Interfacial conditions and electrical properties of the SrBi2Ta2O9/ZrO2/Si (MFIS) structure according to the heat treatment of the ZrO2 buffer layer

The possibility of the ZrO2 buffer layer as the insulator for the metal-ferroelectric-insulator-semiconductor (MFIS) structure was investigated. ZrO2 and SrBi2Ta2O9 (SBT) thin films were deposited on the p-type Si(1 1 1) wafer by the rf magnetron-sputtering method. According to the process with and without the post-annealing of the ZrO2 buffer layer, the diffusion amount of Sr, Bi, Ta elements show slight difference through the glow discharge spectrometer (GDS) analysis. From X-ray photoelectron spectroscopy (XPS) results, we could confirm that the post-annealing process affects the chemical binding condition of the interface between the ZrO2 thin film and the Si substrate, which results in the chemical stability of the ZrO2 thin film. The electrical properties of the MFIS structure were relatively improved by the post-annealing ZrO2 buffer layer. The window memory of the Pt/SBT (260 nm, 800 °C)/ZrO2 (20 nm) structure increases from 0.75 to 2.2 V. This memory window is sufficient for the practical application of the NDRO-FRAM operating at low voltage.