FERROELECTRIC PB(ZR,TI)O_3 CAPACITORS FOR NONVOLATILE FERAM APPLICATION

摘要

Fatigue,thermal imprint and switching behavior were investigated on PZT capacitors with Ir/IrO_2 or Pt electrodes and with various Zr/Ti ratios. Tatigue endurance was drastically improved by using Ir/IrO_2 for both top and bottom electrodes. The PZT capacitors with a top Ir/IrO_2 and a bottom Pt/Ti were almost fatigue-free up to 10~8 cycles ad the use of Ir/IrO_2 for both top and bottom electrodes further improved the fatigue enduance up to 10~11 cycles. It was concluded that the most suitable Zr/Ti ratio for the 2T2C memory cell was 40/60 because of its high bit line voltage and fatigue endurance. The life time of the PZT capacitors for 75 deg C storage was expected to be 23 years from the extrapolated value of the internal bias voltage.