  A wake-up free Hf0.5Zr0.5O2 (HZO) ferroelectric film with the highest remnant
polarization (Pr) value to-date was achieved through tuning of the ozone pulse
duration, the annealing process, and the metal/insulator interface. The ozone
dosage during the atomic layer deposition of HZO films appears to be a crucial
parameter in suppressing the mechanisms driving the wake-up effect. A tungsten
capping electrode with a relatively low thermal expansion coefficient enables
the induction of an in-plane tensile strain, which increases the formation of
the orthorhombic phase while decreasing the formation of the monoclinic phase
during the cooling step of the annealing process. Therefore, increasing the
annealing temperature TA followed by rapid cooling to room temperature resulted
in a substantial increase in the 2Pr value (64 uC/cm2). However, the leakage
current increased considerably, which can affect the performance of
metal-insulator-metal (MIM) devices. To reduce the leakage current while
maintaining the mechanical stress during thermal annealing, a 10 nm Pt layer
was inserted between the W/HZO bottom interface. This resulted in a ~ 20-fold
decrease in the leakage current while the 2Pr value remained almost constant (~
60 uC/cm2). The increase in barrier height at the Pt/HZO interface compared to
that of the W/HZO interface coupled with the suppression of the formation of
interfacial oxides (WOx) by the introduction of a Pt/HZO interface serves to
decrease the leakage current.
