Plasma etching and electrical characterization of Ir/IrO2/PZT/Ir FeRAM device structures

Abstract

We report the effect of top electrode structure on the electrical properties of ferroelectric Pb(ZrxTi1-x)O3 (PZT) capacitors. Samples with Ir/PZT/Ir or Ir/IrO2/PZT/Ir stacks were prepared using reactively sputtered Ir/IrO2 (top) and Ir (bottom) electrodes and MOCVD-deposited PZT on TiAIN/SiO2/Si wafers. Capacitor structures were patterned by plasma etching of the top electrode and show evidence for transient fence formation. Electrical measurements of the capacitors showed good ferroelectric properties (2Pr up to 38 μC/cm2, with leakage <10−6 A/cm2) and low fatigue (<20% drop in Qsw) out to 8×1010 cycles. Samples with top electrode structures containing IrO2 gave higher 2Pr values and lower pre-anneal fatigue, when compared with Ir-only top electrode samples. The sample with top electrode containing the thinnest IrO2 layer showed slightly lower fatigue than the rest. We also briefly describe the use of these structures and etch methods in fabricating backend-integrated ferroelectric capacitors.