Effects of top electrode annealing on the PZT thin films

Effects of top electrode annealing on the ferroelectric properties and reliability characteristics of the PZT films with various Zr/Ti ratios were investigated as a function of top electrode annealing temperature and its thickness. It was observed that the hysteresis loop of the PZT film was seriously deformed by both sputtering and reactive ion etching (RIE) of Pt. An annealing of the top electrode restores the deformed hysteresis loop by removing the effect of structural defects and space charges formed by sputtering and RIE induced damage. An optimum annealing temperature at which maximum in remanent polarization occurs, increases with decreasing Zr/Ti ratio. An excess annealing above the optimum temperature decreases in the remanent polarization probably due to PbO evaporation. For the same annealing temperature, PZT film with thicker top electrode shows larger switching charge because larger compressive stress is induced. The stress effect is larger on (100) oriented film than on (111) oriented film. For the same electric field, PZT film with thinner cop electrode exhibits better endurance characteristics.