Dielectric properties of Ta 2O 5 thin films with RuO 2 and Ru as the bottom electrodes were investigated. The Ta 2O 5 thin films were reactively sputtered on the bottom electrodes and then annealed in oxygen ambient at 700°C 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 RuO 2 electrode remained its structure. However, the annealed Ta 2O 5 exhibited a higher dielectric constant, as well as a smaller leakage current, on the Ru electrode than on the RuO 2 electrode. Accordingly, the Ru bottom electrode is satisfactory for Ta 2O 5 storage capacitors, even in a high temperature, oxidizing environment. The divergent electrical performances of two electrodes are attributed to the different crystallinity of annealed Ta 2O 5 on Ru and RuO 2.
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