Comparison of dielectric characteristics of Ta2O5 thin films on RuO2 and Ru bottom electrodes

Dielectric properties of Ta2O5 thin films with RuO2 and Ru as the bottom electrodes were investigated. The Ta2O5 thin films were reactively sputtered on the bottom electrodes and then annealed in oxygen ambient at 700 degreesC for 30 min. Using X-ray diffraction and Auger electron spectrometry, it has been found that the Ru bottom electrode was partially oxidized during annealing. while the RuO2 electrode remained its structure. However, the annealed Ta2O5 exhibited a higher dielectric constant, as well as a smaller leakage current, on the Ru electrode than on the RuO2 electrode. Accordingly, the Ru bottom electrode is satisfactory for Ta2O5 storage capacitors, even in a high temperature, oxidizing environment. The divergent electrical performances of two electrodes are attributed to the different crystallinity of annealed Ta2O5 on Ru and RuO2. (C) 2001 The Electrochemical Society.