Zirconium-doped hafnia (HfZrOx) ferroelectric capacitor with atomic layer deposited HfO2, ZrO2, and La2O3 interfacial layers

Abstract

Recently, a device using a ferroelectric (FE) material has been spotlighted as a next-generation memory device. However, due to issues such as the interfacial reaction between the Si substrate and the HfO2-based FE thin film in Si-based devices, there are still limitations in applying it to actual devices. In this study, HfO2, ZrO2, and La2O3 were applied as the interlayer (IL) layer to replace the naturally formed SiOx IL layer. This approach aimed to solve the high leakage current and low endurance issues associated with SiOx IL layers. Polarization-voltage (P-V) measurements and phase analysis confirmed that an increased fraction of the orthorhombic (o) phase in the ferroelectric film leads to an enhancement in remnant polarization. Additionally, material with a higher oxygen vacancy formation energy exhibited reduced oxygen vacancy and impurity fractions in both the bulk HfZrOx (HZO) and its interface. And it also results in lower leakage current and improved endurance characteristics during polarization switching. Among the tested IL materials, La2O3 demonstrated the best performance, effectively suppressing oxygen vacancy and impurity formation due to its high oxygen vacancy formation energy, and achieving an endurance of 5 × 105 cycles and the lowest leakage current density. This study shows that selecting IL materials with higher oxygen vacancy formation energy can effectively enhance critical reliability factors, such as endurance and leakage current, in MFIS capacitors.