Characterization of Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) Structures Using (Bi, La)4Ti3O12and HfO2Buffer Layers

We report the electrical properties of metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structures using (Bi, La) 4 Ti 3 O 12 (BLT) thin films with HfO 2 buffer layers for one-transistor(1T)-type FeRAM applications. Since high-capacitance buffer layers are required to realize the high density of MFMIS gate structures, we used a HfO 2 layer as an insulator material. Ferroelectric BLT layers were fabricated by the sol-gel technique and HfO 2 buffer layers were deposited by the RF sputtering method. It is demonstrated that Pt/HfO 2 /n-Si MIS structures have a low leakage current in the 10 -9 A/cm 2 range with an equivalent oxide thickness (EOT) of 3.5 nm. The capacitance–voltage ( C – V ) characteristics of the Pt/BLT/Pt/HfO 2 /n-Si MFMIS diode with an S I / S F area ratio of 6 reveal a large memory window of 3 V due to the ferroelectric properties of the BLT films.