Residual stress and nanomechanical properties of sonoelectrodeposited Cu films

Knowledge of internal stresses in thin copper film structures is essential in understanding the film properties, such as stress migration, adhesion, hardness and elasticity. Internal stresses and nanomechanical properties in thin copper films were investigated by the curvature method, nanoindentation and atomic force microscope. Variations in the abovementioned parameters were studied with decreasing deposition temperature for the films. Irrespective of deposition temperature, the stress was observed to be compressive and increased at low electrolyte temperatures. Hardness and elasticity of the films were found to be increased with reduced deposition temperature. With increasing compressive stress, the hardness of the films increased. The surface adhesion of the film deposited at 5°C was minimum, indicating increased cleanliness and chemical stability with low deposition temperatures.