Thermal characterization of dielectric thin films using an improved genetic algorithm

This paper presents theoretical and experimental investigations of the thermal conductivity and the contact resistance of dielectric materials deposited as thin films. Silicon dioxide and poly(p-phenylene) films deposited on alumina substrates are studied in order to determine simultaneously the thermal conductivity of the film and the resistance of the contact between the film and the substrate. Measurements are obtained by using a photothermal technique, and an improved genetic algorithm (GA), especially suitable for thermal characterizations of thin film structures in the sub-micron range. A theoretical study for evaluating the optimal conditions for the photothermal measurements is presented. This is done by studying the sensitivity of the unknown parameters to the thin film thickness and to the properties of the materials. As the photothermal analysis is basically performed in unsteady state conditions, this study highlights the relation between the intrinsic and effective conductivity of the materials.