Material Design Schemes for Single-Transistor-Type Ferroelectric Memory Cells Using Pt/(Bi,La)4Ti3O12/ONO/Si Structures

概要

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We successfully 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 $1.0\times 10^{-9}$ A/cm2 at 3 MV/cm, respectively. We found that the material and electrical properties of the BLT films were effectively modulated by the crystallographic orientation control of the thin films, which were strongly affected by the first annealing process at relatively 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 $\pm 8$ V. We conclude from these results that the $c$-axis-oriented BLT films formed by the newly proposed fabrication method can be successfully applied to single-transistor-type ferroelectric memory cells.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2003-11-15