Ellipsometric characterization of ITO films deposited by reactive dual magnetron sputtering

Proper characterization of tin doped indium oxide (ITO) films prepared at various deposition parameters is important to produce the layers with low resistivity and high luminous transmittance. Therefore, thin ITO films were grown on insulating substrates by means of pulsed reactive dual magnetron sputtering at different base pressure, magnetron pulse duration and Ar/O2 ratio. To characterize the layers after deposition, spectroscopic ellipsometry (SE) was applied in combination with optical transmittance and resistivity measurements. Surface roughness obtained by SE was corroborated by atomic force microscopy. A significant variation in film deposition rate was observed for experiments with different magnetron pulse duration due to SE results. It agrees with Auger depth profiling data. The latter also showed that the O/In ratio values close to 1.5 correspond to the lowest film resistivity. For ITO films produced at various deposition conditions it was observed that SE derived free electron parameters ratio demonstrates certain minimum. It corresponds to the lowest film resistivity and high transmittance. SE was also applied in situ as a non contact technique to monitor ITO film resistivity optimization during annealing.