Fabrication of MFIS diodes using sol-gel derived SBT films and LaAlO₃ buffer layers

Abstract

We demonstrate the ferroelectric behavior of Sr_0.8Bi_2.2Ta₂O₉ (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 20∼25. 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 750°C 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 750°C 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).

Key Words:

• SBT
• LaAlO₃
• vacuum evaporation
• sol-gel