Effect of the Purity of Plating Materials on the Reduction of Resistivity of Cu wires for Future LSIs

Resistivity difference between Cu wires made with plating using high purity (new plating process) and conventional purity (conventional process) materials has been evaluated in order to develop the process for the realization of high performance LSIs. This resistivity difference is relatively small, i.e., 8% when line width is wide (200 nm). However, it increases with the decrease in line width, and it reaches about 20%, i.e., 2.8 μΩ cm for the former and 3.5 μΩ cm for the latter at 50 nm line width. A 50 nm wide Cu wire formed with the new plating process had more uniform and larger grain sizes and lower impurity concentrations than the wire formed with the conventional process.