Many applications of thin films, especially for electronics devices, require that these materials, which are often anisotropic, have a very high thermal conductivity as well as uniform areal properties to ensure that reproducible performance be attained. These factors necessitate that measurements of thermal transport properties are required both to provide absolute application values for different heat flow directions as well as to evaluate uniformity and homogeneity of a wafer. For diamond, the combination of a very high thermal conductivity with limited size and form of available specimen presents unique challenges to the experimentalist. As a result, a modification of the ac calorimeter method has been developed to evaluate the thermal diffusivity of thin films.
Details of the technique will be provided together with examples of its use to evaluate thermal diffusivity and thermal conductivity of different CVD diamond film composites having thicknesses from 10µm to 600µm and free-standing films. In addition, results using this method will be compared. with those obtained by other techniques involved in a recent international round-robin measurements program designed to evaluate a potential standard method(s).