Effect of hydrogen anneals on niobium-doped lead zirconate titanate capacitors with lanthanum strontium cobalt oxide/platinum electrodes

Ferroelectric capacitors, being oxide ceramics, are very sensitive to the e ffects of hydrogen environments at elevated temperatures [H. Ashida et al.: Integr. Ferroelectr. 21 (1998) 97]. After a capacitor has been exposed dir ectly to a annealing hydrogen environment at low hydrogen partial pressures , the electrical properties of the device can deteriorate and leakage curre nts can increase. At higher hydrogen concentration gradients, such as the f ormidable forming gas annealing, physical failure of the inter-layer dielec tric (ILD) and/or top electrode adhesion can occur. The authors have examin ed various structural approaches to mitigate the effects of hydrogen damage on integrated ferroelectric lead zirconate titanate (PZT) capacitors. Thes e approaches, including the use of a titanium dioxide barrier layer above t he PZT to impede the reducing effect of hydrogen on the ceramic and the use of electrode layers other than platinum to eliminate the generation of fre e hydrogen ions by catalyst action [S. Aggarwal et al.: Appl. Phys. Lett. 7 3 (1998) 1973]. The authors have found that niobium-doped PZT capacitors us ing LSCO/platinum electrodes passivated with titanium dioxide will recover from 1% forming gas annealing within 30 minutes at 450 degrees C in nitroge n.