Characteristics of Al/SrBi2Ta2O9/HfO2/Si structure using HfO2 as buffer layer for ferroelectric-gate field effect transistors

We have investigated the structural and electrical properties of metal-ferroelectric-insulator-semiconductor capacitors with 280-nm-thick SrBi₂Ta₂O₉ (SBT) ferroelectric films grown on Si as well as on Si with buffer layer (HfO₂). The SBT thin films and HfO₂ buffer layer were fabricated using rf magnetron sputtering method. XRD patterns revealed the formation of well crystallized SBT perovskite thin film on the HfO₂ buffer layer which is evident from sharp peaks in XRD spectra. The electrical properties of the metal-ferroelectric-insulator- semiconductor (MFIS) structure were characterized by varying thickness of the HfO₂ layer. The width of memory window in the capacitance-voltage curves for the MFIS structure decreased with increasing thickness of HfO₂ layer. Leakage current density decreased significantly after inserting HfO₂ buffer layer. This shows that the proposed Al/SrBi₂Ta₂O₉/HfO₂/Si structure ideally suitable for high performance ferroelectric memories.