Use of Voigt oscillators to characterize microelectronics materials by Infrared Spectroscopic Ellipsometry

We propose a study on the use of Voigt or Lorentz oscillators on three examples of microelectronics materials: fluorinated silicate glass, silicon nitride and polybenzoxazole. The Voigt oscillator is a convolution of Gauss distribution and Lorentz oscillator and includes both homogeneous and inhomogeneous broadening. It is especially suitable to represent infrared transitions in amorphous materials by considering oscillators in the collection of nominally identical atoms that may have slightly different resonance frequencies because of local surroundings, local crystal structures, defects, dislocations or lattice impurities… Infrared ellipsometry spectra are analyzed and fitted using either of these oscillators. The fits are processed first on the regular part of the spectra and then by progressively extending the fitting range from high to low frequencies to the different absorption bands. Through these three examples it is shown that the Voigt oscillator can simplify the fit process, especially when the materials have absorption bands with complicated structure.