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

Georges Hamaoui,Mihai Chirtoc,Jean-François Robillard,Austin Fleming,Tianqi Zhu,Heng Ban,Zilong Hua,Nicolas Horny

doi:10.1038/s41598-018-29505-4

Abstract

This work presents a direct measurement of the Kapitza thermal boundary resistance Rth, 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.

Highlights

Considering the current rate of technology advancement, the race to find new materials with enhanced electrical/ thermal properties is at its peak
We reported the measurements of the Kapitza resistance at metal-silicon and metal silicide-silicon interfaces
The thermal boundary resistance (TBR) for the annealed samples is found lower than that for the unannealed one, meaning that the heat transfer from metal to silicon is improved due to new bonds created by the interdiffusion of the two layers

Summary

Introduction

Considering the current rate of technology advancement, the race to find new materials with enhanced electrical/ thermal properties is at its peak. Recent studies aim to understand the thermal conduction at the interfaces of these structures and measure their thermophysical properties Due to their high electrical conductivity, they are used as ohmic contacts and as Schottky barrier diodes in silicon integrated circuits[1,2,3,4]. A recent study by Ye et al.[16] revealed that the Kapitza thermal conductance at metal silicide-silicon interfaces is usually higher than the one at metal-silicon interfaces This opens an opportunity to study new interfacial thermal transport phenomena, and to understand the fundamental heat transfer channels at these interfaces. The specific objective of this study is to correlate the interfacial heat transport between metal and semiconductor with the metal’s electronic structure by measuring the Kapitza thermal resistance. Which encourages and enables better usage of these metal silicides in silicon-based devices

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Conclusion