Fabrication of MFIS diodes using sol-gel derived SBT films and LaAlO ₃ buffer layers

We demonstrate the ferroelectric behavior of Sr0.8Bi2.2Ta2O9 (SBT) films grown on Si(100) substrates by using lanthanum aluminate (LaAlO3) buffer layers. LaAlO3 films were prepared by vacuum evaporation method. Then, they were subjected to ex situ dry N2 annealing in a rapid thermal annealing (RTA) furnace. From the capacitance-voltage (C-V) measurement, the dielectric constant of LaAlO3 was estimated to be 2025. On these substrates, SBT films (210nm) were deposited by sol-gel method and they were characterized by XRD analysis after annealing under various conditions. It was found from C-V characteristics that the memory window of an SBT film annealed at 750C for 30min in O2 atmosphere was about 3.0V for the voltage sweep of 10V. It was also found from the retention measurement that the capacitance values of the SBT film annealed at 750C did not change over 12hours. It is concluded from these results that the SBT/LaAlO3/Si(100) structure is one of the most promising structures for realizing MFISFETs (metal-ferroelectric-insulator-semiconductor field-effect-transistors).