Cerium oxide capping on Y-doped HfO2 films for ferroelectric phase stabilization with endurance improvement

The effects of 1 nm thick CeO (x) capping on 7.5 nm thick Y-doped HfO2 films on the ferroelectric characteristics are investigated. From the ferroelectric characteristics of the samples annealed at different temperatures from 450 degrees C to 600 degrees C and annealing durations, the time (tau) required to stabilize the ferroelectric phase at each temperature was shortened by the capping. The identical activation energy (E (a)) of 2.65 eV for ferroelectric stabilization without and with capping suggests the same kinetics for phase transformation. However, an increase in the remnant polarization (P (r)) was obtained. Only a few Ce atoms diffused into the underlying HfO2 film even after 600 degrees C annealing. Ferroelectric switching tests revealed an improvement in endurance from 10(7) to 10(10) by the capping, presumably owing to the suppression of conductive filament formation. Therefore, CeO (x) capping is effective in promoting the ferroelectric phase in HfO2 with high switching endurance.