Characterization of (Ba,Sr)TiO₃ thin-film capacitors with Ir bottom electrodes and its improvement by plasma treatment

(Ba, Sr)TiO₃ (BST) thin-film capacitors with Ir bottom electrodes are recognized to have higher polarization and leakage current as compared to those with conventional Pt electrodes. This paper describes a method to improve the leakage current of BST/Ir films by high-density plasma surface treatment using O₂·N₂O or NH₃ gas in an inductively coupled plasma system. It is found that the leakage current density can be reduced by two orders of magnitude using O₂ plasma treatment. The dielectric constants were very closely to the reference sample except for NH₃ plasma treated sample. The O₂ and N₂O plasma can enhance the lifetime than 10 years at 1.2 V for the Pt/(Ba,Sr)TiO₃/Ir capacitors. It is necessary to trade off the capacitance property for leakage current property.