Porous silicate based sol-gel coatings are promising candidate for low-K dielectric materials for ultra large-scale integrated circuits (ULSIs). To optimize the sol-gel coating process to meet the increasingly stringent requirements in performance and reliability, it is critical to explore advanced analytical tools and techniques to characterize and monitor the coating structure and properties. Spectroscopic ellipsometry, a non-invasive optical technique for determining optical properties and coating thickness, can provide insight into coating structure and properties. In this paper, we determined the refractive index, optical dielectric constant and porosity of sol-gel coatings using ellipsometry with the hypothesis of considering the coating as the mixture of matrix material with void. Models including linear calculation and effective medium approximation (EMA) were employed in ellipsometric data analyses. The ambiguity was effectively reduced for the analyses with EMA model by including the intensity of reflectance of coating in the analyses. This can greatly improve the applicability of the analyses of ellipsometry for porous coatings.

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