Optimization of sputtered ITO films with respect to the oxygen partial pressure and substrate temperature

Abstract

The electrical and optical properties of thin films of ITO (indium tin oxide) have been optimized with respect to the oxygen partial pressure and substrate temperature. Reactive rf sputtering has been applied to a 5-inch target with 10 wt% SnO 2 and 90 wt% In 2O 3. After various preliminary tests, employing a biasing of −50 V and a target voltage of 1.7 kV, a target-substrate distance of 27 mm and a sputter period of 90 min were chosen. The oxygen partial pressure was varied from 0.08% to 30% of the total pressure of 3 Pa at a temperature of 400 °C. The films were investigated with an emphasis on the electrical conductivity. Using the experimentally determined optimum oxygen partial pressure (0.16%), the substrate temperature was varied between room temperature and 520 °C, and similar examinations were made of the electrical conductivity, charge carrier concentration, transmittance, selectivity, etc. The best samples had a resistivity of 2.4 × 10 −6 Ω m, a sheet resistance of 5.5 Ω, and an average transmittance of 95% in the visible spectrum without correction for reflection.