Preparation and characterization of rf sputtered indium tin oxide films

Abstract

Indium tin oxide films have been grown by rf sputtering at various Ar-O2 mixtures, at low substrate temperatures (200 °C), and deposition rates (25 Å/min), followed by post deposition annealing (at 350 °C) in different ambients (O2, N2, and cracked ammonia). Influence of a reactive gas (oxygen) on the sputtering rate of a metallic (indium/tin) alloy target has been investigated. Growth parameters and annealing conditions have been optimized. The films were characterized by electron and x-ray diffraction, scanning electron microscopy, and transmittance as a function of wavelength. The effect of heat treatment in various environments on the structural, electrical, and optical properties has been investigated. Effect of a new annealing ambient, cracked ammonia (reducing atmosphere), on the reactively sputtered oxide films is being reported for the first time. Cracked ammonia was found to be very effective and cheap and resulted in films of high quality (electrical and optical) with good structural properties. Films with low sheet resistances (Rs=30 Ω/⧠ at film thicknesses of 800 Å and Rs=8.5 Ω/⧠ at film thicknesses of 5000 Å) with high visible transmission (∼95%) have been achieved by annealing in cracked ammonia.