Low-temperature plasma annealing of sputtered indium tin oxide for transparent and conductive thin-films on glass and polymer substrates

This paper reports on the development of a low-temperature plasma annealing process for indium tin oxide (ITO) thin-films deposited by magnetron sputtering. The study investigates the influence of the type of plasma (argon (Ar) vs. oxygen (O-2)) and its duration on the optical transmission coefficient and electrical resistivity of the films depending on the power and O-2 concentration during their deposition. A low sputtering power of 100 W combined with an O-2 concentration of 6 vol% followed by a 40-min Ar plasma anneal at 300 W produces ITO films with an average transmission of 94% in the visible spectrum and a resistivity of 2.3 x 10(-3) Omega cm. Sputtering without O-2 results in a transmission of 89% and a resistivity of 9 x 10(-4) Omega cm. The annealing depth is found to be 370 nm. We deposited and annealed conductive, transparent ITO tracks below 50 degrees C on a polyimide substrate and thereby operated integrated light sources on a fully transparent and highly flexible optical probe.