Effects of morphological changes of Pt/SrBi2Ta2O9 interface on the electrical properties of ferroelectric capacitor

Abstract

Morphological changes have been observed at the interface of Pt/SrBi2Ta2O9 (SBT) before and after annealing at 600 and 800 degrees C after depositing Pt top electrode. We have investigated leakage currents, breakdown voltages, and capacitances of Pt/SBT/Pt/SiO2/Si capacitor and Pt/SBT/CeO2/Si gate structure. As a result, the leakage cut-rent density and capacitance are reduced from 10(-7) to 10(-8) A/cm(2) and 1.3 x 10(-10) to 8.5 x 10(-)11 F/cm(2), respectively; and breakdown voltage increases from 5 to 14 V after post-annealing. The reduced leakage current density and increased breakdown voltage in the annealed samples are due to the smooth morphology of the interface of Pt/SBT. In the as-deposited Pt top electrode on SET films, high electric field intensity is generated due to small are of the valleys filled with fine Pt grains, resulting in higher leakage current density than the post-annealed Pt top electrode. Although the total gate capacitance of the post-annealed sample is reduced by the non-contact area due to voids at the interface of Pt/SBT, memory window of the ferroelectric gate is not influenced by such voids.