Attenuated total reflection spectroscopy for infrared analysis of thin layers on a semiconductor substrate

A theoretical analysis based on a perturbation method is used to elucidate the results of attenuated total reflection (ATR) measurements performed on silicon oxide layers of different thicknesses on silicon substrates. This analysis shows that the absorbance ATR spectrum in p polarization is the image of the layer energy loss function, under specific conditions. It is pointed out that the enhanced sensitivity of ATR is controlled by the air gap thickness, the optical properties of the media involved, and the probing light polarization. An exact ATR spectrum simulation using a matrix formalism showed that straightforward interpretation in terms of the layer dielectric function is limited to a very narrow layer thickness range. The ATR spectrum fitting process is considered for layers out of this range and evaluated for the interpretation of experimental silicon oxide layer spectra.