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

Abstract

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 (O2)) and its duration on the optical transmission coefficient and electrical resistivity of the films depending on the power and O2 concentration during their deposition. A low sputtering power of 100 W combined with an O2 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 2.3×10−3Ω cm. Sputtering without O2 results in a transmission of 89% and a resistivity of 9×10−4Ω cm. The annealing depth is found to be 370 nm. We deposited and annealed conductive, transparent ITO tracks below 50 ∘C on a polyimide substrate and thereby operated integrated light sources on a fully transparent and highly flexible optical probe.