Hillock formation and thermal stresses in thin Au films on Si substrates

The wafer curvature technique was used to analyze stresses in fine-grained, 50 nm to 2 μm thick Au films on silicon substrates between room temperature and 500°C. The microstructural evolution was analyzed by scanning electron microscopy (SEM), focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). In situ heating experiments inside a scanning electron microscope provided a comparison between the morphological development and the stress-temperature behavior of the film. Hillock formation was observed, but it can only partially account for the stress relaxation measured by the wafer curvature technique.