Fabrication of Multilayer Ferroelecric Films

Multilayers of strontium bismuth tantalate (Sr_0.9Bi_2.2Ta₂O₉, SBT) with bismuth titanate (Bi₄Ti₃O₁₂, BT), and SBT and strontium bismuth niobate (Sr_0.9Bi_2.2Nb₂O₉, SBN) with BT were prepared by chemical solution deposition (CSD). The CSD solutions were a mixture of strontium, tantalum, niobium and titanium butoxyethoxides and bismuth ethylhexanoate dissolved in butoxyethanol. The multilayer SBT and SBN with BT, and SBT with BT films were deposited by spin casting on Pt(100 nm)/SiO₂/Si substrates. For comparison, SBT films were fabricated and annealed at 800°C for 30 min, a percentage of capacitors could be tested for ferroelectricity, and a 2Pr of 15 µC/cm² at 3V was typically measured. Multilayer SBT, and SBT and SBN with BT were rapidly thermally annealed for a total (including post electrode anneal) of 22-30 min at 750°C. The multilayer SBT and SBN with BT, and SBT with BT films exhibited a wide range of 2Pr values ranging from 2-14 µC/cm² at 3V but had a larger percentage of measurable capacitors after post electrode anneal than the SBT only films. In addition, no fatigue was observed after 10¹¹ cycles in a SBT with BT multilayer structure