THE EFFECTIVE TRANSVERSE THERMAL-CONDUCTIVITY OF AMORPHOUS SI3N4 THIN-FILMS

The effective transverse thermal conductivity of Si3N4 thin films is d etermined as a function of film thickness. Results indicate that the e ffective thermal conductivity behavior of Si3N4 thin films is similar to that exhibited by amorphous SiO2 films; that is, there is no signif icant difference between the thermal conductivity of amorphous Si3N4 a nd amorphous SiO2 thin films as a function of thickness or temperature . The average effective transverse thermal conductivity decreases dras tically as the film thickness is reduced. This strong thickness depend ence is ascribed to a thermal resistance that is localized at the amor phous film/Si-substrate interface. Within the narrow temperature range studied, the interfacial thermal resistance and the intrinsic conduct ivity of amorphous films increase with temperature; however, the inter facial resistance dominates as the film thickness is reduced. In light of the observed similarities between the Si3N4 results and those prev iously obtained on SiO2, the reduction in the effective thermal conduc tivity of amorphous thin films with decreasing thickness is discussed in terms of both interfacial thermal resistance and scattering mechani sms in amorphous solids.