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M. Horkel, C. Eisenmenger-Sittner, J. Mathé, A. Eder, R. Beniaminov, R. Zawrel:
"Determination of the thickness and the refraction index of dielectric thin films with spatial resolution using optical consumer electronic components";
Poster: 18th International Vacuum Congress (IVC-18), Beijing/China; 23.08.2010 - 27.08.2010.

Abstract: Film thickness determination by optical methods is a well known and established field. A huge variety of high precision optical instruments, ranging from spectro-photometers via confocal microscopes to spectroscopic ellipsometers are commercially available.
This paper will describe a novel method to determine the thickness and the refractive index of a thin dielectric layer simultaneously, using the interference of the reflected visible light. The interference patterns of the coated substrates are imaged by a commercially available digital camera, and quantitatively evaluated at three different wavelengths by RGB-splitting. A commercially available digital camera was used, because the sector of optical consumer electronics developed optical instruments which can compete in precision with scientific instruments, but offer a lower price. Generally, a special emphasis was put on a simple and inexpensive experimental setup, using commercially easily available parts, to keep the costs at low as possible. This was achieved, as no special light source or expensive optical components (lenses etc.) except those integrated into the camera are necessary.
The presented instrument can be used in two different modes:
(i) The determination of the thickness profile of thin dielectric films with known refractive index. Measurements have been conducted with Al2O3, TiO2, MgO and MgF2 layers deposited on a silicon wafer via magnetron sputtering or thermal evaporation.
(ii) The simultaneous determination of film thickness and refractive index of a thin dielectric film. This can be achieved by a shift in the interference patterns caused by a change of the incidence light angle. Measurements have been conducted with planar MgF2 layers evaporated on a silicon wafer.
As these two modes do not exclude each other a combination of them is possible as well. To validate the results, measurements with a profilometer were conducted on selected samples.
The financial support of the IWT Flanders, Grant No. SBO-060030 is gratefully acknowledged.

interferometer; dielectric films; spatial resolution; refractive index