Impact of Experimental Timescale and Geometry on Thin-Film Thermal Property Measurements

Integrated circuits require effective removal of increasing heat fluxes from active regions. Thermal conduction strongly influences the performance of micromachined devices including thermal actuators, Peltier-effect coolers, and bolometers. The simulation of these devices requires thermal property data for the thin-film materials from which they are made. While there are many measurement techniques available, it is often difficult to identify the most appropriate for a device. This article reviews thin-film thermal characterization methods with an emphasis on identifying the properties extracted by the techniques. The characteristic timescale of heating and the geometry of the experimental structure govern the sensitivity of the data to the in-plane and out-of-plane conductivities, the volumetric heat capacity, and the interface resistances of the film. Measurement timescales and geometry also dictate the material volume probed most sensitively within the film. This article uses closed-form and numerical modeling to classify techniques according to the properties they measure. Examples of reliably extracted properties are provided for some experimental configurations. This article simplifies the process of choosing the best characterization technique for a given application in microdevice thermal design.