Thermal transport across metal silicide-silicon interfaces: An experimental comparison between epitaxial and nonepitaxial interfaces

Abstract

Silicides are used extensively in nano- and microdevices due to their low electrical resistivity, low contact resistance to silicon, and their process compatibility. In this work, the thermal interface conductance of TiSi$_2$, CoSi$_2$, NiSi and PtSi are studied using time-domain thermoreflectance. Exploiting the fact that most silicides formed on Si(111) substrates grow epitaxially, while most silicides on Si(100) do not, we study the effect of epitaxy, and show that for a wide variety of interfaces there is no difference in the thermal interface conductance of epitaxial and non-epitaxial silicide/silicon interfaces. The effect of substrate carrier concentration is also investigated over a wide range of p- and n-type doping, and is found to be independent of carrier concentration, regardless of whether the interface is epitaxial and regardless of silicide type. In the case of epitaxial CoSi$_2$, a comparison of temperature dependant experimental data is made with two detailed computational models using (1) full-dispersion diffuse mismatch modeling (DMM) including the effect of near-interfacial strain and (2) an atomistic Green' function (AGF) approach that integrates near-interface changes in the interatomic force constants obtained through density functional perturbation theory. At temperatures above 100K, the AGF approach greatly underpredicts the CoSi$_2$ data, while the DMM prediction matches the data well. The full-dispersion DMM is also found to closely predict the experimentally observed temperature-dependent interface conductance for epitaxial NiSi/Si and non-epitaxial TiSi$_2$/Si interfaces. In the case of epitaxial PtSi/Si interfaces, full dispersion DMM significantly overpredicts the experimental data.