Investigation of Ruthenium Electrodes for (Ba,Sr)TiO3 Thin Films

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Abstract
Ru/(Ba, Sr)TiO3(BST)/Ru capacitors were fabricated on TiN/Ti/Poly-Si/SiO2/Si substrate by sputtering technique. The effects of the bottom ruthenium electrode, deposited at various temperatures, on the characteristics of Ru/BST/Ru capacitor were intensively studied. Sputtered ruthenium films were grown in a columnar structure with a grain size ∼30 nm. With an increasing deposition temperature of ruthenium films, the (002) preferred orientation and grain size of ruthenium films gradually increased while the residual compressive stress in the ruthenium films was reduced. The surface of ruthenium films was oxidized to form RuO x on its surface during the deposition of BST films, which dramatically changed the surface morphology of ruthenium films and affected the characteristics of Ru/BST/Ru capacitor. In this work, the electrical properties of Ru/BST/Ru capacitors are explained with an emphasis on the surface morphology and residual stress of ruthenium films.