Electronic contribution in heat transfer at metal-semiconductor and metal silicide-semiconductor interfaces

This work presents a direct measurement of the Kapitza thermal boundary resistance R_th, between platinum-silicon and platinum silicide-silicon interfaces. Experimental measurements were made using a frequency domain photothermal radiometry set up at room temperature. The studied samples consist of ≈50 nm of platinum and ≈110 nm of platinum silicide on silicon substrates with different doping levels. The substrate thermal diffusivity was found via a hybrid frequency/spatial domain thermoreflectance set up. The films and the interfaces between the two layers were characterized using scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. X-ray diffraction was also used to determine the atomic and molecular structures of the samples. The results display an effect of the annealing process on the Kapitza resistance and on the thermal diffusivities of the coatings, related to material and interface changes. The influence of the substrate doping levels on the Kapitza resistance is studied to check the correlation between the Schottky barrier and the interfacial heat conduction. It is suggested that the presence of charge carriers in silicon may create new channels for heat conduction at the interface, with an efficiency depending on the difference between the metal's and substrate's work functions.