Nitridation of (Ba,Sr)TiO₃ films in an inductively coupled plasma

The effects of surface treatment, using ammonia in an inductively coupled plasma, of (Ba,Sr)TiO₃ films on the leakage and dielectric properties of the Pt/(Ba,Sr)TiO₃/Pt capacitors were investigated. To obtain data of the ammonia plasma, a Langmuir probe was used during the experiments. As a result of the exposure of (Ba,Sr)TiO₃ to the plasma, the leakage current density of the (Ba,Sr)TiO₃ capacitor was decreased by two orders of magnitude as compared to that of the non-plasma-treated sample at an applied voltage of 1.5 V. The decrease of leakage currents of (Ba,Sr)TiO₃ films is attributed to the reduction of oxygen vacancies. However, the dielectric constant may be changed by the plasma-induced space charge or ion bombardment. The X-ray photoelectron spectroscopy measurements detected the N 1s peak in the plasma-treated sample. Additional space charges were induced and result in the reduction of the dielectric constant. We assume that the competition of nitrogen incorporation into the oxygen vacancies and plasma-induced damage is the main effect of the nitridation of (Ba,Sr)TiO₃ films in ammonia plasma.