Ferroelectric properties of Pb(Zr,Ti)O-3 thin films deposited on annealed IrO2 and Ir bottom electrodes

Ferroelectric fatigue and hysteresis of reactively sputtered Pb(Zr,Ti)O-3 ( PZT) thin films were investigated by annealing IrO2 and Ir bottom electrode s at various temperatures. These electrodes were annealed to change their c rystallinity and surface morphology in O-2 or N-2 atmosphere, respectively. There was no appreciable roughening of the PZT/IrO2 interface respective t o that of the PZT/Ir; the rms roughness of IrO2 and Ir annealed at 650 degr ees C was about 3.5 and 10 nm, respectively. The ferroelectric properties o f the PZT/IrO2 were found to be overall better than those of the PZT/Ir. Th e PZT/IrO2 thin films exhibited very small fatigue up to 10(11) cycles; the P*r-P<^>r value decreased only from 16.6 to 14 mu C/cm(2) until 10(12) pol arization reversals. This is due to the excellent diffusion barrier propert y of IrO2 and the smooth PZT/IrO2 interface. On the other hand, although th in IrO2 layer was formed between PZT and Ir, the PZT/Ir thin films began to undergo fatigue after 10(9) polarization reversals. (C) 1999 American Vacu um Society. [S0734-2101(99)06105-9].