Influence of local plasma flow on optical properties and thickness of ITO-films observed with spectroscopic imaging ellipsometry


Influence of local plasma flow on optical properties and thickness of ITO-films observed with spectroscopic imaging ellipsometry

Vaupel, M.; Vinnichenko, M.

Tin-doped-indium oxide In2O3:Sn (ITO) is a degenerate n-type semiconductor with high transparency and nearly metallic conductivity. Thin films of ITO find applications in optoelectronics, photovoltaics, and in the liquid crystal display and OLED industry as transparent electrodes. The interaction of the plasma with the growing film surface may be employed to manipulate adatom mobilities and nucleation rates [1, 2], and thus contribute to the definition of the film structure and the evolution of its properties during deposition. The aim of the present work is to investigate the influence of the intentionally inhomogeneous plasma flow on the distribution of the ITO film thickness and optical properties along the substrate. For large scale inspection spectra of Delta/Psi were recorded scanning across the sample. For high resolution (small scale inspection) a spectrum of Delta micromaps with wavelength from 420 nm to 830 nm with 4 µm lateral resolution was recorded using Nanofilm’s imaging ellipsometer EP3 within 3 min. From fitting of the spectrum one obtains maps for each of the fit parameters. It is observed, that the damping of the oscillator is rather independent of location. A negative oscillator frequency shift with thickness increasing from the low towards the high plasma flow area is observed. Such a correlation can be explained by the change of the film microsctructure and stoichiometry [3] which, in turn, can affect electronic structure of the film.
References
1. I. Petrov, P.B. Barna, L. Hultman, and J.E. Greene, J. Vac. Sci. Technol. A 21, 1 (2003).
2. W. Ensinger, Nucl. Instr. Meth. B 127/128, 796 (1997).
3. A. Rogozin, M. Vinnichenko, N. Shevchenko, A. Kolitsch, and W. Moeller, Thin Solid Films 496, 197 (2006) .

Keywords: Imaging ellipsometry; tin-doped indium oxide; reactive magnetron sputtering

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Publ.-Id: 10253