Intrinsic stress development and microstructure evolution of Au/Cr/Si multilayer thin films subject to annealing

Au/Cr/Si microcantilevers were studied in their as-deposited condition and annealed state, with emphasis on a thermal treatment of 225 °C for 24 h. Change in beam curvature was monitored during isothermal hold as a function of time. Secondary grain growth was observed in the gold, which contained non-uniformly distributed twins and dislocation defects. Diffusional transport of the chromium layer was observed during annealing. Nodules arranged in a “rolling hill” topography were observed at the free surface, both before and after annealing. Nanometer thick coatings of alumina grown by atomic layer deposition improved the uniformity of both microstructure evolution and curvature evolution during high-temperature annealing.