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In this work, the evolution of microstructure and the thermo-mechanical behavior of cop-per and dilute copper alloy thin films was investigated. 0.3 to 2.0 µm thick films were de-posited by magnetron sputtering under ultra high vacuum conditions onto diffusion-barrier coated silicon substrates and subjected to wafer curvature measurements. Pure copper films annealed in ultra high vacuum exhibited a large grain size, a sharp (111) texture, and very few twin grains. Grain growth in the single-phase copper-aluminum system was similar to that in pure copper films; abnormal grain growth and inhibition of normal grain growth was observed in the two-phase copper-yttrium system. The thermal stress evolution in pure copper films was described for the first time with a constitutive law for diffusional creep in a thin film under the constraint of a substrate. Diffusional creep was suppressed by aluminum alloying. This was …