Thermal retention of atomic layer deposited Hf0.5Zr0.52 films using H2O and O2–H2 plasma oxidation methods

Abstract

Thermal retention of ferroelectric hafnium zirconium oxide (HZO) is a critical reliability concern impacting its use in applications such as ferroelectric field-effect transistors, ferroelectric random-access memory, and ferroelectric tunnel junctions. Thermal depolarization and thermal imprint are explored for 10 nm thick Hf0.5Zr0.5O2 films. The HZO films were fabricated through atomic layer deposition with two different oxidizing conditions, H2O or sequential O2 and H2-plasmas. A similar virgin state switched polarization of ∼30 μC/cm2 was found by annealing the H2O films at 700 °C and the O2–H2 plasma films at 500 °C. Both O2–H2 plasma and H2O films exhibited same state P–U and |N–D| switched polarization values above 25 μC/cm2 after 100 h at 125 °C. For opposite state switched polarization, however, O2–H2 plasma films showed asymmetric shifts in the coercive fields and subsequent loss of P–U and |N–D| retention after 100 h at 125 °C, while the H2O films exhibited symmetric shifts in the coercive fields, and P–U and |N–D| opposite state thermal retention above 25 μC/cm2 after 100 h at 125 °C.