Influence of Si-Doping on 45 nm Thick Ferroelectric ZrO2 Films

In the last decades, ferroelectricity has been discovered in Si-doped HfO2 and Hf1–xZrxO2 thin films, and the origin of ferroelectricity is considered to be the presence of the polar Pca21 orthorhombic phase. Recently, some investigations suggest that ZrO2 thin films show ferroelectric behavior as well. As a well-known dopant capable of modulating ferroelectricity in HfO2 thin films, Si-doping is applied up to approximately 5.3% to modify the ferroelectric properties of ZrO2 films in this work. The atomic layer-deposited ZrO2 films with a 45 nm thickness shows ferroelectric behavior with a remanent polarization of 7 μC/cm2 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 ZrO2 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 ZrO2 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 ZrO2.