Post-annealing effects on antireduction characteristics of IrO2/Pb(ZrxTi1−x)O3/Pt ferroelectric capacitors

Publisher Website
Google Scholar
Abstract
Antireduction characteristics of IrO2/Pb(ZrxTi1−x)O3(PZT)/Pt ferroelectric capacitors are improved by post annealing. When an as-processed capacitor receives a 3% hydrogen annealing at 300 °C (a process condition for fabricating the interlayer dielectric), capacitor characteristics are heavily degraded. This is because Ir that is produced by IrO2 reduction plays a catalytic role in PZT reduction. By contrast, if the IrO2/PZT/Pt capacitor is post annealed in O2 atmosphere at 600 °C for 1 h, the capacitor characteristics can be maintained even if it undergoes the hydrogen annealing. The O2 annealing improves the crystallinity of the IrO2 top electrode and excess PbOx in sol-gel derived PZT diffuses into the IrO2 film. As a result, antireduction characteristics of the IrO2 top electrode itself are drastically improved and the PZT film becomes stoichiometric at the same time. Exclusion of excess PbOx in PZT results in an increase in spontaneous polarization of the IrO2/PZT/Pt ferroelectric capacitor. Furthermore, the polarization hysteresis characteristics can be preserved after the hydrogen annealing because the reduction of the top IrO2 electrode does not occur and there is no material which causes the PZT reduction.