Structural and electrical characteristics of high-k Tb₂O ₃ and Tb₂TiO₅ charge trapping layers for nonvolatile memory applications

In this study, we investigated the structural properties and electrical characteristics of metal/oxide/high- k material/oxide/silicon (MOHOS)-type memory devices incorporating Tb₂O₃ and Tb ₂TiO₅ films as charge storage layers for nonvolatile memory applications. X-ray diffraction and x-ray photoelectron spectroscopy revealed the structural and chemical features of these films after they had been subjected to annealing at various temperatures. From capacitance-voltage measurements, we found that the MOHOS-type memory devices incorporating the Tb₂TiO₅ film and that had been annealed at 800 °C exhibited a larger flatband voltage shift of 2.94 V (V_g = 9 V for 0.1 s) and lower charge loss of 8.5% (at room temperature), relative to those of the systems that had been subjected to other annealing conditions. This result suggests that Tb₂TiO₅ films featuring a thinner silicate layer and a higher dielectric constant provide a higher probability for trapping of the charge carrier and deeper electron trapping levels.