AVS 53rd International Symposium
    Applied Surface Science Friday Sessions
       Session AS-FrM

Paper AS-FrM4
Ion-Induced Effects during Reactive Sputter Deposition of ITO Films at the RF-biased Electrode

Friday, November 17, 2006, 9:00 am, Room 2005

Session: Thin Film Characterization
Presenter: M. Dudek, Ecole Polytechnique de Montreal, Canada
Authors: A. Amassian, Cornell University
M. Dudek, Ecole Polytechnique de Montreal, Canada
O. Zabeida, Ecole Polytechnique de Montreal, Canada
J.E. Klemberg-Sapieha, Ecole Polytechnique de Montreal, Canada
L. Martinu, Ecole Polytechnique de Montreal, Canada
Correspondent: Click to Email
Research on tin doped indium oxide (ITO) has for many years been stimulated by the need to simultaneously optimize the electrical, optical and mechanical properties, and by new challenges related to the deposition on flexible plastic substrates. In the present work, we systematically studied ITO films deposited by reactive sputtering from an indium-tin alloy target. We found that additional radiofrequency (RF)-biasing at the substrate holder allows one to effectively control the level of stress in the film, as well as its crystalline structure, composition, electrical, and optical properties. A comparison of in situ real-time spectroscopic ellipsometry (RTSE) studies and elastic recoil detection (ERD) depth profiles revealed that even for samples with nominally identical compositional profiles, biased and unbiased films exhibit very different optical and electrical responses. Biased films exhibited a dense morphology with homogeneous n, k, and free carrier concentration depth profiles, whereas unbiased films exhibited columnar morphology, and large gradients of these properties. Using a novel Monte-Carlo TRIDYN simulation approach, which can model the ion bombardment effects of multi-component broad energy ion sources (e.g. RF plasma source and corresponding ion energy distribution function), we show that oxygen subplantation (shallow implantation) plays a crucial role in enhancing oxygen incorporation below the growth surface in the presence of biasing. This leads to both enhanced transparency in the visible spectrum, and an increase by an order of magnitude, of the free carrier concentration. We propose that atomic displacements resulting from intense ion-surface interactions in the presence of biasing are likely responsible for the activation of charge donors by a mechanism of oxygen vacancy formation.