Growth kinetics of SiO₂ and the ellipsometric study of SiO₂ films on silicon

Kao, Shou-Chen
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Doremus, Robert H.
Muraka, Shyamn P.
Tomozawa, Minoru
Watson, E. Bruce
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Materials engineering
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Routine ellipsometric measurements of oxide thickness use a simplified model based on a single, optically homogeneous oxide layer on silicon substrate with plane parallel boundaries between different phases and neglect oxide film stress, a non stoichiometric SiOₓ layer and the roughness at the Si-SiO₂ interface. In this study, the influence of oxide film stress, the SiOₓ layer and Si-SiO₂ interface roughness on the ellipsometric measurements are investigated. A modified ellipsometric model which includes the stress-birefringence effect on the oxide film and a intermediate layer at the Si-SiO₂ interface is also proposed to explain the discrepancy between TEM and ellipsometric thickness measurements. This model is tested and the model parameters are calculated by a liquid immersion technique. This technique replaces the surrounding medium of the sample (air) by liquids with different refractive indices, which provides more than one set of ellipsometric readings, Δ and Ψ, to solve the ellipsometric equations. The results show that a more complicated ellipsometric model than the single layer model is necessary to accurately calculate the oxide thickness for thin oxide films.
December 1992
School of Mechanical, Aerospace, and Nuclear Engineering
Dept. of Engineering
Rensselaer Polytechnic Institute, Troy, NY
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