Thermal stability of RuO2-based bottom electrodes during various ambient annealings

RuO2 thin films were prepared on SiO2/Si, TiN/SiO2/Si and Ru/poly-Si by usi ng DC magnetron sputtering. The annealing of the RuO2-based bottom electrod es was performed in oxygen and argon ambients and in high vacuum in the tem perature range of 400 degrees C similar to 800 degrees C. In oxygen-ambient annealing, the surface morphology was drastically changed due to the evapo ration of ruthenium dioxides in the form of RuO3 and RuO4. The RuO2 thin fi lm annealed in high vacuum was reduced to the Ru metal phase. Evaporation a nd reduction of the RuO2 thin films could actually be observed during the d eposition of (Ba,Sr)TiO3 thin films. Oxygen diffusion through the RuO2/diff usion barrier/poly-Si structures is also discussed.