Investigation of Thermal Properties in Thin Films With the Transient Thermo-Reflectance Technique

The reliability of micro-electronic devices depends on the thermal properties and energy transfer of the thin metallic films used in them. Within the thin film structures thermal transport properties often differ from bulk material and can be highly dependent on the manufacturing techniques. Thermal transport properties can be measured by the Transient ThermoReflectance technique (TTR). The TTR method uses an ultra-short laser pulse to generate a transient thermal response, and a weaker probe pulse to monitor the reflectivity response of the surface. The changes in reflectivity can be related to transient thermal effects in the film. With the use of an ultra short-pulsed laser, the extremely small time scale required to observe the microscale heat transfer phenomena is possible. The goal of this research is to observe and quantify the effect of differing substrates, film thicknesses, and deposition methods on thermal conductivity. This study uses the TTR technique to examine nickel films of varying thicknesses, fabricated on silicon, germanium, and gallium arsenide substrates, using electron beam evaporation and sputtering techniques. The thermal conductivities of the films were measured and compared.