DEPOSITION AND PROPERTIES OF REACTIVELY SPUTTERED RUTHENIUM DIOXIDE THIN-FILMS AS AN ELECTRODE FOR FERROELECTRIC CAPACITORS

Ruthenium dioxide (RuO2) films are studied for use as a bottom electrode of the (Ba,Sr)TiO3 thin-film capacitor. RuO2 films have been deposited by reactive DC magnetron sputtering of ruthenium at a relatively low sputtering power. Stoichiometric RuO2 films are obtained at oxygen partial pressures as low as 0.6 mTorr. The properties of the films have been investigated using techniques such as Rutherford backscattering spectrometry, Auger electron spectrometry, X-ray diffraction, and scanning electron microscopy. The oxygen composition in as-deposited RuOx films increases from 2.0 to 2.4 with the increase of initial O-2 partial pressure from 1.2 to 5.6 mTorr at a sputtering power of 200 W. The films deposited under low oxygen partial pressures followed by annealing show preferential crystal growth in the [110] direction, whereas those deposited in high oxygen partial pressures show growth in the [101] direction. A resistivity of 65 mu Omega-cm is obtained after annealing at 800 degrees C. Even after high-temperature deposition and subsequent annealing processes, clear interfaces between (Ba,Sr)TiO3 and RuO2 films are obtained.