Highly conductive and transparent ITO films deposited at low temperatures by pulsed DC magnetron sputtering from ceramic and metallic rotary targets

Abstract

The fabrication of complex device structures often requires deposition of Indium tin oxide (ITO) thin films on temperature sensitive substrates. For example, substrates containing electronic components or organic materials used in displays, touch panels, and electroluminescent devices often restrict process temperatures to below 100°C. Currently the best ITO quality is attained for films deposited with magnetron sputtering using ceramic targets at substrate temperatures above 200°C. In the present study, ITO layers with thicknesses ranging from 25nm to 200nm were deposited on glass substrates by pulsed DC magnetron sputtering using rotary ceramic ITO targets and reactive sputtering from rotary indium-tin targets. Optical and electrical properties were measured and compared for both types of ITO layers. The as-deposited layers were treated post-growth to enhance electrical conductivity and optical transmission. A standard thermal treatment is compared to flash lamp annealing (FLA) with the goal of keeping substrate temperature below 100°C. The enhancement of both electrical and optical properties has been determined by sheet resistance measurements and optical spectroscopy. ITO coatings with optical transmissions higher than 87% and resistivity lower than 2.5×10−4Ωcm could be achieved. A strong influence of the oxygen flow during deposition has been observed for the electrical and optical properties after post-treatment.