High-density Plasma Etching of RF-Sputtered Indium-Zinc-Oxide Films in Ar, Ar/Cl2, and Ar/CH4/H2 Chemistries

R. Khanna(1)*, W.T. Lim(1), L. Stafford(1), S.J. Pearton(1), Jae-Soung Park(2), Ju-Il Song(2), Young-Woo Heo(2), Joon-Hyung Lee(2), and Jeong-Joo Kim(2)

(1) Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32611, USA,
(2) Department of (2)Inorganic Materials Engineering, Kyungpook National University, Daegu, 702-701, Korea


*Assoc. Applications Engineer Oerlikon USA Inc, St. Petersburg FL 33716
rohit25@ufl.edu, ph no: 352-846-1091

Keywords: Indium-Zinc-Oxide, Transparent Electrodes, Zinc Oxide, Plasma Etching

Abstract

In this work, we investigate the potential of chlorine and methane/hydrogen plasma chemistries for the dry etching of rf-sputtered Indium-Zinc-Oxide (IZO) layers. The influence of the discharge chemistry on the post-etched surface morphology and near-surface stoichiometry is also investigated. While the Cl2-based plasma mixture showed little enhancement over physical sputtering in a pure argon atmosphere, the CH4/H2/Ar chemistry produced a strong increase of the IZO etch rate. The surface morphology of IZO films after etching in Ar and Ar/Cl2 discharges is smooth, whereas that after etching in CH4/H2/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/Cl2 plasmas are constrained to the surface vicinity, etching in CH4/H2/Ar produces a Zn-rich surface layer, whose thickness (~40 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 propagation.

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