A MULTISAMPLE, MULTIWAVELENGTH, MULTI-ANGLE INVESTIGATION OF THE INTERFACE LAYER BETWEEN SILICON AND THERMALLY GROWN SILICON DIOXIDE

Utilizing a sequence of optical models with increasing complexity, the inclusion of an interface layer between silicon and thermally grown o xide for modeling spectroscopic ellipsometric data is shown to be nece ssary to best interpret the data. This interface is clearly shown not to be an analysis artifact, and is important even when the optical con stant spectra for silicon and thermally grown silicon dioxide are simu ltaneously determined. For this work, spectroscopic (0.75-6.5 eV) elli psometric data sets taken at multiple angles of incidence from seven s amples with oxide thicknesses from 2 to 350 nm were analyzed using a s elf-contained multi-sample technique to obtain Kramers-Kronig consiste nt optical constant spectra. A detailed study was made of parameter co rrelation effects involving the optical constants used for the interfa ce layer. The resulting thermal silicon dioxide optical constants were shown to be independent of the precise substrate model used, and were found to be similar to 0.4% higher in index than published values for vitreous silicon dioxide. The resulting crystalline silicon optical c onstants are comparable to previous ellipsometric measurements. (C) 19 98 Elsevier Science S.A.