Memory improvement with high-k buffer layer in metal/ SrBi2Nb2O9/Al2O3/silicon gate stack for non-volatile memory applications

Abstract

We report the structural and electrical properties of Al/SBN/Al2O3/Silicon gate stack for non-volatile memory applications. RF magnetron sputtering was used for thin film deposition of SrBi2Nb2O9, Al2O3 and their stack on the silicon substrate. Structural characterization using X-Ray Diffraction (XRD) show the perovskite structure of SBN film annealed in the temperature range of 500–800 °C. Multiple angle ellipsometric analysis carried out on the deposited film annealed at different temperatures shows the refractive index (n) in the range of 2.0941–2.1804 for the SBN and 1.7–1.73 for sputtered Al2O3. Metal-Ferroelectric-Semiconductor (MFeS), Metal-Ferroelectric-Metal (MFeM) and Metal-Ferroelectric-Insulator-Semiconductor (MFeIS) structures were fabricated to investigate the memory window, leakage current density, hysteresis and fatigue characteristics. The Effect of introducing Al2O3 buffer layer, its thickness and its annealing temperature on the structural and electrical properties were investigated. The capacitance-voltage (C-V) data shows the memory window improvement from 1.977 V for MFeS to 2.88 V for MFeIS structure with 10 nm sputtered Al2O3 buffer layer. MFeI(10nm)S structures shows leakage current density in the range of nA-cm−2 with no fatigue for the iteration cycles 1011.