Growth of patterned island arrays to identify origins of thin film stress

To understand the origins of stress in thin films, we have used wafer curvature to measure the stress evolution during electrodeposition of Ni on lithographically patterned Si substrates. The stress is measured as the hemispherical islands grow and impinge upon each other, forming interfacial boundaries between them. We relate the results to a model for polycrystalline films in which the stress is attributed to competing processes occurring where the layers in adjacent grains grow into each other and form new segments of grain boundary. This model predicts that the stress in each layer depends on the rate at which the grain boundary is growing when that layer is incorporated into the film. The calculations agree with the measured stress vs thickness using a single set of fitting parameters for five different growth rates. (C) 2014 AIP Publishing LLC.