Imprint Characteristics of Ferroelectric Thin Films at Elevated Storage and Operation Temperatures

Abstract

The imprint characteristics of SrBi2Ta2O9 (SBT) and Bi4-xLaxTi3O12 (BLT) thin films have been studied at elevated storage and operation temperatures for the application to ferroelectric random access memories (FeRAMs). After the storage at 125°C, a significant charge shift occurs as a function of the logarithmic time due to the thermally induced voltage shift. At an elevated operation temperature, the voltage shift divided by coercive voltage increases leading to the enhanced imprint degradation of polarization. Since the BLT thin film has larger remanent polarization and smaller voltage shift divided by coercive voltage at an elevated temperature than the SBT thin film, it has higher imprint endurance. In order to investigate the imprint characteristics on a device level, the sensing margin of the FeRAM cells using 0.8 µm complementary metal-oxide-semiconductor (CMOS) technology with SBT and BLT capacitors is also detected.