AVS 53rd International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS1-ThA

Paper PS1-ThA5
Mechanisms of Plasma-Induced Damage during Ion-Assisted Chemical Etching of Indium-Zinc-Oxide Films in Reactive Plasma Chemistries

Thursday, November 16, 2006, 3:20 pm, Room 2009

Session: Plasma Processing for High-K/III-V’s and Smart Materials
Presenter: L. Stafford, University of Florida
Authors: L. Stafford, University of Florida
W.T. Lim, University of Florida
S.J. Pearton, University of Florida
J.-I. Song, Kyungpook National University, Korea
J.-S. Park, Kyungpook National University, Korea
Y.W. Heo, Kyungpook National University, Korea
J.-H. Lee, Kyungpook National University, Korea
J.-J. Kim, Kyungpook National University, Korea
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Because of its good electrical conductivity, wide transmittance window, large work function, excellent surface smoothness, and low deposition temperature, Indium-Zinc-Oxide (IZO) has recently emerged as a very promising material for transparent electrodes in various optoelectronic devices such as liquid crystal displays, light-emitting-diodes, and solar cells. While the growth characteristics of IZO layers are relatively well optimized, the development of a reliable pattern transfer process remains to be examined. In this work, we investigate the potential of Cl@sub 2@ and CH@sub 4@/H@sub 2@ plasma chemistries for the dry etching of IZO films. The influence of the discharge chemistry on the post-etched surface morphology and near-surface stoichiometry is also investigated. While the Cl@sub 2@-based plasma shows little enhancement over physical sputtering in a pure argon atmosphere, the CH@sub 4@/H@sub 2@/Ar chemistry produces a strong increase of the IZO etch rate. The surface morphology of IZO films after etching in Ar and Ar/Cl@sub 2@ discharges is smooth, whereas that after etching in CH@sub 4@/H@sub 2@/Ar presents particle-like features resulting from the preferential desorption of In- and O-containing products. While the etch-induced damage in Ar and Ar/Cl@sub 2@ plasmas are constrained to the surface vicinity, etching in CH@sub 4@/H@sub 2@/Ar produces a Zn-rich surface layer, whose thickness (~55 nm) is well-above the expected range of incident ions in the material (~1.5 nm). Auger electron spectroscopy measurements as a function of plasma exposure time indicate that diffusion of O, Zn and In atoms upon preferential desorption of volatile O- and In-containing reaction products is responsible for damage formation. A diffusion model accounting for the observed depth profiles is proposed. Such damage of the IZO layer is expected to have a significant impact on the transparent electrode properties in optoelectronic device fabrication.