Ferroelectric Enhancement in a TiN/Hf1-xZrxO2/W Device with Controlled Oxidation of the Bottom Electrode

Abstract

Hf1-xZxO2 (HZO) is a promising ferroelectric (FE) material with CMOS compatibility, while the TiN/HZO/W metal-ferroelectric-metal structure provides balanced thermal expansion for stacking. In this study, we developed a 7 nm film of HZO with a FE polarization (2Pr) value of ∼43 μC/cm2 and cycling endurance of 108 by determining the appropriate oxidation state for a W bottom electrode deposited via atomic layer deposition with a relatively low annealing temperature of 400 °C. To visualize FE uniformity, we used X-ray absorption spectroscopy phase mapping to construct a two-dimensional map of the orthorhombic (O), tetragonal (T), and monoclinic (M) phases of the HZO film. Subsequent orientation- and chemical-state-resolved X-ray analysis revealed that the enhanced FE polarization performance can be attributed to the combined effects of interface strain and oxygen vacancies. Piezoelectric force microscopy verified the switching uniformity of the devices and revealed the electrical characteristics for use in device optimization.