Large Remnant Polarization in a Wake-Up Free Hf0.5Zr0.5O2 Ferroelectric Film through Bulk and Interface Engineering

A wake-up free Hf0.5Zr0.5O2 (HZO) ferroelectric film with the highest remnant polarization (P-r) 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 T-A followed by rapid cooling to room temperature resulted in a substantial increase in the 2P(r) value (similar to 64 mu C/cm(2)). However, the leakage current increased considerably, which can affect the performance of metal-insulator-metal 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 an similar to 20-fold decrease in the leakage current while the 2P(r) value remained almost constant (similar to 60 It mu C/cm(2)). 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.

Automated summary

By tuning the ozone pulse duration, annealing process, and metal/insulator interface, a wake-up free Hf0.5Zr0.5O2 (HZO) ferroelectric film with the highest remnant polarization value was achieved. The use of a tungsten capping electrode and insertion of a Pt layer between the interfaces helped reduce leakage current while maintaining the 2Pr value constant.