AVS 53rd International Symposium
    Thin Film Tuesday Sessions
       Session TF-TuM

Paper TF-TuM1
Rapid Thermal Annealing of Indium Tin Oxide (ITO) Films on Flexible Substrates

Tuesday, November 14, 2006, 8:00 am, Room 2022

Session: Materials for Flexible Substrates, Displays, and Optoelectronics
Presenter: R. Thunuguntla, University of Alabama
Authors: R. Thunuguntla, University of Alabama
D. Bottesch, ASU Flexible Display Center
S. Gupta, University of Alabama
Correspondent: Click to Email
Indium tin oxide (ITO) films are widely used for transparent electrodes in various optoelectronic device and display applications, for instance, organic light emitting diodes (OLEDs), and solar cells. Typically, optimization processes for ITO films include either an in-situ or post-deposition annealing step at temperatures ranging from 200-500°C to improve the sheet resistance and transmission properties, achieving resistivities as low as 250 µ@ohm@-cm and close to 100% transmittance. However, for flexible substrates, processing temperatures must be restricted to about 180 °C, resulting in as-deposited films with higher resistivity and lower transmittance. We report the optimization of ITO film properties on flexible substrates by rapid thermal annealing (RTA). ITO films were deposited on flexible substrates by reactive DC magnetron sputtering over a range of processing conditions. Resistivity and transmission was measured before and after atmospheric rapid thermal annealing with tungsten-halogen lamps at temperatures below 180 °C. Atomic force microscopy and X-ray diffraction studies were also carried out before and after annealing to study the effect of the RTA step on crystal growth and orientation as well as on surface morphology and grain size. These results were compared with those on glass substrates where in-situ annealing at high temperatures during deposition was carried out. Rapid thermal annealing shows great promise as a production-compatible technique for ITO on flexible substrates, with more than 50% reduction of resistivity being achieved in several instances. A detailed RTA optimization study for ITO films on flexible substrates by varying annealing parameters such as time, temperature, thermal profiles and ambient gas is presented.