Development of a transmission line model for the thickness prediction of thin films via the infrared interference method

An efficient transmission line model, in the micrometrie order, is presented in this paper, to determine the thickness of thin dielectric films deposited on highly-doped substrates. In particular, the estimation of the thickness is based on the multiple reflections of an incident infrared electromagnetic wave that generate interference on the sensor. To this objective, the periodicity of the local maxima and minima, including the phase shift and wavelength dependence of the reflection at the layer-substrate interface, leads to the extraction of the required thickness. The featured theoretical transmission line model is, finally, validated via a direct comparison with Certified Reference Materials to indicate its overall accuracy and reliability level.