Electrical properties of a metal-ferroelectric-insulator-semiconductor structure with lanthanum dysprosium oxide and SrBi₂Ta₂O₉

The metal-ferroelectric-insulator-semiconductor (MFIS) structure using a SrBi₂Ta₂O₉ (SBT) film as a ferroelectric layer and a lanthanum dysprosium oxide (LDO) film as an insulating buffer layer was prepared. The LDO thin film and the SBT film were deposited by using the sol-gel method. The sol-gel-derived LDO thin films on Si had very flat and smooth surface morphologies. The equivalent oxide thickness (EOT) values were about 10.1 nm, 12.5 nm, and 12.8 nm for 750 °C, 800 °C, and 850 °C, respectively. Also, the relative dielectric constants of the 750 °C-annealed, 800 °C-annealed and 850 °C-annealed LDO films were about 15.4, 12.5, and 12.2, respectively. On the whole, the leakage current densities showed good characteristics regardless of the annealing temperature. Especially, the leakage current property of the 850 °C-annealed LDO film was visibly superior to those of the others at voltages over 6 V. The C-V characteristics of the Au/SBT/LDO/Si structure showed clockwise hysteresis loops, and the memory window width increased as the bias voltage was increased. Also, the leakage current density was lower than 5 × 10^-7 A/cm².