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

The properties of electroplated copper (Cu) film on a thin seed layer of ionized metal plasma deposited Cu have been investigated as a function of annealing temperatures together with the diffusion barrier performance in the EPCu/IMPCu/IMPTaN/SiO₂/Si multi-layer structure. The growth morphology of electroplated Cu film on ionized metal plasma deposited Cu seed layer was found to be more uniform and gave lower root mean square values (∼13.76 nm), resulting in a lower resistivity (1.72 μΩ cm) of electroplated Cu film. Annealing at temperatures of higher than 750°C resulted in slightly higher sheet resistance, larger grain sizes and rougher surface. Scanning Electron Microscopy images showed that the agglomeration of electroplated Cu film occurred only at annealing temperatures higher than 850°C. During annealing, the electroplated Cu grains grew normally and their sizes increased to about five times larger than the thickness of the electroplated Cu film but the (111) preferred orientation was maintained up to 950°C. Furthermore, the interfacial reactions between Cu film layer and ionized metal plasma deposited Tantalum nitride (TaN) diffusion barrier were also detected at annealing temperatures of higher than 750°C.