or O₂-plasma were found to strongly affect electrical characteristics such as permittivity, leakage current density, endurance, and switching kinetics. While HZO films grown via H₂O yielded a higher remanent polarization value of 25 μC/cm², HZO films grown via O₂-plasma exhibited a comparable P_r of 21 μC/cm² polarization and enhanced field cycling endurance limit by almost 2 orders of magnitude. Our study illustrates how oxygen sources (O₂-plasma or H₂O) in ALD can be a viable way to engineer the interface and properties in HZO thin films.