Stress Evolution in Ultra Thin Sputtered Films

Abstract

AbstractThe stress and microstructure of growing thin films evolve with time if the deposition is interrupted or terminated. To establish the parameters which control both kinetic processes ultra thin Au, Cu and Al layers were sputter deposited on Si membranes and the stress evolution was monitored by a vibrating membrane technique. The related surface morphology was studied by scanning tunneling microscopy. Aging after each deposition causes stress evolution towards higher tension and the evolution of the stress with time follows an exponential law with a characteristic relaxation time of the order of tens of seconds. This time was found to depend strongly on the accumulated film thickness as well as the surface morphology. The intrinsic stress of the growing layer increases with the coverage of the film on substrate. Scanning Tunneling Microscopy (STM) shows that the film grows in a Volmer-Weber (VW) mode and the stress reaches a maximum as the film become continuous.