Characteristics of Pt/SrBi ₂Ta ₂O ₉/Y ₂O ₃/Si ferroelectric gate capacitors

We have fabricated metal/ferroelectric/insulator/semiconductor (MEFIS) capacitors using Pt, SrBi ₂Ta ₂O ₉ (SBT), and Y ₂O ₃ thin films. As a buffer layer between the ferroelectric and the Si substrate, a Y ₂O ₃ film is rf-sputtered on the Si substrate and crystallized along the [111] direction during the annealing process. The dielectric constant and the interface trap charge density of the Y ₂O ₃ film are about 9 and 2×10 ¹¹ eV ^-1·cm ^-2, respectively. The SBT thin films deposited on both Si(100) and Y ₂O ₃(222)/Si(100) by using metal organic deposition (MOD) show similar diffraction patterns with randomly oriented polycrystalline phases. The MEFIS capacitors show good ferroelectric hysteresis arising from the polarization switching properties. The memory window in the capacitance-voltage (C-V) curve and the leakage-current density of Pt/SBT(180 nm)/Y ₂O ₃(16 nm)/SiO ₂(4 nm)/Si are 3.08 V and 6.7×10 ^-8 A/cm ², respectively, at a gate voltage of 5 V.