Evaluation of line-edge roughness in Cu/low-k interconnect patterns with CD-SEM

To establish the method for evaluating interconnect LER, resist, low-k, and Cu/low-k samples were observed and electric-field enhancement was simulated. Wedge-shape LER was observed in the edges of low-k and Cu/low-k patterns, and simulations showed that the wedge causes serious electric-field enhancement which can degrade TDDB property. To predict the risk of TDDB, inspections of the wedge angle after low-k etching and Cu CMP are required as well as that of the degree of LER.