Thermal Boundary Resistance of W/Al2O3 Interface in W/Al2O3/W Three-Layered Thin Film and Its Dependence on Morphology

We investigated the dependence of the thermal boundary resistance of the W/Al 2 O 3 interface in W/Al 2 O 3 /W three-layered thin films on the interface morphology. The layered structures, Al 2 O 3 thin layers with thicknesses from 1 to 50 nm covered by top and bottom W layers with a thickness of 100 nm, were fabricated by magnetron sputtering using a W target (99.99%) and an Al 2 O 3 target (99.99%). The fabrication of polycrystalline W and amorphous Al 2 O 3 films was confirmed by structural analysis. The morphology of the bottom W layer/Al 2 O 3 layer and Al 2 O 3 layer/top W layer interfaces showed a wavelike structure with a roughness of about 1 nm. Thermophysical properties and thermal boundary resistance were measured by a pulsed light heating thermoreflectance technique. The thermal boundary resistance of the W/Al 2 O 3 interface was $1.9\times 10^{-9}$ m 2 K W -1 , which corresponds to the thermal resistance of a 3.7-nm-thick Al 2 O 3 film or a 120-nm-thick W film.