MATERIAL DESIGN SCHEMES FOR SINGLE-TRANSISTOR-TYPE FERROELECTRIC MEMORY CELLS USING Pt/(Bi,La)4Ti3O12/ONO/Si STRUCTURES

Authors fabricated metal-ferroelectric-insulator-semiconductor (MFIS) structures using Bi3.465La0.85Ti3O12 (BLT) ferroelectric thin films and SiO2/Si3N4/SiO2 (ONO) stacked buffer layers for single-transistor-type ferroelectric nonvolatile memory applications. The BLT films were deposited on the prepared Pt/Ti /SiO2/Si and ONO/Si substrates by a sol-gel spin-coating method. The dielectric constant and the leakage current density of the prepared ONO film were measured to be 5.6 and 1.0x 10-9 A/cm2 at 3 MV/cm, resp. Authors found that the material and electrical properties of the BLT films were modulated by the crystallographic orientation control of the thin films, which were affected by the first annealing process at low temperature. While the fabricated MFIS capacitors using (117)-oriented BLT films showed a charge injection phenomenon in C-V properties at high operating voltage, c-axis-oriented BLT-loaded MFIS capacitors showed a memory window of 0.6 V even at a voltage sweep of plus/minus 8 V. Authors conclude from these results that the c-axis-oriented BLT films formed by the newly proposed fabrication method can be applied to single-transistor-type ferroelectric memory cells. 15 refs.