Spectroscopic ellipsometry of bonded silicon-on-insulator structures with oxide-nitride-oxide layers

摘要

Bonded silicon-on-insulator (SOI) structures with oxide-nitride-oxide (ONO) layers are investigated nondestructively using spectro-scopic ellipsometry (BE). Results are discussed from three main points of view: the effects of the beam size on evaluating the SOI substrate, the beam divergence, and the effect of applying different data-fitting parameters to get reliable structures. Optimum results for a wavelength range of 250 to 850 nm have been obtained by using a combination of a lens and a slit of nearly 1-mm width to minimize the light-beam divergence. One interesting result is that because of the observed slight vertical error, and because the measured parameter tanψ has values greater than one, we have to avoid in this case fitting tanψ and cosΔ in order to obtain calculated data close to the nominal values. No depolarization effects were found for the obtained ellipsometric data.