Electroplated Cu film on a thin seed layer of IMP deposited Cu has been investigated in the EPCu (1 mum)/IMPCu (150 nm)/TaN (25 nm)/SiO2 (500 nm)/Si multi-layer structure. The characteristics of Electroplated-Cu films before and after annealing were investigated by means of sheet resistance, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Rutherford Backscattering Spectroscopy (RBS). Annealing at temperatures of higher than 750 degreesC resulted in slightly higher sheet resistance, larger grain sizes and rougher surface. SEM micrograph showed that the agglomeration of EP-Cu film occurred only at annealing temperatures higher than 850 degreesC. During annealing, the EP-Cu grain grew normally and their sizes increased to about five times larger than the thickness of the EP-Cu film but the (111) preferred orientation was maintained up to 950 degreesC. Furthermore, the interfacial reactions between Cu layer and IMP-TaN diffusion barrier were also detected at annealing temperatures of higher than 750 degreesC.