Temperature- and Frequency-Dependent Ferroelectric Characteristics of Metal-Ferroelectric-Metal Capacitors with Atomic-Layer-Deposited Undoped HfO Films.

In this study, we evaluated the temperature- and frequency-dependent ferroelectric characteristics of TiN/undoped HfO/TiN metal-ferroelectric-metal (MFM) capacitors in which an undoped HfO film was deposited through atomic layer deposition (ALD). Successful ferroelectric characteristics were achieved after postdeposition annealing at 650 °C, which exhibited a remanent polarization of 8 μC/cm and a coercive electric field of 1.6 MV/cm at 25 °C (room temperature). The ferroelectric property was maintained at 200 °C and decreased as the temperature increased. The ferroelectric property was completely lost above 320 °C and fully recovered after cooling. The frequency dependency was evaluated by bias-dependent capacitance-voltage and s-parameter measurements, which indicated that the ferroelectric property was maintained up to several hundred MHz. This study reveals the ultimate limitations of the application of an undoped HfO MFM capacitor.