Study on electroplated copper thin film and its interfacial reactions in the EPCu/IMPCu/IMPTaN/SiO₂/Si multilayer structure

Electroplated Cu film on a thin seed layer of IMP deposited Cu has been investigated in the EPCu (1 μm)/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°C 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°C. 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°C. Furthermore, the interfacial reactions between Cu layer and IMP-TaN diffusion barrier were also detected at annealing temperatures of higher than 750°C.