In situ observation by AFM of the morphology of copper metallization during electrodeposition

The early stages of the electrodeposition of copper on a polycrystalline gold substrate were examined by in situ atomic force microscopy (AFM). Initial potential sweep measurements were carried out over a potential range of 200 mV to -400 mV (Cu/Cu²⁺) at a scan rate of 0.5 mV s^-1. Potentiostatic deposition was performed at various potentials ranging from -35 mV to -250 mV (Cu/Cu²⁺). The nucleation and growth of well-defined pyramidal features was observed. Initial rapid growth was observed to occur at crystal facets followed by a sudden change to a lower growth rate. Excellent agreement between the film thicknesses measured coulometrically and using AFM was obtained at more negative deposition potentials demonstrating that the areas imaged were representative of the electrode as a whole. At deposition potentials less negative than -50 mV (Cu/Cu²⁺) a discrepancy was observed indicating a higher-than-average density of features in the area imaged. copyright The Electrochemical Society.