Effects of high pressure nitrogen annealing on ferroelectric Hf_0.5Zr_0.5O₂ films

The effect of high-pressure nitrogen annealing at up to 50 atmospheres (atm) on Hf_0.5Zr_0.5O₂ films at relatively low temperatures (450 °C) is analyzed using polarization-electric field curves, bipolar switching endurance measurements, grazing angle incidence X-ray diffraction, and piezoelectric force microscopy. Hf_0.5Zr_0.5O₂ films annealed at 450 °C/50 atm have excellent characteristics, including remanent polarizations greater than 20 μC/cm², a switching speed of 200 ns, and reliability, measured by sustained performance after 10¹⁰ bipolar switching cycles. The enhanced device features are attributed to the transition to the orthorhombic-phase from the tetragonal-phase of Hf_0.5Zr_0.5O₂ at high pressure, which is also consistent with the results of “wake-up” analysis, and the variations of the pure polarization curves, extracted from the total displacement field under pressure.