Ferroelectric Pb(Zr,Ti)O-3 capacitors for nonvolatile FeRAM application

Fatigue, thermal imprint and switching behavior were investigated on PZT ca pacitors with Ir/IrO3 or Pt electrodes and with various Zr/Ti ratios. Fatig ue endurance was drastically improved by using Ir/IrO2 far both top and bot tom electrodes. The PZT capacitors with atop Ir/IrO2 and a bottom Pt/Ti wer e almost fatigue-free up to 10(8) cycles and the use of Ir/IrO2 for both to p and bottom electrodes further improved the fatigue endurance up to 10(11) cycles. It was concluded that the most suitable Zr/Ti ratio for the 2T2C m emory cell was 40/60 because of its high bit line voltage and fatigue endur ance. The life time of the PZT capacitors for 75 degrees C storage was expe cted to be 23 years from the extrapolated value of the internal bias voltag e.