In the last decades, ferroelectricity has been discovered in Si-doped HfO 2 and Hf 1−x Zr x O 2 thin films, and the origin of ferroelectricity is considered to be the presence of the polar Pca2 1 orthorhombic phase. Recently, some investigations suggest that ZrO 2 thin films show ferroelectric behavior as well. As a well-known dopant capable of modulating ferroelectricity in HfO 2 thin films, Si-doping is applied up to approximately 5.3% to modify the ferroelectric properties of ZrO 2 films in this work. The atomic layer-deposited ZrO 2 films with a 45 nm thickness shows ferroelectric behavior with a remanent polarization of 7 μC/cm 2 after post-metallization annealing at 800 °C. According to Raman spectroscopy and grazing incidence X-ray diffraction structural characterizations, the amount of monoclinic and orthorhombic phases decreases, and the presence of the tetragonal phase increases by increasing the Si-doping content in the ZrO 2 films. The electrical properties both at room temperature and at lower temperature demonstrate antiferroelectric characteristics with lower remanent polarization and double hysteresis loops with Si incorporation in the 45 nm thick ZrO 2 films. An extrapolation of the Curie temperature for different Si-doping concentrations is obtained based on temperature-dependent remanent polarization measurements, showing evidence that Si dopants destabilize the polar ferroelectric phase. An increasing in-plane tensile strain with more Si-doping aids in stabilizing the tetragonal phase and leads to an improvement of antiferroelectric properties in 45 nm thick ZrO 2 .

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 Hf0.5Zr0.5O2 /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 x layer at the bottom HZO/TiN interface. The presence of the TiO x 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.

Further optimization of a typically reported ferroelectric capacitor comprised of a Hf0.5Zr0.5O2 ferroelectric thin film with TiN electrodes is explored by introducing an additional non‐ferroelectric La2O3 interfacial layer evaluated at different positions in the capacitor stack. The role of the interface to the ferroelectric layer is investigated and discussed, with the main focus directed toward the reliability of the device for non‐volatile memory applications. With this investigation, different degradation mechanisms determining electric field cycling and polarization retention are observed, and it is concluded that modifying the bottom interface between the electrode and the ferroelectric layer has the best potential to provide a benefit in device performance.

The discovery of ferroelectric properties in the doped HfO2 and mixed Hf1−xZrxO2 systems made precise phase determination very important. However, due to the similarities of the diffraction peaks between the tetragonal and the orthorhombic phases, the discrimination of these two critical phases by x-ray diffraction remains challenging. This work introduces Raman spectroscopy as a structural characterization method to unambiguously identify phases by comparing experimental data with density functional simulation results for the mixed hafnia–zirconia system in the complete composition range. Raman modes for the non-polar monoclinic and tetragonal phases are presented in comparison to those of the polar orthorhombic phase. Changes in phonon mode frequencies in the hafnia–zirconia system with Hf/Zr composition are related to the appearance of ferroelectric properties.

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