Toward Low-Thermal-Budget Processing in Ferroelectric Hf 0.5 Zr 0.5 O 2 Thin Films by Ozone Interface Oxidation

Low-thermal-budget processing is strongly required to implement ferroelectric Hf0.5Zr0.5O2 (HZO) thin films to the back end of line (BEOL) of CMOS technologies. In this work, the O3 oxidation approach is used to form an interface oxidation layer between TiN and the following deposited HZO, achieving robust ferroelectricity under extremely low annealing temperatures. It is shown that, after rapid thermal annealing (RTA) at 350 °C (300 °C), the maximum double remanent polarization ( $2{P}_{r}{)}$ could reach $42.6~\mu \text{C}$ /cm2( $13.3~\mu \text{C}$ /cm $^{{2}}{)}$ with more than $10^{{8}}$ field-cycling endurance. The formation of the TiO2 layer at the interface of HZO/TiN supplies greater tensile stress, which is responsible for the low-RTA-temperature ferroelectricity with an optimum oxidation time of 40s. The proposed TiN surface oxidation method facilitates the BEOL compatibility and provides feasible avenues to high-performance ferroelectric HZO thin films.